THE LIBRARY 
 
 OF 
 
 THE UNIVERSITY 
 OF CALIFORNIA 
 
 PRESENTED BY 
 
 PROF. CHARLES A. KOFOID AND 
 MRS. PRUDENCE W. KOFOID 
 

 
 
 
i * 
 
 
 'anS. -Tar tht Cnameal Effajj from, an ancient. Portrait, in pcsssfficn. cf the ^iuther 
 
 Bacon, like Moses, led MS forth at last, 
 
 The barren, wildernefs lie past, 
 
 Did on the very border stand 
 
 Of the Iblest promis'd land, 
 
 And from the moentams top of his exaltedl wit, 
 
 Sa~w it liimself, and shew'd us it . 
 
 But Life did never to ome man allow 
 
 Time to discover worlds, ana coinqjuer too . Cowi# 
 
 
 
CHEMICAL ESSAYS, 
 
 PRINCIPALLY RELATING TO 
 
 THE ARTS AND MANUFACTURES 
 
 OF 
 
 THE BRITISH DOMINIONS. 
 
 BY SAMUEL I^ARKES, F.L.S. M.R.I. F.S.A. Ed. 
 
 Member of the Royal Asiatic Society of Great Britain and Ireland, 
 
 Fellow of the Geological and Astronomical Societies of London, 
 
 And of the Wernerian, Horticultural and Highland Societies of Scotland ; 
 
 Member of the American Philosophical Society, and 
 
 Master of Arts of Yale College, Connecticut ; 
 
 Member of the Imperial Natural History Society of Moscow, 
 
 The Academy of Sciences, Arts and Belles Lettres at Dijon, 
 
 And the Academy of Medicine at Marseilles ; 
 Honorary Member of the Royal Geological Society of Cornwall, 
 
 The Antiquarian Society of Newcastle upon Tyne, 
 
 The Agricultural Societies of Philadelphia and Massachusetts, and 
 
 The Society for the Promotion of National Industry and the Arts at Lisbon ; 
 
 Corresponding Member of 
 The Literary and Philosophical Society of Manchester ; the Academy 
 
 of Natural Sciences in Philadelphia ; the Philomathiquc 
 Society of Paris ; and the Imperial Agricultural, and Physico-Medical 
 Societies of Moscow, &c. 
 
 AUTHOR OF 
 
 THE RUDIMENTS OF CHEMISTRY*', 
 AND OTHER WORKS. 
 
 THE THIRD EDITION, 
 
 Revised, corrected, enlarged, and illustrated with numerous Copper Plates and 
 Wood Cuts of Machinery and Chemical Apparatus ; 
 
 BY J. W. HODGETTS. 
 
 LONDON : 
 
 PUBLISHED BY BALDWIN AND CRADOCK, 
 PATERNOSTER ROW. 
 
 ,830. 
 

 CntercD at 3>tationcr0' 
 
 PRINTED UY R. TAYLOR, RED LION COURT, FLEET STREET, LONDON. 
 
 
PREFACE 
 
 TO 
 
 THE FIRST EDITION. 
 
 NOTHING can be of more importance to the people of a manu- 
 facturing country than the cultivation of a taste for philosophical 
 and chemical inquiries. Manufactories cannot be conducted 
 without the employment of a variety of artificial as well as na- 
 tural productions, and it behoves the workmen as well as their 
 employers, to become acquainted with the intimate nature and 
 properties of the respective materials on which they have occa- 
 sion to operate. 
 
 To enable such persons to pursue these investigations with 
 advantage, it is requisite that they should not only possess a 
 knowledge of the elements of chemical science, but acquire also 
 a constant habit of observing the effects which different bodies 
 produce upon each other, and hence learn to understand the 
 causes of the various appearances which take place in the several 
 operations that come under their own daily observation or parti- 
 cular superintendence. 
 
 To promote this desirable end, nothing would perhaps be so 
 effectual as the dissemination of several distinct and familiar 
 treatises on the most important manufactures of the country, and 
 on the nature of the materials employed in them. The Essays 
 of Bergman, Scheele, and Watson, are of this nature ; and these 
 have contributed in no small degree to the information of the 
 public mind, and to that growing taste for chemical pursuits 
 which is one of the characteristics of the present age. 
 
 The subjects on which these eminent Essayists have so ably 
 written, are, however, comparatively few, and much remains to 
 be done before an inquirer into the nature and extent of the Bri- 
 tish manufactures can obtain solid and sufficient information 
 respecting the staple products of the country. 
 
 In the course of his business as a manufacturing chemist, the 
 author of the following work has, for many years, been in the 
 habit of visiting the principal manufactories of the kingdom ; 
 of associating occasionally with the most intelligent artists in a 
 great majority of the counties of England and Scotland ; and 
 
 a2 
 
IV PREFACE TO 
 
 of taking notes of every thing that he saw or heard in the course 
 of his journeys which he esteemed worth registering : he there- 
 fore flattered himself that he possessed the means of increasing 
 the stock of general knowledge, and that he might, without pre- 
 sumption, aspire to the honour of treading in the footsteps of 
 those illustrious predecessors above mentioned. 
 
 In selecting the subjects, the author has fixed upon those which 
 seem to have been the least examined by other chemical wri- 
 ters, and in all cases due attention has been paid to the improve- 
 ment of the manufactures of the kingdom. With this view, he 
 has been careful to offer, on every favourable opportunity, such 
 hints as were likely to be most useful to the superintendents of 
 manufactories, and such as should induce a correct chemical in- 
 vestigation of the nature of all those concerns in which persons 
 of this description are usually engaged. 
 
 To attain this object, it has been found necessary to recite 
 many chemical axioms, and to impress these upon the minds of 
 artificers and workmen, though such may appear to the profi- 
 cient in chemical science to be little more than mere truisms or 
 trite observations. In like manner, some of the details are given 
 with no other view than to inform those who are beginning the 
 study of chemistry ; and this may be instanced in the enumera- 
 tion of the many cases in which a knowledge of specific gravity 
 is essential, and where the author's sole aim is to induce such 
 persons to direct their attention to this particular and important 
 subject. 
 
 The superintendents of some manufactories may perhaps deem 
 it superfluous to have described their processes so much in detail, 
 because they themselves are already familiar with them; but 
 such individuals should consider that others may profit by the 
 perusal, and that those who are engaged in very different occu- 
 pations, by reading such accounts may perceive that the improve- 
 ments which are suggested for the adoption of other establishments 
 can, with considerable efficacy and saving, be applied to their 
 own, and thus in the end a great mass of improvement may be 
 gained by the community at large. 
 
 It is an excellent opinion of the writer who obtained a prize 
 from the Economical Society of Berne, for an Essay on the best 
 means of instructing the public, that " a labourer executes easily 
 and exactly all his works in proportion to his knowledge ;- that 
 the ignorance of the people always throws an indolence on the 
 persons of a more elevated order; and that the intelligence of 
 the artist necessarily excites the emulation of the gentry and the 
 nobility." 
 
 Many years having now elapsed since the author began to 
 register every thing of importance that he saw or read respecting 
 
THE FIRST EDITION. V 
 
 the British manufactures, it has become impossible for him in 
 some instances to ascertain whether the facts were obtained from 
 books, or from observation during his intercourse with artists and 
 their employers; and at this distant period he is unable in some 
 cases to discover even whether the language itself is his own, or 
 that of others. He has, however, endeavoured to make his 
 readers amends for this uncertainty, by referring them on every 
 subject to the best writers within his knowledge ; being ambi- 
 tious that his work should be received as a book of reference to 
 the most eminent chemical authors, so far as these have any 
 thing applicable to the subjects on which he treats. It must 
 always be an acceptable service to those who have chemical sub- 
 jects to investigate, to be directed to original authorities, or other- 
 wise to faithful translations, which can always be procured by 
 many readers with greater ease than those works which are 
 printed abroad, or even than any of the foreign Journals. 
 
 Notwithstanding the space which is occupied by such allusions 
 and authorities, the author hopes that these volumes will be 
 found to contain as large a proportion of original matter as any 
 chemical work of the present day; and it is impossible in this 
 advanced state of the science to write on any chemical subject, 
 without recapitulating many facts which have been already es- 
 tablished by a host of predecessors in the same walk of science. 
 " Do not blame me," said Macrobius, an interesting Latin writer 
 and eminent critic of the 4th century, " if what I have collected 
 in reading shall frequently be expressed in the very words of the 
 authors from whom I have taken it; for my view in this work is, 
 not to give proofs of my eloquence, but to collect and digest, into 
 some regularity and order, such things as I thought might be 
 useful to be known to the public*." 
 
 In accomplishing a similar task, the author is aware that he 
 is liable to mistakes and misconceptions, especially in his reason- 
 ings and remarks on the conduct of those manufactures in which 
 he has never been personally engaged : he is however convinced, 
 as Dr. Priestley has observed, " that a person who means to 
 serve the cause of science effectually, must often hazard his 
 own reputation so far as to risk mistakes in things of small mo- 
 ment f ." And if it behoves one in the service of general science 
 to risk that which is so valuable to every man, surely those 
 branches of knowledge which are more intimately connected with 
 the commerce of these dominions have the most imperious 
 demands upon us ; for " what can touch us more nearly than the 
 improvement of our manufactures, on which the riches of our 
 
 * Praefat. acl Saturnalia. 
 
 t Preface to Priestley's Observations on Air, Edit. 1781, vol. i. p. 9. 
 
VI PREFACE TO 
 
 country, and the daily bread of the greatest number of its inha- 
 bitants depend * ?" 
 
 Deeply engaged in a manufactory, which demands great at- 
 tention and often requires the aid of tedious experimental investi- 
 gation, little time could be afforded for preparing these volumes, 
 except in those hours which the generality of men devote to re- 
 laxation or repose. 
 
 The greater part of these Essays were, therefore, necessarily 
 composed during the intervals of business, and often in the midst 
 of manufactories at a great distance from home, when the author 
 could have no access to his own library, or to books of any kind 
 to which he might refer for authority or elucidation respecting 
 the numerous facts which always offer themselves to the attention 
 when treating on chemical or philosophical subjects. 
 
 From these circumstances, the Essays were at first written 
 without any illustrations or references whatever, and the notes 
 were appended occasionally, wherever further explanation seemed 
 to be essential, and whenever the reading or the memory of the 
 author furnished him with any facts of importance to which he 
 had not already alluded. It must however be remarked, that 
 this mode of essay-writing, though it may perhaps give a little 
 more originality to the complexion of the composition, has en- 
 tailed upon the author the very laborious task, of subsequently 
 collecting and examining numerous authorities, in order to enable 
 him to direct the chemist or artisan to the most authentic sources 
 from which he could derive additional and often very valuable 
 information. 
 
 To render these Essays more useful, the author has taken con- 
 siderable pains to procure drawings of all the modern apparatus 
 to which he has referred. These drawings were in general either 
 sketched by himself, or by those proprietors of the several manu- 
 factories who were anxious to contribute to the work, and whose 
 kind assistance he hereby acknowledges with gratitude. 
 
 Thus all the plates were engraved from original drawings, 
 with the exception of the sal-ammoniac apparatus, which is copied 
 from the second volume of the Journal de Physique. This it 
 appeared desirable to describe, because it has not yet excited that 
 attention which its importance and utility deserve, and few per- 
 sons in this country have access to the early volumes of the fo- 
 reign journal from which it was obtained. 
 
 Great care has also been taken in describing all these plates; 
 and in order to enable the reader to construct any of the apparatus, 
 accurate admeasurements have been given wherever there ap- 
 peared to be a probability of their being useful. 
 
 * Experiments on Bleaching, by Francis Home, M.D. p. 147- 
 
THE FIRST ED1TJON. Vll 
 
 The pleasure which arises from the discovery of any facts not 
 generally known ; any new elucidation of interesting truths ; or 
 the acquisition of any scarce treatise which might afford im- 
 portant hints to the reader ; and the prospect of completing a 
 work which is likely to be useful to the public, have been con- 
 stant incitements to the author to persevere in the labour of re- 
 search with unremitting zeal and ardour. 
 
 As a considerable mass of materials still remains with the 
 author, he may perhaps be inclined, should it meet with the 
 approbation of the public, to compose at some future period an 
 additional volume of these Essays. At all events, he will con- 
 tinue to employ the latter years of his life in the same kind of in- 
 vestigations, always keeping in view the examination of every 
 new improvement in the management of the national manufactures, 
 well knowing that the acquisition of one new idea often gives birth 
 to others of very superior importance. 
 
 Cardinal Farnese one day found Michael Angelo, when an old 
 man, walking alone in the Colosseum, and expressed his surprise 
 at finding him solitary amidst the ruins ; to which he replied, " I 
 go yet to school that I may continue to learn." Whether the 
 anecdote be correctly true or not, it is evident that he entertained 
 this feeling, for there is still remaining a design by him, of an old 
 man with a long beard in a child's go-cart and an hour-glass 
 before him, emblematical of the last stage of life ; and on a scroll 
 over his head, ANCORA IMPARO in Roman capitals, denoting that 
 no state of bodily decay or approximation to death was incompa- 
 tible with intellectual improvement. "He established it as a 
 principle," says Mr. Duppa *, who has given us these anecdotes, 
 "that to live in credit was enough, if life was virtuously and ho- 
 nourably employed for the good of others ancl the benefit of 
 posterity : and thus he laid up the most profitable treasure for 
 his old age, and calculated upon its best resources ; making all 
 nature interested in the length of his days." 
 
 London, 
 .My Slh, 1815. 
 
 * The Life of Michael Angelo Buonarroti, with kit Poetry and Letters, by 
 R. Duppa, Esq. 4to, London 1806. 
 
PREFACE 
 
 TO 
 
 THE SECOND EDITION. 
 
 A CONSIDERABLE time has elapsed since the publication of the 
 first edition of these Chemical Essays; and during this period so 
 many new facts have been discovered, and the opinions of the 
 most eminent chemists of every country have so entirely changed 
 respecting some of the more interesting branches of Chemistry, 
 that the very elements of the science have in several instances un- 
 dergone a complete revolution. 
 
 On these accounts it became necessary, when preparing a new 
 edition for the press, not only to revise every page of the work 
 with the utmost care, but also to enlarge most of the Essays by 
 the addition of much new matter. 
 
 It would be useless to attempt to enumerate the whole of the 
 additions and alterations which this impression has undergone ; 
 but a few of the most important may be mentioned, for the in- 
 formation of those persons who may not have seen the former 
 edition of this work. 
 
 When these Essays were written, the importance of the doctrine 
 of definite proportions was not so generally acknowledged as it is 
 at present ; for though Higgins, Richter and Dalton had all writ- 
 ten on the subject, it seems never to have made a general impres- 
 sion on the public mind, until Dr. Wollaston in the year 1814? 
 published his Memoir on Chemical Equivalents, and with it the 
 sliding-rule, which reduced the theory to practice, and convinced 
 all scientific men of the importance of these helps in chemical in- 
 quiries. It was therefore thought to be of consequence, in re- 
 publishing these Essays, to attach the representative number to 
 every substance treated of therein; and this has been done in most 
 cases. 
 
 The Notes which in the former edition were printed at the 
 bottom of the page have been for the most part interwoven with 
 the Text ; and in order to make each Essay a complete Treatise 
 on the subject which it professes to discuss, the various salts and 
 other chemical compounds connected with it have been enume- 
 
PREFACE TO THE SECOND EDITION. IX 
 
 rated, and their properties and uses, where known, fully described. 
 The Essay on the Manufacture of Tin-Plate, first printed in the 
 Memoirs of the Literary and Philosophical Society of Manches- 
 ter, is now appended to the former Essays; a List of the various 
 works referred to in these volumes is also given, for the purpose 
 of showing the editions which have been made use of, and for ena- 
 bling the reader to examine the extracts and verify the quotations ; 
 and much labour has been bestowed in forming a New General 
 Index. 
 
 The most important addition, however, is that of a very ex- 
 tensive Table of Chemical Equivalents. This Table has been 
 drawn up in an alphabetical form for the sake of facility of re- 
 ference; and it may be remarked that it is the only alphabetical 
 Table yet published by any English Chemist which contains the 
 chemical composition of each compound attached to its equiva- 
 lent number. In choosing these numbers, I have adopted those 
 which appeared to me to be derived from the best authorities, 
 though I am well aware that a long time must elapse before any 
 Table of this sort can be formed which will be correct in every 
 instance. 
 
 The writers who have treated more expressly on this subject 
 are Berzelius and Dr. Thomson ; but the largest collection of 
 modern equivalent numbers has been published by Mr. Brande 
 in his Manual of Chemistry, and of this I have availed myself 
 very much in the construction of this Table. Another Table 
 has since been published by Mr. Brande, which in many re- 
 spects varies very considerably from the numbers in his Manual ; 
 but as many of these appeared to me to require confirmation, I 
 thought it most advisable to construct my Table in conformity 
 with the numbers which I had already made use of in the body 
 of the work. 
 
 I have much pleasure in adding, that these Essays have been 
 twice translated into the French language, and are now selling at 
 Paris in three volumes octavo ; and that they have also been ren- 
 dered into German at Weimar, at Erfurt, and elsewhere. 
 
 Mecklenburgh Square, 
 June 1823. 
 

PREFACE 
 
 TO 
 
 THE THIRD EDITION. 
 
 EIGHTEEN months having been allowed to elapse since the 
 last edition of Mr. Parkes's "Chemical Essays" was entirely 
 out of print, some apology is due to the public, for delay- 
 ing so long the republication of the work. One cause of 
 this delay was an error in supposing that many more copies 
 had remained in the publishers' hands than actually were 
 there ; so that the editor was advertised of the sale of the 
 last copy before he had well commenced his preparations 
 for a new edition : another, and by far the most impor- 
 tant, was the unforeseen difficulty of the undertaking, and- 
 length of time required for its execution. The task of pub- 
 lishing the twelfth edition of the "Chemical Catechism" was 
 comparatively easy : the author had been lost to the scien- 
 tific world but a few months; and although he had not actu- 
 ally prepared the sheets for the press, he had noted the 
 changes and additions which he intended to make. Now, 
 however, the case is widely different: four years have passed 
 away since the death of Mr. Parkes, and more than six 
 since these Essays last went to press. During this period, 
 the rapid strides which the science of Chemistry has made, 
 and the quick succession in which one series of improve- 
 ments and discoveries has succeeded another, have only been 
 excelled by the still more quick advances of the manufac- 
 tures of Great Britain, and most particularly of those which 
 are dependent upon Chemistry. 
 
 Thus the various new processes brought to perfection by 
 the Calico-printer, have rendered the Essay on that subject 
 very inadequate to give the reader an idea of the state of 
 the art in the present day ; and the difficulty of obtaining 
 
Xll PREFACE TO 
 
 accurate information of the manipulations required in the 
 new processes of an art where every manufacturer has his 
 particular and highly valued secrets, can only be appreciated 
 by those who have laboured to get details of chemical ope- 
 rations for the purpose of publication. Thanks, however, 
 to the kindness and liberality of a scientific friend, who 
 is a considerable calico-printer near Manchester, I hope 
 that the attempt I have made to describe the new systems 
 will not be found destitute of information and interest to 
 the reader. 
 
 In the Essay on Sulphuric Acid, the manufacture of 
 which has also undergone most important changes, I had 
 less difficulty ; as to give a history of the improvements in 
 that art, I had little more to do than to detail the succes- 
 sive processes which Mr. Parkes and myself adopted in our 
 own chemical works, where that article has always been 
 an object engrossing a considerable portion of our at- 
 tention. 
 
 All the Essays required attentive revision, and many of 
 them great additions. I have altered Mr. Parkes's language 
 as little as possible, preferring, where I could, to add my 
 own matter, in lieu of changing his : and knowing that the 
 author had intended in his next edition to compress the two 
 volumes into one, so that the work might be obtained at 
 one half of the expense, I have pursued that plan ; and by 
 printing in a smaller type and closer page, I have not only 
 given all the original Essays, with rny own additions, be- 
 fore mentioned, but have also added one, at least as inter- 
 esting and instructive as any in the book, I mean that 
 on the Manufacture of Brass, which he wrote for the 
 Royal Geological Society of Cornwall, and the original 
 manuscript of which that Society obligingly lent me, to 
 enable me to correct the imperfect copies which I pos- 
 sessed. 
 
 To get in so much new matter, I have omitted the list 
 of works quoted (which are all referred to so accurately in 
 the notes as to make a separate list of little use), as also 
 the tables of the fusing points of metallic alloys, and some 
 additional notes and parts of the text, which various cir- 
 cumstances have rendered obsolete : as for instance, every 
 
THE THIRD EDITION. Xlll 
 
 thing concerning the abolition of the salt duties, and the 
 laws relating thereto, which abolition was afterwards so 
 happily achieved. 
 
 Chemists having now all agreed that the atomic weight 
 of oxygen is eight (or at least that it is eight times that of 
 hydrogen), and the tables of equivalent numbers being cal- 
 culated on the old system of seven-and-a-half, I have had 
 to alter not only these, but every equivalent mentioned 
 throughout the work. To do this I have almost entirely 
 followed Mr. Brandes " Table of Prime Equivalent 
 Numbers " in a few instances taking those of Dr. Thom- 
 son^ as published in his "First Principles of Chemistry r ." 
 
 It being hardly possible to retain all the plates of the two 
 volumes, I have rejected a few which appeared to be of 
 less utility, some of them being almost duplicates ; but 
 I have preserved fourteen, as necessary to the elucidation of 
 the various processes described. In the Essay on the Ma- 
 nufacture of Brass, and in the additions to that on Calico- 
 printing, I have also given wood-cuts of the furnaces and 
 apparatus, which I hope will tend to render the descriptions 
 of those manufactures more clear and easy to be under- 
 stood. Upon the whole, I have endeavoured to render this 
 edition such as not to be behind the recently rapid im- 
 provements in our manufactures. 
 
 Soon after the last edition of these Essays was published, 
 the then Emperor of Russia (Alexander), in token of his ap- 
 probation of the work, presented Mr. Parkes with a valuable 
 diamond ring. Several translations, both French and Ger- 
 man, not only of the "Essays," but of the "Chemical Cate- 
 chism," and the "Rudiments of Chemistry," have also been 
 sent him by their authors. Indeed, were any thing want- 
 ing to prove the estimation in which Mr. Parkes's books 
 are held, the continued piracies upon them would be suf- 
 ficient. During the lifetime of the author, he was frequently 
 compelled to have recourse to the law to protect his lite- 
 rary property : as late as last year it was found necessary 
 to stop ForsytKs " First Lines of Chemistry? (being 
 almost a reprint of the " Catechism/') by an injunction 
 of the Court of Chancery: and since that time, another 
 free-trader, not content with unmercifully pillagingthe con- 
 
XIV PREFACE TO THE THIRD EDITION. 
 
 tents of the book, has actually carried his assurance so far 
 as to adopt its very name of " Chemical Catechism." 
 
 Having prefixed a short sketch of Mr. Parkes's literary 
 life (with an excellent engraved portrait of him) to the 
 twelfth edition of the " Chemical Catechism," which has 
 for some time been in the hands of the public, I will not 
 unnecessarily swell this volume by a repetition of what has 
 probably been already perused by most of the readers of the 
 present volume. 
 
 JOSEPH W. HODGETTS. 
 
 47 Camden Street, 
 April, 1830. 
 
DESCRIPTION OF THE PLATES. 
 
 PLATE I. 
 
 PORTRAIT OF LORD BACON. 
 
 THIS is a highly-finished likeness of Lord Chancellor Bacon, engraved by an 
 eminent artist from an original portrait in the possession of the author. The 
 lines underneath it were taken from a poem addressed by Abraham Cowley to 
 the Royal Society, on its first formation, and printed in Bishop Sprat's History 
 of the Society. 
 
 PLATE II. 
 
 Is an improved STILL, with its preparatory vessel as lately introduced in some 
 
 of the West India Islands for the distillation of rum. 
 
 On an inspection of the ground plan of this apparatus, it will be perceived 
 that the still, A, is of a square form : but as the bottom and the crown of this 
 still are both curved in the same manner as a round one, the principle on 
 which this acts is nearly the same as in a common still, except in the following 
 particulars : 
 
 The flues under this still reverberate in the direction of the arrows, as shown 
 in the ground plan, and are then taken up on each side of the still into the 
 side flues, from whence the fire or flame proceeds under the preparing vessel 
 B, round a slight partition of brick- work called a bonnet, then into an aperture 
 at the bottom of the perpendicular flue, or tube, C, which passes through the 
 centre of the liquor in the preparatory vessel, and from thence directly into 
 the chimney D. 
 
 In common stills the heat from the fuel is not sufficiently expended under 
 the bottom, as explained at p. 77, but quickly passes off to the sides, where- 
 by the sides of the vessel are very soon burnt through. By this contrivance, 
 however, the light materials which are burnt for fuel in the West Indies are 
 nearly all consumed under the bottom of the still ; and whatever waste heat 
 there may be, this is afterwards expended in raising the temperature of the 
 wash contained in vessel B. 
 
 In this apparatus, b is the man-hole for clearing out the preparatory vessel, 
 c the safety valve, and d the cock for opening or shutting the tube by which 
 the still is filled with heated wash from the preparatory vessel B. The prin- 
 cipal difference between a common still and this one is in the manner in which 
 the liquor of the preparatory vessel of each is heated. That in the former is 
 heated by the flame passing underneath it, and the latter by a heated tube 
 which is fixed within the centre of the liquor itself, as is more particularly 
 described at page 91. 
 
 PLATE III. 
 
 The elevation of an Economical STILL for general purposes. 
 
 A is a still in the usual form. B the copper head with a long pipe passing 
 through the condensing vessel C, to the worm E, fixed within the cask or 
 worm-tub D. 
 
 The condensing vessel C, which lies in a horizontal position, and may be 
 supported from the ceiling or the floor, as may be most convenient, answers 
 
XVI DESCRIPTION OF THE PLATES. 
 
 two important ends in distillation which deserve attention. This preparatory 
 vessel being filled with wash, or any other liquor intended to be distilled, 
 materially cools the gas arising from the still, and condenses the vapour into a 
 liquid, as it passes along the pipe e, before it reaches the worm itself; and this 
 intermediate reduction of temperature is so considerable, that one-fourth of 
 the water usually employed in the worm-tub is found sufficient. The second 
 advantage arising from this peculiar construction, is, that so much caloric 
 passes off from the tube e, into the wash contained in the intermediate 
 vessel c, that the liquor soon becomes heated to 170 or 180 of Fahrenheit ; 
 and hence is in a very desirable state for replenishing the still. This is done 
 merely by turning the cock d, in the pipe, which passes from the preparatory 
 vessel to the still. Each end of the pipe passing through the intermediate 
 vessel is secured with ceme^, that the vessel may at any time be taken off if 
 required. 
 
 The orifices b and c, and the cock d, have the same uses as those in Plate II. 
 marked with similar letters. F is the vessel placed on the ground for the 
 reception of the product of the still. This apparatus is referred to at page 91 
 of this volume. 
 
 PLATE IV. 
 
 A collection of Apparatus for ascertaining the Specific Gravity of bodies. 
 
 Fig. 1 is an areometer for proving the specific . gravity of fluids ; it is de- 
 scribed at page 107 of this volume. 
 
 Fig. 2. An hydrostatic balance. Its use and the different modes of employ- 
 ing it are explained at page 111. 
 
 Fig. 3. A jar of water in which the solids, whose specific gravities are to be 
 ascertained, are immersed, after having been weighed in air. 
 
 Fig. 4. A cube of glass. Its use is particularly described at page 107- 
 
 Fig. 5 is the representation of a set of carat weights, such as are described at 
 page 116, and which are extremely useful in ascertaining the specific gravity of 
 many substances. Tables to facilitate the use of these weights will be found at 
 pages 117 and 119. 
 
 Fig. 6. Knight's travelling case, containing a specific gravity bottle, counter- 
 poise weight, &c. 
 
 Fig. 7 is a drawing of Mr. Knight's gravity bottle with taper neck, for as- 
 certaining the specific gravity of fluids where great accuracy is required. 
 
 Fig. 8 is the representation of a stopper for a specific gravity bottle, with a 
 notch on one side to allow of the escape of the redundant fluid, as described 
 at page 110 of the Third Essay. 
 
 Fig. 9. Mr. Nicholson's specific gravity bottle, with the conical notched 
 stopper (fig. 8.) placed in it. 
 
 Fig. 10. The specific gravity bottle, usually employed by the author when- 
 ever he has occasion to take the specific gravity of fluids, as noted by the carat 
 weights. The bottle itself is marked on the neck with a diamond to show how 
 high it should be filled, and it is blown with a sort of cup at the top to receive 
 any portion of the liquor which would otherwise be spilled in filling ; but this is 
 not well displayed in the engraving. See page 116. 
 
 PLATE V. 
 
 A Barytes Furnace, contrived for the decomposition of Derbyshire cauk, or 
 the common sulphate of barytes. 
 
 Fig. 1. is an elevation of the furnace, as it appears when finished. Fig. 2 is 
 as it appears before the arches are turned over it. 
 
 A is the ash pit. B the fire-place, with the fire-bars. C the bottom of the 
 furnace on which the ground cauk mixed with the carbonaceous matter is to 
 be exposed to the action of the fire, with continual stirring. D is the chim- 
 
DESCRIPTION OF THE PLATES. XVII 
 
 ney for carrying off the smoke, the sulphurous acid gas, and other incondensable 
 products. E a door for emptying the ash-pit. F the furnace arch and open- 
 ing to repair the furnace. G the hopper for feeding the fire. H H the doors 
 into the furnace for the convenience of stirring the materials, and through 
 which the sulphuret of barytes is to be withdrawn when finished. I the arch 
 of the fire-place. For the method of using this furnace, see page 147. 
 
 PLATE VI. 
 
 APPARATUS FOR MAKING COKE. 
 
 Fig. 1 represents the ground plan of one of the coke-ovens belonging to the 
 Duke of Norfolk, at Sheffield. 
 
 The oven is built circular, with a wall of 18 inches in thickness. Its diameter 
 is ten feet in the clear within side, as will be seen by a reference to the scale. 
 
 A is the platform or floor of the oven, which is elevated three feet above the 
 ground, as will appear from an examination of the elevation fig. 2. This is con- 
 trived for the convenience of placing a wheelbarrow under the door to receive 
 the cokes as they are drawn from the oven. 
 
 B is the opening or door-way for drawing out the cokes. It is 2 feet wide 
 and 19 inches high to the springing of the arch. This door-way has a broad 
 cast-iron sill built into the wall when the furnace was erected. ' 
 
 C the oven wall, which is 18 inches thick and 19 inches high, when mea- 
 sured from the floor of the oven. The diameter is then contracted, and the 
 roof is brought in like a glass-house, to the height, when measured perpendi- 
 cularly, of 3 feet 5 inches more, leaving a circular opening of two feet diameter 
 at the top, for supplying the furnace with the coals which are to be converted 
 into coke, and to serve as a chimney when the coals are first ignited. The 
 latter wall is only one brick's length in thickness, and the ends of the bricks 
 are placed towards the fire. The floor is laid with hard common bricks on 
 the edge; common bricks are also sufficient for the first wall of 19 inches high, 
 but it is absolutely necessary to have good fire brick for the whole of the arch 
 or covering. 
 
 D D is a wall built with common unhewn stone, about 20 inches thick, and 
 carried up the whole height of the oven ; the void spaces in the corners to be 
 filled with rubbish well rammed. 
 
 Fig. 2 represents a front elevation of the coke-oven, the ground plan of 
 which has been described already. 
 
 In explaining this elevation, reference must be had to the letters engraven 
 upon the plate. 
 
 C is intended to show the line of the oven floor. 
 
 D the height of the oven wall where the brick-work begins to contract. 
 
 E the door-way for taking out the cokes when sufficiently burnt. 
 
 G G shows a section of the arched roof of the oven; but this is not seen in 
 the front elevation, as the front wall and the backing of earth hide it. 
 
 The coke-ovens are used thus : Small coal is thrown in at the opening fig. 2, 
 sufficient to cover the bottom of the oven 19 inches thick to the springing of 
 the arch, which is about two tons ; they are then levelled, and the door E built 
 up with loose bricks. The heat of the oven sets the coal on fire, which is 
 accelerated by the atmospheric air rushing in through the joints of the loose 
 bricks in the door-way. In the space of two or three hours the door-way is 
 plastered up with a mixture of wet soil and sand, except the top row of 
 bricks, which is left unplastered all night. This is generally plastered up 
 c'ose in about 24 hours after the coals are first put in, the chimney remaining 
 open till the flame is gone, which is generally quite off in 12 hours more. A 
 few loose stones are then laid over the chimney, and those covered up with 
 sand or earth. After this is done, the cokes remain in the ovens 12 hours 
 
 b 
 
XVlll DESCRIPTION OF THE PLATES. 
 
 longer, and are then drawn out into wheelbarrows and carted away by the 
 customers. The whole takes up 48 hours ; and as soon as the cokes are 
 raked out, the ovens are re-filled with small-coal for another burning. 
 
 Fig. 3 represents a new mode of burning cokes in the open air by means of a 
 large chimney round which the coals are piled. The method of managing this 
 process is fully described at page 183. 
 
 PLATE VII. 
 
 This engraving is the representation of an Elaboratory constructed for the 
 express purpose of preparing the Crystallized Citric Acid. 
 
 A A A are pipes of lemon-juice, supposed to be in the state in which the ar- 
 ticle is usually imported. 
 
 B is a large wooden vat for saturating the acid with calcareous earth, and 
 capable of holding two or three hundred gallons. 
 
 C C. These are copper pumps suitable for pumping the juice from the casks 
 into the saturating vat. 
 
 D is a large wooden tub for decomposing the citrate of lime by means of 
 sulphuric acid, when it is removed from the vat B. 
 
 E is a leaden boiler of an oblong square for concentrating the acid liquor 
 from the vessel D. 
 
 F F are two round boilers of lead of different sizes, and suspended in water 
 baths. These are employed for the further concentration of the liquid citric 
 acid. In the smaller of these the acid is brought to that syrupy state which 
 is most suitable for it to be laid out to crystallize. 
 
 G G G G. These are pans of earthenware or glass into which the concen- 
 trated acid is poured to cool and crystallize. 
 
 H is a leaden syphon to be employed in running off the waste liquor from 
 the vat B when the acid has been abstracted from it by the chalk. 
 
 K is a shelf for holding bottles of chemical tests, trial glasses, or any other 
 small articles required in the manufactory. 
 
 L a moveable strainer for clearing the mother liquors, and other purposes of 
 the manufactory. 
 
 PLATE VIII. 
 
 Apparatus for making Charcoal and distilling Pyroligneous Acid. 
 
 Fig. 1 represents a section of a charcoal cylinder when fixed within the fur- 
 nace. It is cut lengthwise through the middle, to show the internal work. 
 
 Fig. 2 is a contrary section of the same cylinder, the end or front wall being 
 in this case taken away to show how the fire plays round it before it passes off 
 by the chimney. 
 
 Fig. 3 is an elevation of the building which incloses a cylinder when pro- 
 perly fixed, together with the fire-place, the tubes to carry oft' the acid and gas, 
 the wine casks to receive pyroligneous acid, &c. complete. 
 
 Fig. 4. The outer shutter, to contain the stopping or luting which makes the 
 cylinder air-tight during the operation of distilling the acid and charring the 
 wood. 
 
 Fig. 5. The inner shutter, or stopper to prevent the stopping from getting 
 among the charcoal. 
 
 PLATE IX. 
 
 The elevation and plan of a Reverberatory Furnace on an improved construc- 
 tion. The separate parts may be thus described : 
 
 A is a door by which the oven is charged, the size of which may with con- 
 venience be 9 inches by 12 inches. 
 
 B B Bare three strong bands which go on each side of the furnace. These are 
 fastened together by cross bars of iron which go through the brick-work of the 
 
DESCRJPTION OF THE PLATES. XIX 
 
 furnace, and over the top of it, and are bound tight against the walls by screws 
 and bars, as shown in the engraving. 
 
 C the ash -pit. 
 
 D an iron damper which runs within a groove in the brick-work of the chim- 
 ney, to regulate the draught or entirely stop it at pleasure. 
 
 E the passage from the oven to the chimney. 
 
 F is a faint line on the wall of the elevation to show how the arch of the 
 roof lessens in height as it approaches the chimney. This is designed for throw- 
 ing the flame more down upon the materials before it enters the chimney, and 
 has the effect of rendering the temperature of the oven the same in all its parts. 
 
 G is the floor of the oven, 4 feet long and 2 feet 2% inches wide. 
 
 H is the fire-place with an iron hopper such as is described at page 81. 
 
 I are the fire-bars, with their ends projecting, as shown in the elevation, for 
 the convenience of drawing them easily whenever it may be necessary either 
 to cool the furnace or take out the clinkers. When the bars of a furnace are 
 fixed in this manner, they may be readily taken out with a pair of tongs, and 
 then the whole of the contents of the fire-place will fall into the ash-pit. 
 
 K is the bridge which divides the floor of the oven from the fire-place. 
 This should be 14 inches thick and 9 inches high, and built with the best fire- 
 bricks. It is important to build it with very close joints and with fire-clay in- 
 tead of mortar, as the bridge usually wants repair before any other part of the 
 furnace. 
 
 As this drawing is an exact representation of a very useful reverberatory fur- 
 nace which was erected at my own manufactory, it may perhaps be acceptable 
 if I annex the measures of the principal parts, for the guidance of those persons 
 who may be desirous of constructing a similar furnace. 
 
 The whole length measured on the outside is 8 feet, the width 4 feet 2 inches, 
 and the height from the floor to the top of the covering 4 feet 6 inches. The 
 fire-place 17 inches by 20 inches, the ash-pit 10 inches wide, and 2 feet 4 inches 
 from the ground to the underside of the fire-bars. The height of the oven from 
 the floor of it to the underside of the arch is 17 inches at the bridge, and 12 
 inches if measured at the chimney. The measures of the oven floor, the door 
 and the bridge, have been noticed before. 
 
 PLATE X. 
 
 Is the representation of Crown Glass in its various states, from the time it is 
 taken out of the furnace until it becomes a perfect circular sheet of window- 
 glass. The whole is fully explained in the Essay. 
 
 PLATE XI. 
 Is descriptive of an Apparatus for Bleaching Cotton Goods. 
 
 Fig. 1 is a section of the bucking apparatus, which may be thus described : 
 
 A is the boiler for heating the alkaline lye. 
 
 B represents a very large wooden vessel in which the calicoes are placed. 
 
 C the cock and pipe, by means of which the hot lye is conveyed upon the 
 goods. 
 
 D is a square box designed for spreading the lye over the calicoes within the 
 vessel B. 
 
 E a pump for raising the liquor again out of the vessel B, whence it is con- 
 veyed by the spout I back into the boiler A. 
 
 F is the furnace for heating the lye. 
 
 G represents the false bottom of the calico vessel, full of holes for the pass- 
 age of the lye when it has run through the goods under operation. 
 
 H is a round wooden staff which completely fits a hole at the bottom of the 
 bucking vessel. It is called a duck, and is intended to be pulled up whenever 
 it is designed to run off the spent alkaline liquor. 
 
 b 2 
 
XX DESCRIPTION OF THE PLATES. 
 
 I is the spout for conveying the liquor back to the boiler as above mentioned. 
 In some houses the boiler is fixed below the bucking vessel, and the pump is 
 placed within the boiler as described in page 391. 
 
 Fig. 2 is the representation of a common whale-boiler. 
 
 A is a metallic boiler to be fixed in brick-work, similar to that in fig. 1. 
 
 B B is the top part of wood, called a crib, with the bottom full of holes. In 
 this the calicoes are placed one above another, often amounting to many hun- 
 dred pieces at one operation. 
 
 C is the pipe through which the lyes boil up, and d d is the umbrella sus- 
 pended over the pipe for the purpose of spreading the lyes more effectually as 
 they fall down again upon the goods. 
 
 This apparatus for bleaching possesses several advantages. The perforated 
 wooden vessel preserves the calicoes from being injured by coming in contact 
 with the boiler, while the pressure occasioned by so great a weight of goods 
 frequently increases the temperature of the lye by some degrees higher than it 
 would acquire in an open vessel, and this additional heat has a powerful effect 
 in bleaching. By this contrivance there is no necessity for pumping ; for, so 
 long as the lye in the vessel A actually boils, a constant stream will flow through 
 the pipe C upon the goods in B, and thus a perpetual circulation may be kept 
 up till the goods have attained the desired whiteness. 
 
 PLATE XII. 
 
 This plate contains two representations of Mr. Lucas's Furnace for converting 
 Cast-iron Cutlery to good Steel Cutlery. 
 
 Fig. 1 is a front view of the furnace complete. 
 
 B B are cast-iron bearers for supporting the grate bars. 
 
 D foundation wall below the floor of the work-shop for supporting the in- 
 terior of the furnace. 
 
 E E the two fire-places for heating the furnace. 2 is the dome or arch of the 
 furnace. 3 3 the internal side of the front wall, in which is an aperture 4, 
 by which the workman enters to place the iron cylinders holding the goods. 
 This being done, the aperture is walled up as shown in the engraving, except 
 two holes left in the bottom of the wall marked 5 5. 
 
 H is the chimney for conveying away the smoke of the fire-places. 
 
 Fig. 2 is a perpendicular section of the same furnace, presenting a side view 
 of its internal parts, and showing how the iron cylinders which hold the cast- 
 iron cutlery are exposed to the action of the fire. The several parts may be 
 thus described : 
 
 A shows the length and depth of the ash-pit. 
 
 B is the representation of one of the grate bars at full length. 
 
 E the fire-place. 
 
 F the opening for supplying the fire with fuel. 
 
 G a dotted line to show the height of the shop floor. 
 
 1 1 the outside wall of the furnace. 
 
 KK the iron cylinders as they stand 3 in height in the furnace, the lower- 
 most of which are raised a few inches from the platform by being placed on 
 pieces of brick, the intention of which is to afford the fire access to every part 
 of them. In describing the other parts of this furnace, it may be said that 2 is 
 the dome of the furnace; 4 is the temporary wall which is built up to close the 
 aperture spoken of in describing the elevation fig. 1, and which in that draw- 
 ing is marked 4 ; 5 is one of the holes left at the bottom of the said wall ; 7 is 
 another temporary wall of loose bricks; 6 is the space between the two walls; 
 8 the chimney; 9 an opening in the outer wall, the same width as 4; 10 a cast- 
 iron bearer reaching across the opening to support the front of the chimney. 
 
DESCRIPTION OF THE PLATES. XXI 
 
 PLATE XIII. 
 
 Mr. Parkinson's Machine for Printing three distinct Colours at once on 
 Calico, referred to at page 555. 
 
 A a screw to give the proper pressure to the main roller. There is a similar 
 one at the other end of the machine. 
 
 B a screw to give the necessary pressure to the copper roller C. 
 
 C a copper roller, with one of the patterns engraved on it. This receives 
 the colour from a small box at the top, which could not be shown in the en- 
 graving. 
 
 D is the main roller of iron, round which the calico passes in order to re- 
 ceive the printed impression from the three smaller rollers C, G and G. 
 
 E a wooden roller to guide the blanket, against which the white calico lies. 
 This blanket could not be distinctly shown in the engraving. 
 
 FF two blankets to receive the colour from the two colour-boxes H H. 
 On these blankets the respective colours become by the rotary motion uni- 
 formly spread by the time they arrive at the rollers G G, on which these are 
 to be deposited. 
 
 G G two wooden rollers with patterns cut upon them. Each of these, as 
 before mentioned, receives the colour from the blanket F, which moves under- 
 neath, and immediately imparts it, in the desired pattern, to the white calico 
 which revolves by an equable motion round the large iron roller D. 
 
 H H two wooden troughs containing the prepared colour. These the 
 workmen call colour-boxes. 
 
 1 1 two large wooden rollers, designed to guide and stretch the colour- 
 blankets. 
 
 K K two wooden rollers revolving within the colour-boxes H H. These are 
 contrived for feeding the blankets with colour. 
 
 L eight rollers of wood, four of which belong to each colour-blanket. 
 These rollers are merely designed for stretching and guiding the blankets. 
 
 M the large roll of white calico in a prepared state fit for printing. 
 
 N the calico in a printed state, after it has received the impression of the 
 three patterns, in three distinct colours, from the rollers C, G and G. 
 
 Twenty pieces of white calico, containing twenty-eight yards each, and 
 skewered together by their ends, are generally printed by this machine at one 
 operation, it being so contrived that they pass over the three different rollers 
 in one continued uninterrupted line until the whole is printed. This machine 
 is capable of printing ahout seven yards of calico every minute. 
 
 PLATE XIV. 
 
 APPARATUS IN CALICO-PRINTING. 
 
 Fig. 10 is the representation of a steam apparatus for drying calicoes. 
 A A A A A A are six distinct hollow copper rollers containing steam. Round 
 these the damp calico is wound in succession, by a power acquired from a 
 steam-engine, and by the heat of these cylinders the cloth is completely dried. 
 B B B are three fans or vanes, also moved by the steam-engine, and calculated 
 for promoting a perpetual circulation of air to expedite the drying process. 
 C is the heap of damp calico intended to be dried. D the calico as it is wound 
 off the cylinders in a dried state. 
 
 Fig. 11 is an apparatus for printing pencil-blue on calicoes, with greater cer- 
 tainty than has ever before been attained. It is fully described at page 545. 
 
CONTENTS. 
 
 ESSAY 1. On the Importance of Chemistry Page 1 
 
 2. On Temperature 24 
 
 3. On Specific Gravity 102 
 
 4. On Barytes 122 
 
 5. On Carbon 148 
 
 6. On the Manufacture of Brass 197 
 
 7. On Sulphuric Acid 212 
 
 8. On Citric Acid 248 
 
 9. On the Fixed Alkalies , 273 
 
 10. On Earthenware and Porcelain 304 
 
 1 1. On the Manufacture of Glass 346 
 
 12. On Bleaching 387 
 
 13. On Water .., 421 
 
 14. On Sal-Ammoniac 457 
 
 15. On Edge Tools 471 
 
 1 6. On the Manufacture of Tin-Plate 508 
 
 17. On Calico-printing 523 
 
 Additional Notes 571 
 
 Table of Equivalent Numbers 603 
 
 Index , 611 
 
DIRECTIONS TO THE BINDER 
 
 RESPECTING THE ARRANGEMENT OF THE PLATES. 
 
 PLATE 1 . Lord Bacon to face the Title. 
 
 2. The improved Still to face page 4 1 
 
 3. Economical Still 91 
 
 4. Specific Gravity 102 
 
 5. Barytes Furnace 122 
 
 6. Coke-making 148 
 
 7. Citric Acid Manufactory 248 
 
 8. Pyroligneous Acid 273 
 
 9. Improved Reverberatory Furnace 303 
 
 10. Manufacture of Crown Glass 346 
 
 1 1 . Bucking Apparatus 391 
 
 12. Furnace for Cutlery 471 
 
 13. Mr. Parkinson's Printing Machine 523 
 
 14. Calico-printing \ miscellaneous 554 
 
CHEMICAL ESSAYS. 
 
 ESSAY I. 
 
 ON THE IMPORTANCE AND UTILITY OF CHEMISTRY 
 TO THE ARTS AND MANUFACTURES OF THE 
 BRITISH DOMINIONS. 
 
 THE discovery of the loadstone and its important application 
 in the construction of the mariner's compass were the means of 
 producing a general intercourse among nations. The subsequent 
 invention of printing occasioned a rapid progress in that civiliza- 
 tion which had thus been much promoted by the increase of 
 commerce, and by the consequent interchange and general dis- 
 semination of the useful arts. 
 
 These arts consisted, however, of mere traditional processes 
 which had been communicated, like the secrets of the alchemists, 
 from generation to generation, without science, or any theory on 
 which the true knowledge of them might be founded ; nor was 
 it until Lord Bacon had shown the necessity of interrogating 
 nature by experiment, that any rational system of philosophical 
 inquiry was pursued or promulgated. 
 
 This illustrious philosopher was indeed the first writer who 
 seems to have had a just view of the character and labours of 
 the Alchemist. By showing how little can be done by reasoning 
 on the works of Nature, until a mass of facts is obtained by ex- 
 periment, he benefited the world more than a host of his pre- 
 decessors had done by their conjectures and conceits. 
 
 From this period, however, general science made rapid ad- 
 vances in improvement; and if one branch be more indebted to 
 this great but unfortunate philosopher than another, it unquesti- 
 onably is that of Chemistry, which has eminently availed herself 
 of his grand precept, and continued her unremitting researches 
 until nothing will now satisfy the curious inquirer, but plain facts 
 and lucid deductions from experiment or analogy. 
 
 In this state of the public mind, what can be expected through- 
 out Europe but a rapid succession of improvements in the arts 
 
4f ON THE IMPORTANCE AND UTILITY 
 
 and which of them may be worked to advantage. Thus he will 
 operate on sure grounds, and be prevented from engaging in 
 expensive and unprofitable undertakings. 
 
 Chemistry will teach him also how to improve the cultivated 
 parts of his estate ; and by transporting and transposing the dif- 
 ferent soils, he will soon learn some method by which each of his 
 fields may be rendered more productive. 
 
 The analysis of the soils will be followed by that of the waters 
 which rise upon, or flow through them ; by which means he will 
 discover those proper for irrigation ; a practice the value of which 
 is sufficiently known to every good agriculturist, and well de- 
 scribed in an excellent essay by the Rev. T. Wright, published 
 by Scatcherd and Co., 1789, which is deserving the attention of 
 every practical farmer. 
 
 Should he himself occupy the farm, and become the cultivator 
 of his own estate ; he must of necessity be a chemist, before he 
 can make the most of his land, or put it into a high state of cul- 
 tivation, at the smallest possible expense. It will be his concern 
 not only to analyse the soils on the different parts of his farm, 
 but the peat, the marie, the lime, and the other manures must be 
 subjected to experiment, before he can avail himself of the ad- 
 vantages which they possess, or before he can be certain of pro- 
 ducing any particular effect by their means. In the second 
 volume of The Memoirs of the Imperial Academy of Sciences at 
 Brussels, quarto, 1780, is an ingenious Chemical Essay, by Mons. 
 De Beunie, on Soils, and more particularly on the Cultivation of 
 Heaths. 
 
 Besides, a knowledge of the first principles of chemistry will 
 teach him when to use lime hot from the kiln, and when slacked; 
 how to promote the putrefactive process in his composts, and at 
 what period to check it, so as to prevent the fertilizing particles 
 becoming effete, and of little value. The Earl of Dundonald has 
 remarked, that " vegetable putrefaction can take place only when 
 attended with air, moisture, and a due degree of heat. Water 
 is then decomposed vital air absorbed heat disengaged and 
 new combinations formed." Treatise on Agriculture, quarto, 
 London, 1803, page 28. It will also teach him the difference in 
 the properties of marie, lime, peat, wood-ashes, alkaline salt, 
 soap waste, sea water, &c., and, consequently, which to prefer in 
 all varieties of soil. Dr. Home in the year 1758 published a 
 valuable treatise on this subject. Indeed he was the first person 
 that we know of, who made direct experiments on the fertilizing 
 properties of saline matters. A knowledge of the chemical pro- 
 perties of bodies will thus give a new character to the agricul- 
 turist, and render his employment rational and respectable. 
 Lavoisier cultivated 240 acres of land in La Vendee on chemi- 
 
OF CHEMISTRY TO THE ARTS AND MANUFACTURES. 5 
 
 cal principles, in order to set a good example to the farmers ; 
 and his mode of culture was attended with so much success, that 
 he obtained a third more of crop than was procured by the usual 
 method, and in nine years his annual produce was doubled. 
 Lalande's Life of Lavoisier. 
 
 Are you a practitioner of MEDICINE, and have you acquired 
 great and deserved reputation in your profession, if you are 
 not a chemist, you must recollect many painful disappointments, 
 and must have witnessed very unexpected results from the effects 
 of medicine, when you have administered two or more powerful 
 remedies in conjunction. A slight knowledge of chemistry would 
 have informed you that many of the formulae in the Pharmaco- 
 poeia, which are salutary and efficacious, are rendered totally 
 otherwise, not to say often destructive, if given with certain other 
 medicines. Many instances of these chemical changes might be 
 adduced, but one will suffice. Mercury and chlorine have both 
 been administered by medical men; and separately^ either of 
 them may be taken in small quantities, without any injury to the 
 animal economy : but if these substances should be given in con- 
 junction^ the most dreadful consequences might ensue, as the 
 product of this mixture (corrosive sublimate} is a most active and 
 powerful poison. Boerhaave more than a century ago wrote a 
 treatise to show the importance of chemistry to the medical pro- 
 fession, under the title De cognoscendis et curandis Morbis. The 
 first person who attempted to improve pharmacy by the intro- 
 duction of the metallic oxides was Paracelsus in the sixteenth 
 century. Philip of Sides had indeed in the fifth, introduced what 
 he called the tincture of Indian iron, but there is no proof that 
 this ever came into general use. 
 
 If the profession of medicine be your son's choice, charge him$ 
 when he shall walk the hospitals, to pay particular attention to 
 the Lectures on Chemistry, and to make himself master of the 
 component parts of the different salts, and of the chemical affi- 
 nities which subsist between them and the various articles with 
 which they are generally employed; for so ignorant were the 
 professors of medicine of the nature of the salts, that no longer 
 ago than the year 1765 there was a public dispute between the 
 celebrated Margraff and Mons. De Maehy respecting the base 
 of the super tartrite of potash, whether or no it was an alkali. 
 This will inspire him with professional confidence ; and he will 
 generally be as sure of producing any particular chemical effect 
 upon his patient as he would if he were operating in his own 
 laboratory. Besides, the human body is itself somewhat analo- 
 gous to a laboratory, in which by the varied functions of secre- 
 tion, absorption, &c., composition and decomposition are perpe- 
 
6 ON THE IMPORTANCE AND UTILITY 
 
 tually going on : how, therefore, can a medical man ever expect 
 to understand animal physiology, so necessary in the practice of 
 physic, if he be unacquainted with the effects which certain causes 
 chemically produce ? Every inspiration we take, and every pulse 
 that vibrates within us, effects a chemical change upon the animal 
 fluids, the nature of which it requires the acuteness of a profound 
 chemist to perceive and understand. The use of the blood in 
 respiration was first demonstrated by Priestley, whose interesting 
 paper on that subject was read to the Royal Society the 25th 
 January 1776. Mr. Professor Brande has written an excellent 
 and very original paper on the colouring matter of the blood, 
 in the Phil. Trans, for 1812, page 90. Neither can a physician 
 comprehend the nature of the animal, vegetable, or mineral poi- 
 sons without the aid of chemistry. Many thousand lives have 
 been lost by poison, which might have been saved had the phy- 
 sician been in possession of the knowledge which he may now 
 acquire by a cultivation of chemical science. And though the 
 operation of many of the poisons upon the system be in these 
 days well understood, nothing but a knowledge of chemistry can 
 enable the practitioner to administer such medicines as will coun- 
 teract their baneful effects. A circumstance which came within 
 my own knowledge, will sufficiently exemplify this position. 
 
 In the year 1 805, an apothecary in one of the northern counties 
 having drunk some bottled porter was seized with symptoms 
 which convinced him that he was poisoned ; but not knowing 
 what noxious matter he had taken, and being incapable of ana- 
 lysing the remainder, no antidote could be applied, and he gave 
 himself up as lost. A physician had been called in : but neither 
 he nor the patient, nor his partner, could get any information by 
 examining the remaining contents of the fatal bottle ; though, I 
 understand, they are all intelligent men, and in great repute in 
 their profession. In this dilemma what could be done ? It was 
 recollected, however, that a neighbouring gentleman had the re- 
 putation of being a good chemist. To him the physician and 
 the partner of the patient hastened, to get the dregs analysed, 
 and to learn what ought to be administered. Fortunately, this 
 gentleman had just received Gottling's Book of Tests, which I 
 had procured for his brother, and which had been sent to him 
 but a very short time before. By this book he was enabled to 
 ascertain that the poison was oxide of antimony : and when the 
 patient was informed of it, he recollected that antimonial wine 
 had been kept in a similar bottle some years before ; and sup- 
 posed that the porter must have been bottled without the dregs 
 being properly washed out. This circumstance led to the proper 
 antklote, which was administered immediately ; and the life of 
 
OF CHEMISTRY TO THE ARTS AND MANUFACTURES. 7 
 
 the unfortunate man was preserved : but, in consequence of the 
 loss of time, the poison had so far taken possession of the system 
 as to deprive him of the use of a limb. 
 
 If we look to the national MANUFACTURES, there is scarcely 
 one of any consequence that does not depend upon chemistry, 
 for its establishment, its improvement, or for its successful and 
 beneficial practice ; though, in order to see the real connexion 
 which subsists between chemistry and the arts, it will be useful 
 to take a short view of the principal trades which are carried on 
 in these kingdoms. 
 
 One of the staple manufactures of the country is that of IRON : 
 and it will be found that, from the smelting of the ore to its con- 
 version into steel, every operation is the effect of chemical affini- 
 ties. In the first place, it requires no small share of chemical 
 knowledge, to be able to appreciate the value of the different ores, 
 and to erect such furnaces for their reduction as may be contrived 
 in the best possible manner for facilitating their fusion, and for 
 producing good pig-iron. The subsequent processes, to convert 
 the crude metal into malleable iron, are also entirely chemical, 
 and will be conducted to the best advantage only by those who 
 have acquired a scientific knowledge of the changes which take 
 place in these operations. The making of CAST STEEL, which 
 has been kept so profound a secret, is now found to be a simple 
 chemical process, and consists merely in imparting to the metal 
 a portion of carbon, by means of fusing it in crucibles with car- 
 bonate of lime, or by cementation with charcoal powder, in a pe- 
 culiar kind of furnace constructed for that particular purpose. 
 
 Some of the steel-works in the North have these furnaces ex- 
 tremely large, and I have been told that the increase in weight 
 which the iron acquires from the carbon to convert it into steel 
 is amply sufficient to defray all the expenses of fuel and attend- 
 ance. The German steel is made directly from cast iron, and 
 this is effected merely by forging the crude metal only to a cer- 
 tain point. 
 
 The ancients, it is believed, had some peculiar method of 
 making steel. This suspicion is grounded on the hardness of 
 some of their statues, as well as on the nature of the Egyptian 
 obelisks, which are carved with a variety of figures, and yet are 
 made out of porphyry that resists the tools of modern times. 
 Dr. Lister (in a paper read before the Royal Society) complains 
 that this valuable secret is now lost. According to Aristotle and 
 Pliny, the ancient steel was made by keeping forged iron for a 
 certain time in melted cast iron. 
 
 The manufacturers of chemical utensils, and other articles too 
 various to be enumerated, in cast iron (called IRON-FOUNDERS) 
 will also acquire some valuable information by the study of che- 
 
 
8 ON THE IMPORTANCE AND UTILITY 
 
 mistry ; as it will teach them how to mix the different kinds of 
 metals; how to apportion the carbonaceous and calcareous mat- 
 ter; and how to reduce the old metal, which they often receive 
 in exchange; many hundred tons of which are annually sent 
 away as ballast for ships, for want of that knowledge which 
 would enable them to convert it into good saleable iron. Indeed, 
 before the smelting of ores was properly understood, great part 
 of the iron was not extracted in the first instance, but was thrown 
 by with the dross ; and I have understood that there are heaps 
 containing many thousand tons of such scoria now lying in the 
 forest of Dean, in the county of Gloucester, which the proprietor 
 finds it his interest to work over again ; as they are not only rich 
 in metal, but yield better iron than could be obtained from the 
 original ore. 
 
 In like manner the founder of printers' types has derived great 
 advantage from a knowledge of the methods of reducing metallic 
 oxides. In this trade fires are kept under the pots the whole 
 day, to preserve the metal constantly in a melted state ; the con- 
 sequence of which is, that the metal at the surface perpetually 
 oxidizes and must be frequently removed. Formerly these skim- 
 mings were called dross, and were thrown away as of no value. 
 At length an individual made an experiment upon them, and at 
 this day every manufacturer knows how to convert this refuse 
 into good useful type-metal : so that a large manufacturer will 
 now annually recover from three to four tons of metallic alloy, 
 worth at least 100/. per ton, from these skimmings. 
 
 When we consider the WOOLLEN, the COTTON, and the CALICO 
 manufactures, how great is the importance of each of these trades 
 to the British dominions ! To preserve these sources of national 
 wealth, the utmost attention must be paid to the beauty, the va- 
 riety, and the durability of their several colours. Now of all the 
 arts, none are more dependent upon chemistry than those o 
 DYEING and CALICO-PRINTING. The first account of dyeing that 
 we have in the English language was written by Sir William 
 Petty, at the desire of the Royal Society, entitled " An Appa- 
 ratus to the History of the common Practices of Dyeing." A 
 copy of this piece may be seen in the Bishop of Rochester's 
 History of the Royal Society, quarto, London, 1667, page 284. 
 Every process is chemical ; and not a colour can be imparted, 
 but in consequence of the affinity which subsists between the 
 cloth and the dye, or the dye and the mordant which is employed 
 as a bond of union between them. It is then surely evident how 
 valuable a chemical education must be to that youth who is de- 
 signed for either of these trades, and how necessary is that por- 
 tion of knowledge which shall enable him in a scientific manner 
 to analyse his different materials, and to determine the kind and 
 
OF CHEMISTRY TO THE ARTS AND MANUFACTURES. 9 
 
 the quantity necessary for each process. After all, his colours 
 will be liable to vary, if he do not take into the account, and cal- 
 culate upon, the changes which take place in them by the ab- 
 sorption of oxygen ; on which subject some valuable information 
 may be found in Fourcroy's System of Chemistry, vol. viii. pages 
 70 78. Berthollet's Elements of the Art of Dyeing., vol. i. pages 
 4<5 -65, and in a memoir " On the Coloration of Vegetable Mat- 
 ters by Vital Air," in the 5th torn, of Annales de Chimie, pages 
 80 91. A knowledge of this, and of the different degrees of 
 oxidizement which the several dyes undergo, requires no small 
 share of chemical skill: and yet this skill is absolutely necessary, 
 to enable either the dyer or the calico-printer to produce in all 
 cases permanent colours of the shade which he intends. More- 
 over, these artists must be indebted to chemistry for any valuable 
 knowledge which they may acquire of the nature of the articles 
 they use in their several processes; not to say that they are 
 wholly dependent upon this science for the artificial production 
 of their most valuable mordants, and for some of their most 
 beautiful and brilliant colours. An instance or two will render 
 this evident. 
 
 Formerly a calico-printer required many weeks to produce a 
 printed cotton with some colours, such as an olive ground and 
 yellow figures ; a scarlet pattern on a black ground ; or a brown 
 ground with orange figures : but, by means of chemical prepa- 
 rations, the whole of this work may now be done in a few days ; 
 patterns more delicate than ever, may be produced ; and all with 
 a degree of certainty of which former manufacturers had no idea, 
 the system being now entirely altered. According to the former 
 practice, the mordant was first applied to those parts of the cloth 
 that were intended to be olive, brown, or black ; it was then ne- 
 cessary for the piece to remain some time before it could be dyed, 
 and afterwards to be exposed in a bleaching-ground a sufficient 
 time to clear those places from the colouring matter of the dye 
 which had not been acted upon by the mordant: a different 
 mordant was then applied by the pencil : and it was necessary to 
 pass the whole piece through the dyeing copper a second time, 
 in order to give the desired colour to those particular parts, and 
 finish the pattern. 
 
 Now, all these effects are produced by dyeing the cloth a self 
 colour in the first instance, and afterwards merely printing the 
 pattern with a chemical preparation, which discharges a part of 
 the original dye, and leaves a new colour in its stead. Thus a 
 brown may be changed in an instant to an orange ; a dark olive 
 to a yellow ; or a black to a bright scarlet. In consequence of 
 similar improvements, rich chintz patterns, which formerly re- 
 
10 ON THE IMPORTANCE AND UTILITY 
 
 quired two years or more to be completed, are now commonly 
 finished in a few weeks. 
 
 Again, it was not known how to dye wool of a perfect scar- 
 let till the preparation of the nitrate of tin was discovered by a 
 foreigner. Cornelius Drebbelius of Alcmar in the United Pro- 
 vinces, a man in great esteem with King Henry VIIL, made 
 this important discovery; and having left in writing a particular 
 method of making this mordant and of its application in dyeing, 
 Kuster, or Kustelaer, his son-in-law, brought it to England, and 
 about the middle of the 16th century settled as a dyer, at Bow, 
 near London, where he acquired considerable emolument. See 
 Dallow's Boerhaave, 4to, 1735, vol. i. page 58. 
 
 The art of BLEACHING, which is so intimately connected with 
 calico-printing and dyeing, has also received such improvements 
 from the science of chemistry, that no man is now capable of con- 
 ducting it to the best advantage, without a knowledge of the real 
 principles on which the present practice is established. The person 
 who has written the most at large on this subject is Charmes ; 
 his book was translated by Mr. Nicholson into the English lan- 
 guage, and was published by Robinsons, 1799, 8vo, with many 
 plates of apparatus, &c. 
 
 The manufactures of EARTHENWARE and PORCELAIN, which 
 were so much improved and extended by the ingenious and in- 
 defatigable Wedgwood, and which are become by his means a 
 source of national wealth, and give employment to thousands of 
 the community, are in like manner dependent upon chemistry 
 for the successful management of all their branches, from the 
 mixture of the materials which form the body of the ware, to 
 the production of those brilliant colours which give a value to 
 the manufactures by their permanency and beauty. Dibutades, 
 a potter of Sicyon, first formed likenesses in clay at Corinth, but 
 was indebted to his daughter for the invention. The girl, being 
 in love with a young man who was soon going from her into some 
 remote country, traced out the lines of his face from his shadow 
 on the wall by candle-light. Her father filling up the lines with 
 clay formed a bust, and hardened it in the fire with the rest of 
 his earthenware. Athenag. Apolog. p. 19. edit. H. Steph. 1557. 
 Porcelain was made by the Chinese and Japanese some hundred 
 years before it was manufactured in Europe. No china was made 
 in this quarter of the world before the beginning of the eighteenth 
 century. 
 
 Mr. Wedgwood was so sensible of the importance of chemistry 
 to these arts, that he not only applied to the study of the science 
 himself, but, upon the death of the celebrated Dr. Lewis (author 
 of the Commercium Philosophico-Technicum), he engaged his 
 
OF CHEMISTRY TO THE ARTS AND MANUFACTURES. 11 
 
 assistant, a Mr. Chisolme, to experimentalize with him, and to 
 devote his whole attention to the improvement of the manufacture 
 by the application of his chemical knowledge, of which perhaps 
 few men in the kingdom at that time had a larger share. A faint 
 idea of the advantages which he derived from these sources may 
 be conceived from the following circumstance: Dr. Bancroft, 
 in his " Philosophy of Permanent Colours," when treating on 
 iron, says, " I remember having been told by Mr. Wedgwood, 
 that nearly all the fine diversified colours applied to his pottery 
 were produced only by the oxides of this single metal." This 
 one fact is sufficient to show with what assiduous application he 
 must have studied chemical science, and how insufficient every 
 attempt to bring his manufacture to the perfection which it has 
 now attained, would have been, without this attention. An ac- 
 count of the respective colours which the different metals produce 
 on porcelain may be seen in the xiiith vol. of the Phil. Mag., 
 page 34-2: and vol. xiv. page 17, &c. 
 
 The sister art, that of making GLASS, is also entirely chemical, 
 consisting in the fusion of siliceous earth with alkali and the ox- 
 ides of lead. In the reign of the Emperor Nero, glass was so 
 scarce at Rome that two small cups made of it sold for the im- 
 mense sum of six thousand sesterces. Pliny, 1. xxxvi. c. 26. In 
 this trade, as well as in many others, the chemical manufacturer, 
 and the man of enlightened experience, will have many advan- 
 tages. He will not only know how to analyse his alkalies and 
 to ascertain their exact value before he purchases them, but he 
 will be enabled on chemical principles to ascertain the exact 
 quantity necessary for any fixed portion of silica, which, to those 
 who are ignorant of our science, must always be a matter of un- 
 certainty, and must repeatedly subject them to losses and dis- 
 appointment. Since it has been understood how to apply the 
 oxides of metals so as to produce various permanent colours in 
 vitrifiable substances, some ingenious workers in glass have been 
 enabled to produce several curious imitations of many of the 
 gems and precious stones. The works of Neri and Blancourt 
 contain the best directions we have at present in print on this 
 subject. 
 
 The TANNING OF HIDES was without doubt a process of remote 
 antiquity ; for the contemporaries of Moses not only tanned lea- 
 ther, but knew also how to colour it. Skins dyed red are often 
 mentioned in the sacred books. Pliny attributes the invention 
 of leather to Tychius of Bceotia. It was formerly carried on by 
 persons who merely followed a routine of operations, to which 
 they had been accustomed, without knowing the real cause of 
 any of the changes produced. It has now, however, been well 
 ascertained that the whole art consists in impregnating the animal 
 
12 ON THE IMPORTANCE AND UTILITY 
 
 matter with that peculiar principle taken from the vegetable 
 kingdom, called tan (or tannin), the effect of which may be ex- 
 plained entirely on chemical principles. It is also now known 
 that many substances, besides oak bark, contain tan ; and to 
 chemistry we are indebted for the means of discovering with ac- 
 curacy the quantity of tan which the several astringent vegetables 
 contain. Besides, this principle having been formed artificially 
 by a modern chemist, it is not improbable, that, whenever these 
 manufacturers pay a proper attention to the science we recom- 
 mend, they may be able to direct us how to prepare for them, in 
 our laboratories, the article in question, so as entirely to super- 
 sede the use of oak bark. This would be an event of great na- 
 tional importance, as the demand at present is so great, that it 
 is not only imported from the continent, but trees, it is well 
 known, have been actually cut down on purpose for the bark. 
 Should the chemical tanner not be fortunate enough to make a 
 discovery of the kind just mentioned, he will at least be able to 
 analyse the substances now in use, and to appreciate their relative 
 value ; a matter of no small moment to a man who operates upon 
 a large scale. And it is not impossible but he might discover 
 some way of employing to advantage the several refuse articles 
 which a tan-yard produces, and which are now put aside as of 
 no value. The old tan which is thrown out of the tan-pits was 
 considered to be of no use until the arrival of King William III. 
 in this island. He had observed that it was employed in Holland 
 for raising orange-trees, and he introduced the use of it here for 
 the same purpose. It has since been brought into general use, 
 and is now in great estimation with most of our gardeners ; the 
 great and continued heat which it produces renders it proper for 
 every species of forcing. Chemistry will enable him also to 
 combine the tanning principle with the skins, so as to form lea- 
 ther the most impervious to moisture; and to give the hides the 
 greatest increase of weight in the least possible time : and these 
 are the main secrets on which the profit of the trade chiefly de- 
 pends. 
 
 The property which tan has of combining with gelatine, and 
 therewith forming an insoluble precipitate, may be applied to the 
 important purpose of purifying rancid fish oil. I once knew a 
 gentleman who fitted up a very complete apparatus with this in- 
 tention ; and by agitating the oil with the tannin and water in a 
 large vessel, to which he gave a rotary motion, the tannin became 
 intimately combined with the gelatinous impurities, and then com- 
 pletely subsided. By this means the oil, which was fit only for 
 burning in the street lamps, was rendered free from smell, nearly 
 equal to the best spermaceti oil, and fit for burning in the closest 
 chambers. 
 
OF CHEMISTRY TO THE ARTS AND MANUFACTURES. 13 
 
 Some of the manufacturers of MOROCCO LEATHER, an article 
 nearly new as a production of this country, have the utmost rea- 
 son to regret the want of chemical knowledge. Until within 
 these few years, the consumers of morocco depended entirely on 
 a foreign supply, many fruitless attempts having been made to 
 prepare the article in this country. Later trials, with various 
 chemical mordants, have, however, so far succeeded, that several 
 manufactories have been established in the metropolis, within 
 the last twenty years, where the most beautiful moroccos are now 
 prepared at prices which have superseded the necessity of all 
 foreign importation. The reds and yellows are the principal 
 colours for morocco leather, and in these our manufacturers were 
 very deficient, till a Mr. Philippo, a native of Turkey, introduced 
 the eastern mode of management, for which he received the gold 
 medal and 1001. from the Society for the Promotion of Arts, 
 Manufactures and Commerce. Since then we prepare this lea- 
 ther in a manner much superior to any that can be brought from 
 abroad, and large quantities of it have been exported to foreign 
 markets. Notwithstanding this, some colours are still produced 
 by our manufacturers in a tedious and expensive way : a series 
 of well-conducted and appropriate chemical experiments would 
 no doubt direct them to prepare the same colours, with greater 
 certainty, and by a more economical process. 
 
 The manufacture of SOAP, is first noticed by one of the Hebrew 
 writers: "Though thou wash thee with nitre and take much 
 soap, yet thine iniquity is marked before me." Jeremiah ii. 22. 
 JEtius, who flourished about the end of the 4th century, and was 
 the first Christian medical writer, speaks of a black soap ; and 
 Paulus JEgineta, a Greek physician, who lived in the early part 
 of the 7th century, says he made an extemporaneous soap from 
 oil and the burned dregs of wine. This art is one of such con- 
 siderable importance, that in the year 1795 the Committee of 
 Public Safety in France, engaged those celebrated chemists 
 Mess. Darcet, Lelievre, and Pelletier, to investigate the nature 
 of the art, and to endeavour to ascertain how the various pro- 
 cesses might be improved by chemical science. Their report is 
 printed at large in the Annales de Chimie, torn. xix. pages 253 
 354. It materially aids the revenue of the country, but has in 
 general been conducted, like many of the foregoing, without any 
 regard to system : and yet, perhaps, there is no manufacture 
 which can be benefited in such various ways by chemistry as this. 
 To those who are designed for this trade I have no hesitation in 
 recommending the study of the science as a matter of the first 
 importance. Many thousands per annum, now lost to the com- 
 munity, would be saved, if the trade were universally carried on 
 upon scientific principles. Make a soap-boiler a good chemist. 
 
14- ON THE IMPORTANCE AND UTILITY 
 
 and you teach him how to analyse barilla, kelp, potass, &c., so 
 as to ascertain the proportion of alkali in each, the only sure 
 guide to purchasing with advantage and profit, which with the 
 common manufacturer is mere chance. When these articles are 
 at an exorbitant price, he will have recourse to various residuums, 
 which he will decompose by chemical means, and make use of as 
 substitutes. In choosing his tallows, he will learn how to avoid 
 those which contain a large portion of sebacic acid, which require 
 much more barilla than good tallow, and yet produce less soap. 
 He will know how to oxidize the common oils and oil dregs, so 
 as to give them consistence, and render them good substitutes 
 for tallow, and how to apportion his lime so as to make his 
 alkali perfectly caustic, without using an unnecessary quantity of 
 that article. He will likewise be aware of the advantage to be 
 derived from oxidizing the soap while boiling. A knowledge of 
 chemical affinities will teach him how, at a cheap rate, to make 
 as good and as firm soap with potash, as with the mineral alkali; 
 and how to take up the heterogeneous salts, so as to give the 
 alkali full opportunity of forming a chemical combination with 
 the tallows and other oleaginous matter upon which he may be 
 operating. And lastly, he will know how to make use of the 
 waste lyes so as to decompose the salts which they contain, and 
 convert them to good and serviceable alkali, fit for future opera- 
 tions. Some of the manufacturers of soap avail themselves of 
 none of these advantages. 
 
 An example of the benefit which may arise to the arts from a 
 chemical examination of the nature of bodies, may be seen in the 
 employment of the chemical residuums just mentioned, and which 
 were formerly thrown away as useless. The old makers of Glau- 
 ber's salt regularly threw away the muriatic acid which resulted 
 from the process; and the sulphate of potash, which remains 
 after the distillation of nitrous acid, was formerly thrown into 
 the Thames. Now, these articles are employed in various 
 manufactories, and turn to a good account. I have indeed 
 been told that Mr. Steer, a very large aqua fortis maker at Bir- 
 stall, near Leeds, was for many years accustomed to lay his glass 
 retorts in a shallow rivulet which ran through his fields, where, 
 in a few weeks, the indurated salt was dissolved, and gradually 
 washed away in the water. By this management he avoided the 
 necessity of breaking the retorts : but from the extent of his bu- 
 siness, I am persuaded that the salt thus lost for a number of 
 years would have brought him some thousands of pounds, if it 
 had been preserved to the present time. 
 
 The manufacture of CANDLES, which is often connected with 
 soap-making, though it is of comparatively small importance, 
 may yet derive advantages from chemistry, which would repay 
 
OF CHEMISTRY TO THE ARTS AND MANUFACTURES, 15 
 
 the study. Candles should be made without any admixture of 
 oil or grease, and when laid up should be preserved from the ac- 
 tion of the atmosphere. If tallows are weak, a part soon becomes 
 converted by exposure to the air to an acid, and this renders the 
 whole, when melted together, unfit for candles. I have heard 
 of some persons who were in the habit of keeping their candles 
 closely covered up in bran, and taking them out only as they 
 wanted to use them. Foreign tallows, which frequently contain 
 a large portion of acid, rendering them inferior to the English, 
 may be purified at a very trifling expense by chemical means ; 
 and by the proper application of chemical agents other brown 
 tallows may be rendered beautifully white, and fit for the best 
 purposes. 
 
 The mode which naturally presents itself as the best for sepa- 
 rating the sebacic acid from tallow, is that of melting it in water 
 containing some alkali ; but old tallows may in general be suffi- 
 ciently purified from their rancidity by melting them upon lime 
 water, and giving a considerable agitation to the whole mixture ; 
 for when the water is again suffered to subside, it will be found 
 to be offensive in smell, and to have subtracted most of the im- 
 purities of the tallow. Should the tallow, however, be found 
 not to be sufficiently purified, a repetition of this process would 
 completely effect it. 
 
 Where great quantities of candles are required, as in large 
 manufactories, mines, collieries, &c. a great saving would arise 
 from the use of carbureted hydrogen gas, which, as the inhabi- 
 tants of most of our large towns can now testify, produces a beau- 
 tiful and intense light, much more cleanly than oil or tallow, and 
 at little or no expense. Oils and tallows when burnt with a wick 
 generally produce a portion of soot ; but this combustible gas is 
 wholly converted into water and carbonic acid gas, and therefore 
 will soil nothing. 
 
 A slight knowledge of the mode of managing the gases would 
 enable the proprietor of all such collieries as may be safely entered 
 with a naked candle, to procure this gas from the small coal, 
 which is trodden under foot : , and to light up his coal-pits with it 
 with the greatest safety, and at NO EXPENSE. If this mode were 
 adopted, the workmen would be lighted much better than they 
 can possibly be by any other means ; thousands of pounds would 
 be annually saved to the community ; and the many tons of tal- 
 low which are now consuming in these subterranean works might 
 be used in the manufacture of soap ; which would tend to lower 
 the price of that necessary article, and render our poor more 
 cleanly and comfortable. 
 
 The BREWING OF FERMENTED LIQUORS, a trade of considerable 
 and increasing consequence, is altogether a chemical process. 
 
16 ON THE IMPORTANT. AND UTILITY 
 
 Isis and Osiris, it has been said, instructed the countries; that 
 were destitute of wine, by \\hat methods they might prepare beer 
 from corn. Sec Cogan's Ditnfarus Siculns^ page. 9. When 
 Tacitus speaks of the. ancient (lennans making wine from cor- 
 rupted corn, he referred, iu> doubt, to a process somewhat similar 
 to Knglish Brewing. Hasil Valentine, an eminent chemist who 
 flourished in the beginning of the fifteenth century, wrote ex- 
 pressly on the different methods of brewing malt liquors. For 
 an account of the curious management by which such kinds of 
 beverage were prepared at the time of the Norman Conquest, 
 the reader may consult l)u Cange Gloss, torn. ii. page 66'2. To 
 those persons whose concerns are so large that it \vonld require 
 a princely fortune to purchase even the utensils, it must be surely 
 of the utmost importance to acquire some knowledge of the prin- 
 ciples of bodies, ami of the nature of those changes which take 
 place in the materials upon which they operate. I would there- 
 lore say to such persons, dive your sons a chemical education, 
 and you will fit them for conducting, in the best possible manner, 
 the business which yon have established. Hence they will learn 
 how the barley, in the first instance, is converted to a saccharine 
 substance by malting; how the fermentative process converts the 
 saccharine to a spirituous substance : and how the latter, by a 
 continuation of the process, becomes changed into vinegar. On 
 these subjects I would recommend a valuable paper on malting 
 in The Memoirs of the Literary and Philosophical Society of 
 Manchester, by Mr. Joseph Collier, vol. v. page 'J(> ~> : also A 
 Memoir on Fermentation by Fourcroy and Vauquelin, which 
 has been translated for The Phil. Mag., vol. xxv. page 176, &c. 
 and continued page 219 and the sequel. The nature of fermen- 
 tation (which until lately was entirely unknown) will be studied 
 and understood : and they will not only have learnt the means 
 of promoting and encouraging this process, but also how to re- 
 tard or check it, whenever it is likely to be carried too far; so 
 that the scientific brewer will be as sure of uniformly obtaining 
 satisfactory results, as he would if he were operating on matter 
 by mere mechanical means. 
 
 In like manner the DISTILLER, the maker of SWEET WINES, and 
 the VINEGAR MANUFACTURER, will all receive benefit from the 
 cultivation of the science we are recommending. When the 
 Romans had possession of this island, the art of distillation was 
 unknown. It is said to have been introduced here in the early 
 part of the reign of Henry II. The latest and best treatise that 
 I have seen on this subject is an octavo volume containing many 
 copper-plate engravings, entitled Essai sur TArt de la Distilla- 
 tion, by L. S Lenormand, Paris, 1811. Chrysippus, who 
 wrote in the third century before Christ, speaks of the excellence 
 
OF CHEMISTRY TO THE ARTS AND MANUFACTURES. 17 
 
 of the Egyptian vinegar. Such was its strength, that it quickly 
 olTeotne finest pearl Cleopatra had in her possession. Pliny, 
 ix. 35. Till the promulgation of the new chemical doctrines, 
 the making of vinegar was carried on like many other trades, in 
 which the makers themselves had no idea of the nature of their 
 own process. An acquaintance with chemistry will teach them 
 many important matters ; particularly how it is that the spirituous 
 fermentation is succeeded by the acetous; and how the liquor 
 acquires the substance necessary to produce this change. An 
 account of the theory of Fermentation must be read and under- 
 stood, before a manufacturer can know how to conduct this pro- 
 cess in a scientific manner. I have seen nothing, however, on 
 the art of making vinegar which is more to the purpose than the 
 directions which were published by Boerhaave nearly a century 
 ago. See Dallow's Translation, in 2 vols. 4to. London, 1735, 
 vol. ii. page 14-3. When the vinegar is removed from the action 
 of the sun, it is customary to break up the pipes into small casks 
 arid to purchase new wine-pipes to put into their place, from an 
 idea that the wine within the wood would add an additional 
 strength to the vinegar; but a knowledge of the cause of the 
 change from the vinous to the acetous fermentation, aided by 
 experience, would inform them that the process will always go 
 on much faster in old vinegar casks. When the subject of fer- 
 mentation is once known, tney will soon find by experiment how 
 to oxygenize their wash at the least expense, and in the least 
 possible time. Indeed, when chemical knowledge is more ad- 
 vanced, the process which now requires several months will pro- 
 bably be completed in as many days-. The adoption of stoves 
 and some other methods, which might easily be devised, would, 
 1 am persuaded, occasion a great saving in this manufactory, 
 besides doing away the necessity of exposing the vinegar in the 
 open air to tne sun for so many months, as is the present prac- 
 tice, whereby the casks sustain so much injury as to entail a heavy 
 annual expense on the proprietor of every large work for this 
 article alone. William Homberg, a well known chemist of the 
 seventeenth century, partially filled a bottle with wine that was 
 not at all acid, and having securely corked it and tied it to the 
 vane of a windmill, it became in three days converted into good 
 vinegar. Might not this idea be improved upon, so as to expe- 
 dite the process in our large manufactories? 
 
 The REFINING OF SUGAR is also a chemical process ; every 
 branch of which depends upon laws well known to chemists. 
 According to Dr. Anderson, in his History of the Origin of 
 Commerce, the refining of sugar was not practised in this country 
 until the restoration of Charles 1 1. It is still conducted by Ger- 
 mans, and little or no improvement has been made in any of the 
 
 c 
 
18 ON THE IMPORTANCE AND UTILITY 
 
 processes since that time. The separation of the sugar from the 
 molasses; the absorption of the superabundant acid; the gra- 
 nulation of the purified sugar ; and the crystallization of candy ; 
 will all be conducted most economically, and with the least dif- 
 ficulty, by those who have studied the science with a view to the 
 improvement of their art. An account of a new mode of boiling 
 sugar by means of heated oil, may be seen in the twelfth edition 
 of the Chemical Catechism, article SUGAR. 
 
 The REFINING OF GOLD AND SILVER may appear to be merely 
 a mechanical operation ; but even in this trade the artist cannot 
 produce a single effect which is not attributable to the play of 
 the chemical affinities. To obtain the best and most profitable 
 results in the business of parting, it is necessary that the nitrous 
 acid should be prepared for this express purpose. Some refiners 
 may imagine this to be of no consequence ; because they purify 
 it, they say, by means of a solution of silver before they use it. 
 But I can assure such refiners that it is impossible to purify some 
 aqua fortis, by means of silver water, as it is usually applied ; and 
 that, when such aqua fortis is employed, a considerable loss in 
 the produce of the gold is the inevitable consequence. Besides, 
 there is great reason to believe that a considerable portion of sil- 
 ver is often lost in the process which succeeds that of quart ation, 
 by the blue water being removed to the verditer-vats before the 
 whole of the silver has been precipitated. A knowledge of che- 
 mical principles would suggest to the refiner a mode by which, 
 without the aid of any apparatus, he might in an instant detect 
 even the tenth of a grain of that metal, if left in the solution. 
 
 In like manner the reduction of the ores of COPPER*, LEAD, 
 TIN, ziNC 2 , and ANTIMONY, and the manufacture of BRASS, have 
 all been very materially improved by the application of chemical 
 knowledge, and have supplied sources of wealth to individuals, 
 an immense revenue to the government, and a profitable employ- 
 ment to many thousands of the community. 
 
 The manufacturers of GUNPOWDER 3 , ALUM% COPPERAS, BLUE 
 VITRIOL, and of all other SALTS, would likewise do well to become 
 chemists, before they attempt to bring their several arts to the 
 perfection of which they are capable. The crystallization of 
 salts depends upon so many adventitious circumstances, that no 
 
 1 The copper mines in Cornwall were worked to great disadvantage until 
 Queen Elizabeth invited one Daniel Houghsetter from Germany to instruct 
 her subjects in the art of managing them. For an account of the exclusive 
 privileges which the Parliament granted him, see Statutes at Large, in the 
 reign of Queen Elizabeth. 
 
 2 Notwithstanding the vast stores of Calamine with which this island abounds, 
 we were in the habit of importing all our zinc for the manufacture of brass 
 from India, until Margraaf instructed some individuals in the method of pro- 
 
OF CHEMISTRY TO THE ARTS AND MANUFACTURES. 19 
 
 small share of knowledge is necessary to enable a manufacturer 
 at all times, and in all seasons, to produce the article he intends. 
 Until within these few years the MAKERS OF ALUM bought alka- 
 lies of every description. An accurate analysis of alum has now 
 discovered that potash and ammonia are the only alkalies which 
 enter into the composition of alum ; and consequently, that du- 
 ring a long series of years large sums have been expended by 
 the manufacturer in the purchase of salts which were compara- 
 tively of no use. 
 
 The article, however, which is more particularly referred to 
 here, is a refuse product of the soap-works called black ash, for 
 which the alum-maker has given from 81. to 151. per ton, though 
 it is composed in a great measure of soda and muriate of soda, 
 neither of which salts is of any use in the preparation of alum. 
 These manufacturers must, surely, have been as careless in their 
 inquiries as the Spaniard of whom Bowles speaks in his Histoire 
 Naturelle de VEspagne, page 80, who on being asked if he knew 
 how the saltpetre was yearly regenerated in his grounds, replied, 
 " I have two fields in the one I sow wheat, and it grows ; in 
 the other I collect saltpetre." 
 
 Even science itself is now reaping the benefit of its own dis- 
 coveries. A few years ago, the MANUFACTURERS OF PAPER were 
 apprehensive that it would be impossible to supply a quantity of 
 that article fit for printing upon, adequate to the increasing de- 
 mand. Necessity, however, often the source of new inventions, 
 had recourse to chemistry; and in this science, of universal ap- 
 plication, found the means of improving the colour of the very 
 coarsest materials ; so that rags which formerly would have been 
 thrown by for paper of the lowest description, are now rendered 
 subservient to the progress of truth, and the promulgation of 
 knowledge. And so easy is the application, that an immense 
 quantity of the materials can be bleached in a few hours ; and 
 paper sufficient to print a copy of the largest work in the English 
 language may thus be whitened at the expense of only a few pence. 
 
 In like manner it might be shown that the making of BREAD, 
 SUGAR, STARCH, VARNISH, and OIL OF VITRIOL ; the felting and 
 
 curing it from this ore. According to Pliny (1. xxxiv.) brass was known to the 
 ancients. 
 
 3 It is a curious fact, that " upon our discovery of China, we found that 
 nation possessed of gunpowder, a composition which could not have been 
 made without a considerable knowledge of chemistry." See the preface to 
 Delaval's Inquiry respecting Colours, page 62. 
 
 4 The first aliim manufactured in England was in the reign of Queen Eliza- 
 beth, at Gisborough in Yorkshire, by one Thomas Chaloner, an ancestor of the 
 present R. Chaloner, Esq. M.P. for the city of York. For some particulars of 
 this intrepid man, see Notes to the Chemical Catechism, tenth edition, page 100. 
 
 C2 
 
20 ON THE IMPORTANCE AND UTILITY 
 
 fulling of HATS, the refining of SALTPETRE, and the manufactures 
 
 Of SMALTS, ULTRAMARINE, PRUSSIAN BLUE 1 , COBALT BLUE, CUD- 
 BEAR 4 , ARCHIL, and other colours 3 , are all dependent upon che- 
 mistry for their improvement and successful practice : but the 
 mention of a few particulars must suffice. 
 
 The success of the starch manufactory depends, in a great 
 measure, upon giving a proper degree of fermentation 4 to the 
 wheat ; it is evident then how much the profit might be increased 
 by a scientific attention to this circumstance. 
 
 In making oil-varnishes it is first necessary to oxygenize the 
 oils by means of metallic oxides, in order to give them the drying 
 property. To do this in the best possible way, requires some 
 chemical skill; and, whether the varnish be made with a resin 
 or a gum-resin, it is of the utmost importance to learn the proper 
 solvent for each particular resin, and the best temperature for 
 producing the solution. 
 
 Within these few years some manufacturers of hats have in- 
 troduced a considerable improvement into their manufactories, 
 by treating the fur of the hare and rabbit with a solution of mer- 
 cury in nitrous acid 5 . As this solution of nitrate of mercury is 
 applied before the fur is removed from the skins, it acts on one 
 side of the hairs only, and renders them crooked, which occa- 
 sions them to felt much easier than they otherwise would. 
 
 In the operation of fulling hat-felts, it has been customary to 
 employ a large proportion of wine lees or tartar ; and it was 
 imagined that the consistence and density which this gives to the 
 
 1 A large proportion of the Prussian blue which is made in this country goes 
 to China ; the captains of the East India Company's ships take it out at the 
 beginning of the year, and it constitutes a part of the private trade to that 
 country. Though the Chinese are ingenious in the manufacture of a variety 
 of beautiful and permanent colours, they have not yet learnt the art of making 
 Prussian blue. 
 
 2 This valuable article in dyeing was discovered by a Florentine merchant 
 about the year 1300, which not only enriched himself, but was so very advan- 
 tageous to the Florentines, that they gave him an honourable title, which was 
 borne by all his family and descendants. 
 
 8 When the science of chemistry was little understood, some colours were 
 extremely rare and valuable. Such was the purple of the ancients, which none 
 but the Caesars were allowed to wear. At the taking of Susa, Alexander the 
 Great found in the royal treasury purple to the value of 50,000 talents, which 
 had lain there 192 years, and still retained its exquisite beauty. 
 
 4 See Fourcroy and Vauquelin on the Germination and Fermentation of 
 Corn and Seeds, in Philosophical Magazine, vol. xxv. pages 176, &c. and 219, 
 &c. 
 
 5 See Monge's Annales dc Chimie, tome vi. p. 300. I have good reason, 
 however, to believe, that this preparation of mercury was in general use by 
 the hatters of America for some considerable time before it was employed in 
 Europe for that purpose. 
 
OF CHEMISTRY TO THE ARTS AND MANUFACTURES. 21 
 
 felt, was attributable to the alkali of the tartar ; and indeed the 
 author of the French Encyclopedic has affirmed that this is the 
 case. But Mons. Chaussier knowing that cream of tartar is a 
 super-tartrate of potash, suspected that it might be the extra 
 tartaric acid which determined the felting; and by direct expe- 
 riment he discovered this to be the fact, and that any other acid 
 would produce the same effect. Of late years, therefore, the 
 manufacturers have derived considerable advantage from the 
 substitution of diluted sulphuric acid. 
 
 The consumption of cobalt blue by the blue potters and ma- 
 nufacturers of porcelain, is very considerable ; and until lately it 
 was made only from zaffre imported from Saxony, although it 
 has long been known that cobalt ores were to be found in some 
 of the English mines. Just now, however, a few enterprising 
 men have accomplished their reduction, and a beautiful colour, 
 worth from two to three guineas per pound, and much better 
 than what is usually made from zaffre, has been produced in 
 considerable quantities. 
 
 Some other cases of equal importance might also be mentioned, 
 but I flatter myself that the examples already adduced are suf- 
 ficient to show that chemistry is now a necessary branch of the 
 education of youth. Even the management of a GARDEN 6 may 
 receive improvement from a cultivation of this science, as it ex- 
 plains the growth of vegetables, shows the use of the different 
 manures, and directs the proper application of them 7 . 
 
 The various operations of Nature 8 , and the changes which take 
 place in the several substances around us, are so much better 
 understood by an attention to the laws of chemistry, that in every 
 walk of life the chemist has a manifest advantage over his illite- 
 rate neighbour. And it may be remarked, that in case of failure 
 or disappointment in any particular line of commercial manufac- 
 ture, the scientific chemist has resources as various as the pro- 
 ductions of the country in which he lives, to which the uneducated 
 man has no access 9 . 
 
 6 An Essay of mine on the advantages of employing common salt in horti- 
 culture, and which obtained the annual gold medal of the Horticultural Society 
 of Scotland for the year 1819, may be seen in the 3d volume of the Memoirs 
 of that Society ; or in the Journal of the Royal Institution of Great Britain, 
 vol. x. p. 52. 
 
 7 Natural history in all its branches is intimately connected with chemistry, 
 as it must depend upon this science for any elucidation of the minute proper- 
 ties of those substances, the outward characters of which it describes. 
 
 8 It was a favourite saying of Lord Bacon's, that " man should observe all 
 the workmanship and the particular workings of Nature, and meditate which 
 of these may be transferred to the arts." Lord Bacon's Advancement of Learn- 
 ing, book v. 148. 
 
 9 A very remarkable instance of a whole nation availing themselves of ad- 
 
22 ON THE IMPORTANCE AND UTILITY 
 
 Were parents aware of this truth, that sordid maxim primb 
 vivere, delude philosophari, would not be heard ; but every youth 
 would be instructed in the first principles of natural philosophy l 
 and chemistry, as the means of qualifying him for conducting with 
 advantage the concerns with which he might be intrusted. If 
 " knowledge is power," surely the love of knowledge, and a taste 
 for accurate investigation, are the most likely means of conduct- 
 ing to opulence, respectability, and rational enjoyment. 
 
 " If," said a late eminent writer, " we would lay a good founda- 
 tion for a philosophical taste, and philosophical pursuits, persons 
 should be accustomed to the sight of experiments, and processes, 
 in early life. They should, more especially, be early initiated 
 in the theory and practice of investigation, by which means, in 
 a great variety of articles, very young persons may be induced to 
 engage with peculiar alacrity in pursuits truly original 2 ." 
 
 Boerhaave, who had a botanical garden of eight acres, and 
 who was so intent upon stocking it with every exotic that he 
 could procure, as once to have styled a present of a few American 
 seeds, " munera auro cariora," gifts more precious than gold, 
 was notwithstanding so captivated with chemistry, that he some- 
 times spent whole days and nights successively in the study and 
 processes of the art. 
 
 The history of the progress of science affords, however, few 
 instances of the advantages of philosophical pursuits, greater than 
 the one which modern times have furnished in the invention of 
 the Miner's Safety Lamp. During his inquiries respecting the 
 nature of flame, Sir Humphry Davy discovered that gaseous 
 matter can only be made to burn by its being kept at a high tem- 
 perature, and that its temperature is lowered in a remarkable 
 manner by making it pass through fine wire gauze. Reflecting 
 on this singular fact, it occurred to him, that some advantage 
 might be taken of the circumstance to prevent the explosions in 
 coal-mines ; and this led to the construction of that instrument 
 which has already been the means of saving the lives of some 
 
 vantages presented to them by chemistry, in a case of the greatest emergency, 
 may be seen in The Chemical Catechism, Additional Notes, No. 22, p. 426. 
 
 1 Thales the Milesian, who flourished 600 years before Christ, used to de- 
 clare that he preferred the study of Natural Philosophy to all other sciences. 
 
 Democritus of Thrace, who was contemporary with Socrates, applied him- 
 self with so much earnestness to his studies, that he was actually absorbed in 
 philosophy, and declared he would prefer the discovery of ONE CAUSE in the 
 works of Nature, to the possession of the whole Persian monarchy. 
 
 Paracelsus not only visited learned and scientific men, but frequented the 
 workshops of mechanics, descended into mines, and thought no place mean or 
 hazardous, if it afforded him an opportunity of increasing his Knowledge of 
 Nature. Chalmers's Biographical Dictionary, vol. xxiv. p. 85. 
 
 2 Preface to Dr. Priestley's Observations on Air, vol. iv. London, 1779. 
 
OF CHEMISTRY TO THE ARTS AND MANUFACTURES. 23 
 
 hundred individuals, and which will probably prove a protection 
 to thousands yet unborn. How poor and insignificant are all 
 the honours which rank and power can bestow, when compared 
 with the delightful satisfaction which this great man must derive 
 from the consciousness of having conferred such benefits ! 
 
 To conclude : It may be remarked, that it is the necessary 
 
 consequence of an attention to the science of chemistry, that it 
 gives the habit of investigation^ and lays the foundation of an 
 ardent and inquiring mind. If a youth has been taught to receive 
 nothing as true, but what is the result of experiment, he will be 
 in little danger of ever being led away by the insidious arts of 
 sophistry, or of having his mind bewildered by fanaticism or su- 
 perstition. The knowledge of facts is what he has been taught 
 to esteem ; and no reasoning, however specious, will ever induce 
 him to receive as true what appears incongruous, or cannot be 
 recommended by demonstration or analogy. 
 
ON TEMPERATURE. 
 
 ESSAY II. 
 ON TEMPERATURE. 
 
 PART I. OF NATURAL TEMPERATURE. 
 
 AFTER having given some account of the Utility of Chemistry 
 to the Arts, it occurred to me that there would be a peculiar 
 propriety in introducing the following Essays to the notice of the 
 reader, by some remarks on Temperature as there is scarcely an 
 operation in chemistry, or a process in any of our manufactories, 
 that does not either require a marked attention to the precise de- 
 gree of heat under which it is conducted, or that would not pro- 
 duce a better result, were this first to be determined by experiment, 
 and made one of the preliminary conditions of the operation. 
 
 Besides, if we contemplate the works of Nature, it will be dif- 
 ficult to name any substance that, in the economy of the world, is 
 of equal importance with the matter of heat. What this matter is, 
 or how it produces the astonishing effects which are attributed to 
 it, we know not ; nor have philosophers as yet agreed whether it 
 be really a material ponderable substance, or only the consequence 
 of a particular motion excited among the particles of bodies. 
 
 Very delicate experiments have been made, which show that 
 bodies when heated do not increase in weight ; but these cannot 
 be considered as decisive, on account of the imperfection of our 
 instruments. A cubical inch of inflammable air requires a good 
 balance to ascertain that it has any sensible weight, and a sub- 
 stance bearing the same relation to this, that this bears to plati- 
 num, could not perhaps be weighed by any methods in our pos- 
 session. 
 
 So important was this subject considered to be by the late Count 
 Rumford, that in the year 1796 he presented to the Royal So- 
 ciety of London, one thousand pounds three per cent, consols to 
 institute a prize medal to be given once in every two years to the 
 author of the most important discovery on heat, or on light. 
 
 The word TEMPERATURE is usually employed to denote the 
 precise state of any region on the face of the earth, with respect 
 to heat and cold ; or the condition of any particular insulated 
 body, produced by the operation of caloric 1 , or by the partial 
 removal of this wonderful and occult power. 
 
 1 This term (caloric) was introduced not from caprice, but for the sake of 
 giving precision to chemical language, and for the purpose of distinguishing 
 between this peculiar matter itself, and the effects which are produced by it. 
 
OF NATURAL TEMPERATURE. 25 
 
 In order to furnish a complete Essay on Temperature, it would 
 be necessary to give a history of all the discoveries which have 
 been successively made respecting the matter of heat, and to de- 
 tail the various experiments which have been performed by the 
 principal philosophers of Europe for the last two hundred years. 
 This, however, would be incompatible with the design of these 
 Essays, and very uninteresting to the class of readers for whom 
 they are more particularly intended. 
 
 But, if I can give such a concise and popular view of the ge- 
 neral causes of the change of temperature in bodies, as shall 
 enable the most unscientific reader to understand the subject, and 
 shall, at the same time, teach him how to avail himself of the best 
 means of applying his knowledge in the common concerns of life, 
 I shall be abundantly satisfied a . To this end it may be most con- 
 venient to divide the subject into two branches, and to treat it 
 under the distinct heads of Natural and Artificial Temperature. 
 
 The variety of climate in the different regions of the earth, the 
 effects of caloric on animal and vegetable life, and the nature of 
 its agency on combustible substances, will arrange themselves 
 under the first division of the subject ; while that on Artificial 
 Temperature will contain a brief detail of a variety of expedients 
 for procuring fire, for modifying the effects of heat and cold, for 
 economizing fuel, and for improving certain operations which 
 have a considerable influence on the success of many of the ma- 
 nufactories of the country. 
 
 In regard to CLIMATE, it is not necessary to enter into the dis- 
 quisition, whether the matter of heat be transmitted to us from 
 an immense globe of fire which we call the sun ; or whether it 
 may not be more probable that the necessary quantity of caloric 
 for the wants of the world and its inhabitants, was made inhe- 
 rent in the earth at the time of its formation, and that this sun is 
 an inhabited world, with a phosphorescent atmosphere that per- 
 petually sends forth rays of light, and that these elicit, and, as 
 it were, put in motion the matter of heat belonging to this as 
 well as to the other planets I say, it is not necessary to adduce 
 arguments in favour of either the one or the other opinion ; for 
 this would open too wide a field of discussion, and would be very 
 unsuitable to that brevity which I am anxious to observe, and to 
 that general UTILITY which I have placed before me as the main 
 object to which I aspire. 
 
 I am desirous, however, of making a few desultory observa- 
 
 2 My idea has been exactly expressed by our immortal poet : 
 " For not to know at large of things remote 
 From use, obscure and subtile, but to know 
 That which before us lies in daily life, 
 Is the prime wisdom." MILTON. 
 
26 ON TEMPERATURE. 
 
 tions on this point, before I proceed. And in the first place it 
 may be remarked, that the sun's rays appear to have no power of 
 giving heat unless they impinge against a solid body. The focus 
 of the most powerful burning glass, if directed on mere air, does 
 not produce the smallest degree of heat. Thus Mons. Charles, 
 the aeronaut, found the air in the neighbourhood of Paris to be 
 47; and when he had ascended to the height of eleven thousand 
 feet, only 21, or 11 below the freezing point. 
 
 The theory of the sun not being the source of caloric enables 
 us to solve the great difficulty concerning the distribution of heat 
 among the different planetary bodies; for, according to this view, 
 those nearest the sun may have no more than those at the most 
 remote distance. We have only to suppose the quantity of ca 
 loric to be proportioned to the distance ; and if a small quantity 
 exists in the planet Mercury, no more heat may be excited than 
 is done by a larger quantity in Saturn. 
 
 Moreover it is evident that there must be other causes besides 
 the sun's rays, which operate in the production of variety of cli- 
 mate; for the hottest days are frequently felt in the coldest cli- 
 mates, and the coldest weather and even perpetual snow are 
 found in countries bordering on, or even immediately under the 
 equator. 
 
 That we are indebted to the sun for some of the most benefi- 
 cial effects of caloric, cannot however for a moment be disputed: 
 nor will it be denied that the difference of climate on the various 
 divisions of the earth, is, in a great measure, occasioned by the 
 relative situation of the different regions with respect to that lu- 
 minary : and that the Author of Nature had an eye to the gene- 
 ral felicity, in the curious adaptation of the animal and vegetable 
 creation (in their primitive constitutional qualities and texture of 
 parts) to this great variety of situation and climate. 
 
 How strange then must that hypothesis of Mons. Buffon ap- 
 pear, which supposes that the earth and all the other planets were 
 once in a state of fusion ; that they are now gradually cooling ; 
 and that a time will come when they will have lost so much of 
 their present heat as to be totally unfit to preserve either animal 
 or vegetable existence ! As if the Great Architect of this stu- 
 pendous world had neglected to provide against its degenerating 
 into an useless mass of inert matter. 
 
 Fortunately, however, we are not obliged, even on the autho- 
 rity of so great a name, to believe this monstrous and incon- 
 gruous representation. For all history abounds with circumstan- 
 tial details, which directly contradict the assertion, and tend, on 
 the contrary, to prove that some of the cold regions of the earth 
 have become much warmer than they were eighteen hundred or 
 two thousand years ago. 
 
OF NATURAL TEMPERATURE. 27 
 
 The following are a very few of the many instances which 
 might be adduced : 
 
 In the Augustan age, the Rhine and the Danube were com- 
 monly frozen over during several months of the year; and when 
 the Barbarians overran the Roman Empire, they transported 
 immense weights and innumerable armies across the ice of these 
 rivers ! ; a thing which in the present times would be impossible. 
 The rein-deer and the elk, which flourish only in the coldest cli- 
 mates, the former being found, not only in the wilds of Siberia, 
 but on the rocks of Spitzberg within ten degrees of the pole, were 
 in the time of the Caesars abundant in the Hercynian forest, 
 which was said to be sixty days journey in length, and which co- 
 vered a great part of that vast country lying between Switzerland 
 and the Black Sea 2 . All the rivers throughout this region were 
 perpetually bound up with ice during the whole winter, which 
 usually lasted for eight months 3 , and the cold was so excessive 
 that the historians of the time evidently supposed that the coun- 
 tries north of this district must be absolutely uninhabitable. Ovid 
 says that at Tomi, which was seven degrees south of London, 
 the snow continued two years on the ground ; and Virgil agrees 
 with him in declaring that the people living on the banks of the 
 Danube were accustomed to cut out their wine with hatchets, and 
 to deliver it to their guests in solid portions 4 . These, and various 
 other instances, incontrovertibly prove that Europe, at least, was 
 formerly much colder than it is at present. 
 
 The same change has also taken place on the continent of 
 America. Formerly the people of Guiana, within five degrees 
 of the equator, could not live without lighting evening fires ; and 
 though it is not a century since a part of this country was cleared 
 from wood, the heat in that part is already excessive 5 . The parts 
 of North America which have been cleared are also much warmer 
 than they were when the woods were standing. 
 
 It has sometimes been imagined that difference in climate is 
 occasioned solely by the relative situation of the different countries 
 with respect to the sun ; but nothing can be more erroneous, as 
 appears from the state of the Andes which may be adduced as a 
 
 1 Diodorus Siculns, lib. v. page 340, edit. Wessel. 
 
 2 Caisar de Bel. Gal. vi. 23, &c. 
 
 3 Herodotus, lib. iv. 28. 
 
 4 " But where Maeotis Scythia's waste divides, 
 And turbid Ister rolls his yellow tides, 
 There stalls inclose the herds that never stray, 
 No grass the field, no leaves the wood array j 
 There crystal chains at once whole pools confine, 
 And hatchets cleave the congelated wine." 
 
 Sotheby's Georgia of Virgil, book iii. 
 5 Supplement to Buffon's Natural History t 8vo. page 346. 
 
28 ON TEMPERATURE. 
 
 complete refutation of this idea; for between the base and the 
 summit of these mountains every degree of temperature may be 
 found. The city of Quito, situated about the middle of one of 
 these, experiences a mild and temperate climate, while the sands 
 beneath it are intensely hot, and the ground above it covered with 
 perpetual snow. 
 
 There are so many facts which tend to prove that the climate 
 of a country is not occasioned solely by its situation on the face 
 of the globe, that I am inclined to think many an inhospitable 
 clime might be rendered healthy and uniformly temperate, by the 
 resolute exertions of a good government and an enlightened po- 
 pulation. 
 
 The country on the borders of the Albany River, and the 
 southern parts of Labradore, are in the same latitude with Great 
 Britain 1 ; and yet the cold is now so severe, and the snow so per- 
 petually on the ground, that the lands lie entirely uncultivated. 
 The climate of Newfoundland, which is situated still further south 
 than this island, is more like that of the north of Russia than 
 England ; and those who have travelled in Canada, which lies 
 in the same parallel of latitude with the finest vineyards of France, 
 assure us that the great river St. Laurence is frozen over for 
 many months, while the correspondent provinces in Europe ex- 
 perience the most genial temperature. 
 
 Dr. Robertson, indeed, supposes 2 that the difference of tem- 
 perature between certain parts of Europe and similar latitudes in 
 America is equal to twelve degrees, and that a place thirty de- 
 grees from the equator in the latter, is as warm as one situated at 
 eighteen degrees from it in the former. 
 
 There is also nearly as much variation in the climate of some 
 countries situated near the line. Thus, many parts of Peru are 
 mild and temperate, while the correspondent latitudes on the con- 
 tinent of Africa are scorched by the burning heats of the torrid 
 zone 3 . 
 
 A person accustomed to the examination of the works of Na- 
 ture, can scarcely avoid being often very much impressed with the 
 consideration of the beauty and excellence of the arrangements 
 which its divine Author has established, for the preservation of 
 the world and the various animated beings which inhabit it. Some 
 of these native and original appointments are contrivances of 
 
 1 According to the observations made at the house of the Royal Society 
 from the year 1772 to 1780, it appears that the mean annual temjperature of 
 London is 52. The greatest usual cold is 20, and happens in January ; and 
 the utmost degree of heat is generally 81, which commonly happens in July. 
 
 2 Hist, of America, vol. ii. page 472. 
 
 3 On the road from Senegal to Podor the heat is frequently 111. At Pon- 
 dicherry it has been 113 and 115. Kirwan On Climate, pages 99 and 101. 
 
OF NATURAL TEMPERATURE. 29 
 
 great wisdom. Of this class, the following appears to me to be 
 a most striking instance, though not often adverted to. 
 
 Land is capable of receiving much more either of heat or cold, 
 than water. Saussure, when the air was at 81, found the Lake 
 of Geneva at the surface was 62, and at the depth of eighty-seven 
 feet only 55. In the neighbourhood of Marseilles, Dr. Ray- 
 mond often observed the land heated to 160; but the sea was 
 never hotter than 77, and even this heat it received chiefly by 
 its communication with land; for in July 1765 he found that the 
 part of the bay next to the land was at 74, the middle of the 
 bay 72, and the entrance of the bay only 70. On the contrary, 
 he frequently observed the earth in winter cooled down to 14 or 
 15 ; but the sea was never lower than 44 or 45. 
 
 That the land has an effect on the waters of the vicinity, also 
 lowering its temperature, appears from the fact that some of the 
 inland seas of Europe, even of great extent, have sometimes been 
 entirely frozen over. In 1668 the Baltic was so firmly frozen 
 that Charles the Xlth of Sweden and his whole army passed 
 over it 4 . 
 
 Were it otherwise, and that the waters on the face of the earth 
 had the property of acquiring the same temperature either of heat 
 or cold as the land, the evaporation in summer would be exces- 
 sive and detrimental ; and in winter all navigation would be sus- 
 pended, and the finny inhabitants of the water would inevitably 
 perish. 
 
 Having adverted to this subject, it would be improper to allow 
 it to pass without noticing one or two of the causes which con- 
 stantly act to modify the temperature of the seas and other large 
 bodies of water. In hot climates, the seas, rivers, and lakes, are 
 prevented from acquiring any thing like the heat of the adjacent 
 lands, by the evaporation which is continually going on at the sur- 
 face, and which carries off the greater part of the heat as fast as 
 it is received. This principle of evaporation producing cold, has 
 been long understood, and will be explained as we proceed. 
 
 On the contrary, in winter, whenever the temperature of the 
 atmosphere is so far reduced as to give the waters a tendency to- 
 wards freezing, those particles of water on the surface which are 
 first cooled, acquire a greater specific gravity, and sinking within 
 the mass, warmer particles of water ascend to supply their place, 
 which are cooled in their turn, and descend also. Thus a circu- 
 lation between the surface and the lowest depths of the sea and 
 of other large bodies of water is constantly kept up, which often 
 tends, among other important purposes, to preserve them from 
 
 4 Pu/end. Hist. Europe. Mod. Univ. Hist, in 8vo. vol. xxx. page 180. In 
 1709 the Adriatic was completely frozen over. Mem. Par. 1749. 
 
30 ON TEMPERATURE. 
 
 congealing for a long period after the air is reduced to the freez- 
 ing point. 
 
 As the operation of this principle is uniform, it might be ex- 
 pected that the deepest lakes would remain the longest unfrozen; 
 and this is really found to be the case. Near Lochness in Scot- 
 land there is a small fresh-water lake on the top of a very high 
 mountain, the water of which never freezes ; and near Moha- 
 nagh, the seat of Roger Fenwick, Esq., in the county of Cork, 
 there are two small lakes, very deep, that produce trout of an 
 unusual size, and never freeze during the most severe winters, 
 owing to the time between the end of one summer and the be- 
 ginning of another not being long enough to allow of this circu- 
 lation being completed '. 
 
 It might however be supposed that whenever this circulation 
 ceases from the increase of the cold, the density of the freezing 
 water would continue to increase also, and that the ice, as fast 
 as it is formed, would be precipitated. But here, Nature, all 
 bountiful, has made a memorable deviation from her usual course; 
 for no sooner is the water cooled down to 40 5, than it not only 
 ceases to increase in density, but, on the contrary, actually be- 
 comes of less and less specific gravity, as the caloric is further 
 abstracted by the cold atmosphere. 
 
 When this diminution of specific gravity has begun to take 
 place, the water continues enlarging its bulk in regular gradation, 
 until the surface becomes cooled down to 32, when, if the water 
 be still, a film of ice forms and covers the whole mass. If the 
 cold continues, this covering of ice increases in thickness, and 
 attaches itself firmly to the banks, so as entirely to cut off all 
 communication with the atmosphere, and thus prevent that abs- 
 traction of caloric which otherwise would soon convert the whole 
 mass of water into ice. 
 
 No person, who has paid even a slight attention to chemical 
 science, can be ignorant of one of its principal axioms, that solids 
 and fluids acquire density by the loss of caloric ; it is therefore 
 surely worth while to inquire why this general law of nature has 
 been departed from in this instance, and to consider, what would 
 have been the result had water been subjected to the same law 
 with other bodies? 
 
 It has before been remarked, that as water loses caloric it be- 
 comes more and more dense until it is cooled down to about 40 ; 
 but if no check had been given to this process, and the density 
 of water had continued to increase until it came down to 32, the 
 superficial stratum would have continued to descend, followed by 
 others in quick succession, and a body of ice would have first 
 
 1 Ancient and Present State of the County of Cork, book ii. chap. iv. p. 264. 
 
OF NATURAL TEMPERATURE. 31 
 
 formed at the bottom instead of at the surface of our lakes and 
 rivers. This would have accumulated with such rapidity, that 
 one severe winter would, in all probability, have converted the 
 whole of most of the rivers of Europe into as many solid masses 
 of ice ; which, on account of their great thickness, no future 
 summer would have been able to dissolve. 
 
 It is certainly extremely curious that the same cause should thus 
 be made to produce effects which, apparently, are diametrically 
 opposite: That water, within a certain range of temperature, 
 should have its specific gravity increased by the loss of its calo- 
 ric ; and then, on a sudden, that the action should be reversed, 
 and its specific gravity lessened by the same operation. 
 
 It will now be perceived, that this curious contrivance was ab- 
 solutely necessary for the preservation of the world ; and it is 
 pleasing to consider how many inconveniences are avoided by 
 this very simple deviation from the usual course of Nature. The 
 sheet of ice which often covers the small seas, as well as the rivers 
 and the lakes, not only preserves a vast body of caloric in the 
 subjacent water, but when it thaws, the fish are not destroyed by 
 the cold ; for not a particle of the cold surface-water can descend, 
 until a change in the temperature of the atmosphere has taken 
 place, so as to raise the temperature of the whole of the water 
 at least ten degrees. 
 
 The next branch of our subject embraces the effects which are 
 produced on animal and vegetable life by change of temperature ; 
 but as these are too various to be even barely enumerated within 
 the compass of an Essay, the mention of a few of the most in- 
 teresting must suffice. 
 
 The first idea which naturally presents itself on this subject is, 
 that nothing but consummate wisdom could have suggested the 
 formation of such an infinitude of animals and vegetables of va- 
 rious natures and properties, and all peculiarly adapted to the 
 various climates in which they are respectively placed. 
 
 It is not, however, a little remarkable, that while every climate 
 on the face of the earth, and almost every situation 2 , has a race 
 of animals peculiarly fitted for it, and that can flourish and pro- 
 pagate no where so well as in their native quarter of the world, 
 and in their own appointed localities, man should be so organized 
 
 2 Messrs. Humboldt and Bojppland, in travelling through the province of 
 Quito in South America, perceived live fish thrown up from the bottom of a 
 volcano, in the course of its explosions, and they appeared to be in perfect 
 health, although the water and heated vapour that came up with them, raised 
 the thermometer to 210; which is only two degrees short of the boiling 
 point. Recueil d* Observations de Zoologie et d'Aiiatomie comparee. 
 
32 ON TEMPERATURE. 
 
 that he can reside, increase and multiply, on every part of the ha- 
 bitable globe. 
 
 It is also observable, that while the cold-blooded animals var^ 
 their animal temperature with every alteration of the medium in 
 which they live 1 , the mechanism of the human body is such, that 
 it is capable of preserving nearly an equable temperament, what- 
 ever may be its situation, or however great the transition from its 
 accustomed state, to the highest degree of heat that it can endure, 
 or to the most intense cold ; that is, the temperature of the hu- 
 man body is always the same, or nearly so, in all climates. 
 
 Of this singular faculty no satisfactory elucidation was afforded 
 until Dr. Crawford, in 1779, published his Experiments and 
 Observations on Animal Heat. This eminent philosopher ex- 
 plained it on the well known chemical principle of different sub- 
 stances having different capacities for caloric; on the property 
 that the matter of heat has of becoming latent; and on the fact, 
 which he discovered, that arterial blood has a greater capacity for 
 the matter of heat than venous blood. But that this maybe more 
 clearly comprehended by all classes of readers, it may perhaps be 
 necessary to proceed a little further into this part of our subject. 
 
 It was formerly presumed that caloric, in whatever state it 
 might be, could always be measured by the thermometer 2 . But 
 the important experiments of Dr. Black and others have shown, 
 that besides the caloric which acts upon, and is appreciable^ by, 
 the thermometer, there are other portions which are in such close 
 union with most bodies, as to occasion no sensible variation in 
 their temperature. That is, caloric may be so combined with a 
 body, as to have lost all power of affecting the most delicate in- 
 strument ; yet, when this latent heat is set at liberty, and con- 
 verted to free caloric, as it is called, this shall be as active, and 
 
 1 To establish the truth of this, many facts might be adduced. Frogs have 
 been frozen so hard, as to chip like a piece of ice, and yet by a careful and gra- 
 dual increase of temperature have been reanimated. On the contrary, worms 
 of the species of Tsenia have been taken alive out of the body of a boiled carp. 
 
 2 There are four different thermometers employed in Europe. This often 
 occasions much inconvenience. Ours has the scale of Fahrenheit, the zero of 
 which commences at 32 below the point at which water freezes ; and between 
 this and the point at which water boils, it is divided into 212 degrees. The late 
 Dr. Kirwan proposed that the use of all these thermometers should be discon- 
 tinued, and a general one constructed, beginning at the congelation of mercury, 
 and terminating at the ebullition of water, and to be divided into 250 degrees. 
 The late Dr. Murray of Edinburgh suggested that it would be convenient to 
 form a scale whose extreme points should be the temperatures of freezing and 
 boiling quicksilver, and to divide this scale into 1000 degrees. Kirwan On the 
 Temperature of different Latitudes, 8vo, 1787, preface, page vii. Murray's Che- 
 mistry, 8vo, 1809, vol. i. page 139. 
 
OF NATURAL TEMPERATURE. S3 
 
 as energetic, as though it had never been confined 3 . A single 
 example will be sufficient to adduce, by the repetition of which 
 any one may satisfy himself of the truth and propriety of this 
 distinction. 
 
 Put about half an ounce of cold water into a small phial, and 
 add to it, very gradually ) about an equal measure of oil of vitriol, 
 gently shaking the phial after every addition of the acid. The con- 
 sequence of this will be, that the water will immediately begin to 
 give out its latent caloric; and when so much oil of vitriol has been 
 added as is equal to double the measure of the water, the mixture 
 will assume a degree of heat superior to that of boiling water. 
 
 In regard to the operation of this principle in the act of re- 
 spiration, Dr. Crawford thus explained it : The oxygen, said he, 
 which is one of the component parts of atmospheric air, has a 
 large portion of caloric chemically combined with it, and a great 
 part of this caloric is taken up by the blood, every time that the 
 atmospheric air passes through the lungs ; the internal surface of 
 which, according to anatomists, is equal to the external superficies 
 of the whole body ; and on this extended surface it is that the 
 venous blood, through the medium of a thin pellicle, is exposed 
 to the influence of the respired air. Every time we make an in- 
 spiration, the bone of the breast rises and the diaphragm sinks. 
 By these two contrivances room is made for a pint and a half, or 
 more, of atmospheric air, at every drawing in of the breath. 
 
 How then is it that the lungs are not injured by this great ac- 
 cession of the matter of heat? This is a difficulty which .Dr. 
 Crawford has explained by the discovery, that arterial blood has 
 the property of arresting this caloric, and of chemically combi- 
 ning with it that is, of absorbing it in the same way as ice at 32 
 absorbs caloric, and is converted into water without becoming 
 warmer, in the least degree, by the addition 4 : and that when this 
 blood flows from the arteries to the veins, the case is altered, and, 
 by some unknown contrivance, its capacity for caloric is then less- 
 ened, and what was latent or combined caloric in the arteries, 
 becomes free caloric, or sensible heat in the veins 5 ; and as these 
 
 3 A luminous explanation of the doctrine of latent heat may be seen in Dr. 
 Robison's preface to Dr. Black's Lectures, 4to. p. 34, &c. 
 
 4 An example of a contrary effect may be found in the conversion of ice into 
 water. Let one pound of ice at 32 be dissolved in one pound of water heated 
 to 172, and it will be found that 140 degrees of heat have disappeared, and 
 become latent in the fluid, which assumes a temperature of 32 only; whereas, 
 if a pound of water at 172 be mixed with a pound of ice-cold water at 32, 
 the temperature of the mixture will be exactly 102, which is the mean of 32 
 and 172. Ice requires 140 degrees of caloric to give it fluidity, and this it re- 
 ceives without the least augmentation of temperature. 
 
 5 If the reader have an opportunity of referring to the" third chapter of the 
 Chemical Catechism, twelfth edition, pages 59 64, he will find several instances 
 adduced, whereby the difference between latent and free caloric is explained. 
 
34? ON TEMPERATURE. 
 
 branch out in infinite ramifications to every extremity of the body, 
 the genial warmth is conveyed through these channels to every 
 part. And when the blood returns to the lungs 1 , its former ca- 
 pacity is restored, and it again loads itself from the atmospheric 
 stores, and distributes the caloric, as before, to every even the 
 most minute vessel in the animal system. 
 
 When this theory was first published, it was naturally asked, 
 WTiat becomes of the azote, which is also a component part of 
 atmospheric air? and whether a great portion of the caloric would 
 not be required to preserve this azote in the state of gas, so that 
 it might be expelled from the lungs when the oxygen was sepa- 
 rated from it ? And that as a part of this oxygen takes up car- 
 bon from the blood, whether the remainder of the inhaled caloric 
 would not be necessary for the formation of carbonic acid gas, 
 which, it is well known, is also thrown off in the act of respiration? 
 
 But here another remarkable contrivance presents itself, and it 
 is one that is equally necessary to the uniform preservation of 
 animal heat. This I cannot explain with more conciseness, than 
 by transcribing the following note from the Chemical Catechism, 
 Chapter II. page 52. 
 
 " It is not simple azote or nitrogen, which is thrown out of the 
 lungs in respiration, but nitrogen gas ; and it has been imagined 
 that, when atmospheric air is decomposed by the lungs, part of 
 the disengaged caloric is required for the nitrogen, to preserve it 
 in the form of gas: but it is a very curious fact, that nitrogen gas 
 and carbonic acid gas have less capacity for caloric than any other 
 gaseous substance. It is a general characteristic of the gases, 
 that they absorb a large portion of caloric to preserve them in a 
 gaseous form. Yet one of these gases has less capacity for caloric 
 than many liquids, and the other (nitrogen gas) less capacity than 
 even ice." 
 
 When this beautiful theory for the explanation of the produc- 
 tion of animal heat was first proposed, most of the philosophers 
 of Europe acquiesced in it, and it continued to be generally re- 
 ceived for many years after the death of its learned and ingenious 
 author. Some considerable physiologists have, however, of late 
 years offered several objections to Dr. Crawford's reasoning, es- 
 pecially Mr. Brodie, whose paper was published in the Philoso- 
 phical Transactions for 1812 ; but none of these writers have as 
 yet favoured the world with a theory that is less objectionable, or 
 that will explain the phenomena attendant on respiration and on 
 the evolution of animal heat, in a more satisfactory manner. 
 
 1 The blood of the veins is black, or purple ; but as it passes through the 
 lungs it deposits charcoal, and becomes, when it enters the arteries, a bright 
 scarlet. 
 
OF NATURAL TEMPERATURE. 35 
 
 We shall, however, at all events, be justified in saying, that 
 the arrangements, whatever they may be, for the production of 
 animal heat, and for the preservation of life, are equally opera- 
 tive in every climate and in every situation in which man is likely 
 to be placed : for, not to advert to other causes, it may be re- 
 marked, that in climes intensely cold the atmospheric air is more 
 condensed, and consequently more caloric is taken in at every 
 inspiration. And be the temperature of the air what it may, a 
 thermometer with its bulb under the tongue or buried in a wound 
 in the flesh always indicates a heat of 97 or 98. 
 
 In many of the habitable parts of the Russian empire the cold 
 is often sufficiently intense to freeze mercury ; although, as is well 
 known, that fluid metal does not become a solid until it be re- 
 duced to the temperature of 71 degrees below the point at which 
 water freezes 2 : and it is observable, that when men have been 
 accustomed to cold climates, so as to know the precautions 3 ne- 
 cessary to be taken, they can endure more severe cold than even 
 this, without sustaining any permanent injury. 
 
 Many of the natives of Great Britain make annual voyages to 
 Greenland, and stay there during the fishing season, where the 
 cold is greater than most people can imagine. Some idea of it 
 may, however, be formed from the account we have of the masses 
 of ice which are generated there, and float occasionally from, 
 thence into the Atlantic Ocean. " These mountains of ice," says 
 Dr. Troil, " which are often seen fifty feet or more above water, 
 are at least nine times 4 the same depth below water 5 . Frequently 
 these immense masses are left in shoal water, fixed, as it were, to 
 the ground, and in that state remain many months, nay years, 
 undissolved, chilling the whole of the atmosphere for many miles 
 round." 
 
 The Stockholm Memoirs for 1757 mention a fact which fully 
 
 2 Some idea of the very low temperature of frozen mercury may be derived 
 from the circumstance, that if a lump of it be dropped into a small quantity of 
 water at the boiling point, it will abstract the caloric with such rapidity that the 
 mercury will instantly become fluid, and the hot water will at the same mo- 
 ment be converted into ice. 
 
 3 One precaution necessary to be observed in such situations, is, not to han- 
 dle any metallic body ; for, if an instrument or utensil of iron, or any other 
 metal, which had been exposed to the cold atmosphere, were touched, a sensa- 
 tion would be felt like that of burning, and the part would, in all probability, 
 be blistered. 
 
 4 Mr. Boyle found by experiment, that a cylinder of ice floating in water of 
 the same specific gravity as that of which it was made, could rise only one 
 tenth of its height above the surface of the water. Boyle's Appendix to The 
 History of Cold, p. 16. 
 
 5 The account which Pennant in his Arctic Zoology has given of the ice 
 mountains at Spitsbergen is grand and interesting. The " collision," says he, 
 " of the great fields of ice, in high latitudes, is often attended with a noise that, 
 for a time, takes away the sense of hearing any .thing else; and the lesser, with 
 a grinding of unspeakable horror." 
 
 D 2 
 
36 ON TEMPERATURE. 
 
 corroborates this statement of the effect of mountains of ice or 
 snow on the atmosphere. " When," says the writer of that pa- 
 per, " a north-west wind blows on the mountains of Norway, it 
 occasions a thaw ; but when it has passed these mountains and 
 entered Sweden, it produces the most intense cold." 
 
 Moreover, Mr. MacNab, when in Hudson's Bay, experienced 
 a cold so intense as to sink the spirit thermometer to 82 below 
 the freezing point, which, if his instrument did not deceive him, 
 was eleven degrees below what is required for freezing mercury. 
 
 On the other hand, whenever an animal is placed in a medium 
 the temperature of which is considerably high, the usual change 
 of arterial into venous blood does not take place ; consequently 
 there will be no evolution of caloric, and the animal heat will not 
 rise much above the natural standard : but the problem has not 
 yet been solved, how high is the degree of heat which the human 
 frame can endure without injury. 
 
 Sir Joseph Banks and Sir Charles Blagden once attempted to 
 ascertain this, and for some time actually breathed an atmo- 
 sphere, in a room prepared by Dr. Fordyce, which was fifty-two 
 degrees higher than that of boiling water. It is related in the 
 History of the Academy of Sciences for 1 764, that the oven- 
 girls in Germany often sustain a heat of from 250 to 280, and 
 one of these girls once breathed in air heated to 825 of Fahr- 
 enheit for the space of five minutes. 
 
 During the time that Sir Joseph Banks and Sir Charles Blag- 
 den submitted themselves to Dr. Fordyce's experiment, the tem- 
 perature of their bodies was not at all raised; though their watch- 
 chains, and every thing else metallic about their persons, were 
 so heated that they could not bear to touch them l . The ther- 
 mometers which hung in the rooms always sunk several degrees 
 when either of the experimentalists breathed upon them or touch- 
 ed them ; and to*prove that there was no fallacy in the degree of 
 atmospheric heat shown by the thermometer, " we put," says the 
 reporter, " some eggs and a beef steak upon a tin frame in the 
 room, and in 20 minutes the eggs were taken out roasted quite 
 hard, and the beef steak was overdone in 33 minutes." 
 
 Water placed in the same room did not, however, acquire a 
 boiling heat until a small quantity of oil was dropped into it, 
 when it soon began to boil briskly. The evaporation from the 
 surface of the water had prevented it from acquiring the heat of 
 212 ; but when that surface became covered with a film of oil, 
 the evaporation could not go on, and ebullition commenced 9 . 
 
 1 " The heat of metals at the temperature of 120 is scarcely supportable ; 
 water scalds at 150, but air may be heated to 240 without being painful to 
 our organs of sensation." Davy's Elem. of Chem. Philosophy. 
 
 2 Sir Charles Blagden's relation of these very interesting experiments may 
 be seen in the Phil. Trans, for the year 1775, pages 111 and 484, &c.; and a 
 
OF NATURAL TEMPERATURE. 3? 
 
 That evaporation produces cold, is a very familiar axiom in 
 chemical science : and this principle is operative also in the re- 
 gulation of animal heat ; for, whenever the human body becomes 
 oppressed by heat, if it be in a state of health, perspiration com- 
 mences, and this carries off the superabundant caloric as fast as 
 it is produced. 
 
 These effects of perspiration, which are so extremely beneficial 
 in the animal economy, arise from a well known chemical prin- 
 ciple, viz. that water cannot be converted to vapour until it has 
 combined with a very large portion of caloric. Thus, in all op- 
 pressive heats, the fluids of the human body are determined to 
 the surface, from whence they escape in the gaseous form, carry- 
 ing off with them that superabundant heat which otherwise would 
 soon have become insupportable. 
 
 That perspiration actually does operate in this way, may be 
 readily conceived by those who know that a thermometer plunged 
 into steam indicates only the same degree that it would in boil- 
 ing water, although the steam contains nearly one thousand 
 degrees more of caloric chemically combined with it, and that, 
 owing to its being in a latent state, it is not appreciable by the 
 thermometer. 
 
 It is by this combination with caloric that steam is enabled to 
 preserve its gaseous form, in which state it occupies a bulk 1 800 
 times greater than that of water ; and this is the only way in 
 which we can account for the loss of that continued stream of 
 caloric which is perpetually passing, and often for many hours, 
 through the bottom of an evaporating vessel, or other boiler of 
 water, when placed over an intense fire ; because, if the fire be 
 the same, the water actually admits as much caloric after it boils, 
 as it did before, although that which it now receives does not, 
 in the least, augment its temperature. 
 
 The temperature of boiling water is usually 212, and the 
 constant evaporation prevents it from ever acquiring a higher 
 temperature, however intense may be the fire that is placed be- 
 neath it. In like manner, the natural temperature of the human 
 body is about 96 or 98 ; and whatever may be the degree of 
 heat to which it is exposed, the animal perspiration always car- 
 ries off the superabundant quantity, and prevents it from ever 
 acquiring a temperature much beyond the usual standard. 
 
 These multiplied contrivances for the preservation of life, by 
 maintaining an uniform animal temperament, were surely not 
 the offspring of chance ; their peculiar adaptation shows them to 
 be a part of the great scheme of unerring Wisdom, effected 
 
 series of experiments by Dr. Crawford, on the power that animals possess oi 
 producing cold, will be found in Phil. Trans, for 1781, page 479. 
 
38 
 
 ON TEMPERATURE. 
 
 by a Being who wills the convenience and felicity of his crea- 
 tures. 
 
 There is still some intricacy respecting the nature of the ope- 
 ration of caloric on combustible substances; and this will not 
 seem surprising when we consider, that all the theories of com- 
 bustion which were promulgated before the time of Lavoisier 
 are now deemed extravagant, or at least very unsatisfactory. A 
 short sketch, therefore, of the very ingenious theory which this 
 eminent philosopher published about the year 1 775, to explain the 
 phenomena of combustion, may perhaps be acceptable to those 
 persons who have had no opportunity of investigating the subject. 
 
 " Some bodies (said he) are combustible, others are incom- 
 bustible. If a body which is formed of combustible materials 
 be heated to a certain degree in atmospheric air, combustion 
 will commence, and its affinity for oxygen will be so great that 
 it will abstract it from the atmosphere. Should the combustible 
 substance be placed in favourable circumstances, with the free 
 access of atmospheric air, this perpetual accession of oxygen will 
 keep up the combustion until the whole of the combustible matter 
 becomes saturated with oxygen, and then, in popular language, 
 it is said to be consumed." 
 
 The heat, in this process, generally arises from the decompo- 
 sition of the oxygen gas of the atmosphere ; but he thought it 
 probable that the light l and the flame in most cases proceed from 
 the combustible body itself, and that combustion is a mere che- 
 mical process, a double decomposition, in which not only two 
 compound bodies are separated into their original elements, but 
 two new compounds are always formed. For while the light, 
 which is extricated from the burning substance, unites with the 
 caloric of the oxygen gas, and produces what is called fire, the 
 oxygen itself combines with the base of the combustible, and 
 forms a new incombustible substance. This incombustible mat- 
 ter will be either water, an acid, or an oxide ; or a compound of 
 two or more of these substances. 
 
 In this view of the subject, combustion can never take place 
 in vacuo. Atmospheric air, or some other compound containing 
 oxygen, must, as he asserted, be present in every instance of 
 combustion ; and this he explained by reference to a variety of 
 direct experiments. 
 
 Since the time of Lavoisier, however, several objections have 
 been urged to this theory ; most of which have been detailed by 
 Professor Brande in his Manual of Chemistry, vol. i. page 317, 
 
 1 For an account of the colours of the light which proceeds from different 
 combustibles, the reader may consult Dr. Fordyce in the Phil. Trans, for 1776, 
 and the Rev. W. Morgan in Phil. Trans, for 1785. 
 
OF NATURAL TEMPERATURE. 39 
 
 and by Dr. Ure in his Dictionary ; and these, together with the 
 discovery that chlorine and iodine will support combustion, 
 neither of which contains oxygen, have entirely confuted the 
 French assertion that oxygen, or some of its compounds, must 
 be present in every case of combustion. We are therefore now 
 compelled to come to the conclusion, " That combustion cannot 
 be regarded as dependent upon any peculiar principle or form 
 of matter, but must be considered as a general result of intense 
 chemical action/' 
 
 It must, notwithstanding, be observed that nothing has oc- 
 curred to refute the generally received opinion, that in all the 
 ordinary cases of combustion, it is the oxygen of atmospheric 
 air, and that alone, which supports the combustion. 
 
 The necessity for the presence of oxygen in the more familiar 
 cases of combustion is so clearly exemplified in a certain opera- 
 tion on cotton goods, not universally known, that I conceive it 
 may be useful to advert to it. The process to which I allude, 
 and which is very common in Lancashire and other calico-print- 
 ing districts, is called singeing, and has been contrived for the 
 purpose of taking off all the ends of the threads and other downy 
 filaments that are usually attached to the piece, and of giving 
 the whole a smooth surface. 
 
 To effect this, several pieces of calico, previously fastened to- 
 gether by their ends, are lapped smoothly round a large wooden 
 roller, from which, by a regular motion, they are passed over a 
 large semicircular piece of cast iron, which, by means of a furnace 
 placed immediately beneath it, is constantly kept at a full red heat. 
 
 Calicoes, muslins, dimities, fustians, &c. are treated in this 
 manner, and the subsequent bleaching takes out any stains which 
 they may have contracted from the iron ; all of which is more 
 minutely described in the Essay on Calico Printing. 
 
 To a stranger, this may seem a very destructive operation 
 (and no one can witness it for the first time without astonish- 
 ment) ; but by the quickness and regularity of the motion, and 
 by the uniform pressure of the cloth upon the hot iron, the com- 
 bustion that would otherwise take place is prevented, and nothing 
 is burnt but the loose threads that rise above the surface of the 
 fabric. The peculiar effect that is here produced, and how the 
 cloth is protected from the red-hot metal, may be thus ex- 
 plained. 
 
 The uniform pressure of the cloth upon the heated cylinder, 
 keeps that part of it which is directly over it in close contact, so 
 that there is no space for the intervention of any more atmo- 
 spheric air than is just sufficient to occasion the combustion of 
 the mere superficial filaments of the cotton or linen ; and this is 
 the only effect which the manufacturer is desirous of producing. 
 
4*0 ON TEMPERATURE. 
 
 This process, which is now universal with the printers of cot- 
 ton goods, explains why our housewives cannot get up their 
 home-spun linen with so neat a face as that has which is sold in 
 the shops. There are some intelligent laundresses, however, 
 who are fully aware of the principle on which the above-named 
 process is founded ; for, when about to iron their clothes, they 
 dismiss all anxiety about the precise degree of heat ; as they well 
 know that, however hot their flat-irons may be, if they press 
 them with all their force upon the linen, and that the linen be 
 smoothly spread, it will never sustain any injury. 
 
 It has already been remarked, that in the ordinary cases of 
 combustion which occur in consequence of, and are supported 
 by, the constant presence of oxygen, during the process the 
 oxygen combines w T ith the base of the combustible : but there is 
 another axiom of equal importance to be impressed on the me- 
 mory of all those who are likely to be engaged in any kind of 
 chemical operations, which I believe was first proved by direct 
 experiment by Lavoisier, viz. " That every body increases in 
 weight by the operation of combustion." This may perhaps 
 require a little explanation, but it is a law of Nature to which 
 there is no exception. 
 
 Even the slow combination of oxygen with a body increases 
 its absolute weight, as is well exemplified in the formation of the 
 metallic oxides ; the metals always acquiring additional weight 
 by being converted into oxides. Thus, by exposing melted lead to 
 the action of the atmosphere, under a peculiar management, red 
 lead is formed, and a ton of pig lead will yield 22 cwt. of red lead. 
 
 But where complete combustion takes place, this increase is 
 generally more considerable: thus, if 100 pounds of zinc are 
 burnt in a proper apparatus, flowers of zinc will be formed, and 
 the product will be 125 pounds. If spermaceti oil be burnt in a 
 way that the product can be examined, it will be found that the 
 whole is converted to carbonic acid and water, and that every 
 hundred ounces of the oil have produced 130 ounces of water. 
 In like manner, if phosphorus be burnt by a rapid combustion, 
 it will attract oxygen from the atmosphere, and become phos- 
 phoric acid, and every pound of the phosphorus thus employed 
 will produce more than two pounds of acid. 
 
 It would be fruitless to enumerate more instances, though I 
 thought it right to mention a few obvious examples in passing, 
 because I have met with many intelligent people who had never 
 annexed any idea to combustion but that of absolute destruction ; 
 and yet I know of no subject connected with the economy of the 
 world, which it is of more importance to investigate, or which is 
 better calculated to give us exalted conceptions of the arrange- 
 ments of that Being who hath not only formed a perfect whole, 
 

 
 
 
 
 
 
 
 
 
^fc* 
 
 CHEMICAL ESSAYS. 
 
OF ARTIFICIAL TEMPERATURE. 4-1 
 
 and pronounced every part to be in itself good, but has so con- 
 stituted things that none of the materials which he has employed 
 in the construction of the world can ever be lost or destroyed. 
 
 Metals, by means of oxygen, may be converted to pulverulent 
 and even impalpable substances ; but, whenever the oxygen is 
 abstracted, every character of the original metal will be restored. 
 All sorts of combustible substances may be employed for the 
 necessary purposes of increasing temperature : the caprice of 
 man may commit many invaluable, as well as worthless sub- 
 stances, to the flames ; or the lightning of the heavens may involve 
 a whole district in one general conflagration, in which every 
 thing combustible shall be reduced to ashes :- but let it be re- 
 membered, that the act of combustion only separates the particles 
 of bodies, and puts them in a state to form a variety of new combi- 
 nations equally useful and necessary in the order of the Universe. 
 
 And shall we be told that such a state of things is the effect 
 of chance? Certainly not. Sir H. Davy has well remarked, in 
 opposition to such absurdity, that " in the Universe nothing can 
 be automatic, as nothing can be said to be without design. An 
 imperfect parallel," says he, " may be found in human inven- 
 tions. Springs may move springs, and wheels, indexes; but the 
 motion and the regulation must be derived from the artist. 
 Sounds may be produced by undulations in the air, undulations 
 of the air by vibrations of musical strings ; but the impulse and 
 the melody must arise from the master." 
 
 PART II. OF ARTIFICIAL TEMPERATURE. 
 
 HAVING proposed in this part of the Essay to treat of certain 
 expedients for increasing arid diminishing temperature, I shall 
 begin with an account of the means which have been employed 
 by different nations, and in different periods of the world, for 
 producing fire. 
 
 FIRE has been known in some part or other of the world in 
 all ages. In ancient times it was always employed in the rites 
 of religion ; it consumed the burnt offerings of the Patriarchs ; 
 it was kept continually burning in the Jewish tabernacle; it was 
 looked upon as the origin of life 1 , the soul of the world 2 , the 
 
 1 Fire was so generally considered as the image of life, that lighted torches 
 were usually placed in the hands of the newly married ; and at their deaths 
 extinguished torches were placed upon their tombs. Essai sur le Feu sacre, 
 $c. 8vo. Amsterdam, 1768. 
 
 2 The fable of Prometheus,, who stole fire from heaven to animate his man, 
 seems to have been founded on this idea. 
 
42 ON TEMPERATURE. 
 
 symbol of Deity ; and, considering it as the visible sign of an 
 invisible Being, it has, from time immemorial, been actually 
 worshipped by the Persians, and by some other Asiatic nations. 
 The sacred fire of the Vestal virgins, among the Romans, was 
 beheld by them with little less than adoration. Numa built a 
 temple to Vesta, the goddess of fire, which in after ages was re- 
 built with great magnificence. 
 
 Notwithstanding, according to Pliny, fire was for a long time 
 unknown to some of the ancient Egyptians ; and when Eudoxus, 
 the celebrated astronomer, showed it to them, they were abso- 
 lutely in raptures. 
 
 The Persians, Phenicians, Greeks, and several other nations, 
 acknowledged that their ancestors were once without the use of 
 fire ; the Chinese confessed the same of their progenitors. Pom- 
 ponius Mela, Plutarch, and other ancient authors, speak of na- 
 tions, who at the time they wrote knew not the use of fire, or had 
 but just learnt it. Facts of the same kind are also attested by 
 several modern relations. 
 
 The inhabitants of the Marian Islands which were discovered 
 in 1521 had no idea of fire. Never was astonishment greater 
 than theirs, when they saw it on the descent of Magellan on one 
 of their islands. At first they believed it to be a kind of animal 
 that fixed itself to and fed upon wood. The inhabitants of the 
 Philippine and Canary Islands were formerly equally ignorant. 
 Africa presents us, even in our own days, with some nations in 
 this deplorable state of ignorance '. 
 
 The production of fire by collision, and the use of flint and 
 steel 2 , were probably known long before the time of Pliny; though 
 the more ancient method of procuring fire was by rubbing two 
 dry sticks one upon the other with violence 3 . The Indians 
 fasten two pieces of wood together, and then putting another 
 stick between them, they turn the latter swift like a wimble, and 
 thus make the whole take fire. In Apulia they wrap a cane 
 within some cords, and then drawing the cords backward and 
 forward, the cane becomes ignited by the motion 4 . 
 
 Fire is also to be procured FROM THE SUN by means of a 
 double convex lens, a concave mirror, or by a combination of a 
 
 1 Goguet's Origin of Laws, Arts, and Sciences, vol. i. page 72. 
 
 2 The Laplanders begin their contracts of marriage with the fire and flint ; 
 for fire with them is the author of life; and the flint, say they, is eternal, for 
 the treasure of fire within it never fails. Scafig. Exerc. 16, 1. Jonston, 
 page 33. 
 
 3 A series of experiments on the heat produced by the attrition of different 
 woods against each other may be seen in Nicholson's Journal, vol. viii. page 
 218; together with a table constructed on the said experiments. 
 
 4 Jonston's History of Nature, page 34. 
 
OF ARTIFICIAL TEMPERATURE. 43 
 
 number of plain mirrors*. It was by some one of these expe- 
 dients that Archimedes contrived to set fire to the ships of the 
 Romans during the siege of Syracuse. That this account is not 
 fabulous, as some writers have imagined, is rendered probable, 
 from the effects which have been actually produced by these 
 contrivances in later ages. Father .Kircher, and his pupil Schot- 
 tus, visited Syracuse for the express purpose of investigating the 
 truth of this story ; and they proved by direct experiment that 
 Archimedes, by a combination of mirrors, might easily have de- 
 stroyed the fleet of Marcellus at the distance at which the ships 
 must have lain from the walls of the city ; and also the possibi- 
 lity of the success of Proclus, who is said to have destroyed a 
 fleet at Constantinople in the same manner. Phil. Trans, vol. 
 xlviii. page 621. The following instances will be sufficient to 
 enumerate. 
 
 At the beginning of the last century Mr. Tschirnhausen, a 
 member of the Royal Academy of Sciences, made several burn- 
 ing glasses, which were each three or four feet in diameter, and 
 had a focus of one inch and a half diameter at the distance of 
 twelve feet. One of these, which was convex on both sides, and 
 weighed one hundred and sixty pounds, was used by M. Hom- 
 berg, who communicated the result of his experiments to the 
 Academy, and announced the following facts. 
 
 " All sorts of wood," says he, " though ever so hard or green, 
 will be fired by this instrument in a moment. Water in a small 
 vessel will boil immediately. Tiles, slates, pumice stones, grow 
 red in a moment, and vitrify. Any metal, put into the crevices 
 of a coal, melts in a moment. Lead and tin volatilize entirely. 
 The ashes of herbs and wood become transparent glass in an 
 instant 6 ." 
 
 Another instrument and one that was still more powerful was 
 constructed in the year 1773, under the direction of M. de Tru- 
 daine, and placed in the garden of the Infanta at the Louvre. 
 It was composed of two large glasses, each four feet in diameter, 
 joined at the edges so as to hold alcohol. These glasses, which 
 were without flaw, were two thirds of an inch thick, and formed 
 two portions of a sphere of eight feet radius, leaving between 
 them a vacuum capable of containing thirty-five French gallons 
 of liquid. The focus of this instrument was at the distance of 
 ten feet ten inches, when filled with alcohol ; at eleven feet eleven 
 
 5 By these means wood may be burned to a coal, even under water. Hoff- 
 man, with the assistance of a concave mirror made by Hoessen, fused the 
 Hungarian asbestos into glass in three seconds. Hopson's Translation of 
 Wcigleb, page 66. 
 
 6 The History of Ike Works of the Learned, 4to. London, 1 702, vol. iv. 
 page 655. 
 
44 ON TEMPERATURE. 
 
 inches when filled with distilled water ; and at seven feet when 
 filled with liquid turpentine. With this apparatus all the effects 
 already mentioned were easily produced, and even the clippings 
 of bar-iron were melted in an instant ! . 
 
 We are informed, however, by Mons. Buffon, who expended 
 a very considerable sum in the construction of different instru- 
 ments for concentrating the rays of the sun, that the only way 
 by which the sun's rays can be made to produce an intense heat 
 at a great distance, is by the combination of a considerable num- 
 ber of plain mirrors, so disposed as to throw numerous images 
 of the sun upon the same spot 2 . 
 
 One of these instruments, which consisted of 360 plain mirrors, 
 each eight inches long and six inches broad, mounted on a frame 
 eight feet high, produced the following very powerful effects : 
 
 When twelve of the mirrors only were used, light combustible 
 substances were kindled at the distance of twenty feet. At the 
 same distance a large vessel of tin was melted by forty-five of 
 these mirrors, and a thin piece of silver with 1 1 7 of them. With 
 the entire machine all the metals and metallic minerals were 
 melted at the distance of forty feet : and when the sky was clear, 
 wood was kindled by it even at the distance of 210 feet. 
 
 In appreciating the comparative value of concave and plain 
 mirrors, Mons. Buffon remarks, that as at the distance of fifty 
 feet the focus, or space in which all the images coincide, is about 
 seven inches broad, metals may be assayed by it, and other cu- 
 rious experiments made in the large way, which it is impossible 
 to execute with concave mirrors, in which the focus is inconve- 
 niently near or weak, and generally a hundred times less than 
 that produced by this machine. 
 
 Among other purposes for which this instrument may be em- 
 ployed, the author has stated that it might be used with advan- 
 tage in the manufacture of salt, by producing a quick evaporation 
 of the salt-water, without the expense of fuel. An assemblage 
 of twelve mirrors, each a foot square, will, he says, be more than 
 sufficient to give a boiling heat to the liquor contained in shallow 
 pans constructed for this purpose. 
 
 There are difficulties however in applying this instrument to 
 purposes of general utility which must not be concealed. A 
 cloud passing over the sun during some processes would be a 
 great inconvenience; and when the sun does shine in its full 
 splendour, the motion of the earth will prevent the focus from 
 ever being kept for a minute at a time on one spot. 
 
 1 The History and Memoirs of the Royal Academy of Sciences at Paris, for 
 the years 1774 and 1777. 
 
 2 Phil. Trans. No. cccclxxxiii, pages 493 and 495. 
 
OF ARTIFICIAL TEMPERATURE. 45 
 
 In describing the burning glasses made on the continent, I 
 have been guilty of a great omission by hitherto neglecting to 
 notice the burning mirror belonging to Sir Isaac Newton, which 
 consisted of seven concave glasses, each of a foot in diameter ; 
 and the glass lens made by Mr. Parker, of Fleet-street, London, 
 at an expense of 700/., which was doubtless the most powerful 
 burning lens ever constructed. The zero of Wedgwood's pyro- 
 meter was fixed by the inventor at the lowest red-heat visible in 
 daylight ; the greatest welding heat of iron by that instrument is 
 95, and the extremity of the scale is 240 : but the power of 
 the lens, estimated by this pyrometer, was found to be 1096, 
 which is a temperature that was never before obtained by any 
 human being. In addition to these few particulars, I am de- 
 sirous of stating that a very circumstantial account of this won- 
 derful instrument has been drawn up by Mr. Parker, jun. for 
 Rees's Cyclopaedia, where it will be found, under the article 
 " Burning Glass," in vol. v. part ii. 
 
 ELECTRICITY is also a means that may be mentioned when 
 treating of the various methods of increasing the temperature of 
 bodies, as it is capable of producing powerful effects. The elec- 
 tric matter collected by the friction of a glass plate or cylinder 
 upon a prepared cushion is received on a metallic conductor, as 
 it is generated ; and from thence it is conducted into a number 
 of glass jars coated with tin-foil. Electricity is best excited by 
 rubbing the cushion with an amalgam of tin and zinc. The ex- 
 citation seems to depend upon the ready oxidizement of the me- 
 tals which form the amalgam ; for such metals as are not easily 
 oxidized produce no electricity. 
 
 By the discharge of one of these electrical batteries, the com- 
 bustion of various substances may be effected ; animal life may 
 be destroyed ; and wires of the different metals will be melted in 
 an instant. But notwithstanding these powerful effects, the elec- 
 tric matter may be thrown gradually upon the human body with- 
 out producing any mischief or inconvenience whatsoever; as is 
 constantly practised in cases of medical electricity. To this silent 
 and harmless employment of the electrical fluid, one of our mo- 
 dern poets refers in the following lines : 
 
 " For if on wax some fearless beauty stand 
 And touch the sparkling rod with graceful hand, 
 Through her fine limbs the mimic lightnings dart, 
 And flames innocuous eddy round her heart." 
 
 By VOLTAIC ELECTRICITY, or galvanism, much more powerful 
 effects may be produced in igniting various substances, and in 
 melting metals, than have ever been occasioned by simple elec- 
 tricity. These, however, depend much on the size and the na- 
 
46 ON TEMPER ATtTREr 
 
 ture of the apparatus; and though most persons may be ac- 
 quainted with this property of galvanism, it is impossible for any 
 one to form an adequate idea of the power which maybe acquired 
 by an extensive apparatus, in which there is a proper combination 
 of number of plates, and an extended surface, unless he actually 
 witnesses some of the effects produced by it. 
 
 " The grandest combination," says Sir H. Davy, " ever con- 
 structed for exhibiting the effects of extensive surface alonc^ was 
 made by Mr. Children ; it consists of twenty double plates four 
 feet by two ; of which the whole surfaces are exposed in a wooden 
 trough, in cells covered with cement, to the action of diluted acids. 
 This battery, when in full action, had no more effect on water, 
 or on the human body, than one containing an equal number of 
 small plates ; but when the circuit was made through metallic 
 wires, the phenomena were of the most brilliant kind." 
 
 " A platinum wire of one thirtieth of an inch in thickness, 
 and eighteen inches long, placed in the circuit between bars of 
 copper, instantly became red hot, then white hot ; the bril- 
 liancy of the light was soon insupportable to the eye ; and in a 
 few seconds the metal fell into globules J . Points of charcoal ig- 
 nited by this power, produced a light so vivid, that even the sun- 
 shine, compared with it, appeared feeble." 
 
 " But the most powerful combination that exists, in which 
 number of alternations is combined with extent of surface, is that 
 constructed, by the subscriptions of a few zealous cultivators and 
 patrons of science, in the laboratory of the Royal Institution. It 
 consists of two hundred instruments, connected together in re- 
 gular order, each composed of ten double plates arranged in cells 
 of porcelain, and containing in each plate thirty-two square 
 inches ; so that the whole number of double plates is 2000, and 
 the whole surface 128,000 square inches. 
 
 " This battery, when the cells were filled with sixty parts of 
 water mixed with one part of nitric and one part of sulphuric acid, 
 afforded a series of brilliant and impressive effects. 
 
 " When pieces of charcoal, about an inch long and one-sixth 
 of an inch in diameter, were brought near each other, within the 
 thirtieth or fortieth of an inch, a bright spark was produced, and 
 more than half the volume of the charcoal became ignited to 
 whiteness ; and by withdrawing the points from each other a con- 
 stant discharge took place through the heated air, in a space equal 
 at least to four inches, producing a most brilliant ascending arch 
 of light, broad and conical in form in the middle. 
 
 1 To form an adequate idea of the power of this apparatus, it should be re- 
 collected that platinum cannot be melted in the most intense heat of an air 
 furnace, nor in a smith's forge, unless oxygen gas be employed ; and yet by the 
 silent action of galvanism it became, in this instance, fused in a few seconds. 
 
OF ARTIFICIAL TEMPERATURE. 47 
 
 " When any substance was introduced into this arch, it instantly 
 became ignited ; platinum melted as readily in it as wax in the 
 flame of a common candle; quartz, the sapphire, magnesia, lime, 
 all entered into fusion ; fragments of diamond, and points of 
 charcoal and plumbago, rapidly disappeared, and seemed to eva- 
 porate in it, even when the connexion was made in a receiver ex- 
 hausted by the air pump ; but there was no evidence of their hav- 
 ing previously undergone fusion." Elements of Chem. Phil. p. 151. 
 
 The CLOUDS may be considered to be another source from 
 whence man has the means of procuring fire. The first idea of 
 the identity of lightning and electricity occurred to the mind of 
 Dr. Franklin in the year 1752; and in the month of June in that 
 year, he elevated a kite for the purpose of ascertaining the fact, 
 and on the first trial he had the satisfaction of finding his conjec- 
 ture verified and the discovery complete 2 . 
 
 In the following year the experiment was repeated in France, 
 and on a large scale, by Mons. Romas, which fully demonstrated 
 the powerful effects of elevated metallic conductors in drawing off 
 the electric matter. 
 
 The kite which he employed had a wire interwoven in the 
 hempen string, and the following were some of the signs of elec- 
 tricity which it exhibited soon after its elevation in the atmosphere. 
 " Electrical sparks three inches long and a quarter of an inch 
 thick were drawn at the distance of a foot from a tin conductor, 
 connected with the apparatus, the snapping of which was heard 
 at 200 paces. On the falling of a little rain, the appearances in- 
 creased amazingly, and a continual rustling noise was heard, like 
 that of a small forge bellows." 
 
 The remainder of the account which Dr. Priestley has given 
 of these very interesting experiments 3 is too long to be intro- 
 duced here ; but I have no hesitation in saying that those of my 
 readers who may have an opportunity of seeing the work, can- 
 not fail of being highly gratified by its perusal. 
 
 By this discovery of Dr. Franklin's we have learnt how to se- 
 cure houses and other more elevated buildings, and ships at sea, 
 from damage by lightning ; and are taught that a very small me- 
 tallic conductor, if elevated above the highest part of an edifice, 
 and connected with the earth, is capable of conveying a very 
 large quantity of electric matter from the clouds to the earth, 
 without noise, and without leaving any signs of its having been 
 present. 
 
 Those who may be desirous of repeating the experiments with 
 
 2 Priestley's History of Electricity. 4to. London. 
 ' Ibid. 
 
48 ON TEMPERATURE. 
 
 an electrical kite, ought, however, not to attempt the thing with- 
 out the utmost caution, and a thorough knowledge of the science 
 of electricity, lest they should share the fate of Professor Rich- 
 man, who through mere inadvertence lost his life, in the midst 
 of his family, during a series of experiments similar to those of 
 which we are now speaking. 
 
 This ingenious and indefatigable man, who was professor of 
 natural philosophy at Petersburg, had elevated an insulated me- 
 tallic rod, and prepared a considerable apparatus to collect the 
 aerial electricity, as Dr. Franklin had previously done at Phila- 
 delphia ; and as he was observing with Mr. Sokolow, engraver 
 to the Royal Academy at Petersburg, the effects of the electri- 
 city upon the balls of his electrometer, during a thunder storm 
 on the 6th of August, 1753, he approached too near the con- 
 ductor, and was instantly struck dead by the side of his philoso- 
 phical friend, who received no injury. An engraving and ample 
 description of the apparatus employed may be seen in the 48th 
 vol. of the Phil. Trans. ; also a drawing of the apartments of the 
 house, marking the room and the exact situation in which the 
 professor stood when he received the fatal stroke. 
 
 The deceased was attending the usual meeting of the Academy, 
 when hearing it thunder at a distance, he hastened home, in 
 company with Mr. Sokolow, to witness its effects upon his appa- 
 ratus, and in less than an hour he became a corpse. 
 
 The explosion which attended this dreadful catastrophe, was 
 as loud as the report of a pistol; the stroke was given at a foot 
 distance from the rod ; and from the description of Mr. Sokolow, 
 the electrical spark which struck the professor must have been of 
 a size several inches in diameter. The metallic rod was broken 
 in pieces ; and the melted fragments being thrown upon Mr. So- 
 kolow's clothes, left the mark of their form and dimensions upon 
 them. 
 
 The professor had seventy rubles of silver in his left coat- 
 pocket which were not in the least altered. But a clock which 
 stood in an adjoining room was stopped, the door of one of the 
 chambers of the house was broken, and the ashes which lay upon 
 the hearth were forced from thence into the middle of the 
 room. 
 
 Mrs. Richman, on hearing the loud stroke of the thunder, has- 
 tened into the chamber, and found her husband past sensation, 
 sitting upon a chest, which happened to be placed behind him. 
 and leaning against the wall, which situation must have been oc- 
 casioned by his falling back upon receiving the electrical charge. 
 He was no sooner struck than killed. There were not the least 
 appearances of life. The surgeons opened a vein of the breath- 
 less body twice, but no blood followed. They endeavoured to 
 
OF ARTIFICIAL TEMPERATURE. 49 
 
 restore sensation by violent friction, and by other expedients, 
 but in vain 1 . 
 
 COLLISION is another means of procuring fire. When fire is 
 produced by COLLISION, particularly when flint and steel are the 
 media, it arises from the sudden extrication of the latent caloric 
 which is forced out by percussion, then becoming free and per- 
 ceptible to our senses. It was first suggested by Mr. Hume 2 , 
 and his opinion is now found to be correct, that oxygen exists in 
 a very large proportion and in a most condensed state in flint and 
 all other siliceous stones. Were I, therefore, to hazard a theory 
 upon the phenomena that take place in this instance, I should 
 say, the latent caloric thus set free had been previously com- 
 bined with the steel, and perhaps with this condensed oxygen ; 
 and that the new compound, the spark which flies off, and is 
 oxide of iron, requiring less latent heat for its composition, per- 
 mits what is now superfluous to become free and active, and to 
 pass to the tinder, gunpowder, or any other combustible sub- 
 stance to which it may be exposed. 
 
 This application of flint and steel to each other has lately been 
 employed not only for procuring fire, but for another very im- 
 portant purpose. 
 
 The late Mr. Spedding, who was an engineer to some large 
 collieries in the North of England, having observed that the coal- 
 damp could only be kindled by flame, and was not liable to be 
 set on fire by red-hot iron, invented a machine, in which, while 
 a steel wheel is turned round with very rapid motion, flints are 
 applied to it, and by the abundance of sparks emitted, the miners 
 are enlightened, and enabled to carry on their work in places 
 where the flame of a lamp or candle would be likely to occasion 
 dreadful explosions. Without some invention of this sort, the 
 working of such mines would have been utterly impracticable 3 . 
 
 PHOSPHORUS may be mentioned as another agent by which 
 fire may be produced extemporaneously, at any hour and in any 
 
 1 Phil. Trans, vol. xlviii. page 765, and vol. xlix. page 61. 
 
 When RICHMAN rear'd, by fearless haste betray' d, 
 The wiry rod in Nieva's fatal shade ; 
 Clouds o'er the Sage with fringed skirts succeed, 
 Flash follows flash, the warning corks recede j 
 Near and more near HE eyed with fond amaze 
 The silver streams, and watch'd the sapphire blaze ; 
 Then burst the steel, the dart electric sped, 
 And the bold Sage lay number'd with the dead ! 
 
 2 In the first edition of The Chemical Catechism, 8vo. 1806, page 151, and 
 Philosophical Magazine, vol. xxx. page 165. 
 
 3 A more particular account of this expedient may be seen in The Trades- 
 man's Magazine, vol. ii. page 445. 
 
50 ON TEMPERATURE. 
 
 season. All that is necessary is to rub a few grains of it for 
 a second or two, with a match or other small piece of wood, 
 upon a piece of cork, when inflammation will quickly take place, 
 and continue till the whole of the phosphorus be consumed. 
 This peculiar substance is chiefly of animal origin, though it be 
 still doubtful whether it is not originally derived from the mine- 
 ral kingdom, and thence passes to vegetables, and so on to the 
 animal system, where it is most abundant. 
 
 Phosphorus was discovered either by Brandt or Kunkel about 
 the year 1669. The product of its combustion is either phos- 
 phorous or phosphoric acid, according to the quantity of oxygen 
 absorbed, and to the mode in which the combustion has been 
 conducted. 
 
 Fire may also be procured with great facility from a saline 
 compound called CHLORATE OF POTASH, formerly HYPER-OXY- 
 MURIATE OF POTASH. If this salt be intimately mixed with any 
 of the highly combustible substances, and the salt be then de- 
 composed, fire and combustion will be the consequence. 
 
 A preparation of this sort may very conveniently be made by 
 mixing some of the salt with about an equal portion of loaf sugar, 
 both in fine powder. This is a mixture which may be kept ready 
 prepared and preserved in a phial for any length of time, with 
 perfect safety. Whenever fire is required, all that is necessary 
 is to put a few grains of this mixture upon a bit of tile or on a 
 plate, and then to drop upon it the most minute quantity of con- 
 centrated sulphuric acid, which will occasion an immediate burst 
 of flame, increasing in size until the whole mass enters into actual 
 combustion. 
 
 A composition of this kind has been lately employed instead 
 of sulphur for coating the ends of matches ; and these are more 
 convenient for procuring fire, or an instantaneous light, than any 
 thing which has ever before been offered to the public. In using 
 them, all that is necessary is to dip the coated end of one of them 
 into sulphuric acid, or into a phial of asbestos impregnated with 
 that acid, and it will take fire immediately. The asbestos is put 
 in merely to prevent the acid from spilling, as cotton is put into 
 a common inkstand. The fire in this case is produced in conse- 
 quence of the decomposition of the chloric salt by the sulphuric 
 acid, which seizes the base of the salt, and liberates the chloric 
 acid, which also becomes decomposed, and occasions this curious 
 phenomenon. 
 
 By mixing this salt with other combustibles, such as sulphur 
 and charcoal, in proper proportions, a preparation will be formed 
 which will inflame merely by percussion or friction; and an 
 ingenious Scotch chemist, the Rev. Alexander Forsyth of Bel- 
 
OF ARTIFICIAL TEMPERATURE. 51 
 
 helvie, has taken advantage of this property of the chlorate of 
 potash, and employed it in the manufacture of a new kind of gun- 
 powder, for which he obtained a patent, and which, for priming 
 the guns of sportsmen and some other purposes, is preferable to 
 common gunpowder. An eighth of a grain of it is sufficient for 
 priming a fowling-piece or a musket, and this of itself makes 
 a very loud report '. Before Mr. Forsyth obtained his patent, 
 M. Berthollet had proposed to manufacture gunpowder with this 
 salt for the use of the French army; but no sooner did the work^ 
 men begin to triturate it than it exploded violently, and occasioned 
 the death of several persons. Notwithstanding this accident, 
 gunpowder made with chlorate of potash was some time after- 
 wards employed by the French army in one of their campaigns. 
 
 To these methods of procuring fire may be added that of 
 COMPRESSION. It is a general maxim in chemical science, that 
 extension and rarefaction occasion cold, but that condensation 
 and compression generally produce heat. 
 
 This principle is well exemplified in a machine erected at one 
 of the mines in Hungary. In this apparatus the air within a large 
 cylinder is very forcibly compressed by a column of water 260 
 feet high. Therefore, whenever a stop-cock which is attached to 
 the lower part of the cylinder is opened, the compressed air 
 rushes out with great violence, and its expansion is so sudden 
 and considerable that the moisture which was contained in the 
 compressed air is immediately condensed, and falls in a shower of 
 snow. PhiL Trans, vol. lii. page 547. 
 
 Some time ago a soldier in the French army discovered that 
 light and heat may be produced merely by the compression of 
 atmospheric air. This curious discovery has been acted upon in 
 various parts of Europe, and is likely to become applicable to a 
 variety of purposes. By adapting a moveable air-tight cap to 
 the bottom of a common syringe, and placing within it a small 
 piece of perfect tinder, and then depressing the piston with a 
 sharp quick motion, heat will be produced sufficient to inflame 
 the tinder. The use of the screw cap at the end of the syringe, 
 is not only to render the instrument air-tight, but for the purpose 
 of receiving the fungus or the tinder to be placed within it. 
 
 These syringes are now sold by most of the philosophical- 
 instrument-makers in London ; and since their exhibition, it has 
 been proposed to make walking-sticks furnished with similar sy- 
 
 1 A more particular account of this new gunpowder, and which T received 
 myself from the patentee, will be found in The Chemical Catechism, Addi- 
 tional Notes, No. 56 : and an account of several curious experiments with the 
 chlorate of potash, will be found in the twelfth edition of the same work, pages 
 191 and 505. 
 
 E 2 
 
52 ON TEMPERATURE. 
 
 ringes, (though for this purpose these syringes must be inverted,) 
 and so contrived that a single stroke of the walking-stick on the 
 ground would be sufficient to inflame the tinder, and afford the 
 traveller a light in any emergency. 
 
 There is another mode of procuring fire, viz. by PERCUSSION. 
 Nothing is more common in some countries, where fuel is dear 
 and fires are not kept up during the night, than for a smith to 
 procure a light in the morning by laying a bar of iron across an 
 anvil and hammering it incessantly till it become hot enough to set 
 fire to tinder. Here, a portion of the caloric which is naturally 
 latent in the iron, and tends to give it malleability, is forced out by 
 the continued hammering, and becomes free and efficient heat. 
 
 FRICTION, which seems to be only a succession of percussions, 
 will also produce intense heat. Mr. Thomas Wedgwood held 
 the edge of a piece of window-glass against the surface of a re- 
 volving grit stone, and the part in contact with the stone became 
 red hot and threw off particles which fired gunpowder. Philos. 
 Trans, for 179^, pages 4-5 and 270. Since then Count Rumford 
 suspended a metallic cylinder within a quantity of cold water 
 measuring eighteen pints, and caused it to revolve, pressing 
 against a boring instrument, at the rate of thirty times in a mi- 
 nute ; and in the course of two hours and thirty minutes it ge- 
 nerated heat enough to make the water actually boil. Phil. 
 Trans, for 1 798, page 80. 
 
 It is also possible to produce combustion by the mere MIXTURE 
 of some fluids. Thus, if certain proportions of nitrous and sul- 
 phuric acid be poured into the essential oil of turpentine, a rapid 
 combustion and inflammation will be occasioned. This, however, 
 is not a very safe experiment, unless it be conducted with cau- 
 tion and prudence. 
 
 It may also be mentioned, that if either POTASSIUM or SODIUM 
 be placed upon ice, fire will be produced, and the metal by this 
 combustion will be converted to an alkali. 
 
 Combustion often occurs spontaneously by the DECOMPOSITION 
 OF WATER ; of this we have many instances. Hay, clover, weld, 
 or other vegetables, if put up in ricks before they are properly 
 dried, are very apt to ferment, and occasion spontaneous combus- 
 tion. Substances that are thoroughly impregnated with animal 
 or vegetable oil, when laid up damp and in large heaps, are also 
 very likely to take fire of themselves from the decomposition of 
 the water and the oil. This happens sometimes to painted oil- 
 cloths, and likewise to woollen cloths ', which have been laid up 
 
 1 There is a singular account of the spontaneous decomposition of a fabric 
 of silk, in the Philosophical Magazine, vol. xvi. page 92. 
 
OF ARTIFICIAL TEMPERATURE. 53 
 
 moist, and in heaps, without having the oil removed which had 
 been employed in dressing them. There are also examples of 
 cotton taking fire by being improperly laid up 2 ; and the spon- 
 taneous firing of a mixture of lamp-black and oil is well known 3 . 
 I believe it is also no very uncommon thing for buildings to be 
 burnt down in consequence of quick lime being incautiously 
 stored in them, and water getting access to it. 
 
 Again, peat laid up in very large heaps for fuel is disposed to 
 take fire; and in coal countries it is universally known that if 
 pyritous coal be stacked without having the martial pyrites pre- 
 viously picked out, there is great danger that the first shower of 
 rain may produce heat enough to set fire to the whole mass 4 . 
 
 This combustion of pyritous coal is probably the cause of 
 many of the subterranean fires which appear in every quarter of 
 the globe. Near Baku in Persia, the inflammable vapour which 
 issues from the earth is so considerable that the inhabitants burn 
 their lime by its means. There is a caravansary built on the spot, 
 and in this live twelve Indian priests and other devotees who wor- 
 ship this fire, which, according to their traditions, has burnt many 
 thousand years. " It is a very old vaulted building, and in its walls 
 are many chinks, whereto if a candle be applied, the fire catches 
 instantaneously, and runs wherever the chinks communicate. 
 They have hollow places in the house fitted to their pots, where 
 they boil without any other fuel; and instead of candles they 
 stick reeds into the ground, from the tops whereof, upon apply- 
 ing fire thereunto, a white flame comes forth, and continues to 
 burn without consuming the reeds, until they think proper to 
 extinguish it, by putting little covers over them for that purpose." 
 Phil. Trans, vol. xlv. page 296. Other curious particulars re- 
 specting this subterranean fire may be seen in Mr. Jonas Han- 
 way's Account of Ids Travels through Persia. 
 
 JDr. Plot speaks of a district near the Staffordshire collieries 
 which was on fire in his time 5 . This spot I have myself visited 
 
 8 Dr. Henry accounts for the fires which have sometimes happened in cot- 
 ton-mills, from the waste cotton, employed to wipe the oil from machinery, 
 having been laid in heaps sufficiently large to occasion combustion. Henry's 
 Chemistry, vol. ii. page 162. 
 
 3 There have been instances in which carburetted earths, being mixed with 
 linseed oil for the purpose of making paints, entered spontaneously into a state 
 of combustion. Gentleman's Magazine, vol. xxi. page 71, and Vol. xxii. page 82. 
 
 4 Dr. Plot relates the case of a person at Ealand in Yorkshire who piled se- 
 veral cart-loads of martial pyrites in a barn, of which the roof being faulty, the 
 rain came upon them, set fire to the building, and occasioned an alarm for the 
 safety of the whole town. Plot's Staffordshire, page 142. 
 
 Dr. Jorden mentions that a heap of coals once took fire at Puddle Wharf, 
 London, in consequence of pyrites being mixed with them. Jorden On Mine- 
 ral Waters, chap. 14. 
 
 b Plot's History of Staffordshire, chap. iii. page 141, 53. 
 
 
54? ON TEMPERATURE. 
 
 more than once, and the mass of coal within the bowels of the 
 earth is still burning, and probably will not cease for ages yet to 
 come. The poor inhabitants of that neighbourhood call it 
 foejiery ground^ and felicitate themselves in living so near it, as 
 many of them make considerable sums of money, early in the 
 year, by the produce of their gardens, which are always some weeks 
 forwarder than any other in that part of the kingdom. Some 
 of the esculent vegetables flourish surprisingly on this spot. 
 
 There is a fountain near Grenoble in Dauphine ; another in 
 Transylvania; a third near Chermay, a village in Switzerland; 
 a fourth in the canton of Friburg; and a fifth not far from Cra- 
 cow in Poland, the waters of which give out gases that will take 
 fire and burn. Campbell's Political Survey, vol. i. page 73. 
 
 I have mentioned elsewhere that His Majesty's ship Ajaxis 
 supposed to have been destroyed in the Mediterranean entirely 
 by the sudden combustion of a heap of pyritous coal, then on 
 board for the use of the ship. I also noticed that a friend of mine 
 had a serious accident from the spontaneous inflammation of a 
 mixture of hyperoxymuriate of potash, charcoal, and sulphur. 
 
 All such accidents may be explained, by referring them to the 
 decomposition of water, and the inflammation of its hydrogen. 
 But there are instances on record of another kind of sponta- 
 neous combustion, which is not so well understood, viz. that of 
 the human body absorbing oxygen with such rapidity as that the 
 whol^ became silently consumed to ashes ' ; and this, indepen- 
 dently of any outward agent, to which the commencement of the 
 combustion could possibly be attributed. 
 
 Several cases of this kind have been described and well authen- 
 ticated ; though it is remarkable that this has never been known 
 to have happened to any but females, and all these were persons 
 who had long indulged themselves in an inordinate use of spiri* 
 tuous liquors 2 . 
 
 The means which have been employed in different parts of the 
 world for MODIFYING the effects of HEAT AND COLD, have been so 
 various, that I can only attempt to enumerate a very small pro- 
 portion of them. But I shall select those which 1 do not consi- 
 der to be very generally known, or such as may probably be 
 applied, though in a different way, to some useful purpose in this 
 country. 
 
 1 There is an account of a great variety of cases of spontaneous combustion, 
 in the 18th volume of the Phil. Mag. extracted from a memoir by Mons. Bar- 
 tholdi in one of the volumes of the Annales de Chimie. 
 
 2 The curious case of the Countess Cornelia Zangari, also of Baridi of Ce- 
 sena, of Grace Pet at Ipswich, whose body is said to have been burnt to a cin- 
 der, and of a woman at Paris, may all be seen in The Gentleman* s Magazine, 
 Vol. vi, page 647, and The Philosophical Transactions, vol. xliii. page 447. 
 
OF ARTIFICIAL TEMPERATURE. 55 
 
 If we begin with that part of the subject which refers to the 
 MODIFICATION of HEAT, or the reduction of temperature, it must 
 be remarked that this is often effected on different principles, ac- 
 cording to situation and circumstances. 
 
 In some cases the principle of producing cold by EVAPORATION 
 is resorted to. Thus in India, where the apartments are sepa- 
 rated from their courts by curtains instead of walls, slaves are 
 employed in perpetually sprinkling these curtains with water, the 
 evaporation of which, when constantly kept up, will reduce the 
 temperature of the rooms ten or fifteen degrees. 
 
 The alcarazas of Spain for cooling wine act on the same prin- 
 ciple. These, which are very porous earthen vessels, are pre- 
 pared for use by soaking them in water for a considerable time, 
 so as to saturate them with that fluid. Within these earthen jars 
 vessels containing the wine are introduced, and the perpetual 
 oozing and evaporation of the water cool the interior of the 
 vessel, and consequently reduce, in some measure, the tempe- 
 rature of the wine or other liquor placed within it. 
 
 These, however, at least all that I have seen, are ill calculated 
 for the purpose ; for, being so much larger than necessary, a 
 sheet of air of the temperature of the room envelops the wine 
 bottle, and prevents the proper action of the alcaraza upon it; 
 whereas, if they were made perfectly cylindrical, instead of being 
 bulged, and no larger than just sufficient to admit a bottle of 
 wine within them, they would be much better refrigerators than 
 those which are usually sold for this purpose. 
 
 This principle of cooling by evaporation is well understood by 
 the caravans who cross the great desert of Arabia. These peo- 
 ple have occasion for a large quantity of water, which they carry 
 with them on camels, in bottles of earthen-ware, and which, in 
 passing over the burning sands of that country, would become 
 very disagreeably hot, were it not for the following expedient, 
 which is universally adopted by them. When they lay in their 
 stock of water, each bottle is infolded in a linen cloth, and some 
 of the company are appointed to keep these cloths constantly 
 wet during the journey; by which means a perpetual evaporation 
 is produced, and the contents of the bottles are preserved at a 
 cool and refreshing temperature. Athenseus relates, that in Egypt 
 the pitchers filled with water, which had become warm by stand- 
 ing all day long in the sun, were kept continually wet during the 
 night by servants destined to that office ; and in the morning, to 
 preserve the water at the cool temperature to which this expedient 
 had reduced it, the pitchers were bound round with straw. The 
 Deipnosophists, iii. page 124. 
 
 In like manner, in the nights in Bengal, when the temperature 
 is not below 50, by the exposure of water in earthen pans upon 
 
56 ON TEMPERATURE. 
 
 moistened bamboos, thin cakes of ice are formed, which are 
 heaped together and preserved under ground by being kept in 
 contact with bad conductors of heat. 
 
 In performing some delicate chemical experiments, the appli- 
 cation of this principle may be found extremely useful. Thus, 
 any fluid body which has been heated by mixture or otherwise, 
 may, in a few minutes, be brought to the desired temperament 
 by frequently wetting the containing vessel with ether, which, 
 by the rapidity of its evaporation ', and consequent abstraction 
 of caloric, instantly lowers the temperature. 
 
 Should any one doubt the efficacy of evaporation in producing 
 cold, let him suspend a thermometer in the air, and, having wet 
 the bulb with ether once or twice, notice its operation as indi- 
 cated by the scale of the instrument. 
 
 Evaporation is also a drying as well as a cooling process. 
 When I have wanted a bottle in haste to be thoroughly dry, for 
 taking specific gravities or any other nice philosophical purpose, 
 after washing it with water, and draining that out as well as I 
 could, I have rinsed it with a little ether, and it has been dry in 
 an instant. 
 
 But the more ancient, and perhaps the most universal mode of 
 reducing the temperature of bodies, was by means of ICE and 
 SNOW. That these were used for this purpose in the time of 
 Solomon, we have the testimony of some of the most ancient 
 writings 3 ; and we are told that Alexander the Great, when he lay 
 before the besieged city of Petra, having an eye to the delicacies 
 of his table, caused thirty trenches to be dug, and filled with 
 snow, which was defended from the sun by oak branches, and 
 preserved for a long time in the state required 3 . 
 
 The celebrated Abbe Nollet, who drew up a memoir on the 
 means of supplying the want of ice in warm countries, advises 
 the keeping of wines and other potable liquors in the following 
 manner, in preference to keeping them in wells, cisterns, or 
 cellars. He recommends the digging a hole in the earth about 
 four feet deep, in which the liquor should be placed in bottles, 
 covering them over with a foot of earth, dug from the bottom of 
 the hole, and moistened with a little water, after which he advises 
 the covering up the mouth of the hole with a plank, strewed over 
 with new dug earth 4 . In adopting this method, it will be essen- 
 
 1 For an account of an expeditious mode of producing ice by the evaporation 
 of sulphuric ether, see Phil. Trans, for 1795, or Monthly Review, New Series, 
 vol. xxi. page 299. 
 
 2 " As the cold of snow in the time of harvest, so is a faithful messenger to 
 them that send him : for he refresheth the soul of his masters." Proverbs xxv. 13. 
 
 3 Aihencei Deipnos. iii. 124. Beckman, vol. iii. page 344. 
 
 4 History of the Royal Academy of Sciences at Paris, for the year 1 756. 
 
OF ARTIFICIAL TEMPERATURE. 57 
 
 tial not only that the liquor should be put into the thinnest bot- 
 tles, but also that these should be of such a form as to afford the 
 greatest quantity of surface to the refrigerating agent. Hence 
 several thin glass bottles will be much better than one larger 
 bottle of thick glass. 
 
 Ice and snow in hot countries being applicable to so many 
 useful purposes, it was natural for mankind to devise some expe- 
 dient whereby they might have these articles in all seasons. 
 Hence ice-houses were built, but the era of their invention is not 
 known. That the ancient Romans were acquainted with them is 
 evident from the writings of Pliny, who passes this severe cen- 
 sure upon them : 
 
 " Hi nives, illi glaciern potant, pcenasque montium in volup- 
 tatem guise vertunt : servatur algor aestibus, excogitaturque ut 
 alienis mensibus nix algeat 5 ." 
 
 It appears, however, that the practice of cooling liquors, at 
 the tables of the great, was not usual in any country of Europe, 
 excepting in Italy and the neighbouring states, before the end of 
 the sixteenth century : and there is a direct testimony on record, 
 that in the middle of that century there were no ice-cellars in 
 France 6 . However, before the end of the seventeenth century 
 the luxury of ice was very common in France ; for about that 
 timeUhere were many persons who were professed dealers in 
 snow and ice; and Quintine, the celebrated French gardener, 
 relates that once, when no ice could be procured on account of 
 the great mildness of the preceding winter, the merchants at 
 Hamburg sent a ship to Greenland for a load of it, by which 
 they acquired great profit 7 . In 1676 there were not less than 
 two hundred and fifty shops, in Paris alone, for the sale of li- 
 quors of different sorts cooled with ice 8 . 
 
 In regard to the receptacles for ice, I have not met with any 
 account of the mode in which the ancient Romans constructed 
 their ice-houses, and therefore I can give only a few particulars 
 respecting the modern practice. 
 
 At Leghorn and in other places in that neighbourhood, they 
 lay the bottom of their ice-pits with a thick covering of corn 
 chaff; and as the ice is placed within them, the chaff is brought 
 up all round the sides, and when the pits are full they are well 
 covered up with the same article. Whenever it is necessary to 
 
 5 Lib. xix. c. 4. Martial in one of his epigrams sports with it thus : 
 
 " Non potare nivem, sed aquam potare rigentem 
 De nive, commenta est ingeniosa sitis." 
 
 MART. xiv. Ep. 117. 
 
 6 Beckman's History of Inventions, vol. iii. page 356. 
 
 7 Instruction pour les Jardins, Paris, 1 730, 4to, i. p. 263. 
 
 8 Beckman, vol. iii. p. 362 and 378. 
 
58 ON TEMPERATURE. 
 
 remove any of the ice to a distance from these pits, it is infolded 
 in similar chaff; and is thus preserved from melting. Phil. 
 Trans, vol. i. page 139. 
 
 Sir Robert Barker has given a very particular account of the 
 method of making ice at Calcutta and other parts of the East 
 Indies lying between C 25\ and 23^ degrees north latitude* where 
 natural ice is never seen. But I shall refer my readers to the 
 paper itself for particulars ! ; and also to any of the modern En- 
 cyclopedias for an account of the present mode of building ice- 
 houses in England, as a full description of them is not compati- 
 ble with my present plan. 
 
 Olearius, in an account of his journey to Muscovy and Persia, 
 relates that at Ispahan the inhabitants have conservatories, which 
 they furnish with solid pieces of ice of a good thickness, only by 
 pouring water at night, at certain intervals, upon a sloping floor 
 of freestone or marble, where it becomes frozen and attached to 
 the former coat of ice, and in two or three successive nights is 
 brought to a very considerable thickness. 
 
 The late Mons. Fourcroy, when treating of temperature, re- 
 marks, that " chemists often avail themselves of the privation 
 of caloric, in order to prevent the effect of chemical action ; to 
 impede the too powerful energy of solutions, combinations and 
 decompositions ; or to prevent those spontaneous changes which 
 do not fail to take place in certain compounds, if they remain for 
 a time exposed to a temperature sufficiently elevated to favour 
 the mutual action of their principles. By these means, namely, 
 by a cold temperature, vegetable and animal substances are pre- 
 served ; and thus it is that an ice-house is scarcely less useful to 
 the chemist than a furnace at its different degrees of heat. 
 
 " In Tibet the inhabitants adopt the practice of preparing their 
 meat by extreme cold. The process is extremely simple. They 
 kill, clean, and strip the animal of his skin ; he is then placed 
 upon his legs in a commodious place, and left exposed to a free 
 access of frosty air, until all the juices in his body are completely 
 dried up, and the whole becomes one uniformly stiffened sub- 
 stance. It is then in a fit state for carriage to any part of Tibet, 
 and for keeping to any season of the year. No salt is used in 
 the preparation. I had supplies of this prepared meat, during 
 all the time I remained at Teshoo Loomboo, which had been 
 cured in the preceding winter. It was perfectly sweet, and I was 
 accustomed to eat heartily of it, without any further dressing, 
 and at length grew fond of it. It had not the appearance of 
 being raw, but resembled in colour that which has been well 
 boiled. It had been deprived of all ruddiness, by the intense cold 2 . 
 
 1 Phil. Traits, vol. Ixv. page 2,52. 
 
 a Turner's Embassy to Tibet, 4to, London, 1806, p. 301. 
 
OF ARTIFICIAL TEMPERATURE. 59 
 
 Captain James, whose ship was frozen up all the winter in one 
 of the coldest regions of the world, writes thus : " We got up 
 our five barrels of beef and pork, and had four butts of beer and 
 one of cyder, which God had preserved for us : it had lain un- 
 der water all the winter, yet we could not perceive that it was 
 any thing the worse 3 . 
 
 As it is well known that some decompositions take place at a 
 temperature below 32, which cannot be effected at one more 
 elevated, it might be worth while for a chemist who has access 
 to an ice-house, to institute a series of experiments, in order to 
 determine the affinities of the simple substances, and some of 
 their compounds, when submitted to the action of intense cold. 
 
 Ice-houses are also employed with advantage by many of our 
 butchers during the summer months in preserving meat 4 . The 
 Hon. Mr. Boyle relates that the physician to the Emperor of 
 Russia assured him that he had had the venison of elks sent him 
 unsalted, and yet untainted, out of Siberia, which is some hun- 
 dreds of leagues distant from Moscow, and that beef and other 
 flesh well frozen would keep for a very long time uninjured ; and 
 that it will have lost none of its natural flavour, provided it be 
 very gradually and thoroughly thawed, before it be dressed for 
 the table 5 . 
 
 We know that from the salmon fisheries in Scotland and the 
 north of England, the fish are sent to the metropolis, during the 
 greater part of the season, packed with ice, in boxes about four 
 feet long and eighteen inches deep. When packed, the ice, 
 which is previously broken as small as bay-salt, is put over them 
 and beaten down as hard as can be without bruising the salmon. 
 In this manner they are kept perfectly fresh for two or three 
 weeks. 
 
 There is another way of modifying heat which has not yet 
 been adverted to, and which is comparatively of late invention. 
 I refer to the use of certain SALINE BODIES, which absorb a large 
 portion of caloric during their solutions, and consequently pro- 
 duce a great degree of cold. 
 
 The salt which was originally used for this purpose was nitre, 
 and the Italians were the first people by whom it was employed. 
 About the year 1550, all the water as well as the wine drunk at 
 the tables of the great and rich families at Rome was cooled in 
 this manner. It was customary to place the bottle containing 
 the wine within a larger vessel of water, and into this they gra- 
 
 3 T. James's Journal, page 74. 
 
 4 " At Spitzburg the extreme cold will suffer nothing to putrefy and corrupt, 
 insomuch that buried bodies are preserved entire for thirty years, and invio- 
 Jated by any rottenness." Bartholinus dc Usu Nivis, cap. xii. 
 
 b Experiment? on Cold, 4 to, London, 1683, page 85. 
 
60 ON TEMPERATURE. 
 
 dually put as much saltpetre as is equal to one-fourth or one- 
 fifth of the weight of the water, and during its dissolution the 
 bottle was driven round by the hand with a quick motion on its 
 axis, in one direction 1 . 
 
 After this, other salts were employed; and Lord Bacon, who 
 died in 1626, asserted that, by a mixture of snow with common 
 salt 2 , he could freeze water 3 . In the Mineralogy of Aldrovandus, 
 first printed in 164-8, it is said "that it was usual in countries 
 where fresh water was scarce, to make deep pits in the earth s to 
 throw rock-salt into them, and to place in them vessels filled 
 with water, in order that it might be cooled." 
 
 When snow is mixed with common salt, both substances soon 
 become in some measure liquid*. Now it is well known that 
 solids can never become fluid without heat being absorbed, and 
 consequently cold produced: therefore the abstraction of that 
 portion of free caloric from the materials which is necessary to 
 produce fluidity*, is sufficient to account for the formation of ice 
 in a fluid that is immersed in it. 
 
 Towards the latter end of the seventeenth century, Mr. Boyle 
 made experiments with various kinds of salts and other substances 
 for reducing the temperature of water, and in the year 1683 
 published his " Experiments and Observations touching Cold ; " 
 a work of great labour and ingenuity 6 . By these researches he 
 discovered that either common salt, alum, vitriol, sal ammoniac, 
 lump-sugar, oil of vitriol, nitrous acid, caustic ammonia, or al- 
 cohol, when mixed with snow, had the power of freezing water, 
 and thus laid the foundation for the modern discoveries respect- 
 ing frigorific mixtures. 
 
 About this time the use of a mixture of snow and common 
 salt had become very common in several countries in Europe. 
 It was by a mixture of this sort that Fahrenheit, in the year 
 1710, fixed the zero of his thermometer, supposing this was the 
 extreme point of cold, but a long period intervened before any 
 
 1 Beckraan, vol. iii. page 363. 
 
 2 The iced creams are now, T believe, usually made by plunging the vessel 
 of cream into a mixture of bruised ice and common salt. 
 
 3 Historia Vita et Mortis, 44. Silva Silvarum, cent. i. 83. 
 
 4 The windows in Russia are frequently covered with frost, and it is a 
 common practice to clean them with salt. By rubbing the glass with a sponge 
 dipped in common salt, the ice quickly dissolves, and the glass becomes imme- 
 diately transparent. 
 
 5 Mr. Boyle so early as the year 1683 noticed that no salt mixed with snow 
 would produce ice, " unless it helps the snow to dissolve faster than else it 
 would." History of Cold, title i. 13. 
 
 6 He describes how snow may be made artificially ; he also speaks of a use- 
 ful syphon which may be made with ice. Additional Experiments, pages 14 
 and 16. 
 
OF ARTIFICIAL TEMPERATURE. 61 
 
 facts of importance were added to those which Mr. Boyle had 
 published on this subject. 
 
 The art of making ice was for many years practised only as 
 an amusement, and no one suspected that it would ever be ap- 
 plied to such important purposes, both of science and luxury. 
 Like gunpowder, and many other valuable discoveries, it was at 
 first considered to be of very trifling consequence. 
 
 Some modern demonstrators in anatomy have availed them- 
 selves of the use of frigorific mixtures in the dissection of the 
 brain and the eyes of animals. To the great Boyle they are 
 probably indebted for the idea ; for in his History of Cold he 
 says, " Many years since, I made an experiment of freezing the 
 eyes of oxen and other animals, whereby the fluid humours of 
 that admirable organ may be so hardened, as to become tracta- 
 ble, even to unskilful dissectors. So I did with the brains of 
 animals, which, though too soft to be easily dissected, may by 
 congelation be made very manageable 7 . 
 
 In the beginning of the seventeenth century, drinking cups 
 made of ice 8 , and iced fruits, were brought to table ; and before 
 its conclusion the French began to congeal all kinds of well- 
 tasted juices, which were served up as refreshments at the tables 
 of the great and wealthy. 
 
 In the year 1621 Barclay's Argenis, an interesting romance, 
 was published at Paris, and its author places on the table of Juba, 
 in the middle of summer, fresh apples for Arsidas, one half of 
 which were incrusted with transparent ice. A bason of ice filled 
 with wine was also handed to him, and he was informed that to 
 prepare all these things in summer was a new art. " Two cups," 
 says the author, " made of copper were placed the one within the 
 other, so as to leave a small space between them, which was filled 
 with water: the cups were then put into a pail, amidst a mixture 
 of snow and unpurified salt coarsely pounded, and the water, in 
 three hours, was converted into a cup of solid ice, as well formed 
 as if it had come from the hands of the pewterer." 
 
 A few years after the publication of the book just mentioned, 
 a new beverage was introduced, called lemonade, which soon 
 came into high repute, and was recommended by physicians 
 against putrid diseases. About the year 1660 an Italian from 
 Florence, having learnt a process of freezing confectionery, which 
 had been before employed only by jugglers, conceived the happy 
 idea of converting such beverage entirely into ice. This found a 
 ready sale, and was the occasion of so great an increase in the 
 
 7 Boyle's History of Cold. Postscript, page 253. 
 
 8 Very easy and simple directions for making ice-cups for drinking of wine 
 in summer, will be found in Mr. Boyle's History of Cold, title xiv. page 137. 
 
62 ON TEMPERATURE. 
 
 number of sellers of lemonade, that in the year 1676 the lemon- 
 adiers of Paris were formed into a company, and received a patent 
 from the Government. 
 
 In the beginning of the next century the process of congealing 
 water by the mixture of salt or nitre with ice and snow was so 
 well known, that it was then become, in Paris and elsewhere, a 
 common amusement for children, who had a trick of placing a 
 jug containing a mixture of snow and saltpetre on a table over 
 which water had been poured, and agitating the mixture with a 
 stick until the jug became firmly frozen to the table. The Duke 
 de Chartres went often to a certain coffee-house in Paris to enjoy 
 a glass of iced liquor. One day, in the year 1774, the landlord, 
 we are told, to the great satisfaction and surprise of the Duke, 
 presented him with his coat of arms formed of eatable ice. 
 
 However, after the investigations of Boyle, no scientific ex- 
 periments on the production of artificial cold seem to have been 
 made till the subject attracted the attention of Dr. Blagden, Mr. 
 Cavendish, Mr. Lowitz, and Mr. Richard Walker, who were at 
 that time separately engaged in the same pursuit. The latter 
 gentleman, however, was the first person who was able to pro- 
 duce ice in the middle of summer, merely by the solution of sa- 
 line substances, without the aid either of ice or snow. 
 
 Having been thus successful, Mr. Walker pursued his expe- 
 riments, and on the 20th of April 1787 actually succeeded in 
 his attempt to freeze mercury. At the commencement of the 
 experiment the temperature of the mercury was 45 ; and as its 
 freezing point is at 39 below zero, he obtained, without using a 
 particle either of snow or ice, a reduction in temperature amount- 
 ing to no less than 84 degrees. 
 
 This experiment, by which mercury was first seen in Great 
 Britain in a state of solidity, was made at Oxford, Mr. Walker 
 being at that time apothecary to the RadclifF Infirmary in that city. 
 The apparatus which he used in this experiment consisted of 
 four pans, progressively diminishing in size, placed one within 
 another, and these, when thus arranged, w r ere all placed in a ves- 
 sel still larger. Some of the materials for producing the reduc- 
 tion of temperature were put in each of these pans, and others in 
 bottles in the spaces between them, so that those in the outer- 
 most pan received, before being put together, the cold produced 
 by the frigorific mixture in the larger vessel ; and those in each 
 of the inner ones received, in like manner, the progressively ac- 
 cumulated cold of the next exterior pan. A more simple and 
 convenient apparatus for freezing mercury has since been con- 
 trived by Dr. Henry, which he describes in his Elements of Che- 
 mistry, plate 4, fig. 42. 
 
 The materials which Mr. Walker employed were strong ni- 
 
OF ARTIFICIAL TEMPERATURE. 63 
 
 trous acid, sulphate of soda, and nitrate of ammonia. Other 
 substances have also been employed for the same purpose, viz. 
 muriatic and sulphuric acids, pure potash, nitrate of potash, 
 muriate of ammonia, sulphate of soda, phosphate of soda, and 
 various other salts. 
 
 It may be observed that the expense of making frigorific mix- 
 tures is trifling, because, in many cases, the salts may be reco- 
 vered by evaporating the water in which they were dissolved. 
 Mr. Walker, who was in the habit of recovering the salt, re- 
 marks that no diminution .was observed in its effect, after many 
 repeated evaporations. 
 
 But the cheapest and most efficacious salt which has been em- 
 ployed for the reduction of temperature is the muriate of lime, 
 which was first used by Mr. Lowitz ; and this when mixt with 
 snow is extremely active in the production of cold. Five parts 
 of this salt well dried, and in the state of crystals, with three 
 parts of snow, sank the thermometer, in Mr. Walker's experi- 
 ment, from 32 to 53, which was a reduction of 85 degrees. 
 The greatest artificial cold which has yet been observed was 
 91, which is 52 lower than the point at which mercury con- 
 geals, and 123 below the freezing point of water. Mr. Lowitz 
 directs, not only that the muriate of lime should be perfectly well 
 dried, but that it should be in that state in which it is crystallized 
 with the largest possible quantity of the water of crystallization, 
 which is effected by putting the solution to cool when of the spe- 
 cific gravity of 1.50 or 1.53. It should be remembered that 
 every frigorific mixture has a certain point of temperature be- 
 yond which it can never act in the production of cold, and this 
 is the point at which the mixture itself becomes frozen. 
 
 The different materials for producing cold may be mixed in a 
 variety of ways; but as several circumstances should be attended 
 to, according to the nature of the articles employed, in order to 
 afford a favourable result, I must refer the reader to Mr. Walker's 
 publication itself for proper instructions. 
 
 Dr. Beddoes has remarked that sulphate of soda, while it re- 
 tains its water of crystallization, produces, on the addition of 
 sulphuric acid diluted with an equal weight of water, 46 degrees 
 of cold ; but when it has fallen into powder by being deprived of 
 its water of crystallization, it produces heat rather than cold; 
 and yet that sal ammoniac and nitre, when well dried in a cruci- 
 ble, "produce a greater degree of cold than if they had not re- 
 ceived this treatment. Where salts of any kind are employed, 
 it is of consequence to have them fresh crystallized, thoroughly 
 dried, and then finely pulverized. The mixtures should be made 
 rapidly, and in vessels as thin as can be procured. 
 
 To this account of the varkms methods of producing ice by 
 
6$ ON TEMPERATURE. 
 
 art, may be added a new mode of effecting the same purpose, 
 which was invented by Dr. Wollaston. 
 
 It is well known that the temperature of liquids is cooled by 
 evaporation, but in close vessels evaporation is limited by the 
 great bulk into which the vapour expands. Dr. Wollaston, in 
 a paper in the Philosophical Transactions, describes an inge- 
 nious contrivance of his, to which he has given the name of 
 CRYOPHORUS, by means of which water may be frozen in close 
 vessels by its evaporation, with great facility. 
 
 " The instrument which he employs is a glass tube, having an 
 internal diameter of about one-eighth of an inch, each extremity 
 blown into a ball, and the tube bent at right angles about half an 
 inch from each ball. One of the balls is filled not quite half full 
 of water. This liquid is boiled for some time to expel the air, 
 and the capillary tube at the extremity of the other ball is then 
 sealed hermetically. If the empty ball of this instrument be 
 plunged into a mixture of snow and salt, the vapour within it is 
 condensed so fast, that the water in the other ball freezes. Ann. 
 Phil. vol. ii. page 230. 
 
 I cannot, however, close this part of my subject, without ad- 
 verting to another philosophical expedient for the reduction of 
 temperature, especially as it is one which has been productive of 
 the most important and beneficial consequences. The discovery 
 to which I refer is connected with the invention of the Miner's 
 Safety Lamp, which has already been alluded to at the close of 
 the first Essay, but which requires to be more particularly ex- 
 plained, now we are enumerating the various ways which have 
 been resorted to for reducing the temperature of bodies by arti- 
 ficial means. 
 
 In the history of mining, nothing has perplexed the proprie- 
 tors of our collieries, or annoyed the workmen, so much as the 
 fire-damp ; and yet many thousand men who had no other way 
 of maintaining their families, were constantly obliged to submit 
 to work in situations of the most imminent danger. It was usual 
 for these poor men to creep with a lighted candle in their hands, 
 inch by inch, as it were, along the galleries of a mine suspected 
 to contain what they call foul air, in order to ascertain its pre- 
 sence, and guard themselves against its dreadful effects. But 
 notwithstanding all their caution, explosions frequently occurred, 
 and the consequences were often of the most melancholy kind. 
 The miners, with the horses and machinery, were sometimes 
 thrown through the shaft into the air, and those individuals who 
 might happen to escape the violence of the concussion, were 
 often gradually suffocated in being obliged to breathe the car- 
 bonic acid gas and azotic gas which always remains in the mine 
 
OF ARTIFICIAL TEMPERATURE. 65 
 
 after such explosions. Great numbers of men and boys are some- 
 times killed on such occasions ; and not long ago no less than 
 ninety-six persons who were working in the Felling colliery were 
 in an instant destroyed by a similar accident. 
 
 These dreadful catastrophes kept the proprietors of our coal 
 mines, and the families of the workmen, in a state of perpetual 
 alarm, and little if any hope was entertained of an effectual re- 
 medy being discovered, until the subject engaged the attention 
 of Sir H. Davy, who undertook to investigate the nature 
 and chemical properties of the fire-damp, for the purpose of 
 endeavouring to arrest its action, and prevent the ravages which 
 it occasioned. . 
 
 In the month of August 1815, Sir H. Davy first turned his 
 attention to the subject, and knowing how desirable it was to find 
 some substitute for the naked candles with which the men had 
 been in the habit of working, he first tried KunkePs, Canton's, 
 and Baldwin's phosphorus, and likewise the electrical light in 
 close glass vessels, but without success. He then constructed a 
 lamp with two valves, so contrived that the valves closed when- 
 ever the lamp was carried into an atmosphere contaminated with 
 fire-damp ; but it was found that this lamp could not be used in 
 explosive atmospheres. 
 
 Having been disappointed in these attempts, he then under- 
 took " a minute chemical examination of the substance with 
 which he had to contend (the fire-damp), and these investigations 
 led him to the discovery of the principles by which explosion 
 and flame may be arrested and regulated ; and by means of 
 which the miner is not only able to subdue and controul, but 
 likewise to render useful, his most dangerous enemy." 
 
 During these experiments, he found that the fire-damp is 
 light-carburetted hydrogen, or hydrogen gas holding carbon in 
 solution ; that it will not explode unless mixed with a portion of 
 atmospheric air; that it explodes with most vehemence when 
 mixed with seven or eight times its volume of air ; that it retains 
 its explosive power when mixed in the proportions of only one of 
 gas to fourteen of air ; and that when the atmospheric air is in 
 greater quantity, the light of a taper merely becomes enlarged 
 when brought within it, and that this effect is perceptible in a 
 mixture of even thirty parts of air to one of gas. He found also, 
 that the fire-damp is much less combustible than other inflam- 
 mable gases ; that it is not exploded by red-hot charcoal or red- 
 hot iron, though iron at a white heat will explode it ; and that 
 " on mixing one part of carbonic acid with seven parts of an 
 explosive mixture of fire-damp, or one part of azote with six 
 parts, their powers of exploding were destroyed." 
 
 In the prosecution of these inquiries he found that it was dif- 
 
66 ON TEMPERATURE. 
 
 ficult to explode the mixture of air and fire-damp in small tubes; 
 and that in tubes of only one-seventh of an inch in diameter, and 
 open to the atmosphere, it could not be inflamed, and especially 
 if the tubes were metallic. 
 
 " In reasoning upon these various phenomena it occurred to 
 him, as a considerable heat was required for the inflammation of 
 the fire-damp, and as it produced, in burning, comparatively a 
 small degree of heat, that the effect of carbonic acid and azote, 
 and of the surfaces of small tubes, in preventing its explosion, 
 depended upon their cooling powers, upon their lowering the tem- 
 perature of the exploding mixture so much that it was no longer 
 sufficient for its continuous inflammation." 
 
 66 This idea led to an immediate result: the possibility of con- 
 structing a lamp, in which the cooling powers of the azote and 
 carbonic acid formed by combustion, or the cooling powers of 
 the apertures through which the air entered or made its exit, 
 should prevent the communication of explosion." 
 
 " I made," says Sir H. Davy, " several attempts to construct 
 safety-lamps which should give light in all explosive mixtures of 
 fire-damp; and after complicated combinations, I at length arrived 
 at one evidently the most simple, that of surrounding the light 
 entirely by wire gauze, and making the same tissue feed the flame 
 with air and also emit light." 
 
 " In plunging a light," continues he, " surrounded by a cy- 
 linder of fine wire gauze into an explosive mixture, I saw the 
 whole cylinder become quietly and gradually filled with flame ; 
 the upper part of it soon appeared red-hot, yet no explosion was 
 produced." 
 
 " It was easy at once to see, that by increasing the cooling 
 surface in the top, or in any other part of the lamp, the heat ac- 
 quired by it might be diminished to any extent ; and I imme- 
 diately made a number of experiments to perfect this invention, 
 which was evidently the one to be adopted, as it excluded the 
 necessity of using glass or any fusible or brittle substance in the 
 lamp, and not only deprived the fire-damp of its explosive powers, 
 but rendered the inflammable gas itself an useful light." 
 
 Omitting the detail of other experiments, it was found that iron 
 wire gauze, composed of wires from one-fortieth to one-sixtieth 
 of an inch in diameter, and containing twenty-eight wires or 
 seven hundred and eighty-four apertures to the inch, was safe 
 under all circumstances; and this material Sir H. Davy was 
 therefore induced to adopt for the construction of lamps for 
 coal-mines. 
 
 In the month of January 1816, these lamps were introduced at 
 some of the large mines in the North of England; and they have 
 been in use, with some few alterations and improvements, ever 
 
OF ARTIFICIAL TEMPERATURE. 67 
 
 since; the utmost confidence being now placed in them by the 
 workmen themselves, as well as by their employers. 
 
 The circumstances which render this lamp an instrument of 
 
 Eerfect safety may be thus stated : " Flame is gaseous matter 
 eated so highly as to be luminous, and that to a degree of tem- 
 perature beyond the white heat of metals or other solid bodies. 
 When an attempt is made to pass flame through a very fine 
 mesh of wire gauze, the gauze cools each portion of the elastic 
 matter that passes through it, so as to reduce its temperature 
 below that degree at which it is luminous ; and the diminution 
 of its temperature is proportional to the suiallness of the mesh, 
 and the mass of the metallic wire." Moreover, the fine wire 
 gauze is not only a conductor but a radiator of heat; conse- 
 quently it possesses great cooling power ; and when by this, or 
 any other means, we cool a body of flame, die effect of cooling 
 it will most certainly be to extinguish it. The wire gauze which 
 encircles the lamp does not prevent the passage of the inflam- 
 mable gas, but it prevents its emission in a state of inflammation; 
 consequently nothing can pass from the interior of a lantern 
 properly constructed, that is, at a temperature sufficiently high 
 to inflame the explosive atmosphere of the mine. The tempe- 
 rature of a metallic body, even when white-hot, is far below that 
 of flame ; therefore, when the wire gauze of die lantern is red- 
 hot, it will abstract heat enough from the flame of the fire-damp 
 to extinguish it before it passes through the meshes. So, if a 
 wire gauze sieve be held over the flame of a common lamp, it 
 will prevent the flame from passing it, although the heated air 
 which passes through will be hot enough to char a piece of paper 
 held above the sieve ; a phenomenon which is precisely similar 
 to that exhibited by the wire gauze cylinder. A very simple 
 experiment for the further illustration of the effect thus produced, 
 has been suggested by Sir H. Davy. "Let," says he, "the 
 smallest possible flame be made by a single thread of cotton 
 immersed in oil, and burning immediately upon the surface of 
 the oil : it will be found to be about one-thirtieth of an inch in 
 diameter. Let a fine iron wire of the one hundred and eightiedi 
 of an inch be made into a circle of one-tenth of an inch in dia- 
 meter, and brought over the flame. Though at such a distance, 
 if it be cold, it will instantly extinguish the flame : but if it be 
 held above the flame, so as to be slighdy heated, the flame may 
 then be passed through it That the effect depends entirely 
 upon the power of the metal to abstract the heat of the flame, is 
 shown by bringing a glass capillary ring of the same diameter 
 and size over the flame : diis being a much worse conductor of 
 heat, will not extinguish it even when cold." 
 
 To pursue the histpry of the discovery and improvement of 
 
 F 2 
 
68 ON TEMPERATURE. 
 
 the safety-lamp, it must be observed, that twelve months after 
 its first adoption by the miners, viz. in January 1817, an impor- 
 tant practical addition was made to it, founded entirely upon a 
 new principle. Sir H. Davy having been told that the perfect 
 safety which attended the use of his lamp, often induced the men 
 to go into more explosive atmospheres than they otherwise would, 
 and that this sometimes occasioned the lights to be extinguished, 
 the genius of our philosopher enabled him, by means of the metal 
 called platinum, to obviate the inconvenience in the most com- 
 plete manner possible. Knowing that platinum has a small ca- 
 pacity for, and is a very slow conductor of heat, in which respects 
 it is not at all analogous to any of the other metals except palla- 
 dium, it occurred to him, that upon those properties of this 
 metal he might found the improvement he was in search of. 
 Pursuing this idea, he contrived to suspend a coil, or little cage 
 of small platinum wire, from one-sixtieth to one-seventieth of an 
 inch in thickness, over the flame of each lamp ; the effect of which 
 is, that the moment the light is extinguished by an increased 
 quantity of fire-damp in the atmosphere, the coil of platinum 
 wire becomes of an intense red heat ; and this affords light enough 
 to enable the men to find their way through the different pas- 
 sages to the entrance of the mine. This alone would have been 
 an important improvement on the original safety-lamp : but 
 this is not all ; for no sooner has the workman arrived at a part 
 of the mine in which the atmosphere is in a state of greater pu- 
 rity, or where it contains less than one-fourth in volume of car- 
 buretted hydrogen gas, than the heated platinum wire of itself 
 re-lights the lamp, and the men are enabled to return to their 
 work without interruption, and in perfect safety. 
 
 There is another advantage attendant on the use of the plati- 
 num, viz. that the red-hot coil of platinum wire consumes the 
 fire-damp within the lantern, and this without flame; yielding 
 only a beautiful light by the ignition of the charcoal, which is 
 one of its component parts. It is also to be observed, that a 
 candle will burn in one of these lanterns made safe with metallic 
 gauze, as well as in the open air ; and that, whenever the fire- 
 damp is so mixed with the external atmosphere, as to render it 
 explosive, the light in the safe lantern will be extinguished, and 
 warning will thus be given to the miners to withdraw from, and 
 to ventilate that part of the mine. Another important circum- 
 stance connected with the use of the safety-lamp is, that the men 
 can never be in any danger with respect to respiration, so long 
 as the platinum continues ignited ; for even this phenomenon 
 ceases when the foul air forms about two-fifths of the volume of 
 the atmosphere ; and before this, it may be breathed without 
 injury. 
 
OF ARTIFICIAL TEMPERATURE. 69 
 
 The action of the platinum wire has been thus described by 
 Sir H. Davy himself: " I introduced (says he) into a wire gauze 
 safe-lamp a small cage made of fine wire of platinum of the one- 
 seventieth of an inch in thickness, and fixed it by means of a 
 thick wire of platinum about two inches above the wick which 
 was lighted. I placed the whole apparatus in a large receiver, 
 in which, by means of a gas-holder, the air could be contami- 
 nated to any extent with coal gas. As soon as there was a slight 
 admixture of coal gas, the platinum became ignited ; the ignition 
 continued to increase till the flame of the wick was extinguished, 
 and till the whole cylinder became filled with flame ; it then di- 
 minished. When the quantity of coal gas was increased so as 
 to extinguish the flame, at the moment of the extinction the cage 
 of platinum became white-hot and presented a most brilliant 
 light, By increasing the quantity of the coal gas still further, 
 the ignition of the platinum became less vivid. When its light 
 was barely sensible, small quantities of air were admitted, its 
 heat speedily increased ; and by regulating the admission of coal 
 gas and air, it again became white-hot, and soon after lighted the 
 flame in the cylinder, which, as usual, by the addition of more 
 atmospherical air, re-kindled the flame of the wick." 
 
 It is also remarkable that the fire-damp and the oxygen of 
 the atmosphere will combine, when in contact with the hot wire, 
 without flame ; and yet produce heat enough to preserve the wire 
 ignited, and to keep up their own combustion ; and this will go 
 on until the inflammability of the mixture is entirely destroyed. 
 A temperature much below ignition is sufficient for producing 
 this curious phenomenon ; and if the wire be taken out of the 
 lantern and cooled in the atmosphere till it ceases to be visibly 
 red, when it is replaced it will again instantly become red-hot. 
 
 At first the miners were very apprehensive respecting the 
 durability of the wire gauze; but time has increased the confi- 
 dence of these men in the apparatus, which has now been in use 
 for five or six years in the most dangerous mines in Britain, and 
 exposed to all circumstances which the variety of explosive mix- 
 tures can occasion. And the idea of the wire gauze burning 
 out is shown to be unfounded; for the carbonaceous matter 
 produced from the decomposition of the oil, tends not only to 
 prevent the oxidation of the metal, but likewise revives any oxide 
 already formed ; and this coaly matter, when the fire-damp is 
 burning in the lamp, chokes the upper apertures of the cylinder, 
 and gradually diminishes the heat by diminishing the quantity 
 of the gas consumed. " I have seen," says Sir H. Davy, "wire 
 gauze lamps in the hands of workmen, which they had used for 
 several months, and which had been often red-hot in explosive 
 atmospheres, and which were still perfect." 
 
 It appears moreover from Mr. Buddie's report, that the brass 
 
70 ON TEMPERATURE. 
 
 collar of the wire gauze cylinders is secured to the bottoms of 
 the lamps by locks, which can only be opened by the lamp- 
 keeper; so that the workmen cannot either by accident or care- 
 lessness expose themselves to danger by separating the wire 
 gauze cylinders from the bottoms of the lamps. 
 
 After finishing their day's work, the colliers bring their Davys 
 (as they call them) to the lamp-keeper's cabin, who, unlocking 
 them, takes the bottoms into his own possession and allows the 
 colliers to take the wire gauze cylinders home for the purpose 
 of cleaning them thoroughly. When the colliers return to their 
 work the following morning, the lamp-keeper, having replenished 
 the lamps with oil and cotton, lights them and screws on their 
 tops, and then examines them with the utmost care, before he 
 delivers them for use; but if the least injury or defect appears 
 in the gauze, or in any other part of a lamp, it is immediately 
 set aside to be repaired, and the person to whom it belongs is 
 supplied with a perfect one. 
 
 The gentleman to whom the public is indebted for the above 
 account concludes another of his reports in the following manner : 
 " It is not necessary," says he, " that I should enlarge upon the 
 national advantages which must result from an invention cal- 
 culated to prolong our supply of mineral coal, because I think 
 they will be obvious to every reflecting mind ; but I cannot con- 
 clude without expressing my highest sentiments of admiration 
 for those talents which have developed the properties and con- 
 trolled the power of one of the most dangerous elements which 
 human enterprize has hitherto had to encounter." 
 
 As some persons, who have no means of conversing with the 
 workmen in mining districts, or of witnessing the action of the 
 lamp in a coal mine, may be gratified in making the experiment 
 for themselves, I shall relate a very simple mode by which the 
 same effect may be produced, though in a different way^lviz. 
 By throwing a little ether into the bottom of a glass or stone 
 jar, the vapour arising from the ether, mixing with the air, will 
 produce what is really an explosive atmosphere, and this, when 
 the lighted lamp is immersed in it, will burn within the wire 
 gauze in a manner exactly similar to the real fire-damp, without 
 inflaming the ether in the bottom of the jar. 
 
 Thus have I given the best account I am able of the discove- 
 ries that led to the invention of the Safety Lamp ; which appears 
 to me to be the most valuable and important instrument that 
 science has presented to the arts since the discovery of the steam 
 engine. 
 
 I have made great use of Sir H. Davy's own account of the 
 progress of his discovery ; and often in his own language * ; and 
 
 1 See an octavo volume entitled " On the Safety Lamp for Coal Miners; 
 with some Researches on Flame. By Sir H. Davy." London, 1818. 
 
OF ARTIFICIAL TEMPERATURE. 71 
 
 I conceive I cannot sum up the whole better than by quoting 
 the paragraph with which he has closed the publication alluded 
 to. " Whatever," says he, " may be the fate of the speculative 
 part of this inquiry, I have no anxiety as to the practical results, 
 or as to the unimpassioned and permanent judgment of the 
 public on the manner in which they have been developed and 
 communicated ; and no fear that an invention for the preserva- 
 tion of human life and the diminution of human misery will be 
 neglected or forgotten by posterity. When the duties of men 
 coincide with their interests, they are usually performed with 
 alacrity ; the progress of civilization ensures the existence of all 
 real improvements; and however high the gratification of possess- 
 ing the good opinion of society, there is a still more exalted 
 pleasure in the consciousness of having laboured to be useful." 
 
 I hope it will not be thought that this detailed account of the 
 invention of the Safety Lamp is misplaced ; I had no idea it 
 would have extended to such a length : but when it is considered 
 that this part of my essay was expressly designed to be employed 
 in " treating of the various expedients for increasing and di- 
 minishing temperature," I trust it will be perceived that it was 
 impossible I could lightly pass over a discovery of such momen- 
 tous interest and importance. 
 
 Having offered these remarks on a variety of expedients for 
 the modification of heat, a few observations on some of the means 
 of guarding against and MODIFYING the effects of COLD, may not 
 be unacceptable to the reader. 
 
 Nature has made choice of several expedients for lessening 
 the power of cold, and moderating the rigour of severe winters. 
 The snow which generally covers the earth at this season is one 
 of these, and it is very efficacious in preserving the earth at one 
 uniform temperature, however cold may be the surrounding at- 
 mosphere. In like manner the atmosphere itself, being a bad 
 conductor of heat, is a great preserver of the earth's temperature. 
 Were it not for the atmosphere, the caloric inherent in the globe 
 would soon pass off and be dissipated in unbounded space. 
 
 The temperature of the human body is uniformly preserved 
 in the same manner. The air which is infolded within our gar- 
 ments prevents the animal heat from passing off, and hence it is 
 that loose clothing is generally warmer than that which is fitted 
 closer to the body. 
 
 There seems to be a living principle in vegetables, in the 
 seeds of vegetables, and in fish, which enables them to resist the 
 effects of cold, and prevents their freezing in temperatures lower 
 than that at which water congeals. For in rivers and other great 
 bodies of water, when the water freezes, the rapidity of the 
 
72 ON TEMPERATURE. 
 
 process is moderated by the water itself giving out a large por- 
 tion of caloric, during the act of freezing. This circumstance is, 
 in a variety of instances, of incalculable benefit to the world, 
 besides shortening the duration of winter, and lessening its 
 severity. 
 
 Dr. Black has an experiment which decisively proves this to 
 be a fact. ".If," says he, " when the air is at 22 we expose to 
 it a quantity of water in a tall glass, with a thermometer in it, 
 and covered, the w r ater will gradually cool down to 22 without 
 freezing. Things being in this situation, if the water be shaken, 
 part of it instantly freezes, and the temperature of the whole 
 rises to the freezing point, so that the water acquires 10 of ca- 
 loric in an instant. 
 
 Man, in different parts of the world, has availed himself of 
 some of these principles, and applied them artificially, either to 
 better his situation with respect to climate, or to aid him in the 
 common operations of life. 
 
 Thus, during the winter at Hudson's Bay, the surface of the 
 lakes and rivers is covered with ice of such great thickness, that 
 no water can be procured without cutting through the ice with 
 axes and wedges, which is a very laborious and tedious opera- 
 tion. As soon, therefore, as the surface of the water which has 
 been laid open has acquired a thin plate of ice, the labourer 
 heaps over it a quantity of snow, which, by being a bad con- 
 ductor of heat, prevents the caloric of the water from passing 
 upwards according to its natural tendency. It is by this expe- 
 dient, that during the remainder of the winter, the inhabitants 
 have only to remove a little of the snow, when occasion may re- 
 quire it, and they have water immediately. In Tibet a different 
 expedient is adopted. " It is the practice of the husbandmen to 
 cover the low lands in the valleys with water, immediately on the 
 approach of winter, which incases their surface with a sheet of 
 ice, and prevents their being stripped of the soil by the violent 
 winds 1 ." 
 
 A traveller of undoubted credit informs me, that the birds 
 killed by the shooting parties during the winter in Hudson's 
 Bay, would be soon frozen if they were carried as is usual with 
 sportsmen in England whilst in quest of a further supply, and 
 that this would occasion much difficulty in removing the feathers. 
 It is, therefore, usual to adopt the following expedient : a hole 
 is made in the snow, and in this the birds are deposited with 
 snow thrown over them, by which means their warmth is pre- 
 served till the party return. 
 
 In some northern regions, where there are fortified places sur- 
 
 1 Turner's Embassy to Thibet, 4to, London, 1806, page 354. 
 
OF ARTIFICIAL TEMPERATURE. 78 
 
 rounded by moats, the inhabitants have staved casks of fish oil 
 into the intrenchments, when they have been afraid of the 
 approach of an enemy, that the oil, thus interposed between the 
 surface of the water and the atmosphere, and being incongeal- 
 able by cold, might protect the subjacent water from freezing, 
 and keep the moats impassable 2 . 
 
 The circumstance of an undisturbed body of atmospheric air 
 defending whatever may be inclosed within it from the accession 
 either of heat or cold, has, of late years, been taken advantage 
 of in a variety of instances. Hence the origin of double doors 
 and double windows, which infold sheets of air between them, 
 and thus preserve the apartments at one uniform temperature. 
 For, as atmospheric air is a bad conductor of heat, the doors 
 and windows guarded in this way neither admit the heats of sum- 
 mer nor the cold of winter, while at the same time they prevent 
 the escape of that genial warmth which it is so desirable to pre- 
 serve in the apartments of the sick and the aged at all seasons. 
 
 In like manner certain culinary utensils are fitted up with 
 double covers of block tin or copper, and in such utensils any 
 fluid will boil sooner than it would in others, and will also be 
 preserved at any particular temperature by the consumption of 
 less fuel than would be required if they were covered only with 
 single covers. By similar contrivances the apparatus in some 
 manufactories is sooner heated and more easily preserved at one 
 and the same temperament. 
 
 Leslie has shown, by direct experiment, the effect of a sheet 
 of air in keeping metallic or other pipes warm which are designed 
 to convey heat ; and at the same time has explained how, by a 
 like expedient, liquids might be preserved in a cool state in hot 
 climates. 
 
 " A cylinder-canister," says he, " of planished tin, two inches 
 in diameter, and of equal height, filled with boiling water, took 
 117' to cool from 30 to 10; but inclosed within a similar canis- 
 ter of four inches in diameter, it required 176' to make the same 
 descent. Another cylindrical canister of four inches, and which 
 took 156' to cool from 20 to 10, required 356' when cased with 
 a similar one of five inches 3 ." 
 
 1 have no doubt but that ice might be transported from place 
 to place in the midst of summer, and preserved for any length 
 of time, if the vessel containing it were, agreeably to Mr. Leslie's 
 proposal, placed within the innermost of a number of tin canisters, 
 which fit one within the other, especially if the outward one were 
 clean and polished. 
 
 2 Olaus Magnus in Historia Gentium Septentrionalium, lib. xi. cap. 20, 21. 
 
 3 Leslie On Heat, 8vo, London, 1804, page 380. 
 
74 ON TEMPERATURE. 
 
 On the same principle Mr. Buchanan has recommended the 
 protecting water-pipes from freezing, by inclosing them in tin- 
 plate tubes, leaving a space of about an inch all round the leaden 
 pipes ! . 
 
 There is a great difference in various substances, in their power 
 of conducting caloric, and this is shown in a remarkable manner 
 in the manufacture of glass ; for when the materials are formed 
 into the state of perfect glass, if the manager of the fire neglect 
 to keep the grate completely covered with coals, a stream of cold 
 air will rise through the bars and strike upon one or more of the 
 crucibles, which it will split or crever, as the workmen call it, from 
 the top to the bottom. But if the materials be not entirely fused, 
 so as to be converted into perfect glass, then this effect will not 
 happen. This is a fact well known to glass-makers, and has 
 always been deemed inexplicable. May it not however be thus 
 explained? The materials of which glass is made have the power 
 of conducting caloric with rapidity; consequently, when the 
 outside of the crucible is suddenly cooled, the caloric from its 
 inner surface can escape among the materials, and allow of its 
 cooling in a degree equal to the cooling of the outside : on the 
 contrary, when the glass is fully formed, it is so bad a conductor 
 of heat that it cannot carry off that which is superabundant ; 
 therefore the crack of the crucible is the inevitable consequence. 
 
 Metals are the best conductors of heat, and hence it is that the 
 pipes which are employed to convey heated air or steam for warm- 
 ing apartments, should always be metallic; and when it is 
 desirable that the heat should be given off rapidly, these pipes 
 should be rough, or otherwise covered with a coat of paint. 
 
 In some distilleries there is a considerable length of metallic 
 pipes between the still-head and the worm-tub or refrigeratory : 
 all such pipes should be painted black. 
 
 On the contrary, whenever it is an object that such pipes 
 should preserve the heat as long as possible, as is always the case 
 when metallic pipes are employed to convey heated air, hot water, 
 or steam to a distance, the pipes should be conveyed under ground 
 or otherwise highly polished, and always kept perfectly clean. A 
 silver tea-pot on the same principle preserves the tea hotter than 
 most others, and consequently extracts the vegetable principle 
 more effectually. For the same reason, our planished tin covers 
 will preserve the warmth of our provisions exactly in proportion 
 to the height of their polish and the degree of cleanliness with 
 which they are kept. 
 
 In some of the print-works in Lancashire, boil ing- water is 
 conveyed by copper pipes under ground from the steam-engine 
 
 1 Buchanan On the Economy of Heai, 8vo, page 128. 
 
OF ARTIFICIAL TEMPERATURE. 75 
 
 boiler to the different workshops, for the uses of the workmen ; 
 and in some cases the heat is so well preserved, that the water is 
 delivered in the various apartments only two or three degrees 
 below the boiling point. 
 
 With respect to the ECONOMY of FUEL, which naturally forms 
 a branch of this essay, so much has been professedly written upon 
 the subject by Count Rumford, that there seems nothing of im- 
 portance left for others to add. I shall therefore presume to 
 offer very little to his observations, except a few hints which arise 
 out of my own practice in the conduct of the manufactory in 
 which I am personally engaged. 
 
 It is impossible, in an economical point of view, to give any 
 general directions for the choice of coal, since this depends so 
 much on the different localities and other circumstances; a 
 description of the several varieties will be found in the Essay on 
 Carbon. It may, however, be observed, that in manufactories 
 where large and expensive iron boilers are employed, sulphurous 
 coals should be avoided, as the sulphur which rises during com- 
 bustion is apt to occasion a rapid decay of that part of the boiler 
 which is exposed to the action of the fire. It produces a sul- 
 phuret of iron, which wastes away as fast as it is formed. This 
 is more particularly the case with those cast-iron stills which are 
 required to be red-hot, such as the pots in which the makers of 
 prussian blue flux a mixture of animal hoofs and horns with a 
 caustic fixed alkali. 
 
 The following table of the comparative heat of different kinds 
 of fuel was drawn up by Mons. Lavoisier. Equal quantities of 
 heat were produced by the combustion of the following quantities 
 of the combustibles annexed. 
 
 Pounds. Measure. Pounds. Measure. 
 
 Cokes 403 17 Charcoal 600 40 
 
 Pitcoal 600 10 Oak wood .... 1089 33 
 
 In this experiment the cokes required 12^ hours for their 
 combustion, the coal 20 hours, the charcoal 5, the oak 4- 4. 
 An estimate has also been made of the relative quantities of heat 
 produced from similar materials by Count Rumford, but I must 
 refer the reader to his work for particulars 2 . 
 
 M. Wiegleb has stated it as his opinion, that in the choice of 
 wood-fuel, the beech and hornbeam are to be preferred ; next 
 the oak, and then any other woods of great solidity. Next to 
 these, the alder, aspen, birch, fir, ash, and the lime. The 
 former excite a greater heat, and burn longer ; the latter exhi- 
 bit more flame, and leave but little residuum. 
 
 Loysel has shown that it is improvident to burn different spe- 
 
 2 Rumford's Essays, vol. ii. pages 75, &c., also pages 134 137- 
 
76 ON TEMPERATURE. 
 
 cies of wood together, and that it is absolutely important in many 
 operations to sort the wood, and never to use more than one kind 
 at a time in those works which require a lively clear fire and a 
 pure flame ! . 
 
 Charcoal is fitter for small chemical operations, as it is more 
 easily managed : that which is made of the more solid woods is 
 to be preferred. 
 
 Refuse tan, made up into cakes, is also very fit for firing, 
 where a gentle and continued heat is advantageous. 
 
 In some places turf is used with advantage. Formerly it was 
 much employed in some of our West Indian islands; but since 
 hands have been scarce in consequence of the discontinuance of 
 the slave trade, the planters cannot spare any of their men to 
 cast turf, and are now obliged to take pitcoal from England. 
 There is a great difference, however, in its internal quality : the 
 heavy bituminous kind called peat 2 is the best; but some care is 
 required in drying it properly to prevent its entering into spon- 
 taneous combustion. 
 
 Mr. Mushet, of the Clyde iron works, gives the following cal- 
 culation of the expense of getting peat in Scotland. A man, 
 he says, will with ease cast 4,000 of an ordinary size in a day. 
 For this quantity are required two carriers, and one person to 
 pile it to dry. The peat when thoroughly dried will weigh nine 
 pounds each; the product, therefore, will be 12,000 pounds, or 
 upwards of five tons. The expense of this is : Man's wages 
 per day, 2s. 6d. Two women, at Is. each, 25. Girl to pile it, Qd. 
 making 55. or one shilling per ton. 
 
 It has been found that four tons of dried peat will make some- 
 thing more than one ton of peat-char, which will produce a much 
 stronger fire than coals or cokes. 
 
 Dr. Plot, after describing the method of cutting turf in Staf- 
 fordshire, says, " the large ones in good weather will dry on one 
 side in eight, on the other in four or five days at most. When 
 dried, if they intend them for fuel in winter, they pile them up 
 round in the manner of a hay-rick, ten or twelve feet high, and 
 let them stand all summer ; but if they are designed for manur- 
 ing their land, they heap them up a good quantity together on 
 the ground and set fire to them, which they will take of them- 
 selves if they are dry 3 . 
 
 1 Essai sur V Art de la Verrerie, page 67. 
 
 2 This article has for ages been used as fuel by the people of the north of 
 Europe; but the learned Torfeus says that its use was first made known to the 
 inhabitants of the Orkney and Shetland islands, by one Einar, a Norwegian, 
 who from that circumstance was named Torf Einar. Jameson's Mineralogy 
 of ike Scottish Isles, quarto, 1800, vol. ii. page 121. 
 
 3 Plot's Staffordshire, chap. iii, 14. 
 
OF ARTIFICIAL TEMPERATURE. 77 
 
 A very economical kind of fuel is charred turf, but it has a 
 very disagreeable smell during its combustion, which is an objec- 
 tion to its use in open fire-places, and there is some nicety 
 required in managing the process of preparing it, which I be- 
 lieve nothing but practice can teach. M. Sage, who has published 
 a paper on this subject in the Memoirs of the Academy of Sciences 
 at Paris, entitled " An Inquiry into the comparative Intensity of 
 the Heat produced by the Combustion of Charcoal and charred 
 Turf," asserts that the heat produced from the latter is nearly in 
 the proportion of three to one 4 . 
 
 The management is, however, generally of greater consequence 
 than the choice of fuel. The kind of fuel which is most suitable 
 for any particular operation, is soon discovered, but how to 
 employ it so as to produce the greatest quantum of heat by its 
 means is not quite so obvious. 
 
 Count Rumford has stated that, in general, not less than seven- 
 eighths of the heat generated, or which with proper management 
 might be generated, from the fuel actually consumed, is carried up 
 into the atmosphere with the smoke, and totally lost. How impor- 
 tant then is it that every proprietor of a manufactory should inves- 
 tigate the causes of this loss, and endeavour to remove them ! 
 
 In the year 1686 Dalesmius contrived a furnace at Paris on a" 
 very simple construction, for economizing fuel by burning the 
 smoke. Since that period we have had many contrivances for 
 the same purpose, possessing different degrees of merit, and an 
 account of most of them may be seen in the periodical journals 
 of the day. 
 
 Where boilers are set in brick-work over closed fire-places, 
 the most common defect is that of having the fire-places too 
 large. This often arises from the obstinacy of an unskilful brick- 
 layer. It is a great want of economy to employ inferior work- 
 men to erect any kind of fire-work. Whatever may be the expense, 
 I have always found an advantage in having furnaces well built 
 in the first instance. The consequence of having the fire-place 
 too large is, that the bars cannot be entirely covered with fuel, 
 and the cold air rushing from the ash-pit, between the uncovered 
 bars, actually counteracts the effect of a great part of the burning 
 fuel. In setting stills or boilers, it should be a general rule to 
 have the fire-places no larger than is absolutely necessary for 
 containing as much fuel as- will be required to produce the in- 
 tended purpose. 
 
 The fire-place should not only be small, but it should be con- 
 structed so that the whole of the bottom of the boiler be exposed 
 
 4 An abstract of this paper may be seen in The Repertory of Arts- vol. v. 
 page 419. 
 
78 ON TEMPERATURE. 
 
 to the action of the burning fuel. This is very effectually ac- 
 complished in some steam-engine boilers. These are of an ob- 
 long form, and they have a flue of from eighteen to thirty inches 
 diameter running from end to end through the middle of them. 
 The fire therefore first plays against the bottom of the boiler, 
 and then passes through the midst of the water before it reaches 
 the chimney. Might not this principle be applied in various 
 other ways with advantage ? It is important that the whole of 
 the flame and heated air do actually impinge upon the bottom 
 before they reach the sides to pass from them to the chimney ; 
 for the heat which is applied at the bottom of a boiler will be 
 infinitely more effective than the same portion of heat when 
 applied to its sides. It is on this account that some large stills and 
 other vessels of copper are made with the bottom to project in- 
 wards, presenting a concave instead of a convex surface to the 
 action of the fire. 
 
 These considerations explain why there is so great a waste 
 of fuel whenever pots or other vessels are heated over an open 
 fire-place ; for in this case, the heat only skims over the bottom, 
 and passes off' immediately into the surrounding atmosphere. 
 
 The doors of closed fire-places also are generally as improper 
 as the fire-places themselves. They are usually made extremely 
 thin, and the frames very light ; which not only occasions them 
 soon to wear out, but is the cause of their warping and twisting, 
 and consequently they never shut close afterwards. These doors 
 are likewise made to fall into a rabbet, and are fitted up with 
 latches, both of which are inconvenient, and indeed useless. 
 
 Having had many years experience in fitting up furnaces, I 
 am decidedly of opinion that where cast-iron doors are employed, 
 an opening of ten inches should have a door not less than three 
 quarters of an inch thick ; and larger fire-places should have 
 thicker doors in proportion. These should be fitted up with 
 strong wrought-iron hinges, such as will allow the doors to 
 fall flat against the frames ; and instead of moveable latches, 
 each door should have a large projecting knob firmly riveted 
 into it. 
 
 I have found it advantageous to have the straps of the hinges 
 thick, and of such a length as to extend entirely across the door; 
 for when these are well riveted to the door, they prevent the lat- 
 ter from warping, however intense may be the fire. 
 
 The cast-iron frames ought to be as thick at least as the doors ; 
 and they should be two or three inches broad, to enable them 
 to stand steadily against the walls of the furnace. In setting the 
 frames, they should be fixed inclining a little towards the fire- 
 place : this gives the doors a tendency to keep shut, and ren- 
 ders latches useless. Bars of wrought-iron, well fastened, should 
 
OF ARTIFICIAL TEMPERATURE. 79 
 
 also go, one from each corner, in a spreading direction, not less 
 than eighteen inches or two feet into the solid mass of brick- 
 work on which the boiler is to stand. 
 
 There is a benefit arising from having these straps long and 
 substantial, which may not at first be apparent. They prevent 
 the frame from receding from the brick-work, the consequence 
 of which would be that air would pass into the fire-place between 
 the frame and the masonry, and thus impair the draught of the 
 furnace. 
 
 It is also of importance in every close fire-place, to have a 
 door to the ash-pit ; one that shuts easily and fits close to the 
 frame on which it hangs ; for without this it is impossible ever 
 to regulate a fire so as to reap every advantage from its effects. 
 
 Having experienced the benefit of ash-pit doors, I have for 
 several years been in the practice of having my fire-places fitted 
 up with double doors and frames ; that is, I have a strong iron 
 frame cast, with two openings ; to one a door is hung for the 
 fire-place, and to the lower opening I adapt another for the ash- 
 pit. The peculiar advantage of this is, that a double frame of 
 this sort is more easily fixed, and can be attached more firmly 
 to the brick-work, than it would be possible to fix two frames, 
 one immediately above the other. 
 
 These doors and frames are expensive at first, because they 
 are weighty ; but in the end they will be found to be more eco- 
 nomical than any ready-made sale-doors that can be found. 
 
 Besides, since I have had these doors to the ash-pits I have 
 dispensed with the registers in the chimneys ; for, I find that by 
 a proper attention to the opening and shutting of the ash-pit 
 door, I can admit any portion of atmospheric air into the fire- 
 place, and thus have a complete command of the temperature 
 and its application. 
 
 For some time I had registers in the chimneys, as well as 
 doors to the ash-pits ; but finding that both were more than ser- 
 vants would attend to, 1 have now discarded the former alto- 
 gether, and perceive that every effect that can be desired may 
 be produced by the ash-pit doors alone. 
 
 However deep the ash-pits may be, it is always advisable to 
 have doors to them. Some scientific men in the metropolis have 
 had doors of three feet in height to the ash-pits of their brewing 
 coppers, and have found them very economical. 
 
 I have sometimes had moveable registers in the centre of the 
 ash-pit doors ; but these are too troublesome to be managed by 
 ordinary servants ; and a common plain ash-pit door, when pro- 
 perly hung, may be readily opened an inch, two inches or more, 
 or entirely shut, according to the choice of the laboratory-man 
 employed. 
 
80 ON TEMPERATURE. 
 
 In reverberatory furnaces for the decomposition of neutral 
 salts and the manufacture of alkalies, ash-pit doors are of no 
 use, as it is never necessary to check the fire suddenly, as in 
 other operations. On the contrary, I have found it advan- 
 tageous to have the ash-pits as deep and the chimneys as high 
 as possible, in order to occasion a strong and uninterrupted 
 draught. 
 
 No chimney should be less than thirty feet high ; and for large 
 fire-places, or where more than one flue goes into a chimney, it 
 ought to be much higher, and larger in proportion. 
 
 At Paddington water-works the chimney is 120 feet from the 
 plinth to the summit, and the chimney of the spinning factory of 
 Messrs. Broom, Sons, and Home f at Kidderminster, is of the 
 enormous height of 220 feet ; and being quite round and beau- 
 tifully constructed, it is a remarkable object for a great distance 
 from the surrounding neighbourhood. 
 
 I cannot suffer this opportunity to pass without remarking that 
 the proprietors of reverberatory furnaces should contrive to con- 
 tinue their processes night and day ; or, if that be impracticable, 
 they should rake up the fire and stop the passage to the chimney 
 so as to prevent the furnace from cooling during the night. Fur- 
 naces thus worked will last six or seven times as long as those do 
 which frequently stand idle. The contraction of the materials 
 during the time of cooling, and the subsequent expansion, wear 
 them out rapidly. 
 
 Where the heat is so intense as it is in these furnaces, doors 
 and frames of the common make, or such as have been just de- 
 scribed, would be quite improper, and even wasteful, for they 
 would be constantly red-hot : hence they would not only soon 
 wear away, but being in this state of incandescence they would 
 carry off a large portion of the heat, which ought to be em- 
 ployed in reducing the materials within the furnace. 
 
 For large reverberatory furnaces, steam-engine boilers, and 
 other great concerns, I have sometimes seen very wide wrought- 
 iron doors lined on the inside with a plate of cast-iron well 
 riveted to the door. By forming these hollow, that is, if they 
 were put together so as to inclose a thick sheet of atmospheric 
 air, the door would become a non-conductor of heat, and would 
 be very suitable for such apparatus. 
 
 Having experienced the inconvenience of common doors and 
 frames, I had recourse to a contrivance of hanging a thin sheet 
 of wrought-iron before the fire-place, which proved to be a great 
 amendment ; and after this I had a door made with fire-bricks, 
 the joints of which were secured with loam, and held in their 
 places by four flat plates of iron screwed together at the corners. 
 This massy door was moved upwards or let down before the fire- 
 
OF ARTIFICIAL TEMPERATURE. 81 
 
 place by means of a weight which exactly balanced it, and was 
 attached to a chain passing over a pulley. 
 
 This was an improvement upon the former ; but both had their 
 inconveniences, and these inconveniences led to the adoption of 
 a small iron hopper fixed horizontally in the brick-work, pro- 
 perly let into the wall to defend it from the fire, and stopped by 
 a thick piece of iron, cast exactly to fit it. This I found to be 
 a most complete way of closing a fire-place, as no air can pos- 
 sibly get admittance but through the ash-pit, this being the only 
 way by which it ought ever to pass. I made use of this kind of 
 hopper twenty years ago, and have never seen any reason to 
 alter my opinion of it. I was indebted to a work of Mr. Dossie, 
 " The Elaboratory laid open," for the idea. 
 
 There is, however, an inconvenience attending these square 
 stoppers of iron, viz. If the wall of the fire-place be not very 
 thick, and the hopper fixed at the very outside of the brick- work ; 
 whenever the fire becomes intense, the stopper is apt to expand 
 by the heat, and get so firmly fixed within the hopper as some- 
 times to be attended with much trouble. I have, however, oc- 
 casionally employed these kind of hoppers for closed fire-places 
 of the very smallest size, and have then been much satisfied with 
 them. In such cases the beat not being so intense, this incon- 
 venience does not happen. 
 
 Reflecting on the objection just referred to, it occurred to me 
 that a hopper might be so fixed as to be stopped with small coal 
 instead of the usual door, and that in this way the difficulty 
 might be avoided. I therefore made such an alteration in the 
 construction of the last reverberatory furnace which I had occa- 
 sion to erect, as enabled me entirely to discard the use of any 
 metallic door or stopper whatever. 
 
 In this furnace the hopper which I employed was five inches 
 square in the clear, and this was fixed upon a broad plate of iron 
 built in the brick-work, and projecting eight inches beyond the 
 face of the wall. The design of this was merely to be a support 
 for the small coal which was to fill the hopper, and be piled 
 against it, as a succedaneum for the iron stopper above men- 
 tioned. Since this was first written I have found that glass-makers 
 stop up the mouths of their ovens with small coal, on the princi- 
 ple of its being a non-conductor of heat, and that this contrivance 
 answers their purpose completely. It appears also that iron- 
 founders stop up the mouths of their air-furnaces in the same 
 manner. 
 
 The small of pit-coal, being a non-conductor of heat, proved 
 to be a mode of stopping the entrance of a furnace as perfect as 
 probably will ever be devised : for, if a furnace draw well, the 
 coal which fills the hopper will not become ignited at all, except 
 
82 ON TEMPERATURE. 
 
 that part of it which is nearest the burning fuel ; and when the 
 hopper is properly stopped, one cannot discover how any of the 
 heat of the furnace can possibly escape by means of the door-way. 
 
 When it becomes necessary to replenish the fire, all that the 
 workman has to do, is to loosen the coal within the hopper, to 
 push the whole of it into the fire-place with a shovel which should 
 be made on purpose to fit it, then to throw in as much fresh fuel 
 as he judges to be sufficient, and again to stop up with small coal 
 as before. It must be observed, that the hopper should be fixed 
 several inches above the level of the fire-bars, that whatever fuel 
 is put through may fall into the fire-place without any difficulty. 
 
 It should be recollected, however, that whatever perfection 
 there may be in the mode of stopping the entrance into a furnace, 
 this will be no cure for a large fire-place ; for if a fire-place be 
 larger than it ought to be, or so constructed that the hopper 
 does not command evey part of it, a continual current of cold 
 atmospheric air will rush in between those bars which are not 
 covered with fuel, and carry much of that heat into the channel 
 of the chimney which ought to be spent within the furnace. 
 
 This is the chief circumstance which renders a hopper fire- 
 place so much better than those with a door and frame; for 
 where there is a hopper there can be no occasion for any door 
 and frame ; and \hefour sides of the furnace may be built exactly 
 alike and all brought up sloping with masonry. Such a furnace 
 will hold much more fuel than one that has only three sides of 
 brick- work; and consequently the area for the bars may be much 
 diminished. Indeed, one of the most important alterations of 
 late years in the building of inclosed fire-places, is that of reduc- 
 ing their length to one half of the former dimensions, and adding 
 something in lieu of the length to the width. The advantages 
 which arise from this alteration will easily be perceived. It was 
 no uncommon thing formerly to build the fire-place of a furnace 
 four feet long. 
 
 Besides, if the four sides of any furnace be sloped very consi- 
 derably, so that its upper diameter be twice the diameter at the 
 bars, there will never be any danger of such a furnace having a 
 false draught through the bars ; because whatever fuel is thrown 
 in through the hopper, will fall on all sides towards the middle 
 of the furnace, and form a uniform covering to the grating. 
 
 I have found it convenient to have the hopper on one side 
 of a furnace and the ash-pit on another, or at the end of the 
 furnace : by this arrangement the assistant can supply his fire 
 without being annoyed by the heat of the ash-pit, which is con- 
 siderable in large furnaces. 
 
 It has lately been found advantageous to have fire-bars much 
 narrower than formerly. By this alteration a fire burns more 
 
OF ARTIFICIAL TEMPERATURE. 83 
 
 regularly, being more equally supplied with atmospheric air than 
 it could be in fire-places with bars three inches wide. Half that 
 substance is sufficient for any fire-place. 
 
 Respecting the width between the bars, the space which I have 
 found to be the best, is half an inch, and this is sufficient for a 
 fire-place of any dimensions. By casting the bars with a shoul- 
 der at each end, exactly a quarter of an inch thick, it gives the 
 proper opening. 
 
 Such furnaces as are designed for producing a great heat, 
 should be furnished with loose bars of a considerable size, rest- 
 ing upon two or three strong bearing-bars; for all grates, or sets 
 of bars cast together and united in one frame, will warp and 
 twist, and are with great difficulty cleared of the scoriae or 
 clinkers. Joggle-bars, as they are called, or such as fall into 
 distinct and separate notches, are also very inconvenient. It is 
 seldom advisable to buy ready-made fire-bars, but it is more 
 profitable for the proprietor of a manufactory to have a pattern 
 in wood, for each kind of furnace, made to his own mind, and 
 to have all the bars of that size cast by it, taking care to have a 
 knob at each end, to keep the bars at a proper distance from 
 each other. 
 
 If such bars be fixed upon strong and plain bearers, they will 
 have room to expand by the heat without bending ; may easily 
 be moved to the right or the left, to loosen the scorias ; and may 
 readily be drawn out of the fire-place at pleasure. 
 
 In building a large furnace I have found it convenient, when I 
 have employed a hopper, to leave an opening of two or three 
 inches immediately above the fire-bars, as long as the whole 
 breadth of the fire-place ; and such an opening may be easily 
 made by inserting a strong bar to support the brick-work over 
 it. Through this opening the workman can occasionally intro- 
 duce a poker for stirring the fire and loosening the scoriae, and 
 through the same opening he can withdraw the bars for the sake 
 of emptying the fire-place, or replace them, as he may have 
 occasion. 
 
 When a fire-place is built after this manner, it will be conve- 
 nient to have a deep ash-pit: then, if the workman wishes at any 
 time to cool the furnace expeditiously, he can draw out the bars 
 through the orifice above mentioned, and the whole contents of 
 the fire-place will fall at once into the ash-pit. 
 
 At some very large steam-engines I have seen a fixed door and 
 frame at the opposite end of the furnace to that at which they 
 feed the fire, for the purpose of drawing out the clinkers of the 
 coals, without incommoding the man who attends the fire; but 
 I know from experience that the construction just described will 
 in the end prove to be the most convenient. The aperture, as 
 
 G 2 
 
84- ON TEMPERATURE. 
 
 it rises only three inches above the surface of the bars, will not 
 injure the draught of the fire-place, because the bed of fuel which 
 covers the bars will be always thick enough to stop up that open- 
 ing completely. 
 
 I have already urged the importance of employing an inge- 
 nious and experienced bricklayer, for it will always be prudent 
 and economical to have every furnace well built at the first : for 
 such furnaces not only answer their respective purposes better, 
 but they consume less fuel, and will frequently last three or four 
 times longer than those which are built by an ordinary workman. 
 
 To effect this in the best manner, it is obvious that the mate- 
 rials should be of the best kind, carefully selected for the respec- 
 tive parts of the work, and calculated for that particular furnace 
 which the proprietor wishes to erect. 
 
 There are, however, a few necessary instructions from which 
 I have derived so much advantage in my own manufactory, that 
 I should be inexcusable were I to neglect to mention them. 
 
 It is a common opinion, that if good fire-bricks be used in the 
 interior of the fire-place and in the flues, any thing will do for 
 the exterior, or for the solid part of the fabric. This is not 
 strictly true, for I have found it advisable to have even the exter- 
 nal parts composed of the best building bricks that I could pro- 
 cure ; because close joints and compact work can only be made 
 with such materials; and if the workman does not lay close joints, 
 and make the whole fabric very compact, he can never be certain 
 that the air will not find a passage into the fire-place through other 
 channels besides the ash-pit. Besides, whenever a furnace is taken 
 down to repair a fire-place, these bricks may be used again and 
 again ; whereas common place-bricks can never be taken down 
 whole, and consequently are useless for a second erection. 
 
 Wherever an intense fire is required, bricks made with the 
 best Stourbridge fire-clay should be used ; the joints should be 
 rubbed very close, and that part of the work should be laid, not 
 with lime mortar but with good fire-lute. 
 
 The fire-lute which I have employed for many years, never 
 having been able to discover a better, is made thus : Good clay 
 two parts, sharp washed sand eight parts, horse-dung one part. 
 These materials are to be intimately mixed, then beaten up with 
 a little water, and afterwards the whole is to be thoroughly tem- 
 pered like mortar, by treading it for a considerable time with the 
 feet. Mr. Watt's fire-lute is a good one, but it is more expen- 
 sive. Take, says he, porcelain clay from Cornwall (not pipe 
 clay), pound it, and mix it to the consistence of thick paint, 
 with a solution of borax, in the proportion of two ounces of 
 borax to a pint of hot water. 
 
 In erecting furnaces which are intended to sustain a great heat, 
 
OF ARTIFICIAL TEMPERATURE. 85 
 
 the composition of the mortar is of the utmost importance. When 
 I was in the habit of using stone-lime, such as is produced in 
 several of the midland counties of England, I found the follow- 
 ing proportions made the hardest and the best mortar. 
 
 Lime fresh burnt, and measured while in lumps, one bushel; 
 sharp river sand, well washed, four bushels. The whole to be 
 intimately mixed and thoroughly tempered. 
 
 For the internal parts, which are not exposed to the air, a still 
 larger proportion of sand might, I found, be used with advantage. 
 
 The best proportions for common chalk-lime are, lime one 
 bushel, and sharp sand two bushels ; though that which is tho- 
 roughly and uniformly burnt will take three bushels of sand to 
 one of lime. 
 
 It has long been a general complaint that the common chalk- 
 lime contains a considerable proportion of unburnt stone, or 
 carbonate of lime, which is a great loss, and renders it difficult 
 to ascertain the exact measure of sand that ought to be used 
 with it. 
 
 In consequence of this, some lime-kilns have been erected at 
 Bow and elsewhere in the neighbourhood of London, with chim- 
 neys which rise thirty fee-t above the body of the kiln ; and these 
 occasion so powerful a draught that the complaint just mentioned 
 is entirely obviated. 
 
 In the Journal de Physique for the year 1775, page 311, are 
 a plan and a description of a kiln for burning lime after it has 
 been once slacked and reduced to powder. The design of this 
 is, that it may be used in mortar quite hot. It is recommended 
 to be employed in the following proportions, and it is said that 
 such mortar will become extremely hard and durable. Fine sand 
 three parts ; well burnt brick, ground, two ; slacked lime two ; 
 lime slacked in the air, and afterwards recalcined, two. 
 
 The stone consistence which mortar acquires is owing partly 
 to the gradual absorption of carbonic acid, and partly to the che- 
 mical combination of a portion of the water which is employed 
 in making it. Hence, if lime reduced to powder and then recal- 
 cined, or burnt lime reduced to powder without being slacked, be 
 added to mortar, the mortar when dry will acquire much greater 
 hardness than it otherwise would. 
 
 For the different works at Woolwich and elsewhere, belong- 
 ing to Government, all the lime which is consumed in making 
 mortar is ground while dry to a very fine powder, and used in 
 that state without being previously slacked. It is taken from the 
 kiln quite hot, and ground in that state. This prevents that 
 absorption of carbonic acid gas which would otherwise take 
 place ; and in making mortar with such lime, as much water is 
 required as would be combined with the lime if treated in the 
 
36 ON TEMPERATURE. 
 
 common way, and a much larger proportion of sand may be 
 employed than can possibly be used even with the best lime if 
 prepared after the old manner ; and it has often been demon- 
 strated that, provided the mortar have sufficient tenacity, it will 
 form a harder cement in proportion to the quantity of sand 
 employed. 
 
 The mortar of the ancients contained more sand than is gene- 
 rally used at present, and the extreme solidity of all the ancient 
 buildings has often been noticed. Pliny and Vitruvius 1 have in- 
 formed us what were the proportions of lime and sand used in 
 their time, and that it was customary to burn the lime close to 
 the spot where the buildings were erected, that the workmen 
 might have it immediately from the kiln. 
 
 " The greatest part of the wall built by King Athelstan in the 
 neighbourhood of Exeter is still remaining. It consists of small 
 unhewn stones as they were dug from the quarry, the interstices 
 filled up with hot lime and rough sand, and faced with ashler 
 work of hewn stone, and the whole strengthened by strong but- 
 tresses. The mortar used in this work is from length of time 
 become so hard and durable, that, on attempting to pull down 
 any part of it, the stones are sooner broken than separated one 
 from the other 2 ." I am inclined to think that the lime made from 
 chalk is always the strongest in proportion to the quantity of iron 
 contained in it. I have found that the whiter the chalk the weaker 
 will be the lime that is made from it; whereas that which is made 
 from the dark gray chalk approaches most to the nature of stone 
 lime, and is less perishable by water. The lime made at Dork- 
 ing in Surrey is of this latter kind, and is in great demand for 
 various purposes of building under water. Other instances in 
 corroboration of the idea now suggested might be easily adduced : 
 thus the chalk of Portsdown-hill in the county of Hants is soft 
 and white, and the lime made from it is used only for common 
 building purposes; whilst the chalk of Butsa-hill, fifty-eight 
 miles from London, and likewise in Hampshire, is a hard gray 
 chalk, making a description of lime which is employed for the 
 foundation works under water of the dock-yard and fortifications 
 at Portsmouth, it being equal or superior to the Dorking lime. 
 
 For some purposes, Stourbridge clay alone is very suitable for 
 imbedding fire-bricks, as it burns into a substance similar to the 
 bricks themselves, and the whole furnace becomes like one solid 
 uniform mass. The Stourbridge clay is of a very peculiar kind; 
 it lies at a great depth in the earth, under the bed of coal, and 
 is known to the workmen by the name of clunch. It is a gray 
 
 1 Plin. Lib. xxxvi. c. 23. Vitruv. Architectura, lib. ii..c. 5, 
 a Jenkins's History of the City of Exeter, 8vo. 1806, page 17- 
 
OF ARTIFICIAL TEMPERATURE. 87 
 
 clay, of a sandy nature, and better adapted for making large 
 crucibles and fire-brick than perhaps any in Europe. 
 
 It is not generally known, but there are some brick-makers at 
 Stourbridge, proprietors of the clay-pits there, who will make 
 bricks of any form or of any dimensions that may be desired. 
 Some friends of mine have had an entire fire-place made with 
 that sort of clay, agreeably to patterns sent for the purpose; and 
 it was so contrived, that though the bricks differed in form and 
 size, every piece had its appropriate place, and fitted the adjoin- 
 ing one with the greatest nicety. 
 
 For some particular purposes it will be worth while to go to 
 this expense : for, when the several parts are put together with 
 a thin mixture of Stourbridge clay, sharp sand, and water, the 
 first fire that is lighted within the furnace, will burn the whole 
 into one entire and compact body. 
 
 In putting up the large stills used in the distillation of nitrous 
 and muriatic acids, I have been accustomed to have an abundance 
 of old iron hoops laid within the solid brick- work, some on every 
 course ; with the view of holding it together and preventing a 
 strong fire from cracking it, or forcing it outwards ; but I am 
 now of opinion that these are not of much use, excepting in 
 chimneys and in the walls which form the flues, and where the 
 brick-work is necessarily very thin ; for even where a great num- 
 ber of hoops have been laid in, the work has sometimes cracked, 
 and produced a false draught in the fire-place. 
 
 A better expedient, and one which I have lately adopted with 
 great success, is that of laying four flat iron bars in the brick- 
 work of each still, one on each side of the fabric, and at the 
 height where the fire has most force. I have these bars three- 
 eighths of an inch thick, and two inches broad, and of a length 
 sufficient to extend the whole length or breadth of the mass of 
 brick-work in which they are to be imbedded. 
 
 These bars are made by the smith to fit the places where they 
 are to lie, and are bent at each end so as to clip the masonry and 
 prevent its moving : but before they are bent there is a slit of 
 about two inches made in the end of each, which enables the 
 smith to divide so much of the bar and to turn one half up and 
 the other half down, by which contrivance it binds two courses 
 of brick-work instead of one. I have been thus minute in de- 
 scribing these binding bars that the method of making them 
 cannot be mistaken. 
 
 The irons being thus prepared, and the work brought up to thf 
 proper height to receive them, the bricklayer places one on on' 
 side of the furnace and another on its opposite side, and the^ 
 raises another course of brick-work all round the whole aret 
 Two of the irons being thus built in, the two others are laid in 
 
88 ON TEMPERATURE. 
 
 the same manner on the other two sides of the furnace, and built 
 in as before. By this arrangement the whole is secured in a very 
 complete manner, and I see no reason to expect that any thing 
 will give way till either the stills or the fire-places are entirely 
 worn out. 
 
 These expedients are all designed for the purpose of making 
 the work durable, and preventing a current of atmospheric air 
 setting in towards the fire-place in any direction otherwise than 
 through the ash-pit : but for the economy of fuel, it is of equal 
 importance that the bricklayer should be careful in the construc- 
 tion of the chimney, on which the goodness of every furnace very 
 much depends. 
 
 In determining the form, the size, and the height of a chim- 
 ney, an experienced workman will have no difficulty ; but it 
 appears to me that a proper attention is not always paid to the 
 thickness of the walls, or to the materials of which they are built. 
 No outer wall of a chimney, however small it may be, should 
 be less than nine inches thick, but it would be better if they were 
 fourteen or eighteen inches in thickness; and such materials 
 should always be chosen as are the worst conductors of heat, 
 provided they are sufficiently compact, and have no crevices for 
 the admission of atmospheric air. 
 
 Speaking of materials which are slow conductors of heat, re- 
 minds me that some improvement might be made in the con- 
 struction of our large boilers and evaporating pans, as to their 
 power of conducting heat. What could possibly be worse con- 
 trived for preserving the heat than the large iron pans of the 
 soap-boiler, which generally stand three or four feet out of the 
 ground without any casing whatever? Our soap-makers for- 
 merly boiled in wood. The French manufacturer boils in brick. 
 But to return to the construction of chimneys : it is not only 
 requisite that a chimney should admit no atmospheric air through 
 its sides, but it is also desirable that the sides of the chimney 
 should not cool the smoke and heated air within it ; for, the 
 higher the temperature can be kept in the interior, the better 
 will be the draught. 
 
 Whatever may be the situation of a chimney, it is always best 
 to have it stand independent of the boiler, still, or furnace to 
 which it belongs. It is best to build the chimney first, and when 
 that is finished, then to erect the apparatus round it, as may be 
 most convenient. 
 
 Some chimneys are placed at the back of a furnace, others 
 Ver the door : some boilers are set immediately over the centre 
 <A the fire-place, others at a considerable distance from it : in 
 s<me cases the still or the boiler is suspended over the furnace, 
 so\hat the bottom is entirely exposed to the action of the fire, 
 
OF ARTIFICIAL TEMPERATURE. 89 
 
 while in other instances the still is supported by brick-work, and 
 only partially exposed to the fire : one is heated only by the 
 flame and hot air which impinge against the bottom; others 
 have split draughts and worm flues of different kinds ; and each 
 of these modes may be applied with advantage to some parti- 
 cular purposes. But, as a skilful workman will never be at a 
 loss to decide these points, I hasten to offer a few remarks on 
 the management of the fuel, previous to the consideration of the 
 necessity of an attention to temperature in our manufacturing 
 processes; which, although the last, is certainly not the least 
 important branch of this interesting subject. 
 
 If a chimney throws out a large quantity of smoke, it is im- 
 possible there can be a proper economy of the fuel ; for the 
 smoke is occasioned by particles of the coal which ought to have 
 been detained in the fire-place, and there consumed in the pro- 
 duction of heat 1 . 
 
 This loss is chiefly occasioned by too much coal being cast 
 into the fire-place at once, which prevents any of it from being 
 properly ignited; whereas, if a small portion were always thrown 
 in at a time, and this suffered to become thoroughly inflamed, or 
 half burnt out, before more were added, the combustion would 
 then proceed regularly, more heat would be produced, and not 
 half the coals would be used which are now consumed. I have 
 found it advisable not to disturb the fire burning in a closed fire- 
 place, more than necessary. Coals should be put so as they 
 may lie light upon the grate. These are points of considerable 
 importance in every manufactory where many coals are burnt ; 
 but it is very difficult to induce ordinary servants to attend to it ; 
 because, when the fire-door is opened, there is less trouble in 
 putting on two or three shovels full of coal at once, than in fur- 
 nishing half a shovel full at a time, and that very frequently. 
 
 The effect of heaping an unnecessary quantity of coals upon a 
 grate in a closed fire-place is very mischievous and detrimental. 
 The great mass, instead of entering properly into combustion, 
 only moulders away, or is carried in the state of smoke 
 through the channel of the chimney into the atmosphere; and 
 the heat which is produced by the coals, instead of rising up to 
 the boiler, and doing its proper office there, is forced through 
 the bars into the ash-pit, and entirely lost. 
 
 A workman who would attend to these particulars would save 
 to his employer what would be equal to his own wages, in fuel ; 
 the work would be better done, and the effect produced with 
 
 1 What Dr. Black has said on this subject is worth the perusal of manufac- 
 turers; it maybe seen in his Lectures, 4to. vol. i. page 31 2 31 G. 
 
90 ON TEMPERATURE. 
 
 more certainty. Besides, when the fuel is burnt to such a point 
 as to have become a kind of charcoal, and no more smoke is 
 given off, instead of heaping fresh coals upon such fuel, the ash- 
 pit door should for a time be shut, to prevent the access of cold 
 air ; and the fuel, in this high state of ignition, should be left 
 undisturbed, in order that it may have its proper influence on 
 the matter submitted to its action. Practice alone can teach how 
 long a fire should remain in this state : but it is of consequence 
 to manage it thus ; for whenever, after this treatment, a proper 
 quantity of fresh fuel is added, this fresh fuel will sooner get into 
 full combustion, and the whole of it will be effective. 
 
 I am desirous, however, of observing, that all these remarks 
 are designed to apply only to such furnaces as are constructed 
 in the usual manner ; being aware that there are patents for 
 erecting fire-places to consume their own smoke, in which the 
 proprietors direct large fires to be made which will not require 
 to be replenished with coals for many hours. Some of these 
 expedients have already been referred to at page 77 of this 
 work. 
 
 I pass over many other important particulars respecting the 
 management and economy of fuel in closed fire-places, because 
 they have already been well considered and explained in excel- 
 lent detail by Count Rumford, whose Essays may be studied 
 with advantage by all those who are desirous of investigating this 
 important subject '. 
 
 Much might be done in the way of economy, by the employ- 
 ment of the waste heat which is now lost in the generality of 
 manufactories, and which the proprietors, by a little reflection, 
 might contrive to put to a good account. 
 
 In large buildings where it is necessary to have iron pillars to 
 support the floors, how easy would it be, as these pillars are 
 usually cast hollow, to convey heated air, or waste steam, from 
 an engine-boiler through them, and thus warm extensive pre- 
 mises at no expense ! There is a perfection peculiar to cast-iron 
 Eillars, that they may be made ornamental at a cheap rate ; and 
 ollow pillars for supporting a roof or floor, cost much less than 
 those which are cast solid, and are still of sufficient strength. 
 
 A gentleman whom I know in the neighbourhood of Man- 
 chester erected a cotton-mill, several stories high, on this prin- 
 ciple. The floors consist of a number of small brick arches, the 
 abutments of which are supported by hollow pillars of cast iron, 
 and these pillars are heated with steam, or kept cool, as he sees 
 occasion. By this construction he also saves insurance, as there 
 
 1 RumforcTs Essays, vol. ii. Essay 6; and vol. iii. Essays 10, 11 and 14. 
 

 
V 5 
 
OF ARTIFICIAL TEMPERATURE. 91 
 
 is nothing combustible employed throughout the building. After 
 his example, many factories have lately been erected on a similar 
 plan in various parts of the kingdom. 
 
 I have often noticed the vast loss of heat arising from the ex- 
 posed state of most of the steam-engine boilers. There would 
 surely be an advantage in building a wall round them, and cover* 
 ing them from the action of the weather. Thus there would 
 be a hot room attached to every steam-boiler, which might be 
 applied to many useful purposes. 
 
 In like manner, to those manufacturers who have occasion 
 for large quantities of coke, if they have coal in their neighbour- 
 hood that will coke, how advantageous would it be to put up a 
 proper oven or two for the purpose, and apply the spare heat for 
 burning lime, heating stoves, &c. ! The heat that is usually lost 
 is very considerable, and it is so intense that it might be made 
 sufficient for almost any purpose. 
 
 In most cases of distillation, the liquid which comes over is run 
 through a refrigerating metallic worm immersed in a vast quan- 
 tity of water. The design of this is to convert the gaseous pro- 
 duct into a fluid nearly as cold as the surrounding atmosphere, 
 and which without this would be mostly lost in steam. Why 
 might not the worm in many cases be passed through an inter- 
 mediate vessel surrounded by the wort or other liquid which is 
 intended to be distilled, and which by this means could be 
 heated to a certain point in readiness for the still, and at no ad- 
 ditional expense ? Plate, No. 2. 
 
 In some of the West India Islands this principle is already 
 acted upon. A worm is made to pass through the sugar- wash, 
 and this heats it ready for the still, and thus enables the planter 
 to draw more rum in a given time. It has been thought, how- 
 ever, that the principle might be applied with more effect, if the 
 heated air and smoke from the fire-place were made to pass 
 through the wash : and several sets of apparatus of this kind have 
 been prepared in London for some houses in Jamaica. A draw- 
 ing of one of these I have procured, and have had it engraved 
 to accompany these Essays. Plates, fig. 8. 
 
 A great saving of fuel is also effected by the introduction of 
 the dome and back copper. This vessel, which is used by some 
 brewers for boiling their wort, is constructed like a common 
 copper, except in the cover, which is made like a very broad- 
 brimmed hat, turned up very high all round the edge. 
 
 When the wort within the copper boils, the attendant turns a 
 cock and fills this broad gutter in the cover with cold liquor. 
 The consequence of this is, that the cover being filled with many 
 gallons of cold wort, it condenses the steam as soon as it is 
 formed, and becomes itself heated to 170 or 180. When the 
 
92 ON TEMPERATURE. 
 
 liquor acquires this heat, it is let off into the copper below, and 
 the cover is refilled with cold liquor. 
 
 For safety, the crown of this cover is furnished with a 
 weighted valve, from whence the steam may escape whenever 
 the fire is greater than it ought to be. By having the wort thus 
 covered all the time it is boiling, the fine aroma or peculiar and 
 grateful flavour of the hop is entirely preserved ; whereas in a 
 common open copper it passes off with the steam. The saving 
 of coals is also considerable. 
 
 These desultory observations on the economy of fuel having 
 been extended much further than was at first designed, I must 
 be more concise than I otherwise would in describing those 
 cases which have been selected as instances of the importance 
 of paying an attention to temperature in the conduct of manufac- 
 turing processes, and with these I shall conclude this Essay. 
 
 There is no complaint so common among workmen, as that of 
 processes sometimes failing which have usually succeeded, and 
 this without any apparent cause. Scarcely do I recollect an 
 instance of such failure, without having had reason to suspect 
 that it arose in some measure from a want of attention to the 
 temperature at which the process was conducted. 
 
 The distiller of ardent spirits knows how important it is to 
 regulate the temperature of the refrigeratory, and that, if it rise 
 above a certain degree, a portion of the distilled spirit will be 
 dissipated in the atmosphere and lost : the glass-maker is aware 
 that the goodness of his glass entirely depends on the care with 
 which he reduces the temperature in the process of annealing : 
 the horticulturist will also acknowledge that it would be absurd 
 to expect success in his crops without attending to the heat of 
 his beds, his walls, or his vinery: and why should the manufac- 
 turer imagine that there can be any chemical operation in which 
 the degree of temperature is of little moment ? 
 
 Formerly the brewer had no certain guide to determine when 
 the water was cool enough for mashing the malt, and the fer- 
 mentation of the wort was conducted only by guess, which occa- 
 sioned frequent failures and disappointments. He has, however, 
 in the thermometer, now found an unerring guide. 
 
 In the preparation of vinegar, the manufacturer depends 
 chiefly upon the sun for the additional temperature which he 
 requires for completing his process. In large establishments, 
 therefore, a great space of land is allotted for the exposure of 
 the casks to its influence. There are, however, some proprietors 
 of vinegar-yards who have found by experiment that the vinegar 
 sooner acquires its maximum of acidity by being kept in a more 
 regular temperature than can be obtained by the sun's rays, 
 since hot days are frequently succeeded by very cold nights. 
 
OJ? ARTIFICIAL TEMPERATURE. 93 
 
 Such manufacturers, having erected stoves and prepared rooms 
 for the reception of the vinegar, keep it at that exact tempera- 
 ment which they have proved to be best adapted to the process, 
 and find they can finish the work in less than two-thirds of the 
 time usually required for perfecting the business. How easy 
 then would it be for every manufacturer to make this experiment 
 for himself, and ascertain by a few trials what is the proper tem- 
 perature for conducting the process to the greatest advantage, 
 and in the least time ! 
 
 Few processes require a more strict attention to temperature 
 than the crystallization of salts. Some require a hot, others a 
 cold situation ; and I am not acquainted with any one species 
 that does not give finer crystals when set to shoot at its own 
 peculiar degree of temperature, in preference to all others. 
 
 The solution of a salt is also as much governed by temperature 
 as its crystallization ; and it is on a knowledge of this principle 
 that the separation of one species of salt from another generally 
 depends. The refining of saltpetre may be mentioned as a 
 familiar instance. In this operation the crude nitre, or rough 
 petre as it is called, is dissolved in hot water, nearly to the 
 point of saturation. Part of the water is then evaporated by 
 boiling ; and as the liquor becomes concentrated, the muriate of 
 soda, which is nearly as insoluble in hot as it is in cold water, 
 separates itself from the nitre, and precipitates. This is succes- 
 sively removed as it falls, and the boiling is continued till the 
 operator is satisfied that all the muriate has fallen: the hot 
 liquor, which contains the purified nitre in a state of solution, is 
 then drawn off' into coolers, that salt may crystallize. 
 
 In the manufacture of earthenware and porcelain many diffe- 
 rent temperatures are required, according to the nature of the 
 articles, and the progress which has been made in their prepa- 
 ration. In connexion with this subject it may also be observed, 
 that the large glass-house crucibles (according to the present 
 management) require two years for drying, previously to their 
 being submitted to the heat of the potter's oven ; and that any 
 kind of earthenware which takes frost during its drying, will 
 inevitably prove very brittle. 
 
 In the tanning of hides it has always been known that the pro- 
 cess went on much better in summer than in winter. How natural 
 then is it to have recourse to artificial temperature ! Mr. Brewin, 
 an ingenious tanner in the Borough of Southwark, is the only 
 person that I know of who has profited by this palpable improve- 
 ment in the manufacture; and he will doubtless be amply repaid 
 the expenses which have been incurred in erecting stoves and 
 building flues, to convey extra heat to the pits in which the hides 
 
94 ON TEMPERATURE. 
 
 are steeped; for the quality of his leather is much improved, and 
 the process is now shortened by several months. 
 
 The working cutler, when he has iron and steel to forge of 
 good qualities, knows that his sole dependence for the excellence 
 of the tools he fabricates, is upon the degree of temperature at 
 which the work is conducted in its different stages. He knows 
 that a sword must be tempered at a heat very different from 
 a pen-knife, an adze different from a saw, and a watch-spring 
 different from a lancet; but the pyrometer has not yet been 
 employed by these manufacturers, and to this circumstance the 
 difficulty and uncertainty of procuring a good edge tool may be 
 attributed. This subject will, however, be further treated of, 
 and some hints for the improvement of the present methods of 
 tempering will be given in the Essay on Edge-tools, which con- 
 stitutes a part of these volumes. 
 
 Neither has the thermometer been made use of by the tallow- 
 chandler, although it is evident that he ought never to make any 
 candles without employing that instrument: indeed, the chipping 
 of the outward coat of candles is owing entirely to the neglect of 
 this circumstance, not to say that there is reason to believe that 
 the tallow is often injured, in the Jirst instance, by melting it at 
 an improper heat. 
 
 The seed-crushers and makers of certain vegetable oils often 
 suffer considerably in consequence of their processes being con- 
 ducted at an improper temperature. One instance may be taken 
 from the operation of drawing linseed oil. The workman knows 
 that unless the seed be in some measure heated, the oil will not 
 flow ; he therefore roasts it over a charcoal fire, and loses ten or 
 fifteen per cent, in weight by that operation. If there be the least 
 want of care, the loss will be much more considerable. In ascer- 
 taining by actual experiment what is the temperature that is 
 really necessary, this process, by a proper arrangement, might 
 be managed with as much certainty as any other. 
 
 A bushel of foreign linseed weighs about 50lbs. ; a bushel of 
 English seed is usually from 60 to 62lbs. In roasting over a 
 charcoal fire to prepare it for the mill, the former generally loses 
 541bs. and the latter 6lbs. ; that is, when the oil which comes 
 from the mill is weighed with the oil cake, there is commonly this 
 deficiency. It strikes me, that if the seed were to be heated by 
 steam, no part of it would burn, and consequently the loss would 
 be very inconsiderable. A still greater saving might also be 
 introduced into this manufactory, were the oil cake itself to be 
 heated by steam ; because this would enable the operator to 
 grind it a second time, and thus express from it more of the oil. 
 
 An attention to temperature is also of great importance to the 
 dealer in Greenland whale oil, who might increase the profits of 
 
OF ARTIFICIAL TEMPERATURE. 95 
 
 his trade very much by preparing his oil for sale when the wea- 
 ther is suitable for the operation. This kind of oil is always puri- 
 fied by passing it through large flannel bags, which retain the 
 impurities, and suffer the finer parts to percolate through them. 
 When the oil has undergone this treatment, it is called bagged 
 oil, and is then deemed fit for sale. At a low temperature, a 
 considerable quantity even of this latter kind would concrete, 
 and might be separated by similar means ; whereas in a warm 
 atmosphere this dissolves, and being less inflammable, very much 
 injures the oil for burning. 
 
 By proper attention to this circumstance, all the oil which is 
 designed for burning might be very much improved, and the por- 
 tion thus separated from it, would be worth more to the soap 
 manufacturer for making yellow soap, than similar oil which had 
 not undergone this process. I conceive that an oil-merchant 
 would do well always to bag different oils in different seasons; 
 though many experiments might be necessary before it could be 
 ascertained what was the exact temperature at which the respec- 
 tive kinds would most copiously deposit this feculence. 
 
 Madder is an article of great consumption throughout Europe. 
 It is chiefly cultivated in Holland, where it enriches the farmer, 
 and is a considerable source of profit to the Dutch merchants. 
 Plantations of madder have also been made in this country, 
 and the thing has been attempted in France ; but it failed, as I 
 understand, in both countries, from the circumstance of the 
 growers not knowing the proper temperature at which the stoves 
 ought to be kept for drying it. 
 
 This might surely be ascertained by common means ; and if 
 the circumstance of making experiments during the time of har- 
 vest should be an objection, how easy would it be for an enter- 
 prising agriculturist to procure a person from Holland to give 
 him the necessary instruction ! 
 
 When the French minister was informed that the workers in 
 silk, although they knew how to prepare it for the woof, were 
 in the habit of importing organized silk from Piedmont, to serve 
 as a chain for their stuffs, because they were ignorant of the 
 method of drawing the silk from the cocoons, he did not hesitate 
 about the proper remedy, but invited the celebrated Vaucanson 
 into France, who not only gave him the information he wanted 
 on that particular point, but invented a machine for platting the 
 stuffs of gold and silver, and giving them the brilliancy of those 
 of the Levant. Thus, by the aid of an ingenious foreigner, the 
 French nation acquired a new and very considerable branch of 
 commerce *. 
 
 1 Carrard's Memoir, presented to the Literary Society of Berne, page 328. 
 
96 ON TEMPERATURE. 
 
 In dyeing woollen cloths with indigo, the blue is more intense, 
 and the colour more permanent, when the vat is used cold. Of 
 these facts no dyer is ignorant ; and yet it is a common practice 
 to employ heat, because this makes the indigo go much further, 
 and the colour strike quicker. I would suggest whether it is not 
 likely that there may be one certain temperature at which the 
 indigo would be completely exhausted, and yet the permanency 
 of the dye not impaired. 
 
 In the china-blue dipping, one of the processes of calico-print- 
 ing, the temperature of the lime- vat is of the utmost importance. 
 When the lime is slacked for this purpose, and the vat is pre- 
 pared with it, there can be no certainty that it will properly fix 
 the printed indigo in the fibres of the cloth, unless it be left at 
 rest till it become as cold as the surrounding atmosphere. To 
 conduct this process with certainty, a thermometer is indispen- 
 sable ; for, as I have understood, the indigo is either fixed or 
 spoiled at the first immersion. 
 
 Printed calicoes sometimes sustain an injury by not being 
 stoved at a proper temperature. The common heat of the stoves 
 is about 90. If they are suffered to rise much above that stand- 
 ard, there is great danger of the acids which have been employed 
 in forming the printed colours injuring the fabric of the cloth, 
 and rendering it tender. On the contrary, some of the colours 
 would spread or enlarge, and perhaps run the one into the other, 
 if the temperature of the stove were allowed to fall, and the cali- 
 coes to become cold before they were cleansed of the superfluous 
 mordants. 
 
 In the neighbourhood of Rochdale in Lancashire, and in some 
 parts of Yorkshire, the clothiers dye yellows and oranges with 
 the common heath, or ling as it is sometimes called, which is 
 taken from the moors and uninclosed common fields. They mow 
 it when in full flower, about the time of hay harvest. It is spread 
 out to dry as they do hay, and is then laid up in ricks or barns 
 in the same manner. 
 
 This vegetable produces by means of a tin mordant, a more 
 beautiful yellow on woollen cloths, than either weld, quercitron- 
 bark, or fustic ; the colour being not only brighter, but much 
 more intense than what can be procured from either of those 
 dyes. This colour is, notwithstanding, of very little real value, 
 because it will not bear the action of the sun and air like that 
 produced from weld, nor even so well as the yellow from fustic. 
 
 The manufacturers, therefore, invariably dry the goods which 
 are dyed with heath, under cover and in the shade. A very large 
 quantity of coarse cloths, called bookings, are d} r ed with this 
 cheap vegetable substance for the American market ; and as the 
 ling has been used in dyeing these kinds of cloth, only a few 
 
OF ARTIFICIAL TEMPERATURE. 97 
 
 years, I fancy the American consumers have not yet learnt to 
 distinguish the goods which are dyed with heath from those which 
 are dyed with fustic. I relate these circumstances merely for the 
 purpose of suggesting whether there may not be some particular 
 temperature at which the heath may be used so as to give & per- 
 manent dye. 
 
 A very excellent yellow may also be given by the quercitron- 
 bark ; but if a printer of calicoes be desirous of getting the very 
 finest colour, it can only be procured by making the decoction of 
 the bark, at a very low temperature '. Jf, for instance, the co- 
 lour be extracted from the wood by a heat of about 86, the 
 goods may be dyed with this decoction at 200 or 205 ; but if 
 the colour be extracted at a higher temperature than 86 or 90, 
 the liquor will inevitably acquire more or less of a brown colour. 
 A high temperature separates the tan 8 as well as the colouring 
 matter, and the tan which is developed, much deteriorates this 
 very useful and beautiful dye. 
 
 The quercitron-bark is also employed in dyeing woollen cloths, 
 and for this purpose the dye may be extracted at a temperature 
 somewhat higher than it is ever advisable to use it for printing 
 calicoes : but if these woollen goods be afterwards hot pressed, 
 which is a customary process in finishing them for the market, 
 the colour will be changed to a brown ; whereas, by submitting 
 the same kind of goods to the action of a cold press, the colour 
 is never impaired. Here the variation in the treatment produces 
 such difference in the effects, that the most unscientific workmen 
 are absolutely compelled to attend to temperature. 
 
 It has been discovered that the solvent power of water in some 
 cases is very much increased by giving it a temperature above 
 that of 212. For instance, if it be heated in closed vessels to 
 220, it is much more efficacious in bleaching cotton goods than 
 water is, merely at a boiling heat. This, however, can only be 
 accomplished by pressure. I mention the circumstance in this 
 place, because I conceive the principle to be important, and that 
 it might be applied with advantage to many other useful pur- 
 poses. It is true, that this additional temperature can never be 
 
 1 The most permanent yellow dye we know of is procured from the weld. 
 I have often made experiments on extracting the colour from this plant, but I 
 never observed that the beauty of the dye was in the least impaired by digest- 
 ing the plant in water at any temperature, or even by boiling it. 
 
 2 I have found that a small portion of muriate of tin will precipitate the 
 tanning principle from vegetable decoctions ; but I have not yet made such ex- 
 periments as will warrant my giving particular directions. In cases where it 
 would be prejudicial to employ muriate of tin, a little isinglass might probably 
 be substituted with propriety, on the principle of the affinity which tan has for 
 gelatine. 
 
 H 
 
98 ON TEMPERATURE. 
 
 imparted to water without employing artificial pressure, as I have 
 remarked; but we know so little of what changes might be 
 effected in the properties of bodies by treating them with caloric 
 under the pressure of several atmospheres, that nothing surely 
 can be more deserving of a diligent and patient investigation. 
 
 It is well known how difficult it is to fuse chalk or marble, 
 because, when these substances acquire a certain temperature, 
 the carbonic acid escapes, and they become lime. Sir James Hall, 
 nevertheless, effected the fusion of chalk at a very moderate tem- 
 perature, by employing a sufficient pressure to prevent the sepa- 
 ration of its carbonic acid and water, and in this way he converted 
 the chalk into perfect marble. The detail of these very interest- 
 ing experiments and others on the cooling of basalt will be found 
 in the fifth and sixth volumes of the Edinburgh Philosophical 
 Transactions. 
 
 Some very unexpected results have also been produced by the 
 different methods of cooling certain mineral substances which 
 had been reduced to a state of fusion. About seven hundred 
 weight of the Rowley rag, a species of basalt, was fused in a 
 common reverberatory furnace, by the late Mr. Gregory Watt, 
 who carefully noticed the changes which it underwent during its 
 different stages of cooling, and communicated the result of his 
 observations to the Royal Society. 
 
 This stone is found in the neighbourhood of Rowley in Staf- 
 fordshire : the village stands upon it. It is of a dark gray colour, 
 and, according to Dr. Withering, it consists of 48 silex, 32 of 
 alumine, and 20 oxide of iron. It is so hard, that Birmingham 
 and some other towns in the neighbourhood are paved with it. 
 It is sometimes employed to mix with the materials for making 
 the common black bottle-glass. 
 
 The basaltic mineral in the experiment just mentioned, melted 
 easily ; and when a portion of it was taken out in a state of fusion, 
 and cooled quickly, it produced a very hard, opaque black glass '. 
 When the fire had been continued for six hours, the chimney 
 was closed, and the whole surface of the liquid mass remaining 
 in the furnace was covered with heated sand ; after which, eight 
 days elapsed before the whole substance was sufficiently cool to 
 admit of examination. 
 
 On removing the indurated mass from the furnace, it exhibited 
 very different appearances, according to the varied action of the 
 heat ; and that which had cooled the slowest, was of a dull dark 
 
 1 I believe any of the common bottle-glass may be reduced to a stony sub- 
 stance, by first melting it, and then cooling it very slowly ; and that it may 
 afterwards be restored to its shining, vitreous appearance, by remelting it, and 
 then abstracting the caloric with rapidity. 
 
OF ARTIFICIAL TEMPERATURE. 99 
 
 gray colour, very similar in appearance to the original rag-stone. 
 In one case a rough granulated substance is produced, and in 
 the other a shining and smooth glass; and though the difference 
 is so striking, it is occasioned entirely by the variation in the 
 length of the time allowed to this matter for its reduction of 
 temperature. 
 
 I have examined some of the specimens which were taken from 
 the furnace at different times during the experiment ; and the 
 difference in their appearance is as great as could well be con- 
 ceived. They were presented to me by a relation of Mr. Watt, 
 soon after the experiment was performed. 
 
 From the discovery of these facts, Mr. Watt has endeavoured, 
 in a very philosophical way, to account for the regular figure of 
 the natural basaltic columns, and even for their regular articu- 
 lations. His reasoning is extremely ingenious ; but the reader 
 must be referred for further particulars to the memoir itself, 
 which may be seen in the Philosophical Transactions for 1804. 
 
 It has been ascertained that steel contains more carbon than 
 wrought-iron, though less than cast iron. From the knowledge 
 of this fact, an ingenious manufacturer at Chesterfield has in- 
 vented a new mode of making cutlery, and certain other imple- 
 ments in cast iron, and afterwards converting them at pleasure 
 to a substance resembling either wrought iron or steel. This he 
 effects by burying the respective articles of cast iron in a mass 
 of native oxide of iron previously pulverized, and submitting 
 the whole to a long continued heat. 
 
 In this operation the oxygen of the oxide combines with the 
 superfluous carbon of the cast iron, and, forming carbonic acid 
 or carbonic oxide, escapes, and leaves the metallic articles in the 
 state of wrought iron or steel, as the operator desires. 
 
 This process, which in general answers very well, sometimes 
 will entirely fail, and disappoint the artist. This I should ascribe 
 to its having been conducted at an improper temperature. For 
 if too little heat be given, the native oxide does not impart its 
 oxygen ; and if the heat be too intense, or continued beyond the 
 proper time, too much of the carbon will be abstracted, and the 
 articles of cutlery which were designed to have the properties of 
 steel, will be reduced to the state of soft wrought iron. A good 
 manageable pyrometer would enable the operator to escape these 
 disappointments. 
 
 In the decomposition of the sulphuric salts for the production 
 of alcalies, a business which I formerly carried on to a consi- 
 derable extent, I was often perplexed by a similar difficulty. 
 Whenever I could superintend the process myself, I couldjudge 
 tolerably well of the progress of the operation from the appear- 
 ances which the materials exhibited within the furnaces; but 
 
 H 2 
 
100 ON TEMPERATURE. 
 
 when the management of the process was left entirely to the 
 workmen, the operation was sometimes very ill conducted, and 
 the alkaline product was of very little value. For, if a sufficient 
 heat had not been duly maintained, the sulphates were not de- 
 composed ; if the decomposition had taken place, and the fire 
 was then suffered to go down, the sulphates would in a great 
 measure be regenerated ; and if, during the latter part of the 
 operation, the heat became too intense, then the nascent alkali 
 was elevated, and passed away through the chimney, to be dis- 
 sipated in the atmosphere. Had I been in possession of a good 
 pyrometer, all these evils might have been avoided. 
 
 I know of nothing that better deserves a premium than the 
 invention of a simple and cheap pyrometer, calculated for gene- 
 ral use, and applicable to the highest temperatures. That invented 
 by Mr. Wedgwood was an instrument of this kind, but unfor- 
 tunately the method by which he prepared the small cylinders of 
 argillaceous earth is entirely lost. This reminds me, that Guyton 
 has proposed platinum as a material of which a useful pyrometer 
 might be constructed, as it is not fusible at the heat of our fur- 
 naces, and would not be eroded by any of the gaseous products 
 evolved by the most intense fires ! . 
 
 The want of a good pyrometer is severely felt by the manu- 
 facturers of Birmingham. Cases daily occur of losses sustained 
 in consequence of their not knowing how to ascertain the precise 
 degree of heat in high temperatures. A single instance will be 
 sufficient to explain my meaning. 
 
 It has been customary to fit up the best fowling-pieces with 
 touch-holes of gold, because those of iron or steel are soon 
 eroded and worn away by the sulphur of the gun-powder, which 
 unites with this metal and converts it to a brittle sulphuret. 
 
 Nothing can be easier than to mould these gold touch-holes 
 properly, and also to fix them firmly within the gun-barrel ; 
 but there is an after-process to be performed, which is attended 
 with considerable difficulty. One of the last operations in finish" 
 ing a gun-barrel is that of hardening the breech, which can only 
 be done by submitting it to a high degree of heat ; and if ever 
 the precise degree that is necessary for the process be exceeded, 
 it is ten to one but the gold melts, and the manufacturer has to 
 replace it with another touch-hole. 
 
 When such an accident does occur, the workman has the 
 trouble of again softening the temper of the barrel before he can 
 fix another touch-hole to it, and consequently the same expense 
 and risk of hardening it must be incurred, besides the loss of 
 
 See Annales de Chimie, xlvi. page 276 j or Nicholson's Journal, vol. vi. 
 
OF ARTIFICIAL TEMPERATURE. 101 
 
 time. Owing to these inconveniences, the gun-smiths have nearly 
 discarded the use of gold, and now make the touch-holes for the 
 best fowling-pieces of platinum, although they cost nearly 
 double the price. I have been informed that Mr. Manton, a very 
 eminent gun-smith of Dover-street, was the first person who 
 employed platinum for this purpose. 
 
 In heating madder for dyeing what are called army-reds, the 
 intelligent dyer well knows that he ought to increase the tempe- 
 rature of the liquor very gradually, and therefore he never 
 attends the operation without carrying a thermometer with him. 
 The scientific gardener has one degree of heat for his cucumber 
 frames, another for the vines, a third for his pinery, and others 
 again for the different exotics, as his experience- has prescribed. 
 The sugar-refiner has a stove at one temperature for the bastard 
 sugar, at another for the loaves, and at a third for the candy. 
 The maker of varnish, the general manufacturing chemist, the 
 hatter, the calenderer, the colour-maker, and a variety of other 
 artists, are all dependent on the habit which they have acquired 
 of seizing some one particular temperature for the success of 
 their respective operations, and often without being conscious 
 of their obligation to that circumstance. Even in the manufac- 
 ture of cheese and the churning of butter recourse must gene- 
 rally be had to an increased temperature : neither will the dough 
 properly ferment, which is designed for making bread, unless it 
 be exposed to a temperature generally higher than that of the 
 atmosphere in this latitude. 
 
 I trust, however, that enough has now been offered to induce 
 every manufacturer, who may peruse these loose hints, to apply 
 them to his own business, and to consider, whether some of his 
 peculiar processes might not be very materially improved by a 
 variation of the temperature at which they have usually been 
 conducted. This is the chief object I had in view in composing 
 this Essay ; and as all the principal observations are founded 
 upon experience and the best information I could procure, I 
 entertain some confidence that it will be acceptable, and prove 
 highly useful, to the British manufacturer. 
 
 The superior knowledge of our manufacturers has been the 
 great source of our excellence as a commercial nation ; but 
 there is a danger, amid the growing intelligence of the age, 
 of our losing this proud preeminence, unless some spirited indi- 
 viduals, in every class of society, aim at informing the public 
 mind, and exciting that emulation among our respective artists, 
 which is sure to stimulate their exertions and lead them on to 
 perfection. 
 
102 ON SPECIFIC GRAVITY. 
 
 ESSAY III. 
 
 ON SPECIFIC GRAVITY. 
 
 JN OTHING can be of more importance to those who are entering 
 on the study of chemistry, or desirous of examining the works 
 of Nature with accuracy, than a competent knowledge of the most 
 convenient methods of taking the specific gravity of bodies. 
 
 Every man of science who has had much intercourse with the 
 world, must have met with many intelligent people who are 
 entirely ignorant of this subject ; and wherever this is the case, 
 it must be a material obstruction to their making any consider- 
 able advances in chemical knowledge. 
 
 It may perhaps appear superfluous to those who are conver- 
 sant with chemistry, to undertake to explain what they them- 
 selves so well know, that they cannot so much as recollect the 
 time when it was not known to them. There are, however, many 
 who are so entirely unacquainted with any of the modes of tak- 
 ing specific gravities, that they cannot even explain how absolute 
 differs from specific weight: to such readers therefore no apology 
 will be necessary. 
 
 Gravity may be defined to be that property inherent in all 
 bodies which gives them a tendency towards the centre of the 
 earth, and which enables us to measure the quantity of matter 
 in any particular mass, by means of the balance. The amount 
 which the balance thus indicates is said to be the WEIGHT of that 
 body. This is what we call the absolute weight, or the absolute 
 gravity of any particular substance, to distinguish it from the 
 specific weight ; or, as it has sometimes been called, its compara- 
 tive gravity. 
 
 By SPECIFIC GRAVITY is meant the relative weight of any sub- 
 stance as compared with the weight of an equal bulk of another, 
 which we agree to call the standard; for which purpose all 
 nations have fixed upon water as unity. Thus the specific gra- 
 vity of one body is less or greater than that of another, though 
 their absolute weights may be the same. The specific gravity of 
 a body is in a direct ratio of the mass, and in an inverse ratio of 
 its bulk. 
 
 The method of ascertaining quantities by means of the 
 balance was known in the remotest ages J ; but a long period 
 
 1 " Just balances and just weights shall ye have, I am the Lord your God." 
 Leviticus, xix. 36. "The spear-head of Goliath weighed six hundred shekels 
 of iron." 1 Samuel, xvii. 7. " Who hath weighed the mountains in scales, 
 and the hills in a balance? " Isaiah, xl, 12. 
 

 
ON SPECIFIC GRAVITY. 103 
 
 probably elapsed before mankind acquired any correct idea of 
 distinguishing between the absolute and the comparative weight 
 of bodies 2 . 
 
 Even the great Archimedes, who lived only in the third cen- 
 tury before Christ, knew of no method of taking the specific 
 gravity of the precious metals, so as to ascertain the amount of 
 their adulteration ; and it was only by long thought that he was 
 at last enabled to succeed. The mode which he devised is mi- 
 nutely described by Vitruvius 3 , and his account has been trans- 
 lated for the General Biographical Dictionary, under the article 
 " Archimedes." 
 
 When Archimedes had made himself acquainted with the 
 nature "of specific gravity, he wrote two books entitled De In- 
 sidentibus Humido, of which the Latin translation is yet extant, 
 though the original in Greek be lost. 
 
 The letter from Synesius to the female philosopher Hypatia, 
 shows that it was understood how to take the specific gravity of 
 water so early as in the fifth century. And Quintius Rhemnius 
 Palasmon, who was a teacher at Rome in the reign of Tiberius, 
 has in his fragment entitled De Ponderibus et Mensuris, made the 
 following observation on the comparative specific gravities of 
 water, wine, oil, and honey. 
 
 Librae, ut memorant, bessem sextarius addet, 
 
 Sen puros pendas latices, sen dona Lyasi, 
 
 Addunt semissera librae labentis olivi, 
 
 Selibramque ferunt mellis superesse bilibri. 
 
 On the revival of learning in Europe, we hear nothing of the 
 examination of bodies by their specific gravities, until this was 
 recommended by Lord Bacon and the Honourable Mr. Boyle. 
 The oldest table of specific gravities now extant, was compiled 
 by the first of these eminent philosophers. It will be found in 
 his tract entitled Historia densi et rari, printed in the second 
 volume of his Works in folio, London, 1741, page 69. The 
 methods which he pursued in order to form this table were as 
 follow. Having formed a perfect cube of pure gold of an ounce 
 weight, he caused cubes of the same size to be made of various 
 other materials, and by weighing these against each other he 
 ascertained their relative specific gravities. In regard to fluids, 
 he found their specific gravities by weighing them in hollow 
 cubes of silver, which he had made for this express purpose. 
 
 Half a century afterwards Mr. Boyle wrote on the subject, 
 and showed the advantages which a student must derive in his 
 
 2 Pliny ascertained the relative weights of several sorts of grain, as may be 
 seen in his Natural History, book 18. Vitruvius, who was contemporary with 
 Pliny, has also given the weight of a known measure of mercury, viz. that of 
 four Roman sextarii. Architecture lib. vii. cap. 8. 
 
 3 Architcciura, lib. ix. cap. 3. 
 
104? ON SPECIFIC GRAVITY. 
 
 examination of minerals, and in his other chemical pursuits, from 
 the habit of paying a constant attention to the specific gravity of 
 the several substances which should come under his observation. 
 Other philosophers of Britain then caught the idea, and the prac- 
 tice has been continued ever since by a few illustrious men, such 
 as Newton, Hales, Black, Lewis, Cavendish, and Priestley ; and 
 now by all who make any pretensions to cultivate the sciences. 
 
 The experiments by Sir Isaac Newton on specific gravity, 
 appear to have been undertaken with a view to his inquiry 
 respecting the densities of bodies when compared with their 
 several refractive powers. The result of these experiments led 
 him to conclude that those transparent substances which are the 
 most refractive, always contain some combustible substance. 
 Hence he concluded that water must be a compound body, a 
 conjecture which has been most fully verified by subsequent dis- 
 coveries, and shows what extraordinary powers of comprehension 
 of mind he must have possessed, for at that time every philoso- 
 pher supposed water to be one of the undecomposable bodies, 
 or simple elements of nature 1 . 
 
 The introduction of this art must, however, have been some- 
 what later on the continent of Europe ; for an eminent French 
 chemical writer tells us, that it was never employed with them 
 in the analysis of minerals till the time of Buffon 2 , who was 
 the first to acknowledge its importance, and render it useful. 
 
 Although Buffon may have been the first philosopher in 
 France who attended to specific gravity in the analysis of mine- 
 rals, it was employed elsewhere in the examination of metals and 
 for other purposes many years before his time. 
 
 Marinus Ghetaldus, a nobleman of Ragusa, published a trea- 
 tise at Rome in 1603, entitled Promotus Archimedes, fyc., wherein 
 he gives a comparison between the specific gravities of water and 
 eleven other different substances. In the year following, Bap- 
 tista Villalpandus published his Apparatus Urbis Hierosolymitani, 
 in which he exhibits a table of the proportional weights of all 
 the metals w ? hich were then known, and of some other substances. 
 Marinus Mersennus printed a similar table at Paris in 1644-, in 
 which he makes gold 100, and water 5-J. In the year 1699, 
 M. Homberg read to the Royal Academy of Sciences at Paris, 
 a memoir, showing " how to discover exactly how much one 
 spirit weighs more than another V 
 
 1 Sir Isaac Newton's table of specific gravities, consisting of 22 articles, was 
 published in his Optics, 4to, London, 1704. 
 
 2 This illustrious man spent fourteen hours a day in study. At five in the 
 morning he retired to a pavilion in his vast gardens, and he was then inacces- 
 sible. Prince Henry of Prussia called this retreat the cradle of natural history. 
 
 3 See Hist. Roy. Academy for 1099, or the 4to History of the Works of the 
 
ON SPECIFIC GRAVITY. 105 
 
 Specific gravity may be considered to be merely another term 
 for the comparative density of bodies ; and as the nature and 
 properties of a great variety both of solids and fluids depend 
 in. a great measure upon their density, nothing surely can be of 
 more consequence in the examination of natural and artificial 
 substances, than an attention to their specific gravities. 
 
 It is thus that the purity of some of the metals, and the value 
 of many liquid preparations, are determined ; and thus only can 
 we decide the classification of some minerals when they are not 
 subjected to a regular analysis. 
 
 To determine the purity of ammonia, the goodness of alcohol, 
 the strength of other ardent spirits, and the concentration of the 
 mineral acids, their manufacturers entirely rely upon the respec- 
 tive indications which their specific gravities afford them. 
 
 In the preparation of alkaline lyes for the manufacture of soap, 
 the operator has to determine the quantity necessary for each 
 operation, and the specific gravity of the solution is his only 
 guide. The makers of Roman vitriol, Epsom, Rochelle, Glau- 
 ber and other salts, have no proper criterion for ascertaining the 
 strength of the several liquors which they have prepared for 
 crystallization, but that of their specific gravity. 
 
 The strength of a variety of metallic solutions, and the con- 
 centration of many of the fluids which are employed in chemical 
 operations as solvents for other bodies, can be decided only by 
 the same means. 
 
 The makers of oil of vitriol have no other way of knowing 
 when the acid is in a proper state to be removed from the cham- 
 bers of combustion ; the calico-printer, who concentrates his own 
 lemon-juice, has nothing else to direct his decision in determining 
 whether the citric solution be fit for this or that particular style 
 of work ; nor does the modern bleacher, who is careful in his 
 operations, ever dare to use the liquid chloride of lime, till he 
 has reduced it to that particular specific gravity at which he 
 knows it may be used with safety. 
 
 Even the malleability, tenacity, and hardness of some of the 
 metals, and the volatilities of many fluid substances, may be as- 
 certained or conjectured by an attention to their respective spe- 
 cific gravities ; but to enumerate more individual instances would 
 be useless, as I conceive the importance of the subject under 
 consideration must be fully apparent. 
 
 It has been before remarked, that specific gravity is only an- 
 other name for comparative gravity, the absolute weight of the 
 substance under examination being always compared with that of 
 
 Learned, vol. iv. 1J02, page 652. Professor Musschenbroek of Utrecht pub- 
 lished a large table of specific gravities in his Elcmenta Pkysic<s t 8vo, Leyden, 
 
106 ON SPECIFIC GRAVITY. 
 
 some other substance exactly of an equal bulk. In fixing this 
 standard, water presented itself as the most convenient substance ; 
 and this, as I before stated, is now generally employed as the 
 datum from which all calculations of specific gravity proceed, 
 water at the temperature of 60 being always called 1.000. 
 
 According to the experiments of Professor Robinson of Edin- 
 burgh, a cubic foot of distilled water at the temperature of 55 
 weighs 998.74 ounces avoirdupoise, of 437.5 grains troy each, 
 which is only one ounce and a small fraction less than 1000 avoir- 
 dupoise ounces, so that rain water at the same temperature will 
 weigh, as has been stated elsewhere, pretty nearly 1000 ounces 1 . 
 
 Some excellent directions for the choice of an accurate pair of 
 scales for philosophical purposes will be found in Dr. Ure's Che- 
 mical Dictionary, article Balance ; and a very ingenious mode of 
 making most minute and accurate weights is described by Lewis 
 in his Commerce of the Arts, p. 544. It will therefore not be 
 necessary for me to enlarge on this branch of the subject. De- 
 cimal weights are the most convenient for general philosophical 
 purposes. These are usually sold in boxes from 1000 grains 
 down to the tenth of a grain. 
 
 In estimating the specific gravity of fluids, it is usual to procure 
 a phial with a narrow neck, to fill this phial up to the small part 
 of the neck with two, four, eight, or some determinate and easily 
 divisible number of ounces, or any other known weight, of pure 
 water, and then to mark the neck of the bottle with a diamond, 
 precisely at the spot to which the water ascends within it. The 
 Dottle being thus prepared, and the quantity of water which it 
 holds up to the fixed mark being remembered, it is ready for use. 
 
 When any liquid substance is to be examined, all that is ne- 
 cessary is to pour into the bottle as much of the liquid under 
 examination as shall exactly rise up to the mark on the neck, 
 and then to weigh it accurately, and calculate the difference by 
 the common rule of three. For instance, if it weigh exactly the 
 same as an equal bulk of water, it is said to be of the specific 
 gravity of water. But if the bottle hold four ounces of water, 
 and the same measure of some other fluid should weigh six, it is 
 evident that this fluid is half as heavy again as water, and water 
 being 1.000, this fluid will be noted to be of the specific gravity 
 of 1.500 ; because 4:6:: 1000 : 1500. The bottle usually em- 
 ployed by the soap-boiler, to ascertain the strength of his alka- 
 line lyes, is of this kind. 
 
 1 For further information consult Mr. John Dalton, " On the Density of 
 Water," in Nicholson's Journal, vol. x. p. 93; Count Itinnford, in the same 
 work, vol. xi. page 225 ; or Dr. Kelly's Universal Cambist, 4to, London 1811, 
 vol. i. page 260. 
 
ON SPECIFIC GRAVITY. 107 
 
 Another method of ascertaining the specific gravity of fluids, 
 is by noting the weight of some solid, such as a cube of glass, in 
 distilled water, and then weighing the same substance in the 
 liquid to be examined. These weights should be noted in 
 grains, and by dividing what the solid loses in the fluid by what 
 it lost when it was weighed in the water, the quotient will be the 
 real specific gravity of the liquid. The specific gravity of fluids 
 is also found by the areometer, a mode that is attended with 
 much less trouble than either of the former, but it is not likely in 
 all cases to be equally accurate. 
 
 This instrument is a graduated glass tube, with a bulb at one 
 end of it, and so contrived, by being balanced with mercury or 
 lead, that it may swim in the fluid, in a perpendicular position. 
 The specific gravity is shown by the degree marked on the stem 
 of the instrument, to which it sinks in the fluid to be examined, 
 and this will consequently always be lower in proportion as the 
 liquid is lighter. The areometer of Baume, which has long 
 been the instrument in common use in France, is upon this con- 
 struction. 
 
 The areometer is an instrument of great antiquity. It was 
 formerly supposed to have been invented at the close of the 
 fourth century by Hypatia, the celebrated mathematician of 
 Alexandria ; but Usebe Salverte, in a memoir on this subject in 
 the twenty-second volume of the Annales de Chimie, has shown 
 that it was undoubtedly invented by Archimedes. This writer 
 has given a Latin description of the instrument, from an author 
 of great antiquity, and from this it appears that the ancient areo- 
 meter was very similar in form to the modern. 
 
 The first instance I have met with of the use of the term 
 areometer is in the Philosophical Transactions, No. 262 ; in 
 which it is applied to an instrument invented by Homberg, and 
 employed by him in conducting some experiments on specific 
 gravity which he has related in the Memoirs of the Academy of 
 Sciences at Paris for the year 1699. The instrument is thus 
 described by Dr. Davies, a writer to whom I am under great 
 obligations for many hints of which I have availed myself in this 
 Essay : " It was an instrument," says the Doctor, " which 
 Homberg had contrived and called an araeometer, it being a 
 large phial, to which he had adjusted a long and slender stem, 
 whereby he could to good exactness determine specific gravities, 
 when it was filled with equal bulks or quantities of the several 
 fluids he proposed to examine 2 . It will, however, be perceived 
 
 ft See Tables of Specif c Gravities, by Richard Davies, M.D. 4to, London, 
 1750, page 12. For an account of an improved areometer for spirits see the 
 Philosophical Transactions, No. 413, page 277? or Baddam's Memoirs of the 
 Royal Society, vol. ix. page 47. 
 
108 ON SPECIFIC GRAVITY. 
 
 that this instrument is entirely on a different principle from the 
 one now known by the name of an areometer. 
 
 The late Mr. Nicholson made a great improvement in the 
 areometer, having adapted it to the measure of the density of 
 solids as well as fluids. It is described in the second volume of 
 the Manchester Memoirs, and a plate of it is given in the first 
 volume of Nicholson's 4- to Journal 1 . 
 
 In France the areometer has long been in use. Those con- 
 structed by Baume were generally employed ; and as they are 
 very frequently mentioned in the writings of the French che- 
 mists, I have deemed it advisable to explain the principle on 
 which they were founded. 
 
 In forming this instrument he had recourse to a process simi- 
 lar to that of graduating the stems of thermometers from two 
 fixed points. The first of these points was obtained by immers- 
 ing the instrument in pure water. At that point of the stem 
 which was intersected by the surface of the fluid, he marked zero, 
 or the first of his graduation, and this commenced at or near the 
 upper extremity of the stem. 
 
 He then provided a number of solutions of pure common salt 
 in water : these solutions contained respectively one, two, three, 
 four, &c. parts of the dry salt, and in each solution the quantity 
 of water was such as to make up the weight equal to one hundred 
 parts in the whole ; so that in the solution containing one part 
 of salt, there were ninety-nine parts of water ; in the solution 
 containing two parts of salt, there were ninety-eight parts of 
 water, and so on with the rest. The instrument was then 
 plunged in the first solution, in which of course it floated with a 
 larger portion of the stem above the fluid, than when pure water 
 was used. The fluid, by the intersection of its surface upon the 
 stem, indicated the place for marking his first degree; the same 
 operation repeated, with the fluid containing two pounds of salt, 
 indicated the mark for the second degree; the solution of three 
 pounds afforded the third degree : and in this manner his enu- 
 meration was carried as far as fifteen degrees. These first de- 
 grees applied with the compasses repeatedly along the stem, 
 served to extend the graduation as far as was required. This 
 instrument, which is applicable to the admeasurement of densi- 
 ties exceeding that of pure water, is distinguished by the name 
 of " the areometer for salts." His areometer for spirits is formed 
 upon the same principle; but in this the counterpoise is so ad- 
 justed, that most part of the stem rises above the fluid when 
 immersed in pure water : consequently the graduations to ex- 
 
 1 See Memoirs of the Literary and Philosophical Society of Manchester, vol. 
 ii. page 370 j and Nicholson's Journal, vol. i. page 110. 
 
ON SPECIFIC GRAVITY. 
 
 109 
 
 press inferior densities are continued upwards on the stem, 
 instead of downwards as in the former instance. 
 
 Here a solution of ten parts by weight of salt, in ninety parts 
 of water, afforded him the first point of zero ; and the mark in- 
 dicated by pure water he called the tenth degree ; whence by 
 equal divisions the remaining degrees were determined . 
 
 Baume's Areometer for Salts. 
 
 Baume's Areometer for Spirits. 
 
 Temperature 55 Fahrenheit. 
 
 Temperature 55 Fahrenheit. 
 
 Deg. Sp. Gr. Deg. Sp. Gr. 
 
 Deg. Sp. Gr. Deg. Sp. Gr. 
 
 1.000 39 1.373 
 
 10 1.000 26 .892 
 
 31.020 421.414 
 
 11 .990 27 .886 
 
 6 1.040 45 1.455 
 
 12 .985 28 .880 
 
 9 1.064 48 1.500 
 
 13 .977 29 .874 
 
 121.089 51 1.547 
 
 14 .970 30 .867 
 
 15 1.114 54 1.594 
 
 15 .963 31 .861 
 
 181.140 57 1.659 
 
 16 .955 32 .856 
 
 21 1.170 601.717 
 
 17 .949 33 .852 
 
 241.200 631.779 
 
 18 .942 34 .847 
 
 271.230 66 1.848 
 
 19 .935 35 .842 
 
 30 1.261 691.920 
 
 20 .928 36 .837 
 
 331.295 72 2.000 
 
 21 .922 37 .832 
 
 36 1.333 
 
 22 .915 38 .827 
 
 
 23 .909 39 .822 
 
 
 24 .903 40 .817 
 
 
 25 .897 
 
 In Great Britain and Ireland the specific gravity of ardent 
 spirits is determined on another principle, and various instru- 
 ments, called hydrometers, have been used for the purpose. 
 Here, unfortunately, the specific gravity is not calculated from 
 that of water, but from the strength of an arbitrary spirit, which 
 the Excise Board calls proof spirit, the specific gravity of which 
 is about 0.933. The relation which all other spirituous liquors 
 have to the standard, is expressed by saying they are so much 
 above or under hydrometer proof. 
 
 For instance, a spirituous liquor is said to be ten per cent 
 over hydrometer proof, when it is so strong that one hundred 
 gallons of it will admit an addition of ten gallons of water to re- 
 duce it to the strength of proof; and it is considered to be ten 
 per cent under proof, when one hundred gallons contain ten 
 gallons of water more than is contained in proof spirits. 
 
 In chemical laboratories it would be inconvenient to depend 
 solely on any instrument of the kind just described ; for the range 
 from the specific gravity of pure liquid ammonia to that of con- 
 centrated sulphuric acid is so great, that several different areo- 
 meters would be required ; it being almost impossible to construct 
 
 a See Baume's Elemens dc Pharmacic, 1784, page 410 ; or Nicholson's 4to 
 Journal, vol. i. page 37. 
 
112 ON SPECIFIC GRAVITY. 
 
 ought always to be employed, as a variation in this respect will 
 inevitably affect the result. A philosophical friend of mine has 
 been in the habit of using water drawn from a deep well for such 
 purposes, finding such water, in all seasons, to be of the same 
 temperature, provided he employed it as soon as it came from 
 the well. Nearly a century ago Mr. Charles Labelye, civil 
 engineer, ascertained the specific gravity of several sorts of stone 
 and other materials used in building. These were afterwards 
 printed in Dodson's Calculator, 8vo, London 1747, and may 
 even now be referred to by builders with advantage. 
 
 The works of most eminence on the subject of weighing hy- 
 drostatically were published in the following order. Medicina 
 Hydrostatica, by the Honourable Robert Boyle, 8vo, London 
 1690; Sir Isaac Newton's Optics, 4to, London 1704; The 
 Young Mathematician's Guide, by John Ward, 1706; Hydro- 
 statical and Pneumatical Lectures, by Roger Cotes, A.M. Plu- 
 mian Professor of Astronomy, &c. at Cambridge, 8vo, 1707; 
 Hauksbee's Hydrostatical Lectures, 4to, 1710; Lectures on se- 
 lect Subjects in Mechanics, Hydrostatics, &c., by James Fer- 
 guson, 8vo, London 1 760, together with A Supplement to this 
 work, 4?to, London 1767. A third edition of Mr. Cotes's Lec- 
 tures was printed in London in 1775 ; in which there are some 
 very minute and useful directions for weighing a variety of sub- 
 stances hydrostatically. 
 
 Dr. Jurin, who was Secretary to the Royal Society in the 
 beginning of the last century, has also published some very 
 useful remarks respecting the cautions necessary to be used in 
 examining the specific gravity of solids, when weighed hydro- 
 statically ; for want of attending to which, several kinds of bodies, 
 from their pores being filled with air, have appeared to be con- 
 siderably lighter than they really are. See Phil. Trans. No. 369. 
 
 This method of weighing, and which can only be employed 
 for solid bodies that are insoluble in water, is commonly con- 
 ducted thus : The substance to be weighed is hung by a fine 
 hair to one of the arms of a small scale-beam, which has a com- 
 mon scale-dish suspended to the other arm. When the article 
 which is intended to be tried is suspended by the hair, it is ac- 
 curately balanced by grain-weights, and the weight of it noted. 
 It is then taken, still suspended to the arm of the balance, and 
 immersed entirely in water, which will destroy the equilibrium, 
 and occasion the opposite scale to preponderate. Weights are 
 then taken out of the scale till the balance is restored ; and the 
 amount of the weights which it is necessary to take out to re- 
 store the equilibrium, shows the difference there is in the weight 
 of the substance when weighed in air and in water. 
 
 When the specific gravity of a substance is required, which 
 
ON SPECIFIC GRAVITY. 113 
 
 cannot be weighed in water, because it is soluble in that fluid, it 
 may probably be weighed in some liquor that will not dissolve 
 it. Thus, if it be a saline substance, it may probably be weighed 
 with accuracy in a saturated solution of that salt. 
 
 It is obvious that, in this method of taking specific gravities, 
 water can be employed only for such substances as are above 
 1.000, or denser than water; because such bodies would not 
 sink in the water, and it is necessary that they should be com- 
 pletely immersed. When it is required to weigh a body hydro- 
 statically, that is specifically lighter than water, some heavier 
 substance must be attached to it, and its weight also must be 
 taken into account in making the calculation. 
 
 A more ready way to determine the specific gravity of solids, 
 when circumstances will admit of it, is to fill a phial with water, 
 and note the weight of the whole accurately in grains. Then 
 weigh 100 grains of the substance to be examined, and drop it 
 gradually into the phial of water. The difference of weight of 
 the bottle with its contents now, and when it was filled with 
 water only, will give the specific gravity of the matter under con- 
 sideration. For example, if the bottle weighs 50 grains more 
 than it did when it was filled with water only, it shows that 100 
 grains of the mineral displace only 50 grains of water, and con- 
 sequently that it is twice the specific gravity of water. 
 
 It was on this principle that Archimedes is said to have dis- 
 covered the deceit which had been practised upon his relative 
 Hiero the Second, king of Syracuse, by an unprincipled gold- 
 smith who had been employed to fabricate a crown of pure gold 
 for him, as an offering to the gods. 
 
 The workman, it seems, had alloyed the crown with a portion 
 of silver, imagining that the fraud could not be detected ; but 
 Archimedes, suspecting that a cheat had been practised, hit upon 
 the following method of ascertaining the fact : 
 
 He made two masses, each of equal weight with the crown, 
 one of gold and the other of silver : when he had done this, he 
 filled a large vessel to the brim with water, and put the silver 
 mass into it, upon which a quantity of water overflowed, equal 
 to the bulk of the mass : then taking the metal out, he filled up 
 the vessel again, measuring the water exactly which he put in : 
 this showed him what measure of water answered to a certain 
 quantity of silver. 
 
 He then tried the gold in like manner, and found that it 
 caused a less quantity of water to overflow; the gold being less 
 in bulk than the silver, though of the same weight. Having 
 filled the vessel a third time, he then put in the crown itself and 
 found that it caused more water to overflow than the mass of 
 gold of the same weight. From these data he calculated, as he 
 
 i 
 
114? ON SPECIFIC GRAVITY. 
 
 imagined, how much gold had been purloined, and what silver 
 had been substituted in its stead ! . 
 
 This piece of history, which has been related a hundred times 
 in various ways, would not have found a place here, but for the 
 design of ingrafting upon it a very necessary and a very import- 
 ant caution. 
 
 A person might conclude, when it had been once clearly 
 ascertained that one of two metals, whose specific gravities dif- 
 fered, was the heaviest metal then known, that there would be 
 no impediment in calculating how much of the lighter metal had 
 been employed in forming an alloy of the two metals : experience, 
 however, proves the fallacy of such a theory. 
 
 Mr. William Lewis, the first person who examined this sub- 
 ject with due care, made a great number of mixtures of the 
 different metals; and the result of these experiments shows, 
 " that the specific gravity of a metal can never be with any cer- 
 tainty deduced from that of its mixture with another metal, as a 
 dilatation or contraction of the volume may result from their 
 action on one another; and that when two metals of known 
 specific gravities are melted together, their proportions cannot 
 be found from the gravity of the compound, without a previous 
 hydrostatic examination of known mixtures of them in different 
 proportions, and, consequently, that the celebrated method of 
 calculation proposed by Archimedes is of more limited use than 
 has generally been supposed." 
 
 The apparent anomaly in the alloy of gold with silver, Mr. 
 Lewis explains by stating, that the proportions of these metals 
 should be calculated from their respective bulks, and not from 
 their weights. A pei'son who was acquainted with this fact, he 
 says, made great profits in buying gold from the Chinese, who 
 usually employ silver in their alloy of gold 2 . 
 
 Mr. Lewis, however, was not the first person who wrote on 
 this subject ; for Mr. Hooke had made some experiments before 
 the Royal Society on a mixture of tin and silver, which tended 
 to a result similar to the one which Mr. Lewis afterwards ob- 
 tained. Dr. Davies also suggested the same idea thirteen years 
 before the publication of the Commercium Philosophico-Techni- 
 cum, which did not make its appearance until the year 1763. 
 " It might be queried," says Dr. Davies, " whether mixed me- 
 tals do not either rarefy or condense upon mixture, so as thereby 
 to acquire a different specific gravity than the natural law of their 
 composition at first seems to require 3 ." 
 
 1 Vitruvius, lib. ix. cap. 3. 
 
 2 Philosophical Commerce of the Arts, pages 125 and 556. 
 
 3 Davies's Tables of Specif c Gravities, page 29. 
 
ON SPECIFIC GRAVITY. 115 
 
 In the mixture of crude platinum with silver, it is well known 
 that there is a diminution of specific gravity ; and in its mixture 
 with iron, an increase. Tin is specifically much lighter than 
 copper, yet the specific gravity of the compound, bell-metal, is 
 greater than that of copper itself. From inattention to such 
 facts many deceptions might arise, and innumerable errors be 
 committed. 
 
 Mr. Scheffer made out a table for determining the quantities 
 of lead and tin in any given mixtures of the two, by taking the 
 specific gravity of the alloy ; and this was published in the 
 Swedish Acts for 1755. But as this table was formed without 
 comparison with standard mixtures, it cannot be depended upon, 
 and is consequently of no value. 
 
 Having thus shown that the specific gravity of a compound 
 metal can never, with any certainty, be deduced by calculation 
 from that of its mixture with another metal, as a dilatation or 
 contraction of the volume results from their mutual action on 
 each other ; it may be observed that just so is it with the melting 
 point of a compound metal. Tin melts at 413 of Fahrenheit, 
 bismuth at 476, and lead at about 612; but a certain mixture 
 may be made with these metals, that will fuse at the temperature 
 of 202. There are also some curious anomalies in the melting 
 points of various mixtures of lead and tin. 
 
 The goodness of tin may be generally known by its specific 
 gravity, though it would be erroneous to judge of the ores of 
 tin by the same means, because some specimens of the best ores 
 are of a specific gravity greater even than that of the pure metal 
 itself. 
 
 A deception equally great would arise from an attempt to cal- 
 culate the proportions of many of the mixtures of liquid sub- 
 stances, without having made previous experiments to determine 
 the amount of their condensation by mixture : for, when two li- 
 quids unite chemically, the compound has generally a density 
 greater than the mean density. 
 
 If we make a mixture of ardent spirit with water, the specific 
 gravity of the mixture will not be a mean specific gravity. Water 
 itself is of far greater gravity than the oxygen and hydrogen gas 
 which compose it. One measure of sulphuric acid and one mea- 
 sure of water, when mixed, will not occupy the space of two 
 measures ; consequently the mixture cannot have a specific gra- 
 vity corresponding to the mean between those of the two original 
 fluids. 
 
 It will be remembered, therefore, that to ascertain the specific 
 gravity of a body may serve to furnish some idea of its purity, 
 some substances being increased, and others diminished, in their 
 
 I 2 
 
116 ON SPECIFIC GRAVITY. 
 
 specific gravities, by sophistication ; that it will indicate the 
 comparative value of certain metallic, acidulous or alkaline solu- 
 tions, and has innumerable other uses in the hands of the manu- 
 facturing or philosophical chemist, some of which have been 
 mentioned at page 105 : it does not, however, afford any means 
 of accurately discovering the amount of adulteration, or establish- 
 ing a proof of the quantities of the components, whether the 
 mixture be fluid or solid. 
 
 A method of calculating the mean specific gravity of a com- 
 pound from those of its component parts has been lately published 
 by Dr. Ure in his Chemical Dictionary before mentioned under 
 the article Specific Gravity ; and in the Journal of Science and 
 the Arts, vol. iv. page 151. 
 
 Nothing now remains but to notice a distinct method of taking 
 the specific gravity of fluids, which differs in some respects from 
 those already described, and is that which I have adopted in my 
 own Chemical Manufactory for many years past. 
 
 This ingenious contrivance, which originated with Dr. Lewis, 
 was communicated to me by the amiable Mr. Samuel Moore, 
 late Secretary to the Society for the Promotion of Arts, Manu- 
 factures and Commerce, who favoured me with a sight of Dr. 
 Lewis's manuscript, and allowed me to make such extracts from 
 it as I conceived might be useful. 
 
 In this scheme the specific gravity of a liquor is estimated 
 from the excess of the weight of a certain measure of it, above 
 that of an equal measure of distilled water. For this purpose, a 
 peculiar set of weights, which he called CARATS, is to be made in 
 the following manner : 
 
 A convenient bottle, with a long narrow neck, being procured, 
 the tare of the bottle is first taken, and a weight made corre- 
 sponding thereto, as the exact counterpoise : it is then to be 
 completely filled with distilled water at 60, or till the water rise 
 to a mark made in such part of the neck as shall be found most 
 convenient. A weight corresponding to the net weight of this 
 water is then to be made, and marked 128; after which this 
 weight is to be accurately divided into two equal parts, and a 
 weight made equal to one of these parts is to be marked 64-. By 
 continuing the subdivision we shall have the weights, 32, 16, 8, 
 4, 2, 1, carats; so that each carat, though in some measure of 
 an arbitrary value, must be one hundred and twenty-eighth of 
 the water required to fill such bottle. 
 
 When these weights are adjusted, it will be proper to make 
 another counterpoise besides that already described for the tare 
 of the bottle, and this must be an exact balance to both the 
 water and bottle. We then make our estimate in this way: 
 
ON SPECIFIC GRAVITY. 117 
 
 So many carats as the bottle when filled with any other fluid, 
 exceeds this united weight or counterpoise, so many carats strong 
 is such fluid to be estimated. 
 
 This small apparatus is equally useful for taking the specific 
 gravities of alcohol, ether, liquid ammonia, oils, or any other 
 fluid body which is lighter than water. In such cases, the only 
 variation necessary is to put the carat-weights in the scale with 
 the bottle, instead of putting them with the water-poise ; and 
 whatever number of carats may be required for bringing the 
 bottle and the water-poise to an equilibrium, so many carats is 
 the fluid lighter than an equal measure of pure water ; and as 
 the perfection of these liquids is in a direct ratio with their levity, 
 their true value is at once demonstrated. 
 
 Soon after I had printed this account of my apparatus for 
 taking the specific gravity of fluids, Mr. Gill informed me that 
 he had formed an apparatus which may be considered to be in 
 some measure an improvement upon mine ; and which he thus 
 describes : He has a phial as usual, with a ground glass stopper, 
 having a groove cut upon it to let the air and superfluous fluid 
 escape on closing the orifice. The weights are contained in a 
 metallic box, the lid of which is made to be exactly equal in 
 weight to the empty glass bottle with its stopper, whilst the other 
 part of the box (weighing 128 carats) is equal to the weight of 
 the distilled water which the bottle at a certain temperature is 
 capable of containing. His weights consist of one of 64 carats, 
 one of 32, one of 16, one of 8, one of 4, one of 2, and two 
 weights of 1 carat each. The last two are of the same denomi- 
 nation, in order that the amount of the whole may be equal to 
 128, without which the specific gravity of a fluid equal to 2000 
 could not be obtained. He has also weights for the half, 
 fourth, eighth, and sixteenth of a carat. 
 
 The following is a Table of Carats, with their corresponding 
 degrees of specific gravities, which I constructed many years ago 
 for the use of my own laboratory. For those persons who have 
 been in the habit of calculating specific gravities by the wine- 
 pint, or, to speak more accurately, by a measure holding exactly 
 sixteen avoirdupois ounces of water, as also for those who may 
 not be conversant with the mode of reckoning specific gravities 
 by decimal arithmetic, I subjoin a column of the weights in 
 ounces and drachms. We know it has been decided that the 
 wine-pint holds rather more than sixteen ounces of water; but 
 it is most convenient for all common purposes, still to consider it 
 as a measure of sixteen ounces, and this table is constructed 
 accordingly. 
 
118 
 
 ON SPECIFJ C GRAVITY. 
 
 
 Fluids 
 
 Weight of 
 
 Fluids 
 
 
 Fluids 
 
 Weight of 
 
 Fluids 
 
 
 heavier 
 
 the wine 
 
 lighter 
 
 
 heavier 
 
 the wine 
 
 lighter 
 
 
 than water. 
 
 pint. 
 
 than water. 
 
 
 than water. 
 
 pint. 
 
 than water. 
 
 Carats. 
 
 Sp. Gr. 
 
 Oz. Drm 
 
 . Sp. Gr. 
 
 Carats. 
 
 Sp. Gr. 
 
 Oz. Drms 
 
 . Sp. Gr. 
 
 1 = 
 
 = 1.00/8 
 
 16 2 
 
 0.9922 
 
 54 = 
 
 = 1.4218 
 
 22 12 
 
 0.5782 
 
 g 
 
 1.0156 
 
 16 4 
 
 0.9844 
 
 55 
 
 1.4296 
 
 22 14 
 
 0.5704 
 
 3 
 
 1.0234 
 
 16 6 
 
 0.9766 
 
 56 
 
 1.4375 
 
 23 
 
 0.5626 
 
 4 
 
 1.0312 
 
 16 8 
 
 0.9688 
 
 57 
 
 1.4453 
 
 23 2 
 
 0.5547 
 
 5 
 
 1.0390 
 
 16 10 
 
 0.9610 
 
 58 
 
 1.4531 
 
 23 4 
 
 0.5469 
 
 6 
 
 1.0468 
 
 16 12 
 
 0.9532 
 
 59 
 
 1.4609 
 
 23 6 
 
 0.5:391 
 
 7 
 
 1.0546 
 
 16 14 
 
 0.9454 
 
 60 
 
 1.4687 
 
 23 8 
 
 0.5313 
 
 8 
 
 1.0625 
 
 17 
 
 0.9376 
 
 61 
 
 .4765 
 
 23 10 
 
 0.5235 
 
 9 
 
 1.0703 
 
 17 2 
 
 0.9297 
 
 62 
 
 .4843 
 
 23 12 
 
 0.5157 
 
 10 
 
 1.0781 
 
 17 4 
 
 0.9219 
 
 63 
 
 .4921 
 
 23 14 
 
 05079 
 
 11 
 
 1.0859 
 
 17 6 
 
 0.9141 
 
 64 
 
 .5000 
 
 24 
 
 0.5001 
 
 12 
 
 1.0937 
 
 17 8 
 
 0.9063 
 
 65 
 
 .5078 
 
 24 2 
 
 0.4922 
 
 13 
 
 1.1015 
 
 17 10 
 
 0.8985 
 
 66 
 
 .5156 
 
 24 4 
 
 0.4844 
 
 14 
 
 1.1093 
 
 17 12 
 
 0.8907 
 
 67 
 
 1.5234 
 
 24 6 
 
 0.4766 
 
 15 
 
 1.1171 
 
 17 14 
 
 0.8829 
 
 68 
 
 1.5312 
 
 24 8 
 
 0.4688 
 
 16 
 
 1.1250 
 
 18 
 
 0.8751 
 
 69 
 
 1.5390 
 
 24 10 
 
 0.4610 
 
 17 
 
 1.1328 
 
 18 2 
 
 0.8672 
 
 70 
 
 1.5468 
 
 24 12 
 
 0.4532 
 
 18 
 
 1.1406 
 
 18 4 
 
 0.8594 
 
 71 
 
 1.5546 
 
 24 14 
 
 0.4454 
 
 19 
 
 1.1484 
 
 18 6 
 
 0.8516 
 
 72 
 
 1.5625 
 
 25 
 
 0.4376 
 
 20 
 
 1.1562 
 
 18 8 
 
 0.8438 
 
 73 
 
 1.5703 
 
 25 2 
 
 0.4297 
 
 21 
 
 1.1640 
 
 18 10 
 
 0.8360 
 
 74 
 
 1.5781 
 
 25 4 
 
 0.4219 
 
 22 
 
 1.1718 
 
 18 12 
 
 0.8282 
 
 75 
 
 1.5859 
 
 25 6 
 
 0-4141 
 
 23 
 
 1.1796 
 
 18 14 
 
 0.8204 
 
 76 
 
 1.5937 
 
 25 8 
 
 0.4063 
 
 24 
 
 1.1875 
 
 19 
 
 0.8126 
 
 77 
 
 1.6015 
 
 25 10 
 
 0.3985 
 
 25 
 
 1.1953 
 
 19 2 
 
 0.8047 
 
 78 
 
 1.6093 
 
 25 12 
 
 0.3907 
 
 26 
 
 1.2031 
 
 19 4 
 
 0.7969 
 
 79 
 
 1.6171 
 
 25 14 
 
 0.3829 
 
 27 
 
 1.2109 
 
 19 6 
 
 0.7891 
 
 80 
 
 1.6250 
 
 26 
 
 0.3751 
 
 28 
 
 1.2187 
 
 19 8 
 
 0.7813 
 
 81 
 
 1.6328 
 
 26 2 
 
 0.3672 
 
 29 
 
 1.2265 
 
 19 10 
 
 0.7735 
 
 82 
 
 1.6406 
 
 26 4 
 
 0.3594 
 
 30 
 
 1.2343 
 
 19 12 
 
 0.7657 
 
 83 
 
 1.6484 
 
 26 6 
 
 0.3516 
 
 31 
 
 1.2421 
 
 19 14 
 
 0.7579 
 
 84 
 
 1.6562 
 
 26 8 
 
 0.3438 
 
 32 
 
 1.2500 
 
 20 
 
 0.7501 
 
 85 
 
 1.6640 
 
 26 10 
 
 0.3360 
 
 33 
 
 1.2578 
 
 20 2 
 
 0.7422 
 
 86 
 
 1.6718 
 
 26 12 
 
 0.3282 
 
 34 
 
 1.2656 
 
 20 4 
 
 0.7344 
 
 87 
 
 1.6796 
 
 26 14 
 
 0.3204 
 
 35 
 
 1,2734 
 
 20 6 
 
 0.7266 
 
 88 
 
 1.6875 
 
 27 
 
 0.3126 
 
 36 
 
 1.2812 
 
 20 8 
 
 0.7188 
 
 89 
 
 1.6953 
 
 27 2 
 
 0.3047 
 
 37 
 
 1.2890 
 
 20 10 
 
 0.7110 
 
 90 
 
 1.7031 
 
 27 4 
 
 0.2969 
 
 38 
 
 1.2968 
 
 20 12 
 
 0.7032 
 
 91 
 
 1.7109 
 
 27 6 
 
 0.2891 
 
 39 
 
 1.3046 
 
 20 14 
 
 0.6954 
 
 92 
 
 1.7187 
 
 27 8 
 
 0.2813 
 
 40 
 
 1.3125 
 
 21 
 
 0.6876 
 
 93 
 
 1.7265 
 
 27 10 
 
 0.2735 
 
 41 
 
 1.3203 
 
 21 2 
 
 0.6797 
 
 94 
 
 1.7343 
 
 27 12 
 
 0.2657 
 
 42 
 
 1.3281 
 
 21 4 
 
 0.6719 
 
 95 
 
 1.7421 
 
 27 14 
 
 0.2579 
 
 43 
 
 1.3359 
 
 21 6 
 
 0.6641 
 
 96 
 
 1.7500 
 
 28 
 
 0.2501 
 
 44 
 
 1.3437 
 
 21 8 
 
 0.6563 
 
 97 
 
 1.7578 
 
 28 2 
 
 0.2422 
 
 45 
 
 1.3515 
 
 21 10 
 
 0.6485 
 
 98 
 
 1.7656 
 
 28 4 
 
 0.2344 
 
 46 
 
 1.3593 
 
 21 12 
 
 0.6407 
 
 99 
 
 1.7734 
 
 28 6 
 
 0.2266 
 
 47 
 
 1.3671 
 
 21 14 
 
 0.6329 
 
 100 
 
 1.7821 
 
 28 8 
 
 0.2188 
 
 48 
 
 1.3750 
 
 22 
 
 0.6251 
 
 101 
 
 1.7890 
 
 28 10 
 
 0.2110 
 
 49 
 
 1.3828 
 
 ^2 2 
 
 0.6172 
 
 102 
 
 1./968 
 
 28 12 
 
 0.2032 
 
 50 
 
 1.3906 
 
 22 4 
 
 0.6094 
 
 103 
 
 1.8046 
 
 28 14 
 
 0.1954 
 
 51 
 
 1.3984 
 
 22 6 
 
 0.6016 
 
 104 
 
 1.8124 
 
 29 
 
 0.1876 
 
 52 
 
 1.4062 
 
 22 8 
 
 0.5938 
 
 105 
 
 1 8202 
 
 29 2 
 
 0.1797 
 
 53 
 
 1.4140 
 
 22 10 
 
 0.5860 
 
 106 
 
 1.8280 
 
 29 4 
 
 0.1/19 
 
ON SPECIFIC GRAVITY. 
 
 119 
 
 
 Fluids 
 
 Weight of 
 
 Fluids 
 
 Fluids 
 
 Weight of 
 
 Fluids 
 
 
 heavier 
 
 the wine 
 
 lighter 
 
 heavier 
 
 the wine 
 
 lighter 
 
 
 tlian water. 
 
 pint. 
 
 than water. 
 
 than water. 
 
 pint. 
 
 than water. 
 
 Carats 
 
 Sp. Or. 
 
 Oz. Drms 
 
 . Sp. Gr. 
 
 Carats. Sp. Gr. 
 
 Oz. Drms 
 
 . Sp. Gr. 
 
 107 
 
 = 1.8358 
 
 29 6 
 
 0.1641 
 
 118 = 1.9218 
 
 30 12 
 
 0.0782 
 
 108 
 
 1.8436 
 
 29 8 
 
 0.1563 
 
 119 
 
 .9296 
 
 30 14 
 
 0.0704 
 
 109 
 
 1.8514 
 
 29 10 
 
 0.1485 
 
 120 
 
 .9375 
 
 31 
 
 0.0626 
 
 110 
 
 1.8593 
 
 29 12 
 
 0.1407 
 
 121 
 
 .9453 
 
 31 2 
 
 0.0547 
 
 111 
 
 1.8671 
 
 29 14 
 
 0.1329 
 
 122 
 
 .9531 
 
 31 4 
 
 0.0469 
 
 112 
 
 1.8750 
 
 30 
 
 0.1251 
 
 123 
 
 .9609 
 
 31 6 
 
 0.0391 
 
 113 
 
 1.8828 
 
 30 2 
 
 0.1172 
 
 124 
 
 .9687 
 
 31 8 
 
 0.0313 
 
 114 
 
 1.8906 
 
 30 4 
 
 0.1094 
 
 125 
 
 .9765 
 
 31 10 
 
 0.0235 
 
 115 
 
 1.8984 
 
 30 6 
 
 0.1016 
 
 126 
 
 .9843 
 
 31 12 
 
 0.0157 
 
 116 
 
 1.9062 
 
 30 8 
 
 0.0938 
 
 127 
 
 .9921 
 
 31 14 
 
 0.0079 
 
 117 
 
 1.9140 
 
 30 10 
 
 0.0860 
 
 128 2.0000 
 
 32 
 
 0.0001 
 
 Since this Essay was composed, a simpler and more accurate 
 method of taking the specific gravities than any of the above 
 has been brought into very general use with scientific manufac- 
 turing chemists. A narrow-necked bottle must be provided, as 
 described page 110, with a ground conical stopper, having a fine 
 indentation filed to allow the fluid to overflow and prevent the 
 existence of air bubbles within the bottle. This bottle must be 
 formed to hold precisely 1000 grains of distilled water. When 
 filled with the fluid to be tried, placed in one scale, and in the 
 other a weight correspondent to the tare of the bottle and stopper, 
 it only requires to take the weight in grains, and every grain above 
 1000 will form an unit in the third place of decimals ; as for 
 instance, if it weighs 1845 grains, its specific gravity will be 
 1.845, which is the gravity of concentrated sulphuric acid. 
 
 Once more, I must inculcate the necessity of attending to the 
 degree of temperature of the atmosphere when the experiment 
 is made, as well as to that of the material to be examined, when, 
 its temperature is raised, or diminished, so as to deviate from the 
 former ; for we know that the specific gravity of all bodies is 
 greatly influenced by sensible caloric, and their bulk increased or 
 diminished in proportion to the quantity they contain. I repeat, 
 that it is of little avail to ascertain the specific gravity of bodies, 
 if proper attention be not at the same time paid to their degree 
 of temperature ; for gases, fluids, and solids, vary in bulk accord- 
 ing to the quantity of free caloric contained in them *. 
 
 1 For an account of the expansion of the gases by heat consult Dalton's 
 Ncio System of Chemical Philosophy, part 1. Manchester 1808. A table of 
 the expansion of glass is given by Dr. Henry in his Elements of Experimental 
 Chemistry, vol. ii. page 524 ; and Mr. John Ellicott published "The descrip- 
 tion and manner of using an instrument for measuring the degrees of the 
 expansion of metals by heat,'' in the Philosophical Transactions, No. 443, page 
 297. A collection of facts respecting the expansion of wood by heat will be 
 found in a memoir by Dr. Rittenhouse, published in the Transactions of the 
 American Philosophical Society. 
 
120 ON SPECIFIC GRAVITY. 
 
 Mr. Nicholson has stated, that he finds by experiment that the 
 fifth decimal figure changes in water at every three degrees of 
 Fahrenheit's thermometer. Other fluids will undoubtedly observe 
 a different ratio ; but a manufacturer, to whom it is often neces- 
 sary to try the specific gravity of one particular liquor, might, 
 for his own use, easily form a table of these variations. 
 
 In chemical manufactories it is often necessary to take the spe- 
 cific gravity of a fluid when nearly at a boiling heat. To do this, 
 I have always employed a stone bottle of a determinate size, 
 because this ware will endure such a temperature without break- 
 ing. I have thought of glass bulbs : but if one of these small 
 instruments be selected which will just swim in a fluid of the 
 specific gravity I want, the same would also swim on a liquor of 
 greater specific gravity, and this might occasion an error of some 
 importance. In like manner, a bulb might be chosen that would 
 just sink in a liquor of a determinate specific gravity, but it 
 would also sink in a lighter fluid, and this might equally pro- 
 duce deception. Mr. London, who has obtained a patent for 
 purifying muriate of soda (rock-salt), has, however, adopted the 
 ingenious expedient of employing two bulbs of different weights 
 at once, and by this means he readily determines when his saline 
 liquor is evaporated to the point which is necessary for his pur- 
 pose. For, if the lixivium be too much diluted, both these bulbs 
 will fall to the bottom ; and if it be too heavy, both of them will 
 swim : but when he perceives that the heaviest of these falls and 
 the other swims, he then knows that he may rely upon the liquor 
 being of the medium specific gravity which he requires. I have 
 for years been in the habit of using Twaddell's hydrometers in 
 boiling fluids, taking a little care to immerse them once or twice, 
 to warm them before I leave them in, and holding them for a 
 few moments exposed to the hot steam before I entirely with- 
 draw them. By means of this trifling precaution, I have never 
 in a single instance had one broken, even by servants in taking 
 the gravity of boiling liquids. 
 
 When I spoke of the necessity of using the thermometer in 
 taking specific gravities, it was my intention to observe, that the 
 important instrument which is generally employed in Great 
 Britain was constructed by Mr. Gabriel Daniel Fahrenheit, a 
 native of Hamburgh, who came to this country in the year 1724, 
 was elected a fellow of the Royal Society of London, and in 
 that year published "A Dissertation on Thermometers." I 
 state these circumstances merely to give me an opportunity of 
 mentioning, that this gentleman was also concerned in investi- 
 
 fiting the specific gravities of various bodies, and that while in 
 ngland he published " A Table of the Specific Gravities of 
 twenty-eight several Substances," with various observations, in 
 
ON SPECIFIC GRAVITY. 
 
 121 
 
 the Philosophical Transactions, No. 283. If any of my readers 
 should know of a memoir, or an engraved portrait, of this 
 eminent man, I shall most thankfully receive such information. 
 There is no notice of him or of his portrait either in Bromley, 
 Grainger, or Noble, all of which I have carefully examined. 
 
 The metals afford the greatest variety in their specific gravities 
 of any order of substances in nature. The following Table, 
 which gives a view of the principal ones arranged according to 
 their specific gravities, I have thought might be useful, and suit- 
 able for admission into this Essay. 
 
 A TABLE 
 
 OF 
 
 THE SPECIFIC GRAVITY OF THE METALS. 
 
 Platinum 21.470 
 
 Gold 19.300 
 
 Tungsten 17.400 
 
 Mercury, frozen t . 14.465 
 
 Ditto, fluid 13.568 
 
 Palladium 11.500 
 
 Lead 11.350 
 
 Rhodium 10.649 
 
 Silver 10.474 
 
 Bismuth 9.822 
 
 Copper 8.735 
 
 Cobalt 8.700 
 
 Molybdenum , 8.611 
 
 Nickel 
 
 Uranium 
 
 Manganese 
 
 Iron 
 
 Tin , 
 
 Zinc, hammered. . 
 Do. cast in bars 
 
 Antimony , 
 
 Tellurium 
 
 Chromium 
 
 Arsenic , 
 
 Sodium 
 
 Potassium , 
 
 8.380 
 8.100 
 8.043 
 7.700 
 7.291 
 7.190 
 6.861 
 6.712 
 6.115 
 5.900 
 5.763 
 0.972 
 0.865 
 
ON BARYTES. 
 
 ESSAY IV. 
 
 ON BARYTES. 
 
 JLN the year 1774, M. Scheele made some experiments on a 
 mineral called Marmor Metallicum, which he found to be a com- 
 bination of sulphuric acid and a peculiar alkaline earth not as 
 yet described. Gahn also minutely examined this mineral in the 
 year 1775, and both these chemists agreed to denominate the 
 base of it " heavy earth." Scheele then published an account 
 of his experiments upon it in a memoir on manganese, and this 
 work directed the attention of most of the chemists in Europe 
 to the investigation of its nature and properties *. 
 
 Bergman at first called the earth terra ponderosa ; Weigleb 
 and Sage called it barogium , afterwards it was called barotes ; 
 and at last Bergman named it, from the Greek word " barus 
 heavy," barites ; and with the alteration of a single letter, it has 
 borne that name ever since. 
 
 Barytes has never been found native otherwise than in com- 
 bination with an acid. Its affinity for the carbonic and other 
 acids is such that it cannot exist in nature in a state of purity. 
 
 The mineral on which the first experiments were made was a 
 sulphate of barytes, the only native substance which was then 
 known to contain this alkaline earth. This mineral, which has 
 been called vitriolated heavy earth, ponderous spar., phosphoric 
 spar, baroselenite, &c., occurs very plentifully in various parts of 
 Great Britain, and in most countries of Europe. Its specific 
 gravity is generally from 4,400 to 4,470. It is perfectly inso- 
 luble in water, and is the only barytic salt that is not poison- 
 ous. 
 
 This native production is found in large masses in the Derby- 
 shire lead mines, where it is distinguished by the name of cawlc ; 
 in the Cornish copper mines ; at Roye in the province of Picardy 
 in France ; in the vicinity of Mount Etna, and in a variety of 
 other places. It occurs in veins nearly four feet wide, traversing 
 the sand-stone in the Isle of Arran, at a small distance from the 
 shore. Also at Pomona in the Orkneys 2 . It is the heaviest 
 native earthy salt with which we are acquainted. 
 
 It is composed of different proportions of acid, base and ex- 
 traneous matter, according to its peculiar locality ; whereas the 
 
 1 See Dr. Hoepfner's paper on Sulphate of Barytes in Crell's Annales, torn. i. 
 p. 132 ; or in Annalcs de CJdmic, torn. i. p. 217- 
 
 2 See Jameson's Mineralogy of the Scottish Isles, 4to, 1800, vol. i. page 71, 
 and vol. ii. page 232. 
 
CHEMICAL ESSAYS, 
 
 Plate 5 
 

 
ON EARYTES. 
 
 sulphate of barytes which is formed by art consists of 66 barytes 
 and 34 sulphuric acid 3 . The native sulphate is sometimes of 
 a flesh colour, and of a foliated texture ; but it occurs also in a 
 great variety of crystalline forms and colours. Thus, very beau- 
 tiful specimens of crystallized sulphate of barytes were formerly 
 procured from the Nutfield fuller's earth pits, at Bletchingly 
 near Godstone in Surry. The workmen found it generally in 
 loose pieces in the midst of the bed of fuller's earth, and called 
 it shining spar. 
 
 Besides the places already enumerated, beautiful specimens of 
 the sulphate of barytes are found in some of the northern coun- 
 ties of England. In Mr. Hutton's museum at Keswick in the 
 county of Cumberland, there is a single crystal which is perfectly 
 formed, and weighs 29lbs. 2oz. When weighed hydrostatically 
 it loses 6lbs. loz., and consequently its specific gravity is 4,8041. 
 It will be perceived that this is a much greater specific gravity 
 than has ever been ascribed to the sulphate of barytes, and I 
 regretted that I could not confirm the fact myself; but having 
 no opportunity of weighing this stupendous crystal hydrostati- 
 cally in the museum of Mr. Hutton, I could only copy the 
 weights from the label affixed to it. This curious specimen was 
 found near Cross-fell in the county of Cumberland. 
 
 A species of this mineral is found about the Apennine moun- 
 tains, and in several other parts of Italy, in round pieces about 
 the size of a walnut, of a light gray colour and uneven surface. 
 These have often the shining appearance of some of the other 
 species of sulphate of barytes ; and after heavy showers of rain, 
 which wash away the earth from the mountains, they are found 
 in abundance 4 . 
 
 These little nodules, which are called Bologna stones, and 
 sometimes Bonona stones, are remarkable for acquiring a phos- 
 phorescent quality by calcination. Lemery relates, that this 
 property was discovered by one Casciarolo, an Italian shoe- 
 maker, who picked up one of these stones at the foot of Mount 
 Paderno, four Italian miles from the city of Bologna 5 . 
 
 This man, imagining from its weight and colour that it con- 
 tained silver, submitted it to calcination, to extract, as he thought, 
 the precious metal : and though he was disappointed in this re- 
 spect, he discovered that the action of the fire had given it the 
 property of being luminous in the dark ; and that not only this 
 
 3 A method of analysing sulphate of barytes is described by M. Afzelius, of 
 Upsal, in Crell's Annales for 1788, and in the Annales dc Chimic, tome iii. 
 page 290. 
 
 4 Busching's Geography, 4to, vol. iii. page 139 & 140. 
 
 5 See Hoinbcrg, Philosophical Transactions, No. 21. 
 
124? ON BARYTES. 
 
 particular stone, but others, which he afterwards treated in a 
 similar manner, acquired the same property 1 . 
 
 It has been said that these stones retain their luminous qua- 
 lity even when laid under water; that their splendour usually 
 lasts three or four years, and that it may then be renewed by a 
 fresh calcination*. 
 
 I am not aware that the native sulphate of barytes is used at 
 present for any other purpose than preparing the Bologna phos- 
 phorus, and for the extraction of pure barytes by means of char- 
 coal and the nitrous acid. It was, however, pretty largely em- 
 ployed some years ago by that ornament of our country, the late 
 Josiah Wedgwood, in the manufacture of his beautiful jasper 
 ware, which rivalled the productions of antiquity, and found its 
 way into the mansions of all the votaries of taste in every corner 
 of Europe. 
 
 From this employment of the sulphate of barytes, Mr. Wedg- 
 wood, for a long time, derived great profit ; none of the work- 
 men having any idea of the nature of the material on which they 
 were operating ; until a letter, containing a bill of parcels of a 
 quantity of the article, fell unfortunately into the hands of a faith- 
 less servant, who sold the secret, and deprived the worthy in- 
 ventor for ever of that particular source of emolument. For, 
 when the article was manufactured by those who employed infe- 
 rior workmen, to whom they did not pay one-fourth of the salary 
 which was given by Mr. Wedgwood, the price of jasper-ware 
 became so reduced that it was no longer in Mr. Wedgwood's 
 power to employ those exquisite modellers whom he had for- 
 merly engaged to superintend that branch of the manufacture. 
 
 The artificial sulphate of barytes has for many years been ap- 
 plied to the purposes of painting in water-colours, and it is the 
 most delicate and perfect WHITE now in use. It was first re- 
 commended and brought forward by Mr. Hume, who has long 
 supplied the public with it under the name of permanent white. 
 I know of nothing so well calculated as this for marking bottles 
 in a chemical laboratory, where the gases soon destroy the ink of 
 common labels, and render them illegible. It is equally useful 
 for marking jars, bottles, or boxes which must be kept in a damp 
 cellar; for it is not only imperishable in such situations, but pre- 
 serves its extreme whiteness, and consequently the distinctness 
 of the characters. 
 
 Sir H. Davy says that the artificial carbonate of barytes, form- 
 
 1 There is a paper on the preparation of the Bologna stone in the Philoso- 
 phical Collections for 1681, published by the Royal Society of London, page 77. 
 
 2 For the best method of making Bologna phosphorus, see LaGrange's Ma- 
 nual of Chemistry, vol. i. p. 188. 
 
ON BARYTES. 125 
 
 ed by pouring a solution of carbonate of ammonia into a solution 
 of nitrate of barytes, also forms a pigment of a very pure white 
 colour. 
 
 If the native sulphate of barytes, reduced to powder, be mixed 
 with a large portion of charcoal, and submitted to a red-heat for 
 several hours, the sulphate will at length be converted to a 
 sulphuret of barytes, and the sulphur may afterwards be preci- 
 pitated by pyroligneous or acetic acid. The acetate of barytes 
 may then be evaporated to dryness, and a moderate heat will 
 dissipate the acid, and leave the barytic earth nearly in a state of 
 purity. 
 
 The following direction is given by Mons. Brisson, the French 
 professor of chemistry. " Pulverize," says he, " sulphate of ba- 
 rytes, and calcine it in a crucible, with an eighth part of its weight 
 of charcoal dust; keep the crucible at a red-heat for about an 
 hour, and then pour the matter into water : the water will as- 
 sume a yellow colour, and exhale a strong odour of sulphuretted 
 hydrogen gas : then filter the liquor, and pour into it muriatic 
 acid : there will be formed an abundant precipitate, which must 
 be separated by a second filtration. The liquor that passes through 
 the filter holds in solution muriate of barytes, which is formed by 
 the addition of the muriatic acid. If you then add liquid carbo- 
 nate of potash, the potash will combine with the muriatic acid, 
 and the barytes with the carbonic acid, from which it may be 
 freed in a great measure by calcination : what then remains is for 
 the most part pure barytes." 
 
 Another process has been described by LaGrange: this con- 
 sists in the mixture of muriate of lime with the barytic sulphate, 
 which mutually decompose each other. The twa salts are to be 
 intimately mixed and fused in a crucible : the result will be sul- 
 phate of lime and muriate of barytes, which are to be separated 
 from each other by means of water 3 . 
 
 Kirwan, who made many experiments on this peculiar earth, 
 has published accurate descriptions of three distinct species of 
 native barytic salts, viz. carbonate of barytes, baroselenite, or 
 sulphate of barytes, and the liver-stone, or hepatic sulphate. 
 The baroselenite, which we have been considering, he divides 
 into five families, consisting of the loose, the compact, the foli- 
 ated, the striated, and the acicular baroselenite 4 . 
 
 Mr. Jameson divides the barytic minerals into five species, in- 
 cluding the sulphate and carbonate of strontian, which belong to 
 another family, and certainly ought not to be arranged with ba- 
 
 3 For a more particular account of the process see the memoir itself, An- 
 nales de Chimie, tome xlvii. 
 
 4 See Kirwan's Elements of Mineralogy, vol.i. page 134143. 
 
126 ON BARYTES. 
 
 rytes. The true barytic salts lie divides, like Kirwan, into three 
 species, which he calls witherite, heavy spar, and hepatite. 
 
 The first of these is the native carbonate of barytes, which will 
 be described hereafter; the second, or heavy spar, he divides into 
 eight subspecies, viz. the earthy, the compact, the granular, the 
 lamellar, the fibrous, the radiated, the columnar, and the pris- 
 matic heavy spar ; and the last, known to modern mineralogists 
 by the name of hepatite, is a compound of sulphate of barytes, 
 uncombined sulphur, and several extraneous matters, and agrees 
 with the mineral which Kirwan has described under the name 
 of liver-stone. 
 
 Notwithstanding this great variety of barytic minerals, for nine 
 years after the discovery of pure barytes by Scheele, the chemists 
 of Europe were unacquainted with any other source for the pro- 
 duction of this alkaline earth, besides the ponderous spar of which 
 we have been treating, until Dr. Withering, a physician of Bir- 
 mingham, announced that among the minerals in Mr. Bolton's 
 cabinet he had discovered a specimen of native carbonate of 
 barytes, which was found in a lead-mine on Alston moor, in the 
 county of Cumberland. This discovery was made in the year 
 1783, and the particulars respecting it were published in the 
 Philosophical Transactions for the year 1784. 
 
 This mineral was first called Witherite, from the name of its 
 discoverer, a gentleman well known to the literary world as the 
 author of a useful treatise on botany, entitled " A botanical Ar- 
 rangement of all the Vegetables naturally growing in Great Bri- 
 tain," 2 vols. 8vo ; a work which has since been enlarged and 
 much improved by Dr. Stokes, an eminent physician now living 
 at Chesterfield in Derbyshire. 
 
 Soon after its discovery, this mineral acquired nearly as many 
 names as those of the persons who wrote upon it, as mephite of 
 barytes, chalk of barytes, aerated heavy earth, aerated baroselenite, 
 aerated ponderous spar, &c. &c. ; and then Lavoisier named it 
 carbonate of barytes, which is an appropriate term, and that 
 which it has borne ever since. 
 
 Not long after this discovery of Dr. Withering's, it was found 
 that a similar mineral existed in abundance in the lead-mines of 
 Anglezark in Lancashire ; and while these mines were worked, 
 the chemists of Europe might have been supplied with any quan- 
 tity of this native carbonate at a small expense ; and according 
 to Leigh, who wrote the history of Lancashire, these mines 
 abound also in sulphate of barytes '. 
 
 Since the discovery of carbonate of barytes at Anglezark, a 
 similar mineral of various degrees of purity has been found at 
 
 1 Leigh's Lancashire, fol. Oxford, 1700. p. 71. 
 
ON BARYTES. 127 
 
 Aldstone in Cumberland ; at Dufton and other places in the 
 county of Durham ; at Merton Fell in Westmorland ; and at 
 Snailback mine in Shropshire. I have heard that it has also 
 been discovered in one particular district in Scotland, and also 
 in Sweden; but Guy ton and Carny in the 19th volume of the 
 Annales de Chimie tell us that at that time it had not been dis- 
 covered in any part of France. 
 
 Carbonate of barytes is found crystallized ; and according to 
 Thomson and Jameson, the crystals have been observed to as- 
 sume four different forms, viz. double six-sided and double four- 
 sided pyramids ; six-sided columns terminated by a pyramid with 
 the same number of faces; and small radiated crystals half an 
 inch in length and very thin, appearing to be hexagonal prisms 
 rounded towards the point. 
 
 The massive varieties occur in thin wedge-shaped distinct con- 
 cretions, which are often very much grown together ; and occa- 
 sionally they pass into coarse granular masses. The crystallized 
 carbonate of barytes is translucent, though but rarely semi-trans- 
 parent. Its colours are greyish and yellowish white ; also pale 
 wine-yellow ; and not unfrequently of a pale flesh-red. It slightly 
 decrepitates before the blow-pipe, and melts readily into a white 
 enamel. It is soluble with effervescence, in diluted muriatic or 
 nitric acid, and may thus be distinguished from sulphate of 
 barytes, which is insoluble in both these acids. Its specific 
 gravity is 4.33 ; though when prepared artificially it scarcely 
 exceeds 3.76. It has no sensible taste, and yet it is an active 
 poison. It is very sparingly soluble either in cold or hot water; 
 and is not altered by exposure to the air. By peculiar manage- 
 ment it may be decomposed when submitted to an intense heat. 
 
 The native carbonate of barytes found at Anglezark consists of 
 22 parts of carbonic acid, and 78 of barytes ; and the factitious 
 carbonate is a similar compound. Pelletier says that he analysed 
 some native carbonate, and found it composed of 22 parts of car- 
 bonic acid, 62 parts of barytes, and 16 parts of water; but I ap- 
 prehend this account is erroneous. 
 
 Those who have done most in investigating the nature of this 
 earth, since the discovery by Dr. Withering, are Pelletier above 
 mentioned, Vauquelin, and Fourcroy in France ; and Professor 
 Hope of Edinburgh. The French chemists published an account 
 of their experiments in the Annales de Chimie for the year 1797 ; 
 but Dr. Hope had published his valuable paper in the Edinburgh 
 Transactions four years before this 2 . It is, however, generally 
 acknowledged that, before these eminent chemists undertook the 
 
 4 See Annales de Chimie, torn. iv. page 62; torn, xxi, pages 113 and 276', 
 and the Edinburgh Transactions, vol. iv. p. 36. 
 
128 ON BARYTES. 
 
 series of experiments in which each of them was engaged, pure 
 barytes was not known. 
 
 At one time no carbonate of barytes was found any where in 
 these kingdoms, except in the lead-mines of Anglezark in the 
 hundred of Salford in the county of Lancaster. Conceiving that 
 this mineral product might probably be usefully employed in 
 some of our manufactures, if an abundant supply could be procured, 
 I determined to go to the mines to make the necessary inquiries ; 
 which I did in the autumn of 1 8 1 0. 
 
 On inquiring at Chorley, I found that the mines are in the 
 midst of the moors, at a considerable distance from any turn- 
 pike road, about eight or nine miles from the town of Bolton, 
 and three from Chorley ; and in so obscure a part of the country 
 that it would be necessary for me to take a guide with me ; and 
 I was so fortunate as to meet with a gentleman in the town, who 
 very kindly offered to accompany me and conduct me thither. 
 
 From the town of Chorley you go about a mile on the road to 
 Bolton, and then turning off to the right, proceed through a 
 very rough stony lane, which brings you near to the village of 
 Limbrick, which is about two miles from Chorley; and then 
 passing over some romantic fields, you arrive at the house of 
 Banister Derbyshire, a fine old man of seventy years of age, who 
 occupies the estate in which the mine is situated. 
 
 This man, who knows more of the history of these singular 
 mines than any one in the neighbourhood, walked with us to the 
 spot, and showed us the places which were formerly occupied for 
 the different purposes connected with the working of the mines. 
 
 From him I learnt that all these are lead-mines, which were 
 in full work more than a hundred years ago : and that they were 
 again opened, long before his time, by Sir Thomas Standish, 
 the father of the present proprietor. 
 
 From the appearance of the land, it is evident that there have 
 formerly been a great number of shafts for drawing up the mi- 
 nerals ; and on making inquiry as to this point, our guide in- 
 formed me that he was sure he could find forty at the least ; 
 whence I conclude that a large quantity of lead ore must some 
 time or other have been raised. 
 
 About forty years ago these mines were worked a third time 
 by the direction of Sir Frank Standish, who drove fresh levels 
 from the foot of the several hills, into the heart of the mine, in 
 order to carry off the water, and enable the men to work : but 
 having engaged several different sets of workmen, who all con- 
 spired to defraud him of their time, and endeavoured to impress 
 his mind with an idea of the small quantity of ore that could be 
 procured, at the moment when they were practising various arts 
 
ON BARYTES. 129 
 
 to induce him to lease the mine to them, he became tired of 
 mining; and about the year 1790, when he had sunk some 
 thousands of pounds in the undertaking, the work was ao-ain 
 discontinued, and all the miners dismissed. 
 
 It is apparent that this proprietor had no idea of working 
 these mines again, for every thing about them has been allowed 
 to go to ruin. Our guide showed us where stood the large water- 
 wheel for winding up the water from those parts of the mine that 
 could not be drained by the levels ; which was the site of the 
 warehouse for storing the washed ore; and where stood the 
 smithy for repairing the tools of the workmen : but there is now 
 scarcely a square yard of walling belonging to any of these 
 buildings left standing entire. 
 
 Knowing that we are all the victims of habit and the creatures 
 of circumstance, I could not help fancying, while exploring 
 this forsaken domain, what a different character the proprietor 
 of these mines might have been, had he been fortunate enough 
 in his youth to receive a liberal education, and to imbibe a taste 
 for literature and science : for, had this been the case, he might 
 have been as eminent for the accurate investigation of the trea- 
 sures which nature has hidden within his most valuable estate, 
 and for other useful and scientific pursuits, as he was, through a 
 long life, for his skill on the turf at Newmarket. 
 
 The quantity of carbonate of barytes in these mines is im- 
 mense, much greater, I understand, than that of the lead ore 
 (five to one, as our guide supposed) ; but as the metallic ore was 
 raised, this was always left behind in the mine, being considered 
 of no value. The workmen called it spar. 
 
 Some of the best-informed people in the town of Chorley say, 
 that the first time any idea was given of the value of this spar, 
 was by the arrival of two Frenchmen about the year 1782. It 
 seems that they were in the town some days without the nature 
 of their business being suspected, till it was at last discovered 
 that they had been at the lead-mines, and had filled two boxes 
 with the spar, which they secured with great care, and sent off 
 by the carrier before they left the town. 
 
 At this, Mr. Tatham, the steward of Sir Frank Standish, 
 immediately took an alarm ; and having given strict orders that 
 in future no one should be suffered to take away any of the spar, 
 set himself to make every inquiry he could into its nature; to 
 learn, if possible, to what uses these foreigners intended putting 
 it ; and whether some methods might not be discovered for con- 
 suming it in this country. In prosecuting these objects of inquiry, 
 however, he never succeeded. 
 
 The papers by Dr. Withering in the Philosophical Transac- 
 
130 ON BARXTES. 
 
 tions, on the carbonate of barytes, and Dr. Crawford's on the 
 muriate of this earth, had now drawn the attention of all the 
 chemists of Europe to this newly discovered mineral; so that its 
 real nature and properties were every where soon understood. 
 But during this investigation, in which every chemist who was 
 fortunate enough to procure specimens was probably engaged, no- 
 thing new occurred at the mine or in the neighbourhood respect- 
 ing it, till it was discovered that a man of the name of Smithels, 
 who occupied a cottage and about forty acres of land under Sir 
 Frank Standish, close to the mines, had long been engaged in 
 disposing of the carbonate of barytes in an illicit manner. 
 
 This man, who was well known in the neighbourhood of 
 Chorley, and is still remembered by many of its inhabitants, 
 used to get the spar from among the heaps of stone and rubbish 
 that lie round the mouths of the old shafts. This he used to 
 pack in strong boxes, and delivered them himself, by his own 
 cart, to the carrier in Chorley, to be conveyed to Liverpool. 
 
 He managed this business so well, that he not only bought the 
 boards for making the boxes, but prepared the boxes himself in 
 the night, and suffered no one to see him pack the article, or 
 carry it away when packed. Besides, it went from Chorley by the 
 common carrier to a broker in Liverpool, who shipped it to a 
 middle-man upon the continent; so that the place where it was 
 actually consumed could never be traced out. 
 
 A neighbouring farmer had, indeed, for some years observed 
 that James Smithels was often engaged in picking something from 
 off the waste land; and that often on moonshine nights, when 
 they imagined no one observed them, he and his wife were em- 
 ployed for hours together upon the mounds which stand round 
 the old shafts ; and on the circumstance being mentioned to the 
 steward of Sir Frank Standish, he put an entire stop to this poor 
 man's little trade. 
 
 However, when he was questioned by the steward, and by a 
 variety of other persons, respecting this transaction, he remained 
 sullen and silent, and would never give them the least informa- 
 tion as to the quantity he had sold, the price he had obtained for 
 it, or even to what part of the world it went, It was, however, 
 imagined, that the two foreigners before mentioned were the 
 people who had engaged this man to collect it, and that they had 
 found some means of regularly paying him for what he procured 
 for them. 
 
 As the quantity of carbonate of barytes thus collected, was 
 much larger than could be employed merely for the preparation 
 of chemical tests, and for a few common purposes of philoso- 
 phical research, I was desirous of ascertaining something more, 
 
ON BARYTES. J31 
 
 if possible, respecting this traffic in the Anglezark spar; and 
 from one Alexander Gerrard ', an intelligent farmer, who resides 
 not far from the mine, and was formerly very intimate with the 
 aforesaid James Smithels, I learnt the following particulars : 
 
 That Smithels, only a short time before his death, informed 
 Gerrard that, in the whole, he had sold a very large quantity of 
 the spar ; that he received five guineas per ton for it ; that it 
 went from Liverpool to some part of Germany; and that he had 
 understood, from the person who usually paid him, that it was 
 consumed in some process in the manufacture of porcelain 2 . 
 
 Being desirous of knowing whether these poor uneducated 
 men had any idea of the nature and properties of the carbonate 
 of barytes, I put some questions to them for that purpose. They 
 told me, all they knew of it was, that it was a strong poison. 
 
 When I endeavoured to ascertain the extent of their know- 
 ledge on this subject, Mr. Derbyshire assured me that some years 
 ago, he lost some cows, who had strayed from their pasture, and 
 were found licking the lumps of spar which at that time lay about 
 the mine in abundance ; and that on opening one of these ani- 
 mals, several small pieces of spar were found in its stomach. 
 
 He told me also, that it was impossible to keep any fowl upon 
 the farm ; for, mistaking the smaller pieces of the spar for white 
 sand, they were sure to pick it up, and die immediately. Ducks 
 and geese, he says, he can keep, as they do not swallow it, 
 except at the time they lay their eggs, and then they never fail 
 to take it, and with the same baneful effect. Doubtless they 
 mistake it for lime or chalk, which all oviparous animals are 
 obliged to swallow at the time of their laying, in order to shell 
 their eggs. For if fowls be pent up in a situation where they 
 are deprived of all calcareous matter, it is well known that they 
 lay their eggs without shells. 
 
 It has been doubted whether the carbonate of barytes be a 
 poison to the human species ; but on examining Leigh's History 
 of Lancashire, written more than a century ago, to see if these 
 mines were noticed by him, I find the question answered in the 
 affirmative 3 . 
 
 Mons. Fourcroy, when examining the question, whether the 
 
 1 I have entered upon this detail, and given the names of these men, in 
 order that, if any persons should wish to prosecute the inquiry, they may know 
 to whom to apply for information. 
 
 2 This circumstance has induced me to write so full an account of this 
 transaction, in the hope that some of our manufacturers of earthenware will 
 be tempted to persevere with experiments on the native carbonate of barytes, 
 till they discover an advantageous method of employing this mineral in some 
 branch of their manufactory. 
 
 3 Leigh's Natural History of Lancashire, folio, Oxford, 1700, page 70. 
 
 K2 
 
132 ON BARYTES. 
 
 carbonate of barytes be a poison, or not, says, " There is every 
 reason to believe that pure barytes is a violent poison, since when 
 combined with the carbonic acid, and having lost all its acrid 
 taste by this union, it speedily poisons animals. Mammiferous 
 animals which have been made to take it, have experienced acute 
 pains, convulsions, vomiting, and death. Their stomach and 
 intestines were inflamed, spotted, sphacelous, and even, as it 
 were, in some parts corroded : its administration in medicine 
 must, therefore, require great caution V 
 
 " Messieurs Huzard and Biron gave to some horses the 
 muriate and carbonate of barytes, in doses of 1 18 grains English, 
 every day ; and these animals died suddenly after having taken 
 them for a few days." " A dog, which Pelletier caused to swal- 
 low 20 grains, was seized with vomiting, and died within eight 
 hours afterwards 2." 
 
 In consequence of the various accidents which occurred in 
 Lancashire after the opening of the Anglezark mines, this spar 
 in the district where the mines are situated, has obtained the 
 name of rats-stone. 
 
 Pelletier relates, that the Society of Health at Paris was 
 engaged in ascertaining what advantages medicine might derive 
 from the use of barytes ; and that both the muriate and car- 
 bonate of this earth were given to horses seized with that highly 
 infectious disease called the^rn/, for which corrosive sublimate 
 is generally administered ; and he adds, that both these me- 
 dicines given to two different horses, in the quantity of two 
 drachms a day, seemed for a while to have effected such a 
 change that they were even considered as cured at the end of 
 a fortnight, but nevertheless they both died within a few days of 
 each other 3 . 
 
 Dr. Withering observed the difficulty there is in decomposing 
 the native carbonate of barytes, and that when submitted to a 
 strong heat it sooner fuses than parts with its carbonic acid. But 
 Dr. Hope announced 4 , that when he submitted it to an intense 
 heat in a black-lead crucible, the carbonic acid was separated, 
 though in an earthen crucible nothing was permitted to escape, 
 and consequently no decomposition was effected. In considering 
 this result, Pelletier was induced to try the effect of mixing it 
 
 1 Fourcroy's General System of Chemistry, vol. ii. p. 273. 
 
 2 Chaptal's Chemistry applied to the Arts, vol. ii. page 70. Nicholson's 
 Journal, 4to, vol. i. page 529. 
 
 3 Annales de Chimie, torn. xxi. page 113, or Nicholson's Journal, 4to, vol. i. 
 page 529. 
 
 4 Dr. Hope published his experiments in the year 1793, in the Edinburgh 
 Transactions, vol. iv. page 36. 
 
ON BARYTES. 133 
 
 with charcoal before he heated it, and by this means he obtained 
 barytes tolerably pure and soluble. 
 
 M. Fourcroy, who has related this circumstance, 'confesses 
 that the theory of the experiment is unknown to him 5 ; but may 
 it not be attributed to the charcoal combining with the carbonic 
 acid of the carbonate of barytes, and with it forming carbonic 
 oxide 6 , which is a gas somewhat lighter than atmospheric air, 
 and very highly combustible ? 
 
 If, however, barytes perfectly pure be required, it can only 
 be obtained by dissolving the native car on ate, or the artificial 
 sulphuret of barytes procured according to the directions given 
 at page 125, in diluted nitric acid; in evaporating the solution 
 either to dry ness, or the point of crystallization, and then decom- 
 posing this salt by heat. The process in detail may be thus 
 described : 
 
 The mineral (the sulphate or the carbonate) is first to be re- 
 duced to powder, and intimately mixed with about one-fourth of 
 its weight of ground charcoal. It is then to be put into a cruci- 
 ble and submitted for an hour to the action of a red heat, well 
 covered with charcoal to secure it from the access of atmospheric 
 air. This treatment, if the sulphate be operated upon, will con- 
 vert the sulphate of barytes to a sulphuret, which is to be dis- 
 solved in water and the impurities suffered to subside. The clear 
 solution is then to be treated with nitric acid, which will com- 
 bine with the barytes and occasion the sulphur to precipitate. 
 The newly formed nitrate of barytes is now to be slowly evapo- 
 rated, until the salt crystallizes ; and then, if the salt be exposed 
 in a crucible to a gradual heat, to separate the remaining water, 
 and afterwards to a stronger heat, sufficient to expel the whole 
 of the nitric acid, pure barytes will remain, which should be 
 quickly removed to a stoppered bottle to prevent its absorption 
 of carbonic acid. 
 
 BARYTES is an oxide of barium, and possesses the following 
 properties : When pure, it is of a greyish white colour, and 
 is so porous that it may very readily be reduced to powder. It 
 consists of 1 proportional of barium =70+1 proportional of 
 oxygen = 8, and consequently in the table of equivalents is 
 represented by 78. Its specific gravity is about 4. When exposed 
 to the air, it changes rapidly ; it swells like quicklime, and, like 
 it, falls into a white powder ; but this slacking is much more 
 violent and speedy than that of lime. In this process it com- 
 bines so intimately with the water of the atmosphere, which it 
 
 5 Fourcroy's System of Chemistry, vol. iv. page 14. 
 
 8 Carbonic acid contains scarcely 27.o per cent, of carbon ; but carbonic 
 oxide contains nearly 43 per cent. 
 
134 ON BARYTES. 
 
 solidifies, that it will not part with it even at a red-heat. In 
 this state it is called the hydrate of barytes, and consists of 1 
 proportional of barytes = 78 + 1 proportional of water = 9: 
 consequently we say the hydrate of barytes is represented by 87. 
 
 If the hydrate of barytes be dissolved in boiling water, and 
 the solution suffered to cool, crystals containing a still larger 
 proportion of water will be deposited. These crystals, white 
 and transparent, generally appear in the form of hexagonal 
 prisms, considerably flattened, and have been found to consist 
 of 1 proportional of barytes = 78 and 20 proportionals of water 
 = 9 x 20 or 180 water; so that the crystallized hydrate must 
 be represented by 258. 
 
 These crystals are sometimes long four-sided prisms, termi- 
 nated at each extremity with a four-sided pyramid. Sometimes 
 they are attached to each other in a peculiar way, and sometimes 
 the crystallized salt precipitates in the liquor in the form of cubes. 
 The crystals of barytes require more than 17 times their weight 
 of water for solution. According to Mr. Dalton, if these crystals 
 be exposed to the air, they will effloresce and fall into a white 
 powder, consisting of 1 proportional of barytes and 5 propor- 
 tionals of water. Hence it seems that there are at least three 
 distinct hydrates of this earth : viz. 
 
 1st hydrate consisting of 78 barytes + 9 water = 87 
 2nd hydrate 78 barytes + 45 water = 123 
 
 3rd hydrate 78 barytes + 180 water = 258 
 
 Barytes has, however, several other properties which must 
 be enumerated. It has a harsh and pungent taste, and is more 
 caustic than quicklime; it has no smell whatever, but when taken 
 into the stomach acts as a most corrosive poison. It is very dif- 
 ficult of fusion, but when strongly heated on charcoal before the 
 blow-pipe, it melts into a grey opake mass. Like the alkalies, it 
 changes the vegetable blues to a deep green ; the red to a violet 
 or blue; and the yellow vegetable colours, such as turmeric, &c. 
 to a brown. It is also similar to the alkalies in being itself a 
 metallic oxide; in its rendering oils miscible with water; inform- 
 ing glass when fused with silica ; in its solubility in water ; and 
 in its capability of dissolving some of the other metallic oxides. 
 
 It is soluble in about 20 parts of water at the temperature of 
 60 ; but boiling water will dissolve half its weight of this earth, 
 part of which, as has been already mentioned, will crystallize on 
 cooling. It absorbs carbonic acid from the atmosphere, and has 
 so strong an affinity for sulphuric acid, that it will not part with 
 it even to pure alkalies. Hence it has the property of decom- 
 posing sulphate of potash, or sulphate of soda. Barytes is unal- 
 terable by light : it is a non-conductor of electricity ; and when 
 dissolved in water, or in certain acids, furnishes excellent tests 
 
ON BARYTES. 135 
 
 for chemical analysis. It is also capable of making a very tena- 
 cious cement. When strongly heated in oxygen gas, or if oxyo-en 
 gas be passed over red-hot barytes, the oxygen will be absorbed, 
 and the barytes will be converted to a grey substance, which 
 may be called the peroxide of barium, consisting of barium 70 
 and oxygen 16 = 86; or it may be stated thus: barytes 1 pro- 
 portional = 78 + 1 additional proportional of oxygen 8 = 86. 
 Barytes may be known from all the other earths, by its superior 
 solubility in water ; by its forming an insoluble compound with 
 sulphuric acid ; and by its imparting to flame a yellow colour. 
 
 When speaking of the native carbonate of barytes, I should 
 have remarked, that neither nitric nor muriatic acid, when con- 
 centrated, has any effect in dissolving carbonate of barytes, as was 
 first shown by Fourcroy '. This chemist was, however, mistaken 
 in asserting that barytes " forms with all the acids the most per- 
 manent compounds, and the most difficult of all to be decom- 
 posed," since it is true only of those acids which form with 
 barytes insoluble salts ; for, if this earth be employed to decom- 
 pose common salt, it only produces a partial decomposition, and 
 may be precipitated again from the acid, by means of either of 
 the carbonated fixed alkalies 2 . 
 
 It has already been observed that the chief use which has 
 hitherto been made of barytes, has been in the preparation of 
 certain tests for chemical analysis; and as these are of the utmost 
 importance to every analytical chemist, I shall now proceed to 
 give an account of the methods of preparing some of the most 
 valuable of these tests. Those in common use are, the nitrate, 
 the muriate, and the acetate of barytes ; and not unfrequently a 
 solution of pure barytes in distilled water. 
 
 By copying the particulars of a few of these processes from 
 my common-place-book, where they stand as they were entered 
 at the time of making the experiments, I shall be in no danger 
 of misleading the reader. For making nitrate of barytes I first 
 diluted 2lbs. of nitric acid, sp. gr. 1.250, with 8lbs. of distil- 
 led water. 
 
 Wlien cold, the mixture had the specific gravity of 1 .0528. 
 
 To this diluted acid one pound of the native carbonate of 
 barytes was added, and the whole submitted to a gentle heat. 
 The acid dissolved the barytes with rapidity; but when the 
 action had ceased, a large portion of residuum, which was chiefly 
 nitrate of barytes in a crystallized state, was found in the vessel 
 wherein the solution had been made. To dissolve this nitric salt 
 more water was added by degrees, until sixteen pounds were 
 employed; when the only residuum remaining was one ounce of 
 
 1 Annales de Chimie, torn. iv. page 62. 
 
 * Ibid. torn. xlix. page 95. Nicholson's Journal, vol. xviii. page 68. 
 
136 ON BARYTES. 
 
 the carbonate of barytes, which the nitric acid was incapable of 
 taking up '. The materials used then were 2lbs. of nitric acid, 
 sp. gr. 1250, 24lbs. of water, carbonate of barytes 15oz., mak- 
 ing together 26lbs. 1 5oz., which produced 22lbs. 6oz., sol. nitrate 
 of barytes, sp. gr. 1.0507, leaving a loss of 4lbs. 9oz., arising 
 from evaporation and disengagement of carbonic acid. 
 
 Finding that so large a portion of water is necessary for hold- 
 ing the nitrate of barytes in solution, I have since diluted the 2lbs. 
 of nitric acid, sp. gr. 1.250, with 24lbs. of pure water. 
 
 When cold, the mixture had the specific gravity of 1.0156. 
 
 To this diluted acid I added 19oz. of the native carbonate of 
 barytes; and though the acid was so very much diluted, it imme- 
 diately acted upon the earth and dissolved it rapidly, even in the 
 cold. When submitted to a gentle heat, the solution went on 
 with still greater rapidity, and in about an hour the whole was 
 dissolved. The produce was 22lbs. 14oz. sol. nitrate of barytes, 
 sp. gr. 1.0600, leaving a loss by evaporation and the disengage- 
 ment of carbonic acid of 4lbs. 5oz. 
 
 It will be observed that there is not only less trouble, but an 
 economy, in thus diluting the acid, as it prevents in some mea- 
 sure the loss of a part of the acid in consequence of too rapid 
 an action. To obtain the nitrate of barytes in a state of purity, 
 the solution should be evaporated to dryness, and the dry salt 
 redissolved and crystallized. The crystals are permanent octa- 
 hedrons, which sometimes adhere to each other in the form of 
 stars. At other times the crystals are obtained in small plates', 
 whose specific gravity is 2.9149. The taste of this salt is hot 
 and astringent. It is soluble in twelve parts of water at 60 and in 
 four parts of boiling water. When submitted to a red heat, the 
 whole of the acid flies off, and pure barytes remains in the cru- 
 cible. The nitrate of barytes is a very convenient test for many 
 purposes, and especially for detecting the adulteration of nitric 
 acid by the addition of sulphuric acid : but in this case it is ab- 
 solutely necessary to dilute the suspected nitric acid very consi- 
 derably with distilled water previously to the application of the 
 test; otherwise, a portion of the barytic salt is apt to precipitate, 
 merely in consequence of the nitric acid abstracting part of the 
 water which held it in solution, and this will occasion deception. 
 The dry salt consists of 1 proportional of barytes 78 + nitric 
 acid 54* = 132. The proportions per cent, are, barytes 59, 
 
 1 Some years ago Mr. Hume noticed that the nitrate and the muriate of 
 barytes are entirely insoluble in the respective acids of which they are formed. 
 This, however, is not the case with the sulphate of barytes, for that salt is 
 perfectly soluble in its own acid. Phil. Mag. 
 
 1 Hassenfratz Annales de Chimie, xxviii. 12. 
 
ON BARYTES. 137 
 
 nitric acid 41. The crystals consist of 1 proportional of dry 
 nitrate 132 -f 2 proportionals of water 18; or per cent, nitrate 
 of barytes 88 + water 12. 
 
 In preparing the muriate of barytes, I have generally used 
 very weak muriatic acid of the specific gravity of 1.0612. Such 
 acid may be formed by mixing muriatic acid at 1.170 with dou- 
 ble its weight of pure water. In this menstruum I dissolve the 
 native carbonate of barytes to the point of saturation. Twenty- 
 four pounds of this diluted acid are capable of dissolving exactly 
 six pounds and a half of the native mineral ; and the solution of 
 the muriate of barytes which results from the process will be of 
 the specific gravity of 1.260. 
 
 It did not occur to me, or I would have mentioned in an 
 earlier part of this essay, that in calculating the equivalent num- 
 bers of bodies, it is most convenient to make hydrogen, which 
 is the lightest substance we know of, unity^ and oxygen 8, be- 
 cause oxygen unites with hydrogen in the proportion of eight of 
 oxygen to one of hydrogen, to form water. The equivalent num- 
 bers throughout these volumes are all deduced from this basis. 
 
 The muriate of barytes, or chloride of barium, in a state of 
 dryness is composed of 1 proportional of barium 70 + 36 chlo- 
 rine = 106, or, barium 66 4- 34, chlorine = 100. 
 
 This salt commonly crystallizes in tables ; but according to 
 Dr. Crawford it sometimes appears in the form of two eight- 
 sided pyramids applied base to base. It is unalterable in the air, 
 and not decomposable by heat 3 . 
 
 The poisonous nature of barytes, in which it differs from all 
 other earths, has been mentioned; but its most distinguishable 
 property is the facility of its crystallization when dissolved in 
 water, and which decidedly marks it to be very different from 
 lime, which is sparingly soluble in water, and does not form 
 crystals when it separates itself therefrom. 
 
 At one time strontites was confounded with barytes, and many 
 chemists were at a loss to know whether there was any real dif- 
 ference between the two minerals ; but an important series of 
 experiments made by Pelletier, in the year 1796, has put this 
 matter beyond all doubt, and established them as two distinct 
 substances 4 . $ 
 
 There are certainly many points of resemblance between 
 
 3 Dr. Crawford has expressly written on the properties of the muriate of 
 barytes. His paper is in the second volume of the London Medical Communi- 
 cations, page 301. 
 
 4 The paper which gave an account of these experiments was read before 
 the National Institute, April 30th, 1796 ; and afterwards published in Annales 
 de Chimie, tome xxi. page 1 13, &c. A translation of it may be seen in Nichol- 
 son's Journal, 4to, vol. i. page 518. 
 
138 ON BARYTES. 
 
 barytes and strontites, such as their being both found native, and 
 only in the state of combination with sulphuric and carbonic 
 acids, these native productions are also decomposable by simi- 
 lar means, both sulphates are nearly insoluble in water, and 
 yet soluble in an excess of sulphuric acid, both carbonates are 
 soluble in diluted muriatic or diluted nitrous acid, and neither of 
 them is precipitated by pure ammonia. 
 
 There are, however, so many differences, and those so dis- 
 tinctly marked, that no chemist can now easily mistake the one 
 earth for the other. The mention of a few particulars will be 
 sufficient. Strontites has less attraction for acids than barytes ; 
 hence the salts of strontites are decomposable by barytes: stron- 
 tites requires much more of any acid for its saturation than ba- 
 rytes does ; the salts formed by the two earths are different in 
 form and in the rate of their solubility in water : for instance, 
 muriate of barytes, as has been already mentioned, crystallizes in 
 plates; whereas muriate of strontites gives slender hexagonal 
 prisms. Moreover, pure barytic earth does not require one- 
 tenth of the quantity of water for its solution that strontites does ; 
 and lastly, if strontites, or the salts formed with it, be dissolved 
 in or mixed with alcohol, the spirit will burn with a flame of the 
 colour of carmine ; whereas barytes, as has been noticed already, 
 gives a bright yellow colour to flame. 
 
 Water at the temperature of 50 takes up about a twenty- 
 fifth part of its weight of barytes in its caustic or pure state; the 
 solution remains transparent and colourless, and is known in the 
 laboratory of the chemist by the term barytic water. It is neces- 
 sary to keep it in bottles well closed, otherwise the earth will 
 acquire carbonic acid from the atmosphere, and separate itself 
 from the water of solution, as lime does in similar circumstances. 
 
 The best method of preserving barytes in a state of purity, is 
 to dissolve it in warm distilled water; and if, during the heat 
 that is generated by the slacking of the earth, the water be sa- 
 turated with it, an abundance of crystals will be procured when 
 the whole has become cold. These crystals should be kept in 
 well stopped bottles, for the purpose of making barytic water as 
 it may be required. It is extremely useful as a chemical reagent 
 for discovering the presence of sulphuric* acid, and for other 
 purposes. 
 
 An Acetate of barytes has also been found to be a convenient 
 preparation of this valuable earth. This may be readily made 
 by dissolving the native carbonate to saturation in acetic acid, 
 when, by spontaneous evaporation, the solution will deposit very 
 beautiful prismatic crystals of acetate of barytes, which will not 
 deliquesce in the atmosphere. 
 
ON BARYTES. 139 
 
 When I first made acetate of barytes in quantity, I proceeded 
 thus : To twelve pounds of acetic acid of the specific gravity 
 of 1.04-20 I added three pounds of the native carbonate of ba- 
 rytes, and submitted the vessel containing it to a gentle heat. I 
 found that, to dissolve the carbonate of barytes in acetic acid, it 
 is only requisite to have the acid a little warm ; 90 of Fahrenheit 
 will be quite sufficient, until the acid approaches the point of satu- 
 ration, and then it will be advisable to give it the heat of 1 30. 
 
 When the action had ceased, and the whole become cold, I 
 poured the solution from the residuum, and found a large por- 
 tion of crystals of acetate of barytes among the carbonate which 
 remained undissolved. Two pounds of water, however, were 
 found sufficient to dissolve these crystals ; and when the whole 
 of the solution was filtrated, and the residuum carefully dried, 
 twelve ounces of the original carbonate of barytes remained ; so 
 that the materials used and the produce obtained stood thus : 
 acetic acid, specific gravity 1.0420, 12lbs. Water 2lbs., and car- 
 bonate of barytes 2^1bs. produced 13lbs. of sol. acet. barytes, 
 specific gravity 1.1870, leaving loss by evaporation, &c. S^lbs. 
 
 If the two pounds of water had been added to the acetic acid 
 in the first instance, the specific gravity of the mixture would 
 have been 1.0380. 
 
 Finding that the acid which I employed was capable of dis- 
 solving more barytes than it could afterwards hold in solution, 
 I have since adopted the following process, which I recommend 
 as the best that I have been able to discover for making the 
 acetate of this earth. Take acetic acid, specific gravity 1.0420, 
 12lbs, pure water 12lbs, and native carbonate well vVashed, 2|lbs. 
 The produce will be, sol. acet. baryt. 1.1480, 2 libs, leaving a loss 
 of5ilbs. 
 
 The specific gravity of equal weights of acetic acid and water, 
 when mixed, will be 1.0260; therefore acetic acid, which may 
 originally be of a strength about equal to this specific gravity, 
 will be very proper for the process. 
 
 The acetate of barytes has a sour and rather a bitter taste ; 
 it is soluble in water, and effloresces in the atmosphere. Its 
 specific gravity is 1.8. It is decomposable by the fixed alkalies, 
 which seize the acetic acid and precipitate the barytes. Most 
 of the soluble sulphates also decompose it ; and on this account 
 it is constantly employed to detect sulphuric acid, or the sul- 
 phuric salts in solution. One hundred parts of water at the 
 temperature of 60 dissolve 88 parts of the salt ; boiling water 
 dissolves nearly its own weight. It is composed of barytes 78 + 
 acetic acid 58 = 128 ; or barytes 61.06 + acetic acid 39 = 100. 
 
 Whether the barytic salts are used in medicine, or as chemical 
 
140 ON BARYTES. 
 
 reagents, it is of the utmost consequence to have them made 
 uniformly the same. I have therefore thought it worth while to 
 give these experiments in detail, in order to furnish, by means 
 of the specific gravity, a standard for each of these solutions ; so 
 that those who may have occasion to employ the nitrate, the 
 acetate, or the muriate of barytes, may know how to procure a 
 solution that will always contain the same proportion of barytic 
 earth. 
 
 The other salts that have been formed with barytes are the 
 following, which I have arranged alphabetically, for the sake of 
 greater facility of reference. 
 
 Antimoniate of barytes. This is a white powder, which may 
 be obtained by mixing muriate of barytes with antimoniate of 
 potash. It is perfectly insoluble in water. It is a light floc- 
 culent precipitate, which does not adhere to the sides of the 
 vessel. It is not decomposed by exposure to the air, but the 
 nitric acid extracts by digestion all the barytes '. It is probably 
 composed of one atom barytes, and one of antimonic acid. 
 
 Antimonite of barytes. If a boiling solution of antimonite of 
 potash be let fall drop by drop into a boiling solution of muriate 
 of barytes, the antimonite of barytes crystallizes gradually on 
 the tube in the form of small white needles of a silky brilliancy. 
 These are slightly soluble in water, and unalterable in the air 2 . 
 The salt consists of one atom barytes and one of antimonous 
 acid. 
 
 Arseniate of barytes may be formed by mixing arseniate of 
 potash with j*iuriate of barytes, which produces an insoluble 
 arseniate of this earth. It is in the form of a white powder, which 
 is not decomposable by heat. It was first formed by Scheele, 
 by dissolving pure barytes in arsenic acid 3 . Supposing this salt 
 to be a compound of 1 atom of barytes and 1 atom of arsenic 
 acid, its equivalent numbers will be, barytes 78 -f arsenic acid 
 62 = 140. 
 
 Ar senile of barytes is formed, like the foregoing, with arsenious 
 acid. It is a white insoluble powder 4 , composed of one propor- 
 tional of barytes 78 + 1 of arsenious acid 54 = 132. 
 
 Benzoate of barytes is soluble in water, and crystallizable. It 
 may be decomposed by heat, but is unalterable in the air. It is 
 a compound of barytes 78 + benzoic acid 120 = 198. 
 
 Boletate of barytes. This salt contains an excess of acid, 
 
 1 Berzelius in Nicholsons Journal, vol. xxxv. page 40. 
 " Ibid, page 45. 
 
 3 Laugier, Annales de Chimie, torn. Ixxxv. page 58. 
 
 4 Ibid. 
 
ON BARYTES. 141 
 
 crystallizes in white plates, and is but little soluble in water, or 
 even in nitric acid. When thrown on a plate of red-hot iron, it 
 burns with a red flame and remarkable scintillation, leaving car- 
 bonate of barytes as a residuum 5 . Braconnot in the year 1811 
 discovered the boletic acid, and to that chemist we are indebted 
 for the chief of what we know respecting the salts which have 
 been formed by its means 6 . The acid is procured from a spe- 
 cies of agaric, the Boletus igniarius of Linnaeus, a fungus so 
 called in consequence of its being frequently used for the purpose 
 of tinder. The boletate of barytes is probably composed of one 
 atom of barytes and one of boletic acid. 
 
 Borate of barytes is a white powder insoluble in water. It is 
 prepared in a way similar to that of the other earthy boracic 
 salts. It is a compound of 78 barytes + 22 boracic acid = 100. 
 
 Camphor ate of barytes may be prepared by mixing camphoric 
 acid with a solution of pure barytes, and boiling the mixed so- 
 lution to the point of crystallization. When the evaporation is 
 conducted slowly, the salt is deposited in thin lamellar crystals, 
 which appear transparent while immersed in the liquor, but be- 
 come opake when exposed to the air. The salt has but little 
 taste, though it leaves at last upon the tongue a slight impression 
 of acidity mixed with bitterness. When exposed to heat it 
 melts easily, and the camphoric acid is volatilized. When the 
 heat is considerable, the acid burns with a lively blue flame, 
 which becomes afterwards red, and at last white 7 . 
 
 Carbonate of barytes. The artificial carbonate is similar in 
 its nature to the carbonate which is found native, and has already 
 been described at large, page 126 133. It is a compound of 
 78 parts of barytes + 22 parts of carbonic acid = 100. 
 
 Chlorate of barytes may be formed by passing chlorine gas 
 into a solution of pure barytes. The salt crystallizes in quad- 
 rangular prisms, and is soluble in about four times its weight of 
 water, at the temperature of 60. The discoverer of chloric 
 acid, M. Gay Lussac, first procured it from this salt by acting 
 upon it with sulphuric acid. It is a compound of one propor- 
 tional of barytes 78 + one of chloric acid 76 = 154. 
 
 Chromate of barytes may be formed by adding chromate of 
 potash to a solution of muriate of barytes. It is a yellow in- 
 soluble powder. Vauquelin has written the most on the chro- 
 mates, in an essay printed in the 70th volume of the Annales de 
 Chimie. According to him the salt consists of 62.2 barytes + 
 37.4? chromic acid = 99.6. 
 
 5 Thomson's System of Chemistry, ii. p. 480. 
 1 Annales de Chimie, Ixxx. 279. 
 
 7 Bouillon Lagrange, Annales de Chimie, xxvii. page 28. Thomson's System, 
 ii. page 480. 
 
142 Oft BARYTES. 
 
 Citrate qfbarytes. When barytes is added to a solution of 
 citric acid, a flaky precipitate appears, which is at first dissolved 
 by agitation, but remains permanent when the saturation is com- 
 plete. The citrate of barytes thus formed, is precipitated in the 
 state of a white powder, but it gradually assumes the appearance 
 of silky flakes, or forms a kind of vegetation very brilliant and 
 beautiful. It requires a great quantity of water to dissolve it. 
 According to Vauquelin it is composed of 50 of the crystallized 
 acid and 50 of barytes, which is nearly equivalent to one pro- 
 portional of the earth 78 + 58 acid =. 136. 
 
 Fluate of barytes, or according to Dr. Thomson fluoride of 
 barium, is in the form of white flocks, insoluble in water, but 
 soluble in an excess of fluoric acid. It is composed of fluorine 
 16, barium 70 
 
 Formate of barytes. This salt is obtained in permanent cry- 
 stals, unalterable by exposure to the air. According to Dr. 
 Thomson, they contain no water of crystallization, and are com- 
 posed of formic acid 32.1 + barytes 67.9 = 100. 
 
 Gallate of barytes is a salt of little solubility; it is of a fawn 
 colour, and dissolves more abundantly in water when mixed with 
 an excess of base, than otherwise '. This salt maybe considered 
 to be a compound of one proportional of barytes 78 + one of 
 gallic acid 63 = 141. 
 
 Hydriodate ofbaryfes. This salt crystallizes in fine prisms 
 similar in appearance to muriate of strontites. It is very soluble 
 in water. By a red heat this salt is converted into iodide of 
 barium. Gay Lussac. Thomson's System of Chemistry. Its 
 composition may be considered to be barytes 78 + hydriodic 
 acid 126 = 204. 
 
 lodate of barytes. This salt may be formed by treating carbo- 
 nate of barytes with iodic acid. It appears in a kind of farina- 
 ceous powder, and is very insoluble in water. Its constituents 
 are, barytes 78 + iodic acid 165 = 243. This has sometimes 
 been called oxiodate of barytes. 
 
 Malate of barytes. This salt is somewhat similar in its pro- 
 perties to malate of lime. It has an acid taste, and consists of one 
 proportional of barytes 78 + one of malic acid 70 = 148. 
 
 Molybdate of barytes. This salt, like the other salts of barytes, 
 is formed of one proportional of barytes 78 + one of molybdic 
 acid 72 = 150. Its properties are unknown. 
 
 Oxalate of barytes. This salt may be formed by adding a solu- 
 tion of oxalic acid to a solution of pure barytes. It first precipi- 
 tates in the state of a white powder, but becomes dissolved by the 
 addition of oxalic acid, which produces needle-formed crystals of 
 
 1 Fourcroy, vol. vii. page 248. 
 
ON BARYTES. 14,3 
 
 . super-oxalate of barytes. The oxalate of barytes is nearly inso- 
 luble in water. It is composed of one proportional of barytes 
 78 + one of oxalic acid 36 = 114. 
 
 Phosphate of barytes may be formed by adding a solution of 
 phosphate of soda to one of muriate of barytes. It appears in 
 the state of a tasteless white powder insoluble in water. It con- 
 sists of barytes 78 + phosphoric acid 28 = 106. 
 
 Phosphite of barytes. Berzelius prepared this salt by pouring 
 muriate of barytes into a solution of phosphite of ammonia. No 
 precipitate appeared at first, but in twenty-four hours the glass 
 was covered with a crust of phosphite of barytes 9 . When washed 
 and dried, its composition was, in 100 parts, phosphorous acid 
 24.31, barytes, 67.24, water, 8.45. 
 
 Seleniate of barytes. Seleniate of barytes is insoluble in water, 
 and can only be obtained in a white powder^ but the biseleniate 
 is soluble. The former Dr. Thomson supposes to consist of one 
 proportional of selenic acid 56 -f one of barytes 78 = 1 34. 
 
 Silicate of barytes. This salt is formed by the mixture of an 
 aqueous solution of barytes with a solution of silicate of potash. 
 The product is a silicate of barytes in white powder. The pro- 
 portions of the constituent parts of this salt are not known. 
 
 Succinate of barytes. This salt was formed by Bergman, by 
 dropping succinate of ammonia into muriate of barytes. In this 
 process the salt partly precipitates, and is partly deposited in 
 small crystals on the sides of the vessel. Bergman: Thomson. 
 According to the above principle, this salt must be formed with 
 one proportional of barytes 78 + one of succinic acid 50 = 128. 
 
 Tartrate of barytes is a sajt sparingly soluble in water, is taste- 
 less and does not redden vegetable blues. It is decomposable by 
 oxalic acid. It is a compound of one proportional of tartaric 
 acid 67 + one of barytes 78 = 145. 
 
 Tungstate of barytes is in the form of a white powder, which is 
 insoluble in water. Its composition and properties are unknown. 
 
 Urate of barytes. This is a white powder in some respects 
 resembling uric acid. Taking 46 for I he equivalent number of 
 uric acid, the composition of this salt will be one proportional of 
 barytes 78 + one of uric acid 46 = 124. 
 
 %umate of barytes is an incrystallizable salt, having the appear- 
 ance of gum. This salt, as appears by the name, is a compound 
 of barytes and zumic acid. This peculiar acid was first procured 
 by Braconnot from a preparation of fermented rice. It was 
 named by Dr. Thomson zumic acid, from a Greek word signi- 
 fying leaven. The properties of zumate of barytes are as yet but 
 little known. 
 
 * Thomson j Berzelius, Annalcs de Chim. et Phys. ii. 231. 
 
144 ON BARYTES. 
 
 Barytes will also combine with sulphur and phosphorus, and 
 with some of the earths. 
 
 Sulphuret ofbarytes, as we have already shown at page 133, 
 may be formed by heating. to redness in a crucible a mixture of 
 the native sulphate of barytes and charcoal, both in fine powder. 
 The sulphuret of barytes, which results is of a reddish yellow 
 colour, and is composed of barium 70 + sulphur 16 = 86. 
 When put into hot water, it decomposes the water, and two new 
 compounds are formed, viz. hydrosulphuret of barytes, and hy- 
 droguretted sulphuret of barytes. The first appears in the form 
 of crystals, while the hydroguret remains in solution. 
 
 Phosphuret of barytes may be prepared by passing phosphorus 
 over heated barytes, or by exposing a mixture of barytes and 
 phosphorus in a glass tube to a heat sufficient to produce the 
 combination. It has the property of decomposing water, and 
 from that decomposition phosphuretted hydrogen gas is evolved, 
 which rises in bubbles to the surface of the water, and inflames as 
 it comes in contact with atmospheric air. 
 
 Phosphuret of barium is composed of barium 70 + phospho- 
 rus 12 = 82. 
 
 Such are the principal salts, &c. which have hitherto been 
 made by means of barytes : the nature of the earth, and its uses 
 in a separate state, remain to be spoken of hereafter. 
 
 When the peculiar properties and the decided characteristics 
 of barytes became known, some persons suspected that it was a 
 metallic oxide, and the usual methods were resorted to for its re- 
 duction. That it is the oxide of a metal very difficult to be re- 
 duced, was the opinion of Bergman and Lavoisier ; but it was 
 reserved for Davy to demonstrate and establish the truth of this 
 conjecture. The detail of the experiments by which he separated 
 the metallic substance, which is the base of barytes, may be seen 
 in the Philos. Trans, for 1810, page 63. 
 
 To those persons who have not the opportunity of referring to 
 the Transactions of the Royal Society, the following concise ac- 
 count of barium, drawn up by Sir H. Davy, will probably be read 
 with interest. 
 
 " To obtain barium" says he, " a quantity of pure barytes is 
 made into a paste with water, and placed on a plate of platinum ; 
 a cavity is made in the paste to receive a globule of mercury ; the 
 mercury is rendered negative, the platinum positive, by means of 
 a voltaic battery, containing about 100 double plates. 
 
 " In a short time an amalgam will be formed, consisting of 
 mercury and barium. This amalgam must be introduced into a 
 little tube made of glass, free from lead, which must be bent in 
 the form of a retort, filled with the vapour of naphtha, and her- 
 metically sealed. Heat must be applied to the end of the tube 
 
ON BARYTES. 145 
 
 containing the amalgam, till all the mercury has been driven off; 
 there will remain a solid difficultly-fusible metal, which is barium. 
 
 " I first gained indications of the decomposition of barytes in 
 the end of October 1807, and I obtained an alloy of it with iron 
 in March 1808. The process of electrifying mercury in contact 
 with the earth, was pointed out to me in the course of my inqui- 
 ries by MM. Berzelius and Pon tin of Stockholm, in May 1808; 
 and in the beginning of June in the same year I obtained the 
 metal. 
 
 " Barium, as procured by heating the amalgam, appeared of 
 a dark gray colour, with a lustre inferior to that of cast-iron. It 
 was considerably heavier than sulphuric acid ; for though sur- 
 rounded by globules of gas, it sunk immediately in that fluid. It 
 instantly became covered with a crust of barytes when exposed 
 to the air, and burnt with a deep red light when gently heated. 
 When thrown into water it effervesced violently, disappeared, 
 and the water was found to be a solution of barytes. 
 
 " Barium as yet has been obtained only in very minute quan- 
 tities. I have never possessed enough of it to ascertain its general 
 chemical and physical characters, and no experiments upon it 
 have been published by any other person." Elem. Chem. Phil., 
 page 338. 
 
 Dr. Clarke of Cambridge, by exposing dry nitrate of barytes 
 on charcoal to the intense heat of the condensed hydroxygen 
 flame, observed metallic globules in the midst of the boiling fluid, 
 and the charcoal was found to be studded over with innumerable 
 globules of a pure metal of the most brilliant lustre and whiteness. 
 On letting these globules fall from the charcoal into water, hy- 
 drogen was evolved in a continued stream. Ure's Dictionary. 
 
 Thus have we seen that there are two minerals abundantly 
 distributed in nature ; the one called witherite or carbonate of 
 barytes, the other cawk or sulphate of barytes; and that by various 
 means the carbonic and sulphuric acids may be detached, and 
 the earth, or pure barytes, obtained in a separate state. We 
 have seen also, that the barytic earth itself is a compound body, 
 the oxide of a peculiar metal, and that by means of voltaic 
 electricity, the oxygen may be abstracted from it, and the metallic 
 base separately obtained. 
 
 Nothing now remains but to offer a few remarks on the uses 
 to which this singular earth may be applied. 
 
 Hitherto it has chiefly been employed as a chemical test, and 
 in the formation of certain barytic salts already described. It 
 has also been used by a few scientific physicians, in certain dis- 
 eases, with very good effect. 
 
 L 
 
14-6 ON BARYTES. 
 
 In the year 1 784? Dr. Crawford made his first experiments on 
 the powers of muriate of barytes on the animal economy; and in 
 the year 1 788 many trials were made of it in desperate cases ad- 
 mitted into St. Thomas's Hospital *, and in a variety of instances 
 these attempts proved remarkably successful. An account of 
 the cases in which it was more particularly useful may be seen 
 in the work quoted below. 
 
 It has been often said, that there is a fashion in medicine ; but 
 it is a singular circumstance, that the English physicians, who 
 were the first to employ barytes as a medicine, should nearly give 
 up its use, when the French, who had been in the habit of giving 
 muriate of lime for scrofulous diseases, began to use it ; and that 
 we in our turn should adopt the muriate of lime, which is now 
 the common English medicine for such complaints, after the 
 French had abandoned it. 
 
 Considering, however, the poisonous quality of barytes, it will 
 surely be. necessary to institute many experiments before suffi- 
 cient confidence in its safety can be acquired, or before the 
 nature of its effects on the animal economy can be thoroughly 
 understood and properly appreciated 2 . 
 
 In preparing the medicine, the utmost care should be taken to 
 have it perfectly pure ; for some specimens of the carbonate of 
 barytes contain copper, and others arsenic. An attention should 
 also be paid to the saturation of the acid ; for it will be very diffi- 
 cult to obtain an uniformity in the doses, unless a saturated solu- 
 tion be always employed, or the water be fully saturated, when- 
 ever the medicine is prepared by dissolving the crystallized salt : 
 not but that a solution, however dilute, might be employed, if 
 the exact quantity of barytes in each dose could be accurately 
 ascertained. 
 
 Dr. Crawford has, however, remarked, that if a saturated solu- 
 tion be administered, a very small quantity of muriatic acid should 
 be previously added to each dose, to remove the bitter taste 
 which is peculiar to this salt, and occasion it to sit pleasantly on 
 the stomach. But no unskilful person should ever venture to 
 administer barytes internally, in any form. 
 
 From the appearances which pure barytes presents when 
 slaked, and especially from its ready solubility in water, one 
 
 1 See a paper on the medicinal properties of the muriated barytes, by Dr. 
 Adair Crawford, in vol. ii. of the Medical Communications, London, 1790, pages 
 301360. 
 
 2 I am credibly informed that the muriate of barytes has been found to be a 
 specific in some obstinate cases of worms, which had resisted all the common 
 formulae ; and that a nostrum, which has been very justly celebrated for the 
 cure of this complaint, has barytes for its base. 
 
ON BARYTES. 147 
 
 would suppose it would be useful in making hard and tenacious 
 cements, particularly for important purposes. This I think was 
 hinted by one of the French chemists ; but I never heard of its 
 having been employed in this way. 
 
 It may, however, be tried at a trifling expense (by any one 
 who is in possession of a good reverberatory furnace) upon the 
 sulphate of barytes. This, when ground small and mixed with 
 one-third of its weight of pulverized charcoal, should be sub- 
 mitted to a red heat, as before mentioned, in order to convert 
 the acid to sulphur. To effect this, the barytic salt, mixed as 
 above, must be put into strong iron vessels, and well covered by 
 charcoal to prevent the access of atmospheric air, which would 
 not fail to re-convert the sulphur to sulphuric acid ; and then 
 submitted to the continued heat of a furnace. The sulphuret of 
 barytes which will result is to be decomposed by any of the com- 
 mon means, and the remaining earth preserved for use in close 
 vessels. 
 
 For some underground works of importance, this earth might 
 be highly valuable and useful. As a cement for porcelain and 
 glass, I should think it would surpass every other preparation. 
 Nevertheless, it must be remembered, that every thing would 
 depend upon its being applied at the moment of its being mixt 
 with the water. 
 
 But there is a purpose not yet mentioned, to which this pecu- 
 liar substance might be applied, that would be of more import- 
 ance, medicine excepted, than any other for which it can be used. 
 I allude to the decomposition of the alkaline sulphates, and the 
 separation of their alkali. 
 
 Whenever the carbonate of this earth shall be found in as 
 great plenty as its sulphate, we shall have within ourselves ample 
 means of preparing the mineral alkali, and not be dependent on 
 Spain and other places, as is the case at present ; or if the native 
 carbonate could not be obtained, it might answer to employ the 
 sulphate in the decomposition of common salt, though it would 
 be necessary to convert the sulphate into a sulphuret, and then to 
 separate the sulphur by some other process 3 . 
 
 If the barytic earth, thus prepared, be simply thrown into a 
 solution of sulphate of soda, it will immediately occasion its 
 decomposition, and sulphate of barytes with caustic soda will 
 be produced. 
 
 3 The opinions of those respectable chemists, Messrs. Guyton and Carny, 
 respecting the means which ought to be adopted in preparing the native barytic 
 salts, for the decomposition of the alkaline residuums, may be seen in the 
 Annales de Chimie, torn. xix. page 109 113. 
 
148 ON CARBON. 
 
 ESSAY V. 
 ON CARBON. 
 
 CARBON is a name now universally adopted for charcoal, or 
 rather for that pure part of its basis which, during combustion, 
 combines with oxygen, and escapes in the form of carbonic acid 
 or fixed air. Carbon is so abundant in nature, that it occurs 
 plentifully in the animal, the vegetable, and the mineral king- 
 doms ; in combination with gas, with fluids, and with solids, it 
 is found in the bowels of the earth, in the mines of plumbago, 
 anthracolite, jet, glance coal, and in every kind of pit coal, of 
 which it forms the most material part. It is also separated from 
 the lungs of all animals in the act of respiration ; and it is the 
 basis or skeleton of all vegetables, from the small anemone of 
 the garden to the huge oak of the forest. 
 
 Notwithstanding this abundant distribution of carbon, there is 
 some doubt whether it has ever occurred perfectly pure in na- 
 ture. The most pure state in which it has ever yet been seen is 
 certainly that of the diamond, which, though deemed to be the 
 most valuable of the precious stones 1 9 and classed with them, is 
 now found to be nothing more than crystallized carbon, so far 
 as the most careful chemical analysis has yet been able to dis- 
 cover. The precious stones are chiefly composed of one or more 
 of the earths and metals ; the diamond, on the contrary, contains 
 no portion of any substance belonging to either of those classes 
 of bodies ; though Sir H. Davy has asserted that it contains a 
 small portion of oxygen. 
 
 There is, however, a great difficulty attending this subject. 
 Has the diamond been dissolved in water in the bowels of the 
 earth, or could it otherwise have acquired that peculiar crystal- 
 line form in which we see it? Arid yet we cannot comprehend 
 how it could be dissolved in that fluid ; for, in our hands, water 
 has no action whatever upon it, nor does water exert any solvent 
 
 1 Diamonds are sold by the carat, a weight equivalent to four grains. Un- 
 blemished diamonds, when polished, are worth about 61. per carat. The mode 
 of calculating their value is by squaring the number of carats which the dia- 
 mond weighs, and then multiplying the amount by the agreed price of a single 
 carat. Thus it is, that those which are of an unusual size always cost immense 
 eurns. That at the court of Russia, which weighs 779 carats, would, upon this 
 calculation, amount to upwards of three millions six hundred and forty thou- 
 sand pounds sterling. But the value of brilliants is often modified by their 
 form, as has been very satisfactorily shown by Mr. Jeffries in his very lucid 
 and ingenious treatise. See Jeffries On Diamonds and Pearls, 69 octavo pages, 
 with 30 plates, price one guinea. 
 

 I 
 
 N 
 
 
 
 

 
 
ON CARBON. 149 
 
 power on carbon, in any state in which we can submit it to its 
 action. 
 
 The diamond is indeed the hardest substance in nature, and 
 hence there is no way of grinding or polishing diamonds but by 
 acting upon them with their own powder, which is obtained by 
 laborious rubbing of them one against another. This method, 
 together with the art of polishing diamonds, was brought into 
 Europe in the year 1456. If the diamond be exposed to the sun, 
 it refracts and decomposes the rays of light more effectually than 
 any other transparent body. 
 
 Carbon has neither taste nor smell ; it is a bad conductor of 
 heat; is altogether insoluble in water, and is perfectly infusible 
 by the strongest fire that can be applied, provided it be defended 
 completely from the access of atmospheric or any other air con- 
 taining oxygen. It has also the property of deoxidizing the 
 oxides of metals, and other combustible substances; and of decom- 
 posing many of the sulphuric salts. In a crystallized state, it 
 forms, as we have seen, the diamond. The representative num- 
 ber of carbon is 6. 
 
 Rouelle the younger proposed a problem in the Journal de 
 Medecine for October 1762, which shows that he imagined he 
 could dissolve vegetable coal in the palm of the hand 2 . How he 
 could effect this I confess I have no idea, as none of the fluid 
 menstrua with which we are acquainted have any perceptible 
 action whatever, as solvents, upon carbon. 
 
 Strong nitrous acid, by peculiar management, may, we know, 
 be made to inflame carbon, and when once thus inflamed it will 
 burn with considerable brilliancy ; but this arises from the de- 
 composition of the acid, and is owing to the rapid combination 
 of its oxygen with the charcoal, for which it has a powerful 
 affinity. 
 
 Carbon, in certain states, combines readily with oxygen ; and 
 two distinct combinations may be formed by their union, viz. 
 carbonic oxide and carbonic acid. Both these are gaseous pro- 
 ducts ; and as the latter contains the lesser proportion of carbon, 
 and was the first discovered, we shall speak of this in the first 
 instance. 
 
 Carbonic acid is always produced by the burning of charcoal 
 or other carbonaceous matter in oxygen gas or in atmospheric 
 air. It is not necessary, however, to burn charcoal for the pro- 
 duction of this gas, as it may be obtained more easily from 
 powdered chalk, limestone, or marble, by the action of diluted 
 
 2 Other curious experiments by Rouelle may be seen in Mem. deTAcad. 
 Roy. de Para, Annee W7> page 49, &c. 
 
150 ON CARBON. 
 
 sulphuric or muriatic acid, and by receiving the gas over water 
 or mercury as it is evolved. It is also produced in every case of 
 vinous fermentation, is given out during the decomposition of 
 animal and vegetable substances, and is very abundantly thrown 
 off by the action of fire in the process of lime-burning. 
 
 For the knowledge of carbonic acid we are indebted to the 
 late Dr. Black, who discovered it in the year 1 755 : Mr. Keir 
 first suspected it to have acid properties, but its composition was 
 not known until 1772, when this was ascertained by Lavoisier, 
 who in the same year burnt a diamond, and found the product 
 to be carbonic acid gas. Certain individuals in the Academy del 
 Cimento at Florence, nearly eighty years before this, had been 
 able to burn the diamond by means of a lens, but they seem to 
 have had no idea of the real nature of the product of the com- 
 bustion. Those of my readers who shall be desirous of repeat- 
 ing this experiment, will be glad to be informed, that a drawing 
 of a new and complete apparatus for this purpose may be seen 
 in Mr. Brande's Manual of Chemistry, second edition, vol. i. 
 page 425. 
 
 Carbonic acid gas has the following properties. It has no 
 colour, and consequently is invisible. It is a heavy gas, its spe- 
 cific gravity being to that of hydrogen as 20.7 to 1. One hun- 
 dred cubical inches, at a mean temperature and pressure, weigh 
 46-37 grains. It is incapable of supporting combustion; for if 
 it be poured from a jar or other vessel into one in which a taper 
 is burning, the flame will be immediately extinguished. 
 
 Carbonic acid is not respirable; but when combined with 
 water, it imparts to it a pleasant acidulous taste and an agree- 
 able smell. At a mean temperature, and under the usual pres- 
 sure of the atmosphere, water is capable of taking up carbonic 
 acid equal to its own volume, and under the pressure of two 
 atmospheres it will take up twice its volume; but whatever may 
 be the quantity that it has condensed, the whole of it is easily 
 expelled by heat. Carbonic acid combines readily with the 
 alkalies, with what are called the alkaline earths, and with several 
 of the metallic oxides, and with them forms those salts called 
 carbonates. It changes litmus-paper, and some other of the 
 delicate vegetable blues, to a red ; and in the proportion in which 
 it usually occurs in the atmosphere is favourable to the growth 
 of vegetables ; though in a large proportion it is injurious. 
 
 Carbonic acid is accumulated in immense quantities in the 
 chalk-beds and in the mountains of limestone and marble ; it is 
 also found in abundance in many natural waters, such as those 
 of Pyrmont, Spa and Seltzer ; and these are imitated in London 
 and other parts of the kingdom by the makers of what are called 
 single and double soda water, which are prepared by the arti- 
 
ON CARBON. 151 
 
 ficial impregnation of water with carbonic acid gas. For the 
 methods of ascertaining the qualities of such waters, whether 
 natural or artificial, Kirwan's Essay on the Analysis of Mineral 
 Waters may be consulted, as it is the best work we have on the 
 subject. 
 
 Carbonic acid abounds also in some wells and caverns, where, 
 in consequence of its great specific gravity, it often occupies the 
 lower part of a pit, . while the upper is tolerably free from it. 
 When in these situations, it is known to miners by the name of 
 the choak-damp. The presence of this gas may be ascertained 
 by letting down a lighted candle into the suspected well, in 
 which, if it be unsafe to enter, the candle would be immediately 
 extinguished ; or by lowering a glass of lime-water, which is 
 rendered turbid by the choak-damp, as carbonic acid precipitates 
 lime in the state of carbonate of lime. 
 
 If hydrogen be taken as unity > the equivalent number for car- 
 bon will be 6 ; and this, when united with two proportionals of 
 oxygen =16, will form carbonic acid, which will consequently 
 be represented by 22. Or its composition may be stated thus : 
 Carbon 27.3 -f oxygen 72.7 =100 carbonic acid. 
 
 Mr. Tennant was the first person who decomposed carbonic 
 acid, which he effected by burning phosphorus in a close vessel, 
 in which was a portion of carbonate of soda. The phosphorus 
 combined with the oxygen of the carbonic acid, and the carbon 
 appeared in the state of a black powder. 
 
 Sir H. Davy effected its decomposition by a different means, 
 by its action upon potassium. " If," says he, " this metal is 
 strongly heated in a retort containing the gas, the potassium 
 takes fire and burns with a red light. Charcoal in fine powder 
 is deposited, the gas disappears, and oxygen is found added to 
 the potassium." Elem. Chem. Phil., page 302. 
 
 Carbonic oxide is the other combination of carbon and oxygen. 
 This gaseous product may be obtained from a variety of sub- 
 stances containing carbonic acid, by mixing such substances in 
 favourable circumstances with others that are capable of abstract- 
 ing a portion of oxygen from the carbonic acid ; as by igniting 
 together dried chalk and the filings of iron or zinc, taking equal 
 weights of each ; or by passing carbonic acid gas over charcoal 
 heated to whiteness, in a tube of earthenware or porcelain. The 
 gas should be well washed with lime-water to abstract any car- 
 bonic acid that may be attached to it ; it may then be preserved 
 in jars confined by water, as water absorbs not more than ^ of 
 its volume of carbonic oxide. This gas was one of the latest of 
 Dr. Priestley's discoveries ; and he obtained it by the ignition 
 of the black oxide of iron with charcoal, and by heating a similar 
 
152 ON CARBON. 
 
 oxide with the carbonate of barytes. We are, however, indebted 
 to Mr. William Cmickshank of Woolwich for the true explana- 
 tion of its nature and properties, in an interesting paper pub- 
 lished by the late Mr. Nicholson in his Journal for April 1801, 
 and in another paper in the month of September in the same 
 year '. Messrs. Clement and Desormes were, I believe, the first 
 persons who undertook to verify Mr. Cruickshank's experiments, 
 the result of whose examination was published in the Annales de 
 Chimie, vol. xxxix. pages 26 64-. Mr. Cruickshank discovered 
 that those metallic oxides which retain their oxygen most obsti- 
 nately, yield the greatest quantity of carbonic oxide 2 . 
 
 Carbonic oxide may be passed through a red-hot porcelain 
 tube without undergoing any change ; it is however combustible, 
 and when mixed with atmospheric air, burns with a lambent blue 
 flame. It produces less heat than other inflammable gases, but 
 may be inflamed at a much lower temperature. None of the 
 metals exert any action upon it, except potassium and sodium, 
 which at a red heat burn in it by abstracting its oxygen, and car- 
 bon is deposited. When burnt in a dry glass receiver of oxygen 
 gas, no moisture is deposited on the glass, which shows that it 
 contains no hydrogen. Like most other gases, it is invisible ; its 
 specific gravity is somewhat less than that of atmospheric air; its 
 smell is offensive ; it has the property of uniting with chlorine, 
 and with it forming a highly interesting compound, which we 
 shall describe hereafter: it is, as has already been said, combus- 
 tible ; but it is a gas that will not of itself either support com- 
 bustion or animal respiration. It may be taken into the lungs, 
 but is fatal to animal life. " I once took," says Sir H. Davy, 
 " three inspirations of it mixed with about a quarter of common 
 air; the effect was a temporary loss of sensation, which was suc- 
 ceeded by giddiness, sickness, acute pains in different parts of 
 the body, and extreme debility ; some days elapsed before I en- 
 tirely recovered." Mr. Witter of Dublin was struck down in 
 an apoplectic condition by breathing this gas; but he was speedily 
 restored by the inhalation of oxygen. He has given an interest- 
 ing account of the transaction in the Philos. Mag. vol. xliii. p. 367. 
 
 Carbonic oxide has a specific gravity when compared with hy- 
 drogen as 13.2 to 1 ; one hundred cubical inches of it weighing 
 29.7 grains. It contains more carbon, and yet is lighter than 
 carbonic acid ; carbonic acid being found to contain exactly twice 
 as much oxygen as carbonic oxide. If the representative num- 
 ber of carbon be considered 6, as already stated, the composi- 
 tion of carbonic oxide gas will be one proportional of carbon 
 6 + one of oxygen 8 = 14 carbonic oxide. 
 
 1 Nicholson's 4to Journal, vol. v. pages 1 and 201. * Ibid, page 3. 
 
ON CARBON. 153 
 
 Chlorocarbonic acid is a compound of carbonic oxide and chlo- 
 rine. These two gases do not combine by mere mixture, or even 
 by passing electric sparks through them: but by exposing a mix- 
 ture of equal volumes to the intense light of the sun, they com- 
 bine rapidly, and a condensation equal to half the original bulk 
 takes place. The ingenious discoverer of this compound gas, 
 Dr. John Davy, in consequence of the mode by which it is pro- 
 duced, named it phosgene gas. This acid gas has a very peculiar 
 and remarkably pungent odour; it is the heaviest of all the known 
 gases, 100 cubical inches of it weighing 105 grains, which is 
 nearly four times as much as an equal volume of atmospheric air. 
 It is decomposed by water, and the resulting gases, as might be 
 expected, are muriatic and carbonic acid gases. The weight of 
 chlorocarbonic acid to hydrogen is as 46.7 to 1. It is capable 
 of saturating more of an alkali, or an alkaline earth, than any 
 other acid. Four times its volume of ammoniacal gas is con- 
 densed by it, and a white salt is produced with a considerable 
 evolution of caloric. Chlorocarbonic acid is a compound of one 
 proportional of carbonic oxide 14 + chlorine 36 = 50. 
 
 Carbon unites with hydrogen^ and forms two gaseous products 
 totally distinct from each other, the one called carburetted hy- 
 drogen gas, similar to what the miners call the fire-damp ; the 
 other super-carburetted hydrogen, or olefiant gas. 
 
 Carburetted hydrogen gas is carbon dissolved in hydrogen. In 
 hot weather this gas is abundantly formed at the bottom of pools 
 of stagnant water, and may be collected by means of a common 
 pneumatic apparatus at its surface. It is procured in the large 
 way by the dry distillation of pit-coal, and is the gas which is 
 now employed for lighting the public streets, manufactories, &c. 
 One pound of coal yields about 24? gallons of this gas, and as 
 this always contains a portion of sulphuretted hydrogen and car- 
 bonic acid gas, it is usual to pass it through a mixture of lime 
 and water, that these gases may be absorbed, and the carbnret- 
 ted hydrogen rendered sufficiently pure to pass into the gasome- 
 ters for use. 
 
 As Professor Brande has been engaged in a laborious series 
 of experiments on this gas, I conceive that I cannot do better 
 than avail myself of his experience for the information of my 
 readers. 
 
 " The specific gravity of the gases obtained from stagnant 
 ponds is liable to great variation, 100 cubical inches weighing 
 from 12 to 20 grains. They burn with a paler flame, and re- 
 
 quire less oxygen than olefiant gas for perfect combustion. 
 " The average specific gravity of purified coal gas is 0. 
 
 4500: 
 
154? ON CARBON. 
 
 100 cubical inches weigh from 14 to 15 grains, and it may be 
 considered as a mixture of about 55 volumes of hydrogen and 
 45 of olefiant gas. 
 
 " The best kind of coal for distillation is that which contains 
 most bitumen and least sulphur. The chaldron should yield 
 about 12,000 cubical feet of purified gas, of which each Argand 
 burner, equal to six wax candles, may be considered as consum- 
 ing from four to five cubical feet per hour. 
 
 " The economy of gas illumination may be judged of by ex- 
 amining the value of the products of the distillation of a chaldron 
 of coals, the average cost of which may be considered as 31. It 
 should afford 
 
 . s. d. 
 
 1 chaldron of coke, at 25s. per chaldron ... 1 11 3 
 
 24 gallons of tar and ammoniacal liquor, at 3d. 060 
 
 12,000 cubic feet of gas, at 15*. per 1000 feet ... 9 00 
 
 10 17 3 
 
 " These products are taken at their lowest value; but they 
 afford ample grounds for showing the advantage of gas illumina- 
 tion, not merely for public purposes, but also in private establish- 
 ments. It appears that where more than fifty lights are required, 
 a coal gas apparatus will be found profitable." 
 
 It is however generally allowed, that the gas which is procured 
 from oil affords more light according to its volume than coal gas ; 
 and it has been estimated that from two to three cubic feet may 
 be regarded as equivalent to five or six of coal gas in this respect. 
 
 " The commonest whale oil," says Mr. Brande, " or even 
 pilchard dregs, quite unfit for burning in the usual way, afford 
 abundance of excellent gas, requiring no other purification than 
 passing through a refrigerator, to free it of a quantity of empy- 
 reumatic vapour. 
 
 " A gallon of whale oil affords about 100 cubical feet of gas, 
 and an Argand burner equal to seven candles consumes a cubical 
 foot and a half per hour. The cost of a lamp fed by oil or coal 
 gas, and giving the light of seven candles, will be three farthings 
 per hour. The cost of an Argand lamp with spermaceti oil 3d. 
 per hour, mould candles 3%d., wax candles Ikd. 
 
 " By a series of experiments, conducted with caution, I found 
 that, to produce the light of ten wax candles for one hour, there 
 were required 2600 cubical inches of olefiant gas, 4875 of oil 
 gas, or 13,120 of coal gas. 
 
 " Experiments thus conducted show that purified coal gas 
 seldom contains more than 40 per cent, in volume of carburetted 
 hydrogen, while oil gas generally affords about 75 per cent. ; 
 
ON CARBON. 155 
 
 hence its superiority for burning, and the relatively small quan- 
 tity consumed l ." 
 
 M. Berthollet instituted a series of experiments on the decom- 
 position of oil for the production of gas, which may be consi- 
 dered important from the results which he obtained. The product 
 which is usually afforded, is a mixture of gases ; but this experi- 
 mental philosopher, by a judicious regulation of the temperature, 
 prevented the other gases from rising, and obtained olefiant gas 
 in a state of purity 2 . 
 
 An ingenious and highly estimable friend of mine, who has 
 lately been engaged in lighting some of the principal streets of 
 Paris with oil gas, does it in a way never before attempted. He 
 thus writes: " We are going on quite a new principle. Coal is 
 very dear and bad here, and it struck me that the oleaginous 
 seeds, which are cheap and abundant, might answer the purpose. 
 We made our experiments, and found that by this means we can 
 produce a cheaper and better gas than from coal, and more so 
 than from oil. For by taking the oil seeds we save all the waste 
 and expense of extracting the oil, and have the substance in a 
 much fitter state for decomposition. We have a patent for this 
 invention in France, and have met with great encouragement 
 from the Government." How delightful is it to observe that the 
 constituted authorities in every country of Europe are lending 
 their assistance in the prosecution of schemes of improvement, 
 and in aiding the efforts of individuals for increasing the comfort, 
 and promoting the civilization of the general community ! 
 
 I had hitherto forgotten to observe that Dr. Henry has de- 
 voted a considerable time to the investigation of the nature of the 
 gas from mineral coal ; and this is the more inexcusable, as he 
 was the first experimental philosopher who avowed that he did 
 not consider this to be a subject beneath his notice. 
 
 So early as the year 1805 Dr. Henry instituted a series of 
 " experiments on the gases obtained from wood, peat, pit-coal, 
 oil, wax, &c. with a view to the theory of their combustion, when 
 employed as sources of artificial light," and the result of his 
 experiments was published in Nicholson's Journal^ 8vo, vol. xi. 
 page 65 75. This memoir contains a table of results, and a 
 variety of very interesting observations. Three years afterwards 
 this ingenious philosopher resumed his experiments, an account 
 of which may be seen in the Phil. Trans. 1808, page 282, &c. ; 
 and in the latter end of the year 1818 and the beginning of the 
 following year, in consequence of an application from the pro- 
 
 1 Brande's Manual, vol. i. pages 438 442. Journal of Science, vol. i. pages 
 7180. 
 
 2 Memoires de la Soc. d'Arcueil, torn. ii. 84. and torn. iii. 154. 
 
156 ON CARBON. 
 
 prietors of some large manufactories lighted by gas in the neigh- 
 bourhood of Manchester, he once more returned to the investi- 
 gation of the subject. The paper giving an account of these 
 latter experiments was read to the Literary and Philosophical 
 Society of Manchester on the 19th March 1819, and afterwards 
 published in their Memoirs, vol. iii. page 391 429. It consists 
 of distinct chapters on the following subjects, viz. on the gases of 
 known composition, the mixtures of which, in various propor- 
 tions, according to his view, compose all the varieties ; on the 
 quality of the gas at different stages of the distillation ; on the 
 purification of coal gas ; on the method of analysis ; and on the 
 chemical nature of the gas from coal ; together with several 
 tabular representations, all which deserve the attention of those 
 persons who are desirous of becoming thoroughly acquainted 
 with this subject. 
 
 Before the middle of the last century, the Rev. Dr. John Clay- 
 ton ascertained by experiment, that mineral coal evolves a per- 
 manently elastic fluid, fit for the purposes of affording light and 
 heat ; and he communicated the discovery in a letter to the Hon. 
 Robert Boyle. This letter was read before the Royal Society in 
 January 1739, and in the year 1741 was printed in the Society's 
 Transactions, vol. xli. page 59. The discoverer calls the gas the 
 spirit of coals. The circumstances which he relates as having 
 led to the discovery, are highly interesting ; but on reading the 
 Doctor's account of the results which he obtained, it seems very 
 extraordinary that neither he nor any of the fellows of the Royal 
 Society, nor others to whom the experiment was shown, should 
 have thought of turning it to an economical account. 
 
 For the first application of carburetted hydrogen gas to the 
 purpose of illumination, the public is certainly indebted to Mr. 
 W. Murdoch, the particulars of which Dr. Henry first published 
 in the year 1805 as a postscript to an account of his own experi- 
 ments l . From this communication I can only make a few brief 
 extracts, and must refer to the paper itself for the remainder. 
 
 In the year 1792, at which time Mr. Murdoch resided at 
 Redruth in Cornwall, as principal agent for Messrs. Boulton 
 and Watt in that county, he commenced a series of experiments 
 upon the quantity and quality of the gases contained in different 
 substances. In the course of these, he remarked that the gas 
 obtained from coal burnt with great brilliancy upon being set fire 
 to; and it occurred to him, that by confining and conducting it 
 through tubes, it might be employed as an economical substitute 
 for lamps and candles. 
 
 At this time Mr. Murdoch was too much engaged to attend 
 
 1 Nicholson's Journal, vol. xi. page 73. 
 
ON CARBON. 157 
 
 further to the subject ; but in 1 797 he repeated the experiments 
 in presence of numerous spectators at Old Cumnock in Ayrshire, 
 and in 1798 he actually constructed an apparatus at Soho foun- 
 dery, which was applied during many successive nights to the 
 lighting of the building. These experiments were occasionally 
 continued until the spring of the year 1802, when upon the 
 occasion of the public rejoicings for the peace, the illumination 
 of the whole of the Soho manufactory afforded an opportunity of 
 making a display of the new lights ; and they were made to con- 
 stitute a principal feature in that exhibition. 
 
 Three years after this public display at Birmingham Messrs. 
 Phillips and Lee of Manchester lighted up their extensive estab- 
 lishment in that town with coal gas issuing from nearly a thou- 
 sand burners. This grand application of the new principle satis- 
 fied the public mind, not only of the practicability, but also of the 
 economy of the application ; and as a mark of the high opinion 
 they entertained of his genius and perseverance, and in order to 
 put the question respecting the priority of the discovery beyond 
 all doubt, the Council of the Royal Society awarded to Mr. 
 Murdoch the gold and the silver medal founded by the late Count 
 Rumford. 
 
 Nothing but the importance 2 of the application of the gases 
 from oil and coal could have justified me in going so far into de- 
 tail, especially if I had had to explain the nature of the carburetted 
 gas which perpetually occurs in the coal districts, and which it 
 would have been incumbent upon me to have treated of in this 
 essay, if I had not anticipated the subject in the Essay on Tempe- 
 rature, pages 64? 71. I proceed now to consider the nature of 
 the other gaseous compounds of carbon. 
 
 Super-carburctted hydrogen is a compound of carbon and hy- 
 drogen, in which the hydrogen combines with exactly twice as 
 much carbon as it does in the carburetted hydrogen gas already 
 described. It is highly inflammable, and emits more light during 
 its combustion than is given out by the inflammation of the former. 
 This super-carburetted gas is now generally known by the name 
 of olefiant gas ; and under that name has been already referred 
 to in the former parts of this essay. 
 
 Olefiant gas is generally evolved during the destructive distil- 
 lation of oil, pit-coal, and other substances; but for the purpose 
 of experiment it is usually procured by heating a mixture of four 
 parts of sulphuric acid and one of alcohol in a retort, and col- 
 
 2 The manufacture of coal gas is important in another view, as the waste 
 liquor now furnishes most of the subcarbonate of ammonia, the common 
 smelling salts of the shops, and is also employed with great advantage as a 
 manure for land. 
 
158 ON CARBON. 
 
 lecting the gas over water as it is generated. When kindled, it 
 burns with a beautiful white flame of great splendour. One 
 volume of this gas, in consequence of the condensation of its 
 hydrogen, requires three volumes of oxygen for its combustion, 
 during which two volumes of carbonic acid are produced. Heat 
 alone will decompose it ; for if one volume of this gas be fre- 
 quently passed through a ret-hot tube, the hydrogen will deposit 
 its charcoal, and become expanded to two volumes, its natural 
 bulk. 
 
 The decomposition of olefiant gas, by heating it in conjunction 
 with oxygen, affords a beautiful exemplification of the system of 
 definite proportions, thus: 1 proportional of carbon 6 + 1 prop, 
 of hydrogen 1=7 olefiant gas. If this be mixed with 3 prop, of 
 oxygen 8 x 3 = 24? making 31, the mixture on detonation will 
 produce as under : 
 
 The 1 prop, of hydrogen 1 -f- 8.0 oxygen = 9.0 water. 
 
 The 1 prop, of carbon 6.0 + 16.0 oxygen = 22.0 carbonic acid. 
 
 31.0 
 
 Carburetted hydrogen is compounded of one proportional of 
 carbon and two of hydrogen; whereas olefiant gas is a compound 
 of one proportional of carbon and one of hydrogen ; and may be 
 represented thus : One proportional of carbon 6.0 + one of 
 hydrogen 1, will give the representative number of 7.0 for 
 super-carburetted hydrogen or olefiant gas. 
 
 Chloric ether may be formed by allowing a current of chlorine 
 and one of olefiant gas to meet in a proper receiver. There 
 should be excess of olefiant gas ; for if the chlorine be in excess, 
 the liquid absorbs it. It is transparent and colourless ; its taste 
 sweet and somewhat acrid; its specific gravity 1.2. It boils at 
 152. It burns with a green flame, evolving muriatic acid, and 
 largely depositing charcoal. As it is produced by equal volumes 
 of chlorine and olefiant gas, it is probably a compound of one 
 proportional of chlorine 36.0 + two of olefiant gas 7.0 X 2 = 
 14.0 = 50 chloric ether '. 
 
 Perchloride of carbon. Mr. Faraday has ascertained that, by 
 exposing olefiant gas, mixed with great excess of chlorine, to the 
 action of light, a white crystalline substance is formed, which, 
 when purified by washing with water, is a perchloride of carbon. 
 This substance is nearly tasteless ; its odour resembles camphor ; 
 its specific gravity is about 2 ; it is a non-conductor of electricity. 
 It is volatile ; and in close vessels fuses at 320, and boils at 360. 
 It is not very combustible, but burns when held in the flame of a 
 spirit lamp, with the emission of much smoke and acid fumes. 
 
 1 Brande, vol. i. page 437. 
 
ON CARBON. 159 
 
 It is insoluble in water, but readily soluble in alcohol and ether, 
 and the solutions deposit arborescent and quadrangular crystals. 
 It also dissolves both in volatile and in fixed oils. It is scarcely 
 acted upon by alkaline and acid solutions ; but most of the 
 metals decompose this substance at a red heat. Potassium burns 
 brilliantly in its vapour, causing the deposition of carbon, and 
 the production of chloride of potassium. It appears from various 
 analytical experiments upon this compound, that 100 parts afford 
 10 carbon and 90 chlorine; whence it would appear to consist 
 of 2 proportionals of carbon 12+3 of chlorine 108, making its 
 equivalent number 120. 
 
 Protochloride of carbon. When the perchloride of carbon is 
 passed through a red-hot tube, containing fragments of rock 
 crystal to increase the heated surface, it gives off a portion of 
 chlorine, and is converted into a liquid protochloride of carbon. 
 It is a limpid colourless fluid; specific gravity 1.55, and not 
 combustible, except retained in the flame of the spirit lamp, 
 when it burns with a yellow flame, much smoke, and fumes of 
 muriatic acid. It does not congeal at ; it rises in vapour at 
 about 165. It is insoluble in water, but soluble in alcohol, 
 ether, and the oils. It is not affected by the acids or alkalies, 
 nor, at common temperatures, by solutions of silver. It dissolves 
 chlorine, iodine, sulphur and phosphorus 2 . This extraordinary 
 substance affords, when decomposed, 14? parts carbon and 84? 
 chlorine ; whence it may be inferred to consist of 1 prop, of car- 
 bon 6 -f 1 of chlorine 36 = 4?2. 
 
 Hydriodide of carbon. When iodine and carburetted hydro- 
 gen are exposed to the action of light, they combine and form a 
 hy driod id e of carbon. This compound was first obtained, in the 
 laboratory of the Royal Institution, by Mr. Faraday. The 
 hydriodide of carbon is a white crystalline solid, volatile without 
 decomposition, and in many respects analogous to the hydrochlo- 
 ride of carbon, or chloric ether above described. Its taste is 
 sweet, and its odour aromatic 3 . 
 
 Carburet of nitrogen. This gas was discovered by Gay Lus- 
 sac, and announced in the Annales de CJiimie for 1815, vol. xcv. 
 page 1 36 231, under the name of cyanogen. It is here generally 
 called prussic gas. It may be obtained by decomposing the 
 cyanuret, or prussiate of mercury, by heat. It has a very powerful 
 smell, somewhat like that of bitter almonds, and affects the nos- 
 trils violently when inhaled by them. It is a permanently elastic 
 fluid, very inflammable, and nearly twice as heavy as atmospheric 
 air ; its specific gravity, compared with hydrogen, being 24.4?. 
 
 2 Brande, vol. i. pages 433 & 434. ' Id. ibid. 438. 
 
160 ON CARBON. 
 
 One hundred cubic inches of it weigh 54.9 grains. Water dis- 
 solves 4.5 volumes, and alcohol 23 volumes of this gas. The 
 aqueous solution is sharp and penetrating to the taste, and highly 
 poisonous. The gas burns with a beautiful purple flame inclin- 
 ing more to blue than red. Carburet of nitrogen, or prussic gas, 
 consists of two proportionals of carbon 12.0 + one of nitrogen 
 14.0 = 26.0, which may be considered to be the representative 
 number of this gaseous compound. 
 
 Chlorocyanic acid. This compound of the prussic and chlorine 
 gases was first formed by M. Gay Lussac, and described by him 
 in the paper already alluded to in the 95th volume of the Annales 
 de Ckimie. He obtained it by passing a stream of chlorine gas 
 into a solution of hydrocyanic or prussic acid in water ; and 
 purified it from the excess of chlorine in a way he there describes. 
 It is void of colour and very volatile. It has a pungent and very 
 peculiar odour ; and reddens litmus like other acids. M. Gay 
 Lussac gave it the name of chlorocyanic acid. It is composed 
 of one prop, of cyanogen 26.0 + one of chlorine 36.0 = 62 
 chlorocyanic acid. 
 
 Hydrocyanic or prussic acid. This is a triple compound of car- 
 bon, nitrogen and hydrogen ; or hydrogen united with prussic 
 gas. It is usually obtained by distilling at a very low heat mois- 
 tened prussiate of mercury with muriatic acid. The acid thus 
 obtained is a colourless liquid, has a strong smell resembling 
 peach blossoms, its taste is very acrid and highly poisonous. At 
 first it gives an impression of sweetness and coolness to the 
 tongue, it then tastes hot and virulent, and sometimes excites 
 sickness and fainting, and often violent coughing. It is a volatile 
 acid, and when exposed the gas volatilizes so rapidly as to freeze 
 itself. This may be shown by taking a drop of it on the end of a 
 tube. It reddens litmus paper, but the red disappears as the acid 
 evaporates \ This acid contains more nitrogen than the other 
 animal acids, but is destitute of oxygen. It is sometimes employed 
 in medicine, but it is preserved with difficulty, as it is the most 
 easily decomposed of all the acids. Some observations by Sir 
 H. Davy on the prussic gas and prussic acid, will be found in 
 two distinct papers in the 1st volume of the Scientific Journal, 
 pages 283 and 288. We have seen that cyanogen or prussic gas 
 is a compound of carbon 12.0 4- nitrogen 14.0; the prussic acid 
 is a similar compound, with the addition of one proportional of 
 hydrogen 1, which makes the representative number 26.0. 
 
 Cyanogen and Iodine. This compound has been formed by 
 Sir H. Davy, by heating iodine with prussiate of mercury. 
 
 1 Mr. Porret Philos. Trans, for 1814. M. Gay Lussac Annales de Chimie, 
 tome xcv. pages 136 &c. 
 
ON CARBON. 161 
 
 " The compound," says he, " is a very curious body ; it is 
 volatile at a moderate heat, and on cooling collects in flocculi, 
 adhering together like oxide of zinc formed by combustion, and 
 it has a very acrid taste and pungent smell." In this paper he 
 intimates a wish that M. Gay Lussac could be prevailed upon to 
 
 five up the inexpressive and difficult names of cyanogen and 
 ydrocyanic acid, and to adopt the simple ones of prussic gas 
 and prussic acid 2 . 
 
 Sulphur et of carbon. This is a colourless liquid of the specific 
 gravity of 1.272, highly inflammable, and capable of forming 
 compounds with the earths and alkalies. It boils at 106, though 
 it has so considerable a specific gravity, and does not freeze when 
 cooled down to 60. Its taste is pungent, and its odour very 
 fetid. It was discovered by Lampadius, who from its extreme 
 volatility gave it the name of alcohol of sulphur. It is obtained 
 by passing the fumes of sulphur over red-hot charcoal. Dr. 
 Marcet has discovered that sulphuret of carbon has the property 
 of producing cold far exceeding that of any other known sub- 
 stance. In the receiver of an air pump mercury may be readily 
 frozen by its means. Iodine dissolves in sulphuret of carbon, 
 and changes it to a dark reddish brown colour. One grain of 
 iodine will impart a deep colour to 1000 grains of the liquid. 
 Sulphuret of carbon is a compound of one proportional of car- 
 bon 6 + two of sulphur 32 = 38. Messrs. Clement and Des- 
 ormes, in a paper on carbon; M. Berzelius; and Professor 
 Brande, have written on this curious compound fluid 3 . 
 
 Phosphuret of carbon. The formation of this substance was 
 first noticed by Proust, who described it under the above name 
 in the Armales de Chimie. There is some difficulty in obtaining 
 it as he directs ; but Dr. Thomson says he never failed to pro- 
 cure it by the following method : " Allow phosphuret of lime to 
 remain in water till it has given out all its phosphuretted hydro- 
 gen gas; then add to the liquid a considerable excess of muriatic 
 acid; agitate for a few moments, and throw the whole upon a 
 filter. Phosphuret of carbon will be found upon the filter, 
 which is to be washed and dried. 
 
 " Phosphuret of carbon thus obtained, is a soft powder of a 
 dirty lemon yellow colour, without either taste or smell. When 
 left in the open air, it very slowly imbibes moisture, emits the 
 smell of carburetted hydrogen, and acquires an acid taste. 
 When the powder is thrown over the fire in small quantities at a 
 
 2 Journal of Science and the Arts, vol. i. 289. 
 
 3 Lampadius in Crell's Annals, 1796, ii. Clement, Annales de Chwme, tome 
 xlii. p. 121 152. Berzelius and Marcet, Philosophical Transactions, 1813. 
 Brande, Phil. Trans. 1820, page 19. 
 
 M 
 
ON CARBON. 
 
 time, it burns in beautiful flashes." It is composed of one pro- 1 - 
 portional of phosphorus 12 -f one of carbon 6. 
 
 In treating of carbon it is usual to adduce charcoal as a fami- 
 liar instance of its existence, carbon being the basis of all char- 
 coal. On this account it may be proper to speak of the methods 
 used for obtaining this article, and also of its peculiar properties, 
 i Charcoal is too well known to require any minute description ; 
 but as every one may not be aware of its characteristic properties, 
 it will be necessary to speak more circumstantially respecting 
 them than I have hitherto under the word Carbon. 
 
 The charcoal of wood is light and porous, so much so that it 
 is possible to blow entirely through it. It is also very brittle, 
 and easily reduced to a fine powder; it absorbs light very abun- 
 dantly, which occasions its blackness; at a red heat it decomposes 
 water and reduces metallic oxides ; it absorbs all the gases in 
 abundance ; it decomposes many of the acids by abstracting their 
 oxygen; it is a powerful antiseptic; is unalterable and indestructi- 
 ble by age ; is a conductor of electricity and a bad conductor of 
 lieat; it has a great affinity for oxygen when ignited ; it is a useful 
 agent in purifying rancid oils, and in abstracting the colour from 
 syrups and saline solutions ; it is one of the principal articles 
 employed in the preparation of Mr. Hatchett's artificial tannin ; 
 and it is one of the bases of the prussic acid and of a great many 
 other compounds. 
 
 One of the most important of these combinations is the article 
 of gunpowder, which is generally made to contain about fifteen 
 per cent, of charcoal. The usual proportions of its ingredients 
 are 76 parts of well purified nitre, 9 of sulphur, and 15 of char- 
 coal. 
 
 The first intimation that was given of gunpowder, was by that 
 great philosopher Roger Bacon, in his posthumous treatise 
 entitled, De Nullitate Magicz, published at Oxford in 1316, nearly 
 150 years before the invention of printing, and about 22 years 
 after the death of its venerable author. " You may," says he, 
 66 raise thunder and lightning at pleasure, by only taking sul- 
 phur, nitre, and charcoal, which singly have no effect, but mixed 
 together, and confined in a close place, cause a noise and ex- 
 plosion greater than that of a clap of thunder." 
 
 It is observable that he only mentions the sulphur and nitre 
 in direct terms ; and, as though he were fearful of imparting the 
 dread secret, conceals the charcoal under an anagram. The 
 words are, " sed tamen salis petrae lure mope can ubre, et sul- 
 phuris, et sic facies tonitrum, et corruscationem, si scias, artifi- 
 cium." The words which are printed in italics form an anagram 
 of CARBON UM PULVERE, charcoal powder. 
 
 Polydore Vergil relates, that gunpowder was invented by 
 
ON CARBON. 163 
 
 Bartholdus Schwartz, a German chemist, who happening to 
 triturate some sulphur, nitre, and charcoal in a mortar, was sur- 
 prised and alarmed at an unexpected explosion, which blew off 
 the head of his mortar to a considerable distance. 
 
 The probability is, that this was a second discovery of the 
 same thing, and that he knew nothing of the disclosure which 
 Bacon had made, and who was doubtless in possession of the 
 secret 100 years before the time alluded to by this author. 
 
 It appears, however, that in the year 1 380 Bartholdus Schwartz 
 did actually instruct the Venetians in the use of gunpowder, and 
 that all Italy complained of it, as a manifest innovation on the 
 rules of warfare ; although it is evident that this was not the first 
 instance of the use of gunpowder in war ; for it is related by 
 Peter Mexia, that " when the Moors, in 1343, were besieged by 
 Alphonsus XI. king of Castile, he discharged a sort of iron 
 mortars upon them, which made a noise like thunder." 
 
 Similar effects, and even in a much higher degree, may be 
 produced by the mixture of carbon with chlorate of potash and 
 sulphur ; and for some purposes this terrible compound is pre- 
 ferable to common gunpowder. Its explosive effects are truly 
 astonishing. Some particulars respecting this new kind of gun- 
 powder may be seen in the Additional Notes, No. LVI. of the 
 Chemical Catechism. 
 
 " Pent in dark chambers of cylindric brass 
 Slumbers in grim repose the sooty mass; 
 Lit by the brilliant spark, from grain to grain 
 Runs the quick fire along the kindling train ; 
 On the pain'd ear-drum bursts the sudden crash, 
 Starts the red flame, and death pursues the flash. 
 Fear's feeble hand directs the fiery darts, 
 And strength and courage yield to chemic arts." 
 
 Charcoal, when made on a large scale, is generally prepared 
 in the following manner: A large quantity of billet-wood is 
 piled in a heap ; this is covered with turfs and sand to prevent 
 the access of atmospheric air as much as possible, and then the 
 heap is set fire to at several holes near the bottom, which are 
 always made for that purpose. At first a. hole is left open at the 
 top to occasion a draught, and produce a better and more 
 regular combustion. After a time this orifice is covered with turf; 
 and when it is perceived that the flame has pervaded every part 
 of the heap, the holes at the bottom are closely stopped also. 
 By this management the whole of the wood becomes ignited, 
 though it is not burnt to ashes as it would be were a free circu- 
 lation of air to be permitted ; but, by closing the openings and 
 leaving the fire smothered up, a heat is preserved sufficient to 
 decompose and dissipate every thing of a fluid or gaseous nature 
 in the wood, so as to leave the whole pile in a carbonized state. 
 
 M 2 
 
164- \ ON CARBON. 
 
 The rnass^ is then allowed to cool sufficiently to be uncovered, 
 and the billets, now converted into charcoal, to be removed. 
 
 This method of making charcoal is doubtless very ancient. 
 Theophrastus Eresius, the pupil and successor of Aristotle, who 
 lived more than 300 years before Christ, has described it very 
 fully. This excellent philosopher, who wrote more than 200 
 different treatises, chiefly on subjects of natural history, lamented, 
 at the age of eighty-five, " that he was to die, just when he began 
 to know how to live." 
 
 Pliny informs us that in his days the wood was formed into a, 
 pyramid, the apex of which was covered with clay 1 . There is, 
 indeed, abundance of evidence that the ancients were acquainted 
 with several of the properties of charcoal, and employed it for 
 various purposes. 
 
 It has, however, been discovered within a few years, that char- 
 coal can be much more perfectly prepared by a method different 
 from that which has just been described, and which is now gene^ 
 rally adopted for the preparation of that which is consumed in 
 the manufacture of gunpowder. 
 
 In this process the wood, previously freed from the bark, is 
 placed within large cast-iron cylinders, which are fixed horizon- 
 tally in brick-work so as to be easily heated red-hot by fires 
 placed beneath them. 
 
 These cylinders during the distillation have no communication 
 with the external air, but at one opening, and this is destined to 
 allow of the escape of the acid and the different gases ; so that, 
 when the operation is over, nothing remains in the cylinders but 
 the charred wood divested of all impurities. 
 
 In some manufactories the charcoal is drawn from the cylin- 
 ders, while red-hot, into immensely large canisters, made with 
 riveted plates of sheet-iron, end with moveable covers, which fit 
 perfectly, so as to close them completely. In these it remains 
 safely preserved from the action of the atmosphere till it is 
 entirely cold. These canisters are so contrived, as to their num- 
 ber and size, as to contain the whole produce of one charge. I 
 should be culpable, however, were I not to caution my readers 
 against adopting this mode of conducting the business ; for the 
 circumstance of removing the charcoal from the cylinders while 
 red-hot must very much injure the health of die workmen so 
 employed. 
 
 In some other manufactories the wood is not put into the cy- 
 linders which are fixed in the brick-work, but into others which 
 are made of sheet-iron, and contrived so as to fit within the 
 former. Here the cast-iron cylinders acquire a red heat, as in 
 
 1 Holland's Pliny, folio, London, 1601, book xvi. page 459. 
 
ON CARBON. 165 
 
 the former case, and that heat is found to be sufficient to char 
 the wood contained in the wrought-iron vessels. 
 
 When the operation is finished and the wood is found to be 
 sufficiently charred, which is always known by the volatile parts 
 having ceased to distil over, a block and tackle are affixed to the 
 inner cylinders, which are drawn out in a moment, and others 
 of the same dimensions, previously filled with billets of wood, 
 are by the same means directly swung into their places. In this 
 way the process goes on without interruption, and the proprietor 
 is enabled to allow the charcoal to cool completely, before it is 
 removed from the vessel in which it is prepared. In order to 
 adhere strictly to this rule, it is of course requisite to have a 
 number of the wrought-iron moveable cylinders proportionate 
 to the extent of the work; so that while some are cooling, others 
 may be recharged with wood, and exposed in the fixed cast-iron 
 apparatus to the action of the fire, and thus no time will be fruit- 
 lessly expended. Drawings of the apparatus will be found in the 
 plates, figures 13 and 14?. 
 
 It is remarkable that, although the charcoal prepared by this 
 process is so superior for making gunpowder, it is not well cal- 
 culated for some other processes. It is not of half the specific 
 gravity of the charcoal which is made out of doors in the com- 
 mon way, and merely covered up with turf. The makers of iron 
 particularly will not buy it. 
 
 This method of working does however produce better charcoal 
 for gunpowder, and it has the advantage of furnishing a large 
 supply of an impure kind of vinegar, or acetic acid, which is 
 very useful in several of our manufactories. This acid was for- 
 merly considered to be of a peculiar nature, and distinct from all 
 others; it was named the pyroligneous acid, and in commerce it 
 is still known by that appellation. Before this acid begins to 
 distil over, there comes a peculiar fluid called naphtha or pyro- 
 ligneous ether, which is used, when purified by a subsequent dis- 
 tillation with lime and animal charcoal, for spirit lamps, for the 
 solution of shellac and the gums, and indeed for most purposes 
 in which alcohol was formerly required ; but at present the 
 greatest consumption is by Mr. Macintosh in dissolving caout- 
 chouc (Indian Rubber) for the preparation of his water-proof and 
 air-proof cloth, for great coats, cloaks, &c. ; and indeed to such 
 perfection has he now brought it, that he makes air-tight pillow- 
 cases and beds, which only require to be blown full of air by the 
 mouth, to be ready for use when required, and in the morning 
 the air may be let out and the bed folded up and put away into 
 the traveller's trunk. 
 
 When this acid is suffered to stand a few weeks undisturbed, 
 it deposits a peculiar kind of tar, and this in considerable quail- 
 
166 ON CARBON. 
 
 tity. Every kind of wood will produce this acid and tar, when 
 treated by what is called the destructive distillation. Peat also 
 will yield it in abundance. A friend of mine distilled some 
 which was dug in Wholmer Forest, and procured pyrol igneous 
 acid from it. When this acid was redistilled, it left a residuum 
 of tar, similar to that which is produced from the second distil- 
 lation of wood acid. For some years past this tar has been a 
 great burden on the hands of those who have been largely con- 
 cerned in making the pyroligneous acid. For, though it has 
 been employed in a great variety of ways, the consumption has 
 never kept pace with the quantity produced, and within my own 
 knowledge many tons of it have been buried in the earth, merely 
 to get rid of it. 
 
 It was tried in one of the public dock-yards ; but the quantity 
 produced at that time in Great Britain was, in comparison with 
 the quantity of pitch and tar required for the royal navy, too in- 
 significant to permit the idea to be ever entertained of its being 
 generally used in the Government dock-yards ; particularly as it 
 will not combine with the imported pitch and tar in common use. 
 
 I have myself, in various ways, made experiments upon this 
 tar; and, notwithstanding this inconvenience, I am so convinced 
 of its value, that I am desirous of making it an object of public 
 attention. 
 
 For every kind of wood fence, it is the best preservative of any 
 thing that can be applied. It should be gently heated in an iron 
 pot, and put on with a brush. When first put on, it gets so 
 completely into the wood, that it might be supposed that it could 
 be of little use. It soaks in, and seems to leave no body, as the 
 artists express it : but if the work thus treated be examined after 
 it has been exposed for some days to the sun, the surface and the 
 texture of the wood will evidently be much altered ; for it will 
 now be found so impervious and hard, that it will be very diffi- 
 cult to make any impression upon it. 
 
 If a second, and especially if a third coat of this tar be put 
 upon wood, it will then bear out, as the painters call it, suffi- 
 ciently well ; and I have reason to believe that it will preserve 
 all outside wood-work much more effectually than it can be pre- 
 served by any other expedient that has hitherto been contrived 
 for this very important purpose. 
 
 For ornamental paling, and indeed for all good outside work, 
 a first, or perhaps a first and second, coat of this tar might be 
 used with great advantage ; and when these shall be completely 
 dry, the work might be finished with white lead and oil, as usual. 
 
 Besides the extreme hardness which this article imparts to 
 wood, it has also the advantage of effectually preserving it from 
 worms and from all other insects. Even where wood has become 
 
ON CARBOtf. 167 
 
 worm-eaten, I have observed that this tar will stop the progress 
 of the decay; and I am inclined to think, 'from what I have seen, 
 that a paling of worm-eaten deal, if it be not absolutely rotten, 
 will last longer when covered with this article, than a similar 
 fence made with new deal without such treatment. It may how- 
 ever be necessary to remark, that the article here spoken of is 
 very different from the tar which is distilled from mineral coal, 
 and that was recommended by the Earl of Dundonald, thirty 
 years ago, for a similar purpose* 
 
 To those persons to whom a little additional expense would- 
 be no object of consideration, the following preparations are re- 
 commended. They will be found to improve the appearance of 
 the wood to which it is applied very considerably: 1 gallon of the 
 tar, loz. of tallow, and 2oz. of pulverized rosin, melted together 
 and put on warm; or 1 gallon of the tar, and 2oz. of pulverized 
 sulphate of iron, to be used in the same manner as the foregoing 
 mixture. 
 
 The first of these prescriptions looks the best, but the latter 
 has been proved, and has lasted good for twenty years. How 
 much longer it will be an effectual preservative for the wood, 
 time only can discover. 
 
 I have occasionally made many other trials of the tar from 
 pyroligneous acid, and I find ijt useful not only for wood, but 
 also as a varnish for a variety of goods made of rolled iron, or 
 of cast iron. A more beautiful varnish for these purposes may 
 however be prepared by the following process : Take 1 gallon of 
 the wood tar, and % pint of rectified spirits of wine, and let these 
 be intimately mixed by a gentle heat. 
 
 If this composition be laid on hot and properly hardened by 
 the air, it will prove a beautiful and durable black varnish. 
 
 Some time ago a very remarkable circumstance respecting the 
 collection of pyroligneous acid from the charcoal-cylinders, came 
 to my knowledge, which I think worth recording, as it may pre- 
 serve some individuals from great loss and disappointment, and 
 must be of considerable importance to us as a nation. 
 
 A gentleman of opulence, residing near the metropolis, who 
 was the proprietor of some large gunpowder works, and who 
 prepared his own charcoal for that manufactory, sustained a con- 
 siderable pecuniary loss from the following occurrence. 
 
 He had for some time been collecting a portion of the pyro- 
 ligneous acid, which arises from the wood in the act of charring ; 
 when a certain chemical adventurer persuaded him to make an 
 alteration in the apparatus, with the view of procuring, as it 
 was pretended, more than double the quantity of acid. 
 
 According to this advice, he put up at a considerable expense 
 
168 ON CARBON. 
 
 an entirely new apparatus, which was so constructed that the 
 pipes which conveyed the acid, as it arose from the ignited wood, 
 passed through a large body of water, which so completely 
 cooled it, that the whole of it was condensed and collected in 
 the recipient. In the last pipe, exactly at the place where it 
 emerged from the water, there was a small hole, to prevent any 
 part of the apparatus from bursting. Whenever the cylinders 
 had done working, it was directed that this hole should be firmly 
 stopped, and that then the whole apparatus should be suffered to 
 cool. 
 
 By this arrangement a much larger quantity of acid was pre- 
 served, as the adviser had predicted, and which promised an 
 ample repayment of the expense of the alteration : but it was 
 quickly perceived that the gunpowder was very much deterio- 
 rated ; and this happening at a time when the house had a con- 
 tract with Government (in which case the gunpowder is always 
 accurately proved) several parcels were complained of, and one 
 large delivery was actually returned as unfit for the public service. 
 
 These complaints were not only unexpected, but peculiarly 
 mortifying, because the manufacturer had been pleasing himself 
 with the idea that the gunpowder would be improved, and lie 
 could not at all account for the cause of this unfortunate change 
 in the quality of his article. 
 
 At first he suspected that the nitre might contain some deli- 
 quescent salts; but even when he had made his gunpowder from 
 the nitre which had been refined at His Majesty's private works, 
 where the utmost care is taken in the process, the powder was 
 still the same. Then the sulphur was examined ; and when no- 
 thing amiss could be discovered there, he began, for the first 
 time, to suspect that the fault must be in the charcoal, although 
 that which they were then using was in appearance finer and 
 handsomer than any they had ever had. 
 
 The proprietor was now, however, convinced that the altera- 
 tion in the quality of the powder could not possibly be otherwise 
 accounted for than by attributing it to this alteration in his ap- 
 paratus: he therefore instantly ordered the whole to be removed, 
 and reverted to his old plan of distillation, by which one-third, 
 at least, of the acid is dissipated in gas, and entirely lost. But 
 the consequence was evidently favourable, and the error fully 
 detected. The gunpowder manufactured since is as good as it 
 had formerly been, and he has received no more complaints. 
 
 This circumstance was not mentioned to me until after the new 
 apparatus was destroyed, or I certainly would have advised the 
 proprietor to continue the new arrangement, and to make no 
 other alteration than merely to provide the means for the incon- 
 densable gaseous products to be properly dissipated. For, by 
 
ON CARBON. 169 
 
 stopping up the vent-hole, the latter portions of the inconden- 
 sable gas could not get away ; and every chemist knows the pro- 
 perty which charcoal has of absorbing with avidity all the gases, 
 and in considerable quantity. If, instead of stopping up the 
 vent-hole, several others had been opened during the last stage 
 of the process, and suffered to remain so while the cylinders 
 were cooling, I doubt not that this charcoal would have turned 
 out equal in goodness to the former. 
 
 The kinds of wood which are preferred for making this kind 
 of charcoal, are the dog-wood, the alder, and the willow l ; 
 and since these woods have been made use of, and the last-men- 
 tioned process has been employed for making the charcoal, any 
 given quantity of the British gunpowder will drive a ball one- 
 third further than the powder prepared with ordinary charcoal. 
 
 This may in some measure be owing to the charcoal of these 
 woods taking fire more quickly ; for we know how much sooner 
 the coal of some linen, when used as tinder, will take fire, than 
 that of others, and how readily that kind of fungus burns which is 
 called German tinder 2 , a species of agaricus, known to botanists 
 by the name of Boletus igniarius. The slightest spark communi- 
 cated to this tinder will be sufficient to occasion a commencement 
 of combustion. 
 
 The Government of France has for some time been aware of 
 the importance of attending to the preparation of charcoal for 
 public use. The old method was discontinued several years 
 ago, and the gunpowder charcoal has since been made in large 
 trenches cut within the ground, and lined with brick, the super- 
 intendents of the gunpowder works having found that by this 
 management the same kinds of woods will produce lighter and 
 softer charcoal than when the wood is carbonized in large piles 
 in the open air 3 . 
 
 For philosophical experiments charcoal may be readily made 
 by filling a large crucible with short pieces of wood, covering 
 these with sand, and submitting the whole to a red heat for half 
 an hour or more in a common fire-place. When I have had 
 occasion to melt a block of tin, preparatory to making the ni- 
 trate or muriate of that metal, I have sometimes prepared very 
 
 1 Within these twenty years very large plantations of clog- wood and alder 
 have been made in the counties of Kent, Sussex, and Surry ; so that at this time 
 His Majesty's and other private manufactories of gunpowder are entirely sup- 
 plied with charcoal from wood of the above descriptions. 
 
 * To render this fungus still more combustible, the Germans purify it from 
 all extraneous matter by boiling it in an alkaline lye. They then dry it, and 
 boil it again in a solution of saltpetre. Therefore the tinder sold in the shops 
 is not the simple female agaric, but a compound of that vegetable production 
 and nitre. 
 
 3 See Chaptal's Chemistry applied to the At Is, vol. ii. p. 28$. 
 
170 ON CARBON. 
 
 excellent charcoal by immersing pieces of wood in the melted 
 metal, and holding them beneath the surface until the whole was 
 charred entirely through. When this method is adopted, the 
 charcoal may be plunged either into a vessel of mercury or a 
 bed of cold sand, the moment it is drawn from the melting-pot, 
 according to the purposes for which it may be wanted ; and it 
 will be found that by either of these modes it will be sufficiently 
 preserved from the action of the atmosphere. 
 
 Whenever pieces of wood or other vegetable matters are 
 charred without being disturbed during the operation, the grain 
 of the wood and the form of the filaments are always preserved 
 distinct and entire. If we examine writing paper or linen which 
 has been covered up and burnt without the free access of atmo- 
 spheric air, the wire marks of the paper and the threads of the 
 linen will still be seen with distinctness. 
 
 When Sir William Hamilton explored the ruins of Hercu- 
 laneum, he found corn that was converted to charcoal by the 
 eruption of Vesuvius in the year 79 of the Christian era, and 
 which was so well preserved that the grains of wheat were easily 
 distinguishable from those of rye. We read indeed of some who 
 have been so dexterous as to char an arrow without altering the 
 form even of the feather ! . 
 
 On the contrary, if wood be burnt in the open air, the greatest 
 part of it will be dissipated in gas. Common oak, if charred in 
 a proper manner, will lose only from two-thirds to four-fifths of 
 its weight; whereas if the same kind of wood be burnt in an 
 open fire-place, the residuum of the combustion will not be 
 more than about one 200 th or one 250 th of the original weight 
 of the wood employed. 
 
 This, however, will vary according to the age and the dry- 
 ness of the wood, and also to the different ways in which it may 
 be burnt ; and this accounts for the different statements which 
 have been given of these results. Dr. Watson says that he pro- 
 cured 22 grains of charcoal from 96 of dry oak. Van Helmont, 
 that 62lb. of the charcoal of oak will produce lib. of white ashes; 
 whereas Sage says that lOOlb. of charcoal will not give more 
 than 2oz. of ashes. 
 
 The following table of the quantity of charcoal yielded by dif- 
 ferent woods, has been published by Mr. Mushet, from his own 
 experiments in the small way, carefully conducted. He says, 
 the woods before being charred were thoroughly dried, and 
 pieces of each kind were selected as nearly alike in every respect 
 as possible. One hundred parts of each sort were taken, and 
 they produced as follows : 
 
 Neumann's Chemistry, by Lewis, vol. ii. page 2/7. 
 
ON CARBON. 
 
 171 
 
 Lignum Vita) afforded 26.0 of 
 
 Mahogany .... 25.4 . 
 
 Laburnum .... 24.5 
 
 Chesnut .... 23.2 
 
 Oak 22.6 
 
 Walnut .... 20.6 
 
 Holly 19.9 
 
 Beech 19.9 
 
 Sycamore . . . 19.7 
 
 Elm 19.5 
 
 Norway Pine . . . 19.2 
 
 Sallow .... 18.4 
 
 Ash . . . . . 17.9 
 
 Birch 17.4 
 
 Scottish Pine . 16.4 
 
 charcoal of a grayish colour resembling coke. 
 . tinged with brown, spongy and porous, 
 velvet black, compact, very hard, 
 glossy black, compact, firra. 
 black, close, very firm, 
 dull black, close, firm, 
 dull black, loose and bulky, 
 dull black, spongy, firm, 
 fine black, bulky, moderately firra, 
 fine black, moderately firm, 
 shining black, bulky, very soft. 
 velvet black, bulky, loose and soft, 
 shining black, spongy, firm, 
 velvet black, bulky, firm, 
 tinged with brown, moderately firm. 
 
 Messrs. Allen and Pepys from 100 parts of the following 
 woods obtained the quantities of charcoal as under : 
 
 Beech . . 15.00 I Lignum Vitce . 17-25 I Fir . . 18.17 
 Mahogany . 15.75 | Oak . . 17.40 | Box . . 20.25 
 
 It is observable that the quantities obtained by Messrs. Allen 
 and Pepys are in general less than those given by Mr. Mushet, 
 which may be owing to Mr. Mushetnot having applied sufficient 
 heat, or operated long enough to dissipate the aqueous matter or 
 the gaseous products. Charcoal was formerly considered to be 
 a kind of oxide of carbon ; but Messrs. Allen and Pepys have 
 shown that this is not the case ; and that when it is well prepared 
 it requires as much oxygen for its complete combustion as the 
 diamond *. 
 
 To those persons who buy charcoal by weight, it is important 
 to purchase it as soon after it is made as possible, as it quickly 
 absorbs a considerable portion of water from the atmosphere. 
 Different woods, however, differ in this respect. Messrs. Allen 
 and Pepys found that by a week's exposure to the air, the char- 
 coal of 
 
 Lignum Vitae gained 
 
 Fir 
 
 Box 
 
 9.6 per cent. 
 13.0 ditto 
 14.0 ditto 
 
 Beech gained 
 
 Oak 
 
 Mahogany 
 
 16.3 per cent. 
 16.5 ditto. 
 18.0 ditto. 
 
 I have already adverted to the porosity of charcoal, page 
 and to the avidity with which fresh made charcoal absorbs all the 
 gases. The following is a tabular view of the volumes of the 
 different gases which were absorbed in the course of 24- hours, 
 by one volume of charcoal, in the experiments of M. Theodore 
 de Saussure, which were conducted in a way likely to produce cor- 
 rect results. Each portion of charcoal was heated afresh to a red 
 heat, and allowed to cool under mercury. When taken from the 
 mercury, it was instantly plunged into the vessel of gas. 
 
 - Philosophical Transactions for 1807, part ii. page 267- 
 
172 ON CARBON. 
 
 Ammoniacal ga<5 . . 90 
 
 Muriatic acid gas . . 85 
 
 Sulphurous acid . . 65 
 
 Sulphuretted hydrog. 55 
 
 Nitrous oxide . . 40 
 Carbonic acid gas . 35 
 Bicarburett. hydr. 35.00 
 Carbonic oxide , 9.42 
 
 Oxygen gas ... 9.25 
 
 Nitrogen .... 7-50 
 
 Carburettcd hydr. 5.00 
 
 Hydrogen gas . . 1.75 
 
 I have already remarked, in another work, that a very inter- 
 esting application may be made of this property of charcoal. 
 The gases which are absorbed suffering so great a condensation, 
 two gases introduced at once into the pores of the charcoal may 
 perhaps be made to combine. Water has actually been formed 
 from hydrogen and oxygen gases by this means '. 
 
 Caspar Neumann, who made many experiments on charcoal, 
 informs us that for the reduction of the metallic oxides, the char- 
 coal of the heavier woods, as that of the oak and the beech, is 
 preferable, and that, for common fuel, such charcoal gives the 
 greatest heat, and requires the most plentiful supply of air to 
 keep it burning; while those of the lighter woods preserve a 
 glowing "heat" with a much less draught of air; and that for pur- 
 poses where it is desirable to have a steady and a still fire, char- 
 coal should be employed which has been made from wood pre- 
 viously divested of its bark, since it is the cortical part which 
 crackles and flies off in sparks during combustion, while the 
 coal of the wood itself seldom does 2 . 
 
 For making crayons of charcoal, the willow is the best wood 
 that can be employed, as the softness is in all its parts uniform. 
 The coals of the hard woods, such as box and guaiacum, are 
 considerably harder than others, while the charcoal of the ker- 
 nels of fruits is peculiarly soft and friable 3 . But as a pigment 
 the coal of ivory is the most intensely black and the most beau- 
 tiful. I speak here, not of the common ivory-black of the shops, 
 but of the charcoal which is prepared by burning real ivory in 
 closed vessels. As a powder for cleaning the teeth, the best 
 charcoal is that made from the shell of the cocoa-nut. 
 
 The perfect durability of carbon as a pigment, may be seen in 
 several of our old churchyards, where the letters made with lamp- 
 black are still perfect, though the white lead with which the body 
 of the stones was painted is entirely destroyed. Some few years 
 ago I remember to have noticed this circumstance on Sir Hans 
 Sloane's monument in the churchyard at Chelsea. This property 
 of carbon is shown, however, in a more striking manner by the 
 writings that were found in the ruins of Herculaneum, which 
 have retained their original blackness for two thousand years. 
 The ancients wrote with ink made from ground charcoal. * 
 
 1 Chemical Catechism, Addit. Notes, No. If. Annales de Chimie ) vol. xxxii. 
 
 2 Neumann's Chemistry, vol. ii. page 277. 
 
 3 See Lewis's Commcrcium Tcchnicum, page 337; also Dr. Grew On the 
 Analowy of Plants. 
 
ON CARBON. 173 
 
 A friend of mine, who is engaged in refining rancid fish oil 
 by means of tannin, has fitted up an apparatus for burnino- the 
 gelatinous or leather kind of precipitate which results from his 
 operation, and which he says is of little value for any other pur- 
 pose. This charred powder, or soot, he informs me, proves to 
 be a finer and better black for printers' ink and other purposes, 
 than any he can procure by other methods. I think it would be 
 worth while to try this gelatinous precipitate, when properly 
 charred, in abstracting the colour from sugar, refiners' syrups, 
 and certain valuable saline solutions, as it is well known that 
 animal charcoal is much more efficacious for such purposes than 
 any kind of vegetable charcoal. 
 
 The article known in commerce by the name of lamp-black, 
 is carbon in the state of a light impalpable powder, and is pro- 
 cured by burning the refuse of resin and pitch in peculiar fur- 
 naces, with long flues terminating in a close chamber, the ceiling 
 of which is covered with porous cloth, through which the gas 
 that is disengaged in the process may escape and the soot be left 
 behind. 
 
 In drawing spirits of turpentine from the crude turpentine, 
 there is a large residuum known in commerce by the name of 
 rosin ; and as a considerable portion is often found to be too im- 
 pure to sell as rosin, it is profitably burnt for the production of 
 lamp-black ; and lately carburetted hydrogen has been obtained 
 from it, much purer and giving a clearer and more vivid light 
 than what is procured either from coal or oil. The library of the 
 Royal Institution is lighted by means of gas produced from rosin. 
 
 The coal of all resinous substances is of a similar nature. If 
 lamp-black be heated red-hot in a crucible, and allowed to cool 
 before the crucible be uncovered, we shall have, perhaps, as per- 
 fect a sample of pure carbon as can easily be prepared. Sir H. 
 Davy says, " The purest known form in which carbon can be 
 obtained, is by passing oils or spirits of wine through ignited 
 tubes. It then appears as an impalpable black powder : it has 
 neither taste nor smell; it is a conductor of electricity, and it is 
 more than twice as heavy as water." El. Chem. Phil, page 299. 
 
 Some artists, for very nice purposes, have collected the car- 
 bonaceous matter which arises in burning the vegetable oils, by 
 
 v -1 T 
 
 suspending some convenient substance at a proper distance over 
 
 the flame of the lamp. 
 
 The beautiful brown pigment called bistre is prepared from an 
 aqueous infusion of wood-soot. Some account of its preparation 
 is related by Lewis in his " Commerce of the Arts," but more 
 ample directions for making it are given in the French Encyclo- 
 pedia. 
 
 If it be required to purify any carbonaceous matter, to render 
 
174 ON CARBON. 
 
 it fitter for a pigment or other nice purpose, it may be done by 
 first well calcining it in a close vessel, and then lixiviating it in 
 water slightly acidulated by nitric acid. This process will sepa- 
 rate the earthy or metallic particles with which it may be con- 
 taminated ; and by heating it a second time in a very brisk fire 
 properly secured from the air, we' obtain a charcoal very near to 
 the state of pure carbon. 
 
 Charcoal may also be obtained from animal substances burnt 
 in closed vessels; but this differs from vegetable coal in some 
 particulars, and, as I have already said, is better for some pur- 
 poses. It is always more dense ; and if it be made in a glass or 
 earthen vessel, it adheres to it more than the carbon of vegetables ; 
 it is also less combustible, and generally contains phosphate of 
 iron and other foreign matter. 
 
 It may be ascertained whether any carbonaceous matter be 
 produced from animal or from vegetable substances, by the fol- 
 lowing trial. A vegetable coal will burn, on a red-hot iron, into 
 white ashes, 'and these will be readily dissoluble by sulphuric acid 
 into a bitterish liquor ; whilst the ashes of animal substances are 
 very sparingly affected by that acid, and form with it a compound 
 having a very different taste '. This fact is of importance to 
 those sugar-refiners and others who use large quantities of animal 
 charcoal in the state of powder, and which is often in danger of 
 being adulterated with vegetable charcoal, an article that is not so 
 efficacious, but is always to be obtained at a much lower price. 
 
 Charcoal is endowed with many singular properties, which can- 
 not be too generally known, as some of them qualify it for render- 
 ing very important services to the arts. The intractable nature 
 of carbon has been already mentioned ; and whether coherent in 
 charcoal, or in powder, is infusible by any heat that has hitherto 
 been applied. " I have exposed it," says Sir H. Davy, " to the 
 powers of intense ignition of different voltaic batteries; that of 
 Mr. Children, one of 40 double plates of 18 inches square, and 
 the battery of 2000 double plates of 4 inches, both in vacuo and 
 in compressed gases, on which it had no power of chemical 
 action. A little hydrogen was given off from it, and it slowly vola- 
 tilized in these experiments, and the part remaining was much 
 harder than before, so as in one case to scratch glass, and the 
 lustre was greater ; but its other properties were unaltered, and 
 there was no appearance of fusion." Chem. Phil, page 300. 
 
 It has been before mentioned, that charcoal is a bad conductor 
 of heat ; but I cannot avoid remarking that few persons, compa- 
 ratively speaking, have availed themselves of this property, al- 
 though there are innumerable instances in which charcoal might 
 
 1 Lewis's Commercium Philosophico-Techmcitm, 4to, 1703, page 3/7. 
 
ON CARBOX. 175 
 
 be employed as a slow conductor of heat with very great advan- 
 tage. The mention of a few of the most important of these must, 
 however, suffice on the present occasion. 
 
 One of the most beneficial applications of charcoal, as a slow 
 conductor of caloric, would be in some processes where it is 
 necessary to preserve for a given time an equable temperature. 
 
 Thus, if all those vessels which are heated by steam, were 
 made treble instead of double, and the space between the two 
 outer vessels filled with ground charcoal, the heat would be so 
 prevented from escaping, that any one particular temperature 
 might be kept up for a great length of time, and a material saving 
 of fuel would be accomplished. Guyton has shown that ground 
 charcoal will conduct heat more slowly than even dry sand, and 
 this in the proportion of three to two. 
 
 In extracting the colouring matter of dye-woods, and in making 
 some other colours for the use of calico-printers, it is of great 
 consequence to heat the vessels by steam ; for by this mode of 
 preparing decoctions the workmen are prevented from ever giving 
 the materials a greater heat than that of 212, and the injury 
 which was formerly done by the grosser matters burning at the 
 bottom and sides of the copper, is avoided. Several manufacturers 
 have now adopted this method, and I have lately seen some ap- 
 paratus in two or three establishments constructed on this prin- 
 ciple, that appeared to me to be complete in every respect, ex- 
 cepting that they suffered much of the heat to escape ; all of 
 which might have been saved, and turned to a good account, by 
 employing powdered charcoal in the way I have just described. 
 
 Again, whenever churches or other large buildings are to be 
 warmed by steam, so much of the conducting pipe as is not 
 actually within the building should always be surrounded in this 
 manner : then no part of the heat could escape until it had been 
 delivered within the space destined to be warmed by it. 
 
 In like manner, in the manufactories of starch, paper, gun- 
 powder, Prussian blue, and a variety of other articles that might 
 be mentioned, every part of the apparatus for drying these by 
 steam, and which is not actually within the drying-rooms, ought 
 to be secured in the same way. 
 
 The common steam-cooking apparatus and other culinary 
 utensils would be much improved were they fitted with double 
 covers, and the inner spaces between these covers filled up with 
 charcoal-powder. 
 
 Moreover, by securing the conducting pipes in this manner, 
 buildings might be effectually warmed, and processes conducted, 
 at any distance from the side of the boiler, as " steam is the most 
 faithful carrier of heat that can possibly be ;" for it cannot de- 
 posit it on any bodies that have already acquired the temperature 
 of 2 12. 
 
176 ON CARBON. 
 
 Owing to this non-conducting property of charcoal, it is very 
 commonly employed in France to coat furnaces, and to confine 
 the heat, for which its incombustible nature fits it in a peculiar 
 manner ', it being the most refractory body we know of, provided 
 it be excluded from oxygen. 
 
 In domestic economy, charcoal is invaluable. From its pro- 
 perty of retarding putrefaction it surpasses, as a preserver of 
 meat, any thing we know of. Game, or any kind of animal food 
 that has been over-kept, will be rendered perfectly sweet and 
 wholesome by covering it with a few pieces of fresh burnt char- 
 coal. Or, if it be far gone, boiling it for some minutes in water 
 with a few ounces of such charcoal will effectually purify it*. 
 
 How much better must the charcoal made in cylinders be for 
 all these purposes than common charcoal ! as the cylinder char- 
 coal is free from the sap and acid of the wood, and consequently 
 more tasteless in itself and lighter than the charcoal prepared in 
 any other way. Those individuals who may be desirous of 
 having such charcoal, may at any time procure it from the per- 
 sons who manufacture either pyroligneous acid or gunpowder. 
 
 By its means also molasses or treacle may be deprived of its 
 disagreeable taste, so that it might be used in families instead of 
 sugar. M. Cadet Devaux says that he diluted twenty-four pounds 
 of treacle with the same weight of water, and boiled it for half an 
 hour with six pounds of pulverized charcoal, which entirely de- 
 prived it of its empyreumatic taste and smell. He then strained 
 the saccharine liquid from the charcoal ; and, having evaporated 
 it to a due consistence by a gentle heat, found its flavour equal 
 to that of good sugar. Those who have occasion to use honey, 
 and yet have an objection to its peculiar flavour, may deprive it 
 of this taste by a similar management. 
 
 The principle of refining sugar by means of charcoal is indeed 
 the basis of the patent taken out by Mons. Cronstat, and for the 
 transfer of which he required of the joint body of sugar-bakers 
 in London a remuneration of fifty thousand pounds : and I have 
 reason to think that the proprietors of a small concern established 
 only a few years ago in the metropolis, where double loaves are 
 manufactured of a finer quality than are produced at any other 
 house, effect the purpose by the same means. 
 
 In like manner the disagreeable empyreumatic flavour which 
 some brandies acquire in distillation, may be removed by digesting 
 them on charcoal ; and common malt-vinegar, if boiled on char- 
 
 1 Fourcroy's System of Chemical Knowledge, vol. i. p. 248. 
 
 4 That water impregnated with carbonic acid gas is such an effectual preserver 
 of meat, is probably altogether owing to the carbon of which this acid gas is 
 composed. An interesting letter from Sir William Lee, Bart, to Dr. Priestley 
 on this subject, will be found in the Appendix to the fourth volume of the 
 Doctor's " Observations on Air" 
 
ON CARBON. 177 
 
 coal, becomes quite colourless like distilled vinegar, without being 
 impaired in strength ; whereas it always becomes much weaker 
 by distillation. 
 
 On the same principle charcoal is frequently employed by the 
 manufacturing chemist in purifying any of the salts which may 
 have become coloured from accidental circumstances, or from 
 their combination with heterogeneous matters. It is only neces- 
 sary to redissolve them, and boil their solutions on charcoal, and 
 when re-crystallized they will be found pure and colourless. 
 
 Even the common salt of hartshorn (carbonate of ammonia), 
 which is prepared from a liquor distilled from bones, and which 
 often requires great labour to render it of the desired purity, loses 
 the whole of its foetid smell by being mixed with charcoal powder, 
 and re-sublimed. 
 
 On long voyages the water, which has been laid in for the 
 ship's crew, generally acquires a disagreeable taste and smell 
 from standing so long in the wooden casks ; but whenever this 
 happens, it can be entirely purified by filtrating it through 
 ground charcoal. It is always best, however, to send out water 
 in casks that are charred within side, as water kept in such casks 
 is always sweet. In London and elsewhere, it is very common 
 to pitch water-casks on the whole of their inner surface ; but 
 surely it would be cheaper, and much more effectual for making 
 them into good water-casks, to light a fire of wood-shavings 
 within them, and keep it burning until the whole of the surface 
 on the inside is completely charred. 
 
 It is difficult to understand how charcoal acts, so as to purify 
 so many vegetable and animal substances, and io remove the 
 colour and the noxious taste and smell of such a variety of articles, 
 and in such a variety of states and cases ; but as it has the pro- 
 perty of absorbing all the known gases, and condensing them in 
 its pores 3 in quantities far exceeding its own bulk, to this the 
 effect is probably due. 
 
 That these processes may always answer, it is necessary that 
 the charcoal should be fresh made, or that it should be heated 
 red-hot under a cover of sand immediately before it is used ; and 
 that in nice operations the necessary quantity should be ascer- 
 tained by previous experiment: for, if too much be employed, 
 the articles on which it is intended to operate will sometimes be 
 decomposed, especially if heat be applied ; and if a sufficient 
 quantity be not taken, the effect will be produced only partially. 
 
 3 Some interesting disquisitions on this subject may be seen in the Journal 
 de Physique for 1783; in the Annales de Chimie, tome xxxii. ; in Murray's 
 Chemistry, second edition, vol. ii. page 486; and in the 26th number of The 
 Journal of Science, Literature, and the Arts, from M. A. Bussy's Memoir in the 
 Journal de Pharmacie for June 1822. 
 
178 ON CARBON. 
 
 M. Lowitz, who has pursued this subject further than any one 
 else, has given some very important directions, which are neces- 
 sary to be attended to by those who employ this substance as an 
 article of purification in any manufacturing processes ] . 
 
 In some cases it is necessary to use it in a pulverized state ; 
 but in all these instances it should be pounded immediately from 
 the fire, before it is exposed to the air ; and what is not used 
 should be preserved in glass bottles closely stopped, on account 
 of the property it has, as we have already seen, of absorbing 
 water and the gases in abundance. 
 
 In addition to the experiments of Messrs. Allen and Pepys, 
 M. Chaptal has shown, that charcoal absorbs 1 5 or 20 per cent, 
 of water from the atmosphere, while cooling, and that soft coke 
 acquires 25 per cent, of water in the same time 2 . 
 
 Besides those which have been already mentioned, charcoal 
 has many other uses in the arts. It is used by mathematical in- 
 strument makers and engravers to polish brass and copper plates ; 
 by horners in polishing Ian thorn-leaves; and by artists for tracing 
 the outlines of drawings. On account of its powerful affinity for 
 oxygen, it is employed by the makers of glass, by soap-boilers, 
 and chemists, in decomposing the sulphates of soda and potash, 
 so as to enable them to use their alkaline bases in the room of 
 barilla. More of this, however, will be found in the second 
 volume, in the Essays on the fixed alkalies and on glass. 
 
 Charcoal is employed also by the makers of coloured glass to 
 communicate some peculiar tints of brown and yellow to their 
 artificial gems. The late Mr. Samuel Moore, who was many 
 years the Secretary to the Society for the Promotion of Arts, 
 Manufactures and Commerce, made an extensive series of expe- 
 riments on this subject. Some account of his processes may be 
 seen in the " Commercium Technicum" published by his friend 
 Dr. Lewis, page 628, &c. 
 
 In connexion with this subject, I am desirous of suggesting 
 whether the tar which precipitates from pyroligneous acid, if 
 judiciously employed, might not furnish these manufacturers 
 with coloured glass possessing some original tints; for, on visiting 
 an extensive charcoal-work, where the cylinders are erected 
 within a very capacious building, I observed that the vapours 
 which escaped during the distillation had coated the glass in the 
 windows of a very lively colour between brown and orange. 
 
 On the Continent, it is a common practice to char one end of 
 all the posts or other timbers which are to be fixed within the 
 
 1 These directions will be found in Crell's C/iem. Journal^ vol. ii. pp. 165 & 237. 
 * Chaptal's Elements of Chemistry, vol. iii. page 199. 
 
ON CARBON. 179 
 
 ground ; and if this be carefully and properly done, and so much 
 of the timber be charred as is to be covered with the soil, it will 
 be rendered imperishable, or at least it will last much longer than 
 the parts above the ground which have not been charred. In- 
 deed charcoal is perfectly incorruptible if buried in the earth ; 
 therefore the deeper the surface of the wood is charred, provided 
 enough be left to give sufficient strength to such posts, the more 
 effectually will they be preserved. 
 
 This method of charring timber is already practised in some 
 parts of England ; and, being convinced of the economy and effi- 
 cacy of the practice, I mention it here with the hope of rendering 
 it more general. All that is necessary is to light a fire upon the 
 ground, which should be surrounded with a wall built with loose 
 bricks or stones, and then, when the pieces of timber are laid 
 across the walls, to have a contrivance to turn them regularly 
 round so as to present every part to the action of the fire in suc- 
 cession ; and when the whole surface to the depth of three quar- 
 ters of an inch or an inch is converted to charcoal they will be 
 sufficiently prepared. While charring, they should have a tem- 
 porary covering of green boughs or other matter to preserve them 
 from the action of the atmosphere, which would be apt to convert 
 part of the wood into ashes. 
 
 The incorruptibility of charcoal was well known to the ancients, 
 and they availed themselves of this property on all important 
 occasions. Of this we have abundant evidence. 
 
 In making the foundation for the temple of Diana at Ephesus, 
 more than two thousand years ago, it was necessary to drive 
 piles ; and when some of these were taken up of late years it was 
 found that they had been charred. fa Again, it has been stated 
 that "about sixty years ago a quantity of oak stakes were found 
 in the bed of the Thames, in the very spot were Tacitus says 
 that the Britons fixed a vast number of such stakes, to prevent 
 the passage of Julius Caesar and his army. These stakes were 
 charred to a considerable depth, had retained their form com- 
 pletely, and were firm at the heart 3 . 
 
 That it is actually possible to render wood indestructible, will 
 appear from the recollection of the process of nature usually called 
 petrifaction. About seventy years ago, one of the timbers that sup- 
 ported the bridge which the Emperor Trajan threw over the Da- 
 nube a little below Belgrade, was taken up, and the outer part to 
 the depth of half an inch was found to be converted to an agate, 
 the inner parts were slightly petrified, and the central were still 
 perfect wood, though this timber had been in the water 1700 years 4 . 
 
 3 Dr. Robison's Introduction to Dr* Black's Lectures. 
 
 4 Kir wan' s Geological Essays. 
 
 N 2 
 
180 ON CARBON. 
 
 There are. few collections of minerals that do not contain some 
 specimens of wood thus mineralized ; and in the Emperor's col- 
 lection at Vienna there are many pieces converted more or less 
 into agates of various colours. Among them there are billets of 
 half a foot or a foot in diameter thus petrified, and capable of 
 taking a very fine polish. One of these is agate at one end, and 
 retains its ligneous nature at the other. 
 
 In the History of the Academy of Sciences at Paris for the 
 year 1763, is an account of Mr. Moll's cabinet of minerals, which 
 is very effectual towards the conviction of those who deny the 
 possibility of wood being thus agatized. The comparison which 
 this eminent collector has made between certain woods and plants 
 said to be petrified, and the same kinds of bodies in their natural 
 state, seems to put this matter out of dispute. 
 
 Having made a large collection of wood that was converted 
 into agate, he sawed off the thinnest laminae possible from many 
 of the pieces, and after polishing them he examined them by the 
 microscope, and perceived plainly the difference of texture in the 
 different specimens. It was observable that one of these was 
 doubtless fir, another reed, or some aquatic plant of that class ; 
 and on examining shavings or small pieces of the wood to which 
 he supposed the specimens belonged, it was impossible to resist 
 the evidence furnished by this comparison. In both sets of ob- 
 jects the same direction of the longitudinal and transverse fibres of 
 the wood is perceived, and the same arrangement of the vesicles '. 
 
 In returning from this digression, it may be remarked that it 
 were much to be wished that the English builders would adopt 
 the practice above mentioned, and char every piece of wood 
 before it is placed within the ground. Several years ago Dr. 
 Watson suggested the propriety of charring all the wood used in 
 mines and subterraneous drains, and particularly that employed 
 in the covering of soughs, through which there is a current of 
 water, and which rots in a few years by the alternate change of 
 wet and dry 2 . 1 would remark, in addition, that if this had been 
 the general practice, many sad accidents which happen from the 
 breaking of such timbers would have been prevented, and some 
 lives saved. 
 
 Most of the houses in Venice stand upon piles of wood, which 
 have all been previously charred for their preservation 3 . In this 
 country, estates were formerly marked out by charred stakes 
 driven to a considerable depth under ground. 
 
 1 More on this subject may be seen in the Appendix to the Monthly Review, 
 vol. xxxvi. page 557. 
 
 2 Watson's Chemical Essays, London, 1789, vol. iii. page 48. 
 
 3 See Phtt's Jewel House of Art and Nature, page 33. 
 
ON CARBON. Sl 
 
 It is perhaps worth mentioning, " that when old chesnut or 
 other trees are rotted within the trunk, and threatened with 
 speedy destruction by the progress of the carious taint, it may be 
 stopped by applying fire to the decayed part, so as to char the 
 whole of the neighbouring surfaces 4 . By this management the 
 life of a favourite tree may often be preserved. 
 
 In enumerating many of the uses of charcoal, I have hitherto 
 omitted to mention its employment in the manufacture of bar- 
 iron, and the conversion of iron into steel ; to the perfection of 
 which, both the one and the other, wood-charcoal is, I believe, 
 essential. Formerly, all the wrought iron that was made in this 
 country was manufactured with charcoal ; but as wood became 
 scarce, and the Government restricted its use, the iron-masters 
 gradually introduced the use of cinders and coke, and now most 
 of the bar-iron which is made in these kingdoms is prepared 
 chiefly by the latter methods. This, however, has reduced the 
 quality of the English iron so much, that, for many purposes, 
 the artificer is under the necessity of employing Russian and Swe- 
 dish iron, which is all prepared by means of the coal of wood. 
 
 Mons. Hassenfratz is of opinion that the superiority of the 
 iron which is made with charcoal, is owing to its combining with 
 a portion of potassium : and when it is considered how great is 
 the difference between iron and steel, and how small is the 
 quantity of carbon that produces this difference, it may easily be 
 believed that the potassium of the wood is capable of effecting the 
 change in question*. 
 
 The ores of iron are very abundant in this country, and for 
 some hundred years had been worked to a great extent for the 
 production of this metal ; and as nothing was at first used for the 
 reduction of these ores but wood-charcoal, the consumption of 
 wood became so enormous that the legislature thought it advisable 
 to interfere, and prevent its indiscriminate use. 
 
 By the act of the 1st of Queen Elizabeth, chap. 15, it was en- 
 acted, that no oak, beech, or ash timber, of the breadth of one 
 foot square at the stub, should be cut down to be converted to 
 charcoal for making of iron, in any part of the kingdoms of En- 
 gland and Wales, except in the county of Sussex, in the weild of 
 Kent, and in certain parishes therein named in the county of 
 Surry. 
 
 Notwithstanding this enactment, the makers of iron gave up 
 the use of charcoal with great reluctance, as they imagined that 
 it was impossible to make useful malleable iron without charcoal. 
 
 However, about the middle of the last century some few iron- 
 
 4 See Chaptal's Chemistry applied to the Arts. 
 
 5 Nicholson's Journal, xxv. page 51. 
 
182 ON CARBON. 
 
 masters acquired the habit of making bar -iron with the coke of 
 pit-coal, prepared from a particular sort of coal, and in a manner 
 which was kept secret from their competitors in the trade. 
 
 In the year 1773 Mr. Henry Home published his " Essays 
 on Iron and Steel" with directions for reducing the common iron 
 ore, by means of coke, into pig-iron, and then into bar-iron, fit 
 for the most curious purposes ; and in the same work he gave 
 directions for a more perfect method than any before known, of 
 charring pit-coal so as to render it a proper succedaneum for 
 wood-charcoal in the manufacture of iron. This little volume is 
 now become scarce : it contains, however, many interesting parti- 
 culars, and is, I think, worth the perusal of those who are engaged 
 either in making iron or steel. 
 
 Since the publication of Mr. Home's book, the coke of pit- 
 coal has been brought into more general use, so that at this day 
 many thousand tons of coal are annually converted into coke, 
 not only for the purpose of making iron, but for various other 
 Employments connected with the trade and manufactures of the 
 country. 
 
 The coke of pit-coal is used largely in the drying of malt, and 
 in the fires of a variety of artists, to whom the smoke of pit-coal 
 would be injurious ; in refining gold and silver ; and in the smelt- 
 ing of metals. In the preparation of this coke, the fuliginous, 
 bituminous, and sulphurous parts of the coal, which would give 
 a taint to the malt, and a brittleness to the metals, are dissipated, 
 whilst the more pure and carbonaceous matter is left '. 
 
 The consumption of coke is now so considerable, that within 
 these few years great attention has been paid to the selection of 
 the best kind of pit-coal for its preparation, and to the improve- 
 ment of the ovens in which the operation is performed. Those 
 in the neighbourhood of Sheffield, belonging to the Duke of 
 Norfolk, are the best which I have seen 2 . 
 
 It has been usual in the large iron-works to prepare the coke 
 without ovens, merely by making large piles of common coals 
 in the open air, somewhat similar to that mode of making wood- 
 charcoal described at page 163, and setting fire to these heaps 
 at different places at the same time ; and when the mass appears 
 to be thoroughly lighted, to cover, or smother up as it is called, 
 the whole heap with dust. In this state the combustion is con- 
 tinued until all the coal is converted into coke. 
 
 A new method of making coke has, however, of late years 
 
 1 See some further observations on this subject in Lewis's Translation of 
 Neumann's Chemical Works, vol. ii. page 277. 
 
 * A very particular description of these ovens will be found in the Additional 
 Notes to the Chemical Catechism t No. L. ; and also in the description of the 
 plates to the present volumes. 
 
ON CARBON. 183 
 
 been adopted at an extensive iron-work in the neighbourhood of 
 Chesterfield, which has been found very advantageous. 
 
 For this purpose a substantial brick-chimney is built on an 
 open space of ground, and the coal is piled round it. When the 
 pile is constructed, instead of lighting it in different places on the 
 outside of the heap, a quantity of ignited coal is thrown down 
 this brick-chimney; which being built upon arches, the fire 
 readily communicates through them to those parts of the pile 
 which are immediately contiguous to the chimney, so that the 
 fire commences in the middle instead of at the outside of the heap, 
 and soon spreads through the whole mass. When sufficiently 
 burnt, and partially cooled, the heap is broken into, and the 
 whole is quenched by water. * 
 
 The coke thus prepared is so much better than that which is 
 produced in the common way, that a less proportion of it is suffi- 
 cient for making any specific quantity of iron. 
 
 This enables the blast-furnace to hold an additional charge of 
 iron-stone, and consequently the manufacturer can run consi- 
 derably more pig-iron at every operation. The annual saving 
 which this has occasioned is, I understand, far exceeding that 
 which the proprietors themselves had expected ; for, the quantity 
 of the coke produced is much greater from a given measure of 
 the coals, and, what is of still greater importance, the iron is of 
 a much better quality. 
 
 The proprietors of these works, who deem this new method of 
 cokeing to be a most important improvement in their manufactory, 
 consider the cause to be totally inexplicable. 
 
 To hazard a conjecture respecting the nature of this obvious 
 improvement, I should certainly attribute all these advantages to 
 the chimney, which from the nature of its construction occasions 
 a constant draught of air through the whole body of the burning 
 materials, and carries off all the gaseous products which would 
 otherwise be absorbed by the coke, and impair its quality ; simi- 
 lar to the injury which the wood-charcoal received by stopping 
 up the vent-holes, as related at pages 167 169 of this volume. 
 
 Having given an ample account of the preparation of charcoal, 
 and of the uses to which it is applied, and also of the various 
 compounds which have been formed by its means, it will now be 
 proper to speak of the principal natural productions which con- 
 tain carbon as one of their component parts. 
 
 Of these we have native mineral carbon and carburet of iron, 
 besides the diamond already treated of; and a great variety of 
 minerals containing carbonic acid as one of their component 
 parts, such as carbonate of lime including chalk, limestone mar- 
 
184- ON CARBON. 
 
 ble, calcareous spar, slate spar, satin spar, lucullite, and seve- 
 ral others; of some of which there are vast mountains in various 
 parts of the world; Witherite, or carbonate of barytes ; stron- 
 tianite, or carbonate of strontites ; natron, or carbonate of soda, 
 besides others which might be mentioned : but, as it would ex- 
 tend this Essay to too great a length to describe all these produc- 
 tions of Nature, I shall content myself with offering a few remarks 
 on some of the varieties of mineral coal, of all which the basis 
 is carbon. 
 
 Mineralogists in their classification of coals have divided the 
 whole into four species, very distinct from each other; viz. plum- 
 bago, or the graphite of Werner, which is a carburet of iron ; 
 the anthracite of Haiiy, or, as it is more commonly called, an- 
 thracolite ; jet and cannel coal; and all the varieties of common 
 pit-coal. 
 
 Plumbago, usually known by the very improper name of black- 
 lead, occurs in some particular spots in most countries in the 
 world. It is well known as the article of which pencils are 
 made ', and is found in various situations, such as in the midst 
 of mountains, in beds of quartz, and in masses of calcareous 
 earth. It generally occurs in kidney-form lumps of various di- 
 mensions from the size of a pea to pieces of some considerable 
 weight. Its specific gravity is about twice that of water ; though 
 Dr. Freind states it to be only 1.714, and Boyle 1.860. When 
 pure, it consists of about ninety-five parts carbon and five of 
 iron. Hence, as might be expected, it is as incombustible and 
 indestructible as charcoal, unless heated with atmospheric air 2 ; 
 there is, however, considerable difficulty attending the analysis 
 of this mineral, from certain causes which have been pointed out 
 by Mr. Brande 3 . Some kinds of plumbago are very impure. 
 Vauquelin has given the analysis of a French specimen which 
 contained only 23 per cent, of carbon, 2 of iron, 38 of silica, 
 and 37 of alumina. 
 
 To the modern methods of analysis we are entirely indebted 
 for a knowledge of the nature of this substance. Camden, our 
 celebrated historian, calls it " a metallic earth, or hard glittering 
 
 1 From a remark of Sir John Pettus, I imagine black-lead pencils have not 
 been in use more than 150 or 160 years. " Of late" says he, speaking of black- 
 lead, " it is curiously formed into cases of deal, or cedar, and so sold as dry 
 pencils, something more useful than pen and ink." Sir John Pettus's Fleta 
 Minor y folio, London, 1686, article Lead. 
 
 8 It is this property which renders plumbago one of the best substances in 
 nature for the fabrication of those crucibles which are designed to resist the 
 most intense heat. 
 
 3 Brande's Manual, vol. ii. page 121. 
 
ON CARBON. 185 
 
 stone, used by painters to draw with. Whether," says he, " it 
 be pnigitis, or melanteria of Dioscorides, or ochre burnt black 
 by the heat of the earth, I cannot determine 4 ." 
 
 Boyle calls it " a mineral sui generis, approaching to a talc," 
 and says that " it has nothing metallic in its nature 5 ." The inge- 
 nious Scheele was the first person who pointed out the real nature 
 of this mineral. He showed that by burning it in a peculiar 
 manner it might all be converted into carbonic acid gas, except 
 a small residuum, which he found to be iron 6 . 
 
 The finest plumbago that has ever been discovered is pro- 
 cured from a mine at Borrowdale, about six miles from Keswick, 
 and in the neighbourhood of the lofty mountain of Skiddaw, in 
 the county of Cumberland. I know of no other mine which 
 produces this mineral in a state fit for making good black-lead 
 pencils : it is on account of its excellency therefore exported to 
 all parts of the world 7 . The superior quality of this article is 
 indeed so generally allowed, that on the Continent the pencils 
 made with it are called crayons cT Angleterre. 
 
 Plumbago has within these few years been found of tolerably 
 good quality, and in very considerable quantities, in an estate 
 lying about seven or eight miles north of the town of Ayr in 
 Scotland. In some parts of that neighbourhood it occurs at the 
 surface of the ground. It has been discovered also at a consi- 
 derable depth at the foot of the mountains in the island of 
 Ceylon 8 . 
 
 Dr. Campbell, in his Political Survey of Great Britain, speak- 
 ing of the Borrowdale mine, says that this mine is private pro- 
 perty, that it is opened but once in seven years, and no greater 
 quantity than is equal to the consumption is allowed to be sold. 
 At the mine it is called wadd, and those who are concerned in 
 raising it suppose it to be impregnated with lead and antimony. 
 Dr. Campbell considered it to be a mixture of talc and zinc 9 . 
 When this mineral was first raised, it was employed for mark- 
 ing sheep. It was afterwards used in medicine, for disorders of 
 the bowels, and in nephritic complaints 10 . 
 
 Although the mine at Borrowdale may alone produce plum- 
 bago fit for making the best sort of pencils, there are many other 
 
 4 Cough's edition of Camden's Britannia, folio, vol. iii. 170. 
 
 5 Boyle's Works, vol. v. page 27. 
 
 6 Scheele's Chemical Essays, page 243. 
 
 7 According to Dr. Campbell, this mineral is used with great success by dyers 
 in fixing blue colours, vol. ii. page 38. 
 
 8 Cordiner's Description of Ceylon, 4to, 1807, vol. i. page 13. Knox's History 
 of Ceylon, folio, page 31. 
 
 9 Political Survey of Great Britain, London, 1774, 4to, vol. ii. page 37. 
 
 10 Philosophical Transactions, No. 240, page 183. 
 
JS6 ON CARBON. 
 
 places where this mineral is to be found, and sufficiently good 
 for all other purposes. At present it is applied chiefly to the 
 following uses. 
 
 It is employed to make crayons and black-lead pencils ; to 
 cover the best sort of iron castings to give them a shining coat, 
 and preserve them from rust ; to give a polish to small leaden 
 shot; to rub on the cogs of wheels and other machinery, in 
 order to diminish friction, and impart smoothness and lubricity 
 to the parts which have most wear; to mix with potter's clay for 
 the production of some particular sorts of earthenware ; to make 
 crucibles and other utensils which are to undergo intense heats; 
 and, when kneaded with clay, to line all sorts of portable fur- 
 naces which are designed to be used in the reduction of ores and 
 other chemical operations. 
 
 The natural incombustibility of plumbago peculiarly fits it for 
 other purposes to which it has not yet been applied in this 
 country; but especially for the covering of certain parts of 
 wooden buildings to preserve them from accidents by fire. 
 
 It is lamentable to perceive with what facility and success 
 some people impose upon the public. Even the article of plum- 
 bago has been employed for purposes of quackery. The follow- 
 ing is the substance of the specification of a patent, dated the 
 6th of June 1812, for what the patentee calls his " Anti- Attri- 
 tion Paste." It is merely that 1 cwt. of plumbago be mixed with 
 4 cwt. of pork-lard, or with a like quantity of suet, or of some 
 one of the other articles enumerated in the specification *. Surely 
 this patentee could not be ignorant of the fact that such a mix- 
 ture had been long used for similar purposes prior to the date of 
 his patent, particularly in many of the manufacturing counties. 
 In order, however, to expose this pretension to originality the 
 more effectually, the following recipe is selected from a printed 
 volume, which may be had of any of the principal booksellers 
 in London or elsewhere. " Mix one pound of hog's lard with 
 half a pound of black-lead ; stir them well together, whilst melt- 
 ing over a slow fire. If the axles and bushes of the wheels be 
 true, a carriage may safely be run one hundred or one hundred 
 and fifty miles, with once using the above composition 2 . 
 
 Some time ago, a gentleman, a native of the state of North 
 Carolina, informed me that a mine of black-lead had been dis- 
 covered in the neighbourhood of Raleigh, one of the cities of 
 that state, which promises to be of very considerable conse- 
 quence to the whole of North America. The mineral occurs in 
 large solid lumps, and the mine is so extensive that it is thought 
 
 1 See The Retrospect, No. 34 ; or The Repertory of Arts, No. 130. 
 * The Family Receipt Book, Murray, London, 1811, page 414. 
 
ON CARBON. 187 
 
 to be inexhaustible. It is usually sold in its native state, packed 
 in barrels, at 18s. or 205. per cwt. 
 
 This native carburet of iron is used very extensively in the 
 state of North Carolina for a variety of purposes. They grind 
 it with oil for painting the wooden roofs of their houses and even 
 their best buildings. It is found to answer extremely well for 
 preserving the wood from decay, and for keeping out the rain; 
 and it is a great preservative against fire. 
 
 In America, where most of the fires are made ,with wood, 
 accidents often happen from the circumstance of the sparks set- 
 ting fire to the wooden roofs of their houses, and occasioning 
 dreadful conflagrations : but this can never occur to those roofs 
 which have been treated in this way; for I learn that the wooden 
 shingles, which have been painted with two or three coats of this 
 preparation, have been purposely exposed to the full heat of a 
 large fire for a considerable time, without their sustaining any 
 injury. 
 
 This seems rather extraordinary, as one would have imagined 
 that the oil would have still retained its combustible properties. 
 It may, however, be a circumstance well worth the investigation 
 of those who have it in their power to procure plumbago at a 
 cheap rate. 
 
 On a journey to the lakes of Westmoreland and Cumberland, 
 in the summer of the year 1814, I heard that the celebrated mine 
 of black-lead in Borrowdale had been lately opened, and that the 
 workmen were then engaged in raising and dressing the mineral. 
 Rejoiced at this intelligence, I immediately determined not to 
 lose so favourable an opportunity of visiting this curious spot, 
 and therefore fixed myself at Keswick, the nearest town to the 
 mine, in order to collect the necessary preliminary information, 
 and learn how to procure the most intelligent guide which the 
 neighbourhood could afford. In travelling from the north, the 
 road lies thus :-i-From Carlisle to Wigton 1 1 miles ; from 
 thence to Keswick 22 miles ; and from Keswick to the mine 9 
 miles. From Keswick to the mine saddle-horses are necessary, 
 as some of the defiles through the mountains are too narrow to 
 admit the passing of a carriage. As no account has hitherto 
 been given of this celebrated mine, where black-lead is found of 
 a quality far superior to what is known in any other part of the 
 world, I trust the following particulars will not be uninteresting 
 to my readers. 
 
 The neighbourhood of Keswick has for ages been celebrated 
 as a mining country. In the reign of Queen Elizabeth, gold and 
 silver were procured in considerable quantity from the mountain 
 called Gold-scarpe in the vale of Newlands near Keswick. At 
 that time the mine was worked by a company of Germans, who 
 
188 ON CARBON. 
 
 raised a large quantity of copper and lead, and not only con- 
 verted these to their own use, but also laid claim to the precious 
 metals, in opposition to the Queen, who demanded them as well 
 as the usual royalty. However, on an appeal to common law, 
 her majesty gained the point, and the foreigners soon after ab- 
 sconded. 
 
 It was during this reign that the very valuable mine of black- 
 lead was discovered. The inhabitants of the neighbourhood say 
 that this rich depository was first brought to light by a tremen- 
 dous hurricane, which blew up a large ash- tree and discovered a 
 mass of fine plumbago at its root. The mine now at work is in 
 the midst of a mountain which chiefly consists of slate and that 
 species of rock called grauwacke; it is about 2000 feet high, it 
 rises at an angle, as near as I could guess, of 45 degrees, and is 
 situate among other stupendous hills in a district known by the 
 name of Borrowdale. When the value of this mine became 
 known, the proprietors found it very difficult to guard it so as to 
 prevent depredations. The practice of robbing it was become 
 so common, that several persons living in the neighbourhood 
 were said to have made large fortunes by secreting and selling 
 the mineral : this, however, is now entirely prevented by some 
 expedients hereafter to be mentioned. Even a guard stationed 
 on the spot was of little avail, for 70 or 80 years ago a body of 
 miners broke into the mine by main force, and held the possession 
 of it in spite of the proprietors themselves. At one time the 
 depredations had arrived to such a pitch, and so great was the 
 quantity which had been stolen, that the delinquents were actually 
 able to deprive the proprietors of their regular customers, by 
 lowering the price of the article in the London market. This 
 circumstance so annoyed the original company, that at last they 
 thought it expedient to buy up the whole stock that remained in 
 the hands of the robbers, as the only way of putting an end to 
 the competition. It is not many years since a very large quantity 
 of fine black-lead was found on Vickers Island, situated in Der- 
 went-water ; and it is supposed that this was secreted there at 
 the time the robbers had possession of the mine in Borrowdale. 
 
 It has been already mentioned that the black-lead mountain 
 has an altitude of about 2000 feet ; and as that part of the mine 
 which is now working is near the middle of the mountain, the 
 present entrance is about 1000 feet from its summit. There are 
 indeed two entrances; a small one by which the workmen descend 
 by means of a flight of steps ; the other is a large horizontal one 
 capable of admitting hand-carts and wheel-barrows for the re- 
 moval of the rubbish and loose earth by which the black-lead is 
 enveloped ; and through this entrance the water passes off which 
 constantly runs through the mine. 
 
ON CARBON. 189 
 
 In order to secure the vast treasure which is contained within 
 this mountain, the proprietors have now erected a strong brick 
 building, consisting of four rooms on the ground-floor, one of 
 which is immediately over the opening by which the workmen 
 enter the mine as they go to their work. This opening is secured 
 by a trap-door, and the room connected with it is called the 
 dressing-room; for, when the men enter it, they strip off their 
 usual clothes, and each of them puts on a dress suitable for work- 
 ing in a mine. The men work six hours each, and then they are 
 relieved by others. When the hour of relief comes, the steward 
 attends in the dressing-room, to see the men undress, as they 
 come up the steps one by one out of the mine, when they put on 
 their usual clothes, which are also examined by the steward to 
 see that they have no black-lead concealed within them. This 
 room contains no furniture except the pegs on which the clothes 
 are hung, and which extend all round the room, each man know- 
 ing his own. When these have dressed and departed, another 
 set of men clothe themselves for their work and enter the mine 
 as before ; the trap-door is then again shut, and the steward is 
 relieved to attend his other occupations. 
 
 I have said that the house consists of four rooms, and these are 
 contrived so as to be connected with each other. In the inner- 
 most of these rooms there is a kind of counter or strong table, 
 under the window, at which two men sit who are constantly em- 
 ployed in assorting and dressing the mineral. This is necessary, 
 because it is usual to divide the black-lead into two kinds, called 
 best and coarse; and as the finest specimens have generally 
 pieces of iron-ore or other impurity attached to them, these are 
 dressed off by peculiar tools adapted to the purpose. These 
 men are constantly shut in when at work, and the steward walks 
 backwards and forwards in an adjoining room furnished with two 
 loaded blunderbusses, which hang within his reach, for the sake 
 of further security. As the black-lead is cleaned, it is put into 
 firm casks which hold about 1 1 2lb. each, and these are sent by 
 waggon to the warehouse of the proprietors in London. For- 
 merly this mine was opened only once in six or seven years, as I 
 have before said ; but in consequence of the demand being greater, 
 and the quantity which they have discovered not being so large, 
 it has been found expedient to open the mine, and dig for the 
 ore during six or seven weeks in every year. At this time the 
 mine is guarded night and day ; and it is thought necessary that 
 the steward, who only lives at the village of Seatkwait at the foot 
 of the mountain, should not leave the house at any time during 
 the whole of this period, except an hour or two on the Sunday 
 to visit his family, and even then, as he told me, he was always 
 careful to return to his dwelling on the mountain while it was yet 
 
190 ON CARBON. 
 
 day-light. In consequence of the mine having of late years been 
 opened every summer, they now raise all the black-lead they find, 
 and then the mine is securely shut up in the following manner: 
 The workmen wheel back the rubbish which had been removed 
 at the opening of the mine, and this is laid in one continued heap, 
 to the amount of some hundred cart-loads, which securely blocks 
 up both the passages into the mine. The door is then locked, 
 as well as the door into the house, and all the men then leave the 
 premises in a state of safety ; for the mass of rubbish which is 
 thus wheeled in at the larger door, dams up the small rill of water 
 which usually flows through the mine, and this has the effect of 
 flooding it completely. Thus, if an attempt were made to break 
 the house and enter the mine by that road, the robbers would 
 find that the water had arisen to such a height as would drown 
 any individual who should attempt to search for the ore. 
 
 From an examination of the exterior of the mountain, it appears 
 that in former times various small shafts have been sunk for getting 
 the black-lead ; and the mine which they are now working was one 
 of those which had been closed for a century, but was again 
 opened in the year 1769, in consequence of another mine in the 
 immediate vicinity having failed. The expense of raising the 
 black-lead varies very much in different years, according to the 
 size of the masses which the workmen happen to meet with : for 
 instance, that which they found in the year 1778 was four yards 
 in diameter, and twelve yards high ; that of 1 803 was twenty-one 
 yards and a half high, two yards and a half in diameter, and per- 
 fectly round like a column ; that which they found in 1812 was 
 rather less than twenty yards in height, and only two foot in 
 diameter ; and what they are now getting is found only in a nar- 
 row string. The expenses of driving the level, of building the 
 house, and working the mine, from the 23d of April 1798 to the 
 4th of April 1814, have amounted to 6637/. 9s. 4d.\ and during 
 this period there have been produced 736 casks of fine black- 
 lead, and 1816 casks of the coarse kind, amounting together to 
 2552 casks of about 112lb. each. 
 
 It might be a matter of difficulty to those who visit the mine, 
 to conceive how these casks of black-lead can be conveyed with 
 safety down the face of so steep a mountain. This is done by 
 men who have been long accustomed to the task. The cask is 
 fixed upon a light sledge with two wheels, and the man, who is 
 well used to this sort of precipitous path, walks coolly down before 
 the sledge, taking care that it does not acquire too great a mo- 
 mentum, and thus overpower him. The empty sledge he then 
 carries back upon his shoulders, and takes another cask. All 
 the black-lead is sent to London, as I have already mentioned, 
 where it is deposited in the warehouse of the proprietors, and 
 
ON CARBON. 191 
 
 afterwards disposed of by public auction held at Essex-street in 
 the Strand, London. This happens on the first Monday of every 
 month throughout the year ; and the best kind usually sells for 
 two guineas or more per pound. There are some considerable 
 manufactories of pencils at Keswick, but I was told that the 
 makers are under the necessity of sending to London for all the 
 black-lead they use in the trade, although they reside so near the 
 place of its production. 
 
 l s he propriety of this valuable mine is divided, as I understand, 
 into two equal parts, one of which belongs to Henry Bankes, 
 Esq. member of parliament for Corfe Castle; and the other 
 moiety is divided into ten or twelve shares belonging to the exe- 
 cutors of the late Sir Joseph Banks, Sir John Mitford, and others. 
 In some years the net produce of the black-lead has amounted to 
 thirty or forty thousand pounds. Mr. Otley has stated, that by 
 an account drawn up in 1804 the stock of black-lead then on 
 hand was valued at 54,000/., and the annual consumption about 
 3500/. ; the best black-lead was then sold at 355. per pound ; 
 since that time the price has been from 305. to 455. and the con- 
 sumption is much increased. It is remarkable that this mine, 
 which was valued in making the grant of the manor of Borrow- 
 dale by King James I. at 155. 4d, was on the last assessment for 
 the property tax, estimated at 2700/. sterling a year. Some 
 other particulars respecting this singular mine may be seen in 
 the works quoted below 1 . 
 
 The second kind of coal, which is called anthracolite, is 
 seldom found but in the primitive mountains. It is generally 
 amorphous, but sometimes occurs in a crystallized form. It is 
 what is called incombustible coal, and by Werner glance-coal ; 
 and as it contains more carbon than most of the common pit- 
 coal, it may with propriety be classed next to plumbago. It 
 burns slowly and without flame ; its specific gravity varies from 
 1300 to 1500. This species, which is composed of 64 carbon, 
 33 silica, and 3 parts of iron, is considered by some mineralogists 
 not to be of vegetable origin. 
 
 The third kind of coal mentioned above, is jet and cannel coal. 
 Both these varieties Werner denominates by the name of black 
 coal. They are found in many parts of the world, and are often 
 used in forming ornamental trinkets, particularly in France, 
 where they occur in abundance. 
 
 1 Robinson's Natural History of Westmoreland and Cumberland, 8vo, London, 
 1709, page 75; Colonel Thornton's Sporting Tour through the Northern Parts of 
 England, 4to, London, 1804, page 282; Mr. Otley in Memoirs of the Literary 
 and Philosophical Society of Manchester, second series, vol. iii. pp. 168 175. 
 
192 ON CARBON. 
 
 The carmel coal does not cake in the fire; and though it flames 
 like a candle in the beginning of its combustion, this lasts but 
 for a short time, and the residuum is considerable. Its specific 
 gravity is from 1.234 to 1.250. A specimen of the Lancashire 
 cannel coal analysed by Mr. Kirwan, contained 75 per cent, 
 carbon, 22 maltha, and 3 alumina and silica. 
 
 The fourth species includes all the varieties of the common 
 pit-coal. These are composed of bitumen, carbon, and hetero- 
 geneous matters in different proportions, according to the places 
 from whence they are procured. Some of these are black and 
 ponderous, and, from the quantity of bitumen and sulphur which 
 they contain, burn very freely, and give out a great heat, though 
 the combustion is of short duration. This sort generally contains 
 a large admixture of martial pyrites, which sometimes occasions 
 spontaneous combustion when they are laid in large heaps, and 
 are exposed to the affusion of water. 
 
 There are other coals that burn very freely, which cake into a 
 mass when laid on the fire ; these burn without any sulphureous 
 smell, and leave no residuum but a very inconsiderable quantity 
 of ashes. 
 
 Respecting the specific gravity of coals, the accounts which I 
 have seen vary in themselves as much as they do from the results 
 which I obtained. Mr. Charles Labelye makes the specific 
 gravity of Newcastle coal to be 1.270. Boyle gives the specific 
 gravity of Scotch coal 1.300. The Oxford Philosophical Society 
 states the specific gravity of pit-coal from Staffordshire to be 
 1.240. Mr. John Caswali makes the same coal to be 1.238. 
 The Philosophical Society at Oxford found a cubic foot of pump- 
 water to be 62 pounds avoirdupoise ; the same measure of Staf- 
 fordshire coals 63 pounds; and of Newcastle coals 67lb. 12oz '. 
 Kirwan gives the specific gravity of six species of coal which 
 vary from 1.232 to 1.357. A specimen of slate-coal he found to 
 be as high as 1.426 2 . 
 
 There is a peculiar kind of hard coal raised at Pontetaive, a 
 few miles from Swansea, which is much approved by those who 
 are afflicted with some kinds of pulmonary disorders; for it burns 
 like coke, and yields no smoke. It does not soil the fingers, and 
 the chimneys seldom or never want sweeping. In consequence 
 of this, many persons troubled with asthma have taken up their 
 residence in that neighbourhood. 
 
 There is a very singular kind of coal, as I have been informed, 
 found in some parts of Pembrokeshire, called stone-coal. This 
 coal is so devoid of sulphur that it is commonly employed without 
 
 1 See Philosophical Transactions, No. 169. 
 
 2 Kirwan's Mineralogy, vol. ii. page 514 528. 
 
ON CARBON. 193 
 
 being previously coked, even in the operation of drying malt, for 
 which purpose either wood-charcoal or coke is usually employed. 
 The small of this coal is known by the name of culm, and is* ex- 
 ported in large quantities from Miiford Haven, for the particular 
 purpose above mentioned. The inhabitants of the county where 
 this mineral substance is found, are in the habit of making the 
 culm into balls with clay and water, and laying these up for their 
 winter's consumption. The inhabitants of Pembrokeshire have 
 also a very singular way of using this fuel. When a fire of 
 the large coal has burnt up, a quantity of the culm mixed with 
 clay and water as above mentioned, is plastered over the whole 
 of the fire, of the thickness of three or four inches ; and then 
 having made two holes with a poker through this plaster, for the 
 purpose of keeping up a proper draught, it will preserve a good 
 fire, of a perfect glow, without flame or smoke, for 12 or 14- hours. 
 
 Hugh Platt in his " Jewel House of Art and Nature," first 
 printed in the year 1594-, offers to sell a receipt for making fuel 
 for the poor, which he says will prove more durable and much 
 cheaper than coals. A copy of this work, which is now extremely 
 rare, I had an opportunity of consulting at Chetham's library, in 
 the College, Manchester ; and from minutes made in this copy it 
 appears that a Mr. Gosling, merchant of London, disclosed the 
 said method gratis in the year 1628, and was at the expense of 
 printing hand-bills to be distributed in every parish in London 
 and its vicinity, to direct the poor how to make the said fuel. 
 One of these printed hand-bills is attached to the volume above 
 mentioned, from which I have copied the following directions, in 
 the hope of their being useful. " Get," says Mr. Gosling, " a 
 load of stiff loam or clay, and take half a peck of it, and with a 
 shovel make it soft with water, then put one peck of small coal 
 to it, and incorporate or mix them all together until you may roll 
 it or mould it into several parts like pieces of charcoal or long 
 eggs. As many may be made in a day as will last a quarter of a 
 year. Any other combustible may be mixed up with it, such as 
 peat turf, saw dust, curriers' or shoemakers' shreds, tanners' 
 waste bark, and such like." It is added in a note, that " he has 
 dispersed freely many thousands of these hand-bills for the good 
 of all people in the land." 
 
 In some districts, coals are raised which have more the appear- 
 ance of slate or schist than coal, and which only burn in conse- 
 quence of the bitumen with which they are impregnated. These 
 leave a bulky and stony kind of residuum, and are very unpro- 
 fitable for most purposes. 
 
 There are other pit-coals which are so intimately mixed with 
 sulphuret of iron that they become decomposed by the action of 
 the air, and fall into dust, or what is called very small slack. 
 
 o 
 
194 ON CARBON. 
 
 Such coals are fit only for heaping upon large fires, for the 
 burning of limestone, or the preparation of coke. 
 
 The decomposition of such coal by the accession of water is no 
 doubt the origin of the hydrogen gas, or what is called the coal- 
 damp of many of our collieries, and which often occasions deplo- 
 rable accidents. 
 
 In Lancashire, the workmen get rid of this gas by sending 
 down one of their party to set fire to it, which he does with safety 
 to himself by lying flat upon the ground, and letting it explode 
 over him ; but this is a method which could not be practised in 
 some districts with safety. 
 
 A method of clearing a coal-pit of the coal-damp, by making 
 a fire and fixing pipes to occasion a circulation, as described by 
 Sir Robert Moray more than a century ago, may be seen in the 
 Phil. Trans, vol. i. page 79, accompanied with a drawing of the 
 whole of the apparatus. 
 
 The situations in which coal is found are as various as the 
 composition and properties of the several species of coals them- 
 selves. Our deepest mines are in the counties of Durham and 
 Northumberland, and the thickest beds are found in Staffordshire. 
 The most productive vary from 8 to 10 yards, and one was found 
 near Wednesbury of the enormous thickness of 16 yards. In 
 the counties of Gloucester, Worcester and Stafford; at New- 
 castle-upon-Tyne ; in the neighbourhood of Sunderland ; and in 
 many other parts of the kingdom, the coal is raised from very 
 considerable depths ; but in the vicinity of Stainthorpe, in the 
 county of Durham, nothing more is necessary than to pare off 
 the turf, and dig out this valuable production at the surface of 
 the ground. 
 
 This coal is of excellent quality, much superior to that which 
 is raised in Northumberland for the supply of the London mar- 
 ket. If a rail- way were made from Stainthorpe to Stockton-on- 
 Tees, a distance, I believe, of not more than 20 miles, this coal 
 might be conveyed thither at a small expense, and from thence 
 coastwise to London, to the great advantage of the metropolis, 
 and to the enrichment of the district from whence it is to be pro- 
 cured. 
 
 A very singular kind of coal is found near the village of Seaton, 
 in the neighbourhood of Hartlepool, in the county of Durham, 
 which is brought up by the tide, and that only occasionally. It is 
 in the form of very coarse sand, the grains of which are so polished 
 that they may be handled freely without soiling the hands, and 
 yet they are so small, that it would be difficult, among a large 
 heap, to find a piece larger than a cherry-stone. 
 
 This coal, which abounds with bitumen, and consequently 
 makes excellent fuel, is generally left by the tide on the sea-shore, 
 
ON CARBON. 195 
 
 in a continued ridge, extending sometimes from a quarter of a 
 mile to a mile in length, three or four inches thick, and only of 
 a few feet in width. 
 
 As a considerable time often elapses between the periods when 
 these supplies arrive, a very interesting scene is exhibited when- 
 ever one of these strata is thrown up by the tide. In an instant, 
 as it were, all the inhabitants of the village hasten down to the 
 shore, and are seen busily employed in raking it together, and 
 in carting it away before the return of high water, which would 
 wash all that remained off the shore. 
 
 Thus, by the bounty of Nature, are the poor of the whole 
 neighbourhood supplied with an article of the first necessity ; 
 and merely by a little industry in the summer months are they 
 enabled to lay up an ample store of excellent fuel for the whole 
 of their winter's consumption. 
 
 Among the inflammable substances of the mineral kingdom may 
 be classed what is called elastic bitumen, or mineral caoutchouc, a 
 fusible and very singular substance found in the Odin mine, near 
 Castleton in Derbyshire. It has been fully described by Mr. 
 Hatchett ', as a compound of carbon, bituminous oil, carburetted 
 hydrogen gas, &c/ 2 
 
 Retinasphaltum is another peculiar inflammable body which 
 occurs in the Bovey coal of Devonshire. It is a substance which 
 seems to connect the resins with the bitumens. It was first ana- 
 lysed by Mr. Hatchett 3 , and found to consist of 55 resin, 41 
 asphaltum, 4 earthy matter, &c. =. 100. 
 
 Mellilite is a rare substance that sometimes is found in the 
 brown coal of Arten in Thuringia, and also in Switzerland. It 
 is of the colour of honey, and from this circumstance was named 
 by Werner honey- stone. It occurs crystallized in octohedrons. 
 Its surface is smooth, it is translucent, and doubly refractive. Its 
 specific gravity is 1.666. According to Klaproth it is a com- 
 pound of a peculiar acid, which he n#med the mellitic acid, 46 
 + alumina 16 + water 38 = 100. By proper evaporation of the 
 solution, the acid may be obtained in crystals. M. Klaproth 
 seems to have analysed the mellilite, and also its acid, with great 
 care 4 . Vauquelin has likewise published a distinct paper on the 
 mellilite, in which he confirms the analysis of Klaproth 5 . 
 
 It may not be irrelevant to remark, that if a line be drawn 
 upon the map of England across the country from Sunderland 
 
 1 Scherer's Journal, No. 21, page 282. 
 
 2 Klaproth 's Essays, ii. page 87. 
 
 3 Hatchett, Philosophical Transactions for 1804. 
 
 4 Klaproth's Analytical Essays t vol. ii. page 89 105. 
 
 * Vauquelin, Annales de Chimie y xxxvi. page 203 214. 
 o 2 
 
196 ON CARBON. 
 
 to Bristol, all the counties on the west of this line will be found 
 to contain coal l . Formerly these counties were the least valuable 
 districts, and the parts of the country which were the most thinly 
 inhabited. Hence, when the constitution of the British Parlia- 
 ment was established, the greatest weight of representation was 
 given to the rich counties which were on the other side of that 
 line. The 12 English and the 12 Welch counties, lying on the 
 western side, send, together, only 114? members to the British 
 Parliament ; whereas the 28 eastern counties return 399 mem- 
 bers. Whereas, now, owing to the establishment of manufactures, 
 the coal-counties have become the most populous and wealthy, 
 and the agricultural districts have either been comparatively de- 
 serted, or at least have not much increased in population. 
 
 This, in my opinion, accounts in some measure for the in- 
 equality of our representation, and shows, very distinctly, the 
 value of our mines of coal, and that by the establishment of 
 manufactures, even the most sterile and forbidding country may 
 be rendered populous, flourishing and opulent. The conse- 
 quences of the establishment of manufactures have been pecu- 
 liarly striking in some parts of Austrian Flanders. The industry 
 of the inhabitants of Brussels has been such, that an acre of land 
 in the environs of that city will yield in manufactures an amount 
 equal to the revenues of the whole province of Champaigne. 
 Carrard On. the Spirit of Legislation, page 313. 
 
 To the patient and unremitting industry of our mechanics, 
 and the frugality of their habits, we are beholden for our success 
 as a manufacturing people 2 . Unlike many of the nations of 
 Europe, who through indolence or inattention suffer the richest 
 treasures of Nature to remain undisturbed in the bowels of their 
 respective countries, it has become a custom among us to hus- 
 band all our resources, and to appropriate every thing, even 
 down to the very residuums of our manufactories, to some useful 
 purpose. 
 
 To what degree.of excellence our manufacturers and mechanics 
 may arrive in the economy of their materials, when chemical 
 science is better understood by them, and when a knowledge of 
 her laws is more generally diffused, it is impossible to conceive; 
 but this is the point in which we are most deficient, and this is 
 the important desideratum which every person who has any in- 
 fluence in the country should do his utmost to supply. 
 
 1 Coals are also found plentifully in Scotland ; but a line drawn on the south 
 of the Tay from the bank opposite to Dundee, along the Ochil hills to Stirling, 
 is esteemed the northern boundary of the coal of this island. 
 
 2 1 have read of an Emperor of China, who, when he was about to suppress 
 the monasteries of bonzes, declared aloud to the mandarines of the nation, that 
 if he had a man that did not labour, or a woman that did not spin, he was sure 
 some one must suffer cold or hunger in the empire. 
 
ON THE MANUFACTURE OF BRASS. 197 
 
 ESSAY VI. 
 
 ON THE MANUFACTURE OF BRASS. 
 
 OF all the numerous metallic alloys at present known, that of 
 copper with zinc is by far the most important and generally use- 
 ful. This compound, which in common language is called 
 brass, is of high antiquity, for we read of it in the very earliest 
 period of sacred history, where Tubal-cain is described as "an 
 instructor of every artificer in brass and iron l ;" and in a subse- 
 quent book, that " Moses made a serpent of brass ." It has 
 indeed been asserted, by some writers of great credit, that brass 
 is a modern invention ; but they surely must allude to the mode 
 of manufacturing it, and not to the alloy itself; for the late Bishop 
 of Llandaff and other respectable authors have stated, that the 
 orichalcum of the Romans resembled our brass in all respects, 
 and was composed of the same materials. My principal object, 
 however, in this paper is, to give a detailed account of the 
 methods by which brass is now made in this country, having, 
 on a late occasion, and for this particular purpose, minutely 
 examined one of the most extensive works in Great Britain, 
 where the only article of manufacture is that of brass. 
 
 It is well known that it is difficult to unite zinc in its metallic 
 state with copper in the direct way, the former being readily 
 oxidized at a high temperature, occasioning considerable loss. 
 Some ores of zinc, particularly calamine, an impure carbonate 
 of the metal, is therefore chosen, having been proved to answer 
 every purpose. This mineral is found plentifully in the Mendip 
 hills in Somersetshire ; at Wirksworth and Bonsai-moor in Der- 
 byshire; also in North Wales and at several other places in 
 Great Britain. As this ore is never so pure as to be employed 
 in its crude state, it is necessary that it should undergo the pro- 
 cesses of washing, calcination, grinding, and sifting, before it 
 can be fit for making brass. 
 
 The copper which is employed in the manufacture of this 
 metallic alloy is previously granulated by being poured in a 
 melted state into water. The method of preparing it is as 
 follows : 
 
 The product of what is called the roaster furnace of a copper 
 smelting work, generally consists of from 90 to 92 per cent, of 
 copper, the remaining 8 or 10 per cent, being iron, lead, tin, 
 sulphur, or other matter accidentally present in the ores from 
 
 1 Genesis iv. 22 . a Numbers xxi. 9. 
 
198 ON THE MANUFACTURE OF BRASS. 
 
 which it was reduced. This compound having been cast into 
 masses called pigs, is, to the amount of a ton and a half to three 
 tons, put into a furnace of the reverberatory kind called the 
 refinery. The floor or hearth of this furnace is made of clean 
 sea-sand, the grains of which are agglutinated together by heat ; 
 it is laid with an inclination from the bridge to the mouth of the 
 furnace, opposite to which a small pool or basin is formed in 
 the floor, so that the depth of the copper, when melted, may be 
 always sufficient, in that place, to allow the workmen to fill their 
 ladles when lading it out for the granulating operation. 
 
 The furnace being charged with pigs as above mentioned, the 
 door in front is closely luted, and heat applied sufficient to melt 
 the metal ; and when the whole is in perfect fusion, the follow- 
 ing changes will be found to have taken place. The sulphur 
 will have passed off in the state of sulphurous acid gas, and the 
 iron, tin and lead will have become oxidized ; which oxides, toge- 
 ther with any sand that adhered to the pigs from the moulds in 
 which they were cast at the roaster-furnace, will have melted into 
 a slag or glassy scoria, holding a portion of oxide of copper, 
 which imparts to it various tints of red, purple, &c. 
 
 This slag, in consequence of its inferior specific gravity, swims 
 on the surface of the melted copper, and is skimmed off' with an 
 iron rake or rabble as it is technically called. 
 
 The refiner, in order to be certain that the afore-mentioned 
 changes have taken place, takes out of the furnace a small quan- 
 tity of the copper called an assay, and when this is cold he cuts 
 it half through with a chisel, and completes the separation by 
 breaking it in a vice. If it is brittle, and the fracture exhibits a 
 deep red colour, and a fibrous, or rather a hackly structure, the 
 copper is in a proper state for lading into the water, which is 
 done in iron ladles coated with clay, and holding from 25 Ibs to 
 30 Ibs. each of the melted metal. By this treatment the copper 
 is broken into granular pieces from the size of small shot to that 
 of a horse-bean. 
 
 It has already been remarked that the calamine, which is de- 
 signed for making brass, undergoes a previous calcination ; but 
 preparatory to its being calcined, it is broken down into pieces 
 varying from the size of a hen's egg to that of a walnut. With 
 these the floor of a reverberatory furnace is covered, which gene- 
 rally takes about five hundred weight, and there it is frequently 
 stirred with an iron rake until each piece becomes red hot through- 
 out, this being sufficient to drive off the carbonic acid, which is 
 usually effected in one hour. The loss by this process is about 
 34> to 36 per cent, and it incurs a further loss of 3 or 4 per cent. 
 by picking after the calcination, the action of the fire rendering 
 the presence of any extraneous mineral, or deads, as such matter 
 is called, more apparent. By these processes a ton of calamine, 
 
ON THE MANUFACTURE OF BRASS. 199 
 
 as received from the mine, is reduced to 12J or 12 cwt. before it 
 is fit to be sent to the mill. 
 
 The chief disadvantages that would arise from the calamine 
 not being sufficiently calcined, are the difficulty of grinding it, 
 and the obtaining a less produce of brass from a given weight put 
 into the crucibles, in consequence of part of that weight being 
 carbonic acid. Some inconvenience would also result from the 
 extrication of a large quantity of carbonic acid during the pro- 
 cess ; though this is the case to a considerable degree at present, 
 from the decomposition of the oxide of zinc, by the charcoal 
 which is mixed with it. Care and experience are necessary in 
 conducting this process of calcination ; for if the calamine be not 
 properly calcined, the zinc will not be sufficiently volatile to rise 
 through the materials in the crucible, so as to unite with the cop- 
 per ; and if it be over calcined, the brass resulting from it will 
 be brittle. Another disadvantage also arises from its being ex- 
 posed to too great a degree of heat, namely, its vitrification on 
 the surface, especially when either siliceous earth or the silicate 
 of zinc is present, which is not unfrequently the case ; and the 
 part which is vitrified cannot afterwards be reduced by the usual 
 means. 
 
 When the calamine has been calcined, it is ground to a fine 
 powder, and this is rendered more uniform by passing it through 
 proper sieves ; it is then removed to a building called the buddle- 
 house, where it is washed in an apparatus of a singular construc- 
 tion, for the purpose of separating the sulphuret of lead and 
 other extraneous matters which are frequently mixed with the 
 calamine. 
 
 The zinc-ore having been thus prepared, it is mixed either 
 with small pit-coal, or ground wood-charcoal, in the proportion 
 of rather more than one bushel of carbon to one bushel of cala- 
 mine. In the best manufactories, mineral or pit-coal is now en- 
 tirely discarded, as it frequently contains minute veins of sulphuret 
 of iron ; and experience has proved, that when such coal is used, 
 it either spoils the brass, or makes it of an inferior quality. 
 
 In order to charge the furnace, 60 pounds of the prepared 
 calamine, with a proportional quantity of ground charcoal, are 
 carefully mixed with 4?5 pounds of the granulated copper above 
 mentioned, and then the whole is put into eight cruci>les, this 
 being the number that is usually taken to charge the bed of one 
 of the furnaces. For making the finest and best alloy, a quantity 
 of old scrap brass is generally added to the mixture in the cru- 
 cibles, as this is found to render the metal more ductile, and 
 consequently much fitter for making brass wire. When the 
 crucibles thus charged have been placed at regular distances 
 from each other on the floor of the furnace, the spaces between 
 them are filled with pit-coal, which immediately becomes ignited 
 
200 
 
 ON THE MANUFACTURE OF BRASS. 
 
 by the previous heat of the furnace. The orifice in the top of the 
 oven is then partly closed by a circular piece of clay about 18 
 inches diameter, and the whole suffered to remain undisturbed 
 for seven or eight hours ; the workman having nothing to do 
 with the operation during this period, but merely to keep open 
 the draught-holes in the bed of the furnace, and to regulate the 
 temperature by enlarging or contracting the orifice in the arch 
 of the furnace from time to time, as the state of the process may 
 require. 
 
 It will be proper, however, before entering upon the particu- 
 lar manipulations of this business, to describe the peculiar con- 
 struction of the furnace and of the several apparatus connected 
 with it. 
 
 In erecting a brass-work, the first thing is to sink a cellar be- 
 neath the intended building, for the reception of the furnaces, 
 and of such a depth as will contain the whole height of the fur- 
 naces, and allow the opening in the roof to be exactly level with 
 the surface of the floor of the chamber above them. One of these 
 vaults generally contains four furnaces, each of which is built 
 upon a cast-iron plate, called the furnace-bottom, three inches 
 thick, and of a diameter somewhat larger than the area of the 
 furnace. These plates are cast with eleven circular two-inch 
 holes in each, for the purpose of allowing a sufficient access of 
 atmospheric air, and these are distributed as in the annexed 
 sketch, in which the circles represent the holes, the black spots 
 the crucibles : Figure 1 . 
 
 A sketch of one of the furnaces. 
 Scale an inch to the foot. 
 
 Floor on which the crucibles stand. 
 
 Figure 1. represents a perpendicular section of one of the furnaces. It is built 
 perpendicular for 18 inches in height, or to a a. It is then contracted for 
 18 inches more, measured diagonally, to b b, at which place its diameter is 
 1 foot 6 inches. It is. then contracted for 6 inches more, but at a different 
 angle, to c c> where the diameter is only I foot 1 inch, on which a massy cast- 
 iron ring, 3 inches deep and 3 inches thick, is placed at d d as a hoop to 
 keep the brick-work together, and this forms the orifice of the furnace. F is 
 a flue to the chimney described at page 202. 
 
ON THE MANUFACTURE OF BRASS. 
 
 201 
 
 Figure 2 . 
 A ground plan of the four furnaces to the scale of l-8th of an inch to the foot. 
 
 Figure 2. is a ground plan of the four furnaces under each dome. A A A A the 
 interior of each furnace. B B B B the walls of the furnaces. C C C C 
 the flues to the chimneys. D D the two chimneys which convey the smoke 
 of the fires into the great dome or main chimney. 
 
 Figure 3. 
 Scale l-16th of an inch to the foot. 
 
 Figure 3. A, an elevation of the dome 
 or great chimney which covers the 
 four furnaces, and rises 42 feet per- 
 pendicularly above them. B B, two 
 arches which support the front wall 
 of the dome, and allow a passage 
 to the hearth underneath the dome. 
 C, a partition wall of brick-work 
 called the midfeather, which facili- 
 tates the current and strengthens 
 the building. E E, the hearth within 
 the walls of the dome. F F F F, the 
 entrances into the furnaces. 
 
 The plates are fixed upon brick-work of a sufficient height to 
 admit of the removal of the ashes which fall through the orifices; 
 and when one of these is properly fixed, the wall of the intended 
 furnace is carried up in the usual manner upon it. The furnace 
 is in a peculiar form, a perpendicular section of which is de- 
 scribed in the accompanying plan (Figure 1), which is drawn to 
 the scale of half an inch to the foot. 
 
202 ON THE MANUFACTURE OF BRASS. 
 
 At F a flue of about 6 or 7 inches square commences, and is 
 carried up perpendicularly along the inside wall of the great 
 dome, to the height of 9 feet, where it discharges its contents. 
 Each furnace has a similar flue, and each flue is furnished with a 
 register, which is occasionally opened to excite a quicker draught 
 through the holes in the furnace bottom, whenever it is necessary 
 to raise the heat very considerably. 
 
 The furnace is built with fire-bricks made expressly for the 
 purpose, each brick being somewhat in the form of the key- 
 stone of an arch, or similar to the annexed figure ; 
 so that the small or concave side of each brick, when 
 laid down, forms a segment of the whole circular area 
 of the interior of the furnace. 
 
 When the four furnaces are completed, a quantity of loose 
 earth is thrown in between them, and properly rammed, so as 
 to form a floor, which is covered with a mixture of earth and 
 carbonaceous matter. If it were paved with stones or bricks, 
 the power of these in conducting caloric would render it impos- 
 sible for the workmen to stand upon this floor ; but as it is, 
 there is but little inconvenience to those accustomed to it. When 
 the work has so far proceeded, a chimney is erected of a suffi- 
 cient size to cover the four furnaces and carry off the fumes of 
 the crucibles, and the smoke from the fires, which are con- 
 stantly burning underneath. This chimney, at its base, is 
 about 24? feet by 8, and it is carried up of these dimensions 
 to the height of 7 feet ; it is then gradually narrowed for about 
 30 feet more, when it rises 6 feet perpendicularly, and finishes 
 with an orifice of about 8 feet square. The carbonaceous floor 
 which is immediately under this large chimney, is called the 
 hearth, and is usually about 24 feet long by 8 feet wide. It 
 is a perfectly regular floor, except that it has the four circular 
 apertures, each 13 inches diameter, which proceed from the fur- 
 naces beneath. 
 
 It is to be noticed, that the two ends of the large chimney and 
 one of its sides are supported by strong brick walls, while the 
 other side remains partly open to the height of 6| feet, the upper 
 part of that side of the chimney being upheld by brick pillars 
 and arches, for the sake of leaving spaces or archways through 
 which the workmen can pass from the adjoining workshop to 
 the hearth. By this arrangement a room of any size may be 
 attached to the hearth, and still the draught up the chimney 
 preserved. In the works which I have seen, this room is about 
 24 feet square, which gives to the whole workshop an area 
 of 24 feet by 32, and allows sufficient space for all the ope* 
 rations. 
 
 The crucibles in which the brass is made are round and of 
 the usual form. Internally they are 8 inches in diameter at the 
 
ON THE MANUFACTURE OF BRASS. 203 
 
 top, 13 inches deep, and \\ inch thick. As there is a great con- 
 sumption of these crucibles, they are generally made in the 
 brass- works. They are composed chiefly of a mixture of Stour- 
 bridge clay with another species found in the neighbourhood, 
 together with some old broken glass-house pots coarsely ground, 
 and a large portion of sand. The mixture of the ground pots 
 with the other materials, enables the crucibles to bear sudden 
 transitions from heat to cold, and vice versa, without cracking. 
 Some of these vessels, which are worn out, present when broken, 
 a beautiful amethystine colour throughout their texture, occa- 
 sioned probably by the union of some particular proportion of 
 carbon with the copper and zinc; as others, even after long wear, 
 are not stained in this manner. 
 
 In commencing a new operation, the crucibles are filled one 
 by one, as they are taken out of the furnace ; and when nearly 
 filled with the calamine, copper, scrap-brass and charcoal, the 
 mixture is covered with a thick coat of ground charcoal only ; 
 and it may be remarked, that although the crucibles are red- 
 hot, the workman smooths the surface of the charcoal and 
 presses it down in the crucibles with the naked hand. When 
 a crucible is thus filled, an attendant workman takes hold of it 
 with a long pair of tongs, and, letting it down into the furnace, 
 places it on the spot where it stood in the former operation. 
 Having delivered this, he draws out another empty crucible to 
 be filled in like manner, and this course is continued till the 
 whole are charged, and commonly with such success that the 
 same crucibles serve over and over again, sustaining the changes 
 of temperature without accident for several operations. 
 
 The crucibles having been thus arranged, a man brings three 
 bundles of gorse or furze, cut from the common, and thrusts them 
 into the furnace ; then large coals are thrown in till the oven is 
 full. The gorse is intended to prevent the falling of the coals 
 from breaking the crucibles, and also to favour the combustion, 
 by keeping the coals hollow. When the furnace is thus charged, 
 the mouth is partially covered by a thick piece of baked clay as 
 before mentioned; the consequence of which is, that the draught 
 to the chimney is kept up, which otherwise would have been 
 checked or obstructed entirely by the large mass of fuel which 
 is thrown in at once, and which remains some time before any 
 considerable part of it can become ignited. 
 
 As soon as the combustion has fairly commenced, a curious 
 spectacle presents itself, viz. that of furnaces burning beneath 
 our feet, and four large bodies of flame rising through the floor 
 on which we stand, and this so constructed that one may walk be- 
 tween these fires without danger, and without being even annoyed 
 by the smoke. At this moment the workman is very attentive to 
 the process, occasionally opening or closing the orifice on the top 
 
204< ON THE MANUFACTURE OF BRASS. 
 
 of each furnace, BO as to keep up with exactness the proper 
 draught and no more. It is indeed necessary throughout the 
 whole process to pay the greatest attention to the state of the 
 fire, that there may be heat enough to decompose the oxide of 
 zinc, and yet not enough to occasion that rapid reduction of it 
 which would liberate the zinc-fumes faster than the copper could 
 absorb them. The heat must be so regulated that it shall be suf- 
 ficient to separate the zinc from its ore, and yet not great enough 
 to melt the grains of copper, which would defeat the principal 
 intention ; because the granulated copper becomes soft in a red 
 heat, so that the zinc-fumes can penetrate it ; and this is all that 
 is required until nearly the end of the operation, when the heat 
 is raised so as to bring the whole into a state of perfect fusion, 
 which is known to be the case by the apparent heat of the fur- 
 nace, and the rapid extrication of the vapours of zinc. 
 
 It may here be observed, that in the old brass-works the cala- 
 mine and charcoal were usually beaten into a hard mass at the bot- 
 tom of the crucible, and then covered with a round plate of cop- 
 per, which in a few hours became impregnated by the fumes of zinc 
 from below. This, however, was a tedious mode of manufacture, 
 as it was always necessary to re-melt the plates before an alloy of 
 an homogeneous quality could be obtained. By the present 
 management the copper absorbs the zinc gradually, and when it 
 has acquired the proper quantity, the two metals melt together 
 into one uniform mass. 
 
 In order to have the temperature of the ovens under constant 
 control, care is taken to keep the holes in the floor of the furnace 
 perpetually open, and this is effected by the workman now and 
 then thrusting a long slender rod of iron through the arch of the 
 furnace into them ; as he well knows that if he can procure a good 
 draught from below, he will have no difficulty in regulating that 
 draught by opening or shutting the register in the chimney, and 
 enlarging or contracting the orifice on the top of the furnace. In 
 first charging the furnace, he also takes care that the draught- 
 holes are all covered with fuel ; for if it were otherwise, the air 
 which passes through them could not be decomposed, but would 
 considerably cool the furnace. However, as there is generally 
 only one of these draught-holes between every two crucibles, a 
 careful workman has little difficulty in keeping them sufficiently 
 open, that is, free from slag or clinkers, and yet constantly covered 
 with the fuel. 
 
 When the metal is ready for casting, a man opens the orifice 
 in the arch of the furnace, and with a large pair of tongs draws 
 out the middle crucible, and places it with its contents in the 
 midst of a heap of hot ashes. He then withdraws another cru- 
 cible in the same manner, when the foreman thrusts an iron rod 
 into it, and stirs the melted brass a little, which has the effect of 
 
ON THE MANUFACTURE OF BRASS. 205 
 
 cooling it in some measure, this being necessary, and of bringing 
 to the surface any calcareous, carbonaceous, or foreign matter 
 that may have adhered to the sides of the crucible. These being 
 removed with an iron spatula from the surface of the melted 
 metal, another man takes up the crucible with a pair of tongs and 
 empties its contents into* the first crucible. He then returns the 
 empty one into the furnace and withdraws another, which is 
 stirred, skimmed, and emptied as before. In this manner they 
 proceed until the contents of the eight crucibles are collected 
 together into one only. 
 
 A stranger cannot witness these operations without being 
 surprised at the adroitness with which they are performed, and 
 pleased with the unusual appearances that present themselves. 
 
 When the iron rod is thrust into the crucible by the workman, 
 it occasions a combustion of the uncombined zinc, which burns 
 with a white flarne of peculiar brilliancy and beauty. The edge 
 of this flame has sometimes a tinge of blueish green, which pro- 
 bably occasions the whole body of flame to exhibit a more chaste 
 and delicate white than it otherwise would. Melted brass when 
 exposed to the atmosphere in a state of rest, although at a high 
 temperature, is protected from decomposition by a thin pellicle 
 of oxide which forms on its surface ; but when the melted mass 
 is agitated by stirring it, there is a rapid and brilliant combustion 
 of a portion of the zinc, which of course produces the white oxide 
 of that metal, which is known to the workmen by the name of 
 calamine bloom. 
 
 It may here be observed that the calamine is paid for according 
 to the brass which is produced; the waste of zinc which is occa- 
 sioned by this combustion is therefore the miner's loss, and not 
 that of the manufacturer. 
 
 The whole of the metal having been collected into one crucible 
 in the manner already described, the workman stirs it again 
 with his iron rod, which produces another brilliant combustion. 
 He then carefully skims the whole mass to remove whatever 
 extraneous matter the stirring had brought to the surface, and 
 wipes the edge of the crucible to remove any thing that may ad- 
 here to it. Every thing being thus prepared, another workman 
 brings a pair of callipers of a peculiar construction, with an iron 
 cover attached to them, so that when the instrument is opened 
 to embrace the crucible, the cover slips over it to prevent any 
 thing from falling in, and to preserve the heat of the metal while 
 it is carried to the moulds on the other side of the laboratory. 
 This is done by two men, who lift the crucible between them, 
 and pour its whole contents into a mould formed of two blocks 
 of granite, to be described hereafter. A plate of sheet brass is 
 thus formed, which is usually 5J feet long, 15 or 16 inches wide, 
 and half an. inch thick, weighing about 108lbs. 
 
206 ON THE MANUFACTURE OF BRASS. 
 
 Sixty pounds of calamine will produce about 22jlbs of zinc, 
 which, with 45lbs of copper and 40lbs of scrap brass called 
 shrtiffl produce a sheet of brass of the above weight. The whole 
 process is usually finished in about seven or eight hours : I am 
 informed, however, that when the brass-works were going at 
 Holywell, they required from eighteen to twenty hours to com- 
 plete the process. Formerly, indeed, the operation was never 
 finished in any of the English brass-works in less than two days 
 and nights, and from that to four or five days, according to the 
 goodness of the calamine. 
 
 Frequently, however, a mineral called black jack or blende is 
 used instead of calamine for making brass. This is found in 
 abundance in many mining countries, and has long been in use 
 at the Bristol brass-works ; though, being a sulphuret and not a 
 carbonate of zinc, it requires a long calcination in a reverberatory 
 furnace to burn off the sulphur, before it is fit for forming an 
 alloy with copper. On the other hand, the red oxide of zinc, 
 which occurs in several parts of the United States of America, 
 will, without any previous preparation, produce, when united with 
 copper, brass of the best quality, possessing a very great degree 
 of malleability and ductility '. 
 
 The moulds which are employed in England for casting sheet 
 brass are made of granite from Cornwall, though formerly we im- 
 ported this stone from Holland, and afterwards from St. Maloes 
 in France, not knowing that it might be procured at home. The 
 great brass-works at Aix la Chapelle were supplied also from St. 
 Maloes. The blocks employed in our brass-works are generally 
 about 6 feet long, 3 feet wide, and from 7 to 9 inches thick, and 
 usually weigh one ton each : but they require much preparation 
 before they are fit for the purpose above mentioned, and in a 
 large work many pairs of them are required to be in constant 
 readiness. Care is also taken in the selection of the granite, 
 for if it be of too close a grain it is apt to fly on the application 
 of heat ; whereas on the contrary, if the crystals of felspar are 
 large, they are apt to fall out when the blocks have been used a 
 short time, and the moulds, whatever may have been the expense 
 in preparing them, are spoiled. When the granite is suitable for 
 the purpose, a pair of moulds will sustain constant wear for 
 eighteen months or two years. 
 
 To prepare the granite for use, each block is surrounded with 
 a strong iron band, one inch thick and two inches wide, the nar- 
 row edge of the iron being placed against the edge of the stone. 
 To these bands strong hooks are firmly affixed, and by means of 
 these the blocks of stone can at any time be connected with a 
 crane and moved to any part of the room as occasion requires. 
 
 1 Bruce's American Mineralogical Journal, page 69. 
 
ON THE MANUFACTURE OF BRASS. 207 
 
 The hooks are also useful for raising the upper block from the 
 lower one to take out the sheet of brass that has been cast, and 
 to dress the face of each stone for the next casting. In order to 
 separate these massy stones from each other with the greater ease, 
 the upper one is hung upon two strong iron pins which serve 
 instead of hinges, so that whenever the hook of the crane is at- 
 tached to the swivel in the upper stone, a few turns of the windlass 
 will elevate that stone on its back edge, and allow the workman 
 to dress the face of either as he sees occasion ; but in fastening 
 them together the longest stone is fixed below, and this is allowed 
 to project a few inches at one end beyond the upper one, to form 
 a kind of bed, on which the brass is poured from the crucible, and 
 from whence it readily runs into the mould. When these stones 
 are thus fixed on their pivots, they open like the leaves of a book 
 without being entirely separated from each other ; and are put 
 together again by means of the crane and pulley with the greatest 
 ease ; though it will be obvious that they are never allowed to 
 come into actual contact. There must be room for the metal 
 which is to form the sheet of brass to run between them ; and to 
 effect this, the two blocks of granite are kept at a proper distance 
 from each other by ribs of iron, which vary in thickness according 
 to the thickness of the plate of brass intended to be cast. These 
 are not fastened in the first instance, but are merely laid loose 
 upon the undermost block, and the screwing of the two blocks 
 together fastens them. They are called shin irons. 
 
 It should have been observed that before these blocks of Corn- 
 ish stone are fit for use they are in some measure dressed by a 
 mason, and then the inner surface of each is plastered over with 
 a very thin coat of common loam, for the purpose of giving it a 
 smooth face. Any small fissures that afterwards appear in the 
 loam, from the heat of the melted brass cast upon it, are filled 
 up by smearing the surface over with a little cow-dung, which is 
 generally done each time; and by this trifling expedient the mould 
 is rendered fit for receiving the next casting. Formerly the 
 moulds were covered with a coating of ground coal and tallow, 
 but the present method is the more efficacious. 
 
 When the mason has prepared a pair of new blocks of granite, 
 and the smith has bound them with iron and attached the appa- 
 ratus for screwing them together, they are fastened by a kind 
 of swivel to a strong beam of wood, for the purpose of altering 
 their horizontal position, whenever the brass is required to be 
 poured into them. 
 
 Things being so far arranged, the two slabs of granite are 
 screwed firmly together, with the ribs of iron already mentioned 
 between them. A perfect stone mould is thus formed, open at 
 one end for the sake of pouring in the fluid metal. 
 
 The beam of wood to which the blocks of stone are attached, 
 
208 ON THE MANUFACTURE OF BRASS. 
 
 is so contrived that when the crane is hooked to one end of the 
 mould, it can thereby be raised, while the other end sinks into an 
 excavation in the floor of about two feet deep, which gives the 
 stones an angle of 30 or 35 degrees ; and this has been found to 
 be the most convenient declivity for pouring in the metal. 
 
 It may be mentioned that the moulds for casting sheet brass 
 were very different formerly, as appears from plate xxxv. in the 
 Fleta Minor by Sir John Pettus. 
 
 When the plate of brass has been cast in the way already de- 
 scribed, a minute or two is only allowed to intervene before the 
 workman loosens the screws to take out the new plate of metal, 
 and again dresses the interior of the mould with the usual coating, 
 to prepare it for the next casting. He then covers the slabs of 
 granite with thick flannel blankets doubled together, and lays 
 four or five one over the other, in order to preserve the mould of 
 a proper temperature for receiving the castings of the next day. 
 The coating of loam first spoken of requires to be renewed after 
 every ten or twelve castings; the old coating being previously re- 
 moved by rubbing the face of one block against the other. To 
 effect this purpose a quantity of brass shot of a size less than that of 
 pepper-corns is introduced between the two blocks, which causes 
 the upper stone to move with comparative ease over the face of 
 the lower one, and by this abrasion to disengage the whole of the 
 old indurated coating. 
 
 These are the methods by which the manufacture of brass- 
 plates is usually conducted. When the metallic alloy is of an 
 ordinary quality it is generally not cast into plates,* but into 
 ingots of about 8 inches long, 2 broad, and l inch thick. 
 These are sold to the brass founders for the purpose of small 
 castings, and for making the alloys of tombac, pinchbeck, &c. 
 These ingots are usually formed in moulds made with cast-iron. 
 
 The plates of which 1 have described the manufacture so much 
 in detail, are generally taken from the brass-works to the mills : 
 there some are rolled whole into large sheets of very thin brass 
 called latten; others are cut into long slips, and these are again 
 rolled to about the thinness of one- twentieth of an inch ; they are 
 then slit into strings as they are called, and in that state are 
 taken to the wire mill to be drawn into wire, for making pins or 
 for any other purpose to which brass wire is applicable. 
 
 This, however, is an operation of some nicety, because the act 
 of drawing the brass through steel plates renders it so brittle that 
 it is necessary to anneal it afresh after each drawing; and for 
 small wire this is frequently repeated, as the metal is successively 
 drawn through holes of different degrees of fineness before it is 
 sufficiently reduced. The annealing is performed by heating the 
 wire to a little below a red-heat, and then suffering it to cool 
 
ON THE MANUFACTURE OF BRASS. 209 
 
 gradually, which renders it as soft and as pliable as at first. It is 
 not plunged into cold water like copper wire, though by so doing 
 it would not be hardened like iron and steel wire when so treated. 
 Copper wire when annealed is plunged whilst red-hot into cold 
 water, but this is more for the sake of throwing off the oxide 
 which it has contracted by being heated in contact with atmo- 
 spheric air. It may here be remarked as a curious fact, that to 
 anneal iron wire a contrary practice must be adopted ; the iron 
 wire must be heated red and suffered to cool gradually, for if it 
 were treated like copper wire it would be rendered perfectly 
 brittle. In annealing brass wire care must be taken not to heat 
 it up to what is called a cherry red, which is easily done in wire 
 of great fineness, because the zinc in that case would be separated 
 and copper reproduced. 
 
 The largest consumption of brass wire is in the manufacture of 
 pins, and tor this purpose it is indispensable ; the reasons will 
 appear when we come to consider the properties of brass as di- 
 stinct from those of copper. There is likewise a considerable con- 
 sumption of brass in the manufacture of what are called brasses 
 or bushes, in which the spindles of machinery usually run ; also 
 for carriage harness, the furniture of houses, culinary utensils, 
 and other domestic purposes. 
 
 Brass was made with the utmost secrecy in Germany for seve- 
 ral hundred years; and some individuals raised themselves to 
 great opulence by its manufacture. The first work for the manu- 
 facture of brass that was erected in this kingdom, was begun at 
 Esher, in Surry, by one Daniel Demetrius a German, in the year 
 1649, and the whole of the metal was then made with rose copper 
 imported from Sweden ' ; some English merchants however, who 
 had been accustomed to export our calamine to the continent and 
 derived profit from the importation of foreign brass, contrived to 
 involve Demetrius in a suit at law, which ruined him and obliged 
 him to give up the concern. Other works were erected soon 
 afterwards in South wark and at Woolwich; and Lord Byron 
 had a large establishment in Nottinghamshire for making brass, 
 and these together with the London works employed 8000 men 
 daily. But Sir John Pettus, who wrote in 1670, tells us* that in 
 his time the works had decayed and " the art of making brass was 
 almost gone, as well as the artists, from the kingdom." 
 
 The first mill in Great Britain for drawing brass wire, was 
 erected by a Dutchman near Richmond in the year 1663. 
 
 The places in this country where brass is now manufactured 
 
 1 Houghton's Collections, vo\. ii. page 188. 
 8 FwKwe Kcgfi/cs, page 33. 
 P 
 
210 ON THE MANUFACTURE OF BRASS. 
 
 to any extent are at Framilode in Gloucestershire, at Bristol, 
 at Birmingham, and at the towns of Cheadle and Stone in Staf- 
 fordshire. The works at Bristol are the most extensive in the 
 kingdom, and have been the longest established. The manu- 
 facture of brass was indeed confined to the city of Bristol for 
 many years, and as other works became established the workmen 
 were generally procured from thence. There were formerly 
 two great works near that city, but one of these has been long 
 shut up. The house of Harford and Co. has been the longest 
 established, and is now in full work. There are no less than 
 four works in Birmingham where brass is made for sale ; besides 
 which several of the consumers themselves in that town make a por- 
 tion of what they use, though this is chiefly of an inferior sort. 
 
 The most useful alloy of copper and zinc, as far as I have been 
 able to ascertain, is that which is composed of two parts by 
 weight of copper and one of zinc ; and this is not far from one 
 proportional of each metal, reckoning the equivalent number for 
 copper to be 64? and that of zinc 35 ; but the proportions of the two 
 metals are frequently varied according to the purposes for which 
 the alloy is required. Dutch-brass, which is imported for the use 
 of the manufacturers of watch movements, is a compound of two 
 proportionals of copper 64? x 2 = 128 + one of zinc 35 = 163. 
 Prince's metal is composed of one proportional of copper 64? + 2 
 of zinc 35 x 2 = 70, forming a metallic alloy = 134% 
 
 According to Weigleb, the alloy called Manheim-gold is com- 
 posed of 
 
 3 proportionals of copper 64 x 3 = 192 
 1 proportional of zinc . . . = 35 
 
 227 
 
 Pinchbeck is said to contain a less proportion of zinc than any. 
 of the alloys of copper usually made in this country, but I am 
 not acquainted with the proportions. 
 
 French brass is formed occasionally with different proportions 
 of the two metals ; but that which is manufactured for common 
 consumption is a compound of 
 
 4 proportionals of copper 64 x 4 = 256 
 1 proportional of zinc 35 
 
 291 
 
 It is observable that this alloy contains very little more than 
 1 2 per cent, of zinc, whereas our brass holds usually more than 
 35 per cent, of that metal. The best English tombac however 
 contains still less of zinc ; but then the colour of the copper is 
 lowered by the addition of tin. Tombac is usually made with 16 
 parts of copper by weight, with one of tin and one of zinc. Its 
 
ON THE MANUFACTURE OF BRASS. 
 
 real proportions, considering the loss which arises from the vola- 
 tile nature of the oxide of zinc, are probably, 
 
 15 proportionals of copper 64 x 15 = 960 
 
 1 proportional of tin 59 
 
 1 proportional of zinc 35 
 
 1054 
 
 Brass is peculiarly useful to many of our artists and workers 
 in metals, because it may be easily combined by fusion with 
 additional portions either of zinc or copper ; thus if brass be com- 
 bined with a large proportion of zinc, it forms an alloy known in 
 Birmingham by the name of white metal, which is used in large 
 quantities for the manufacture of what are called white-metal- 
 buttons ; on the contrary, pinchbeck, tombac, Dutch-gold, Man- 
 heim-gold, semilor and Prince's metal, are made by fusing brass 
 with an additional quantity of copper. The alloys last mentioned 
 have all a rich yellow colour and will bear a high polish. 
 
 The peculiar properties of brass may be thus enumerated : 
 Brass is harder than copper, but not sufficiently hard to strike 
 fire like steel. It melts with less heat than copper, which 
 makes it more convenient for small castings. It does not rust 
 or oxidize so soon as copper. It is also more suitable for 
 turning in the lathe, as it is worked with greater ease and cuts 
 smoother, and it will also bear a higher polish. It is ductile only 
 when cold, but this ductility greatly exceeds that of copper ; con- 
 sequently it can be drawn into wire of superior fineness. It is re- 
 markable that copper should acquire such great ductility by its 
 union with zinc, as zinc is of itself a very brittle metal. Brass 
 is more combustible than copper, which is proved by the circum- 
 stance of a brass wire burning in chlorine gas, which is not the 
 case with copper. Brass is more tenacious than copper, and 
 therefore fitter for being fashioned by hammering. On this 
 account it is commonly used for very fine work, such as mathe- 
 matical, philosophical, and astronomical instruments. It expands 
 by heat more than copper, but in a less degree than zinc. The 
 degrees of its expansion at different temperatures were deter- 
 mined by Mr. Smeaton nearly seventy years ago. Its colour is 
 paler than that of copper, which gives it a great resemblance to 
 gold. It is more sonorous than copper, which occasions its em- 
 ployment very generally for musical instruments ; and from the 
 experiments of Lewis, as detailed in the Commercium Technicum, 
 it appears that a very useful alloy of platinum and brass may be 
 formed, which bears a very fine polish and does not tarnish by 
 exposure to the atmosphere. Mr. Leslie has discovered that of 
 all the metals or metallic alloys brass possesses the property of 
 reflecting light and heat in the highest degree. This circum- 
 stance will probably occasion its employment for purposes to 
 which it has not hitherto been applied. 
 
212 ON SULPHURIC ACID. 
 
 ESSAY VII. 
 
 ON SULPHURIC ACID. 
 
 WHEN sulphur mixed with a certain portion of nitre is burnt 
 over water, in a closed vessel containing atmospheric air, a pe- 
 culiar acid is formed during the combustion, which is known to 
 chemists by the name of SULPHURIC ACID. 
 
 This acid is formed in many of the operations of nature ', but 
 we have no reason to believe that the ancients knew this, although 
 they were well acquainted with its base, sulphur % which they 
 sometimes employed with other combustible substances in reli- 
 gious oblations. So early as in the first century sulphur was 
 employed in bleaching woollen cloth, and for other purposes, as 
 may be seen in the Essay on Bleaching. 
 
 Vitriol, or sulphate of iron, is mentioned by Pliny in his 
 Natural History ; but it does not appear that he knew any thing 
 of its chemical composition. 
 
 Aulus Gellius relates that Archelaus, one of the generals of 
 Mithridates, washed over a wooden tower with a solution of alum, 
 and by this project rendered it so much proof against fire, that 
 all the attempts of Sylla to set it in flames proved abortive. There 
 is, however, no question but that this was sulphate of iron which 
 was applied, for it has been proved that the ancients gave this 
 salt the name of alum. 
 
 The first mention of sulphuric acid occurs in the writings of 
 Basil Valentine, a celebrated chemist of Erfurt. In his time, 
 however, the quantity produced must have been small, and its 
 consumption very circumscribed. It was also known to Para- 
 celsus, the Swiss alchemist, who died so early as the year 1541 ; 
 and it is evidently referred to likewise in a work entitled De Re 
 Metallica, which was published by George Agricola, a German 
 physician, in the year 1542 ; but I know of no proper character- 
 istic description of this acid by any of the writers of that period. 
 The first person who gave any thing like a correct account of 
 sulphuric acid was Gerard Dornaeus, in a work which he pub- 
 lished in the year 1570; and again in another edition of the same 
 work, which he republished at Frankfort in the year 158 1 3 . 
 
 1 Disengaged sulphuric acid has occasionally been found native in some 
 parts of Italy j Journal de Phys. torn. vii. page 39a. 
 * Pliny, lib. xxxv. cap. 15. 
 
ON SULPHURIC ACID. 213 
 
 When sulphuric acid was first prepared by art, it was distilled 
 from dried sulphate of iron, the common green-vitriol of com- 
 merce. Hence, when the component parts neither of the salt 
 nor of the acid were known, it was very naturally called oil of 
 vitriol : or it might have acquired the name of oil of vitriol from 
 the circumstances of its resemblance to oil in adhering to the sides 
 of a vessel containing it, and in its occasioning little noise when 
 poured from one vessel to another. 
 
 This name should now be expunged, as it tends to give false 
 ideas of the nature of the acid, and may mislead and bewilder a 
 young chemist. Oil does not mix with water, but sulphuric acid 
 does in all proportions ; oil is composed of hydrogen and carbon; 
 but neither of these substances enters into the composition of 
 sulphuric acid, which has been demonstrated by analysis as well 
 as synthesis to be formed only of sulphur, oxygen, and water. 
 
 Sulphate of iron is prepared from martial pyrites, which is a 
 native sulphuret of iron. It is found in abundance on the island 
 of Sheppy and elsewhere. By exposing this to the air in large 
 beds, oxygen is absorbed, the sulphur becomes sulphuric acid, 
 and the newly formed salt is separated by washing. 
 
 All the sulphuric acid which is prepared in Saxony, and in 
 many other parts of Germany, is still procured from sulphate of 
 iron. In the Journal de Physique there is a very particular ac- 
 count, by Mr. Fragoso, of the distillation of this acid from cop- 
 peras, as it is now practised- at Bleyl, a village in Bohemia 4 . To 
 conduct the operation in the best manner, seven or eight days 
 will be required, and during two-thirds of this time the fire must 
 be kept at the highest pitch. Bernhardt, who was well acquainted 
 with this process, tells us that he procured only 64 pounds of 
 sulphuric acid from six hundred weight of sulphate of iron. 
 Directions for conducting the operation have also been given by 
 Glauber ; but according to him, a much purer sulphuric acid 
 may be obtained from sulphate of zinc, and with less labour 5 . 
 
 At one time the English makers of sulphuric acid distilled the 
 green vitriol in earthen vessels called long-necks, placed within 
 a reverberatory furnace with a glass receiver luted to each retort. 
 It was usual to put fifty or more of these into one furnace 6 . 
 
 3 This work is entitled " Congeries Paracelsicse Chemise de Transmutatio- 
 nibus Metallorum, ex omnibus quae de his ab ipso scripta reperire licuit hacte- 
 nus ; access. Genealogia Mineralium atque Metallorum omnium." 8vo. Francf. 
 Wechel. 1581. 
 
 4 An abridgement of this account may be seen in the thirteenth volume of 
 the Repertory of Arts, page 261). 
 
 The Works of John Rudolph Glauber, folio, London, 1689, page 17. 
 c Dr. Lewis's Edition of Neumann, vol. i. page 277- 
 
214 ON SULPHURIC ACID. 
 
 The makers of sulphuric acid having found great inconvenience 
 in procuring it from sulphate of iron, on account of the length of 
 time which was necessary for the operation, the small quantity of 
 acid that was procured by this means, and the intense heat re- 
 quired for its distillation, which always destroyed the stills with 
 great rapidity, and entailed upon them a perpetual and enormous 
 expense, had at length recourse to the base itself, to the sulphur, 
 which, in conjuction with nitre, was burnt in very large globes 
 of glass, and the product was concentrated by boiling it in retorts 
 or other glass vessels, until the fluid was of a sufficient strength 
 for sale. 
 
 It may be proper, however, before we proceed with the account 
 of the manufacture of sulphuric acid, to say a word or two re- 
 specting the sulphur. 
 
 Sulphur^ or brimstone as it has usually been called, is a simple 
 combustible substance, quite undecomposable, at least by any of 
 our present methods of analysis, and it differs in its nature and 
 properties from all other known bodies. It is chiefly procured 
 in the neighbourhood of volcanoes, and also from some of the 
 native sulphurets; but what is used in this country is usually im- 
 ported from Sicily. Its chief consumption is in the manufacture 
 of sulphuric acid; though it should be recollected, that if sulphur 
 be burnt without any admixture, sulphurous and not sulphuric 
 acid will be formed. 
 
 Sulphur burns very differently in different circumstances; 
 Stahl found that an ounce of sulphur, burnt with a wick, may 
 be made to yield a constant flame for six hours ; and that when 
 the wick was very small, only 15 or 16 grains were consumed in 
 an hour. When sulphur is heated to about 190, combustion 
 begins, and a pale blueish flame is emitted with the production 
 of a very small degree of heat. The heat thus generated is so 
 inconsiderable that Baume contrived to burn off the whole of 
 the sulphur from a quantity of gunpowder without exploding the 
 powder '. 
 
 I have seen no account of the preparation of sulphur in any 
 of the modern systems of chemistry. A few particulars relating 
 to the process which I shall insert, believing they will be accept- 
 able to the reader, appeared in the Phil. Trans. 1665, page 45. 
 
 " The mineral out of which brimstone is extracted at Liege 
 is not much unlike lead-ore, having also oft-times much lead 
 mingled with it, which is separated from it by picking. To make 
 brimstone, they break the ore into small pieces, which they put 
 into crucibles made of earth, five feet long, square and pyramid- 
 
 1 Macquer's Dictionary, article Sulphur. 
 
ON SULPHURIC ACID. 215 
 
 wise. The entry is near a foot square. These crucibles are laid 
 sloping, eight undermost, and seven above them, as it were be- 
 twixt them, that the fire may come at them all, each having its 
 particular furnace or oven. The brimstone, being dissolved by 
 the violence of the heat, drops out at the small end of the crucible, 
 and falls into a leaden trough or receiver common to all the said 
 crucibles, through which there runs a continual rivulet of cold 
 water, conveyed thither by pipes for the cooling of the dissolved 
 sulphur, which is ordinarily four hours in melting." From the 
 ashes left in the crucibles they afterwards make crystallized sul- 
 phate of iron. 
 
 Sulphur is a hard and brittle substance of a yellow colour, 
 which very much varies in its intensity ; it has neither taste nor 
 smell unless it be heated. When melted in a large mass, it 
 crystallizes on cooling. Such crystals as are transparent are in 
 a high degree doubly refractive; and its specific gravity, when 
 tolerably pure, is about 1.990. It has the property of becoming 
 negatively electrical by heat and by friction. It liquefies at the 
 heat of 225, and this liquid becomes thicker and thicker as the 
 heat is increased ; and when it has acquired the heat of 560 or 
 600, it begins to sublime, and the article known in commerce 
 by the name of powers of sulphur is produced. Roll sulphur is 
 generally procured from British sulphuret of copper : this is at 
 first separated from the mineral by sublimation, and then the 
 sublimed sulphur is remelted and purified before it be cast into 
 sticks for sale. When sulphur is pure, it will evaporate en- 
 tirely, and leave no residuum. Its purity may also be judged of 
 by dissolving a portion in boiling oil of turpentine ; for if pure, 
 every particle will be dissolved by the action of that menstruum. 
 The equivalent number for sulphur is 16. 
 
 It is generally understood that the sulphur which is imported 
 varies very much in its quality ; and this is confirmed by the dif- 
 ferent accounts we have of its specific gravity, which varies from 
 1.800 to 2.3440. 
 
 The process of forming sulphuric acid by the combustion of 
 sulphur is so very different from the original method of procuring 
 it by the simple distillation of sulphate of iron, and has occasioned 
 such important changes in a variety of the manufactures of the 
 country, that I have considered it to be right to take some pains 
 to trace the progress of the new method ; especially as it will in 
 a few years be difficult to acquire any correct information on the 
 subject ; and as I had formerly some connexion with the family 
 of one of the principal original manufacturers, I obtained the 
 possession of some facts which I am desirous of communicating 
 to the public. Moreover, the gratification which arises from 
 
216 ON SULPHURIC ACID. 
 
 being the means of recording the origin of a manufactory of so 
 much importance as the process for producing this acid in an 
 economical way, will, I trust, be my excuse for allowing the fol- 
 lowing detail to occupy so much room in this Essay. 
 
 The method of forming sulphuric acid by the combustion of 
 sulphur was first adopted in this country by Dr. Ward, the vender 
 of many celebrated nostrums which bear his name. It has ge- 
 nerally been said that Dr. Ward was the author of this impor- 
 tant discovery; but Fourcroy attributes it to two French chemists, 
 Lefevre and Lemery. The works of the latter I have consulted, 
 and in an edition printed more than a century ago, I find an ex- 
 press process for producing sulphuric acid by the combustion of 
 sulphur and nitre; though it is probable that before Dr. Ward's 
 time the quantity made in this way was very inconsiderable; for 
 Lemery tells us that he prefers the acid made without nitre '. 
 An exclusive right to this mode of making sulphuric acid in 
 Great Britain was, however, granted to the Doctor by patent ; 
 and, by way of distinction, the article which he prepared was 
 called " Oil of vitriol made by the bell," and was sold from ISd. 
 to 2s. 6d. per pound. 
 
 The glass vessels which were employed for this process were 
 made with wide necks, and as large as they could be blown with 
 safety, and capable of holding forty or fifty gallons. These were 
 placed in two rows on a bed of sand, and at a sufficient distance 
 from each other to be conveniently approached. A few pounds 
 of water being poured into each glass, a stone-ware pot was in- 
 troduced into the neck, and on this was placed an iron ladle 
 previously made red-hot. Into this last, by means of another 
 ladle of tin-ware, a mixture of sulphur and nitre was put, and 
 then the aperture of the glass vessel was immediately closed with 
 a stopper of wood. The heat of the iron ladle set the sulphur 
 and nitre on fire ; and when the combustion was finished, the iron 
 ladle was taken out, and the vapours suffered to condense. 
 
 The same operation was successively conducted in each of the 
 glass vessels composing the two rows; so that the workman, after 
 passing through the whole range, arrived at the first vessel at the 
 time when the vapours were totally condensed, and the vessel 
 consequently in a state to receive a new portion of the matter for 
 burning. 
 
 The British manufacture of this acid was thus monopolized by 
 Dr. Ward for a considerable time : but when the term of his 
 patent expired, several other persons became engaged in the 
 
 1 Fourcroy's System of Chemical Knowledge, London, 1804, vol. ii. p. 83. 
 Lemery's Chemistry, London, 1^98, page 448. 
 
ON SULPHURIC ACID. 217 
 
 business, and conducted it after an improved method. Mr. Dossie 
 has given a very particular description of his method, and of 
 the glass globes and other apparatus which were employed in 
 his time for the purpose ; from the perusal of which the nature 
 of the manufacture will be thoroughly understood 2 . At length, 
 however, chambers of lead were employed for the combustion of 
 the sulphur and nitre, which were so contrived that the floor of 
 each might be constantly covered with a sheet of water, capable 
 of absorbing the sulphuric acid gas at the time of its formation. 
 
 The introduction of the leaden apparatus is a memorable event 
 in the history of the progress of this manufacture, as it has laid 
 the foundation of its present magnitude, and in a short time re- 
 duced the price to about one twelfth part of its former rate. 
 
 The credit of this very important improvement belongs to the 
 late Dr. Roebuck, an eminent physician of Birmingham, who, 
 in conjunction with his partner, the late Mr. Samuel Garbett, 
 erected the first leaden chamber for this purpose, at Birmingham, 
 about the year 1746. 
 
 Owing to the interior situation of these works, and the great 
 expense and risk of land carriage, there being at that time no 
 conveyance by canals, the consumption was almost entirely con- 
 fined to that town and neighbourhood. A considerable portion 
 of the acid was employed in the distillation of nitrous acid, which 
 is in great demand there for the use of the various manufactories. 
 Much of it was also used as a solvent for copper, for the double 
 purpose of making Roman-vitriol, and of recovering the gold 
 and silver from waste gilt and plated metal. 
 
 These manufacturers, however, were not long satisfied with 
 this confined consumption : in order therefore to create a more 
 extensive demand, and likewise with a view to the introduction 
 of it for the purpose of bleaching in the linen manufactories of 
 Scotland and Ireland, in the year 1749 they established works 
 at Prestonpans on the eastern coast of Scotland on a very ex- 
 tensive scale. 
 
 That nothing might be neglected which was likely to promote 
 this object, Dr. Home, then professor of chemistry in the univer- 
 sity of Edinburgh, entered upon a course of experiments to 
 ascertain the powerful effects of sulphuric acid, when properly 
 employed, in whitening linen cloth without prejudice to the 
 fabric. These experiments were afterwards published, together 
 with directions as to the mode in which the new agent ought to 
 be employed. This, by degrees, had the desired effect, and 
 
 - Dossie's ^laboratory laid open, Oct. 1758, Introduction, page 44. 
 
218 ON SULPHURIC ACID. 
 
 finally exploded the use of sour milk, which till then was the 
 only acidulous article that had ever been used in bleaching. 
 
 In reverting to the manufacture of sulphuric acid, it ought to 
 be noticed that for several years Messieurs Roebuck and Gar- 
 bett carried on their works in England and Scotland with great 
 success and without any opposition. They not only supplied the 
 demands of Great Britain and Ireland, but exported very large 
 quantities of sulphuric acid to the continent of Europe. 
 
 About the year 1756, one of their workmen at Birmingham 
 absconded from their service ; and being a native of Bridgenorth, 
 went thither, and had the art to induce a Mr. Rhodes, an emi- 
 nent seed-crusher, and proprietor of large oil-mills in that town, 
 to embark in the business. 
 
 A small work was accordingly set up at Bridgenorth, on the 
 banks of the Severn, and there the manufacture was carried on 
 for many years. This man did not, however, continue long 
 with Mr. Rhodes; but engaged himself to Mr. Skey of Bewdley, 
 who had just begun a manufactory of sulphuric acid on a scale 
 much larger than that at Bridgenorth. 
 
 This establishment was also on the banks of the Severn, at a 
 place called Dowles, near the town of Bewdley, in the county of 
 Worcester, and was the third English work for manufacturing 
 this valuable commodity by the combustion of sulphur in leaden 
 chambers. 
 
 At first these chambers were only six feet square; but Mr. 
 Skey erected his ten feet square, and in vessels of that size he 
 continued the manufacture for many years. 
 
 These chambers were erected under the direction of a man 
 who had formerly worked at Prestonpans, and who, having been 
 discharged from thence, was travelling through the country with 
 his family in search of employment. 
 
 Mr. Skey, who was a man of great enterprise, having by acci- 
 dent seen this individual and heard his account of the nature of 
 the business, at once determined that he would engage in it, and 
 manufacture the article on as large a scale as its demand should 
 require. 
 
 Such was the origin of the extensive manufactory at Bewdley ; 
 and as the materials at that time were cheap, arid the acid was 
 sold dear, this establishment was the means of raising its founder 
 to a state of great opulence. At his decease, the whole of the 
 chemical works were carried on by his son the late Samuel Skey, 
 Esq., and since his death they have been continued, and are still 
 in full work, for the benefit of his children. 
 
 Considering the nature and importance of Dr. Roebuck's im- 
 provement, it is a remarkable circumstance that similar esta- 
 
ON SULPHURIC ACID. 219 
 
 blishments were not sooner formed in various parts of the king- 
 dom ; and that twenty-five years should have elapsed before any 
 spirited individual in the metropolis, or in its vicinity, had availed 
 himself of the advantages of the invention. 
 
 According to the best information which I have been enabled 
 to obtain, Messieurs Kingscote and Walker, druggists of Lon- 
 don, were the first persons south of Birmingham who attempted 
 to make sulphuric acid in vessels of lead. Their manufactory 
 was established in the year 1772, at Battersea, four miles from 
 London, and on the 24th day of December 1771 the first barge- 
 load of lead was navigated on the Thames up to Battersea for 
 the construction of the chambers. 
 
 This establishment consisted of seventy-one circular leaden 
 vessels, each six feet in diameter and six feet in height, con- 
 structed in the following manner : A sheet of lead was folded 
 round a wooden cylinder prepared for the purpose, and upon 
 this immense maundrel the vessels were formed into shape, and 
 then the edges of the sheets were lapped together and soldered. 
 Each vessel was afterwards reared on one end upon a bottom of 
 lead, and when thus fixed, it was covered with a dome of lead 
 firmly soldered upon it. 
 
 These receptacles had each one aperture, which, during the 
 time of the combustion of the sulphur, was closed by a door of 
 mahogany nicely adapted to it : besides which, each vessel had 
 an outer door of the same species of wood to be shut before the 
 former, in order to close the opening the more effectually. These 
 rooms stood in five separate rows, independently of each other, 
 and all were inclosed in one large brick building, to preserve 
 them from the effects of the sun and wind. 
 
 Besides the apparatus which I have described, these manufac- 
 turers erected also several square houses of lead, which were 
 perfect cubes of twelve feet each ; and these, together with the 
 former, were regularly employed for many years. I have been 
 the more particular in describing this work, as I conceive it to 
 have been the most curious and expensive establishment that was 
 ever formed in these kingdoms for a similar purpose. 
 
 Several unfortunate circumstances, not worth relating at this 
 period, conspired to render this manufactory unproductive of 
 profit ; in consequence of which it was at length broken up, the 
 vessels were taken down, and every thing was sold by auction 
 under the description of old materials. 
 
 Soon after the destruction of this manufactory, Mr. Walker, a 
 nephew of one of the late partners at Battersea, connected him- 
 self with two other gentlemen, and they, under the firm of Baker, 
 Walker, and Singleton, some time about the year 1783 esta- 
 blished a sulphuric acid manufactory of very considerable extent 
 at Pitsworth-Moor near Eccles in the county of Lancaster. This 
 
220 ON SULPHURIC ACID. 
 
 manufactory, which was the first establishment of the kind in 
 that county, consisted of four vessels each twelve feet square, 
 and four others, each of which was forty-five feet long and ten 
 feet wide. 
 
 Not long after the formation of this manufactory, another work 
 was established at Leeds ; and by degrees they have spread into 
 most parts of England and Scotland, as well as Ireland. 
 
 When the formation of sulphuric acid by combustion in leaden 
 chambers was completely established by Dr. Roebuck, little or 
 no improvement was made in the manufacture for many years. 
 However, in the year 1788, a memorable era in the history of 
 the trade of this country, when the new method of bleaching by 
 chlorine was introduced, the sale of sulphuric acid was much 
 increased, especially in some particular districts. From this time 
 the demand became enormous, and almost unlimited in extent; 
 so that, from this single and unexpected circumstance, the manu- 
 facturers of this acid found it necessary to erect chambers of 
 much larger extent for the combustion of the sulphur ; and these 
 have been enlarged again and again by the great makers, so that 
 now a common rate manufactory for sulphuric acid is really an 
 establishment of serious concern in respect to capital and mag- 
 nitude. 
 
 The size of the leaden chambers in modern use is from 20 
 feet long and 12 wide to 40 or 60 feet long and 16 or 18 feet 
 wide. One manufacturer, however, in Lancashire, has several 
 leaden chambers of the enormous dimensions of 120 by 40 feet, 
 and 20 feet high, consequently forming a space of 96,000 cubic 
 feet each. 
 
 The process, however, whatever may be the size of the cham- 
 bers, is generally conducted in the following manner : A quan- 
 tity of common brimstone, coarsely ground, is carefully mixed 
 with crude saltpetre in the proportion of seven or eight pounds 
 of the former to one pound of the latter ; and this mixture is 
 afterwards divided into separate charges, containing quantities 
 proportioned to the size of the chamber in which they are in- 
 tended to be burnt. 
 
 The best method for apportioning the mixture of sulphur and 
 nitre to the size of the house, appears to me to be this : to allow 
 one pound for every 300 cubical feet of atmospheric air contained 
 within the chamber ; that is, if a house be ah oblong square of 
 40 feet by 15 feet, and 15 feet high, the contents in cubic feet 
 will be 9,000, and such a chamber will take 30 pounds of the 
 mixture at each charge. 
 
 The mixture of sulphur and nitre is usually spread upon 
 several plates either of iron or of lead ; and these are afterwards 
 placed upon stands of lead within the chamber, at some distance 
 from each other, and a foot or two above the surface of the water. 
 
ON SULPHURIC ACID. 221 
 
 Things being thus arranged, the sulphur is lighted by means of 
 a hot iron, and the doors are then closed. 
 
 If well mixed, the brimstone and nitre will soon be in rapid 
 combustion, which will continue for 30 or 40 minutes, during 
 which time the chamber will become entirely filled with gas. 
 
 Three hours, calculating from the time of lighting, are gene- 
 rally allowed for the condensation of this gas ; and then it is cus- 
 tomary to throw open the doors for a quarter of an hour or half 
 an hour, for the free admission of atmospheric air and the ex- 
 pulsion of all the incondensable gas, in order that the house 
 may be thoroughly sweetened, as it is called, for the next 
 burning. 
 
 During this interval the plates are again charged, and prepa- 
 ration is made for a fresh combustion, which is thus repeated 
 every four hours, day and night, without intermission, until the 
 water at the bottom of the chamber is thought to be sufficiently 
 acidified, which is generally when it has attained the specific 
 gravity of 1.350. It is then drawn offj by means of a syphon, 
 into a reservoir of lead conveniently placed for its reception, 
 and the floor of the chamber replenished with water for another 
 operation. 
 
 Whatever number of leaden chambers a manufactory may 
 consist of, it is customary to work them all in this way, day and 
 night, without interruption : for, as it requires a large sum in 
 the first instance to form a sulphuric acid establishment, the ope- 
 ration being tedious, the return slow, and the product very small 
 compared with the capital, the interest of money must be a heavy 
 charge on the trade ; and this is a constant spur to the manu- 
 facturer, making him anxious to get as large a produce as pos- 
 sible from each chamber. 
 
 When the acid has been drawn from the house, it is pumped 
 from the reservoir into a large leaden boiler, which is usually an 
 oblong square, and there evaporated down till it has attained 
 the specific gravity of 1.700 or thereabouts. 
 
 Another reservoir is placed contiguous to the boiler, into 
 which the concentrated acid is syphoned, where it is preserved, 
 closely covered from the action of the atmosphere, until it is con- 
 venient to remove it to the rectifying house. There it is boiled 
 in retorts of glass, until the remainder of the sulphurous and 
 nitrous gas is driven off, and the acid has acquired the usual 
 concentration for sale. 
 
 To explain why these different operations are necessary for 
 procuring sulphuric acid in its highest state of concentration, it 
 may be remarked, that whenever the acid in the leaden cham- 
 bers has acquired a certain specific gravity, it will refuse to 
 absorb the gas with the same avidity as at first ; therefore, in 
 order to conduct the process economically, the acid liquor must 
 
222 ON SULPHURIC ACID. 
 
 at that time be removed, and water poured in to supply its 
 place. 
 
 It is equally necessary, when in the leaden boiler, to draw it 
 off before it becomes too much concentrated ; because the boil- 
 ing point of sulphuric acid always increases with the increase of 
 its specific gravity ; and its boiling point is so very near to that 
 at which lead melts ', that there would be great danger of the 
 metal giving way, were an attempt made to concentrate the acid 
 beyond a certain point in such utensils ; to say nothing of the 
 loss of that portion of acid which would be decomposed by the 
 metal, and of the impurity which the remaining acid would ac- 
 quire from the large quantity of lead that would then be dis- 
 solved. 
 
 From some late experiments which I have made on the fusi- 
 bility of various compounds of lead and tin, 1 have been con- 
 vinced that in the fabrication of leaden boilers the utmost atten- 
 tion ought to be paid to the purity of the metal, and care taken 
 that no lead be used but such as is free from every alloy. 
 
 Having occasion a few years ago to purchase several tons of 
 sheet-lead for the construction of an oil-of-vitriol chamber and 
 other chemical apparatus, I accidentally discovered that there 
 is often a great deal of sheet-lead in the market which has been 
 manufactured from old lead, which usually contains some solder 
 and other impurities. In the construction of steam boilers for 
 the concentration of sulphuric acid, such lead ought to be care- 
 fully avoided ; for a small portion of tin or plumber's solder, 
 which is usually found in old lead, will when mixed with pure 
 pig-lead reduce the melting point of the whole of the metal very 
 considerably. 
 
 Having thus given but a brief account of the nature of this 
 manufacture, it will be necessary to add a few words upon the 
 properties of the acid which is the subject of this Essay. 
 
 I have already noticed that sulphuric acid is a compound of 
 sulphur, oxygen, and water; but it must be observed, that sul- 
 phur is capable of forming with oxygen three distinct compounds, 
 containing different proportions of oxygen, and possessing very 
 different properties. Thus, if sulphur be burnt in oxygen gas 
 over water, the water will absorb the sulphurous gas which pro- 
 ceeds from the combustion, and be converted to sulphurous acid ; 
 but if a certain proportion of nitrate of potash be mixed with 
 the sulphur before it be ignited, the product of the combustion 
 will be sulphuric acid. 
 
 Hypo-sulphurous acid, which exists only in combination with 
 
 1 Lead melts at 612 of Fahrenheit; and Mr. Dalton states that the con- 
 centrated sulphuric acid of commerce of the specific gravity of 1.848 boils at 
 590; but that if the specific gravity amount to 1.849, it will require a heat 
 of 650 to bring it to the state of ebullition. 
 
ON SULPHURIC ACID. 223 
 
 salifiable bases, and may be obtained by digesting the solution 
 of a sulphite with sulphur, is composed of one proportional of 
 sulphur =16, and 1 of oxygen = 8 = 24 its equivalent number. 
 
 Sulphurous acid gas is composed of 1 proportional of sulphur 
 = 16, and 2 of oxygen = 16 ; so that its equivalent number must 
 be represented by 32. 
 
 Sulphuric acid is composed of 1 proportional of sulphur =16, 
 and 3 of oxygen =24; so that the number representing dry 
 sulphuric acid, or sulphuric acid in the state in which it is found 
 in the native sulphuric salts, and in several artificial compounds, 
 will be 40. 
 
 The strongest liquid sulphuric acid is composed of 1 propor- 
 tional of sulphur =16; 3 of oxygen = 24; and 1 of water =9, 
 making its equivalent 49. 
 
 It is remarkable, that when sulphur is burnt in dry oxygen 
 gas, the sulphur combines with the gas without increasing its 
 volume. One hundred cubic inches of oxygen weigh 33.75 
 grains, and this volume of oxygen is capable of combining with 
 33.75 grains of sulphur ; from whence it follows, that 100 cubic 
 inches of sulphurous acid gas must weigh 67.5 grains, and this 
 by experiment is found to agree exactly with the theory. The 
 composition of sulphurous and sulphuric acids is therefore put 
 beyond all doubt. 
 
 It was usually imagined that the formation of sulphuric acid 
 is brought about by the union of the oxygen of the nitre with 
 the sulphurous acid ; but it was soon found by calculation that 
 the nitre usually burnt with the sulphur is not adequate to the 
 supply of one-thirtieth of the oxygen that is required for the 
 conversion of sulphurous to sulphuric acid. The theory of its 
 formation, which is borne out by experiment, is now considered 
 to be this : The two acid gases, the sulphurous and the nitrous, 
 which enter the chamber together, have the property of com- 
 bining and forming minute crystals on the sides of the chamber, 
 which fall off and drop into the water. Here a decomposition im- 
 mediately ensues, the sulphurous robs the nitrous of one portion 
 of its oxygen, and becomes sulphuric acid, leaving the latter 
 deutoxide of nitrogen ; but this gas, immediately it again comes 
 in contact with the common air of the chamber, unites with 
 the oxygen and reforms nitrous acid, which again meeting with 
 sulphurous, once more forms crystals, and is deprived of its 
 oxygen as before, thus constantly acting as a carrier of oxygen 
 from the atmospheric air to the sulphurous acid as long as any of 
 these two substances remains in the chamber. To prove the 
 truth of this theory, Mr. Dalton contrived the following beautiful 
 and satisfactory experiment 2 : 
 
 ~ New System of Chemical Philosophy, page 390. 
 
224 ON SULPHURIC ACID. 
 
 " Let 100 measures of sulphurous acid gas be put into a dry 
 tube over mercury, to which add 60 of oxygen gas; let then 10 
 or 20 measures of nitrous gas (nitric oxide) be added to the mix- 
 ture ; in a few seconds the inside of the tube becomes covered 
 with a crystalline appearance, like hoar-frost, and the mixture is 
 reduced to one-third or one-fourth of its original volume. If 
 now a drop of water be admitted, the crystalline matter is quickly 
 dissolved in the water, sparkling as it enters, and the gases en- 
 tirely lose their elasticity, except a small residuum of azote and 
 nitrous gas. If the tube be then washed out, the water tastes 
 strongly acid, but has no smell of sulphurous acid. It is evident, 
 that in this process the nitrous gas unites to the oxygen, and 
 transports it to the sulphurous acid, which, receiving it from the 
 nitrous gas, becomes sulphuric acid. It appears, moreover, that 
 solid sulphuric acid is formed when no water is present ; and 
 consequently this is the natural state of sulphuric acid entirely 
 free from water." 
 
 Sir H. Davy, however, discovered that nitric oxide has no 
 action whatever on sulphurous gas, unless moisture be present, 
 but that with a very small proportion of water they form a white 
 crystalline matter, which is instantly decomposed by the addition 
 of more water, with the extrication of nitric oxide; and this bv 
 the contact of atmospheric air, or oxygen, becomes nitrous acid 
 as before. 
 
 When sulphuric acid is pure, it is entirely devoid of colour 
 and smell ; it is extremely acid and corrosive, and one of the most 
 ponderous fluids we are acquainted with. It is capable of uniting 
 with the earths, the alkalies, and most of the metallic oxides, 
 and in these combinations it forms those salts which are known 
 by the name of sulphates. 
 
 Having said that sulphuric acid is corrosive, I am desirous, 
 before I proceed to mention its other properties, of observing 
 that instances may occur of its being taken into the stomach by 
 mistake, and without immediate relief its corrosive properties 
 would produce fatal effects. If magnesia should be at hand, 
 that earth mixed with water and sweetened with sugar, would be 
 the best possible antidote to the poison ; but in case this could 
 not be immediately procured, soap-water, which can be furnished 
 by all families, and which is one of the next best remedies, should 
 be drunk plentifully. The unfortunate death of an infant son of 
 the Hon. and Rev. E. Knox, at Dungarvon Park, in consequence 
 of his swallowing a quantity of oil of vitrol which had been care- 
 lessly left on the table by a female domestic, shows how important 
 it is for the public to be acquainted with the proper remedy in 
 such cases. 
 
 The most distinguishing characteristics of sulphuric acid are, 
 
ON SULPHURIC ACID. 225 
 
 its peculiar affinity for barytes, which it is capable of separating 
 from all other combinations ; and its attraction for water, which 
 it absorbs with great avidity, even from the atmosphere, when- 
 ever it is exposed to it in a state of concentration. The attraction 
 which sulphuric acid has for water is so powerful, that in certain 
 operations of the laboratory it is often employed for the purpose 
 of creating a dry atmosphere. 
 
 The great affinity of sulphuric acid for water may be shown 
 by the following very easy experiment : If the bulb of a ther- 
 mometer be dipped in concentrated sulphuric acid, it will pro- 
 bably not be perceived that the immersion has occasioned any 
 alteration in the temperature of the thermometer; but if it be 
 withdrawn and held in the open air, the small portion of acid 
 which adheres to the bulb will absorb water from the atmosphere 
 with so much rapidity (especially if it be in damp weather) that 
 in a few seconds the mercury in the thermometer will be seen to 
 rise several degrees. 
 
 The mixture of sulphuric acid and water occasions a great 
 extrication of caloric. If a thermometer be placed in a glass of 
 water, and concentrated sulphuric acid gradually added, the 
 mercury will instantly begin to ascend, and progressively to a 
 certain extent; and if two pounds of this acid be suddenly mixed 
 with one pound of water, the temperature will immediately be 
 raised much higher than that of boiling water ! . No advantage 
 seems, however, to have been taken of this property of sulphuric 
 acid, though it affords the means of furnishing a variety of de- 
 grees of heat in an instant. Indeed, the rapidity with which the 
 temperature becomes afterwards reduced, would probably be an 
 obstacle to its employment in any of the operations of the labo- 
 ratory, or in the affairs of common life. I have, however, as a 
 matter of curiosity, constructed the following table of the different 
 temperatures which are produced by the mixture of water in 
 various proportions with this acid. 
 
 The temperatures of the water which I employed and of the 
 atmosphere of the room were both at 50. The acid was the 
 common oil of vitriol of commerce at the temperature of 56, 
 and of the specific gravity of 1.844, and fresh oil of vitriol and 
 fresh water were taken for every distinct experiment. 
 
 The effect produced by the mixture of sulphuric acid and 
 water is well known ; but no writer has noticed the property 
 which heated sulphuric acid has of retaining its caloric, or of 
 imparting it more slowly than most other fluid bodies usually do. 
 
 1 On the contrary, it may be remarked, that if two pounds of diluted sul- 
 phuric acid be mixed with three pounds of snow, the temperature of the snow 
 will immediately be reduced 55 degrees, or from 32 to 23. 
 
226 
 
 ON SULPHUKIC ACID. 
 
 I have observed that the workmen frequently pour this article 
 from the retorts into large empty glass bottles called carboys, at 
 a temperature of from 190 to 200 without inconvenience; 
 whereas, if water were used at the same, or even at a lower tem- 
 perature, it would not fail to split them in an instant. 
 
 I. A Table of the Temperatures produced by the Mixture of Sulphuric Acid 
 and Water; lOlbs. avoirdupois of water being used in each experiment. 
 
 Sulph. 
 acid 
 in 
 pounds. 
 
 Acquired 
 Temper, 
 of 
 Fahrenht. 
 
 Sulph. 
 acid 
 in 
 pounds. 
 
 Acquired 
 Temper, 
 of 
 Fahrenht. 
 
 S ulph. 
 acid 
 in 
 pounds. 
 
 Acquired 
 Temper, 
 of 
 Fahrenht. 
 
 Sulph. 
 acid 
 in 
 pounds. 
 
 Acquired 
 Temper, 
 of 
 Fahrenht. 
 
 1 
 
 2 
 3 
 4 
 5 
 6 
 
 78 
 100 
 110 
 128 
 138 
 144 
 
 7 
 8 
 9 
 10 
 11 
 12 
 
 156 
 168 
 
 186 
 204 
 214 
 
 222 
 
 13 
 14 
 15 
 16 
 17 
 18 
 
 229 
 236 
 241 
 246 
 250 
 253 
 
 19 
 20 
 25 
 *30 
 35 
 40 
 
 256 
 258 
 266 
 264 
 254 
 248 
 
 In making these experiments, I observed that in the first two 
 it required five minutes for the mixture to arrive at the maximum 
 of temperature ; that afterwards it acquired the maximum in two 
 minutes ; and that when the weight of the sulphuric acid was 
 more than half that of the water with which it was mixed, the 
 heat was evolved with still greater rapidity, till at last the change 
 seemed to be instantaneous. 
 
 The accurate performance of these experiments is attended 
 with some difficulty, on account of the steam which arises from 
 the surface of the mixture ; for when the weights of the sulphuric 
 acid exceeded those of the water, the steam, in some of the expe- 
 riments, was so great as to render it very difficult to determine 
 the exact point to which the mercury had ascended. In the 
 latter experiments, when the weight of the acid amounted to 
 nearly double that of the water, although the temperature occa- 
 sioned by the mixture of those fluids was higher, little or no 
 vapour was formed, and the graduation of the thermometer 
 could, at each experiment, be observed with exactness. 
 
 Fourcroy, in his System of Chemical Knowledge, relates 1 that 
 " the mixture of water and sulphuric acid which produces the 
 greatest heat, consists of four parts of acid and one of water, and 
 that the temperature rises to 120 of Reaumur's scale," equal to 
 302 of Fahrenheit. This statement I find to be incorrect ; for 
 
 * An experiment was made with the same proportion of the ingredients in 
 ounces instead of pounds : viz. ten ounces of water at 50 were mixed with 
 thirty ounces of sulphuric acid at 56; and though the mixture was made in 
 favourable circumstances, the temperature did not exceed 246 of Fahrenheit. 
 
 1 Nicholson's Translation of Fourcroy, vol. iu page 94. 
 
ON SULPHURIC ACID. 227 
 
 the real maximum of temperature is obtained by a mixture of 
 between two and three parts of acid to one of water ; and the 
 greatest elevation of temperature which I have been able to pro- 
 cure, is that of 266. Had the experiments, however, been 
 made in summer, it is probable the temperature might have been 
 raised some degrees higher. 
 
 It may be necessary to caution those who have not been ac- 
 customed to chemical operations, and yet would like to repeat 
 these experiments, to be careful to add the acid to the water, and 
 not to reverse it by pouring the water upon the acid, which would 
 be apt to occasion a part of the mixture^ to fly up, and endanger 
 the face and the clothes of the operator. 
 
 Several years ago, I was frequently applied to by persons in 
 different parts of the kingdom, for instructions respecting some 
 mode of ascertaining the quantity of acid in diluted sulphuric 
 acid of various specific gravities ; and I invariably referred them 
 to Dr. Kirwan's Table, which was published in the year 1793 in 
 the fourth volume of the Transactions of the Royal Irish Academy. 
 This, however, generally proved unsatisfactory to those who ap- 
 plied to me, inasmuch as few manufacturers could understand 
 how to accommodate that table to the common oil of vitriol, or 
 make it applicable to any practical purpose. This has arisen 
 from the circumstance of Dr. Kirwan having taken for his 
 standard sulphuric acid as it exists in sulphate of potash, instead 
 of employing the oil of vitriol of commerce. 
 
 Having found the inconvenience of this in my own concerns, 
 I long ago formed a table for private use, founded upon the sul- 
 phuric acid of commerce, by diluting that acid with several suc- 
 cessive portions of water ; a table which I employed for several 
 years with great advantage. But as this table was formed at a 
 temperature above the mean temperature of the atmosphere, and 
 its range was too confined to be of use in every instance, I resolved 
 to undertake the formation of a new one that would be more 
 generally useful, and which should proceed by very slow but 
 regular gradations up to the highest point of dilution that any 
 consumer of sulphuric acid would be likely to require 2 . 
 
 Having at no small expense of time and labour completed this 
 table, it will be inserted in this Essay, from a persuasion that it 
 will prove useful to many individuals in various branches of trade 
 and manufacture. 
 
 To compose this table, I might have taken purified sulphuric 
 acid, i. e. such as had undergone an actual distillation ; but as 
 
 2 The first line of the table shows the specific gravity of a mixture of one part 
 water and 100 parts of strong sulphuric acid. The latter, the specific gravity 
 of one part of sulphuric acid mixed with 100 parts of water. 
 
228 ON SULPHURIC ACID. 
 
 this is an article which is never employed but for philosophical 
 purposes, I thought it better to make use of the common acid, and 
 to take as good a sample of that kind as could possibly be procured. 
 I therefore chose some of my own manufacture, made in the usual 
 way, and concentrated, as is common in large manufactories, by 
 steaming it in a boiler of lead, and finishing it in a retort of glass. 
 When I began the experiments of dilution, the atmosphere of 
 the room was 60, and the acid was of the specific gravity of 
 1.8494, which at this temperature ' is as strong as it is ever sold. 
 
 In order to form the annexed table, I proceeded as follows : 
 
 I first accurately weighed ten thousand grains of the acid into 
 a stoppered bottle of glass, and then added to it 100 grains of 
 pure water. When the mixture was become cool, after having 
 been sufficiently agitated, the specific gravity of it was taken, and 
 the result forms the first line of the table. In this way I con- 
 tinued to dilute the acid with successive portions of water, taking 
 care to let it rest a sufficient time between each addition of the 
 water, that a complete union between the acid and the water 
 might take place ; having found by experiment that a mixture of 
 sulphuric acid and water, even after it has become cold, requires 
 several hours to arrive at the maximum of condensation. I took 
 also the precaution of keeping it in stoppered bottles, that it might 
 not imbibe water from the atmosphere, and frequently agitated it 
 during each interval. And in order to attain as great accuracy 
 as possible, I procured a specific-gravity-bottle larger than usual, 
 one that holds nearly ten ounces of water, and with a stem so 
 small that at the part to which the fluid rises when properly 
 filled, a single drop of the liquor will occasion a rise of nearly 
 one-sixteenth of an inch. 
 
 The balance which I made use of in these experiments will 
 turn with the twentieth part of a grain ; and as the acids will 
 erode the common scale-dishes, if dropt upon them, and endanger 
 the accuracy of a result, I have long been in the habit of using 
 those made of Wedgwood's ware, and such were employed in 
 making this table. Those parts of the table which have a star 
 opposite to them, were founded on actual experiment ; the inter- 
 mediate ones were the results of calculation. 
 
 Since I concluded these experiments it occurred to me, that it 
 might be useful to some manufacturers to know the quantity of 
 acid per cent, in diluted acid of any given strength ; I have there- 
 fore calculated the quantity in each, and annexed it. The column 
 of ounces and drachms is added for the use of those who are ac- 
 customed to this mode of reckoning, and also for those who are 
 
 1 For the difference which is occasioned in the specific gravity of sulphuric 
 acid by change of temperature, consult Table III. in this Essay. 
 
ON SULPHURIC ACID. 229 
 
 not conversant with the usual method of stating specific gravities ; 
 and it is calculated on the supposition of the wine-pint holding 
 exactly sixteen ounces avoirdupois of pure water. 
 
 It is a convenient way of measuring, to have a glass bottle with 
 a narrow neck, holding rather more than a pint of water, with a 
 mark on the stem at the place to which the water ascends when it 
 contains exactly 16 ounces avoirdupois of that fluid. It was 
 formerly understood that the standard wine-pint was the exact 
 measure of 1 Bounces of pure water; but in opposition to a de- 
 cision made by the Board of Excise in the year 1688, it has since 
 been determined that the English wine-pint holds 7272 grains 
 of pure water, which is 272 grains more than an avoirdupois 
 pound. However, as it has long been usual, for all common 
 purposes, still to consider it of the capacity of 16 ounces avoir- 
 dupois, I have taken it at that in the construction of this table. 
 
 If the wine-pint of water (7272 grains) be divided by 16, this 
 will give 454- J grains for the weight of the ounce measure of 
 water, which if expressed in decimal figures will stand thus, 
 454?. 5 ; and it is worth remarking, that there is a singular coin- 
 cidence here which is very favourable to the memory, viz. the 
 pint measure is seven two seven two / and the ounce measure, 
 four Jive four jive. 
 
 The sulphuric acid which is consumed in these kingdoms 
 amounts to upwards of three thousand tons annually, of which 
 the greater part is used in a state of dilution. For the purposes 
 of dissolving iron or zinc, it should be diluted with at least five or 
 six times its weight of water. Sulphuric acid is consumed in large 
 quantities by bleachers, for making the chloride of lime, and they 
 always use it in a state of dilution. The calico-printers also use 
 this acid, in various states of dilution, for making what they call 
 sours. 
 
 To these and other manufacturers this table will be of use, 
 not only in assisting them in the formation of diluted acid of any 
 given strength, but it will enable them at any time to ascertain 
 whether their servants have observed due care in making the 
 different preparations, which is a matter of great moment; for -it 
 often happens, that for want of this the printer and manufacturer 
 suffer great loss, and the printed goods sustain an irreparable 
 injury. 
 
 I need scarcely add that the sulphuric-acid- makers themselves 
 may also derive benefit from attending to this table ; for by its 
 assistance they can at all times form a pretty accurate estimate 
 of the value of any sample of the unrectified acid, or of the weak 
 acid while in the state of operation in any of their leaden cham- 
 bers. 
 
230 
 
 ON SULPHURIC ACID. 
 
 II. A Table of the Specific Gravities of Sulphuric Acid, when diluted with 
 different portions of water, constructed for the use of manufacturers ; being 
 the result of experiments made with the strongest sulphuric acid of com- 
 merce. The specific gravities taken at the temperature of 60 ; and 100 
 drachms of sulphuric acid, sp.gr. 1.8494, used in each experiment. 
 
 Drachms 
 
 Specific 
 
 Weight of 
 
 Acid per 
 
 Drachms 
 
 Specific 
 
 Weight of 
 
 Acid per 
 
 of 
 
 Gravity. 
 
 th 
 
 e 
 
 Cent. 
 
 of 
 
 Gravity. 
 
 
 the 
 
 Cent. 
 
 Water. 
 
 
 Wine 
 
 -pint. 
 
 
 Water. 
 
 
 Wi 
 
 le-pint. 
 
 
 
 
 Oz. 
 
 Drms. 
 
 
 
 
 Oz. 
 
 Drms. 
 
 
 *1 
 
 1 .8484 
 
 29 
 
 9* 
 
 99.009 
 
 49 
 
 1.5645 
 
 25 
 
 01 
 
 67-114 
 
 *2 
 
 1.8465 
 
 29 
 
 81 
 
 98.039 
 
 50 
 
 1.5585 
 
 24 
 
 15 
 
 66.666 
 
 *3 
 
 1.8445 
 
 29 
 
 8J 
 
 97.087 
 
 51 
 
 1.5526 
 
 24 
 
 13ft 
 
 66.225 
 
 #4 
 
 1.S416 
 
 29 
 
 n 
 
 96.153 
 
 52 
 
 1.5478 
 
 24 
 
 12| 
 
 65.789 
 
 *5 
 
 1.8387 
 
 29 
 
 6i 
 
 95.238 
 
 53 
 
 1.5129 
 
 24 
 
 11 
 
 65.35.9 
 
 6 
 
 1.8358 
 
 29 
 
 6 
 
 94.339 
 
 *54 
 
 1.5390 
 
 24 
 
 10 
 
 64.935 
 
 * 7 
 
 1.8319 
 
 29 
 
 5 
 
 93.457 
 
 55 
 
 1.5351 
 
 24 
 
 9 
 
 64.516 
 
 8 
 
 1.8270 
 
 29 
 
 3| 
 
 92.509 
 
 56 
 
 1.5312 
 
 24 
 
 8 
 
 64.102 
 
 9 
 
 1.8222 
 
 29 
 
 2h 
 
 91.743 
 
 57 
 
 1.5273 
 
 24 
 
 7 
 
 63.694 
 
 *10 
 
 1.8163 
 
 29 
 
 1 
 
 90.909 
 
 58 
 
 1.5234 
 
 24 
 
 6 
 
 63.291 
 
 11 
 
 1.8104 
 
 28 
 
 151 
 
 90.090 
 
 59 
 
 1.5195 
 
 24 
 
 5 
 
 62.893 
 
 12 
 
 1.8046 
 
 28 
 
 14 
 
 89.285 
 
 60 
 
 1.5156 
 
 24 
 
 4 
 
 62.500 
 
 13 
 
 1.7988 
 
 28 
 
 121 
 
 88-495 
 
 61 
 
 1.5117 
 
 24 
 
 3 
 
 62. 1 1 1 
 
 14 
 
 1.7.929 
 
 28 
 
 11 
 
 87.719 
 
 *62 
 
 1.5078 
 
 24 
 
 2 
 
 61.728 
 
 *15 
 
 1.7880 
 
 28 
 
 91 
 
 86.956 
 
 63 
 
 1.5039 
 
 24 
 
 1 
 
 61.349 
 
 16 
 
 1.7821 
 
 28 
 
 8 
 
 86.206 
 
 64 
 
 1.5000 
 
 24 
 
 
 
 60.9/5 
 
 17 
 
 1-7744 
 
 28 
 
 6i 
 
 85.470 
 
 65 
 
 1.4960 
 
 23 
 
 15 
 
 60.606 
 
 IS 
 
 1.7666 
 
 28 
 
 4i 
 
 84-745 
 
 66 
 
 1.4921 
 
 23 
 
 14 
 
 60.210 
 
 19 
 
 1.7588 
 
 28 
 
 2* 
 
 84-033 
 
 67 
 
 1.4882 
 
 23 
 
 13 
 
 59.880 
 
 20 
 
 1.7510 
 
 28 
 
 01 
 
 83.333 
 
 68 
 
 1.4843 
 
 23 
 
 12 
 
 59.523 
 
 *2i 
 
 1.7431 
 
 27 
 
 144- 
 
 82.644 
 
 69 
 
 1.4804 
 
 23 
 
 11 
 
 59.1/1 
 
 22 
 
 1.7353 
 
 27 
 
 12i 
 
 81.967 
 
 *70 
 
 1.4765 
 
 23 
 
 10 
 
 58.823 
 
 23 
 
 1.7275 
 
 27 
 
 10ft 
 
 81.300 
 
 71 
 
 1.4726 
 
 23 
 
 9 
 
 58.481 
 
 24 
 
 1.7207 
 
 27 
 
 81 
 
 80,645 
 
 72 
 
 1.4687 
 
 23 
 
 8 
 
 ,08.139 
 
 25 
 
 1.7138 
 
 27 
 
 61 
 
 80.000 
 
 73 
 
 1.4648 
 
 23 
 
 7 
 
 57.803 
 
 26 
 
 1.7070 
 
 27 
 
 5 
 
 79.365 
 
 74 
 
 1.4609 
 
 23 
 
 6 
 
 57.471 
 
 *27 
 
 1.7002 
 
 27 
 
 8| 
 
 78.740 
 
 75 
 
 1.45/0 
 
 23 
 
 5 
 
 57.142 
 
 28 
 
 1.6933 
 
 27 
 
 14 
 
 78.125 
 
 76 
 
 1.4531 
 
 23 
 
 4 
 
 56.818 
 
 29 
 
 1.6865 
 
 26 
 
 15| 
 
 77-519 
 
 77 
 
 1.4502 
 
 23 
 
 3i 
 
 56.497 
 
 30 
 
 1.6796 
 
 26 
 
 14 
 
 76.923 
 
 *78 
 
 1.4473 
 
 23 
 
 21 
 
 56.179 
 
 31 
 
 1.6728 
 
 26 
 
 12i 
 
 76.335 
 
 79 
 
 1.4433 
 
 23 
 
 ft 
 
 55.865 
 
 32 
 
 1.6660 
 
 26 
 
 101 
 
 75.757 
 
 80 
 
 1.4395 
 
 23 
 
 04 
 
 55.555 
 
 *33 
 
 1.6582 
 
 26 
 
 84 
 
 75.187 
 
 81 
 
 1 .4365 
 
 22 
 
 15| 
 
 55.248 
 
 34 
 
 1.6523 
 
 26 
 
 7 
 
 74.626 
 
 82 
 
 1.4336 
 
 22 
 
 15 
 
 54.945 
 
 35 
 
 1.6464 
 
 26 
 
 51 
 
 74.074 
 
 83 
 
 1.4306 
 
 22 
 
 Mi 
 
 54.644 
 
 *36 
 
 1.6406 
 
 26 
 
 4 
 
 73.529 
 
 84 
 
 1.4276 
 
 22 
 
 $4 
 
 54.347 
 
 37 
 
 1.6348 
 
 26 
 
 2! 
 
 72.992 
 
 85 
 
 1.4257 
 
 22 
 
 I2f 
 
 54.054 
 
 38 
 
 1.6289 
 
 26 
 
 1 
 
 72.463 
 
 *86 
 
 1.4218 
 
 22 
 
 12 
 
 53.763 
 
 39 
 
 1.6230 
 
 25 
 
 151 
 
 71.942 
 
 87 
 
 14189 
 
 22 
 
 ni 
 
 53.475 
 
 *40 
 
 1.6171 
 
 25 
 
 14 
 
 71.428 
 
 88 
 
 1.4160 
 
 22 
 
 10<- 
 
 53.191 
 
 41 
 
 1.6113 
 
 25 
 
 121 
 
 70.921 
 
 89 
 
 1.4130 
 
 22 
 
 &f 
 
 52.910 
 
 42 
 
 1.6054 
 
 25 
 
 11 
 
 70.422 
 
 90 
 
 1.4101 
 
 22 
 
 9 
 
 52.631 
 
 43 
 
 1.5995 
 
 25 
 
 91 
 
 69.930 
 
 91 
 
 1.4072 
 
 22 
 
 81 
 
 52.356 
 
 44 
 
 1.5937 
 
 25 
 
 8 
 
 69.444 
 
 92 
 
 14042 
 
 22 
 
 74 
 
 52.083 
 
 *45 
 
 1.5879 
 
 25 
 
 61 
 
 68.965 
 
 93 
 
 1.4013 
 
 22 
 
 6i 
 
 51.813 
 
 46 
 
 1.5820 
 
 25 
 
 5 
 
 68.493 
 
 *94 
 
 1.3984 
 
 22 
 
 6 
 
 51.546 
 
 47 
 
 1.5761 
 
 25 
 
 31 
 
 68.027 
 
 95 
 
 1.3955 
 
 22 
 
 5* 
 
 51.282 
 
 48 
 
 1.5703 
 
 25 
 
 2 
 
 67.567 
 
 96 
 
 1.3926 
 
 22 
 
 41 
 
 51.020 
 
ON SULPHURIC ACID. 
 
 231 
 
 Drachms Specific 
 of Gravity. 
 W r ater. 
 
 97 
 98 
 99 
 
 100 
 105 
 
 110 
 115 
 
 *120 
 125 
 
 130 
 135 
 
 *140 
 145 
 
 *160 
 155 
 
 160 
 165 
 170 
 175 
 
 *180 
 185 
 190 
 195 
 
 *200 
 210 
 
 *220 
 230 
 
 *240 
 250 
 
 *260 
 270 
 
 *280 
 290 
 
 *300 
 310 
 320 
 330 
 
 340 
 350 
 360 
 370 
 
 *380 
 390 
 400 
 
 Acid per 
 Cent. 
 
 1.3906 
 1.3886 
 1.3867 
 13848 
 1.3/30 
 1.3632 
 1 .3535 
 1.3437 
 1.3359 
 1.3281 
 1.3203 
 1.3125 
 1.3056 
 1.2988 
 1.2919 
 1.2851 
 1.2783 
 1.2724 
 1.2676 
 1.2627 
 1.2568 
 1.2520 
 1.24/0 
 1.2421 
 1 .2343 
 1.2265 
 1.2187 
 1.2129 
 1.2060 
 1.1992 
 1.1933 
 1.1875 
 1.1825 
 1.1776 
 1.1728 
 1.1679 
 1.1630 
 1.1582 
 1.1552 
 1.1523 
 1.1494 
 1.1464 
 1.1426 
 1.1338 
 
 Drachms 
 
 of 
 Water. 
 
 Specific, 
 Gravity. 
 
 Acid per 
 
 Cent. 
 
 *420 
 
 440 
 
 *460 
 
 480 
 
 500 
 
 *550 
 
 *600 
 
 650 
 
 *700 
 
 750 
 
 800 
 
 *850 
 
 POO 
 
 950 
 
 *iOOO 
 
 1100 
 
 *1200 
 
 *1300 
 
 *1400 
 
 Weight of 
 
 Wine-pint. 
 
 Oz. Drms. 
 
 22 4 50.761 
 
 22 3 50.505 
 
 22 3 50.256 
 
 22 2J 50.000 
 
 21 15i 48.780 
 
 21 13 47.619 
 
 21 10 46.511 
 
 21 8 45.454 
 
 21 6 44.444 
 
 21 4 43.478 
 
 21 2 42.553 
 
 21 41.666 
 
 20 Hi 40.816 
 
 20 12i 40.000 
 
 20 10- 39.215 
 
 20 9 38.461 
 
 20 7i 37.735 
 
 20 5| 37037 
 
 20 4 36.363 
 
 20 3i 35.714 
 
 20 If 35.087 
 
 20 34.482 
 
 19 15i 33.898 
 
 19 14 33.333 
 
 19 12 32.258 
 
 19 10 31.250 
 
 19 8 30.303 
 
 19 6-J 29.411 
 
 19 4| 28.571 
 
 19 3 27.777 
 
 19 H 27.027 
 
 19 26.315 
 
 18 14| 25.641 
 
 18 13 25.000 
 
 18 12i 24.390 
 
 18 11 23.809 
 
 18 9 1 23.255 
 
 18 8 22.727 
 
 18 7i 22.222 
 
 18 7 21.739 
 
 18 6i 21.276 
 
 18 5 20.833 
 
 18 4i 20.408 
 
 18 2i 20.000 
 
 This table was compiled in the year 1812, and printed in the 
 Phil. Mag. for the September of that year; but since its publi- 
 cation I have been informed there is a table by Vauquelin in 
 vol. 76, page 260, of the Annales de Chimie. on a similar plan. To 
 this I have referred ; and on comparison, allowing for the diffe- 
 rence in the strength of the acid which we severally employed, 
 I find that his table and mine very nearly coincide, except in one 
 instance, and in this there is a very material disagreement. His 
 
 1600 
 
 1700 
 1800 
 
 1900 
 *2000 
 *2250 
 *2500 
 *2750 
 *3000 
 *3500 
 4000 
 4500 
 6000 
 
 5500 
 *6000 
 *6500 
 *7000 
 
 7500 
 *8000 
 
 8500 
 *9000 
 
 9500 
 *10000 
 
 1.1328 
 1.1279 
 1.1240 
 1.1181 
 1.1132 
 1.1054 
 1.0966 
 1.0898 
 1.0839 
 1 .078 1 
 1.0732 
 1.0693 
 1.0664 
 1.0625 
 1.0602 
 1.0546 
 1.0507 
 1.0488 
 1.0458 
 1.0429 
 1.0390 
 1.03/0 
 1.0351 
 
 1.0337 
 1.0322 
 1.0283 
 1.0254 
 1.0234 
 1.0214 
 1.0185 
 1.0166 
 1.0146 
 1.0127 
 1.0117 
 1.0107 
 1.0102 
 1.0098 
 1.0093 
 1 .0088 
 1.0083 
 1.0078 
 1.0073 
 1.0068 
 
 Weight of 
 the 
 
 Wine-pint. 
 
 Oz. 
 
 Drms. 
 
 18 
 
 2 
 
 18 
 
 l 
 
 17 
 
 
 17 
 
 Hi 
 
 17 
 
 13 
 
 17 
 
 11 
 
 17 
 
 Si 
 
 17 
 
 7 
 
 17 
 
 62 
 
 17 
 
 4 
 
 17 
 
 2| 
 
 17 
 
 
 17 
 
 r 
 
 17 
 
 
 
 16 
 
 1^2 
 
 16 
 
 14 
 
 16 
 
 13 
 
 16 
 
 ]2 
 
 16 
 
 j]i 
 
 16 
 
 a 4 
 
 16 
 
 10 
 
 16 
 
 0* 
 
 16 
 
 9 
 
 16 
 
 8* 
 
 16 
 
 Si 
 
 16 
 
 7^ 
 
 16 
 
 4 
 
 16 
 
 6 
 
 16 
 
 5 A 
 
 16 
 
 4f 
 
 16 
 
 
 16 
 
 3& 
 
 16 
 
 4 
 
 16 
 
 3 
 
 16 
 
 2a 
 
 16 
 
 2| 
 
 16 
 
 2i 
 
 16 
 
 21 
 
 16 
 
 2* 
 
 16 
 
 2^r 
 
 16 
 
 2 
 
 16 
 
 1-8- 
 
 16 
 
 If 
 
 19.230 
 
 18.518 
 
 17.857 
 
 17.241 
 
 16.666 
 
 15.384 
 
 14.285 
 
 13.333 
 
 12.500 
 
 11.764 
 
 11.111 
 
 10.526 
 
 10.000 
 
 9.523 
 
 9.090 
 
 8.333 
 
 7.692 
 
 7.142 
 
 6.666 
 
 6.250 
 
 5.882 
 
 5.555 
 
 5.263 
 
 5.000 
 
 4.761 
 
 4.265 
 
 3.846 
 
 3.508 
 
 3.225 
 
 2.777 
 
 2.439 
 
 2.173 
 
 1.960 
 
 1.785 
 
 1.639 
 
 1.515 
 
 1.408 
 
 1.315 
 
 1.234 
 
 1 162 
 
 1.098 
 
 1.041 
 
 0.990 
 
232 ON SULPHURIC ACID. 
 
 table, however, is a very confined one, for it affords only twelve 
 examples of the specific gravity of diluted sulphuric acid; whereas 
 mine contains no less than 183 such examples. 
 
 In my table it is stated that the diluted acid of the specific 
 gravity of 1.023 contains only 3.508 per cent, of the strongest 
 sulphuric acid of commerce ; whereas he says it contains 6.600 
 per cent, of acid and 93.400 of water. This has induced me to 
 repeat so much of the experiment as was necessary for satisfaction 
 on this point, and I find that this repetition only confirms the 
 accuracy of the experiments on which my table was founded. 
 
 However, as the sulphuric acid which Vauquelin employed 
 had a specific gravity only of 1.8420, I procured some acid 
 exactly of the same strength; and having carefully mixed 66 
 drachms of it with 934 drachms of pure water, both measured 
 by weight, and left the mixture at rest a proper time for a com- 
 plete combination to be effected, I found its specific gravity at 
 60 of Fahrenheit to be 1.0474, instead of 1.0230 as Vauquelin 
 has stated. Pursuing the experiment still further, I found that 
 66 drachms of such acid, instead of taking 934 drachms of water, 
 actually require 2084 drachms of that fluid to reduce the whole 
 to the specific gravity in question, viz. that of 1.023. 
 
 As the foregoing table proceeds entirely on the dilution of the 
 concentrated sulphuric acid with different portions of water, it 
 will not be misplaced if I add a caution respecting the keeping of 
 this acid in a state of dilution, which in certain cases is highly 
 dangerous. 
 
 Some years ago, being in conversation with a sulphuric-acid- 
 maker, I inadvertently remarked that this acid might be rendered 
 colourless and pellucid without submitting it to the process of 
 rectification in glass, and I told him how the thing might be 
 effected. 
 
 Delighted with this intelligence, on his return home he imme- 
 diately put the process to the test, without having previously 
 communicated his intention to his partner, and he actually pre- 
 pared more than one hundred carboys, holding about 150lbs 
 each, of this weak acid, in readiness to be sent off to customers 
 whom he had hitherto supplied with the usual sulphuric acid of 
 commerce, and who would not, as he imagined, perceive the dif- 
 ference. 
 
 But, unfortunately for this crafty individual, it was in the midst 
 of winter when this grand scheme of sophistication was adopted, 
 and every carboy which he had prepared became frozen. Bottle 
 after bottle, therefore, burst by the expansion of the acid in the 
 act of freezing ; and if he had not adopted the method of filling 
 fill the large vessels on the premises with tepid water, and immer- 
 
ON SULPHURIC ACID. 233 
 
 sing the packed carboys in it, not a single bottle would have been 
 saved from the general wreck. 
 
 To prevent accidents from the inadvertent mixture of water 
 with oil of vitriol, it cannot be too generally known, that sulphuric 
 acid diluted to the specific gravity of 1.780, which is twenty- 
 eight ounces and a half to the wine-pint, will freeze much sooner 
 than water l . If 12 or 13 per cent, of water be mixed with the 
 strongest sulphuric acid of commerce, it will form an acid of 
 about this specific gravity, and such acid would freeze at some 
 degrees of temperature higher than that at which water congeals. 
 Mr. Dalton has, however, by experiment ascertained a curious 
 fact which had been hinted by Mr. Keir, respecting the dilution 
 of sulphuric acid 2 , viz. that if the liquid acid be of greater or 
 less specific gravity, so as to contain even one per cent, more or 
 less real acid, in that case it cannot be frozen in a temperature 
 above 32. 
 
 It was known to many of the old chemists that concentrated 
 sulphuric acid would congeal at a very low temperature; but this 
 very curious and singular property respecting the dilution of sul- 
 phuric acid was first noticed in this country by Mr. Keir. 
 
 From the experiments of this eminent chemist, it appears that 
 there is a certain degree of strength at which sulphuric acid 
 proves more congealable even than water. He exposed concen- 
 trated sulphuric acid to a frosty air in open vessels, and when it 
 had imbibed enough water from the atmosphere to reduce it to 
 about 1.780 it became congealed, and the congealed part, when 
 thawed, was found to be of the standard of easiest freezing. After- 
 wards, in another experiment, he found the congealed part ' to 
 thaw, in the open air, even while the cold increased, the continued 
 absorption of moisture having weakened it below the degree of 
 congelation. It is of importance that these facts should be known 
 by all persons who either manufacture or employ sulphuric acid. 
 
 The affinities of sulphuric acid are in the following order : 
 Barytes, Strontites, Potash, Soda, Lime, Magnesia, Ammonia. 
 
 The boiling point of the best sulphuric acid of commerce, viz. 
 that of 1.84-3, according to Mr. Dalton, on whom the utmost 
 reliance may be placed, is 590 of Fahrenheit; but if it contain 
 one per cent, more of acid, which would give it a specific gravity 
 of 1.849, the boiling point will be raised to 605; and if at the 
 temperature of 60 it be one degree higher, viz. 1.850, it will 
 not boil until it be heated to 620 . 3 
 
 In a commercial point of view, and for every purpose of philo- 
 
 1 Keir, Philosophical Transactions, part ii. for 1787. 
 z See New System of Chemical Philosophy, page 406. 
 3 Dalton's Chemical Philosophy, page 404. 
 
234- 
 
 ON SULPHURIC ACID. 
 
 sophical chemistry, it is of importance to become acquainted with 
 the variations in the specific gravity of this acid in consequence 
 of change of temperature. I know, however, of no one except 
 Kirwan who has given any information on the subject; and 
 in my opinion he has been peculiarly unfortunate in having 
 made choice of diluted acid for his experiments, instead of the 
 best concentrated acid V For to most persons, and especially 
 those who are large buyers of sulphuric acid, it must surely be 
 of more importance to know what the strong sulphuric acid of 
 commerce ought to be in all the variety of temperatures to which 
 this climate is liable. To supply this desideratum, I undertook 
 a series of experiments with such acid, and the several results 
 have enabled me to construct the following table; which, in 
 order that it might embrace every possible exigency, has been 
 extended to 192 degrees of Fahrenheit. 
 
 III. A Table of the Variations in the Specific Gravity of concentrated Sul- 
 phuric Acid, by change of Temperature. Barometer 29.5 inches. 
 
 Temperature 
 according to 
 Fahrenheit. 
 
 Contents in Grains 
 of a bottle holding 
 4266 grains of pure 
 water, at 42.5 deg. 
 of Fahrenheit. 
 
 Specific 
 Gravities. 
 
 Temperature 
 according to 
 Fahrenheit. 
 
 Contents in Grains 
 of a bottle holding 
 4266 grains of pure 
 water, at 42.5 deg. 
 of Fahrenheit. 
 
 Specific 
 Gravities. 
 
 10 
 
 8000 
 
 1.8752 
 
 80 
 
 7816 
 
 1.8381 
 
 20 
 
 7964 
 
 1.8668 
 
 84 
 
 7794 
 
 1.8343 
 
 24 
 
 7952 
 
 1.8640 
 
 88 
 
 7788 
 
 1.8346 
 
 27 
 
 7940 
 
 1.8612 
 
 92 
 
 7780 
 
 1.8349 
 
 30 
 
 7932 
 
 1.8593 
 
 96 
 
 7772 
 
 1.8343 
 
 32 
 
 7920 
 
 1.8565 
 
 102 
 
 7748 
 
 1.8308 
 
 36 
 
 7912 
 
 .8546 
 
 108 
 
 7729 
 
 .8280 
 
 38 
 
 7906 
 
 .8532 
 
 112 
 
 7750 
 
 .8267 
 
 40 
 
 7904 
 
 .8527 
 
 120 
 
 7710 
 
 .8270 
 
 42 
 
 7901 
 
 .8520 
 
 126 
 
 7702 
 
 .8277 
 
 44 
 
 7898 
 
 .8522 
 
 134 
 
 7692 
 
 .8279 
 
 46 
 
 7895 
 
 1.8519 
 
 140 
 
 7676 
 
 .8280 
 
 48 
 
 78.92 
 
 1.8517 
 
 146 
 
 7648 
 
 .8248 
 
 52 
 
 7886 
 
 1.8511 
 
 154 
 
 7632 
 
 .8258 
 
 56 
 
 7880 
 
 1.8501 
 
 162 
 
 7610 
 
 .8240 
 
 60 
 
 7864 
 
 1.8468 
 
 170 
 
 7582 
 
 .8225 
 
 63 
 
 7854 
 
 1.8449 
 
 178 
 
 7567 
 
 .8233 
 
 68 
 
 7846 
 
 1.8435 
 
 184 
 
 7558 
 
 .8247 
 
 70 
 
 7842 
 
 1.8430 
 
 192 
 
 7546 
 
 .8271 
 
 74 
 
 7833 
 
 1.8413 
 
 
 
 
 It must be understood, that in forming this table the low de- 
 grees of temperature were produced by immersing a vessel con- 
 taining the sulphuric acid in a frigorific mixture of snow and 
 
 1 The account of these experiments by Dr. Kirwan, may be seen in Nichol- 
 son's quarto Journal, vol. iii. page 211. 
 
ON SULPHURIC ACID. 235 
 
 muriate of soda ; and that the high temperatures were obtained 
 by gradually heating the specific-gravity-bottle, containing the 
 same acid, before a common fire. Some allowance must there- 
 fore be made for the contraction and expansion of the glass, and 
 which would, in some measure, alter the capacity of the contain- 
 ing vessel ; but this is unavoidable. In each experiment the acid 
 was poured from the phial, and thoroughly mixed, in order to be 
 sure that the temperature was uniform before the thermometer 
 was immersed in it. 
 
 From these experiments it appears that a vessel capable of 
 containing 8000 grains of concentrated sulphuric acid at 10 of 
 Fahrenheit, will not hold more than 754-6 grains of this acid if 
 at the temperature of 192, and that sulphuric acid which is of 
 the specific gravity of 1.8752 at 10, will become of the specific 
 gravity of 1.8271 when brought within 20 degrees of the tempe- 
 rature of boiling water. 
 
 It must, however, be remarked, that the chief design in con- 
 structing this table was to furnish the buyers and sellers of sul- 
 phuric acid with a scale by which they might ascertain the proper 
 specific gravity of this acid at all temperatures. For instance, 
 1.845 is well known to be the proper strength at the temperature 
 of 63"; but by the inspection of this table it will appear, that, 
 when the atmosphere has for some time been at the temperature 
 of 36, such acid must be deficient in strength if it does not reach 
 the specific gravity of 1.8546. 
 
 It has been ascertained that the maximum density of water is 
 at the temperature of 42 5, and that it becomes specifically 
 lighter, whether it be heated above or cooled below that point. 
 In making the foregoing table therefore, it was necessary in 
 the first place to fix the weight of the bottle of pure water at the 
 temperature of 42 5. This I found to be 4266 grains, and this 
 I made the divisor in every case from 10 up to 42 inclusive. 
 After this the weight of the water was taken at 44, and at every 
 other degree between that and 192; and in calculating the spe- 
 cific gravity of the sulphuric acid at 44, and at all the higher 
 temperatures, the weight of the acid in every instance was divided 
 by the weight of the same measure of water at the corresponding 
 temperature. This method of constructing the table (and I could 
 not devise any other that would not have presented still greater 
 difficulties) will perhaps account for several anomalies in the 
 specific gravities of the acid when heated above 84. For in- 
 stance, the acid at 96 appears to have the same relative weight 
 as at the temperature of 84; also the acid at 108 and at 140, 
 seems to have the same specific gravity. This irregularity may 
 be accounted for by supposing that sulphuric acid in its expan- 
 sion, observes a different law from that of pure water, which, in 
 
236 ON SULPHURIC ACID. 
 
 the formation of this table, as has been before noticed, was made 
 the divisor in every instance '. 
 
 Mr. Dal ton has remarked that " it is a mistaken notion, that 
 the common sulphuric acid of commerce is of the maximum 
 strength, though it is of the maximum density nearly. The fact 
 is, acid nearly of the maximum strength varies very little in its 
 specific gravity, by the addition or subtraction of a small quan- 
 tity of water. The specific gravity ought not therefore to be the 
 criterion of strength in acids above 70 per cent. ; the temperature 
 at which they boil is a much better criterion, because it admits 
 of a range of ] 2 or 15 for one per cent, of acid. Or the strength 
 may be found by determining what quantity of water must be 
 added to reduce the acid to some known strength, as that of the 
 glacial acid, of 1.78 specific gravity." 
 
 The subject must not be dismissed without adverting to the 
 USES of this acid. The USES of sulphuric acid are very nume- 
 rous. It is employed in large quantities, as has been already 
 mentioned, for preparing bleaching-powder ; by dyers for dis- 
 solving indigo, and for other purposes ; by calico-printers for 
 preparing sours ; and by the manufacturing and the philosophi- 
 cal chemist, as a test for lead and barytes, and for a great variety 
 of other purposes, some of which only can be enumerated. 
 
 The makers of the nitric and muriatic acids are large con- 
 sumers of sulphuric acid ; as also are the makers of sulphate of 
 zinc, sal-ammoniac, phosphate of soda, Glauber's and other salts; 
 as well as the manufacturers of Roman vitriol, Prussian blue, 
 and some other colours. 
 
 Sulphuric acid is likewise employed by some modern farmers 
 in the preparation of their seed-wheat, to prevent what is called 
 the smut; by manufacturers of the citric and tartaric acids, and 
 by the makers of glass to convert the muriate of potash, which is 
 one of their residuums, into sulphate of potash, an article which 
 has lately been used by them as a substitute for soda. It is also 
 consumed in large quantities by the manufacturers of tin-plate, 
 by brass-founders, button-makers, japanners and gilders ; to all 
 of whom this acid is become absolutely necessary for the removal 
 of the oxide which forms on the surface of the iron or the copper 
 on which they work, and which, if not removed, would prevent 
 or impede all their operations. 
 
 Sulphuric acid is likewise a necessary article to some paper- 
 makers, to fell-mongers, and to tanners; it is used in con- 
 siderable quantities by the modern hatter in the operation of 
 
 1 A new table of the expansion of water by increase of temperature, will be 
 given in the Essay on Water. 
 
ON SULPHURIC ACID. 237 
 
 felting 2; and it may be mentioned that refiners use it in the 
 process of stripping metals; oil-merchants, in refining rape-oil, 
 which it effects by carbonizing the farinaceous matter and the 
 mucilage; and brewers in fining what is called gray beer: 
 that the professors of pharmacy as well as the chemists are con- 
 stant customers for sulphuric acid ; that it is employed in 
 making the astringent and stomachic water of Rabel 3 , and for 
 other purposes of medicine as well as surgery; that distillers 
 and rectifiers of ardent spirits consume it in still larger quan- 
 tities ; and that many tons are annually consumed in the pre- 
 paration of liquid blacking. 
 
 It has occurred to me that it may be useful to be able to see 
 at one view what minerals and native salts there are which con- 
 tain sulphuric acid. I have therefore made out the following 
 list, omitting such as afford a trace only, or a very small quan- 
 tity of this acid. 
 
 Sulphate of ALUMINA, or native alum. This occurs on an 
 estate belonging to Mr. Mackintosh at Hurlet, near Paisley, and 
 as an incrustation on the alum-slate of Whitby in Yorkshire. It 
 is found also in Norway, in Bohemia, and in other places in 
 Europe, Africa, and America. There is another species found 
 at Hurlet, called Rock-butter, which is a native alum, mixed 
 with alumina and oxide of iron. A specimen which he calls 
 plumose alum, from Brandenburg, was analysed by Klaproth, 
 and found to consist of alumina 15.25, oxide of iron 7.50, potash 
 0.25, sulphuric acid and water of crystallization 77.0. 
 
 The specimens of alum-slate from Hurlet have the most beau- 
 tiful incrustations of plumose alum that can be conceived. 
 
 Alum-stone contains from 12 to 25 per cent, of sulphuric acid, 
 and the mineral called native argil or aluminite, 21 per cent of 
 this acid. 
 
 Mascagnine, or native sulphate of AMMONIA. This mineral 
 substance occurs among the products of Etna and Vesuvius, and 
 is also obtained from certain districts in Tuscany. Karsten 
 named it Mascagnine from its discoverer Professor Mascagni. 
 Its colours are yellowish-gray and lemon-yellow 4 . One hun- 
 dred parts, according to Kirwan 5 , contain ammonia 29.7, sul- 
 phuric acid 55.7, water 14.16. 
 
 Sulphate O/'BARYTES. This native production has already been 
 amply described at pages 122 and 147 of this volume. Some of 
 
 2 See an explanation of this in Essay I, page 21. 
 
 3 See Fourcroy's System of Chemistry, vol. viii. page 240. 
 
 4 Jameson, vol. ii. page 339. 
 
 5 Kirwan' s Mineralogy, vol. ii. page 10. 
 
238 
 
 ON SULPHURIC ACID. 
 
 the crystals of this mineral are extremely beautiful. According 
 to Withering, it is a compound of 32.8 sulphuric acid, and 
 67.2 barytes. A specimen from Berlin in Connecticut l was 
 found to consist of 
 
 Pure barytes . 
 Pure strontites 
 Sulphuric acid 
 
 57.33 
 
 3.92 
 
 33.50 
 
 Silica 2.50 
 
 Oxide of iron and alumina 1.75 
 Water .... . 1.00 
 
 The native sulphate of barytes of Europe is found to vary in 
 its composition according to the places from whence it is ob- 
 tained. 
 
 Cekstine, or native sulphate of STRONTITES. This mineral is 
 found at Inverness; in Yorkshire; and at other places in Great 
 Britain ; more particularly at Aust Passage in the neighbour- 
 hood of Bristol. Klaproth's analysis makes it to consist of 56 
 strontites, and 42 sulphuric acid. 
 
 Some very fine specimens of crystallized sulphate of strontites 
 have been procured from Strontian Island, Lake Erie, in the 
 United States of America 2 . 
 
 Sulphate of COBALT. This is a native salt which has been 
 found near Hanau in Germany. Its colour is a light flesh-red. 
 It has a very caustic taste, and is soluble in water. It is a com- 
 pound of sulphuric acid 19.74 + oxide of cobalt 38. 7 1 -f water 
 41.55 = 100 sulphate of cobalt. This analysis was made by 
 M. Kopp, an account of which was published by Bucholz, with 
 the analysis of other minerals 3 . 
 
 Sulphate of COPPER, or native blue vitriol. This mineral 
 occurs in Pary's mine in the Isle of Anglesea ; in the county of 
 Wicklow in Ireland; and also in many other of the copper 
 mines of Europe. Its colour is dark sky-blue. According to 
 Berzelius it is composed of oxide of copper 32.13 sulphuric acid 
 31.57 water 36.30 = 100 sulphate of copper. 
 
 Glauberite. This mineral is found imbedded in rock-salt at 
 Villaruba, near Ocana in New Castile, in Spain. It was first 
 analysed by Brongniart 4 . He found it to be composed of sul- 
 phate of lime 49, and sulphate of soda 51. 
 
 Pitchy IRON Ore, or the pitchy bog-iron ore of Aikin. This 
 mineral occurs in a mine near Freyberg, and in the district of 
 Plessin Upper Silesia. Klaproth has analysed it, and found it to 
 consist of 5 oxide of iron 67, and sulphuric acid and water 33. 
 
 1 American Journal of Science, vol. iv. page 327- 
 
 2 Silliman's Journal, vol. iv. page 279. 
 
 3 Annales de Chimie, vol. Ixx. page 55. 
 
 4 Jameson, vol. ii. page 255. 
 
 * Phillips's Elements, page 209. 
 
ON SULPHURIC ACID. 239 
 
 IRON vitriol, or native sulphate of iron, occurs under a 
 variety of forms in several coal-mines in this country and on the 
 continent of Europe. A specimen of native sulphate of iron was 
 analysed by Berzelius, and found to consist of oxide of iron 25.7, 
 sulphuric acid 28.9, and water of crystallization 45 4. 
 
 LEAD vitriol, or native sulphate of lead, occurs at Penzance in 
 Cornwall, at Pary's mine in the Isle of Anglesea, and at Lead- 
 hills in Scotland. It is found also in Siberia and in the United 
 States of America. A specimen from the Lead-hills was found 
 by Klaproth 6 to consist of oxide of lead 70.50, sulphuric acid 
 25.75, and water of crystallization 2.25. 
 
 Sulphate O/"LIME is a mineral that is procured in great abun- 
 dance at Chelaston near Derby, and at Beacon-hill near Newark. 
 It is a compound of 32 lime, 30 of sulphuric acid, and 38 water. 
 It is found also in various parts of North America, where it is 
 employed as a manure. The Anhydrite, or Muriacit of Werner, 
 contains a still larger portion of sulphuric acid. A specimen 
 analysed by Klaproth was found to consist of 
 
 Sulphuric acid .... 56.50 1 Muriate of soda . . . 0.25 
 Lime 42.00 ] Loss ....... 1.25 
 
 It occurs in beds in the salt-mines of Austria ; in granular 
 gypsum near Brunswick ; and has sometimes been met with in 
 the gypsum of Nottinghamshire 7 . 
 
 Sulphate of MAGNESIA, is commonly found in spring water; it 
 occurs at Hurlet near Paisley in connexion with native alum, 
 and at various places on the continent of Europe, especially in 
 the quicksilver mines of Idria; in the province of Andalusia in 
 Spain ; and in Bohemia. According to Kirwan, its constituent 
 parts are sulphuric acid 29.46, magnesia 17, water of crystalliza- 
 tion 53.54. In a cave in the Indiana territory in Kentucky, it is 
 found perfectly crystallized in delicate white prisms, and in 
 such abundance that the inhabitants carry it away by the wag- 
 gon-load 8 . 
 
 Corneous MERCURY, or horn quicksilver, occurs in most of 
 the quicksilver mines. Its constituent parts, according to Kla- 
 proth, are oxide of mercury 76.0, muriatic acid 16.40, sulphuric 
 acid 7.60. 
 
 Egyptian NATRON. This natural production is found in con- 
 siderable quantity at the town of Nitria and other parts of Egypt. 
 Klaproth analysed it, and found it to consist of 
 
 Subcarbonate of soda . . 32.6 I Muriate of soda . . . . 15.0 
 Sulphate of soda . . . 20.8 ( Water 31.6 
 
 6 Klaproth's Analytical Essays, vol. ii. page 129. 
 
 7 Jameson, vol. ii. page 248. 
 
 8 American Journal of Science, vol. i. page 49. 
 
240 ON SULPHURIC ACID. 
 
 Native NITRE. This production of Nature occurs in every 
 quarter of the globe. The natural nitre of Molfetta in the king- 
 dom of Naples consists, according to Klaproth, of 
 
 Nitrate of potash . . . 42.55 I Carbonate of lime . . . 30.40 
 Sulphate of lime . . . 25.45 | Muriate of potash and loss 1.60 
 
 Reussite occurs as an efflorescence in the country around 
 Sedlitz, and is also found crystallized in flat six-sided prisms, 
 and in aggregated acicular crystals. It appears to consist of 
 
 Sulphate of soda . . . 66.04 I Muriate of magnesia . . 2.19 
 Sulphate of magnesia . . 31.35 Sulphate of lime . . . 0.42 
 
 Sassoline. This is a natural production found on the edges of 
 some hot springs near Sasso, a town in the territory of Florence. 
 Its constituent parts are boracic acid 86, and sulphate of mag- 
 nesia and lime 14. 
 
 RED SILVER ore. A specimen of this mineral, found near 
 Freiberg, was analysed by Klaproth, and found to consist of 
 
 Silver 62.0 [ Sulphur 11.0 
 
 Reguline antimony . . . 18.5 | Concrete sulphuric acid . 8.5 
 
 Sulphate of SODA, or native Glauber's salt, occurs at Eger in 
 Bohemia, efflorescent on meadow ground ; on the banks of many 
 salt lakes in Siberia and in Egypt. It is found also on the walls 
 of old buildings, and sometimes on those of new buildings in 
 many parts of the world. It is found in small proportion in sea- 
 water; but according to the analysis of the waters of the several 
 spas at Cheltenham by Professor Brande and myself, they contain 
 from 10 to 23.5 grains of this salt in a wine-pint of the water ! . 
 
 A specimen of native sulphate of soda from Eger was found to 
 consist of 
 
 Sulphate of soda . . . 67.024 I Muriate of soda . . . 11.000 
 Carbonate of soda . . 16.333 | Carbonate of lime . . 5.643 
 
 Native SULPHURIC- ACID has been mentioned already in a note 
 at page 212. I learn from Professor Brande, that it was disco- 
 vered by Baldassari in the cavities of a small volcanic hill called 
 Zoccolino, near Sienna 2 . Sulphuric acid is found in considerable 
 quantity in urine, though it does not exist in the blood. The 
 elder Rouelle showed this long ago; and Berzelius asserts that he 
 believes it to be an essential constituent of the urine. 
 
 White vitriol, or native sulphate of ZINC, is found at Holy well 
 in Flintshire, and in other parts of Europe. A specimen analysed 
 by Klaproth afforded 
 
 Oxide of zinc .... 27-5 | Sulphuric acid .... 22.0 
 Oxide of manganese . . 0.5 | Water 50.0 
 
 1 Journal of Science, fyc. vol. iii. page 54 72. 
 Brande' s Manual of Chemistry ,vo\. i. page 396. 
 
ON SULPHURIC ACID. 241 
 
 The law which governs the formation of the sulphuric salts is 
 this : In the neutral sulphates, the proportion of oxygen in the 
 acid is to that of the base as 3 to 1. Thus, sulphate of soda is a 
 compound of 1 proportional of soda 32, containing 8 of oxygen, 
 and 1 proportional of sulphuric acid 40, containing 3 propor- 
 tions = 24 of oxygen. If the composition of any of the other 
 neutral sulphates be examined, they will be found to be formed 
 in the same manner. 
 
 Since the above Essay was written, and indeed I may even add 
 since the death of its author, so many and so important have been 
 the improvements in the manufacture of sulphuric acid, that the 
 system as accurately and minutely described by him has in many 
 respects become exploded, and quite a new plan of burning the 
 sulphur used in its stead. It would take too much room to detail 
 the course of the various improvements which have been progres- 
 sively adopted, and to describe their imperfections and the dif- 
 ferent methods which manufacturers have had recourse to for 
 their remedy. I will only attempt to give a brief outline of the 
 plan, which appears to me the best, of the utensils employed, and 
 the methods of manipulation, without at all entering into the 
 endless variations which occur in different works. 
 
 The chamber itself has not undergone many alterations, but 
 the most important one is in its height. Those which have been 
 latterly erected, only 6 feet high, are found to answer in every re- 
 spect as well, and to give as good a produce, as those built upon 
 the old plan, 12 to 16 feet high. The water-lute, too, is discon- 
 tinued. The present chamber is an immense leaden room 60 to 80 
 feet long, 10 to 14 feet broad, and 6 to 8 feet high, the floor 
 being formed of sheets of lead soldered together with very coarse 
 solder (that is, containing much less tin than usual, or it would be 
 acted on by the acid), and laid flat upon planks. The sides are 
 hung by leaden fillets to upright pieces of timber, and are soldered 
 carefully together ; across the top other timbers are laid, to 
 which the lead beneath is attached by small straps soldered fast 
 to the sheets and passed over the wood. 
 
 A great advantage arising from the chamber being so much 
 reduced in height is, that it may, instead of being placed on the 
 ground, be supported on timbers 6 or 7 feet from the surface ; by 
 which three objects are effected. 1st, It takes no room, as the 
 space beneath may all be employed for the purposes of the manu- 
 factory. 2nd, Any flaw in the bottom or leakage may be easily 
 got at and repaired. 3rd, The acid may be conveyed by leaden 
 pipes or spouts to the boilers, or to any part of the manufactory 
 
242 ON SULPHURIC ACID. 
 
 where it is required, without the labour of putting it in bottles and 
 carrying it. 
 
 I must now proceed to what is by far the most important part 
 of the process, the burning of the sulphur; and before entering 
 upon it in its most improved form, (the result of numerous and 
 long-continued experiments of my own, combined with all the 
 information I have been able to obtain from others,) it will be well 
 first to state the objections to the old system so long pursued, 
 and even now not universally abandoned. 
 
 It has been seen that atmospheric air and vapour are essential 
 requisites in the chamber, and that without them no sulphuric 
 acid can be formed. The former was attained by throwing open 
 all the doors every four hours as already described, by which im- 
 mense waste of the gases was caused, amounting to one-third of 
 the produce from a given quantity of sulphur; and the latter was 
 produced by the heat of eight or ten fires within the house, causing 
 an evaporation from the surface of the water : this varied with 
 the different seasons of the year, and the house worked ill or well 
 accordingly ; besides which, the labour of charging and taking out 
 the ashes six times during every 24 hours was great ; and clean- 
 sing the house by opening the doors was not only suffocating to 
 the operator, but filled the neighbourhood with gases destructive 
 to vegetation and unbearably offensive to the smell. 
 
 These inconveniences and losses gave rise to many plans for 
 burning the sulphur and nitre in separate ovens outside of the 
 house, and conducting the gas to it by pipes. 
 
 The great cause of the total failure of many of these, and the ill 
 operation of all, was, that sulphur burnt without sufficient access 
 of atmospheric air, or at too great a heat, instead of becoming 
 sulphurous gas, sublimes, and when condensed is still sulphur 
 unaltered as to any of its chemical properties. 
 
 To prevent the sublimation of a portion greater or less of the 
 sulphur consumed in these furnaces was found almost imprac- 
 ticable, from which two serious inconveniences accrued. The 
 first is obvious, the loss of the sulphur, which, instead of forming 
 sulphuric acid, lies useless, adhering to the sides of the chamber: 
 but it is worse than useless; for when the acid is put into the leaden 
 vessel before described, to be evaporated to a proper strength, 
 and has attained a certain degree of heat, the sulphur floating on 
 its surface robs it of part of its oxygen, converting both the sul- 
 phur and the sulphuric acid the one by the addition, and the 
 other by the loss of oxygen into sulphurous acid gas, which flies 
 away; the sublimed sulphur thus not merely wasting itself, but 
 also part of the acid already formed. 
 
 I will now describe the apparatus which I have found most 
 efficacious, not only to obviate these defects, but also to produce 
 
ON SULPHURIC ACID. 243 
 
 the greatest quantity of acid which I have ever succeeded in ob- 
 taining, viz. 2|lbs of concentrated sulphuric acid, sp. gr. 1.848, 
 from iJb of sulphur, with its proper proportion of saltpetre. 
 
 The chamber having been already described, we will proceed 
 with the furnace and its appendages. 
 
 The furnace is a round oven built of fire bricks about 4- or 5 
 feet in diameter, and the floor 2 feet from the ground; the roof 
 is a brick arch, the crown of which rises at most 2 feet from the 
 floor. 
 
 Iron plates are more generally used for both the floor and the 
 top instead of a brick arch ; but I find one constructed of brick 
 so much cooler, that I give it a decided preference; as on iron 
 the sulphur is apt to melt and run instead of burning away. The 
 door is merely an aperture left in the front of the brick-work 
 large enough to admit the workman's shovel, about 15 inches 
 high and 10 inches broad. Into this a plate of sheet-iron is 
 closely fitted, which having a handle is taken off at pleasure; in 
 this plate a hole of 6 inches diameter is cut, before which a thin 
 piece of tin plate is made to slide backwards and forwards, so 
 that the precise quantity of atmospheric air required may be 
 admitted. 
 
 Through the roof an iron pipe of 12 inches diameter is carried, 
 and a large leaden vessel about 5 feet square and 2 feet high is 
 placed flat on the top of the furnace ; within this vessel another 
 vessel not so high, so broad, or so long, by six inches each way, 
 is placed bottom upwards, and soldered down to the bottom of 
 the longer one, so that all communication between the two is 
 effectually cut off; consequently as the pipe from the furnace 
 passes through the bottom of the larger vessel into the small 
 one, the fumes are confined within the latter; and the large vessel 
 being completely filled with water, the small one is entirely im- 
 mersed in that fluid, top and all four sides. From one end an- 
 other smaller pipe conveys the fumes into the chamber ; and as 4 
 inches of water are always kept on the bottom of the vessel, part 
 of the gas is actually condensed and sulphuric acid formed, and 
 the remainder thoroughly cooled by being passed through the 
 water vessel, before it arrives in the chamber. 
 
 The apparatus being prepared, we will now proceed to charge 
 the furnace. Crude sulphur is taken, coarsely ground, made into 
 a paste with water, and as little pipe-clay or plaster of Paris 
 added as is absolutely necessary to give it a consistency; an 
 eighth or tenth is sufficient. This mass is with a common shovel 
 cut up into cakes of the form of a large brick, about 20lbs each, 
 which are put upon a shelf on the top of the furnace to dry just 
 enough to prevent their falling to pieces, when they are removed, 
 as the damper they are when used the better, 
 
 R2 
 
244- ON SULPHURIC ACID. 
 
 Four or five of these (according to the size of your chamber 
 or chambers) are now put into the centre of the furnace, standing 
 on their ends; and immediately over them on a light stand is a 
 small iron dish containing saltpetre in the proportion of one-tenth 
 of the sulphur used, with enough sulphuric acid to decompose it. 
 A hot iron or cinder is now applied to the cakes, which imme- 
 diately ignite; and if proper care has been taken in the admission 
 of atmospheric air, they require no further attention for many 
 hours, but burn gently away, leaving nothing in the furnace but 
 the pipe-clay and any impurities contained in the sulphur. The 
 dish above is worked off on the principle of an aquafortis pot, 
 the nitrous fumes having passed off' and left sulphate of potash 
 as a residuum. By these means the heat caused by burning the 
 saltpetre mixed with the brimstone is avoided, and the gases as 
 above described, being passed through water and over water, 
 attain the chamber in the requisite state for quick condensation. 
 As the water above is formed into sulphuric acid, it flows through a 
 waste pipe into the chamber, and fresh water is constantly sup- 
 plied by a small hole in the top of the vessel, which it will be 
 remembered is always covered with water. 
 
 Although by these precautions the requisite supply of atmo- 
 spheric air may be kept up and regulated, still the proper degree 
 of vapour within the chamber is not insured ; and accordingly 
 most manufacturers now throw in steam from a boiler in such 
 proportions as to supply all the water required : so that instead 
 of commencing as formerly with water and making it stronger 
 and stronger till of the strength required, then drawing it all off 
 and re-commencing with water, if proper precaution be taken to 
 throw in exactly the quantity of vapour required by the sulphur 
 consumed, your acid may be kept at one uniform strength, and 
 drawn off as required for the boilers or for the purposes of your 
 manufactory. 
 
 To ascertain that your chamber is going on well, three little 
 contrivances are requisite. 1st, A leaden shelf fixed to the outside 
 of the house just large enough for a glass containing a hydrometer 
 to stand upon, with a waste pipe to carry back into the chamber 
 the fluid as it flows over. Over this glass hangs a small pipe 3 
 or 4 inches long, passing through the side of the chamber, in the 
 interior of which a bit of lead should be soldered to stop the liquor 
 as it runs down the side of the house, and cause it to pass through 
 this pipe, falling drop by drop into the glass in which the hydro- 
 meter stands. This constantly going on, the rising or falling of 
 the hydrometer of course denotes the increase or decrease of the 
 strength at which the chamber is making: but this is not sufficient; 
 as, supposing your men were to stop the steam from entering, and 
 neglect the sulphur furnace, no decrease of strength would take 
 
ON SULPHURIC ACID. 245 
 
 place, but there would be no increase of quantity. To ascertain 
 the latter, a simple plan suffices. Let an open-topped leaden cistern 
 6 inches square be attached to the bottom of the chamber with a 
 free communication, and in this place a tube open at both ends, but 
 at one decreasing almost to a point; the tube should be graduated 
 in eighths of inches: by dipping the small end to the bottom of the 
 cistern, and when filled applying your thumb closely to the top, 
 and then withdrawing the tube from the vessel, you see at once 
 the exact depth, and what it has increased in quantity since you 
 last tried it. You may thus know its strength and quantity at any 
 time, as the former merely requires looking at, and the latter only 
 taking a tube in your hand ; so that no alterations in the working 
 of your chamber, however slight, can take place without being 
 instantly perceived. 
 
 The third simple but very useful instrument is called the sub- 
 liming rod. It is merely a round bar of lead passed through a 
 hole in the side of the chamber, so that about two feet are within 
 the chamber and one without for a handle. It is kept steady by 
 being passed through a thick piece of lead attached to the side, 
 which it exactly fits. By withdrawing this rod at any time, the 
 way in which the chamber is working will be evident ; as if there 
 is the slightest sublimation, the flowers of sulphur will be visible 
 upon it ; but if it is wet, and the acid hanging upon it in drops, we 
 may conclude that all is going on well. 
 
 The next thing to attend to is the method of getting rid of the 
 incondensable gases without waste, as it will be recollected we 
 have no doors as formerly to throw open and to clear out alto- 
 gether. 
 
 A vessel is carried outside the whole length of the house, or 
 still better if all round the house, 18 inches broad and 6 inches 
 deep: another vessel not quite so broad, but 18 inches high, is 
 turned bottom upwards and placed in the small one, which is filled 
 with water to the depth of 3 inches. This is called a water-lute, 
 and is the principle on which all the chambers were formerly 
 built ; it will easily be seen that the water effectually prevents any 
 escape of gas. One end of the upper vessel is connected by a 
 pipe to that part of the top of the chamber which is furthest from 
 the furnace, and to the other end of this water-lute is a waste pipe 
 connected with a high brick chimney, generally the one belong- 
 ing to your steam boiler. 
 
 In this latter pipe is fixed a valve to regulate the draught and 
 prevent the escape of sulphurous gas, which would happen if it 
 were too quick. Thus the whole apparatus is kept in motion ; 
 the suction of this chimney (if I may be allowed rather an un- 
 philosophical mode of expression) causes a draught through the 
 water-lute and the chamber all the way back to the furnace: 
 
246 ON SULPHURIC ACID. 
 
 another and still greater cause of draught is that which the vacuum 
 in the chamber itself, caused by the condensation of the gases 
 within it, produces. 
 
 This draught once existing, atmospheric air constantly rushes 
 into the furnace; the gases then pass with it through the cooling 
 cisterns into the chamber; there nine-tenths are condensed; the 
 remainder before they can escape have to travel through perhaps 
 300 feet of water-lute, condensing as they go; and by the time they 
 arrive at the chimney it may be presumed that little is left but 
 the azote and other useless incondensable gases. The acid formed 
 in the water-lute flows into the house through waste pipes placed 
 there for the purpose. 
 
 Thus I have described briefly, but I fear obscurely, what I 
 consider the best system now in use for making sulphuric acid 
 of the strength it is in the chamber. A pipe from the bottom con- 
 veys it either to those parts of the manufactory where it is con- 
 sumed in this weak state for bleaching powder, muriatic acid, &c. 
 or leads it into the leaden boiler, where it is evaporated, as already 
 described by Mr. Parkes, to as high a strength as lead is capable 
 of allowing. It is then finished in open-necked glass retorts, 
 on sand heats, with a separate fire under each. By putting a 
 few strips of platinum into every retort, the jerks and spoutings 
 of the acid, which frequently break the glass, are prevented ; 
 and by the simple contrivance of a sheet-iron cap over the top 
 of each, the danger arising from draughts of cold air is avoided; 
 and a manufacturer with whom I am acquainted lessened his 
 yearly breakages nearly three-fourths by this one addition. The 
 acid lies in the retorts till a little cooled, and each retort is then 
 lifted out, and the contents emptied into a carboy previously 
 warmed to receive them. But by some makers a much better 
 system has been introduced, by which the extreme danger of this 
 frightful task is avoided, a task in the execution of which, men 
 have been so severely wounded by the bursting of the retorts con- 
 taining the hot acid, as to be confined to their beds for many 
 months with inveterate scalds. This improvement is to extract 
 the acid from the retort standing in its sand heat by means of a 
 syphon with a cock at one end. By a [little management in not 
 quite emptying each retort, but leaving in about half an inch of 
 acid, the syphon never empties, but may be carried round to fifty 
 retorts without requiring refilling. 
 
 All the monstrous expense of coals, breakage of glasses, labour, 
 and personal danger, is now avoided in large manufactories by 
 the use of platinum vessels instead of glass. The only objection 
 is the enormous first cost. Mr. Pariss, of Battersea, has lately 
 erected one, capable of concentrating 20 carboys per diem, which 
 cost him 1 200 guineas : it is perhaps the most complete one 
 
ON SULPHURIC ACID. 24-7 
 
 that has been made ; and allowing amply for wear, tear, and in- 
 terest of money upon it, he finds that it is a saving to him of 
 several hundreds per annum. Mr. Parkes found a leaden cover 
 to answer equally well with one of platinum ; and if this alteration 
 were adopted, I believe that half the sum I have specified would 
 suffice to erect one capable of doing as much work and as well. 
 A platinum vessel also gives you the opportunity of throwing 
 back into your chamber the gases which arise from the boiling 
 liquor, and the sulphuric acid which distills over during the latter 
 partof the operation; by which, not merely a saving is effected, 
 but the intolerable nuisance which those gases are to the sur- 
 rounding neighbourhood is entirely avoided. And I think it is a 
 general rule which admits but few exceptions, that in proportion 
 to the smells and annoyance arising out of any chemical manu- 
 factory, are the waste, mismanagement and inattention within its 
 walls. 
 
248 ON CITRIC 'ACID. 
 
 ESSAY VIII. 
 
 ON CITRIC ACID. 
 
 The Median fields rich citron fruits produce, 
 Though harsh the taste, and clammy be the juice ; 
 Blest antidote ! which, when in evil hour 
 The stepdame mixes herbs of poisonous power, 
 And crowns the bowl with many a muttered spell, 
 Will from the veins the direful draught expell. 
 Large is the trunk, and laurel-like its frame, 
 And 'twere a laurel were its scent the same ; 
 Its lasting leaf each roaring blast defies, 
 Tenacious of the stem, its flowrets rise : 
 Hence a more wholesome breath the Medes receive, 
 And of their Sires the lab'ring lungs relieve. 
 
 WARTON'S Translation of VIRGIL'S Georgics. 
 
 1 HERE is a peculiar acid in the juice of lemons, citrons, limes, 
 and a variety of other fruits, different in some of its properties 
 from all others, and known to chemists by the name of the 
 CITRIC ACID. 
 
 It does not appear that the ancients set any value on the juice 
 of these fruits, except as an antidote against poison, or that they 
 ever employed it in considerable quantities for any purpose what- 
 ever; though from some lines in Virgil's Georgics, part of which 
 I have taken as a motto for this Essay, it is evident they had a 
 high opinion of its virtues in counteracting the effects of some 
 deleterious drugs or vegetables. 
 
 As lemon juice can be procured with advantage only at one 
 season of the year, and is apt, whatever care may have been taken 
 with it, to spoil in keeping, on account of the sugar, the water, 
 the extractive matter, and the mucilage which it contains, all of 
 which tend to throw it into a state of fermentation, it became an 
 object to chemists to divest it of these imperfections, and thus to 
 procure the real acid of the fruit in a state of perfect purity. 
 
 Scheele and other practical men attempted to separate these 
 matters by means of alcohol: but this intermedium effects the 
 desired purpose very imperfectly ; for though it will divide the 
 mucilage, it has not the power of separating the extractive matter 
 or the sugar. 
 
 In the year 1774, M. Georgius, a Swedish chemist, published 
 in the Stockholm Memoirs a process for separating the mucilage 
 and concentrating the acid, by keeping the lemon juice for some 
 
ON CFTR1C ACID. 249 
 
 time in a cool place in inverted bottles, and then exposing it to 
 cold at some few degrees below the freezing point ; and in this 
 way separating the water, which, with the remaining mucilao-e, 
 freezes; and this frozen portion is directed to be repeatedly re- 
 moved. The liquor is then submitted again and again to the 
 action of the frost, till it is reduced to one-eighth of its original 
 quantity. By this management none of the acid is lost ; and when 
 it is thus concentrated, it may be kept for many years without 
 sustaining any injury. 
 
 On this process, to which there is little objection except the 
 time required for its completion, and that it can be effected only 
 at one season of the year, it is necessary to remark, that care 
 should be taken not to expose the juice to a degree of cold too 
 intense, lest part of the acid also be congealed with the aqueous 
 portion, and thus defeat the intention. Whereas, if it be sub- 
 mitted to the action of the frost when the thermometer is between 
 28 and 32, and the ice be carefully removed as it forms, the 
 juice may be reduced to an eighth part of its former bulk, and 
 consequently increased in strength, because the remaining eighth 
 will really be equal in its saturating power to the whole of the 
 original acid. 
 
 This process will answer very well for domestic purposes, and 
 the concentrated acid may be long preserved by mixing it with 
 7 or 8 times its weight of refined sugar in powder : but it affords 
 no assistance in furnishing the concrete citric acid ; for, after the 
 juice has been thus condensed, still enough of the extractive mat- 
 ter will remain in it to prevent the crystallization of the acid. 
 
 After the publication of this paper by Georgius, a Mons. Du 
 Buisson of Paris announced another method of concentrating and 
 preserving lemon juice. This consisted in reducing its quantity 
 by the action of a gradual heat kept up for a considerable time, 
 which has the effect of thickening the mucilaginous matter, and 
 occasioning its separation in a glutinous mass on the surface of 
 the liquor. When this is removed, the remaining juice may be 
 preserved a long time unaltered. 
 
 Both these proposals may be viewed as approximations towards 
 the development of the true method of purification, which was 
 reserved for that enterprising and renowned Swedish chemist, 
 who has immortalized his name by discoveries of far greater im- 
 portance than that which is now under consideration. 
 
 The ingenious Scheele was the first who exhibited this acid in 
 a solid form ; and to accomplish this end, he adopted merely the 
 same method which he had employed long before in the purifi- 
 cation and crystallization of the tartaric acid. 
 
 It consists in separating the real acid by means of carbonate of 
 lime, and then decomposing the citrate of lime by the interme- 
 
250 ON CITRIC ACID. 
 
 dium of diluted sulphuric acid ; a process which has been uni- 
 versally adopted throughout Europe ; there being no other means 
 yet discovered of putting this acid into a crystalline form. 
 
 Having myself had some experience in this process by fre- 
 quently superintending its progress, and more than once to the 
 extent of several hogsheads of juice in one operation, I shalJ now, 
 with some confidence in their correctness, proceed to give what 
 appear to me to be the best directions for obtaining a successful 
 and economical result. 
 
 The juice, which is imported in pipes and hogsheads, should 
 be drawn off into a large open vessel; a square vat made of fir 
 is very proper for the purpose. In this vessel the juice is to be 
 saturated with lime, by the gradual addition of clean soft chalk, 
 or whiting. Care must be taken to note down the quantity of 
 carbonate of lime employed, which should be added till it occa- 
 sions no further effervescence, and until the liquor shows no 
 signs of acidity on test paper. 
 
 I have said that the chalk should be added very gradually, 
 because otherwise the effervescence, by the disengagement of 
 carbonic acid, will be so considerable as to occasion a great part 
 of the contents of the vat to flow over and be lost. 
 
 If the cask containing the juice be rolled near to the vat, a 
 small copper hand-pump may be put in at the bung-hole ; and 
 while one man is slowly pumping it into the vat, another should 
 not cease to agitate the whiting; and whenever there is any 
 danger of the mixture rising too high in the vessel, the operators 
 will have only to rest a moment, arid all will be safe. In this 
 way the saturation will be complete, and it will be done in the 
 least possible time. 
 
 In this process all the real acid of the lemon juice is absorbed 
 by the calcareous earth ; and when the combination is completely 
 formed, the citrate, of lime, which is an insoluble salt, precipitates 
 to the bottom of the vessel. When the whole of this has fallen, 
 the supernatant liquor, which will be nearly tasteless, will be 
 found to contain nothing besides the mucilage, except a portion 
 of the essential oil of the rind of the fruit, some extractive and 
 saccharine matter, and a little malic acid. This supernatant 
 liquor is therefore to be drawn off; and the precipitate preserved 
 for use. 
 
 If it be desirable for any part or the whole of the malic acid 
 to be saved, it may readily be distinguished from the citric by 
 the following properties : The malic acid does not crystallize ; it 
 precipitates silver, mercury, and lead, from their solutions in ni- 
 tric acid, while citric acid has no such effect; and it forms a 
 soluble salt when combined with lime. 
 
ON CITRIC ACID. 251 
 
 It is usual, as I have seen in some of these establishments, to 
 have plugs in the side of the vat, and at different heights, for the 
 purpose of drawing off the supernatant liquor: but a syphon 
 with a stop-cock is much more convenient; for with it the liquor 
 may at any time be drawn off perfectly close, and the danger 
 from a plug flying out be avoided. 
 
 When the supernatant liquor is removed by a syphon or other- 
 wise, the precipitate, or citrate of lime, is to be passed through a 
 sieve, and then frequently washed with warm water, until all the 
 remaining mucilage and other soluble impurities be entirely 
 washed off; which will be known, when the whole has remained 
 at rest for some time, by the water coming off clear and tasteless. 
 
 The precipitate, having been thus well washed, let it be treated 
 with diluted sulphuric acid in the following manner : For every 
 ten pounds of chalk or whiting, which has been employed in the 
 process, it is necessary to take the quantity of nine pounds and 
 a half of sulphuric acid of the specific gravity of 1.84- or 1.845, 
 which is to be diluted with about seven gallons, or fifty-six 
 pounds of water. 
 
 The diluted sulphuric acid is to be poured gradually upon the 
 citrate of lime, and the whole mixture well stirred, for a conside- 
 rable time, with a strong wooden spatula, that there may be no 
 chance of any of the citrate remaining unbroken, and conse- 
 quently unacted upon by the stronger acid. 
 
 In conducting this part of the process, I have noticed an ap- 
 pearance worth mentioning, which is this: It being necessary 
 to stir up the mass very frequently during the gradual addition 
 of the sulphuric acid, I have observed that whenever the citrate 
 of lime became nearly all decomposed, and the earth mostly 
 saturated with sulphuric acid, the sulphate of lime precipitates 
 quicker and quicker after every addition of this acid, and that 
 the supernatant liquor considerably increases in quantity. The 
 latter circumstance is occasioned by the increased density of the 
 precipitate ; and both appearances should always be looked for, 
 as they afford a good criterion for judging of the progress of the 
 operation. 
 
 It is, however, proper to remark, that it would not be prudent 
 for the operator to rely solely on these appearances ; for, if he is 
 to ensure the best possible management of the process, he must 
 have recourse to the agency of chemical tests, as they will -afford 
 the only sure criterion by which the real state of the saturation 
 of the lime can be known. 
 
 In many chemical operations, preparations of barytes, or a 
 simple solution of this earth in water, are employed to detect the 
 presence of sulphuric acid. But as citrate of barytes would im- 
 mediately precipitate on the addition of barytic water to a solu- 
 
252 ON CITRIC ACID. 
 
 tion of citric acid, this reagent cannot be conveniently employed to 
 show when the exact quantity of sulphuric acid has been used. 
 
 Whenever the saturation of the citrate of lime is nearly com- 
 pleted, and the operator is fearful of supersaturating it, all that 
 is necessary is to take out a little of the clear liquor, after the 
 precipitate has subsided, to filtrate this liquor through paper, 
 and then treat it with a few drops of acetate of lead. In this 
 instance a citrate of lead will be formed, and precipitate, which 
 precipitate will be immediately redissolved on the addition of a 
 little of the nitric acid. On the contrary, should too much sul- 
 phuric acid have been used, there will be a mixed precipitate of 
 citrate of lead and sulphate of lead ; and the latter of these salts 
 not being soluble in nitric acid, leads to the detection of an ex- 
 cess of the decomposing acid. 
 
 But to return to the process. The consequence of this affusion 
 of the citrate of lime with sulphuric acid is this, the sulphuric 
 acid having a more powerful affinity with the lime, it combines 
 with that earth immediately as it is poured upon the washed 
 pulp of citrate of lime, and by this action it displaces the citric 
 acid, which will then be found in the supernatant fluid. 
 
 The insoluble part of the mixture is now sulphate of lime; and 
 when sufficient time has been allowed for the whole of this to 
 precipitate, the fluid, which is the pure citric acid in a state of 
 solution, may be drawn off for use. 
 
 In order, however, to procure the whole of the citric acid, 
 more water must be poured on the sulphate of lime, and this 
 washing repeated time after time, until the last portion of water 
 comes off clear and tasteless. 
 
 In opposition to some directions which I have seen, I would 
 advise that cold water be employed for these washings, as it will 
 separate the fluid citric acid from the precipitate, equally well 
 with hot water, and will dissolve less of the sulphate of lime, 
 which is a substance very unfavourable to the process of crystal- 
 lization. 
 
 The whole of these washings are to be put together, and the 
 mixed liquor is afterwards to be concentrated by evaporation, 
 which is performed in leaden vessels cased with wood, with a coil 
 of pipe covering the bottom, connected at one end with your steam 
 boiler, and the other having a small cock to let off the condensed 
 water. By these means a great saving of fuel is effected, and no 
 danger need be apprehended of decomposing the acid by too 
 great a heat, which was frequently the case when it was boiled 
 down over a naked fire. When these larger boilers have brought 
 the liquor into about one-eighth of its bulk, their contents are 
 transferred into one of a smaller size, and they are again filled 
 with weak acid washed from the sulphate of lime. 
 
ON CITRIC ACID. 253 
 
 In this last vessel the liquor is to be further evaporated until 
 it acquire the consistence of very thin molasses, and then it 
 should be watched with the greatest attention for the appearance 
 of the pellicle, which may now be expected to rise on the surface. 
 This pellicle will first show itself in small detached spots, and 
 these, by degrees, will increase in size and number until the 
 whole of the liquor is nearly covered with them. The concen- 
 trated citric acid should then be immediately taken out of the 
 bath, and laid aside in other shallow leaden vessels to cool and 
 crystallize. 
 
 It is of the utmost consequence to attend to this circumstance; 
 for so much of the fluid is evaporated before the pellicle appears, 
 that, if it were to remain in the concentrating vessel half an hour 
 longer, the whole might be carbonized and reduced to a useless 
 and inert mass. 
 
 When removed, it should remain undisturbed for three or four 
 days, that the largest possible quantity of crystals may be ob- 
 tained from the liquor. After this time has elapsed, the mother- 
 water may be drained from the crystals; because, after that 
 period, it will be in vain to expect a further increase without a- 
 further abstraction of water by a fresh evaporation. 
 
 It is likewise proper to remark that, however carefully the 
 process may have been conducted, the whole of the calcareous 
 earth will not precipitate while the supernatant liquor is loaded 
 with the citric acid ; for we know that this is capable of holding 
 the citrate of lime in solution. Dize having dissolved 100 parts 
 of crystallized citric acid in pure water at 212, found that the 
 solution would take up 50 parts of calcareous citrate 1 . Hence 
 some nicety is required in separating the. lime, without adding 
 an unnecessary and injurious quantity of sulphuric acid. It will 
 therefore be advisable, as the acid becomes concentrated, to add 
 occasionally a small portion of diluted sulphuric acid, which will 
 arrest the lime, and precipitate it. To this end, the steaming 
 should every now and then be discontinued for some hours, to 
 allow time for the sulphate of lime to separate, which otherwise 
 would prevent the crystallization of the pure citric acid ; for 
 Crell has shown, that a very small quantity of calcareous earth 
 will have this effect. A single drop of sulphuric acid will, how- 
 ever, be a sufficient test, at any time, to show whether the con- 
 centrated citric acid holds any citrate of lime in solution. More- 
 over, a small excess of sulphuric acid is not injurious, but will 
 rather favour the crystallization of the citric acid. 
 
 In opposition to what Crell has observed respecting the cry- 
 stallization of the citric acid being prevented by the presence of 
 
 1 Journ. de Phys. 1794, torn. ii. page 231. 
 
ON CITRIC ACID. 
 
 lime, Westrumb says that most of the citric acid, even when 
 crystallized, contains a considerable quantity oflime. However, 
 where this is suspected, it may quickly be known by dissolving 
 some of the crystals in water, and, when the solution has been 
 saturated with ammonia, by treating it with an oxalate of that 
 alkali, which, if there be lime, will immediately separate it in a 
 palpable form. 
 
 When the product is laid by for crystallization, it will not be 
 necessary to attend much to the temperature of the room, as I 
 have discovered by experience that the crystals shoot equally 
 well in a warm as in a cold situation. 
 
 The crystals thus produced will sometimes, though not gene- 
 rally, be needle-formed ; though it has been repeatedly said by 
 the writers on citric acid, that the crystals produced by the first 
 evaporation are always needle-formed ; but I am inclined to think 
 that this will never be the case if the citrate of lime has been 
 properly freed from the mucilage, and the solution of citric acid 
 not evaporated beyond the due point of concentration, before it 
 be laid aside for crystallization. Indeed, by proper management, 
 I know that perfectly formed rhomboidal crystals may always be 
 procured from the liquor of the first boiling. As the process is 
 usually conducted, these first crystals will be nearly as dark as 
 the brownest sugar. Indeed, every writer on citric acid, whom 
 I have consulted, tells us, that the first crystals will be either 
 dark brown, or black; but I am confident, if the article has not 
 been burnt during the evaporation, that this must be owing to 
 the mucilage not having been sufficiently washed out of the 
 citrate of lime before it is treated with the sulphuric acid ; for I 
 have more than once seen crystals of the first crop of a very 
 bright light brown, and even distinct in their form ; and such, I 
 conceive, they always will be when the proper precautions have 
 been taken. 
 
 Although the crystals of citric acid in any of these states may 
 very well answer most of the purposes to which they are applied 
 by the calico-printer, it is sometimes desirable to have them 
 quite pure; and by dissolving them in pure water, boiling them 
 up with a small quantity of animal charcoal, by means of a pipe 
 blowing steam into your dissolving tub, and then passing the 
 liquor through a flannel filter in a regular filtering box, all 
 colour will be destroyed; and when you have evaporated and 
 crystallized as before, very white and beautiful solid crystals of 
 citric acid will be produced ; for though the first product may 
 be in needle-shaped crystals, the acid when further purified will 
 always appear in rhomboidal prisms : and if this second crystal- 
 lization should not in every instance bring them to the requisite 
 form and degree of whiteness, another boiling and charcoal filter- 
 
ON CITRIC ACID. 255 
 
 ing may always be depended upon, unless gome gross neglect 
 occurs during the operation, and the acid is carbonized by being 
 evaporated too far, or discoloured by dirt falling into it. 
 
 There is another point respecting the conducting of this busi- 
 ness which deserves our notice, and that is the management of 
 the mother-waters. In the manufacture of every kind of salt, or 
 crystalline acid, the profit very much depends upon the economy 
 which is observed in reducing the mother-waters to a solid and 
 a marketable form. But in this article, the high value of the cry- 
 stals, and the peculiar difficulties attendant on the reduction of 
 these residuary liquors, render this part of the subject important 
 to those who operate upon a large scale. 
 
 Whenever this acid is first boiled to a sufficient strength for 
 crystallization, the small excess of sulphuric acid carbonizes a 
 portion either of the acid or the mucilage ; and therefore, when 
 several parcels of lemon-juice have been concentrated, there will 
 at last be a considerable quantity of very black uncrystallizable 
 mother-liquor. 
 
 This liquid residuum has given much trouble to some opera- 
 tors, and it has often been thrown away as useless. By the fol- 
 lowing management, however, the whole of the citric acid which 
 it contains may be turned to a good account, and produce fair 
 and clean crystals. The process which I would recommend 
 is as follows : 
 
 Whatever the quantity of mother-liquor may be, let it be 
 diluted with ten or twelve times its measure of pure water, and 
 the water intimately mixed with it. Then add carbonate of lime 
 to it, by degrees, until it is completely saturated, and proceed 
 with it in all respects as directed at page 250, as if it were fresh 
 lemon-juice. 
 
 Here it will be necessary to wash the product of citrate of 
 lime with several successive portions of water ; and, if this be at- 
 tended to, the crop of crystals which it will yield will be as fine 
 as any before obtained. 
 
 On referring to the notes which I made in the year 1810, 
 while operating on some large parcels of lime juice, I find the 
 following entry, which is descriptive of the whole process, and 
 is given in the hope that it may furnish some useful hints to those 
 who have had less practical experience, and enable them to avoid 
 some errors into which I had fallen before I had that knowledge 
 of the process which I have since acquired. 
 
 Three casks of lime juice, which measured together 270 gal- 
 lons, were drawn off into a large wooden vessel ; and to this 
 were added 118lbs. of clean carbonate of lime, which completely 
 saturated it. When the citrate of lime had precipitated, the 
 
256 ON CITRIC ACID. 
 
 supernatant liquor was taken away and reserved for another pur- 
 pose '. The precipitate was then carefully washed with hot water 
 from the worm-tub of the laboratory still, and this was drawn off 
 the next morning. The precipitate was afterwards washed several 
 times with cold water ; in all seven times, the first washing only 
 being with hot water. The water which was drawn off even at 
 the third washing was considerably coloured. 
 
 While the citrate of iime was precipitating after the last wash- 
 ing, (and 1 allowed it due time to subside, in order to separate 
 as much as possible of the water which rested on its surface,) I 
 drew off into another vessel the contents of five pipes more of 
 lime juice, which in the whole measured 450 gallons. Lime 
 juice is generally stronger than the juice of lemons, and when it 
 is of the full standard strength it will require half a pound of 
 chalk to every gallon of the juice. Hence it appeared, when too 
 late, that a good price had been paid for a very inferior article ; 
 an inferiority which I imagined was not occasioned by adul- 
 teration, but proceeded merely from the natural effects of age. 
 And here it is important to remark, that ordinary juice not only 
 takes less lime, but that sometimes even a considerable portion 
 of what is used does not remain in the vat, but is drawn off with 
 the malic and acetic acids ; the rnalate and the acetate of lime 
 being both soluble salts. Hence the necessity of always employ- 
 ing a chemical test to determine the quantity of sulphuric acid 
 required for the subsequent operation, lest a dependence on the 
 quantity of carbonate of lime used, might mislead. The five 
 pipes of lime juice above mentioned required 149 pounds of car- 
 bonate of lime for its complete saturation. 
 
 The precipitate now obtained was treated and washed with the 
 same attention and care as the former, to separate the whole of 
 the malate and acetate of lime, the extractive matter, and the 
 mucilage. Both the precipitates were then removed to a leaden 
 cistern, and 500 pounds of soft water were poured over them, 
 which enabled us very thoroughly to mix the whole. 
 
 Two hundred and forty pounds of sulphuric acid of the specific 
 gravity of 1.845 were now diluted with 256 pounds, or 32 gal- 
 lons wine measure, of soft water, and this diluted sulphuric acid 
 was immediately, whilst hot from the mutual action of the two 
 fluids upon each other, gradually poured in successive portions 
 
 1 When I reserved this liquor, it was my intention to have separated most 
 of the water, either by evaporation or freezing, and then to have treated the 
 malic acid and the mucilage which would remain with nitric acid, with the 
 view of obtaining oxalic acid, which I thought would be a means of producing 
 some profit, and thus economizing the first process. But I never pursued 
 this object. 
 
ON CITRIC ACID. 257 
 
 into the leaden cistern upon the mixture of citrate of lime and 
 water. 
 
 While this was doing, two of the workmen never ceased stir- 
 ring up the whole from the bottom of the cistern, with large and 
 strong wooden spatulas, the more effectually to prevent any part 
 of the citrate of lime from escaping the action of the sulphuric acid. 
 
 Notwithstanding this, I perceived that the precipitate conglo- 
 merated very much on every addition of the sulphuric acid ; a 
 circumstance which was occasioned, as I afterwards discovered, 
 by using this acid in too concentrated a state. There is besides 
 another evil attending this ; for as sulphuric acid, fully concen- 
 trated, will convert the citric into acetic acid, there will always 
 be a danger of lessening the quantity of the produce, when the 
 sulphuric acid is not sufficiently diluted before it is employed. 
 Indeed, from the last operations which I superintended, I am 
 led to believe that it cannot be economical to use this acid in a 
 higher state of concentration than one part of strong sulphuric 
 acid to six parts of water. 
 
 The whole quantities used were as follow: Lime juice 720 gal- 
 lons ; carbonate of lime 267 pounds ; sulphuric acid 240 pounds ; 
 water, mixed with the sulphuric acid, besides the quantity which 
 was before in the citrate of lime, 756 pounds. 
 
 It may here be observed, that if the citrate be treated with oil 
 of vitriol immediately after it has been washed, as is frequently 
 the case, a dilution of three parts of water to one part of sul- 
 phuric acid may be sufficient, as there will be much water in a 
 state of mixture with the citrate of lime. 
 
 Several other parcels of citrate of lime were afterwards treated 
 with sulphuric acid properly diluted, and the several inconve- 
 niences which I have adverted to were avoided ; but it is not 
 in my power to furnish the amount of the crystals that were pro- 
 duced from any of these parcels, as I disposed of my share of the 
 whole of the citric acid in a state of solution, and the task of con- 
 centrating it for crystallization fell into other hands. 
 . From other experiments, however, I have reason to conclude 
 that 20 gallons of good lemon juice will generally give 18 pounds 
 of dry citrate of lime, and that if the whole process be well con- 
 ducted, these 18 pounds of citrate of lime will furnish 10 pounds 
 of good white crystals of citric acid. A well known and highly 
 respectable chemical writer has stated, that " the quantity of 
 solid citric acid in a gallon of lime juice, varies from 14? to 18 
 ounces." I confess, however, that I have not been able to pro- 
 cure this proportion from any of the parcels on which I have 
 operated ; but there is reason to believe that his experiments were 
 made with lime juice recently expressed from the fruit. 
 
258 ON CITRIC ACID. 
 
 Fourcroy in his " General System of Chemical Knowledge," 
 vol. vii. pages 277 and 287, and in the Lectures which he de- 
 livered at Paris, recommended to his fellow-citizens to send proper 
 persons over to their American possessions to collect the vast 
 quantities of limes and lemons which are annually lost there ; to 
 saturate the expressed juice with chalk; and to send the washed 
 and dried precipitate, closely packed in barrels, to France, where 
 it might be decomposed, and the citric acid obtained pure. 
 Whether any of the Parisians ever embraced this proposal I have 
 not been able to learn ; but I know that some persons have gone 
 from England to different parts of Italy for this purpose, and that 
 considerable quantities of the citrate of lime have been imported 
 from thence into Great Britain. 
 
 Having been introduced to a person, who some years ago 
 formed an establishment of this sort in the island of Sicily, I have 
 learned several important circumstances relating to this business, 
 which have never yet been given to the public. I have also been 
 favoured with the perusal of a great part of the correspondence 
 which passed on the occasion ; and having obtained leave to-print 
 the whole, or any part of these letters, I shall subjoin such ex- 
 tracts as I conceive will be interesting to those who may be de- 
 sirous of acquiring more information on the subject. 
 
 In the first letter, which is dated Messina the 6th September, 
 1 808, this intelligent correspondent says, " The time of pressing 
 is generally in the latter end of the month of November or De- 
 cember, for until that period the lemons yield little or no juice." 
 
 " The country round Messina consists of mountains of im- 
 mense height, rising one above another, and thickly covered to the 
 very tops with fruit-trees, chiefly olives and lemons, which render 
 this place the very best in the world for procuring lemon juice." 
 
 " The quay surpasses most others, extending for a mile and a 
 half, close to the edge of which ships lie in 20 fathom water. 
 Formerly a range of superb houses, perfectly uniform, extended 
 the whole length of this marino, or quay ; but ever since the earth- 
 quake these magnificent mansions lie in ruins." 
 
 " As soon as the country people press the juice, they bring it 
 in here for sale. The buyers do not afford it warehouse-room, 
 but roll it into the street, where it remains exposed to the weather 
 and to the heat of the sun, till an opportunity offers for shipping 
 it. It is therefore not surprising that so much is imported that 
 is musty and perished, and that the English merchants often 
 find it so bad on its arrival in England as to create a difficulty in 
 procuring for it even the amount of the import duty." 
 
 In one of his letters he remarks, that in the autumn 200 
 lemons are generally required to furnish one gallon of juice; and 
 that on this account, there are presses in the island which are so 
 
ON CITRIC ACID. 
 
 259 
 
 constructed that they will squeeze many thousands of lemons 
 at once. 
 
 April 15th, 1809. " I have hitherto found no difficulty in 
 saturating the chalk in any quantity ; but the drying is extremely 
 tedious and difficult ; it requires very hot and dry weather, which 
 we have had little or none of as yet. I have had parcels lie up- 
 wards of a fortnight before they became perfectly dry. When 
 spread out for this purpose, it occupies a vast deal of room, and 
 when the drying-places are all full, I am obliged to stand still, 
 although I have procured the use of a vast terrace belonging to 
 a convent not far distant." 
 
 " The cistern in which I work is capable of containing 12 
 pipes ; but notwithstanding the large size of the apparatus, the 
 effervescence occasions me much trouble ; and this I attribute to 
 the chalk being sifted to so fine a powder." 
 
 " Neither the monks nor any of the inhabitants seem to have 
 the slightest curiosity to know what the article is, although, until 
 it is dry, it continually occasions a most agreeable odour." 
 
 June 22, 1810. " I find as much difference in lemon juice as 
 in wine, and both have more or less body, according to the par- 
 ticular soil on which the fruit grows. When fresh squeezed, all 
 seems equally sharp and good. The hot weather, however, is 
 the test, and there is much of the juice we buy which will not 
 bear it; it often changes very quickly, and a mawkish vinegar- 
 sort of taste alone remains. Though the early juice resists the 
 heat the best, I can positively assert that, with the utmost care, 
 there is no certainty of preserving its native sharpness in the hot 
 months, but by the addition of lime, or some other similar agent." 
 
 The following is a tabular view of the quantities of citrate of 
 lime sent from this establishment to England at each shipment ; 
 with the respective quantities of juice and carbonate of lime that 
 were employed in its formation. 
 
 Times of Shipment. 
 
 Avoirdupois 
 Pounds of 
 Citrate. 
 
 Pounds of 
 Chalk em- 
 ployed. 
 
 Gallons of 
 Juice em- 
 ployed. 
 
 Ounces avoirdu- 
 pois of Citrate 
 from every Pound 
 of Chalk. 
 
 Ounces avoirdu 
 pois of Citrate 
 from every Gal- 
 lon of Juice. 
 
 1809, May 8 
 
 3329 
 
 2386 
 
 4773 
 
 Oz. Drms. 
 
 22 5J 
 
 Oz. Drms. 
 
 11 2% 
 
 25 
 
 2047 
 
 1318 
 
 2638 
 
 24 13| 
 
 12 6| 
 
 July 1 
 
 6426 
 
 3981 
 
 8029 
 
 25 13J 
 
 12 12| 
 
 15 
 
 3750 
 
 2231 
 
 4885 
 
 26 14 
 
 12 4| 
 
 1810, June 5 
 
 4987 
 
 3230 
 
 6485 
 
 24 11 
 
 12 4} 
 
 22 
 
 8022 
 
 5314 
 
 10917 
 
 24 2 
 
 11 12 
 
 July 15 
 
 7181 
 
 5827 
 
 13117 
 
 19 ll 
 
 8 4i 
 
 Aug. 22 
 
 6798 
 
 4930 
 
 11098 
 
 22 1 
 
 9 6^ 
 
 
 7362 
 
 5800 
 
 13022 
 
 20 4f- 
 
 9 Oj 
 
 
 49902 
 
 35017 
 
 74964 
 
 
 
 
 Average Produce .... 
 
 22 12} 
 
 10 10| 
 
260 ON CITRIC ACID. 
 
 On account of the great disproportion which there is in the 
 amount of the different parcels of citrate of lime, produced from 
 their respective parcels of lemon juice, less reliance is to be 
 placed on this table as a perfect document of general reference, 
 than otherwise might be : but as this must have been owing to 
 the operator not being aware of the great difference which there 
 is in the quality of the juice offered for sale, I have taken the 
 pains of throwing the whole of the results into this tabular form, 
 that they may appear at one view, and be a warning to future 
 speculators how they make contracts for lemon juice without 
 submitting the^ several parcels to previous chemical examination. 
 
 As to the disproportion in the quantities of citrate of lime pro- 
 duced from the respective parcels of chalk, and which vary from 
 20 to nearly 27 ounces for each pound of the earth employed, 
 this must have arisen from his having taken the same quantity of 
 carbonate of lime per gallon for every parcel of lemon juice, as 
 he intimates in one of his letters, than which nothing could have 
 been more improper; as the produce of citrate would sometimes 
 not only be much less than it ought to have been, but, from the 
 earth not being saturated, the article would be of very inferior 
 value. 
 
 Considering the difficulties which I have already stated, I am 
 inclined to think that by purchasing lemon juice in London or 
 Liverpool, at favourable opportunities, citrate of lime might be 
 made in England nearly as cheap as it could be imported from 
 Sicily, to say nothing of the inconveniences and disadvantages 
 which must inevitably attend its formation in a distant country. 
 The reader, however, will be able to form his own opinion from 
 the facts which I have detailed. 
 
 I am desirous of observing that the juice of several other fruits, 
 besides those of limes and lemons, will furnish the citric acid, 
 either alone or mixed with other vegetable acids. Thus, the 
 cranberry, the vaccinium oxycoccus of Linnaeus ; the red whortle- 
 berry, vaccinium vitis idaa ; the birds cherry, prunus padus, a 
 fruit that is often infused in wine or brandy, to give it an agree- 
 able flavour ; the berry of the nightshade, solanum dulcamara ; 
 and the hep, or fruit of the wild briar, cynosbatus vel rosa canina, 
 yield chiefly the citric acid ! : while in the red gooseberry, ribes 
 grossularia ; in the garden currant, ribes rubrum ; the bilberry, 
 vaccinium myrtillus 2 , the hawthorn, cratcegus aria * ; the black 
 
 1 Westrumb has shown that the juice of the common cherry contains 
 scarcely any other acid than the citric. 
 
 2 The juice of this berry has been employed to stain paper, or linen, purple. 
 In autumn the moor-game chiefly live upon the product of this shrub. 
 
 8 The wood of the cratcegus aria, on account of its great toughness, is much 
 used for making wheels and axletrees; it is also so hard and smooth a wood 
 that it is highly esteemed for making the handles of sundry tools used by car- 
 penters and others. 
 
ON CITRIC ACID. 261 
 
 cherry, prunus cerasus ; the wood strawberry, fragaria vesca ; 
 the knout or cloudberry, rubus chamamorus; and in the raspberry, 
 rubus id&uS) it is mixed with nearly an equal proportion of malic 
 acid. From all of these the citric acid may however be separated 
 by means of carbonate of lime, if ever a scarcity of limes and 
 lemons should occur. 
 
 Simon Pauli has published the method of making a concrete 
 salt from the juice of the barberry ; and directions for making 
 barberry-punch of a beautiful red colour are given by Weigleb 4 . 
 
 It may also be worth mentioning, that sometimes there is a 
 large quantity of damaged tamarinds in the market, which might 
 be bought cheap enough for the use of calico-printers, and which 
 would afford their citric acid to calcareous earth, in the same 
 way as the common lemon juice. Vauquelin, who has made 
 direct experiments upon the tamarind, has shown that one pound 
 of the pulp contains one ounce and a half of solid citric acid *. 
 
 In adverting to the PROPERTIES of the citric acid, its chemical 
 affinities first present themselves to our notice. These, as de- 
 termined by Bergman, and by Mons. de Breney of the Academy 
 of Sciences at Dijon, arlt in the following order : 
 
 Barytes, Soda, *o* r Manganese, Copper, Antimony, 
 
 Lime, Strontites, 5 y Iron, Tellurium, Silver, 
 
 Magnesia, Ammonia. '?| \ Lead, Arsenic, Gold, 
 
 Potash, O V. Cobalt, Mercury, Platinum. 
 
 It is obvervable, however, that Vauquelin places Magnesia 
 after Potash, Soda, and Strontites 6 . 
 
 When the citric acid is pure and concentrated, it crystallizes 
 in rhomboidal prisms, the sides of which are inclined towards 
 each other at angles of 60 or 120 degrees, terminated at both 
 ends by summits with four faces, which intercept and include the 
 solid angles 7 . Its taste when crystallized is strongly acid and 
 pungent ; but when dissolved in water, mild and agreeable. It 
 reddens litmus and other blue vegetable colours. The crystals 
 are soluble in their own weight of water, or according to 
 Vauquelin 7.5 Ibs. of water at the temperature of 60 are capable of 
 dissolving 100 pounds of the crystals : boiling water will dissolve 
 twice its weight of them. When the crystals are heated gra- 
 
 4 Hobson's Translation of Weigleb' s Chemistry, 4to, London, 1789, page 178. 
 
 5 Vauquelin's Memoir on the Analysis of the Tamarind will be found in 
 the Annales de Chimie, torn. v. page 92. 
 
 6 See Fourcroy, vol. vii. page 287. 
 
 7 Dize, Nicholson's Journal, 4to, vol. ii. page 44. 
 
262 ON CITRIC ACID. 
 
 dually over a fire, the acid becomes dissolved in its own water of 
 crystallization. It undergoes spontaneous decomposition, if long 
 kept in solution, even in close vessels ; though lime juice may 
 be preserved good for a long time in glass bottles, if covered 
 with a thin stratum of oil. By concentrated sulphuric acid it is 
 converted to acetic acid ; and lastly, the alkaline citrates are de- 
 composed by barytic water. 
 
 The crystals of citric acid according to Berzelius consist of 
 100 acid 4 26.5 water, or 100 parts of the pure crystals are com- 
 posed of 79 acid and 21 water. The same chemist determined l 
 that the constituents of the acid are in 100 parts : oxygen 54.831, 
 hydrogen 3.800, carbon 41. 369; or 4 proportionals of oxygen 
 32, 2 of hydrogen 2, 4 of carbon 24, making its equivalent 
 number 58. 
 
 The citric was formerly supposed to be identical with the tar- 
 taric acid ; but they differ in one remarkable particular, viz. that 
 the citric acid does not decompose muriate of potash. It is also 
 readily distinguished from the oxalic acid by its incapacity of de- 
 composing sulphate of lime. 
 
 Acetate of lead is decomposed by citric acid, and the citrate of 
 lead that is formed is precipitated in a white powder. The nitrate 
 and acetate of mercury are also decomposed by it ; and it im- 
 parts a green tinge to the solutions of acetate and sulphate of 
 iron. 
 
 The SALTS which have been formed by means of the citric 
 acid, being more the objects of curiosity than of utility, a very 
 brief account of them will be sufficient. They are as follow : 
 
 Citrate of AMMONIA. This salt is formed by dissolving car- 
 bonate of ammonia in citric acid. To produce it in crystals, the 
 solution must be evaporated to a thick syrup. Its crystals are 
 elongated prisms, composed, according to Vauquelin, of 62 acid 
 and 38 ammonia 2 . They are very soluble in water. 
 
 Citrate o/^ BARYTES is prepared by adding a solution of pure 
 barytes to a solution of citric acid. The salt forms itself into a 
 kind of bush of a silvery whiteness, very brilliant and beautiful ; 
 though sometimes it appears in more distinct acicular crystals. 
 It is composed of 50 parts by weight of crystallized acid, and 50 
 of barytes. 
 
 Citrate O/*BISMUTH was formed by Vauquelin, and found to 
 be an insoluble white powder. 
 
 Citrate of COBALT. This compound is formed by the union of 
 
 1 Annals of Philosophy, vol. v. page 93. 
 
 2 Fourcroy's General System, vol. vii. page 283. 
 
ON CITRIC ACID. 263 
 
 the oxide of cobalt with citric acid. The product is a soluble 
 salt, whose properties are unknown. 
 
 Citrate of COPPER. Citric acid acts very feebly on metallic 
 copper ; but this salt may be formed by boiling the oxide of cop- 
 per in a solution of citric acid. The concentrated solution, on 
 cooling, yields light green crystals. 
 
 Citrate C/GLUCINA. This salt may be readily formed, but it 
 does not seem that its properties were examined by Vauquelin 
 when he was engaged in investigating the nature of the other 
 citric salts. 
 
 Citrate of IRON has been formed by Vauquelin. When he 
 added iron to citric acid, the effervescence continued four days ; 
 the solution was of a brown colour ; and by spontaneous evapo- 
 ration it deposited small crystals of citrate of iron. By concen- 
 tration, it became black like ink, and ductile like hot resin, but 
 brittle when cold. It tastes very astringent, and is very soluble 
 in water. 
 
 Citrate O/*LEAD may be formed by adding a solution of citric 
 acid to a solution of acetate of lead. The salt is in the form of 
 a powder, and is nearly insoluble in water. According to Ber- 
 zelius, it is formed of citric acid 34.5, and oxide of lead 65.5. 
 
 Citrate O/'LIME. The formation of this salt has been already 
 described at page 250. When dried, it is in the form of a white 
 powder, nearly tasteless, and scarcely soluble in water. It is 
 soluble, however, in its own acid, which accounts for the con- 
 centrated acid generally containing a portion of lime. It is a 
 compound of lime 33, and citric acid 67. Or it may be said to 
 consist of, 1 proportional of acid 58, and 1 of lime 28, making 
 its equivalent number 86. 
 
 Citrate O/'MAGNESIA is readily formed by dissolving carbonate 
 of magnesia in citric acid. It does not crystallize, but forms, ac- 
 cording to Vauquelin, a white mass which rises in the vessel like 
 a mushroom 3 . According to this chemist, it is composed of citric 
 acid 66.66, and magnesia 33.34. 
 
 Citrate of MANGANESE. Citric acid dissolves the black oxide 
 of manganese, and produces, according to Professor Brande, 
 white arborescent crystals 4 . 
 
 Citrate of MERCURY. Citric acid will not dissolve metallic 
 mercury ; but with the red oxide it forms an insoluble white 
 mass. A proto-citrate and a per-citrate may be formed with 
 this metal ; but they are both insoluble salts. 
 
 Citrate of POTASH. To form this salt, nothing more is neces- 
 sary than to dissolve carbonate of potash in citric acid, and con- 
 
 3 Fourcroy's System of Chemistry, vol. vii. page 283. 
 
 4 Manual of Chemistry, vol. iii. page 95. 
 
264? ON CITRIC ACID. 
 
 centrate the solution by evaporation. It is extremely soluble, 
 and crystallizes with difficulty. It was called the salt ofRiverius 
 in the old Pharmacopoeias, and is still much used in medicine. 
 It is deliquescent and decomposable by barytes and lime. Vau- 
 quelin, who paid considerable attention to this salt, found it to 
 consist of citric acid 55.55, and potash 44.45. 
 
 Citrate of SILVER. Silver is not acted upon by citric acid ; it 
 dissolves its oxide, however, and forms with it a salt in the form 
 of a white powder, which has a harsh styptic taste, arid is inso- 
 luble in water. Though white when it is first formed, it becomes, 
 like other salts of silver, black by exposure to the light. It is a 
 compound of citric acid 36, and oxide of silver 64. 
 
 Citrate O/*SODA. This salt is formed by dissolving soda or its 
 carbonate in citric acid. It has a faint and saline taste, and is 
 difficultly cry stall izable; but when crystallized, it requires nearly 
 two parts of water for its solution. It crystallizes in six-sided 
 prisms, or in hexahedral tables. It consists of citric acid 60.7, 
 and soda 39.3. 
 
 Citrate O/'STRONTITES was formed by Vauquelin by the mix- 
 ture of citrate of ammonia with nitrate of strontites. It is a cry- 
 stallizable salt, and soluble in water. 
 
 Citrate of URANIUM has been formed by digesting oxide of 
 uranium in citric acid. The salt crystallizes with difficulty, but 
 it is soluble in water. 
 
 Citrate of ZINC. Citric acid acts freely on metallic zinc or its 
 oxide. Small brilliant crystals of citrate of zinc are formed which 
 have a strong metallic taste, but they are scarcely soluble in water 1 . 
 The salt is a compound of citric acid 59, and oxide of zinc 41. 
 
 It would be improper to dismiss this subject, without adverting 
 to the application and general USES of the citric acid. 
 
 Besides the common medicinal* purposes to which the citric 
 acid is applied, such as the making of saline draughts, &c., it is 
 often combined with opium to prevent the stupifying effects of 
 that very powerful narcotic ; and I have been told that it has 
 been given with good effect to counteract such an over-dose of 
 it as would otherwise have proved fatal. 
 
 Its operation in obviating the destructive power of this or 
 some other powerful drug, was known to the ancients ; for it is 
 evidently alluded to in Virgil's Georgics, as may be seen in the 
 motto prefixed to this Essay 3 . 
 
 1 Fourcroy's System of Chemistry, vii. 284. 
 
 2 Speaking of the medicinal uses, reminds me of what I have read respecting 
 the effect of citric acid on milk. Jt is said that although it curdles the milk of 
 most animals, it has not this effect upon human milk, whether used hot or 
 cold. Voltelen Obs. Chem. Mcd. dc Lacte humano. Traj. Data v. 1775. 
 
 3 See also Girfanner in Annalcs de Chimie, torn, xxxiv, p. 306. 
 
ON CITRIC ACID. 265 
 
 In domestic economy the citric acid is employed with advan- 
 tage as a condiment for a variety of food, it being more grateful 
 than vinegar on account of the fine aroma derived from the 
 essential oil peculiar to the rind of the fruits which produce it. 
 Likewise for taking out iron-moulds or other stains of iron ; as 
 this metal is not only soluble in citric acid, but the solution is so 
 permanent that it is not precipitated again by the application of 
 soap, which sometimes happens when other salts are used for 
 this purpose. It is useful also for removing spots occasioned by 
 alkalies, or the alkaline earths, from scarlet cloth ; for making 
 a solution of iron for bookbinders, to give the mottled appear- 
 ance to the surface of calf-skin; for improving that peculiar 
 solution of tin which is employed for producing the most exqui- 
 site specimens of the scarlet dye; for altering the hue of some 
 colours which are exclusively used in the dyeing of silk; for 
 the preparation of the best Morocco leather; and for improving 
 candles, by whitening and hardening the tallow which is em- 
 ployed in making them. 
 
 A very considerable quantity of citric acid, in the form of 
 lemon juice, is also consumed by the seamen of the British navy 4 . 
 It was formerly bought in London, having first been submitted 
 to the judgement of a respectable chemist, who was regularly 
 employed tor the purpose. As the managers of this department 
 have found that it can be brought from Sicily at a much more 
 reasonable price, and of the best quality, they now procure it 
 from that island, and decline all other sources. To preserve it 
 on long voyages, they generally put about 10 gallons of brandy 
 to every 100 gallons of the juice, which has the effect of precipi- 
 tating the mucilage, that otherwise would not fail, during an ex- 
 tended voyage, to throw the whole into a state of fermentation, 
 and convert much of it into vinegar. 
 
 Dize 5 says that a lemonade of the most agreeable taste and 
 appearance may be made by dissolving 40 grains of citric acid 
 in a pint of water, with the addition of a sufficient quantity of 
 refined sugar, and that it may be rendered fragrant by dissolving 
 in it a small quantity of oleo-saccharum, prepared by rubbing a 
 lemon on a lump of sugar. The sugar, by imbibing the volatile 
 oil of the lemon, renders it perfectly soluble. By this means it 
 is easy to preserve the volatile oil of any number of lemons. The 
 oleo-saccharum thus obtained may be mixed in a mortar with a 
 sufficient quantity of sugar ; and when this has been dried by a 
 very gentle heat, it may be kept in well stopped bottles unim- 
 
 4 liord Anson and Captain Cook were the first navigators who employed 
 lemon juice on their ships' crew for the prevention and cure of the sea-scurvy. 
 3 Nicholson's 4to Journal, vol. ii. page 45. 
 
266 ON CITRIC ACID. 
 
 paired for any length of time. This is preferable to the volatile 
 oil of lemons obtained by distillation, because the fire often im- 
 parts an unpleasant or empyreumatic flavour to it. 
 
 Other domestic and economical purposes might be enumerated, 
 to which citric acid is applicable, especially now that it can be 
 kept in its crystallized state in every family, in which form it is 
 liable neither to decay nor even to the slightest alteration. 
 
 Citric acid is principally consumed by the calico-printer, who 
 uses it in several processes of his art, especially to discharge iron, 
 and to preserve white grounds on certain parts of a pattern, by 
 means of the property it has of resisting the operation of sundry 
 dyes, as is more fully explained in the Essay on Calico-printing. 
 
 The person who first prepared this acid in large quantities in 
 England, and chiefly for the use of the calico-printers, was Mr. 
 Coxwell, late of Fleet-street, who sold it at a high price in the 
 form of clean white crystals. With this the printers were sup- 
 plied for many years; but when the demand became greater 
 than he could well answer, he began to furnish them with the 
 brown crystals, that is, with the acid in the first or second stage 
 of crystallization, and consequently at a much lower price. 
 
 The discovery that citric acid can be used in a brown state 
 for calico-printing occasioned the printers pretty generally to 
 turn their attention to the preparation of the citric acid ; and now 
 most of the proprietors of the large establishments buy lemon 
 juice for themselves, and use it in different states of concentra- 
 tion, according to the nature of the processes to which it is to 
 be adapted. 
 
 For most of the styles of work in which citric acid is employed, 
 they find that the common impurities in lemon juice are of very 
 little consequence; and that when the juice itself has undergone 
 no other process than that of being concentrated by the evapo- 
 ration of a portion of the water it contains, it very well answers 
 their purpose, and supersedes the use of the crystallized acid. 
 
 As there is always abundance of spare heat in every large 
 calico-print work, the process of evaporation may be conducted 
 at no expense : and if it be continued very slowly for some con- 
 siderable time, the acid will be sufficiently concentrated, and this 
 without waste. For when it arrives at a certain point of concen- 
 tration most of the mucilage will be separated, one part of which 
 generally rises to the surface, and the other precipitates. 
 
 It is time, however, to come to the particular point which first 
 induced me to think of writing on this subject, namely the know- 
 ledge of the circumstance, that the printers depend solely on the 
 hydrometer for ascertaining the goodness of lemon juice. This 
 made me very desirous of recommending to them some less fal- 
 lacious guide. 
 
ON CITRIC ACID. 267 
 
 Various reasons may be adduced to show the uncertainty of 
 the hydrometer ; but one or two will suffice. It is possible, for 
 instance, that two parcels of juice may appear to differ very 
 much, when examined by the hydrometrical test, from the diffe- 
 rence of the quantity of mucilage, though the same parcels may 
 be of equal goodness as to the produce of the crystals or real acid 
 that may be procured from them. In like manner, a pipe of 
 lemon juice may be sophisticated with other acids, so as to make 
 it pass the hydrometer, and yet be worth little for the printer's 
 use. 
 
 On these accounts it appears to me that there can be no safety 
 in purchasing this article, unless the buyer avail himself of the 
 use of chemical tests, especially as an experienced calico-printer 
 has assured me that fine wheat flour is sometimes employed to 
 adulterate lemon juice. It certainly may be so incorporated with 
 the mucilage as to affect the hydrometer considerably. 
 
 Whenever, therefore, a parcel of lemon juice is offered for 
 sale, the first thing should be to take its specific gravity by the 
 hydrometer, or by means of a specific-gravity bottle, and note 
 that down. Should it prove to be only of the specific gravity of 
 about 1.0156, which is 16 ounces 4? drachms to the wine-pint, it 
 may at once be rejected as not worth purchasing; for good juice 
 varies from a specific gravity of 1.0312 (16 ounces 8 drachms) 
 to that of 1.0625, or 17 ounces avoirdupois the wine-pint. 
 
 Should the parcel appear good by the hydrometer, take then, 
 for the next experiment, a wine glass of the juice, dilute it plen- 
 tifully with pure water, and add to it a few drops of a solution 
 of acetate of lead as directed at page 252 : this will produce an 
 immediate precipitate, chiefly of citrate of lead, which should 
 then be treated with a little pure nitrous acid, and the effect 
 carefully observed ; for, if the nitrous acid dissolve the whole of 
 the precipitate, it will prove that the juice under examination 
 contains no sulphuric acid. By proceeding in the same way with 
 an acidulous solution of nitrate of silver, instead of acetate of lead, 
 it will be seen whether the juice contains any muriatic acid ; this 
 and the sulphuric being the only two acids, except the acetic, 
 that are ever likely to be employed in the adulteration of lemon 
 juice. And if the presence of acetic acid is suspected, saturate the 
 juice with carbonate of lime (whiting) : as long as effervescence 
 continues, filter the supernatant liquor, and drop into it, when 
 clear, a few drops of oxalic acid in solution. If acetic acid is 
 present, the liquor will contain acetate of lime, which earth will 
 instantly be precipitated by oxalic acid, or even by sulphate of 
 iron, the common green copperas. It should be observed, that 
 what little malic acid it contains will have the same effect, so 
 that a trifling precipitate may be expected even in good juice. 
 
268 ON CITRIC ACID. 
 
 When it has thus been found that a sample of lemon juice 
 contains no admixture of other acids, the next step ought to be 
 to ascertain how much real citric acid any given quantity of such 
 juice actually holds in solution. For though it may not have 
 been designedly sophisticated by any extraneous matters, it may 
 be very inferior from other causes, the extent of which can only 
 be accurately discovered by the application of another chemical 
 test. 
 
 For instance, the fruit of which it was made may have been 
 gathered in an unfavourable month, after the descent of the 
 heavy rains ; or deteriorated by the spontaneous decomposition 
 which is occasioned by age ; or it may have been diluted with 
 water ; all of which may be apprehended, when it is not known 
 how many hands the juice has passed through before it comes 
 into the possession of the consumer. 
 
 The mode which naturally suggests itself of ascertaining this 
 point, is by means of an alkali ; for if it be proved by the fore- 
 going tests that the juice contains no admixture of other acids, 
 the amount of the crystals of citric acid which it will yield will 
 be in exact proportion to the quantity of alkali which it requires 
 for its saturation. 
 
 To adapt this theory to practice, all that is necessary is to select 
 some alkali, such as pearl-ash, or the crystals of soda, of which a 
 solution is to be made, something below the point of saturation ; 
 and when this has been filtrated through blotting-paper, and its 
 specific gravity noted down, it will be ready for use, and should 
 be carefully laid by, to have recourse to whenever occasion re- 
 quires. 
 
 Let one thousand grains, or any given quantity, of the lemon 
 juice be weighed out; and having previously balanced a phial of 
 the solution of alkali in an accurate pair of scales, let a portion of 
 the alkali be gradually added to the juice, which should be well 
 stirred with a glass rod, or poured from one vessel to another, be- 
 tween every addition of the alkali. When the effervescence seems 
 to grow less and less, a slip of the blue test-paper of the shops 
 should be dipped in, to ascertain whether the mixture approaches 
 the point of saturation. If the paper comes out red, it indicates 
 that the acid still predominates, and more alkali must therefore 
 be cautiously dropped in. After waiting a minute or two, to allow 
 time for them to unite, another slip of test-paper is to be applied, 
 and in this way repeated until the liquor has lost the power of 
 occasioning any change in the colour of the test. 
 
 When this is the case, a slip of the test-paper reddened by 
 very dilute vinegar should be dipped in, which will acquire a 
 blue colour if too much of the alkali has been used ; but if the 
 liquor be brought to that state that it will cause no visible change 
 
ON CITRIC ACID. 269 
 
 of colour in either the red or the blue litmus paper, the lemon 
 juice may then be considered to be accurately saturated, and 
 brought to the neutral state. 
 
 Now, replace the phial of dilute alkali in the scale, note down 
 how many grains in weight are requisite to balance it, and call 
 this the quantity of alkali expended in saturating the juice. When 
 the operator has by previous experiment determined how much 
 of his standard alkali is necessary to saturate any given quantity 
 of the pure crystals of citric acid, he may at once, by the common 
 rule of proportion, find how much solid citric acid is contained 
 in any particular sample of lemon juice, which has been submitted 
 to the tests already described. 
 
 In order to lay the foundation for a table of the quantities of 
 pure alkali which are taken up by this acid in various states of 
 concentration, I prepared some pure carbonate of potash, and 
 found that 54-4? grains of such alkali are required to saturate one 
 ounce avoirdupois, or 437.5 grains of pure dry solid crystals of 
 citric acid ; or, that one ounce and a quarter, omitting fractions, 
 will render neutral one ounce of the crystallized citric acid. When 
 this fact was ascertained, a foundation was laid for the construc- 
 tion of the Table No. I. 
 
 It is worthy of notice, that this test may be employed, not only 
 in purchasing lime juice, but also in ascertaining the quantity of 
 real acid in acid liquors of different degrees of concentration ; a 
 matter of considerable consequence to those printers who are de- 
 sirous of being accurate in the proportion of acid which they em- 
 ploy in any particular style of work. 
 
 As some of the calico-printers in the North of England have 
 found it advantageous to buy lemon juice instead of citric acid, 
 and use it, after it is concentrated by evaporation, without further 
 purification, as mentioned at page 266, I would here take the 
 opportunity of suggesting, that when the juice has been partially 
 concentrated by being exposed for some time to a very moderate 
 heat, it would be useful to remove it to a situation where the 
 evaporation will be suspended, and where it can remain undis- 
 turbed for a day or two, to give time for the thickened mucilage 
 entirely to subside. It will then be advisable to draw the fluid 
 from the precipitated impurities, by a syphon, or other means, 
 and to pass it through a filter, before it be submitted to any 
 further process of concentration. 
 
 Should the printer be desirous of purifying his lime juice by 
 the chalk process as described at page 250, &c., I see no reason 
 why he may not afterwards evaporate the fluid by some such 
 method as is directed above, and use it in any stage of its con- 
 centration that may be most suitable, without being at the expense 
 of reducing it to the solid form. 
 
270 ON CITRIC ACID. 
 
 To render this more easy, I have constructed a table of the 
 quantities of purified acid in a given portion of liquor of different 
 strengths, as indicated by their specific gravity : and another 
 table of a similar nature for the unfinished acid, or brown crystals ', 
 which I presume will be used with more propriety than the former, 
 whenever it is necessary to ascertain the quantity of acid in the 
 liquor of the first boiling. Both these tables will be found in the 
 subsequent pages marked No. II. and III. 
 
 That nothing of importance may be omitted which respects this 
 acid, the following circumstances, for which I am indebted to 
 Dr. Thomson, may be added to the numerous facts already de- 
 tailed in the preceding Essay: 
 
 Chlorine converts gum into citric acid, according to the expe- 
 riments of Vauquelin. This chemist passed a current of chlorine 
 gas through a diluted solution of gum in water. In a few days 
 almost the whole of the gum was acidified ; and he detected citric 
 acid by the formation of super-citrate of lime, soluble in water, 
 and decomposable by oxalic acid. If nitric acid be slightly heated 
 upon gum until it has dissolved it, and until a little nitrous gas 
 is exhaled, the solution on cooling deposits saclactic acid. Malic 
 acid is formed at the same time ; and if the heat be continued, the 
 gum is at last changed into oxalic acid. Thus, no less than four 
 acids are formed by the action of nitric acid on gum. We are, 
 however, indebted to Mr. Cruikshanks for the most precise ex- 
 periments on the quantity of oxalic acid obtainable from gum by 
 nitric acid. By digesting 480 grains of gum with 6 ounces of 
 nitric acid, he obtained 210 grains of oxalic acid. No artificial 
 tannin is formed during this process. 
 
 1 It will be perceived, that the specific gravity of the solution of brown 
 crystals is greater than that of the pure crystals. This I apprehend arises from 
 the brown crystals generally retaining a portion of sulphuric acid. 
 
ON CITRIC ACID. 
 
 271 
 
 TABLES. 
 
 No. I. A TABLE of the Quantity of pure Crystals of Citric Acid which maybe 
 obtained from different Parcels of Lime or Lemon Juice, as indicated by the 
 Proportions of DRY Salt of Tartar required for their Saturation ; one ounce 
 measure of Lemon Juice being saturated by the test in each experiment. 
 
 Quantity of 
 dry Salt of Tartar 
 employed. 
 
 Quantity of 
 Crystals of Citric 
 Acid which may be 
 obtained from one 
 Gallon of such Juice. 
 
 Quantitv of 
 dry Salt of Tartar 
 employed. 
 
 Quantity of 
 Crystals of Citric 
 Acid which may be 
 obtained from one 
 Gallon of such Juice. 
 
 Grains. 
 
 Ounces avoirdupois. 
 
 Grains. 
 
 Ounces avoirdupois. 
 
 4^ 
 
 1 
 
 42 5 
 
 10 
 
 85 
 
 2 
 
 46f 
 
 11 
 
 17 
 
 4 
 
 51 
 
 12 
 
 Hi 
 
 5 
 
 55 
 
 13 
 
 25 \ 
 
 6 
 
 59 
 
 14 
 
 29f 
 
 7 
 
 63| 
 
 15 
 
 34 
 
 8 
 
 68 
 
 16 
 
 38^ 
 
 9 
 
 
 
 No. II. A TABLE of the Solution of WHITE Crystals of Citric Acid. 
 
 Crystallized 
 Acid. 
 
 Ounce 
 
 Measures 
 of 
 Water. 
 
 Sp. Grav. 
 at the 
 Temp. 55 
 Degrees. 
 
 Avoirdupois 
 Weight of the 
 Wine-pint. 
 
 Quantity of Crystals 
 dissolved by^ one 
 Gallon;;of Water. 
 
 
 Oz. 
 
 
 Oz. Dms. 
 
 Lbs. Oz. Dms. 
 
 1 Ounce 
 
 1 
 
 1.2187 
 
 19 8 
 
 800 
 
 Avoirdu- 
 
 2 
 
 1.1395 
 
 18 3| 
 
 400 
 
 pois. 
 
 3 
 
 1.1016 
 
 17 10 
 
 2 10 10 
 
 
 4 
 
 1.0799 
 
 17 4J 
 
 200 
 
 
 5 
 
 1.0663 
 
 17 1 
 
 1 9 9 
 
 
 6 
 
 1.0575 
 
 16 14| 
 
 1 5 5* 
 
 
 7 
 
 1.0494 
 
 16 12 
 
 1 2 4$ 
 
 
 8 
 
 1.0433 
 
 16 11 
 
 1 
 
 
 10 
 
 1.0352 
 
 16 9 
 
 12 12| 
 
 
 12 
 
 1.0298 
 
 is n 
 
 10 10 
 
 
 14 
 
 1.0250 
 
 16 6 
 
 9 2i 
 
 
 16 
 
 1.0216 
 
 16 5 
 
 080 
 
 
 20 
 
 1.0162 
 
 16 4i 
 
 6 6* 
 
 
 24 
 
 1.0135 
 
 16 3 
 
 5 i 
 
 
 28 
 
 1.0115 
 
 16 3 
 
 4 9f 
 
 
 32 
 
 1.0101 
 
 16 2| 
 
 040 
 
 To prevent the possibility of any misconception respecting the 
 nature of this Table, it may be proper to state an example of 
 its use. For instance, if it be required to examine a parcel of 
 lemon juice by the dry salt of tartar, all that is necessary is to 
 take an ounce measure, or the sixteenth part of a wine-pint of 
 
272 ON CITRIC ACID. 
 
 such juice ; and having noted the number of grains required for 
 its saturation, to look for the same number in the second column 
 of the first Table; and opposite thereto, in the third column, will 
 be seen the quantity of crystals of citric acid which may be ob- 
 tained from a gallon of such juice. 
 
 No. III. A TABLE of the Solution of BROWN Crystals of Citric Acid. 
 
 Crystallized 
 Acid. 
 
 Ounce 
 Measures 
 of 
 Water. 
 
 Sp. Grav. 
 at the 
 Temp. 55 
 Degrees. 
 
 Avoirdupois 
 Weight of the 
 Wine-pint. 
 
 Quantity of Crystals 
 dissolved by one 
 Gallonof Water. 
 
 
 Oz. 
 
 
 Oz. Dms. 
 
 Lbs. Oz. Dms. 
 
 1 Ounce 
 
 1 
 
 1.2656 
 
 20 4 
 
 800 
 
 Avoirdu- 
 
 2 
 
 1.1640 
 
 18 10 
 
 400 
 
 pois. 
 
 3 
 
 1.1171 
 
 17 14 
 
 2 10 lOi 
 
 
 4 
 
 1.0937 
 
 17 8 
 
 200 
 
 
 5 
 
 1.0820 
 
 17 5 
 
 1 9 94 
 
 
 6 
 
 1.0664 
 
 17 1 
 
 1 5 5|: 
 
 
 7 
 
 1.0566 
 
 16 14 
 
 1 2 44 
 
 
 8 
 
 1.0526 
 
 16 134 
 
 1 
 
 
 9 
 
 1.0488 
 
 16 124 
 
 14 34 
 
 
 10 
 
 1.0448 
 
 16 114 
 
 12 121 
 
 
 12 
 
 1.0390 
 
 16 10 
 
 10 104 
 
 
 14 
 
 1.0332 
 
 16 84 
 
 9 2i 
 
 
 16 
 
 1.0312 
 
 16 8 
 
 080 
 
 
 18 
 
 1.0273 
 
 16 7 
 
 7 ll 
 
 * 
 
 20 
 
 1.0254 
 
 16 64 
 
 6 6i 
 
 
 24 
 
 1.0214 
 
 16 54 
 
 5 5-J 
 
 
 28 
 
 1.0195 
 
 16 5 
 
 4 9f 
 
 
 32 
 
 1.0156 
 
 16 4 
 
 040 
 
 The Tables Nos. II. and III. are founded on actual experi- 
 ments, undertaken for the purpose of ascertaining the specific gra- 
 vities of the solutions of this acid at different degrees of concen- 
 tration. A single example will be sufficient to explain their 
 design. 
 
 Suppose a printer, who uses purified crystals of citric acid, 
 should find that a solution of the specific gravity of 1.0162 is 
 suitable for any particular purpose, he will learn, by reference 
 to the Table No. II., that he may prepare a similar solution by 
 dissolving one ounce of crystals in 20 ounces of water, or 6 ounces 
 6 drachms in one gallon of water. The Table No. III. is con- 
 structed upon the same principle, and is intended for the use of 
 those printers who employ the brown crystals. 
 

ON THE FIXED ALKALIES. 273 
 
 ESSAY IX. 
 
 ON THE FIXED ALKALIES. 
 
 
 
 FROM the nature and origin of this class of bodies, it is evident 
 that mankind must have arrived at a considerable degree of civi- 
 lization before either of the alkalies could have been brought 
 into general use : we shall, however, be able to demonstrate that 
 they were employed in very remote periods of antiquity. 
 
 To those who are unacquainted with chemical subjects, and who 
 have never had an opportunity of examining these substances, it 
 will be impossible to convey a full idea of their nature and pro- 
 perties by any description that can be given of them ; though it 
 may be said, that when in a state of purity their chief characters 
 are, an acrid and peculiar taste ; that they have the property of 
 changing blue vegetable juices to a green, and some yellows to 
 brown ; have a great affinity for animal and vegetable oils, with 
 which they unite to form soap, the oils, or other fatty substances, 
 being in this way rendered miscible with water ; that they them- 
 selves are also very soluble in water ; and lastly, which is one of 
 their most decisive characteristics, that they readily combine with 
 and neutralize the acids, forming neutral salts, which differ in 
 their appearances and properties according to the nature of the 
 respective acids, or alkalies, of which the salts are composed. 
 
 There are only four proper alkalies at present known, viz. the 
 three fixed alkalies, and the volatile alkali. The former, which 
 are known by the names of potash, soda and lithia, will constitute 
 the principal subject of the present Essay. 
 
 The word lixivium, which was in use among the ancient 
 Romans, is evidently derived from lix, which signifies a lye made 
 with ashes : it therefore appears that the preparation of the fixed 
 alkalies from the ashes of certain burnt vegetables, must have 
 been known very early ; especially as lixa^ another Latin term, 
 signifies a worker in ashes. Both of these words are used in the 
 same acceptation by Columella 1 and also by Pliny 2 , who flou- 
 rished in the century immediately preceding the commencement 
 of the Christian era. 
 
 Marcus Terentius Varro, the renowned Roman general, who 
 wrote in the first century, affords other evidence to the same 
 
 1 Lib. xii.cap. 41. ~ Nat. Hist, lib. xiv. cap. 2. 
 
 T 
 
ON THE FIXED ALKALIES. 
 
 purpose ; for he tells us that some of the inhabitants upon the 
 Rhine, being in want of sea-salt, used a substitute which they 
 procured from some species of wood *. These people had pro- 
 bably learnt a method of neutralizing the alkali which their forests 
 afforded them, so as to form a salt that would answer some of the 
 purposes to which our culinary salt is generally applied. 
 
 That the ancient Romans were acquainted with the fixed 
 alkalies, or with one of them at least, is evident from a circum- 
 stance that occurred in exploring one of the streets of the ancient 
 city of Pompeii, which was overwhelmed by an eruption of Vesu- 
 vius in the 79th year of the Christian era. On examining the 
 excavations that were made on the spot where this famous city 
 formerly stood, a complete soap-boiler's shop was discovered, 
 with soap in it which had evidently been made by the combination 
 of oil and an alkali. This soap was still perfect, though it had 
 been manufactured more than seventeen hundred years 2 . 
 
 Aristotle, who flourished nearly four hundred years before 
 Christ, says that the ashes of certain burnt reeds and bulrushes, 
 when macerated in water, yield a plentiful supply of salt 3 : and 
 according to one of the sacred writers, who lived still earlier, 
 his cotemporaries were not only acquainted with the alkalies, 
 but had learnt to apply them to some of the common purposes 
 of life 4 . 
 
 It does not with certainty appear which of the fixed alkalies 
 was first known, though I conceive there is some reason for 
 assigning the priority to soda as having been first in use for 
 domestic purposes, as nature affords it to the inhabitants of seve- 
 ral parts of the East without any contrivance or preparation of 
 their own. It appears likewise to have been known by the term 
 nitrum^ and it is so described by several of the ancient writers. 
 
 In the ninth century, an Arabian author of the name of Geber 
 describes soda very distinctly, and actually distinguishes it from 
 potash. But, on the other hand, Pliny has as plainly told us 
 that the Germans of his day used potash in making soap ; so that 
 the matter of priority will probably ever remain in uncertainty. 
 
 The word alkali is of Arabian origin, and is derived from 
 Kali, the name of a species of vegetable from which soda is gene- 
 rally extracted. If we believe Albertus Magnus 5 , the word sig- 
 nifies fax amaritudinisy " the dregs of bitterness ;" the particle 
 AL having, as he says, been added by the Arabs, with the design 
 
 1 Varro De Re Rustica, lib. i. cap. 7. 
 9 See Miss Starke's Letters from Italy. 
 
 3 Meteor ii. cap. 3. 
 
 4 " Though thou wash thee with natron, and take thee much soap, yet thine 
 iniquity is marked before me." Jeremiah ii. 22. 
 
 6 Theatrum Chemicum, ii. 470. Thomson, 8vo, 1804, vol. i. 463. 
 
ON THE FIXED ALKALIES. 275 
 
 of expressing the superiority of the article obtained from the 
 plant over the plant itself. In the days of Pliny the word Kali 
 was, throughout Egypt, generally used to signify a certain 
 vegetable abounding in alkaline salt, which grew on the sea- 
 shore, on the banks of the Nile, and on the confines of the river 
 Bel us in Syria. The same word is in use also with us, and has 
 the same signification. 
 
 The alkalies have a very peculiar taste, so different from that 
 of all other bodies, that it will be no difficult matter for the 
 student, when he has once made himself acquainted with it, to 
 recognise them at all times by this peculiarity alone: but as 
 these substances, when in a dry and pure state, are very cor- 
 rosive, and would not fail to blister the tongue, it will always be 
 necessary, for this purpose, to dilute them plentifully with water. 
 
 It is another property belonging to the alkalies, that they 
 change many of the blue vegetable juices, such as the violet and 
 mallow flowers, to a green; though if litmus be treated with 
 either potash or soda, the colour will be rendered rather more 
 intensely blue. By making this experiment, which may be done 
 without any peculiar apparatus or expense, this characteristic of 
 the alkalies will be imprinted on the mind so as never to be 
 effaced. 
 
 Let the student prepare a solution of the potash or pearlash 
 of commerce, and when a little of this is poured into a wine-glass 
 containing one of the common blue vegetable decoctions, the 
 whole will immediately be changed to a green. If a few drops 
 of diluted sulphuric acid be then added, the alkali will be 
 saturated, and the colour will in some measure be restored ; and 
 by adding a very little more of the acid, the whole fluid will 
 assume a beautiful crimson. Hot water poured on a few slices 
 of the red cabbage will produce a blue decoction, very suitable 
 for this experiment ; or a strong infusion of the dried flowers of 
 the red rose will answer the same purpose. 
 
 Although the alkalies, as has just been stated, convert the blue 
 vegetable juices to a green, they produce a deep brown in the 
 vegetable yellows. Thus, if a few drops of the solution of potash 
 or of soda be added to an infusion ojf turmeric, the yellow will 
 instantly be converted to a brown ; and this new colour will be 
 permanent, unless it be afterwards treated with an acid, which 
 has the power of restoring the original yellow; acids and alkalies, 
 according to the predominance of either, having the property of 
 alternately changing the hue of most vegetable colours. Hence 
 the great use of this class of substances in the arts, especially in 
 dyeing, and in the manufacture of several of the blue and green 
 colours which are prepared for the painter. 
 
 The potash and pearlash of commerce were thought to be 
 
 T2 
 
2*76 ON THE FIXED ALKALIES. 
 
 pure simple suostances, until Dr. Black, in the year 1756, satis- 
 factorily proved that they all contain a considerable portion of 
 carbonic acid. The readiness with which lime deprives this 
 alkali of its carbonic acid may be shown by the following very 
 simple experiment. Pour a little clear solution of carbonate of 
 potash into a wine-glass of transparent lime water ; and though 
 both liquors were perfectly limpid as the purest water while 
 separate, they will instantly become turbid on mixture; for the 
 lime, absorbing the carbonic acid from the alkali, will be con- 
 verted to carbonate of lime or chalk, which, being an insoluble 
 compound, will precipitate in a white powder. 
 
 The largest consumption of the alkalies is chiefly in the making 
 of soap and glass. The principal part of the kelp that is pre- 
 pared on the coasts of Wales, Scotland, and Ireland, is employed 
 in the first of these compounds, besides some thousand tons of 
 barilla annually imported from the Continent, particularly from 
 Spain, and from certain islands in the Mediterranean. 
 
 In the manufacture of soap, these rough alkalies are bruised 
 by means of a horse-mill ; and when mixed with a portion of 
 quick-lime sufficient to deprive them of their native carbonic 
 acid, or fixed air as it was formerly called, they are put as lightly 
 as possible into large cast-iron vats capable of holding from one 
 to five or six tons each. 
 
 When these vats are thus charged, water is let in until it rises 
 an inch or two above the surface of the materials, care being 
 taken that it run on in a regular gentle stream, so as not to 
 render the charge too solid, which would prevent the lye from 
 running properly through it. The design of the water is to 
 dissolve the alkali that is contained in the kelp, or barilla, and 
 in this way to separate it from the various insoluble matters 
 which these articles always contain. 
 
 The lime does not impart any of its own properties to the lye 
 or the soap, as is often believed ; it is employed merely to de- 
 prive the alkali of the carbonic acid which has just been noticed, 
 and which would incapacitate the alkali for forming that intimate 
 union with the oil or tallow which is required to render the 
 whole into a perfect soap, soluble in water. 
 
 When the charge has stood thus covered with the fluid for 
 twelve hours or more, the wooden plug near the bottom of the 
 vat is loosened, and the alkaline lye which has been formed is 
 suffered to run off gradually into a large iron receiver, fixed 
 underneath and below the floor of the manufactory. This is 
 called lye of the first running ; and, being the strongest, it is 
 generally reserved for the last operations in the manufactory. 
 The lixivium which has run from an adjoining but weaker vat, 
 is now pumped upon that which has just been drained, and the 
 
ON THE FIXED ALKALIES. 277 
 
 whole is suffered to remain at rest us before. The liquor is 
 thus pumped from beneath one vat upon the contents of another, 
 and that again is replenished from the adjoining one, day after, 
 day, in regular succession, until the last of the series, which has 
 frequently been covered with simple water, is thought to be 
 entirely spent. When this is the case, the plugs are at once 
 taken out of the whole row of vats, and the contents are suffered 
 to drain for some time, preparatory to their being cast, as it is 
 called, which is performed in the following manner : The ashes 
 of the spent vat are first thrown out as a refuse article; and 
 when this vat is entirely empty, the contents of the adjoining 
 one are thrown in, and so on to the end of the row, or to the 
 beginning of the series, when the first vat, being then empty, is 
 re-filled with a new charge of kelp or barilla. The plugs are 
 now replaced, and the ashes in each vat are again covered with 
 the weak lye from the receiver that is immediately underneath 
 it. Thus the whole of the alkali and alkaline salts are dissolved, 
 and the lixivium formed at a small expense of labour. By suffering 
 the ashes thus to drain themselves entirely dry, and then casting 
 them with large shovels into another vat, such parts as may have 
 become conglomerated are broken, so that every thing which is 
 soluble has a chance of coming in contact with the fluid, and of 
 being dissolved by it. 
 
 This narrative might perhaps have appeared with more pro- 
 priety in an essay upon soap-making ; but while treating ex- 
 pressly on the fixed alkalies, I was desirous of describing the 
 method by which they can be rendered caustic at the least 
 expense. 
 
 The alteration which is produced in the alkalies of commerce 
 by the admixture of quick-lime is so manifest, and is attended 
 with such important consequences, that the circumstance ought 
 never to be forgotten by those who are engaged in any of the 
 manufactories where large quantities of potash or soda are 
 consumed : for in some, the quality of the manufactured article 
 is much influenced by the state of the alkali; and in others, very 
 great savings might be made by using caustic potash, or soda, 
 in cases where the mild alkalies are now employed. 
 
 Many instances of these peculiar effects might be adduced : 
 but I shall select one from the detersive property of the alkalies, 
 that will sufficiently elucidate the practice which I am now at- 
 tempting to enforce. 
 
 In scouring woollen yarn to free it from the oil which is com- 
 bined with it in combing and spinning, it is no uncommon thing 
 for the workmen to prepare a large boiler of lye, by dissolving 
 American or Russian pearhibh in water, by means of heat. 
 
278 ON THE FIXED ALKALIES. 
 
 When this liquor is hot, they immerse their brown yarn in it, 
 and soon find it sufficiently freed from the oil and other filth 
 that is attached to it. More is then immersed, but this takes a 
 longer time to become clean; and the next parcel longer still; 
 till at length it is so far spent as to have little or no effect upon 
 the yarn, and is therefore suffered to run away to make room 
 for a fresh lixiviation, although one half of the alkali in the 
 former one is not consumed. Instead of proceeding in this way, 
 let the workman mix a quantity of potash with one-fourth of its 
 weight of fresh burnt quick-lime, (if pearlash be used, one-half 
 its weight of lime should be taken,) put it into a vat, or into an 
 iron pan, and then by the addition of water make a lixivium 
 from it, as described above, and put only so much of this into 
 the hot water as is necessary to scour that quantity of wool or 
 yarn which is usually cleansed at once. Then let him add a 
 few quarts more for the next parcel, and proceed in this way 
 until the whole be finished, and he will find that any given 
 quantity of work may be done with more expedition, and with 
 less than half the alkali that is usually employed. 
 
 The lye made in the common mode operates very well at first, 
 because a portion of the alkalies of commerce is generally in a 
 caustic state ; but as soon as this is saturated with the oil of the 
 yarn, the remaining, and often the greater part, having no effect 
 in the way they use it, is thrown away as useless, and is a total 
 loss to the manufacturer. Many thousand pounds, I believe, 
 are thus lost to the community annually, which might be saved 
 by a general knowledge of this simple fact, that alkalies will not 
 combine with oleaginous matter, unless they are actually in a state 
 of causticity. The greater part of our American pearlash is 
 combined with a very large portion of carbonic acid, and there- 
 fore it is not in a condition to combine with oil ; but let it be 
 divested of this acid, and it will not only form an intimate union 
 with whatever oil or grease it comes in contact with, but it will 
 render these impurities so completely soluble in water, that the 
 whole will be as easily washed out from the yarn, and dissolved, 
 as if it were sugar or salt. 
 
 Potash, as has before been mentioned, is prepared from the 
 ashes of burnt wood, and is chiefly manufactured in those coun- 
 tries where there is an abundant supply of timber. It is ob- 
 servable, that in the middle of the last century it was not known 
 how to make either potash or pearlash in any part of North 
 America, equal in quality to that which had usually been im- 
 ported from Russia. This was, however, at length effected by 
 the persevering endeavours of a Mr. Thomas Stephens, who 
 about the year 1753 received a grant from the Parliament of 
 
ON THE FIXED ALKALIES. 279 
 
 England for his encouragement 1 . The Russian method of 
 making potash from large wood is fully described by Boerhaave 
 in his System of Chemistry* : he has also given ample directions, 
 in the same work, how various smaller vegetables may be 
 managed in different circumstances, so as to be burnt for the 
 production of potash ; and though there may be few cases in 
 which his processes would answer, in this country, on a large 
 scale, yet a perusal of his narrative will not fail to give the reader a 
 very correct idea of the methods for obtaining this singular sub- 
 stance. More economical directions, however, and perhaps the 
 best hitherto devised, may be seen in the Annales de Chimie, 
 torn. xix. page 157 193. 
 
 It has generally been imagined that the alkali which is pro- 
 cured from vegetables is the creature of fire ; but I know of one 
 case (and there may be many others), in which vegetables are 
 employed for the sake of the alkali they contain, without pre- 
 viously burning them. I refer to the operation of fulling woollen 
 cloth. 
 
 When woollen cloth comes from the hands of the weaver, it 
 is carried to the fulling mill, where it undergoes a long-con- 
 tinued beating by ponderous wooden hammers, which are moved 
 with considerable force by a large water-wheel. By this treat- 
 ment the cloth becomes considerably thicker, closer, and better ; 
 losing in its length and breadth exactly in proportion to its in- 
 creased thickness. But it is rather a curious circumstance, that 
 no woollen cloth will thicken by this operation until it be divested 
 of the oil or grease which the wool had acquired in the process 
 of combing and carding. To effect this, the following articles 
 are made use of, viz. an earth which is principally brought from 
 the county of Kent, called fullers'-earth, common hard soap, and 
 a portion either of potash, or the crystals of soda. 
 
 In the county of York, however, where there are many hun- 
 dreds of poor weavers who work in their own small cottages, and 
 produce perhaps one piece of cloth only in a week or a fortnights 
 it is customary for them to take it to a public mill, with the 
 necessary quantity of scouring materials, and there to superin- 
 tend the operation, until the cloth is brought to that thickness 
 which they conceive will occasion it to sell most to their advan- 
 tage. 
 
 Now I understand it is no unusual thing for those poor people 
 who wish to avoid the expense of buying alkalies, to send their 
 
 1 See The Method and plain Process for making Potash t by Thomas Stephens, 
 4to, with plates, London. 
 
 2 Dallowe's edition of Boerhaave's Elements, of Chemistry, vol. i. page 443, 
 and vol. ii. page 2835. 
 
280 ON THE FIXED ALKALIES. 
 
 wives and children to an adjoining common to collect fern, which 
 they throw into the mill with the piece, where its alkaline juices 
 are expressed and worked into the cloth : and that by this as 
 good an effect is produced as if soda or potash had been em- 
 ployed. And in other cases, where soap and alkali have been 
 used, and too small a quantity of these has been taken, so that 
 the cloth will not thicken sufficiently, a small parcel of fern will 
 occasion the operation to commence, and it will then go on as 
 well as could be desired. Some of the lower class of weavers 
 derive, as I have been told, considerable advantage from their 
 knowledge of this very valuable plant 1 . 
 
 Potash may also be procured from the ashes of burnt peat : but 
 this is not a source from which it is generally obtained ; nor do I 
 know that the method is at all practised any where but in the 
 Highlands of Scotland, where the poor inhabitants have learnt 
 how to make the soap for their domestic uses from the ashes of 
 their own peat fires. 
 
 Potash may likewise be obtained from saltpetre, by heating it 
 sufficiently with charcoal, or any carbonaceous matter that will 
 decompose its acid. In this way one hundred weight of nitre 
 will yield nearly half a hundred weight of pure potash ; and 
 whenever the relative prices of American potash and nitre will 
 admit of it, the latter substance may be employed with profit for 
 the production of this alkali. During our dispute with America, 
 when the importations of pot- and pearl-ash were so small as to 
 occasion a considerable advance on the customary prices of 
 those articles, a large quantity of saltpetre was consumed in 
 Great Britain for the above purpose ; and for the Jiner kinds of 
 flint glass, saltpetre may generally be substituted for potash with 
 advantage. 
 
 Potash has been obtained in Germany, in pretty large quanti- 
 ties from the pyroligneous acid, by pouring this acid on wood 
 ashes, and then fluxing the whole in a furnace of brick or stone. 
 The process is described by Glauber, in his Miraculum Mundi, 
 with considerable minuteness 2 . Where saw-dust, straw, the 
 tendrils of the hop, or bean-haums can be had in abundance, it 
 might perhaps be advantageous to soak such materials in this 
 acid, and then to burn and flux the whole into a saleable ash. 
 But the oil should, if possible, be previously separated as much 
 as possible from the pyroligneous acid. 
 
 Macquer relates, that in some parts of Germany potash is 
 prepared from the same parcels of wood of which charcoal is 
 
 1 See a paper by Monge on the Fulling of Woollen Cloth in the sixth 
 volume of the Annales de Chimie, pages 300 311. 
 * Glauber, Chemical Works, folio, page 188. 
 
ON THE FIXED ALKALIES. 281 
 
 made. A number of tubes made of plate iron or of copper, are 
 so disposed in the pile of wood intended to be burnt into char- 
 coal, that the acid, &c. is collected in reservoirs ; and when the 
 oil is separated the fluid is boiled in iron vessels, and the re- 
 siduum is converted by calcination to an alkali 3 . 
 
 Potash is a component part of pumice-stone, and of some other 
 mineral productions. Professor Abilgaart found that this alkali 
 formed also a constituent part of animal blood 4 ; but it sel- 
 dom occurs in other animal substances, except in very minute 
 .quantities. 
 
 Before I close this account it may be useful to remark, that the 
 buyers of American potash generally prefer that which breaks 
 red, which is, as I apprehend, a mere prejudice ; for I have rea- 
 son to think that this colour arises chiefly from the presence of 
 sulphur, and perhaps oxide of iron, neither of which can be of 
 any use where a good alkali is required. I have ascertained that 
 some English makers of potash who are acquainted with this 
 effect of sulphur, designedly add a portion of that substance to 
 their ash, while it is in a state of fusion ; and by taking a little 
 from the melted mass after every addition of the sulphur, and 
 suffering that to cool for examination, they are easily enabled to 
 bring the whole to that colour which will best suit the market. 
 
 Whenever this alkali is employed for nice purposes, the article 
 called pearlash is generally preferred to potash. This is prepared 
 by a long continued calcination of potash, at a low heat, whereby 
 the sulphur and carbon which it contains are mostly burnt off*. 
 But as all the pearlash which comes from Russia and America 
 contains a considerable proportion of neutral salts, it has long 
 been, and still continues to be, our task to deprive it of these 
 adulterations. And lately, several persons in various parts of 
 this kingdom have established manufactories for preparing this 
 alkali, and have produced considerable quantities, and compa- 
 ratively in a state of great perfection, from various chemical re- 
 siduums, which were formerly rejected as of no value. 
 
 Having thus fully treated on the history and origin of potash ; 
 on its various sources foreign and domestic; and on its nature 
 and properties, it will now be proper to give some account, 
 however concise, of the several salts which are formed by its 
 means, or which contain potash as one of their principal ingre- 
 dients. 
 
 Acetate of potash, formerly called digestive salt of Sylvius. It 
 
 3 See the article " Alkali," in Macquer's Chemical Dictionary, vol. i. 
 
 4 Parkinson's Memoranda Chemica t fourth edition, 1807, page 11. 
 
282 ON THE FIXED ALKALIES. 
 
 is in the form of plates or prismatic crystals. These dissolve in 
 their own weight of water at 60. The solution has an acrid 
 saline taste. The salt is composed of 1 proportional of potash 
 48, and 1 of acetic acid 50, making its equivalent number 98. 
 
 Ammonio-sulphate of potash. This salt is formed by adding 
 ammonia to the bi-sulphate of potash. The process is described 
 by Link in Crell's Annals for 1796, vol. i. p. 26. It has a bitter 
 taste like the common alkaline sulphates, and crystallizes in bril- 
 liant plates, which are not altered by exposure to the air. The 
 salt consists of sulphate of potash 88, and sulphate of ammo- 
 nia 57. 
 
 Antimoniate of potash. This is a white powder possessing an 
 acrid and metallic taste. It dissolves in boiling water, but is 
 scarcely acted upon by cold water. According to Berzelius, it 
 is composed of antimonic acid 79.2, and potash 20.8. 
 
 Antimonite of potash. In an Essay on Chemical Nomencla- 
 ture, Berzelius states this salt to be composed of antimonious 
 acid 76.6, and potash 23.4. See Nicholson's Journal, vol. xxxv. 
 p. 44. This salt is insoluble in cold, but soluble in boiling 
 water. 
 
 Arseniate of potash. This salt is formed by saturating arsenic 
 acid with potash. It is deliquescent when exposed to the air, and 
 is incapable of crystallization. It renders syrup of violets green, 
 but has no effect on an infusion of turnsole. 
 
 Arsenite of potash. This is a very soluble and incrystallizable 
 salt. It is formed by boiling white arsenic in a solution of potash. 
 This salt is the most important ingredient in Fowler's tasteless 
 ague drop. 
 
 Benzoate of potash. This is a deliquescent salt, very soluble 
 in water. If this salt be digested with benzoic acid, a bibenzoate 
 will be produced in acicular and lamellar crystals, which require 
 ten parts of cold water for their solution. See Bucholz, Annales 
 de Chimie, vol. Ixxxiv. page 311. 
 
 Bicarbonate of potash. This salt is usually made by passing 
 carbonic acid gas into a solution of potash in water, and evapo- 
 rating the fluid to the point of crystallization. The crystals 
 which separate are in the form of four-sided prisms, with dihe- 
 dral summits. The dry salt consists of 2 proportionals of car- 
 bonic acid 44, and 1 of potash 48. When crystallized it con- 
 sists of dry salt 92, and water 9. 
 
 Bichromate of potash crystallizes in rectangular tables of an 
 exquisitely beautiful orange colour much used as a pigment and 
 by the calico-printers. It consists of 2 proportionals of chromic 
 acid 104, and one of potash 48. 
 
 Binarseniate of potash. A salt formerly known by the name 
 of the arsenical neutral salt of Macquer. It may be formed by 
 
ON THE FIXED ALKALIES, 283 
 
 adding arsenic acid in excess to potash, and evaporating the so- 
 lution. The salt appears in quadrangular crystals, terminated 
 by four-sided pyramids. It is much employed for the cure of 
 agues. It is soluble in water ; and, like the acids, it changes the 
 blue juices of vegetables to a red. It is composed of 1 propor- 
 tional of potash 48, and 2 of arsenic acid 124. 
 
 Binoxalate or superoxalate of potash is formed merely by dis- 
 solving the crystals of oxalate of potash in oxalic acid. It also 
 exists ready formed in wood-sorrel, the Oxalis acetosella of Lin- 
 naeus. When extracted it is sold under the improper name of 
 essential salt of lemons. It is composed of 1 proportional of 
 potash 4-8, and 2 of oxalic acid 72. 
 
 Biphosphate or superphosphate of potash. This salt is easily 
 formed by dissolving phosphate of potash in phosphoric acid, 
 and evaporating the liquor to the point of crystallization. It 
 crystallizes in small striated prisms, which are exceedingly soluble 
 in water. The salt when dry has the specific gravity of 2.851. 
 Hassenfratz, Annales de Chimie, tome xxviii. page 14. 
 
 Bisulphate or super sulphate of potash. This salt, which is 
 the arcanum duplicatum of the old chemists, may be formed by 
 dissolving the common sulphate of potash in hot sulphuric acid. 
 It generally separates from its water of solution in thin rhom- 
 boidal crystals, which are soluble in two parts of water at 60. 
 This salt contains twice as much acid as the sulphate of potash. 
 
 Bitartrate or supertartrate of potash is the cream of tartar of 
 commerce. It exists in the juice of the grape, and when depo- 
 sited on the sides of wine-casks is known by the name of argoL 
 It is composed of 2 proportionals of acid 134, and 1 of pot- 
 ash 48. This salt requires 120 parts of water at 60, or 30 parts 
 at 212, for its solution. 
 
 Boletate of potash. The boletic acid is obtained from the 
 juice of the Boletus pseudo-igniarius. The boletate of potash was 
 formed by Braconnot : but all that he has said of it is, that it is 
 very soluble in water, that it is not easily procured in crystals, 
 and that other acids precipitate the boletic acid from it. See 
 Annales de Chimie, tome Ixxx. page 278. 
 
 Borate of potash. This salt may be obtained either in a dry 
 mass or crystallized. The crystals are quadrangular prisms, 
 unalterable by exposure to the air. The properties of this salt 
 are little known. Berzelius attempted to ascertain its consti- 
 tuent parts, but without success. It may be procured by boiling 
 boracic acid in a solution of potash. 
 
 Camphor ate of potash may be made by saturating a solution of 
 carbonate of potash with camphoric acid. The salt crystallizes 
 in regular hexagons, which are soluble in about 100 parts of 
 
284- ON THE FIXED ALKALIES. 
 
 water at 60, or in 25 parts at 212. It is soluble in alcohol, and 
 the solution burns with an intense blue flame. 
 
 Carbonate of potash. Large quantities of this salt are im- 
 ported into this country under the names of potash and pearlash 
 articles very generally known. It is sometimes procured from 
 nitre, and also from tartar. If these salts are submitted to a 
 red heat with carbonaceous matter, their acids are separated 
 thereby, and carbonate of potash is formed. It consists of car- 
 bonic acid 22, and potash 4-8. 
 
 Chlorate of potash, formerly called hyper-oxymuriate of potash, 
 is made by passing a current of chlorine gas into a solution of 
 potash, or carbonate of potash in water. It crystallizes in thin 
 plates. When mixed with sulphur or phosphorus it explodes 
 by trituration. If concentrated sulphuric acid be dropped upon 
 a small quantity of this salt, the decomposition will be so rapid 
 as to produce violent explosion with bright flame. It is upon 
 this principle that the instantaneous light boxes are formed, the 
 bottle containing asbestus saturated with the acid, and the matches 
 being coated with a mixture of chlorate of potash and sugar. 
 See an account of many of these experiments in the Chemical 
 Catechism. This salt is composed of 1 proportional of chloric 
 acid 76, and 1 of potash 48. 
 
 Chromate of potash crystallizes in slender prisms ; it is of an 
 intense lemon colour, and decomposes most of the metallic salts, 
 forming with those of lead a beautiful yellow much used as a 
 pigment. It is composed of chromic acid 52, and potash 48. 
 
 Citrate of potash. This salt has been already described in the 
 Essay on Citric Acid, page 263. 
 
 Columbate of potash. By boiling the columbic acid in a solu- 
 tion of potash, this salt is produced in white scales resembling 
 those of boracic acid. When the mineral acids are added to a 
 solution of this salt, the columbic acid is separated in the form of 
 a white powder. See Hatchett, Phil. Trans, for 1802. 
 
 Ferrocyanate of potash is a salt much used in calico-printing. 
 It may be prepared by digesting Prussian blue in a hot solution 
 of caustic potash. It is a triple salt, composed of hydrocyanic 
 acid, potash, and oxide of iron. It crystallizes in fine cubic and 
 tabular crystals of a bright yellow colour, and unchangeable in 
 the air. See the Essay on Calico-printing. 
 
 Ferrotartrate oj potash may be made by digesting iron filings 
 with tartar, in the proportion of one part of iron with two parts 
 of tartar, and then boiling the mass in a proper quantity of water 
 to dissolve the triple salt which is formed by the process. In the 
 old pharmacopoeias this salt was known by the name of Tartarizcd 
 tincture of Mars. 
 
ON THE FIXED ALKALIES. 285 
 
 Fluate of potash. This salt may be formed by the combination 
 of pure potash with fluoric acid. Heat is given out on the mix- 
 ture, and by subsequent evaporation the salt is obtained. It is 
 deliquescent, and very soluble in water. It may be decomposed 
 by the mere addition'of sulphuric acid, which combines with the 
 alkali and liberates the acid in the form of vapour. 
 
 Hydrate of potash. The fixed alkalies contain a considerable 
 portion of water, even after they have undergone a red-heat. 
 Hence the alkalies of commerce are always in the state of hy- 
 drates. The hydrate of potash consists of 1 proportional of pot- 
 ash 48, and 1 of water 9, making its equivalent number 57. 
 
 Hydriodate of potash is formed by dissolving carbonate of 
 potash in hydriodic acid. The constituents of this salt are, hy- 
 driodic acid 125, and potash 48. 
 
 Hydroguretted sidphuret of potash. This salt may be formed 
 by mixing flour of sulphur with a solution of hydro-sulphuret of 
 potash, and digesting the mixture in a gentle heat. Thus an 
 additional portion of sulphur will be dissolved, and an hydro- 
 guretted sulphuret of potash formed, which is a salt of a deep 
 yellow colour, with a very pungent and bitter taste, and a very 
 offensive smell. It may also be formed by boiling flowers of 
 sulphur in a weak solution of caustic potash. 
 
 Hydrosulphuret of potash may be produced by saturating potasli 
 with sulphuretted hydrogen. The fluid will be colourless and 
 transparent, and on evaporation will yield crystals not unlike 
 ihose of sulphate of soda. See Vauquelin, Annales de Chimie, 
 tome xlii. page 40. 
 
 Hypophosphite of potash. This is a deliquescent salt, very 
 soluble either in water or alcohol. When submitted to heat, 
 phosphorus and phosphuretted hydrogen escape, and the salt 
 is converted to phosphate of potash. See Dulong, Annales de 
 Chimie et Phys. tome ii. page 142. 
 
 Hyposidphite of potash. This salt is prepared by treating 
 hydrosulphuret of potash with liquid sulphurous acid, and eva- 
 porating the solution to the point of crystallization. On cooling, 
 needle-formed crystals are produced, which have a bitter taste, 
 and deliquesce when exposed to the atmosphere. 
 
 lodate of potash. This is a white salt in very minute crystals. 
 It is not altered by the air; but if heated to redness, oxygen gas 
 is given off, and iodide of potassium is produced. One hundred 
 parts of water at 14 centr., or 5?i of Fahrenheit, will dissolve 
 7.43 parts of this salt. Gay-Lussac, Annales de Chimie^ tome 
 xci. page 74. 
 
 Tractate of potash may be obtained by decomposing carbonate 
 of potash with lactate of lime. The salt has the appearance, 
 
286 ON THE FIXED ALKALIES. 
 
 when the water is abstracted by evaporation, of a yellowish 
 brown gum of a soft consistence. It is soluble in heated alcohol. 
 
 Malate of potash is a deliquescent salt, and so extremely soluble 
 in water as to be incapable of crystallizing. 
 
 Meconiate of potash forms itself in four-sided tables, which are 
 soluble in two parts of water at 60, and composed of 60 parts 
 potash, 40 meconic acid, and 13 water. See Brande's Manual, 
 vol. iii. page 71. 
 
 Mellate of potash is a salt which crystallizes in elongated 
 prisms. By a further addition of the acid, a supermellate may be 
 formed. Vauquelin, Annales de Chimie, tome xxxvi. page 209. 
 
 Molybdate of potash may be formed by digesting molybdic acid 
 in a solution of potash. The salt crystallizes in small rhomboids, 
 running into one another. These are soluble in hot water : but 
 the molybdic acid may be precipitated therefrom by the addition 
 of sulphuric or muriatic acid. See Annales de Chimie, tome viii. 
 page 106. 
 
 Muriate of potash. This salt when dry is in fact a chloride of 
 potassium, consisting of potassium 40, and chlorine 36. It crys- 
 tallizes in cubes which deliquesce slightly in the atmosphere. In 
 philosophical chemistry it is very much employed to produce 
 artificial cold. 
 
 Nitrate of potash, or what is usually called Saltpetre, is pro- 
 duced naturally in some particular districts in all hot countries : 
 but that which is consumed here is chiefly brought from the 
 East Indies. It crystallizes in hexagonal prisms. One hundred 
 parts of water at 60 dissolve fourteen parts of this salt, and 
 boiling water dissolves more than its own weight. This salt is 
 composed of nitric acid 54, and potash 48. 
 
 Nitrite of potash is a salt which was first observed by Scheele. 
 His process for preparing it is to fill a large crucible with nitre, 
 and keep it in a red-heat for half an hour. During this time a 
 portion of oxygen escapes, and what remains in the crucible is 
 nitrite of potash, a salt which will deliquesce when exposed to 
 the action of the air. 
 
 Oxalate of potash. This salt is formed by dissolving potash 
 in a solution of oxalic acid. It crystallizes in flat rhomboids, 
 soluble in three parts of water at 60. It is composed of 1 pro- 
 portional of oxalic acid 36, and 1 of potash 48. 
 
 Oxychlorate of -potash, which is a very insoluble salt, crystal- 
 lizes in elongated octoedrons. It consists of 1 proportional of 
 oxychloric acid 92, and 1 of potash 48. It is unalterable in the 
 air, and possesses no bleaching properties whatever. 
 
 Phosphate of potash. This salt may be produced by adding 
 carbonate of potash to hot phosphoric acid until the point of 
 
ON THE FIXED ALKALIES. 287 
 
 saturation be attained. If the solution be much concentrated and 
 then suffered to cool gradually, small prismatic crystals of phos- 
 phate of potash will be obtained, consisting of 1 proportional of 
 potash 48, and 1 of phosphoric acid 28. 
 
 Phosphite of potash. This is a deliquescent salt, incapable of 
 crystallization. Its properties, or even its component parts, are 
 not yet known. 
 
 Quadroxalate of potash was discovered by Dr. Wollaston. 
 When the Binoxalate of Potash is digested in dilute nitric or 
 muriatic acid, a part of the alkali is taken up, and a salt remains 
 consisting of four times as much oxalic acid as exists in oxalate 
 of potash. It is formed of four proportionals of oxalic acid 144, 
 and one of potash 48, making its equivalent number 192. 
 
 Saclactate of potash. Scheele has treated on this salt in his 
 Essay on the Sugar of Milk. He describes the salt to be in 
 small crystals soluble in eight times their weight of water at 212. 
 Silicate of potash was known to the old chemists. It may be 
 prepared by fusing three parts of good potash with one part of 
 ground silica, both calculated by weight. The resulting com- 
 pound forms a kind of glass on cooling which is soluble in water. 
 The solution thus formed is called liquor silicum. 
 
 Sorbate of potash. The sorbic acid was discovered in 1815 by 
 Mr. Donovan in the juice of the berries of the mountain ash. 
 United with potash this acid forms two distinct salts, viz. the sorbate 
 of potash which is incrystallizable, and the bisorbate, which gives 
 permanent crystals soluble in water, but insoluble in alcohol. 
 
 Suberate of potash is best prepared by digesting suberic acid 
 with a solution of crystallized carbonate of potash. The salt 
 crystallizes in prisms, and these are very soluble in water. 
 Annales de Chimie, tome xxiii. page 52. 
 
 Subphosphate of potash. This salt has been formed by fusing 
 pure potash, with the phosphate of this alkali, in a platinum cru- 
 cible. It is either a white solid, or a white powder, according to 
 the mode of its preparation. 
 
 Succinate of potash is a salt which crystallizes in small prisms, 
 deliquesces in the air, and is very soluble in water. Its taste is 
 saline and bitter. 
 
 Sulphate of potash. This salt is produced as a residuum in 
 large quantities by the makers of nitric acid, and is sold under 
 the name of sal enixwn. It has a saline bitter taste, and when 
 dissolved in water crystallizes for the most part in short six-sided 
 prisms, terminated by hexangular pyramids. It is composed of 
 40 sulphuric acid, and 48 potash. 
 
 Sulphite of potash. This salt, which was formerly known by 
 the name of the sulphurous salt of Stahl, may be formed by pass- 
 ing sulphurous acid gas into a saturated solution of very pure 
 
288 ON THE FIXED ALKALIES. 
 
 carbonate of potash, until the effervescence entirely ceases. The 
 solution becomes warm during the combination, and the salt 
 crystallizes on cooling in the form of rhomboidal plates. These 
 by exposure to the air are converted to sulphate of potash. See 
 a memoir by Fourcroy and Vauquelin in Nicholson's Journal, 
 4to, vol. i. page 317. 
 
 Sulphuret of potassium is formed by the fusion of a mixture of 
 sulphur and potash. This was formerly called liver of sul- 
 phur, and consists of 1 proportional of potassium 40, and 1 of sul- 
 phur 16. 
 
 Tartrate of potash is formed by adding a quantity of potash to 
 the bitartrate of potash sufficient to saturate the excess of acid. It 
 is called soluble tartar, and is used in medicine as an aperient. 
 It consists of 1 proportional of acid 67, and 1 of potash 48. 
 
 Tartrate of potash and antimony. This is that important com- 
 bination usually known under the name of emetic tartar. It is 
 a white salt, requiring 14 times its weight of cold water, or two 
 parts of water at 212, for its solution. It is composed of 2 pro- 
 portionals of tartaric acid 134, 2 of protoxide of antimony 106, 
 and 1 of potash 48, making its equivalent number 288. 
 
 Tartrate of potash and soda,, or Rochelle salt, is usually pre- 
 pared by adding the crystals of carbonate of soda to the super- 
 tar trate of potash, until the excess of tartaric acid is saturated. 
 It is then purified by repeated crystallizations, and appears in 
 irregular prismatic crystals. It consists of tartrate of potash 115, 
 and tartrate of soda 99. 
 
 Tellurate of potash. If oxide of tellurium be mixed with nitre, 
 and the mixture be exposed to heat, the nitre first melts without 
 acting on the oxide ; but at the temperature in which the oxide 
 begins to liquefy, it decomposes the nitre with a violent efferves- 
 cence, the nitric acid is driven off, and the oxide dissolves in the 
 potash. The mass when cold very much resembles an enamel. 
 Jt dissolves in boiling water, and the solution on cooling deposits 
 an imperfectly crystallized white powder. This is tellurate of 
 potash. It has a slight metallic taste, and acts feebly as an alkali 
 on vegetable blues. Thomson, vol. ii. page 665. Berzelius, 
 Nicholson's Journal, vol. xxxvi. page 130. 
 
 Tungstate of potash is a salt which may be prepared by dis- 
 solving the oxide of tungsten in a strong solution of carbonate of 
 potash. When this saturated solution is concentrated by evapo- 
 ration a white powder falls down, which is the tungstate of potash. 
 This salt deliquesces when exposed to the air, and consequently 
 is very soluble in water. 
 
 Urate of potash. This salt is stated by Dr. Thomson to be a 
 white powder nearly similar to uric acid in appearance and solu- 
 bility. It is also soluble in a lye of caustic potash. 
 
ON THE FIXED ALKALIES. 289 
 
 Zumate of potash. Zumic acid is obtained by a peculiar pro- 
 cess from rice. It was first described by Braconnot, but the 
 name which it now bears was given by Dr. Thomson. The 
 zumate of potash is a deliquescent salt, incapable of crystalli- 
 zation, and soluble in alcohol. Annales de Chimie, tome Ixxxvi. 
 page 84. 
 
 The other alkali of which we have to treat is SODA, which is 
 also known by the names of natron, barilla, mineral alkali, and 
 fossil alkali. This substance is met with in abundance, and even 
 used for various purposes, in China, Persia, in the environs of 
 Smyrna and Tripoli, and in general all over the East, as well as 
 on the northern coast of Africa, in Hungary, and Siberia. It 
 likewise occurs in the state of carbonate of soda in many of the 
 mineral waters of Germany. 
 
 Native soda is also found in large quantities, on the surface of 
 the ground, in the plains of the Delta in Egypt, from whence it is 
 brought to this country under the name of natron. It occurs in 
 the same state in the East Indies, and in the islands of Sicily and 
 Teneriff. These islands furnish us likewise with a large quantity 
 of soda, in the form of barilla, which is chiefly consumed in the 
 soap trade, as already mentioned. 
 
 Barilla is likewise imported in very considerable quantities 
 from Spain. This is made by the incineration of the salsola soda, 
 a marine plant, which is so highly valued by the Spaniards, that 
 the exportation of the seed is, by the law of the country, punish- 
 able with death. It is cultivated with great care in the neigh- 
 bourhood of Alicant and Carthagena, for the production of 
 barilla; but that of Alicant is generally the most esteemed. 
 
 And here we must not omit to mention the manufacture of 
 kelp upon our own shores, and which is so considerable as to 
 furnish the English market with many thousand tons of soda 
 annually. The manufacture of this article was introduced into 
 the Highlands of Scotland about the year 1730, by a gentleman 
 of the name of MacLeod, who brought the art of cultivating it 
 from Ireland. 
 
 Since the manufacture of kelp has been introduced into the 
 Orkneys, small farms of forty pounds a year have risen to 300/. a 
 year ' ; and " it is said that Lord MacDonald of the Isles realized 
 ten thousand pounds a year from his kelp shores alone, which his 
 ancestors looked upon as of no value whatever. So much indeed 
 are the proprietors of the sea-coast now impressed with the value 
 and importance of the kelp manufacture, that they have found 
 the means of producing it on thevery sands. They place stones 
 within flood-mark of the sea, which are soon covered with ware, 
 
 1 Jameson's Account of the Scottish Isles> vol. ii. page 244. 
 U 
 
290 ON THE FIXED ALKALIES. 
 
 as it is commonly called, and which is the vegetable substance 
 from which kelp is made ! . 
 
 The British kelp is prepared by the burning of various plants 
 of the genus salsola of Linnaeus, (the common sea- wrack,) and 
 similar to the salsola soda of the Spaniards ; but the article 
 which is procured from these plants is much inferior to barilla, 
 inasmuch as it contains a large portion of neutral salts, a quantity 
 of potash, and a much larger proportion of carbonaceous matter 
 than is generally found in the former article. 
 
 In making either barilla or kelp, the weed is collected into 
 heaps to ferment ; it is then spread to dry in the air, and is after- 
 wards burnt to ashes in ovens made with brick or stone, and built 
 within the ground. By increasing the heat, the alkali in the 
 ashes melts, and combines the whole into one solid mass. When 
 cold, it is broken up with iron bars into large ponderous masses, 
 and in that state it is sent to market. The best account that I 
 have seen of the manufacture of kelp is in Jameson's " Minera- 
 logy of the Scottish Isles" 4to, vol. ii. page 244. See also my own 
 " Prize Essay on Kelp and Barilla" in the fifth vol. of the Trans- 
 actions of the Highland Society a/Scotland^ pages 65 122. 
 
 It has long been a desideratum with the soap-makers and other 
 purchasers of kelp and barilla, who happen to have no knowledge 
 of chemistry, to find a method of ascertaining the exact portion 
 of alkali in any sample which may come under their examination ; 
 and as no accurate directions have been published, at least that 
 I have seen, I shall here give a detail of the mode which I have 
 followed for several years, in many hundreds of cases, and which 
 has in no instance deceived me. In preparing for the analysis, 
 it will be necessary to attend to the following directions. 
 
 In the first place, procure a pair of good small scales with a 
 set of decimal weights from one grain to a thousand grains ; a 
 graduated drachm measure, also a two-ounce measure, both of 
 glass ; a strong phial that will pour well ; some litmus-paper of 
 both kinds, viz. blue and red; a bottle of the solution of muriate 
 of platinum ; and some sulphuric acid diluted with pure water 
 until it be reduced, when cold, to the specific gravity of 1.100. 
 
 When any parcel of kelp or barilla is to be examined, it will 
 be proper to select as fair an average sample as possible. This 
 can only be done by taking several lumps from different parts of 
 the heap, by breaking a small piece from each of these lumps, and 
 mixing them with a fair proportion of the small which may be- 
 long to the lot. The sample should then be pulverized in an iron 
 mortar, that the whole may be more completely mixed ; and a 
 small quantity of this, say about an ounce, should be returned 
 
 1 Tradesman's Magazine. 
 
ON THE FIXED ALKALIES. 291 
 
 into the mortar and ground to an impalpable powder, that the 
 alkali may be dissolved out of it with greater ease and certainty. 
 Things being thus prepared, the analysis is to be proceeded with 
 in the following manner : 
 
 Take the weight of one hundred grains of the alkaline powder, 
 put it into a convenient vessel, and pour over it a two-ounce 
 measure of pure water. Stir the mixture with a piece of glass, 
 repeating it now and then during the space of a few hours. 
 When the insoluble matter has been suffered to subside, pour 
 the supernatant liquor upon a paper filter, and add another 
 measure of water to the residuum, which should be well stirred 
 once or twice, and then be suffered to remain as before. It is 
 necessary to attend to the circumstance of filtrating the solution : 
 otherwise there might be a portion of lime or carbonate of lime 
 in it, which would absorb part of the acid employed in the 
 analysis, and occasion an inaccurate result. When this lixivium 
 has been thus filtrated, the residuum itself should be put upon 
 the filter, and small portions of water poured over it occasionally, 
 until the watenpasses through it devoid of taste and colour. 
 
 These solutions are now to be mixed, and put into a convenient 
 vessel, in which they should boil until the whole is reduced to 
 about two or three ounces, when it will be sufficiently concen- 
 trated for the examination, which should be conducted in the 
 following manner : 
 
 Take about two ounces of diluted sulphuric acid, as above 
 mentioned, of the specific gravity of ] . 1 00 ; and having weighed 
 it accurately, together with the phial, note down the united 
 weight of both in grains. Then pour a portion of the acid very 
 gradually into the alkaline solution, and stir it well with a glass 
 rod, till the effervescence occasioned by the escape of the carbonic 
 acid has ceased. 
 
 A slip of the reddened litmus-paper should now be dipped 
 into the solution ; and if this becomes blue, it shows that the 
 liquid still contains alkali, and that more acid must be added. 
 In the beginning I generally put one drachm in measure of the 
 diluted acid to the lixivium after every trial with the test paper. 
 This, however, must now be done cautiously, taking care to stir 
 the mixture well after every addition of the acid. 
 
 When the effervescence becomes less, and the test paper 
 receives only a slight blue tinge by immersion in the lixivium, 
 the acid should be added still more gradually, and by a very few 
 drops at a time, that no more acid may be employed than is 
 absolutely requisite for the complete saturation of the alkali ; 
 which may be known by the cessation of the effervescence, the 
 unchangeable appearance of the test paper on immersion, and 
 the separation of the sulphur which was held in solution by the 
 
 u 2 
 
292 ON THE FIXED ALKALIES. 
 
 alkali, and which separates when the alkali becomes saturated 
 with an acid. 
 
 The alkali havingbeen in this way neutralized, the remainder 
 of the acid with its phial is to be weighed again, to ascertain 
 how much of the diluted sulphuric acid has been consumed ; and 
 this will show the precise quantity of real alkali which is con- 
 tained in the sample under examination, when it is known how 
 much acid an alkali in a state of purity is capable of taking up. 
 
 In order to provide a scale for calculating this, I took 1 00 
 grains of dry potash purified by means of alcohol ; and having 
 treated it with the diluted sulphuric acid of the specific gravity 
 of 1.100, I found that it required exactly 520 grains of the acid 
 to saturate it. In like manner I treated pure soda; but 100 
 grains of this alkali require 812 grains of acid of the same strength 
 for its saturation. 
 
 These results being considered as the basis, it is easy, by the 
 rule of proportion, to calculate how much real alkali there is in 
 any sample of kelp, natron, or barilla, by the weight of acid 
 required to saturate it. 
 
 But as the two alkalies combine with different portions of acid, 
 the analysis cannot be accurate unless it be ascertained whether 
 the alkali in the sample be soda only, or a mixture of soda and 
 potash ; and, if it be of the latter kind, in what relative propor- 
 tions these alkalies exist. 
 
 The most useful test in this case is the liquid muriate of 
 platinum, made by dissolving the crystals of that salt in pure 
 water ; for, if a drop of this reagent be added to a small quantity 
 of any alkaline solution, a yellow precipitate, which is a triple 
 compound of potash, oxide of platinum and muriatic acid, will 
 appear if the alkali contain potash ; whereas, if it be a solution 
 of soda only, no precipitate will occur. If the alkali under 
 examination should contain muriate of potash^ (which, however, 
 very rarely occurs,) this would likewise produce a precipitate, 
 and might occasion deception ; for the muriate of platinum de- 
 tects all the salts of potash as well as pure potash. Should a 
 sample be suspected to contain this salt, a small portion of the 
 lixivium might be supersaturated with sulphuric acid, by which 
 means the muriatic acid would be driven off and easily detected 
 by its peculiar smell, or by presenting ammoniacal gas ; and the 
 potash, in the form of sulphate, would be separated by its cry- 
 stallizing before the sulphate of soda. 
 
 There are several other methods by which the fixed alkalies 
 may be distinguished from each other. These are all described 
 in The Chemical Catechism, twelfth edition, page 127, &c. The 
 use of muriate of platinum has often been stated to be a new 
 method of detecting potash; but in justice to the memory of 
 
ON THE FIXED ALKALIES. 293 
 
 Margraff it ought to be known, that he pointed it out for this 
 especial purpose more than seventy years ago 1 . 
 
 SODA in its pure state is very similar in the causticity of taste 
 to potash ; though in its usual condition it does not so readily 
 absorb water from the atmosphere ; on the contrary, its crystals 
 effloresce, and entirely lose their water of crystallization by such 
 exposure. If, however, pure soda be rendered very dry and 
 then moistened with water, it will absorb the water with avidity, 
 and heat will be given out during this absorption, owing to the 
 water becoming actually solidified by the alkali. 
 
 Although soda is so analogous to potash in many of its 
 habitudes, that it can only on certain occasions be distinguished 
 by chemical tests, yet the action of these two alkalies in some 
 manufactures, and the combinations they form, are so dissimilar, 
 that we are under the necessity of considering them to be per- 
 fectly distinct bodies. 
 
 The most remarkable difference in the effects of these alkalies, 
 when employed in manufacturing processes, is in the articles of 
 soap and glass. In that of glass, the mineral alkali more easily 
 combines with the silica ; consequently the frit is formed with 
 greater facility and certainty. Soda also produces a glass of 
 greater hardness. 
 
 In the manufacture of common hard soap, soda is an essential 
 ingredient. Pure potash will also combine with oil or tallow, 
 and form a complete soap ; and it is by this alkali that all the 
 soft soap is made which is prepared in Great Britain. But if 
 more than a certain proportion of potash be used in the manu- 
 facture of hard soap, although the soap might have sufficient 
 consistence, and appear perfectly good when finished, its cha- 
 racter would be entirely changed the first day of its exposure to 
 the action of the air in damp weather; for it would then become 
 soft and unsaleable. Great losses were formerly sustained by 
 many manufacturers of soap, from their ignorance of this cir- 
 cumstance. However, if this imperfect soap be dissolved in 
 hot water, and brought to a boiling heat, and while boiling a 
 sufficient portion of common salt be added, the moment these 
 substances come in contact with each other, the potash will quit 
 the tallow to unite with the muriatic acid of the salt, and the 
 soda will then supply its place, and combine with the tallow, so 
 as to form a hard, firm and saleable soap. 
 
 Having already given some account of the salts of potash, it 
 will now be proper to notice the principal salts which have been 
 
 1 See Macquer's Chemical Dictionary, article Alkali. 
 
294? ON THE FIXED ALKALIES. 
 
 formed by means of soda. These may frequently be known 
 from the former by their greater degree of solubility in water, 
 and by their containing much water of crystallization, though 
 to this there are some exceptions. They may also be distin- 
 guished from the salts of potash by their yielding no precipitate 
 when treated with tartaric acid, or with a solution of muriate of 
 platinum. 
 
 Acetate of soda. This salt was known in the old pharmaco- 
 poeias by the name of crystallized foliated earth. It crystallizes 
 in prisms similar to sulphate of soda ; but these cannot be ob- 
 tained unless the solution contains an excess of soda. It con- 
 sists of 32 soda -f- 50 acetic acid. 
 
 Arseniate of soda. This salt differs from arseniate of potash, 
 inasmuch as it crystallizes in six-sided prisms : whereas the latter 
 is incapable of crystallization. If there be, however, an excess 
 of acid in the solution, the arseniate of soda will not crystallize. 
 Arsenite of soda. This, like the arsenite of potash, is incapable 
 of crystallization, being a thick yellow liquid, with an odour that 
 is peculiarly nauseous. This salt is decomposable by heat, and 
 the arsenious acid escapes in vapour. It is a compound of 
 arsenious acid 54?, and soda 32. 
 
 Benzoate of soda. Unlike its correspondent salt of potash, 
 which is deliquescent, this salt effloresces in the atmosphere, but 
 its taste is similar, and it is also very soluble in water. The 
 crystals likewise are considerably larger than the crystals of 
 benzoate of potash. 
 
 Bicarbonate of soda. This, like the bicarbonate of potash, 
 may be prepared by passing a stream of carbonic acid gas into a 
 saturated solution of the soda of commerce, when it precipitates 
 in small crystals, as it requires much more water for its solution 
 than the carbonate. If the bicarbonate of soda be exposed to a 
 red-heat, it will lose exactly one-half of its carbonic acid, and 
 thereby be reduced to common carbonate. It may be observed, 
 that this salt is found native in some parts of Africa in con- 
 siderable quantities, and has been imported into this country, 
 and sold under the name of trona. There is a process in the 
 London Pharmacopoeia for preparing this bicarbonate, by treating 
 the carbonate of soda with carbonate of ammonia, which see. 
 
 Borate of soda is readily formed by saturating common borax 
 with the boracic acid ; borax itself being a sub-borate of soda. 
 According to Bergman, two pounds of borax will require one 
 pound of boracic acid for its saturation. 
 
 Camphorate of soda is similar to camphorate of potash in most 
 of its properties, and may be formed in the same manner. Its 
 crystals are in irregular forms, but they may be obtained very 
 white and transparent. If submitted to heat, the acid burns 
 
ON THE FIXED ALKALIES. 295 
 
 with a beautiful blue flame at the first, and afterwards with one 
 of a purple hue. 
 
 Carbonate of soda. This salt, which is employed in large 
 quantities in the manufactures of the country, is usually produced 
 from four distinct sources, viz. from the barilla of Spain and 
 Sicily, from the kelp which is made on our own shores, from a 
 native production which is brought from Egypt under the name 
 of natron, and now, perhaps in larger quantities than either, from 
 the decomposition of sulphate of soda, the residuum which is left 
 in the pots after the distillation of muriatic acid from common 
 sea salt. It crystallizes in octohedrons, with a rhombic base, 
 forming a solid with ten faces. The dry salt consists of soda 32, 
 and carbonic acid 22. 
 
 The crystallized salt consists of carbonate of soda 54-, and 10 
 waters 90. 
 
 Chr ornate of soda is a crystallizable salt of an orange colour. 
 If a solution of chromate of soda be added to a solution of lead, 
 copper, iron, mercury, or silver, it forms an insoluble precipitate, 
 varying in colour according to the nature of the metallic solution 
 into which it is poured. In the solutions of zinc, tin, and some 
 other metals it forms no precipitate 1 . 
 
 Citrate of soda. This salt agrees in several of its properties 
 with citrate of potash. It crystallizes in hexahedral tables, is 
 soluble in two parts of water at 56, and effloresces when exposed 
 to the air. It consists of citric acid 58, and soda 32. 
 
 Fluate of soda is formed by pouring a solution of pure soda 
 into fluoric acid. The salt crystallizes on cooling. It has less 
 taste than fluate of potash, and is not altered, like that salt, by 
 exposure to the air. 
 
 Hydrate of soda is a compound of caustic soda and water. 
 Though this alkali be purified as much as possible by lime and 
 alcohol, and afterwards by fusion, it will still contain a portion 
 of water. It consists of 32 soda + 9 water. 
 
 Hydrosulphuret of soda crystallizes in four-sided prisms, ter- 
 minated by quadrangular pyramids. Its taste is intensely bitter, 
 though the crystals are transparent and colourless. It is very 
 soluble in water, and deliquesces in the air, during which process 
 the solution acquires a green colour. 
 
 For some account of the formation of this salt, see the article 
 Sulphuret of soda. 
 
 lodate of soda. This salt has been formed and examined by 
 Gay Lussac. It may be made by dissolving iodine in a solution 
 of pure soda. It forms itself in small prismatic crystals. 
 Armales de Chimie, tome xci. 
 
 1 See John, Annals of Philosophy t vol. iv. page 425. 
 
296 ON THE FIXED ALKALIES. 
 
 Lactate of soda. This salt is very similar to lactate of potash. 
 It has been examined by Berzelius, who thinks the two salts can 
 only be distinguished by analysis. 
 
 Malate of soda. This salt is uncrystallizable, very soluble in 
 water, and deliquescent in the atmosphere. 
 
 Molybdate of soda agrees with molybdate of potash in many of its 
 properties ; but it is more soluble in water, and affords transparent 
 crystals, vr?^H are unalterable by exposure to the atmosphere. 
 
 Muriate of soda, or chloride of sodium dissolved in water, is 
 one of the most abundant salts in nature. It is the chief ingre- 
 dient in sea-water, and abounds in salt springs in most parts of 
 the world. When the water is expelled from it, by which means 
 the oxygen is abstracted from the soda, and the hydrogen from the 
 muriatic acid, chloride of sodium is re-obtained, which is found 
 in immense masses in the county of Chester in the form of rock- 
 salt. A valuable paper by Dr. Henry on the various kinds of 
 common salt, will be found in the Philosophical Transactions for 
 1810, page 89, &c. 
 
 Chloride of sodium consists of 24? sodium + 36 chlorine; 
 muriate of soda, of 32 soda + 37 muriatic acid, or of water 9, and 
 chloride of sodium 60. 
 
 Nitrate of soda is the cubic nitre of the old chemists. It forms 
 itself in rhombic crystals, which require three parts of water at 
 60 for their solution. It has in a slight degree the property of 
 deliquescence, and is soluble in less than its own weight of water 
 at 212. It is a compound of soda 32, and nitric acid 54. 
 
 Dr. Lewis has treated at length on the nature of this salt 1 . 
 
 Oxalate of soda is a salt which appears in small crystals like 
 grains of sand. This salt dissolves in cold water with difficulty, 
 but is perfectly soluble in hot water. Its taste is cooliiig and 
 bitter, and it falls to powder when submitted for some time to a 
 gentle heat. It consists of oxalic acid 36, and soda 32. 
 
 Phosphate of soda. This is the sal perlatum of the old che- 
 mists. It possesses a very mild saline taste, and on this account 
 was introduced into the practice of medicine by Dr. George 
 Pearson. It consists of soda 32 + phosphoric acid 28, and 
 when crystallized combines with 12 proportionals of water 108 
 -f 60 phosphate of soda = 168. 
 
 Phosphite of soda. The properties of this salt are not much 
 known. The hypophosphite of soda is very soluble both in 
 water and in alcohol, and indeed is more deliquescent even than 
 muriate of lime itself. 
 
 Silicate of soda. This salt may be formed in the same way 
 as silicate of potash, with the substitution of the mineral for the 
 
 1 philosophical Commerce of the Arts> pages 642 646. 
 
ON THE FIXED ALKALIES. 297 
 
 vegetable alkali. Glass is a subsilicate, containing a considerable 
 excess either of potash or soda. See the Essay on the Manu- 
 facture of Glass. 
 
 Subborate of soda is brought from the East Indies in a very 
 impure state, and sold under the name of tincal. Formerly 
 none but the Dutch were capable of purifying it ; but now this 
 is well done both in France and in England, and when purified 
 is called borax. The crystals are irregular hexangular prisms, 
 which are slightly efflorescent. These, according to Bergman, 
 are composed of boracic acid 34, soda 17, and water 49. 
 
 Boracic acid is usually procured from this salt by the affusion 
 of sulphuric acid ; but its chief consumption is as a flux, and by 
 the braziers for solder. 
 
 Suberate of soda. This salt differs from the suberate of potash 
 chiefly in the circumstance of its being incapable of crystallization; 
 whereas suberate of potash crystallizes in prisms. The best 
 account we have of these salts will be found in a copious extract, 
 in the Annales de Chimie, tome xxiii. pages 42 62, from a 
 memoir on cork, and on the combinations of its acid, read to 
 the Institute of Paris by Bouillon La Grange. 
 
 Succinate of soda. This salt differs in several respects from 
 succinate of potash. It crystallizes in hard transparent four- 
 sided and hexagonal prisms, which are unchangeable in the air; 
 whereas the succinate of potash is extremely soluble, is cry- 
 stallized with difficulty, and the salt, which is in the form of very 
 small prisms, readily deliquesces in the atmosphere. 
 
 Sulphate of soda. This is the sal mirabile of the old chemists, 
 and has been long known in this country under the name of 
 Glauber's >salt. It usually crystallizes in large four-sided prisms, 
 hard and transparent; but they effloresce when exposed long to 
 the atmosphere, and fall into powder. Sulphate of soda is pro- 
 duced in considerable quantities by the makers of muriatic acid. 
 It is composed of sulphuric acid 40, and soda 32, and when cry- 
 stallized it consists of dry sulphate of soda 72, and water 90. 
 
 Sulphite of soda. This is a cry stall izable salt, not quite so 
 soluble as the sulphate of soda. It consists of sulphurous acid 
 32, and soda 32. 
 
 The crystals are composed of one proportional of the salt, and 
 eight proportionals of water. 
 
 Sulphurrt of soda. When sulphur and soda are fused together, 
 a red compound is formed, whose taste is bitter and otherwise 
 disagreeable. This is sulphuret of soda. For an account of its 
 nature and properties, see Vauquelin, Annales deChimie, tome xli. 
 page 190. When this sulphuret, which is very deliquescent, is 
 dissolved in water, it produces a yellow solution of hydrosul- 
 phuret of soda. 
 
298 ON THE FIXED ALKALIES. 
 
 Supertartrate of soda is readily obtained by adding tartaric acid 
 to a solution of tartrate of soda. Thenard has treated upon this 
 salt. See Annales de Chimie, tome xxviii. page 12. 
 
 Tartrate of soda. This salt may be formed by the direct 
 union of tartaric acid and soda. It is composed of tartaric acid 
 67, and soda 32. 
 
 It crystallizes in needle-formed crystals, which are much more 
 soluble in water than the tartrate of potash. 
 
 Tungstate of soda. This salt differs much from the tungstate 
 of potash already described, as it crystallizes in solid elongated 
 hexahedral tables ; whereas the latter is incapable of crystalliza- 
 tion, and, when concentrated as much as possible, deliquesces 
 by exposure to a damp atmosphere. Tungstate of soda, which 
 may be prepared by dissolving tungstic acid in a solution of soda, 
 is soluble in four parts of cold, or two parts of boiling water. 
 Vauquelin and Hecht have investigated the nature of the salts 
 formed with tungstic acid 1 . 
 
 Urate of soda. This salt is in the form of a white powder, 
 having, according to Dr. Thomson, the same appearance as pure 
 uric acid 2 . It is soluble in a lye of caustic soda. 
 
 It had for many years been usual to consider the fixed alkalies 
 to be simple undecomposable bodies ; but when the present 
 modes of chemical analysis were adopted, it was soon suspected 
 that soda and potash would ultimately be found to be compound 
 substances. Morveau had long ago published an opinion that 
 the fixed alkalies were not simple substances ; and in the first 
 edition of The Chemical Catechism, printed in the year 1806, I 
 fully expressed my opinion of the compound nature of these 
 bodies. In the year 1 807 a very important paper was read by 
 Sir H. Davy before the Royal Society, on the agencies of gal- 
 vanism in the decomposition of a variety of alkaline and earthy 
 salts. The experiments which he detailed in that paper were 
 sufficient to produce an alteration in all our former ideas of 
 chemical affinity, as they proved decisively that the formation of 
 all chemical compounds may depend on the electrical state of the 
 materials of which they are composed. Soon afterwards, by 
 means of the large galvanic apparatus at the Royal Institution, 
 he was enabled to decompose the fixed alkalies, and to exhibit 
 their metallic bases in an insulated and separate state. 
 
 It was on the 19th day of November, in the year 1809, that 
 Sir Humphry Davy, in a paper read before the Royal Society, 
 
 1 Journal des Mines, No. xix. page 80. 
 ~ System of Chemistry, vol. ii. page 454. 
 
ON THE FIXED ALKALIES. 299 
 
 announced thai he had succeeded in his attempts to decompose 
 these bodies. In his first attempts for the decomposition of the 
 fixed alkalies, he entirely failed, in consequence of his having 
 acted upon their aqueous solutions. He afterwards used potash 
 in the state of igneous fusion, and acted upon it by an electrical 
 power, which was produced from a galvanic battery of 100 
 plates, of 6 inches square, highly charged. 
 
 Here some brilliant phenomena were produced. A most 
 intense light and a column of flame were exhibited, which seem- 
 ed to be owing to the development of combustible matter ; and 
 when the order was changed, so that the alkali was brought in 
 contact with the negative side of the battery, aeriform globules, 
 which inflamed in the atmosphere, rose through the potash. Being, 
 however, unable to collect the products of decomposition by this 
 means, he had then recourse to pure potash in its usual state, and 
 depended on electricity alone for its fusion as well as its decom- 
 position. 
 
 A small piece of pure potash, moistened a little by the breath, 
 was placed upon an insulated disc of platinum, connected with 
 the negative side of a battery consisting of 100 plates of 6 inches 
 and 150 of 4 inches square, in a state of intense activity, and 
 a platinum wire, communicating with the positive side, was 
 brought in contact with the upper surface of the alkali. Under 
 these circumstances a vivid action soon commenced. The pot- 
 ash began to fuse at both its points of electrization, and small 
 globules having a high metallic lustre, and precisely similar in 
 visible characters to quicksilver, appeared, some of which burnt 
 with explosion and bright flame. These globules, which appear 
 to be metallic, are the basis of potash, that alkali being com- 
 posed of this peculiar base and oxygen. 
 
 Soda, when acted upon in the same manner, exhibited an 
 analogous result, and these effects equally took place in the at- 
 mosphere, and when the alkali was acted upon in the vacuum 
 of an exhausted receiver : but these globules could not in either 
 case be produced from crystallized alkalies. 
 
 When a globule of the base of potash was exposed to the at- 
 mosphere, it immediately attracted oxygen, and a white crust 
 formed upon it, which proved to be pure potash. When the 
 globules were strongly heated and then suspended in oxygen 
 
 fas, a rapid combustion with a brilliant white flame was pro- 
 uced, and these metallic globules were converted to an alkali, 
 whose weight greatly exceeded that of the combustible matter 
 consumed. 
 
 When Sir H. Davy had thus detected the bases of the fixed 
 alkalies, he had considerable difficulty to preserve and confine 
 them, so as to examine their properties and submit them to ex- 
 
300 ON THE FIXED ALKALIES. 
 
 periments. He found, however, that in recently distilled naphtha 
 they may be preserved many days, and that their physical pro- 
 perties may be easily examined in the atmosphere when they 
 are covered by a thin film of it. 
 
 The basis of potash at 60 Fahrenheit is only imperfectly fluid; 
 at 70 it becomes more fluid; and at 150 its fluidity is perfect, 
 so that different globules may be easily made to run into one. 
 At 50 it becomes a soft and malleable solid, which has the 
 lustre of polished silver; and at about the freezing point of 
 water it becomes harder and brittle, and when broken in frag- 
 ments exhibits a crystalline texture of perfect whiteness and high 
 metallic splendour. 
 
 To be converted into vapour, it requires a temperature ap- 
 proaching that of a red-heat. It is an excellent conductor of 
 heat, and a perfect conductor of electricity. 
 
 Resembling the metals in all these properties, it is, however, 
 remarkably different from most of them in specific gravity; for 
 it will not sink in double-distilled naphtha, whose specific gravity 
 is only .770, that of water being considered as 1.000. Sir H. 
 Davy has determined by experiment that its specific gravity is 
 to that of mercury as 10 to 223, which gives a proportion to 
 that of water nearly as 6 to 10; so that it is the lightest metallic 
 body known. When this substance is introduced into chlorine 
 gas, it burns spontaneously with a bright red light, and chloride 
 of potash is formed. When thrown upon water, it decomposes 
 it with great violence, and instantaneous explosion is produced 
 with brilliant flame, and a solution of pure potash is the result. 
 When a globule is placed upon ice, not even the solid form of 
 the two substances can prevent their union; for it instantly burns 
 with a bright flame, and a deep hole is made in the ice, which 
 is found to contain a solution of potash. When a globule is 
 dropped upon moistened turmeric paper, it instantly burns, and 
 moves rapidly upon the paper, as if in search of moisture, leav- 
 ing behind it a deep reddish brown trace. 
 
 So strong is the attraction of the basis of potash for oxygen, 
 that it discovers and decomposes the small quantities of water 
 contained in alcohol and ether, even when they are carefully 
 purified. When thrown into the mineral acids, it inflames and 
 burns on the surface. In sulphuric acid, sulphate of potash 
 is formed ; in nitric acid, nitrous gas is disengaged, and nitrate 
 of potash formed. When brought in contact with a piece of 
 phosphorus, and pressed upon, there is a considerable action ; 
 they become fluid together, burn, and produce phosphate of pot- 
 ash. When a globule is made to touch a globule of mercury about 
 twice as large, they combine with considerable heat: the com- 
 pound is fluid at the temperature of its formation; but when cool it 
 
ON THE FIXED ALKALIES. 301 
 
 appears as a solid metal, similar in colour to silver. If this com- 
 pound be exposed to air, it rapidly absorbs oxygen ; potash which 
 deliquesces is formed ; and in a few minutes the mercury is found 
 pure and unaltered. When a globule of the amalgam is thrown 
 into water, it rapidly decomposes it with a hissing noise, potash is 
 formed, hydrogen disengaged, and the mercury remains free. 
 The basis of potash readily reduces metallic oxides when heated 
 in contact with them. It decomposes common glass by a gentle 
 heat, and at a red heat effects a change even in the purest glass. 
 
 In his experiments on SODA, Sir H. Davy has discovered that 
 its base, like that of potash, is white, opaque, and has the lustre 
 of silver. The property of welding, which belongs to iron and 
 platinum, at a white heat only, is possessed by this substance at 
 common temperatures. It is very similar in its more obvious 
 properties to the base of potash; but it has greater specific 
 gravity, being to that of water nearly as nine to ten, or as .9348 
 to 10.000. In oxygen gas it produces a white flame, and sends 
 forth bright sparks, occasioning a very beautiful effect. In 
 chlorine gas it burns vividly, with numerous scintillations of a 
 bright red colour. In the quantity of one-fortieth, it renders 
 mercury a fixed solid, of the colour of silver, and forms an alloy 
 with tin. When amalgamated with mercury, the amalgam will 
 combine with other metals. Sir H. Davy tried this with iron 
 and platinum, and had reason to believe that these latter metals 
 remain in combination with the mercury, even when deprived 
 of the new substance by exposure to the air. 
 
 The whole of the sixth chapter of this very interesting paper 
 is occupied with the detail of several curious and ingenious 
 experiments to ascertain the proportions of the bases and oxygen 
 in the two fixed alkalies; from whence he concludes that potash 
 may be considered as consisting of about 5 parts basis, and 1 of 
 oxygen ; and soda of 3 basis, and 1 oxygen. 
 
 In reply to the question, whether the bases of potash and 
 soda should be called metals, it might be said that they agree 
 with metals in opacity, lustre, malleability, conducting powers 
 as to heat and electricity, and in their qualities of chemical 
 combination. Even their low specific gravity does not appear 
 a sufficient reason for making them a new class ; for amongst 
 the metals themselves there are remarkable differences in this 
 respect, platinum being nearly four times as heavy as tellurium ; 
 and tellurium is not much more than six times as heavy as the 
 basis of soda. Conceiving the basis of the two fixed alkalies to 
 be metals, Sir H. Davy has named one Potassium, and the other 
 Sodium, adopting that termination which, by common consent,, 
 has been applied to other newly discovered metals. 
 
 In concluding this very important communication, Sir H. 
 Davy remarks that an immense variety of objects of research 
 
302 ON THE FIXED ALKALIES. 
 
 is presented in the powers and affinities of the new metals pro- 
 duced from the alkalies. In themselves they will undoubtedly 
 prove powerful agents for analysis ; and, having an affinity for 
 oxygen stronger than any other known substances, they may 
 possibly supersede the application of electricity to some of the 
 undecompounded bodies. 
 
 In sciences kindred to chemistry, the knowledge of the nature 
 of the alkalies, and the analogies arising in consequence, will 
 open many new views ; they may lead to the solution of many 
 problems in geology, and show that agents may have operated 
 in the formation of rocks and earths which have not hitherto 
 been suspected to exist. 
 
 With respect to the properties of potassium, it may be said, 
 in addition to those already detailed, that it is ductile and of the 
 consistence of soft wax ; and, though originally of great lustre, 
 it immediately loses its brilliancy by exposure to the air. At 
 a temperature higher than that at which water congeals, it is a 
 hard and brittle substance; and at a red heat becomes dissipated 
 in vapour. But it is, perhaps, one of the most curious pro- 
 perties of these metalloids, that if an alloy be formed, composed 
 of one part of potassium and three of sodium, the compound 
 will continue fluid at the low temperature of 32. 
 
 Since the first edition of these Essays was published, a new 
 fixed alkali called lithia has been discovered in the petalite, a 
 mineral brought from the mine of Utoen in Sweden. This 
 discovery was made by M. Arfvredson, a young Swedish che- 
 mist. The mineral called spodumene also affords the same sub- 
 stance, and it has likewise been found in crystallized lepidolite. 
 
 When lithia is submitted to the action of the voltaic pile, it 
 becomes decomposed ; and, similar to potash and soda, a metallic 
 substance of great brilliancy and highly combustible is separated 
 from it. Hence it appears that lithia, like the other fixed 
 alkalies, is a metallic oxide, and from hence its metallic base is 
 called lithium. 
 
 During the first analysis of the petalite, M. Arfvredson sup- 
 posed its alkali to be soda; but he soon found that it differed 
 from that alkali, and that it maybe distinguished both from potash 
 and soda by its power of neutralizing a much larger quantity of 
 any acid. 
 
 Like the other alkalies, lithia is very soluble in water; and its so- 
 lution, like theirs, possesses an acrid and nauseous taste. Accord- 
 ing to Vauquelin, lithia attracts carbonic acid from the atmosphere 
 with great avidity, and in neutralizing the acids is more powerful 
 even than magnesia. It consists of lithium 10, and oxygen 8. 
 
 Several compounds have already been formed by the artificial 
 combination of this new alkali with the acids, the chief of which 
 

 
 
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CHEMICAL ESSAYS. 
 
 
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ON THE FIXED ALKALIES. 80$ 
 
 are the chloride, the iodide, and the sulphuret of lithium; and 
 the sulphate, the nitrate, the muriate, the phosphate, and the 
 carbonate of lithia. Of these, the sulphate of lithia.crystallizes 
 in small prisms of a shining white colour. It is more fusible and 
 soluble than sulphate of potash, and, unlike that salt, its taste is 
 not bitter, but merely saline. The muriate and nitrate of lithia 
 are both deliquescent salts; while the carbonate is efflorescent and 
 sparingly soluble in water. 
 
 Lithia, like the other fixed alkalies, has the property of con- 
 verting the vegetable blues to a green, and of turning the vegetable 
 yellows brown. It is very sparingly soluble in alcohol. 
 
 In speaking of the fixed alkalies in connexion with the trade of 
 the country, I might have observed that the supplies of soda to be 
 derived from the decomposition of common salt are inexhaustible. 
 
 The rocks of salt in the British Islands are far from inconside- 
 rable ; but the many thousands of tons of it which are continually 
 washing our shores will furnish a most plentiful supply for every 
 purpose whatever, whether for manufacture, agriculture 1 , or 
 any other branch of the arts : especially now that its decom- 
 position is so generally understood and practised, and the aboli- 
 tion of the duty upon it has rendered it so cheap. Most of the 
 large soap makers now manufacture soda for their own use, which 
 they call English Barilla. 
 
 I ought here to state that for twenty years Mr. Parkes was 
 indefatigable in his efforts to obtain the abolition of the duties 
 on salt. For a long time he could get little attention paid to 
 the subject; but by that incessant perseverance which charac- 
 terized all his actions, he succeeded in calling the attention of the 
 public towards it; and had the pleasure of receiving the con- 
 gratulations of the members of the house of commons who had 
 warmly interested themselves in the measure, when it was at last 
 carried almost by acclamation. His most sanguine predictions 
 have since been verified ; even in London the price has fallen from 
 351. per ton to 21. 105.; and the quantity used for agricultural and 
 manufacturing purposes has far exceeded even his anticipations. 
 
 1 Sea salt is perhaps of still more importance to the grazier than to the 
 mere agriculturist, which is shown by the fattening quality of our salt marshes, 
 and by the avidity with which all Neat Cattle devour their food when sprinkled 
 with salt. See A Letter to the Farmers and Graziers of Great Britain, on the 
 advantages of using Salt in the various branches of agriculture, and in feeding 
 all kinds of farming stock ; with a large Appendix of Proofs and Illustrations." 
 By the author of these Essays. The fourth edition, price 2s. 
 
304 ON EARTHENWARE AND PORCELAIN. 
 
 ESSAY X. 
 
 ON EARTHENWARE AND PORCELAIN. 
 
 THE origin of Earthenware and Porcelain may probably be 
 ascribed to accident. It is very possible that the peculiar changes 
 which clay experiences on being burnt in the fire, may have 
 afforded to some of the early inhabitants of the world the first 
 hints for applying this earth to a variety of useful purposes. 
 
 When mankind had no shelter from the dews of the night, or 
 the burning sun of noon-day, but what could be derived from 
 the trees of the forest, how anxious must they have been to im- 
 prove their condition, and how solicitous to discover some mode 
 of fortifying their miserable huts against the vicissitude of the 
 seasons ! It is therefore not unlikely that baked clay in the form 
 of bricks was made use of for this important purpose in an early 
 stage of society. This application of it is indeed known to have 
 been very ancient. The celebrated Tower of Babel, 2200 years 
 before Christ, was built with bricks ' ; and when the Israelites 
 sojourned in Egypt 600 years afterwards, their task-masters 
 employed them chiefly in this kind of manufactory 2 . Bricks of 
 clay were used also by other nations of antiquity. The Romans 
 in particular had acquired great skill in the method of making, 
 and also in the manner of burning, their bricks. This will 
 appear by a comparison of the bricks that compose any of their 
 edifices, with those of the present day. The Roman wall at St. 
 Alban's (the ancient city of Verulam) is a direct proof of this 
 assertion 3 . 
 
 It was probably not long after the employment of clay in 
 making bricks, that mankind learnt the art of using it in various 
 other ways, and acquired methods of moulding it into vessels of 
 capacity, and utensils for culinary purposes. Accordingly the 
 
 1 " And they said one to another, Let us make bricks, and burn them 
 thoroughly." Genesis xi. 3, 4. 
 
 * Exodus, chap. i. verses 13, 14. See also chap. v. verses 6 19. 
 
 3 See Mr. J. Webster's Letter to Bishop Littleton, on this subject, in the 
 2d vol. of the ArchcEologia, page 184. See also some observations on the Ruins 
 of a Roman wall at York, by Martin Lister, Esq. in the Phil. Transactions, 
 vol. xiii. p. 238. The bricks in this wall were 17 inches long, 11 inches broad, 
 and %% inches thick, and they were all extremely hard. 
 
ON EARTHENWARE AND PORCELAIN. 305 
 
 most ancient writers we have, mention earthen vessels 4 , and they 
 speak of them as if they had been in use from time immemorial. 
 It appears also that considerable pains were taken in tempering 
 the clay for these purposes, for we read that this process was 
 performed by treading it with the naked feet 5 . 
 
 In the fifth volume of the Archceologia is an account of two 
 vases, of great antiquity, which were found on the Mosquito 
 shore in South America, and which are now in the possession of 
 Lord Hillsborough. The account of them is transmitted by 
 Governor Pownal, who says, " It is a decided fact that they were 
 made in South America, and that they are curious exemplars of 
 some of the first efforts of human ingenuity, and remains of what 
 are become antiquities even among the Indians." He also says 
 that remains of ancient potteries have been discovered high up 
 the Black River, on the Mosquito coast, and that Father D. 
 Acuina mentions, that some of the Indians on the river of the 
 Amazons had carried this ancient manufactory to a great extent, 
 so as even to establish a traffic for it with the neighbouring 
 nations 6 . 
 
 From a variety of testimonies we learn that the Greeks very 
 early acquired proficiency in the arts of pottery. Mr. Fordyce, 
 in describing the theatre of Herculaneum, has told us, that they 
 had contrived how to form earthen vessels which had the pro- 
 perty of increasing the voices of their actors 7 . 
 
 According]to Herodotus, however, vessels of earthenware were 
 in his time extremely scarce, and highly esteemed by the nations 
 around them. " Twice in every year," says he, " there are 
 exported from different parts of Greece to Egypt, and frohi 
 Phoenicia in particular, wine secured in earthen jars, not one of 
 which jars is afterwards to be seen ; for the principal magistrate 
 of every town is obliged to collect all that are imported to the 
 place where he resides, and send them to Memphis. The Mem- 
 phians fill them with water, and afterwards transport them to the 
 Syrian deserts. Thus all the earthen vessels carried into Egypt, 
 and there carefully collected, are continually added to those 
 already in Syria 8 ." 
 
 According to Vitruvius, who wrote in the time of Augustus 
 Caesar, the ancient Romans made their water-pipes of potter's 
 clay. These were generally two inches thick, and joined together 
 with common mortar mixed up with oil. When they had a joint 
 to make, they employed also a piece of free-stone, which they 
 pierced through to receive the two ends of the pipes to strengthen 
 
 4 " But the earthen vessel wherein it is sodden shall be broken." Levit. vi. 28. 
 
 5 " And he shall come upon princes as upon mortar, and as the potter tread- 
 eth clay." Isaiah xli. 25. 6 Archceologia, vol. v. p. 318. 
 
 7 Memoirs concerning Herculaneum, by W. Fordyce, M.A. London, 8vo, 
 1750, p. 16. 9 Beloe - s Herodotus, book iii, s, 6. 
 
 X 
 
306 ON EARTHENWARE AttD PORCELAIN. 
 
 and secure them in the manner of a bandage. Some of these 
 pipes were taken up a few years ago in Hyde Park l . 
 
 The people of Britain in ancient times were furnished with 
 earthen vessels by the Phoenicians ; and they no doubt soon 
 learnt to make others in imitation of them. Many urns of 
 earthenware, supposed to have been the workmanship of the 
 ancient Britons, have been found in barrows in different parts of 
 this kingdom. It is also well known that the Romans made use 
 of earthenware, and that they greatly excelled in the art of making 
 it 2 , as well as in the manufacture of bricks and tiles. Vestiges 
 of several of their great potteries are still discernible in many 
 parts of this island. 
 
 There is reason to believe that there was once a considerable 
 manufactory of Roman earthenware on a small island which 
 2000 years ago stood in the mouth of the Thames, at the back 
 of Margate Sand, now known by the name of the Queen's 
 Channel, at about two leagues from the coast. Governor 
 Pownal, who has written a memoir on this subject, says that 
 fishermen have occasionally, for many years, taken up with their 
 nets complete pieces of earthenware from this particular spot. 
 They are all of coarse workmanship ; but he supposes that this 
 was a manufactory specially employed in making earthen vessels 
 to be used according to the Roman ritual in their religious cere- 
 monies. Each vessel has Atillianus, the name of the maker, 
 neatly impressed upon it 3 . 
 
 It is probable that the early inhabitants of the world arrived 
 nearer to perfection in the modelling of clay, and in the making 
 of earthen wares, than in the management of any other manu- 
 factures ; for in the kingdoms of China and Japan 4 , not only 
 common earthenware, but even porcelain of very excellent quality, 
 was made long before the commencement of the Christian sera. 
 
 " First China's sons, with early art elate, 
 Forni'd the gay tea-pot and the pictured plate ; 
 Saw with illumined brow and dazzled eyes 
 In the red stove vitrescent colours rise 5 : 
 
 1 Switzer's Hydrostatics, 4to, 1729, p. 116. 
 
 2 In the Philosophical Transactions, vol. xv. page 1017, is an account of a 
 fine Roman earthen vessel found near York, with the figure of a female face 
 upon it, of the natural size. It was sent to the Ashmolean Museum in Oxford. 
 
 3 Archceologia,vo]. v. page 282, &c 
 
 4 This manufacture is still of great importance in China. At present " there 
 are five hundred furnaces at work, and nearly a million of men employed, at 
 King-to-Ching, a province of Kian^si." ChaptaTs Elements of Chemistry, 8vo, 
 1791, vol. n. page 94. 
 
 5 " No colour is distinguishable in the red-hot kiln of the potter, but the 
 red itself, till the workman introduces a small piece of dry wood ; which by 
 producing a white flame renders all the other colours visible in a moment." 
 DARWJN. 
 
ON EARTHENWARE AND PORCELAIN. 307 
 
 Speck'd her tall beakers with enamell'd stars, 
 Her monster-josses and gigantic jars ; 
 Smear'd her huge dragons with metallic hues, 
 With golden purples, and cobaltic blues; 
 Bade on wide hills her porcelain castles glare 6 , 
 And glazed pagodas tremble in the air." 
 
 It appears also that porcelain, as well as earthenware, was 
 made in ancient Egypt; for several small earthen figures are 
 frequently found deposited with the Egyptian mummies, resem- 
 bling them in shape, and covered with a blue glazing similar to 
 that of the Chinese porcelain. Du Halde has said that lapis 
 lazuli abounds in Egypt, and hence some have supposed that this 
 blue has been produced by ultramarine. This, however, could 
 not have been the case, as it is now well known that any colour 
 made from lapis lazuli would instantly be destroyed by the intense 
 heat of a potter's oven 7 . 
 
 Anxious to ascertain what article could have been employed 
 to produce so beautiful a colour in such early times, Mr. Delaval 
 broke off a piece of the blue enamel from one of these small 
 images, and submitted it to a variety of experiments and to the 
 action of several chemical tests. In all these cases, the results 
 were exactly what he would have expected had he operated on 
 a piece of modern enamel which had been coloured with the blue 
 oxide of cobalt 8 ; the very article which the potters of the present 
 day employ. What an idea does this give of the attainments of 
 the Egyptians, more than two thousand years before the science 
 of chemistry had made any progress in Europe ! 
 
 That porcelain was not uncommon in Europe during the first 
 century of the Christian aera, is evident from the discoveries 
 that were made in the excavations^of those cities which were de- 
 stroyed by the eruption of Vesuvius in the first year of the reign 
 of the emperor Titus. For, according to the catalogue made 
 by Bayardi, there were no less than 193 vases and other utensils 
 of earthenware and porcelain taken out of the ruins of Hercu- 
 laneum 9 . 
 
 We are not however to suppose that these porcelain vessels 
 were of European manufacture ; for we are expressly informed 
 that the first porcelain which was seen at Rome was brought 
 
 6 This refers to the porcelain buildings of the Chinese. An account of a 
 very singular one will be found in the Chemical Catechism, twelfth edition 
 page 103. 
 
 7 See Klaproth, Annales de Chimie, xxi. p. 150, and Guyton on the colour- 
 ing Principle of the Lapis Lazuli, in the xxxivth vol. of the Annales de Chimie, 
 p. 58; also, in Nicholson's Journal, 4to, vol. i. p. 77 and vol. iv. p. 311. 
 
 8 See " An Experimental Inquiry into the Cause of the Changes of Colours in 
 Opake and Coloured Bodies" By Edward Hussey Delaval, 4to, London, 1777- 
 
 y See the 1st vol. of Martyn and Lettice's History of the Antiquities of Her- 
 culaneum. 
 
SOS ON EARTHENWARE AND PORCELAIN. 
 
 thither from Pontus in Asia by the victorious army of Pompey, 
 and that this was only sixty-four years before Christ '. 
 
 This in some measure accounts for the great excellence which 
 the Persians have arrived at in this elegant art. Sir John Chardin, 
 who travelled through Persia about the middle of the 17th 
 century, has taken notice of their beautiful porcelain, and quotes 
 a passage from Propertius, one of the writers of the Augustan 
 age, to show the antiquity of the art among that people 2 . 
 
 The Etruscans, who were probably a colony from Phoenicia, 
 are noted by the early writers for their excellence in the manu- 
 facture of porcelain. Dr. Darwin, who was intimately acquainted 
 with the great Mr. Wedgwood, and knew all his sources of infor- 
 mation, supposes that their principal manufactories were about 
 Nola, at the foot of Vesuvius, and that they learnt the art from the 
 Chinese. This elegant writer has thus given his testimony to the 
 superiority of their productions : 
 
 " ETHURIA ! next beneath thy magic hands 
 Glides the quick wheel, the plastic clay expands: 
 Nerved with fine touch, thy fingers (as it turns) 
 Mark the nice bounds of vases, ewers, and urns ; 
 Round each fair form in lines immortal trace 
 Uncopied Beauty and ideal Grace." 
 
 The art of painting vases in the manner of the Etruscans has 
 been lost for ages, and this is supposed, by the author of the 
 Dissertations on Sir William Hamilton's Museum, to have 
 happened in the time of Pliny. The honour of the recovery 
 of this long-lost art does not however belong to the late Mr. 
 Wedgwood, as has been asserted ; for though he was the first 
 to imitate the correct and beautiful forms of the Etruscan vases 
 and the paintings upon them, his vases were painted by a 
 different process from that which was employed on the urns, &c. 
 of the ancients. 
 
 Mr. Harrner informs us that the best Asiatic porcelain is 
 manufactured at Skiraz, the capital of that province, which is 
 distinguished from the other provinces of that country by the 
 name of Persia properly so called ; also at Metched, the capital 
 ofBactriana; at Yesd, and at Kirman, in Caramania; and in 
 particular in a town of Caramania called Zorendi. The earth of 
 which these vessels are made is a pure enamel within, as well as 
 without, like that of the Chinese porcelain ; its grain is as fine, 
 and it is as transparent ; so that it frequently equals and sometimes 
 even excells that of the Chinese, its varnish is so exquisite. 
 
 The Persian porcelain has another excellence, that it resists 
 
 1 Pliny, 1. xxxvii. 2. 
 
 * Sir John Chardin's Travels in Persia, folio, London, 1686. 
 
ON EARTHENWARE AND PORCELAIN. 309 
 
 fire, so as not only to allow of water being boiled in it, but the 
 vessels for the express purpose of boiling are made of it. It is 
 so hard, that it is employed in making mortars for grinding 
 colours and for pounding other things, and also for the moulds for 
 making bullets. The materials of which this beautiful porcelain 
 is made are glass and the small pebbles found in rivers, ground 
 very fine ; with a slight mixture of argillaceous earth. 
 
 It is said that the potters of the city of Yesd, in Caramania, 
 already mentioned, sent one day to the potters of Ispahan, as it 
 were in defiance, a porcelain vessel, which would hold six 
 English quarts of water, and yet weighed only the eighth part 
 of an ounce. Harmer's Observ. vol. i. page 75. 
 
 In connexion with this account of the excellence of the Persian 
 porcelain, it is related that in the year 1666 an ambassador of 
 the Dutch East India Company having brought many rich pre- 
 sents for the Persian court, and being ignorant of the value which 
 this people set upon their own manufacture, brought, among 
 other articles, fifty-six pieces of old China porcelain ; and that 
 the king when he saw them laughed heartily in derision, asking 
 with an air of contempt what they were. The Dutch merchants 
 frequently mix this Persian porcelain with that of China in what 
 they send to Holland for the supply of that market. 
 
 The Barbarini or Portland vase, has sometimes been adduced 
 as a proof that the ancients had arrived at great excellence in 
 the manufacture of porcelain. This beautiful piece of antiquity 
 was discovered in the tomb of Alexander Severus, who died so 
 early as the year 235, and the late duchess of Portland actually 
 paid a thousand guineas for it. But, unfortunately for such a 
 speculation, this exquisite piece of workmanship is not made of 
 porcelain, but of glass. 
 
 A thick coat of white semi-transparent glass covers the whole 
 of this urn, which is itself made of a deep blue glass, and the 
 white covering appears to have been cut by the lapidary in the 
 same way as the subjects of antique cameos on coloured grounds. 
 Siracides relates that the ancients had also the art of covering 
 earthen vessels with a crust of glass. Mr. Wedgwood's imita- 
 tion of this elegant piece of antiquity is however of porcelain, 
 and deserves every commendation that can be bestowed upon it. 
 The history of this production may be given in a few words. 
 
 Several of the nobility and gentry being desirous of having a 
 copy of this beautiful piece of antiquity, they engaged Mr. Wedg- 
 wood to endeavour to imitate it ; and he actually produced a vase 
 which for elegance and beauty was considered to be fully equal 
 to the original. The subscription was for fifty vases at 50/. each ; 
 and, notwithstanding the large sum to which this subscription 
 amounted, such heavy expenses \vere incurred in their fabrication, 
 
310 ON EARTHENWARE AND PORCELAIN. 
 
 that Mr. Byerley, the partner of Mr. Wedgwood, has assured 
 me that they lost money by the undertaking. Mr. Webber the 
 artist received five hundred guineas for modelling it. 
 
 In attempting the history of the manufacture of European 
 porcelain, it may be remarked, that although porcelain had been 
 brought into this quarter of the world before Christ, as has 
 been mentioned above, there is reason to believe that the intro- 
 duction of the knowledge of making porcelain in Europe was 
 but of late years, as will be seen in the sequel. Porcelain is not 
 made even now in the Indies ; what is consumed there is all im- 
 ported either from Persia, Japan, or China, and the other king- 
 doms between China and Pegu. 
 
 The English cannot, I presume, lay claim to much excellence 
 in their manufacture of earthenware before the time of the late 
 Mr. Wedgwood, who began his indefatigable researches about 
 the year 1750: for in the beginning of the last century, all the 
 best tiles and even the finer sort of bricks were imported from 
 Denmark, Germany, and Holland. Not but that bricks and 
 tiles of clay had long been made amongst us ; for there is an act 
 of parliament now on the statute books, that was passed in the 
 17th year of the reign of Edward IV., which directs the time 
 for digging the earth, the manner of making the bricks, &c.; 
 and it is so expressed, that we have reason to conclude that 
 bricks had been made in England from time immemorial. While 
 on this article, I am desirous of mentioning that there is a paper 
 on the process of burning bricks, in the third volume of Berg- 
 man's Chemical Essays, and that it contains many hints which 
 may be useful to those who are engaged in that occupation. 
 
 It seems strange that our remote ancestors did not arrive at 
 greater perfection in the manufacture of all these articles, when 
 it is considered that the island produces not only a great variety 
 of clays, but also all the other materials necessary for the pro- 
 duction of the best earthenware and porcelain: Dr. Martin 
 Lister, who wrote in the latter part of the seventeenth century, 
 distinguishes no less than two-and-twenty different sorts of clay 
 in Britain which fell under his own observation. Moreover, the 
 exquisite pieces of workmanship which were produced at different 
 periods by the English sculptors, show that there was no defi- 
 ciency of genius and skill among our artists, who probably con- 
 ceived that the working in clay was beneath their attention. 
 
 In returning from this digression, I have to observe, that the 
 common stoneware, and that called white enamel, have been 
 made in various countries of Europe ever since the fifteenth 
 century. The former of these is distinguished by a glaze made 
 by means of muriate of soda ; the latter is covered with a real 
 
ON EARTHENWARE AND PORCELAIN. 311 
 
 glass, rendered opaque by the white oxide of tin l . Stoneware 
 is the only article of pottery that can be employed for chemical 
 purposes, where a great heat is required. Macquer says that 
 our best common stoneware is the most perfect pottery that can 
 be, and that it has all the essential qualities of the finest old 
 Japanese porcelain. Mr. Pott, the author of Lithogeognosia, 
 has written a treatise expressly to explain the requisite per- 
 fections of stoneware for the purpose of chemical vessels ; but I 
 conceive that what is made at Lambeth near London by the 
 best of those manufacturers, is susceptible of but little improve- 
 ment. For boiling syrups, and for many other culinary purposes, 
 the Lambeth stoneware is the best article that can possibly be 
 employed ; as it is cheap, will stand a great heat, and is perfectly 
 wholesome ; whereas many of the earthen utensils used in our 
 kitchens are glazed with lead, and consequently are extremely 
 dangerous. Several years ago, I adverted to this subject in 
 another work ; but I was desirous of repeating the admonition 
 now, because I consider the health of the community must be 
 impaired by the frequent use of earthen vessels which are covered 
 with the common Staffordshire glaze. The acetic acid will 
 readily dissolve the oxide of lead ; hence the boiling of pickles, 
 and the making of other culinary preparations in such vessels, 
 must be highly improper. 
 
 The white enamel ware was brought to its present state of per- 
 fection by Bernard de Palissy, a native of the diocese of Agen, in 
 the province of Guienne in France ; a spot celebrated for being 
 the birth-place of the memorable Joseph Scaliger. 
 
 Palissy was in a low station of life ; but he was eminent for his 
 knowledge, industry, and talents. There were indeed so many 
 interesting traits in his character, that I trust I shall be excused 
 if I recite a few of the chief circumstances of his history. 
 
 He is said to have been a skilful painter upon glass 2 , but he 
 was more generally known as a chemist. Originally h?3 was a 
 land surveyor and draughtsman; but his taste for natural history 
 led him to abandon this employment, and induced him to travel 
 for instruction over the whole of France and Lower Germany* 
 An accidental circumstance threw into his hands a cup of ena- 
 melled pottery ; and, from that time, his whole attention and for- 
 
 1 The oxides of many other metals are used in different branches of pottery, 
 as will be shown in connexion with the latter part of this subject. 
 
 * In the time of Palissy the art of painting upon glass was nearly lost. In 
 this country it was classed with the ARTES PERDIT^E ; but Mr. Walpole has 
 shown, by a regular series of artists and their performances, that this secret 
 was never entirely lost. Walpole's Anecdotes of Painting. 
 
312 ON EARTHENWARE AND PORCELAIN. 
 
 tune were taken up in experiments on enamels '. Nothing can be 
 more interesting than the narrative which he himself has given of 
 his labours. 
 
 He exhibits himself as building and rebuilding his furnaces, 
 always on the eve of success ; worn out by labour and misfortune ; 
 the derision of the public; the object of the angry remonstrances 
 of his wife; and then as being reduced to such an extremity as 
 to burn his furniture, and even some of the wood- work of his 
 house, to keep his furnaces going. His workman presses him 
 for money, he strips himself, and gives him part of his clothes. 
 But at length, by dint of indefatigable labour, constancy, and 
 genius, he arrived at the desired degree of perfection, which 
 gained him the esteem and consideration of the greatest men of 
 his age. 
 
 He was the first who formed a collection of natural history at 
 Paris. He even gave lectures on that science, and received a 
 moderate subscription from each of his auditors, under the 
 obligation of returning it four-fold if any thing he taught should 
 prove false. He was the author of many singular books on 
 subjects of agriculture, fire, earth, salts, &c. that are now very 
 difficult to be found, and it is to him especially that Buffon is 
 indebted for many useful hints. 
 
 Palissy was the first who ventured, in the face of the priests, 
 to ' affirm that fossil shells and calcareous mountains are the 
 remains of real shells; he was also the first who taught the 
 true theory of springs, and was in all respects an eminent and 
 accomplished man. The very form of his works exhibits a proof 
 of original genius; they consist of dialogues between Theory 
 and Practice, in which Practice is always the instructor, while 
 Theory is represented as a scholar proud of his own understand- 
 ing, but indocile and ignorant. 
 
 The high reputation he acquired, and the obligations under, 
 which his countrymen stood indebted to him, were however not 
 sufficient to defend him from the persecution of the League ; for, 
 being a protestant, Matthew de Lawn ay, one of the greatest 
 fanatics of his day, caused him to be dragged to^the Bastile at 
 the age of ninety years, where he signalized himself by acts of 
 firmness and heroism. 
 
 His reply to Henry III. deserves to be commemorated. " My 
 good man," says the king, " if you cannot reconcile yourself to 
 
 1 The modern enamel painting is quite a different art. This was invented 
 by John Petitot of Geneva. An account of his experiments and discoveries 
 may be seen in the Biographical Dictionary, article Petitot, and also in 
 Granger's Biographical History, vol. ii. p. 288. 
 
ON EARTHENWARE AND PORCELAIN. 313 
 
 the matter of religion, I shall be compelled to leave you in the 
 bands of my enemies." " Sire," said Palissy, " I was perfectly 
 ready to surrender my life ; and if the action could have been 
 accompanied with any regret, certainly it must have vanished, 
 after hearing the great king of France say, ' I am compelled.' 
 This, Sire, is a situation to which neither yourself, nor those 
 who force you to act contrary to your own disposition, can ever 
 reduce me, because I am prepared for death ; and because neither 
 Your Majesty nor your whole people have the power to compel 
 a simple potter to bend his knee before the images which he 
 fabricates V This venerable man died about the year 1590. 
 
 Several of the nations of Europe at the dawn of the eighteenth 
 century, could not but regret that the knowledge of the manufac- 
 ture of porcelain had not been introduced among them. At this 
 time, however, a fortunate circumstance aroused the attention of 
 the French people, and directed it to this important subject. 
 
 Francis D'Entrecolles, who had resided many years in China 
 as a Christian missionary, a man of insinuating manners, and of 
 a miM and affable deportment, had the address to procure 
 specimens of the materials used by the natives in their porcelain, 
 and these he sent to France with a summary description of the 
 Chinese processes. 
 
 When the specimens arrived in France, the celebrated 
 Reaumur undertook a series of experiments to discover the 
 method of imitating the Chinese productions ; and he persevered 
 with amazing industry until he had obtained the main object he 
 had in view. 
 
 The difficulties which he had to encounter ; the mistakes he 
 made during the investigation; the cause of those mistakes, 
 and the extent of his success, are all well detailed in the French 
 Dictionary of Chemistry, translated by Mr. Keir, and will be 
 found under the article Porcelain. Mr. Reaumur himself in the 
 years 17^7 and 1729 also published a full account of his progress 
 in this inquiry, in two memoirs addressed to the Academy of 
 Sciences, and which were printed in their Transactions. 
 
 While Reaumur was engaged in these experiments, porcelain 
 was begun to be manufactured in Saxony, and soon afterwards 
 other manufactories of it started up in different parts of Germany. 
 We had also an establishment for making it at Chelsea ; and 
 since that period various companies in different parts of England, 
 France, and Italy, have been founded for the same purpose. 
 
 The first person who made porcelain for sale in Saxony was 
 the Baron Botgar, and it is probable that his was the first ma- 
 
 2 ChaptaPs Elements of Chemistry, vol. ii. p. 90; and the Biographical Dic- 
 tionary, article Palissy. 
 
314? ON EARTHENWARE AND PORCELAIN. 
 
 nufactory of real porcelain in Europe. In order as much as 
 possible to preserve this art as a secret, the works were rendered 
 impenetrable to any but those who were immediately employed 
 in them. 
 
 M. De la Condamine, in his journey into Italy, visited a ma- 
 nufactory of porcelain established at Florence by the Marquis de 
 Ginori, governor of Leghorn, where he saw statues and groups 
 half as large as nature, and modelled from some of the finest 
 antiques. He describes the body of the ware as being equal to 
 the best Chinese manufacture, and that it would be extremely 
 beautiful if it had a whiter glazing; but that the Marquis was 
 determined to use only such materials as were found in his own 
 country. 
 
 The establishments of the most consequence among the mo- 
 derns are, one at Dresden ; the King of Prussia's own manu- 
 factory at Berlin ; and the extensive works which belonged to 
 the late King of France at Sevres 1 , near Paris. There is also 
 a considerable establishment for the manufacture of porcelain at 
 Montpellier ; a descriptive account of which, together with the 
 process for making the peculiar glaze which is employed there, 
 was published some years ago in the Annales de Chimie^ torn. ii. 
 page 7385. 
 
 Frederick the Second, King of Prussia, had conceived so high 
 an opinion of the importance of the manufactory at Dresden, 
 that when he conquered Saxony he took many of the best work- 
 men away by force, and transported them to his own pottery at 
 Berlin 8 . This manufactory at Berlin since the year 1763 has 
 been carried on for His Majesty's own private account, with 
 success and with good taste. Five hundred men have constant 
 employment in it, and large quantities of the porcelain are annu- 
 ally exported. 
 
 Mr. Jonas Hanway, in the account of his travels, has published 
 a particular detail of an immense collection of porcelain which is 
 laid up in the Chinese palace at Dresden. The whole recital 
 would be unsuitable to these Essays ; but the following particulars 
 will show how the Elector of Saxony valued himself on account 
 of the perfection to which the manufacture of porcelain had 
 arrived in his dominions s . 
 
 " The vaults of this palace," says he, " consist of fourteen 
 
 1 For an interesting account of the establishment and management of the 
 manufactory at Sevres, see the Memoir of Brongniart, the superintendant of 
 the works. Phil. Mag. vol. xiii. p. 342 ; and vol. xiv. p. 17, &c. 
 
 2 Wraxall's Memoirs of the Courts of Berlin, Dresden, $c. 2 vols. 8vo, 
 London, 1806. 
 
 3 The potters of Dresden were always as curious in the management of 
 their ovens as they are in the manufacture of their porcelain. Nothing but 
 white wood is employed for heating the kilns, and this is never used till it is 
 become thoroughly dry. 
 
ON EARTHENWARE AND PORCELAIN. SI 5 
 
 apartments filled with Chinese and Dresden porcelain. One 
 would imagine there was sufficient to stock a whole country ; and 
 yet they say, with an air of importance, that a hundred thousand 
 pieces more are wanted to complete the intention of furnishing 
 this single palace." 
 
 " Here are a great number of porcelain figures of wolves, bears, 
 leopards, &c., some of them as big as the life; a prodigious 
 variety of birds, and a curious collection of different flowers. A 
 clock is preparing for the gallery, whose bells are to be also of 
 porcelain : I heard one of them proved, and think they are suf- 
 ficient to form any music; but the hammers must be of wood." 
 
 " Here are forty-eight large China vases, which appear to be of 
 no use, nor any way extraordinary, except for their great size ; 
 and yet His Polish Majesty purchased them of the late Bang of 
 Prussia at the price of a whole regiment of dragoons 4 ." 
 
 In the course of the narrative, Mr. Hanway mentions one very 
 interesting circumstance, viz. that samples of the Jlrst efforts to 
 make china in Saxony were laid up by the King of Poland in 
 this palace, together with specimens of all the improvements, 
 in their several gradations, from the first, till the time when 
 the manufactory arrived at its utmost state of perfection 5 ; an idea 
 truly philosophical, and which reflects more honour on his 
 memory than the bartering away the liberties of his subjects for 
 pieces of foreign porcelain. 
 
 The passion for collecting porcelain has been common in most 
 countries. Dr. Campbell remarks that to Ormus, at the proper 
 season of the year, resorted the merchants from Persia, Arabia, 
 and Turkey. At these seasons," he says, "the city wore a new 
 face, the outsides of the houses were adorned with cabinets of 
 porcelain and with beautiful paintings ; and all the riches of the 
 East blazed in the eyes of the captivated spectator 6 ." 
 
 The greatest part of the earthenware that is now made in 
 England is manufactured in a particular district of about ten 
 miles extent, well known by the name of the Staffordshire Pot- 
 teries. Here earthenware has probably been made ever since 
 the time of the Romans 7 ; but there did not appear to have been 
 any ambition among the manufacturers to improve the art, or to 
 
 4 An Historical Account of the British Trade over the Caspian Sea, with a 
 Journal of Travels, by Jonas Hanway, 4 vols. 4to, London, 1753. 
 
 5 The potters in Saxony are so exact in the management of their manufac- 
 
 foreign ingredie 
 
 6 Political Survey, vol. i. p. 37. 
 
 7 In sinking pits very evident remains of Roman potteries have been dis- 
 covered, and at a considerable depth below the present surface of the land. 
 
316 ON EARTHENWARE AND PORCELAIN. 
 
 produce any works of taste, till the late Mr. Wedgwood en- 
 gaged in the business. This most excellent man brought mo- 
 dellers from Italy and from other parts of the continent, whom he 
 engaged at high wages ; and he also constantly employed a 
 competent chemist in experiments, that nothing might be wanting 
 which could conduce to extend the employment of earthenware 
 throughout Europe, or that could in any way tend to give a per- 
 manency to the staple manufactory of the county which had given 
 him birth. 
 
 Notwithstanding the energy with which Mr. Wedgwood de- 
 voted his inventive talents and chemical knowledge to the im- 
 provement of his favourite manufacture, during the course of a 
 long and industrious life, I have no doubt that chemistry might 
 still confer many benefits on the potter's art, if the manufacturers 
 in general would bestow such an education upon their children 
 as would enable them to pay a proper attention to the cultivation 
 of this science. 
 
 Impressed with this idea, I have myself frequently inspected 
 several of the largest manufactories of earthenware in this king- 
 dom, as well as many others of inferior note, and have examined 
 their various processes with the utmost care and attention. A 
 residence of several years at Stoke-upon-Trent, in the midst of 
 the Staffordshire potteries, afforded me the best opportunities for 
 this purpose, and enabled me to make those inquiries at my lei- 
 sure, and to acquire that information, which none but an inhabi- 
 tant could easily have obtained. 
 
 It will not, however, be necessary for me, while giving an 
 account of this manufactory as at present conducted, to go much 
 into detail; because, if this were the object I had in view, it 
 would be necessary to devote a volume or more to the purpose ; 
 for I am acquainted with few manufactories in which the opera- 
 tions are more numerous and diversified. 
 
 On this account, I shall content myself with giving such an 
 outline of the business as will afford the general reader a correct 
 idea of the nature of the different operations ; and at the same 
 time shall propose, for the consideration of the manufacturers 
 themselves, such hints for the improvement of some of the pro- 
 cesses, as I conceive to be worth their attention. 
 
 Before I proceed to a descriptive detail of the several processes 
 in the manufactory of earthenware, it will be proper to say a few 
 words on the nature of the different materials which are usually 
 employed to form the body of the ware itself. 
 
 It is well known that the chief ingredients are clay and flint ; 
 the former of which, when pure, is known to chemists by the 
 
ON EARTHENWARE AND PORCELAIN. SI 7 
 
 name of alumina, and the latter by the name of silica; and that 
 no kind of earthenware can ever be perfect, unless it be made of 
 a suitable sort of clay *, and in that proportion only which shall 
 be correspondent to the quantity of flint employed. The ex- 
 perience of ages has confirmed this, and has proved that good 
 pottery, as Vauquelin has remarked, differs from bad, less in the 
 diversity of its elements, than in their proportions. How crude 
 have been the notions of men respecting the chemical nature of 
 bodies ! The great Buffon " considered clay to be merely silica 
 attenuated, and, as it were, rotted by the action of water, the 
 air, and the sun." 
 
 Baume was of opinion that sulphuric acid is a component 
 part of all clays, and that the difference which is observable in 
 different samples of this earth is chiefly owing to variation in the 
 quantity of this acid but this opinion is also erroneous. 
 
 There are four kinds of clay in common use in the Stafford- 
 shire potteries, and they are known by the following appellations, 
 viz. Black clay, Cracking clay, Brown clay, and Blue clay. The 
 two former are the produce of the south of Devonshire, the others 
 are brought from the Isle of Purbeck in the county of Dorset. 
 With regard to the price of these clays, that of the two first is 14-s. 
 per ton delivered on board the vessel, or 44?s. when delivered in 
 the potteries. The price of the two latter is 21s. on board, or 
 from 4-85. to 525. per ton when delivered to the works. 
 
 The black clay takes its name from the colour which it usually 
 bears, and this is derived from a quantity of bitumen or coaly 
 matter which it contains. This carbonaceous portion is, however, 
 entirely consumed when the clay passes through the potter's oven, 
 for the articles made with it become when properly fired of a 
 good white 2 . It is, indeed, a curious fact, that the blacker this 
 clay is when it is first dug, the more white will the earthenware 
 be which is made with it. 
 
 The second kind, called cracking, has acquired its name from 
 a property which it has of occasioning the ware to crack during 
 the first process of burning, or while making it into biscuit if 
 by accident a larger quantity than usual of it has been employed. 
 But, notwithstanding this singular property, the manufacturers 
 are fond of it, on account of its extreme whiteness. It is, how- 
 
 1 Macquer's Paper on Clays, in the Memoirs of the Academy for the year 1758, 
 is highly deserving of perusal. 
 
 2 The Roman potters must have learnt that the native clays differ very 
 much in their nature and properties, for they had different names to dis- 
 tinguish them; such as Argilla for potter's clay; Terra pinguis, black clay; 
 Leucargillmi, white clay ; Terra sigillaris, fine clay ; and Tasconium, the clay 
 for crucibles. 
 
318 ON EARTHENWARE AND PORCELAIN. 
 
 ever, always dangerous to use it unless it be employed with 
 judgement, because it has a peculiar tendency to crack even 
 when mixed with the usual proportion of silica. Every kind of 
 clay, when dried without any admixture, will be liable to this 
 inconvenience; because, if pure argillaceous earth be made suf- 
 ciently soft to be modelled by the potter's wheel, it will shrink 
 one inch in twelve during the process of drying, and this will in- 
 evitably produce the effect in question. 
 
 The third kind which I have mentioned, is what is known by 
 the name of brown clay. The excellency of this sort is, that it 
 burns white, without danger of its cracking like the last species, 
 although it is liable to another imperfection which is termed 
 crazing. Some manufacturers, however, employ this clay largely, 
 while others, on account of this peculiar property, refuse it 
 entirely. 
 
 CRAZING is a technical term to denote the cracking of the 
 glaze. It is believed that this generally arises from a defective 
 union of the glaze with the body, owing to the clay, or the 
 mixture of the clay with the other materials, being ill calculated 
 to receive the glaze properly. But may it not be occasioned 
 rather by the glaze itself being not perfectly fusible ? I suspect, 
 however, that it more frequently originates from the circum- 
 stance of the ware being drawn out of the oven before it has 
 time to cool gradually, and for the glass to become properly 
 annealed. See the article Annealing^ in the Essay on Glass in 
 this work. If lime be mixed with the materials which form the 
 body of the ware, that will unavoidably occasion the crazing of 
 the glaze. 
 
 The fourth kind, called blue clay, is considered to be the best, 
 and, indeed, it always costs the highest price. This not only 
 burns white, but it forms a very solid kind of ware, and will 
 bear a larger proportion of flint than any other ; and it is well 
 known to potters, that the greater the quantity of silica, the 
 whiter will be the earthenware ; though if more of this species 
 of earth should be employed than the clay will admit, it would 
 occasion the goods to crack in the second burning. Both this 
 and the brown clay are now much used for making porcelain. 
 
 It requires much practice to be enabled to understand the 
 nature of clays sufficiently to employ them in pottery to the best 
 advantage. Dr. Lewis, in his notes to Neumann's Chemistry, has 
 given the results of many experiments on the mixture of clay 
 with the different earths and earthy compounds for the purposes 
 of making pottery, which may be read with advantage by those 
 who are desirous of investigating this subject. 
 
 Silica, or pure flint, as I have stated above, is likewise an im- 
 
ON EARTHENWARE AND PORCELAIN. 319 
 
 portant article in the manufacture of earthenware ; forming, in 
 general, a fourth, a fifth, or a sixth part of the whole of the bulk 
 of the prepared mixture or paste, when taken by weight. 
 
 There is however one remarkable difference in the properties 
 of silica and alumina, which has a very manifest effect on porce- 
 lain. Pure silica is transparent ; but the thinnest lamina of alu- 
 mina is entirely opake. 
 
 Alumina has such an affinity for silica that it will unite with it 
 even in the humid way, and form a kind of mortar, which will 
 harden by time, and be afterwards incapable of decomposition by 
 the action of the atmosphere. This combination is the basis of 
 many of the gems and precious stones. 
 
 Much of the flint used in England is brought from the neigh- 
 bourhood of Larne in the county of Antrim in Ireland ; but as 
 this comes out of a bed of limestone, it is not so good for the 
 potter's use as the chalk flint. 
 
 It has been suggested by a friend of mine, that an inex- 
 haustible source, for supplying the manufacturers with very ex- 
 cellent flint, would be the sea-shore ; and that a person conver- 
 sant with chemistry might readily examine a few samples of peb- 
 bles, and determine which were most suitable for making good 
 pottery. On the coast of Sussex alone, particularly about 
 Brighton, there is enough of shingle, as it is called, to serve the 
 whole of England for ages, and at no other cost than the car- 
 riage. Such, indeed, is the abundance and inconvenience of 
 this natural production, that it would be worth while for the 
 inhabitants of Brighton to give a small premium to encourage 
 its exportation. 
 
 For making the finer kinds of earthenware a considerable 
 quantity of Cornish clay is also used, known commonly by the 
 name of China-clay. This is the decomposed felspar of the gra- 
 nite ; and it is prepared in Cornwall by the clay-merchants them- 
 selves before it is transmitted to the Staffordshire potteries. 
 
 There are huge masses or rather mountains of white granite in 
 Cornwall, and in some parts of the county this is found to be par- 
 tially decomposed ; and it is where this is the case, that the mi- 
 neral is raised and prepared for the purpose of making earthen- 
 ware and porcelain, it having been discovered some years ago, by 
 Mr. Cookworthy of Plymouth, that this mineral furnishes us with 
 the true kaolin, and also with the petuntse of the Chinese. 
 
 Granite is composed of quartz, felspar, and mica : and Mr. 
 Gerhard found, in making an experiment on granite, that the 
 felspar melted into a transparent glass ; under it the mica lay in, 
 the form of a black slag, and the quartz remained unaltered. 
 Nicholson's Chem. Diet. 
 
 To render the decomposing granite of Cornwall fit for the 
 
320 ON EARTHENWARE AND PORCELAIN. 
 
 manufacturer, the following method is adopted. The stone is 
 broken up by means of a pickaxe, and then thrown into a stream 
 of running water. This washes off the light argillaceous parts 
 and keeps them in suspension, whilst the quartz and the mica, 
 thus separated, are allowed to subside near the place where the 
 stone is first raised. 
 
 At the end of these rivulets are a certain kind of catch-pools, 
 where the water is at last arrested, and time is allowed for the 
 pure clay, with which the water is thus charged, to separate 
 entirely from it. As soon as all the clay has subsided, the 
 water is drawn out of these receptacles. The solid matter is then 
 dug up in square blocks, and laid on what are called linnees, 
 which are several connected series of strong shelves, erected so 
 as to allow of a proper circulation of air, in order that the clay 
 may be more effectually dried for sale. It is then packed in 
 casks and sent to the Staffordshire potteries, and elsewhere, under 
 the name of China-clay. Thus prepared, it is extremely white 
 and in the state of an impalpable powder. It may here be ob- 
 served that none of the native clays are entirely free from foreign 
 ingredients. If pure argillaceous earth be required, it can only 
 be procured from alum, which may be dissolved in water, and 
 then decomposed by an alkali. In this process the pure clay will 
 subside, which should then be thoroughly washed for use. 
 
 The price of these Cornish clays is considerably higher than 
 that of any other kind ; but for many of the finer purposes of 
 pottery, they are absolutely indispensable. They are very smooth 
 and ductile, and their extreme whiteness is very remarkable. It 
 was analysed by Mr. Wedgwood, and found to consist of 60 
 parts alumina and 20 of silica. 
 
 The Cornish clay is also extremely useful for making cruci- 
 bles, as it will not fuse by the addition of any of the common 
 fluxes. In using these crucibles, however, they should always 
 be put within others which are of little value ; the inner ones 
 will then acquire the heat gradually, otherwise they would be in 
 great danger of breaking. 
 
 Besides the clays already mentioned, some of the Cornish gra- 
 nite itself is often used with the clay on account of the binding 
 quality which it possesses, and its knitting as it were the other 
 materials more closely by its fusibility, it being naturally more 
 fusible than the earths usually employed in this manufactory: 
 for it is a curious fact, that neither clay, silica, nor lime, will 
 melt singly; but by mixing these three species in due proportions 
 the greatest degree of fusibility is acquired. 
 
 Having thus briefly described the several articles which are 
 most commonly employed in making pottery, it will now be 
 
ON EARTHENWARE AND PORCELAIN. 321 
 
 necessary to explain in what manner these are separately pre- 
 pared for use. 
 
 The flints are managed in this way : they are first burnt in a 
 kiln constructed for the purpose, and somewhat similar in form 
 to a common lime-kiln ; and then they are ground between very 
 hard stones by a great power, which is given either by the water- 
 wheel or by a steam-engine. In constructing the apparatus the 
 purity and hardness of the stones are of very material conse- 
 quence; for should they contain calcareous earth, a portion of 
 this would be abraded during the grinding of the flint, which 
 would prove very detrimental to the pottery of which it formed 
 a part. 
 
 To enable the operator to expedite the process, and at the 
 same time to grind the flints finer, a quantity of water is thrown 
 into the mill with them, so that the article, when finished, has 
 much the appearance and the consistence of cream. The health 
 of the workmen is also preserved by this expedient ; for, before 
 this method was adopted, the atmosphere of the room often be- 
 came charged with the finer particles of the flint, which, entering 
 into the lungs, sometimes produced the most disastrous conse- 
 quences. 
 
 The grinding the flint with water was first practised by the 
 celebrated Brindley, well known for his skill in the construction 
 of inland canals. The mills now in use were also invented by 
 him; and are composed of a very hard siliceous stone called 
 chert, which is found in abundance in the neighbourhood of 
 Bakewell in Derbyshire. 
 
 I have already hinted, that it is important to attend to the 
 nature of the stone which is employed in these mills, and some 
 years ago I was told of a very severe loss which was sustained 
 by many of the large potters, in consequence of their having 
 been supplied with great quantities of prepared flint which had 
 been ground by stones containing a considerable portion of car- 
 bonate of lime, which being mixed with the flint, and eventually 
 -with the material itself, occasioned to the body of manufacturers 
 a loss of many thousand pounds. 
 
 In order to prepare the clay, it is first mixed with water to 
 the consistence of cream : the design of this is, that it may be 
 the more easily passed through the sieves, and intimately united 
 with the ground flint, which could not be done with uniformity 
 and certainty if these earths were mixed dry. 
 
 The mixture of the clay and water in the first instance, is 
 generally effected by means of long wooden instruments, which 
 the men move backwards and forwards with considerable force 
 
322 ON EARTHENWARE AND PORCELAIN. 
 
 throughout the whole mass. It is an operation of great labour, 
 and is distinguished by the term blunging. 
 
 The ground flint is mixed in a similar way with water, and 
 the stirring is continued until it become one uniform fluid mass. 
 But these earths, the clay and the flint, are always blunged sepa- 
 rately ; because, if otherwise, and the two earths were mixed 
 before being deprived of their impurities, which cannot be done 
 till they are brought into a fluid state, it would be impossible to 
 observe the requisite proportions of each. 
 
 The Purification of these earths is effected by a process similar 
 to that which the chemist calls Elutriation. When the earth 
 has been well broken and thoroughly mixed with water, it is put 
 into vats, or other large vessels ; and when it has stood long 
 enough for the grosser parts to subside, the fluid containing the 
 finer particles is drawn off by a plug, and reserved for use. 
 
 In every preparation of these materials for the formation of 
 earthenware or porcelain, it is of the utmost consequence to 
 attend to the relative quantities of each : therefore, whenever 
 these mixtures of the fluid clay with the flint are to be made, 
 they are always done with some nicety, an attention being paid 
 to the specific gravity of each of the fluids, which is either made 
 heavier, or diluted further with water, as the case may require. 
 The mixture of clay and water after it has passed once through 
 the sieve, is generally brought to the specific gravity of 24 ounces 
 the wine pint. A pint measure of the ground flint and water, 
 when in the same state, is usually 32 ounces. 
 
 When the clay and the flint are mixed in suitable proportions, 
 the whole mass, in this state of semifluidity, is passed through 
 the sieves to take out any remaining impurities, and also to 
 detain those particles which have not been sufficiently levigated. 
 The mixture is then passed through the finest silk lawn, to 
 ensure the certainty of no unbroken pieces remaining in it, and 
 to reduce the whole to a state of the utmost uniformity and 
 smoothness. 
 
 The next object is, to separate the water which has been em- 
 ployed with such profusion, and the readiest way of effecting this 
 is found to be by the direct application of heat. The mass is 
 therefore now poured into very long brick troughs, which are 
 built with flues under them of a sufficient size to afford heat 
 enough to produce an ebullition in the mixture ; and this is con- 
 tinued until so much of the water is evaporated as will reduce 
 the mass to the desired consistence. 
 
 The evaporation is, indeed, never carried beyond a certain 
 point; because, if this mixture of the earths were allowed to 
 become nearly dry, it would not be kneadable by the usual 
 
ON EARTHENWARE AND PORCELAIN. 523 
 
 methods; neither could it be worked, by the hand or the wheel, 
 into any of those forms which it may be the intention or the 
 interest of the potter to impart to it. 
 
 I ought to have mentioned, that the mixture of the clay and 
 the flint with water, is known in the trade by the name of slip / 
 that the place in which it is kept is the slip-house ; and the trough 
 on which it is boiled is called the dip-lain. 
 
 When the mixture has been thus brought to a proper con- 
 sistence, it ought to be kept for a considerable time, that the 
 materials may become more intimately united than they can ever 
 be by mere mechanical force : but in general this is not much 
 attended to, although every manufacturer is fully aware of its 
 importance. Want of room, of time, and often of capital, occa- 
 sions it to be sometimes used warm from the slip-kiln, and not 
 uncommonly when it has been lying for only a few hours or days. 
 In China it is no unusual thing for the prepared clay to remain 
 from 14< to 20 years before it is thought to be in a fit state for use ; 
 and I have heard of some districts where it is customary for a 
 father to prepare as much porcelain-clay as will be sufficient for 
 the use of his son throughout the whole period of his life. 
 
 When the dried mass has been removed from the kiln, the 
 next process is that of tempering it, which is effected by first 
 beating it with mallets, and then turning it and beating it again, 
 and again, with small spades, or paddles as the workmen call 
 them, until it is thought to be as well tempered as it can be by 
 these operations. 
 
 It should be recollected that this is not pure clay, but a mix- 
 ture of all the ingredients. Vauquelin says that " Silex constantly 
 forms at least two-thirds of most pottery ; alumine from a fifth 
 to one-third ; lime from one five-hundredth to one twenty-hun- 
 dredth part; and iron from the minutest quantity to twelve or 
 fifteen per cent." 
 
 The mass, after the operation of beating, undergoes a process 
 called dapping. For this purpose it is removed, in the state of 
 large lumps, to a convenient bench or table, where a man having 
 cut it across with a brass wire, unites it again by slapping one 
 of the halves down upon the other with all his force ; he then 
 cross-cuts it again and again, and as often unites it by main force, 
 as before. 
 
 This cutting the clay in pieces and slapping it together, is a 
 laborious operation ; but it must always be continued until the 
 air-bubbles, which the mass at first contained in great abund- 
 ance, are all driven out of it ; because, if the air was not thus 
 carefully expelled from the clay, it would escape when it became 
 rarified in the oven, and this would produce such blisters as 
 would spoil the manufactured goods. On this account the slap- 
 
 Y 2 
 
ON EARTHENWARE AND PORCELAIN. 
 
 ping is continued until the mass exhibits, wherever it may be cut, 
 a perfectly smooth and homogeneous surface. 
 
 Of late years Mr. Wedgwood and some other considerable 
 potters have, however, employed an apparatus invented by Mr. 
 Thomas Lowe of Nottingham, which effects all these purposes 
 at once. It is moved by a steam-engine, and performs all these 
 operations with a surprising economy of time and labour. It 
 first breaks the burnt flint ; it then grinds it in water, and another 
 part of the apparatus performs the hitherto laborious operation 
 of blunging the clay in water and breaking it into a semifluid 
 and uniform mass. When this is done, it is run off and sifted 
 by several sieves of different degrees of fineness, all which are 
 moved by the same power. This earthy fluid then runs down 
 to a lower room, where it goes through other sieves in the same 
 way. In like manner, another part of the apparatus squeezes 
 the dried clay, to save the expensive operation of slapping; 
 after which it passes to an iron cylinder full of knives, where 
 it is cut into pieces with great expedition ; which saves the ex- 
 pense of cutting it by hand with brass wires, as before mentioned. 
 This receptacle is not properly a cylinder, but a large hollow 
 inverted cone of iron, and the knives are fixed in an upright shaft 
 which revolves within it and passes through its centre. These 
 knives are so contrived that the clay, as it is cut, is forced lower 
 and lower by every revolution, until at last it is pressed by the 
 power of the machinery through a square hole near the bottom 
 of the apparatus, from whence it is removed as it falls, and is 
 carried in blocks to the other parts of the manufactory. 
 
 The clay having undergone these varied operations, it is now 
 fit for being formed into any shape, or employed for any pur- 
 pose, for which it is designed. Accordingly, it is fashioned into 
 various forms by means of a variety of moulds made of plaster of 
 Paris ; or put into as great a diversity of shapes by the potter's 
 wheel. 
 
 Nothing is found to answer so well for making the potter's 
 moulds as plaster of Paris ; because, when rightly prepared, it has 
 the property of absorbing the water so very rapidly from the 
 ware, that it occasions it to slip out of the mould, or to deliver 
 itself easily, as the technical phrase is. 
 
 To prepare the plaster for making the moulds, it is first ground 
 in a mill exactly similar to that which is generally used for grind- 
 ing corn by means of a pair of flour stones; it is then baked, or 
 rather boiled 1 , to expell the water which is one of its component 
 parts when in a native state. 
 
 1 Boiled. This may appear to be an incongruous expression when applied 
 to a dry earthy substance ; but the fact is, that when the ground plaster is 
 
ON EARTHENWARE AND PORCELAIN. 325 
 
 This plaster, which is the native sulphate of lime, is boiled in 
 very long brick troughs, having a fire flue running underneath 
 them. The man who superintends the process has a handker- 
 chief tied over his mouth for safety ; as the small particles getting 
 upon the lungs, or into the stomach, have been found to be very 
 injurious to the health of the operator. 
 
 When this plaster has been thus deprived of water, it is in 
 the state of a soft and impalpable powder ; and if its own pro- 
 portion of water be again mixed with it, it will immediately set 
 into a hard compact mass. It is this property which renders it 
 so peculiarly fit for making the potter's moulds. 
 
 The manipulations by which the different articles of earthen- 
 ware are made, are so various and multiplied, that it would be 
 very difficult, if not impossible, to describe them. They can be 
 known only by those who have had opportunities of visiting a 
 pottery. A short outline of these processes will however be 
 expected from me, and may be acceptable to the generality of 
 my readers. 
 
 Much of the common earthenware is formed by means of the 
 potter's wheel, which is a round board attached to a lathe, and 
 capable of being moved thereby, either rapidly or otherwise, as 
 the occasion may require. This round board moves in a hori- 
 zontal position ; and when in use, the clay which is to be fashioned 
 is fixed on the centre of it ; and it is put in motion either by a 
 person who constantly attends it when at work, or by means of 
 a treadle which is moved by the foot of the workman himself. 
 
 As the clay revolves upon this machine, the workman either 
 models it by his fingers, or forms it, by means of an instrument 
 which he holds in his hand, into any kind of circular shape that 
 he may desire; and when the object is to make a number of 
 vessels exactly similar to each other, the size is generally deter- 
 mined by a gauge fixed without the circumference of the, revolv- 
 ing wheel, but projecting over it in such a manner that, whenever 
 the yielding clay is spread out until it touch this gauge, the 
 artist knows that the article which he is making has attained the 
 exact figure which he intends. 
 
 The potter's wheel is probably the most ancient of the manu- 
 facturing instruments now in use. It was known to the author 
 of that book in the Jewish Scriptures, which claims the highest 
 antiquity of any writings we have, and who must have lived at 
 least 3000 years ago. This simple instrument has however of 
 late years been much improved by adapting a strap to it, which 
 
 heated it has so much the appearance of ebullition, that the term which I have 
 employed is made use of by the workmen universally. The finished article is 
 always called boiled plaster. 
 
326 ON EARTHENWARE AND PORCELAIN. 
 
 passes over a large taper cylinder of wood, by means of which 
 the artist is enabled to increase or diminish the rapidity of the 
 motion at pleasure. This contrivance is known to mechanics by 
 the name of the cone pulley. 
 
 In going through a pottery, it will be observed, that all the 
 articles are very thick and coarse when they come from the 
 wheel. This is perhaps unavoidable. They are therefore taken 
 to a lathe, where the extra quantity of clay is removed, in the 
 same manner as the wood-turner forms his work by shaving off 
 successive portions of the wood. These parings of clay are 
 afterwards kneaded as before, and then worked over again for 
 similar purposes. 
 
 It is curious to notice the great variety of circular things that 
 may thus be made by means of the potter's wheel ; but it must 
 be remembered that this machine is calcula ed only for cylindri- 
 cal, conical, or round articles, and not for such as are of an oval 
 or an irregular form. All such are made in plaster moulds, 
 which divide in halves for the convenience of taking out the ware 
 whenever it is found to be sufficiently dry to be removed. The 
 handles of cups and jugs are also made in moulds, and these are 
 afterwards put on the vessels for which they were designed. 
 
 The consumption of sulphate of lime, gypsum, or alabaster, 
 (for this substance is known by these various names,) is so con- 
 siderable for making the moulds for plates and dishes, that in the 
 course of the year many tons of worn out moulds are thrown 
 away as useless. I would suggest, that these might be ground 
 and used as manure, instead of purchasing fresh gypsum for that 
 purpose, 
 
 As the plaster moulds absorb water with avidity, the articles 
 which are made in them dry much sooner than would generally 
 be imagined. For instance, the moulds on which the common 
 table-plates are formed, are put into a very temperate stove as 
 the plates are made, and in about two hours the whole will be 
 dry enough to be removed to make room for a fresh parcel. In 
 the usual way of conducting a manufactory, every mould is capa- 
 ble of taking four or five fresh plates in the course of a day of 
 twelve hours. The plate-stove is generally a very small room 
 built with bricks, and shelved with boards from the floor to 
 the ceiling. It is usually heated by an iron pipe which passes 
 through it. 
 
 When the plates are removed from this stove, they are taken 
 off the moulds, and pared round the edges with a small knife ; and 
 when they have been slightly polished by the hand, they are laid 
 by to become hard enough for the biscuit oven. 
 
 From this short account it may be easily conceived that a com- 
 mon-sized pottery must require a great deal of room, especially 
 
ON EARTHENWARE AND PORCELAIN. 327 
 
 as every article, whether made by the wheel, the lathe, or the 
 moulds, must be spread out upon shelves to dry: and this reminds 
 me o an expedient which I lately observed at the works of an 
 ingenious potter in Staffordshire, and which I conceive to be so 
 far an improvement upon the old practice, as to deserve being 
 mentioned, and which I have the leave of the proprietor to make 
 public. 
 
 The improvement to which I refer, is that of having a chamber 
 shelved entirely round, not with stones or boards as is usual, but 
 with shelves of prepared plaster made as smooth as polished 
 marble, and of the thickness of an inch and a half each. 
 
 Upon these plaster shelves, instead of those of wood and stone 
 as commonly adopted at other works, the goods are placed to 
 dry : and the great advantage which must accrue to the manu- 
 facturer from the practice is very obvious ; for the plaster not 
 only absorbs the water sooner, but the articles will dry more re- 
 gularly and uniformly than they possibly can when placed upon 
 substances which cannot abstract the water. Being persuaded 
 of the utility of this expedient, I have no hesitation in recom- 
 mending it for general imitation. Moreover, why may not the 
 floors of a potter's warehouses be covered with plaster? The 
 expense would be very inconsiderable ; and then, whenever these 
 were not in use for storing the finished ware, they might be 
 advantageously employed in hastening the drying of the goods 
 newly made. 
 
 In some counties it is usual to form the floors of cheese cham- 
 bers with plaster, and I have been told that the cheese becomes 
 sooner ripe on these floors than on others ; though Mr. Twamley 
 directs that it should not be placed on plaster until time has been 
 allowed for the first moisture to exude and evaporate ] . 
 
 An important improvement might be made in the manufacture 
 of earthenware, if it were possible to contrive an expeditious mode 
 of spreading the goods out so as they might always dry gradually. 
 The property which clay has of contracting by heat or by drying 
 is well known, and the excellence of earthenware depends in a 
 great measure on its being very gradually dried before it be ex- 
 posed to the kiln. 
 
 When the articles of pottery have been modelled or fashioned 
 to the design of the artist by any of the foregoing methods, and 
 have been partially dried, either by an exposure to the action of 
 the atmosphere, or by placing them for a certain time in stoves 
 or drying rooms constructed for the purpose, they are carried to 
 the potter's oven, where they are placed in deep oval boxes made 
 of fire clay. These are called seggars ; and being flat at bottom, 
 
 1 Josiah Twamley On Dairying, 8vo, Warwick, 1784, p. 100. 
 
328 ON EARTHENWARE AND PORCELAIN. 
 
 one of these vessels forms a cover for another, so that the work- 
 men are enabled without difficulty to place them in piles nearly 
 to the top of the oven, which is a large cylinder of brick sur- 
 mounted by a dome. 
 
 When the oven is properly filled, heat is applied by means of 
 ignited coal, which is thrown into several receptacles built on the 
 outside, but communicating, by means of flues, with the inner 
 part. These are called mouths ; they stand about four feet in 
 height from the ground, and project about three feet from the 
 sides of the kiln. 
 
 In the beginning the heat is kept at a low state ; but after a 
 lapse of twelve hours it is gradually increased, and the augmen- 
 tation of temperature is continued until the kiln and its contents 
 acquire the proper maximum. 
 
 An attention to the degree of baking is an object of extreme 
 importance. Vauquelin has remarked that " the heat should be 
 such as to expell the moisture, and agglutinate the parts which 
 enter into the composition of the paste ; but incapable of effecting 
 the fusion, which, if too far advanced, will render the ware of so 
 homogeneous a texture as to become brittle." 
 
 It has been found that alumina loses 0.46 of its weight even 
 when the fire is not urged beyond the temperature of ignition for 
 silver; whence it appears that it contains nearly half its weight 
 of water, and it does not part with the last portion but with great 
 difficulty. 
 
 The operation of burning usually lasts two days and two nights. 
 This, however, varies in the different charges; and the fireman 
 judges when the ware is sufficiently burnt, by examining the trial 
 pieces which are placed in those parts of the oven where they 
 may be taken out with ease, and without causing any diminution 
 of the heat. 
 
 These trial pieces are made of the common red clay of the 
 Staffordshire brick-makers. It is found in the Potteries, and has 
 the property of changing its colour at every change of tempera- 
 ture ; therefore, by comparing one of these, taken out of each 
 part of the oven, with a trial piece made of the same kind of clay 
 and properly burnt, and which is kept on purpose for a standard, 
 the exact state of the ware under operation may at any time be 
 exactly known. 
 
 All the common ware undergoes two firings : that is, when it 
 has been sufficiently dried in the air, it is put into an oven and 
 made into what is called biscuit, which is earthenware partially 
 burnt. 
 
 Many ladies are in the habit of buying china in the state of 
 biscuit, for the purposes of painting and gilding. When they 
 
ON EARTHENWARE AND PORCELAIN. 329 
 
 have imparted their own designs, these are sometimes returned 
 to the potter, who burnishes the gold and completes the baking. 
 This is mentioned with the view of directing those females who 
 may not be already acquainted with it, to a new object for the 
 exercise of their taste and genius, and also for the better expla- 
 nation of the nature of biscuit ware. 
 
 All the English earthenware and china undergoes this previous 
 firing, because, were it not first made into biscuit, it would not 
 bear to be immersed in the mixture of lead and water, called the 
 glaze, without suffering injury thereby: that is, it would not fail 
 to be rendered soft, and liable to be put out of form, by its ab- 
 sorption of the water. Neither would it sustain the process of 
 printing, nor allow of its being painted upon with any good effect. 
 
 The composition of the Chinese porcelain is different, and its 
 nature is now pretty accurately known. Mr. John Bradley Blake, 
 who was settled as a resident Supercago at Canton, and died there 
 at the age of 29, sent, a short time before his death, to Mr. Samuel 
 Moore, the then Secretary to the Society for the Promotion of 
 the Arts, specimens of the earths, clays, sand, stones, and other 
 materials used in making the true Nankin porcelain, all which 
 Mr. Moore put into the hands of the late Mr. Wedgwood, who 
 from these materials produced some pieces of excellent porcelain, 
 and declared that those earths were so complete a set of speci- 
 mens, that he had no doubt of their being the true materials of 
 the Oriental porcelain. Had Mr. Blake lived, further informa- 
 tion would have been procured. 
 
 It was ascertained by Mr. Blake, and we have learnt from other 
 sources, that in China the earthenware and porcelain are merely 
 dried in the air before glazing ; as their composition so effectually 
 resists water, that it can be immersed in an aqueous glaze, without 
 being first made into biscuit, and consequently that the Chinese 
 are enabled to burn their ware by one single firing. 
 
 It is therefore a desideratum with the potters of this country, 
 to find some substance to mix with the clay which shall give it 
 the property of resisting the action of water before it has under- 
 gone the first burning. This would be a great acquisition to our 
 English manufacturers, because it would not only be a saving of 
 fuel, but a great economy of time and of the expense of wages, as 
 one operation would be thereby entirely saved. 
 
 Dr. Woodward mentions the Soap Rock at the Lizard Point, 
 and the steatites in other places, as very likely to make good 
 porcelain *. Dr. Campbell also, who seems to understand this 
 
 1 Woodward's History of Fossils, vol. i. page 6. 
 
330 ON EARTHENWARE AND PORCELAIN. 
 
 subject, strongly recommends this article to be employed in the 
 manufacture of china l . Whether steatites will improve the body 
 of the ware, as above mentioned, I do not know, but I know it 
 has been used at some of our porcelain works in considerable 
 quantities. 
 
 Should the English potter be able to make the body of his 
 ware equal to that of the East, it would then be necessary, as I 
 apprehend, to discover some other material for the glaze ; be- 
 cause, if our ware were burnt, as it is in China, by one operation, 
 the earth would contract more than the glaze, and consequently 
 the latter must either crack, or partially fly off. 
 
 I hazard this opinion, because I know that in China the glaze 
 is infinitely better than ours, inasmuch as it consists purely of 
 felspar, and is so extremely hard that it cannot be operated upon 
 by any of our common cutting instruments. Even the wheel of 
 the glass-grinder will not touch it ; whereas ours becomes 
 scratched and defaced by common usage and ordinary wear. 
 
 If the glaze on porcelain be too thick, this will occasion it to 
 break ; it is therefore important to apply a thin glaze, the fusi- 
 bility of which should be as nearly as possible approaching to 
 that of the body of the ware, in order that the combination may 
 be more intimate and lasting. Chaptai describes a glaze which 
 perhaps our potters may imitate with advantage. " It consists," 
 says he, "in mixing the earth of Murviel in water, and dipping 
 the pottery therein. When dry, they are plunged into a second 
 water, in which levigated green glass is mixed. This covering of 
 vitreous powder fuses with the clay of Murviel, and the result is 
 a very smooth, very white, and very cheap glazing 2 ." 
 
 The great durability of the Oriental china is its main excel- 
 lence. We make porcelain in this country which is equally 
 beautiful ; and, if the symmetry of the figures and the merit of the 
 painting be considered, far more elegant, although it possesses a 
 less degree of tenacity and hardness. We have, indeed, lately 
 noticed the introduction of what is called stone-china, which is 
 made very thick and clumsy to imitate some of the best produc- 
 tions of the East : the glaze upon this, however, is as poor and 
 soft as upon other English china. 
 
 Is it not natural then to ask, Why do not our potters make 
 use of a better glaze, especially as the county of Cornwall can 
 furnish felspar in abundance and at a reasonable price? 
 
 The true answer to this question seems to be this: that our 
 ovens are not capable of fusing a glaze similar to that which is 
 
 1 Political Survey of Great Britain, vol. ii. page 19. 
 
 fl Chaptal's Elements of Chemistry, English Transl., vol. ii. page 88. 
 
ON EARTHENWARE AND PORCELAIN. 331 
 
 employed in China. The heat of the potter's oven in that country 
 must be tremendous. The materials could not be vitrified as we 
 see them, with less heat than would fuse Cornish granite. 
 
 An ingenious mode of discovering when the glaze on china is 
 not sufficiently hard, has been given by the late Mr. Nicholson. 
 It consists in dropping a small quantity of strong ink upon it, 
 drying this before the fire, and then washing it. If the glaze be 
 too soft, an indelible brown stain will remain upon it. 
 
 It must here be remarked, that for those who choose to incur 
 the expense, there is porcelain manufactured in some parts of this 
 kingdom which is more durable than that commonly made in the 
 Staffordshire potteries. Such was formerly the Bow china, and 
 that also made at Chelsea ; and I have been credibly informed, 
 the china now manufactured at Worcester is nearly equal to the 
 best Dresden 3 , or to the true Nankin, in all those properties 
 which give the most value to this production of art. 
 
 The common heat of the potter's kiln in England is about 60 
 of Wedgwood's pyrometer 4 , which is equal to 8877 degrees of 
 Fahrenheit for the cheapest cream-coloured ware, and about 80 
 of Wedgwood for the Staffordshire porcelain ; though I have 
 reason to believe that the manufacturers of the best cream- 
 coloured ware seldom allow the heat of the kiln to exceed 4.5 of 
 Wedgwood's pyrometer. It must be recollected, however, that 
 we fire twice, and that these heats refer to what are employed in 
 converting the ware into what is called biscuit. 
 
 I am not myself acquainted with the respective temperatures 
 at which the other porcelain manufacturers fire their ware ; but 
 Dr. Henry has stated that the Worcester china vitrifies at 94, 
 that the Chelsea porcelain is fired at 105, and the Derby at 112 
 of Wedgwood. 
 
 In the Staffordshire potteries the temperature of the gloss-oven 
 is generally about 10 of Wedgwood, or 2377 degrees less of 
 Fahrenheit than the heat of the biscuit oven. The reason of this 
 is, that there may never be any danger of the ware, in this last 
 operation, undergoing a higher degree of heat than it experienced 
 in the first burning ; it being absolutely necessary for the operator 
 to be careful of this point, because, as clay will continue to con- 
 
 3 Dresden china was formerly in such high estimation in this country, that 
 in the year 1763 a single service of it was sold by auction in London, at Mr. 
 UhthoiTs sale, for 115 pounds. Gentleman's Magtiz. vol. xxxiii. p. 312. 
 
 4 For an account of the construction of Wedgwood's pyrometer the reader 
 is referred to the Ixxiid and several of the subsequent volumes of the Philoso- 
 phical Transactions, or to Murray's System of Chemistry, vol. i. p. 150. The 
 pieces of baked earth which he employed for the pyrometers were analysed by 
 Vauquelin, who states them to have consisted of silica 64, alumina 25, charcoal 0, 
 oxide of iron 0-2, water 6-2. Nicholson's 4to Journal, vol. iii. p. 265. 
 
332 ON KARTHENWARE AND PORCELAIN. 
 
 tract by every addition of heat, it must follow, that should it ever 
 be pushed beyond that degree which it sustained in the state of 
 biscuit, the body of the ware would experience a greater con- 
 traction, and consequently every piece within the oven would 
 either become crooked, or the glaze would be injured. The 
 firing of the gloss-oven generally requires from 12 to 14 hours. 
 
 The glazing for the common cream-coloured earthenware con- 
 sists usually of certain portions of litharge of lead and ground 
 flints, mixed with as much water as will form them to the consis- 
 tence of thin cream, which is found to be a state the most suitable 
 for the immersion of the ware. One hundred pounds of litharge 
 and 40 pounds of ground flints are the common proportions; but 
 it is usual to take 80 pounds of Cornish granite to 100 pounds of 
 litharge, whenever that is used instead of flints. Flint is the 
 article which is employed in making glaze for the porcelain as 
 well as for the coarse earthenware, it being nearly all silica. 
 Klaproth found common flint to consist of ignited silica 98 parts, 
 lime 0*50, alumina 0'25, ignited oxide of iron 0'25 parts, volatile 
 in the fire, 1. Analyt. Essays, vol. i. page 42. 
 
 For the finer kinds of earthenware and for porcelain, it is made 
 with white lead, ground flint glass, ground silica, and common 
 salt. Some manufacturers, however, add other materials; most 
 of those who superintend this department imagining that they 
 possess a valuable secret, and that in consequence of it their glaze 
 is much better or cheaper than that of others. 
 
 In all manufactories it is found necessary to vary the compo- 
 sition of the glaze, according to the nature of the materials which 
 form the body of the ware; and the former cannot be perfect un- 
 less it be capable of contracting and expanding by heat and cold, 
 in the same proportion as the ware itself will contract or expand 
 by change of temperature. The writer of the article Porcelain 
 in the French Chemical Dictionary very properly remarks that 
 "a glass which makes a fine glazing for one porcelain, will make 
 a very bad glazing for another sort of porcelain, will crack in 
 many places, and have no lustre. The glazing must be appro- 
 priated to the density of the ware and the ingredients of its com- 
 position." 
 
 As the number of potters has increased very much within the 
 last 50 years, the competition has become so great that every 
 manufacturer is under the necessity of consulting economy, and 
 of sometimes sacrificing the utility and goodness of the ware, for 
 the sake either of appearances or of adopting the cheapest modes 
 of manufacture that can be devised. 
 
 To one of these causes, may be attributed the introduction of 
 bones into the manufacture of porcelain. Of this article there is 
 now so large a consumption in the Staffordshire potteries, that 
 
ON EARTHENWARE AND PORCELAIN. 333 
 
 some of the great manufacturers have extensive rooms which are 
 used solely for the reception of bones. Animal bones are com- 
 posed of lime and phosphoric acid, in different proportions ac- 
 cording to the age and species of the respective animals to which 
 they belonged. These are either bought of the indigent bone- 
 collectors in the country, and then burnt and ground by the pot- 
 ter, or they are purchased ready burnt and ground for use, di- 
 rectly from those who distill volatile alkali or spirit of hartshorn. 
 It is, however, generally known to the china manufacturers, that 
 this article is injurious to the texture of the ware : its use, there- 
 fore, cannot be justified on any account whatever. 
 
 I allow that ground bones have the effect of rendering the 
 goods very white, and also that they produce a transparent ap- 
 pearance ; but I doubt whether this be a real transparency, or 
 only a deception. Thus far, however, one may venture to assert, 
 that the modern English porcelain, which has the usual propor- 
 tion of bones in its composition, is of much less specific gravity 
 than it ought to be, and is very apt to crack with hot water. As 
 the base of animal bones is phosphate of lime, it might be worth 
 while for the potter who is determined to use bones, to try whe- 
 ther the native phosphate of lime can be useful in making porce- 
 lain, and if phosphate of alumina may also be employed in this 
 manufacture. 
 
 In returning to the subject of glazing, it will be proper to state 
 that the common earthenware would be too porous, and many 
 kinds of fluids would pass through it, were it not defended by 
 an artificial covering or permanent glaze. It became necessary 
 therefore to contrive a composition which should vitrify and flow 
 in the fire, so as to cover these materials of earth with an entire 
 coating of perfect glass. 
 
 Such a glaze having been found in a mixture of oxide of lead 
 and silica, as mentioned above, a certain proportion of each of 
 these, ground to an impalpable powder, is thrown into a tub of 
 water, and stirred therein till the mixed powder becomes sus- 
 pended and uniformly dispersed throughout the fluid. 
 
 The glaze having been thus prepared, it is applied to the ware 
 in the following manner. A workman to whom this duty belongs, 
 receives the goods from a boy, who delivers them to him one at 
 a time ; and as he receives each single piece, he dips it in the 
 liquid, lets it drain for a moment, and then, placing it on a board 
 standing beside him, he is ready to receive another piece, which 
 he immerses in like manner. 
 
 It is in this way that the glaze is applied to all the various 
 articles which are made of the common earthenware ; and as it 
 is only partially baked or in the state of biscuit, when it is im- 
 
&34< OK EARTHENWARE AND PORCELAIN. 
 
 mersed in the glaze, a sufficient quantity attaches itself to the 
 surface, which, when it has been fused, will form over it a com- 
 plete covering of glass. This mixture has great fusibility, though 
 silica alone does not melt in the focus of the most powerful burn- 
 ing mirror. Mr. Hare, however, fused it completely by submit- 
 ting it to the flame of a stream of mixed oxygen and hydrogen 
 gases, and found that it formed when cold a kind of enamel. 
 
 There are, however, strong objections to this mode of glazing 
 pottery. The men who work in it for a considerable time are 
 apt to become paralytic, probably from the lead; and where 
 acids, which have the power of dissolving the lead, are employed 
 in preparing condiments for our food, such a glaze must be ex- 
 tremely unwholesome. 
 
 Aware of the pernicious effects of lead, when taken into the 
 stomach, M. Fourmy, an ingenious manufacturer at Paris, has 
 prepared water-coolers, in which he has employed lava for the 
 glaze, instead of the deleterious metallic covering which is more 
 commonly used for that purpose. Pumice-stone has also, as 1 
 understand, been used for covering earthenware, and with very 
 good effect. 
 
 Some of the French potters, at the suggestion of Chaptal, 
 have substituted common flint glass for lead in their glazing, 
 and have found it not only safer, but more economical. They 
 grind broken flint glass to a fine powder; and when this is mixed 
 with a due portion of clay and water, the goods are dipped into 
 it, as our potters dip their ware. 
 
 The potters of Bristol and Lambeth glaze their stone ware 
 with common salt. When the oven has acquired a certain tem- 
 perature, the salt is cast in, and the vapours arising from it 
 attach themselves to the goods, and completely cover them. The 
 alkali of the salt probably combines with the silica of the ware, 
 and forms a true glass upon their surfaces. 
 
 The English potters are however fond of using a glaze made 
 with lead and silica, because, whatever the articles may be which 
 are employed for this purpose, it is necessary to give them a heat 
 sufficient to vitrify the materials and convert them into a perfect 
 glass ; and when the best articles are made use of in forming a 
 glaze, the heat which is employed must be very considerable ; 
 whereas lead alone will readily fuse and form a glaze that may 
 be finished at a very low heat indeed. This, however, if used 
 alone, would make a glaze too soft, and so extremely fusible that 
 it would be apt to run very much towards the lower parts of the 
 ware, and leave the upper ones imperfectly covered. 
 
 Half a century ago our potters were so'careless in their man- 
 ner of applying the salt glaze to the stone wares of Staffordshire, 
 that large importations were made from France and Holland, 
 
ON EAHTHENWARE AND PORCELAIN. 335 
 
 where the manufacture was better conducted ; and had it not 
 been for Mr. Wedgwood's timely invention of the Queen's-ware, 
 it is probable that the best part of the trade would long ago have 
 been lost to this country. 
 
 A variety is sometimes given to the glaze by mixing certain 
 oxides of the metals, especially that of copper, or otherwise the 
 filings of copper ; but this coloured glaze is generally applied only 
 partially, and merely for goods of inferior quality. The edges of 
 common plates are sometimes coloured by this method '. 
 
 It is about sixty years since the plain cream-coloured ware of 
 Mr. Wedgwood was introduced. At that time this unadorned 
 and simple article was thought sufficient for every purpose where 
 porcelain was not employed; and the neatness and cleanliness of 
 its appearance gave it such a decided preference that her late 
 Majesty allowed the worthy inventor to call it Queen' s-wares 
 but, when a demand arose for more expensive services of pot- 
 tery, recourse was had to the pencil. From that period a great 
 number of artists have been constantly employed in painting 
 earthenware as well as porcelain, and often great taste is dis- 
 played in these productions. 
 
 It must not however be imagined that painting on earthen- 
 ware was a new invention. The paintings of the ancients of this 
 kind are rare and valuable. The Marquis Marcello Venuti, in 
 his description of the curiosities found in the ancient city of He- 
 raclea, speaks of one upon slate, representing a muse crowned 
 with laurel, with a musical instrument hanging on her shoulders, 
 which was found in one of the subterraneous cavities, and is de- 
 scribed as being then in the possession of Signer Nicolo Vagnucci 
 of Cortona, one of the principal supporters of the Academy of 
 Tuscany. 
 
 Nevertheless, it must not be concealed that Chaptal has shown, 
 that the Romans of the first century were not acquainted with 
 any of the metallic fluxes with which the moderns fix and vitrify 
 the coverings of their pottery. For the particulars consult his 
 very instructive account of certain colours which were found in 
 the shop of a colour-merchant in one of the streets of the ancient 
 Pompeia, especially as he has there told us what was the com- 
 position of the glaze which the potters of that day did actually 
 employ 2 . 
 
 To return to the consideration of the paintings on English 
 
 1 The beautiful black glaze, which is seen on a peculiar sort of ware made 
 at Nottingham, is composed of 21 parts by weight of white lead, 5 of flints, 
 and 3 of the oxide of manganese. Watson's Chemical Essays, vol. ii. page 271. 
 
 3 Annalcs dc CAirnie, tome Ixx, p. 22. 
 
336 ON EARTHENWARE AND PORCELAIN. 
 
 earthenware, it must be observed that the variety of effect is pro- 
 duced by means of the different metallic oxides, each of which 
 affords a different colour, and these colours are again multiplied 
 by such mixtures of two or more of the oxidized metals, as expe- 
 rience has shown to be useful. 
 
 In employing these various colours, the ground oxide is first 
 mixed with a prepared flux, which is also reduced to an impal- 
 pable powder, and then this mixture is well incorporated with 
 gum water, the acid of tar, oil of turpentine, or some other es- 
 sential oil, as may be most suitable, in point of expense or other- 
 wise, for the goods on which it is to be employed. The fluids 
 are used merely to lay on the colour ; for it is necessary that, 
 whatever oil be employed, it should have the property of evapo- 
 rating entirely. 
 
 The preparations which are commonly used, are the metallic 
 oxides and their combinations with acids. Thus cobalt yields a 
 blue ; antimony and silver give yellows and oranges ; platinum a 
 silver colour ; gold violet and purple ; copper the greens ; while 
 the reds, the browns, and the blacks, are derived from iron. 
 
 The oxide of cobalt employed in the pottery is usually pre- 
 pared from zaffre, which is an expensive article imported from 
 Saxony, though a few years ago very fine oxide of cobalt was 
 procured from Cornwall ; for preparing antimonial yellows, the 
 crude antimony is first calcined with four times its weight of 
 nitre, and is then mixed with a certain proportion of vitrified 
 lead. The precipitate of Cassius is the article which is generally 
 used for the production of violets and purples, though sometimes 
 the oxide of gold precipitated by copper is employed. For greens, 
 the copper has usually been taken in the state of a precipitate ; 
 but some potters have found an article of more value in the pure 
 oxide of copper, which they procure by placing sheets of copper 
 in the ovens in which the ware is glazed : and it has lately been 
 discovered that a small portion of copper mixed with the iron 
 very much increases the intensity of the blacks on earthenware. 
 Besides, iron itself is capable of giving a great variety of colours, 
 according to the way in which it is managed. For instance, the 
 black oxide of this metal produced by the action of heated air only, 
 will be a very different article when used as a pigment from an 
 oxide of bon prepared by other means. 
 
 It is here necessary to remark, that in painting on the biscuit 
 no oil is used; the metallic oxides are mixed with water only; and 
 it is owing to this circumstance that such ware may be glazed at 
 once without being put into an oven, as is the case with those 
 goods which are known by the appellation of Hue-printed. 
 
 For certain purposes, however, the painting is performed upon 
 
ON EARTHENWARE AND PORCELAIN. 33? 
 
 the glaze, as some colours would be injured, and others destroy- 
 ed, by the heat of the gloss-oven. Thus, where iron is employed 
 to produce blacks or browns, the painting is always done upon the 
 glaze; the ware is then finished in an enamel-oven, at about 6 of 
 Wedgwood's pyrometer. 
 
 Some metallic oxides are used for another purpose besides that 
 of painting, viz. for covering the ware entirely on the exterior, as 
 is the case when the sulphuret of antimony is employed for pro- 
 ducing a common kind of yellow ware ; and also for those arti- 
 cles known by the names of GOLD and SILVER LUSTRE. The first 
 of these lustres is effected by means of gold, the latter by the oxide 
 of platinum. For gilding porcelain the metal is used in its metallic 
 state. To procure it in a pulverized form, it is dissolved in aqua 
 regia, and then the acid is driven off by heat, and the gold re- 
 mains ; this is then mixed with borax and gum-water, which form 
 together a proper vehicle for fixing it upon the goods. After this 
 it is baked, and finished by burnishing. 
 
 For preparing the lustre-ware, as it is called, the oxide, of 
 whatever kind it may be, is mixed with some one of the essential 
 oils, and in that state it is brushed upon the surface of the arti- 
 cles. It should have been observed, that when the manufacturer 
 intends to make lustre-ware, the articles are glazed before the 
 gold or the platinum is applied. For go/rf-lustre, the ware is made 
 of a red clay, which, when burnt and glazed, shows so much of 
 its colour through the covering of gold, as is sufficient to give 
 the goods that peculiar brown tint which is always observable on 
 this singular kind of pottery. 
 
 When the metallic oxide has been properly applied to the sur- 
 face of the goods, they are carried to an enamelling-oven, where 
 the heat dissipates the oxygen, and restores these precious me^ 
 tals to their metallic state, I cannot say quite to their primitive 
 metallic brilliancy, because this is often much injured by the fluid 
 menstruum employed in the operation. The great difference 
 which there is in the appearance of this ware, especially in that 
 which is covered with platinum, can only be thus accounted for. 
 Some of it looks like silver, while the articles from other manu- 
 factories are more like iron or steel. 
 
 I once imagined that this variation might arise from a different 
 mode of preparing the oxide of platinum. I therefore prepared 
 two samples of this oxide, the one precipitated by caustic anrn 
 monia, and the other by muriate of ammonia ; but when I had 
 them tried by an experienced potter, both produced precisely the 
 same colour. 
 
 I wish some manufacturer would attempt to produce this ware 
 by mixing the oxide of platinum with pure water only ; for in 
 
338 ON EARTHENWARE AND PORCELAIN. 
 
 that case I am persuaded the ware when finished would be as white 
 as the platinum itself. 
 
 The potters of England have derived great advantage from 
 the introduction of the printing-press. The use of this valuable 
 machine, which is comparatively of late date, has enabled these 
 manufacturers to produce a greater variety of patterns, and of 
 neater execution, than could possibly be acquired at a small ex- 
 pense by the pencil. 
 
 As this is a curious branch of the business, it will be proper to 
 describe it a little more particularly. It consists in first printing 
 the intended pattern with some metallic colour, chiefly the oxide 
 of cobalt, on what is called silver paper, and then in transferring 
 the colour from the paper to the surface of the porcelain. This 
 style of colouring earthenware is a very successful imitation of the 
 old blue porcelain of China, and of late years has been the means 
 of extending the consumption of British pottery throughout Eu- 
 rope more than any other improvement in the manufactory ; for 
 the potters of China are totally unacquainted with the printing- 
 press, and consequently all their designs are produced by the 
 pencil alone. 
 
 This mode of imparting designs to the surface of earthenware 
 or porcelain, and which is known in the trade by the appella- 
 tion of BLUE PRINTING, is managed somewhat in the following 
 manner : 
 
 One man constantly attends the press, which is very similar 
 to our common copper-plate printing-press ; and as soon as he 
 has applied the colour which is laid on the copper in the same 
 manner as the copper-plate printers apply the ink he lays it 
 upon a hot iron, to thin the oil with which the colour is always 
 mixed for this purpose. The oil which is used is a peculiar pre- 
 paration of boiled linseed oil. When the colour upon the copper- 
 plate is thus reduced to a proper consistence, a sheet of silver 
 paper is laid over it, and the workman passes it, with the paper, 
 through the press. 
 
 For blue printing, the oxide of cobalt is the only mineral which 
 is employed. This is largely prepared in the Staffordshire pot- 
 teries, and sells at from 405. to 605. the pound, according to its 
 intensity and goodness. Indeed, such improvements have been 
 made in the manufacture of this colour, that the Chinese potters 
 are now supplied from England with all the cobalt they consume. 
 
 When the paper comes from the printing-press, it is, of course, 
 found to be stamped with the intended pattern. It is then de- 
 livered, while wet with the colour, to a girl, who cuts off the 
 superfluous paper with a pair of scissars, and passes it to another 
 
ON EARTHENWARE AND PORCELAIN. 339 
 
 girl, who immediately applies it to a piece of biscuit ware, and 
 then delivers it to a third, who fixes it more firmly by rubbing it 
 very hard with a piece of flannel tightly rolled up in the form of 
 a short cylinder. 
 
 The design of this hard rubbing is to force the colour into 
 the pores of the ware. When the papers which have been thus 
 applied have lain on for about an hour, the colour is generally 
 found to be sufficiently fixed to admit of their being detached. 
 This is effected by putting the articles into a tub of water, where 
 the paper soon becomes soft and pulpy enough to allow of its 
 being peeled off by gentle friction, leaving the full impression of 
 the pattern upon the biscuit. 
 
 The papers having been removed, the ware is suffered to stand 
 a sufficient time to become dry, and then it is put into an oven 
 at a low heat, for the purpose of dissipating the oil, and preparing 
 it for receiving the glaze. 
 
 It must be obvious that it is necessary to employ a glaze which 
 is transparent, in order to give full effect to the brilliancy of the 
 cobalt colour. A little of this blue oxide is also generally mixed 
 with the glaze, for the same purpose as laundresses employ smalt 
 with their starch, viz. to increase the whiteness, by subduing any 
 yellow tint that might otherwise impair its lustre. 
 
 Here I cannot avoid observing, that it would be an important 
 acquisition if some suitable article, instead of oil, could be dis- 
 covered for mixing with the colours which are employed in print- 
 ing on earthenware, and which could be of such a nature as not 
 to require to be burnt off previously to the application of the 
 glaze. It appears to me to be worth while to institute a series of 
 experiments for this particular object ; because, if it could be at- 
 tained, what immense quantities of printed goods, besides those 
 which are ornamented by the pencil, might be completely finished 
 with two firings, instead of three, which, on the present plan, such 
 goods always require ! Were it on no other account than the ex- 
 pense of this vehicle, it is desirable to find a substitute. Some 
 of the first enamel-painters think it necessary to use even the best 
 rectified oil of amber, and this, of late years, has been very costly. 
 
 It was my intention to have offered some remarks on the ma- 
 nufacture of crucibles, retorts, and other chemical vessels, which 
 are required to sustain a great heat; but having already extend- 
 ed this Essay much beyond its proposed limits, I must content 
 myself with merely referring to those authors who have already 
 treated on this subject. The most important of these is Pott, who 
 wrote a work expressly upon it \ as I have already mentioned. 
 
 1 Lithogeognosie Pyrotechnique, ou Examen Chymique des Pierres et dcs 
 Terres. 12mo,2 vols. Paris, 1753. 
 
 z 2 
 
340 ON EARTHENWARE AND PORCELAIN. 
 
 I shall detain the reader, however, just to notice that the chief 
 difficulty which the manufacturer finds in preparing such utensils 
 as crucibles, &c. is, that if the portion of silica were employed 
 which is necessary to give sufficient compactness, the ware would, 
 from this very circumstance, be liable to become useless ; because 
 many of our chemical articles have the property of dissolving 
 silica. An expedient has therefore been adopted of mixing a large 
 portion of old pottery with the fresh clay, which gives it the de- 
 sired weight, and yet is not liable to be dissolved by the alkalies, 
 like pure flint or sand. 
 
 I am informed by a Sheffield manufacturer, that their cast-steel 
 makers mix ground coke with the best Stourbridge clay, and that 
 their crucibles for melting steel are made with this mixture. Pure 
 earthenware is not fit for crucibles, or for any vessels that must 
 expand or contract by change of temperature. This has been 
 long known ; Dryden notices it in one of his poems. 
 
 It is said that in France the very best crucibles which they 
 have, are made with fine clay mixed up with old ground butter 
 pots ; and that these are composed of a peculiar kind of stone- 
 ware, which is manufactured in Normandy '. 
 
 Where crucibles are required for melting metals, those made 
 with plumbago are decidedly the best; but these are unsuitable 
 for other purposes of the laboratory, especially when salts and 
 alkaline fluxes are employed in any process. 
 
 More than eighty years ago the celebrated Reaumur, in making 
 some trials on glass, discovered, that if a vessel made of the com- 
 mon green bottle-glass be submitted to theheat of a potter's oven, 
 imbedded in a mixture of sand and ground sulphate of lime, the 
 glass of which it is composed will be changed in its appearance, 
 and acquire some of the properties of the best Oriental china; 
 become so hard as to strike fire with steel ; be semi-transparent 
 like porcelain, and will endure sudden changes of temperature 
 without breaking. An account of these results was given in the 
 Memoirs of the Royal Academy of Sciences for the year 1739. 
 
 The subject, however, appears to me to be highly deserving of 
 still further investigation, especially as useful vessels of a difficult 
 form may be made more easily of glass than of earthenware. If, 
 therefore, a cheap arid certain method of performing this species 
 of cementation could be adopted, the operative chemist would 
 have it in his power to procure a greater variety of chemical 
 vessels, and those not only more durable but of more convenient 
 forms, than he can possibly obtain by any other means. I wish some 
 potter would commence a manufactory of this kind. Such ware 
 would be highly useful for many domestic purposes, to which none 
 
 1 See the article Pottery in the second vol. of The French Chemica! Dictionary. 
 
ON EARTHENWARE AND PORCELAIN. 341 
 
 of the common pottery can be applied either with convenience or 
 safety. 
 
 In returning to the subject of earthenware, it is proper I should 
 state my opinion, that chemical vessels are often injured by the 
 oxide of iron originally pertaining to the clay itself, as it acts like 
 a flux, rendering this earth too fusible to admit of a proper union 
 with the siliceous material of the ground pottery, which is em- 
 ployed in the manufacture of such articles. A question arises here, 
 whether oxide of iron alone is prejudicial in this way, although 
 its sulphuret, the pyrites, may. It may, perhaps, be worth while 
 to decide this by experiment. Macquer says, that if a bit of py- 
 rites be left in clay which is to be exposed to a baking fire, it will 
 form a cavity in the ware, arid that this may be known by the cir- 
 cumstance of the cavity being stained black. 
 
 There is an old pamphlet of nine pages in the London Institu- 
 tion, without title-page or date, on making porcelain, in which the 
 writer speaks of a practice the Chinese have of purifying the earth 
 they employ for the glaze, by means of aqua-fortis. On reading 
 this, it occurred to me, that it might perhaps be worth trying, 
 whether this expedient could be adopted with advantage in puri- 
 fying such of our clays as are designed for the finest purposes. 
 
 For those articles in which the chemical nature of the body of 
 the ware is of importance, it would perhaps be advisable always 
 to wash the clay thoroughly ; for, if pyrites be contained in it, 
 the greater part of this would subside, on account of its superior 
 specific gravity, while the argillaceous earth remained suspended 
 by the water. For chemical jars, still-heads, &c., a, small portion 
 of iron would probably not be injurious. Vauquelin analysed the 
 clay of which Hessian crucibles are made, and found it to con- 
 sist of 8 parts oxide of iron, combined with 69 of silica, 22 alu- 
 mina, and 1 carbon. 
 
 Clay which contains lime is equally improper for the manufac- 
 ture of chemical vessels. If a clay be suspected to contain lime, 
 or rather carbonate of lime, it may readily be discovered by an 
 acid, which, if this earth be present, will occasion an efferves- 
 cence. When lime does not exceed five or six per cent., it ap- 
 pears to do no harm to the quality of the pottery; but when more 
 abundant, it communicates too great a degree of fusibility : in 
 like manner there are cases in which an admixture of the oxide 
 of iron is useful and even necessary. 
 
 In the manufacture of what is called Delfware it has been cus- 
 tomary to mix a portion of ferruginous clay with the other ingre- 
 dients, because of its possessing a binding quality from which 
 other species are exempt. The following are the usual propor- 
 tions: Two parts of red clay, three of blue clay, and five of marie 2 . 
 
 2 See Macquer's Chemical Dictionary, article Delfware. 
 
342 ON EARTHENWARE AND PORCELAIN. 
 
 Most of the red clay is indebted to iron for the colour which it 
 assumes ; but when iron enters in any considerable quantity into 
 the composition of the finer kinds of earthenware, it imparts 
 either a red or a brown tinge to it; and besides this, it adds more 
 fusibility to it than even lime. 
 
 Recollecting the circumstance just mentioned respecting delf- 
 ware, it occurred to me, in reading one of the volumes of the 
 Archceologia, that a certain iron-ore found in Scotland would 
 probably be useful, when mixed in a small proportion, for some 
 articles of pottery. I will give an abstract of the passage which 
 caught my attention ; And if any ingenious manufacturer should 
 be able to avail himself of this hint, and convert it to profit, I 
 shall be rejoiced, and shall at any time be glad to be informed of 
 the result, and the respective particulars which attended it. 
 
 In the Highlands of Scotland some very singular ancient walls 
 are to be seen, which consist of " stones piled rudely upon one 
 another, and firmly cemented together by a matter which has 
 been vitrified by means of fire, and which forms a kind of artifi- 
 cial rock that resists the vicissitude of the weather, better than any 
 artificial cement that has ever yet been discovered." 
 
 Mr. James Anderson, the person who has written upon these 
 curious remains of antiquity, has found that through all the 
 northern parts of Scotland, a peculiar kind of iron ore of a very 
 vitrescible nature is in great abundance. Hence he supposes that 
 " when the walls were reared and made as firm as could be by 
 dry stones piled one upon another, the interstices between them 
 were filled with this vitrescible iron ore, and the whole supported 
 by a backing of loose stones piled behind it. When this wall was 
 thus far completed, nothing more was necessary to give it the en- 
 tire finishing, but to kindle a fire all round it, sufficiently intense 
 to melt the vitrescible ore, and thus to cement the whole into one 
 coherent mass." 
 
 Dr. Lewis has related a remarkable instance of the affinity of 
 iron for silica. Having immersed some pieces of green glass in 
 the red oxide of iron which remains after the acid has been ex- 
 pelled from green copperas, and baked it for several hours in the 
 upper chamber of a wind furnace, the glass and oxide of iron 
 were found to have run together into a black mass, of sufficient 
 hardness to strike fire freely with steel. " It is remarkable," says 
 he, " that a metallic substance so refractory in the fire, should be 
 so greatly disposed to melt with green glass l ." 
 
 Nothing can be of more importance to a potter than a thorough 
 knowledge of the properties of the different kinds of clays. Dr. 
 Campbell, in his Political Survey of Great Britain, states that we 
 
 Commercium Philosophico-Technicum, p. 245. 
 
ON EARTHENWARE AND PORCELAIN. 34-3 
 
 have not less than twenty-two distinct species s ; and Macquer, 
 who examined more than eight hundred specimens, says that in 
 all that number he did not find one that was entirely free from 
 metallic matter 3 . 
 
 There is only one method, however, by which clays can be 
 examined with any accuracy, and that is by the aid of chemistry. 
 Such of my readers who are potters but not chemists, will there- 
 fore allow me to advise them to lose no time in acquiring the 
 knowledge of analysing earths and minerals. Ample directions 
 for the attainment of this art will be found in Kirwan's Elements 
 of Mineralogy, or in Klaproth' s Analytical Essays ; and I con- 
 ceive it impossible that any manufacturer will ever regret the 
 time which it may be necessary for him to devote to the acqui- 
 sition of that elementary knowledge which would enable him to 
 consult these distinguished writers with pleasure and advantage. 
 
 One or two instances of the mistakes which may occur in the 
 examination of mineral substances, when they are not submitted 
 to chemical analysis, will be sufficient to show the importance of 
 this inquiry, and will, I hope, induce the junior practitioners at 
 least, to adopt this advice, and enter upon that course of study 
 which will be most likely to afford profit as well as entertainment. 
 
 The precious stones were formerly classed with siliceous fossils; 
 and until Bergman and Klaproth analysed several of them, they 
 were generally supposed to be entirely composed of silica com- 
 bined with a portion of colouring matter, to which they were 
 solely indebted for their distinctive characters and appearances. 
 An accurate analysis of several of these gems, particularly of the 
 Sapphire, the Topaz, the Hyacinth, and the Ruby, has, however, 
 proved that either alumina, or zircone, and not silica, is in these 
 instances the predominant ingredient. The Sapphire, according 
 to Klaproth, consists of clay 98*50, oxide of iron 1, lime 0*50. 
 The Topaz consists of clay 46, silica 39, lime 8, iron 6. The 
 Hyacinth of zircone 70, silica 25, oxide of iron 0*50, loss 4'50 4 . 
 The Ruby is composed of clay 40, silica 39, lime 9, and iron 10 5 . 
 
 The well-known article called Fuller's Earth, from its sapona- 
 ceous texture had been supposed to consist almost entirely of clay 
 or alumina ; but, on an accurate analysis, it has been ascertained 
 that the earth which enters into its composition in the largest 
 proportion is silica. According to the analysis of Bergman, 
 Fuller's Earth consists of silica 51*8, alumina 25, lime 3*3, mag- 
 nesia 0'7, iron 0*7 5 water 15'5. Hence it may be accounted for, 
 
 8 Campbell's Political Survey of Great Britain, vol. ii. p. 16. Morton's 
 Natural History of Northamptonshire, p. 71. 
 
 3 Macquer's Memoir upon Clays, presented to the French Academy in 1762, 
 and abridged in the French Chemical Dictionary, under the article Clay. 
 
 4 Klaproth's Analytical Essays, vol. i. p. 198. 
 
 5 Bergman's Essays, vol. ii. p. 101. 
 
344 ON EARTHENWARE AND PORCELAIN. 
 
 why it falls into a powder when put into water, and is incapable 
 of forming a ductile paste. On the contrary, Emery, which has 
 very much the appearance of sand or ground silica, is for the 
 most part argillaceous earth or alumina, and the siliceous earth 
 is in a very inconsiderable quantity. 
 
 The last instance which I shall adduce is one that is intimately 
 connected with our subject, and which shows decisively how ne- 
 cessary it is for a potter to be capable of undertaking a chemical 
 analysis. 
 
 The porcelain earth of BaudhTero was pronounced by Mac- 
 quer and Baume to be a CLAY superior in quality to that which 
 was then employed in the manufactory belonging to the French 
 King at Sevres ; and on their authority this was generally be- 
 lieved, till Mr. Giobert discovered that not a particle of clay 
 could be found in it. For, when this chemist attempted to con- 
 vert it into alum, he found, to his great surprise, nothing but very 
 pure crystals of Epsom salt, or sulphate of magnesia. After this, 
 Giobert analysed this mineral with great care, and found it to 
 consist of magnesia 68, carbonic acid 12, silica 15*6, sulphat of 
 lime 1 '6, and water 3 '. 
 
 Since that period magnesian earth has been much employed 
 in the composition of porcelain, it having been ascertained that a 
 small portion of it prevents that great degree of contraction which 
 always takes place in the fire, when clay and silica alone are made 
 use of. The Cornish steatites or soap rock being a mineral con- 
 taining magnesia, some of the English potters now employ it for 
 this purpose. 
 
 There is a clay found in the territory of Sienna, in the province 
 of Tuscany, called fossil meal, and by Kirwan Argillomurite, 
 which is capable of making hard compact bricks that will float 
 in water, either baked or unbaked. M. Fabroni, who examined 
 some of these bricks in consequence of their having been men- 
 tioned by Pliny 2 , says that they may be of great use in the con- 
 struction of reverberatory furnaces ; for they are such bad con- 
 ductors of heat, that although one of such bricks should be made 
 completely red-hot from one end to its middle, any person may 
 take it up in his hand by the other end with impunity 3 . May it 
 not then be worth while to inquire, whether a clay possessed of 
 similar properties cannot be found in Great Britain ? 
 
 Moreover, considering the improvements which have been made 
 in the manufacture of pottery, might it not be easy to make bricks 
 to imitate stone, and yet be as durable as the bricks now in use? 
 
 By means of the metallic oxides, would it not be possible at a 
 
 1 Nicholson's Journal, vol. xii. p. 277, from the Journal de Physique, vol. 1x. 
 lj See Pliny's Natural History , lib. xxxv. cap. 14. 
 3 See Philosophical Magazine, vol. ii. p. 180. 
 
ON EARTHENWARE AND PORCELAIN. 34-5 
 
 cheap rate to stain bricks of any colour, and might not such bricks 
 be made to imitate marble? 
 
 A method of employing sulphate of barytes in pottery is indeed 
 alluded to by Sage, in the Journal de Physique. " The Chinese," 
 says he, " know the remarkable property which gum adracanth 
 has of giving a coherence to minute stony substances, which are 
 then unalterable by fire; and that if this gum be mixed with 
 pounded sulphate of barytes, it may be formed into masses which 
 neither alter their shape nor solidity from exposure to an intense 
 fire." I have not heard that any English potter has yet availed 
 himself of this suggestion. 
 
 In concluding this Essay, I trust I shall stand excused, if I en- 
 deavour to confirm an opinion already given, that a potter should 
 never employ a new porcelain-clay without previous analysis ; 
 for there are few of these clays that can be employed with the 
 certainty of a good result, unless some fusible material be used 
 with them ; and the quantity of this can only be known by a che- 
 mical examination of the clay in question. The necessity of ana- 
 lysis will appear from the comparison of the chemical nature of 
 three of these native productions. The porcelain earth t>f Limoges, 
 and which is often used without any admixture, is, according to 
 Hassenfratz, composed of 62 parts silica, 19 alumina, 12 mag- 
 nesia, and 7 sulphate of barytes ; whereas the porcelain-clay of 
 Cornwall is a compound of 20 per cent, of silica and 60 per cent, 
 of alumina; while that found in the department of the Loire in 
 France, of a beautifully white colour, consists entirely of carbo- 
 nate of magnesia and silica. 
 
 The business of a potter affords so large a field for the exercise 
 of taste and genius, and the art itself is so intimately connected 
 with chemical knowledge and experience, that it would be super- 
 fluous to urge, by further arguments, the absolute necessity of cul- 
 tivating the science of chemistry, in order to arrive at perfection 
 in any branch of the manufacture. 
 
346 ON THE MANUFACTURE OF GLASS. 
 
 ESSAY XL 
 
 ON THE MANUFACTURE OF GLASS. 
 
 AMONG the various productions of art, there is, perhaps, no one 
 so truly surprising, when we consider the materials from which it 
 is formed, as that of glass. It is the only instance that I recollect 
 of a substance perfectly transparent being produced by the union 
 of two dissimilar and entirely opake bodies. Many of the ancients 
 who wrote on Glass seem however to have known nothing of its 
 real nature. Agricola, lib. xii. " de Metallis" calls it a concrete 
 juice; Vincent Belluascensis, lib. xi. calls it a stone; and Fallo- 
 pius classes it with the middle minerals. 
 
 The word Glass is generally considered to be derived from the 
 Latin word glacies, in consequence of its resemblance to ice. 
 
 The date of this elegant and useful invention is involved in 
 great obscurity. According to Pliny, the first vessels of glass 
 were made in the city of Sidon ' ; but Loysel asserts that the 
 glass works of the Phoenicians were in high renown more than 
 three thousand years ago, and that they had merely depots for the 
 sale of their glass at Sidon and at Tyre 2 . The Egyptians also 
 lay claim to having first made it, and say that they were instructed 
 in the art by the great Hermes 3 . 
 
 Flavius Vopiscus, who wrote the lives of Tacitus and others, 
 in the reign of Dioclesian, observes, when speaking of Alexandria, 
 that " it was very rich, abounding in corn ; and that no one in 
 the city was idle, for that one part of the poorer inhabitants were 
 employed in the manufacture of paper, and the other in making 
 glass" A late traveller who explored the interior of Egypt, has 
 also assured us that the ancient inhabitants of that country made 
 glass 4 . 
 
 Pliny attributes the invention of glass entirely to chance, and 
 relates, that it was first made in Syria by some mariners who were 
 driven on shore on the banks of the river Belus ; and who, having 
 occasion to make large fires on the sands, burnt the kali which 
 abounded on that shore; and that the alkali of the plant uniting 
 
 1 Pliny, lib. xxxvi. cap. 26. 
 
 2 Essai sur VArt de la Verrerie par le C. Loysel, 8vo., Paris, an viii. Discours 
 Preliminaire, p. 1. 
 
 s Blancourt's Art of Glass, p. 9. 
 
 4 Belzoni's Researches in Egypt, <^c. quarto, p. 173. 
 

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ON THE MANUFACTURE OF GLASS. 34? 7 
 
 with a portion of the sand on which the fire stood, produced the 
 first stream of melted glass that had ever been observed b . 
 
 However this may be, there can be no doubt of glass having 
 been in use during the time of Pliny, as it is often mentioned not 
 only by hirn, but by many contemporary authors. The city of 
 Herculaneum, which was destroyed about this period by an erup- 
 tion of Vesuvius, contained glass. Besides utensils of glass, a 
 large sized plate of the same compound was taken from one of 
 the excavations. Josephus relates, that not far from Mount Car- 
 mel there is a round valley full of a clear sand fit for making 
 glass ; and that when the place has been emptied for this pur- 
 pose, the wind from the mountains fills it again immediately 6 . 
 But this historian could have known nothing of the nature of the 
 manufacture of glass ; for he asserts, that any metal when thrown 
 upon this sand will be instantly converted into glass, and that, if 
 glass be cast upon it, the glass itself will likewise be changed into 
 sand 7 . 
 
 Tacitus mentions the river Bel us, but he speaks more ration- 
 ally of the glass which was made in that neighbourhood than 
 Josephus. He says, that this river flows into the sea of Judea, 
 at the mouth whereof, the sand that is taken up, in consequence 
 of the great quantity of nitre contained in it, is by the heat of a 
 furnace readily converted into glass ; and that although the shore 
 be small, the sand is inexhaustible. 
 
 The time when glass was discovered is unknown. Herodotus 
 and Diodorus Siculus relate that the Ethiopians formerly in- 
 closed their dead bodies in glass, and that the ancient Egyptians 
 made glass of a dark colour in imitation of that manufactured in 
 Ethiopia. But their magnificent cups evince a considerable 
 knowledge in the art of making glass ; and of which the Empe- 
 ror Hadrian, then residing at Alexandria, thus writes to the 
 consul Servius : " I have sent to you," says he, " some Alassian 
 cups of various colours, given to me by the priest of the temple. 
 They are dedicated to you, and particularly to my sister ; and I 
 desire that you will always produce them at your feasts on holi- 
 days." 
 
 Several ancient writers relate, that, in the reign of Tiberius, 
 an eminent Roman architect acquired great celebrity from the 
 manner in which he had repaired a large portico in the city, 
 which was giving way and seemed likely to fall ; and that on 
 account of his popularity, or some other such cause, the emperor 
 banished him from Rome, forbidding him ever to return again. 
 
 5 Pliny, lib. v. cap. 19. 
 
 6 History of the Wars of the Jews, book ii. chap. 9. 
 
 7 Ibid, book ii. chap. 17. 
 
348 ON THE MANUFACTURE OF GLASS. 
 
 This individual, it is further stated, when in banishment, made 
 experiments on glass, and, having discovered a mode of render- 
 ing it malleable, ventured again to Rome and found means of pre- 
 senting one of his glasses to Tiberius, in the hope of not only 
 being pardoned for returning without leave, but having his sen- 
 tence altogether remitted ; and that, on the contrary, the emperor 
 was displeased at the invention, supposing that it would tend to 
 lower the value of gold ; and having learned from him that no one 
 was acquainted with the method but himself, he ordered his head 
 to be immediately struck off, that the dangerous secret might not 
 transpire ! . Pliny relates, that an artist who had acquired the art 
 of making malleable glass, had his house destroyed by the en- 
 raged populace. 
 
 Blancourt asserts, that an ingenious Frenchman, in the reign 
 of Lewis the JUST, also discovered the art of making malleable 
 glass, and that he presented a fine image or bust, made with such 
 glass, to the Cardinal Richlieu; who, foreseeing the injury which 
 such an invention would do to the glass manufacture, ordered 
 the artist into perpetual imprisonment 3 . 
 
 We read of glass-houses being in use very early in the city of 
 Tyre : and there is reason to believe that great part of the known 
 world was at one time supplied with glass by the Tyrians, though 
 it appears uncertain whether the great manufactories were in their 
 city or in Phoenicia, as before mentioned. It has also been said, 
 that glass-houses were erected in Great Britain before it was 
 visited by the Romans. 
 
 It is very uncertain when glass was first employed for the trans- 
 mission of light and other optical purposes, or how long any of 
 the nations of Europe have enjoyed the benefit of glass windows. 
 The best buildings in Herculaneum had windows made with a 
 sort of transparent talc 3 . 
 
 One of our oldest English historians, Bede, tells us that in the 
 seventh century it was not known how to make window glass in 
 England ; and that in the year 674, the Abbot Benedict sent for 
 artists from abroad to glaze the church and monastery of Were- 
 mouth in the county of Durham. These men came probably 
 from Venice; for the first glass that was manufactured in Europe 
 was made there. Loysel thinks that the emigration of refugee 
 artists of Phoenicia to Italy brought the glass trade first among 
 them 4 . We learn also from Bede that the agents of the Abbot 
 
 1 Dion Cassius, Hist. Rom. y Isidorus, and Petronius Arbiter. 
 4 Blancourt's Art of Glass, p. ] 5. 
 
 3 See an Account of the Antiquities of Herculaneum translated from the 
 Italian by Messrs. Martyn and Lettice, in quarto, with engravings. 
 
 4 Essai sur V Arl dc la Ferrerie, Discours Preliminaire, p. 3. 
 
ON THE MANUFACTURE OF GLASS. 349 
 
 " brought several glass-makers with them when they returned, 
 who not only performed the work required by Benedict, but in- 
 structed the English in the art of making window glass for them- 
 selves, also glass for lamps, drinking-vessels, and other uses V 
 
 Notwithstanding the interest which so important an applica- 
 tion of glass was likely to occasion, it is probable that glazed 
 windows were not common in these kingdoms until several cen- 
 turies after the period above mentioned. Dr. Henry says posi- 
 tively, that although the art of making glass was introduced in 
 the seventh century, it was afterwards so much neglected, that 
 no private house had glass windows till after the conclusion of 
 the tenth century 6 . Before that period the windows of houses 
 and even of cathedral churches admitted the light through fine 
 linen cloths or lattices of wood 7 . 
 
 To prevent the surprise that may be occasioned to some per- 
 sons, by the assertion that glass windows are comparatively but 
 of late introduction in Europe, it may be remarked, that there 
 are some countries on the face of the globe which have never yet 
 enjoyed this luxury. This is the case at present at Rio- de- Janeiro 
 in South America; for a friend of mine, who is largely concerned 
 in the manufacture of glass, sent a considerable quantity of win- 
 dow glass cut into panes of different sizes, to that country, when 
 the court of Portugal removed thither, in expectation of making 
 a great advantage of it : but, when it arrived, the captain of the 
 vessel had the mortification of learning that there were no win- 
 dow-frames in any of their houses, and consequently the glass 
 would be useless. The glass was therefore sold for embellishing 
 the images of the saints, it being customary to decorate the walls 
 of every house with such images and statues with glass before 
 them, something in the way in which stuffed birds are preserved 
 in this country. 
 
 It would seem that glass had not been long in common use 
 for windows, or for the mere transmission of light, before the 
 Monks became desirous of decorating it with ornamental paint- 
 ings; for the art of painting on glass was brought into this coun- 
 try in the early part of the thirteenth century, during the reign of 
 King John 8 ; it having been practised in France some time be- 
 fore that period, and must then have arrived at a considerable 
 degree of perfection, for it appears that the windows in the Abbey 
 of $t. Denys were painted in the twelfth century. The subjects 
 of these paintings were the representation of the first Croisade, in 
 
 5 See Bede's History of Wercmouth. 
 
 6 Henry's Ilidory of Great Britain, 8vo, vol. iv. p. 118. 
 
 7 William of Malmsbury De Geslis Pontijlc, p. 141). 
 ? Walpole's Anecdotes of Painting, p. 5. 
 
350 ON THE MANUFACTURE OF GLASS. 
 
 ten -different compartments, of which the engravings may be seen 
 in Montfaucon l . 
 
 So late as in the thirteenth and fourteenth centuries, the houses 
 of the lower classes in England had not glass windows. Nor is 
 it improbable that such windows were thought very magnificent 
 even in churches ; for Chaucer, who wrote towards the latter end 
 of this period, in describing the dress of his parish clerk Absalom, 
 says that the upper parts of his shoes were cut in imitation of the 
 church window 2 . 
 
 It is generally understood, that the houses in Italy were the 
 first in Europe that were decorated with glass windows ; that the 
 custom was adopted in France soon afterwards ; and that the 
 French nation enjoyed that luxury a considerable time before 
 England availed herself of the improvement. 
 
 Even now, in some of the least civilized parts of the Russian 
 Empire, a kind of laminated gypsum called lapis specularly found 
 in abundance in that country, is used in windows as a substitute 
 for glass. 
 
 Coloured glass, or glass stained during its manufacture, was 
 known to the ancient Greeks and Romans; but it is only of late 
 years that the English artists have acquired a knowledge of this 
 process. Dugdale informs us, that when the citizens of London 
 in the reign of Henry V. undertook to beautify St. Paul's, one 
 John Prudde, a glazier in Westminster, engaged to glaze the 
 chapel " with glass from beyond the seas, of the finest colours, of 
 blue, yellow, red, purpure, sanguine, and violet, and of all other 
 colours that shall be best to embellish the matters, images and 
 stories that shall be delivered to him, by patterns on paper, in rich 
 colour, at his charges 3 ." 
 
 From this testimony it appears that glass in considerable quan- 
 tities was made on the continent of Europe earlier than in this 
 country. In Bohemia glass is now made to a very great extent. 
 There are even many towns that are dependent upon this manu- 
 factory, and the Continent is chiefly supplied by these artists. 
 Their practice is to fix upon a large wood, and cut down timber 
 enough to allow them room to build. With this timber they erect 
 a wooden house, together with sheds and warehouses ; they then 
 dig for clay to make the furnace : when this is ready they cut 
 down timber for fuel, and from the ashes of the fuel and those of 
 the brush-wood they prepare the alkali for the use of the manu- 
 factory. When the wood is cleared, and their fuel exhausted, 
 
 1 Montfaucon, Les Monuments de la Monarchic Francaise, folio, Paris 1729, 
 tome i. p. 384. 
 
 2 Chaucer's Works, p. 26. 
 
 3 Dugdale's Antiquities of Warwickshire, vol. i. p. 446. 
 
ON THE MANUFACTURE OF GLASS. 351 
 
 these buildings are pulled down, and the workmen remove to 
 another district. 
 
 The Government of France, in the early part of the four- 
 teenth century, took great pains to improve the manufacture of 
 glass, and ordained that none but gentlemen or the sons of the 
 nobility should be allowed to exercise the trade, or even to work 
 as artificers in the manufactories of this most highly esteemed 
 commodity. In consequence of this injunction, a company of 
 persons of this description was incorporated, and obtained many 
 important privileges and immunities from the state, particularly 
 that of being allowed to work at this curious art without deroga- 
 ting from their nobility. It is indeed asserted, by the writer who 
 is the best authority we have on this subject, that there never was 
 an instance of any one being attainted to whom these privileges 
 had been granted ; for they conducted themselves so irreproach- 
 ably, that their honours were invariably transmitted inviolate to 
 their posterity 4 . 
 
 It was, probably, the success of the Venetians in this elegant 
 art which induced the French authorities to interest themselves 
 in promoting its establishment ; for it appears that, in the thir- 
 teenth century, these people had established a manufactory of 
 large glass mirrors at Murano, a populous village within one 
 mile of Venice, where mirrors of such an uncommon size were 
 made that they astonished all Europe. Henry III. King of 
 France, when visiting Venice, was so charmed with the work of 
 the artificers at Murano, that he ennobled both them and their 
 posterity 5 . 
 
 In the year 1453, Anthony de Brossard, Lord of St. Martin 
 and Prince of the blood royal, finding the business of glass- 
 making to be so considerable, and knowing that it did not dero- 
 gate from nobility, obtained a grant from the Prince to establish 
 a glass-house in his own county, with prohibition of any other ; 
 and, in consequence of this, the elder sons of that family continued 
 uninterruptedly to exercise the art till the latter end of the six- 
 teenth century, when the proprietor was killed while commanding 
 a troop at the siege of Chartres. Some time before this period, 
 the Messieurs de Caquer^ay, gentlemen of ancient extraction, pro- 
 cured the right of glass-making by an alliance in marriage which 
 one of their ancestors in the year 1468 contracted with a daughter 
 of the Lord of St. Martin above mentioned, who gave up half of 
 his right to the monopoly of glass for part of her marriage portion. 
 
 4 Blancourt's Art of Glass, p. 28. 
 
 5 Busching's Geography, vol. iii. p. 83. Misson's Voyage to Italy, vol. i. 
 pp. 300 & 301. 
 
352 ON THE MANUFACTURE OF GLASS. 
 
 This grant was afterwards confirmed in the Chamber of Accounts 
 of the French Government 1 . 
 
 On the death of Anthony de Brossard, the younger sons of his 
 family undertook to carry on the art, and continued it for more 
 than a century. Whether the trade continues still in the same 
 line, I have not hitherto been able to ascertain. 
 
 An ancient family of the name of Vaillant also obtained the 
 grant of a glass-house as a recompense for their valour and public 
 services, together with a poignard d'or, on azure, for their arms. 
 Mr. Blancourt, who long resided in France, likewise notices that, 
 at the time he wrote, they had many other great families among 
 them, who were descended from gentlemen glass-makers that had 
 declined following the art, and that some of these had been ho- 
 noured with purple, and with the highest dignities and offices in 
 the state. 
 
 Here it may be observed that the art of grinding and cutting 
 glass for ornamental purposes was not practised till about the be- 
 ginning of the 1 7th century. The inventor is said to have been 
 Caspar Lehmann, who obtained in the year 1609, from the Em- 
 peror Rodolphus II., the title of " Glass-cutter to the Court V 
 The art of engraving on glass by fluoric acid was introduced by 
 Henry Swanhard, an artist of Nuremberg, in the year 1670 3 . 
 
 The glass made in France had never been equa! to that fabri- 
 cated in Italy. But while the great Colbert was Minister of that 
 country, a fortunate event enabled that eminent man to lay the 
 foundation of this manufactory in the way which they had so long 
 desired. 
 
 Certain French artists, established at Venice, found means to 
 obtain at Murano an exact knowledge of the processes employed 
 in the fabrication of plate glass, and they returned to France with 
 the hope of enriching their native land with that splendid branch 
 of art and of commerce. The Minister received them graciously ; 
 and, having empowered them to select such a situation as they 
 might deem the best suited to their undertaking, they established 
 themselves in the year 1665 at Tourlaville, near Cherbourg 4 . 
 This Company afterwards obtained a patent for making plate 
 glass, and an advance of 12,000 livres for four years was granted 
 them by the French Government. 
 
 In the year 1688, Abram Thevart, an ingenious manufacturer, 
 made a proposal to the Court for casting glass mirrors, and en- 
 gaged that they should be of a larger size than any ever before 
 
 1 Blancourt 's Art of Glass, p. 30. 
 
 * Beckmann, vol. iii. p. 223. 3 Nicholson's 4to Journal, vol. iv. p. 1. 
 
 4 Loysel, Discours Preliminaire, pp. 5 & 6. 
 
ON THK MANUFACTURE OF GLASS. 353 
 
 made s , This individual obtained likewise a patent to continue 
 for thirty years ; and the first plates which he cast 6 were made 
 at Paris, and were of the extraordinary dimensions of 84* inches 
 by 50 inches, a size which surprised all the artists of that day 7 . 
 
 Notwithstanding this success, not more than three years elapsed 
 before these proprietors found it expedient to remove their esta- 
 blishment to St. Gobin, in the department of the Aisne ; and there 
 they laid the foundation of a manufactory which is still in a flou- 
 rishing condition, and is perhaps the most important one of the 
 kind which is yet in existence. 
 
 In these stupendous works, plates for mirrors are now made 
 of the vast size of 105 inches in height by 60 inches in breadth; 
 and when they have been properly annealed they are conveyed 
 to the Gobelins in Paris to be polished 8 . The double convex 
 lens which I have described in the Essay on Temperature, page 43, 
 was made in the same manufactory. The instrument described 
 above has been broken, and the Government have since caused 
 to be fabricated at the same manufactory a massive plate of 2 
 metres diameter by 0*067 in thickness, weighing 500 kilogrammes; 
 the largest piece of workmanship in glass that was ever executed, 
 being in English measure 2 j inches thick, 6 feet 6 inches in diame- 
 ter, and weighing eleven hundred pounds avoirdupois. 
 
 It is now time, however, for us to look into the progress of this 
 manufacture in England. The method of working in glass, as 
 we have already seen, was introduced here so early as the seventh 
 century ; but I am inclined to think that for many ages our arti- 
 ficers made no improvement whatever in this curious art. Their 
 business was probably confined to the manufacture of coarse win- 
 dow glass, and the most rude kind of culinary and drinking vessels. 
 
 Nevertheless, about the middle of the sixteenth century this 
 country began to acquire eminence in the manufacture of glass, 
 of which we have abundant evidence: thus in the year 1575 one of 
 the London glass-houses was destroyed by fire ; and Holinshed, 
 speaking of it, says, " The same house which had consumed great 
 quantities of wood in making Jine drinking-glasses is now itself 
 consumed 9 ." 
 
 Manufactories of considerable consequence were afterwards 
 established at Crutched Friars, and in the Strand, London ; and 
 these w r ere much encouraged by King James I. and Charles I., 
 
 5 Mirrors of glass were attempted to be made in the ancient glass-houses of 
 Sidon; but the artists could not succeed in the attempt. Pliny, lib. xxxvi. cap. 26. 
 
 6 A very interesting and instructive paper on the antiquity of metallic mir- 
 rors may be read in Beckmann's History of Inventions, vol. iii. p. 164. 
 
 ? Savary Diet, de Commerce, tome iii. p. 87. Beckmann, vol. iii. p. 216. 
 8 Busching's Geography, vol. ii. p. 398. Holinshed's Chronicle, p. 
 
 2 A 
 
854 ON THE MANUFACTURE OF GLASS. 
 
 who both prohibited the importation of all foreign glass, excepting 
 that of the most inferior kinds '. 
 
 The former of these monarchs, as an expedient to raise money 
 without the aid of Parliament, granted to Sir Robert Mansel an 
 exclusive patent for making glass, and allowed it to be given out, 
 that this monopoly was afforded him in consideration of, and as 
 a reward for, his having substituted pit coal for wood in its manu- 
 facture ; and that on the same ground he should be allowed the 
 exclusive privilege of importing drinking-vessels and every other 
 article of glass from Italy, which could be made there of a finer 
 quality than had at that time been produced in England 2 . Com- 
 mon pit coal is however the fuel which is now employed through- 
 out England for making all kinds of glass. 
 
 In the reign of King Charles the Second a Mi 1 . Ravenscroft 
 very materially improved the manufacture of flint glass. He is 
 said to have made all kinds of glass drinking-vessels of a quality 
 fully equal to any that were then manufactured abroad. 
 
 The Duke of Buckingham, who had brought workmen from 
 Venice for the purpose, was likewise the means of establishing, 
 about the year 1670, a considerable work at Lambeth for the 
 manufacture of fine plate glass s . 
 
 Thus by degrees was the manufacture of every kind of glass in- 
 troduced into this country ; and the trade made such rapid pro- 
 gress amongst us, that in the year 1696 there were no less than 
 ninety glass-houses in different parts of the kingdom. Of this 
 number twenty-four were in London and Southwark, seventeen 
 at Stourbridge, eleven at Newcastle-upon-Tyne, and nine at 
 Bristol. The rest were dispersed in those other counties of En- 
 gland where coal is readily procured. Of these different manu- 
 factories forty-two were called Bottle-houses, or such as were 
 chiefly employed in making the common black bottles ; five were 
 employed for crown glass ; twenty-seven for flint, green, and 
 other ordinary glass; two in making plate-glass for mirrors, &c. ; 
 and fourteen were exclusively appropriated to the manufacture of 
 window glass. 
 
 We may naturally suppose that such a variety of establishments 
 would give a permanence to any manufacture. This has really 
 been the case ; for, at this day, the art of glass-making has become 
 one of the staple manufactures of our country. 
 
 It has already been shown that there are five different kinds of 
 glass-houses in this kingdom ; but before we attempt to describe 
 any of the operations which are performed in them, it will be ne- 
 
 1 Rymer, tome xix. p. 663. 
 
 4 Campbell's Political Survey of Great Britain, vol. ii. p. 28. 
 
 3 Houghton's Collections on Husbandry and Trade, vol. ii. p. 43. 
 
ON THE MANUFACTURE OF GLASS. 355 
 
 cessary to enumerate them afresh, as they are now rather diffe- 
 rently distinguished from what they were a hundred-and-twenty 
 years ago, the time of which we have just been speaking. 
 
 The English glass-houses are now known by the names of the 
 Crown or Window glass-house; the Broad glass-house; the Bottle- 
 house; the Flint-house ; and the Plate glass-house. The glass 
 trade of Great Britain has indeed become so considerable, that 
 in general there are separate and distinct establishments for each 
 of these species of glass. I know of no instance of the same pro- 
 prietors being concerned in more than one or two of these diffe- 
 rent branches of glass-making. 
 
 It will be most convenient, however, and the nature of the 
 whole manufacture will probably be better understood, if we 
 begin the account of the different manipulations, by a description 
 of the method which is adopted in making^'?*/ glass. 
 
 A very small quantity of nitre, of manganese, and of white ar- 
 senic, is added to 3 cwt. of Lynn sand, 2 cwt. of red lead, and 
 1 cwt. of pearlash ; and when these materials have been well 
 mixed, the whole are combined with about one-fourth of their 
 weight of old broken flint glass. These proportions are fre- 
 quently a little varied, each manufacturer having his own ideas 
 and peculiar practical knowledge on the respective properties of 
 every ingredient. 
 
 It should however be mentioned, before we proceed, that some 
 houses, instead of Lynn sand, use a very white sand, from Alum- 
 bay in the Isle of Wight, and others procure it from Maidstone 
 in Kent ; and that the pearlash is always previously purified for 
 this purpose. The following is the process: First, it is dissolved 
 in water, and suffered to remain some time undisturbed, to allow 
 the impurities and contingent matters to subside ; after this the 
 clear solution is submitted to the action of heat, to expell the 
 water and to reduce the alkali again to a dry state. One hun- 
 dred weight ofjirst American pearlash is thus generally reduced 
 to 70 or 80 pounds. 
 
 The materials being mixed, they are then, by a few shovels full 
 at a time, cast into the crucible, previously brought to a white 
 heat; and as these melt, more is thrown in until the pots or cru- 
 cibles are all full, care being taken that the same temperature is 
 continued till the ingredients are thoroughly united, and the whole 
 formed into a perfectly transparent glass. The operation requires 
 generally from 20 to 30 hours. 
 
 Flint glass is known to be perfect when the silica is all dissolved, 
 and the paste is entirely free from sand specks and air bubbles. 
 This however is never the case till the highest point of heat is at- 
 tained, and the metal (a technical term of the workmen for glass 
 in a state of fusion) has become sufficiently fluid to allow of the 
 
 2A 2 
 
356 ON THE MANUFACTURE OF GLASS. 
 
 carbonic acid gas and other volatile matters to rise freely through 
 the mass and escape. It is usual to ascertain the purity of the 
 glass, by taking out a few ounces and blowing it into the shape of 
 a long pear, with a small cavity within. This when cold is in- 
 spected, as a kind of proof or sample of the state of the glass in 
 fusion. 
 
 When the glass is found to be completely formed, the workmen 
 dip their instruments, which are long hollow tubes of iron, into 
 the melted metal, and, turning them about several times, they 
 collect, on the point of the instrument, as much of it as they re- 
 quire for any particular purpose which they may have in view. 
 Then, by blowing with the mouth and rolling the hot metal upon 
 a smooth horizontal iron plate, they form it into any shape that 
 may be desired, such as glasses, decanters, phials, &c. 
 
 This part of the process is extremely interesting and even cap- 
 tivating to those who have never before seen the operation ; for, 
 without inspecting, no one can form an adequate idea of the faci- 
 lity with which the workmen form all sorts of vessels and instru- 
 ments of this very curious and valuable material. 
 
 As it may be difficult for some persons who have not seen a 
 glass-house to conceive how so much glass in the state of melting, 
 as is necessary for making a large vessel, can be taken up on the 
 end of an iron tube, it is proper to state, that every time the work- 
 man dips the instrument into the crucible of melted glass he ex- 
 poses it a moment to the current of air, which chills the surface, 
 and enables another portion of metal to attach itself to the former ; 
 and this he repeats till he has collected a quantity sufficient for 
 his purpose. 
 
 In the large houses, many workmen are constantly employed 
 both day and night, because it is necessary that the work should 
 go on without intermission, till all the metal in the furnace be 
 exhausted. Each of these men has a boy to attend him ; and 
 these children are perpetually employed in carrying the articles, 
 the moment they are made, one by one, to the Her or annealing 
 furnace, where they are kept for many hours, in order that they 
 may cool gradually. 
 
 The Her is a very long heated chamber, furnished with many 
 shallow iron pans, called lier-pans or fraichcs, for holding the 
 goods ; and these are moved further and further from the fire by 
 means of a set of pulleys and a windlass, till they are brought 
 to the other end of the gallery, where the temperature is so much 
 reduced, that in general the articles are all sufficiently cool to be 
 taken out with safety. 
 
 I observe, in passing, that the term lier-pan is perhaps derived 
 from the French word Her, to bind or knit together ; from an 
 idea that the glass was not completely formed, or its particles 
 
ON THE MANUFACTURE OF GLASS. 357 
 
 properly united, until it had gone through the process which we 
 now call annealing ; and that the word fraiches is derived pro- 
 bably from the French fraiche, cool, or refraichir, to cool. 
 
 This process of annealing is absolutely necessary for the pro- 
 duction of perfect glass, whatever may be the kind, or whatever 
 the form of the article which is made with it. Hence it may be 
 understood why glasses often break without any apparent cause ; 
 for, whenever this happens, it may be attributed to imperfect an- 
 nealing, unless one side of a piece be more exposed than the other 
 to heat or cold ; for then it will inevitably crack, because glass is 
 a worse conductor of heat than any manulactured commodity with 
 which we are acquainted. This property of glass being a non- 
 conductor of heat, is often exemplified in a curious manner in the 
 glass-house. The following is a case that may be mentioned. 
 When a crucible full of liquid glass breaks by accident, a large 
 tub of water is brought to the mouth of the oven, and the fluid 
 metal is laded with all possible expedition into it, to prevent its 
 running into the furnace and being lost among the ashes. When 
 this large mass of glass has been some little time in the water, its 
 surface will become nearly cold, while the centre of it will be red 
 hot, and continue so for several hours after the outside has been 
 cold enough to be handled with safety. 
 
 Having thus given a brief account of the method of making 
 flint glass, it may be remarked, that either of the fixed alkalies, 
 with a due proportion of flint or sand, will, without any other in- 
 gredient, make a pure and transparent glass. A century ago the 
 best glass was always made from ground flints : hence it was that 
 white glass acquired the name of flint glass ; but when it was dis- 
 covered that good sand is nearly all siliceous earth, this was sub- 
 stituted for flints. 
 
 The other materials, viz. the lead, manganese, nitre, and arse- 
 nic, are therefore added with different intentions ; and the pro- 
 portions which are noted above are sometimes varied, for the 
 sake of producing a glass of a quality different from that which 
 is usually made. 
 
 Thus, the lead is employed with the design of giving a greater 
 degree of fusibility to the silica, to add weight to the glass, to 
 enable such of it as is designed for ornamental work to take a 
 higher polish, and to render it less liable to break by sudden 
 changes of temperature. 
 
 Besides the several uses of lead which I have enumerated, it 
 has another effect upon all ornamental flint glass, which is of 
 great importance ; for it has the property of increasing the refrac- 
 tive power of the glass ; and hence we are enabled to decompose 
 the bolar rays of light, by means of a glass prism, into what are 
 
358 ON THE MANUFACTURE OF GLASS. 
 
 called the prismatic colours. Lead is a simple combustible, and 
 so are the diamond and hydrogen. It was Sir Isaac Newton who 
 first suggested that the diamond, from its retractive power, was 
 of a combustible nature, and that water also must have something 
 in its composition that would burn, as it breaks the rays of light. 
 Thus can we account for the superior beauty of the English flint 
 glass. Plate-glass possesses no such brilliancy. 
 
 The employment of oxide of lead in the manufacture of glass 
 is very ancient. In the collection of antiquities at St. Denis, an 
 ancient mirror was shown which was said to have belonged to 
 Virgil. It was an oval glass, 14 inches in length and 12 in breadth, 
 and weighed 30 pounds. This was found on analysis to consist 
 of artificial glass, mixed with a considerable portion of lead. 
 
 To explain the use of the other ingredients, it may be said that 
 the manganese and the nitre are of service in destroying whatever 
 carbonaceous substances may be in the mixture. The white oxide 
 of arsenic is also used with the same intention. But this is seldom 
 employed now, except where the manager suspects that the ma- 
 terials have been either not sufficiently purified, or that the cal- 
 cination had not been properly conducted; each of these articles 
 having the property of abstracting the carbon, and dissipating it 
 in the form of carbonic acid gas, leaving the glass whiter and 
 more transparent. There is however some nicety always required 
 in the use of the oxide of arsenic ; for, though it makes the glass 
 whiter, it will give it an opake or rather an opal appearance, if too 
 much of it be employed. Some manufacturers of flint glass have 
 discontinued it altogether, because they conceive that the lead 
 renders the arsenic too volatile to be of much service. 
 
 The next species of glass to be described is that which is known 
 in the trade by the name of crown-glass, being in fact the best sort 
 of window glass which is made in this country. 
 
 The apparatus employed in the manufacture of CROWN-GLASS 
 are, a reverberatory furnace for calcining the materials ; a large 
 furnace containing the pots or crucibles for melting these materials 
 and forming them into glass ' ; and other furnaces for heating or 
 annealing the crucibles, previously to their being employed. 
 Besides these, there are others which contain 110 crucibles, but 
 are merely employed for re-heating the metal time after time, to 
 enable the workmen to keep it sufficiently ductile for being thrown 
 into such forms as they require. The bottoming-hole and the 
 flashing-furnace, as they are called, both come under this descrip- 
 tion. There are many other technical terms in this business : but 
 they are all formed either from the Italian or French language, 
 
 1 One of these furnaces generally takes four or six pots ; and these are so 
 large, that some of them are capable of holding more than a ton weight of glass. 
 
ON THE MANUFACTURE OF GLASS. S59 
 
 glass having been long made in those countries, and it was from 
 them that this art passed into the other states in Europe. 
 
 The materials which are employed in making the best crown 
 glass, are six bushels of fine Lynn sand and twelve bushels of 
 Orkney kelp. 
 
 These are the usual proportions ; but some kelp will vitrify 
 more and some less sand than has been mentioned, because of 
 the variation which there is in the quality of what is called best 
 kelp. 
 
 Orkney kelp is preferred for window glass, because it makes 
 it of a better colour than the Western Isle or the Scotch kelp. 
 This is probably owing to the sand of the latter containing more 
 iron. Mr. Bowles, the celebrated maker of crown-glass at Cock- 
 hill, Ratcliffe-highway, London, always used Spanish barilla in- 
 stead of kelp, and his glass was ever preferred to that of others. 
 This gentlemanhad also an establishment at Vauxhall for mak- 
 ing plate-glass : but the concern has been abandoned for more 
 than twenty years, the proprietor having retired with an ample 
 fortune. 
 
 It appears to me, that it would be a better practice to dry the 
 materials thoroughly, and then to apportion them by weight in- 
 stead of by measure as above mentioned. By repeated inquiries 
 I have indeed learnt that one of the large manufacturers has 
 adopted this method, and that his general proportions are, 450 
 Ibs. of Irish kelp dried and ground; 325lbs. of Lynn sand dried ; 
 and 25lbs. of slaked and sifted lime. 
 
 These materials, when thoroughly mixed, are calcined for 
 about two hours in a degree of temperature inferior to that of 
 fusion ; the fusion being in some measure prevented by constantly 
 stirring the mass, which occasions a fresh surface to be perpetu- 
 ally presented to the action of the fire, and also favours the escape 
 of the aqueous, gaseous, and other volatile matters which are re- 
 quired to be dissipated by the process. The heat is then increased 
 till the whole becomes pasty; and it is preserved in this state for 
 three or four hours more, constantly stirring the mass during the 
 whole period. The materials, which are still in a soft and pasty 
 state, are at length removed from the furnace, and, advantage 
 being taken of the softened state of the mass, the whole is put 
 very hastily into the form of square cakes, which are known to the 
 workmen by the name of frit, the operation itself being called 
 fritting. Some years ago I remember to have been very much 
 at a loss to discover why it was necessary to make the glass first 
 into frit, and why it might not be begun and finished by one pro- 
 cess ; but I now understand that whenever this previous opera- 
 tion is not performed, the alkali is apt to be driven off by the 
 heat of the furnace, before it has time to combine sufficiently 
 
360 ON THE MANUFACTURE OP GLASS. 
 
 with the silica ; whereas, in the operation of fritting, the tempera- 
 ture is powerful enough to effect this, and yet not equal to vola- 
 tilize the uncombiried alkali. 
 
 The manufacturers of glass, I trust, will not be displeased at 
 my remarking on a circumstance which is of more consequence 
 than many persons are aware of. From my own experiments, I 
 am warranted in saying that pure alkali evaporates at a lower 
 temperature than is generally imagined. Hence great attention 
 ought to be paid, in preparing the frit, not to give it too great a 
 heat, or to remove it from the calcining oven before it be tho- 
 roughly prepared; otherwise, the alkali will fly off in vapour in- 
 stead of combining with the silica. This maybe often seen arising 
 as a vapour from the surface of the crucibles in a glass-house fur- 
 nace. There is on this account an advantage in using soda in 
 preference to potash, because soda combines more readily with 
 the siliceous earth. 
 
 The manufacturers are desirous of keeping the frit as long as 
 they can ; and hence it is that the cakes are seldom employed 
 immediately, but are generally piled up in a corner of the manu- 
 factory for future use, it being a prevailing idea, that the frit is 
 better the older it is ; and I have been informed that some of the 
 opulent makers have a regular succession of it in store, and never 
 use any that is not twelve months old. 
 
 To prepare for making crown-glass, this frit is put into cruci- 
 bles in the melting furnace ; and when the crucibles are filled, 
 old glass is piled upon the frit, as high as it can be placed with 
 safety. The furnace is then made hot, and the heat is regularly 
 increased till it acquire the maximum, at which state it is con- 
 tinued for 30 or 40 hours. During this time the materials become 
 so thoroughly united as to form one perfectly homogeneous and 
 transparent mass of fused metal, fit for the iabrication of sheets 
 of best window glass, 
 
 To make this species of glass, the workman commences the 
 operation as he would in the flint-house, already described. He 
 dips the long iron pipe into the melted metal, and by repeated 
 dippings gathers as much of it round the end of the pipe as he 
 knows by experience will be enough to form a table of glass. A 
 table is the workman's phrase for a circular sheet of finished win- 
 dow glass. These are generally 4 feet in diameter, and weigh 10, 
 10|, or 1 1 pounds each. Twelve of these are called a side or a 
 crate of ^ias*> 
 
 When tne lump of metal is properly attached to the pipe, it is 
 rolled frequently backwards and forwards upon a polished iron 
 table, to change it from a globular to a cylindrical form. The 
 workman then blows down the tube, to which the red-hot piece 
 of glass is attached ; and by this means, and a continuation of 
 
ON THE MANUFACTURE OF GLASS. 361 
 
 the rolling, it becomes expanded into a form similar to figure A, 
 in Plate XIX., and which is called by the workmen a Parisienne. 
 He then carries it to the mouth of the melting furnace to heat it 
 afresh, that it may be in a proper state for being further expand- 
 ed by the breath, till it takes the form described by figure B ; 
 when it is immediately transferred to the furnace called the bot- 
 toming-hcle, to be again heated : and this enables the workman 
 to enlarge it, by the mere force of his breath, till it acquire the 
 form described at figure C; after which, by heating it and blow- 
 ing afresh, it assumes the shape of figure I). The artist having 
 brought it into this latter form, the next object is to affix another 
 working iron to the opposite side of the piece, to enable him to 
 detach with safety the first instrument. The intention of this 
 contrivance will be rendered manifest as we proceed in our de- 
 scription of the process. 
 
 To effect this, the workman takes the glass which has been 
 so far modelled, to a table covered with ashes, which are de- 
 signed to prevent the adhesion of the glass to the table, and also 
 to preserve the glass from too great a reduction of temperature ; 
 and while lying there, a supernumerary workman brings another 
 working iron ! , with a small lump of hot metal at the end of it; 
 and this he attaches to the piece of glass under operation, at the 
 letter Y, exactly opposite to Z, the place where the first iron is 
 still united. 
 
 Having by means of this small lump of fresh glass attached a 
 new working iron, it becomes necessary to withdraw the former, 
 as before mentioned, and this is effected by the usual expedient. 
 The workman wets the end of a small iron utensil with a little 
 cold water ; with this he touches the glass at letter , where it 
 produces a crack; then by a smart stroke he detaches the old 
 instrument from it, which leaves a hole in the piece of glass of 
 about two inches in diameter, and which has then the appearance 
 shown by figure E. 
 
 A new working iron being now attached to the glass at the 
 point exactly opposite to that where the former one adhered, the 
 workman carries it by the punt 2 or new rod, to the flashing fur- 
 nace, and turning it gently in his hand, holds it for a few minutes 
 at the small opening called the nose hole. This is a technical name 
 by which these openings are known to the workmen in the North 
 of England. Agricola and other old writers on glass called them 
 boccas. This small opening into the large furnace is contrived 
 
 1 This instrument differs from the former, in its not being a tube, but a rod 
 of solid iron. It is called a punt or pontiL 
 
 * These instruments are smaller and lighter than the blowing irons, and 
 consequently more manageable in these latter parts of the process, when it is 
 necessary to make them revolve in the hand with greater velocity. 
 
362 ON THE MANUFACTURE OF GLASS. 
 
 merely for the purpose of heating that part of the glass to which 
 the cold water had been applied. By this means it is put in a 
 proper condition to be introduced into the larger opening in the 
 same furnace, where it acquires heat by degrees till the operator 
 perceives that the whole mass has again become sufficiently ductile. 
 He then begins to turn it quicker and quicker, holding it the whole 
 time at the mouth of the oven, till it becomes so much softened, 
 that merely by the centrifugal force communicated by the rapid re- 
 volution of the iron instrument to which it is attached, and which 
 requires great dexterity on the part of the workman, the whole 
 mass opens itself by degrees, extending further and further till it 
 assumes the forms of JP, G, and H in succession ; and when it has 
 attained the latter figure, it flies entirely open in an instant, as 
 shown at K, and becomes one immense circular sheet of glass, 
 48 or 50 inches in diameter, and of one uniform thickness. It 
 was formerly thought to be a great acquisition to be able, by this 
 process, to make a perfect table of glass four feet in diameter ; 
 but I understand that Messrs. Attwood and Smith, of Gateshead 
 in the county of Durham, are enabled to produce tables of five 
 feet, which are the more valuable, as they yield larger squares 
 than were ever made, except in plate glass ; and the quality of it 
 is of the best kind. The centre of the table of glass, where the 
 punting iron was attached, is of course somewhat thicker, and is 
 known to the w r orkmen by the name of the bull's eye. Notwith- 
 standing this, it is curious to observe how very uniform in thick- 
 ness all the rest of the plate is. 
 
 This account of the varied manipulations is presented to my 
 readers in considerable detail, together with drawings of the 
 glass in every stage of its progress l , because I believe the pro- 
 duction of this peculiar species of glass to be one of the most 
 curious and interesting processes which any of the manufactures 
 of this or any other country can exhibit. The tenacity of heated 
 glass is shown in a very striking manner by this operation ; for 
 though the plate be 50 inches in diameter, and not more than a 
 line in thickness, it bears to be revolved in the hands of the work- 
 man with considerable celerity ; and when it changes by its cen- 
 trifugal power from figure H to figure K, it expands with a force 
 sufficient to dash it, if it were cold, into ten thousand pieces. The 
 workmen assured me that this circumstance never fails to arrest 
 the attention of every visitor. 
 
 When the crown-glass is thus finished, the perfect plate is re- 
 moved into the annealing arch, and there placed on its edge that 
 it may become properly tempered by gradual cooling, as is prac- 
 tised "in the manufacture of every sort of glass. It is a very nice 
 
 1 See the engraving prefixed to this Essay. 
 
ON THE MANUFACTURE OF GLASS. 363 
 
 point to regulate the temperature of the annealing arch, for a small 
 excess of heat would render the plates so soft that they would 
 bend out of the perpendicular and be much injured : on the con- 
 trary, if the furnace be not hot enough there is great danger of 
 the plates flying in pieces, though if this should not happen the 
 defect would inevitably be discovered by the glazier ; since glass 
 so imperfectly annealed is operated upon by the diamond with 
 great difficulty, and it is almost impossible ever to cut it with 
 exactness. 
 
 In the fabrication of crown-glass, nothing is of more impor- 
 tance than to keep the melting furnace at its full heat during the 
 whole time of the operation ; for, whenever the men fall asleep, 
 which they are apt sometimes to do, the heat of the oven gets 
 checked, and it is almost impossible to bring it again to the 
 former temperature. 
 
 This arises from the peculiar property which glass possesses, 
 of being a slow conductor of heat ; and, unfortunately, the fur- 
 ther the glass is advanced towards perfection the greater will 
 be its liability to damage from this cause ; and therefore the more 
 solicitous should the manufacturer be, to watch this part of the 
 process. This accident is of such frequent occurrence, that it 
 alone has been the chief means of occasioning crown-glass to be 
 divided into four classes, viz. firsts, seconds, thirds, and fourths; 
 between the two extremes of which there is a difference of 50 per 
 cent, in price. Indeed, if the excise duty be put out of considera- 
 tion, the glass of the fourth quality nets the manufacturer less 
 than half the price of the first. In one of the largest crown-houses 
 which I have seen, where they make 1800 tables or 150 sides per 
 week throughout the year, they consider one-half to two-thirds 
 of this quantity to consist of seconds and thirds. When the firsts 
 were sold at 61. 105. per side, the thirds brought only 4/. 18s., 
 the duty being paid by the maker. 
 
 The next species to be described is BROAD-GLASS, or inferior 
 window glass. This is quite a distinct manufacture from that of 
 crown-glass, and the process of fabricating it is also totally dissi- 
 milar. The materials which are employed, and the method of 
 conducting the operation, are as follow : 
 
 Six bushels of soap-boilers' waste, three bushels of kelp, and 
 four bushels of sand are mixed together and cast into a calcining 
 furnace. But there is no absolute rule for the proportions, be- 
 cause the two first of these materials are as variable in their qua- 
 lities as can well be conceived, and therefore the operator is al- 
 ways guided by his own judgement in apportioning the respective 
 quantities, and nothing but practice can direct him. 
 
 I have not found that the proprietors of those houses where 
 
36 i ON THE MANUFACTURE OF GLASS. 
 
 broad-glass is made lay any stress on the fineness of the sand; 
 but this is certainly an important circumstance. Loysel has 
 stated, as the result of his own experience, that if coarse sand be 
 used, 2lbs. of pure alkali must be put to every 4-lbs. of sand, or 
 it will not melt; whereas if the sand were very fine, lib. of pure 
 soda would be sufficient. Hence it follows, that there remains 
 in the finished glass, as a constituent part of its substance, only 
 one half of the alkali at first employed. The other half is dissi- 
 pated during the process, and entirely lost. 
 
 The process of calcining the materials requires from twenty 
 to thirty hours, and is designed to burn off all the inflammable 
 and heterogeneous matters which would spoil the colour of the 
 glass, as well as endanger its boiling over when it came into the 
 melting furnace. It is observable that the materials are not suf- 
 fered to melt while in the calcining furnace, but are kept at a 
 great heat arid stirred very frequently with an iron rake, which 
 facilitates the separation of the gas, and completes the combus- 
 tion of all such contingent matters as are capable of this change. 
 
 When the mass has been thus properly calcined, it is removed 
 with iron shovels while red hot, and carried to the melting fur- 
 nace, where the pots are entirely filled with it ; and in the course 
 of twelve or fifteen hours of exposure to a due degree of heat, the 
 whole will become perfect glass. To form this into sheets, the 
 following method is pursued : 
 
 The glass is withdrawn from the pots by iron tubes in the way 
 already described for the flint- and crown-glass, and it is blown 
 into globes, or rather into hollow cones, of about a foot diameter. 
 It must be recollected that all glass, the large plate-glass ex- 
 cepted, whatever be its form, whether that of an electrical tube, 
 a goblet, a decanter, or a sheet of window glass, is fashioned 
 from a hollow sphere produced by the action of the breath. That 
 is, a piece of fluid metal is first blown into a hollow globe, and 
 then it is moulded by the workman into the desired shape. When 
 these globes are formed, they are carried again to the mouth of 
 the oven, and while there, one side is touched with a cold iron 
 dipped in water. This produces a crack, which runs along it 
 longitudinally in nearly a direct line. W T hen this crack is pro- 
 duced, the cone is opened upon a smooth iron plate fixed at the 
 mouth of the furnace, and it then forms a sheet of thin transpa- 
 rent window glass in a shape somewhat like that of a fan. In a 
 few minutes this becomes hard enough to admit of being re- 
 moved to the annealing apartment, that its temperature may 
 gradually diminish. This species, which is, probably, the first 
 that was ever manufactured lor the use of windows, is called 
 broad or spread window glass, to distinguish it from what is 
 termed the crown-glass. 
 
ON" THE MANUFACTURE OF GLASS. 365 
 
 Another kind not yet described, is a green glass, known to the 
 trade by the name of BOTTLE-GLASS, and the works at which it 
 is manufactured are called bottle-houses. 
 
 To make this species they take three bushels of soap-makers' 
 waste ashes, and one bushel of coarse river sand. Sometimes a 
 portion of kelp is also added, but this is not used in all manufac- 
 tories. These materials are calcined either in a distinct furnace, 
 or in arches attached to the furnace of fusion, where they are 
 kept at a red heat for twenty or thirty hours. From thence the 
 mixture is removed, still of a red heat, to the melting furnace, 
 where by means of iron shovels the pots or crucibles are filled 
 with it, and an intense heat is again applied. By continuing the 
 materials in this high temperature for twelve, fifteen, or eighteen 
 hours longer, they become perfectly fused and converted into a 
 true glass, fit for making wine bottles, garden bell glasses, che- 
 mical retorts, aquafortis carboys, and any other large vessels for 
 chemical laboratories or other purposes. 
 
 These articles are all fashioned by a method similar to that 
 which has been described under the article flint glass, excepting 
 half-pint, pint, and quart bottles, which are blown in a mould 
 either of iron or brass. These goods are likewise removed, while 
 yet very hot, to the annealing furnace, for the purpose already 
 mentioned in describing the other species of glass. 
 
 The bottle metal is peculiarly fit for making chemical carboys, 
 as it bears the action of all the mineral acids without sustaining 
 any injury; whereas flint glass, which is usually made with a large 
 portion of lead, is very unfit for any chemical purpose that re- 
 quires much heat. Bottle-glass, which is always made without 
 lead, will bear a greater heat without melting, and therefore is 
 much better adapted to many of our operations. 
 
 A few observations now present themselves as necessary to be 
 offered on the process of bottle-glass, before we proceed with the 
 remainder of our subject. 
 
 The soap-makers' residuum contains a very great proportion 
 of carbonate of lime, which is better for this purpose than lime 
 itself, inasmuch as it helps to decompose the sulphates of soda and 
 potash, which are always contained more or less in soap waste, as 
 well as in kelp and the other alkalies of commerce. 
 
 There must be a great loss in using the sand in its coarse state, 
 for the reasons already assigned. In some glass-houses on the 
 Continent it is usual to heat the sand red hot, and then throw it 
 suddenly into cold water, in the same way as the potters treat 
 their flint to break it into smaller grains. Why might not our 
 manufacturers, where coal is cheap, adopt this practice? If pains 
 were also taken to wash the Woolwich sand repeatedly in several 
 
366 ON THE MANUFACTURE OF GLASS. 
 
 waters, the colour of the glass made with it, would, I conceive, 
 be much improved. 
 
 Government will not allow the makers of this species of glass 
 to use any but the commonest river-sand, lest the glass should be 
 too good, and the revenue be defrauded by its being applied to 
 purposes for which the best glass is generally used, and which 
 pays a higher duty. The greatest proportion of the sand which 
 is used in bottle-glass is obtained from the river Thames at 
 Woolwich. 
 
 I have reason to believe that at most of our English bottle- 
 houses, the calcining is conducted in arches communicating with 
 the furnace in which the metal is founded. In those houses which 
 I have seen there is an arch at each corner of the main furnace, 
 and in these arches the materials remain not only the whole time 
 of founding the former parcel of glass, but also during the time 
 of its being worked up into bottles, &c. which is generally 10 or 
 12 hours more. Care is taken at the latter part of this period to 
 bring the calcined mixture in the arches to such a temperature, 
 that it may be moved immediately from thence into the hot cru- 
 cibles without danger of breaking them. 
 
 In the neighbourhood of Newcastle-upon-Tyne, bottle-glass 
 is made very profitably from a mixture of lime and sea sand, the 
 mass having been first repeatedly wetted with salt-water. Where 
 glass is thus attempted to be made without any alkali, except 
 what is contained in the muriate of soda, lime is absolutely ne- 
 cessary; for this earth when in conjunction with silica seems in 
 a high temperature to have the power of decomposing common 
 salt. 
 
 The preference which is given to the Orkney kelp, may, I sus- 
 pect, be accounted for on similar principles. This species of kelp 
 contains usually 2 cwt. of lime in every ton, produced from the 
 incineration of the sea shells which are entangled in the weed, 
 and this lime is useful in decomposing the muriate of soda which 
 is always contained more or less in every kind of kelp. 
 
 The only species of glass which now remains to be described 
 is that of PLATE-GLASS. Of this there are two kinds, viz. the one 
 made by blowing and opening, somewhat similar to the mode of 
 making the spread window-glass already described ; the other is 
 produced by casting upon a table in a way something like that 
 of forming sheet lead. Plate-glass of a considerable size may be 
 made by the first of these methods, but the largest mirrors can 
 only be made by casting. Much of the small plate is consumed 
 in the navy and by merchant vessels for glazing the cabin win- 
 
ON THE MANUFACTURE OF GLASS. 367 
 
 dows, as no other kind of glass can be depended upon in rough 
 weather. 
 
 There are, I believe, only two establishments throughout the 
 united kingdom for the fabrication of plate-glass. The first and 
 most considerable is at Ravenhead in Lancashire, where the 
 largest plates in the world, and inferior to no foreign plates, are 
 made, and these are produced by casting. The other is at East 
 Smithfield, London, where the work is performed by blowing. 
 
 I express myself in this decided manner respecting the work at 
 Ravenhead, in order to counteract the declaration of an eminent 
 French manufacturer, who has thought proper to publish the fol- 
 lowing statement: " All that the English glass-houses do, may," 
 says he, " be executed, and in fact is executed, with more facility 
 in ours. But they are obliged to give up to us the fabrication 
 of plate-glass, and of our fine light glass, made with pure saline 
 fluxes." Loysel, page 86. Those who have seen the superb col- 
 lection of English plate-glass which is constantly on show at 
 Blackfriars, will be not a little surprised at the unqualified nature 
 of this assertion. 
 
 In the formation of good plate-glass, the first consideration is 
 that of preparing the soda, this being the species of alkali which 
 is usually employed, and, I believe, from sound reasoning, always 
 preferred for plate-glass. To procure the soda for this purpose, 
 muriate of soda (common salt) is decomposed by means of sub- 
 carbonate of potash, both salts being in a state of solution and 
 assisted by heat. After this, a portion of the muriate of potash 
 is separated from the solution by priority of crystallization, when 
 the remaining alkaline solution is boiled to dryness and reserved 
 for use. Formerly kelp-ashes and even weed-ashes were em- 
 ployed, without any previous lixiviation, in making plate -glass. 
 Consequently the glass was then coloured, and not so brilliant as 
 the modern. In the great work at St. Gobin they used nothing 
 but wood-ashes for many years. 
 
 After the alkaline salt has been prepared as above, it is in some 
 measure necessary to analyse it, with a view to ascertain how 
 much real alkali is contained in it, and hence how much sand 
 such a salt will require. When this is known, the calculation is 
 made without difficulty ; for it has been found that one pound of 
 pure soda is sufficient for four pounds of sand ; and if this quan- 
 tity of sand be employed, a hard compact glass will be produced 
 that cannot be injured by the action of water, or even any of the 
 common mineral acids. But where so large a proportion of silica 
 is used, it is necessary to employ a heat not less than 18,000 of 
 Fahrenheit, it having been determined that silica is dissolved by 
 alkali in proportion to the height of the temperature at which the 
 founding is conducted. 
 
368 ON THE MANUFACTURE OF GLASS. 
 
 On the principle that one pound of soda, free from every im- 
 purity, will be sufficient for four pounds of sand, then, if the pre- 
 pared alkali should contain 40 per cent, of real soda, which is 
 about the usual quantity, the remainder being muriate of potash, 
 carbonic acid, and water, the operator would take 160 Ibs. of sand 
 to every 100 Ibs. of such salt. Upon these data, therefore, the 
 following proportions of the materials will produce a glass suit- 
 able for the best plates : 
 
 Ibs. 
 Lynn sand, previously well washed and dried . . 720 
 
 Alkaline salt prepared as above 450 
 
 Quick-lime slacked and sifted 80 
 
 Nitre 25 
 
 Gullet, or broken plate-glass 425 
 
 1700 
 
 These quantities of the different materials are required to pro- 
 duce one pot of metal ; and if the process be well conducted, this 
 will make 1200 Ibs. of good plate-glass. This will, however, de- 
 pend in some measure on the size of the establishment. Loysei 
 has given a detailed account of the principal dimensions of the 
 French houses for making plate-glass, and has introduced it by 
 saying that those proportions have already served as a model in 
 several glass-housesj and that experience has justified his opinion 
 of their goodness. 
 
 Dr. Merret calculates that 1 cwt. of sand yields 150 pounds of 
 glass. This produce is, however, greater than can be realized, if 
 the founding be properly conducted. 
 
 The whitest sand which I ever saw is found in the Isle of Wight, 
 at Alum Bay, very near the Needles. I suspect this would make 
 finer glass than the Lynn sand above mentioned. The impor- 
 tance of pure sand for the manufacture of glass has been acknow- 
 ledged for many ages. For more than a thousand years before 
 the commencement of the Christian sera, the sand found on the 
 shore of Belus, a river in Phoenicia, was reckoned the only kind 
 fit for making glass ; and even after the time of Christ it was col- 
 lected, and taken away by vessels that came annually from foreign 
 countries, as Strabo, Joseph us, Tacitus and others affirm. 
 
 Lime is employed on account of the property which it gives to 
 glass, of being a better conductor of heat, and consequently ren- 
 dering it less liable to break by sudden change of temperature ; 
 and because such glass cuts more readily by a diamond than that 
 which is purely siliceous. It is important, however, to use quick- 
 lime, and not the carbonate, as the latter occasions so much swell- 
 ing of the materials as to endanger their flowing over the sides of 
 the crucibles. 
 
 The quality of the lime is of considerable importance. Lime 
 
ON THE MANUFACTURE OF GLASS. 369 
 
 for this purpose has sometimes been made with stone brought as 
 ballast from Gibraltar, and it answered better than the chalk lime 
 in the neighbourhood of London. I am informed, however, that 
 the best lime for the glass business is that of St. Vincent's Rock, 
 near Bristol. 
 
 Nitre is very effectual towards depriving the materials of every 
 species of carbonaceous matter ; and hence it improves the colour 
 of the glass, its oxygen uniting with the carbon, and forming with 
 it carbonic acid gas, which goes off in vapour. Nitre has also the 
 property of rendering glass more transparent. 
 
 The following is the process which has usually been adopted 
 by those makers of glass who prepare their own alkali : 
 
 Any quantity of common salt is dissolved in a boiler of hot 
 water, and nearly double its weight of American or Russian pearl- 
 ash is added to it. This mixture will produce a double decom- 
 position, and two new salts will be produced, viz. muriate of 
 potash and carbonate of soda. 
 
 When the liquor in which these salts have been dissolved is 
 concentrated by evaporation to a certain point, which may be 
 easily known by a little experience, the muriate of potash will 
 crystallize ; and then the remaining alkaline liquor may be further 
 evaporated till the carbonate of soda be recovered in a dry state. 
 The mineral alkali thus produced may be used instead of purified 
 pearl-ash, in the manufacture of the finest kinds of glass, and the 
 muriate of potash may be sold for the purpose of making alum, 
 for which it is a very suitable salt. 
 
 I conceive it might be worth while for a scientific glass-maker 
 to institute a series of experiments to determine whether muriate 
 of potash or muriate of soda, in their entire form, might not be 
 employed to advantage in making some species of glass. 
 
 In resuming the relation of the process of making plate-glass, 
 I feel much difficulty in marking out, without being tedious, the 
 exact line of description, so as to render the account in any de- 
 gree interesting ; for I am aware that, were I to enter into all the 
 minutia2 of this business, the mere detail would of itself occupy a 
 volume. The following circumstances, however, which all refer 
 to the method of making plate-glass by the process of blowing, 
 seem to deserve our attention. 
 
 When the materials employed have been sufficiently commi- 
 nuted and properly united by turning them frequently backwards 
 and forwards upon a floor, the crucibles within the furnace are 
 carefully filled with the mixture, the conciator or founder taking 
 care to have the furnace previously made as hot as possible. 
 Ten hours generally elapse before these materials are totally 
 melted ; for during this time the pots are much cooled, and the 
 
 2B 
 
370 ON THE MANUFACTURE OF GLASS. 
 
 fusion checked by the repeated addition of fresh portions of the 
 materials. 
 
 " The solvent power of a saline flux upon silica in a state of 
 fusion, is proportioned to the extent of surface presented to its ac- 
 tion and the existing force of aggregation. Thus, if a mixture of 
 one part of fixed alkali with two of quartz reduced to powder, be 
 pul into a crucible exposed for a due time to the heat of a glass- 
 furnace, the vitrification will be complete ; but if the quartz be 
 mixed in lumps instead of powder, vitrification will only take place 
 on the surface and in strata; a portion of the alkali will be dissi- 
 pated by the fire, a small quantity of glass will be produced, and 
 there will remain a great portion of the quartz unmelted." Loy- 
 sel, page 18." 
 
 The articles being all melted, the next object is to refine the 
 metal thoroughly ; and this is effected by continuing the heat at 
 its maximum for several hours longer, till all the neutral salts, the 
 aqueous, carbonaceous, and gaseous matters have disappeared, 
 and the glass is become free from specks or globules of air, and 
 destitute of colour. To describe this state the workmen employ 
 a technical phrase, and say that the metal is become plain ; and 
 when it is announced that the glass is quite plain, they mean that 
 it is entirely finished and quite perfect; whereas in the crown- 
 glass-houses the metal at this stage of the preparation is said to 
 bejine, meaning that it is refined or purified by the dissipation of 
 the air bubbles, &c. 
 
 When the contents of all the crucibles are brought exactly to 
 this state, a workman goes into the ash-pit, or cave, as it is called, 
 and carefully closes up the openings between the bars of the grate 
 with a composition consisting of clay and cut straw, to prevent 
 the introduction of any air into the furnace through the fire-place, 
 which would endanger the rupture of the pots, and produce too 
 rapid a cooling of the furnace. Some excellent directions for the 
 construction of furnaces, so as to prevent the walls from cracking, 
 are given by Loysel in his work on glass. 
 
 It is necessary in this stage to secure every opening into the 
 furnace ; because when the metal has become plain, it is not in 
 a fit state for being worked into plates of glass by the process of 
 blowing; for at this high temperature it would be too fluid to 
 adhere to the irons when dipped into it, or to preserve the shape 
 which it is necessary to give it before it can be converted into a 
 plane surface fit for being made into mirrors. It must therefore 
 be allowed to cool gradually for nine or ten hours after every 
 orifice has been closed, as before mentioned. 
 
 The temperature of the prepared metal being thus reduced to 
 the working state, it is modelled in a manner very similar to that 
 of flint-glass, already described. A workman dips an iron pipe 
 
ON THE MANUFACTURE OF GLASS. 371 
 
 into the crucible, and having taken out a little of the fused glass 
 upon the point of the iron, waits a moment till that has adhered : 
 he then dips it in again and rolls another portion round the 
 former : this he repeats, till he finds he has taken up enough for 
 his purpose. Then, by blowing down the iron tube, he expands 
 the mass of glass a little, and produces a hollowness within it : 
 this he enlarges by repeated blowings till it forms a globe of 12 
 or 14 inches in diameter, or more, according to the size of the 
 intended glass-plate. 
 
 At St. Gobin it is usual to sprinkle with water the first portion 
 of metal that is taken up on the point of the iron, in order to 
 make it adhere better to the instrument, and thus be able to sup- 
 port a greater weight of glass in the subsequent immersions in 
 the crucible. 
 
 The next object, in this stage of the process, is to convert the 
 globe into a cylinder. This the workman effects by giving the 
 rod to which the soft glass is attached, the motion of a pendulum. 
 It is then heated afresh at the mouth of the furnace, and a hole 
 is punched in the centre of that end of the cylinder which is 
 furthest off the working rod. This is done with an iron chisel 
 and mallet ; and as the glass is previously softened by heat, there 
 is no danger in the operation. The orifice which has been thus 
 made is afterwards widened by an instrument kept for the pur- 
 pose ; and then, a pair of shears being introduced, a slit is made 
 in the cylinder of glass extending to one half of its length. 
 
 It being necessary, however, that the cylindrical form should 
 for the present be preserved, another workman applies a tempo- 
 rary rib of glass, which has been previously attached to a work- 
 ing rod, across that end of the cylinder which has thus been cut 
 open. This instrument, which is called a pontil) is not hollow 
 like the blowing irons, but is merely a metallic rod about 6 feet 
 long. In France the pontil for making plate-glass has a bar o 
 iron across the end of it, forming a T, and the rib of glass de- 
 signed to be attached to the cylinder is put within a slit in the 
 edge of the cross bar, which is designed for that purpose. 
 
 When this is done, the other rod is detached, in order to allow 
 of that end of the cylinder being also heated, opened, and slit up 
 with shears as before practised. The whole of the cylinder being 
 thus divided, the pontil is detached from it, and the glass is car- 
 ried to the spreading oven, where it is laid upon an elevated floor 
 covered with a thick stratum of sand, to prevent the adhesion of 
 the glass in its softened state. In a few minutes it is pushed on 
 to an adjoining apartment, where it is quickly placed in a vertical 
 position to anneal. So much care is necessary in this business, 
 and the work is so laborious, that one man seldom makes more 
 than 10 or 12 plates in the course of twenty-four hours. 
 
 2 B 2 
 
372 ON THE MANUFACTURE OF GLASS. 
 
 The annealing kiln or oven having been thus filled with the 
 plates of glass, each standing on its edge, the doors and the 
 chimney are closed and carefully luted with clay, to prevent the 
 possibility of any cold air entering the chamber for the space of 
 twelve or fourteen days ; after which the lutings are gradually 
 loosened, and the glass is removed into an open part of the glass- 
 house to attain by degrees the temperature of the surrounding 
 atmosphere. When an hour or two has elapsed, these plates 
 may be carried with safety to the cutting-room, and there they 
 are trimmed round the edges with a diamond, and by other 
 means, to prepare them for the operation of grinding. Accord- 
 ing to Pliny, the ancients used diamond powder for polishing the 
 precious stones : but Beckmann says that the first mention of a 
 diamond being used for writing on glass occurs in the sixteenth 
 century. Francis I. of France wrote the following lines with his 
 diamond ring upon a pane of glass, to let the duchess of Estampes 
 know that he was jealous : 
 
 " Souvent femme varie, 
 Mai habil qui s'y fie." 
 
 The ancients must however have been acquainted with our 
 method of grinding glass, for Pliny speaks of its being turned by 
 the wheel and engraved on like silver. Plin. lib. xxxvi. 26. 
 
 To describe all the preparations arid conveniences of the 
 grinding apartment in an English plate-glass-house, together 
 with the varied processes of rubbing down the plates to one uni- 
 form thickness, would extend this Essay beyond its prescribed 
 bounds : but an outline of this part of the business must be given. 
 And with regard to the uniformity of thickness, this is necessary 
 not only for mirrors but for the navy, where the superintendants 
 are very circumspect in having the glass all of the defined thick- 
 ness. There is an officer at each of His Majesty's dock-yards 
 who is provided with a gauge to measure it, and whose duty it 
 is to reject all those squares that do not correspond to the fixed 
 rule. The size which is most commonly used is of the thickness 
 of 3-16ths of an inch. 
 
 In the grinding apartment the glass plates designed for mirrors 
 or other purposes, to which plate-glass is applied, are imbedded 
 in plaster of Paris upon a suitable table or bench, care being first 
 taken to fix them perfectly horizontal. When the table is thus 
 filled, other plates are attached by plaster of Paris to another 
 plane surface; and these being suspended over the lower table, 
 are made to traverse by a regular motion upon the surface of 
 the former. This is effected by means of a power obtained from 
 a steam-engine ; and when the upper set of plates are thus set in 
 motion, the attendant casts a certain quantity of sand and occa- 
 sionally a little water between the two surfaces : it may therefore 
 
ON THE MANUFACTURE OF GLASS. 373 
 
 easily be conceived that, by continuing this motion with repeated 
 additions of sand and water, both surfaces will be abraded and 
 ground down to any thickness that the operator may require. 
 When these plates are properly ground by a succession of sands 
 of different degrees of fineness, which are all distinguished by 
 well-known numbers in the same way as the sportsman distin- 
 guishes his leaden shot, the plates are detached from the plaster of 
 Paris; and having been turned so as to present the other side, they 
 are reset in the plaster, and the same operations are repeated. 
 
 There is a process which precedes this, called ruffing, and 
 other manipulations, before this business of grinding is finished. 
 But these are so varied and multiplied that it is impossible to 
 describe them without more prolixity than I am willing to im- 
 pose upon my readers ; and even then the manufactory must be 
 visited before I could be thoroughly understood. 
 
 It may, nevertheless, be noticed, that the process of grinding 
 reduces every hundred weight of rough plates, independently of 
 breakage, to less than half a hundred, and that the glass which 
 is ground off' is deemed unfit for any other purpose of glass- 
 making except that of black bottles, because it is mixed with so 
 large a portion of common river sand, which always contains a 
 large portion of iron. It has therefore generally been either sold 
 at a very low rate for scouring pewter, &c. or entirely thrown 
 away : and I remember having calculated some years ago, on the 
 supposition of from one-half to two-thirds of the glass being 
 abraded, that the loss of real glass at the London plate-house 
 cannot be less than two tons per week, and the sand expended 
 will weekly amount to at least sixteen or twenty tons. 
 
 A method has however been contrived of saving the whole of 
 this refuse, and preserving it in a state fit for being again formed 
 into any of the best species of glass. It consists in grinding the 
 plates with purejiint^ instead of the river-sand hitherto employ- 
 ed ; therefore, when the flints have been ground so as to have no 
 admixture of iron with them, this residuum is very fit for the 
 purpose above mentioned, and the glass contained in it may be 
 estimated at more value than an equal weight of pure cullet, as 
 old broken glass is technically called. In the operation of grind- 
 ing the plates, three or four tons of prepared flints are equal in 
 effect to twenty tons of sand ; the work is done in much less time ; 
 and the abraded matter, instead of being a cumbrous and useless 
 mass, is actually an estimable residuum, admirably adapted to the 
 purposes of the manufactory, and capable of yielding considerable 
 profit. 
 
 In resuming the subject, I have only to add, that when the 
 grinding is finished, the next process is that of smoothing, which 
 
374- ON THE MANUFACTURE OF GLASS. 
 
 may indeed be considered to be a continuation of the grinding 
 process ; but this is performed by the hand, and with emery of 
 different fineness, instead of sand. 
 
 Emery is imported in very hard solid lumps ; these are ground 
 by a powerful mill, and then sifted. The finer parts which pass 
 through the sieve are separated into portions of different degrees 
 of fineness, by a peculiar apparatus constructed for the purpose; 
 but the effect is produced by a process somewhat similar to that 
 of elutriation, an operation well known to chemists. 
 
 Emery, which is used for polishing metals as well as glass, is 
 a native substance consisting of iron, alumina, and silica. It is 
 brought from different parts of the Continent, but it is found no 
 where in such abundance as in the mountains on the western 
 coast of the Island of Naxia, the most fertile of all the islands in 
 the Archipelago. It occurs so plentifully there, that the adjoin- 
 ing cape has acquired the name of Cape Emery. According to 
 Mr. Boyle, its specific gravity is 400. From the analysis of 
 Mr. Smithson Tennant, emery is composed of 80 parts of alu- 
 mina, 3 silica, and 4 iron. The emery which is used in making 
 scouring paper has lately been much adulterated by the admix- 
 ture of old bottle glass, which is ground fine for the purpose. 
 The common sand-paper is covered with a mixture of this ground 
 glass and sharp sand. 
 
 The last operation is that of polishing. This is done with 
 colcothar of vitriol, and is a process of only a few hours. The 
 plates are then well washed, and squared by a diamond for sale. 
 Such are the processes by which that kind of plate-glass is made 
 which is produced by blowing. 
 
 Little can be known of those manufactories where large mir- 
 rors are made by casting, as the proprietors have always con- 
 ducted their works with the utmost caution and secrecy. There 
 are, indeed, only two establishments of the kind that I know of; 
 the one at the Castle of St. Gobin in the forest of Fere, in the 
 department of the Aisne, in France, as before mentioned, and 
 the other at Ravenhead near St. Helens, in the county of Lan- 
 caster, which was established about the year 1771 or 1772, and 
 the proprietors were incorporated by Act of Parliament. 
 
 In consequence of the secrecy which has always been observed 
 in the conduct of this manufactory, a detail of the various mani- 
 pulations for the formation of cast plate-glass could hardly be 
 expected. But since the first edition of these Essays went to 
 press, I have been fortunate enough to be allowed to go through 
 the whole of these very extensive works and to examine the va- 
 rious operations usually carried on there, and which I was allowed 
 to see in consequence of my having taken the precaution to pro- 
 cure a letter of introduction from the Committee in London, 
 
ON THE MANUFACTURE OF GLASS. 375 
 
 without which I understood the resident Managers would not 
 have been justified in admitting me. 
 
 The first thing the attendant showed me, was the operation of 
 grinding the plates, which is a concern of great magnitude. Those 
 plates which are designed for mirrors and other purposes where 
 the surface must be perfectly true, are firmly imbedded, in a ho- 
 rizontal position, upon a wooden table or platform, and these are 
 made to revolve one upon the other by strong mechanical power 
 obtained from a steam engine, and by these means they grind 
 one another ; sand and water being occasionally thrown in be- 
 tween them, and afterwards emery and water in a way very similar 
 to the method already described at page 372 when treating on 
 the manufacture of plate-glass by blowing. It is observable that 
 the plates of glass are ground in pairs, and to see so many of 
 these of several feet diameter in one room, moving in all direc- 
 tions by means of machinery and with considerable velocity, asto- 
 nished me not a little. 
 
 When by this method the plates are ground to one uniform 
 thickness, they are detached from the beds of plaster and re- 
 moved to the polishing room. Here the process is performed by 
 an article called colcothar of vitriol, which is- merely sulphate of 
 iron first calcined to redness and then reduced to an impalpable 
 powder. This colcothar is spread upon a piece of hat-felt, which 
 is attached to a very singular kind of machine kept in constant mo- 
 tion by means of a power communicated by the steam engine. 
 
 The last process of polishing is performed by the hand. This 
 is managed by women, who traverse one plate of glass over the 
 surface of another, with great velocity and adroitness. The ar- 
 ticle which is used in this finishing process is called tutty. It is 
 the white oxide of tin finely levigated. This work being com- 
 pleted, the plates are well washed with water, and then taken to 
 the cutting-room, where they are squared for sale, as described at 
 page 374. 
 
 When I had examined these processes, the guide conducted 
 me to the Foundry, which is the great room containing the melt- 
 ing furnaces, the table for casting, and the annealing ovens. The 
 building containing all these is very lofty, and by far the largest 
 room under one roof, that has ever yet been erected in Great 
 Britain. It is 339 feet long, and 155 feet in width. 
 
 The furnace for founding the metal and the ovens for heating 
 the crucibles, occupy a very long range in the middle of this im- 
 mense room : they stand in a longitudinal direction, and fill up 
 about one third of the whole area. 
 
 The method of heating the furnace is very important; but as 
 I was not at the manufactory when this operation was performed, 
 I am unwilling to attempt to describe it. The mode adopted at the 
 
376 ON THE MANUFACTURE OF GLASS. 
 
 Castle of St. Gobin is, however, too curious for a description of 
 it to be omitted. Two persons stripped to their shirts run round 
 the furnace without making the least stop, and with a speed equal 
 to seven leagues in six hours : as they go along they take up two 
 small billets of wood, of about lj or 2 inches in diameter, which 
 are cut for the purpose ; these they throw into the first opening, 
 and continuing their course do the same at the second, and at 
 every other opening into the furnace. This circuit they continue 
 without interruption for six hours successively, and then are re- 
 lieved by others who continue the same course till the glass is 
 completely finished. It has been thought surprising that the fre- 
 quent application of two such small parcels of wood, and which 
 are consumed in an instant, should keep the furnace to the pro- 
 per degree of heat, which is such that a large bar of iron laid at 
 one of the mouths of the furnace, becomes red-hot in less than 
 half a minute. 
 
 At Ravenhead a row of annealing ovens stands on each side of 
 the foundry, occupying the greatest part of the side walls of the 
 building. These are each 1 6 feet wide and forty feet deep. The 
 arrangement of these ovens is such that the plates of glass can be 
 deposited in them immediately as they are cast, in order that they 
 may cool as gradually as possible ; and the floor of each is con- 
 trived to be on an exact level with the casting table, for the more 
 easy removal of the plates into them. When each oven has re- 
 ceived its destined quantity, it is shut up by an iron door, and this is 
 secured all round with mortar to prevent any access of atmospheric 
 air. The plate-glass remains in these ovens about a fortnight, 
 when it is taken out, and removed to the store-room. This pro- 
 cess of annealing is one of the most important in the whole manu- 
 factory. If it were neglected, the plates of glass would be liable 
 to crack at every change of temperature. 
 
 The most curious part of this business, however, is the process 
 of casting the plate-glass, which is conducted somewhat in the 
 following manner: When the metal has been properly prepared 
 and has become completely refined and settled, it is laded into 
 smaller crucibles called cisterns, which stand in the same furnace. 
 In these vessels it remains some hours longer, or until they be- 
 come of a white heat throughout, which is one of the first crite- 
 rions by which the workmen judge of its fitness for being formed 
 into plates. When the glass has acquired that exact degree of 
 temperature which has been found by experience to be best suited 
 for its flowing properly under the roller, the crucible containing 
 the fluid metal is taken out of the furnace by means of a crane, and 
 placed upon a low carriage for the conveniency of moving it to 
 the casting table, which is sometimes a considerable distance from 
 the melting furnace. 
 
ON THE MANUFACTURE OF GLASS. 377 
 
 When the crucible of hot metal is brought near the table, it is 
 raised by a crane with a pair of gallipers a few feet from the 
 ground, to give the workmen an opportunity of scraping the 
 scoria from the bottom and outer sides of the crucible, which 
 otherwise might drop off, and spoil the beauty of the plates. The 
 pot of glass is then let down to the ground and the scum is very 
 carefully taken off; it is then wound up again by means of the 
 crane, and when at a sufficient height, is gently swung over the 
 upper end of the casting table, where it is drawn on one side, and 
 by a peculiar contrivance for throwing the crucible into an in- 
 clined position, a torrent of melted glass is suddenly poured out 
 on the smooth iron surface beneath it. The crucible is no sooner 
 emptied of the metal, all of an intense red-heat, than the iron 
 roller is set in motion, and by this massive instrument the whole 
 of the glass is spread out into one single sheet of a great size 
 and of an uniform thickness; the thickness of the plate being de- 
 termined by ribs of brass which are fixed one on each side of the 
 casting table, and upon which the iron roller runs. The length 
 of each plate is however in some measure determined by the quan- 
 tity of metal which the crucible happens to contain ; and if it 
 should have held more than was absolutely necessary for covering 
 the surface of the table, the extra quantity falls into a vessel of 
 water and is employed in the next operation. 
 
 The spectacle of such a vast body of melted glass poured at 
 once from an immense crucible on a metallic table of great mag- 
 nitude, is truly grand ; and the variety of colours^ which the plate 
 exhibits immediately after the roller has passed" over it, renders 
 this an operation far more splendid and interesting than can pos- 
 sibly be described. Indeed the effect which it produces is quite 
 inconceivable to such as have not been eye-witnesses of the mani- 
 pulations in this surprising establishment. 
 
 Notwithstanding the immense scale upon which the manufac- 
 tory in Lancashire is established, it appears to me, that it differs 
 from the one in London more in the circumstance of the plates 
 being cast, than in the composition of the glass itself. 
 
 From information which I have received by various channels, 
 I apprehend the founding the metal is the same at both places ; 
 except that at Ravenhead, when the metal is made ready it is re- 
 moved into other receptacles called cisterns, as already mentioned, 
 and so contrived that they may be readily hoisted out of the fur- 
 nace when every thing is in a state of preparation, and the fluid 
 body poured from them at once, and as quickly as possible, upon 
 the table, where the plate of glass is ultimately formed. 
 
 This table formerly consisted of one massive plate of copper 
 twelve feet long and of a proportionate width, ground and polished 
 so as to present throughout an uniformly smooth surface. It was 
 
378 ON THE MANUFACTURE OF GLASS. 
 
 soon foundj however, that copper is an improper metal for the 
 purpose, it being liable to crack from the sudden transition of the 
 heat from the torrent of melted glass poured upon it. 
 
 Several copper tables having been thus rendered useless, and 
 a vast expense incurred in substituting one new copper table after 
 another, the managers at length came to the determination of try- 
 ing iron, and accordingly a cast-iron table of great thickness was 
 forthwith prepared for the purpose. This immense mass of iron 
 weighed so many tons that it was necessary to build a peculiar 
 kind of carriage to transport it, and the other expenses of con- 
 veying it from the iron foundry to the glass works were enormous. 
 This table, like the former ones of copper, was fixed upon a suit- 
 able frame, and this is supported by casters, for the convenience 
 of moving the table from the mouth of one annealing oven to 
 another. 
 
 Whether it must be attributed to the extra thickness of this 
 metallic table or to any other cause, it may be difficult to deter- 
 mine; but this certainly answered the intended purpose, and ap- 
 pears to have sustained no injury whatever from the frequent and 
 sudden accessions of heat to which it has been exposed. When 
 I saw it, it had been in constant use for some years, and I was told 
 that the proprietors thought it would last for any length of time 
 that they could possibly require it. 
 
 It should have been remarked, that as soon as these plates 
 have become fixed by cooling, they are thrust by main strength 
 off the table and gradually slipped into the annealing oven im- 
 mediately contiguous, and there they are treated like the smaller 
 plates already described, excepting in one circumstance, that of 
 their being spread out, one by one, in a horizontal position, in- 
 stead of being piled on their edges, as they usually have been in 
 those works where plate- glass is made by blowing. 
 
 The reader may conceive the advantage which must result from 
 this arrangement, when the vast size of these plates is considered. 
 The method of blowing answers extremely well for small plates, 
 or for plates which do not exceed 4< feet in length and 2 feet 3 in 
 breadth ; but when larger, they have not a sufficient thickness to 
 bear the grinding, and besides, no man could have strength suf- 
 ficient to wield in his arms that quantity of glass which is required 
 to form such immense plates as are made at Ravenhead. 
 
 The proprietors of this establishment announce by public ad- 
 vertisement, that they have constantly on sale at their warehouse, 
 Blackfriars Bridge, London, glass-plates of the enormous size of 
 six feet by twelve feet each. 
 
 That one plate should contain more than seventy square feet 
 of glass, and yet have a surface perfectly true, is really astonish- 
 ing; and when we consider that there is only one establishment 
 
ON THE MANUFACTURE OF GLASS. 379 
 
 in the world that can at all compare with the works at Ravenhead, 
 we need not hesitate in pronouncing the latter to be the most 
 curious and interesting manufactory in the British empire. 
 
 In concluding the account of the manufacture of plate-glass, it 
 must be noticed that the great expenses necessarily attendant 
 upon the making of cast plates have obliged some of the artists in 
 France to return to the old method of blowing ; and some have 
 been so fortunate in improving this branch of manufacture, that 
 plates are now formed in that country, by blowing, which are 64? 
 Flemish inches in height and 23 in breadth, (in English measure 
 60 inches by 21^ inches,) a size which it had been impossible to 
 attain before, except by the process of casting. The mass of 
 matter necessary for this purpose, weighing more than a hundred 
 pounds, is by the workman blown into the shape of a large bag ; 
 it is then reduced to the form of a cylinder, and, being cut up, is 
 by stretching, rolling with a smooth iron, and other means not yet 
 known but to those employed in the art, transformed into an even 
 plane. Beckmann, vol. iii. page 207. 
 
 Having thus briefly described the modes of making the five 
 different species of glass, it may be proper to advert to a recent 
 discovery in the art, and then to say a few words on the properties 
 of glass itself. 
 
 The discovery to which 1 refer is that of glass incrustations, 
 for which a patent has been obtained under the name of Crystallo 
 Ceramic, by Messrs. Pellatt and Green of London. In descri- 
 bing this elegant and ingenious manufactory, I cannot do better 
 than avail myself of Mr. Pellatt's own memoir on the subject. 
 
 The ancients were not altogether ignorant of this art ; but 
 their incrustations were very imperfect in consequence of their 
 not being in possession of a substance for forming the device or 
 figure to be inserted within the body of the glass, that was less 
 fusible than the glass itself. 
 
 About forty years ago, a manufacturer in Bohemia attempted 
 to incrust in glass small figures made with a peculiar kind of clay ; 
 but his experiments were in but few instances successful, in conse- 
 quence of the clay not being adapted to adhere properly to the 
 glass. It was, however, from the Bohemian that the idea was 
 caught by some French manufacturers, who, after having ex- 
 pended a considerable sum in the attempt, at length succeeded in 
 incrusting several medallions of Buonaparte, which were sold at 
 an enormous price. From the extreme difficulty of making these 
 medallions, and their almost invariably breaking, very few were 
 finished ; and I understand that the French have since then con- 
 tented themselves with confining the art to the decoration of small 
 trinkets, &c. 
 
 A patent has, however, as before mentioned, been recently 
 taken out in this country for making these ornamental incrusta- 
 
380 ON THE MANUFACTURE OF GLASS. 
 
 tions; and, if we may judge from the manner of their execution, 
 they promise to produce a new era in the art of glass-making. 
 By this process, ornaments of any description, heraldic crests, or 
 portraits of any variety of colour, may be introduced into the glass, 
 so as to become perfectly imperishable. It must be understood 
 that the substance of which these devices are composed is less 
 fusible than glass, incapable of generating air, and at the same 
 time susceptible of contraction or expansion, as, in the course of 
 manufacture, the glass becomes hot or cold. The ornamental 
 figures are introduced into the body of the glass while hot, by 
 which means they become actually incorporated with it. 
 
 The composition used in'the patent incrustations, and which 
 does great credit to the taste and chemical acquirements of 
 Messrs. Pellatt and Green, is of a silvery appearance, which has 
 a very superb effect when introduced into richly cut glass. And 
 as miniatures and other paintings may be enamelled upon it, 
 without the colours losing any of their brilliancy, it may be 
 adapted to any purpose that the taste or judgement of the artist 
 may suggest. 
 
 A most important advantage to be derived from this elegant in- 
 vention, respects the preservation of dates and inscriptions. Casts 
 of medals and coins present no equal 'security for perpetuating 
 them. Had this art been known to the ancients, it would have 
 preserved to us many interesting memorials. The inscription, 
 when once incrusted in a solid block of crystal, like the fly in 
 amber, will effectually resist for ages the destructive action of the 
 atmosphere. 
 
 In reverting to the nature of glass as a chemical compound, it 
 may be said that glass possesses several distinct and very remark- 
 able properties, which may be enumerated in the following order. 
 It is transparent and elastic, it possesses strong electrical powers, 
 is ductile and fusible by heat, becomes very brittle by sudden 
 change of temperature, and is imperishable in the fire. Dr. 
 Merret has enumerated no less than 26 distinct properties which 
 glass possesses, some of which were new to me and curious l . 
 
 It is the ductility of glass which qualifies it for being fashioned 
 into such numerous shapes and employed for such a variety of 
 purposes. Dr. Merret says, that when James Howell was at 
 Venice he saw a complete galley, with all her masts, sails, cables, 
 tackling, poop, forecastle, anchors, and her long-boat, all made 
 in glass. Cardan relates that he saw a cart with two oxen in it, 
 made with glass, and yet small enough to be covered with the wing 
 of a fly 2 . 
 
 The transparency of glass is not a little surprising, when we 
 
 1 See page 214 of his Translation of Neris Art of Glass. 
 
 2 De Varietatc, lib. x. cap. 52. 
 
ON THE MANUFACTURE OF GLASS. 381 
 
 consider that it is formed of substances which in themselves are 
 perfectly opake. 
 
 It was the transparency of glass which occasioned it to be so 
 much esteemed by the ancients. The emperor Nero paid 6000 
 sestertia, nearly equal to 50,000/. sterling, for two small trans- 
 parent glass cups with handles 3 . Glass not transparent was then 
 in common use for various domestic utensils, also a red coloured 
 opake glass called vitrum Jicematimon 9 probably from liccmatitis 
 the blood stone. Some of the windows in the ancient city of 
 Pompeii were glazed with a thick sort of glass, but this was only 
 semi-transparent. Martial, however, mentions glass in such a 
 manner as shows it to have been common in his time for drink- 
 ing vessels, and also of so transparent a texture as to admit an 
 accurate examination of the liquor contained in them. 
 
 "Nos bibimus vitro, tu inyrrha Pontice: quare? 
 Prodat perspicuus ne duo vina calix." Epig. iv. 86. 
 
 There must, indeed, have been a considerable number of 
 makers of glass in ancient Rome ; for we read of their having a 
 district near the Appian gate assigned them for carrying on the 
 manufactory. The elasticity of glass may be proved by a pane 
 of common window-glass, which may be bent out of a straight 
 line and yet will return again to its place without being fractured ; 
 and if glass be run out very fine like a thread, it may be folded 
 round the finger without breaking. 
 
 If it be drawn into fine strings, it may be bent into a complete 
 circle, and held in that position for any length of time without 
 impairing its elasticity; for the moment the pressure is removed 
 it recovers its form, and becomes a straight rod as before. 
 
 A few years ago a person travelled through most of the coun- 
 ties of England to exhibit the spinning of glass. He would spin 
 many hundred yards of it, and as fine as silk, in a minute. 
 
 In consequence of the ready excitability of glass by friction, 
 and its impermeability to electricity, it is the only material which 
 is now made use of for the construction of electrical cylinders. 
 
 Unannealed glass possesses some very singular properties. 
 Vessels of capacity made with such glass will often bear a con- 
 siderable blow from without, and yet be shivered to pieces by 
 the smallest fragment of stone, even less than a pea, if dropped 
 in the inside ; and the thicker the bottom the more easily will 
 the effect be produced. Cups of green glass, some of them three 
 inches' thick at bottom, and which had borne the shock of a 
 musket ball dropped from a considerable height, were shivered 
 into fragments by letting a bit of flint weighing only two grains 
 drop into them. 
 
 3 Pliny, lib. xxxvi. cap. 26. 
 
382 ON THE MANUFACTURE OF GLASS. 
 
 It lias been determined by Loysel that for the manufacture of 
 the furnaces and crucibles an argillaceous earth which contains 
 at least 95 per cent of quartz and alumina, and less than 5 per 
 cent of carbonate of lime and oxides, may be employed in most 
 of the small white glass works, where the fire is not very intense; 
 but that the proportion of alumina and quartz ought to be 97 in 
 each 100 pounds when it is to be employed in the great furnaces 
 for plate and bottle glass, especially for the fabrication of the cru- 
 cibles. Art de la Verrerie, page 16. 
 
 The same writer states, that the materials of which these are 
 made ought to be infusible in the degree of heat which is neces- 
 sary to be employed ; not susceptible of corrosion by the action 
 of the mixtures in fusion, and capable of taking and preserving 
 those forms which are found to be most suitable for these con- 
 structions. The best directions that have ever been given on the 
 necessary thickness of the crucibles are to be seen in the same 
 work. Some experiments on this subject having been made by 
 him, he formed a valuable table for the use of the manufacturers 
 of glass, to show the respective thickness of the crucibles of va- 
 rious diameters, all which are estimated according to the different 
 degrees of the tenacity of the materials. 
 
 In addition to the various remarks which I have made on the 
 construction of the crucibles, I am desirous of annexing the fol- 
 lowing important observations. 
 
 " Pottery," says Loysel, " is one of the most difficult and de- 
 licate parts of the art of glass-making, and merits the strictest 
 attention. If the pottery is perfect, the artist has the power to 
 manage the action of the heat, to vary at pleasure the vitrifiable 
 compositions, to regulate the melting, the refining, and the whole 
 works. He knows beforehand the products of his fabrication, 
 and directs it to his greatest advantage. If on the contrary the 
 pottery is bad, all is confusion. The first cost of the materials, 
 their preparation, and the expense of the workmanship, turn to 
 entire loss, and the ruin of the proprietor is inevitable. No ex- 
 pense therefore, or care, ought to be spared to procure good 
 pottery." 
 
 The English glass-makers labour under an inconvenience 
 which is not felt in France and some other countries on the Con- 
 tinent of Europe. In consequence of their heating their furnaces 
 with pit coal, they are under the necessity of making their best 
 flint glass in covered pots ; and as the heat is much lower in the 
 interior of a covered crucible than in an open one, we are obliged 
 to make our glass of more fusible materials ; and consequently, 
 by using a large portion of lead, and less silica, we produce a 
 softer glass than is prepared by those who have an abundance of 
 wood fuel. 
 
ON THE MANUFACTURE OF GLASS. 383 
 
 It appears to me that there can be no certainty in the process 
 of annealing without the use of a pyrometer ; and as the glass 
 manufacturers have frequently to make experiments on clays, have 
 not such persons excellent opportunities of contriving such an in- 
 strument as would suit not only this purpose, but serve for the 
 large furnace also? Glass made with alkali and silica only, is 
 more difficult to anneal with certainty than such as contains lime 
 and lead in its composition. 
 
 Soda is preferable for making glass, inasmuch as it requires 
 more silica for its saturation than potash ; and it will not be denied 
 that the greater the quantity of the siliceous earth which can be 
 made to enter into the composition of glass, the harder will that 
 glass be, and the less liable to be injured by abrasion. 
 
 In making glass, " if the combination be such that in 1000 
 parts there remain only 200 or even only 150 parts of alkali, the 
 glass is hard, clear, brilliant and transparent, and approaches the 
 beauty of rock crystal. The excellence of flint glass is in direct 
 ratio to the quantity of silica, and in inverse ratio of the quantity 
 of alkali." Loysel, page 113. 
 
 Moreover, soda, as was before mentioned, will make a more 
 fluid metal, and thus the manufacturer will at all times be more 
 likely to separate all the sandiver, for this rises with more diffi- 
 culty to the surface when the glass is made with potash ; and it 
 is well known that, wherever any of the sandiver or glass-gall 
 remains in the finished glass, it will occasion striae, clouds or bub- 
 bles, either of which very much lessen its value. 
 
 When plate-glass is to be made with potash, it is generally 
 thought requisite to add some borax to the composition to render 
 the metal more fluid, otherwise it is apt to stiffen before the plates 
 can be completely formed. This is another objection to the use 
 of potash for this particular species of glass. On these accounts 
 it is of importance always to use soda for plate-glass, and also for 
 such flint glass as is intended to be employed for particular pur- 
 poses; especially for such articles as are required to sustain 
 much wear. 
 
 It is however generally imagined that potash will make the 
 whitest glass, though such glass is more apt to be seedy, as the 
 workmen call it, that is, to be full of very minute specks, which 
 greatly impair its beauty, and diminish its value. 
 
 A friend of mine in the glass trade has however assured me 
 that he never could make flint glass, even with the purest soda, 
 so perfectly white as he could with pearl-ash, though he repeated 
 the experiment many times and with every precaution. 
 
 Since then I have had an opportunity of examining several 
 specimens of flint glass made with soda and others with potash ; 
 and I am now inclined to think that very brilliant flint glass, per- 
 
384? ON THE MANUFACTURE OF GLASS. 
 
 fectly pellucid and colourless, cannot be made with soda, but that 
 potash is absolutely necessary for this particular species of glass. 
 The potash ought however to undergo a complete purification 
 from all neutral salts, before it be employed for wine glasses or 
 for any kind of ornamental flint glass. 
 
 It may in some cases be safer to use soda, because, where too 
 much alkali has been employed, such glass will be less likely to 
 be injured by exposure to the atmosphere in damp situations than 
 glass made with the vegetable alkali, which is always liable to de- 
 liquescence. I am, perhaps, justified in this observation by a 
 remark of Dr. Merret, in his examination of Neri's Art of Glass. 
 " In old windows of French glass, in that part," says he, " which 
 lies towards the air, you may discern pieces of salt; and in the 
 finest glass, where there is a great proportion of salt to the sand, 
 you shall find that such glasses standing long in subterraneous 
 places, will fall to pieces, the union of the salt and sand decaying." 
 Fourcroy also says, that glass made with soda is best for holding 
 the mineral acids, as such glass is decomposed with more diffi- 
 culty by acids than such as is made with potash. 
 
 Borrichius relates, that he saw several glass lacrymatories dug 
 up at Rome which had lain in the ground several hundred years, 
 and that the glass was split into an infinite number of laminae 
 like the Muscovy talc, and yet these Iamina3 were smooth and 
 transparent. This effect was probably occasioned by the use of 
 potash in the glass, and the employment of too large a quantity 
 of that alkali. 
 
 I would not, however, in these remarks be misunderstood ; for 
 it is impossible to be sure of having perfect glass unless an extra 
 quantity of alkali be employed : but then care must be taken to 
 prolong the process till the whole of this excess be separated from 
 the mass and volatilized. 
 
 Shaw has a remark to the same purpose. " In order," says he, 
 66 to give our glass the desired degree of hardness, it is proper 
 to continue it long in the fire, which is constantly found to add 
 strength and hardness to glass. Common glass, by being con- 
 stantly kept in a strong fusion for a month or six weeks, has be- 
 come of a stony hardness, approaching to the native hardness of 
 the flint or sand employed in its preparation." Chem. Lcct. p. 4-27. 
 
 I have also to recommend that frequent attention be paid to 
 the price of salt-petre, because I am persuaded that whenever 
 this article is at a low rate it must be advisable to employ it for 
 flint and crown glass in preference to American pearl-ash ; inas- 
 much as it contains a large portion of alkali, and is free from those 
 neutral salts with which pot- and pearl-ash of every kind are con 
 taminated. Where metallic oxides have been employed to colour 
 glass, either for windows or for the imitation of the precious 
 
ON THE MANUFACTURE OF GLASS. 385 
 
 stones, nitre is found to be of great use, as it tends to preserve 
 the metallic oxides in a high state of oxidizement, and thus im- 
 parts great vivacity to the colours. Nitre is composed of 47 per 
 cent, of pure potash and 53 per cent, of dry nitric acid. 
 
 Agricola knew the value of nitre in making glass. " The first 
 place," says he, " must be given to saltpetre, the second to fossil 
 salt V 
 
 It has been said that borax (subborate of soda) will make a 
 harder glass than either of the pure alkalies. Borax consists, ac- 
 cording to Bergman, of 34 parts of boracic acid, 17 parts of soda, 
 and 49 parts of water. 
 
 This saline substance was known to the ancient Romans. We 
 read of the Circus in the time of one of the early Caesars being 
 covered with vermilion and borax*. Whether borax or tincal 
 could be procured in quantity cheap enough to be employed in 
 glass-making, I know not. Dr. Shaw relates, that with four 
 ounces of borax and one ounce of fine white sand he formed a 
 pure glass, which was so hard that it cut common glass like the 
 diamond. Chem. Lect. p. 426. 
 
 It would be advantageous, I conceive, if some method could 
 be devised of frequently stirring the fluid metal in the crucibles, 
 so as always to ensure the production of glass that shall have a 
 perfectly homogeneous character. In a former part of this Essay 
 I have mentioned the circumstance of veins or strias appearing in 
 flint glass. These might generally be prevented by the adoption 
 of the expedient which is now suggested, because they arise from 
 the want of due uniformity in the mixture of the compound mass. 
 
 Loysel-has shown that the various specific gravities of the dif- 
 ferent compounds which are formed, such as those with alkali 
 and silica; alkali and clay; and, lastly, alkali with the metallic 
 oxides; are fully sufficient to account for the production of these 
 imperfections, and that nothing but a more uniform mixture of 
 the different materials, together with complete fusion, can pre- 
 vent their appearance. 
 
 " Glass made at a great degree of heat will always be lighter 
 than that made at a lower temperature. The first contains more 
 silica and less alkali, whereas the specific gravity of glass aug- 
 ments according to the greater quantity of alkali that is combineo 1 
 with it." " Glass made to contain 80 silica and 20 alkali will 
 have a specific gravity of 2.36, whereas that which is composed 
 of 54 silica and 46 alkali will be 2.54." Might it not be advisable 
 for the proprietor of every glass-house to take the specific gravity 
 of each pot of metal when finished ? as this would always be a 
 
 1 Agricola De Re Met. allied. 2 Suetonius in Vita Caligute, 18. 
 
386 ON THE MANUFACTURE OF GLASS. 
 
 guide to show whether the workmen had observed due care in 
 keeping the furnace at a proper degree of temperature. 
 
 In treating this subject, Loysel remarks, that " glass made 
 with silica and the fixed alkalies has a specific gravity of 2.3 
 to 2.4-; that formed with alkali and clay 2.5; that with alkali 
 and chalk 2.7 to 2.8 ; the oxide of manganese if vitrified by itself 
 3.2 or 3.3; while the glass made with oxide of lead will be 7.2 
 to 7.3 of specific gravity." When these different kinds of vitrified 
 products occur in the same crucible, and a complete mixture of 
 them has not been effected, it is not surprising, he observes, that 
 the glass should be imperfect. 
 
 The art of making glass seems to depend upon the successful 
 or perfect union of two or more metallic oxides which have an 
 affinity for each other. On this principle it is that potash, an 
 oxide of potassium, and silica, the oxide of silicium, are fused 
 together and form glass. One part of silica and two parts of 
 borate of soda unite and form a transparent colourless glass. 
 One part of silica and three of oxide of lead form good green 
 glass, and it is well known at all the iron furnaces that silica, 
 when united to the oxide of iron, produces a perfect black glass 
 of extreme hardness and durability. 
 
 The principal Acts of Parliament now in force respecting the 
 manufacture and sale of glass, are as follow : viz. 19th Geo. II. 
 chap. 12; 17th Geo. III. chap. 39; 24th Geo. III. chap. 41 ; 
 35th Geo. III. chap. 114; 38th Geo. III. chap. 33; 38th Geo. 
 III. chap. 89; 43d Geo. III. chap. 69; and the 53d Geo. III. 
 
ON BLEACHING. 387 
 
 ESSAY XII. 
 ON BLEACHING. 
 
 I 1 LAX and hemp were employed in the fabrication of cloth many 
 ages ago, and in those early times such cloth was highly esteemed; 
 it must therefore long before that period have been discovered 
 that these fabrics were improved in colour by exposure to the 
 action of the atmosphere. The effect of hot water in whitening 
 brown linen would also soon arrest the attention of mankind ; and 
 when it became a practice with the early inhabitants of Asia to 
 employ certain earths and alkaline plants in the operations of 
 washing and scouring their garments, the whitening, as well as 
 the detersive properties of these vegetables, could not fail to be 
 observed, and, by degrees, would naturally occasion the intro- 
 duction of regular processes for bleaching ; and that this art was 
 practised very early, is, I think, evident from the great progress 
 which it had made in the beginning of the Christian sera. 
 
 That the ancients had learnt some method of rendering their 
 linen extremely white, may be supposed from many remarks 
 which are interspersed among their writings. 
 
 There is a passage of Pliny, an author whom I have often 
 quoted, and who published his Natural History in the first cen- 
 tury, which to me appears perfectly conclusive. 
 
 " Of late days," says he, " there were seen in the amphitheatres 
 of the Emperor Nero, fine curtains of blue azure colour like the 
 sky, and the very floor of the ground under men's feet was co- 
 loured red. But for all these paintings and rich dyes, yet, when 
 all is done, the white linen held the pre-eminence still, and w r as 
 highly esteemed above all colours '." 
 
 Pliny has likewise informed us, that the Gauls and Britons of 
 his time were acquainted with a method of bleaching linen cloth, 
 and he thus describes their process. " After the flax is spun 
 into yarn, it must," says he, " be bleached and whitened by being 
 pounded several times in a stone mortar with water : and lastly, 
 when it is woven into cloth, it must be beaten again upon a smooth 
 stone with broad-headed cudgels, and the more frequently it is 
 beaten it will be the whiter and softer 2 ." The same author tells 
 us that they sometimes put the roots of wild poppies into the 
 
 1 Holland's Pliny, vol. ii. p. 5. * Plin. Hist. Nat. lib. xix. cap. 1. 9. 
 
 2 c2 
 
388 ON BLEACHING. 
 
 water, to make it more efficacious in bleaching linen '. " There 
 is a kind of poppy (says he) much sought after for bleaching linen 
 cloth ; for, being scoured therewith, it is wonderful how white and 
 pure they will look. And yet people are grown to this disorder 
 and vain enormity, that they have essayed to stain and dye their 
 linen into other colours, as well as their woollen cloths 9 /' 
 
 We learn from Theophrastus, who was the son of a fuller in 
 the Isle of Lesbos, and who wrote 300 years before Christ, that 
 lime was then employed in bleaching. He relates, that a ship 
 partly loaded with linen, and partly with lime for bleaching it, 
 was destroyed by the accidental access of water to the lime. 
 
 Although it should be proved that the bleaching of linen is a 
 process of very great antiquity, it must not, however, be supposed 
 that any people were acquainted with it in the earliest stages of 
 their society, or before they had acquired some degree of civili- 
 zation. 
 
 The vestments of the early inhabitants of the world discovered 
 neither art nor industry. They made use of such as nature pre- 
 sented, and needed the least preparation. Some nations covered 
 themselves with the bark of trees, others with leaves, or bulrushes, 
 rudely interwoven 3 . The sJcins of animals were also universally 
 used as garments, worn without preparation, and in the same state 
 as they came from the bodies of the animals 4 . 
 
 In process of time recourse was had to the wool of animals, and 
 this led to the further discovery of the art of uniting the separate 
 parts into one continued thread, by means of the spindle ; and this 
 would consequently lead to the next step, the invention of weaving, 
 which, according to Democritus, who flourished four hundred 
 years before Christ, arose from the art of the spider, who guides 
 and manages the threads by the weight of her own body. That 
 the invention of weaving was long prior to the time of Democritus, 
 appears from the sacred writings. 
 
 After the art of weaving had been invented, it was probably 
 not long before flax, hemp, and cotton, were employed in the 
 fabrication of garments, especially as the President Goguet has 
 abundantly proved that vestments of cotton were in use in the 
 Patriarchal ages 5 ; and there can be no doubt that in the time of 
 Christ several nations had acquired great proficiency in the ma- 
 nufacture of linen cloth. 
 
 Pliny describes, as growing in the higher parts of Egypt, the 
 cotton shrub of which cloth was made, and "of which," he says, 
 
 ' Plin. Hist. Nat. lib. xx. cap. 19. 2. Holland's Pliny, vol. ii. p. 5. 
 
 5 Strabo, lib. xi. p. 781. Senec. Epist. xc. p. 406. 
 
 4 Lucretius, lib. vi. ver. 1011. Pausanias, lib. xx. c. 38. 
 
 5 Goguet, book ii. p. 127- 
 
ON BLEACHING. 389 
 
 " the Egyptian priests were wont to have surplcsses, in which they 
 took a singular delight 6 ." He also tells us 7 that vestments of 
 cotton were worn by the ancient Egyptians; and more than a 
 thousand years before the commencement of the Christian sera, 
 Moses speaks of robes of linen, and commands his people " not 
 to wear a garment of divers sorts, as of woollen and linen to- 
 gether 8 ." The dress of the ancient Babylonians consisted of a 
 tunic of lawn, which they wore next to their skin. It descended, 
 in the Eastern mode, to their feet 9 . The Athenians wore long 
 robes of fine linen dyed purple 10 . 
 
 It is not likely that the materials of which we have been speak- 
 ing were long employed in the manufacture of garments, before 
 some method was adopted of improving their colour by artificial 
 means, as has been already hinted. This will appear still more 
 probable, when we consider that some of the early inhabitants 
 of the world had several methods which in themselves tended very 
 much to whiten linen and cotton cloth. 
 
 The evidence of Pliny is alone sufficient to prove the truth of 
 this assertion. " The Faventine cloth," says he, " is always 
 far whiter than the Allian, which is ordinarily brown when it 
 is new woven, and before it be bleached. The Retovine linen is 
 exceeding fine; the thread itself is more even (if evener may be) 
 than that which the spider spinneth." " I myself have seen so 
 fine and small a thread of Cumes flax, that a whole net knit thereof 
 would pass through the ring of a man's finger. I have also known 
 one man carry so many of them (easily) as would go round and 
 compass a whole forest H ." 
 
 Homer describes Nausicaa and her companions washing their 
 clothes by treading them with their feet 12 ; and according to Pliny, 
 the ancient Greeks and Romans were acquainted with the deter- 
 sive properties of several kinds of earth, as well as of several plants, 
 which they employed in scouring linen 13 . 
 
 Having hazarded these few introductory remarks, it may per- 
 haps be convenient to divide the subject itself into two parts, con- 
 sisting of the European methods of bleaching before the discovery 
 of chlorine gas, and of the practices which have been adopted 
 since that period. I shall then conclude this Essay with a brief 
 account of some of the present most important desiderata in 
 bleaching, accompanied with such hints or proposals which, on a 
 chemical review of the subject, may suggest themselves as proper 
 to be submitted to the consideration of practical men. 
 
 c Holland's Pliny, vol. ii. p. 3. ? pij ny> lib. xix. 2. 
 
 8 Deutcron. xxii. 11. Goguet, vol. iii. p. 187. Herotlot. lib.i. n. 195. 
 10 Thucyd. lib. i. p. (>. n. 6. Holland's Pliny, book xix. chap. 1. 
 
 " Odyss. lib. vi. ver. 92. '' Pliny, lib. xxxv. 57; lib. xxvii. 88. 
 
390 ON BLEACHING. 
 
 Half a century ago the linens of Holland ere the most es- 
 teemed of any in Europe, and this arose in a great measure from 
 the superior skill of the Dutch in bleaching. An account of the 
 process in the great work at Haarlem, and which I copy from a 
 scarce book, printed in the year 1754, entitled " Select Essays on 
 Commerce, fyc." will therefore, I trust, not be uninteresting to the 
 modern bleacher. 
 
 " The whitening grounds of Haarlem," says the author, " are 
 situated about a league from the city gates, and the most consi- 
 derable of all is in the neighbourhood of the village Bloemendaal. 
 The cause of the wonderful whiteness in the Dutch cloths is 
 ascribed to the lye-ashes of Muscovy, and to the water of their 
 downs ; which is nothing else than sea-water, which, filtrating 
 through the downs and mountains of sand, bursts out perfectly 
 sweet and clear. 
 
 " When a piece of linen is to be bleached, it is in the first 
 place steeped in a lixivium or lye, where other cloth hath been 
 trod ; afterwards it is trod in a new lye of lye-ashes, poured upon 
 it boiling hot. This is boiled in large copper caldrons, and is 
 never poured upon the cloth till it is as clear as wine. The linen 
 is left eight days in this lye, after which it is washed and pressed 
 in this manner. 
 
 " They empty some buckets of butter-milk into wooden vessels 
 fixed in the ground, then they throw in a piece of linen, which 
 three men tread with their feet as much as possible. Afterwards 
 they pour in more butter-milk, and then another piece of cloth, 
 proceeding thus alternately till the vessels are nearly filled, when 
 they lay planks over the linen, upon which they raise a large 
 round piece of wood, or great stake, touching the lower side of a 
 beam, between which and the stake they drive wedges, to press 
 the cloth. Six or seven days after, they take the cloth out of 
 these vessels ; and if it be not white enough, they steep it as we 
 have described above. Afterwards it is washed, and spread out 
 upon the ground to bleach. It must be remarked that, after 
 every dipping, the cloth is washed first with black soap, then with 
 clear water, and, after each of these operations, is wrung by means 
 of a machine that turns with a wheel." 
 
 It will not much interrupt this narrative to remark, that at this 
 period, no one attempted to explain the operation of the atmo- 
 sphere in bleaching.* Many years afterwards, Mons. Berthollet, 
 in order to be able to account for the effect of crofting linen and 
 cotton goods, examined the dew which falls from the atmosphere, 
 and also that which transpires from the grass, and found both to 
 contain a sufficient portion of oxygen to destroy the colour of 
 turnsol paper. Annales de C/iimie, torn. ii. p. 1 58. 
 
 " The whitening grounds are cut with canals in sundry places, 
 

CHEMICAL ESSAYS. 
 
 x^ y , ff . 
 D. y&a&M/ttf 
 
 . . E. 
 
 &. H. 
 
 '.Dari,. 
 
ON BLEACHING. 391 
 
 that there may be no trouble of fetching water from a distance. 
 The cloth is watered with long narrow shovels made in the shape 
 of a scythe. The water of these canals comes from the downs, 
 and it is that which contributes most to the lustre of the Dutch 
 cloth. To prevent the water from becoming thick and muddy, 
 they are extremely careful in cleaning their canals. The washing 
 tubs are built in with bricks, with two trap doors, or sluices, for 
 admitting or excluding the water, according as it is necessary. 
 
 It would occupy too much room in these pages to describe se- 
 parately each of the processes that were formerly adopted in these 
 kingdoms for bleaching; but, as that of flax yarn was one of the 
 most important, I have thought it worth while to relate how this 
 was conducted, under an idea that such a detail will prove inter- 
 esting to the young bleacher, who has yet had no opportunity of 
 witnessing any operation but that which is effected by chlorine 
 gas, or the salts which are formed by its means. 
 
 A pound of linen yarn cannot be bleached at less than four 
 times the expense of bleaching a pound of cotton yarn. The 
 reason is, that the quantity of colouring and resinous matter to 
 be abstracted from the one is much greater than from the other. 
 The thread made with flax will lose 27 per cent, of its original 
 weight before it becomes perfectly bleached ; whereas cotton yarn 
 will lose only 4J or 5 per cent, by a similar operation. The 
 following was the process usually adopted for bleaching flaxen 
 yarn. 
 
 The first operation, that of steeping, is extremely simple. It 
 consists merely in immersing the brown yarn in hot water, or 
 otherwise allowing it to -macerate cold in waste alkaline lyes. 
 When pure water only was used, the goods were generally kept 
 in it for three or four days, whereas with cold alkaline waste lyes 
 forty-eight hours were usually deemed sufficient. 
 
 The intention of steeping was to occasion a kind of vegetable 
 fermentation, which loosened the saliva employed in spinning the 
 yarn, and so far separated the other impurities attached to it, that 
 the whole were afterwards easily removed by washing in river or 
 spring water, and which, in large concerns, was usually performed 
 by machinery. 
 
 The next operation was that of boiling in an alkaline lye, or 
 bucking, after which the skeins were exposed on the grass for two 
 or three weeks, and then boiled or bucked a second time, again 
 well washed, and then crofted as before. Bucking is a technical 
 term for boiling, or steeping, in hot alkaline lyes, in an appara- 
 tus which is so contrived that the lye flows alternately over the 
 goods and into a heated copper l . From this a pump, which is 
 
 1 A drawing of this apparatus will be seen in the Plate of the Bucking Appa- 
 ratus. 
 
392 ON BLEACHING. 
 
 usually worked by steam, throws it again on the goods, through 
 which it percolates till it reaches the bottom of the vessel, when, 
 by the removal of a plug, it is run off again into the boiler, where 
 it becomes again heated, and from whence it is pumped up as be- 
 fore, and the process goes on uninterruptedly for many hours. 
 According to Dr. Home, clear sunshine, with a very little wind, 
 is the best weather for bleaching. Crofting is a technical phrase 
 for the act of exposing linen or cotton goods on the grass. These 
 alternate operations of bucking, washing, and crofting, were ge- 
 nerally repeated four or five times, each time lessening the strength 
 of the alkaline lixivium in which the bucking was performed. 
 
 The next process" was that of souring, which consisted in soak- 
 ing the yarn in milk which had become acidulous by age, and 
 which was usually employed for the first time immediately after 
 the fourth or the fifth repetition of the bucking or the boiling ope- 
 ration. In this liquor, which was technically called theirs/ sour, 
 the goods generally lay for two or three weeks, or until such time 
 as the scum began to crack and subside, when they were usually 
 taken out and submitted to a repetition of the several operations 
 already described. 
 
 Thus, whenever the goods had been once soured, the operations 
 of bucking, washing, souring, and crofting, were repeated in re- 
 gular rotation, until the yarn came to a good colour, and was es- 
 teemed perfectly clean. And it should be remarked, that these 
 alternate applications of the alkali and the acid, in this mode of 
 bleaching, were absolutely necessary to give the oxygen of the 
 atmosphere an opportunity of acting upon the colouring matter, 
 and preparing it for the next operation. In these operations the 
 alkali probably carbonizes the colouring matter, or puts it in a 
 suitable state for the oxygen to convert it into carbonic acid, or 
 into a gaseous substance, easily carried away by the wind, viz. 
 carbonic acid gas. For if any portion of the alkali was left in the 
 goods when they were laid on the meadow, it would not only pre- 
 vent the whitening process from going on properly, but would 
 impair the strength of the article, and in like manner, though in 
 a less degree, the goods would be injured by the remaining acid ; 
 but by the contrivance of using the acid and the alkali alternately, 
 each of them becomes neutralized, the resulting salt has no in- 
 jurious action on the fabric, and yet it is in a state for being 
 easily removed by washing in pure water. In these latter ope- 
 rations a portion of soap was always employed, it having been 
 found that this had the effect of making the goods handle better, 
 and also of cleansing them more effectually. 
 
 This method of bleaching was extremely tedious, so much so, 
 that if the first operation was begun in the month of March, the 
 goods were seldom finished before September ; and such as were 
 laid on the grass for the first time at Midsummer, were only 
 
ON BLEACHING. 393 
 
 about half bleached that year, and were laid by to be finished in 
 the spring of the following year. The probable reason why the 
 proprietors of bleaching grounds took no measures to prevent 
 this interruption of the process was, because they had found by 
 experience that the atmosphere during the months of March, 
 April, and May, acted more efficaciously in whitening the goods. 
 
 About the middle of the last century, these tedious operations 
 were much shortened, by the employment of sulphuric acid, in- 
 stead of sour milk; an improvement first suggested by Dr. Home, 
 in consequence of the new and important process, adopted about 
 that time by Dr. Roebuck, for manufacturing sulphuric acid, 
 which reduced that acid to one-fourth of its original price. 
 
 The public was, however, much alarmed by the introduction 
 of this acid, on account of its corrosive nature, till Dr. Home 
 published a volume on bleaching, in which he stated how much 
 the sulphuric acid is always diluted for this purpose, and that " he 
 had kept linen in a strong sour of oil of vitriol for many months, 
 and that the cloth was as strong after it was taken out as when it 
 was put in." 
 
 No sooner was this new agent employed in bleaching, than it 
 was discovered that one souring with sulphuric acid might be 
 finished in 12, 18, or, at most, in 24? hours; whereas every sour- 
 ing by the milk process required from two to six weeks, according 
 to the state of the weather and other adventitious circumstances. 
 Besides, sours of this description hasten very fast to corruption. 
 Indeed, as the milk is generally kept very long, it is often cor- 
 rupted before it is used, and then, without acting as an acid, it 
 has all the bad effects of putrefaction in injuring the fibre and 
 weakening the cloth; whereas the sours made with sulphuric 
 acid are not liable to putrefaction. 
 
 The mere introduction of sulphuric acid occasioned such an 
 improvement in the art of bleaching, that the whole process might 
 then have been easily finished in four months, though it had for- 
 merly required seven or eight months for its completion. 
 
 The most important discovery, however, in this business is that 
 of chlorine, and its application in whitening goods made either of 
 linen or cotton. The introduction of this article forms absolutely 
 a new aera in the history of this art ; for it not only expedites the 
 process surprisingly, but has become the means of reducing the 
 practice of bleaching to a perfect science. 
 
 For this most important discovery we are indebted to Scheele, 
 who in the year 1774? first obtained chlorine by art, and after- 
 wards ascertained its power in destroying vegetable colours ' ; 
 although it appears that at first he investigated its nature more 
 as a matter of curiosity than of use. 
 
 See Schecle'& Chemical Essays, translated by Eeddoes, p. 00. 
 
394? ON BLEACHING. 
 
 Several years seem to have elapsed before any one thought of 
 applying the peculiar properties of this singular gas to any im- 
 portant purpose ; and I presume it was not suspected that this 
 powerful agent might be employed in any considerable process of 
 bleaching linen or cotton until about the year 1784. 
 
 The first person who made experiments upon this gas, with a 
 view to its successful application in the arts, was M. Berthollet, 
 the French chemist, who in the Journal de Physique for June 
 1785, and again in the number for August 1786, explained the 
 nature of its action on vegetable colours, and suggested how it 
 might be employed with advantage in any of the existing esta- 
 blishments. 
 
 In the year 1787, the Academy of Montpellier transmitted to 
 Chaptal several observations on chlorine, in order to their being 
 printed in the National Memoirs for that year ; and a report on 
 the subject of this communication was immediately presented to 
 the Royal Academy of Sciences. This report, which contains 
 many very interesting particulars, was afterwards given to the 
 world in the Annales de Chimie, tome i. p. 69. 
 
 In the early part of the year 1787, Mr. Copland, Professor of 
 Natural Philosophy in Marischal College, Aberdeen, was ac- 
 companying the present Duke of Gordon in his travels on the 
 Continent, and they passed some weeks at Geneva, with Professor 
 de Saussure, under whose direction His Grace had studied in the 
 early part of his life ; and he showed these travellers the experi- 
 ment, which they had already heard of, but had never before seen, 
 of discharging vegetable colours by means of chlorine gas. 
 
 Impressed with the idea of the importance of this discovery to 
 our manufactures, Professor Copland, on his return home, com- 
 municated all the circumstances and displayed the properties of 
 the new gas to Messrs. Milnes, particular friends of mine, emi- 
 nent manufacturers in that neighbourhood, who immediately en- 
 tered upon a course of experiments for the preparation of chlorine, 
 with a Woolfe's apparatus, and obtained a very satisfactory result. 
 
 This was about the end of July 1787, being, I believe, the first 
 actual application of chlorine to the purpose of bleaching either 
 linen or cotton goods for sale in Great Britain; and from that time 
 these gentlemen continued to apply this mode of bleaching in 
 their manufactory, especially for finishing such orders as were 
 limited in point of time. But, in applying this discovery to ac- 
 tual practice on a large scale, they very soon perceived that the 
 circumstance of the gas being prepared in an apparatus of glass, 
 would be a serious obstacle to its general adoption ; and there- 
 fore, when they came to extend its application to larger quantities, 
 they made use of vessels of white wood instead of glass. 
 
 At the time of which I have been speaking, M. Berthollet 
 had been engaged for twelve months in investigating the nature of 
 
ON BLEACHING. 395 
 
 chlorine gas, for the purpose of ascertaining the best and most 
 economical methods of applying it in whitening cotton and linen 
 cloth. Just then, Mr. James Watt, of the Soho, Birmingham, 
 happening to be at Paris, M. Berthollet invited that eminent man 
 to witness his experiments ; and it appears that he communicated 
 to him, without reserve, the full amount of the discoveries which 
 he had made in the new process of bleaching. 
 
 On the return of Mr. Watt to Great Britain, he appears to 
 have lost no time in communicating the whole of the information 
 he had obtained, to his relative Mr. MacGregor, a large bleacher 
 at Glasgow ; for, in his subsequent correspondence with M. Ber- 
 thollet, he informed him, that he had applied his discovery to real 
 practice, and in his first attempt had bleached five hundred pieces 
 of cloth by the new method. He adds that Mr. MacGregor was 
 so highly satisfied with the result, that he had determined to con- 
 tinue the process. 
 
 When these circumstances are all considered, it may be diffi- 
 cult, at this distance of time, to determine whether chlorine gas 
 was first employed in the bleach-field of Mr. MacGregor at Glas- 
 gow, or in the works belonging to Messrs. Milnes at Aberdeen; 
 or, in other words, whether Professor Copland or Mr. Watt is 
 entitled to the credit of having first introduced gas bleaching into 
 some of the then existing establishments of Scotland. Be this, 
 however, as it may, it is pretty clear that both these gentlemen 
 were zealously engaged in the same undertaking about the same 
 period, and that the process was fully established at Aberdeen 
 and at Glasgow long before it was employed in any other part 
 of Great Britain. 
 
 But to pursue the account : In the year 1788, the attention of 
 several persons at Manchester, particularly that of Mr. Thomas 
 Henry, was directed to the subject, and an experimental exami- 
 nation of the nature of the new bleaching agent was entered upon 
 by several individuals who had usually been engaged in different 
 pursuits, but who were all stimulated by the hope of obtaining 
 either private or public advantage from the result of their inves- 
 tigations. Just now, however, an unexpected circumstance oc- 
 curred, which was thought likely to be very injurious to the town 
 and trade of Manchester, and this had the effect of uniting the 
 efforts of those persons in that town and neighbourhood, who had 
 been endeavouring to acquire a knowledge of the new process of 
 bleaching by means of chlorine gas. MM. Bourbollon de Bon- 
 nueil and Co., French Chemists, had applied to the English Par- 
 liament for an exclusive right to the invention of a liquid for 
 whitening linen and cotton in a shorter time than by the old me- 
 thod ; and this so alarmed the printers and bleachers of Man- 
 chester, that a meeting of the manufacturers and merchants of the 
 
396 ON BLEACHING. 
 
 town was called by public advertisement, for the express purpose 
 of considering the plans and the petition of the said foreigners. 
 
 At this meeting half a piece of calico was produced which had 
 been bleached immediately before, by Messrs. Cooper, Baker and 
 Taylor, by the new method; and at the same meeting Mr. Thomas 
 Henry produced, not indeed half a piece, but half a yard of calico, 
 which he had just bleached by chlorine gas. What was wanting, 
 however, in quantity, was made up by the quality of the work ; 
 and the smaller specimen was declared to be superior in white- 
 ness to the larger one. 
 
 The result of the public meeting was, that in consequence of 
 the specimens of bleached calico which had been produced, and 
 of the facts stated by Mr. Henry, and Mr. Thomas Cooper, who 
 was also a man eminent for scientific attainments, and of a letter 
 from Mr. Watt to Mr. Henry, which was read to the meeting, 
 stating that he had at that very time 1500 yards of linen bleach- 
 ing by the new process under his direction, the members for the 
 county w r ere instructed to oppose the petition above mentioned, 
 when presented to Parliament. The consequence of this was, 
 that the petition was refused; and afterwards, when the same 
 people made application for a patent to secure to themselves the 
 sole right of selling a bleaching liquid, Mr. Henry drew up a 
 Memorial, which was presented to the attorney-general against 
 the claim of the petitioners, and which contributed in a conside- 
 rable degree to their want of success. This document is dated 
 July 2, 1788, and contains an account of the processes then ac- 
 tually practised by Mr. Henry, and comprehends everything at 
 this day known respecting the use of chlorine gas in bleaching, 
 with the exception of the application of lime to the condensation 
 of the gas. This document, which is still preserved, places be- 
 yond all controversy Mr. Henry's right to rank among the first 
 improvers of the process of bleaching. 
 
 Soon after the Manchester meeting of which I have spoken, Mr. 
 Charles Taylor, a calico-printer of Manchester, in conjunction 
 with Mr. Thomas Cooper, also of Manchester, bleached a whole 
 piece of cotton by the new process, and printed and calendered it 
 fit for the market in less than three days. The success of this 
 experiment was so decisive and unexceptionable, that Mr. Cooper 
 and some other neighbouring gentlemen were induced to establish 
 at Raikes, near Bolton, in Lancashire, a bleaching concern of 
 very considerable magnitude, to be dependent entirely upon the 
 agency of chlorine gas. 
 
 In the year 1789, which was one year after those favourable 
 specimens of the facilities of the new method of bleaching had 
 been exhibited in Manchester, as mentioned above, M. Ber- 
 ihollet brought the subject again before the public in a masterly 
 
ON BLBACHING. 397 
 
 memoir, entitled " Du Blanchiment des Toilcs et des Fils par 
 rAcide muriatique oxigene, et de quelques autres Proprictes de cette 
 Liqueur relatives auy Arts." His directions are, to use 
 
 6 ounces of pulverized oxide of manganese, 
 
 1 Ib. of sea salt, 
 
 12 ounces of sulphuric acid, and 
 12 ounces of water. 
 
 A folio plate, accurately engraved, accompanies the volume, 
 with letters of reference, and such an ample description that no- 
 thing can be mistaken. 
 
 This memoir contains so many interesting particulars respect- 
 ing the progress of the new art, that it would be impossible for 
 me to do justice to the subject which I have undertaken to eluci- 
 date, without repeating some of the circumstances related by this 
 very acute writer. 
 
 At first he was perplexed by the discovery that the cloth was 
 injured by the process; but in subsequent experiments he found 
 that, when the liquor was considerably diluted, he was enabled 
 to bleach without impairing the strength of the fabric. Another 
 difficulty which he had, arose from the cloth sometimes becoming 
 yellow after an interval of a few weeks; and this occasioned him 
 much trouble. However, when he began to try the alternate ac- 
 tion of the chlorine gas and alkaline lyes, he discovered that he 
 was able to procure a perfect and permanent white. I doubt not 
 that Berthollet speaks here of his success in bleaching cotton, be- 
 cause the process which he describes always leaves a yellowness 
 on linen goods, which can only be removed by a few days ex- 
 posure on the grass. 
 
 In the mean time, while M. Berthollet was engaged in these 
 experiments, a M. Bonjour, who had been an assistant to Ber- 
 thollet in his first attempts, connected himself with a M. Con- 
 stant, a cloth finisher at Valenciennes, for the purpose of forming 
 a bleaching establishment at that town; but, owing to the violent 
 opposition of the neighbouring bleachers, they were unable to 
 procure ground for the purpose on any reasonable terms. 
 
 In this difficulty, a patriotic French nobleman, the Count de 
 Bellaing, who favoured the enterprise, and was made acquainted 
 with the extent of the opposition, gave them possession of a piece 
 of land at some distance from the town, which had all the ne- 
 cessary conveniencies for the business. Her a large establish- 
 ment was formed in the course of the year 1788; but notwith- 
 standing the support which the proprietors had thus received, 
 the opposition of the old bleachers, and the inveterate prejudices 
 of the neighbourhood, were so great, that Mons. Bonjour was 
 under the necessity of addressing the National Bureau of Com- 
 
398 ON BLEACHING. 
 
 merce on the occasion. The chief 'prejudice arose from the cir- 
 cumstance of the new proprietors intending to substitute chemical 
 bleaching for the old process of ashing and crofting. 
 
 Soon after this period, some manufacturers at Javelle, near 
 Paris, announced in several journals, that they had discovered a 
 particular liquor, which they called the Lye ofjcrjelle, having the 
 property of bleaching cloth by a few hours immersion. This 
 composition, which was immediately analysed by Berthollet, was 
 found to be nothing more than a solution of the chloride of potash ; 
 and, on his attempting to prepare the solution, he immediately 
 perceived that the addition of the potash to the water caused it to 
 imbibe the gas sooner, and that it likewise formed a more con- 
 centrated liquor. This was similar to the liquid which is now 
 sold in London in small bottles, under the name of bleaching 
 liquid, for the use of private families. A convenient article for 
 this purpose may be prepared by receiving the gas which arises 
 from the distillation of 3 pounds of common salt and 1 pound of 
 manganese, into a receiver containing 1 pound of best American 
 pearl-ash dissolved in 4? pounds of water. Two pounds of sul- 
 phuric acid previously diluted with 4? pounds of water, will be 
 sufficient for extricating the gases from the materials above men- 
 tioned. 
 
 At the time when Berthollet published the memoir from which 
 I have taken some of the foregoing particulars, few persons in 
 England were acquainted with any mode of bleaching by means 
 of chlorine, except when in the state of gas; and in this way 
 many attempts were made, in various places, by some of the best 
 informed and most practical men in their respective districts. 
 
 At Nottingham, some considerable manufacturers succeeded 
 tolerably well in bleaching small parcels of linen yarn, linen, and 
 cotton, hose, and other small goods, which they effected in the 
 following manner : The articles having been suspended within 
 large wooden boxes, each of which had a close bottom capable 
 of holding water, the gas was conveyed into these receptacles ; 
 and, to prevent any injury by the immediate application of the 
 gas, the goods were, by means of a frame and pulley, let down 
 occasionally, and indeed frequently, into the water beneath. But 
 by this method there was great difficulty in exposing all the sur- 
 faces of the goods equally, without which no perfect bleaching 
 can ever be effected. 
 
 This practice was continued, 4iowever, with considerable ad- 
 vantage, though not without its inconveniencies, until the manu- 
 facturers of Javelle, before mentioned, having been disappointed 
 in their commercial prospects at home, came over to England, 
 and settled at Liverpool, for the purpose of manufacturing the 
 
ON BLEACHING. 399 
 
 solution of chloride of potash, which they proposed to sell to the 
 English bleachers in bottles, and which they still denominated 
 the Liquor de Javelle. 
 
 These men, although they had been unable to introduce their 
 article in France, so that it might have been consumed in suf- 
 ficient quantities to answer their purpose, were so sanguine re- 
 specting the sale of it in England, that they applied to the Bri- 
 tish Parliament for an exclusive right to the invention, for the 
 term of 28 years, as before mentioned. Fortunately, however, 
 one of the gentlemen who first applied chlorine to the purposes 
 of bleaching in this country, as mentioned at page 393, hap- 
 pening to be in the gallery of the House of Commons at the 
 time the application was made in behalf of these foreigners, he 
 took immediate measures to inform the principal members that 
 this was not a new process ; that he himself had long ago pre- 
 pared an article equally efficacious, and that he would be ready 
 to substantiate the truth of his statement when required. This 
 representation, together with the petition from the town of Man- 
 chester, had the desired effect the purpose of these Frenchmen 
 was defeated, arid the Act which they had petitioned for, was not 
 obtained. 
 
 Notwithstanding this disappointment, these gentlemen conti- 
 nued to carry on their work at Liverpool fora considerable time: 
 but, from the article being bulky, and from its constant loss of 
 strength by the action of light, or by exposure to the air, the ob- 
 stacles to its consumption continued to augment, until in the end 
 they were obliged to relinquish the establishment altogether. 
 
 After this, a Mr. Foy, who had been one of their operators at 
 Liverpool, waited upon some of the principal manufacturers, and 
 proposed, for a considerable premium, to erect for them the ne- 
 cessary apparatus, and to instruct them in the process of making 
 the Liquor de Javelle at their respective works. 
 
 This proposal was acceded to by many, and the chloride of 
 potash was for some time generally employed. The combination 
 of potash with the chlorine has the effect, however, of weakening 
 its bleaching power ; but this is more than compensated by the 
 circumstance of this compound being less obnoxious to the work- 
 men than the chlorine gas alone. 
 
 In the year 1798, Mr. Tennant, of Glasgow, took out a patent 
 for a new bleaching liquor, which was a solution of chloride of 
 lime instead of that of chloride of potash, and which he engaged 
 to sell much cheaper than the article that had been prepared by 
 the foreigners ; but as this was also sold in a liquid state, one of 
 the main objections to the Liquor de Javelle still remained. 
 
 In order, however, to remove this objection, Mr. Tennant 
 undertook to convey to several manufacturers, for the sum of 
 
400 ON BLEACHING. 
 
 200/. to be paid by each, a right to work under his patent ; and 
 this proposal having been accepted by many of the principal ma- 
 nufacturers, this method of chemical bleaching was soon very 
 generally adopted throughout the kingdom. 
 
 Some time after Mr, Tennant had made these arrangements 
 with several of the manufacturers, some spirited individuals un- 
 dertook to impugn the validity of his patent ; the consequence 
 of which was, that on the question being submitted to a legal de- 
 cision, the cause went in favour of the public, and the right of 
 patent was lost. 
 
 Since this determination, which gave great satisfaction to the 
 whole body of manufacturers, there has been no impediment to 
 the method of bleaching by chlorine gas ; and this chemical agent 
 was for some time prepared at most of the great works by the 
 proprietors themselves. 
 
 The peculiar advantages of combining the chlorine gas with 
 lime or potash, consists in this circumstance, that the saline so- 
 lution gives out the gas gradually to the goods which require 
 bleaching, but does not give it out with facility to the atmosphere. 
 In consequence of this, the operation of bleaching is now not 
 injurious, nor even very disagreeable, to the workmen ; whereas 
 in the former process, when the gas was merely received into 
 water, it was given out again so freely that no man could long 
 endure to work in it, or even for any considerable time to super- 
 intend the operation. 
 
 Now that I have ventured these remarks, the next step will be 
 to give an account of some of the MODERN processes in bleach- 
 ing, which I shall endeavour to do with as much brevity as is 
 consistent with perspicuity. It will be most convenient to begin 
 with the process of bleaching linen yarn and linen cloth. 
 
 In effecting this, the same methods are followed, as far as to 
 the fourth or fifth bucking, as were formerly employed in bleach- 
 ing linen long before the application of chlorine, and which have 
 already been detailed at page 391 ; only good washing is re- 
 sorted to instead of crofting. This being premised, the remain- 
 ing operations may be described with less difficulty. 
 
 It may be asked, Why is not chlorine now employed in these 
 first processes of bleaching linen goods ? The reason is, because 
 it would be too expensive ; for there would be a greater expen- 
 diture of the chlorine gas in the removal of the filth and the re- 
 sinous matter than is now incurred in the whole process, and these 
 are all taken out in a much cheaper way by the solution of alkali 
 and by repeated washings in pure water. The solution of chlorine 
 is not necessary for the removal of the resin, but it is indispen- 
 sable in discharging the colouring matter and the carbon. 
 
ON BLEACHING. 401 
 
 It should be recollected, that no bleaching can ever be carried 
 on to advantage, unless the water be pure and in great abun- 
 dance. Hence Scotland seems to be peculiarly calculated for 
 such establishments ; for, there are many parts of that kingdom 
 which abound with spring water that comes from the granite rocks 
 nearly in a state of absolute purity. 
 
 After the fourth or fifth bucking, the goods are immersed in a 
 solution of chloride of lime, and are then well washed by ma- 
 chinery in pure water. They are now carried to the souring 
 vessels containing a portion of very dilute sulphuric acid ; and 
 when taken out of these vessels, they are again well washed in 
 water ; and lastly, they are submitted once more to the alkaline 
 process mentioned at page 391. 
 
 This kind of goods requires at least three immersions in the 
 solution of chloride of lime, followed by an equal number of al- 
 ternate immersions in the sours and in the alkaline solution, care- 
 fully and thoroughly washing them in pure water between each 
 of these processes. It should be remembered, however, that 
 linens require generally a greater number of immersions in the 
 bleaching liquor than cottons, and also that the preparation be 
 less diluted with water. 
 
 By this method of bleaching, linen goods constantly acquire a 
 yellowish tinge ; this however is so superficial, that mere expo- 
 sure to the air for a few days generally removes it. The goods 
 are then finished by boiling them for a short time in a dilute so- 
 lution of pearlash and white soap. This last operation has the 
 effect of removing the disagreeable odour which otherwise would 
 for a long time be attached to every article bleached by this pro- 
 cess. It must here be remarked, that when cotton goods are 
 bleached after this manner, there is no necessity for crofting ; as 
 the yellow tinge just mentioned does not appear in them when 
 finished ; any stain of that kind being completely removed by the 
 sulphuric acid, though this acid will riot remove it from linen 
 goods. 
 
 There is a considerable trade now carried on in the bleaching 
 of hose. The following is the process usually adopted, the ac- 
 curacy of which may be relied on, as it was communicated to me 
 some years ago by one of the partners in an extensive manufac- 
 tory, who had come to London for the purpose of consulting me 
 respecting some difficulties which had occurred in their manu- 
 factory, and which at that time were attended with considerable 
 loss and inconvenience. 
 
 In the establishments for the manufacture of cotton hose, the 
 stockings are first scoured in soap and water, to divest them of 
 the oil and other impurities applied in the process of weaving; 
 
 2 D 
 
402 ON BLEACHING. 
 
 because the weavers of cotton hose always dissolve mutton suet 
 in melted soap, and pass the goods through the mixture. This 
 serves a double purpose ; it occasions the thread to work better, 
 and renders the goods heavier when they are returned in a finished 
 state to the owner. 
 
 It is in consequence of this practice that the bleacher is under 
 the necessity of scouring such goods in a solution of soap made 
 scalding hot ; for it would be in vain to attempt to bleach them 
 without first divesting them of this tallow, and of the dust and 
 other impurities which will unavoidably be attached to it. To 
 obtain this the more effectually, they are removed from the scour- 
 ing vessels into pure water and thoroughly washed, the water be- 
 ing changed as often as is considered necessary. Many inexpe- 
 rienced persons, who have begun the business of bleaching and 
 also that of dyeing, have failed of success in consequence of their 
 not being aware of the absolute necessity there is tor observing 
 the utmost cleanliness in both these occupations. 
 
 The second process consists in boiling the hose in a weak alka- 
 line solution, made by dissolving three pounds of American 
 pearlash in three hundred gallons of water. When boiled in this 
 lixivium, they are merely rinsed in clear water, and are then con- 
 sidered to be sufficiently prepared for being submitted to the action 
 of the bleaching liquor. The bleacher of piece goods would con- 
 sider this to be a very weak lixivium, for in that process it is not 
 an unusual thing to dissolve the above weight of caustic potash in 
 so small a quantity as ten gallons of water. 
 
 The bleaching liquor for cotton hose is prepared by mixing six 
 or eight quarts of the solution of chloride of lime, in the state in 
 which it is prepared at the still, with 20 gallons of water. In this 
 mixture the hose are immersed, and they are suffered to remain 
 an hour and a half or two hours. They are then taken out, and 
 washed thoroughly in cold water. 
 
 The process of immersion in the bleaching liquid is now re- 
 peated, and this is followed by boiling the goods in an alkaline 
 lixivium, as before. These processes of steeping in the chloride 
 of lime and of boiling in a solution of alkali, are repeated four 
 times alternately, and then the hose are generally found to be 
 bleached sufficiently. The necessity there is for these repeated 
 steepings in the solution of the chloride of lime, may be thus ex- 
 plained. The chlorine that is liberated decomposes a portion of 
 the water, the oxygen of which combines with the colouring mat- 
 ter, and renders it soluble in the alkali. 
 
 These processes being finished, the goods are then immersed 
 in diluted sulphuric acid, which has been so much lowered with 
 water that it is become little more acidulous than vinegar, and 
 may be taken into the mouth with perfect safety. This carries off 
 
ON BLEACHING. 403 
 
 any earth or other matter not sufficiently soluble in the alkali. 
 The steeping in this weak acidulous liquor is generally continued 
 about three hours, though sometimes the hose are suffered to 
 remain in it for a whole night. 
 
 It has been found, by repeated experiments, that so long as the 
 goods are actually immersed in the sours, they sustain no injury; 
 whereas, if they were taken out and suffered to become dry, their 
 texture would be much weakened, and the damage would be ir- 
 reparable. This, I have no doubt, is occasioned by the evapo- 
 ration of the water, by which the sulphuric acid attached to the 
 goods becomes concentrated and caustic. 
 
 To divest the hose of the remains of the sulphuric acid, they 
 are washed many times in cold water, and even submitted to the 
 action of a kind of fulling mill, called fuller s, which cleanses these 
 goods more effectually than could be done by any other method. 
 But so difficult is it to remove the last portions of the sulphuric 
 acid, that the manufacturers find it necessary, even after all this 
 washing, to immerse them in a hot solution of soap and vegetable 
 alkali, to finish their purification. The proportions are 4 pounds 
 of white soap, 1 pound of best pearlash, and 150 gallons of water. 
 This process is technically called scalding. This removes the 
 disagreeable smell of the chlorine gas, at the same time that it 
 improves the appearance of the goods to the eye, and occasions 
 them to feel softer. 
 
 The hose are now carried again to the fallers ; where they are 
 scoured and beaten in soap and water, as before, the remains of 
 which are perfectly washed out with successive portions of pure 
 cold water. This is said to complete the process of bleaching. 
 
 These goods are afterwards exposed to another process called 
 getting up, which is performed in the following manner. They 
 are put into a copper of hot water, containing a weak solution of 
 soap, with the addition of a little indigo, sufficient to give them 
 a tinge of blue, and then they are returned to the fallers to be 
 scoured in a still stronger solution of soap. This solution is strong 
 enough to produce an actual lather, and the remains of it are 
 thoroughly washed out with cold water, which finishes what is 
 called the cleansing process. The whitening effect of indigo when 
 laid on a yellow ground is very remarkable, and is well known to 
 laundresses. 
 
 When the operator has very fine goods to bleach, he has re- 
 course to a process somewhat different, which consists in immer- 
 sing them in a very hot solution of soap, with the addition of a 
 little ground indigo. The hot soap gives them a gloss which is 
 much approved of and occasions them to handle better than com- 
 mon hose, and the indigo improves their colour. The common 
 goods are immersed in indigo and water only. 
 
 2o 2 
 
404 ON BLEACHING. 
 
 When all these successive operations have been duly practised, 
 the hose are removed to the drying stove, where care is taken 
 that they shall be dried completely. From this they are carried 
 to a room called the brimstone stove, where they are entirely en- 
 veloped by the vapours of sulphurous acid gas, arising from the 
 burning of sulphur in a close chamber. 
 
 The use of this process is to decompose any portion of soap 
 that may still be attached to the surface of the goods ; for it has 
 been found that, if they are laid up for any considerable length 
 of time without their having undergone this operation, the smallest 
 portion of soap remaining in them will occasion them to turn 
 yellow. The manufacturer would, indeed, be glad to dispense 
 with the use of soap altogether; but there is no article besides 
 this that will effectually take away the smell of the chlorine gas. 
 
 When the hose are returned from the brimstone stove, they are 
 slightly damped with common water, to prepare them for the 
 finishing operation, known by the name of dressing. This con- 
 sists in drawing each stocking separately on a stocking-leg board, 
 in which state they are either put collectively into a powerful 
 press, or ironed singly with a hot box-iron. 
 
 These are the methods which are generally adopted in bleach- 
 ing and finishing thread and cotton hose, and they appear to be 
 so well adapted to their respective purposes, that but very few re- 
 marks upon them will be needful. 
 
 It occurs to me, however, that the goods might be materially 
 injured were they ever to be put into the brimstone stove in a 
 damp state ; for the vapour would then be condensed upon them 
 in the form of sulphurous acid; and when treated afterwards with 
 the hot iron, this acid would become concentrated and impair the 
 texture. When the hose are dressed by the press only, it is not 
 so necessary to attend to this circumstance. Another injury would 
 result from this management, viz. that, being put damp into the 
 stove, some parts would retain more water than others; and here, 
 I conceive, dark spots would arise should the goods be laid by 
 for a considerable time undisturbed, a circumstance which often 
 actually happens in the shop of the retailer. 
 
 Only one thing more occurs to me, which is this, that the omis- 
 sion of weaving the blue and the red lines in the top of hose which 
 are intended to be bleached, will conduce to injure the credit of 
 the manufacturer in foreign markets '. I propose, however, to 
 offer a few remarks on this at the close of the Essay. 
 
 Nothing has yet been said of the method of bleaching CALICOES 
 
 1 At the desire of a respectable bleacher in the county of Nottingham, I pub- 
 lished a few years ago some observations on this subject in the Tradesman s 
 Magazine. See vol. ii. p. 105. 
 
ON BLEACHING. 405 
 
 for the u.se of the printer / for this embraces a great number of 
 questions, and is a subject of very considerable difficulty. The 
 following is the process which is generally adopted in the neigh- 
 bourhood of Manchester, and throughout the county of Lan- 
 caster. 
 
 When the goods have been fired to remove the nap, as de- 
 scribed in the Essay on Calico Printing, they are steeped for a 
 certain time in pure water, usually until so much of the impu- 
 rities is loosened from them as occasions a very sensible fermen- 
 tation in the water, the time varying from twelve to twenty-four 
 hours ; or in soap and water, or in an alkaline lye which has 
 been already used in the process of bucking, or bowking, as it is 
 commonly called in this district. This appears to me, however, 
 to be a very bad practice, because such lyes are always very dirty 
 and loaded with resinous matter and other filth of a similar kind 
 to that which it is the object of the bleacher to remove. Nothing 
 but pure water, or clean lye, or good white soap and water, ought 
 ever to be employed for these steeps. The temperature at which 
 this steeping is conducted varies from that of 100 to 160 or 180 
 degrees, according to circumstances or the particular views of 
 the operator. 
 
 The pieces are then washed in pure water; in large works this 
 is done by means of a dash- wheel, which washes them more ef- 
 fectually than they could be by any other method; arid then they 
 are immediately bucked 2 , or boiled in a solution of caustic pot- 
 ash, and the boiling is continued for eight or ten hours. From 
 the boilers they are again taken to the wash-wheel, and cleansed 
 thoroughly. The process of boiling is repeated two or three 
 times, taking care to wash well after every operation. Each of 
 these boilings is usually continued for the same length of time, 
 but care is taken that the alkaline lixivium be reduced in strength 
 at every repetition of the process. In large concerns, where the 
 process of bleaching is continually going on night and day, the 
 boiling is generally done in the night, and the subsequent opera- 
 tion of washing is performed in the day-time. After two of these 
 boilings, some people pass the goods into the sours, whereas 
 others do not sour them until they have been three or four times 
 boiled. 
 
 The goods are then laid on the grass for two or three days ; 
 or, if crofting be not employed, an effect, similar to that which 
 would be produced by exposure to the atmosphere, is obtained 
 by an immersion in a solution of chloride of lime, of about the 
 specific gravity of 1*005. In this they steep for twelve hours; 
 
 2 For an account of the bucking apparatus, see the description of the plates 
 which accompany this volume, and also page 391 of this Essay. 
 
406 ON BLEACHING. 
 
 and then they are removed into sulphuric acid, diluted with 
 about forty times its weight of pure water. Mr. Murray says that 
 this last souring imparts a much finer whiteness to the cloth than 
 it would acquire without this treatment, as it dissolves the re- 
 maining colouring matter which had resisted the action of the 
 alkali and chlorine, as well as a small quantity of iron contained 
 in all vegetable matter, or deposited on the cloth from the alka- 
 line lyes. 
 
 After this, the pieces are washed with the greatest care in suc- 
 cessive portions of water, and are then hung up in the dry-houses, 
 to be dried completely for use, by a current of atmospheric air, 
 which is perpetually passing through them. 
 
 When the operation is to be performed on fine cloth, it is 
 usual to boil once or twice more in a still weaker solution of pot- 
 ash, and to finish them in strong sours, made by the mixture of 
 one measure of sulphuric acid with 46 measures of water, or one 
 pound of the acid to twenty-five pounds of water. This is not 
 because fine cloths require the most bleaching, but on account 
 of such cloth being generally used for the finest kind of printing; 
 for the heaviest pieces are generally the most difficult to bleach 
 perfectly. In some houses it is customary to lessen the weight 
 of the potash one-third for every subsequent boiling. 
 
 Some printers, instead of potash, use lime water, and others 
 even cream of lime for the first bowking ; washing and souring 
 being adopted the same as if potash were employed; but in these 
 cases care is taken not to allow the liquor to acquire more than a 
 scalding heat. 
 
 This is truly a cheap method ; but I conceive it to be a very 
 bad practice, because where this mode is adopted plenty of se- 
 lenite will unavoidably be formed in the cloth, and nothing will 
 perfectly remove it, It is well known to many printers whose 
 works are situated upon rivers, that if a piece which has been 
 thoroughly prepared, should by accident drop into the river at 
 the time of flood, when the water is charged with earth, it would 
 be entirely spoiled for the madder-copper. No kind of souring, 
 nor any mode of treatment, which we are at present acquainted 
 with, would repair the injury. 
 
 Some printers use the common potash of commerce, while 
 others employ an alkali which has been made completely caus- 
 tic by lime ; others, again, mix a portion of soft soap with the 
 potash for one or two of the first bowkings ; so far are these ma- 
 nufacturers from being agreed as to every particular respecting 
 these operations. 
 
 I must not, however, forget to mention that in large works, 
 after every process of ashing, souring, or bleaching, the pieces 
 are submitted to a powerful press, usually one of Brumah's, to 
 
ON BLEACHING. 407 
 
 force out the chemical liquor which remains in them ; and that 
 it is from the press they are taken, either to the river or to the 
 wash-wheel, for further purification. Some of the printers have 
 not yet adopted the use of the press ; but the professed bleachers 
 are aware of its importance, and employ it constantly. In se- 
 veral works, I find it is a common practice to pass the goods 
 through a pair of wooden rollers made of sycamore: these force 
 out a great deal of impurity, and they make all the pieces of an 
 equal dryness. This is not general, but I consider it to be an 
 eligible practice, and that it ought to be performed after every 
 operation. 
 
 Although I have now given a short account of the processes 
 which are employed in bleaching common calicoes, or what is 
 known in some districts by the term of surface-bleaching, I still 
 consider the series of operations to be very imperfect, because the 
 goods thus bleached are often unfit for the purposes for which 
 they are intended, and very frequent and serious losses have been 
 sustained in consequence of it, as every printer can testify. This 
 is very severely felt by those who print for hire, as such printers 
 are expected to make allowances for all imperfect work, arid these 
 are often so enormous as to absorb all the cost of materials and 
 the expense of printing. 
 
 A knowledge of this circumstance first induced me to turn my 
 attention to the subject of bleaching; and the hope of being able 
 to offer some useful hints to the consideration of practical men 
 laid the foundation of this Essay. 
 
 From frequent and repeated conversations with many of the 
 most intelligent bleachers in various parts of the kingdom, I have, 
 I presume, clearly ascertained that, in preparing goods for the 
 purpose of calico-printing, the following are the most important 
 desiderata. 
 
 First. To form such a preparation of bleaching liquid, with 
 the respective materials so nicely balanced, that neither the salt, 
 nor the fluid which remains after the abstraction of the chlorine, 
 shall have any injurious effect upon the fabric of the cloth. Those 
 who bleach with chlorine should never lose sight of the circum- 
 stance, that common muriatic acid is always produced at the mo- 
 ment when the oxygen of the water unites with the colouring 
 matter ; and that this acid, if not corrected by other ingredients, 
 will have an unfavourable action on the goods under operation. 
 
 Secondly. To bleach the calicoes in so perfect a manner that 
 each piece of every parcel shall be completely fit for madder- 
 work ; that is, when cleared after being dyed in a madder-cop- 
 per, that the whites shall be uniformly good and free from those 
 stains which the superintendants in this department of our ma- 
 
408 ON BLEACHING. 
 
 nufactures call spangs. For this purpose, some manufacturers 
 lay great stress on the use of an apparatus somewhat similar in its 
 principle to a Papin's digester, and known by the name of a whale- 
 boiler. For a description of this vessel, see the Plate No. 1 1 . and 
 the explanation of it at the beginning of the volume. 
 
 Thirdly. To prepare calicoes, so that they shall readily take 
 a light and uniform shade in the blue vat. Cloth dried in sum- 
 mer and in the open air, when the atmosphere is dry and warm, 
 dips much more freely in the blue vat than that which is dried 
 in winter, especially in frosty weather, when the pieces require 
 more exposure. In like manner, stove-drying is never esteemed 
 so good as tenter- dry ing, for any purpose of fine printing. 
 
 In dipping pale blues, the printer often sustains great loss by 
 the pieces coming out of the vat with white streaks, so as to ren- 
 der it necessary to bleach them afresh, and then to appropriate 
 them for the reception of other colours. This is occasioned by 
 a substance existing in the cloth, which resists the action of the 
 blue vat, and yet is not of sufficient consequence to rise to a spang 
 when it is afterwards passed into the madder-copper. 
 
 Every man has a different process for preparing his blue- vats; 
 therefore the want of uniformity in the shade of these colours 
 may sometimes arise from the vats being in bad order, or it may 
 be owing to the employment of bad indigo. I would suggest that 
 it might perhaps be advisable to appropriate a vat of either the 
 finest Guatarnala, or of the purest East Indian indigo, entirely to 
 the purpose of dyeing pale blues ; and that where the style of 
 work will allow of it, (though it often will not,) it might be worth 
 while to try whether superior dunging, previously to the blue dip- 
 ping, would prevent the evil complained of. 
 
 Fourthly. To prepare any number of pieces which shall be fit 
 for both the above purposes, yet still be preserved perfectly sound. 
 
 It is evident to me that, in effecting these points, the main dif- 
 ficulty originates with the weaver; and therefore, to those who 
 are not conversant with the business, it may be advisable to ex- 
 plain how this happens, before we attempt to suggest a remedy. 
 
 The weaver of calicoes generally proceeds thus. Having a fine 
 warp delivered to him, frequently spun beyond what the staple 
 of the cotton authorizes, and consequently not capable of bear- 
 ing much hardship, he is compelled to throw in as much weft as 
 will make the cloth of a very close texture; his only aim being 
 to accomplish this object with the least possible trouble, and at 
 the least expense. 
 
 As soon, therefore, as he has fixed the warp in the loom and 
 stretched it out ready for weaving, he dresses it by rubbing it 
 longitudinally between two brushes which have been previously 
 dipped in a paste made of potatoes, or flour and water. This 
 
ON BLEACHING. 409 
 
 paste is generally suffered to become sour before it is used, and 
 frequently it is kept in an iron kettle till this change takes place. 
 
 When this dressing has become dry, in order to make the 
 warp still smoother, he applies a different dressing, made with 
 such greasy or oleaginous matters as he can the most easily pro- 
 cure. This generally is either tallow or butter, and is sweet or 
 rancid as may accidentally happen; but tallow is the article which 
 is the most commonly used, and it is applied in the following 
 manner. The weaver having prepared a hot iron, he takes that 
 in one hand and a lump of tallow in the other, and pressing them 
 together, the tallow becomes partially melted and drops in patches 
 on various parts of the warp. This is afterwards dispersed and 
 spread over the whole warp, by means of the brushes which were 
 employed to spread the paste before mentioned. 
 
 Instead of tallow, why might not soft soap be employed ? It 
 would be desirable for some manufacturer to give this a fair trial. 
 Should it answer the weaver's purpose, it might afterwards be 
 readily removed by washing. 
 
 It will be manifest to those who have considered this mode of 
 procedure, that the subsequent spreading of the tallow cannot be 
 effected without the grease being left in the largest quantity on 
 those places where it was first applied. Accordingly, it is found 
 that these spots are often particularly discernible when the goods 
 come to be dyed, although the operator may have supposed that 
 they were well cleaned, having undergone the usual routine of 
 steeping, boiling, souring, bleaching, washing, printing, and 
 dyeing. For an account of some methods for examining the 
 goodness of the bleaching of white calicoes, see the Essay on 
 Calico Printing. 
 
 Printed calicoes are also often stained in larger blotches, 
 though not so conspicuous as those just mentioned, but evidently 
 arising from grease ; generally covering a larger portion of the 
 cloth, and very difficult to be removed. The workmen distin- 
 guish these by the name of copper stains, supposing them to have 
 arisen in the madder-copper from an unequal application of the 
 heat. This, however, is undoubtedly an erroneous opinion. 
 
 In reviewing the preceding observations the following ques- 
 tions suggest themselves. 
 
 If grease be the chief impediment to perfect bleaching, what 
 are the best means of removing it? Are any of the alkaline so- 
 lutions we have mentioned, capable of effecting its removal? In 
 answer to this query, I would say, Take caustic potash, properly 
 diluted with water, and not the dirty waste lye, an article often 
 resorted to. For, in preparing for fine madder-work, I am con- 
 fident that what is considered to be a cheap, economical, and, I 
 
4-10 ON BLEACHING. 
 
 may be permitted to add, dirty mode of bleaching, can never do. 
 On the contrary, for such work, the most expensive bleaching will 
 generally prove to be the cheapest eventually; for the pieces have 
 ,a better chance of being perfect, and the dyeing materials will go 
 further. 
 
 Is soap (either soft or hard) of any service in the process of 
 steeping, or that of boiling ? Is lime of itself a solvent for grease ? 
 If lime should be found to be adequate to this purpose, is there 
 any probability of its injuring the texture of the cloth when used 
 in the manner already described ? And is there not some danger 
 of particles of this earth remaining in the cloth after the most 
 careful washing, and of its forming a sulphate of lime by immer- 
 sion in the sours. 
 
 When goods have turned out spangged, is it advisable, in order 
 to prevent a repetition of the evil, and will it be consistent with 
 the preservation of the texture of the cloth, to have recourse 
 to more of the alkali, to greater heat, or to more frequent boil- 
 ings? Or is any other plan preferable to all or any of these? 
 Where perfect work is required, I conceive the proper answer to 
 this query to be this. Let the alkaline lye be reduced in strength, 
 and then let the usual number of boilings be doubled. That is, 
 let them be boiled at least seven or eight times. 
 
 On the principle of boiling in a vessel somewhat analogous to a 
 Papin's digester, what degree of heat can be employed with safety 
 to the cloth? It will be seen, that in the common process of boil- 
 ing the pieces, the lye being weak and exposed to the pressure of 
 the atmosphere it can never much exceed the temperature of 212. 
 
 What is the substance contained in cotton which resists the 
 action of the blue-vat, or of cold water, and yet does riot act as a 
 mordant in the madder-copper? I am disposed to think that this 
 is a question which, in the present state of chemical knowledge, 
 no one is able to answer, although it is well known to every 
 printer of the present day, that such a substance does exist, and 
 that it often occasions much trouble and perplexity. 
 
 What is the cause of those marks called copper-stains, already 
 noticed ? Are they owing to a portion of alkali being left in the 
 cloth during the operations of bleaching, or may they may be as- 
 cribed to insufficient washing after the process of dunging? These 
 are certainly not copper-stains but are possibly owing to improper 
 bleaching. It is likely, indeed, in most cases, that these would 
 not have appeared, had the bleaching been prolonged or the dif- 
 ferent operations oftener repeated. 
 
 The whole of these questions seem to arise naturally from a 
 due consideration of this subject, and all of them, I believe, have 
 at one time or other been proposed to me by various practical 
 men, for my opinion ; a circumstance which convinces me that 
 
ON BLEACHING. 
 
 much remains to be done before the art of bleaching calicoes for 
 the use of the printer shall have attained that degree of perfec- 
 tion of which many other arts can already boast. 
 
 When the process of bleaching by chloride was first practised, 
 the art of calico-printing may be said to have been in its infancy, 
 and consequently very little variation was then made in the ope- 
 ration of bleaching the brown pieces, whatever might have been 
 the style of work for which they were intended. When the 
 competition was less, the perfection of bleaching was compara- 
 tively of small importance. But now the case is materially altered, 
 and all the best printers know, that the common routine of pro- 
 cesses, and such as I have described at page 404, is insufficient 
 for bleaching calicoes which are designed for best madder-work. 
 The common mode of bleaching is not sufficient, because goods 
 so treated are never fully bleached internally; and, therefore, 
 when they come into the madder-copper, the remaining impuri- 
 ties will in some measure rise to the surface, and there becoming 
 a mordant for the madder, will occasion those parts of the cloth, 
 which were intended to be preserved w f hite, to acquire an indelible 
 stain, or at least will inevitably produce what are called dull whites. 
 To remedy this, nothing will prove effectual, I suspect, but to 
 increase the number of the operations, as mentioned above, and 
 to conduct every process with the strictest regard to cleanliness, 
 and to the purity of the articles employed. Here I had more 
 particularly in mind the practice of using old dirty alkaline solu- 
 tions ; but it will also be equally impossible to produce fine 
 bleaching where the goods, at all times of the year, can be washed 
 only in a river; because in time of flood the water will be charged 
 with calcareous earth, which afterwards, when they are immersed 
 in the sulphuric acid, will form an insoluble selenite within the 
 pores of the cloth. 
 
 Knowing that a great deal of very excellent bleaching is ac- 
 complished in Scotland, I have procured from a scientific printer 
 in that part of the kingdom, an exact account of the plan he pur- 
 sues whenever he bleaches calicoes for madder-work, or resist- 
 work, or for the fine pale blue-dipping, and which he assures me 
 I may recommend with confidence. The following concise out- 
 line of the process will, I trust, be sufficiently explicit to be un- 
 derstood by every practical man. 
 
 The goods having been singed and steeped in pure water, as 
 is customary in common bleaching, they are passed through a 
 pair of rollers to press out the impurities which have been loosened 
 by the steeping. It must here, however, be observed, that where 
 the expense of one extra dyeing can be afforded, the process might 
 be very much improved by steeping the brown calicoes for thirty 
 or forty hours before singeing, because this would separate much 
 
4-12 ON BLEACHING. 
 
 of that impurity which usually becomes fixed in the stuff on its 
 being passed over the hot cylinders. When the pieces have been 
 thus singed, steeped, and pressed, they are boiled four times, ten 
 or twelve hours at e&ch time, in a solution of caustic potash, of 
 the specific gravity of from 1-0127 to ] -0156, washing them care- 
 fully and thoroughly in pure water between each of these boil- 
 ings. They are then immersed in a solution of the chloride of 
 potash, originally of the strength of 1 -0625, and afterwards re- 
 duced with twenty-four times its measure of water. The specific 
 gravity of the chloride of lime or of potash, is not an absolute 
 rule for the determination of the bleaching power of either ; for, 
 sometimes the specific gravity will be what it ought to be, and 
 yet the liquor, owing to the impurity of the materials, will be 
 nearly effete. For this reason, the solution of indigo is generally 
 employed to ascertain the goodness of all bleaching liquors. 
 When the preparation is good, the proportions mentioned above 
 will whiten cotton goods completely in eight hours. In this pre- 
 paration they are however generally suffered to remain twelve 
 hours. It is of importance to remark, that here the common 
 bleaching liquor (chloride of lime) cannot, without injury, be 
 substituted for chloride of potash. 
 
 Some printers take the pieces from this solution, and, while 
 wet, lay them on the grass, and there expose them to the sun and 
 weather for two or three days. From thence they are removed 
 to the sours, made of the specific gravity of about 1*0254- at the 
 temperature of 1 10 degrees of Fahrenheit. In bleaching common 
 goods, and such as are not designed for the best printing, the 
 specific gravity of the sours is varied from that of 1 -014-6 to that 
 of 1*0238, if taken when they become of the temperature of the 
 atmosphere. In these they are suffered to lie for five or six 
 hours, after which they are taken to the wheel and washed tho- 
 roughly. When this operation is finished, they are submitted to 
 four more boilings as before, with a solution of caustic potash; 
 taking care to wash well between each of these boilings. Some- 
 times pearl-ash, made caustic, is used for the last of these boilings, 
 lest the sulphur, which always exists in the potash of commerce, 
 should impair the whites. They are then immersed in the diluted 
 chloride of potash, of the strength before mentioned ; after which 
 they are well washed in pure water, and then winched for half an 
 hour in common sours. The last process is that of careful wash- 
 ing in plenty of clean water, after which they are not put into the 
 stove, but are immediately hung up in the airing sheds to dry 
 gradually. I know several print-works where it would be im- 
 possible to produce fine bleaching, because they are not supplied 
 with a sufficiency of water. For this purpose the water must be 
 good, and there ought to be plenty of it at all seasons. 
 
ON BLEACHING. 413 
 
 The number of operations, as here described, is great; but I 
 know of no other mode of procedure by which perfect bleaching 
 is so likely to be effected at all times and in all seasons, without 
 disappointment. It must here be remarked, that, for the best 
 purposes of printing, it would not be sufficient to take goods 
 which have been bleached in the common way and finish these 
 by the better process; because the selenite deposited in the cloth 
 by that operation, will for ever spoil them for madder colours ; 
 at least, a printer who is curious in his work would not dare to 
 use such for those purposes. 
 
 Whilst I am upon the subject of bleaching, it will be necessary 
 to mention that print-clearing powder, which is chloride of lime 
 mixed with about one-tenth part of its weight of carbonate of 
 soda, is now employed in clearing the whites of maddered goods, 
 and that this has almost entirely superseded the operation of 
 crofting, which was a tedious and expensive process. The me- 
 thod is to mix a small portion of the powder with a large quantity 
 of warm water, and then to suffer the maddered pieces to lie in 
 this preparation till the grounds become perfectly white. 
 
 This, which is one of the last improvements in calico printing, 
 is of very considerable importance; for, the finest ginghams, as 
 they are called, and the most expensive chintz work, which con- 
 tain a variety of very delicate colours, and formerly required many 
 weeks exposure on the grass, can now be cleansed in a few hours, 
 so as to produce the most perfect whites, without impairing any 
 of the colours themselves. 
 
 In conducting this process, it is of the utmost consequence to 
 attend to the precise strength of the preparation of chlorine, that 
 it may be strong enough to clear the whites completely, and yet 
 incapable of discharging or impairing any of the printed colours. 
 This is usually ascertained by means of a very dilute solution of 
 sulphate of indigo, prepared in the following manner. 
 
 One pound of the best Spanish indigo that can be procured, 
 is to be dissolved by the usual method, in four pounds of con- 
 centrated sulphuric acid. These proportions will generally sa- 
 turate each other. When the whole of the indigo is dissolved, 
 one part by measure of this solution is to be diluted with sixteen 
 parts by measure of water, and then it will be fit for use. To 
 obviate any deception which might arise in case of a difference 
 in the quality of the indigo, it is always best to preserve some of 
 the old solution, and then, having compared the new with this, 
 to alter the proportion of water a little, if this be found necessary. 
 The quantity of water which is employed in diluting the solution 
 of indigo is not very material, provided the operator accustoms 
 himself to the use of one certain determinate proportion ; and 
 indeed this test is used of various degrees of strength according 
 
414 ON BLEACH I NQ. 
 
 to the fancy of different printers; but one printer should always 
 use it of one particular strength. 
 
 The object in making this preparation is to have a standard 
 always at hand, by which the printer can with precision ascertain 
 the exact strength of any of his bleaching liquor; and this is al- 
 ways to be determined by the quantity of it that is required to 
 destroy the colour of any given portion of the test, or vice versa. 
 
 In employing this reagent, it is customary to have two long 
 graduated glass tubes, in one of which the diluted sulphate of 
 indigo is put, and in the other the bleaching liquor. By gra- 
 dually pouring some of the former into the latter, it is imme- 
 diately seen how much of the coloured test is destroyed, by a 
 given number of parts of the preparation of chlorine. This, 
 however, for the reasons already adduced, is not a sufficient test 
 of itself for ascertaining the goodness of a bleaching liquor with- 
 out attending also to its specific gravity. 
 
 The compressed steam of boiling water has been lately em- 
 ployed instead of chlorine in bleaching cottons. It is said that 
 this method of bleaching has long been practised in some parts 
 of the East. Chaptalwas the first writer who recommended it to 
 the European bleacher '. By the continued and alternate im- 
 mersion of cotton goods in an alkaline liquor, and the exposure 
 of them to the action of the vapour arising from the same lixivium 
 when heated to 220 or 230, the goods are said to be whitened 
 very effectually without the fabric sustaining any injury. The 
 resinous and other colouring matter of the cloth, which is inso- 
 luble in a dilute solution of alkali at the temperature of boiling- 
 water, becomes soluble in this menstruum, when heated a few 
 degrees beyond that point. The operation consists, first, in im- 
 mersing the goods in the alkaline lixivium, and then exposing 
 them to the heated aqueous vapour ; and these methods are pur- 
 sued alternately till the whitening is completely attained. 
 
 This mode of bleaching linen goods has been adopted in France 
 for domestic washing. Chaptal tried it on 200 pair of sheets be- 
 longing to the Hospital of the Hotel-Dieu of Paris, with the ut- 
 most success. The linen was perfectly cleansed, and the expense 
 was reduced in the proportion of four to seven 2 . I have had no 
 opportunity of observing the effect of this process myself: but I 
 can easily conceive that a superior temperature may be of service 
 in bleaching, because I have noticed that when brown calicoes, 
 which have undergone only one boiling, have lain all night in the 
 
 1 See his Chemistry applied to the Arts, vol. iii. p. 100. Delametherie also 
 wrote a memoir upon it in the Journal de Physique for the year 1801, at p. 305, 
 of which some account may be seen in Nicholson's 4to Journal, vol. iv. p. 4G9. 
 
 * For the details see Annales de Chimic, tome xxxviii. p. 291. 
 
ON BLEACHING. 415 
 
 kier, or whale boiler 8 , those parts of the pieces which had been 
 in immediate contact with the iron fountain, standing in the mid- 
 dle of the apparatus, were quite white, while the others were very 
 little improved in colour by the operation. This I attribute to 
 the lengthened continuance of a high temperature, as a great 
 degree of heat is always communicated to the middle of the vessel, 
 by the constant circulation of the boiling liquor through the foun- 
 tain, the metallic part of which, at times, may perhaps exceed the 
 temperature of 212. 
 
 The bleaching of linen and cotton goods by means of com- 
 pressed steam, will however be always attended with some diffi- 
 culty on account of the danger of the bursting of the apparatus 
 by the force of the confined vapour, if the valves should ever be 
 improperly loaded : but, notwithstanding this objection, it ap- 
 pears to me that the practice deserves further investigation ; for 
 it would doubtless be a great advantage to the arts, if it were pos- 
 sible to bleach our manufactured goods in as short a time as they 
 are at present finished, and yet save the expense of chlorine alto- 
 gether. The apparatus employed for this purpose in Great Bri- 
 tain is generally made with large slabs of stone cramped together 
 with iron, and sufficiently massy to sustain the effects of great 
 pressure. 
 
 It was originally my intention to have offered some remarks 
 on the methods of bleaching wool and woollen goods, silk, bees- 
 wax, writing paper, books, prints, &c. : but as the Essay has 
 already exceeded its prescribed bounds, I must content myself 
 by merely referring the reader to the sources from whence he 
 may obtain some information on these subjects. 
 
 Wool has usually been bleached by the fumes arising from the 
 slow combustion of sulphur, an article which was employed six- 
 teen hundred years ago for the same purpose. It has, however, 
 been found that this mode only whitens the surface of the goods : 
 therefore, of late years, recourse has, in some instances, been had 
 to the liquid sulphurous acid, which bleaches wool more effec- 
 tually than that acid does when in a gaseous state. Some ac- 
 count of the usual process by the means of sulphurous acid gas, 
 may be seen in Pajot Des Charmes' Art of Bleaching, translated 
 by Nicholson, 8vo. London, 1799, page 280. The burning of 
 brimstone in atmospheric air is called the slow combustion, in 
 opposition to the burning it in oxygen gas, or by the mixture of 
 nitre; but Stahl has shown that in bleaching woollen, the more 
 slowly the sulphur is burnt, the more effect will it produce. 
 Apuleius, who lived in the time of the Antonines, tells an anec- 
 
 3 For an explanation of the nature of this apparatus see the description of 
 the plates. 
 
416 ON BLEACHING. 
 
 dote, in the Romance of the Golden Ass, of a fuller who unex- 
 pectedly bringing home n friend to sup with him at the instant 
 when his wife was engaged with a gallant, she on the sudden 
 alarm hides him in the wicker apparatus which had just been 
 employed to bleach garments by the fumes of burning sulphur. 
 Presently, while they are at supper, the gallant stifled with the 
 fumes sneezes aloud ; the fuller removes the coop, and the poor, 
 panting, half-smothered culprit is discovered. It appears from 
 this story, that the ancient fullers bleached their woollen cloths 
 by hanging them round an apparatus made of wicker work, and 
 then setting fire to a portion of sulphur placed underneath it. 
 Messrs. Roland, Laplatiere and Allard, who were general in- 
 spectors of manufactures in France, published several memoirs 
 on the bleaching of wool, and the above account by Charmes ap- 
 pears to have been taken from these papers. 
 
 In bleaching bees-wax the following is the process, as it is 
 usually conducted in England. Common bees-wax is melted 
 upon hot water ; and when in a fluid state, it is laded out of the 
 copper, together with a part of the water, into a wooden vessel, 
 and in this it is allowed to remain a few hours for the impurities 
 to subside from it. The purified wax is then put, while still hot, 
 into a cullender full of holes, through which it runs, and falls upon 
 a revolving metallic roller, which dips into cold water contained in 
 a vessel placed underneath. As the melted wax runs through the 
 cullender upon the revolving roller, the motion of the cylinder 
 forms it into thin shavings, which cool as they come in contact 
 with the water, and fall in an accumulated heap into the water 
 below. These shavings of wax being now in a suitable form for 
 absorbing oxygen, they are taken out of the tub, and exposed in 
 a field to the action of the atmosphere till they become sufficiently 
 white. 
 
 A memoir by Baume on the bleaching of silk will be found in 
 Nicholson's 4to Journal, vol. i. pp. 32 and 88. This memoir, 
 which is extremely interesting, was first published in the Journal 
 de Physique, torn. xlii. p. 376, &c. The method consists in di- 
 gesting the silk in a large quantity of spirit of wine previously 
 mixed with a few ounces of muriatic acid. Some account of the 
 bleaching of bees- wax may be seen in Fourcroy's System of Che- 
 mistry, vol. x. p. 483. 
 
 The specifications of several patents which have been obtained 
 of late years for divers modes of bleaching paper, may be read in 
 the Repertory of Arts: and ample directions for bleaching old 
 copper-plate engravings and old printed books, will be found in 
 ChaptaFs System of Chemistry applied to the Arts, vol. iii. p. 108. 
 A memoir by Loysel on the bleaching of pulp for making paper 
 may be seen in the Annales de Chimie, torn, xxxix. p. 137. 
 
ON BLEACHING. 
 
 The art of bleaching has also been introduced of late years 
 into the straw manufactory. The manufacture of straw into the 
 form of hats for females has become very considerable, and con- 
 sequently important, especially as it gives employment to a very 
 great number of the children of the poor. I have not yet learned 
 the methods employed for bleaching the straw when it is intended 
 for white hats, but a 1'riend of mine has assured me that the sul- 
 phurous acid is employed. 
 
 I have now only to make a few desultory observations which I 
 conceive may be useful, and with these I shall close the Essay. 
 
 In a large bleaching establishment it is of great importance to 
 know how to procure manganese of the best quality. There are 
 several mines of this mineral in various parts of these islands, of 
 very variable qualities. Many kinds are of little value to the 
 bleacher, inasmuch as they require a larger portion of sulphuric 
 acid and yet produce less oxygen. Those, however, which con- 
 tain the largest proportion of the crystallized oxide are generally 
 to be preferred. 
 
 Being desirous of obtaining the best information respecting 
 manganese, I took an opportunity, in the year 1810, of visiting 
 the celebrated mine of Upton Pine in the county of Devon, 
 where, from the proprietors themselves and from some of the 
 intelligent inhabitants of the neighbourhood, I learnt several 
 particulars which may be worth recording. 
 
 This mine is situated between the two turnpike roads from 
 Exeter to South Moulton and from Exeter to Crediton, and, as 
 far as I could collect, had then been worked about forty years ; 
 though at first the quantity of the manganese that was raised was 
 small, as it was then employed only in the manufacture of glass, 
 and in some processes in the Staffordshire potteries. This mine 
 was accidentally discovered by a person passing along the road ; 
 as the mineral originally came out at the surface of the ground, 
 and the roads in the neighbourhood were occasionally repaired 
 with it. 
 
 Some thousand tons of manganese and loose earth having been. 
 removed, the mine is now in such a state as to allow persons to 
 descend into it by a winding path cut within the hill, and which 
 conducts to the foot of a perpendicular rock fifty feet high. The 
 entrance into that part of the mine which is now worked is through 
 an archway cut in the face of this rock. An immense quantity of 
 manganese having been raised since this entrance was made, the 
 excavations are now of considerable extent, the upper ground 
 being supported by large masses of manganese which are left for 
 pillars. Here, by help of a pick-axe, I broke off some tine spe- 
 cimens of the mineral. 
 
 At some distance from the entrance of which I have been 
 
418 ON BLEACHING. 
 
 speaking, two shafts are sunk of the depth of fifty feet each, which 
 lead to the lowest part of the mine, and which I was desirous of 
 exploring, as I could distinctly hear the men at work under my 
 feet : but being told that I could not descend without being tho- 
 roughly wet, and having no dress with me fit for the undertaking, 
 I was induced to decline the offer which the superintendant made 
 of accompanying me. In order to drain the mine as well as pos- 
 sible, without an engine, they sink as low as they can in the first 
 instance, and then work upwards to get the mineral. The part 
 which I explored is 50 feet below the surface of the ground, and 
 the part they were then working is 50 feet lower still. 
 
 The captain of the works informed me that the lode runs north- 
 east and south-west; and from his account I calculate that it dips 
 regularly at an angle of 40 degrees. In some places the vein is 
 twelve feet thick, in others not more than two feet. The capel, 
 as they call it, which covers the mineral, is a hard rock composed 
 of a mixture of sand, red clay, and manganese. 
 
 It was usual with the bleacher, to cast away the residuum of 
 the stills as a worthless article; but it is now consumed in large 
 quantities by the manufacturers of carbonate of soda, who de- 
 compose the alkaline sulphate by means of carbonaceous matter 
 and lime in reverberatory furnaces, and obtain the soda very 
 pure and in beautiful large white crystals. It is also used largely 
 in making Glaubers salt, which is effected simply by dissolving 
 the residuum, decomposing the salts of manganese, and precipi- 
 tating the oxide of that metal by means of lime, filtering the clear 
 solution, evaporating it to the proper strength, and then setting 
 it by in shallow vessels to cool and crystallize. 
 
 M. Humboldt has found that seeds which do not commonly 
 germinate in our climates, and which of course we cannot hope 
 to naturalize, become capable of doing so when immersed for 
 some days in a weak solution of chlorine; and I am anxious to 
 remark, that gardeners, whose grounds are in the neighbourhood 
 of bleach-fields, would do well in availing themselves of all the 
 advantages their situation affords them for making experiments 
 on this interesting and important subject. 
 
 In bleaching with chlorine, it is of consequence to expose all 
 the surfaces equally, and in proper succession ; for, when the 
 goods lie one upon another, the gas does not properly penetrate 
 them, and they are never uniformly bleached : whereas, in the 
 bucking process, with the solution of potash, they are disposed 
 as it were in masses of a considerable thickness, and the opera- 
 tion still goes on well. It was probably the knowledge of this 
 circumstance which has induced many bleachers to have their 
 vessels constructed very broad and shallow ; but this has occa- 
 sioned another very serious inconvenience. The chlorgdes beiii 
 
ON BLEACHING. 419 
 
 more liable to lose the chlorine the greater the surface of the ap- 
 paratus be in which the liquors are exposed, it is more difficult 
 for the men to secure themselves from injury, and the waste is 
 much more considerable. Where there is a contrivance for ex- 
 posing all the surfaces equally to the action of the bleaching li- 
 quor, the deeper the vessels are in comparison of their diameter, 
 the better will they be adapted to convenience and economy. 
 
 It is also important to rinse the goods immediately after they 
 come out of the alkaline liquor. It is no unusual thing for the 
 manufacturer to allow them to lie in heaps for a considerable time 
 before washing. But this I conceive to be a bad practice; for 
 while the goods are warm the pores are open, and the filth which 
 has been loosened by the recent action of the alkali, will be more 
 effectually removed by washing immediately than if they be al- 
 lowed to lie till they become cold. 
 
 In order that no waste of alkali should arise in the process of 
 boiling or bucking the calicoes, it has been customary with many 
 persons to use the lyes a second and a third time, and often to 
 the great injury of the goods which are so treated. Instead of 
 this, I would advise, that all such impure lyes should be concen- 
 trated by evaporation, and, when of a due consistence, removed 
 from the evaporating pan to the floor of a small reverberatory 
 furnace similar to that described in the plates. Where there is 
 a convenience for fully concentrating such waste lyes by evapo- 
 ration, a common baker's oven might be employed for the subse- 
 quent calcination, provided the precautions were taken in heating 
 it which are advised by Pajot des Charmes, p. 87 of his well- 
 known work on this subject. In such a furnace they would easily 
 be purified, because a gentle calcination would burn the colour- 
 ing matter and restore the alkali to its original state. In districts 
 where coal can be had cheap, and the consumption of alkali is 
 considerable, this would be a very economical process. 
 
 Nothing now remains but to redeem the pledge which I gave 
 at page 404, to offer a few remarks on the introduction of the 
 blue and red stripes, which are often seen at the top of cotton 
 hose. But these remarks must be very brief. 
 
 Although the bleacher of hose may easily determine the real 
 quantity of bleaching liquid to be used, yet there is still consider- 
 able risk in the process, and a danger of the texture of the arti- 
 cles being in some measure injured if the operation be conducted 
 with carelessness, or by those who are unacquainted with the 
 properties of the bleaching liquor. On this account, therefore, 
 it is desirable that the public should be acquainted with a test 
 that would in every case show, whether the chemicals had been 
 properly applied or not; or, in other words, whether the goods 
 
 2 E2 
 
420 ON BLEACHING. 
 
 which an individual may be about to purchase, have or have not 
 been impaired by the process of bleaching. 
 
 The makers of thread and cotton hose were so convinced of 
 the importance of having a test of this kind, that some few years 
 ago the principal manufacturers adopted the practice of running 
 a line of vat-blue thread dyed very dark, or of Turkey-red, along 
 the top of each stocking; and those bleachers only were employed 
 by them who could render the hose beautifully white, without 
 effacing the blue or red stripes, or even lessening their intensity 
 of colour. 
 
 The chloride of lime will destroy indigo-blue or the Turkey- 
 red dye, if it be used of a considerable strength ; and yet it may 
 be so diluted, that it will be strong enough to bleach linen or cot- 
 ton goods effectually, and still be incapable of injuring the colours 
 above mentioned. On this account it appears to me that these 
 dyes will always afford excellent tests for ascertaining when the 
 bleaching process has been properly or improperly conducted. 
 
 Great advantages might indeed accrue to the manufactures 
 of this country if the makers of plain calicoes, dimities, hempen 
 cloths, cambrics, and Irish linens, as well as the makers of cotton 
 hose, would adopt the method of running a line of such coloured 
 threads along one of the edges of their goods, before they send 
 them to be bleached ; and that they would employ no bleacher 
 who would not engage to preserve those colours entire, and of 
 their original perfection or intensity. 
 
 This expedient can never be of use for printed cottons, because 
 the varied processes to which white calicoes are usually submitted 
 by the printer, would inevitably destroy the indigo-blue, and pro- 
 bably the Turkey- red line also. It can be of use as a test of good 
 bleaching only, when the goods are intended to remain white. 
 
 The following are some of the sources from whence further 
 information may be obtained on the subject of this Essay. " Ad- 
 ditions to the Description of the Bleaching Process in France," 
 by M. Berthollet, tome vi. of the same work, page 204% " A 
 Letter from M. D. Hellancourt to M. Lavoisier, giving an Ac- 
 count of the Method of bleaching Cloth in Beauvoisis in Flanders, 
 and in Lower Picardy," tome vii. page 263277. " Memoir on 
 the Distillation of Manganese with Sulphuric Acid," by Vau- 
 quelin and Bouvier, tome vii. page 287. " The Manner of pre- 
 paring at all times, and in all places, and at little cost, a sapona- 
 ceous Liquor for whitening Cloth." Pelletier, tomexix. page 349. 
 
ON WATER. 421 
 
 ESSAY XIII. 
 
 ON WATER. 
 
 IN the beginning of the last century it was supposed, that there 
 were four elementary bodies in Nature, and that this terrestrial 
 world was entirely composed of those elements. Of these first 
 principles, WATER was one; and consequently this was always 
 considered to be a simple substance that entered into the com- 
 position of most other bodies, but was itself incapable of decom- 
 position. 
 
 The ancient Persians looked upon water as the principle of all 
 bodies, and many other ancient nations considered it to be the 
 first principle of all created things. Milton likewise favours the 
 idea : 
 
 " On the watery calm 
 
 His brooding wings the spirit of God outspread, 
 
 And vital virtue infus'd, and vital warmth 
 
 Throughout the fluid mass." Parad. Lost, book vii. line 234. 
 
 The same doctrine is also taught in the Koran. " Do not the 
 unbelievers therefore know that the heavens and the earth were 
 solid, and we clave the same in sunder, and made every living 
 thing of water?" Sale's Koran, vol. ii. p. 155. 
 
 Of late years, however, it has been discovered that this notion 
 of the simplicity of water is erroneous, and that the four sub- 
 stances which the ancients had fixed upon as the simple elements 
 of Nature are themselves all compound bodies. 
 
 Water is composed of oxygen and hydrogen in the proportions 
 of 8 parts by weight of the former to 1 of the latter ; so that 8 
 ounces of oxygen gas when united with 1 ounce of hydrogen gas 
 will form 9 ounces of water. Some experiments by Ritter seem 
 to prove that frozen water contains a less proportion of oxygen. 
 These were communicated by Professor Jameson to Mr. J. Mur- 
 ray, who has given an interesting account of them in the 2nd 
 volume of his System of Chemistry. The most beautiful, and 
 apparently the most decisive of these experiments, is that of dif- 
 fusing in various portions of water a quantity of newly prepared 
 white prussiate of iron, (a substance which, by the blue colour 
 it assumes when it receives oxygen, is a very delicate test of that 
 principle,) and excluding the action of atmospheric air by a thin 
 
422 ON WATER. 
 
 layer of oil on the surface of the liquid. These vessels were ex- 
 posed to various degrees of cold, and as soon as the water in either 
 of them froze, the white precipitate became blue. 
 
 Since the compound nature of water has been understood, many 
 ways have been discovered of decomposing and re-forming it 
 from its original elements, so that there is now no longer the least 
 doubt either of its composition, or of the proportion of each of 
 the elements of which it consists. 
 
 Water may be decomposed by the agency of some combustible 
 substances ; also by means of common Voltaic electricity. Vege- 
 tables of all kinds, while alive and fresh, are likewise furnished 
 with organs for the decomposition of water, by which they ap- 
 propriate its hydrogen and part of the oxygen to the formation 
 of oil, sugar, starch, and numberless others of the combinations 
 to which we apply the term vegetable principles. 
 
 Fish, especially those of the cetaceous tribe, constantly decom- 
 pose water and live upon its hydrogen. We have also reason to 
 believe that some terrestrial animals are endowed with the same 
 faculty. Count Rumford in his Essays, vol. i. p. 194, has very 
 satisfactorily shown, that the surprisingly small quantity of so- 
 lid food which is sufficient for nourishment when converted into 
 rich and palatable soup, is owing to the culinary process having 
 prepared the water for decomposition, and that this is ultimately 
 effected during the act of digestion. I suspect that tainted wooden 
 vessels have the property of decomposing water. It is related in 
 the Philosophical Transactions, that a company of English who 
 had provided themselves with good wholesome water at St. Jago, 
 which was put into hogsheads, found on their arrival at the Island 
 of Borneo, that the water was become exceedingly fetid, and 
 that it emitted a vapour which caught fire on a lighted candle 
 being brought near it. An account of a similar change in some 
 water taken from the Thames, may be seen in the same work, 
 No. 268, p. 838. It is a curious fact, that if an electric spark be 
 passed through oxygen and hydrogen gases, whatever may be the 
 proportions of the mixture, 8 parts by weight of oxygen and 1 
 of hydrogen will be the only proportions that unite to form water, 
 arid that the remainder will still continue in the state of gases. 
 
 There can be no doubt that water is also decomposed in many 
 of our chemical processes, and that the effects which are pro- 
 duced in some of our manufacturing operations are owing en- 
 tirely to the same cause. I will adduce one instance. 
 
 Considerable advantage is derived by the woollen-dyers from 
 the use of water in the preparation of rasped logwood. As the 
 wood is cut into chips, they sprinkle it abundantly with water, 
 and in that moistened state it is thrown into large heaps, and 
 sometimes into bins of great size, where it is suffered to lie 
 
ON WATER. 425 
 
 as long as is convenient. By this treatment the chips become 
 heated, or they ferment as the dyers call it, and thus undergo a 
 very remarkable change ; for, after having lain a few months in 
 this state, they give out the colouring matter in the dyeing cop-' 
 per much more easily ; and any given quantity of such chips will 
 produce a more intense dye than could have been obtained from 
 an equal quantity of chips which had not been thus treated. It is 
 difficult to account for this, unless we suppose that the water be- 
 comes in part decomposed, and that its oxygen, uniting with the 
 vegetable colouring matter, renders it more intense, similar to 
 the case of fruits, which deepen in colour as they ripen, by their 
 gradual absorption of oxygen. 
 
 From the observations which I have made during the super- 
 intendance of a variety of chemical processes, I think I am jus- 
 tified in asserting that, whenever this subject comes to be tho- 
 roughly investigated, it will be found that water has more to do 
 in influencing the results of most of the operations of nature and 
 art than has generally been imagined. This will perhaps appear 
 probable, when it is considered that water is a solvent for the al- 
 kalies as well as for almost all saline bodies, acids and earths ; 
 and that by its decomposition it often imparts oxygen to one 
 principle and hydrogen to another. 
 
 It is from this idea that I am induced to fix upon water as one 
 of the subjects of these Essays, with a view of directing the at- 
 tention of our various artists and manufacturers to this one par- 
 ticular point. 
 
 The subject is so important, and embraces such a variety of 
 matter, that it would be impossible in the course of a short essay 
 to enter into that amplification of detail which the matter de- 
 serves. A history of the different opinions respecting water, and 
 of the progress of the various discoveries in this branch of na- 
 tural philosophy, will therefore not be expected ; but if such evi- 
 dence can be adduced as will be sufficient to convince the in- 
 quiring reader that the most common fluid we have, and that 
 which is the least thought of, is capable of effecting the most im- 
 portant; changes in the materials on which he operates l , or of 
 producing results which will at times disappoint all his expecta- 
 tions ; something will be done towards informing the public mind, 
 or, at least, the young manufacturer will be furnished with an 
 idea that may be of use to him in the conduct of some of those 
 processes which it will be his business to superintend. 
 
 Water exists in four separate and distinct forms, viz. in the 
 
 1 Scheele dissolved even glass by boiling a small quantity of distilled water 
 for several days in a matrass made' of that material. -See the Preface to his 
 Treatise on Air and Fire. 
 
424- ON WATER. 
 
 state of ice: in that of a fluid ; in the state of vapour; and in a 
 state of chemical combination with other bodies. 
 
 The most simple form in which it is probable that water will 
 ever be exhibited, is that of ice ; for by the mere combination of 
 ice with caloric fluid water will be formed, and a further portion 
 of caloric will convert this fluid into steam, the most attenuated 
 aqueous vapour being nothing more than ice dissolved and rare- 
 fied by the solvent and expansive power of caloric. 
 
 Besides these different appearances of water, which are familiar 
 to every one, water is known to exist in chemical combination 
 with other bodies, forming an essential part of their substance, 
 and contributing towards the semblance, forms and qualities which 
 they respectively exhibit ; but in these cases it undergoes so con- 
 siderable a degree of condensation, that it loses all the common 
 characters of water. The water, in these instances, unites in cer- 
 tain definite proportions, and such compounds are known to the 
 modern chemist by the name of hydrates. 
 
 Some students at Florence having provided a hollow globe of 
 gold, filled it with water and then submitted it to the action of a 
 very powerful press : but they were not able to produce any con- 
 densation of the fluid whatever, though the press was sufficiently 
 powerful to occasion the water to exude through the pores of the 
 metallic vessel in which it was inclosed '. 
 
 Canton Ions ago proved the expansibility of water ; but Mr. 
 Jacob Perkins has lately contrived an instrument which he calls 
 a Piezometer, in which he has subjected water to a pressure of 
 326 atmospheres, and has succeeded in increasing its density 3.5 
 per cent 2 . Nature however, as has already been hinted, effects 
 the condensation of water in many of her operations, and it will 
 be sufficient to establish the truth of the assertion just to mention 
 a few examples. 
 
 It is an axiom in chemical science, that bodies in acquiring con- 
 densation give out caloric 3 . Thus water always parts with calo- 
 ric in the act of freezing, though it takes such a form during its 
 crystallization as disguises the actual condensation of its parts, 
 and occasions a diminution of its specific gravity. But water 
 thrown upon quick lime gives out more heat than it does in the 
 act of freezing : consequently it becomes more condensed when 
 combined with the lime, than when it exists in the state of ice. 
 
 If a hot saturated solution of sulphate of soda be corked up in 
 a glass bottle containing a thermometer, and then laid aside to 
 
 1 Essays of Natural Experiments made in the Academic del Cimento : Waller's 
 Translation, 4to, London 1684, page 203. 
 
 2 Quarterly Journal of Science, vol. x. p. 399. 
 
 3 The constant rise of temperature in the atmosphere after rain, is owing to 
 the aqueous- vapour giving out caloric while it is changing into water. 
 
ON WATER. 4*25 
 
 acquire the temperature of the atmosphere, the solution will cool 
 without the salt crystallizing. When the whole has become suf- 
 ficiently cold, and the degree noted at which the mercury stands 
 in the thermometer, if the cork be then removed to admit the at- 
 mospheric air, the salt will instantly shoot into crystals, and the 
 mercury will rise in the thermometer several degrees. What can 
 this rise of the thermometer be owing to, if it be not to the 
 water parting with its caloric as it unites with the sulphuric salt 
 and becomes condensed in the newly formed crystals ? 
 
 This salt, which will preserve its figure and solidity so long as 
 it retains this water in its composition, will become smooth and 
 pulverulent, when it loses the water of crystallization, by expo- 
 sure to the action of the atmosphere. Those who are conversant 
 with salts well know, that some lose the water of crystallization 
 and effloresce, while others absorb water and deliquesce, by ex- 
 posure to the atmosphere. Sulphate of soda, borate of soda, sul- 
 phite of lime, and phosphite of soda, belong to the first; and mu- 
 riate of lime, muriate of magnesia, and nitrate of lime, belong to 
 the latter of these classes. 
 
 Sometimes one salt will rob another of its water of crystalliza- 
 tion. Thus, crystallized muriate of lime will take the water from 
 the crystals of carbonate of soda. If both salts be inclosed in the 
 same vessel, and yet not in contact, the carbonate of soda will fall 
 into powder and the muriate of lime will become fluid. 
 
 Not only the artificial but also the natural salts, whether they 
 be earthy, alkaline or metallic, are chiefly indebted to their re- 
 spective portions of water for their transparency, for their crystal- 
 line appearance, and even in part for their solidity. 
 
 Few of the saline productions of nature are better known than 
 sulphate of lime, or common plaster of Paris, which when taken 
 out of the earth is a substance very hard and compact. For the 
 use of masons, statuaries, and some other artists, this earthy salt 
 is broken into small pieces, and then submitted to the heat of a 
 common oven to dissipate so much of the water of its compo- 
 sition as can be separated by this means. After this operation, 
 the sulphate of lime may be easily reduced to the state of a soft 
 impalpable powder. 
 
 When the plaster which has been thus prepared, is to be used, 
 the workman, in order to give it its original solidity, mixes it with 
 a certain portion of water, and then pours it hastily into moulds, 
 to form statues, busts, cornices, or other ornamental work for 
 which it is generally employed. In this instance the dried piaster 
 has such an affinity for water and a capacity to regain what it 
 had lost, that it instantly attracts and condenses a very consider- 
 able quantity, and the whole becomes changed into one entire 
 and very compact mass. 
 
426 ON WATEH. 
 
 Pure alumina has a similar affinity for water, and the union is 
 so intimate that it is almost impossible ever to separate the water 
 with which it has been united. Saussure, who made experiments 
 on this subject, declares that this earth has so powerful an at- 
 traction for water, that it will retain a tenth of its weight of that 
 fluid, even though it be submitted to a heat that will fuse iron. 
 
 Potash after having been submitted to a red heat is found to 
 retain more than 13 per cent., and soda nearly 19 per cent., of 
 water. According to the analysis of D' Arcet, the proportion of 
 water is even greater than this. Annales de Chimie 9 torn. Ixxii. 
 p. 96. and Ixviii. p. 175. 
 
 Seeing then that water has so great an affinity for many bodies, 
 and that it imparts transparency to one and hardness to another, 
 it is surely worth while to examine whether it may not fulfil an 
 important office in some mechanical and manufacturing pro- 
 cesses in which its operation has been least suspected. 
 
 If a perfectly compact crucible be well filled with dry chalk, 
 and then submitted to the strongest heat that is usually raised in 
 a common fire-place, it will be extremely difficult, if not impos- 
 sible, to convert the whole of the chalk into lime. But if a hole 
 be perforated in the bottom of the crucible, and this fixed in a 
 situation where a current of aqueous vapour, or atmospheric air, 
 can freely pass through it, the carbonic acid will be separated, 
 and the lime completely formed, in less time and with less heat 
 than it could have been effected at without such an accession. 
 The water aids the separation of the carbonic acid, and enables 
 it to pass off in the form of gas. This fact was first communi- 
 cated to me by Mr. Dalton of Manchester ; and my own obser- 
 vations have since confirmed the truth of his statement. 
 
 Our common lime kilns are all built with an opening at the 
 bottom, for the removal of the lime when burnt. This allows of 
 a constant current of atmospheric air through the whole mass of 
 stone, and consequently a considerable portion of water is con- 
 veyed to it during the whole progress of the operation. I would 
 therefore suggest to the burners of lime, that it may be worth 
 while, whenever they draw the contents of a kiln not sufficiently 
 burnt, (which often happens,)to notice whether the atmosphere 
 had not been in an unusually dry state at that period, and whe- 
 ther the imperfection of the lime should not have been ascribed 
 rather to this than any other cause. 
 
 Should this be found to be the case, the inconvenience might 
 be obviated by placing a broad vessel of water at the mouth of 
 each kiln; because the heat of the kiln would occasion a constant 
 evaporation from its surface, and the current of air which sets 
 through the kiln would convey the aqueous vapour to every part. 
 
 In like manner, there is reason to believe that quick lime would 
 
ON WATER. 42? 
 
 not combine with carbonic acid, however long it might be ex- 
 posed to its action, provided water were not present; and that the 
 mortar or cement employed in buildings would never acquire the 
 hardness of which it is capable, were it not for the gradual ab- 
 sorption of the water of the atmosphere. 
 
 Vegetable fermentation cannot take place without water ; and 
 I suspect that the excellence of wine and all other fermented 
 liquors depends in a great measure on the proportion which the 
 water bears to that of the sugar and the mucilage. The perfec- 
 tion of the process of malting, as is well known to all good malt- 
 sters, depends in a great measure on the couch being properly 
 sprinkled with water. In forming solutions of the metals in the 
 muriatic and some other acids, the water becomes decomposed in 
 proportion as its oxygen is required to oxidize the metal, and its 
 hydrogen escapes through the fluid in the form of gas. This in 
 some degree accounts for the great loss of weight which is always 
 experienced in making the solutions of tin and other metals. 
 
 Here it may perhaps not be amiss to advert to a circumstance 
 which may involve the safety of some individuals. What I al- 
 lude to is this; that those persons who are in the habit of prepar- 
 ing large quantities of muriate of tin, are perpetually liable to 
 misfortunes by an explosion of the hydrogen gas which escapes 
 during the process. Very lately, a friend of mine in the country 
 was much cut in the face and otherwise injured by the fragments 
 of an apparatus in which this operation was going on, and which 
 burst with a tremendous report, in consequence of a lighted can- 
 dle having been incautiously brought too near it. 
 
 Though water is decomposed and a loss of weight is sustained 
 in many chemical operations, water, on the contrary, is often pro- 
 duced in certain cases of combustion, where the presence of this 
 fluid is least suspected ; and this may influence the results of 
 many operations in a way that is quite inexplicable to those who 
 are unacquainted with the principles of chemistry. Spirits of wine, 
 oils, wax, tallow, and many other substances, always produce 
 water during their combustion. If a cold glass vessel be inverted 
 over the flame of burning alcohol, water may be collected that is 
 perfectly free from taste or smell, and in every respect like dis- 
 tilled water. One pound of alcohol will produce eighteen ounces 
 of water. 
 
 The PURITY of the water that is employed in some of our ma- 
 nufactures is an object of the most material consequence. A few- 
 instances may easily be adduced to substantiate the truth of this 
 assertion. 
 
 In the processes of bleaching, dyeing, and calico-printing ; in 
 those of refining sugar, of brewing malt liquors; in the manufac- 
 ture of paper, and in many others which might be enumerated; 
 
428 ON WATER. 
 
 the quality of the article is much influenced by the nature of the 
 water which has been employed in its production. 
 
 More than two thousand years ago Hippocrates wrote ex- 
 pressly on the difference observable in waters. Celsus gave di- 
 rections for examining the specific gravity of water ', and Pliny 
 attempted to direct his readers how to distinguish the salubrious 
 from that which is unwholesome. But, till the time of Boyle or 
 towards the end of the seventeenth century, no means had been 
 devised of analysing water, or of pronouncing with certainty on 
 its nature and properties. 
 
 There is a letter still extant from Synesius, a Christian bishop 
 of the fifth century, to the female philosopher Hypatia, under 
 whom he had formerly studied, in which he complains of being 
 ill ; says that he wishes to use a hydroscopium, and requests that 
 she would cause one to be constructed for him. " It is a cylin- 
 drical tube," he adds, "of the size of a reed or pipe. A line is 
 drawn upon it lengthwise, which is intersected by others, and 
 these point out the weight of water." It is probable that the 
 bishop was in an infirm state, that his physicians had ordered 
 him to drink none but pure water, and that the instrument he 
 wanted was one similar to our hydrometer for the purpose of ex- 
 amining the weight of different waters, in order to ascertain which 
 would be best for his use. 
 
 Those which are generally known by the appellation of hard 
 waters, hold certain salts in solution, and are unfit for private 
 use as well as for manufacturing processes. Frequently, however, 
 according to the remark of Bergman, the sum of all the saline sub- 
 stances dissolved in a mineral water does not exceed a six-thou- 
 sandth part of its weight, and yet may be composed of six or eight 
 different substances. Mr. Daiton asserts, from the result of his 
 own experiments, that the hardest spring water seldom contains 
 so much as one-thousandth part of its weight of any foreign body 
 in solution 2 . 
 
 Nature, who in her inexhaustible bounty gives us distilled 
 water from heaven, has so ordained it, that there are few districts 
 of much extent where spring water may not also be found, which 
 is sufficiently pure for most purposes either of manufacture or 
 domestic economy 3 . 
 
 It may here be remarked, that in sinking wells it is impor- 
 tant to line them with free-stone, and not with bricks as is usual, 
 
 1 Celsus I)e Medicina, lib. ii. cap. 18. 
 
 2 New System of Chemical Philosophy, p. 271. 
 
 3 A rare instance to the contrary is mentioned by Dr. Plot in his History of 
 Staffordshire, who relates a case of* a well which was sunk in that county to the 
 depth of 2,600 feet, without meeting with water. See Journ. da Syav. 1680, 
 p.- 14. 
 
ON WATER. 4-29 
 
 because most of the bricks which are made in this country have 
 the property of hardening the water; whereas the stone has not 
 this effect. 
 
 Nearly seventy years ago Dr. Home explained why hard water 
 is injurious to dyers and bleachers. It is related by him that Mr. 
 Samuel Hart, who was a celebrated bleacher in the middle of 
 the last century, was about to establish a new bleach-field in a 
 particular place, which seemed favourable for his purpose on ac- 
 count of the appearance of the water and the abundance of the 
 supply; but when he came to examine it by some of the best che- 
 mical means then known, it was found so impure, that he deemed 
 it expedient to form his intended establishment on another spot. 
 Most of our spring water contains common salt, w r ith carbonate 
 and muriate of lime ; but it is the sulphate of lime which consti- 
 tutes what we call hard water. 
 
 In coal districts, where the coal occurs near the surface of the 
 ground, the brooks and rivers in the neighbourhood are often 
 contaminated by the result of the decomposition of the sulphuret 
 of iron called martial pyrites, which is washed into them by the 
 rains. I know of one instance in Yorkshire where an establish- 
 ment for scouring and dyeing woollen yarn must have been entirely 
 broken up from this cause alone, if the proprietors had not found 
 the means of leading a current of water from an adjacent spring 
 for the supply of the manufactory. 
 
 They had been in the habit of using the water from the river 
 Calder, which has constantly a portion of the coal-pit water 
 running into it ; and in the summer months, or in very dry sea- 
 sons when there is less good water to dilute the coal-pit stream, 
 the Calder water, for most of the purposes for which a dyer re- 
 quires it, is rendered nearly useless. This had long been a cause 
 of vexation and inconvenience to these individuals, when the 
 bursting of one of the worn-out coal-pits so inundated the bed of 
 the Calder with the solution of sulphate of iron, that its water 
 became totally unfit for their purpose ; and this induced them to 
 resolve upon incurring the expense of supplying themselves from 
 another source. The establishment of which I have been speak- 
 ing is not a large one, and yet the proprietors have repeatedly 
 assured me that the consumption of soap in scouring their wool- 
 len yarn is, in consequence of the softness of the present water, 
 so much diminished as to occasion a saving to them of more than 
 fifty pounds per annum. 
 
 To those persons who have no idea that difference of water can 
 produce such important effects in bleaching, I would earnestly 
 recommend the repetition of the following easy experiment. 
 Take half a pint of distilled water drop into it a single drop of 
 the tincture of galls and an equal quantity of solution of sulphate 
 
 
430 ON WATER. 
 
 of iron, and let the whole be stirred with a glass rod. On ob- 
 serving the effect which this minute quantity of these reagents has 
 produced in the water, it will be perceived that only a very slight 
 change of colour has been occasioned by it ; whereas, if an equal 
 quantity of spring water be added to the former mixture, the 
 whole will immediately become black. 
 
 In some processes of calico-printing the perfection of the 
 water is of great moment, and to the dyer of fine colours pure 
 water is indispensable ; but the case which has just been related 
 refers chiefly to the bleaching of linen and calicoes, which can 
 never take a perfect white if the water employed be contaminated 
 with saline substances or with minerals of a metallic nature. The 
 term pure water is not intended to be taken in the strictest sense 
 of the words, for rain water itself is not absolutely pure. Such 
 water, when collected by spouts from the tops of buildings, is 
 found to have dissolved a portion of selenite from the tiles ; and 
 if caught in an open field it is generally contaminated by the 
 heterogeneous particles which are always floating in the atmo- 
 sphere. For the purposes of chemical analysis nothing can be 
 depended upon but distilled water. The ancient chemists, how- 
 ever, always preferred rain water for all their processes. 
 
 In reference to bleaching it may be worth while to mention, 
 that there are many manufacturing districts in this kingdom 
 which are situated near to peat mosses, some of which are of con- 
 siderable extent ; and that all such places are very improper for 
 the establishment of bleach-works, because at flood time these 
 marshes pour into the adjacent rivers large quantities of iron in 
 a state of solution which contaminate the waters for many miles. 
 
 A remarkable instance of the impurity of spring water occurs 
 in Portugal. In several parts of that kingdom the waters are so 
 hard that for many purposes they are entirely useless. The fol- 
 lowing is a case of peculiar difficulty. 
 
 The wool which is produced in Spain and Portugal contains 
 so much animal oil and other impurities, that when scoured it 
 will not produce more than half its original weight, and in some 
 cases three pounds will not yield more than one pound of clean 
 wool fit for the English market. As these wools pay a consider- 
 able duty to the Spanish and Portuguese Governments on their 
 exportation, the Spaniard finds it his interest to clean them tho- 
 roughly before they are shipped for sale to Britain or elsewhere ; 
 but in Portugal the merchant cannot avail himself of this expe- 
 dient, because the waters of that country are unfit for the ope- 
 ration. 
 
 I know a merchant who has an establishment in Portugal for 
 the purchase of wool and for the sale of English woollen cloth, 
 and he informs me that he is under the necessity of shipping very 
 
ON WATER. 431 
 
 large parcels of wool in its original state, which occasions a great 
 reduction of profit, merely for want of the means of having this 
 wool properly washed in Portugal. 
 
 I suggested to this gentleman the scheme of collecting urine 
 for the purpose. I stated that this fluid, when it becomes stale, 
 produces a large portion of volatile alkali, and that the addition 
 of a small quantity of quick lime would remove its offensive smell 
 and render it fit for any operation of washing or scouring : and 
 that it would, if added in a small proportion to hard water, render 
 such water soft and fit for any detersive process whatever. But 
 he assured me that this could not be done ; for that the inhabi- 
 tants of this country have so much pride, and so little idea of the 
 importance of manufactures, or of any economical improvements, 
 that it would be impossible, by any reward, to induce the poorest 
 man in the country to engage in such an occupation. 
 
 The ancient Romans had recourse to urine for scouring woollen 
 cloths. It is, indeed, probable that it was more largely employed 
 by them for this purpose than even by the moderns, from the cir- 
 cumstance of the Emperor Vespasian having laid a tax upon it, 
 which remained long in force, and continued to be exacted for 
 more than 200 years. The scourers of old were so careful in the 
 collection of this article, that the Government extorted the pay- 
 ment of the tax even from those who kept cattle, vectigal pro 
 urina jumentorum. Athanasius, however, although he was the 
 most frugal and economical of all the Roman emperors, relieved 
 his people from this odious impost. Pliny, lib. xxviii. 6. &c. 
 
 It is probable that the ancients had no conception of the me- 
 thod above mentioned, of sweetening stale urine, because it ap- 
 pears that the scourers at Rome were all obliged to reside in the 
 most unfrequented parts of the city. 
 
 It would extend this Essay to too great a length to lay down 
 rules for the complete analysis of all the various kinds of water 
 which these islands produce, especially as Dr. Kirwan and others 
 have written expressly on this branch of the subject : but some 
 directions for ascertaining the comparative goodness of water may 
 be of especial service to the manufacturing part of the community, 
 and this may perhaps be done without occupying much room, or 
 occasioning fatigue to the general reader ; and it may be observed, 
 as we proceed, that it is of consequence also to the agriculturist 
 to be able, in some measure, to analyse water; for those who have 
 studied the subject of irrigation, and carefully observed its effects, 
 have found that the benefits resulting from this practice very 
 much depend upon the nature of the water which is employed '. 
 
 1 See Boswell's Treatise on Watering Meadows, p. 10, &c. 
 
4-32 ON WATER. 
 
 Even horses will refuse hard water when they have long been ac- 
 customed to soft. 
 
 In examining water, the first thing to be attended to is its spe- 
 cific gravity ; and I conclude, from a remark which is made by 
 Pliny, that this method of trying the purity of water was known 
 to his contemporaries. " Good water," says he, "ought to have 
 neither taste nor odour at all. Some there be who judge of their 
 wholesomeness by the balance, and they keep weighing and poiz- 
 ing of waters one against another V 
 
 There can be no doubt of the importance of attending to the 
 specific gravity of spring or river water, as this alone will often 
 lead to a knowledge of its nature and purity ; for those waters 
 which are the most unfit for culinary purposes, or for the use of 
 manufacturers, are generally specifically heavier in proportion to 
 their impurity. If, therefore, a sample of water should prove to 
 be of the same weight, or but a little heavier than rain or dis- 
 tilled water, and devoid of colour, taste, and smell, it may gene- 
 rally be pronounced to be fit for most purposes, either of the 
 arts or of domestic economy. 
 
 Should it be intended to prosecute the examination further, it 
 will be an easy experiment to put a thin slice or two of white 
 soap into a clean glass tumbler, and then to pour half a pint of 
 the water over it, which is required to be examined. When this 
 has stood undisturbed for half an hour, the appearance of the 
 water will be a good evidence of its relative purity, as it will then 
 be seen whether it be what is called hard, and consequently im- 
 pure, water, or otherwise. The Spanish soap, usually known by 
 the name of Castile soap, an article sold by the chemists, and 
 which is made of soda and oil of olives or oil of almonds, is the 
 best ; but good English white soap will generally be found very 
 suitable for the purpose. A little Venice soap dissolved in alcohol 
 will form a test by which the comparative hardness of water may 
 be determined in an instant. 
 
 Water which holds any of the earths in solution, or any of the 
 metallic or earthy salts, has the property of decomposing soap, 
 while pure water will completely dissolve it. In the former case 
 the alkali separates, and the earth combines with the oil or the 
 tallow ; in the latter, the soap is decomposed by double affinity, 
 the acid uniting with the alkali, while the earth or the metal com- 
 bines with the oil, and forms an earthy or metallic soap. In both 
 instances the new compound is insoluble, which occasions the 
 coagulation above mentioned. It may therefore be said that in 
 this experiment, if the fluid present a smooth equable appearance, 
 without any white flakes or curdly particles interspersed among 
 
 1 Holland's Pliny, book xxxi. chap. 3. 
 
ON WATER. 433 
 
 it, the water may be considered good ; otherwise it must be 
 deemed hard, and this in proportion to the quantity of the white 
 insoluble matter which is perceived in it. 
 
 One of the substances most commonly found in water, and the 
 most injurious to manufacturers, is iron. To discover the pre- 
 sence of iron, prussiate of potash, or tincture of galls, may be 
 employed. The first of these reagents will occasion a blue colour 
 in the water if iron be present; the tincture of galls will produce 
 at first a purple and then a black tinge. 
 
 These short directions will be enough to enable manufacturers 
 in general to ascertain whether the water in their vicinity has a 
 degree of purity sufficient for their respective purposes : and 
 wherever a complete analysis is required, recourse must be had 
 to Kirwan 9 , or to some other chemical writer who has given the 
 proper di r Actions for conducting such an examination. In pur- 
 suing this inquiry, " Bergman's Physical and Chemical Essays," 
 " Dr. Henry's Elements of Experimental Chemistry," " Dr. 
 Thomson's and Murray's Systems of Chemistry," and the fourth 
 volume of" Fourcroy's General System of Chemical Knowledge," 
 may all be read with advantage. 
 
 It may however be worth while to embrace this opportunity of 
 showing that brooks, rivers, and springs, are liable to be con- 
 taminated with a variety of impurities, all of which may be de- 
 tected by chemical reagents in the following order. Other sub- 
 stances however, besides those which are enumerated in the sub- 
 joined list, have been found in natural waters; but as these are 
 such as are chiefly to be expected, it has not been thought neces- 
 sary to enlarge the catalogue. 
 
 A tabular View of those Reagents which are usually employed to de- 
 tect the Impurities of Spring and River Water. 
 
 dicier } LUne, or either of the saUs of Ihne. 
 
 { Uncoined acids. 
 
 The same slightly redden- \ c 
 
 ed by vinegar ; or tur- .... < Pure alkalies and pure earths. 
 
 meric paper j v. 
 
 Muriate of platinum Potash, or the salts of potash. 
 
 Acidulous nitrate of silver 
 Muriate of barytes 
 Lime water 
 Acetate of lead 
 Muriate of lime 
 Polished iron or steel 
 Phosphate of soda 3 
 Sulphuret of potash 
 
 Muriatic acid, or the muriatic salts. 
 Sulphuric acid, or the sulphuric salts . 
 Carbonic acid, magnesia and alumina. 
 Sulphuretted hydrogen. 
 Carbonated alkalies. 
 Sulphate of copper. 
 Magnesia. 
 Lead. 
 
 2 See his Essay on the Analysis of Mineral Waters, London, 1799. 
 5 This test for magnesia was first recommended by Dr. Wollaston. For the 
 method of managing it, see Dr. Henry's Chemistry, vol. ii, page 431. 
 
 2 F 
 
43t ON WATER. 
 
 The manufacturer having ascertained, by means of one or more 
 of these tests, that the water upon his premises is not fit for his 
 purpose, it then becomes a question of prudence whether he shall 
 attempt to purify this water, or search for some other source from 
 whence he may draw such as is naturally pure enough for the 
 use of his manufactory. 
 
 It is probable that in many parts of this kingdom such a search 
 would be crowned with success. Dr. Home has stated that " the 
 water of the Edinburgh wells not only thoroughly dissolves soap, 
 and retains its transparency when salt of tartar is mixed with it, but 
 even shows no lactescency when nitrate of mercury is dropped in." 
 
 The means which might be adopted for the purification of 
 water are various, and Nature herself makes use of several of them 
 in order to present us with this article of the first necessity, in a 
 state of sufficient perfection for all the common purposes of life ; 
 and among other operations she chiefly employs those of distilla- 
 tion and filtration. 
 
 The most contaminated waters on the face of the earth are 
 daily purified by the action of the sun's beams, which separate the 
 limpid particles from the polluted mass, and elevate them into 
 clouds, from whence they are distilled in showers of rain, hail or 
 snow. The hills and mountains of the globe also perform a si- 
 milar office, by allowing the waters in their vicinity to percolate 
 through them, and hence are presented to us in various degrees 
 of purity, according to the nature of the different strata of earths 
 or minerals though which they have permeated *. 
 
 The former of these methods is successfully imitated whenever 
 we prepare distilled water ; but this is a process which is too ex- 
 pensive for most manufacturing purposes. The latter, that of 
 percolation, may be copied by art on a large scale ; and the water 
 which is thus purified, may be employed for some uses with con- 
 siderable advantage. Here, however, we can only strain off some 
 common contingent matters without changing the soluble prin- 
 ciples ; while Nature, by her superior powers, can even decom- 
 pose what is injurious, and cause the impurities to subside or se- 
 parate entirely. 
 
 I have often thought that at those large works where a steam- 
 engine is constantly employed, a sufficient quantity of distilled 
 water for all the nicer purposes might be collected from the waste 
 steam, if a proper receptacle were contrived for condensing it. 
 The advantages that would accrue from such an arrangement to 
 the dyer of rich colours, and to the printer of fine calicoes, are 
 incalculable. 
 
 1 Those springs which arise out of lime-stone rocks are generally hard ; 
 whereas, the waters which have filtrated through a long extent of gravel are 
 often extremely soft. 
 
ON WATER. 435 
 
 Here it may be observed, that when fresh water becomes .scarce 
 at sea, excellent soft water may be readily procured for the use 
 of the ship's crew, by distilling the salt water with some wood- 
 ashes or other vegetable alkali. A memoir expressly on this sub- 
 ject may be seen in the Philosophical Transactions for the year 
 1758. 
 
 I had some time since an opportunity of examining the plan 
 of an extensive reservoir, at that time making by a very ingenious 
 manufacturer for the sole purpose of filtrating water, and which 
 was of the enormous size of sixty yards long and forty yards wide. 
 This vast receptacle was formed near the side of a river, and sunk 
 several feet below the surface of the adjacent ground. When the 
 soil had been carried out to a depth which was thought sufficient, 
 several broad trenches were sunk a foot or two deeper than the 
 main bottom, and these were filled with boulder stones or very 
 large pebbles, to prevent the possibility of these passages for the 
 water from ever being filled up. Over these, and over the whole 
 bottom of the reservoir, a large bed of gravel was laid, and then 
 the remainder of the pit was filled up with fine screened sand. 
 
 In using this reservoir, it was the intention of the proprietors 
 to fill it with water, by means of a pump fixed within the river 
 and worked by the steam-engine ; arid it was considered that the 
 water would be purified in its passage, while pervading the sand 
 and gravel ; that the trenches below would be constantly full of 
 pure water, and that the manufactory would be furnished with a 
 perpetual and transparent limpid stream. 
 
 I have not yet heard of the success of this project, but I have 
 no doubt of its answering fully all the expectations of the pro- 
 jectors ; though it must be recollected by those who may be de- 
 sirous of practising this mode of purification, that it is only 
 capable of separating the argillaceous earth, or such impurities 
 as are merely suspended in the water, and not any of the earths 
 or salts which are chemically combined or dissolved in it. 
 
 In making a reservoir of this kind, there are many circum- 
 stances to be attended to, which may appear insignificant in 
 themselves, and yet the neglect of one of them may be sufficient 
 to defeat the whole of the intention. Thus, if precautions are not 
 taken, worms will burrow through the bottom and sides of such 
 receptacles, and by the passages thus formed will divert the water 
 from the bed of the filtrating materials into other channels. 
 
 To guard against this, it is necessary, when the bed of the 
 reservoir has been well puddled with clay, to lay a thin coat of 
 coal-ashes over it, and to secure the sides in the same manner ; 
 it having been found that this will effectually prevent these small 
 animals from penetrating. 
 
 2 F 2 
 
4-36 ON WATER. 
 
 It is also necessary, when the gutters are filled with the boulder 
 stones, to cover them with long straw to prevent the gravel from 
 running among them. The same expedient should likewise be 
 adopted afterwards, when all the gravel has been laid on, to pre- 
 vent the sand which is then to be spread over from running among 
 it ; but where a large sum is to be expended in one of these reser- 
 voirs, I would earnestly recommend that the advice ,of a person 
 should be taken who has had experience in these matters. 
 
 In pursuing the subject of purifying waters for the use of our 
 respective manufactories, I would remark that it is right to en- 
 courage the growth of weeds, and the different kinds of aquatic 
 vegetables, in all large reservoirs of water belonging to such es- 
 tablishments, as they have the faculty of very materially purify- 
 ing the water in which they grow. Some very interesting dis- 
 sertations on this subject will be found in Priestley's Experiments 
 on Air, p. 16 63, under the article " Green vegetable matter 
 floating on stagnant water." Hard waters have the property of 
 retarding animal and vegetable putrefaction ; but when putrefac- 
 tion does take place in such waters, it alters their quality, and 
 they become entirely soft. The antiseptic quality of hard waters 
 was known to Celsus, an eminent physician of the first century. 
 " If this were the proper place," says Dr. Home, " we could 
 easily account for all the bad effects of hard water on the human 
 body ; and show that by the separation of the acid from the ter- 
 restrial base, which will happen in the body, several diseases 
 must arise. These unwholesome effects of hard water may be 
 prevented by previously mixing alkaline salts with it." Some 
 waters are purified sufficiently for manufacturing purposes, 
 merely by an exposure to the action of the atmosphere. Thus 
 some chalybeate waters deposit the iron in a thin pellicle on their 
 surface, owing to its becoming insoluble by its absorption of 
 oxygen. I know also of an instance at a print work, where a very 
 shallow stream of water, which ran through the works, was found 
 too impure for many of their purposes : but when the same rivulet 
 had passed these premises, and had reached another work which 
 belonged to the same proprietors, situated at a considerable di- 
 stance from the former, it was always found to be fit for most of 
 their operations. 
 
 A large portion of the spring water of this country is rendered 
 unfit for many manufacturing purposes by the selenite which is 
 contained in it; but surely such water might, at a trifling expense, 
 be sufficiently purified for most occasions, unless the consump- 
 tion of it were so large, as that this circumstance alone would 
 create an insurmountable objection. 
 
 Water contaminated by selenite (sulphate of lime) may be ren- 
 
ON WATER. 437 
 
 dered pure by means of a solution of barytes, an article which 
 may be prepared at a comparatively small expense, and would be 
 of incalculable advantage in many processes of art. I have here 
 in view the preparation ofbarytic earth from the common Derby- 
 shire cauk, as described in Essay 4, and which I conceive would 
 be sufficiently pure for this purpose. All that would be necessary 
 would be to drop the solution of that earth, by degrees, and in 
 small portions, into the water intended to be purified, till it oc- 
 casions no further precipitate. In this way pure water might at 
 any time be had for chemical experiments; for, if too much of 
 the barytic solution should by accident be employed, the carbonic 
 acid inherent in the water, or that of the atmosphere, will soon 
 combine with it, and occasion it to precipitate along with the de- 
 composed selenite. I cannot however recommend the water puri- 
 fied in this way to be used for domestic purposes, as the barytic 
 earth is poisonous. 
 
 When barytes is not to be had, and in all cases where it would 
 be improper to employ that earth, such water may be rendered 
 soft, though not perfectly pure, by the addition of a small quan- 
 tity of the sub-carbonate of potash (the pearlash of the shops), or 
 a few of the crystals of soda. Either of these alkalies will com- 
 bine with the sulphuric acid and precipitate the lime ; and when 
 a sufficient time has been allowed for the deposit to be formed, 
 such water will be fit for every culinary, and for most manufactu- 
 ring or domestic purposes. Where there is the convenience of 
 proper reservoirs, this is a most effectual way of softening hard 
 waters ; and for every purpose of washing or scouring, the effect 
 may be produced at a still cheaper rate by means of stale urine. 
 This might be sweetened as directed at page 431, and then poured 
 into the water by degrees till the object was completely attained. 
 
 The great desideratum, however, with bleachers, dyers, and 
 calico-printers, is to discover a cheap method of precipitating 
 iron from any of those waters in which it may be dissolved, as 
 the salts of iron held in solution by the waters of brooks and 
 rivers are often very injurious in the practice of those arts. 
 
 The solvent of the iron in these cases is often, if not generally, 
 sulphuric acid; therefore, in those situations where it is convenient 
 to have cisterns or other reservoirs for the water, the solution of 
 pure barytes might be employed with equal effect. The barytic 
 earth would immediately seize the sulphuric acid and precipitate 
 it; and the iron, having thus lost its solvent, would fall also. This 
 precipitation of these impurities will commence immediately upon 
 the application of the barytes; and when the whole has remained 
 v ,a few hours undisturbed, the water will be fit for use. It will be 
 obvious that care must be taken to add no more of the barytic 
 solution than is absolutely necessary to throw down the iron ; 
 
4-38 ON WATER. 
 
 otherwise, when the iron has been separated, the water will be 
 found to be contaminated by the reagent itself. In Scotland the 
 poor get up their own household linen, and bleach it themselves 
 in their own gardens. Dr. Home relates the case of a poor 
 woman who watered some webs she was bleaching, from a spring 
 near her own house. To her great surprise, they became redder 
 and redder every day. She attributed it to witchcraft; imputed 
 the crime to the neighbour she hated most ; and sold the cloths 
 for a trifle. The Doctor afterwards analysed the water, and found 
 it contained iron. To discover whether the iron be held in solu- 
 tion by the sulphuric, the muriatic, or the carbonic acid, treat it 
 with a small quantity of the nitrate of barytes. If this throws 
 down a yellow precipitate, and the water loses its brackish taste, 
 it may be concluded that the iron is dissolved by the former of 
 these acids ; but if these effects are not produced, some other 
 acid must be considered to be the solvent. Boiling the water will 
 show whether it is carbonic acid that holds it in solution. 
 
 In cases where no danger would arise from a small portion of 
 lime, waters may, indeed, be divested of iron merely by the ad- 
 dition of a little of this earth in powder '. It would be proper to 
 use fresh burnt lime ; and should more of this be employed than 
 is necessary to separate the iron, the superabundant quantity may 
 be precipitated by allowing it time to absorb carbonic acid from 
 the atmosphere. And where time could not be spared for the 
 completion of this process, the judicious application of a very 
 small quantity of sulphuric acid would separate the whole in the 
 course of twenty-four hours, and leave the mass of water in a 
 state of purity fit for any purpose either of manufacture or do- 
 mestic economy. 
 
 To accomplish this on a large scale it will be necessary to have 
 two reservoirs, which might adjoin each other, and then the im- 
 purities would be subsiding in one, and its water becoming fit for 
 use by the time the water of the other was expended. 
 
 From repeated observations I am convinced that large sums 
 of money have been needlessly spent in the purchase of expensive 
 cements for making underground water-cisterns, and that brick 
 walls properly built and well puddled with clay are fully suffi- 
 cient for the purpose. I have myself more than once constructed 
 a large underground cistern in this manner, which held perfectly 
 tight for several years, and probably would last at least a century. 
 A detail of the methods which I pursued would occupy more 
 room than I can spare ; but I refer the reader to a work where 
 he may obtain an abundance of useful information on this sub- 
 
 1 Pliny speaks of purifying brackish water with chalk, which is a carbonate 
 See lib. xxiv. cap. 1, 
 
ON WATER. 4-39 
 
 ject, viz. Switzer's System of Hydrostatics, in 2 vols. quarto, 
 London 1729, vol. i. p. 129, illustrated with a copper -plate en- 
 graving of the sections of several reservoirs of different forms 
 and dimensions. Vitruvius says that the ancients contructed their 
 underground cisterns with a composition made of lime-mortar, 
 sand and pebbles, well beaten together. Vitruv. de Arcliit. lib. 
 viii. cap. 6. 
 
 I am acquainted with some gentlemen in the north of Scotland 
 who are proprietors of a very extensive establishment for bleach- 
 ing and printing calicoes, and who for many years had been in 
 the habit of bleaching with the water from the river Don, but 
 had long been dissatisfied with the uncertainty that attended all 
 their processes, and which they could ascribe to nothing but the 
 impurity of the water. 
 
 These gentlemen possessing much chemical knowledge, at 
 length came to the determination of analysing the waters of all 
 the neighbouring springs, and then to bleach a parcel of goods 
 with the utmost care in that which appeared to possess the great- 
 est purity. The result answered their most sanguine expectations. 
 Less alkali was required in the process, and the difference in the 
 appearance of the finished goods was very considerable and ob- 
 vious. 
 
 When the superiority of this spring of water was thus ascer- 
 tained, the individuals above referred to were at the expense of 
 conducting it in pipes three miles through their own estate, ta- 
 king care to divert the waters of those springs which contained 
 iron into another channel. The good water was made to empty 
 itself into one vast cistern capable of containing many thousand 
 gallons. 
 
 This reservoir, which is formed with large slabs of Scotch gra- 
 nite, put together witK Parker's cement, is fifty feet long, thirty feet 
 wide, and ten feet deep. 
 
 It is observable that the reservoir is very shallow in compari- 
 son with its extent, and this form was given to it in order that a 
 large surface of water should be constantly exposed to the at- 
 mosphere. The design of this will be immediately perceived, 
 when it is understood that this water passes through a bed of 
 lime-stone, and that when it is delivered at the reservoir it holds 
 a portion of that earth in solution. For by this exposure of it 
 to the air, it loses that excess of carbonic acid which dissolved 
 the carbonate of lime, and then this earth from its natural inso- 
 lubility separates, and falls to the bottom of the cistern. Mr. 
 Cavendish determined that 1200 grains of water impregnated 
 with fixed air and yet not fully aerated, could hold in solution 
 one grain of chalk. Berthollet in Mem. Paris 1780, p. 127, 
 states, that 500 grains of water fully impregnated with fixed air 
 
44-0 ON WATER. 
 
 can hold one grain of aerated lime ; and Kirwan has shown, that 
 when the proportion of water to that of chalk is very considera- 
 ble, for instance, as 12,000 to one, then the weight of fixed air 
 necessary to keep the lime in solution is about half its weight when 
 aerated ; and if the proportion of water be still more considera- 
 ble, a still smaller weight of fixed air is required. He also states 
 that if the weight of the carbonic acid which is united to water 
 exceeds that of the chalk, it will dissolve it let its volume with 
 respect to that of the water be ever so small. It having, how- 
 ever, been foreseen that the precipitate of calcareous earth would 
 constantly accumulate in this reservoir, and soon become consi- 
 derable, the water from the pipe of conveyance is not allowed to 
 rush in at the surface, but is delivered into a capacious wooden 
 trough which goes nearly to the bottom of the cistern. By this 
 contrivance no water can enter but at the bottom, and there it be- 
 comes distributed, without occasioning the least disturbance to 
 the surface ; which is a point of considerable consequence, espe- 
 cially as the manufactory is supplied, as will be explained here- 
 after, only from the uppermost stratum. 
 
 At first an inconvenience arose from the circumstance of con- 
 veying the water from the spring in iron pipes, as those parts 
 which were not constantly covered with water became oxidized 
 by the action of the atmosphere, and in consequence of this the 
 contents of the reservoir were soon contaminated by iron in a con- 
 siderable degree. However, by adapting a stop-cock, and other- 
 wise preventing the circulation of air within the pipes, the iron 
 is now preserved from solution, and the complaint of having a 
 chalybeate water is no more heard. 
 
 It being a main object with the proprietors of this manufactory 
 to improve the water by exposing it to the action of the air, in 
 the way already noted, they conceived that the upper stratum 
 must always be the purest, and therefore they determined never 
 to draw any off for the use either of bleaching or calico print- 
 ting but from the surface, and this they effect by the following 
 expedient. 
 
 A copper pipe, with a large stop-cock attached to it, is firmly 
 fixed in one side of the reservoir, at a convenient distance from 
 the bottom ; and at that end of the pipe which is within the 
 water, a flexible tube of leather about 18 inches long is affixed 
 and supported upon rings of copper, sewed withinside to prevent 
 the pressure of the water from occasioning the leather to collapse. 
 It will be obvious that where the water is not to be consumed 
 close to the reservoir, a series of pipes, instead of the stop-cock, 
 might be attached to the flexible tube, and thus the water might 
 be conveyed to any distance. To the other end of this flexible 
 pipe, one of copper is fixed, with a rose-head, as it is called, at 
 
ON WATER. 44-1 
 
 the other extremity ; that is, this end of the pipe is pierced full 
 of small holes for the entrance of the water, and this is surmounted 
 by a large air ball made of thin copper so as to be capable of 
 swimming in water. By this contrivance, whatever depth of water 
 there may be in the reservoir, one half of the air bail is always out 
 of the water, for the flexible tube allows it to rise or fall with the 
 water, arid consequently the perforated end of the copper pipe 
 at which the water enters is never more than an inch or two be- 
 neath the surface, so that none but the very purest portion of water 
 within the reservoir can ever be drawn off for use. 
 
 It appears to me, that this is a very simple and effectual con- 
 trivance for obtaining good water ; and the improvements which 
 have obviously appeared in several of the processes of this esta- 
 blishment justify my recommendation of the scheme, and induce 
 me to say that it is my decided opinion that a similar one should 
 be adopted not only at other works in Scotland, but throughout 
 the British dominions by all those bleachers or printers whose si- 
 tuations will admit of it. 
 
 The necessity there is of pure water for the use of the bleacher 
 has been fully explained in the foregoing Essay; but to the printer 
 of fine calicoes it is, perhaps, of still greater importance. Such 
 water must be used in every process from the first to the last for 
 the light coloured prints ; for a single operation either of dunging, 
 washing or dyeing such pieces in common water, would spoil the 
 delicacy of the grounds, and decidedly impair the beauty of the 
 goods. 
 
 Bleachers are not always aware of the loss they sustain, in the 
 extra consumption of potash, by the use of hard water ; nor are 
 they apprised that the saline substances which render the water 
 hard, must either be all neutralized or decomposed at the expense 
 of the alkali, before such water can be rendered efficient in any 
 of their processes. A table of the comparative power of various 
 substances with regard to softening and hardening of water, will 
 be found in the work of Dr. Home already quoted, page 249. 
 Likewise several curious experiments on the effects of different 
 waters in sundry culinary operations, pages 288 298. 
 
 Brewers of malt-liquors labour under as great an inconvenience 
 from the use of hard water ; for it is well known that the largest 
 portion of extractive matter cannot be drawn or separated from 
 the vegetable substance by means of such water. The annual 
 profit of a brewer must therefore in a great measure depend upon 
 the purity of the water he employs, as well as on the goodness of 
 his malt. 
 
 To the grower of flax for the operation of steeping, soft water 
 is of the utmost consequence. In such water the process usually 
 goes on with regularity and safety, whereas in water that has a 
 
4-42 ON WATER. 
 
 considerable degree of hardness, the flax may lie month after 
 month until its texture be injured, and still the ligneous matter 
 will not be properly separated. The intention of steeping is to 
 loosen the harl or bark of the flax from the bun or woody part of 
 the plant; and this is accomplished by a solution of the mucila- 
 ginous substance which occasions them to cohere. Putrefaction 
 being the means employed to attain that end, hard water must be 
 improper for steeping, because all such waters have the property 
 of resisting the putrefactive process. Dr. Home, who made many 
 experiments on this particular branch of our subject 1 , assures us 
 that flax may lie even four or five months in moss-water before 
 it will be sufficiently steeped. Hence he recommends " that the 
 steeping should be made a business distinct from the raising of 
 flax," and says that in Holland it is managed by lint-dressers, 
 who buy the flax standing on the ground, and carry it to their 
 own premises to steep. He has also remarked that the flax, when 
 properly watered, acquires a slippery oiliness on its skin, owing 
 to a solution of the mucilage ; but Pliny's rule is still the most 
 certain, "Maceratos indicio est membrana laxatior 2 ." 
 
 From the experiments which I have myself made in DYEING, 
 I am convinced there are few of the dye-woods or other vegeta- 
 ble substances that are employed in that art, which will yield 
 their colours freely to any but pure water. Dr. Bancroft disco- 
 vered that if logwood be boiled in distilled water, it will give a 
 yellow decoction 3 , whereas we all know that a decoction of this 
 wood when made with common spring water is of a full red, or a 
 dark blood-colour. 
 
 By the experiments of Dr. Percival it has been ascertained, 
 that soft water acts more powerfully as a menstruum on vegetable 
 bitters and astringents than hard pump water, and that it dis- 
 solves some resinous bodies without any medium, or at least with 
 a much smaller proportion of mucilage than is commonly em- 
 ployed 4 . 
 
 The baneful effects of impure water on the human constitution 
 have been already noticed in a former part of this Essay ; and I 
 am now desirous of impressing upon my readers the importance 
 of their examining the nature of the water they drink, and of 
 advising them, should it be impure, to adopt some of the means 
 already recommended for obtaining it in a state of greater per- 
 fection. Herodotus relates, that in Ethiopia the inhabitants live to 
 
 1 See his Treatise on Bleaching, page 318. 2 Plinii Hist. Nat. lib. xix. 
 
 3 Bancroft's Philosophy of permanent Colours, vol. ii. p. 341. 
 
 4 Experiments and Observations on the Pump Water of Manchester, by Dr. 
 Percival, octavo, London 1769. 
 
ON WATER. 443 
 
 be an hundred and twenty years old; that they eat animal food 
 and drink the water of their own country, which is so light that 
 wood will not swim upon it, and that it is the use of this water 
 that prolongs their lives 5 . Dr. Percival says that the Spaniards 
 are entirely exempt from many of our cutaneous diseases ; and 
 the reason he assigns for this remarkable fact is, that the air of 
 Spain is clear and serene, and the water they drink pure and 
 wholesome. 
 
 In the water of the Pei-ho river in China, the mud is suspend- 
 ed in such large quantities as to render it scarcely potable. This 
 water is, however, quickly refined for use by the following simple 
 process. A small lump of alum is put into the hollow joint of a 
 bamboo, which is perforated with several holes. The water taken 
 from the river is stirred about with this bamboo for three or four 
 minutes, during which the earthy particles uniting with the alum 
 are precipitated to the bottom, leaving the water above them 
 pure and clear. Persons of rank in China are so careful about 
 the quality of the water intended for their own consumption, that 
 they seldom drink any but what has been distilled 6 . 
 
 It was formerly a general complaint that the health of mari- 
 time people was much injured by the internal use of water which 
 had become in some degree putrid by age, or in other words by 
 being kept stagnant for so long a period as is sometimes neces- 
 sary on long voyages. In modern times, however, various ex- 
 pedients have been contrived to obviate this great inconvenience. 
 Dr. Stephen Hales discovered that good wholesome water may 
 be procured on a voyage by the distillation of sea water, if jib 
 of chalk be previously mixed with every gallon of water put into 
 the still. A remarkable circumstance respecting the obtaining 
 of fresh water at sea by those who may be so unfortunate as to 
 have their ship frozen up in the ice all winter, is related by Mr. 
 Boyle. "An old sea captain," he says, " assured him, that when 
 his ship was immured with ice in the frigid zone, so that they 
 could not in a long time get so much as a barrel of salt water, 
 he made wells of the thick pieces of ice, to receive the liquor of 
 the thawed ice, and found this water (though on the main sea) to 
 be good fresh water fit for drinking, for dressing their meat, and 
 other uses, and that he never feared the want of fresh water in 
 those seas." 
 
 I am happy to embrace this opportunity of suggesting to those 
 who may have to supply large vessels with stores, that it is always 
 advisable to make choice of hard water for the use of the ship's 
 crew, as this resists putrefaction, and consequently will keep good 
 
 5 Herodotus, lib.iii. cap. 125. 
 
 6 Macartney's Embassy to China, by Sir George Staunton, Bart. 2 vols. quarto, 
 London, 1797, vol. ii. page 68. 
 
444? ON WATER. 
 
 much longer than soft water. The inconvenience of having none 
 but hard water to use for the different culinary and domestic pur- 
 poses, and the danger resulting from the continued drinking of 
 such water, can be easily obviated by the use of an alkali, which 
 might be employed occasionally to precipitate the impurities, and 
 on such quantities only as would be required for the wants of 
 those on board, as before directed at page 437. 
 
 Such ships as are fitted out from the port of London usually 
 take in their supply of water from the Thames, as this water is 
 said to possess properties which render it peculiarly fit for sus- 
 taining a long sea-voyage. At first, after being kept for some 
 time it turns in some degree putrid and offensive, probably from 
 some kind of fermentation; after which it again becomes pure and 
 palatable, so as to serve better than all others for sea-stock. Al- 
 though the question is of great consequence, I have never yet 
 heard any rational explanation of this phenomenon. " Water 
 taken'from the New River in London," says a writer in the Phi- 
 losophical Transactions, No. 127, page 652, "stank very mnch 
 after being kept stagnant for eight days, but when it arrived at 
 Virginia it again became sweet." The water of the Rhone, if it 
 be suffered to stand for the impurities to subside, and then be 
 put into earthen vessels, will not putrefy by heat, though it will 
 soon become fetid if put into wooden ones. Act. Lips. 1683. 
 
 Dr. Priestley, in his Observations on Air, vol. ii. p. 185, re- 
 lates, on the testimony of Mr. Garrick, that the reservoirs for 
 water in the town of Harwich are generally very foul on their 
 sides and at the bottom; and that provided these are not cleansed 
 of what adheres to them, they always preserve the water sweet, 
 otherwise it will become fetid and unfit for use, and the vessel 
 will not recover its sweetness till the sides and bottom grow very 
 foul again. Dr. Priestley supposes, that what they call impurities 
 is merely vegetating matter that adheres to the sides of the vessel, 
 and imbibes every thing tending to putrefaction. May not the 
 change which is effected in the Thames water be attributed to a 
 similar cause? 
 
 A curious fact has indeed been recorded by Dr. Boerhaave 
 respecting the preservation of water in a wholesome state under 
 the equator and between the tropics, where stagnant waters al- 
 ways breed an innumerable quantity of insects, and soon become 
 extremely putrid. Water, he says, which has thus spontaneously 
 grown offensive, may be easily rendered wholesome again, and 
 this merely by occasioning it to boil for a moment ; for this ope- 
 ration will destroy the animalcula, which, with the rest of the im- 
 purities, will subside, and then the addition of a very small quan- 
 tity of any strong acid, particularly the sulphuric, will render it 
 fit for use. Or if a small portion of sulphuric acid be put to the 
 
ON WATER. 44-5 
 
 water at the first, this will preserve it from animalcula or from 
 putrefying '. 
 
 I must not however suffer this part of the subject to pass over 
 without inserting a caution respecting the use of leaden reservoirs 
 and pumps of lead, for the preservation and conveyance of water 
 designed for drinking, because I have reason to believe that this 
 practice has been attended with many very fatal consequences. 
 
 The poisonous nature of lead when taken into the stomach in 
 a state of solution is now pretty generally known ; but as lead 
 when immersed in water is not soluble in that fluid, persons are 
 apt to imagine that no noxious effects can arise from the use of 
 leaden pipes and cisterns. But, though pure water of itself will 
 neither dissolve nor oxidize this metal, yet the oxygen of the at- 
 mosphere combined with the action of the water will convert it to 
 an oxide, when it absorbs carbonic acid gas with avidity from the 
 air, and this renders it capable of solution. The oxides of lead 
 are insoluble in water, but a small portion of any acid, even one 
 of the weakest kind (carbonic acid), will render them soluble. So 
 small a portion as 16 parts of carbonic acid is sufficient to acidify 
 83 parts of oxide of lead, the whole of which then becomes solu- 
 ble in water, impregnated with carbonic acid. 
 
 The white line which may be seen at the surface of the water in 
 leaden cisterns, is occasioned by the oxidizement of the metal ; 
 and as this oxide absorbs the carbonic acid of the atmosphere, 
 the oxide of lead becomes converted to carbonate of lead, and is 
 taken into the stomach of those who drink the water which has 
 been standing in such receptacles. Dr. Percival, Dr. Johnstone, 
 Sir G. Baker, Dr. Lambe, and other physicians, have related many 
 deplorable instances of individuals and even whole families being 
 taken off by this insidious poison. I have myself reason to believe 
 that some years ago I lost an amiable and highly valued relative 
 in this way, and therefore am desirous of inserting an account 
 of these facts, in the hope of recalling the attention of the public 
 to the state of their reservoirs for water, and thus being the humble 
 means of prolonging, if not of saving, the lives of many individuals. 
 
 It is necessary, however, to offer a few remarks on some of the 
 properties peculiar to water, and on the various applications of 
 this important fluid. The more obvious properties of water have 
 been mentioned in the early part of this paper, but there are se- 
 veral others to which it is also necessary to advert. 
 
 The different appearances and forms which water is capable 
 of assuming have already been slightly noticed. Some further 
 particulars, however, deserve our attention. In the state of elastic 
 
 Dallowe's Translation of Boerhaave, vol. i, page 348. 
 
446 ON WATER. 
 
 vapour it is perfectly transparent, or invisible to the eye. In this 
 condition it is completely soluble in atmospheric air; and though 
 it may by increase of temperature be attenuated in so remarkable 
 a degree, yet caloric, or the matter of heat necessary to convert 
 it into vapour, is incapable of occasioning any permanent change 
 or alteration in the chemical nature of this fluid. 
 
 Atmospheric air and water act reciprocally on each other. 
 The former dissolves aqueous vapour, and water dissolves or ab- 
 sorbs atmospheric air. In its natural state, water is generally 
 esteemed to be 850 times heavier than atmospheric air; but waters 
 differ a little in their specific gravity. I found that a bottle which 
 would hold only 4258 grains of distilled water at the temperature 
 of 60 would contain 4260 grains of New River water, or 4262 
 grains of pump water such as rises in Goswell Street, London. 
 
 Christopher Clavius, the eminent German mathematician, 
 poured some water into a bolt-head, and then sealed the mouth 
 of its neck hermetically, and marked with a diamond the place to 
 which the water rose at that time: he then hung it up, and eighty 
 years afterwards it was found in Kircher's study, just as full as it 
 was at first. Dallowe's Boerkaave, vol. i. p. 326. 
 
 The great fluidity of water is one of its most remarkable pro- 
 perties. This property has furnished Shakespeare with one of 
 his beautiful similes: 
 
 " Men's evil manners live in brass, their virtues 
 
 We write in water." 
 
 It is this which renders it so useful in many of the mechanical 
 arts, some of which I shall particularize hereafter; and it is owing 
 to this that it has always a tendency to find its own level. Hence 
 it has for many ages been employed to determime the plane of the 
 horizon, and for other philosophical purposes. The solvent power 
 of water is increased by removing the atmospheric pressure from 
 its surface. 
 
 The experiment with the solution of sulphate of soda, related 
 at page 424 of this Essay, though introduced for another purpose, 
 is sufficient to prove this fact also ; for the water holds all the 
 salt in solution, no longer than the bottle is closely corked ; and 
 as soon as the action of the atmosphere is restored, part of the 
 salt precipitates in a crystalline form. Hence, I conceive it to 
 be extremely desirable to try whether some important effects in 
 the art of dyeing, or rather in the processes of extracting the 
 colouring matter of vegetable substances, by means of water, 
 mio'ht not be produced by conducting those operations in a par- 
 tial vacuum. 
 
 Another circumstance respecting water is, that its specific gra- 
 vity is lessened, except in particular cases, by increase of tempe- 
 rature. This fluid might consequently be expected to increase 
 
ON WATER. 
 
 447 
 
 in its specific gravity in exact ratio with its reduction of tempera- 
 ture ; and this is found by experiment to be actually the case, 
 till it be reduced to 42 of Fahrenheit; but after that it becomes 
 specifically lighter by every further abstraction of caloric, and 
 furnishes a memorable instance of one of those deviations from 
 the usual course of nature which its omniscient and beneficent 
 Author has appointed for the preservation of the world, and the 
 welfare and felicity of its inhabitants. I need not, however, par- 
 ticularize, because the fact has already been sufficiently explained 
 in the second of these Essays. 
 
 In a variety of chemical operations it is important to know the 
 specific gravity of the water employed. A Table of its specific 
 gravity from 30 to 80 Fahrenheit will be found in the 1st volume 
 of Mr. Brande's Manual, where it is accompanied by an example 
 of its use in reducing the weight or bulk of water employed in 
 any case, to that which it would have at any other common tem- 
 perature. The solvent power of water is generally influenced by 
 its specific gravity. 
 
 Having, in the foregoing paragraph, adverted to the solvent 
 power of water, that circumstance has reminded me of a Table 
 of the solution of salts which I constructed some time ago for my 
 own use. This Table has been extremely serviceable in my own 
 laboratory: I shall therefore insert it, in the hope that it may be 
 of some use to many of those persons who may take the trouble 
 of perusing this volume. I cannot vouch for its perfect accu- 
 racy, in every instance, as some of the experiments are difficult 
 to accomplish ; but I believe it will be found to be sufficiently 
 correct for every purpose of real business. 
 
 A New Table of the Quantity of Water required to dissolve 100 
 Pounds of each of the following Salts. 
 
 Salts. 
 
 At 
 60. 
 
 Boil-l 
 ing. 
 
 Salts. 
 
 At 
 6<P. 
 
 Boil- 
 ing. 
 
 Sulphate of Magnesia . . 
 
 100 
 00 
 1670 
 200 
 500 
 
 2000 
 
 25 
 100 
 200 
 300 
 720 
 500 
 1120 
 50 
 84 
 
 75 
 190 
 500 
 100 
 
 224 
 
 133 
 20 
 
 50 
 100 
 50 
 
 335 
 
 Muriate of Magnesia 
 
 100 
 286 
 300 
 340 
 560 
 400 
 400 
 2000 
 1180 
 200 
 
 200 
 400 
 
 280 
 
 100 
 
 180 
 200 
 304 
 590 
 100 
 
 100 
 125 
 
 Potash 
 
 Pnfri^h 
 
 
 
 
 
 
 Phosphate of Ammonia 
 
 Potash . 5 
 Nitrate of Lime . . . 
 
 Chlorate of Potash . 
 Borax 
 
 
 Carbonate, sub, Ammon 
 
 Soda 
 
 , Prfn-h 
 
 
 
 
 
 
 Muriate of Lime .... 
 
 
 
 
448 
 
 ON WATER. 
 
 It appears, however, that the contraction and expansion of 
 water by change of temperature were well known to the early 
 chemists. Bacon and Boyle ' have both written expressly on the 
 subject; but I know of no author (except Sir Charles Blagden 
 and Mr. John Dalton) who has made any direct experiments 
 to determine what kind of ratio is observed by this fluid, in its 
 variation of bulk by the addition or abstraction of caloric. It 
 having occurred to me that a Table of the Expansion and Con- 
 traction of Water might be formed which would be very useful to 
 our manufacturers and other practical men, I undertook, some 
 time ago, a series of experiments for that purpose, and the fol- 
 lowing Table was the result. The specific gravity-bottle and 
 scales which were chosen on this occasion, are described in page 
 228, and are the same as were employed in making the Sulphu- 
 ric Acid Tables which are printed in the 7th Essay. 
 
 A New Table of the Expansion and Contraction of Water by Change 
 of Temperature. (The Barometer at 29|- Inches.) 
 
 Temp, 
 ac. to 
 Fahren- 
 heit. 
 
 Contents in grains 
 of a bottle holding 
 4265 grains of 
 pure water at 42. 
 
 Temp, 
 ac. to 
 Fahren- 
 heit. 
 
 Contents in grains 
 of a bottle holding 
 426.5 grains of 
 pure water 3142^. 
 
 Temp, 
 ac. to 
 Fahren- 
 heit. 
 
 Contents in grains 
 of a bottle holding 
 4265 grains of 
 pure water at 4:2-. 
 
 32 
 
 4260 
 
 64 
 
 4257 
 
 120 
 
 4220 
 
 34 
 
 4.261 
 
 68 
 
 4256 
 
 126 
 
 4214 
 
 36 
 
 4262 
 
 70 
 
 4255 
 
 134 
 
 4208 
 
 38 
 
 4263 
 
 74 
 
 4254 
 
 140 
 
 4199 
 
 40 
 
 4264 
 
 80 
 
 4252 
 
 146 
 
 4191 
 
 42 
 
 4265 
 
 84 
 
 4249 
 
 150 
 
 4185 
 
 44 
 
 4264 
 
 88 
 
 4245 
 
 154 
 
 4180 
 
 46 
 
 4263 
 
 92 
 
 4240 
 
 162 
 
 4172 
 
 48 
 
 4262 
 
 96 
 
 4237 
 
 170 
 
 4160 
 
 50 
 
 4261 
 
 100 
 
 4234 
 
 178 
 
 4150 
 
 52 
 
 4260 
 
 102 
 
 4232 
 
 184 
 
 4142 
 
 56 
 
 4259 
 
 108 
 
 4228 
 
 192 
 
 4130 
 
 60 
 
 4258 
 
 112 
 
 4226 
 
 200 
 
 4116 
 
 Flattering myself that this Table may be of very essential use in 
 many cases of real business, I am desirous of giving an example 
 of its application before I pass on to any other branch of the sub- 
 ject. Suppose a boiler, or other vessel of capacity, to hold 4260 
 pints, or 532^ gallons of water at any temperature on the range 
 of Fahrenheit's scale between 32 and 52 degrees, by looking at 
 the figures opposite to 150 in the second column of temperature, 
 it will be seen that such boiler would contain only 4185 pints, or 
 little more than 523 gallons, if heated to that degree; and on look- 
 ing at the last line, it will appear that such vessel would hold only 
 4116 pints, or 514^ gallons, at 200: therefore, should a boiler 
 
 1 Experimental History of Cold, by the Honourable Robert Boyle ; quarto, 
 London 1683, pages 92 and 113. 
 
ON WATER. 449 
 
 be completely filled by 532^ gallons of water of the temperature 
 of 52, no less than 18 gallons of it would flow over the sides of 
 the vessel before the remainder could be heated to 200. The 
 maximum of the density of water is at about 4-2 : this fluid there- 
 fore becomes of less specific gravity, whether it be heated above 
 or cooled below that point. This accounts for the seeming ano- 
 maly in the table, by which it appears that water occupies the 
 same room at 32 as it does at 52. 
 
 There are some phenomena of water which seem inexplicable, 
 though the authorities I have for them cannot be disputed. 
 
 If water be thrown into a crucible of melted glass in a high 
 state of incandescence in a glass-house furnace, the globules of 
 water will dance upon the surface of the melted glass for a con- 
 siderable time, like so many globules of mercury upon a rum- 
 head ; but if a small quantity, or even a pint, of water were to be 
 thrown into such a crucible before the glass is completely fused 
 and while the sandiver is upon its surface, the water would be 
 rarefied into steam in an instant, an explosion would be the con- 
 sequence, and the furnace would probably be blown into pieces. 
 
 In like manner does water sooner evaporate from a plate of iron 
 that is heated to a red-heat only, than from one that has been 
 brought to a welding heat, or nearly to the point of fusion. 
 
 Again, in the manufacture of black bottles it frequently hap- 
 pens, while the workmen are engaged in moulding and blowing 
 the bottles, that the metal becomes more cooled than they could 
 desire, so that they find it necessary to give directions to their 
 attendants to throw in more coal and increase the fire. This, 
 however carefully it may be done, will sometimes produce so much 
 dust that the surface of the glass becomes covered with carbona- 
 ceous matter. Whenever this occurs, it occasions such a motion 
 within the crucible, that the metal appears as though it were ac- 
 tually boiling ; and if it were to be used in this state, every bottle 
 would be speckled throughout and full of air bubbles. But as it 
 would be very inconvenient to wait for the whole of this carbona- 
 ceous matter to be consumed by combustion, and as, by being 
 partly mixed with the glass itself, it might occasion it to boil over 
 the sides of the crucible, it was thought very desirable to discover 
 an easy and immediate remedy for the accident, and this has been 
 found in common water. 
 
 Whenever the accident occurs, the workman throws a little 
 water into each crucible ; and this has the effect, not only of still- 
 ing the mass immediately, but it renders the metal as smooth 
 and pure as before. This curious and almost instantaneous effect 
 is probably owing to the water becoming decomposed, and afford- 
 ing its oxygen to the coal-dust, and converting it to carbonic 
 
 So 
 
450 ON WATER. 
 
 acid gas, which immediately escapes and is dissipated in the at- 
 mosphere. 
 
 Nothing now remains but to describe some of the various USES 
 to which water has been applied, in different parts of the world, 
 a knowledge of which I conceive may be turned to advantage by 
 some classes of readers. 
 
 In enumerating the several purposes to which water has been 
 applied in all ages and countries, I shall slightly pass over the 
 account of the musical instruments of antiquity which were made 
 to play various tunes by means of the pressure of water ; and 
 shall also decline any lengthened detail of the methods which were 
 formerly adopted by superstition for the trial of supposed delin- 
 quents, by the immersion of the unhappy individuals in water, as 
 these are matters more of curiosity than utility and improvement. 
 Andrew Brice, in describing one of the palaces of the Grand 
 Duke of Florence, says, "The pilasters are adorned with an organ, 
 which by means of water plays several tunes ;" and in a note states, 
 that such hydraulic organs are to be seen in several grottos in 
 Italy. Brice's Geog. Diet. vol. i. p. 574. The invention, how- 
 ever, is not modern ; for Cresibus of Alexandria, who lived in the 
 reign of Ptolemy Euergetes, is said to have contrived them. 
 Archimedes and Vitruvius have left descriptions of the instru- 
 ment, and we find the figure of one on the reverse of a large me- 
 dallion of Valentinian. 
 
 It was formerly a custom in several countries to weigh those 
 that were suspected of magic, it being generally imagined that 
 sorcerers were specifically lighter than other men. This was the 
 origin of the practice of throwing the accused person into water; 
 when, if his body floated upon the surface, he was convicted of 
 witchcraft and burnt, but if it sunk to the bottom he was acquitted. 
 M. Ameillon has published a curious paper in the 37th volume of 
 the Memoirs of the Royal Academy, on this particular subject, in 
 which he endeavours to show the probability that some of these 
 miserable persons did actually float on the water. He states that 
 among the multitude of persons subject to hysteria and other si- 
 milar complaints there are several who cannot sink in the water ; 
 and hence he concludes that the pretended magicians and sor- 
 cerers who floated when tried by the water-ordeal^ were persons 
 deeply affected with nervous disorders. Pomme, the celebrated 
 French physician, in his Traite des Affections Vapoureuses, sup- 
 ports the same opinion. 
 
 Water may be employed as a mechanical power in some of our 
 large manufacturing concerns with great advantage. In the 448th 
 Number of the Philosophical Transactions, page 231, there is a 
 description of a very ingenious water-bellows, invented by Mr. 
 
ON WATEH. 451 
 
 Triewald, for the use of Iron forges and other ftirnaces, where 
 a great heat is to be produced by forcing a large quantity of at- 
 mospheric air into the fire-place. Since the publication of that 
 account, water-bellows upon different constructions have been 
 employed in various parts of this kingdom, for the business 
 already mentioned, and also by those makers of utensils in iron 
 called iron-founders ; but the power which may be thus given 
 by water is so great, and the principle is in itself so simple, that 
 I cannot help wishing it were more universally known ; for I am 
 confident that it might be brought into greater practice, and ex- 
 tended to a multiplicity of arts and manufactures to which it has 
 not yet been applied. It is not possible, however, to give the 
 reader an accurate idea of this curious mechanical contrivance 
 without a drawing ; I must therefore refer him to the copper- 
 plate engraving which accompanies the account of it in the num- 
 ber of the Philosophical Transactions above mentioned. 
 
 Bellows moved by water have been long in use at the iron 
 forges in Sweden ; and water-bellows on a different construction, 
 and which are employed at Tivoli in Italy, are described in one 
 of the early volumes of the Philosophical Transactions ; but those 
 by Mr. Triewald are more simple and on a better principle. 
 
 In some particular situations, water is very profitably employed 
 in drawing coals and other minerals from the bowels of the earth. 
 Thirty years ago I recollect having been much gratified in view- 
 ing an apparatus of this kind which was then at work in the coal 
 district of Derbyshire, I think somewhere near Ham ; it may be 
 thus described : 
 
 Two wooden vessels, or buckets hooped with iron, are fas- 
 tened one at each end of a very thick hempen rope, and this rope 
 is made to pass over a large wheel which is fixed exactly perpen- 
 dicular to the mouth of the shaft of the mine. In the commence- 
 ment of the operation, one of these empty buckets is first lowered 
 to the bottom of the pit, and when it is filled with coals, a boy 
 who is stationed above, and close to the mouth of the pit, lowers 
 the end of a leathern pipe which he holds in his hand, and this 
 immediately fills the upper bucket with water. This being now 
 heavier than the loaded bucket below, it begins to descend with 
 considerable velocity into the mine, while the other ascends with 
 equal speed, and soon arrives at the surface, charged with the 
 coal or other mineral designed to be raised. When the bucket 
 of water reaches the bottom of the pit, it is interrupted by a strong 
 iron pin placed vertically in the ground, exactly in the centre of 
 the spot where the bucket must rest; and this pin forces up a 
 large valve in the bottom of that receptacle, allowing the whole 
 mass of water to escape in an instant. The vessel which has ar- 
 rived at the top of the pit being emptied, this is now, in its turn, 
 
4- 5 2 ON WATER. 
 
 filled with water, while the men below are loading the other with 
 the mineral, which is then to be raised by the power of the de- 
 scending water, as before ; the buckets continuing to ascend and 
 descend in rotation and without interruption. The specific gra- 
 vity of water being only a trifle greater than that of a mass of 
 loose coal, this circumstance renders water peculiarly fit for the 
 use of a colliery in the manner above described. 
 
 It is obvious however that this contrivance cannot be adopted 
 every where ; but I am persuaded there are many places in this 
 kingdom where minerals are raised at a very great expense, 
 though their situations are in every respect favourable for the em- 
 ployment of this machine; and it is this consideration which made 
 me desirous of explaining the scheme in this Essay. 
 
 Mines are, moreover, frequently opened on the side of a hill 
 or mountain : and as springs of water are generally to be found 
 in those situations, this method might be employed in all such 
 places, provided there be either a rivulet at the bottom of the 
 mine, or that a fissure in the rock can be found, to carry off the 
 descending water. 
 
 I had forgotten to remark, that in providing a stream for set- 
 ting this apparatus in motion, all that is needful is, to fix a wooden 
 spout into the side of a pool or other contiguous reservoir of 
 water, exactly even with the surface of the water, and then to adapt 
 a flexible tube of leather or other suitable material to that end of 
 the trough which comes to the mouth of the mine. In consider- 
 ing this arrangement, it will be seen that the mere elevation of the 
 leathern end of the pipe a few inches only, will entirely prevent the 
 running of the water; the machine therefore may be kept in motion 
 at any time by a child ; and when it is not at work, all that is re- 
 quired is to hang the end of the pipe upon a hook fixed in a post 
 at the side of the pit, when the current will instantly cease. 
 
 I might here attempt to describe the various methods of raising 
 water from great depths ; but as this would lengthen the Essay 
 more than would be desirable, I must refer the inquiring reader 
 to Nicholson's quarto Journal of Natural Philosophy, vol. iv. 
 p. 16-5466, where he will find several elaborate memoirs on that 
 subject, accompanied with plans and engravings. 
 
 The fertility of Egypt in consequence of the annual inundation 
 of the Nile, is a matter of general notoriety ; and many of the 
 well informed agriculturists of these kingdoms, availing them- 
 selves of the knowledge of this fact, do periodically supply their 
 estates with artificial currents of water, and derive great benefit 
 from the practice. 
 
 The Chinese have long known how to value the practice of 
 watering land artificially. " I observed," says Van Braam, " se- 
 veral mills which raise the water of the river above the banks, 
 
ON WATER. 4-53 
 
 whence it runs into reservoirs, to be afterwards diffused, by 
 means of canals and aqueducts, over the fields that require irri- 
 gation. These mills are of simple construction, and entirely com- 
 posed of an assemblage of thin bamboos, except the axle-tree of 
 the wheel, which is of timber. In no part is the smallest piece 
 of iron or any other metal employed. The whole machine, as 
 well as I was able to judge, is from 18 to 28 feet in diameter 1 ." 
 Being myself one of those who have never entertained a fear of 
 the state being injured by the land becoming too productive, and 
 recollecting that it was said of old, that he deserved well of his 
 country who could make two blades of grass to grow where only 
 one grew before, it is incumbent on me to recommend, in the 
 most forcible terms, the practice of irrigation, and to urge its ge- 
 neral adoption. 
 
 Mr. Boswell, who has written an elaborate treatise on this sub- 
 ject, says, "It is inconceivable what twenty-four hours water pro- 
 perly conveyed over the land will do in a dry season; a beautiful 
 verdure will arise in a few days, where a parched, rusty soil could 
 only be seen ; and one acre will then be found to maintain more 
 stock than ten acres without such management. Moreover, al- 
 most the whole of the expense in this mode of cultivation, is the 
 actual manual labour of a class of people who can be employed 
 in no other way for the support of their families ; consequently 
 the expenses can be comparatively but small, though the im- 
 provement must be great and durable*. 
 
 It is related of Mons. Pestre, a skilful physician and an en- 
 lightened cultivator of land among the Cevennes mountains, that 
 at the first threatenings of a storm he used to clothe himself in a 
 long garment of oil cloth, with an enormous hat of tinned iron 
 firmly fixed by means of straps. Thus defended, he hastened 
 into the midst of his possessions, where alone, with a mattock in 
 his hand, he directed the water to the feet of his trees, and col- 
 lected the surplus in cavities which he had formed in the rock it- 
 self. By these exertions he constantly prevented injurious inun- 
 dations on his estate, and procured water for his ground at such 
 times when the burning heats rendered it necessary. His neigh- 
 bours, who, as usual in such cases, at first derided him, were con- 
 strained to admire his industry and envy his gains ; for, in con- 
 sequence of this labour, he quadrupled the usual product of his 
 grounds. 
 
 Another equally striking proof of the influence of water on 
 
 1 Van Braam's Embassy to the Court of the Emperor of China, London 1798, 
 vol. i. p. 72. 
 
 2 Boswell's Treatise on Watering Meadows, illustrated with five copper-plates. 
 Third edition, octavo, London, 17U2, p. 12. 
 
454 ON WATER. 
 
 vegetation may be found in the very remarkable industry of the 
 gardeners who cultivate the marshes near Paris. From these 
 marshes, situate all around that great city, they derive large pro- 
 fits ; they cover the ground with abundant and uninterrupted 
 crops, and they are indebted for this almost astonishing series of 
 vegetable production to the enormous quantity of water, which 
 they are incessantly conveying into their grounds, and to the 
 continual waterings with which they fertilize them. 
 
 We read of a very extraordinary stream of water that supplies 
 the public baths of St. Philip, in Tuscany, which carries a pecu- 
 liar kind of earth, or earthy salt, in its current. This earth, when 
 it is collected and condensed in the cavities of any body that is 
 employed to oppose its course, acquires the nature, hardness, and 
 colour of alabaster, and assumes the forms of the cavities in which 
 it is thus collected. The ingenious Mr. Latapie, convinced by 
 repeated experiments of this singular property of the water of 
 these baths, had moulds made of several single figures, and even 
 groups ; and, by placing them in a certain manner against the 
 current of this stream, he collected in their cavities the earth in 
 question, and thus formed basso relievos of beautiful alabaster. 
 This success enabled him at length to establish a manufacture, 
 which has rendered the finest productions of sculpture more easily 
 attainable in that part of the country than they had hitherto been, 
 and much more precious by the accuracy of the copy l . 
 
 But it would be an endless attempt to endeavour to enumerate 
 all the various kinds of water which have been noticed by the re- 
 spective writers who have given us accounts of their travels into 
 different parts of the world. I therefore conclude with the more 
 pleasing task of inviting the contemplative reader to devote a 
 moment or two to the recollection of a few of the more obvious 
 advantages which we derive in every quarter of the globe from 
 the possession of water. 
 
 Water is indispensable as the beverage of man and other ani- 
 mals ; as the medium for conveying nourishment to vegetables ; 
 and for rendering effective those important senses of sight, taste, 
 and smell. It has been well remarked, that that most wonderful 
 machine the eye can only represent objects to our senses by the 
 means of humours composed chiefly of water ; and that the glassy 
 coats of this important organ must lose their transparency, were 
 they not constantly moistened with water. 
 
 I am supported in this assertion by the testimony of an anato- 
 mist of great credit and respectability. " Because," says he, " the 
 
 1 For an account of this singular manufactory see Rozier's Journal for June 
 177G; or the Monthly Review for November 1/76, p. 391. 
 
ON WATER. 455 
 
 outermost coat of the eye might be pricked, and this humour let 
 out, therefore nature hath made provision to repair it by the help 
 of certain water-pipes, or lymphaeducts, inserted into the bulb of 
 the eye, proceeding from glandules that separate this water from 
 the blood 2 ." 
 
 In like manner with regard to smell, the respective odours of 
 bodies are collected, blended, perfected, and preserved, by means 
 of water ; nor could they be conveyed to the proper nerves had 
 not nature supplied these parts with humidity, at once to lubri- 
 cate the vessels, and to collect the odoriferous exhalation. " The 
 use o this pitu'ita," says Mr. Cooper, "is to keep the membrane 
 soft. By this means the olfactory nerves expanded on this mem- 
 brane, are rendered capable of the perception of odoriferous 
 effluvia, which otherwise the dryness of the part would destroy 3 ." 
 Neither is any body sapid, unless it either contain water or be dis- 
 solvable therein ; for it is well known that those substances which 
 are most soluble in water, soonest imprint the sense of taste upon 
 the organs which are destined to receive that impression : a dry 
 tongue can no more taste than dry nostrils smell, or a dry eye 
 distinctly see 4 . 
 
 The most beautiful tints of flowers would also be unable to please 
 us if they were divested of water ; nor would any of the products 
 of the vegetable kingdom be capable of fermentation, were it not 
 for the intervention of this important fluid. Clay would be mere 
 useless dust without water, and incapable of being modelled into 
 any of the beautiful forms in which we now see it, or applied to 
 any of its present important uses. Lime and sand might be mix- 
 ed and blended for ever without their forming a compact mass ; 
 but by the addition of water they acquire the property of harden- 
 ing, and of forming for us excellent cements and durable habi- 
 tations. 
 
 Almost all chemical operations require the presence of water, 
 and many others cannot be conducted to any advantage without 
 its assistance. The most powerful and heterogeneous salts, if per- 
 fectly dry, may be mixed without any seeming effect ; and few if 
 any decompositions could be produced without the agency of this 
 all-pervading and important fluid. The processes of decoction, 
 solution, distillation, precipitation and crystallization, are all de- 
 pendent upon water for their success. Starch, glue, and every 
 other kind of mucilage, owe their tenacity to water; and it is pro- 
 bable that most of the substances on the face of the earth would 
 
 * Ray's Physico-Theological Discourses. 
 
 9 Mr. William Cooper's Dissertation on the Smell, published in Drake's Ana- 
 tomy, vol. ii. London, Third Edition, page 313. 
 4 See Dr. C. Lucas on Water, 8vo, London 175G, p. 70. 
 
456 ON WATER. 
 
 fall into shapeless or pulverulent masses, useless and inert, were 
 it not for the binding effects of this most accommodating and 
 wonderful fluid. 
 
 There are also various reasons for believing that the salubrity 
 of the atmosphere is preserved by means of water ; and we are 
 surely not a little indebted to the Great original Contriver of all 
 things for that immense accumulation of this fluid which is col- 
 lected in the ocean, by means of which we are enabled, without 
 labour or fatigue, to visit every clime on the surface of our globe ; 
 to barter the valuable products of each with one another; and to 
 interchange all the important blessings of religion, literature, sci- 
 ence, civilization, and the arts. 
 
ON SAL-AMMONIAC. 457 
 
 ESSAY XIV. 
 
 ON SAL-AMMONIAC. 
 
 SAL-AMMONIAC, or Muriate of Ammonia, is a peculiar neutral 
 salt, well known to the ancients. From the name which this pro- 
 duction has always borne, it is extremely probable that it was 
 first collected at Ammonia, a country which occupies the midland 
 part of Libya in Africa, closely bordering on Egypt. 
 
 The ancient Temple of Jupiter Ammon was also situated in the 
 country above mentioned, and the proprietors of the stables for 
 the reception of the camels of the pilgrims had contrivances for 
 preserving the urine of these animals lor the manufacture of sal- 
 ammoniac 1 . In consequence of this, the traffic in muriate of am- 
 monia became very considerable, and the ancient Greeks and Ro- 
 mans, who employed this singular salt for many purposes, pro- 
 cured their supply from that quarter. In process of time, the na- 
 tive Egyptians also learnt how to make sal-ammoniac, and for 
 many ages the whole of Europe had no means of obtaining this 
 salt, except by importing it from that country. 
 
 According to Pococke and Niebuhr, manufactories in later 
 times were erected for the express purpose of making this saline 
 compound, at Dsjise, at Geeza, and at Rosetta a sea-port on the 
 coast of Alexandria, as it was found impossible for the whole of 
 Europe to be supplied from the original manufactory. 
 
 In the year 1716 GeofFroy, a celebrated chemist and physician 
 of Paris, read to the Academy a memoir on the composition of 
 muriate of ammonia, and gave it as his opinion that it came from 
 Egypt and was the product of sublimation. In the year 1720 he 
 published an account of a series of experiments, to prove that 
 sal-ammoniac might be made profitably in Europe. 
 
 Little was known however of the methods by which this salt 
 was procured in Egypt, until the year 1719, when Lemere, the 
 French Consul at Grand Cairo, sent an account of its manufac- 
 ture to the Academy of Sciences at Paris, who published it in one 
 of the volumes of their Transactions. I suspect this French Con- 
 sul to have been a different person from Nicholas Lemery, the ce- 
 
 1 Pliny, lib. xxxi. cap. / 
 
458 ON SAL-AMMONIAC. 
 
 > % 
 
 lebrated chemist of Rouen, who I believe died early in the eigh- 
 teenth century. He might perhaps have been a son of the afore- 
 mentioned Nicholas, for he was also an eminent chemist and like- 
 wise physician to the French king. The following is however an 
 abridged detail of the process, as given by Lemere. 
 
 The natives of Egypt (says he) collect for this purpose the ex- 
 crements of camels, oxen, and other animals which feed on sa- 
 line plants. These excrements are dried by applying them to 
 the surface of walls; and when they are sufficiently dry, they are 
 burned as fuel in their common household fires. It is from the 
 soot afforded by these burning substances that the muriate of 
 ammonia is extracted. For this purpose the soot is put into large 
 glass bottles 18 or 19 inches in diameter, terminating in a neck 
 several inches high. These glasses are filled to within four 
 fingers breadth of the neck, and gradually heated for 72 hours. 
 Towards the second day the muriate of ammonia sublimes and 
 adheres to the upper part of the bottles. When the process is 
 finished and the whole apparatus has been well cooled, the vessels 
 are broken, and the lumps of ammoniacal salt are taken out for 
 sale 1 . Five pounds of the soot procured from the burning of this 
 excrementitious matter are expected to produce one pound of 
 muriate of ammonia. 
 
 Here it may be worth observing that the soot of Newcastle 
 coals will produce an abundance of sal-ammoniac. Some few 
 years ago there was a considerable manufactory of this salt in the 
 neighbourhood of London, which was supplied entirely by the 
 common soot collected from the chimneys in the metropolis. 
 
 Respecting the African sal-ammoniac, other writers relate, that 
 as sea salt is always given copiously to the camels, during their 
 journeys in the caravans over the Desert to Alexandria, their urine 
 and dung consequently become very replete with the salt. The 
 dung of these animals being burnt in the public ovens for hatch- 
 ing chickens for the caravans, and also in their common fires for 
 culinary purposes, the volatile salt is produced in the soot, and 
 this requires only to be purified by sublimation, in order to form 
 the cakes of muriate of ammonia which are exported to Europe. 
 
 Chaptal relates, that he obtained sal-ammoniac from the soot 
 of cow-dung and that of horses, which run wild in the immense 
 plains of Camargue and Crau, and upon the borders in the nu- 
 merous marshes in the vicinity of the Mediterranean, but that 
 he soon found he could only procure it from the dung of these 
 animals while they continued to live on marine plants. 
 
 Another account of the Egyptian manufacture may be seen in 
 Hasselquist's Travels in the Levant. It differs in some respects 
 
 1 Fourcroy's System of Chemistry, vol.iii. p. 275. 
 
ON SAL-AMMONIAC. 4-59 
 
 from the foregoing, but it is extremely interesting. He relates 
 that the poor inhabitants of Egypt are occupied for several 
 months of the year in collecting the excrementitious products 
 already spoken of; that they mix these with cut straw to assist 
 its drying ; that when dried they use it as fuel, having in reality 
 no other kind ; and that they make a business of collecting the 
 soot from all parts of the country to sell to the sal-ammoniac 
 makers at Grand Cairo. 
 
 When the origin of this volatile salt had thus been made known, 
 it was soon discovered that it was a compound body ; that it ex- 
 isted ready formed in some parts of the earth ; and that it con- 
 sisted of a peculiar alkaline substance, in close union with mu- 
 riatic acid. 
 
 The acid which was found to be one of its component parts 
 had been known for a century before, and employed for a variety 
 of purposes; but this was not the case with its base, the ammonia, 
 or volatile alkali, which engaged the attention of chemists for many 
 years afterwards, and long before its nature and properties were at 
 all understood, or that it had been even suspected to be any thing 
 more than a simple undecomposable body. 
 
 Tournefort was the first chemist who asserted that sal-ammo- 
 niac is composed of muriatic acid and ammonia : he made this 
 known in the year 1 700. Muriate of ammonia is sometimes found 
 in the environs of volcanoes, and in a state of solution in some 
 lakes in Italy and Tuscany 2 , It exists also in the mountains of 
 Tartary, in Thibet, and in the grottos in the vicinity of Pouzzola 3 . 
 This salt is likewise found in the country of the Kalmucks, and 
 sent from thence into various parts of Russia for sale. The spe- 
 cific gravity of muriate of ammonia is 1.420; it is soluble in ra- 
 ther more than three times its own weight of water in the tem- 
 perature of 60, and in an equal weight of water when at 212 . 
 Its solution produces cold. 
 
 According to the Baron Riedesel, muriate of ammonia is found 
 plentifully in the neighbourhood of Mount Etna. He remarks 
 that ^ the lava is not various and beautiful like that of Vesuvius, 
 of which above forty kinds have been collected, for that the lava 
 of this mountain contains chiefly iron and sal-ammoniac 4 . Wieg- 
 leb states, that sal-ammoniac is met with at the apertures and 
 fissures of the internal crater of Mount Vesuvius, but that the 
 sublimation is never observed till two months after the eruption 5 . 
 
 Basil Valentine, who wrote in the 15th century, speaks of sal- 
 
 a Rozier's Journal, xvi. p. 362. 
 
 3 Fourcroy's System of Chemical Knowledge, vol.iii. p. 274. 
 
 4 Riedesel's Travels through Sicily, translated by Foster, 8vo, London 1779. 
 * Hopson's Translation of Wiegleb, p. 226. 
 
460 ON SAL-AMMONIAC. 
 
 ammoniac; and Geber, who lived 600 years earlier, classes it 
 among volatile bodies, and gives directions about subliming it 1 . 
 
 In the year 1773, Dr. Priestley separated the ammonia from 
 sal-ammoniac by means of quick lime, and exhibited this alkali 
 for the first time in the state of gas. He may therefore be said 
 to have been the real discoverer of ammoniacal gas*. This gaseous 
 substance was afterwards examined by him in various ways, and 
 he even succeeded in decomposing it by means of electricity ; but 
 it does not appear that he had conceived any idea of the nature 
 of its composition, though he seems to have been well acquainted 
 with the compound nature of the salt from which he extracted 
 the alkaline gas. The honour of this latter discovery was re- 
 served for Scheele and Bergman ; and about the year 1785 Ber- 
 thollet published a memoir which confirmed the account previ- 
 ously given by the foregoing chemists, that ammonia is a com- 
 pound of nitrogen and hydrogen. Berthollet pronounced am- 
 monia to be a compound of 121 parts by weight of nitrogen, with 
 29 of hydrogen. It is now found to consist of one proportional of 
 nitrogen 14, and three of hydrogen 3, which will make its equiva- 
 lent number 17. Muriate of ammonia, or sal- ammoniac, is com- 
 posed of one proportional of ammonia 1 7 combined with one pro- 
 portional of muriatic acid 37, and its equivalent number is 54. 
 
 Pure ammonia is known only in the state of gas. This gas has 
 a very pungent and acrid smell, but when plentifully diluted with 
 atmospheric air its odour is rather pleasant and refreshing ; it is 
 a colourless gas, and being much lighter than atmospheric air, it 
 is of course volatile. 
 
 Ammonia is also caustic and corrosive, and will unite with oil 
 into a saponaceous compound ; but it has not the power of act- 
 ing violently on animal substances like the fixed alkalies, potash, 
 and soda. 
 
 Ammonia is capable of uniting with most of the acids, and 
 forming with them neutral salts. Thus we have carbonate of am- 
 monia, nitrate of ammonia, sulphate of ammonia, muriate of am- 
 monia, and other salts, with this alkali for their base. 
 
 The sulphate and muriate of ammonia have been found native 
 in the neighbourhood of volcanoes and in other parts of the globe: 
 the triple salt called phosphate of soda and ammonia is found in 
 human urine; and since the decomposition of sal-ammoniac has 
 been understood, several other salts have been formed in the la- 
 boratory by its means for purposes of medicine and for various 
 uses in the arts. Klaproth analysed a specimen of native sal- 
 
 1 See Russet's Translation of Geber 's Works, London 1678, p. 7- 
 
 3 See Priestley's Experiments on Air, 8vo, London 1/81, vol. i. p. 166. 
 
ON SAL-AMMONIAC. 40 1 
 
 ammoniac from Mount Vesuvius, and found it to be an uncon- 
 taminated muriate of ammonia, free from sulphuric acid, though 
 the salt must have been generated in an atmosphere impregnated 
 with sulphureous exhalations. He considers this salt to be a pro- 
 duct of the mountain ; that its basis, the ammonia, is composed of 
 the hydrogen and nitrogen from the water, and the atmospheric 
 air, which during that great chemical operation of nature under- 
 go decomposition ; and that this ammoniacal gas uniting with the 
 acid gas from the decomposed muriate of soda of the sea water 
 which finds its way into the volcano, forms the muriate of am- 
 monia in question. The Bokarian Tartary, a district of Usbeck 
 Tartary, in Asia, also furnishes a native muriate of ammonia. 
 Klaproth examined a specimen of this salt, and found 100 parts 
 of it to consist of muriate of ammonia 97.50 and sulphate of am- 
 monia 2.50. Analytical Essays, vol. ii. p. 71. 
 
 We have also fluate of ammonia, the arseniate of ammonia, the 
 acetate of ammonia, the oxalate of ammonia, and the phosphate 
 of ammonia; the latter of these is much employed as a flux for 
 the blow-pipe, and in making pastes to imitate precious stones. 
 
 None of the ammoniacal salts however are consumed or manu- 
 factured in such abundance as the muriate of ammonia, the im- 
 mediate subject of this Essay ; its uses and application are very 
 general and too various to be enumerated, though the mention 
 of a few of them will show the great importance of this saline 
 compound. 
 
 It is employed by the dyer to moderate the action of nitric 
 acid in the preparation of nitrate of tin, and also to modify the 
 hue of some particular colours. The alkaline part of this salt is 
 employed by dyers in connection with archil, an article which 
 cannot be prepared without ammonia. It is likewise used by 
 certain artists in the process of soldering; by the workers in cop- 
 per and iron, to prevent the oxidizement of the metallic surfaces 
 which they intend to cover with tin ; in pharmacy, for the pre- 
 paration of several important medicines : by the makers of snuff, 
 in order to render that article more stimulant and poignant; and 
 by the manufacturing and philosophical chemist, for the produc- 
 tion of artificial cold ; for analysing certain metallic substances ; 
 for the extraction of pure liquid ammonia, and for the prepara- 
 tion of the ammoniacal salt with which smelling-bottles are filled, 
 and which on account of its solid form is in a variety of ways con- 
 venient and useful. I have been informed by a chemist of Bir- 
 mingham, that not less than 20 tons of sal-ammoniac are annually 
 consumed in that town by the workers in metal only. 
 
 When chemists had discovered the methods of separating the 
 volatile alkali from sal-ammoniac, and had become generally ac- 
 quainted with the nature of this gas, attempts were soon made to 
 
462 ON SAL-AMMONIAC. 
 
 discover other sources from whence it might be procured, be- 
 sides that of muriate of ammonia. It had been perceived that it 
 was frequently disengaged from animal and vegetable substances 
 when in a state of putrefaction ; it was therefore natural to ex- 
 amine a variety of these substances for its production, and it was 
 soon found that fish, animal horns, bones, hoofs, &c. when sub- 
 mitted to dry distillation, would yield this curious and peculiar 
 substance in abundance. It should be remembered that all the 
 above animal substances yield ammonia exactly in proportion to 
 the quantity of nitrogen contained in them. Dr. Austin asserts, 
 that ammonia is always formed where iron rusts in water which 
 has a constant communication with the atmosphere. 
 
 A plentiful source of ammonia, accessible to the people of all 
 countries, and at all seasons, having thus been discovered, it im- 
 mediately became a desideratum how to combine it, at a cheap 
 rate, with muriatic acid, so as to form muriate of ammonia, and 
 preclude the necessity of sending in future to Egypt for a supply 
 of this useful and important salt ; and this gave rise to the several 
 manufactories established in different parts of Europe for this 
 purpose. 
 
 Wiegleb, the eminent German chemist, says that the first Eu- 
 ropean sal-ammoniac manufactories were established in England 
 and Scotland ; that, soon after these, one was set up at Paris by 
 Baume, and then another at Brunswick in Germany, in the year 
 1759, by two brothers of the name of Gravenhorsts, which were 
 followed by divers others. In the year 1756, a very considerable 
 manufactory of this salt was established by Messrs. Dovin and 
 Hutton at Edinburgh. 
 
 When the ammonia had been procured as above mentioned, 
 the most obvious method of forming sal-ammoniac was that of a 
 direct mixture of the acid with the alkali ; but when the first cost 
 of the two materials, the muriatic acid and the ammonia, was con- 
 sidered, together with the great loss of gas which is always sus- 
 tained by the mixture of these two volatile substances, it was 
 found that the process, thus conducted, could not be carried on 
 to any advantage in this country. 
 
 At this period however the resources of chemists had become 
 much augmented, and every eminent practitioner in Europe was 
 beginning to avail himself of the method of forming new sub- 
 stances by means of double elective attraction, or an interchange 
 of principles, arising from the mixture of different compounds, 
 one of the most valuable branches of chemical science. 
 
 Here it may be remarked, that Stahl seems to have been the 
 first person who propagated the idea, that a compound substance 
 could not be decomposed without the intervention of some other 
 substance which has a superior affinity for one of the component 
 
ON SAL-AMMONIAC. 4-63 
 
 parts of the original compound. In the year 1718 Geoffroy pub- 
 lished the first table of chemical affinity. This table was enlarged 
 and improved by Gellert in the year 1750, and in the year 1775 
 Bergman gave to the world his inestimable treatise on elective 
 attractions, which was published in English in the year 1785 : and 
 since then our knowledge of the subject has been much increased 
 by Morveau, Kirwan, Wollaston, and other eminent labourers 
 in this important department of science. 
 
 The knowledge of the property which several of the salts pos- 
 sess of mutually decomposing each other, naturally laid the foun- 
 dation for the discovery of a more economical method of forming 
 the muriate of ammonia, so as to avoid the great loss of gas which 
 always happens on the direct mixture of liquid ammonia with 
 muriatic acid, of which there had hitherto been so much complaint. 
 This ingenious method consists in first saturating the alkali with 
 sulphuric acid, which may be done with little or no loss of the 
 ammoniacal gas, and then decomposing the sulphate of ammonia 
 which is thus formed, by the mixture of a determinate portion of 
 muriate of soda. In this process it is observable that the sulphuric 
 acid is not entirely lost, for it combines with the soda, and pro- 
 duces Glauber's salt. 
 
 The result of this mixture and of the reciprocal decomposition 
 of the two salts just mentioned, being muriate of ammonia and 
 sulphate of soda, it is customary to concentrate the saline mass by 
 evaporation to that point at which, when the liquor becomes cold, 
 the sulphate of soda will separate itself by priority of crystalliza- 
 tion, and then to boil the remaining fluid to a dry salt, which, by 
 an adequate degree of heat, is afterwards sublimed into solid cakes 
 of sal-ammoniac, for sale. 
 
 By this process most of the sal-ammoniac made in this country 
 has for many years past been prepared. But the price of the En- 
 glish salt has been so high, owing to the first cost of the materials 
 and the expense of the process, that the foreign sal-ammoniac has 
 been sold much cheaper ; so that most of the consumers have 
 given the preference to the latter, and this has occasioned the 
 consumption of the English to be limited and very inconsiderable. 
 This state of things has however lately undergone a complete re- 
 volution ; and from some circumstances to be adverted to here- 
 after, sal-ammoniac can now be prepared in England as cheaply 
 as in any part of the world. 
 
 Sal-ammoniac does not acquire any new properties by the 
 process of sublimation. In some works on the Continent it is 
 never sublimed, but merely inspissated by evaporation, and then 
 moulded into the shape of a cone. In saying that the consumers 
 preferred the foreign sal-ammoniac, I do not mean that this was 
 on account of its quality, because it is undoubtedly more impure 
 
464- ON SAL-AMMONIAC. 
 
 than that which is made at home ; it was its price which gave it 
 this preponderance. 
 
 A more economical process than the one already described, for 
 making this very important salt, was devised some years ago. 
 This consisted in decomposing the impure solution of carbonate 
 of ammonia by means of gypsum, or sulphate of lime; and a Mr. 
 Minish ofWhitechapel obtained a patent for the discovery. Per- 
 fectly dry sulphate of lime consists of one proportional of lime,, 
 or oxide of calcium, 28 -f- one proportional of sulphuric acid 
 40, and its equivalent number is 68. 
 
 In conducting the patent process, the rough spirit as it is called,, 
 or the aqueous product of the distillation of bones, is digested 
 upon ground plaster of Paris; when, in consequence of a double 
 decomposition, carbonate of lime is formed, which precipitates, 
 and sulphate of ammonia, which remains in the solution. The 
 fluid containing the sulphate of ammonia is then poured from the 
 precipitate upon a definite quantity of muriate of soda (common 
 salt), when another change takes place, which gives sulphate of 
 soda and muriate of ammonia; and these are then treated and se- 
 parated as the others, by sublimation. 
 
 This process was carried on for several years till the term for 
 which the patent was granted expired, when the proprietor re- 
 linquished the concern, and retired from business with an ample 
 fortune, acquired by the manufacture of sal-ammoniac, merely in 
 consequence of the great superiority of his process. 
 
 Another method of 'making sal-ammoniac was invented by 
 Dr. Hector Campbell, which consisted in mixing the solutions of 
 muriate of soda, sulphate of magnesia, and rough carbonate of am- 
 monia technically called bone spirit. This process, in a theo- 
 retical view of it, appeared likely to be profitable, as it would give, 
 if the decompositions were complete, three valuable products for 
 sale, viz. sal-ammoniac, carbonate of magnesia, and Glauber's 
 salt; but I have reason to think that it has proved otherwise, or 
 the concern would not have been altogether relinquished. I have 
 also some doubt as to the separation of the muriatic acid from the 
 common salt by this mixture, because we know that muriate of 
 soda and sulphate of magnesia are not incompatible salts, for they 
 are constantly found together in considerable quantities in the 
 waters of the ocean. 
 
 Much has been said at different times about the Liege process 
 of making sal-ammoniac ; which consists in mixing small sea 
 coal, common salt, and the soot produced from pit coal, and then 
 uniting these into a paste with tempered clay and water. The 
 mass is afterwards formed into slabs in the form of flat tiles, and 
 these are then placed in a furnace with bones, laid stratum super 
 stratum, and the product of the combustion collected in appro- 
 
ON SAL-AMMONIAC. 465 
 
 priate chambers. When these furnaces are set to work, they are 
 generally kept burning for five or six months. 
 
 This appears to me to be a better process than that of mixing 
 the ammonia with liquid muriatic acid, but I am inclined to think 
 it is too tedious an operation ever to become profitable in this 
 country. Weber states that the soot of the Dutch turf yields 
 also a perfect sal-ammoniac by sublimation. The Earl of Dun- 
 donald advises to mix fresh slacked lime with ground peat, and 
 then to distill for ammonia. 
 
 In the year 1794, Lelievre, Pelletier, D'Arcet, and Giroud, 
 eminent French chemists, were employed by the Committee of 
 Public Safety in Paris, to make a Report on the divers means of 
 extracting soda from sea salt with advantage ; and they, in their 
 account of that process, have given one which was at that time 
 conducted by M. Leblanc, at St. Denis near Paris, for the ma- 
 nufacture of sal-ammoniac. Ann. de Chimie, torn. xix. p. 58. 
 
 His method consists in decomposing muriate of soda by sul- 
 phuric acid in a kind of reverberatory furnace, the floor of which 
 is covered with lead ; and as the current of muriatic gas is de- 
 termined into an adjoining leaden chamber, it is there, at the same 
 instant, met by a current of volatile alkali, produced from a variety 
 of animal matters, which they burn in three cylinders of iron, 
 placed in a furnace, side by side of each other. 
 
 In this process, the vapours of the muriatic salt are condensed 
 in the leaden chamber, not only by their combination with the 
 ammonia 1 , but also by means of an eolipile, which was heated by 
 the same furnace in which the iron cylinders were fixed for the 
 combustion of the animal substances. 
 
 The decomposition of the muriate of soda was not, however, 
 entirely finished in this operation, because the sheet of lead which 
 covered the floor of the reverberatory furnace could not, without 
 melting, endure a degree of heat sufficiently strong to effect this 
 purpose. The operator therefore moves the matter into a third 
 reverberatory furnace pavedjwith brick, where it receives a degree 
 of heat sufficient to make it enter into fusion, and complete the 
 decomposition. It was necessary for the proprietors of this es- 
 tablishment to complete the decomposition of the common salt, 
 because the economy of their process consisted in the employ- 
 ment of the alkaline residuum for the production of crystallized 
 soda. 
 
 There is, however, a mode of making sal-ammoniac, which I 
 
 1 If the stopper he taken out of a phial of muriatic acid, in the presence of 
 some liquid ammonia, it will be seen, hy the cloud of muriate of ammonia in 
 vapour which will appear in the atmosphere, how eager these gases are to unite 
 to form the new compound. 
 
 2 H 
 
4-66 ON SAL-AMMONIAC. 
 
 conceive would be more economical than any of those already 
 mentioned. It consists in the employment of the bittern of the 
 salt-works, or the mother-waters which remain after the extraction 
 of common salt from sea water. This is not a mere theoretical 
 notion, for the process has more than once been acted upon, and 
 at this time large quantities of sal-ammoniac are actually made 
 according to this principle in some parts of Scotland. 
 
 The desire of making this valuable and economical process for 
 preparing muriate of ammonia from the bittern of the salt-pans 
 more generally known, was the motive that induced me to ren- 
 der the manufacture of sal-ammoniac one of the subjects of these 
 Essays. ' 
 
 The preparation of this important salt by means of bittern is 
 not, as I have said, a new process, for I recollect reading an ac- 
 count of it many years ago in the Annales de Chimie, torn. xx. 
 p. 186, and in other works; but knowing the board of Excise in 
 England would neither allow the use of bittern, nor even the burnt 
 pickings of the salt-pans, free of excise duty, I imagined this to 
 be one of those processes which are interdicted by the high price 
 of the materials, till an accidental circumstance which occurred 
 a few years ago recalled my attention to the subject in a very par- 
 ticular manner. 
 
 Mr. Astley of the town of Borrowstoness near Leith, who had 
 taken out a patent for the manufacture of sal-ammoniac by com- 
 bustion, in which he proposed to burn bones, blood *, and other 
 animal matters, with the bittern, proceeded by due course of law 
 against a gentleman of the same town for having infringed his 
 patent, and the cause came to be tried before the Lords of Ses- 
 sion in Scotland. The question, however, not having been de- 
 termined by the Court, it was agreed between the parties to defer 
 final judgement until the opinions of some practical chemists in 
 London should be obtained on the subject; and it was during my 
 examination before the Commissioner appointed by the Lords of 
 Session to take our report, that I first obtained the information 
 that the Board of Excise allows the inhabitants of Scotland the 
 bittern of the salt-works free of duty. 
 
 On acquiring a knowledge of this fact, a question immediately 
 occurred If the inhabitants of one part of the empire are allow- 
 ed an article which is capable of being used in our manufactories 
 duty free, why should not the same indulgence be universal in 
 England and Ireland, as well as in Scotland? 
 
 It still however appears to me, as I suggested several years ago 
 
 1 Dr. Thomson says, that if the fibrous part of blood be left in water it soon 
 putrifies, and then yields more ammonia than any other animal substance. 
 
ON SAL-AMMONIAC. 467 
 
 in the Chemical Catechism, that the best situation for a manu- 
 facture of ammonia is on the sea coast, where pilchards, herrings, 
 or the dogfish, arrive in such immense shoals as to be periodi- 
 cally employed in manure for land. The dogfish (the Squalus ca- 
 nicula of Linnaeus) is caught all along the coast of Scotland from 
 Peterhead to Bamffl They generally follow the herrings, and 
 might probably be caught wherever shoals of herrings are found. 
 The value to the fishers is in the liver, of which they make oil : 
 therefore, the carcase, after extracting the liver, is sold for ma- 
 nure. 
 
 At Bamberg, in the circle of Franconia, the Germans have long 
 been accustomed to boil the sediment of the salt-pans with stale 
 urine, and sell it cheap for making sal-ammoniac. A similar kind 
 of salt is still prepared in the neighbourhood of Vienna. In se- 
 veral other parts of Germany, and particularly iu the vicinity of 
 Gottenburgh, ammonia is prepared from the dregs which remain 
 after the expression of train oil. Why might not the whale blub- 
 ber be employed for the distillation of ammonia ? Means might 
 be devised for correcting its offensive smell, and rendering it very 
 productive of volatile alkali. 
 
 The ingenious Mr. Dossie, already mentioned, who was a ma- 
 nufacturing chemist of the last century, and who had the honour ' 
 of being one of the first English writers who undertook, with a 
 noble superiority to all considerations of private advantage, to 
 describe and elucidate many of the most important chemical pro- 
 cesses without reserve, has, however, fallen into a considerable 
 error respecting the use of bittern ; an error which has probably 
 misled many, and may have been the occasion of deterring some 
 individuals from establishing the identical mode of making sal- 
 ammoniac which I am now so anxious to explain and recom- 
 mend. 
 
 The conclusion which Mr. Dossie draws, that pure sal-ammo- 
 niac cannot be made by the admixture of carbonate of ammonia 
 with bittern, appears to have been occasioned by his supposing 
 that sea-water consists only of muriate of soda and sulphate of 
 magnesia : whereas, a large portion of magnesian muriate is also 
 contained in it. This becomes decomposed as soon as it is added 
 to the ammoniacal liquor, arid the result, as far as the muriate of 
 magnesia is concerned, is the formation of a true sal-ammoniac. 
 
 When urine is employed for the production of ammonia, it is 
 necessary to keep it till it becomes putrid, this alkali being one 
 of the products of putrefaction. In summer one week will gene- 
 rally suffice, but in cold weather it ought to be kept three weeks 
 or a month. 
 
 It is not, however, very surprising that Mr. Dossie should have 
 
 2 H 2 
 
ON SAL-AMMONIAC. 
 
 fallen into the error respecting the bittern just noticed; for even 
 Fourcroy, who died but lately, overlooked the magnesian mu- 
 riate, and describes the waters of the ocean as containing only 
 "muriate of soda, sulphate of magnesia, sulphate of lime, and 
 much extractive matter V 
 
 The latest analysis which can be depended upon, and perhaps 
 the best, is that by the late Dr. Murray, who obtained by the 
 evaporation of a pint of sea water, , 
 
 Common salt . . . f . 180.5 grains 
 
 Muriate of magnesia .... 23.0 
 
 Sulphate of magnesia . . . 15.5 
 
 Sulphate of lime . . . . 7.1 
 
 226.1 
 
 By this estimate it appears that the proportion of muriate of 
 lime, and muriate of magnesia, in sea-water is considerable: I am, 
 therefore, fully justified in recommending the use of bittern for 
 the preparation of the ammoniacal muriate, and the production 
 of magnesia. 
 
 Another advantage will also result from the use of this refuse 
 article, which is this, that the sulphate of magnesia may also be ren- 
 dered efficient towards the production of sal-ammoniac ; inasmuch 
 as it will decompose the liquid carbonate of ammonia, and form 
 ammoniacal sulphate, which, by the addition of common salt, may 
 at any time be converted to the true ammoniacal salt of which we 
 are now treating. If the process be thus improved and carried 
 to its full extent, the products for sale will be sal-ammoniac, car- 
 bonate of magnesia, and Glauber's salt. 
 
 It is important to remark, that the mixture of a proportion of 
 sulphate of ammonia with the true sal-ammoniac will, for many 
 purposes, be no injury: for instance, the ammoniacal sulphate is 
 well adapted to the soldering of metals, and equally applicable with 
 the muriate of that alkali for the preparation of liquid ammonia, 
 although it is not quite so productive of alkali. 
 
 On the nature and properties, and on the formation and de- 
 composition of muriate of ammonia, or sal-ammoniac, the Annales 
 de Chimie may be consulted, viz.Westrumb on its decomposition 
 by magnesia and carbonate of magnesia, vol. ii. pages 118 136; 
 Vogler on its effects with madder in dyeing linen and cotton, 
 vol. iv. pages 1 15 & 1 4-4 ; Dr. Blagden on its use in freezing water, 
 page 236; on its analysis, vol. xiv. page 210 ; Hassenfratz on its 
 specific gravity, vol. xxviii. page 1 3 ; Fourcroy and Vauquelin 
 on the change in the form of its crystal by its union with urea, 
 
 1 Fourcroy's System of Chemical Knowledge^ vol. iv. p. 409. 
 
ON SAL-AMMONIAC. 469 
 
 vol. xxi. page 67, and vol. xxxii. page 130: on its extraction 
 from urine, page 162 ; Mons. Virey on its formation in volcanoes, 
 vol. xxxvi. page 290 ; Vauquelin ori its existence in tobacco, 
 vol. Ixxi. page 153 ; Berzelius on its composition, vol.lxxix. page 
 233, and vol. Ixxxi. pages 5 13. 
 
 Since the introduction of gas lights, the principal part of the 
 sal-ammoniac manufactured in England has been obtained from 
 the ammoiiiacal liquor of the gas works, which being a cheap 
 article and to be had in immense quantities, has almost superseded 
 the processes described above. By the distillation of common pit- 
 coal to procure carburetted hydrogen gas for the purposes of il- 
 lumination, a considerable quantity of ammoniacal liquor is ob- 
 tained in the condensing vessel. This liquor, which contains a 
 portion of carbonate and sulphate of ammonia in solution, is sold 
 to the makers of sal-ammoniac, who obtain the salt from it by 
 the following process. It is first treated with sulphate of lime, 
 and afterwards with sulphuric acid, which is added gradually 
 until the whole of the carbonate of ammonia is decomposed, and 
 a sulphate of ammonia formed. By subsequent evaporation of the 
 superfluous liquor the sulphate of ammonia is obtained in crystals. 
 At other times common salt is added to the solution of sulphate 
 of ammonia; and this, by the play of chemical affinities, produces 
 two new salts, viz. sulphate of soda, and muriate of ammonia. 
 The liquor containing these two salts is then reduced in quantity, 
 by evaporation, to that point at which it is known by experience 
 that the sulphate of soda will separate itself on cooling. When this 
 salt has been removed, the remaining liquor is then evaporated till 
 the muriate of ammonia will crystallize, as has already been de- 
 scribed at page 463. After this, the muriate of ammonia is dried 
 carefully, and then by the usual process of sublimation, it is form- 
 ed into cakes of the true sal-ammoniac. A good butt of gas-liquor, 
 108 gallons, which costs about eight shillings, will generally afford 
 94lbs of crystallized sulphate of ammonia, which when decom- 
 posed with common salt and sublimed will yield 50lbs of finished 
 sal-ammoniac. The liquor varies in strength ; but since it has 
 become so considerable an article of commerce, most of the large 
 gas establishments pay great attention to get it of as uniform 
 a quality as possible. 
 
 Since the duty has been removed from common salt, and mu- 
 riatic acid has become the cheapest article in a chemical manufac- 
 tory, much sal-ammoniac has been made by pouring the acid at 
 once into the gas liquor, evaporating to the proper strength, and 
 crystallizing the muriate of ammonia, which is afterwards dried 
 and sublimed. 
 
 With a little care and attention, the waste which was formerly 
 
470 ON SAL-AMMONIAC. 
 
 complained of as a necessary attendant on this process is nearly, 
 or indeed entirely, obviated. 
 
 Hence an entirely new trade has arisen from the removal of an 
 impolitic and oppressive impost. Long has the island of Britain 
 enjoyed the blessings and luxuries which arise from an extended 
 trade ; and though we are now in the possession of the greatest 
 part of the traffic of the world, we must not expect to preserve 
 this proud pre-eminence, unless the Government determine to 
 pay the most sedulous attention to our most minute interests as a 
 manufacturing and commercial people. 
 
 

ON THE MANUFACTURE OF EDGE TOOLS. 
 
 ESSAY XV. 
 ON THE MANUFACTURE OF EDGE TOOLS. 
 
 THE history of the invention of EDGE TOOLS is involved in much 
 obscurity. The materials employed by the ancients for making 
 them were various ; but the metal in general use in modern times 
 and among civilized nations for the fabrication of such instruments, 
 is iron s though this metal varies in its nature, and is differently 
 prepared according to the purposes to which the instrument or 
 weapon is applicable. 
 
 Although iron was known before the Deluge, yet there is rea- 
 son to believe that the method of making it was afterwards lost. 
 Tubalcain, who lived nearly four thousand years before the com- 
 mencement of the Christian aera, was " an instructor of every 
 artificer in brass and iron," and we are told that Abraham took a 
 knife to slay his son Isaac. 
 
 In these early times mention is also made of shears, and of the 
 shearing of sheep ; and yet many of the ancient nations knew no- 
 thing of iron, but used stones, flints, the horns and bones of va- 
 rious animals, the bones and shells offish, reeds, and thorns, for 
 every purpose in which the moderns now use edge tools of iron 
 and steel l . 
 
 Cutting instruments of stone are frequently found in various 
 parts of South America, Asia, and Europe, particularly in the tombs 
 of the ancient inhabitants of Peru ; and in Carmania, a province of 
 Persia, hammers frequently occur which are made entirely of stone. 
 These are known by the name of ceraunia, or thunder-stones, 
 and are preserved in some cabinets. They are perforated for the 
 reception of handles, in the place most proper for receiving them, 
 so as to leave no doubt of their having been intended for hammers, 
 and used in the same way as we employ such implements at the 
 present day 2 . 
 
 There is a very circumstantial account of the stone weapons of 
 the ancients, accompanied with several copper-plate engravings, 
 in Dr. Wood ward's History of Fossils. The same writer informs 
 us that Captain Dampier found such implements still in use at 
 Guam, one of the Ladrone Islands, and also in Nova-Britannia, 
 
 1 Goguet's Origin of Laws, $c. vol. i. p. 140. 
 
 * Agricola De Natura Fossitium, lib. v. cap. 1.3. p. 262. 
 
472 ON THE MANUFACTURE 
 
 an island lying south of the equator and the furthest to the east of 
 any then known 1 . 
 
 Herodotus, in describing the ceremonies which the Arabians 
 observe in making alliances, says, that " on these occasions some 
 one who is connected with both parties stands betwixt them, and 
 with a sharp stone opens a vein of the hand of those who are about 
 to contract. He then takes a piece of the vest of each person and 
 dips it in their blood 2 ." 
 
 The ancient embalmers of Egypt were in the habit of using an 
 Ethiopian stone for opening the dead bodies, in order to take out 
 the bowels 3 ; and it may be presumed, from its being the practice 
 to circumcise with a sharp flint*, that edge tools of iron, if they 
 were known, were not very common among any of the primitive 
 nations. 
 
 Hesiod, who lived probably a thousand years before the time 
 of Christ, says plainly, that " the plough-share was made with a 
 species of very hard oak 6 ;" and from his manner of describing 
 the ploughs that were then employed, there is no reason to sup- 
 pose that any iron was used in constructing them. 
 
 The following is a modern translation of the passage to which 
 
 I allude : 
 
 " If hill or field supply an ilex bough, 
 Of bending figure like the downward plough, 
 Bear it away ; this durable remains, 
 While thy strong steers in ridges cleave the plains ; 
 If with firm nails thy artists join the whole, 
 Affix the share-beam, and adapt the pole 6 ." 
 
 Dr. Kirwan, the late president of the Royal Irish Academy, 
 who had travelled much on the continent of Europe, used to re- 
 late, when speaking of the difficulty of introducing improvements 
 in the arts and manufactures, and of the prejudices entertained for 
 old practices, that, in Normandy, the farmers had been so long 
 accustomed to the use of ploughs whose shares were made entirely 
 of wood, that they could not be prevailed on to make trial of those 
 with iron, that they considered them to be an idle and useless 
 innovation on the long-established practices of their ancestors ; 
 and that they carried these prejudices so far as to force the Go- 
 vernment to issue an edict on the subject. And even to the last 
 they were so obstinate in their attachment to plough-shares of 
 wood, that a tumultuous opposition was made to the enforcement 
 
 1 Woodward's History of Fossils, octavo, London 1728, p. 40. 
 ' Beloe's Herodotus, book iii. 8. 
 
 3 Herodotus, lib. ii, n. 86. Goguet's Origin of Laws> vol.i. p. 198. 
 
 4 " Then Zipporah took a sharp stone," &c. Exodus iv. 25. 
 
 5 Hesiod. Oper. et Dies, ver. 436. 
 
 6 Elton's Translation of Hesiod' s Works and Days, line 586-591. 
 
 ' 
 
OF EDGE TOOLS. 4-73 
 
 of the edict, which for a short time threatened a rebellion in the 
 province. 
 
 On the arrival of the Saxons in Great Britain, our ancestors 
 were in as low a state of civilization. One of their laws enacts, 
 that no man should undertake to- guide a plough who could not 
 make one, and that the cords with which it is drawn should be 
 formed of twisted willows 7 . 
 
 Homer describes Achilles as offering a large quoit of iron for 
 one of the prizes at the games instituted in honour of Patroclus ; 
 whence it would appear that this metal was still an article of con- 
 siderable value. 
 
 " Then hurl'd the hero, thundering on the ground 
 A mass of iron, (an enormous round,) 
 Whose weight and size the circling Greeks admire, 
 Rude from the furnace, and but shaped by fire. 
 Let him whose might can hurl this bowl, arise, 
 Who furthest hurls it, take it as his prize 8 ." 
 
 Madame Dacier on this passage remarks, " It must be remem- 
 bered, that in those times iron was very scarce ; and a sure sign 
 of this scarcity is, that their arms were usually of brass." 
 
 If any kind of edge tools of iron were in use at this period, their 
 employment must have been confined to but few individuals ; for 
 several ancient authors assert that Daedalus, the Greek architect, 
 who flourished in the age immediately succeeding that in which 
 the temple was built, knew nothing of the saw. The invention of 
 this instrument they ascribe to the nephew of Daedalus, who, as 
 they say, having accidentally met with the jaw of a serpent which 
 he used with success to divide a small piece of wood, thus ac^ 
 quired the first idea of the use of such an implement, and soon 
 afterwards formed a metallic instrument in imitation of it 9 . 
 
 Of all the metals, there is none which is so universally distri- 
 buted over the face of the earth as iron ; but the heat which is ne- 
 cessary for the separation of it from the ore is so intense, that we 
 cannot wonder at many nations remaining long entirely ignorant 
 of its use, and even of its existence ; or that, when the knowledge 
 of making it was lost at the Flood, a long period should elapse 
 before this curious art was entirely recovered. 
 
 Accordingly, we find that spears and other instruments for ex- 
 terminating wild beasts, and even implements of agriculture I0 , 
 were formerly made with gold and silver; and in confirmation of 
 
 i Leges WalliccB, p. 283. 
 
 8 Pope's Homer's Iliad, book xxiii. line 973. 
 
 9 Diodorus Siculus, lib. iv. p. 319. Ovid. MetamAib. viii. ver. 241. The 
 invention of the potter's wheel is also attributed to this young architect. 
 
 10 Diodorus Siculus, lib. i. p. 19. Goguet's Origin of Laws, &c. vol. i. 
 p. 153, &c. 
 
ON THE MANUFACTURE 
 
 this, Diodorus Sicuius says that the Arabians, "because they have 
 abundance of gold, and contrarily are in want of brass and iron, 
 exchange the one for the other with merchants 1 ." 
 
 As the wants of mankind, however, increased, many of the pur- 
 poses to which these precious metals were applied were accom- 
 plished by means of copper, this being a metal more easy to be 
 procured than malleable iron. Thus we find that the domestic 
 implements and most of the instruments of war of antiquity, which 
 in our times are occasionally found in every quarter of the globe, 
 are all either of copper or brass. Until very lately, indeed, all 
 the edge tools that were in use in the island of Japan were of cop- 
 per, or made with some alloy of that metal 2 . 
 
 There is one circumstance, however, which shows that instru- 
 ments of steel were known to the ancient Egyptians, and, after 
 them, to the Greeks and Romans. What I refer to is the exist- 
 ence of obelisks, statues and urns of porphyry^ which, though of 
 undoubted antiquity, are curiously carved and engraved, in a way 
 which could not have been effected with tools of a common tem- 
 per. It has been generally understood that nothing but emery or 
 diamond powder would touch porphyry, and I believe we have no 
 tools at the present day that are capable of engraving it. The 
 porphyry obelisks at Rome are however not only very curiously 
 carved, but graven also with hieroglyphics ; and though these are 
 distinctly cut, the obelisks themselves have not suffered in the 
 least by their exposure to the weather through so long a series of 
 ages. This shows their extreme hardness, and how highly the 
 tools must have been tempered by which they were sculptured 
 and engraved. Among other notices in the 8th volume of the 
 Philosophical Transactions, at page 6014, "to retrieve the art of 
 hardening and tempering of steel for cutting of porphyry," is men- 
 tioned as an important desideratum. 
 
 In the time of the Grecian historian Agatharcides, who lived 
 nearly two hundred years before Christ, chisels and hammers of 
 copper were very commonly found among the rubbish of old mines: 
 and since that period hatchets of copper have been discovered in 
 the tombs of the ancient Peruvians 3 . All these may probably 
 have been very useful utensils, especially if the fabricators of them 
 were acquainted with any method of giving hardness to that metal. 
 
 It may here be remarked, however, that because no iron instru- 
 ments of considerable antiquity are now found, we are not to con- 
 clude that the ancients never employed iron for such purposes ; 
 
 1 Cogan's Translation y folio, London, 1653, p. 141. 
 8 See Goguet's Origin of Laws, vol. i. p. 158. 
 
 3 Many authorities for these facts may be seen in Goguet's Origin of Laws % 
 vol. i. p. 158. 
 
OF EDGE TOOLS. 475 
 
 tor it is easy to imagine that tools of iron or steel may have ex- 
 isted and been destroyed by the hand of time. Iron is so neces- 
 sary for the support of animal and vegetable life, that nature has 
 endowed it with an affinity for oxygen, carbon and sulphur, much 
 greater than that of most other metals, in order that it might be 
 universally distributed. It is therefore difficult to conceive how 
 an implement of iron could lie in the ground for a thousand years 
 without being destroyed. 
 
 If we inquire respecting the state of the metallic arts among 
 the ancient Britons, it will appear, from the prodigious numbers 
 of copper instruments of different sizes and kinds which have been 
 found in this country, such as axes, swords, spear-heads, arrow- 
 heads, &c., all of which are known among antiquaries by the ge- 
 neral name of celts, that our ancestors were well acquainted with 
 the art of forming metallic copper in any way which they thought 
 proper *. 
 
 So lately as the year 1735, more than one hundred of these cop- 
 per celts were found on Easterly moor, twelve miles from the city 
 of York, together with several lumps of metal intermixed with a 
 quantity of foundry cinders, so that there can be no doubt of there 
 having formerly been a forge at that place for making such arti- 
 cles '. 
 
 The war-chariots of the ancient Britons afford abundant proof 
 that they were expert in the working of metals as well as in the 
 modelling of wood. " The covinus" says Dr. Henry, " was a 
 war-chariot, and a very terrible instrument of destruction, being 
 armed with sharp scythes and hooks for cutting and tearing all 
 who were so unhappy as to come within its reach. It held few 
 men, but was designed to be driven with great force and rapidity 
 and to do execution chiefly with its hooks and scythes 6 ." 
 
 Notwithstanding the abundance of iron ore which this country 
 affords, it appears that the use of metallic iron is comparatively 
 but of late introduction : for at the time of the first Roman inva- 
 sion, this metal was so scarce and rare a commodity that the Bri- 
 tons fabricated their money with it, and even the trinkets for 
 adorning their persons 7 . But when the Romans had made them- 
 selves masters of the country they established imperial foundries 
 for making iron, and built forges for manufacturing spears, 
 lances, battle-axes and implements of every kind, in different 
 parts of the kingdom. 
 
 4 See Leland's Itinerary, vol. i. p. 127. Henry's History of Great Britain, 
 vol. ii. p. 138. 
 
 5 Borlase's Antiquities of Cornwall, p. 283. 
 
 5 Mela, lib. Hi. cap. 6. Tacitus, Vita Agricoltz, cap. 36. 
 7 Caesar, de Hello Gallico, lib. v. cap, 12. Henry's History of Great Britain, 
 vol. ii. p. 139. 
 
4-76 ON THE MANUFACTURE 
 
 Accordingly we find that the offensive armour of the cavalry 
 in the time of William the Conqueror was a long spear or lance 
 pointed with steel) very sharp and well tempered ; the long and 
 broad sword double-edged, and a short dirk or dagger 1 . 
 
 The art of working in iron and steel had arisen to such a state 
 of improvement in the 10th century, that even the horses of some 
 of the chief knights and barons were covered with steel and iron 
 armour. Artificers who wrought in iron were so highly re- 
 garded in those warlike times, that every military officer had his 
 smith, who constantly attended his person, to keep his arms and 
 armour in order. The chief smith was an officer of considerable 
 dignity in the courts of the Anglo-Saxons, and Welsh kings, 
 where he enjoyed many privileges, and his weregeld wa$Tnuch 
 higher than that of any other artificer. In the Welsh court the 
 king's smith sat next to the domestic chaplain, and was entitled to 
 a draught of every kind of liquor that was brought into the hall. 
 
 The skill which our ancestors acquired under the instruction 
 of the Romans, seems never to have been lost ; for at the battle 
 of Hamildon in the year 1402, the repulse of the Scots appears 
 to have been entirely owing to the goodness and excellent temper 
 of the arrows which were employed by the English army. Even 
 the armour of the Earl of Douglas, which had been three years 
 in making, was perforated by them ; for, as the account states, 
 "they were so sharp and strong that no armour could repell 
 them 2 . 
 
 Dr. Martin Lister was of opinion that the ancients made their 
 instruments hard, and converted them into steel, by one and the 
 same operation ; that they first fashioned them out of good soft 
 wrought-iron, and then boiled them, as he expresses it, in fluid 
 cast-iron. I have no doubt that good steel might be made by this 
 process 3 . 
 
 We read but little of swords in the beginning of the 15th cen- 
 tury, though no doubt they were then in use, since there is the 
 evidence of Geoffrey Chaucer, who died only two years before 
 the memorable battle of Hamildon was fought, that Sheffield 
 was, even then, famous for its cutlery : 
 
 " A dagger hanging at his belt he had, 
 
 Made of an ancient sword's well tempered blade ; 
 He wore a Sheffield whittle in his hose." 
 
 Canterbury Tales. 
 
 Table-knives, which probably were not in use in the time of 
 Chaucer, were first made in London in the year 1563, by one 
 
 1 Hoveden's Annals, p. 350, col. 1. 
 
 12 Walsingham's Historia Erevis, p. 36(>. Henry, vol. x. p. 193. 
 
 ' Sec Philosophical Transactions, vol. xvii. p. 8(J5. 
 
OF EDGE TOOLS. 477 
 
 Thomas Matthews of Fleet-bridge 4 . I have not been able to as- 
 certain the date of the introduction of other kinds of cutting instru- 
 ments ; but when the utility and convenience of these domestic 
 implements were once experienced, there can be no doubt that 
 the practice of using them quickly became very general, and that 
 manufactories of knives and other edge tools were consequently 
 soon established in various parts of the kingdom. But in what- 
 soever manner this may have been, what has been offered will 
 suffice to give the reader some idea of the progress of the art of 
 cutlery, and of its gradual introduction into this country. 
 
 It is time now, however, to say a word or two respecting the 
 design of this Essay, which is principally intended to explain some 
 of the most important of the modern processes in tempering edge 
 tools, and to point out such improvements as have occurred to 
 me while examining some of the manipulations of the various 
 artists who are now employed in the different branches of cutlery, 
 and in the manufacture of steel % both in its cementation and the 
 operation called tilting. 
 
 Good edge tools cannot be made without steel, which, accord- 
 ing to the analysis of Vauquelin, is generally nothing more than 
 soft iron combined with a small portion of carbon, silica and 
 phosphorus, and sometimes a minute quantity of manganese 6 . 
 Steel acquires the magnetic property better than iron. Hence 
 good mariners' compasses cannot be made without needles of steel. 
 The different kinds of steel may in some measure be known by 
 their specific gravities 7 . The smell of putrid garlic, which is 
 emitted by steel when dissolving in diluted sulphuric acid, is pro- 
 bably owing to the small portion of phosphorus contained in this 
 compound metal. 
 
 Our makers of steel always use Swedish iron for this purpose. 
 That which comes from Roslagen, a district in the neighbourhood 
 of Upsal, is the best. The steel which is produced from it is, in 
 its first state, denominated blistered steel. A very particular ac- 
 count of the method of making steel at Dalecarlia in Sweden, 
 will be found under the article Steel in Keir's Translation of 
 
 4 See The present State of Great Britain, London 1683, p. 77. 
 
 * For an account of the methods of making steel consult Cramer's Elements 
 of the Art of Assaying Metals, octavo, London, 1741, p. 344-350; the article 
 STEEL in Macquer's Chemical Dictionary, vol. iii.j orChaptal's Chemistry applied 
 to the Arts, vol. ii. p. 197. 
 
 6 Vauquelin, from the Journal des Mines, in Nicholson's Quarto Journal, 
 vol. i. p. 210. 
 
 7 See Dr. George Pearson's Memoir in the Philosophical Transactions for 
 1795, p. 324. 
 
478 ON THE MANUFACTURE 
 
 Macquer's Chemical Dictionary. The various sorts of steel are 
 made by very different managements, and are thus rendered suit- 
 able for as many different purposes. 
 
 It may, however, be noticed that the largest English steel-works 
 are at Newcastle-upon-Tyne, at Masbro near Sheffield, at Stour- 
 bridge, at Birmingham, and at the Brades. At Newcastle between 
 twenty-five and thirty thousand weight of steel is cemented at a 
 single operation, in two cases contained in one furnace. The 
 operation lasts five days and five nights. 
 
 There are five kinds of steel generally employed in this country; 
 viz. blistered, shear, spur, star, and cast steel. The cheapest sort of 
 edge tools, and all articles of minor importance, are usually made 
 with the first-mentioned kind, united to a large proportion of bar- 
 iron. Clothiers' shears, firmer chisels, plane-irons, coopers' adzes, 
 scythes, reaping-hooks and large knives, are commonly made 
 with what is called shear steel. The spur and the star steel are 
 used only for particular purposes, and these according to the 
 fancy of the master cutler. Besides these, there is also a German 
 steel which is made immediately from the iron ore, by simple 
 fusion. Vandermonde and his associates have published an ac- 
 count of the mode of producing it *. 
 
 Shear steel is prepared by a peculiar process. Several bars 
 of common steel are laid together and regularly heated in an 
 appropriate furnace, until they acquire the welding temperature, 
 when they are beaten together by a massy forge-hammer, and 
 then drawn out again into bars for sale. By this second operation 
 the blisters are removed, and the texture of the metal is much 
 improved. 
 
 Mr. Joseph Collier to his observations on Iron and Steel in 
 the Manchester Memoirs, vol. v. p. 109, has annexed a drawing 
 of a furnace for converting bar-iron into steel, with a full descrip- 
 tion thereof, which is worth the attention of persons interested 
 in this subject. An abstract from this paper, together with the 
 plate, may be seen in Nicholson's Journal, vol. iii. p. 88. 
 
 The different kinds of iron and steel vary very much in price. 
 The following are about the present prices of most of the sorts 
 in the London market. 
 
 Common bar iron, 75. and 85. per cwt. 
 
 Best Swedish iron, 165. and 185. per cwt. 
 
 Common steel, usually called blistered steel, 525. per cwt. 
 
 Shear steel, "1 
 
 Star steel, >685. to 885. per cwt. according to the sizes. 
 
 Spur steel, ) 
 
 1 See Nicholson's Quarto Journal, vol. ii. p. 64. 
 
OF EDGE TOOLS. 479 
 
 Cast steel rolled into sheets, 605, per cwt. 
 Cast steel drawn into bars, 885. to 1005. per cwt. according 
 to size. 
 
 The high price of Swedish iron is owing to the great superi- 
 ority of its quality when compared with common English iron ; 
 and this is attributed to the circumstance of its being manufac- 
 tured with wood charcoal, whereas most of the English iron is 
 prepared by means of mineral coke. The Swedish iron, how- 
 ever, differs very much in its quality ; even one part of the same 
 bar will often be of much greater value than the other. Formerly 
 the wire-workers in Yorkshire used to go to Sheffield to buy 
 foreign iron, on account of the circumstance above mentioned : it 
 was usual with them to cut the bars into two-feet lengths, and 
 then to select only such pieces as were fit for their purpose, leav- 
 ing the other to be converted into steel. It is no uncommon thing 
 to find a bar of foreign iron tough on one side and quite hard 
 and brittle on the other. If such yron be exposed to the weather, 
 this would soon become apparent by one side rusting and the 
 other remaining quite clean, owing probably to the unequal dis- 
 tribution of the carbon in its manufacture. 
 
 I have also been informed that we have no artist in England 
 who can make iron-wire fit for musical instruments, and that all 
 such wire is imported from Holland, and sold at very extrava- 
 gant prices. The larger kind, such as is used in a piano-forte, 
 cannot be bought for less than Sd. or lOd. per ounce. 
 
 With regard to cast steel, the best penknives, scissors and ra- 
 zors, fine saws, surgical instruments, and every edge tool which 
 requires a fine polish, together with a great variety of implements 
 employed in cutting iron, are now all made with cast steel. 
 
 There are several cogent reasons for the preference of cast 
 steel, for its nature is totally different from that of every other spe- 
 cies. The proportions of the substances which combine with iron 
 to convert it into steel are comparatively very minute ; it is there- 
 fore necessary that these should be intimately and uniformly 
 blended with the whole mass, and this is better effected by fu- 
 sion than in any other way. By the fusion which this particular 
 steel undergoes, the grain becomes closer, and the metal conse- 
 quently much harder. These causes are sufficient to account for 
 cast steel bearing a higher polish than most other kinds. 
 
 The superior beauty of those instruments which are made 
 with cast steel would have occasioned a very great consumption 
 of this article, had it not been for the difficulty of welding or uni- 
 ting it properly with iron, and which, at first, occasioned it to be 
 employed only for those smaller instruments, such as lancets and 
 penknives, which are generally made entirely of steel. 
 
 However, it is necessary to be a little more explicit on this 
 
480 ON THE MANUFACTURE 
 
 part of our subject. Bar-iron cannot be welded to another piece 
 of iron unless both be heated to nearly 60 of Wedgewood's py- 
 rometer, which is equal to 8.877 of Fahrenheit's scale, and is 
 called the Welding-heat ; but if cast steel be heated to this point, 
 it would be fused, and run from under the hammer ; and hence 
 it was for a long time deemed impossible to use it in conjunction 
 with iron, in the same manner as the other kinds of steel are em- 
 ployed. 
 
 Some nicety is required even in the process of welding iron, 
 that the outside of the metal does not oxidize too much and fly 
 off in scales, before the inside is brought up to a welding-heat. 
 When therefore a skilful workman is about to weld two pieces 
 of iron, he carefully observes the progress of the heat; and if one 
 becomes too hot, he rolls it in sand to preserve it from the action 
 of the atmosphere ; and when one piece acquires the necessary 
 temperature before the other, he covers that with sand while he 
 brings the corresponding piece up to a sufficient heat for it to 
 unite properly with the former. Silica when mixed with the 
 oxide of iron forms a very fusible compound, which covers the 
 work under operation, and prevents a further oxidation of the 
 metal. 
 
 I have said that it was formerly deemed impossible to unite cast 
 steel to iron by welding ; but about thirty years ago it was dis- 
 covered by Sir Thomas Frankland, who made many experiments 
 on this subject, that if the cast steel be made only of a white-heat, 
 and the iron of a welding-heat, the steel will then be soft enough 
 to unite with the iron, and yet the former will not become fluid by 
 the operation. It will, however, be proper to give the necessary 
 temperatures to the two metals separately, and then to unite them 
 at one single heat. Phil. Trans. 1795. p. 296. 
 
 Since this important discovery, cast steel has been brought into 
 more extensive use, and the instruments which are thus con- 
 structed are much better than those which are made entirely of 
 cast steel. The circumstance of an instrument having its back 
 made of iron, renders it not so apt to fly from the work to which 
 the edge or steel part is applied, and eventually less liable to 
 break. 
 
 Mr. Nicholson, in his annotations on a Memoir by Vander- 
 monde and others, informs us, he is convinced from his own ex- 
 perience that cast steel is preferable not only for polished steel 
 goods, but also for cold chisels and all hard gravers for turners 
 in metal. 
 
 I have been the more desirous of mentioning these particulars, 
 because, on a late journey into the country, 1 have conversed with 
 several ingenious cutlers, who had no idea that it was possible 
 to unite iron and cast steel by the operation of welding. Many 
 
OF EDGE TOOLS. 481 
 
 artists, long after the invention of cast steel, used to unite it to the 
 iron by means of rivets. Hoes are still made by riveting or screw- 
 ing the back, together with the eye, upon a blade made with cast 
 steel. 
 
 Besides the various sorts of steel already enumerated, there is 
 a peculiar kind which is manufactured at Bombay, called wootz, 
 which admits of a higher temper than any other steel. Mr. Stodart 
 of the Strand forged a piece of wootz for a penknife, at the tem- 
 perature of ignition in the dark. It then received the requisite 
 temper at 450, and the edge became as fine, and cut as well, as 
 the best steel instrument. From this experiment, this ingenious 
 artist gave it as his opinion that wootz is superior, for many pur- 
 poses, to any steel used in this country. He thought it would 
 carry a finer, a stronger, and a more durable edge and point, and 
 that hence it might be particularly valuable for lancets and other 
 fine chirurgical instruments 1 . 
 
 Mr. Mushet of the Clyde Iron-works has written an interesting 
 paper on the properties of wootz, in which he gives an account 
 of the separate analysis of five cakes of this foreign production, 
 which he undertook at the desire of Sir Joseph Banks and sent 
 to the Royal Society. In concluding this important communica- 
 tion, he makes the following remarks on the East Indian ore from 
 which wootz is made : " The possession," says he, " of this ore 
 for the fabrication of steel and bar-iron, might to this country be 
 an object of the highest importance. At present," he adds, " it 
 is a subject of regret, that such a source of wealth cannot be an- 
 nexed to its capital and talent." Phil. Trans, vol. xcv. p. 175. 
 
 The methods which are employed in making edge tools, are 
 almost as various as the articles themselves. It cannot, therefore, 
 be expected that I should describe in detail, or even completely 
 understand, the nature of every process, especially as I was never 
 personally engaged in any branch of the manufacture. The enu- 
 merating of a few of the more important of the manipulations, on 
 which the artists chiefly rely, will, I trust, be deemed sufficient. 
 
 The cooper's adze and the carpenter's axe are first formed by 
 the white-smith in iron, together with the eye for the helve. This 
 being finished, the instrument is again heated, and then the edge 
 of the cutting part is slit down with a chisel, and this slit filled 
 with a thin piece of steel, of a corresponding size and form. The 
 iron which had been slit open is then folded down upon the steel, 
 and the whole is again submitted to the action of the fire till the 
 
 1 See an account of experiments on wootz, in the 85th volume of the Phi- 
 losophical Transactions for the year 1795, p. 322326. Mr. Faraday on the 
 Analysis of Wootz, in The Quarterly Journal of Science, vol. vii. p. 288. 
 
 2 i 
 
482 ON THE MANUFACTURE 
 
 metal acquire a welding-heat, when the sledge-hammer quickly 
 unites the iron and the steel into one compact mass. When the 
 white-smith is desirous of finishing these implements in the best 
 manner, he allows them to be beaten on the anvil more than is 
 absolutely necessary for putting them into the proper form, 
 because the more the metal is hammered the tougher it becomes. 
 This is the chief reason why horse-nail stubs are chosen for mak- 
 ing chains and other works in iron which require great tenacity 1 . 
 
 Scythes and such other large instruments are forged at the 
 mill, by means of a large hammer moved by water. The process 
 is called skelping. 
 
 Augers, gouges, large chisels, table-knives, razors, and other 
 instruments of a similar bulk, are forged upon a large anvil by 
 the principal workman, aided by an assistant called the striker, 
 who stands on the side of the anvil opposite to that where the 
 chief operator stands, and puts in a heavy blow with a sledge- 
 hammer occasionally, while the former is fashioning the instru- 
 ment with a small hand hammer, and turning it round on the 
 anvil, that it may receive now and then a blow from the sledge- 
 hammer on those places where he perceives that it is required. 
 This is usually done with considerable adroitness, and by these 
 means such instruments are fashioned in a quarter of the time 
 that would be necessary for the purpose if they were forged by 
 a single workman. 
 
 For making the articles which are enumerated in this list, shear- 
 steel is generally employed, as it is necessary such instruments 
 should be entirely free from flaws ; and this would not be the 
 case were the common steel to be used for them. A facility is 
 given to the forging of razors and some other instruments, by the 
 steel being previously drawn out to a correspondent size at the 
 tilting-forge. 
 
 Penknives, lancets, gravers, surgical instruments, and other 
 small edge tools, are generally forged on a small anvil firmly 
 fixed within a large one in order to give greater steadiness. 
 These are usually fashioned out of steel only, and forged by one 
 workman singly and alone. Scissars are also forged by a single 
 hand : but the anvil on which they are fashioned is of a peculiar 
 construction, having bosses or dies, and beak-irons of various sizes 
 occasionally adapted to it, so as to suit the different shapes and 
 dimensions of the separate parts of these particular instruments. 
 
 The beak-iron, or bickern as it is sometimes called, is a round 
 taper instrument fixed upon an anvil in an horizontal direction, 
 
 1 The method which is adopted of converting old nails into bar-iron is 
 curious, and may be seen fully described in Aikin's Chemical Dictionary, 
 vol. i. p. COO. 
 
OF EDGE TOOLS. 483 
 
 and designed for fashioning hollow work upon, which could not 
 be beaten upon the straight face of the anvil. Some anvils have 
 beak-irons adhering to them, and others have square holes at one 
 end for a moveable beak-iron to drop into. 
 
 It should have been noticed, that many other tools besides the 
 axe and the adze are originally forged out of a piece of iron, with 
 a little steel welded to it for the cutting part of the instrument. I 
 have also heard of one instance in which the steel is affixed to a 
 tool of cast iron, and that an excellent instrument is produced by 
 this method. This is in the manufacture of Bingley's patent 
 plane-irons, which are constructed in the following manner. 
 
 It is well known that it is the circumstance of drawing down 
 the shear-steel under the tilt hammer that gives it the superiority 
 over common steel. Mr. Bingley therefore thought that, if he 
 could roll out his steel much thinner than it had ever been done 
 before, he should improve its quality ; and accordingly a very 
 thin piece of steel is let into the face of a plane-iron made of cast- 
 iron; and, as the steel for this particular purpose has to go 
 through the rollers several times to make it sufficiently thin, it 
 becomes of a peculiar texture, and the tool made with it is found to 
 suit the joiner much better than the plane-irons heretofore in use. 
 
 In the manufacture of edge tools, the process which immedi- 
 ately succeeds the forging is that of hardening. All these cutting 
 instruments are therefore fashioned when the metal is in its ori- 
 ginally soft state; and when they have attained the intended 
 forms, they are heated afresh to a particular temperature suitable 
 to the article. When they have acquired that degree of heat, 
 they are instantly plunged into cold water, which gives them great 
 hardness, and renders them capable of cutting soft iron or even 
 steel. 
 
 The best cutlers have ascertained that it is always desirable 
 not to give an instrument a greater degree of heat by this operation 
 than is absolutely necessary ; but this will be better understood 
 as we proceed in describing that process. 
 
 Nothing augments the hardness of steel but increasing the cold- 
 ness of the water ; and hence some have had recourse to the 
 solution of salts in the water to be employed in hardening. A 
 stream of running water will make steel harder than still water, 
 as fresh portions of the same fluid are incessantly presented to the 
 heated metal. Some cutlers have assured me that they can make 
 the best instruments when they employ urine in the process of 
 hardening. May not this be attributable to the phosphoric salts 
 contained therein, as it has been demonstrated that phosphorus 
 is one of the component parts of steel ? 
 
 It is now generally understood that hardening by means of the 
 
 2 I 2 
 
484? ON THE MANUFACTURE 
 
 strong mineral acids has no peculiar advantage ; but I find that 
 Reaumur, from his own experience, recommends the use of diluted 
 nitric acid 1 . For the discoveries; which this eminent man made 
 respecting the conversion of iron into steel, the Duke of Orleans 
 settled a pension upon him of 12,000 livres a year; and, at his 
 request, this was settled upon the Academy, to be applied after 
 his death for defraying the expenses of future attempts to improve 
 the arts 3 . 
 
 Experience has proved that instruments which are the hardest 
 acquire the keenest edge and are the most capable of cutting ; but 
 then a great degree of hardness always occasions the metal to be 
 brittle ; and when the edge is very fine, such instruments are 
 useless for dividing hard substances, because the sharp part is 
 not tenacious enough to endure the operation without snapping 
 asunder. It is necessary therefore to be content with less hard- 
 ness in order to obtain the requisite tenacity, and this is effected 
 by the operation called tempering. 
 
 Hence, when an instrument has been properly hardened, it 
 must be softened again in some measure, or to that degree which 
 is thought to be most suitable for that particular purpose for 
 which it is intended. To effect this, it is heated again only to a 
 certain point, which is usually determined by the colour which 
 the metaFassumes, and then it is instantly plunged into cold water. 
 This is called letting it down to the proper temper. 
 
 In France it has been the practice, in hardening small steel 
 instruments, to cover them with soft soap and then to roll them 
 in common salt. This treatment prevents the articles from scaling, 
 and does not prevent the hardening. The salt fluxes to a glass 
 which covers the metal and protects it from oxidizement 3 . 
 
 Pliny informs us, that in his time the more delicate iron instru- 
 ments were steeped in oil to quench them, lest they should grow 
 too hard and brittle with water 4 . On the contrary, Jonston says 
 that " if iron be plunged in vinegar it will endure no hammering, 
 but will sooner break than draw 5 ." The Lacedaemonians, who 
 made their coins of iron rods, were used to steep them in vinegar 
 when red hot, that, being thus rendered brittle, they might never 
 be put to any other use 6 * 
 
 Mr. Rhodes, an eminent cutler of Sheffield, has published some 
 very important observations on the process of hardening steel. 
 
 1 See U Art de convertir le Per en Acier, par M. Reaumur, p. 359. 
 8 Chalmers, vol. xxvi. pp. 93, 94. 
 
 3 Berthoud's Treatise on Margie Clocks. 4to, Paris 1773. 
 
 4 Pliny, lib. xxxiv. cap. 14. 
 
 5 Jonston's History of the Things of Nature, p. 123. 
 
 6 Plutarch in Vita Li/curgi. 
 
OF EDGE TOOLS. 485 
 
 " Articles manufactured of steel for the purposes of cutting," says 
 Mr. Rhodes, "are, almost without an exception, hardened from 
 the anvil ; in other words, they are taken from the forger to the 
 hardener without undergoing any intermediate process ; and 
 such is the accustomed routine, that the mischief it contains has 
 escaped observation. The act of forging produces a strong scale 
 or coating, which is spread over the whole of the blade ; and, to 
 make the evil still more formidable, this scale or coating is un- 
 equal in substance, varying in proportion to the degree of heat 
 communicated to the steel in forging ; it is, partially, almost im- 
 penetrable to the action of water when immersed for the purpose 
 of hardening. Hence it is that different degrees of hardness 
 prevail in nearly every razor manufactured : this is evidently a 
 positive defect ; and so long as it continues to exist, great dif- 
 ference of temperature must exist likewise." 
 
 " Razor-blades not unfrequently exhibit the fact here stated 
 in a very striking manner : what are termed clouds, or parts of 
 unequal polish, derive their origin from this cause : and clearly 
 and distinctly, or rather distinctly though not clearly, show how 
 far this partial coating has extended, and where the action of the 
 water has been yielded to, and where resisted. It certainly can- 
 not be matter of astonishment, that so few improvements have 
 been made in the hardening of steel, when the evil here com- 
 plained of so universally obtains, as almost to warrant the sup- 
 position that no attempt has ever been made to remove it. The 
 remedy, however, is easy and simple in the extreme, and so evi- 
 dently efficient in its application, that it cannot but excite surprise, 
 that, in the present highly improved state of our manufactures, 
 such a communication should be made as a discovery entirely 
 new. 
 
 " Instead of the customary mode of hardening the blade from 
 the anvil, let it be passed immediately from the hands of the 
 forger to the grinder; a slight application of the stone will remove 
 the whole of the scale or coating, and the razor will then be pro- 
 perly prepared to undergo the operation of hardening with advan- 
 tage. It will be easily ascertained, that steel in this state heats 
 in the fire with greater regularity, and that when immersed, the 
 obstacles being removed to the immediate action of the water on 
 the body of the steel, the latter becomes equally hard from one 
 extremity to the other. To this may be added, that, as the lowest 
 possible heat at 'which steel becomes hard is indubitably the best^ 
 the mode here recommended will be found the only one by which 
 the process of hardening can be effected with a less portion of 
 fire than is, or can be, required in any other way." " These 
 observations are decisive, and will, in all probability, tend to 
 establish in general use what cannot but be regarded as a very 
 
486 ON THE MANUFACTURE 
 
 important improvement in the manufacturing of edged steel in- 
 struments V 
 
 It has always been difficult to explain how the water acts in 
 hardening iron and steel ; it is a subject that has ever been in- 
 volved in obscurity, and I do not recollect to have seen any 
 plausible conjecture or theoretical view offered upon it. 
 
 I am desirous, before we proceed with the subject, to make one 
 observation on the property which iron possesses, almost exclu- 
 sively, of acquiring various degrees of hardness arid of becoming 
 soft again at any time, as occasion may require. 
 
 It should be remembered, however, that steel differs from iron 
 in this circumstance, that if it be made red-hot and then imme- 
 diately plunged into cold water, it becomes much harder than it 
 is possible to make iron by such treatment. It may however at 
 any time hereafter be softened again, merely by heating it afresh 
 and then allowing it to cool gradually. 
 
 The property which iron and platinum possess of welding is 
 very important, as has before been remarked ; but were it not for 
 this singular quality in iron, of being hardened and softened at 
 pleasure, and which seems to me to be a striking and peculiar 
 adaptation of a material to the uses for which it was originally 
 designed, none of the arts dependent upon the uses of this metal 
 could have been brought to the perfection which they have now 
 attained ; and if it were possible for iron and steel to lose this 
 property of becoming hard and soft, such arts, however complete 
 they may now be, would be lost with it. 
 
 I recollect having been very forcibly impressed with this idea 
 when I first visited a manufactory of printers' types. There the 
 largest steel punches which are employed in making the brass 
 moulds for receiving the type-metal, and some of these are very 
 heavy, are all formed by other punches ; and the largest and 
 deepest letters are cut out in this manner, by main force. As 
 these tools of steel are not hardened till they are completely formed 
 by others that are already hardened, the latter cut out the former 
 with as little difficulty, to all appearance, as if they were operating 
 upon a piece of tin or lead ; and yet these same articles, which 
 are cut with so much ease, require only to be submitted to the 
 hardening process, and then they will be as capable of operating 
 upon soft iron or steel, and of cutting either of them as readily 
 into any shape, as they were themselves cut when in their original 
 state of native steel. 
 
 Here I should be guilty of great injustice if I were to omit to 
 notice the improvements in softening anti hardening iron and 
 
 1 See an Essay on the Manufacture of a Razor, by E. Rhodes, cutler, Shef- 
 field, 8vo, p. 20. 
 
OF EDGE TOOLS. 487 
 
 steel which have been discovered by Messrs. Perkins and Fair- 
 man of London, and employed by them in preparing steel plates 
 on which they engrave bankers' notes. The methods are kept 
 secret; but Mr. Brande has published a very curious and inter- 
 esting account of what the inventors have been enabled to do by 
 these means, accompanied by a most beautiful specimen . 
 
 In the manufacture of edge tools the most important process, 
 as was before mentioned, is that of tempering. But, to effect this 
 in the best manner possible, there must be, as Mr. Nicholson 3 
 has happily expressed it, " a precise mean between too soft and 
 too brittle, which will be best suited for the respective purposes 
 to be accomplished. A spring must be tenacious, and need not 
 be very hard. A knife for cutting leather and other soft sub- 
 stances must be somewhat harder than a spring. Penknives and 
 razors must be still harder ; and files and tools for working metal 
 must be hardest of all ; though, even in these, care must be taken 
 not to destroy their tenacity by making them too hard." 
 
 Hence it will be apparent that great nicety must always be 
 observed in the operation of tempering ; and if due care be not 
 taken, there can be but little chance of the instruments ever ful- 
 filling the respective purposes for which they are designed. The 
 temper of a lancet is generally the highest of any polished steel 
 instrument, and therefore it is merely owing to its being so very 
 thin that it springs a little at the extreme point. 
 
 The usual mode of ascertaining the temperature to which any 
 edge tool has arrived, is by attending during the operation to the 
 shades of colour, which, as the metal becomes more and more 
 heated, the bright parts assume in rotation, and then when it has 
 acquired that particular hue which may be desired, removing it 
 from the fire into water. But the nature of the operation is such, 
 that this must always be attended with some uncertainty, especially 
 as different tools require different management in the process, and 
 it is often a very uncertain task to give the same temperature to 
 every part of the same instrument. 
 
 It was on account of these and some other difficulties which the 
 makers of edge tools constantly labour under, that I was induced 
 to turn my attention to the subject, trusting that I should be 
 enabled to suggest to the unscientific cutler, some improvement 
 in this most important though very uncertain branch of the art. 
 But, in order that the reader may be better able to appreciate 
 what I have to propose, I shall first show what particular colours 
 are usually required for the tempering of a few of the instruments 
 
 The Quarterly Journal of Science, vol. ix. p. 124. 
 Nicholson's Quarto Journal, vol. i. p. 3bl. 
 
488 ON THE MANUFACTURE 
 
 which are most in demand, and then explain some of the methods 
 now practised for the attainment of some peculiar purposes. 
 
 This detail of the gradation of colours, I have copied from Mr. 
 Nicholson's account of some experiments by Mr. Stodart J , and 
 from Mr. Aikin : but the opinions of scientific men on the cause 
 of these variations of colour, have been very different ; and in 
 my opinion all of them are very unsatisfactory. Sir Isaac New- 
 ton supposed that the size of the metallic particles must have been 
 altered by the action of the fire. Later writers have attributed 
 these changes to the different degrees of oxidizement which the 
 steel undergoes ; and M. Prieur has endeavoured to account for 
 them by supposing that they are occasioned by an alteration in 
 the arrangement of the particles, and that the colours are appa- 
 rently in concentric rings. This he has endeavoured to explain 
 by the feathers of the peacock, the neck of the pigeon, the duck's 
 wing, &c. 2 
 
 In tempering edge tools, the first colour, which appears at 
 430 of Fahrenheit, is very pale and only a little inclining to the 
 yellow; this is the temperature at which lancets are usually 
 tempered. 
 
 At a little higher temperature, say 450, the pale straw colour 
 appears, which is a heat suitable for the best razors and most of 
 the surgical instruments, Then comes the full yellow, at 470, 
 which is proper for common razors, penknives, and some other 
 implements of surgery. 
 
 By increasing the temperature to 490, the brown colour will 
 be produced, which is generally looked for by those who have to 
 temper garden-hoes, small shears, and scissars, and all those 
 chisels which are designed for cutting cold iron. Then at 510 
 comes the brown, dappled with purple spots, which shows the 
 proper heat for tempering axes, firmer-chisels, plane-irons, and 
 pocket-knives. The next colour in succession is the purple, at 
 530, the heat at which table-knives and large shears are usually 
 tempered. The next is the bright blue, at 550, which will give 
 a proper temper to swords, watch-springs, springs for trnsses, 
 bell-springs, &c. Then comes thefall blue, at 560, which being 
 the highest spring temper is usually employed for small fine saws, 
 daggers, augers, &c. This is the proper heat also for tempering 
 most of those instruments which require to be elastic. The last 
 degree in succession is the dark blue approaching to black, which 
 shows itself at 600, and is the softest of all the gradations of tem- 
 per, when the metal becomes suitable to few other instruments 
 than hand and pit saws, which are necessarily made very soft in 
 
 1 Nicholson's Quarto Journal, vol. iv. p. 129. 
 
 2 Annalcs de Chimie, tonic Ixi. p. 154 179. 
 
OF EDGE TOOLS. 489 
 
 the first instance, that the workmen may be able to file them up 
 and set them whenever they find occasion for it, without being 
 obliged to soften them every time that operation is to be performed. 
 This great heat is likewise employed in tempering some particu- 
 lar kinds of springs. 
 
 Some curious facts respecting the properties of blued steel are 
 related by Mr. Nicholson on the testimony of Mr. Stodart, who 
 says " that he has found the spring or elasticity of the steel to be 
 greatly impaired by taking off' the blue with sand-paper or other- 
 wise ; and, what is still more striking, that it may be restored 
 again by the blueing process, without any previous hardening or 
 other additional treatment 3 ." 
 
 Extraordinary as these facts may appear, they have been fully 
 confirmed by a manufacturer of Sheffield, who signs T. B. (pro- 
 bably Mr. Boulsover) and who writes thus: " I took," says he, 
 " a steel plate 30 inches long, 12 broad, and about ,04< thick; I 
 hardened it in a composition of oil and tallow, and afterwards 
 tempered it down to a spring temper ; it was now so elastic as to 
 recover its position after being bended by hammering it to set it 
 straight, it lost a part of its elasticity; after being ground in the 
 same manner as a saw, the elasticity became still less, having 
 nearly returned to the same state as before hardened : it was 
 then very uniformly heated until it became blue ; it now recovered 
 the whole of its elasticity: after being glazed bright upon a 
 glazier coated with emery, the elasticity was found to be impaired, 
 but in a less degree than when it was ground ; the same effect 
 was also produced by rubbing with emery or sand-paper, and 
 also by burnishing; invariably the elasticity was recovered by 
 blueing, and hence this is always the last operation in the manu- 
 facture of elastic steel plate 4 ." 
 
 Every maker of edge tools well knows that their temper is in- 
 dicated by the colour which they assume ; thus by observing the 
 progress of the colours, he is guided in operating on the different 
 kinds of instruments, experience alone being the rule in these 
 cases ; but in order to obtain the most favourable results in some 
 instances of nicety, there are other minutiae which require much 
 care and observation. 
 
 Thus, in tempering penknives and other tools which have a 
 thick back and a very jine edge, they are always laid with the 
 backs downwards, either in heated sand or on a hot iron plate ; 
 otherwise they would become too soft at the edge, before the 
 backs could be entirely heated. 
 
 In hardening knife blades it is usual to plunge them perpen- 
 
 Nicholson's Journal, vol. xii. p. 60. 
 Ibid. vol. xiv. p. 266. 
 
490 ON THE MANUFACTURE 
 
 dicularly into the water, to prevent their warping by being cooled 
 with too great rapidity. And here it may be remarked, that if 
 steel be heated only to that point when it begins to become red 
 in the dark, and then plunged into cold water, such metal will 
 not become hard. The heat for hardening must indeed be so 
 great, that in winter the workman is obliged to take the chill off 
 the water before the goods are immersed in it, to prevent them 
 from cracking by the suddenness of the transition. Mr. Stodart 
 says that one of his workmen makes up his charcoal fire with 
 shavings of leather, finding that this is effectual in preventing the 
 tools from cracking by this process. 
 
 For the best methods of preventing the warping of steel instru- 
 ments in the operation of hardening, a paper by Mr. E. Lydiatt 
 may be consulted with advantage ; there are few cutlers who 
 could not derive some valuable information from its perusal *. 
 
 For hardening very small instruments various other schemes 
 have been adopted. Thus, fine drills and small gravers are har- 
 dened by heating them with a blow-pipe over a candle, and then 
 running them instantly into the body of the same candle. In this 
 way only one instrument can be hardened at a time ; and as such 
 minute tools would be cooled too much before they could possibly 
 be immersed in water, this expedient has been adopted, and suc- 
 ceeds sufficiently. 
 
 Formerly some cutlers employed suet, oil, solutions of sal- 
 ammoniac and other salts for immersing the heated goods into in 
 the process of hardening ; but these methods are now, I believe, 
 all abandoned. Mr. Nicholson has stated that " Mr. Stodart has 
 not found that any advantage is obtained from the use of salt in 
 the water," though he adds that " questions respecting the fluid 
 to be used in hardening are, properly speaking, applicable only 
 to files, gravers, and such tools as are intended to be left at the 
 extreme of hardness V It was found, indeed, that oil had an 
 injurious effect, and that such cutting-instruments as had been 
 hardened by being plunged into cold oil would never take a fine 
 edge. 
 
 I know, however, an artist who makes a large quantity of truss 
 and other springs, and who has very ingeniously taken advantage 
 of this property which oil has of giving steel a coarse grain. He 
 conceived that if the steel were less compact than usual, such 
 springs would have greater elasticity ; and this he has long found 
 to be the fact : he therefore now hardens all his springs by heat- 
 ing them till they acquire the full blue colour, and then plunges 
 them into a vessel of cold linseed oil. 
 
 1 See Nicholson's Journal, vol. xxxiv. p. 31. 
 8 Nicholson's Quarto Journal, vol. iv. p. 128. 
 
Of EDGE TOOLS. 491 
 
 Saw-makers temper their goods in a different way. They rub 
 them over with suet or other grease, and then heat them gradu- 
 ally until the temperature of each tool is raised sufficiently to set 
 fire to the grease of itself, and occasion it to blaze. By this 
 means they are thought to acquire a temper equal to what would 
 be obtained by heating them in the usual way till they became of 
 a deep blue. The operation is called blazing. The great manu- 
 factory of saws is at Sheffield, and there this practice is observed. 
 It usually brings the article to the temperature of about 600 of 
 Fahrenheit. 
 
 Mr. Hardy, a skilful artist, who has written on the construc- 
 tion of Time-pieces, says, " that the saw-makers first harden their 
 plates in the usual manner, in which state they are more or less 
 contorted or warped, and are brittle, that they then blaze them ; 
 which process deprives them of all springiness, so that they may 
 be bended and hammered quite flat, which is a delicate part of 
 the art of saw-making ; and that they blue them on a hot iron, 
 which renders them stiff and springy without altering the flatness 
 of their surface." He adds, that " soft unhardened steel may be 
 rendered more elastic by blueing, and that hard steel is more 
 expansible by heat than soft 3 ." 
 
 I know of no instruments, however, which require so great 
 nicety in hardening, as the files which are intended for sharpening 
 carpenters' hand-saws. The saws themselves being made of cast- 
 steel are extremely hard, and therefore the file must be still 
 harder before it can make any impression upon them. But there 
 is a difficulty attending this process, namely, that if these small 
 instruments be made any harder than is absolutely necessary, they 
 become brittle, and their teeth will be liable to fly at'every stroke. 
 I mention this, because I consider that a method of bringing 
 these small tools to a proper temper, with certainty, is an object 
 well worth the pursuit of persevering and ingenious men. 
 
 In file-making, the great desideratum is to unite tenacity with 
 hardness. If steel for this particular purpose were made with 
 animal instead of vegetable charcoal, this excellence might pro- 
 bably be attained. 
 
 It is rather a digression from the subject of hardening steel in- 
 struments, but it may be acceptable to several of my readers, to 
 mention, that Mr. G. Cumberland of Bristol has recommended 
 the making of large files with a compound of clay and ground 
 silica, and, when they become sufficiently dry, to form the teeth 
 by the pressure of muslin of various degrees of fineness; after 
 which they are to be burnt, to bring them to the hardness of the 
 
 3 Nicholson's Journal t vol. xii. p. 63. 
 
492 ON THE MANUFACTURE 
 
 best stoneware '. Such tools might be made much cheaper than 
 the commonest steel files, and for many purposes that might be 
 mentioned they would be of great utility. 
 
 In visiting a manufactory of files, I could not avoid noticing an 
 expedient which the workmen adopt in the process of hardening 
 that instrument, and which is, perhaps, as perfect and efficient as 
 any they could have been directed to by the most correct know- 
 ledge of chemical science, though it was doubtless the mere result 
 of accident and observation, without the aid of any theory what- 
 ever. 
 
 Some of the large files are very thick, and require to be sub- 
 mitted to an intense heat in order to give them the requisite degree 
 of hardness ; and yet the teeth of these instruments are sometimes 
 so delicate, that the action of the fire, aided by that of the atmo- 
 sphere, would, if they were unprotected, be quite sufficient to 
 convert them at one heat to a crumbling oxide, and of course to 
 render the tool useless. These manufacturers therefore make a 
 mixture of common salt and powdered bone-ash with grounds or 
 settlings of ale ; and when these become of a proper consistence, 
 each file is completely covered with it before it is thrust into the 
 body of the fire. 
 
 When first covered with this preparation, they are laid one by 
 one at some distance above the fire, and across some slight bars 
 of iron fixed within the brick- work on purpose to receive them. 
 Here they acquire a sufficient degree of heat just to bake on the 
 mixture, and harden it so as to prevent its removal by the friction 
 of the coals as it is put into the fire-place. When this is properly 
 baked on, they are heated red-hot, and immediately plunged into 
 cold water, or some other fluid, to complete the hardening pro- 
 cess. This is done rather slowly, and at the same time care is 
 taken to introduce them into the water in a perpendicular position, 
 which is necessary to prevent these instruments from warping by 
 the sudden transition. Diluted sulphuric acid was formerly em- 
 ployed for this purpose, it being imagined that it rendered the 
 files harder ; but this has lately been given up, and recourse is 
 now generally had to cold water only. Reaumur recommends 
 aquafortis for this purpose 2 , as before mentioned ; but I appre- 
 hend it is not better than cold water alone. 
 
 Though the mode just described may be perfect, the compo- 
 sition of the article with which the files are covered may perhaps 
 be still improved. Thus, several artists mix some animal substance 
 with the saline compound, and this is likely to be a considerable 
 
 1 Nicholson's Octavo Journal, vol. xxv. p.25/. 
 
 2 IJ Art de converter Ic Per -en Acicr, p, .559. 
 
OF EDGE TOOLS.. 493 
 
 improvement. On the contrary, some file-makers use common 
 flour instead of bone-ash, and mix it with the saturated solution 
 of salt till the whole acquires the consistence of treacle. There 
 is an advantage in this mixture, namely, that a mere single im- 
 mersion of the files in it is sufficient to coat them entirely, and 
 perfectly protect them from oxidizement. 
 
 I had forgotten to mention, that when these instruments have 
 been tempered in the manner already described, they are well 
 washed in water, and then brushed with dry coke-dust, which 
 makes them quite clean, and gives them a considerable degree 
 of brightness. 
 
 It has been recommended to make files for some particular 
 trades, with iron, and then to case-harden their surfaces, because 
 such files would bend, and hence might be made useful for many 
 purposes to which common steel files cannot well be applied. 
 This method of preserving the teeth of files and rasps while tem- 
 pering, is described, under the idea that a general knowledge of 
 it might perhaps furnish some useful hints respecting the preser- 
 vation of metals, especially iron, from oxidizement during the 
 progress of this and other similar processes in the arts. 
 
 From these few observations the readeronay conceive, that the 
 discovery of some certain and infallible mode of imparting any 
 specific degree of heat to iron or steel, that may be necessary for 
 the processes of hardening and tempering, must be an important 
 desideratum in the manufactory of edge tools. 
 
 In the year 1789 Mr. David Hartley took out a patent for a 
 method of tempering steel by themid of a pyrometer or thermo- 
 meter applied near to the surface of the article, and at the same 
 time recommended the use of heated oil, in which he says many 
 dozens of razors or other tools might be tempered at once with the 
 utmost facility, and the various degrees of heat necessary for the 
 different purposes might speedily be determined by experiment. 
 
 "When I first saw this announced in the public journals, it im- 
 mediately occurred to me that the principle might be improved 
 upon ; and if a bath of oil, or of some kind of fusible metal, were 
 contrived for the tempering of every species of edge tool, that a 
 greater degree of certainty would be given to this operation, than 
 the persons who have generally the conduct of such manufactories 
 have ever experienced. 
 
 Influenced by these views of the subject, I determined long ago, 
 that I would embrace some opportunity of instituting a series of 
 experiments, to determine at what degrees of temperature all the 
 common kinds of oil enter into ebullition, and also the melting 
 points of several metallic compounds, in order to be able to fur- 
 nish the practical cutler^with a few tables, whence he might learn 
 
494- ON THE MANUFACTURE 
 
 how to construct a bath in which he could at all times impart the 
 desired temper to the particular instruments of his manufacture, 
 with the utmost certainty and with unusual dispatch '. 
 
 In the application of this principle of tempering edge tools in a 
 fluid menstruum, whether metallic or otherwise, it will be advisable 
 to have the bath which is to contain the heated fluid, made of 
 cast-iron, which should vary in form and size so as to adapt it to 
 the particular sort of tools or instruments which are to be tem- 
 pered within it. And where the business is considerable, it 
 would be convenient to have two such baths fixed in brickwork, 
 adjoining to each other and heated by the same fire, with regis- 
 ters to cut off the communication of either of them with the fire- 
 place at pleasure, so that one might be heating while the workman 
 was tempering his goods in the other. 
 
 Many advantages would result from this method of tempering 
 edge tools. In the first place, there could never be any uncer- 
 tainty as to the degree of temper which the articles would acquire ; 
 for, when the manufacturer had once ascertained which of the 
 metallic baths was suitable for any particular kind of edge tool, 
 all that would be necessary would be to arrange the goods in rows 
 upon the surface of the congealed metal, to light a fire underneath 
 the containing vessel, and then carefully to observe when the 
 surface of the fusible metal begins to melt. As soon as this takes 
 place, the edge tools are immediately to be removed and plunged 
 into cold water, by which means the whole parcel will have ac- 
 quired exactly the same temper. 
 
 Secondly, where instruments have a thick back and a fine edge, 
 it is almost impossible ever to- give them an uniform temper by 
 the old method ; for there will always be a danger of the edge 
 being lowered too much before the other parts become regularly 
 heated throughout. This difficulty occurs particularly in razors, 
 where the thickness of the back is always a formidable obstacle 
 to' the attainment of an uniform regularity of hardness. It may 
 however be determined by means of nitric acid, whether a razor 
 or other polished edge tool be of an equal degree of hardness : 
 for, on applying this acid to bright steel, the black tinge will ap- 
 pear more speedily and strongly upon the hard parts than on the 
 rest of the surface. The inconvenience attendant on the manu- 
 facture of this particular instrument has been so great, that Messrs. 
 Rhodes and Champion, eminent cutlers of Sheffield, have in- 
 vented what they call the " New frame-bladed Razor," in which 
 the back and the finger-hold are made with an alloy of copper, 
 
 1 These experiments were tried by Mr. Parkes, and the results given in a 
 tabular form in the Additional Notes to the 2nd edition of these Essays in 
 2 vols. 8vo, but from their great length are unavoidably omitted in reprinting 
 the work in one volume. 
 
OF EDGE TOOLS. 495 
 
 not subject to rust, and the blade only is made with steel. These 
 blades being nearly as thin at the back as at the edge, they can 
 be tempered without incurring the danger already mentioned ; 
 and when one of these is let into the copper back, it becomes a 
 complete instrument. This however is attended with a consider- 
 able additional expense, which would be unnecessary if the plan 
 of the metallic bath be adopted. 
 
 In the hardening of large files and rasps, which require to lie 
 a considerable time in the fire before they become heated through- 
 out, this expedient would be of incalculable advantage ; indeed, 
 I know of no instrument, except the 'scythe, and the pit-saw, 
 which might not be tempered with more certainty by means of a 
 fluid bath than by the process in common use. And there is no 
 reason for excepting these but their great size, which would ren- 
 der the tempering of them in metallic baths both troublesome and 
 expensive. 
 
 When the sword was the chief weapon of war, it must, as Mr. 
 Nicholson has observed, have been an object of great interest and 
 demand to give to its blade a durable keen edge, and a degree of 
 firmness or strength, which, without rendering it unwieldy, should 
 ensure the warrior against exposure to the fatal accident of its 
 breaking in the act of combat. 
 
 Formerly, no man in Great Britain knew how to temper a sword 
 in such a way that it would bend for the point to touch the heel 
 and spring back again uninjured, except one Andrew Ferrara,who 
 resided in the Highlands of Scotland. The demand which this 
 man had for his swords was so great that he employed workmen 
 to forge them, and spent all his own time in tempering them ; and 
 found it necessary, even in the day-time, to work in a darlc cellar, 
 that he might be better able to observe the progress of the heat, 
 and that the darkness of his workshop might favour him in the 
 nicety of the operation. Had this ingenious artist thought of a 
 bath of oil, he might have heated this by means of a fur- 
 nace underneath it, and by the use of a thermometer, to the 
 exact point which he found necessary; though it is inconvenient 
 to have to employ a thermometer for every distinct operation. Or, 
 if he had been in possession of a proper bath of fusible metal, he 
 would have attained the necessary certainty in his process, and 
 need not have immured himself in a subterranean apartment. 
 
 The swords which were formerly in the highest repute, were 
 made at Damascus in Syria. The method by which these were 
 made, has long been lost ; or perhaps it was never thoroughly 
 known to Europeans ; but it is supposed that they were formed 
 by alternate layers of extremely thin plates of iron and steel bound 
 together with iron-wire, and then firmly cemented together by 
 welding, These weapons never broke, even in the hardest con- 
 
496 ON THE MANUFACTURE 
 
 flict, and yet they retained so powerful an edge, that the armour 
 made like net-work with scales of iron, or with small iron rings, 
 called coats of mail, was instandy divided under their force. 
 
 This manufactory at Damascus had formerly the greatest repu- 
 tation throughout Europe and through a great part of Asia ; but 
 in the latter end of the fourteenth, or at the beginning of the fif- 
 teenth century, Tirnour Bee, usually called Tamerlane, on his 
 conquest of Syria ', carried away all the best workers in steel from 
 Damascus to Persia; and we know so little of Persia, that it may 
 be difficult now to ascertain whether this peculiar manufactory is 
 still carried on in that country, or not. 
 
 A writer in Nicholson's Journal, who had the opportunity of 
 examining a real Damascus blade, which had cost the possessor 
 twelve guineas at Constantinople, has thus described it : " It had 
 (says he) a dull grey or blueish appearance, was scarcely harder 
 than common steel from the forge, was not easily bended, and 
 when bended had no spring to recover its figure. Its back was 
 smooth, as were also two narrow sloped surfaces which formed 
 its edge under an angle of about 40 degrees ; but its flat sides 
 were every where covered with minute waving lines in masses in 
 all directions, not crossing each other, and, for the most part, 
 running in the direction of its length. The lines were in general 
 as fine as harpsichord wire, not extremely well defined nor con- 
 tinued ; and their distinction from each other was effected by no 
 perceptible indentation of the surface, but rather by the succession 
 of parts differing in the degree of polish or brightness." 
 
 " I was informed," says the writer of the memoir, " that if any 
 part of this blade were made smooth by grinding or whetting, the 
 wavy appearance, called the water, could be again produced by 
 means of lemon juice ; and that its excellencies were, that it 
 could be depended upon not to break ; and that it would cut 
 deeper into a soft substance, such as a pack of wool, or into flesh, 
 than any other kind of sword blade." 
 
 " I infer therefore," adds the writer, " that the Damascus steel 
 is in fact a mechanical mixture of steel and iron ; that it is inca- 
 pable of any considerable degree of hardness, and consequently 
 is in no danger of breaking from its brittleness ; that its tenacity 
 is ensured not only from the admixture of iron, but likewise from 
 the facility with which its soundness may be ascertained through- 
 out, by the same process which exhibits the water or fibrous ap- 
 pearance ; and, lastly, that the edge of a weapon formed of this 
 material must be rough, on account of the different resistance 
 which the two substances afford to the grindstone, in consequence 
 of which it will operate as a saw, and more readily cut through 
 
 1 Gibbon's History of thcDechne and Fall of the Roman Empire, 8vo, vol. xii. 
 pp. 21 and 45. 
 
OF EDGE TOOLS. 497 
 
 yielding substances than such cutting tools as are formed of a 
 more uniform substance." Vol. i. p. 468 471. 
 
 The conjectures of this writer respecting the methods by which 
 these blades were manufactured at Damascus, and the account of 
 the experiments which he himself undertook for the purpose of 
 enabling him to imitate them, are extremely interesting and in- 
 structive, so much so that I have no hesitation in recommending 
 the whole paper to the perusal of all those who are curious in the 
 manufacture of edge tools. 
 
 1 have some other observations to make before I conclude this 
 Essay. " It is a generally prevailing opinion," says Mr. Rhodes, 
 " amongst men accustomed to the process of hardening steel, 
 that if it be overheated previously to immersion, an extra portion 
 of heat is likewise required to reduce it, or what is termed let it 
 down, to a proper degree of hardness ; and that without this a 
 good cutting edge cannot possibly be produced. This, indeed, 
 to* say the least of it, is a miserable and ineffectual attempt to re- 
 medy one error by the introduction of another. That this is an 
 extremely injurious opinion, and that it operates perhaps more 
 than any other cause whatever, to produce a mass of inferior 
 cutlery, must be obvious to every one who thinks at all upon the 
 subject. 
 
 " It may be laid down as a position, which is not in much dan- 
 ger of being controverted, that the lowest possible heat at which 
 steel becomes hard is indubitably the best ; and that to impart to 
 it any extra portion, is essentially to affect its most valuable pro- 
 perties. If over-heated, the pores of steel become open and ex- 
 panded, the fineness of its texture is annihilated, and it is ren- 
 dered so extremely susceptible of injury from the influence of heat, 
 that a small portion acting upon it, when it is in this state, entirely 
 destroys its capability of sustaining a cutting edge. 
 
 " It must not be inferred from these remarks, that any degree 
 of temper whatever will operate to restore to steel the pure pro- 
 perties of which it has been deprived by being over-heated. 
 Workmen, however, acting under the influence of the preposte- 
 rous opinion here deprecated, manifest great carelessness in the 
 performance of this very critical operation, always imagining the 
 evil effects of this carelessness may be remedied by resorting to a 
 practice most palpably erroneous V 
 
 From the information which I have collected in various quarters, 
 I am inclined to think that the bad temper of many of our small 
 edge tools may be attributed to improper management in tilting 
 
 2 An Essay on the Manufacture of a Razor. By E. Rhoctes, Sheffield, 
 octavo, 1809, p. 18. 
 
 2 K 
 
498 ON THE MANUFACTURE 
 
 the steel ; I therefore, on a late journey to the north of England, 
 embraced that opportunity of visiting the public forge which is em- 
 ployed by most of the cutlers in the town of Sheffield, and where 
 these manufacturers send their steel to be drawn out into bars of 
 different forms and of different sizes, according to the various 
 purposes for which it is intended. I observed that the process 
 of tilting, or drawing out into fine bars, is conducted in the follow- 
 ing manner. 
 
 The steel, which is usually in bars of 2J inches square and about 
 2J feet long, is put, several bars together, into a wind furnace, 
 that it may be sufficiently softened by heat to render it quite 
 ductile under the forge-hammer. This hammer, which is very 
 weighty, is moved by a water-wheel, and strikes incessantly upon 
 an anvil fixed immediately beneath it. By means of this apparatus 
 the heated bars may be drawn down to any size which the manu- 
 .facturer requires ; and one man and a boy are all the hands which 
 are necessary for performing the work. 
 
 To conduct this operation the man seats himself in a hanging 
 wooden seat, very similar in appearance to one of the wooden 
 planks suspended to a pair of large scales, and which is fixed to 
 the ceiling by four strong iron wires, in such a position as to swing 
 directly opposite to the anvil on which the steel is to be laid and 
 drawn into bars. 
 
 When the man has properly fixed himself in this seat, the boy 
 brings him one of the heated bars and slides it under the forge- 
 hammer. The workman immediately takes charge of it, and 
 moves it a little either backwards or forwards according to his 
 judgement, every time the hammer rises, so that every part of the 
 metal in its turn may be uniformly submitted to the action of the 
 forge-hammer. By this repeated hammering the steel is soon 
 drawn very considerably thinner ; and when the workman finds 
 that it is becoming too cold for the forging to make the proper im- 
 pression upon it, it is once more or oftener heated in the furnace, 
 and as often submitted to the action of the tilting hammer, until 
 it be reduced to the desired size and shape. 
 
 As only one extremity of the bar is at first submitted to the 
 action of the hammer, and as it is necessary to slide it gradually 
 further and further underneath it, the workman is under the ne- 
 cessity of approaching nearer to the anvil or of receding from it, 
 every time the hammer rises or falls. To enable him therefore to 
 do this with facility, there is a small well of about a foot deep, 
 sunk within the floor for the reception of his legs, and directly 
 under that part of the ceiling to which his seat is suspended. Things 
 being thus arranged, the operator is enabled by a slight motion 
 of his foot, and without any painful exertion, to move himself 
 either backwards or forwards as his work requires. 
 
OF EDGE TOOLS. 499 
 
 While I attended thi*s operation, I observed that very different 
 degrees of heat were given to the strong bars in order to soften 
 them for the tilt-hammer ; and I can readily conceive that the in- 
 jury which I have spoken of as being done to bar-steel at the 
 til ting-house, may be entirely attributed to this circumstance the 
 unequal or superfluous application of heat. 
 
 I observed, also, that those bars which were unnecessarily 
 heated, threw off a prodigious number of thin scales at every blow 
 of the hammer ; and when I made inquiry respecting this, I was 
 informed that the manufacturers generally expect that the steel 
 which they send to this establishment will lose five per cent, in 
 weight by the operation of tilting ; and that when the bars are 
 heated more than necessary, this loss is always proportionably 
 greater. The charge usually made for drawing steel into fine bars, 
 is from 55. to 6s. 6d. per cwt. according to the size required. 
 
 After I had visited this public forge and witnessed the care- 
 lessness with which the bar-steel is heated, I felt extremely desi- 
 rous of ascertaining the degree of effect produced on cast-steel by 
 being brought to too high a temperature, not doubting that the 
 badness of many of our edge tools might be chiefly ascribed to 
 this cause. Therefore, before I left Sheffield, I procured a small 
 bar of cast-steel, and having borrowed the use of a hearth, I made 
 the following experiment. 
 
 The bar of steel was first broken into three pretty equal parts; 
 I then heated one of these to a low red heat, and immediately cooled 
 it by sinking it very gradually into a trough of cold water. The 
 second was heated considerably more, even to a full red, and . 
 cooled in the same manner. The third was brought to an intense 
 white heat, and then instantly quenched in cold water, like the 
 preceding parts. 
 
 Afterwards, on breaking a small piece from one end of each of 
 these bars, the following appearances presented them selves, which 
 completely satisfied me of the decisive nature of the experiment. 
 The first exhibited a very fine, close, and compact grain ; the 
 second was of a much coarser texture ; and the grain of the third 
 was analogous in all respects, and quite as coarse as that of a 
 piece of common cast-iron. 
 
 It is well known that cast-steel is brittle and useless before it be 
 tilted, or drawn out by the forge-hammer ; but if it be heated too 
 much for this operation, the texture of the metal will be so much 
 altered by this excess that it will be rendered entirely unfit for the 
 fabrication of fine instruments. It may here however be men- 
 tioned, that such steel as will suit one implement is often not fit 
 for another. That which has the most blisters is generally the 
 hardest and fittest for files, &c. ; but the softest steel, or that 
 
 2 K2 
 
500 ON THE MANUFACTURE 
 
 which approaches the nearest to the state of wrought-iron, is most 
 suitable for many other purposes. 
 
 There is another circumstance which militates very much 
 against the perfection of the finer sort of edge tools, namely, the 
 velocity that is given to the motion of the stones on which the in- 
 struments are usually ground and polished. The workmen at 
 Sheffield are not paid for their time, but by the piece, or according 
 to the quantity of work finished ; it is consequently their interest 
 to use the utmost dispatch, and urge the grinding-stones to the 
 most rapid motion, because the amount of the work will, in fact, 
 be in proportion to the celerity of the revolving stones. 
 
 At Sheffield the stones are usually moved either by a steam- 
 engine or a powerful water-wheel ; therefore any degree of velo- 
 city may be given to them, by simply moving the strap to a pulley 
 of a larger or srnallei diameter. This indeed has sometimes been 
 pushed to such an extent, that the stones, merely by the centri- 
 fugal force which they had thus acquired, have been dashed into 
 innumerable pieces, and have occasioned the death of the work- 
 men and bystanders. 
 
 Those who have paid attention to the process of tempering 
 steel will readily conceive the great injury that a fine edge tool is 
 likely to suffer from the accumulated heat occasioned by a re- 
 volving grindstone, or other rough mineral substance in rapid 
 motion. This is an evil of great magnitude ; but unless men of 
 real principle be found who would willingly engage in this em- 
 ployment, and be content that their own interests should be sub- 
 servient to that of their master, and that their first aim be to give 
 perfection to the quality of the goods they fabricate, I am afraid 
 that no effectual remedy can be adopted. 
 
 In a late voluminous but very respectable publication it is said, 
 that the Wicker sley stone is usually employed for grinding edge 
 tools, because this stone has the peculiar property of not heating 
 to a great degree any substance ground upon it. This appeared 
 to me to be so very extraordinary that I determined to make an 
 inquiry, on mynextjourney in to Yorkshire, respecting this circum- 
 stance. I have since however been assured by some of the most 
 extensive cutlers at Sheffield, that the assertion is without foun- 
 dation, and that there are other reasons for the preference which 
 is often given to this particular stone. 
 
 Wickersley is a village situated between Rotheram and Don- 
 caster, about ten miles north-east of Sheffield. From the inquiries 
 which I have made, I learn that this stone, which is of a light-buff 
 colour, with a slight shade of red intermingled, is used for grinding 
 all the fine hard steel goods, such as razors, penknives, and the best 
 
OF EDGE TOOLS. 501 
 
 scissars ; and it is preferred for these, not because it produces a 
 less degree of heat in the operation, but from the fineness of its 
 texture, from the rapidity with which it cuts, and from its not 
 being subject to have hard or knotty places interspersed in it, an 
 imperfection to which most other grindstones are liable. The 
 workmen in general give the preference to these stones for articles 
 made with hard steel ; but soft or unhardened goods, such as fork- 
 shanks, for example, are usually ground with a stone which pos- 
 sesses a much greater degree of hardness. 
 
 In the Supplement to the Encyclopedia Britannica, article 
 CUTLERY, mention is made of a green stone found in some parts 
 of the old pavement of London, as the only known material capa- 
 ble of giving to lancets the smooth edge which they require. This 
 stone, which is now extremely rare and valuable, is a soft horn- 
 stone. Its analysis has been published by Mr. Faraday. Qicar- 
 terly Journal, vol. vii. p. 400. 
 
 Another kind of edge tool remains to be described, which is 
 made of cast-iron and afterwards converted into steel. The 
 method of conducting this process was discovered by Mr. S. 
 Lucas of Sheffield, and he has obtained a patent for the inven- 
 tion. In order that all classes of readers may be able to appre- 
 ciate the merits of this very ingenious process, it will be necessary 
 to explain what constitutes the difference in the various sorts of 
 iron, and likewise in what respect this differs from steel. 
 
 Iron is found in the state of an ore in the bowels of the earth, 
 and, in abstracting from this an useful metal, the first product is 
 generally cast-iron, which owes its fusibility to the combination 
 of carbon. This varies, however, in quality according to the 
 quantity of carbon combined with it; and consequently such kinds 
 are selected as are thought to suit the different purposes to which 
 they are to be applied. That which contains the most carbon is 
 chosen for small castings and for the neater kinds of ornamental 
 work, while the harder metal, which has less carbon, is always 
 preferred for railways, water-wheels, and all other large articles 
 which are designed to sustain much wear. 
 
 It is necessary that the carbon be intimately united with the 
 metal to form good pig-iron. This accounts for the preference 
 which is always given to that iron which is made with wood- 
 charcoal, for this enters more readily into combination with the 
 iron than even the best mineral coke. When coke is employed 
 in the process of making pig-iron, that which is the softest is 
 always found to be the best, while the hard coke is selected for 
 heating the blast furnaces. 
 
 JVrought-iron is malleable though very infusible, and it acquires 
 these changes in its properties by continued heat and repeated 
 
502 ON THE MANUFACTURE 
 
 hammering, which deprive the metal in a great measure of the 
 carbon which occasioned its great fusibility when in the state of 
 cas/-iron. But it varies very much in its quality, according to 
 the mode of its preparation, and the nature of the coke or charcoal 
 which has been employed in its manufacture/ 
 
 Steel differs from wrought- as well as from cast-iron, in having 
 resumed a small portion of carbon, and likewise by containing a 
 very minute proportion of silica and phosphorus. Steel is a most 
 important preparation of iron ; for it possesses the malleability of 
 wrought-iron without its infusibility, and also has the fusibility of 
 cast-iron without the brittleness of that substance. It completely 
 unites the malleability of the one with the fusibility of the other. 
 A particular account of the methods by which steel was usually 
 prepared in the middle of the last century is given by Mr. Dossie 
 in his Institutes 1 . Some account of the present modes of making 
 both the blistered and the shear steel has already been given. 
 Cast-steel, according to Mr. Aikin, is made by the following pro- 
 cess : 
 
 " The finest kind of steel, called English cast steel, is com- 
 monly prepared," says he, " by breaking to pieces the blistered 
 steel, and then melting it in a crucible with a flux composed of 
 carbonaceous and vitrifiable ingredients. The vitrih'able part of 
 the mixture is of use only in as much as it is a fusible body, which 
 flows over the surface of the metal in the crucibles, and prevents 
 the access of the oxygen of the atmosphere. Broken glass is 
 sometimes used for this purpose. 
 
 " When the metal is thoroughly fused, it is cast into ingots, 
 which by gentle heating and careful hammering are tilted into 
 bars. By this process the steel becomes more highly carbonized 
 in proportion to the quantity of flux, and in consequence is more 
 brittle and fusible than before. Hence it surpasses all other steel 
 in uniformity of texture, hardness, and closeness of grain, and 
 is the material employed in all the finest articles of English 
 cutlery' 2 ." 
 
 In the year 1820, Oostad Muhammed Ali described in the 
 Laboratory of the Royal Institution of Great Britain the method 
 of making cast-steel in Persia. The iron, he said, is brought 
 from the mountains : a square place is built up, about four feet in 
 the side, and five or six feet high, the walls eight or nine inches 
 thick ; stones of a slaty kind are placed in the inside about 18 
 inches from the bottom, so as to form a grate ; below this is a 
 chamber for the reception of the melted steel, and above it is 
 placed the iron in bars, and charcoal intermingled together. 
 
 1 Dossie's Institutes of Experimental Chemistry, vol. ii. p. 375 388. 
 
 2 Aikin's Chemical Dictionary, article /ron, vol. i. p. 602. 
 
OF EDGE TOOLS. 505 
 
 There are three apertures above the grate into the furnace, into 
 which air is propelled from bellows worked by men sitting ; a fire 
 is lighted, and the heat raised ; fresh charcoal is thrown on as 
 that in the furnace burns away ; and as the iron becomes carbo- 
 nized, it melts and falls through the grate as fluid cast-steel, into the 
 chamber beneath, whence it is taken and cast into ingots. 
 
 To prepare the cast-steel, three or four hundred weight of iron 
 is placed in such a furnace, and there is a loss of about one-third 
 from oxidation, and adhesion to the sides. The operation re- 
 quires from two to three days, with constant blowing. M. Mu- 
 hammed described the charcoal that was employed, as being 
 exceedingly hard and heavy, and very unlike our charcoal, but 
 did not know of what wood it was made. Quarterly Journal^ 
 vol. viii. p. 1 60. 
 
 The invention by Mr. Lucas, of con verting edge tools made of 
 cast-iron into good steel, appears to be an important improve- 
 ment. It consists in stratifying the cast articles, in cylindrical 
 metallic vessels, with native oxide of iron pulverized, or sand con- 
 taining oxide of iron, and then submitting the whole to a regular 
 heat in a furnace built for the purpose. It is not necessary that 
 the oxide employed should be a native oxide, any artificial oxide 
 being equally effective ; that kind which can be had cheapest is 
 therefore generally preferred. The operation may be thus ex- 
 plained : 
 
 The cast-iron, of which this cutlery is made, is brittle in the 
 first instance, like other cast-iron, in consequence of the carbon 
 contained in it ; but the great heat which it undergoes, aided by 
 the pulverized oxide, separates the carbon : this uniting with the 
 oxygen of the ground oxide of iron, is dissipated in the state either 
 of carbonic oxide or carbonic acid gas, and the goods are then 
 converted into a state very similar to that of good cast-steel cutlery. 
 
 To prevent misconception, it may be necessary to state, that 
 cast-iron which contains a large proportion of carbon is less 
 brittle than that which is combined with a smaller quantity. It 
 can also be filed and cut with a cold chisel, while the latter, al- 
 though it may be more readily broken, effectually resists the 
 action both of the chisel and the file. In conformity with these facts, 
 small machinery made of common cast-iron may be softened 
 merely by cementation with a carbonaceous substance, thereby 
 augmenting its dose of carbon, and rendering it capable of being 
 smoothed by the file. 
 
 I understand that the best pig-iron is always chosen for making 
 the various articles of cutlery, while the poorest iron ore, if free 
 from sulphur, may be pulverized and stratified with them to afford 
 oxygen. 
 
504- ON THE MANUFACTURE 
 
 After several years experience, Mr. Thomas Lucas has been 
 enabled to bring this process to such a state of perfection, that his 
 cast cutlery will bear a polish equally brilliant with the best cast- 
 steel goods, as I can testify from my own observation ; and will 
 also take as fine an edge, so that some of the best judges of 
 cutlery cannot distinguish the difference. When, however, the 
 cast cutlery wares which have been thus annealed, are submitted 
 to the usual processes of hardening and tempering, they are apt 
 to be more brittle than those edge tools which are made in the 
 usual way with the best steel. 
 
 It has also been found that by varying the process small pig- 
 iron castings can be converted into good malleable iron : in conse- 
 quence of this the patentee now makes a great variety of small 
 iron utensils by casting, which were formerly made only on the 
 anvil of the blacksmith ; and when he has converted the metal to 
 the quality of soft malleable iron, these articles are found to be 
 equally fit for a great variety of purposes, and can be afforded at 
 a much lower rate than similar goods which have been modelled 
 by hand, as heretofore. He has become so complete a master of 
 this business, that he can convert cast-iron goods either into the 
 state of wrought-iron or steel at pleasure. 
 
 Mr. Lucas has shown me articles made with pig-iron which 
 appeared perfectly malleable. I have seen cast nails which would 
 bend like common wrought-iron nails, and small articles that 
 would bear even to be welded together by the usual process. 
 
 In conducting these operations, he has sometimes observed 
 that when dark or highly carburetted cast-iron is fused in small 
 quantities, plumbago is separated, and the metal, by thus losing 
 a part of its carbon, becomes white. Here a question occurs; 
 Why did not the plumbago separate on the first cooling ? Is it 
 not probable that crude iron combined with a certain portion of 
 carbon, is thereby rendered capable of dissolving and retaining 
 in combination a quantity of plumbago, in the same manner as 
 water saturated with carbonic acid, will dissolve an extra portion 
 of carbonate of lime ? 
 
 I have also to observe, that the steel which the patentee 
 makes by the process of cementation, possesses, in common with 
 that manufactured in the usual way, the susceptibility of being 
 powerfully magnetized, and appears to retain the magnetic pro- 
 perty as well as other steel. He has indeed in his possession a 
 small instrument in the form of a horse-shoe magnet, made with 
 cast-iron, and afterwards converted by his peculiar process to steel, 
 which he has had magnetized, and it is now capable of sustaining 
 by its magnetic power, a weight nearly equal to three pounds. 
 
 I have only to add that Mr. Lucas has very obligingly fur- 
 nished me with a drawing of the furnace which he employs in 
 
OF EDGE TOOLS. 505 
 
 these processes, and, with his permission, I have had a copper- 
 plate engraving of it made to accompany this Essay. 
 
 Since the publication of the first edition of these Essays, Messrs. 
 Stodart and Faraday have undertaken a series of very important 
 experiments on the alloys of iron and steel, with various other me- 
 tals ; the object of which was, first to ascertain whether any alloy 
 could be artificially formed, better for the purpose of making 
 cutting instruments than steel in its purest state; and, secondly, 
 whether any such alloys would, under similar circumstances, 
 prove less susceptible ol' oxidation. An account of these experi- 
 ments having been given in considerable detail, both in the Phi- 
 losophical Transactions, and in the Quarterly Journal of Science, 
 I trust that a careful abridgement of all the papers on this subject, 
 or at least a transcript of the most important results of the 
 several experiments, will be useful and highly acceptable to the 
 public. 
 
 These experimentalists found that by combining a very small 
 portion of alumina with good steel, an artificial wootz was produced, 
 which, when the surface was polished, gave, on the application 
 of dilute sulphuric acid, the beautiful damask appearance which 
 has hitherto peculiarly belonged to the Asiatic steel. It is re- 
 markable that the wootz, although repeatedly fused, retains the 
 peculiar property of presenting a damasked surface, when forged, 
 polished, and acted upon by dilute acid. 
 
 " Platinum, rhodium, gold, silver, nickel, copper, and tin, were 
 alloyed with both English and Indian steel, and in various pro- 
 portions. All these metals have an affinity for steel sufficiently 
 strong to make them combine ; and this is so remarkable with 
 platinum, that it will fuse when in contact with steel, at a heat at 
 which the steel itself is not affected. 
 
 " When one part of silver to 500 parts of steel were properly 
 fused, a very perfect button was produced. The specimen forged 
 remarkably well, although very hard. By a delicate test every 
 part of the bar gave silver. This alloy, they say, is decidedly su- 
 perior to the very best steel, and this excellence is unquestionably 
 owing to combination with a minute portion of silver. It has been 
 repeatedly made, and always with equal success. Various cutting 
 tools have been made from it of the best quality. This alloy is 
 perhaps only inferior to that of steel with rhodium, and it may be 
 procured at a small expense ; the value of silver where the pro- 
 portion is so small, is not worth naming ; it will probably be ap- 
 plied to many important purposes in the arts. 
 
 " The alloys of steel with platinum, when both are in a state 
 of fusion, are very perfect, in every proportion that has been tried. 
 Equal parts by weight form a beautiful alloy, which takes a fine 
 
506 ON THE MANUFACTURE 
 
 polish, and does not tarnish ; the colour is the finest imaginable 
 for a mirror. The specific gravity of this beautiful compound is 
 9-862. 
 
 " The proportions of platinum that appear to improve steel for 
 edge instruments are from 1 to 3 per cent. ; 1 '5 per cent, will pro- 
 bably be very nearly right. 
 
 " The alloys of steel with rhodium are likely to prove highly 
 valuable. The scarcity of that metal must, however, operate 
 against its introduction to any great extent. This alloy was made 
 at the suggestion of Dr.Wollaston. The proportions of rhodium 
 used, were from 1 to 2 per cent. The valuable properties of the 
 rhodium alloys are hardness, and sufficient tenacity to prevent 
 cracking either in forging or in hardening. This superior hard- 
 ness is so remarkable, that in tempering a few cutting articles 
 made from the alloy, they required to be heated full 30 of 
 Fahrenheit higher than the best wootz, wootz itself requiring to 
 be heated full 40 above the best English cast-steel. Thermo- 
 metrical degrees are named, that being the only accurate method 
 of tempering steel." 
 
 " Gold forms a good alloy with steel. Experience does not yet 
 enable us," say they, " to speak of its properties. It certainly does 
 not promise to be of the same value as the alloys of silver, plati- 
 num and rhodium." 
 
 The authors conclude this valuable paper ', by observing that, 
 ** from the facility of obtaining silver, it is probable that its alloy 
 with steel is the most valuable of those we have made. To enu- 
 merate its applications would be to name almost every edge tool. 
 It is also probable that it will prove valuable for making dies, 
 especially when combined with the best Indian steel." 
 
 In a subsequent paper 2 these experimentalists give an account 
 of the manufacture of the alloys upon a larger scale. In these 
 experiments they discovered, with regard to the silver alloy, that 
 " steel will only retain one 500dth part in union ; when more was 
 used, it either evaporated, or separated as the button cooled, or 
 was forced out in forging. The alloy was excellent, and the tri- 
 fling addition of price furnishes no obstacle to its general em- 
 ployment." 
 
 " Steel alloyed with the lOOdth part of platinum, though not 
 so hard as the silver alloy, has more toughness ; hence its value, 
 where tenacity as well as hardness is required : the extra cost is 
 more than repaid by its excellence. 
 
 " The action of acids on these alloys is curious, and especially 
 in respect to that of platinum, which is acted upon by diluted 
 
 1 Quarterly Journal of Science, vol. ix. p. 319330. 
 
 * Philosophical Transaction* for the year IS22, part ii. p. 253270. 
 
OF EDGE TOOLS. 50? 
 
 sulphuric acid with infinitely greater rapidity than the unalloyed 
 steel ; indeed, an acid that scarcely touches the pure steel, dis- 
 solves the alloy with energetic effervescence. This is probably 
 referable to electrical excitation." 
 
 It is remarkable that when pure iron is substituted for steel, 
 the alloys so formed are much less subject to oxidation. Three 
 per cent, of iridium and osmium, fused with some pure iron, gave 
 a button, which, when forged and polished, was exposed, with 
 many other pieces of iron, steel and alloys, to a moist atmosphere; 
 it was the last of all showing any rust. The colour of this com- 
 pound was a distinct blue. 
 
 Dr. Brewster states that Mr. Stodart favoured him with spe- 
 cimens of several of these alloys for optical purposes ; and though 
 various plates of polished steel kept beside them for more than a 
 year, were all affected with rust, yet not one of the alloys had 
 suffered the least change 3 . 
 
 When the public had been informed of the success which 
 had attended the experiments of Messrs. Stodart and Faraday, 
 M. Berthier was induced to try the effect to be obtained by ad- 
 ding a portion of chromium to steel. " Two alloys of cast-steel 
 and chromium were made, one with 0*01, the other with 0*015 of 
 chromium. These, he says, both forged well, the first better than 
 cast-steel. A knife and a razor were made from them, and both 
 proved very good; their edges were hard and solid, but their 
 most remarkable character was the fine damask they took, when 
 washed over with sulphuric acid. This damask was composed 
 of white silvery veins, and nearly resembled that given by the 
 alloy of steel and silver. The white parts are probably pure 
 chromium, on which acids have no action. This chromic steel 
 was prepared by fusing together cast-steel and the alloy of chro- 
 mium and iron V 
 
 3 The Edinburgh Philosophical Journal, vol. vii. p. 350. 
 
 4 Quarterly Journal of Science, vol. xii. p. 1 74. Annales de Chimie ft de 
 Physique, toine xvii. p. 55. 
 
508 ON THE MANUFACTURE OF TIN-PLATE. 
 
 ESSAY XVI. 
 ON THE MANUFACTURE OF TIN-PLATE. 
 
 [First printed in the MEMOIRS OF THE LITERARY AND PHILOSOPHICAL SO- 
 CIETY or MANCHESTER, Vol. III. New Series; and copied from thence into the 
 Annalcs de Chimie et de Physique, tome xii. for the year 1819, p. 153.] 
 
 As the processes in this manufacture are more numerous and 
 complicated than they are generally imagined, it may be advisa- 
 ble to preface the account with an enumeration of some of those 
 properties of tin which will be most likely to explain the rationale 
 of the principal operations. 
 
 Tin has a great affinity for several of the other metals par- 
 ticularly for zinc, mercury, copper, antimony, lead and iron ; and 
 owing to these affinities, its employment in the arts is very con- 
 siderable. 
 
 Tin, with zinc, forms a metal of close grain, very useful for 
 many purposes, especially for the formation of pewter. The zinc 
 is found to impart great hardness to the tin, without lessening its 
 ductility. 
 
 The combination of mercury and tin, in which the tin is dis- 
 solved by the mercury into a very soft amalgam, is largely em- 
 ployed, as is well known, in silvering the backs of mirrors, and 
 for other purposes in the arts. An amalgam of tin of greater con- 
 sistence was formerly in use in the museums of Paris for closing 
 the mouths of glass-bottles containing sundry curious and valua- 
 ble preparations. 
 
 Copper is also alloyed with tin for various purposes of manu- 
 facture. This metallic mixture is employed in making what are 
 called bronze statues; for casting bells, and pieces of artillery, 
 and also for the fabrication of medals and medallions. In some 
 of these cases the tin is mixed with copper, on account of its pro- 
 perty of rendering the copper more fusible ; and this was pro- 
 bably the reason why the ancient Romans used that metal in the 
 greater part of their brass coinage. It is owing to the affinity of 
 tin for copper, that vessels of capacity, made with the latter me- 
 tal, for culinary and other purposes, are so readily covered with 
 a coating of tin, to preserve them from the action of substances 
 
ON THE MANUFACTURE OF TIN-PLATE. 509 
 
 which would not fail to erode copper, if unprotected by some such 
 covering. The affinity of tin for copper is further exemplified 
 by the process of whitening pins 9 which is effected by boiling the 
 pins with granulated tin in a lye made with alum and tartar 1 . 
 
 An useful alloy is likewise formed by the mixture of tin and 
 antimony. This metallic compound is very white, extremely hard, 
 and will bear a very fine polish. On these accounts it is employed 
 in making specula for telescopes, and also for the manufacture of 
 rolled plates to engrave music upon. 
 
 The next metal which 1 have mentioned as uniting readily with 
 tin, is lead. This metal will combine with tin in^any proportion; 
 and in most proportions the lead acquires a greater degree of fu- 
 sibility by its union with the tin. It is this alloy which forms 
 plumbers' solder ; but that compound is prepared with different 
 proportions of tin, according to the purpose for which it is in- 
 tended. The article called tin-foil, used for lining tea-caddies, 
 for coating electrical jars, and for other purposes, is also made 
 from a mixture of these two metals. 
 
 But what is more relevant to the subject of this paper is the 
 chemical affinity which subsists between tin and iron. One of the 
 strongest proofs of this affinity is derived from the circumstance 
 that even cast-iron may be tinned in the same manner as wrought- 
 iron. Of late years, cast-iron saucepans, and pots of a large size, 
 are permanently tinned on their inner surfaces, to prevent the li- 
 quors which are boiled in them from acquiring any stain by a 
 partial dissolution of the iron. Many other articles, such as bri- 
 dle-bits, common stirrups, small nails, &c. are now made much 
 cheaper than formerly, by first fabricating them in cast-iron, and 
 then covering them with a thin coat of tin, by the immersion of 
 them in a hot mass of that metal in a state of fluidity. 
 
 That these effects are owing to chemical affinity, cannot be 
 doubted, when it is considered, that in all these cases the pores 
 of the iron are in some degree actually penetrated by the tin. 
 
 In the manufacture of tin-plate, which I am now about to de- 
 scribe, a similar effect is produced, and also by the same means. 
 Plates of iron properly prepared, are immersed in a large mass 
 of melted tin, which is kept hot by a fire constantly burning un- 
 derneath it ; the consequence of which is, that the tin in some 
 measure penetrates the iron, and this attaches other tin to it, so 
 that the whole surface of the iron acquires, by this means, a com- 
 plete covering of that metal. 
 
 As no accurate account has ever yet been given of the various 
 
 1 An interesting Memoir (by M. Gaddlin) on the Tinning of common Pins, 
 will be found in the Journal de Physique, 1789. 
 
510 ON THE MANUFACTURE OF TIN-PLATE. 
 
 processes by which this is effected, the following outline may pro- 
 bably be acceptable to the public. 
 
 English bar-iron of the finest quality, called tin-iron, and which 
 is generally prepared with charcoal instead of mineral coke, and 
 made with the greatest care, for this particular purpose, is first 
 cut to the necessary length, and then rolled at the mill, between 
 a pair of cast-iron rollers of about 17 inches long and 12 or 13 
 in diameter, into plates of the requisite thinness, and of such 
 form as is suitable for the business. These plates are then cut by 
 hand-shears to the sizes suitable for the different markets 1 . And 
 as the shearer shears the plates, he piles them in heaps, occasion- 
 ally putting one plate the cross way, to keep each box separate. 
 Two hundred and twenty-five plates are called a box ; but they 
 are not put into boxes of wood in this stage of the operation. The 
 iron plates now go into the hands of the sealer, who takes them 
 from the shear-house, and bends each of them singly across the 
 middle, into this form A, preparatory to their being cleaned for 
 tinning, and for the conveniency of putting them into the scaling 
 furnace, as will be more fully explained hereafter. 
 
 This furnace, or oven, is heated byjlame thrown into it from a 
 fire-place of a peculiar construction ; and it is this flame that 
 scales the plates, which are put into the oven in rows, and ar- 
 ranged three in each row, until the oven is full. It will be ob- 
 vious that if they lay flat on the floor of the oven, the flame could 
 play only on one side of each plate, whereas by being bent in the 
 form already described, the flame can operate equally on both 
 sides. It may here be remarked that the form of all tin-plates, 
 one sort excepted, is that of a parallelogram, and that if a piece 
 of stiff paper or pasteboard, 13f inches long, and 10 inches wide, 
 be bent in the centre at an angle of about sixty degrees, and then 
 ut to stand on the two ends, we shall have the form of a plate 
 ~o. 1. properly bent for the scaling oven. 
 
 The operation of cleansing, as it is called, and which is prepa- 
 ratory to the process of scaling, is commenced by steeping the 
 plates for the space of four or five minutes in a mixture of mu- 
 riatic acid and water, in the proportion of four pounds of acid to 
 three gallons of water. This quantity of the diluted acid will ge- 
 nerally be sufficient for eighteen hundred plates, or eight boxes 
 of 225 plates each. 
 
 When the plates have been steeped for the time prescribed, 
 they are taken out of the liquor, and placed upon the floor, three 
 
 1 These plates are generally cut by hand; but an ingenious whitesmith in 
 Glamorganshire a few years ago invented a method of shearing them by a ma- 
 chine. This machine is worked by a water-wheel, and will shear 100 boxes per 
 day; whereas a hand-shearer cannot complete more than 25 boxes in the same 
 period of time. 
 
ON THE MANUFACTURE OF TIN-PLATE. 511 
 
 in a row, and then by means of an iron rod put under them, they 
 are conveyed to a furnace heated red-hot, where they remain 
 until the heat takes off the scale, the removal of which was the ob- 
 ject in submitting them to that high temperature. 
 
 When this is effected, the plates are taken to a floor, where 
 they are suffered to cool; they are then straightened, and beaten 
 smooth upon a cast-iron block. The workman knows by the ap- 
 pearance of the plates during this operation, whether they have 
 been well scaled ; for if they have, that is, if the rust or oxide 
 which was attached to the iron has been properly removed, they 
 will appear mottled with blue and white, something like marbled 
 paper. The operation that we have now been describing is called 
 scaling. 
 
 As it is impossible the plates can go through this process with- 
 out being in some measure warped, or otherwise disfigured; they 
 are now rolled a second time, in their cold state, between a pair 
 of cast-iron rollers properly hardened and finely polished. This 
 operation makes both sides of the plates perfectly smooth, and 
 imparts a sort of polish to their surfaces. These cold rollers are 
 each about 22 inches long, and 17 or 18 inches in diameter. 
 
 The technical name of this apparatus is rolls, not rollers. All 
 the rolls which are employed in rolling plates, either hot or cold, 
 in this manufactory, are hard rolls; and there is as much dif- 
 ference between a pair of hard cast-iron rolls, and a pair of soft 
 rolls, although they may both be run out of the same pot of me- 
 tal, as there is between iron and steel. The workmen inform me 
 that the difference is entirely occasioned by the manner of casting 
 them, the soft rolls being cast in sand, whereas the hard rolls 
 are formed by pouring the metal into a thick cast-iron box, and 
 that the metal, by coming in contact with the cold box is suffi- 
 ciently chilled to render the whole face of the roll entirely hard. 
 The difference in the temper of these two kinds of rolls is so 
 great, that when they are put into the lathe to be turned perfectly 
 true, the turnings from the one will be th of an inch in thickness, 
 whilst the turnings which come from the other are not larger than 
 very fine needles. The temper of cast-iron thus varying accord- 
 ing to the nature of the mould into which it is poured, is a cir- 
 cumstance that appears to me to be deserving of attention in the 
 manufacture of a variety of other utensils employed in the arts 3 . 
 
 4 The art of making good hard rolls appears to be very imperfectly under- 
 stood, because the difficulty of producing them is very great. Not one in three 
 can be called thoroughly good. For, if they are not sufficiently hardened on 
 the surface, they will not wear; whereas, if they are made hard throughout, or 
 struck hard to the centre, as the workmen call it, they will generally crack across 
 the middle and become useless. This fault is quite independent of air bubbles 
 or flaws, which are always discoverable in turning by the lathe. 
 
.512 ON THE MANUFACTURE OF TIN-PLATE. 
 
 These rollers are used without heat ; but they are screwed down 
 very close one upon the other, only leaving bare room for the 
 plates to pass, that the utmost attainable degree of pressure may 
 be given to them. This last operation is called COLD ROLLING. 
 
 When the plates have undergone this process, they are put 
 one by one into troughs filled with a liquid preparation called the 
 lyes. 
 
 This is merely water in which bran has been steeped for nine 
 or ten days until it has acquired a sufficient acidity for the pur- 
 pose. The design of putting the plates into the troughs singly, 
 is, that there may be more certainty of the liquor getting between 
 them, and both the sides of every plate being soaked alike in the 
 lyes. In this liquor they remain for ten or twelve hours standing 
 on the edges; but they are turned, or inverted, once during that 
 time. This operation is called working in the lyes. 
 
 The next operation is that of steeping in a mixture of sulphuric 
 acid and water, in proportions which vary according to the judge- 
 ment of the workmen. 
 
 The trough in which this operation is conducted, is made with 
 thick lead, and the interior is divided by partitions of lead. Each 
 of these divisions is by the workmen called a hole, and each of 
 them will contain about one box of plates. In the diluted sul- 
 phuric acid which is in the different compartments of this vessel, 
 the plates are agitated for about an hour, or until they have be- 
 come perfectly bright, and entirely free from the black spots which 
 are always upon them when they are first immersed in it. 
 
 Some nicety however is required in this operation ; for, if they 
 remain too long in the acid, they will become stained, or blistered 
 by it, as the workmen term it; but practice enables a careful 
 operator to judge of the time when they ought to be removed. 
 This, however, is one of the most difficult parts of the business, 
 as few men like to work in it ; though I understand that a good 
 pickler is highly valued by his employers, and obtains great wages. 
 It is necessary to notify that this, and the former process with the 
 acidulated water, are both hastened by giving to those menstrua 
 an increase of temperature; and this is effected by means of heat- 
 ed flues which run under each trough. Little additional heat is 
 necessary in summer, however, as 90 or 100 of Fahrenheit is a 
 temperature sufficiently high for either of these operations. 
 
 When the plates come, out of the pickle, they are put into pure 
 water, and scoured in it with hemp and sand, to remove any re- 
 maining oxide, or rust of iron that may be still attached to them ; 
 for, wherever there is a particle of rust or even dust upon them, 
 there the tin will riot fix ; and they are then put into fresh water, 
 to be there preserved for the process of tinning. The design of 
 putting the plates into pure water, after they come out of the 
 
ON THE MANUFACTURE OF TIN-PLATE. 513 
 
 sours, is to prevent their becoming again oxidized ; for it has 
 been found that after these operations they will acquire no rust, 
 although they should be kept twelve months immersed in water. 
 
 It will be perceived that all these processes are nothing more 
 than preparatory measures for the operation which is to succeed, 
 viz. that of TINNING. 
 
 For this purpose an iron pot is nearly filled with a mixture of 
 Hock and grain tin, in a melted state ; and a quantity of tallow 
 or grease, sufficient, when melted, to cover the fluid metal to the 
 thickness of four inches, is put to it. However, as some persons 
 may not be acquainted with the difference between block and grain 
 tin, it may be remarked, before we proceed, that the metal known 
 in commerce by the name of block tin, is prepared either from the 
 mineral called tin-stone, or the one known in Cornwall by the 
 name of tin-pyrites, whilst the article called grain tin is smelted 
 from an ore which is found in grains, called stream tin ore, under 
 beds of alluvial soil, in low situations, whither in the course of 
 ages it has been washed from the hills by a succession of torrents 
 of rain. The former, which is produced in the greatest abundance, 
 is always contaminated with a portion of iron, sulphur, and other 
 injurious substances, and is therefore only employed for common 
 purposes ; while the grain tin, which is nearly free from every 
 impurity, and usually from twenty to thirty shillings per hundred 
 weight dearer, is used in many processes of dyeing, and in all 
 other cases where pure tin is required. I am also desirous of re- 
 marking, that in my opinion it would be more profitable to the 
 proprietor of a tin-plate work, if he were to use grain tin alone, 
 or grain tin mixed with that kind which is known by the name of 
 " Refined Tin," because these kinds not only contain less dross, 
 but they melt, as I know by my own experience, into a more fluid 
 metal ; and consequently, more would run off the plates in the 
 operation of tinning, and less tin would be consumed. At present 
 these manufacturers use the block and grain tin, in equal propor- 
 tions. 
 
 When the tin-pot has been charged in the way above men- 
 tioned, the metal is heated from a fire-place underneath it, and 
 by flues which go round the pot, until it is as hot as it can be 
 made without actually inflaming the grease which swims upon its 
 surface. The use of the grease is to preserve the tin from the 
 action of the atmosphere, and consequently to prevent it from 
 oxidizing. By melting a little tin or lead in an iron ladle, and, 
 when the dross is skimmed off, putting a morsel of tallow upon the 
 metallic fluid, the effect of the tallow in cleansing the face of the 
 metal will be evident. The workmen also say, that it increases 
 the affinity of the iron for the tin, or, as they express it, that it 
 makes the iron plates take the tin better. 
 
 2 L 
 
ON THE MANUFACTURE OF TIN-PLATE. 
 
 It is curious that burnt grease^ or any kind of empyreumatic fat, 
 effects this purpose better than pure fresh tallow. 
 
 Another pot, which is fixed by the side of the tin-pot, is filled 
 with grease only ; and in this the prepared plates are immersed, 
 one by one, before they are treated with the tin ; and when the 
 pot is filled with them, they are suffered to remain in it so long as 
 the superintendant thinks necessary. If they remain in the grease 
 an hour, they are found to tin better than when a shorter time is 
 allowed them. 
 
 From this pot they are removed, with the grease still adhering 
 to them, into the pot just before spoken of, which contains the 
 body of melted tin ; and in this they are placed in a vertical po- 
 sition. Three hundred and thirty-eight or three hundred and 
 forty plates are usually put into this pot at once l j and for the sake 
 of their being thoroughly tinned, they usually remain in it one 
 hour and a half; but occasionally more time is required to com- 
 plete this operation. 
 
 When the plates have lain a sufficient time immersed in the 
 melted tin, they are taken out and placed upon an iron grating, 
 that the superfluous metal may drain from them ; but, notwith- 
 standing this precaution, when they become cold there is always 
 more metal found adhering to them than is necessary ; and this 
 is taken off by a subsequent process called washing. As this pro- 
 cess is rather complicated, it will be necessary to describe it with 
 some minuteness. 
 
 In the first place, the wash-man prepares an iron pot which he 
 nearly fills with the best grain-tin in a melted state another pot 
 of clean melted tallow, or lard free from salt a third pot with 
 nothing within it but a grating to receive the plates and a fourth, 
 called the listing-pot, with a little melted tin in it, about enough to 
 cover the bottom to the depth of a quarter of an inch. The whole 
 will however be better understood by referring to the following 
 drawing, which exhibits the several vessels in the order in which 
 they stand in the manufactory, all supported by substantial brick- 
 work. 
 
 1 It is immaterial how many plates are put into the tin-pot at once but this 
 number is usually fixed upon, because it amounts to about one box and a half 
 of plates : though, as they are put in edgewise, it is necessary the pot should 
 be nearly filled, to prevent their falling down in which case they could not 
 be got out, through so heavy a body of metal, without much difficulty. 
 
ON THE MANUFACTURE OF TIN-PLATE. 
 
 515 
 
 The building in which the pots are fixed is called the Stow. 
 The plates are worked from the right to the left of the stow, as 
 will be evident by attending to the uses of the separate pots. 
 
 No. 1. represents the tin-pot. 
 
 2. The wash-pot with the parting within it. 
 
 3. The grease-pot. 
 
 4. The pan, containing a grating at the bottom, for the 
 
 reception of the plates as the boy takes them out of 
 the grease-pot. It has no fire underneath it. 
 
 5. The list-pot. 
 
 The drawing represents the surface of the pots. The asterisks 
 show the places where the workmen stand, and also mark those 
 pots which have heated flues under them. No. 4 has no fire 
 under it. 
 
 The parting in the wash-pot No. 2 is a late improvement. The 
 design of it is to keep the dross of the tin from lodging in that 
 part of the vessel where the last dip is given to the plates. By 
 using the common tin in the first process of tinning, much oxide, 
 or dross, adheres to the surface of the plates, and this runs off in 
 the wash-pot, and comes to the face of the new metal ; but this 
 parting enables the operator to prevent it from spreading over 
 the whole surface of the pot. Were it not for this parting, the 
 wash-man must skim the oxide off the fluid metal every time he 
 puts plates into it. 
 
 The pots of which I have given a sketch being all in a state of 
 fitness, the wash-man commences his part of what remains of the 
 business, by putting the plates which have undergone the various 
 operations hitherto described into the vessel of grain-tin, called 
 the wash-pot 2 . The heat of this large body of melted metal soon 
 
 2 None but grain-tin is ever put into this vessel ; for the whole of the com- 
 mon tin which is consumed in such manufactories, is used in thejirst process, 
 viz. that which is called tinning. 
 
 2 L.2 
 
516 ON THE MANUFACTURE OF TIN-PLATE. 
 
 melts all the loose tin on the surface of these plates, and so dete- 
 riorates the quality of the whole mass, that it is usual, when sixty 
 or seventy boxes have been washed in the grain-tin, to take out 
 the quantity of a block, say three hundred weight, and replenish 
 the wash-pot with a fresh block of pure grain-tin. These vessels 
 generally hold three blocks each or about half a ton weight of 
 metal. That which is taken out of the wash-pot when it is re- 
 plenished with pure metal, is given to the tin-man to put into his 
 pot. 
 
 When the plates are taken out of the wash-pot, they are care 
 fully brushed on each side with a brush of hemp of a peculiar 
 kind, and made expressly for the purpose. As this part of the 
 business requires considerable adroitness and expedition, it may 
 be worth while to explain it a little more in detail. 
 
 The wash-man first takes a few plates out of the wash-pot, and 
 lays them together before him on the stow; he then takes one 
 plate up with a pair of tongs, which he holds in his left hand, and 
 with a brush held in his right hand brushes one side of the plate ; 
 he then turns it, and brushes the other side, and immediately 
 dips it once more into the hot fluid metal in the wash-pot, and 
 without letting it out of the tongs instantly withdraws it again, 
 and plunges it into the grease-pot (marked No. 3) adjoining to 
 the wash-pot from whence he had just taken it. 
 
 A person who has not seen the operation, can form but a very 
 inadequate idea of the adroitness with which this is performed : 
 practice, however, gives the workman so much expedition, that he 
 is enabled to make good wages, although he obtains only three- 
 pence for the brushing and metallic-washing of 225 plates. I am 
 informed that an expert wash-man, if he makes the best of his 
 time, will wash 25 boxes, consisting of 5625 plates, in twelve 
 hours; notwithstanding every plate must be brushed on both 
 sides, and dipped twice into the pot of melted tin. 
 
 Why the plates should be dipped twice during this part of their 
 manufacture, may perhaps require some explanation. It must be 
 recollected that they are brushed quite hot, and before the tin is 
 set ; therefore, if they had not the last dip, the marks of the brush 
 would be visible. Moreover, the brush takes the greatest part 
 of the tin off them, so that if they were removed to the grease-pot 
 without being re-dipped, the hot grease would take off what re- 
 mained. 
 
 The only use of the grease-pot is to take off any superfluous 
 metal that may be upon the plates : but this is an operation that 
 requires great attention, because, as the plate is immersed in the 
 grease while the tin is in a melting, or at least in a soft, state 
 upon it, a part must run off, and the remainder become less and 
 less while the plate continues in it: therefore, if these plates 
 
ON THE MANUFACTURE OF TIN-PLATE* 517 
 
 should ever be left in the melted tallow longer than is absolutely 
 necessary, they will doubtless require to be dipped a third time in 
 the tin. On the other hand, if the plates were to be finished 
 without passing through the grease, they would retain too much 
 of the tin, which would be a loss to the manufacturer ; and besides, 
 the whole of the tin would appear to be in waves upon the iron. 
 
 It is also equally necessary to attend to the temperature of the 
 melted tallow, which must be colder or hotter in proportion as 
 the plates are thicker or thinner ; for if, when the tallow is of a 
 proper temperature for a thin plate, a thick one was to be put into 
 it, it would come out, not of the colour of tin as it ought to be, 
 but as yellow as gold. The reason of this is evident. The thick 
 plate contains more heat than a thin one, and consequently re- 
 quires the tallow to be at a lower temperature. On the contrary, 
 if a parcel ofthm plates were to be worked in a pot of tallow which 
 had been prepared for thick plates, such a pot would not be hot 
 enough to effect the intended purpose. 
 
 It is a common observation that in most of our manufactures, 
 and in all chemical speculations, theory and practice are generally 
 at variance : but there are few manufactures, perhaps, where there 
 are so many minutiae which would escape the notice of a casual 
 observer, and yet that require to be carefully attended to, in order 
 to produce a good result, as in that which we have now been de- 
 scribing ; and should the perusal of this paper occasion but one 
 individual to pause, who was about to enter into a new concern 
 with which he was only partially acquainted, I shall have written 
 to a good purpose. 
 
 But to return to the process. When the plates are sufficiently 
 brushed, they are again immersed one by one in the pot of melted 
 tin, as has already been remarked, and immediately from this 
 they are put into the pot of tallow above mentioned. This pot has 
 pins fixed within it, in such a manner as to prevent the plates from 
 touching each other ; and this part of the process is conducted in 
 the following manner: 
 
 When the wash-man has passed^yft^ of the plates through the 
 melted tin, and from thence into the pot of tallow above men- 
 tioned, a boy takes out one of them and puts it into the empty pot 
 to cool, and the wash-man puts in the sixth plate. The boy then 
 takes out a second plate, and lays it to cool likewise ; when the 
 man puts in his seventh, and so they go on, in this regular man- 
 ner, until the whole of the parcel is finished. 
 
 In consequence of the plates being immersed in the melted tin 
 in a vertical position, there is always, when they have become cold, 
 a wire of tin on the lower edge of every plate which is necessary 
 to be removed, and this is done by a boy, called the list-boy, who 
 takes the plates when they are cool enough to handle, and puts the 
 
518 
 
 ON THE MANUFACTURE OF TIN-PLATE. 
 
 lower edge of each, one by one, into the list-pot, which is the 
 vessel that was before described, as containing a very small quan- 
 tity of melted tin, and the same as that which I have marked 
 No. 5. When the wire of tin is melted by this last immersion, the 
 boy takes out the plate, and gives it a smart blow with a thin 
 stick, which disengages the wire of superfluous metal, and this 
 falling off, leaves only a faint stripe in the place where it was at- 
 tached. This mark may be discovered on every tin-plate which 
 is exposed for sale ; the workmen, in the manufacture of them, 
 call it the list. 
 
 Nothing now remains but to cleanse the plates from the tallow. 
 This is done by means of bran, and as they are cleansed they are 
 put into strong wooden boxes, or boxes of sheet-iron, made ex- 
 actly to fit them ; and this completes the whole business. Each 
 box contains a determinate number of plates ; and the following 
 table will show the different sizes of tin plate which are made in 
 Great Britain, the marks by which each kind is known in com- 
 merce, and the current wholesale prices of each size. 
 
 Names. 
 
 Sizes. 
 
 No. in 
 a Box 
 
 Weight of 
 each Box. 
 
 Marks put 
 on the Boxes 
 
 Prices 
 per Box 
 in Sept. 
 1817. 
 
 Prices 
 per Box 
 in!830. 
 
 
 [nch 
 
 
 
 
 
 
 S. 
 
 6. 
 
 Common . . . No. 1. 
 
 13| by 10 
 
 225 
 
 1 
 
 
 
 
 
 CI 
 
 41 
 
 40 
 
 Do 2. 
 
 131 by 9* 
 
 
 
 3 
 
 21 
 
 CII 
 
 39 
 
 38 
 
 Do. . .3 
 
 *J 4 LIJ */, 
 
 12f by 9 
 
 
 
 3 
 
 16 
 
 cm 
 
 37 
 
 36 
 
 Cross . . . . No. 1. 
 
 ISfbylU 
 
 
 1 
 
 1 
 
 
 
 XI * 
 
 **f 
 
 49 
 
 46 
 
 Two Cross . . . 1. 
 
 
 
 1 
 
 1 
 
 21 
 
 XXI 
 
 55 
 
 52 
 
 Three Cross . . . 1. 
 
 
 
 1 
 
 g 
 
 14 
 
 XXXI 
 
 61 
 
 56 
 
 Four Cross . . . 1. 
 
 
 
 1 
 
 3 
 
 7 
 
 XXXXI 
 
 67 
 
 64 
 
 Common Doubles . 
 
 16fbyl2 
 
 100 
 
 
 3 
 
 21 
 
 CD 
 
 37 
 
 36 
 
 Cross Doubles . . 
 
 
 
 1 
 
 
 
 14 
 
 XD 
 
 45 
 
 42 
 
 Two Cross do. . . 
 
 
 
 1 
 
 ] 
 
 7 
 
 XXD 
 
 51 
 
 48 
 
 Three Cross do. . 
 
 
 
 1 
 
 2 
 
 
 
 XXXD 
 
 57 
 
 54 
 
 Four Cross do. . . 
 
 
 
 1 
 
 2 
 
 21 
 
 XXXXD 
 
 63 
 
 60 
 
 Com. small Doubles 
 
 15 by 11 
 
 200 
 
 1 
 
 2 
 
 
 
 CSD 
 
 63 
 
 62 
 
 Cross do. . do. . 
 
 
 
 1 
 
 2 
 
 21 
 
 XSD 
 
 69 
 
 68 
 
 Two Cross do. . 
 
 
 
 1 
 
 3 
 
 14 
 
 XXSD 
 
 75 
 
 74 
 
 Three do. . do. . 
 
 
 
 2 
 
 
 
 7 
 
 XXXSD 
 
 81 
 
 80 
 
 Four do. . do. . 
 
 
 
 2 
 
 1 
 
 
 
 XXXXSD 
 
 87 
 
 86 
 
 Wasters Com . No. 1 
 
 13f by 10 
 
 225 
 
 1 
 
 
 
 
 
 WCI 
 
 35 
 
 34 
 
 Do. Cross . . 1 
 
 ISfbylO 
 
 
 1 
 
 1 
 
 
 
 WXI 
 
 43 
 
 40 
 
 Having given so detailed an account of the manufacture of 
 tin-plate, it may be expected that I should say a few words on 
 the origin of the art. 
 
 Formerly none of the English workers in iron or tin had any 
 knowledge whatever of the methods by which this useful article 
 could be produced ; our ancestors, from time immemorial, hav- 
 
ON THE MANUFACTURE OF TIN-PLATE. 519 
 
 ing supplied themselves with it from Bohemia and Saxony. The 
 establishment of this manufacture in those districts, was doubtless 
 owing to their vicinity to the tin mines in the circle of Ersgebirg, 
 which, next to those of Cornwall, are the largest in Europe. The 
 ore which is found there is not the tin-pyrites, but the mineral 
 called tin-stone; and it is curious that it should occur in abun- 
 dance, both on the Bohemian and Saxon sides of the mountain 
 group : accordingly, manufactories of tinned iron have been es- 
 tablished in both those kingdoms. Alluvial deposits of grain-tin 
 are also found in the same vicinity. 
 
 From the time of the invention of tin-plate to the end of the 
 seventeenth century, not only England but also the whole of Eu- 
 rope depended upon the manufactures of Bohemia and Saxony 
 for their supply. However, about the year 1665 Mr. Andrew 
 Yarranton, encouraged by some persons of property, undertook 
 to go over to Saxony to acquire a knowledge of the art ; and on 
 his return, several parcels of tin-plate were made of a superior 
 quality to those which we had been accustomed to import from 
 Saxony ; but owing to some unfortunate and unforeseen circum- 
 stances, which are all detailed by Mr. Yarranton in his very va- 
 luable publication 1 9 the manufactory was not at that time esta- 
 blished in any part of Great Britain. 
 
 As it is now difficult to procure a copy of the work from which 
 I have obtained a knowledge of the manner in which this manu- 
 factory was brought into England, an abridgement of the author's 
 own account of the transaction will probably be interesting to the 
 public. 
 
 " Knowing," says Mr. Yarranton, "the usefulness of tin-plates, 
 and the goodness of our metals for that purpose, I did (about 
 sixteen years since 2 ) endeavour to find out the way for making 
 thereof; whereupon, I acquainted a person of much riches, and 
 one that was very understanding in the iron manufacture ; who 
 was pleased to say, that he had often designed to get the trade 
 into England, but never could find out the way. Upon which 
 it w r as agreed, that a sum of monies should be advanced, by se- 
 veral persons, for the defraying my charge of travelling to the 
 place where these plates were made ; and from thence to bring 
 away the art of making them. Upon which, an able fire-man, 
 that well understood the whole nature of iron, was made choice 
 of to accompany me; and being fitted with an ingenious inter- 
 
 1 England's Improvement by Sea and Land,vfhh many plates of Plans, Charts, 
 &c. in two parts, by Andrew Yarranton, Gent. Part I. Quarto. London, 1677. 
 Part II. London, 1681. 
 
 * This account is dated February 2nd, 1681; I therefore conclude that Mr. 
 Yarranton' s journey to Saxony must have been about the year 1665. 
 
520 ON THE MANUFACTURE OF TIN-PLATE. 
 
 preter, that well understood the language, and that had dealt much 
 in that commodity, we marched first for Hamburg, then to Lips- 
 tick; and from thence to Draisden, the duke of Saxonies Court, 
 where we had notice of the place where the plates were made; 
 which was in a large tract of mountainous land, running from a 
 place called Seger-Hutton, unto a town called Awe, being in length 
 about twenty miles ; the tin-works being there fixed upon a great 
 river running clear along the valley, and also upon some little 
 rivulets that run out of the mountains of Bohemia and Saxony; 
 and coming to the works, we were very civilly treated, and, con- 
 trary to our expectation, we had much liberty to view, and see 
 the works go with the way and manner of their working and 
 extending the plates, as also the perfect view of such materials as 
 they used in clearing the plates, to make them fit to take tin, with 
 the way they use in tinning them over, when cleared from their 
 rust and blackness. And having (as we judged) sufficiently ob- 
 tained the whole art of making and tinning the plates, we then 
 came for England, where the several persons concerned in the 
 affair thought fit to make some trial in making some small quan- 
 tities of plates and tinning them, which was done ; and all work- 
 men that wrought upon them agreeing that the plates were much 
 better than those which were made in Germany ; upon which, 
 preparation was making to set this beneficial thing at work ; 
 but, it being understood at London, A PATENT was trumpt up, and 
 the patentee was countenanced by some persons of quality and 
 what with the patent being in our way, and the richest of our 
 partners being afraid to offend great men in power, who had their 
 eye upon us, it caused the thing to cool, and the making thereof 
 was neither proceeded in by us, nor possibly could be by him that 
 had the patent ; because neither he that hath the patent, nor those 
 that have countenanced him, can make one plate fit for use I ." 
 
 This enterprising individual, who spent the greater part of his 
 life in promoting schemes for the good of his country, and who, 
 in the opinion of Bishop Watson, ought to have had a statue 
 erected to his memory, proceeds to inform us, that before they 
 were stopped by the patent they had made " many thousand plates 
 from iron raised in the forest of Dean, and tinned them over with 
 Cornish tin, and the plates proved far better than the German 
 plates, by reason of the toughness and flexibleness of our forest 
 iron. One Mr. Dison," says he, " a tinman in Worcester, one Mr. 
 Lydiate near Fleet-bridge, and one Mr. Harrison near the Kings- 
 bench, have wrought many, and they know their goodness 2 ." 
 
 In another place this interesting writer informs us, that " when 
 he was in Saxony the different establishments for making tin-plates 
 
 1 England's Improvement, $c. p. 149152, Part II. 2 Page 173. 
 
ON THE MANUFACTURE OF TIN-PLATE. 521 
 
 were very numerous, and that most of them belonged to the 
 duke 3 ." "The trade," says he, "is so great, that by compu- 
 tation, no less than 80,000 men depend upon it ; and when the 
 plates are finished, they are sent by land to Lipsick, from thence 
 to the Elbe river, and so down to Hamburg, and from thence sent 
 by sea as far as trade is known 4 ." " There was," says he, " no 
 tin any where in Europe, except in Cornwall, until a Cornish 
 man found tin in the mountains of Saxony, near a town called 
 Awe, where his statue is yet to be seen. The tin works are fixed 
 upon a great river running down the valley ; and the tin, iron and 
 woods, grow in and upon the mountains adjoining to both sides 
 the river ; and those tin-works have proved so beneficial to the 
 place, that there are several fine cities raised by the riches pro- 
 ceeding therefrom V He adds, " The trade of making tin-plates 
 was about sixty years since fixt in Bohemia, and had there long 
 continued ; but the woods decaying, and there being at that time 
 a wise duke of Saxony, willing and ready to improve his own 
 revenue, and his subjects, did accept of directions how this trade 
 might be brought away and fixt in the duke of Saxony's terri- 
 tories 6 . A Romish priest, converted to be a Lutheran, was the 
 chief instrument in the whole affair, until it was perfected and a 
 Cornish miner, a Protestant who had been banished out of En- 
 gland for his religion, found out the tin in Saxony both which 
 persons proved instruments of great wealth to that duke and 
 country V 
 
 The following particulars which I have collected respecting 
 Mr. Yarranton, will justify Bishop Watson in the opinion he has 
 given of him. 
 
 He was bound as an apprentice, early in life, to a linen dra- 
 per, but after some years he left that situation in disgust. In the 
 year 1652 he took some iron works, which he carried on for se- 
 veral years ; and during this period he made regular surveys of 
 the three great rivers in England, and by means of associations 
 which were formed by himself, he rendered three other rivers 
 navigable : he studied agriculture with such effect, that many of 
 the arable estates in the midland counties were rendered doubly 
 productive by the new methods of husbandry which he either 
 brought from abroad, or discovered ; he laid a plan for the junc- 
 tion of the Thames and Severn at that spot where of late years 
 this very scheme has been effected ; he proposed the cutting of 
 several navigable canals, half a century before any such project 
 had been executed in this country. He made the necessary sur- 
 
 3 Ibid. 1 55. 4 Page 172. 5 Yarranton, part II. p. 176. 6 Ibid. p. 178. 
 7 Saxony is separated from Bohemia by a chain of mountains called the 
 Erzegclerg; which in German signifies, hills that contain mines. 
 
522 ON THE MANUFACTURE OF TIN-PLATE. 
 
 veys and planned docks for the cities of London and Dublin : 
 besides his journey to Saxony already mentioned, he went to Hol- 
 land, under the patronage of the ancestors of some of our present 
 nobility, to examine the inland navigations of the Dutch, and to 
 investigate the nature of their linen manufactures ; and on his 
 return promulgated the plan for a new manufacture of linens, 
 which he calculated would employ all the poor of England. He 
 published schemes for the improvement of our national fisheries; 
 he made several tours through Ireland, for the express purpose 
 of planting new manufactures and devising the increase of the 
 staple trades of that country : he made a regular survey and esti- 
 mate of the expense of rendering the river Slade in Ireland navi- 
 gable for the purpose of bringing timber down to the coast for 
 His Majesty's navy ; and rendered many other signal services to 
 his country. 
 
 Notwithstanding Mr. Yarranton had so completely introduced 
 the knowledge of making tin-plate into this country, I do not find 
 that any manufacture of that article was established in these king- 
 doms until some time between the years 1720 and 1730, which 
 must have been long after Mr. Yarranton's death. The first 
 establishment of this kind, was fixed at the town of Pontypool, 
 in Monmouthshire, where it continued to flourish many years ; 
 and it is remarkable, that after the lapse of nearly a century, the 
 manufacture has recently been re-established at the same town 
 on a very extensive scale. 
 
 About the time that this manufactory was established, the ami- 
 able and intelligent M. Reaumur, to whom the French are in- 
 debted for a new mode of graduating the thermometer, for in- 
 troducing the methods of making porcelain into France, and for 
 many discoveries and improvements in the arts, undertook to 
 discover the method of making tin-plates for the French people. 
 This eminent man, whose mind was cast in a mould very similar 
 to that of Mr. Yarranton, but who possessed more science, never 
 relinquished any thing which he undertook ; and accordingly, 
 notwithstanding the innumerable difficulties which he had to en- 
 counter, at length succeeded in acquiring such a knowledge of 
 the principles of the manufacture, as enabled him to instruct se- 
 veral people in the vicinity of Paris, in an art which, until then, 
 had never been practised in that country. 
 
 Soon after the time of which I am speaking, several similar 
 manufactories were erected in Great Britain ; and now the esta- 
 blishments of this nature are so numerous and extensive in many 
 parts of these kingdoms, that the manufacture of tin-plate is be- 
 come of great national importance, and more than one hundred 
 thousand boxes of these plates are annually exported. 
 

JPARKES'S 
 
 AAa.ni rarkiuson's Machine 
 for Prin till g tlvtee Coltnu-s at 
 once on Calicoes . 
 
ON CALICO-PRINTING. 523 
 
 ESSAY XVII. 
 
 ON CALICO-PRINTING. 
 
 CALICO-PRINTING is an art of very considerable importance to 
 this country ; it has proved the source of immense wealth to many 
 individuals, and for several years past has brought a great reve- 
 nue to the state. Notwithstanding its value and national con- 
 sequence, the majority even of well-informed people know little 
 or nothing of the processes by which this peculiar manufacture is 
 conducted. 
 
 This ignorance will appear the more remarkable, when it is 
 considered that linens were fabricated, and the arts of dyeing and 
 staining garments, something like the present calico-printing, 
 were known and practised in the earliest ages of which history 
 gives us any detail. 
 
 Hence it may very fairly be presumed that a faithful account of 
 the nature of this business would be very acceptable to the public, 
 and that, in the course of the narration, if any improvements on 
 the present practice should be suggested, it is possible that such 
 an account may not, even to the calico-printer himself, be totally 
 uninteresting and useless. We shall begin with an attempt to 
 trace the history of the art, and of its progress towards that per- 
 fection to which it has now attained. 
 
 In the time of Moses the land was employed for the growth of 
 flax as well as of corn ; and that this flax was used for the fabrica- 
 tion of cloth, may be collected from a variety of circumstances, 
 especially from an examination of some Egyptian mummies, the 
 most ancient of which (at least such as have been brought to 
 Europe) are bound round with folds of linen similar to the flaxen 
 cloth of the present day. 
 
 There is a paper of Dr. Hadley, in the fifty-fourth volume of 
 the Philosophical Transactions, giving an account of the exami- 
 nation of an Egyptian mummy, in the presence of several of the 
 Fellows of the Royal Society. After describing its general ap- 
 pearance, he says, " The outward painted covering being re- 
 moved, nothing but linen fillets were to be seen, which inclosed 
 the whole mummy. The uppermost fillets were of a degree of 
 fineness nearly equal to what is now sold in the shops under the 
 name of long lawn, and were woven something after the manner 
 of Russian sheeting." This mummy was taken from a catacomb 
 
524; ON CALICO-PRINTING. 
 
 near Cairo ; and when the age of these catacombs is considered, 
 it gives great antiquity to the art of weaving fine linen. 
 
 We have evidence, however, that the invention of weaving is 
 still more ancient than even the times when the embalming of the 
 Egyptian mummies was in vogue. This is evident from the 
 answer which Abram gave to the King of Sodom : " I will not," 
 said he, " take from a thread of the woof, even to a shoe-latchet, 
 lest thou shouldest say, I have made Abram rich." Genesis 
 xiv. 23. 
 
 Moses informs us that Abimelech made a present of a veil to 
 Sarah. He observes also, that Rebecca covered herself with a 
 veil, when she perceived Isaac ; and that Pharaoh arrayed Joseph 
 in a vesture of fine linen or cotton, when he made him viceroy of 
 Egypt. A weaver's shuttle is also ' mentioned in the Book of 
 Job, chap. vii. 6. These facts incontrovertibly prove the great 
 antiquity of the art of weaving with warp and woof. 
 
 In these very ancient times this work was performed in a stand- 
 ing posture 1 , which was owing to the construction of their looms, 
 in which the warp was extended perpendicularly from top to bot- 
 tom, and kept firm by means of a piece of wood, to which they 
 hung very heavy weights 2 . 
 
 " Inventress of the woof, fair Lina flings 
 The flying shuttle through the dancing strings, 
 Inlays the broider'd weft with flowery dyes, 
 Quick beat the reeds, the pedals fall and rise ; 
 Slow from the beam the lengths of warp unwind, 
 And dance and nod the massy weights behind." 
 
 Five hundred years after the death of Moses, and nearly a 
 thousand years before Christ, it is related that Solomon imported 
 linen yarn from Egypt : and after this period the city of Tyre is 
 represented as abounding in fine linen ; for, when Ezekiel is de- 
 scribing the grandeur of that city, and the opulence of her mer- 
 chants, he says : " They have made all thy ship-boards of fir 
 trees ofSenir; they have taken cedars from Lebanon to make 
 masts for thee ; FINE LINEN with broidered work from Egypt, 
 was that which thou spreadest forth to be thy sail." Ezekiel 
 xxvii. 7. 
 
 From the manner in which this is introduced, it is evident that 
 the writer considered fine linen to be an article of great rarity. 
 In his days matting was commonly used for sails ; hence sails of 
 linen must have been thought extremely magnificent. " The 
 sails of the ancient Phoenicians were made of different substances, 
 
 1 Junius de Pictura Veter. lib. i. cap. 4. p. 26. 
 
 2 Goguet's Origin of Laws, &c. vol. i. p. 126. 
 
ON CALICO-PRINTING. 525 
 
 such as hemp, rushes, long-leaved plants, mats, and skins. Yet 
 those of the Greeks at the same period were most commonly of 
 cloth 3 ." Sails of matting are still used on the vessels navigated 
 by the Arabs on the Red Sea. We are entitled however, from 
 this body of concurrent testimony, to conclude, that linen cloth 
 has been in use, though perhaps not very commonly, from the 
 time of Moses to the present day. 
 
 On the other hand we have the positive evidence of Pliny, that 
 in his time there were many ancient families at Rome, who 
 boasted of never having admitted linen cloth into their houses, 
 considering the use of it as a mark of great and criminal 
 effeminacy 4 . 
 
 Pliny says also, that " Lentulus Spinter was the first man who 
 in the games drew fine curtains over the great amphitheatre of 
 Rome ; and that not long after this, Caesar Dictator caused the 
 high fair street called Sacra to be hung on both sides, from his 
 own dwelling-house to the very Capitol ; which magnificent and 
 sumptuous sight was much wondered at, and seen with great ad- 
 miration." He adds, that " Alexander the Great was the first 
 person who had sails or linen flags that were dyed with colours, 
 that he borrowed it from the Indians, and that afterwards a red 
 purple banner erected on the top of the mast was the badge of 
 the royal admiral's ship." Holland's Pliny, vol. ii. p. 5. 
 
 Equally decisive is the testimony of history respecting the an- 
 tiquity of coloured linens, which appear to have been known 
 almost in the very earliest ages. 
 
 More than three thousand years ago, a shrewd matron tied a 
 scarlet thread round the hand of one of Tamar's children s ; and 
 Homer, who flourished nine hundred years before Christ, speaks 
 of the variegated cloths of Sidon as very magnificent productions 6 . 
 
 The books of the Pentateuch frequently mention the ornaments 
 for the Tabernacle, as composed of blue and purple and scarlet 
 and fine linen ; and it has been remarked by Mr. Delaval, that in 
 those ancient writings these colours are constantly arranged 
 exactly in the same order 7 , and that this order is the true prismatic 
 series of those colours. 
 
 This is certainly a very striking fact ; and it is also not a little 
 curious, that after a lapse of several centuries which intervened 
 between the period described in Exodus and the time of Solomon, 
 
 3 Goguet's Origin of Laws, &c. vol. ii. p. 326. 
 
 4 Plin. Hist. Nat. lib. ix. c. 1. 
 
 5 Genesis xxxviii. 27- 6 Iliad, lib. vi. line 289. 
 
 7 See Exodus xxv. 4. xxvi. 1. 31. 36. xxvii. 16. xxviii. 6. 8. 15. xxxv. 6. 
 23. 25. 35. xxxvi. 8. 35. 37. xxxviii. 23. xxxix. 129, and several other 
 places. 
 
526 ON CALICO-PRINTING. 
 
 the colours employed in the Temple ornaments should be still 
 mentioned in the same order as those of the Tabernacle had been 
 formerly noticed ; which is exactly the case, excepting in one sin- 
 gle instance, where the red is called crimson instead of scarlet ! . 
 
 May not this very interesting fact be considered as an internal 
 proof of the antiquity of the sacred writings ? We know how 
 much mankind have at all times been addicted to the practice of 
 imitating Nature ; and next to the great luminary of our system, 
 the rainbow was surely the grandest object which the writers of 
 these early books had ever Beheld. 
 
 I must not, however, forget that I shall be expected to give 
 some account of the progress of the art of staining, painting, or 
 printing linen and calico. 
 
 Herodotus, who wrote more than four hundred years before 
 the commencement of the Christian aera, when describing the 
 nations which inhabited Caucasus, a mountain extending through- 
 out the region of Georgia and Armenia, affirms that by means of 
 vegetables ground and diluted with water, these people adorned 
 their cloth with the figures of various animals, and that the dyes 
 were permanent which were thus obtained. 
 
 Valerius Flaccus, an historian who wrote in the age imme- 
 diately succeeding that of Christ, distinguishes a warrior slain at 
 Colchis, during the Argonautic expedition, by a painted garment, 
 and at the same time specifies that his dress was of fine white 
 linen. Lib. vi. 221 et seq. 
 
 That dyeing materials were, in ancient times, plentifully pro- 
 duced at Colchis and Tournefort, is well known ; and according 
 to Mr. Delaval, great quantities of these materials are]still used in 
 the very same species of dyeing. Besides, more than two thou- 
 sand camel loads of madder are annually sent from Georgia to 
 Diurbeck and India, where the finest calicoes are still printed or 
 painted with it 2 . 
 
 Strabo, the Greek philosopher, who was contemporary with 
 our Saviour, relates that the Indians wore flowered linens 3 , and 
 that India abounded with drugs, roots, and colouring substances, 
 from which some very beautiful dyes were produced*; and we 
 know that the inhabitants of India used a purple and scarlet dye 
 resembling cochineal in colour and in the manner of its produc- 
 tion. 
 
 Moreover, the statues of Isis, which formerly were so abun- 
 dant in Egypt, were generally adorned with parti-coloured cloths, 
 which, as has been remarked, must have been of linen, or of 
 cotton 5 , because woollen was so much abhorred by the Egyp- 
 
 1 2 Chronicle* iii. 14. 2 Delaval, p. 21. s Strabo, lib. xv. p. 709. 
 
 4 Strabo, lib. xv. p. 694699, de India. 5 Delaval, p. 34. 
 
ON CALICO-PRINTING. 52? 
 
 tians that the lowest of the people would neither use it 6 nor allow 
 it to be employed even in their interments. Such indeed was 
 their aversion, that it extended to the flocks, and to the very 
 shepherds themselves who attended them. " Every shepherd," 
 says the writer of the Pentateuch, " is an abomination unto the 
 Egyptians". Genesis xlvi. 34. 
 
 The methods which the Egyptians adopted to produce these 
 parti-coloured linens is very particularly described by the Elder 
 Pliny, who perished by an eruption of Vesuvius in the year 79 of the 
 Christian agra. " The Egyptians," says he, " began by painting, 
 or drawing, on white cloths with certain drugs, which in them- 
 selves possessed no colour, but had the property of attracting or 
 absorbing colouring matters. After which, these cloths were im- 
 mersed in a heated dyeing liquor ; and though they were colour- 
 less before, and though this dyeing liquor was of one equable and 
 uniform colour, yet when taken out of it soon afterwards they 
 were found to be wonderfully tinged of different colours, accord- 
 ing to the peculiar natures of the several drugs which had been 
 applied to their respective parts ; and that these colours could not 
 be afterwards discharged by washing. Plin. lib. xxxv. cap. 11. 
 42. 
 
 The agreement which there is between this account of the 
 management of the ancients and the present practice, cannot fail 
 to strike any one who is at all conversant with the processes now in 
 use. And from this relation, and other testimony still on record, 
 there can be no doubt but that these people employed both iron 
 and alum as mordants, though these mordants might not be pre- 
 pared exactly in the same way, or in so effective a manner, as they 
 are by the moderns. 
 
 Native soda, which abounded in Egypt, was also known to the 
 ancients ; and we have the direct assurance of Pliny that the dyers 
 of antiquity were in the habit of using it in their processes. 
 Lib. xxxi. cap. 10. 
 
 But amongst the countries of the East which practised dyeing, 
 the Phoenicians were the most celebrated, and particularly for 
 their purple colour. So great was the demand for this article, 
 that the city of Tyre grew to a vast extent, from the number of 
 workmen employed in its manufacture; and it was from a sense of 
 the great national utility of their purple dye, that the Phoenicians 
 attributed its invention, which was the principal foundation of 
 their trade and wealth, to the gods. Strabo, lib. xvi. 757. 
 
 Besides the purple which was thus prepared at Tyre and other 
 
 6 " And it shall come to pass, that when they enter in at the gates of the 
 inner court, they shall be clothed with linen garments, and no wool shall come 
 upon thm." Eneltiel xliv. 17. 
 
528 ON CALICO-PRINTING. 
 
 parts of Syria, the ancient inhabitants of India were also in the 
 habit of using a purple and scarlet dye, which they procured from 
 the cochineal insect, or from some other insect resembling it. 
 For Ctesias, who flourished about four hundred years before 
 Christ, and was a great favourite at the court of Persia, and 
 JElian the philosopher, who taught rhetoric at Rome in the 
 reign of Alexander Severus, both give an account of the insects 
 which yielded it, and of the plants on which they fed. We also 
 learn that so large a quantity of this colouring matter was pro- 
 duced in India, as to become an article of export in those early 
 times. It is probable, therefore, that it was by means of this 
 insect, whatever it might be, that these Asiatics were supplied 
 with that abundance of purple, which enabled even the lowest 
 ranks among them to wear clothes of that colour 1 . 
 
 There can indeed be little doubt but that the true cochineal, 
 was known in Persia very early. The king of Persia, we are told, 
 sent to the emperor Aurelian, among other things of value, some 
 woollen cloth which was of a much brighter purple than any that 
 had ever been seen in the Roman empire, and in comparison of 
 which all the other purple cloth worn by the emperor and the 
 ladies of the court appeared dull and faded 2 . 
 
 From various accounts it appears, that formerly, in India, the 
 cotton cloths, when brought from the weavers, partly bleached, 
 were worn next to the skin, by the dyer and by all his family, 
 during the space of eight or ten days. These cottons could not 
 however have been of a length equal to the pieces of the present 
 day ; they were probably nothing but the mere shawls, which 
 have been common in India from time immemorial. Among the 
 magnificent dresses of the present Asiatics, there is nothing more 
 esteemed than shawls of various colours, and these are frequently 
 given to the great by way of presents. 
 
 When the cloth had been thus worn until it was thoroughly 
 soiled, the several pieces underwent repeated macerations in water, 
 with goats' dung, and were afterwards submitted to frequent wash- 
 ings and to as frequent dryings in the rays of an intense sunshine. 
 Afterwards, they were soaked for some time in the mixture of the 
 astringent fruit of the yellow myrobalans^ and of curdled buffalo's 
 milk. When thoroughly impregnated therewith, they were 
 squeezed, dried by exposure to the sun, and then, by pressure 
 and friction, they were made smooth enough for being drawn 
 upon by the pencil, with the different mordants. 
 
 The first of these mordants was an iron liquor, made by dis- 
 solving iron in a mixture of sour palm wine and rice-water, or 
 
 1 See Delaval's preface, p. 24. 
 
 2 Beckman, from Vopiscus in Vita Aureliani, cap. 29. 
 
ON CALICO-PRINTING. 529 
 
 water in which rice had been boiled for a considerable time. This 
 liquor was applied to the figures or spots intended to become 
 black, and afterwards the aluminous mordant was applied, com- 
 monly by children, with the pencil, to the parts intended to be 
 made red. The pieces were then exposed to the hottest sunshine, 
 that the parts to which the mordants had been applied might be 
 dried as much as possible; and then they were thoroughly 
 soaked in pits of water, to cleanse them from the superfluous 
 mordants, as well as from the buffalo's milk, &c. ; and lastly, they 
 were dyed in water, with certain roots answering nearly in their 
 effects to those of madder. 
 
 It was in this way the manufacture of printed cottons was 
 conducted by the Indians, in former times. The following is an 
 account of the modern practice, in one particular branch of their 
 manufacture, which I procured from a gentleman who has spent 
 some time in India, and which I now subjoin, rather for the 
 amusement than the instruction of the British calico-printer. 
 
 The finest cotton chintz counterpanes, says he, which the na- 
 tives call pallampoors, are manufactured at Madras. These are 
 woven in one piece from two to four yards square, and are printed, 
 or rather painted, with various designs, and in various colours. 
 Their method is to draw the pattern first on sheets of paper sewn 
 together, of the size of the intended pallampoor ; and then to prick 
 out the same in the paper with a sharp instrument. When this is 
 done, the paper pattern is smoothly fixed upon the cloth, which 
 is previously damped, and then a small muslin bag containing 
 some kind of black powder is rubbed over the whole, in order to 
 pass a part of the powder through the pin-holes, and completely 
 mark out the pattern. 
 
 The pattern being thus sketched upon the cloth, the paper is 
 removed ; and when the outline of the various figures is drawn 
 with a pencil, the piece is considered to be ready for receiving the 
 colours. 
 
 One colour is then laid on with a brush made with a tough 
 root of a particular kind of tree, or with the husk of the cocoa 
 nut; and when this is dry, the piece of cotton is given to a woman 
 to wear, or to use in the family, till it be very much dirtied ; in 
 order that it might necessarily undergo a thorough washing, 
 which is thought requisite to prove the goodness and permanency 
 of the colour. Another colour is then laid on in the same man- 
 ner, and the piece is again submitted to the same trial of wearing 
 and washing. The Asiatics may not be aware of it; but doubtless 
 the long exposure to the air in thesfe cases, is the important 
 point, as it is well known that the atmosphere is a prime agent in 
 rendering many colours permanent, which under a different treat- 
 
 2 M 
 
530 ON CALICO-PRINTING. 
 
 ment would be heavy and fugitive. This management is repeated 
 for every colour that is employed ; and when any one of these 
 colours is found to be deteriorated by this treatment, it is printed 
 afresh ; and so are all the rest, till the workman is satisfied that 
 all the colours are actually permanent. 
 
 This tedious process is adopted, however, only when the ma- 
 nufacturer means to warrant the article; but in all cases, even in 
 those pieces which will not bear washing, the colours are laid on 
 by a brush, as before mentioned. 
 
 Whether they are all substantive colours which are thus ap- 
 plied, or whether they use any species of mordant in their fast 
 work, I am unacquainted, as my friend had no information on this 
 subject. 
 
 Such are the facts which I have been able to collect respecting 
 the progress of calico-printing from the earliest ages ; and also of 
 the present state of the art among the Asiatics. The more diffi- 
 cult part now remains, viz. to give a brief detail of the most im- 
 portant processes of our own artists. This, however, I shall 
 endeavour to do with the utmost plainness, and shall not fail to 
 suggest any improvement that may have occurred to me during 
 my inquiries respecting this very interesting and varied branch of 
 manufacture. 
 
 I have not yet been able to ascertain when calico-printing was 
 introduced into this country, though there are various reasons 
 for believing that it is an art, among us at least, but of modern 
 date. 
 
 As the whole of this ingenious business, as it is now conducted, 
 depends upon the proper application of a few compounds called 
 mordants, it will be necessary, in the first place, to explain their 
 nature and uses. In doing this, one or two preliminary remarks 
 will assist us. 
 
 The colouring substances chiefly employed in this art, are divi- 
 ded into two classes, viz. substantive and adjective. A SUBSTAN- 
 TIVE colour is one which is capable of itself of producing a per- 
 manent dye ; such is the juice of the buccinum, used by the an- 
 cients for producing the imperial purple; such are also the woad 
 and indigo employed by the moderns for producing a permanent 
 blue; and we may add the metallic solutions, particularly those of 
 iron, cobalt, gold, platinum, and silver, which give various co- 
 lours, according to the processes by which they are prepared. 
 
 By ADJECTIVE colours are meant all those which are incapable 
 of giving permanent dyes without the aid of certain intermedia, 
 which form as it were a bond of union between them and the sub- 
 stances intended to be dyed. 
 
ON CALICO-PRINTING. 531 
 
 These intermedia are what are known by the term MORDANTS, 
 and they are used for this purpose in very considerable quantities 
 by the calico-printer of the present day. 
 
 Several expedients were employed by the ancients to produce 
 fast, or, more properly, permanent colours, by means of mor- 
 dants, as appears from the testimony of Aristotle and Pliny. The 
 chief articles in use at present in Great Britain, are the acetate of 
 iron, the acetate of alumina, and the various solutions of tin, all 
 of which should be very carefully and correctly prepared. 
 
 When piece-goods are designed to be dyed of one uniform 
 adjective colour, they are first immersed in a solution of one of 
 these mordants, and are then hung up to dry and to absorb the 
 oxygen of the atmosphere. When sufficiently exposed to the air, 
 they are washed or dunged 1 , to remove the superfluous mordant; 
 that is to say, that part of it which is not chemically combined 
 with the cloth ; and the pieces are then submitted to a bath of 
 that particular kind of colouring matter which is to be imparted 
 to them. 
 
 Whenever it is meant that a colour should be partially insert- 
 ed, the mordant is applied to those particular parts only ; so that, 
 when the piece is immersed in the colouring bath, no other place 
 will receive the permanent stain. For though the whole surface 
 of the cloth will be coloured, yet having in itself no affinity with 
 the vegetable with which the decoction is impregnated, the whole 
 of the colouring matter will be easily removed by exposure to the 
 air, and the ground of the piece restored to its original whiteness; 
 while those parts to which the mordant was applied, will retain 
 and fix the colours in a way which will be more fully explained 
 hereafter. 
 
 In my opinion every printer should bleach his own goods, for 
 it is impossible always to rely with confidence on the care of those 
 who bleach for hire; and good bleaching is absolutely a necessary 
 preliminary in the production of good printing. 
 
 No people have taken more pains to excell in bleaching than 
 the Irish, and their credit is established accordingly. The Ger- 
 man linen is, I believe, generally better than theirs ; but the Irish 
 has always the preference in foreign markets, owing to the su- 
 periority of the Irish in bleaching and finishing. Chloride of 
 lime is the agent generally employed in bleaching, a minute de- 
 
 1 The dung of the cow is used in such large quantities by the calico-printer, 
 that it has become an article of great expense. The proportion that is employed 
 is usually about one bushel to one hundred gallons of water, though frequently 
 a larger proportion would be more effectual. The brightness of the colours, 
 and the purity of the whites, are always dependent upon the quantity of the 
 dung employed. 
 
 2 M 2 
 
532 ON CALICO-PRINTING. 
 
 scription of which process will be found detailed in the Essay 
 on Bleaching. 
 
 By whatever means the bleaching is performed, the printer 
 commences his part of the business in the following manner. 
 
 The goods are first DRESSED by singeing off' the whole of the 
 nap which is attached to them. This is effected by the following 
 contrivance : Ten pieces are generally wired together, and wound 
 upon a roller, from whence they are passed over a hot iron, nearly 
 in the form of half a cylinder, and received upon another roller ; 
 from thence they are returned to the iron, which is still kept red 
 or nearly at a white heat 1 . The use of repeating this process is 
 to remove the nap more effectually than it would be done by pass- 
 ing it only once over 3 . 
 
 The next operation is that of STEEPING, which consists merely 
 in soaking the pieces for 24 hours in a vessel of weak alkaline 
 lye, at a temperature of about 100. These operations of singe- 
 ing and steeping are going on at one and the same time, which 
 effectually prevents any accident that might otherwise arise from 
 the effects of the hot iron. 
 
 The goods are then boiled or else bowked in a solution of pot- 
 ash ; (some workmen prefer to have this alkali in a pure caustic 
 state ;) they are then well cleansed, by thorough washing in wash- 
 wheels, or in stocks to ensure their being entirely divested of the 
 alkali. The intention of thus treating them with potash, is to re- 
 move any grease or impurity that may be attached to them, which 
 would otherwise endanger the evenness and uniformity of the 
 colours. This process is called ASHING. 
 
 By some calico-printers it has been imagined that the render- 
 ing the lye caustic is apt to impair the texture of the cloth ; and 
 I doubt not but that this has often been the case. Under the 
 eye of the master, however, I am sure it may be employed with 
 advantage and safety; with advantage, because mild alkali has 
 but a slight affinity for the grease ; whereas caustic alkali forms 
 a real soap with any oleaginous matter, and then the compound 
 is readily soluble in water ; and though the alkali be made per- 
 fectly caustic, if the solution be sufficiently diluted, it may be used 
 with perfect safety. A convenient mode of mixing the potash and 
 
 1 A beautiful apparatus has lately been introduced for singeing off the nap by 
 means of the flame from carburetted hydrogen gas, which bids fair to super- 
 sede the old system of hot iron cylinders. 
 
 When goods are padded or blocked for a full rich colour, and printed, they 
 may be dried in the dunged state and singed again to take off the superfluous 
 nap left by the first dressing; the mordant is not injured in the slightest de- 
 gree, and the goods are much improved, 
 
ON CALICO-P1UNTING. 553 
 
 lime, and digesting them with water so as to prepare a caustic 
 lye, will be found described in the Essay on the fixed alkalies. 
 
 Itmay be remarked, that in weaving calicoes the workman 
 generally greases the reeds, in order to make them move easier. 
 Wherever this grease is in the cloth, it becomes fixed by the ope- 
 ration of singeing ; and if it be not taken out before bleaching, it 
 will not come out afterwards by the usual process of ashing and 
 souring : for, when the pieces are submitted to a blue vat to be 
 dyed of a uniform self-colour, all those greasy places will be found 
 to have taken the dye in a very imperfect manner. Tallow is also 
 employed for dressing the warp, and this has a baneful effect on 
 all goods which are designed for printing. 
 
 This defect in the operation of the pale blue dipping is often 
 attended with very serious consequences, so that I know of no 
 subject which better deserves the patient investigation of the ca- 
 lico-printer. I have seen a large number of pieces of printed 
 calicoes which had all taken a solution of iron so as to form an 
 extremely good black; also the acetate of alumina, which had 
 formed with the madder a beautiful red ; likewise the citric acid, 
 which produced a perfect resist and yet, when these goods came 
 into the blue vat, certain parts of the pattern intended for blue, 
 still remained quite white, the indigo having had no action what- 
 ever on those parts; a circumstance which is sufficient of itself 
 to spoil the goods, and render the whole expense of printing the 
 other colours totally lost. 
 
 To cleanse such goods previously to their being printed, va- 
 rious expedients have been adopted, but I apprehend nothing but 
 a solution of caustic alkali can be depended upon. To prove the 
 effect of any method which may be tried, it is a good way to run 
 the pieces through water, and then to pass them from the water 
 so gradually over a roller, as to give the superintendant an oppor- 
 tunity of examining every inch of the surface ; and if any part 
 remains greasy, it will be seen at once, for that part will continue 
 dry while all the rest of the cloth is wet. 
 
 There is another way inVhich the goodness of bleaching might 
 be proved. Let a few of the suspected pieces be run once or 
 twice through a madder-copper, at the temperature of about 180. 
 This will inevitably mark any part that may be imperfectly bleach- 
 ed ; whereas, if the operation has been properly performed, they 
 will come out so little stained, that an intelligent workman, who 
 has been used to a madder-copper, will at once be satisfied that 
 they contain no impurity that can form a permanent mordant. 
 
 The next process in calico-printing is one with diluted sulphu- 
 ric acid. A quantity of soft water having been poured into a 
 leaden vessel, oil of vitriol is gradually added to it, in the propor- 
 tion of about twenty pounds of oil of vitriol to every hundred gal-* 
 
534; ON CALICO-PRINTING. 
 
 Ions of water, which by weight is in the proportion of about one 
 to forty. 
 
 When this mixture has been well stirred, it is ready for use. 
 Sometimes it is employed in this state, at others it is heated to 90 
 or upwards of Fahrenheit, according to the nature of the work 
 to be done, and the goods are immersed in it. They are not 
 suffered to lie in this acidulous liquor, but are wound by means 
 of a winch over a wooden cylinder, that every part of the cloth 
 may be successively immersed in the fluid, and every part exposed 
 alternately to the action of the atmosphere. 
 
 This operation is generally continued for about twenty minutes, 
 and is designed to remove any iron-moulds or other stains which 
 the cloth may have acquired. It has also the effect of neutraliz- 
 ing any portion of potash that may have been left in contact with 
 the cloth. The process is called SOURING. 
 
 After this operation it is necessary to wash the goods tho- 
 roughly, that no part of the acid may be left in them, to injure'their 
 texture; and this is best effected by means of the wash- wheel. The 
 calicoes are then to be regularly and thoroughly dried, which 
 finishes these preliminary operations, known in the trade by the 
 term PREPARATION: so that those cloths which have passed 
 through these manipulations are said to have undergone a pre- 
 paration. 
 
 Besides the uses already mentioned, there is another advantage 
 attending these processes, viz. that the cloth which has undergone 
 this preparation will after maddering bleach or clear sooner, the 
 colours will be brighter, and the whites more delicate, than they 
 would have been had they not gone through these previous ope- 
 rations. 
 
 The next process is that of CALENDERING. Here the goods 
 are passed through a set of rollers, which gives them a gloss, and 
 the appearance of having been ironed. They are now fit for print- 
 ing. But for copper-plate printing, or cylinder work, the pro- 
 cess of calendering is omitted. 
 
 In printing fast colours, the artist usually proceeds in this way: 
 He lays the piece of calico, which has been already smoothed by 
 calendering, upon a strong thick table, made of a flat stone, which 
 is previously covered with a woollen cloth. He then proceeds 
 to apply one or more mordants, as the case may require, for fix- 
 ing the intended colours. These mordants are applied by means 
 of wooden blocks, with the patterns formed upon them. These 
 blocks were formerly made of holly, or other hard wood, and the 
 cutting them was a separate branch of the business. Of late years, 
 however, a considerable improvement has been made in this de- 
 partment, by the introduction of brass or copper; that is, the pat- 
 
ON CALICO-PRINTING. 535 
 
 tern, instead of being actually cut in the wood, is now formed by 
 means of slender pieces of one of those metals being firmly fixed 
 to the block, so as to produce the pattern intended. The pattern 
 when thus formed with copper, is not only more lasting, but it 
 has also the advantage of giving greater sharpness and beauty to 
 the impression. 
 
 When it was customary to use wooden blocks, the patterns were 
 not enchased in the wood, but the wood was cut away in such a 
 manner as to leave the pattern in relief. It will be obvious that 
 this must always be the case in block-printing. 
 
 When the mordant is ready, it is mixed up either with flour- 
 paste, or with a thick aqueous solution of gum arabic, gum Sene- 
 gal, or gum tragacanth. 
 
 Flour is an article of considerable consumption with the printers 
 for making paste. Should it be musty from keeping, it is of little 
 consequence for their use ; but they are careful to buy none but 
 such as has been made with sound wheat, for if unsound it will 
 be of no value for their purposes, and if sour it must be used up 
 the same day it is made ; for on the next day it becomes watery 
 and unfit for use, materially injuring the mordant. Gum traga- 
 canth is much dearer than the other gums ; but notwithstanding 
 this, it must be had for some styles of work, as no other will an- 
 swer for any of those colours or mordants which are prepared with 
 nitrous acid. A solution of gum Senegal would be coagulated in 
 an instant by any of those preparations. Of late years an article 
 called British gum has also been much in use for the same pur- 
 pose ; so much so that the making of it has become a distinct 
 and considerable trade. It is merely common STARCH calcined 
 till it assumes a cinnamon brown colour, and then pulverized and 
 passed through sieves of various degrees of fineness. 
 
 When the colour has been properly mixed with flour-paste, 
 or with a solution of either of the gums above mentioned, it is 
 spread upon a piece of superfine woollen cloth strained tight upon 
 a hoop. 
 
 This is placed within another hoop, covered either with sheep- 
 skin or oil-cloth. These hoops are both so broad as to give to each 
 of them the appearance of a tambarine. That which is covered, 
 with the woollen cloth is called a sieve, the other a case. The sieve 
 within its case is now placed in a small tub of gum-water, and is 
 ready for use. The tub is usually 28 inches wide at top and 32 
 at bottom, it being of great consequence to have it wider at bot- 
 tom than at top, to give the sieve and case full play when dipped 
 upon by the printer ; for were it to get fast to the sides of the tub, 
 the surface of the sieve would be uneven. 
 
 When the apparatus is thus prepared, the mordant is applied 
 by a brush to the surface of the sieve. This is called TEERING. 
 
536 ON CALICO-PRJNTING. 
 
 It should have been remarked, that when a colourless mordant, 
 like the acetate of alumina, is employed, the colourman generally 
 mixes a little of the decoction of Brazil wood, or of any other 
 fugitive dye, with it, which must, however, only be done by an 
 experienced man, or considerable mischief may ensue. This is 
 called SIGHTENING; and is for the purpose of making the pattern 
 more obvious to the workman, that he may see its progress, and 
 the efficacy of the materials, as he proceeds in printing. The ma- 
 nipulation may be thus described. 
 
 Taking the block containing the pattern in one hand, the work- 
 man applies it gently to the surface of the sieve, so that a suffi- 
 cient quantity of the thickened mordant may adhere to the figures. 
 When the block is thus charged, he applies it to the calico, and 
 gives it a blow with a small mallet, either slightly or otherwise, 
 according to the nature of the pattern. 
 
 This alternate application of the block to the sieve and to the 
 calico, is continued until he has gone over the whole piece. In 
 this way several different mordants are sometimes applied to the 
 same piece of goods. This is indeed always necessary, when the 
 finished piece is intended to contain a variety of colours, the 
 different colours requiring different mordants to fix them and 
 render them permanent. 
 
 The calico, which is always perfectly dry before it leaves the 
 printers, is now removed to a room called the hanging-room, for 
 age, where a degree of heat seldom higher than 70 or 80 is given 
 to it by means of flues, which go round the room on the inside 
 near the floor. The intention of this is to evaporate the acids 
 used in the preparation of the mordants, which might otherwise 
 injure the texture, and also to fix the base more surely within the 
 fibres'of the cloth. It remains in this room about 24 hours when 
 colours produced by acetate of alumina are required ; but for 
 those made from acetate of iron, as blacks, chocolates, purples, 
 &c., it should hang five or six days to oxidize and evaporate the 
 acids. 
 
 Whenever acetate of alumina is printed as a mordant upon ca- 
 lico, it appears to me that the pieces ought not to go into the 
 hanging-room until the work has been first thoroughly dried in 
 the open air, because it is well known that the earth of alumina 
 is precipitated from a solution of this salt in a high temperature. 
 I suspect this to be the cause of many of those disappointments 
 which are perpetually occurring in the production of the various 
 shades of yellow and madder reds. 
 
 Of late years a more convenient method has been adopted, 
 which consists in passing the calicoes by means of machinery 
 along a set of apparatus known by the name of steam-chests. These 
 are large square cast-iron vessels fixed at some little distance from 
 
ON CALICO-PRINTING. 537 
 
 each other, sometimes on an inclined plane, and in other cases 
 perpendiculary one above the other : they are kept constantly full 
 of steam, and are connected with each other by bent pipes either 
 of iron or lead. It is so contrived that the pieces of calico are 
 made to pass over each of these heated chests in contact with their 
 surfaces ; and in consequence of the access of atmospheric air, as 
 they pass from one of these chests to the other, they are generally 
 found to have become thoroughly dried by the time they arrive 
 at the end of the series. 
 
 If iron-liquor has been employed in printing the goods, it is an 
 excellent practice to keep them for several days exposed to the 
 atmosphere ' after their removal from the hanging-room, as the 
 blacks, pompadours, olives, and indeed every other colour pre- 
 pared with that metal, will increase in intensity ; the goods will 
 clean better in the dung- vessels, as will be explained hereafter, 
 and the colours will rise higher and brighter when they come into 
 the copper of bark or madder. 
 
 It may be worth an experiment to discover whether the colours 
 containing iron would not be better if they were suffered to be 
 only a very short time in the stove, but were hung up instead for 
 several days, exposed to a current of air at the temperature of the 
 atmosphere ; as the iron would thus acquire the oxygen slower, 
 and consequently would be fixed more firmly in the fibres of the 
 cloth. 
 
 When the pieces are removed from the hanging-room, they 
 are passed, by means of a winch, through water at various tem- 
 peratures, with a little cow-dung mixed in it. The intention of 
 the dung is to absorb and remove that portion of the mordant 
 which is not actually combined with the cloth, and which other- 
 wise might stain the white or unprinted parts. 
 
 This part of the business was formerly conducted in a very 
 uncleanly and negligent way ; but of late years some printers have 
 incurred a considerable expense in the construction of their dung- 
 ing machines, with cocks for hot and cold water attached to them, 
 and thermometers to regulate the temperature. 
 
 I suspect, however, that the dung of the cow is serviceable in 
 another way besides that of cleansing, though few printers may be 
 aware of the nature of its operation. It is acknowledged that 
 madder, cochineal, and some other dyes, produce much better 
 colours on woollen than on cotton cloths, owing to the former 
 being of animal, and the latter of vegetable origin. I presume, 
 therefore, that the dung imparts an animal matter to the fibres of 
 
 1 The iron in an acetous solution is in the state of theblac/c oxide; but by 
 exposure to the air it acquires a further dose of oxygen, and obtains the state 
 of the red or peroxide. 
 
538 ON CALICO-PRINTING. 
 
 the cotton, and that this animal matter acts as an additional mor- 
 dant, and thus more powerfully attracts the colouring particles of 
 the dye, than the mordants alone would be capable of doing. 
 
 If a piece of calico, prepared with the acetate of alumina, be di- 
 vided into two parts, and the superfluous mordant removed from 
 the one by cow-dung and water, and from the other by water only, 
 at the same temperature, it will be found, on passing the two por- 
 tions through a decoction of weld or quercitron bark, that the 
 yellow will be much more intense and bright in that which had 
 been submitted to the action of the cow-dung i. 
 
 The process of DUNGING calicoes is an operation that varies in 
 time from five to forty minutes, according to the style of the work. 
 The pieces are then taken to the river or wheel, to be more ef- 
 fectually washed ; and after this they are passed through tepid 
 water, in order that the workman may be aseared that every im- 
 purity is removed. 
 
 His next care is to provide a copper boiler of pure cold water, 
 into which a sufficient quantity of madder is broken, and then a 
 fire is lighted underneath the copper. The calicoes, printed and 
 rinsed as above, are now put into this boiler, and from the time 
 they are immersed, the workman never ceases to turn the winch, 
 so as to pass every part of the goods repeatedly through the liquor, 
 until the whole acquires a boiling heat. Indeed, this operation is 
 sometimes continued for ten or fifteen minutes after the bath of 
 madder actually boils, when the pieces are taken out and washed 
 thoroughly. In most of the large calico-works, a considerable 
 improvement in the method of maddering has been adopted since 
 the publication of the first edition of these Essays. This consists 
 in giving a perpetual motion to the calico by means of the steam- 
 engine. The ends of several pieces are fastened together, and 
 then they are put into constant motion through the madder ves- 
 sels, which are heated by steam, and made of wood five feet long, 
 three feet broad, and three feet deep, this shape being more con- 
 venient than round vessels, when the motion is given to the winch 
 by the steam-engine. The steam is let into them through two-inch 
 copper pipes, and is regulated by a valve or stop-cock, so that 
 they can be brought up to the boiling point, or to any degree be- 
 low it, with greater regularity than can be done by fire under a 
 copper ; yet coppers are necessary for some styles of work. By 
 these means the colours are rendered more uniform ; and one man 
 is enabled to attend to three dyeing-vessels at one time, which is 
 found to be a great economy of labour. 
 - Madder is one of the most valuable drugs we have, for a variety 
 
 1 Berthollet, who analysed the dung of the cow, found in it a substance 
 partaking of the nature of animal bile. 
 
ON CALICO-PRINTING. 539 
 
 of purposes in dyeing and calico-printing : as it is the agent by 
 which the best and most permanent blacks are produced ; also 
 the finest purples, and every shade of red from a pale pink to a 
 crimson. But perhaps it may not be generally known that this 
 article improves by age. For instance : If a quantity of madder- 
 roots be ground, and then packed tight in a cask, so as to exclude 
 the air, and kept thus for six months, they will dye a much better 
 colour, and go much further, than they would have done had 
 these roots been used as soon as they were ground. 
 
 The process which is called MADDERING, has the effect of im- 
 parting all the requisite colours to the goods by means of one 
 operation, which may be thus explained : 
 
 While one mordant precipitates the colouring matter of the 
 madder to a red, another precipitates a different portion of it of 
 a purple, another precipitates it black, and so of every possible 
 shade, from a lilac to a black, and from a pink to a deep red. 
 
 If a portion of weld or bark be added to the madder, every 
 shade, from a brown to an orange may be produced ; whereas, if 
 weld or bark alone be employed, all colours between a dark olive 
 and a bright lemon can be imparted to the cloth. These changes 
 are all occasioned by the play of chemical affinities, for the know- 
 ledge of which we are indebted to the improved state of chemical 
 science. 
 
 The only materials which are employed by the calico-printers 
 for the production of fine yellows are the quercitron bark and the 
 weld plant ; the former is the bark of a peculiar kind of oak grow- 
 ing in America, the latter is the produce of our own country. The 
 weld plant (the reseda luteola of Linnaeus) is for the most part 
 cultivated about Doncaster in Yorkshire. It is found, however, 
 that nothing impoverishes the land so much; otherwise it produces 
 a very heavy and profitable crop. 
 
 Here it may be worth remarking, that whenever it is of conse- 
 quence to produce the finest yellows or more delicate lemon colour, 
 it is necessary to dry the pieces in the open air, as the stove would 
 not fail to injure such colours; for stove-drying has always a ten- 
 dency to convert a yellow to an orange. It is also necessary to be 
 equally careful in the operation of dunging the mordants for these 
 pale yellows ; for, should this be done at a higher temperature than 
 96 or 100, their beauty will certainly be impaired. There is 
 another advantage in this, viz., by dunging at this low tempera- 
 ture, the dyeing may be completed even at 110 or thereabouts, 
 which will give a much livelier colour than where a higher tempe- 
 rature has been employed. 
 
 The mordants generally used in calico-printing, are acetate of 
 iron for browns, blacks, lilacs, &c. ; and acetate of alumina for all 
 the different shades of reds and yellows. 
 
540 ON CALICO-PRINTING. 
 
 The best method that I am acquainted with of preparing the 
 acetate of iron for making the common black colour for calico- 
 printing is as follows : Take the iron liquor of its full strength, 
 or lowered with one or two waters according to the goodness of 
 this mordant in the first instance, and then add about 2^1bs of 
 flour to every gallon of the fluid, more or less according to the 
 goodness of "the flour and the kind of work for which it may be 
 designed. Having well incorporated the flour with the iron li- 
 quor, let the whole remain twelve hours or more. After this it is 
 to be boiled for about half an hour, or till the whole be con- 
 verted into a paste of due consistence, when it will be fit for use. 
 The 'materials become better incorporated, and the colour is 
 found to work better, by lying thus long before it is finished by 
 boiling. 
 
 Formerly the acetate of iron was made by digesting old iron 
 hoops in sour beer, or in very weak vinegar ; but of late years it 
 has chiefly been made with the pyroligneous acid ', the oleaginous 
 impurities of which tend, in some cases, to improve the mordant. 
 
 Blacks are also produced by the nitrate of iron 2 and gallic acid ; 
 the mixture is called chemical black. The nitrate of iron is made 
 by dissolving metallic irbn in a peculiar kind of aqua-fortis. 
 Common aqua-fortis will not answer for this purpose; for, though 
 it may dissolve the iron with rapidity, part of the metal is apt very 
 soon to precipitate; which not only weakens the colour, but 
 leaves the remainder so acidulous that there is always a danger 
 of such a preparation injuring the texture of the cloth. 
 
 Chemical black is made by mixing a decoction of galls with 
 the nitrate of iron just described; this produces gallate of iron, 
 and probably some tannate of that metal : the disengaged nitrous 
 acid then dissolves the two newly formed salts. The colour called 
 chemical black may therefore more properly be said to be an 
 union of the colouring matter of galls with the per-oxide of iron, 
 than a mixture of gallic acid with nitrate of iron. The gallic 
 acid is probably like the pyroligneous, or nothing but the acetous 
 acid holding a peculiar vegetable substance in solution ; and either 
 the muriate or the sulphate of iron, if applied to cloth in conjunc- 
 tion with the colouring matter of galls, will in time produce as 
 
 1 If wood be submitted to an intense heat, when inclosed in an iron vessel 
 of any kind with a proper aperture to allow the vapour to pass, this vapour on 
 being condensed forms the acid in question, and is now known to be a kind of 
 impure vinegar. The wood in this case is converted into charcoal, of which a 
 great deal is prepared by this process, particularly for the formation of gun- 
 powder. 
 
 2 Nitrate of iron was not applied to calico-printing till within the last fifty 
 years. This discovery formed an important aera in the trade, as it afforded the 
 manufacturer the means of varying his styles of work in a multiplicity of ways 
 and forms, which till then were entirely unknown. 
 
ON CALICO-PRINTING. 541 
 
 intense and durable a black as the nitrate ; but the difficulty of 
 thickening the solutions of these salts, and the time which is re- 
 quired to convert their base into a per-oxide, render them less fit 
 for the calico-printer's purpose. 
 
 It is, however, necessary to remark that the black which is 
 formed by this solution of iron, is produced in a different way 
 from blacks in general ; for, when common iron liquor is used 
 for this purpose, it is first printed on the calico ; and when it has 
 been sufficiently oxidized by exposure to the air, the goods are 
 boiled in a decoction of madder, which renders such parts as had 
 been printed with the acetate of iron an intense black. But the 
 black from nitrate of iron and galls is applied at once to the cloth, 
 and is not afterwards increased in intensity, or raised, as it is 
 termed, by dyeing. 
 
 The calico-printer by using a black ready formed is thus ena- 
 bled to mix it with other colours, in cases where by dyeing alone 
 it could not be produced, as in conjunction with yellows and olives, 
 raised by weld or quercitron bark. 
 
 The acetate of alumina is prepared by a mixture of the sulphate 
 of alumina and potash with acetate of lead, both in a state of solu- 
 tion; so that, on the theory of double decomposition, sulphate of 
 lead is formed, which precipitates, while the acetate of alumina 
 remains in solution. 
 
 Since the demand for this article has been increased on account 
 of the extension of the printing-trade, it has been prepared from 
 the pyroligneous acid, by means of lime and alum. The following 
 is the method : 
 
 The pyroligneous acid is first passed through a still, to divest 
 it of a portion of the oil or tar which is always dissolved in it; it 
 is then saturated with lime or whiting ; and lastly, the acetate of 
 lime thus formed, is decomposed by a heated solution of sulphate 
 of alumina and potash. The result of this double decomposition 
 are sulphate of lime, which precipitates, and acetate of alumina, 
 which is drawn from the sediment of the calcareous sulphate, and 
 preserved for use. 
 
 In reverting to the remaining processes of the print-work, it 
 must be noticed, that when the goods have passed through the 
 weld or madder copper, they are usually carried to a boiler con- 
 taining wheat-bran and water, in which they are winched for a 
 considerable time, for the purpose of freeing the white grounds 
 from the stain which they had acquired from the madder or the 
 weld. This process always impairs, in some measure, the inten- 
 sity of the colours ; but it is a necessary operation, as there is no 
 other mode so convenient for removing the stain which is always 
 given to the white part of the print by the madder, the bark, or 
 the weld, which has been used in dyeing it. 
 
54-2 ON CALICO-PRINTING. 
 
 Branning has also the effect of giving a pink hue to all madder 
 reds. But it is not generally known what a peculiar richness may 
 be imparted to madder colours, by raising them with a mixture of 
 bran and madder ; that is, by mixing a portion of bran with the 
 madder in the first instance. I have myself sometimes produced 
 colours in this way whose brilliancy has astonished me. 
 
 This mode of dyeing red with a mixture of bran and madder 
 is called in the trade Growse's or London pink, and was invented 
 by a journeyman calico-printer near London, of the name of 
 Growse, who sold the recipe for 100 guineas. In this process the 
 acid of the bran prevents the precipitation of the fawn-coloured 
 particles of the madder, and the red produced is consequently 
 more rosy and pure. 
 
 Madder contains two distinct species of colouring particles, a 
 beautiful red or rose colour and a degraded yellow or fawn colour 
 both are precipitated on the cloth, in the usual dyeing process, 
 to the great injury of the tint obtained. The object of the tedious 
 Turkey-red process is to fix the red colouring particles so firmly 
 as to allow the fawn-coloured ones to be dissolved and discharged 
 by long boiling in solution of soap or soda, by chloride of soda or 
 by acid solutions of tin. A dilute super-sulphate of potash has 
 lately been used with success for this purpose in France. 
 
 It frequently is the case, however, that goods will not bear to 
 be sufficiently branned to clear the whites entirely by that one 
 operation l ; such goods, therefore, are partially cleansed in the 
 branning-copper, and are then either laid on the grass for some 
 days, until they become perfectly clean and white, or immersed 
 for a certain length of time in a very weak solution of print-clear- 
 ing powder ; which is chloride of lime mixed with about one-tenth 
 part of its weight of carbonate of soda. 
 
 This simple process, which effects in a few minutes what would 
 require more than as many days in grass-bleaching, is now gene- 
 rally practised, and has nearly superseded crofting altogether. 
 This is a most important improvement, as some of the large prin- 
 ters formerly required as much land to spread out their goods 
 upon, as would make a farm of a very considerable size. 
 
 Besides the kinds of calico-printing already mentioned, there 
 are others which it will be proper to notice in this place. Of 
 these, what is called resist-work is now done in considerable 
 quantities. It is conducted in the following manner: 
 
 1 The temperature at which the operation of branning is performed, is very 
 important. If bark yellows are dyed at 100, it is customary to bran such 
 goods at 115 or 120, as it is a principle always to bran at a higher tempera- 
 ture than the goods are dyed at. Madder-work must be branned at a boiling 
 heat. 
 
ON CALICO-PRINTING. 543 
 
 A preparation of sulphate of copper, mixed either with flour- 
 paste, with gum, or with pipe-clay and gum, is printed on the 
 calico, in any shape or of any pattern that may be desired. When 
 this is sufficiently dry, the goods are repeatedly dipped in the 
 blue vat till they have acquired that depth of tint which may be 
 required. The art of making an indigo-vat, or blue-vat as it is 
 sometimes called, consists in forming such a mixture of lime and 
 sulphate of iron as shall most effectually deoxidize the indigo; as 
 indigo has no affinity for cloth in its natural or oxygenized state. 
 Hence, those parts of a piece which are printed with a solution 
 of copper will never be dyed blue in one of these vats ; because 
 the deoxidized indigo becomes oxygenated the moment it touches 
 the copper, which parts with its oxygen to the indigo, and occa- 
 sions it to become insoluble, and consequently incapable of form- 
 ing a dye. 
 
 Thus, while sulphate of iron has the power of deoxidizing in- 
 digo, sulphate of copper, or any other salt of that metal, is inca- 
 pable of retaining its oxygen, whenever it comes in contact with 
 that singular substance in a state of deoxidizement ; and it is a 
 curious instance of the different degree of intensity by which 
 oxygen is held by the different metals. 
 
 I suspect, however, there is often great waste in the manage- 
 ment of these vats, and that the contents are often thrown away 
 long before the indigo is spent, in consequence of the want of a 
 due admixture of the lime and the sulphate of iron with the co- 
 louring matter ; whereas, if a dyer or calico-printer be acquainted 
 with chemical science, he will understand the nature of the ope- 
 ration of these substances upon each other, and hence can be at 
 no loss how to keep up the vat to its original strength, by reple- 
 nishing it occasionally with one or other of the ingredients as may 
 be required. 
 
 The fact is, that indigo, unless it be deoxidized, is insoluble 
 either in the alkalies or the alkaline earths ; but when this is ef- 
 fected by the iron of the copperas, the lime dissolves it, and forms 
 it into a perfect solution of indigo. At first a portion of the lime 
 abstracts the sulphuric acid from the copperas, and precipitates 
 with it in the state of sulphate of lime. The detached metal being 
 now in the state of the protoxide of iron, and having in that stage 
 of its oxidizement a great affinity for oxygen, it takes it from the 
 indigo, and thus becomes changed to the per-oxide of iron, which 
 being insoluble precipitates likewise. Thus the acid and the base 
 of the sulphate of iron are at length both precipitated, when the 
 remaining portion of lime seizes the deoxidized indigo and forms 
 with it the solution desired. When the principle of the blue-vat 
 is thus properly understood, it is an easy thing for the manager 
 
544- ON CALICO-PRINTING. 
 
 at any time to discover which of the three materials is deficient, 
 and to add it accordingly. I am the more desirous of offering 
 these remarks, because I have many times heard the proprietors 
 of a manufactory declare that they have occasionally thrown away 
 the whole contents of a new vat, containing many pounds worth 
 of indigo, because the foreman or manager of the works had not 
 observed the due proportions of the lime and the copperas to put 
 the indigo into a proper state for working; and they have an 
 idea, that if it is once wrong it must be always so, and therefore 
 they throw it away without attempting to correct the error. 
 
 To revert to the process of resist-work, it is necessary to say, 
 that when the pieces have been sufficiently immersed in the blue- 
 vat and have been washed and passed through diluted sulphuric 
 acid, those parts which had been printed with the preparation of 
 copper, are found to be preserved a good white ; the preparation 
 having effectually resisted the operation of the indigo, though all 
 the other parts of the cloth have received a permanent dye. The 
 various deep blue calicoes with white spots or white figures, 
 which are now so common, are generally done in this way ; and 
 by a similar management with subsequent dyeing in madder, in 
 weld or quercitron bark, figures in red or yellow (as the case may 
 be) are exhibited upon a blue ground. 
 
 In some particular styles of work the operation of certain co- 
 lours is resisted by means of stopping out with wax ; but this is 
 too expensive a method to be adopted often, in these times, when 
 it is the object of every manufacturer to finish his prints at the 
 least possible expense. Formerly this mode was very generally 
 practised, and is still used in the East Indies for preserving the 
 whites. 
 
 In printing those silk handkerchiefs called Bandanas, a process 
 called waxing is still followed. It consists in making a prepara- 
 tion of tallow and rosin very liquid by heat, and in printing it in 
 that state with a block upon the silk. When such goods are 
 passed through the blue-vat, those parts which are covered with 
 the tallow and rosin are preserved from the action of the indigo, 
 and remain white, while all the rest is dyed a fast blue. The 
 method afterwards taken to discharge a part of this blue, and 
 produce yellow, orange, &c., will be mentioned hereafter. 
 
 A very singular-looking substance was discovered a few years 
 ago near Stockport, which being handed about from one to 
 another, created considerable interest in that neighbourhood. 
 Every body supposing it to be a natural production, specimens 
 of it were sent to a variety of persons into various parts of the king- 
 dom, for their opinion and analysis, and among others a portion 
 was sent to myself. However, after every one had been busily 
 
ON CALICO-PRINTING. 545 
 
 engaged in examination and conjecture, respecting this unknown 
 substance, it was announced, that some seventy or eighty years 
 before, a calico-work had stood on the spot where the article was 
 found, and that this was nothing more than a large heap of the 
 refuse compound of flour, wax, and gum, above mentioned. 
 
 The reader will perceive that these resists are employed for the 
 purpose of preserving certain parts of a piece white, and of giving 
 other varieties to those goods in which blue is the predominant 
 colour : but if the ground is to be white, and the piece is only to 
 have one small object in indigo blue, such as a single sprig, then 
 a different management is necessary, and the colour is imparted 
 by a process which is called pencil-blue. 
 
 Here the indigo is deoxidized by means of orpiment, which is 
 a sulphuret of arsenic ; and formerly, whatever objects were done 
 with it were put in by means of a pencil : hence its name, PENCIL- 
 BLUE. 
 
 Pencil-blue is composed of the following ingredients, viz. Ten 
 ounces of indigo finely ground in water ; twenty ounces of quick- 
 lime in lumps ; the same quantity of potash of commerce, or the 
 impure sub-carbonate of this alkali; and ten ounces of orpiment. 
 These proportions require one gallon of water, and when the 
 whole has been properly mixed, and time has been allowed for 
 the sediment to subside, the clear colour is to be carefully poured 
 off and thickened with gum Senegal. 
 
 The intention in using this preparation had always been to im- 
 part it to the calico, before the indigo had time to recover its 
 oxygen : hence a small quantity only was mixed at once, or no 
 more than could be penciled on in a very short time ; but the in- 
 convenience which attended this plan, gave rise at length to an 
 invention which has nearly superseded the use of the pencil. 
 
 The invention to which I refer is the spring-sieve, which may 
 be thus described : A fine canvass sieve is suspended within a 
 tub of pencil-blue colour, so contrived that the canvass should be 
 in contact with the colour, and follow it as it wasted. But as the 
 colour was consumed, the sieve did not always exactly sink with 
 it, which occasioned great uncertainty, and sometimes consider- 
 able disappointment from the admission of too much atmospheric 
 air : to obviate these inconveniences many schemes w r ere resorted 
 to, but none of them completely answered the purpose. 
 
 This utensil has, however, now been much improved by a par- 
 ticular friend of mine, who has kindly allowed me. to give a plate * 
 and description of it ; and I doubt not that I shall have the thanks 
 of some of the manufacturers of printed cottons for having made 
 
 1 See the plate on calico-printing, fig, 11. 
 2 N 
 
546 ON CALICO-PBINTING. 
 
 public an invention of so much utility and ingenuity. It may be 
 thus described : 
 
 A is the box which contains the colour ; B is the sieve which 
 floats within the colour ; C. G. C. C. are the four springs which 
 keep the canvass of the sieve close down upon the dissolved indigo; 
 and D is a vessel from which the blue-tub is constantly supplied 
 with colour, as the same is exhausted by the printer, and is upon 
 the principle of a common bird -fountain 1 . The improvement 
 chiefly consists in the addition of this vessel, which in the begin- 
 ning is completely filled with the prepared indigo, and closely 
 corked and sealed, to prevent the possibility of the access of any 
 atmospheric air. 
 
 Another kind of process remains to be noticed, called CHEMI- 
 CAL-DISCHARGE work. Here the cloth is first dyed of some uni- 
 form colour, by means of a mixture of iron-liquor, and someone 
 or more of the common vegetable dyeing substances ; and calicoes 
 thus prepared are said to be dyed of self-colours. They are 
 then washed and dried ; and when properly pressed or calendered, 
 they are fit for receiving any pattern whatever, according to the 
 taste or design of the artist. 
 
 This is generally effected by means of the mineral acids, which 
 are previously prepared for the purpose, by dissolving in them a 
 portion of one or more of the metals, according to the nature of 
 the dye which is intended to be discharged, or of the colour to be 
 produced. In doing this, care is taken that the discharging liquor 
 be made so as to be capable of dissolving the iron which is con- 
 tained in the dye, and which is always used in such quantity as 
 to cover, or at least to disguise in a great measure, the other co- 
 lour or colours which had been employed with it, and at the same 
 time to act as a mordant in beautifying and fixing those colours. 
 
 Thus a piece treated with a decoction of Brazil-wood, and 
 dyed black by being padded 2 with iron-liquor, if, when dried, it 
 be printed with a peculiar solution of tin, the ferruginous portion 
 of the dye will be dissolved, and the printed part will instantly be 
 converted from a deep black to a brilliant crimson. 
 
 In the same way an olive-coloured calico, dyed in a solution of 
 iron and a decoction of weld, will as quickly be changed to a pale 
 bright yellow ; and the various drabs and slates of every shade 
 
 1 The stop-cock, which is placed in the tube, is to prevent any loss of colour, 
 in case the barrel should by any accident admit atmospheric air, and cause the 
 box to overflow. 
 
 2 By the term padding is understood the operation of passing the pieces from 
 a roller through a trough containing a solution of iron, or any other mordant. 
 Blotching is another terra used in calico-printing, and is nearly synonymous with 
 padding. 
 
ON CALICO-PRINTING. 547 
 
 which have iron in their composition, will undergo as sudden a 
 change by the same treatment ; though the colour of the figures 
 produced on them will depend on the materials with which the 
 cloths were originally dyed. Even the deepest gold colours, or 
 strongest buffs, if produced by iron only, may, by a peculiar pre- 
 paration of tin, be discharged ; and such parts of the cloth as have 
 been treated with this metallic solution will be restored to their 
 pristine whiteness. 
 
 By similar management, calicoes dyed of a light blue in the 
 indigo-vat, then run through sumach and copperas, and finished 
 in a bath of quercitron bark and alum, may have figures of a 
 bright green imparted to them. Here the green is originally 
 formed by means of the indigo-vat and the bark, though it is en- 
 veloped by the iron of the copperas, which overcomes the other 
 colours, till the solution of tin is applied, which removes the iron 
 from those particular parts, and gives a brilliancy to the remaining 
 colours which they would not otherwise have possessed ; the tin 
 being a powerful mordant for the bark, by which the yellow of 
 the green is produced. 
 
 Again, a good self-colour may be given to calicoes, merely by 
 dyeing them in sumach and copperas, and then running them 
 through an alkaline solution of annotto ; and here the figures 
 produced by the application of a colourless solution of tin will be 
 of a bright orange. But it is needless to enumerate more instances, 
 as the workman accustomed to a dve-house will have little diffi- 
 culty in varying these in a thousand ways, when he becomes ac- 
 quainted with the nature of the solution of tin which he employs. 
 
 The whole of this, however, refers to that branch of discharge- 
 work only, where all the purposes are attained by dissolving the 
 iron which makes a part of the colour tha,t is intended to be dis- 
 charged ; whereas, the finer and more expensive work is done in 
 a different way, and by a process which it will be necessary for 
 me presently to describe. 
 
 It is, however, proper to remark, that there is an objection to 
 the particular kind of chemical discharge-work of which I have 
 been speaking, namely, that it is not perfectly fast ; that is, the 
 goods produced in this way will not bear such frequent washing, 
 as those which are done by the bath of madder or bark. 
 
 It is certainly an object of great national importance to give a 
 permanency and beauty to the calico-printing of the country; 
 and a great deal of very excellent printing is now done in various 
 parts of the kingdom, especially for the best chintz-work and other 
 furniture patterns. But, in what is called fast-work, there is a 
 great variety of qualities, and some of it little deserves the name 
 of permanent. 
 
 2 N2 
 
548 ON CALICO-PRINTING. 
 
 The mention of permanent colours reminds me of a very valua- 
 ble GREEN which was invented some years ago by a Mr. Islet of 
 London, and which deserves to be noticed in this Essay. This 
 colour is produced by printing ground indigo mixed with a pecu- 
 liar kind of solution of tin, and in then fastening the indigo 
 within the fibres of the calico by means of that process, which is 
 well known to printers by the technical designation of china-blue 
 dipping ! . After this the goods are dyed in a copper of bark or 
 weld, which converts the blue to a green, and the whites are 
 afterwards cleansed by croft-bleaching, &c. 
 
 There is another mode of producing very beautiful blues which 
 has been much practised lately, and therefore deserves notice. 
 This consists in printing some solution of iron, and then passing 
 the goods through a very dilute and neutral solution of prussiate 
 of potash. The prussian blue which is thus formed upon the 
 cloth may be rendered tolerably permanent by a variety of expe- 
 dients s and this by means of any of the yellow dyes may after- 
 wards be formed to any shade of green or of olive. 
 
 Begging to be excused for the irregularity of these digressions, 
 I must not forget to revert to that other kind of discharge- work 
 which I have engaged to describe, and which I will now attempt 
 as concisely as is consistent with perspicuity and correctness. 
 
 Here, the agent which is employed is the citric acid, and this 
 is used in various states of concentration according to the purpose 
 to which it is to be applied, and the strength of the ground in- 
 tended to be discharged. It is chiefly employed for the production 
 of white figures upon self-coloured grounds produced by madder 
 and sundry other dyes. For this intention the acid, in whatever 
 state of concentration it may be, is mixed with either gum or with 
 flour-paste 2 to a proper consistency for the block, the plate, or 
 the cylinder, and thence it is transferred to the piece ; and where- 
 ever it attaches, the mordant, whether iron or alumine, is dis- 
 charged, and a delicate white arises in its stead 3 . 
 
 The acid here referred to is produced from the juice of limes 
 or lemons, and formerly it was not employed by the calico-printer 
 
 1 China-blue is produced thus : Indigo ground fine, and then thickened, 
 is printed upon the cloth, and afterwards it is dissolved, and chemically united 
 to the fabric, by alternate immersion in a solution of sulphate of iron and in 
 lime water. 
 
 * When citric acid is used for resist-work, it is always mixed with gum 
 Senegal and pipe-clay. The clay gives it a greater body, and likewise acts 
 mechanically as a resister. 
 
 3 It should be understood, that the discharge is printed upon the mordants 
 before the goods are dyed. In using citric acid for this purpose, a portion of 
 one of the mineral acids is sometimes mixed with it. 
 
ON CALICO-PRINTING. 549 
 
 until it had been reduce*! to the utmost point of concentration 5 
 and appeared in a crystalline form. Even then, it was not thought 
 sufficiently pure, but was dissolved again, and redissolved and 
 recrystallized, until it became as white and pellucid as any other 
 pure salt in a crystallized state, and was then generally s'old for 
 36s. the pound, at which high price it could only be employed on 
 the best styles of work. Now, however, it is oftener used in the 
 brown, or first state of crystallization ; and some of the larger 
 printers purchase lime juice, and concentrate it themselves; and in 
 many cases they use it largely both for discharge- and resist- work, 
 without crystallizing it 4 . More on this subject may be seen in 
 the Essay on Citric Acid, which was written with the hope of ren- 
 dering an essential service to a large body of manufacturers in 
 various parts of these kingdoms. 
 
 This mention of discharge-work by citric acid 5 reminds me of 
 another species of discharge, which is employed by the printers of 
 Bandana handkerchiefs, and which I am under the promise of 
 noticing before I conclude this Essay. 
 
 The agent which these printers employ is the nitrous, and some- 
 times the nitro-muriatic acid. It is used for the purpose of putting 
 yellow figures upon blue silk handkerchiefs. The following is the 
 process which is principally adopted. 
 
 Aqua-fortis, or nitro-muriatic acid, of such a strength as is 
 suitable for the kind of blue which is intended to be discharged, 
 is mixed either with gum tragacanth, or with flour-paste, to a pro- 
 per consistence, and in this form it is printed on the silk, by 
 means of a common block, on which the intended pattern is cut. 
 The consequence of this is, that wherever the acid attaches, there 
 the original colour is discharged, and a yellow dye is produced in 
 its place. The pieces are then steamed, by passing them over a 
 vessel containing boiling water, which gives brilliancy to the colour 
 and finishes the operation. 
 
 If a stronger dye than the usual yellow, or even a deep orange 
 be desired, all that is necessary is to immerse the goods, for a 
 moment, in lime water, or in a solution of lime and potash ; and 
 by varying the proportions of these ingredients a great variety of 
 shades may be produced. 
 
 It must be noticed that this method is applicable only to the 
 
 4 Since Mr. Parkes published the last edition of these Essays, the use of 
 crystallized citric acid has been entirely abandoned : concentrated juice is quite 
 sufficient, and it is now frequently imported at 45 to 50 degrees of Ronchetti's 
 citrometer. EDIT. 
 
 5 Mr. Thomson, a scientific printer, who has an establishment near Clithero, 
 which is carried on under the firm of Thomson and Chippendale, has taken 
 out a patent for discharging the Turkey-red dye by means of the citric acid 
 and chlorine ; and the work executed in this way has a very pleasing effect. 
 
550 ON CALICO-PRINTING. 
 
 discharge of the colour from silk handkerchiefs ; the process for 
 producing the spots on cotton Bandanas being entirely different. 
 This manufacture, which is of considerably more importance 
 than the former, was established some years ago in Scotland, for 
 the purpose of producing imitations of the Bandana handkerchiefs 
 which are imported from India. It is .conducted in the following 
 manner. 
 
 Pieces of fine calico are dyed by the Turkey- red process, of a 
 colour as nearly approaching to scarlet as can be produced on 
 cotton by that means ; and, upon this plain dyed calico, white 
 spots are produced by a method to be described hereafter. The 
 pieces of calico having been bleached to a perfect white before 
 they are dyed Turkey-red, the present object is, not only to dis- 
 charge the dye on certain parts of the cloth, but by the same 
 agent to restore those parts to their original whiteness. 
 
 These discharged parts are usually in the form of spots, some- 
 times round and sometimes square or triangular, and these marks 
 or spots are produced by the action of a chemical liquid, while 
 the pieces of calico are under the action of a powerful press. The 
 machinery for this purpose is made in an expensive manner, as it 
 is required to be of very great strength, and it is put together 
 with the utmost exactness. 
 
 To this press two horizontal plates are adapted, for the purpose 
 of receiving the calico which is to be placed between them. The 
 pattern intended to be given to the handkerchiefs is first marked 
 upon these plates ; and in the bottom plate, holes are cut of the 
 exact form and size of the intended spots ; whereas, in the upper 
 plate every spot is marked out by a small copper tube which goes 
 through the plate and is firmly cemented within it. 
 
 When the plates are about to be fixed, there is a contrivance 
 for ascertaining that the orifices of the tubes in the upper plate 
 are exactly perpendicular to the respective holes in the under 
 plate ; which is a circumstance of the utmost importance, as the 
 discharging liquor which is poured into the tubes is designed to 
 pass through the folds of calico irto the corresponding holes in 
 the lower plate. 
 
 The apparatus being thus prepared, the handkerchief pieces are 
 neatly folded into squares of the size of a single handkerchief and 
 of the thickness of about ten cr a dozen folds. One of these 
 pieces, consisting of ten or twelve handkerchiefs, is then laid 
 smoothly upon the lower plate, and is so disposed as to lie square 
 with the plate. By means of a lever, the cover of the press, to 
 which the upper plate is attached, is then lowered, and by conti- 
 nuing the action of the lever, these plates, with the folds of calico 
 between them, are screwed firmly together. 
 
 The consequence of this is, that the ends of the tubes fixed in 
 
ON CALICO-PRINTING. 551 
 
 the upper plate, are brought to press upon the surface of the 
 cloth ; and as these are made to press upon it with great force, 
 and as each tube has a corresponding hole immediately beneath 
 it in the under plate, it is evident that the fluid which is poured 
 into these tubes will be directed into the holes below, and cannot 
 pass in any other direction. 
 
 When things are thus arranged, and the press is firmly screwed 
 down, a very dilute solution of chloride of lime, containing a 
 small portion of sulphuric acid, is poured upon the upper plate 
 of the press ; and as this plate has an iron rim round its upper 
 surface, the fluid which is poured upon it is determined into the 
 tubes, and as it percolates through the cloth, it discharges the 
 colour on those particular parts, and passes off through the holes 
 of the lower plate into a trough placed underneath to receive it. 
 
 It is observable that the chemical liquid is prepared sufficiently 
 strong to discharge the colour in the course of about ten or twelve 
 minutes, and yet not so powerful as to endanger the fabric of the 
 cloth ; and that the great pressure of the screw prevents the fluid 
 from spreading beyond the precise limits marked out by the tubes 
 and the corresponding holes underneath. 
 
 As soon as the discharging liquor is found to have entirely 
 passed through, the press is slackened, and the cloth is removed 
 to make room for another piece, which is immediately substituted ; 
 and in this way the process is continued throughout the day with- 
 out interruption. One press, requiring the attention of tw T o men 
 only,' will print fifty pieces, containing one dozen handkerchiefs 
 each, in the course of the day. 
 
 When the pieces are first taken from the press, the spots which 
 have been produced by the discharging liquid are not perfectly 
 white ; it is therefore necessary to have recourse to a subsequent 
 process similar to the one usually employed for clearing the whites 
 on common printed calicoes ; and this not only removes every 
 stain, but also heightens the brightness of the Turkey -red dye. I 
 am aware that at one time there was a general complaint of such 
 handkerchiefs, after frequent washings, becoming tender in those 
 parts which had been acted upon by the chemical liquor : this I 
 think must be owing either to the employment of a liquor too 
 much concentrated, or to the remains of the acid not having been 
 perfectly removed before the goods were dried and pressed for 
 sale ; as I am persuaded that with due caution the process may 
 be safely conducted. 
 
 When speaking of yellows, it was my intention to have men- 
 tioned, that there is a mode of producing yellows on calico which 
 is not very frequently practised, and yet has a very good effect. 
 The process is as follows : 
 
 A strong decoction of quercitron bark, thickened with gum 
 
552 ON CALICO-PRINTING. 
 
 tragacanth, is to be mixed with a portion of very pure muriate of 
 tin, and this, when printed with the usual management, will pro- 
 duce a colour of great brightness and durability. I mention this 
 the rather, because very many pleasing effects may be obtained 
 by this method which cannot be produced in the usual way, by 
 means of the acetate of alumina, and any of the yellow dyes that 
 may be employed with it. 
 
 There is one very important advantage which this mode pos- 
 sesses, viz. that should it be necessary to pad a piece in diluted 
 acetate of alumina to obtain a pale lemon ground, the yellow 
 figures, previously imparted by the above process, will not give 
 out any part of their colour to the second mordant ; whereas, 
 whenever a strong yellow has been produced in the common way, 
 the pattern is very apt to spread and become irregular, and 
 oftentimes to stain the white ground, when the piece comes a 
 second time into the acetate of alumina. 
 
 The most expensive kind of calico-printing called CHINTZ- 
 WORK still remains to be described. The term chintz- work is 
 descriptive of that kind of calico-printing which is employed for 
 window-curtains and other furniture, and it differs more in the 
 richness and variety of the colours, than in any other circumstance. 
 
 In relating the processes by which these beautiful prints are 
 produced, I shall suppose the calico to be already properly 
 bleached and smoothed ready to receive the impressions of the 
 block. The first thing then to attend to, is to apply the mordant 
 for the colour which is intended to be imparted in the first 
 instance. Thus, if a black be designed, a mordant of acetate of 
 iron, commonly called iron-liquor, is thickened with gum, and 
 printed upon the cloth in any pattern that may have been selected 
 for the purpose. If this same mordant be diluted with water, it will 
 form a proper mordant for a purple ; and the same, still further 
 diluted, will, when it comes into the dyeing-copper, form a 
 lilac. In this way, all the varieties of shades from a pale lilac to 
 a strong purple, and from a purple to a black, may be produced 
 by acetate of iron diluted with various portions of water, and then 
 dyed with madder. 
 
 In like manner, a colourless solution of acetate of alumina 
 thickened with gum or flour-paste, forms a mordant for dark red ; 
 if diluted with water, it makes a common red ; and by diluting it 
 further and further, every shade of pink may be produced. Again, 
 by the admixture of acetate of iron and acetate of alumina, a 
 mordant for chocolate colours, maroons, &c., is formed, either 
 approaching to the purple or the red, according to the admixture; 
 that is, according to the proportion of either of these original 
 mordants which may predominate in the mixture. 
 
ON CALICO-PRINTING. 553 
 
 When these several mordants have been printed upon the 
 calico, they are allowed to hang for age, in a warm room for 
 three or four days, as described page 536 ; they then go through 
 the operation of dunging, which consists in rinsing them in warm 
 water in which a little cow-dung is diffused, as has been already 
 described. When the pieces are sufficiently dunged, which is 
 not the case till all the superabundant mordants are removed, 
 they are well washed in clean water, and then boiled in a decoc- 
 tion of madder, until the madder-bath is exhausted. In conse- 
 quence of different mordants having been applied to the cloth, 
 this one boiling in the madder-liquor will at once produce all the 
 colours above mentioned. When the pieces are thus dyed, they 
 are to be rinsed in cold water, and rendered perfectly white by 
 exposure to the air, or by print-clearing powder as already 
 described. 
 
 The processes which have now been detailed, will produce 
 what is called common chintz- work ; but if it be desired to make 
 the goods still richer by the addition of yellows, bright olives, 
 drabs, &c. the cloth must undergo another series of operations, 
 which may be thus described : 
 
 Upon those parts of the calico which still remain white, any of 
 the above mordants may be printed, according to the effect 
 designed to be produced ; after which, all the preceding manage- 
 ments are to be repeated, except that instead of boiling in a decoc- 
 tion of madder, they are to be immersed for about half an hour, 
 more or less, in a warm decoction of quercitron bark, (the Quercus 
 nigra of LinnaBus,) a most important dye-wood, introduced by 
 Dr. Bancroft, and which is found to give out a much brighter 
 colour to tepid water than it does when treated with boiling 
 water, or with water nearly approaching to that temperature. 
 
 The effect produced upon these prints by an immersion in a 
 lukewarm decoction of this American bark, will be quite different 
 from that produced by the madder ; upon those parts of the cloth 
 where the mordants have been printed which before produced a 
 black, a dark olive only will be apparent ; and instead of pompa- 
 dours will be drabs ; and instead of reds we shall have yellows, 
 which will vary in intensity according to the strength of the alu- 
 minous mordant. 
 
 Again : a further variety may be given to these prints, if the 
 yellow mordant, or acetate of alumina, be applied to any of the 
 colours which have already been dyed with madder ; but this 
 must be done before the pieces are immersed in the decoction of 
 bark. This application will convert the reds and pinks into 
 different shades of oranges, and the lilacs into cinnamon colours. 
 By means of these different processes, an endless variety may be 
 given to the goods, and a calico-printer of taste will never be at a 
 
554- ON CALICO-PRINTING. 
 
 loss how to produce a pleasing effect, whatever may be the pat- 
 terns which he has to imprint upon the cloth. This second 
 immersion in the dyeing vessel will, however, give a yellow tinge 
 to the remainder of the whites, but a short exposure on the grass 
 will obliterate it. 
 
 When chintz-furniture prints are designed to have as much 
 variety of colouring as possible, a part of the remaining white is 
 often coloured blue or green, or of any shade between those 
 colours, by a still different process. This is done with what is 
 called pencil-blue, which is a preparation that has already been 
 described. The blue is given by putting in the prepared indigo 
 with a pencil ; and the green is produced by pencilling some of 
 the same colour over certain parts of the pattern which has already 
 been dyed yellow. 
 
 When these colours have been imparted, the printing is said 
 to be finished, and the pieces are hung up to dry for at least 
 twenty-four hours ; after which they are rinsed thoroughly in 
 cold water ; and when they have been dried with care, they are 
 properly calendered and put up for sale. For the purpose of 
 drying finished goods, an excellent apparatus has been invented, 
 consisting of an arrangement of cylinders made of tinned iron 
 or copper filled with steam, and round which the calico is made 
 to pass in succession, as]shown at figure 10 of the plate on calico- 
 printing. In this apparatus there is a vane fixed underneath every 
 two of these cylinders, which is moved by means of the steam- 
 engine, and agitates the air so as to very much facilitate the 
 drying process. This mode of drying printed calicoes is so 
 effectual, that although the cloth be wound from the heap 
 marked C upon the first cylinder quite in a wet state, it becomes 
 thoroughly dry by the time it has passed over the whole of the 
 apparatus, and falls in a perfect state on the heap marked D ; all 
 which will be better understood by a reference to the plate. 
 
 Nothing now remains but to notice an improvement which 
 has been made of late years by the introduction of CYLINDER- 
 PRINTING, which has the advantage of superior accuracy and 
 neatness, as well as of great expedition. 
 
 The plate which accompanies this Essay will afford a general 
 idea of the nature of the expensive machines which are employed 
 for this purpose ; the construction of which may be thus further 
 explained : They are so contrived that the cylinders on which 
 the patterns are engraved, furnish themselves with the prepared 
 colour during their revolutions; their surfaces are kept clean by a 
 steel knife, or doctor as it is called, passing over them the moment 
 they have charged themselves with the thickened colour ; and 
 they have such a pressure given to them, either by means of 
 screws or levers, which can be tightened or slackened at pleasure, 
 

 
 
 
ON CALICO-PRINTING. 555 
 
 that the whole cylinder is made to deposit its colouring matter 
 with the greatest certainty and exactness on the cloth, while this 
 rolls over it in succession, from one end of the piece to the other. 
 
 These cylinders, which are made of copper, are from twenty- 
 eight to forty-two inches in length, according to the width of the 
 calico to be printed, and four to five inches in diameter; and 
 these massy rollers have the patterns enchased upon their surfaces, 
 in the same way as a pattern is cut upon a flat plate of copper, 
 that is intended to be employed in copper-plate printing ! . 
 
 Many of these machines are contrived so as to carry two of 
 these cylinders, each of which has a trough of colour attached 
 to it, by which means two different colours may be printed on 
 the same calico at one and the same time ; and Mr. Adam Par- 
 kinson of Manchester has invented a machine capable of printing 
 at one time, by means of one cylinder and two surface rollers, or 
 by two of the former and one of the latter, three distinct colours. 
 See Plates, fig. 12. 
 
 These machines have not only the excellence of printing more 
 correctly than can possibly be done by means of the block, but 
 the saving of time and labour which they afford is great indeed. 
 A piece of calico which would take a man and a boy one hour and 
 a half to print with one colour, or three hours to finish with two 
 colours, may by this means be printed in three minutes and a half, 
 and the work will be much more completely done than could even 
 have been imagined before the introduction of this invention. 
 
 Besides these cylinders there are others which are called SUR- 
 FACE-MACHINES, which contain cylinders, not of copper but of 
 wood, and which have the pattern formed upon their surfaces in 
 relief exactly similar to the blocks described in page 534. These 
 are employed in particular styles, especially on light grounds, and 
 for certain kinds of resist- and discharge-work. 
 
 It must be obvious to every one who is acquainted with the 
 subject, what an astonishing facility these machines must have af- 
 forded to the production of printed calicoes ; and also what an 
 advantage they give to the British printer in foreign markets. 
 
 During the few years which have elapsed since the publication 
 of this Essay and the death of its author, so important have been 
 the discoveries and improvements in the art of calico-printing, 
 
 1 As these cylinders were formerly made with plates of copper hammered 
 into a circular form and joined by brazing, great loss was sometimes sustained 
 by the engraving giving way upon the brazed joint. To obviate this, a patent 
 was obtained for boring the copper cylinder from the solid metal in the modern 
 way of boring cannon. 
 
556 ON CALICO-PRINTING. 
 
 that I, as editor, should be justly censured for leaving it incom- 
 plete, were I not to enumerate and briefly describe them. This 
 I think it preferable to do by an addition to the Essay, rather 
 than to interweave my remarks in the text of the author. The 
 invention most decidedly new in every respect, and the most im- 
 portant, as to the great extent to which it has been carried, is that 
 system of printing which is known by the name of steam-colours. 
 
 A steam-colour is simply colouring-matter permanently fixed 
 upon cloth by means of steam : it is usually a decoction extracted 
 from vegetable substances by hot water, printed upon a cloth, 
 prepared for its reception, by being previously passed through a 
 certain^mordant commonly called oxymuriate of tin. This mor- 
 dant is however in reality a very strong solution of nitromuriate, 
 or, what is preferable, of muriate of tin, the metal being converted 
 into a perfect peroxide by the sudden addition of nitric acid, which 
 acting with a violent effervescence, is decomposed, leaving one 
 portion of its oxygen with the tin, thereby converting it from the 
 state of a protoxide to that of a peroxide, and the nitrous acid 
 flying away in the form of gas. 
 
 After printing, the colours are rendered brighter, deeper, and 
 faster, by being exposed to the action of steam, as will be pre- 
 sently described ; and they are much improved by one or two 
 nights' age both before and after steaming. Mineral acids are in 
 general too active, and when combined with tin are apt to injure 
 the cloth ; on this account it is usual to prepare the cloth with an 
 alkaline solution of tin, and then to print the colouring-matter 
 with a vegetable acid and an aluminous mordant. Alum may 
 however be employed, though its acid is mineral. 
 
 I shall first describe the preparations of the cloth, which may 
 be done either with an acid, or an alkaline solution of tin, the 
 latter however being preferable for all colours excepting Prussian 
 blue. In 10 gallons of water dissolve 15lbs of potash and 7jlbs 
 of fallen lime: boil for fifteen minutes, then add 1 oz. of very 
 finely ground litharge ; stir well, and let the sediment subside. 
 Pour off the clear liquor, wash the sediment repeatedly, till by 
 the addition of the washings you have reduced the liquor to 20 
 of Twaddell's hydrometer, or riOO l . When it is cool, add one 
 gallon of the oxymuriate of tin at 120 or T600, to 14 gallons of 
 the caustic alkali. With this liquor pad your pieces, taking care 
 not to dry them entirely, but finish the drying them over three 
 or four drums of the drying machine, (Vide plate 6, fig. 10.) 
 
 1 When I mention degrees of specific gravity during this Essay, I wish to be 
 always understood to take those of Twaddell's hydrometer, that being the inr 
 struiuent universally employed by the Lancashire calico-printers. 
 
ON CALICO-PRINTING. 557 
 
 Let the machine at the same time 
 roll them to the number of 15 pieces 
 on each roll, and keep them warm with 
 blankets. Have in readiness a tub 
 holding from 150 to 200 gallons of 
 water, in which dissolve 6 oz. of sal 
 ammoniac per gallon. Run the pieces 
 through this liquor at the rate of a mi- 
 nute and a half to each piece, with rollers after this manner ; 
 then wash them well and dry. 
 
 The pieces should always be tubbed off the same day on which 
 they have been padded, and whilst they are warm from the dry- 
 ing machine. For every 15 pieces passed through the sal-ammo- 
 niac tub, you add, well stirring all the time, one gill of sulphuric 
 acid, and when filling up your tub, always put 6 oz. of sal-ammoniac 
 to every gallon of water you pour in. It is of great importance 
 to the success of the work, that the alkaline solution should not 
 precipitate whilst padding; and to prevent this, keep it well stirred 
 in the trough, and let a regular supply of liquor be kept up. The 
 cloth thus prepared will keep for any length of time, and the tin 
 is so firmly combined with it that no process will take it out ; so 
 that the pieces are rendered quite useless for any other purpose 
 than steam colours. 
 
 You now print the colours on the cloth by machines. (Vide 
 plate 5.) A few examples of the methods of preparing the principal 
 colours will suffice. For Cochineal Pink, add five pounds of 
 ground cochineal, in a copper pan tinned inside, to three gallons 
 of distilled water; scald it for an hour at a heat of 200 Fahren- 
 heit, taking care not to let it boil ; pour off the liquor, and to the 
 cochineal add Ij gallon of fresh water; BOIL this for an hour to 
 extract the whole of the colour, repeating the operation with half 
 a gallon of water if necessary. Put all the liquors together, 'and 
 evaporate them down to three gallons. 
 
 Take seven pints of this liquor and one pint of acetate of alu- 
 mina (made with 4lbs of alum and 4|lbs of white sugar of lead), 
 thicken with starch, and when boiled add 4 ounces of oxalic acid, 
 cooling the colour as soon as possible ; for the more quickly that 
 is effected the better. Print the pieces and hang them up for one 
 night, steam them twenty minutes, hang them one night more, 
 then rinse them in clean water, wash, and finish. 
 
 For Blue, dissolve in one gallon of cold water l^lb of Tar- 
 taric acid, to which add l^lb of prussiate of potash; thicken 
 the clear liquor with starch, taking care to cool the colour 
 as quickly as possible. Print, hang and steam as for the pink ; 
 but the more age you give the blue after steaming, the richer 
 will be the colour. 
 
55S 
 
 ON CALICO-PRINTING. 
 
 For Green, thicken with starch one gallon of Persian berry 
 liquor, made at the rate of two pounds of berries per gallon, and 
 half a pound of alum. When cold, add one gallon of the thickened 
 blue equally cold, and mix them well together. Print, hang and 
 steam as before. 
 
 For Purple, take a decoction of logwood, at 10 of Twaddell, 
 add one-sixteenth of acetate of iron, and treat this in the same 
 way as the cochineal. 
 
 For Yellow, take best Persian berries eight or ten ounces to 
 the gallon of water, boil them until all the colouring matter is ex- 
 tracted, add eight ounces of alum to the gallon, thicken with 
 flour and British gum. 
 
 For Orange, take one measure of the cochineal liquor, and 
 as many of the above yellow as will produce the shade required ; 
 thicken with starch, and when cool add four ounces of oxalic acid 
 to each gallon. 
 
 Brown, Cinnamons, &c. are made merely by a mixture of pink, 
 yellow, and purple, or of purple and yellow to any shade that 
 fancy may dictate, and are then treated as above. 
 
 The cloth being prepared and the colours printed on it, as 
 we have just described, all that remains to be explained is the 
 apparatus for steaming; a sketch of which will be found in the an- 
 nexed cuts, having the tin part coloured red, and the copper black . 
 
 No. 1. The steam-guage. A two-inch iron pipe A 
 is brought from the boiler to a convenient room, near 
 to the steam, rising ten or twelve inches above the floor. 
 On this is placed a copper two-inch pipe B with a stop- 
 cock in the middle of it, and a cone eight inches by five 
 on the upper part with a mouth one inch and a quarter 
 wide. 
 
 No. 2. The cylinder. The middle tube C is made 
 of strong copper, brought through the lower end of 
 the cylinder six inches ; it is two inches and a half in 
 diameter, and thirty-eight inches long, pierced full of 
 holes about the size of a pea, and an inch apart from 
 each other. Over this is a tin cylinder D, nine inches 
 in diameter, leaving of course all round a space of 
 three inches and a quarter. It is thirty-two inches 
 long, soldered in the copper at both ends, and also 
 pierced full of small holes, a quarter of an inch apart, 
 to the breadth of twenty-seven inches, leaving a part at 
 each end F F without holes. At the lower end are 
 six or seven holes, E, to let out the water produced 
 from the steam, and to the upper end is an affixed 
 iron handle for the purpose of winding on the pieces. 
 
 The printed pieces, ten or fifteen at a time, are wound upon the 
 
 No. 1. 
 
ON CALICO-PRINTING. 559 
 
 tin cylinder on three or four folds of blanket. The apparatus is 
 then placed upright on the cone B, which it fits firmly, and is sup- 
 ported by a hoop at the top. The steam is turned on by means 
 of the stop- cock, and passing up the tube C fills the space between 
 the tube and the tin cylinder, and forcing itself through the 
 small holes, into the pieces, penetrates the whole mass and 
 escapes l . After the calicoes have been exposed to the action of 
 the steam for twenty minutes, it is turned off, the apparatus taken 
 down, the pieces removed, and ten or fifteen more rolled on in 
 their room. Where much work is done, it is necessary to have 
 three or four of these cylinders, and one or two of larger dimen- 
 sions for wide calicoes. During these manipulations, it is of the 
 utmost importance that iron should not in any shape be allowed 
 to touch the cloth, otherwise the colours would be certainly 
 spoiled ; copper and tin, it will be observed, are used for every 
 part of the apparatus. 
 
 When the prints are removed from the steamer, they are quite 
 wet, and so hot that it is difficult to touch them, but they are 
 pulled off with great rapidity, and on exposure to the air are in- 
 stantly dry ; they are then sent to the hanging-room to age, which 
 completes the operation. 
 
 The improvement next in importance to steam colours, which 
 I deem it necessary to describe, is a certain course of resist-work 2 , 
 technically called neutral, which can be performed with all the 
 colours of a chintz, viz., black, three shades of red, and purple, 
 and dipped blue. These colours are all block work excepting 
 white and black, which can be done by a machine : the method of 
 doing them is as follows : The first block is printed with a paste 
 made of a solution of citric acid at 16, eight or ten ounces of 
 sulphate of copper per gallon, British gum, and a little pipe-clay. 
 This is the white or neutral resist 3 . 
 
 The second block is a paste made of acetate of alumina at 14 
 added to one-fourth part of nitrate of zinc, or sulphate of copper, 
 with British gum and a little soft soap. This is the red resist, 
 which for paler shades of red is diluted with gum Senegal. The 
 third block is a paste made of acetate of iron andjlour for blacks. 
 
 The fourth block, if a lilac is introduced, is acetate of iron at 
 4, and nitrate of zinc with gum Senegal or British gum, as may 
 do best for the pattern, diluted for paler shades. 
 
 1 Three or four folds of blanket between the tin cylinder and the pieces are 
 necessary to absorb moisture. The same quantity must be applied to the out- 
 side of the pieces, otherwise the last piece would not get its due proportion of 
 steam. 
 
 2 For the description of resist-work see pages 542 to 545. 
 
 3 It may at first appear extraordinary to speak of any other than a white re- 
 sist ; but it will be noticed that they all four act as perfectly white resists in the 
 indigo blue vat ; it is afterwards in the madder-copper that the first only is in 
 
560 ON CALICO-PRINTING. 
 
 These are all printed one after the other on the calicoes, which 
 are then hung up in a cool room for two or three days, after which 
 they are taken and dipped blue in a neutral vat l , which is usually 
 set with one hundred pounds of good indigo ; the pieces are not 
 hooked on a frame, but passed through the vat in one minute and 
 a half for each piece, by means of rollers up and down, after the 
 same manner as the sal-ammoniac tub, described page 557. 
 Twenty or twenty-five pieces are fastened end to end by a wire, 
 and by this method they can be run through in less time than five 
 could be hooked on a frame. They are now taken to the wash 
 wheel and washed twice, then dunged and maddered in the me- 
 thod usually employed for madder goods, and afterwards yellowed 
 with berry yellow, as bark yellow is apt to injure the scarlet ground. 
 
 This style of work was a first produced about the year 1805, and 
 has sold more extensively than any print that ever came out. It 
 is not necessary for the printer to confine himself to red, black, 
 or blue grounds, as they can be* varied to any shade of orange, 
 olive, &c., by the addition of quercitron bark to the madder. In 
 the notes to the second volume of Dr.Ure's translation of Berthol- 
 let On the Art of Dyeing, this style is described under the name 
 of "Lapis" but the description is not quite correct : in fact, when 
 BerthoUet wrote that work, neither the French nor Swiss knew 
 how to do them ; but the printers at Mulhausen and Ghent have 
 since executed them in a beautiful manner, and sold them under 
 the name of " Lapis" 
 
 For best work in madder-grounds, viz., chocolate, black or 
 scarlet, it is necessary to pass the goods twice through the madder- 
 baths or coppers. If for instance fifty pounds of madder are re- 
 quired to dye ten pieces, thirty pounds of it are taken for first dye- 
 ing in cold water, and the pieces turned in it till the liquor arrives 
 at 190 in two hours or two and a quarter; they are then taken 
 out and washed ; this is called the scald, after which they are en- 
 tered again with the remaining twenty pounds of madder into cold 
 water, turned as before, and brought up to the boiling point in 
 two hours and a half: they should remain in the boiling liquor 
 five, ten, or fifteen minutes, as maybe required, and afterwards be 
 well washed and branned. 
 
 It has lately been discovered that the prussiate of potash of 
 commerce, being in reality the ferro-prussiate, contains a suffi- 
 ciency of iron to produce a beautiful madder purple, without em- 
 reality a resist, and the remaining three are mordants to produce three different 
 colours from one madder-bath. 
 
 1 Neutral vat is merely the technical term for the indigo vat employed in 
 neutral resist-work. Mr. Parkes gives a detailed account of the method of 
 setting an indigo vat in the preceding part of the Essay, pages 543 and 544. 
 The neutral vat is usually set in the first instance with one hundred pounds of 
 
ON CALICO-PRINTING. 561 
 
 ploying any acetate or other solution of iron whatever. The 
 process is, to dissolve one pound of prussiate of potash and one 
 pound of tartaric acid in a gallon of water ; thicken the clear li- 
 quor with starch, and then print the pattern on the calico with 
 your cylinder in the usual manner ; hang the pieces after printing, 
 'for one night, then steam them for ten or fifteen minutes, and 
 afterwards hang them for another night. Pass them now through 
 a cold and clear chloride of lime pit, upon a roller frame, in a 
 minute and a half; wash them well, and then run them for fifteen 
 minutes through water heated to 120 or ISO of Fahrenheit. 
 Wash afterwards, dye them as other maddered goods, bran, 
 white, and lastly croft or clear them. This is a very fast colour, 
 and can be executed to any shade required. 
 
 The next material improvement in madder colours left for me 
 to describe, and which, to be understood thoroughly, will require 
 considerable minuteness of detail, is that beautiful addition to our 
 previously known colours, chrome yellow on madder grounds. 
 It will be necessary first to explain the process required for the 
 preparation of the cloth. 
 
 To one gallon of Gallipoli oil, add twelve gallons of water with 
 four ounces of pearlash dissolved in each gallon ; pad your pieces 
 with this liquor five times successively, dry them each time over 
 the flue, and then hang them in a warm room for thirty- six hours ; 
 take care to stir the liquor whilst padding. 
 
 First steep. Prepare a clean vessel of water with one ounce 
 of pearlash dissolved in each gallon; warm it to 115 or 120, 
 enter the pieces, pushing them well over head in the liquor, and 
 cover them up with blankets for nine hours ; skim the liquor 
 before they are taken out, to prevent any dirt from adhering to 
 the cloth ; squeeze them as dry as possible, but let no water touch 
 them. 
 
 Second steep. Set the vessel again with pearlash liquor, and 
 proceed in every respect as with the first, calculating about two 
 gallons of liquor to each piece. 
 
 well ground indigo : for the first working of the vat one hundred and forty 
 pounds of lime and one hundred pounds of copperas are put in the night be- 
 fore it is worked ; afterwards the quantities may be regulated by the number 
 of pieces to be done on the following day. When the vat is new, sixty or 
 eighty pieces may be dipped on the first day, then add ten pounds of lime 
 and eight pounds of copperas and dip sixty or eighty more, and let the vat rest 
 one day. After it has dipped five hundred pieces it becomes too weak for 
 neutrals, and is set apart for more common or paler shades of blue; if for the 
 latter, it is yet strong enough to dip many hundreds. A neutral or any blue 
 vat for best work may be used warm, and heated to about 80 by passing a 
 steam pipe along the bottom; but this is not absolutely nscessary, excepting in 
 cold weather, though some houses work all their vats warm for dark blues and 
 neutrals. It is necessary to have three or four of these neutral vats. 
 
 2 o 
 
562 ON CALICO-PRINTING. 
 
 Third steep. Proceed exactly as with the first and second ; but 
 it is now necessary to squeeze the pieces, then to wash them well, 
 and to dry them in a warm stove ; on the next day put them 
 into a clean bath of hot water at 170 for fifteen minutes; repeat 
 this three times, drying and washing between each bath ; they 
 will now be quite fit for printing : and we shall describe the pro- 
 cess of rainbow shades, as they are called, a beautiful style of 
 printing, now become very common. 
 
 For Red, take acetate of alumina at 10 (No. 1 ) and thicken with 
 gum Senegal for darkest or first shade ; then take one measure of 
 No. 1, and add ten measures of gum water for second shade; 
 and one measure of the same (No. 1 ) and twenty of gum water for 
 third shade, and so on, reducing the original standard (No.l) by 
 ten measures of gum water for every lighter shade. 
 
 For Purples, use acetate of iron in the same way as acetate of 
 alumina for reds, and the admixture of these two mordants will 
 give chocolate shades. The reds and purples are all printed at the 
 same time with one dip of the block : the block is a plain surface 
 covered with cloth; the shades are spread upon a sieve by means of 
 a brush, the block is then accurately dipped upon it and placed 
 on the piece. I shall not attempt to describe the various modes 
 which are adopted for spreading the mordants on the sieve, as 
 scarcely two printers use the same method. 
 
 After printing, the goods must hang in a warm room for three or 
 four days at the least, or more if convenient. DUNG them over 
 rollers in liquor heated to 160, pass a piece per minute, and 
 then wash them well. 
 
 Branning. Set a vessel rich with bran, boil it for five minutes, 
 cool it down to 160, then turn the pieces in it for ten minutes, 
 and wash them well. 
 
 Dyeing. Take for a dyeing often pieces, two pounds of glue, 
 and allow seven pounds of fine old crop madder for each piece. 
 Commence with cold water, heating it gradually during the first 
 hour to 125, during the second to 180, and in a quarter of an 
 hour afterwards to the boiling point. Boil them fifteen minutes, 
 making in the whole two hours and a half; then wash them well 
 and squeeze them. 
 
 Tubbing after dyeing. Pour one quart of aquafortis at 32 of 
 Twaddell into a tub of fifty gallons of water. Turn five pieces 
 over a winch in this for ten minutes, let them then be well washed 
 and squeezed. Add now a gill more of the acid, and turn five 
 other pieces ; after thirty pieces are thus tubbed, pour off the liquor 
 and re-set the tub with fresh acid and water, as at first, proceed- 
 ing in the same manner with any quantity of goods that may be 
 required ; they must all at last be twice well washed in the wheel. 
 
 Clearing. 'Boil two hundred and fifty gallons of water in a 
 
ON CALICO-PRINTING. 563 
 
 clean vessel, and whilst boiling dissolve in it twenty pounds of 
 white soap ; enter ten pieces, and turn them for fifteen minutes at 
 an easy boil. Wash them well, and the madder dyeing will be 
 entirely completed. 
 
 To put a pattern of chrome yellow on the above red or purple 
 shades, take one gallon of nitrate of lead, five pounds of tartaric 
 acid dissolved in cold water, thickened, if you print with the block, 
 with British gum and pipe-clay ; but if you use the cylinder 
 machines, it will be necessary to use British gum only. After 
 printing, hang the pieces in a warm room for two or three hours. 
 
 Discharging. Having a vat ready prepared of a solution of 
 chloride of lime with excess of lime in water, standing at 10 
 or 12 of Twaddell and heated to 80, let the pieces be hooked 
 on to a dipping frame, and previous to their immersion, let the 
 vat be raked up till the liquor appears quite white. Dip your 
 frame in and keep it gently in motion for four or five minutes, 
 then rinse the pieces immediately in cold water over the winch, 
 and afterwards wash them well. The only process now remain- 
 ing will be 
 
 Chroming. In a clean tub, with a winch over it, holding 
 thirty or forty gallons of cold water, dissolve two ounces of bi- 
 chromate of potash to every gallon of water. Into this solution 
 enter the pieces, two at a time, over the winch, and turn them 
 for fifteen minutes, or till the yellow is sufficiently bright. 
 
 The alkaline preparation of the cloth for these rainbow shades 
 will also answer for plain ground Turkey-reds, if the padding 
 and steeping are well managed. For aluming and galling pieces 
 for plain reds, they may be either tubbed or padded, as best suits 
 the convenience of the party doing them. 
 
 All goods that are to be discharged for chrome yellows must 
 undergo the oil preparation, or the chloride of lime will materially 
 injure all the colours where it is not intended that they should be 
 acted upon. 
 
 There is another style of chrome yellows which varies a little 
 from the one which has just been described with such minuteness; 
 but in this also it is absolutely necessary to use prepared cloth. 
 The red mordant is acetate of alumina at 14, dunged, and dyed 
 full red, branned and cleared ; the drab is then printed on by 
 means of prussiate of potash and tartaric acid in equal quantities, 
 steamed twenty minutes, washed and dried. 
 
 The pattern by block is then printed in nitrate of lead and tar- 
 taric acid, after which it is dipped in a warm chloride of lime 
 vat, which converts the prussiate of potash stripe to a drab, except- 
 ing where the tartaric acid and nitrate of lead have prevented it. 
 
 It is now taken to the chrome tub and raised, when the lead on 
 the red becomes instantly yellow, and that on the drab green, 
 
 2 o 2 
 
564- ON CALICO-PRINTING. 
 
 having the appearance of being printed with two different blocks, 
 whereas only one has in reality been employed. 
 
 This is an exquisitely beautiful operation, and gives so many 
 ideas as to what it is possible to effect, that there really seem no 
 bounds to the varied tints that may be produced whenever a 
 renovation iii the state of trade shall give the spirited printer 
 some hope of reimbursement for the time, talents, and capital 
 which he must necessarily employ in pushing this elegant style 
 of work into the various ramifications of which it is capable. 
 
 I have lying by my side, whilst writing, specimens of this and 
 of every other style which I have described, and wish it were 
 possible to give coloured plates of them, as they would tend mate- 
 rially to elucidate the several processes; but I fear it will be found 
 impracticable. 
 
 Another excellent colour has been lately invented, and has 
 been produced in very large quantities ; I allude to the brown 
 from sulphate of manganese. The process is as follows : Reduce 
 the solution of sulphate of manganese to 15 (it is usually sold at 
 50), pad the pieces over a w r arm flue, and hang them in a cool 
 room twenty-four hours ; pass them then through caustic lye 
 at 14, and afterwards through hot water for a few minutes ; wash 
 and dry them. 
 
 Discharge. For the white, take muriate of tin 120 and 
 thicken with starch. For yellow, take nitrate of lead at 70, mu- 
 riate of tin 120, and starch. For blue, prussiate of potash, 
 muriate of tin, a little nitrate of iron, and thicken with saloup. 
 For pink, a strong decoction of Brazil wood, with two ounces of 
 muriatic acid per gallon, thickened with gum tragacanth, then add 
 one quart of muriate of tin 120 to three quarts of colour; wash, 
 dry, and finish. 
 
 For brown objects on white grounds, dissolve two pounds and a 
 half of brown salt (sulphate of manganese in powder] in one gal- 
 lon of water, to which add two pounds of sugar of lead and half a 
 pound of sulphate of iron; stirwell for three hours, and then let all 
 subside ; thicken with gum Senegal, and add a quarter of a gill 
 of Gallipoli oil to prevent it from frothing. Print the pieces, and 
 hang them for twenty-four hours, then pad them with caustic lye 
 at 12 over a cold flue, and wash well ; pass them through a clear 
 chloride of .lime vat at 4 in three or four minutes, then wash 
 again, squeeze, and finish. If the pieces can be laid on the grass 
 in the open air for an hour or two, it will much improve their 
 colour ; the sulphate of iron is merely to give an olive brown ; 
 without it, a reddish brown will arise, and iron liquor will pro- 
 duce another shade. 
 
 A common red mordant from machine work may be steamed 
 ten minutes the same day it is printed, and then hung one night ; 
 
ON CALICO-miNTlNG. 565 
 
 this management causes the mordant to penetrate the cloth, and 
 brings up the finest stippled work of the engraving. Chocolate 
 may be proceeded with exactly in the same way; but in all cases 
 it must be recollected that as a portion of the mordant is carried 
 off by the steam, it is necessary to use it stronger than you would 
 if it were not steamed. A purple produced from iron liquor will 
 not do steamed, but one from prussiate of potash, as described 
 pages 560 and 561, will be much improved thereby. 
 
 Considering that an Essay on calico-printing would be incom- 
 plete, without some detail of the process for dyeing Turkey-red, 
 I applied to Mr. John Thompson, of Glasgow, a highly esteemed 
 friend of Mr. Parkes, who is probably at least as well acquainted 
 with both its theory and practice as any individual in Great Bri- 
 tain. For the former he refers me to a paper which he published 
 in the Annals of Philosophy, vol. viii. page 463, and which he 
 says he has since seen no reason to deviate from. With respect 
 to the latter, he states that he can add nothing to the process 
 with which he furnished Dr. Ure, and which was published in 
 the notes to his translation of Berthollet, excepting he were to 
 give a practical detail of the manipulations, which differ at the 
 various manufactories, and which would fill a volume. He kindly 
 allows me to copy both, which I will therefore do in his own 
 words. The process which he adopts for one hundred weight of 
 cloth or yarn is as follows : 
 
 "1st. Boil the goods with white soap and pearlash, or soda 
 ley. Twelve pounds of white soap are dissolved in water in a 
 copper, along with six gallons of the ley, pretty strong ; the 
 boiling is continued for five or six hours. 
 
 " 2nd. The sheep' s-dung liquor. To make this, take twelve 
 gallons of soda liquor No. 3 (sp. gr. 1.015), two gallons Galli- 
 poli oil, six gallons sheep' s-dung, ^twenty-four gallons soda liquor 
 No. 5 (sp.gr. 1.025). 
 
 " Tramp the cloth or yarn well in this liquor, then hang it in 
 the air to dry, and next in the stove. This dunging is repeated 
 a second and a third time as above, drying the goods after each 
 repetition. 
 
 " The yarn or cloth is to be steeped all night in warm water 
 at 100 Fahr., with four gallons of soda liquor No. 12 (sp. gr. 
 1.060). Out of this, it is to be well wrung next morning, hung 
 in the air, and lastly dried in the stove. 
 
 " Take now twelve gallons of weak soda liquor No. 3 (sp. gr. 
 1.015), Gallipoli oil two gallons, soda liquor No. 5 (sp.gr. 
 1.025), thirty gallons; tramp the cloth or yarn in this "mixture 
 three or four times, then put in the air, and finish in the stove 
 every time. 
 
566 ON CALICO-PRINTING. 
 
 Steep Jbr clearing away the Oil. 
 
 " Steep the goods in warm water at 140 Fahr. with four gallons 
 of soda liquor for each cwt., wring it out next morning, wash 
 well and dry it ; when it is ready for the galls. 
 
 Gall Liquor. 
 
 " Take twenty -four or twenty-five pounds of nut-galls, and boil 
 them for eight hours; 'take the clear liquor and tramp the cloth 
 or yarn as warm through this liquor as the skin can bear ; wring, 
 put in the air, and then in the stove. 
 
 Alum Liquor. 
 
 " Take twenty-five pounds of alum, dissolve in warm water, add 
 four gallons of soda No. 12 (sp. gr. 1.060) ; next morning take 
 the clear liquor, put it into a copper, and warm it as hot as the 
 hands can bear ; tramp the stuff through this liquor, wring, and 
 put in the stove to dry. 
 
 Second Aluming as above. 
 
 " Steep the alumed goods in luke-warm water all night, next day 
 wash them well in the river ; then they are ready for drying. 
 
 To dye twelve dozen of Cloths (pieces}. 
 
 " Allow two pounds of madder to each pound of cloth, bring it 
 to the boiling point in an hour, and keep boiling for half an hour ; 
 then enter the goods into the copper, adding two gallons of blood 
 well mixed ; let the goods be now well washed and dried. For 
 the cue, take half soda and half pearlashes, half a gallon of oil, 
 and as much water as will bring the liquor to No. 6 of the hy- 
 drometer (sp.gr. 1.030), but the oil must have been previously 
 mixed with twelve gallons of soda liquor No. 3 (sp. gr. 1.015). 
 Put the goods through this liquor as through the white bath ; 
 wring, and stove-dry. 
 
 For Clearing. 
 
 " Fill a copper with clean water ; dissolve four or five pounds 
 of white soap in it, and half a pound of pearlashes ; boil slowly 
 from six to eight hours, then wash and wring the goods. Lastly, 
 fill a copper with clean water, adding a pound or two of white 
 soap, and boil the goods an hour or two. They are now finished." 
 
 Having thus given Mr. Thompson's account of his method of 
 dyeing Turkey-red, I cannot do better then transcribe his very 
 ingenious and satisfactory opinions as to a theory which from the 
 first period of its introduction to the present day has probably more 
 puzzled scientific men than any other application of chemistry to 
 the arts. Indeed so long ago as 1794?, I)r. Bancroft said that "it 
 is an unaccountable process that chemical analysis does not 
 elucidate." 
 
ON CALICO-PRINTING. 567 
 
 " Silk and worsted," says Mr. Thompson, " have a natural 
 varnish which cotton does not possess. To supply this defect, 
 the repeated immersions, followed by exposure to the atmosphere 
 and to the heated air of a stove, may give the oil the proper con- 
 sistency, by the absorption of oxygen, for forming a varnish, with 
 which the colouring matter unites, and through which it may be 
 said to shine, which causes that superior brilliancy which the 
 goods attain when they are cleared, or, as it may be called, po- 
 lished. I therefore presume that the fixedness and brilliancy 
 of the colour will depend on the quantity of oil imbibed, as every 
 repetition of drying presents new fibres to be varnished with an 
 additional quantity ; for I have always found that the permanency 
 was in proportion to the number of manipulations in the sapona- 
 ceous liquor, and a proportionable freedom could also be used in 
 reducing or clearing. The white immersions, omitting the sheep' s- 
 dung, are just applying successive coats of varnish. Clearing is 
 never attempted from the madder-copper, without immersing the 
 goods again in soda and oil, and drying them in a stove, which I 
 consider to be also supplying them with an additional coat. 
 
 " The alkaline ley occasions a greater separation in the particles 
 of the oil, by which it combines more closely with the fabric of 
 the cloth. The sheep' s-dung in the first immersions may serve 
 as a covering or great coat, to keep the goods moist for a consi- 
 derable time, that they may more fully imbibe the liquor, by 
 preventing the evaporation from being too quick in the great heat 
 to which they are exposed. 
 
 " After the frequent immersions the cloth feels like leather, no 
 doubt from a superfluity of liquor. It is then steeped in a ley 
 of carbonate of soda, and afterwards well washed and dried, as a 
 preparation for the galling and aluming. The astringent princi- 
 ple has been long known for darkening and fixing common red 
 colours on cotton, by uniting with the earth of alum, and 
 strengthening the basis. To the use of blood in the madder- 
 copper I attribute nothing ; as in the rancid and putrid state in 
 which I have seen it used, were it not for the prejudice of the 
 operator, it might be safely dispensed with. 
 
 " In proof of the above idea, that it is only the oil uniting with 
 the earth of alum that is of use, I may refer to the mode of dye- 
 ing that colour in the East, quoted by Dr. Bancroft, viz. soaking 
 their cotton in oil (no matter of what description) during the 
 night, and exposing it to the sun and air during the day, for seven 
 successive days, rinsing it only in running water, and then im- 
 mersing it in a decoction of galls and the leaves of sumach 
 previous to aluming. 
 
 " I would therefore request the practical dyer, who wishes to 
 arrive at a knowledge of this unaccountable process, to give up 
 
568 ON CALICO-PRINTING. 
 
 the idea of animalization, if by it be meant impregnating the 
 cloth* with an animal matter, and by the power of the microscope, 
 or any better method, look for the whole truth from some other 
 source than chemical analysis. I am at present inclined to believe 
 that it is a mechanical operation united to a chemical, and that 
 the frequent immersions in the imperfect soap are equivalent to 
 laying on the first, second, third, &c. coats preparatory to finish- 
 ing a fine painting in oil." 
 
 The operations with the Turkey-red most particularly con- 
 nected with calico-printing are, First, the discharging process by 
 means of perforated plates, which will be found particularly 
 described by Mr. Parkes in the preceding part of this Essay, 
 pages 550 551. Secondly/ the methods of discharging the Tur- 
 key-red, and supplying its place with other colours, as detailed 
 at great length in the specification of the patent granted to James 
 Thompson, Esq. of Clitheroe, in 1813. The object of this patent 
 was to discharge certain parts of the cloth, which had been dyed 
 Turkey-red, white, and afterwards to print those white parts of 
 any colours required, by the usual methods. This, Mr. Thomp- 
 son effected by first printing upon the cloth some vegetable acid, 
 metallic oxide, or acidulous salt, which had a stronger affinity for 
 lime than chlorine has, so that it would speedily decompose 
 chloride of lime or bleaching powder ; he preferred a mixture of 
 supersulphate of potash with citric or tartaric acid : when this 
 was printed upon the cloth to the required pattern, and dried, he 
 immersed the cloth in a solution of chloride of lime ; the acid 
 immediately seized upon and combined with the lime, thereby 
 disengaging the chlorine, which instantly deprived of their colour 
 those parts of the cloth which had been printed with the acid. 
 He thus describes his usual process : 
 
 First 9 he thickens in the usual way with starch, a gallon of pure 
 acetous acid, mixed whilst hot with five pounds of crystallised 
 tartaric acid ; or sometimes, instead of this, he thickens in the same 
 way a gallon of concentrated lemon juice (or two pounds and a half 
 of citric acid dissolved in a gallon of water), with two pounds of 
 supersulphate of potash added to it whilst hot. 
 
 Secondly, he prints on the Turkey-red cloth this paste in the 
 usual way. 
 
 Thirdly, he immerses the cloths when dry in a solution of 
 bleaching powder (sp. gr. 1.050), by hooking them on to a frame 
 called a dipping-frame, such as is used in dyeing indigo, taking 
 care that no two folds of the cloth touch each other, and keeps 
 them constantly moving in this liquor for five or ten minutes. He 
 then washes, brans, clears, and applies other colours according 
 to the usual methods employed by calico-printers. 
 
 In the year 1815, Mr. Thompson took out another patent for 
 
ON CALICO-PRINTING. 569 
 
 an improved process, by which he did not merely discharge the 
 original colour to a white, and then by a subsequent process ap- 
 plied other colours in the white spaces, but at once and by the 
 same operation he discharged the colour (be what it might, 
 excepting only Turkey-red), and at the same time applied a 
 metallic oxide or earthy base, which was itself a colour, or served 
 as a mordant to some colour to be afterwards produced. 
 
 His process was to print upon those parts of the cloth, which 
 he wished to deprive of one colour and to receive another, some 
 earthy or metallic salt, the acid of which, having a greater affinity 
 for lime than chlorine has, will disengage the chlorine ; and the 
 metallic or earthy base being deposited upon the cloth, will either 
 be itself a colour, or will act as a mordant to some other colour. 
 The cloth is then passed through the solution of bleaching pow- 
 der, as before described, washed, and the mordant (which may be 
 a salt of alumina, iron, tin, or copper, according to the colour or 
 colours wanted) is raised according to the usual operations of 
 dyeing. If for instance a yellow figure or stripe be wanted, 
 acetate of alumina is printed upon the cloth, which then passes 
 through the bleaching liquor, and is afterwards raised by quer- 
 citron bark or other yellow dye; and by the use of various 
 mordants great varieties of colours and shades may be obtained. 
 
 My additions to this Essay have extended further than I at 
 first contemplated ; but so great have been the changes and im- 
 provements since it was first published, that I considered it to be 
 incumbent upon me to give a brief summary of them : and calico- 
 printing being an art entirely dependent upon chemistry, I have 
 no doubt that it will continue, as it has hitherto done, to ad- 
 vance as rapidly as the science from whence it derives its very 
 being. EDIT. 
 
APPENDIX. 
 
 ADDITIONAL NOTES. 
 
 NOTES TO ESSAY I. 
 
 1. Invention of printing. Page 1, line 4. 
 
 " WE have a fact established beyond controversy, that WILLIAM 
 CAXTON, an eminent mercer and negotiator, first introduced the art of 
 printing with fusible types into England ; and some suppose that 
 Frederick Corsellis, or some other foreigner, used wooden types a few 
 years before him. He was succeeded by Wynkyn de Worde, who im- 
 proved the art very much, and first introduced musical notes, and (some 
 think) Roman numerals : but the Roman character was first used in 
 printing by Pynson, who was by extraction a Norman. The progress of 
 the typographic art among us was very rapid. Margaret, Duchess of 
 Somerset, or more properly Countess of Richmond and Derby, took it 
 under her patronage, and Pynson had a formal appointment to the office 
 of king's printer, in the beginning of the reign of her grandson Henry 
 VIII." Herbert's Preface to Ames's Typographic al Antiquities. The 
 first book known to be printed in England was by Caxton in the year 
 1474. The first by his successor, Wynkyn de Worde, appeared in 1494. 
 
 " The storied pyramid, the laurelled bust, 
 The trophied arch, had crumbled into dust ; 
 The sacred symbol, and the epic song, 
 (Unknown the character, forgot the tongue,) 
 Till to astonish'd realms Papyra taught 
 To paint in mystic colours Sound and Thought, 
 With Wisdom's voice to print the page sublime, 
 And mark in adamant the steps of Time." 
 
 2. The alchemists. Page 1, line 9. 
 
 The following proclamation respecting two noted alchemists was pub- 
 lished by King Edward III. A.D. 1329. " Know all men, that we have 
 been assured, that John Rows and Mr. William de Dalby know how to 
 
572 ADDITIONAL NOTES. 
 
 make silver by the art of alchymy j that they have made it in former 
 times, and still continue to make it ; and considering that these men by 
 their art, and by making that precious metal, may be profitable to us, 
 and to our kingdom, we have commanded our well-beloved Thomas Gary 
 to apprehend the foresaid John and William wherever they can be found, 
 within liberties or without, and bring them to us, together with all the 
 instruments of their art, under safe and sure custody.'' Rymer's Fcedera, 
 torn. iv. pag. 384. 
 
 So lately as the year 1784, Dr. James Price, F.R.S. of London, at- 
 tempted to revive the spirit of alchemy. He produced a red and a white 
 powder, with which he boasted that he could convert mercury into gold 
 or silver. He made several experiments before a number of respectable 
 persons ; but when the powders were exhausted, and he was importuned 
 on all sides to renew his powders and repeat his experiments, before men 
 of science, he swallowed laurel water and put an end to his existence. 
 Crell's Chemical Annals, 1784. 
 
 3. Soap waste. Page 4, line 39. 
 
 The use of soapers' ashes as a manure, was known more than 200 
 years ago, though it is a commonly received opinion that its application to 
 this purpose is a modern invention. In Platt's Jewel House of Art and 
 Nature, 4to, London, 1 594, page 77, is a wood-print engraving of an ear 
 of corn that was produced from a field which had been enriched with 
 this manure. The writer of the work also states that a good mortar for 
 building maybe made by a mixture of two loads of such ashes, one of lime, 
 one of loam, and one, of Woolwich sand. He says that just before he 
 wrote, a soap-boiler at Aldgate built a large house for his own family 
 with such mortar, in order to encourage others to buy soap-ashes for the 
 same purpose. 
 
 4. Metallic oxides. Page 5, line 26. 
 
 In the beginning of the 17th century, Jean Rey, a physician at Peri- 
 gord, published a work, which is now extremely rare, to prove that the 
 increase which metals acquire in calcination arises from the air. An 
 apothecary at Bergerac having informed him that two pounds of fine 
 tin, during six hours calcination, had increased seven ounces in weight, 
 he answers, " This increase of weight proceeds from the air, which mixes 
 with the calx, and attaches itself to its minutest particles, in the same 
 manner as water adheres, and adds weight, to those of sand." See 
 Hosier's Journal, torn. v. Paris, 1777. This writer surely discovers great 
 sagacity for the time in which he lived ; for he must have preceded 
 Mayow nearly half a century, whose celebrated Tractatus quinque were 
 not published till the year 1 674. A copy of Key's book was lately dis- 
 covered in Paris, and an English translation of it has lately been printed 
 in the Journal of Science, Literature, and the Arts. 
 
 5. The blood. Page 6, line 11. 
 
 The source of the iron in animal blood is very mysterious ; for it is well 
 known that the quantity maybe increased either by medicine or exercise. 
 " In hard-working people," says Mr. Johnson, " the red particles 
 abound ; and by the exercise of particular parts, the same takes place, as 
 
ADDITIONAL NOTES. 573 
 
 in the wings of those birds accustomed to fly, and in the legs of those ac- 
 customed to walk a great deal." Johnson's Animal Chemistry , vol. i. 
 page 42. 
 
 6. Morocco leather. Page 13, line 1. 
 
 The manufacture of Russia leather is not thoroughly understood in 
 England. The best account of the process hitherto published, is in 
 Tooke's View of the Russian Empire, 8vo, London, 1799, vol. iii. page 
 514. A respectable tanner in the North of England informed me that 
 there is more of the tanning principle in the root of the common plant 
 called Burnetj the Sanguisorba of Linnaeus, than in oak bark. It is a 
 plant that bears a red flower, and was, a century ago, the clover of the 
 day. He thinks it might be cultivated for cattle, as they are all fond of 
 it -j and that it might be plowed up every three years in order to collect 
 together the roots for the purpose of tanning. 
 
 7. Intense light. Page 15, line 28. 
 
 It is so important to obtain an intense light at the public light-houses, 
 that great expense has been incurred in the construction of reflectors of 
 silver. It has occurred to me that strontites and some other substances 
 might be employed to make coloured lights for greater distinction in hazy 
 nights or foggy weather. If moisture be present in the mixture of stron- 
 tites with inflammable bodies, the flame will be of the colour of carmine. 
 Thus, if any of the salts of this earth be dissolved in alcohol, the spirit 
 will burn with a flame of this colour. In like manner the flame of any of 
 the salts of barytes, under similar treatment, will produce a brilliant 
 yellow flame, and boracic acid a flame of a beautiful green colour. It 
 has long been known that strontites, barytes, and boracic acid, will pro- 
 duce these colours, but I have not heard of their being used for this pur- 
 pose. 
 
 8. Scientific brewer. Page 16, line 34. 
 
 Since this edition went to press, the 57th and 60th numbers of the 
 " Library of Useful Knowledge" have appeared, containing the very best 
 and most scientific treatise on " The Art of Brewing" that has ever been 
 laid before the'public } who are, I believe, indebted for it to the able pen of 
 Mr. David Booth, author of the " Analytical Dictionary of the English 
 Language,'' and other works. 
 
 Its perusal will materially assist every person who has a wish to 
 understand the subject either theoretically or practically ; he will find a 
 detailed account of the process in all its parts, accompanied with draw- 
 ings of the utensils and apparatus, a description of the necessary philoso- 
 phical instruments, of the ingredients allowed by law to be used, and of 
 the illegal ingredients, distinguishing those which are wholesome, and 
 which if allowed would be improvements, from those which are delete- 
 rious, and employed only by worthless and unprincipled brewers. All 
 the needful manipulations are minutely detailed, as is also a process by 
 which raw grain may be used as a substitute for malt, or rather may be 
 converted into malt in the mashing tub instead of the malting floor. 
 Although this important discovery may be employed by private families 
 who brew^at home, the absurd prohibitions of the Legislature prevent not 
 
574? ADDITIONAL NOTES. 
 
 only this but any other improvement from being adopted by the public 
 brewer whilst the present code of excise laws remains in existence. 
 
 This writer has also invented an improved saccharorneter, which to 
 private families in particular will prove of inestimable advantage ; effec- 
 tually preventing the uncertainty and disappointment now so frequently 
 experienced by those who brew at home, in the quality and strength of 
 their ale, arising from variations in the goodness of the malt and other 
 causes. For a particular description of this valuable instrument, which 
 no family ought to be without, who in brewing their own beer are not 
 regardless of economy and careless of quality, I must refer the reader to a 
 pamphlet, entitled " Description and Use of the Brewer's Saccharometer, 
 #c. #c." sold, together with the instrument, by Baldwin and Cradock. 
 Price two guineas. EDIT. 
 
 9. Sugar. Page 17, line 41. 
 
 Sugar is said to contain more nutriment in a given bulk than any 
 other known substance. For this and other reasons it would be a proper 
 article, when corn is scarce, for feeding cattle, if Government would remit 
 the duties. In consequence of such an intention having been entertained, 
 (in the summer of the year 1808,) I underwent several examinations by a 
 committee of the house of commons, and at their request undertook a 
 series of experiments upon sugar, and also drew up a memoir on the 
 subject, which the committee ordered to be printed, accompanied with 
 their own remarks, for the use of the members of the house. As this 
 memoir contains a variety of new experiments on the nature of sugar, 
 and several curious facts not generally known, I embrace this oppor- 
 tunity of referring to the paper, which will be found in the fourth Report 
 of the Honourable the West India Committee to the House of Commons, 
 and also in the Philosophical Magazine, where it was reprinted in Sep- 
 tember of the same year. 
 
 10. Zinc. Page 18, line 29. 
 
 I would recommend it to those who have occasion for large quantities 
 of hydrogen-gas to use zinc instead of iron j it not only produces a purer 
 gas, but the sulphate of zinc (white vitriol) that results from the process 
 would indemnify the operator for his expense in purchasing the materials ; 
 whereas, when iron is used, the residuum is of little value. 
 
 Hellot speaks of the deleterious powers of zinc, but 1 do not know that 
 any other writer has considered this metal to be poisonous. A few years 
 ago a mine of zinc-ore was discovered on Lord Ribblesdale's estate at Cra- 
 ven in Yorkshire. This ore is found there in a state of such purity as to 
 have been sold as a substitute for white lead in painting. In the year 1805, 
 Messrs. Hobson and Silvester of Sheffield obtained a patent fora method 
 of manufacturing zinc into wire, also into vessels of capacity, and into 
 rolled plates for a variety of purposes. Zinc is a brittle metal at the 
 temperature of the atmosphere ; but these gentlemen discovered that 
 when it is heated to 220, and from that to 300, it becomes malleable, 
 and capable of enduring the rolling press or the hammer. 
 
 11. Black-ash. Page 19, line 11. 
 Black-ash is prepared by the following process. The waste lye which 
 
, ADDITIONAL NOTES. 575 
 
 is pumped out of the boiler of the soap manufacturer, is evaporated in 
 large pans of wrought iron,, until the salt separates from it, which is 
 removed as it precipitates. These salts, usually consisting of the sul- 
 phate, muriate and sebate of soda and potash, are then taken to a rever- 
 beratory furnace, where they undergo a heat sufficient to melt and par- 
 tially decompose them j and when they are in a state of pasty fusion a 
 hole is opened in the side of the furnace, through which the matter flows 
 into an iron pan placed underneath to receive it. This saline mixture, 
 freed from much of its impurity by the process, becomes a ponderous and 
 solid mass as it cools, and in this state it is sold again to the soap-boiler 
 for the manufacture of common yellow soap. 
 
 12. Salt-petre. Page 20, line 1. 
 
 Salt-petre might probably be made to considerable advantage in certain 
 situations in Great Britain. Wherever stables or cow-houses are so si- 
 tuated that the floors, on one or more of the sides, are considerably above 
 the surface of the ground, an abundant efflorescence of salt-petre will 
 generally be found between the joinings of the bricks, it being formed 
 from the urine of the cattle, assisted by the combined action of the air 
 and the lime of the mortar used in the construction of the buildings. A 
 particular account of the method of collecting and crystallizing salt-petre 
 in the East Indies will be found in the Philosophical Transactions for 
 1665, p. 103. 
 
 A most interesting detail of the methods by which a very extraordinary- 
 collection of salt-petre was formed throughout the several provinces of 
 France, in a case of great emergency, is printed in the Tradesman, or 
 Commercial Magazine, vol. ii. p. 533. 
 
 NOTES TO ESSAY II. 
 13. Enlarging its bulk. Page 30, line 24. 
 
 The expansive force of water when in the act of freezing is a curious 
 subject. Many interesting particulars will be found in Mr. Boyle's work 
 already quoted, in pages 86, 90, 204, &c. A modern traveller has also 
 noted the following circumstances which occurred in Canada in the win- 
 ter of 1 806 or 1 807. " Experiments," says he, " have been made on iron 
 shells, by military men, to ascertain the expansion of freezing water. 
 After having nearly filled the shells with water, iron plugs were strongly 
 driven in at the fuse-hole by means of sledge hammers ; but they could 
 never be so firmly fixed as to resist the expanding ice, which some time 
 afterwards pushed out the plugs with great force and velocity j a bolt or 
 cylinder of ice immediately shooting up from the hole. When a plug was 
 used with springs to lay hold of the inside of the shell, so that it could not 
 possibly be pushed out, the force of the expansion split the shell. The 
 great distance to which these iron plugs were thrown shows the amazing 
 power of the expansion of frost; a plug of 2|lbs weight being thrown 
 415 feet from the shell." Letters from Canada, by Hugh Gray, 8vo, 
 London, 1809. 
 
576 ADDITIONAL NOTES. 
 
 14. Change of temperature. Page 31, line 21. 
 
 Not only animals and vegetables, but mineral bodies also, are affected 
 by the changes of atmospheric temperature. .Metals are well known to 
 expand or contract by such alteration ; and in the 75th volume of the 
 Philosophical Transactions, General Roy has shown that the expansion 
 of the steel pendulum of u clock is such, that every four degrees of the 
 thermometer will cause a variation of a second per day in the going of 
 the clock. See an Essay on this subject in Nicholson's Journal, 4to, 
 vol. i. p. 56. Brass wire will be absolutely altered in its nature, merely 
 by being suspended in a damp atmosphere. Madame Roland describes 
 a very singular krnd of harp which she says she saw in the garden of Mr. 
 Haz, type-founder at Basle in Switzerland, which must have been made 
 on this principle of expansion. " It is composed," she says, " of fourteen 
 wires, closely disposed, fastened at one end to a pavilion, and at the other 
 to a wall at the extremity of the garden, and at the distance of about 500 
 feet. The variations of the temperature of the atmosphere excite the vi- 
 brations of these wires, and make them sound in a singular manner. In 
 settled weather, constantly fair, or constantly rainy, the instrument is 
 silent. If any change is to happen, if any distant storm is rising, of 
 which no appearance is yet perceived, if contrary winds are ready to 
 contend for empire, the aerial music begins, and thus announces the re- 
 volutions of its element sometimes twenty-four hours beforehand." 
 Madame Roland's Tour through Switzerland. 
 
 15. Impaired by boiling. Page 97, note 1, line 3. 
 
 In making decoctions of dye-woods, it is often important not to exceed 
 a certain temperature ; but this is very difficult to *>e attained by boiling 
 them over a naked fire. Recourse has therefore been had to the expe- 
 dient of conducting these processes by the agency of steam. It has how- 
 ever been found, that where vessels are heated by the steam being thrown 
 within-side them, the contents cannot be made hotter than within one or 
 two degrees of the boiling temperature j whereas if one vessel be fitted 
 within-side another vessel, and the cavity between them be regularly sup- 
 plied with vapour from a high-pressure steam-engine, and accurately 
 closed so as to preserve every portion of the steam from escaping, the water 
 or other liquid in the inner vessel will be readily brought to a full boiling 
 heat, and it will acquire this temperature even much sooner than a similar 
 vessel with its contents would, if placed over an open fire, or fixed in a 
 common furnace of brick-work as boilers usually are. 
 
 Being some time ago at a large manufactory in the North of England, 
 where the proprietors are as obliging and communicative as they are sci- 
 entific and intelligent, 1 took the opportunity of making some experi- 
 ments as to the time that vessels of this latter construction require, in 
 order to be fully heated by steam. These gentlemen have a row of five 
 small coppers, purposely for making colours, and they are as completely 
 fitted up as could well be devised. An iron pan that has a broad flange 
 is first set in the brick- work, with a furnace door as usual. Within this 
 iron pan a smaller one of copper is fixed, having a small flange by which 
 
ADDITIONAL NOTES. 577 
 
 it hangs so as to preserve it about an incli from the outer one in every 
 part. A strong hoop of wrought iron is then laid upon the flanges of 
 both, with a layer of cloth between, and riveted on, so as to make the 
 whole air-tight. A steam-pipe communicates with the outside of each 
 of these copper boilers ; therefore, by merely turning a small cock, the 
 steam rushes into the space between the two vessels, and heats in a few 
 minutes the copper pan with its contents. 
 
 The vessel I made choice of for my experiments measures 18 inches 
 deep, 20 inches in diameter at the top, and is of a capacity to hold 20 
 gallons. This was filled with cold water taken immediately from the river, 
 the temperature of which was at 52 of Fahrenheit. When the steam 
 had been turned on six minutes, the 20 gallons of water were raised from 
 52 to 190, in two minutes more to 200, in other two minutes to 208, 
 and in one minnte more, making in the whole eleven minutes, to 2 12. 
 
 Being desirous, however, of taking the temperature at shorter intervals, 
 I fixed upon another copper of the same dimensions, that was fitted up in 
 the same way j and as this, like the former, was quite cold, not having 
 been used for some time, it was very proper for my purpose. 
 
 When 20 gallons of water at 52 were measured into it, the steam was 
 turned on, and the time accurately noted by a stop-watch. 
 
 The water rose, 
 
 in 1 minute, to 82 in 6 minutes, to 176 in 10 minutes, to 206J 
 
 2 minutes, 
 
 to 108 
 
 64 
 
 182 
 
 104 . 
 
 208 
 
 3 .. . . 
 
 . 128 
 
 7 :: 
 
 ..188 
 
 11 .. 
 
 209 
 
 34 
 
 137 
 
 71 
 
 . ..193 
 
 Ill 
 
 210 
 
 4- 
 
 . 146 
 
 8 
 
 . .. 198 
 
 * 2 
 
 12 
 
 . 2104 
 
 4 
 
 . 154 
 
 84 .. 
 
 201 
 
 124 . 
 
 .. 211 
 
 5 
 
 ..162 
 
 9 
 
 203 
 
 13 
 
 212 
 
 54.. 
 
 . 169 
 
 9' 
 
 . 205 
 
 
 
 This vessel was in the form of an inverted bee-hive, with the bottom 
 brought to a small point ; that in preparing colours any sediment might 
 be the more readily collected together and removed. The outer vessel is 
 of cast iron, the inner as before said of copper, with a space of about an 
 inch between them. A pipe is adapted to the bottom of the outer vessel, 
 with a stop-cock for occasionally drawing off the water that proceeds from 
 the condensed steam ; for, if this be not done frequently, it retards the 
 heating of the inner vessel. To the want of proper attention to this I 
 attribute the difference in the time which was required in these experi- 
 ments to bring the water to a boiling heat; for, though both vessels were 
 of the same capacity, the one boiled in eleven, whilst the other required 
 thirteen minutes ; though the treatment in every other respect was the 
 same. The outer vessels are lapped over with straw, and so are the con- 
 ducting pipes j and both are then neatly plastered with mortar, to pre- 
 vent any unnecessary escape of caloric. The main pipes are of cast iron, 
 screwed together by double flanges; the smaller pipes are of lead 
 although copper is better for these, lead being very liable to bend and 
 become out of order. 
 
 In preparing some of the colours for calico-printing, the decoctions are 
 boiled with flour-paste for a very considerable time, until the whole be- 
 
 2 P 
 
578 ADDITIONAL NOTES. 
 
 comes a thick mass. In this process, if the heat be given as usual by a 
 coal fire underneath the vessel, it is extremely difficult, if not impossible, 
 to prevent the matter from burning in some measure by its adhesion to 
 the sides or the bottom of the pan, and this never fails to attect the beauty 
 of the colour, independently of the loss that is sustained by that portion 
 which actually becomes carbonized by the accident. Now, wherever 
 steam is employed in preparing colours, this effect cannot happen j and 
 though the colour may perhaps be injured by its being treated at too 
 high a temperature, it can never suffer by burning to the bottom of the 
 vessel j for the heat is equal in every part, and can never be so great as 
 to produce this effect. 
 
 A very complete apparatus for the preparation of pharmaceutical ar- 
 ticles by means of steam, has been erected by the Company of Apothe- 
 caries, at Apothecaries' Hall, London, and found very useful and highly 
 economical. 
 
 Indeed, for most of those processes that would require no higher tem- 
 perature than that of about 208 any common culinary utensil, either of 
 earthenware or metal, might be employed, and this would fully answer 
 for most purposes. 
 
 16. Hot-pressed. Page 97, line 21. 
 
 A considerable expense and some uncertainty attend the operation of 
 hot-pressing that species of stuff goods called bombazets, besides a waste 
 of heat that is truly surprising. It has occurred to me that an important 
 improvement might be made in the process, and therefore I think it right 
 to describe the operation as it is now conducted, and then suggest the 
 alteration I would recommend. In the manufactory which I had the op- 
 portunity of inspecting, they have six very powerful presses, each of which 
 will contain at least thirty pieces of goods when piled singly one above 
 the other, with a cast-iron plate one inch thick between each piece. As 
 the pressure would not produce the desired effect without heat, they ob- 
 tain this by heating the iron plates preparatory to the operation. For 
 this purpose they have two very large ovens, each of which has an iron 
 bottom several inches thick j and when these ovens are to be used, fires 
 are lighted underneath them, and kept burning until the bottom becomes 
 of an intense red heat. These ovens are for the express purpose of heat- 
 ing the iron plates j but as the workmen have no means of ascertaining 
 with accuracy when they are of a proper heat, they usually keep them in 
 the oven until they are nearly red-hot j they are then drawn out, and the 
 heat lowered, by placing a cold plate of iron between each of them. In 
 this state they remain for an hour or two, exposed to the cold atmosphere, 
 till the superadded plates become nearly of the same temperature. But 
 notwithstanding this precaution, they are often found too hot to put be- 
 tween the goods at a time when the presses are emptied to receive them ; 
 they are therefore sprinkled with water to cool them to that particular 
 point when they may be used with safety. The iron plates which I saw 
 employed, were twenty-one inches long, ten inches wide, and one inch 
 thick. The pieces of bombazets are folded with a sheet of that kind of 
 glazed pasteboard known by the name of press paper, placed between 
 each fold ; and when the whole piece is thus folded up, it is of a proper 
 
ADDITIONAL NOTES. 579 
 
 width and length to be exactly covered by three of these hot iron plates 
 laid side by side of each other. When a piece thus folded is placed in 
 the press, and covered with three of the iron plates, another piece is laid 
 upon it, which is covered with plates in like manner ; and this alternate 
 arrangement of the manufactured goods and the iron plates is continued 
 until the press becomes full. 
 
 It appears to me that it would be easier and cheaper to have steam 
 chests adapted to each of the four sides of these presses, and also between 
 the goods occasionally, if the steam at the sides only should be found to 
 be insufficient. 
 
 NOTES TO ESSAY III. 
 
 ON SPECIFIC GRAVITY. 
 
 17. Purity of the metals. Page 105, line 7. 
 
 In the year 1 670, Mr. Smethwick, a Fellow of the Royal Society, 
 published a table of the weights of a cubic inch of several of the metals, 
 which was printed in one of the early volumes of the Transactions of the 
 Royal Society. It was afterwards published in a small octavo volume, 
 entitled The Secrets of the Goldsmith's Art" London 1676. Dr. Mus- 
 grave also published a table of the specific gravity of various bodies, 
 from experiments made hydrostatically. See Philosophical Transactions, 
 No. 1 69. Mr. John Gas wall, in the year 1 693, likewise published a table 
 of specific gravities, under the signature of J. C. This was printed in 
 the Phil. Trans. No. 199. 
 
 NOTES TO ESSAY IV. 
 
 ON BARYTES. 
 
 18. Sulphate of barytes. Page 124, line 16. 
 
 In addition to the various kinds of native sulphate of barytes already 
 mentioned, it may be proper "to notice the foliated baro-selenite of Kirwan, 
 or what Jameson calls the straight lamellar heavy spar ; because it has 
 been applied to some peculiar uses to which the other species are not 
 applicable. It occurs massive as well as crystallized in different forms, 
 and of a great variety of colours. It is found in veins in the different 
 primitive rocks -, and beautiful crystallized varieties are brought from the 
 lead mines of Cumberland, Durham and Westmoreland j it is known also 
 on the continent of Europe and in America. It is sometimes used as a 
 dressing for land ; and when burnt and finely ground, it has been used 
 instead of bone-ash for making cupels. The white varieties of the foli- 
 ated baro-selenite have been employed as white colours in painting, and 
 for pastil -pencils ; and it has sometimes been used as a flux for ores of 
 particular kinds. 
 
 "The granular baro-selenite is one of the rarer species of this genus 
 of ponderous earth. That of Peggau in the duchy of Stiria occurs of a 
 beautiful milk-white colour, is massive, resplendent, finely grained, semi- 
 indurated, and brittle. It bears a very strong resemblance to the white 
 
 2 r2 
 
580 ADDITIONAL NOTES. 
 
 fine-grained Carara marble, to such a degree, that, by its mere appear- 
 ance, it might easily be mistaken for it, were it not for its greater specific 
 gravity, which is 4.380, and by which it is readily distinguished." 
 KlaprotlisAnalyi. Essays, vol. i. p. 375. On analysis it is found to consist 
 of barytes 60, sulphuric acic! 30, and silex 10. 
 
 19. Barytes and strontites. Page 138, line 1. 
 
 Having in the Essay on Barytes adverted only to the most striking 
 marks of difference between that earth and strontites, I am desirous in 
 this place of noticing the other differences which have been observed 
 respecting them. 
 
 Muriate of strontites is much more soluble in hot water than in cold j 
 muriate of barytes, on the contrary, is nearly as soluble in cold water as in 
 hot, and crystallizes by evaporation. An ounce of pure water at 70 dis- 
 solves 9 drachms and 50 grains of the former salt ; whereas the same 
 quantity of water at the same temperature, only dissolves 3 drachms and 
 35 grains of the latter. The former produces 25 of cold by its solution j 
 the latter not more than 5. Carbonate of barytes is highly poisonous j 
 carbonate of strontites may be taken internally without danger. The 
 usual colour of carbonate of barytes is a yellowish or grayish white ; the 
 colour of carbonate of strontites is usually light green, though it is some- 
 times found colourless and transparent. ' When both these native salts 
 are submitted to heat, it is found that the carbonic acid is less strongly 
 retained in the carbonate of strontites than in that of barytes. See Pel- 
 letier's Observations on Strontites in the Annales de Chimie, torn. xxi. 
 p. 1 13 ; or Nicholson's 4to Journal, vol. i. p. 518, &c. 
 
 NOTES TO ESSAY VI. 
 
 ON CARBON. 
 
 20. The diamond. Page 149, line 3. 
 
 In the year 1745, Mr. John Ellicott, F.R.S. ascertained the specific 
 gravity of 14 large diamonds, with a pair of assay scales, which very sen- 
 sibly turned with the 200dth part of a grain, and the mean of his experi- 
 ments gave a specific gravity of 3.517. See the Philosophical Transac- 
 tions^ No. 47 6. For an explanation of the principle on whicli the diamond 
 carat weight was originally constructed, see Dr. Davies's Tables of Spe- 
 cific Gravities, 4to, London 1/50, p. 19. 
 
 The largest known diamond is that, mentioned by Tavernier, in the 
 possession of the Great Mogul. Its size is about that of half a hen's 
 egg -, it is cut in the rose form, and when rough, weighed 900 carats. It 
 was found in Golconda about the year 1550. The Pitt diamond be- 
 longing to the Crown jewels of France is the most perfect and beautiful 
 diamond yet found} it weighs 136 carats, and was purchased for 
 100,000/., and is now valued at double that sum. 
 
 The ancients were unacquainted with the art of cutting the diamond. 
 The four large diamonds that ornamented the clasp of Charlemagne's 
 mantle, which is still preserved in Paris, are uncut octohedral crystals. 
 
ADDITIONAL NOTES. 581 
 
 The primitive form of the diamond is the regular octohedron, each tri- 
 angular facet of which is sometimes replaced by six secondary triangles, 
 bounded by curved lines, so that the crystal becomes spheroidal, and 
 presents 48 facets. Diamonds with 12 and 24 facets are not uncommon. 
 Brande, vol. i. p. 415. The transparent snow-white diamond is con- 
 sidered to be the most valuable ; the green and yellow varieties are also 
 much esteemed, and the least valuable are the gray and brownish varie- 
 ties. Black diamonds are the most rare, and consequently are much 
 prized by collectors. Jameson's Mineralogy, vol. i. p. 1 14. 
 
 21. Gunpowder. Page 162, line 26. 
 
 Before the introduction of gunpowder, a highly inflammable com- 
 pound called the Greek fire was in use 5 and this, having the pro- 
 perty of burning under water, could not easily be extinguished ; conse- 
 quently it did surprising execution. In the 12th century the Emperors 
 of Constantinople used to send quantities of this dreadful combustible 
 to princes in friendship with them, as the most valuable present they 
 could give them, and the greatest mark of their favour. This was con- 
 sidered to be so important an article of offence, that the use of it was 
 continued long after the introduction of gunpowder ; for it appears, 
 when an English army commanded by the Bishop of Norwich besieged 
 Ypres in the year 1383, the garrison defended themselves so well with 
 stones, arrows, Greek fire, and certain engines called guns, that they 
 obliged the English to raise the siege with such precipitation, as to leave 
 their great cannon, which were of inestimable value, behind them. 
 Walsingham (Thomas), Historia Brevis ab Edwardo I. ad Henricum V. 
 folio, London 1574, p. 303. 
 
 Iron cannon were not made in England for a long time after they 
 had been in use on the Continent, as the first foundry of this kind is said 
 to have been formed in 1535 by an individual of the name of Owen ; and 
 in the year 1547 one Pierre Baudet, a foreigner, cast-iron cannon in the 
 neighbourhood of London. The first reference in Rymer to the use of 
 iron cannon balls is in J 530. Rymer's Foedera, vol. xv. p. 18. 
 
 22. Mire. Page 163, line 2. 
 
 "The History of the making of Saltpetre, by Mr. Henshaw," together 
 with directions how to proceed in refining it, was published in Sprat's 
 History of the Royal Society, 4to, p. 260 276. An elaborate memoir 
 by Chaptal, on the formation of saltpetre and the establishment of arti- 
 ficial nitre beds, will be found in the Annales de Chimie, tome xx. 
 p. 308 369. An account of the French method of procuring saltpetre 
 since the Revolution, may be seen in the Tradesman's Magazine, vol. ii. 
 p. 533. 
 
 In the xixth volume of the Annales de Chimie, p. 365, it is announced 
 that M. Lowitz has published in Crell's Chemical Annals for the year 1 792, 
 a new Essay on the purification of saltpetre by powdered charcoal. 
 
 23. Ink of the ancients. Page 172, line 42. 
 A writer of the 16th century recommends "the preparation of an 
 
582 ADDITIONAL NOTES. 
 
 aqueous decoction of galls, and that when ink groweth thick, to thin it 
 with this rather than with beer, vinegar, or any other fluid." Platt's Jewel 
 House of Nature and Art, p. 43. There is great room for improvement 
 both in the manufacture of writing- and printing-ink. Dr. Lewis has 
 written on both these kinds of ink with great knowledge of his subject. 
 See the Commercium Philosophico- Technicum, p. 37 1 40 1 . It seems ex- 
 traordinary, but for a long time much finer ink for the use of the printer 
 was manufactured at Madrid than in any other part of Europe. " The 
 art of printing was carried into Spain by the Germans, who travelled from 
 city to city with their types and presses. Ibarra, who is well known by 
 his superb edition of Don Quixote in four volumes 4to, employs an ink 
 so superior to all others, that our printers have often endeavoured to dis- 
 cover the secret of its composition, the works which he published having 
 rivalled those of the renowned Bodoni of Florence. Punches, matrices, 
 types and paper, are all fabricated in Spain, not only at Madrid, but also 
 in several of the provinces ; where the Spanish presses have produced 
 editions of books not less fine than that of the Sallust printed by Don 
 Gabriel the younger." See The Campaigns of the French Armies in Spain 
 and Portugal in the Years 1808 and 1809, with a statistical Description 
 of those Kingdoms, 8vo, Paris 1809. Excellent directions by Desor- 
 meaux for making good writing-ink may be seen in the Philosophical 
 Magazine, vol. v. p. 158. Some important remarks by Ribaucourt on the 
 same subject will be found in the Repertory of Arts, vol. ix. p. 205. 
 
 NOTES TO ESSAY VII. 
 
 ON SULPHURIC ACID. 
 
 24. From sulphate of iron. Page 213, line 2. 
 
 I have stated that the sulphuric acid formerly made in this country 
 was procured from sulphate of iron ; but I forgot to notice that the oil 
 of vitriol which is prepared in this way, gives out acid fumes when it is 
 exposed to a damp atmosphere. It also congeals sometimes and cry- 
 stallizes as it were, and hence such acid acquired the name of glacial oil 
 of vitriol. From these circumstances it is evident that it must differ in a 
 considerable degree from the sulphuric acid as it is now usually prepared. 
 Dr. Thomson considers it to be of greater strength than the common sul- 
 phuric acid, that it is pure anhydrous acid j but Professor Brande thinks 
 it more probable that it consists of sulphuric acid, combined with a por- 
 tion of sulphurous acid. The subject deserves further examination, 
 especially as so much sulphuric acid is now made by a patent process 
 from martial pyrites or sulphuret of iron. 
 
 25. Martial pyrites. Page 213, line 16. 
 
 In the year 1818 Thomas Hills and Uriah Haddock, of Bromley in the 
 county of Middlesex, obtained a patent for making sulphuric acid from 
 martial pyrites, or other native sulphurets, without the use of nitre. The 
 process consists in submitting these native productions to a red heat in 
 
ADDITIONAL NOTES. 583 
 
 a reverberatory furnace, and conducting the fumes arising from the com- 
 bustion into a leaden chamber formed as usual, arid with the floor covered 
 with water. As these patentees have made offers to various other manu- 
 facturers to sell them the right to make use of this process, they have 
 stated that the sulphur passes in the act of combustion at once into the 
 state of sulphuric acid, without the aid of nitre. 
 
 Having expressly written on the manufacture of sulphuric acid, I have 
 thought it right to apprize my readers of the existence of this patent, and 
 to give it as my decided opinion, that what they profess to do is utterly 
 impossible. I know Messrs. Hills have a large establishment for the 
 production of sulphuric acid from iron pyrites, and that the sulphuric acid 
 they make is of very good quality ; but I believe it is not made without a 
 considerable quantity of nitre, though they have thought fit entirely to 
 omit the mention of that article in their specification. They speak of 
 throwing steam and some imponderable substance into the leaden cham- 
 ber occasionally ; but what this imponderable substance can be, it is im- 
 possible to imagine, as it is well known that nothing except nitre has yet 
 been discovered, that can with economy be employed to convert sulphu- 
 rous to sulphuric acid. 
 
 NOTES TO ESSAY VIII. 
 
 ON CITRIC ACID. 
 
 26. Separating the mucilage. Page 248, line 25. 
 
 The mucilage contained in lemon or lime juice has always been con- 
 sidered to be the main obstacle to the crystallization of the citric acid 
 contained in the expressed juice of these fruits. Having lately, however, 
 seen a Report made to His Majesty's Victualling Board by an eminent 
 chemist, staling that the concrete acid may be obtained from lemon juice 
 by the simple mode of evaporation only, an assertion contradicting 
 every thing which I had hitherto observed respecting the concentration 
 of this article, I wrote to a friend who has had more experience than 
 myself in the preparation of concrete citric acid, and received the 
 following reply to my letter: Cf An attempt to procure the crystallized 
 acid by the mere evaporation of the lemon juice was," says he, " among 
 the earliest experiments I made on this subject. The simple evaporation 
 of the juice, I find, produces merely a thick treacley kind of substance, 
 and by pushing the concentration further, it may be brought into the 
 state of honey. I still prosecuted the inquiry, in the vain hope of being 
 able to procure a concrete acid by the agency of lime. The mass pro- 
 cured by evaporation I diluted with cold water, making my solution about 
 four or five times the strength of good lemon juice. To one pint of this 
 solution I added one ounce of alcohol j and having reduced this one-fourth 
 by evaporation, it was set aside to cool. On the following day I found 
 a considerable precipitate, which I separated by filtration, and I again 
 evaporated the mother liquor. This treatment I continued from time to 
 time till the whole was reduced to a thick substance similar to molasses 
 as before, but there was no sign of any tendency to crystallization. I 
 
584- ADDITIONAL NOTES. 
 
 repeated this experiment with different proportions of alcohol, but the 
 result was always the same ; and I closed the series of experiments with 
 a conviction of the impossibility of procuring concrete citric acid by the 
 mere evaporation of lemon juice." For further information on the cry- 
 stallization of citric acid, see the xvth volume of The Repertory of Arts 
 and Manufactures ; also volume xii. of the same work, p. 347. 
 
 NOTES TO ESSAY IX. 
 
 ON THE FIXED ALKALIES. 
 
 27. Rendered caustic. Page 277, line 27. 
 
 As it is important to those who use large quantities of the fixed alka- 
 lies to know when a proper quantity of lime has been used to render 
 them caustic the following directions will probably be acceptable to 
 many individuals. When the solution of caustic alkali is prepared, take 
 a little of the clear liquor in a wine-glass:, and breathe into it through a 
 small glass tube, or otherwise add a few drops of a clear solution of sub- 
 carbonate of potash ; for if there be a redundance of lime, the dissolved 
 earth will abso/b carbonic acid from the carbonate of potash or from the 
 human breath, and this will render the liquor turbid. If this treatment 
 should not occasion the liquor to become turbid, it should then be treated 
 with a little lime-water ; and if this occasions a turbidness, it shows 
 that the liquor contains carbonated alkali, and consequently has not had 
 a sufficient quantity of lime ; whereas, if the lime be in due proportion, 
 the lixivium will suffer no change from the addition of the above tests, 
 nor will it effervesce with acids. 
 
 Directions for the preparation of pure potash and soda by means of 
 alcohol are given in Dr. Henry's Elements of Chemistry, vol. i. When- 
 ever it is necessary to open a bottle of pure alkali, it should be done in 
 a dry air or near a fire, and then the stopper immediately returned, and 
 carefully secured by wax as at first. 
 
 28. Kelp. Page 289, line 30. 
 
 Jameson states, that barilla contains from 8| to 23 per cent, of pure 
 alkali divested of water and carbonic acid, and that kelp contains from 
 2 to 5 per cent. From an analysis which I myself made of three parcels 
 of barilla in the year 1801, one of which was from Alicant, another from 
 Carthagena, and the third from Teneriffe, all of which were at that time 
 esteemed to be the best samples in the London market j I found that 
 1121bs of the first contained 191bs 2 oz. of pure dry caustic alkali ; 
 112lbs of the second contained 22^1bs of alkali -, and the Teneriffe 
 22Jlbs, which was esteemed much better than is usually brought from 
 that island. 
 
 Four parcels of barilla which I examined with great care on the 4th 
 of June 1810, were found to be composed as under : The first parcel 
 consisted of 19 parts pure soda, 22 of neutral salts and carbonic acid, 
 pnd 59 of insoluble matter. The second parcel gave 18 per cent, of 
 
ADDITIONAL NOTES. 585 
 
 pure alkali, 21 of neutral salts, &c., and 61 of insoluble matter. Another 
 contained 10J pure alkali, 24 neutral salts, &c., 65 of insoluble matter, 
 and ^ loss. The fourth parcel consisted of 1 1 parts of pure alkali, 20 
 neutral salts, &c., and 69 of insoluble matter. 
 
 Two other samples were analysed on the 1st of February 1813 : one 
 of which contained 30 J per cent, of pure dry soda, lOf- neutral salts, 
 9 carbonic acid, and 50 insoluble matter. This was the best sample of 
 barilla that I recollect ever to have come under my examination. Kelp 
 is of very various quality ; I have seen some which contained 8 per cent, 
 and others which would not yield one per cent, of pure soda. The par- 
 ticulars of the analysis of several parcels of kelp and barilla which I made 
 for the Highland Society of Scotland in the year 1816, will be found in 
 the 5th vol. of the Transactions of that Society, p. 65, &c. 
 
 29. Kelp ovens. Page 290, line 1 2. 
 
 The ovens in which kelp is made are generally of the rudest kind, being 
 nothing more than excavations within the ground, lined with rough un- 
 hewn stones. I would earnestly recommend it to the proprietors of our 
 kelp shores to erect one or more reverberatory furnaces similar to that 
 described in the plate which accompanies the Essay on the Fixed Alkalies j 
 for by means of such furnaces a greater heat would be produced, and the 
 matter might be stirred with greater convenience -, and hence there 
 would be a more effectual decomposition of the muriate of soda by means 
 of the vegetable alkali which these plants always furnish in abundance. 
 By such management I apprehend much of the Irish and Scotch kelp 
 might be rendered of double its present value. See the plate and the 
 descriptions given of it at the beginning of this volume. 
 
 30. Supplies of salt inexhaustible. Page 303, line 14. 
 
 " We read of a salt mine in Poland, one mile from Cracow, which is 
 200 fathoms below the surface, where there were 1000 men constantly 
 employed. In order to descend into this stupendous work, it was cus- 
 tomary for the person descending to fasten himself by a cord to the main 
 rope, and then to take another man on his lap. The large rope being 
 then lowered a little, a third person made a seat for himself with a rope 
 fastened to the main rope, taking another on his lap j and being also let 
 down a little way, he gave an opportunity for another pair to fasten them- 
 selves in the same way : in which manner thirty, forty, or more people 
 were let down at once ; of whom the first having touched the ground at 
 the bottom, steps out and goes aside, the rest following him in regular 
 order and doing the like. Thus they descended to the depth of 100 
 fathoms j and after passing through several passages they came to cer- 
 tain ladders by which they descended 100 fathoms deeper." Phil. Trans, 
 for 1670, p. 1099. 
 
 The salt mine above mentioned is at the town of Wielitska, a German 
 mile from Cracow : it is the largest in Europe, and has been constantly 
 worked for more than 600 years : it is eleven hundred feet in width, and 
 6700 feet in length. The subterranean passages or galleries are very 
 spacious, and in many of them altars or chapels are hewn out of the salt 
 rock. In these chapels, crucifixes or the images of saints are set up ; 
 
586 ADDITIONAL NOTES. 
 
 'and a light is kept continually burning before them. The places where 
 the salt is hewn out of the mine, are called chambers j and some of these 
 are so spacious that a large church might be inclosed in one of them. 
 When candles are brought into these places, the numerous rays of light 
 reflected by the crystals of salt emit a surprising lustre. About 600,000 
 quintals of salt are annually dug out of these mines. That part of the 
 mine which has been most excavated, and which appears like a vast plain, 
 is interspersed with clusters of huts belonging to the miners and their 
 families, many hundreds of whom are born and finish their lives in this 
 subterranean inclosure. 
 
 While on the subject of salt, I embrace the opportunity of mentioning 
 a new purpose to which salt has been applied, and which certainly de- 
 serves to be registered for the benefit of the public. Some merchants of 
 Liverpool, who in the year 1815 had prepared several hundred carboys 
 of oil of vitriol to be exported to America, had them stowed on board two 
 ships, and filled up all the vacant spaces between the baskets with com- 
 mon salt to prevent the bottles from being broken by the motion of 
 the vessels. Proposals for the insurance of these precious cargoes were 
 sent to Lloyd's, and the circumstance of the stowage in salt was men- 
 tioned to induce the underwriters to insure at a lower premium. Some 
 gentleman, however, who knew the effect which would be produced by 
 the affusion of oil of vitriol upon salt, saw the proposals at Lloyd's, and 
 stated that if a single bottle should by any accident become broken on 
 the passage, every individual on board would inevitably be suffocated. It 
 was, however, too late to take any precautionary measures, for the vessels 
 had then bo|h actually sailed. The names of the ships which were then 
 crossing the Atlantic in such a perilous situation were the Lewis and the 
 Margaret, I believe both of Liverpool. Should either of these vessels have 
 sprung a leak, so as to dissolve much of the salt, the stowage of the car- 
 boys would have been loosened, and some of the bottles would unavoid- 
 ably have been broken, by the rocking of the ship. Here we have 
 another instance how necessary it is that all classes of society should 
 become acquainted with the elements of chemical science. 
 
 31. Rocks of salt. Page 303, line 15. 
 
 Notwithstanding these immense masses of salt found in various parts 
 of the world, there are places where salt has never yet been discovered : 
 this is the case in many parts of Africa. Mungo Park relates that " the 
 greatest of all luxuries in the interior of Africa is salt. It would," says 
 he, " appear strange to an European to see a child suck a piece of rock 
 salt as if it were sugar. This, however, I have frequently seen j although 
 the poorer class of inhabitants are so very rarely indulged with this pre- 
 cious article, that to say that a man eats salt with his provisions, is the 
 same as saying he is a rich man. I have suffered great inconvenience 
 myself from the scarcity of this article. The long use of vegetable food 
 creates so painful a longing for salt, that no words can sufficiently de- 
 scribe it." Park's Travels into the Interior of Africa, quarto, 1799. 
 
ADDITIONAL NOTES. 587 
 
 NOTES TO ESSAY X. 
 
 ON EARTHENWARE AND PORCELAIN. 
 
 32. Roman bricks. Page 304, line 18. 
 
 Brick-making was esteemed an art of great consequence by the an- 
 cient Romans j in proof of which the folio wing evidence presents itself. 
 ABDALA, the slave who waited on the person of the empress Livia the 
 wife of Augustus, was set over all the slaves that made bricks j and in the 
 year 1738, on exploring the remains of the ancient city of Heraclea, it 
 was observed that one of the bricks bore the name of Abdala and also 
 that of his mistress the empress. This appears the more extraordinary, 
 because soon after the time of Augustus a law was enacted, ordaining 
 that no architect should be allowed to affix his name upon any part of a 
 building which he had erected, even though it should have been built at 
 his own expense. See A Description of the first Discoveries of the an- 
 cient City of Heraclea, translated by Wickes Skurray, 8vo, 1750, p. 58. 
 Pliny says that " Euryalus and Hyperbius, two brothers, at Athens, 
 caused the first brick- and tile-kiln to be erected/yea and houses thereof 
 to be made ; whereas before that time men dwelled in holes and caves 
 within ground. Gellius is of opinion that Doxius the son of Crelus 
 devised the first houses that were made of earth or clay." Holland's 
 Pliny, vol. i. book vii. p. 188. 
 
 33. Water-pipes. Page 305, line 38. 
 
 Some idea of the state of the potter's art among the ancient Romans 
 may be conceived from the following passage in Pliny. " How benefi- 
 cial," says he, " is the earth unto us in yielding us conduit-pipes for con- 
 veying water, tiles flat yet hooked and made with crotchets at one end to 
 hang upon the sides of the roof, chamfered to lye in gutters to shoot off 
 water, curbed for crests to clasp the ridge on both sides, to say nothing 
 of the vessels that be turned with the wheel and wrought round 5 yea and 
 great tuns and pipes of earth devised to contain wine and water also ! In 
 regard of which Numa ordained at Rome a seventh confraternity of pot- 
 ters." Pliny's Natural History, book xxxv. chap. 12. p. 551. 
 
 34. Roman earthenware. Page 306, line 14. 
 
 A large vessel of Roman earthenware was found during the winter of 
 1813 at Ambleside in the county of Westmoreland, where it is supposed 
 an old Roman city originally stood. But the most interesting detail that 
 I have met with of their earthen vessels is in the account of the discovery 
 of the ancient city of Heraclea, as described by Marquis Don Marcello di 
 Vinuti, in a work already quoted. " Through a door of white marble," 
 says the marquis, " we came into a room 1 4 yards long and eight broad, 
 which led into another room of the same length, but almost square. 
 Round the inside of both these rooms there ran along close to the wall, 
 
588 ADDITIONAL NOTES. 
 
 about half a yard high, a kind of bench covered with a marble pavement, 
 which seemed at first sight to have been used for a seat j but on coming 
 to examine it nearer, I perceived on the top some round stones or stopples 
 of marble ; which, being removed, I found were the covers of some great 
 earthen jars, set in with mortar, the necks of which were inclosed just 
 within the bench. These vessels were of a roundish form, and would 
 hold ten barrels Tuscan measure each. On one of these vessels was this 
 inscription : OPUS. DOLIARE. VINARIUM. The names which were on the 
 handles and necks of these vessels were the names of the makers. Those 
 wrote with ink were the names of the owners of the liquor contained 
 within ; and by reason of the multiplicity of names, it is imagined to have 
 been a cellar for the use of the soldiers who were stationed there to guard 
 the walls; and that whosesoever name was wrote on the vessel, to him 
 belonged the wine contained therein, whether he bought it, or it was his 
 allowance." Skurray's translation of the Description of the Discoveries 
 at Heraclea, page 110. 
 
 It is generally believed that the ancient Egyptians had also made great 
 progress in the knowledge of the manufacture of Earthenware. Mons. 
 Belzoni says. " The art of varnishing and baking the varnish on clay 
 were in such perfection that I doubt if it could be imitated at present j" 
 and this remark was the result of his own observations. Belzoni's Re- 
 searches in Egypt, quarto, p. 173. 
 
 35. Lapis lazuli. Page 307, line 1 1 . 
 
 "This mineral/' says' Guyton, te may be urged to a red heat, and even 
 lose 0.2 of its weight, without any visible alteration in its colour j but 
 with a stronger heat, such as that of the furnace of an enameller, its 
 colour changes to gray." Guyton, Annales de Chimie, torn, xxxiv. p. 58. 
 Mr. Delaval supposes that the colour produced from lapis lazuli was ap- 
 plied to the painting of porcelain, after the ware had undergone the heat 
 of the furnace, and before the introduction of cobalt. Delaval's Inquiry 
 into the Cause of the Changes of Colours in opake and coloured Bodies , 
 4to, London 1777, p. 58. 
 
 36. Bernard de Palissy. Page 311, line 25. 
 
 Palissy is said by Fontenelle to have gone as far in the character of a 
 philosopher as genius without learning could carry him. This eminent 
 man, when in his pleasant moments, used to say, in reference to his trade 
 as a potter, that " he had no property whatever, except heaven and 
 earth." Nouveau Diet. Hist. art. PALISSY, viii. p. 261. No one can 
 have read the History of the Life of Palissy without wishing to know 
 every thing respecting him. For an account of the books published by 
 him, and of the nature of his writings, the reader may consult Platt's 
 Jewel House ofArt^and Nature, part ii. quarto, London 1594. 
 
 37. Fuses. Page 315, line 12. 
 
 A beautiful collection of Engravings of the ancient vases in the British 
 Museum and elsewhere, has been published by Mr, Moses, with disser- 
 
ADDITIONAL NOTES. 589 
 
 tations on the vases of antiquity. This superb work is entitled A Collec- 
 tion of Vases, Altars, Patera, Tripods Candelabra, Sarcophagi, fa. from 
 various Museums and Collections, engraved on 1/0 Plates, by Henry 
 Moses, with Historical Essays, quarto, 1814. Another splendid work of 
 this kind is Sir William Hamilton's Collection of Engravings from ancient 
 Vases, mostly of pure Greek Workmanship : three imperial folio volumes, 
 Naples 1791 1795. 
 
 38. An unwholesome glaze. Page 334, line 12. 
 
 In addition to what I have said respecting the danger of using a glaze 
 of lead on any of the articles made in earthenware which are to be em- 
 ployed in preparing condiments for our food, I must add another caution, 
 which is, never to prepare pickles or any thing in which vinegar is used, 
 in jars of cream-coloured ware ; for this ware is always glazed with lead, 
 and the lead being soluble in vinegar would impart a poisonous quality to 
 the preparations contained in it. When will the community entertain 
 proper notions respecting the deleterious properties of this insidious 
 poison ? In Lancashire I have observed it is a common practice to have 
 brewing-coppers constructed with the bottom of copper, and the whole 
 sides of lead. In the same county the dairies are furnished with milk- 
 pans made of lead ; and when I expostulated with some individuals on 
 the clanger of this practice, I was told that leaden milk-pans throw up 
 the cream much better than vessels of any other kind. In some parts of 
 the north of England it is customary for the innkeepers to prepare mint- 
 salad by bruising and grinding the vegetable in a large wooden bowl with 
 a ball of lead of twelve or fourteen pounds weight. In this operation the 
 mint is cut, and portions of the lead are ground off at every revolution of 
 the ponderous instrument. 
 
 39. Printing press. Page 338, line 4. 
 
 If we consider the many beautiful coins and medals which the ancients 
 produced when the Roman empire was in all its glory 5 likewise the 
 cornelian and agate seals which they engraved for stamping on soft wax ; 
 together with the practice which was very general among that people, of 
 having their names impressed in capital letters on the large earthen jars 
 in which they kept their wine, we cannot avoid being surprised that they 
 never arrived at some method of printing books. An interesting dis- 
 sertation on this subject may be seen in the Philosophical Transactions, 
 No. 450, p. 388. Procopius, in his Hist. Arcana, says, that the Emperor 
 Justin, not being able to write his name, had a thin piece of board, 
 through which were cut holes in form of the four first letters, which was 
 laid on the paper, and served to direct the point of his pen. For the date 
 of the origin of printing on paper, see the 1st Additional Note. 
 
 40. Crucibles and retorts. Page 339, line 38. 
 
 The Indians of Louisiana form their culinary utensils with clay mixed 
 with a sort of calcined mica. Of this composition they also make crucibles 
 
590 ADDITIONAL NOTES. 
 
 capable of enduring the strongest heat they can produce. The galena, 
 which is found there in abundance, is fused in these crucibles, by ex- 
 posing it to a strong heat, in a sort of furnace made by excavating a bank 
 of earth, and forming a chimney through the top of the cave to produce a 
 strong draught of air. The lead thus obtained is employed only for the 
 purpose of sinking their fishing nets. 
 
 There are remains of many ancient potteries in the neighbourhood of 
 Salem in the United States, on the shore of lake Erie. On the Ohio and 
 Mississippi, they are found of a more recent era. In the ancient sepul- 
 chral barrows, vessels are found equal to any now manufactured in any 
 part of the world. Two covers of vessels were found in Ross county 
 highly polished and made of a calcareous breccia ; fragments of these 
 were examined by my friend Professor Silliman, of Yale College, Con- 
 necticut } and were found to be equal in texture and execution to vessels 
 of a similar material now manufactured in Italy. See Archceologia Ame- 
 ricana, vol. i. p. 219 227. 
 
 NOTES TO ESSAY XL 
 
 ON GLASS. 
 
 41. Coloured glass. Page 350, line 19. 
 
 Strabo, who visited Alexandria in the first century, was told by the work- 
 men there, that their country afforded an ingredient without which co- 
 loured glass could not be made. Strabo, lib. xvi. p. 758. There is in 
 the British Museum a mummy 01 great antiquity which is covered with 
 beads of coloured glass. According to Seneca, coloured glass has been 
 made in Europe for more than 2000 years. " Democritus," says he, 
 " brought into Europe the method of making coloured glasses, and thereby 
 counterfeiting gems." Seneca's Epistles, 90. 
 
 42. Virgil's glass mirror. Page 358, line 10. 
 
 This must have been an uncommon utensil at the time in which Virgil 
 lived, for in that age and long afterwards mirrors were usually metallic. 
 Job describes the heavens as a molten looking-glass j and by the order of 
 Moses the brazen laver of the priests was manufactured with the mirrors 
 of the women assembling at the tabernacle. Exodus, chap, xxxviii. 
 verse 8. Valerian made the Emperor Probus a present of a silver cup, the 
 inside of which was cut into mirrors. Pliny and Seneca relate that every 
 young woman in their times expected to have a silver mirror. Pliny, 
 book xxxiv. chap. 1 7. Indeed the mirror-makers of Rome, who were 
 generally silversmiths, were so numerous that they were formed into a 
 Company. 
 
 43. Manganese. Page 358, line 15. 
 
 For a further explanation of the action of the black oxide of manganese 
 in purifying flint glass, consult the article " Glass" in Aikin's Chemical 
 
ADDITIONAL NOTES. 591 
 
 Dictionary, orLoysel Sur I" Art de la Verrerie, page 168, 101. When 
 too much of this oxide has been employed, so as to occasion a purple 
 colour in the glass, it is usual for the workmen to thrust a piece of wood 
 into the mass of melted metal, which quickly abstracts the colour. This 
 oxide imparts its colour to glass only when it is in a high state of oxidize- 
 ment : the wood therefore becoming carbonized abstracts a part of the 
 oxygen, and the colour of the glass disappears. 
 
 44. Technical terms. Page 358, line 42. 
 
 The technical terms in the glass trade are most of them taken from 
 the Italian or French, but some are derived from the German language. 
 Pontilla is from the Italian, meaning any thing drawn to a point or de- 
 rived from a point. Cavelletta, the head or crown of the reverberatory 
 furnace, is also from the Italian. Schrower is the room at the end of the 
 Her, where the goods are received when annealed ; this is from the Ger- 
 man. Fraiche is the iron pan in which the glass is placed to be cooled 
 or annealed. Parcellas is a kind of pincers with a spring back, which is 
 in constant use in those houses where flint glass is made. These terras 
 are all still employed by the glass-makers of Great Britain. 
 
 NOTES TO ESSAY XII. 
 
 ON BLEACHING. 
 
 43. Wool of animals. Page 388, line 24. 
 
 Although the woollen manufacture appears to have been lost during 
 the reigns of Henry III., Edward I., and some of their successors, there 
 is abundant evidence that the ancient Britons were very famous for the 
 manufacture of woollen cloth. Pliny says that " the ancient Britons 
 made a kind of cloth or felt which was so strong and firm, when vinegar 
 was used in making it, that it resisted the blow of a sword, and was even 
 some defence against fire. In after times, these arts were much im- 
 proved amongst us by the Romans, who formed colleges and corporations, 
 with various privileges, for instructing the people, and improving the ma- 
 nufacture of all articles made of woollen. One of these imperial manu- 
 factories, according to Camden, was established on the spot where the 
 city of Winchester now stands. These efforts were so successful, that 
 some hundreds of years afterwards we find that the fleece, by the Anglo- 
 Saxon laws, was valued at two-fifths of the price of the whole sheep. In 
 after times, King Edward III. took so much pains to improve this im- 
 portant manufacture, that during his reign it became completely esta- 
 blished. This appears evident from a curious paper published by Mr. 
 llymer, containing a grant from Richard II. in the year 1382, to 
 Cosmo Gentilis, to export several pieces of cloth of various colours, 
 without paying any duty j the first article of which consists of six pieces 
 of tapestry of u green ground, powdered with roses, which the King sent 
 
592 ADDITIONAL NOTES. 
 
 as a present to the Pope. Pliny's Natural History, book viii. chap. 48. 
 Cod. Theod. torn. iii. p. 524. Camden's Britannia, vol. i. p. 139. Wilkins's 
 Leges dnglo-Saxonicce, #c. p. 23. Ryraer's Feeder a, vol. vii. p. 356. 
 
 \ 
 
 NOTES TO ESSAY XIII. 
 
 ON WATER. 
 
 46. Logwood. Page 422, line 43. 
 
 The art of dyeing must surely have been ill understood in the 1 6th 
 century, for the Government of Queen Elizabeth to have procured a 
 statute to be enacted entirely forbidding the use of logwood. It is en- 
 titled " An Act for the abolishing of certeine deceitful Stufte used in 
 dyeing of Clothes," &c. The preamble states, that " whereas there hath 
 been brought from beyond the seas a certaine kinde of stuffe called log. 
 wood, alias blockwood, wherewith divers dyers," &c. 5 and " whereas the 
 clothes therewith dyed, are not only solde and uttered to the great 
 deceyte of the Queenes loving subjects, but beyond the seas to the great 
 discredit and sclaunder of the dyers of this realme," &c. ; " for reformation 
 whereof, be it enacted by the Queene our Soveraygne Ladie, that all such 
 logwood, in whose handes soever founde, shall be openly burned by 
 authentic of the Maior," &c. This prohibition was renewed in the 39th 
 year of the same reign, subjecting the person so offending to imprison- 
 ment, and on conviction thereof to stand on the pillory in the market 
 town where the offence was committed. See 23d of Elizabeth, cap. ix., 
 also 39*/i of the Queen, cap. xi. Eighty years elapsed before the real 
 virtues of this useful substance were acknowledged. It has, however, been 
 discovered that this wood is one of the most valuable articles the dyer 
 possesses, especially for dyeing blacks. A black may be procured by the 
 combination of several vegetable substances with the peroxide of iron : 
 but I have reason to believe that neither galls, madder, nor any other 
 vegetable, will produce a fine black on cotton if logwood be entirely 
 omitted. Hence, all the most approved receipts for writing-ink, include 
 logwood as a principal ingredient. 
 
 47. The fullers in ancient Rome. Page 431, line 16. 
 
 The inhabitants of Rome, except the lower orders of people, generally 
 wore white woollen garments, but especially at public festivals. Ovid, 
 Fasti i. 79. This made fullers as necessary as laundresses. They were 
 for the most part slaves, but sometimes free ; for an inscription in the col- 
 lection of Fabrettus, c. 4. page 333, mentions the Collegium Fullonum, 
 the Fullers' Company, at Rome. The place where the fullers worked was 
 generally in the fields, on account of the offensive nature of their 
 business. Hence Plautus, Asin.V. 11. 57. 
 
 It appears, from the testimony of ancient writers, that the fullers first 
 threw the clothes into water, where they trod them with their feet. 
 Hence, as Horapollo, Hieroglyphics, i. 65, has observed, the Egyptians- 
 
ADDITIONAL NOTES. 593 
 
 
 
 expressed afuller by the representation of two human feet in water. This 
 washing by treading with the feet, the Romans called Consilmm, ci Con- 
 siliendo. In order to provide themselves with urine, the fullers placed 
 earthen pitchers at the corners of the streets. See Martial xii. 58. 
 
 The clothes, having been thus repeatedly trodden upon in water and 
 urine, were laid upon a block and beaten with staves or battledors. It 
 was with one of these, according to a fragment of Hegesippus preserved 
 by Eusebius, that the Jews beat the Apostle James the younger until he 
 died. When the clothes had been trodden and beaten, they were hung 
 up for the water to drain from them. They then scoured them with 
 fullers' earth and a portion of nitre : after thi'sthey fumigated them with 
 sulphur ; then they carded them with a sort of thistle, and last of all they 
 applied chalk in some way or other to brighten the colour, as Pliny says 
 xxxv. 17: Veros autem et pretiosos colores emollit cimolia, et quodam 
 colore exhilarat contristatos sulphure. Schoettgenio On the ancient 
 Methods of Fulling. See also The present State of the Republic of Let- 
 ters, vol. i. page 150. 
 
 48. Green vegetable matter. Page 436, line 16. 
 
 " The transition," says Sprengel, " of one organical kingdom of na- 
 ture into the other, and the impossibility of separating the two by an exact 
 line of demarcation, becomes obvious to those who, with Needham, 
 Priestley, and Ingenhousz, have observed the metamorphosis of the 
 animalcula infusoria into real confervse. To make this experiment, no 
 particular infusions are required j a vessel filled with pump-water, and 
 exposed to the sun, without being agitated, is sufficient for the purpose. 
 First of all, a delicate green covering is seen to be formed on the surface 
 of the water, consisting of numberless and infinitely minute molecules, 
 that manifest animal motion j these, after some time, disappear, and are 
 transformed into vegetable filaments, which, like all green surfaces of 
 plants, yield oxygen gas when exposed to the influence of the sun." 
 Sprengel's Introduction to the Study of Cryptogamous Plants, octavo, 
 London 1810. 
 
 49. Lead an insidious poison. Page 445, line 30. 
 
 In the province of Poitou there was formerly a disease called the colic 
 of Poitou : but this is no longer common either in France or Germany, 
 since the laws of these countries have made the adulteration of wine with 
 lead, punishable by death. A similar disease was prevalent in the counties 
 of Hereford, Gloucester and Worcester, when leaden utensils were em- 
 ployed in making cider. Dr. Baker, who was physician to Her late Ma- 
 jesty, the Queen of George III., relates that this disease was likewise 
 prevalent in the cider districts of Devonshire, and that on inquiry he 
 found the stones which compose the circular trough in which the apples 
 are ground, to be cramped together by iron, with melted lead poured 
 into the interstices j and also that many cider presses were to be seen 
 which were lined entirely with lead. Dr. Saunders actually procured 
 44 grains of lead from 18 quarts of Devonshire bottled cider. See An 
 Essay on the Endemial Colic of Devonshire, by George Baker, M.D. 
 
594 ADDITIONAL NOTES. 
 
 London 1767. Dr. Franklin has stated, that leaden-worms were for- 
 merly used at Boston in America, for the distillation of rum, and that 
 such disorders were produced in consequence of this practice, that the 
 Government found it expedient to enact a law forbidding the use of any 
 worms for stills except such only as were made of pure tin. Some in- 
 teresting observations on the danger of employing leaden vessels for 
 holding water, or for culinary purposes, will be found in Dr. Lambe's 
 Essay on the Properties of Spring Water, Svo, 1803. 
 
 50. Processes of decoction, distillation, #c. Page 455, line 38. 
 
 Steam has long been employed for the purposes of evaporation and 
 distillation in the laboratory belonging to the Apothecaries' Company of 
 London ; and very lately its use has been considerably extended, and a 
 more complete apparatus for effecting a great variety of processes of so- 
 lution, evaporation, and distillation, by the agency of steam, has been 
 erected. This extensive apparatus was constructed by Mr. Mainwaring 
 under the direction of W. T . Brande, Esq., who has furnished me with 
 the following description of the whole : 
 
 The steam laboratory is a brick building lighted from above, about 50 
 feet long, lofty and well ventilated by apertures in the roof. The steam 
 is supplied from two boilers placed in buildings separate from the labo- 
 ratory j the largest of which is of the common waggon shape, made of 
 copper, and calculated for the supply of a six-horse steam engine. It is 
 furnished with a float-stone, which acts by means of a lever upon an index 
 placed in the laboratory for the purpose of showing the level of the 
 water j with a mercurial gauge indicating the pressure of the steam, 
 which is usually worked at between 7 and 8 inches ; and with a safety 
 valve which opens whenever the pressure exceeds that which is capable 
 of supporting 12 inches of mercury in the syphon. A forcing-pump is 
 also annexed to the boiler, by which it is occasionally supplied with hot 
 water resulting from the condensation of the steam in the various 
 vessels. 
 
 The main steam pipe, which is 6 inches in diameter, is conducted round 
 the laboratory in a cavity of brickwork covered by moveable cast-iron 
 plates, and is accompanied by a smaller pipe, which receives and conveys 
 the water resulting from the condensation of the steam into a cistern pro- 
 perly supplied with valves, whence it is occasionally pumped back into 
 the boiler. A small steam pipe with a register-cock passes to each of the 
 stills and evaporators, each of which also sends off a condensed liquor- 
 pipe into the main for its reception. 
 
 The boilers and evaporators are twelve in number : 4 are of pewter, I 
 of iron, and 7 of copper. Four of these are capable of holding from 150 
 to 300 gallons j four contain about 100 gallons j and four from 10 to 20 
 gallons : there are also some smaller vessels of the same kind, generally 
 used as water baths. 
 
 The stills are seven in number: of these the largest contains 500 
 gallons, and has a distinct worm-tub 5 two contain 200 gallons each, and 
 one contains 150 gallons j these are of copper. There is also a pewter 
 still of about 30 gallons, and one of lead for the distillation of ether. 
 
ADDITIONAL NOTES. 595 
 
 These five stills have two condensing tubs. Lastly, there is a still which 
 with its head and worm are entirely of stone-ware j it is chiefly -em- 
 ployed for distilling spirit of nitric ether. 
 
 With the exception of the leaden ether-still, all the'above vessels are 
 heated by the circulation of steam upon their exterior, being coated with 
 cast- iron jackets, and having a space between the two of about half an 
 inch diameter, into which the steam passes from the main by the register 
 cocks, and from which the condensing pipes pass off. A blow-cock is 
 attached to each vessel, to allow of the escape of the air when the steam 
 is first turned on. 
 
 The other boiler above adverted to is calculated for the production of 
 high-pressure steam, with a pressure of 100 Ibs. on the square inch -, it is 
 applied in another part of the building to various purposes of evaporation, 
 solution, decoction, &c., and in addition only supplies the ether still in 
 the steam laboratory, which is heated by a coil of leaden pipe, by which 
 the temperature requisite for the production of ether from alcohol and 
 sulphuric acid is obtained. The waste steam of these boilers is condensed 
 into a large cistern of water in another part of the building. 
 
 Independent of the saving of fuel in consequence of the employment of 
 steam as above described, there result from it other more important 
 advantages, such as safety from fire in the distillation of spirituous and 
 ethereal preparations ; prevention of burning or of empyreuma in the 
 evaporation of extracts and exclusion of the dust and smoke which fires 
 under the separate vessels would necessarily occasion. 
 
 Besides the distillatory and evaporatory apparatus, there are also two 
 large drying stoves heated by steam, and several wooden and other 
 vessels for saline solutions, &c. which are occasionally adapted to the 
 steam apparatus, and heated by an immense coil of leaden pipe. 
 
 This lengthened description of the apparatus at Apothecaries' Hall 
 has been given for the purpose of showing the great economy of using 
 steam in all the common operations of a chemical laboratory. Another 
 expedient for evaporating heavy or viscous fluids with safety and economy 
 has also been lately introduced, which consists in making oil at a high 
 temperature the medium by which the heat is conveyed. 
 
 In the refining of sugar, great inconvenience had arisen from the cir- 
 cumstance of the sugar being usually boiled by a naked fire, which gene- 
 rally burns a part of the sugar, and occasions a portion of the remainder 
 to be converted into molasses, which is more a product of the fire than a 
 natural educt from the raw sugar. In consequence of this, Mr. Daniel 
 Wilson invented a mode of boiling sugar in coppers without fire-places, 
 merely by forcing heated whale-oil through a coil of metallic pipes lying 
 in the midst of the syrup within the boiler. 
 
 For a full account of this important apparatus, which in my opinion 
 might be employed with great advantage in many processes besides that 
 of refining sugar, the reader is referred to an octavo volume entitled A 
 Report of the Trial of the Action brought by Messrs. Severn, King and 
 Co. against the Imperial Insurance Company , before Lord Chief Justice 
 Dallas and a Special Jury, &c. and to some papers of mine in the 20th, 
 21st, and 23rd Numbers of the Journal of Science, Literature and the 
 Arts, edited at the Royal Institution of Great Britain 
 
 2 Q2 
 
596 ADDITIONAL NOTES. 
 
 NOTES TO ESSAY XIV. 
 
 ON SAL-AMMONIAC. 
 
 51. Known to the ancients. Page 457, line 2. 
 
 It was not until after the Essay on Sal-ammoniac was printed, that I 
 became acquainted with Professor Beckmann's opinion respecting the 
 pretended antiquity of this salt. My readers must however now be in- 
 formed, that this learned man has asserted that the sal-ammoniac of the 
 ancients was nothing more than impure marine salt. He acknowledges 
 the name is old j but, says he, " as those who, in consequence of the 
 name, considered the alumen of the ancients to be our alum, and their 
 nitrum to be our salt-petre, were in an error, we should be equally so were 
 we to consider their sal ammoniac to be the same as ours." Diosco- 
 rides and Pliny speak of sal-ammoniac in some places as though it were 
 common salt j but Pliny says also that it was found in the dry sandy 
 deserts of Africa, as far as the oracle of Ammon j and on the other side 
 of the question, Columella, in a prescription for the eye, recommends 
 rock-salt, either Spanish, Ammoniacal, or Cappadocian. See Beck- 
 mann's History of Inventions and Discoveries, London, 1814, vol. iv. 
 p. 360. Sal-ammoniac was however most certainly known in the J5th 
 century, as Agricola describes it as a salt entirely dissipated in the fire, 
 and as employed in the production of a celestial blue colour ; and Birin- 
 goccio, who wrote in 1540, recommends nitric acid prepared with sal- 
 ammoniac for dissolving gold. 
 
 52. Uses of ammonia. Page 461, line 22. 
 
 In addition to the list of uses of ammonia which I have enumerated, I 
 wish to notice that a modern traveller has related the case of an Indian 
 who was bitten by a rattlesnake, and perfectly cured in a few days by 
 the external and internal use of volatile alkali alone, although the poor 
 creature lay at the point of death, and betrayed the most dreadful sym- 
 ptoms. Travels in South America by Don Felix di Azara, 4 volumes 
 octavo, Paris 1809. 
 
 NOTES TO ESSAY XV. 
 
 ON EDGE TOOLS. 
 
 53. Instruments of stone. Page 471, line 20. 
 
 In the 1st volume of the Transactions of the American Antiquarian 
 Society, an antique axe-head is described, made of a species of green 
 stone equal to /Egyptian granite and polished in the neatest manner. In 
 the same work mention is made of a fish-spear, with six or seven long 
 prongs, perfectly separated and barbed, carved out of calcedony. It is 
 difficult to conceive how such instruments could have been made even by 
 means of steel instruments. Page 230. 
 
ADDITIONAL NOTES. 597 
 
 54. Imperial foundries. Page 475, line 37. 
 
 What has been said of the foundries -which were established in this 
 country by the Romans for making iron might be confirmed, if there 
 were any doubt of the fact, by a circumstance which occurred about forty 
 years ago in Wales, near the town of Brecknock. In October 1783, as 
 some 'labourers were felling a tree, the roots of which tore up the earth, 
 some small pillars were presented to view. It afterwards appeared that 
 these belonged to a Roman work consisting of three baths ; one hot, the 
 two others cold. The state of this curious relic is described by Mr. Hay, 
 who has also given a good engraving of it. In one of the passages to 
 the baths, was found a bar of malleable iron, four feet long. See Archceo- 
 logia, vol. vii. At this period few persons in Europe were acquainted 
 with a method of making cutting-instruments either of iron or steel for 
 it is related that the inhabitants of the northern countries of Europe be- 
 lieved that swords were made by certain pygmies who were concealed in 
 the mountains. Bergman's Physical Essays t vol. iii. p. 89* 
 
 55. First made in London. Page 476, line 41 . 
 
 As many centuries have elapsed since our ancestors learnt the art of 
 making armour and offensive weapons of steel, it seems extraordinary 
 that so long a period should have intervened before they acquired the 
 method of making the most useful implements of common life in that 
 metal. It has already been shown that table-knives were not fabricated 
 in London until the year 1563 j and it is related by Stowe, that needles 
 were not sold in Cheapside until the reign of Queen Mary, and then they 
 were made by a Spanish Negro, who refused to discover the secret of 
 his art. 
 
 Even the pin was not known in England till towards the middle, or 
 latter end, of the reign of Henry VIII. the ladies until then using rib- 
 bons, loops, skewers made of wood, of brass, silver, or gold. 
 
 56. Damascus swords. Page 495, line 40. 
 
 The sabres of Damascus have given rise to a curious art in the work- 
 ing of iron and steel called Damaskeening, which consists in making in- 
 cisions therein and filling those up with gold or silver wire. This process 
 is employed chiefly in enriching sword blades, and the locks of pistols. 
 Dr. Rees in the Cyclopedia, vol. xi. has described the method by which 
 this artificial damasking is effected, and which I think worth transcribing. 
 
 " The name which this art bears shows the place of its origin, or at 
 least the place where it has been practised in the greatest perfection, 
 viz. the city of Damascus in Syria j though M. Felibien attributes the 
 perfection of the art to his countryman Cursinet, who wrought under 
 the reign of King Henry IV. 
 
 " Damaskeening is partly mosaic work, partly engraving, and partly 
 carving: as mosaic work, it consists of pieces inlaid -, as engraving, the 
 metal is indented or cut in creux ; and as carving, gold and silver are 
 wrought therein in relievo. 
 
598 ADDITIONAL NOTES. 
 
 " There are two ways of damaskeening - y in the first, which is the most 
 beautiful, the artists cut into the metal with a graver and other tools 
 proper for engraving on steel, and afterwards fill up the incisions or 
 notches with a pretty thick silver or gold wire. In the other, which is 
 only superficial, they content themselves to make hatches, or strokes 
 across the iron, &c. with a cutting knife, such as is used in making small 
 files. As to the first, it is necessary the gravings or incisions be made 
 in the dove-tail form, that the gold or silver wire, which is thrust forcibly 
 into them, may adhere the more strongly. As to the second, which is 
 the more usual, the method is this : Having heated the steel till it changes 
 to a violet or blue colour, they hatch it over and across with the knife, 
 then draw the ensign or ornament, intended, on this hatching, with a 
 fine brass point or bodkin. This done, they take fine gold wire, and con- 
 ducting or chasing it according to the figures already designed, they 
 sink it carefully into the hatches of the metal with a copper tool." Some 
 of this work is very durable and extremely beautiful. See p. 495497 
 and p. 505 of this volume. 
 
 - NOTES TO ESSAY XVII. 
 
 ON CALICO-PRINTING. 
 
 57. Alum. Page 527, line 27. 
 
 Professor Beckmann, in a memoir published in the Gottingen Philoso- 
 phical Transactions for the year 1 778, and also in his History of Inven- 
 tions and Discoveries, has asserted that alum was entirely unknown to 
 the Greeks and Romans ; and that the triple salt, the true sulphate of 
 alumina and potash, was first discovered in the East so late as the 12th 
 century. 
 
 Herodotus mentions Egyptian alum, and says when the people of 
 Delphos were collecting a contribution to rebuild their temple, the King 
 of Egypt sent them a thousand talents of alum. Herodotus, lib. ii. 
 cap. 180. Diodorus Siculus and Pliny say that the island of Melos was 
 celebrated in their time on account of its alum. But Mr. Beckmann as- 
 serts that the article which these writers refer to was martial vitriol, and 
 not alum, and that it was celebrated in medicine, and used for dyeing 
 black. He proceeds to remark, that the invention of the true alum must 
 have been later than the 12th century; that in the 15th century there 
 were alum-works in the neighbourhood of Constantinople, and that in 
 the middle of that century the discovery was brought into Europe. 
 
 One of the earliest works in Europe for the manufacture of alum was 
 at Tolfa in the Italian States, founded by the son of a celebrated lawyer 
 who traded to Constantinople in Italian cloths, and took that opportu- 
 nity of making himself acquainted with the method of boiling alum. In 
 England the first alum-work was erected at Gisborough in Yorkshire, in 
 the reign of Queen Elizabeth, by Sir Thomas Chaloner, an ancestor of 
 the present representative in parliament for the city of York, who, not- 
 withstanding the anathemas of the Pope, was warmly patronised in his 
 own county by Lord Sheffield and other neighbouring landholders. 
 
ADDITIONAL NOTES. 599 
 
 Notwithstanding this positive assertion of Professor Beckmann, I think 
 alum must have been known much earlier, from many considerations, es- 
 pecially from the perfection to which the art of dyeing had attained in 
 several parts of the East, and in some countries of Europe j and also 
 from some Asiatic proverbs and superstitions which are connected with 
 this salt. It was an opinion of Mr. Harmer, that the practices and cus- 
 toms of the East are the same now as they were several centuries ago ; 
 and the superstitions of a people are generally of great antiquity. Dr. 
 Russell gives the following relation : "Of all the species of superstition, 
 that of the Arabian belief of the influence of evil eyes is," says he, " the 
 most extraordinary. Children are supposed to be more liable to this 
 malignant fascination than others, and they are provided with various 
 charms for their defence ; but the most depended upon is a piece of 
 alum fastened upon the head-dress of the child. The alum, as they 
 assert, intercepting the baleful influence of the eye, is split by it into 
 pieces, and the child remains unhurt." Dr. Russell relates, that while 
 he was at Aleppo he heard it asserted, and it was generally believed, 
 that a Kurdeen lately deceased had been known to crack a large crystal 
 vase, by merely looking at it with steadfastness from a distance. 
 Dr. Russell's Natural History of Aleppo, in two volumes, 4to, London 
 1794. 
 
 58. The Phoenicians. Page 527, line 35. 
 
 That the Phoenicians made great profit by their trade to Britain for 
 tin, is evident from a story which is told by Strabo, who says that " in 
 the most ancient times the Phoenicians from Cadiz were the only persons 
 who traded to these islands, concealing that navigation from all others." 
 When the Romans once followed a Phoenician ship with a design to dis- 
 cover this market, the master wilfully ran his ship amongst shallows, and 
 the Romans following him were involved in the same danger. The 
 Phoenician, by throwing part of his cargo overboard, made his escape ; 
 and his countrymen were so well pleased with his conduct, that they or- 
 dered all the loss he had sustained to be paid out of the public treasury." 
 Strabo, lib. iii. By these prudent precautions the Phoenicians enjoyed 
 a profitable and exclusive trade to these islands for about three hundred 
 years. The people of Cornwall and of the Scilly Islands understood the 
 arts of refining and working this valuable metal several centuries before 
 the first Roman invasion. Diodorus Siculus says that "those Britons 
 who lived near the promontory Belcrium, (the Land's End) by means of 
 their conversation with merchants which come thither for tin, are more 
 civil than the rest to strangers. They dig their tin out of a stony ground 5 
 and when they have dilated it by the fire, they carry it to a certain British 
 island called Icta, near which there are places which appear to be islands 
 when it is full sea, but at low water, the shore being then dry, they carry 
 over their tin in carts. Out of these islands the merchants transport 
 their tin into Gallia, and from thence they convey it by horses to the head 
 of the river Eridanus." Cogan's Diodorus Siculus, London 1653, p. 236. 
 The tin mines of Cornwall have been worked ever since this period. 
 Even so long ago as the year 1198, Henry de Casteilun, Chamberlain 
 of London, charges himself with 3791. ISs. (a large sum in those days) 
 
600 ADDITIONAL NOTES. 
 
 which he had received in fines from the merchants of London for leave to 
 export tin. Madox's History and Antiquities of the Exchequer, folio, Lon- 
 don 17 1 1, p. 53 1. Dr. Campbell says that the mines of Cornwall produce 
 annually two hundred thousand pounds worth of tin, which is four times 
 as much as they did in the last century. Campbell's Political Survey of 
 Great Britain, vol. i. p. 40. The quantity of tin raised is so much more 
 than the consumption of Europe requires, that the miners of late years 
 have allowed the East India Company to take sometimes one-half and at 
 other times two-thirds of the whole quantity raised, at the low price of 
 70s. per cwt., which is not more than two-thirds of the usual price j a 
 circumstance which very much enhances the price of tin to the British 
 manufacturers. The Prince of Wales receives a royalty of 4s. 4d. per 
 cwt. from about 3500 to 4000 blocks quarterly, each block weighing on 
 an average three hundred weight and a quarter ; besides which, he has 
 the perquisite of a piece cut off the corner of each block, when it goes to 
 Truro or Penzance, to receive the royal stamp. 
 
 59. Laid on with a brush. Page 529, line 34. 
 
 As all the colours on Indian calicoes are imparted by the pencil, it ap- 
 pears to me that whenever the trade to the East is completely open, a 
 fine opportunity will be afforded of selling immense quantities of British 
 printed goods ; for though this is an article of manufacture which the 
 East India Company has not yet been able to introduce, on account of 
 the attachment of the natives to their own peculiar style of work, yet 
 the case might be otherwise, if the country were regularly supplied 
 with British goods, printed in a style suitable to that market, and 
 in colours equally permanent with those of their own production. The 
 difference there would be in price is almost incalculable ; for patterns 
 which would require several weeks to complete in India, might, by 
 means of the copper-plate-press and the cylinder, be done here in a few 
 hours. 
 
 60. Weaving calicoes. Page 533, line 3. 
 
 Weaving calicoes by steam was adopted nearly twenty years ago by 
 Messrs. Horrocks and Co. of Stockport in Cheshire, and by other indi- 
 viduals at Glasgow j but since then Messrs. Lightholder and Anderton at 
 Chorley in Lancashire have had a large establishment for weaving calicoes 
 by steam on a new principle. Being desirous of seeing this manufactory, 
 in the year 18131 obtained permission of one of the proprietors to view 
 it, who attended me himself, and with the utmost politeness explained to 
 me the nature and use of every part of the machinery. The first room I 
 entered was full of machines for dressing the warp. This is done by hard 
 brushes about four feet long, attached at each end to a strap that is car- 
 ried round a small wheel, so that the brush revolves with it, and at every 
 revolution brushes the warp, which is properly extended, and passes 
 during the operation slowly from one roller, and is wound by the ma- 
 chinery upon another situated at some distance from it. At every revo- 
 lution of the brush, the warp dips into a long narrow trough of thick flour 
 paste, which is designed to keep the whole moist and make the brushes 
 
ADDITIONAL NOTES. 601 
 
 work well : the whole of these motions are given to the machinery by 
 steam. In the upper rooms there are 60 looms, which are constantly in 
 motion. The shuttles move with great rapidity, and one woman is found 
 to be sufficient to attend three looms. 
 
 6 1 . British gum. Page 535, line, 26. 
 
 Having only slightly adverted to this substance in the Essay on Calico- 
 printing, it may be expected that its manufacture should in some measure 
 be explained : For producing the article, all that is necessary is, to ex- 
 pose dry starch in shallow iron pans to the heat of an oven for an hour or 
 more, until it assumes a peculiar colour well known to those who are 
 in the habit of conducting the process. It is then removed from the fur- 
 nace, and ground to a very fine powder, for sale. 
 
 When the starch has acquired the heat of about 600, it swells consi- 
 derably, becomes soft, and exhales a very powerful smell. At this time 
 it becomes yellow, and afterwards of a cinnamon brown j when it is 
 drawn from the oven, and allowed to cool. 
 
 It is observable that starch by this treatment loses all its amylaceous 
 properties, and acquires the properties of gum. It is soluble in cold water, 
 which is not the case with starch j and, unlike starch, it will not produce 
 a blue compound when its solution is mixed with a dilute solution of iodine. 
 For the other properties of this substance see a memoir by Mons. Dcebe- 
 reiner, Professor of Chemistry at Jena, in the Annales de Chimie, torn. xc. 
 p. 294-2. 
 
 tn the years 1817 and 1818, Messrs. Turner, Woodheads & Co. of 
 Rotheram had a tedious dispute with the Board of Excise, in consequence 
 of some officers from that Board having made several seizures of large 
 quantities of British gum which had been prepared in their starch-manu- 
 factory, and were seized under the pretence of its being brown starch 
 that had not paid duty. There being an act of parliament to restrain the 
 makers of starch from having at one time more than 281bs of loose starch 
 in their possession, under the penalty of 100Z. on each seizure, and 10$. 
 for every pound of starch so found, three distinct seizures of British gum 
 belonging to Messrs. Turner & Co. were made, with a view to the reco- 
 very of these penalties, which amounted to more than 3000Z. 
 
 In this exigency I was applied to, and samples of the article seized 
 were sent to me for analysis. These were examined with great care ; 
 and when I found that they did not possess the properties of starch, and 
 was assured that it could be proved on oath that the starch from which 
 the British gum had been made had paid the usual duty, I advised the 
 manufacturers to resist the payment of the penalties. Accordingly in 
 the month of February 1818 the cause came on to be tried in the Court 
 of Exchequer, in which I was subpoenaed as an evidence for the defend- 
 ants -j and having obtained permission to repeat in Court the experiments 
 by which 1 had ascertained the points in which British gum differs from 
 starch, the proofs were considered to be so decisive, especially the one 
 by the solution of iodine, that a verdict was immediately pronounced foi 
 the defendants. 
 
A TABLE 
 
 OF 
 
 THE EQUIVALENT NUMBERS 
 
 OF 
 
 VARIOUS SUBSTANCES, 
 
 MOST OF WHICH ARE MENTIONED IN THESE ESSAYS 
 
 Substances and Composition. *& u !, v - 
 
 Acid, acetic, hyd.2, carb.24,oxy.24 50 
 
 arsenic, arsen. 38, oxy. 24 ... 62 
 
 arsen ious, arsen. 38, oxy. 16. . 54 
 benzoic, hyd. 6, carb. 90, oxy. 
 
 24 120 
 
 boracic, boron 8, oxy. 16 .... 24 
 
 carbonic, carb. 6, oxy. 16 22 
 
 chloric, chlor. 36, oxy. 40 76 
 
 chloriodic, iod. 125, chl. 36 .. 161 
 chlorocarbonic, chlor.36, carb. 
 
 ox. 14 50 
 
 chlorocyanic,chlor.36,cyan.26 62 
 
 chromic, chr. 28, oxy. 24 .... 52 
 citric (dry), carb. 24, oxy. 32, 
 
 hyd.2 58 
 
 cryst. cit. ac.58, waterlS 76 
 
 columbic, col. 144, oxy. 8. ... 152 
 
 fluoboric, fluor. 16, boron 6. . . 22 
 
 fluoric, fluor. 16, hyd. 1 .... 17 
 
 gallic, carb. 36, oxy. 24, hyd. 3 63 
 
 hydriodic, iod. 125*, hyd. 1 ... 126 
 hydrocyanic, carb. 12, nit. 14, 
 
 hyd. 1 27 
 
 hydrophosphorous,phos.ac. 40, 
 
 water 9 49 
 
 hyposulphuric, sulph. 16,oxy.20 36 
 hyposulphurous, sulph. 16,oxy. 
 
 8 24 
 
 iodic, iod. 125, oxy. 40 165 
 
 lactic 46 
 
 malic 70 
 
 molybdic, moly. 48, oxy. 24 . 72 
 
 molybdous, moly. 48, oxy. 16 . 64 
 
 muriatic, chlor. 36, hyd. 1 .... 37 
 
 nitric, dry, nit. 14, oxy. 40 ... 54 
 
 liquid, (sp. gr. 1.50) nit. 
 
 ac. 54, water 18 .... 72 
 
 nitrous, nit. 14, oxy. 32 46 
 
 oxalic, carb. 12, oxy. 24 36 
 
 cryst. 4 waters, oxal. 
 
 ac. 36, water 36 .... 72 
 
 Substances and Composition. K q"v. 
 Acid, oxychloric, chlo. 36, oxy. 56 92 
 
 oxyodic, iod. 125, oxy. 40 165 
 
 phosphoric, phos. 12, oxy. 16 28 
 phosphorous, phos. 12, oxy. 8 . 20 
 saccholactic, hyd. 4, carb. 36, 
 
 oxy.64 ]04 
 
 selenic, sel. 40, oxy. 16 56 
 
 succinic,carb.24,oxy. 24,hyd. 
 
 sulphuric, (dry,) sulph. 16, 
 
 oxy. 24 
 
 liquid, (sp. gr. 1.85) 
 sulph. ac. 40, water 
 
 9 
 
 50 
 40 
 
 49 
 
 sulphurous, sulph. 16, oxy. 16 . 32 
 tartaric, carb.24,oxy.40Jnyd.2 66 
 tungstic, tung. 96, oxy. 24 ... 120 
 uric, carb. 36, nit. 28, oxy. 8 . 72 
 Alum, (dry) sulph. alumi. 132, bt- 
 
 sulph. pot. 128 260 
 
 cryst. (25 waters,) alum, dry 
 
 260, water 225 485 
 
 Alumina, alum. 18, oxy. 8 26 
 
 acetate, al um . 26, ac. acid 
 
 , 30 76 
 
 sulphate, ox. alum. 26, 
 
 sulph. ac. 40 66 
 
 Alumium jg 
 
 Ammonia, nitrog. 14, hyd. 3 n 
 
 acetate, amm. 17, acet. 
 
 ac. 50 67 
 
 arseniate, amm. 17, ars. 
 
 ac. 62 79 
 
 benzoate, amm. 17, ben. 
 
 ac. 120 137 
 
 carbonate, amm. 17, carb. 
 
 ac. 22 39 
 
 bicarbonate, amm. 17, 
 
 carb. ac. 44 61 
 
 chlorate, amm. 17, chlor. 
 
 ac.76 . 93 
 
AN ALPHABETICAL TABLE OF CHEMICAL EQUIVALENTS. 603 
 
 Substances and Composition. Equir. 
 
 Barytes,borate,bar.78.bor.ac.24. . 102 
 carbonate, bar. 76, carb. 
 
 ac. 32 100 
 
 chlorate, bar. 78, chl. 76. . 154 
 chromate, bar.78,chr.ac.52 130 
 citrate, bar. 78, cit. ac. 58. 136 
 fluate,bar. 78,fluor. ac. 17 95 
 gallate, bar. 78, gal. ac. 63 141 
 hydrate, bar. 78, water 9. 87 
 hydriodate,bar.78,hyd.!26 204 
 iodate, bar. 78, iod. ac. 165 243 
 malate, bar. 78, mal. ac. 70 148 
 molybdate, bar. 78, mol. 
 
 ac.72 150 
 
 muriate, bar. 7 8, mur. ac.37 115 
 nitrate, bar. 78, nit. ac. 54 132 
 cryst. nit. bar. 132, 
 
 water 18 150 
 
 oxalate, bar. 78, ox. ac. 36 114 
 phosphate, -bar. 78, phos. 
 
 ac. 28 106 
 
 phosphite, bar. 78, phos. 
 
 ac. 20 98 
 
 seleniate, bar. 7 8, sel. ac. 56 134 
 succinate, bar.7S, sue. ac.50 128 
 sulphate, bar. 78, sulph. ac. 
 
 40 118 
 
 sulphite, bar.78,sulp.ac. 32 110 
 tartrate, bar. 7 8, tart, ac.67 145 
 tungstate, bar. 78, tung. ac. 
 
 120 198 
 
 urate, bar. 78, ur. ac. 72 150 
 
 Bismuth 71 
 
 acetate, ox. bis. 79, acet. 
 
 ac.50 129 
 
 arseniate, ox. bis. 79, ar. 
 
 ac. 62 141 
 
 chloride, bis. 71, chl. 36.. 107 
 citrate, ox. bis. 79, cit. ac. 
 
 58 137 
 
 iodide, bis. 71, iod. 125.. 196 
 nitrate,ox.bis.79,nit.ac.54 133 
 oxalate, ox. bis. 79, oxa. 
 
 ac.36 115 
 
 oxide, bis. 71, oxy. 8 79 
 
 sulphate, ox. bis. 79, sulp. 
 
 ac. 40 119 
 
 sulphuret, bis. 71, sulph. 16 87 
 tartrate, ox. bis. 79, tart. 
 
 ac. 67 146 
 
 Borax, soda 32, bor. ac. 48 80 
 
 Boron 6 
 
 Calcium 20 
 
 chloride, cal. 20, chl. 36.. 56 
 fluoride, calc. 20, fluor. 16 36 
 iodide, calc. 20, iod. 125 . . 145 
 oxide, (lim) calc.20, oxy.8 28 
 phosphuret,calc. 20 phos.12 32 
 sulphuret,calc.20,sulph.l6 36 
 
 Calomel, mere. 200, chlor. 36 23o 
 
 Substances and Composition. % uiv< 
 
 Ammonia, chromate, amm. 17, chr. 
 
 ac. 52 69 
 
 citrate, amm. 17, cit. ac. 58 75 
 molybdate, amm. 17, mol. 
 
 ac. 72 . 89 
 
 muriate, amm. 17, mur. ac. 
 
 37 54 
 
 nitrate, amm. 17. nit. ac.54 71 
 oxalate, amm. 17, oxa. ac. 
 
 36 53 
 
 phosphate, amm. 17, phos. 
 
 ac. 28 45 
 
 phosphite, amm. 17, phos. 
 
 ac. 20 37 
 
 succinate, amm. 17, sue. 
 
 ac. 50 67 
 
 sulphate, amm. 17, sulph. 
 
 ac. 40 57 
 
 sulphite, amm. 17, sulph. 
 
 ac. 32 49 
 
 tartrate, amm. 17, tart. ac. 
 
 67 84 
 
 A ntimony 45 
 
 chloride, ant. 45, chl. 36 . 81 
 
 iodide, ant. 45, iod. 125 . . 170 
 
 oxide 1st, ant. 45, oxy. 8. 53 
 
 2nd, ant. 45, oxy. 16 61 
 sulphate, ox. ant. 53,sulph. 
 
 ac. 40 93 
 
 sulphuret, ant.45, sulph. 16. 61 
 oxalate, ox. ant. 53, oxal. 
 
 ac.36 89 
 
 phosphate, ox. ant. 53, 
 
 phos. ac. 28 81 
 
 phosphuret, ant. 45, phos. 
 
 12 57 
 
 tartrate, ox. ant. 53, tart. 
 
 ac. 67 120 
 
 Arsenic 38 
 
 acid, ars. 38, oxy. 24 62 
 
 chloride, ars. 38, chl. 72 ... 110 
 muriate, ox. ars. 54, mur. ac. 
 
 74 128 
 
 white oxide, ars. 38, oxy. 16. 54 
 
 sulphuret, ars. 38, sulph, 16 . 54 
 
 Azote 14 
 
 Barium 70 
 
 chloride, bar. 70, chlor. 36 106 
 
 iodide, bar.70, iod. 125 . . 195 
 
 oxide, bar. 70, oxy. 8 78 
 
 peroxide, bar. 70, oxy. 16. 86 
 
 phosphuret, bar.70, phos. 12 82 
 
 sulphuret, bar. 70,sulph. 16 86 
 
 Bary tes, bar. 70, oxy. 8 78 
 
 acetate, bar. 78, acet. ac. 
 
 50 128 
 
 arseniate, bar.78, ars. ac. 62 140 
 
 arsenite, bar. 78, ars. ac.54 132 
 benzoate, bar.78, benz. ac. 
 
 120 198 
 
604 
 
 AN ALPHABETICAL TABLE 
 
 Substances and Composition. Equiv. 
 
 Carbon 6 
 
 hydrochloride,chlo. 36, olef. 
 
 gas 14 50 
 
 perchloride, carb. 12, chlo. 
 
 108 120 
 
 protochloride,carb.6, chlor. 
 
 36 42 
 
 oxide, carb. 6. oxy. 8 14 
 
 phosphuret,carb. 6, phos. 12. 18 
 sulphuret, carb. 6, sulph. 
 
 32 38 
 
 Carburet of nitrogen, carb. 12, nit. 
 
 14.. 26 
 
 Carburetted hydrogen, carb. 6. hyd. 
 
 1 7 
 
 Chloride of nitrogen, nit. 14, chl. 
 
 H4 158 
 
 Chlorine 36 
 
 Chloric ether, chlor. 36, olef. gas. 
 
 14... V 50 
 
 acid, chlor. 36, oxy. 40. 76 
 
 Chromium. 28 
 
 1st oxide, chrom. 28, oxy. 
 
 8 36 
 
 2nd oxide, chrom. 28, oxy. 
 
 16 44 
 
 3rd oxide, (acid) chrom. 
 
 28, oxy. 24. 52 
 
 Cobalt 30 
 
 arseniate, ox. cob. 38, ars. ac. 
 
 62 100 
 
 citrate, ox. cob. 38, cit. ac. 
 
 58. 96 
 
 oxalate, ox. cob. 38, oxal. 
 
 ac. 36 74 
 
 oxide, cob. 30, oxy. 8 38 
 
 sulphate, ox. cob. 38, sulph. ac. 
 
 40 78 
 
 tartrate, ox. cob. 38, tart. ac. 
 
 66 104 
 
 Columbium 144 
 
 Copper 64 
 
 acetate, ox. copp.80, acet.ac. 
 
 100 180 
 
 carbonate, ox. copp. 80, 
 
 carb. ac. 22 102 
 
 citrate, ox. copp. 80, cit. ac. 
 
 116 196 
 
 muriate, ox. copp. 80, mur. 
 
 ac. 74 154 
 
 nitrate, ox. copp. 80, nit.ac. 
 
 108 188 
 
 oxalate, ox. copp. ,80, oxal. 
 
 ac. 72 152 
 
 and ammonia, oxalate of, 
 oxal. copp. 152, oxal. am. 
 
 53 205 
 
 and potash, oxalate of, oxal. 
 
 copp. 152, ox. pot. 84. ... 236 
 and soda, oxalate of, oxal. 
 copp. 152, ox. sod. 68. . . 220 
 
 Substances and Composition. 
 
 Nos. 
 
 Copper, oxide, copp. 64, oxy. 8. . . 72 
 2nd, copp. 64, oxy. 
 
 16 80 
 
 perarseniate, ox. copp. 80. 
 
 ars. ac. 124. 204 
 
 protarseniate of, ox. copp. 
 
 72, ars. ar. 62 134 
 
 sulphate, ox. copp.80, sulph. 
 
 ac. 80 160 
 
 crystallized, siltph. 
 
 copp. 160, water 90 250 
 sulphite, ox. copp. 80, sulph. 
 
 ac. 32 112 
 
 succinate, ox. copp. 72, sue. 
 
 ac. 50 122 
 
 tartrate, ox. copp. 80, tart. 
 
 ac. 132 212 
 
 Corrosive sublimate, mere. 
 
 200, chlor. 72 272 
 
 Cyanogen, carb. 12, nit. 14. 26 
 
 Diamond 6 
 
 Fluorine 16 
 
 Glucinum 18 
 
 Glucina, glue. 18, oxy. 8 26 
 
 Gold 200 
 
 chloride, gold 200, c hlor. 36. .. 236 
 
 iodide, gold 200, iod. 125 325 
 
 oxide, 1st, gold 200, oxy. 8. .. 208 
 2nd, gold 200, oxy.24 . . 224 
 phosphuret, gold 200, phos. 12. 212 
 sulphuret, gold 200, sulph. 48.. 248 
 
 Gum 
 
 90 
 
 Hydrogen ...................... 
 
 carburetted, carb. 6, hyd. I. . . 
 phosphuretted,phos. 12,hyd. 1 
 
 7 
 13 
 sulphuretted, sulph. 16, hyd. 1.. 17 
 
 Iodine ......................... 125 
 
 Iron ........................... gs 
 
 acetate, ox. iron 36,acet.ac. 50. 86 
 carbonate of, ox. iron 36, carb. 
 
 ac. 22 ................... 58 
 
 1st chloride, iron 28, chlor. 36 64 
 
 2nd chloride, iron 28, chlor. 54 82 
 chromate, ox. iron 36, chr. ac. 
 
 52 ...................... 88 
 
 citrate, ox/ ir. 36, cit. ac. 58. . 94 
 
 gallate, ox. ir. 36, gal. ac. 53. 99 
 
 muriate, ox. ir. 36, mur. ac. 37. 73 
 
 nitrate, ox. ir. 36, nit. ac. 54. 90 
 
 pernitrate,ox. ir. 40, nit. ac.81 121 
 
 oxalate, ox. ir. 36, ox. ac. 36. . 72 
 
 oxide, iron 28, oxy. 8 ........ 36 
 
 peroxide, iron 28, oxy. 12. ... 40 
 
 phosphate, ox. ir. 36, ph. ac.28 64 
 
 phosphuret, ir. 28, phos. 12. . 40 
 
 succinate, ox ir. 36. suc.'ac.SO 86 
 
OF CHEMICAL EQUIVALENTS. 
 
 605 
 
 Substances and Composition. % ulv< 
 
 Iron, sulphate (dry), ox. ir. 36, 
 
 sulp. ac. 40 76 
 
 crystallized (7 waters), gulph. 
 
 ir. 76. wat. 63 139 
 
 sulphuret, ir. 28, sulph. 16... . 44 
 bisulphuret, ir. 28. sulph. 32 . 60 
 perarseniate,ox. ir. 40, ars. ac. 
 
 93 133 
 
 protnrseniate,ox. ir.36,ars.ac. 
 
 62 98 
 
 tartrate, ox. ir. 36, tar. ac. 67. 103 
 
 Lead 104 
 
 acetate, ox. lead 112,ac. ac. 50 162 
 arseniate, ox. lead 112,. ars. ac. 
 
 62 174 
 
 benzoate,ox. lead 1 12, ben. ac. 
 
 120 232 
 
 carbonate, ox. lead 112, carb. 
 
 ac. 22 134 
 
 chlorate, ox. lead 112, chlor. 
 
 ac.76 188 
 
 chloride, lead 104, chlor. 36. 140 
 chromate, ox. lead 112, chr. 
 
 ac.52 164 
 
 citrate, ox. lead 112, cit. ac. 
 
 58 170 
 
 gallate, ox. lead 1 12, gall. ac. 
 
 63 175 
 
 molybdate,ox. lead 112, mol. 
 
 ae. 72 184 
 
 nitrate, ox. lead 112, nit. ac. 
 
 54 166 
 
 subnitrate,ox. lead 224,nit. ac. 
 
 54 278 
 
 oxalate, ox. lead 112, oxal. ac. 
 
 36 148 
 
 oxide, 1st, lead 104, oxy. 8 .. 112 
 
 2nd, lead 104, oxy. 12 . 116 
 
 3rd, lead 104, oxy. 16.. 120 
 
 phosphate, ox. lead 112, ph. 
 
 ac.28 140 
 
 phosphite, ox. lead 112, ph.ac. 
 
 20 132 
 
 phosphuret,lead 104, phos. 12. 116 
 uccinate, ox. lead 112, sue. ac. 
 
 50 162 
 
 sulphate, ox. lead 1 12, sulp. ac. 
 
 4 152 
 
 sulphite, ox. lead 1 12, sulp. ac. 
 
 32 14 
 
 eulphuret, lead 104, sulph. 16. 120 
 tartrate, ox. lead 112, tar. ac. 
 
 67 179 
 
 and potash, ox. lead 
 112,tar.ac.l34,pot. 
 
 48 29 
 
 Lime, calcium 20, oxy. 8 28 
 
 acetate, lime 28, ac. ac. 50. 78 
 
 arseniate, lime 28, ars. ac. 
 
 62 90 
 
 Substances and Composition. Eqhr. 
 
 Nos. 
 ,ime, benzoate, lime 28, hen. ac. 
 
 120 148 
 
 borate, lime 28, bor. ac. 24. . . 52 
 carbonate, lime 28, carb.ac. 
 
 22 50 
 
 chlorate, lime 28, chlor. ac. 
 
 f6..., 104 
 
 chromate, lime 28, chr. ac. 52 80 
 
 citrate, lime 28, cit. ac. 58. 86 
 
 hydrate, lime 28, water 9 . 37 
 
 iodate, lime 28, iod. ac. 165. 193 
 
 malate, lime 28, mal. ac. 70 . 98 
 
 muriate, lime 28, mur. ac. 37. 65 
 
 nitrate, lime 28, nit. ac. 54. 82 
 
 oxalate, lime 28, ox. ac. 36. 64 
 oxyiodate, lime 28, oxy. iod. 
 
 ac. 165 193 
 
 phosphate, lime 28, phos. ac. 
 
 28 56 
 
 biphosphate,lime 28, phos. ac. 
 
 56 84 
 
 succinate, lime 28, sue. ac. 50. 78 
 
 sulphate, lime 28, sulp. ac.40. 68 
 crystallized, sulph. 
 
 lime 68, water 18. 86 
 sulphite, lime 28, sul. ac. 32. 60 
 tartrate, lime 28, tart. ac. 67. 95 
 tungstate, lime 28, tungsU acid 
 
 120 148 
 
 Lithia, lith. 10, oxy. 8 18 
 
 carbonate, lith. 18, carb. ac. 
 
 22 40 
 
 chlorate, lith. 18. chlor. ac. 
 
 76 94 
 
 nitrate, lith. 18, nit. ac. 54. . 72 
 
 phosphate, lith.18, phosph. ac. 
 
 28. 
 
 46 
 
 sulphate, lith. 18, sulph. ac. 
 
 40 58 
 
 Lithium 10 
 
 chloride, lith. 10, chlor. 
 
 36 46 
 
 oxide, lith. 10, oxy. 8 18 
 
 iodide, lith. 10, iod. 125 135 
 
 sulphuret, lith. 10, sulph. 
 16.. 
 
 Magnesia, mag. 12, oxy. 8 
 
 acetate, mag. 20, ac. ac. 
 
 50 
 
 arseniate, mag.20, ars. ac. 
 
 borate, mag. 20, bor. ac. 
 
 24. 
 
 26 
 20 
 70 
 
 82 
 44 
 
 carbonate, mag. 20, car. 
 
 ac. 22 42 
 
 bicarbonate, mag. 20. car. 
 
 ac. 44 64 
 
 chlorate, mag. 20. chlor. 
 
 ac. 76 96 
 
 citrate, mag. 20, cit. ac. 58 78 
 
606 
 
 Substances and Composition. Eq uiv - 
 Nos. 
 
 Magnesia, hydrate, mag. 20, water 
 
 9 29 
 
 hydriodate,mag.20, hyd. 
 
 ac. 126 146 
 
 muriate, mag.20, mur. ac. 
 
 37 57 
 
 nitrate, mag. 20, nit. ac. 
 
 54 74 
 
 oxalate,mag.20,ox.ac.36. 56 
 phosphate, mag. 20, ph. 
 
 ac.28 48 
 
 succinate, mag. 20, sue. 
 
 ac. 50 70 
 
 sulphate, mag. 20,sul. ac. 
 
 40 60 
 
 crystallized, sul. 
 mag. 60, water 
 
 63 f 123 
 
 sulphite, mag.20,sul. mag. 
 
 32 52 
 
 tartrate,mag. 20, tar. ac. 
 
 67 87 
 
 Magnesium 12 
 
 chloride, mag. 12, chlor. 
 
 36 48 
 
 oxide, mag. 12, oxy. 8.. 20 
 
 Manganese 28 
 
 acetate, ox. man. 3fi, ac. 
 
 ac. 50 86 
 
 arseniate, ox. man. 36, 
 
 ars. ac. 62 98 
 
 carbonate, ox. man. 36, 
 
 car. ac.22 58 
 
 chloride,man.28, chlor. 
 
 36 64 
 
 citrate, ox. man. 36, cit. 
 
 ac. 58 94 
 
 muriate, man. 28, mur. 
 
 ac.37 65 
 
 nitrate, ox. man. 36, nit. 
 
 ac.54 90 
 
 oxalate,ox. man.36,ox. 
 
 ac. 36 72 
 
 oxidelst,man.28,oxy.8. 36 
 2nd, man. 28, oxy. 
 
 12 40 
 
 3rd,peroxide,man. 
 
 28, oxy. 16 44 
 
 phosphate, ox. man. 36, 
 
 ph. ac. 28 64 
 
 phosphuret, man. 28, 
 
 phos. 12 40 
 
 succinate, ox. man. 36, 
 
 sue. ac. 50 86 
 
 sulphate, ox. man. 36, 
 
 sul.ac. 40 76 
 
 tungstate, ox. man. 36, 
 
 tun. ac. 120 156 
 
 Mercury 200 
 
 acetate, ox. mer. 208, ac. 
 ac. 50 .258 
 
 AN ALPHABETICAL TABLE 
 
 Substances and Composition. 
 
 Nos. 
 Mercury, arseniate, ox. mer. 208, 
 
 ars. ac. 62 270 
 
 perarseniate, ox. mer.216, 
 
 ars. ac. 124 340 
 
 borate, ox. mer. 208, bor. 
 
 ac. 24 232 
 
 perborate, ox. mer. 216, 
 
 bor. ac. 48 264 
 
 carbonate, ox. mer.jgOS, 
 
 car. ac. 22 230 
 
 bicarbonate,ox. mer.216, 
 
 car. ac. 44 260 
 
 chloride, mer. 200, chl.36. 236 
 bichloride, mer. 200, chl. 
 
 72 272 
 
 citrate, ox. mer. 208, cit. 
 
 ac. 58 266 
 
 cyanuret, mer. 200, cyan. 
 
 52 252 
 
 hydriodate, ox. mer. 208, 
 
 hyd.ac. 126 334 
 
 iodide, mer. 200, iod. 125 325 
 periodide, mer. 200, iod. 
 
 250 450 
 
 nitrate, ox. mer. 208, nit. 
 
 ae. 54 262 
 
 pernitrafe, ox. mer.216, 
 
 nit.ac. 108 324 
 
 snpernitrate,ox. mer. 432, 
 
 nit. ac. 54 486 
 
 oxalate,ox. mer. 208, ox. 
 
 ac.36 244 
 
 oxide, mere. 200, oxy. 8. 208 
 peroxide, mere. 200, oxy. 
 
 16 :. 216 
 
 phosphate, ox. mer. 208, 
 
 ph. ac.28 236 
 
 perphosphate,ox. mer.216, 
 
 ph. ac. 56 272 
 
 sulphate, ox. mer. 208, 
 
 sul. ac.40 248 
 
 persulphate, ox. mer. 216, 
 
 sul. ac. SO 296 
 
 subsulphate, ox. mer. 216, 
 
 sul. ac. 40 256 
 
 sulphite, ox. mer. 208, sul. 
 
 ac. 32 240 
 
 sulphuret,mer.200,sul.l6. 216 
 bisulphuret, mer. 200, sul. 
 
 32 232 
 
 tartrate,ox. mer. 208, tar. 
 
 ac. 67 275 
 
 tartrate and potash, ox. 
 mer. 208, tar. ac. 134, 
 
 pot. 48 390 
 
 Molybdenum 48 
 
 lstoxide,mol.48,oxy.8. 56 
 2nd ditto, mol. 48, oxy. 
 
 16 64 
 
 3rd ditto, mol. 48, oxy. 
 24 72 
 
OF CHEMICAL EQUIVALENTS. 
 
 607 
 
 Substances and Composition. % u l v 
 Molybdenum, sulphuret,mol.48,sul. 
 
 32. 
 
 80 
 
 Nickel SO 
 
 borate,ox.ni.38,bor.ac.24. 62 
 carbonate, ox. ni. 38, car. 
 
 ac. 22 60 
 
 chloride, nic. 30, chl. 36. . . 66 
 
 citrate, ox. ni.38, cit. aQ.58. 96 
 
 hydrate, ox. ni. 38, water 9. 47 
 
 iodide, ni. 30, iod. 125. ... 155 
 
 nitrate, ox. ni. 38, nit. ac.54 92 
 
 oxala(e,ox.ni.38,ox. ac.36 74 
 
 oxide, ni. 30, oxy. 8 38 
 
 phosphate, ox. ni. 38, phos. 
 
 ac.28 66 
 
 phosphuret,nic.30,phos.!2. 42 
 sulphate, ox. nic. 38,sul. ac. 
 
 40 78 
 
 crystallized,sul.nic. 
 
 78, water 63 141 
 
 sulphuret, nic. 30, sul. 16. . 46 
 tartrate, ox. nic. 38, tar. 
 
 ac. 67 105 
 
 Nitric oxide, nit. 14, oxy, 16 30 
 
 Nitrogen 14 
 
 chloride of, nit. 14, chl. 
 
 144 158 
 
 Nitrous oxide, nit. 14, oxy. 8 22 
 
 Olefiant gas, carb. 6, hyd. 1 7 
 
 Oxygen 8 
 
 Phosphuretted hydrogen, pho. 12, 
 
 hyd. 1 13 
 
 Phosphorus 12 
 
 sulphuret of, pho. 24, 
 
 sul. 16 40 
 
 Platinum 96 
 
 perchloride,plat.96,chlor. 
 
 72 168 
 
 protochloride, plat. 96, 
 
 chlor. 36 132 
 
 Potash (dry), pot. 40, oxy. 8 48 
 
 acetate of, pot. 48, ac. ac.50. 98 
 ammonio-sulphate, pot. 48, 
 
 sul. ac. 80,amm. 17 145 
 
 arseniate, pot. 48, ars. ac. 
 
 62 110 
 
 binarseniate, pot. 48, ars. 
 
 ac. 124 172 
 
 arsenite, pot. 48, ars. ac.54. 102 
 benzoate, pot. 48, ben. ac. 
 
 120 168 
 
 borate, pot. 48, bor. ac. 24. 72 
 carbonate, pot. 48, carb.ac. 
 
 22 70 
 
 bicarbonate, pot. 48, carb. 
 
 ac.44 92 
 
 crystallized, dry 
 
 salt 92, water 9 101 
 
 Substances and Composition. Equiv. 
 Nos. 
 
 Potash, chlorate, pot. 48,chl. ac.76 124 
 chromate, pot. 48, chr. ac. 
 
 52 100 
 
 citrate, pot. 48, cit. ac. 58. 106 
 columbate, pot. 48, col. ac. 
 
 152 200 
 
 fluate, pot. 48, flu. ac.17.. 65 
 ^ gallate, pot.48, gall. ac. 63 1 1 1 
 hydrate, pot. 48, water 9 . . 57 
 hydriodate, pot. 48, hyd. 
 
 ac. 125 173 
 
 hydrosulphuret,pot. 48, sul. 
 
 hyd. 17 65 
 
 iodate, pot. 48, iod. ac. 165. 213 
 molybdate,pot. 48,mol. ac. 
 
 72. 120 
 
 nitrate of, pot.48, nit. ac.54 102 
 nitrite, pot. 48, nit. ac. 46 94 
 oxalate, pot. 48, ox. ac. 36 84 
 binoxalate, pot. 48, ox. ac. 
 
 72 120 
 
 quadroxalate, pot. 48, ox. 
 
 ac. 144 192 
 
 oxychlorate,pot.48,ox.chl. 
 
 ac.92 140 
 
 phosphate,pot.48, phos. ac. 
 
 28 76 
 
 biphosphate, pot. 48, phos. 
 
 ac.56 *... 104 
 
 phosphite, pot.48, phos. ac. 
 
 20 68 
 
 succinate,pot.48,suc. ac.50. 98 
 sulphate, pot.48, sul. ac.40. 88 
 bisulphate, pot. 48, sul. ac. 
 
 80 120 
 
 sulphite, pot. 48, sul. ac. 
 
 32 80 
 
 tartrate, pot.48, tar. ac. 67. 115 
 bitartrate, pot. 48, tar. ac. 
 
 134 182 
 
 tungstate, pot. 48, tung. ac. 
 
 120 168 
 
 Potassium 40 
 
 chloride, pot. 40, chlo. 
 
 36 76 
 
 iodide, pot. 40, iod. 125... 165 
 peroxide, pot.40, oxy. 24. 64 
 phosphuret, pot. 40, pho. 
 
 12 52 
 
 protoxide, pot.40, oxy. 8. 48 
 sulphuret, pot. 40, sul. 16. 56 
 
 Selenium 40 
 
 acid, sel. 40, oxy. 16 56 
 
 oxide, sel. 40, oxy. 8 48 
 
 sulphuret, sel. 80, sul. 48. . 128 
 
 Silica, sil. 8, oxy. 8 16 
 
 Silicium 8 
 
 Silver HO 
 
 acetate, ox.sil.118, ac.ac..50 168 
 
 areniate,ox.9iU 18, ars. ac.62 180 
 
608 
 
 AN ALPHABETICAL TABLE 
 
 Substances and Composition. 
 
 Silver, carbonate, ox. sil. 11 8, car. . 
 
 ac.22 ............... ____ 140 
 
 chloride, sil. 1 10, chl. 36 ..... 146 
 
 chromate, ox. sil. 1 18, chr. ac. 
 
 52 ...................... 170 
 
 citrate, ox. sil. 118, cit. ac. 58. 176 
 
 cyanuret, sil.HO,cya. 52 ____ 162 
 
 raolybdate, ox. sil. 118, m. a. 
 
 72 ...................... 190 
 
 nitrate, ox. sil. 118, ni.ac. 54. 172 
 
 oxalate, ox. sil. 118, ox.ac.36. 154 
 
 oxide, sil. 110, oxy. 8 ..... 118 
 
 phosphate,ox. sii.118, p. a.28. 146 
 
 phosphuret,sil.UO, phos.12.. 122 
 
 sulphate, ox. sil. 1 1 8, s. ac. 40. 158 
 
 6ulphuret,sil. 1 10, sul. 16. . . . 126 
 
 tartrate, ox. s.U8, tar. ac.67. 185 
 tartrate, and potash, ox. s. 11 8, 
 
 tar. ac. 134, pot. 48 ...... 300 
 
 tungstate,ox.s.U8,tung.ac.20. 238 
 
 Soda, aod. 24, oxy. 8 ............. 31 
 
 acetate, sod. 32, ac.ac. 50 ---- 82 
 
 arseniate, sod.32,ars. ac. 62. . 94 
 
 arsenite, sod. 32, ars. ac. 54. .. 86 
 
 benzoate,sod. 32, ben. ac.120. 152 
 
 borate, sod. 32, bor. ac. 24. ... 56 
 
 carbonate, sod. 32, car. ac. 22. 54 
 crystal! tzed,carb. sod. 54, water 
 
 90. 
 
 . 144 
 
 bicarbonate, sod-32, car. ac. 44. 76 
 chlorate, sod. 32, chl. ac. 76.. . 108 
 oxychlorate, sod. 32, oxychl. 
 
 ac. 92 124 
 
 chromate, sod. 32, ch. ac. 52. . 84 
 
 citrate, sod. 32, cit. ac.58 90 
 
 fluate, sod. 32, flu. ac. 17 49 
 
 hydrate, sod. 32, water 9 41 
 
 iodate, sod. 32, iod. ac. 1 65 197 
 
 molybdate, sod. 32, mol.ac-72.-l04 
 muriate, sod. 32, mur. ac. 37 .. 69 
 nitrate, sod. 32, nit. ac. 54. .. 86 
 
 oxalate, sod. 32, ox. ac. 36 68 
 
 phosphate, sod . 32, phos. ac.28. 60 
 biphosphate, sod. 32, phos. ac. 
 
 56.... 88 
 
 phosphite, sod. 32, phos. ac. 20. 52 
 succinate, sod. 32, sue. ac- 50. . 82 
 sulphate, sod. 32, sulp. ac.40. . 72 
 crystallized, sulp. sod. 
 
 '72, water 90 162 
 
 bisulphate, sod. 32, sulp. ac.80. 112 
 sulphite, sod. 32, sulp. ac. 32. . 64 
 tartrate, sod. 32, tart. ac. 67 .. 99 
 and potash, sod .32, tart. 
 
 ac. 134, pot. 48 214 
 
 tungstate, sod. 32, tung. ac.120. 152 
 
 Sodium ^ 24 
 
 chloride, sod. 24, chl. 36. . . 60 
 
 iodide, sod. 24, iod. 125 149 
 
 peroxide, sod. 24, oxy. 12 .. 36 
 phosphuret,sod.24,phos.l2. 36 
 
 Substances and Composition. Equiv. 
 
 Nos. 
 
 Sodium, protoxide, sod. 24, oxy. 8. 32 
 sulphuret, sod. 24, sulp. 16.. 40 
 
 Strontite?, stron. 47, oxy. 8 55 
 
 acetate, stron. 55, ace. ac. 
 
 50.. 105 
 
 arseniate, stron. 55, ars. 
 
 ac. 62 *r 117 
 
 borate, stron. 55, bor. ac. 
 
 24 79 
 
 carbonate,stron. 55, carb. 
 
 ac.22 77 
 
 chlorate, stron. 55, chl. 
 
 ac. 72 127 
 
 citrate, stron.55,cit.ac.58. 113 
 hydrate,stron.55,water9. 64 
 iodate, stron. 55, iod. ac. 
 
 165 220 
 
 muriate, stron. 55, mur. 
 
 ac.37 92 
 
 nitrate, stron. 55, nit. ac. 
 
 54 109 
 
 oxalate, stron. 55, ox. ac. 
 
 36 91 
 
 phosphate, stron.55, phos. 
 
 ac.28 83 
 
 succinate, stron. 55, sue. 
 
 ac. 50 105 
 
 sulphate, stron. 55, sulp. 
 
 ac. 40 95 
 
 sulphite, stron. 55, sulp. 
 
 ac.32 87 
 
 tartrate, stron . 55, tar. ac. 
 
 67 122 
 
 Strontium 47 
 
 chloride, stron.47, chl. 36. 83 
 iodide, stron. 47, iod. 125. 172 
 oxide, stron. 47, oxy. 8. . 55 
 phosphuret, stron. 47, 
 
 phos.12 59 
 
 sulphuret, stron. 47, sulp. 
 
 16 ; 63 
 
 Sulphur ".. 16 
 
 Sulphuretted hydrogen, sulp. 16, 
 hyd. 1 17 
 
 Tannin 70 
 
 Tellurium 38 
 
 chloride, tell. 38, chl. 36. 74 
 
 oxide, tell. 38, oxy. 8. . . 46 
 
 Tin '.' . 59 
 
 acetate, ox. tin 67, ace. ac. 50. 117 
 
 arseniate, ox. tin 67, ars. ac. 62. 129 
 
 chloride, 1st, tin 59, chl. 36 . . 95 
 
 chloride, 2nd, tin 59, chl. 72.. 131 
 
 citrate, ox. tin 67, cit. ac. 58. 125 
 
 muriate, ox. tin 67, mur. ac.37. 104 
 permuriate, ox. tin 67, mur. ac. 
 
 74 149 
 
 nitrate, ox. tin 67, nit. ac. 54.. 121 
 
 oxalate, ox. tin. 67, ox. ac. 36. 103 
 
 peroxide, tin 59, oxy. 8 67 
 
OF CHEMICAL EQUIVALENTS. 
 
 Substances and Composition. Equiv. Substances and Composition. 
 
 609 
 
 Tin, protoxide, tin 59, oxy. 16 75 
 
 phosphuret, tin 59, phos. 12.. . -71 
 succinate, ox. tin 67, sue. ac. 
 
 50 117 
 
 sulphate, ox. tin67, sulp. ac. 40. 107 
 
 sulphuret, tin 59, sulp. 16 .... 75 
 
 tartrate,ox.tin67,tart.ac.67. 134 
 
 Tungsten 96 
 
 tungstic acid,tung.96,oxy. 
 
 24 120 
 
 Uric acid 45 
 
 Water, oxy, 8, hyd. 1 9 
 
 Yttrium 32 
 
 Yttria, y ttr. 32, oxy. 8 40 
 
 Zinc 
 
 acetate, ox. zinc 43,'acet. ac. 
 
 50 .................... 93 
 
 arseniate, ox. zinc 43, ars. ac. 
 
 62 ..................... 105 
 
 borate, ox. zinc43,bor. ac.24. 67 
 
 Equiv 
 Nos 
 Zinc, carbonate, ox. zinc 43, carb. 
 
 ac. 22 65 
 
 chlorate, ox. zinc 43, chl.ac. 
 
 76 119 
 
 chloride, zinc 35, chl. 36 71 
 
 citrate, ox. zinc 43, cit.ac. 58. 101 
 
 iodide, zinc 35, iod. 125 160 
 
 nitrate, ox. zinc 43, nit. ac. 54. 97 
 oxalate,ox.zinc43,ox. ac. 36. 79 
 
 oxide, zinc 35, oxy. 8 43 
 
 phosphate, ox. zinc 43,pbos. 
 
 ac. 28 71 
 
 phosphuret, zinc 35, phos. 12. 47 
 succinate, ox. zinc 43, sue. ac. 
 
 50 93 
 
 sulphate, ox. zinc43,sulp. ac. 
 
 40. 83 
 
 crystallized,sulp.zinc 
 
 83, water 63 146 
 
 sulphite, ox. zinc 43, sulp. ac. 
 
 32 75 
 
 sulphuret, zinc 35, sulp. 16 ... 51 
 tartrate, ox. zinc 43, tart. ac. 
 
 67 110 
 
 Zirconium 37 
 
 Zirconia, zirc. 37, oxy. 8 45 
 
 THE END. 
 
 2 II 
 
INDEX. 
 
 A. 
 
 ABBE NOLLET on the cooling of 
 wines, 56 
 
 Abilgaart, Professor, 281 
 
 Abraded glass, 373 
 
 Accidents in coal mines, 65 
 
 from spontaneous combustion, 52 
 
 Accurate weights for taking specific 
 gravities, 116 
 
 Acetate of alumina, 531 
 
 an observation on storing it, 536 
 
 of barytes, 138 
 
 of barytes, process for preparing, 
 
 139 
 
 a better process for making, 139 
 
 of iron, 531 
 
 of iron, how prepared, 540 
 
 of iron and alumina, 539 
 
 Achilles, his ctfering of a quoit of iron, 
 473 
 
 Acid and alkali employed alternately 
 in bleaching, 392 
 
 acetic, 139 
 
 boletic, 140 
 
 carbonic, 149 
 
 citric, 248 
 
 muriatic, 465 
 
 nitric, 136 
 
 oxalic, 283 
 
 pyroligneous, 165, 167 
 
 sebacic, 14 
 
 sulphuric, 212 
 
 how formed, 21 5 
 
 zumic, 143, 289 
 
 Acts of parliament respecting glass, 
 386 
 
 Adjective colours, 530 
 
 Adulteration of liquid substances not 
 accurately discovered by speci- 
 fic gravity, 115 
 
 Adulterations of lemon-juice how de- 
 tected, 267 
 
 Advice to gardeners, 418 
 
 respecting the construction of 
 
 water reservoirs, 439 
 
 Affinities altered by change of tempe- 
 rature, 59 
 
 2R 
 
 Afzelius on analysing sulphate of 
 
 barytes, 123 
 
 Agate, collections of, 180 
 Agatized wood at Belgrade, 179 
 Agricola on glass, 346 
 
 on the use of nitre in glass, 385 
 
 Agriculture improved by Chemistry, 
 
 4 
 
 Air, heated, its effect on the body, 36 
 breathed by Sir Joseph Banks, 
 
 &c.36 
 
 the effect of a sheet of, 73 
 
 its property of defending from 
 
 cold, 73 
 
 and water act reciprocally on 
 
 each other, 446 
 Albany river, 28 
 Albertus Magnus, 274 
 Alcarazas manufactured in Spain, 55 
 Alchemists of Europe, 1 
 
 , a proclamation respecting, 571 
 Alchemy, attempt at its revival, 571 
 Alcohol of sulphur, 161 
 
 in burning produces water, 427 
 
 Alkali, origin ofthe word, 274 
 
 mineral, home preparation of, 
 
 99 
 
 nature of its action in bleaching. 
 
 403 
 
 proper for plate glass, 369 
 
 its use in bleaching, 392, 403 
 
 caustic in calico-printing, 532 
 
 the temperature of its evapora- 
 tion when melted, 360 
 Alkalies, fixed, their character, 273 
 
 four species of, 273 
 
 antiquity of their use, 274 
 
 known to Aristotle, 274 
 
 their peculiar taste, 275 
 
 their effect on vegetable juices, 
 
 275 
 
 of great use in dyeing, 275 
 
 employed in soap and glass, 276 
 
 mode of their preparation for 
 
 s oap, 276 
 how rendered caustic, 276 
 
 the economy of using them 
 
 caustic, 278, 584 
 
 2 
 
612 
 
 INDEX. 
 
 Alkalies, said to be produced by fire, 
 
 279 
 
 chemical tests for, 275 
 
 how distinguished, 275, 293 
 
 manufacture of, 99 
 
 the chief consumption of, 276 
 
 combine with different portions 
 
 of acid, 292 
 
 fixed, certain differences in, 293 
 
 their change by carbonic acid 
 
 first explained by Dr. Black, 
 
 276 
 
 their compound nature, 298 
 
 fixed, their corrosive nature, 
 
 275 
 directions for examining the state 
 
 of their causticity, 584 
 directions for preparing them in 
 
 a state of purity, 584 
 decomposed by Sir H. Davy, 298 
 a history of their first decompo- 
 sition, 299 
 the proportions of their bases and 
 
 oxygen, 301 
 Alkaline sulphates decomposed by 
 
 barytes, 147 
 materials, necessity of analysing 
 
 for glass. 367 
 preparation for rainbow shades 
 
 in calico-printing, 561 
 Allen and Pepys on the formation of 
 
 charcoal, 171 
 Alloy of platinum and silver, 115, 505 
 
 of platinum and iron, 115 
 
 of tin and copper, 1 15 
 
 of mercury and barium, 144 
 
 of iron and potassium, 181 
 
 of potassium and sodium, 302 
 
 of steel and platinum, 505 
 
 of steel with silver, 506 
 
 of steel with silver valuable for 
 
 making dies, 506 
 
 of gold with steel, 506 
 
 Alloys of steel with rhodium, 506 
 
 of copper and zinc, 197, 210 
 
 of steel and platinum remarkably 
 
 affected by acids, 506 
 of iron less subject to oxidation 
 
 than alloys of steel, 507 
 
 of iron and iridium, 507 
 
 of osmium and iron rust with 
 
 difficulty, 507 
 metallic, their melting points, 
 
 Alum, the first manufactory of, 19 
 = unknown to the Greeks and Ro- 
 mans, 598 
 
 Alum of the ancients was probably 
 martial vitriol, 598 
 
 its manufacture brought into 
 
 Europe, 598 
 
 an Asiatic superstition respect- 
 ing, 599 
 
 when first made in England, 
 
 598 
 
 earliest manufactories of, 598 
 
 native, 237 
 
 Alum-bay, the sand there, 368 
 
 Alum-stone, 237 
 
 Alumina, pure, to prepare, 320 
 
 its affinity for water, 426 
 
 its loss of weight by heat, 328 
 
 and silica, their affinity, 319 
 
 Aluminous mordant of India, 529 
 Amalgam for electrical machines, 45 
 
 of potassium, 300 
 
 of sodium, 301 
 
 Ameilhon, M., on the trial for witch- 
 craft by means of water, 450 
 
 America, change of climate in, 27 
 
 American bark, its use in calico-print- 
 ing, 553 
 
 potash, for glass, 355 
 
 Ammonia, its composition, 460 
 
 its properties, 460 
 
 produced from urine, 467 
 
 procured artificially, 462 
 
 from what substances best pro- 
 cured, 462 
 
 and muriatic acid, experiment 
 
 with, 465 
 
 its affinities, 468 
 
 various writers upon, 468 
 
 its compound nature explained 
 
 by Berthollet, 460 
 
 a product of putrefaction, 467 
 
 -uses of, 461,596 
 
 used as a cure for the bite of the 
 
 rattlesnake, 596 
 
 manufacture of, on the sea- 
 coast, 467 
 
 native sulphate of, 237 
 
 - citrate of, 262 
 
 subcarbonate of, 157 
 
 Ammoniacal gas discovered by Dr. 
 Priestley, 460 
 
 decomposed by electricity, 
 
 460 
 
 salts, 460 
 
 salt, how made in Germany, 467 
 
 liquor of the gas-works, 469 
 
 Ammonius, the preceptor of Plutarch, 
 
 437 
 Saceas, 437 
 
INDEX. 
 
 613 
 
 Ammonius, the preceptor of Simpli- 
 cius, 43? 
 
 Amphitheatre of Rome, 525 
 
 Amphitheatres of Nero, 387 
 
 Anagram of Roger Bacon, 1 62 
 
 Analysis, its importance to the farmer, 
 4 
 
 of manures, 4 
 
 of barilla, &c. 14 
 
 of carbonate of barytes, 127 
 
 of fullers' earth by Bergman, 
 
 343 
 
 of steel by Vauquelin, 477 
 
 Anatomists, their employment of fri- 
 gorific mixtures, 61 
 
 Ancient purple, 20 
 
 potteries discovered in the Uni- 
 ted States, 590 
 
 domestic implements of copper, 
 
 474 
 
 patent for glass, 354 
 
 Andersonian Institution, 3 
 
 Andes, have different climates ac- 
 cording to the elevation, 27 
 
 Anecdote of poisoning, 6 
 
 respecting wax for resisting 
 
 colours, 544 
 of a bleacher of antiquity, 416 
 
 respecting private bleaching, 
 
 438 
 
 of a Roman architect, 347 
 
 Anecdotes respecting the black-lead 
 mine, 187 
 
 Anglezark lead mine, 127 
 
 the author's visit to this mine, 
 
 128 
 
 its present state described, 129 
 
 visited by Frenchmen, 129 
 
 account of several occurrences 
 
 there, 130 
 
 inquiry respecting, further pro- 
 secuted, 131 
 
 Animal heat, 34 
 
 . heat, the same in all climates, 34 
 
 heat, contrivance for modifying, 
 
 37 
 heat, Crawford's experiments on, 
 
 32 
 
 temperament, its uniformity, 37 
 
 food, prepared by freezing, 58 
 
 charcoal, 173, 491 
 
 charcoal for hardening files, 491 
 
 food, an expedient for preserving, 
 
 176 
 and vegetable charcoal, how 
 
 distinguished, 174 
 Animals, different mechanism of, 32 
 
 Animals, their power of producing: 
 
 cold, 37 
 
 Annealing furnace of the elass-house, 
 356 
 
 cast cutlery, 504 
 
 of glass, 372 
 
 of crown glass, 362 
 
 of plate glass, 378 
 
 ovens for cast plate glass, 376 
 
 Anomalies in the specific gravities of 
 
 metallic compounds, 114 
 in the melting points of mixtures 
 
 of lead and tin, 1 1 5 
 Anthony de Brossard, glass house of, 
 
 351 
 
 Anthracolite, 191 
 Anti-attrition paste, its composition, 
 
 186 
 
 Antimoniate of barytes, 140 
 Antimonite of barytes, 140 
 Antimony, a case of poisoning by, 6 
 Antiquity of charring stakes, 179 
 Anti-septic quality of hard water, 436 
 Anvil, a peculiar one for scissars, 
 
 482 
 
 Apartments, how cooled in India, 55 
 Apothecaries' Company of London, 
 
 their laboratory, 594 
 Apparatus, galvanic, 46 
 
 employed in freezing water, 61 
 
 glass, for burning sulphur, 216 
 
 for squeezing clay at Etruria, 
 
 324 
 for drying calicoes, described, 
 
 554 
 
 for freezing mercury, 62 
 
 for steaming printed calicoes, 
 
 558 
 
 wood cut of, 558 
 
 new one, for burning the dia- 
 mond, 150 
 
 for making charcoal, 150 
 
 for extracting the colour of dye- 
 wood, 175 
 
 for making crown glass, 358 
 
 for bucking linen, 391 
 
 for bleaching by steam, 414 
 for the compression of water, 
 
 424 
 
 French, for sal-ammoniac, 465 
 
 at Apothecaries' Hall, full de- 
 
 scription of, 594 
 Apuleius, his anecdote on bleaching, 
 
 by sulphur, 416 
 Aquafortis recommended by Reaumur 
 
 for tempering files, 492 
 
 maker at Birstall, 14 
 
614 
 
 INDEX. 
 
 Aquafortis, its quality, of great impor- 
 tance to the calico-printers, 
 540 
 
 carboys of glass for, 365 
 
 Aquatic vegetables, their effect in pu- 
 rifying water, 436 
 
 Arabian caravans, their mode of cool- 
 ing water, 55 
 
 Arabs, account of their sails, 525 
 
 Archimedes, 2, 103 
 
 set fire to the ships of the 
 
 Romans, 43 
 
 how he found the specific 
 
 gravity of gold, 1 13 
 
 the use of this piece of 
 
 history, 114 
 
 his error explained, J 14 
 
 hisDeinsidentibus humido, 
 
 103 
 
 his method of determin- 
 metallic alloys by their 
 gravity fallacious, 
 
 ing 
 
 specific 
 114 
 
 Architect, an eminent Roman, ba- 
 nished for his popularity, 347 
 Architects of Rome not allowed to af- 
 fix their names on buildings, 
 587 
 Areometer, 107 
 
 for fluids described, 107 
 
 for solids, 108 
 
 Baume's for salts, 109 
 
 how prepared by him, 108 
 
 a term employed by Hoin- 
 
 berg, 107 
 
 for 'spirits, 109 
 
 Arfvredson, M., of Sweden, 302 
 
 Argol, 283 
 
 Armour of the Anglo-Saxons, 476 
 
 of the ancient Normans, 476 
 
 of the ancient British, 476 
 
 of the Earl of Douglas, 476 
 
 Aroma of the hop, how preserved 
 
 %f3S 
 Arrangements necessary for making 
 
 citric acid, 250 
 
 Arrows of the English in 1402, 4/6 
 Arsenic, its use in glass, 358 
 the difficulty of combining it 
 
 with lead, 358 
 Arseniate of barytes, 140 
 Arsenite of barytes, 140 
 Artificers in iron in great estimation 
 
 formerly, 476 
 of Murano ennobled by 
 
 Henry III., 35 1 
 Asbestos fused by Hoffman, 43 
 
 Ashing in calico-printing, 532 
 
 Ash-pit doors, 79 
 
 better than registers, 
 
 80 
 
 Asiatic porcelain, places of its manu- 
 facture, 308 
 
 Astley, Mr., his patent for sal-ammo- 
 niac, 466 
 
 Atmosphere, its use in preserving the 
 warmth of the earth, 71 
 
 Atmospheric air, inhalation of, 33 
 
 Atomic system, 158 
 
 Attraction, double elective, 462 
 
 Attrition, experiments on,- 42 
 
 Augers, gouges and chisels, how 
 made, 482 
 
 AulusGellius,212 
 
 Austin, Dr., on the formation of am- 
 monia, 462 
 
 Authors, a list of, on hydrostatics, 
 112 
 
 Axes of stone, 596 
 
 how made, 48 1 
 
 Azote, escape of, from sulphuric acid 
 chambers, 246 
 
 B. 
 
 Bacon, Roger, the discoverer of gun- 
 powder, 162 
 
 Francis,lord chancellor, 121 
 
 his process of freezing 
 
 water, 60 
 
 the first rational expe- 
 
 rimentalist, 1 
 
 his anagram for de- 
 scribing gunpowder, 162 
 
 chemistry peculiarly 
 
 indebted to him, 1 
 
 the first writer who 
 
 recommended a mixture of 
 snow and salt for freezing wa- 
 ter, 60 
 
 on specific gravity, 1 03 
 
 and Boyle on the ex- 
 pansion of water, 448 
 
 Bagging of oil, 95 
 
 Baker, Sir George, on the poison of 
 lead, 445 
 
 Balance, the antiquity of, 102 
 
 directions for choosing, 106 
 
 Baldwin's phosphorus, 65 
 
 Ballast for ships, 8 
 
 Bancroft, Dr., his experiments on log- 
 wood, 442 
 
 his opinion of Turkey red, 
 
 566 
 
INDEX. 
 
 615 
 
 Bandana handkerchiefs, 544 
 
 Bands for furnaces, 87 
 
 Banks, Sir Joseph, his experiment 
 
 on respiration, 36 
 Barberini or Portland vase, 309 
 Barberry punch, 261 
 Barclay's Argenis, some account of,6 
 Barilla, 289 
 
 imported from Spain, 276 
 
 its manufacture, 290 
 
 and kelp, difference of, 290 
 
 directions for analysis of, 290 
 
 employed for crown glass, 359 
 
 Bar-iron, its difference from cast-iron 
 
 501 
 for tin-plate prepared with 
 
 charcoal, 510 
 Barium, 133 
 
 how obtained, 144 
 
 chloride of, 137 
 
 oxide of, 133 
 
 Baroselenite, 122 
 
 analysed 
 
 by Klaproth, 
 
 580 
 
 Bartholdus Schwartz, 163 
 
 Barytes, essay on, 1 22 
 its original names, 122 
 
 different chemists who have 
 
 treated of it, 127 
 
 its action on the stomach of 
 
 animals, 131 
 
 how obtained pure, 133 
 
 hydrate of, 134 
 
 = three hydrates of, 134 
 
 its peculiar properties, 134 
 
 nitrate of, 135 
 
 muriate of, 137 
 
 citrate of, 262 
 
 sulphate of, 237 
 
 the facility of its crystalliza- 
 tion, 137 
 
 and strontites, their resem- 
 blance, 137 
 
 gives a yellow colour to flame, 
 
 138 
 
 how best preserved, 138 
 
 acetate of, 138 
 
 pure, preparation of, 634 
 
 how procured byPelletier,132 
 
 a process for the preparation 
 
 of, 125 
 
 a French process for prepa- 
 
 ring, 125 
 
 used in the manufacture of 
 
 pottery, 346 
 
 and strontites, difference be- 
 tween, 137, 580 
 
 Barytes, its solubility in water, 138 
 for the arts, how to be pre- 
 pared, 147 
 
 decomposed by Sir H. Davy, 
 
 144 
 
 remarks on its uses, 145 
 
 proposals for experiments on, 
 
 in making pottery, 345 
 
 an agent for purifying water, 
 
 436 
 
 singular circumstances re- 
 specting its medicinal use, 
 146 
 
 Barytic salts poisonous, 132 
 
 poison, nature of, 132 
 
 crystals, 134 
 
 cements, 146 
 
 . water, 138 
 
 chemical tests, 135 
 
 Basalt, Sir James Hall's experiments 
 on, 98 
 
 employed in glass-making, 98 
 
 Basil Valentine, 212 
 
 Bason of ice, filled with wine, 61 
 
 Basso-relievos formed in running wa- 
 ter, 454 
 
 Baths of St. Philip, 454 
 
 for tempering steel, 494 
 
 Batteries, electrical, 45 
 
 Battle of Hamildon in 1402, 476 
 
 Baum^ on clay, 317 
 
 on bleaching silk, 416 
 his areometer, 107 
 
 for salts, 109 
 
 for spirits, 109 
 
 Beak-irons or Bickerns, 482 
 Beckmann on writing upon glass, 372 
 on the antiquity of sal-am- 
 moniac, 596 
 3eddoes, Dr., on frigorific mixtures, 
 
 63 
 
 3eds of retorts, for oil of vitriol, 246 
 Bellainge, Count de, 397 
 
 his efforts in the art of gas- 
 bleaching, 397 
 Sell-metal, its specific gravity, 115 
 Selzoni, Mons., his account of Egyp- 
 tian pottery, 588 
 ienzoate of barytes, 140 
 Bergman on brick-making, 310 
 
 on elective attraction, 462 
 
 on the earth of gems, 343 
 
 on mineral water, 428 
 
 his analysis of sea-water, 
 
 468 
 
 Bernard de Palissy, 588 
 Jerries used for steam yellows, 560 
 
616 
 
 INDEX. 
 
 Berthier on the alloy of chromium 
 
 with steel, 507 
 Berthollet on the dune of the cow, 
 
 538 
 
 on decomposition of oil, 155 
 
 on dew, 390 
 
 first employed chlorine in 
 
 bleaching, 394 
 his memoir on bleaching, 
 
 397 
 his materials for bleaching, 
 
 397 
 
 his difficulties in gas bleach- 
 
 ing, 397 
 Dr. lire's translation of his 
 
 work, 565 
 
 Beunie, Mons., on soils, 4 
 Billets of wood agatized, 180 
 Bingley's patent plane-irons, 483 
 Birds, how preserved at Hudson's Bay, 
 
 72 
 
 Birds-cherry, produces citric acid, 260 
 its infusion in wine, &c. 
 
 260 
 Biscuit-ware of the potter described, 
 
 328 
 method of painting on, 
 
 336 
 
 Bismuth, citrate of, 262 
 Bistre, its preparation, 173 
 Bittern of salt-works, 466 
 why so proper for making sal- 
 ammoniac, 468 
 in Scotland, allowed free of 
 
 duty, 466 
 Black, Dr., his chemical lectures, 3 
 
 his theory of latent heat, 3 
 
 his discovery of latent heat, 32 
 
 on freezing, 72 
 
 on chimneys, 89 
 
 discovery of carbonic acid, 150 
 
 on the consumption of smoke, 
 
 89 
 
 his discovery respecting the al- 
 kalies, 276 
 
 on alkaline carbonates, 276 
 
 Black produced by iron and madder, 
 
 541 
 Black-ash, 19 
 
 < preparation of, 574 
 
 Black-jack, a sulphuret of zinc, 206 
 
 used in making brass, 206 
 
 Black-lead mine in Borrowdale, when 
 
 discovered, 188 
 method of securing, 
 
 189 
 pencils first made, 184 
 
 Black-lead pencils, expense of procur- 
 ing, 190 
 
 value of the mine, 190 
 
 quantity raised at Borrow- 
 dale, 190 
 
 its prices, 191 
 
 names of the proprietors of 
 
 the mine of, 191 
 
 annual consumption of, 191 
 
 Blacks, how dyed on calicoes, 540 
 
 Blacksmith, his expedient for pro- 
 ducing fire, 52 
 
 Blagden, his experiments on heat, 36 
 
 Blake, Mr. John Bradley, his attempts 
 to improve pottery, 329 
 
 Blancourt, his account of malleable 
 glass, 348 
 
 Blazing, saws, process of, 491 
 
 Bleachers' residuum of use in garden- 
 ing, 418 
 
 residuum effectual in pre- 
 venting infectious fever, 418 
 
 waste lyes, 419 
 
 method of regenera- 
 
 ting, 419 
 Bleaching, a chemical process, 10 
 
 an essay on, 387 
 
 paper, 19, 416 
 
 calicoes, 531 
 
 the goodness of, proved,533 
 
 of the ancient Britons, 387 
 
 grounds at Haarlem, 390 
 
 the old process tedious,392, 
 
 412 
 
 with sour milk, 392 
 
 at Nottingham, 398 
 
 the modern process of, 400 
 
 liquor for hose, 402 
 
 calicoes for the printer, 
 404 
 
 questions concerning, 409 
 
 hints for improving the art 
 of, 409 
 
 of wool, 415 
 ' bees wax, 415 
 
 of straw, 417 
 
 liquid, test for, 420 
 
 vessels, 419 
 
 a test for, proposed, 420 
 
 treatises on, 420 
 
 liquor for private families, 
 
 398 
 
 Bleach-works must not be esta- 
 blished in some districts, 430 
 
 Blende used in making brass, 206 
 
 a sulphuret of zinc, 206 
 
 Block-cutting, 535 
 
INDEX. 
 
 617 
 
 Block-printing of calicoes, 536 
 Block tin prepared from tin-stone,513 
 Blood, on the colouring matter of, 6 
 
 its use in respiration, 6 
 
 capacity of, for caloric, 33 
 
 - arterial and venous, 33 
 
 - the colour of, 572 
 
 - Mr. Brande's paper on, 6 
 Blue for steam colours, how pro- 
 duced, 557 
 
 Blue-dipping, observations on, 533 
 
 vat, art of making, 543 
 method of replenishing, 543 
 
 Blue-printing of the potter, 338 
 
 a desideratum in, 339 
 
 the glaze employed for, 339 
 Blued steel, curious properties of, 489 
 Bodily temperature, how preserved, 
 
 Boerhaave, 22 
 
 on the application of che- 
 
 mistry to medicine, 5 
 
 on vinegar- making, 16 
 
 on the purification 
 
 of 
 
 water under the equator, 444 
 Boilers, remarks on setting, 77 
 
 with concave bottoms, 78 
 
 of brick for soap, 88 
 
 of steam-engines, 91 
 
 Boiling, theory of, 37 
 
 water conveyed under ground, 
 
 74 
 
 Boletate of barytes, 140 
 Boletic acid, 141 
 Boletus pseudo igniarius, 141, 169, 
 
 283 
 Bologna stones, 123 
 
 phosphorus, 124 
 
 Bombazets, hot-pressing of, described, 
 
 578 
 Bombazine presses, an improvement 
 
 in them suggested, 578 
 Bone spirit, 464 
 Bones, animal, analysis of, 332 
 
 injurious to porcelain, 333 
 
 employed in pottery, 332 
 
 distillation of, for ammonia, 
 
 464 
 
 Bonjour, Mr., a French bleacher, 397 
 Booth, Mr. David, his treatises on 
 
 brewing, 573 
 
 his saccharometer, 574 
 
 Borate of barytes, 141 
 
 Borax sometimes used in plate glass, 
 
 383 
 employed by Dr. Shaw in 
 
 making glass, 385 
 
 Borax known to the ancients, 385 
 Boring of copper cylinders, 555 
 Borrowdale, mine at, some account of 
 
 185 
 
 Boswell, on watering meadows, 453 
 Bottle glass, 98 
 
 - manufacture of, 365 
 
 - materials for, 365 
 
 - method of fashioning, 365 
 
 - a peculiar kind made at New- 
 
 castle, 366 
 
 Bourbollon de Ronnueil, 395 
 Bovey coal, 195 
 Bow china, 331 
 Bowking-houses, 405 
 Boyle, Mr., his experiments for pro- 
 
 ducing cold, 60 
 
 - on the freezing of animal food, 
 
 59 
 
 - his expedient for freezing the 
 
 humours of the eye, 61 
 
 - his syphon of ice, 60 
 on specific gravity, 103 
 
 - on procuring fresh water at sea, 
 
 443 
 
 Brahe, Tycho, 3 
 Bramah's press employed by bleachers, 
 
 406 
 
 Bran, its use in maddering, 542 
 Brande, Mr. Professor, on the blood, 6 
 
 - his experiments on carbu- 
 
 the 
 
 retted hydrogen gas, 153 
 
 - on the combustion of 
 diamond, 150 
 
 - on the economy of gas illumi- 
 nation, 154 
 
 - on sulphuret of carbon, 161 
 
 - on the analysis of plumbago. 
 184 
 
 - on the analysisof Cheltenham 
 water, 240 
 
 - - on the chemical apparatus at 
 
 Apothecaries' Hall, 594 
 Brandies, how purified, 176 
 Branning of calicoes, 541 
 Brass, introduction of, 18 
 manufacture of, 197 
 
 - furnaces, for making, 200 
 
 - combustion of, a cu- 
 
 rious spectacle, 203 
 
 old mode of manufacturing, 
 
 204 
 
 stirring the crucibles of, a bril- 
 liant spectacle, 205 
 
 moulds for casting, 206 
 
 time required for manufacturing, 
 
 206 
 
618 
 
 INDEX. 
 
 Brass wire requires frequent anneal- 
 ings, 208 
 
 drawing an operation of 
 
 nicety, 208 
 
 annealed by gradual cooling 
 
 208 
 
 erection of first mill for 
 
 drawing, 209 
 
 consumed in making pins, 
 
 209 
 
 shot, use of, 208 
 
 ordinary, cast into ingots, 208 
 
 various manufactures in which it 
 
 is used, 209 
 
 method of making kept secret in 
 
 Germany, 209 
 
 work first erected in England, 
 
 209 
 
 alloys, utility of, 211 
 
 ease with which it combines by 
 
 fusion, 211 
 
 peculiar properties of, 211 
 
 alloy of, and platinum, 21 1 
 
 Breakage of retorts, how avoided,246 
 
 Breweries, 91 
 
 Brewing fermented liquors, 15 
 
 Brewster, Dr., on Mr. Stodart's alloys 
 of steel, 507 
 
 Brice on hydraulic organs, 450 
 
 Bricks, their antiquity, 306 
 
 on the choice of, 84 
 
 process of burning, 310 
 
 of fossil meal float in water, 344 
 
 bad conductors of heat, 
 
 344 
 
 Bricklayer, on the choice of, 77, 84 
 
 Brick-making an art of great conse- 
 quence among the Romans,587 
 
 Bridge of Trajan, 179 
 
 Brilliants, their value, 148 
 
 Brimstone-stove for hose, 404 
 
 Britain, observations on the trade of, 
 470 
 
 British manufactures, their preemi- 
 nence, 101 
 
 gum, 535 
 
 manufacture of, described, 
 
 601 
 
 a large quantity of, seized 
 
 by the Excise, 601 * 
 
 Broad-glass, 363 
 
 Brodie, Mr., his objection to Craw- 
 ford's theory, 34 
 
 Brown salt of manganese, 564 
 
 Brussels, industry of its inhabitants, 
 196 
 
 Buchanan on heat, 74 
 
 Bucking, a technical term, 391 
 
 Buddie-house, 199 
 
 Buddie's report on the safety lamp, 
 69 
 
 Buffbn, some account of, 1 04 
 
 his 1 singular notion respecting 
 
 the temperature of the planets, 
 26 
 
 his combination of burning mir- 
 rors, 44 
 
 on the specific gravity of mine- 
 rals, 104 
 
 his crude notion of silica, 317 
 
 Bulbs for ascertaining the weight of 
 fluids, 120 
 
 Buonaparte, medallions of, in cry- 
 stallo-ceramie, 379 
 
 Burning mirror, an economical use of, 
 44 
 
 Burnt bone, its use in pottery, 332 
 
 Butter-milk formerly used in bleach- 
 ing, 390 
 
 C. 
 
 Caesar, Julius, 2 
 
 Calamine, calcination of, 198 
 
 extrication of carbonic acid 
 
 from, 199 
 
 vitrification of, 199 
 
 use of, 197 
 
 where found, 197 
 bloom, 205 
 
 quantity of brass produced from, 
 
 206 
 
 Calcination of calamine, 1 98 
 of the materials for bottle glass, 
 
 366 
 
 Calendering calicoes, 534 
 Calico-printers require pure water, 
 
 430 
 
 souring, 534 
 
 Calico-printing, 523 
 
 essay, additions to, 555 
 specimens of, 564 
 
 an art dependent on chemistry, 
 
 569 
 
 chemical, 9, 555 
 improvements in, 10 
 
 in Great Britain, 531 
 in India, 528 
 
 modern practice of, in India, 
 
 529 
 
 surface machines, 555 
 
 Calicoes, wet, how dried instantane- 
 ously, 559 
 
 dressing of, 532 
 
INDEX. 
 
 619 
 
 Calicoes, mode of printing, 534 
 
 for printing, how bleached, 405 
 
 Caloric, its distribution, 26 
 
 how distributed by the blood, 
 
 33 
 
 capacity for, 32, 614 
 
 free and latent, 32 
 
 conducting of, 74 
 
 Campbell, Dr. H., his method of ma- 
 king sal-ammoniac, 464 
 
 Camphorate of barytes, 141 
 
 Candles, manufacture of, 14 
 how best preserved, 15 
 
 Cannel coal, 191 
 
 Cannon, iron, when first made in Eng- 
 land, 581 
 
 Canton's phosphorus, 65 
 
 Caoutchouc, 195 
 
 Caqueray, Messrs, de, obtain the 
 right of making glass, 351 
 
 Carat weights, 115 
 
 Carbon, an essay on, 148 
 
 its properties, 149 
 
 natural compounds of, 183 
 
 how separated from the blood, 
 
 34 
 
 its proportions in iron and steel, 
 
 502 
 
 Carbonate of barytes, 125, 141 
 
 its decomposition, 133 
 
 illicit trade in, 130 
 
 Carbonic acid, 149 
 
 properties of, 150 
 
 its affinity for water, 426 
 
 dissolved by water, 150 
 
 sources of, 150 
 
 decomposed by Mr. Ten- 
 nan t, 151 
 
 oxide, 151 
 
 inhalation of, 152 
 
 oxide gas, produces apoplexy, 
 
 152 
 
 Carburet of nitrogen, 159 
 
 Carburetted hydrogen gas, 153 
 hydrogen, its composition, 158 
 
 Caspar Lehmann, glass-cutter to the 
 Court, 352 
 
 Cassius, the purple precipitate of, 
 used in China, 336 
 
 Castings of pig-iron converted to 
 malleable iron, 504 
 
 Cast-iron plane-irons, 483 
 
 varieties of, 501 
 
 cutlery, how converted to steel, 
 
 503 
 
 goods converted into wrought 
 
 iron or steel, 504 
 
 Cast-iron tinned, 509 
 Cast-nails made flexible, 504 
 Cast plate-glass, how made, 376 
 Cast-steel, the making of, 7, 479 
 
 process for making, 502 
 
 difficulty of welding, 479 
 
 formerly united to iron by rivets, 
 
 how made in Persia, 502 
 
 Casts of medals and coins, how pre- 
 served in glass, 380 
 
 Casting of plate-glass a grand spec- 
 tacle, 377 
 
 Cauk of Derbyshire, 122 
 
 Caustic potash in a dry state, direc- 
 tions for preparing, 584 
 
 lime necessary for plate-glass, 
 
 368 
 
 Causticity of alkalies, how produced, 
 276 
 
 Caxton, William, the first English 
 printer, 571 
 
 Celestine, 238 
 
 Celsus and Pliny on water, 428 
 
 Celts of antiquity, 475 
 
 Cement of the ancients for water- 
 cisterns, 439 
 
 Cementation of iron, 7 
 
 Cements made with barytes, 147 
 
 Ceraunia or thunder stones, 471 
 
 Chaloner, Thomas, 19 
 
 Chaptal on domestic washing, 414 
 
 on bleaching by means of com- 
 pressed steam, 41 5 
 
 on bleaching old prints, 416 
 
 his glaze for pottery, 330 
 
 his experiments on charcoal, 
 
 178 
 
 his account of French sal-ammo- 
 niac, 458 
 
 Charcoal, its preparation, 163 
 
 its comparative value as fuel, 
 
 75 
 
 its nature, 162 
 
 for gunpowder, 167 
 
 a bad conductor of heat, 174 
 
 extemporaneous, 169 
 
 found in Herculaneum, 170 
 
 quantities obtained by Allen and 
 
 Pepys, 171 
 
 its porosity, 162, 171 
 
 its selection for different pur- 
 poses, 172 
 
 pigment of, 172 
 
 from oil refuse, 173 
 
 of resins, 173 
 
 animal, 1 74 
 
620 
 
 INDEX. 
 
 Charcoal, perfectly infusible, 174 
 
 its use in domestic economy, 
 
 176 
 
 its action in purifying various 
 
 substances, 1/7 
 
 its uses in the arts, 178 
 
 employed in manufacturing iron, 
 
 181 
 
 Elizabeth's restriction in making, 
 
 181 
 
 Charles the aeronaut, 26 
 Charmes on bleaching, 1 1 
 Charred turf, 76 
 Charring of timber, 178 
 
 of wood, facts respecting, 170 
 
 of living chesnut trees, 181 
 
 Chaucer's account of English edge- 
 tools, 476 
 Chemical black, how made, 540 
 
 bleaching, its advantages, 401 
 
 discharges, 9 
 
 furnaces, observations on erect- 
 ing, 82 
 
 lectures, a national advantage, 
 
 3 
 
 mordants of antiquity, 527 
 
 residuums, 14 
 
 * tests for bleachers, 414 
 
 vessels of stone- ware, 31 1 
 
 Chemist, his peculiar resources, 21 
 Chemistry, an essay on its importance, 
 
 calico-printing dependent upon, 
 
 569 
 
 interesting to every nation, 3 
 
 its value to land-owners, 4 
 
 eminently indebted to Lord 
 
 Bacon, 1 
 should be a branch of education, 
 
 2 
 its importance in detecting 
 
 poisons, 6 
 
 its use in dyeing, 9 
 
 to tanners, 1 1 
 
 to glassmakers, 1 1 
 
 to soapmakers, 13 
 
 to brewers, 15 
 
 to sugar-refiners, 17 
 
 to refiners of gold and 
 
 silver, 18 
 
 of use to paper-makers, 19 
 
 knowledge of, useful in gar- 
 dening, 21 
 gives the habit of investigation, 
 
 23 
 
 Cherry abounds with citric acid, 260 
 Chimney registers, 79 
 
 Chimney walls, 88 
 
 for brass furnaces, 202 
 
 Chimneys, remarks on, 80 
 China blue dipping, 96, 295 
 Chinese porcelain, 10 
 
 method of purifying water, 443 
 
 Chinese, their practice of watering 
 
 land artificially, 452 
 Chintz printing, 552 554 
 Chlorate of barytes, 141 
 
 of potash, accident with, 50 
 
 Chloric ether, 158 
 Chloride of lithium, 303 
 
 of lime, 531, 401 
 
 its use in handkerchief 
 
 printing, 551 
 
 its action in bleaching, 
 
 402 
 
 of barium, 137 
 
 Chlorine, its discovery, 393 
 
 - its introduction in bleaching, 394 
 
 introduced in Scotland, 394 
 
 preparations, the strength of, in- 
 
 bleaching, of great importance, 
 413 
 
 converts gum to citric acid, 270 
 
 Chloro-carbonic acid, 153 
 
 Chloro-cyanic acid, 160 
 
 Choke-damp, 151 
 
 Chromate of barytes, 141 
 
 Chrome yellows on madder-grounds r 
 561 
 
 oil preparation ne- 
 cessary for, 563 
 
 - cloth prepared for, 
 
 561 
 
 563 
 
 patterns how put on, 
 
 a new style of, 563 
 colours a beautiful operation, 
 
 564 
 varied colours to be produced 
 
 from, 564 
 Chroming, 563 
 
 Chromic steel, how prepared, 507 
 Citrate of barytes, 142, 262 
 
 of lime, 263 
 
 cautions in making, 258 
 
 . quantity procured from 
 
 lemon-juice, 259 
 Citric acid, an essay on, 248 
 
 its use in calico-printing, 549 
 
 establishment for making, 250 
 
 directions for crystallizing, 254, 
 
 257 
 
 establishment for in the island 
 
 of Sicily, 258 
 
INDEX. 621 
 
 Citric acid found in several vegeta- 
 bles, 260 
 
 its chemical affinities, 261 
 
 the form of its crystals, 261 
 
 its composition, 262 
 
 uses of, 264 
 
 its action on milk, 264 
 
 its action with opium, 264 
 
 of use in dyeing, 265 
 
 used largely by the calico-printers 
 
 266 
 
 CStfic and tartaric acids, their differ- 
 ence, 262 
 
 salts, list of, 262 
 
 Clarke, Dr., his mode of producing 
 
 barium, 145 
 
 Clay, ancient method of tempering, 
 305 
 
 its variety in Britain, 310 
 
 how prepared in Saxony, 315 
 
 four kinds employed in the pot- 
 teries, 317 
 
 prices of, in Staffordshire, 317 
 
 how prepared in Staffordshire, 
 
 321 
 
 the tempering process in Staf- 
 
 s ford shire, 323 
 . different properties of, 343 
 
 Stourbridge, 86 
 
 its various uses, 318 
 Clays, how distinguished by the Ro- 
 mans, 317 
 Clayton, Dr. John, the discoverer of 
 
 coal gas, 156 
 Cleanliness necessary to good bleach- 
 ing, 411 
 
 Cleansing calicoes, 533 
 Clearing rainbow shades, 562 
 Clement and Desormes, 1 52 
 
 on sulphuret of carbon, 161 
 
 Climate, variety of, 25, 26, 31 
 
 causes of changes in, 35 
 
 Cloth, fulling of, 279 
 
 prepared for steam colours quite 
 
 useless for other purposes, 557 
 Cloudberry of Norway, 260 
 Coal, mineral, 1 92 
 
 on the methods of economizing 
 
 89 
 
 the waste of, explained, 89 
 
 best kind for furnishing gas 
 
 154 
 
 variety of its strata, 194 
 
 of Stainthorpe, 194 
 
 a singular kind found at Seaton 
 
 194 
 thrown up from the sea, 194 
 
 !oal sometimes fires spontaneously, 
 53 
 
 of Pontetaive, 192 
 
 sulphurous, to be avoided, 75 
 
 an economical stopper for fur- 
 nace mouths, 81 
 
 its boundary line in Scotland, 196 
 
 district of, in Britain, 196 
 
 damp,method of destroying, 194 
 
 mines, explosions in, 22 
 gas, cost of, 154 
 
 tar, 166 
 
 Coals, classification of, 184 
 
 specific gravity of, 192 
 
 observations on the consump- 
 
 tion of, 75 
 Cobalt-blue, 20 
 
 citrate of, 262 
 
 Cochineal employed by the ancients, 
 528 
 
 pink, how prepared, 557 
 
 Coins of iron, ancient, 484 
 Coke, its various uses, 182 
 
 ovens, 91, 182 
 
 for making iron, 182 
 
 ground with clay for making 
 
 crucibles, 340 
 
 new method of making, 183 
 
 Cold, method of modifying, 71 
 
 provisions of nature against, 71 
 
 artificial, directions for produ- 
 cing, 63 
 
 the greatest degree of, hitherto 
 
 observed, 63 
 
 produced by evaporation, in- 
 stances of, 55 
 
 theory of its production by snow 
 
 and salt, 60 
 Collier, his furnace for making steel, 
 
 478 
 
 Collieries, mode of lighting, 15 
 Colour for pencil blue, how prepared, 
 545 
 
 shades of, in tempering steel, 
 
 488 
 of logwood improved by water, 
 
 422 
 Colours, chemical, 9 
 
 on the extraction of, 97 
 
 various, produced from madder, 
 
 539 
 
 employed in Solomon's temple, 
 
 526 
 
 in the Jewish tabernacle, obser- 
 vations on, 525 
 
 _ on Indian calicoes imparted by 
 the pencil, 600 
 
622 
 
 1ND1LX. 
 
 Colours, vegetable, changed by alka- 
 lies, 275 
 
 various, produced by chemical 
 
 discharge, 546 
 
 how applied to calicoes in India, 
 529 
 
 Coloured linens, their antiquity, 525, 
 526 
 
 stripes on cotton hose, 420 
 
 Columns, basaltic, 99 
 
 Combustion, theories of, 38 
 
 new theory of, 38 
 
 not destruction, 40 
 
 the products of, 40 
 
 produced by the mixture of fluids 
 
 52 
 
 i ice and potassium, 
 
 52 
 
 spontaneous cases of, 52 
 
 . , of the human body, 
 
 54 
 
 Combustibles and incombustibles, 38 
 
 Composts, on the management of, 4 
 
 Compressed steam used in bleaching, 
 414 
 
 Condensation of water, 424 
 
 Conductors for lightning, 47 
 
 Confectionary, when first prepared 
 with ice, 61 
 
 Cooling of fluids by ether, 56 
 
 Cooper, Dr. Thomas, of America, 396 
 
 Cooper's dissertation on the Smell, 
 455 
 
 Coopers' adze, how made, 481 
 
 Copland, Mr. Professor, 394 
 
 Copland and Watt, their claims re- 
 specting gas bleaching, 395 
 
 Copper and zinc, alloys of, 197, 210 
 
 furnace for refining, 198 
 
 granulation of, 198 
 
 quantity of brass produced from, 
 
 206 
 
 wire annealed in cold water, 
 209 
 
 mines of Cornwall, 18 
 
 _ art of tempering for edge-tools, 
 475 
 
 implements of great antiquity, 
 
 475 
 
 celts abundant, 4/5 
 
 various solutions of, 543 
 
 its employment in calico-print- 
 ing, 543 
 
 citrate of, 263 
 
 plate-printing on china, 338 
 
 plate engravings, bleaching of, 
 
 416 
 
 Cornish clay, 319 
 
 granite, 319 
 
 Cornwall, tin mines of, 600 
 
 Cotton garments, their antiquity, 388, 
 
 526 
 
 mills, erection of, 90 
 
 no varnish upon, 567 
 
 Covinus, a terrible war-chariot, 475 
 
 Coxwell, Mr.,266 
 
 Crawford, Dr., his experiments on 
 
 heat, 32 
 
 on respiration, 33 
 
 on muriate of barytes, 137 
 
 Crayons of charcoal, 172 
 
 Crazing, a technical term in pottery, 
 
 318 
 
 Crell on citric acid, 253 
 Crofting calicoes, 392 
 Cronstat's sugar patent, 176 
 Crown-glass, 358 
 
 materials for making, 359 
 
 the process of forming, 360 
 
 divided into four classes, 363 
 
 Crucibles, on the manufacture of, 340 
 for glass-making, 74 
 
 how made in France, 340 
 
 of clay and calcined mica, 589 
 
 for melting brass, 203 
 
 for brass, curious colour of, when 
 
 broken, 203 
 
 Cruickshank on carbonic oxide, 152 
 Cryophorus of Wollaston, 64 
 Crystal, a remarkable one of sulphate 
 
 of barytes, 123 
 Crystallization of salts, 18 
 Crystallo- ceramic, patent for, 379 
 Cudbear, 20 
 Culinary utensils, use of double ones, 
 
 73 
 
 Cullet of the glass-house, 373 
 Culm of Pembrokeshire, 193 
 Cumberland's earthen files, 491 
 Cutlery, its progress in England, 476 
 Cutting instruments of stone, 471 
 instruments improved by the ad- 
 dition of silver, 505 
 Cyanogen and iodine, 160 
 Cylinder, charcoal, 164 
 printing, 554 
 
 D. 
 
 Dacier, Madame, on the ancient scar- 
 city of iron, 473 
 Dalesmius on burning smoke, 77 
 
INDEX. 
 
 62S 
 
 Dalton, Mr., on hard water, 428 
 
 on the density of water, 106 
 
 on the expansion of water, 448 
 
 1 on the expansion of gases, 119 
 
 on lime burning, 426 
 
 - his experiment on the formation 
 of sulphuric acid. 224 
 
 Damascus swords, 495, 597 
 sword blade described, 496 
 
 Damask appearance of the polished 
 alloy of steel and chromium,5( )7 
 
 Damaskeening, the art of, 598 
 
 Davies, Dr., on the areometer, 107 
 
 his tables of specific gravity, 107 
 
 his observations on mixed me- 
 tals, 114 
 
 Davy, Sir H., on the diamond, 148 
 
 on prussic gas and prussic acid, 
 
 160 
 
 on charcoal, 1 73 
 
 on the formation of sulphuric 
 
 acid, 224 
 
 on the agencies of galvanism. 
 
 298 
 
 his discovery that the affinities of 
 
 bodies are altered by their 
 states of electricity, 298 
 
 his decomposition of the alkalies, 
 
 299 
 
 a detail of these discoveries, 299 
 
 301 
 
 his decomposition of carbonic 
 
 acid, 151 
 
 his attempt to breathe carbonic 
 
 oxide, 152 
 
 his investigation of the fire-damp, 
 
 65 
 
 his safety lamp, 22 
 
 his own remarks on the safety 
 
 lamp, 71 
 
 his observation on the construc- 
 tion of the universe, 41 
 
 Davy, Dr. John, the discoverer of 
 chloro-carbonic acid, 153 
 
 his reason for naming it phos- 
 gene gas, 153 
 
 Decimal weights, 106 
 
 Decoction of bark for dyeing, 97 
 
 Decoction, distillation, &c. processes, 
 594 
 
 Decomposition ot water may reduce 
 combustion, 52 
 
 of sulphate of barytea, 1 25 
 
 Decompositions produced by extreme 
 cold, 59 
 
 Delame'therie on steam bleaching, 414 
 
 D elf- ware, manufacture of, 341 
 
 Demetrius, Daniel, first maker of 
 
 brass in England, 209 
 Democritus of Thrace, 22 
 
 on the origin of weaving, 388 
 
 Density of bodies, 105 
 
 Description of the manganese mine, 
 
 Desiderata in glass-making, 382 
 
 observations on, 382 
 
 in bleaching calicoes, 407 
 
 Devonshire mines of manganese, 417 
 Dew, its effect in bleaching, 390 
 Diamond, 148 
 
 method of valuing, 148 
 
 of the Emperor of Russia, 148 
 
 method of polishing, 149 
 
 decomposes the rays of light, 149 
 
 burnt at Florence, 150 
 
 burnt by Lavoisier, 150 
 
 Diamonds, large size of some, 580 
 Dibutates of Sicyon, 10 
 Discharge work in printing, 546 
 Discharges by citric acid, 548 
 Discharging process for Turkey red, 
 
 568 
 
 for chrome yellows, 563 
 
 Distillation, 16, 91 
 
 of pyroligneous acid, 167 
 
 Distilleries, 74 
 
 Dize on the manufacture of citric acid 
 
 253 
 on flavouring lemonade, 265 
 
 Dog-fish, proposal respecting, 467 
 
 Dome and back copper, 91 
 
 Domestic implements of antiquity 
 made with copper, 475 
 
 Doors of fire-places, 77 
 
 for reverberatory furnaces, 80 
 
 double, use of, 73 
 
 Dossie, Mr., on furnaces, 81 
 
 on the preparation of steel, 502 
 
 his character, 467 
 
 an error of his, corrected, 467 
 
 his account of sal-ammoniac, 467 
 
 Dragoons, a regiment of, bartered for 
 porcelain, 315 
 
 Drebbelius, the inventor of the scarlet 
 dye, 10 
 
 Dresden porcelain, 314 
 
 Drills of steel, how hardened, 490 
 
 Drying printed calicoes, 536 
 
 Du Buisson's process for concentra- 
 ting lemon-juice, 249 
 
 Dundonald, Earl, his treatise on agri- 
 culture, 4 
 
 on ammonia, 465 
 
 Dung of the cow, its use inprinting, 53 1 
 
624- 
 
 INDEX. 
 
 Dunging process of the calico printers, 
 
 ool 
 
 calicoes, 537 
 
 machines, 537 
 
 Durability of charcoal, 172 
 Dutch bleaching, 390 
 
 -brass, 210 
 
 Dyeing, a chemical process, 9 
 
 antiquity of, 526 
 
 with madder, 101 
 
 rainbow shades, 562 
 
 Dyers and bleachers require pure 
 
 water, 430 
 
 Dye woods, management of, 97 
 decoctions of, made in vessels 
 
 heated by steam pipes, 576 
 
 E. 
 
 Early life of Mr. Yarranton, 521 
 
 Earthen conduit pipes of the Romans, 
 587 
 
 vessels, Roman, 305 
 
 vessels of the Phoenicians, 306 
 
 Earthenware, an essay on, 304 
 manufacture of, 10 
 
 and porcelain, 93 
 
 materials for, 316 
 
 evidences of its antiquity, 304 
 
 ancient traffic in, 305 
 
 of Egypt, 307 
 
 English, 310 
 
 manufacture of, improved by Mr. 
 
 Wedgwood, 310 
 
 a caution respecting, 311 
 
 white enamel, 31 1 
 
 burning of, 328 
 
 manufacture of, in Egypt, 588 
 
 Earths, their analysis important to the 
 potter, 343 
 
 Economy of using soft water, 429 
 
 Edge-tools, essa}' on the manufacture 
 of, 471 
 
 of ancient nations, 471 
 
 of Japan made with an alloy of 
 
 copper, 474 
 
 of steel known to the ancient 
 
 Egyptians, 474 
 
 some of the various methods of 
 
 making, 481 
 
 motive for writing on their ma- 
 nufacture, 487 
 
 tempered at various tempera- 
 tures, 488 
 
 certain minutiae respecting, 489 
 
 cause of their warping, 490 
 
 Edge-tools, improved mode of tem- 
 pering, 494 
 
 injured by grinding, 500 
 
 of cast-iron, 501 
 
 made with various metallic 
 
 alloys, 505 
 
 formed with an alloy of steel 
 
 and chromium, 507 
 
 Edinburgh spring-water remarkably 
 pure, 434 
 
 Efflorescence and deliquescence of 
 salts, 425 
 
 Egypt, fertility of, 452 
 
 Egyptian obelisks, 7 
 
 mummies, 523 
 
 embalmers, 472 
 
 method of calico-printing, 527 
 
 sal-ammoniac, 457 
 
 Egyptians, their antipathy to wool, 
 526 
 
 claim the invention of glass, 346 
 
 magnificent glass cups of, 347 
 
 Elastic bitumen, 195 
 
 Elasticity of glass, instances of, 381 
 
 Electricity, 45 
 
 a mode of producing combus- 
 tion, 45 
 
 on the excitation of, 45 
 
 voltaic, 45 
 
 Electrical kite, 47 
 
 kite, cautions respecting, 48 
 
 Electrical and chemical attraction, 
 
 298 
 
 Electrical excitability of glass, 381 
 Elk and rein-deer, 27 
 Ellicott, John, his instrument for 
 
 measuring the expansion of 
 
 metals, 119 
 on the specific gravity of the 
 
 diamond, 580 
 Emery, 344 
 
 a native substance, 374 
 
 whence procured, 374 
 
 how prepared for glass grinding, 
 
 374 
 
 Emperor of China, declaration of, 196 
 
 Empyreumaof brandies, 176 
 
 Empyreumatic fat more efficacious in 
 tinning than fresh tallow, 514 
 
 Enamel painting, 31 1 
 
 England formerly supplied with tin 
 plates from Bohemia and Sax- 
 ony, 519 
 
 English cloths formerly bleached in 
 Holland, 390 
 
 process for making sal ammo- 
 niac, 463 
 
Engraving on porphyry, 474 
 
 of bankers' notes, 487 
 
 Entrecolles, Francis tie, 313 
 Equivalent numbers, the theory of, 137 
 
 an extensive Table 
 
 of, 601 
 
 Ersgebirg, tin mines of, 519 
 Essay on the importance of chemistry, 
 
 on sulphuric acid, additions to, 
 
 241 
 on calico-printing, additions to, 
 
 555 
 Establishment of the manufacture of 
 
 tin-plate in Paris, 522 
 Ether, its effect in producing cold, 
 
 56 
 Ethiopians inclosed their dead in glass, 
 
 Etruria, an account of its manufactory, 
 
 316 
 Etruscans noted for fine porcelain, 
 
 308 
 
 Etruscan vases, 588 
 Eudoxus the astronomer, 42 
 Europe formerly colder than it is at 
 
 present, 27 
 
 Expansion of gases by heat, 119 
 Expedients for preserving the warmth 
 
 of provisions, 74 
 for producing permanent colours, 
 
 531 
 
 Experiment of glass heated on a re- 
 volving grit stone, 52 
 
 on dunging calicoes, 538 
 
 on burning lime, 426 
 
 on the quality of water, 429 
 
 on tempering iron and steel, 
 
 486 
 
 on heating steel, 499 
 
 on blueing steel, 489 
 
 for condensing water, 424 
 
 Explosions of the fire-damp, 65 
 Eye, aqueous humours of, 455 
 Eyes, of animals, frozen for dissection, 
 
 61 
 
 F. 
 
 Fabbroni on bleaching old prints, 
 
 416 
 
 Fahrenheit, his thermometer, 60, 120 
 Faraday, Mr., his discovery of hy- 
 
 driodide of carbon, 159 
 his analysis of a peculiar hone, 
 
 501 ' 
 
 on the analysis of wootz, 481 
 
 2 
 
 INDEX. 625 
 
 Faraday, Mr., on perchloride of car- 
 bon, 158 
 
 on protochloride of carbon. 
 
 159 
 
 on the alloys of iron and steel, 
 
 505 
 
 Farish, Professor, his lectures, 3 
 Felting of hats, 20 
 Females destroyed by spontaneous 
 
 combustion, 54 
 Fermentation, acetous, 17 
 
 vinous, 17 
 
 Fern employed in fulling, 280 
 Ferrara, Andrew, his mode of temper- 
 ing swords, 495 
 Ferroprussiate of potash, 560 
 Fiery ground of Staffordshire, 53 
 Files, an expedient for hardening, 
 492 
 
 how finished, 493 
 
 of case-hardened iron, 493 
 
 manufactory of, 491 
 
 of earthenware, 491 
 
 Filtrating water, 434 
 Fire bricks for brass furnace, peculiar 
 form of, 202 
 
 expedients for producing, 41 
 
 venerated by the ancients, 41 
 
 an ancient image of life, 41 
 
 worshipped by the Persians, 42 
 
 unknown to some nations, 42 
 
 procured from the sun, 42 
 
 its production by collision, 42, 
 
 49 
 
 produced by phosphorus, 49 
 
 produced by compression, 51 
 
 produced by compression of air, 
 
 51 
 
 procured by percussion, 52 
 
 produced by friction, 52 
 
 damp of the collieries, 64, 194 
 
 chemical nature of, 65 
 
 its combination with oxy- 
 gen, 69 
 
 places of furnaces, 81 
 
 bars, their construction, 82 
 
 lute, directions for making, 84 
 
 management of, 89 
 
 some memoirs on the prevention 
 
 of, 212 
 
 subterranean, 53 
 
 Fish decompose water, 422 
 
 oil, how purified, 12 
 
 thrown from a volcano, 31 
 
 Flame, its nature, 67 
 
 its peculiar temperature, 67 
 
 Flax, its early cultivation, 523 
 
626 
 
 INDEX. 
 
 Flax, method of bleaching in Holland, 
 
 442 
 
 Flaxen yarn, how bleached, 391 
 Flint, a native oxide, 49 
 and steel of the Laplanders, 
 
 42 
 their employment in 
 
 the collieries, 49 
 
 glass, cause of its superior bril- 
 liancy, 357 
 
 in potters' glaze, 334 
 
 process of making, 355 
 
 Flints, ground, formerly used in glass, 
 
 357 
 
 how prepared for pottery, 321 
 
 Fluate of barytes, 142 
 Flues for furnaces, 88 
 Fluids, the specific gravity of, how 
 
 estimated, 106 
 Fordyce, Dr., on the colours of light, 
 
 38 
 
 his heated chamber, 36 
 
 Forging of small edge tools, 482 
 Formate of barytes, 142 
 Forsyth's percussion gunpowder, 50 
 Fossil alkali, 289 
 
 meal, 344 
 
 Founderies established in this country 
 
 by the Romans, 597 
 Fourcroy,his account of sea- water, 468 
 his proposals for making citric 
 
 acid, 258 
 Fourmy, Mr., on the potter's glaze, 
 
 334 
 
 Fowler's drop, 282 
 Fowling-pieces, 100 
 Foy, Mr., his bleaching proposal, 
 
 399 
 France, young nobility of, formerly 
 
 laboured in the manufactory of 
 
 glass, 351 
 Frankland, Sir Thomas, on cast-steel, 
 
 480- 
 Franklin on lightning and electricity, 
 
 47 
 
 French gunpowder, 169 
 method of hardening steel in- 
 struments, 484 
 
 -. brass, 210 
 
 Frigorific mixtures, materials for, 62 
 
 of Mr. Boyle, 60 
 
 Frit, its preparation, 359 
 Frozen mercury, experiment with, 35 
 Fruit artificially frozen at Paris, 61 
 Fuel, comparative heat of, 75 
 
 on the oeconomy of, 75 
 
 manufactured, 193 
 
 Fuller, anecdote of, 416 
 
 Fuller's earth, 279, 343 
 
 Fullers in ancient Rome, 431, 592 
 
 Fulling, the process of, explained, 279 
 
 Fulling-mill, 279 
 
 for hose, 403 
 
 Furnace bars, varieties of, 82 
 
 for copper, 198 
 
 for making brass, description of, 
 
 200 
 
 for brass, plans of, 201 
 
 Furnaces, best method of feeding, 8!) 
 a curious mode of heating at 
 
 St.Gobin,376 
 
 doors and frames, 78 
 
 for annealing cast-iron cutlery, 
 
 505 
 
 on their erection, 77 
 
 on the method of heating them, 
 
 80 
 
 reverberatory, 80 
 
 Fusion of basalt, 98 
 
 of chalk and marble, 98 
 
 G. 
 
 Gallate of barytes, 142 
 
 of iron, 540 
 
 Galvanic battery, Mr. Children's, 46 
 of the Royal Institu- 
 
 tion, 46 
 Galvanism, 45 
 
 powerful effects of, 46 
 
 Game preserved by charcoal, 176 
 Gardeners of Paris, 454 
 Garments anciently of bulrushes, 388 
 Gas bleaching introduced at Man- 
 chester, 396 
 
 introduced in France, 397 
 
 illumination, osconomy of, 154 
 
 inflammable, in Persia, 53 
 
 lights, 15 
 
 procured from oil seeds, 155 
 
 its produce from coal, 1 54 
 
 Gases expelled from the lungs, 33 
 quantity absorbed by charcoal, 
 
 their capacity for caloric, 34 
 
 Gay-Lussac on the formation of chlo- 
 
 rocyanic acid, 160 
 the discoverer of carburet of 
 
 nitrogen, 160 
 
 Geber on sal-ammoniac, 460 
 Gellert's table of affinities, 463 
 Geoffrey, his memoir on sal-ammoniac, 
 
 457 
 
INDEX. 
 
 627 
 
 Geoffrey, his table of chemical affini- 
 ties, 463 
 
 German steel, 7, 478 
 
 tinder, 169 
 
 Germination of seeds, 20 
 
 Gill's apparatus for taking specific 
 gravities, 117 
 
 Ginori, Marquis de, his porcelain ma- 
 nufacture, 314 
 
 Glance-coal, 191 
 
 Glass, a metallic compound, 386 
 
 an essay on the manufacture of, 
 
 346 
 
 transparent produced from two 
 
 opake bodies, 346 
 
 etymology of the word, 346 
 
 when invented, 346 
 
 used in the time of Pliny, 346 
 
 found in the ruins of Hercula- 
 
 neum, 347 
 
 malleable, discovered by a Ro- 
 man architect, 348 
 
 house, establishment of, at Tour- 
 
 laville, 352 
 
 house Her, 356 
 
 houses of the Tyrians, 348 
 
 houses, early ones in Great 
 
 Britain, 348 
 
 houses established in London, 
 
 353 
 
 houses, their number in 1696, 
 
 354 
 
 houses, five different kinds of, 
 
 354 
 
 windows, when introduced into 
 
 England, 348 
 
 windows, late introduction of, 
 
 into Europe, 348 
 
 the art of painting on, first in- 
 troduced, 349 
 
 the art of staining, lately known 
 
 in England, 350 
 
 stained, known to the Greeks 
 
 and Romans, 350 
 
 quantity of made in Bohemia, 
 
 350 
 
 substitue for, in Russia, 350 
 converted to a kind of porcelain, 
 
 340 
 
 history of the manufacture of, 
 
 in Bohemia, 350 
 
 manufacture of, encouraged in 
 
 France, 351 
 
 making considered honourable 
 
 in France, 352 
 
 grinding and cutting, when intro- 
 duced, 352 
 
 2 
 
 Glass known to the ancients, 372 
 
 engraving on, by fluoric acid, 
 
 352 
 
 manufacture, improvements of, 
 
 in England, 353 
 
 pit-coal first used in the manu- 
 facture of, 354 
 
 method of ascertaining the pu- 
 rity of, 356 
 
 utensils, how formed, 356 
 
 a bad conductor of heat, 357 
 
 its nature as a chemical com- 
 pound, 380 
 
 26 distinct properties of, 380 
 
 its ductility, 380 
 
 its transparency, 380 
 
 of the ancient Romans, 381 
 
 in the windows of Pompeii, 381 
 
 drinking-vessels of antiquity, 
 
 381 
 
 eminently elastic, 381 
 
 impermeable to electricity, 381 
 
 unannealed, curious properties 
 
 of, 381 
 grinding, an improvement in, 
 
 373 
 
 incrustations, 379 
 
 made in Bohemia, 
 
 379 
 
 observations on annealing, 383 
 
 gall, 383 
 
 for holding acids, 384 
 
 lachrymatories at Rome, 384 
 
 of peculiar hardness made by 
 
 borax, 385 
 
 made by the union of metallic 
 oxides, 386 
 
 ancient, coloured, 590 
 
 trade, technical terms in, 591 
 
 annealing ovens at Ravenhead, 
 
 376 
 
 plates, how cast -at Ravenhead, 
 
 376 
 
 mirror, a French one of uncom- 
 mon size, 353 
 
 mirrors, manufactory of, at Mu- 
 
 rano, 351 
 
 manufactories of, at St. Go- 
 bin, 353 
 
 Glass-makers' crucibles, 93 
 
 method of decomposing salt, 
 
 369 
 
 Glass-making, 11 
 
 antiquity of, 353 
 
 technical terms of, 358 
 
 the circumstances on which its 
 
 success depends, 386 
 
 S2 
 
628 
 
 INDEX. 
 
 Glauber on making sulphuric acid, 
 213 
 
 his salt, 14, 297 
 
 Glauberite, 238 
 
 Glaze of china, a chemical test for, 
 331 
 
 how applied to pottery, 330, 333 
 
 of the French potters, 334 
 
 Glazed windows still unknown at Rio 
 
 de Janeiro, 349 
 
 Glazing of pottery a pernicious opera- 
 tion, 334 
 
 . of earthenware, 330 
 
 Glucina, citrate of, 263 
 Goettling, his book on tests, 6 
 Goguet on the antiquity of cotton gar- 
 ments, 388 
 Gold and silver refining, 18 
 
 scarpe mountain, 187 
 
 touch-holes of gun-locks, 100 
 
 Government, an instance of its injuri- 
 ous interference in the glass- 
 trade, 366 
 Gradation of colours in tempering edge 
 
 tools, 488 
 
 Grain-tin found in Bohemia and Sux- 
 ony, 519 
 
 prepared from an ore called 
 
 stream tin-ore, 513 
 Granite used for moulds to cast brass, 
 206 
 
 of Cornwall, 319 
 
 Cornish, employed in pottery, 
 
 320 
 Gravity, absolute and specific, 102 
 
 definition of, 102 
 
 comparative, 105 
 
 Grease a great impediment to good 
 
 bleaching, 409 
 
 its mischievous effects on cali- 
 coes, 533 
 
 used in making tin-plate, 514 
 
 Greek-fire of antiquity, 581 
 
 Greeks, their proficiency in the arts of 
 
 pottery, 305 
 Green stone for setting lancets, 501 
 
 for steam colours, how produced, 
 
 558 
 
 Grinding-stones of Sheffield, 500 
 Gum converted to citric acid, 270 
 largely employed in calico- 
 printing, 535 
 
 Senegal, 535 
 
 tragacanth, 535 
 
 Gun-barrels, hardening the breech of, 
 
 100 
 Gunpowder a chemical compound, 18 
 
 Gunpowder, its composition, 162 
 its introduction, 581 
 the peculiar strength of the Bri- 
 tish, 169 
 Guyton and Carny on chemical resi- 
 
 duums, 147 
 on charcoal, 1 75 
 his pyrometer, 100 
 
 H. 
 
 Haarlem bleaching grounds, 390 
 
 Hadley, Dr., on the Egyptian mum- 
 mies, 523 
 
 Hales, Dr., on the distillation of sea- 
 water, 443 
 
 Hall, Sir James, his experiments on 
 temperature, 98 
 
 Hamildon, the battle of, 476 
 
 Hannibal's passage over the Alps, 
 2 
 
 Hard water fittest for ship-board, 
 443 
 
 how softened, 444 
 
 injurious in brewing, 441 
 
 unfit for horses and cattle, 
 
 432 
 
 unwholesome effects of, 436 
 
 waters, 428 
 
 of Portugal, 430 
 
 Hardening of edge tools, 483 
 
 of files, 491 
 
 Hardy, Mr., on steel-plates, 491 
 
 Hartley's (David) patent for temper- 
 ing steel, 493 
 
 on tempering edge tools, 493 
 
 Hasselquist's account of the manufac- 
 ture of sal-ammoniac in Egypt, 
 458 
 
 Hassenfratz on the manufacture of 
 iron, 181 
 
 Hatchets of copper used by the an- 
 cients, 474 
 
 Hatchett, Charles, Esq. on elastic 
 bitumen, 195 
 
 his analysis of retinasphaltum, 
 
 195 
 
 on tannin, 162 
 
 Hat-felts, 20 
 
 Hearth of brass furnaces, 202 
 
 Heat, how produced by combustion, 
 38 
 
 the matter of, 24 
 
 method of modifying, 54 
 
 methods for preserving, 
 
 on the economy of, 90 
 
 Heath, a good yellow dye, 96 
 
INDEX. 
 
 629 
 
 IJpnry, Mr. Thomas, 395 
 
 his merit with regard to the 
 
 bleaching process, 396 
 Henry, Dr. William, his apparatus for 
 
 freezing mercury, 62 
 his experiments on coal gas, 
 
 155 
 
 his memoirs on coal gas, 155 
 
 on spontaneous combustion, 53 
 
 on the temperatures of the porce- 
 lain ovens, 331 
 Heraldic crests preserved in the centre 
 
 of glass, 379 
 Hercynian forest, 27 
 Herodotus on Arabian alliances, 472 
 
 on pure water, 442 
 
 on the earthenware of his time, 
 
 305 
 
 Hesiod on the plough-shares of an- 
 tiquity, 472 
 Hill's and Haddock's patent for 
 
 making sulphuric acid from 
 
 martial pyrites, 582 
 Hippocrates on water, 428 
 Hoepfner on sulphate of barytes, 122 
 Homberg's areometer, 104 
 
 experiment on vinegar, 17 
 
 memoir on specific gravity, 104 
 
 Home, Dr., his experiment in bleach- 
 
 ing, 393 
 
 on agriculture, 4 
 
 on hard water, 429, 436 
 
 on the water of Edinburgh, 434 
 
 Honeystone of Werner, 195 
 
 Hooke, Mr., on the alloy of tin and 
 
 silver, 114 
 
 Hope, Dr., on barytes, J27 
 Hopper doors for furnaces, 81 
 
 fire-place, advantages of, 82 
 
 Horn-quicksilver, 239 
 
 Home's essays on iron and steel, 182 
 
 on making coke, 182 
 
 Horse-nail stubs, their employment, 
 
 482 
 Hose, bleaching, 398, 401 
 
 bleaching, a test for, 420 
 
 Houghsetter, Daniel, 18 
 
 Houses secured from lightning, 47 
 
 the first made of earth or clay, 
 
 587 
 
 Hudson's Bay, climate of, 36 
 Human body, the temperature of, 32 
 Humboldt on enlarging the growth of 
 
 vegetables, 418 
 Hume on the solution of barytic salts. 
 
 136 
 Hume's permanent white, 124 
 
 Hydrate of barytes, 134 
 Hydrates, 424 
 
 alkaline, 285 
 
 Hydraulic organs of the ancients, 
 
 450 
 
 Hydriodate of barytes, 142 
 Hydriodide of carbon, 159 
 Hydrocyanic orprussic acid, 160 
 Hydrometers for spirits, 109 
 Hydroscopium of Synesius, 428 
 Hypatia's areometer, 107 
 
 I. 
 
 Ice employed in the salmon fisheries, 
 
 59 
 basins used as a receptacle for 
 
 wine, 61 
 
 cups of Mr. Boyle, 61 
 
 dealers in France, 57 
 
 house useful to the chemist, 59 
 
 houses, their antiquity, 57 
 
 how formed at Ispahan, 58 
 
 how produced in Italy, 59 
 
 imported from Greenland, 57 
 
 making at Calcutta, 58 
 
 mountains of Greenland, 35 
 
 specific gravity of, 35 
 
 at Spitzbergen, 35 
 
 pits at Leghorn, 57 
 
 prepared in the middle of sum- 
 mer, 61 
 
 produced artificially at Bengal, 
 
 55 
 
 produced expeditiously by ether, 
 
 56 
 
 the want of, supplied, 56 
 
 Improvement in bleaching calicoes, 
 542 
 
 Improvements in calico-printing, 9, 
 555 
 
 in soap-making, 13 
 
 Incombustible gases how expelled, 
 245 
 
 Incorruptibility of charcoal, 1 79 
 
 India abounds in colouring substances, 
 526 
 
 Indian iron, tincture of, 5 
 
 steel, 481 
 
 Indigo, the management of, for calico- 
 printing, 543 
 
 how deoxidized, 543 
 
 test, directions for making, 413 
 
 . vats, 96 
 
 vat, neutral, 560 
 
 Infusibility of charcoal, 174 
 
 Ink of the ancients, 581 
 
630 
 
 INDEX. 
 
 Instruments, new ones for producing 
 
 fire by compression, 51 
 Intense light, 573 
 lodate of barytes, 142 
 Iodide of lithium, 303 
 Irish bleaching, 531 
 Iron, an instance of its increase of 
 
 weight, 7 
 
 cannon, 581 
 
 citrate of, 263 
 
 coins of the Lacedaemonians, 
 
 484 
 
 foreign irregularity of, 479 
 
 founders, remarks on, 7 
 
 injurious in bleaching, 437 
 
 its remarkable affinity for silica, 
 
 342 
 
 liquor of the calico-printer, 529 
 
 made with wood charcoal, 501 
 
 manufactories dependent on che- 
 mistry, 7 
 
 mines, 8 
 
 money of the Britons, 475 
 
 foundries of the ancient Romans, 
 
 475 
 
 not to touch steam colours, 559 
 
 ore of the Forest of Dean, 8 
 
 ores abundant, 181 
 
 plates tinned with a mixture of 
 
 block and grain tin, 513 
 why bad to burn sulphur 
 
 on, 243 
 
 stills, observations on, 75 
 
 superiority of that made with 
 
 charcoal, 181 
 
 Swedish, 477 
 
 the antiquity of its manufacture, 
 
 471 
 
 the basis of many colours, 547 
 
 universally distributed, 473 
 
 knowledge of making it lost at 
 
 the Flood, 473 
 vitriol, 239 
 water-pipes, how prevented from 
 
 oxidizing, 440 
 
 white prussiate of, 421 
 
 wire imported from Holland, 
 
 479 
 
 Ironing, an observation respecting, 40 
 Irrigation, 431 
 importance of, in agriculture, 
 
 4,453 
 
 memoirs on, 453 
 
 of lands, 4 
 
 Isinglass and tan, 97 
 Isis and Osiris, 16 
 Islet's patent green, 548 
 
 taly, glass windows first used there, 
 350 
 
 J. 
 
 Javelle, liquor of, 398 
 
 Jet, 191 
 
 Johnstone and Lambe, Drs., on the 
 
 poison of lead, 445 
 Josephus, his account of sand fit for 
 
 making glass, 347 
 Julius Caesar, the dismay of his army 
 
 on approaching Britain, 2 
 Jupiter Ammon, temple of, 457 
 Jurin,Dr.,on weighing hydrostatically, 
 
 112 
 
 K. 
 
 Kali of Pliny, 275 
 
 Kaolin of the Chinese, 319 
 
 Kelp, 276 
 
 weed, how cultivated, 289 
 
 manufacture of, 290 
 
 introduced by Mac Leod, 289 
 
 its variation in price, 289 
 
 ovens, 290, 585 
 
 a prize essay on, 290 
 
 directions for the analysis of, 290 
 
 the particulars of some analyses, 
 
 584 
 
 in glass-making, 359 
 
 Kilns for kelp-burning, 290 
 Kirwan on the analysis of water, 43 1 
 on the difficulty of introducing 
 
 improvements, 472 
 Klaproth on native sal-ammoniac, 460 
 Koran of Mahomet on water, 421 
 Kunkell's phosphorus, 65 
 
 L. 
 
 Labelye on specific gravities, 112 
 
 Lake of Geneva, 29 
 
 Lakes, circulation of caloric in them, 
 30 
 
 the deepest, never freeze, 30 
 
 Lamp-black, its manufacture, 1 73 
 
 Land, cultivated rationally by Lavoi- 
 sier, 4 
 
 how preserved in Thibet from 
 
 tornadoes, 72 
 
 improved by regular waterings, 
 
 452 
 
 owner, chemistry important to 
 
 the, 4 
 
 Lapis, a name for neutral resist-work, 
 560 
 
INDEX. 
 
 631 
 
 Lapis executed at Mulhausen and 
 Ghent, 560 
 
 lazuli, the effect of heat on its 
 
 colour, 588 
 
 specularis used in Russia for 
 
 windows, 350 
 
 Lava employed as a glaze on earthen- 
 ware, 334 
 Lavoisier a chemical farmer, 4 
 
 his theory of combustion, 38 
 
 Lead, an insidious poison, 589 
 
 citrate of, 263 
 
 glaze, very unwholesome, 589 
 
 its use in glass, 357 
 
 the antiquity of its use in glass, 
 
 358 
 
 vitriol, 239 
 
 Leaden boilers, advice respecting, 
 222 
 
 chambers for making sulphuric 
 
 acid, 220 
 
 erection of, 241 
 
 = necessary appendages 
 
 to, 243 
 
 cisterns, caution against, 445 
 
 milk-pans, 589 
 Leather, improvements in, 93 
 
 first made by Tychius, 1 1 
 
 Leblanc's, M., manufacture of sal-am- 
 moniac, 465 
 
 Lectures, chemical, a national advan- 
 tage, 3 
 
 Lemere's account of Egyptian sal-am- 
 moniac, 457 
 Lemon-juice, an experiment on, 267 
 
 directions for the choice of, 266 
 
 employed largely in the navy, 
 
 265 
 
 how adulterated, 267 
 
 causes of its deterioration, 268 
 
 how concentrated in Sicily, 258 
 
 how treated for the navy, 265 
 
 its strength ascertained, 267 
 
 methods of purifying, 248 
 
 mode of separating the mucilage 
 
 of, 583 
 
 purified by freezing, 249 
 
 Lemonadiers of Paris, 62 
 
 Lentulus Spinter, 525 
 
 Lepidolite, 302 
 
 Leslie, his experiments on cooling 
 
 liquids, 73 
 
 Lewis, Dr., his experiments on clays, 
 318 
 
 his method of taking specific 
 
 gravities, 114 
 
 Lewis, Dr., on the making of accurate 
 weights, 106 
 
 on the specific gravity of metal- 
 lic alloys, 114 
 
 Liege process of making sal-ammo- 
 niac, 464 
 
 Lier-pans, 356 
 
 Light and heat produced by compres- 
 sion, 51 
 
 colours of, 38 
 
 decomposed by the diamond, 1 49 
 
 Lignum-vita?, its produce of charcoal, 
 
 Limb, the loss of one, occasioned by 
 
 antimony, 6 
 Lime anciently employed in bleaching, 
 
 388 
 
 burning, a hint respecting, 426 
 
 burnt by means of inflammable 
 
 gas, 53 
 
 citrate of, 263 
 
 employed in bowking calicoes, 
 
 406 
 
 employed in crown-glass, 359 
 
 in agriculture, 4 
 
 its quality, very important for 
 
 making glass, 368 
 
 its use to soapmakers, 276 
 
 lactate of, 285 
 
 Lime-mortar, 85 
 
 Linen cloth, its antiquity, 525 
 
 Linens of Holland, 390 
 
 Linen, the difficulty of bleaching, 391 
 
 Liquor silicum, 287 
 
 Lister, Dr., on ancient edge-tools, 7 
 
 on the manufacture of steel, 476 
 
 Lithia, 302 
 
 sulphate of, 303 
 
 muriate of, 303 
 
 nitrate of, 303 
 
 carbonate of, 303 
 
 Lithium, 302 
 
 Litmus paper, its uses, 291 
 
 Lixivium, its derivation, 273 
 
 Loadstone, 1 
 
 Lochness, 30 
 
 Logwood, how prepared for the dyer, 
 
 422 
 
 interdicted by Elizabeth, 592 
 London bleaching liquid, 393 
 mean temperature of, 28 
 
 Mr., his apparatus" for 
 
 taining the weight of fluids, 120 
 
 plate glass-house, 372 
 
 Lowitz, his directions for purifying 
 salts, 178 
 
 on artificial cold, 63 
 
632 
 
 INDEX. 
 
 Loysel, his observations on glass- 
 making, 382 
 
 on the sand proper for glass- 
 making, 364 
 
 on the specific gravity of glass, 
 
 385 
 
 on the construction of crucibles, 
 
 382 
 
 on wood-fuel, 75 
 
 Lucas, his patent edge-tools, 501 
 
 his steel, capable of being mag- 
 netised, 504 
 
 Lungs, on their construction, 33 
 
 Lust re- ware, 347 
 
 Lydiatt on the warping of edge-tools, 
 490 
 
 Lye, alkaline, how prepared, 276 
 
 of Javelle, 398 
 
 Lympheducts of the eye, 455 
 
 Lynn sand, 355 
 
 M. 
 
 Mac Donald, Lord, a great kelp 
 grower, 289 
 
 Mac Gregor, the Scotch bleacher, 395 
 
 Machine, curious one in Hungary, 
 51 
 
 for cutting tin plates, 510 
 
 Macquer's arsenical salt, 282 
 
 Madder, cultivation of, 95 
 
 process in calico-printing, 539 
 
 its properties, 539 
 
 two colours contained in, 542 
 
 Maddered goods, how cleared, 413 
 
 Magic, those suspected of, formerly 
 tried by water, 450 
 
 Magnesia, citrate of, 263 
 its use in porcelain, 344 
 
 Malate of barytes, 142 
 
 Malic acid procurable from lemon 
 juice, 250 
 
 Malleable glass, the discoverer of, 
 executed by Tiberius, 348 
 
 a subsequent inventor of, impri- 
 soned by Richelieu, 348 
 
 Malting of barley, 1 6 
 
 remark on, 427 
 
 Manganese, citrate of, 263 
 
 its use in glass, 358 
 
 residuum, 418 
 
 would accelerate vegetation, 
 
 418 
 
 the action of its oxide in purify- 
 ing flint glass, 590 
 
 whence procured, 417 
 
 brown salt of, 564 
 
 Manganese, sulphate of, employed in 
 
 calico-printing, 564 
 Manheim gold, 210 
 Manner of printing calicoes, 534 
 Mansel's, Sir Robert, patent for 
 
 making glass with coal fuel, 
 
 354 
 Manton's touch-holes of gun-locks, 
 
 101 
 
 Manufactories heated by steam, 90 
 of steel in England, 477 
 
 influenced by the nature of the 
 
 water, 427 
 
 Manufacture of crown glass highly in- 
 teresting, 362 
 
 of printers' types, 486 
 
 of brass, essay on, 1 97 
 
 Manufacturers of England, superior 
 knowledge of, 101 
 
 Manufactures dependent on chemistry, 
 
 the consequences of their esta- 
 blishment, 196 
 
 Manures, saline and earthy, 4 
 
 Marcet, Dr.,' on sulphuret of carbon, 
 161 
 
 Margraaf on calami ne, 18 
 
 Marian islands, inhabitants of, 42 
 
 Mariner's compass, 1 
 
 Marinus Ghetaldus on specific gravi- 
 ties, 104 
 
 Mersennus on specific gravity, 
 
 Marmor metallicum, 122 
 Mars, tartarized tincture of, 284 
 Martial pyrites, now used in making 
 
 sulphuric acid, 582 
 Mascagnine, 237 
 Matter indestructible, 40 
 Means to be adopted for purifying 
 
 water, 435 
 
 Meat effectually preserved, 176 
 the process of freezing at Thibet, 
 
 58 
 
 Medical electricity, 45 
 Medicine dependent upon chemistry, 
 
 o 
 
 profession of, 5 
 
 Mellilite, 195 
 Mercury, citrate of, 263 
 
 corneous, 239 
 
 first frozen by art at Oxford, 62 
 
 frozen in Russia, 3o 
 
 and tin, amalgam of, used for 
 
 mirrors, 508 
 Merret, Dr., his proportions for plate 
 
 glass, 368 
 
INDEX. 
 
 633 
 
 Metals affected by change of atmo- 
 spheric temperature, 576 
 
 ascertained by their specific gra- 
 vity, 105 
 
 deoxidized by carbon, 149 
 
 increase of weight in, 40 
 
 melted at the distance of 40 feet, 
 
 44 
 
 phenomena in burning, 40 
 
 purity of, 579 
 
 Metallic alloy that will fuse at 202, 
 115 
 
 alloys cannot be estimated by 
 
 their specific gravity, 114 
 
 arts of the ancient Britons, 476 
 
 baths for cutlers, 494 
 
 tables in the plate glass works, 
 
 377 
 
 oxides, 572 
 
 employed in potter's 
 
 glaze, 335 
 
 solutions determined by their 
 
 specific gravity, 105 
 
 Metalloids in the alka'lies, 30! 
 
 Method of detecting badly bleached 
 linens, 420 
 
 Mexia, Peter, 163 
 
 Milnes, Messrs., 394 
 
 Milton, on water, 421 
 
 Mine at Upton Pine, 421 
 
 Mineral alkali, 289 
 
 acid too active for steam colours, 
 
 556 
 
 Minerals, analysis of, 3 
 
 the Emperor's collection of, 1 80 
 
 Miners' lamps, history of, 64 
 
 safety lamp, 22 
 
 their confidence in the safety 
 
 lamp, 69 
 
 Mines of Anglezark, 128 
 
 Minish, his patent method of making 
 sal-ammoniac, 464 
 
 Mirrors, large ones cast by Thevart, 
 352 
 
 of ancient Rome, 590 
 
 plain and concave, 44 
 
 Mixture of fluids, 115 
 
 of some fluids will produce com- 
 bustion, 52 
 
 of sulphuric acid and water, 
 
 115 
 
 Mixtures of ardent spirits, 115 
 
 Molasses, purified, 176 
 
 Moll's cabinet of minerals, 1 80 
 Molybdate of barytes, 142 
 Moore, Mr. Samuel, on the colouring 
 artificial gems, 178 
 
 Mordant for steam colours cannot be 
 
 discharged, 557 
 Mordants, chemical, 9 
 
 explained, 531 
 
 how applied to calicoes, 535 
 
 used in maddering, 539 
 
 Morgan on the colours of light, 38 
 Morocco leather, 13, 573 
 Mortar, the best to be used for che- 
 mical furnaces, 85 
 
 of the ancients, 86 
 
 Moses, Mr., his collection of ancient 
 
 vases, 588 
 
 Mother-waters of citric acid, 255 
 Moulds for casting brass described,206 
 Mountainous districts improved, 453 
 Muhammed, M., on Persian steel, 502 
 Murdoch, Mr., first employed coal gas 
 for illumination, 156 
 
 rewarded by the Royal Society. 
 
 157 
 
 Muriacit of Werner, 239 
 Muriate of barytes, 137 
 
 directions for using, 
 
 146 
 
 first employed by 
 
 Crawford, 146 
 of lime, 63 
 
 acts injuriously in bleach- 
 
 ing, 407 
 
 of potash, produced by glass- 
 makers, 369 
 
 of soda, 464 
 
 of tin, accident in making, 427 
 
 used in dyeing yellows, 652 
 
 of peroxide of tin, 556 
 
 Murray, Dr., his analysis of sea-water, 
 468 
 
 Muschenbroek, his table of specific 
 gravities, 105 
 
 Mushet on the preparation of char- 
 coal, 170 
 
 Mr., on wootz, 481 
 
 Musical water-instruments, 450 
 
 wire, 479 
 
 Myrobalans employed in dyeing, 528 
 
 N. 
 
 National manufactures, 101 
 Native barytic salts, 125 
 
 sal-ammoniac, 460 
 
 sulphuric acid, 212 
 
 Natron, 289 
 
 Egyptian, 239 
 
 Nature, a deviation from its usual 
 
 course, 30 
 Nausicaa and her companions, 389 
 
634 
 
 INDEX. 
 
 Neri on glass, 1 1 
 Nero's cups of glass, 381 
 Neumann on the varieties of char- 
 coal, 172 
 Neutral resist-work, 559 
 
 style, when first produced, 560 
 
 vat described, 560 
 
 Newfoundland, climate of, 28 
 Newton, Sir Isaac, his burning mirror, 
 45 
 
 his conjecture respecting the 
 
 diamond, 358 
 
 his fondness for chemistry, 3 
 
 his opinion of the cause of change 
 
 of colour in edge tools, 388 
 
 on specific gravity, 1 04 
 
 his conjectures respecting water, 
 
 104 
 
 Nicholson on tempering steel, 487 
 Nicholson's areometer, ] 08 
 Nitrate of iron, 540 
 
 of silver, 267 
 
 Nitre employed to obtain potash, 280 
 
 first employed for producing cold, 
 
 59 
 
 its use in making glass, 358, 369 
 
 its use in making coloured glass, 
 384 
 
 the method of refining, 93 
 
 native of Molfetta, 240 
 
 Nitric acid employed in calico-print- 
 ing, 549 
 
 acid employed in purifying clay, 
 
 341 
 Nitromuriate of tin for steam colours, 
 
 556 
 
 Nitrum known to the ancients, 274 
 Nottingham black glaze, 335 
 Number of operations in bleaching, 
 413 
 
 of plates tinned by one man in a 
 
 day, 516 
 
 O. 
 
 Obelisks, Egyptian, 7 
 
 statues, &c. of porphyry, 474 
 
 Observations on the property which 
 
 iron possesses of being hardened 
 
 and softened at pleasure, 486 
 Odin mine, 195 
 Oil and coal gas, comparative value 
 
 of, 154 
 baths for tempering edge-tools, 
 
 493 
 , heated, employed in refining 
 
 sugar, 595 
 
 Oil, its effect when used for harden- 
 ing steel, 490 
 
 its use in the northern regions, 
 
 73 
 
 merchants, 95 
 
 of vitriol by the bell, 216 
 
 preparation for chrome yellows, 
 
 563 
 
 presses, management of, 94 
 
 produce of, in burning, 40 
 
 Old iron, its reduction, 8 
 Olefiant gas, 157 
 Olfactory nerves, 455 
 Operation of tinning iron, 514 
 Operations in calico-printing, 532 
 Opium, its effects counteracted, 264 
 Ores, metallic, 18 
 
 of cobalt, 21 
 
 Orichalcum of the Romans, 197 
 Orkney kelp, why best for bottle 
 
 glass, 366 
 
 Oven girls of Germany, 36 
 Oxalate of barytes, 142 
 Oxalis acetosella, 283 
 Oxalic acid from gum, 270 
 Oxides, metallic, 336 
 Oxymuriate of tin, 556 
 
 P. 
 
 Padding of calicoes, 546 
 
 Painting upon glass, 31 1 
 
 Pale blue dipping, 408 
 
 Palissy, Bernard de, 311 
 
 his reply to Henry III., 313 
 
 Pallampoors of Madras, 529 
 
 Paper-making, 19 
 
 Paracelsus, 22 
 
 his improvement of pharmacy, 5 
 
 Paralysis of the potter, 334 
 
 Paris gardeners, 454 
 
 lighted with oil gas, 1 55 
 
 Pariss, Mr., his platinum vessels, 246 
 
 Parker's burning lens, 45 
 
 Parkinson's printing machines, 555 
 
 Parliamentary representation, inequa- 
 lity of accounted for, 196 
 
 Parting, business of, 18 
 
 Paste of the calico-printer, 535 
 
 Patent method of grinding plate-glass, 
 373 
 
 Patterns, how sketched in India, 529 
 
 Pauli on the barberry, 261 
 
 Paulus ^Egineta, 13 
 
 Pearl-ash, different kinds of, 355 
 prepared, 281 
 
 Pearl of Cleopatra, 17 
 
INDEX. 
 
 685 
 
 Peat, its properties as fuel, 76 
 
 expense of getting in Scotland, 
 
 76 
 
 inflamed spontaneously, 53 
 
 acid of, 166 
 
 Pellatt, Mr., his memoir on glass in- 
 crustations, 379 
 
 Pelletier, his saponaceous liquor, 420 
 
 on strontites, 137 
 
 Pencil blue process, 545 
 
 Pentateuch, books of, 525 
 
 Perchloride of carbon, 158 
 
 Percival, Dr., on lead, 445 
 
 Perforated plates, for discharging, 568 
 
 Perkins and Fairman's improvement 
 in engraving, 487 
 
 Perkins's compression of water, 424 
 
 Permanency of Indian colours, 530 
 
 Peroxide of barium, 135 
 
 of tin, muriate of, 556 
 
 Persian berry liquor, 558 
 
 Persians, the excellence of their porce- 
 lain, 308 
 
 their idea of water, 421 
 
 Perspiration, phenomenon of, 37 
 
 Pestre, Mons., interesting account of, 
 453 
 
 Petalite, 302 
 
 Petitot, John, of Geneva, 312 
 
 Petty, Sir William, on dyeing, 8 
 
 Petuntse of China, 319 
 
 Pharmacopoeia, formula? of, 5 
 
 Pharmacy much indebted to Paracel- 
 sus, 5 
 
 Phials dried by ether, 56 
 
 Philip of Sides, 5 
 
 Philippo, Mr., introduced morocco, 1 3 
 
 Phillips and Lee of Manchester, 157 
 
 Phoenicia, glass works of, 347 
 
 Phoenicians reduced commerce to a 
 science, 527 
 
 the most ancient dyers, 527 
 
 Phosgene gas, 153 
 
 Phosphate of barytes, 143 
 
 of lime, 333 
 
 of soda and ammonia, 460 
 
 Phosphoric matches, 50 
 
 Phosphorus, its discovery, 50 
 
 may be procured from urine, 483 
 
 generally found in steel, 477 
 
 its produce of acid by combus- 
 tion, 40 
 
 Phosphuret of barytes, 144 
 of barium, 144 
 
 of carbon, 161 
 
 Piezometer, 424 
 
 Pig-iron, its manufacture, 7 
 
 Pinchbeck, 210 
 
 Pink from cochineal, how prepared, 
 
 557 
 Pins first made in this country, 597 
 
 the tinning of, 509 
 
 - whitening process of, 509 
 Pipe-clay employed in calico-printing, 
 
 Pipes for conveying steam, 74 
 
 Pit-coal a bad conductor of heat, 81 
 
 Pit-coals, variety of, 193 
 
 Pitch ey bog-iron ore, 238 
 
 Plan for getting the tin-plate trade 
 
 into England, 519 
 Planetary bodies, 26 
 Planished covers, 73 
 Plantations, national, of wood for 
 
 gunpowder, 169 
 Plaster, how prepared in the potteries, 
 
 324 
 
 of Paris, 425 
 
 Plate-glass, patent for, 352 
 
 manufactory established by the 
 
 Duke of Buckingham, 354 
 
 manufactories of, 367 
 
 materials for making, 368 
 
 made by blowing, 369, 379 
 
 house, management of, 369 
 
 employed by the navy, 372 
 
 the method of grinding, 372 
 
 made by casting, 374 
 
 French establishments for, 374 
 
 manufactory at Ravenhead, 374 
 
 the history of its first establish- 
 ment, 374 
 
 a detail of the processes at Ra- 
 venhead, 375 
 Platinum, important use of, 68 
 
 imparts great tenacity to steel, 
 
 50t> 
 
 its oxide employed in covering 
 
 earthenware, 337 
 
 a singular use of, 246 
 
 its use in the safety lamp, 68 
 
 muriate of, 292 
 
 used for touch-holes, 100 
 
 vessels for concentrating sulphu- 
 ric acid, 246 
 
 enormous cost of, 246 
 
 leaden cover for, 247 
 
 . saving in using, 247 
 
 various advantages of, 247 
 
 and silver, alloy of, 115 <- 
 
 Pliny on hardening steel instruments, 
 484 
 
 on the relative weight of grain, 
 
 103 
 
636 
 
 INDEX. 
 
 Pliny, his history'of the first invention 
 
 of glass, 346 
 Plott, Dr., his account of spontaneous 
 
 combustion, 53 
 
 on turf-cutting, 76 
 
 Plough-shares of wood, 472 
 Plumbago, 184 
 
 crucibles, 184, 340 
 
 employed in dyeing, 185 
 
 its various uses, 186 
 
 incombustible, 186 
 
 its use in America, 187 
 
 Polidore Virgil, 162 
 
 Polish, superior, of cast-steel, 479 
 
 Polishing glass, 374 
 
 of diamonds, 149 
 
 Poppies employed in bleaching, 387 
 Porcelain, an essay on, 304 
 
 manufacture of, 307 
 
 of China and Japan, 306 
 
 manufacture at King-to-Ching, 
 
 306 
 
 buildings in China, 307 
 
 of Persia, its peculiar properties, 
 
 308 
 
 from Pontus in Asia, 308 
 
 of comparatively late manufac- 
 ture in Europe, 310 
 
 the art of, stolen from China, 
 
 313 
 
 works of Saxony, 313 
 
 of Florence, 314 
 
 modern manufactories of, 314 
 
 of Montpellier, 314 
 
 manufacture at Berlin, 314 
 
 account of a large collection of, 
 
 at Dresden, 314 
 cabinets of, at Grains, 315 
 
 the temperatures at which it 
 
 should be burnt, 331 
 
 earth of BaudhTero, 344 
 
 clay, necessity of analysing, 345 
 
 of Limoges, composition of, 
 
 345 
 
 of Cornwall, composition 
 
 of, 345 
 
 of France, how composed, 
 
 345 
 
 Porosity of charcoal, 162, 171 
 Porphyry, its hardness, 7 
 Portland vase, 309 
 Potash, 275 
 
 carbonate of, 276 
 
 Russian mode of making, 279 
 
 preparation of, 279 
 
 procured from burnt peat, 280 
 
 obtained from saltpetre, 280 
 
 Potash procured from pyroligneous 
 acid, 280 
 
 how prepared in Germany, 280 
 
 its colour accounted for, 281 
 
 found in blood, 281 
 
 ; English manufactories of, 281 
 
 acetate of, 281 
 
 ammonia, sulphate of, 282 
 
 antimoniate of, 282 
 
 antirnonite of, 282 
 
 arseniate of, 282 
 
 arsenite of, 282 
 
 benzoate of, 282 
 
 bibenzoate of, 282 
 
 bicarbonate of, 282 
 
 bichromate of, 282 
 
 binarseniate of, 282 
 
 binoxalate of, 283 
 
 biphosphate of, 283 
 
 bisulphate of, 283 
 
 bitartrate of, 283 
 
 boletate of, 283 
 
 - borate of, 283 
 
 camphorate of, 283 
 
 carbonate of, 284 
 
 chlorate of, 50, 284 
 
 hyperoxymuriate of, 50, 284 
 
 chromate of, 284 
 
 citrate of, 263, 284 
 
 columbate of, 284 
 
 ferrocyanate of, 284 
 
 ferrotartrate of, 284 
 
 fluate of, 285 
 
 hydrate of, 285 
 
 hydriodate of, 285 
 
 hydroguretted sulphuret of, 285 
 
 hydrosulphuret of, 285 
 
 hypophosphite of, 285 
 
 hyposulphite of, 285 
 
 iodate of, 285 
 
 lactate of, 285 
 
 malate of, 286 
 
 meconiate of, 286 
 
 mellate of, 286 
 
 supermellate of, 286 
 
 molybdate of, 286 
 
 muriate of, 286 
 
 nitrate of, 286 
 
 nitrite of, 286 
 
 oxalate of, 286 
 
 oxychlorate of, 286 
 
 phosphate of, 286 
 
 phosphite of, 287 
 
 quadroxalate of, 287 
 
 saclactate of, 287 
 
 silicate of, 287 
 
 sorbate of, 287 
 
INDEX. 
 
 637 
 
 Potash, bisorbate of, 287 
 
 suberate of, 287 
 
 subphosphate of, 287 
 
 succinate of, 287 
 
 sulphate of, 287 
 
 sulphite of, 287 
 
 tartrate of, 288 
 
 tartrate of, and sod:i, 288 
 
 tartrate of, and antimony, 288 
 
 tellurate of, 288 
 
 tungstate of, 288 
 
 urate of, 288 
 
 zumate of, 289 
 
 a test for, 292 
 
 analysis of, 301 
 
 when to be preferred for flint 
 
 glass, 383 
 
 its affinity for water, 426 
 
 Pot- and pearl-ash, 284 
 Potassium, chloride of, 286 
 
 its characters, 300 
 
 its metallic nature, 301 
 
 its properties, 302 
 
 method of preserving, 300 
 
 sulphuret of, 288 
 Pott on chemical vessels, 311 
 Potters of Yesd, 308 
 
 - ovens, how heated at Dresden, 
 
 314 
 
 moulds, 324 
 
 wheel, 324 
 
 moulds, a hint respecting, 326 
 
 chambers, an improvement in, 
 
 suggested, 327 
 
 oven, English, 327 
 
 kiln, its temperature, 331 
 
 gloss-ovens, temperature of, 332 
 
 . cream-coloured glaze, its com- 
 position, 332 
 
 glaze, variety of, 332 
 
 printing press, 338 
 
 use of chemistry to, 345 
 
 wheel, its invention, 473 
 
 ovens in the form of a cylinder, 
 
 328 
 
 Pottery, an important desideratum in, 
 329 
 
 for glass-making, 382 
 
 its comparative durability, 331 
 
 Pownal, Governor, 305 
 Precious stones, analysis of, 343 
 Preparation of calicoes, 534 
 
 of cloth for steam colours, 
 
 556 
 
 Pressing of woollen cloths, 97 
 Price, Dr. James, the last alchemist, 
 
 572 
 
 po- 
 
 Prices of iron and steel, 478 
 
 of tin-plate, 518 
 Priestley, Dr. Joseph, 22 
 
 on aerial electricity, 47 
 
 first decomposed ammonia, 460 
 
 his discovery respecting the 
 
 blood, 6 
 on stagnant water, 444 
 
 on the growth of vegetable 
 
 matter on stagnant water, 
 
 436 
 the discoverer of ammoniacal 
 
 gas, 460 
 the discoverer of carbonic oxide, 
 
 151 
 Prieur on the varied colours of 
 
 lished steel, 488 
 Prince's metal, 210 
 Principle, the living^ in vegetables, 
 
 Printed books, method of cleaning, 
 
 416 
 
 Printers' types, 8, 486 
 Printing, invention of, 1, 571 
 
 press, 589 
 
 silk handkerchiefs, 544 
 
 rainbow shades, 562 
 
 Problem of Rouelle, 149 
 Process of the ancient fullers, 592 
 of bleaching by sulphurous acid 
 
 gas, 415 
 
 of bleaching in Holland, 390 
 
 in Scotland, 411 
 
 for bleaching hose, 401 
 
 for chintz work, 552 
 
 of dressing hose, 404 . 
 
 for forming broad glass, 363 
 
 for making cast-steel, 502 
 
 of making plate-glass by blow- 
 ing, 371 
 
 of making sal-ammoniac in 
 
 Egypt, 457 
 
 of tilting steel, 498 
 
 of welding iron, 480 
 
 Proclus, his burning mirrors, 43 
 
 Profit in making steel explained, 7 
 
 Prometheus, the fable of, 41 
 
 Proof spirit, 109 
 
 Protochloride of carbon, 159 
 
 Prunus cerasus, 261 
 
 Prussian blue, 20 
 
 Prussiate of potash produces a purple, 
 560 
 
 , its use in printing, 548, 
 
 560 
 
 Prussic gas, or carburet of nitrogen, 
 159 
 
638 
 
 INDEX. 
 
 Public meeting respecting gas-bleach- 
 ing, 396 
 
 Pumice-stone, 281 
 
 a glaze for pottery, 334 
 
 Pure water necessary to the bleacher 
 441 
 
 Purple of the ancients, 20 
 
 a new one, 560 
 
 from iron liquor not to be 
 
 steamed, 565 
 
 from prussiate of potash to be 
 
 steamed, 565 
 
 Putrefaction, vegetable, 4 
 
 Pyritous coal, danger of keeping, 53 
 
 Pyroligneous acid, 165 
 
 singular case respecting its 
 
 distillation, 167 
 
 tar, 166 
 
 Pyrolignite of alumina, 541 
 
 of iron, 540 
 
 Pyrometer, importance of, 99 
 
 of Wedgwood, 331 
 
 its use in glass-making, 383 
 
 Q. 
 
 Quartation, 18 
 
 Queen's ware, its introduction, 335 
 
 Quercitron bark, 97, 539 
 
 Quito, city of, 28 
 
 R. 
 
 Rainbow shades, how produced, 562 
 
 red, 562 
 
 purple, 562 
 
 Ravenscroft, Mr., improved the 
 
 quality of flint-glass, 354 
 Reaumur, his experiments on porce- 
 lain, 313 
 
 on hardening steel, 484 
 
 his pension for his discoveries in 
 
 making steel, 484 
 the inventor of a new mode of 
 
 graduating thermometers, 522 
 his experiments on tin-plate, 
 
 522 
 
 Reduction of old iron, 8 
 Refined tin, 513 
 .Refiners' aquafortis, 18 
 Refinery of copper, 198 
 Reservoir for water, construction of, 
 
 439 
 
 for filtrating water, 435 
 
 construction of a peculiar one, 
 
 439 
 
 Resin, its manufacture, 173 
 Resist black, 559 
 
 lilac, 559 
 
 white, 559 
 
 red, 559 
 
 work, neutral, 559 
 
 in calico-printing, 542 
 
 Respiration, some account of, 33, 34 
 
 Retinasphaltum, 195 
 
 Retorts, breakage of, how avoided, 
 
 246 
 
 Reussite, 240 
 
 Reverberatory furnaces, 80 
 Rhine and Danube frozen, 27 
 Rhodes, his important observations on 
 hardening steel, 484, 497 
 
 on the manufacture of razors, 
 
 485 
 
 on the temperature of iron and 
 
 steel, 485 
 
 his frame-bladed razors, 494 
 
 Rhodium effects a remarkable change 
 
 in steel, 506 
 Richman, circumstances attending his 
 
 death, 48 
 
 Riedesel, Baron, on muriate of am- 
 monia, 459 
 Rittenhous on the expansion of wood, 
 
 119 
 
 Ritter on ice, 421 
 River Calder, 429 
 
 sand, none but the commonest 
 
 kind allowed to be used in 
 making bottle glass, 366 
 
 St. Lawrence, 28 
 
 Rivers, how preserved fluid, 30 
 Robertson, Dr., on climate, 28 
 Robinson's experiments on the gravity 
 
 of water, 106 
 Rochelle salt, 280 
 Rock salt, 303, 586 
 Roebuck, Dr., his improvement of the 
 manufacture of sulphuric acid, 
 217 
 
 his character, 218 
 
 further particulars of, 218 
 
 Roland and Co. on bleaching by sul- 
 phur, 416 
 Roman bricks and tiles, 304, 306 
 
 earthenware, 587 
 
 ancient manufactory of, 
 
 306 
 
 vessels of earthenware, 587, 588 
 
 Romas, Monsieur, on the electrical 
 
 kite, 47 
 
 Rouelle the younger, 149 
 Rowley Rag, 98 
 
Royal Institution galvanic battery, 46 
 
 Rumford's experiment with a revolv- 
 ing cylinder, 52 
 
 on the density of water, 106 
 
 on fuel, 75 
 
 on the management of fuel, 77 
 
 on the nutritive property of 
 
 water, 422 
 
 the late Count's prize essay, 24 
 
 S. 
 
 Safety-lamp of Sir H. Davy, 66 
 
 first introduced, 64, 66 
 
 a national benefit, 70 
 
 easily imitated, 70 
 
 its action shown by ether, 70 
 
 Sage, his experiments on charred turf, 
 
 76 
 on the use of barytes in pottery, 
 
 345 
 
 Sails of matting, 524 
 Sal-ammoriiac, an essay on, 457 
 
 known to the ancients, 457, 596 
 
 made at Geeza and at Rosetta, 
 
 457 
 
 procured from soot in Egypt, 458 
 
 its various uses, 461 
 
 progress of its manufacture in 
 
 Europe, 462 
 furnished from the chimneys in 
 
 the metropolis, 458 
 the advantages of making from 
 
 bittern, 466 
 a new source for its production, 
 
 469 
 
 procured from coal-gas, 469 
 
 abounds in the lava of Vesuvius, 
 
 461 
 
 makers at Grand Cairo, 459 
 
 first analysed by Tournefort, 459 
 
 native, 459 
 
 its chemical properties, 460 
 
 improved French process for, 465 
 
 formed by double decomposition, 
 
 463 
 
 procured from turf, 465 
 
 patent, law proceedings respect- 
 ing, 466 
 
 tub, 557 
 
 Sal enixum, 287 
 Saline manures, 4 
 Salsola-soda, 289 
 Sal mirabile, 297 
 
 perlatum, 296 
 
 Sand from Alum-bay, 355, 368 
 of the river Belus, 368 
 
 INDEX. 639 
 
 Sand, how broken on the continent for 
 
 making glass, 365 
 Sand-paper, new kind of, 374 
 Sandiver, 383 
 
 Salt, its use in horticulture, 21 
 its use to the grazier, 303 
 
 extraordinary employment for, 
 
 on the repeal of the duties on, 
 
 303 
 
 of lemons, 283 
 
 petre, 575 
 
 refining, 93 
 
 when to be employed in 
 
 glass-making, 384 
 
 mines of Poland, 585 
 
 carboys of sulphuric acid packed 
 
 in, 586 
 
 decomposition of, 465 
 
 depositions of, in various parts 
 
 of the world, 586 
 
 value of, in Africa, 586 
 
 sulphurous, of Stahl, 287 
 
 used in glazing stoneware, 334 
 
 of Sylvius, 281 
 
 of hartshorn, 177 
 
 Salts, crystallization of, 93 
 
 of barytes, 140 
 
 employed for the production of 
 
 cold, 62 
 
 purified by charcoal, 177 
 
 proper for frigorific mixtures, 63 
 
 of ammonia, 460 
 
 alkaline, 274 
 
 indebted to water for some of 
 
 their properties, 425 
 
 oflithia, 302 
 
 Sapphire, topaz, and hyacinth, their 
 
 analysis, 343 
 
 Sasso, the hot springs of, 240 
 Saussure on the gases absorbed by 
 
 charcoal, 171 
 
 on alumina, 426 
 
 Saw, its invention, 473 
 
 makers of Sheffield, 491 
 
 Scales, directions for the choice of, 1 06 
 Scaliger, the memorable, 31 1 
 Scaling-furnace for tin-plate, 510 
 Scarlet dye, discovery of, 10 
 Scheele, the discoverer of chlorine, 393 
 
 on manganese, 122 
 
 process for concentrating citric 
 
 acid, 249 
 
 Scheffer, Peter, his table of the mix- 
 tures of tin and lead fallacious, 
 
 115 
 Schools, chemical, in France, 3 
 
640 
 
 INDEX. 
 
 Scissars, how formed, 482 
 
 Scotch method of bleaching, 411 
 
 handkerchief printing, 550 
 
 Scouring of hose, 402 
 
 Sculptors, English, 310 
 
 Sea salt, 303 
 
 Sea, temperature of, 29 
 
 water, various analyses of, 468 
 
 wrack, 290 
 
 Seed-crushers, 94 
 
 Seleniate of barytes, 143 
 
 Semilor, 211 
 
 Sevres, porcelain of, 314 
 
 Shaw on glass-making, 384 
 
 Shawls of the present Asiatics, 528 
 
 Shear, spur, and star steel, 478 
 
 steel, how made, 478 
 
 Sheet brass, size of a plate of, 205 
 
 Shin irons, 207 
 
 Shingle on the coast of Sussex, 319 
 
 Ship Ajax destroyed by a heap of pyri- 
 tous coal, 54 
 
 Sienna, clay of, 344 
 
 Sightening in calico-printing, 536 
 
 Silica, a native oxide, 49 
 
 its quantity in flint glass, 383 
 
 and alumina, a remarkable dif- 
 ference in, 319 
 
 Silicate of barytes, 143 
 
 Silk-workers in France, 95 
 
 Silk and worsted have a natural var- 
 nish, 567 
 
 Silk-bleaching, 416 
 
 Silver, red ore of, 240 
 
 citrate of, 264 
 
 probably the best metal to unite 
 
 with steel, 505 
 
 Singeing of calicoes, 39, 532 
 
 Skelping, 482 
 
 Slip-house of the potter, 323 
 
 Smelting of ores, 572 
 
 Snow, artificial, 51 
 
 Soap, manufacture of, 13 
 
 its antiquity, 13 
 
 known to the ancient Romans, 
 
 274 
 
 method of hardening, 293 
 
 how made in Scotland, 280 
 
 waste, 572 
 
 decomposed by impure water, 
 
 432 
 
 soft, 293 
 
 Soap-boilers, 88 
 
 Soap-boiler's shop found in ancient 
 Pompeii, 274 
 
 Soap-makers' residuum used in bottle- 
 glass, 365 
 
 Soap-makers* lyes, 14 
 Soap-making, French report on, 13 
 Soda, 293 
 
 sulphate of, in glass-making, 1 1 
 
 acetate of, 294 
 
 arseniate of, 294 
 
 arsenite of, 294 
 
 benzoate of, 294 
 
 bicarbonate of, 294 
 
 found native, 294 
 
 borate of, 294 
 chloride of, 542 
 camphorate of, 294 
 carbonate of, 295 
 chromate of, 295 
 citrate of, 264, 295 
 flu ate of, 295 
 
 hydrate of, 295 
 
 hydrosulphuret of, 295 
 
 iodate of, 295 
 
 lactate of, 296 
 
 malate of, 296 
 
 molybdate of, 296 
 
 muriate of, 296 
 
 nitrate of, 296 
 
 oxalate of, 296 
 
 phosphate of, 296 
 
 phosphite of, 296 
 
 silicate of, 296 
 
 sub-borate of, 297 
 
 suberate of, 297 
 
 succinate of, 297 
 
 sulphate of, 297 
 
 sulphite of, 297 
 
 sulphuret of, 297 
 
 supertartrate of, 298 
 
 tartrate of, 298 
 
 tungstate of, 298 
 
 urate of, 298 
 
 native, 289 
 
 component parts of, 301 
 
 in soap-making, 293 
 
 one reason for preferring in glass- 
 making, 360 
 
 why preferable to potash, 383 
 
 how prepared for plate-glass, 367 
 
 makes harder glass than potash, 
 
 384 
 
 its superior power in saturating 
 
 silica, 383 
 
 Sodium and ice produce combustion, 
 52 
 
 method of preserving, 303 
 
 its characteristics, 301 
 
 its metallic nature, 301 
 
 Soft water, how to be procured at 
 sea, 435 
 
INDEX. 
 
 641 
 
 Soft water of consequence to the 
 
 grower of flax, 441 
 Soho manufactory, 157 
 Soils, transposition of, 4 
 Solder, plumber's, 509 
 Solution of salts, 93 
 
 of tin, alkaline, 556 
 
 Solvent power of water increased, 97 
 Soot of Newcastle coals abounds in 
 
 sal-ammoniac, 458 
 Souring with sulphuric acid, 392 
 Spears formerly made of gold and 
 
 silver, 473 
 Specific gravity, 102 
 
 bottle, 106 
 
 no criterion for metallic alloys, 
 
 114 
 of compounds, how calculated, 
 
 116 
 
 of solids, how ascertained, 1 1 1 
 
 calculated by the wine pint, 117 
 
 how ascertained by decimal 
 
 arithmetic, 111 
 its use in the classification of 
 
 minerals, 104 
 its use in various manufactures, 
 
 104 
 Speculation respecting printing on 
 
 earthenware, 339 
 Spedding, his machine for producing 
 
 light, 49 
 Sprat's History of the Royal Society, 
 
 8 
 
 Spring-sieve for printing, 545 
 Spring-water, 428 
 
 on the choice of, 432 
 
 Spodumene, 302 
 Spontaneous combustion, 52 
 Squalus canicula of Linnaeus, 467 
 Staffordshire potteries, antiquity of, 
 
 315 
 Stahl on bleaching woollens, 415 
 
 on chemical decompositions, 462 
 
 Starch-making, 20 
 Statues of porphyry, 7 
 
 of Isis, 526 
 
 Steam, its latent caloric, 37 
 
 comparative bulk of, 37 
 
 on conducting it, 74 
 
 engine, 2 
 
 engine boilers, 91 
 
 chests of the calico-printer, 536 
 
 pipes, 175 
 
 cooking apparatus, 1 75 
 
 colours described, 556 
 
 preparation of cloth for, 
 
 556 
 
 Steam colours, definition of, 556 
 
 mordant for, 556 
 
 printed by machines, 557 
 
 blue, 558 
 
 pink, 558 
 
 yellow, 558 
 
 green, 558 
 
 bleaching, 414 
 
 economy of, 414 
 
 laboratory at Apothecaries' Hall, 
 
 594 
 
 Steaming calicoes, apparatus for, 558 
 Steatites in earthenware, 330 
 of Cornwall, 344 
 
 Steel works, 7 
 
 of the ancients, 7 
 
 cast, the making of, 7 
 
 the profit of its manufacture, 7 
 
 made by digesting wrought iron 
 
 in fluid cast-iron, 476 
 
 for magnets, 477 
 
 blistered, 477 
 
 varieties of, 478 
 
 varies in its time of acquiring 
 
 rust, 479 
 
 altered remarkably by the blue- 
 ing process, 489 
 
 springs, 490 
 
 of Damascus, 495 
 
 made with animal charcoal, 491 
 
 drills, mode of hardening, 490 
 
 injured in tilting, 498 
 
 its chemical difference from iron, 
 
 502 
 
 combined with alumina, 505 
 
 improved by a small addition of 
 
 silver, 505 
 improved by a small addition of 
 
 platinum, 506 
 
 and chromium, alloy of, 506 
 
 St. Gobin glass manufactory, 371 
 Stephens, Mr., parliamentary grant 
 
 to, 278 
 
 Still, economical one, 91 
 Stills, on setting, 77 
 Stodart, Mr., on wootz, 481 
 and Faraday on some alloys of 
 
 iron and steel, 505 
 Stone-coal, 192 
 Stone hammers of ancient Persia, 471 
 
 weapons of the ancients, 471 
 
 china, 330 
 
 instruments of, 596 
 
 ware, 310 
 
 retorts, 590 
 
 its durability, 311 
 
 ., htfw glazed, 334 
 
 2 T 
 
642 
 
 INDEX. 
 
 Stone ware, a proposal for improving, 
 340 
 
 Stourbridge clay, 84 
 
 Stove of the sugar-refiner, 101 
 
 Stoving of printed calicoes, 96, 536 
 
 Strabo, 526 
 
 Straw-bleaching, 417 
 
 Strontites confounded with barytes, 
 137 
 
 and barytes, how distinguished, 
 
 138 
 
 salts of, 138 
 
 power of saturating acids, 138 
 
 gives a scarlet colour to flame, 
 
 138 
 
 citrate of, 264 
 
 Stub-nails converted to bar-iron, 482 
 
 Sublimation of sal-ammoniac, 463 
 
 of sulphur, inconveniences ari- 
 sing from, 242 
 
 Subliming rod, 245 
 
 Substances, their varied power in con- 
 ducting caloric, 74 
 
 Substantive and adjective colours, 530 
 
 Succinate of barytes, 143 
 
 Sugar, 574 
 
 refining, 1 7, 9 1 
 
 new mode of boiling, 18 
 
 refined by charcoal, 1 76 
 
 of milk, 287 
 
 Sulphate of potash, 1 4 
 
 of alumina, 237 
 
 of strontites, 238 
 
 of cobalt, 238 
 
 of copper, 238 
 
 of barytes, 122, 237 
 
 of barytes employed in pottery, 
 
 124, 345 
 
 of ammonia, its uses, 468 
 
 of magnesia, 239, 464 
 
 of iron known to Pliny, 212 
 
 of iron, native, 212, 239 
 
 of lime, 239 
 
 of manganese, 564 
 
 of soda, 297 
 
 of soda, native, 240 
 
 Sulphur a simple substance, 214 
 
 whence -procured, 214 
 
 its combustion, 214 
 
 process of preparing, 214 
 
 its purity, how ascertained, 215 
 
 variety of, 215 
 
 combustion of, 215 
 
 its nature, 214 
 
 flowers of, 215 
 
 roll, 2 15 
 
 liver of, 288 
 
 Sulphur used early in bleaching, 212 
 
 bleaching, the antiquity of, 416 
 
 and saltpetre, proportions of, 243 
 
 furnace, how changed, 244 
 
 door, valve in, 243 
 
 condensing vessel, describ- 
 
 ed, 243 
 brick 
 
 one, why preferable 
 
 to iron, 243 
 
 described, 243 
 
 draught in, how caused, 245 
 
 furnaces, causes of failure, 242 
 
 various plans of burning, 242 
 
 old mode of burning, 242 
 
 causes of the sublimation of, 
 
 242 
 greatest quantity of acid obtained 
 
 from, 243 
 
 cakes of, for burning, 243 
 
 Sulphuret of barytes, 144, 125 
 
 of copper, 215 
 
 of carbon, 161 
 
 of iron, 429 
 
 of lithium, 303 
 
 Sulphuric acid, an essay upon, 212 
 
 manufacture, its history, 217 
 
 manufacture established in 
 
 Birmingham, 217 
 manufacture in other parts 
 
 of England and in Scotland, 2 18 
 the theory of its formation 
 
 explained, 223 
 
 when first made, 212 
 
 known to George Agricola 
 
 in 1542, 212 
 first described by Dorneas. 
 
 212 
 
 its early manufacture, 213 
 
 its manufacture in Germany, 
 
 213 
 
 how made at Bleyl, 213 
 
 formerly made in glass, 216 
 
 Dr. Ward's patent for, 216 
 
 when first made in leaden 
 
 chambers, 217 
 its manufacture established 
 
 in London, 219 
 large establishment of, at 
 
 Battersea, 219 
 its sale greatly extended by 
 
 its introduction in bleaching, 
 
 220 
 modern method of making, 
 
 220 
 directions for concentrating, 
 
 221 
 cautions respecting, 222 
 
INDEX. 
 
 6*3 
 
 Sulphuric acid, antidote against its 
 poison, 224 
 
 account of an accident from 
 
 swallowing, 224 
 
 its distinguishing charac- 
 teristics, 224 
 
 its affinity for water, 225 
 
 effect of its mixture with 
 
 water, 225 
 
 its retention of caloric, 225 
 
 a caution in mixing with 
 
 water, 227 
 
 method of forming a table 
 
 of, 227 
 
 uses of the table, 229 
 
 determined by its specific 
 
 gravity, 105 
 
 native, 240 
 
 formed in urine, 240 
 
 properties of, 222, 224 
 
 how purified, 221 
 
 anecdote respecting its ma- 
 nufacture, 232 
 
 a caution respecting diluting 
 
 it in winter, 233 
 
 experiments on its freezing, 
 
 233 
 
 its chemical affinities, 233 
 
 ' its boiling point, 233 
 
 variations in its specific gra- 
 vity, 233 
 
 a tabular view of these va- 
 riations, 234 
 
 method of constructing this 
 
 table, 235 
 
 its law of expansion different 
 
 from that of water, 235 
 its strength, how ascertain- 
 ed by Mr. Dalton, 236 
 
 its various uses, 236 
 
 the true theory of its for- 
 mation, 223 
 
 essay, additions to, 241 
 
 recent improvements in 
 
 making, 241 
 
 best system of making, 
 
 241 
 
 chambers, reduction of 
 
 their height, 241 
 
 size of, 241 
 
 description of, 241 - 
 
 advantages of low 
 
 ones, 241 
 
 how supplied with 
 
 air, 244 
 
 how supplied with 
 
 vapour, 244 
 
 2T2 
 
 Sulphuric acid, strength of, how ascer- 
 tained, 244 ' 
 
 increase in its quantity, how 
 
 ascertained, 245 
 
 retorts, new mode of em- 
 ploying, 246 
 
 concentrated in platinum 
 
 vessels, 246 
 
 chamber, azote expelled 
 
 from, 246 
 
 how concentrated, 246 
 
 retorts, tin caps for, 246 
 
 glass retorts for, 246 
 
 retorts, strips of platinum 
 
 why put in, 246 
 
 dilution of, for decomposing 
 
 the citrate of lime, 257 
 
 formerly made from sul- 
 phate of iron, 582 
 
 when first used in bleach- 
 ing, 393 
 
 amount of its consumption, 
 
 229 
 
 its use in calico-printing, 
 
 534 
 
 its composition, 223 
 
 a tedious process when 
 
 made from copperas, 213 
 
 salts, decomposition of, 99 
 
 a law respecting, 241 
 
 decomposed by carbon, 1 49 
 
 Sulphurous acid employed in bleaching, 
 415 
 
 gas, 223 
 
 Sun not the source of caloric, 26 
 
 Supercarburetted hydrogen, 157 
 
 Surface bleaching, 407 
 
 Surplices of the Egyptian priests, 389 
 
 Swords of Damascus, 495 
 
 in the fifteenth century, 476 
 
 Sword-makers of Damascus carried off 
 to Persia, 496 
 
 Sylvius, salt of, 281 
 
 Synesius, his letter to Hypatia, 103, 
 428 
 
 Syphon for drawing sulphuric acid, 
 246 
 
 T. 
 
 Table of carats for fluids, with the cor- 
 responding weights of the wine 
 pint, 118 
 
 for glass, 360 
 
 of the expansion of gas, 1 19 
 
 of the specific gravity of the me- 
 tals, 121 
 
644 
 
 INDEX, 
 
 Table of the specific gravities of sul- 
 phuric acid, 230 
 
 of the temperatures produced by 
 
 the mixture of sulphuric acid 
 and water, 226 
 
 of reagents used to detect im- 
 purities in water, 433 
 
 of the solution of salts, 447 
 
 of sizes of tin-plates, 518 
 
 Tables of Baume, how constructed, 
 108 
 
 of citric acid, 271 
 
 of citric acid, how formed, 269 
 
 Table-knives, forging of, 482 
 
 first made in London, 476, 597 
 
 Tacitus, his account of the sand of the 
 river Belus, 347 
 
 Tallow, choice of, 14 
 method of purifying, 15 
 
 employed in weaving calicoes, 
 
 409,533 
 
 used in tinning, its temperature 
 
 of great consequence, 517 
 
 Tamarind abounds with citric acid, 261 
 
 Tan, artificial, 12 
 
 its affinity for gelatine, 12 
 
 old, first employed, 12 
 
 prepared for fuel, 76 
 
 its separation by muriate of tin, 
 
 97 
 
 precipitated by isinglass, 97 
 
 Tanners of Southwark, 93 
 
 their refuse, 12 
 
 Tannin, artificial, 162 
 
 Tanning, 11 
 
 of hides, 93 
 
 Tar, pyroligneous, proposed for co- 
 louring glass, 178 
 
 Tartar, 283 
 
 a dispute respecting, 5 
 
 cream of, 283 
 
 soluble, 288 
 
 emetic, 288 
 
 Tartrate of barytes, 143 
 
 Technical terms in glass-making, 358 
 
 . in the manufacture of 
 
 tin-plate, 511 
 
 Teeth of files, how preserved in tem- 
 pering, 492 
 
 Telescopes, specula for, 509 
 
 Temperature, remarks on, 24 
 
 the term defined, 24 
 
 natural and artificial, 25 
 
 its importance in manufactures, 
 
 92 
 
 its importance in chemical pro- 
 cesses, 92 
 
 Temperature, attention to, of univer- 
 sal utility, 101 
 
 to be attended to in taking the 
 
 specific gravities of bodies, 119 
 
 proper for maddering, 542 
 
 at which tin-plate is made, 513 
 
 some ancient modes of reducing, 
 
 56 
 Tempering edge-tools, 477, 484 
 
 of saws, 491 
 
 of swords, 495 
 
 Temple at Ephesus, 179 
 Tennant, Mr., his patent, 399 
 
 his bleaching process, 399 
 
 his patent overturned, 400 
 
 Terra ponderosa, 122 
 Test papers, 268 
 
 for pure water, 433 
 
 for water containing iron, 433 
 
 for water containing selenite,437 
 
 for citric acid, 267 
 
 Thales, 22 
 
 Theophrastus, Eresius, 164 
 Theory of calico-printing, 531 
 Thermometer, its use to manufactu- 
 rers, 94 
 
 Thermometers, the different ones de- 
 scribed, 32 
 
 proposed by Kirwan, 32 
 
 Dr. Murray, 32 
 
 Thevart, his patent for casting glass 
 mirrors, 352 
 
 Thomson, Dr., on phosphuret of car- 
 bon, 161 
 
 on zumic acid, 143 
 
 on some facts respecting citric 
 acid, 270 
 
 on the production of ammonia, 
 
 466 
 
 Thomson, Mr. James, his two patents, 
 568 
 
 his method of discharging Tur- 
 key-red, 568 
 
 his patent method of printing, 
 
 569 
 
 Thomson, Mr. John, his theory for 
 Turkey-red dyeing, 566 
 
 his process for Turkey- red dye- 
 ing, 565 
 
 Thread, ancient, its fineness, 389 
 
 bleaching, 420 
 
 Tilting of steel, 498 
 
 Tin, refining and working of, 599 
 
 a remark on its specific gravity, 
 
 , 115 
 
 -T its affinity for several other me- 
 tals, 508 
 
INDEX. 
 
 645 
 
 Tin and zinc, alloy of, 508 
 
 amalgam of, used for closing the 
 
 mouths of bottles, 508 
 
 and copper, alloy of, used for va- 
 rious purposes of manufacture. 
 508 
 
 and copper, alloy of, used by the 
 
 ancient Romans in their brass 
 coinage, 508 
 
 and lead, alloy of, 509 
 
 and antimony, alloy of, 509 
 
 in Saxony discovered by a Corn- 
 ish miner, 521 
 
 trade carried from Bohemia to 
 
 Saxony, 521 
 
 trade introduced into Saxony by 
 
 a Romish priest, 521 
 
 foil, 509 
 
 pyrites of Cornwall, 513 
 
 mines of Ersegebirg, 519 
 
 plate, an essay on, 508 
 
 process of making, 510 
 
 plates steeped in a mixture of 
 
 muriatic acid and water, 510 
 
 made near Awe in Saxony, 
 
 520 
 
 origin of the art of making, 
 
 518 
 
 made by Yarranton, 520 
 
 establishments belongingto 
 
 the Duke of Saxony, 520 
 
 manufacture in Monmouth- 
 shire, 522 
 
 manufacture of great na- 
 tional importance, 522 
 
 Tincal, 297 
 
 Tincture of Indian iron, 5 
 
 Tinning, process of, 513 
 
 Tombac, 210 
 
 Tombs of the ancient Peruvians, 4/4 
 
 Tools, steel, of the ancients, 7 
 
 Trial pieces of the potter, 328 
 
 Trona, 294 
 
 Trudaine, Monsieur, his burning- 
 glasses, 43 
 
 Tschirnhausen, his burning-glasses, 
 43 
 
 Tubbing of pieces for steam-colours, 
 557 
 
 Tungstate of barytes, 143 
 
 Tunics of the Babylonians, 389 
 
 Turf in the Scottish Isles, 76 
 
 employed as fuel, 76 
 
 Turkey-red, 642 
 
 discharge work, 550 
 
 description of, 565 
 
 Mr. Thomson's theory for, 566 
 
 Turkey-red dyeing an unaccountable 
 process, 566 
 
 Twaddle's areometers, 110 
 
 hydrometer used by calico- 
 printers, 556 
 
 Type-founders, 8 
 
 Tyre famous for its purple colour, 527 
 
 U. 
 
 Ultramarine, 307 
 Uranium, citrate of, 264 
 Urate of barytes, 143 
 Ure, Dr., his lectures, 3 
 
 on the mixture of fluids, 1 (6 
 
 his translation of Berthollet, 565 
 
 Urine employed in manufactures, 431 
 taxed by Vespasian, 431 
 
 Usebe Salverte, 107 
 
 V. 
 
 Vaillant, grant of a glass-house to, 352 
 Valerius Flaccus, 526 
 Valve in sulphuric acid chamber, 245 
 Van Braam on the Chinese method of 
 
 watering their lands, 452 
 Vandermonde on making steel, 478 
 Van Helmond on charcoal, 170 
 Variegated cloths of Sidon, 525 
 Varnish-making, 20 
 Varnish from pyroligneous acid, 167 
 Varro, Marcus Terentius, 273 
 Vases of antiquity, 305 
 
 number of, in Herculaneum, 307 
 
 Vats of the soap-boiler, 276 
 Vauquelin on the tamarind, 261 
 
 his table of sulphuric acid, 231 
 
 an error in this table, 232 
 
 on the mellilite, 195 
 
 his analysis of Hessian crucibles. 
 
 341 
 
 on the earth of pyrometers, 331 
 
 on pottery, 317 
 
 on baking earthenware, 328 
 
 on steel, 477 
 
 Vegetable putrefaction, 4 
 
 Vegetables decompose water, 422 
 
 Venetian houses, 180 
 
 Venison, how preserved in Siberia, 59 
 
 Villalpandus, Baptista, 104 
 
 Vinegar-making, 16 
 
 Vinegar, Egyptian, 17 
 
 its effect in hardening iron, 484 
 
 yards, 92 
 
 suggestions respecting, 93 
 
 Virgil on the juice of the citron, 248 
 
646 
 
 INDEX. 
 
 Virgil, his glass mirror, 358, 590 
 
 Vitriol, xvhite, 240 
 
 Vitruvius, 103 
 
 Vogler on the use of sal-ammoniac in 
 
 dyeing, 468 
 Volcanoes productive of sal-ammoniac, 
 
 459 
 
 W. 
 
 Walker, Mr., his first attempt to freeze 
 mercury, 62 
 
 his apparatus for ditto, 62 
 
 Walls of the Romans, 304 
 
 curious ones in the Highlands, 
 
 342 
 
 War-chariots of the Britons, 475 
 
 Ward, Dr., the first maker of sulphuric 
 acid, 216 
 
 Warlike instruments of copper, 475 
 
 Washing, directions for, in bleaching, 
 419 
 
 Waste of zinc the miner's loss, 205 
 
 Water, a curious change in its density, 
 30 
 
 its latent caloric, 33 
 
 ceases to boil in a certain atmo- 
 sphere, 36 
 
 made to boil by a revolving cylin- 
 der, 52 
 
 expedient of the caravans for 
 
 cooling, 55 
 
 ; how procured at Hudson's Bay, 
 72 
 
 preserved by oil from freezing, 
 
 73 
 
 the datum for determining spe- 
 cific gravities, 106 
 
 the weight of a cubic foot of, 
 
 106 
 
 weight of the wine pint, 229 
 
 purified by charcoal, 1 77 
 
 impregnated with carbonic acid, 
 
 176 
 
 expansion of, 448 
 
 its expansive force, 575 
 
 a new table of its expansion and 
 
 contraction, 448 
 
 an essay on, 421 
 
 opinion of the ancients respect- 
 ing, 421 
 
 its composition, 421 
 
 decomposition of, 422 
 
 decomposed in chemical pro- 
 cesses, 422 
 
 formed by the electric spark, 422 
 
 its use in cutting logwood, 422 
 
 Water, its various effects in chemical 
 processes, 423 
 
 exists in four separate states, 423 
 
 exists in chemical combination 
 
 with bodies, 424 
 
 unites with bodies in definite pro- 
 portions, 424 
 
 condensed by quick lime, 424 
 
 parts with caloric in uniting with 
 
 salts, 425 
 
 of crystallization, 425 
 
 its action on plaster of Paris, 
 
 425 
 
 necessary in fermentation, 427 
 
 decomposed by metals, 427 
 
 produced in some chemical pro- 
 cesses, 427 
 
 its purity often of great conse- 
 quence, 427 
 
 comparative goodness of, 431 
 
 to be chosen by its specific gra- 
 vity, 432 
 
 purified by distillation, 434 
 
 purified by filtration, 434 
 
 purified by the operations of na- 
 ture, 434 
 
 purified by the growth of vege- 
 tables, 436 
 containing selenite purified, 436 
 
 how purified from iron, 437 
 
 purified by exposure to the at- 
 mosphere, 439 
 importance of drinking such as 
 
 is pure, 442 
 
 how purified in China, 443 
 
 supply of, for ship-board, 443 
 
 of the Rhone, 444 
 
 cisterns of lead, 445 
 
 its various properties, 445 
 
 specific gravity of, 446 
 
 its unchangeable nature, 446 
 
 its solvent power, 446 
 
 variation in its specific gravity, 
 
 447 
 its solvent power influenced by 
 
 its specific gravity, 447 
 quantity requisite to dissolve 
 
 sundry salts, 447 
 curious phenomena respecting, 
 
 449 
 a singular effect of, in making 
 
 bottle-glass, 449 
 employed in drawing coals from 
 
 the earth, 451 
 methods of raising from great 
 
 depths, 452 
 advantages derived from, 454 
 
INDEX. 647 
 
 Water, its effect in perfecting sight, 
 
 taste, and smell, 455 
 ' its influence in chemical opera- 
 tions, 455 
 
 some of its peculiar uses in the 
 
 arts, 455 
 
 lute, 245 
 
 pipes of earthenware, 587 
 
 of antiquity, 305 
 
 protected, 74 
 
 Water-ordeal of superstitious ages, 
 450 
 
 Water bellows, 451 
 
 used in Sweden and Italy, 
 
 451 
 
 Waterings of the Paris gardens, 454 
 
 Waters producing inflammable gas, 54 
 
 how rendered hard, 429 
 
 of the baths in Tuscany, 454 
 
 Watson, Bishop, his opinion of Yar- 
 ranton, 520 
 
 on charcoal, 170 
 
 Watt, his experiments on fusing ba- 
 salt, 98 
 
 his exertions to introduce gas 
 
 bleaching, 395 
 
 his fire lute, 84 
 
 his first ideas on the steam en- 
 gine, 2 
 
 on basaltic columns, 99 
 
 Wax, how bleached, 416 
 
 how employed in printing, 544 
 
 Weremouth monastery glazed by fo- 
 reign artists, 348 
 
 Weaver of calicoes, 408 
 
 injudicious practices of, 409 
 
 Weaving and dressing calicoes by 
 steam, 600 
 
 Weaving, its invention, 388, 524 
 
 Wedgwood, Thomas, his experiment, 
 52 
 
 Wedgwood, Josiah, 10 
 
 his pyrometer, 100 
 
 jasper ware, 124 
 
 his imitation of the Portland 
 
 vase, 309 
 
 his expedients for improving 
 
 earthenware, 316 
 
 cream-colour ware, 335 
 
 Weighing hydrostatically, 1 12 
 Weight, increase of, by combustion, 40 
 Weld a yellow dye, 97 
 Welding heat, 480 
 
 - of iron, 480 
 
 Well of immense depth in Stafford- 
 shire, 428 
 Well-sinking, 428 * 
 
 Westrumb on crystallized citric acid. 
 
 254 
 Whale-blubber, 467 
 
 boiler described, 408 
 
 White cloths, a proposal respecting, 
 
 metal, 211 
 
 Whitening of cloths by the ancients. 
 387 
 
 Whites, how preserved in calico-print- 
 ing, 544 
 
 Wickersley stone, 500 
 
 Wiegleb on the manufactories of sal- 
 ammoniac, 462 
 
 on wood fuel, 75 
 
 Wilson, Mr. Daniel, his patent for 
 boiling sugar by means of oil, 
 595 
 
 Window or broad glass, 363 
 
 Windows, method of cleaning in Rus- 
 sia, 60 
 of St. Denis, when painted, 349 
 
 the action of double ones, 73 
 
 Wine, an improvement in cooling, pro- 
 posed, 55 
 
 cut with hatchets, 27 
 
 coolers, 55 
 
 making, 427 
 
 pint, its capacity, 229 
 
 Wire for piano-fortes, 479 
 
 gauze, its great cooling power, 
 
 67 
 
 workers, 479 
 
 Witherite, 126 
 
 Witter, his accident with carbonic 
 oxide, 152 
 
 Woad and indigo, 530 
 
 Wollaston, Dr., his new method of 
 freezing, 64 
 
 Wood-ashes formerly employed for 
 plate-glass, 367 
 
 Wood burned in water, 43 
 
 converted to an agate, 179 
 
 fuel best for making glass, 382 
 
 choice of, 75 
 
 in decaying decomposes water, 
 
 422 
 
 its loss in charring, 170, 
 
 the kinds best for charcoal, 169 
 
 Wool of Spain and Portugal, 430 
 
 scourers in ancient Rome, 431 
 
 the antiquity of collecting, 388 
 Woollen-cloth abhorred by the Egyp- 
 tians, 527 
 
 manufacture of Flanders, 196 
 
 Woolwich sand, 366- 
 Wort, boiling of, 91 
 
648 
 
 INDEX. 
 
 Wootz, English, 505 
 
 . of Bombay, 481 
 
 Worcester china, 331 
 
 Worms of stills, 91 
 
 Worsted and silk have a natural var- 
 nish, 567 
 
 Wright, Rev. T., on irrigation, 4 
 
 Writers, several, on bleaching, 420 
 
 to be consulted on the purity of 
 
 water, 433 
 
 Writings found in Herculaneum, 172 
 
 Wynkyn de Worde, 571 
 
 Y. 
 
 Yarn, woollen, scouring of, 277 
 Yarranton, Mr. Andrew, 519 
 
 his journey to Saxony to see the 
 
 tin-plate manufactories, 519 
 interesting account of his jour- 
 ney, 520 
 
 his return with the process of 
 
 tinning, 520 
 
 his various plans for improving 
 the country, 521 
 
 Yarranton, Mr. Andrew, his proposed 
 plan for the junction of the 
 Thames and Severn, 521 
 
 planned docks for Dublin and 
 
 London, 522 
 
 his journey to Holland to exa- 
 mine the linen manufactures, 
 522 
 
 Yellow, method of dyeing, 97 
 
 requires peculiar care in dyeing, 
 
 539 
 
 Z. 
 
 Zaffre, 21 
 Zinc, 574 
 
 citrate of, 264 
 
 for brass-making, 18 
 
 native sulphate of, 240 
 
 brilliant colours of the flame of, 
 
 205 
 
 red oxide of, makes good brass, 
 
 206 
 
 Zumate of barytes, 143 
 Zumic acid named by Dr. Thomson, 
 143 
 
 
 
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