THE LIBRARY 
 
 OF 
 
 THE UNIVERSITY 
 OF CALIFORNIA 
 
 LOS ANGELES 
 
 GIFT OF 
 
 GJ. Cummings
 
 I 
 

 
 A PRACTICAL TREATISE 
 
 ON 
 
 WARMING BUILDINGS 
 
 BY 
 
 HOT WATER, STEAM, AND HOT AIR; 
 
 ON 
 
 VENTILATION, 
 
 AND THE 
 
 VARIOUS METHODS OF DISTRIBUTING ARTIFICIAL HEAT, AND THEIR 
 EFFECTS ON ANIMAL AND VEGETABLE PHYSIOLOGY. 
 
 TO WHICH ABE ADDED AN 
 
 INQUIRY INTO THE LAWS OF RADIANT AND CONDUCTED HEAT, 
 
 THE CHEMICAL CONSTITUTION OF COAL, AND 
 
 THE COMBUSTION OF SMOKE. 
 
 BY 
 CHARLES HOOD, F.R.S., F.R.A.S., &c. 
 
 SIXTH EDITION. 
 
 
 E. & F. N. SPON, 125, STBAND, LONDON. 
 
 NEW YOKK: 35, MURRAY STREET. 
 
 1885. 

 
 Engineering 
 Library 
 
 Tfl 
 
 PKEFACE 
 
 TO THE FIFTH EDITION. 
 
 A NEW Edition of the TREATISE ON WARMING 
 AND VENTILATING BUILDINGS being required, it 
 has been thought desirable not only to revise the 
 former edition, but also to enlarge it with a con- 
 siderable quantity of new matter. 
 
 The various inquiries addressed to the Author 
 from time to time, have led to the conclusion that 
 fuller information on certain subjects treated in 
 this work would be desirable, and it has been his 
 endeavour to supply this information in the present 
 edition. 
 
 The ever-varying conditions under which the 
 Warming and Ventilating of Buildings are sought 
 to be applied, necessarily produce new combina- 
 tions. In the present edition considerable addi- 
 tions have been made with the view of meeting, as 
 
 549403
 
 Vi PREFACE. 
 
 far as possible, these requirements. A chapter on 
 heating large bodies of water for Baths and other 
 purposes has been added ; and considerable addi- 
 tions have been made to the chapters on forced 
 and spontaneous ventilation, and on the action of 
 the various forms of ventilators and chimney 
 cowls. The causes of failure in several forms of 
 apparatus have also been pointed out, and remedies 
 suggested; and generally, throughout the work, 
 many additional points of practical experience have 
 been investigated, and it is hoped the results may 
 be found useful. 
 
 In the former editions of this work all the para- 
 graphs were numbered consecutively. In the 
 present edition many new paragraphs have been 
 added without being numbered, and in other cases 
 duplicate numbers, with an asterisk prefixed, have 
 been inserted. This plan has been adopted ad- 
 visedly. Not only was it deemed undesirable to 
 disturb the original numbering of the paragraphs 
 as given in the former editions; but further, the 
 references throughout the work, from one part to 
 another, are so numerous, that it was found to be 
 scarcely practicable to alter the original numbering 
 of the paragraphs, without great risk of error, and
 
 PREFACE. Vll 
 
 an amount of additional labour which would be 
 hardly justified. 
 
 All that was given in the former editions will 
 be found in the present work. But the additions 
 which have been made will, it is hoped, throw 
 some further light on various points of practice 
 which have occasionally caused difficulties. 
 
 Very copious extracts from the former editions 
 of this work have for many years past been made 
 both at home and abroad, by other authors. Not 
 only paragraphs and tables, but whole pages, and 
 even entire chapters, have been thus appropriated 
 without acknowledgment. It may therefore be 
 well to state that the first edition of this treatise 
 was published in 1837. The extensive appropri- 
 ation of parts of this work by other authors, 
 without proper acknowledgment, has sometimes 
 led to the borrowers being credited with the 
 original production, and the real author esteemed 
 to be the plagiarist. This is the excuse for noticing 
 what might otherwise lead some persons to suppose 
 an unfair use had been made by the author of what 
 properly belonged to others; but he believes that 
 he has in every instance quoted the authors from
 
 Vlll PREFACE. 
 
 whom he has derived any of the information con- 
 tained in the following pages. 
 
 In this edition, as in those which preceded it, 
 the plan of throwing into Notes a good deal of the 
 information which is explanatory of the subject- 
 matter of the work, has been followed. The object 
 of this is to render the text more simple for those 
 who only wish for the practical information, apart 
 from any scientific discussion. 
 
 C. H. 
 
 No. 1, UPPER THAMES STBEET, 
 
 LONDON ; AND 
 LEINSTEB GABDENS, HYDE PABK. 
 
 Tliis sixth edition is a reprint of the fifth.
 
 CONTENTS. 
 
 PART FIRST. 
 
 ON WARMING BUILDINGS BY HOT WATER. 
 
 PAGE 
 
 INTRODUCTION 1 
 
 CHAPTER I. 
 
 ON THE CIRCULATION AND COMPRESSION OF WATER, AND THE 
 INCLINATION AND LEVEL OF PIPES, ETC. 
 
 Cause of Circulation of the Water Inclination of the 
 Pipes Necessity for Air Vents Open and Close 
 Boilers Pressure of Water Expansive Power of 
 Steam Effect produced on the Circulation by in- 
 creased Height of the Pipe Compression of Water 
 Branch Pipes Variations in Level of Pipes 9 
 
 CHAPTER II. 
 
 ON THE MOTIVE POWER AND VELOCITY OF CIRCULATION OF 
 WATER. 
 
 On the Motive Power of the Water On increasing the 
 Motive Power Velocity of Circulation Circulation 
 of Water below the Boiler Direct and Reversed 
 Circulation Air Vents Supply Cisterns Expan- 
 sion of Pipes, &c 24
 
 CONTENTS. 
 
 CHAPTER III. 
 
 ON THE RELATIVE SIZES OF PIPES, AND THE USE OF STOP-COCKS 
 AND VALVES. 
 
 PAGE 
 
 On the Resistance by Friction Relative Size of Main 
 Pipes and Branch Pipes Vertical and Horizontal 
 Main Pipes Small Connecting Pipes Branch Pipes 
 at different Levels Stop-Cocks and Valves Their 
 Use and proper Size Their place supplied by 
 Cisterns Inconvenience of them Remedies 51 
 
 CHAPTER IV. 
 
 ON TEMPEBATTJBE, PIPES AND BOILERS, DURABILITY OF MATERIAL, 
 -" AND FUEL. 
 
 Permanence of Temperature Rates of Cooling for dif- 
 ferent-sized Bodies Proper Sizes for Pipes Relative 
 Size of Pipes and Boiler Various Forms of Boilers, 
 and their Peculiarities Boilers heated by Gas 
 Objections against contracted Waterway in Boilers 
 Proper Size of Boilers for any given lengths of 
 Pipe What constitutes a good and efficient Boiler 
 Durability of different materials for Boilers 
 Effect of Impure Fuel 63 
 
 CHAPTER V. 
 
 ON FURNACES, THEIR CONSTRUCTION, AND MODES OF FIRING. 
 
 On the Construction of Furnaces Combustion dependent 
 on Size of Fire Bars Furnace Doors, and other parts 
 of Furnaces Proportionate Area of Furnace Bars to 
 the Fuel consumed Confining the Heat within the 
 Furnace Directions for Building the Furnace for 
 diiferent Boilers Advantage of large Furnaces 
 Modes of Firing Size of Chimneys 88
 
 CONTENTS. XI 
 
 CHAPTER VI. 
 
 ESTIMATE OF THE HEATING SURFACE REQUIRED TO WARM ANY 
 DESCRIPTION OF BUILDINGS. 
 
 PAGE 
 
 Heat by Combustion Quantity of Heat from Coal 
 Specific Heat of Air and Water Measure of Effect 
 for Heated Iron Pipe Cooling Power of Glass 
 Effect of Vapour Quantity of Pipe required to warm 
 a given space Time required to heat a Building 
 Facile Mode of Calculating the quantity of Pipe re- 
 quired in any Building Quantity of Coal consumed 105 
 
 CHAPTER VII. 
 
 ON VARIOUS HOT-WATER APPARATUS. 
 
 Various Modifications of the Hot -water Apparatus 
 Kewley's Siphon Principle The High-pressure 
 System Holmes' and Coffey's Modifications 
 Eckstein and Busby's Rotary Float Circulator 
 Fowler's Thermo-siphon Price's improved Hot- 
 water Boxes Rendle's Tank System Corbett's 
 Trough System for Evaporation Theory of Evapo- 
 ration 131 
 
 CHAPTER VIII. 
 
 GENERAL REMARKS ON HOT-WATER APPARATUS. 
 
 General Summary of the Subject Points requiring 
 particular attention Abstraction of Air from the 
 Pipes Vertical Alteration of Level Effect of 
 Elbows in Compensating unequal Expansions of the 
 Pipe Different Floors heated by one Main Pipe 
 from the Boiler Method of connecting Coils to 
 Main Pipes Reduced Effect from Pipes laid in 
 Trenches Effect of Cold Currents of Air in neu- 
 tralizing Heating Apparatus Heating Apparatus 
 placed in Vaults Cements for Joints Sediment 
 in Boilers Use of Salt in Pipes to prevent Freezing 
 Deposition of Vapour in inhabited Rooms Ne- 
 cessity for Ventilation Construction of Drying- 
 rooms . 163
 
 Xil CONTENTS. 
 
 CHAPTER IX. 
 
 ON APPARATUS FOB BATHS AND DOMESTIC SERVICE. 
 
 PAGE 
 
 Inconvenience from Deposits in Boilers Deposit in 
 Cisterns Circulation necessary throughout the 
 Pipes Proper position of the Hot-water Cistern 
 Two different Modes of drawing off Hot Water 
 Heating Tanks by Coils, or by Direct Circulation 
 Mode of estimating the power of a Coil Estimate 
 of Boiler Surface Plunging Baths 194 
 
 CHAPTER X. 
 
 ON HEATING BY STEAM. 
 
 Variableness of Temperature Alterations in the Level of 
 the Pipes Removal of Condensed Water Proper 
 Steam Pressure to be Employed Mode of calculating 
 the Heating Surface required Size of Boilers 
 Quantity of Water Condensed Boiler Surface re- 
 quired Forms and Power of Boilers Quantity of 
 Coal Size of Furnace Bars Mode of supplying 
 Water to the Boiler Safety Valves, Gauges, and 
 other Appendages required Air Vents and Outlets 
 for the Condensed Water 202 
 
 CHAPTER XI. 
 
 ON HEATING BY HOT AIR. 
 
 Sylvester's Cockle Stove Improved Cockle Stove Es- 
 timate of Heating Power Hot-air Stoves with Pro- 
 jecting Plates, and their Heating Power Bern- 
 hardt's, Hazard's and other Hot-air Apparatus- 
 Difficulty with Horizontal Flues Multitubular Hot- 
 air Apparatus Hot-blast Apparatus 218
 
 CONTEXTS. xiii 
 
 CHAPTER XII. 
 
 ON THE LAWS AND PHENOMENA OF HEAT. 
 
 PACK 
 
 Radiation and Conduction General Law of cooling Bodies 
 in Air and other Gases Different Laws for Conduc- 
 tion and Radiation Effect by Incidence of the Rays 
 Effects of Surface on Radiation Effects of Colour 
 Effects of Roughness Absorptive Power of Bodies 
 for Heat Conducting Power of Metals Conducting 
 Power of Wood Conducting Power of Liquids 
 Cooling Influence of Water and Air Reflective 
 Powers of Bodies Specific Heat of Bodies Latent 
 Heat Spontaneous Evaporation Heat and Cold 
 by Condensation and Rarefaction of the Air 
 Motion of Liquids influenced by Heat Effect of 
 Heat on Strength of Materials 234 
 
 CHAPTER XIII. 
 
 EXPERIMENTS ON COOLING. 
 
 Velocity of Cooling of a Heated Body Tredgold's Ex- 
 periments Cooling of Cast-iron Surfaces Ratio 
 of Cooling of Painted Surfaces Cooling Effect of 
 Window -glass Leslie's Experiments on Cooling 
 Power of Wind Importance of in Buildings used for 
 , Horticultural Purposes Effect of Sheet Iron in 
 Cooling Buildings 271
 
 xiv CONTENTS. 
 
 PART SECOND. 
 
 ON THE WARMING AND VENTILATION OF BUILDINGS 
 BY THE COMBUSTION OP FUEL. 
 
 CHAPTER I. 
 
 ON THE VARIOUS METHODS OF WARMING AND VENTILATING 
 BUILDINGS, THE COMBUSTION OF FUEL, ETC. 
 
 PAGE 
 
 Early Methods of Warming Buildings The Eomans; 
 their Stoves Baths Flues Mode of Preparing 
 their Firewood The Persian Method of Heating 
 Chinese Method of Flues Method of the Ancient 
 Britons Invention of Chimneys Burning of Coals 
 in England Early Writers on the Subject Im- 
 provements in the Form and Construction of Stoves 
 and Fireplaces 281 
 
 CHAPTER II. 
 
 ON THE VARIOUS FORMS OF FIREPLACES AND STOVES. 
 
 Forms of Fireplaces and Chimneys Should be made 
 to reflect Heat Contraction of Chimney-breast 
 Hollow Hearths and Backs for Fireplaces Rum- 
 ford's Principles of Construction Errors in the 
 Construction of Stoves Register Stove in a Case 
 Jeffrey's Stove Franklin's Pennsylvania Stove 
 Cutler's Torch Stove Sylvester's Radiating Stove 
 Russian and Swedish Stove Cundy's Stoves Ger- 
 man Stoves Hot-air Stoves Cockle Stoves Dr. 
 Nott's Stove Dr. Arnott's Stove Franklin's Vase 
 Stove Gas Stoves Joyce's Stoves Beaumont's 
 Stove Palmaise Stove 290
 
 CONTENTS. XV 
 
 CHAPTER III. 
 
 ON THE CHANGES PRODUCED IN ATMOSPHERIC AIR BY HEAT, 
 COMBUSTION, AND RESPIRATION. 
 
 FAOB 
 
 Necessity for Ventilation Constitution of the Atmo- 
 sphere Ventilation, its early Invention Subsequent 
 Inventions for Ventilating Effects of Contaminated 
 Air on the Human Frame Effects of Climate 
 on Health and Longevity Cause of Miasmata 
 Effects of excessive Moisture and excessive Dry- 
 ness of the Atmosphere Respiration ; its Pro- 
 ducts and Effects Impure Air Carbonic Acid 
 Gas Vapour from the Body Effect of Diminished 
 Pressure Electric Condition of the Air Production 
 of Ozone Decomposition of Extraneous Matter in 
 the Air Effects of Hydrogen, Carburetted Hydro- 
 gen, and Carbonic Oxide Quantity of Air required 
 for Ventilation Importance of the Air to Animal 
 and Vegetable Life 317 
 
 CHAPTER IV. 
 
 ON THE VARIOUS METHODS OF PRODUCING VENTILATION. 
 
 Spontaneous and Mechanical Methods of Ventilation 
 Cause of Motion in Spontaneous Ventilation 
 Velocity of Discharge Effects of Unequal Height of 
 Discharge Pipes Defects in Ventilation of Churches 
 Proportions of Induction and Abduction Tubes 
 Quantity of Air discharged through Ventilators 
 Ventilating by Heat and by Chimney Draughts 
 Mechanical Ventilation by Fans, Bellows, and 
 Pumps Quantity of Air discharged by these 
 Means Calculations of the Power Expended 
 Cowls for promoting Ventilation Effect of different 
 Cowls . . 357
 
 X vi CONTENTS. ' 
 
 CHAPTER V. 
 
 ON THE THEORY OF GASEOUS EFFLUX. 
 
 FAGK 
 
 Theoretical Determination of the Velocity of Gaseous 
 Fluids Investigated by Dr. Papin} Dr. Gregory, 
 Davies Gilbert, Sylvester, Tredgold, &c. Hydro- 
 dynamic Law of Spouting Fluids Basis of Dr. 
 Gregory's Formulae for Calculating the Velocity of 
 Air Mr. Davies Gilbert's Method of Calculation- 
 Mr. Sylvester's Process Tredgold's Theory Mont- 
 golfier's Mode of Calculating the most simple and 
 correct Comparison of Theoretical Calculations with 
 the Results of Experiments Accuracy of this Method 
 - of Calculation 386 
 
 CHAPTER VI. 
 
 ON THK CHEMICAL CONSTITUTION OF COAL, AND THE COM- 
 BUSTION OF SMOKE. 
 
 Early Use of Coal in England Chemical Composition 
 of Coal Analysis of Coal Combustion of Coal 
 Loss by imperfect Combustion Loss from the Escape 
 of Smoke Loss by Carbonic Oxide Causes of im- 
 perfect Combustion Theory of Combustion Tem- 
 perature required for Combustion Effects of Rare- 
 faction of the Air Effects of Hot Air Quantity of 
 Air required for Combustion Methods of admitting 
 Air Combustion of Anthracite Coal Description 
 of various Plans for consuming Smoke Artificial 
 Fuels .397 
 
 APPENDIX 441 
 
 INDKX .451
 
 INTEODUCTION. 
 
 THE practice of employing hot water, circulating 
 through iron pipes, for diffusing artificial heat, is 
 an invention of acknowledged utility ; and the 
 present extensive and extending use of this in- 
 vention renders it extremely desirable that its 
 principles should be clearly defined, and the rules 
 for its practical application laid down with pre- 
 cision. Without this knowledge its success will 
 be uncertain, its application limited, and its re- 
 sults unsatisfactory. 
 
 It can scarcely excite surprise, that prejudices 
 should formerly have existed against this inven- 
 tion, while its merits and its principles were alike 
 imperfectly known. Even at the present time 
 they are but partially understood ; and, therefore, 
 to investigate these two subjects is the proposed 
 object of the present treatise, with the view of 
 facilitating its application, and extending the sphere 
 of its utility. 
 
 There is scarcely any branch of science, or of 
 art, in which an acquaintance with the laws of 
 Nature does not enable us to derive greater ad- 
 vantages in its application than we could other- 
 wise possess. There is no art, however humble, 
 in which a knowledge of the laws that regulate 
 matter does not open a wide and extensive field 
 of useful improvement; and no man can hope to
 
 2 INTRODUCTION. 
 
 advance the sphere of useful invention, in any 
 considerable degree, without some knowledge of 
 the principles on which it depends. But, having 
 this knowledge, he may, to use the words of a 
 well-known writer, " if he have only a pot to 
 boil, be sure to learn from science lessons which 
 will enable him to cook his morsel better, save 
 his fuel, and both vary his dish and improve it." 
 Although it is true that we are still ignorant of 
 the more subtile agents which exist in the vast 
 chain of causation, the laws which regulate the 
 various phenomena of Nature are sufficiently 
 known to afford the most beneficial assistance to 
 every branch of the arts and sciences: and the 
 most recondite of scientific discoveries, as well as 
 the most valuable inventions and improvements 
 in the arts, are not more demonstrative of the 
 truth of this assertion, than those which are the 
 most simple and inartificial. 
 
 For an illustration of the utility of this know- 
 ledge, we may refer to the law of gravity, not 
 only because it is, of all natural phenomena, the 
 most constant in its operation, and the most 
 universal in extent, but because its influence is 
 closely connected with the present subject of in- 
 quiry. 
 
 That all falling bodies gravitate with the same 
 velocity, and, therefore, descend through a cer- 
 tain definite space in a given time, is, we know, 
 an effect, of which gravity is the cause. It is on 
 the operation of this invariable law that many of 
 our most valuable inventions depend. Its influ- 
 ence is equally exerted on all objects alike ; the 
 most mighty as well as the most minute. It is 
 this which gives stability to the grandest produc- 
 tions of Nature, as well as to the most minute or 
 artificial of our own works. It is from this cause 
 that we obtain the unerring action of our pendulums
 
 INTRODUCTION. 3 
 
 and clocks ; and it is by this we obtain the circu- 
 lation of hot water, with which we warm our 
 dwellings. By a knowledge of the cause of these 
 effects, of the extent of its operations, and of the 
 laws by which it acts, we can, by varying the 
 circumstances of a gravitating body, alter also the 
 velocity of its descent. We accomplish this by 
 bringing other causes into operation, which modify 
 the result, notwithstanding the immutability of 
 the laws of gravity: and thus, by a knowledge 
 of the physical laws, we can modify and subject to 
 our will one of the most constant and universal 
 agents in Nature. 
 
 The study of the laws which govern natural 
 phenomena which in all cases are so simple, so 
 beautiful, so perfect is, therefore, one of the most 
 fruitful sources of inquiry which the mechanician 
 can pursue. It opens to him new fields of useful 
 inquiry; new applications of known inventions; 
 new and simpler means of accomplishing known 
 effects. And while it points to improvement in 
 every direction, it restrains the judgment from 
 false principles. Where it exists not, it is almost 
 certain that the plans of the mechanician will 
 either be only modified copies of existing inven- 
 tions, or they will degenerate into wild speculations, 
 unsupported on any reasonable foundation. 
 
 This is particularly observable in the case before 
 us. The numerous failures which have occurred 
 in the practical application of the invention of 
 heating buildings by the circulation of hot water, 
 are all distinctly referrible to the want of this kind 
 of knowledge, and not to the object aimed at being 
 itself unattainable. For whenever the physical 
 laws are intended to be employed as the principal 
 agents in producing any mechanical effect, it is an 
 indispensable condition that simplicity of action be 
 kept in view. While it may further be observed, 
 
 B 2
 
 4 ' INTRODUCTION. 
 
 that the endeavours to trace and elucidate the 
 operating causes of the various phenomena, which 
 occur in the course of practical experiments, are 
 the surest means of facilitating original discoveries, 
 as well as of promoting new adaptions of recog- 
 nized principles. 
 
 The origin of the invention of employing hot 
 water for diffusing artificial heat appears to be hid 
 in considerable obscurity. It is not improbable 
 that, like many other discoveries, it has been re- 
 produced at various periods. It seems, however, 
 to have been first used in France, by M. Bonnemain, 
 in the year 1777, and was employed by him during 
 several years for hatching chickens by artificial 
 heat. The French Revolution, which followed 
 shortly afterwards, put a stop to this, as well as 
 many other useful and scientific inventions, in that 
 country ; and for several years the invention ap- 
 pears to have been entirely dormant ; nor indeed, 
 does it appear ever to have been used by M. Bonne- 
 main except for the purpose above mentioned. 
 About the year 1817, the Marquis de Chabannes 
 introduced a similar apparatus into this country 
 for heating a conservatory, and also heating some 
 rooms in a private house, by pipes leading from the 
 kitchen boiler. In the following year he published, 
 in London, a pamphlet describing this apparatus, 
 and some ingenious modifications of hot-air stoves. 
 The invention appears to have made very little pro- 
 gress for some years. In 1822, Mr. Bacon, a 
 gentleman of fortune, introduced the use of hot 
 water into his forcing-houses, using for the purpose 
 a single pipe of large diameter, communicating with 
 the boiler ; and, by giving a slight elevation to the 
 pipe from the horizontal line, he was thus enabled 
 to produce a circulation of the water, the hot water 
 slowly passing along the upper part of the nearly 
 horizontal pipe, and the colder water returning to the
 
 INTRODUCTION. 5 
 
 boiler along the lower part of the same pipe. The 
 circulation in this apparatus was very imperfect ; 
 and Mr. Atkinson, an architect, almost immedi- 
 ately afterwards suggested the addition of a second 
 pipe to bring back the colder water to the boiler ; 
 and thus at once the apparatus assumed the form 
 which it has ever since retained. By this alter- 
 ation the apparatus was brought very nearly to 
 the same form as that contrived by M. Bonnemain 
 more than forty years before ; the principal 
 difference being that M. Bonnemain used only very 
 small pipes of gun-barrel size, while Mr. Atkinson 
 used pipes of four or five inches diameter. 
 
 The honour of this invention has been claimed 
 for Mr. Watt, prior to the time of M. Bonnemain 
 using it in France ; but there appear no grounds 
 for supposing he ever employed it without the in- 
 tervention of steam, as a distributor of heat by 
 circulation, in the manner in which it is now used. 
 The mere motion of hot water in pipes is an in- 
 vention of far greater antiquity than the time 
 either of Watt or Bonnemain. Seneca has accu- 
 rately described the mode of heating the water in 
 the Thermae of Rome, of which Castell has given 
 drawings ; * and which show that the method 
 of heating baths by passing the water through a 
 coil of pipes which passed through the fire was 
 known and practised previous to the Christian era. 
 And, except that these tubes were of brass, instead 
 of iron, they were precisely similar,, both in form 
 and arrangement, to those occasionally used at the 
 present day for the like purpose ; the lapse of nine- 
 teen centuries having apparently added nothing to 
 our knowledge on this subject. 
 
 Since the first introduction of the hot-water ap- 
 
 * Castell's "Illustrations of the Villas of the Ancients," 
 p. 10.
 
 6 INTRODUCTION. 
 
 paratus for warming buildings, the variations made 
 in its more complicated arrangements appear to 
 have been very gradually adopted. Each time 
 that an apparatus has been erected, experimentalists 
 have deviated in some small degree from the model 
 of that which preceded; apparently afraid of 
 venturing on too great a variation, yet requiring, 
 from contingent circumstances, some alteration of 
 its form and application. This mode of proceeding, 
 though natural while the principles were not 
 thoroughly understood, has frequently led to both 
 inconvenience and loss, in consequence of the 
 numerous failures to which it has given rise, by 
 unintentional deviations from the true principles. 
 In the present attempt to elucidate the subject, it 
 will, however, be shown that success needs not be 
 uncertain, provided only that the laws of physics 
 be justly applied and strictly adhered to, 
 
 So numerous have been the failures which have 
 occurred in this method of heating buildings, that 
 nothing but the intrinsic merits of the invention 
 could possibly have made it retain its hold on the 
 public favour. Every imaginable kind of mistake 
 has been made in apparatus erected on this plan. 
 And these mistakes still continue to be made 
 almost as frequently as ever, notwithstanding the 
 vast number of buildings in which it has been 
 successfully applied, and which might be consulted 
 for correct information. 
 
 Neither the capabilities of this method of warm- 
 ing, nor the various useful purposes to which it is 
 applicable, are even yet fully appreciated. There 
 are no buildings, however large, to which it cannot 
 be advantageously adapted, nor any that present 
 insurmountable difficulties in its practical applica- 
 tion. In many useful purposes connected with 
 arts and manufactures, it can be most advan- 
 tageously employed, though its application to these
 
 INTRODUCTION-. 7 
 
 purposes has hitherto been greatly overlooked. Its 
 merits, however, will best appear by the plain 
 statement of facts in the following pages. 
 
 Since the publication of the first edition of this 
 work, in 1837, ample opportunities have occurred 
 for testing in every variety of form the accuracy 
 of the rules and calculations which were then given, 
 for constructing and apportioning the hot-water 
 apparatus to the varying circumstances under 
 which it could be applied. The most important 
 of the calculations are those on the heated surfaces 
 required to warm a given building, and the proper 
 size of the boiler and the furnace. The data on 
 which were founded the rules, and tables for calcu- 
 lating these proportions, were carefully compared, 
 both experimentally and practically ; and the ex- 
 tensive use which has been made of these rules, 
 with perfect success, leaves no doubt whatever as 
 to their complete accuracy. 
 
 The object which has been aimed at in this 
 treatise, has been to render the work as clear as 
 possible to practical men ; while at the same time, 
 it should not be below the notice of those who 
 might desire either to acquaint themselves with the 
 scientific principles of the invention, or with the 
 general bearing of the subject, on the health, the 
 comfort, the physical development, and even the 
 duration of life, of a large portion of the human 
 race. The effects of unwholesome air on the 
 animal economy from imperfect ventilation and 
 deleterious methods of producing artificial warmth, 
 is a subject which has hitherto excited far too 
 little attention. The laws which connect man 
 with the physical universe are of far higher general- 
 isation than many are inclined to believe. They 
 bind together not alone the phenomena of our own 
 world, but of the entire material universe. And 
 yet mankind vainly suppose they can act as they
 
 8 INTRODUCTION. 
 
 please with relation to these immutable laws, 
 that they can fashion them to their own will, and 
 to their own imagined wants; and instead of 
 endeavouring to make themselves more thoroughly 
 acquainted with these laws, devised by unerring 
 Wisdom for the universal good, they choose rather 
 to act either in direct opposition, or, at least, in 
 total neglect of those great truths which philosophy 
 has been permitted to discover and unfold. But it 
 is certain that they cannot with impunity neglect 
 the great truths which physiology discloses; nor 
 can they place themselves in opposition to those 
 fundamental laws which bind together the whole 
 physical universe, without entailing upon them- 
 selves the penalties which the Great Author of 
 those laws has made the inseparable condition of 
 their infringement. 
 
 It is hoped the following pages will place this 
 matter in a clear point of view, in a sufficiently 
 popular manner.
 
 A PEACTICAL TKEATISE, 
 
 PART FIRST. 
 
 ON WARMING BUILDINGS BY HOT WATER, AND ON 
 THE LAWS OF HEAT, ETC. 
 
 CHAPTER I. 
 
 Cause of Circulation of the Water Inclination of the Pipes 
 Necessity for Air- vents Open and Close Boilers Pressure 
 of Water Expansive Power of Steam Effect produced 
 on the Circulation by increased Height of the Pipe 
 Compression of Water Branch Pipes Variations in 
 Level of Pipes. 
 
 (AKT. 1.) In endeavouring to explain the prin- 
 ciples of the various forms of apparatus in which 
 hot water, circulating through iron pipes, is em- 
 ployed as a means for distributing artificial heat, 
 the first object should be to point out, as clearly as 
 possible, the power which produces the circulation 
 of the water ; for without a clear perception of this 
 part of the subject, there will always be an uncer- 
 tainty as to the results which will obtain, when any 
 departure is made from the most simple form and 
 arrangement of the different parts of the appa- 
 ratus. It is this circulation which causes all 
 the water in the apparatus to pass successively 
 through the boiler, and then communicates the 
 heat that is thus received from the fuel to the
 
 10 CAUSE OF CIRCULATION. 
 
 various buildings or apartments which it is de- 
 signed to warm. Without this circulation, those 
 parts of the apparatus which are remote from the 
 fire would not receive any heat ; because water is 
 so bad a conductor that it is only when there 
 exists perfect freedom of motion among its par- 
 ticles, that it acts at all as a conductor of heat, so 
 far, at least, as regards any practical and useful 
 effect. It is in a complete and perfect circulation, 
 therefore, that the efficiency of a hot-water appa- 
 ratus depends, and that the greatest amount of heat 
 is obtained by it from a given quantity of fuel. 
 
 (2.) The only treatise hitherto published, in 
 which any attempt has been made to explain the 
 cause of the circulation of the water in this de- 
 scription of apparatus, is Mr. Tredgold's work on 
 heating by steam ; and the effect is there referred 
 entirely to an erroneous cause. In the Appendix 
 to that work, the cause of motion is thus explained. 
 
 FIG. i. " H tne vesse ls A B, and 
 
 pipes, be filled with water, 
 ' 6 and heat be applied to the 
 vessel A, the effect of heat 
 will expand the water in 
 the vessel A, and the sur- 
 face will, in consequence, 
 rise to a higher level, a d, the former general level 
 surface being b b. The density of the fluid in the 
 vessel A will also decrease in consequence of its 
 expansion ; but as soon as the column c d (above 
 the centre of the upper pipe) is of a greater weight 
 than the column /?, motion will commence along 
 the upper pipe from A to B, and the change this 
 motion produces in the equilibrium of the fluid 
 will cause a corresponding motion in the lower 
 pipe from B to A." 
 
 (3.) Now it is certain that this theory will not 
 account for the circulation of the water under all
 
 CAUSE OF CIRCULATION. 11 
 
 circumstances, and every variety of form of the 
 apparatus ; and as the cause of motion must be the 
 same in all cases, any explanation which will not 
 apply universally must necessarily be erroneous. 
 Were this the true cause of motion, there would be 
 no difficulty in obtaining a circulation in all cases ; 
 for, according to this reasoning, whenever the level 
 of the water is higher in the boiler than in the 
 pipes or even if an upright pipe were placed on 
 the top of a close boiler, by which the pressure on 
 the surface would be increased the water must 
 of necessity circulate through the pipes : while, on 
 the other hand, if this hypothesis were correct, 
 the water in an apparatus constructed as in the 
 following figure would not circulate at all. 
 
 (4.) Suppose the apparatus, fig. 2, to be filled 
 with cold water, and the two stop-cocks, fg t to be 
 closed : on applying 
 heat to the vessel A, 
 the water it contains 
 will expand in bulk, 
 and a part of it will 
 flow through the small 
 waste-pipe x, which 
 is so placed as to prevent the water rising higher 
 in the vessel A than the top of the vessel B. The 
 water which remains in the vessel A, after it has 
 been heated, and a portion of it has passed 
 through the waste-pipe #, will evidently be 
 lighter than it was before, while its height will 
 remain unaltered. Suppose, now, the two cocks, 
 fg, to be simultaneously opened ; the hot water 
 in the boiler A will immediately flow towards B 
 through the upper pipe, and the cold water in B 
 will flow into A through the lower pipe ; although, 
 by the hypothesis previously alluded to, unless 
 the water in the vessel A, above the pipe c, were 
 heavier, or rose to a higher level than the water
 
 12 CAUSE OF CIRCULATION. 
 
 in the vessel B, no circulation could take place. 
 In this case, therefore, we must find another ex- 
 planation of the cause of motion. 
 
 (5.) The power which produces circulation of 
 the water will be found to arise from a different 
 cause than that which is here stated ; for we see 
 that this reason is insufficient to account for the 
 effect, even in one of the simplest forms of the 
 apparatus. 
 
 In order to explain this, let us suppose heat to 
 be applied to the boiler A, fig. 2. A dilation of 
 the volume of the water takes place, and it be- 
 comes lighter ; the heated particles rising upwards 
 through the colder ones, which latter sink to the 
 bottom by their greater specific gravity, and they 
 in their turn become heated and expanded like 
 the others. This intestine motion continues until 
 all the particles become equally heated, and have 
 received as much heat as the fuel can impart to 
 them. But as soon as the water in the boiler be- 
 gins thus to acquire heat, and to become lighter 
 than that which is in the opposite vessel B, the 
 water in the lower horizontal pipe d is pressed by 
 a greater weight at z than at y, and it therefore 
 moves towards A with a velocity and force equal 
 to the difference in pressure at the two points y 
 and z* The water in the upper part of the 
 vessel B would now assume a lower level, were it 
 not that the pipe c furnishes a fresh supply of 
 water from the boiler to replenish the deficiency. 
 
 * To any person unacquainted with the science of Hydro- 
 statics, this may probably appear erroneous, because the quan- 
 tity of water contained in A is much greater than that in B. 
 It is, however, one of the first laws of Hydrostatics that the 
 pressure of fluids depends for its amount on the height of the 
 fluid only, and is wholly irrespective of the bulk, or actual 
 quantity of fluid : therefore, a pipe which is not larger than a 
 quill will transmit the same amount of pressure as though it 
 were a foot, or a yard, in diameter, provided the height be 
 alike in both cases. (See Art. 10.)
 
 INCREASED VELOCITY OF CIRCULATION. 13 
 
 By means of this unequal pressure on the lower 
 pipe, the water is forced to circulate through the 
 apparatus, and it continues to do so as long as the 
 water in B is colder, and therefore heavier, than 
 that which is in the boiler. And as the water in 
 the pipes is constantly parting with its heat, both 
 by radiation and conduction, while that in the 
 boiler is as continually receiving additional heat 
 from the fire, an equality of temperature never 
 can occur ; if it did, the circulation would cease. 
 
 (6.) We see, then, that the cause of the circula- 
 tion is the unequal pressure on the lower pipe of 
 the apparatus ; and that it is not the result of any 
 alteration which takes place in the level of the 
 water, as has been erroneously supposed. Indeed, 
 the truth of this appears so plain, that it would 
 scarcely require explanation at such a length, were 
 it not that false opinions in this matter appear to 
 have led to many errors in practice. 
 
 As the tircukdiou_isjc^ 
 
 descending pipe bemff colder, and therefore heavier 
 than that which is in the boiler, it follows, as a 
 necessary consequence, that the colder_the_jwater_ 
 in the descending pipe shall be, relatively to that 
 which is in the boiler, so P^C^ the_jnQre rapid 
 wiUbe_jts_iiiQJiQi]^ In such 
 
 an arrangement of Flo 
 
 pipes as fig. 3, the 
 water in the de- 
 scending pipe e f, 
 having to travel 
 farther before it 
 descends to the 
 
 lower part of the boiler than when the pipes are 
 arranged as in fig. 2, it will of course be colder at 
 the time of its descent, in the case fig. 3 than in 
 fig. 2, and therefore the circulation will be more 
 rapid. The height of the descending pipe is sup-
 
 14 INCREASED VELOCITY OF CIRCULATION. 
 
 posed to be alike in both cases, because c d and 
 ef are together equal to a b. 
 
 (7.) Some persons have imagined that if the 
 pipes be inclined, so as to allow a gradual fall of 
 the water in its return to the boiler, additional 
 power will be gained; as, for instance, by in- 
 clining the lower pipe of fig. 3, so as to make the 
 part e lower than d, and then reducing the vertical 
 height of the return pipe ef. This, at first, ap- 
 pears very plausible, particularly with regard to 
 some peculiar forms of the apparatus ; but the 
 principle is, in fact, entirely erroneous. The 
 author of the Appendix to Tredgold's work, 
 already quoted, in consequence of adopting the 
 erroneous hypothesis, that the motion of the water 
 commences in the upper pipe instead of the lower 
 one, as already described, appears to recommend 
 an inclination being given to the pipes in this 
 manner; and he has described an apparatus that 
 he erected, to which a fall of four feet was given 
 to the water by this method. 
 
 This error appears to arise from treating the 
 subject as a simple question of hydraulics, instead 
 of a compound result of hydrodynamics. But, in 
 order to ascertain what is the effect of thus inclin- 
 ing the pipes, let us suppose an extreme case. 
 
 It is evident that the farther the water flows, 
 the colder it becomes. It must, therefore, be 
 hotter at A (fig. 4) than it is at B, and hotter at B 
 than c, and so on. Let us, now, suppose any 
 arbitrary number to represent the specific gravity 
 of the water at A ; say, for instance, 94. The 
 water at B, in consequence of having flowed farther, 
 and therefore become colder and heavier, will be, 
 we will suppose, of the specific gravity of 95 ; at 
 c, for the same reasons, it will be -96, and so on 
 to F, where, from having run the greatest dis- 
 tance from the boiler, it will be the heaviest of
 
 INCREASED VELOCITY OF CIRCULATION. 15 
 
 all ; * and the sum of all these numbers represents 
 the pressure at F. But had the pipe, instead of 
 inclining gradually from the boiler, continued on a 
 level to a, as represented by the dotted lines, the 
 water would have been as cold, and therefore as 
 heavy, at a as by the former arrangement it is at 
 F, and therefore its specific gravity would be the 
 same, namely, "99. Now, as the pressure of water 
 
 FIG. 4. 
 
 is as its vertical height, by dividing the vertical 
 pipe, a/, in the same manner as we have done 
 with the inclined pipe, we shall have a, b, c, d, e, 
 /, each equal in altitude to the corresponding divi- 
 sions of the inclined pipe; and as the specific 
 gravity of each division is equal to *99, the total 
 number representing the sum of all these will show 
 the pressure at the point/. We shall hence find 
 the pressure of the vertical pipe, compared with 
 that of the inclined pipe, will be as 5*94 is to 
 579.t 
 
 (8.) It is evident from this that there must be 
 a considerable loss on the effective pressure by 
 making the return pipe incline below the horizontal 
 level. Nor can this loss be compensated in any 
 
 * The real specific gravities could not conveniently be used 
 in this illustration, as they would require several decimal 
 places of figures. (See Table IV., Appendix.) 
 
 | If the strict analogy were carried out, the difference ought 
 to be greater than is here represented, because it is evident 
 that instead of a, 6, c, d, &c., being each of equal density, b 
 will be heavier than a, and c heavier than 6, and so on ; but 
 the illustration, as now given, will be sufficient to show the 
 principle.
 
 16 AIR- VENTS. 
 
 manner; for the total height being the same, 
 whether the water descends through a vertical or 
 through an inclined pipe, the force or pressure 
 will only be equal to the specific gravity of the 
 matter. And as there is actually more matter in 
 a pipe filled with cold water than in a similar pipe 
 filled with hot water, the gravitating force will be 
 inversely proportional to the temperature ; that 
 is, it will be less in proportion as the temperature 
 of the water is greater. There must, therefore, 
 under all circumstances, be a positive loss of effect 
 by inclining the pipe in the manner stated.* 
 
 (9.) In such a form of apparatus as fig. 3, there 
 would be no circulation of the water, unless some 
 plan were adopted by which the air would be 
 dislodged from the pipes, and a ready escape 
 provided for it. Nothing is more necessary to 
 be attended to than this. In the more com- 
 plicated forms of the apparatus, the want of an 
 efficient means of discharging the air has been 
 the cause of innumerable failures. Suppose we 
 require the apparatus fig. 3 to be filled with water : 
 by pouring it in at the boiler, the pipe ef will of 
 course be filled simultaneously with it, and then the 
 lower pipe d ; and the water will then gradually 
 rise higher in the boiler until it partially fills the 
 upper pipe. At last the orifice of the pipe x will 
 become full, and the air which is in the pipe c x, 
 being thus prevented from escaping, will be forced 
 towards c by the weight of water behind it ; and 
 if the quantity of air be sufficiently large, it will 
 entirely prevent the junction of the water at c, and 
 cut off the communication between the two pipes at 
 
 * It must not be supposed that this reasoning at all applies 
 to any case of pure hydraulics. If the question were only as 
 regards a fluid of uniform temperature, then the greatest effect 
 would be obtained by using an inclined pipe ; but the fluid 
 which we are now regarding is one of a varying density and 
 temperature, which materially alters the conditional results.
 
 AIR VENTS. 17 
 
 c d. If an opening be now made in the pipe at e, 
 the air will immediately escape, being forced out 
 by the greater density of the water; and there- 
 fore, either a valve or a cock must be placed there, 
 to allow of its discharge, for otherwise no circu- 
 lation of the water can ensue. As water, while 
 boiling, always evolves air, it is not sufficient 
 merely to discharge the air from the pipes on first 
 filling them with water, because it is continually 
 accumulating:* and in many instances, particu- 
 larly with a close-topped boiler, it is desirable to 
 have the air-vent self-acting, either by using a 
 valve or a small open pipe ; in others, a cock will 
 often be found most convenient. 
 
 The size of the vent is not material, as a very 
 small opening will be sufficient to allow the air to 
 escape. For the rapidity of motion in fluids when 
 pressed by equal weights being inversely propor- 
 tional to their specific gravities, as water is 827 
 times more dense than air, an aperture which is 
 sufficiently large to empty a pipe in fourteen 
 minutes if it contained water, would, if it con- 
 tained air, empty it in about one second.f Air 
 being so very much lighter than water, it is of 
 course necessary that the vents provided for its 
 escape be placed in the highest part of the appa- 
 ratus, for it is there it will always lodge ; and 
 sometimes it will be found necessary to have 
 several vents in different parts of the apparatus. 
 
 Though it is perfectly easy, as far as the mere 
 mechanical operation is concerned, to provide for 
 the discharge of the air from the pipes, it requires 
 
 * If the water were always kept boiling, the air, after being 
 once expelled, would not again accumulate. But when the 
 water cools, it again imbibes air; and thus a continual dis- 
 charge of air occurs in a hot-water apparatus. 
 
 f Manchester Memoirs, vol. v., p. 398 ; and Nicholson's Journal, 
 vol. ii., p. 269, also Bobinson's Philosophy, vol. iii., pp. 682-696. 
 Regnault (Ann. de CUmie) states this to be 813-67 to 1. 
 
 C
 
 18 CLOSE BOILERS. 
 
 much consideration and careful study to direct 
 the application of those mechanical means to the 
 exact spot where they will be useful. The sub- 
 ject will, therefore, be again adverted to in a 
 subsequent chapter, when we have investigated 
 the principles of the apparatus in some of its more 
 complex forms of arrangement. 
 
 (10.) The plan of the boiler and pipes which 
 has been given in the preceding figures is ap- 
 plicable to comparatively but few purposes; for, 
 in consequence of the boiler being open at the 
 top, the pipes must be laid level with it, other- 
 wise the water would overflow. When the pipes 
 are required to rise higher than the boiler, the 
 latter must be closed at the top, and the pipes can 
 then be carried upwards to any required height. 
 This arrangement possesses considerable advan- 
 tages : for the higher we make the ascending and 
 descending pipes, the more rapid is the circulation 
 of the water.* This effect will necessarily result 
 from the principles already explained : because, 
 as motion is obtained in consequence of the differ- 
 ence in weight of the ascending and descending 
 columns of water, the greater the height of these 
 columns, the greater must be the difference in 
 their weight, and therefore the greater must be the 
 force and velocity of motion. 
 
 The advantages which may be derived from an 
 increased height in the ascending pipe cannot, how- 
 ever, be applied in an unlimited manner, because 
 it might lead to inconvenience, and even be at- 
 tended with some degree of danger to the appa- 
 ratus, if the increased height were not regulated by 
 
 * In this and the preceding figures, the pipes are drawn 
 so as to show the flow and return pipes lying one above the 
 other. A moment's consideration will satisfy anyone that 
 the effect will be the same if they were placed side by side on 
 the same level ; and frequently this arrangement is far more 
 convenient.
 
 PRESSURE OF WATER, 
 
 19 
 
 FIG. 5. 
 
 certain rules, and these, when ascertained, applied 
 with judgment. 
 
 The pressure produced by water is calculated 
 by its columnar height, reckoned from the bottom 
 of the vessel in which it is contained. Whether 
 the vessel be open at 
 the top and very deep, 
 or closed at the top 
 and very shallow, but 
 with a pipe attached 
 to the top, like the 
 boiler and pipe A B, 
 fig. 5, the pressure 
 will be exactly alike 
 in either case, if the 
 deep open boiler be 
 equal in height to that 
 of the shallow boiler and upright pipe conjointly ; 
 notwithstanding the quantity of water may be ten 
 times, or 100 times, larger in the one case than the 
 other. Neither is the pressure increased, however 
 large may be the diameter of the pipe which is 
 used ; nor is it lessened if the pipe be inserted at 
 the side of the boiler, as in the dotted lines y z, 
 fig. 5, instead of being placed on the top. 
 
 As the pressure of water on each square inch of 
 surface increases at the rate of about half a pound * 
 for every foot of perpendicular height, if the height 
 from the bottom of the boiler to the top of the pipe 
 be six feet, the pressure on the bottom will be three 
 pounds on every square inch of surface ; but if the 
 boiler be two feet high, the pressure on the top 
 
 * The exact weight of a perpendicular foot of water with a 
 base in one square inch, is 3030 24 grains, at the temperature 
 of 60 ; which is therefore only 4328 of a pound avoirdupois. 
 A column of water 30 feet high only gives a pressure of 
 12-68 Ibs., instead of 15 Ibs., as usually reckoned; and there- 
 fore the real height of a column of water, which will give a 
 pressure equal to one atmosphere, must be 34 feet. 
 
 c 2
 
 20 COMPRESSION OF WATER. 
 
 which will be a pressure upwards will be only 
 two pounds on every square inch of surface, because 
 it will only have four perpendicular feet of water 
 above it. If the height of the pipe be increased to 
 28 feet, and the depth of the boiler be two feet, as 
 before, making 30 feet together, the pressure will be 
 15 Ibs. on each square inch of the bottom, 14 Ibs. 
 on each square inch of the top, and an average 
 pressure of 14J Ibs. on each square inch of the 
 sides of the boiler. Suppose, now, a boiler to be 
 three feet long, two feet wide, and two feet deep, 
 with a pipe 28 feet high from the top of the boiler ; 
 when the apparatus is filled with water there will 
 be a pressure on the boiler of 66,816 Ibs., or very 
 nearly 30 tons.* 
 
 (11.) When a great pressure is used in a hot- 
 water apparatus, in the manner here described, it 
 is necessary that the materials of the boiler should 
 be stronger than they otherwise need be; and 
 more care is also required in making the joints 
 very sound, for attaching the pipes to the boiler 
 so as to prevent any leakage. But when these 
 mechanical difficulties are overcome, the amount 
 of danger arising from a great pressure of water 
 must not be overrated, for it might otherwise deter 
 some persons from adopting this form of the appa- 
 ratus, notwithstanding its numerous advantages. 
 
 (12.) The great danger that arises from the 
 bursting of a steam apparatus is in consequence 
 of the elastic force of steam, which, at very high 
 temperatures, is immense. But water possesses 
 
 * This enormous pressure on vessels which contain water 
 does not occur in the case of pipes merely used for the conveyance 
 of water ; for in this case, when the water runs out of the 
 lower end of a long vertical pipe as fast as it runs in at the 
 top, although it be always kept perfectly full, still there may 
 probably be no pressure whatever on any part of the pipe, 
 however great its length may be. Robinson's Mechanical Philo- 
 sophy, vol. ii., p. 580, et seq.
 
 BRANCH-PIPES. 21 
 
 very little elasticity compared with steam, its ex- 
 pansive force being almost inappreciable under 
 ordinary circumstances. At the pressure of 15 Ibs. 
 per square inch, the water in the boiler last de- 
 scribed, which holds about 75 gallons, would be 
 compressed rather less than one cubic inch, or about 
 1-3 5th part of a pint.* The expansive force of 
 the water in this apparatus, therefore, even sup- 
 posing it were to burst, would be perfectly harm- 
 less ; for it could only expand as much as it had 
 been compressed; namely, one cubic inch. The 
 effect on a boiler, by the pressure of the water, 
 will be precisely similar to a weight pressing upon 
 it equal to the estimated pressure of the water, 
 which is quite different from the sudden and violent 
 force produced by the expansive power of steam. 
 As an apparatus of this kind could never be forced 
 asunder, as in the explosion of a steam-boiler, the 
 only result, under the worst circumstances that 
 could occur, would be a leakage of the water, in 
 consequence of the cracking of some part of the 
 boiler. 
 
 Neither the principle nor the practical working 
 of the apparatus is in the least affected by having 
 any additional number of pipes leading out of or 
 into the boiler. The effect is the same whether 
 there are more flow-pipes than return-pipes, or, 
 conversely, more return -pipes than flow- pipes. 
 If there be two or more flow-pipes, whether they 
 lead from the boiler separately, or branch from 
 one main pipe, or whether they lead from op- 
 
 * According to the experiments of Professor Oerstead, the 
 compression of water is '0000461 by a pressure of 15 Ibs. per 
 square inch ; and he has found that it proceeds pari passu as 
 far as 65 atmospheres, which was the limit to which his experi- 
 ments extended. This compression is about equal to reducing 
 a given bulk of water -^ of its volume by a pressure of 
 20,000 Ibs. per square inch. Eeport British Scientific Associa- 
 tion, vol. ii., p. 353.
 
 22 BRANCH-PIPES. 
 
 posite sides of the boiler, or all from one side, 
 each range of pipes will act separately and have a 
 velocity of circulation peculiar to itself. One 
 range of pipes may act efficiently, while another, 
 though attached to the same boiler, may have no 
 circulation whatever through it; and this effect 
 will not be altered whether the pipes return into 
 the boiler separately, or all unite into one main 
 pipe. The pressure, supposing the pipes to rise 
 vertically from the boiler, will likewise be pre- 
 cisely the same, however numerous the pipes 
 may be. This circumstance is one of the pecu- 
 liarities which distinguish fluids from solids. For 
 if the fluid in any close vessel be pressed by the 
 fluid contained in an upright pipe, so as to pro- 
 duce a pressure of 10 Ibs. on a square inch ; if a 
 second pipe, capable of exerting a similar pres- 
 sure with the first, be placed upon the same 
 vessel, the united pressure will still be only 
 10 Ibs. per square inch; and it would be no more, 
 though ever so large a number of pipes were 
 added, provided the vertical height were not in- 
 creased. 
 
 (13.) One advantage may be obtained by caus- 
 ing the water to rise from the boiler by an as- 
 cending pipe, as in fig. 5, which cannot be 
 accomplished by any other means; and it is of 
 considerable importance to ascertain its true effect, 
 as it has produced consequences which are not 
 generally attributed to the right cause. 
 
 The force and velocity of motion of the water, 
 being proportional to the vertical height of the 
 ascending and descending pipes ; by increasing 
 this height, a facility is afforded for taking the 
 pipes below the horizontal level, as, for instance, 
 when it is required to pass them under a door- 
 way, or other similar obstruction, before they 
 finally return to the bottom of the boiler. In-
 
 VARIATIONS OF LEVEL. 23 
 
 numerable failures have occurred in attempting to 
 make the water descend and again to ascend in 
 this manner, the success of the experiment 
 depending entirely upon the vertical height of 
 the ascending pipe above the boiler. These alter- 
 ations of the horizontal level, which are frequently 
 very desirable, have, of course, their limits, 
 beyond which they cannot be carried. It is from 
 not having ascertained what are these limits, and 
 what the cause of the limitation, that such 
 uncertainty has hitherto prevailed with regard to 
 this experiment; for it frequently succeeds, but 
 more frequently fails, in practice. It will be most 
 convenient, however, to consider this subject after 
 we have ascertained what is the amount of motive 
 power of the water in this kind of apparatus.
 
 24 
 
 CHAPTER II. 
 
 On the Motive Power of the Water On increasing the Motive 
 Power Velocity of Circulation Circulation of Water 
 below the Boiler Direct and Eeversed Circulation Air- 
 Vents Supply Cisterns Expansion of Pipes, &c. 
 
 (14.) IT has already been mentioned that the 
 power which produces circulation of the water is 
 the unequal pressure on the return-pipe, in conse- 
 quence of the greater specific gravity of the water 
 in the descending pipe, above that which is in 
 the boiler. Whether this force acts on a long 
 length of return-pipe, as y z, fig. 2, or only on a 
 very short length, as /, fig. 3, the result will be 
 precisely similar. 
 
 Now, it is evident that, if this unequal pressure 
 is the vis viva, or motive power, which sets in 
 motion the whole quantity of water in the ap- 
 paratus, it is only necessary, in order to ascertain 
 the exact amount of this force, that we know the 
 specific gravities of the two columns of water; 
 and the difference will, of course, be the effective 
 pressure, or motive power. This can be accurately 
 determined when the respective temperatures of 
 the water in the boiler and in the descending pipe 
 are known.* 
 
 * A thermometer suitable for this purpose was long since 
 proposed by M. Fourier, and called by him the thermometer 
 of contact. It consists of a very small iron cup, just large 
 enough to hold the bulb of the thermometer, but without 
 a bottom to it. Over the bottom, a piece of goldbeaters' skin 
 is to be tied, and the cup is then to have a little mercury put 
 in it, into which the bulb of the thermometer is to dip. The
 
 MOTIVE POWER. 25 
 
 As this difference of temperature rarely exceeds 
 a very few degrees in ordinary cases, the differ- 
 ence in the weight of the two columns must 
 necessarily be very small. But, probably, the 
 very trifling difference which exists between 
 them, or, in other words, the extreme smallness 
 of the motive power, is very imperfectly compre- 
 hended, and will, perhaps, be regarded with 
 some surprise when its amount is shown by exact 
 computation. 
 
 (15.) In order to ascertain, without a long and 
 troublesome calculation, what is the amount of 
 motive power for any particular apparatus, the 
 following Table has been constructed. An ap- 
 paratus is assumed to be at work, having the 
 temperature in the descending pipe 170 ; and 
 the difference of pressure upon the return-pipe is 
 calculated, supposing the water in the boiler to 
 exceed this temperature by from 2 to 20. This 
 latter amount exceeds the difference that usually 
 occurs in practice. 
 
 By refering to the annexed Table, it will be 
 found that when the difference between the tem- 
 perature of the ascending and the descending 
 columns amounts to 8, the difference in weight 
 is 8*16 grains on each square inch of the section 
 of the return-pipe, supposing the height of the 
 boiler A, fig. 2, to be 12 inches. This height, how- 
 ever, is only taken as a convenient standard from 
 which to calculate ; for, probably, the actual 
 height will seldom be less than about 18 inches, 
 and, in many cases, it will be considerably more. 
 
 cup, when placed on any hot surface, will accurately show the 
 temperature, the contact between the skin and the surface 
 being extremely perfect. As a permanent adjunct, however, 
 to the hot-water apparatus, it is much better to use a ther- 
 mometer fitted with a hollow screw-nut, by which it can be 
 accurately fixed to the apparatus, and the bulb actually dips 
 into the water of the apparatus.
 
 26 
 
 TABLE OF PRESSURES. 
 
 TABLE I. 
 
 in Weight of Two Columns of Water, each One 
 Foot high, at various Temperatures. 
 
 Difference In 
 
 
 
 Temperature 
 Two Columns 
 
 Difference in Weight 
 of Two Columns of Water contained in different- 
 Pipes, each One Foot in height 
 
 sized 
 
 of Water : 
 
 
 
 in Degrees of 
 
 
 
 Fahrenheit's 
 
 
 
 
 
 Scale. 
 
 1 in. diam. 
 
 2 in. diam. 
 
 3 in. diam. 
 
 4 in. diam. 
 
 per sq. in. 
 
 
 grs. weight. 
 
 grs. weight. 
 
 grs. weight. 
 
 grs. weight. 
 
 gre. weight. 
 
 2 
 
 1-5 
 
 6-3 
 
 14-3 
 
 25-4 
 
 2-028 
 
 4 
 
 3-1 
 
 12-7 
 
 28-8 
 
 51-1 
 
 4-068 
 
 6 
 
 4-7 
 
 19-1 
 
 43-3 
 
 76-7 
 
 6-108 
 
 8 
 
 6-4 
 
 25-6 
 
 57-9 
 
 102-5 
 
 8-160 
 
 10 
 
 8-0 
 
 32-0 
 
 72-3 
 
 128-1 
 
 10-200 
 
 12 
 
 9-6 
 
 38-5 
 
 87-0 
 
 154-1 
 
 12-264 
 
 14 
 
 11-2 
 
 45-0 
 
 101-7 
 
 180-0 
 
 14-328 
 
 16 
 
 12-8 
 
 51-4 
 
 116-3 
 
 205-9 
 
 16-392 
 
 18 
 
 14-4 
 
 57-9 
 
 131-0 
 
 231-9 
 
 18-456 
 
 20 
 
 16-1 
 
 64-5 
 
 145-7 
 
 258-0 
 
 20-532 
 
 %* The above Table has been calculated by the formula 
 given with Table IV., in the Appendix, for ascertaining the 
 specific gravity of Water at different temperatures. The 
 assumed temperature is from 170 to 190. 
 
 Now, suppose, in such a form of apparatus as 
 fig. 2, the boiler to be two feet high ; the distance 
 from the top of the upper pipe to the centre of the 
 lower pipe to be 18 inches ; and the pipe four 
 inches diameter ; if the difference of temperature 
 between the water in the boiler and in the de- 
 scending pipe be 8, the difference of pressure on 
 the return-pipe will be 153 grains, or about one- 
 third part of an ounce weight : and this will be the 
 whole amount of motive poioer of the apparatus, 
 whatever be the length of pipe attached to it. If 
 such an apparatus have 100 yards of pipe, four 
 inches diameter, and the boiler contains, suppose 
 30 gallons, there will be 190 gallons, or 1,900 Ibs.
 
 MOTIVE POWEK. 27 
 
 weight of water kept in continual motion by a 
 force only equal to one-third of an ounce.* This 
 calculation of the amount of the motive power, in 
 comparison with the weight moved, will vary 
 under different circumstances ; and in all cases the 
 velocity of the circulation will vary simultaneous^ 
 with it. 
 
 (16.) It will be observed in the foregoing Table 
 that the amount of motive power increases with 
 the size of the pipe : for instance, the power is 
 four times as great in a pipe of four inches dia- 
 meter as in one of two inches. The power, how- 
 ever, bears exactly the same relative proportion 
 to the resistance or weight of water to be put in 
 motion in all the sizes alike. For although the 
 motive power is four times as great in pipes of 
 four inches diameter as in those of two inches, 
 the former contains four times as much water as 
 the latter ; the power and the resistance, therefore, 
 are relatively the same. 
 
 (17.) As the motive power is so small, it is not 
 at all surprising that, by an injudicious arrange- 
 ment of the different parts of an apparatus, the 
 
 * M. Dutrochet made some experiments on the influencing 
 causes of the motion of currents of liquids. He found that a 
 difference of temperature of 1 -800th of a degree was sufficient 
 to produce currents when aided by light, but the motions 
 ceased on light being excluded. In the absence of light (except 
 what was necessary to distinguish the orbject) the sound of a 
 violoncello or of a bell produced circulation in the liquid. He 
 therefore concluded that the most minute differences of tem- 
 perature will produce motion among the particles of a fluid 
 when aided by light or any other cause which produces feeble 
 vibrations to the particles of the fluid. Quart. Journal of 
 Science, vol. xxix., p. 194. It is not stated how this small 
 excess of heat was ascertained. The effects of sound may 
 possibly be in some way connected with a fact which Biot at- 
 tempted to demonstrate by experiment that every vibration 
 of a sonorous body in elastic media is accompanied with a 
 change of temperature. Memoires de la Societe d'Arcueil, 
 1809 ; and Betrospcct of Science, vol. v., p. 429.
 
 28 MOTIVE POWER. 
 
 resulting motion may frequently be impeded, and 
 sometimes even totally destroyed; for the slower 
 the circulation of the water, the more likely is it 
 to be interrupted in its course. There are two 
 ways by which the amount of the motive power 
 may be increased; one, by allowing the water to 
 cool a greater number of degrees between the time 
 of its leaving the boiler and the period of its return 
 through the descending pipe; the other, by in- 
 creasing the vertical height of the ascending and 
 descending columns of water. The effects pro- 
 duced by these two methods are precisely similar ; 
 for, by doubling the difference of temperature 
 between the flow-pipe and the return-pipe, the 
 same increase in power is obtained as by doubling 
 the vertical height ; and tripling the difference in 
 temperature is the same as tripling the vertical 
 height.* This can be ascertained by referring to 
 the preceding Table. Thus, suppose, when the 
 difference of temperature is 8, and the vertical 
 height four feet, that the motive power is 32*6 
 grains per square inch : if the difference of tem- 
 perature be increased to 16, while the height 
 remains the same, or if the height be increased to 
 eight feet while the temperature remains as at 
 first, the pressure, in either case, will be 65*2 
 grains per square inch, or twice the former 
 amount. The same rule applies to other differ- 
 ences, both of height and temperature. 
 
 (18.) Almost the only two methods of increasing 
 the difference of temperature between the ascend- 
 ing and the descending columns, are, either by in- 
 creasing the quantity of pipe, so as to allow the 
 water to flow a greater distance before it returns 
 to the boiler; or, by diminishing the diameter of 
 the pipe, so as to expose more surface in proportion 
 
 * This is without reference to friction : the effect will there- 
 fore be a little modified by this cause. (See Art. 22 and 4.3.)
 
 MOTIVE POWER. 29 
 
 to the quantity of water contained in it, and by 
 this means to make it part with more heat in a 
 given time. (See Art 61.) The first of these 
 two methods, however, is necessarily limited by 
 the extent of the building that is to be heated, to 
 which the quantity of pipe must be adjusted in 
 order to obtain the required temperature : and, as 
 to the second, there are many objections against 
 reducing the size of the pipes, which will be con- 
 sidered presently. The increase of motive power 
 to be obtained by increasing the height of the 
 ascending column of water is, therefore, what 
 must principally be depended on, when additional 
 power is required to overcome any unusual ob- 
 structions. 
 
 (L9.) In all cases the rapidity of circulation is 
 proportional to the motive power ; and, in fact, 
 the former is the index of the latter, and the 
 measure of its amount. For if, while the resistance 
 remains uniform, the motive power be increased in 
 any manner or in any degree, the rate of circula- 
 tion will increase in a relative proportion. Now 
 the motive power, irrespective of retardation by 
 friction, may be augmented, as we have already 
 seen, either by increasing the vertical height of 
 the pipe, by reducing its diameter, or by in- 
 creasing its length. If by any of these means the 
 circulation be doubled in velocity, then, as the 
 water will pass through the same length of pipe 
 in half the time it did before, it will only lose half 
 as much heat as in the former case, because the 
 rate of cooling is not proportional to the distance 
 through which the water circulates, but to the 
 time of transit. If, then, by sufficiently increasing 
 the vertical height, and doubling the velocity of 
 the circulation, the difference between the tem- 
 perature of the flow-pipe and the return-pipe be 
 diminished one-half, it might be supposed that the
 
 30 MOTIVE POWER. 
 
 motive power of the apparatus would remain the 
 same, and no advantage would appear to be gained 
 by this means. But this is not exactly the case. 
 For although, whether we double the vertical 
 height, or double the horizontal length, we shall, 
 in either case, increase the velocity of motion; 
 yet it will require a quadruple increase of verti- 
 cal height, or a quadruple increase of horizontal 
 length, to obtain double the original rate of cir- 
 culation. (See Art. 21.) The increased velocity 
 is, therefore, indicative of increased power ; and, 
 in a hot-water apparatus, it is the increased velo- 
 city of circulation which overcomes any obstruc- 
 tions of a greater amount than ordinary. 
 
 (20.) The velocity with which the water cir- 
 culates in this kind of apparatus, although con- 
 tinually subject to variation, can nevertheless be 
 calculated theoretically, when certain data are 
 agreed upon, or are ascertained to exist. 
 
 When the two legs of an inverted siphon A, 
 fig. 6, are filled with liquids of unequal density, 
 if the stop-cock, z, be turned, so as 
 FIG. 6. to open the communication between 
 them, the lighter liquid will move 
 upwards with a force proportional 
 to the difference of weight of the 
 two columns, provided the bulk of 
 the two liquids be equal. If one 
 leg contains oil and the other con- 
 tains water, the relative weights 
 will be about as nine to ten ; therefore it will re- 
 quire 10 inches of vertical height of oil to balance 
 9 inches of water, and no motion will in that case 
 take place. But when equal bulks of the two 
 fluids are used, the velocity of motion with which 
 tne lighter fluid is forced upwards is equal to the 
 velocity which a solid body would acquire in fall- 
 ing, by its own gravity, through a space equal to
 
 VELOCITY OF CIRCULATION. 31 
 
 the additional height which the lighter body would 
 occupy in the siphon, supposing a similar weight 
 of each fluid be used. This velocity is easily cal- 
 culated. A gravitating body falls 16 feet in the 
 first second of time of its descent, 64 feet in two 
 seconds, and so on, the velocity increasing as the 
 square of the time ; therefore the relative velocities 
 are as the square roots of the heights. Now, in the 
 case of the siphon, which we have supposed to con- 
 tain a column of water and a column of oil, as the 
 oil ought to be 10 inches high to balance the 9 inches 
 of water, the oil in the one leg will be forced up- 
 wards with a velocity equal to that which the 
 water (or any other body) would acquire by falling 
 through one inch of space ; and this velocity, we 
 shall find, is equal to 138 feet per minute* 
 
 (21.) To estimate the velocity of motion of the 
 water in a hot-water apparatus, the same rule will 
 apply. If the average temperature be 170, the 
 difference between the temperature of the ascend- 
 ing and the descending columns 8, and the height 
 
 * The velocity will be as the square root of 16 feet per second 
 to the square root of the additional height which an equal 
 weight of the lighter liquid would occupy, reduced to the 
 decimal of a foot ; and asfthe acquired velocity of a body at 
 the end of a given time is twice as much as the distance it 
 passes through in arriving at any given velocity by accele- 
 rated motion, or, in other words, as a body which falls through 
 16 feet of space, in one second, will proceed at the rate of 
 32 feet per second afterwards, without receiving any additional 
 impulse ; so the velocity found by this rule will be only half 
 the real velocity; and the number thus obtained must be 
 multiplied by 2. The velocity will, therefore, be found by 
 multiplying the square root of the difference between the 
 height of the two columns in decimals of a foot by the square 
 root of 16, and then, multiplying that product by 2, will give 
 the real velocity per second. 
 
 The discharge through a siphon, employed to empty casks 
 and other vessels, can also be calculated by this rule: the 
 velocity of motion will be equal to the difference in length of 
 the two legs.
 
 32 VELOCITY OF CIRCULATION. 
 
 10 feet ; when similar weights of water are placed 
 in each column, the hottest will stand '331 of an 
 inch higher than the other;* and this will give a 
 velocity equal to 79 2 feet per minute. If the height 
 be 5 feet, the difference of temperature remaining 
 as before, the velocity will be only 55*2 feet per 
 minute ; but if the difference of temperature in this 
 last example had been double the amount stated 
 that is, had the difference of temperature been 16, 
 and the vertical height of the pipe 5 feet then the 
 velocity of motion would have been 79 2 feet per 
 minute, the same as in the first example, where the 
 vertical height was 10 feet, and the difference of 
 temperature 8. This, therefore, proves, in cor- 
 roboration of what has been already stated (Art. 
 19), that reducing the temperature of the water, 
 either by using smaller pipes, or by increasing the 
 length through which it flows, has the same effect 
 on the circulation as increasing the vertical height, 
 leaving out of consideration the question of friction. 
 The velocity for 3 feet of vertical height, by the 
 same rule, will be 43 2 feet per minute, for 2 feet of 
 vertical height it will be 36 feet per minute, and 
 for 18 inches of vertical height it will be 30 '7 feet 
 per minute, if the difference of temperature between 
 the two columns be in each case 8, the same as in 
 the former examples. It must here be observed, 
 however, that, although it appears by these calcu- 
 lations that increasing the vertical height of the 
 pipe fourfold will produce a double velocity of 
 circulation, as the water will then pass through 
 the pipe in half the time, the difference between 
 the temperature of the flow -pipe and the return- 
 pipe will be lessened, and the velocity will at last 
 become a mean rate ; so that the mere quadruple 
 increase of vertical height, without the horizontal 
 
 * The expansion of water will be found in Table IV., 
 Appendix.
 
 VELOCITY OF CIRCULATION. 33 
 
 length be at the same time increased, will only 
 produce a rate of circulation about one and a half 
 times the original velocity. 
 
 (22.) Such is the result of theory ; but, although 
 this be true in itself, we shall, in practice, find but 
 few cases that in any way agree with these results, 
 in consequence of other causes modifying the 
 effects. Even in an apparatus in which the length 
 of pipe is not very considerable, where the pipes 
 are of large diameter, and the angles few, a large de- 
 duction from the theoretical amount must be made^ 
 to represent, with tolerable accuracy, the true velo- 
 city. And in more complex apparatus the velocity 
 of circulation is so much reduced by friction, that 
 it will sometimes require from 50 to 90 per cent, 
 and upwards to be deducted from the calculated 
 velocity, in order to obtain the true rate of circu- 
 lation.* The calculation of the friction of water 
 
 * It has been found by experiment (Robinson's Philosophy, 
 vol. ii., p. 336), that a smooth pipe 4^ inches in diameter, and 
 500 yards long, yields but one-fifth of the quantity of water 
 which it ought to do, independent of friction. And Mr. George 
 Eennie found (Philosophical Transactions, 1831) that the velo- 
 city of a half-inch pipe was reduced nearly three-fourths (that 
 is, from 3 - 7 to 1) by increasing its length from 1 foot to 
 30 feet ; that three semicircular bends reduced the velocity ^ 
 in a short pipe, and 14 such bends reduced it ^ of its velo- 
 city, while 24 right-angled bends reduced the velocity nearly 
 two-thirds. The results of M. Prony's experiments led him 
 
 to adopt the formula V = 26-79 for the discharge 
 
 through straight pipes : D being the diameter of the pipe ; Z 
 the altitude of the head of water ; L the length of the pipe in 
 metres ; and V the mean velocity. M. Dubuat's formula for 
 
 diminution by flexure is E = -^^ ; where E is the resist- 
 
 oOOO 
 
 ance ; V the mean velocity ; S the sine of the angle of inci- 
 dence ; n the number of equal rebounds. Dr. Young (Philo- 
 sophical Transactions, 1808) objects to this theory, and gives a 
 different one, which he considers more nearly to represent 
 the true result. 
 
 D
 
 34 VELOCITY OF CIRCULATION. 
 
 passing through pipes is alike complicated and 
 unsatisfactory. Though the question has been 
 investigated by some of the most able philosophers 
 and mathematicians, a simple and correct formula 
 on this subject is still a desideratum ; and in the 
 present state of knowledge of the subject it would 
 be almost impossible to determine what would be 
 the resulting velocity of circulation in a hot-water 
 apparatus of complicated construction.* 
 
 (23.) In addition to these ordinary causes which 
 impede the circulation, and which are common to 
 all hydraulic experiments, there is another that is 
 still more important, and is peculiar to the hot- 
 water apparatus. The vertical angles in the pipe, 
 or those angles which carry the pipe below the 
 horizontal level, increase the resistance in this 
 case to a very considerable extent, for they oppose 
 not merely a passive resistance by friction, but 
 they engender a force of their own, tending in an 
 opposite direction to that of the prime moving 
 power. 
 
 The motion of the heated particles of water is 
 very different in passing through an ascending 
 pipe, compared with that which takes place in a 
 descending pipe. The heated particles rise up- 
 wards through an ascending pipe with great 
 rapidity, and when the space occupied by the 
 displaced particles is supplied by water from 
 
 * In Robinson's Mechanical Philosophy, vol. ii., pp. 261-627, 
 will be found much information on this subject, with the re- 
 sults of nearly all the experiments that have been made. 
 Also see Dr. T. Young, Philosophical Transactions, 1831 ; 
 Nicholson's Journal, vol. xxii., p. 104, and Philosophical 
 Magazine, vol. xxxiii., p. 123 ; Mr. G. Kennie, Philosophical 
 Transactions, 1831, and Reports Brit. Sci. Assoc., vol. ii., 
 p. 153, and vol. iii., p. 415. In these several works are 
 given the experiments of Bossut, Prony, Dubuat, Eytelwein, 
 Vonturi, Borda, and others, which comprise nearly all that 
 is known on this difficult subject.
 
 OBSTRUCTIONS TO CIRCULATION". 35 
 
 below, the motion becomes general in one di- 
 rection, being most rapid in the centre, and 
 gradually decreasing towards the circumference, 
 where, on account of the friction, it becomes com- 
 paratively slow. But in a descending pipe the 
 circumstances are very different, the motion being 
 much more like that of a solid body. For as the 
 heated particles are unable to force their way 
 downwards through those which are colder and 
 heavier than themselves, the only motion arises 
 from the cold water flowing out at the bottom, its 
 place being then supplied at the top by that 
 which is warmer, the whole apparently moving 
 together, instead of the molecular action which 
 has been described as the proper motion in an 
 ascending pipe. 
 
 (24.) In an apparatus constructed as fig. 7, the 
 motion through the boiler and pipe A B, and through 
 the descending pipe 
 c D, takes place ac- 
 cording to the two 
 methods here descri- 
 bed. But it is evident 
 that, on motion com- 
 mencing in the return 
 pipe y z, in conse- 
 quence of the greater 
 pressure of c D than of A B, the water from A will 
 be forced towards e, at the same time that the 
 water in e, /, #, h flows towards c. But when a 
 very small quantity of hot water has passed from 
 the pipe and boiler, A B, into the pipe e /, the 
 column of water g h will be heavier than the 
 column 0/, and therefore there will be a tendency 
 for motion to take place along the upper pipe 
 towards the boiler, instead of from it. This force 
 whatever be its amount, must be in opposition to 
 that which occurs in the lower or return pipe, in 
 
 i) 2
 
 36 OBSTRUCTIONS TO CIRCULATION. 
 
 consequence of the pressure of c D being greater 
 than A B ; and unless, therefore, the force of motion 
 in the descending pipe c D be sufficient to over- 
 come this tendency to a retrograde motion, and 
 leave a residual force sufficient to produce direct 
 motion, no circulation of the water can take 
 place. 
 
 (25.) An extremely feeble power, as we have 
 already seen (Art. 15), will produce circulation of 
 the water in an apparatus where there are no un- 
 usual obstructions ; but it is a necessary result of 
 the motive power being so very small, that it is 
 easily neutralized. So trifling a circumstance as a 
 thin shaving planed off a piece of wood, and acci- 
 dentally getting into a pipe, has been known effec- 
 tually to prevent the circulation in an apparatus 
 otherwise perfect in all its parts. 
 
 It is not sufficient, then, when such an obstruc- 
 tion as the vertical dip from the horizontal level, 
 shown by the last figure, has to be surmounted, 
 merely to make the direct force of motion suffi- 
 cient to overcome the antagonist force, and to 
 leave the smallest possible residual amount, for 
 the purpose of causing circulation; because an 
 amount which would be sufficient for this purpose, 
 as an undivided force, would not be found sufficient 
 as a residual force. 
 
 (26.) In estimating the additional height which 
 it is necessary to give to the ascending column, 
 in order to overcome such an obstruction as shown 
 in fig. 7, it will be necessary to take into account 
 what is the length and diameter of the pipe 
 through which the water will have to pass ; for on 
 this depends the difference of temperature be- 
 tween the ascending and descending columns, 
 which we have seen materially affects the amount 
 of the motive power of the apparatus. If the 
 length of pipe be considerable, a somewhat smaller
 
 OBSTRUCTIONS TO CIRCULATION. 37 
 
 increase of the vertical height of the ascending 
 pipe will suffice ; but if the length of pipe be 
 short, a greater height must be allowed.* The 
 temperature to which the air surrounding the 
 pipes is to be raised will also modify the result ; 
 for on this will depend the quantity of heat given 
 out by the pipes per minute, which likewise affects 
 the temperature of the descending pipe. (Art. 
 222.) 
 
 (27.) Under such a great diversity of circum- 
 stances, it would be difficult to form a rule for 
 estimating what ought to be the height of the 
 ascending pipe in such cases ; because not only 
 are these circumstances different in each appa- 
 ratus, but they likewise differ, in some respects, 
 in the same apparatus in the different stages of its 
 working. The difficulty is also increased by not 
 being able to fix on an absolute minimum measure- 
 ment, which is sufficient, under all circumstances, 
 to cause a circulation of the water in the common 
 form of the apparatus. There have been instances 
 where apparatus have succeeded, though con- 
 
 * This applies merely to the possibility of producing motion, 
 and not to the resulting velocity of the circulation. For it 
 must be borne in mind that, although in every case, by in- 
 creasing the length of the pipe, or by reducing its diameter, 
 we cause the water to assume a greater difference of tempera- 
 ture between the ascending and the descending columns, and 
 thereby increase the circulation, still, in both these cases, we 
 greatly increase the friction, which therefore considerably 
 detracts from the advantages gained by this greater differ- 
 ence of temperature. And as the friction is a certain quan- 
 tity, compounded of the square root of the length of the pipe 
 directly, and the diameter of the pipe inversely, it follows 
 that the friction may become so great, by increasing the 
 length and reducing the diameter, as completely to neutralize 
 all beneficial effect. Unless, therefore, the circulation is 
 moderately active, the apparatus will be of such unequal tem- 
 perature as to render it nearly useless. The utmost caution 
 is necessary, in order that the friction may not become so 
 great as to interfere with the due circulation of the water.
 
 38 OBSTRUCTIONS TO CIRCULATION. 
 
 ' 
 
 structed on the very worst principles, in conse- 
 quence of various circumstances having favoured 
 the result. Thus in an apparatus constructed as 
 fig. 8, where the pipes 
 were not more than 
 three inches apart, the 
 water circulated with 
 perfect freedom ; but 
 in this case, not only 
 was the pipe of considerable length, and without 
 angles or turns, but the size of the pipe was only 
 two inches diameter, so that the water cooled 
 twice as fast as it would have done had pipes of 
 four inches diameter been used (Art. 61). It is, 
 however, quite certain that such a distance be- 
 tween the pipes, at their insertion into the boiler, 
 as that which has just been described, is in- 
 sufficient, under ordinary circumstances, to give a 
 steady and good circulation. But when the two 
 pipes are about 12 inches apart, at the place 
 of their insertion into the boiler x /, fig. 3 (or 
 16 inches from centre to centre when the diameter 
 of the pipe is four inches), it will be sufficient 
 to produce a good circulation for almost any ordi- 
 nary length of pipe, when it is not required to 
 dip below the horizontal level. If this be con- 
 sidered as the minimum height, which, under 
 ordinary circumstances, will obtain a good circu- 
 lation when the pipes are not required to dip 
 below the horizontal level, then an average height 
 can be estimated for enabling any vertical decli- 
 nation of the pipes to be made. 
 
 (28.) When the pipe dips below the horizontal 
 level, the height of the ascending pipe should 
 generally be just so much greater than the above 
 dimensions, as the ttepth which the circulating 
 pipe is required to dip Mow the horizontal level ; 
 bearing in mind the circumstances mentioned
 
 OBSTRUCTIONS TO CIRCULATION. 
 
 39 
 
 (Art. 26), which modify the general results* 
 Thus, suppose the depth of the dip, shown by the 
 dotted line a b, fig. 9, to be 24 inches, then the 
 distance y z ought to be 40 inches, if the pipes be 
 four inches diameter ; that is, 36 inches from cen- 
 tre to centre, or 40 inches from the top of the pipe 
 y to the bottom of the pipe z ; and with these 
 dimensions, as good a circulation will be obtained 
 (excepting the friction from the additional elbows) 
 as when the distance between the top and bottom 
 pipes is 16 inches from centre to centre, in the 
 common form of the apparatus. It will be ob- 
 
 
 
 FIG 
 
 _y , 
 
 . 9. 
 
 '. * , /I 
 
 / 
 
 
 '. 
 
 \ f =" 
 I J* 
 
 /I 
 
 y A \ 
 
 
 'f ^ 
 
 s \ 
 
 fj 
 
 
 
 Pi 
 
 I/"- 
 
 '-->*, 
 
 
 served that, by this arrangement, the distance c cf, 
 from the under side of the flow-pipe to the upper 
 side of the return-pipe, is just 12 inches, which is 
 the same height that was stated to be necessary to 
 insure a good circulation, on the ordinary plan, 
 without a vertical dip. The reason why this 
 height is sufficient in the present case, notwith- 
 
 * So greatly, in fact, do these circumstances affect the 
 general result that it is very possible, in particular circum- 
 stances, to make the water descend below the bottom of the 
 boiler to a considerable depth without stopping the circulation. 
 It is therefore evident that the dimensions which are here 
 given for the height of the ascending pipe, relative to the dip, 
 must not be taken as an absolute minimum, but simply as a 
 general rule, which will succeed in all cases. See Art. 30 
 and 31.
 
 40 OBSTRUCTIONS TO CIRCULATION. 
 
 standing the increased friction of the angles, is be- 
 cause there must always be a greater difference 
 between the temperature of e and / than between 
 either g and A, or between i and , or even more 
 than between both these together; therefore the 
 tendency to direct motion is greater than towards 
 retrograde motion, in proportion to this difference, 
 and is sufficient to overcome the increased friction 
 caused by the vertical declination ; while the ad- 
 ditional height of 12 inches beyond the height of 
 the dip, possessed by the descending pipe /, is 
 sufficient to produce circulation of the water. If 
 g and A, and also i and k, were very wide apart, 
 say 40 or 50 feet, instead of being, as usual, only 
 about three or four feet, the balance of effect, 
 though still in favour of direct motion, would not 
 be so great as in the last supposed case ; because 
 there would be a greater difference in temperature 
 between g and h (that is, h would be heavier than 
 g in a greater degree), which would give a greater 
 tendency to retrograde motion. In many cases, 
 therefore, it will be advisable to make the ascend- 
 ing pipe higher in proportion to the dip than is 
 here stated, particularly when there are several 
 such alterations required in the level of the pipes ; 
 and, in all cases, as has been before observed, the 
 higher the ascending pipe is made, the more rapid 
 will be the circulation, and, therefore, the more 
 perfect the apparatus will become. 
 
 (29.) The remarks which have been made with 
 respect to the height of the ascending pipe, rela- 
 tively to the vertical declination, or dip, below the 
 level of the horizontal pipe, applies to all the usual 
 forms which are given to the apparatus. But 
 there are peculiar arrangements which may be 
 adopted that will allow the dip of the circulating 
 pipe to be much greater than the proportion which 
 has here been stated. For, in some cases, the dip
 
 CIRCULATION OF WATER BELOW TFIE BOILER. 41 
 
 pipes may even pass below the bottom of the 
 boiler to a considerable depth, without destroying 
 the circulation; arid from the very extensive use 
 that is now made of the hot-water apparatus for 
 heating buildings of every description, it is very 
 desirable to examine this part of the subject at 
 some length, as its application will, in many cases, 
 entirely depend upon the possibility of making 
 the pipes descend below the boiler. 
 
 (30.) In an arrangement of pipes such as fig. 10, 
 the circulation will depend entirely upon the quan- 
 tity of heat given off by the coil c ; for it is evident 
 that when the boiler B and pipe a are heated, 
 the direct motion will arise in consequence of the 
 greater weight of 
 the water in the coil Fl - 10 - 
 
 c and pipe c?, above 
 that which is in the 
 boiler and pipe, B a. 
 But as the water in 
 the pipe e, below 
 the dotted line, will 
 be lighter than that 
 in the pipe /, the 
 tendency in that 
 part of the apparatus 
 will be towards a 
 retrograde motion. 
 The result of these 
 
 two forces will be that if the water in the whole 
 length of pipe w x is heavier than that of the 
 whole length, y z, in a sufficient degree to over- 
 come the increased friction, circulation of the 
 water will take place ; and the velocity of motion 
 will depend upon the amount of this difference in 
 weight. 
 
 (31.) Another form, though somewhat more 
 complicated, may be given to this arrangement
 
 42 
 
 CIRCULATION OF WATER 
 
 of the apparatus. In fig. 11, B represents the 
 boiler; and the effective or direct motion is, in 
 this case, caused by the water in the coil and pipe 
 
 c d being so much 
 
 FIG. 11. heavier than that 
 
 in the boiler and 
 pipe, B a, that it 
 overcomes the re- 
 trograde motion 
 which is produced 
 by all the other 
 parts of the appa- 
 ratus. Thus the 
 water in g h, be- 
 ing heavier than 
 that in i , and 
 that in ef (below 
 
 the dotted line) being lighter than that in I m, 
 has in both cases a tendency to retrogression; 
 and this will be more considerable in proportion 
 as the pipes i k, and g h, &c., are more distant 
 from each other. The motive power, therefore, 
 entirely depends upon the quantity of heat given 
 off by the coil ; for the water must be cooled down 
 many degrees, in order to give it a sufficient pre- 
 ponderance over the water in B a, to cause a cir- 
 culation ; and the circulation must necessarily be 
 very slow, and, therefore, the temperature very 
 unequally diffused. 
 
 If the coil, in the last two figures, be placed in 
 any lower position than is here shown, the effect 
 will be proportionately less in producing circula- 
 tion; and if placed below the dotted lines, it 
 would be scarcely possible to obtain any circulation 
 at all. Nor would there be any circulation if the 
 coil were omitted, because the mere descent of the 
 water through a straight pipe would not cool it 
 sufficiently to give the necessary preponderance
 
 BELOW THE BOILER. 
 
 43 
 
 to the descending column, unless some other con- 
 trivance for the purpose of cooling the water to an 
 equal extent were adopted. 
 
 (32.) The principle which governs the circula- 
 tion in these last-mentioned cases is capable of 
 many applications. And it must be remembered 
 that, as a coil of pipes produces an enormous 
 degree of friction in the fluid passing through it, 
 which must be overcome before circulation can be 
 produced, a smaller difference of temperature 
 between the ascending and descending columns 
 
 FIG. 12. 
 
 ID 
 
 would produce circulation, if the apparatus were 
 contrived so as to cause less friction to the fluid 
 passing through it. 
 
 In an apparatus constructed as fig. 12 the water 
 rises directly from the boiler into an open cistern, 
 A ; and it then descends through the pipe B, which 
 communicates with the bottom or the side Of this 
 cistern. In cases of this kind it has been gene- 
 rally assumed that the water will descend as far 
 below the boiler as the rising pipe and the cistern 
 are above the boiler; and, practically, it is often 
 found that this is the case, though the explanation
 
 44 CIRCULATION OF WATER BELOW THE BOILER. 
 
 of the fact must be sought for among a different 
 class of phenomena than those which merely regard 
 the height of the ascending pipe. 
 
 (33.) The advantage of conveying the water 
 into an elevated cistern, as shown in the last 
 figure, appears to be twofold.* It allows the 
 freest escape of air and of steam, either of which 
 would prevent the circulation, if it lodged in the 
 part of the apparatus a, y, i, in fig. 11 ; and which 
 part is in fig. 12 occupied by the open cistern. 
 This cistern also facilitates the circulation, by 
 increasing both the actual as well as the relative 
 weight of the descending column of water ; because 
 no part of the descending pipe B can possibly con- 
 tain steam, as the water will remain in the cistern 
 A until it has become colder than that in the pipe 
 E, and boiler F ; and it is evident that, by such an 
 arrangement as fig. 12, this difference of tempe- 
 rature must constantly increase, after heat is applied 
 to the boiler, until it becomes sufficient to give a 
 preponderance to the water in B. And even if the 
 heat were sufficient to raise steam in the pipe E, 
 this would only still further increase the effect, in- 
 stead of diminishing or even wholly stopping the 
 circulation, as would be the case with an apparatus 
 like fig. 11, under similar- circumstances. 
 
 (34.) Many other arrangements of the apparatus 
 answering the same purpose as these last three 
 figures, might be contrived ; but while these forms 
 are advantageous when difficulties of adaptation 
 have to be surmounted, it must not be imagined 
 that they are recommended above the more simple 
 forms shown in figs. 3, 7, and 9. It requires great 
 judgment in adopting some of these complicated 
 
 * The Marquis de Chabannes was the first to employ an 
 elevated cistern in this way. His apparatus is described in 
 his pamphlet, published in 1818, on " Warming and Venti- 
 lating Buildings."
 
 REVERSED CIRCULATION OF WATER. 45 
 
 arrangements ; for many causes may interfere to 
 prevent complete success. It is sometimes very 
 difficult to detect the various causes of interfer- 
 ence, and the impediments which arise are often, 
 apparently, so insignificant in their extent, that 
 even when ascertained they are frequently neg- 
 lected. Those, however, who bear in mind how 
 small is the amount of motive power in any 
 apparatus of this description, will not consider 
 as unimportant, any impediment, however small, 
 which they may detect; but, in the more com- 
 plicated forms of the apparatus, so many causes 
 become operative, that the reason of failure may 
 sometimes elude the detection of even an expe- 
 rienced practitioner. 
 
 (35.) It has occasionally occurred that the cir- 
 culation of the water in an apparatus has been 
 reversed, the hot water passing along what should 
 be the return-pipe, and the colder water following 
 the course of the flow-pipe. This effect has some- 
 times been exceedingly puzzling; but it will be 
 found to arise in those apparatus which have but 
 small motive power, and in which the principle 
 has not been followed out of making the water rise 
 to the highest point of the apparatus as soon as 
 possible, and allowing it, in its return to the boiler, 
 to give out its heat to the various pipes, coils, or 
 other distributing surfaces which it is intended to 
 heat. If the opposite course to this be adopted, 
 the friction in the flow-pipes often becomes so con- 
 siderable that the direct and natural action of the 
 ascending column is altered, and the hot water, 
 meeting less resistance by passing through what 
 ought to be the return-pipe, converts it at once 
 into a flow-pipe, and entirely reverses the ordinary 
 action of the apparatus. This is particularly 
 liable to occur in boilers which have but little 
 depth ; and it sometimes happens that the appa-
 
 46 LEN'GTH OF CIRCULATION'. 
 
 ratus, when constructed in this way, will operate 
 most capriciously, the circulation sometimes being 
 direct and sometimes retrograde, and sometimes 
 stopping altogether. Whenever, therefore, the 
 pipes rise to any considerable height above the 
 boiler, it is very desirable that the most direct 
 route should be provided for the water to flow 
 first to the highest elevation, after which in its 
 return to the boiler, it may be made to pass 
 through the various pipes, coils, and other heat- 
 distributing surfaces, which will thus secure its 
 most efficient action and the most perfect cir- 
 culation. 
 
 (36.) The distance through which the water 
 will circulate in a hot-water apparatus is very con- 
 siderable ; its limit has not yet been ascertained, 
 and probably never will be, as it must depend upon 
 many circumstances totally differing in almost 
 every apparatus. The higher the water rises 
 above the boiler, the greater is the length through 
 which it may afterwards be made to circulate ; 
 and many apparatus are successfully working 
 where the water circulates through several hundred 
 feet of pipe, in a continuous course, before it again 
 returns back to the boiler to be reheated. In 
 general, however, it is very desirable to shorten 
 this circulation as much as possible, and an appa- 
 ratus will always be more efficient if it can be so 
 arranged, by altering the position of the boiler, or 
 the disposition of the pipes, that the water shall 
 run through two or more distinct and short cir- 
 culations, rather than through one long one. Nor 
 is this at all at variance with what has been pre- 
 viously stated about the velocity of circulation 
 being increased by lengthening the circulating 
 pipe (Art. 19). For while impediments to the 
 circulation may be overcome by a considerable 
 difference of temperature in the flow and return-
 
 AIR VENTS. 47 
 
 pipes, the apparatus will always be more efficient 
 when the temperature of the various parts of the 
 apparatus does not very widely differ. 
 
 (37.) When an apparatus is so constructed that 
 the boiler is considerably below the pipes or 
 other surfaces giving out heat, the circulation is 
 sure to be very rapid, and the greatest effect 
 will always be obtained by making the circulation 
 as short as possible, so as to have as little differ- 
 ence as may be in the temperature of the flow 
 and the return-pipe. But when, on the other hand, 
 the pipes and boiler are nearly on a level, it is 
 frequently necessary that a greater difference shall 
 exist between the temperature of the flow and 
 return-pipes, in order to produce a good circu- 
 lation, and to overcome any obstructions arising 
 from dips in the pipes or any other disturbing 
 cause. 
 
 (38.) The necessity for making provision for the 
 escape of the air from the pipes has already been 
 mentioned. It may be observed that, in such 
 forms of the apparatus as are described in the last 
 four figures, the difficulty of its expulsion is much 
 increased, as there are several points where it will 
 collect and stop the circulation, unless proper 
 means be taken to prevent this result. In the 
 apparatus, fig. 9, the air will collect at three 
 points, /, m, and n ; and the nature of the outlets 
 provided for its escape will depend, in some 
 measure, upon the plan adopted for supplying the 
 apparatus with water. In some cases open-air 
 pipes will be the best : in other cases air-cocks will 
 be necessary to prevent an over-flow of water 
 through an open-air pipe. It frequently requires 
 the greatest care and the closest attention to dis- 
 cover where the air is likely to lodge, as the most 
 trifling alteration in the position of the pipes will 
 entirely alter the arrangements with respect to
 
 .{x SUPPLY CISTERN?. 
 
 the air-vents. Want of attention to this has been 
 the cause of innumerable failures; and the dis- 
 covery of the places where the air will accumulate 
 is, occasionally, a matter of some difficulty. For 
 although it be true, in a general seuse, that the 
 air will rise to the highest part of the apparatus, 
 it will frequently be prevented getting to those 
 parts by alteration in the level of the pipes, and 
 by other causes. This is the case at m, fig. 9, 
 w'here, it will be seen, the air that accumulates 
 in that part of the apparatus is prevented from 
 escaping to a higher level, by the vertical angle 
 at / on the one side, and t on the other. In the 
 apparatus, fig. 11, the air will accumulate at y and 
 at tr, and must be carried off by proper outlets ; 
 and in every case provision must be made for the 
 air to pass, either by a level pipe or by ascend- 
 ing gradients, for in no case can it be made to 
 pass downwards (however small the extent) in its 
 passage to the vent provided for its escape. 
 
 (39.) When a boiler is open at the top, or merely 
 has a loose cover laid on it, no particular care is 
 necessary respecting the supply of water. It can 
 generally be poured in at the boiler, taking care 
 not to fill it quite full, so as to allow for the ex- 
 pansion of the water when heated, as otherwise it 
 will overflow. But when, as figures 7, 9, 10, 
 11, and 12, the boiler is close at the top, it is 
 necessary to place a supply cistern on a level with, 
 or above the highest part of the apparatus, so as 
 to keep it always full of water. But as water ex- 
 pands about ~ part of its bulk, when it is heated 
 from 40 (the point of its greatest condensation) to 
 212, it is indispensably necessary to provide for 
 a part of the water returning back to the supply 
 cistern when this expansion takes place. The 
 cistern, however, need not contain so much water 
 as i part of the whole contents of the apparatus;
 
 EXPANSION OF PIPES. 49 
 
 for it is found in practice, that a less quantity 
 than this returns back into the cistern on the 
 apparatus being heated. This arises from the 
 fact of the water not reaching to so high a tem- 
 perature as 212, and also in consequence of its 
 being generally at a higher temperature than 40 
 before it is heated, and by both these causes the 
 expansion is considerably lessened. For if the water 
 be raised from 50 to 180, the expansion will only 
 be about ^ part of its bulk ; and the expansion of 
 the iron itself, by giving an increased capacity to 
 the apparatus, will also tend still further to di- 
 minish the quantity of water returned back into 
 the cistern. A very good proportion for general 
 purposes is to make the supply cistern contain 
 about ^ of the whole quantity of water in the pipes 
 and boiler; though, for the reasons above stated, 
 a smaller size will answer in many cases, where 
 economy or convenience requires it to be reduced. 
 A table is given at the end of this volume, show- 
 ing the contents of pipes of all sizes, and which 
 will enable any one easily to ascertain the correct 
 size of these expansion and supply cisterns for any 
 apparatus. 
 
 (40.) The usual plan for a supply cistern is 
 shown at A, in fig. 13. The cistern is placed in 
 some convenient situation, and then attached, by 
 a small pipe, to any 
 part of the appara- 
 tus usually, to the 
 lower pipe, and it is 
 then less likely to 
 allow of the escape of 
 vapour than if it were 
 fastened to the top of 
 the boiler. But a still better plan is to bend the 
 pipe, attached to the cistern, into the form shown by 
 x y, which is a preventive to the escape of any heat or
 
 50 EXPANSION OF PIPES. 
 
 vapour at that part, as the legs of the siphon x 
 generally remain quite cold. 
 
 (41.) One very important part of the subject of 
 expansion is the necessity which exists for allow- 
 ing sufficient room for the elongation of the pipes 
 when they become hot. Want of attention to this 
 has caused several accidents; for the expansive 
 power of iron, when heated, is so great, that 
 scarcely anything can withstand it. The linear 
 expansion of cast iron, by raising its temperature 
 from 32 to 212, is -0011111, or about ^ part of 
 its length, which is nearly equal to 1| inches in 
 100 feet. Therefore it is necessary to leave the 
 pipes unconfined, so that they shall have free 
 motion lengthways, to this extent at least. In- 
 stead of confining them, as sometimes has been 
 done, facilities should be provided for their free 
 expansion, by laying small rollers under them at 
 various points; for as the contraction on cooling 
 is always equal to the expansion on heating, un- 
 less they can readily return to their original 
 position when they become cool, the joints are 
 very likely to get loose, and to become leaky. 
 These rollers may be made simply of a piece of 
 rod iron, about half inch or five-eighths of an 
 inch diameter, which may be fixed in a frame 
 to support the pipes, or they may lie loose on a 
 stone or brick pier, the pipes being supported by 
 this means at about every alternate joint. In very 
 short ranges of pipes this provision is not neces- 
 sary, as the longitudinal expansion is not sufficient 
 to become a matter of importance.
 
 51 
 
 CHAPTER III. 
 
 On the Resistance by Friction Relative size of Main-Pipes 
 and Branch-Pipes Vertical and Horizontal Main-Pipes 
 Small connecting Pipes Branch-Pipes at difference Levels 
 
 Stop- cocks and Valves Their Use and proper Size 
 Their place supplied by Cisterns Inconvenience of them 
 
 Remedies. 
 
 (42.) WHEN treating, in the preceding chapter, 
 on the velocity of the circulation of water, it was 
 observed that the theoretical velocity is always 
 considerably reduced by friction. Although the 
 calculation of the friction of water, in passing 
 through pipes, is intricate,* the relative friction 
 for different sizes of pipes is easily ascertained ; 
 and this appears to be nearly all that is neces- 
 sary to be acquainted with for the purpose of the 
 present inquiry. 
 
 The friction occasioned by water passing through 
 small pipes is very much greater than in those 
 which are larger. This arises from two causes 
 the increased surface with which a given quantity 
 of water comes into contact by passing through a 
 small pipe, and the greater velocity with which the 
 water circulates, in consequence of losing more heat 
 per minute.f 
 
 (43.) The relative friction for different sizes of 
 pipes, when the velocity with which the water 
 
 * See Art. 22. 
 
 t See Chap. IV., Art. 61. This latter remark of course 
 only applies to water circulating in a hot-water apparatus: 
 the former applies to all cases of hydraulics. 
 
 E 2
 
 52 FRICTION OF PIPES. 
 
 passes is the same in all, may be seen in the fol- 
 lowing table : 
 
 Diameter of Pipes , 1, 2, 3, 4 inches. 
 Friction . . 8, 4, 2, 1-3, 1. 
 
 Taking the friction, in pipes of four inches diameter, 
 as unity, that of a pipe two inches diameter is 
 twice as much, and a one-inch pipe four times as 
 much as the pipe of four inches ; the friction being 
 as the surface directly, and the whole quantity of 
 water inversely* 
 
 (44.) The friction which arises from increased 
 velocity is nearly as the square of the velocity ; but 
 this calculation it is unnecessary to enter into 
 here, because the velocity of circulation of the 
 water, in a hot-water apparatus, is constantly sub- 
 ject to fluctuation. For as the friction increases 
 with the velocity of circulation, so the velocity is 
 checked by the increased friction ; and it finally 
 assumes a mean rate, proportioned to the friction 
 on the one hand, and the theoretical velocity on 
 the other, calculated according to the rule (Art. 21) 
 in the preceding chapter. 
 
 (45.) Closely connected with the subject of 
 friction is the question of the proper size for 
 leading or main pipes. It has been supposed by 
 many persons that, where two or more circulating 
 pipes are attached to one main-pipe, the area or 
 section of the main-pipe ought to be equal to the 
 sum of the areas of all the branch-pipes. This has 
 led to most inconvenient arrangements having been 
 resorted to in particular cases. In some instances, 
 pipes as large as nine inches diameter have been 
 used for the main-pipes, where those of four inches 
 would have answered the purpose infinitely better ; 
 and other proportions equally erroneous have 
 frequently been adopted. 
 
 * Dr. Young's Hydraulics, Nicholson's Journal, vol. iii, p. 31.
 
 RELATIVE SIZE OF PIPES. 53 
 
 (46.) It has been already explained (Art. 23), 
 that the motion of water is more rapid in an up- 
 right than in a horizontal pipe. If four branch- 
 pipes be supplied by one upright main-pipe, this 
 latter needs be very little, if any, larger than the 
 circulating pipes; but if only two, or even three, 
 branches are to be supplied by one main-pipe, it 
 will be quite unnecessary in ordinary cases that 
 the upright main-pipe should be any larger than 
 the branches, unless the length of the horizontal 
 pipe be unusually great. If the branches exceed 
 this number, it may be desirable to increase the 
 diameter of the upright main-pipe, in a moderate 
 degree; but the motion of the water through it, 
 however, will be just so much the more rapid in 
 proportion as there are more branches for it to 
 discharge the water into. It is evident that, if the 
 outlet from the boiler be by a pipe four inches 
 diameter, the flow of water will be more impeded, 
 than if a pipe of six inches diameter were used ; 
 and the water will therefore become specifically 
 lighter in the boiler than in the descending pipe, 
 in a greater degree in the former case than in the 
 latter; and this will consequently cause a more 
 rapid circulation through the apparatus. But, 
 though the friction of the water will be greater in 
 the ascending pipe by this arrangement, yet it will 
 not be of importance, except when very small 
 pipes are used. For the friction is extremely 
 small in a vertical pipe to an ascending current 
 of water. As a general rule, it may be observed, 
 that all horizontal leading pipes require to be 
 much larger in proportion to the branches than is 
 requisite with vertical leading pipes, in conse- 
 quence of the friction being so exceedingly small 
 in the latter <case. 
 
 (47.) Another advantage will arise from this 
 arrangement, in consequence of a small pipe, under
 
 54 RELATIVE SIZE OF PIPES. 
 
 these circumstances, losing less of its heat than a 
 large one. For, suppose four branch-pipes, four 
 inches diameter, are to be supplied by one main- 
 pipe ; one pipe of eight inches diameter would 
 have the same sectional area as the four pipes of 
 four inches diameter ; but if, instead of being eight 
 inches diameter, the main-pipe be made only four 
 inches diameter, then the water must travel four 
 times faster through this pipe than it would do 
 through the one of eight inches diameter, in order 
 to supply the same quantity of heat to the branch- 
 pipes. This it will do very nearly ; and it may 
 easily be deduced that, under these circumstances, 
 the water will only lose one-half as much heat by 
 passing through the small pipe as it would in 
 passing through the larger one ; for the loss of heat 
 which the water sustains is directly as the time and 
 the surface conjointly.* 
 
 (48.) On the same principle, it will frequently 
 be found exceedingly convenient, when two rooms 
 or buildings somewhat distant from each other 
 are required to be warmed by one boiler, to make 
 the connecting pipe between them smaller than 
 the pipe used for radiating the heat to warm the 
 buildings. For, on the principle already men- 
 tioned, there will be a saving as well of heat as 
 in the cost of the apparatus, by reducing the size 
 of the pipe in that part which is not required to 
 give off heat, but which is merely used to connect 
 different parts together.f In this manner, a pipe 
 of one inch diameter may frequently be made to 
 supply a pipe of four inches diameter ; and it will 
 sometimes be found convenient to connect pipes 
 
 * See Chap, xiii., Art. 270. 
 
 f As all alterations in the size of the pipe, either by enlarg- 
 ing or contracting its diameter, materially alter the velocity of 
 the circulation of the water, care should be taken that these 
 alterations be not made capriciously, and without some decided 
 advantage appears to be attainable by so doing. Venturi
 
 MAIN-PIPES. 55 
 
 of large diameter with the boiler by this means, 
 when the total length of pipe is not great. But it 
 must always be borne in mind, that the size of the 
 leading or main pipes ought to bear some propor- 
 tion to the total quantity of water that is required 
 to pass through them. And while it might be ex- 
 tremely convenient, in particular instances, to con- 
 nect pipes of four inches diameter to the boiler by 
 the intervention of small pipes of one-inch bore, 
 when the total quantity of pipe is small, it would 
 be a fatal mistake to adopt the same arrangement 
 if three or four hundred feet of large pipe were 
 connected to a boiler by means of so small a pipe 
 as is here stated. The connecting pipe therefore 
 ought to bear some proportion to the total quantity 
 of water that has to pass through it. It should be 
 larger in diameter when the quantity of water con- 
 tained in the apparatus is greater, and smaller 
 when the quantity of water is less. 
 
 (49.) Very important results frequently arise 
 from errors with respect to main-pipes which are 
 placed vertically, in consequence of the great velo- 
 city with which the water circulates through such 
 pipes. It frequently happens that the pipes which 
 branch out from an upright main-pipe are required 
 to circulate at very different heights ; as, for in- 
 stance, in warming the several floors of a ware- 
 house or manufactory. In this case either one of 
 two methods may be adopted : the pipe may either 
 rise to the highest floor or level first, and, after 
 passing round such uppermost room, descend and 
 circulate round that which is below it; then pro- 
 found by experiments that enlargements in a pipe reduce the 
 velocity of discharge as follows : When a given quantity of 
 water was discharged through 
 
 A straight pipe in .... 109 seconds, 
 A pipe with one enlargement required 147 
 three . . . . 192 
 
 five . 240
 
 56 MAIN-PIPES. 
 
 ceed to the next lowest, and so on, till it finally 
 returns again to the boiler; or each floor may 
 have a separate range of pipes branching off from 
 the main-pipe, and finally returning, either to- 
 gether or separately, into the boiler. In the first 
 of these cases it is* obvious that the temperature 
 of the water and of the pipes will be much greater 
 in the higher floors than in the lower. For the 
 water, by having passed through a great length 
 of pipe before it reaches the lower rooms, will be 
 much reduced in temperature, and the upper rooms 
 will be heated long before the others become at all 
 warm ; and at all times the temperature will be 
 very unequal. To obviate this, each floor should 
 be warmed separately by its own range of pipes. 
 But this requires particular management. For, if 
 the several pipes merely branch out sideways from 
 a vertical main-pipe, the whole of the hot water 
 will rise to the upper pipe in consequence of the 
 extremely rapid circulation in a vertical pipe, and 
 leave all the lower lateral branches without any 
 circulation of hot water through them. In order 
 to avoid this, it is necessary either to have a 
 separate pipe rising directly from the boiler for 
 each floor, or some means must be adopted to 
 check the water in its upward course through the 
 vertical main-pipe when only one is used for sup- 
 plying the several different floors. In fig. 14 it 
 will be perceived that the water which passes up 
 the pipe B receives a check at B, and thereby, of 
 course, facilitates the flow of water through the 
 first horizontal pipe, which would otherwise have 
 been left stagnant. The same occurs also at c for 
 the same reason ; and by this means a nearly 
 equal flow of hot water may be obtained ; while, 
 had the supplying main from the boiler passed 
 directly upwards in a perfectly straight line, all 
 the hot water would have passed at once into the
 
 MAIN-PIPES. 
 
 57 
 
 upper pipe, and the lower ones would have been 
 left comparatively cold. But even with this 
 arrangement, it is extremely difficult sometimes 
 to prevent all the hot water passing up to the 
 upper floor, and 
 
 leaving the lower FIG. 14. 
 
 floors unheated. 
 It is, therefore, 
 oftentimes very 
 necessary to make 
 a distinct rising 
 pipe for the lower 
 floors, in order to 
 equalize the flow 
 of hot water to 
 the different le- 
 vels. The verti- 
 cal main pipes 
 should likewise 
 diminish in size 
 as they rise up- 
 wards. If one 
 main only be 
 used, it is very 
 desirable conside- 
 rably to reduce 
 
 the size as it passes upwards, commencing perhaps 
 with 4-irich pipe for the first floor, reducing it to 
 3 inches as it passes upwards to the second floor, 
 and then reducing it still further in size as it leads 
 upwards to the third floor. And unless some such 
 contrivance be used, it is almost impossible to pre 
 vent the whole of the hot water passing to the 
 upper floor first, and making a most defective cir- 
 culation in the lower ranges of pipes. 
 
 Whenever lateral pipes are taken off at right 
 angles from an upright or vertical pipe which 
 passes in a straight direction to a still higher level,
 
 58 MAIN-PIPES. 
 
 the water will always pass by such lateral pipes unless 
 checked in its upward course as here described. But 
 the same effect very often occurs also in horizontal 
 pipes, particularly where the branch pipes are 
 smaller than the mains or leading pipes. One 
 mode of preventing this in the case of vertical 
 pipes has already been shown. But another mode, 
 applicable both* to vertical and horizontal main 
 pipes, when these main pipes are sufficiently large 
 in diameter, is the following: Suppose A to be 
 a main pipe, either vertical or 
 FIG. 14B. horizontal, and BCD branch 
 
 pipes leading out of this main 
 pipe. The water is supposed 
 to flow in the direction shown 
 by the arrows. Now in a 
 vertical pipe always, and in a 
 horizontal pipe frequently 
 particularly when the branch 
 pipes are much smaller than 
 the main pipe the hot water 
 will pass by the branches 
 B c and i>, and leave them 
 
 r quite cold and without any 
 circulation. To prevent this 
 a small strip of thin sheet 
 copper, extending rather less 
 than half way across the 
 main pipe as shown b c d, 
 may be fixed on to the upper side of the branch 
 pipe when the main pipe is vertical; or to the 
 opposite side to the direction of the current, when 
 all the pipes lie horizontal. This slight check 
 to the direction of the current is sufficient to cause 
 a circulation in the lateral or branch pipes under 
 almost any possible circumstances, and when done 
 with judgment it causes no sensible diminution of 
 the circulation through the main pipe.
 
 STOP-COCKS. 59 
 
 (50.) It is perfectly immaterial how many pipes 
 lead out of or into the boiler ; but it will generally 
 much simplify the apparatus if branch-pipes be 
 used, as in fig. 14, instead of making several 
 separate outlet pipes, and various inlet pipes to 
 the boiler. 
 
 Very frequently it happens that several branch- 
 pipes are required from the boiler, to circulate 
 nearly at the same level, particularly in horti- 
 cultural buildings, where two or three hothouses 
 are 'required to be warmed by one boiler. This 
 seldom presents much difficulty, unless it be re- 
 quired occasionally to stop off certain of these 
 houses, while the others are heated. In these cases, 
 a complicated and expensive arrangefnent of cocks 
 or valves become necessary. But here the rule, 
 which has already been given (Art. 46 and 48), 
 for connecting pipes may likewise be followed, 
 where stop-cocks are required occasionally to shut 
 off the communication between different parts of 
 an apparatus, so as only to warm one particular 
 room or part of a building. The cocks used for 
 this purpose need not always be so large as the 
 bore of the pipes. Some judgment, however, must 
 be exercised in all such cases; for, both with 
 connecting pipes and cocks, if the size be very 
 disproportionate, the free circulation of the water 
 will of course be impeded. In many cases a cock 
 of two inches diameter will be sufficiently large to 
 use with pipes of four inches diameter ; and a cock 
 of one and a half inch diameter, with pipes of 
 three inches diameter: but, for very small pipes, 
 the relative proportions should perhaps be more 
 nearly equal to the size of the pipes, on account 
 of the increased friction. It should also be ob- 
 served, that when an apparatus has but an in- 
 different circulation, this alteration in the bore of 
 the water-way will be very objectionable, and
 
 60 STOP-COCKS AND VALVES. 
 
 likely still further to impede it, though the exact 
 result will depend upon a variety of causes, for 
 which it is not easy to lay down a general rule, 
 In such an arrangement of pipes as fig. 14, it 
 is frequently desirable to use small-sized cocks or 
 valves, for the purpose of checking the flow of 
 water in particular directions; while in an ap- 
 paratus like fig. 9 the same proportionate sizes of 
 cocks might be very injudicious, and greatly im- 
 pede the circulation. 
 
 (51.) When cocks or valves are used to stop off 
 the circulation of a particular part of the appara- 
 tus, it is not sufficient merely to stop the upper or 
 flow-pipe; but the corresponding pipe which re- 
 turns the water to the boiler must also be stopped, 
 otherwise the hot water will circulate backwards 
 through the return-pipe, and pass into the flow- 
 pipe, and thus the whole will become heated. 
 This more particularly applies to those cases 
 where the boiler is placed at any considerable 
 depth below the circulating pipes; for then, as 
 already stated, the circulating power will be much 
 increased. But it may be laid down as a general 
 rule, that where the circulation is tolerably good, 
 it is not enough to place a cock or valve on the 
 flow-pipe alone ; but the return-pipe requires to be 
 stopped also. Cases undoubtedly sometimes occur 
 in which a valve or cock placed in the flow-pipe 
 will effectually shut off the circulation, without 
 also putting one in the return-pipe. But it will 
 generally be found that in these instances the 
 boiler is either too small for its work, or that it 
 is not worked at its full power, or that there is 
 something peculiar in the arrangement, which ren- 
 ders the portion of the circulation thus stopped 
 off naturally more sluggish and inert than the 
 rest of the apparatus ; and therefore a very small 
 obstruction will be sufficient to stop entirely the
 
 STOP-COCKS AND VALVES. 
 
 61 
 
 circulation through it. But in almost all the 
 apparatus which have a good circulation and a 
 boiler sufficiently powerful, it will be found neces- 
 sary to stop the return-pipe as well as the flow- 
 pipe, in order effectually to shut off the circula- 
 tion. 
 
 (52.) In order to avoid the expense of cocks or 
 valves in these cases, an open cistern, as in fig. 15, 
 has sometimes 
 been used. 
 From this cis- 
 tern all the 
 several flow- 
 pipes are made 
 to branch out ; 
 and then, by 
 placing a wood 
 plug into any 
 one or more ^b 
 
 of these pipes, 
 
 the circulation will be stopped in those particular 
 pipes until the water throughout the whole ap- 
 paratus becomes heated, when it will generally 
 flow back through the return-pipe, as above men- 
 tioned. This inconvenience, however, may be 
 prevented by such a contrivance as shown in the 
 return-pipe of fig. 15, which is simply an inverted 
 siphon of a few inches in depth. This will not 
 prevent the circulation when the flow-pipe remains 
 open ; but if that be closed by a plug in the cis- 
 tern, then the hot water will not return back 
 through the lower pipe. This inverted siphon, 
 however will, in process of time, be liable to be 
 choked up with dirt, which will accumulate in the 
 lower part of the bend ; and for the purpose of re- 
 moving this it will be necessary to make a cap 
 or covering to the lower part of it, which can be 
 removed at pleasure, for the purpose of clearing
 
 G2 STOP-COCKS AND VALVES. 
 
 away any sediment that may accumulate. These 
 cisterns, however, when thus used, are at best but 
 a clumsy way of supplying the place of cocks or 
 valves. The latter are sometimes made to stop off 
 both the flow and return-pipe at one operation ; 
 but, in whatever way they are arranged, they are 
 generally one of the most troublesome parts of 
 the apparatus, as cocks and valves of all kinds are 
 liable to get out of repair unless they are in the 
 hands of those who perfectly understand them, and 
 will keep them in proper order. 
 
 (53.) Though some of the statements respect- 
 ing the relative sizes of connecting pipes, main- 
 pipes, and cocks, may appear to be at variance 
 with the laws of hydraulics, they will neverthe- 
 less be found correct; because several of the 
 effects are to be referred either entirely to hydro- 
 static laws, or to a complicated result of hydro- 
 dynamics, and therefore they are not to be judged 
 of by simple hydraulic principles. They rest not 
 on mere hypothesis, but may be relied on as practi- 
 cal results obtained under almost every variety of 
 circumstances, and too fully tested to admit of any 
 doubt of their accuracy.
 
 63 
 
 CHAPTER IY. 
 
 Permanence of Temperature Eates of Cooling for different 
 sized Bodies Proper sizes for Pipes Eelativc Size of 
 Pipes and Boiler Various Forms of Boilers, and their 
 Peculiarities Boilers heated by Gas Objections against 
 contracted Water-way in Boilers Proper Size of Boilers 
 for any given lengths of Pipe What constitutes a good 
 and efficient Boiler Durability of different Materials for 
 Boilers Effect of Impure Fuel. 
 
 (54.) ONE of the greatest advantages which 
 the plan of heating by the circulation of hot 
 water possesses over all other inventions for dis- 
 tributing artificial heat is, that a greater per- 
 manence of temperature can be obtained by it 
 than by any other method. The difference be- 
 tween an apparatus heated by hot water and one 
 where steam is made the medium of communi- 
 cating heat, is not less remarkable in this parti- 
 cular than in its superior economy of fuel. 
 
 (55.) It seldom happens that the pipes of a 
 hot-water apparatus can be raised to so high a 
 temperature as 212; and, in fact, it is not desir- 
 able to do so, because steam would then be 
 formed, and would escape from the air-vent or 
 safety pipe, without affording any useful heat. 
 Steam-pipes, on the contrary, must always be at 
 212 at the least, because, at a lower temperature, 
 the steam will condense. A given length of 
 steam pipe will therefore afford more heat than 
 the same quantity of hot-water pipe: but if we
 
 64 HEAT IN WATER AND STEAM. 
 
 consider the relative permanence of temperature 
 of the two methods, we shall find a very remark- 
 able difference in favour of pipes heated with hot 
 water. 
 
 (56.) The weight of steam at the temperature 
 of 212, compared with the weight of water at 
 212, is about as 1 to 1694; so that a pipe which 
 is filled with water at 212 contains 1694 times as 
 much matter as one of equal size filled with steam. 
 If the source of heat be cut off from the steam- 
 pipes, the temperature will soon fall below 212, 
 and the steam immediately in contact with the 
 pipes will condense : but in condensing the steam 
 parts with its latent heat ; and this heat, in passing 
 from the latent to the sensible state, will again 
 raise the temperature of the pipes. But as soon as 
 they are a second time cooled down below 212, 
 a further portion of steam will condense, and a 
 further quantity of latent heat will pass into a 
 state of heat of temperature ; * and so on, until the 
 whole quantity of latent heat has been abstracted, 
 and the whole of the steam condensed, in which 
 state it will possess just as much heating power as 
 a similar bulk of water at the like temperature ; that 
 is, the same as a quantity of water occupying ~- 4 
 part of the space which the steam originally did. 
 
 (57.) The specific heat of uncondensed steam 
 compared with water is, for equal weights, as 
 8470 to 1 : but the latent heat f of steam being 
 estimated at 1000, we shall find the relative heat 
 
 * The heat of temperature is that which is appreciable by 
 the thermometer ; and the term is used in contradistinction to 
 latent heat, which is not capable of being measured in a direct 
 manner by any instrument whatever. 
 
 f The results of different experiments on the subject of the 
 latent heat of steam, although somewhat various, are yet suffi- 
 ciently near for all practical purposes. Watt's experiments 
 gave 900 to 950 ; Lavoisier and Laplace, 1000 ; Mr. Southern, 
 945; Dr. Ure, 967 to 1000; and Count Kumford, 1000.
 
 HEAT IN WATER AND STEAM. 65 
 
 obtainable from equal weights of condensed steam 
 and of water by reducing both from the tempera- 
 ture of 212 to 60, to be as 7-425 to 1 ; but for 
 equal bulks it will be as 1 to 228 ; that is, bulk for 
 bulk, water will give out 228 times as much heat 
 as steam, on reducing both from the temperature 
 of 212 to 60. A given bulk of steam will there- 
 fore lose as much of its heat in one minute as the 
 same bulk of water will lose in three hours and 
 three quarters. 
 
 (58.) When the water and the steam are both 
 contained in iron pipes, the rate of cooling will, 
 however, be very different from this ratio; in 
 consequence of the much larger quantity of heat 
 which is contained in the metal itself than in the 
 steam with which the pipe is filled. 
 
 The specific heat of cast iron being nearly the 
 same as water (see Table V., Appendix), if we 
 take two similar pipes, four inches in diameter, 
 and one quarter of an inch thick, one filled with 
 water, and the other with steam, each at the 
 temperature of 212, the one which is filled with 
 water will contain 4 -68 times as much heat as 
 that which is filled with steam : therefore if the 
 steam-pipe cools down to the temperature of 60 
 in one hour, the pipe containing water would 
 require four hours and a half, under the same 
 circumstances, before it reached the like tempera- 
 ture. But this is merely reckoning the effect of 
 the pipe and of the fluid contained in it. In a 
 steam apparatus this is all that is effective in 
 giving out heat; but in a hot-water apparatus 
 there is likewise the heat from the water con- 
 tained in the boiler, and even the heat from the 
 brickwork around the boiler, which all tends to 
 increase the effect of the pipes, in consequence of 
 the circulation of the water continuing long after 
 the fire is extinguished ; in fact, so long as the 
 
 F
 
 66 PERMANENCE OF TEMPERATURE. 
 
 water is of a higher temperature than the sur- 
 rounding air of the room. From these causes, 
 the difference in the rate of cooling of the two 
 kinds of apparatus will be nearly double what is 
 here stated; so that a building warmed by hot 
 water will maintain its temperature, after the fire 
 is extinguished, about six or eight times as long 
 as it would do if it were heated with steam. 
 
 This is an important consideration, wherever 
 permanence of temperature is desirable ; as, for 
 instance, in hothouses, conservatories, and other 
 buildings of a similar description. And even in 
 the application of this invention to the warming of 
 dwelling-houses, manufactories, &c., this property, 
 which water possesses, of retaining its temperature 
 for so long a time, and the very great amount of 
 its specific heat, prevents the necessity for that 
 constant attention to the fire which has always 
 been found so serious an objection to the general 
 use of steam apparatus. 
 
 (59.) The velocity with which a pipe or any 
 other vessel cools, when filled with a heated fluid, 
 depends principally upon two circumstances the 
 quantity of fluid that it contains, relatively to its 
 surface and the temperature of the air by which it 
 is surrounded; or, in other words, the excess of 
 temperature of the heated body above that of the 
 surrounding medium. The subject of the radiation 
 of heat, and the rate at which a heated body cools, 
 under various circumstances, will be fully considered 
 in another chapter (see Chapter XII.). But for 
 temperatures below the boiling point of water, and 
 under such circumstances as we are now considering 
 with regard to hot-water pipes, the velocity of 
 cooling may be estimated simply in the ratio of the 
 excess of heat, which the heated body possesses 
 above the temperature of the surrounding air. The 
 variation in the rate of cooling, arising from a
 
 PERHAXENCE OF TEMPERATURE. 67 
 
 difference in proportion of the superficies to the 
 mass, is, for bodies of all shapes, inversely, as the 
 mass divided by the superficies. Therefore, the 
 relative ratio of cooling, for any two bodies of 
 different shapes and temperatures, is the inverse 
 numbers obtained by dividing the mass by the 
 superficies, multiplied by the direct excess of heat 
 above the surrounding air; provided the tempera- 
 ture of the heated bodies be below 212. Thus, 
 suppose the relative ratio of cooling be required, 
 for two cisterns filled with hot water, one a cube of 
 18 inches, at the temperature of 200 ; the other a 
 parallelopiped, 24 inches long, 15 inches wide, and 
 3 inches deep, at the temperature of 170 ; the 
 surrounding air in both cases being 60. Then, as, 
 
 INCHES. INCHES. 
 
 The cube contains 5832, divided by 1944, the superficies = 3'0 
 
 The parallelepiped contains. 1080, do. 954, do. =1-13 
 
 The inverse of these numbers is, to call the cube 
 1*13, and the parallelopiped 3*0. Then multiply 
 1'13 by 140 (the direct excess of temperature of 
 the cube), and the answer is 158-2: and multiply 
 3-0 by 110 (the direct excess of temperature of 
 the parallelopiped), and the answer is 330'0; 
 therefore the parallelopiped will cool, in com- 
 parison with the cube, in the proportion of 330 
 to 158, or as 2'08 to 1. So that if it required two 
 hours to cool the cube any proportional part of 
 its excess of heat, the other vessel will lose the 
 same proportional part of its excess of heat in one 
 hour. 
 
 (60.) It is evident that these different velocities 
 of cooling are quite independent of the total effect 
 that the respective bodies will produce in warming 
 a given space. For as the cube contains six times 
 as much water as the other vessel, so it would warm 
 six times as much air, if both vessels were of the 
 same temperature. But if six of the oblong vessels 
 
 F 2
 
 68 RATE OF COOLING. 
 
 were used, they would heat just the same quantity 
 of air as the cube; but the latter would require 
 rather more than two hours and a half to do what 
 the oblong vessels would accomplish in one hour, 
 supposing the temperature to be the same in both 
 cases. In the previous example, the temperatures 
 are supposed to be different ; otherwise the rela- 
 tive ratio of cooling of the two vessels would have 
 been as two and a half to one, instead of two to 
 one, as stated. 
 
 (61.) In estimating the cooling of round pipes, 
 the relative ratio is very easily found, because the 
 inverse number of the mass divided by the superficies, 
 which gives the relative cooling for all bodies, 
 is exactly equal to the inverse of the diameters. 
 Therefore, supposing the temperature to be alike 
 in all, 
 
 If the diameter of the pipes be 1, 2, 3, 4 inches. 
 
 The ratio of cooling will be 4, 2, 1 3, 1. 
 
 That is, a pipe of one inch diameter will cool four 
 times as fast as a pipe of four inches diameter; 
 and so on with the other sizes. These ratios, 
 multiplied by the excess of heat which the pipes 
 possess above that of the air, will give the relative 
 rate of cooling when their temperatures are dif- 
 ferent, supposing they are under 212 of Fahren- 
 heit. But if the temperatures are alike in all, the 
 simple ratios given above will show their relative 
 rate of cooling, without multiplying by the tem- 
 peratures. When the pipes are much above 212, 
 as, for instance, with the high-pressure system of 
 heating, the ratio of cooling must be calculated by 
 the rules given in Chapter XII. 
 
 (62.) The unequal rate of cooling of pipes of 
 various sizes, renders it necessary to consider the 
 purpose to which any building is to be applied 
 that is required to be heated on this plan. If it
 
 SIZE OF PIPES. 69 
 
 be desired that the heat shall be retained for a 
 great many hours after the fire is extinguished, 
 then large pipes will be indispensable ; but if the 
 retention of heat be unimportant, then small pipes 
 may be advantageously used. It may be taken as 
 an invariable rule, that in no case should pipes of 
 greater diameter than four inches be used in any 
 ordinary building, because, when they are of a 
 larger size than this, the quantity of water they 
 contain is so considerable, that it makes a great 
 difference in the cost of fuel, in consequence of the 
 increased length of time required to heat them. 
 (See Art. 108.) For hothouses, greenhouses, 
 conservatories, and such like buildings, pipes of 
 four inches diameter will generally be found the 
 best; though, occasionally, pipes of three inches 
 diameter may be used for such purposes, but rarely 
 any of ;a smaller size. In churches and manufac- 
 tories, &c., pipes of either four or three inches 
 diameter will generally be found most convenient, 
 in consequence of the difficulty which almost 
 always occurs of placing a sufficient quantity of 
 pipes of smaller diameter in these buildings. But 
 in dwelling-houses pipes of two inches diameter 
 will generally be preferable, for they will retain 
 theirC heat sufficiently long for ordinary purposes, 
 and their temperature can be sooner raised than 
 larger pipes, and, on this account, a somewhat less 
 number of superficial feet will suffice to warm a 
 given space. 
 
 (63.) In adapting the boiler to a hot-water 
 apparatus, it is not necessary, as is the case with 
 a steam boiler, to have its capacity accurately pro- 
 portional to that of the total quantity of pipe which 
 is attached to it :* on the contrary, it is sometimes 
 desirable even to invert this order, and to attach 
 a boiler of small capacity to pipes of large size. It 
 * See Chapter 'X. on heating by steam.
 
 70 SHAPE OF BOILERS. 
 
 is not, however, meant, in recommending a boiler 
 of small capacity, to propose also that it shall be 
 of small superficies ; for it is indispensable that it 
 should present a surface to the fire proportional 
 to the quantity of pipe it is required to heat ; and 
 in every case, the larger the surface on which the 
 fire acts, the greater will be the economy in fuel, 
 and the greater also will be the effect of the 
 apparatus. 
 
 (64.) The sketches of the boilers, figs. 16 to 30, 
 are several different forms which present various 
 extents of surface in proportion to their capacity. 
 
 All except the first two, however, have but a 
 small capacity, relatively to their superficies, com- 
 pared with boilers which are used for steam. 
 There is no advantage whatever gained by using 
 a boiler which contains a large quantity of water. 
 For, as the lower pipe brings in a fresh supply of 
 water, as rapidly as the top pipe carries the hot 
 water off, the boiler is always kept absolutely full. 
 The only plausible reason which can be assigned 
 for using a boiler of large capacity is, that as the 
 apparatus then contains more water, it will retain 
 its heat a proportionably longer time. This, 
 though true in fact, is not a sufficient reason for 
 using such boilers : for the same end can be 
 accomplished, either by using larger pipes, or by 
 having a tank connected with the apparatus, 
 which can be so contrived, by being enclosed in 
 brick or wood, or some other non-conductor, as to 
 give off very little of its heat by radiation, and yet 
 be a reservoir of heat for the pipes after the fire 
 has been extinguished. If this tank communicate 
 with the rest of the apparatus by a stop-cock, the 
 pipes can be made to produce their maximum 
 effect in a much shorter time than if this addi- 
 tional quantity of water had been contained in the 
 boiler; and a more economical and efficient appa-
 
 SHAPE OF BOILERS. 71 
 
 FIG. 16. FIG. 17. FIG. 18. FIG. 19. 
 
 FIG. 20. FIG. 21. FIG. 22. 
 
 FIG. 24. FIG. 25. FIG. 30A.
 
 72 CONSTRUCTION" OF BOILERS. 
 
 ratus will be obtained. The circulation will 
 likewise be more rapid from a boiler which con- 
 tains but a small quantity of water, because the 
 fire will have greater effect upon it, and will 
 render the water which is contained in it relatively 
 lighter than that which is in the descending or 
 return-pipe. 
 
 (65.) The boilers, figs. 16 and 17, are but 
 seldom used for hot-water apparatus. Fig. 18 is 
 an excellent form of boiler ; it is, in fact, the very 
 best boiler for general use that has ever been 
 made, and has been far more extensively used 
 than any other. It is generally made of wrought- 
 iron. Fig. 19 is something similar, though deci- 
 dedly inferior, on account of the inconvenience of 
 a flat top ; which not only prevents the easy flow 
 of the hot-water to the ascending pipe (which 
 ought always to be placed on the top), but also 
 the flues do not act so efficiently on the flat top of 
 this boiler. Fig. 20 is a good boiler, but is best 
 for either very small or very large apparatus (and 
 not for intermediate sizes), depending on the mode 
 of setting ; which subject will be described in the 
 following chapter. Fig. 21 is only suitable for 
 a very small apparatus. Figs. 22 and 23 (the 
 former of which is a section and the latter an 
 elevation) represent a cast-iron circular boiler of 
 very efficient construction, and suitable for either 
 large or small apparatus. Fig. 24 is a section of 
 the boiler known as Roger's conical boiler ; which 
 is a circular boiler, externally resembling the fig. 25. 
 This boiler has undergone much alteration of form 
 since its first invention. It was first open at the 
 top, and the fuel supplied there ; this, however, is 
 now supplied at A, and B is the smoke flue. Fig. 25 
 is a boiler nearly similar to the last, but contrived 
 so as to be used without any brickwork. The 
 radiation of heat from the surface of this boiler is
 
 CONSTRUCTION OP BOILERS, 73 
 
 of course considerable, and is generally entirely 
 wasted ; though when the boiler is placed inside 
 the room or building to be warmed, this loss may 
 be avoided. Fig. 26 is a boiler consisting of a 
 double row of pipes (of which the external row 
 alone is shown), connected at each end by an arch, 
 by which the water is supplied to the pipes forming 
 the body of the boiler. This boiler heats rapidly, 
 but is necessarily very wasteful of fuel, as no flues 
 can be formed in setting it. Fig. 27 is also a 
 boiler to be used without brickwork, and for many 
 purposes is very useful, particularly where the heat 
 from the external surface of the boiler can be 
 beneficially employed. Fig. 28 is another boiler 
 very similar to the last, but can be adapted to a 
 much smaller size, as the fire is contained in a fire- 
 clay receptacle, by which means a smaller fire may 
 be made to keep alight for many hours without 
 attention ; and by this contrivance a very much 
 smaller boiler may be made to act efficiently than 
 it otherwise could do. Both these boilers answer 
 extremely well. The boilers, figs. 29 and 30, are 
 more remarkable for their ingenuity than for their 
 practical utility, and it is probable that the compli- 
 cation of their construction renders them peculiarly 
 liable to accidents. The boiler, fig. 3(U, is a useful 
 boiler in some cases when used of small size, but 
 it becomes wasteful when made of large dimen- 
 sions. 
 
 (66.) Boilers heated by gas are occasionally used, 
 and they often possess advantages when coal or 
 coke cannot be conveniently employed. The cost 
 of burning gas in this way is however consider- 
 able. In the earlier editions of this work the cost 
 of burning gas was estimated at six times the cost 
 of coal, when the products of combustion were not 
 allowed to escape into the open air ; and at twelve 
 times the cost of coal when the products of coin-
 
 74 CONSTRUCTION OF BOILERS. 
 
 bustion passed away directly into the open air. 
 These estimates were perfectly correct when they 
 were given ; but since that time improved methods 
 of burning gas have been invented, by mixing the 
 gas with about twelve times its volume of atmo- 
 spheric air, previous to the gas reaching the place 
 of its actual combustion. This invention is popu- 
 larly known by the term "atmospheric gas." By 
 means of this invention and also by considerable 
 reductions in the price of gas relatively to the price 
 of coal, the cost of burning gas in this manner 
 may now be estimated at about three times the cost 
 of coal. In experiments made with this method 
 of burning Carburetted Hydrogen Gas, it has 
 been found that 720 cubic feet of gas gave the same 
 amount of heat that could be obtained by 75 Ibs. of 
 good average coal, and this at the price of three 
 shillings and sixpence per thousand cubic feet for 
 the gas, and twenty-four shillings per ton for the 
 coal, would be nearly in the proportion of about 
 three to one. When gas is to be burned in this 
 way, the boiler ought to be made of copper ; and 
 perhaps the best form of boiler for the purpose is 
 like the upper part of that shown in fig. 25, which 
 would then represent a shallow dome-topped boiler, 
 well suited to receive the burners now generally 
 used for the "atmospheric gas." Or another form 
 of boiler for this purpose consists of a copper 
 drum with several vertical copper tubes, approach- 
 ing nearly to a locomotive boiler standing vertically 
 instead of horizontally.* 
 
 (67.) There are many other forms of boilers 
 which have been proposed for the hot-water appa- 
 ratus, and, in fact, the multiplication of them 
 appears almost without limit. It is, perhaps, 
 scarcely any exaggeration to say they amount to 
 
 * See also Art. 306 for remarks on improved method of 
 burning Carburetted Hydrogen Gas.
 
 CONSTRUCTION OP BOILERS. 75 
 
 hundreds. When strictly considered, however, 
 there is scarcely one that presents any real 
 novelty, and generally they are mere colourable 
 adaptations of some one of those which have been 
 described; and the wonderful effects which some- 
 times are attributed to them arise either from the 
 parties being deceived in the results, or from 
 their being unacquainted with what has previously 
 been accomplished by others. The principles on 
 which a boiler must be constructed in order to 
 become efficient, are as fixed and immutable as 
 the laws of nature ; and the modes by which these 
 principles are to be applied are all determinable 
 by experience, and can be correctly judged of by 
 certain rules, beyond the possibility of error. The 
 mode of doing this may, perhaps, in some degree 
 tend to prevent the erroneous notions which fre- 
 quently prevail upon this subject. 
 
 (68.) The adoption of boilers of small capacity 
 having been recommended (Art. 64), it is neces- 
 sary to accompany the recommendation with a 
 caution against running into extremes ; for this 
 error has been the cause of failure, and of the 
 inefficiency of the apparatus in many instances. 
 The boiler, fig. 21, is an instance of this sort, in 
 which an absurd extreme has occasionally been 
 adopted. The contents of a boiler of this shape 
 sometimes do not exceed a couple of gallons, 
 even when applied to a very large furnace; and 
 though this boiler presents a large surface to the 
 fire, the space allowed for the water is so small 
 that the neutral salts and alkaline earths, de- 
 posited by the water which evaporates from the 
 apparatus,* contract the water-way, already far 
 too small, and effectually impede the circulation, 
 and also prevent the full force of the fire from 
 acting on the water. In a very small apparatus, 
 however, this form of boiler has occasionally
 
 76 REPULSION OF WATER. 
 
 been used with advantage, the fire being less 
 intense. 
 
 (69.). But perhaps the more immediate cause of 
 failure of this shaped boiler arises from a different 
 and very singular circumstance. The quantity of 
 water which it contains being so small, and the 
 heat of the fire, therefore, when the furnace is 
 large, being very intense upon it, a repulsion is 
 caused between the iron and the water, and the 
 latter does not receive the full quantity of heat. 
 This extraordinary effect is not hypothetical ; it 
 has been proved to exist by the most satisfactory 
 experiments; particularly some which were made 
 by the Members of the Franklin Institution of 
 Pennsylvania. The repulsion between heated 
 metals and water they ascertained to exist, to a 
 certain extent, even at very moderate degrees of 
 heat; being appreciably different at various tem- 
 peratures below the boiling point of water. But, 
 as the temperature rises, the repulsion increases 
 with great rapidity; so that iron, when red hot, 
 completely repels water, scarcely communicating 
 to it any heat, except, perhaps, when under con- 
 siderable pressure.* 
 
 The boiler in question, however, seldom or 
 never reaches the temperature of luminosity, 
 though it is still sufficiently high to make a con- 
 
 * Mr. Jacob Perkins brought this curious fact prominently 
 forward during his ingenious experiments on high-pressure 
 steam. It has, however, long been known as a philosophical 
 fact, and was first observed in 1756, by M. Leindenfrost. M. 
 Klaproth subsequently investigated it, and published some ex- 
 periments on the subject (Nicholson's Journal, vol. iv., p. 208). 
 In the "Parliamentary Eeport and evidence on the Scotch 
 Distilleries for 1798 and 1799" (p. 610), there is a quotation 
 from " Chaptal's Chemistry," showing that he was well ac- 
 quainted with the fact ; and also some experiments by M. 
 Zeigler, by which he ascertained that a drop of water took 89 
 seconds to evaporate from metal heated to 520 Fahrenheit,
 
 SURFACE OF BOILERS. 77 
 
 siderable difference in the heating of the water. 
 Added to this, the form of it prevents the full 
 effect of the heat being communicated to the 
 pipes ; for the extreme smallness of the water- 
 way prevents the rapid communication between 
 the various parts, and therefore the upright or 
 flow-pipe receives its principal supply of heat 
 from that portion of the boiler which is imme- 
 diately beneath where it is fixed, instead of that 
 equable communication of heat from all parts, 
 which is the ordinary process in boilers of good 
 proportions. There is likewise a probability that 
 steam would form in this boiler, which would still 
 farther interfere with the circulation of the water. 
 But were the water-way to be enlarged, all these 
 inconveniences and probable causes of failure 
 would proportionably decrease. All these causes 
 of inefficient action may not exist simultaneously, 
 yet they may act at different stages of the working 
 of the apparatus. But they all apply equally to every 
 boiler in which the rational limits of the surface, 
 relatively to the capacity or contents of the boiler, 
 have given place to wild chimeras and fanciful no- 
 tions, not based on sound principles of philosophy. 
 
 These remarks are exemplified in a boiler which 
 has received the name of the Trentham boiler, and 
 was at one time much lauded for its extraordinary 
 economy. In shape it is exactly like the Cornish 
 
 but that it only required one second when the metal was at 
 300 Fahrenheit. 
 
 In the recent experiments "On the Explosion of Steam 
 Boilers," by the Franklin Institution of Pennsylvania, a very 
 thick iron ladle was perforated with a number of small holes, 
 and then made red hot. When water was poured into this 
 ladle, none of it escaped through the holes, until the ladle 
 cooled down below redness ; and the quantity which after- 
 wards passed through increased with every reduction of the 
 temperature, the difference being quite appreciable even be- 
 tween the temperature of 60 and 80 Fahrenheit.
 
 78 SURFACE OF BOILERS. 
 
 boiler, fig. 20. But the theory was propounded that 
 the less water it contained the greater the effect 
 would be ; and in large boilers of eight or ten feet 
 long, the water-way was reduced all round the boiler 
 to about an inch and a quarter. Practical working 
 proved this to be a fallacy : and the much lauded 
 Trentham boiler has now resolved itself into the 
 ordinary Cornish boiler, which has been known 
 and extensively used for a century and a half. 
 
 (70.) It is obvious that the extent of surface 
 which a boiler ought to expose to the fire should 
 be proportional to the quantity of pipe that is 
 required to be heated by it ; and it is not difficult 
 to estimate these relative proportions with suffi- 
 cient accuracy, notwithstanding the various cir- 
 cumstances which modify the effect. 
 
 (71.) It has been proved by experiments that 
 four square feet of surface of an iron boiler will 
 evaporate one cubic foot of water per hour, when 
 exposed to the direct action of a tolerably strong 
 fire. This, however, requires free exposure to 
 the radiant heat of the fire; for the heat com- 
 municated to the flue surfaces is only equal to 
 one-third of that which is derived by the direct 
 action of the fire, acting upon the bottom or sides 
 of the boiler.* And it can be ascertained by 
 
 * Mr. Eobert Stephenson's experiments on this subject 
 clearly prove this proportion between the relative heating 
 of flue surface and boiler, surface to be correct. In his ex- 
 periments the flues consisted of tubes passing through the 
 water ; and he found that while six square feet of boiler sur- 
 face evaporated six gallons of water in 38 minutes, the flue 
 surface, consisting of 24 square feet, had, in the same time, 
 evaporated eight gallons. This will be found equal to evapo- 
 rating one cubic foot of water per hour, from 3 7 square feet 
 of the boiler surface exposed to the direct action of the fire ; 
 and the same quantity of water evaporated by 11-9 square 
 feet of the flue surface ; being in the proportion of 1 to 3. 
 (See Wood's Treatise on Bait-roads, 3rd edition, p. 524.) In the 
 best locomotive engines, the power of the boiler is equal to
 
 SURFACE OF BOILERS. 79 
 
 calculation, that the same extent of heating sur- 
 face which will evaporate one cubic foot of water 
 per hour from the mean temperature of 52, will 
 be sufficient to supply the requisite heat to 232 
 feet of pipe four inches diameter, when the tem- 
 perature of this pipe is to be kept at 140 above 
 
 one cubic foot of water evaporated per hour by 1'7 square 
 foot of boiler surface exposed to the direct action of the fire. 
 This appears to be almost the greatest effect that can be 
 produced at present. (Experiments on Great Western Railway, 
 1838.) In 1834, the Chevalier Pambour found the average 
 of the engines on the Liverpool and Manchester Kailway to 
 be one cubic foot of water evaporated per hour, from 2' 5 
 square feet of surface exposed to the direct action of the fire. 
 The flue surface in all these experiments was calculated as 
 equal to one-third that of the boiler surface. This high 
 evaporating power can only be maintained when a very 
 powerful draught is produced by mechanical means; and in 
 all these cases there is a very great waste of fuel. In the 
 original experiments of Watt, on steam boilers, he found that 
 the average of eight square feet of boiler surface was required 
 to evaporate one cubic foot of water per hour. This propor- 
 tion is still very generally used; and by employing a large 
 heating surface, economy of fuel is always produced. This is 
 strikingly exemplified in the Cornish engines, the boilers of 
 which have a larger surface than any others ; and the con- 
 sumption of fuel (per horse's power of the engine) throughout 
 Cornwall only averages one-fourth of that of the manufactur- 
 ing districts of England. The whole of this saving, however, 
 is not due to increased surface of the boilers ; a large propor- 
 tion of it is owing to the mode of using the steam expansively, 
 which is there carried to the extreme. (See Art 95.) 
 
 Pambour has questioned the accuracy of the estimate for 
 the proportionate effect of flue and boiler surfaces, which he 
 considers do not differ so much in heating power as is gene- 
 rally supposed ; but the doubt only applies to the boilers of 
 locomotive engines where a very powerful blast is applied, 
 and he agrees that, in other cases, the proportionate heating 
 power of 3 to 1 for the boiler surface and flue surface is nearly 
 correct. (Pambour's Treatise on Locomotive Engines, 2nd edition, 
 p. 269.) 
 
 Tredgold also gives the proportions as about three feet of 
 boiler surface exposed to the direct action of the fire, to 
 evaporate one cubic foot of water per hour, when the furnace 
 bars are one-fourth the area of the boiler surface.
 
 80 SURFACE OF BOILERS. 
 
 that of the surrounding air.* From this, then, it 
 appears that one square foot of boiler surface 
 exposed to the direct action of thvfire, or three square 
 feet of flue surface, will be sufficient in a hot-water 
 apparatus to supply the necessary heat to about 58 
 superficial feet of pipe ; or in round numbers, the 
 proportion may be stated as one foot of boiler to 
 50 feet of pipe. As this, however, is almost the 
 maximum quantity of pipe which can be heated, 
 or, in other words, the maximum effect which can 
 be produced without mechanical means of producing 
 draught, it is very desirable in all cases to allow 
 an increased surface of the boiler; bearing in 
 mind that not only will economy of fuel be thereby 
 produced, but the apparatus will be much easier 
 managed, and thus become more effective and cer- 
 tain in its operation. The following Table gives 
 the maximum quantity of pipe which a boiler will 
 heat, calculated by the above rule, and supposing 
 the best coals alone to be used : 
 
 Surface of Boiler 
 exposed to the 
 direct action of 
 the Fire. 
 
 4 square feet 
 
 TABLE I 
 
 4-in. Pipe. 
 
 will heat 200 feet, 
 300 
 
 I. 
 
 3-in. Pipe 
 
 or 266 fe 
 400 
 533 
 666 
 933 
 1333 
 
 et, 
 
 2-in. Pipe. 
 
 or 400 feet. 
 600 
 800 
 1000 
 1400 
 2000 
 
 8 . 
 
 400 
 
 
 10 . . . . 
 
 . . 500 
 
 14 . . . . 
 
 . . 700 
 
 20 . 
 
 1000 
 
 * It appears by calculation (Art. 99), that a four-inch pipe 
 will lose -851 of a degree of heat per minute, when the excess 
 of its temperature above the circumambient air is 125. If 
 therefore, this excess were 140, the loss per minute would be 
 953 of a degree of heat. Calculating, therefore, this loss to 
 be 57-18 degrees per hour, and estimating also (the latent 
 heat of steam being 1000) that the cubic foot, or 1728 cubic 
 inches of water evaporated, has received 1160 of heat, and 
 that one foot in length of a four-inch pipe contains 150'7 
 
 cubic inches of water, we shall obtain 1 ^ Q 2 ^ X g* 6 - = 232 feet, 
 as stated in the text.
 
 SURFACE OF BOILERS EXPOSED TO FIRE. 81 
 
 A small apparatus ought always to have more 
 surface of boiler, in proportion to the length of 
 pipe, than a larger one ; as the fire is less intense, 
 and burns to less advantage in a small than in a 
 larger furnace. The effect also depends greatly 
 upon the quality of the coal, the height of the 
 chimney, the rapidity of draught, the construction 
 of the furnace, and many other particulars ; and it 
 will always be found more economical, as regards 
 the consumption of fuel, to work with a larger 
 surface of boiler at a moderate heat, than to keep 
 the boiler at its maximum temperature.* 
 
 (72.) But beside all these causes that modify 
 the effect, there is another, that will alter the 
 proportions which may be employed. The data 
 from which the calculation of the boiler surface is 
 made, assume the difference to be 140 between 
 the temperature of the pipe and the air of the 
 room which is heated ; the pipe being 200, and 
 the air 60. But if this difference of temperature 
 be reduced, either by the air in the room being 
 higher, or by the apparatus being worked below 
 its maximum temperature, then, in either case, a 
 given surface of boiler will suffice for a greater 
 length of pipe. For if the difference of tempera- 
 ture between the water and the air be only 120 
 instead of 140, the same surface of boiler will 
 supply the requisite degree of heat to one-sixth 
 more pipe ; and if the difference be only 100, the 
 same boiler will supply above one-third more pipe 
 
 * A useful formula for calculating the effect of boilers and 
 furnaces in most common cases is as follows : 
 
 One square foot of boiler surface exposed to the direct action 
 of the fire, will boil 11 gallons of water, from 52 to 212 
 Fahrenheit per hour; or, in other words, it will add 160 of 
 heat to 11 gallons of water. Or the same surface will 
 evaporate 1 gallon of water per hour. 
 
 The area of the furnace bars should be about one-sixth 
 that of the boiler surface (see note to Art. 79). 
 
 (J
 
 82 SURFACE OF BOILERS EXPOSED TO FIRE. 
 
 than the quantity before stated. It will, there- 
 fore, sometimes occur in practice (where economy 
 in construction is the primary object), that the 
 quantity of pipe in proportion to a given surface of 
 boiler may be even increased beyond the amount 
 which is given in the preceding Table ; because, in 
 forcing-houses, for instance, the temperature of the 
 air will always be above 60 ; and in the warming 
 of churches, 'warehouses, or other large buildings, 
 the temperature of the water will generally be 
 considerably below 200 the pipe not being 
 required to be worked at its greatest intensity, 
 and, therefore, in both these instances, a larger 
 proportion of pipe may be applied to a given 
 sized boiler. It therefore follows, that although 
 a smaller boiler surface would really supply a 
 sufficient quantity of heat, under strict manage- 
 ment and constant attention, it will generally be 
 better not to reduce the size of the boiler below 
 what has here been stated ; for not only will the 
 apparatus need less attention, but also the required 
 temperature of the building can be thus much 
 sooner attained, as well as more easily continued. 
 A very good proportion, suitable for nearly every 
 purpose, is to allow about one foot of boiler sur- 
 face (calculated, as already described, Art. 71) to 
 about 40 superficial feet of pipe, or other radiating 
 surface, or about one-fifth more boiler surface than 
 the preceding Table states. 
 
 (73.) It may be desirable here to state what are 
 the peculiar characteristics of a good boiler for this 
 purpose, and how the qualifications of each par- 
 ticular shape are to be judged of. A minute detail 
 of the peculiarities of each of the various forms 
 would scarcely be worth the space such a descrip- 
 tion would require. The principal recommenda- 
 tions of a boiler are, that it shall expose the 
 largest surface to the fire in the smallest space ;
 
 SURFACE OF BOILERS EXPOSED TO FIRE. 83 
 
 that it shall effectually absorb the heat given out 
 from the fuel, so that as little heat as possible 
 shall escape up the chimney ; that it shall allow 
 free circulation of the water throughout its entire 
 extent; and that it shall not be liable to get out 
 of order, nor rapidly deteriorate by continued use. 
 The first of these qualifications is of itself a com- 
 pound question. We have seen (Art. 71) that any 
 surface exposed to the direct action of the fire, or, 
 in other words, to the radiant heat, receives three 
 times as much heat as a similar surface exposed 
 merely to the conducted heat, or that which is 
 afforded by the products of combustion after they 
 are thrown off from the burning fuel. Here, then, 
 is a very important distinction in boilers ; for as 
 radiant heat passes in straight lines in every 
 direction, it follows that the largest possible sur- 
 face ought to be exposed immediately over the 
 burning fuel, and that, too, at the least possible dis- 
 tance ; because the effect of radiant heat decreases 
 as the square of the distance between the radiating 
 and the recipient bodies (Art. 235). It is no re- 
 commendation of a boiler, therefore, to say that 
 it contains a certain number of square feet of 
 heating surface in a given space ; for unless this 
 surface can be acted upon by the radiant heat of 
 the furnace, a boiler of less than one-half the 
 superficial measurement, if judiciously contrived 
 for this object, may greatly exceed it in power.* 
 
 * The most remarkable illustration of the effect of exposing 
 a large surface to the direct action of the radiant heat is afforded 
 by the evidence given before the Committee of the House of 
 Commons, in 1798, on the Distillers of Scotland. Owing to 
 the mode of levying the duty at that time, it became an object 
 to work off the liquor from the still as rapidly as possible, 
 irrespective of the cost of the apparatus or the expenditure of 
 fuel. To such an extent was this carried, that the stills were 
 actually charged, the wash distilled, and the refuse discharged 
 about 520 times in 24 hours, or 2| minutes for each charge of 
 
 G 2
 
 84 ADVANTAGEOUS CONSTRUCTION OF BOILERS. 
 
 It is by not attending to this distinction that so 
 many people deceive themselves in the construc- 
 tion of boilers. In order to increase the surface 
 of the boiler as much as possible, they overlook 
 this important distinction whether the surface so 
 added is or is not exposed to the radiant heat of 
 the fire ; and they frequently contract the surface 
 exposed to the radiant heat in order to add a rather 
 larger surface somewhere else ; overlooking the 
 fact that, unless they can add three feet of surface 
 in place of each foot they subtract from the former, 
 the boiler will have less power than it had before. 
 In this way complicated forms of boilers have been 
 constructed, expensive in making, and inferior in 
 power, as well as in economy of fuel, to other more 
 simple forms. There are no boilers which possess 
 these advantages in a greater degree than the 
 boilers shown in figs. 18, 22, and 23 ; the former 
 being the arched boiler, which appears to accom- 
 plish all that can be desired as an efficient useful 
 boiler, and the latter is the bell- shaped boiler, now 
 comparatively little used, but still possessing great 
 merit as a most efficient form of construction. The 
 comparative disuse of this latter boiler probably 
 arises from the great difficulty of setting it properly, 
 and from being not so easily worked and kept clean 
 in the flues as some others. It is almost neces- 
 
 16 gallons. There is no other instance known in the least 
 approaching this extraordinary result, in which a small vessel 
 of the measurement of 40 gallons could distil a charge of 
 16 gallons of wash in If minutes, half a minute more being 
 required for charging the still, and the like time for discharg- 
 ing the refuse. This was accomplished by having the still 
 exceedingly flat, so that the largest possible surface was exposed 
 to the direct action of the radiant heat, and the flame acted 
 intensely upon the whole bottom surface of the still, and then 
 passed off at once into the chimney. The waste of fuel was of 
 course immense, but the rapidity of action was fully accom- 
 plished. Report on Scotch Distilleries, 1799, pp. 517-731.
 
 ADVANTAGEOUS CONSTRUCTION OP BOILERS. 85 
 
 sarily made of cast iron, as the form is difficult to 
 make of wrought iron. The part exposed to the 
 fire is covered with a series of ribs two inches deep, 
 and about one-fourth or three-eighths of an inch 
 thick, radiating from the crown of the arch, at an 
 average distance of two inches from each other. 
 These ribs, it is evident, must increase the surface 
 exposed to the fire to an enormous extent, and 
 that, too, precisely where the effect is by far the 
 greatest, being immediately over the burning fuel, 
 and receiving the whole of the radiant heat from 
 the fire.* 
 
 (74.) The second qualification, that the boiler 
 shall absorb the greatest quantity of heat from the 
 fuel, is partly dependent on the cause already 
 explained, and partly on the conducting power of 
 the metal itself. In this respect the boiler (fig. 18) 
 possesses an advantage over the other, in conse- 
 quence of being made of wrought iron, and there- 
 fore very much thinner. Were it made of copper, 
 its effect would be still further increased (see 
 Art. 245) ; but the greater expense of copper is an 
 objection. 
 
 * As early as the year 1828, the author adopted the plan of 
 increasing the heating surface of these boilers by means of a 
 great number of protuberances cast on the bottom, which 
 protuberances were one inch long and seven-eighths of an inch 
 diameter, and placed two inches apart from each other. Sub- 
 sequently these pins, or protuberances, were still further ex- 
 tended, so as to form continuous bars or ribs, radiating from 
 the centre of the boiler ; and they were made one inch and a 
 half deep, and three-eighths of an inch thick, and they were 
 then placed as well on the surface exposed to the water as that 
 exposed to the fire. This plan of increasing the heating surface 
 was, in the year 1835, patented by Mr. Sylvester, both for cast 
 and wrought-iron boilers ; and in 1841, Mr. C. W. Williams 
 patented the same plan for wrought-iron steam boilers, the pins 
 being, by his plan, screwed into the substance of the plate, 
 instead of being formed by rolling, as proposed by Mr. Sylvester. 
 
 It has been generally supposed that all sharp protuberances
 
 86 INJURIES TO BOILERS. 
 
 (75.) The third recommendation of a boiler, 
 that it shall allow of a free circulation of the water, 
 is entirely dependent on its form; and on this 
 subject some remarks have already been made 
 (Art. 68). And the last test of a good boiler, that 
 it shall not be liable to get out of order, nor 
 rapidly deteriorate, is one that depends partly on 
 the goodness of the materials and workmanship, and 
 partly on the mode of producing the combustion 
 of the fuel. Some very important chemical effects 
 appear to result occasionally, both from the fuel 
 employed as well as from the method of combustion. 
 The effects on copper are the most destructive ; 
 and instances have occurred where the bottoms of 
 copper boilers have separated entirely from the 
 sides, as though cut through with a chisel, just at 
 the part where the principal action of the .fire 
 occurs; and others have become entirely riddled 
 throughout the surface exposed to the fire. These 
 are very rare occurrences, and the cause appears 
 somewhat obscure ; but the subject will be better 
 explained in a subsequent chapter (Chapter VI., 
 Part II.). Generally speaking, a wrought-iron 
 
 inside a boiler caused a more rapid ebullition of the water than 
 a flat surface ; and the author in 1828 originally adopted this 
 mode of increasing the water-surface as well as the fire-sur- 
 face ; and the plan was afterwards followed both by Mr. Syl- 
 vester and Mr. Williams in their patents. Subsequent experi- 
 ments, however, have convinced the author that it is 
 unnecessary to increase the water-surface by these means. 
 In particular Mr. Josiah Parkes's experiments in 1840 (vide 
 his published Eeport), on Mr. M. A. Perkins' patent steam- 
 boiler, proved that, owing to the great conducting power of 
 water, the whole of the heat generated by 117 superficial feet 
 of iron exposed to the fire was abstracted by 44 superficial feet 
 exposed to the water ; or that the water will absorb the heat 
 at least 2 6 times as fast from the iron as the iron can receive 
 it from the fire; and therefore it appears the internal pro- 
 tuberances on the water-surface of a boiler are unnecessary. 
 See also Art. 251.
 
 INJURIES TO BOILERS. 87 
 
 boiler will heat quicker, and with less expenditure 
 of fuel, than a cast-iron boiler : it will also be less 
 liable to accidents, as cast-iron boilers occasionally 
 crack, particularly if they contain sharp angles in 
 their construction, or if they are so formed that 
 the fire acts unequally on them, and expands 
 one part more than another. From these defects 
 wrought-iron boilers are exempt. But, on the 
 contrary, wrought iron will corrode much more 
 rapidly than cast iron ; and in very damp situa- 
 tions, where the stoke-hole or boiler-house is some- 
 times left for half the year some inches deep in 
 water, a wrought-iron boiler would be rapidly 
 corroded, when a cast-iron one would be compa- 
 ratively uninjured. 
 
 Very destructive effects have sometimes been 
 produced by using fuel strongly impregnated with 
 sulphur. The effect produced by such fuel on the 
 durability of boilers is very rapid. Boilers heated 
 with such fuel will oftentimes be destroyed in one- 
 fourth the time that they would have lasted, had 
 a better fuel, free from sulphur, been employed. 
 With a sulphurous coal the plates are very rapidly 
 destroyed, and still more the rivet heads, which are 
 sometimes entirely eaten away, leaving the boiler 
 in a leaky and dangerous state.
 
 88 
 
 CHAPTER V. 
 
 On the Construction of Furnaces Combustion dependent on 
 size of Furnace-bars Furnace-doors, and other Parts of 
 Furnace Proportionate Area of Furnace-bars to the Fuel 
 consumed Confining the Heat within the Furnace Direc- 
 tions for building the Furnace for different Boilers Advan- 
 tage of large Furnaces Modes of Firing Size of Chimneys. 
 
 (76.) THE construction of the furnace for a hot- 
 water apparatus is a matter which requires con- 
 siderable care; for although, from the small size 
 of the boilers generally used, the furnaces are by no 
 means difficult to construct, it is a very common 
 fault in building them to allow of such a very 
 easy exit for the flame and heated gaseous matter, 
 that a large portion of the heat passes up the 
 chimney, instead of being received by the water 
 in the boiler. This arises principally from the 
 shortness of the flues in these boilers, in com- 
 parison with those of steam-engine boilers ; and, 
 in setting boilers for hot- water apparatus, it there- 
 fore requires great caution to prevent an unneces- 
 sary waste of fuel by erroneous principles in con- 
 structing the furnaces. 
 
 In giving some general instructions on the sub- 
 ject of furnaces for hot-water apparatus, it is not 
 intended minutely to describe the proper furnace 
 for each different form of boiler ; but the plan of 
 building the furnaces for three or four different 
 forms of boilers will be given, and the application 
 of the principles to other forms must be left to the 
 discretion of those who erect them.
 
 CONSTRUCTION OF FURNACES. 89 
 
 (77.) The rate of combustion of the fuel in a 
 furnace depends very little upon the total size of 
 the furnace, but chiefly on the proportionate size 
 of the furnace-bars. A furnace which possesses, 
 for instance, an area of 12 square feet would not 
 necessarily burn a much larger quantity of fuel 
 per hour than one that had only an area of eight 
 square feet, provided the area of the furnace-bars 
 was the same in both cases, and that no more air 
 was admitted to the former than to the latter. 
 But, by building the furnace of considerable dimen- 
 sions, and with a moderately small area of fire- 
 bars, the fuel can be made to burn for a much 
 longer period without attention or renewal ; and 
 this is a very important object for this description 
 of apparatus. For, so intense a fire is not required 
 as is the case with a steam-boiler. A very small 
 degree of attention is necessary with a furnace of a 
 hot-water apparatus, which, when well constructed, 
 ought to burn for ten or twelve hours without 
 replenishing the fuel.* 
 
 (78.) In all cases, a good and perfectly tight 
 furnace-door is requisite; for, if the door does 
 not fit accurately, a large quantity of cold air 
 enters, and passes between the fuel and the 
 bottom of the boiler, and cools the boiler to a 
 considerable extent.f The furnace-door should 
 always be double ; J and also a door to the ash- 
 pit should be used, in order to shut off the excess 
 
 * In some steam boilers, particularly in the Cornish boilers, 
 the fuel is burned with slow combustion ; but the furnaces and 
 boilers are very large in proportion to the work done by them, 
 and great economy of fuel results from this plan of heating 
 them (see Chapter VI., Part II.). 
 
 f In a subsequent chapter, the combustion of smoke will be 
 discussed, and it will then be shown that the admission of air 
 at or near the furnace-door is sometimes desirable, but only 
 in particular stages of the combustion. 
 
 J Count Eumford first introduced these double furnace- 
 doors, of which many modifications have been since adopted.
 
 90 AREA OF THE FURNACE-BARS. 
 
 of air below the furnace-bars when the fire is 
 required to burn slowly for a great length of time. 
 Immediately within the furnace-door there should 
 be a dumb-plate ; and the larger this is the better, 
 provided it does not project the furnace-bars too 
 far back, so as to cause the most active part of 
 the combustion to take place at the posterior part 
 of the furnace, instead of immediately under the 
 boiler. The use of a large dumb-plate in front of 
 the furnace-bars is to allow the fuel to be gradually 
 coked, by placing it first on this dumb-plate, and 
 then, when well heated, pushing it backward upon 
 the furnace-bars, where it enters into active com- 
 bustion, and then a fresh charge of fuel is to be 
 again laid on the dumb-plate, in order to undergo 
 the same operation. By this plan of coking the 
 coals on the dumb-plate, nearly all the smoke from 
 the furnace may be consumed; by which a con- 
 siderable saving of fuel will be effected,* and a 
 great nuisance prevented. 
 
 (79.) The size of the fire-grate, or furnace-bars, 
 must be regulated by the quantity of pipe or 
 other heating surface which the apparatus con- 
 tains. The quantity of heat given off by a cer- 
 tain extent of iron pipe, or other heated surface, 
 can be exactly ascertained, and will be shown in 
 the next chapter. From the data there given, 
 we learn the quantity of coals required to be 
 burned per hour in order to maintain the re- 
 quired temperature. Having already given (Art. 
 
 * See Chapter VI., Part II., on the "Combustion of 
 Smoke," where it is shown that nearly 40 per cent, is saved 
 by the combustion of the smoke. Those who wish to learn the 
 endless forms which may be given to furnaces may see 
 several hundred different forms and arrangements described in 
 the various volumes of the following periodicals, namely : 
 The Technical Repository, The Eepertory of Arts and Patent 
 Inventions, The Mechanics' Magazine, The Quarterly Journal 
 of Science The Reports of the British Scientific Association, &c.
 
 AREA OF THE FURNACE-BARS. 91 
 
 71) the extent of boiler surface required to heat 
 a given quantity of pipe, it will be desirable 
 now to show the area of the furnace-bars which 
 will be required. It has already been stated 
 (Art. 72) that the extent of boiler surface ex- 
 posed to the fire may with advantage be increased 
 beyond the dimensions already given ; and that 
 economy of fuel will generally result from this 
 increased surface. But the quantity of fuel that 
 is burned ought not to be also increased in the 
 same way ; and therefore the size of the furnace- 
 bars, which alone regulates the quantity of fuel con- 
 sumed, should be proportioned rather to the quan- 
 tity of surface which radiates heat into the building, 
 instead of bearing an exact ratio to the surface of 
 the boiler. 
 
 With ordinary furnace-bars, the spaces for the 
 admission of air will generally vary from one- 
 fourth to one-third of the total area of the space 
 occupied by the furnace-bars. In such cases one 
 square foot of furnace-bars will be sufficient to 
 burn about 10 Ibs, or 11 Ibs. of coal per hour, 
 under ordinary circumstances ; * and on this cal- 
 
 * The consumption of fuel, on any given area of furnace- 
 bars must depend upon the rapidity of the draught. In loco- 
 motive engines, with an artificial blast from the steam, the 
 consumption of fuel is about 80 Ibs. from each square foot of 
 fire-grate per hour. In some furnaces the consumption is not 
 more than 6 Ibs. per square foot, or about T ^ of the locomotive- 
 engine furnace ; but the quantity given in the text is a mean 
 rate. Mr. Andrew Murray (Minutes of Institution of Civil En- 
 gineers, June, 1844) estimates the average consumption in 
 steam-engine furnaces at 13 Ibs. of coal per square foot of 
 furnace-bars, and that 150 cubic feet of air should pass through 
 the furnace for each pound of coal consumed in order to pro- 
 duce perfect combustion. Taking Dr. Ure's estimated velocity 
 of 36 feet per second as the average rate at which the air 
 passes through a furnace, Mr. Murray estimates the size of the 
 opening over the bridge of the furnace ought to be 26 square 
 inches for each square foot of furnace bars. The temperature 
 of an ordinary furnace is assumed to be about 1000 of Fahren-
 
 92 AREA OF THE FURXACE-BARS. 
 
 culation the following Table has been con- 
 structed : 
 
 TABLE III. 
 
 Area of Bars. 4-in. Pipe. 3-in. Pipe. 2-ln. Pipe. 
 
 75 square inches will supply 150 feet, or 200 feet, or 300 feet. 
 100 200 266 400 
 
 150 300. 400 600 
 
 200 
 250 
 300 
 400 
 500 
 
 400 533 800 
 
 500 666 1000 
 
 600 800 1200 
 
 800 1066 1600 
 
 1000 , 1333 , 2000 
 
 Thus, suppose there are 600 feet of pipe, four 
 inches in diameter, in an apparatus ; then the 
 area of the bars should be 300 square inches, so 
 that 14 inches in width and 22 inches in length 
 will give the requisite quantity of surface.* 
 
 heit, and at this temperature the gases passing through it 
 would be expanded to three times their original bulk; and 
 these proportions will allow sufficient air to pass through the 
 furnace to compensate for that portion which is not completely 
 consumed. Tredgold, in his calculations, assumes the tem- 
 perature of an average furnace at 800 Fahrenheit. See also 
 Art. 397 and the notes appended thereto. 
 
 * The proportions deducible from the above Table, and 
 those given Art. 71, for ascertaining the boiler surface, are 
 very different from those generally used in steam-engine boilers. 
 It will be observed that, by the rules here given, the area of 
 the furnace-bars is about one-sixth of the area of the boiler- 
 surface exposed to the direct action of the fire, whereas in steam 
 boilers the flue and boiler surfaces conjointly are usually in 
 proportion to the surface of the furnace-bars as 11 to 1, and 
 sometimes even as 18 to 1 (British Scientific Reports for 1842, 
 p. 107). When this latter calculation, however, is reduced to 
 the same standard as the other, viz. three feet of flue surface 
 being equal to one foot of boiler surface exposed to the radiant 
 heat, the difference will not be near so great as it here appears. 
 And it must also be remarked that in large boilers the pro- 
 portions must necessarily differ from those of the very small 
 boilers required for a hot-water apparatus ; for the effect of 
 radiant heat decreases as the square of the distance between 
 the recipient surface and the hot body ; and therefore it is very 
 easy to see how a considerable difference may arise between 
 surfaces placed so differently in this respect as they necessarily 
 must be in large and in small boilers.
 
 AREA OF THE FURNACE-BARS. 93 
 
 When it is required to obtain the greatest heat 
 in the shortest time, the area of the bars should 
 be proportionably increased, so that a larger fire 
 may be produced; and, on the contrary, when 
 the object is to obtain slow combustion of the fuel, 
 and when the rapidity with which the apparatus 
 becomes heated is of little or no consequence, then 
 the area of the bars may be reduced. The best 
 method, however, will generally be found in using 
 a sufficiently large surface of fire-bars for the 
 maximum effect required, and to regulate the 
 draught by means of an ash-pit door and a 
 damper in the chimney; by these means almost 
 any required rate of combustion can be obtained, 
 with any common degree of care.* 
 
 (80.) When the size of the furnace will allow 
 of it, a portion of brickwork should extend at the 
 
 * When a rapid draught and quick combustion are required, 
 the furnace-bars may very advantageously be made very narrow 
 and deep, so as to allow a larger proportionate space for the 
 entrance of the air. Instead, therefore, of using furnace-bars 
 one and a half or one and three-quarters of an inch wide, with 
 half an inch air-space between the bars, they may be made 
 about three-eighths or half an inch in width, and about four 
 and a half or five inches deep, tapering at the lower edge to 
 about one-eighth of an inch, and made with shoulders, as usual, 
 to allow about half-inch air-spaces. Bars of this kind will 
 have many advantages in particular cases. They will allow 
 more than twice the quantity of air to pass through that the 
 other bars will do, and therefore twice the quantity of coal can 
 be burned on each square foot of the bars ; and they will last 
 longer than bars of the ordinary construction. The author, at 
 the latter end of 1842, suggested the use of these bars in loco- 
 motive engines, which is the most severe test they could be 
 put to, and the result proved completely successful. Owing 
 to the extreme thinness of the bars, the air passing between 
 them keeps them always cool, which is impossible if the bars 
 much exceed this thickness. The great depth of the bar gives 
 the necessary stiffness ; and the result of nearly twelve months' 
 trial, and with nearly twenty locomotive engines, was a very 
 great increase in the durability of the furnace-bars, in addition 
 to the obvious advantage of admitting much more air into the
 
 94 CONSTRUCTION OF FURNACE-FLUES. 
 
 back of the furnace-bars, and level with the bars, 
 so as to make a dead-plate behind the bar as 
 well as in the front, which makes the furnace 
 hold more fuel without actually increasing the 
 consumption. 
 
 (81.) It is a matter of very great importance, 
 that the heat should be confined within the fur- 
 nace as much as possible, by contracting the 
 farther end of it, at the part called the throat, so 
 as to allow only a small space for the smoke and 
 inflamed gases to pass out. The neglect of this 
 causes an enormous waste of fuel; for, in conse- 
 quence of the shortness of the flues of these 
 boilers, the heated gaseous matter passes too 
 readily from the boiler, and escapes through the 
 chimney at a very high temperature. The only 
 entrance for the air should be through the bars of 
 the grate,* and the heated gaseous matter will 
 then pass directly upwards to the bottom of the 
 boiler, and should be there detained as long as 
 possible by the contraction at the throat of the 
 
 furnace. Some of these bars, after having been used for ten 
 months, and with which the engines ran nearly 20,000 miles, 
 were still perfectly good, after having done nearly four times 
 the work of ordinary bars. The best size for this purpose is 
 five and a half inches deep by half an inch thick, tapered to a 
 quarter of an inch. In furnaces which have less intense heat 
 than a locomotive engine, bars of four or four and a half inches 
 deep are quite sufficient. 
 
 When the old form of furnace-bars is used, and they are 
 required to bear a very intense heat, their durability is in- 
 creased by making a longitudinal groove in the upper surface 
 about three-eighths of an inch deep. This groove becomes 
 filled with ashes, which, being a slow conductor of heat, pre- 
 serves the bars from the intense heat of the fire. 
 
 * These observations apply exclusively to the small furnaces 
 and boilers used for hot-water apparatus, and not to large 
 furnaces for steam-boilers or for other purposes. In the 
 latter, air may very advantageously be introduced at or near 
 the furnace-door, or in many other ways, as will be shown in 
 the chapter on the " Combustion of Smoke." Even in these
 
 CONSTRUCTION' OF FURXACE-FLUES. 
 
 95 
 
 FIG. 31. 
 
 furnace ; * and if this part of the furnace be pro- 
 perly constructed (by not making the throat too 
 near the crown of the boiler, and making it suffi- 
 ciently small in proportion to the total quantity 
 of gaseous matter required to pass through it), a 
 reverberatory action of the flame and heated 
 gases will take place, by which a far greater 
 effect will be produced than if too easy an exit 
 were allowed into the flues and chimney. 
 
 (82.) A furnace constructed on this plan is 
 shown in fig. 
 31, 32, and 33, 
 which is the 
 mode in which 
 many thou- 
 sands of furn- 
 aces have been 
 constructed 
 and applied to 
 the boiler 
 shown in fig. 
 18; this plan 
 having been 
 recommended 
 by the author 
 many years 
 ago, and used 
 with the most 
 uniform suc- 
 cess, f The way 
 
 FRONT VIEW. 
 
 to construct this furnace is as 
 
 small furnaces, a limited quantity of air might in certain stages 
 of the combustion be advantageously introduced ; but this would 
 require so much more attention than is usually given, or indeed 
 required, for an apparatus of this kind, that the rule given 
 in the text will be found most advisable for ordinary practice. 
 
 * See also note to Article 79, ante. 
 
 f This plan of setting boilers was first used by the author 
 in 1830, and was published subsequently, by consent, in the 
 Horticultural Transactions.
 
 96 
 
 CONSTRUCTION OF FURNACE-FLUES. 
 
 follows. After building up the foundation of the 
 boiler to the proper height, the bars are to be placed 
 so that the front of the bars shall lie even with the 
 front of the boiler, and the upper surface of the bars 
 shall be level with the bottom of the boiler. The 
 bars will generally be about two-thirds the length 
 of the boiler; the remainder of the length of 
 the furnace being made up with brickwork be- 
 yond the bars towards the back end of the boiler. 
 In front of the bars should come the dead-plate, 
 about 9 inches wide ; and immediately in front of 
 this dead-plate should come the furnace-door: 
 the bottom of the furnace-door, the dead-plate, 
 the furnace-bars, and the brickwork beyond the 
 furnace-bars being all exactly on the same level. 
 The distance between the front of the boiler and 
 
 FIG. 32. 
 
 FIG. 33. 
 
 BACK VIEW. 
 
 PLAN. 
 
 the furnace-door will, by this arrangement, be 
 just nine inches ; and this space is made up with 
 the brickwork, which forms the general front of 
 the whole furnace. In this brickwork are placed 
 three soot-hole doors, to clean out the three flues. 
 Two of these doors are shown in fig. 31; the
 
 CONSTRUCTION OP FURNACE-FLUES. 97 
 
 other one is supposed to be removed, to show the 
 inside of the flue. At the back of the boiler 
 are placed two fire-lumps, shown in fig. 32, and 
 which are made to fit the size of the boiler. 
 When these two fire-lumps are placed as shown 
 in fig. 32, they leave an opening between them of 
 from 3} to 4| inches, according to the size of the 
 boiler. This opening should come, as nearly as 
 may be, to the centre of the arch of the boiler: 
 and it is the only passage for the flame and smoke 
 to escape into the flues, which here divide to the 
 right and left hand, passing along the sides of the 
 boiler, and following the direction of the arrows, 
 fig. 31. Two cast-iron plates are built into the 
 brickwork, in the position shown by G, fig. 31, to 
 divide the lower from the upper flue. These flue- 
 plates do not come to the front of the boiler by 
 from four to five inches, thus leaving a passage 
 from the lower into the upper flue, and from the 
 latter into the chimney. The whole of these flues, 
 of which there is one on each side of the boiler 
 and one on the top, are to be made as deep as ever 
 the boiler will allow, and the brickwork should 
 stand off from the boiler about 4i inches, forming v 
 the width of the flues. By this arrangement it will 
 be perceived, that nearly the power of a reverbera- 
 tory furnace is obtained. The upper fire-lump, 
 shown in fig. 32, partly stops the flame, and retains 
 it as long as possible in contact with the inner arch 
 of the boiler; and on this mainly depends the 
 economy and efficiency of this plan of setting these 
 boilers. The flame and smoke then pass between 
 the two fire-lumps, dividing right and left into the 
 two lower flues, and then in the direction of the 
 arrows, fig. 31, into the two upper flues, and from 
 thence passing into the top flue of the boiler, 
 which latter should be nearly as large as the 
 other two together. A damper must be placed 
 
 H
 
 98 CONSTRUCTION OF FURNACES. 
 
 in the chimney in such a position as to be easily 
 got at. 
 
 (83.) This plan of setting arched boilers is per- 
 fectly available for all boilers, from eighteen inches 
 long up to about six feet long ; for boilers beyond 
 that length, it is advisable somewhat to modify the 
 plan, by placing a fire-lump within the inner arch, 
 so as to form a bridge, which bridge should be 
 formed to fit the arch of the boiler, but leaving 
 a space of about five inches in depth, and the width 
 of the arch, between the crown of the arch and the 
 top of the fire-lump. When this bridge is used, 
 the bottom fire-lump, already described, is not 
 required. This latter mode of setting is only 
 suitable for such boilers as are six feet long and 
 upwards. In this case the bridge is best placed at 
 the distance of about five feet from the front end 
 of the boiler. 
 
 (84.) The boiler, figs. 22 and 23, requires nearly 
 the same arrangement; but in this boiler the 
 aperture for the escape of the flame and smoke is 
 generally made a part of the boiler itself. This 
 opening is also somewhat lower down towards 
 the level of the furnace-bars, and the boiler being 
 circular, the flue generally winds round the boiler, 
 instead of passing separately on the right hand 
 and on the left. The boiler, fig. 21, may be set in 
 the same kind of furnace as the boiler, fig. 18. If 
 the two legs or protuberances at the bottom be 
 very short and close together, the fire may be 
 made to act upon the whole under-side of the 
 boiler (the bars being fixed at some distance 
 below), and the flame returned through a flue 
 along the top. 
 
 (80.) The boiler, fig. 20, may be set in two 
 different ways. When the inside tube is suffi- 
 ciently large, it is best to place the fire inside 
 this tube, the furnace-bars being placed at about
 
 CONICAL BOILERS. 
 
 one-third the diameter of the tube from the 
 bottom. In this case the action of the furnace 
 becomes very similar to that already described 
 for the boiler, fig. 18 ; except that the water-way 
 is continued below as well as above the fire. The 
 throat of the furnace must be contracted, as 
 already described for fig. 18; but in this case the 
 flues must first pass directly under the boiler, and 
 then pass along the two sides and top. 
 
 When this boiler, fig. 20, is very small, the fire 
 must be made entirely below the boiler ; and the 
 boiler is then best made of an oval or flattened 
 shape, both externally and in the tube. The 
 flame, in this case, passes from the surface below, 
 first through the tube, and then returns over the 
 top of the boiler, and from thence the heated gases 
 escape into the chimney. Or still another plan 
 may be used, by making Fl(J 
 
 the fire act first on the 
 bottom of the boiler, then 
 return to the front through 
 the central flue, and then 
 divide right and left on the 
 outside of the boiler, then 
 so on to the chimney as in 
 fig. 33A. 
 
 (86.) The boiler, fig. 24, as originally con- 
 structed, had no external flue. It was chiefly 
 used for very small apparatus, and it possessed 
 the advantage, when a very slow draught was 
 used (somewhat similar to that of the Arnott's 
 stoves), of holding sufficient fuel to allow of the 
 fire burning for a long time without attention, 
 which is generally difficult to accomplish with 
 very small boilers. The ingenious inventor of 
 this boiler (Mr. Eogers) preferred this plan, 
 though many new modifications of the boiler have 
 been introduced. It is now frequently used with 
 
 ii 2
 
 100 
 
 MODES OF FIRING. 
 
 an external flue. The temperature of this boiler 
 is somewhat more difficult to regulate than that 
 of the arched boiler , as the more the fuel burns 
 away, the greater the heat becomes, in consequence 
 of a larger surface of the boiler being then ex- 
 posed to the radiant heat, and also because the 
 fuel burns quicker, in consequence of the air meet- 
 ing less obstruction in passing through it. In this 
 case, the greatest heat is produced when about 
 two-thirds of the fuel has burnt away. When 
 the boiler has an external flue, the best mode of 
 setting is to make the flue proceed from openings 
 of about three inches by six inches, left at the 
 bottom of the boiler, and leaving a free space for 
 the flue, around the boiler, of two and a half or 
 three inches, or thereabouts. The draught of air 
 meeting less obstruction in passing through the 
 external flue than by passing through the large 
 body of fuel contained in the body of the boiler, 
 
 the whole exter- 
 FIG. 35. nal surface be- 
 
 comes available 
 for receiving heat 
 from the fire, in- 
 stead of being 
 entirely useless, 
 as in the other 
 mode of setting. 
 Of course, the 
 same sized boiler 
 will by this ar- 
 rangement heat a 
 
 larger quantity of pipe. Figs. 34 and 35 show 
 this mode of setting these boilers. These boilers, 
 however, will, under any form, expose but little 
 surface to the radiant heat of the fire, and the 
 external surface will scarcely exceed the flue sur- 
 face of the arch-boiler, in its power of absorbing 
 
 FIG. 34.
 
 MODES OF FIRING. 101 
 
 heat. This flue surface, we have already seen, 
 only possesses one-third the absorbent power 
 which those surfaces have that are exposed to the 
 direct action of the radiant heat. The fire of this 
 boiler, however, is not difficult to manage, and 
 burns with but little attention. 
 
 (87.) In the boiler, fig. 26, there is necessarily 
 a considerable waste of fuel, in consequence of 
 the flame escaping immediately into the chimney 
 without passing through any flues, this form of 
 boiler not admitting of any kind of flues being 
 used. The flame passes between the several pipes 
 which form the boiler, and of course can only act 
 upon their under side. If the draught be rapid, 
 a partial vacuum must be formed on the upper sides 
 of the pipes, the flame passing in straight lines up- 
 wards ; and, therefore, a loss of heat by radiation 
 would take place from the upper side of the pipes 
 which form this boiler. The boiler, however, heats 
 rapidly, as the consumption of fuel in the furnace, 
 owing to the rapid draught, is very considerable. 
 
 (88.) The advantage of making the furnace to 
 contain a large quantity of fuel has already been 
 mentioned. But, independent of the smaller de- 
 gree of attention required, when sufficient fuel to 
 last for many hours is supplied at once, it is found 
 practically that great economy results from this 
 plan. From experiments made on this subject 
 with steam-engine furnaces, it appears that the 
 increased consumption of fuel always bears a direct 
 proportion to the frequency with which it is 
 supplied to the furnace ; and that in the experi- 
 ments in question the greatest economy resulted 
 when the fuel was supplied only once a day.* 
 
 * Mr. Josiah Parkes on " The Evaporation of Water from 
 Steam Boilers," in the Transactions of the Institution of Civil 
 Engineers for 1838. This result, however, was obtained by 
 a peculiar kind of furnace, in which air was admitted at the 
 bridge as well as through the fire-bars.
 
 102 MODES OF FIRING. 
 
 When this plan is followed, the combustion is less 
 intense than with more frequent firing ; and, 
 therefore, a larger boiler surface is always required. 
 Care also should be taken to prevent the ingress of 
 an undue quantity of air through the ash-pit, when 
 the fuel burns away and the furnace-bars thus be- 
 come unequally covered ; for, in this case, a large 
 quantity of cold air will rush in and cool the boiler. 
 
 (89.) The rate of combustion materially de- 
 pends upon the thickness of fuel on the furnace- 
 bars, and on its compact or open state, as illus- 
 trated in the two cases of small coal and of large 
 well-burned coke. The quantity of air passing 
 through the fire-grate or bars must be very different 
 in these two cases, and the combustion wholly 
 depends upon the quantity of air admitted to the 
 fuel. For unless a sufficient quantity of air be 
 admitted to convert the whole of the carbon into car- 
 bonic acid gas, it will escape in the form of carbonic 
 oxide, and a loss of effect will thereby arise (see 
 Chap. VI., Part II., on the Combustion of Smoke). 
 
 (90.) The greatest economy of fuel is produced 
 when the fires are kept thin and bright ; the coal 
 well coked, by means of a large dumb-plate in 
 the front of the furnace, and the damper kept as 
 close as possible consistent with allowing a suffi- 
 cient draught. The Cornish engines, so cele- 
 brated for their economy of fuel, are thus worked. 
 The thinner the fire, the less is the probability of 
 the formation of carbonic oxide, which always 
 causes a loss of heat. When thick fires are 
 used, this loss is frequently very considerable^ 
 unless (as in Mr. Parkes's experiments already 
 mentioned) air is supplied above the fuel as well 
 as through the furnace-bars.* In the small fur- 
 
 * In locomotive engines, the fires are frequently as much as 
 17 inches thick ; and the quantity of carbonic oxide formed in
 
 SIZE OF CHIMNEYS. 103 
 
 nace of a hot-water apparatus, it is frequently 
 difficult, if not impossible, to adopt this plan of 
 using a dumb-plate sufficiently large to coke the 
 whole of the fuel which is used ; but the principle 
 should be borne in mind in all cases, and applied 
 as far as circumstances will permit. The theory 
 of combustion will be given in the chapter on the 
 Combustion of Smoke. 
 
 (91.) It may, perhaps, not be amiss here to give 
 some rules for the proper size of chimne} T s. Very 
 elaborate rules have been given for this purpose 
 by different authors, and the most extraordinary 
 differences exist between them; their calculations 
 giving results totally at variance with each other. 
 But the practical rules are very simple. Mr. Mur- 
 ray* estimates the area of the chimney should be 
 about 18 square inches for a boiler consuming 
 12 Ibs. of coal per hour. Mr. Armstrong estimates 
 the area at 20 square inches for the same consump- 
 tion of coal.f Tredgold'sJ calculations give an 
 area of about 14 square inches for the same quan- 
 tity of coal consumed per hour, when the boiler 
 is worked at a low temperature, and very con- 
 siderably less than this when the temperature is 
 high. Some of these calculations, however, are 
 
 consequence of this great thickness is very considerable, and 
 the loss of heat enormous. The thinner the fire, the more 
 perfect must be the combustion. Carbonic oxide is formed by 
 the carbonic acid (which is the result of perfect combustion) 
 passing through the red-hot coke, by which it imbibes an 
 additional quantity of carbon, and is converted into carbonic 
 oxide. Ou all the carbonic acid that undergoes this change 
 there arises a loss of one-half the heat derived from its ori- 
 ginal conversion. The various methods of admitting air at the 
 bridge, and at other places above the fuel, are all intended to 
 obviate the loss ; reconverting the carbonic oxide into car- 
 bonic acid, by supplying it with an additional dose of oxygen. 
 
 * Minutes of Institution of Civil Engineers, June, 1844. 
 
 t Armstrong on " Steam-boilers," p. 80. 
 
 J Tredgold on " Warming and Ventilating," &c., p. 114.
 
 104 SIZE OF CHIMXEYS. 
 
 for much higher chimneys than are ever used for 
 the purpose that we are here considering, and the 
 lower the chimney the larger the area ought to be. 
 But, from what has been stated, sufficient may be 
 gathered to estimate the size of chimneys for such 
 common purposes as are here supposed to be 
 required.* 
 
 * Those who wish to investigate this subject further may 
 refer to PecleCs Traite de la Chaleur, p. 79 et seq. Wyman " On 
 Ventilation," &c., p. 392 et seq. ; Sylvester " On Chimneys " ; 
 Rees' " Encyclopedia, and Annals of Philosophy," &c. ; 
 Gilbert " On Ventilation," &c. ; Quarterly Journal of Science 
 for 1822; and Tredgold "On Warming and Ventilating," 
 p. 114 et seq. ; and Dr. Ure, Pliil. Transactions, 1836.
 
 105 
 
 CHAPTER VI. 
 
 ESTIMATE OP THE HEATIXG SURFACES REQUIRED 
 TO WARM ANY DESCRIPTION OP BUILDIXGS. 
 
 Heat by Combustion Quantity of Heat from Coal Specific 
 Heat of Air and Water Measure of Effect for Heated Iron 
 Pipe Cooling Power of Glass Effect of Vapour Quantity 
 of Pipe required to warm a given Space Time required to 
 heat a Building Facile Mode of calculating the Quantity 
 of Pipe required in any Building Quantity of Coal con- 
 sumed. 
 
 (92.) Having in the preceding chapters investi- 
 gated the fundamental principles of the hot-water 
 apparatus, we proceed to consider some particulars 
 which are necessary to be known in order to apply 
 the preceding remarks, and correctly to apportion 
 the various parts of the apparatus, and calculate 
 the effects which will be produced under various 
 circumstances. 
 
 Very erroneous notions are entertained by many 
 persons as to the absolute quantity of heat con- 
 tained in different substances. This subject has 
 already been mentioned ; and in the present chapter 
 we shall have occasion to apply this law of specific 
 heat in several important calculations. 
 
 (93.) It will, however, be desirable first to ascer- 
 tain the quantity of heat which can be obtained 
 by the decomposition of combustible materials by 
 fire; for in this also, it may be observed, very 
 erroneous notions prevail. The quantity of heat 
 obtainable by the combustion of any substance is
 
 106 HEATING EFFECT OF COAL. 
 
 not, as many persons appear to consider, illimitable, 
 but it is as fixed and determinate as any other of 
 the laws of heat. The amount of heat by com- 
 bustion depends on the chemical composition of 
 the particular substance ; but although this heat 
 may be either wasted or advantageously applied, 
 according as the apparatus used for its combustion 
 is imperfect or otherwise, still it must be remem- 
 bered there is a maximum effect, which has been 
 accurately ascertained, and which cannot be ex- 
 ceeded in any form of apparatus : though in no 
 apparatus yet invented has it been possible abso- 
 lutely to render available the whole of this heat. 
 
 Although every kind of fuel differs in the quan- 
 tity of heat that it affords, it is unnecessary here 
 to inquire into any other than the ordinary de- 
 scriptions used for purposes similar to that we are 
 now considering. The calculations, therefore, will 
 be made with reference only to coal and coke of 
 ordinary and average qualities. 
 
 (94.) It is stated by Watt that one pound of 
 coal will raise the temperature of 45 Ibs. of water 
 from 55 to 212. Eumford states the same quan- 
 tity of coal will raise 36^ Ibs. of water from 32 to 
 212; and Dr. Black has estimated that one pound 
 of coal will make 48 Ibs. of water boil, supposing 
 it previously to be at a mean temperature. These 
 quantities, when reduced to a common standard, 
 vary but little from each other. Watt's experi- 
 ment, of 45 Ibs. of water being heated from 55 to 
 212, is equal to 39J Ibs. only, if heated from 32 
 to 212; and this nearly agrees with Count Rum- 
 ford's calculation ; at least, the variation is not 
 more than might be expected from a slight dif- 
 ference in the quality of the coal. Dr. Black's 
 estimate is as much in excess over the experiments 
 of Watt as Rum ford's is in defect ; we may, there- 
 fore, take the average of these three experiments,
 
 HEATING EFFECT OF COAL. 107 
 
 which will give us a result, that 39 Ibs. of water may 
 be heated from 32 to 212 by one pound of coal. 
 
 (95.) The results of later experiments show 
 that, as an average effect, the above calculations 
 are very accurate, when practically applied on a 
 large scale. Mr. Parkes * found that the greatest 
 effect he could produce, by his improved mode of 
 firing, was 10'3 Ibs. of water at the temperature 
 of 212 evaporated by one pound of coal; and 
 that, by the ordinary methods of firing, the 
 average obtained is only 7' 5 Ibs. of water of the 
 like temperature evaporated by one pound of 
 coal. The first of these is equal to 57 '2 Ibs. of 
 water heated from 32 to 212 by one pound of 
 coal ; and the latter is equal to 41 6 Ibs. of water 
 heated to the like extent, and which very nearly 
 agrees with the experiments of Watt, Kumford, 
 and Black. In the Cornish engines, however, a 
 much higher result is obtained. Mr. Parkes has 
 given the results obtained in the " United Mines," 
 during eight months, from which it appears the 
 greatest evaporation is 15*3 Ibs., and the average 
 quantity 11*8 Ibs. of water evaporated from the 
 temperature of 212 by one pound of coal. The 
 former of these gives 85 Ibs., and the latter 
 65 Ibs. of water, raised from 32 to 212 by one- 
 pound of coal ; which results appear to be the 
 highest that are practically attainable, and are 
 very much greater than can be produced with any 
 other boilers, or qualities of coal, than those with 
 which the experiments were made. In all the 
 subsequent calculations, therefore, the average of 
 
 * Mr. Parkes " On the Evaporation of Water from Steam- 
 Boilers," in the Transactions of the Institution of Civil Engi- 
 neers, 1838; and these results very nearly agree with the 
 results arrived at by Mr. Herepath from purely physical calcu- 
 lations. (Herepath's Mathematical Physics, vol. i., p. 351.), 
 See also note to Art. 71, ante.
 
 108 SPECIFIC HEAT OF AIR AND WATER. 
 
 the experiments of Watt, Rumford, and Black 
 will be adhered to, as being the most correct for 
 ordinary practice ; and we shall shortly have 
 occasion to apply them, in elucidating that branch 
 of the subject which is included in the present 
 chapter. 
 
 (90.) In order to ascertain the effect that a 
 certain quantity of hot water will produce in 
 warming the air of a room, there appears to be no 
 better method than that of computing from the 
 specific heat of gases compared with water. 
 
 (97.) Every substance, it is well known, has its 
 own peculiar specific heat : that is, a given weight, 
 or volume, of any particular substance at a certain 
 temperature, contains a definite amount of heat, 
 which, if imparted to any other substance, will 
 produce upon this last a certain known effect, 
 though it will be different for every different body 
 or substance. Now, it is ascertained that one 
 cubic foot of water, by losing one degree of its 
 heat, will raise the temperature of 2990 cubic feet 
 of air the like extent of one degree ; and by 
 losing 10 of its heat, it will raise the temperature 
 of 2990 cubic feet of air 10 or 29,900 cubic feet 
 one degree, and so on.* 
 
 (98.) But this calculation regards only the 
 ultimate effect which will be produced, without 
 
 * The specific heat of equal weights of water and air, by the 
 experiments of Berard and Delaroche, is found to be as 1 to 
 26669 : but as the volume or bulk of an equal weight of atmo- 
 spheric air is to water as 827-437 to 1, we shall have -26669 : 
 1 : : 827-437 = 3102, which is the number of cubic feet of air 
 that has the same specific heat as one cubic foot of water. 
 This, however, appears to be rather too high a calculation ; for 
 Dr. Apjohn, in a memoir recently published (Rept. Brit. Sci. 
 Assoc., vol. iv.), gives the result of a new mode of determining 
 the specific heat of permanently elastic fluids, by which he 
 makes the specific heat of atmospheric air -2767 when that of 
 water is represented by unity. Therefore 2767 : 1 : : 827 437 
 = 2990, which is the number given in the text.
 
 SPECIFIC HEAT OF AIR AND WATER. 109 
 
 reference to the time which will be required to 
 obtain the result. To ascertain the time that is 
 required to heat the air, which is a most essential 
 element in every calculation connected with the 
 subject under consideration, recourse must be had 
 to direct experiments ; for the rate at which a 
 given quantity of hot water will impart its heat to 
 the surrounding air depends upon the nature and 
 extent of surface of the body which contains it, as 
 well as upon the degree of motion which the air 
 possesses. The effect of the velocity of the air, 
 however, is not necessary here to be considered, 
 as it is only to a still atmosphere in a building 
 that these calculations are to be applied. But as 
 the radiating and conducting powers of different 
 substances vary considerably, it is necessary to 
 make experiments with the same substance or 
 material as the pipes for which we wish to estimate 
 .the effect, before we can arrive at any conclusions 
 as to the quantity of heated surface that will be 
 required to produce any desired temperature in a 
 building. 
 
 (99.) From experiments made to determine 
 this question, it appears that the water contained 
 in an iron pipe of four inches diameter internally, 
 and four and a half inches externally, loses *851 
 of a degree of heat per minute, when the excess 
 of its temperature is 125 above that of the cir- 
 cumambient air. Therefore (by Art. 97) one foot 
 in length of pipe four inches diameter will heat 
 222 cubic feet of air one degree per minute, when 
 the difference between the temperature of the pipe 
 and the air is 125.* 
 
 * From the data given in Art. 270, Chap. XIIL, it appears 
 that 171-875 cubic inches of water, exposed to the cooling 
 influence of the air by 287 -177 square inches of surface of 
 cast iron, loses 8 of a degree of Fahrenheit per minute when 
 
 the air is 79 colder than the pipe : therefore =^- = 1-265
 
 110 SPECIFIC HEAT OF AIR AND WATER. 
 
 This calculation will serve as the basis by 
 which we may estimate the quantity of heating 
 surface for any building. But before we can 
 apply it practically, we must know what quantity 
 of heat the building will lose per minute, by the 
 cooling power of the glass, by ventilation, radia- 
 tion, and all other causes which may tend to 
 lower its temperature ; for on these several causes 
 must obviously depend the quantity of heat that 
 is required to be added to it by the warming 
 apparatus. 
 
 (100.) The quantity of air required for ventila- 
 tion, and the method of ventilating buildings, are 
 considered in subsequent chapters (Chapters III. 
 and IV., Part II.). It is unnecessary, therefore, 
 in this place to pursue the subject further than to 
 state that, in large buildings and rooms of dwell- 
 ing-houses, a quantity of air equal to from three 
 and a half to five cubic feet for each individual 
 the room contains must be changed per minute, 
 in order to preserve the wholesomeness and purity 
 of the atmosphere.* 
 
 will be the loss of heat per minute when the temperature of 
 the pipe is 125 above that of the air. But this quantity of 
 water, if exposed in a pipe of four inches diameter inside, 
 and four and a half inches outside, will only be surrounded 
 by 193-435 square inches of radiating surface; therefore 
 
 193-435x1-265 OK , ...,, ,, , 
 
 - Q = -851 , will be the loss of heatjper irmiute by 
 
 ^o7 * 177 
 
 a four-inch pipe, when the excess of temperature is 125 above 
 the circumambient air. As all pipes are technically known 
 by their internal diameter, this mode of measuring is here 
 used, although the external measurement would be a more 
 correct definition for these calculations. 
 
 * This estimate is given for ordinary buildings. In the 
 Houses of Parliament, and in some other buildings, where 
 expense is of no consideration, a much larger quantity of air 
 has been introduced for ventilation very beneficially; and 
 when the cost of the apparatus is unimportant, it may be 
 assumed that the larger the quantity of fresh air introduced, 
 the greater will be the comfort and salubrity. In Chap, iv.,
 
 LOSS OF HEAT IX BUILDINGS. Ill 
 
 (101.) The loss of heat in all buildings having 
 any great extent of glass we shall find to be very 
 considerable. It appears by experiment* that 
 one square foot of glass will cool 1*279 cubic feet 
 of air as many degrees per minute as the internal 
 temperature of the room exceeds the temperature 
 of the external air; that is, if the difference 
 between the internal and the external temperature 
 of the room be 30, then 1 279 cubic feet of air will 
 be cooled 30 by each square foot of glass, or, 
 more correctly, as much heat as is equal to this 
 will be given off by each square foot of glass ; 
 for, in reality, a very much larger quantity of 
 air will be affected by the glass, but it will be 
 cooled to a less extent. The real loss of heat 
 from the room will therefore be what is here 
 stated. 
 
 (102.) But though this amount is only calcu- 
 lated for a still atmosphere, as intense cold is 
 seldom or never accompanied with high winds,f 
 no additional allowance needs be made for this 
 cause, provided we estimate sufficiently low for 
 the external temperature. For the highest winds 
 are generally about March and September, and 
 the average temperature of the former month is 
 
 Part 2, where the ventilation of public buildings is considered, 
 it will be observed that twelve feet per minute is assumed as 
 the minimum quantity for each person ; and as a general 
 rule it may be stated that the more people who are crowded 
 into a given space the larger should be the supply of air to 
 each individual. 
 
 * "Experiments on Cooling," Art. 271. 
 
 | That intense cold is rarely accompanied by high winds is 
 matter of common experience. The obliquity of the sun's 
 rays on the higher latitudes of the northern hemisphere, 
 when near the time of the winter solstice, prevents the atmo- 
 sphere of those places which are distant from the tropics from 
 receiving any considerable quantity of heat ; and, therefore, 
 the air being all of nearly equal density, there is but little 
 tendency to aerial currents in the lower strata.
 
 112 LOSS OP- HEAT IN BUILDINGS. 
 
 46, arid the latter 59J . The greatest diurnal 
 variation of the thermometer is 20 in March, 
 and 18 in September; so that the average tem- 
 perature of the nights will be 36 in March, and 
 50 in September.* But we shall presently find 
 (Art. 106) that when the external atmosphere is 
 at 36, the quantity of pipe required to warm a 
 building to 65 is only about one-half of what 
 would be necessary were the external air at 10. 
 Therefore, in calculating the quantity of pipe to 
 warm buildings used during the night, we should 
 estimate that the external temperature may fall as 
 low as 10 Fahrenheit. Or if the building is re- 
 quired to be warmed during the daytime only, we 
 may estimate the external temperature may fall as 
 low as 25 Fahrenheit. If we adopt these as the 
 external temperatures we shall find that generally no 
 further allowance needs be made for the effect ol 
 high winds; because such high winds only occur 
 when the external air is much above these limits, 
 and therefore the quantity of pipe calculated by these 
 rules will be correct both for cases of extreme cold 
 and also for cases of very high winds ; which two 
 conditions, as already stated, never occur simul- 
 taneously.! 
 
 * These temperatures are for the neighbourhood of London. 
 In March, 1837, the night temperature, obtained by a register 
 thermometer, only averaged 31-1, which is nearly 5 lower 
 than has been known for many years. Mr. L. Howard, in his 
 " Climate of London," states that the average temperature, 
 ascertained by observation for ten years, is as follows : 
 
 In London. In the Country. 
 
 March . 
 September 
 
 Mean highest temperature . 47 31 48 46 
 
 Mean lowest temperature . 37-32 34-57 
 
 Mean highest temperature. 65-91 65-52 
 
 Mean lowest temperature . 52-45 47-03 
 
 t By reckoning the external air at the above temperatures, 
 the wind may have a velocity of from twenty to thirty miles 
 an hour, without producing any diminution of the internal
 
 LOSS OF HEAT IX BUILDINGS. 113 
 
 But in such situations as are very much exposed 
 to high winds, it will perhaps be prudent to calcu- 
 late the external temperature from zero, to com- 
 pensate for the increased cooling power of the wind ; 
 and, in very warm and sheltered situations, a less 
 range in the temperature will be sufficient. Local 
 knowledge of the situation will therefore be neces- 
 sary to guide the judgment in particular cases. 
 
 (103.) The difference between the cooling effect 
 of glass which is glazed in squares and that which 
 is lapped is very trifling in those buildings where 
 the air contains much moisture. This is the case 
 in hothouses, where the plants are constantly 
 steamed ; and therefore, for such buildings, no 
 farther allowance should be made on this account 
 for loss of heat.* But in skylights of dwelling- 
 houses, in consequence of the greater dryness of 
 
 temperature ; for it is probable that the cooling effect of wind 
 on ordinary window glass is not above one-half so much as 
 appears by the experiments, Art. 271, in which the glass was 
 so much thinner than ordinary window glass. 
 
 * The calculations of the specific heat of air, given in the 
 note, Art. 97, are only for dry air. If the temperature be at 
 60 and the air saturated with moisture, then the same quan- 
 tity of heat will only raise the temperature of 2,967 cubic feet 
 of this saturated air any given number of degrees, which would 
 have raised 2,990 cubic feet of dry air to the like temperature. 
 This 2,967 cubic feet of saturated air will contain 68 cubic 
 inches of water; and this quantity of water will absorb as 
 much heat during its conversion into vapour as would raise 
 the temperature of 117,507 cubic feet of air one degree. This 
 is equal to the entire heat that 46 feet of pipe, four inches 
 diameter, will give off in ten minutes, when the temperature 
 is 140 above that of the air. The glass will, however, cool 
 much less of this saturated air than of dry air, for the 
 mixture of air and vapour has greater specific heat than dry 
 air. With lapped glass the loss of heat will be less with 
 saturated than with dry air, because the vapour, when con- 
 densed upon the glass, will run down and nearly fill up the 
 crevices between the laps, and effectually prevent the escape 
 of the air, and thereby avoid the loss of heat. 
 
 I
 
 114 LOSS OF HEAT IN BUILDINGS. 
 
 the atmosphere, the heated air will escape through 
 the laps of the glass in greater quantity, in pro- 
 portion as less vapour is condensed on the surface. 
 The height of the skylight will also make a con- 
 siderable difference in the velocity of the escape of 
 air through the laps, as it depends upon the same 
 principles which have been explained (Art. 21) as 
 governing the motion of water, the increased 
 velocity being relatively as the height and the 
 difference of temperature between the internal and 
 external air.* 
 
 (104.) In making an estimate of the quantity 
 of glass contained in any particular building, the 
 extent of surface of the woodwork must be care- 
 fully excluded from the calculation. This is par- 
 ticularly necessary in buildings used for horticul- 
 tural purposes, where, from the smallness of the 
 panes, the wood-work occupies a considerable 
 space. The readiest way of calculating, and suffi- 
 ciently accurate for ordinary purposes, is to take 
 the square surface of the sashes, and then deduct 
 one-eighth of the amount for the woodwork. In 
 the generality of horticultural buildings, the wood- 
 work fully amounts to this quantity ; but in some 
 expensively finished conservatories, &c., it is con- 
 siderably less, and therefore the allowance must 
 be made accordingly. When the frames and 
 sashes are made of metal, the radiation of heat 
 will be quite as great from the frame as from the 
 glass ; therefore, in such cases, no deduction must 
 be made.f 
 
 * See also Chapter V., Part II. 
 
 | Some persons have imagined that the loss of heat from a 
 glass roof will vary greatly with the angle which the roof 
 forms with the horizon. But this variation in the effect can- 
 not be very considerable. It can only be that portion of the 
 heat lost by conduction of the air that can vary in this 
 manner; and calculating the ordinary excess by which the
 
 LOSS OF HEAT IN BUILDINGS. 115 
 
 Some loss of heat will likewise arise from the im- 
 perfect fitting of doors and windows. In these cases 
 
 temperature of the hothouse exceeds the temperature of the 
 external air, this portion of the heat is only about three- 
 sevenths of the whole (see Art. 227, &c.). But a small part 
 only of this quantity will be affected by the angle of the glass. 
 For the cooling effect of wind will be in proportion to the num- 
 ber of particles of air brought into contact in a given time ; 
 aud with a horizontal wind this will be directly as the sine of 
 the angle which the roof forms with the horizon. Supposing, 
 then, the roof to be at an angle of 34, as recommended by 
 Mr. Knight (Horticul Trans, vol. i. p. 99;, we shall find that 
 the sine of the angle multiplied by the above-mentioned por- 
 tion of the heat affected by the conducting power of the air 
 will give as a result that, at the angle of 34, there will be 
 about two-ninths more of the heat carried off by the conduct- 
 ing power of the air than would be the case if the glass were 
 placed horizontally. But, practically, this loss will be very 
 materially lessened by an effect which is not capable of being 
 reduced to any exact calculation. When a stream .of air 
 strikes an upright surface of glass, it is not reflected back 
 again upon itself, but glides along the surface, and try the 
 increased heat will be' directed upwards in a vertical line. 
 (" Quetelet's Philosophy," note 5, Appendix.) Passing, then, 
 in this direction, it meets another stream of air proceeding in 
 a line parallel to the original line of its motion ; and it is by 
 this again driven more closely in contact with the glass. But, 
 having been warmed by the contact in the first instance, it 
 will abstract less heat from the glass, and will thus prevent, 
 to a considerable extent, the further loss of heat, until by the 
 upward motion of the air it finally escapes into space. The 
 same effect will be produced by a glass roof lying at any 
 angle ; but it is clear the heated particles will escape upwards 
 more easily in proportion as the angle of the roof is smaller. 
 Now, these effects are exactly the opposite of each other. 
 The cooling effect of the wind increases with the angle of the 
 roof, and is greatest on a vertical surface ; while the counter- 
 acting influence, by the interference of the particles of air 
 with each other, also increases in nearly the same proportion ; 
 and therefore the variation in the angle of the roof makes far 
 less difference than might at first be expected in the cooling 
 effect. The difference, however, between the cooling of a 
 vertical pane of glass and a perfectly horizontal one is not 
 inconsiderable in high winds ; but the angle of a roof must 
 be very small indeed before it can escape the influences above 
 described, and be brought to assimilate with a horizontal roof. 
 
 i 2
 
 116 QUANTITY OF PIPE 
 
 the circumstances vary very considerably ; but, in 
 the majority of instances, no allowance is neces- 
 sary for these sources of loss of heat, the external 
 temperature of the air having been reckoned (Art. 
 102) sufficiently low to supersede the necessity of 
 any farther deduction. 
 
 (105.) From the preceding calculations, the fol- 
 lowing corollary may be drawn : The quantity of 
 air to be warmed per minute in habitable rooms 
 and in public buildings must be from three and a 
 half to five "cubic feet for each person the room 
 contains, and one and a quarter cubic feet for each 
 square foot of glass.* This air has to be heated 
 from the external temperature, to the temperature 
 at which the room or building is required to be 
 kept. For conservatories, forcing-houses, and 
 other buildings of this description, the quantity of 
 air to be warmed per minute, must be one and a 
 quarter cubic feet for each square foot of glass 
 which the building contains ; and this air also will 
 have to be heated from the external temperature 
 to the proposed temperature of the building. When 
 the quantity of air to be heated per minute has been 
 thus ascertained, the quantity of pipe that will be 
 necessary to heat the building may be found by 
 the following rule : 
 
 RULE : Multiply 125 by the difference between 
 the temperature at which the room is purposed to 
 be kept, when at its maximum, and the tempera- 
 ture of the external air; and divide this product 
 by the difference between the temperature of the 
 pipes and the proposed temperature of the room ; 
 then the quotient thus obtained, when multiplied 
 
 * As corrugated sheet-iron is coining much into use, it may 
 
 be proper to observe that the loss of heat from this kind of 
 
 material is exactly the same as from the like extent of glass 
 
 - (see " Experiments," Chapter XIII.), and must be allowed for 
 
 accordingly, whenever it is used.
 
 FOR WARMING BUILDINGS. 117 
 
 by the number of cubic feet of air to be warmed 
 per minute, and this product divided by 222, will 
 give the number of feet in length of pipe, four 
 inches diameter, which will produce the desired 
 effect.* 
 
 When the pipes which are to be used are three 
 inches diameter, then the number of feet of four- 
 inch pipe, obtained by this rule, must be multi- 
 plied by 1 33, which will give the length of three- 
 inch pipe ; or, to obtain the quantity of two-inch 
 pipe, the length of pipe four inches diameter, ob- 
 tained by the rule, must be multiplied by two ; 
 the length required of three-inch pipe being one- 
 third more than four-inch, and the length of two- 
 inch pipe being double that of the four-inch, when 
 the temperatures are the same in all. 
 
 (106.) By the following Table, however, even 
 the simple calculations given in this rule may be 
 dispensed with. The Table shows the quantity 
 of pipe four inches in diameter which is required 
 to heat 1,000 cubic feet of air per minute wc\y number 
 of degrees. The temperature of the pipes is as- 
 sumed to be 200 of Fahrenheit, this being the 
 most usual temperature at which they can be easily 
 maintained. But, according to the length of pipe 
 
 * Let p be the temperature of the pipe, and t the tempera- 
 
 125 
 tore the room is required to be kept at, then = x, which 
 
 will represent the number of feet of pipe that will warm 222 
 cubic feet of air one degree per minute, when p t is different 
 to the proportions given in Art. 98. If d represents the dif- 
 ference between the internal and the external temperature of 
 the room, and c the number of cubic feet of air which are to 
 
 be wanned per minute, then x- ' = F will be the number of 
 ISul 
 
 feet of pipe, four inches diameter, which will warm any quantity 
 of air per minute, according to the calculations, Art. 98. 
 
 The rule given in the text has been arranged in such a 
 manner that it may be worked without decimals.
 
 118 QUANTITY OF PIPE 
 
 which is heated by one boiler, the temperature 
 will sometimes be greater and sometimes less than 
 this estimate, the temperature of the water being 
 generally higher when only a small quantity of 
 pipe is used. When the quantity of air to be 
 warmed per minute is greater or less than 1,000 
 cubic feet, the proper quantity of pipe will be 
 found by multiplying the length given in the 
 Table by the actual number of cubic feet of air to 
 be warmed per minute, and dividing that product 
 by 1,000. 
 
 (107.) If the building which it is designed to 
 warm is required to be used only during the day, 
 the air, in this part of the country at least, is 
 scarcely likely to be below 25; but if as for a 
 forcing-house, for instance it is required to be 
 heated both by day and by night, then, perhaps, 
 10 will not be too low to calculate from, or 22 
 below the freezing point. Suppose, now, we want 
 to calculate the quantity of pipe required to heat 
 a forcing-house to 75 in the coldest weather 
 which we will assume to be 10 of Fahrenheit's 
 scale, or 22 below freezing. We have already 
 seen (Art. 101 105) that the quantity of heat 
 required for horticultural buildings is merely so 
 much as is necessary to replace the heat given off; 
 or, in other words, to compensate for the loss 
 sustained by the glass. The actual cubic measure- 
 ment of the house signifies nothing in this case. 
 It is the glass alone which gives off any appre- 
 ciable heat ; and therefore whatever quantity of 
 pipe will compensate for this loss of heat by the 
 glass will also warm the house in the first instance 
 and maintain it at the required temperature after- 
 wards ; because, until the air of the house is heated 
 to its maximum temperature, the glass will cool 
 proportionally less air, the cooling power of the 
 glass being obviously exactly proportional to the
 
 FOR WARMING BUILDIXGS. 
 
 119 
 
 TABLE IV. 
 
 Table showing the Quantity of Pipe, four inches diameter 
 which will heat 1,000 Cubic Feet of Air per Minute, any 
 required number of Degrees: the Temperature of the 
 Pipe being 200 Fahrenheit. 
 
 Temperature 
 of external 
 Air. 
 
 Fahrenheit's 
 Scale. 
 
 Temperature at which the Room is required to be kept. 
 
 45 
 
 50 
 
 55 
 
 60 
 
 65 
 
 70 
 
 75 
 
 80 
 
 85 
 
 90 
 
 10 
 
 126 
 
 150 
 
 174 
 
 200 
 
 229 
 
 259 
 
 292 
 
 328 
 
 367 
 
 409 
 
 12 
 
 119 
 
 142 
 
 166 
 
 192 
 
 220 
 
 251 
 
 283 
 
 318 
 
 357 
 
 399 
 
 14 
 
 112 
 
 135 
 
 159 
 
 184 
 
 212 
 
 242 
 
 274 
 
 309 
 
 347 
 
 388 
 
 16 
 
 105 
 
 127 
 
 151 
 
 176 
 
 204 
 
 233 
 
 265 
 
 300 
 
 337 
 
 378 
 
 18 
 
 98 
 
 120 
 
 143 
 
 168 
 
 195 
 
 225 
 
 256 
 
 290 
 
 328 
 
 368 
 
 20 
 
 91 
 
 112 
 
 135 
 
 160 
 
 187 
 
 216 
 
 247 
 
 281 
 
 318 
 
 358 
 
 22 
 
 83 
 
 105 
 
 128 
 
 152 
 
 179 
 
 207 
 
 238 
 
 271 
 
 308 
 
 347 
 
 24 
 
 76 
 
 97 
 
 120 
 
 144 
 
 170 
 
 199 
 
 229 
 
 262 
 
 298 
 
 337 
 
 '26 
 
 69 
 
 90 
 
 112 
 
 136 
 
 162 
 
 190 
 
 220 
 
 253 
 
 288 
 
 327 
 
 28 
 
 61 
 
 82 
 
 104 
 
 128 154 
 
 181 
 
 211 
 
 243 
 
 279 
 
 317 
 
 30 
 
 54 
 
 75 
 
 97 
 
 120 
 
 145 
 
 173 
 
 202 
 
 234 
 
 269 
 
 307 
 
 Freezing 32 
 
 47 
 
 67 
 
 89 
 
 112 
 
 137 
 
 164 
 
 193 
 
 225 
 
 259 
 
 296 
 
 I'omt. 340 
 
 40 
 
 60 
 
 81 
 
 104 129 
 
 155 
 
 184 
 
 215 
 
 249 
 
 286 
 
 36 
 
 32 
 
 52 
 
 73 
 
 96 
 
 120 
 
 147 
 
 175 
 
 206 
 
 239 
 
 276 
 
 38 
 
 25 
 
 45 
 
 66 
 
 88 
 
 112 
 
 138 
 
 166 
 
 196 
 
 230 
 
 266 
 
 40 
 
 18 
 
 37 
 
 58 
 
 80 
 
 104 
 
 129 
 
 157 
 
 187 
 
 220 
 
 255 
 
 42 
 
 10 
 
 30 
 
 50 
 
 72 
 
 95 
 
 121 
 
 148 
 
 178 
 
 210 
 
 245 
 
 44 
 
 3 
 
 22 
 
 42 
 
 64 
 
 87 
 
 112 
 
 139 
 
 168 
 
 200 
 
 235 
 
 46 
 
 
 15 
 
 34 
 
 56 
 
 79 
 
 103 
 
 130 
 
 159 
 
 190 
 
 225 
 
 48 
 
 ,' t 
 
 7 
 
 27 
 
 48 
 
 70 
 
 95 
 
 121 
 
 150 
 
 181 
 
 214 
 
 50 
 
 < 
 
 }t 
 
 19 
 
 40 
 
 62 
 
 86 
 
 112 
 
 140 
 
 171 
 
 204 
 
 52 
 
 M 
 
 tt 
 
 11 
 
 32 
 
 54 
 
 77 
 
 103 
 
 131 
 
 161 
 
 194 
 
 
 
 
 
 
 
 ' | 
 
 
 
 
 %* To ascertain by the above Table the quantity of Pipe 
 which will heat 1,000 cubic feet of air per minute, find, in the 
 first column, the temperature corresponding to that of the 
 external air ; and at the top of one of the other columns find 
 the temperature at which the room is to be maintained ; then, 
 in this latter column, and on the line which corresponds with 
 the external temperature, the required number of feet of pipe 
 will bo found.
 
 120 QUANTITY OF PIPE 
 
 difference between the internal and external tem- 
 perature. The pipe, therefore, gives off more 
 heat to the air in the earlier stages of the operation 
 than the glass transmits by radiation to the external 
 atmosphere. This difference in the effect is actually 
 the rate at which the building becomes heated; 
 and the increase of the temperature of the building 
 continues until the radiating power of the glass 
 exactly balances the heat given off by the pipes. 
 But the heat given off by the pipes, it may be 
 observed, constantly decreases, while the cooling 
 power of the glass increases with every addition to 
 the temperature of the internal air. We see, then, 
 that when we have estimated the surface of glass 
 in such a building, we can calculate the quantity of 
 pipe that will heat it. For suppose the house has 
 800 square feet of glass : we find (Art. 105) that 
 every square foot of glass cools one and a quarter 
 cubic feet of air per minute as many degrees as the 
 internal exceeds the external temperature. If 
 therefore the external temperature be 1 0, and the 
 internal temperature is required to be 75, then 
 800 square feet of glass will (as above stated) cool 
 1,000 cubic feet of ^ per minute from 75 down to 
 10. By the Table, then, in the column marked 
 75, and on the line marked 10 for external tem- 
 perature, we find the quantity 292; which is the 
 number of feet in length of pipe, four inches 
 diameter, that are required to heat this 1,000 cubic 
 feet of air per minute the required number of 
 degrees. This quantity of pipe, therefore, will 
 heat a building having 800 square feet of glass, 
 whatever the actual size of the building may be. 
 And whenever the quantity of air to be heated 
 per minute is either greater or less than 1,000 
 cubic feet (or, in other words, when the quantity 
 of glass is greater or less than 800 square feet), 
 then the proper quantity of pipe will be obtained
 
 FOR WARMING BUILDINGS. 121 
 
 by the rule of proportion, as already stated (Art. 
 106). 
 
 (108.) The above rule will not, however, give 
 the length of time required to heat any particular 
 building. This will, of course, depend upon many 
 circumstances; nevertheless, some approximation 
 may be made to the average time required. Sup- 
 pose the maximum temperature of the pipe to 
 be 200, the water being at 40 before lighting the 
 fire ; then the maximum temperature in horti- 
 cultural buildings will be attained with 
 
 Four-inch pipes, in about four and a half hours. 
 Three-inch pipes, in about three and a quarter hours. 
 Two-inch pipes, in about two and a quarter hours. 
 
 But if a larger quantity of coal than that given by 
 the Table (Art. 114) be used if the surface of 
 the boiler be much increased in proportion to the 
 length of pipe if the quantity of pipe used be 
 excessive or the temperature of the external air 
 be higher than the estimated amount, then, in each 
 of these cases, the time required for heating will be 
 less. If, on the contrary, the required temperature 
 be not attained in the time given above, then 
 either too small a quantity of pipe, too small a 
 surface of boiler, or too small a quantity of coal 
 has been used. 
 
 It should, however, be observed, that although 
 the maximum temperature will not be reached, on 
 an average, in less time than is above stated, still 
 the required temperature will very often not take 
 longer than half or two-thirds of this time, to be 
 attained ; because the quantity of pipe being 
 always apportioned to meet the case of extreme 
 cold, when the external temperature is above that 
 extreme limit, the pipe, by being superabundant, 
 will warm the same space in a shorter time.
 
 122 QUANTITY OF PIPE 
 
 (109.) These calculations of the time required to 
 heat buildings will only apply to those cases where 
 the cooling surfaces are very large, and the propor- 
 tion of the pipe very considerable, relatively to the 
 actual dimensions of the building. Wherever, on 
 the contrary, the cubical content of the building is 
 large in proportion to its cooling surfaces, the 
 time required to raise its temperature will be 
 greater than is above stated, in consequence of 
 the very small proportionate quantity of pipe; 
 and this will be found to vary greatly in different 
 descriptions of buildings. Churches and other 
 large buildings (which only require a small heat- 
 ing surface relatively t to their cubic contents) will 
 generally require the longest time to heat ; dwell- 
 ing-houses will require a shorter time, and horti- 
 cultural buildings the shortest of all. The length 
 of time above estimated only applies to the latter 
 description of buildings. For the other kinds of 
 buildings the period will be very variable, and 
 can scarcely be determined, except for each in- 
 dividual case. 
 
 (110.) Yarious circumstances may, however, in- 
 terfere to diminish the effect of the apparatus; 
 such, for instance, as damp walls particularly if 
 the building is new excess of ventilation, &c. 
 The effect of damp walls in reducing the apparent 
 power of an apparatus is very considerable, in 
 consequence of the great quantity of heat which 
 is necessary to evaporate the moisture. It will 
 require as much heat to vaporise one gallon of 
 water from the walls of a building as would raise 
 the temperature of 47,840 cubic feet of air 10. 
 The true power of an apparatus can, therefore, 
 never be ascertained unless the building be per- 
 fectly dry. The same cause, though in a much 
 less degree, becomes operative in buildings which 
 are only occasionally warmed ; and a longer time
 
 FOR WARMING BUILDINGS. 123 
 
 will always be necessary to heat such places than 
 those that are in constant use. 
 
 (111.) For estimating the quantity of pipe which 
 is required to warm any building, rules of a much 
 more facile character, though at the same time 
 more loose and inaccurate than those that have 
 been already given, may be deduced.* They are 
 the results of experience, and they have been 
 found so generally useful in practice, and in most 
 cases so nearly accurate in their results, that they 
 are here given at considerably greater length than 
 in the earlier editions of this work. 
 
 CHURCHES AND LARGE PUBLIC ROOMS. To heat 
 these when they have an average number of doors 
 and windows, and only moderate ventilation, 
 divide the cubic measurement of the building by 
 200, and the quotient will be the number of feet in 
 length of pipe four inches diameter, that will be re- 
 quired to produce a temperature of about 55 in 
 very cold weather. t This is equivalent to allow- 
 
 * The following rules must not be confounded with that 
 already given. The former rule gave the result entirely from 
 an estimate of the quantity of glass, without any reference to the 
 cubic contents of the building ; the present rules, on the contrary, 
 are founded entirely on the cubic contents of the building 
 without direct reference to the quantity of glass. The results, 
 however, of the two rules will be found to agree with sufficient 
 accuracy for most practical purposes. 
 
 f Churches and other buildings for containing large assem- 
 blages of people ought never to be heated to a very high tem- 
 perature, on account of the great quantity of animal heat 
 given off in crowded congregations. It has been ascertained, 
 by calculations founded on the amount of oxygen consumed, 
 that a man generates a quantity of heat in 24 hours sufficient 
 to raise 63 Ibs. of water from the freezing to the boiling point. 
 Of this quantity, as much heat is expended in forming the 
 vapour that passes off by perspiration and by transpiration 
 from the lungs as would heat about 36^ Ibs. of water 180 ; 
 and the remainder of the heat, which is equal to raising the 
 temperature of 26 Ibs. of water 180, passes off by radiation 
 from the body. (QucteleCs Philosophy, Art. " Heat.") Now these
 
 124 QUANTITY OF PIPE 
 
 ing five feet of four-inch pipe for every thousand 
 cubic feet of space which the building contains. 
 If the apparatus is so contrived that the warming 
 of the air is effected before it actually circulates 
 in the room, and that the same portions of air are 
 not returned to be heated a second time, but fresh 
 portions of external air are brought successively 
 in contact with the heating apparatus, it will re- 
 quire from 50 to 70 per cent, more pipe to pro- 
 duce the same effect ; but the air will, of course, 
 be more pure and fresh.* . 
 
 results, if reduced to the same standard that has been adopted 
 in the preceding calculations, will lead to the conclusion that 
 as much heat is given off per minute from the body of an 
 adult man as would be produced by an iron pipe four inches 
 diameter and three-and-a-half feet long, filled with water at 
 200. This estimate, however, in practice, would be found too 
 high ; for where there is no muscular exertion less heat is 
 produced; and the increased temperature of the surrounding 
 medium would also prevent its free radiation. For, as all 
 bodies only give off heat in proportion to their excess of tem- 
 perature, the human body being constantly at the temperature 
 of 98 nearly twice as much heat would be given off (if the 
 body were freely exposed) when the surrounding medium is 
 at 50 as would be the case if the latter were raised to 70. 
 It is found also that, on an average, women only consume 
 about half as much oxygen as men (Combe's Principles of 
 Physiology, 4th edition, p. 222), and therefore they can only 
 produce half as much heat ; the consumption of oxygen always 
 being proportional to the heat generated. From these facts 
 it will appear that not only should buildings such as those we 
 are now considering, not be too highly heated, but that the 
 pipes should be moderately small in diameter, in order to 
 allow of the temperature being more easily lowered when the 
 building is filled with people. Some experiments on the heat 
 thus given off from the human body are given in Wyman 
 " On Ventilation," p. 185, Boston, 1846. 
 
 * This mode of calculating the quantity of pipe will differ 
 from the previous mode of calculating by the surface of glass 
 and the allowance necessary for ventilation, to a much greater 
 extent in the case of churches than almost any other kind of 
 building. The reasons for this are twofold : not only does 
 the proportion of glass to the area of the building differ to a
 
 FOR WARMIXG BUILDIXGS. 125 
 
 DWELLIXG-ROOMS. These will generally require 
 about 12 feet of four-inch pipe to every thousand 
 cubic feet of space contained in them, to give a 
 temperature of about 65. To raise the temperature 
 to 70 will require about 14 feet of four-inch pipe. 
 
 HALLS, SHOPS, WAITING-ROOMS, ETC., will require 
 about ten feet of four-inch pipe to every thousand 
 cubic feet of space, to raise the temperature to 
 about 55. For a temperature of 60, about twelve 
 feet of four-inch pipe will be required. 
 
 WORK-ROOMS, MANUFACTORIES, ETC., where a tem- 
 perature of about 50 to 55 only is required, will 
 generally be sufficiently heated by six feet of four- 
 inch pipe for every thousand cubic feet of space 
 they contain. For a temperature of 60 about eight 
 feet of pipe will be required. 
 
 very great extent in different churches; but, besides this, if 
 the quantity of pipe were only just sufficient to compensate 
 for the loss by the cooling power of the glass, it would require 
 far too long a time to heat the church to a required tem- 
 perature, in consequence of its very great area in proportion 
 to the total heating surface. In college chapels, and some 
 other ecclesiastical buildings, where the quantity of glass is 
 particularly small, this is remarkably the case ; and the former 
 rule would hardly give one-fourth the quantity of pipe found 
 by the latter. Now, in these cases, when the quantity of 
 glass is so very small, a less quantity of pipe would certainly 
 suffice than that obtained by the latter rule of allowing five 
 feet of four-inch pipe for each thousand cubic feet of space: 
 and it must be decided by experience which rule shall be 
 adopted in such cases. In those cases where the warming 
 apparatus is kept constantly in operation, the smaller quantity 
 of pipe obtained by the first rule would suffice ; but in cases 
 where the apparatus is only heated once or twice a week, it 
 requires to be much more powerful, in order to produce the 
 required effect in a sufficiently short time. In a very large 
 majority of churches, the last rule given will be correct; 
 but when any doubt may exist as to its applicability to any 
 particular case, a very safe plan will be to calculate the 
 quantity of pipe by both rules ; add the results together, and 
 divide the resulting quantity by two. This plan will give a 
 result which will safely meet almost any case that can arise.
 
 126 QUANTITY OP PIPE 
 
 SCHOOLS, AND LECTURE-ROOMS, requiring a tem- 
 perature of 55 to 58, will require from six to 
 seven feet of four-inch pipe to every thousand 
 cubic feet of space. 
 
 DRYING-ROOMS, or closets, for drying wet linen 
 and other substances, require from 150 to 200 feet 
 of four-inch pipe to every thousand cubic feet of 
 space to raise the temperature to 120 when empty, 
 or about 80 when the room is filled with wet 
 linen.* 
 
 DRYING-ROOMS, for curing bacon, or for drying 
 paper, or leather, or damp hides, will require 
 twenty feet of four-inch pipe to every thousand 
 cubic feet of space to give a temperature of about 
 70. 
 
 GREENHOUSES AND CONSERVATORIES, requiring a 
 temperature of about 55 in the coldest weather, 
 must have 35 feet of four-inch pipe for each thou- 
 sand cubic feet of space they contain. 
 
 GRAPERIES AND STOVE-HOUSES, requiring a tem- 
 perature of 65 to 70 in the coldest weather, will 
 require 45 feet of four-inch pipe for each thousand 
 cubic feet of space ; and if a temperature of 70 to 
 75 is required, 50 feet of four-inch pipe must be 
 allowed for each thousand cubic feet of space. 
 
 PINERIES, HOTHOUSES, and CUCUMBER-PITS, re- 
 quiring a temperature of 80, must have about 55 
 feet of four-inch pipe for every thousand cubic feet 
 of space the house contains. 
 
 Modern refinements have introduced heating by 
 hot water in many other forms of buildings than 
 originally contemplated. Thus STABLES are often 
 thus heated, and they usually require about five 
 feet of four-inch pipe per thousand cubic feet of 
 space. COACHHOUSES require about the same 
 quantity, and so also do DOG HOUSES and FOWL 
 HOUSES. DAIRIES are also now frequently warmed 
 
 * See also Arts. 176 and 177.
 
 FOR WARMING BUILDINGS. 127 
 
 in this manner. They require about 16 to 18 feet 
 of four-inch pipe per 1000 cubic feet of space to 
 give a temperature of about 56 Fahrenheit. 
 
 The quantity of pipe estimated in this way will 
 only suit for such buildings, whether horticultural 
 or otherwise, as are built quite upon the usual 
 plan and of the ordinary proportions; for, if they 
 vary much from the most ordinary construction, 
 these rules will not be accurate, and the method 
 given in the former part of this chapter should then 
 be employed. 
 
 (112.) Although these calculations are all made 
 on the supposition of using pipe of four inches 
 diameter as the heating surface, it is by no means 
 intended to recommend that as the best size for all 
 purposes. For all horticultural purposes it is the 
 best, where it can be used ; but for most other 
 purposes, smaller pipes, or even other forms of 
 heating surfaces, may generally be more advan- 
 tageously employed. If the pipes used are only 
 three inches diameter, we must add one-third to 
 the quantities here given ; and if pipes of two 
 inches diameter are used, double the quantity will 
 be required. 
 
 (113.) It should here be mentioned, that the 
 calculations for the quantity of pipe required for 
 horticultural buildings have been made with a 
 view to the most economical mode of effecting' 
 the desired object. Some of the most successful 
 horticulturists, however, have adopted the plan 
 of using a much stronger heat in their forcing- 
 houses, and allowing, at the same time, a much 
 greater degree of ventilation than usual. This 
 plan is stated to produce a finer fruitage ; but 
 it will only be obtained at an increased cost in the 
 apparatus, and by a larger expenditure of fuel. 
 Where economy is not required, it may perhaps be 
 desirable to adopt this plan ; and then the quantity
 
 128 QUANTITY OF COAL 
 
 ot pipe which is used must be proportionally 
 increased above the estimates which are given in 
 this chapter. 
 
 (114) The quantity of coal necessary to sup- 
 ply any determinate length of pipe is easily 
 ascertained, from the data given in Art. 270. 
 After the water in the pipes is heated to its 
 maximum, the quantity of coal consumed is, 
 obviously, just what is required to supply the 
 heat given off from the pipes. Now, by Art. 
 99 we find that when pipes four inches diameter 
 are 146-8 hotter than the air of the room, the 
 water contained in them loses exactly i per 
 minute of its heat. By Art. 94, we find that 
 1 Ib. of coal will raise the temperature of 39 Ibs. 
 of water 180; and as 100 feet in length of four- 
 inch pipe contains 544 Ibs. of water, it will 
 require 13*9 Ibs. of coal to raise the temperature 
 of this quantity of water 180. If, therefore, the 
 water loses 1 of heat per minute, or 60 per hour, 
 this quantity of coal will supply 100 feet in length 
 of pipe for three hours, if its temperature con- 
 tinue constant with regard to the air of the room. 
 On this principle the following Table has been 
 constructed. The temperature of the pipe is 
 assumed to be 200: then, knowing the tem- 
 perature of the room, if we take the difference 
 between the temperature of the pipe and that of 
 the room, by looking in the Table for the corre- 
 sponding temperature, we shall find under it the 
 number of pounds weight of coal which will be 
 required per hour for every 100 feet in length 
 of pipe, in order to maintain the stated tempera- 
 ture. Thus, suppose the pipe to be four inches 
 diameter, and its temperature 200, while the room 
 is at 75, then, under the column headed 125 
 (which is the difference between these two tem- 
 peratures), we find 3-9 Ibs. as the quantity re-
 
 FOR WARMING BUILDINGS. 
 
 129 
 
 quired per hour for every 100 feet of pipe. The 
 quantities stated in the Table are given in pounds 
 and tenths of a pound. 
 
 TABLE; V. 
 
 Table of the Quantity of Coal used per Hour to heat 100 Feet 
 in length of Pipe of different Sizes. 
 
 Diameter 
 of 
 
 Difference between the Temperature of the Pipe and 
 the Room in Degrees of Fahrenheit. 
 
 Pipe, 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 in Inches. 
 
 150 
 
 145 
 
 140 
 
 135 
 
 130 125 
 
 1201151110 
 
 105 
 
 100 
 
 96 
 
 90 
 
 85 
 
 80 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 4 
 
 4-7 
 
 4-5 
 
 4-4 
 
 4-2 
 
 4-1 
 
 3-9 
 
 3-7 
 
 3-6 3-4 
 
 3-2 
 
 3-1 
 
 2-9 
 
 2-8 
 
 2-6 
 
 2-5 
 
 3 
 
 3-5 
 
 8-4 
 
 3-3 
 
 3-1 
 
 8-0 
 
 2-9 
 
 2-8 
 
 2-7 2-5 
 
 2-4 
 
 2-8 
 
 2-2 
 
 2-1 
 
 2-0 
 
 1-8 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 2 
 
 2-3 
 
 2-2 
 
 2-2 
 
 2-1 
 
 2-0 
 
 1-9 
 
 1-8 
 
 1-8 1-7 
 
 1-6 
 
 1-5 
 
 1*4 
 
 1-4 
 
 1-3 
 
 1-2 
 
 1 
 
 1-1 
 
 1-1 
 
 1-1 
 
 1-0 
 
 1-0 
 
 9 
 
 9 
 
 9 -8 
 
 8 
 
 7 
 
 i 
 
 /? 
 
 6 
 
 6 
 
 (115.) It should, however, be borne in mind 
 that an apparatus will not always consume the 
 same quantity of coal ; in fact, it will seldom 
 require near so much as the Table shows, because 
 that is the calculation for the maximum effect. 
 Suppose the quantity of pipe in a room has been 
 accurately calculated, in order to maintain the 
 temperature at 75 when the external air is at 
 30, the consumption of coal for pipes of four 
 inches diameter will then be 3-9 Ibs. per hour 
 for every 100 feet of pipe. But should the ex- 
 ternal temperature now rise to 40, 77 feet of 
 pipe would produce the same effect as 100 feet 
 would in the former case ; therefore the pipe must 
 be heated to a lower temperature; and it will 
 be found by calculation, that only 3 Ibs. of coal 
 would be used, instead of 3 9 Ibs. As much coal, 
 therefore, as would supply 77 feet of pipe at the 
 maximum temperature would suffice for 100 feet 
 at this reduced temperature. The quantity of
 
 130 QUANTITY OF COAL, ETC. 
 
 fuel which is consumed will, therefore, be con- 
 tinually subject to variation, as it will alter with 
 the temperature of the external atmosphere ; and, 
 in general, the average quantity of coal required 
 will be fully one-third less than the amount given 
 in the Table. 
 
 It is almost unnecessary to observe that, in cal- 
 culating this Table, it has been assumed that the 
 boiler and furnace are of good construction; for 
 on no other basis could an estimate be formed. 
 Very great differences, however, exist in this 
 respect ; and for such cases no estimate whatever 
 can possibly be made.
 
 131 
 
 CHAPTER VII. 
 
 Various Modifications of the Hot- Water Apparatus Kewley's 
 Siphon Principle The High-pressure system Holmes and 
 Coffey's modifications Eckstein and Bushy 's Eotary Float 
 Circulator Fowler's Thermo-siphon Price's improved 
 Hot- water Boxes Eendle's Tank System Corbett's Trough 
 System of Evaporation Theory of Evaporation. 
 
 (116.) UNDER the common and generic term of 
 "hot-water apparatus" various plans have been 
 brought forward by different inventors, which, 
 though essentially different in some of their features 
 from those that have been already described, are, 
 nevertheless, merely modifications of the general 
 principles that have been explained. In the pre- 
 sent chapter some of these peculiar modifications 
 of the invention will be investigated ; and it will 
 appear that the original principles of all are the 
 same, but that other of the fundamental laws of 
 Nature are here brought into action conjointly 
 with those that we have already examined, and 
 give rise to an apparent diversity of operation. 
 
 (117.) The first notable invention of this sort 
 which shall be mentioned, is Kewley's siphon 
 principle. The sketch, fig. 36, shows this appa- 
 ratus in its simplest form. The boiler is open at 
 the top, and the two pipes dip into the water ; the 
 pipe A descending only a very short distance below 
 the surface, and the pipe B reaching nearly to the 
 bottom of the boiler. A small flexible metal pipe, 
 ^, is attached to the highest part of the pipes. To 
 
 K 2
 
 132 THE SIPHON PRINCIPLE. 
 
 this an air-pump is connected, and the air in the 
 pipes being exhausted by this means, the atmo- 
 spheric pressure forces the water up the pipes and 
 
 fills them 'completely. 
 This avoids the ne- 
 cessity of having a 
 reservoir of water 
 higher than the top 
 of the boiler ; for it 
 is well known, that 
 the usual atmospheric 
 pressure is capable of 
 
 raising a column of water in a vacuum to about 
 30 feet in height, varying, however, with the degree 
 of pressure shown by the barometer. 
 
 The water in the longer pipe B will acquire a 
 preponderance of weight over that in the pipe A 
 even if it be at first of an equal temperature and 
 density ; because the pipe B only receives the par- 
 ticles of hot water which rise immediately under 
 its base, while the other receives the heat from all 
 parts of the bottom as well as the sides of the 
 boiler; the water on the top being hotter than 
 that at the bottom. But as soon as the water cir- 
 culates through the pipes, it parts with its heat, 
 and the whole length of the pipe B will then be 
 colder than the pipe A, and the water will descend 
 through B with greater force. 
 
 In consequence of the long pipe B being sur- 
 rounded by the hot water in the boiler, the water, 
 while descending through it, receives a small portion 
 of heat, which lessens the difference of temperature 
 between the two pipes, and reduces the velocity 
 of the circulation. It appears probable, therefore, 
 that additional velocity of circulation would be 
 gained by placing the descending pipe B outside 
 the boiler, and attaching it to the side in the same 
 manner as the return-pipe in fig. 5. The prin-
 
 THE SIPHON PRTNCIPLF. 133 
 
 cipal inconvenience attending this would be the 
 difficulty of stopping the ends of the two pipes A 
 and B, which is now done by the simple con- 
 trivance of a plate screwed moveably to the base 
 of each of the pipes, by means of an external rod 
 passing over the pipes A and B, with a screw 
 attached on the top ; and by turning this the plate 
 is drawn up into close contact with the end of 
 the pipe. This completely stops the water when 
 necessary, the ends of the pipes being turned true 
 to the plates, to make them water-tight ; and by 
 reversing the action of the pump, attached to the 
 pipe #, and thus making it into a force-pump, the 
 soundness of the joints can then be ascertained. 
 A leaky joint is difficult of detection by any other 
 means, as there is no emission of water from it in 
 the usual way. The only immediate consequence 
 of a leaky joint is the immission of air, and it is not 
 observable except by its stopping the circulation of 
 the water, which occurs by the air accumulating 
 and cutting off the connexion of the water between 
 the two pipes. 
 
 If this plan of having the return-pipe placed out- 
 side the boiler were found to increase the motive 
 power of the apparatus, an advantage would be 
 gained in all those cases where the pipes are 
 required to pass under a doorway, because, in all 
 such cases, the boiler for this apparatus must be 
 set much further below the level of the floor than 
 is required for the common hot-water apparatus. 
 But by increasing the motive power, a less height 
 would be sufficient ; and it would therefore prevent 
 the inconvenience sometimes found to attend this 
 particular form of the apparatus, arising from the 
 great depth the furnace is required to be sunk 
 beneath the level of the pipes, in consequence of 
 the very large size of the boiler which is generally 
 used.
 
 134 THE SIPHOX PRINCIPLE. 
 
 (118.) A singular fact is connected with this 
 invention, which deserves notice, because it arises 
 from a philosophical principle, which, in some 
 other instances, has been applied in a most useful 
 manner;* though, with this particular invention, 
 it is rather disadvantageous than otherwise. It 
 has already been stated, that the height to which 
 the water will rise in a vertical column, by the 
 atmospheric pressure, is about 30 feet above the 
 boiler. Supposing this to be the extreme limit to 
 which the water will ascend in the pipes, the 
 slightest elevation above this will cause a vacuum 
 to be formed, similar to that at the top of a baro- 
 meter, and the water at the top of the pipe will, 
 in this case, be without any pressure. But if, 
 instead of 30 feet, the pipe be continued upwards 
 only 15 feet, then the pressure on the water, in 
 the upper part of the pipe, will be 7i Ibs. on the 
 square inch, or half the usual atmospheric pres- 
 sure ; and so on for other heights. Now, the 
 boiling-point of all liquids varies with the pres- 
 sure. Water boils at 212, under the mean pres- 
 sure of 15 Ibs. per square inch ; but by reducing 
 the pressure, it boils at a lower temperature; so 
 that at half the mean pressure of the atmosphere 
 it boils at about 186. Suppose now that the 
 pipes just described rise 30 feet above the boiler, 
 the water at the top will boil at the temperature 
 of 161, and will form steam in the upper part of 
 the pipe ; and this, by its great expansion, will 
 force the water down and overflow the boiler or 
 the supply cistern. For, at the ordinary pres- 
 sure of the atmosphere, steam occupies about 
 
 * The boiling of liquids in vacua is well known, and has 
 been most extensively applied in many cases. The boiling of 
 sugar in vacuum-pans is one of the most successful appli- 
 cations of science to the arts which modern times has pro- 
 duced.
 
 THE SIPHON PRINCIPLE. 135 
 
 1,700 times as much space as the water from 
 which it is formed, and still more at a diminished 
 pressure, its expansion being inversely as the 
 pressure. When the pipes rise to other heights 
 above the boiler than that described above, the 
 boiling-points will be as follows : 
 
 At 5 feet high, the boiling point will be 203 
 10 .. . 195 
 
 15 
 20 
 25 
 30 
 
 186 
 178 
 169 
 161 
 
 Therefore the water in the boiler must always be 
 kept below these temperatures, according to the 
 height to which the pipes ascend.* 
 
 This peculiarity, which applies only to pipes on 
 the siphon principle, is more a philosophical fact 
 than a practical difficulty ; for the water can 
 generally be kept at a temperature sufficiently 
 low for any ordinary height that is required. 
 And, in fact, the boiling-point will generally be 
 higher than the temperatures here stated because a 
 small portion of air always remains in the pipes, 
 which increases the pressure on the water, and 
 
 * These calculations are made by Wollaston's rule for his 
 thermometric barometer. But this rule, although accurate at 
 moderately small differences of pressure, becomes erroneous at 
 considerable reductions of pressure. Professor Kobinson esti- 
 mates the boiling-point of water in vacuo at only 88, instead 
 of 161, which the above calculation shows ; and it is probable 
 that the relative proportion between the pressure and the 
 boiling-point is in a logarithmic ratio, instead of the common 
 arithmetical proportion of Wollaston's rule. This, in fact, is 
 found to be the case at temperatures above 212. But it is 
 probable that, in the present case, Wollaston's rule will give 
 a more accurate result than the other, because, as the vacuum 
 in the pipes cannot be at all perfect, the boiling-points will 
 be much higher than the calculated temperature; perhaps 
 even higher than stated in the text. See Robinson's Mechanical 
 Philosophy, vol. ii., pp. 22-37 ; and Wollaston " On the Ther- 
 mometric Barometer," Philosophical Transactions, 1817, p. 183.
 
 136 THE HIGH-PRESSURE SYSTEM. 
 
 makes the boiling-point higher than the calculated 
 amount. This form of the apparatus answers the 
 intended purpose when worked with care, and is a 
 very ingenious application of scientific principles ; 
 but it requires more care in working than the 
 ordinary apparatus, and is now comparatively but 
 little used. 
 
 (119.) The next invention which we shall con- 
 sider is the High-Pressure hot-water apparatus.* 
 This apparatus consists of a coil of small iron 
 pipe, built into a furnace, the pipe being continued 
 from the upper part of the coil, and passes round 
 the room or building which is to be warmed, 
 forming a continuous pipe when again joined to 
 the bottom of the coil. The diameter of this pipe 
 is one inch externally, and half an inch internally. 
 A large pipe, of about two and a half inches 
 diameter, is connected in some part of the cir- 
 culation, either horizontally or vertically, with 
 the small pipe, and is placed at the highest point 
 of the apparatus. This large pipe, which is called 
 " the expansion pipe," has an opening near to its 
 lower extremity, by which the apparatus is filled 
 with water, the aperture being afterwards secured 
 by a strong screw ; but the expansion pipe itself 
 cannot be filled higher than the opening just 
 named. After the water is introduced, the screws 
 are all securely fastened, and the apparatus be- 
 comes then hermetically sealed. The expansion 
 pipe, which is thus left empty, is calculated to 
 hold about -^ as much water as the whole of the 
 small pipes ; this being necessary in order to allow 
 for the expansion that takes place in the volume 
 of the water when heated, and which otherwise 
 would inevitably burst the pipes, however strong 
 they may be. For the expansive force of water is 
 almost irrepressible, in consequence of its possess- 
 
 * Eepertory of Arts, &c., vol. xiii. (1832), p. 129.
 
 THE HIGH-PRESSURE SYSTEM. 137 
 
 ing but a very small degree of elasticity ; and the 
 increase which takes place in its volume, by raising 
 the temperature from 39 (the point of greatest 
 condensation) to 212, is equal to about ^ part of 
 its bulk, and at higher temperatures the expansion 
 proceeds still more rapidly.* 
 
 The temperature of these pipes, when thus 
 arranged, can be raised to a very great extent; 
 for, being completely closed, and all communi- 
 cation cut off from the atmosphere, the heat is 
 not limited, as usual, to the point of 212, because 
 the steam which is formed is prevented from 
 escaping, as it does in the common form of hot- 
 water apparatus. The most important considera- 
 tion respecting it, however, is the question as to 
 its safety; for most persons are aware that steam, 
 when confined beyond a certain point of tension, 
 becomes extremely dangerous ; and in this ap- 
 paratus the bounds of what hitherto has been used 
 in other cases are very far exceeded. 
 
 (120.) On the first introduction of this plan, it 
 was usual to make the coil consist of one-fourth 
 part of the total quantity of pipe which was used 
 in the apparatus ; and it was considered that, 
 when this proportion was observed, the heat of 
 the pipes could not be raised so high as to 
 endanger them by bursting. But in practice 
 this has not always proved a preventive to acci- 
 dent, even when the proportion which the coil 
 bears to the radiating surface is much smaller 
 than is here mentioned.! 
 
 * See Table IV., Appendix. The force which would be 
 exerted on the pipes by this expansion of -^ of the volume of 
 the water would be equal to 14,121 Ibs. per square inch, 
 according to the experiments of Professor (Erstead. Report, 
 British Scientific Association, vol. ii., p. 353. 
 
 t The specification to the patent for this invention states, 
 that when the radiating surface is three times that of the coil, 
 the pipes cannot burst. It has, however, been found ncces-
 
 138 THE HIGH-PRESSURE SYSTEM. 
 
 The average temperature of these pipes is 
 stated to be generally about 350 of Fahrenheit. 
 But a most material difference of temperature 
 occurs in the several parts of the apparatus, the 
 difference amounting sometimes to as much as 
 200 or 300. This arises from the great resist- 
 ance which the water meets with, in consequence 
 of the extremely small size of the pipes, and also 
 from the great number of bends, or angles, that 
 of necessity occur, in order to accumulate a suffi- 
 cient quantity of pipe. In these angles, the bore 
 of the pipe, already extremely small, is still fur- 
 ther reduced, which causes the water to flow so 
 very slowly, that a great portion of its heat is 
 given out long . before it has circulated round 
 the building which is to be warmed. The tem- 
 perature of the coil, however, is what we must 
 ascertain, if we wish to know the pressure this 
 apparatus has to sustain, and thence to judge 
 of its safety : for, by the fundamental law of the 
 equal pressure of fluids, whatever is the greatest 
 amount of pressure on any part of the apparatus 
 must also be the pressure on every other part. 
 
 (121.) Now the temperature of this apparatus 
 is found to vary, not only with the intensity of 
 the heat of the furnace, but also with the propor- 
 tion which the surface of the coil bears to the 
 surface of the pipe which radiates the heat. In 
 some apparatus, if that part of the pipe which is 
 immediately above the furnace be filed bright, 
 the iron will become of a straw colour, which 
 proves the temperature to be about 450.* In 
 other instances it will become purple, which 
 
 sary greatly to increase the proportion of radiating surface, in 
 order to prevent the bursting by excessive pressure ; and the 
 radiating surface is now frequently made ten times that of the 
 coil in the furnace, in order to secure its safety. 
 * See Table VI., Appendix.
 
 THE HIGH-PRESSURE SYSTEM. 139 
 
 shows the temperature to be about 530 ; while, 
 in some cases, it will become of a full blue colour, 
 which proves that the temperature is then 560. 
 By this means the pressure on the pipes may be 
 known ; for, as there is always steam in some 
 part of the apparatus, the pressure may be calcu- 
 lated so soon as the temperature is ascertained. 
 By referring to Table I. in the Appendix, we 
 shall find that a temperature of 450 produces a 
 pressure of 420 Ibs. per square inch, while a 
 temperature of 530 makes the pressure 900 Ibs. ; 
 and when it reaches 560, the pressure is then 
 1,150 Ibs. per square inch. 
 
 (122.) Those who are acquainted with the work- 
 ing of steam-engines are aware that a pressure of 
 three or four atmospheres is considered as the 
 maximum for high-pressure boilers : but we see 
 that in this apparatus the pressure varies from ten 
 times to twenty times that amount. And it will 
 also be borne in mind that, in consequence of the 
 extremely small quantity of water used in these 
 pipes, the slightest increase in the heat of the 
 furnace will cause an immediate increase in the 
 pressure on the whole apparatus. For it appears 
 by a reference to the Table last mentioned, that 
 if the temperature of the pipes be increased 50 
 above the amount before stated, the pressure will 
 be raised to 1,800 Ibs. per square inch ; and by in- 
 creasing the temperature 40 more, the pressure 
 will be immediately raised to 2,500 Ibs. per square 
 inch ; so that any accidental circumstance, which 
 causes the furnace to burn more briskly than usual, 
 may, at any moment, increase the pressure to an 
 immense amount.* 
 
 * This increased pressure is also extremely likely to occur 
 in this apparatus when a portion of the pipe is occasionally shut 
 off by means of cocks or valves. In this case the coil in the 
 furnace becomes too powerful for the apparatus, and an explo-
 
 140 THE HIGH-PRESSURE SYSTEM. 
 
 (123.) The pipes which are used for this appa 
 ratus are stated to be proved with a pressure of 
 2,800 Ibs. per square inch.* This is very probable : 
 for as wrought iron of the best quality requires a 
 longitudinal strain of 55,419 Ibs. to break a bar one 
 inch square, so the force necessary to break a 
 wrought-iron pipe of one inch diameter externally, 
 and half an inch diameter internally, would be 
 13,852 Ibs., which is equal to 8,822 Ibs. per square 
 inch on the internal diameter. But, on account of 
 the strain on these pipes being transverse to the 
 grain of the iron, and also in consequence of the 
 welded joint of the pipe not being so strong as the 
 solid metal, these pipes will not bear anything 
 like the calculated amount of pressure. It is 
 evident, however, that no ordinary force can burst 
 them ; but, as this casualty does sometimes occur, 
 this great strength of the materials proves the im- 
 possibility of regulating the temperature in her- 
 metically sealed pipes, so as to keep the expansive 
 force of the steam within even this immense 
 limit. 
 
 (124.) Although this description of apparatus 
 has been erected by many different individuals, 
 possessing various degrees of mechanical know- 
 ledge, and severally performing their work with 
 different degrees of excellence, much uniformity 
 appears in the result, in those cases where failure 
 has occurred. From a comparison of a number of 
 cases where accidents have happened to apparatus 
 erected on this system, more than one-half have 
 
 sion is then very likely to occur, unless the utmost caution be 
 observed in regulating the fire. This source of danger is pecu- 
 liar to the high-pressure system of heating, and does not at all 
 apply to any of the other plans which have been described. 
 
 * As pipes are always proved when they are cold, this does 
 not at all show the strain they will bear when heated. On 
 this subject see the following Note.
 
 THE HIGH-PRESSURE SYSTEM. 141 
 
 arisen from the bursting of the coil, notwithstand- 
 ing the increased size of the expansion pipe renders 
 this latter apparently the weakest part of the appa- 
 ratus; the relative strength of pipes, with the 
 same thickness of metal, being inversely as their 
 diameters. 
 
 (125.) The cause of the explosions occurring 
 principally in the coil is owing to the iron becom- 
 ing weaker in proportion as its temperature is 
 raised ; so that, as the pressure increases, the iron 
 decreases in strength to resist the strain.* Another 
 circumstance also tends to produce the same effects. 
 It is found, on breaking one of these pipes, after it 
 has been used for some time in or near the fire, 
 that the iron has lost its fibrous texture, and that 
 it presents a crystallized appearance, similar to 
 what is known as "cold short iron." This sin- 
 gular change in the texture of iron has been 
 noticed in other instances. Mr. Lowe (Report, 
 British Scientific Association, 1834) has found that 
 wrought iron at a red heat exposed to the steam 
 of water for a considerable time, becomes crystal- 
 lized ; and in many other instances also, even 
 without the presence of steam, the same effect has 
 been observed. The cause of this, phenomenon 
 has not been clearly ascertained ; but, whatever it 
 
 * The temperature of maximum strength for cast iron has 
 been estimated at about 300 ; but the " Committee on the 
 Explosion of Steam-Boilers," appointed by the Franklin Insti- 
 tution, consider that the maximum for wrought iron is higher 
 than this, and that 572 may be considered as the temperature 
 of maximum strength. After the temperature of maximum 
 strength is once passed, the decrease in the strength of wrought 
 iron is considerable : at a red heat, or about 800, it loses about 
 one-fifth of its strength. The maximum strength of copper, 
 on the contrary, is at a very low temperature ; for the strength 
 increases with every reduction of temperature down to 32, 
 which is the lowest that has been tried. See Chapter XII., 
 Arts. 265 and 266.
 
 142 THE HIGH-PRESSURE SYSTEM. 
 
 may be, the effect undoubtedly is to weaken the 
 tenacity and cohesive strength of the metal to a 
 very great extent.* 
 
 (126.) But we shall find that, enormous as the 
 pressure appears to be, with which these pipes are 
 proved, it is not adequate to the working pressure 
 which they sometimes have to resist. It has been 
 ascertained that the strength of wrought iron 
 decreases considerably at temperatures above 572, 
 and as it also loses a great deal of its strength 
 when it assumes the crystallized state, varying 
 with the circumstances, and sometimes amounting 
 to three-fourths of its original strength, it will 
 appear that the proof pressure, when cold, for 
 pipes which are to be used in this kind of apparatus 
 ought, in fact, to be much greater than the amount 
 to which they are actually proved ; and hence the 
 cause of these pipes bursting after they have been 
 in use for some considerable time, if they happen 
 accidentally to get heated to very high tem- 
 peratures. 
 
 (127.) The question has sometimes been asked, 
 What would be the effect on this apparatus if the 
 
 * The author, in a paper which was read before the Insti- 
 tution of Civil Engineers (Minutes of the Institution, June, 1842), 
 endeavoured to trace the cause of the extraordinary change 
 which iron undergoes in these and some other circumstances. 
 Percussion at certain high temperatures produces an instanta- 
 neous change, and, at lower temperatures, longer-continued 
 percussion produces the same effect. Heating and rapid cooling 
 likewise produce crystallization ; and, in every case, magnetism 
 appears to accompany the phenomena ; but whether as cause 
 or effect is not easy to determine. The subject is altogether 
 of great interest, both in a practical and in a scientific point 
 of view ; and experiments on a large scale are in progress in 
 order to determine the question. Other metals besides iron 
 are, probably to some extent, affected in a similar manner; 
 and it is probable that, under certain circumstances, sponta- 
 neous change in the molecular structure of iron occurs, though 
 far more slowly than by the action of percussion and heat.
 
 THE HIGH-PRESSURE SYSTEM. 143 
 
 expansion-pipe were to be filled with water, as 
 well as the small circulatory pipe? The almost 
 immediate consequence would be the bursting of 
 the pipes; for scarcely anything can resist the 
 expansive power of water. The force necessary 
 to resist its expansion is equal to that which is 
 required for its artificial condensation. Now, at 
 the temperature of 386, water expands rather 
 more than ^ of its bulk; and to condense water 
 this extent (Note, Art. 12) requires a pressure of 
 27,104 Ibs. per square inch; therefore, the bursting 
 pressure at this temperature would be enormous. 
 If the pipes were filled completely full of cold 
 water, without allowing any room for expansion, 
 and if they were then hermetically sealed, as 
 before described, by increasing the temperature of 
 the water only about 60, the expansion of the 
 water would cause a pressure of 2,000 Ibs. per 
 square inch on every part of the apparatus, 
 reckoned by the internal measurement. 
 
 (128.) The assertion has often been made, that 
 the heated fluid contained in an apparatus con- 
 structed on this plan will not scald, even if the 
 pipes should chance to burst, because high-pressure 
 steam, it is well known, is not injurious in this 
 respect. But this is quite a mistaken notion ; for 
 high-pressure hot water will scald, though high- 
 pressure steam will not ; and the fluid which 
 would issue through any fissure that might occur 
 in these pipes could only be partially converted 
 into steam, unless its temperature were at least 
 1,200. This is obviously impossible ; were it the 
 case, the water would be all converted into steam 
 the instant that it issued from the pipe. The 
 reason that high-pressure steam does not scald is 
 in consequence of its capacity for latent heat being 
 greatly increased by the high state of rarefaction 
 it instantaneously assumes when suddenly liberated ;
 
 144 THE HIGH-PRESSURE SYSTEM. 
 
 this lowers its sensible temperature, and causes it 
 to abstract heat from everything that it comes in 
 contact with. The scalding effect of high-pressure 
 hot water, on the contrary, when suddenly pro- 
 jected from a pipe or boiler by explosion, will 
 always be the same, whatever its temperature 
 may be while confined within the pipe; for, the 
 instant it is liberated, a portion of it is converted 
 into steam, and the remainder sinks to the tem- 
 perature of about 212. 
 
 (129.) Among the advantages which have been 
 supposed to arise from the use of this invention, 
 it has been imagined that, in consequence of the 
 quantity of water which the pipes contain being 
 so small, the consumption of coal would be less 
 with this than with any other description of hot- 
 water apparatus. We have seen, however (Art. 
 114), that the quantity of coal which is used is in 
 proportion to the heat that is given off in the room 
 that is warmed; and a reference to the Table 
 (Art. 114) will show that the size of the pipe 
 makes no difference in the consumption of coal 
 per hour, provided the same effect is required to 
 be produced, the only difference being in the 
 length of time required to warm the water in the 
 first instance. But there will, on the contrary, 
 be a greater expenditure of fuel in this apparatus, 
 in consequence of the coil affording less surface 
 for the fire to impinge against than would be 
 obtained by using a boiler. In addition to this, 
 the colder any surface may be when exposed to 
 the action of a fire, the more heat will it receive 
 in a given time; therefore, as the heat of these 
 pipes is nearly three times as great as that of a 
 boiler, there must be a waste of fuel from this 
 cause. 
 
 (130.) In consequence of the intense heat of 
 these pipes, it is sometimes found that rooms
 
 THE HIGH-PRESSURE SYSTEM. 145 
 
 which are heated by them have the same dis- 
 agreeable and unwholesome smell which results 
 from the use of hot-air stoves and flues. In 
 reality, the cause is the same in both cases; for 
 it arises partly from the decomposition of the 
 particles of animal and vegetable matter that 
 continually float in the air, and partly from a 
 change which atmospheric air undergoes by pass- 
 ing over intensely heated metallic surfaces. The 
 electric state of the air is likewise altered by highly 
 heated metallic surfaces, and exerts an important 
 effect on all animal bodies exposed to its influence. 
 Some experiments on this subject are recorded in 
 the Philosophical Transactions of the Royal Society 
 (Vol. XXVII. p. 19&). Also in the year 1874 the 
 French Royal Academy appointed a commission to 
 examine the effect produced on atmospheric air by 
 cast iron surfaces, made red hot. Babbits were 
 made to breathe air passed over stoves of cast iron 
 heated to redness ; and afterwards chemical ex- 
 amination of the blood of the animals was made to 
 ascertain the presence of carbonic oxide. The 
 Commissioners reported that " the experiments 
 made upon rabbits do not permit us to fix with 
 any precision the proportions of carbonic oxide 
 absorbed by their blood, nor that of the oxygen 
 which has been expelled from it; but the results 
 all agree to show that the use of stoves of cast iron 
 heated to a red heat, causes in the blood (by the 
 presence of carbonic oxide) a gas eminently poisonous, 
 and causes changes whose repetition may become 
 dangerous." Whether wrought iron produces the 
 same effect is not clearly ascertained. 
 
 (131.) The high temperature of these pipes, 
 and the intensity at which the heat is radiated 
 from them, have sometimes been urged as an 
 objection against this invention, when applied to 
 horticultural purposes, because any plants which
 
 146 THE HIGH-PRESSURE SYSTEM. 
 
 are placed within a certain distance of them are 
 destroyed. Although, no doubt, this effect really 
 takes place, it can be easily avoided with proper 
 care; for, as radiated heat decreases in intensity 
 as the square of the distance, it only requires that 
 the plants should be placed farther off from these 
 pipes than from those which are of a lower tem- 
 perature. In comparing the effect of two dif- 
 ferent pipes, if one be four times the heat of 
 the other (deducting the temperature of the air 
 in both cases), the plants must be placed twice 
 as far off from the one as from the other, in 
 order to receive the same intensity of heat from 
 each. The only inconvenience, therefore, is the 
 loss of room, which in some cases may not be of 
 much importance. But a more serious objection 
 by far appears to lie in the inequality of tem- 
 perature which any building heated by these 
 pipes must have, in consequence of their being so 
 very much hotter in one part than in another. 
 This difference of temperature between various 
 parts of the same apparatus has already been 
 stated to amount, in some cases, to as much as 
 200 or 300 ; varying, of course, with the length 
 of pipe through which the water passes. From 
 what has been stated in Chapter IV., it will also 
 be observed that, owing to the smallness of these 
 pipes, this kind of apparatus cools so rapidly when 
 the fire slackens in intensity, that the heat of a 
 building which is warmed in this manner will be 
 materially affected by the least alteration in the 
 force of the fire, instead of maintaining that perma- 
 nence of temperature which is so peculiarly the 
 characteristic of the hot-water apparatus with large 
 pipes. 
 
 (132.) This invention undoubtedly exhibits great 
 ingenuity ; and could it be rendered safe, and its 
 temperature be kept within a moderate limit, it
 
 THE HIGH-PRESSURE SYSTEM. 147 
 
 would be an acquisition in many cases, in conse- 
 quence of its facile mode of adaptation. Its safety 
 would perhaps be best accomplished by placing a 
 valve in the expansion-pipe, which, from its large 
 size, would be less likely to fail of performance than 
 one inserted in the smaller pipe. If this valve were 
 so contrived as to press with a weight of 135 Ibs. 
 per square inch, the temperature of the pipes would 
 not exceed 350 in any part ; the pressure would 
 then be nine atmospheres, which is a limit more 
 than sufficient for any working apparatus where 
 safety is a matter of importance. 
 
 (133.) A modification of this apparatus was 
 proposed, and a patent taken out in 1832, by Mr. 
 Holmes, for using oil instead of water.* As fixed 
 oils boil only at very high temperatures, it was 
 supposed there would be no liability to bursting 
 the apparatus, as the temperature could not be 
 raised sufficiently high to produce any pressure 
 similar to that from steam. The temperature pro- 
 posed to be employed was about 400, but the plan 
 entirely failed, in consequence of oil, when exposed 
 to very high temperatures for any considerable 
 length of time, becoming thick and viscid, finally 
 losing its fluidity, and becoming a gelatinous mass. 
 Of course, under these circumstances, no circulation 
 of the oil could be produced, so as to render the 
 apparatus practically useful. 
 
 (134.) A patent was also taken out in December, 
 1866, by Mr. John A. Coney, for using distilled 
 mineral oil, very nearly in the same manner as 
 above described. This mineral oil, when properly 
 distilled, is not inflammable, and it may be heated 
 to nearly 1000 Fahrenheit without producing any 
 pressure in the pipes, and still retain its fluidity. 
 The death of the inventor, and other circumstances, 
 have hitherto prevented the general use of this 
 
 * Repertory of Arts, <tc., vol. xv. (1833), p. 79. 
 
 L 2
 
 148 THE HIGH-PRESSURE SYSTEM. 
 
 invention, beyond a few isolated experiments ; but 
 it appears to possess points of great utility where 
 intense heat is required. The author has heated the 
 refined mineral oil up to 800 Fahrenheit, without 
 producing any sensible pressure on the apparatus. 
 The only inconvenience appeared to be that by 
 long continued boiling at these intense temperatures 
 the oil deposited slightly a black sediment like 
 powdered charcoal. This might endanger the 
 stopping up the pipes of very small bore, unless 
 some special provision were made for its removal. 
 The sediment appears to be heavier than the oil, 
 and would probably settle in the lowest parts of the 
 apparatus. There is also a mechanical difficulty in 
 making the various joints of the apparatus sound 
 at these extreme temperatures, notwithstanding 
 there is no pressure exerted by the fluid. 
 
 (135.) An apparatus of a totally different cha- 
 racter from the preceding follows next to be 
 described. It is an invention which, at first, 
 appears to be singularly at variance with the 
 general principles that have been laid down in 
 this treatise. But however its mode of action 
 may at first appear to differ from the principles 
 which have been explained, it is certain that if 
 these principles are derived from the laws of 
 Nature, they must act equally at all times and 
 under all circumstances; for the operation of the 
 physical laws can never be suspended, though 
 they may be occasionally neutralized by a supe- 
 rior antagonist force. In the case of two oppos- 
 ing forces, the resulting action is proportional to 
 their difference of power; but when the anta- 
 gonist force is removed, each will act according 
 to its own peculiar laws. 
 
 This is the case with the invention now to be 
 described. By it hot water is made to descend to 
 any required depth below the boiler apparently
 
 ROTARY FLOAT CIRCULATOR. 
 
 149 
 
 FIG. 37. 
 
 in opposition to the law of gravity while the 
 
 cold water will ascend, though of greater specific 
 
 weight. 
 
 (136.) Eckstein and Busby's Patent Circulator, 
 
 or Rotary Float, is an invention by which centri- 
 fugal force is made to overcome the force of gravity, 
 
 in the circulation of 
 
 hot water.* The boiler, 
 
 which is either open 
 
 or closed at the top, 
 
 has a pipe, a, attached 
 
 to its circumference, 
 
 which is carried in 
 
 any direction, either 
 
 downwards, or around 
 
 the room to be warmed, 
 
 and finally returns into 
 
 the boiler, and ends exactly in its centre, as shown 
 
 at b in the annexed figure. 
 The float, or circulator, has motion given to it 
 
 by means of a fly, similar to a smoke-jack, which 
 
 is placed in the chimney, and is turned by the 
 smoke of the fire that is used to heat the boiler, 
 the float being fixed on centres, and revolving 
 freely in the boiler. The centrifugal force im- 
 parted to the water by the rapid rotation of this 
 float causes it to rise higher at the periphery than 
 in the centre of the boiler ; and the velocity with 
 which the float moves determines the extent of 
 this deviation from the level. The end of the 
 pipe b, being in the centre, is then under a less 
 pressure or head of water than the pipe a, the 
 former being, by its position, removed from the 
 greater pressure at the sides, which is caused by 
 the centrifugal force imparted to the water by 
 the float, which acts on the pipe a placed at the 
 circumference. 
 
 * Repertory of Arts, <Cv., vol. xiv. (1832), p. 137.
 
 150 ROTARY FLOAT CIRCULATOR. 
 
 (137.) Suppose now the velocity of rotation to 
 be such as to impart a centrifugal force sufficient 
 to raise the water one inch higher at the circum- 
 ference than in the centre, there will then be a 
 pressure of 246| grains per square inch upon the 
 pipe a more than upon the pipe ft, supposing the 
 temperature of the water be about 180. This 
 additional pressure will allow the water in the 
 pipe a to descend 42 feet below the boiler, if it 
 does not lose more than 6 of heat before it 
 returns back again to the boiler through the pipe 
 b : if it lose 10, then it will only descend 25J feet, 
 and so on for other temperatures. Now, as a pipe 
 four inches diameter loses '817 of a degree of heat 
 per minute when its temperature is 120 above 
 that of the room (Art. 270), this pipe may be of 
 as great a length as the distance through which 
 the water will flow in seven minutes and a half in 
 the first case, or twelve minutes in the second. 
 
 (138.) The length of pipe through which the 
 water will circulate in the above-mentioned times 
 will depend upon the depth to which it descends 
 below the boiler. In this apparatus, the shorter 
 the distance through which the water flows, the 
 greater is the rapidity of circulation an effect 
 which is the reverse of what occurs in the common 
 form of hot-water apparatus. In general, the cir- 
 culation is here very rapid; but the distance 
 through which the water will travel is more limited 
 than with the common plan of circulation. For, 
 suppose the water to be raised by the centrifugal 
 force one inch higher at the periphery than at the 
 centre of the boiler, and that it descends 42 feet; 
 if the water in the pipe lose six degrees of heat 
 during its transit, the circulation will then be 
 extremely slow; because, by the Table (Art. 15) 
 we find that the difference of weight between two 
 columns of water 42 feet high, and six degrees
 
 ROTARY FLOAT CIRCULATOR. 151 
 
 difference of temperature, is 242 grains per square 
 inch on the area of the pipe ; and this is within 
 four grains of the additional weight which the cen- 
 trifugal force produces, under these circumstances, 
 at the side of the boiler. But if the difference 
 between the temperature of the two pipes be 
 only four degrees, then the difference between the 
 weight of the two columns will be 160 grains per 
 square inch of the area of the pipe ; and (by Art. 21) 
 we shall find that this will give a velocity of 
 81 feet per minute, so that the pipe may in this 
 case be about 400 feet long. If the water only 
 lose three degrees of heat during its transit through 
 the pipes, then (by Art. 21) its velocity will be 
 100 feet per minute, provided it descends only 
 42 feet below the boiler ; and therefore the pipe 
 may be about 350 feet in length. If the depth of 
 the descent below the boiler be only one half the 
 amount above mentioned, or 21 feet instead of 42, 
 than the length of pipe through which the water 
 will circulate will be just double the amount that 
 has been stated for the several differences of tem- 
 perature.* 
 
 These calculations are all made for pipes of four 
 inches diameter ; but if smaller pipes be used, the 
 distance through which the water will circulate 
 will be less, because, as the quantity of heat lost 
 in a given time by different sized pipes is as the 
 inverse of their diameter $, so also will be the distance 
 that the water will flow, if the velocity of its 
 motion be the same.f 
 
 * This being exclusive of friction, the actual length of pipe 
 will be less than is here calculated. 
 
 I It will be observed, from what has been stated respecting 
 the common plan of circulation, that the whole of these effects 
 are exactly the reverse of what there occurs. In that, the 
 greater the difference of temperature between the pipes, the 
 more rapid the circulation : in this, the circulation is more
 
 152 NOTARY FLOAT CIRCULATOR. 
 
 (139.) If greater velocity be given to the fly- 
 wheel and float, the centrifugal force and the 
 height of the water at the circumference of the 
 boiler will both be increased ; and the distances 
 to which the pipes can be carried may then like- 
 wise be extended. 
 
 (140.) By using a close boiler instead of an 
 open one, a range of pipes may be taken upwards 
 which will act on the common plan of circulation, 
 while another range of pipes may proceed from 
 the bottom, and act on the principle which has 
 here been explained. In this case, the centrifugal 
 force, of which the additional height at the cir- 
 cumference of the boiler is merely the index or 
 measure of effect, will still be of equal power, 
 provided the velocity of the float continues the 
 same ; and the water will therefore descend to the 
 same extent as before. The spindle of the float 
 must, in this latter case, pass through a stuffing- 
 box on the top of the boiler, or some other con- 
 trivance to answer the same purpose must be 
 adopted. 
 
 This invention, which is a happy application 
 of dynamical principles to overcome one of the 
 most constant of Nature's laws, by the develop- 
 ment of an antagonist force, has hitherto been but 
 little used. It is, however, clearly capable of being 
 applied in cases where the same object cannot be 
 accomplished by any of the more simple means 
 which have been previously described. 
 
 (141.) A plan proposed by Mr. Edward Weeks 
 for circulating water at different heights was some 
 years since (1829) made the subject of a patent, 
 but it is not necessary here to be described, as it 
 
 rapid in proportion as the pipes are nearer to the same tem- 
 perature. In the former, the circulation is more rapid when 
 the pipes are moderately small ; in the latter, the larger the 
 pipe the greater the velocity of circulation.
 
 FLAT RADIATIXG SURFACES. 153 
 
 has long since been superseded by more efficient 
 means. A boiler, also of his invention, is described 
 in Art. 87. 
 
 (142.) Mr. Thomas Fowler, of Great Torrington, 
 in 1828, took out a patent for an apparatus which 
 he called a Thermo-siphon.* It was, however, 
 wholly inapplicable to the purposes intended, in 
 consequence of the complication of valves and 
 cocks required to work it ; the whole of which 
 complication is overcome by the invention of Mr. 
 Kewley, described in Art. 117. 
 
 (143.) An apparatus was invented by Mr. H. C. 
 Price, and patented in 1829, which was designed 
 principally to alter the form of the radiating sur- 
 faces.f These surfaces, instead of being composed 
 of pipes, are formed of flat close vessels, about 
 three feet square, and 2 inches thick, placed 
 edgeways (or vertically), so that when several of 
 them are fixed together, a thin stratum of air 
 passes upwards between them, and becomes heated 
 in its passage. A main-pipe connects all these 
 vessels together at the bottom, another similar 
 pipe is fixed at the top ; and these main-pipes 
 lead to and from the boiler, thus keeping up the 
 circulation of water in all these flat vessels at the 
 same time. This is often a very convenient mode 
 of applying a large extent of heating surface in a 
 moderately small space; but the principle of 
 the circulation is in no way different from the 
 ordinary hot-water apparatus. The vessels con- 
 taining the hot water are usually placed in a vault 
 or chamber below the room or building to be 
 warmed; arid the air, when heated, ascends to 
 the room above through ventilators in the floor, 
 or other similar contrivances. 
 
 For large buildings this plan answers exceed- 
 
 * Eepertory of Arts, &c., vol. ix. (1830), p. 393. 
 | Ibid. vol. x. (1830), p. 65.
 
 154 TANK SYSTEM. 
 
 ingly well, and many very extensive apparatus 
 have been erected with perfect success, as it is 
 always combined with a system of ventilation, 
 which is too often neglected in other methods of 
 heating buildings. 
 
 (144.) A plan has lately been proposed by Mr. 
 Rendle, of Plymouth, as a novel mode of heating 
 horticultural buildings, and which he has denomi- 
 nated the " Tank System." The principal object 
 proposed is to afford bottom-heat to plants, with- 
 out the use of bark, tan, dung, or other expen- 
 sive and troublesome materials. The plan re- 
 commended is to construct a tank, either of 
 brick, wood, slate, stone, or metal, immediately 
 below the beds of the hothouse, the tank being 
 the full width of the bed, and about four or five 
 inches deep. A partition divides this tank up the 
 centre, except about two or three inches at the 
 further end; and then, by^ connecting two pipes 
 to the end of the tank nearest to the boiler one 
 leading from the flow-pipe of the boiler, and the 
 other to the return-pipe and placing these on 
 the opposite sides of the before-mentioned parti- 
 tion, a circulation of water is produced, the hot 
 water passing up one side of the tank and return- 
 ing back along the other side, the partition merely 
 separating the two currents. The tank is first 
 covered with large and strong slates, and then a 
 layer of loose stones is laid, and subsequently 
 layers of sand and earth ; and the sides of the 
 tank are so constructed as to rise sufficiently high 
 to make a convenient receptacle for these several 
 layers of materials, through which the heat 
 ascends to the plants placed in the earth on the 
 top. 
 
 This form of apparatus is represented in fig. 38, 
 which shows the tank without the cover, and also, 
 without the sides which support the layers of
 
 TANK SYSTEM. 155 
 
 stones and earth. The tank, if made of brick, 
 requires to be well stuccoed, in order to make it 
 
 FIG. 38. 
 
 hold the water without percolation through the 
 bricks ; but the expansion caused by the heat 
 renders it difficult to keep the tank perfect. Wood 
 tanks are also liable to become leaky; and when 
 used, require to be made in the most substantial 
 manner. 
 
 (145.) The plan of affording bottom-heat in 
 this manner possesses but small claims to novelty, 
 except as regards the form of the vessel which 
 contains the heated water. In 1788 steam was 
 first used for giving a bottom-heat to plants by 
 T. Wakefield, Esq., of Northwich. His experi- 
 ments were continued for several years with con- 
 siderable success, and in 1792 the plan was 
 adopted at Lord Derby's gardens, at Knowsley, 
 apparently on the model of Mr. Wakefield's, and 
 was attended with perfect success.* From 1801 
 to 1806 the use of hot water, flowing through 
 leaden pipes, placed about nine inches below the 
 surface of the mould, was employed by T. N. 
 Parker, Esq., of Sweeney Hall, Oswestry, for 
 giving bottom-heat for melon-pits, the water 
 circulating through a single pipe only, which was 
 
 * A long account of these experiments will be found in the 
 Repertory of Arts, vol. xiv. (1st series), p. 235, et seq. ; and 
 also in the Transactions nf the Society of Arts and Manufac- 
 tures, &c.
 
 356 TANK SYSTEM. 
 
 attached to a small copper boiler. Mr. Weston, 
 of Leicester, in 1800, employed for the same 
 purpose leaden pipes three inches diameter, filled 
 with hot water, which, from the slow conduct- 
 ing power of the metal, retained the heat for a 
 great length of time.* In 1826, Mr. MacMurtie, 
 gardener to Lord Anson, described a method of 
 giving bottom-heat jointly by flues and steam, 
 which he had successfully employed for a period 
 of twelve years; f and in 1831 the author applied 
 the circulation of hot water, on the common plan, 
 through iron pipes of four inches diameter, for 
 producing bottom-heat in forcing pits, without the 
 use of dung. 
 
 All these plans have been successful to a con- 
 siderable extent ; but they all have one defect in 
 common with Mr. Rendle's system. It is difficult 
 to regulate the quantity of moisture ; and by some 
 of those plans particularly those where steam 
 was allowed to evaporate in large quantities 
 there was too much damp for the plants, and by 
 others they were too dry. Mr. Rendle's tanks are 
 liable to the same objections. It is probable that 
 the most efficient way of applying hot water cir- 
 culation for producing bottom-heat would be by 
 passing large iron pipes of four inches diameter 
 through troughs made water-tight, placed beneath 
 the bed required to be heated, and filled with small 
 loose stones. These stones, when once heated, 
 will retain their temperature for a great length of 
 time, and by pouring water into the trough, 
 vapour can be raised to any extent that may 
 be required, the quantity being much or little as 
 circumstances may render desirable ; or the heat 
 may be continued without any vapour, whenever 
 
 * Repertory of Arts, vol. xiii., p. 238 (1st series), 
 f Horticultural Transactions, vol. vi. ; and Quarterly Journal 
 of Science, vol. xxii., p. 341.
 
 TANK SYSTEM. 157 
 
 a dry heat is required. The pipes need not be 
 placed very close together; about 12 or 18 inches 
 apart from each other would probably be a good 
 distance when four-inch pipes are used, depending 
 principally upon the quantity of vapour which is 
 required to be raised. 
 
 (146.) Mr. Rendle proposes to make his tanks 
 supply -sufficient heat to warm the air of the 
 house, as well as to produce a bottom-heat for the 
 plants. Those who adopt this plan will soon 
 find that it can only be used as an adjunct to any 
 other method, and that it cannot supersede the 
 ordinary modes of heating horticultural buildings. 
 The chief merit of this plan consists in bringing 
 into action a large reservoir of hot water, con- 
 tained in slow-conducting materials ; by which 
 (when the tank is connected with the pipes that 
 heat the air of the house in the usual way) greater 
 equality of temperature can be maintained in a 
 hothouse than by any other method which com- 
 prises only a smaller body of hot water. This, 
 however, does not appear to form any part of 
 Mr. Rendle's system. In a pamphlet, published 
 by him, the apparatus is described as intended 
 both to heat the air of the house, as well as to give 
 bottom-heat to the plants ; but when the tank is 
 made of brick, according to his recommendation, 
 the quantity of heat radiated from the exterior 
 surface must necessarily be so small that sufficient 
 heat to warm the air of the house in cold weather 
 cannot possibly be obtained. Iron tanks, instead 
 of brick, have been proposed by other parties; 
 by which this latter objection .would be overcome : 
 but by the greater radiating power of the iron 
 the advantages contemplated by Mr. Rendle would 
 not be obtained. The brick tank, when used only 
 for bottom-heat, and as an addition to the usual 
 arrangement of pipes for warming the air, may
 
 158 THEORY OF EVAPORATION. 
 
 frequently form a very useful apparatus ; but it 
 will probably give way to some better arrangement, 
 by which the vapour can be regulated with more 
 certainty than this form of apparatus appears 
 capable of doing. 
 
 (147.) A patent was obtained in 1838, by Mr. 
 Corbett, of Plymouth, for heating buildings by 
 hot-water circulation in open troughs, instead of 
 pipes of the usual form.* The objection to this 
 plan is the difficulty of regulating the quantity of 
 vapour given off by the open troughs, to suit the 
 varying requirements of the plants. The inven- 
 tor proposes to do this by means of moveable 
 covers to be placed on the troughs, which would 
 prevent the vapour rising so rapidly. But all 
 the advantages of this plan appear to have been 
 anticipated several years previous, by the use 
 of pipes with troughs of about three inches deep 
 cast on the top, and extending nearly the whole 
 length of the pipe. The trough, being formed by 
 the surface of the pipe itself, is always kept hot : 
 and any quantity of vapour can be obtained, up 
 to the actual saturation of the atmosphere of the 
 house, by filling these troughs partially or wholly, 
 as the case may require. 
 
 (148.) The last two inventions which have 
 been described appear to be founded on a very 
 imperfect knowledge of the physical laws which 
 they call into action. The tank system, when 
 used as the inventor of it recommends, must 
 necessarily fail to afford sufficient heat to the air, 
 as a very slight acquaintance with the laws of 
 radiant heat will show; and the use of open 
 troughs, to supersede the previous method of 
 .pipes with troughs cast on them, is founded on a 
 misconception of the laws of vaporization. 
 
 (149.) Mr. Corbett states, in the specification 
 
 * Repertory of Arts, dc., vol. xi. (1839), p. 346.
 
 THEORY OF EVAPORATION. 159 
 
 to his patent, that the quantity of vapour which 
 is given off from the troughs depends upon the 
 temperature of the air and the depth of the 
 troughs. This last circumstance (inasmuch as by 
 increasing the depth, the radiating surface must 
 be enlarged and the temperature of the water 
 thereby lowered) will certainly somewhat alter 
 the rate of evaporation, though not necessarily its 
 final quantity ; but the temperature of the air in 
 no way influences either the quantity or the rate 
 of evaporation, unless it be so cold as to condense 
 the vapour. 
 
 (150.) Dr. Dalton* has shown that the only 
 circumstances which affect the vaporization of 
 water in atmospheric air are "First, the quan- 
 tity evaporated is in direct proportion to the 
 surface exposed, all other circumstances being 
 alike. Second, an increase in the temperature 
 of the liquid is attended with an increase of 
 evaporation not directly proportionate. Third, 
 evaporation is. greater where there is a stream of 
 air, than where the air is stagnant. Fourth, the 
 evaporation from water is greater, the less the 
 humidity previously existing in the atmosphere, 
 all other circumstances being alike." The rate 
 of evaporation, therefore, from water under 212 01 
 Fahrenheit is directly as the surface of water 
 exposed, and as the evaporating force ; which latter 
 is the name that has been given to the difference 
 in the elasticity of the vapour which rises from 
 the water as the given temperature, and that of 
 the vapour already existing in the air. Dr. Dalton 
 found that " the same quantity is evaporated with 
 the same evaporating force, whatever be the tem- 
 perature of the air." 
 
 (151.) This theory of evaporation is here more 
 
 * Memoirs of the Phil sophicnl Society of Manchester, vol. v., 
 p. 576, et seq.
 
 160 THEORY OF EVAPORATION. 
 
 particularly dwelt upon, because many persons 
 have adopted the notion that any quantity of 
 vapour, without limitation, can be produced by 
 means of open troughs, such as have been de- 
 scribed. Nothing, however, can be more erro- 
 neous. "When once the air is saturated, the evapo- 
 rating force ceases,* until either a portion of the 
 vapour it contained be condensed, or the tem- 
 perature of the evaporating fluid be increased, 
 when of course a new state of circumstances 
 obtains, and the condition of equilibrium ends. 
 Practically, however, evaporation never ceases 
 when the evaporating liquid is kept at a high 
 temperature ; because the air being at a much 
 lower temperature, the vapour contained in it 
 must always have less elasticity than that given 
 off from the water. The result will be that the 
 water evaporated will be condensed by the air, 
 and will be precipitated ; while, at the same time, 
 the latent heat of the vapour will be rendered 
 sensible, and will raise the temperature of the 
 air.f If the air were confined in a place where it 
 could not lose any portion of this acquired heat, 
 this process would ultimately stop the evaporation ; 
 but in horticultural buildings the loss of heat 
 from the large surface of glass is so considerable, 
 that this result cannot follow. 
 
 * These remarks apply to the case of fluids under the tem- 
 perature of 212. A different state of things obtains when 
 the vapour formed exceeds the total atmospheric pressure, as 
 in the ordinary process of generating steam. 
 
 f The quantity of heat given out by the condensation of 
 vapour is very considerable. By the note to Art. 97, it will 
 be seen that a cubic foot of water will heat 2,990 cubic feet of 
 air as many degrees as the water itself loses. As the latent 
 heat of vapour is about 1,000, it follows that every cubic inch 
 of water which is evaporated, and then again condensed from 
 vapour, as above mentioned, will communicate 5 of heat to 
 348 cubic feet of air.
 
 THEORY OF EVAPORATION. 161 
 
 (152.) As the quantity of vapour given off to 
 the air depends, as we have here shown, on the 
 surface and the temperature of the water exposed, 
 it follows that no possible advantage can be ob- 
 tained from a large quantity of water in an open 
 gutter over the same surface of water obtained by 
 the old method of troughs fixed or cast on the top 
 of the pipes. The latter are more easily regulated 
 to suit the requirements of different plants and 
 different seasons, and are also free from several 
 practical difficulties which attend the application 
 of the other method.* 
 
 (153.) The preceding remarks are descriptive 
 of the principal modifications which have hitherto 
 been introduced into the hot-water apparatus, 
 though many deviations of a minor character have 
 been proposed, several of them, indeed, being in- 
 troduced apparently for the sake of novelty. The 
 advantage, however, which may be derived from 
 these peculiar forms or modifications of the appa- 
 ratus must depend upon the purpose for which it 
 is required. Thus, in places where a long con- 
 tinuance of heat and uniformity of temperature 
 are required, the form of the pipes, tanks, vessels, 
 and other radiating surfaces should be such as to 
 afford only a small surface, while they contain a 
 large quantity of water. This may be obtained 
 by using pipes of large diameter, or tanks of a 
 large cubical content, and approaching in form 
 either to the sphere or the cube; while, on the 
 contrary, where the heat is required to be quickly 
 raised, and permanence of temperature is unim- 
 
 * Those who wish to follow further the subject of sponta- 
 neous evaporation may with advantage consult the Memoirs 
 of the Manchester Philosophical Society, already quoted ; also 
 Nicholson's Journal, vol. xxvii., p. 17 ; Journal de Physique, 
 vol. Ixv., p. 446 ; Quarterly Journal of Science, vol. xvii., p. 46 ; 
 and Philosophical Transactions, vol. Ixxxii., p. 400. 
 
 M
 
 162 PECULIAR FORMS OP APPARATUS. 
 
 portant, the radiating surfaces may be greatly 
 increased, in proportion to the actual quantity of 
 water contained in the apparatus. In this case, 
 therefore, pipes of small diameter, or tanks which 
 are very flat in form, may advantageously be 
 used; and many varieties of the apparatus will 
 necessarily be adopted, amongst ingenious per- 
 sons who practically apply this invention to the 
 vast number of useful purposes to which it is 
 applicable. For many of the purposes to which 
 it is extremely suitable it has not hitherto been 
 applied; and its advantage, in other cases, has 
 not even yet been sufficiently appreciated. Such 
 are the uses to which it may be adapted in various 
 manufactories in paper-making, calico-printing, 
 dyeing, and starch-making; and also for drug- 
 gists, seedsmen, and numerous other purposes of 
 general utility ; and for drying-rooms for every 
 purpose where a mild and equable heat is desir- 
 able. For many of these purposes it is exceed- 
 ingly convenient, as the form of the heating 
 surface can be made to suit the peculiar object to 
 which it is to be applied; and the inconveniences 
 that arise from unequal degrees of heat, conse- 
 quent on most other methods of warming, are by 
 this means entirely avoided.
 
 1G3 
 
 CHAPTER VIII. 
 
 General Summary of the Subject Points requiring particular 
 attention Abstraction of Air from the Pipes ; Vertical 
 Alteration of Level Effect of Elbows in compensating 
 unequal Expansions of the Pipe Different Floors heated 
 by one main Pipe from the Bailer Method of connecting 
 Coils to main Pipes Reduced Effect from Pipes laid in 
 Trenches Effect of Cold Currents of Air in neutralizing 
 heating Apparatus Heating Apparatus placed in Vaults 
 Cements for Joints Sediment in Boilers Use of Salt in 
 Pipes to prevent freezing Deposition of Vapour in inhabited 
 Rooms, and necessity for Ventilation Construction of 
 Drying-rooms. 
 
 (154.) HAVING, in the preceding chapters, ar- 
 ranged, under distinct heads, the various remarks 
 on the principles of warming by the circulation of 
 hot water, it may here be desirable to bring under 
 general review the principal facts which it has 
 been the object of this work to explain. There 
 are, besides, many minor points connected with 
 the invention that could not conveniently be 
 brought under notice in any of the foregoing 
 divisions under which the subject has been treated, 
 but which, nevertheless, may be found very useful 
 to those who are investigating its principles, or 
 adapting it to practice. 
 
 (155.) A correct knowledge of the cause of cir- 
 culation of the water (it has already been observed) 
 is absolutely necessary to the successful application 
 of this invention in many of its more complicated 
 arrangements. Some estimate must be formed of 
 the amount of the motive power possessed by an 
 
 M 2
 
 164 GENERAL REMARKS. 
 
 apparatus of this sort, otherwise it will be impos- 
 sible to ascertain what will be the result of any 
 particular position, or determinate length of the 
 pipes, in many -peculiar cases ; as, for instance, in 
 such forms of apparatus as figures 10, 11, and 28. 
 It is also necessary, in order to make provision 
 for the escape of the air from an apparatus of this 
 kind, to have some knowledge of the laws which 
 regulate the motion of fluids, in order to ascertain 
 where the air will lodge, and why it should 
 accumulate in one place rather than another. No 
 circumstance connected with the subject requires 
 greater caution than this. In almost every part 
 of the apparatus where an alteration of the level 
 occurs, a vent for the air must be provided ; 
 because, from the extreme levity of air compared 
 with water (Art. 9), it is impossible that the air 
 can ever descend, so as to pass an obstruction 
 lower than the place where it is confined. Thus, 
 in fig. 7, if the air accumulate in the pipe between 
 A and e, it is evident that a vent at c, although it 
 would take off the air from g h and from c D, 
 could not receive any portion of that which is 
 confined between A e, or between e f, because, in 
 that case, it must descend through the pipe e f 
 before it could escape. The principle is the same 
 in all cases, however large or however small the 
 descent may be ; and the accidental misplacing of 
 a pipe in the fixing, by which one end may be 
 made a little higher than the other, will as 
 effectually prevent the escape of air through a 
 vent placed at the lower end as though the devia- 
 tion from the level were as many feet as it may, 
 perhaps, be inches. It is, however, impossible to 
 give multiplied examples of this part of the sub- 
 ject, for probably no two instances precisely 
 similar may occur ; but it deserves the most 
 serious attention in following out its practical
 
 GENERAL REMARKS. 165 
 
 consequences, for innumerable failures have arisen 
 from its neglect, and no part of the subject is more 
 puzzling to an experienced practitioner. 
 
 (156.) When any particular obstructions are 
 required to be overcome, in consequence of nume- 
 rous alterations in the level of the pipes ; when 
 the pipes are required to descend below the boiler ; 
 or, in short, when any other variation from what 
 may be considered as the usual form and arrange- 
 ment of the apparatus may be desirable, it is 
 essentially necessary to have some data on which 
 to found a calculation as to what will be the 
 practical result of the required deviation. For no 
 partial experiment of a tentative character, nor 
 even the effect shown by a miniature model, will 
 give anything like an accurate idea of what will be 
 the result, when the experiment is made on a large 
 scale. The reason of this is obvious. It has been 
 shown that the greater the distance through which 
 the water flows, the greater does the motive power 
 become, in consequence of the water being colder 
 in the return-pipe relatively to the flow-pipe, while 
 at the same time the friction is increased, though 
 not always in an equal degree. This will, there- 
 fore, prevent partial experiments that is, working 
 models exhibiting only a particular portion of the 
 whole apparatus from being conclusive ; and 
 with a miniature model, although the decreased 
 time and distance of transit are compensated by 
 the reduced size of the pipe exerting a greater 
 cooling power on the water, the friction being 
 much greater in small than in large pipes, the 
 velocity will be reduced in a very sensible degree, 
 and the results rendered wholly inconclusive. In 
 general, the successful working of a miniature 
 model will be conclusive that the experiment on 
 a larger scale will perform still better; but the 
 failure of the model will be no proof that the 
 larger apparatus will not be successful.
 
 166 GENERAL REMARKS 
 
 Calculations on this subject possessing any 
 claims to accuracy are extremely difficult, and 
 exact results, indeed, are perhaps impossible, in 
 the present state of our knowledge on this difficult 
 branch of hydraulics, notwithstanding the many 
 eminent and learned men who have both written 
 and experimented on the motion and resistance of 
 water moving in pipes.* Notwithstanding this 
 acknowledged difficulty, the remarks made in the 
 preceding chapters will enable an approximate 
 estimate to be formed as to the general effect that 
 may be expected from any particular form of the 
 apparatus, and whether the motive power will be 
 increased or diminished by the arrangement pro- 
 posed. And, by following out in detail the rules 
 which have been given, a tolerably accurate judg- 
 ment may be arrived at as to the result that may be 
 expected, under almost every form of the apparatus 
 that may be adopted. 
 
 (157.) In the diagrams which have been given 
 in the first and second chapters, the simplest 
 possible arrangements of the pipes have been 
 shown. To give the various forms in which the 
 pipes and heating surfaces may be laid would 
 obviously be impossible; it must be left to the 
 ingenuity of the adapters of the apparatus to 
 deduce, from the general rules which have been 
 given, the form of apparatus best suited to the 
 particular case ; and, while bearing in mind the 
 causes which produce and increase the circulation, 
 it will not be difficult to contrive an almost in- 
 finite variety of arrangements for accomplishing 
 the desired result. 
 
 (158.) In the simple form of the apparatus as 
 generally used in hothouses, there is seldom much 
 difficulty, except when the pipes are required to 
 dip below the doorways. When the boiler is 
 
 * See Chapter II., Art. 22.
 
 ^X THE HOT- WATER APPARATUS. 167 
 
 placed sufficiently low (Art. 28), the difficulty of 
 taking off the air from the pipes at the places 
 where the dips occur is principally to be attended 
 to. It has sometimes been the practice to place 
 an open upright pedestal on the top of the pipe 
 at /, fig. 9, for the supposed purpose of adding by 
 the weight of its column of water to the downward 
 pressure at that part, and by this means to increase 
 the circulation. But the real effect of such a 
 column of water pressing on the pipe must be to 
 increase the pressure on every part of the apparatus 
 alike, and not on this part in particular ; and there- 
 fore it is probable that any effect obtained by this 
 means is attributable only to a more easy escape 
 being provided for the air. Any air accumulating 
 at this part must be particularly prejudicial, by 
 occupying a portion of the space which ought to 
 be filled with water, and thus diminishing the 
 pressure on the descending column. A very small 
 accumulation of air at this part of the apparatus 
 might seriously retard, or even totally obstruct, 
 the circulation, and therefore a ready escape for 
 the air at this point is particularly desirable. The 
 same effect is no doubt to some extent produced 
 by the open cistern A, fig. 12 (Art. 32) ; for, 
 although its effect is generally beneficial, it is 
 difficult to account for it on the ground of increased 
 pressure ; while it is obviously quite possible that 
 benefit may arise from the air having so easy an 
 escape,* and from the difference in the temperature 
 of the two pipes. 
 
 * It has been supposed that, although this increased pres- 
 sure by a vertical column of water undoubtedly extends 
 every part of the apparatus, an advantage must arise in con- 
 sequence of the bubbles of steam and hot water (which rise 
 continually upwards from the bottom of the boiler, strongly 
 acted on by the fire) being relatively lighter than the rest of 
 the water, when the latter is thus condensed by the increased
 
 168 GENERAL REMARKS 
 
 (159.) It will be apparent from these remarks 
 how essential it is that the pipes be free from any 
 accumulation of air, when such difficult cases of 
 circulation are attempted as those described in 
 Arts. 30 34, or any of an analogous character. 
 It is probable that many failures have arisen 
 entirely from this cause, which a very slight 
 alteration would have prevented; and attention 
 to this point, in the construction of all hot-water 
 apparatus, can hardly be urged too strongly. 
 
 (160.) When the pipes dip below the doorways 
 of hothouses, it is sometimes very difficult to allow 
 sufficient depth for two pipes of large diameter 
 below the step of the door, when placed as shown 
 in fig. 9. When this is the case, a smaller pipe 
 may be used at this particular part ; and just at 
 the dip, the large iron pipe may be reduced to one 
 of smaller diameter, and again increased when it 
 rises from below the door. The circulation will 
 by this means always be reduced to some extent 
 (Art. 48), and it is by no means advisable to adopt 
 it whenever it can be avoided. All unnecessary 
 variations in the size of the pipe ought always to 
 be avoided, and, when adopted, the alterations are 
 better to be gradual than sudden, as there will be 
 less obstruction to the water passing through a 
 trumpet-shaped pipe, either from a large to a small 
 pipe, or from a small pipe to a larger, than when 
 these changes are made abruptly. 
 
 Inconvenient as these vertical dips in the pipe 
 frequently are, they, as well as the horizontal 
 bends, are sometimes useful in counteracting an 
 
 vertical height. This, however, must needs be erroneous, 
 because steam produced under pressure is of greater density 
 exactly in proportion to this pressure, and therefore the 
 relative proportions between the densities of the steam-bubbles 
 and the water must be preserved, however much the pressure 
 may be increased.
 
 OX THE HOT- WATER APPARATUS. 169 
 
 inconvenience which otherwise might occur from 
 the expansion of the pipe in its horizontal length. 
 When there is a very long length of perfectly 
 straight pipe passing along the side of a building 
 and returning again in the same direction, it 
 often happens that the expansion of one of these 
 lengths of pipe is so much greater than the other, 
 owing to its higher temperature (and this parti- 
 cularly happens when the circulation is slow), 
 that some of the joints become loose, and a 
 leakage occurs. This inconvenience is more 
 likely to occur when three or four pipes are 
 placed one above another; in which case the 
 upper pipes always become heated first, and 
 thence become more expanded in length. And so 
 great is the force of this expansion, that unless 
 there is some degree of elasticity given to the 
 pipes, either by elbows intervening or by some 
 other means, a leakage is almost certain to occur ; 
 and generally it happens at the extreme end of 
 the pipes farthest from the boiler. When steam 
 pipes were used for heating buildings, this cause 
 of leakage was very inconvenient; and Count 
 Rumford introduced an ingenious mode of coun- 
 teracting it, by attaching both the upper and 
 lower pipe to a copper drum, which, being more 
 pliable than the cast-iron, corrected the evil. In 
 all cases where there is a great length of pipe 
 running in a straight line, it is necessary to bear 
 in mind the certainty of expansion occurring, and 
 to provide for its effects ; for serious accidents 
 have occurred to buildings by neglecting this 
 precaution, as the expansion cannot be prevented 
 under any circumstances, and its power is im- 
 mense against anything that resists it. 
 
 (161.) In all cases where pipes are placed at 
 various elevations above the boiler, for the pur- 
 pose of warming different floors of a building, or
 
 170 GENERAL REMARKS 
 
 where from any other cause the pipes descend by 
 steps or gradations from a high elevation to a 
 lower before the water returns to the boiler, it is 
 desirable that the water should be made to ascend 
 at once from the boiler to the highest elevation. 
 By this means the best possible circulation is 
 always insured, as there will then be the greatest 
 difference between the weight of the ascending 
 and descending columns. It will, however, often 
 be found convenient, when different floors of a 
 building are required to be heated by one appa- 
 ratus, to have a separate pipe leading from the 
 boiler to each floor; as it is difficult to make 
 horizontal branch-pipes effective when leading out 
 at different elevations from a general main-pipe 
 rising vertically from the boiler. This arises from 
 the extremely rapid motion of the water in vertical 
 pipes, by which means the whole of the heated 
 Avater passes directly to the highest level, without 
 delivering any to the lower horizontal branches. 
 This plan of having separate pipes for each floor 
 is better than having one pipe gradually descending 
 through them all, as, the shorter the circulation, 
 the more equal will be the effect, in consequence 
 of greater equality in the temperature of the pipes 
 (Art. 49). When it is inconvenient to have 
 separate flow-pipes from the boiler to each floor, 
 an equal circulation may be obtained by the 
 arrangements shown Art. 49. 
 
 When several coils are fixed in succession in 
 different places, being supplied by means of one 
 general main pipe with its return pipe passing 
 underneath the main or flow-pipe, it is not unusual 
 to connect the coils into both the flow and the 
 return-pipe, thus 
 
 FIG. 38B.
 
 OX THE HOT- WATER APPARATUS. 171 
 
 This plan of connecting coils very often fails 
 entirely, the circulation stopping at the second, 
 third, or fourth coils, as the case may be. When 
 the main-pipe is very large, say 3 or 4 inches 
 diameter, and the connections from the main-pipe 
 to the coils are about 1 inch diameter, this mode 
 of connection succeeds tolerably well, and several 
 coils in succession may be connected in this way ; 
 but when the main-pipe is small, such, for instance, 
 as 1J inch or 2 inches diameter, it is very rarely 
 that the circulation can be forced beyond the first 
 or second coil, and sometimes it stops entirely after 
 the first coil. The reason of this is obvious. The 
 circulation returns at once to the boiler after passing 
 through the first coil, the friction being too great and 
 the quantity of heated water being too small, when 
 passing through the very small main-pipe ; and in 
 this case the water returns to the boiler through 
 the shortest route instead of flowing through the 
 whole arrangement of pipes. This rarely takes place 
 when the main-pipe is very large, unless the con- 
 nections from the main-pipe to the coils are out 
 of due proportion. Although it is a great mistake 
 (but one that is often committed) to make the 
 main-pipe too small, proportionately to the number 
 and size of the coils it is expected to supply, a 
 much smaller main pipe may be used when the 
 coils in a range are connected in this manner that 
 
 FIG. 38c. 
 
 is, all the connections being made to the flow-pipe 
 alone. By this means of connecting coils, a circu- 
 lation can be secured through almost any number 
 of coils without any inequality in their tem- 
 perature.
 
 172 GENERAL REMARKS 
 
 When coils are connected by lateral pipes placed 
 at some distance from the main-pipes, another 
 difficulty frequently occurs. In this case the 
 circulation is very likely to pass by the lateral or 
 side connection, and refuses to be diverted from 
 its straight course. Sometimes a lateral connection 
 of 4 or 5 feet long, at right angles from the main 
 pipe, will entirely stop the circulation into the coil, 
 at other times it may be carried very much further. 
 This difference probably arises from a variation in 
 the velocity of the circulation ; for it has sometimes 
 happened that the water in a coil fixed laterally, a 
 few feet off from a main-pipe, will circulate when the 
 apparatus is first set to work, and then gradually 
 cease to act as the water in the general apparatus 
 gets hotter and hotter. This effect may be pre- 
 vented when the main-pipe is sufficiently large, by 
 placing a stop half way across the main-pipe, as ex- 
 plained, Art. 49, with regard to vertical main-pipes. 
 
 (162.) In those cases where the radiating surfaces 
 are not placed actually in the room or building 
 which is to be heated, but which produce their 
 effect by heating successive portions of air, which 
 then pass into the room that is to be warmed, there 
 will always be considerable loss of heat, which will 
 require a correction to be made in the calculations 
 already given. This applies also to those cases 
 where the pipes are placed in drains or trenches 
 below the floor, with trellis gratings or ventilators 
 in the floor to cover the pipes and to emit the heat. 
 The proportion of heat lost by this means will 
 depend upon various circumstances. When the 
 pipes freely radiate their heat into the room to be 
 warmed, about one-fifth of the total effect is pro- 
 duced by radiation, and the rest by contact of the 
 air with the heated surface (Art. 227, et seq.). 
 But that portion of the heat obtained by radiation 
 will be considerably reduced by placing the pipes
 
 OX THE HOT- WATER APPARATUS. 173 
 
 in a trench. For the interior surface of the trench 
 will become considerably heated ; and as the heat 
 given off by radiation depends in a great degree 
 upon the difference of temperature between the 
 heated body and the medium by which it is sur- 
 rounded, it follows that the hotter the trench 
 becomes the less radiant heat will be given off by 
 the pipes. The loss of effect by this means would 
 be considerable were it not for the circumstance 
 that the heated surface of the trench itself gives out 
 heat by conduction to the air. The effect, there- 
 fore, becomes a very complicated one. But it may 
 probably be assumed, as a tolerably correct result, 
 that the loss of heat by placing tbe pipes in a 
 trench which is well covered for nearly its whole 
 length with trellis gratings, will not exceed five per 
 cent, in ordinary circumstances. When the trench 
 is only partially covered with trellis gratings, the 
 loss of heat will be more ; and therefore, when this 
 plan of placing the pipes is adopted, at least two- 
 thirds of the entire trench ought to be covered 
 with the trellis grating, and, if possible, the whole 
 length should be so covered, in order that the 
 freest possible escape be allowed for the heated air. 
 The trench also should not be made too large. 
 The best size will be, to have it just large enough 
 to hold the pipes, and to allow the workmen easily 
 to fix them ; and all the space beyond that will only 
 tend to diminish the effect of the apparatus.* 
 
 * It is sometimes desirable to make the bottom and sides 
 of these trenches full of holes, for the purpose of admitting 
 fresh air into the building. Some remarks on this subject 
 will be found under the head of " Ventilation," in a subse- 
 quent chapter (Art. 353). It requires great judgment in 
 this case in order to prevent the cold air being discharged 
 into the room instead of first warming it by proper contact 
 with the pipes. A much smaller surface of trellis grating is 
 required in this case, but a much larger surface of pipe is 
 necessary.
 
 174 GEXERAL REMARKS 
 
 The same remarks will, of course, apply to all 
 cases where the pipes or other radiating surfaces 
 are .placed in vaults or chambers below the rooms 
 intended to be heated ; and, in all cases of this 
 kind, allowance must be made for the loss of effect 
 arising from the causes here described. It should 
 also be observed that when the heating surfaces 
 are placed ia vaults or chambers below the rooms 
 to be heated, and are so contrived that the air 
 from the rooms does not pass over them a second 
 time, but fresh external air alone is made to pass 
 over them and then to escape from the heated 
 room by means of ventilators, from 50 to 70 per 
 cent, more pipe is necessary to heat a given space 
 than will be required if the air of the heated room 
 be made to circulate repeatedly over the heating 
 surfaces. The air will be more salubrious when it 
 is not heated over again a second time, but the cost 
 of the apparatus will be greatly increased. 
 
 Whenever the heating surfaces are placed in 
 vaults or chambers, and not distributed generally 
 in the rooms to be heated, it requires great judg- 
 ment in placing the openings for the emission of 
 heated air in a proper position: for if there is a 
 current of cold air from one end of the room or 
 building as, for instance, in a church which has 
 the entrance at one end it is impossible to make 
 the hot air travel to the extremity of the building ; 
 but, being met by the cold current from the door, 
 it will be forced back and prevented from reaching 
 the colder end. This circumstance has entirely 
 destroyed the beneficial action of innumerable 
 apparatus; and so strong frequently is the action 
 of the cold current of air in such buildings, when 
 rushing into a somewhat rarefied atmosphere, that 
 it has not unfrequently happened that under these 
 circumstances the building has become considerably 
 colder when the heating apparatus is used than it
 
 OX THE HOT-WATER APPARATUS. 175 
 
 was before the pipes were warmed or tfye fire 
 lighted. The only remedy is to place the openings 
 for the emission of hot air in such parts of the 
 building that it shall not meet with these opposing 
 currents of cold air. It is sometimes very difficult 
 to accomplish this, and it requires great judgment 
 efficiently to warm buildings under these circum- 
 stances. 
 
 (163.) One of the most efficient plans for warm- 
 ing large buildings, and at the same time the 
 most difficult to accomplish, except when directed 
 by great experience and judgment, is by combining 
 the two methods of placing part of the heating 
 surfaces in vaults or chambers, and part in flues 
 or drains. By this method perfect ventilation can 
 be secured, but the expense is considerably in- 
 creased. Not only will the heating surfaces require 
 to be increased at least 50 per cent, beyond the 
 ordinary method of heating, but proper arrange- 
 ments must be made for extracting the foul or 
 contaminated air from the ceiling or roof (see 
 Art. 360, &c.). But this plan of warming requires 
 likewise very special arrangements. The air in 
 this case must be admitted into a vault or chamber, 
 and there heated by means of coils, or pipes, or 
 other surfaces, on which the admitted air must 
 impinge and be kept sufficiently in contact to be- 
 come heated. It is then to be conveyed into the 
 room or building which is required to be warmed 
 through drains or channels in which a certain 
 quantity of hot water pipes are placed, as the hot 
 air will not travel along cold lateral drains for any 
 considerable distance. To decide what proportion 
 of the whole heating surface shall be placed in the 
 vault, and what in the channels or drains, requires 
 great consideration and experimental knowledge. 
 If these proportions are erroneous, the heating may 
 become entirely neutralized in certain states of the
 
 176 GENERAL REMARKS 
 
 wind, and a reverse action may take place by which 
 all the* hot air may be discharged through the cold 
 air drains when the wind blows from certain quarters. 
 The form of the building and its exposed or sheltered 
 situation have great influence in this case. In some 
 buildings no such reverse action ever takes place. 
 In perfectly plain straight buildings, this action of 
 the wind is most likely to occur. In others of 
 irregular form, and where there are numerous pro- 
 jections, or buttresses, or anything likely to break 
 the force of the wind, the reverse action is the least 
 likely to happen. In some cases less than a fourth 
 of the entire heating surface laid in the trenches is 
 sufficient to give motion to the air : in other cases 
 half or two-thirds laid in the trenches will not be 
 more than is necessary for the purpose of causing 
 the heated air to flow readily through the drains. 
 There is no plan so effectual as this for bringing 
 warm fresh air into a building, and thus combining 
 ventilation and warming, but the contingencies 
 attending it are not inconsiderable. 
 
 In all those forms of the apparatus where the 
 effect depends on bringing in a body of cold fresh 
 FTO. 880. air from the exte- 
 
 rior of the build- 
 
 ing and this 
 applies also to all 
 forms of hot air 
 apparatus and 
 cockle stoves a 
 very high wind 
 will sometimes 
 stop the action of 
 the apparatus en- 
 tirely. Suppose 
 fig. 38o to repre- 
 sent the ground plan of a building to be warmed by 
 any kind of heating apparatus placed in a vault or
 
 OX THE HOT-WATER APPARATUS. 177 
 
 chamber shown by the dotted lines. When the 
 wind blows from any of the points shown by the 
 arrows, the air will enter the vault or chamber 
 without much difficulty if the channel is sufficiently 
 large. But if the wind blows strongly from any 
 other quarters than those shown by the arrows, the 
 air, instead of being drawn into the chamber or 
 vault, will experience a reverse action, and the air 
 will be drawn or sucked out from the building. 
 This arises from the greater pressure of the air on 
 the windward side of the building, which causes a 
 partial vacuum to be produced on the opposite 
 side where the cold air drain is placed. Under 
 these circumstances the whole action is reversed, and 
 the heated air is sucked out of the building entirety. 
 
 When the force of the wind is much broken by 
 the irregular form of the building, or by surround- 
 ing objects, this effect is scarcely likely to happen. 
 Where it does occur, the best remedy is to make 
 a second entrance for the air from the opposite 
 side of the building and temporarily to close the 
 one or the other, as the direction of the wind may 
 render necessary. 
 
 The most effectual way of preventing the reverse 
 action which is here described, is to bring the cold 
 air into the hot air chamber by a very large flue 
 or channel from above the roof. This flue must 
 stand as high, or higher than the roof, and it should 
 be surmounted by a cowl or turncap, balanced so 
 as to turn towards the wind instead of from the 
 wind, as usual for ventilating or smoke purposes. 
 The large size, however, of this flue and the sur- 
 mounting turncap is a very serious obstacle to its 
 use. Thus, suppose a room containing 500 people. 
 The quantity of air required to ventilate this room 
 would be (Art. 360) 5,000 cubic feet per minute ; 
 and this would require the flue or channel to have 
 a capacity of 21 square feet. It would be almost 
 
 N
 
 178 GENERAL REMARKS 
 
 impossible to make so large a flue in any ordinary 
 building; and unless the flue was of sufficient 
 size, it would be of very little use. For a private 
 house, heated on this principle, of course a very 
 much smaller flue would be sufficient, but even a 
 flue of 2 feet square (or 4 square feet area) would 
 be a most inconvenient incumbrance if it passed 
 from the roof to the basement of the house to 
 supply air to the hot air chamber. 
 
 There is also another error to be guarded against 
 in adopting this mode of placing the heating sur- 
 faces in a separate vault or chamber. It is indis- 
 pensable that the vault should not be too large. 
 If it is much larger than the heating surfaces, or 
 if the heating surfaces be placed too far apart from 
 each other, the entering air will pass by or escape 
 without sufficient contact, and will enter the room 
 or building as a cold draught. The more confined 
 the space of the heating chamber, the better will 
 be the effect, provided there is sufficient space to 
 allow the air a tolerably free passage: if it can 
 escape round the sides of the chamber without 
 coming in contact with the heating surfaces it will 
 certainly do so, as there is a natural repulsion 
 between these heated surfaces and the entering air. 
 
 (164.) The mechanical operation of fitting to- 
 gether the pipes is a subject known to most good 
 workmen who are acquainted with iron-work. 
 The usual and best kinds of pipes for the purpose 
 are those with socket-joints, those with flange- 
 joints having long ceased to be employed for hot- 
 water apparatus. And even for steam, where 
 flange-joints were formerly invariably used, the 
 socket-joints are now very frequently employed, 
 as they make a much neater and at the same time 
 an equally strong joint. In fact, when the joints 
 of socket-pipes are well made, the pipes themselves 
 will break before the joints will yield, or before the
 
 OX THE HOT-WATER APPARATUS. 179 
 
 faucet-end of one pipe can be drawn out of the 
 socket of the other. The joints require to be 
 well caulked with spun yarn, and then filled up 
 with cement. The strongest cement is that knowu 
 to engineers under the name of iron cement, con- 
 sisting of iron borings, sal ammoniac, and sulphur ; 
 but it requires to be used with great caution, 
 as it expands very much, and very frequently 
 bursts the pipes. But other cements are -fre- 
 quently used, the principal of which are a mixture 
 of white and red lead, which makes a very good 
 cement ; and a cement made of quicklime mixed 
 into a paste with boiled linseed oil* has occa- 
 sionally been employed with considerable success. 
 Fire-clay sifted fine and mixed with boiled 
 oil also makes a good cement ; and Portland 
 cement mixed with water has also been used 
 for jointing pipes where there is little or no 
 pressure. But perhaps the hardest cement of all 
 is red and white lead mixed with a considerable 
 quantity of iron borings, which is very enduring 
 as well as an extremely hard cement. For all 
 ordinary purposes, the best cement is red and 
 white lead ; and a very small quantity of iron 
 cement applied as a means of finishing the joint 
 the red and white lead being used at the bot- 
 tom of the joint, and the iron cement at the top 
 forms perhaps the best joints that can be made. 
 Many thousands of pipes have been burst at the 
 joints from improper modes of using the cement. 
 Whenever iron cement is used in too large quan- 
 tities, and too strong in its chemical proportions, 
 the sockets are almost certain to burst after they 
 have been made a few months. For a chemical 
 
 * This composition is very liable to spontaneous combustion, 
 and should therefore be used with caution, particularly by 
 mixing it apart from anything likely to ignite by the heating 
 of the materials. 
 
 N 2
 
 180 GENERAL REMARKS 
 
 action takes place in the iron cement, which 
 slowly expands, and thus bursts the sockets of the 
 pipes, if the quantity used is at all in excess ; and 
 this slow chemical action has been found to go on 
 for many months, and sometimes even for years, 
 causing the most serious loss and inconvenience 
 by the destruction of the pipes. 
 
 (165.) It may be desirable to make a few obser- 
 vations on the water that is to be used in this 
 kind of apparatus. Sometimes the foulest and 
 most filthy water is used in a hot-water apparatus, 
 by which a thick coating of mud is deposited, and 
 which must necessarily not only much reduce 
 the effect of the apparatus, but also injure the 
 boiler. But a far more general and, in fact, an 
 extremely common error lies in using hard water, 
 which contains a large quantity of earthy salts. 
 Bain-water ought to be used when it can possibly 
 be obtained, because all hard waters are impreg- 
 nated with saline matter, which forms the sediment 
 or incrustation so common in those vessels in 
 which water is boiled. This incrustation always 
 accumulates in the boiler of a hot-water apparatus 
 in which hard water is used, and forms a coating, 
 varying in substance from the thinnest lamina to 
 three or four inches in thickness. When this 
 deposit of saline matter occurs in a boiler, not 
 only is less heat received by the water, in conse- 
 quence of the conducting power being lessened 
 by the interposed substance, but the boiler will be 
 much injured by the increased heat of its external 
 surface, and more fuel will be consumed. 
 
 The quantity of sediment formed in a hot-water 
 apparatus, however, bears no comparison in ordi- 
 nary cases with that of steam-boilers. In the 
 latter, the quantity is so large as sometimes to 
 require its removal at least once in every three or 
 four days, and sometimes even oftener. But, as
 
 ON THE HOT- WATER APPARATUS. 181 
 
 there is scarcely any evaporation from a hot-water 
 boiler under ordinary circumstances, the quantity 
 of sediment is so small, if the water is good, that 
 the boiler does not require cleaning out even after 
 many years' use. This remark, however, will not 
 apply to such forms of apparatus as Mr. Een die's 
 or Mr. Corbett's (Art. 144 and 147) ; for in these 
 the evaporation of the water is so great that the 
 sediment in the boiler must necessarily be very 
 considerable, and, without proper care, it may 
 become a most serious evil. Owing to the ex- 
 treme smallness of the boilers used for hot- water 
 apparatus, it is very difficult to clean them from 
 sediment, and with the majority of them it is 
 impossible. When, therefore, such boilers are 
 applied to an apparatus on the tank system, or to 
 Mr. Corbett's open troughs, they will probably 
 fail in a comparatively short time, unless the use 
 of rain-water be strictly adhered to. The plan of 
 open troughs cast on the pipes (Art. 147) is not 
 of course liable to the same objection; for, how- 
 ever large the evaporation may be, the boiler 
 cannot be affected by it, as the sediment will 
 necessarily remain in the troughs, and can easily 
 be removed. 
 
 (166.) This kind of sediment can only be 
 removed from a boiler with great difficulty. It 
 consists principally of carbonate of lime and 
 sulphate of lime, together with the sulphates of 
 soda and magnesia, and several other salts, vary- 
 ing considerably in different localities. A weak 
 solution of muriatic acid (one part of acid by 
 measure to 20 or 30 parts of water) will generally 
 reduce this concreted sediment into a substance of 
 less tenacity, which may then be removed with 
 slight mechanical force. Sometimes this sediment 
 is so hard as to bear polishing, when it exactly 
 resembles marble, being beautifully speckled or
 
 182 GENERAL REMARKS 
 
 veined. At other times it shows successive layers 
 loosely aggregated. In some places where the 
 water is obtained in mineral districts, large sedi- 
 ments of iron or even of copper may be found in 
 the pipes and boilers of hot-water apparatus, 
 causing the greatest possible annoyance. In this 
 case the deposit is more usually found in the pipes 
 than in the boilers, forming either a brown or a 
 yellow deposit according as the iron may be in the 
 state of a sulphate or a carbonate.* By using 
 rain-water the inconvenience arising from these 
 deposits will, however, be entirely avoided, and 
 the apparatus will both last longer and be more 
 efficient. 
 
 (167.) Some inconvenience has occasionally 
 been experienced when a hot-water apparatus has 
 been left for a long time without being used, and 
 exposed to considerable degrees of cold, by the 
 water becoming frozen in the pipes; for it is not 
 only difficult in such cases to thaw the water, but 
 sometimes also the pipes burst. To prevent the 
 pipes from cracking, it will generally be sufficient 
 to draw off a portion of the water, so that the 
 
 * There are forty-three ascertained substances, which are 
 known as contaminating different waters. Of these, seven 
 are gases, two are free acids, and thirty-four are neutral salts. 
 The salts of lime most commonly found in water have been 
 mentioned above in the text. The other impurities, with the 
 exception of iron, are not of usual occurrence. Iron is found 
 in water in two different states, the Carbonate and the 
 Sulphate. In the state of carbonate, the iron gives a yellow 
 ochre colour to the sediment. The carbonate of iron easily 
 parts with its carbonic acid, and passes into an oxide of iron, 
 which is insoluble in water. The sulphate of iron, which is 
 very soluble in water, absorbs oxygen very easily and then 
 becomes insoluble and is precipitated in the form of a brown 
 oxide or ochre. These oxides are very destructive to the 
 pipes and boilers of hot-water apparatus. The neutral salts 
 thus formed, rapidly choke up the pipes and boilers, while 
 the acids set free in their formation, seriously injure the me- 
 tallic substance of the apparatus itself.
 
 OX THE HOT- WATER APPARATUS. 183 
 
 horizontal pipes shall not be quite fall; for the 
 cracking of the pipes arises from the sudden 
 expansion which takes place in the water, at the 
 moment of its passing into the solid state of ice. 
 But when the apparatus is not likely to be used 
 for a considerable time, it would be much better, 
 if the weather be very cold, to empty the 
 pipes entirely of water ; for it is always trouble- 
 some to thaw the water when once frozen in the 
 pipes.* In an apparatus used in a building of 
 which the temperature is always above 32 this 
 is obviously unnecessary, as the water cannot 
 then be frozen. A plan, however, might be adopted 
 which will effectually prevent the water freezing 
 with any ordinary degree of cold, namely, by 
 using salt water in the apparatus, instead of fresh 
 water. This plan would certainly be somewhat 
 injurious to the apparatus, on account of the 
 action of the salt on the iron ; but the injury 
 would not be extensive, and would be very slow 
 in its operation. Perhaps in this country such a 
 plan is unnecessary ; but should this kind of 
 apparatus be adopted in colder climates, the sug- 
 gestion might be useful. The larger the quantity 
 of salt which a given portion of water contains, 
 the greater is the degree of cold necessary to 
 congeal it. Thus, the quantity of salt contained 
 in sea-water is about three per cent. ; f this re- 
 
 * It is perhaps not generally known, that water which has 
 been boiled freezes sooner than that which has not been boiled. 
 This circumstance was observed by Dr. Black, in 1775 (Philo- 
 sophical Transactions, vol. Ixv., p. 124). But it has since been 
 remarked that Aristotle, Pliny, and others of the ancients, 
 have noticed the same fact in their writings (Memoirs of the 
 Manchester Philosophical Society, vol. i., p. 261). 
 
 j" This quantity varies considerably in different localities. 
 In the English Channel the quantity is as above stated ; but 
 on the coast of Spain it contains about 6 per cent., while the 
 water of the Baltic only contains about 1 per cent. ^Between
 
 184 GENERAL REMARKS 
 
 quires, according to Dr. Marcet, a temperature of 
 about 28 to freeze it ; but if the quantity of salt 
 be increased to 4*3 per cent., the water will not 
 freeze until the cold be reduced to 27 of Fahren- 
 heit, or 4J below the ordinary freezing-point of 
 fresh water. When the water contains 6'6 per 
 cent, of salt, it will not freeze until the temperature 
 be reduced to 25^ of Fahrenheit ; and if it con- 
 tains 11-1 per cent., the temperature must reach 
 as low as 21 J before the water will congeal.* 
 
 The effect which would be produced on cast- 
 iron pipes and boilers, by any of these quan- 
 tities of salt, would not be of much importance; 
 although, in process of time, it would certainly in 
 some degree corrode the apparatus, f When the 
 apparatus has been once filled with salt water, the 
 waste which occurs in the water, by evaporation, 
 should only be supplied with fresh water ; for, as 
 the salt does not evaporate, the same quantity of 
 salt will remain in the apparatus, and will com- 
 bine with the fresh water when added. 
 
 (168.) As water at a medium temperature can 
 hold in solution nearly 36 per cent, of common 
 salt (chloride of sodium), and nearly 40 per cent, 
 at the boiling temperature, there is no fear of any 
 deposit forming in the boiler from this cause. J 
 
 the Tropics the quantity is very large ; as much as 10 per 
 cent, is stated to exist in some of the tropical seas and oceans. 
 (Ure's " Chemical Dictionary," art. " Muriatic Acid.") 
 
 * Ure's " Chemical Dictionary," art. " Caloric ; " and 
 " Blagden's Experiments" Philosophical Transactions, vol. 
 Ixxviii., p. 279. 
 
 f A remarkable difference obtains in the rate at which 
 oxidation acts on cast and on wrought-iron. Hard-cast iron 
 will resist oxidation about three times as long as wrought-iron ; 
 and, according to the experiments of Mr. Daniell, the same 
 difference exists in the length of time requisite to produce a 
 given effect by acids. The effect on soft cast-iron will approach 
 nearer to that of wrought-iron, varying with its hardness. 
 
 t Ure's " Chemical Dictionary," art. " Salt."
 
 OX THE HOT-WATER APPARATUS. 185 
 
 The reason of a deposit forming in boilers where 
 hard water is used, is because the water leaves 
 behind, on evaporation, the saline compounds 
 which it held in solution ; and as the water which 
 is added to supply the place of that which has 
 evaporated likewise contains the same extraneous 
 matter, the quantity presently becomes larger 
 than the water can hold in solution, and the 
 residue is precipitated and hardened by the heat 
 of the fire. All the salts of lime, which are 
 usually contained in hard water, are likewise 
 soluble in this fluid only in a very limited degree. 
 For instance, sulphate of lime, one of the most 
 common ingredients in hard water, is soluble in it 
 only to the extent of '2 or one-fifth of one per 
 cent. ; and carbonate of lime in a still smaller pro- 
 portion ; therefore the precipitation begins to take 
 place so soon as the quantity exceeds this small 
 amount. 
 
 It should also be observed that hot water 
 sustains less of the salts of lime in solution than 
 cold water, which latter deposits lime on being 
 heated. If, therefore, the water in a hot-water 
 apparatus is frequently or constantly changed, 
 there is a rapid deposit of lime formed in the 
 pipes or boilers or cisterns which contain it. This 
 is particularly the case in all apparatus used for 
 bath purposes, where from the constant change of 
 the water, by the addition of fresh water to 
 supply the place of that drawn off for use, the 
 choking up of the boilers and pipes is extremely 
 rapid unless constant attention is given to the 
 removal of the sediment.* 
 
 A patent has recently been taken out by Mr. 
 Stainton for the use of chloride of calcium mixed 
 with water in certain quantities in order to pre- 
 vent the water freezing, more particularly appli- 
 
 * See Chap. IX., art. 179* et seq.
 
 186 GENERAL REMARKS 
 
 cable to the high-pressure and small pipe system 
 (Art. 119 133). It is favourably spoken of as a 
 remedy for the pipes freezing, which is a casualty 
 to which the small pipes are liable when used in 
 colder climates than our own. It is likewise 
 stated that the mineral oil used in Coffey's Patent 
 (Art. 134) will not freeze, and retains its fluidity 
 at all temperatures. 
 
 (169.) In Chapters XII. and XIII., some of the 
 most important of the laws of heat, which are 
 applicable to the general subject / of this treatise, 
 are described, and also the experimental data on 
 which are founded several of the calculations 
 given in the preceding chapters. Those who are 
 desirous of investigating for themselves the accu- 
 racy of the various rules which have been given, 
 will thus be enabled to judge of the subject in its 
 more scientific bearings. 
 
 (170.) Before concluding these remarks, how- 
 ever, it may be proper to observe that buildings 
 which are heated by hot water ought always to 
 have some efficient mode of ventilation ; for, even 
 though the air may not be injured by the appa- 
 ratus employed to heat it, the air of all inhabited 
 rooms must necessarily be deteriorated by the 
 respiration of the inmates. This remark would 
 have been superfluous were it not that cases have 
 occurred where the evils that have arisen from 
 defective ventilation have been erroneously attri- 
 buted to this plan of warming by hot water. 
 The vapour which is given off from the lungs of 
 the inmates of a room, under these circumstances, 
 is condensed upon the windows, and has been 
 supposed to arise from the water in the apparatus 
 being converted into steam, and escaping through 
 the joints of the pipes. If this were a solitary 
 opinion, it might, like many others equally erro- 
 neous, be passed over in silence ; but as this
 
 OX THE HOT-WATER APPARATUS. 187 
 
 has been seriously objected against the inven- 
 tion by many who ought to know better, it 
 may be worth while to state the cause more at 
 length. 
 
 (171.) The quantity of vapour given off from 
 the lungs, and also by exhalation from the skin, 
 has been estimated at from twelve to thirteen 
 grains per minute for each person. If, in conse- 
 quence of imperfect ventilation of inhabited rooms, 
 the air cannot escape after it has received this 
 additional quantity of vapour exhaled from the 
 body, it must, as soon as it has acquired a larger 
 quantity of moisture than the temperature of the 
 external air will support in the form of vapour 
 (Art. 330), deposit a portion of it upon the glass; 
 because, the glass being nearly of the same tem- 
 perature as the external air, whatever quantity of 
 the internal air comes in contact with it, its tem- 
 perature is immediately lowered, and the excess of 
 its vapour is condensed upon the surface of the 
 glass. Thus, suppose the temperature of the air 
 in a room to be 65, and the dew-point 55, then, if 
 the temperature of the external air be only 35, as 
 much of the air in the room as comes in contact 
 with the glass will deposit whatever vapour it con- 
 tains above the quantity that a temperature of 35 
 will enable it to sustain. Under these circum- 
 stances, the amount deposited on the glass will be 
 (Art. 330) about two grains for each cubic foot of 
 air that is cooled by the glass ; and the same effect, 
 though in a less degree, will take place on all the 
 other cold surfaces in the room. As each square 
 foot of glass will cool one and a quarter cubic 
 feet of air per minute, from the internal to the 
 external temperature (Art. 101), we shall find 
 that, under the circumstances we have supposed, 
 which is purposely taken as an extreme case, 
 the quantity of vapour deposited in this manner
 
 188 GENERAL REMARKS 
 
 will amount to two and a half grains per minute 
 on each square foot of glass. 
 
 (172.) We need be at no loss, then, to discover 
 the cause of this accumulation of vapour on the 
 windows and walls of rooms which are badly 
 ventilated ; and whenever the quantity of mois- 
 ture thus condensed appears to be considerable, 
 it may be taken as good evidence that the venti- 
 lation of the room is imperfect. That the same 
 amount of condensation does not result from the 
 use of hot air and cockle-stoves, is in consequence 
 of a portion of the vapour being decomposed by 
 the intense heat ; but when this method of avoiding 
 the inconvenience is adopted, a worse evil is 
 produced than that which is attempted to be 
 removed, although, perhaps, it is not so obvious 
 to the sight. 
 
 (173.) A similar error is very frequently com- 
 mitted in the construction of drying closets and 
 rooms intended for drying various articles in 
 manufactures and the arts. It is frequently sup- 
 posed that a sufficient degree of heat is all that 
 is required for this purpose, and the amount of 
 ventilation is considered quite an unimportant 
 matter. It need scarcely be observed that the 
 reverse of this is the proper course, and that 
 ventilation is, in these cases, of far more import- 
 ance than the degree of heat maintained in the 
 room. 
 
 (174.) The experiments of Dr. Dal ton long 
 since demonstrated that evaporation was inde- 
 pendent of. the air; that the vapour arising from 
 any liquid depends upon its temperature, and 
 that the air retards the velocity of the discharge 
 by its vis inertice* If the air were wholly re- 
 moved from the surface of the water, the vapour 
 
 * Memoirs of the Manchester Philosophical Society, vol. v., 
 p. 575 ; and Philosophical Magazine, vol. xvi., p. 346.
 
 OX THE HOT- WATER APPARATUS. 189 
 
 proper to the particular temperature would be 
 discharged instantaneously, instead of rising gra- 
 dually, as when the water is exposed to the 
 atmosphere. The quantity of evaporation is not 
 affected by these causes. If water be placed under 
 the receiver of an air-pump and the air exhausted, 
 the full quantity of vapour which can be formed 
 at that particular temperature will rise instan- 
 taneously ; but if the air be allowed to fill the 
 receiver, the same quantity of vapour will rise, and 
 it will have slowly to filter its way and disperse 
 itself through the air which fills the receiver. In 
 these cases, we of course suppose that the vapour 
 is not removed ; but that, when once formed, it is 
 allowed to remain in the receiver, and that the 
 temperature is kept constantly the same. But 
 when the vapour is allowed to escape, or to con- 
 dense, the rate of its formation is very different in 
 air and in vacuo; for Mr. Darnell's experiments 
 proved that, in the same time, the quantity of 
 vapour raised from a constant surface of water in 
 vacuo and in air of atmospheric density was as 
 90 to 1 ; and that at all intermediate pressures the 
 quantity of vapour was inversely proportional to 
 the elasticity of the incumbent air.* 
 
 When, however, the air possesses motion, its 
 effect on the quantity of vapour emitted from the 
 surface of water over which it passes will be very 
 different. The effect is, then, to drive off the 
 vapour from the surface of the evaporating body 
 as fast as it is formed ; and this Dr. Dalton found 
 to be proportional to the velocity of the air.f 
 This latter case is precisely that with which we 
 are concerned, while considering the effect of 
 
 * Quarterly Journal of Science, vol. xvii., p. 52. 
 f Memoirs of the Manchester Philosophical Society, vol. v., 
 p. 576 ; and Watson's Chemical Essays, vol. ii., p. 57.
 
 190 GENERAL REMARKS 
 
 ventilation, and more particularly in the ventilation 
 of drying-rooms. 
 
 (175.) It is quite a mistaken notion to suppose 
 that a better effect will be produced by prevent- 
 ing too rapid a motion of the air through drying- 
 rooms, for the purpose of allowing the air to 
 imbibe more of the moisture by this means. The 
 infiltration of moisture into the air, or the absorp- 
 tion of moisture, as it is generally called, is ex- 
 tremely slow, as the experiments of Daniell and 
 of Leslie have proved ; and therefore it is, by the 
 brisk motion of the air driving off the vapour as 
 fast as it is formed, that the principal effect is 
 produced in the ventilation of dry ing- rooms.* 
 The quantity of air which really becomes humid 
 by such means is extremely small; and Leslie 
 has estimated that, in a case of ordinary evapora- 
 tion, where the air possessed but small velocity, 
 only the 184th part of the air that passed over 
 the wet surface became saturated.f 
 
 (176.) It is extremely difficult to estimate the 
 quantity of heating surface that is required for a 
 dr} 7 ing-room ; for not only will the temperature 
 vary greatly with the nature of the substances to 
 be dried, but also with the degree of dampness 
 they possess, and likewise with the amount of 
 ventilation. The same quantity of heating surface 
 that would raise the temperature of a drying- 
 room to 80 or 90 with an imperfect ventilation, 
 might possibly not heat it above 60 or 70 if the 
 ventilation were perfect; and yet in the latter 
 case, probably, the drying effect would be greater 
 
 * The drier the air the more rapidly will it absorb the 
 moisture exhaled into it ; but, under every condition of dry- 
 ness, the absorption of moisture will be much less rapid by 
 the air than its discharge from the vaporizing body would be 
 were the pressure of the air entirely removed. 
 
 f Leslie On Heat and Moisture, p. 86.
 
 OX THE HOT-WATER APPARATUS. 191 
 
 than in the former. This, however, is not with- 
 out certain limitations in its operations. When- 
 ever the ventilation is sufficient to carry off the 
 vapour as fast as it is formed, anything beyond 
 this must be injurious, as it will lower the tem- 
 perature of the room without promoting the 
 dispersion of the vapour; and we have already 
 seen that the quantity of vapour raised depends, 
 in the first instance, upon the temperature of the 
 vaporizing body. When, however, an atmosphere 
 of vapour exists immediately around the body 
 emitting the vapour, the emission is enormously 
 reduced, and sometimes even wholly stopped ; and 
 this will occur, however high the temperature of 
 the vaporizing body and of the air may be. In 
 this case, therefore, even a very much lower tem- 
 perature, accompanied by a brisk motion of the 
 air, would be far more effectual than a high tem- 
 perature with defective ventilation. 
 
 (177.) For common drying-rooms, where arti- 
 cles of various thicknesses are dried at the same 
 time, and where the quantity of moisture to be 
 evaporated is considerable, it has been found that 
 150 to 200 square feet of heating surface to each 
 1,000 cubic feet of space produces a temperature 
 of about 120 when the room is empty and the 
 ventilating apertures are closed. The tempera- 
 ture falls about 15 or 20 on opening the venti- 
 lating apertures ; and when the room is filled 
 with wet clothes the temperature falls to about 
 80 or 90, and sometimes considerably lower, 
 varying with the nature of the articles which are 
 placed in the room. Mr. Buchanan states * that 
 about 63 square feet of steam-pipe to 1,000 cubic 
 feet of space produced a temperature of 100 in a 
 drying-room ; and in another instance 44 square 
 feet of heating surface to 1,000 cubic feet of space 
 
 * Buchanan's Treatise on Economy of Fuel, dc., 211-218.
 
 192 GENERAL REMARKS 
 
 produced a temperature of 86 in a drying-room, 
 both being partially filled with damp goods. The 
 temperature of the steam is not stated in these 
 instances ; but the pipes would naturally be hotter 
 than hot-water pipes, and therefore less surface 
 of them would be required; but the quantity of 
 pipe thus given is considerably less than was re- 
 quired in any instance which has come under the 
 author's own knowledge. In general, it would 
 not be safe to use much less than 150 square feet 
 of heating surface of hot-water pipes to 1,000 cubic 
 feet of space in any drying-room used for drying 
 linen, where quick drying is essential. For manu- 
 facturing purposes it will often happen that much 
 smaller quantities of heating surface will suffice ; 
 for the goods often contain far less moisture, and 
 are not required to be dried so quick as in a 
 common closet for drying linen. 
 
 Tredgold has given rules for calculating the 
 required heating surface for drying-rooms for dif- 
 ferent purposes, but the} 7 " are much too refined 
 for ordinary use.* A large amount of heating- 
 surface is, however, absolutely indispensable 
 where quick drying is required ; but attention 
 to the perfect ventilation of the room is of 
 more importance than its actual temperature. 
 It is also advisable to have some ready means 
 of altering the quantities of air admitted into 
 a drying-room ; for not only is it desirable, if 
 possible, to alter the quantities of air admitted at 
 the different stages of the drying process, but in 
 different states of the weather the quantities of 
 air admitted ought to be likewise altered. When 
 the air is very humid, much less air ought to 
 be admitted than in dry bright weather. In 
 damp weather the drying process will go on much 
 faster, in proportion as a less quantity of air is 
 
 * Tredgold On Beating Buildings by Steam, p. 241 et seq.
 
 ON THE HOT- WATER APPARATUS. 193 
 
 admitted, and a higher working temperature main- 
 tained in the drying-room. In dry weather the 
 opposite of this will often be desirable, and a 
 much larger quantity of air may advantageously 
 be admitted under these circumstances. 
 
 (178.) The physiological effects resulting from 
 particular modes of warming and ventilating in- 
 habited rooms form a most interesting subject of 
 inquiry, and are not only interesting as matters of 
 scientific research, but they closely concern every 
 individual member of the community. It is a 
 question which affects not merely the personal 
 comfort of individuals, but, according to the opinion 
 of the ablest pathologists, it influences the health, 
 and affects the duration of life. In a subsequent 
 chapter we shall endeavour to trace some of the 
 physiological effects of various methods of artificial 
 heat, and the most important consequences will be 
 found to result from the use of some of these 
 different inventions.
 
 194 
 
 CHAPTER IX. 
 
 ON APPARATUS FOR SUPPLYING BATHS, AND HOT 
 WATER FOR DOMESTIC AND OTHER PURPOSES. 
 
 Inconvenience from Deposits in the Boiler Deposit in Cisterns 
 Circulation necessary throughout the whole range of Pipes 
 Proper position of the Hot Water Cistern Two different 
 modes of drawing off the Hot Water Heating Tanks by 
 Coils or by direct circulation from the Boiler Mode of 
 estimating power of a Coil Estimate of Boiler Surface 
 Plunging Baths. 
 
 (179.*) WHEN large quantities of hot water are 
 required for baths, laundries, or other purposes, 
 considerable modifications of the apparatus become 
 necessary from that which is generally used for 
 warming buildings. From what has already been 
 stated Art. 166, it will be seen that in any apparatus 
 where the object is to supply large quantities of 
 hot water by continually drawing off the heated 
 water, and supplying its place by fresh cold water, 
 a large deposit of mineral substances constantly 
 occurs. When rain water alone is used this 
 deposit does not occur. But in every other case 
 it is absolutely necessary to provide some form of 
 boiler which can readily have the mineral deposit 
 removed. These deposits sometimes become of 
 enormous thickness unless frequently removed; 
 the destruction of the boiler is inevitable under 
 these circumstances. Some form of boiler different 
 to the usual forms used for warming buildings is 
 therefore indispensable. 
 
 There are many forms of boilers quite suitable
 
 APPARATUS FOR BATH?. 195 
 
 for this purpose, and so long as they admit of an 
 easy removal of the deposit, the particular form is 
 not very material. Any of the forms used for 
 steam purposes answer very well, and the remarks 
 on them need not be here repeated. 
 
 (180.*) It is usually the practice to heat the 
 water by means of large cisterns connected with 
 the boiler by a flow-pipe and return-pipe. A 
 deposit very frequently occurs in these cisterns as 
 well as in the boilers, and hence it is necessary to 
 have ready access to the interior of the cisterns. 
 The deposit in the cistern is not so serious as the 
 deposit in the boiler, the principal inconvenience 
 being the diminished capacity of the cistern, and 
 the liability to stop up the various pipes connected 
 with it. In public baths, wash-houses, hospitals, &c., 
 constant inspection is necessary in order to watch, 
 and if necessary remove these accumulations of 
 sediment. In private houses, the apparatus may 
 be used for long periods without inconvenience. 
 Sometimes an apparatus may become choked and 
 partially, or even wholly useless in a very few 
 months or even weeks; and in other cases where 
 the work is less severe, the deposit may be trifling 
 even after years of operation. 
 
 (181.*) In erecting an apparatus intended to 
 supply hot water in many different parts of the 
 same building, very great difficulties frequently 
 occur. It is not sufficient to heat a large tank and 
 then draw off the heated water by various long or 
 short lengths of pipe leading to the respective baths, 
 taps, washing tubs, &c. The water in such cases 
 generally becomes perfectly cold in the various 
 pipes, and it frequently happens that many gallons 
 of cold water must be drawn out of the pipes before 
 any hot water can be obtained from the hot water 
 cistern. The only effectual way to prevent this is 
 so to arrange the system of pipes, that each one 
 
 o 2
 
 196 
 
 APPARATUS FOR BATHS. 
 
 FIG. 44 A . 
 
 shall have a continuous circulation through it from 
 the cistern to the boiler, or vice versa from the 
 boiler to the cistern. This of course much increases 
 the expense of such an apparatus, but it is absolutely 
 necessary in order to obtain success. 
 
 (182.*) The usual way of fixing this kind of 
 apparatus is to place the hot water cistern on the 
 highest level at . which hot water is required ; and 
 then to draw off the hot water through a pipe or 
 pipes passing through the various floors where hot 
 water taps are fixed and finally descending to the 
 boiler, thus to complete the circulation. But a far 
 better plan is to place the hot water cistern near to 
 the boiler and beloiv the draw-off taps, and thus 
 draw the hot water upwards; the upward action 
 being produced by the pressure from the large cold 
 water cistern placed higher than any of the draw- 
 off taps, as in the 
 figure annexed. The 
 advantages of this 
 plan are sometimes 
 very important. For 
 as *it is generally 
 necessary to draw off 
 the hot water from 
 the bottom of the 
 cistern, when the cis- 
 tern is fixed at an 
 elevation above the 
 draw-off taps, it is 
 most difficult to avoid drawing off the cold water 
 instead of hot when thus fixed, the cold water 
 naturally lying towards the bottom of the cistern. 
 No such inconvenience arises when the hot water 
 cistern is fixed as in fig. 44A, where B is the hot 
 water cistern, and c the cold water supply. 
 
 (183.*) In many cases it is desirable to use 
 steam as a means of heating water in large
 
 STEAM COILP. 197 
 
 quantities for the purposes here described. This 
 may be done either by blowing steam direct into 
 the hot water cistern, or it may be made to pass 
 through a coil fixed inside the cistern. In this 
 case the action is produced by the colder water in 
 the cistern condensing the steam as it passes through 
 the coil, and the condensed steam then runs out at 
 the other end of the coil. When the steam is blown 
 direct into the hot water cistern there is some saving 
 of expense, both in the cost of the apparatus and 
 also in fuel, but this plan is attended with some 
 serious inconvenience. Considerable noise is pro- 
 duced by steam suddenly blown into colder water 
 in this way. This noise can be prevented to a 
 great extent by closing the end of the pipe, and 
 then allowing the steam to escape through a great 
 number of very small holes drilled in the pipe ; or 
 it may be likewise prevented by making the steam 
 pipe end in a small iron box filled with iron grape 
 shot, about the size of a small marble, and then 
 piercing the surface of the box with a great number 
 of moderate sized holes. This latter plan was the 
 subject of a patent many years ago. Both these 
 plans are attended with some inconvenience. When 
 the steam pressure in the pipe ceases, a vacuum is 
 formed in the pipe, and the water in the cistern 
 passes backwards into the boiler and may cause it 
 to overflow. This result can be prevented by 
 means of back-pressure valves, but an awkward 
 complication is the result. 
 
 (184.*) To estimate accurately the proper 
 length of a coil to heat a given quantity of water 
 by means of steam is not very easy, as the effect 
 varies every moment of time according to the tem- 
 perature of the water in the cistern, and the pressure 
 of the steam in the boiler. As a rough estimate 
 for ordinary purposes, it may be stated that a coil 
 made of iron pipe 50 feet long and 1 inch internal
 
 198 STEAM BOILERS FOR BATHS. 
 
 diameter (which is equal to about 12 square feet 
 of surface for the inside diameter), and conveying 
 steam of 30 Ibs. pressure per square inch, will boil 
 about 300 gallons of water per hour. If the steam 
 be only 15 Ibs. pressure, it will take a coil of about 
 80 feet in length to boil the same quantity of water. 
 
 If it be intended to heat the cistern by means of 
 a coil of pipe with hot water instead of steam, 
 the coil will require to be about one-half longer 
 than a steam coil working at 15 Ibs. pressure. A 
 very long coil has many objections, and therefore 
 when a coil of considerable length becomes neces- 
 sary in order to give sufficient surface, it is better 
 to increase the diameter of the pipe than to extend 
 its length. 
 
 (185.*) To estimate the size of a boiler to heat 
 any given quantity of water, the rules already given 
 in Chapter IV., Art. 71 may be sufficient. But it 
 may be here stated, that as a general result 1 square 
 foot of boiler surface exposed to the direct action of 
 the fire will boil about 11 gallons of water from 52 
 to 212 Fahrenheit per hour. 
 
 From these data it will not be difficult to calcu- 
 late approximately the effect of almost any apparatus 
 that may be desired. Suppose a tank containing 
 1,000 gallons of water has to be boiled in (say) 
 three hours. The boiler, whether used for steam 
 or the circulation of hot water, must be of some 
 shape that can be easily cleaned out from the 
 deposit. In either case the boiler must be of such 
 size, that it shall expose a surface of 30 square feet 
 to the direct action of the fire. Such a boiler, sup- 
 posing it were the waggon shape shown figure 16, 
 would be 5J feet long, by 3 feet wide, and 2^ feet 
 deep. But if the water were only required to be 
 heated to about 140 instead of 200 or 212, then 
 a similar boiler 4 feet long, by 2J feet wide, and 
 2^ feet high would be sufficient.
 
 MIXED TEMPERATURES. 199 
 
 (186.*) There is usually a considerable deposit 
 formed in the cistern by all these several modes of 
 heating water. It sometimes forms in great thick- 
 ness on the outside surfaces of the coils used in 
 this manner, whether they are heated by steam or 
 by the circulation of hot water. It is therefore 
 necessary in all these cases that the cisterns should 
 occasionally be opened and cleaned out from any 
 deposit, as otherwise the heating power of the 
 apparatus is very seriously reduced. The deposit 
 which occurs in the cisterns is not so destructive 
 as that which takes place in the boiler. The deposit 
 in the boilers unless frequently removed, is absolute 
 destruction to them : in the cisterns the deposit only 
 causes loss of power, though this may in some cases 
 occur to a very serious extent. 
 
 ( 187.*) It may perhaps be useful to state the mode 
 of estimating what will be the resulting tempera- 
 ture by mixing together any given quantities of 
 water at different temperatures. Whether the 
 quantities be large or small, the same rule will 
 apply. Suppose we mix together two gallons of 
 water at 200 Fahrenheit, and four gallons at 50 ; 
 the resulting temperature will be found by multi- 
 plying each quantity by its respective temperature, 
 adding these numbers together, and then dividing 
 the product by the total quantity of water, thus 
 
 2 gallons x 200 = 400 
 4 gallons x 50 = 200 
 
 Divide by 6 gallons) 600 = 100 
 
 giving 100 Fahrenheit as the average temperature 
 of the whole six gallons. Or suppose a plunge 
 bath of 40,000 gallons at 60 Fahrenheit mixed 
 with 2,000 gallons of hot water of 200 Fahrenheit. 
 In this case 40,000 multiplied by 60, and 2,000
 
 200 TIME OF HEATING BATHS. 
 
 multiplied by 200, added together gives 2,800,000. 
 This number divided by 42,000, the total quantity 
 of water will give 66 J as the resulting temperature 
 of the entire quantity of water thus mixed together. 
 If steam and water are mixed together, the re- 
 sulting temperature is calculated in the same way, 
 bearing in mind that the heat of steam, taking its 
 sensible and latent heat together as a constant 
 quantity (see Art. 257), is equal to 1200 Fahren- 
 heit. Thus, if one gallon of water, converted into 
 steam, be mixed with ten gallons of water at 50 
 Fahrenheit, the result will be 
 
 10 gallons water at 50 = 500 
 1 gallon of water in the 
 state of steam at 1200 = 1200 
 
 1700 
 
 Divided by 11 the whole quantity of water will 
 give 154^ as the average temperature. There are 
 many cases which occur in practice, where such 
 calculations as these are extremely useful. 
 
 (188.*) In some experiments on warming the 
 water in a large plunging bath containing 11,000 
 gallons of water, it was found that with an arched 
 boiler having (equal to) 30 square feet of direct 
 action surface exposed to the fire, it took 12 hours 
 to raise the temperature of the bath from 52 to 86, 
 or to add 34 to the temperature with a moderate fire ; 
 or with a strong fire it raised the temperature 54 in 
 twelve hours. This heat was communicated to the 
 water by means of a coil of 75 feet of 4in. pipe, laid 
 at the bottom of the bath, which, in consequence of 
 the rapid conducting power of the water in the 
 bath, abstracted all the heat as fast as it could be 
 generated (see note to Art. 251). The water in 
 this case merely circulated through the coil of pipes,
 
 TIME OF HEATING BATHS. 201 
 
 and the same water returned again to the boiler. 
 In another case of a bath containing 40,000 gallons 
 of water, the estimated quantity of pipe laid as a 
 coil in the bath was 200 feet of 4in. pipe ; the 
 arched boiler was 10 feet long x 3i feet wide 
 outside, and the time of heating was 40,000 gallons 
 of water raised 20 degrees in seven hours.
 
 202 
 
 CHAPTER X. 
 
 ON HEATING BY STEAM. 
 
 Variableness of Temperature Alterations in the Level of 
 Pipes Removal of condensed Water Proper Steam-pres- 
 sure to be employed Mode of Calculating the Heating- 
 surface required Size of Boilers Quantity of Water 
 condensed Boilar Surface required Forms and Power of 
 Boilers Quantity of Coal Size of Furnace-bars Mode 
 of supplying Water to the Boiler Safety Valves, Gauges, 
 and other Appendages required Air-vents and Outlets for 
 the condensed Water. 
 
 (179.) SINCE the introduction of the invention 
 of heating buildings by hot water, the use of 
 steam for this purpose has been comparatively 
 neglected ; still there are many situations where 
 its employment may be advantageous, particularly 
 in buildings used for manufacturing and commer- 
 cial purposes. No work containing rules for its 
 application has been published for many years. 
 The only books on the subject which the author 
 has met with are Buchanan's Treatise on Htatiny 
 by Steam, last published in 1815, and Tredgold's 
 Principles of Wanning and Ventilating Public 
 Buildings, $c., last published in 1836. Both these 
 works have been out of print for many years, and 
 it therefore appears desirable in the present work 
 to give such rules as may be necessary for erecting 
 steam-heating apparatus for such ordinary purposes 
 as it is likely now to be applied to.
 
 ALTERATIONS IX LEVEL OF PIPES. 203 
 
 (180.) The principal difficulty with an apparatus 
 for heating by steam is the constant attendance it 
 requires, not only to ensure its safety, but to 
 secure a continuance of its heating power. Unlike 
 the hot-water apparatus, which retains its heating 
 power for many hours, the steam apparatus 
 ceases to afford heat as soon as the fire fails to 
 possess sufficient force to raise steam in the boiler. 
 The risk of explosion in inexperienced hands is 
 also a serious objection to its use. But when the 
 apparatus is of sufficient magnitude to warrant 
 the continued superintendence of an experienced 
 person, it may be considered perfectly safe. 
 
 (181.) One great convenience in a steam appa- 
 ratus is the facility with which the ^ pipes can be 
 conveyed in almost any direction. 'Provided the 
 condensed water be carried off, and the pipes 
 thereby be kept clear, it matters not whether the 
 pipes are carried above or below the boiler, and 
 that to almost any extent. But in carding out 
 this principle, it must be borne in mind that 
 wherever there are considerable alterations of 
 level, the condensed water must have a proper 
 outlet from the lowest part; for otherwise the 
 pipes will very quickly become choked with water 
 and cease to act ; and hence any sudden and 
 considerable alterations in level become extremely 
 difficult to deal with in practice, although in 
 principle there is nothing whatever to hinder the 
 most rapid, multifarious, and even eccentric al- 
 terations in level that can possibly be contrived. 
 But as every sudden dip or alteration of level in 
 the pipe will require a separate outlet for the con- 
 densed water, it becomes exceedingly difficult, and 
 very undesirable in practice, to make these sudden 
 alterations in level. Like the hot-water apparatus, 
 it is therefore found most advantageous to lay the 
 pipes with a very small but gradual inclination, so
 
 204 AMOUNT OP PRESSURE REQUIRED. 
 
 as to allow the condensed water to flow out at one 
 place, or at least from as few places as possible. 
 The condensed water must not only be carried off 
 in order to keep the pipes clear for the passage of 
 the steam, but likewise to prevent the pipes from 
 breaking. For if the condensed water remains in 
 the pipes after they become cold, the next time 
 the pipes are heated they are extremely likely to 
 crack, if they are of cast iron, in consequence of 
 the great difference of temperature which there 
 would then be between the upper and the lower 
 sides of the pipes. 
 
 (182.) In arranging a steam apparatus, the first 
 thing is to calculate the proper quantity of heating 
 surface. In order to do this, it is necessary to 
 determine at what pressure the boiler is to work. 
 Formerly it was considered that 2^ Ibs. pressure 
 per square inch of the boiler was quite as much as 
 could safely be used for this purpose, and the old 
 writers on the subject recommend this pressure to 
 be employed. But of late years the use of high- 
 pressure steam has so accustomed engineers to 
 regard boilers as perfectly safe with pressures of 
 80 Ibs. or 100 Ibs. and upwards to the square inch, 
 that no one would now object to employ steam of 
 5 Ibs., 10 Ibs., or even 20 Ibs. pressure per square 
 inch, for heating buildings of any description, 
 whenever such pressures are deemed desirable. 
 The higher the pressure in the boiler, the higher 
 will be the temperature of the pipes or other 
 radiating surfaces ; and therefore the higher the 
 pressure the smaller the size or less the quantity 
 of the radiating surfaces which will be required. 
 
 (183.) In heating manufactories and other com- 
 mercial buildings, it is often desirable to use the 
 surplus steam from a steam-engine boiler, or the 
 waste steam after it has passed through the 
 cylinder of a high-pressure engine. In other
 
 AMOUNT OF PRESSURE REQUIRED. 205 
 
 cases, where a separate steam-boiler is used for 
 heating the apparatus, it is seldom desirable to 
 use steam of much more than about 5 Ibs. to 
 10 Ibs. per square inch. Whatever pressure, how- 
 ever, is fixed upon, the quantity of radiating 
 surface necessary may be found in the following 
 manner: 
 
 In Chapter VI. (ante) rules are given for calcu- 
 lating the radiating surfaces necessary to heat 
 most kinds of buildings with hot-water pipes. If, 
 then, by these rules the required amount of 
 radiating surfaces be calculated, the reduced quantity 
 that is required when steam-heat is to be applied 
 may be ascertained as follows: In Table I., Ap- 
 pendix, the temperature of steam at all pressures 
 is given. Suppose now that to heat a building to 
 60 with hot water, it has been found (by rules 
 given in Chapter VI.) that 300 feet of four-inch 
 pipe is required. If it is proposed to use steam 
 of 5 Ibs. pressure, that is, 5 Ibs. in addition to 
 the 1 5 Ibs. which is necessary to prevent a vacuum 
 in the boiler, if we look in Table I., Appendix, 
 for the nearest pressure to 20 Ibs., we shall find 
 the temperature of the steam is 225. Now the 
 temperature of hot-water pipes being reckoned at 
 only 180, or 120 above the proposed temperature 
 of the room, and the temperature of the steam- 
 pipes (at this pressure of 20 Ibs.) being 225, 
 or 165 above the proposed temperature of the 
 room, the quantity of steam-pipe will be found 
 by a common rule-of-three sum ; namely, as 165 
 is to 120 so is 300 feet of hot- water pipe to 
 the quantity of steam-pipe required to produce 
 the same effect, which in this case will be 218 feet. 
 Again : suppose the pressure of the steam is 
 30 Ibs., that is, 30 Ibs. above the 15 Ibs. neces- 
 sary to prevent a vacuum. If we look in the Table 
 for the temperature of steam at 45 Ibs. pressure,
 
 206 STEAM-SPACE IX THE BOTLER. 
 
 we shall find it is 275, or 215 above the proposed 
 temperature of the building. In this case the 
 calculation will be, as 215 is to 120 so is 300 feet 
 the quantity of hot-water pipe required to the 
 quantity of steam-pipe necessary to give the same 
 heat, which in this case is 167 feet. 
 
 (184.) These calculations are not absolutely 
 correct ; but they are sufficiently accurate for 
 every purpose of practical utility. For it will be 
 shown in another chapter (Chapter XII.) that the 
 radiation of heat is proportionately greater at high 
 temperatures ; and therefore while the above mode 
 of calculation is quite sufficient for all practical 
 purposes, such as those here contemplated, the 
 rule must not be construed to include scientific 
 exactness. 
 
 It may here be observed that the rule already 
 given (Art. 41), for the elongation and expansion of 
 hot- water pipes, must be observed wherever steam- 
 pipes are applied to any heating purposes. 
 
 (185.) In apportioning the boiler for heating 
 any given quantity of pipe, both Tredgold and 
 Buchanan assume that the steam-space in the boiler 
 ought to be equal to the whole contents of the pipes, 
 go as to fill the pipes easily with steam when the 
 valves are opened; and, further, that the steam- 
 space ought to be about half the entire capacity of 
 the boiler. These proportions, however, do "not 
 appear suited to modern practice, now that steam 
 of much higher pressure is used. And although 
 exposing a large surface of the boiler to the fire 
 is always economical, a boiler of large capacity is 
 not always convenient, nor, indeed, is it necessary 
 for successfully applying steam to the heating of 
 buildings. 
 
 (186.) Tredgold deduces from his experiments 
 that with steam of 2^ Ibs. pressure above the 
 atmosphere (or 17 Ibs. actual pressure), 182
 
 PROPORTIONS OF BOILER SURFACE. 207 
 
 superficial feet of iron pipe will condense as much 
 steam as will produce one cubic foot of water per 
 hour, when the temperature of the room is 60 
 Fahrenheit. In this case he assumes the average 
 temperature of the entire surface of the pipe to be 
 200 Fahrenheit. From this datum the proper size 
 of the boiler can be calculated. 
 
 It appears (by Art. 71) that four square feet of 
 boiler surface exposed to the direct action of the 
 fire will evaporate one cubic foot of water per 
 hour. The boiler for a steam apparatus ought 
 therefore to evaporate as much water per hour 
 as the pipes will condense in the same time ; 
 hence a boiler possessing four square feet of 
 surface exposed to the direct action of the fire 
 will just supply sufficient steam to heat 
 
 1 82 sq. ft. of pipe when the pressure is 2 1 Ibs. above the atmosphere. 
 161 10 
 
 149 20 
 
 135 30 
 
 and supposing that in each case the temperature 
 of the room is 60 Fahrenheit. It follows also 
 that each of these several quantities of pipe will 
 give off the same amount of heat in equal times. 
 
 (187.) It by no means follows that these pro- 
 portions of boiler surface are desirable to be 
 adopted. Although they certainly will heat the 
 pipe when skilfully applied and carefully attended, 
 it is desirable to allow about one-half more boiler 
 surface to meet the common contingencies of 
 most apparatus, and to prevent the necessity for 
 heavy firing. Watt allowed eight square feet 
 of boiler surface to evaporate one cubic foot of 
 water per hour, and in the Cornish engines even 
 a larger surface than this is allowed.* It will 
 therefore be desirable to assume that six square 
 
 See note to Art. 71.
 
 208 FORMS 'OF BOILERS. 
 
 feet of boiler surface exposed to the direct action 
 of the fire will be necessary to heat the several 
 quantities of pipe here mentioned. 
 
 (188.) Having ascertained the surface of the 
 boiler to be exposed to the fire, it becomes neces- 
 sary to determine its shape and capacity. The 
 forms of steam-boilers are almost as numerous 
 as those which have been proposed for the hot- 
 water apparatus. But for the ordinary purposes of 
 heating buildings by steam, it is absolutely indis- 
 pensable that the boilers should be simple in form, 
 tolerably easy to clean out, of rather large capacity 
 in proportion to their fire surface, and so durable 
 as to require very little repair. For many pur- 
 poses, these qualifications are frequently sacrificed, 
 and necessarily so in order to obtain lightness, 
 rapid draught, and high evaporating power. 
 
 (189.) For low-pressure boilers where the steam 
 does not reach beyond 8 Ibs. or 10 Ibs. per square 
 
 FIG. 39. FIG. 40. FIG. 41. 
 
 inch, there is no better form than the old wag- 
 gon boiler, fig. 39, which can be used of any size. 
 The Cornish boiler, fig. 40, is only suitable for 
 larger apparatus, and is scarcely desirable for 
 boilers of less size than about ten feet long and 
 four feet diameter. The cylindrical boiler with 
 hemispherical ends, fig. 41, is very suitable for 
 high pressures, as it is one of the strongest forms 
 for a boiler, and is therefore always regarded as 
 one of the safest boilers that can be made. 
 
 Any of these boilers have sufficient capacity, in
 
 QUANTITY OP COAL REQUIRED. 209 
 
 proportion to their surfaces, to render them very 
 desirable for the purpose of applying steam-heat 
 to buildings. In calculating the proper size for a 
 boiler to produce a given effect, the same rule 
 must be applied that has already been given 
 (Art. 71) for calculating the power of boilers for 
 the hot-water apparatus, namely, that the flue- 
 surface of the boiler is only to be taken at one- 
 third its actual measurement, when we want to 
 estimate the extent of surface exposed to the direct 
 action of the fire. Thus in fig. 39, suppose the 
 boiler to be 6 feet long, 2^- feet wide, and the 
 flue-surface 2 feet deep all round the boiler; in 
 this case the bottom of the boiler will have 
 6 feet x 21 feet =15 feet of surface. The flue- 
 surface measured entirely round the boiler by 
 2 feet deep, will be equal to 34 square feet ; and 
 one-third of this latter measurement will be equal 
 to 11^ feet, which, added to the former quantity 
 of 15 feet, will make the boiler-surface equal to 
 26^ square feet exposed to the direct action of the 
 fire. This boiler (by Arts. 186 and 187) would be 
 sufficient to heat 798 square feet of steam-pipe at a 
 pressure of 2|- Ibs. per square inch, when the tem- 
 perature of the room is kept at 60 Fahrenheit. 
 
 (190.) The quantity of coal that will be neces- 
 sary to produce a given effect with a steam 
 apparatus may be ascertained as follows : The 
 quantity of water condensed by the pipes must 
 first be ascertained as already pointed out. Sup- 
 pose in the case already stated, that 182 square 
 feet of pipe, in a room of 60 temperature, con- 
 denses one cubic foot of water per hour, when the 
 pressure is 2^ Ibs. per square inch : then, by the 
 data already given (Arts. 94 and 95), it will be 
 found that about 9 Ibs. of coal is required to 
 evaporate one cubic foot of water ; and this must 
 be the quantity required to replace the loss of 
 
 p '
 
 210 SIZE OF FURNACE-BARS. 
 
 heat by condensation of steam in the pipes; 
 therefore the coal burnt would be 9 Ibs. per hour, 
 if there were 182 feet of steam-pipe in a room of 
 60, and the steam at the pressure of 2^ Ibs. per 
 square inch. Whatever quantity of water the 
 pipes will condense per hour, and which quantity 
 can be estimated by the preceding rules, the con- 
 sumption of coal will be 9 Ibs. for every cubic foot 
 of water thus condensed. 
 
 It has been already explained (Arts. 71 and 95) 
 that a very great difference exists in the heating 
 effects of coal burned in different furnaces. The 
 quantity above stated is a full allowance, and much 
 more than some steam-boilers will require when 
 very carefully worked. 
 
 (191.) The size of the furnace-bars should be one 
 square foot to burn about 10 Ibs. to 11 Ibs. of coal 
 per hour ; and the surface of the boiler exposed 
 to the direct action of the fire will generally be 
 about five times the area of the furnace-bars. The 
 furnace of a steam apparatus will very seldom 
 allow the use of a door to the ash-pit, as it re- 
 quires a stronger draught than a hot-water appa- 
 ratus, and the ash-pit door is very liable to reduce 
 the draught. Unlike the hot-water apparatus, the 
 heating effect of a steam apparatus ceases directly 
 the fire fails to produce its full effect on the boiler ; 
 and therefore a brisk fire and constant attention 
 are absolutely necessary for a steam apparatus, 
 in order to keep up the proper action in the 
 pipes. 
 
 (192.) The various apparatus necessary to 
 secure a proper supply of water to the boiler, 
 and likewise to prevent danger by any undue 
 pressure in the boiler, as well as the contrivances 
 required to carry off the air from the apparatus, 
 and to remove the condensed water from the 
 pipes, are all much more complicated and expen-
 
 MODE OF SUPPLYING WATER TO BOILERS. 
 
 211 
 
 sive than anything required for these purposes in a 
 hot-water apparatus. 
 
 The boiler is generally supplied with water by 
 means of a stone-float apparatus, of which there are 
 several varieties (Figs. 42 and 43). A stone placed 
 in the boiler, by a wire passing through a stuffing- 
 box balanced by a lever with an attached weight, 
 is made to turn a cock which communicates by a 
 pipe from the boiler with an elevated cistern of 
 water. When the stone falls in the boiler by the 
 partial evaporation of the water, the cock is opened 
 by the lever, and as much water comes into the 
 boiler as will again float the stone, and thus shut 
 
 FIG. 42. 
 
 FIG. 43. 
 
 the cock. The cistern must always be high enough 
 to have the column of water of greater weight than 
 the pressure of the steam; otherwise on opening 
 the cock either water or steam would escape up the 
 pipe, instead of the water coming down from the 
 cistern. The pressure from the water in the cistern 
 should be not less than from one-fifth to one-fourth 
 greater than the pressure of the steam in the boiler ; 
 and as every two feet vertical height of the water in 
 the cistern and pipe is equal to 1 Ib. pressure of 
 the steam in the boiler, the supply cistern ought to 
 
 p 2
 
 212 SAFETY-VALVES. 
 
 be not less than the following height above the 
 boiler : 
 
 6 feet high to supply a boiler working 2^ Ibs. steam, 
 12 5 
 
 24 10 
 
 75 30 
 
 and generally a little more than this may be 
 desirable in order to secure certainty of action. 
 
 These elevations are very difficult to obtain for 
 the higher pressures, and hence one of the diffi- 
 culties in working very high pressures except in 
 conjunction with a steam-engine ; in which case a 
 force-pump is used to inject the water into the 
 boiler without the aid of the elevated cistern. A 
 modern invention of a self-acting injector has been 
 introduced, but it is doubtful how far a compli- 
 cated, though ingenious, apparatus can be safely 
 trusted, unless it is under the constant and 
 daily inspection of experienced and careful super- 
 intendents. 
 
 (193.) A safety-valve is an indispensable ap- 
 pendage to a steam-boiler. Whatever form of 
 safety-valve be used, the size of its clear opening 
 ought to be not less than one circular inch for 
 every six square feet of the boiler exposed to the 
 direct action of the fire; or, in other words, one 
 circular inch for each cubic foot of water per hour 
 which the boiler will evaporate. A valve of this 
 size is sufficient, whatever the pressure of the 
 steam may be. When the boilers are large, two 
 or more valves may be used, so as to give in the 
 aggregate this amount of opening for the escape 
 of steam. 
 
 (194.) A steam-gauge is a very desirable adjunct 
 to a steam-boiler. For low-pressure boilers a 
 mercurial steam-gauge is frequently used. But 
 a very convenient gauge for either high or low 
 pressures is the ingenious instrument known as
 
 GAUGES. 213 
 
 "Bourdon's Pressure Gauge," which shows oil a 
 small clock-face the correct pressure of the steam. 
 
 (195.) A water-gauge is also another very useful 
 addition to the fittings of a steam-boiler. This 
 gauge consists of a glass tube, about 1 foot long, 
 fixed between two cocks communicating directly 
 with the boiler, generally in the front, near the 
 furnace-door, and so placed that the water-level 
 in the boiler can be seen in the glass* gauge, 
 which is so fixed that the water-level is nearly 
 about the middle of the glass tube. The water 
 always stands at the same height in the tube as 
 in the boiler. Any variation, therefore, in the 
 height of the water in the boiler can be easily 
 seen by looking at the height in the glass tube. 
 The use of the two cocks of the glass gauge is 
 merely to shut off the communication with the 
 boiler, in case the glass tube should break : on all 
 other occasions the cocks are to be left open. 
 
 (196.) Every steam-boiler ought also to be 
 supplied with two gauge-cocks, placed at the front 
 of the boiler, at such height that one is always 
 above the water-level, and the other about two or 
 three inches below the water-level. By these 
 cocks (as well as by the instrument last described), 
 the proper height of the water in the boiler can 
 be ascertained. If the upper cock, when opened, 
 gives off water instead of steam, the boiler is too 
 full of water : while if the lower cock, when it is 
 opened, should give off steam instead of water, 
 then the boiler is deficient of water, and danger 
 may be apprehended. 
 
 (197.) A large cock is also required to be fixed 
 in the boiler, called a " blow-off cock." It is for 
 the purpose of emptying the boiler, and cleaning 
 out the sediment, and requires to be frequently 
 used. The boiler should be emptied once every 
 two or three days, less or more, according to the
 
 214 FITTINGS FOR STEAM-BOILERS. 
 
 hardness of the water, and the amount of work 
 which the boiler performs. The pipe for the 
 " blow-off cock " may be either fixed at the lowest 
 point of the boiler, and be used simply to run the 
 water off; or the pipe may enter the top of the 
 boiler, and descend within a couple of inches of 
 the bottom of the boiler ; in which latter case the 
 water is forced out through the pipe and cock by 
 the pressure of the steam, taking care that the 
 fire is so much slackened when this operation is 
 performed that the boiler shall not be injured by 
 the heat of the fire while the boiler is thus being 
 emptied. 
 
 (198.) All these various fittings for steam- 
 boilers can so easily be obtained ready made, that 
 it is not considered necessary here to describe 
 them more particularly, as it is only in their ap- 
 plication and general use that they require ex- 
 planation. There are, however, still some further 
 appliances necessary for working a steam-heating 
 apparatus which must not be passed over in this 
 description. A cock is generally placed between 
 the boiler and the pipes which heat the building. 
 On opening this cock the steam drives before it 
 all the air which was contained in the pipes ; and 
 unless a ready outlet for this air is provided, a 
 portion of the pipes will remain full of air, and 
 continue nearly cold. If the pipes are laid 
 horizontally, there is but little difficulty in getting 
 rid of this air, through a " blow-pipe " at the 
 farther extremity, which may be opened when 
 the pipes are about to be heated; and when they 
 are quite hot the blow-pipe may be nearly closed, 
 in order to prevent the waste of steam which 
 would necessarily occur after the air was expelled. 
 But when the heating surfaces occupy several 
 different levels, and particularly when they assume 
 the form of coils, steam-plates, or ornamental
 
 AIR-VENTS. 215 
 
 columns, it is not always very easy to discharge 
 the air without a good deal of care and con- 
 trivance. The air is considerably heavier than 
 steam, and therefore it naturally falls to the lower 
 levels ; and it is from these lower levels that the exit 
 for the air must therefore be provided. These 
 eduction pipes ought never to be wholly closed, 
 even when the air has been expelled ; but the 
 management of these air-pipes is often a serious 
 difficulty. In very extensive apparatus it has 
 occasionally been found so difficult to drive out the 
 air from the pipes and other heating vessels, that 
 the employment of an air-pump to exhaust the air 
 has sometimes been found necessary each time that 
 the apparatus is warmed, in order to prevent the 
 great delay in heating the apparatus which other- 
 wise would occur. 
 
 (199.) It is also necessary to provide for the 
 escape of the condensed water. When steam of 
 very low pressure is used, and the apparatus is 
 upon a small scale, an inverted siphon-pipe is 
 frequently used for this purpose. This inverted 
 siphon-pipe must be of sufficient depth to resist 
 the pressure of the steam, and frequently this be- 
 comes extremely inconvenient. Thus if the steam 
 is 2 Ibs. pressure, the siphon will require to be 
 about 5 feet deep ; if the steam FIG. 44. 
 be 5 Ibs. pressure, the siphon 
 will require to be about 12 feet 
 deep. These siphon-pipes for 
 the condensed water are only 
 suitable for steam of very low 
 pressure. When steam of higher 
 pressure is employed, there are 
 several contrivances for stopping 
 the escape of steam, and at the same time allowing the 
 waste water to run off. One of these plans is shown 
 in fig. 44. This is a close box or vessel about 10
 
 216 OUTLETS FOR CONDENSED WATER. 
 
 or 12 -inch diameter and the same in height, in 
 which is placed an extremely light copper pan 
 or cup about 2 inches smaller in diameter and 
 in height than the outer box. A pipe passes 
 through the lid of the outer box, and dips down to 
 within about 1 inch of the bottom. The condensed 
 water runs into the box, between the outer case 
 and the inner copper vessel. As the water gradually 
 runs in, it soon floats the light copper vessel, which 
 is empty, and thus presses it up against the open 
 end of the pipe, which passes through the lid of 
 the outer box. This goes on until the space be- 
 tween the outer box and the inner copper vessel 
 becomes quite full of water, when having no other 
 escape, the water runs over into the empty copper 
 vessel which sinks by its increased weight. When 
 it sinks, it opens the outlet in the pipe passing 
 through the lid of the outer box ; and then the 
 pressure of the steam acting on the surface of the 
 water in the copper vessel, forces all the water in 
 the vessel upwards through the pipe. When this 
 occurs, the copper box again floats, being relieved 
 of the increased weight, and in rising stops the 
 exit through the central pipe. This apparatus thus 
 becomes self-acting, discharging the water, but 
 stopping the escape of the stearn. 
 
 Another plan is by means of a very thin and 
 small copper cylinder, about an inch and a half or 
 two inches diameter, filled with a5ther, and which 
 floats on an outer case of copper, into which the 
 condensed water runs. When steam enters the 
 outer case, the heat causes the small cylinder to 
 elongate in a slight degree, sufficient to close a 
 small opening against which it is thus pressed. 
 The condensed water being colder than the steam, 
 when the condensed water fills the outer case, the 
 small cylinder again contracts and opens the out- 
 let for the escape of the water.
 
 ADVANTAGES OF STEAM OVER HOT WATER. 217 
 
 If the condensed water from the apparatus is to 
 be used for any purpose, either as distilled water, 
 or to supply the boiler again with fresh water, it 
 can be collected as it flows out from the valve- 
 box; or it may be collected from the siphon-pipe 
 previously described. 
 
 (200.) The advantages of a steam apparatus 
 over a hot-water apparatus appear to consist 
 principally in the greater ease of application of 
 the heating surfaces, where great inequalities and 
 frequent alterations in the levels occur, and par- 
 ticularly where the boiler is necessarily placed 
 considerably higher than the places which are to 
 be heated ; and likewise in the somewhat smaller 
 extent of heating surface which is required. The 
 disadvantages of the steam apparatus are its 
 greater danger, and the absolute necessity which 
 exists for ' constant attendance and watchfulness ; 
 its want of permanence of temperature, except 
 when the greatest possible care is bestowed ; and 
 its somewhat increased cost of fuel above that of 
 a hot-water apparatus. The first cost incurred for 
 the erection of the two kinds of apparatus will 
 differ but little when the work is done in an 
 equally substantial manner ; but the wear and 
 tear, and repairs, of a hot-water apparatus will 
 be less than that of a steam apparatus, as in the 
 former there is absolutely nothing that can wear 
 out except the boiler ; while in a steam apparatus 
 there are various things which constantly require 
 attention and repair, in addition to the greater 
 amount of wear in the steam-boiler itself, caused 
 by the large quantities of sediment which require 
 to be constantly removed, otherwise the boiler is 
 very speedily destroyed.
 
 218 
 
 CHAPTER XI. 
 
 ON HEATING BY HOT AIR. 
 
 Sylvester's Cockle-Stove Improved Cockle-StoveEstimate 
 of Heating-power Hot-air Stoves with Projecting Plates, 
 and their Heating-power Bernhardt's, Hazard's, and other 
 Hot-air Apparatus Difficulty of Horizontal Flues Multi- 
 tubular Hot-air Apparatus Hot-blast Apparatus. 
 
 (201.) THE application of fire-heat to metallic 
 surfaces on which atmospheric air is made to 
 impinge directly, without the intervention of 
 either water or steam, is usually called a HOT-AIR 
 APPARATUS. This distinguishes it from any other 
 apparatus in which air, although frequently quite 
 as highly heated, receives its heat from pipes 
 or vessels heated by steam or hot water. This 
 method of heating atmospheric air possesses con- 
 siderable utility. Previous to the introduction of 
 the hot-water apparatus, this method of heating 
 was much more used than it is ever likely again 
 to be. The hot-water apparatus is so much more 
 wholesome than the hot-air apparatus, that the 
 latter can only be recommended where either 
 partial vitiation of the air is of no great moment, 
 or else where the object is merely to produce 
 a drying and warming effect of considerable 
 intensity for certain manufacturing or economic 
 purposes. In such cases as these, the hot-air 
 apparatus frequently presents considerable advan- 
 tages, as a drying effect of greater intensity can
 
 SYLVESTER'S COCKLE-STOVE. 219 
 
 be thus obtained than by any of the apparatus 
 which have been already described. 
 
 (202.) The hot-air apparatus in the form in 
 which it is now best known, was employed at the 
 close of the last century by Mr. Strutt, of Belper, 
 near Derby, for warming his cotton mills. It was 
 subsequently improved, and extensively intro- 
 duced into general use by Mr. Sylvester, who, in 
 1819, published his description of the apparatus, 
 with experiments on its heating powers. The 
 construction recommended by Mr. Sylvester, how- 
 ever, appears to be defective in one particular: 
 for in his apparatus the furnace or fire-grate was 
 placed so far below the surface of the cockle-case, 
 that its effect was considerably diminished. In 
 his apparatus the fire-grate was placed about two 
 feet below the bottom of the cockle-case, or about 
 from 7 feet to 8 feet below the surface which was 
 to be heated by the fire. In some recent cases in 
 which this form of apparatus has been used by 
 the author, the furnace and fire-bars are placed 
 entirely within the cockle-case, so as to make 
 the fire-bars lie about one foot above the bottom 
 of the cockle-case, and about five feet higher than 
 those used by Mr. Sylvester. The figs. 45 and 
 46 show the apparatus in the last-mentioned form, 
 but in all other respects it is the same as that 
 proposed by Mr. Sylvester. 
 
 Fig. 45 is a section of the furnace, constructed 
 of fire-brick inside the cockle-case. The cockle- 
 case is of wrought iron one-fourth of an inch 
 thick, and made arch-shape and closed both back 
 and front, except at the furnace-door, which is 
 fixed to the front. Between the sides of the 
 furnace and the inside of the cockle-case is a 
 vacant space about 4 in. to 5 in. wide, and the 
 flame, smoke, and heated gases all pass downwards 
 between these spaces and enter the longitudinal
 
 220 
 
 IMPROVED COCKLE-STOVE. 
 
 flues, which extend along the bottom at both sides 
 of the cockle-case. These smoke-flues should 
 be about 9 in. by 6 in., and their upper sides 
 are partially covered by two plates of iron, which 
 so cover them as to leave a narrow open slit from 
 three-fourths of an inch to one inch wide all 
 the length of the cockle-case on both sides. These 
 slits are the only places where the smoke can 
 escape into the flues. These side flues communi- 
 cate with another flue at the back, similar in size, 
 but entirely covered on the top. This last flue 
 
 FIG. 45. 
 
 FIG. 46. 
 
 leads into the chimney. There must be a soot- 
 door at one or both ends of this back flue, to 
 enable it to be cleaned out. To clean out the 
 longitudinal or side flues, there is a soot-door in 
 the front, at each side of the furnace-door: and 
 a rod with a handle at one end, and a small rake 
 at the other end, is made to slide along the 
 narrow slit already described, which keeps it 
 constantly clear of soot, by merely drawing out the 
 handle occasionally when the fire is replenished 
 with fuel. 
 
 (203.) The fire is entirely contained within the 
 cockle, without any other outlet whatever for the
 
 IMPROVED COCKLE-STOVE. 221 
 
 heated gases, flame, and smoke, except the two 
 narrow slits left in the horizontal flues, already 
 described. The cockle-case thus becomes heated. 
 Between the outside of the cockle-case and the 
 brickwork which surrounds it, a vacant space is 
 left of from 4 in. to 6 in., extending entirely round 
 the iron case ; and at the lower part of this vacant 
 space or air-chamber, a triple row of small pipes 
 about 2 in. diameter, or 2 in. square, passes 
 through the brickwork, and extends to within 
 three-fourths of an inch of the iron surface of the 
 cockle-case. These pipes require to be numerous. 
 The cockle-case here shown and described is sup- 
 posed to be about 5 feet wide, 5 feet long, and 5 feet 
 high. Such a cockle would require about 150 to 
 200 such pipes. The use of them is to bring 
 fresh air into immediate contact with the surface 
 of the cockle; and when once it is brought in 
 through these pipes, it cannot escape or return 
 back again, as these pipes, when thus placed, 
 form as it were a trap, which prevents the return 
 of the air, and projects it against the highly- 
 heated sides of the cockle. The air thus brought 
 in passes over the entire surface of the cockle into 
 the upper part of the air-chamber. Through the 
 top of the brickwork, in the upper part of this 
 hot-air chamber, any required number of pipes of 
 large diameter lead the heated air into the dif- 
 ferent rooms to be warmed, passing through the 
 necessary flues or channels provided for the pur- 
 pose. These large hot-air pipes are so fixed in 
 the brickwork as to extend quite through the hot- 
 air chamber, until they reach within one inch of 
 the surface of the iron-cockle case (fig. 45). By 
 these means the air is prevented from too easy an 
 escape from contact with the heated cockle which 
 otherwise would occur. The numerous small 
 tubes at the lower part of the cockle which pro-
 
 222 ESTIMATE OF HEATING POWER. 
 
 ject the cold air against the heated iron are also 
 essentially necessary. They were not used when 
 the cockle-stove was first invented ; and Mr. 
 Sylvester states that, in some stoves to which 
 they were subsequently added, the heating power 
 was just doubled when these induction pipes were 
 used. 
 
 (204.) It is obvious that this apparatus, when 
 the furnace or fire-box is built inside the cockle- 
 case, can only be used on a rather large scale. 
 It can scarcely be made less than 4^ to 5 feet 
 square ; and perhaps the best form that can be 
 used is a square base with a top in the form of 
 a groined arch, so that the air may be easily 
 brought in from all the four sides ; and a cockle- 
 case of five feet square and five feet high would 
 have a heating power equal to nearly 650 feet of 
 four-inch pipe heated by hot water. A smaller 
 apparatus of this kind could be made if the furnace 
 were constructed of cast iron, with merely a lining 
 of fire-brick ; and in this way a cockle of about 
 3i feet square might be used, but the furnace 
 itself would probably not be very durable, in con- 
 sequence of the thinness of the fire-brick. 
 
 (205.) To estimate the power of this cocke 
 stove the experiments of Mr. Sylvester afford a 
 very good guide. From these experiments, it 
 appears that with his improved hot-air apparatus 
 or cockle-stove, 17 square feet of heating surface 
 warmed 344,600 cubic feet of air 56 in twelve 
 hours, with the consumption of 60 Ibs. of coal. 
 This is equal to 15 74 cubic feet of air raised 
 1 per minute, when the consumption of coal was 
 5 Ibs. per hour, the heating-surface being 17 
 square feet ; or it is also equal to 321,626 cubic feet 
 of air raised 1 by the combustion of 1 Ib. of coal. 
 If we compare these results with the calculations 
 (Art. 99) for estimating the power of the hot-
 
 ESTIMATE OF HEATING POWER. 223 
 
 water apparatus, we shall find that each square 
 foot of the cockle is equal in heating power to 
 7 square feet of hot-water pipe. Therefore, in 
 calculating the proper size of the cockle, we can 
 either estimate it by the quantity of air required 
 to be heated per minute, by Mr. Sylvester's rule, 
 or we can ascertain by the rules given (Arts. 99 to 
 111) the surface of hot- water pipe required, and 
 one-seventh of this quantity will be the proper 
 superficies of the iron case of the stove to produce 
 the same effect. 
 
 (206.) The actual temperature of the cockle- 
 stove itself can also be estimated without any great 
 difficulty. If the radiating power of the stove is 
 seven times that of hot-water pipes heated to 200 
 Fahrenheit, we shall find by the experiments on 
 cooling by Petit and Dulong, in Chapter XII. 
 (Art. 227, et seq.), and by reducing the figures 
 there given to Fahrenheit's scale, that 4*3 times 
 the temperature of hot-water pipes will give seven 
 times the effect. Therefore, hot-water pipes being 
 (we will assume) at 200 (or 140 above the tem- 
 perature of the air), the stove will be of the actual 
 temperature of about 560 Fahrenheit to produce 
 seven times the effect of hot-water pipes. As this 
 kind of stove burns with rather a slow draught, it 
 is probable that this statement of the temperature 
 is not far from the truth. 
 
 (207.) It must be borne in mind that in this 
 form of apparatus the back and front of the cockle, 
 as well as the sides, can be made available for 
 heating the air, if properly constructed and placed 
 at a distance from any wall, and so arranged as to 
 bring a supply of fresh air to act upon it on all 
 sides. It should also be observed that this estimate 
 of the heating power of the cockle, compared with 
 hot-water pipes, must be taken with this limita- 
 tion: That the usual mode of fixing hot-water
 
 224 THE GOLDSWORTHY GURNET COCKLE-STOVE. 
 
 pipes allows the air already in the room or build- 
 ing to be heated repeatedly by the radiating surfaces ; 
 while with the cockle-stove it is always (except in 
 some very peculiar cases not here contemplated) the 
 external air which is brought into contact with the 
 stove, to be heated to the required temperature. 
 This will make a very considerable difference in 
 the effect produced in heating any given building 
 (Art. 162), whatever may be the nature of the 
 heating surface. 
 
 (208.) Another form of the cockle-stove was in- 
 vented by the son and successor of Mr. Sylvester, 
 
 FIG. 47. 
 
 about the year 1830. It was subsequently adopted 
 by Mr. Goldsworthy Gurney, and called by his 
 name. It can be made of almost any size, and 
 usefully employed in many cases. The invention 
 consists of a cast-iron cockle, on the outer side of 
 which are a great number of projecting plates 
 extending to as much as eight or ten, or even 
 twelve inches, beyond the surface of the cockle, 
 which is exposed to the direct action of the fire ; 
 and by this means the radiating surfaces are greatly
 
 ESTIMATE OF HEATING POWER. 225 
 
 increased in extent, and their temperature propor- 
 tionally lower. Fig. 47 shows this kind of cockle- 
 stove, which requires to be cased in brickwork, 
 with a very free admission of air to the external 
 projecting plates. The air is admitted below the 
 level of the furnace-door, and, after receiving the 
 required warmth from the heated plates, is con- 
 veyed from the upper part of the cockle into 
 channels or hot-air flues, and from thence conveyed 
 into the various places to be heated. 
 
 (209.) To estimate the heating power of these 
 stoves, it is only necessary to ascertain the sur- 
 face of the inner arch, which is exposed to the 
 direct action of the fire. The projecting plates 
 add nothing whatever to the heating power of 
 the stove. They merely conduct the heat of the 
 inner arch, and thereby rapidly lower its actual 
 temperature, and thus to a great extent prevent 
 the deleterious effects which result from the air 
 coming into contact with intensely heated surfaces. 
 The actual heating effect, however, would be the 
 same whether these projecting plates were present 
 or not, provided the air were made to impinge 
 with sufficient force and rapidity against the in- 
 tensely heated sides of the stove immediately in 
 contact with the fire. 
 
 (210.) The temperature of the cockle-stove with 
 its slow combustion and isolated fire-box having 
 been estimated at 560 Fahrenheit (Art. 206), we 
 may well suppose that this stove, with the fire 
 in actual contact with the sides of the inner arch 
 of the stove, the temperature of the arch itself 
 would be not less than 700 Fahrenheit, if the 
 heat were not rapidly conducted away by the 
 projecting plates. This temperature will make 
 the heating effect of this stove ten times that of 
 hot-water pipes ; and therefore, if we measure the 
 actual surface of the inner arch of this stove (leav- 
 
 Q
 
 226 BERNHARDT'S HOT-AIR APPARATUS. 
 
 ing out the back, which is not used for heating the 
 air), and multiply the number of square feet thus 
 found by ten, we shall have the number of square 
 feet of hot-water pipe that will be equal to the 
 surface of this stove. 
 
 It is difficult, however, to estimate the real 
 power of this stove, because by making a very 
 fierce fire the effect may be increased so much 
 as to invalidate any ordinary calculation of the 
 power. This is not the case with a hot-water 
 apparatus, because there the limit to the tem- 
 perature of the heat-distributing surface is abso- 
 lutely fixed, and can never exceed the heat of 
 boiling water. But with all hot-air stoves, there 
 is no absolute limit of this kind; by skilful or 
 unskilful treatment of the fire, the heating power 
 may be so greatly altered as to render any calcula- 
 tion uncertain. 
 
 (211.) Another form of hot-air apparatus was 
 some years since rather extensively used. In the 
 year 1834 a patent was taken out by M. Bernhardt 
 for a peculiar form of hot-air apparatus. The 
 inventor failed to carry out the invention beyond 
 a very limited extent; and in the year 1842 the 
 same plan was again patented, with very little 
 variation, by Mr. Hazard, of Clifton. The general 
 form of this -apparatus is shown, fig. 48. 
 
 In this apparatus the smoke and products of 
 combustion pass from the furnace directly into 
 a set of cast-iron tubes, generally five or six in 
 number, which tubes form a long coil as shown in 
 the figure. By the peculiar form given to this 
 coil, the various pipes, after passing in a straight 
 line for 5 or 6 or 8 feet, enter into a cast-iron box 
 (shown in the figure), and from thence through 
 another set of pipes, again pass into another box 
 like the first, and so on, passing backward and 
 forward until five or six or more alternations have
 
 BERNHARDT'S HOT-AIR APPARATUS. 227 
 
 been made, and the smoke and products of com- 
 bustion have thus passed through a coil of pipes 
 of the aggregate length of 300 feet, or upwards, 
 and usually about two or three inches diameter. 
 
 FIG. 48. 
 
 The whole of these pipes are then enclosed in a 
 brick casing, into which cold air is admitted at 
 the bottom, which, after passing upward, and 
 successively coming into contact with the various 
 pipes, finally escapes at the top of the case, highly 
 heated, and is from thence conveyed into any 
 building or room where it is required. 
 
 (212.) This plan of heating air is no doubt very 
 economical ; and for many manufacturing and 
 
 Q 2
 
 228 DIFFICULTY OF HORIZONTAL FLUES. 
 
 drying purposes it would possess very great ad- 
 vantages, if it were not for the extreme difficulty 
 of cleaning the pipes from the soot. The cast-iron 
 boxes which connect the pipes can be made to 
 open at the ends, and possibly (though with much 
 more difficulty) in the front also ; but it scarcely 
 appears possible effectually to clean out the pipes 
 themselves, and the constant dirt and extreme 
 annoyance of the efforts to keep the pipes clear 
 necessarily disqualifies this apparatus for general 
 use. Like many other patent inventions, this ap- 
 paratus could boast of numberless certificates of 
 high approval from parties of unquestioned veracity ; 
 but, notwithstanding these testimonials, the use of 
 this form of apparatus appears now to have entirely 
 ceased. 
 
 (213.) These several forms of hot-air apparatus 
 are all subject to one general objection to their 
 application. Whenever the furnace and heating- 
 surfaces are placed at a distance from the place 
 to be heated, and are not directly under it, there 
 is great difficulty in conveying the heated air 
 laterally through horizontal flues, unless the flues 
 have first given to them a very great vertical 
 height. This vertical height of flue gives velocity 
 to the current of heated air ; and without this it is 
 most difficult to make the current travel horizon- 
 tally along the flues which are requisite to convey 
 it to the different rooms. Mr. Sylvester, in his 
 description of Mr. Strutt's hot-air cockle, states, 
 that it is necessary to have the cockle and furnace 
 from 20 to 30 feet below the rooms which are to 
 be heated, in order to obtain sufficient velocity of 
 the air before it passes in a horizontal direction. 
 It is almost impossible to obtain this depth for the 
 furnace below the rooms which are to be heated 
 in any ordinary buildings; and unless, therefore, 
 the furnace can be fixed immediately under the
 
 MULTI-TUBULAR HOT-AIR APPARATUS. 229 
 
 place to be heated, the hot-air apparatus becomes 
 extremely difficult of application. The only way 
 to overcome the difficulty is to warm the horizontal 
 flues by some extraneous means. When this can 
 be done, the hot air travels readily through 
 the horizontal flues, and when once the current 
 has been established, it continues readily to flow. 
 This is now sometimes done by means of hot- 
 water pipes, which are laid in the horizontal flues ; 
 and these pipes can be heated by means of a 
 coil of wrought-iron pipes passing through the 
 furnace of the cockle-stove. The proper size of 
 this subsidiary apparatus for warming the flues 
 may be easily ascertained. In very large flues of 
 from three to four feet square (or from nine to 
 sixteen square feet area) two hot-water pipes of 
 four inches diameter, laid the whole length of the 
 flue, are sufficient ; and in smaller flues two pipes 
 of two inches diameter will be large enough for the 
 purpose. The size of the coil to heat this pipe can 
 be ascertained by the rules given (Art. 71) for 
 apportioning the size of boilers; by which it 
 will be seen that one superficial foot of coil placed 
 in the furnace will be sufficient to heat from 40 to 
 50 feet of 4 inch pipe in the flue, or twice that 
 length of 2 inch pipe. 
 
 (214.) Another apparatus for heating air to a 
 moderate extent, and well suited for warming and 
 ventilating purposes, is shown in figs. 49 and 50. 
 It consists of a number of iron pipes of 10 to 15 
 feet long, and about 2 or 2 inches diameter, 
 fixed at each end into a tube-plate (fig. 49), and 
 as close together as they can be easily placed. 
 This series of tubes, with its two end-plates, is then 
 built into a furnace in such manner that the 
 flame and heated gases shall act as extensively as 
 possible upon the outside of the tubes. The air 
 to be heated enters the tubes above the furnace-
 
 230 MULTI-TUBULAR HOT-AIR APPARATUS. 
 
 door at one end, and passing through the tubes, is 
 delivered at the opposite end into a channel or 
 
 FIG. 49. 
 
 Fir. 50. 
 
 flue, by which it is conducted into the room or 
 building which is required to be heated.* 
 
 (215.) The power of this form of apparatus can 
 be estimated by reckoning every square foot of 
 pipe thus exposed to the fire as equal to about 
 seven square feet of hot-water pipes. In point of 
 
 * This form of apparatus, by no means new, though not 
 much used, has recently (in the year 1873) been made the 
 subject of a Patent by Messrs. Truswell of Sheffield.
 
 HOT-AIR APPARATUS. 231 
 
 heating power, therefore, it will be about equal to 
 the Belper hot-air cockle; but in economy of 
 fuel it will be decidedly inferior. The apparatus 
 will also require to be frequently cleared from 
 soot, which will speedily condense upon the sur- 
 face of the pipes, and must be removed through 
 proper openings made in the sides and ends of 
 the brick casing in which the tubes are enclosed. 
 
 (216.) All these several forms of hot-air appara- 
 tus require a very free admission of air into 
 the air-channels of the apparatus. Unless this 
 be attended to in fixing the stoves, the heating 
 power will be greatly curtailed ; and therefore a 
 small close furnace-room, or stoke-hole, will ob- 
 viously be improper for any of these previously 
 described forms of apparatus. 
 
 (217.) There is yet another form of hot-air 
 apparatus which it may be desirable to mention, 
 although it is solely applicable to manufacturing 
 and drying purposes, and would be altogether 
 unfit for warming buildings used for habitation. 
 This apparatus has long been known and used in 
 the manufacture of iron, under the name of the 
 " hot-blast apparatus." It is very much like the 
 apparatus described as "Bernhardt and Hazard's 
 Patents," only that instead of the smoke and 
 heated gases passing through the pipes as in that 
 arrangement, in this case it is the air which passes 
 through the pipes, and the pipes themselves are 
 heated in a furnace very much after the fashion 
 of a gas retort. The form of the apparatus has 
 undergone many changes, and it has been used 
 in an infinite variety of shapes. It has some- 
 times been used as a continuously coiled pipe, 
 of rather large diameter ; sometimes a number 
 of small pipes branch out from a much larger pipe, 
 and form an arch ; and sometimes a form almost 
 similar to Bernhardt's patent has been used.
 
 232 HOT-BLAST APPARATUS. 
 
 In all cases the air is forced through the pipes by 
 mechanical means, and the pipes themselves are 
 heated externally in a sort of reverberatory fur- 
 nace. The pipes thus become red hot, and the 
 air in passing through them is heated to any 
 required temperature, varying from 300 to 600 
 Fahrenheit.* For manufacturing purposes, this 
 form of apparatus may sometimes be extremely 
 useful, where motive power by a fan or otherwise 
 can be obtained; and enormous quantities of air 
 can be heated by this means. The apparatus is 
 subject to a considerable amount of wear and tear, 
 in consequence of the great heat of the furnace ; 
 but by proper arrangements of the parts this may 
 be considerably modified. 
 
 (218) The proportions of this form of appara- 
 tus, to suit it for any of the ordinary purposes to 
 which it may be applied, are not easily deduced 
 from the experiments published respecting its 
 application to iron manufacture. The velocity of 
 the air passing through the pipes when the 
 apparatus is used in the blast-furnaces, is from 
 350 to 400 miles per hour ; the volume of heated 
 air from 2,000 to 3,000 cubic feet per minute; 
 and the heated surfaces of the pipes from 1,200 
 to 1,800 square feet. These quantities are so 
 enormous, and the alteration of any one of them 
 so completely invalidates any calculation founded 
 upon their joint effect, that no useful data can be 
 drawn from them to apply the apparatus to any 
 other purpose. Nevertheless, it is clear that 
 where a motive-power for forcing air through 
 the heated pipes can be employed, a very useful 
 apparatus in this form might be obtained, which 
 would be applicable for drying purposes, as the 
 
 * See Dufrenoy's " Eeport on the Use of Hot Air in the 
 Iron Works of England ; " and also a Translation, published 
 by Murray. London, 1836.
 
 HOT-BLAST APPARATUS. 233 
 
 force and temperature of the blast may be regu- 
 lated to almost any extent. 
 
 (219.) The best mode of producing a blast of 
 air for the purpose here described is by the fan 
 described (Art. 363, et seq.). Where steam-power 
 is used, this application will present no difficulty ; 
 but unless some mechanical means of forcing the 
 air through the tubes with considerable velocity 
 can be employed, this form of apparatus would be 
 utterly unsuitable. When used in this way, there 
 is no apparatus that can compare with it in power, 
 wherever large volumes of intensely heated air 
 are required for desiccating purposes. For drying 
 timber in very large quantities; for the rapid 
 evaporation of moisture in many processes; for 
 curing-stoves for animal substances ; and for many 
 other purposes of manufacturing economy this 
 mode of heating and drying presents advantages of 
 no inconsiderable extent, though, up to the present 
 time, it has not been used in this manner. 
 
 The deterioration of the air by passing over 
 highly-heated metallic surfaces must not be lost 
 sight of when considering any of the plans for hot- 
 air apparatus. This part of the subject is fully 
 treated on in Chapter III., Part II., of this work, 
 to which the reader is referred.
 
 234 
 
 CHAPTER XII. 
 
 ON THE LAWS AND PHENOMENA OF HEAT. 
 
 Kadiation and Conduction General Law of Cooling Bodies 
 in Air and other Gases Different Law for Conduction and 
 for Radiation Effect by the Incidence of the Hays- 
 Effects of Surface on Radiation Effects of Colour Effects 
 of Roughness Absorptive Power of Bodies for Heat 
 Conducting Power of Metals Conducting Power of Wood 
 Conducting Power of Liquids Cooling Influence of 
 Water and Air Reflective Powers of Bodies Specific 
 Heat of Bodies Latent Heat Spontaneous Evaporation 
 Heat and Cold by Condensation and Rarefaction of the 
 Air Motion of Liquids influenced by Heat Effect of 
 Heat on Strength of Materials. 
 
 (220.) HOWEVER various are the methods by 
 which artificial heat is distributed in the warming 
 of buildings, they are all reducible to certain 
 rules, which constitute the primary laws of heat. 
 These laws are very numerous, and some of them 
 extremely complicated; but they possess a very 
 high degree of philosophic interest. They are 
 far too extensive, however, to allow in this work 
 even a bare outline of all the various phenomena 
 to be given, which this branch of science exhibits. 
 But in the present chapter such of the laws of 
 heat as relate to the subject more immediately 
 before us shall be stated, in order to afford a 
 more ready and convenient reference for those who 
 wish to study the scientific principles of warming 
 buildings by artificial heat.
 
 RADIATION AND CONDUCTION. 235 
 
 (221.) There are four distinct properties of 
 heat, which all bodies possess in a greater or less 
 degree, which we shall first consider. These 
 are, radiation, absorption, conduction, and reflection. 
 There are also others, which will be subsequently 
 mentioned, such as the specific heat of bodies, 
 their change of state, and other subjects connected 
 with their chemical constitution. 
 
 (222.) Heated bodies give off their caloric by 
 two distinct modes radiation and conduction. 
 These are governed by different laws: but the 
 rate of cooling by both modes increases con- 
 siderably in proportion as the heated body is of 
 a greater temperature above the surrounding 
 medium. This variation was long supposed to 
 be exactly proportional to the simple ratio of the 
 excess of heat; that is to say, supposing any 
 quantity of heat given off in a certain time at a 
 specified difference of temperature, at double that 
 difference twice the quantity of heat would be 
 given off in the same time. This law was origi- 
 nally proposed by Newton, in the Principia, and, 
 although rejected as erroneous by some philo- 
 sophers, it was followed by Eichmann, Kraft, 
 Dalton, Leslie, and many others ; and was 
 usually considered to be nearly accurate, until 
 the masterly and elaborate experiments of MM. 
 Petit and Dulong proved that, although approxi- 
 mately correct for low temperatures, it becomes 
 extremely inaccurate at the higher degrees of 
 heat. 
 
 (223.) The cooling of a heated body, under 
 ordinary circumstances, is evidently by the com- 
 bined effects of radiation and conduction. The 
 conductive power of the air is principally owing 
 to the extreme mobility of its particles, for other- 
 wise it is one of the worst conductors we are 
 acquainted with ; so that when confined in such a
 
 236 ON THE LAWS AND 
 
 manner as to prevent its freedom of motion, it is 
 a most useful non-conductor. 
 
 (224.) The proportions which radiation and 
 conduction bear to each other have, in- general, 
 been very erroneously estimated. Count Eumford 
 considered the united effect, compared with radia- 
 tion alone, was as five to three; and Franklin 
 supposed it to be as five to two. Dr. Murray also 
 considered a certain relation existed between 
 radiating and conducting powers. 
 
 No such general law, however, can be deduced ; 
 for the relative proportions vary with the tem- 
 perature, and with the peculiar substance or sur- 
 face of the heated body. For while the cooling 
 effect of the air by conduction is the same on all sub- 
 stances, and in all states of tJie surface of those sub- 
 stances, radiation varies materially, according to 
 the nature of the surface. 
 
 (225.) The elaborate experiments of Petit and 
 Dulong have placed on record a vast amount of 
 most valuable information on this subject ;* and 
 by their researches some of the most important of 
 the laws of heat have been deduced. The follow- 
 ing abstract will give such of their deductions as 
 are most applicable to the subject under inquiry. 
 
 (226.) The influence of the air by its power of 
 conduction varies with its elasticity or barome- 
 tric pressure. The greater the elastic force, the 
 greater also is its cooling power, according to the 
 following law : When the elasticity of the air varies 
 in a geometrical progression whose ratio is 2, its cool- 
 ing power changes likewise in a geometrical progres- 
 sion whose ratio is 1*366. 
 
 The same law holds with all gases, as well as 
 with atmospheric air ; but the ratio of the pro- 
 gression varies for each gas. 
 
 * Ann. de Chimie, vol. vii., p. 113, et seq. ; and Annals of 
 Philosophy, vol. xiii., p. 112, et scq.
 
 PHENOMENA OF HEAT. 
 
 237 
 
 (227.) To show the relative velocities of cool- 
 ing at different temperatures, the following Table, 
 constructed from the experiments of Petit and 
 Dulong, is given. The first column shows the 
 excess of temperature* of the heated body above 
 the surrounding air ; f the second column shows 
 
 TABLE VI. 
 
 Excess of 
 Temperature of 
 the Thermometer 
 above that of 
 the Air ; 
 Centigrade Scale. 
 
 Total Velocity 
 of Cooling of the 
 naked Bulb. 
 
 Total Velocity 
 of Cooling 
 of Bulb covered' 
 with Silver 
 leaf. 
 
 Amount of 
 Cooling due to 
 Conduction 
 of the 
 Air alone. 
 
 260 
 
 24-42 
 
 10-96 
 
 8-10 
 
 240 
 
 21-12 
 
 9-82 
 
 7-41 
 
 220 
 
 17-92 
 
 8-59 
 
 6-61 
 
 200 
 
 15-30 
 
 7-57 
 
 5-92 
 
 180 
 
 13-04 
 
 6-57 
 
 5-19 
 
 160 
 
 10-70 
 
 5-59 
 
 4-50 
 
 140 
 
 8-75 
 
 4-61 
 
 3-73 
 
 120 
 
 6-82 
 
 3-80 
 
 3-11 
 
 100 
 
 5-57 
 
 3-06 
 
 2-53 
 
 80 
 
 4-15 
 
 2-32 
 
 1-93 
 
 60 
 
 2-86 
 
 1-60 
 
 1-33 
 
 40 
 
 1-74 
 
 96 
 
 80 
 
 20 
 
 77 
 
 42 
 
 34 
 
 10 
 
 37 
 
 19 
 
 14 
 
 * The temperatures in all these experiments of Petit and 
 Dulong are expressed in degrees of the Centigrade thermo- 
 meter. As the zero of this thermometer is the freezing-point 
 of water, and from that to the boiling point of the same fluid 
 is 100, in order to find the number of degrees of Fahrenheit's 
 scale, which answers to any given temperature of the Centi- 
 grade, multiply the number of degrees of Centigrade by nine 
 and divide the product by five ; add 32 to the quotient thus 
 obtained, and this sum will be the number of degrees of 
 Fahrenheit required. As, however, in the above Table, the 
 temperatures given are only the excess, and not the absolute 
 temperatures, the 32 to be added by this rule must be 
 omitted. 
 
 t In these experiments, the temperature of the air was at 
 Centigrade, therefore these temperatures are both the 
 excess and also the absolute temperatures.
 
 238 ON" THE LAWS AND 
 
 the rate of cooling of a thermometer with a plain 
 bulb ; and the third column gives the rate of 
 cooling when the bulb was covered with silver- 
 leaf. The fourth column shows the amount due 
 to the cooling of the air alone ; and by deducting 
 this from the second and third columns respec- 
 tively, we shall find what is the amount of radia- 
 tion under the two different states of surface, noticed 
 at the top of the second and third columns. 
 
 (228.) Some very remarkable effects may be 
 perceived by an inspection of the above Table. 
 It appears that the ratio of heat lost by contact 
 of the air alone is constant at all temperatures ; 
 that is, whatever is the ratio between 40 and 80, 
 for instance, is also the ratio between 80 and 
 160, or between 100 and 200. This law is 
 expressed by the formula 
 
 v = n . t 1 ' 233 
 
 where t represents the excess of temperature, and 
 n a number which varies with the size of the heated 
 body. In the case represented in the foregoing 
 Table, n = 0-00857. 
 
 (229.) Another remarkable law is, that the cool- 
 ing effect of the air is the same for the lik*, excess of 
 heat on all bodies without regard to the particular 
 state or nature of their surface. This was ascertained 
 by Petit and Dulong, in a series of experiments 
 not necessary here to detail, but which abundantly 
 prove the accuracy of the deduction.* 
 
 (230.) By comparing the second and third 
 columns in the preceding Table, it will be imme- 
 diately perceived that the loss of heat by radiation 
 (deducting the cooling by conduction of the air, 
 given in the fourth column) varies greatly with the 
 nature of the radiating surface ; though, whatever 
 be the nature of the surface, the loss of heat follows 
 the same law in all cases, though in a different ratio. 
 * Annals of Philosophy, vol. xiii.
 
 PHENOMENA OF HEAT. 239 
 
 It should be observed that in this Table the 
 second, third, and fourth columns show the 
 number of degrees of heat which were lost per 
 minute by the body which was the subject of 
 experiment; and, therefore, these numbers repre- 
 sent the velocity of cooling. 
 
 When the numbers in the last column are 
 deducted from those in the second and third 
 columns, the difference will show the loss of heat 
 by radiation for the plain and silvered bulb re- 
 spectively ; the fourth column being the loss by 
 conduction of the air, which is the same for all 
 surfaces. It will immediately be perceived, there- 
 fore, that the loss of heat by conduction and by 
 radiation bear no constant ratio to each other. 
 But, while conduction proceeds by a regular geome- 
 trical progression, radiation follows another law, 
 viz., when a body cools in vacua, surrounded by a 
 medium whose temperature is constant, the velocity of 
 cooling, for excess of temperature in arithmetical pro- 
 gression, increases as the terms of a geometrical pro- 
 gression, diminished by a constant quantity. This 
 law is represented by the formula 
 V = m. a 9 (a< - 1) 
 
 where a is the constant quantity for all bodies = 
 1'0077 ; t the excess of temperature of the radia- 
 ting body: 9 the temperature of the surrounding 
 medium ; and m a co-efficient, which varies with 
 the size and nature of the radiating body, to be 
 determined for each particular case. It will like- 
 wise appear that, when we compare the total cooling 
 of two different surfaces, the law is more rapid 
 at low temperatures, and less rapid at high tem- 
 peratures, for the body which radiates the least, in 
 comparison with that which radiates with greater 
 power. 
 
 (231.) But the cooling of a body by conduction
 
 240 
 
 OX THE LAWS AND 
 
 of the air differs from the effect of radiation in a 
 remarkable manner, in this particular that while 
 the ratio of loss by conduction continues the same 
 for the same excess of temperature, whatever be the 
 absolute temperatures of the air and heated body; 
 radiation increases in velocity, for like excess of tem- 
 perature, when the absolute temperatures of the air and 
 heated body increase. The following Table shows 
 the law of cooling by radiation for the same body at 
 different temperatures : 
 
 TABLE VII. 
 
 Excess of 
 Temperature 
 
 Velocity of Cooling when the surrounding Medium is at 
 the undermentioned Temperatures. 
 
 of the 
 Thermometer. 
 
 
 
 20 
 
 40 
 
 60 
 
 220 
 
 8-81 
 
 10-41 
 
 11-98 
 
 _ 
 
 200 
 
 7-40 
 
 8-58 
 
 10-01 
 
 11-64 
 
 180 
 
 6-10 
 
 7-04 
 
 8-20 
 
 9-55 
 
 160 
 
 4-89 
 
 5-67 
 
 6-61 
 
 7-68 
 
 140 
 
 3-88 
 
 4-57 
 
 5-32 
 
 6-14 
 
 120 
 
 3-02 
 
 3-56 
 
 4-15 
 
 4.84 
 
 100 
 
 2-30 
 
 2-74 
 
 3-16 
 
 3-68 
 
 It will be observed in this Table that, when 
 the absolute temperatures of the surrounding 
 medium and radiating body are increased 20 of 
 Centigrade, the difference between their temperatures 
 continuing the same, the velocity of cooling is 
 multiplied by 1 * 165, which is the mean of all the 
 ratios in the above Table, experimentally deter- 
 mined. 
 
 (232.) The total cooling of a body by radiation 
 and conduction, then, we shall find to be repre- 
 sented, under all circumstances, by this formula 
 
 777. a 6 (a* 1) + n. ? 
 
 The quantities a and b are constant for all bodies, 
 and under all circumstances; the first being = 
 1-0077 and the latter = 1-233. The coefficient
 
 PHENOMENA OF HEAT. 241 
 
 m will depend on the size and nature of the heated 
 surface, as well as upon the nature of the sur- 
 rounding medium. The co-efficient n is inde- 
 pendent of the absolute temperature, as well as of 
 the nature of the surface of the body; but will 
 vary with the elasticity and nature of the gas in 
 which the body is plunged : t is the excess of 
 temperature of the heated body, and 6 the tem- 
 perature of the surrounding medium. 
 
 (233.) The fact, already adverted to, that the 
 ratio of cooling of those bodies that radiate least 
 is more rapid at low temperatures, and less rapid 
 at high temperatures, than those bodies that 
 radiate most, is perhaps one of the most remark- 
 able of the laws of cooling. It was first deduced 
 experimentally by Petit and Dulong, and it may 
 be mathematically proved from their formula?.* 
 It appears, however, that when the total cooling 
 of two bodies is compared, the law is more rapid 
 at low temperatures for the body which radiates 
 least, and less rapid for the same body at high 
 temperatures ; though separately, for conduction 
 and for radiation, the law of cooling is, for the 
 former, irrespective of the nature of the body, and 
 for the latter, that all bodies preserve, at every 
 difference of temperature, a constant ratio in their 
 radiating power. 
 
 (234.) To revert to the first Table in this 
 chapter. We find the total cooling at 60 and 
 120 (of Centigrade) to be about as 3 to 7 ; at 60 
 and 180, as 3 to 13 ; and at 60 and 240, as 3 
 to 21 : whereas, according to the old theory of 
 Newton, they should have been respectively as 
 3 to 6 ; as 3 to 9 ; and as 3 to 12. But we find 
 that the deviation increases greatly with the 
 increase of temperature, and that when the excess 
 of temperature of the heated body above the 
 
 * Annals of Philosophy, vol. xiii., p. 335. 
 
 R
 
 242 ON THE LAWS AND 
 
 surrounding air is as high as 240 of Centigrade 
 (432 of Fahrenheit), the real velocity of cooling 
 is nearly double what it would appear to be by 
 the old and imperfect theory, varying, however, 
 with the nature of the surface. 
 
 (235.) But radiant heat is subject to other laws 
 besides those we have yet considered. Rays of 
 heat diverge in straight lines from every part of 
 a heated surface, and likewise from extremely 
 minute depths below the surface of hot bodies, 
 being subject to the laws of refraction, the same 
 as light. The intensity of these rays decreases as 
 the square of the distance, and the emission of the 
 rays is greatest in a line perpendicular to the 
 surface. The same law obtains here, also, as with 
 light that the effect of the ray is as the sine of 
 the angle which it forms with the surface from 
 which it emanates.* This law of the sines, first 
 discovered experimentally by Leslie, suggests a 
 practical caution connected with the subject before 
 us, namely, that the shape of the pipes used to 
 warm a building is not wholly unimportant; for, 
 if flat pipes be used, and they be laid horizontally, 
 the major part of the radiated heat from the upper 
 surface will be received on the ceiling, and 
 therefore will produce but little beneficial effect. 
 The loss sustained in this way will be greater in 
 proportion to the higher temperature of the pipes ; 
 for it will be seen by the Table at the beginning 
 of this chapter, that the relative proportion which 
 radiation bears to conduction increases with the 
 temperature : at the ordinary temperature of hot- 
 
 * This law is thus stated by Fourier : " The rays of heat 
 which issue under different angles from the same point of the 
 surface of any body, have an intensity which decreases propor- 
 tionally to the sine of the angle formed by their direction with 
 the plane tangential to the surface at the point of emission." 
 London and Edinburgh Philosophical Magazine, vol. ii., p. 104 ; 
 also, Report, British Scientific Association, vol. iv. (1835), p. 22.
 
 PHENOMENA OF HEAT. 
 
 243 
 
 water pipes, about one-fourth the total cooling is 
 due to radiation. 
 
 (236.) The radiation of heat, we have already 
 seen, is greatly either increased or diminished 
 according to the nature of the surface of the 
 radiating body. Professor Leslie has given the 
 following as the relative powers of radiation by 
 different substances : * 
 
 TABLE VIII. 
 
 Lamp-black . 
 
 100 
 
 Tarnished Lead . . 45 
 
 Water (by estimate) 
 
 100 
 
 Thin Film of Jelly (one 
 
 Writing Paper 
 
 
 98 
 
 quarter of former) 
 
 38 
 
 Resin . 
 
 
 96 
 
 Tin scratched with Sand 
 
 
 Sealing-wax 
 
 
 95 
 
 paper 
 
 
 22 
 
 Crown Glass 
 
 
 
 90 
 
 Mercury . 
 
 
 20 
 
 China Ink 
 
 
 
 88 
 
 Clean Lead . 
 
 
 19 
 
 Ice 
 
 
 
 85 
 
 Iron, polished 
 
 
 15 
 
 Red Lead 
 
 
 
 80 
 
 Tin Plate . 
 
 
 12 
 
 Isinglass 
 
 
 
 80 
 
 Gold, Silver, and Copper 12 
 
 Plumbago 
 
 
 
 75 
 
 Thin LaminsB of Gold, 
 
 Thick Film of Oil 
 
 59 
 
 Silver, or Copper Leaf, 
 
 Film of Jelly 
 
 54 
 
 on Glass ... 12 
 
 Thinner Film of Oil 
 
 51 
 
 
 (237.) It is very generally supposed that colour 
 has a considerable influence on radiant heat, and 
 also upon the absorption of heat, the two effects 
 being similar and equal. Sir Humphrey Davy, 
 by exposing surfaces of various colours to the 
 heat of the sun, proved experimentally f that 
 the absorbing power of different colours was in 
 this order : black, blue, green, red, yellow, and 
 white; black being the best, and white the worst 
 absorbent. In this order, then, we should expect 
 to find the radiating powers of different colours, 
 and that by painting a body with a dark colour 
 we should increase its power of radiation. This, 
 
 * Leslie, On Heat, pp. 81-110. 
 
 t Beddoe's Contributions, p. 44; also, Dr. Stark's "Re- 
 searches on Heat," Philosophical Transactions, 1834 ; and 
 Repertory of Arts, 1834, pp. 257, 312. 
 
 ii 2
 
 244 ON THE LAWS AND 
 
 however, is not the case ; and there are the strongest 
 reasons for supposing that the absorption and 
 radiation of simple heat that is, heat without light, 
 or heat from bodies below luminosity are wholly 
 irrespective of colour, and depend upon the nature 
 of the surface. 
 
 (238.) By comparing the results given in the 
 above Table, it will appear that the radiation of 
 heat bears no relation to colour, when the radiating 
 body is below the temperature of boiling water. 
 By the Table it appears that lamp-black and white 
 paper are nearly equal in power ; while Indian ink 
 is much less, and black-lead still lower in the scale ; 
 though, as far as colour only is concerned, these 
 last are nearly the same as lamp-black. Professor 
 Powell considers, as also did Leslie, that softness 
 may probabty tend to increase the radiation of simple 
 heat;* and the former found that a thermometer- 
 bulb coated with a paste of chalk was affected (by 
 this kind of heat that is, heat below luminosity) 
 even more than a similar one coated with Indian 
 ink ; but the same result does not occur with 
 luminous hot bodies.f Professor Bache has like- 
 wise made an extensive series of experiments on 
 this subject, which confirm this result.J The 
 experiments of Leslie proved that radiation proceeds 
 not only from the surface of bodies, but also from 
 small depths below the surface ; and therefore the 
 thickness of coating of any good radiating substance 
 materially affects the results, as may be observed by 
 
 * It is necessary to distinguish particularly between simple 
 heat from bodies of a limited temperature and that which is 
 given off from luminous hot bodies. From these latter, the 
 experiments of Nobili and Melloni prove the existence of two 
 distinct kinds of heating rays given off at the same time from 
 the same body. 
 
 f Professor Powell's " Eeport on Heat," British Scientific 
 Association, vol. i., p. 279. 
 
 t Ibid., vol. ix. (1840), p. 18.
 
 PHENOMENA OF HEAT. 245 
 
 the above Table.* The thickness which produces 
 the greatest effect, however, probably varies with 
 different substances; and it is therefore necessary 
 to separate this effect from anything merely re- 
 sulting from the colour of the heated body. 
 Professor Powell, after an elaborate examination 
 of all the phenomena attending the heat received 
 from the sun, is of opinion that there is no simple 
 radiant heat received by us from the sun's rays ; 
 and that the simple radiant heat, which no doubt 
 is initially radiated from the sun, is absorbed by 
 the atmosphere of that luminary, some small 
 portion, perhaps, which escapes being stopped in 
 the higher regions of our own atmosphere.f The 
 experiment of Sir H. Davy, on the absorption 
 and radiation of solar heat by different colours, is 
 therefore not applicable to the case of simple heat, 
 or such heat as is given out by bodies below 
 luminosity. And in conformity with this view is 
 the experiment of Scheele, in which he found 
 that if two thermometers filled with alcohol, one 
 red, and the other colourless, were exposed to the 
 sun's rays, the coloured one would rise in tem- 
 perature much more rapidly than the other ; but if 
 they were both plunged into the same vessel of hot 
 water, they rose equally in equal times. 
 
 (239.) We are fully justified, then, from these 
 and other analogous experiments, in drawing the 
 conclusion that the radiation of SIMPLE HEAT is not 
 influenced by the colour of the heated body. Any dif- 
 ference which appears to obtain in this respect 
 is, therefore, solely referable to the nature of the 
 colouring substance. 
 
 (240.) The effect of roughness of the surface 
 was also investigated by Sir J. Leslie; and he 
 found that either tarnished surfaces, or such as 
 
 * Leslie, On Heat, pp. 106-110. 
 
 f Report of the British Scientific Association, vol. i., p. 290;
 
 246 ON THE LAWS AXD 
 
 are roughened by emery, by the file, or by drawing 
 streaks or lines with a graving tool, always had 
 their power of radiation considerably increased.* 
 The accuracy of this deduction had not been 
 questioned until some recent experiments of M. 
 Melloni, by which it has been ascertained that 
 this increased effect from roughened surfaces is 
 not a general law, but is only a particular result, 
 for which another explanation must be sought. 
 M. Melloni experimented with four plates of silver, 
 two of which, when cast, were left in their natural 
 state, without hammering, and the other two were 
 planished to a high degree under the hammer. 
 All the plates were then finely polished with 
 pumice-stone and charcoal ; and after this one 
 of each of the pairs of plates was roughened by 
 rubbing with coarse emery paper in one direction. 
 The quantity of heat radiated from these plates 
 was as follows : 
 
 Hammered and polished plate . . .10 
 
 and roughened . . .18 
 
 Cast and polished plate . . . .13-7 
 
 and roughened . . . .11-3 
 
 In comparing these effects, it appears that the 
 hard hammered plate increased in radiating power 
 four-fifths by roughening its surface; while the 
 soft cast plate lost nearly one-fifth of its power by 
 the same process. M. Melloni, therefore, draws 
 the . conclusion that the roughness of the surface 
 merely acts by altering the superficial density, and 
 that this will vary according as the body is of a 
 greater or less density previous to the alteration of 
 its surface by roughening.f 
 
 * Leslie, On Heat, p. 81, &c. 
 
 t Melloni, "On Emissive Power of Bodies," &c., Comptes 
 Jtendus de I'Academie des Sciences, and Edinburgh Philosophical 
 Journal, 1838.
 
 PHENOMENA OF HEAT. 247 
 
 (241.) It was deduced from experiments by 
 Leslie that the absorptive power of bodies for heat 
 was very nearly proportional to the radiative power ;* 
 and Dr. Ritchie has subsequently proved that these 
 effects are precisely equal to each other.f 
 
 (242.) The velocity with which heat enters into 
 and quits any body is supposed to be equal, though 
 this velocity is different for each different body. 
 On this property of bodies with regard to heat, 
 many of the experiments have been founded which 
 constitute the laws of heat. It has also been 
 established, by the experiments of MM. Melloni and 
 Nobili, that the radiating powers of surfaces, for 
 simple heat, are in the inverse order of their conduct- 
 ing powers. It follows, therefore, that neither the 
 radiating powers nor the conducting powers of 
 bodies will discover their actual rate of cooling 
 comparatively with any other body. 
 
 (243.) We might be led to conclude, from all 
 that precedes, that those metals which are the worst 
 conductors would be the most proper for vessels or 
 pipes for radiating heat ; because we find that the 
 heat lost by contact of the air is the same for all 
 bodies, while those which radiate most, or are the 
 worst conductors, give out more heat in the same 
 time than those bodies which radiate least, or are 
 good conductors. Such would be the case if the 
 vessels were infinitely thin ; but, as this is not 
 possible, the slow conducting power of the metal 
 opposes an insuperable obstacle to the rapid 
 cooling of any liquid contained within it, by 
 preventing the exterior surface from reaching 
 so high a temperature as would that of a 
 more perfectly conducting metal, under similar 
 circumstances ; thus preventing the loss of heat, 
 both by contact of the air and by radiation, the 
 
 * Leslie, On Heat, &c., pp. 19-98. 
 
 | Journal of the Eoyal Institution, vol. v., p. 305.
 
 248 ON THE LAWS AXD 
 
 effect of both being proportional to the excess of 
 heat of the exterior surface of the heated body. If 
 a leaden vessel were infinitely thin, the liquid con- 
 tained in it would cool sooner than in a similar 
 vessel of copper, brass, or iron : but the greater 
 the thickness of the metal, the more apparent 
 becomes the deviation from this rule ; and, as the 
 vessels for containing water must always have 
 some considerable thickness, those metals which 
 are the worst conductors will oppose the greatest 
 resistance to the cooling of the contained liquid, 
 although apparently in opposition to the result of 
 the preceding experiments. 
 
 It is difficult on these grounds to account for 
 the effect which lead-paint has in preventing the 
 free radiation of caloric from bodies coated with it ; 
 because, in this case, the lead must be extremely 
 thin, and ought, therefore, to increase the amount 
 of radiation. The effect probably arises from the 
 total change of state which the lead undergoes by 
 its chemical combination with the carbonic acid 
 in the process of making it into white lead. Practi- 
 cally, it is found to have an injurious tendency on 
 the free radiation of heat from most bodies, varying, 
 however, with their radiating powers. On a good 
 radiator, its effect is the most injurious ; on a bad 
 one, less so : but its use should be avoided as much 
 as possible in all cases where the free radiation of 
 heat is the object in view. 
 
 (244.) Various experiments have been made by 
 Bichmann, Ingenhausz, and Dr. Ure, to ascertain 
 the conducting power of metals. Dr. lire's results, 
 which differ but little from the others, place the 
 metals in the following order as regards their 
 conducting power, namely silver he found by far 
 the best conductor ; next copper ; and then brass, 
 tin, and wrought iron, nearly equal ; then cast iron 
 and zinc ; and lead he found by far the worst of all.* 
 
 * Ure's Dictionary of Chemistry, Art. " Caloric."
 
 PHENOMENA OF HEAT. 249 
 
 (245.) The only accurate experiments, however, 
 which have been made on this subject are those 
 by M. Despretz,* which give the following re- 
 sults : 
 
 Gold 
 
 Platina 
 
 Silver 
 
 Copper 
 
 Iron 
 
 Zinc 
 
 TABLE IX. 
 
 100-0 I Tin 
 
 98-10 ! Lead 
 
 97-30 i Marble . 
 
 89-82 i Porcelain 
 
 37-43 
 36-30 
 
 Fire-brick 
 
 30-39 
 
 17-96 
 
 2-36 
 
 1-22 
 
 1-14 
 
 This Table gives a very useful practical enun- 
 ciation of the value of different substances as con- 
 ductors of heat. But to ascertain the absolute 
 conducting power of the various substances is 
 extremely difficult ; the preceding Table obviously 
 only shows their relative conducting powers. Ex- 
 periments, however, have been made on the 
 absolute conducting powers of some substances, 
 which are of considerable practical value, although 
 they leave much yet to be desired. 
 
 (246.) M. Biot ascertained the conducting power 
 of a bar of iron, by plunging one end of it into a 
 bowl of mercury heated to 102| Centigrade (216 
 Fahrenheit), and ranging along the bar eight 
 thermometers at various distances from each other. 
 The observations were made after the temperature 
 became permanent ; the air during the experiment 
 was 16^ Centigrade (61 Fahrenheit), and the 
 results were as follow : 
 
 * Despretz, Trade de Physique, p. 201 ; and Quarterly Journal 
 of Science, vol. xxv., p. 220. Professor Daniell (Chemical Philo- 
 sophy, p. 107) places platina much lower in the scale than 
 M. Despretz, namely, 38-1. See also experiments by Calvert, 
 Proceedings of Eoyal Society, vol. ix., p. 170 (for March, 1858), 
 and Quctelet's Natural Philosophy (by Wallace), p. 144.
 
 250 
 
 ON THE LAWS AND 
 
 TABLE X. 
 
 
 Distance 
 
 Excess of 
 
 Distance 
 
 Excess of 
 
 No. of 
 Thermometer. 
 
 from 
 Mercury, 
 Decimeters. 
 
 Temperature 
 above the Air, 
 Centigrade. 
 
 from 
 Mercury, 
 Inches. 
 
 Temperature 
 above the Air, 
 Fahrenheit. 
 
 
 
 
 
 86-25 
 
 
 
 155 
 
 1 
 
 2-115 
 
 29-375 
 
 8-326 
 
 53 
 
 2 
 
 3-115 
 
 17-5 
 
 12-263 
 
 81J 
 
 3 
 
 4-009 
 
 11-25 
 
 15-783 
 
 20 
 
 4 
 
 4 970 
 
 7-1875 
 
 19-566 
 
 13 
 
 5 
 
 5-902 
 
 4-6875 
 
 23-236 
 
 8 
 
 6 
 
 7-777 
 
 2-1875 
 
 30-618 
 
 4 
 
 7 
 
 9-671 
 
 1-25 
 
 38-074 
 
 2 
 
 8 
 
 11-556 Insensible 
 
 45-495 
 
 Insensible 
 
 In this Table, the first column gives the num- 
 bers of the thermometers in their regular order ; 
 the second column gives the distance of each 
 thermometer from the source of heat, viz., the bowl 
 of mercury; and the third column gives the ex- 
 cess of temperature of the thermometers above that 
 of the atmosphere, measured by the Centigrade 
 scale. The fourth and fifth columns are the same 
 as the second and third, only the measures are 
 given according to the English scales, Instead of 
 the French. 
 
 (247.) A similar experiment,* in which the 
 source of heat was melted lead, is given in the 
 Table XI. The temperature of the air was 18 1 25 
 Centigrade (64J Fahrenheit), and that of the iron 
 bar was not taken until it had been exposed to the 
 heat of the lead for several hours, in order to 
 ensure permanence of temperature. 
 
 * For these experiments, see Biot's Trade de Physique, tome 
 iv., p. 670, et seq. Also, Beports, British Scientific Association, 
 vol. x. (1841), p. 15, et seq.
 
 PHENOMENA OF HEAT. 
 TABLE XI. 
 
 251 
 
 
 Distance 
 
 Excess of 
 
 Distance 
 
 Excess of 
 
 No. of 
 
 Thermometer. 
 
 from 
 Extremity, 
 Decimeters. 
 
 Temperature 
 above the Air, 
 Centigrade. 
 
 from 
 Extremity, 
 Inches. 
 
 Temperature 
 above the Air, 
 Fahrenheit. 
 
 1 
 
 2-230 
 
 76-875 
 
 8-78 
 
 138-37 
 
 2 
 
 3-230 
 
 47-187 
 
 12-71 
 
 84-93 
 
 3 
 
 4 120 
 
 29-375 
 
 16-22 
 
 52-87 
 
 4 
 
 5-081 
 
 17-812 
 
 20-00 
 
 32-06 
 
 5 
 
 6-028 
 
 10-625 
 
 23-73 
 
 19-12 
 
 6 
 
 7-899 
 
 3-750 
 
 31-09 
 
 6-75 
 
 7 - 
 
 9-783 
 
 1-562 
 
 38-51 
 
 2-73 
 
 (248.) A third experiment, also by M. Biot, was 
 made with a bar of copper, plunged at one extre- 
 mity into melted lead. It had fourteen thermo- 
 meters ranged along it, of which, however, only 
 eleven were available. The unit of distance was 
 101 millimeters,* and the temperature of the air 
 was 15-75 Centigrade (60^- Fahrenheit). 
 
 TABLE XII. 
 
 
 Distance 
 
 Excess of 
 
 Distance 
 
 Excess of 
 
 No. of 
 
 Thermometer. 
 
 from 
 Extremity, 
 Decimeters. 
 
 Temperature 
 above the Air, 
 Centigrade. 
 
 from 
 Extremity, 
 Inches. 
 
 Temperature 
 above the Air, 
 Fahrenheit. 
 
 4 
 
 5-25 
 
 80-50 
 
 20-87 
 
 144-9 
 
 5 
 
 6-25 
 
 65-75 
 
 24-85 
 
 118-3 
 
 6 
 
 7-25 
 
 53-75 
 
 28-82 
 
 96-7 
 
 7 
 
 8-25 
 
 43-75 
 
 32-80 
 
 78-7 
 
 8 
 
 9-25 
 
 35-50 
 
 36-77 
 
 63-9 
 
 9 
 
 11-25 
 
 24-00 
 
 44-73 
 
 43-2 
 
 10 
 
 13-25 
 
 15-70 
 
 52-68 
 
 28-2 
 
 11 
 
 15-25 
 
 11-00 
 
 60-63 
 
 19-8 
 
 12 
 
 17-25 
 
 7-50 
 
 68-58 
 
 13-5 
 
 13 
 
 19-25 
 
 5-25 
 
 76-53 
 
 9-4 
 
 14 
 
 21-25 
 
 3-75 
 
 84-49 
 
 6-7 
 
 * The millimeter is -03937 of an inch English measure, 
 and therefore the 101 millimeters are equal to 3*97637 inches.
 
 252 
 
 OX THE LAWS AXD 
 
 (249.) Some experiments by M. Despretz,* 
 similar to the preceding, and extending also to 
 other substances, are contained in the following 
 Table. In these experiments the distance between 
 each of the consecutive thermometers was 10 cen- 
 timeters (3 '937 inches English), and the tempera- 
 tures are given by the Centigrade scale. 
 
 TABLE XIII. 
 
 Excess of 
 Temperature 
 above the Air, 
 Centigrade Scale. 
 
 .0. 
 
 of the Thermometers. 
 
 Temperature 
 of 
 the Air, 
 Centigrade. 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 Copper 
 Iron . 
 Pewter 
 Zinc . 
 Lead . 
 Marble 
 
 66-36 
 62-9 
 63-41 
 64-17 
 65-13 
 63-91 
 
 46-2832-62 
 36-6920-52 
 35 -17^21 -52 
 38-0225-43 
 29-4214-93 
 6-08 1-95 
 
 24-32 
 12-32 
 15-52 
 17-93 
 9-99 
 1-47 
 
 18-63 
 8-19 
 
 __ 
 
 16-18 
 6-61 
 
 17-08 
 17-34 
 17-34 
 5-62 
 17-12 
 17-15 
 
 In all these experiments the substances were 
 exposed to the cooling influence of the air. In 
 Mr. Kellard's Report on the Laws of Conduction of 
 Heat, made to the British Scientific Association 
 (vol. x.), the mathematical formulae of MM. 
 Fourier, Libri, Poisson, and others, are given at 
 considerable length, for estimating the conducting 
 powers for heat; but they are not suitable for 
 insertion here. 
 
 (250.) Experiments on the same plan as the 
 preceding were made by MM. Delarive and Con- 
 dolle on the conducting power of wood: the re- 
 sults are given in the following Table.f They 
 show the difference in conducting power, accord- 
 
 * Traite de Physique, par M. Despretz. 
 
 | Ann. de Chimie, vol. xl., p. 91 ; and Quarterly Journal of 
 Science, vol. xxvii., p. 188.
 
 PHENOMENA OF HEAT. 
 
 253 
 
 ing to the direction of the fibre. The bars of 
 wood were about five inches long, one and a half 
 inch broad, and one inch thick. The first ther- 
 mometer was three centimeters (one and one-eighth 
 inch English) from the end; and the others were 
 two centimeters (three-quarters of an inch English) 
 apart from each other. The temperatures given 
 are the excess above the atmosphere, at the respec- 
 tive distances from the heated end. 
 
 TABLE XIV. 
 
 
 No. of Thermometers, Centigrade Scale. 
 
 Names of the Woods. 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 Walnut 
 Oak . 
 
 Hi 
 
 80-13 
 81-7 
 
 43-0 
 41-2 
 
 19-63 
 17-5 
 
 9-19 
 
 7-2 
 
 5-13 
 
 3-7 
 
 Fir . 
 
 Jt%3 
 
 84-0 
 
 39-25 
 
 20-6 
 
 8-5 
 
 3-7 
 
 Poplar 
 
 33- 
 
 79-8 
 
 34-2 
 
 14-2 
 
 6-2 
 
 2-8 
 
 Walnut 
 
 
 99-5 
 
 37-43 
 
 13-9 
 
 6-0 
 
 3-25 
 
 Oak . 
 
 NI 
 
 79-3 
 
 22-75 
 
 7-5 
 
 3-6 
 
 2-4 
 
 Fir . 
 
 %*2 
 
 70-9 
 
 13-8 
 
 4-5 
 
 2-5 
 
 1-9 
 
 Poplar 
 
 %* 
 
 78-5 
 
 13-75 
 
 3-44 
 
 1-56 
 
 1-0 
 
 (251.) Fluids, both in the liquid and aeriform 
 state, are bad conductors of heat, unless they have 
 perfect freedom of motion, in which case they 
 become far better conductors than solids on 
 account of the extreme mobility of their particles.* 
 Water, under these circumstances, is a far better 
 conductor of heat than any of the metals (except 
 mercury) ; and air, particularly when charged with 
 moisture, is also an excellent conductor, under like 
 
 * In aeriform fluids, radiant heat is transmitted, with 
 extreme rapidity without any visible motion of the particles ; 
 but this is a very different case to that stated in the text.
 
 254 
 
 ON THE LAWS AXD 
 
 circumstances. Count Rumford made some experi- 
 ments to ascertain the cooling power of different 
 fluids, based upon the principle that their con- 
 ducting power and absorbing power are equal.* 
 The mode of operating was to enclose a thermo- 
 meter in a glass balloon filled with the particular 
 substance of which the conducting power was to 
 be ascertained; and to place it first in freezing 
 water, and then plunge it into boiling water. The 
 respective times required to raise the thermometer 
 from to 70 Reaumur were supposed to indicate 
 the conducting powers of the different substances, 
 and would therefore be their cooling powers upon 
 any heated body placed in them. The following 
 Table shows the results of these experiments, the 
 times being given in minutes and seconds. 
 
 TABLE XV. 
 
 Substances. 
 
 Times of Cooling. 
 
 Ratio of 
 Conducting 
 Power. 
 
 Mercury 
 Moist Air 
 
 0'-36" 
 1 -51 
 
 1000 
 330 
 
 Water .... 
 
 1 -57 
 
 313 
 
 Common Air 
 
 7 -36 
 
 80-41 
 
 Earefied Air, density \ 
 Do. do. ^V 
 
 7 -37 
 7 -51 
 
 80-23 
 78 
 
 Torricellian Vacuum 
 
 10 -53 
 
 55 
 
 These experiments, however, are by no means 
 conclusive ; and there is every reason to believe 
 that, by varying the method of the experiment, 
 a vast difference would be found in the results. 
 The glass balloon which surrounded the ther- 
 mometer was only one inch and a half diameter, 
 the thermometer itself being half an inch diameter. 
 
 * Eumford's Essays, vol. ii., p. 425.
 
 PHENOMENA OF HEAT. 255 
 
 This space was far too small to allow a free and 
 rapid motion among the particles of the various 
 media which were the subject of experiment; 
 and therefore the conducting powers of the 
 liquids, which have less facility of motion among 
 their particles than the aeriform fluids, appear far 
 less than they really are. Dr. Osborne ascertained 
 the refrigerating power of water compared with 
 air of the same temperature to be as 14 to 1,* 
 while Rumford's experiments show it to be less 
 than four to one: but there is reason to believe 
 that, when due provision is made for allowing 
 perfect mobility among the particles of water, the 
 cooling power of water will be very much greater 
 than the amount even which is stated by Dr. 
 Osborne ; f and Leslie states that water at the 
 boiling-point conducts heat five times more ra- 
 pidly than the same fluid when near the freezing- 
 point. J 
 
 (252.) The power of reflection in all bodies is 
 
 * Reports of the British Scientific Association, vol. iv. (1835), 
 p. 96. 
 
 | Some experiments of the author led him to conclude that 
 the conducting power of boiling water, compared with air, was 
 fully double the amount stated by Dr. Osborne ; and these 
 agreed so well with the experiments of Mr. Parkes, already 
 quoted (Art. 73, note), that the author was induced to adopt 
 the proportion of 28 to 1 as the cooling power of water and air, 
 in an extensive and peculiar apparatus which required the 
 cooling powers of these media to be properly adjusted. The 
 result has proved that the cooling power of water is fully 
 equal to this estimate ; but it is probable that the relative 
 conducting power varies with the temperature of the heated 
 body. For unless the temperature be sufficiently high to give 
 free motion to the particles of water, the cooling power will be 
 reduced; while the tame diiference can scarcely occur in the 
 air, in consequence of the extreme mobility of the particles. 
 The diminished adhesion of liquids by increased temperature 
 has been experimentally determined by Dr. Ure. (See 
 Art. 264.) 
 
 | Leslie, Heat and Moisture, p. 17,
 
 256 ON THE LAWS AND 
 
 inversely as their radiating power, as was ex- 
 perimentally determined by Leslie.* The follow- 
 ing Table shows the reflective power of different 
 substances. 
 
 Brass . 
 Silver . 
 Tinfoil . 
 Block Tin 
 Steel 
 
 TABLE XVI. 
 100 I Lead 60 
 
 90 
 85 
 
 80 
 
 Tinfoil softened by Mer- 
 cury .... 10 
 Glass . 10 
 
 70 ! Glass coated with Wax 5 
 
 (253.) The specific heat of different substances is 
 a subject of considerable importance, as connected 
 with the heating of buildings ; for on the theory 
 of specific heat are based many of the calculations 
 for ascertaining the proportions of the various 
 apparatus employed. 
 
 (254.) Every substance contains a certain dis- 
 tinctive quantity of heat, called the specific heat of 
 that particular body, which can be ascertained by 
 mixing together (with proper precautions) known 
 quantities of different substances. Thus, if a certain 
 weight of quicksilver, one pound for instance, of 
 the temperature of 40, be mixed with the same 
 weight of water, of the temperature of 156 the re- 
 sulting temperature will be 152*3; so that the 
 water will lose 3 7 of temperature, and the quick- 
 silver will be raised 112'3. Or, if a pound of water 
 at 100 be mixed with a pound of oil at 50 the re- 
 sulting temperature will be 83*5, and not 75, 
 which would be the mean temperature of the two. 
 Thus it appears that the same quantity of heat that 
 will raise a pound of water 1 will raise the tem- 
 perature of a pound of oil 2, or a pound of mercury 
 23 ; and so of other substances, which all possess 
 
 * Leslie, On Heat, pp. 20 and 98.
 
 PHENOMENA OF HEAT. 
 
 257 
 
 a capacity for caloric, each peculiar to itself. The 
 following Table shows the specific heat of some of 
 the principal substances, which have been ascer- 
 tained, chiefly from the experiments of Berard and 
 Delaroche, and Petit and Dulong. They are all 
 referred to water, as the standard, and are supposed 
 to be the quantity of heat contained in equal weights 
 of the several substances.* 
 
 TABLE XVII. 
 
 Water 
 Aqueous Vapoi 
 Alcohol . 
 Ether . 
 Oil. 
 Air. 
 Hydrogen 
 Azote 
 Oxide of Azote 
 
 ir 
 
 1-0000 
 0-8470 
 0-7000 
 0-6600 
 0-5200 
 0-2669 
 3-2936 
 0-2754 
 0-2369 
 
 Oxygen . 
 Carbonic Acid 
 Carbonic Oxidt 
 Charcoal . 
 Sulphur . 
 Iron (wrought 
 Mercury . 
 Platinum. 
 Gold 
 
 s 
 
 0-2361 
 0-2210 
 0-2884 
 0-2631 
 0-1850 
 0-1100 
 0-0330 
 0-0314 
 0-0298 
 
 (255.) It has, however, been much questioned 
 whether the several substances possess the same 
 capacity for heat at all temperatures ; and MM. 
 Petit and Dulong, as also Dr. Dalton, appear to 
 have established the fact that the capacity for heat 
 of every substance increases with the temperature ; 
 or, in other words, that the quantity of heat given 
 out by any body, in cooling a given number of 
 degrees, is greater at high temperatures than at low 
 temperatures. The following Table exhibits the 
 specific heat of several bodies between the tem- 
 peratures of and 100, and also between and 
 300 of Centigrade. 
 
 * A further list will be found in Table V., Appendix.
 
 258 
 
 OX THE LAWS AND 
 
 TABLE XVIII. 
 
 Substances. 
 
 Mean Capacity ' 
 between and 100 
 Centigrade. 
 
 Mean Capacity 
 between and 300 
 Centigrade. 
 
 Iron . 
 
 1098 
 
 1218 
 
 Mercury 
 Zinc . 
 
 0330 
 0927 
 
 0350 
 1015 
 
 Antimony 
 Silver 
 
 0507 
 0557 
 
 0549 
 0611 
 
 Copper 
 Platinum 
 
 0949 
 0335 
 
 1013 
 0355 
 
 Glass 
 
 1770 
 
 1900 
 
 (256.) But independent of the sensible heat of 
 bodies as ascertained by direct measurement, when 
 any change of state occurs, as from the solid to the 
 liquid, and from the liquid to the aeriform, or vice 
 versa, certain quantities of heat enter into or quit 
 the respective substances, which, not being directly 
 measurable by the thermometer, have been termed 
 latent heat. Ice at 32 requires 140 of heat to 
 enter into combination with it before it assumes 
 the liquid state ; and it then becomes water, though 
 still only at the temperature of 32. And water at 
 212 requires 1000 of heat to enter into combina- 
 tion with it before it assumes the state of steam, 
 though in the latter state it still only shows a ther- 
 mometric temperature of 212. The following 
 Table gives the quantity of heat rendered latent 
 when certain solids assume the liquid state and 
 certain liquids assume the state of vapours : the 
 degrees are those of Fahrenheit's thermometer.
 
 PHEXOMEXA OF HEAT. 
 
 259 
 
 TABLE XIX. 
 
 TABLE OF LATENT HEAT.* 
 
 Of Liquids : by Dr. Irvine. 
 
 Of Vapours : by Dr. Ure. 
 
 Water . 
 Sulphur . 
 
 
 140 
 143-7 
 
 Vapour of Water at 212, 1000 
 Alcohol . 457 
 
 Spermaceti 
 
 
 145 
 
 
 Ether . 312-9 
 
 Lead . 
 
 
 162 
 
 
 OilofTurp. 183-8 
 
 Bees'-wax 
 
 
 175 
 
 
 Nitric Acid 550 
 
 Zinc 
 
 
 493 
 
 
 Ammonia 865-9 
 
 Tin 
 
 
 500 
 
 
 Vinegar . 903 
 
 Bismuth 
 
 
 550 
 
 Petroleum 183-8 
 
 (257.) Many important facts arise from the 
 theory of latent heat. One of the most important, 
 in regard to the arts, is the peculiar properties of 
 steam. But without entering at any length into 
 this important and extensive subject, it may be ob- 
 served that experiments have clearly proved that 
 at all temperatures and pressures steam contains 
 exactly the same absolute quantity of heat. For 
 while under increased pressure, steam can be made 
 to exhibit almost any thermometric temperature, 
 the latent heat of high-pressure steam always de- 
 creases exactly in the same ratio as its sensible heat 
 increases, so that its latent and sensible heat to- 
 gether always amount to 1180 above the freezing 
 point of water. Thus a certain weight of steam at 
 212, when condensed into water at 32, gives out 
 
 Sensible Heat 
 Latent Heat 
 
 180 
 1000 
 
 1180 
 
 * Dr. Ure's Dictionary of Chemistry, Art. " Caloric." 
 
 s 2
 
 260 ON THE LAWS AND 
 
 And the same weight at 400, when condensed into 
 water at 32, gives out 
 
 Sensible Heat . . . 368 
 Latent Heat ... 812 
 
 1180 
 
 The same holds good with steam at all other tem- 
 peratures, and extends from 212 to the highest 
 range of steam pressures. 
 
 (258.) The phenomena of spontaneous evapora- 
 tion presents some important facts connected with 
 the subjects of our present inquiry. To Dr. Dalton 
 we owe much of the knowledge which we possess 
 of the laws that govern the vaporization of liquids ; 
 and his numerous experiments on the subject rank 
 among the most valuable contributions to science. 
 Evaporation is distinguished from ebullition by 
 this circumstance: that during the latter pheno- 
 menon, the liquid which is converted into vapour 
 maintains an invariable temperature, provided the 
 pressure upon it does not change ; while, with the 
 former, the temperature is constantly subject to 
 change, the quantity of liquid evaporated being 
 proportional to the temperature and to the surface 
 exposed. Evaporation is wholly independent of 
 the pressure of the air, and is the same in a vacuum, 
 in the natural atmosphere, or in a condensed me- 
 dium : but this is only true as regards the absolute 
 quantity which can exist in a given space, for the 
 air is found greatly to impede evaporation, by its 
 inertia opposing a mechanical obstruction, and 
 thereby retarding the time required for the opera- 
 tion, when such obstruction does exist. In a 
 vacuum, the evaporation is almost instantaneous ; 
 but, in a space containing air, the time required for 
 the evaporation of the maximum quantity of vapour
 
 PHENOMENA OP HEAT. 261 
 
 is longer in proportion to the density of the air, 
 though ultimately the quantity is the same.* 
 
 (259.) The quantity of liquid discharged into 
 free space by spontaneous evaporation is, under 
 these circumstances, much influenced by the mo- 
 tion of the air, which thus carries off the succes- 
 sive strata of vapour that rise from the liquid, a 
 very strong wind causing about twice as much 
 vapour to be discharged as a still atmosphere. 
 Dr. Dalton's experiments enable us to estimate the 
 evaporating force under all circumstances. He 
 ascertained that from a circular vessel of six inches 
 in diameter, kept at the temperature of 212, the 
 quantity of water evaporated was 120 grains per 
 minute in a still atmosphere, 154 grains per minute 
 with gentle motion of the air, and 189 grains per 
 minute with a brisk motion of the air. The tem- 
 perature of the air does not influence the evapora- 
 tion ; and he found that, at any other temperature 
 of the water, the evaporation was exactly pro- 
 portional to the elastic force of the vapour at that 
 temperature. 
 
 The following Table was constructed by Dr. 
 Dalton from his experiments : 
 
 * Professor Daniell made some experiments on this subject, 
 by which he was led to conclude that " the amount of evapo- 
 ration is cceteris paribus in exact inverse proportion to the 
 elasticity of the incumbent air." (Quarterly Journal of Science, 
 vol. xvii., p. 52.) This remark, however, applies only to the 
 rate of evaporation, and not to the quantity which can exist 
 in a given space. Even from ice, the evaporation is very 
 considerable ; and some experiments of M. Schuebler show, 
 that during the very coldest weather, the spontaneous evapo- 
 ration of ice in the open air is sometimes nearly l-40th of 
 an inch in depth from each square foot of surface every 
 twenty-four hours. Quarterly Journal of Science, vol. xxvii., 
 p. 187.
 
 262 
 
 ON THE LAWS AND 
 
 TABLE XX. 
 
 Showing the force of Vapour and the full Evaporating Force 
 for every Temperature, from 20 to 212 Fahrenheit, 
 expressed in grains of water, that would be raised per 
 minute, from a vessel six inches in diameter, supposing 
 there were no vapour already in the atmosphere. 
 
 Temperature. 
 Fahrenheit. 
 
 Force 
 of 
 Vapour. 
 
 Evaporating Force 
 in Grains. 
 
 Temperature. 
 Fahrenheit. 
 
 Force 
 of 
 Vapour. 
 
 Evaporating Force 
 in (trains. 
 
 Still. 
 
 Gentle. 
 
 Brisk. 
 
 Still. 
 
 Gentle. 
 
 Brisk. 
 
 20 
 
 129 
 
 52 
 
 67 
 
 82 
 
 68 
 
 676 
 
 2-70 
 
 3-47 
 
 4-24 
 
 22 
 
 139 
 
 56 
 
 71 
 
 88 
 
 70 
 
 721 
 
 2 88 
 
 3-70 
 
 4-53 
 
 24 
 
 150 
 
 60 
 
 77 
 
 94 
 
 72 
 
 770 
 
 3-08 
 
 3-96 
 
 4-84 
 
 26 
 
 162 
 
 65 
 
 82 
 
 1-02 
 
 74 
 
 823 3-29 
 
 4-23 
 
 5-17 
 
 28 
 
 174 
 
 70 
 
 90 
 
 1-10 
 
 76 
 
 880 3-52 
 
 4-52 
 
 5-53 
 
 30 
 
 186 
 
 74 
 
 95 
 
 17 
 
 78 
 
 940 
 
 3-76 
 
 4-83 
 
 5-91 
 
 32 
 
 200 
 
 80 
 
 1-03 
 
 .26 
 
 80 
 
 1-000 
 
 4-00 
 
 5-14 
 
 6-29 
 
 34 
 
 214 
 
 86 
 
 1-11 
 
 35 
 
 82 
 
 1-07 
 
 4-28 
 
 5-50 
 
 6-73 
 
 36 
 
 229 
 
 92 
 
 1-18 
 
 45 
 
 85 
 
 1-17 
 
 4-68 
 
 6-07 
 
 7-46 
 
 38 
 
 245 
 
 98 
 
 1-26 
 
 54 
 
 90 
 
 1-36 
 
 5-44 
 
 6-98 
 
 8-56 
 
 40 
 
 263 
 
 1-05 
 
 1-35 
 
 65 
 
 95 
 
 1-58 
 
 6-32 
 
 8-11 
 
 9-95 
 
 42 
 
 283 
 
 1-13 
 
 45 
 
 78 
 
 100 
 
 1-86 
 
 7-44 
 
 9-54 
 
 11-71 
 
 44 
 
 305 
 
 1-22 
 
 1-57 
 
 92 
 
 110 
 
 2-53 
 
 10-12 
 
 12-98 
 
 15-93 
 
 46 
 
 327 
 
 1-31 
 
 68 
 
 2-06 
 
 120 
 
 3-33 
 
 13-32 
 
 17-09 
 
 20-97 
 
 48 
 
 351 
 
 1-40 
 
 80 
 
 2-20 
 
 130 
 
 4-34 
 
 17-36 
 
 22-27 
 
 27-34 
 
 50 
 
 375 
 
 1-50 
 
 1-92 
 
 2-36 
 
 140 
 
 5-74 
 
 22-96 29-46 36-16 
 
 52 
 
 401 
 
 1-60 
 
 2-06 
 
 2-51 
 
 150 
 
 7-42 i 29-68 
 
 38-08 
 
 46-74 
 
 54 
 
 429 
 
 1-71 
 
 2-20 
 
 2-69 
 
 160 
 
 9-46 37-84J 48-56 
 
 59-59 
 
 56 
 
 458 
 
 1-83 
 
 2-35 
 
 2-88 
 
 170 
 
 12-13 48-52 
 
 62-26 
 
 76-41 
 
 58 
 
 490 
 
 1-96 
 
 2-52 
 
 3-08 
 
 180 
 
 15-15 ! 60-60 77-77 
 
 95-44 
 
 60 
 
 524 
 
 2-10 
 
 2-70 
 
 3-30 
 
 190 
 
 19-00 
 
 76-00 
 
 97-53119-7 
 
 62 
 
 560 
 
 2-24 
 
 2-88 
 
 3-52 
 
 200 
 
 23-64 
 
 94-56 121 -35 148-9 
 
 64 
 
 597 
 
 2-39 
 
 3-07 
 
 3-76 
 
 210 
 
 28-84 115-36 148-04il81-6 
 
 66 
 
 635 
 
 2-54 
 
 3-27 
 
 3-99 
 
 212 
 
 30- 120' 
 
 |154- 
 
 189- 
 
 In this Table,* the first column gives the tempe- 
 rature of the water; the second, the elastic force 
 of the vapour at that temperature ; and the third, 
 fourth, and fifth columns show the number of 
 grains' weight of water evaporated per minute, 
 from a vessel six inches diameter (or 28*274 square 
 
 * See Dr. Dalton's experiments, Memoirs of the Manchester 
 Philosophical Society, vol. v., p. 579, et seq. The Table given 
 by Dr. Dalton only extends to the temperature of 85 : the 
 temperatures above that are calculated from his data.
 
 PHENOMENA OF HEAT. 263 
 
 inches, equal to '196 of a square foot), when the 
 air is still, or in gentle or in brisk motion re- 
 spectively. 
 
 (260.) In order to know exactly the quantity 
 of vapour that will be evaporated per minute, we 
 must know the quantity which already exists in 
 the atmosphere. For this purpose we must find 
 the dew-point of the air, that is, the temperature 
 at which the vapour in the air just begins to con- 
 dense.* By referring to the Table we shall then 
 find the quantity of vapour in the air at that time ; 
 and this, deducted from the quantity shown by the 
 Table to be given off at the ascertained tempera- 
 ture of the evaporating liquid, will give the exact 
 quantity of water that will be evaporated per 
 minute. Thus, suppose the dew-point of the air 
 to be 48, and the temperature of the air and of 
 the evaporating liquid to be 70, with a still atmo- 
 sphere : the vapour in the air, as shown by the 
 Table, at the temperature of 48, is 1 4 grains ; 
 which, subtracted from that at 70, viz. 2 88 grains, 
 gives 1-48 grains per minute for the quantity ol 
 vapour given off from a surface of six inches 
 diameter. 
 
 It will be observed, that if the temperature of 
 the air be lower than the temperature of the eva- 
 porating fluid, the vapour will again condense; 
 but the rapidity of this condensation will depend 
 upon the relative temperatures, and the quantity of 
 moisture contained in the air. 
 
 * Dr. Dalton used for this purpose a very thin glass vessel, 
 into which he poured cold water, and noted the temperature. 
 If the vapour was instantly condensed, he poured out this 
 water and applied some a little warmer, and so on, until he 
 obtained the proper temperature at which he could just 
 perceive a slight dew deposited on the glass. This tem- 
 perature then was the dew-point. Daniell's Hygrometer is 
 a much more elegant instrument, hut more difficult to 
 manage. See Daniell's " Chemistry," art. " Hygrometer."
 
 264 ON THE LAWS AND 
 
 (261.) The heat and cold caused by the con- 
 densation and rarefaction of the air produce 
 important effects, both in natural phenomena, and 
 in the mechanical application of this agent in the 
 arts. When the air is partially exhausted in a 
 receiver enclosing a thermometer, the temperature 
 sinks considerably ; but if the air be again suddenly 
 admitted to the original pressure, the temperature 
 rises considerably higher than in the first instance. 
 The reverse of this occurs when the air is first 
 condensed, and then allowed to resume the original 
 pressure ; in which case the temperature sinks 
 considerably lower on the original pressure being 
 restored, than the thermometer indicated before the 
 condensation.* 
 
 This result, however, appears to be produced 
 by an unavoidable imperfection in the experiment. 
 For the vessel that contains the air communicates 
 its heat in the one case, and abstracts it in the 
 other, which causes the apparent difference; and 
 this difference is therefore dependent upon the 
 rapidity' of the operation, thereby allowing more 
 or less time for the interchange of heat between 
 the air and the vessel containing it. 
 
 In Dr. Dalton's experiments,! the thermometer 
 which sank 2 on rarefying the air rose 4 on again 
 allowing it suddenly to resume its original pressure. 
 When the air was first condensed and then sud- 
 denly allowed to resume its original pressure, the 
 thermometer rose 2 on the condensation, and then 
 sank 3^ on diminishing the pressure suddenly to 
 its original amount. These inequalities, however, 
 although an accompaniment of the experiment, 
 are not due to the mechanical expansion or con- 
 densation of the air; and the results will vary 
 
 * Manchester Memoirs, vol. v., p. 515; and Nicholson's 
 Journal, vol. iii., p. 160. 
 Ibid.
 
 PHENOMENA OF HEAT. 
 
 265 
 
 with every alteration in the condition of the 
 containing vessel, and of the quantity of air. 
 
 (262.) Professor Leslie investigated this subject, 
 both experimentally and theoretically, and he 
 found that the quantity of heat evolved under 
 these circumstances was very great; but as the 
 specific heat of air increases as its density di- 
 minishes, only a small portion of the heat thus 
 produced becomes appreciable. When air of the 
 following densities is restored to its original pres- 
 sure, represented by 1, the heat evolved is as 
 follows : 
 
 TABLE XXI. 
 
 Density of the 
 Air. 
 
 Heat Evolved 
 (Fahrenheit). 
 
 Density of the 
 Air. 
 
 Heat Evolved 
 (Fahrenheit). 
 
 1-0 
 
 
 
 0-4 
 
 94-5 
 
 0-8 
 
 20-6 
 
 0-2 
 
 216- 
 
 0-6 
 
 48- 
 
 0-0003 
 
 13500- 
 
 This evolution of heat he considered to be owing 
 to the diminution of the specific heat of the air by 
 condensation. When air was condensed so as to 
 double its density, the mathematical formula 
 which he constructed from his experiments showed 
 that the sensible heat which would be evolved 
 would be equal to 67*5 Fahrenheit.* 
 
 (263.) Mr. Ivory also investigated the mathe- 
 matical law of the heat produced under these 
 circumstances ; f and he found " that the heat 
 extricated from air, when it undergoes a given 
 condensation, is equal to three-eighths of the 
 diminution of temperature required to produce the 
 
 * Dr. Thomson " On Heat and Electricity," p. 126, et seq. 
 f Philosophical Magazine (Second Series), vol. i., p. 89 ; and 
 Quarterly Journal of Science, vol. xxiii., p. 228.
 
 266 ON THE LAWS AND 
 
 same condensation, the pressure being constant." 
 Air, under a constant pressure, diminishes l-480th 
 of its volume for every degree of depression of 
 Fahrenheit's scale ; and therefore 1 of heat will be 
 extricated from air when it undergoes a condensa- 
 tion equal to ^-^ x f- = y^. If a mass of air were 
 suddenly reduced to half its bulk, the heat evolved 
 would be ^ ~ -j-^-0 = 90.* M. Despretz made some 
 experiments to ascertain whether water evolved heat 
 when subjected to great pressure ; and he found that 
 a compressive force equal to 20 atmospheres caused 
 the disengagement of only one sixty-sixth part of 
 a degree of heat.f This result might reasonably 
 be expected from the small degree of compression 
 to which water can be subjected. 
 
 (264.) Dr. Ure instituted some experiments to 
 ascertain the influence which heat had in increas- 
 ing the fluency of various liquids; and he found 
 in all cases a great increase in the velocity of 
 their efflux through a given aperture, by raising 
 their temperature. In some liquids of a viscid 
 nature, the increase appears to be very great. 
 Such, for instance, is the case with some kinds of 
 oil, which, by raising the temperature from 65 
 to 254, had the velocity of efflux increased 
 nearly six times. With those which were less 
 viscid, the increase was less. Water, by having 
 its temperature raised from 60 to 164, had its 
 velocity increased about one-sixth.! These re- 
 sults are wholly independent of any effect from 
 alterations of pressure, but appear to arise from 
 the particles of the fluids possessing less adhe- 
 siveness among themselves by the increased tem- 
 perature. 
 
 * Ibid. 
 
 | Quarterly Journal of Science, vol. xxiv., p. 20. 
 t Reports of the British Scientific Association, vol. viii., p. 23. 
 (See also Art. 251.)
 
 PHENOMENA OF HEAT. 267 
 
 (265.) The effects of heat in producing varia- 
 tions in the strength of materials is a subject 
 which has received but little attention ; and with 
 the exception of some experiments made by the 
 Franklin Institute of Pennsylvania, on the strength 
 of iron and copper, little appears to be known. 
 By these experiments * the maximum strength of 
 wrought iron, estimated by its resistance to a 
 longitudinal strain, was obtained by heating the 
 iron to 572 Fahrenheit; at which temperature 
 the strength is 15 -17 per cent, greater than at the 
 ordinary- mean temperature of the air. The rule 
 deduced for the strength of iron at high tempera- 
 tures is, that " the thirteenth power of the tem- 
 perature above 80 Fahrenheit is proportionate to 
 the fifth power of the diminution from the maxi- 
 mum tenacity." And it appears that, at the tem- 
 perature of about 1050, iron loses about one-half 
 of its maximum strength ; at 1 240 it loses about 
 two-thirds; and at 1317 seven-tenths of its maxi- 
 mum tenacity is overcome. 
 
 The following Table shows the diminution of 
 tenacity at various temperatures. The maximum 
 tenacity of the fourth column is a calculated 
 amount, obtained by adding 15 '17 per cent, to 
 the strength of the metal when tried cold. The 
 seventh column shows that the mean irregularity 
 of structure is 10 per cent, of the strength when 
 tried cold. 
 
 * " Report on the Explosion of Steam Boilers, by a Com- 
 mittee of the Institute ; " Journal of the Franklin Institute, 
 vols. xix. and xx.
 
 268 
 
 ON THE LAWS AND 
 
 TABLE XXII. 
 
 .1 
 
 1 
 
 
 
 to 
 
 B 
 
 
 
 il 
 
 i 
 
 II 
 If* 
 
 +"3 
 
 II 
 
 11 
 
 1 t 
 1J 
 
 Si! 
 
 rt 
 a 
 
 s 
 
 |l 
 
 s 
 
 If 
 
 II 
 
 it| 
 
 |.s| 
 
 
 H 
 
 H 
 
 
 i 
 
 1 1 
 
 Ijt 
 
 1 
 
 520 
 
 58451 
 
 63267 
 
 experiment 
 
 0761 
 
 0992 
 
 2 
 
 570 
 
 60398 
 
 66146 
 
 
 
 0869 
 
 1125 
 
 3 
 
 596 
 
 57682 
 
 63386 
 
 calculation 
 
 0899 
 
 2401 
 
 4 
 
 600 
 
 56938 
 
 63086 
 
 
 
 0964 
 
 2401 
 
 5 
 
 630 
 
 60010 
 
 67033 
 
 experiment 
 
 1047 
 
 1440 
 
 6 
 
 662 
 
 58182 
 
 65785 
 
 
 
 1155 
 
 0644 
 
 7 
 
 722 
 
 54442 
 
 64483 
 
 calculation 
 
 1436 
 
 0507 
 
 8 
 
 732 
 
 53378 
 
 62736 
 
 experiment 
 
 1491 
 
 1310 
 
 9 
 
 734 
 
 57903 
 
 68407 
 
 calculation 
 
 1535 
 
 0644 
 
 10 
 
 766 
 
 54819 
 
 65176 
 
 experiment 
 
 1589 
 
 1563 
 
 11 
 
 770 
 
 54781 
 
 65445 
 
 calculation 
 
 1627 
 
 0234 
 
 12 
 
 824 
 
 55892 
 
 70080 
 
 
 
 2010 
 
 0413 
 
 13 
 
 932 
 
 45531 
 
 68202 
 
 
 
 3324 
 
 0413 
 
 14 
 
 947 
 
 42401 
 
 66193 
 
 experiment 
 
 3593 
 
 0446 
 
 15 
 
 1030 
 
 37587 
 
 68071 
 
 calculation 
 
 4478 
 
 0460 
 
 16 
 
 1111 
 
 27603 
 
 61531 
 
 
 
 5514 
 
 0330 
 
 17 
 
 1155 
 
 21967 
 
 54992 
 
 
 
 6000 
 
 0330 
 
 18 
 
 1159 
 
 25620 
 
 64234 
 
 
 
 6011 
 
 1102 
 
 19 
 
 1187 
 
 21913 
 
 60102 
 
 
 
 6352 
 
 0330 
 
 20 
 
 1237 
 
 21298 
 
 63065 
 
 
 
 6622 
 
 1147 
 
 21 
 
 1245 
 
 20703 
 
 63065 
 
 
 
 6715 
 
 0347 
 
 22 
 
 1317 
 
 18913 
 
 63065 
 
 
 
 7001 
 
 1147
 
 PHENOMENA OF HEAT. 
 
 269 
 
 (266.) In the experiments made with copper, at 
 various temperatures, the Committee found that 
 unlike iron, the maximum strength of copper was 
 at a very low temperature , and that it increased 
 in strength at every reduction of temperature 
 down to 32, which was the lowest at which they 
 could try it. The mean strength of copper at 
 ordinary temperatures was found to be 32,146 Ibs. 
 per square inch ; and the following Table exhibits 
 the diminution of strength at high temperatures. 
 To obtain the actual temperature of each .experi- 
 ment, 32 must be added to the temperatures 
 given in the second column. 
 
 TABLE XXIII. 
 
 Number of the 
 Experiment. 
 
 Temperature above 32 
 Fahrenheit. 
 
 Diminution from the 
 Strength at 32. 
 
 1 
 
 90 
 
 0175 
 
 2 
 
 180 
 
 0540 
 
 3 
 
 270 
 
 0926 
 
 4 
 
 360 
 
 1513 
 
 5 
 
 450 
 
 2046 
 
 6 
 
 460 
 
 2133 
 
 7 
 
 513 
 
 2446 
 
 8 
 
 529 
 
 2558 
 
 9 
 
 660 
 
 3425 
 
 10 
 
 769 
 
 4398 
 
 11 
 
 812 
 
 4944 
 
 12 
 
 880 
 
 5581 
 
 13 
 
 984 
 
 6691 
 
 14 
 
 1000 
 
 6741 
 
 (267.) The strength of cast iron at high tempe- 
 ratures has not been ascertained with the same 
 accuracy. It has, however, been estimated that its 
 maximum strength is at the temperature of about 
 300 Fahrenheit, which is considerably below that 
 of wrought iron.
 
 270 ON THE LAWS AND PHENOMENA OF HEAT. 
 
 (268.) The effects of heat, which have here 
 been mentioned, are a few of the laws and pheno- 
 mena of this important branch of science. They 
 appear to be those which are most closely connected 
 with the subject of the present inquiry : but it must 
 not be supposed that they are given as an epitome 
 of the general laws of heat, as the subject would 
 be far too extensive for the present work. Many 
 most important and interesting phenomena have 
 therefore been entirely omitted ; but those which 
 are here mentioned, and others that are alluded to 
 and interspersed in various parts of this treatise, 
 appear to be all that are requisite for the illustration 
 of the subject now before us, and will afford useful 
 suggestions to those who wish to investigate the 
 principles of heating buildings theoretically and 
 scientifically, as well as to learn the mere practical 
 details.
 
 271 
 
 CHAPTER XIII. 
 
 EXPERIMENTS ON COOLING. 
 
 (269.) FROM what has been stated in the pre- 
 ceding chapter, it is evident that the velocity 
 with which a heated bod} r cools depends upon 
 various circumstances ; and experiments are ne- 
 cessary, in order to obtain data for the calcula- 
 tions which the known laws of heat enable us 
 afterwards to apply to the subject now under 
 investigation. 
 
 No experiments on cooling are extant, that 
 appear to be suitable to the present purpose, 
 except some that were made by Tredgold,* and 
 these are erroneous in the application he has 
 made of them. For he has neglected all con- 
 siderations of the thickness of the body on which 
 he experimented, and has therefore estimated 
 that the rate of cooling of a very thin sheet-iron 
 vessel, containing a heated fluid, is the same only 
 as a cast-iron pipe, though the latter is fully six 
 or eight times the thickness of the former. The 
 same error also occurs in his experiments on the 
 cooling of glass; and, consequently, his conclu- 
 sions on the dispersion of heat, as applied to the 
 warming of buildings, are erroneous to a con- 
 siderable extent. Another source of error lies in 
 his having estimated the quantity of water which 
 
 * Tredgold " On Heating Buildings by Steam," &c.
 
 272 EXPERIMENTS ON COOLING. 
 
 the vessel contained at rather too large an amount, 
 in allowing for the specific heat of the vessel; 
 which latter could not possibly have had quite the 
 same temperature as the water, owing to loss by 
 imperfect conduction, and to the cooling influence 
 to which it was exposed. The effect of each of 
 these errors is to make the rate of dispersion appear 
 more rapid than the true velocity ; and the result 
 is, that in some of the calculations founded on these 
 experiments the errors amount to upwards of 16 
 per cent. 
 
 (270.) To ascertain the velocity of cooling for a 
 surface of cast iron, a pipe thirty inches long, two 
 inches and a half diameter internally, and three 
 inches diameter externally, was used in the follow- 
 ing experiments. The ends of the pipe were closed 
 by corks which entered into the pipe one inch and 
 a half at each end ; and the bulb of a thermometer 
 was inserted into the water about three inches from 
 one end, the temperature of the water being the 
 same in every part of the pipe. The exposed sur- 
 face of the pipe (including the surface exposed by 
 the thickness of the metal at the ends) was 287*177 
 square inches. The quantity of water contained in 
 it was 132-534 cubic inches ; and the equivalent to 
 be added to this for the specific heat of the pipe is 
 39-341 cubic inches ; making the estimated quan- 
 tity of water 171 875 cubic inches.* The rates of 
 cooling were tried with different states of the sur- 
 face : first, when it was in the usual state of cast-iron 
 pipes covered with the brown surface of protoxide 
 of iron ; next, it was varnished black ; and finally, 
 
 * In estimating the equivalent of water which was required 
 to represent the specific heat of the pipe, the difference be- 
 tween the external and internal temperatures necessarily re- 
 quired an allowance to be made on account of the thickness of 
 the pipe being considerable. This diminution of specific heat 
 was estimated to be equal to a superficies of the pipe one-
 
 EXPERIMENTS OX COOLIXG. 
 
 273 
 
 the varnish was scraped off, and the pipe was 
 painted white with two coats of lead paint. The 
 following Table shows the observed time of cooling, 
 corrected and reduced to the same excess of tem- 
 perature above the circumambient air. 
 
 TABLE XXIV. 
 
 TABLE OF THE COOLING OF IEON. 
 
 Temperature of Room, 67. Maximum Temperature of 
 Thermometer, 152. 
 
 Thermometer 
 Cooled. 
 
 Rusty Surface. 
 
 Black Varnished 
 Surface. 
 
 White Surface. 
 
 from 
 
 to 
 
 Observed 
 Time. 
 
 Calcu- 
 lated 
 Time. 
 
 Observed 
 lime. 
 
 Calcu- 
 lated 
 Time. 
 
 Observed 
 Time. 
 
 Calcu- 
 lated 
 Time. 
 
 152 
 
 150 
 
 2' 30" 
 
 2' 21" 
 
 2' 16" 
 
 2' 16" 
 
 2' 19" 
 
 2' 24" 
 
 152 
 
 148 
 
 5 
 
 4 44 
 
 4 38 
 
 4 36 
 
 4 53 
 
 4 51 
 
 152 
 
 146 
 
 7 45 
 
 7 12 
 
 7 28 
 
 7 3 
 
 7 28 
 
 7 22 
 
 152 
 
 144 
 
 10 15 
 
 9 44 
 
 9 45 
 
 9 27 
 
 10 13 
 
 9 57 
 
 152 
 
 142 
 
 12 45 
 
 12 15 
 
 12 2 
 
 11 54 
 
 12 57 
 
 12 36 
 
 152 
 
 140 
 
 15 
 
 15 
 
 14 32 
 
 14 32 
 
 15 22 
 
 15 22 
 
 Minutes. 
 
 The ratios of ( Black Varnished Surface . . .1-21 
 
 Cooling 1 are I Iron Surface 1-25 
 
 therefore, ( White Tainted Surface . . .1-28* 
 
 These ratios are in the proportion of 100, 103 '3, 
 and 105' 7; but as the relative heating effect is 
 the inverse of the time of cooling, we shall find 
 that 100 feet of varnished pipe, 103^ feet of plain 
 
 sixteenth of an inch thick. The total equivalent of water 
 which would represent the specific heat of the pipe, supposing 
 it to be exactly of the same temperature as the water con- 
 tained in it, would be 52-455 cubic inches; from this must be 
 deducted 13-114 cubic inches as above stated, leaving the 
 equivalent specific heat of the pipe equal to 39*341 cubic 
 inches of water, as stated in the text. 
 
 * These ratios of cooling, it will be observed, are for pipes 
 of three inches in diameter ; but the cooling of any other size 
 can be calculated from the data here given. 
 
 T
 
 274 
 
 EXPERIMENTS ON COOLING. 
 
 iron pipe, or 105| feet of iron pipe painted white, 
 will each produce an equal effect. 
 
 In these experiments, it might have been ex- 
 pected to find greater differences between the effects 
 of the various states of the surface, than appears 
 really to obtain. The greatest difference only 
 amounts to about 5f per cent., but it would pro- 
 bably be greater in proportion, with an increased 
 thickness of the coating of paint. 
 
 (271.) To ascertain the effect of glass windows 
 in cooling the air of a room, the following experi- 
 ments were made, with a vessel as nearly as possible 
 of the same thickness as ordinary window-glass. 
 The temperature of the room, in these experiments, 
 was 65; the thickness of the glass was *0825 of 
 an inch; the surface of the vessel measured 34*296 
 square inches, and it contained 9 -794 cubic inches 
 of water, including the equivalent for the specific 
 heat of the glass. The time in which this vessel 
 cooled, when filled with hot water, is shown as 
 follows : 
 
 TABLE XXV. 
 
 TABLE OF THE COOLING OF GLASS. 
 
 Thermometer Cooled 
 
 Observed 
 Time 
 of Cooling. 
 
 Calculated 
 Time 
 of Cooling. 
 
 Average Bate 
 of the 
 Observed Time 
 of Cooling. 
 
 from 
 
 to 
 
 150 
 150 
 150 
 150 
 
 140 
 130 
 120 
 110 
 
 6' 40" 
 14 15 
 23 30 
 34 
 
 6' 54" 
 14 43 
 23 40 
 34 
 
 f 1-176 per 
 minute, at an 
 j excess of 65 
 1 above the 
 Temperature 
 of the air. 
 
 From the average rate of cooling which is here 
 given, the effect of glass in cooling the air of a room 
 may easily be calculated. As the specific heat of
 
 EXPERIMENTS OX COOLIXG. 275 
 
 equal volumes of air and water* is as one to 2990 
 the above average will show that each square foot 
 of glass will cool 1 ' 279 cubic feet of air 1 per 
 minute, when the temperature of the glass is 1 
 above that of the external air. 
 
 But by this we shall only find the effect of glass 
 in a still atmosphere ; and therefore, to ascertain 
 the cooling effect of external windows, when ex- 
 posed to the action of winds, further experiments 
 are necessary .f 
 
 (272.) In some researches of Leslie's, on the 
 cooling power of wind, he used a bright metallic 
 ball filled with hot water, and noted the time of 
 cooling when it was exposed to wind at different 
 velocities. The result he obtained was, that the 
 cooling effect on the ball was very nearly in a 
 direct ratio with the velocity. But it will be 
 obvious, by referring to the experiments of Petit 
 and Dulong, in the preceding chapter, that the 
 relative cooling of heated bodies, when exposed to 
 air moving at different velocities, must depend 
 upon the nature of the surfaces. For, while the 
 quantity of heat which is abducted by the air is 
 proportional to the number of particles of air 
 which pass over the heated body in a given time, 
 the heat that is lost by radiation is not only inde- 
 pendent of this effect, but the relative proportion 
 
 * See Art. 97. 
 
 f In some experiments by Wyman, on the cooling influence 
 of glass windows, he obtained the following results, in a room 
 of 1930 cubic feet, and having 531 square feet of walls, and 
 33-21 square feet of windows. The room was allowed to cool 
 about 10, first with the windows uncovered, and then with 
 the windows covered with double blankets. The average of 
 the experiments gave 
 
 Room cooled 0-150 per minute, with windows uncovered ; 
 
 0'106 per minute, with windows covered ; 
 or 1 in 6-6 minutes, with windows uncovered, and 1 in 9 4 
 minutes with the windows covered. Wyman " On Ventila- 
 tion." Boston, 1846. 
 
 T 2
 
 276 EXPERIMENTS ON COOLING. 
 
 of heat lost by radiation differs for each particular 
 substance. As the bright metal ball that Leslie 
 employed in his experiments would lose only an 
 extremely small proportion of its heat by radia- 
 tion, it might naturally be concluded that the 
 rate of cooling would be nearly in a direct ratio 
 with the velocity of the air. But with a surface 
 of glass, the result must be very different, because 
 the radiation is then very considerable ; and, 
 therefore, the total cooling will be much slower 
 than the simple ratio of the velocity. For while 
 a surface of glass of the temperature of 120, and 
 at an excess of 52 above the surrounding medium, 
 loses about two-thirds of its heat by radiation, a 
 bright metallic surface of the same temperature 
 will only lose one-eleventh part of its heat by the 
 same cause. 
 
 (273.) In the following experiments it appears 
 that the cooling effect of wind, at different veloci- 
 ties, on a thin surface of glass, is very nearly as the 
 square root of the velocity. In these experiments, 
 the velocity of the air was measured by the revolu- 
 tion of the vanes of a fan ; the temperature of the 
 air was 68 ; the time required to cool the ther- 
 mometer 20 was noted for every different velocity, 
 and the maximum temperature of the thermometer, 
 in each experiment, was 120. In still air it 
 required 5' 45" to cool the thermometer this extent 
 of 20 degrees ; and the annexed Table shows the 
 time of cooling by air in motion.
 
 EXPERIMENTS ON COOLING. 
 
 277 
 
 TABLE XXVI. 
 
 TABLE OF THE COOLING OF GLASS BY WIND. 
 
 
 Times of Cooling the Thermometer 20, 
 from 120 to 100 of Fahrenheit 
 
 Velocity 
 of the Wind, 
 in Miles, 
 per Hour. 
 
 Observed 
 Time 
 of Cooling. 
 
 Time 
 reduced to 
 Decimals of 
 a Minute. 
 
 Calculated Time ; being 
 the Inverse of the 
 Square Root of the 
 Velocities; in Decimals 
 of a Minute. 
 
 3-26 
 
 2' 35" 
 
 2-58 
 
 2-58 
 
 5-18 
 
 2 10 
 
 2-16 
 
 2-04 
 
 6-54 
 
 1 55 
 
 1-91 
 
 1-82 
 
 8-86 
 
 1 40 
 
 1-66 
 
 1-56 
 
 10-90 
 
 1 30 
 
 1-50 
 
 1-41 
 
 13-36 
 
 1 15 
 
 1-25 
 
 1-27 
 
 17-97 
 
 1 5 
 
 1-08 
 
 1-10 
 
 20-45 
 
 1 
 
 1-0 
 
 1-03 
 
 24-64 
 
 55 
 
 91 
 
 94 
 
 27-27 
 
 48 
 
 81 
 
 88 
 
 (274.) In consequence of the large quantity of 
 glass in buildings used for horticultural purposes, 
 the cooling effect of wind is of considerable im- 
 portance. We see, however, that with an in- 
 creased velocity the cooling effect is considerably 
 less, in proportion, on glass than on metal. And 
 it will be very much less on window-glass than 
 even what is here stated: for, as glass is an ex- 
 tremely bad conductor of heat, the increased thick- 
 ness which window-glass possesses over that which 
 composes the bulb of a thermometer, will make 
 a material difference in the quantity of heat that 
 is lost by the abduction of the air, as there will 
 be, in this case, a greater difference between the 
 temperature of the external and the internal sur- 
 face. The cooling effect of wind is therefore not 
 near so considerable on glass as is generally sup- 
 posed ; and it will probably be nearly one-half 
 less on window-glass than what is shown by the
 
 278 
 
 EXPERIMENTS OX COOLING. 
 
 preceding experiments. Exact experiments on 
 this subject, however, are extremely difficult, 
 owing to the unequal action of the air on different 
 parts of the surface. Thus, if a cylindrical or 
 spherical vessel be employed, the action of the 
 wind will be such that the particles of air striking 
 the surface in front will cause a vacuum at the 
 back part of the vessel, from which latter part the 
 heat will be given off by radiation alone. It thus 
 becomes impossible to ascertain accurately what 
 would be the effect, if the whole of the surface 
 could be acted upon by the wind; and the same 
 remark will apply to most other forms of surface 
 which could be employed experimentally. 
 
 (275.) The following Table shows the results of 
 Tredgold's experiments on cooling, already referred 
 to. They are here given, principally, to show the 
 cooling power which thin sheet-iron will have in 
 any building in which it is used ; and they may 
 therefore be useful now that corrugated iron is so 
 frequently employed in many descriptions of build- 
 ings. In these experiments the specific heat of the 
 vessels was added to the quantity of water they con- 
 tained. The vessels were always cooled from 1 80 
 down to 150 of Fahrenheit ; the time required for 
 this cooling, and the other particulars of the experi- 
 ments, being noted in the Table. 
 
 TABLE XXVII. 
 
 Nature of Surface. 
 
 si 
 p 
 
 Equivalent Quantity 
 of Water. 
 Cubic Inches. 
 
 1 
 
 lit 
 
 Time of Cooling. 
 Minutes. 
 
 Average Excess of 
 Temperature 
 (Fahrenheit). 
 
 Loss of Heat per 
 Minute 
 (Fahrenheit). 
 
 Tinned plate . 
 Sheet Iron 
 Glass . . . 
 
 79 
 76-7 
 71 
 
 62-28 
 61-7 
 61-2 
 
 55 
 57 
 561 
 
 - 
 
 46 
 29 
 81* 
 
 124| 
 123 
 123^ 
 
 759 
 1-18 
 1-075
 
 EXPERIMENTS OX COOLING. 279 
 
 In these experiments, as already stated, the cool- 
 ing of the sheet-iron will not afford a fair criterion 
 for the effect of cast-iron pipes ; but it will be per- 
 ceived that thin sheet-iron has, in a still atmosphere, 
 the same cooling power as glass ; and therefore its 
 effect in cooling the air of any building in which it 
 is used will be very great, and in high winds it will 
 produce a far greater cooling power than the same 
 extent of glass (Art, 272), as its cooling power will 
 be nearly in the direct ratio of the velocity of the 
 wind. 
 
 These remarks on the cooling power of different 
 substances when employed in buildings must of 
 course be understood merely to apply to those cases 
 in which the interior temperature of the building 
 is higher than that of the external temperature. 
 Under other circumstances these experiments would 
 not be applicable.
 
 281 
 
 PART SECOND. 
 
 ON THE VAKIOUS METHODS OF WARMING AND 
 
 VENTILATING BUILDINGS. 
 THE COMBUSTION OF FUEL, ETC. 
 
 CHAPTER I. 
 
 Early Methods of Warming Buildings The Romans : their 
 Stoves Baths Flues Mode of Preparing their Firewood 
 the Persian Method Chinese Method of Flues Method 
 of the Ancient Britons Invention of Chimneys Burning 
 of Coals in England Early Writers on the subject 
 Improvements in the Form and Construction of Stoves and 
 Fire places.* 
 
 (276.) THE various methods of warming build- 
 ings have consisted, in all countries and in all ages, 
 until a very recent period, of the rudest appliances 
 and the most inartificial inventions. At a very 
 early period, it is true, the Romans were acquainted 
 with the method of heating rooms and buildings 
 by flues; and these were elaborate in their con- 
 struction, and complicated in their arrangements. 
 
 * In this and the following chapters, the articles on 
 "Stoves" and "Ventilation," written by the author, and 
 published in the " Encyclopaedia Metropolitana," have been 
 incorporated with such further observations as the want of 
 space prevented him from making in the work in question.
 
 282 ANCIENT METHODS OF 
 
 But they were so expensive in their construction, 
 and so wasteful in their expenditure of fuel, that 
 this method of warming buildings could only be 
 adopted by very few of even that rich and luxu- 
 rious nation. The comparatively late invention of 
 chimneys fully accounts for the immense size and 
 peculiar construction of the flues used by the 
 ancients; for unless a large space were provided 
 for the combustion of the fuel and the entrance of 
 the air, the heat could not have been conducted 
 through the flues, owing to the absence of the 
 necessary draught produced by the use of a high 
 chimney. The hypocaustum of the Romans was 
 this plan of flues. It appears to have consisted of 
 a long furnace ; and a number of narrow arches 
 (testudines alvei) received the fire of the hypocaus- 
 tum, and conducted it along and underneath the 
 floor of the room to be warmed.* The whole 
 of the hypocaustum was immediately below the 
 room which was to be heated. Sometimes a great 
 number of short columns or pillars supported the 
 floor instead of these arches. They were set in four 
 rows very close together, and the flame of the furnace 
 passed between them, as appears by some very per- 
 fect specimens which have been discovered.! Pliny 
 the younger, in his letter to Glallus, giving the 
 description of his villa Laurentinum, mentions 
 that his bedchamber was warmed by a small 
 hypocaustum : J and this plan was generally 
 adopted in heating the baths. For this latter 
 purpose, however, an improved method was 
 adopted when the Thermas of Rome were built, 
 
 * Castell's "Illustrations of the Villas of the Ancients," 
 pp. 8, 9. 
 
 t Philosophical Transactions, vol. xxv., p. 2225, and vol. xli., 
 p. 855. 
 
 J Castell's " Illustrations," p. 13. 
 
 Ibid., p. 9.
 
 HEATING- BUILDINGS. 283 
 
 and which has been described by Seneca.* The 
 water of the bath was heated by passing it through 
 the fire in a brass pipe of a serpentine form, thence 
 called Draco. The most approved mode was to 
 employ the Miliariumfi which appears to have been 
 a leaden vessel of large circumference, the middle 
 part being open for the spiral pipe, and for the 
 draught of the fire to pass through. This vessel 
 of water that surrounded the flame was also placed 
 upon part of the same fire, and for that reason the 
 bottom was obliged to be made of brass, as were 
 also the pipes. 
 
 (277.) But the method of warming by the 
 hypocaustum was far too expensive for general use. 
 The Romans used portable furnaces, containing 
 embers and burning coals, to warm the different 
 apartments of their houses, which were placed in 
 the middle of the room.j: These were sometimes 
 made to contain water, which was heated by the 
 fuel of the furnace, and probably they were also 
 used for cooking. One of these boilers and furnaces, 
 found at Herculaneum, was in the shape of a castle 
 with four towers. The usual kind of stoves, 
 however, were nearly on the plan of our braziers. 
 They were mostly elegant bronze tripods, sup- 
 ported by satyrs and sphinxes, with a round 
 dish above for the fire, and a small vase below to 
 hold perfumes, which were thrown into the brazier 
 to correct the smell of the coals. A square stove 
 of bronze, of the size of a moderate table, found 
 at Herculaneum, rested on lions' paws, and was 
 ornamented upon the border with foliage. The 
 bottom was a strong iron grating, walled up with 
 bricks above and below, so that the fire could not 
 
 * " Seneca, Nat. Qusest.," lib. 3, cap. 24. 
 
 t " Palladius," lib. i., tit. 40. 
 
 J Adams's " Eoman Antiquities," p. 454. 
 
 Fosbroke's " Archaeology," 4to, vol. i., p. 233.
 
 284 ANCIENT METHODS OF 
 
 touch the sides of the stove, nor fall through the 
 bottom. It was similar to those still used in large 
 rooms in Italy.* But the smoke from these stoves 
 was so considerable, that the furniture of the 
 winter rooms was different from the summer rooms ; 
 and Yitruvius expressly states that these winter 
 apartments had plain cornices, and were without 
 carved work or mouldings, in order to allow the 
 soot to be easily and frequently cleaned away.f 
 At great entertainments it was usual to have 
 watchmen stationed to be ready to extinguish any 
 fire which might happen ; the smoke issuing from 
 the kitchen windows being so great on these 
 occasions, that it was common to speak of this 
 great smoke as synonymous with a great enter- 
 tainment.;]: The utmost care, however, was taken 
 to prevent the smoke as much as possible, and to 
 procure wood which gave the smallest quantity of 
 smoke in combustion. A great deal of the firewood 
 used by the Romans was procured from Africa. 
 The bark of the wood was peeled off; the wood 
 was then suffered to lie a long time in water, and 
 afterwards dried and anointed with the lees of oil, 
 which was considered the most effectual way to 
 prevent it from smoking. || 
 
 (278.) In the time of Seneca (A.D. 64), another 
 method of heating buildings was adopted ; which 
 consisted of pipes built in the walls, that conveyed 
 the heat from a furnace, constructed in the earth 
 under the edifice. These pipes or flues were con- 
 ducted to the different rooms; and the upper end 
 was often ornamented with the representation of 
 
 * Fosbroke's " Archaeology," vol. i., p. 237. 
 
 f " Vitruvius," lib. vii., cap. 5. Beckmann's " History of 
 Inventions," vol. ii., p. 74. 
 
 J " Beckmann," vol. ii., p. 71. 
 
 Ibid, vol. ii., p. 300. 
 
 || Adams's " Koman Antiquities," p. 454. " Beckmann," 
 vol. ii., p. 79.
 
 HEATING BUILDINGS. 285 
 
 a lion's or a dolphin's head, or any other figure, 
 and it could be opened or shut at pleasure. These 
 pipes, however, were liable to become full of soot ; 
 and as they were very likely to catch fire by being 
 over-heated, laws were made forbidding them to 
 be brought too near to the wall of a neighbouring 
 house* 
 
 (279.) The Persians used a stove consisting of 
 an iron vessel sunk in the earth in the centre of 
 the apartment. After a fire had been kindled, and 
 had well warmed the place, a wooden top, like a 
 small low table, was placed over the hole in the 
 floor which contained the stove, and this top was 
 then spread with a large coverlet quilted with 
 cotton, which hung down on all sides to the floor. 
 Those people who were not very cold, only put 
 their feet under the table or covering; but those 
 who required more heat put their hands under it 
 also, or crept under it altogether.! The Jews 
 likewise used such stoves in their houses, and the 
 priests had them also in the Tern pie :J in fact, 
 throughout the East this mode of warming apart- 
 ments appears to have been commonly adopted. 
 
 (280.) In China, a very elaborate system of flues 
 has been long in use, b} T which the floors of the 
 rooms are heated by a furnace constructed below, 
 with a moderate expenditure of fuel. A very 
 equable te;nperature appears to be maintained by 
 these means, notwithstanding the winter tempera- 
 ture of some parts of China is so low that the 
 thermometer nearly reaches the zero of Fahrenheit's 
 scale. Father G-ramont described this mode of 
 heating in 1771, but the date of its introduction 
 does not appear to be known. 
 
 (281.) Although the Romans must have intro- 
 
 * " Beckmann," vol. ii., p. 90. 
 
 t Ibid., vol. ii., p. 83. J Ibid, vol. ii., p. 85. 
 
 Philosophical Transactions, 1771, p. 61.
 
 286 INVENTION OF CHIMNEYS. 
 
 duced their methods of warming buildings into 
 England at a very early period, as appears by 
 various remains which have been excavated in 
 recent times,* the inhabitants of Britain long 
 contented themselves with contrivances of the 
 rudest and simplest character. Among the ancient 
 Britons, in each dwelling there was only one place 
 for a fire, which was merely a hole in the centre 
 of the floor. In the time of the Anglo-Saxons, 
 the ordinary plan was to place the ignited fuel on 
 the hearth in the middle of the floor, and an 
 opening in the roof, immediately above the hearth, 
 permitted the escape of the smoke. In the better 
 class of buildings, an ornamented turret was 
 erected in the centre of the roof for carrying off 
 the smoke, while in ordinary houses, the opening 
 in the roof was merely defended from the weather 
 by louvre boards, in the manner now practised in 
 many of our commonest buildings used for manu- 
 factories. 
 
 (282.) The invention of chimneys necessarily 
 made a great alteration in the mode of heating 
 buildings. The date of their introduction has been 
 much debated : but there appears to be no positive 
 evidence of their existence before the middle of 
 the fourteenth century, the earliest record being, 
 that an earthquake at Venice, in 1347, threw down 
 a great many chimneys.f Twenty years after this 
 they appear to have been unknown at Eome; for 
 in that year Francesco da Carraro, lord of Padua, 
 came to Rome, and, finding no chimneys at the inn 
 where he lodged, he caused two chimneys to be 
 built by workmen whom he had brought with him ; 
 and over these chimneys, the first ever seen at 
 Rome, he caused his arms to be affixed. J This 
 
 * Philosophical Transactions, vols. xxv. and xli. 
 
 f Beckmann's " History of Inventions," vol. ii., p. 98. 
 
 t Ibid., p. 99.
 
 IXVEXTIOX OF STOVES. 287 
 
 slow communication of such an important inven- 
 tion, so closely connected with health and comfort, 
 contrasts most strangely with the rapid promulga- 
 tion of every discovery and improvement of the 
 present time. 
 
 The introduction of chimneys into England 
 appears to have been in the reign of Richard II. ; 
 and one of the first is supposed to have been at 
 Bolton Castle, built in this reign.* It was long 
 before they came into general use ; but in the reign 
 of Elizabeth, most rooms in respectable houses were 
 furnished with them, and apologies were made to 
 visitors if they could not be accommodated with 
 rooms with chimneys.f 
 
 (283.) It is uncertain at what time stove-grates 
 were first used, though probably they were not 
 invented till coals became the ordinary fuel. For, 
 though coals were known to the Britons before the 
 arrival of the Romans, their use was barely tolerated 
 in England till the seventeenth century, as it was 
 supposed that the air was rendered unwholesome 
 by their use.J 
 
 After the improved method of burning fuel 
 under open chimneys was introduced, they were 
 used not only as the receptacle for the fire, but 
 they also became the ordinary place of resort for 
 conversation and conviviality for all the inmates 
 of the house. The chimney corner was the post of 
 honour ; and the custom of the whole family sitting 
 under the chimney-breast is not even yet entirely 
 exploded in some of our rural districts. 
 
 (284.) The earliest writers who endeavoured to 
 improve the construction of stoves were Keslar, of 
 Frankfort, in 1614; Savot, in 1625; Glauber, in 
 
 * Fosbroke's "Archaeology," vol. i., p. 113. 
 t Ibid., vol. i., p. 112. 
 
 J See chapter vi., Art, 382. Also Fosbroke's " Archaeology," 
 vol. i., p. 72, &c.
 
 288 EARLY IMPROVEMENTS 
 
 1669 ; and Delesme, in 1686. In 1713 (or perhaps 
 even in 1709), M. Gauger published a most excellent 
 treatise on the construction of fireplaces, which, 
 in 1715, was translated and published in this 
 country by Dr. Desaguliers.* This treatise, which 
 is now scarce, contains a most lucid explanation 
 of the methods of economizing fuel, based on the 
 soundest principles of philosophy. It was the first 
 attempt which had been made to apply the known 
 laws of heat to the construction of fireplaces ; and 
 though, in consequence of wood being the fuel 
 universally used in France at that period, and this 
 fuel being always burned upon the hearth, the 
 author made no mention of stoves, but merely of 
 fireplaces, the translator, Dr. Desaguliers, added 
 a chapter on the shoves to be used in these improved 
 fireplaces ; and the work in that new form was a 
 complete epitome of all those principles which 
 Franklin, and, after him, Count Rumford, so success- 
 fully brought under the public notice, and which, if 
 strictly carried out, would form, even at the present 
 day, the best guide to the proper construction of 
 stoves and fireplaces. An epitome of this little work 
 would be, in fact, a recapitulation of all the most 
 approved methods of constructing fireplaces, stoves, 
 and chimneys; but most of these principles are now 
 too well known to require explanation, and others 
 
 * Dr. Desaguliers, in his " Experimental Philosophy," 
 vol. ii., p. 557, published in 1744, mentions this book, and 
 states that the author concealed his name, but that he knew 
 him to be Monsieur Gauger, of Paris ; and he mentions 
 a curious circumstance of a Frenchman coming over to this 
 country, who, although so ignorant that he could scarcely 
 read three pages of the book, professed himself its author, 
 and applied to the king to grant him a patent, free of expense, 
 on account of the great value of the stoves described in the 
 book, and that he was too poor to pay for the patent. The 
 real author of this book still remains a subject of conjecture, 
 and it has been sometimes attributed to the Cardinal de 
 Polignac.
 
 IN STOVES AND FIREPLACES. 289 
 
 which are less so, will be touched upon in another 
 form in the course of this treatise. 
 
 (285.) The word stove is used in this treatise to 
 signify either a close or an open firegrate to burn 
 fuel in ; and, in general, this is what the word is 
 now supposed to mean. In horticulture, the build- 
 ing itself which is heated, and not the place which 
 holds the fire, is called a stove, and this expression 
 is employed by many old writers. Anciently, 
 however, the term hothouse, which we now use to 
 signify a building for horticultural purposes, was 
 descriptive of a sudorific bath, the use of hot- 
 houses for the purposes of horticulture being an 
 invention of comparatively recent date. At the 
 beginning of the seventeenth century hothouses 
 were used for the cultivation of orange trees, and 
 were considered a mark of royal magnificence.* 
 
 (286.) The various elegant forms given to the 
 stove grates of the present day are quite a modern 
 invention. Formerly they were called " cradles of 
 iron for burning sea-coal,"f from which we should 
 suppose them to be very different in construction 
 to ours ; and even those described in Dr. Desagu- 
 liers' work, as late as the beginning of the eighteenth 
 century, are nothing more than a few bars bent into 
 a semicircle and fastened into the back. How far 
 the utility of stove grates has been affected by the 
 modern alterations of form, we shall endeavour to 
 show in the following chapter ; and subsequently 
 we shall inquire into the physiological effects pro- 
 duced by some of the modern methods of distribut- 
 ing artificial heat. 
 
 * Fosbroke's " Archaeology," vol. i., p. 275. 
 t Ibid., vol. i., p. 268.
 
 290 
 
 CHAPTER II. 
 
 Forms of Fireplaces and Chimneys Should be made to 
 reflect heat Contraction of Chimney-breast Hollow 
 Hearths and Backs for Fireplaces Kumford's Principles 
 of Construction Errors in the Construction of Stoves 
 Register Stove in a case Jeffrey's Stove Franklin's Penn- 
 sylvania Stove Cutler's Torch Stove Sylvester's Radiat- 
 ing Stove Russian and Swedish Stoves Cundy's Stoves 
 German Stoves Hot-air Stoves Cockle Stoves Dr. 
 Nott's Stove Dr. Arnott's Stove Franklin's Yase Stove 
 Gas Stoves Joyce's Stoves Beaumont's Stove Pal- 
 maise Stove. 
 
 (287.) PREVIOUS to the publication of M. Ganger's 
 treatise (already alluded to, Art. 284) chimney 
 fireplaces were generally made in the form of a 
 large square recess, and the breast of the chimney 
 was of the same size as the recess itself. The 
 error of this construction was pointed out, in the 
 work by M. Gauger, by a reference to the known 
 laws of heat. Eadiant heat is subject to the same 
 law as light, that the angle of reflection is equal 
 to the angle of incidence. Hence it follows that 
 a ray of heat, falling perpendicularly on the flat 
 sides of the chimney recess, will be reflected back 
 upon itself: if the ray forms an angle vertically 
 with the side, it must be reflected up the chimney ; 
 and if the ray forms an angle horizontally with 
 the flat side of the chimney, this angle must 
 necessarily be so small that it cannot be reflected 
 forward beyond the jambs of the mantel-piece. 
 On these considerations, M. Gauger recommended 
 that the back of the recess should be contracted
 
 CONSTRUCTIOX OF STOVES. 291 
 
 so that the sides should incline outwards at a con- 
 siderable angle, by which means the radiant heat 
 would be reflected into the room, and much more 
 effect produced. The fig. 51 will explain this: 
 it is supposed to be the ground plan of a fireplace 
 with straight sides ; 
 A B c are the jambs, FIG. 51. 
 
 sides, and back of the 
 fireplace, and D the 
 body which radiates 
 heat. If now a ray 
 w falls on the side, it 
 will be reflected at the 
 same angle, and fall 
 
 just within the jamb at x; but if the side be in- 
 clined, as shown by the line /, then a ray y falling 
 upon it, will be reflected into the room in the 
 direction of z, and of course a vast difference in 
 the effect will be experienced. 
 
 But this author likewise recommended other 
 improvements. He advised a considerable con- 
 traction of the breast of the chimney, by which 
 less heat would escape through the funnel or shaft 
 of the chimney, while at the same time he proved 
 that the smoke would escape with equal facility 
 as before. Another improvement which he sug- 
 gested was in making the hearth and back of the 
 fireplace hollow, by means of metal plates, so 
 that by having these hollow spaces to communi- 
 cate with the external atmosphere, the air in 
 passing through them would be warmed before it 
 entered the room, and would prevent the cold 
 currents of air which otherwise would enter 
 through the crevices of the doors and windows. 
 This construction of fireplaces was intended for 
 the burning of wood, and as the fire was there- 
 fore merely laid on the hearth, the effect of these 
 hollow spaces, and particularly the hollow hearth, 
 
 u 2
 
 292 RUMFORD'S IMPROVED 
 
 would of course be very considerable, by warming 
 a large quantity of air. 
 
 (288.) Subsequent inventors have been much 
 indebted to this work by M. Gauger. Franklin 
 acknowledged the great assistance he had derived 
 from it ; and the methods of economizing fuel, 
 afterwards so successfully introduced by Count 
 Rumford, in his improved stoves, are all similar 
 in principle to the plans recommended by the 
 French author. 
 
 (289.) In the year 1796, Count Rumford pub- 
 lished his Essays on the Management of Fire and 
 the Economy of Fuel ; and he there describes those 
 improvements which have ever since that time 
 been followed in the construction of stove grates. 
 The error shown by M. Gauger to exist in the 
 construction of fireplaces, by making the sides 
 parallel to each other, was, at the time that Rum- 
 ford wrote his treatise, still continued. In pointing 
 out the error of this mode of construction, he 
 showed that, in order to obtain the greatest effect 
 from the fuel, the sides of the fireplace ought 
 to be placed at an angle of 135 with the back 
 of the grate, or (which is the same thing) at an 
 angle of 45 with a line drawn across the front 
 of the fireplace. This angle must necessarily 
 reflect the greatest number of rays into the room ; 
 the difference of effect between this mode of 
 construction and that of the parallel sides being 
 very great. The reduction in the size of the 
 throat of the chimney was likewise another im- 
 provement which he effected, though this also 
 had been recommended by M. Gauger nearly a 
 century previous. The angular covings for the 
 sides of the fireplaces, Rumford considered should 
 not be formed of iron, but of some non-conducting 
 substance, such as fireclay, in order that more 
 heat might be reflected from them into the room.
 
 REGISTER STOVES. 293 
 
 A circular form for these sides or covings, he con- 
 sidered produced eddies or currents, which would 
 be likely to cause the chimney to smoke; and he 
 likewise objected to the old form of registers or 
 metal covers to the breast of the chimney for the 
 same reason, and because by their sloping upwards 
 towards the back of the fireplace, thej T caused the 
 warm air from the room to be drawn up the chimney, 
 and thus impeded the passage of the smoke. These 
 registers are now made so as to be lower at the 
 back than at the front of the stove ; but, in general, 
 they are placed far too high up. And the very 
 same reasons which decide the angle of greatest 
 effect for the cheeks or sides of the fireplace to be 
 45, also apply to this case ; and a large quantity 
 of heat now lost by the ordinary register stoves 
 would be saved if the register top were placed at 
 this angle, and sufficiently low down to allow it to 
 reflect the heat from the fire into the room. The 
 dimensions of the firegrate itself Count Rumford 
 recommended to be much less than formerly; and 
 the best proportions for the chimney recess, he 
 stated, were that the width of the back should be 
 equal to the depth from front to back, and the 
 width of the front, or the opening between the jambs, 
 should be three times the width of the back. 
 
 (290.) Although the best form for register stoves 
 has now for several years past been adopted, the 
 desire for novelty has 
 caused the true principles Fiat 
 
 of construction to be fre- 
 quently departed from ; 
 and we accordingly find, 
 in the most modern 
 stoves, considerable de- 
 viations from these prin- 
 ciples. Fig. 52 is a section of a register stove 
 constructed on the best possible plan for diffusing
 
 294 EEGISTER STOVES. 
 
 heat into the room. The two sides are a right 
 angle of 90 A u c ; and the bars d e describe a 
 quadrant of a circle whose radius is just half the 
 length of the side A B. If now we wish to follow 
 Eumford's rule of making the back one-third the 
 width of the front, we obtain this by taking one- 
 third of the length A B, which will give B / ; and 
 then, if we draw the line / g, we shall obtain exactly 
 the required dimensions. By this arrangement it 
 will be perceived that the sides of the stove form 
 an angle of 135 with the back ; and all the rays of 
 heat which fall upon these sloping sides will there- 
 fore be reflected into the room, directly in front of 
 the stove, in right lines. The falling cover, or 
 register top, should also form an angle of 135 with 
 the back, by which a large portion of heat will be 
 radiated downwards into the room. These propor- 
 tions however, cannot well be adopted in stoves of 
 very large size, as they will be found to throw the 
 stove too far back ; but for all moderate-sized stoves 
 no form can be adopted which will produce so good 
 an effect. 
 
 (291.) Yarious methods have been contrived to 
 render available some further portion of the heat 
 which is given off by the fuel during combustion 
 in these stoves, in addition to that which is 
 obtained by radiation. These contrivances are 
 nearly all of them mere modifications of that 
 pointed out by M. Gauger, by means of the 
 double back and hearth of his improved fireplaces. 
 Notwithstanding this invention is at least 150 
 years old, it has, during the last thirty years, 
 been repeatedly brought forward, and more than 
 once patented, by different persons, as a new 
 invention. The principle has been the same in 
 all the different cases, with but very little difference 
 in the mode of applying it. A current of air is 
 brought from the external atmosphere, and is made
 
 JEFFREY'S STOVES. 295 
 
 to pass through a small flat box at the back of the 
 stove ; the back of the stove itself forming one side 
 of the box ; and in order to prevent the air from 
 escaping into the room before it is sufficiently 
 warmed, the box is divided horizontally by several 
 partitions so as to check the passage of the air, 
 which is carried successively through them all 
 before it escapes into the room. This mode of warm- 
 ing the air is exceedingly useful, and is capable of 
 various modifications. It is not only economical 
 in fuel, but frequently is very efficacious in remedy- 
 ing smoky chimneys, and in preventing those cold 
 draughts from doors and windows, which are so 
 exceedingly unpleasant and unhealthy. 
 
 (292.) A most efficient mode of applying this 
 principle is to enclose the whole of the register 
 stove in an ornamental case. In this way the stove 
 stands forward in the room a few inches, and the 
 case forms an air-chamber entirely round the back 
 and sides of the stove, by which a very large heating 
 surface is obtained, which moderately warms the 
 air, while the whole effect of the radiant heat is 
 obtained from the open fire, the same as in an 
 ordinary register stove. When the air-chamber 
 communicates with the external air, this forms 
 a very excellent stove, and the atmosphere is purer 
 than when the air of the room only is made to pass 
 over the heated surface. 
 
 (293.) A stove invented by Mr. Jeffrey (the 
 inventor of the well-known instrument called the 
 Respirator) accomplishes the same object in a some- 
 what different manner. This stove stands extremely 
 prominent in the room, without being at all sunk 
 in the wall as fireplaces usually are. The entire 
 back of the stove above the fire consists of a series 
 of flat tubes, one inch wide, and about nine inches 
 deep from back to front, which are placed edge- 
 ways, one inch apart from each other, so as to
 
 296 PENNSYLVANIA STOVES. 
 
 present alternately a close and an open space of 
 one inch in width. These tubes are about eighteen 
 inches long, and reach quite to the top of the stove, 
 and pass just through the mantel-piece. The only 
 way by which the smoke can escape into the 
 chimney is by passing through the openings left 
 between these flat tubes, which are so connected at 
 the top as to prevent the smoke passing into the 
 room. The lower end of these tubes opens into 
 a small air-chamber which communicates with the 
 external atmosphere, and the air therefore passes 
 from this chamber through the flat tubes, and 
 escapes at rather an elevated temperature into the 
 room from the upper part of the tubes ; having been 
 warmed in its passage through the tubes by the 
 heat which has been abstracted from the smoke 
 passing between them. Nothing new in principle 
 is obtained by this arrangement; the only difference 
 between this plan and that of the many previous 
 contrivances for the same purpose is, that the heat 
 which warms the air is derived from the smoke, in 
 the others it is obtained by bringing the air into 
 contact with the surface that is heated directly by 
 the fuel contained in the stove itself. The method 
 employed by Mr. Jeffrey appears very likely to 
 cause the chimney to smoke, unless the draught is 
 particularly good ; for the smoke must have so large 
 a portion of its heat abstracted by passing between 
 the flat tubes, that its power of ascending must 
 necessarily be very much reduced. The stove also 
 presents some practical difficulties in removing the 
 soot from the chimney, for which purpose a part 
 of the jamb has to be removed. 
 
 (294.) Dr. Franklin, in 1744, in vented a stove for 
 burning wood, which he called the Pennsylvania 
 stove; in which he introduced the principle of 
 heating the air much in the manner first recom- 
 mended by M. Ganger, by means of a double or
 
 TORCH STOVES. 297 
 
 hollow back. This stove* was in the form of an 
 oblong box with the front removed. At about 
 three or four inches from the back of this box, a flat 
 close chamber was fixed, three inches deep, the 
 whole width of the stove, and reaching to within 
 about four inches of the top. The smoke escaped 
 over the top of this flat chamber, and passed down- 
 wards between it and the real back of the stove, 
 and thence passed into the chimney. This hollow 
 chamber communicated underneath the stove with 
 a tube opening into the external atmosphere, and 
 a considerable quantity of air thus passed through 
 the flat chamber, and escaped into the room through 
 small holes left at the sides, after traversing the 
 length of the chamber three or four times by means 
 of divisions placed across it for that purpose. The 
 heated surface of the stove 'itself also warmed the 
 air of the room, and a large quantity of radiant 
 heat was also given off from the burning fuel. This 
 stove is very economical. It was a good deal used 
 in America, and some of them have been used in 
 England, in those parts of the country where wood 
 is abundant. 
 
 (295.) An ingenious stove was proposed in 1815, 
 by Mr. Cutler, and called the torch stove.f It 
 possessed an open fire, exactly like an ordinary 
 register stove, but it was made to consume its own 
 smoke on a very ingenious principle. Below the 
 bars of the grate there was a deep box which sank 
 down into the hearth, and which contained the 
 fuel. The fire was lighted at the top, and as the 
 fuel burned away, the box was wound up by a 
 chain passing over a rack and pinion, placed out 
 of sight, in the interior of the stove. By this 
 means the fuel burned only at the top ; and the 
 quantity of heat could be regulated at pleasure, 
 
 * Franklin's " Works," vol. ii., p. 225, et seq. 
 
 f Repertory of Arts, vol. xxviii. (second series), p. 203.
 
 298 TORCH STOVES. 
 
 according to the height to which the fuel was 
 supplied from the box below. For, as the sides 
 of the box were solid, and therefore no air could 
 pass through the fuel it contained, the combustion 
 took place only in that part of the fuel which was 
 raised up to the level of the firebars : and as this 
 part of the fuel always burnt clear, the raw coal 
 below was gradually and slowly heated, and the 
 gaseous parts were consumed while passing slowly 
 through the ignited fuel at the top. This stove 
 was rather cumbrous in appearance, and there was 
 an inconvenience attending its use, arising from 
 the trouble of relighting the fire and filling the 
 box with fuel, when the latter did not contain a 
 sufficient quantity to last the entire day ; and 
 this alone is almost sufficient to prevent its 
 general use. The principle, however, of lighting 
 the fire at the top, and supplying fresh fuel from 
 below, is undoubtedly good, as it affords the most 
 perfect control over the intensity of the fire, and 
 consumes nearly the whole of the smoke. To 
 obviate the inconvenience of supplying the coals 
 in this way, and still retaining the advantage of 
 burning the fuel from the top, downwards, Mr. 
 Dowson patented a plan* for supplying the fresh 
 fuel below the ordinary bars of the grate, whilst 
 the fire was burning, by a peculiar apparatus, 
 which delivered the fresh coals at the bottom of 
 the grate ; but neither this, nor the plan proposed 
 by Mr. Cutler, ever came at all into extensive 
 use, as both are troublesome and expensive. Dr. 
 Arnott has very recently (1854) again revived 
 Mr. Cutler's plan of the torch stove, and has pro- 
 posed it as a remedy for the inconveniences, real 
 and imaginary, which are attributed to our ordinary 
 open grates or fireplaces. There is not the least 
 probability that this plan will ever come into gene- 
 
 * Repertory of Arts, vol. xxix. (second series), p. 76.
 
 SYLVESTER'S STOVES. 299 
 
 ral use : for its greater cost, its complicated manage- 
 ment, its practical inconvenience in replenishing 
 the fuel, and its somewhat difficult adaptation to 
 existing fireplaces, all militate against it, even were 
 its advantages greater than they really are. In 
 fact the plan, somewhat modified, has been several 
 times brought forward. Several years ago it was 
 proposed in America, by simply making each side 
 of the stove consist of a hollow box, of which the 
 hob formed the lid. The bottom of the box was 
 level with the bottom grate of the stove ; and an 
 opening from the side of the box, close to the bot- 
 tom, allowed the coals which were put in these side 
 boxes to be pushed under the burning fuel in the 
 grate, and thus produced the same effect as the 
 winding box of Cutler's stove. This plan, like each 
 of the others, is attended with difficulties in prac- 
 tice; for, although descriptively it appears very 
 easy, in practice it is found extremely difficult to 
 force any sufficient quantities of fuel under a mass 
 of burning coals. 
 
 (296.) Another modification of the register stove 
 is the invention of Mr. Sylvester. In this stove 
 the hearth consists of a great number of hollow 
 bars fitted into an appropriate frame. The hollow 
 bars not only form the hearth, but at their extreme 
 end the fuel is placed, and the bars thus form the 
 grating on which the fuel is burned. The air to 
 support the combustion passes through the hollow 
 bars, and also through the front of the fire. The 
 ends of these bars on which the fire is placed be- 
 come hot, and the remaining part of the bars also 
 becoming heated by the conducting power of the 
 metal, a radiation of heat into the room is produced 
 by the bars which form the hearth. The fire being 
 placed as it were on the hearth, the cheeks or sides 
 of the stove are of much greater length than usual, 
 and a larger quantity of heat is radiated into the
 
 300 RUSSIAN AND SWEDISH STOVES. 
 
 room. The smoke escapes through openings in the 
 back, which are placed something like louvre boards. 
 The ashes from the stove fall into a box below the 
 hearth, which requires to be occasionally emptied 
 by removing the loose bars forming the hearth. 
 
 The principle of this stove is extremely good, 
 but the arrangement is much too expensive ; and 
 there are several inconveniences which must prevent 
 its general use, not the least of which is the exten- 
 sive alteration in the brickwork and woodwork 
 which surround the fireplaces, in order to adapt 
 them to rooms not purposely built for them. But 
 there is ample room for improvement in the ordi- 
 nary open fireplaces, and many ingenious inventions 
 already exist for this purpose. The great obstacle, 
 however, to their general use, even supposing their 
 merits greater than they really are, is the extensive 
 alterations generally required when they are made 
 to replace stoves of the old construction. For 
 while several of the modern stoves economise fuel 
 to a considerable extent, their expense puts them 
 beyond the reach of those to whom this economy of 
 fuel would be important ; and to those who can afford 
 the expense of their application, the economy of 
 fuel is a matter of indifference. The old principle 
 of open stoves is undoubtedly wasteful of fuel, as a 
 large portion of heat escapes up the chimney ; but 
 it is doubtful whether any of these modern inven- 
 tions yet accomplish great economy of fuel, accom- 
 panied with moderate cost and easy application.* 
 
 (297.) The stoves which come now to be men- 
 tioned are of a different character, and form that 
 class (the only one known in many parts of 
 
 * In the Report of the Commissioners presented to Parlia- 
 ment, 25th August, 1857, "On Warming and Ventilating 
 Dwellings," there is 'a very good epitome of all the patents, 
 91 in number, taken out for stoves between the years 1781 
 and 1857.
 
 CUNDY'S STOVES. 301 
 
 Europe) which heat the air by contact with their 
 surfaces, and not by radiation directly from the 
 burning fuel itself. In most of these stoves the 
 fire is wholly concealed from view ; while in a few 
 of modern invention, a part of the fire is dimly 
 seen through talc placed in the front. 
 
 (298.) In the north of Europe, close stoves are 
 alone used for heating buildings. In Russia and 
 Sweden, the stove is generally made of brick, tiles, 
 or stone, and it occupies a large space at one end 
 of the room. It is usually either square or oblong, 
 and is divided by partitions into different compart- 
 ments, so as to increase the surface over which the 
 smoke and heated gases pass before they finally 
 escape into the chimney. The materials which 
 compose the stove being slow conductors of heat, 
 they retain the heat for a long time when once 
 warmed ; and these stoves seldom require replenish- 
 ing with fuel more than once a day. They usually 
 burn wood for fuel, and are supplied by a firedoor 
 exterior to the room intended to be warmed. M. 
 Guyton endeavoured to introduce these stoves into 
 France at the close of the last century, and paid 
 much attention to the best form of construction 
 and the comparative cost of fuel, the results of 
 which were published in the Annales de Chimie* 
 
 Mr. Cundy took out a patent in this country, 
 in 1844, for a stove made of fireclay, which it 
 was supposed would combine the advantages of 
 an open fire with the mild heat from earthen or 
 pottery surfaces. The large size which such a 
 stove requires to be, in order to afford sufficient 
 heating surface for a building of any considerable 
 extent, must necessarily prevent, its general appli- 
 cation; and it has not hitherto proved generally 
 successful where large areas are required to be 
 heated. 
 
 * See also Repertory of Arts, vol. xvi ., p. 254, et seq.
 
 302 COCKLE STOVE. 
 
 (299.) In Germany, iron stoves are used, which 
 heat the air by contact with their surfaces. A very 
 superior stove is also used, made of glazed earthen- 
 ware, which is very similar to the Swedish stoves 
 just described, and which gives a mild and agree- 
 able heat. This stove necessarily occupies much 
 room ; but it is decidedly the best construction for 
 a close stove, as the quality of the air is less injured 
 by it than by the heated metal from ordinary close 
 stoves. With all these close stoves it is usual to 
 employ a vase of water to supply moisture to the 
 air, to prevent the unpleasant effects which would 
 otherwise be experienced, and which will be 
 noticed in the following chapter. 
 
 (300.) In this country, hot-air stoves constructed 
 of iron have been usually employed for warming 
 large buildings, until the introduction of the plan 
 of warming by steam and by hot water. 
 
 The hot-air stove is too well known to need 
 description. It may be observed, however, that 
 the great defect of these stoves is that they heat 
 the air too highly, and thereby render it unwhole- 
 some ; and whatever plan of construction tends to 
 increase the heated surface exposed to the air 
 without increasing the size of the firebox itself, 
 will of course lower the temperature of the surface 
 which heats the air, and thereby render the stove 
 less objectionable. This has been accomplished 
 in a very ingenious manner by Mr. Sylvester, by 
 means of covering the cast-iron case, which receives 
 the heat from the fire, with iron ribs projecting 
 three or four inches beyond the surface of the 
 case. These ribs greatly increase the surface, 
 and thereby reduce the temperature, which is the 
 great desideratum in these stoves. 
 
 (301.) The method of heating by cockle stoves is 
 but little more than a modification of the ordinary 
 hot-air stoves adapted to a larger scale. Mr. Strutt,
 
 NOTT'S STOVES. 303 
 
 of Belper, in Derbyshire, appears to have been the 
 first person to introduce an improved method of 
 heating by cockle stoves ; and from the year 1792, 
 when he first warmed his large cotton factories in 
 this manner, various improvements have been 
 made in these stoves, which, without at all altering 
 their principles, have rendered their application 
 more general. 
 
 The cockle stove consists of a very thick iron 
 case, which forms the top and sides of the furnace. 
 This case, or cockle, is enclosed in another case of 
 brick or stone, placed so as to allow a space of 
 three or four inches, or more, between them in 
 every part ; and appropriate openings are left for 
 the admission of cold air at the bottom, and for 
 the emission of the hot air at the top, which is 
 from thence conveyed through channels or pipes 
 to any place which is required to be warmed. A 
 vast number of ingenious contrivances have been 
 proposed for the improvement of this apparatus, 
 and for many years it was the principal method of 
 warming all the large buildings in England. It 
 has been sometimes called the Belper stove, after 
 the name of the residence of the inventor. The 
 unwholesome effects of these stoves, however, have 
 caused them to be now nearly superseded by the 
 use of hot-water pipes, which, from their lower 
 temperature, are free from the injurious tendency 
 which the hot-air stoves have always been found 
 to exhibit.* 
 
 (302.) A stove invented by Dr. Nott, of Phila- 
 delphia, has been found to produce very consider- 
 
 * The heating power of these cockle stoves is very con- 
 siderable. Mr. Sylvester states, in his work " On Heating the 
 Derby Infirmary," that a cockle which has 17 square feet of 
 heating surface warmed 344,600 cubic feet of air 56 in twelve 
 hours, with the consumption of 60 Ibs. of coal. This is equal 
 to 26,768 cubic feet raised 1 per minute by 17 square feet of
 
 304 ARNOTT'S STOVES. 
 
 able effect with but small expenditure of fuel, and 
 requiring very little attention. This stove is 
 usually something of a pyramidical form. The 
 lower part, which forms the firebox, is lined with 
 firebricks, and the stove is divided vertically into 
 two compartments. The fuel is put into this 
 stove through an opening near the top, which 
 forms a reservoir for the fuel, and occupies the 
 front part of the stove, and the smoke passes 
 downwards through a grating placed at the 
 bottom, and then escapes through the back part 
 of the stove into the chimney. The air for the 
 support of the combustion enters the stove prin- 
 cipally on the top of the fuel, and a small portion 
 also enters below. As the fuel burns but slowly 
 in consequence of the small quantity of air ad- 
 mitted, the firebox and reservoir, when once 
 filled, will supply fuel for several hours, and give 
 a very great heat. In fact, the heat is generally 
 so considerable, and the air is thereby rendered 
 so arid, that it is extremely unpleasant and un- 
 wholesome to those who are exposed to its in- 
 fluence. 
 
 (303.) One of the most economical stoves as 
 regards the consumption of fuel, that has yet been 
 invented, is that which has been introduced by 
 Dr. Arnott. This invention is an improvement 
 (in some respects) upon Dr. Nott's stove above 
 described, the principal difference being the limiting 
 the admission of air by which the combustion 
 is regulated, and by separating the burning fuel 
 more perfectly from actual contact with the heat- 
 heating surface, or 1574 cubic feet of air raised 1 per minute 
 by each square foot of the surface of the cockle. This is just 
 7 times the effect produced by hot-water pipes (See Art. 99 
 and 105) ; but in economy of fuel it is inferior, being in the 
 proportion of about 19 to 22. For a full description of the 
 cockle stove, see chapter xi., part i.
 
 ARNOTT'S STOVES. 305 
 
 ing surface of the stove, by which means the 
 excessive heat of Dr. Nott's stove is in a great 
 measure avoided. The plan used in these stoves 
 for regulating the admission of air was, long pre- 
 vious to its application by Dr. Arnott, employed 
 for limiting the intensity of the heat of furnaces; 
 for which invention Dr. Ure, some years since, 
 obtained a patent. Dr. Arnott's stove consists of 
 an external case of iron, of any shape that fancy 
 may dictate ; within this case a fireclay ' box, to 
 contain the fuel, is placed, having a grating at the 
 bottom, and a space is left between the firebox and 
 the exterior case, so as to prevent, as much as 
 possible, the communication of too much heat to 
 the exterior case. The pedestal of the stove forms 
 the ashpit, and there is no communication between 
 the stove and the ashpit, except through the 
 grating at the bottom of the firebox. A small 
 external hole in the ashpit, covered by a valve, 
 admits the air to the fire, and according as this 
 valve is more or less open, the vividness of the 
 combustion is increased or diminished, and thence 
 the greater or less heat produced by the stove. 
 The quantity of air admitted by this valve is 
 governed by a self-regulating apparatus, either by 
 the expansion and contraction of air confined by 
 mercury in a tube, or by the unequal expansion of 
 two bars of different metals riveted together, on 
 the plan proposed by Dr. Ure.* The smoke escapes 
 through a pipe at the back of the stove : very little 
 smoke, however, is eliminated from these stoves, 
 
 * This ingenious and simple invention consists of two thin 
 narrow bars, one of brass or copper, and the other of iron, 
 about eighteen inches or more in length, riveted together at 
 each end. On subjecting this compound bar to heat, the 
 brass expands considerably more than the iron, and the 
 elongation of the bars causes them to open in the centre and 
 recede from each other (forming a bow), in consequence of 
 
 X
 
 306 ARNOTT'S STOVES. 
 
 the fuel being always either coke or anthracite coal. 
 By adjusting the regulator so as to admit only 
 a small quantity of air, the temperature of the stove 
 is kept within the required limits; and owing to 
 the slow conducting power of the fireclay, of which 
 the firebox is formed, the heat of the fuel is con- 
 centrated within the firebox, and the fuel burns 
 with less air, and therefore more slowly than it 
 would otherwise do. This slow combustion of the 
 fuel, however, produces a large quantity of carbonic 
 oxide, which is liable to escape into the room, and 
 being a strong narcotic poison, is attended with 
 considerable danger to those who breathe it. The 
 escape of this gas from these stoves has been 
 experimentally ascertained by Dr. Ure, by attaching 
 to the ashpit of a stove a glass vessel containing 
 a solution of sub-acetate of lead, which was speedily 
 acted upon by the carbonic gas, and formed into 
 the insoluble carbonate of lead.* Carburetted 
 hydrogen gas is also frequently formed in these 
 stoves, and many dangerous explosions have in 
 consequence occurred, and many calamitous fires 
 have been produced by them. They require, there- 
 fore, to be used with the utmost caution. The 
 endeavours to prevent these explosions have hitherto 
 been unsuccessful,- and so long as the principle 
 of the extreme slow combustion and small admission 
 of air is preserved, it will probably be impossible 
 to prevent them occasionally taking place. They 
 arise from the inflammable gases, generated during 
 the combustion of the fuel, being detained in the 
 
 their being riveted together at both ends. The greater the 
 heat, the more the centres of the bars recede from each other, 
 or the greater the arc of the bow becomes; and by com- 
 bining together a series of these bars, almost any extent of 
 motion may be obtained for the purpose of opening or closing 
 valves or air passages of furnaces or ovens. 
 
 * Ure's " Dictionary of Arts," &c. ; art. " Stove."
 
 ARNOTT'S STOVES. 307 
 
 stove and in the chimney by the want of sufficient 
 draught ; and they are particularly liable to occur 
 when the chimney is very large, or if it consists 
 merely of an iron pipe and is much exposed to the 
 cooling influence of the atmosphere. In such cases 
 the heat which escapes into the chimney is insuffi- 
 cient to cause the ascent of the liberated gases ; 
 they therefore collect in the stove, or in the chimney, 
 and the explosive effects occur whenever the air 
 and the gases mix together in certain proportions. 
 The compound thus formed is similar to the gas 
 known in mines by the name of firedamp; and 
 this mixture will explode whenever the carburetted 
 hydrogen is not less than one-twelfth and not more 
 than one-sixth of the whole mass. The explosion 
 of carbonic oxide only takes place under particular 
 circumstances ; but red-hot charcoal will cause it 
 to explode when mixed in the proportion of two 
 measures of oxide to one of atmospheric air.* 
 Dr. Dal ton has remarked other circumstances under 
 which this gas may explode when mixed with 
 atmospheric air, the carbonic oxide being not less 
 than one-fifth, and the oxygen not less than one- 
 thirteenth of the whole mixture.f Many plans to 
 remedy these evils have been proposed, principally 
 by the admission of air above the fuel as well as 
 through the ashpit in the usual manner; but 
 occasionally this increases the evil, during certain 
 stages of the combustion, though generally the 
 effect is to increase the temperature of the stove so 
 much as to render it extremely unpleasant, and 
 liable to all the objections which exist against the 
 old hot-air stoves. The immense number of serious 
 accidents which have occurred from these stoves 
 ought to render those persons who use them 
 extremely careful. The great source of danger 
 
 * Dr. Henry's " Chemistry," vol. ii., p. 347. 
 t Dr. Dalton's " Chemical Philosophy," p. 373. 
 
 x 2
 
 308 VASE STOVES. 
 
 arises from their fancied security. This erroneous 
 notion has caused them to be placed in situations 
 not sufficiently protected ; and either by explosions, 
 or by the stoves from accidental causes becoming 
 red-hot, many buildings have been set on fire, and 
 most serious damage sustained.* 
 
 (304.) A very excellent contrivance for a stove, 
 which burns coal, and at the same time consumes 
 its own smoke, was invented by Dr. Franklin in 
 the year 1771. Nearly a century previous to that 
 time, M. Delesme, a French engineer, described an 
 exceedingly rude contrivance on a similar principle, 
 which was afterwards mentioned by Dr. Leutmann 
 in a work on stoves, published by him in Germany, 
 in 1723. Dr. Franklin expressly acknowledged 
 that this stove of Delesme gave rise to his own 
 invention. This stove is in the shape of a large 
 vase, of which fig. 53 is a section, and it is fully 
 described in Dr. Franklin's works.f Near the 
 bottom of the body of the vase a grating c is placed, 
 on which the fuel rests, and the top A B opens 
 for the purpose of supplying the fuel : D is a square 
 box forming the pedestal of the stove, at the 
 bottom of which another grate is fixed to allow 
 the ashes to fall into the box E. This latter box 
 is open at the back, and communicates with the 
 
 * The author is in possession of an extensive list of accidents 
 caused by these stoves, some involving total destruction of 
 the buildings and many more of serious damage. In one of 
 the former three lives were lost ; and among buildings totally 
 destroyed is to be reckoned Okehampton Church and (almost 
 beyond a doubt) the Armoury at the Tower of London in 1841. 
 Howth Castle near Dublin; Larkfield House, Sussex; and a 
 vast number of other private and public buildings have had 
 narrow escapes from destruction from this cause. Wherever 
 these stoves are used the utmost caution ought to be observed 
 to keep them insulated from everything of an inflammable 
 nature. 
 
 t Franklin's " Works," vol. ii., pp. 296-300.
 
 VASE STOVES. 309 
 
 hot-air passages // and g g, through which the 
 heated gaseous matter given off from the fuel passes 
 before it enters the chimney. It will be perceived 
 that the draught of this stove is downwards ; that 
 is, the air enters at a small hole, Fra 53 
 
 about one and a half inch dia- 
 meter, at the top of the stove, 
 passes through the fuel in the 
 vase, and escapes, together with 
 the gaseous products of the fuel, 
 through the pedestal D, the box 
 E, and the hot-air passages // 
 and gg. That portion of the 
 fuel which lies on the grate c is ir-girT-ir* iir^-ii n 
 always red-hot; and the smoke l '-' 1 p * "' " 
 from any fresh fuel having to pass through this 
 heated medium, is consumed, and the gases pass off 
 in a clear and almost invisible state, so that no 
 smoke lodges in the air-passages, or in the chimney. 
 Like all stoves with a downward draught, the fire is 
 troublesome to light in the first instance ; but when 
 once lighted, it can be made to burn for almost any 
 length of time without attention by merely adjust- 
 ing the opening at the top for the admission of air, 
 and the consumption of fuel is extremely small. 
 
 This stove, with some slight alterations, has been 
 brought before the public on more than one occasion 
 since Franklin's time as a new invention, and 
 within the last few years it has been again brought 
 forward with arrangements very decidedly inferior 
 to those proposed by Franklin. As designed by 
 him, this stove is the best and most economical of 
 its class, superior to Dr. Arnott's stove in its equality 
 of temperature, economy of fuel, and permanence 
 of action ; though like the latter, and all others of 
 the same general character, the want of ventilation, 
 and the peculiar effects produced on atmospheric 
 air by highly heated iron, render it undesirable for
 
 310 GAS STOVES. 
 
 constant use in rooms for ordinary and domestic 
 occupation. 
 
 (305.) The application of a method of burning 
 carburetted hydrogen or coal gas, for the produc- 
 tion of artificial heat for warming buildings, is an 
 invention of rather recent date. The apparatus in 
 which this is effected is very simple. A metallic 
 ring, pierced on its upper side with a great number 
 of holes of very small size, is connected with a pipe 
 communicating with the gas main, and is placed 
 within a double drum or cylinder of iron, raised an 
 inch or two from the floor on small legs. This 
 double drum is so made that there is a space between 
 the inner and outer cylinder of about two inches ; 
 and in this space, near to the bottom, the ring 
 pierced with holes is fixed. A stop-cock in the pipe 
 connecting the pierced ring with the gas main shuts 
 off the supply of gas when the stove is not in use. 
 On opening this cock, and applying a light to the 
 pierced ring, a brilliant ring of flame is immediately 
 produced, which soon warms both the inner and 
 outer case of the stove by the heat generated during 
 the combustion of the carburetted hydrogen gas. 
 The top of the drum is covered with a large open 
 ventilator, by which the heated air that passes 
 through the inner cylinder is allowed to escape 
 into the room ; but the products of the combustion, 
 having no means of escape, pass downwards from 
 the bottom of the stove into the room. This 
 having been found exceedingly unwholesome, a plan 
 has been contrived by which a considerable portion 
 of the products of the combustion are carried off 
 by a pipe inserted between the two cylinders, 
 which conveys away the gaseous products into 
 the open air. 
 
 A moderate sized stove of this description burns 
 from 12 to 15 cubic feet of carburetted hydrogen 
 gas per hour ; and this is converted into two new
 
 GAS STOVES. 311 
 
 compounds water and carbonic acid gas. The 
 quantity of water formed will be 2 6 cubic inches 
 for each cubic foot of carburetted hydrogen, or 
 about a pint to a pint and a quarter of water per 
 hour; and from 12 to 15 cubic feet of carbonic acid 
 gas, and eight times that quantity of nitrogen, will 
 be the constant products of the combustion, and 
 produce the most serious deterioration in the quality 
 of the air. When these gaseous products are 
 carried off by a chimney, the loss sustained will 
 be very nearly one-half the total heat which is 
 produced by the burning of the gas. 
 
 (306.) Dr. Dalton's experiments have proved 
 that the combustion of one pound in weight of 
 carburetted hydrogen generated sufficient heat to 
 melt 85 Ibs. of ice. A cubic foot of this gas weighs 
 292 '89 grains; and a stove burning 15 cubic feet 
 an hour, for fifteen hours a day, will consume 225 
 cubic feet, or 9 '41 Ibs. of gas, which therefore 
 would melt 799 Ibs. of ice ; and the cost of this 
 quantity of gas at the present price of three shillings 
 and sixpence per 1000 cubic feet, would be nine- 
 pence halfpenny. The latent heat of water being 
 140, the same quantity of heat that would melt 
 799 Ibs. of ice would heat 179-2 cubic feet of 
 water 10. And as one cubic foot of water will 
 raise the temperature of 2990 cubic feet of air as 
 many degrees as the water loses (Art. 97), the 
 combustion of 225 cubic feet of carburetted hydro- 
 gen gas would raise the temperature of 535,808 
 cubic feet of air 10. This, then, will be the total 
 effect of a stove of this kind. But we find (Art. 
 94), that 15-91 Ibs. of coal will produce exactly the 
 same quantity of heat, the cost of which, at 24 
 shillings per ton, will be only about twopence. It 
 therefore appears that the cost of fuel for a gas stove 
 without a flue will be about five times as much as 
 a hot-air stove that burns coal, and about ten times
 
 312 GAS STOVES. 
 
 as much as for coal, if the gas stove has a flue for 
 carrying off the products of the combustion.* Sir 
 John Robison, who did much to improve the gas 
 stoves, and particularly in applying them to the 
 purposes of cooking, in a paper read before the 
 Society of Arts for Scotland, after describing some 
 of his improvements, concluded by stating, " on the 
 whole, it may be assumed that this mode of heating 
 apartments is the most expensive, the least efficient, 
 and, excepting that by Joyce's charcoal stove, the 
 most insalubrious that can be resorted to." f 
 
 Since the early editions of this work were writ- 
 ten, an improved method of burning gas, where 
 heat and not light is required, has been introduced. 
 It consists in mixing atmospheric air with the gas 
 at some distance before it reaches the actual] place 
 of combustion. The quantity of air thus mixed 
 is about twelve measures of air to one of gas, and 
 by this means the expenditure of gas is reduced 
 one-half when the same effect is produced. (See 
 Art. 66, ante.) Scarcely any light is produced 
 when gas is burnt in this way , but where heat 
 only without light is required, the saving is very 
 considerable, the cost of gas being then about three 
 times the cost of coal. J 
 
 * See Art. 66, ante. 
 
 f Mechanics' Magazine, vol. xxxii., p. 292. 
 
 J It may be doubted whether the most economical method 
 of burning gas has yet been practised. The burning of 
 " atmospheric gas " in the Bunsen burner will probably be 
 further improved if the true principles of combustion be 
 studied. There can be no true and perfect combustion until 
 the gaseous products attain a temperature of between 800 
 and 900 of Fahrenheit (Art. 391 et seq.). If this heat, or 
 any considerable portion of it, could be communicated to the 
 atmospheric air, before it was mixed with the carburetted 
 hydrogen, there is every reason to suppose greatly increased 
 economy would be the result. The vast economy by the 
 use of the " hot blast," in the manufacture of iron is a well 
 known scientific fact: and further that the nearer the tern-
 
 JOYCE'S STOVES. 313 
 
 (307.) The stove invented by Mr. Joyce, for 
 burning charcoal, has been so universally admitted 
 as too unwholesome for use, that it would be 
 almost unnecessary to describe it, were it not for 
 the vast interest it excited on its first announcement 
 to the public. The stove consists of a thin metal 
 case, generally in the form of an urn or vase. 
 Through the bottom of this, there is a small pipe 
 which rises for two or three inches into the body 
 of the stove, and terminates about the centre in a 
 conical-shaped funnel, closed at the top, and 
 pierced full of holes. This pipe conveys air to 
 the fuel; and at the top of the stove there is a 
 valve or regulator, by which the rate of combustion 
 can be controlled ; for no more air will enter the 
 lower pipe than is sufficient to replace the volume 
 of gas given off from the valve at the top of the 
 stove. A small quantity of ignited charcoal being 
 placed in the stove, the remaining space is filled up 
 with charcoal not ignited; and the combustion is 
 slowly carried on by the air, which enters at the 
 lower pipe, and can be continued for a vast number 
 of hours without any attention. The whole of the 
 charcoal is converted into carbonic acid gas, the 
 effects of which are fatal to animal life. Little or 
 
 perature of the air can be raised to the point of complete 
 combustion (800 or 900) the greater the economy that 
 results from the operation. There is but little doubt that if 
 the air admitted to the Bunsen burner could be heated to 
 400 or 500 Fahrenheit before it entered into combination 
 with the carburetted hydrogen gas in the Bunsen burner, a 
 greatly increased economy would be the result. It is by no 
 means easy to effect this process of extrinsically heating the 
 air to any considerable extent, as it involves many difficulties 
 of a practical character (see Art. 217, &c.); but it is pro- 
 bable that any considerable improvement in the combustion 
 of gas may be looked for in this direction, if greater economy 
 is to be obtained, than that which results from the present 
 Bunsen burner, and the employment of the "atmospheric 
 gas."
 
 314 . JOYCE'S STOVES. 
 
 no smell is emitted by these stoves, the charcoal 
 being deprived of its usual pungent quality by 
 reburning it thoroughly in a close oven, and 
 quenching it while hot with an alkaline solution. 
 Independent of all other considerations, these stoves 
 are a most expensive mode of producing heat, 
 owing to the high price which charcoal always 
 bears in this country. 
 
 These stoves are remarkable chiefly for the 
 extraordinary interest they excited on their first 
 introduction to public notice. Before the speci- 
 fication for the patent was enrolled, one of these 
 stoves was publicly exhibited for several weeks ; 
 and probably no invention ever excited so much 
 attention in so short a time ; as the nature of the 
 fuel and plan of combustion were strictly kept 
 secret, and it was supposed a new era in the pro- 
 duction of artificial heat was about 'to commence. 
 No sooner did the stoves come into use, however, 
 than their deleterious effects were apparent. 
 Several persons were suffocated by using them ; 
 and the high anticipations which at first were 
 entertained of them were quickly dissipated, and 
 their use reduced within very narrow limits. 
 
 (308.) An immense number of stoves have been 
 brought before the public during the last few years, 
 of which the novelty consists in nothing but their 
 names. To describe them would be useless. Like 
 other ephemeral productions they will mostly 
 sink into oblivion, and probably be succeeded by 
 others as devoid of originality. There is still room, 
 however, for great improvements in the production 
 of stove heat ; but, until the salubrity of the open 
 firegrate can be combined with the greater economy 
 of the close stove, there does not appear much 
 probability of satisfying the required conditions, 
 as all which have hitherto been invented are 
 deficient in one or other of these particulars.
 
 THE BEAUMONT STOVE. 315 
 
 (309.) The same objections also, to a greater or 
 less extent, apply to all the methods of heating by 
 flues. The extremely unequal temperature of the 
 flues causes an insurmountable objection to their 
 general adoption, even if their great expense and 
 difficulty of adaptation to dwelling-houses or pub- 
 lic buildings did not operate against them. One 
 of the best systems of flues was proposed a few 
 years since, by Mr. Alfred Beaumont, in which 
 the principal novelty consisted in the furnaces 
 being built above the flue and having a down- 
 ward draught. By this means the smoke from the 
 fire was nearly or quite consumed, and a very great 
 evil of common flues thereby prevented, as the sur- 
 face of the flues being by this means free from soot, 
 which is a non-conductor of heat, a more free distri- 
 bution of heat took place than by the old flues, and 
 the fire was also much more under control. The 
 principle, already described, for downward draughts 
 applies equally to this plan. The furnace (in some 
 cases) was merely a circular hole sunk in the floor, 
 about two or three feet deep. The bottom, when in 
 use, was a solid plate ; which was movable, to take 
 away the ashes. About three inches from the 
 bottom there was an entrance into the flue; 
 through this the flame and the products of com- 
 bustion passed to the flues, and the fire being 
 always bright at the bottom, the combustible 
 gases from the fresh fuel, by passing through this, 
 were converted into other products, which did not 
 deposit smoke. In other cases, a stove made of 
 fireclay was raised on the floor; and the flame 
 and heated gases passed into the flues, which 
 formed the stone flooring of the room to be heated. 
 In all these cases the principle was the same ; 
 and several public buildings were heated on this 
 plan,which is probably the best of any system of flues. 
 
 The Palmaise system of heating was, a few
 
 316 THE PALMAISE SYSTEM. 
 
 years since, a great favourite with some persons 
 who anticipated from it results which a very 
 slight acquaintance with true science would have 
 shown to be utterly fallacious. This plan was in 
 reality nothing more than the old mode of flue- 
 heating, with a very slight modification in the 
 form and construction of the furnace. The plan 
 is now so completely abandoned, that it hardly 
 merits more than a very casual description. The 
 furnace was merely a plain square or oblong box 
 of firebrick, with a strong cast-iron plate forming 
 the entire top ; and beyond this were the usual 
 flues, such as were ordinarily used in the old plan 
 of heating greenhouses. The only novelty, there- 
 fore, consisted in using a cast-iron plate to cover 
 the top of the furnace ; and this plate becoming 
 intensely heated, the air was brought in a con- 
 tinued stream over it, thus imbibing heat in its 
 passage into the room or building to be heated. 
 It is useless to point out the defects of this plan ; 
 they were numerous and palpable. It combined 
 all the defects of the old flue system, added to 
 those of the cockle stove, and others peculiar to 
 itself, arising from its primary construction, which 
 rendered it so liable to accident and derangement 
 that it was found utterly valueless for any prac- 
 tical purpose. Its name was derived from a small 
 town in Scotland, where this particular form of 
 flue-heating was first used; and its supposed 
 cheapness of construction obtained for it at first 
 many advocates, who, however, shortly found 
 that its want of durability rendered it unsuitable 
 for general use, while in other respects it was 
 decidedly inferior to the old system of heating by 
 flues. During its short-lived popularity it, like 
 many preceding inventions, was supposed to be 
 the perfection of economy and efficiency, which 
 belief was soon dissipated when the apparatus was 
 applied to general use.
 
 317 
 
 CHAPTER III. 
 
 ON THE CHANGES PRODUCED IN ATMOSPHERIC AIR, 
 BY HEAT, COMBUSTION, AND RESPIRATION. 
 
 Necessity for Ventilation Constitution of the Atmosphere 
 Ventilation first proposed in Sixteenth Century Subse- 
 quent Inventions for Ventilating Effects of Contaminated 
 Air on the Human Frame Effects of Climate on Health 
 and Longevity Cause of Miasmata Effects of Excessive 
 Moisture and Excessive Dryness of the Atmosphere Ke- 
 spiration: its Products and Effects Impure Air Carbonic 
 Acid Gas Vapour from the Body Effect of Diminished 
 Pressure Electric Condition of the Air Production of 
 Ozone Decomposition of Extraneous Matter in the Air 
 Effects of Hydrogen, Carburetted Hydrogen, and Carbonic 
 Oxide Quantity of Air required for Ventilation Impor- 
 tance of the Air to Animal and Vegetable Life. 
 
 (310.) PROBABLY no subject connected with the 
 health and vigour of the mind and body deserves 
 more and receives less attention than the condition 
 of the internal atmosphere of our houses and 
 apartments. Attempts are indeed occasionally 
 made to introduce some system of ventilation in 
 public buildings, but they are far more frequently 
 unsuccessful than otherwise, in consequence of the 
 arrangements not having formed any part of the 
 original plan, and being mere additions of a very 
 imperfect character. In private dwellings, ventila- 
 tion appears never to be considered as at all 
 necessary ; but if the contaminations and impuri- 
 ties that are frequently contained in the air, which
 
 318 VENTILATION. 
 
 forms the pabulum vitce of human beings, could be 
 seen by the eye, in the same way as contaminations 
 or impurities in ordinary alimentary food, the evil 
 would not be endured for even the smallest period 
 of time. 
 
 (311.) The real constitution of the atmosphere 
 has been known, comparatively, but a short time ; 
 the experiments of Priestley, Scheele, and Lavoisier, 
 in the latter part of the last century, having first 
 made known its true nature. More than twenty 
 centuries previously, however, Hippocrates wrote 
 so justly on the immense importance of breathing 
 pure air, of the great influence which it exerted on 
 health and longevity, and laid down such excellent 
 rules upon the subject, that few writers, even of 
 the present day, appear to have more correct notions 
 of the vast and important effects which the air 
 produces on the human frame, than were possessed 
 by this great father of medicine.* Agricola, how- 
 ever, in the sixteenth century, appears to have been 
 the first writer on artificial ventilation ; he having 
 recommended the ventilation of mines by producing 
 a current of air by fire, much in the same manner 
 as has been practised in the ordinary ventilation of 
 mines ever since his time. Nothing of any consider- 
 able importance occurred after this, until Desaguliers 
 in 1727 proposed a ventilating pump,f which some 
 years afterwards Dr. Hales J applied in a better 
 manner, and to a considerable extent, in the 
 ventilation of ships, hospitals, prisons, and other 
 places, which were found to be unwholesome by 
 confined air. In 1734, Desaguliers invented a 
 centrifugal ventilating wheel, or fan ; and in 
 1739 Button proposed a plan of ventilating ships, 
 
 * " Hippocrates," lib. " De Aere, Aquis, et Locis." 
 f Philosophical Transactions, 1727, vol. xxxv., p. 353. 
 t Ibid., 1743 ; and Dr. Hales " On Ventilators." London, 
 1743.
 
 DELETERIOUS EFFECTS OF IMPURE AIR. 319 
 
 which consisted in drawing the air required for 
 the combustion of the fuel in the ship's cooking 
 apparatus through pipes leading from the hold, 
 and other confined places,* precisely on the same 
 plan that has been repeatedly adopted since his 
 time, and has also been applied (in the year 1836) 
 to the temporary Houses of Parliament. Since the 
 time of Hales, many plans have been proposed for 
 ventilating buildings, but they are mostly modifi- 
 cations of one or the other of the methods here 
 described ; and these methods, if properly applied, 
 are amply sufficient to accomplish all that is 
 required. 
 
 (312.) Few persons have any notion of the vast 
 consequences which result from impure air ; and 
 how seriously the duration of human life is affected 
 by want of proper attention to this important sub- 
 ject. Dr. James Johnsou,f speaking of the effects 
 of impure air, says, " that ague and fever, two of 
 the most prominent features of the malarious in- 
 fluence, are as a drop of water in the ocean, when 
 compared with the other less obtrusive but more 
 dangerous maladies that silently disorganise the 
 vital structure of the human fabric, under the 
 influence of this deleterious and invisible poison ; " 
 and experience proves that multitudes shorten 
 their lives by breathing impure air, and many 
 more lay the foundation of diseases, accompanied 
 by years of pain and sorrow, by neglecting to 
 avail themselves of the bountiful provision of 
 nature, which spontaneously affords to all who 
 choose it, an unlimited supply of this important 
 element, and requiring merely an unrestricted and 
 free passage to diffuse itself abundantly in every 
 direction. 
 
 * Philosophical Transactions, 1742, vol. xlii., p. 42. 
 | " Diary of a Philosopher."
 
 320 DELETERIOUS EFFECTS 
 
 (313.) The powerful effects which are produced 
 on the animal functions by certain deleterious gases 
 are very imperfectly known, as they are generally 
 found in so diluted a state as to render their action 
 slow and almost imperceptible. But to be aware 
 of their real nature and influence, we should see 
 their effects in a more concentrated form. Dr. 
 Christison, in his work on Poisons, quotes from 
 Halle a description of the effects of the gases 
 from the fosse d'Aisance of Paris on those who 
 inhale them; and Dr. Kay gives the following 
 account of them in his work on Asphyxia.* 
 " Often the individual exposed to them perishes 
 in a moment, his head and arms falling, and the 
 trunk being doubled up from the instantaneous loss 
 of muscular power. If death does not immediately 
 occur, the victim, when he recovers from the first 
 effects of this exposure, is affected with pains in 
 the head, nausea, fainting fits, severe pains in the 
 stomach and limbs, and constriction of the throat. 
 Sometimes he utters involuntary cries, or lapses 
 into delirium, accompanied with the sardonic- 
 laugh and convulsions, or tetanus ensues. The 
 face is pale ; the pupil dilated and motionless ; 
 the mouth filled with a white or bloody froth ; 
 respiration convulsive ; the pulsation of the heart 
 irregular ; the skin cold ; until at length complete 
 asphyxia and death terminate the scene of suffer- 
 ing." The gases which produce these effects are 
 combinations of ammonia, sulphuretted hydrogen, 
 and nitrogen ; and all these gases are occasionally 
 to be found in the contaminated air of close ill- 
 ventilated rooms, though of course in smaller 
 quantities. The effects of climate are of the same 
 kind. The impurity of the air in certain localities 
 produces the most frightful results. Cretinism, 
 
 * Dr. Kay's "Physiology and Treatment of Asphyxia," 
 p. 326.
 
 OF IMPURE AIR. 321 
 
 although its cause is not positively ascertained, is 
 ascribed by medical writers to confined air and 
 other agencies ;* and so frightful and revolting is 
 this state of degeneracy of both body and mind, 
 that Dr. James Johnson's description of the disease 
 fully realises the character which he has given it 
 that " Goitre (or the enlarged neck), on such a 
 scale as we see in the Yallais is bad enough ; but 
 Cretinism is a cure for the pride of man, and may 
 here be studied by the philosopher and physician 
 on a large scale, and in its most frightful colours."f 
 The picture is almost too frightful to copy, and is 
 only second to his description of another scourge, 
 Pellagra, arising from the same cause, which afflicts 
 nearly one-seventh of the inhabitants of the Loin- 
 bardo- Venetian Plains,J and the wretched victims 
 of which rot away in a state so painful and disgust- 
 ing, that the description absolutely sickens the 
 reader, and prepares him for the announcement 
 that multitudes of these wretched beings end their 
 state of hopeless misery by committing suicide, 
 which they generally do by drowning. 
 
 (314.) The statistical reports laid before Parlia- 
 ment by the War Office, on the sickness and mor- 
 tality of the troops of the United Kingdom stationed 
 in different parts of the world, prove most clearly 
 the immense effect upon human life produced by 
 small and almost inappreciable differences in the 
 quality of the atmosphere. For on the same class 
 of persons performing the same duties, and placed 
 as nearly as possible in the same circumstances, the 
 average mortality varies in different parts of the 
 world from 1-37 per cent, per annum to 66 '83 per 
 cent, per annum ; or the mortality is nearly forty- 
 
 * Dr. Hawkins's " Medical Statistics," p. 198. 
 t Dr. James Johnson's " Change of Air ; or, the Pursuit 
 of Health," &c., p. 56. 
 J Ibid., p. 75. 
 
 Y
 
 322 
 
 DELETERIOUS EFFECTS 
 
 nine times as great in some localities as in others.* 
 The morbific influence of certain gaseous emanations 
 from the earth, in various parts of the globe, is well 
 known. " The banks of the Nile about Sennaar," 
 Fays Bruce, " resemble the pleasantest part of Hol- 
 land in the summer season ; but soon after, when the 
 rains cease, and the sun exerts his utmost influence, 
 the dora begins to ripen, the leaves to turn yellow 
 and to rot, the lakes to putrify, smell, and be full 
 of vermin, and all .this beauty suddenly disappears 
 bare-scorched Nubia returns ; and all its terrors 
 of poisonous winds and moving sands, glowing 
 and ventilated with sultry blasts, which are fol- 
 lowed by a troop of terrible attendants epilepsies, 
 
 * These reports present the result of twenty years' obser- 
 vation, and were laid before Parliament in the years 1838, 
 1839, and 1840, being respectively for " The West Indies," 
 "The United Kingdom, the Mediterranean, and British 
 America ; " and " Western Africa, the Mauritius, &c." The 
 following list is extracted from these reports, and gives the 
 mortality per cent, per annum, among white troops only, ex- 
 clusive of the native troops : 
 
 British Guiana 
 
 Per Cent. 
 
 . 8-4 
 
 Sierra Leone 
 
 Per Cent. 
 
 48-3 
 
 Trinidad 
 
 .10-63 
 
 Cape Coast Castle 
 
 66-83 
 
 Tobago. 
 
 .15-28 
 
 St. Helena . 
 
 3-3 
 
 Grenada 
 
 . 6-18 
 
 Cape of Good Hope 
 
 1-37 
 
 St. Vincent's 
 
 . 5-49 
 
 Cape of Good Hope, 
 
 
 Barbadoes . 
 
 . 5-85 
 
 Frontiers. 
 
 0-98 
 
 St. Lucia . 
 
 .12-28 
 
 Mauritius . 
 
 2-74 
 
 Dominica 
 
 .13-74 
 
 Ionian Islands 
 
 2-52 
 
 Antigua, &c. 
 
 . 4-06 
 
 New Brunswick ,, 
 
 1-47 
 
 St. Kitts 
 
 . 7-10 
 
 United Kingdom 
 
 1-4 
 
 Jamaica 
 
 .12-13 
 
 Canada . ; 
 
 1-61 
 
 These interesting reports give many particulars relating to 
 the climate of each place. The principal characteristic of 
 Sierra Leone and Cape Coast Castle is the extreme humidity 
 of the atmosphere. In the year 1828 upwards of 313 inches 
 of rain fell in three months at the former place ; and in the 
 following year the quantity was 144^ inches in six months ; 
 but owing to the registers being imperfect, the annual mean 
 quantity has not been exactly ascertained.
 
 OF IMPURE AIR. 323 
 
 apoplexies, violent fevers, obstinate agues. and linger- 
 ing and painful dysenteries, still more obstinate and 
 mortal."* So pestilential is this spot, that "no 
 horse, mule, ass, or any beast of burden will breed 
 or even live at Sennaar, or many miles round it. 
 Poultry does not live there. Neither dog nor cat, 
 sheep nor bullock, can be preserved a season there. 
 They must all go every half-year to the sands."f 
 Dr. James Johnson's graphic account of the Cam- 
 pagna di EomaJ and its poisonous exhalations, 
 and Signor Gaetano Giorgini's account of some 
 other pestiferous localities, give a sufficient idea 
 of the effects of apparently small corruptions of the 
 atmosphere. And these accounts, to which vast 
 numbers of others might be added, all prove how 
 very small an alteration in the constitution of the 
 atmosphere materially affects the health of all who 
 expose themselves to its influence. Professor Daniell 
 has lately ascertained some facts, which render it 
 probable that many of the localities desolated by 
 malaria owe their unwholesomeness to small quan- 
 tities of sulphuretted hydrogen, produced by decom- 
 position of the sulphates contained in sea-water 
 by decayed vegetable matter. || 
 
 (315.) We have seen the effect of climate on the 
 military, by the returns from the War Office, already 
 alluded to. The duration of life among the inhabi- 
 tants of different countries is not less remarkable. 
 The average deaths annually, throughout England 
 and Wales, are in the proportion of one for every 
 
 * Bruce's " Travels," vol. vi., p. 387. 
 
 f Hid., vol. vi., p. 381. 
 
 + Dr. James Johnson's "Change of Air," &c., pp. 117 and 
 219. 
 
 Ann. de Chimie, vol. xxix. ; also, London and Edinburgh 
 Philosophical Magazine, vol. xix., p. 15. 
 
 || Daniell " On Sulphuretted Hydrogen," &c. ; London and 
 Edinburgh Philosophical Magazine, vol. xix., pp. 1-19. 
 
 Y 2
 
 324 
 
 DELETERIOUS EFFECTS 
 
 sixty inhabitants ; and they vary in every country,* 
 being nearly three times more numerous in some 
 parts of Europe than in England. Yery remarkable 
 differences occur also in localities differing but very 
 little from each other. M. Quetelet, in his celebrated 
 work on Man, states, in reference to the effects of 
 climate on the duration of life, that the deaths 
 annually in the different localities are as follow : 
 
 Department de 1'Orne . .1 death in every 52 -4 inhabitants. 
 
 de Finisterre 1 30 '4 ., 
 
 Province of Namur . . 1 51 '8 
 
 of Zealand 1 . 2R - 
 
 (Netherlands) $ X 
 
 This great excess of mortality in the last-named 
 place, M. Quetelet attributes to the extreme and 
 constant humidity of the atmosphere, which pro- 
 duces an immense number of fevers and other 
 maladies.f The observations of M. Bossi also 
 
 * Dr. Hawkin's in his "Medical Statistics," pp. 30-74, 
 gives the following average of the annual deaths in different 
 localities : 
 
 England 
 
 1 in 60 
 
 Leghorn 
 
 1 in 35 
 
 Pays de Vaud 
 
 1 in 49 
 
 London 
 
 1 in 40 
 
 Sweden . . 
 
 1 in 48 
 
 Manchester . 
 
 1 in 74 
 
 Holland. 
 
 1 in 48 
 
 Birmingham . 
 
 1 in 43 
 
 France . . , . 
 
 1 in 40 
 
 Paris and Lyons . 
 
 1 in 32 
 
 Prussia . 
 
 1 in 35 
 
 Strasburg and Bar- 
 
 
 Kingdom of Naples 
 
 1 in 35 
 
 celona . 
 
 1 in 32 
 
 Wurtemburg . 
 
 1 in 33 
 
 Berlin . 
 
 1 in 34 
 
 Eussia . 
 
 1 in 41 
 
 Madrid. . . 
 
 1 in 29 
 
 Venetian Provinces 
 
 1 in 28 
 
 Rome . 
 
 1 in 25 
 
 United States . 
 
 1 in 40 
 
 Amsterdam . 
 
 1 in 24 
 
 Nice . 
 
 1 in 31 
 
 Vienna . 
 
 1 in 221 
 
 Naples .' . 
 
 1 in 28 
 
 
 
 , This average for England, which is stated to extend to the 
 year 1821, does not quite agree with more recent calculations, 
 founded on the Eeport of the Registrar-General ; and the 
 difference probably arises from some variations in the mode 
 of taking the averages. 
 
 | Quetelet " Sur 1'Homme, et le Developpement de ses 
 Facultes," &c. ; and London Statistical Journal, vol. i., p. 176.
 
 OF IMPURE AIE. 325 
 
 confirm this opinion ; for, by dividing the Departe- 
 ment de rAinmto four districts, he found the deaths 
 annually to be as follow : * 
 
 In the Mountainous Parts 1 death in every 38 3 inhabitants. 
 On the Banks of the Kivers 1 26-6 
 
 On the level Parts sown } , 0,1 
 
 with Corn .... 5 1 
 In Parts interspersed with ) , on Q 
 
 Ponds and Marshes . ( J 
 
 K 
 
 And it can be shown that, in England also, the rate 
 of mortality follows nearly the same ratio, from the 
 same causes :f and in the reports on the mortality 
 among troops already alluded to, the excessive 
 unwholesomeness of some particular districts is 
 attributed entirely to the excessive moisture of the 
 atmosphere, particularly when accompanied by high 
 temperature. All physiologists have agreed as to 
 the injurious effects of a heated atmosphere saturated 
 with moisture. Hippocrates, by a comparison of 
 the prevailing diseases with the state of the weather, 
 and particularly as respected the moisture of the 
 air, drew conclusions which the observations of 
 succeeding ages have fully confirmed. Excessive 
 dry ness, however, not less than an extraordinary 
 degree of moisture, equally destroys the salubrity 
 of the air ; though the diseases produced by these 
 opposite states are, as might be imagined, of a very 
 different character.^ The monsoon, or rainy season 
 of India, the campsin, or southerly wind of Egypt, 
 and the simoon, or hot wind of the Asiatic continent, 
 
 * London Statistical Journal, vol. i., p. 177. 
 
 f Dr. Buckland, at a public meeting (March, 1844) stated 
 that in the parish of St. Margaret's, Leicester, containing 
 22,000 inhabitants, one part was effectually drained, some 
 parts partially so, and others not at all. In the latter the 
 average duration of life is 13 J years, while in those parts 
 partially drained the average duration is 22^ years. 
 
 J Dr. Arbuthnot, " On the Effects of Air on Human Bodies ; " 
 and Dr. Paris, " Pharmacologia," vol. i., p. 197, 325, &c.
 
 326 DEW-POINT OF THE AIR. 
 
 more rapidly destructive than either of the others, 
 and which sometimes strikes down its victims with 
 instant death, are some among the numerous 
 instances which might be adduced to prove the 
 effects of various excessive degrees of heat, moisture, 
 and dryness of the air, upon the animal system. 
 
 (316.) The effects produced on the hygrometric 
 condition of the air by various modes of artificial 
 heat are of much importance. Dr. Ure has described* 
 the result of his examination into the effects produced 
 upon a great number of the gentlemen in the Long 
 Room of the Custom House, London, arising from 
 the use of the powerful hot-air or cockle stoves, 
 used for heating that establishment. He_found 
 they were all affected with the same sensations and 
 complaints ; tension or fulness of the head, flushings 
 of the countenance, frequent confusion of ideas, 
 remarkable coldness and languor in their extremities, 
 feeble pulse, and other sensations of an unpleasant 
 character. The stoves, he found, were frequently 
 red hot, and the air passing over them was some- 
 times heated to 110, and was thereby rendered 
 intensely dry. The animal and vegetable matters 
 floating in the air were decomposed, and imparted 
 a disagreeable smell to the atmosphere. This 
 apparatus was found to be so pernicious that it was 
 removed, and a different mode of heating adopted. 
 But these effects, described by Dr. Ure, are by no 
 means uncommon. The author examined a school 
 heated in the same manner ; and it was found to 
 be so pernicious to the health of the children, that 
 they occasionally dropped off their seats in lainiiag 
 fits^ and when this did not occur, they suffered 
 so much by the debilitating effects of the intensely 
 heated atmosphere, that they constantly required 
 the relief of going for a few minutes into the fresh 
 air. The usher of the school, a strong, healthy 
 
 * Philosophical Transactions, June, 1836.
 
 DEW-POINT OF THE AIR. 327 
 
 young man, also suffered in the same way ; and on 
 one occasion he fainted away in the school-room, and 
 it was with difficulty that animation was restored. 
 These pernicious effects, though generally in a some- 
 what less degree, always result from the use of 
 intensely heated metallic surfaces. They are, how- 
 ever, much modified by tempering the air by the 
 evaporation of water. In Russia and Sweden, the 
 Apennines, and other places, where close stoves 
 are used, an earthern vessel of water is always 
 placed on the stove for this purpose, and greatly 
 mitigates the oppressive effects which would other- 
 wise be experienced. The desiccating power of 
 the air increases with its temperature to a very 
 great extent. Air at 32 contains, when saturated 
 with moisture, T^th of its weight of water ; at 59 
 it contains ^ih ; at 86 it contains T \yth ; its capacity 
 for moisture being doubled by each increase of 27 
 of Fahrenheit.* But when air is heated artificially, 
 without being in contact with water, it is prevented 
 from acquiring this additional quantity of vapour, 
 and it then possesses a harsh and arid feel, the 
 effects of which we have already seen. This extreme 
 aridity of the air causes it rapidly to absorb moisture 
 from the skin and lungs of persons exposed to its 
 influence ; and the evaporation, by its refrigerating 
 effect, contracts the blood-vessels at the surface, 
 while other parts, not being exposed to this influence, 
 become in consequence surcharged with the fluids 
 which are repelled from the extremities.f 
 
 (317.) A comparison of the dew-point of the air, 
 made at those seasons of the year which are the 
 most salubrious and agreeable, shows that, in rooms 
 artificially heated, the most healthy state of the 
 atmosphere will be obtained when the dew-point 
 
 * Leslie " On Heat and Moisture," p. 123. 
 t Ure " On Ventilation," &c. ; Philosophical Transactions, 
 1836.
 
 328 DEW-POINT OP THE AIR. 
 
 of the air is not less than 10, nor more than 20 
 Fahrenheit, lower than the temperature of the room. 
 When these limits are exceeded, the air will be 
 either too dry or too damp for healthy and agree- 
 able respiration ; and attention to the hygrometric 
 condition of the air would, perhaps, tend more to 
 the amelioration of that numerous class of pulmonary 
 complaints which so peculiarly distinguish the in- 
 habitants of this country, than any other remedial 
 measure. 
 
 The quantity of vapour contained in the free 
 external atmosphere, is found to average throughout 
 the year 82 per cent, of the total quantity it can 
 contain. This, therefore, should be the quantity 
 that we should endeavour to maintain in artificially 
 heated rooms. In the extensive experiments made 
 by Mr. Goldsworthy Gurney in heating the House 
 of Lords,* it was found that when the temperature 
 of the House was 64 Fahrenheit, the most agree- 
 able condition of the air was obtained when the 
 degree of moisture coincided with that shown by 
 Mason's Wet and Dry Bulb Hygrometer, when the 
 difference between the two bulbs varied from 3 to 
 9 degrees. This reading of the hygrometer would 
 therefore agree with a dew-point varying from 6 to 
 16 degrees below the temperature of the room.f 
 In large assemblages of people, such as the Houses 
 of Parliament, the Courts of Law, and other places 
 occupied for many hours consecutively, it is most 
 important that the dew-point of the air should be 
 properly regulated, as it exercises a most serious 
 
 * Parliamentary Report, August, 1857, " On Warming and 
 Ventilating Dwellings," p. 129. 
 
 | See Glaisher's flygrometric Tables. Also Quarterly 
 Journal of Science (1820), vol. viii., p. 298, for Professor 
 Daniell's account of his new Hygrometer, and the method of 
 calculating from it the quantity of vapour in the air, corre- 
 sponding with any given dew-point.
 
 EFFECTS OF RESPIRATION. 329 
 
 influence on the mental activity as well as the bodily 
 powers of those exposed to its influence. Old 
 people, and those of delicate constitution or impaired 
 health, cannot bear so low a dew-point of the air 
 that is, air with so large a difference between the 
 actual temperature and the dew-point as those 
 who are younger and more robust. When the 
 dew-point is low, the air carries away both from 
 the lungs and from the skin, a larger portion of 
 moisture than is agreeable or healthy for an old 
 person, or one in infirm health. For this reason 
 a higher dew-point would probably be required in 
 the House of Lords than in the House of Commons ; 
 and hence the rather high range of the dew-point 
 noted in the House of Lords by Mr. Goldsworthy 
 Gurney, in his experiments. (Art. 330.) 
 
 (318.) The decreased consumption of oxygen, 
 when a highly heated atmosphere is breathed, is 
 also another circumstance which exerts considerable 
 influence on health. The experiments of Seguin, 
 Crawford, and De la Roche,* on this subject, show 
 that, under these circumstances, the blood is not so 
 thoroughly decarbonized as when a colder atmo- 
 sphere is breathed ; and this, as we shall presently 
 have occasion to show, quickly operates on the 
 nervous system, affecting the animal functions as 
 well as the mental faculties. In winter, fully one- 
 eighth more oxygen is consumed, than in the 
 summer during the same period.f 
 
 (319.) The contamination of the air, produced 
 by respiration and by artificial heat and com- 
 bustion is very considerable. Wide-spreading as 
 are the consequences of the malarious influences 
 of climate, the effects produced by the contamina- 
 tions of the air, by the causes now to be described, 
 are scarcely less extensive, though less capable of 
 
 * Murray's " Chemistry," vol. iv., p. 480. 
 t Liebig's " Animal Chemistry," pp. 16, 17.
 
 330 EFFECTS OF RESPIRATION. 
 
 being numerically determined; and as the pro- 
 gress of civilization causes larger numbers of 
 persons to congregate together, the necessity for 
 attending to these effects becomes continually of 
 greater importance. 
 
 (320.) Respiration is a never-ceasing and most 
 extensive source of contamination of the air, and 
 the theory of its operation has long engaged the 
 attention and divided the opinions of physiologists. 
 The opinion held by some of the most eminent is 
 that inspiration is involuntary, being caused by the 
 pressure of the air on the lungs ; while expiration 
 is the effort of the lungs to discharge the air after 
 it has been changed in its nature, and become hurt- 
 ful to them.* The effects produced by breathing 
 over again a portion of this mephitic air depends 
 upon the constitution of the individual who is ex- 
 posed to its influence, and upon the amount of the 
 contamination which the air has sustained. Con- 
 siderable differences exist in the experiments which 
 have been made upon the changes produced by respi- 
 ration on atmospheric air : but this is unavoidable, 
 on account of the very different capacity of the 
 lungs of different individuals, and also in conse- 
 quence of the mephitis itself differing in the same 
 individual during the various stages of digestion, 
 exertion, or repose, and according to the nature of 
 the ingesta which he receives. 
 
 The contamination of the air is produced not 
 only by respiration but by animal exhalations, which 
 are given off by both the lungs and the skin. 
 That which is produced by respiration is chiefly 
 by the formation of carbonic acid gas, and by the 
 vapour which is exhaled from the lungs. The 
 proportion of both the vapour and the carbonic 
 acid gas has been variously estimated by different 
 
 * Blumenbach's "Institutes of Physiology," by Eliotson, 
 p. 84.
 
 EFFECTS OF RESPIRATION. 331 
 
 experimentalists. Dr. Prout* has collected together 
 the results of the different experimenters on the 
 quantity of carbonic acid given off in respiration. 
 His own experiments give a mean of about three 
 and a half per cent, as the quantity expired by him- 
 self, and four and a half per cent, when his experi- 
 ments were made on another person. Sir Humphry 
 Davy's estimate is about four per cent. ; Menzies, 
 five per cent. ; Mr. Murray, six per cent. ; Allen and 
 Pepys, eight per cent. ; Dr. Fife, eight and a half 
 per cent. ; Goodwin, and also M. Jurin, ten per cent. 
 But Dr. Prout has shown that the quantity varies 
 greatly at different periods of the day, and that the 
 maximum quantity is given off about noon, up to 
 which period it gradually increases from the begin- 
 ning of twilight ; and after noon it as gradually de- 
 creases till evening, and is at its minimum during 
 the night.f Some recent and extensive experiments 
 have confirmed these results generally; but it 
 appears the times of maxima and minima depend 
 principally on the state of digestion and the periods 
 of taking food.J 
 
 The quantity of vapour given off from the lungs 
 has also been very variously estimated. Dr. Menzies 
 calculated it at six ounces; Mr. Abernethy, nine 
 ounces; Sanctorius, eight ounces; and Dr. Hales, 
 twenty ounces, in twenty-four hours ; and the 
 average is supposed to be about three grains per 
 minute. The amount of vapour given off from the 
 skin was found by Thenard to vary from nine to 
 twenty-six grains per minute. Keil found it to 
 amount to thirty-one ounces in twenty-four hours, 
 or ten and a half grains per minute. Seguin ascer- 
 
 * Annals of Philosophy, vol. ii., p. 336. 
 t Ibid., p. 330. 
 
 J London and Edinburgh Philosophical Magazine, vol. xiv. 
 p. 401. 
 
 Dr. Paris's " Medical Chemistry," p. 316.
 
 332 EFFECTS OF GASES 
 
 tained that it varied from eight to twenty- four grains 
 per minute ; and it is generally considered that the 
 average quantity is about ten grains per minute, 
 which agrees with the experiments of Lavoisier. 
 
 (321.) It is also found that the quantity of 
 oxygen consumed in respiration varies with the 
 state of exertion or repose. Lavoisier found that by 
 a man, while engaged in strong muscular exertion, 
 compared with the same individual while in a 
 state of repose, the consumption of oxygen was as 
 32 to 14. It is also ascertained that the quantity 
 of oxygen consumed in respiration exceeds the 
 bulk of carbonic acid gas which is expired from 
 the lungs; the remainder unites with the hydrogen 
 derived from the food, and forms the vapour given 
 off from the lungs and skin : and these proportions 
 differ so greatly with the nature of the food, that 
 while some animals expire a quantity of carbonic 
 acid equal to that of the oxygen consumed, others 
 do not expire more than half as much carbonic 
 acid as the oxygen consumed would produce.* 
 
 (322.) Notwithstanding these differences of opi- 
 nion among physiologists respecting various points 
 connected with respiration, there are certain funda- 
 mental facts which are agreed upon, that we shall 
 find amply sufficient for the illustration of the subject 
 before us. 
 
 (323.) The quantity of air admitted into the 
 lungs varies in different individuals, and even in 
 the same individual at different times, being 
 greatly influenced, as already stated, by the 
 
 * Liebig's " Animal Chemistry," p. 26. The production 
 of carbonic acid gas by respiration is stated to be as follows : 
 By a man, 13 '9 ounces; by a horse, 97 '8 ounces; and by a 
 cow, 69-9 ounces in 24 hours. Dr. Carpenter states that air 
 once passed through the lungs contains 1*26 per cent, of 
 carbonic acid. For other changes produced in the blood by 
 respiration, see Liebig's "Animal Chemistry," pp. 12 and 
 272, &c.
 
 ON THE NERVOUS SYSTEM. 333 
 
 relative amount of exertion or repose. Some 
 experimentalists have estimated that as much 
 as 800 cubic inches of air enters the lungs per 
 minute ; but it is more generally supposed to be 
 about 330 cubic inches per minute under ordinary 
 circumstances : * and this air, after passing through 
 the lungs, returns charged with carbonic acid gas 
 and vapour of water, as already stated. 
 
 (324.) Whenever the same portion of air is 
 breathed a second time, a great sensation of un- 
 easiness is experienced. This arises from several 
 causes. The quantity of oxygen contained in the 
 air, when in its natural state, varies from 20 '58 to 
 21-12 per cent;f but it is found impossible to 
 separate the whole of this oxygen by respiration, 
 on account of the affinity which exists between 
 the gases ; and, however often the air is breathed, 
 only about one-half of this quantity of oxygen can 
 be separated from it. If, therefore, the process of 
 respiration consumes (in forming the carbonic acid 
 and the vapour) a quantity of oxygen, varying 
 from six to eight per cent., by merely passing the 
 air once into the lungs, it is evident that but very 
 little can be afterwards abstracted by any further 
 process of respiration .J Carbonic acid gas con- 
 tains its own volume of oxygen ; therefore, when 
 any deficiency of oxygen occurs, the proper quan- 
 
 * Menzies and Goodwyn estimate the quantity of air taken 
 into the lungs, at each inspiration, at 12 cubic inches ; Jurin, 
 at 20 ; Cuvier, at 16 or 17 ; Davy, at 15 ; and Thomson, at 33 
 (Dr. Kay, " On Asphyxia," p. 123). The number of inspi- 
 rations in a minute, Haller considers to be about 20 ; Men- 
 zies, 14 ; Davy, 26 or 27 ; Dr. Thompson, 19 ; and Majendie, 
 15. (Dr. Paris's " Medical Chemistry," p. 315.) 
 
 | Dalton " On the Atmosphere " : London and Edinburgh 
 Philosophical Magazine, vol. xii., p. 402. 
 
 J See the experiments of Messrs. Allen and Pepys, Philo- 
 sophical Transactions, 1808 ; and Nicholsons Journal, vol. xxii., 
 p. 204.
 
 334 EFFECTS OF GASES 
 
 tity of carbon cannot be given off from the lungs 
 a process which is absolutely indispensable for 
 the preservation of life. 
 
 (325.) The physiological effects of a deficiency 
 of oxygen are very remarkable. When the lungs 
 are not sufficiently supplied with oxygen, sangui- 
 fication ceases to be performed; and the arterial 
 blood retaining the dark colour of venous blood, 
 circulates in this state through the system. Bichat 
 proved by experiments,* that when venous or dark- 
 coloured blood is injected into the vessels of the 
 brain through the carotid artery, the functions of 
 the brain are immediately disturbed, and in a very 
 short time cease entirely ; the heart instantly loses 
 its motion, and death speedily follows. Bichat 
 considers the effect of the venous blood circulating 
 through the brain to be similar to the action of 
 a narcotic poison; and this takes place when the 
 air is impure, and does not perfectly oxygenate 
 the blood. When the lungs receive impure air, 
 imperfectly oxygenated blood is circulated through 
 the brain, producing a cessation of the functions of 
 that organ, by which respiration is immediately 
 affected, and the heart ultimately ceases to act. 
 Sir B. Brodie also found by experiments made with 
 various active poisons,f that when the action of 
 the brain is impeded by other causes than that 
 produced by the blood, a similar result obtains : for 
 the instant the brain loses its action, respiration 
 stops, the heart gradually fails of its power of con- 
 tracting and propelling forward the blood, and 
 death speedily ensues. But it has been found 
 that, after the brain has ceased to act, if an arti- 
 ficial rsepiration of pure air be produced, and con- 
 tinued for a short time, the functions of the brain 
 will be restored, and the animal ultimately recovers. 
 
 * Bichat " Recherches physiologiques sur la Vie et la Mort." 
 t Philosophical Transactions, 1811, pp. 36 and 178, et seq.
 
 ON THE NERVOUS SYSTEM. 335 
 
 (326.) The effects so speedily experienced by 
 some persons in close and ill-ventilated rooms 
 are by these experiments easily accounted for. 
 Headache is usually the first sensation of uneasi- 
 ness which is experienced; and the succeeding 
 symptoms of languor, uneasy respiration, faintness, 
 and syncope, are all clearly referrible to the same 
 cause as that which produced in Bichat's experi- 
 ments the cessation of the vital functions. These 
 effects always result from breathing air containing 
 any considerable quantity of carbonic acid gas.* 
 When the quantity of this gas is very considerable, 
 it produces such a painful irritation of the epi- 
 glottis, as immediately causes it to close spasmodi- 
 cally on the glottis, and thus prevents the entrance 
 of the gas into the lungs; but this also prevents 
 the entrance of the atmospheric air, and thus pro- 
 duces immediate suffocation. 
 
 (327.) Physiologists are divided in opinion as 
 to the precise nature of the action on the human 
 frame exerted by carbonic acid gas. Sir Humphry 
 Davy, Dr. Christison, Dr. Bird, and Dr. Paris, 
 appear to consider that it acts as a strong narcotic 
 poison. Dr. Thompson, and some others, entertain 
 a different opinion, and think it only acts on the 
 animal economy by preventing the proper quantity 
 of oxygen from entering the lungs, and thence 
 producing suffocation. 
 
 (328.) The greatest proportion of carbonic acid 
 gas which may be breathed with impunity has 
 not been exactly determined, and opinions re- 
 specting it are very various.f But it is evident 
 
 * Keport of the British Scientific Association, 1839, p. 108. 
 Experiments by Coathupe. 
 
 f In the Parliamentary Report, August, 1857, on Warming 
 and Ventilating Dwellings, p. 127, it is stated that 1 per cent, 
 of carbonic oxide is fatal to animal life, while 5 per cent, of 
 carbonic acid may be breathed for a short time without 
 fatal consequences.
 
 336 QUANTITY OF VAPOUR 
 
 that a given quantity of the gas produced by re- 
 spiration or combustion will reduce the propor- 
 tion of oxygen in atmospheric air to a much 
 greater extent than the same quantity of carbonic 
 acid gas added by simple mechanical mixture. 
 For, in the formation of a given quantity of car- 
 bonic acid gas, either by combustion or respiration, 
 exactly the like volume of oxygen is consumed 
 carbonic acid gas being a compound of one volume 
 of gaseous carbon united to one volume of oxygen ; 
 therefore, by these modes of forming carbonic acid 
 gas, we both reduce the quantity of oxygen, and 
 increase the quantity of carbonic acid ; and it has 
 been estimated that two per cent, of carbonic acid 
 gas produced by combustion, deteriorates the air 
 as much as 10 per cent, added mechanically by 
 simple mixture.* But in ill-ventilated rooms this 
 is by no means the only cause of the oppression 
 and inconvenience which are experienced. The 
 vapour given off from the lungs and from the skin 
 forms a very important source of contamination; 
 and, being charged with animal effluvia, its effects 
 in contaminating the air are very considerable. 
 The baneful effects of mephitic exhalations from 
 animal respirations are not confined to the human 
 frame. The glanders, of horses ; the pip, of fowls ; 
 and a peculiar disease to which sheep are subject, 
 all arise from the bad air generated by their being 
 too closely crowded together ; f and in no case can 
 animals be confined in a vitiated air for any length 
 of time, without serious injury resulting, although 
 the effects may be shown in various ways. In 
 ordinary cases the contamination is insufficient to 
 produce these violent and fatal effects; but the 
 slow and insidious effects of a less deteriorated 
 atmosphere are matters of far more importance 
 
 * The Lancet, for December, 1838. 
 f Paris, " Medical Chemistry," p. 309.
 
 PROM THE HUMAN BODY. 337 
 
 than most persons believe ; * and we have already 
 seen by the unerring evidence of statistical facts, 
 how fearfully human life is shortened by even the 
 smallest conceivable differences in atmospheric and 
 climatic influences. 
 
 (329.) The quantity of vapour given off from 
 the body (which we have already seen averages 
 about 12 or 14 grains per minute) is greatly in- 
 fluenced, not only by the different degrees of 
 muscular exertion and repose, but also under the 
 ever-changing hygrometric condition of the atmo- 
 sphere : for the greater the quantity of vapour 
 which the air contains, the less will the air be able 
 to carry off from the human body. For the air 
 possesses a desiccating power on the human body ; 
 but, of course, that pow'er is lessened in proportion 
 as it is nearer to the point of saturation. 
 
 (330.) The hygrometric condition of the atmo- 
 sphere is ascertained by the dew-point.] The 
 lower the dew-point, the greater will be the 
 quantity of moisture carried off from the lungs 
 by the air in respiration ; and therefore less will 
 be given off by perspiration from the skin, than 
 when the dew-point is higher. This is often the 
 case in very cold weather, when a large quantity 
 of vapour is carried off from the lungs, and but 
 
 * Some most excellent observations on this subject may be 
 found in Dr. Combe's " Principles of Physiology," 4th edition, 
 pp. 236-238, and 244-248. 
 
 f The dew-point is that thermometric temperature of the 
 atmosphere at which vapour is condensed. By exposing a 
 cold body to the air, a fine dew is deposited on its surface, 
 and by observing the temperature of this cold body, we know 
 the exact quantity of vapour contained in the air at that time. 
 Warm air contains a larger quantity of vapour than that 
 which is colder ; for air has the property of taking up water 
 in solution in a quantity proportional to its temperature. The 
 Table II., Appendix, shows the quantity of vapour that the 
 air contains when the dew-point is obtained in this manner. 
 
 Z
 
 338 QUANTITY OF VAPOUR FROM THE HUMAN BODY. 
 
 little by perspiration. When air is respired from 
 the lungs it is nearly of the temperature of the 
 blood, which is 98 Fahrenheit; and it is then 
 charged with a large quantity of vapour. If we 
 ascertain the quantity of vapour which the air 
 contains when expired, and deduct what it pos- 
 sessed before it was inhaled, we shall learn the 
 amount given off by the lungs ; the quantity of air 
 breathed per minute being known. Now, suppose 
 the temperature of the air before it is inhaled to be 
 40, and the dew-point 30 ; as 330 cubic inches of 
 air is the average quantity breathed per minute, -^ 
 of a grain* of vapour will be received into the lungs 
 with the air per minute. But when the air is again 
 expired, the temperature will be 98, and the dew- 
 point is always found to be 94 ; it will then contain 
 3*07 grains of vapour in the 330 cubic inches ; so 
 that upwards of two and a half grains per minute 
 are given off from the lungs under these circum- 
 stances. But if the dew-poinfbf the air before it 
 is breathed be 50, which is frequently the case in 
 damp or warm weather, then a less quantity of va- 
 pour will be given off in the same time. Dr. Dalton 
 states that in the torrid zone, the dew-point some- 
 times rises to 80, and that even in this country it 
 occasionally reaches to 60, while in winter if is 
 sometimes below zero. This easily accounts for 
 the variable quantity of moisture which is exhaled 
 from the body and lungs at different times. 
 
 (331.) The atmosphere, during damp weather, 
 when it is frequently nearly in a state of saturation, 
 is unable to carry off the full quantity of vapour 
 from the body. This causes the oppressive sensa- 
 tion that is so often experienced under such circum- 
 stances ; and the slightest exertion causes the per- 
 spiration to condense upon the surface of the body, 
 and a degree of heat is experienced much greater 
 
 * See Table II., Appendix.
 
 PRODUCTS OF RESPIRATIOX. 339 
 
 than the simple thermometric temperature would 
 occasion. 
 
 (332.) Although the carbonic acid gas given off 
 from the lungs is rather more than 37 per cent, 
 heavier than the oxygen which is consumed ; still, 
 in consequence of the dilatation of its volume by the 
 increased heat, and the greater levity of the vapour 
 given off from the lungs, the air is specifically 
 lighter at the moment of its expiration than at its 
 inspiration. For 800 cubic inches of pure air at 
 the temperature of 60, and the dew-point 40, will 
 weigh 243-395 grains; but 800 cubic inches of air 
 at 95, containing eight and a half per cent, of car- 
 bonic acid gas,* and 5 6 grains of vapour, with the 
 dew-point 85, will only weigh 232*450 grains; 
 being nearly five per cent, lighter. Hence air, when 
 expired from the lungs, always rises upwards, and 
 will flow through ventilators in the ceiling, or the 
 upper part of the walls of a room, if such be pro- 
 vided for its escape ; but otherwise the vapour con- 
 denses, and the volume of the air collapses as it 
 
 * The quantity of carbon given off from the lungs being so 
 considerable, we cannot wonder that the subject of its origin 
 has been a deeply disputed question. Supposing 26 cubic 
 inches of carbonic acid gas to be given off from the lungs per 
 minute on an average, that quantity will contain 3*3 grains of 
 pure carbon, which in 24 hours will amount to 11 ounces. 
 Besides this, if the quantity of vapour from perspiration and 
 pulmonary transpiration be taken at 10 grains per minute for 
 the former, and three grains for the latter, they will amount 
 to 42 ounces in 24 hours, making the vapour and carbon 
 together amount to nearly 3- 3 Ibs., besides other excre- 
 mentitious matter from the body. Some other source, then, 
 besides the food, must exist for obtaining the matter which 
 supports vitality, and this probably is the air. Liebig has 
 shown (Animal Chemistry, p. 287) that a man takes in with 
 his food about 13-9 ounces of solid carbon daily; and that 
 the more food he consumes, the greater quantity of oxygen he 
 inspires. It has been ascertained by Dr. Prout, that a 
 vegetable diet diminishes the quantity of carbonic acid gas 
 given off, and, of course, reduces the quantity of oxygen 
 
 z 2
 
 340 PRODUCTS OP RESPIRATION. 
 
 cools; it then becomes heavier than the substrata 
 of air, and sinks to the lower part of the room, 
 contaminated with impurities. 
 
 (333.) The sensation of uneasiness produced by 
 breathing impure air is an indication of the in- 
 jurious effects that result from it which is too 
 often neglected. When the air is not sufficiently 
 pure to effect the complete decarbonization of the 
 blood, we have already seen that the result is the 
 circulation of venous blood through the brain ; the 
 respiration then becomes impeded, and the nervous 
 system deranged ; the extent of these effects, of 
 course, varying with the amount of the exciting 
 cause, and with the peculiar constitutions of the 
 individuals exposed to their influence. Dr. 
 Harwood remarks on this subject, "The want of 
 wholesome air, however, does not manifest itself 
 on the system so unequivocally, or imperatively ; 
 no urgent sensation being produced, like that of 
 hunger, and hence the greater danger of mistaking 
 
 consumed ; because carbonic acid gas contains exactly its own 
 bulk of oxygen, united to the given weight of pure carbon. 
 The accuracy of Dr. Prout's experiments has been confirmed 
 by divers, and persons making use of the diving-bell. In all 
 hot climates, also, where from the rarefied state of the air, less 
 oxygen is received at each inspiration than in the higher 
 latitudes, the inhabitants feel but little desire for animal 
 food, and use principally a vegetable diet ; while on the con- 
 trary, the inhabitants of the Arctic regions use animal food 
 almost exclusively. Dr. Richardson, who accompanied Captain 
 Franklin on his voyage of discovery to the Polar seas, says 
 that himself and the other individuals who composed the 
 expedition, never felt the slightest wish for vegetable diet, 
 but desired the most stimulating animal food, and in much 
 larger quantities than they had ever before been accustomed 
 to. In such a climate, in consequence of the coldness and 
 density of the atmosphere, the quantity of oxygen inhaled is 
 much greater than in warmer regions, and therefore allows 
 the larger quantity of carbon to be carried off, which the 
 dieting on animal food produces. These results, therefore, 
 accord with Dr. Prout's experiments.
 
 DIMINISHED PRESSURE OF THE ATMOSPHERE. 341 
 
 its indications. The effects of its absence are only 
 slowly and insidiously produced ; and thus, too 
 frequently, are overlooked until the constitution 
 is generally impaired, and the body equally en- 
 feebled." * 
 
 (334.) The diminished pressure of the air in in- 
 habited rooms, caused by rarefaction, by chimney 
 draughts, or by exhaustion of the air by mechanical 
 means for the purpose of ventilation, has been sup- 
 posed by some physiologists to produce consider- 
 able effects on the health of persons exposed to its 
 influence. It cannot, indeed, be doubted that a 
 diminished pressure of any considerable extent 
 would be productive of great inconvenience, and 
 cause considerable derangement of the animal 
 economy. But the diminution of pressure from 
 these causes seldom exceeds a quantity equal to 
 about y-^o f an i ncn f tne common mercurial 
 barometer, and generally it does not reach ^j- of an 
 inch. The ordinary fluctuations of the barometer, 
 produced by meteorological causes, amounts to 
 upwards of two inches and a half in the altitude 
 of the mercurial column ; and this difference is 
 not found generally to produce any remarkable 
 effects on the animal functions a difference of 
 pressure so very far exceeding anything which can 
 occur in consequence of the rarefaction of the air 
 in an ordinary room, that it cannot be conceived 
 possible that this is the cause of the pathological 
 effects which are experienced by persons much 
 confined within doors. 
 
 The extremely small differences of pressure 
 which occur by the rarefaction of the air in inha- 
 bited rooms by heat and ventilation, can only be 
 detected by experiments with the differential 
 barometer. But the natural differences of pressure 
 
 * Harwood's " Curative Influence of the Southern Coast 
 of England," p. 282.
 
 342 DIMINISHED PRESSURE OF THE ATMOSPHERE. 
 
 which occur in many parts of the world are very 
 great. At Mont Louis, in Roussillon of the Pyre- 
 nees, one -of the highest of the inhabited parts of 
 Europe, the mean height of the barometer is only 
 24* 65 inches,* which is more than five inches below 
 the standard mean height in London ; and many 
 other places might be named where the pressure of 
 the atmosphere is much reduced below our own 
 standard. Some physiologists, indeed, have been 
 of opinion that the inhabitants of places and districts, 
 of which the height above the level of the sea is 
 such as to cause a pressure considerably less than 
 ours, are subject to peculiar diseases arising from 
 this cause. Even the comparatively small differ- 
 ences which occur in the several parts of our own 
 island, have been supposed to produce very marked 
 pathological effects. Dr. Harwood has written at 
 large on this subject ; f and Drs. Wells, Darwin, 
 Beddoes, and Cullen, and also Mr. Mansfield, have 
 given similar opinions. From the facts they have 
 collected, it appears that the inhabitants of high 
 situations, where the atmospheric pressure is, of 
 course, reduced, are more liable to pulmonary con- 
 sumption than those residing in low, and even in 
 marshy districts. But whether these effects are 
 attributable or not to a diminished atmospheric 
 pressure, the small difference which is caused by 
 rarefaction and ventilation, wholly inappreciable as 
 it is by the ordinary test of the barometer, can 
 scarcely be supposed capable of producing any 
 important results: while we possess the most 
 ample evidence that in the vitiated atmosphere, and 
 altered hygrometric condition of the air, there exists 
 'abundant cause for the languor and deficiency of 
 vital energy which are so frequently experienced 
 by persons exposed to their influence. 
 
 * Kirwan " On Temperature," p. 89. 
 
 f Harwood "On the Curative Influence of the Sjuthern 
 Coast of England."
 
 ELECTRIC CONDITION OF THE ATMOSPHERE. 343 
 
 (335.) Another cause, however, exists, which 
 probably exerts far greater influence than that 
 arising from altered pressure ; a more accurate 
 knowledge of which would enable us to account 
 for frequent apparent anomalies in the sensations 
 experienced in buildings which are artificially 
 heated. The electric condition of the air, and its 
 influence on the nervous system, are subjects 
 apparently of the highest importance ; but unfor- 
 tunately our knowledge at the present time is so 
 imperfect on this interesting and important branch 
 of science, and almost daily experience of new 
 discoveries convinces us we have still so much to 
 learn respecting it, that it is difficult at present 
 to assign to this agent its due place among the 
 operative causes which undoubtedly combine to 
 render many methods of artificial heat peculiarly 
 prejudicial to the animal economy. 
 
 (336.) Experiments of a very extensive character 
 have shown that the electric state of the atmosphere 
 when no peculiar disturbance takes place, is always 
 of that kind which is known by the name of positive 
 or vitreous electricity. The quantity of electricity 
 contained in the air appears to be far greater than is 
 generally supposed, as the experiments of Mr. Crosse, 
 Mr. Sturgeon, and Mr. Weekes, clearly show.* The 
 quantity undergoes diurnal variations, there being 
 two maxima and two minima in twenty-four hours ;f 
 the greatest quantities being a few hours after sun- 
 rise and after sunset ; and the smallest quantities 
 being just before sunrise, and again a few hours 
 before sunset or, as some suppose, about mid-day 
 and midnight. 
 
 * Noad's " Electricity," pp. 89-102. 
 
 t Ibid., p. 99; Daniell's "Chemical Philosophy," p. 253. 
 Schubler's " Researches " : Quarterly Journal of Science, vol. 
 ii., p. 416.
 
 344 ELECTRIC CONDITION OF THE ATMOSPHERE. 
 
 (337.) The experiments which have been made 
 on the electric state of the air of close and ill- 
 ventilated rooms, have shown that in these cases 
 the electric condition of the air is reversed, and 
 that instead of being positively electric, the elec- 
 tricity of the air is of that kind which is called 
 negative or resinous electricity. This subject has 
 generally excited so little attention, that but few 
 experiments have been made upon it; and the 
 causes of interference are so numerous, that it 
 requires much delicacy both in the instruments 
 and in the manipulation to arrive at satisfactory 
 conclusions. The similarity of the effects produced 
 on the human frame under these circumstances, 
 compared with the effects which are frequently 
 experienced during the passage of thunder-clouds, 
 when the air is generally negatively electric, or 
 else in a constant state of oscillation between the 
 positive and negative, also leads to the conclusion 
 that the electric state of the air of close rooms 
 performs a very important part in the production 
 of those unpleasant effects which are generally 
 experienced in such cases. In the natural state 
 of the atmosphere, the earth is always found to be 
 negatively ' electric with respect to the air (the air 
 itself being positively electric), and of course all 
 conducting bodies in communication with the 
 earth are in a similar electric state. But when 
 the air also becomes negatively electric, the earth 
 still retains its original condition, and the human 
 body thus becomes charged with electricity ; the 
 air in this condition being unable to carry off the 
 electricity, as would be the case with a moderately 
 moist atmosphere positively electric. The body 
 in this case receives a charge of electricity similar 
 to what is called the electric bath, produced by 
 placing the person on a glass stool, and commu- 
 nicating a charge from an electric machine. The
 
 ELECTRIC COXDITIOX OF THE ATMOSPHERE. 345 
 
 effects of the electric bath, when it is continued 
 for a considerable time, are similar to those which 
 result from the atmosphere of close rooms 
 headache and nervousness. Drowsiness, which is 
 another frequent consequence of close rooms, is 
 produced by a different cause, arising from the 
 imperfect arterialization of the blood circulating 
 through the brain, as we have already seen (Art. 
 325). Whatever therefore increases the positive 
 electricity of. the air, also relieves to a considerable 
 extent the unpleasant effects of close, ill-ventilated 
 and highly-heated rooms. Evaporation of water, 
 and, at certain periods of the day, vegetation, both 
 tend to relieve the oppressive effects of close rooms ; 
 and both are known to produce positive electricity 
 of the air.* So greatly does evaporation affect 
 the electric condition of the air, that the diurnal 
 variation in the quantity of electricity follows 
 nearly the same course as the exhalation of 
 moisture, and evaporation is considered to be the 
 principal source of atmospheric electricity .f But 
 evaporation, by adding to the moisture of the air, 
 also renders it a good conductor of electricity; 
 while dry air, on the contrary, is an extremely 
 bad conductor ; and hence it follows, that evapo- 
 ration of water in a highly-heated and desiccated 
 atmosphere must produce salutary effects in re- 
 lieving the unpleasant effects experienced in close 
 rooms. It must not, however, be understood, 
 that adding moisture to the air is at all times 
 desirable. Sometimes the air may be deteriorated 
 by any additional moisture, and the proper quan- 
 tity of moisture is a question of great importance 
 on health, as the fluids from the body cannot be 
 carried off if the air be too moist; while on the 
 
 * Thomson, " On Heat and Electricity," pp. 440 and 502. 
 f Noad's " Electricity," pp. 92 and 100.
 
 346 ELECTRIC CONDITION OF THE ATMOSPHERE. 
 
 other hand, the electric condition of the body will 
 be disturbed if the air be too dry. 
 
 (338.) The disturbance of the electric condition 
 of the air certainly adds another link to the chain 
 of causes which produce the unwholesome and 
 depressing effects of ill-ventilated rooms. Dr. 
 Faraday * considers that the deterioration of the 
 air under these circumstances " depends as much 
 or more on matters communicated to the air by 
 the living system, as by any direct injury to the 
 air due to the deficiency of oxygen or presence 
 of carbonic acid ; " and as electricity is produced 
 by every change of state, both respiration and 
 the vaporization of the fluids of the body must 
 produce considerable effect upon the electric con- 
 dition of the atmosphere of rooms where large 
 numbers of persons are congregated together. It 
 is also probable that other causes of deterioration 
 of the air may be discovered ; for various reasons 
 appear to point to the existence of a distinct sub- 
 stance being found mixed with atmospheric air 
 when analytically searched for under these cir- 
 cumstances. Dr. Faraday has on more than one 
 occasion alluded to the probable discovery, that 
 some new substance may be formed in atmo- 
 spheric air under the circumstances we are con- 
 sidering ; and all that is known respecting the 
 formation of ozone renders it highly probable 
 that to this newly-discovered agent in chemistry 
 many of the injurious effects of close rooms and 
 a contaminated atmosphere are referrible; and 
 that most important results to the animal system 
 are produced by it, even when it exists in the 
 smallest possible quantities.! And we may look 
 
 * " Keport of Select Committee on Ventilation of Houses 
 of Parliament," p. 21. 
 
 f Faraday's "Lectures on Non-Metallic Elements," de- 
 livered at the Eoyal Institution ; with Notes, &c., by Scrofiern 
 (1853), pp. 105-116.
 
 EFFECTS OF GASES ON ANIMAL LIFE. 347 
 
 to the further discoveries in ozone or ozonized 
 oxygen for an elucidation of many of the effects 
 which have hitherto baffled philosophers in account- 
 ing for various phenomena produced by gaseous 
 influences on the animal functions. 
 
 (339.) The preceding remarks will enable us to 
 estimate the comparative wholesomeness of various 
 methods of distributing artificial heat. Many of 
 these methods are highly injurious to the animal 
 economy, and cannot be persevered in without per- 
 manent derangement of the health of those who 
 are exposed. to their influence. 
 
 (340.) There are always suspended in the air 
 myriads of particles of animal and vegetable mat- 
 ter; but these almost unheeded atoms possess a 
 high philosophical importance, however they may 
 generally be disregarded. They are the evidences 
 of the unceasing changes which the material world 
 is continually undergoing the irrefragable proofs 
 that the visible matter of the universe is slowly 
 and almost imperceptibly passing through a series 
 of transmutations, which affect both organic and 
 inorganic nature. Many of these particles are 
 easily decomposed by heat, and are then resolved 
 into the various gases, either in their elementary 
 or mixed state. Hence many of the methods of 
 producing artificial heat are materially affected, as 
 regards their wholesomeness, by the fact of their 
 being able or not able to decompose or chemi- 
 cally alter these floating particles of matter. To 
 this cause is mainly attributable the unpleasant 
 smell produced by several modes of warming 
 buildings by highly-heated metallic surfaces; and 
 we have already seen that the hygrometric and 
 electric condition of the air is also altered by the 
 same means. All the different descriptions of 
 hot-air stoves are more or less liable to these 
 objections ; as also the high-pressure system of
 
 348 EFFECTS OF GASES 
 
 hot-water apparatus, and still more the cockle 
 or hot-air furnaces. Dr. Nott's stoves, and also 
 the Eussian and German stoves, are subject to 
 this inconvenience; and asphyxia is frequently 
 produced in Russia by the use of these stoves.* 
 The cockle or hot-air furnace is particularly liable 
 to these objections ; for, not only will it act power- 
 fully in decomposing the floating particles of ex- 
 traneous matter contained in the air, resolving 
 them into sulphuretted, phosphuretted, and car- 
 buretted hydrogen, with various compounds of 
 nitrogen and carbon, but it will likewise decom- 
 pose a portion of the vapour contained in the 
 air, absorbing the oxygen and liberating the 
 hydrogen. 
 
 (341.) These various gases thus exhaled into 
 the air cannot be breathed without considerable 
 inconvenience. Signor Cardone made some expe- 
 riments on breathing hydrogen gas. He inhaled 
 30 cubic inches, which is about one-ninth part 
 of the total quantity of air contained in the lungs ; 
 and the almost immediate effects he experienced 
 were an oppressive difficulty of breathing, and 
 painful constriction at the superior orifice of the 
 stomach, followed by abundant perspiration, tre- 
 mor of the body, heat, nausea, and violent head- 
 ache ; his vision became indistinct, and a deep 
 murmur confused his hearing. Some of these 
 symptoms lasted a considerable time, and were 
 with difficulty got rid of.f Sir Humphry Davy 
 tried the effect of inhaling carburetted hydrogen. 
 He made three inspirations of the gas. " The 
 first inspiration produced a sort of numbness and 
 loss of feeling in the chest, and about the pectoral 
 muscles. After the second inspiration, he lost all 
 power of perceiving external things, and had no 
 
 * Dr. Kay " On Asphyxia," p. 344. 
 t Annals of Science, vol. xxviii., p. 149.
 
 ON ANIMAL LIFE. 349 
 
 distinct sensation, except a terrible oppression on 
 the chest. During the third inspiration this feel- 
 ing disappeared, and he seemed sinking into 
 annihilation, and had just power enough to drop 
 the mouthpiece from his unclosed lips." The 
 effects of this experiment lasted for several hours, 
 producing excessive pain, extreme weakness, nau- 
 sea, loss of memory, an'd deficient sensation.* 
 Carbonic oxide is still more prejudicial in its 
 action on the animal system. Sir Humphry Davy, 
 on trying the effects of inhaling a small quantity 
 of it, was seized with a temporary loss of sensa- 
 tion, succeeded by giddiness, sickness, and acute 
 pains in different parts of his body, and it was 
 some days before he entirely recovered ; but Mr. 
 Witter, of Dublin, who tried to repeat the experi- 
 ments, was immediately affected with apoplexy, 
 and was restored with difficulty .f 
 
 This last-mentioned gas is generated by all 
 stoves which are constructed so as to burn with 
 a very slow draught : and Dr. Arnott's stove 
 has been found peculiarly liable to produce this 
 deleterious gas, which escapes into the room 
 through the ventilator in the ashpit, and is ex- 
 tremely unwholesome in small close rooms. The 
 carburetted hydrogen is abundantly produced by 
 the gas stoves, in consequence of a portion of the 
 gas escaping unburned from the stove ; and this 
 unburned gas, when combined with the large 
 quantity of vapour which is produced by the com- 
 bustion of carburetted hydrogen, as already de- 
 scribed (Art. 305), renders these stoves peculiarly 
 unwholesome. All these causes of deterioration 
 of the air affect different persons in very different 
 
 * Davy's " Eesearches on Nitrous Oxide " ; also Paris, 
 : On Diet," p. 296. 
 f Ure's " Dictionary of Chemistry," art. " Carbonic Oxido."
 
 350 QUANTITY OF AIR 
 
 degrees ; but wherever the causes exist, the result 
 will necessarily be derangement of the animal 
 system, however robust the persons may be who 
 are exposed to their influence ; but, of course, the 
 sensations will be soonest experienced by the delicate 
 and the valetudinarian. 
 
 (342.) It remains to estimate the quantity of 
 air which is required to be changed by ventilation, 
 in order to preserve its purity when deteriorated 
 by respiration and the exhalations from the human 
 body. 
 
 (343.) The quantity of air necessary for respira- 
 tion is very much less than is required to absorb 
 the vapour given off from the skin and from the 
 lungs. The amount of vapour from this cause, we 
 have already seen, is about 12 grains per minute, 
 when the individual is not making any particular 
 muscular exertions. If the temperature of the room 
 be 60, the air, when quite dry, will absorb 5*8 grains 
 of vapour per cubic foot ; but the average dew-point 
 being about 45, the air will previously contain 
 3-5 grains ; so that each cubic foot of air will be 
 able to absorb only 2i grains of vapour. Under 
 these circumstances, the perspiration from the body 
 will saturate 5i cubic feet of air per minute. But, 
 in estimating the quantity of air which is to be 
 warmed, in order to allow of sufficient ventilation, 
 this amount may be considerably reduced ; because, 
 as 45 is the average dew-point for the whole year,* 
 it will be much lower in winter and higher in 
 summer, and probably will not exceed 20 or 25 on 
 an average during the time that artificial heat is 
 
 * This is for the neighbourhood of London. It varies of 
 course in different places, and is much influenced by the pre- 
 vailing winds. An easterly wind travelling to us from the 
 Continent of Europe, and across the dry and arid countries 
 of the Asiatic Continent, must necessarily part with much of 
 its moisture, acquired from the Pacific Ocean, before it reaches
 
 REQUIRED FOR VENTILATION'. 351 
 
 required. Every cubic foot of air will then absorb 
 an additional quantity of about 3^ to 4 grains of 
 vapour ; and we may therefore estimate the quantity 
 of air which is requisite to carry off the insensible 
 perspiration at 3 cubic feet, and for the pulmonary 
 supply, a quarter of a cubic foot per minute, for 
 each individual. 
 
 This calculation is sufficient for estimating the 
 quantity of air which in winter is required to be 
 warmed per minute, as explained (Art. 105). But 
 for the purpose of summer ventilation, a larger 
 allowance should be made. As the dew-point is 
 much higher in summer, the air will absorb less 
 moisture from the body, while at the same time the 
 exhalations from the body are considerably greater 
 in summer than in winter. For summer ventilation, 
 therefore, from five to ten cubic feet of air per 
 minute, for each person, is the smallest quantity 
 which ought to be changed, in order to maintain 
 the purity of the room. 
 
 (344.) Other causes of deterioration of the quality 
 of the air exist, such as the consumption of oxygen 
 and the elimination of extraneous gases by the 
 burning of fires, candles, lamps, &c. ; but as all 
 gases are capable of absorbing equal quantities of 
 vapour, it follows that, when air has been deterio- 
 rated by these causes, so as to be less fit for 
 respiration, it is still just as capable of carrying off 
 the vapour from the surface of the body as pure 
 air; and therefore no special allowance need be 
 made for these causes of vitiation. 
 
 ns, and therefore it will be to us a dry wind; while, on the 
 contrary, a westerly wind is always charged with a large 
 quantity of moisture, absorbed during its passage from the 
 American Continent, across the Atlantic. Its passage over 
 this ocean a distance of 3000 miles occupies a period 
 varying from 3 to 10 days, during which time it is constantly 
 imbibing moisture from the ocean.
 
 352 QUANTITY OF AIR REQUIRED FOR VENTILATION. 
 
 (345.) Some persons have calculated the quan- 
 tity of air which is required for ventilation at a 
 much greater amount than is here stated. Dr. Reid 
 considers that ten feet per minute ought to be 
 allowed for each individual ; and in some of his ex- 
 periments at the House of Commons, he states that 
 30 cubic feet and sometimes even 60 cubic feet, per 
 minute, has been allowed.* Such cases of extreme 
 ventilation are not absolutely necessary ; f and 
 although in the House of Commons, where these 
 experiments were made, a larger proportionate 
 amount of ventilation is requisite than in almost 
 any other case, it is very difficult, if not impossible, to 
 avoid the effect of draughts when such excessive 
 ventilation is produced. In all ordinary cases also, 
 the expense of providing such a great amount of 
 ventilation would be an insuperable objection; 
 though in such buildings as the Houses of Parlia- 
 ment, the expense is perfectly unimportant, provided 
 the desired object of an improved atmosphere be 
 obtained. 
 
 (346.) The important changes in the chemical 
 constitution of the atmosphere which we have seen 
 result from respiration, heat, and combustion, im- 
 peratively demand a constant change in the air, in 
 order to maintain its purity and to enable it to 
 support organic life. It would be difficult to de- 
 scribe this fact in more forcible language than that 
 which formed the concluding lecture, at the Ecole 
 de Medecine, by M. Dumas, on "The Chemical 
 Statics of Organized Beings." From this most 
 interesting lecture some very short extracts can 
 alone be given ; but those who have the means of 
 
 * Reports of the British Scientific Association, vol. vii., 
 p. 131. 
 
 f Wyman " On Ventilation," p. 296, considers that in hos- 
 pitals ^0 cubic feet per minute is necessary to maintain proper 
 purity of the air.
 
 EFFECT OF GASES ON ANIMAL LIFE. 353 
 
 consulting the document at large will derive both 
 pleasure and instruction from its perusal.* 
 
 " We have proved in fact," says M. Dumas, " that 
 animals constitute, in a chemical point of view, a 
 real apparatus for combustion, by means of which 
 burnt carbon incessantly returns to the atmosphere 
 under the form of carbonic acid ; in which hydro- 
 gen, burnt without ceasing, on its part continually 
 engenders water, whence, in fine, free azote is in 
 cessantly exhaled by respiration, and azote in the 
 state of oxide of ammonium by the urine. Thus 
 from the animal kingdom, considered collectively, 
 constantly escape carbonic acid, water in the state 
 of vapour, azote, and oxide of ammonium ; simple 
 substances, and few in number, the formation of 
 which is strictly connected with the history of the 
 air itself. Have we not, on the other hand, proved 
 that plants, in their normal life, decompose carbonic 
 acid for the purposes of fixing its carbon, and of dis- 
 engaging its oxygen; that they decompose water 
 to combine with its hydrogen, and to disengage 
 also its oxygen ; that, in fine, they sometimes bor- 
 row azote directly from the air, and sometimes in- 
 directly from the oxide of ammonium or from nitric 
 acid, thus working, in every case, in a manner the 
 inverse of that which is peculiar to animals ? If the 
 animal kingdom constitutes an immense apparatus 
 for combustion, the vegetable kingdom in its turn 
 constitutes an immense apparatus for reduction ; 
 in which reduced carbonic acid yields its carbon, 
 reduced water its hydrogen, and in which also re- 
 duced oxide of ammonium and nitric acid yield 
 their ammonium or their azote. 
 
 " If animals, then, continually produce carbonic 
 acid, water, azote, oxide of ammonium plants 
 incessantly consume oxide of ammonium, azote, 
 
 * Translated in the London and Edinburgh Philosophical 
 Magazine, vol. xix., p. 338, et seq. 
 
 2 A
 
 354 EFFECT OF GASES ON ANIMAL LIFE. 
 
 water, carbonic acid. What the one class of 
 beings gives to the air, the others take back from 
 it ; so that, to take these facts at the loftiest point 
 of view of terrestrial physics, we must say that as 
 to their truly organic elements, plants and animals 
 spring from air are nothing but condensed air." 
 
 These views have been beautifully investigated 
 and explained in the lecture of M. Dumas, here 
 alluded to, and also by M. Liebig, in his excellent 
 works on animal and vegetable chemistry. The 
 effects of animal respiration we have already ex- 
 amined at some length. The respiration of plants 
 is a subject of much interest to the horticulturist, 
 although several points connected with it are still 
 undecided, and remain matters of dispute even 
 among men of the first rank in science. 
 
 (347.) The effects of a factitious atmosphere are 
 less injurious to vegetable than to animal life. 
 Vegetables appear to have a power of accom- 
 modating their functions, in some degree, to the 
 nature of the gaseous elements by which they are 
 surrounded. That solar light has a powerful 
 effect on vegetables has long been acknowledged ; 
 and under this influence they exhale large por- 
 tions of oxygen and moisture. Dr. Daubeny has 
 ascertained that the same action is produced in 
 the absorption of moisture by the roots, and the 
 exhalation of it by the leaves of plants, whether 
 they are exposed to a strong light, or with a 
 smaller degree of light they receive a consider- 
 able portion of radiant heat.* So powerful, 
 indeed, is the action of light, that M. Condolle 
 has found that plants, during the day, and when 
 exposed to the light, are wholly uninjured by the 
 action of gases which quickly destroy them at 
 night; and even the application of chlorine and 
 other deleterious substances to the roots of plants 
 
 * Reports of the British Scientific Association, vol. iv., p. 73.
 
 EFFECT OF GASES ON VEGETABLE LIFE.- 355 
 
 is innocuous during the day, though they are 
 presently destroyed by similar treatment at night. 
 Sulphuretted hydrogen, nitrous acid gas, muriatic 
 acid gas, and chlorine, were severally tried in this 
 manner, with similar results in each case.* 
 
 It has been generally supposed that plants 
 exhale carbonic acid gas during the night ; but 
 this, by Dr. Dalton's experiments, appears doubt- 
 ful : for he states that, by numerous analyses of 
 the air of hothouses, he has always found it to 
 contain during the day, as well as during the 
 night, the same proportions of carbonic acid gas.f 
 
 The action of fruits on the air has been stated by 
 M. Berard in his essay, which received the prize 
 from the French Academy of Sciences, to produce 
 a constant elimination of carbon, under all circum- 
 stances.! This opinion has been controverted, and, 
 as it is supposed, successfully, by M. de Saussure, 
 who states that green fruit has the same influence 
 on the air as the leaves have the action of the 
 former being rather less intense ; but, in proportion 
 as the fruit ripens, its power to decompose carbonic 
 acid gas becomes feebler. 
 
 Although it would appear that the purity of the 
 air is not of so much importance to vegetation as 
 it is to the animal economy, still, as many of the 
 gases which are innocuous to plants during the day 
 are deleterious to them in the night, it is necessary 
 to prevent any considerable deterioration of the 
 air, in order to preserve them in a healthy state. 
 Hence it becomes an important matter, when it is 
 an object to obtain fruits and flowers of the finest 
 
 * London and Edinburgh Philosophical Magazine, vol. iv., 
 p. 316. 
 
 f Beports of the British Scientific Association, vol. vi., p. 58. 
 
 J Annales de Chimie, vol. xvi., p. 152 ; and Quarterly Journal 
 of Science, vol. xi., p. 395. 
 
 Quarterly Journal of Science, vol. xiii., p. 152. 
 
 2 A 2
 
 356 EFFECT OF GASES ON ORGANIC LIFE. 
 
 descriptions, to employ only such means of pro- 
 ducing artificial heat as do not eliminate extraneous 
 gases to the air; and experience has proved that 
 since the general introduction of the plan of heating 
 buildings by hot water, horticulturists have found 
 their plants to be more healthy and productive, than 
 with the old methods of warming buildings. 
 
 The general principles of physiology, which have 
 here been discussed, will enable a correct opinion to 
 be drawn as to the effects on organic life of any 
 method of producing artificial heat. It is not to 
 any particular invention that these remarks apply 
 they equally affect all ; and when any new plans 
 for heating buildings are brought under the public 
 notice, it will be well for those who value their 
 health, to test the merits of these inventions by the 
 general principles which have here been explained. 
 That a vast amount of ill-health, and great con- 
 sequent physical suffering, is produced solely by 
 ignorantly using noxious modes of artificial warm- 
 ing, is certain ; and it is really lamentable sometimes 
 to see people slowly and surely undermining their 
 health, by persisting in the use of some of these 
 modern inventions, and thus sacrificing the greatest 
 blessing which Heaven bestows on man, by wilful 
 ignorance of, and even setting at defiance, those 
 laws which bind man to the whole physical universe, 
 and of which not even the smallest can be violated 
 with impunity.
 
 357 
 
 CHAPTER IV. 
 
 ON THE VARIOUS METHODS OF PRODUCING 
 VENTILATION. 
 
 Spontaneous and Mechanical Methods of Ventilation Cause 
 of Motion in Spontaneous Ventilation Velocity of Dis- 
 charge Effects of unequal height of Discharge Pipes 
 Defects in Ventilation of Churches Proportions of Induc- 
 tion and Abduction Tubes Quantity of Air discharged 
 through Ventilators Ventilation by Heat and by Chimney 
 Draughts Mechanical Ventilation by Fans, Bellows, and 
 Pumps Quantity of Air discharged by these Means 
 Calculation of Power expended Cowls used for promoting 
 Ventilation Effect of different Forms of Cowls. 
 
 (348.) THE different modes of producing ventila- 
 tion may all be classed under two general heads 
 the natural and the mechanical. All the methods 
 of spontaneous effusion, produced by the unequal 
 density of two columns of air, whether caused by 
 chimney draughts or otherwise, belong to the former 
 class ; while the various methods of ventilating by 
 fans, bellows, pumps, and other similar contrivances, 
 belong to the latter class. Of these different modes, 
 the mechanical is the most effective ; the natural 
 generally, but not always, the most economical. 
 
 (349.) The primary force which produces motion 
 in spontaneous ventilation is the difference of 
 specific gravity of the two columns of air. If a 
 column of air contained in a tube or chimney be 
 heated, it expands according to an ascertained
 
 358 ON THE VARIOUS METHODS 
 
 law, applicable to all gaseous bodies, namely, that 
 the expansion is equal to ^ of its volume for each 
 degree of Fahrenheit that the temperature is raised 
 from 32 to 212. If this column of air be 10 feet 
 high, and have its temperature raised 20, then it 
 will expand -gfo, or ^\ of its bulk ; so that its specific 
 gravity would be diminished, and it would require 
 a column of air 10 feet 5 inches high to balance 
 a column of the external air 10 feet high, when the 
 temperature of the latter is 20 lower than that of 
 the former. But as the height of the heated column 
 is limited by the height of the tube or chimney, 
 which we suppose to be only 10 feet high, the 
 colder column presses it upwards with a force 
 proportionate to this difference in weight, and with 
 a velocity equal to that acquired by a body falling 
 through a space equal to the difference in height 
 that two columns of equal weight would occupy, 
 which in this case is 5 inches. Now the law of 
 gravitation is this : that the velocity of descent is 
 relatively as the square root of the distance through 
 which the body falls ; and as the body falls 16^- feet 
 in a second (or 16 feet, neglecting the fraction), 
 the velocity will be, agreeable to the well-known 
 law of gravitation, equal to eight times the square 
 root of the height of descent, in decimals of a foot ; 
 or 2 \/ g . h, where g is the distance through which a 
 falling body descends in one second of time, namely, 
 16*09 feet, and h the height of the descent.* 
 
 In the case we have supposed, five inches is the 
 height of the effective descent of the heavy column 
 of air. This fall of five inches is equal to '416 of 
 a foot ; therefore, by the rule, 2 V 16'09 x -416 
 = 5-174 feet per second, or 310 feet per minute, 
 will be the velocity with which the heated column 
 of air would be forced through the tube or chimney 
 
 * See Chapter V., Part II.
 
 OF PRODUCING VENTILATION. 359 
 
 under the circumstances we have supposed.. If, 
 therefore, the tube were one foot square, there 
 would pass out 310 cubic feet of air per minute. 
 This rate of efflux, however, is subject to certain 
 corrections, on account of the contaminations which 
 increase the specific gravity of the escaping air, and 
 also in consequence of friction, arising from various 
 causes, but more particularly in consequence of 
 angular deviations in the tubes. In straight tubes> 
 the friction is found to be in all cases directly as 
 the length of the tube, and inversely as the diameter. 
 In general practice, a deduction of from one-fourth 
 to one-third of the initial velocity is necessary to 
 compensate for these several effects, and to represent 
 the true rate of efflux. The velocity of discharge 
 per second through ventilating tubes, or chimneys, 
 will therefore be found (after the difference in height 
 of the two columns of air has been calculated in the 
 manner already stated) to be equal to eight times 
 the square root of the difference in height of the two 
 columns of air in decimals of a foot ; this number 
 reduced one-fourth, to allow for friction, and the 
 remainder multiplied by 60, will give the true 
 velocity of efflux per minute ; and the area of the 
 tube in feet, or decimals of a foot, multiplied by 
 this latter number, will give the number of cubic 
 feet of air discharged per minute. 
 
 (350.) In calculating the rate of efflux of the 
 air from any room or building, it is not merely 
 the height of the room which must be considered, 
 but the total height of the column of heated air. 
 Thus, if the ventilating tube passes through 
 another room or loft over the room to be ventilated 
 before it discharges the vitiated air into the 
 atmosphere, the total vertical height from the floor 
 of the room to the top of the tube is the effective 
 height of the column of heated air. If the tube in 
 its course passes horizontally, this additional length
 
 360 ON THE VARIOUS METHODS 
 
 may be neglected in the calculation in all ordinary 
 cases, as it makes no other difference in the result 
 except that of increasing the friction by so much 
 additional length. The vertical height is that 
 which alone governs the rate of the discharge, and 
 the horizontal length of the tube is merely one of 
 the fortuitous circumstances which slightly modify 
 the result.* 
 
 (351.) As the vertical height of the column of 
 heated air governs the velocity of discharge in the 
 ratio of the square root of the height of the column, 
 it is necessary if more than one ventilating tube or 
 opening for the escape of the heated and vitiated 
 air be made, that they shall all be similar in height, 
 otherwise the highest vent will prevent the efficient 
 acting of the lower one, and the discharge may even 
 be less through the two tubes than it would be with 
 the upper one alone. The cause of this apparently 
 paradoxical effect is not difficult of explanation. 
 If we suppose a tube, open at both ends, to be filled 
 with heated air, it is evident the velocity of the 
 ascent will be proportional to the height of the tube 
 and the excess of temperature of the air which it 
 contains, the weight of the external air pressing the 
 lighter column upwards, as already explained. But 
 if another opening be made at the side of the tube, 
 at one-half the total height, then this opening at 
 the side will not emit any portion of the heated 
 air, but will, on the contrary, admit a quantity of 
 cold air ; and the velocity of its admission will be, 
 like that of the cold air at the bottom of the tube, 
 in proportion to the height of the heated column 
 of air in the tube above the opening. Now, as the 
 
 * This remark must be taken with its proper limitation, 
 for cases may arise where the friction caused by the horizontal 
 tube may become a very important element in reducing the 
 velocity of the discharge when the horizontal length is great 
 in proportion to the vertical height.
 
 column of air above this opening is only one-half ^ui^ 
 the height of that above the former opening at the 
 bottom of the tube, the velocity with which the air 
 enters it will be, compared to the velocity with 
 which it enters the opening at the bottom, as the 
 square root of the height of the heated column of 
 air above the respective openings. Both these 
 openings will therefore admit cold air at the same 
 time ; but, by the admission of the cold air at the 
 middle of the tube, the temperature of the superin- 
 cumbent atmosphere above the lower opening will 
 be reduced, and the velocity with which the air 
 enters the lower opening will therefore be dimi- 
 nished ; the excess of temperature of the air in the 
 tube being the primum mobile of the efflux. The 
 interference of the different currents will likewise 
 reduce the quantity of air discharged; and the 
 total result will be that somewhat less air would 
 be discharged under these circumstances than if 
 the whole of the air had entered at the bottom. 
 
 (352.) Precisely the same effects as here de- 
 scribed take place in the ventilating of rooms by 
 openings at any height above the level of the floor. 
 The highest opening alone will act as the abduc- 
 tion tube, and all openings below this will act as 
 induction tube, reducing the discharge by lower- 
 ing the temperature of the air of the upper part 
 of the room, and also by causing in it counter- 
 currents. Some modifications of this result will, 
 however, occasionally occur, as, for instance, when 
 the abduction tube is too small; in which case, 
 the next lowest opening will also act in carrying 
 off the heated air. On the other hand, when 
 the openings for the admission of cold air are too 
 small in proportion to those for the egress of the 
 hot air, then the current of cold air will descend 
 through part of the hot-air tube, and the hot air 
 will ascend through the other part of the same tube.
 
 362 ON THE VARIOUS METHODS 
 
 These effects are frequently very sensibly felt in 
 churches and other buildings, where part of the 
 ventilation is effected by means of the windows. 
 The cold air entering at these windows generally 
 descends upon the heads of those who are placed 
 near them. The effect of this entering current is 
 to lower the temperature of the vitiated air, which 
 parts with a portion of its heat to the fresh air 
 entering the building, and the vitiated air being 
 heavier than fresh air of the same temperature, it 
 falls by its greater specific gravity, and is again 
 breathed by the persons assembled, instead of the 
 pure air which they would have received, had the 
 openings for the admission of the fresh air been at 
 or near the floor of the building. 
 
 No plan of ventilation can be worse than that 
 just described, which, however, is the method 
 adopted in a very great majority of churches and 
 other large buildings. Notwithstanding this plan 
 has obtained such extensive adoption, it is certain 
 that it is opposed to every sound principle of 
 science, and has had its rise in the most perfect 
 ignorance of the physical laws ; and no better 
 proof than this need be adduced to show how 
 very little the true principles of ventilation have 
 been studied, and how erroneous any conclusions 
 on this subject are likely to prove that are not 
 based on the known laws which govern the 
 motion of fluids. 
 
 (353.) In all the methods of ventilation, it is 
 advisable to make the aggregate area of the open- 
 ings that admit the fresh air larger than the 
 aggregate openings for the efflux of the vitiated 
 air. This becomes necessary notwithstanding 
 the increase of volume which takes place in the 
 heated and vitiated air. If the opposite course be 
 adopted, and the abduction tubes be larger than 
 the eduction, then a counter-current takes place in
 
 OF PRODUCING VENTILATIOX. 363 
 
 the hot-air or ventilating tubes, and the cold air 
 descends through them ; but by making the induc- 
 tion tubes numerous, and of a large total area, 
 the velocity of the entering current is reduced, 
 and unpleasant draughts are avoided. It is also 
 expedient to divide the entering current as much 
 as possible. By so doing it prevents the dan- 
 gerous effects of cold draughts, when the enter- 
 ing current is colder than the air of the room ; 
 and when it is hotter than the air of the room, it 
 prevents the air from rising too rapidly towards 
 the ceiling, and therefore distributes it more 
 equally throughout the apartment. Provided the 
 aggregate openings for the admission of cold air 
 be not less in size than those for the emission of 
 the heated air, the quantity of air which enters 
 a room depends less upon the size or number of 
 the openings which admit the fresh air than upon 
 the size of those by which the vitiated air is 
 carried off. This will be evident when it is con- 
 sidered that, the room being always absolutely 
 full of air, no more air can enter until a portion 
 of that already in the room be removed. But as 
 soon as a portion of the air which previously 
 occupied the room is removed, a similar quantity 
 of fresh air rushes in to supply its place, the 
 quantity entering being exactly equal to that 
 which escapes.* The only exception which occurs 
 to this rule is the slow interchange among the 
 particles of air which takes place, according to the 
 laws of gaseous diffusion, through the lower as 
 well as the upper openings of the room, and which 
 
 * This description, perhaps, scarcely gives the exact cir- 
 cumstances of the case ; for in spontaneous ventilation a 
 small portion of the cold air will enter before any discharge 
 takes place from the room. The compression produced by 
 the fresh air entering causes the heated air to flow out as 
 described Art. 350.
 
 364 
 
 ON THE VARIOUS METHODS 
 
 continues so long as any inequality exists either in 
 the specific gravity or in the composition of the 
 gaseous matter. This diffusion among the particles 
 of different gases is known as the laws of endosmose 
 and exosmose, and the effects are remarkable in 
 many cases. 
 
 (354.) The following Table will show the dis- 
 charge per minute through a ventilator one foot 
 square, for various heights and differences of tem- 
 perature, the allowance which has already been 
 stated (Art. 349) having here been made. The 
 discharge through a ventilator of any other size 
 
 TABLE XXVIII. 
 
 Table of the Quantity of Air, in Cubic Feet, discharged per 
 Minute through a Ventilator of which the Area is one 
 Square Foot. 
 
 Height 
 
 Excess of Temperature of Boom above the 
 External Air. 
 
 of 
 
 
 in Feet. 
 
 5 
 
 10 
 
 15 
 
 20 
 
 25 
 
 30 
 
 10 
 
 116 
 
 164 
 
 200 
 
 235 
 
 260 
 
 284 
 
 15 
 
 142 
 
 202 
 
 245 
 
 284 
 
 318 
 
 348 
 
 20 
 
 164 
 
 232 
 
 285 
 
 330 
 
 368 
 
 404 
 
 25 
 
 184 
 
 260 
 
 318 
 
 268 
 
 410 
 
 450 
 
 30 
 
 201 
 
 284 
 
 347 
 
 403 
 
 450 
 
 493 
 
 35 
 
 218 
 
 306 
 
 376 
 
 436 
 
 486 
 
 531 
 
 40 
 
 235 
 
 329 
 
 403 
 
 465 
 
 518 
 
 570 
 
 45 
 
 248 
 
 348 
 
 427 
 
 493 
 
 551 
 
 605 
 
 50 
 
 260 
 
 367 
 
 450 
 
 518 
 
 579 
 
 635 
 
 %* The above Table shows the discharge through a venti- 
 lator of any height, and for any difference of temperature. 
 Thus, suppose the height of the ventilator, from the floor of 
 the room to the extreme point of discharge, to be 30 feet, 
 and the difference between the temperature of the room and 
 of the external air to be 15, then the discharge through a 
 ventilator one foot square will be 347 cubic feet per minute. 
 If the height be 40 feet, and the difference of temperature 
 20, then the discharge will be 465 cubic feet per minute.
 
 OF PRODUCING VENTILATION. 365 
 
 may easily be calculated, because, as the area is 
 here 144 square inches, we have only to multiply 
 the number of feet found by the Table, by the 
 number of square inches in the area of the proposed 
 ventilator, and then, by dividing that number by 
 144, the quotient . will be the quantity sought, 
 which will represent the number of cubic feet of 
 air that will be discharged per minute by the pro- 
 posed ventilator. 
 
 (355.) As the discharge through any given 
 height and size of ventilator is less in proportion as 
 the difference between the external and internal 
 temperature is smaller, it follows that it will be 
 most difficult to obtain ventilation in hot weather. 
 In summer, either the number or the dimensions of 
 the ventilators should be increased ; otherwise a 
 room which is well ventilated in winter will be 
 extremely uncomfortable in summer. The increase 
 in size can be effected by having movable ventila- 
 tors, which can be contracted at pleasure ; and the 
 actual size of the trunk or channel which conveys 
 the air away should be sufficiently large to carry 
 off the greatest quantity of air required for summer 
 ventilation. 
 
 (356.) The method of spontaneous ventilation 
 which has been described requires, in every case, 
 that the air of the room to be ventilated shall be 
 of a higher temperature than the external air. In 
 very hot weather and with crowded assemblies, this 
 method is generally insufficient to secure a whole- 
 some and comfortable state of the atmosphere. 
 But artificial means have long been in use for 
 increasing this effect. This is accomplished in 
 two ways : either by heating the air in the upper 
 part of the ventilating tube, which causes it to 
 ascend with greater rapidity, and thereby to draw 
 it out of the room or building ; or by causing the 
 air of the building to pass through a furnace,
 
 366 ON THE VARIOUS METHODS 
 
 from which all other supply of air is excluded. 
 Both these plans have been extensively used, and 
 both answer the intended purpose. The principal 
 theatres in London are ventilated by the former 
 method, advantage being taken of the heat of a 
 large chandelier placed near the ceiling in the 
 centre of. the house. The heat of this chandelier 
 causes a great rarefaction of the air, and increases 
 the draught ; and it thence passes out through 
 tubes into the open atmosphere, the buildings being 
 supplied with fresh air from below. The method 
 of ventilating by causing the vitiated air to pass 
 through a furnace has also been long and exten- 
 sively employed.* In many manufactories, this 
 method is economically applied, where fire-heat is 
 used either for steam-engines or other purposes. 
 All that is necessary is to conduct the air from 
 the rooms requiring ventilation, through tubes, 
 into the ashpit of the furnace, all other supply 
 of air to the ashpit being prevented ; and the 
 draught of the fire causes, a rapid abstraction 
 of air from the building, which is immediately 
 supplied by fresh air, and produces a thorough 
 ventilation.t 
 
 (357.) The most extensive application yet made 
 of this principle was that employed by Dr. Reid, for 
 the ventilation of the temporary Houses of Parlia- 
 ment in the year 1836. For this purpose a large 
 
 * In 1739, Mr. Sutton proposed this plan of ventilation ; 
 but Dr. Desaguliers, in 1723, appears to have adopted a plan 
 somewhat similar for ventilating the House of Commons 
 (Desagulier's Experimental Philosophy, vol. ii., p. 560) ; though 
 in reality the invention of applying fire-heat to produce a 
 draught of air was long prior to either of these dates, and 
 was first proposed by Agricola, in the sixteenth century. 
 (See Chapter III., Part II., Art. 311.) 
 
 f The quantity of air which would be thus withdrawn from 
 a building by these means may be estimated by what is stated 
 in the Note, Art. 397.
 
 OF PRODUCING VENTILATION. 367 
 
 chimney was erected, with a furnace of propor- 
 tionate size, and the air was drawn off from the 
 ceilings of the buildings with great rapidity, passing 
 downwards through a tunnel into the bottom of 
 the furnace, and thence through the fire. The 
 quantity of air thus withdrawn is governed by the 
 force of the fire. In this case it was very great, 
 for by means of this furnace the whole air in the 
 House of Commons could be changed in a very few 
 minutes. 
 
 (358.) The ventilation of the old House of Com- 
 mons was, for many years, a subject of complaint, 
 and it engaged the attention of many practical 
 and scientific men. The apparatus which was 
 erected for this purpose in the temporary House 
 of Commons in the year 1836, appears, however, 
 to have been a most expensive contrivance for 
 accomplishing the object. 
 
 Dr. Ure has written a useful memoir on the 
 subject of ventilation,* in which he compares the 
 advantages of these two methods; and he esti- 
 mates the relative cost of ventilating by a fan, 
 compared with that by chimney draught, as about 
 1 to 38. In his calculations on this subject, 
 however, he has apparently been led into an 
 error. His experiments on the consumption of 
 fuel to produce a given effect by chimney draught 
 were all made on furnaces used either for steam- 
 boilers or for brewers' coppers. But, as it could 
 only be the residual heat of the furnace which be- 
 came available in his experiments, after the prin- 
 cipal part of the heat given off by the coal had 
 been absorbed by the boiler, it is certain that any 
 calculation founded on the effect produced in this 
 manner must be considerably below the truth. 
 But although the relative cost of fuel will not be 
 so greatly different as Dr. Ure supposes, under 
 
 * Proceedings of Royal Society, 16th June, 1836.
 
 368 ON THE VARIOUS METHODS 
 
 any circumstances the difference between the two 
 methods must be very considerable. 
 
 (359.) The efficiency of the mechanical method 
 of ventilation by a fan turned by machinery, has 
 been proved so extensively in some of the largest 
 buildings and manufactories in the kingdom, that 
 it might perhaps appear singular Dr. Reid should 
 have adopted so expensive a method of ventilation 
 as that obtained by chimney draught. But the 
 requirements of such buildings as the Houses of 
 Parliament are quite different to all other buildings : 
 and the successive experiments made in the ventila- 
 tion of these buildings for now nearly forty years, 
 appear to result in the conclusion that ventilating 
 by chimney draught, though very much the most 
 expensive, possesses advantages for these particular 
 buildings, hardly obtainable by other means. 
 
 These experiments, which have been carried on at 
 a cost, as it is supposed, of half-a-million of money, 
 commenced in the year 1836, under Dr. Reid. By 
 his plan large coke fires, burning under an im- 
 mense chimney, were employed to draw out the 
 foul air from the house. This was afterwards com- 
 bined with revolving fans, 30 feet in diameter, 
 driven by steam, for forcing in fresh air, either 
 heated or cooled, according to the season of the 
 year, for supplying the place of the air extracted 
 by the chimney draught. On the retirement of 
 Dr. Reid, about the year 1848, various schemes 
 for the warming and ventilating these buildings 
 were proposed and partially carried out, with- 
 out any very definite results. In 1851, Mr. 
 Goldsworthy Grurney was consulted, and a year or 
 two later he received the appointment for arranging 
 and superintending all the warming and ventila- 
 ting arrangements. Great alterations were then 
 made. The steam jet was now applied for the 
 ventilation, and after considerable trials was given
 
 OF PRODUCING VENTILATION. 369 
 
 up as unsuitable for the purpose. The warming 
 arrangements were all reconstructed. The venti- 
 lation was changed from an upward to a downward 
 draught, and the windows of the House were made 
 to open which had before been closed. These 
 plans underwent several alterations. The venti- 
 lation by chimney draught was again introduced. 
 Fans for giving motion to the air were again 
 employed; and the heating was effected by high- 
 pressure steam in conjunction with an arrange- 
 ment called "steam batteries," constructed on the 
 same principle as Sylvester's stoves, described 
 Art. 208. After various alterations the present plan 
 was adopted, by which the powerful furnaces with 
 an upcast shaft were used for extracting the foul 
 air from the ceiling. The fresh air, either heated 
 by steam batteries in winter, or cooled by ice in 
 summer, was made to enter through the cast-iron 
 perforated floor covered with a peculiar open 
 matting of whipcord, and also partly forced in by 
 air pumps or bellows worked by steam. The 
 arrangements of Dr. Reid for washing the air by 
 passing it through canvas wetted by fine spray 
 jets, were improved and extended, and the arrange- 
 ments may now be considered as a conbination of 
 all the previous plans which had been separately 
 tried, condemned, and approved, but which in 
 combination appear to accomplish all that can 
 reasonably be expected in such a building. By the 
 present arrangement any degree of warmth; any 
 amount of ventilation ; any degree of moisture or 
 dryness of the air can be produced. Any one of 
 these conditions can be altered in a few moments 
 to almost any extent, and with absolute certainty ; 
 and could the various members of the two Houses 
 only agree as to the temperature, the quantity of 
 air and its degree of moisture, which they prefer, 
 every one of these conditions could be fulfilled by 
 
 2 B
 
 370 ON THE VARIOUS METHODS 
 
 the present apparatus with instant and unfailing 
 precision. This agreement of opinion is never 
 likely to be attained. The different physical con- 
 ditions of the occupants of these buildings, by age, 
 constitution, arid habit, and the ever-varying 
 feeling of excitement, or repose, or exhaustion 
 which they experience, renders it impossible to 
 meet the desires of individuals so variously affected. 
 If satisfaction in this matter could be looked for 
 under such circumstances, it might be found under 
 the present very efficient arrangements carried on 
 under the superintendence of Dr. Percy, and those 
 with whom he is associated. 
 
 (360.) The Marquis de Chabannes, about the 
 year 1816, extensively applied the other mode of 
 ventilation which has been alluded to, by arti- 
 ficially heating the air by means of stoves, after 
 it has passed through openings in the ceiling. By 
 these means the draught is greatly increased. This 
 plan was applied to several very large buildings, 
 and among others to the old Houses of Parliament. 
 It has been fully described by the Marquis, in a 
 pamphlet published by him in 1818 ; but it appears 
 now to have fallen into disuse. More recently the 
 same principle has been applied by using hot-water 
 apparatus fixed in the roof to heat the air, instead 
 of stoves, and by these means producing a rapid 
 and continuous ventilation. For moderate-sized 
 buildings, where a fan moved by steam power 
 would be unsuitable, this plan of ventilation offers 
 many advantages, and has been used in several 
 very important buildings. 
 
 The proper dimensions of such an apparatus 
 would be thus calculated : Suppose a room to be 
 ventilated which holds 500 people. By Art. 345 
 we estimate the quantity of air for each person at 
 ten cubic feet per minute. Five thousand feet of 
 air per minute must thus be abstracted through the
 
 OF PRODUCING VENTILATION. 371 
 
 ventilators. If we raise the temperature of this 
 air 20 in the heating chamber in the roof by the 
 hot-water apparatus, we shall find by Table IV., 
 Art. 106, that to raise 1000 cubic feet per minute 
 from 50 to 70 (the assumed temperature for the 
 purpose of calculation of the room and of the 
 heating chamber) it will require 86 square feet of 
 heating surface. Therefore 430 square feet of hot- 
 water piping would be required to heat the 5000 
 cubic feet of air. By Table XXVIIL, Art. 354, 
 it appears that a velocity of 235 feet per minute 
 will be acquired by a difference of 20 Fahrenheit ; 
 therefore an opening of 21 square feet will be re- 
 quired to provide for the escape of 5000 cubic feet 
 of air per minute under the circumstances here 
 assumed. 
 
 (361.) The mechanical method of ventilation 
 appears to possess many advantages. It is of 
 course only suitable for extensive buildings, on 
 account of the cost of erection and maintenance of 
 the apparatus being too great in any case, except 
 where a large quantity of air is required to be 
 withdrawn. A rotary fan was used as long ago as 
 the year 1734, by Dr. Desaguliers, for ventilating 
 hospitals, prisons, and other buildings ; * though 
 the plan he recommended appears to have been but 
 little used for that purpose. In fact, although the 
 principle was good, it failed in consequence of the 
 trouble attending its use. About the year 1741, 
 Dr. Hales introduced his method of ventilation by 
 bellows; and it was applied in many -cases with 
 great success. Several of the prisons, hospitals, 
 and other buildings of the metropolis, as well as 
 nearly all the ships in the navy, were successfully 
 ventilated by this apparatus, which was extremely 
 simple in its construction and operation.! It con- 
 
 * Philosophical Transactions, 1735, vol. xxxix., p. 41. 
 f Dr. Hales, " On Ventilators." London, 1743. 
 
 2 15 2
 
 372 ON THE VARIOUS METHODS 
 
 sisted of a large box with valves opening inwards, 
 and other valves opening outwards, which alter- 
 nately admitted and discharged the air, when an in- 
 ternal diaphragm, fixed by leather hinges to the 
 centre of the box, was moved up and down by a 
 handle passing through the upper part of the box. 
 One defect, however, was common both to this appa- 
 ratus and that of Dr. Desaguliers ; they, were both 
 made dependent for their operation on manual 
 labour, and therefore their use was limited both in 
 duration and extent. For, however efficacious 
 the operation might be, the trouble attending it, 
 when the whole effect was produced by manual ex- 
 ertion, rendered it inconvenient, expensive, and un- 
 certain. The extensive introduction of machinery 
 throughout every department of manufactures has 
 again, after a lapse of many- years, brought into use 
 both these methods of ventilating buildings. The 
 ventilating fan of Dr. Desaguliers, with some im- 
 provements suggested by modern discoveries and 
 experiments, is now extensively used in the manu- 
 facturing districts of England ; the fan being turned 
 by the steam power employed in the manufactories. 
 The bellows of Dr. Hales, slightly altered in their 
 form, have also again been recently brought in to use. 
 The late Mr. Oldham, the engineer to thp Bank of 
 England, applied this principle of ventilation, in 
 the year 1838, to a part of that establishment with 
 complete success. This apparatus differs, however, 
 slightly from that of Dr. Hales, particularly in 
 being fitted with a piston instead of a movable 
 diaphragm, which gives it more of the character of 
 a pump, though the difference in its construction 
 is very inconsiderable. In this case also the motive 
 power is steam, the powerful machinery constantly 
 in use at the Bank being employed to work the 
 pump which ventilates the building. Both these 
 methods of ventilating, when thus applied, are
 
 OF PRODUCING VENTILATION. 373 
 
 unerring in their operation, and appear to accom- 
 plish all that is necessary or desirable on this 
 important subject; for the quantity of air dis- 
 charged can, by both methods, be either increased 
 or diminished at pleasure, by the mere shifting of 
 the band which drives the pulley. 
 
 (362.) By these methods of ventilation, the 
 rarefaction or diminished pressure of the air can 
 be effectually prevented. In the method adopted 
 at the Bank of England, instead of the vitiated air 
 being drawn from the building by the apparatus, 
 the operation consists in forcing in fresh air, which 
 in cold weather is warmed by passing through a 
 steam chamber; and the vitiated air escapes from 
 the room in consequence of its greater levity ; the 
 quantity which escapes being equal to that which 
 is forced in by the -pump. By this means no 
 diminution of pressure can arise; but, from what 
 has already been stated (Art. 334), it may be 
 questioned whether the small diminution of pressure 
 which occurs under ordinary circumstances is a 
 matter of any importance. 
 
 (363.) The fans that were used by Dr. Desagu- 
 liers were seven feet in diameter, and one foot wide. 
 They revolved in a concentric case, closed in every 
 part, except an opening at the centre, which com- 
 municated by a pipe with the room to be ventilated, 
 and another pipe at the circumference, by which the 
 foul air that was drawn in at the centre was thrown 
 out with considerable force by the rotating leaves 
 of the fan. This construction, however, has been 
 found objectionable. Considerable loss of power 
 accrues from employing a fan moving concentric 
 with the case, on account of a large quantity of air 
 being carried round by the leaves of the fan, instead 
 of passing out through the discharge-pipe at the 
 circumference. The most advantageous form is 
 when the case is eccentric to the revolving leaves
 
 374 ON THE VARIOUS METHODS 
 
 of the fan, the discharge-pipe being placed at that 
 part of the circumference of the case where the 
 eccentricity is the greatest ; the air being admitted 
 at the centre in the same manner as before stated. 
 In this form there is comparatively little loss of 
 power; but owing to the inertia of the air, some 
 loss must always occur between the calculated 
 and the actual discharge, the difference being 
 always greater in proportion to the greater speed 
 with which the fan revolves. 
 
 (364.) The mode of calculating the quantity of 
 air discharged by any mechanical method, as also 
 the power expended in discharging it, is necessary 
 to be known, in order to apportion an apparatus of 
 a proper size to any particular building. Both 
 these subjects have been investigated by Dr. Ure,* 
 who has made various experiments connected with 
 this branch of inquiry. The mean velocity of the 
 portion of the vanes of the fan by which the air is 
 discharged is about seven-eighths of the velocity of 
 the extremities of the leaves ; but, owing to the 
 inertia of the air, there will be a further loss in the 
 velocity of the issuing current, increasing with the 
 greater velocity of the vanes ; so that, under ordinary 
 circumstances, the current will be discharged with 
 a velocity equal to about three-fourths of the velocity 
 of the extremities of the leaves. This velocity, in 
 feet per second multiplied by the area of the 
 discharge-pipe in square feet, will give the number 
 of cubic feet of air discharged per second. To 
 estimate the force necessary to cause the rotation 
 of the fan, the following method of calculation, 
 founded on the ordinary mode of estimating steam 
 
 * Philosophical Transactions, 1836. See also Peclet, " Traite 
 de la Chaleur," 3rd edition, p. 100 et seq., for some useful 
 calculations on the relative cost of various methods of dis- 
 charging air for ventilating purposes. Also Wyman "On 
 Ventilation," p. 169.
 
 OF PRODUCING VENTILATION. 375 
 
 power, will be found sufficiently accurate. Suppose 
 the effective velocity of the vanes of the fan to be 
 70 feet per second, and the sectional area of the 
 eduction tube to be 3 square feet, then 70 x 3 = 210 
 cubic feet will be the quantity of air discharged 
 per second ; and this number, multiplied by 60, will 
 give the quantity per minute. As a cubic foot of 
 air weighs 527 grains, there will be about 13 cubic 
 feet of air to a pound ; therefore ^1 = 969 Ibs. is 
 the weight of air put in motion per minute with 
 a velocity of 70 feet per second. The height from 
 which a gravitating body must fall in order to acquire 
 a velocity of 70 feet per second is ~ = 76-5 feet, 
 which, multiplied by the number of pounds weight 
 moved per minute, will give the power necessary 
 to be expended in order to discharge this quantity 
 of air at the stated velocity; and this product 
 divided by 33,000 (the number of pounds weight 
 that one horse will raise one foot high per minute) 
 will give the amount of steam power required. 
 Therefore '-^ = 2 24, or nearly 2 horses' power, 
 will be necessary to discharge the given quantity 
 of air at the velocity stated. 
 
 The quantity of air discharged by bellows is 
 easily calculated. The cubic contents of the box 
 (or that portion of it which is filled and emptied 
 at each alternation of the handle), multiplied by 
 the number of strokes per minute, will, of course, 
 give the quantity of air discharged ; making such 
 deduction from this amount as may be necessary 
 for imperfect fitting of the diaphragm. The ven- 
 tilating pump differs from the bellows simply in- 
 making the whole diaphragm move up and down, 
 instead of one end being fixed. The force re- 
 quisite for discharging the same quantity of air 
 by either of these methods is the same as with a 
 fan. For, suppose a ventilating pump three feet
 
 376 OX THE VARIOUS METHODS 
 
 square and five feet high, and that the piston 
 makes 25 double strokes per minute, each four 
 and a half feet long; in this case 2025 cubic feet 
 of air per minute will be discharged ; and if the 
 valve for its discharge be 10 inches square, the 
 velocity of its discharge will be equal to 48 6 feet 
 per second. This quantity of air reduced into 
 weight will be ^ = 155 Ibs., put into motion 
 every minute at the rate 'of 48 6 feet per second ; 
 and therefore we shall have ~ = 36 -9 feet, as the 
 height from which a gravitating body must fall to 
 obtain the velocity of 48 '6 feet per second; and 
 - = 17, or one-sixth of a horse's power, as the 
 
 155 X 36-9 
 
 33,000 
 
 necessary force to discharge this quantity of air at 
 the stated velocity. 
 
 (365.) The Archimedean screw has repeatedly 
 been proposed for the ventilation of buildings, and 
 its application to this purpose has been more than 
 once the subject of a patent. In comparison with 
 a fan, it appears to be every way inferior; for 
 neither in quantity nor in velocity can it at all 
 approach the performance of the fan in discharging 
 air from buildings. By the fan almost any velocity 
 of the discharged current may be obtained ; but not 
 so by the Archimedean screw. The friction between 
 the air and the threads or spirals of the revolving 
 screw must be the power which produces the 
 discharge ; but so soon as the pressure or conden- 
 sation of the air between the spirals equals the 
 friction existing between the air and the surface 
 of the spirals, any further increase in the amount 
 of the discharge ceases ; and the screw might revolve 
 with any increased velocity without increasing the 
 quantity of air discharged, and a loss of power in 
 turning the screw would then necessarily occur. 
 The plan, however, has been used with some success 
 in large manufactories in Leeds and elsewhere,
 
 OF PRODUCING VENTILATION. 377 
 
 where an abundance of steam power is alwa} 7 s in 
 operation. 
 
 (366*.) In the year 1873, a patent was obtained 
 by Mr. Tobin of Leeds, for a mode of ventilation 
 which excited much attention, and a Joint Stock 
 Company was formed to carry out the invention on 
 an extensive scale. The plan was to introduce cold 
 fresh air through tubes, tunnels, or drains, under 
 the floors of rooms, and thence by means of upright 
 or vertical pipes, placed at the corners of the room, 
 or elsewhere, to give the air an upward direction, 
 through open pipes, of from four to six feet in 
 height. It was assumed that this method would 
 produce ventilation without draught, but this 
 assumption was a perfect fallacy. It was, more- 
 over, discovered that this same invention had been 
 extensively tried more than 90 years previously, 
 and a full description of it published in 1794, taken 
 from the. papers of Mr. John Whitehurst, F.R.S., 
 who died in 1788, who several years before his 
 death had applied the plan in question to various 
 buildings. The patent of Mr. Tobin is described 
 almost in the identical words of Mr. Whitehurst; 
 and both the legal validity of the patent and the 
 plan itself appear to be equally worthless. In cold 
 windy weather the draughts become intolerable ; 
 and in warm and still weather, when ventilation 
 is most needed, no effect whatever is produced. 
 The principle, as applied by Mr. Tobin, is founded 
 on a fallacy, which, however excusable in 1780, 
 when first used by Mr. Whitehurst, is utterly 
 unsuited either to the requirements or to the know- 
 ledge of the present day. The fallacy of the plan 
 consists in supposing that perfectly cold external 
 air can be introduced into rooms in this way 
 without causing cold currents; but when the air 
 is heated before admission into the room to be 
 ventilated, this mode of introducing fresh air 
 possesses advantages in many cases.
 
 378 ON THE VARIOUS METHODS 
 
 (367*.) More than twenty years before Mr. Tobin 
 revived this invention of Mr. Whitehurst, a much 
 more judicious plan for bringing in warmed air 
 through upright ducts or channels above the heads 
 of the occupants of a room, had been successfully 
 employed. In one of the courts of the Old Bailey 
 Sessions House in London, the ventilation was 
 obtained by setting the panelling of the court about 
 six inches off from the wall for about seven or 
 eight feet in height. Through this large channel, 
 extending almost round the court, a large volume 
 of air was forced into the court, and having an 
 upward motion given to it, by the position of the 
 channel, no inconvenient draught was experienced. 
 
 (368*.) This plan of ventilating, though pos- 
 sessing much to recommend it, is not absolutely 
 perfect. It requires, in addition, that a further 
 supply of air be brought in at a lower level. 
 When this is not done the air nearer the floor is 
 not in so fresh a state as it ought to be; and it 
 requires, therefore, for perfect ventilation, that a 
 portion of air should enter near the floor as well as 
 at the higher level already described. 
 
 By heating the air before it enters the room to 
 be ventilated, the motive power of the wind is 
 almost entirely lost. Some other motive power is 
 therefore necessary when any considerable quantity 
 of air is required. In the Old Bailey Court House, 
 the air is set in motion by a large fan. And either 
 by mechanical means, or by exhaustion by heat 
 by some of the methods previously described, a 
 sufficient motive power must be applied to produce 
 a current varying from sixty to one hundred feet 
 per minute. A greater velocity than this produces 
 a very sensible and unpleasant draught. 
 
 (369*.) Very extensive use has at various times 
 been made of ventilating cowls, similar in principle 
 to those used for increasing the draught of smoky
 
 OF PRODUCING VENTILATION. 379 
 
 chimneys. These cowls are extremely useful in 
 many cases, but they are limited in their effects ; 
 and they depend altogether on the action of the 
 wind, their effects being scarcely appreciable in 
 still and warm weather when ventilation is most 
 required. 
 
 (370*.) Cowls of almost every imaginable variety 
 of form have been invented. They all owe their 
 efficacy to one general law belonging to all aeriform 
 fluids, that a current moving in any direction at 
 a high velocity, readily imparts its own velocity to 
 another current moving at a lower velocity in the 
 same or nearly the same direction. This peculiar 
 property of fluids, both liquid and aeriform, to 
 communicate motion to other similar bodies, not in 
 immediate contact with them, may be illustrated as 
 follows : Suppose a pipe several feet in length, 
 and of considerable diameter say for example 
 twelve or fourteen inches and open, at both ends. 
 Let there be also a small pipe, of about one inch 
 diameter, inserted into one end of the large pipe 
 for a short distance, and let there be a current of 
 air or steam forced through the small pipe with 
 considerable velocity. The action of this current 
 of air or steam will be such, that it will continue 
 its course after leaving the small pipe for a very 
 considerable distance along the large pipe, at its 
 original velocity, and with scarcely any lateral ex- 
 pansion ; and it will communicate its own velocity 
 to a very great body of air in the large pipe, which 
 will thus have a current produced in it of consider- 
 able intensity. The distance to which the current 
 passing along the small pipe will proceed without 
 losing its velocity and mixing with the aeriform 
 fluid contained in the large pipe, will depend upon 
 the initial velocity which is given to it ; but this 
 distance is considerable, and the quantity of air is 
 very great which may be put in motion in the large
 
 380 ON THE VARIOUS METHODS 
 
 pipe, by an extremely small jet of air in the small 
 pipe. The currents and eddies of many rivers and 
 lakes have their origin in this cause. The draught 
 caused in the chimneys of locomotive engines by a 
 jet of steam, the action of all chimney cowls, and 
 other of the phenomena which occasionally present 
 themselves in practical science, are due to this fact. 
 In the case of chimney cowls the effect is very re- 
 markable. Whatever efficacy any chimney cowl 
 really possesses arises from this cause ; though 
 very few of the contrivers of these machines are 
 aware of the fact. Some interesting experiments 
 on the action of cowls, by Mr. Ewbank, are in- 
 structive on this point.* The figures 54 to 62 are 
 some of the forms on which he experimented. His 
 models were made of glass, and a strong blast of 
 air was made to blow equally on them all. The 
 lower ends of the models were all made to dip into 
 a trough of water, and the height to which the 
 water rose in the stem of the model, showed the 
 relative effect produced by each different form. 
 The annexed cuts show the models in the pro- 
 gressive order of their efficiency, namely 
 
 * See EwbanVs Hydraulics, New York, 1854; Franklin 
 Journal of Pennsylvania; Mechanic's Magazine, vol. xxxvii., 
 p. 372 ; and Wyman on Ventilation, Boston, 1846.
 
 OF PRODUCING VENTILATION. 
 
 381 
 
 No. of Figure 
 
 Height to which ) 
 the water rose, > 
 in inches. J 
 
 54 
 
 55 
 
 56 
 
 57 
 
 58 
 
 59 
 
 60 
 
 61 
 
 62 
 
 21 
 
 2* 
 
 H 
 
 *b 
 
 i 
 
 H 
 
 8 
 
 15 
 
 18 
 
 In the case of fig. 54, the blast was made to act 
 in direct line with the outlet ; but when the blast 
 acted at an angle of 45 degrees with this direction, 
 the water rose 3^ inches ; and when it acted at an 
 angle of 90 degrees, the water rose only 21 inches. 
 The other forms, acted on by the same blast, caused 
 the water to rise to the heights stated against each. 
 This height of water may fairly be assumed as the 
 relative exhausting power of these different forms 
 of cowls, when acted upon by a strong blast. It 
 is, however, considered that in such forms as those 
 of Nos. 58 and 62, the effect is best secured by 
 bringing the small blow-pipe tube beyond the 
 vertical junction of the main tube, as otherwise it 
 is liable to blow downwards. 
 
 (371*.) There are many other forms of venti- 
 lating and smoke cowls which possess considerable 
 advantages, some being more suited for smoke and 
 some being only fit for ventilation, by reason of the 
 difficulty of freeing them from deposits of soot. 
 Except for this latter objection, whatever form is 
 best for one purpose would be equally advantageous 
 for the other. Hawkesley's Patent Cowl, fig. 63, 
 is an extremely useful apparatus, and so also is the 
 Funnel, or Cowl, fig. 64, known as the Himalaya 
 funnel. Both these owe their effective action to 
 the well-known principle that the wind is deflected 
 at the same angle at which it strikes any object. 
 In both these last shown figures, this deflection is 
 produced, upwards, by the wind striking against 
 surfaces fixed at angles of about 45 from a hori- 
 zontal line. In figure 63 the striking surfaces are
 
 382 ON THE VARIOUS METHODS 
 
 slightly curved, which is supposed to give a still 
 further advantage to the upward current. 
 
 Another patented invention for this purpose is 
 Carson's Ventilator,* which has been extensively 
 used. It is precisely similar in principle to the 
 "Blow Pipe Ventilators," shown figures 58 and 62. 
 It is almost one of the best forms of those venti- 
 lators which turn round on a centre with the wind. 
 In all forms of revolving cowls increased steadiness 
 and certainty of action is produced by making the 
 acting portion of the vane double, and so placed 
 that the heavy end of the vane or director shall 
 form a figure like the capital letter Y, the diver- 
 gence between the two members being about 30. 
 
 In a somewhat recently patented invention by 
 Boyle and Son, of Glasgow, a ventilator is employed 
 which is divided vertically into four parts. The 
 action arises from the wind striking on a number 
 of inclined surfaces fixed vertically and forming an 
 external circumference of many narrow inclined 
 surfaces surrounding the centre tube which carries 
 off the air from the room to be ventilated. These 
 inclined surfaces stand off from the main ventilating 
 tube some two or three or more inches. The 
 effective action in this ventilator is due to the 
 wind being driven against the inclined surfaces of 
 one of the sides of the ventilator; and as the 
 pressure of the wind will then be a plenum on this 
 side, while one of the other sides will be a vacuum, 
 the foul air of the room will be withdrawn through 
 the inner tube with a corresponding velocity to 
 that of the external current. The action of this 
 ventilator is precisely the same as that of the 
 Himalaya funnel, or of Carson's, Hawkesley's, and 
 other ventilators already described. They are all 
 subject to the same laws, and are all dependent on 
 the action of the wind to produce any effect what- 
 
 * See Repertory of Arts, vol. xv. (1841), p. 71.
 
 OF PRODUCING VENTILATION. 383 
 
 ever. In still weather no effect is produced by 
 any of these ventilators beyond what would result 
 from merely cutting a hole through the roof or 
 ceiling of equal size. 
 
 (372*.) Such modes of ventilating as have been 
 here described may be useful where only compara- 
 tively small quantities of air are required to be 
 changed. They are all of them utterly inefficient 
 in calm and warm weather. Where very large 
 numbers of persons are congregated together, and 
 consequently a large supply of fresh air becomes 
 absolutely indispensable, no plan of spontaneous 
 ventilation is sufficient. The several plans de- 
 scribed in the early part of this chapter are alone 
 to be relied on for this purpose. They may be 
 classed under three heads. Either by mechanically 
 forcing in, or sucking out, air by means of fans, 
 bellows, or pumps ; or by heating the air in a false 
 roof or chamber above the room to be ventilated ; 
 or by drawing the foul air either upwards or 
 downwards through a large furnace, in the manner 
 used by Dr. Reid in the Houses of Parliament. 
 Which of these plans may be most suitable must 
 depend upon the character and size of the building 
 in which it is to be applied. 
 
 (366.) Considering the great importance of ven- 
 tilation, it is much to be regretted that so little 
 attention has generally been devoted to the sub- 
 ject by scientific men. The treatises which have 
 been written upon it are extremely few, and those 
 generally but too indefinite and inconclusive. In 
 the year 1835, a Committee of the House of 
 Commons was appointed to report upon the best 
 plan of ventilating the Houses of Parliament ; but 
 the various scientific men who were then ex- 
 amined were unable to point out any public 
 building of which the ventilation was at- all 
 deserving of the consideration of the Committee,
 
 384 ON THE VARIOUS METHODS 
 
 as a model for adoption. In fact, it is not merely 
 the method but the amount of ventilation which 
 is desirable, that appears to have been hitherto 
 unascertained. When Sir Humphry Davy ven- 
 tilated the House of Lords, in 1811, he used a 
 pipe only one foot diameter to convey away the 
 foul air. In 1813, this was increased to three 
 feet diameter; an alteration which allowed nine 
 times the quantity of air to escape ; but even this 
 was found quite insufficient for the purpose. And 
 the various experiments of Watt, Bumford, Davy, 
 Chabannes, and others, in ventilating various 
 public buildings, prove that their methods were 
 inadequate for the purpose, notwithstanding their 
 plans might be considered as improvements upon 
 preceding arrangements. The subject of ventila- 
 tion has now, however, attracted more of public 
 attention ; and we may therefore hope that this 
 important means of improving the public health 
 will henceforth be more fully considered, and 
 that the time may come when architects will 
 consider it as great a defect to neglect providing 
 the means for the admission and discharge of the 
 air required for ventilation, as they would to omit 
 the doors and windows of the buildings they are 
 called upon to design and erect. The vast import- 
 ance of ventilation was most forcibly demonstrated 
 by the evidence taken before the Committee of the 
 House of Commons on the Health of Towns, in 
 the year 1840. Scrofulous diseases are stated by 
 the medical witnesses to be the result of bad venti- 
 lation; and that in the case of silk weavers, who 
 pass their lives in a more close and confined air than 
 almost any other class of persons, their children 
 are peculiarly subject to scrofula and softening of 
 the bones.* Most of the witnesses state that a 
 deterioration of the race undoubtedly occurs among 
 * " Keport on the Health of Towns," pp. 18 and 201.
 
 ON PRODUCING VENTILATION. 385 
 
 those classes most exposed to defective ventilation ; 
 and they consider that bad air deadens both the 
 mental and bodily energies.* The statement of 
 some of the diseases produced by bad air is abso- 
 lutely sickening ; and presents the consequences of 
 violating the physical laws, in a point of view, 
 which will scarcely find a parallel^ These are 
 undoubtedly extreme cases ; but although the 
 ordinary effects of defective ventilation are less 
 marked, it is certain that no violation of the physi- 
 cal and organic laws, however slight, can possibly 
 be allowed without the consequences becoming- 
 apparent in the deteriorated health of those who 
 violate them ; and it will be well when this fact is 
 as universally acted upon, as it is generally assented 
 to. 
 
 * Ibid., pp. 54 and 201. 
 
 t Ibid, Mr. Walker's Evidence, p. 211, et seq. 
 
 2 c
 
 38G 
 
 CHAPTER Y. 
 
 OX THE THEORY OF GASEOUS EFFLUX.* 
 
 (3t)7.) IN the preceding chapter the theoretical 
 determination of the flowing of air and other gases 
 through apertures has been given, and its utility 
 in calculating the proper size of ventilators pointed 
 out : it will here be desirable to show the grounds 
 for believing that this theory truly represents the 
 case with the accuracy required for determining a 
 physical law. 
 
 (368.) The theoretical determination of the 
 velocity with which gaseous fluids are discharged 
 through tubes and apertures under pressure has 
 often been submitted to mathematical investiga- 
 tion ; and the subject being of importance in 
 various branches of practical science, it is to be 
 regretted that considerable differences exist in the 
 results of the several formulas which have been 
 propounded for its elucidation. Dr. Papin,f in 
 1686, first showed that the efflux of all fluids 
 follows a general law ; and that the velocities are 
 
 * This chapter contains the paper by the author which was 
 read before the Institution of Civil Engineers, May 1840, 
 ' On the Efflux of Gaseous Fluids under Pressure." Since 
 it was written, anemometers for registering the velocity of 
 aerial currents have been greatly improved, and as now con- 
 structed they afford an easy mode of measuring the velocity 
 of aeriform fluids with very considerable accuracy. 
 
 f Philosophical Transactions, 1686.
 
 OX THE THEORY OF GASEOUS EFFLUX. 387 
 
 inversely as the square roots of the specific gra- 
 vities. Dr. Gregory has likewise given various 
 formulae for calculating the velocities of air in 
 motion under different circumstances; and Mr. 
 Davies Gilbert, Mr. Sylvester, Mr. Tredgold, and 
 many other writers of equal authority, have also 
 investigated the subject. 
 
 (369.) The hydrodynamic law of spouting fluids 
 has by all writers been applied in the calculations 
 for the determination of this question. This law, 
 it is well known, is the same as that of the acce- 
 lerating velocity of falling bodies; and is propor- 
 tional to the square root of the height of the 
 superincumbent column of homogeneous fluid. 
 But, although the various writers all agree in this 
 fundamental principle, they differ materially in the 
 mode of applying it, and the several corrections 
 introduced in their theorems; and the results 
 they have arrived at are of a very contradictory 
 character. 
 
 (370.) Dr. Gregory's formulae for calculating the 
 velocity with which air of the natural density will 
 rush into a place containing rarer air, is based upon 
 the velocity with which air flows into a vacuum. 
 This is equal to the velocity a heavy body would 
 acquire by falling freely from a height equal to 
 that which a homogeneous atmosphere would have 
 whose weight is equal to thirty inches of mercury. 
 The height of this homogeneous atmosphere is 
 27,818 feet: and the velocity which a body would 
 acquire by falling from this height (and consequently 
 the velocity with which air will flow into a vacuum) 
 is V/ (27,818 x 64-36) = 1339 feet per second. 
 The density of the rarefied air divided by the 
 density of the natural atmosphere, and this number 
 subtracted from unity, represents the force which 
 produces motion ; and the square root of this 
 number multiplied by 1339 feet (the velocity with 
 
 2 c 2
 
 388 OX THE THEORY 
 
 which air rushes into a vacuum) is the velocity 
 with which the atmosphere will rush into any 
 place containing rarer air.* 
 
 (371.) The method employed by Mr. Davies 
 Gilbert is also based upon the velocity with which 
 air rushes into a vacuum, when pressed by a homo- 
 geneous atmosphere equal to the weight of the 
 natural atmosphere at the earth's surface. This 
 supposed homogeneous atmosphere is, according to 
 Mr. Davies Gilbert's calculation, 26,058 feet: and 
 the velocity with which air would rush into a 
 vacuum when pressed by this weight, will be 
 v/ (26,058) x 8 = 1295 feet per second. When this 
 calculation is applied to two columns of air of un- 
 equal density as for instance, the discharge of 
 air through a chimney-shaft the height of the 
 heated column of air divided by the height of this 
 homogeneous atmosphere, and the square root of 
 this number multiplied by the velocity with which 
 air flows into a vacuum, and this product again 
 multiplied by the square root of the number repre- 
 senting the expansion of the heated air, will give 
 the velocity in feet per second. The expansion of 
 air when heated is found (by Mr. Gilbert's method) 
 by raising the decimal 1*002083 (which represents 
 a volume of air expanded by one degree of 
 Fahrenheit) to the power whose index is the 
 number of degrees which the temperature of the 
 air is raised; or it is equal to the fraction gl|" 
 n being the number of degrees of Fahrenheit which 
 the temperature of the ascending column exceeds 
 that of the external atmosphere. f 
 
 (372.) Mr. Sylvester's method of calculation pro- 
 ceeds upon the supposition that the respective 
 columns of light and heavy air represent two un- 
 
 * Gregory's " Mechanics," vol. i., p. 515. 
 
 f Quarterly Journal of Science, vol. xiii., p. 113.
 
 OF GASEOUS EFFLUX. 389 
 
 equal weights suspended by a cord hanging over 
 a pulley; and this mode of calculation gives a 
 result very much less than by any other method. 
 
 The unequal weight of two columns of air is 
 found by Mr. Sylvester nearly in the same manner 
 as by Mr. Gilbert. The volume of air expanded 
 by one degree of heat is equal to 1 00208 ; and this 
 number, when raised to the power whose index is 
 the excess of temperature of the heated column, 
 gives the expanded volume of the air ; and assum- 
 ing the atmospheric density to be unity, we have 
 1 - (p^i) 6 = d ; e being the excess of temperature 
 of the heated column, and d the difference of density 
 between the two columns. This difference of density 
 multiplied by eight times the square root of the 
 height of the tube or shaft containing the heated 
 air, gives the velocity in feet per second.* 
 
 (373.) In Mr. Tredgold's theorem for calculating 
 the efflux of air, the force which produces motion 
 is assumed to be the difference in weight of a 
 column of external and one of internal air, when 
 the bases and heights are the same. The difference 
 of temperature of the two columns by Fahrenheit's 
 scale, divided by the constant number 450 plus the 
 temperature of the heated column, and this quotient, 
 multiplied by the height of the tube or shaft, gives 
 the difference in weight. Then by the common 
 theorem for falling bodies, eight times the square 
 root of this number will give the velocity in feet per 
 second ; or, accurately, V = v/ ^Lo+T^ ^ being the 
 height of the tube, t the temperature of the internal, 
 and x the temperature of the external air.f 
 
 (374.) The method of calculation proposed by 
 Montgolfier appears, however, by recent experiments 
 to be the most accurate, as it is also the most simple 
 
 * Annals of Philosophy, vol. xix., p. 408. 
 
 t Tredgold, " On Warming Buildings," p. 76.
 
 390 OX THE THEORY 
 
 of all the modes of determining this question. The 
 difference in height must be ascertained which two 
 columns of air would assume when the one is heated 
 to the given temperature, the other being the tem- 
 perature of the external air ; and the rate of efflux 
 is equal to the velocity that a heavy body would 
 acquire by falling freely through this difference 
 of height. 
 
 The space which a gravitating body will pass 
 through in one second, we know to be 16*09 feet; 
 but, by the principle of accelerating forces, the 
 velocity of a falling body at the end of any given 
 time is equal to twice the space through which it 
 has passed in that time ; or the velocity is equal to 
 the square root of the height of the fall, multiplied 
 by the square root of 64*36 feet ; or, again, to the 
 spuare root of the number obtained by multiplying 
 64-36 feet by the height of the fall in feet 
 
 When the vis viva is the difference in weight be- 
 tween two columns of air, caused by the expansion 
 of one of these columns by heat, the decimal 00208, 
 which represents the expansion of air by one degree 
 of Fahrenheit, must be multiplied by the number 
 of degrees the temperature is raised, and this 
 product again by the height of the heated column. 
 Thus, if the height of the column is 50 feet, and 
 the increase of temperature 20, we shall have 
 20 x -00208x50 =2 -08 feet; or 52-08 feet of hot 
 air will balance 50 feet of the cold air, and the 
 velocity of efflux of the heated column when pressed 
 by the greater weight of the colder column will be 
 equal to ^(2*08 x 64) = 11*55 feet per second.* 
 
 * This mode of calculation supposes an equal expansion of 
 air by equal increments of temperature, which is generally 
 assumed to be true at all moderate differences of temperature. 
 There can, however, be but little doubt that air expands more, 
 proportionately, at high temperatures than at low ones, for 
 equal increments of heat ; but, as all other bodies expand even
 
 OP GASEOUS EFFLUX. 391 
 
 The efflux of air under any given pressure can 
 also be calculated by the same means ; for the 
 pressure being known, it is only necessary to cal- 
 culate the height of a column of air which would 
 be equal in weight to this pressure. Thus, if the 
 pressure be equal to one inch of mercury, water is 
 827 times the weight of air, and mercury 13-5 
 times the weight of water; therefore, 827 x 13 '5 
 = 11164 inches, or 930*3 feet; and according to 
 the preceding formula ^(930 '3 x 64) = 244 feet 
 per second for the velocity of efflux under this 
 pressure of one inch of mercury. 
 
 (375.) In all these cases the velocity thus ascer- 
 tained is independent of any loss by friction ; a 
 certain deduction must be made for this loss, which 
 will vary greatty, according to the nature and size 
 of the tube or shaft through which the air passes, 
 as well as with the velocity of the air. Like all 
 other fluids, the retardation of the air by friction, 
 in passing through straight tubes of any kind, will 
 be directly as the length of the tube and the square 
 of the velocity, and inversely as the diameter. 
 This question, however, becomes very compli- 
 cated under these circumstances, and particularly 
 so when there are angular turns in the tube through 
 which the air passes. The present state of our 
 knowledge on this subject does not allow of any 
 very accurate determination of the amount which 
 
 more irregularly than air, we possess no means of measuring 
 this deviation from regular expansion. Mr. Davies Gilbert's 
 and Mr. Sylvester's mode of calculating the expansion of air 
 already given, supposes a very considerable increase in the 
 rate of expansion, and the following formula is used by Dr. 
 Gregory : The expansion of air for 180 is '376 ; therefore, any 
 
 other temperature will be (1 376) T ^ x (1 ' 376)* = (1 0018) X 
 (1-376) 1 = V ; x being the temperature required, and V the 
 volume of the air at this increased temperature (Gregory's 
 " Mechanics," vol. i., p. 486). This mode of calculation gives 
 a less expansion than that of Mr. Gilbert.
 
 392 ON THE THEORY 
 
 ought to be deducted for friction from the initial 
 velocity obtained by calculation ; and it is only by 
 empirical means we can arrive at an estimate of its 
 amount. 
 
 (376.) We shall proceed now to ascertain how 
 far these theoretical calculations agree with the 
 results obtained loy experiments. 
 
 In some new furnaces which Sir John Guest 
 has lately added to his extensive ironworks at 
 Dowlais, some experiments have been made on 
 the quantity of blast injected into the furnaces. 
 In these experiments, the machinery employed 
 being new and of the best construction, the loss 
 occasioned by the escape of air through imper- 
 fections of the apparatus, was, perhaps, as small as 
 possible. The engine for blowing the furnaces 
 made, at the time of the experiments, 18 double 
 strokes per minute. The diameter of the blowing 
 cylinder was 100 inches, and the effective length 
 of the stroke seven feet six inches. From 
 these dimensions, therefore, it appears that 14,726 
 cubic feet of air was taken into the blowing 
 cylinder per minute ; and the tubes through which 
 it was discharged from the receiver were six of 
 four inches diameter, and six of one and a quarter 
 inch diameter; the area of all these tubes was 
 therefore 5747 of a square foot, and the pressure 
 of the blast, measured by a mercurial gauge, was 
 equal to four and a half inches of mercury. Cal- 
 culating by the formula already given, we shall 
 have v/ (827 x 13-58 x 4-5 + 12 x 64)= 519-2 
 feet, which is the velocity per second ; and this 
 number multiplied by 60, and then by the area of 
 the tubes, will give 519 -2 x 60 x '5747 = 17,903 
 cubic feet of air discharged per minute. From 
 this amount some deduction must be made for 
 friction. The velocity of the discharged air is 
 354 miles per hour; and with this immense ve-
 
 OF GASEOUS EFFLUX. 393 
 
 locity, and through such small pipes, the friction 
 is no doubt considerable. By deducting 18 per 
 cent, from the calculated amount of 17,903 cubic 
 feet, we shall have 14,681 cubic feet, which agrees 
 within a fraction (namely, 45 feet) with the quan- 
 tity obtained by measurement. 
 
 (377.) In other experiments made at the same 
 place, the following were the results: The quan- 
 tity of air which entered the blowing cylinder was 
 the same as before, namely, 14,726 cubic feet; 
 the total area of the tubes which discharged the 
 blast was -5502 of a square foot, and the pressure 
 of the blast was equal to four inches of mercury. 
 The calculation, therefore, will be ^ (827 x 13*58 
 x 4 -T- 12 x 64) = 489-5 feet per second: and 
 therefore 489 '5 x 60 x '5502 = 16,159 cubic feet 
 discharged per minute. The velocity of the blast 
 in this case was 333 miles per hour, and if we 
 deduct for friction nine per cent, from the calcu- 
 lated amount, the remainder is exactly the quan- 
 tity of air which is ascertained by experiments to 
 be discharged through the tubes. 
 
 (378.) In a work published in 1834 by Mr. 
 Dufreno}% being a Report to the Director-General 
 of Mines in France on the use of the Hot-Blast in 
 the Manufacture of Iron in England, the results 
 are given of many similar experiments to the 
 above; but with two exceptions, the details are 
 not sufficiently ample to found any calculations 
 upon. The two exceptions named are the furnaces 
 at the Clyde, and at the Butterley Iron Works, 
 when they were blown with cold air. Both these 
 blowing machines are described as having been in 
 use for several years ; and it is therefore natural to 
 suppose the various parts were more worn and 
 fitted less accurately than in those experiments 
 already described. The experiments were also 
 made with less care. They show a different result
 
 394 OX THE THEORY 
 
 to those already detailed ; as in these the calculated 
 quantity of air appears to be less than the quantity 
 which entered the blowing cylinders, in about the 
 same proportion as it exceeded it in the former 
 cases. This difference, no doubt, arises from the 
 imperfect fitting of the piston of the blowing cylin- 
 der, which by allowing a portion of air to escape, 
 would diminish the apparent pressure on the mer- 
 curial gauge placed at the further extremity of the 
 apparatus, and hence the calculated rate of efflux 
 would of course be diminished. 
 
 (379.) In the experiments at the Clyde works 
 the quantity of air which was discharged into the 
 furnaces, when estimated by the quantity that 
 entered the blowing cylinder, was 2827 cubic feet 
 per minute. The pressure of the blast was equal 
 to six inches of mercury, and the area of the tubes 
 0681 of a cubic foot. Calculating the discharge 
 of air under this pressure, it amounts to 2450 cubic 
 feet, being 13 per cent, less than the measured 
 amount, supposing no loss to occur by imperfect 
 fitting of the apparatus. 
 
 (380.) At the Butterley works, the quantity of 
 air discharged into the furnace, estimated by the 
 contents of the cylinder, was 2500 cubic feet per 
 minute. The pressure of the blast was equal to 
 five inches of mercury, and the area of the tubes 
 0681 of a cubic foot. The quantity, by calcula- 
 tion, appears to be 2235 cubic feet, being less by 
 10J per cent, than that shown by experiment. In 
 both these last cases, however, there is but little 
 doubt that the loss of air from the cylinder caused 
 the pressure on the mercurial gauge to be less than 
 it would have been had the apparatus been per- 
 fectly tight; and a very small diminution in the 
 observed height of the mercury would account for 
 a much greater difference in the velocity of efflux 
 than is here shown.
 
 OF GASEOUS EFFLUX. 
 
 395 
 
 We are fully warranted in the conclusion from 
 these experiments, that this method of calculation 
 is as accurate as any theoretical determination of 
 such a question can be ; but, from the results so 
 obtained, an allowance must always be made for 
 friction, which will necessarily vary with the 
 peculiar circumstances of each case. 
 
 The following Table will exhibit the results of 
 the preceding experiments at one view : 
 
 TABLE XXIX. 
 
 Place and 
 Number of 
 Experiment. 
 
 Dowlais, No. 1 
 No. 2 
 
 Clyde, No. 3 
 Butterley, No. 4 
 
 * 
 
 4-5 
 4-0 
 60 
 5-0 
 
 <a 
 
 5747 
 5502 
 0681 
 
 a 
 II 
 
 354 
 
 333 
 408 
 372 
 
 14726 
 
 14726 
 
 2827 
 
 2500 
 
 17903 
 
 16159 
 
 2450 
 
 2235 
 
 + 18 
 + 9 
 13 
 - 10-5 
 
 In order to show the results of the several modes 
 of calculation which different mathematicians have 
 adopted, the following Table has been calculated 
 from the data given in experiment the second 
 of the preceding Table ; and it shows how far the 
 several modes differ from each other in their 
 re suits : 
 
 TABLE XXX. 
 
 Place of 
 Experiment. 
 
 Pressure of Blast, 
 in Inches 
 of Mercury. 
 
 .a 
 
 1 
 
 Quantity of Air discharged (by Calculation). 
 
 Mont- 
 golfler. 
 
 Gre- 
 gory. 
 
 Gilbert. 
 
 Sylvester. 
 
 Tredgold. 
 
 Dowlais 
 
 4 
 
 5502 
 
 14726 
 
 16159 
 
 15152 
 
 14855 
 
 5017 
 
 15555
 
 396 ON THE THEORY OF GASEOUS EFFLUX. 
 
 Considering the amount of friction which must 
 result from the discharge of air at the immense 
 velocity which was -obtained in this experiment, 
 namely 333 miles per hour, and also that some of 
 the tubes were only H inch diameter, it will pro- 
 bably be considered that the highest of these cal- 
 culations is the nearest the truth, as it only allows 
 of a deduction of nine per cent, being made for 
 friction, to reduce the calculated amount to the 
 quantity obtained by experiment. It may, there- 
 fore, be concluded that the method which gives 
 this result is the most accurate, as it is also the 
 most simple for general use.
 
 307 
 
 CHAPTER VI. 
 
 ON THE CHEMICAL CONSTITUTION OP COAL, AND 
 THE COMBUSTION OF SMOKE.* 
 
 Early Use of Coal in England Chemical Composition of Coal 
 Analyses of Coal Combustion of Coal Loss by Imper- 
 fect Combustion Loss from the Escape of Smoke Loss 
 by Carbonic Oxide Causes of Imperfect Combustion 
 Theory of Combustion Temperature required for Com- 
 bustion Effects of Earefaction of the Air Effects of Hot 
 Air Quantity of Air required for Combustion Methods of 
 admitting Air Coir.bustion of Anthracite Coal Descrip- 
 tion of various Plans for consuming Smoke Artificial 
 Fuels. 
 
 (381.) THE value and importance of coal, whether 
 considered in its commercial or its physical charac- 
 ter, or in the effects it has produced upon civili- 
 zation, are sufficient to render all investigations 
 concerning it singularly interesting. The changes 
 which have been effected in the social condition of 
 man by the instrumentality of this valuable sub- 
 stance are as instructive as they are interesting; 
 and great as are the other mineral riches of England, 
 they would be comparatively valueless without the 
 possession of that substance which, under the 
 generic name of coal, is so extensively distributed 
 throughout its various districts. 
 
 * This chapter contains the principal part of a Paper read 
 before the Institution of Civil Engineers, May 10th, 1840, 
 and also the evidence given by the author before a Committee 
 of the House of Commons " On the Prevention of Smoke."
 
 398 COMBUSTION OF COAL. 
 
 Important, however, as coal has now become, 
 its value has been fully recognised for compara- 
 tively but a few years; and the apathy and in- 
 difference with which it was formerly regarded, 
 contrast most singularly with the present impor- 
 tance which it assumes. 
 
 (382.) The ancient Britons were acquainted with 
 the use of coals before the arrival of the Romans. 
 The Anglo-Saxons also knew and partly used them ; 
 but they are not mentioned by any of the writers 
 in the times either of the Danes or Normans, till 
 the reign of Henry III., who, in 1234, granted a 
 charter to the inhabitants of Newcastle to work 
 them. In 1306, they were prohibited at London 
 as a nuisance; but in 1321 they were used at the 
 Palace, and became soon afterwards an important 
 article of commerce. They, however, gradually 
 fell into disuse except among the poor ; and even 
 in the seventeenth century their use was confined 
 to the lower orders, except for the working of 
 metals.* Such a prejudice existed against them in 
 the middle of the sixteenth century, that, in the 
 reign of Elizabeth, an attempt was made again to 
 prohibit their use in London, even for manufactur- 
 ing purposes, during the sessions of Parliament; 
 it being supposed that the air was rendered un- 
 wholesome by the smoke which they produced. 
 
 Previous to the commencement of the seven- 
 teenth century the smelting of iron and other 
 metallic ores was performed with charcoal ; but at 
 that period the large consumption of wood for 
 making charcoal had so thinned the country of 
 timber, that a probability appeared that many iron- 
 works would be stopped for the want of fuel. An 
 important era now commenced. In 1619 a patent 
 was obtained by Dudley, for smelting iron with 
 the coke made from bituminous coal, which in- 
 
 * Fosbroke's " Archaeology," vol. i., p. 72.
 
 COMBUSTION OF COAL. 399 
 
 vention was applied on a limited scale for several 
 years. Shortly previous to this, other persons 
 had attempted the same process without success. 
 Sturtevant in 1612 and Ravenson in 1613, both 
 obtained patents for methods of using coal in blast 
 furnaces for smelting iron ; but both failed of success. 
 Many years, however, elapsed before the use of coke, 
 for this purpose, became general; but, from the 
 period of the middle of the seventeenth century the 
 use of coal became common, both for domestic and 
 manufacturing purposes, in all cases where heat 
 was required to be produced ; and its consumption 
 has steadily increased from that period. 
 
 These few historical remarks on the use of coal 
 show, in a striking point of view, the neglect with 
 which this valuable substance was formerly treated ; 
 and it contrasts most singularly with the vast im- 
 portance which is now attached to it. And when 
 we consider the gigantic effects produced by its 
 agency in our own times, and the still greater 
 effects of which it yet gives promise, we can 
 scarcel}* credit the apathy with which it was re- 
 garded at a period so little remote from our own age. 
 
 (383.) The several properties of coal are the re- 
 sult of two distinct substances, which are combined 
 in different proportions in the specimens obtained 
 from different localities. Carbon and bitumen are 
 the two substances which give to coal its distinctive 
 characters, though other substances exist in it in a 
 greater or less degree ; some being extraneous and 
 the result of mere local situation, and others partak- 
 ing of a more generic character. In discussing this 
 subject we shall proceed to consider first, the chemi- 
 cal character and composition of coal ; secondly, 
 its properties as a combustible ; and, lastly, the 
 methods of consuming the smoke given off during 
 its combustion, and of rendering it available in in- 
 creasing the calorific effects of the fuel.
 
 400 COMBUSTION OF COAL. 
 
 (384.) Some chemists have objected to the opinion 
 that coal is a compound of carbon and bitumen. 
 No process has yet been devised by which it has 
 been possible, in the analysis of coal, to resolve it 
 entirely into these two substances ; but, together 
 with them, there is always obtained a quantity of 
 gaseous matter. Some portion of this gaseous mat- 
 ter readily distils from coal with comparatively a 
 very slight increase of temperature ; while other 
 portions, evidently resulting from the decomposition 
 of the bitumen, require for their elimination a much 
 more intense heat. No specimens of coal yet dis- 
 covered are entirely free from these gaseous products. 
 The only kinds which may be supposed to be ex- 
 empt from them are the anthracites ; but these all 
 contain a small portion of volatile matter, consi- 
 dered by some to be merely water, or its elements ; 
 but by others, on more accurate analysis, decided to 
 be similar in composition, though far less in quantity, 
 to the products obtained from bituminous coal. 
 
 Considerable discrepancies exist in the analyses 
 by different chemists of some varieties of coal. 
 Enough, however, is known to afford very valuable 
 information in the successful application of coal to 
 the various useful purposes of the arts ; though it 
 must be confessed that hitherto the operations of 
 the practitioner have availed far more than the 
 theories of philosophy. 
 
 (385.) No accurate analyses of coal were made 
 previous to those of Dr. Thompson, in 1819. The 
 method previously employed, by ascertaining the 
 quantity of residuary carbon left after the volatile 
 matter was driven off, was necessarily very inac- 
 curate; because the gaseous products of the coal 
 carried off a considerable portion of carbon in the 
 form of carburetted hydrogen and carbonic oxide, 
 by which the quantity of carbon in any given 
 specimen appeared to be considerably less than
 
 COMBUSTION OF COAL. 
 
 401 
 
 really existed. Such a mode of analysis, however, 
 is not without its use ; because it shows, more 
 accurately than any other, the quantity of coke 
 which can practically be obtained from any given 
 specimen of coal, and which by any other mode 
 can only be found by calculation. 
 
 The earliest analyses of coal by this process 
 
 TABLE XXXI. 
 
 Name of Coal. 
 
 Carbon. 
 
 Ashes. 
 
 Volatile 
 Matter. 
 
 Specific Gravity 
 . of the Coal. 
 
 Specific Gravity 
 of the Coke. 
 
 Authority. 
 
 Welsh Furnace Coal . . 
 
 88-068 
 
 3-432 
 
 8 500 
 
 1-337 
 
 1-0 
 
 
 Alfreton Furnace Coal 
 
 52-456 
 
 2-044 
 
 45-50 
 
 1-235 
 
 
 
 Butterley Furnace Coal 
 
 52-882 
 
 4-288 
 
 42-830 
 
 1-264 
 
 1-100 
 
 
 Welsh Stone Coal 
 
 89-700 
 
 2-300 
 
 8-000 
 
 1-368 
 
 1-393 
 
 
 Welsh Slaty Coal . 
 
 84-175 
 
 6-725 
 
 9-100 
 
 1-409 
 
 
 
 Derbyshire CannelCoal 
 
 48-362 
 
 4-638 
 
 47-000 
 
 1-278 
 
 
 Miishf-t * 
 
 Kilkenny Coal .. 
 
 92-877 
 
 2-873 
 
 4-250 
 
 1-602 
 
 1-656 
 
 1VLUSI1CI. 
 
 Do. Slaty Coal . 
 
 80-475 
 
 6-525 
 
 13-000 
 
 1-445 
 
 
 
 Scotch Cannel Coal . 
 
 39-430 
 
 4-000 
 
 56-570 
 
 
 
 
 Boolavoonen Coal 
 
 82-960 
 
 3-240 
 
 13-800 
 
 1-436 
 
 1-596 
 
 
 Corgee Coal 
 
 87-491 
 
 3-409 
 
 9-100 
 
 1-403 
 
 1-656 
 
 
 Queen's County Coal 
 Stone Wood, Giant's 1 
 Causeway . j 
 Caking Coal 
 Splint Coal 
 
 86-560 
 54-697 
 
 75-900 
 55-230 
 
 3-140 
 11-933 
 
 1-500 
 9-500 
 
 10-300 
 33-370 
 
 22-600 
 35-270 
 
 1-403 
 1-150 
 
 1-269 
 1-290 
 
 1-621 
 
 1 D'. 
 
 Cherry Coal . .. 
 CannelCoal 
 
 42-246 
 29-000 
 
 10-00047-754 
 11-00060-000 
 
 1-265 
 1-272 
 
 
 j-Thomson.t 
 
 Kilkenny Coal . 
 
 89-3 
 
 4-0 
 
 6-7 
 
 1-435 
 
 
 1 
 
 Anthracite, Lehigh 5" 
 
 90-1 
 
 3-3 
 
 6-6 
 
 
 
 
 Do. Rhode Island 3 
 
 90-03 
 
 5-07 
 
 4-9 
 
 
 
 ,'Vanuxem.$ 
 
 Do. Do. 
 
 77-7 
 
 15-6 
 
 6-7 
 
 
 
 
 Anthracite, Llanelly ?. 
 
 41-62 
 
 39-98 
 
 18-4 
 
 1-571 
 
 
 I 
 
 Do. Milford Lower Vein 
 
 88-74 
 
 2-46 
 
 8-8 
 
 1-374 
 
 
 >Daniells. 
 
 Do. American 
 
 85-98 
 
 4-62 
 
 9-4 
 
 1-518 
 
 
 
 * Philosophical Magazine, vol. xxxii., p. 140. The 
 author has recently increased this list by some hundreds of 
 analyses of different coals, and published the results in his 
 " Papers on Iron and Steel." 
 
 | Annals of Philosophy, vol. xiv., p. 81 ; and vol. xv., 
 p. 394. 
 
 J Ibid, vol. xxvii., p. 104. In this analysis the volatile 
 matter is considered to be entirely composed of water. 
 
 2 D
 
 402 
 
 COMBUSTION OF COAL 
 
 which have been published, with the exception of 
 those by Kirwan, were made by Mr. Mushet : they 
 are given in the preceding Table, together with 
 several other more recent analyses by different 
 experimentalists. 
 
 These analyses show the very great difference 
 which exists in the composition of the various 
 descriptions of coal. This difference not only exists 
 between the several species of coal, but likewise in 
 
 TABLE XXXII. 
 
 Name of Coal. 
 
 Carbon. 
 
 Hydro- 
 gen. 
 
 Azote. 
 
 Oxygen. 
 
 Specific 
 Gravity. 
 
 Authority. 
 
 Caking Coal .. .. 
 Splint Coal 
 Cherry Coal .. .. 
 
 75-28 
 75-00 
 74-45 
 
 4-18 
 6-25 
 12-40 
 
 15-96 
 6-25 
 10-22 
 
 4-58 
 12-50 
 2-93 
 
 1-269 
 1-290 
 
 1-265 
 
 IDr. Thomson.* 
 
 CannelCoal .. .. 
 
 64-72 
 
 21-56 
 
 13-72 
 
 o-o 
 
 1-272 
 
 
 Splint Coal 
 Cannel Coal .. .. 
 
 70-90 
 72-22 
 
 4-30 
 3-93 
 
 o-o 
 
 2-8 
 
 24-80 
 21-05 
 
 1-266 
 1-228 
 
 \ Dr. Ure.f 
 
 
 
 
 Oxygen & Azote. 
 
 Ashes. 
 
 
 Splint Coal, Wylam . . 
 
 74-823 
 
 6-180 
 
 5-085 
 
 13-912 
 
 V 
 
 Ditto, Glasgow .. .. 
 
 82-924 
 
 5-491 
 
 10-457 
 
 1-128 
 
 I 
 
 Cannel Coal, Lancas. 
 
 83-753 
 
 5-660 
 
 8-039 
 
 2-548 
 
 
 Ditto, Edinburgh 
 Cherry Coal, Newcas. 
 
 67-597 
 84-846 
 
 5-405 
 5-048 
 
 12-432 
 8-430 
 
 14-566 
 1-676 
 
 > Richardson.* 
 
 Ditto, Glasgow .. .. 
 Caking Coal, Newcas. 
 
 81-204 
 87-952 
 
 5-452 
 5-239 
 
 11-923 
 5-416 
 
 1-421 
 1-393 
 
 J 
 
 Ditto, Durham .. 
 
 83-274 
 
 5-171 
 
 9-036 
 
 2-519 
 
 i" 
 
 Anthracite, Wales . . 
 Ditto, Pennsylvania . . 
 
 92-56 
 90-45 
 
 3-33 
 2-43 
 
 2-53 
 2-45 
 
 1-58 
 4-67 
 
 Eegnault. 
 
 Ditto, Meyenn .. .. 
 
 91-98 
 
 3-92 
 
 3-16 
 
 0-94 
 
 . 
 
 Ditto, Eoldue .. .. 
 
 91-45 
 
 4-18 
 
 2-12 
 
 2-25 
 
 
 Ditto, Wales .. .. 
 Ditto, Pembrokeshire 
 
 89-43 
 92-43 
 
 3-56 
 3-37 
 
 3-95 
 2-49 
 
 1-70 
 1-73 
 
 Jacquelain.|| 
 Schafhaeutl.l 
 
 * Annals of Philosophy, vol. xiv., p. 95. 
 
 f " Chemical Dictionary," Art. " Coal." 
 
 t London and Edinburgh Philosophical Magazine, vol. xiii., 
 p. 131. 
 
 Annales de Chimie, vol. Ixvi., p. 337. 
 
 || London and Edinburgh Philosophical Magazine, vol. xvii., 
 p. 213. In this analysis the coal contained 1'36 per cent, of 
 water. 
 
 f Ibid., p. 215. In the ashes of this analysis 12 per cent, 
 is sulphur.
 
 COMBUSTION OF COAL. 403 
 
 the different specimens of the same species obtained 
 from different localities. This is particularly the 
 case with the anthracite coal, which passes through 
 every stage of difference, from nearly a pure carbon, 
 down to the state of ordinary bituminous coal. 
 
 (386.) A more intimate knowledge of the nature 
 of coal was obtained by Dr. Thomson's analyses, 
 before alluded to, by which the exact constituents 
 of the volatile matter were ascertained. The pre- 
 ceding Table gives these analyses, together with the 
 results obtained by other chemists in determining 
 the nature of the gaseous products obtained from 
 coal. 
 
 By comparing together the resultsof Dr. Thomson's 
 analyses, given in the preceding Tables, we shall see 
 how greatly the nature of the volatile matter con- 
 tained in any specimen of coal affects the resulting 
 quantity of coke. By Table XXXII. it appears that 
 the aggregate quantity of the gaseous products of 
 caking, splint, and cherry coal, are very nearly 
 similar ; while by Table XXXI. we perceive that the 
 quantity of coke obtainable from these several species 
 varies more than 45 per cent. This, however, can 
 readily be accounted for, when we ascertain the 
 nature of the gas which predominates in each species : 
 for, where hydrogen and oxygen abound, a large 
 quantity of carburetted hydrogen and carbonic 
 oxide is formed, at the expense of a certain propor- 
 tion of the carbon ; while in such specimens as 
 contain azote in the largest proportion, a far smaller 
 loss of the carbonaceous portion of the coal is 
 sustained. 
 
 (387.) Of all the volatile constituents of coal, 
 the azote is that which quits it with the greatest 
 difficulty. Professor Proust* considers that coal 
 always contains azote, even when reduced to coke ; 
 for when coke is treated with potass, a prussic 
 
 * Nicholson's Journal, vol. xviii., pp. 166 and 173. 
 
 2 D 2
 
 404 COMBUSTION OP COAL. 
 
 lixivium is always obtained ; and the same he even 
 found to be the case with anthracite coal. The 
 prussic radical is a compound of azote and carbon ; 
 and it may be a question whether any part of the 
 difference which is known to exist in the heating 
 power of " oven coke " and " retort coke," is owing 
 in the former case to the presence of a larger portion 
 of nitrogen. Some of the prussic compounds are 
 very inflammable, and may therefore be supposed to 
 produce some calorific effect by their presence. 
 
 Sulphur, which is another substance retained 
 with the greatest pertinacity by coal, exists in 
 nearly all the species in a greater or less degree. 
 It is, perhaps, the only one of the constituents 
 which, according to our present knowledge, is 
 wholly valueless. Its injurious tendency is not 
 more remarkable than the tenacity with which the 
 coal retains it. Generally it exists in combination 
 with iron, in the form of pyrites. In the process 
 of coking a portion of the sulphur escapes in the 
 state of sulphuretted hydrogen gas ; but no degree 
 of heat is sufficient to drive off the whole of the 
 sulphur; and many beds of coal are rendered 
 almost useless in consequence of the large quantity 
 of sulphur which the coal contains, preventing its 
 use in metallurgy and many other processes in the 
 arts. The presence of sulphur, indeed, is generally 
 more perceptible in coke than in coal : the mass of 
 volatile matter which escapes from the latter dis- 
 guises the presence of the sulphur in a great degree ; 
 while, with coke, the fumes of sulphurous acid are 
 generally very perceptible. No mode, practically 
 applicable, has yet been discovered for freeing coal 
 from the sulphur it contains. By treating it with 
 nitric acid the pyrites are dissolved, and the sulphur 
 and the iron may be washed out ; but the coal is 
 converted by the operation into a bulky coke, and 
 is entirely changed in its character, and ceases to
 
 COMBUSTION OF COAL. 405 
 
 afford the same gaseous products as before.* It is 
 probable that some kinds of anthracite coal are 
 nearly free from the presence of sulphur; and, 
 indeed, several kinds afford no evidence of its ex- 
 istence. 
 
 (388.) The application of coal to the purposes 
 of fuel depends like that of all other combustible 
 bodies, on the chemical change which it undergoes 
 in uniting by the agency of heat with some body 
 for which it possesses a powerful affinity. In all 
 ordinary cases this effect is produced by its union 
 with oxygen; and we shall therefore inquire into 
 the modes of effecting this in the best manner. 
 
 When coal is entirely consumed, the carbon is 
 wholly converted into carbonic acid gas, and the 
 hydrogen into water the latter being in the state 
 of vapour. The air supplies the necessary oxygen 
 for this purpose ; and in this state the products of 
 the combustion are nearly or quite invisible, both 
 the products being colourless fluids. Smoke, there- 
 fore, is always the result of imperfect combustion. 
 
 (389.) It has generally been considered that 
 when coal is perfectly coked, the residuary coke 
 will produce as much heat when applied as a fuel 
 as the original quantity of coal would have done 
 from which it was produced. This of course can 
 only be taken in a general sense; because much 
 must depend upon the method of coking and the 
 prevention of waste, as well as the extent to which 
 the process of coking has been carried. Many 
 experiments confirmatory of this general view of 
 the relative values of coal and coke have been 
 made ; the most recent are those of Mr. Apsley 
 Pellat, Mr. Parkes, and the Count de Pambour. 
 But it should be observed that in the residuary 
 coke from the process of gas-making, the peculiar 
 mode of carbonization lessens its heating power to 
 
 * Nicholsons Journal, vol. xviii., p. 170. 

 
 406 COMBUSTION OF COAL. 
 
 a considerable extent ; and it is principally to what 
 is known as " oven-made coke " that this remark 
 will therefore apply. 
 
 We have the clearest evidence from the fact of 
 the great difference in the heating powers of equal 
 weights of coal and of coke, that the waste must be 
 very great in the usual modes of burning coal. We 
 know that a large proportion of the gaseous pro- 
 ducts of coal which we have already seen consti- 
 tute on a rough average about one-fourth of its 
 total weight consists of matter which is capable 
 of producing the most intense heat : and yet we 
 find, practically, that its effect in furnaces is abso- 
 lutely negative. This can arise only from some 
 imperfection in our methods of combustion ; and 
 we may obtain a tolerably accurate notion of the 
 extent of the loss thus sustained, by a reference 
 to the analyses of coal already given. Let us take 
 as an example the caking coal, according to Dr. 
 Thomson's analysis in Table XXXII. which is the 
 Newcastle coal so generally used. We find that 
 in every 100 Ibs. of coal there are contained 4*18 Ibs. 
 of hydrogen, and 4' 58 Ibs. of oxygen. When these 
 gaseous products are driven off by heat, they will 
 both combine with a portion of carbon. The quan- 
 tity of carbon which combines with the hydrogen 
 is very variable; differing with the degree of 
 heat to which it is exposed. When the tempera- 
 ture is very high the hydrogen will combine 
 with three times its weight of carbon, forming 
 the true carburetted hydrogen; but, from a coke 
 oven, a large portion of the hydrogen escapes 
 nearly in an uncombined state, and therefore the 
 quantity of carbon thus abstracted will be only 
 about one-half the quantity which would con- 
 stitute true carburetted hydrogen ; or about 6 Ibs. 
 of carbon may be assumed as the quantity carried 
 off in the latter case. Dr. Dalton ascertained that
 
 COMBUSTION OF COAL. 407 
 
 the combustion of 1 Ib. of hydrogen would melt 320 
 Ibs. of ice; therefore, 4 '18 Ibs. would melt 1337 
 Ibs. of ice ; and the heat produced by 6 Ibs. of carbon 
 will be sufficient to melt 376 Ibs, of ice, according 
 to the average of the experiments of Watt, Rumford, 
 and Black.* The 4*58 Ibs. of oxygen contained in 
 the coal will combine with 3 * 5 Ibs. of carbon, and 
 form 8'08 Ibs. of carbonic oxide. According to 
 Dr. Dalton, 1 Ib. of this gas will melt 25 Ibs. of ice ; 
 therefore 8 '08 Ibs. will melt 202 Ibs. of ice. These 
 results amount together to 1915 Ibs. of ice melted by 
 the heat obtainable from these several substances ; 
 which number, multiplied by 140 degrees, the la- 
 tent heat of ice, and this product divided by 7020, 
 the number of pounds weight of water which can 
 be raised 1 degree by the combustion of 1 Ib. of 
 coal, we shall find the total heat of these several 
 gaseous products are equal to the calorific effects of 
 38 Ibs. of coal. It is not known whether the azote 
 which the coal contains produces any heating effect ; 
 nor will the heat necessary for its expulsion from 
 the coal cause any loss which is appreciable, even if 
 the whole of it be driven off by heat, which, how- 
 ever, we have already seen, is not the case. By the 
 experiments of Berard and Delaroche, on the specific 
 heat of gases, we find that to raise the temperature 
 of the 15 96 Ibs. of azote to the temperature of 500 
 degrees Fahrenheit, will only require 4 9 ounces of 
 coal a quantity too small to be taken into account. 
 The loss, therefore, by the escape of these gaseous 
 products of the coal, amounts by these calculations 
 
 * The average of the experiments of Watt, Eumford, and 
 Black, gives 39 Ibs. of water raised 180 degrees, by the com- 
 bustion of 1 Ib. of coal ; or 7020 Ibs. of water raised 1 degree. 
 The latent heat of ice being 140 degrees, this will be equal to 
 melting 50-14: Ibs. of ice with 1 Ib. of coal; and the heating 
 power of coke, compared with coal, being as 10 to 8, 1 Ib. of 
 coke will melt 62 7 Ibs. of ice.
 
 408 COMBUSTION OF COAL. 
 
 to 38 per cent. ; and the coke which remains will be 
 of the description known by the name of "oven 
 coke," and will produce the same calorific effect 
 as the original quantity of coal would have done, 
 provided the coal were burned in the usual manner. 
 
 Another method may be employed for ascertain- 
 ing the loss sustained by the escape of the volatile 
 matter of coal, by calculating the heating power of 
 the various products obtained from coal in the pro- 
 cess of gas-making. The quantity of carburetted 
 hydrogen gas obtainable from 100 Ibs. of caking 
 coal, of good average quality, may be stated at about 
 450 cubic feet; of which the specific gravity is 
 about 50 to 55. Twenty-four cubic feet of this gas 
 will weigh 1 Ib. ; and as 1 Ib. weight of this gas 
 will melt 85 Ibs. of ice, according to Dr. Dalton's 
 experiments, we shall have ^ x 85 = 1593 Ibs. of 
 ice melted by the combustion of the gas obtainable 
 from 100 Ibs. of coal. Reducing this, as in the 
 former case, to the mean of the results obtained by 
 Watt, Rumford, and Black, we shall find that it is 
 equal to the total effect of 31*76 Ibs. of coal. In 
 addition to this there will be about 8 Ibs. of tar 
 obtained from 100 Ibs. of coal. This, when decom- 
 posed by heat, yields about 100 cubic feet of an 
 impure hydro-carburet, mixed with about one-third 
 by weight of carbonic oxide. Reckoning the heat 
 of this by the data already given, it will be equal 
 to the effect of 10 4 Ibs. of coal. The other product 
 of the distillation is ammoniacal liquor. Of this 
 about 7^ Ibs. will be obtained from 100 Ibs. of coal ; 
 consisting of 5| Ibs. of water, and If Ibs. of am- 
 monia ; the former containing in its composition 
 64 Ib. of hydrogen, and the latter -29 Ib., making 
 together '93 Ib. of hydrogen ; and the heat obtain- 
 able from this quantity of hydrogen will be equal 
 to 5 "93 Ibs. of coal. These several results amount 
 together to a loss equivalent to 43 09 Ibs. of coal,
 
 COMBUSTION OF COAL. 409 
 
 but as the residuary product of the distillation will 
 be only " retort coke," which is inferior to " oven 
 coke " in its heating power to the extent of 12^ per 
 cent., according to the experiments of M. de Pam- 
 bour, we must deduct from the above amount the 
 difference between the heating power of this coke 
 and that which was supposed to be obtained by the 
 former mode of calculation the quantity lacing 
 considered the same in both cases. We shall there- 
 fore find the statement will stand as follows : 
 
 Ibs. of Coal. 
 Heat obtainable from 450 cubic feet of carbnretted hydrogen = 31-76 
 
 Do. 8 Ibs. of tar = 10-40 
 
 Do. -93 Ibs. of hydrogen contained in the l! _ 5 . g3 
 
 ammoniacal liquor . / ~ 
 
 48-09 
 
 Deduct difference in heating power of residuary coke, viz.\ _ q .o 7 
 75 Ibs., at 12J per cent / ~ 
 
 Total loss 38-72 
 
 By this method of calculation, the loss occasioned 
 by the non-combustion of the volatile products of 
 the coal amounts to 38^ per cent., which is an ex- 
 tremely near approximation to the result obtained 
 by the former method. We cannot, however, con- 
 sider that the whole of this amount is always lost 
 by the escape of smoke in the combustion of coal. 
 With open fires, no doubt, this is the case, as well 
 as other sources of loss peculiar to this method of 
 combustion. But in furnaces, however imperfectly 
 they are constructed, some portion of the smoke is 
 always consumed ; and by that amount, whatever 
 it may be, the loss is diminished. The smaller the 
 quantity of volatile matter which the coal contains, 
 the less will be the loss in this way ; but the kind 
 of coal selected for these calculations is a quality 
 which may be considered to afford a fair average. 
 
 (390.) But, in addition to the loss of calorific 
 effect which is here shown by the escape of uncon-
 
 410 COMBUSTION OF COAL. 
 
 sumed smoke, there is another source of loss which 
 always exists in a greater or less degree, arising from 
 the formation of carbonic oxide. It is of importance 
 to understand correctly the theory of the formation 
 of this carbonic oxide, as it materially affects the 
 question of economy in the combustion of fuel. 
 
 (391.) When atmospheric air comes in contact 
 with coal or coke at a very high temperature, the 
 combination of the oxygen of the air with the car- 
 bon of the fuel always forms carbonic acid gas, and 
 produces the phenomenon of combustion* Such 
 is the effect of atmospheric air entering through 
 the grate-bars of a furnace, on a lower stratum of 
 fuel, lying immediately on the bars. But while 
 this carbonic acid gas passes upwards through the 
 upper strata of the heated fuel, a further portion of 
 carbon combines with it, and it becomes converted 
 into carbonic oxide carbonic acid consisting of 
 two volumes of oxygen and one volume of carbon ; 
 while carbonic oxide is composed of equal volumes 
 of oxygen and carbon. 
 
 The result of this conversion of carbonic acid 
 gas into carbonic oxide, by passing the former 
 through highly-heated carbon, is a considerable 
 loss of heat when the carbonic oxide escapes from 
 the furnace in this state ; for a given weight of 
 carbon, converted into carbonic oxide, only produces 
 half the heat which it would do were it converted 
 into carbonic acid gas. The combustion of fuel, 
 therefore, cannot be perfect where any considerable 
 quantity of carbonic oxide escapes undecomposed ; 
 
 * The lowest temperature at which this combination of 
 oxygen and carbon takes place, is a little above the boiling 
 point of mercury. At this temperature carbonic acid gas is 
 formed without any luminous appearance ; at higher tempera- 
 tures true combustion occurs, and carbonic acid is produced 
 with great rapidity. (Davy's " Experiments on Flame," 
 Philosophical Magazine, vol. 50, p. 10.)
 
 COMBUSTION OF COAL. 411 
 
 although it may often happen that no smoke is 
 visible even when there is a large escape of carbonic 
 oxide. This is particularly the case when coke is 
 used as fuel. There is in this case no smoke ; but 
 if there is a deficiency of atmospheric air to supply 
 the necessary amount of oxygen to convert the 
 product of the combustion wholly into carbonic 
 acid gas, a large quantity of carbonic oxide is 
 formed, which not only causes a very great loss of 
 fuel, but it is probably even more unwholesome than 
 the most dense smoke. No system of combustion 
 can therefore be perfect which does not provide a 
 supply of atmospheric air above the fuel, sufficient 
 to reconvert the carbonic oxide (which has been 
 formed by passing the carbonic acid through the 
 mass of burning fuel) into carbonic acid; and in 
 this process it absorbs just its own volume of 
 oxygen, and it gives out another measure of heat 
 exactly equal to that already produced by it in the 
 furnace, the heat from a given volume of carbonic 
 acid being just double what is obtained from the 
 same volume of carbonic oxide. The combustion 
 of the furnace is therefore produced by the oxygen 
 of the air forming carbonic acid with the lower 
 stratum of fuel lying on the furnace-bars ; this is 
 changed into carbonic oxide as it passes through 
 the super-stratum of heated fuel ; and this carbonic 
 oxide is again reconverted back into carbonic acid, 
 by bringing the oxide into union with a further 
 quantity of atmospheric air. 
 
 (392.) In the case of bituminous coal, the 
 economy of fuel must necessarily consist both in 
 consuming the smoke and in preventing the escape 
 of undecomposed carbonic oxide. Smoke always 
 arises from one of two causes deficiency of air, or 
 an insufficient degree of heat to cause the chemical 
 union between the constituents of the fuel and the 
 oxygen derived from the air; and sometimes it
 
 412 COMBUSTION' OF COAL. 
 
 arises from both these causes combined. The loss 
 arising from the carbonic oxide is almost entirely 
 owing to deficiency of oxygen. In open fireplaces 
 the smoke is caused by deficiency of heat ; in close 
 furnaces it is generally caused by deficiency of air ; 
 and all the different methods which have been 
 proposed for consuming smoke in close furnaces, 
 however variously these plans may be applied, are 
 all based on the principle of supplying additional 
 air to the burning fuel. Two or three plans, 
 indeed, for destroying smoke have been proposed, 
 which will presently be mentioned ; but we shall 
 first inquire into the methods of beneficially apply- 
 ing the combustion of the gaseous products of coal 
 to the ordinary purposes of fuel. 
 
 (393.) A vast deal of misconception upon a very 
 simple subject has occurred from parties interested 
 in particular inventions discussing the general 
 question of the combustion of smoke in the way 
 best calculated to recommend their own inven- 
 tions, and to depreciate those of others. The 
 inquiries as to whether hot air or cold air is most 
 advantageous for consuming smoke, or whether 
 smoke is really capable of being consumed after it 
 is once formed, or whether the only remedy for it 
 is to prevent its formation, are entirely of this 
 kind. But that which will be found to be the 
 fact is, that smoke is as capable of being consumed 
 as any other combustible, and that there are many 
 methods of accomplishing this both by hot and by 
 cold air. 
 
 The combustion of smoke, and indeed of any 
 other substance, is not to be supposed to involve 
 its total annihilation ; for matter of all kinds, so 
 far as our knowledge extends, is indestructible. 
 But the combustion of smoke is that change of 
 state produced by chemical union with other sub- 
 stances, which entirely alters its character and 
 appearance.
 
 COMBUSTION OP COAL. 413 
 
 (394.) The constituents of smoke can be accu- 
 rately judged of from a knowledge of the chemical 
 composition of the coal which produces it. Nitro- 
 gen, oxygen, hydrogen, and carbon, with the 
 various combinations of these bodies, namely, 
 carbonic acid, carbonic oxide, carburetted hy- 
 drogen, ammonia, and vapour of water, together 
 with minute portions of various resins, salts, 
 earthy matters, and volatile inflammable vapours, 
 must necessarily constitute the substance known 
 under the general name of smoke. All these sub- 
 stances, except the carbonic acid, are capable of 
 further combinations with atmospheric air, by 
 means of a high temperature; and practically 
 they do all undergo a change, except that the 
 nitrogen exists in too large a quantity to enable 
 any considerable proportion of it to combine 
 chemically with the other substances. Thus, then, 
 there is nothing to prevent a " true combustion of 
 smoke " from taking place ; by which means chemical 
 combinations are produced, the principle being 
 that the uncombined carbon which gives the black 
 colour to smoke unites with oxygen derived from 
 the air, and becomes converted into the colourless 
 carbonic acid gas ; while the carbonic oxide is also 
 changed into the same chemical compound 
 namely, carbonic acid. 
 
 As regards the actual destruction of the black 
 colour of smoke, it matters but little whether hot 
 or cold air be admitted into the furnace ; for so 
 long as the furnace is sufficiently hot, and the 
 quantity of air is sufficiently abundant, the com- 
 bustion will take place. But before the air can 
 enter into combustion, it is necessary that it be 
 raised to a high temperature ; in most cases, about 
 800 or 900 of Fahrenheit being required for this 
 purpose.* When the air is not heated previous to 
 
 * See note to Art. 391, ante.
 
 414 COMBUSTION OF COAL. 
 
 its entrance into the furnace, this heat which is 
 necessary for its combination is obtained from the 
 bodies with which it combines; their temperature 
 is therefore necessarily lowered, by parting with 
 the requisite heat to raise the temperature of the 
 air to that high degree at which it will enter into 
 chemical union with the gaseous and solid matter 
 of the fuel. 
 
 (395.) The experiments of Sir Humphry Davy 
 on combustion,* clearly show the necessity of a 
 high temperature before active combustion can take 
 place, and the advantages that must therefore 
 result from extrinsically heating the air which 
 supports combustion. They also entirely refute 
 the assertions that the rarefaction of the air by 
 heat is injurious to complete combustion, his ex- 
 periments having in fact been undertaken with 
 the view of testing the accuracy of a theory to 
 this effect, propounded by M. de G-rotthus and 
 others, and which he found to be erroneous. 
 
 When Sir Humphry Davy caused a jet of hy- 
 drogen gas, one-sixth of an inch in height, to 
 burn in the receiver of an air-pump, the flame 
 enlarged as the receiver was exhausted by the 
 pump, and was at its maximum when the pressure 
 of the air was between four and five times less than 
 that of the atmosphere ; and when a larger jet was 
 used, the same phenomenon occurred even when 
 the air was rarefied ten times. This effect, from a 
 larger jet, was found to arise from the increased 
 heat produced : and the conclusion drawn from all 
 the experiments was, "that among combustible 
 bodies, those which require least heat for their com- 
 bustion, burn in more rarefied air than those that 
 require more heat; and those that produce much 
 
 * " Kesearches on Flame," by Sir Humphry Davy. Philo- 
 sophical Transactions, Part I., for 1817 ; and Philosophical 
 Magazine, vol. 50, p. 1, et seq.
 
 COMBUSTION OF COAL. 415 
 
 heat in their combustion, burn, other circumstances 
 being the same, in more rarefied air than those that 
 produce little heat." The experiments also proved 
 that " by preserving heat in rarefied air, or giving 
 heat to a mixture, inflammation may be continued 
 when, under common circumstances, it would be 
 extinguished." When these mixtures were heated 
 before combustion, Sir Humphry Davy found " that 
 expansion by heat, instead of diminishing the com- 
 bustibility of gases, on the contrary enables them to 
 explode apparently at a lower temperature ; which 
 seems perfectly reasonable, as a part of the heat 
 communicated by any ignited body must be lost in 
 gradually raising the temperature." It was also 
 found that " the cooling power of mixtures of elastic 
 fluids in preventing combustion increases with their 
 condensation and diminishes with their rarefac- 
 tion ; at the same time the quantity of matter en- 
 tering into combustion in given spaces is relatively 
 increased and diminished. The experiments on 
 flame in rarefied atmospherical air show that the 
 quantity of heat in combustion is very slowly 
 diminished by rarefaction, the diminution of the 
 cooling power of the azote being apparently in a 
 higher ratio than the diminution of the heating 
 powers of the burning bodies." When the rarefac- 
 tion of the air, however, is produced by heat, not 
 only is there no loss whatever in the available heat 
 produced by combustion, but the extensive applica- 
 tion of heated air by means of the " hot blast " to 
 the smelting of iron, proves that there is an enor- 
 mous increase in the effect, both on the solid matter 
 of the fuel as well as on its gaseous products. And 
 the same result will necessarily occur with respect 
 to all kinds of furnaces for the combustion of fuel. 
 The heated air, when carefully kept from imbibing 
 moisture, will always enter into combustion more 
 readily than cold air ; will cause a much greater heat
 
 416 COMBUSTION OF COAL. 
 
 in the furnace ; and will produce more perfect com- 
 bustion of the fuel. Sir Humphry Davy not only 
 proved "that the combustion of all gaseous mix- 
 tures is increased by rarefaction by heat," but he 
 ascertained by his experiments, that a general law 
 obtained "that at high temperatures gases not 
 concerned in combustion will have less power of 
 preventing that operation, and likewise, that steam 
 and vapours, which require a considerable heat for 
 their formation, will have less effect in preventing 
 combustion (particularly of those bodies requiring 
 low temperatures) than gases at the common heat 
 of the atmosphere." The well-known effect of cold 
 frosty air, in causing fires to burn clear and bright, 
 in no way militates against these conclusions. 
 The effect produced by cold air arises from the 
 decreased quantity of moisture which it then con- 
 tains, and not from the greater density of the air : 
 for Sir Humphry Davy found that even with atmo- 
 spheric air condensed to jive times its natural density, 
 scarcely any appreciable difference could be per- 
 ceived in its effect on combustion. Neither can 
 these effects be different, whether the combustible 
 be a solid or a gaseous body ; except that the latter 
 would be more easily lowered in its temperature 
 and reduced below the temperature requisite for its 
 accension. 
 
 (396.) The expansion of air by heat, previous 
 to its entrance into the furnace, cannot at all 
 reduce the quantity of oxygen which combines 
 with the fuel. For as air will not support com- 
 bustion until it be raised to a very high temperature 
 (about 800 or 900), its expansion must neces- 
 sarily be the same, whether this heat be communi- 
 cated to it within or without the furnace. 
 
 (397.) The quantity of ' atmospheric air required 
 for the combustion of coal is very great. Taking 
 Richardson's analysis of Newcastle coal (Table
 
 COMBUSTION OF COAL. 417 
 
 XXXII., Art. 386), it appears that 355,376 cubic 
 feet of air, of ordinary density, would be required 
 for the combustion of one ton of this coal. If 
 heated air be used, the number of cubic feet must 
 be increased according as the density of the air is 
 diminished; so that sometimes when the air is 
 very highly heated, twice, or even three times this 
 number of cubic feet of air may be necessary for 
 the perfect combustion of the coal. 
 
 The actual quantity of air which enters into a 
 furnace, where complete combustion takes place, 
 must be sufficient to convert the carbon into car- 
 bonic acid, and the hydrogen into water. The 
 former requires 2*66 times, and the latter eight 
 times its weight of oxygen to make these com- 
 binations; and the oxygen of the air being one- 
 fifth of its total volume, or nearly one-fourth of its 
 weight, we can thus calculate the quantity of 
 atmospheric air required for the combustion of any 
 particular kind of coal.* 
 
 But this quantity of atmospheric air, large as 
 appears its amount, will not be sufficient for per- 
 fect combustion ; for this calculation supposes that 
 the whole of the oxygen is abstracted from the air 
 in the process of combustion, a result which ex- 
 perience proves is never practically produced. 
 Some interesting experiments on this subject have 
 been made by Mr. Hunt,f on the furnaces of the 
 principal engines in Cornwall ; and the average of 
 the analysis of the air, taken from the chimneys 
 of the furnaces, after it has performed its office in 
 the combustion of the fuel, shows that the mixed 
 gases passing off through the chimney contain 
 
 * The constituents of atmospheric air by weight are oxygen 
 22 22, and nitrogen 77 77 ; but by volume the constituents are 
 oxygen 21, and nitrogen 79, or very nearly these proportions. 
 
 t Transactions of the Cornwall Polytechnic Society, 1843; 
 and Glasgow Engineers' Magazine, vol. iii., p. 93. 
 
 2 E
 
 418 COMBUSTION OF COAL. 
 
 one-tenth of their volume of free oxygen. The 
 amount of carbonic acid was also found to be, on 
 an average, one-ninth of the total volume of the 
 gaseous matter passing through the chimney. It 
 appears, therefore, that but little more than one- 
 half the oxygen of the air is abstracted in the 
 process of combustion ; and these experiments prove 
 that practically it requires double the quantity of 
 air to produce complete combustion in furnaces 
 that theoretical calculations would give, when based 
 on the assumption of the entire abstraction of the 
 oxygen from the air.* 
 
 (398.) Whenever the gases eliminated from the 
 combustion of coal are made to unite with the 
 proper quantity of oxygen, and the temperature 
 of the mixture is sufficiently high, the smoke 
 will be consumed, in whatever part of the furnace 
 or flues the admixture takes place. This fact has 
 been disputed, but without any grounds for so 
 doing. It has also been asserted that more atmo- 
 spheric air is required to produce combustion of 
 the smoke after it is mixed with the carbonic acid 
 formed in the furnace, than would be required 
 previous to this intermixture. This is true, theo- 
 retically, as the experiments of Sir Humphry Davy 
 proved ; for he ascertained that carbonic acid gas 
 has rather a greater power of preventing the firing 
 of explosive mixtures than azote would have.f 
 Perhaps, therefore, the most advantageous place to 
 introduce atmospheric air would be at the front of 
 the furnace ; but, in all probability, the difference 
 in this respect is very small, as we have already 
 
 * These experiments made by actual working on a very 
 large scale, show that 812 cubic feet of air, weighing 23^ Ibs., 
 is required for the combustion of each pound weight of coal 
 of the quality used in those experiments. 
 
 f Philosophical Transactions, Part II., 1815; and Philo- 
 sophical Magazine, vol. xlvi., p. 449.
 
 COMBUSTION OF COAL. 419 
 
 seen that, in ordinary cases of combustion, only 
 about one-half the oxygen of the air combines 
 in the process of combustion, arising, no doubt, 
 from the difficulty of sufficiently mixing the gases 
 together during their passage through the furnace. 
 But the longer these gases are in contact, and the 
 more they are agitated and mixed together by 
 passing through the different obstructions of a 
 furnace, the more likely is the oxygen of the air 
 to be abstracted, and chemical combination to take 
 place.* And, contrary to the opinion that smoke 
 after it is once formed cannot be burned, a recent 
 patent has been obtained for burning the smoke of 
 furnaces by passing it over a second fire, at a con- 
 siderable distance from the principal fire, with a 
 fresh supply of atmospheric air; and, however 
 distant this second fire may be from the primary 
 one, the combustion of the smoke is complete, and 
 an immense heat is derived from these gaseous 
 products, which, under ordinary circumstances, 
 would only produce the black smoke of common 
 furnaces.f 
 
 (399.) The actual quantity of heat produced by 
 different qualities of coal does not exactly depend 
 upon the quantity of oxygen with which they 
 combine. Dr. Ure made experiments J on the actual 
 amount of heat given out by several qualities of 
 coal, when consumed in a calorimeter of very perfect 
 construction ; by which, as nearly as possible, the 
 entire heat from the coals was obtained ; and, 
 taking the number of pounds of water raised 1 by 
 
 * See Parliamentary Eeport on " Smoke Prevention," 1843, 
 for much useful information on this subject. Also three Re- 
 ports on Coals suited to the Eoyal Steam Navy, published by 
 the Museum of Practical Geology. 
 
 f See Collier's " Patent," Art. 456. 
 
 J Eeports of the British Scientific Association, vol. viii. (1839), 
 p. 20. 
 
 2 E 2
 
 420 COMBUSTION OF COAL. 
 
 the combustion of 1 Ib. of coal as the standard 
 of comparison, * the proportions were 
 
 Lambton's Wall's End . . . 7,500 
 Llangennech Coal . . \ . 9,000 
 Anthracite Coal . . . . 12,000 
 
 The cause of the less degree of heat by the 
 combustion of coals containing large quantities of 
 hydrogen, Dr. Ure considers to arise from the great 
 amount of heat rendered latent by the formation 
 of steam and carburetted hydrogen gas ; though 
 the experiments of Dalton, Davy, Lavoisier, and 
 Crawford all proved that the heat produced by the 
 combustion of hydrogen is greater than from any 
 other substance.f All experiments, however, agree 
 in proving the great heat which is derivable from 
 the combustion of anthracite coal. Considerable 
 difficulty attends its combustion, on account of this 
 kind of coal always breaking up in the furnace into 
 small pieces, except it be very gradually heated ; and 
 unless this precaution be adopted, the draught of 
 the fire is wholly stopped. The breakage of the 
 coal arises from its slow-conducting power, which 
 causes the outside surfaces to expand more than 
 the inner parts, when exposed to a high tempera- 
 ture ; and this expansion causes the exterior parts 
 continually to separate from the interior, until the 
 whole substance is broken up. The elasticity 
 which bitumen gives to coal prevents this result 
 with the ordinary qualities of bituminous coal. To 
 remedy this inconvenience with anthracite coal, 
 various plans have been proposed for supplying it 
 with vapour of water, in order to render it less 
 brittle. The advantages of this operation, how- 
 
 * These numbers represent the number of Ibs. weight of 
 water heated 1 by 1 Ib. of coal. 
 
 j" Ure's " Dictionary of Chemistry," Art. " Combustion."
 
 COMBUSTION OF COAL. 421 
 
 ever, are very questionable. For, in America, 
 where large quantities of anthracite are burned, 
 experiments have been made in order to ascertain 
 the cause of the corrosion which sometimes occurs 
 to boilers, iron chimneys, and stove pipes, by the 
 combustion of anthracite coal : and from a report 
 of the Franklin Institute of Pennsylvania,* it ap- 
 pears that in these cases the ashy deposit has been 
 found to contain muriate and sulphate of ammo- 
 nia, sometimes as much as three-fourths of the 
 deposit consisting of these salts. Where moisture 
 is present, the action of these salts must be much 
 increased in activity ; and it therefore deserves 
 serious inquiry whether by the addition of vapour 
 of water, all descriptions of anthracite become in 
 some degree corrosive, or whether the effect is 
 peculiar to the coal of certain districts.f It is 
 probable, that the destructive effect which is some- 
 times produced on thin copper boilers by par- 
 ticular kinds of fuel may arise from something of 
 this kind. Where the boiler is of such a form 
 that the fire acts particularly on the sharp edges 
 which form the connection between the bottom 
 and sides of the boiler, instances have repeatedly 
 occurred of the corrosion being so active, that the 
 bottom has separated from the sides as though it 
 had been cut with a chisel; and in other cases, 
 the surface of the boiler, when very thin, has been 
 so corroded as to become full of holes in the course 
 of a few months' wear (Art. 75). 
 
 * Mechanics' Magazine, vol. xxxvi., p. 439. 
 
 f Experiments have led the author to conclude that this 
 effect is not peculiar to anthracite coal, but that coke when 
 burned with moisture produces the same results. The cir- 
 cumstance is interesting in a chemical point of view ; and if 
 more careful and extensive experiments show this opinion to 
 be correct, they may give rise to important inquiries con- 
 cerning the compound nature of certain (so-called) simple 
 substances.
 
 422 COMBUSTION OP COAL. 
 
 The inventions which have been brought for- 
 ward for consuming and for preventing smoke 
 are very numerous. The following list will give a 
 tolerable idea of the plans which have been pro- 
 posed, and of the general methods by which the 
 object is sought to be obtained. Those of which 
 a description is known to have been published 
 have a reference to such description ; but the list 
 is not given as a perfectly accurate account of 
 all the inventions for this purpose, as no doubt 
 there are others which have escaped the author's 
 notice.* 
 
 (400.) The first attempt at consuming smoke 
 appears to have been made by M. Delesme, some 
 time prior to 1669, by means of a stove with a 
 downward draught ; but it was not at all suitable 
 for furnaces. (Philosophical Transactions, 1686.) 
 
 (401.) Dr. Papin (1695) proposed a plan for 
 forcing air down a shaft upon the fuel, in order to 
 burn the smoke of furnaces. (Philosophical Trans- 
 actions, 1697). 
 
 (402.) James Watt (1785), patent for consuming 
 smoke by admitting air through openings in the 
 front of the furnace door, and also by gradually 
 coking the coals. (Repertory of Arts, vol. iv. (1796), 
 p. 226.) 
 
 (403.) C.W.Ward (1792), patent for condensing 
 smoke by drawing it, by means of an air-pump or 
 bellows, through cold water. (Repertory of Arts, 
 vol. i. (1794), p. 373.) 
 
 (404.) W. Thompson (1796) proposed a furnace 
 
 * In the following descriptions of the various inventions, 
 there are several which profess to accomplish results utterly 
 unattainable by the means proposed. The statements are 
 chiefly taken from the published accounts of the various plans, 
 and several of them are totally contrary to the principles of 
 science. The description given must, therefore, not be taken 
 as the author's explanation of the operations or the effects, 
 but as those of the several inventors.
 
 COMBUSTION OF COAL. 423 
 
 to burn smoke, by letting air in behind the bridge. 
 (Repertory of Arts, vol. iv. (1796), p. 316.) 
 
 (405.) Roberton, of Glasgow (1800), patent for 
 admission of heated air in thin streams over the 
 fire-door ; for coking the coals in front of the 
 furnace; and also a hopper to supply the fuel. 
 (Repertory of Arts, vol. xvi. (1802), p. 364.) 
 
 (406.) M. de Prony (1809 or 1810), Report on 
 apparatus erected at the Royal Mint, Paris, foe 
 consuming smoke, by two pipes passing from the 
 front of the furnace door and delivering hot air at 
 the bridge. He also states that this plan had 
 previously been used by MM. Clement and Desormes, 
 and others. (Annales de Chimie and Retrospect of 
 Science, vol. v., p. 439.) 
 
 (407.) Wm. Sheffield (1812), patent for hollow or 
 split bridge, which delivered the air in a horizontal 
 stream towards the front of the furnace. (Gill's 
 Technical Repository, vol. i., pp. 16 and 42.) 
 
 (408.) J. Wakefield (Manchester), a similar 
 patent to the above, and of subsequent date. (Ibid.) 
 
 (409.) Wm. Johnson (Salford), a similar and 
 subsequent patent. (Ibid.) 
 
 (410.) Losh (1815), patent for dividing the 
 furnace into two parts, lengthways ; the two 
 compartments being supplied with fuel alternately, 
 by which the smoke from the fresh fuel passed 
 over the more perfectly ignited fuel, and was thus 
 consumed. 
 
 (411.) Brunton(1816), patent for revolving grate 
 and feeding hopper ; by which the fuel was equally 
 distributed over the furnace, and in small quantities 
 at a time, thereby preventing all dense smoke. 
 (Mechanics' Magazine, vol. i., p. 121.) 
 
 (412.) John G-regson (1816), patent for bringing 
 air down a shaft, near the bridge, to promote com- 
 bustion. Mechanical means were used to supply the 
 fuel by a snail wheel moved by springs. ( Quarterly 
 Journal of Science, vol. iii., p. 348.)
 
 424 COMBUSTION OF COAL. 
 
 (413.) Josiah Parkes (1820), a patent for split 
 bridge, precisely similar to Sheffield's patent of 
 1812. (Mechanics Magazine, vol. ii., p. 250.) 
 
 (414.) W. Pritchard (1820), a patent for a 
 regulating weight to close gradually the furnace 
 door, so as to vary the quantity of air passing into 
 the furnace. (Repertory of Arts, vol. xxxix. (1821), 
 p. 140.) 
 
 (415.) Mr. Marsh (1824) consumed the smoke of 
 furnaces by leaving two openings in the flue at the 
 back of the furnace. (Gill's Technical Repository, 
 vol. vi., p. 213.) 
 
 (416.) Chapman (1824) described a plan for 
 hollow furnace bars, that conveyed heated air into 
 the furnace through a split bridge which projected 
 the heated air horizontally. Also a hopper to 
 supply the fuel. (Transactions of the Society of 
 Arts, vol. xlii., p. 32 ; and Quarterly Journal of 
 Science, vol. xix., p. 138.) 
 
 (417.) James Nevill, patent for a fan fixed in 
 the flue, which produced a rapid draught up the 
 chimney. 
 
 (418.) Stanley's patent for a feeder for furnaces 
 which consisted of a hopper, and grooved rollers 
 to crush the coal. Two revolving pans scattered 
 the coal over the fire in small quantities at a time, 
 and thus prevented the dense smoke. 
 
 (419.) Jeffries (1824), patent for destroying 
 smoke by a shower of water. Two chimneys are 
 used, and the smoke passes up one and down the 
 other, in which latter a shower of water falls from 
 a colander, and carries the smoke in the form 
 of soot into a drain. (Mechanics Magazine, vol. 
 xxxiv., p. 198.) 
 
 (420.) Mr. Oldham, of the Bank of England, 
 employed a plan of rocking bars, moved by a small 
 eccentric on a shaft worked by the engine. 
 
 (421.) G. Chapman, of Whitby, plan for con-
 
 COMBUSTION OF COAL. 425 
 
 suming smoke by the use of hollow furnace bars 
 delivering heated air at the bridge of the furnace, 
 1825. (Repertory of Arts, vol. xlvi., p. 360.) 
 
 (422.) J. Gilbertson (1828), patent for making 
 the sides of the furnace of hollow plates, through 
 which the air passes, and is delivered in a heated 
 state at the back of the furnace. (Repertory of Arts, 
 vol. vii. (1829), p. 65.) 
 
 (423.) Win. Taylor (1830), patent for consuming 
 smoke, by forcing it through the fire mixed with 
 atmospheric air by means of an air pump. Also 
 for a mode of passing the smoke through red-hot 
 pipes placed in the furnace among the fuel, which 
 pipes form the only outlet to the chimney. (Reper- 
 tory of Arts, vol. i. (1834), p. 282.) 
 
 (424.) J. C. Douglass (1833), patent for two or 
 more sets of bars. The smoke from the first set 
 passes downwards below a bridge, and then up- 
 wards through a second set of bars, on which 
 burning fuel is placed. (Repertory of Arts, vol. v. 
 (1836), p. 346.) 
 
 (425.) J. G. Bodmer (1834), patent for traversing 
 bars, moved by machinery, which receive the fuel 
 from a feeder, and discharge the ashes at the further 
 end of the furnace. 
 
 (426.) Richard Goad (1835), patent for heating 
 the air by passing it through pipes placed in the 
 flues, and delivering the air at the bridge of the 
 furnace. (Mechanics' 1 Magazine, vol. xxvii., p. 375.) 
 
 (427.) T. Hedley's patent for purifying smoke 
 by four or six flues, of which one half ascend and 
 the other half descend. A shower of water falls 
 through the descending flues and washes the smoke, 
 depositing the carbon in the form of lamp-black. 
 
 (428.) William Richard, of Leeds, patent for 
 gasometer applied to furnaces, so that on opening 
 the furnace door to feed the fire a passage is opened 
 from the gasometer, containing condensed air, to a
 
 426 COMBUSTION OF COAL. 
 
 number of holes at the back of the bridge, and the 
 supply of air gradually diminishes as the fire burns 
 clear. 
 
 (429.) Samuel Hall (1836), patent for cast-iron 
 pipes placed upright in the flue at the back of 
 the furnace, and then passing towards the front. 
 The air is thus heated to about 300, and the gases 
 inflame in front of the furnace. (Mechanics' 1 Maga- 
 zine, vol. xxviii., p. 226.) 
 
 (430.) John Hopkins (1836), patent for a curved 
 bridge, by which the smoke and gases are thrown 
 back again upon the burning fuel. (Repertory of 
 Arts, vol. vii. (1837), p. 252.) 
 
 (431.) Jacob Perkins (1836), patent for two sets 
 of bars and two ashpits. The second ashpit is 
 closed, and supplied with air by a fan, so as to give 
 more air to that part of the furnace, and thus burn 
 the smoke from the fuel on both sets of bars. 
 (Repertory of Arts, vol. viii. (1837), p. 268.) 
 
 (432.) Joseph Chanter (1837, &c.,) several 
 patents for smoke burning, principally by in- 
 clined bars double sets of bars air supplied 
 through tubes placed under the first set of bars 
 and hot air supplied at the bridge. 
 
 (433.) James Drew, Manchester, patent for two 
 sets of bars. The coal is coked on the first set, 
 and passed on to the second set, which is then 
 raised by rack-work as near the boiler as possible. 
 
 (434.) Paul Chappe, patent for injecting small 
 jets of boiling water over the fire, in front of the 
 bridge. 
 
 (435.) Ivison and Bell (1838), patent for inject- 
 ing small jets of steam into the furnace, and also 
 for heating the air by passing it through tubes. 
 (Mechanics' Magazine, vol. xxviii., p. 221, and vol. 
 xxx., pp. 69 arid 107.) 
 
 (436.) Kodda's patent for a furnace divided 
 across in two parts. The fuel is first put into the
 
 COMBUSTION OF COAL. 427 
 
 compartment nearest the door, and afterwards 
 thrown backwards to the further compartment. 
 The smoke is burned by passing over the clear fire 
 of the second compartment. (Mechanics Magazine, 
 vol. xxxi., p. 386.) 
 
 (437.) Cheetham and Bayley, patent for a fan 
 which catches the smoke and forces it, mixed 
 with fresh air, through the ashpit and furnace 
 bars, the ashpit being made air-tight. 
 
 (438.) Thomas Hall (Leeds), patent for dividing 
 the furnace into two compartments lengthways, 
 which are supplied with fuel alternately, and the 
 smoke thereby passes over red-hot fuel. 
 
 (439.) James Nevill (1837), patent for two sets 
 of hollow bars containing water. A downward 
 draught is produced by the chimney drawing 
 only from the lower set of bars and the smoke 
 burned by passing through the hot fuel in contact 
 with the bars. (Repertory of Arts, vol. xii. (1839), 
 p. 220.) 
 
 (440.) John Juckes (1838), patent for heating 
 the fuel by passing it through highly-heated pipes 
 or other surfaces, by which it is coked before it 
 passes into the fire, which is effected by mecha- 
 nical meaus. (Repertory of Arts, vol. xiii. (1840), 
 p. 122.) 
 
 (441.) J. A- Caldwell (1839), patent for a rotary 
 fan, by which air is forced into a closed ashpit ; 
 the furnace bars are placed very close together, 
 and a movable damper is applied in the chimney, 
 by which the velocity of the smoke escaping is 
 retarded, and the heated gases retained longer in 
 the furnace. (Repertory of Arts, vol. xiii. (1840), 
 p. 83.) 
 
 (442.) William Miller (1839), patent for rocking 
 bars, by which each alternate bar is made to move 
 lengthways in opposite directions, backwards and 
 forwards; and thus preventing clinkers, and con-
 
 428 COMBUSTION OF COAL. 
 
 suming the smoke by allowing a free passage for 
 the air through the bars. (Repertory of Arts, vol. 
 xvii. (1842), p. 143.) 
 
 (443.) C. W. Williams (1839), patent for sup- 
 plying air in jets to the furnace, principally 
 behind the bridge, by a diffusion box. The air is 
 supplied cold. 
 
 (444.) Andre Kurtz (1840), patent for three sets 
 of bars, those at each end inclined, and the middle 
 set lower than the others, Hollow bearing bars 
 which convey heated air into the furnace, (Me- 
 chanics Magazine, vol. xxxiv., p. 397.) 
 
 (445.) Junius Smith (1840), patent for a double 
 fan or blower, which passes heated air with the 
 smoke through the furnace bars a second time. 
 The heavy gases are allowed to fall by their 
 gravity below the fan, which then forces them 
 down, and niters them through gravel or sand. 
 (Repertory of Arts, vol. xvi. (1841), p. 81.) 
 
 (446.) Baron Yon Eathen (1840), patent for 
 hollow firebars, resting upon bearers with steps, 
 forming two sides of a triangle, which allows more 
 air to pass into the furnace. Also, a coal-feeder 
 placed over the dead-plate, which supplies fuel 
 without opening the door. (Mechanics Magazine, 
 vol. xxxv., p. 27.) 
 
 (447.) Godson and Foard (Jan., 1841), patent 
 for a box placed below the furnace bars with a 
 movable bottom. The box being filled with fuel, 
 the bottom is gradually raised by a lever, and 
 supplies fuel from below, the smoke from which is 
 consumed by passing through the red-hot fuel. 
 (Repertory of Arts, vol. xviii. (1842), p. 129.) 
 
 (448.) M. Coupland (Sept., 1841), a patent for 
 movable centre bars which pass downwards into 
 a box ; nearly similar to Godson's. (Repertory of 
 Arts, vol. xviii., p. 207.) 
 
 (449.) F. Heindruckx (1841), patent for a fur-
 
 COMBUSTION OF COAL. . 429 
 
 nace without bars. The sides of the furnace are 
 inclined, and a narrow opening is left at the bot- 
 tom and whole length of the furnace, through 
 which the air enters, and is regulated by a longi- 
 tudinal valve. (Mechanics Magazine, vol. xxxv., 
 p. 366.) 
 
 (450.) J. C. March (1841), patent for causing 
 air to be blown in streams on the upper surface of 
 the fuel without passing through the fire. No 
 furnace bars are used by this plan. (Mechanics 
 Magazine, vol. xxxv., p. 492.) See also a some- 
 what similar plan, Art. 401. 
 
 (451.) John Juckes (1841), patent for a furnace 
 grating passing over rollers at each end of the 
 furnace like an endless chain. The bars revolve 
 by machinery, receiving fuel from a feeder placed 
 near the door, and deliver the ashes at the further 
 end of the furnace. (Repertory of Arts, vol. xvii., 
 (1842), p. 210.) 
 
 (452.) J. Prosser (1842), patent for a furnace 
 bridge, with square holes for the admission of air. 
 The bridge is fixed close against the bottom of the 
 boiler. 
 
 (453.) Kymer and Leighton (1843), patent for 
 diagonal bars resting in small loDgitudinal troughs 
 of water. A closed ashpit is used, and a fan 
 forces air through the bars and also over the fuel. 
 The plan used principally for anthracite coal. 
 
 (454.) Schofield, of Leeds (1842), proposed the 
 use of very narrow furnace bars, a quarter of an inch 
 wide at top, and as thin as possible at bottom, and 
 two inches deep. These bars admit a larger quan- 
 tity of air than usual, and thus consume the smoke. 
 
 (455.) E. Billingsley, of Bradford (1842), pro- 
 posed a focal bridge beyond the furnace bars, and 
 a sliding rack or grating in front of the furnace to 
 admit air. (Mining Journal, Jan., 1843.) 
 
 (456.) E. H. Collier (1843), patent for the use
 
 430 COMBUSTION OF COAL. 
 
 of a second fire at a distance from the usual fire. 
 The smoke, after passing through the ordinary 
 flues, is carried over this second fire, and there 
 mixed with an additional quantity of air, when it 
 inflames, and is carried through a second set of 
 flues before passing into the chimney. 
 
 (457.) Butler's (1845) registered plan for mov- 
 able bridge, which opens to regulate supply of air. 
 (Mechanics Magazine, vol. xlii., p. 50.) 
 
 (458.) Whiteley's (1845) registered plan for 
 feeding apparatus and admitting fresh air. (Mecha- 
 nics' Magazine, vol. xlii., p. 147.) 
 
 (459.) Blackwell's (1848) patent for a double- 
 chambered furnace for coking the fuel. (Mechanics' 
 Magazine, vol. xlix., p. 122.) 
 
 (460.) Acock's (1848) patent for a feeding hop- 
 per and other improvements. ( Mechanics' Magazine, 
 vol. xlix., p. 554.) 
 
 (461.) Burrow's (1848) patent for a regulating 
 feed-roller to furnaces. (Mechanics' Magazine, 
 vol., 1., p. 425.) 
 
 (462.) James Robertson (1848), patent for per- 
 forated tubes to convey air into the furnace. 
 (Mechanics' Magazine, vol. 1., p. 429.) 
 
 (463.) Grist's (1849) patent for revolving fur- 
 nace bars. (Mechanics' Magazine, vol. I., p. 1081) 
 
 (464.) Newcombe's (1849) reciprocating fur- 
 nace bars, moved by a cam. (Mec/wnics' Magazine, 
 vol. li., p. 67.) 
 
 (465.) Samuel Hall (1849), reciprocating fur- 
 nace bars moved by eccentrics. (Mechanics' Maga- 
 zine, vol. li., p. 286.) 
 
 (466.) Elijah Galloway (1849), oscillating fur- 
 nace bars. (Mechanics' Magazine, vol. Hi., p. 239.) 
 
 (467.) Joseph Johnson (1849), patent for heated 
 air delivered through pipes, at or near the bridge. 
 (Mechanics' Magazine, vol. lii., p. 318.) 
 
 (468.) William Hargreaves (1850), patent for
 
 COMBUSTION OF COAL. 431 
 
 oscillating bars combined with a feeding-bed which 
 forces the fuel gradually forward in the furnace. 
 (Mechanics Magazine, vol. liii., p. 335.) 
 
 (469.) D. L. Williams (1850), patent for hollow 
 furnace bars. (Mechanics' Magazine, vol. lv., p. 1.) 
 (470.) T. S. Prideaux (1850), patent for air- 
 valve closing gradually to regulate the quantity of 
 air which passes into the furnace through perfora- 
 tions in the inner door; the air becoming heated 
 by passing through them. (Mechanics Magazine, 
 vol. lv., p. 18.) 
 
 (471.) George Anstey (1851), patent for passing 
 smoke through a series of apertures to keep it in 
 contact with flame. (Mechanics' Magazine, vol. lv., 
 p. 75.) 
 
 (472.) Johann Stierba (1852), patent for feed- 
 ing hopper, and air tubes for delivering air at the 
 bridge. (Mechanics Magazine, vol. Ivii., p. 422.) 
 
 (473.) Sorrell's (1852) patent for oscillating 
 furnace bars worked by cams; a feeding hopper 
 worked by a roller ; and for admitting air at the 
 bridge of furnace. (Mechanics Magazine, vol. lix., 
 p. 26.) 
 
 (474.) Green's (1853) patent for double fires, to 
 be fed alternately, together with peculiar system of 
 flues. (Mechanics' 1 Magazine, vol. Ixi., p. 2.) 
 
 (475.) Jearrard (1853) hollow perforated fire- 
 brick sides, &c., for admission of air to furnace. 
 (Repertory of Arts, July, 1854.) 
 
 (476.) Gilbertson (1854), a perforated iron tube 
 over the fuel to deliver air to furnace. (Repertory 
 of Arts, March, 1855.) 
 
 (477.) Simpson (1854), stops or inverted bridges 
 in the furnace to deflect air on to the fuel. (Reper- 
 tory of Arts, April, 1855.) 
 
 (478.) Yates (1854), mechanical feeding appa- 
 ratus for furnaces. (Repertory of Arts, March, 
 1855.)
 
 432 COMBUSTION OF COAL. 
 
 (479.) Taylor (1854), furnace supplied with 
 air above the fuel and not through furnace bars. 
 (Repertory of Arts, September, 1855.) 
 
 (480.) Manley's (1854) method of descending 
 stream of water, in the shaft or upright flue. 
 (Mechanics Magazine, vol. Ixi., p. 205.) 
 
 (481.) W. Woodcock (1854), patent for air- 
 tubes at sides of furnace, above the furnace bars, 
 delivering heated air beyond the bridge of furnace 
 in jets. (Mechanics Magazine, vol. Ixi., p. 410.) 
 
 (482.) Parker's (1854) patent for a loose or 
 movable box or bridge, pierced with holes, and 
 placed in front of the ordinary bridge, on the bars ; 
 by which heated air is delivered to the gases as 
 they pass over the furnace bridge. (Mechanics 
 Magazine, vol. Ixi., p. 445.) 
 
 (483.) Galloway's (1854) patent for pipes placed 
 below the furnace bars, and delivering air into a 
 hollow or double bridge. (Mechanics' Magazine, 
 vol. Ixi., p. 458.) 
 
 (484.) It appears unnecessary to describe more 
 of these inventions for burning smoke. The recent 
 plans have been far less numerous than they were 
 a few years ago, partly because almost every con- 
 ceivable form has been patented repeatedly before, 
 and also because since the passing of the Act for 
 the consumption of smoke in large towns, people 
 appear to have become aware that there are many 
 ways of accomplishing this object, and that no 
 patent process whatever is necessary for the pur- 
 pose' The process of smoke burning is indeed 
 extremely simple in itself, and, with the exception 
 of some very few of the preceding inventions, 
 which are clearly founded on a misconception of the 
 chemistry of combustion, they all attempt to effect 
 the same object ; namely, to bring a larger quantity 
 of atmospheric air into contact with the fuel, or 
 with the products of the first combustion. It will
 
 COMBUSTIOX OF COAL. 433 
 
 be remarked that all the later plans, without ex- 
 ception, are mere modifications of the very earliest 
 inventions ; and that the first six or eight plans 
 described in this list contain the gist of the many 
 subsequent inventions for this purpose. In fact, 
 it will be perceived that the same identical plans 
 have been again and again patented by different 
 individuals : and it is extremely doubtful whether 
 any patent of the present day is really valid in law, 
 and whether it cannot be shown to have been long 
 previously known to the world, and free for general 
 use. 
 
 In most of these plans the design of bringing 
 a larger quantity of air into the furnace is obvious. 
 But in some few this principle is not so plainly 
 developed. Among these latter may be notice'd 
 the inventions in which a jet of steam is thrown 
 into the furnace, and two other inventions in 
 which a shower of water falls down the flue with 
 considerable velocity. In all these cases the great 
 velocity of the steam and the water give an addi- 
 tional impetus to the motion of the gaseous bodies 
 within their immediate sphere ; and these again 
 communicate their velocity to those which are more 
 distant, and thus draw into the furnace an addi- 
 tional quantity of air. There are practical diffi- 
 culties, however, attending the use of a shower of 
 water used in this way, which must effectually 
 prevent these inventions coming into very general 
 use. 
 
 (485.) A second class of inventions are those in 
 which the fuel is gradually coked, before it enters 
 into combustion. When coal is suddenly exposed 
 to a high temperature, a very large quantity 
 of gaseous matter is given off, which quantity 
 gradually diminishes as the coal becomes more 
 nearly converted into coke. By slowly heating the 
 coal, a more equable evolution of gas is produced. 
 
 2 F
 
 434 COMBUSTION OF COAL. 
 
 This result is very effectually accomplished by 
 using a large dead or dumb plate in front of the 
 furnace. The coals being placed on this plate are 
 gradually warmed, and at last arrive at a state of 
 incandescence, when all the gas has been driven off ; 
 by which gradual distillation of the volatile gases, 
 the necessary quantity of air to produce combustion 
 is more easily obtained, as the demand for it thus 
 continues nearly uniform throughout the whole of 
 the process of combustion, instead of the very large 
 additional quantity required when a fresh charge of 
 coal is thrown on the fire in the ordinary method 
 of supplying fuel. The use of a large dead plate 
 in this way is quite sufficient of itself, without any 
 additional contrivance, to consume all the smoke 
 of a furnace, provided the fire on the bars be kept 
 thin, so as to allow a more ready entrance for the 
 air through the fuel. Considerable attention is, 
 however, required on the part of the fireman, that 
 the fuel on the dead plate be gradually pushed 
 forward into the furnace as it becomes heated. 
 When the fuel is supplied through a hopper, placed 
 in front of the furnace, the necessity for opening 
 the furnace door becomes much less frequent, and 
 the unnecessary cooling of the furnace is thus pre- 
 vented. Where no air is admitted except through 
 the furnace bars, there will, however, always be 
 a considerable quantity of carbonic oxide formed 
 during the combustion ; and although, under these 
 circumstances, there is no smoke, the greatest 
 effect of the fuel is not, by this means, produced. 
 A moderate quantity of air ought to be introduced 
 into the furnace, to mix with the gases distilled 
 from the coal, and also to convert the carbonic 
 oxide formed by the upper strata of coal into carbonic 
 acid. This air ought to be heated before it enters 
 the furnace, as it thus more readily inflames, mixes 
 more easily with the heated gases of the furnace,
 
 COMBUSTION OF COAL. 435 
 
 and prevents injury by the unequal action of cold 
 currents impinging against the bottom of the boiler. 
 It perhaps matters but little in what part of the 
 furnace this air be introduced ; but the more 
 it is diffused the better, as the heat is then less 
 likely to become too intense on one particular 
 part. Various simple methods of introducing 
 heated air may be used ; and the plan of using 
 two pipes in the manner originally employed at 
 the Royal Mint at Paris (Art. 406), as long ago 
 as the year 1809, answers the purpose extremely 
 well. The apertures to the pipes should be fur- 
 nished with covers which can be partially closed ; 
 and by the experiments of Mr. Houldsworth,* it 
 appears that an aperture for the air, varying from 
 1 J to three square inches, for each square foot of 
 the area of the furnace bars, will be sufficient for 
 this purpose, the size of the pipes varying with 
 the nature and quality of the coals. 
 
 (486.) The gradual coking of the fuel is likewise 
 effected by such plans as those of Drew, Godson, 
 and Coupland. Godson's plan effectually cokes the 
 coal, and is perfectly compatible with any method 
 of introducing additional air above the fuel to con- 
 sume the carbonic oxide. The plans of Losh, 
 Rodda, Thomas Hall, Collier, and some others, in 
 which the flame from one fire passes over a second 
 fire of clear bright burning fuel, is another mode of 
 accomplishing the same object, but apparently less 
 simple in its operation ; and the mechanical means 
 of continually feeding the fire, used by Stanley and 
 by Brunton, produce nearly the same effect as the 
 method of coking the coals would do ; as by these 
 means the evolution of the gases from the coal is 
 equalised throughout the combustion, and the extra- 
 ordinary demand for air, when fresh charges of 
 
 * " Report of the Select Committee of the House of Com- 
 mons on the Prevention of Smoke," p. 105. 
 
 2 F 2
 
 436 COMBUSTION OF COAL. 
 
 coal are supplied in the common mode of firing, is 
 thereby avoided. 
 
 (487.) The method of supplying heated air 
 through a split bridge has been repeatedly patented. 
 Mr. Sheffield, in 1812, was undoubtedly the first 
 to propose this plan, and his method of making the 
 aperture deliver the heated air horizontally into 
 the furnace, is perfectly correct in principle. The 
 defect of these plans has frequently been that too 
 large a quantity of air has thus been brought into 
 the furnace, and the effect has been to lower its 
 temperature. Mr. C. W. Williams' plan of diffusion 
 would be very good, if it were used with hot air, 
 instead of cold air, which latter is specially directed 
 by the patent to be used ; but by the former method, 
 it would approach very near to the prior patent of 
 Mr. Samuel Hall, differing only in being more 
 simple and inexpensive. It should not, however, 
 be overlooked, that it is not so easy to heat large 
 quantities of atmospheric air to a high temperature 
 as some persons imagine. When hot air is applied 
 to blast furnaces,* it is found that to heat the air 
 to about 600 Fahrenheit, it is necessary for it to 
 traverse a surface of cast-iron pipes at nearly a red 
 heat, for a distance of about 5J feet. The mere 
 instantaneous passing of air through a heated me- 
 tallic perforated plate, would therefore add but little 
 to its temperature, unless it were also made to travel 
 through heated pipes for some considerable distance. 
 
 (488.) Probably one of the most effectual 
 methods of burning smoke is the plan of Mr. 
 March (Art. 450), by blowing air downwards upon 
 the fuel by a fan, and dispensing with the use of 
 furnace bars. There can be no question that a 
 most perfect combustion of the fuel may be thus 
 produced; but it is very doubtful whether the 
 
 * Dufrenoy's Report on Hot Air in Iron Works of England, 
 London, 1836, p. 77.
 
 COMBUSTION OF COAL. 437 
 
 additional trouble which this method would cause, 
 and the necessity for a mechanical power to pro- 
 duce the requisite blast of air, will not prevent its 
 adoption to any considerable extent. A similar 
 plan to this is stated to have been tried experi- 
 mentally in some of the furnaces used in the 
 manufacture of iron ; and as the whole of the 
 carbonic oxide must, by this plan, be consumed, 
 there will necessarily be a considerable saving 
 of fuel.* 
 
 (489.) It has been objected to the various plans 
 for the admission of air to the gases above the fuel 
 of the furnace, that the air, when thus admitted, 
 prevents to a certain extent the admission of the air 
 through the furnace bars, and thus reduces the rate 
 of the combustion of the fuel on the furnace bars. 
 This to a certain extent is true, but it can be no 
 argument against the plan ; for it can only be when 
 the air is improperly admitted, and escapes through 
 the flues in an uncombined state, that the total 
 combustion of the furnace can be reduced by the 
 admission of air above the fuel. And in general it 
 will follow that the heat of the furnace being in- 
 creased by the perfect combustion of the gases on 
 the top of the fuel, the draught of the furnace will 
 be increased, and therefore there will be a greater 
 tendency to the influx of air through the furnace 
 bars as well as through the other apertures. The use 
 of heated air, however, in preference to cold air, is 
 far more likely to prevent any loss by the passing 
 of air in an uncombined state through the flues. 
 When cold air is used, this result is not unlikely to 
 
 * Some interesting researches by M. Ebelmen, on the appli- 
 cation of the carbonic oxide from blast furnaces to useful 
 purposes, have shown that the loss of effect by the escape of 
 the carbonic oxide amounts to 62 per cent, of the total 
 quantity of fuel consumed in blast furnaces. Repertory of 
 Arts, vol. xviii. (1842), pp. 116-313.
 
 438 COMBUSTION OF COAL. 
 
 occur ; for gases, at temperatures differing consider- 
 ably from each other, mix together very slowly ; and 
 therefore it may often happen that by introducing 
 cold air into a furnace, the mixture of the air with 
 the gases will not take place until they have passed 
 into the flues, and the temperature becomes too 
 much reduced to cause their accension. 
 
 (490.) The practical result of these remarks is, 
 that there are many effectual contrivances for the 
 combustion of smoke, combining the advantage of 
 great economy of fuel. For this purpose, the 
 more simple the apparatus the better ; and with a 
 very slight degree of attention on the part of the 
 firemen, several of the plans which have been 
 described would be certain to succeed in abating 
 the nuisance of smoke entirely, and with con- 
 siderable economy in the consumption of fuel. 
 The saving in fuel would necessarily be very 
 considerable. In very few furnaces the saving 
 would be not less than twenty-five per cent. ; and 
 in many which now produce large volumes of smoke 
 the saving would be considerably greater. A 
 large amount of the present evil of smoke arises 
 from most furnaces being overworked, in con- 
 sequence of their being too small for the duty 
 required from them. But, with a moderate degree 
 of attention on the part of the firemen, the pre- 
 sent furnaces, with a very slight alteration, could 
 be made effectually to burn their smoke ; and the 
 most effectual way would be to combine the plan of 
 delivering air through numerous small openings 
 made in the inner plate of the furnace door (sup- 
 plied by one or two large openings in the outer 
 door covered with a slide) ; and also by allowing a 
 further quantity of air to pass to the bridge 
 through pipes laid along the furnace bed. For 
 small furnaces either of these plans singly will 
 suffice ; but for larger furnaces the best effect will re-
 
 COMBUSTION OF COAL. 439 
 
 suit from the two modes conjointly. Means must 
 be taken to stop off a portion of the air at certain 
 stages of the combustion, or there will be more air 
 admitted than will be desirable. Both these plans 
 have long been in use, many years prior to the date 
 of any existing patents ; and the necessary altera- 
 tions to adapt them to ordinary furnaces need not 
 involve anything beyond a very moderate expense. 
 (491.) Before concluding these remarks, a few 
 words on artificial fuels may not be amiss. A great 
 number of patents have been obtained for forming 
 artificial fuel, the principle of them all being to 
 combine the small and refuse coal into a solid body. 
 As early as 1799, a patent was obtained by M. 
 Chabannes for this purpose, and it is difficult to 
 discover in what this patent differs from the various 
 subsequent and recent ones for the same object. 
 The principal ingredients used in all these com- 
 positions are coal-dust, coke, peat, bark, saw-dust, 
 tan, clay, sand, pitch, coal-tar, alum, nitre, vegetable 
 matter, and animal excrement. Different persons 
 combine these substances in different proportions, 
 and some omit altogether certain of these ingre- 
 dients. A very powerful and efficient fuel can be 
 composed by mixtures of these substances ; and 
 it appears by some experiments reported by Dr. 
 Buckland to the British Scientific Association,* 
 that when tried against Welsh coal, Pontop coal, 
 and Wylam Main coal, the artificial compound was 
 found to be very considerably more powerful in 
 heating effect than either of these coals. These 
 compound fuels, however, are subject to one incon- 
 venience when used by themselves in furnaces ; that 
 the coal tar is very liable to distil from the fuel 
 without being consumed, in which case it clogs up 
 the furnace bars, and partially stops the due admis- 
 sion of air. When it is used with a certain propor- 
 
 * Report of British Scientific Association, vol. vii. (1838), p. 85.
 
 440 COMBUSTION OF COAL. 
 
 tion of ordinary coal, this inconvenience is less 
 likely to occur, and probably with moderate care it 
 may be avoided. And these methods of combining 
 refuse coal, which must otherwise be nearly value- 
 less, may in many places be most efficiently applied 
 to obtaining a powerful and useful fuel at a moderate 
 expense. 

 
 44] 
 
 APPENDIX. 
 
 TABLE I. 
 
 Table of the Expansive Force of Steam in Atmospheres, and 
 in Ibs. per square inch ; for Temperatures above 212 of 
 Fahrenheit. 
 
 N.B. The steam is supposed to be in contact with the water from which 
 it is formed, and the water and steam to be alike in temperature. 
 
 
 
 Pressure. 
 
 8 
 
 Pressure. 
 
 
 
 Pressure. 
 
 "3 
 
 Pressure. 
 
 ii 
 
 5j a 
 
 i 
 
 
 IN 
 
 i 
 
 
 If 
 
 i 
 
 
 1| 
 
 t 
 
 
 SI 
 
 1 
 
 Ibs. 
 
 ! 
 
 1 
 
 Ibs. 
 
 .S-3 
 
 1 
 
 Ibs. 
 
 fll 
 
 
 
 Ibs. 
 
 r 
 
 I 
 
 
 r 
 
 3 
 
 
 r 
 
 1 
 
 
 I 
 
 ! 
 
 
 212 
 216 
 
 i 
 
 15 
 16-5 
 
 351 
 359 
 
 9 
 10 
 
 135 
 150 
 
 487 
 499 
 
 40 
 45 
 
 600 
 675 
 
 663 170 
 671 180 
 
 2550 
 2700 
 
 220 
 
 
 
 17-7 
 
 367 
 
 11 
 
 165 
 
 511 
 
 50 
 
 750 
 
 679 190 
 
 2850 
 
 225 
 
 
 
 19-5 
 
 374 
 
 12 
 
 180 
 
 521 
 
 55 
 
 825 
 
 686 200 
 
 3000 
 
 230 
 
 
 
 21-5 
 
 381 
 
 13 
 
 195 
 
 531 
 
 60 
 
 900 
 
 694 210 
 
 3150 
 
 235 
 
 
 
 23-6 
 
 387 
 
 14 
 
 210 
 
 540 
 
 65 
 
 975 
 
 700 220 
 
 3800 
 
 240 
 
 
 
 25-8 
 
 393 
 
 15 
 
 225 
 
 549 
 
 70 
 
 1050 
 
 707 230 
 
 3450 
 
 245 
 
 
 
 28-1 
 
 399 
 
 16 
 
 240 
 
 557 
 
 75 
 
 1125 
 
 713 '240 
 
 3600 
 
 250 
 
 2 
 
 30-9 
 
 404 
 
 17 
 
 255 
 
 565 
 
 80 
 
 1200 
 
 719 250 
 
 3750 
 
 255 
 
 
 
 33-6 
 
 409 
 
 18 
 
 270 
 
 572 
 
 85 
 
 1275 
 
 726 1260 
 
 3900 
 
 260 
 
 
 
 36-1 
 
 414 
 
 19 
 
 285 
 
 579 
 
 90 
 
 1350 
 
 731 270 
 
 4050 
 
 265 
 
 
 
 39-0 
 
 418 
 
 20 
 
 300 
 
 586 
 
 95 
 
 1425 
 
 737 280 
 
 4200 
 
 270 
 
 
 
 43-1 
 
 423 
 
 21 
 
 315 
 
 592 100 
 
 1500 
 
 742 290 
 
 4350 
 
 275 
 
 3 
 
 45-0 
 
 427 
 
 22 
 
 330 
 
 605 110 
 
 1650 
 
 748 300 
 
 4500 
 
 294 
 
 4 
 
 60 
 
 431 
 
 23 
 
 345 
 
 616 120 
 
 1800 
 
 753 310 
 
 4650 
 
 308 
 
 5 
 
 75 
 
 436 
 
 24 
 
 360 
 
 627 130 
 
 1950 
 
 758 !320 
 
 4800 
 
 320 
 
 6 
 
 90 
 
 439 
 
 25 
 
 375 
 
 636 140 
 
 2100 
 
 763 330 
 
 4950 
 
 332 
 
 7 
 
 105 
 
 457 
 
 30 
 
 450 
 
 646 150 
 
 2250 
 
 768 340 
 
 5100 
 
 342 
 
 8 
 
 120 
 
 473 
 
 35 
 
 525 
 
 655 
 
 160 
 
 2400 
 
 772 
 
 350 
 
 5250 
 
 %* The pressures above three atmospheres in the above 
 Table are deduced from the experiments of MM. Dulong and 
 Arago. Their calculations extend only as far as 50 atmospheres ; 
 from thence the pressures are now calculated to 350 atmo- 
 spheres by their formula, viz. : t = el 
 
 where e represents the pressure in atmospheres, and t the tern-
 
 442 
 
 APPENDIX. 
 
 perature above 100 of Centigrade. In this equation each 100 
 of Centigrade is represented by unity. 
 
 In reducing these temperatures from Centigrade to Fahren- 
 heit's scale, where the fractions amount to '5, they have been 
 taken as the next degree above, and all fractions below 5 have 
 been rejected. 
 
 More than twenty different formulae for this purpose are 
 given in the Encyclopedia Britannica, art. Steam. 
 
 TABLE H. 
 
 Table of the quantity of Vapour contained in Atmospheric Air, 
 at different Temperatures, when saturated. 
 
 s 
 
 S 
 
 ]s 
 
 If 
 
 "8 
 
 Ill 
 
 I 1 
 
 & ! 
 
 r 
 
 It 1 
 
 I 1 
 
 1 
 
 20 
 
 1-52 
 
 48 
 
 3-94 
 
 76 
 
 9-38 
 
 22 
 
 1-64 
 
 50 
 
 4-19 
 
 78 
 
 9-99 
 
 24 
 
 1-76 
 
 52 
 
 4-46 
 
 80 
 
 10-59 
 
 26 
 
 1-89 
 
 54 
 
 4-77 
 
 82 
 
 11-29 
 
 28 
 
 2-03 
 
 56 
 
 5-C6 
 
 84 
 
 11-98 
 
 30 
 
 2-16 
 
 58 
 
 5-40 
 
 86 
 
 12-68 
 
 32 
 
 2-31 
 
 60 
 
 5-76 
 
 88 
 
 13-36 
 
 34 
 
 2-43 
 
 62 
 
 6-12 
 
 90 
 
 14-15 
 
 36 
 
 2-62 
 
 64 
 
 6-50 
 
 92 
 
 14-93 
 
 38 
 
 2-80 
 
 66 
 
 6-91 
 
 94 
 
 15-81 
 
 40 
 
 2-99 
 
 68 
 
 7-31 
 
 96 
 
 16-76 
 
 42 
 
 3-21 
 
 70 
 
 7-77 
 
 98 
 
 17-83 
 
 44 
 
 3-45 
 
 72 
 
 8-27 
 
 100 
 
 19-00 
 
 46 
 
 3-69 
 
 74 
 
 8-80 
 
 
 
 
 
 %* The above Table is computed from Dr. Dalton's experi- 
 ments on the Elastic Force of Vapour. 
 
 The weight of a cubic foot of steam, at the pressure of 
 30 inches of mercury, is 257-119 grains ; therefore at any other 
 pressure p, the weight will be p -^, = a/. But as vapours ex- 
 pand | 7 for each degree of Fahrenheit, this equation must be 
 corrected for the difference in the expansion of the vapour at 
 the temperature of 212, and the temperature p, in the pre-
 
 APPENDIX. 
 
 443 
 
 ceding equation. Therefore, the volume of the vapour at the 
 temperature j?, will be 1 -f- JTTK j the volume at 212, being 
 
 480 
 
 212 
 
 1 + -- = 1 441, when the volume is assumed to be unity at 
 zero. The weight of a cubic foot of vapour will therefore be 
 1-441 x x 
 
 TABLE HI. 
 
 Table of the Expansion of Air and other Gases by Heat, when 
 perfectly free from Vapour. 
 
 Temperature, 
 Fahrenheit's 
 
 Expansion. 
 
 Temperature, 
 Fahrenheit's 
 
 Expansion. 
 
 Scale. 
 
 
 Scale. 
 
 
 32 
 
 1000 
 
 100 
 
 1152 
 
 35 
 
 1007 
 
 110 
 
 1178 
 
 40 
 
 1021 
 
 120 
 
 1194 
 
 45 
 
 1032 
 
 130 
 
 1215 
 
 50 
 
 1043 
 
 140 
 
 1235 
 
 55 
 
 1055 
 
 150 
 
 1255 
 
 60 
 
 1066 
 
 160 
 
 1275 
 
 65 
 
 1077 
 
 170 
 
 1295 
 
 70 
 
 1089 
 
 180 
 
 1315 
 
 75 
 
 1099 
 
 190 
 
 1334 
 
 80 
 
 1110 
 
 200 
 
 1354 
 
 85 
 
 1121 
 
 210 
 
 1372 
 
 90 
 
 1132 
 
 212 
 
 1376 
 
 95 
 
 1142 
 
 
 
 
 
 %* The above numbers are obtained from Dr. Dalton's 
 experiments, which give an average of ^^ part, or 00207 for 
 the expansion by each degree of Fahrenheit. Gay Lussac 
 found it to be equal to -^ part, or 002083 for each degree of 
 Fahrenheit; and that the same law extends to condeusible 
 vapours when excluded from contact of the liquids which 
 produce them. Professor Daniell (Chemical Philosophy, p. 90) 
 makes the expansion of air equal to 373 for 180 of Fahren- 
 heit : and in the Parliamentary Eeport " On Warming and 
 Ventilating Dwellings, 1857," the expansion of air by 180 
 Fahrenheit is stated to be '366 of its volume. Eegnault (Ann. 
 de Chimie) gives the expansion at -00203 for each degree of 
 Fahrenheit, or 3654 for 180.
 
 444 
 
 APPENDIX. 
 
 TABLE IV. 
 
 Table of the Specific Gravity and Expansion of Water at 
 different Temperatures. 
 
 Temperature, 
 Fahrenheit's 
 Scale. 
 
 Expansion. 
 
 Specific 
 Gravity. 
 
 Weight 
 of 
 1 Cubic 
 Inch, 
 in Grains. 
 
 Temperature, 
 Fahrenheit's 
 Scale. 
 
 Expansion. 
 1 
 
 Specific 
 Gravity. 
 
 Weight 
 of 
 1 Cubic 
 Inch, 
 in Grains. 
 
 30 
 
 00017 
 
 9998 
 
 252-714 
 
 121 
 
 01236 
 
 9878 
 
 249-677 
 
 32 
 
 00010 
 
 9999 
 
 252-734 
 
 124 
 
 01319 
 
 9870 
 
 249-473 
 
 34 
 
 00005 
 
 9999 
 
 252-745 
 
 127 
 
 01403 
 
 9861 
 
 249-265 
 
 36 
 
 00004 
 
 9999 
 
 252-753 
 
 130 
 
 01490 
 
 9853 
 
 249-053 
 
 38 
 
 000002 
 
 9999 
 
 252-758 
 
 133 
 
 01578 
 
 9844 
 
 248-836 
 
 39 
 
 00000 
 
 0000 
 
 252-759 
 
 136 
 
 01668 
 
 9836 
 
 248-615 
 
 43 
 
 00003 
 
 9999 
 
 252-750 
 
 139 
 
 01760 
 
 9827 
 
 248-391 
 
 46 
 
 00010 
 
 9999 
 
 252-734 
 
 142 
 
 01853 
 
 9818 
 
 248-163 
 
 49 
 
 00021 
 
 9997 
 
 252-704 
 
 145 
 
 01947 
 
 9809 
 
 247-931 
 
 52 
 
 00036 
 
 9996 
 
 252-667 
 
 148 
 
 02043 
 
 9799 
 
 247-697 
 
 55 
 
 00054 
 
 9994 
 
 252-621 
 
 151 
 
 02141 
 
 9790 
 
 247-459 
 
 58 
 
 00076 
 
 9992 
 
 252-566 
 
 154 
 
 02240 
 
 9780 
 
 247-219 
 
 61 
 
 00101 
 
 9989 
 
 252-502 
 
 157 
 
 02340 
 
 9771 
 
 246-976 
 
 64 
 
 00130 
 
 9986 
 
 252-429 
 
 160 
 
 02441 
 
 9760 
 
 246-707 
 
 67 
 
 00163 
 
 9983 
 
 252-349 
 
 163 
 
 02543 
 
 9751 
 
 246-483 
 
 70 
 
 00198 
 
 9981 
 
 252-285 
 
 166 
 
 02647 
 
 9741 
 
 246-233 
 
 73 
 
 00237 
 
 9976 
 
 252-162 
 
 169 
 
 02751 
 
 9731 
 
 245-982 
 
 76 
 
 00278 
 
 9972 
 
 252-058 
 
 172 
 
 02856 
 
 9721 
 
 245-729 
 
 79 
 
 00323 
 
 9967 
 
 251-945 
 
 175 
 
 02962 
 
 9711 
 
 245-474 
 
 82 
 
 00371 
 
 9963 
 
 251-825 
 
 178 
 
 03068 
 
 9701 
 
 245-218 
 
 85 
 
 00422 
 
 9958 
 
 251-698 
 
 181 
 
 .03176 
 
 9691 
 
 244-962 
 
 88 
 
 00476 
 
 9952 
 
 251-564 
 
 184 
 
 03284 
 
 9681 
 
 244-704 
 
 91 
 
 00533 
 
 9947 
 
 251-422 
 
 187 
 
 -03392 
 
 9671 
 
 244-446 
 
 94 
 
 00592 
 
 9941 
 
 251-275 
 
 190 
 
 03501 
 
 9660 
 
 244-187 
 
 97 
 
 00654 
 
 9935 
 
 251-121 
 
 193 
 
 03610 
 
 9650 
 
 243-928 
 
 100 
 
 00718 
 
 9928 
 
 250-960 
 
 196 
 
 03720 
 
 9640 
 
 243-669 
 
 103 
 
 00785 
 
 9922 
 
 250-794 
 
 199 
 
 03829 
 
 9630 
 
 243-410 
 
 106 
 
 00855 
 
 9915 
 
 250-621 
 
 202 
 
 03939 
 
 9619 
 
 243-151 
 
 109 
 
 00927 
 
 9908 
 
 250-443 
 
 205 
 
 04049 
 
 9609 
 
 242-893 
 
 112 
 
 01001 
 
 9901 
 
 250-259 
 
 208 
 
 04159 
 
 9599 
 
 242-635 
 
 115 
 
 01077 
 
 9893 
 
 250-070 
 
 212 
 
 04306 
 
 9585 
 
 242-293 
 
 118 
 
 01156 
 
 9885 
 
 249-876 
 
 
 
 
 
 %* In the above Table the expansions are calculated by Dr. 
 Young's formula, 22 / 2 (1 - 002 /) in 10 millionths. The 
 diminution of specific gravity is calculated by this equation : 
 0000022 /2- -00000000472 / 3 . In both equations / repre- 
 sents the number of degrees above or below 39 of Fahrenheit. 
 The absolute weight of a cubic inch of water, at any tempera- 
 ture, may be found by multiplying the weight of a cubic inch 
 at 39, by the specific gravity at the required temperature. 
 Water is 829 times the weight of air; and 13-2 cubic feet of 
 air weigh 1 Ib. There are 437 5 grains in an ounce, and 
 7000 grains in a pound.
 
 APPENDIX. 
 TABLE V. 
 
 445 
 
 Table of the Specific Heat, Specific Gravity, and Expansion by 
 
 Heat of different Bodies. 
 Barometer 30 Inches. Thermometer 60. 
 
 
 Specific Heat 
 
 Specific 
 Gravity 
 
 Weight of 
 100 Cubic 
 Inches. 
 
 Linear Expansion by 
 180 of Heat, 
 from 32 to 212. 
 
 Of equal 
 Weights, by 
 Berard, 
 Delaroche, 
 
 and Petit 
 and Dulong. 
 
 
 Barometer 
 30 Inches. 
 
 Thermo- 
 meter 6&- 
 
 Air (atmospheric) 
 (dry) .. Apjohn 
 Aqueous vapour 
 Azote 
 
 2669 
 2767 
 8470 
 2754 
 2369 
 2210 
 2884 
 3-2936 
 4207 
 2361 
 
 1-000 
 0288 
 
 1498 
 0949 
 0298 
 
 1100 
 0293 
 1035 
 
 1-000 
 
 633 
 9722 
 1-5277 
 1-5277 
 9722 
 0694 
 9722 
 1-1111 
 
 1-000 
 9-880 
 7-824 
 8-396 
 8-600 
 8-900 
 19-250 
 2-760 
 2-520 
 7-248 
 7-788 
 11-350 
 8-279 
 
 Grains. 
 30-519 
 
 19 : 058* 
 29-65 
 46-596 
 46*596 
 29-65 
 2-118 
 29-65 
 33-888 
 Ounces. 
 57-87 
 571-7 
 452-77 
 485-87 
 497-6 
 515-0 
 1114-0 
 159-72 
 145-83 
 418'9 
 450-2 
 656-8 
 478-5 
 
 1242"-4 
 605-8 
 
 453 : 7 
 452-31 
 115-1 
 353-5 
 421-9 
 416-0 
 
 00186671 =,ks 
 00193000 = jig 
 
 00172244 = ^ 
 00146606 = ^ 
 00081166 =^W 
 00087572 = TT J nr 
 00111111 = T i ff 
 00122045 = JL 
 00284836 = ,fc. 
 
 00228300 = :r U 
 00099180 =T 
 00208260 = _j_ 
 00250800 = ^i 
 00205800 = ! 
 00107875 = ^* 
 00136900 = 31 
 
 00217298 = * 
 00294200 = Jf; 
 
 oxide of 
 Carbonic acid 
 oxide 
 
 Hydrogen 
 OlefiantGas .. .. 
 Oxygen 
 
 Water 
 
 Bismuth 
 Brass 
 wire 
 Cobalt .. .. '.. .. 
 Copper 
 Gold .. 
 
 Glass (flint) .. .. 
 (tube) .. .. 
 Iron (cast) 
 -(bar) 
 Lead 
 Nickel 
 Pewter (fine) 
 
 
 
 Platinum 
 Silver 
 Solder (lead 2 + tin 1) 
 Spelter(brass2+zinc 1) 
 Steel (untempered) . . 
 (yellow tempered) 
 Sulphur 
 Tellurium 
 Tin 
 
 
 
 0314 
 0557 
 
 1880 
 0912 
 0514 
 0927 
 
 21-470 
 10-470 
 
 7-840 
 7-816 
 1-990 
 6-115 
 7-291 
 7-191 
 
 Zinc 
 
 ** Air is taken as the standard for the specific gravity of the gases, 
 and water as the standard for the solids. 
 
 The specific heat of gases has been recently investigated by Dr. 
 Apjohn and a somewhat different result obtained. (See London and 
 Edinburgh Philosophical Magazine, vol. xii. 102; xiii. 261, 339.) 
 
 The expansion in volume may be obtained without sensible error, 
 by trebling the number which expresses the increase in length, where 
 the fraction of its length is small. 
 
 * Specific gravity of steam at 212 = -481. Weight of 100 cubic inches, 14-879 grains.
 
 446 APPENDIX. 
 
 TABLE VI. 
 
 TABLE OF THE EFFECTS OF HEAT. 
 
 Fahrenheit's 
 
 Scale. 
 
 Soft iron melts (Clement and Desormes) . . . 3945 
 
 Maximum temperature by Daniell's Pyrometer . . 3280 
 
 Cast iron melts . 2786 
 
 Gold melts -...-. . - 2016 
 
 Copper melts . . 1996 
 
 Silver melts 1873 
 
 Bronze melts (copper 15 parts, tin 1 part) . . . 1750 
 
 Brass melts (copper 3 parts, zinc 1 part) . . .1690 
 
 (copper 2 parts, zinc 2 parts) . . .1672 
 
 Diamond burns 1552 
 
 Bronze melts (copper 7 parts, tin 1 part) . . . 1534 
 
 (copper 3 parts, tin 1 part) . . . 1446 
 
 Enamel colours burnt 1392 
 
 Iron red-hot in daylight 1272 
 
 in the twilight 884 
 
 in the dark 800 
 
 Charcoal burns 802 
 
 Heat of a common fire 790 
 
 Zinc melts (Davy 680) (Daniell) .... 773 
 Mercury boils (Black 600) (Crichton 655) (Dalton 
 660) (Petit and Dulong 656) (Irving 672) 
 
 (Secondat 644) 660 
 
 Linseed oil boils 640 
 
 Lowest ignition of iron in the dark .... 635 
 Lead melts (Guyton and Irving 594) (Crichton) . . 612 
 Steel becomes dark blue, verging on black . . . 600 
 
 a full blue 560 
 
 Sulphur burns 560 
 
 Steel becomes blue 550 
 
 purple 530 
 
 brown, with purple spots . . . 510 
 
 brown . .- 490 
 
 Bismuth melts 476 
 
 Steel becomes a full yellow 470 
 
 a pale straw colour .... 450 
 
 Tin melts 442 
 
 Steel becomes a very faint yellow .... 430 
 Tin 3 -f- lead 2 -j- bismuth 1, melts .... 334 
 Tin and bismuth, equal parts, melts .... 283 
 
 Sulphur melts 218 
 
 Bismuth 5 + tin 3 + lead 2, melts . . . .212
 
 APPENDIX. 
 
 447 
 
 Table of the Effects of Heat (continued}. 
 
 Water boils (barometer 30 inches) 
 
 Wax melts ........ 
 
 Spermaceti melts 
 
 Tallow melts (Nicholson 127) .... 
 
 Acetic acid congeals 
 
 Olive oil congeals ...... 
 
 Water freezes ....... 
 
 Milk freezes ........ 
 
 Vinegar freezes ....... 
 
 Sea-water freezes .28 
 
 Strong wine freezes 20 
 
 Oil of turpentine freezes 14 
 
 Mercury congeals 39 
 
 Sulphuric asther congeals . . . . . . 47 
 
 Natural temperature of Hudson's Bay . . . . 51 
 
 Greatest artificial cold . ... . -91 
 
 Fahrenheit's 
 Scale. 
 
 . 212 
 
 . 149 
 
 . 112 
 
 . 92 
 
 . 50 
 
 . 36 
 
 . 32 
 
 . 30 
 28 
 
 "* See also many other effects of heat in Chapter XII. Part 1. 
 
 TABLE VII. 
 
 Table of the Quantity of Water contained in 100 Feet of 
 Pipe, of different Diameters. 
 
 Diameter 
 of Pipe. 
 
 Contents of 100 Feet 
 in length. 
 
 Inches. 
 
 Gallons. 
 
 i 
 
 84 
 
 1 
 
 3-39 
 
 1* 
 
 7-64 
 
 2 
 
 13-58 
 
 34 
 
 21-22 
 
 3 
 
 30-56 
 
 4 
 
 54-33 
 
 5 
 
 84-90 
 
 6 
 
 122-26
 
 448 APPENDIX. 
 
 TABLE VIII. 
 
 Table of the Strength, or Cohesive Force, of different Sub- 
 stances. By Mr. GEORGE KENNIE. 
 
 Bars of six inches long and a quarter of an inch square will 
 break with the following weight suspended lengthways : 
 
 Ibs. per square inch. 
 
 Cast Iron (horizontal) . . .1166 equal to 18,656 Ibs. 
 
 Ditto (vertical) . . . 1218 19,488 
 
 Cast Steel (tilted) . . . 8391 
 
 Blistered Steel (hammered). . 8322 
 
 Shear Steel (ditto) . . 7977 
 
 Swedish Iron . . . . 4504 
 
 English Iron .... 3492 
 
 Hard Gun-metal .... 2273 
 
 Wrought Copper (hammered) . 2112 
 
 134,256 
 133,152 
 127,632 
 72,064 
 55,872 
 36,368 
 33,792 
 
 19,072 
 17,968 
 4,736 
 1,824 
 
 Cast Copper .... 1192 
 Fine Yellow Brass . . .1123 
 
 Cast Tin 296 
 
 Cast Lead 114 
 
 Per Quetelet. 
 
 Iron Wire, -0769 inches diameter, bears . 432 to 615 Ibs. 
 Copper wire ditto . . 302 to 386 
 
 Per Committee of the Franklin Institute.* 
 Iron Wire. l-3rd inch diameter, bears 81,387 Ibs. per square 
 
 inch, and 14 per cent, less when annealed. 
 Best Cable Iron . . . 59,105 Ibs. per square inch. 
 Ditto ditto (hammer hardened) 71,000 Ibs. 
 
 Russian Iron .... 76,069 Ibs. 
 
 Table of the Relative Cohesive Strength of Metals. 
 By SIOKENGEB. 
 
 Gold 150,955 
 
 Silver 190,771 
 
 Platinum . . . . " . . 262,361 
 
 Copper 304,696 
 
 Soft Iron 362,927 
 
 Hard Iron 559,880 
 
 By MUSCHENBROEK. 
 
 Copper 6 + Tin 1 . . . . 41,000 
 
 Swedish Copper 6 + Malacca Tin 1 . 64,000 
 
 Brass 51,000 
 
 Block Tin 3 + Lead 1 ... 10,200 
 
 Ditto 8 -f Zinc 1 . . . . 10,000 
 
 Tin 4 + Regulus of Antimony 1 . . 12,000 
 
 Lead 8 -f Zinc 1 4,500 
 
 Tin 4 + Lead 1 + Zinc 1 . . . 13,000 
 
 For strength of iron, &c., at various temperatures, see Chap. XII., Part 1,
 
 APPENDIX. 
 
 449 
 
 TABLE IX. 
 
 The following Table of the relative values of various sorts 
 of fuel is compiled from Marcus Bull's Experiments on Fuel. 
 In these experiments all the smoke was consumed. 
 
 Name. 
 
 Specific 
 Gravity. 
 
 Weight 
 per Bushel, 
 Ibs. 
 
 Relative 
 Heating 
 Value. 
 
 Hickory Charcoal 
 
 625 
 
 32-89 
 
 166 
 
 Cannel Coal .... 
 
 1-240 
 
 65-25 
 
 230 
 
 Liverpool Coal .... 
 
 1-331 
 
 70-04 
 
 215 
 
 Newcastle Coal .... 
 
 1-204 
 
 63-35 
 
 198 
 
 Scotch Coal 
 
 1-140 
 
 59-99 
 
 191 
 
 Karthaus Coal .... 
 
 1-263 
 
 66-46 
 
 208 
 
 Richmond Coal .... 
 
 1-246 
 
 65-56 
 
 205 
 
 Stony Creek Coal . . . 
 
 1-396 
 
 73-46 
 
 243 
 
 Maple Charcoal .... 
 Oak Charcoal .... 
 
 431 
 401 
 
 22-68 
 21-10 
 
 114 
 116 
 
 Pine Charcoal .... 
 
 285 
 
 15-0 
 
 75 
 
 Coke 
 
 557 
 
 29-31 
 
 126 
 
 The bushel measure in this Table is much smaller than the 
 English Imperial bushel. 
 
 2 G
 
 450 
 
 APPENDIX. 
 
 TABLE X. 
 
 Velocity of chimney draught at different temperatures, the 
 external air being at 32 Fahrenheit. From Peclet's " Traite 
 de la Chaleur," p. 79. 
 
 Tempera- 
 ture of 
 Warm Air, 
 Fahrenheit. 
 
 Relative 
 Velocity. 
 
 Tempera- 
 ture of 
 Warm Air/ 
 Fahrenheit. 
 
 Relative 
 Velocity. 
 
 Tempera- 
 ture of 
 Warm Air, 
 Fahrenheit. 
 
 Relative 
 Velocity. 
 
 86 
 
 4-93 
 
 356 
 
 8-09 
 
 608 
 
 8-25 
 
 104 
 
 5-51 
 
 374 
 
 8-14 
 
 662 
 
 8-21 
 
 122 
 
 5-98 
 
 392 
 
 8-17 
 
 752 
 
 8-13 
 
 140 
 
 6-35 
 
 410 
 
 8-21 
 
 842 
 
 8-03 
 
 158 
 
 6-66 
 
 428 
 
 8-23 
 
 932 
 
 7-92 
 
 176 
 
 6-92 
 
 446 
 
 8-25 
 
 1022 
 
 7-80 
 
 194 
 
 7-13 
 
 464 
 
 8-26 
 
 1112 
 
 7-62 
 
 212 
 
 7-33 
 
 482 
 
 8-27 
 
 1202 
 
 7-56 
 
 230 
 
 7-48 
 
 500 
 
 8-273 
 
 1292 
 
 7-44 
 
 248 
 
 7-62 
 
 518 
 
 8-278 
 
 1382 
 
 7-33 
 
 266 
 
 7-73 
 
 527 
 
 8-279 
 
 1472 
 
 7-22 
 
 284 
 
 7-83 
 
 536 
 
 8-276 
 
 1562 
 
 7-11 
 
 302 
 
 7-92 
 
 554 
 
 8-275 
 
 1652 
 
 7-00 
 
 320 
 
 7-98 
 
 572 
 
 8-27 
 
 1742 
 
 6-90 
 
 338 
 
 8-05 
 
 590 
 
 8-26 
 
 1832 
 
 6-80 
 
 It will be seen from this Table that the velocity of chimney 
 draught diminishes at the extremely high temperatures, in 
 consequence of the very great expansion of the air.
 
 INDEX. 
 
 PAGE 
 
 ABSORPTIVE power of boilers, experiments on 86 
 
 bodies for heat 247 
 
 Air always discharged from water . . . . . . . . . . 17 
 
 vents, size of . . . . . . . . . . . . . . . . 17 
 
 and water, relative weight and velocity of .. .. .. .. 17 
 
 vents, necessity for 16,47,164 
 
 velocity of, in passing through furnaces . . . . . . . . 91 
 
 ., and water, their specific heat compared .. .. 108,113,157 
 
 and water, relative heating power of .. .. .. 108,160 
 
 ,, quantity required for ventilation .. .. .. .. 110,351 
 
 ,, quantity cooled by glass in buildings .. .. .. .. Ill 
 
 moist and dry, its cooling power and specific heat .. .. 113 
 
 quantity that can be heated by iron pipes .. .. .. .. 110 
 
 quantity to be warmed per minute in buildings .. .. .. 116 
 
 effect produced on, by heated metal . . . . . . . . 145 
 
 will only retain a certain quantity of vapour . . . . . . 160 
 
 ,, when highly heated, injurious effects of .. .. .. .. 145 
 
 small quantity that imbibes moisture from wet surfaces . . .. 190 
 
 its effect on evaporation 188,261 
 
 currents of, effect on heating apparatus . . . . . . . . 174 
 
 heat evolved from, by compression .. .. .. .. .. 261 
 
 and water, relative cooling powers of .. .. .. .. .. 255 
 
 cooling power at high velocities .. .. .. . .. 277 
 
 impure, its effect on human life 319,322 
 
 how contaminated in respiration . . . . . . . . . . 333 
 
 diminished pressure, its effects . . . . . . . . . . 341 
 
 its electric condition, important effects of . . . . . . . . 343 
 
 its rate of expansion by heat .. .. .. .. .. 359 
 
 its velocity of discharge calculated .. .. .. .. .. 358 
 
 dry, its effects on health 326 
 
 quantity required for respiration .. .. .. 110,333,350 
 
 decomposed matter contained in . . . . . . . 348 
 
 its importance philosophically considered^ 
 
 factitious, its effects on plants 
 
 quantity discharged through ventilators . . 
 
 velocity of discharge under pressure 
 
 hot and cold, its effects on combustion 
 
 condensed and rarefied, effect on combustion 
 
 ought to be introduced above the fuel in furnaces 
 
 352 
 354 
 364 
 387 
 414 
 414 
 436 
 
 size of openings for admission to furnaces.. .. .. .. 437 
 
 quantity to produce perfect combustion in furnaces . . 417, 418 
 
 Alterations in size of pipes, objectionable .. .. .. .. 54 
 
 2 G 2
 
 452 INDEX. 
 
 PAGE 
 
 Angle of roof, its effect in cooling .. .. .. .. ..114 
 
 Angles, their effect in water pipes . . . . . . . . . . 33 
 
 vertical, their effect on circulation .. .. .. .. 33 
 
 Animal heat, its effect in public buildings .. .. .. .. 124: 
 
 life, effect on, by highly heated metallic surfaces .. .. 145 
 
 and vegetable life, their relation . . . . . . . . 354: 
 
 Anthracite coal, its combustion . . . . . . . . . . . . 420 
 
 corrosion caused by .. .. .. .. ..421 
 
 Arnott, Dr., his stove described 298,306 
 
 his stove liable to explosion . . . . . . . . 308 
 
 Archimedean screw, its power as a ventilator . . . . . . . . 376 
 
 Artificial fuel, composition of 441 
 
 Ascending pipes may be smaller than descending . . . . . . 55 
 
 should pass to highest point first .. .. .. 170 
 
 Atkinson, Mr., early use of hot- water apparatus . . . . . . 5 
 
 Atmospheric pressure, column of water equal to .. .. .. 19 
 
 Asphyxia from impure air . . . . . . . . . . . . 320 
 
 Azote, its effect in coal 403 
 
 BACON, MR., early use of hot- water circulation .. .. .. 4 
 
 Baths, special arrangements required for heating .. .. .. 1!J4 
 
 plunging, how to warm them . . . . . . . . . . 200 
 
 Beau*nont, Mr., his method of flues .. .. 315 
 
 Bends and elbows, efiect in water pipes . . . . . . . . 33 
 
 Bends sometimes advantageous .. .. .. .. .. ..169 
 
 Bellows, ventilating, described .. .. .. .. .. 375,471 
 
 Bernhardt's hot-air apparatus . . . . . . . . . . . . 227 
 
 Biot, M., his experiments on sonorous bodies . . . . . . . . 27 
 
 Boiler, description of what forms a good one . . . . . . 70, 83 
 
 various forms described .. .. .. .. ..' .. 71 
 
 heated by gas described 73 
 
 surface, calculation of heating power .. .. .. 78,81,198 
 
 Boi ers, useful formula for calculating power of . . . . 79, 81 
 
 their capacity considered .. ., 70 
 
 surface for a given length of pipe . . . . . . . . 82 
 
 how to judge their relative merits . . . . . . . . 83 
 
 rapidly destroyed by impure fuel . . . . . . . . 87 
 
 surface, their proportion to the furnace bars .. .. 81,92 
 
 pressure on, by increased height of pipes .. .. .. 20 
 
 for hot water, not liable to burst .. .. .. .. 21 
 
 as used in Scotch distilleries 83 
 
 effect of projections on their surface . . . . . . . . 85 
 
 absorptive power of fire and water surfaces . . 
 
 75 
 
 .. 95 
 .. 183 
 .. 135 
 4 
 
 of small capacity, effect of 
 various methods of setting them 
 Boiled water easily freezes 
 Boiling point of water at different pressures 
 Bonnemain, M., first used hot-water circulation 
 
 Bottom heat in hothouses, remarks on .. .. .. .. ..155 
 
 Boyle's ventilator described .. .. .. .. .. .. 382 
 
 Branch pipes, any number may be used .. .. .. .. 21 
 
 difficulty when heights vary 57,170 
 
 how to secure circulation in . . . . . . . . 58 
 
 Buildings, various, proper sizes of pipes for . . . . . . . . 69 
 
 quantity of pipe required to heat .. .. .. 116,123 
 
 time required to heat 121 
 
 early methods of heating 283 
 
 Bursting of pipes by frost prevented 182
 
 INDEX. 
 
 453 
 
 CALCIUM of lime prevents water freezing 
 Carbon, quantity exhaled from the lungs 
 Carbonic oxide, its effect and loss of heat in furnaces 
 its dangerous effects 
 
 heat of, in blast furnaces 
 
 Low formed 
 
 effect of breathing, fatal 
 
 acid, its effects on respiration .. 
 quantity produced in combustion 
 
 exhaled by respiration . . . . 
 
 effect of breathing 
 
 temperature at which it is formed 
 
 its effects in preventing combustion . . 
 
 Carburetted hydrogen, effect of breathing 
 Carson's ventilator 
 
 Cause of circulation in hot- water apparatus 
 Cements for joints of pipes .. 
 Centigrade thermometer, its relative scale 
 Chabannes, Marquis, hot-water apparatus used by 
 Chambers or vaults, loss of heat in 
 Chimneys, rules for size of 
 Churches, quantity of pipe to heat 
 cause of draughts in .. 
 Chimney cowls, action of.. 
 Chimneys, earliest invention of .. 
 Circulation of water known to the Romans 
 how to be calculated 
 
 affected by vertical angles 
 
 obstructions to 
 
 through different floors .. 
 
 into different branch pipes 
 
 length of 
 reversed, cause of 
 ,, how stopped by cocks and valves 
 how regulated by cisterns . . 
 of water, cause of 
 ,, increased by height 
 
 of liquids affected by light and sound 
 of water, how increased in hot-water pipes 
 ,, when there are dips in the pipes 
 
 below bottom of boiler 
 
 is sometimes reversed 
 
 ,, through pipes, length of .. 
 
 ,, affected by alterations in size of pipes 
 
 the motive power calculated 
 
 Cisterns for regulating the circulation . 
 expansion and supply 
 increasing circulation 
 Climate, its effect on longevity . . 
 Coal, its heating power estimated 
 
 quantity required to warm any building., 
 quantity consumed in a steam apparatus 
 quantity burned per square foot of furnace bars 
 its cost compared with heating by gas . . 
 its early use in England 
 
 Table of its analyses 
 
 loss of effect by the escape of smoke 
 heat produced by different qualities 
 
 FAGE 
 .. 185 
 .. 339 
 103, 410 
 335, 34J 
 
 .. 411 
 335, 349 
 
 .. 334 
 
 .. 417 
 
 .. 331 
 
 .. 334 
 
 .. 410 
 
 .. 418 
 
 .. 348 
 
 10 
 179 
 237 
 4,44 
 174 
 103 
 123 
 362 
 381 
 
 5 
 
 .. 31 
 35 
 36 
 
 .. 170 
 .. 172 
 .. 46 
 .. 45 
 .. 59 
 .. 61 
 10 
 
 18,28 
 
 .. 27 
 
 28,35 
 
 39, lt>8 
 
 .. 48 
 
 .. 45 
 
 .. 46 
 
 .. 55 
 
 .. 25 
 
 61 
 
 49 
 
 43, 167 
 
 .. 322 
 
 106, 406 
 
 .. 129 
 
 .. 209 
 
 92 
 
 . 312 
 
 401 
 408 
 420
 
 454 
 
 INDEX. 
 
 .. 405 
 .. 417 
 .. 418 
 .. 219 
 222, 303 
 60 
 
 147 
 197 
 170 
 406 
 111 
 264 
 243 
 91 
 410 
 405 
 414 
 
 Coal and coke, their relative heating power .. .. ,. 
 quantity of air required for its combustion 
 theory of its combustion 
 
 Cockle stoves, Sylvester's 
 
 ,. heating power'of 
 
 Cocks for stopping pipes, their size and position 
 Coffey, J. A., patent for circulating mineral oil at high 
 
 peratures 
 
 Coil, length that will heat a certain quantity of water 
 Coils, mode of connecting to main pipes 
 Coke, its effect compared with coal 
 Cold, intense, not accompanied with high wind 
 produced by rarefied air .. .. .. 
 
 Colour, effect on radiation of heat .. .. .. .. 
 
 Combustion of fuel regulated by size of furnace bars . . . . - 
 
 temperature of active 
 
 of smoke 
 
 Davy, Sir Humphry, experiments on 
 
 depends on quantity of air admitted . . . . . . 103 
 
 quantity of air required for combustion of coal . . . . 417 
 
 Compression of water, extremely small . . . . . . . . . . 21 
 
 Condensed water in steam pipes, effect of . . . . . . . . 203 
 
 valve for saving . . . . . . . . . . 215 
 
 steam, how to prevent noise from . . . . . . . . 197 
 
 Conduction of heat, its proportion to radiation . . . . . . 236-241 
 
 Conducting power of water and air . . . . . . . . . . 255 
 
 various substances .. .. .. ., .. 249 
 
 Connection pipes, proper size for .. 54 
 
 Consumption of fuel in furnaces . . . . . . . . . . . . 89 
 
 Contamination of air by breathing and animal exhalations . . . . 330 
 
 Cooling of heated surfaces, relative rate of . . . . . . . . 67 
 
 velocity of, at high temperature . . . . . . . . 241 
 
 relative velocity of hot-water and steam pipes . . . . 65 
 
 relative power of air and water .. .. .. .. 255 
 
 of iron pipes, experiments on 68, 273 
 
 of glass surfaces, experiments on . . . . . . . . 274 
 
 power of wind . . . . . . . . . . , . . . 277 
 
 of bodies in air and in vacuo . . . . . . . . . . 237 
 
 Copper boilers, injury by particular fuels . . . . . . 86, 421 
 
 its strength affected by heat 269 
 
 Cowls for ventilating, their action explained . . . . . . . . 379 
 
 experiments 381 
 
 Crystallization of iron decreases its strength .. .. .. .. 141 
 
 Cretinism produced by bad air . . . . . . . . . . . . 321 
 
 Cundy's fireclay stove . . . . . . . . . . . . . . 301 
 
 Currents of air, their effect on heating apparatus .. .. .. 174 
 
 in liquids affected by light and sound . . . . . . 27 
 
 Cutler's Torch stove 297 
 
 D ALTON, Dr., experiments on vaporization .. .. .. .. 159 
 
 Damp walls, their cooling effect .. .. .. .. .. .. 122 
 
 Daniell, Professor, experiments on evaporation . . . . . . 261 
 
 Davy, Sir H., experiments on combustion .. .. .. .. 414 
 
 Deaths, comparative, in different localities . . . . . . 322, 324 
 
 Deposit in boilers from hard water .. .. .. .. ..180 
 
 Dew-point, mode of ascertaining .. .. .. .. .. 263,328 
 
 its effect on health 328 
 
 Descent of pipes below bottom of boilers . . . . . . . . 43
 
 INDEX. 455 
 
 PAGE 
 
 Discharge of air from pipes ........ . 16,17 
 
 35,168 
 .. 39 
 .. 168 
 
 39, 168 
 33 
 
 Dip-pipes below doorways 
 
 their depth ascertained . . . , 
 
 ,, may sometimes be made smaller 
 Dip in pipes affects the circulation 
 Discharge of water through pipes, theory of . . 
 Doorways, mode of passing under 
 Double-doors for furnaces, used by Count Eumford 
 
 Drains or trenches for containing hot-water pipes .. . .. 173 
 
 Drainage, its effects on mortality . . . . . . . . . 325 
 
 Draughts in churches, cause of . . . . . . . . . . . . 362 
 
 Dry air, its effects on health 327 
 
 Drying-rooms, quantity of pipe required for .. .. .. 126,191 
 
 . how moisture evaporated from . . . . . . . . 190 
 
 necessity for ventilating 188 
 
 Dumb plate, its use in furnaces . . . . . . . . . . . . 90 
 
 Dutrochet, M., his experiments on light and sound as affecting 
 
 circulation of water . . . . . . . . . . . . . . 27 
 
 Dwelling-rooms, quantity of pipe required to heat .. .. .. 125 
 
 EARLY method of using hot-water circulation .. .. .. 5, 157 
 
 methods of warming buildings .. .. .. .. .. 283 
 
 Eckstein and Busby's rotary float circulator . . . . . . . . 149 
 
 Effect of alteration in size of pipes . . . . . . ' . . . . 55 
 
 Efflux of air under pressure . . . . . . . . . . . . 387 
 
 of fluids affected by heat 266 
 
 Elasticity of air, its effect on conduction of heat 236 
 
 Electric condition of the air, important effects of . . . . . . 344 
 
 Elbows and bends, effect of, in water pipes 33 
 
 Elongation and expansion of pipes .. .. .. .. 50,169 
 
 how compensated .. .. ., 169 
 
 Endosmose and exosmose, what . . . . . . . . . . . . 364 
 
 Evaporation of water by highly-heated metals 76 
 
 in drying-rooms .. .. .. .. .. .. 190 
 
 its laws determined 159,261 
 
 its velocity and quantity ascertained .. .. .. 189 
 
 is produced at all temperatures .. .. .. .. 261 
 
 Expansion and supply cisterns, size of . . . . . . . . . . 49 
 
 of pipes .. 50,169 
 
 Experiments on cooling iron pipes .. .. .. ..' .. 272 
 
 on cooling .. .. .. .. .. .. .. 273 
 
 Explosion of Arnott's stoves .. .. .. .. .. .. 307 
 
 FALLIXG bodies, their velocity calculated 31,358,387 
 
 Fans for ventilating described 373 
 
 power required to work . . . . . . . . . . . . 375 
 
 Flue and fire surface of boilers, heating power of . . . . . . 78 
 
 Flues, early use of, by the Eomans .. .. .. .. .. 281 
 
 their construction considered 
 
 Fluids, conducting power of . . . . . . . . . . . . 254 
 
 pressure of, the law explained .. .. .. .. 19 
 
 Franklin's stove described 296,309 
 
 Freezing of hot- water pipes, how prevented .. .. .. 183,185 
 
 Friction of water through pipes 33,52 
 
 Furnaces, their construction considered . . . . . . . 94 
 
 temperature of . . 
 
 consume fuel proportional to air admitted .. .. .. 91 
 
 large advantage of 89,101
 
 456 
 
 INDEX. 
 
 Furnaces, general temperature of 92 
 
 numerous patents described .. 422,432 
 
 Furnace bars, proper size of .. .. .. .. .. 81,92 
 
 their form and depth . . . . . . . . . . 93 
 
 thin, their great durability 94 
 
 size of, for steam boilers .. .. .. .. .. 210 
 
 Fuel, destructive effect when impure . . . . . . . . . . 86 
 
 thickness of, in furnaces 103 
 
 quantity burned on a square foot of bars .. .. .. 91 
 
 economy of, affected by extent of boiler surface . . . . 70 
 
 artificial, the composition of . . . . . . . . . . 441 
 
 GAS-BOILERS, cost of heating them 
 
 stoves described 
 Gases deleterious, their effect on animal life . . 
 
 on vegetable life 
 
 Gauges for steam boilers 
 Glass, experiments on rate of cooling . . 
 
 cooling effect of, on air 
 
 roofs, effects of their angular elevation . . 
 Goitre produced by bad air 
 Greenhouses, quantity of pipe required to heat 
 Gratings for drains or trenches, size of 
 Gurney's hot-air stoves .. 
 
 HALLS, quantity of pipe required to heat 
 Hard water not good for hot-water apparatus 
 Hawkesley's ventilator described 
 Hazard's hot-air apparatus 
 Healthiness of troops in different countries 
 Heat, rate at which it is given out by pipes 
 radiant, its effect on boilers 
 ,, obtainable from coal, estimated . . 
 its effect on the strength of iron . . 
 
 quantity requisite for different buildings 
 
 in steam and hot water, relative effect . . 
 
 latent contained in steam 
 
 specific, estimate of 
 
 absorption of, affected by colour 
 
 simple, how influenced by colour 
 
 Melloni's experiments on 
 
 latent, theory of 
 
 affects the velocity of efflux 
 
 conducting power of different substances 
 
 specific, of different substances .. 
 
 produced by condensed air 
 
 increases the fluency of liquids . . 
 
 its effect on the strength of metals 
 
 from human beings, its quantity estimated 
 
 from condensed vapour 
 
 from different qualities of coal 
 
 regulator, Dr. Ure's 
 
 Heated bodies, how they become cooled 
 ., air, its effect on health .. 
 
 Heating, rate of, by different-sized pipes 
 power of iron pipes 
 different floors, failure in 
 
 aults 
 
 74, 311 
 
 .. 310 
 
 .. 348 
 
 .. 353 
 
 .. 212 
 
 .. 274 
 
 .. Ill 
 
 .. 114 
 
 .. 321 
 
 .. 126 
 
 .. 173 
 
 .. 224 
 
 . 125 
 
 .. 180 
 
 .. 381 
 
 .. 226 
 
 .. 322 
 
 .. 110 
 
 .. 84 
 
 .. 106 
 
 .. 141 
 
 .. 173 
 110,125 
 65 
 
 .. 64 
 
 44, 1(18 
 
 .. 243 
 
 .. 245 
 
 .. 246 
 
 .. 258 
 
 .. 260 
 
 .. 249 
 
 .. 256 
 
 .. 264 
 
 .. 266 
 
 .. 2G7 
 
 .. 124 
 
 .. 160 
 
 .. 420 
 
 .. 305 
 
 .. 240 
 
 .. 326 
 
 .. 121 
 
 .. 109 
 
 57, 170
 
 Himalaya ventilator and cowl 
 High -pressure hot- water apparatus 
 
 pipes, their temperature measured 
 
 steam does not scald 
 
 apparatus worked by oil 
 
 Hot-water apparatus, its permanence of temperature 
 
 circulation, origin of its discovery 
 
 ,, pipes, quantity of heat from 
 Hot iron, repulsion of, to water .. 
 Hot-air stoves, their construction 
 
 and cockles, their heating power and construction 
 r s, reverse action, cause of 
 
 chambers, 
 
 ,, apparatus, heating power compared with hot-water 
 Hot-blast apparatus for heating and drying 
 
 Hot flues, difficulty with horizontal 
 Hothouses, quantity of pipe required to warm 
 Holmes' patent hot-oil apparatus 
 
 Horizontal pipes at different levels, how to produce circulation in 
 Horizontal main pipes, branches from 
 Houses of Parliament, warming and ventilating of .. 
 early experiments in ventilating 
 
 Human bodies, quantity of heat from 
 
 IXDEX. 457 
 
 FAGE 
 
 Heating by gas, relative cost of .. .. .. .. .. .. 74 
 
 buildings, early methods of 
 
 381 
 136 
 138 
 143 
 147 
 63 
 5 
 10 
 110 
 76 
 302 
 220 
 177 
 223 
 231 
 228 
 126 
 147 
 56 
 57 
 368 
 384 
 124 
 Hydrostatic pressure, what .. .. .. .. .. .. 12 
 
 Hydrogen gas, effect of breathing .. .. .. .. .. 348 
 
 its heating power . . . . . . . . . . 406 
 
 Hydratilic experiments referred to . . . . . . . . . . 34 
 
 Hygrometric condition of air, its effect on health . . . . 325, 337 
 
 Hypocaustum of the Romans . . . . . . . . . . . . 282 
 
 IMPUBE air, its effect on human life . . . . . . . . . . 320 
 
 Inclination of pipes not necessary .. .. .. .. .. 14 
 
 of glass roofs, effect of 115 
 
 Increased height affects velocity of circulation . . . . . . 18 
 
 Inhabited rooms, quantity of pipe required to warm . . . . . . 125 
 
 Iron at high temperatures repulses water .. .. .. .. 76 
 
 specific heat of 65 
 
 at high temperatures, its strength impaired . . . . 141, 268 
 
 the strain it will bear when cold .. .. .. .. ..140 
 
 change of structure produced by heat .. .. .. .. 141 
 
 crystallization of .. .. .. .. .. .. ,. 142 
 
 wrought and cast, effect of oxidation on .. .. .. .. 184 
 
 pipes, experiments on the rate of cooling . . . . . . 273 
 
 its temperature ascertained by colour . . . . . . . . 138 
 
 temperature of its greatest strength .. .. .. 141,265 
 
 table of rate of cooling 273,278 
 
 JEFFREY'S stove described . . . . . . . . . . . . 295 
 
 Jointing pipes, cements for .. .. .. .. .. .. 179 
 
 Joyce's charcoal stove . . . . . . . . . . . . . . 313 
 
 KEWLEY'S siphon principle of heating buildings . . . . . . 132 
 
 LATENT heat of steam 64,259 
 
 laws of, and table of effects . . . . . . . . 259 
 
 Lead paint, its effect on radiation .. .. .. .. 248,273
 
 458 INDEX. 
 
 PAGE 
 
 Length of the circulation of water in pipes . . . . . . . . 46 
 
 Light, its effect on the circulation of water . . . . . . . . 27 
 
 Lime, quantity contained in water .. - .. .. .. .. 185 
 
 Liquids, motion produced in, by sound . . . . . . . . . . 27 
 
 their fluency increased by heat . . . . . . . . 266 
 
 conducting power of .. .. .. .. .. .. 254 
 
 Longevity, relative, of different localities . . . . . . . . 322 
 
 Loss of heat by water exposed in pipes .. .. .. ..109 
 
 MAIN pipes, proper sizes for . . . . . . . . . . . . 52 
 
 difficulty with, when vertical 57 
 
 Materials, strength of, affected by heat .. .. ,.. .. .. 207 
 
 Mechanical ventilation .. .. .. .. .. .. 3G8 
 
 Metals heated, effect in repelling water 76 
 
 conducting power for heat . . . . . . . . . . 252 
 
 ,, reflective power for heat .. .. .. .. .. .. 256 
 
 Mixed temperatures, the result calculated .. .. .. ..199 
 
 Moisture, its effect in lowering temperature . . . . . . . . 122 
 
 theory of its evaporation .. .. .. .. ..159 
 
 ,, deposited on windows, cause of .. .. .. .. 186 
 
 Mortality, relative, of different climates 322 
 
 Motive power of the circulation . . . . . . . . . . . . 25 
 
 how increased .. .. .. .. .. .. 165 
 
 NOTT'S hot-air stove 303 
 
 OERSTEAD'S experiments on the compression of water . . . . 21, 137 
 
 Oil employed as a conductor of heat .. .. . .. .. 147 
 
 Oxygen, quantity consumed in respiration 
 
 effects of deficiency of .. 
 Oxidation of wrought and cast iron, different . . 
 Ozone in the air, its effects on the human body 
 
 332 
 334 
 184 
 346 
 
 PALMAISE system of heating .. .. .. .. .. .. 316 
 
 Pambour, Chevalier, experiments on boilers . . . . . . . . 79 
 
 Parkes, Josiah, on conducting and radiating power of iron and 
 
 water 86 
 
 Parkes, Josiah, experiments on supplying furnaces with coal .. 101 
 
 the heat obtained from coal . . 107 
 
 Patents for combustion of smoke . . . . . . . . . . 422 
 
 Permanence of temperature of hot-water apparatus . . . . 63, 66 
 
 Perkins's high-pressure hot-water apparatus . . . . . . . . 136 
 
 Pipes, how arranged to heat different floors .. .. .. .. 57 
 
 small, sometimes used at dips . . . . . . . . . . 168 
 
 great strain they will bear .. .. .. .. .. 140 
 
 experiments on cooling . . . . . . . . . . . . 273 
 
 vertical, relative size of . . , . . . . . . . . , 55 
 
 discharge of water through . . . . . . . . . . 33 
 
 connecting, size of . . . . . . . . . . . . 54 
 
 outlet and inlet, their number .. .. .. .. .. 59 
 
 proper size, for different buildings 69 
 
 quantity required to heat any quantity of air .. .. .. 110 
 
 small pressure on, by running water . . . . . . . 20 
 
 number of, does not alter the pressure . . 
 which dip below the horizontal line 
 can descend below bottom of boiler 
 longitudinal expansion of 
 friction of water in 
 
 22 
 
 23, 39, 168 
 
 .. 43 
 
 .. 50 
 
 33, 52
 
 IXDEX. 459 
 
 PAGE 
 
 Pipes, main, proper proportions for .. .. .. .. .. 52 
 
 alteration of size, affects circulation 55 
 
 upright, occasional difficulty with 
 
 , relative rate of cooling for different sizes .. .. .. 63 
 
 quantity that can be heated by any boiler .. .. 80,82 
 
 quantity of heat they lose per minute .. .. .. 89,109 
 
 quantity required to heat any building .. 116, 119, 174 
 
 of different sizes, relative time of heating buildings . . . . 121 
 
 in drains or trenches, loss of heat by .. .. .. .. 173 
 
 in vaults, effects described .. .. .. .. .. 174 
 
 methods of jointing 170 
 
 Plants, effect of various gases on .. .. .. .. .. 354 
 
 Plunging baths, how to heat 200 
 
 Pressure of water, how estimated .. .. .. .. '19 
 
 on boiler not affected by number of pipes 21 
 
 produced by the expansion of water .. .. .. 137 
 
 hydrostatic 19 
 
 Price, Mr. H. C., his radiating hot-water boxes .. .. .. 153 
 
 Projecting surfaces on boilers .. .. .. ,. .. .. 85 
 
 Public buildings, quantity of pipe to heat . . . . . . . . 123 
 
 RADIANT heat, its peculiar laws 242 
 
 how affected by colour 243 
 
 its effect on boilers 83 
 
 Radiation and conduction of heat, their relative effect . . . . 236 
 
 its proportion in the total cooling of pipes ... 173, 243 
 
 effect of surface upon 243,246 
 
 effect of colour upon . . . . . . . . . . 243 
 
 by luminous and non-luminous bodies .. .. .. 245 
 
 Rate of cooling for various shaped vessels .. .. .. .. 67 
 
 ,, ,, with different sizes of pipes .. .. .. .. 121 
 
 Reflection of heat by different substances .. .. .. ..256 
 
 Register stove which heats the air . . . . . . . . . . 295 
 
 Regulator of heat in furnaces, Dr. Ure's 305 
 
 Relative time of cooling for hot-water and steam .. .. .. 65 
 
 Rendle, Mr., his tank system .. ..154 
 
 Repulsion between hot iron and water . . . . . . . . . . 76 
 
 Respiration, experiments on .. .. .. .. .. .. 331 
 
 effects produced on atmospheric air . . . . . . 330 
 
 Reversed circulation of water .. .. .. .. .. .. 45 
 
 Romans, their ancient method of wanning buildings . . . . 282 
 
 Rotary float circulator .. .. 149 
 
 Roof, effect of high angles of glass 115 
 
 Rules for estimating quantity of pipe for different buildings .. 116 
 
 Running water, pressure by, on pipes .. .. .. .. .. 20 
 
 Rust or oxydati on, different for wrought and cast iron .. .. 184 
 
 SALT water does not freeze 183 
 
 Salt, quantity contained in sea water 174,184 
 
 Safety valves, proper size for .. .. .. .. .. ..212 
 
 Scotch distilleries, rapid heating of their boilers .. .. .. 83 
 
 Schools, quantity of pipe required to heat .. .. .. ..126 
 
 Sediment in boilers, what 180 
 
 Siphon principle of hot-water apparatus .. .. .. .. 132 
 
 its principle explained .. .. .. .. .. .. 31 
 
 Smoke, cause of 405,411 
 
 combustion of .. .. .. .. .. .. .. 413 
 
 inventions for burning . . . . . . . . . . . . 422
 
 460 INDEX. 
 
 PAGE 
 
 Smoke, quantity of heat lost by .. .. .. .. .. .. 408 
 
 what are its constituents 413 
 
 Specific heat of steam and water 64 
 
 of air and water .. .. .. .. .. ... 108 
 
 general law of 256 
 
 of different substances 258 
 
 of dry and damp air compared .. .. .. ..113 
 
 Spontaneous evaporation . . . . . . . . . . . . . . 262 
 
 Stainton, Mr., his patent for preventing pipes freezing .. .. 185 
 
 Steam and water, relative heat and weight .. .. .. .. 64 
 
 relative time of cooling . . . . . . . . 65 
 
 Steam pipes, proper pressure for . . . . . . . . . . 204 
 
 how to calculate the quantity and effect .. .. 205 
 
 boilers, how proportioned . . . . . . . . . . 207 
 
 best forms for 208 
 
 heat not so permanent as hot water .. .. .. ..210 
 
 boilers, how supplied with water .. .. .. ..211 
 
 latent heat of 259 
 
 high-pressure, does not scald . . . . . . . . . . 143 
 
 pipes, effect of condensed water in . . . . . . . . 204 
 
 boilers, size of, for given quantity of pipe . . . . . . 209 
 
 fittings necessary for .. .. .. .. ..211 
 
 traps for condensed water .. .. .. .. .. 215 
 
 Stephenson, Robt., Ms experiments on boilers .. .. .. 78 
 
 Stop cocks, their size 59 
 
 Stoves, rules for their construction . . . . . . . . . . 291 
 
 Rumford's improvements in . . . . . . . . . . 292 
 
 Franklin's 296,308 
 
 earliest use of 287 
 
 description of 91 Patents for 300 
 
 Dr. Arnott's 304 
 
 Cutler's torch-stove 297 
 
 re-invented by Dr. Arnott .. ..298 
 
 Sylvester's improvements in 219,299 
 
 Cundy's fireclay 301 
 
 Dr. Nott's improvements in . . . . . . . . . . 303 
 
 cockle, their heating power estimated .. .. .. .. 303 
 
 gas, their construction and cost of burning .. .. .. 310 
 
 Joyce's charcoal .. .. .. .. .. .. .. 313 
 
 ., earliest writers on . . . . . . . . . . . . 287 
 
 with hollow back and sides 291 
 
 Stone-float apparatus for steam boilers .. .. .. .. 211 
 
 Strength of materials affected by heat 267 
 
 Surface of boilers required to heat a given quantity of pipe . . . . 80 
 the measure of their power . . . . . . . . 78 
 
 bodies, the effect on radiation 244,246 
 
 Supply cisterns, their size and position . . . . . . . . . . 49 
 
 Sulphur, its effect in coal .. .. .. .. .. .. 404 
 
 TABLE of motive power of water . . . . . . . . . . 26 
 
 of boiler surface to heat pipes . . . . . . . . . . 80 
 
 of area of furnace bars . . . . . . . . . . . 93 
 
 of quantity of pipe to heat any building .. .. .. 119 
 
 of quantity of coal to heat any building .. .. .. 129 
 
 of radiating power of different substances . . . . . . 243 
 
 of conducting power of different substances . . . . 249, 252 
 
 of reflection of heat by different substances . . . . . . 256
 
 INDEX. 461 
 
 PAGE 
 
 Table of specific heat of different substances 257 
 
 of latent heat of different substances .. .. .. ..259 
 
 of evaporation at all temperatures . . . . . . . . 262 
 
 of strength of iron at high temperatures . . . . . . 268 
 
 of heat evolved by compression . . . . . . . . 265 
 
 of strength of copper at high temperatures .. .. .. 269 
 
 of experiments on cooling iron pipes . . . . . . . . 273 
 
 of experiments on cooling glass . .. .. .. .. 274 
 
 of velocity on cooling at different temperatures . . 237, 240 
 
 of cooling power of wind on glass . . . . . . . . 277 
 
 of cooling iron plates . . . . . . . . . . . . 279 
 
 of quantity of air discharged through ventilators . . . . 364 
 
 of analysis of coal 401,402 
 
 of expansive force of steam .. .. .. .. ..441 
 
 of vapour contained in air . . . . . . . . . . 442 
 
 of expansion of gases by heat . . . . . . . . . . 443 
 
 of specific gravity and expansion of water . . . . . 444 
 
 of general specific gravities and expansions 
 
 of general effects of heat 
 
 of quantity of water contained in pipes 
 of cohesive strength of materials 
 
 Tank system of heating 
 
 Temperature of ordinary furnaces 
 
 .. 445 
 
 .. 446 
 
 .. 447 
 
 ... 448 
 154, 156 
 91 
 
 spring and autumn .. .. .. .. .. 112 
 
 the high-pressure hot-water apparatus .. .. 138 
 
 hot-air stoves . . . . . . . . . . . . 223 
 
 permanence of, how obtained .. .. .. .. 68 
 
 gases affected by sound . . . . . . . . 27 
 
 perfect combustion . . . . . . . . . . 413 
 
 Thermometer of contact, a peculiar one 
 
 for hot-water pipes . . . . . . . . . . 24 
 
 Thermometers, relative scales of 237 
 
 Time required to heat buildings 121 
 
 Time of cooling pipes containing steam and water . . . . . . 65 
 
 Tobin's patent for ventilating . . . . . . . . . . . . 377 
 
 Trenches or drains, loss of heat by pipes in . . . . . . . . ] 
 
 Troughs open for producing moisture .. .. .. .. ..158 
 
 UPRIGHT pipes, relative size of 55 
 
 Ore, Dr., his heat regulator described 305 
 
 his experiments at the Custom House 326 
 
 VALVES and cocks, their size, use and position 
 
 Vapour in the air, laws which regulate . . . . . . . . 159 
 
 condensed on windows, cause of . . . . . . . . 187 
 
 quantity condensed on cold surfaces .. .. .. .. 188 
 
 its formation in drying-rooms .. .. .. .. .. 188 
 
 its quantity and rate of production . . . . . . 188, 261 
 
 quantity given off from the lungs and skin . . . . . . i 
 
 of water, qualifies excessive heat . . . . . . . . 345 
 
 Vase stove, Franklin's 309 
 
 Vaults or chambers for heating, loss of heat in . . . . . . 174 
 
 Vegetable and animal life, their relation .. .. .. .. 353 
 
 life, effect of different gases .. .. 354 
 
 Velocity of circulation, how to calculate 31 
 
 affected by friction and other causes . . . . 33 
 
 of air passing through furnaces .. .. .. .. 91
 
 462 INDEX. 
 
 PAGE 
 
 Velocity of air discharged through ventilators . . . . . . 359 
 
 wind, its effect in cooling 111,258 
 
 circulation increased by height .. .. .. 18,28 
 
 Venturi, his experiments on enlargement of pipes . . . . . . 55 
 
 Ventsforair 16,47,164 
 
 Ventilation, necessity for 187 
 
 Tobin's patent for 377 
 
 Ventilators, proper size for 354 
 
 how to calculate their discharge . . , . . . . . 358 
 
 Ventilating flues or channels, size of . . . . . . . . . . 177 
 
 Ventilation, quantity of air required for .. .. .. .. 350 
 
 rule for calculating . . . . . . .... . . 360 
 
 by chimney draughts . . . . . . . . . . 367 
 
 by fans and bellows 372 
 
 early contrivances for . . . . . . . . . . 318 
 
 necessity for, in drying closets . . . . . . . . 188 
 
 , quantity of air discharged by .. .. .. .. 364 
 
 Vertical main pipes for different floors . . . . . . . . . . 56 
 
 ,, how to regulate their action .. ... .. 57 
 
 height of pipes, effect on circulation . . . . . . . . 19 
 
 angles, their effect on circulation . . . . . . 35, 169 
 
 dip pipes, their depth ascertained . . . . . . . . 39 
 
 pipes, their relative size . . . . . . . . . . 56 
 
 Vis viva, what 24 
 
 Vitiated air, effect on animals .. 336 
 
 WARMING buildings, early method of 282 
 
 Water, cause of circulation .. .. .. .. .. .. 10 
 
 weight of, its columnar pressure .. .. .. .. 19 
 
 its compression very small .. .. .. .. .. 21 
 
 and air, their specific heat compared .. .. .. .. 108 
 
 loss of heat per minute, when exposed .. .. .. .. 109 
 
 ,, for hot-water apparatus should not be hard .. .. .. 180 
 
 quantity evaporated by steam boilers 78, 207 
 
 and air, relative cooling powers . . . . . . . . . . 255 
 
 heat evolved from, by compression . . . . . . . . 266 
 
 boiling, discharges air . . . . . . . . . . . . 17 
 
 and air, relative weight and velocity of . . . . . . 17 
 
 discharge through pipes, rules for . . . . . . . . 33 
 
 circulation below the boiler 43,149 
 
 and steam, relative heat of . . . . . . . . . . 64 
 
 its pressure dependent on vertical height only . . . . 12 
 
 running, its small pressure on sides of pipes . . . . . . 20 
 
 circulation of, known to the ancient Romans . . . . . . 5 
 
 expansion of, in heating .. .. .. .. .. .. 48 
 
 impure, its effects on hot-air apparatus . . . . . . 181 
 
 chemical constituents of .. .. .. .. .. .. 182 
 
 of different temperatures, effect of mixing .. .. .. 199 
 
 repelled by heated metals . . . . . . . . . . 76 
 
 quantity that can be heated by 1 Ib. of coal . . . . . . 106 
 
 boiling point at different pressures . . . . . . . . 135 
 
 expansive force by compression .. .. .. .. ..137 
 
 relative conducting power of hot and cold . . . . . . 255 
 
 velocity of circulation .. .. .. .. .. .. 31 
 
 motion of, in ascending and descending pipes . . . . 34 
 
 Water-way of boilers should not be very small . . . . . . 75
 
 INDEX. 463 
 
 Weight of a column of water 19 
 
 Wind, its effect in cooling glass surfaces 111,274 
 
 on hot-water apparatus . . . . . . . . . . 176 
 
 Windows, their effect in cooling rooms .. .. .. .. .. 275 
 
 Work-room, quantity of pipe required to heat . . . . . . . . 125 
 
 Wood, conducting power of 253 
 
 method of ancients to prevent smoke from . . . . . . 284
 
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 Sanitation- What should constitute a good Sanitary Arrangement ; Examples (with 
 illustrations) of Well- and Ill-drained Houses ; How to Test Drains ; Ventilating Pipes, etc. 
 
 Water Supply. Care of Cisterns ; Sources of Supply ; Pipes ; Pumps ; Purification 
 and Filtration of Water. 
 
 Ventilation and Warming 1 . Methods of Ventilating without causing cold 
 draughts, by various means ; Principles of Warming ; Health Questions ; Combustion : Open 
 Orates ; Open Stoves ; Fuel Economisers ; Varieties of Grates ; Close-Fire Stoves ; Hot-air 
 Furnaces ; Gas Heating ; Oil Stoves : Steam Heating ; Chemical Heaters ; Management of 
 Flues ; and Cure of Smoky Chimneys. 
 
 Lighting 1 . The best methods of Lighting ; Candles, Oil Lamps, Gas, Incandescent 
 Gas, Electric Light ; How to test Gas Pipes ; Management of Gas. 
 
 Furniture and Decoration. Hints on the Selection of Furniture ; on the most 
 approved methods of Modern Decoration ; on the best methods of arranging Bells and Calls; 
 How to Construct an Electric Bell. 
 
 Thieves and Fire. Precautions against Thieves and Fire ; Methods of Detection ; 
 Domestic Fire Escapes ; Fireproofing Clothes, etc. 
 
 The Larder. Keeping Food fresh for a limited time ; Storing Food without change, 
 such as Fruits, Vegetables, Eggs, Honey, etc. 
 
 Curing: Foods for lengthened Preservation, as Smoking, Salting, Canning, 
 Potting, Pickling, Bottling Fruits, etc. ; Jams, Jellies, Marmalade, etc. 
 
 The Dairy. The Building and Fitting of Dairies in the most approved modern style ; 
 Butter-making ; Cheesemaking and Curing. 
 
 The Cellar. Building and Fitting; Cleaning Casks and Bottles ; Corks and Corking ; 
 Aerated Drinks ; Syrups for Drinks ; Beers ; Bitters ; Cordials and Liqueurs ; Wines ; 
 Miscellaneous Drinks. 
 
 The Pantry. Bread-making; Ovens and Pyrometers; Yeast j German Yeast; 
 Biscuits; Cakes; Fancy Breads; Buns. 
 
 The Kitchen. On Fitting Kitchens ; a description of the best Cooking Ranges, close 
 and open ; the Management and Care of Hot Plates, Baking Ovens, Dampers, Flues, and 
 Chimneys; Cooking by Gas; Cooking by Oil; the Arts of Roasting, Grilling, Boiling, 
 Stewing, Braising, Frying. 
 
 Receipts for Dishes Soups, Fish, Meat, Game, Poultry, Vegetables, Salads, 
 Puddings, Pastry, Confectionery, Ices, etc., etc. ; Foreign Dishes. 
 
 The Housewife's Room. Testing Air, Water, and Foods ; Cleaning and Renovat- 
 ing ; Destroying Vermin. 
 
 Housekeeping, Marketing. 
 
 The Dining-Room. Dietetics ; Laying and Waiting at Table ; Carving ; Dinners, 
 Breakfasts, Luncheons, Teas, Suppers, etc. 
 
 The Drawing-Room. Etiquette ; Dancing ; Amateur Theatricals ; Tricks and 
 Illusions ; Games (indoor). 
 
 The Bedroom and Dressing- Room ; Sleep ; the Toilet ; Dress ; Buying Clothes ; 
 Outfits; Fincy Dress. 
 
 The Nursery. The Room ; Clothing ; Washing ; Exercise ; Sleep ; Feeding ; Teeth- 
 ing ; Illness ; Home Training. 
 
 The Sick-Room. The Room ; the Nurse ; the Bed ; Sick Room Accessories ; Feeding 
 Patients; Invalid Dishes and Drinks; Administering Physic ; Domestic Remedies; Accidents 
 and Emergencies; Bandaging; Burns; Carrying Injured Persons; Wounds; Drowning; Fits; 
 Frtst -bites; Poisons and Antidotes; Sunstroke; Common Complaints ; Disinfection, etc.
 
 PUBLISHED BY E. & F. N. SPON. 3 
 
 The Bath-Room. Bathing in General ; Management of Hot-Water System. 
 
 The Laundry. Small Domestic Washing Machines, and methods of getting up linen ; 
 Fitting up and Working a Steam Laundry. 
 
 The School-Room. The Room ,-.nd its Fittings ; Teaching, etc. 
 
 The Playground.. Air and Exercise; Training ; Outdoor Games and Sports. 
 
 The Workroom. Darning, Patching, and Mending Garments. 
 
 The Library. Care of Books. 
 
 The Garden. Calendar of Op-rations for Lawn, Flower Garden, and Kit .hen 
 Garden. 
 
 The Farmyard Management of the Horse, Cow, Pig, Poultry, Bee=, etc., etc. 
 
 Small Motors. A description of the various small Engines useful for domestic 
 purposes, from i man to i horse power, worked by various methods, such as Electric 
 Engines, Gas Engines, Petroleum Engines, Steam Engines, Condensing Engines, Water 
 Power, Wind Power, and the various methods of working and managing them. 
 
 Household Law. The Law relating to Landlords and Tenants, Lodgers, Servants, 
 Parochial Authorities, Juries, Insurance, Nuisance, etc. 
 
 On Designing' Belt Gearing. By E. J. COWLING 
 
 WELCH, Mem. Inst. Mech. Engineers, Author of ' Designing Valve 
 Gearing.' Fcap. 8vo, sewed, 6d, 
 
 A Handbook of Formula, Tables, and Memoranda, 
 
 for Architectural Surveyors and others engaged in Building. By J. T. 
 HURST, C. E. Fourteenth edition, royal 321110, roan, $s. 
 
 " It is no disparagement to the many excellent publications we refer to, to say that in our 
 opinion this little pocket-book of Hurst's is the very best of them all, without any exception. 
 It would be useless to attempt a recapitulation of the contents, for it appears to contain almost 
 everything that anyone connected with building could require, and, best of all, made up in a 
 compact form for carrying in the pocket, measuring only 5 in. by 3 in., and about \ in. thick, 
 in a limp cover. We congratulate the author on the success of his laborious and practically 
 compiled little book, which has received unqualified and deserved praise from every profes- 
 sional person to whom we have shown it." The Dublin Builder. 
 
 Tabulated Weights of Angle, Tec, Bulb, Round, 
 
 Square, and Flat Iron and Steel, and other information for the use of 
 Naval Architects and Shipbuilders. By C. H. JORDAN, M.I.N.A. Fourth 
 edition, 32010, cloth, 2s. dd. 
 
 A Complete Set of Contract Documents for a Country 
 
 Lodge, comprising Drawings, Specifications, Dimensions (for quantities), 
 Abstracts, Bill of Quantities, Form of Tender and Contract, with Notes 
 by J. LEANING, printed in facsimile of the original documents, on single 
 sheets fcap., in paper case, IOJ. 
 
 A Practical Treatise on Heat, as applied to the 
 
 Useful Arts; for the Use of Engineers, Architects, &c. By THOMAS 
 Box. IVtih 14 plates. Third edition, crown 8vo, cloth, \2s. 6<J. 
 
 A Descriptive Treatise on Mathematical Drawing 
 
 Instruments : their construction, uses, qualities, selection, preservation, 
 and suggestions for improvements, with hints upon Drawing and Colour- 
 ing. By W. F. STANLEY, M. R.I. Fifth edition, with numerous illustrations, 
 crown 8vo, cloth, $s.
 
 4 CATALOGUE OF SCIENTIFIC BOOKS 
 
 Quantity Surveying. By J. LEANING. With 42 illus- 
 
 trations. Second edilion, revised, crown 8vo, cloth, f)s. 
 CONTENTS : 
 
 A complete Explanation of the London ' Schedule of Prices. 
 
 Practice. Form of Schedule of Prices. 
 
 General Instructions. Analysis of Schedule of Prices. 
 
 Order of Taking Off. Adjustment of Accounts. 
 
 Msdes of Measurement of the various Trades. Form of a Bill of Variations. 
 
 Use and Waste. Remarks on Specifications. 
 
 Ventilation and Warming. Prices and Valuation of Work, with 
 
 Credits, with various Examples of Treatment. Examples and Remarks upon each Trade. 
 
 Abbreviations. The Law as it affects Quantity Surveyors, 
 
 Squaring the Dimensions. with Law Reports. 
 
 Abstracting, with Examples in illustration of \ Taking Off after the Old Method. 
 
 each Trade. ' Northern Practice. 
 
 Billing. I The General Statement of the Methods 
 
 Examples of Preambles to each Trade. recommended by the Manchester Society 
 
 Form for a Bill of Quantities. of Architects for taking Quantities. 
 
 Do. Bill of Credits. Examples of Collections. 
 
 Do. Bill for Alternative Estimate. Examples of ' ' Taking Off" in each Trade. 
 
 Restorations and Repairs, and Form of Bill, i Remarks on the Past and Present Methods 
 
 Variations before Acceptance of Tender. of Estimating. 
 Errors in a Builder's Estimate. 
 
 Spans Architects and Builders Price Book, ivith 
 
 useful Memoranda. Edited by W. YOUNG, Architect. Crown 8vo, cloth, 
 red edges, 3-r. 6</. Published annually. Sixteenth edition. Now rfady. 
 
 Long-Span Railway Bridges, comprising Investiga- 
 tions of the Comparative Theoretical and Practical Advantages of the 
 various adopted or proposed Type Systems of Construction, with numerous 
 Formulae and Tables giving the weight of Iron or Steel required in 
 Bridges from 300 feet to the limiting Spans ; to which are added similar 
 Investigations and Tables relating to Short-span Railway Bridges. Second 
 and revised edition. By B. BAKER, Assoc. Inst. C.E. Plates, crown 8vo, 
 cloth, 5-r. 
 
 Elementary Theory and Calculation of Iron Bridges 
 
 and Roofs. By AUGUST RITTER, Ph.D., Professor at the Polytechnic 
 School at Aix-la-Chapelle. Translated from the third German edition, 
 by H. R. SANKEY, Capt. R.E. With 50x3 illustrations, 8vo, cloth, \$s. 
 
 The Elementary Principles of Carpentry. By 
 
 THOMAS TREDGOLD. Revised from the original edition, and partly 
 re-written, by JOHN THOMAS HURST. Contained in 5 1 7 pages of letter- 
 press, and illustrated "with 48 plates and 150 wood engravings. Sixth 
 edition, reprinted from the third, crown 8vo, cloth, I2s. 6d. 
 Section I. On the Equality and Distribution of Forces Section II. Resistance of 
 Timber Section III. Construction of Floors Section IV. Construction of Roofs Sec- 
 lion V. Construction of Domes and Cupolas Section VI. Construction of Partition? 
 Section VII. Scaffolds, Staging, and Gantries Section VIII. Construction of Centres for 
 Bridges Section IX. Coffer-dams, Shoring, and Strutting Section X. Wooden Bridges 
 and Viaducts Section XI. Joints, Straps, and other Fastenings Section XII. Timber. 
 
 The Builders Clerk : a Guide to the Management 
 
 of a Builder's Business. By THOMAS BALES. Fcap. 8vo, cloth, u. 6d.
 
 PUBLISHED BY E. & F. N. SPON 
 
 Practical Gold-Mining: a Comprehensive Treatise 
 
 on the Origin and Occurrence of Gold-bearing Gravels, Rocks and Ores, 
 and the methods by which the Gold is extracted. By C. G. WARNKORU 
 LOCK, co- Editor of ' Gold, its Occurrence and Extraction.' With'S plates 
 and 271 engravings in the text, super-royal 8vo, cloth, 2/. 2s. 
 
 Hot Water Supply : A Practical Treatise upon the 
 
 Fitting of Circulating Apparatus in connection with Kitchen Range and 
 other Boilers, to supply Hot Water for Domestic and General Purposes. 
 With a Chapter upon Estimating. Fully ilhislrattd, crown 8vo, cloth, 3-r. 
 
 Hot Water Apparatus : An Elementary Guide for 
 
 the Fitting and Fixing of Boilers and Apparatus for the Circulation of 
 Hot Water for Heating and for Domestic Supply, and containing a 
 Chapter upon Boilers and Fittings for Steam Cooking. 32 illustrations, 
 fcap. 8vo, cloth, u. 6<i. 
 
 The Use and Misuse, and the Proper and Improper 
 
 Fixing of a Cooking Range. Illustrated, fcap. 8vo, sewed, f>d. 
 
 Iron Roofs : Examples of Design, Description. Illus- 
 trated with 64 Working Drawings of Executed Roofs. By ARTHUR T. 
 WALMISLEY, Assoc. Mem. Inst. C.E. Second edition, revised, imp. 410, 
 half-morocco, 3/. y. 
 
 A History of Electric Telegraphy, to the Year 1837. 
 
 Chiefly compiled from Original Sources, and hitherto Unpublished Docu- 
 ments, by J. J. FAHIE, Mem. Soc. of Tel. Engineers, and of the Inter- 
 national Society of Electricians, Paris. Crown 8vo, cloth, $s. 
 
 Spons' Information for Colonial Engineers. Edited 
 
 by J. T. HURST. Demy 8vo, sewed. 
 No. i, Ceylon. By ABRAHAM DEANE, C.E. 2s. 6d. 
 CONTENTS : 
 
 Introductory Remarks Natural Productions Architecture and Engineering Topo- 
 graphy, Trade, and Natural History Principal Stations Weights and Measures, etc., etc. 
 
 No. 2. Southern Africa, including the Cape Colony, Natal, and the 
 Dutch Republics. By HENRY HALL, F.R.G.S., F.R.C.L With 
 Map. 3J. 6d. CONTENTS : 
 
 General Description of South Africa Physical Geography with reference to Engineering 
 Operations Notes on Labour and Material in Cape Colony Geological Notes on Rock 
 Formation in South Africa Engineering Instruments for Use in South Africa Principal 
 Public Works in Cape Colony : Railways, Mountain Roads and Passes, Harbour Works, 
 Bridges, Gas Works, Irrigation and Water Supply, Lighthouses, Drainage and Sanitary 
 Engineering, Public Buildings, Mines Table of Woods in South Africa Animals used for 
 Draught Purposes Statistical Notes Table of Distances Rates of Carriage, etc. 
 
 No. 3. India. By F. C. DANVERS, Assoc. Inst. C.E. With Map. 4*. 6d. 
 CONTENTS : 
 
 Physical Geography of India Building Materials Roads Railways Bridges Irriga- 
 tion River Works Harbours Lighthouse Buildings Native Labour The Principal 
 Trees of India Money Weights and Measures Glossary of Indian Terms, etc.
 
 6 CATALOGUE OF SCIENTIFIC BOOKS 
 
 Our Factories, Workshops, and Warehouses : their 
 
 Sanitary and Fire-Resisting Arrangements. By B. H. THWAITE, Assoc. 
 Mem. Inst. C.E. With 183 wood engravings ; crown 8vo, cloth, gs. 
 
 A Practical Treatise on Coal Mining. By GEORGE 
 
 C,. ANDRE, F.G.S., Assoc. Inst. C.E., Member of the Society of Engineers. 
 With 82 lithographic plates. 2 vols., royal 410, cloth, 3/. I2J. 
 
 A Practical Treatise on Casting and Founding, 
 
 including descriptions of the modern machinery employed in the art. By 
 N. E. SPRETSON, Engineer. Third edition, with 82 plates drawn to 
 scale, 412 pp., demy 8vo, cloth, iSs. 
 
 The Depreciation of Factories and their Valuation. 
 
 By EWING MATHESON, M. Inst. C.E. 8vo, cloth, 6s. 
 
 A Handbook of Electrical Testing. By H. R. KEMPE, 
 
 M.S.T.E. Fourth edition, revised and enlarged, crown 8vo, cloth, i6s. 
 
 Gas Works: their Arrangement, Construction, Plant, 
 
 and Machinery. By F. COLYER, M. Inst. C.E. With yi folding plates, 
 8vo, cloth, 24?. 
 
 The Clerk of Works: a Vade-Mecum for all engaged 
 
 in the. Superintendence of Building Operations. By G. G. HOSKINS, 
 F.R.I.B.A. Third edition, fcap. 8vo, cloth, u. f>d. 
 
 American Foundry Practice: Treating of Loam, 
 
 Dry Sand, and Green Sand Moulding, and containing a Practical Treatise 
 upon the Management of Cupolas, and the Melting of Iron. By T. D. 
 WEST, Practical Iron Moulder and Foundry Foreman. Second edition, 
 with numerous illustrations, crown 8vo, cloth, icxr. 6J, 
 
 The Maintenance of Macadamised Roads. By T. 
 
 COIJRINGTON, M.I.C.E, F.G.S., General Superintendent of County Roads 
 for South Wales. 8vo, cloth, 6s. 
 
 Hydraulic Steam and Hand Power Lifting and 
 
 Pressing Machinery. By FREDERICK COLYER, M. Inst. C.E., M. Inst. M.E. 
 With 73 plates, 8vo, cloth, i8j. 
 
 Pumps and Pumping Machinery. By F. COLYER, 
 
 M.I.C.E., M.I.M.E. With 23 folding plates, 8vo, cloth, 12s. 6d. 
 
 Pumps and Pumping Machinery. By F. COLYER. 
 
 Second Part. With u large plates, 8vo, cloth, 12s. 6d. 
 
 A Treatise on the Origin, Progress, Prevention, and 
 
 Cure of Dry Rot in Timber; with Remarks on the Means of Preserving 
 Wood from Destruction by Sea-Worms, Beetles, Ants, etc. By THOMAS 
 ALLEN BRITTON, late Surveyor to the Metropolitan Board of Works, 
 etc., etc. With 10 plates, crown 8yo, cloth, "js. 6d.
 
 PUBLISHED BY E. & F. N. SPON. 
 
 The Municipal and Sanitary Engineer s Handbook. 
 
 By H. PERCY BOULNOIS, Mem. Inst. C.E., Borough Engineer, Ports- 
 mouth. With numerous illustrations, demy 8vo, cloth, izs. 6d. 
 CONTENTS : 
 
 The Appointment and Duties of the Town Surveyor Traffic Macadamised Roadways- 
 Steam Rolling Road Metal and Breaking Pitched Pavements Asphalte Wood Pavements 
 Footpaths Kerbs and Gutters Street Naming and Numbering Street Lighting Sewer- 
 age Ventilation of Sewers Disposal of Sewage House Drainage Disinfection Gas and 
 Water Companies, etc., Breaking up Streets Improvement of Private Streets Borrowing 
 Powers Artizans' and Labourers' Dwellings Public Conveniences Scavenging, including 
 Street Cleansing Watering and the Removing of Snow Planting Street Trees Deposit of 
 Plans Dangerous Buildings Hoardings Obstructions Improving Street Lines Cellar 
 Openings Public Pleasure Grounds Cemeteries Mortuaries Cattle and Ordinary Markets 
 Public Slaughter-houses, etc. Giving numerous Forms of Notices, Specifications, and 
 General Information upon these and other subjects of great importance to Municipal Engi- 
 neers and others engaged in Sanitary Work. 
 
 Metrical Tables. By G. L. MOLESWORTH, M.I.C.E. 
 
 32mo, cloth, is. 6d. 
 
 CONTENTS. 
 
 General Linear Measures Square Measures Cubic Measures Measures of Capacity- 
 Weights Combinations Thermometers. 
 
 Elements of Construction for Electro- Magnets. By 
 
 Count TH. Du MONCEL, Mem. de PInstitut de France. Translated from 
 the French by C. J. WHARTON. Crown 8vo, cloth, 4^. 6d. 
 
 Practical Electrical Units Popularly Explained, with 
 
 numerous illustrations and Remarks. By JAMES SWINBURNE, late of 
 J. W. Swan and Co., Paris, late of Brush-Swan Electric Light Company, 
 U.S.A. i8mo, cloth, is. f>d. 
 
 A Treatise on the Use of Belting for the Transmis- 
 sion of Fouer. By J. H. COOPER. Second edition, ilhistra.'ed, 8vo, 
 cloth, 15-r. 
 
 A Pocket-Book of Usefid Formulce and Memoranda 
 
 for Civil and Mechanical Engineers. By GuiLFORD L. MOLESWORTH, 
 Mem. Inst. C.E., Consulting Engineer to the Government of India for 
 State Railways. With numerous illustrations, 744 pp. Twenty-second 
 edition, revised and enlarged, 32mo, roan, 6s. 
 SYNOPSIS OF CONTENTS: 
 
 Surveying, Levelling, etc. Strength and Weight of Materials Earthwork, Brickwork, 
 Masonry, Arches, etc. Struts, Columns, Beams, and Trusses Flooring, Roofing, and Roof 
 Trusses Girders, Bridges, etc. Railways and Roads Hydraulic Formulae Canals, Sewers, 
 Waterworks, Docks Irrigation and Breakwaters Gas, Ventilation, and Warming Heat. 
 Light, Colour, and Sound Gravity : Centres, Forces, and Powers Millwork, Teeth of 
 Wheels, Shafting, etc. Workshop Recipes Sundry Machinery Animal Power Steam and 
 the Steam Engine Water-power, Water-wheels, Turbines, etc. Wind and Windmills- 
 Steam Navigation, Ship Building, Tonnage, etc. Gunnery, Projectiles, etc. Weights, 
 Measures, and Money Trigonometry, Conic Sections, and Curves Telegraphy Mensura- 
 tion Tables of Areas and Circumference, and Arcs of Circles Logarithms, Square and 
 Cube Roots, Powers Reciprocals, etc. Useful Numbers Differential and Integral Calcu- 
 lus Algebraic Signs Telegraphic Construction and Formulae.
 
 8 CATALOGUE OF SCIENTIFIC BOOKS 
 
 Hints on Architectural Draughtsmanship. By G. W. 
 
 TUXFORD HALLATT. Fcap. 8vo, cloth, is. 6d. 
 
 Spons Tables and Memoranda for Engineers; 
 
 selected and arranged by J. T. HURST, C.E., Author of 'Architectural 
 Surveyors' Handbook,' ' Hurst's Tredgold's Carpentry,' etc. Ninth 
 edition, 64010, roan, gilt edges, is. ; or in cloth case, u. dd. 
 This work is printed in a pearl type, and is so small, measuring only 2j in. by if in. by 
 i in. thick, that it may be easily carried in the waistcoat pocket. 
 
 " It is certainly an extremely rare thing for a reviewer to be called upon to notice a volume 
 measuring but 2$ in. by if in., yet these dimensions faithfully represent the size of the handy 
 little book before us. The volume which contains 118 printed pages, besides a few blank 
 pages for memoranda is, in fact, a true pocket-book, adapted for being carried in the waist- 
 coat pocket, and containing a far greater amount and variety of information than most people 
 
 would imagine could be compressed into so small a space The little volume has been 
 
 compiled with considerable care and judgment, and we can cordially recommend it to our 
 readers as a useful little pocket companion." Engineering. 
 
 A Practical Treatise on Natural and Artificial 
 
 Concrete, its Varieties and Constructive Adaptations. By HENRY REID, 
 Author of the ' Science and Art of the Manufacture of Portland Cement.' 
 New Edition, with 59 woodcuts and 5 plates, 8vo, cloth, 15*. 
 
 Notes on Concrete and Works in Concrete; especially 
 
 written to assist those engaged upon Public Works. By JOHN NEWMAN, 
 Assoc. Mem. Inst. C.E., crown 8vo, cloth, 4^. 6iL 
 
 Electricity as a Motive Power. By Count Tir. Du 
 
 MONCEL, Membre de 1'Institut de France, and FRANK GERALDY, Inge- 
 nieur des Fonts et Chaussees. Translated and Edited, with Additions, by 
 C. J. WHARTON, Assoc. Soc. Tel. Eng. and Elec. With 113 engravings 
 and diagrams, crown 8vo, cloth, 7^. 6</. 
 
 Treatise on Valve-Gears, with special consideration 
 
 of the Link-Motions of Locomotive Engines. By Dr. GUSTAV XEUNER, 
 Professor of Applied Mechanics at the Confederated Polytechnikum of 
 Zurich. Translated from the Fourth German Edition, by Professor J. F. 
 KLEIN, Lehigh University, Bethlehem, Pa. Illustrated, 8vo, cloth, \2s. 6d. 
 
 The French- Polisher s Manual. By a French- 
 
 Polisher; containing Timber Staining, Washing, Matching, Improving, 
 Painting, Imitations, Directions for Staining, Sizing, Embodying, 
 Smoothing, Spirit Varnishing, French-Polishing, Directions for Re- 
 polishing. Third edition, royal 32mo, sewed, 6d. 
 
 their Cultivation, Commerce, and Uses in 
 
 various Countries. By P. L. SlMMONDS. Crown 8vo, cloth, 4^. 6d. 
 
 The Principles of Graphic Statics. By GEORGE 
 
 SYDENHAM CLARKE, Capt. Royal Engineers. With 112 illustrations. 
 4to, cloth, 12s. 6J.
 
 PUBLISHED BY E. & F. N. SPON. 
 
 Dynamo- Electric Machinery : A Manual for Students 
 
 of Electro-technics. By SILVANUS P. THOMPSON, B.A., D.Sc., Professor 
 of Experimental Physics in University College, Bristol, etc., etc. Third 
 edition, illustrated, 8vo, cloth, i6s. 
 
 Practical Geometry, Perspective, and Engineering 
 
 Drawing; a Course of Descriptive Geometry adapted to the Require- 
 ments of the Engineering Draughtsman, including the determination of 
 cast shadows and Isometric Projection, each chapter being followed by 
 numerous examples ; to which are added rules for Shading, Shade-lining, 
 etc., together with practical instructions as to the Lining, Colouring, 
 Printing, and general treatment of Engineering Drawings, with a chapter 
 on drawing Instruments. By GEORGE S. CLARKE, Capt. R.E. Second 
 edition, with 21 plates. 2 vols., cloth, loj. 6d. 
 
 The Elements of Graphic Statics. By Professor 
 
 KARL VON OTT, translated from the German by G. S. CLARKE, Capt. 
 R.E., Instructor in Mechanical Drawing, Royal Indian Engineering 
 College. With 93 illustrations, crown 8vo, cloth, $s. 
 
 A Practical Treatise on the Manufacture and Distri- 
 bution of Coal Gas. By WILLIAM RICHARDS. Demy 410, with numerous 
 wood engravings and 29 plates, cloth, 28^. 
 
 SYNOPSIS OF CONTENTS: 
 
 Introduction History of Gas Lighting Chemistry of Gas Manufacture, by Lewis 
 Thompson, Esq., M.R.C.S. Coal, with Analyses, by J. Paterson, Lewis Thompson, and 
 G. R. Hislop, Esqrs. Retorts, Iron and Clay Retort Setting Hydraulic Main Con- 
 densersExhaustersWashers and Scrubbers Purifiers Purification History of Gas 
 Holder Tanks, Brick and Stone, Composite, Concrete, Cast-iron, Compound Annular 
 Wrought-iron Specifications Gas Holders Station Meter Governor Distribution 
 Mains Gas Mathematics, or Formulae for the Distribution of Gas, by Lewis Thompson, Esq. 
 Services Consumers' Meters Regulators Burners Fittings Photometer Carburization 
 of Gas Air Gas and Water Gas Composition of Coal Gas, by Lewis Thompson, Esq. 
 Analyses of Gas Influence of Atmospheric Pressure and Temperature on Gas Residual 
 Products Appendix Description of Retort Settings, Buildings, etc., etc. 
 
 The New Formula for Mean Velocity of Discharge 
 
 of Rivers and Canals. By W. R. KUTTER. Translated from articles in 
 the ' Cultur-Ingenieur,' by Lowis D'A. JACKSON, Assoc. Inst. C.E. 
 8vo, cloth, 12s. 6d. 
 
 The Practical Millwright and Engineers Ready 
 
 Reckoner; or Tables for finding the diameter and power of cog-wheels, 
 diameter, weight, and power of shafts, diameter and strength of bolts, etc. 
 By THOMAS DIXON. Fourth edition, 12010, cloth, 3^. 
 
 Tin: Describing the Chief Methods of Mining, 
 
 Dressing and Smelting it abroad ; with Notes upon Arsenic, Bismuth and 
 Wolfram. By ARTHUR G. CHARLETON, Mem. American Inst. of 
 Mining Engineers. With plates, 8vo, cloth, 12s. f>d. 
 
 B 3
 
 lo CATALOGUE OF SCIENTIFIC BOOKS 
 
 Perspective, Explained and Illustrated. By G. S. 
 
 CLARKE, Capt. R.E. With illustrations, 8vo, cloth, 3*. 6d. 
 
 Practical Hydraulics ; a Series of Rules and Tables 
 
 for the use of Engineers, etc., etc. By THOMAS Box. Fifth edition, 
 numerous plates, post 8vo, cloth, 5-r. 
 
 The Essential Elements of Practical Mechanics; 
 
 based on the Principle of Work, designed for Engineering Students. By 
 OLIVER BYRNE, formerly Professor of Mathematics, College for Civil 
 Engineers. Third edition, with 148 wood engravings, post 8vo, cloth, 
 is. 6d. 
 
 CONTENTS : 
 
 Chap. I. How Work is Measured by a Unit, both with and without reference to a Unit 
 of Time Chap. 2. The Work of Living Agents, the Influence of Friction, and introduces 
 one of the most beautiful Laws of Motion Chap. 3. The principles expounded in the first and 
 second chapters are applied to the Motion of Bodies Chap. 4. The Transmission of Work by 
 simple Machines Chap. 5. Useful Propositions and Rules. 
 
 Breweries and Mailings : their Arrangement, Con- 
 struction, Machinery, and Plant. By G. SCAMELL, F.R.I.B.A. Second 
 edition, revised, enlarged, and partly rewritten. By F. COLYER, M.I.C.E., 
 M.I.M.E. With 20 plates, 8vo, cloth, iSs. 
 
 A Practical Treatise on the Construction of Hori- 
 zontal and Vertical Watcrwheels, specially designed for the use of opera- 
 tive mechanics. By WILLIAM CULLEN, Millwright and Engineer. With 
 II plates. Second edition, revised and enlarged, small 410, cloth, 12s. 6d. 
 
 A Practical Treatise on Mill-gearing, Wheels, Shafts, 
 
 Riggers, etc. ; for the use of Engineers. By THOMAS Box. Third 
 edition, with 1 1 plates. Crown 8vo, cloth, 7-r. 6</. 
 
 Mining Machinery: a Descriptive Treatise on the 
 
 Machinery, Tools, and other Appliances used in Mining. By G. G. 
 ANDRE, F.G.S., Assoc. Inst. C.E., Mem. of the Society of Engineers. 
 Royal 4to, uniform with the Author's Treatise on Coal Mining, con- 
 taining 182 plates, accurately drawn to scale, with descriptive text, in 
 2 vols., cloth, 3/. I2.r. 
 
 CONTENTS : 
 
 Machinery for Prospecting, Excavating, Hauling, and Hoisting Ventilation Pumping 
 Treatment of Mineral Products, including Gold and Silver, Copper, Tin, and Lead, Iron 
 Coal, Sulphur, China Clay, Brick Earth, etc. 
 
 Tables for Setting out Curves for Railways, Canals, 
 
 Roads, etc., varying from a radius of five chains to three miles. By A. 
 KENNEDY and R. W. HACKWOOD. Illustrated, 321110, cloth, 2s. 6d.
 
 PUBLISHED BY E. & F. N. SPON. 
 
 The Science and Art of the Manufacture of Portland 
 
 Cement, with observations on some of its constructive applications. With 
 66 illustrations. By HENRY REID, C.E., Author of 'A Practical 
 Treatise on Concrete,' etc., etc. 8vo, cloth, i8j. 
 
 The Draughtsman s Handbook of Plan and Map 
 
 Drawing; including instructions for the preparation of Engineering, 
 Architectural, and Mechanical Drawings. With numerous illustrations 
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 with Essays on the Principles involved in Design and Construction. By 
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 or cheaper edition, cloth, 2$s. 
 
 This work is not, in any sense, an elementary treatise, or history of the steam engine, but 
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 recent arrangements of Horizontal, Vertical, Beam, Pumping, Winding, Portable, Semi- 
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 A Practical Treatise on the Science of Land and 
 
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 general description of the several Instruments required for Surveying, 
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 PRINCIPAL CONTENTS : 
 
 Part i. Introduction and the Principles of Geometry. Part 2. Land Surveying ; com- 
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 Hilly Ground To Survey an Estate or Parish by the Chain only Surveying with the 
 Theodolite Mining and Town Surveying Railroad Surveying Mapping Division and 
 Laying out of Land Observations on Enclosures Plane Trigonometry. Part 3. Levelling 
 Simple and Compound Levelling The Level Book Parliamentary Plan and Section 
 Levelling with a Theodolite Gradients Wooden Curves To Lay out a Railway Curve 
 
 Setting out Widths. Part 4. Calculating Quantities generally for Estimates Cuttings and 
 Embankments Tunnels Brickwork Ironwork Timber Measuring. Part 5. Description 
 and Use of Instruments in Surveying and Plotting The Improved Dumpy Level Troughton's 
 Level The Prismatic Compass Proportional Compass Box Sextant Vernier Panta- 
 graph Merrett's Improved Quadrant Improved Computation Scale The Diagonal Scale- 
 Straight Edge and Sector. Part 6. Logarithms of Numbers Logarithmic Sines and 
 Co-Sines, Tangents and Co-TangentsNatural Sines and Co-SinesTables for Earthwork, 
 for Setting out Curves, and for various Calculations, etc., etc., etc. 
 
 Health and Comfort in House Building, or Ventila- 
 
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 mode of Calculating the Draught in Hot- Air Flues, and with some actual 
 Experiments. By J. DRYSDALE, M.D., and J. W. HAYVVARD, M.D. 
 Second edition, with Supplement, with plates t demy 8vo, cloth, Js. 64,
 
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 The Assayers Manual: an Abridged Treatise on 
 
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 illustrations, 8vo, cloth, I2s. 6d. 
 
 Dynamo - Electric Machinery : a Text - Book for 
 
 Students of Electro-Technology. BySiLVANUS P. THOMPSON, B.A., 
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 The Practice of Hand Turning in Wood, Ivory, Shell, 
 
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 Ornamental Turning. (A book for beginners.) By FRANCIS CAMPIN. 
 Third edition, with wood engravings, crown 8vo, cloth, 6s. 
 
 CONTENTS : 
 
 On Lathes Turning Tools Turning Wood Drilling Screw Cutting Miscellaneous 
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 Rev. H. L. NELTHROPP, M.A., F.S.A. With 32 illustrations, crown 
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 CONTENTS : 
 
 Definitions of Words and Terms used in Watchwork Tools Time Historical Sum- 
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 Trains, etc. Of Dial Wheels, or Motion Work Length of Time of Going without Winding 
 up The Verge The Horizontal The Duplex The Lever The Chronometer Repeating 
 Watches-Keyless Watches The Pendulum, or Spiral Spring Compensation Jewelling of 
 Pivot Holes Clerkenwell Fallacies of the Trade Incapacity of Workmen How to Choose 
 and Use a Watch, etc. 
 
 Algebra Self-Taught. By W. P. HIGGS, M.A., 
 
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 and Proportionate Parts Transformation of System of Logarithms Common Uses of 
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 Fractions, and Ratio Continued Proportion The Series and the Summation of the Series- 
 Limit of Series Square and Cube Roots Equations List of Formulae, etc. 
 
 Spam Dictionary of Engineering, Civil, Mechanical, 
 
 Military, and Naval; with technical terms in French, German, Italian, 
 and Spanish, 3100 pp., and nearly 8000 engravings, in super-royal 8vo, 
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 PUBLISHED BY E. & F. N. SPON. 15 
 
 Notes in MecJianical Engineering. Compiled prin- 
 cipally for the use of the Students attending the Classes on this subject at 
 the City of London College. By HENRY ADAMS, Mem. Inst. M.E., 
 Mem. Inst. C.E., Mem. Soc. of Engineers. Crown 8vo, cloth, zs. 6d. 
 
 Canoe and Boat Building: a complete Manual for 
 
 Amateurs, containing plain and comprehensive directions for the- con- 
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 By W. P. STEPHENS. With numerous illustrations and 24 plates oj 
 Working Drawings. Crown 8vo, cloth, "js. 6d. 
 
 Proceedings of the National Conference of Electricians, 
 
 Philadelphia, October 8th to 1 3th, 1884. i8mo, cloth, 3*. 
 
 Dynamo - Electricity, its Generation, Application, 
 
 Transmission, Storage, and Measurement. By G. B. PRESCOTT. With 
 545 illustrations. 8vo, cloth, I/, u. 
 
 Domestic Electricity for Amateurs. Translated from 
 
 the French of E. HOSPITALIER, Editor of "L'Electricien," by C. J. 
 WHARTON, Assoc. Soc. Tel. Eng. Numerous illustrations. Demy 8vo, 
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 CONTENTS : 
 
 I. Production of the Electric Current 2. Electric Bells 3. Automatic Alarms 4. Domestic 
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 8. Domestic Application of the Electric Light 9. Electric Motors 10. Electrical Locomo- 
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 cationsWorkshop of the Electrician. 
 
 Wrinkles in Electric Lighting. By VINCENT STEPHEN. 
 
 With illustrations. l8mo, cloth, 2s. 6d. 
 
 CONTENTS : 
 
 i. The Electric Current and its production by Chemical means 2. Production of Electric 
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 Manual for Gas Engineering Stiidents. By D. LEE. 
 
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 Hydraulic Machinery, Past and Present. A Lecture 
 
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 By H. ADAMS, Mem. Inst. C.E. Folding plate. 8vo, sewed, is. 
 
 Twenty Years with the Indicator. By THOMAS PRAY, 
 
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 2 vols., royal 8vo, cloth, I2s. (>d. 
 
 Annual Statistical Report of the Secretary to the 
 
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 Well Sinking. The modern practice of Sinking 
 
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 By ERNEST SPON, Assoc. Mem. Inst. C.E., Mem. Soc. Eng., and of the 
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 Tlie Voltaic Accumulator: an Elementary Treatise. 
 
 By EMILE REYNIER. Translated by J. A. BERLY, Assoc. Inst. E.E. 
 With 62 illustrations, 8vo, cloth, gs. 
 
 List of Tests (Reagents], arranged in alphabetical 
 
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 By HANS M. WILDER. Crown 8vo, cloth, 4?. 6d. 
 
 Ten Years Experience in Works of Intermittent 
 
 Downward Filtration. By J. BAILEY DENTON, Mem. Inst. C.E. 
 Second edition, with additions. Royal 8vo, sewed, 45. 
 
 A Treatise on tJie Manufacture of Soap and Candles, 
 
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 PUBLISHED BY E. & F. N. SPON. 17 
 
 The Stability of Ships explained simply, and calculated 
 
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 3-r. 6</. 
 
 Steam Making, or Boiler Practice. By CHARLES A. 
 
 SMITH, C.E. 8vo, cloth, icw. 6d. 
 
 CONTES rs : 
 
 The Fireman s Guide ; a Handbook on the Care of 
 
 Boilers. By TEKNOLOG, foreningen T. I. Stockholm. Translated from 
 the third edition, and revised by KARL P. DAHLSTROM, M.E. Second 
 edition. Fcap. 8vo, cloth, 2s. 
 
 A Treatise on Modern Steam Engines and Boilers, 
 
 including Land Locomotive, and Marine Engines and Boilers, for the 
 use of Students. By FREDERICK COLYER, M. Inst. C.E., Mem. Inst. M.E. 
 With 36 plates. 410, cloth, 2$j. 
 
 CONTENTS : 
 
 i. Introduction 2. Original Engines 3. Boilers 4. High-Pressure Beam Engines 5. 
 Cornish Beam Engines 6. Horizontal Engines 7. Oscillating Engines 8. Vertical Hig).- 
 Pressure Engines 9. Special Engines 10. Portable Engines n. Locomotive Engines 
 12. Marine Engines. 
 
 Steam Engine Management; a Treatise on the 
 
 Working and Management of Steam Boilers. By F. COLYER, M. Inst. 
 C.E., Mem. Inst. M.E. i8mo, cloth, 2s. 
 
 Land Surveying on the Meridian and Perpendicular 
 
 System. By WILLIAM PENMAN, C.E. 8vo, cloth, Ss 6d. 
 
 The Topographer, his Instruments and Methods, 
 
 designed for the use of Students, Amateur Photographers, Surveyors, 
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 Indicators, and Slide 
 
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 Magneto-Electric Ma- 1 Ores, Machinery and 
 
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 chines. Processes employed to 
 
 Antimony. 
 
 Dynamometers. Dress. 
 
 Axles and Axle-boxes. 
 
 Electrical Engineering, 
 
 Piers. 
 
 Barn Machinery. 
 
 Telegraphy, Electric 
 
 Pile Driving. 
 
 Belts and Belting. 
 
 Lighting and its prac- 
 
 Pneumatic Transmis- 
 
 Blasting. Boilers. 
 
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 sion. 
 
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 Explosives. Fans. 
 
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 other Power. 
 
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 SYNOPSIS OF CONTENTS. 
 
 Freezing. 
 
 Fulminates. 
 
 Furniture Creams, Oils, 
 
 Polishes, Lacquers, 
 
 and Pastes. 
 
 Bookbinding. 
 
 Bronzes and Bronzing. 
 
 Candles. 
 
 Cement. 
 
 Cleaning. 
 
 Colourwashing. 
 
 Concretes. 
 
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 Drying Oils. 
 
 Dynamite. 
 
 Electro - Metallurgy Glass Making. 
 
 (Cleaning, Dipping, Glues. 
 
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 Deposits of every Gums. 
 
 description). 
 Enamels. 
 Engraving on Wood, Horn Working. 
 
 Copper, Gold, Silver, : Indiarubber. 
 
 Steel, and Stone. 
 Etching and Aqua Tint. 
 Firework Making Lacquers. 
 
 (Rockets, Stars, Rains, Lathing. 
 
 Gerbes, Jets, Tour- Lubricants. 
 
 billons, Candles, Fires, Marble Working. 
 
 Lances,Lights,Wheels, Matches. 
 
 Fire-balloons, and 
 
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 Fluxes. 
 
 Paper. 
 
 Paper Hanging. 
 
 Painting in Oils, in Water 
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 Carriage Painting. 
 
 Frosting, Drilling, Photography. 
 Darkening, Bending, Plastering. 
 Staining, and Paint- Polishes. 
 
 Pottery (Clays, Bodies, 
 Glazes, Colours, Oils, 
 Stains, Fluxes, Ena- 
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 Scouring. 
 
 Silvering. 
 
 Soap. 
 
 Solders. 
 
 Tanning. 
 
 Taxidermy. 
 Japans, Japanning, and Tempering Metal 
 
 Gilding. 
 
 Glass Cutting, Cleaning, 
 
 ing. 
 
 Gun Cotton. 
 Gunpowder. 
 
 kindred processes. 
 
 Mortars. 
 
 Nitro-Glycerine. 
 
 Oils. 
 
 Treating Horn, Mother- 
 o'-Pearl, and like sub- 
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 and Use of. 
 
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 Washing. 
 
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 Welding. 
 
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 WORKSHOP RECEIPTS, 
 
 SECOND SERIES. 
 BY ROBERT HALDANE. 
 
 SYNOPSIS OF CONTENTS. 
 
 Acidimetry and Alkali- 
 metry. 
 Albumen. 
 Alcohol. 
 Alkaloids. 
 Baking-powders. 
 Bitters. 
 Bleaching. 
 Boiler Incrustations. 
 Cements and Lutes. 
 Cleansing. 
 Confectionery. 
 Copying. 
 
 Disinfectants. 
 Dyeing, Staining, and 
 Colouring. 
 : Essences. 
 Extracts. 
 Fireproofing. 
 Gelatine, Glue, and Size. ' 
 | Glycerine. 
 Gut. 
 Hydrogen peroxide, 
 : Ink. 
 Iodine, 
 lodoform. 
 
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 Ivory substitutes. 
 Leather. 
 Luminous bodies. 
 Magnesia. 
 Matches. 
 Paper. 
 Parchment. 
 Perchloric acid. 
 Potassium oxalate. 
 Preserving. 
 
 Pigments, Paint, and Painting : embracing the preparation of 
 Pigments, including alumina lakes, blacks (animal, bone, Frankfort, ivory, 
 lamp, sight, soot), blues (antimony, Antwerp, cobalt, caeruleum, Egyptian, 
 manganate, Paris, Peligot, Prussian, smalt, ultramarine), browns (bistre, 
 hinau, sepia, sienna, umber, Vandyke), greens (baryta, Brighton, Brunswick, 
 chrome, cobalt, Douglas, emerald, manganese, mitis, mountain, Prussian, 
 sap, Scheele's, Schweinfurth, titanium, verdigris, zinc), reds (Brazilwood lake, 
 carminated lake, carmine, Cassius purple, cobalt pink, cochineal lake, colco- 
 thar, Indian red, madder lake, red chalk, red lead, vermilion), whites (alum, 
 baryta, Chinese, lead sulphate, white lead by American, Dutch, French, 
 German, Kremnitz, and Pattinson processes, precautions in making, and 
 composition of commercial samples whiting, Wilkinson's white, zinc white), 
 yellows (chrome, gamboge, Naples, orpiment, realgar, yellow lakes) ; Paint 
 (vehicles, testing oils, drier-;, grinding, storing, applying, priming, drying, 
 filling, coats, brushes, surface, water-colours, removing smell, discoloration ; 
 miscellaneous paints cement paint for carton-pierre, copper paint, gold paint, 
 iron paint, lime paints, silicated paints, steatite paint, transparent paints, 
 tungsten paints, window paint, zinc paints) ; Painting (general instructions, 
 proportions of ingredients, measuring paint work ; carriage painting priming 
 paint, best putty, finishing colour, cause of cracking, mixing the paints, oils, 
 driers, and colours, varnishing, importance of washing vehicles, re-varnishing, 
 how to dry paint ; woodwork painting). 
 
 London : E. & F. N. SPON, 125, Strand. 
 
 New York : 12, Cortlandt Street.
 
 PUBLISHED. 
 
 In demy Svo, cloth, 600 pages, and 1420 Illustrations, 6s. 
 
 SPONS' 
 MECHANICS' OWN BOOK; 
 
 A MANUAL FOR HANDICRAFTSMEN AND AMATEURS. 
 
 CONTENTS. 
 
 Mechanical Drawing Casting and Founding in Iron, Brass, Bronze, 
 and other Alloys Forging and Finishing Iron Sheetmetal Working 
 Soldering, Brazing, and Burning Carpentry and Joinery, embracing 
 descriptions of some 400 Woods, over 200 Illustrations of Tools and 
 their uses, Explanations (with Diagrams) of 116 joints and hinges, and 
 Details of Construction of Workshop appliances, rough furniture, 
 Garden and Yard Erections, and House Building Cabinet-Making 
 and Veneering Carving and Fretcutting Upholstery Painting, 
 Graining, and Marbling Staining Furniture, Woods, Floors, and 
 Fittings Gilding, dead and bright, on various grounds Polishing 
 Marble, Metals, and Wood Varnishing Mechanical movements, 
 illustrating contrivances for transmitting motion Turning in Wood 
 and Metals Masonry, embracing Stonework, Brickwork, Terracotta, 
 and Concrete Roofing with Thatch, Tiles, Slates, Felt, Zinc, c. 
 Glazing with and without putty, and lead glazing Plastering and 
 Whitewashing Paper-hanging Gas-fitting Bell-hanging, ordinary 
 and electric Systems Lighting Warming Ventilating Roads, 
 Pavements, and Bridges Hedges, Ditches, and Drains Water 
 Supply and Sanitation Hints on House Construction suited to new 
 countries. _ _ 
 
 London: E. & F. N. SPON, 126, Strand. 
 
 New York : 12, Cortlandt Street.
 
 UNIVERSITY OF CALIFORNIA LIBRARY 
 
 - Los Angeles 
 This book is DUE on the last date stamped below. 
 
 PSTT 
 
 INTERLIBRARY LOAN! 
 
 OCT 251979 
 
 THREE WEEKS FROM DATE 
 NON Rf.NEW.ABLE 
 
 Form L9-25m-9,'47(A5618)444
 
 TH 
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 1885 
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