"C-NRLF ^S 753 331 f : ■:■- ■ •/cH>'"' ' .OS--' >,'<^te'/'V"^ ■^.•«i THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA niiiiurciwn (C/JgWV ff^" f^r»!f^ j^i^^'^'^yyy^l w M im V. . > v. -yW^wv^w-A jw!. '^ Vv/s^vv;vvu, M^tt^i sj'^\i \f*V >o ♦. f WORKS HENRY, LORD BROUGHAM. LIVES OF PHILOSOPHERS OF THE TIUK OF QEOKGE IIL I WORKS or HEMY, LORD BROUGHAM, RR.S. MEMBEB OF THE NATIONAL INSTITUTE OF FRANCE, AND OF THE BOTAL ACADEMY OF NAPLES. VOL. I. LONDON AND GLASGOW: RICHARD GRIFFIN AND COMPANY, I TO TRB VnTBBnTT 07 OLASOOW 1856. LIVES PHILOSOPHERS OF THE TIME OF GEORGE HI. HENRY, LORD BROUGHAM, F.R.S., mXBBB OF TH« IfATIOWAL WB T ITOTK OF FEAKCB, AMD OF THK BOTAL ACAOEXT OF BAPLBS. LONDON AND GLASOQW : 1 I<^ H AUD GRIFFIN AND CO> mUmM TO THB irBITBBBITT OF OLASOOW. 1855. GLASGOW: PRISTED BT BELL AND PREFACE '37 A /^ v./ I The reign of George III. may in some important respects he justly regarded as the Augustan age of modem history. The greatest statesmen, the most consummate captains, the most finished orators, the first historians, all flourished (luring this period. For excellence in these departments it was un.surpassed in foniier times, nor had it even any rivals, if we except the warriors of Louis XIV. 's day, one or two statesmen, and Bolingbroke and Massillon as orators. But its glories were not confined to those great departments of human genius. Though it could show no poet like DaiiU^", Milton, Tasso, or Dryden ; no dramatist like Shak- -I)eare or Comeille; no philosopher to equal Bacon, Newton, or Locke, — it nevertheless in some branches, and these not the least imjwrtant of natural science, ver}' far surpassed the achievements of former days, while of political science, the roost important of all, it first laid the foundations, and then rearcil the superstructure. The science of chemistry almost (Mitirely, of political economy entirely, were the i^rowth of this remarkable era; while even in the pure mathematics a progress w.u< made which nearly changed its a.spfd since the days of Leibnitz and Newton. The iiaihi (.1 Hlack, Watt, (cavendish, Priestley, Lavoisier, Davy, may justly be placed far alwve the Boylos, the Stahls, the llales,the Hookes of former times; while Euler. Clairaut, D'A^hiIbjIiiImmmh La Place, must be ranked 352 VI PREFACE. as analysts next after Newton himself, and above Descartes, Leibnitz, or the Bernouillis ; and in economical science, Hume, Smith, and Quesnai really had no parallel, hardly any forerunner. It would also be vain to deny great poeti- cal and dramatic genius to Goldsmith, Voltaire, Alfieri, Monti, and the German school, how inferior soever to the older masters of song. But, above all, it must not be forgotten, that in our times the mighty revolution which has been effected in public affairs, and has placed the rights of the people throughout the civilized world upon a new and a firm foundation, was brought about, immediately indeed by the efforts of statesmen, but prepared, and remptely caused, by the labours of philosophers and men of letters. The diffusion of knowledge among the community at large is the work of our own age, and it has made all the conquests of science both in recent and in older times of incalculably greater value, of incomparably higher importance to the ] interests of mankind, than they were v/hile scientific study i was confined within the narrow circles of the wealthy and the learned. Having, therefore, on retii-ing from office, more time left for literaiy pursuits than professional and judicial duties had before allowed me, I was not minded to waste, indolent and inactive, or enslaved by lower occupations, that excel- lent leisure : — " Non fuit consilium socordia atque desidi^ bonum otium conterere ; neque vero agrum colendo, aut venando, servilibus officiis intentum, a?tateni agere. Statu- tum res gestas populi nostri carptim, ut qii^eque memoria digna videbantur, perscribere ; eo magis qucd mihi a spe, metii, partibus reipublicse, animus liber erat." * For I conceived that as portrait-painting is true historical painting * Sail., Cat., cap. iv. I PRBFACE. Vll in one sense, so the lives of eminent men, freely written, are truly the history of their times ; and that no more authentic account of any age, its transactions, the springs which impelled men's conduct, and the merits which difier- ent actors in its scenes possessed, can be obtained than by studying the biography of the personages who mainly guided affairs, and examining their characters, which by their influence they impressed upon the times they flourished in. Such a work had moreover this advantage, that beside preserving the memory of past events, and the likeness of men who had passed from the stage, it afforded frequent opportunities of inculcating the sound principles of an enlightened and virtuous policy, of illustmting their ten- dency to promote human happiness, of exhibiting their lK)wer to exalt the genuine glory as well of individuals as of nations. Though 1 could entertain Uttle doubt that this plan was exiMjdient, no one could more doubt than I did the capacity brought to its execution, or feel more distrustful of the pen held by a hand which had so long been lifted up only in the contentions of the Senate and the Forum. My only confidence wa* in the spirit of fairness and of truth with which 1 entered on the i>erformance of the task ; and 1 now acknowledge with respectful gratitude the favour which the work has hitherto, so far above its deserts, experienced from the public, both at home, in spite of party opposition, and abroad, where no such miworthy influence could have place. It is fit that 1 also express my etjual satisfaction at the testimony which has been bonie to its strict impartiaUty by those whose opinions, and the opinions of whose iK)litical associates, differed the most widely from my own. That m composing the work 1 never made ajiy sacrifice of those principles which liavo ever guided my public conduct, is certain ; that 1 never concealed them in Vlll PEEFACE. the course of the book is equally true ; nay, this has been made a charge. against it, as if I was at liberty to write the history of my own times, nay, of transactions in many of which I had borne a forward part, and not show what my own sentiments had been on those very affairs. But if my opinions were not sacrificed to the fear that I might offend the living by speaking plainly of the dead, so neither were truth and justice ever sacrificed to those opinions. The Statesmen of George the Third's age having thus formed the subject of the volumes first published, I then gave a more full and elaborate view of the Learned Men who flourished in the same period. In my opinion, these, the teachers of the age, covered it with still greater glory than it drew from the Statesmen and the Warriors who ruled its affairs. It was necessary to enter much more into detail here than in the other branch of the work, because a mere general description of scientific or of Hterary merit is of exceedingly little value, conveying no distinct or pre- cise idea of the subject sought to be explained. It appeared the more necessary to discuss these matters minutely, because upon some of them much prejudice prevailed, and no attempt had hitherto been made to examine them com- pletely, or even impartially. Of this a remarkable example is afforded by the want of anything that deserves the name of a Life of Voltaire, and by the great prejudices, both favourable and unfavourable to him, which, among different classes, exist on the subject. But it must also be observed that Dr. Black's discoveries have been far from attaining the reputation which they so well deserve as the foundation of modern chemistry ; and justice to this illustrious philo- sopher required that the consequences arising from his modesty and his great indifference to fame should be coun- teracted by a full history of his scientific labours, comparing the state of the science as he found it with that in which PHEPACE. IX lie left it. — My own personal acquaintance with some of the ^eat men whose history I ventured to write, enabled me to throw additional light upon it ; and respecting one, whom of course I could not have known, Mr. Hume, I ob- tained information from good sources through the kindness of friends. The materials of liis life are, however, chiefly to be souglit in his writings, and especially in his letters. The same remark is applicable to the Life of Voltaire. Those who have written it, like the Marquis de Condorcet, without ever referring to the fourteen large volumes (con- taining nine thousand closely-printed pages) of his Corres- pondence, might just as well have undertaken to give a life of Rousseau without consulting his 'Confessions,' or of Hume, without reading his 'Autobiography.' — I have, l)e8ides, had access to valuable original documents both of Voltaire, Robertson, and Cavendish ; to some respecting Watt and Simson. Sfjientific and literary history, the record of the progress of science and of letters, and which is most usefully given in the lives of their cultivators, serves two purposes ; the one historical and critical, the other didactic. It is of •^Teat importance to trace the progress of mankind in the advancement of knowledge, and its diffusion ; to show by what steps improvements have been made and applied ; to estimate the relative merits of those whose claims upon our gratitude are the most unquestionable ; and to ascertain the position in which their labours have left the subjects of those labours, with the aspect and extent of the region that yet remains unexplored. But, it is hardly a less valuable service of such works that they promote the knowledge of the subject matter, l)oth by exciting the desire of it, and by facilitating its acquisition. The history of a philoso- pher's life, that is, of his lalwurs, the tracing of those steps by which he advanced beyond his predecessors, the com- X PEEFAC^. parison of the state of the science as he found it, with that in which he left it, tends mightily to interest the reader, to draw him t awards the same inquiries, and to fix his views more closely upon the details of the subject, if it has already somewhat occupied his mind. In like manner, the recording and the description of literary labours and merits, in con- nexion with the historians, poets, and orators themselves, has a powerful effect in making the reader familiar with the subject, while it cultivates and refines his taste. Under the head of Philosophers, it is unnecessary to observe upon any of the lives except those of Adam Smith, D'Alembert, and Simson, except to note, that those of Black and Lavoisier give a full statement of the relative merits of these great men, and of the conduct of the latter, both with regard to Black and Priestley. But as many persons entertain a prejudice against the pretensions, or it may be, against the practical conclusions of the Political Economists, they may be apprised that the subjects on which the great and well-estabhshed fame of Adam Smith is founded, are here treated without any of the exaggerations wherewith speculative economists have been charged, and that the Life, and the Analysis of his great work were written long before the question respecting Free Trade and the repeal of the Corn Laws had assumed a practical form. Whatever touches that question, was composed as a treatise upon a subject of science only, with the desire to discover and to expound the truth, and without any view to the interests of any party, — the author, though he en- tirely approved the repeal, yet neither agreeing with those who hoped, nor with those who feared, so much from its consequences. The Lives of Simson and D'Alembert, are designed not only to give the history of these eminent men — the restora- tion of the ancient geometry by the former, and the improve- PREFACE. XI ment of the modem analysis by the latter — but also to convey a competent knowledge of those great methods ; while in both lives, especially that of D'Alembert, there is further presented a strong recommendation of mathematical pur- suits, by showing the gratification which they are fitted to bestow. Great as is the value of Montucla's History, in the light of a didactic work, many readers have lamented not more that he left it unfinished, and the latter half very unsatisfactorily edited, than that he did not enter mon' fully into the detailed statement of the subject, in several of the earlier portions. By such historical and critical works, then, the desire and the acquisition of science is promoted ; and surely no more important duty can be performed, than that of affording l)oth the excitement and the gratification, in however moderate a degree. They who are wholly incapable of advancing science themselves, may help others to the knowledge of what the great masters have done ; and they may do this best by not disdaining the office of elementary explanation and discussion. Two thousand years ago, the wisest of the ancients was said to have brought philoso- phy down from heaven to earth ; certainly, he chiefly valued himself on his constant efforts to stir up iji men's minds the desire of knowledge.* What he found necessarv* with regard to the nature of the subject, we in our day may perceive to be equally necessary because of the clouds in which great men, almost unavoidably, involve their scientific researches. The mathematical writings of Newton and hi.s immediate successors require to bo made plain, and also to be illustrated by comparative discussion, in order both to show exactly what they accomplished, and to excite an in- telligent curiosity respecting their labours. This has been * V\o. Acad., Qtt. L 4, Txuc v. -1. XU PEErACE. the object both of the Life of D'Alembert, and of the Analytical View of the Principia.* The course of this work kept me for the most pai-t, at a distance from questions touching poHticai affairs, or the constitution and progress of society, but not always. The reader will find that no opportunity has been left unimproved, as far as I was capable of seizing it with any effect, for inculcating or illustrating the great doc- trines of peace, freedom, and religious liberty. The observations on historical composition in the Life of Robertson, I especially consider as pointing to an improve- ment in that department of letters, highly important to the best interests of mankind, as well as to the character of historians. But although I had no poHtical animosities to encoun- ter, I feared my historical statements and my commentaries on some Hves, as those of Voltaire, Rousseau, and Hume, might find enemies among the two great parties whose principles came in question. The Free-thinkers might object to the blame which I ventured to pronounce upon their favourite authors ; the friends of the Church might take exception to the praises occasionally bestowed. It may, however, be expected from the justice of both these conflicting bodies, that they will read with attention and with calmness before they condemn. From the former class I could expect no favour beyond what every one has a * The Analytical View, first published in 1839, omitted the SecoTid and part of the Third Book. The whole is now nearly completed. The object was to enable persons having little mathematical knowledge, be}'ond elementary geometry and algebra, to follow the demonstrations of the fun- damental propositions, and to understand by what kind of reasoning the others are proved. That it was successful in this respect, there were un- doubted proofs ; but the discussions with which the investigations were g interspersed had also a very material effect. I PEEFACE. Xlll right to claim from avowed adversaries; a fair hearing was all I desired. To the latter a few words might be addressed in the spirit of respectful kindness, as to those with whom I generally agree. Whoever feels disposed to treat as impious any writer that has the misfortune not to be among the great body of believers, like the celebrated men above named, should bear in mind that the author of these pages, while he does justice to their great literary merits, has himself published, whether anonymously or under his own name, nearly as much in defence of rehgion as they did against it ; and if, with powers so infinitely below theirs, he may hope to have obtained some little success, and done some small service to the cause of truth, he can only ascribe this fortune to the in- trinsic merits of that cause which he has ever supported.* He ventures thus to hope that no one will suspect him of being the less a friend to religion, merely because he has not permitted his sincere belief to make him blind regard- ing the literary merit of men whose opinions are opposed to his own. His censures of all uidecorous, all imfair, all ribald or declamatory attacks, however set off by wit or graced by eloquence, he has never, on any occasion, been slow to pronounce. Brouoham, SdJamuny, 1865. * It hoi* given me a moi 334 D'Alemuebt, 383 Additional Appendix to the Lives of Adam Smith and Sib Joseph Banks, 468 Note to the Lives of Cavp vimmit Watt wn Black, .... 473 Note to the Life of Simson, ... 4S3 Im)k.v is<> PHILOSOPHERS THE TIME OF GEORGE III. BLACK. The physical sciences have few more illustrious names to boast than that of Joseph Black. With all the habits and the disciplined faculties of a tnie philosopher, with the temper as well as the capacity of a sage, he possessed that happy union of strong out disciplined imagination, with powers of close undivided attention, and ample resources of reasoning, which forms original genius in scientific pursuits ; and, as all these qualities may be combined m an individual without his happening to sig- nalise his investigations of nature by any discovery, we must add that his life was crowned with the good fortune of opening to mankind new paths in which both himself and his followers successfully trod, enlarging to an in- calculable extent the bounds ofhuman knowledge. The modesty of his nature making him averse to publish his speculations, and the genuine devotion to the investiga- tion of truth, for its o\vn sake, rendering him most open in his communications with all who were engaged in the same pursuits, his incontestable claim to be regarded as the founder of modem chemistry has been oftentimes ' >verlooked; and, while some have endeavoured more or less obscurely to mingle themselves with his discoveries, others have thought it becoming to post-date the new 5? BLACK. system, 'hat it miglit seea- t:ie produce of a somewhat later age. The interests of truth and justice therefore require that we should ^niuuteiy examine the facts of the ca33 ; £.nd, happiij, t^ie e^'idence is so clear that it only requires an attentive consideration to remove all doubt from the subject. I feel it a duty imperatively cast upon me to undertake a task from which, did I not regard it as less difficult than sacred, I might shrink. But I had the great happiness of being taught by him- self, having attended one of the last courses of lectures which he delivered ; and the knowledge thus gained cannot be turned to a better use than in recording the glory and in vindicating the fame of my illustrious master. The story of a philosopher s life is soon told. Black was born, in 1721, at Bordeaux, where his father, a native of Belfast, was settled as a merchant : he was, however, a Scotchman, and his wife too was of a Scot- tish family, that of Gordon of Hillhead, in Aberdeen- shire, settled like Mr. Black at Bordeaux. The latter was a person of extraordinary virtues, and a most amiable disposition. The celebrated Montesquieu honoured him with his especial regard ; and his son preserved, as titles of honour in his family, the many letters of the President to his parent. In one of them he laments the intended removal of the Black family as a thing he could not reconcile himself to, for his greatest pleasure was seeing them often, and living himself in their society. Though Mr. Black sent his son, at the age of twelve, for some years to a school in Ireland, he was removed to the College of Glasgow in the year 1746, and ever after lived in that which was, properly speaking, his native country. At that college he studied under the celebrated CuUen, then Professor of Anatomy and Lecturer on Chemistry ; and, having removed in 1750 to Edinburgh for the benefit of that famous medical school, he took his degree there in 1754. In 1756 he was appointed to succeed Dr. BLACK. 3 Cullen in the chair of anatomy and chemistry at Glas- gow, and he continued to teach there for ten years, when he was appointed to the chemistry professorship at Edinburgh. He then lectured for thirty years to numerous classes, and retiring in 1796 lived till 1799, and died on the 26th of November in that year. His health never was robust ; it was indeed precarious at all times from a weakness in the bronchia and chest, but he prolonged life by a system of the strictest absti- nence, frequently subsisting for days together on water- fruel and diluted milk. He never was married ; but e cherished with unvarying affection his near relatives, who well deserved his care. His favourite niece. Miss Burnet, a person of great sense and amiable temper, was married to his friend and second cousin. Professor Ferguson, the historian and moral philosopher. Dr. Black lived in a select circle of friends, the most illus- trious men of the times in science and in letters. Watt, Hutton, Hume, Robertson, Smith, and afterwards with the succeeding generation of Scottish worthies, Robi- son, Playfair, Stewart. Delighting to commune, to speculate, and to investigate with them, he was care- less of the fame which however he could not but be sensible his labours must achieve. He was extremely averse to publication, contemning the impatience with which so many men of science hurry to the press, often while their speculations are crude, and their inquiries not finished. Nor could the reason often urged in defence of this find much favour with one who seemed never to regard the being anticipated by his feUow- labourers as any very serious evu, so the progress of science was secured. Except two papers, one in the * London Philosophical Transactions' for 1775 on the freezinfr of boiled water ; the other, in the second vol- ume of the * Edinburgh Transactions,' on the Iceland hot springs ; he never published any work after that of which we are now to speak, in 1755, and which, but for the accidental occasion that gave rise to it, 4 BLACK. would possibly, like his other original speculations, never have been given by himself to the press. Upon taking his degree at Edinburgh College he wrote and published a Latin Thesis, after the manner of that as well as the foreign universities. The subject was ' Magnesia, and the Acid produced by Food in the Stomach' {De Acido e Cihis orto; et de Magnesia)^ and it contained the outline of his discoveries already made. Having sent some copies of this Thesis to his father at Bordeaux, one was given to Montesquieu, who at once saw the vast importance of the truths which it unfolded. He called a few days after and said to Mr. Black, " I rejoice with you, my very good friend : your son will be the honour of your name and of your family." But though the discoveries were sketched distinctly enough in this writing, they were only given at large the fol- lowing year in his celebrated work ' Experiments on Magnesia, Quicklime, and other Alkaline Substances,' incontestably the most beautiful example of strict in- ductive investigation since the ' Optics' of Sir Isaac Newton. His fervent admiration of that masterly work was indicated by his giving it to Professor Robison, then a student, and desiring him to " make it the model of all his studies," recommending him at the same time a careful study of the mathematics. It appears that this important inquiry concerning the alkaHne earths, the results of which were destined to change the face of chemical science, was suggested by the attempts then making to find a solvent for the stone. I dis- tinctly recollect Dr. Black, in his lectures, prefacing the admirable and most interesting account which he gave of his discoveries, with the statement that the hopes of finding a solvent which should not, like the caustic alkalies, destroy the substance of the bladder in melting the stone, first led hhn to this investigation. Professor Robison has given a note from his memo- randum-book indicating that he had at first fallen into the notion of alkalies, when treated with quicklime, BLACK. 6 deriving from it their caustic quality; the common belief (which gave rise to the term caustic) being that lime obtained ifrom the fire the quality of growing ex- tremely hot, even to ignition when united with water. But experiment soon corrected this idea ; for, having exposed the caustic or quicklime to the air till it be- came mild, he says, " Nothing escapes (meaning no fire or heat) ; the cup rises considerably by absorbing air." Another observation on the comparative loss of weight sustained by chalk when calcined (in the fire), and when dissolved in an acid, is followed by the ac- count of a medical case, which the Professor knew to have occurred in 1752. A third note follows, and proves him to have now become possessed of the true theory of causticity, namely, the expulsion of air, and of mddness, namely, its absorption. Tlie discovery was therefore made as early as 1752 — it was published generally in 1754 — it was given in its fullest details in 1755. At this time M. Lavoisier was a boy at school — nine years old when the discovery was made — eleven when it was published — twelve when it was as fully given to the world as its author ever delivered it. No possibility therefore existed of that great man finding out when he composed his great work that it was a discovery of his own, as he did not scruple to describe oxygen, though Dr. Priestley had first communicated it to him in the year 1774 ; or that Black and he dis- covered it about the same time, as he was in the habit 'f stating with respect to other gases, with a convenient legree of ambiguity just sufficient for self-defence, should he be chargea with uniair appropriation. Who that reflects on the noble part which this great philo- sopher acted, both in his life and in his death, can avoid lamenting that he did not rest satisfied with the fame really his due, of applying the discoveries in which he had no kind of share, to the investigation of scien- tific truths, as entirely the result of his extraordinary faculty of generalization, and genius for philosophical 6 BLACK. research, as those discoveries, the materials of his in- duction, were the undivided property of others ! The capital discovery of Black, thus early made, and to any share in which no one has ever pretended, was that the causticity, as it was formerly termed upon a false theory, of the alkalis and alkaline earths, was owing to the loss of a substance with which they had been combined, and that their reunion with this substance again rendered them mild. But the nature of this sub- stance was likewise ascertained by him, and its detection forms by far the most important part of the discovery, for it laid the foundation of chemical science. He found that it was a permanently elastic fluid, like air in some of its mechanical qualities, those of being transparent or invisible, and incondensable, but differ- ing entirely from the air of our atmosphere in its chemi- cal properties. It was separated from alkaline substan- ces by heat, and by the application of acids, which, having a stronger elective affinity for them, caused it to be precipitated, or to escape in the aeriform state ; it was heavier than common air, and it gave a slight acidulous flavour to water on being absorbed by it ; hence the inference that it was an acid itself. A short time afterwards (in 1757) he discovered that this pe- culiar air is the same with that produced by the fer- mentation of vegetable substances. This he ascer- tained by the simple experiment of partially emptying in a brewer's vat, where the fermenting process was going on, the contents of a phial filled with lime-water. On shaking the liquid that remained with the air that had entered, he found it become turbid, from the lime having entered into union with the air, and become^i chalk. The same day he discovered by an experiment, equally simple and equally decisive, that the air which comes from burning charcoal is of the same kind. He fixed a piece of charcoal in the broad end of a bellows nozzle, unscrewed ; and putting that in the fire, he in- serted the other end in a vessel filled with lime-water. BLACK. 7 The air that was driven through the liquid again pre- cipitated the lime in the form of chalk. Finally, he ascertained by breathing through a syphon filled with lime-water, and finding the lime again precipitated, that animals, by breathing, evolve air of this description. The great step was now made, therefore, that the air of the atmosphere is not the only permanently elastic body, but that others exist, having perfectly different qualities from the atmospheric air, and capable of los- ing their elasticity by entering into chemical union with solid or with liquid substances, from which being afterwards separated, they regain the elastic or aeriform state. He gave to this body the name of fij:ed air^ to denote only that it was found fixed in bodies, as well as elastic and separate. He used the term "air" only to denote its mechanical resemblance to the atmos- pheric air, and not at all to imply that it was of the same nature. No one ever could confound the two substances together ; and accordingly M. Morveau, in explaining some years afterwards the reluctance of chemists to adopt the new theory of causticity, gives as their excuse, that although this doctrine " admirably tallies with all the phenomena, yet it ascribes to fixed air properties which really make it a new body or ex- istence * C'^forment reellement un nouvel etre')* In order to estimate the importance of this discovery, and at the same time to show how entirely it altered the whole face of chemical science, and how completely the doctrine was original, we must now examine the state of knowledge which philosophers had previously attained upon the subject. It has often been remarked that no great discovery was ever made at once, except perhaps that of loga- rithms ; all have been preceded by steps which con- ducted the discoverer's predecessors nearly, though not quite, to the same point Some may possibly think * Supplement to the • EnojrdopMit,* vol. U., p. S74, pabllilMd in 1777. « BLACK. that Black's discovery of fixed air affords no second exception to this rule ; for it is said that Van Hehnont, who flourished at the end of the sixteenth and begin- ning of the seventeeth century, had observed its evo- lution during fermentation, and given it the name of gas silvestre, spirit from wood, remarking that it caused the phenomena of the Grotto del Cane, near Naples. But though he as well as others had observed 'an aeri- form substance to be evolved in fermentation and in effervescence, there is no reason for affirming that they considered it as differing from atmospheric air, except by having absorbed, or become mixed with, certain impurities. Accordingly, a century later than Van Helmont, Hales, who made more experiments on air than any other of the old chemists, adopts the com- monly received opinion that all elastic fluids were only different combinations of the atmospheric air with various exhalations or impurities ;* and this was the imiversal belief upon the subject, both of philosophers and of the vulgar. It is now fit that we see in what manner the subject was treated by scientific men at the period immediately preceding Black's discoveries. The article 'Air' in the French 'Encyclopedic' was published in 1751, and * It may safely be affirmed that Van Helmont's observation, which lay for a century and a half baiTcn, threw no light of any value upon the sub- ject. No one questions Newton's title to the discovery of the different refrangibility of light, and the true theory of the rainbow ; yet, at the beginning of the 17th century, Antonio de Dominis, Archbishop of Spalatro, had really made an ingenious and well-grounded experiment on the similarity of the rainbow colours with those formed by the sun's rays refracted twice and reflected once in a globe filled with water. The doc- trine of universal gravitation was known to both Kepler and Galileo ; and Boulland (Astronomia Philolaica, lib. i., 1645), distinctly stated his belief or conjecture that it acted inversely as the squares of the distances. The famous proposition of equal areas in equal times was known to Kepler. The nearest approach to the Fluxional Calculus had been made by Har- riott and Koberval and Fermat ; and to take but one other example, the electrical explosion of the Leyden jar, discovered in 1747, obtained the name of the coup-foudroyant, and was by Abbe Nollet conjectured to be identical with lightning, Franklin's celebrated experiment being only made in 1752. BLACK. 9 written by D'Alembert himself. It is, as might be expected, able, clear, elaborate. He assumes the sub- stance of the atmosphere to be alone entitled to the name of air, and to be the foundation of all other per- manently elastic bodies : " L'air ^l^mentaire, ou I'air proprement dit," he says. He describes it as " homo- fene," and terms it " I'ingredient fondamental de tout air de I'atmosphere, et qui lui donne son nom." Other substances or exhalations mix with it, he says, but these he terms " passageres," passing vapours, and not per- manent : the air alone (that is, the atmospheric air) he calls " permanent," or permanently elastic (vol. i. p. 225). So little attention had the observation of Van Helmont respecting the Grotto del Cane excited, that we find a conjecture hazarded in the article 'Grotte* (vol. vii. p. 968), which appeared in 1756, — "peut- etre respirent ils (les chiens), au lieu d'air, des vapeurs min(5rales ;" but this was some time after Black's dis- covery had taught us to distinguish such permanently elastic vapours from atmospheric air. In the article 'Fermentation' (vol. vi. p. 523) we find Van Hel- mont's doctrines of the connection between fermenta- tion and digestion treated with ridicule, and those who adopted them jocularly called the " fermentateurs." A few years later, however, the face of things changed. In the 'Supplement,' published in 1776, we find an article on ' Fixed Air, and a reference to Dr. Black's discovery ; but nothing can be more indis- tinct than the author, M. Morveau's, ideas respecting it ; for he leaves us in doubt whether it be the atmos- pheric air or a separate substance, and yet he states that the phenomena of fermentation and putrefaction are explained by the evolution or absorption of this air, ana that mineral waters derive from its presence their flavour. An abstract of M. Venel's boot had in 1765, under the head of 'Mineral Waters,' given this explanation j but instead of representing tlie air com- bined with liie water as a different substance, he calls 10 BLACK. it "veritable air et meme tres pure." We have, how- ever, seen that, in the following year (1777), M. Mor- veau's ideas were perfectly distinct on the subject; for he treats it as a new substance, wholly different from atmospheric air. The slowness with which Black's doctrine made its way in France may be presumed from Morveau's remark on causticity, already cited, and also from this, that the article on 'Magnesia,' published in 1765, dogmatically asserts Black to be in error when he describes Epsom salts as yielding that earth, "because," says the author, "those salts are purely Seidlitian," " entierement Seidlitiens " (vol. x. p. 858). In fact, Epsom salts, magnesia, limestone, and sea-water are the great sources from which all magnesia is obtained. The first of these substances is in truth only a combination of magnesia with sulphuric acid. The other discoveries to which Black's led were as slowly disseminated as his own. Oxygen gas had been discovered, in August, 1774, by Priestley, and soon after by Scheele without any knowledge of Priestley's previous discovery ; yet in 1777 Morveau, who wrote the chemical articles in the ' Supplement,' never men- tions that discovery, nor the almost equally important discovery of Scheele, chlorine, made in 1774, nor that of azote, discovered by Rutherford in 1772, nor hydro- gen gas, the properties of which had been fully inves- tigated by Cavendish as early as 1766. Lavoisier's important doctrine, well entitled to be called a dis- covery, of the true nature of combustion, had likewise been published in 1774 in his ' Opuscules,' yet Mor- veau doggedly adheres to his own absurd theory of the air only being necessary to maintain those oscilla- tions in which he holds combustion to consist ; and finding that the increase of weight is always the result of calcination as well as combustion, he satisfies him- self with making a gratuitous addition to the hypo- thesis of phlogiston, and supposes that this imaginary BLACK. 11 substance is endowed witli positive levity ; nor does he allude to the experiments of Lavoisier on gases, on combustion, and on oxidation, further than to say that he had for a considerable time been engaged in these inquiries. It was not indeed till 1787 that he became a convert to the sound and rational doctrine, and aban- doned the fanciful hypothesis, simple and ingenious though it be, of Stahl. BerthoUet, the earliest con- vert, had come over to the truth two years before. Thus, discoveries had been made which laid the foun- dation of a new science, and on which the attention of all philosophers was bent ; yet the greatest scientific work of the age made no more mention of them than if Black, Cavendish, Priestley, and Scheele had not been. The conjecture may be allowed to us, that if any of these great things had been done in France, M. Morveau would not have been suffered to preserve the same unbroken silence respecting them, even if his invincible prejudices in favour of the doctrine of phlo- giston had disposed him to a course so unworthy of a philosopher. The detail into which I have entered, sufficiently proves that the discovery of fixed air laid at once the toundation of the great events in the chemical world to which reference has just been made, because the step was of incalculable importance by which we are led to the fact that atmospneric air is only one of a class of permanently elastic fluids. When D'Alembert wrote the article * Air,' in 1751, he gave the doctrine then universally received, that all the other kinds of air were only impure atmospheric air, and that this fluid alone was permanently elastic, all other vapours being only, like steam, temporarily aeriform. Once the truth was made known that there arc other gases in nature, only careful observation was required to find them out. Inflammable air was the next which became the subject of examination, because, though it had long been known, before Black's discovery it had 12 BLACK. been supposed only to be common air mixed with unc- tuous particles. His discovery at once showed that it was, like fixed air, a separate aeriform fluid, wholly distinct from the air of the atmosphere. The other gases were discovered somewhat later. But it is a very great mistake to suppose that none of these were known to Black, or that he supposed fixed air to be the only gas different from the atmospheric. The na- ture of hydrogen gas was perfectly known to him, and both its qualities of being inflammable and of being so much lighter than atmospheric air ; for as early as 1766 he invented the air balloon, showing a party of his friends the ascent of a bladder filled with inflammable air. Mr. Cavendish only more precisely ascertained its specific gravity, and showed what Black could not have been ignorant of, that it is the same, from what- ever substance it is obtained. But great as was the discovery of fixed air, and impor- tant as were its consequences, the world was indebted to its illustrious author for another scarcely less re- markable, both from being so unexpected, and from producing such lasting effects upon physical science. About the year 1763 he meditated closely upon the fact, that on the melting of ice more heat seems to disappear than the thermometer indicates, and also that on the condensation of steam an unexpected propor- tion of heat becomes perceptible. An observation of Fahrenheit, on the cooling of water below the tem- perature of ice until it is disturbed, when it gives out heat and freezes at once, appears also to have attracted his careful consideration. He contrived a set of simple but decisive experiments to investigate the cause of these appearances, and was led to the discovery oi latent heat, or the absorption of heat upon bodies passing from the solid to the fluid state, and from the fluid to the aeri- form, the heat having no effect on surrounding bodies, and being therefore insensible to the hand or to the thermometer, and only by its absorption maintaining the i \- BLACK. 13 body in the state which it has assumed, and which it retains until, the absorbed heat being given out, and becoming again sensible, the state of the body is changed back again from fluid to solid, from aeriform to fluid. He never published any account of this dis- covery, but he explained it fiiUy in his Lectures, both at Glasgow and Edinburgh, and he referred to it in the paper already mentioned, which was printed in the * Philosophical Transactions' for 1775. Well, then, may we marvel that no mention whatever of latent heat is made in the celebrated ' Encyclopi^die,' which owed its chemical contributions to no less a writer and experimentalist than Morveau. The doctrine of latent heat, however, was immediately applied by all philo- sophers to the production of the different airs which were successively discovered. They were found to owe their permanently elastic state to the heat absorbed in their production from solid or fluid substances, and to regain their fluid or solid state by combining either together or with those substances, and in the act of union giving out in a sensible form the heat which while absorbed and latent, had kept them in the state of elastic and invisible fluids.* The third great discovery of Black was that which has since been called the doctrine of specific heaty but which he called the capacity of bodies for heat. Dif- ferent bodies contain different quantities of heat in the same bulk or weight ; and different quantities of heat are required to raise different bodies to the same sen- sible temperature. Thus, by Black's experiment, it was found that a pound of gold being heated to 150*, and added to a pound of water at 50°, the temperature of both became not 100", the mean between the two, but 55**, the gold losing 95**, and the water gaining 5% * It is by no roeana impoflrible that one day w« nay ba aUa to radoco the pheDomeiM of light withb the theory of iatent Itaat. It mav be that this bodj whn abaorbcd, that ia, fixed in aobatanoM, ghraa out beat; aa, while pMrin^tft^ugh diaphanooabodieaaud raoMiaing unfixed, ka heat la notaesalble. 14 BLACK. because the capacity of water for heat is nineteen times that of gold. So twice as much heat is required to raise water to any given point of sensible heat as to raise mercury, the volumes of the two fluids compared being equal. The true doctrine of combustion, calcination of metals, and respiration of animals, which Lavoisier deduced from the experiments of Priestley and Scheele upon oxygen gas, and of Cavendish on hydrogen gas, and which has changed the whole aspect of chemical science, was founded mainly upon the doctrines of latent and specific heat. It was thus the singular fe- licity of Black to have furnished both the pillars upon which modern chemistry reposes, and to have furnished them so long before any one attempted to erect the superstructure, that no doubt could by any possibility arise respecting the source of our increased knowledge, the quarter to which our gratitude should be directed. Fixed air was discovered in 1752, and fully explained to the world in 1754 and 1755. Latent heat was yearly, fiom 1763, explained to nu- merous classes of students, before whom the experi- ments that prove it were performed by the author's own hands. Cavendish made his experiments on in- flammable air in 1766; Priestley began his in 1768, first publishing in 1772 ; and he discovered oxygen in 1774, in which year the nature of combustion was first explained by Lavoisier, a boy at school when fixed air was discovered, and having made no experiments nor written any one line upon chemical subjects for seven years after latent heat was discovered. But we shall form a more striking idea to ourselves of the revolution which Black thus efiected in che- mistry, if we attend a little to the state of that science in general before he began his labours. We have already seen the low condition of the knowledge then possessed respecting aeriform fluids ; the general condi- tion of the science was in the same proportion humble. BLACK. 15 The celebrated ' Preliminary Discourse,' to the * En- cyclopedic' makes hardly any mention of chemistry araongthe sciences; and in the ' Arbre Encyclopedique,' on which the authors (D'Alembert and Diderot) plume themselves much, we find it not very distinctly repre- sented, or in very good company. It is termed the science of interior and occult qualities of bodies, its objects being to imitate and rival nature, by decom- posing, reviving, and transferring substances. It is represented as holding among the sciences the place which poetry occupies among other branches of litera- ture. Its fruits are said to be alchemy, metallurgy, natural magic, and chemistry properly so called, which is stated to consist of pyrotechny and dyeing. Strange to tell, pharmacy is not given as one of its fruits, being referred wholly to the branch of medical science. But the state of chemistry is better understood by the article itself in the ' Encyclopedic,' the elaborate work of M. Venel of Montpelier, well known for his researches concerning mineral springs, and author of most of the chemical articles m the original work, us M. Morveau was of those in the * Supplement,' and whose mistakes on the subject of magnesia, aris- ing from prejudice, have already been mentioned. He begins this article with lamenting the low condition of his favourite science; " EUe est pen cultiv($e parmi nous. Cette science n'est que tr^s mi^diocrement r^pandue, mOme parmi les savans, malgre la pretention, k I'uni- versalit(j des connaissances qui font aujourd'hui le f^oAt dominant. Les chemistes forment un peuple distmct, tr6s-peu nombrcux, ayant sa langue, ses mysteres, scs loix, et vivent presque isoles au milieu aun grand peuple peu cuncux de sa connaissance, n'entcndant presque ricn de son Industrie." He then goes on to show that this " incuriosit(i, soit reelle, soit simult'e," is yet extremely unphilosophical, inasmuch as it leads to a rash condemnation ; ana that those who know any 16 BLACKc subject superficially may possibly be deceived in their own judgment upon it, " the consequence of which has been," he adds, " that owing to the prejudices enter- tained against the nature and reach of the science, it becomes a matter of no small difficulty or slight con- troversy to say clearly and precisely what chemistry is. Some make no distinction between the chemist and the quack who seeks after the philosopher's stone (souffleur) ; others think any one a chemist who has a still for preparing perfumes or colours. Many con- sider the compounding of drugs as containing the whole of the art. Even men of science know scarcely any thing about the chemists." — " What natural phi- losopher,*' he asks, " so much as ever names Becker or Stahl ? Whereas those who, having other scientific illustrations, as John Bernouilli and Boerhaave, have written chemical works, or rather works on chemical subjects, are very differently thought of; so that the for- mer's work on * Fermentation,' and the latter's on ' Fire,' are known, cited, and praised, while the far greater views of Stahl on the same subjects only exist for a few chemists." He then goes on to cite other proofs of the low estimate formed of the science, and even the pre- vailing impression of chemists being mere workmen ; and concludes, that " the revolution which should raise chemistry to the rank it merits, and place it on a level with natural philosophy, can only be accom- plished by a great, an enthusiastic, and a bold genius." While waiting for the advent of this new Paracelsus, he says, it must be his task to present chemistry in a light which may show it worthy the notice of philosophers, and capable of becoming something in their hands. If we go back to an earlier period, we shall find that Lord Bacon, although he quite clearly perceived that chemistry might one day be advanced to the rank of a science (De Dig. et Aug. iii.), yet always treats the chemistry of his day as merely empirical (Nov. Org. BLACK. 17 s. Ixiv. Ixxlii.*). But I have preferred taking the account of chemical science from the ' Encyclopedie,' first, because it gives, if not the opinion or the testi- mony of the learned body at large who prepared that work, yet certainly an opinion and a testimony which had the sanction of its more eminent members ; and, secondly, because its date is at the eve of the great revolution in natural science of which we are speaking. The last passage which has been cited from that work strikingly illustrates the low ebb at which chemical science then was. — It is certain that after the discov- eries of Black had opened vast and new views of nature, both as regards the operations of heat, the most power- ful and universal of all agents, and as regards the con- stitution of elastic fluids, the most unknown of the four elements, no natural philosopher would have had the hardihood to doubt if chemistry was an important branch of his science, and no chemist would have performed the superfluous task of vindicating its claim to the title. • " Itaque talis philosophia (in paacoram experimentornm argatiis et obscuritate fundata) illis qui in hujusmodi experimentis quotidie versantur atquo ex ipsis phantasmatis contaminarunt, probabills videtur, et quasi ccrta ; eastern incre