JC-NRLF 
 
 SB 5b2 3Eb 
 
GIFT OF 
 MlSS E-T.W 
 
7 
 
ON 
 
 ECONOMY OF FUEL, 
 
 PARTICULARLY WITH RWKRENCK TO 
 
 REVERBERATOR! FURNACES 
 
 THE MANUFACTURE OF IRON, AND TO STEAM BOILKRS. 
 
 BY 
 
 T. STMES PBIDEAUX, ESQ. 
 
 ft 
 
 AUTHOR OP VARIOUS PAPERS IV THB ZOIST. 
 
 " In a manufacturing nation such as England, the application 
 of scientific results to the arts, should be the prime object of 
 every employer of skilled labour, who would not be left behind, 
 in the race of improvement." WettmimUr Review. 
 
 LONDON: 
 JOHN WEALE, 59, HIGH HOLBOEN. 
 
 MDCCCLIII. 
 
V 
 
 SYNOPSIS OF CONTENTS. 
 
 Introduction v 
 
 General Considerations 1 
 
 SECTION I. On attaining perfect Combustion, and appor- 
 tioning the supply of air to the wants 
 
 of the fuel 3 
 
 II. On the employment of Slack or small coal, 
 1st., by the use of Furnaces with per- 
 forations in the sides, 2ndly, by the use 
 of compressed air in a closed ash-pit ... 15 
 III. Additional advantages of working with com- 
 pressed air in Reverberatory Furnaces 21 
 
 IV. Advantages of ditto in Steam Boilers 33 
 
 V. Economy to be attained by increasing the 
 
 Temperature of Furnaces 38 
 
 VI. On feeding Furnaces with Hot Air 47 
 
 VII. Economic application of Heat 54 
 
 VIII. On the employment of Waste Heat , 58 
 
 IX. On the Manufacture of Iron 61 
 
 X. On the quantity of Heat in Steam, and its 
 
 Economic Application 90 
 
 APPENDIX. 
 
 On Dwelling-house Grates and Ventilation 109 
 
 On the Ventilation of Coal Mines 127 
 
 248209 
 
INTRODUCTION. 
 
 1. IT would be difficult to exaggerate the importance of the part 
 played by heat, both on a grand scale in the laboratory of 
 nature, and on a minor scale, in the domain of human art and 
 science. In the former respect it is not only an essential con- 
 dition to the existence of life on this planet, but also the prime 
 agent in putting in motion most of the physical changes which 
 take place at the earth's surface. In the latter, it must be re- 
 garded not only as furnishing man with the chief means he 
 possesses of imitating in miniature the processes of nature, and 
 moulding and modifying natural productions to his wants ; but 
 also as bestowing on him the ability to generate and apply at 
 pleasure, a force equally stupendous and easy of control. 
 
 2. Yes, it is to heat we are indebted for the aliment which 
 nourishes the sinews of that all powerful giant, yet obedient 
 slave, which the genius of a Watt subdued, and left as a legacy 
 to all succeeding generations. That unwearied drudge of all 
 work, which grinds our corn, weaves our clothing, forges our 
 tools, drives our printing presses, twists a massive cable of iron, 
 or spins a gossamer thread of cotton down, impels our steam 
 ships on their ocean routes, defying wind and wave, or whirls 
 us through space when we journey on land, with thrice the 
 speed of the race horse. A slave more patient than Caliban, 
 fleeter than Ariel, such an one as it never entered into the imagi- 
 nations of our forefathers in their most sanguine dreams, to hope 
 for the possession of. 
 
 3. Nothing furnishes man with greater cause for congratu- 
 lation and even an excusable pride, than the feats of that mighty 
 impersonation of brute force and human intellect, the steam 
 engine, the Hercules of the nineteenth century, which once 
 launched into the worlds arena, has gone forth " conquering and 
 
VI . INTRODUCTION. 
 
 to conquer," fulfilling his high destiny as a great civilizing agent, 
 with an energy which no human arm can arrest, and a rapidity 
 which fills us with astonishment, admiration, and hope. 
 
 4. For all these achievements man is indebted to the laws 
 which govern the combination of certain electro-positive bodies, 
 such as carbon and hydrogen, with oxygen. It is by carefully 
 studying the laws of the universe, and employing them for his 
 benefit, that he raises himself from the lowest pitch of barbarism, 
 to the height of civilization from the state of a naked defence- 
 less savage, shivering with cold and hunger, to the well clad, 
 well housed, well fed product of modern civilization, master of 
 an ample supply of the necessaries and comforts of life, with 
 leisure to spare for moral and intellectual cultivation. The same 
 forces of nature, so astonishing and often so destructive to the 
 savage, become, when a knowledge is attained of the circum- 
 stances under which they act, the docile assistants, instead of 
 the rude enemies of man the allies by whose aid he obtains the 
 mastery over brute matter, employs the elements as couriers, 
 and yokes them to his triumphal car. 
 
 5. What is the lesson such a career of progress ought 
 to teach us? at least this, a wise humility as to the perfec- 
 tion of our present knowledge, and our manufacturing pro- 
 cesses founded upon it, diametrically opposed to that narrow- 
 minded conceit of infallibility, and incredulity as to further 
 improvement, which exist in their greatest vigour, just in those 
 narrow arched crania, where ignorance of general principles is 
 the most profound, and incapacity for lifting the mind to 
 imagine a state of things widely differing from the present, 
 the most complete. Just in short, in that class of persons, 
 where this self satisfied state of mind is most misplaced, the 
 most injurious to the interests of the individual, and the most 
 ridiculous in the eyes of others. 
 
 6. There are few manufacturing processes that have not been 
 greatly revolutionized, simplified, and extended within these fifty 
 years, and had none but this narrow arched crania race been en- 
 gaged in them, these improvements would never have been made; 
 for if no one can be found with sufficient knowledge, enterprise, 
 and love of perfection, to be the first to try a new thing, progress 
 becomes impossible. Just the state of things in fact, which 
 exists amongst many nations, whose civilization is stationary or 
 retrograde, and whom we justly look upon as our inferiors 
 laggards in the race of improvement, whose rank in the scale of 
 
INTRODUCTION. vii 
 
 manhood even when industrious, is only that of plodding 
 labourers the hodmen of humanity who can no more origi- 
 nate a structure that is new and beautiful, without the inspira- 
 tion of a superior race, than a bricklayer's labourer can erect, 
 without an architect, the splendid building on which he toils 
 from morn till eve, most praiseworthily employed according to 
 the talent committed to his care, but nevertheless a mere beast 
 of burden, whose task, genius can at pleasure, arrange a few 
 cogs and wheelwork more efficiently to perform. 
 
 7. Nations are not generally aware of the extent of their 
 obligation to their leaders, the men who head the career of pro- 
 gress and improvement, fulfilling the part of generals to an army; 
 nor how small a number of such men suffice, where the people 
 are honest and industrious, to redeem the whole body from stag- 
 nation, to leaven the inert mass with the inspiration of their own 
 genius, and to impart character, tone, and an object to the 
 national mind, by bestowing its leading ideas. 
 
 8. He must be blind indeed, who does not see that ideas 
 rule the world, as absolutely and as necessarily, as the mind the 
 muscles of the body. The whole course of sublunary affairs is 
 in fact but a commentary on the text that " knowledge is power" 
 and teaches the entire subjugation of physical, to intellectual 
 force. The former is in reality but the manifestatipn of the 
 latter, the weapon it employs to execute its volitions, with no 
 independent vitality of its own, but necessarily ceasing to exist 
 with the ideas which called it into life. A fact from which 
 we at least derive the consolation of knowing, that all material 
 interests and brute forces which represent ideas not having truth 
 for their basis, are necessarily doomed to decay, whilst such as 
 are salutary, beneficial, and consequently founded in truth, must 
 eventually prevail and overcome all opposition. The product of 
 the former class of ideas, inherits the seeds of decay ; those of 
 the second, of vitality. How insignificant become in a few years 
 the results of the deeds of a great conqueror. Time would 
 appear to take a pleasure in obliterating with die furrows of his 
 ploughshare every trace of his career ; whilst on the other hand, 
 the result of a luminous idea like that of Watt's on the steam 
 engine, essentially prolific in its nature, for ever expands itself 
 as it stretches into the future, giving birth to a numerous progeny 
 of ideas, each in its turn destined to be prolific like its parent, 
 till the imagination loses itself at the vastness of the field of 
 view which opens before it. 
 
Vlll . INTRODUCTION. 
 
 9. So low however at present, is the scale of humanity 
 amongst us, that for one individual who could be found \vith 
 open purse and liberal heart, animated with the glorious ambition 
 of aiding in the development of ideas so fraught with great and 
 beneficial results to mankind, as those of Watt ; it is to be feared 
 that one hundred would be met with, who, deaf to all such con- 
 siderations, or perhaps even holding them in derision, would re- 
 ject the opportunity open to them of furthering so good a work, 
 to achieve in preference the grander result ! ! ! of leaving a some- 
 what heavier money bag to an impatient heir. 
 
 10. Let it never be forgotten, that clear, simple, and ob- 
 viously indubitable, as was the improvement of Watt on the 
 steam engine, requiring, it would be supposed by all (except 
 those who have had practical experience of the vis inertia of 
 ignorance,) only to be seen, to be adopted with acclamation, yet 
 it was eight years before he succeeded in getting any one to try 
 it, and had not a fortunate chance at that period introduced him 
 to a liberal, enlightened, and enterprising man in Boulton, another 
 eight years of fruitless efforts might have had to have been 
 undergone, or even the full appreciation of the invention indefi- 
 nitely delayed. In which case, the whole of that vast career of 
 progress on which the human race entered as a consequence of 
 the steamSngine, would have been postponed ; the issue of the 
 great European war might have been different ; colonies rapidly 
 increasing in wealth and importance, would have remained desert 
 wastes ; large cities now flourishing, would have been unbuilt, 
 and millions now living, unborn. How little and pitiful beside 
 a Boulton, appear the men who devoid of all love of perfection, 
 hug themselves with secret self-complacency on their superior 
 wisdom, in leaving to others the risk of making a first experi- 
 ment, reserving to themselves the more gainful part of appro- 
 priating the discoveries revealed and established by the researches 
 and experiments of their contemporaries. Glorying in what 
 constitutes their disgrace, they form the drones of the hive, who 
 contribute nothing to the common fund, but exist by the labours 
 of others. Strangers to the honest pride of being the creditors, 
 rather than the debtors of society, and receiving nothing from it 
 for which they do not return an ample equivalent. 
 
 11. Numerous as are the inventions for which society 
 stands indebted to the fertile genius of Watt, his first, that of 
 the condensation of steam in a vessel separate from the cylinder, 
 transcends all others in importance. For half a century after 
 
INTRODUCTION;. ix 
 
 the introduction of the steam engine, the mode of forming the 
 vacuum beneath the piston, was by conducting the condensing 
 process in the cylinder itself, and the cooling down of this vessel 
 necessarily resulting from this operation, was productive of an 
 enormous waste of fuel, entailing as it did, the necessity of re- 
 heating it to its previous temperature upon the readmission of 
 steam, a process performed by the first portion of the entering 
 steam at the expense of its own condensation. Such was the 
 loss of time and heat consequent upon this bungling arrange- 
 ment, that when Watt solved the problem of condensing the 
 steam without cooling the cylinder, by having recourse to what 
 now appears to us the obvious expedient of employing a separate 
 condensing vessel, he increased at one bound the efficacy of 
 the steam engine 75 per cent. Now if I am not greatly mis- 
 taken, at the present day, with regard to the management of 
 some kinds of furnaces, practices prevail, scarcely less productive 
 of waste, than the old plan of cooling down and re-heating 
 the cylinder at every stroke, was, with reference to the steam 
 engine. 
 
 12. Considering the importance of the question of furnace 
 management, and the amount of capital involved in it, I am 
 struck with surprise at the little aid it has hitherto derived 
 from science. There is scarcely a process in manufacture in 
 which heat is not one of the prime agents employed, so that 
 it may without exaggeration be stated, that the question of 
 consumption of firing, lies at the foot of the cost of production. 
 Has then anything like the amount of intellect been devoted 
 to the examination of this subject of economy of fuel, which 
 the magnitude of the interests involved in it, and its importance 
 in a national point of view, render it deserving of? Are the 
 processes and appliances we have recourse to, the result of 
 careful deductions, made from a searching and scientific con- 
 sideration of the question from an elevated point of view, 
 'untrammelled by those narrow notions which daily routine 
 too frequently engenders or rather, have not methods and 
 systems, which originated at a period of comparative darkness 
 in physical science, been continued from habit down to the 
 present day, without adequate reflection and research? Methods 
 in fact, which gradually developed themselves as necessity 
 dictated, to the untutored intellect of uncultivated men ; and 
 which, however creditable to our forefathers who devised them, 
 inasmuch as they availed themselves of all the sources of infor- 
 
X INTRODUCTION. 
 
 matiori within their reach, are nevertheless a reproach to the 
 more advanced knowledge of physical, chemical, and mechanical 
 science, enjoyed by the present generation. 
 
 13. So paralizing with most persons seems to be the effect 
 of habit and routine upon the intellect, in checking all original 
 ideas with regard to operations it has from childhood been 
 daily accustomed to see performed in a certain manner so 
 entirely in such cases does the mode, become identified with the 
 result, that the power of independent reasoning on the subject 
 appears to be lost. It is a notorious fact, that most of the 
 greatest improvements in arts and manufactures, have been 
 achieved by individuals not educated to the calling ; the illus- 
 trious Watt, for example, was bred a mathematical instrument 
 maker, Arkwright a barber, and Stevenson with his iron steed, 
 emerged from the depths of a coal mine. Conversing on this 
 topic lately with an engineer of celebrity, he related in corrobo- 
 ration of the sentiments I expressed, that a highly intelligent 
 friend of his, who had been very successful in business as 
 a manufacturer, declared that when practicable, he always 
 made it a rule in his establishment to select for the super- , 
 intendants of the different processes, individuals of intelligence 
 who had not been brought up in that department, giving as a 
 reason, that if there was any improvement to be made, they 
 were ten times more likely to discover it, than a man who had 
 become a mere unreasoning creature of habit. 
 
 14. To produce rapid combustion and intense heat in a 
 furnace, it is necessary for the fuel to be rapidly supplied with 
 air. A current of air must in fact, be kept constantly rushing 
 through it, a desideratum which may be effected in two ways, 
 either by allowing the products of combustion to pass into the 
 chimney, at a sufficiently high temperature to produce by their 
 rarefaction a partial vacuum adequate to cause the requisite 
 current of air through the fuel by atmospheric pressure, or by 
 compressing the air by some mechanical appliance, and forcing * 
 it through. Thus sucking the air through the fuel in the first 
 instance, and blowing it through in the latter ; producing the 
 current in one case by a partial vacuum behind, in the other 
 by a compression before, the fuel. 
 
 15. Now however compatible with the objects sought to 
 be attained, and allowable as a question of economy, may be the 
 plan of keeping up the draft through a fire, solely by the instru- 
 mentality of a chimney, where slow combustion only is required, 
 
INTRODUCTION. \i 
 
 as in the case of the domestic grate, or the Cornish steam boiler ; 
 whenever on the contrary, rapid combustion and intense heat 
 are a desideratum, such a system can only be carried out, and 
 the air discharged by the chimney at a temperature sufficiently 
 high to produce the powerful draught required, by an enormous 
 sacrifice of fuel. It is true that an inordinately high chimney, 
 by lowering the temperature at which it is necessary to keep the 
 ascending column of air, may palliate the evil, but as a question 
 of economy the remedy is almost as bad as the disease, besides 
 being in very many cases, as in marine engines, and locomotives 
 for example, inadmissible from other causes. 
 
 16. I shall no doubt excite general surprise, and perhaps 
 some incredulity, when I state that from a calculation I entered 
 into on the subject (the result of which certainly surprised 
 myself), I find that 1 Ib. of coal expended through the mechanical 
 agency of a steam engine, will generate more force, and con- 
 sequently is capable of producing a stronger current of air, than 
 SOOlbs. of coal expended in heating a column of air to act by 
 its diminished specific gravity, through a chimney 35 feet high; 
 and that consequently, all the products of combustion which 
 are allowed to escape out of the furnace into the chimney, 
 before they have fallen below the temperature at which they 
 can be usefully employed, -for the sake of producing draughty 
 are most prodigally misapplied. 
 
 17. Strange to say however, this is the system at pre- 
 sent almost universally employed, apparently in utter uncon- 
 sciousness of its wastefulness, and notwithstanding the fact, that 
 numerous collateral advantages are attendant on the employment 
 of compressed air, not the least of which are the perfect control 
 it gives over the action of the furnace, and the extent to which it 
 enables us to utilise the escaping heat. All that can be said in 
 behalf of the present system, is, that it possesses a certain rude 
 simplicity and easiness of application, qualities which might 
 be equally urged in favour of a pair of bellows compared with 
 a blast cylinder, or of panniers and pack-saddles compared with 
 wheel carriages. 
 
 18. The result of the employment of this wasteful and 
 unscientific system, is seen in the fact, that in steam engines 
 where an intense draught is employed, the consumption of fuel is 
 25 per cent, more than that of those where the products of com- 
 bustion are reduced to a comparatively low temperature before 
 they enter the stack. In fact, unless working with compressed air 
 
Xll INTRODUCTION. 
 
 be resorted to, we cannot have midtnm in parvo in a steam engine 
 great power in little space, without great waste of heat. To burn 
 a large quantity of fuel in a small area, we must have a rapid rush 
 of air through the furnace, to produce a rapid rush of air through 
 the furnace, we must bave a powerful draught in the stack, to 
 attain a powerful draught in the stack, we must discharge the 
 products of combustion into the stack at a high temperature, 
 and to discharge the products of combustion into the stack at 
 a high temperature, necessarily entails an enormous waste of 
 fuel the actual, though very unsatisfactory result at present. 
 Enclosed in a vicious circle, each step in the process is necessary 
 and inevitable, as long as so erroneous a path is pursued, and 
 there is no avenue of escape, but by having recourse to a blowing 
 machine, and producing the required current of air, with --- 
 part the fuel at present wasted in the chimney, in effecting less 
 efficiently the same object. 
 
 19. In no case is the wasteful result of trusting solely to 
 draught in the slack, to create draught through the fuel, more 
 striking, than in furnaces for the manufacture of iron. Here, 
 from the iron lying at the bottom of the furnace out of the axis 
 of the line of draught, and the impossibility of causing the heat 
 to circulate round it as in a steam boiler, only a small fractional 
 part of the heat generated, enters the iron. In fact it is im- 
 possible to be otherwise, as the stack, acting the part of a suction 
 pump through an orifice 1\ foot in area, empties the furnace of 
 its gaseous contents twice in a second, keeping up at the same 
 time a state of exhaustion, which draws in cold atmospheric air 
 at every crack and cranny, and particularly in puddling furnaces 
 at the working hole; oxydising and wasting, or, as the workmen 
 say, cutting the iron. In the principal axis of the draught, the 
 products of combustion dart in a straight course from fire bridge 
 to flue bridge, at the rate of 30 feet per second, and can, as a 
 matter of course, leave but a small portion of their heat behind 
 them. If we contrast with such a state of things, that of a 
 furnace distended with heat impelled by pressure from behind, 
 and struggling to escape in all directions faster than a compara- 
 tively contracted neck will allow of, and suffering moreover no 
 cold air to enter, it will be easily seen with which system the 
 superiority lies. 
 
 20. Injudicious as the method of working furnaces on 
 which I have animadverted must appear to my readers, yet 
 they are I suspect, scarcely prepared to learn the actual results : 
 
INTRODUCTION. xiii 
 
 viz:, that in a melting furnace, the amount of fuel consumed, is 
 adequate to produce twelve times as much heat, as would if all 
 absorbed by the metal, raise its temperature from 60 to the 
 nelting point ; whilst in puddling furnaces the disproportion is 
 still greater, the heat generated being, if the fuel employed be 
 taken as an index, 16 fold more, than can be contained in tfye 
 metal during any period of the operation. 
 
 21. Now I am not so visionary as to suppose that a furnace 
 can be constructed so as to make all the heat generated enter 
 the iron. It is impossible to isolate the body of heat contained 
 in a furnace and prevent its loss by radiation, and where 
 processes requiring intense heat are carried on, from the neces- 
 sity that exists for keeping up a rapid supply of fresh heat to 
 replenish this loss, and enable the requisite temperature to be 
 maintained, discharging also at the same time from the other 
 end of the furnace, the slightly cooled ', though still intensely hot 
 gaseous products the consumption of fuel must ever be very 
 great, in proportion to the actual amount of heat taken up. In 
 short, we must never lose sight of the fact, that the quantity of 
 available heat generated for any process, has no relation to the 
 whole quantity generated, but is merely the amount of the excess 
 of the temperature produced, above the temperature required. 
 Fully weighing these considerations however, I am nevertheless 
 still sanguine enough to believe, that the results obtained in the 
 puddling, and heating furnaces, may be effected with a great 
 diminution in the quantity of fuel now consumed ; and notwith- 
 standing it ever must be necessary in order to keep up the 
 requisite heat in the body of iron furnaces, to discharge the 
 products of combustion whilst still at a very high temperature, 
 yet at the same time, there is nothing to prevent our economising 
 this heat, by applying it to various purposes for which its 
 temperature, though no longer equal to the manufacture of iron, 
 is amply sufficient. 
 
 22. This introduces us to the Subject of the difference 
 between quantity and quality or intensity of heat, through 
 losing sight of which, many errors have been committed, and 
 various chimerical attempts made to economize this agent. 
 For since we possess no means of condensing it, an unlimited 
 quantity becomes valueless for any purpose requiring a higher 
 temperature than it is capable of furnishing. Were not this the 
 case, our steam engines when once set in action, might be kept 
 
MV INTRODUCTION. 
 
 at work for ever, without any further expenditure of fuel than 
 would suffice to replace the trifling amount of heat lost by 
 radiation from the surface of the machinery, since we get back 
 in the condenser, the heat we bestow in the boiler. The heat we 
 impart to a cubic inch of water, to raise it into a cubic foot of 
 steam, being returned to us when the atmospheric temperature 
 is 50, in the shape of 24 cubic inches of water at 100, virtually 
 representing a power capable of raising 1 ton weight a foot high, 
 though practically we can make no use of it, unless we can 
 discover some employment for it, for which a temperature of 
 100 suffices. 
 
 23. The preceding observations must have made it apparent, 
 that processes of manufacture requiring intense heat, and where, 
 as a necessary corollary, the products of combustion must be 
 discharged at a high temperature, can never be economically con- 
 ducted, unless some- employment be found for the waste heat so 
 discharged. In an iron work, none can exist more advantageous 
 and convenient than the generation of steam for the machinery em- 
 ployed, for which object, strange to say, at the present moment, 
 separate furnaces and fires are extensively employed, in the midst 
 of dozens of puddling and heating furnaces, each briskly engaged 
 in dissipating into the atmosphere, heat sufficient to generate 
 steam for an engine of 20-horse power. 
 
 24. A vast field for economy is here open, by the intro- 
 duction of the system of working with compressed air ; for 
 without this invaluable assistant, our power to employ the waste 
 heat is limited to a comparatively narrow compass, inasmuch as 
 precisely in the ratio that our arrangements for this purpose 
 become more perfect, do we destroy the draught of the furnace. 
 By the employment of compressed air however to furnish a 
 current for the supply of our fires and by this means only 
 do we possess the power of using the waste heat at pleasure, 
 however high may be the temperature demanded, and, as a con- 
 sequence, keen the draught through the fuel required. 
 
 25. An opinion that much unnecessary waste of heat takes 
 place at present, and that there is scope for great saving, seems 
 to exist almost universally as a sort of obscure impression, 
 without sufficient knowledge of the subject being possessed, to 
 know where, and how, the saving is to be effected; and in groping 
 in the dark to achieve this object, great errors are often com- 
 mitted, of which we have recently had a notable example, in the 
 
INTRODUCTION. X^ 
 
 various attempts that have been made to puddle iron with the 
 gases that escape from the top of the blast furnace. 
 
 26. Now, it is not surprising that persons who understand 
 nothing of the principles of physics and chemistry involved in 
 the right management of a furnace, should be incapable of 
 appreciating a system, based on correct data, when presented 
 to them. Accordingly, in the few opportunities I have enjoyed 
 of conversing on furnace management with those whose interests 
 ought to have made them best acquainted with the subject, 
 1 have met with nothing but a strange confusion of ideas, 
 and a deplorable ignorance. When for instance, I have attempted 
 to discuss the question of working with compressed air, with a 
 view to elicit their opinions, I have discovered that the parties I 
 addressed, were deficient in that ground-work of knowledge, 
 necessary for the appreciation of scientific facts and arguments, 
 *md without which, appeals to the reasoning faculties are fruit- 
 less. 
 
 27. I confess, I did at the outset, delude myself so far as to 
 suppose, that the notorious fact that furnaces work better with 
 a breeze blowing into the ash-pit, and also when the barometer 
 is high, than when it is low would have secured a favorable 
 opinion on behalf of a proposal for merely further carrying out 
 these conditions, and making them constant by artificial means. 
 Even with those whose knowledge did not enable them to see 
 very deeply into the matter, the analogy was, I thought, too 
 obvious to be overlooked : observation has taught me however, 
 that where the mind possesses no fixed scientific principles for 
 its guidance, every process is surrounded with mystery, and 
 every proposal for change invested with doubt. Incapable of 
 separating the accidental from the necessary, no a priori con- 
 victions are possible. 
 
 28. Deeply impressed with the belief, that it would be 
 difficult to over-estimate the beneficial effects which would arise, 
 from the general diffusion amongst the practical men who carry 
 on our manufacturing processes, of a knowledge in outline of 
 the scientific principles involved in the various operations they 
 conduct, I have determined to contribute my mite towards 
 realizing such a result. 
 
 29. In carrying out this intention, it has been my especial 
 aim to condense the largest possible amount of information into 
 the smallest possible compass, and to express what I had to say, 
 
XVI INTRODUCTION. 
 
 in the clearest and most familiar language. Such a compendium 
 would at one period have been most thankfully welcomed by 
 myself : in fact, it was experiencing the want of such an one, that 
 caused me to make for my own satisfaction, those inquiries, the 
 result of which I here present for the benefit of others. The 
 absence of a compendium of the kind, has, I have reason to 
 know, long been felt and regretted in manufacturing districts ; 
 and I trust and believe, that the present imperfect attempt 
 partially to remedy the deficiency, will not prove entirely 
 useless. 
 
 ERRATUM. 
 
 Page 4. 7th line from bottom, for 967'26 Ibs. x 181'5, read 967*26 + 181'5 
 
ON 
 
 ECONOMY OF FUEL. 
 
 GENERAL CONSIDERATIONS. 
 
 1. THE subject of Economy of Fuel appears at first sight to 
 resolve itself into, firstly, the attainment of perfect combustion; 
 and secondly, the application of the heat thus obtained, so as to 
 make the largest portion available for the object to which it is 
 devoted. 
 
 2. A closer scrutiny however, shews that practically speaking, 
 it comprises two other departments, which by no means yield to 
 the former in commercial importance, viz. : contrivances for the 
 employment of inferior kinds of fuel, and methods for turning 
 to account the refuse heat, which, having fallen below the tem- 
 perature required for the particular process carried on, is yet 
 available for other processes for which a lower heat suffices. 
 
 3. In getting the better kinds of coal a large quantity of 
 an inferior description is at the same time obtained (technically 
 denominated slack), in some cases its inferiority having reference 
 solely to the mechanical attribute of size, in others comprising 
 also a slight difference in structure and chemical composition, 
 with perhaps the admixture of a certain portion of earthy matter. 
 When it is considered that at present this article has so little 
 commercial value, as in the majority of cases, to be totally wasted 
 and not deemed worth removal, it becomes evident that any 
 method by which it can be made to do the duty of ordinary coal 
 
 B 
 
OF FUEL. 
 
 is valuable, even should the quantity consumed be greatly in 
 excess of that demanded of the latter ; and though a method 
 for ensuring more perfect combustion, and thus effecting a saving 
 of perhaps 20 per cent, in weight of fuel, is of priceless value 
 where steam navigation is concerned, and the fuel constitutes- 
 ex necessitate a portion of the freight, and such an achievement 
 would be doubtless fraught with much greater interest to the 
 man of science than a scheme for burning slack, it is nevertheless 
 unquestionable that a rough and ready method of accomplishing 
 this latter object, even with a large expenditure of the material,, 
 presents, in many cases, greater attractions in a commercial point 
 of view. 
 
 4. To appreciate the value to be expected from the use of 
 judicious means for applying waste heat, it should be known, 
 that so high is the temperature required in various stages of the 
 manufacture of iron, that a stream of ignited gases is required 
 to be kept constantly rushing through the body of the furnaces, 
 the whole atmospheres of which are renewed in many cases twice 
 in a second. The current of heated gases however issuing from 
 such furnaces is still of an intensely high temperature, from 2,500 
 to 2,800, and although not sufficient for the manufacture of 
 iron, which demands a temperature of 3,000 and upwards, is- 
 fully equivalent for working tin, lead, or zinc, the melting points 
 of which are respectively 442, 612, and 773, whilst that of 
 cast iron is 2,786. Even after having done serviceable duty in 
 fusing these metals, it would still retain a temperature adequate 
 for raising steam, soap -boiling, and various other industrial 
 operations ; and there really exists no reason whatever why as- 
 much duty as possible should not be extracted from it before 
 its final dismissal into the atmosphere. In short, this department 
 of Economy of Fuel is a very fertile one, though hitherto so all 
 but entirely neglected, that it might be supposed that fuel, like 
 air, was an article inexhaustible in supply, and costing nothing 
 to procure, instead of demanding for its attainment the wear 
 and tear of human sinews, and the risk of human life. 
 
ECONOMY OF FUEL, 3 
 
 SECTION I. 
 
 ON THE BEST MEANS OF RENDERING COMBUSTION PERFECT. 
 
 5. COMBUSTION is, strictly speaking, the development of 
 heat by chemical combination, but though this may take place 
 from the union of a variety of bodies, the omnipresent agent 
 oxygen plays so vastly more important a role than all others in 
 the disengagement of light and heat, that the act of its com- 
 bination with other bodies is preeminently entitled combustion,. 
 and except in the mouths of chemists, has quite monopolised the 
 appellation. Since combustion, in the ordinary acceptation of 
 the word, is the only means had recourse to in the arts for the 
 development of artificial heat, perfect combustion may, for our 
 purpose, be denned to be the combination of a combustible 
 body with the largest measure of oxygen with which it is capable 
 of uniting. In fact, for all practical purposes, the fuel or com- 
 bustible body employed may be regarded as composed exclusively 
 of carbon and hydrogen, so that our enquiry becomes narrowed 
 to the combinations of oxygen with these two elementary sub- 
 stances. 
 
 6. Most of my readers are doubtless aware that chemical 
 combinations take place only in certain definite proportions which 
 are multiples of each other. One atom of A, for instance, com- 
 bines with one, two, three or more atoms of B ; or two of A, with 
 three, five, or more of B ; from which fact it follows, as a necessary 
 consequence, that the chemical equivalents (or combining weights) 
 of all bodies may be considered as expressing the relative weight 
 of their atoms. Bodies may be mingled together in any propor- 
 tions, but it is only in certain definite ones that they unite and 
 form one homogeneous whole. Thus six parts (by weight) of 
 carbon combine with eight (by weight) of oxygen to form car- 
 bonic oxide, and with twice this quantity, or sixteen parts, to form 
 carbonic acid ; and there exists no intermediate combination of 
 
 B 2 
 
4 ECONOMY OF FUEL. 
 
 these two bodies in which six of carbon is united with more 
 than eight, and less than sixteen of oxygen. Carbonic oxide and 
 carbonic acid gases may, it is true, be mingled in any proportion, 
 and thus a gas obtained in which six parts of carbon are present 
 with more than eight, and less than sixteen parts of oxygen, but 
 this is a mixture and not a chemical unity, as may be shewn by 
 the addition of potash, which will separate the carbonic acid and 
 leave the carbonic oxide behind. 
 
 7. Different coals vary much in their component parts, and 
 in the proportion of these to each other ; carbon and hydrogen 
 however, are the essential ingredients of all, as far as their heating 
 capabilities are concerned, and throughout this essay, I shall 
 -assume as a convenient standard, that 100 parts of coal consist 
 'of 80 parts of carbon, and 5 of hydrogen, leaving out of view 
 
 the other elementary substances which enter into their composi- 
 tion, (consisting of oxygen, nitrogen, sulphur, and incombustible 
 -ashes in various proportions,) as only likely to complicate the 
 details, without being essential to the argument. 
 
 8. Assuming lOOlbs. of coal to consist of 801bs. of carbon 
 -and 51bs. of hydrogen, then, since the oxygen is to the carbon, in 
 ^carbonic acid, as 16 to 6, to effect perfect combustion, SOlbs. of 
 carbon will require 313Jlbs.=2,527 cubic feet of oxygen, to 
 furnish which, 967'261bs. =12,635 cubic feet of atmospheric air 
 will be required, air consisting of 1 volume of oxygen to 4 of 
 nitrogen, or 8 parts by weight of the former, to 28 parts of the 
 latter; and since oxygen is to hydrogen, in water, as 8 to 1, 51bs. 
 of hydrogen will require 401bs. = 473 cubic feet of oxygen, or 
 181*5lbs = 2,365 cubic feet of atmospheric air. 
 
 967-261bs. x 181-5 = 1148-761bs. = 15,000 cubic feet of 
 atmospheric air, required for the perfect combustion of lOOlbs. 
 of coal. 
 
 And the product resulting will be : 2,527 cubic feet of 
 carbonic acid, 946 cubic feet of steam, and 12,000 cubic feet of 
 un combined nitrogen. 
 
 9. We thus perceive that each lib. of coal requires 150 cubic 
 
ECONOMY OF FUEL. 5 
 
 feet of air for its perfect combustion, or, in other words, for 
 the conversion of all its carbon into carbonic acid, and all its 
 hydrogen into water ; and it must be remembered, that just in 
 proportion as this proper quantity is deficient, is combustion 
 imperfect and fuel wasted, whilst the supply of a surplus quan- 
 tity is but a change of evils, and equally injurious in an economic 
 point of view, since all the air which passes through a furnace 
 without giving up its oxygen to the fuel, serves only to abstract 
 heat, without yielding any in return. However difficult may be 
 the regulation of the admission of just the proper quantity of 
 air to the fuel, it is not the less certain, that exactly in proportion 
 as we deviate from the correct standard, will be the loss we incur,, 
 for the laws of chemical affinity are unerring and inexorable. 
 
 10. It is commonly but erroneously supposed, that when 
 no smoke appears at the chimney top, combustion is perfect. 
 Smoke, however, may be absent, and yet the carbon may only 
 have united with 1 atom of oxygen, forming carbonic oxide, (a 
 colourless gas), instead of with 2 atoms, forming carbonic acid, 
 and consequently have only performed half* the duty, as a fuel, 
 
 * I have said half from a desire rather to understate than overstate the 
 argument, but tivo-jifths is probably a near approximation to the truth. 
 There is no doubt, but that the combination of the secoud atom of oxygen 
 with carbon, sets free more caloric than that of tli3 first, since, in the first 
 combination, a considerable portion of heat must necessarily be swallowed up 
 arid become latent, to produce the gasification of the carbon, and experiment 
 confirms what might a priori have been expected. 
 
 The figures in the following columns show how many parts of water are 
 heated 1 by the combustion of 1 part of carbon, according to the three 
 observers, D along, Andrews, and Grassi. 
 
 D. A. G. 
 
 1 part of carbon in becoming CO 2 . . . 
 1 part of carbon as C in becoming CO 2 
 1 part of carbon in becoming C O 
 
 13267-8 
 
 10569-6 
 
 2698'2 
 
 14220 
 10209-6 
 4010-4 
 
 13885-2 
 
 7786-8 
 6098-4 
 
 It thus appears that if the whole heat generated by the combination of 
 1 atom of carbon with 2 atoms of oxygen forming CO 2 , be regarded as a 
 unit, the proportional quantity developed by the combination of the carbon 
 with the first atom of oxygen, will be, according to Duloug, only 20 per 
 cent., according to Andrews, 28 per cent., and according to Grassi, 43 per cent. 
 
 [Dulong's 
 
6 ECONOMY OF FUEL. 
 
 of which it was capable, whilst the loss of duty on the coal taken 
 as a whole (supposing all its hydrogen to have become oxydised) 
 will be upwards of 40 per cent. 
 
 11. Hydrogen, having a stronger affinity than carbon in the 
 gaseous state, for oxygen, when the supply is short, still seizes 
 on its equivalent, and leaves the carbon minus. Thus, when 
 coal gas (carburetted hydrogen) is inflamed with an insufficient 
 supply of air to effect the perfect combustion of both its consti- 
 tuents, the hydrogen is still converted into water, whilst the 
 carbon, in different proportions according to the oxygen present, 
 becomes deposited in the form of soot converted into carbonic 
 oxide, or partly into carbonic oxide and partly into carbonic 
 acid. 
 
 12. This great cardinal point in economy of furnace manage- 
 ment, viz. the exact apportionment of the supply of air to the 
 wants of the fuel, so as to convert all its carbon into carbonic 
 acid, and all its hydrogen into water, could be achieved with 
 comparative ease were the same conditions always present in the 
 interior of the furnace, so as to cause the quantity of air required 
 by the fuel to be uniform. In this case, the average rarefaction 
 in the stack being once attained, a steady supply would enter 
 the furnace according to the area of the grate bar openings, the 
 size of which once adjusted, the equable and economic working 
 of the furnace would be secured. Unfortunately however the 
 reverse is the case, and the great practical difficulty to be over- 
 come in apportioning the supply of air to the demands of the fuel, 
 arises from the fact, that in furnaces of the ordinary construction, 
 
 Dulong's figures are manifestly erroneous. That four times (!) as much 
 lieat should he developed by the comhination of carbon with the second atom 
 of oxygen, as hy its comhination with the first., is so discordant with every- 
 thing we know of the principles of chemistry, as to he quite incredihle. 
 Dulong however, has unfortunately been the authority followed by Professor 
 Bunsen and Dr. Lyon Playfair, in their report on Blast Furnaces (see Report 
 of the British Association for 1845), and there is no doubt but that great 
 deductions require to be made from their statements in consequence. 
 
ECONOMY OF FUEL. 7 
 
 this demand is not only variable, but fluctuates within very wide 
 limits. 
 
 13. Where a fresh supply of coal is put on a briskly-burning' 
 fire, the first thing which takes place is, that the coal softens and 
 swells, attended with the evolution of a large quantity of 
 carburetted hydrogen gas, requiring for its combustion a corres- 
 pondingly large supply * of atmospheric air the coal undergoing, 
 in fact, in the first stage of combustion, just the same process as 
 it does in the retort in the manufacture of gas, but with this 
 difference in the result : that the gas, which in the latter case is 
 preserved and found so valuable a commodity, here escapes 
 unconsumed up the chimney, not only furnishing no heat itself, 
 but abstracting from the heat arising from the combustion of 
 the carbonaceous portion of the fuel, the heat for its own gasi- 
 faction, a circumstance which readily explains the fact, that 
 more heat is practically obtained in many kinds of furnaces from 
 coke (or in other words, coal deprived of J part by weight of 
 that portion of its combustible matter which is richest in fur- 
 nishing material for heat,) than from coal in its pure state, with, 
 all its hydrogenous portion intact. From the same cause also 
 (viz. the imperfection of our furnaces), the commercial value of 
 coal is often in the inverse ratio to the quantity of its bituminous 
 constituents and its real heat-giving powers, had we the capacity 
 to render them practically available. It could not in fact be 
 otherwise. A furnace immediately after a fresh supply of fuel, 
 requires more than double the quantity of air it did the instant 
 before, whilst we have no contrivance for furnishing such a supply, 
 although without it, throughout the space of time during which 
 rapid gasifaction of the hydrogenous portion* is going on, more 
 than half the fuel consumed is wasted, and passes off unburnt, 
 becoming thereby not only totally unproductive in itself, but 
 absolutely an agent of evil, by robbing the furnace of the heat 
 absorbed in its own volatilization. 
 
 * 1 measure of carburetted hydrogen or coal gas, requires for its perfect 
 combustion 10 measures of air. 
 
8 ECONOMY OF FUEL. 
 
 14. Whether it be from an inadequate appreciation of the 
 magnitude of the evil, or from the difficulties attendant upon 
 overcoming it, I will not determine ; but certain it is, that 
 99 furnaces out of 100, are worked without any attempt being 
 made at a remedy. Large quantities of coals are thrown over 
 brightly-glowing cinders, the heat from which they absorb; a 
 rapid evolution of gas takes place, which, passing oft* unburnt 
 at a comparatively low temperature, most injuriously cools down 
 the heat of the furnace and flues, and by lessening the amount 
 of rarefaction in the stack, enfeebles the draught, and thus still 
 further diminishes the already insufficient supply of air, and re- 
 produces the original evil in an aggravated form. In furnaces 
 so managed, for the first two or three minutes after coaling, the 
 useful effect of the furnace is comparatively paralyzed, and the 
 process in which it is employed partially suspended ; and it is 
 only gradually that it regains its full vigour of action. 
 
 15. Only two methods present themselves by which the 
 supply of air and the wants of the furnace can be made to cor- 
 respond, either loth must be made constant and regular, or the 
 
 fluctuations of one, must be made to coincide with those of the 
 other. 
 
 16. If a continuous and equable supply of air is to be fur- 
 nished to a furnace, then, in order that this supply of air may 
 exactly correspond with its requirements, the supply of fuel must 
 be made continuous and equable also ; so that at all times there 
 shall be just the same quantity of fuel in the same state, that is 
 to say, at the same stage of combustion. This appears to be 
 the most perfect method of working a furnace, and the most 
 obvious mode of overcoming the difficulty, and it is accordingly 
 to accomplish this object, that most of the attempts to prevent 
 smoke and attain perfect combustion have been hitherto directed. 
 Brunton's revolving grate, Juckes' endless chain of fire bars, 
 and more than one kind of rotating feeder, all fulfil with tolerable 
 efficiency the purposes for which they were designed ; but the 
 great drawback is, that unfortunately all require machinery and 
 
ECONOMY OP FUEL. 9 
 
 motive power constantly at work to keep them in action, whilst 
 some are in addition unhandy, and others expensive, both to 
 construct arid keep in repair. 
 
 17. The result of none being free from these objectionable 
 qualities is, that none have been able to force their way into use 
 to any extent, 99 furnaces out of every 100 at the present 
 moment, being fired by the rough and ready method of throwing 
 the coals on by hand, without any contrivance being resorted to, 
 to mitigate the evils resulting from the inadequacy of the supply 
 of air, to the wants of the fire at the periods of coaling. 
 
 18. Fully recognizing the force of those objections to the 
 present contrivances which have prevented their coming into use, 
 and impressed with the belief that no plan of the sort will ever 
 force its way, that does not come recommended by much greater 
 simplicity ; in seeking a remedy for existing evils, it has been 
 my aim to adapt myself to present usages, and devise some 
 method by which the supply of air and the wants of the fuel 
 may be mutually adjusted, without either serious innovation on 
 established arrangements, demand for motive power, or costly 
 apparatus. 
 
 19. The contrivance by which, without infringing either of 
 these conditions, I propose to achieve the great desideratum 
 sought, effects its object by admitting an increased supply of air 
 at the periods of coaling, thus acting on the principle of causing 
 t\& fluctuation* between the supply and demand to coincide, with- 
 out undertaking the more formidable, and I think superfluous 
 task, of adjusting the one to the other, by making both uniform 
 and unvarying a feat hitherto only accomplished at the sacrifice 
 of simplicity. 
 
 20. Whatever opinions may be entertained as to the general 
 merits of my contrivance, it is I think impossible to deny that 
 it has the recommendation of great simplicity, and presents in 
 this particular a striking contrast to those at present before the 
 public. All the existing arrangements for coaling remain unin- 
 terfcred with. The stoker, when he closes the furnace door after 
 
 B 3 
 
10 ECONOMY OF FuEL. 
 
 firing, will raise the arm of a lever appended to it ; this move- 
 ment throws wide open a sliding valve in the face of the door, 
 which immediately commences closing slowly and automatically, 
 by the gravity of the lever, regulated and restrained by the 
 motion of a balance wheel connected with it by appropriate 
 gearing, and affords, during the progress of its descent, a gra- 
 dually diminishing supply of air to the fire, in harmony with the 
 gradually diminishing requirements of the fuel. The area of the 
 valve, and the period of time throughout which the act of closing- 
 is to be prolonged, are of course questions of detail to be deter- 
 mined by circumstances, and should be so adjusted according to 
 the nature of the coal, and the average quantity supplied at one 
 time, as entirely to prevent the appearance of smoke. The 
 -door of the furnace should be double, and the air should pass 
 into the furnace through a series of perforations in the inner 
 plate. By this arrangement three important points are secured: 
 Istly, the heating of the air; 2ndly, its subdivisison into minute 
 jets ; and 3rdly, the keeping of the outer surface of the furnace 
 door comparatively cool, and thereby both economising heat, 
 and preventing its radiation outwardly to the annoyance of the 
 attendants. 
 
 21. An attempt is often made by careful stokers to mitigate 
 the smoke and imperfect combustion, arising from the inadequacy 
 of the supply of air to the wants of the fuel at the periods of 
 coaling, by leaving the furnace door ajar for a certain period 
 after the addition of fresh fuel. The great superiority of a valve 
 self closing, and with a gradually diminishing aperture, over such 
 .an imperfect expedient, is too obvious to be contested. Not 
 only does the air. in the former plan, enter en masse and cold, 
 instead of in small jets and hot, but the means of gradually and 
 regularly lessening the supply, according as the gasifaction cf 
 the bituminous portion of the fuel becomes completed, is totally 
 wanting ; whilst, should the closing of the door be forgotten, 
 and thus delayed till after the completion of gasifaction, more 
 harm will probably be done by the air entering during the latter 
 
ECONOMY OF FUEL. 11 
 
 portion of the time, than the amount of good achieved by the 
 portion which entered previously. In short, one method requires 
 superintendence to effect imperfectly, what the other accom- 
 plishes much better without any, and both superiority of effect, 
 and easiness of application, are found united in favour of the 
 method of adjusting the supply of air by means of an automati- 
 cally-closing valve. 
 
 22. In ordinary furnaces, the air becomes heated in passing 
 through the grate bars and burning fuel. Where air is suffered 
 to enter the furnace above the fuel, too much stress cannot be 
 laid upon the necessity for either supplying it hot, or making a 
 provision for subjecting it, together with the volatile products of 
 the fuel, to an adequate amount of heat before they are allowed 
 to escape by the flues : otherwise a mass of cold air, mingling 
 with the gases arising from the fuel, may reduce the temperature 
 of the mixture below the point at which its inflammation is insured, 
 and the gases consequently pass off unburnt, though provided with 
 the requisite supply of air. This is peculiarly the case in steam 
 boiler furnaces, where the gases issuing from the fuel are liable 
 to be chilled by coming in contact with the boiler plate, which, 
 having water on the other side, is consequently preserved at a low 
 temperature, whilst being metallic, and consequently a good con- 
 ductor of heat, its refrigerating action is rapid and powerful. 
 In this circumstance will be found an explanation of the fact, 
 that little practical benefit is to be derived from leaving the door 
 of steam boiler furnaces ajar for a certain period after coaling. 
 The fuel unquestionably demands a larger supply of air at this 
 period, but this air being admitted en masse, and cold, and the 
 heat of the furnace having been just previously lowered by the 
 refrigerating effect of the fresh supply of coals and sudden de- 
 velopment of gas, at the expense of the stock of heat previously 
 existing, the result is, that the temperature produced by the 
 union of the cold air with the gases from the fuel, is below the 
 point required for inflammation. 
 
 23. In reverberatory furnaces for the manufacture of iron, on 
 
12 ECONOMY OF FUEL. 
 
 the contrary, the gases arising from the fuel in the grate, have to 
 pass through the intensely heated body, or working chamber of the 
 furnace in their way to the stack ; and this cavity, which may 
 be said to be an oven with the sides and roof at a white heat, 
 although having another office, becomes in reality a provision for 
 subjecting the gases and the air with which they are mingled 
 to an adequate amount of heat, to insure their inflammation; and 
 the result is, that if an adequate quantity of air be admitted, 
 whether cold or hot, all the combustible matter is consumed, 
 and smoke entirely prevented. 
 
 24. Many times have I stood before such a furnace just after 
 a fresh supply of coals has been added, with my hand on the 
 open door, and found that by regulating the width at which I 
 kept it open, I could exercise a perfect control over the action 
 of the furnace. If closely shut, a dense black smoke would issue 
 from the chimney ; if opened a very little, the smoke would be 
 slightly but perceptibly diminished ; if opened a little more, 
 the change would be denoted by a still further diminution of 
 smoke ; whilst an opening of a certain extent would cause the 
 smoke to cease altogether. As the process of gasifaction pro- 
 gressed, and the demands of the fuel for air became less, the 
 same effect would follow from a smaller and smaller orifice, 
 till at length the door might be closed altogether without smoke 
 resulting, the ordinary supply of air through the grate bar open- 
 ings being adequate to the current demands of the fire. 
 
 25. In furnaces of this description, beyond all doubt a self- 
 closing valve, which should perform automatically, what I effected 
 by watching and close supervision, would be a valuable acquisi- 
 tion and tend greatly to economy, whilst nothing can be more 
 easy and simple than its application. 
 
 26. A consideration of the phenomena exhibited by rever- 
 beratory furnaces has led me to the conviction, that a very great 
 improvement might be effected in the action of steam boiler fur- 
 naces, particularly those of marine boilers, by coating the under 
 side of the boiler plate, where it forms the roof of the furnace, 
 
ECONOMY OF FUEL. 13 
 
 with a thin layer of fire-brick material, which, instead of cooling 
 the mingled stream of coal gas and atmospheric air below the 
 point of inflammation, as is now done by the iron surface of the 
 toiler, would contribute heat, if necessary, to assist in kindling 
 them. The sheathing of fire-brick should extend from the sur- 
 face of the fuel on one side, over the roof of the furnace, to the 
 surface of the fuel on the other side, and closely in apposition 
 with the boiler plate, by which means its melting or rapid burn- 
 ing away will be prevented. 
 
 27. Such an arrangement would not only be productive of 
 great economy of fuel by the more perfect combustion which 
 would be attained, but would likewise tend very materially to 
 preserve the supply of steam constant and regular a point of 
 great value ; whilst at the same time the durability of the boiler 
 would be much increased by its being withdrawn from those 
 sudden alternations of temperature to which it is now exposed, 
 and which practice has shown to be so injurious to its stability. 
 
 28. Considering the powerful refrigerative effect exercised 
 on the furnace by the addition of a fresh charge of coal, where, 
 as is now the case, a large quantity of the gases generated by 
 the rapid absorption of the previous heat of the furnace are al- 
 lowed to pass off unburnt, (thus robbing the furnace of the heat 
 required for their volatilization, and yielding none in return,) and 
 therefore how greatly the heat to which the boiler is subjected, is 
 diminished on such occasions, I am of opinion that the whole 
 amount of heat imparted to the boiler surface in contact with 
 the fire-brick, would equal that which it obtains from the direct 
 action of the fire under the present system ; and if so, since the 
 heat imparted to the flues behind it would be unquestionably 
 greater, the capacity of the boiler for generating steam would be 
 increased. To turn however the access of heat obtained by the 
 more perfect combustion to the best account, an increase should 
 be made in the heating surface of the boiler, the simplest and 
 best way of doing which, is by inserting a few water-tubes in the 
 main flue behind the fire-bridge : so placed, they act as stays to 
 
14 ECONOMY OF FUEL. 
 
 the boiler, and are at the same time most advantageously situated 
 for the generation of steam. 
 
 29. There is nothing mysterious, unintelligible, or recondite 
 in the views here developed on the subject of furnaces ; on the 
 contrary, their general accuracy will be universally admitted, 
 whilst the simplicity of the remedies proposed, constitutes in the 
 opinion of the writer, their chief claim to attention. Tor rever- 
 beratory furnaces, the automatically- closing valve is complete in 
 itself; but for steam boilers, though the valve is useful alone, 
 to reap the full measure of the benefit it is capable of conferring, 
 it should be conjoined with the fire-brick sheathing, and some 
 increase of heating surface, as before recommended. With 
 these adjuncts to its utility, I feel assured that the economy 
 resulting from its use would be great and decided, particularly 
 with regard to the furnaces of marine engines, which, as at present 
 constructed, present great scope for improvement. 
 
 30. Some method for economising fuel for the purposes 
 of ocean steam navigation may be said to be the great 
 want of the day, for this vast and rapidly increasing means of 
 transit, is at present fettered in its development, and shorn of 
 half its utility and advantages, by the necessity which exists for 
 loading the vessels with coal, to an extent which leaves but 
 little room for profitable cargo. A writer in one of our periodi- 
 cals lately declared, that " the man who should achieve a great 
 reduction in the consumption of fuel in marine engines, would 
 deserve, not only the largest fortune and general thanks of man- 
 kind, but the gratitude of the latest posterity ;" nor will this 
 view of the importance of the subject appear exaggerated, when 
 it is considered, that for every ton of coals dispensed with, a ton 
 of freight may be substituted the cost of the former saved, and 
 the price of the latter gained ; that several Ocean Steam Navi- 
 gation Companies are in existence, to whom a saving in the 
 consumption of fuel, to the extent of only ten per cent., would 
 be equivalent to an annual saving of 50,000 ; and that, concomi- 
 tantly with the attainment of increased economy in the cost of 
 
ECONOMY OF FUEL. 15 
 
 conducting these great undertakings, the existing obstacle to a 
 reduction in the fare for the conveyance of passengers would be 
 removed, and an impetus given to our intercourse with the most 
 remote corners of the globe, the bearing of which on the future 
 destinies of the human race it would be difficult to estimate. 
 
 SECTION II. 
 
 ON CONTRIVANCES FOR THE EMPLOYMENT OF INFERIOR 
 KINDS OF FUEL. 
 
 31. IN getting the better kinds of coal, as has been already 
 observed, a large quantity of an inferior description is at the 
 same time obtained (technically denominated slack), in some 
 cases its inferiority having reference solely to the mechanical 
 attribute of size, in others comprising also a slight difference 
 in structure and chemical composition, with perhaps the ad- 
 mixture of an extra portion of earthy matter. 
 
 32. In entering upon the question of the employment of 
 inferior kinds of fuel, it is advantageous clearly to discriminate 
 between what is possible, and what is impossible, between what 
 can, and what can not, be effected. By so doing, will abortive 
 schemes, with the disappointment attending them, be best pre- 
 vented. It is not then possible, even by the most ingenious 
 contrivances, to generate heat from the alumina and silex pre- 
 sent in considerable quantities, in the more inferior descriptions 
 of slack. Neither can such earthy matter be dissipated and con- 
 sumed, nor prevented from remaining as a vitreous residuum on 
 the grate bars, and choking up the furnace unless removed. It 
 is however possible to make slack perform all the duty of good 
 coal, where its inferiority has reference solely to its deficiency of 
 
16 ECONOMY OF FUEL. 
 
 size, and this is accomplishing a great deal ; since, for want of 
 knowing how to effect this object, thousands of tons of it are 
 now annually abandoned as valueless. Something more how- 
 ever than this may be effected ; for, if its proportion of earthy 
 matter be not too excessive, good service may be got out of it 
 by means of the appliances which I shall describe, even for pro- 
 cesses where, without their assistance, small coal of the best 
 quality would be found insufficient. 
 
 33. We should however always carefully distinguish between 
 inferiority resulting from mere smallncss of size, and that de- 
 pending upon the presence of an undue portion of earthy matter, 
 since, without keeping this distinction in view, no clear ideas can 
 be entertained on the subject of slack burning. If, by superior 
 furnace arrangements, we enable slack, even when alloyed with 
 25 per cent, of earthy matter above the average of good coal, 
 to do the ordinary duty of the latter, it will nevertheless be found 
 that f of the weight of pure coal in the same improved description 
 of furnace, would do the same work with still greater facility. 
 In fact, it is evident that the utmost point to which human in- 
 genuity can arrive, is to burn all the combustible matter any 
 sample of coal may contain, and the less percentage of this 
 present, the greater weight of coal required for a given amount 
 of work. Notwithstanding the visionary expectations which 
 have been indulged in on the subject, to expect more, is an hal- 
 lucination that could not enter into the mind of any one grounded 
 in even the first principles of chemistry. 
 
 34. The principal use to which the better descriptions of 
 slack are now applied, is the generation of steam in the steam 
 boilers, used in the manufacturing processes carried on in the 
 locality where it is raised. This channel is, however, quite in- 
 adequate for the consumption of the quantity found in getting the 
 immense supply of good coal demanded for our great iron works. 
 
 35. Many attempts have been made to substitute slack, or 
 even a mixture of slack and coal, for best coal in the manu- 
 facture of iron ; but in the ordinary reverberatory furnace this 
 
ECONOMY ON FUEL. 17 
 
 cannot be done, without a diminution in the activity of the 
 combustion and the intensity of the heat generated, entailing a 
 delay in the process, prejudicial to the yield of iron. And when 
 it is considered that 1 cwt. of iron is of about the same value as 
 1 ton of coals, it will readily be perceived that no profit is to be 
 derived by economising the latter at the expense of the former. 
 
 36. The desideratum required is evidently a furnace fur- 
 nished with some contrivance, by means of which the com- 
 bustion of slack can be so stimulated and quickened, as to vie in 
 vigour and intensity with the combustion of best coal in the 
 ordinary furnace. 
 
 37. The great difficulty in the way of attaining rapid com- 
 bustion and intense heat from slack, even of the best quality, 
 arises from the fact that its small size makes it lie so close 
 together, as to form a mass almost impervious to air, and over- 
 lying and closing the grate bar openings, the passage of air into 
 the furnace is" in great measure cut off. 
 
 38. The remedies for this difficulty are, either the admission 
 of air through orifices in the sides of Che furnace, to compensate 
 for the diminished quantity which enters through the grate bars, 
 or the attainment of the same object by the use of compressed 
 air in a closed ash-pit. 
 
 39. Many circumstances induce me to give the preference to 
 the latter plan, independently of any partiality I may be sup- 
 posed to entertain towards it as its originator. To the former 
 however must be conceded the advantage of requiring no colla- 
 teral assistance in the shape of a machine for compressing air, &c. ; 
 and where the slack is of good quality, that is to say, not too 
 small, and containing but a moderate proportion of earthy matter, 
 this furnace will do its work very efficiently, provided the flues for 
 heating the air entering at the sides be judiciously constructed, 
 and proper means be employed to keep the orifices from becom- 
 ing stopped up by the melted scoria or slag, which forms from 
 the vitrifaction of the sand and clay contained in the fuel, and 
 adheres to the sides of the furnace. 
 
18 ECONOMY OF FUEL, 
 
 40. The first furnaces of the kind that were constructed, 
 failed from this cause. The ingress of the air at the sides being 
 arrested through the blocking up of the perforations by melted 
 slag, and no efficient contrivance for keeping them clear sug- 
 gesting itself to the mind of the experimenter, strange to say, 
 the plan was abandoned without any effort being made to over- 
 come the difficulty. 
 
 41. It being represented to me that the failure arose solely 
 from an inferior fire-brick having been used for building the 
 sides of the furnace, the melting and running of which had 
 sealed up the orifices, and that all that was necessary to the 
 success of the scheme was the employment of fire-brick of a 
 better quality, I was induced to try the experiment. The plan 
 adopted, originated with a Mr. Coad, and its principle was the 
 supplying the furnace with air (previously heated in a flue or 
 chamber) through small orifices in the sides of the grate. The 
 only deviation I made from the original design, consisted in 
 changing the source from which the supply of air for the a.ir 
 chamber was drawn, by which a great obstacle to the successful 
 working of the furnace was removed, and a higher temperature 
 at the same time secured to the air entering the sides. 
 
 42. The first time I entered an iron work, I was struck with 
 the enormous quantity of heat escaping to waste in all directions, 
 to the annoyance of the workmen. Upon closer inspection, I 
 found there were various draft holes leading to the space beneath 
 the iron bottom of puddling furnaces, for the express purpose of 
 allowing the air to circulate freely, and carry off the heat from 
 the iron bottom plates with sufficient rapidity to prevent their 
 melting ; whilst conjointly with this arrangement I saw that the 
 fire grates of these same furnaces were fed with a supply of cold 
 air from the atmosphere. My first attempt to partially remedy 
 this waste was by constructing flues beneath the bottom plates, 
 so arranged as to convey the air, heated by passing over the 
 surface of these plates and through the bridges, into the side 
 flues for the supply of the air .chamber of the improved furnace, 
 
ECONOMY OF FUEL. 19 
 
 instead* of allowing these flues to draw their supply direct from 
 the atmosphere, as had previously been done. 
 
 43. The result achieved by this furnace worked with ordi- 
 nary coal was a saving of 17i per cent, in weight of fuel, not as 
 compared with the average consumption, but when matched 
 against the best furnace in a work containing about forty. These 
 furnaces are constantly at work night and day, from Monday 
 morning to Saturday night, so that it is only once a week that 
 an opportunity for inspecting the interior occurs. On getting 
 inside the grate of the furnace after its first week's work, I 
 found that the small orifices round the sides communicating 
 with the air chamber were either partially or entirely sealed up, 
 by the melting and running of the face of the bricks, and also 
 by the adhesion of the clinkers or slag. This had occurred, not- 
 withstanding the best Stourbridge bricks had been employed, 
 and I saw at once I had been led into an error, in being taught 
 to believe that all the furnace required to complete its efficiency 
 was a good quality of fire-brick ; for it was clear, that even sup- 
 posing a perfectly infusible brick could be obtained, the melted 
 scoria from the fuel alone, would suffice to choke up the perfora- 
 tions, and consequently, that unless some method could be adopted 
 for cleaning them from time to time, the plan was a failure. 
 
 44. As it was evident that a large proportion of these holes 
 had been more or less completely stopped up during the latter 
 part of the week, I came to the conclusion that a portion of the 
 saving should be attributed to the less amount of heat lost by 
 radiation into the atmosphere from the sides of the furnace s 
 owing to the circumstance of its being surrounded by a bad 
 conductor of heat in the air chamber. Could I* then unite this 
 saving in fuel, from the smaller amount of radiation, with the 
 still further increase that might be expected from more perfect 
 combustion if I succeeded in keeping the holes from the air 
 chamber into the grate permanently open, there was room to 
 hope that a great addition might be made to the economy 
 already effected. 
 
20 ECONOMY OF FUEL. 
 
 45. Whilst inspecting the interior of the furnace, it occurred 
 to me that this object might be attained, by having suitable 
 openings in the external wall of the furnace, leading into the air 
 chamber, by means of which a tool might be passed through the 
 orifices in^the internal wall of the air chamber, into the fire, 
 once or twice a day, for the purpose of cleaning ; * such 
 openings at other times being kept closed by doors, so as to 
 prevent the entrance of cold air ; and I accordingly lost no 
 time in carrying out my ideas, but erected a furnace on these 
 principles. Its success was complete, and though eventually 
 abandoned from the opposition of the workmen, who set their 
 faces against it the moment they found it was to be applied to 
 burning an inferior description of coal, which they considered 
 inimical to their interests, it is nevertheless unquestionably a 
 great step in advance of any furnace previously employed in the 
 iron trade, and must ultimately, unless interfered with by some 
 further improvement, force its way into use. 
 
 46. This further improvement is however, in my opinion, to 
 be found in the system of working with compressed air in the 
 ash-pit. In this powerful mode of stimulating combustion, we 
 have precisely the desideratum required to overcome the diffi- 
 culties which the tardy passage of the air through small coal 
 
 * In the first furnace which I constructed with these cleaning openings, 
 with a view to prevent the men destroying the brick-work of the side of the 
 grate, in passing the cleaning bar through the perforations, I had an iron 
 plate cast, with perforations in it corresponding to those in the brick-work, 
 to serve as a guide for the cleaning tool. In order to gain space for the air 
 chamber, and at the same time to confine the exterior of the furnace as far 
 as possible within its former dimensions, it was found necessary to build the 
 side of the grate of only 2 \ in. brick-work, the iron plate being relied upon to 
 give the requisite strength. After being in use a short time, a considerable 
 portion of one of the sides fell down, leaving the iron plate intact. To 
 my surprise, instead of melting, it stood alone, and proved as efficient and 
 durable as the other parts of the grate. Acting on the hint, I have since 
 repeatedly made use of iron as a material for grate sides, where these are 
 required with perforations, as more durable than brick-work, which is apt to 
 be damaged by the passage of the cleaning tool. 
 
ECONOMY OF FUEL. 21 
 
 throws* in the way of eliciting from slack the rapid combustion 
 and intense heat required in many manufacturing processes. 
 The power of control possessed by the workman over the action 
 of his fire is greater than that bestowed by any other system, 
 and the increased efficiency of the furnace, in every point of view, 
 compensates ten-fold for the additional apparatus required. An 
 engine of 10-horse power is amply sufficient to compress the air 
 for twenty furnaces, being at the rate of half-a-horse power per 
 furnace , and since there is a superabundance of waste heat, no 
 expense is incurred for fuel, but the whole outlay is limited to 
 the first cost of the machinery and the keeping it in repair. 
 
 47. The money saving effected by the substitution of slack 
 for coal is just one half; coal in Staffordshire being worth 5s., 
 and the best slack 2s. 6d. per ton. The quantity consumed in 
 the puddling furnace is about 16 tons per week, so that the cost 
 of the weekly consumption would be, with coal J64 ; with slack, 
 2 ; or, speaking in round numbers, the entire substitution of 
 slack for coal would save 100 per annum per furnace, and the 
 use of a mixture of equal parts of slack and best coal, would be 
 attended with a saving of 50 per annum per furnace. 
 
 SECTION III. 
 
 OX THE USE OF COMPRESSED AIR IN REVERBERATORY 
 FURNACES. 
 
 48. WITH regard to the plan of working furnaces with com- 
 pressed air in closed ash-pits, believing it destined to play a very 
 important part in furnace management, I shall give a brief nar- 
 rative of the steps by which I was led to a perception of its ad- 
 vantages. According to my ideas, its use will not be restricted 
 to the burning of small coal, though this alone would give it a 
 
22 ECONOMY OF FUEL. 
 
 very extensive field of operations, but will extend to its general 
 employment, as an adjunct to rarefaction in the stack, for fur- 
 nishing the force required for producing the rapid rush of air 
 through a fire, necessary for rapid combustion and intense and 
 concentrated heat. By means of its assistance, the power re- 
 quired may be obtained at a much cheaper rate than by 
 trusting entirely to rarefaction in the stack, which only produces 
 a powerful draught, at the expense of discharging the products of 
 combustion at a proportionally high temperature. 
 
 49. Although a great saving had been effected by the 
 furnace with perforated sides, with the improvement of cleaning 
 doors for keeping the perforations open, far from resting con- 
 tented with what had been already accomplished, I regarded it 
 rather as an earnest of future advances ; and my notions of the 
 state of perfection that ought to be attained were particularly dis- 
 satisfied with the fact, that whilst a great quantity of heat escaped 
 to waste, the principal supply of air entered under the ash-pit 
 bars cold. As there was ample waste heat for the purpose, why 
 should not the whole supply of air furnished to the fire be pre- 
 viously heated ? 
 
 50. Whenever I took any steps to effect this object in the 
 puddling furnace however, I encountered the fact, that precisely 
 as my arrangements for heating the air became more perfect, did 
 I destroy the draught through the fuel, deaden the fire, and lessen 
 the yield of iron. This unexpected result I attributed to the 
 rarefaction of the air in the ash-pit. When the atmosphere is 
 at 60, air is doubled in volume at 568, a temperature below 
 what is practically attained by causing it to circulate in contact 
 with the heated bottom and sides of a puddling furnace. When 
 thus rarified, a much smaller quantity will pass in a given time, 
 under the ordinary pressure of the atmosphere through the 
 interstices of the fire-bars, than would pass were the air at 60, 
 and consequently of double the density, and the result is a greatly 
 diminished draught, and less intense combustion ; and it is to 
 not having rightly appreciated these conditions, that the numer- 
 
ECONOMY OF FUEL. 23 
 
 ons failures which have been incurred in attempting to apply 
 heated air to furnaces, must in part be attributed. 
 
 51. In puddling furnaces, the body or working chamber of 
 the furnace, where the operation of iron making is carried on, 
 and through which the products of combustion rush in their path 
 to the stack, is freely open to the atmosphere at the working hole, 
 and it is the air with its full compliment of oxygen which enters 
 at this aperture, which is principally instrumental in oxydising- 
 and wasting, or, as the workmen say, cutting the iron : the air 
 which has passed through the fire having yielded its measure of 
 this gas to the fuel. When therefore we supply the ash-pit 
 exclusively with air which is expanded to double its volume by 
 heat, whilst on the one hand we have a greatly diminished 
 weight of air entering the fire through the bars, and a less in- 
 tense combustion, we have on the other hand the usual quantity, 
 that is to say, under the new state of things, double the propor- 
 tionate quantity of cold oxydising air entering at the working 
 hole, and hence the waste and poor yield of iron. 
 
 52. The desideratum in puddling, is to have so free a draught 
 through the fire, as to keep the body of the furnace full of flame y 
 and prevent as much as possible the indraught of cold unde- 
 oxydised air, through the working hole. A certain amount of 
 exhaustion being created in the body of the furnace by the 
 action of the stack, it is clear, that just in proportion as the pro- 
 ducts of combustion rushing from the grate are slow in supplying 
 this void, will the quantity of cold air that enters through the 
 working hole be increased. 
 
 53. That the quantity of air passing by the working hole, 
 should form an influential element in the result attained, will not 
 excite surprise, if we examine what this quantity may amount to, 
 and how greatly it may vary. The application of a pressure 
 gauge to the stack of a puddling furnace, shows a vacuum equal 
 to '24 of an inch of water, or a pressure of '2 of an ounce per 
 square inch, at which pressure the theoretical rate of influx is 
 39 feet per second, and consequently, supposing the size of the 
 
24 ECONOMY OF FUEL. 
 
 working* hole to be 4 in. by 4 in., or 16 square inches, this would 
 allow of 260 cubic feet of cold air entering the furnace per 
 minute. Deducting 25 per cent, for friction, would still leave 
 nearly 200 cubic feet as the quantity practically entering. The 
 average quantity will however fluctuate greatly, as the relative 
 pressure of the atmosphere acting through the grate bars or 
 through the working hole, varies with varying currents of air. 
 
 54. I thus arrived at a clear perception, that to give the 
 system of supplying the fuel with hot air the fullest develop- 
 ment of which it was capable, it would be necessary to supply 
 this air to the fire under pressure ; but whether the benefits ac- 
 cruing would so greatly outweigh the expense and trouble of the 
 additional appliances necessary, as to render its adoption advan- 
 tageous in a pecuniary point of view I was not prepared to say. 
 
 55. It was not fated however that I should remain long in 
 doubt : I had yet to witness the operation of puddling in a gale of 
 wind blowing in the direction of the working hole. Being in an iron 
 work one squally day, my attention was arrested by a volume of 
 oaths from one of the puddlers, whose furnace, being situated 
 at the extremity of a rank, was particularly exposed to the 
 wind, which blew directly into his working hole. With two 
 large pieces of sheet iron suspended behind him, in the vain 
 hope of warding off his adversary, he was labouring away in a 
 state of great exasperation, and apparently to but little purpose. 
 The dull red colour of the iron showed the deficiency in tempera- 
 ture, and it was with difficulty it could be made to cohere into a 
 mass. When the more violent gusts of wind came, so great was 
 the quantity that entered the furnace, and so completely did it 
 destroy the draught, that puffs of smoke were forced out at the 
 ash-pit. 
 
 56. The workman himself was in much too ill a humour for 
 conversation, but another puddler who was standing by, observ- 
 ing the interest with which I watched the proceedings, addressed 
 me, saying, " You see, sir, how very badly this furnace works; the 
 man can hardly make his iron at all. Well now, if the wind should 
 
ECONOMY OF 1-UEL. 25 
 
 change jn the course of the day, and a nice steady breeze set 
 into the ash-pit, this furnace will work as well as any furnace on 
 the works ; and this man's partner who comes on to-night, will 
 do his work with comfort in two hours less time, and perhaps 
 make 1 cwt. more iron." 
 
 57. Now it immediately occurred to me that if the accident 
 of the wind's blowing into the ash-pit made such a difference, 
 the same difference ought to be created artificially, and made 
 constant, and concomitantly with this idea, I recognized the fact, 
 that with the immense quantity of waste heat escaping by the 
 stack, no fuel would be required for a steam engine to compress 
 the air, and that therefore the expense of the system would 
 be restricted to providing the machinery, and keeping it in 
 repair. 
 
 58. The more I reflected on the subject, the more I became 
 convinced that whilst we were dependent upon the caprice of the 
 wind for the working of our furnaces, we were in fact in a state 
 of barbarism ; and though such extreme cases as the one I have 
 just related might not be very frequent, yet lesser fluctuations must 
 be constantly taking place with every change of the barometer, 
 making in the course of the year, a large aggregate amount of loss 
 from bad working. Indeed, that perhaps a more exact view of 
 the case would be, to regard our furnaces as being constantly 
 kept at work at a point of efficiency, far below what a little con- 
 trivance would enable them to reach. 
 
 59. Led as I had been by another path, and for another 
 object, to contemplate the alternative of having recourse to the 
 employment of compressed air, the subject had of course for me 
 a peculiar interest, and I determined forthwith to examine it in 
 all its details. The result of this examination was, that the 
 further I proceeded with my task, the more agreeably was 1 
 surprised to find how completely, with many advantages peculiarly 
 its own, it remedied the defects and supplied the wants of the 
 present system; and I soon became impressed with the firm 
 conviction, that it formed the only route by which we could ever 
 
 
 
26 ECONOMY OF FUEL. 
 
 hope to attain to a satisfactory point of perfection in furnaces 
 where a powerful draught and intense heat are required. 
 
 60, To produce rapid combustion and an intense heat, re- 
 quires a rapid current of air. The essence of the present system 
 of furnace management, is to procure the power necessary fox* 
 forcing or rather sucking this supply of air through the fuel, 
 from the levity (=heat) of the ascending column of gases in the 
 stack. That there are many defects in such a system is obvious. 
 In the first place, the power of stimulating the combustion, 
 being dependent upon the combustion itself, the capability of 
 independent control is wanting, and energetic combustion can 
 never be otherwise than gradually attained. Thus after fresh 
 lighting, it takes four or five hours to bring the puddling, heat- 
 ing, and melting furnaces used for iron, to a working heat. Not 
 only so however, but precisely at the moment when from op- 
 posing causes you require to spur on the action of the furnace, 
 not only does such a power fail you, but the energy of the fur- 
 nace languishes, from the very cause which rendered a stimulus 
 desirable. You get a reaction, but one in the wrong direction, 
 and which allows the original evil to be reproduced in increased 
 intensity. Por instance, in the case of the puddler I have alluded 
 to, the working of whose furnace was so much impaired by the 
 wind blowing into his working hole, it would have been desirable 
 to have removed the ill effect as quickly as possible, and lessened 
 its power of recurring in the same intensity, by increasing the 
 pressure of air in the ash-pit, and the fierceness of the combus- 
 tion ; but what actually took place, was, that the amount of cold 
 air which entered the furnace at the working hole, reduced the 
 temperature of the ascending column in the stack, and en" 
 tailed, as a necessary consequence, a diminished draught of air 
 through the fire, and an enfeebled combustion, just when the 
 contrary condition of things was most urgently needed. 
 
 61. In working with compressed air, on the contrary, the 
 action of the furnace is always under direct control, and can be 
 heightened or diminished at pleasure, and in such a case as the 
 
ECONOMY OF FUEL. 27 
 
 one jijst referred to, by turning on an adequate current of 
 air, the power of the wind acting in the adverse direction might 
 be defied, and none of it allowed to enter the furnace ; with the 
 result of a saving of iron, of fuel, of labour, and of time. 
 Indeed, in the manufacture of iron, the saving in the latter ingre- 
 dient always entails that of the three former, and is of all 
 others, the most certain channel by which their economy can be 
 attained. 
 
 62. Another advantage attendant upon a diminution of 
 the time occupied in manufacturing processes is, that a smaller 
 number of furnaces will turn out a given quantity of work, thus 
 diminishing the amount of capital employed, and the expense of 
 repairs. 
 
 63. The desideratum being to keep the atmosphere of the 
 body of the furnace at a given intensity, with the least expendi- 
 ture of fuel, it will not be difficult to show that the plan of doing 
 so solely by exhaustion, by sucking as it were the heated gases 
 from the fire rapidly through the furnace into the stack, is 
 essentially defective ; that under no point of view can it sus- 
 tain, except at a disadvantage, a comparison with the contrary 
 system of using compressed air as an aid to rarefaction in the 
 stack, for promoting draught. 
 
 64. In one case we have the furnace distended with flame 
 struggling to escape, and only discharged as it becomes forced 
 out by the pressure of the volume of flame behind it ; whilst a 
 pressure being maintained above that of the atmosphere, no- 
 draught of cold air can enter the furnace, either through the work^ 
 hole or any accidental fissure, to lower its temperature, oroxydize 
 its contents. In the other case, on the contrary, the exhaustion 
 operating through the neck, has a constant tendency to empty 
 the furnace of flame, and, at the same time, to suck in cold air 
 directly from the atmosphere through every available aperture, 
 to the lowering of its temperature, and the injury of its 'con- 
 tents. The very conditions on which the draught through the 
 fire depends, necessitate a facile egress for the products of coin* 
 
 C 2 
 
28 ECONOMY OF FUEL. 
 
 bustion because an independent power is wanting, to overcome 
 the friction of forcing them through a more contracted orifice, 
 the resistance, eddies, and commingling of gaseous currents, 
 occasioned by which process, are so instrumental in making them 
 yield up their heat to the parietes of the furnace, instead of 
 carrying it into the stack. The larger the neck, the larger the 
 axis of draught, and the larger the quantity of gaseous matter 
 which darts in a straight line through the centre of the furnace, 
 leaving little of its heat behind it, and imperfectly performing its 
 duty. 
 
 65. Where an opportunity exists for substituting slack for best 
 coal, by means of taking advantage of the stimulating influence 
 of compressed air on combustion, the benefit in an economic 
 point of view attending the use of air under pressure (amounting 
 to a saving of half) is of course so great and decided as not to 
 admit of dispute. I have endeavoured however to show that it 
 has more general and universal claims on our attention, than 
 that of being merely regarded as an admirable instrument for 
 slack burning, great, though these unquestionably are : in short, 
 I wish to recommend it for general employment, as an adjunct 
 to rarefaction in the stack, whenever powerful draught is re- 
 quired; maintaining that the combined use of the two, offers a 
 cheaper means of obtaining the force required, than trusting 
 solely to the latter ; and that whenever heat which might be 
 otherwise beneficially employed, is dismissed into the stack for 
 the sake of heightening the temperature, and consequently the 
 draught, it is sadly misapplied, inasmuch as the hundredth 
 part of it employed in raising steam to be applied mechanically, 
 would be productive of a greater effect. 
 
 66. Before entering into any calculation on the subject, I 
 fdt that the having recourse to the comparatively inert power of 
 gravity (through the ascending power of a column of heated air,) 
 must be a wasteful mode of obtaining the force requisite for 
 producing the necessary draught of air through the fuel, when 
 compared with the expedient of generating the same force, by the 
 
ECONONY OF FUEL. 29 
 
 vastly more energetic power developed by tlie chemical law of 
 vaporisation, (upon the addition of heat to a liquid,) as in the case 
 of converting water into steain. I was not however prepared for 
 the actual results which presented themselves, viz : that lib. of 
 coals employed to raise steam, and applied in a steam engine, 
 will do the work of 5001bs. expended in rarefying air, such air 
 acting through a height of 35 feet, the elevation of the stack of a 
 puddling furnace. 
 
 67: The force of the draught in a stack or chimney, is the 
 preponderance in weight of a column of air of the area and height 
 of the stack, and of the temperature of the atmosphere, over the 
 column of ratified air with which the stack is filled. 
 
 68. Now, since the air at 60 expands -g-J-g- for every degree 
 of heat imparted to it, when the atmospheric temperature is 
 60 (), the number of degrees the air is raised in the stack 
 above the external atmosphere, multiplied by (Ji) the height of 
 
 the stack, and divided by 508, (?-2!-f!) will equal the height 
 
 \ 508 ' 
 
 of a column of rarefied air, equivalent in weight to the deficiency 
 
 in the stack, and l = the height of a column of air at 
 
 508 x n 
 
 the atmospheric density equivalent to the above. The rate of 
 efflux, is the velocity a heavy body would acquire in falling this 
 height, to find which, multiply the square root of the height of 
 the fall, by 8, or in practice, to allow for friction, by 6. 
 
 69. One part of carbon, will raise 14,220 parts of water 1, 
 and if we estimate the specific heat of air at '25, that of water 
 being 1, then 14,220 x 4 = 56,880 parts of air raised 1 by 
 1 part of carbon. 
 
 70. Now, since the heating power of hydrogen is to that of 
 carbon as 60,854 to 14,220, or about four-fold, if we estimate 
 coal as composed of 80 parts of carbon, and five of hydrogen in 
 the 100 parts, the 5 parts of hydrogen being about equivalent 
 to 20 parts of carbon, we may calculate the heating power of 
 coal to be weight for weight, the same as carbon. 
 
30 ECONOMY OF FUEL. 
 
 71. Now the stack of a puddling furnace is 35 feet high, and 
 we will assume the temperature of the ascending column of 
 rarefied air to be 2,600, an estimate above the truth. 
 
 72. Supposing then that lib. of coal will raise 56,8801bs. 
 of air 1, it will raise 22'31bs. 2,540, and 2,540 -f- 60 for 
 the temperature of the atmosphere 2.600, the estimated tem- 
 perature of the ascending column of rarefied air in the stack. 
 
 73. Since air at 60 increases in bulk -g-i-g- for every degree 
 of heat imparted, at 2, 600 its volume is increased six- fold, and 
 the difference in weight between a column of air weighing 
 22-31bs. at 2,600, and a column the same size at 60, will 
 be lirsibs., and 111-5 X 35, the height of the stack, = 
 3, 90 2' 5 Ibs., the lifting force capable of being exerted through 
 the space of a foot by lib of coal employed in rarifying air, such 
 air being transmitted through a stack 35 feet high: and supposing 
 no loss to take place by friction, eddies, and progressive loss of 
 temperature in the ascent. Deduct for these, the odd 9 02* 5 Ibs., 
 or 23 per cent., and we get lifting force exerted by lib. coals 
 employed in rarefying air, such rarefied air being discharged 
 through a shaft 35 feet high, = 3,000 Ibs. raised 1 foot. Now 
 in some of the Cornish, engines, the duty performed by lib of 
 coals is 500-fold the above, = l,500,0001bs. raised 1 foot ; or 
 in other words, lib. of coals employed to raise steam, will do the 
 work of 5 00 Ibs. expended in rarefying air, such air being dis- 
 charged through a stack 35 feet in height. 
 
 74. The above calculation clearly shows that it is a sad 
 misapplication of heat, to employ it in generating power through 
 the ascending force of a column of heated air, and consequently, 
 that whatever heat might be economically employed in other 
 ways, is most prodigally wasted, when allowed to escape by the 
 stack for the sake of draught, a tolerably decisive fact in favour 
 of the superiority of the system of ventilating coal mines by 
 mechanical agency, as proposed by Mr. Brunton, over the old 
 method of rarefying the air in a shaft by a fire at the bottom. 
 
 75. The best instrument for compressing the air' for furnaces, 
 
ECONOMY OF FUEL. 31 
 
 where only a slight condensation is required, as in reverberatoiy 
 furnaces and steam boilers, is a fan. Though theoretically 
 making but a small return for the power expended, it is prac- 
 tically the most convenient, and half-a-horse power is sufficient 
 for a puddling or mill furnace. And for such furnaces, the 
 whole expense of employing the system of working with com- 
 pressed air, is restricted to the cost of the machinery, since no 
 expenditure will be incurred for fuel. On the contrary, the re- 
 sult of the adoption of the plan, is greatly to increase the quantity 
 of available heat. Under the present system, heat sufficient to 
 generate steam for about 5 -horse power, is as much as can be 
 substracted from the flue of a puddling furnace, without in- 
 juriously affecting the draught ; the flues of 4 furnaces being 
 applied to a 20-horse boiler. By the assistance of compressed 
 air however, double this quantity may be taken with safety, so 
 that the extra quantity rendered available by its application to 
 one furnace, would suffice to furnish power to compress the air 
 for ten. 
 
ECONOMY OF FUEL. 
 
 TABLE 
 
 Of the Temperature in Stacks of different heights, necessary to produce a 
 Pressure. External air at 60. 
 
 Pres- 
 
 Pres- 
 
 Weight 
 
 Weight 
 
 Theoret 
 ical rate 
 
 Tempera 
 ture in 
 
 Tempera- 
 ture in 
 
 Tempera- 
 ture in 
 
 Tempera- 
 ture in 
 
 sure in 
 
 sure in 
 
 on sq. foot 
 
 ?*' 
 
 >f efflux 
 
 stack 
 
 stack 
 
 stack 
 
 stack 
 
 water. 
 
 air. 
 
 in Ibs. 
 
 in 
 
 in feet 
 
 34 feet 
 
 69 feet 
 
 138 feet 
 
 276 feet 
 
 
 
 
 T<h> 02 - 
 
 per sec. 
 
 high. 
 
 l.igh. 
 
 high. 
 
 high. 
 
 Inches. 
 
 Feet. 
 
 
 
 
 Deg. Fah 
 
 Deg. Fah. 
 
 Deg. Fah. 
 
 Deg. Fah. 
 
 2 
 
 138 
 
 10-564 
 
 116 
 
 94 
 
 
 
 
 568* 
 
 1 
 
 134'55 
 
 10-2999 
 
 113-1 
 
 92,8 
 
 
 ... 
 
 
 51-3-22 
 
 1 
 
 131-1 
 
 10-0358 
 
 110-2 
 
 91-6 
 
 
 ... 
 
 
 519-61 
 
 if* 
 
 127'65 
 
 9-7717 
 
 107-3 
 
 90-4 
 
 
 
 
 497-11 
 
 ig 
 
 124-2 
 
 9-5076 
 
 104-4 
 
 89-2 
 
 
 . . . 
 
 4632* 
 
 475-63 
 
 i 
 
 12075 
 
 9-2435 
 
 101-5 
 
 88 
 
 . 
 
 
 3616 
 
 455-11 
 
 J 
 
 117-3 
 
 8-9794 
 
 98-6 
 
 86-6 
 
 
 
 2938-66 
 
 435-47 
 
 } 
 
 113-85 
 
 8-7153 
 
 95'7 
 
 85 
 
 . 
 
 
 2454-85 
 
 416-68 
 
 H 
 
 110-4 
 
 8-4512 
 
 92-8 
 
 84 
 
 
 
 2092* 
 
 398-66 
 
 H* 
 
 10695 
 
 8-1871 
 
 89-9 
 
 82-75 
 
 
 ... 
 
 180977 
 
 381-38 
 
 1 
 
 103-5 
 
 7'923 
 
 87 
 
 81-4 
 
 
 
 1584* 
 
 364-8 
 
 Jft 
 
 100-05 
 
 7'6589 
 
 84-1 
 
 80 
 
 
 
 1406 
 
 348'8f> 
 
 1ft 
 
 96'6 
 
 7*3948 
 
 81'2 
 
 78.6 
 
 i 
 
 
 1245-33 
 
 333-53 
 
 Jft 
 
 93-15 
 
 7-1307 
 
 783 
 
 77-2 
 
 
 
 1115 
 
 318-8 
 
 ift 
 
 89-7 
 
 6-86(56 
 
 75-4 
 
 75-7 
 
 
 ... 
 
 1003-42 
 
 304-59 
 
 1ft 
 
 86'25 
 
 6*6025 
 
 72-5 
 
 74"2 
 
 
 
 906-66 
 
 290 
 
 Vo 
 
 82-8 
 
 6-3384 
 
 696 
 
 72-8 
 
 
 
 822 
 
 277-71 ' 
 
 ** 
 
 79-35 
 
 6-0743 
 
 66'7 
 
 71-3 
 
 
 
 747-3 
 
 272 
 
 *ft 
 
 75-9 
 
 5-8102 
 
 63-8 
 
 69-7 
 
 . . . 
 
 ... 
 
 680-88 
 
 252-C9 
 
 1ft 
 
 72-45 
 
 5.5461 
 
 60-9 
 
 68 
 
 
 
 621-47 
 
 240-8 
 
 1 
 
 69 
 
 5-282 
 
 58 
 
 664 
 
 
 
 568* 
 
 229-33 
 
 if 
 
 65-55 
 
 5-0179 
 
 55"! 
 
 64-75 
 
 
 
 519'f.l 
 
 21823 
 
 ) 8 
 
 2TT 
 
 62-1 
 
 4-7538 
 
 52-2 
 
 63-1 
 
 
 4632* 
 
 475-63 
 
 207-48 
 
 JLi 
 
 ao 
 
 58-1)5 
 
 4-4897 
 
 49'3 
 
 61-27 
 
 
 2938-66 
 
 435-47 
 
 197- 
 
 
 
 55*2 
 
 4-2256 
 
 46-4 
 
 59-5 
 
 
 
 2092* 
 
 398-66 
 
 187- 
 
 1 5 
 
 U17 
 
 51-75 
 
 3-9615 
 
 43-5 
 
 57-5 
 
 
 1584* 
 
 364-8 
 
 177-23 
 
 M 
 
 48-3 
 
 3-6974 
 
 40-6 
 
 55-6 
 
 ... 
 
 1245-33 
 
 333-53 
 
 107-75 
 
 1 3 
 
 3^5" 
 
 44-85 
 
 3*4333 
 
 37-7 
 
 53-6 
 
 
 1003-42 
 
 304-5 ( / 
 
 15856 
 
 u 
 
 41-4 
 
 3-1692 
 
 34-8 
 
 51-5 
 
 
 822 
 
 277-71 
 
 149-64 
 
 1* 
 
 37-95 
 
 2-9051 
 
 31-9 
 
 49-25 
 
 ... 
 
 680-88 
 
 252-69 
 
 141 
 
 tt 
 
 34-5 
 
 2-6410 
 
 29 
 
 47 
 
 
 568* 
 
 229-33 
 
 132-57 
 
 A 
 
 31-05 
 
 2-3769 
 
 26-1 
 
 44-5 
 
 4632* 
 
 475-63 
 
 207-48 
 
 124-39 
 
 ft 
 
 276 
 
 2-1128 
 
 23*2 
 
 42 
 
 2092* 
 
 398-66 
 
 187 
 
 116-44 
 
 ft 
 
 24-15 
 
 1-8487 
 
 20-3 
 
 39-3 
 
 1245-33 
 
 333-53 
 
 167-75 
 
 108-7 
 
 ft 
 
 20-7 
 
 1-5846 
 
 17'4 
 
 36-4 
 
 822 
 
 277-71 
 
 149-64 
 
 101-18 
 
 ft 
 
 17-25 
 
 1-3205 
 
 14-5 
 
 33 
 
 5CS* 
 
 229-33 
 
 132-5? 
 
 93-86 
 
 ft 
 
 13-8 
 
 1-0564 
 
 11-6 
 
 29-7 
 
 398-66 
 
 187 
 
 116-44 
 
 SG'73 
 
 ft 
 
 1035 
 
 7923 
 
 8-7 
 
 25-75 
 
 277-71 
 
 149-64 
 
 101-18 
 
 79-79 
 
 A 
 
 6-9 
 
 5282 
 
 5-8 
 
 21 
 
 187 
 
 116-44 
 
 86-73 
 
 73- 
 
 ft 
 
 3-45 
 
 2641 
 
 2-9 
 
 14-75 
 
 11644 
 
 86-73 
 
 73 
 
 66-43 
 
 * Air of 60 has its volume increased 
 
 Double *t . . . 5fih 
 
 Fivefold at ... 2092 Eightfold at . . S616 C 
 
 Threefold at . . 107C 
 
 Sixfold at . . .2600 Ninefold at . . .4124 
 
 Fourfold at . . . 1584 
 
 Sevenfold at : . 310b Tenfold at ... 4632 
 
ECONOMY OF FUEL. 33 
 
 SECTION IV. 
 
 ON THE APPLICATION OF THE SYSTEM OF WORKING WITH 
 COMPRESSED AIR, TO STEAM BOILERS. 
 
 76. WHERE space is of no object in a steam engine, and a 
 large grate, a large boiler, and a high stack are admissible, the 
 use of compressed air is unnecessary. Whenever, on the con- 
 trary, space and weight have to be economised (and the import- 
 ance of doing so in marine engines and locomotives can scarcely 
 be exaggerated), aiding the draught in the stack by blowing the 
 lire with compressed air ought to be considered indispensable, 
 and must and will one day be so deeme 1, inasmuch a > it is a 
 vastly more economical method of producing the keen draught 
 required, than that at present employed. 
 
 The fuel burnt per hour per square foot of fire-grate is 
 In Cornish engines from .... 3^1bs. to 41bs. 
 In factory arid marine engines from 10 16 
 In locomotives . . . ' .A . 80 100 
 
 The number of square feet of heating surface in boiler 
 required to evaporate 1 cubic foot water per hour = I. H. P is 
 
 In Cornish boilers 70 
 
 In factory and marine boilers . . 9 11 
 In locomotives 6 
 
 The number of square feet of heating surface to each square 
 foot of lire-grate is 
 
 In Cornish boilers 40 
 
 In factory and marine boilers . 13 to 15 
 In locomotives 50 70 
 
 77. In Cornish engines, with only a consumption of 41bs. of 
 coal per hour, per square foot of fire-grate, a very moderate 
 draught only is required ; consequently the temperature of the 
 products of combustion, after they have yielded all their available 
 heat to the boiler, sufficing for this purpose, there is no expendi- 
 
 C 3 
 
34 .ECONOMY OF FUEL. 
 
 ture of fuel for the sake of producing rarefaction in the stack, and 
 hence one source of their economy. They do not, in consequence of 
 their slow draught, produce more perfect combustion than other 
 classes of engines, as is commonly but erroneously supposed (for 
 there is no connection between the perfection of combustion and 
 the rate at which it is effected) ; but the fuel wasted by other 
 engines in producing a keen draught, they employ in the genera- 
 tion of steam. 
 
 78. Some persons entertain the chimerical notion that when 
 the products of combustion leave the boiler, they ought to be 
 reduced nearly to the temperature of 212, or at least to a tem- 
 perature but little above that of the water contained within. 
 Till boilers however can be made infinitesimally thin, there must 
 always remain a considerable difference between the temperature 
 of their internal and external surfaces, (at least of such portions 
 of the latter as are exposed to the heat of the flues,) increasing 
 with the thickness of the boiler plate ; for the temperature of a 
 transmitting surface, must be plus that of a receiving one. This 
 rule applies with full force to the temperature of the current of 
 heated gases, and the surface of the boiler to which they impart 
 heat, since here we get only temporary contact for a very short 
 period of time. Air is besides a bad conductor of heat, and in 
 addition, we have to take into consideration the fact, that as 
 bodies approximate to each other in temperature, the rate of the 
 transmission of heat becomes rapidly diminished ; the law of 
 < cooling by contact/ for gases, being, that when the difference of 
 temperature is doubled, the velocity of cooling is increased 2 '3 5 
 (Petit and Dulong). For these reasons, I am totally incredulous 
 as to many of the tales told of the extraordinary extent to which 
 the products of combustion are cooled down, in certain instances, 
 before leaving the boiler, and believe parties deceive themselves, 
 by being unaware how high a temperature may be borne by the 
 hand without inconvenience, when the draught is slow. 
 
 79. The path by which the utmost practicable economy can 
 be attained, is obviously pointed out by the preceeding considera- 
 
ECONOMY OF FUEL.- 85 
 
 tions to be, by introducing the feed water immediately over the 
 last portion of the flue traversed by the heated air before it 
 enters the stack, and by diminishing the thickness of the shell 
 ol the boiler, which latter can only be done with safety, by making 
 it consist of an aggregate of cylinders or tubes of moderate dimen- 
 sions, instead of one enormous vessel, as at present. The change 
 proposed, would be attended with the further advantage, of 
 presenting more surface for the same capacity, thus enabling the 
 size and weight of the boiler to be greatly diminished. 
 
 80. The first desideratum with regard to the place of ad- 
 mission for the feed water, is carefully studied in the Cornish 
 boiler, but the second, is by no means fulfilled ; and considering 
 its enormous size, I believe it would be quite possible to construct 
 a boiler on the principles above mentioned, where, as a question 
 of first cost, the extra workmanship would be fully compensated 
 for, by the diminished size and weight, whilst the thinner shell, 
 would produce some addition to the economy in fuel. 
 
 81. If we allow 50 for the difference in temperature between 
 the interior boiler surface in contact with the water, and the 
 exterior in contact with the heated products of combustion, and 
 150, when the draught is very slow, for the excess in tempera- 
 ture of these products, over the boiler surface at the instant of 
 quitting it, making together a difference of 200 between the 
 temperature of the water in the boiler, and that of the gases 
 entering the flue, we shall I believe be making an estimate of a 
 degree of perfection very rarely attained in practice. 
 
 82. If then a Cornish boiler works at 751bs. pressure, the 
 temperature of the water within will be 308, and 308+50-{- 
 150= 508 for the estimated temperature of the gases at the 
 moment of their quitting the boiler and entering the stack ; and 
 even in a low pressure engine I greatly doubt the practicability 
 of ever reducing the temperature below 450. In fact such 
 temperatures, or any near approximation to them, can only be 
 attained in cases where, as in the Cornish engine, the consump- 
 tion of fuel per square foot of fire-grate is very small, the 
 
36 ECONOMY OF FUEL. 
 
 draught slow, and the fuel not wasted to produce highly rarefied 
 air in the stack. 
 
 83. In factory engines, where a draught is required suffi- 
 ciently rapid to burn from 12 to IGlbs. of fuel per square foot of 
 fire-grate, with the flues of the usual horizontal and winding 
 form, I doubt the practicability of reducing the temperature of 
 the products of combustion below 550 or 600; and even to 
 realize this, a high stack and capacious boiler will be necessary, 
 and with these adjuncts, in this class of engines the employment 
 of compressed air may be dispensed with. 
 
 84. In marine engines however, and still more in locomo- 
 tives, where a fierce draught is required, a high stack inadmissible, 
 and economy of space necessary, all the conditions exist which 
 render the use of compressed air advantageous, and I believe its 
 application to these two classes of engines to be imperatively 
 necessary, if economy is to be attained. 
 
 85. In marine engines evaporating from 14 to 161bs. of 
 coal per square foot of fire-grate, where moreover, from the 
 desirability of having a small boiler, the products of combustion 
 have to be forced through small tubes, and this accomplished 
 without the aid of the elevated stack of the factory, nothing but 
 a very high degree of rarefaction in the chimney can furnish the 
 requisite draught, and it is next to impossible under the circum- 
 stances present, that the products of combustion can leave the 
 boiler at a lower temperature than 800, a temperature entailing 
 an enormous waste of fuel. To burn off the quantity of fuel 
 required in the limited grate area, a keen draught is indispens- 
 able ; and if the power to produce this, is to be attained by the 
 ascentional force of the column of heated air in the stack, when 
 the stack is of limited height, the temperature must be high, and 
 the waste of fuel great : these vicious consequences are inevitably 
 linked together, and there is no means of escape, but by generating 
 the force required for the keen draught in a cheaper way, and 
 calling in the aid of compressed air, which, by enabling the 
 extent of heating surface in the boiler to be increased, and the 
 
ECONOMY OF FUEL. 87 
 
 draught still maintained, would cool down the current of gases 
 from the fire to the more economical temperature of 400 or 500. 
 
 86. The whole question of draught in steam engines, is one 
 GI ratio of power, to space, and cceteris paribus, the greater the 
 concentration required, the greater the draft necessary. The 
 amount of rarefaction requisite to produce a given draft, is 
 dependant upon : Istly, resistance, comprehending area and 
 form of grate bar openings, thickness and closeness of the layer 
 of fuel, and area and direction of flues, whether horizontal or 
 vertical, curved or straight ; and 2ndly, upon height of stack. 
 The greater the resistance, and the lower the stack, the higher 
 the amount of rarefaction required to produce a given draft, arid 
 vice versa. 
 
 87. It is through losing sight of the intimate mutual depen- 
 dance of these conditions, and of the necessity which exists for 
 each being adjusted to the other, that so many abortive attempts 
 have been made to increase the evaporative power of boilers, and 
 economize fuel, by suspending a vessel for feed water at the 
 lower part of the stack. The effect of such an expedient being 
 to diminish the draft, if it were attempted to burn the same 
 quantity of fuel on the same area of grate bar, as had been 
 previously done, unless the spaces between the bars were widened, 
 or the height of the stack increased, the result would be, that 
 nn insufficient quantity of air would pass, for the combustion of 
 the gaseous products of the coal, unless we suppose that the 
 quantity passing before was too great ; but as the opposite defect 
 is more common, the probable result would be as before stated, 
 so that the little heat saved at the bottom of the stack, being 
 counterbalanced by the more inefficient combustion, the result 
 produced, in an economical point of view, would be nil, or 
 something nearly approaching it, which, as far as I can learn, is 
 the usual product. 
 
 88. Such contrivances are in fact expedients for increasing 
 the heating surface of boilers, which, it is evident, cannot be in- 
 definitely extended with advantage, inasmuch as its proper ratio is 
 
ECONOMY OF FUEL; 
 
 confined within certain limits, determined by the draught necessary 
 to make a certain area of fire grate do the work demanded of it, 
 In short, nothing can more clearly show how completely the subject 
 has been shrouded in mist, and the general prevalence of the 
 want of any comprehensive view of the principles involved in it, 
 than the many absurd and futile attempts which have been made 
 to produce effects as intrinsically unattainable, as perpetual 
 motion, or the philosopher's stone ; for whilst the high amount 
 of rarefaction in the stack, is the necessary condition, by which 
 the force of draught required for burning off 161bs. of coal 
 hourly per square foot of grate area is generated, it is never- 
 theless sought to remove the former, and retain the latter. 
 
 SECTION V. 
 
 ON THE ECONOMY TO BE ATTAINED, BY INCREASING 
 THE TEMPERATURE OF FURNACES. 
 
 89. THE existence of this very important channel for 
 effecting economic results, seems hitherto to have escaped due 
 recognition. The principles on which its value depends, may 
 be briefly explained as follows. It is only that portion of the 
 heat of a furnace which is in excess over the temperature of 
 the body to be heated, which constitutes in reality, available 
 heat, conducive to the performance of its office. Thus the 
 nearer the temperature of the body operated upon, approaches 
 the temperature of the furnace, the larger is the portion of the 
 heat of the latter which becomes ineffective, whilst the more 
 the temperature of the furnace predominates, the larger becomes 
 the proportion of serviceable heat, to the whole heat generated. 
 Therefore, if by any means the intensity of the heat of a furnaee 
 
ECONOMY OF FUEL. 39 
 
 can be heightened, Us efficiency will be increased in the ratio 
 of the acccession made to Us surplus Jieat y (or the degree by which 
 it exceeds the temperature of the body to which heat is to be 
 imparted); so that for processes requiring very high temperatures, 
 and where the ordinary heat of the furnace is but slightly in 
 excess, a very small increment of temperature, will be productive 
 of a great efficiency, and corresponding saving of fuel. As the 
 principle involved is an important one, from the wide field it 
 opens up for practical results, and has never yet been treated on, 
 I shall do my best to make it intelligible to the reader. 
 
 90. Let us suppose, by way of illustration, that there is 
 some process of manufacture carried on in a vessel containing 
 120 gallons of hot water, and that to carry it on favourably, the 
 temperature of the water must never be allowed to fall below 
 200, and further, that the loss by radiation and conduction from 
 the sides of the vessel, is such, that in order to insure this 
 temperature being maintained, it is necessary to keep a constant 
 stream of boiling water at 212 flowing in at one end, at 
 the rate of 2 gallons per second, and an equal quantity of 
 partially cooled water, just on the verge of falling below 200, 
 constantly flowing out at the other. At this rate, the whole 
 contents of the vessel, viz. 120 gallons, will be discharged and 
 renewed every minute. The loss by cooling, will amount there- 
 fore, to 120 gallons of water cooled 12 per minute, and the 
 fuel required to carry on the operation, will be, the quantity 
 necessary to raise 120 gallons of water to the boiling point, every 
 minute, or supposing the atmospheric temperature to be 56, to 
 impart 156 of heat to 120 gallons of water per minute, which, 
 we will assume, requires in practice, 26 ounces of ceal per minute. 
 
 91. Now let us suppose a means is found of imparting an 
 additional 12 of heat to the supply water. Since the loss bj 
 radiation, is such that 120 gallons of water lose 12 of heat 
 per minute, they will be 2 minutes* losing 24, and consequently 
 
 * The slight increase in the velocity of cooling, with the increase in 
 temperature, ia too trifling to affect the argument. , 
 
40 ECONOMY OF FUEL. 
 
 this trifling addition of ^ more heat, will enable half the 
 amount of supply, or 1 gallon at 224, instead of 2 gallons at 
 212, to suffice for preserving the temperature from falling 
 below 200 ; and the contents of the vessel will only require 
 to be renewed every 2 minutes, instead of every minute, whilst 
 the saving of fuel per minute, will be the difference between 
 the quantity of coal required to raise 120 gallons of water 156, 
 and that required to raise 60 gallons 168, or nearly half; the 
 quantities being 14 ounces in the latter case, and 26 ounces in 
 the former. If we assume however, that the amount of additional 
 heat imparted to the water, is obtained by some contrivance for 
 making the combustion more perfect, which we should do, to 
 make the parallel and argument as regards furnaces complete, 
 then the result will be, that this trifling addition of T ' to the 
 temperature, will effect a saving in fuel amounting to half. 
 
 92. Precisely the same considerations which apply to a 
 manufacturing process requiring to be carried on in a vessel of 
 water of a certain temperature, apply to the operations carried 
 on in furnaces, the only difference besides that of temperature 
 being, that the fluid employed in one case is flame, or hot air, 
 and in the other, hot water. 
 
 93. A large class of furnaces may be regarded as vessels 
 in which changes are wrought in certain substances, by their 
 being immersed in a bath of flame or hot air of a given tempera- 
 ture, either with, or without being subjected at the same time 
 to certain manipulations, and the operation of certain chemical 
 agents ; and, as in the case of the water vessel, to preserve this 
 temperature, it is requisite to have a constant supply of the fluid 
 used, whether air or water, plus the temperature required to 
 compensate for the loss by radiation and conduction, together 
 with a means of egress, for that which has become minus. 
 
 94. Now the important principle involved in the matter 
 under discussion, as I have before explained, is, that if, by any 
 means, we are enabled to increase our temperature, such increase 
 will effect a saving of fuel in the direct ratio of the proportion it 
 
ECONOMY OF FUEL. 41 
 
 bears to the DIFFERENCE between the temperature ice were 
 previously generating r , and that which the process we are carrying. 
 on demands. No matter how small the amount of that difference 
 may be, if we succeed in gaining it, we at once diminish our con- 
 sumption of fuel by -J-, if we gain twice as much, by - , Sec., &c. 
 Let us suppose, in illustration, that we are generating an atmo- 
 sphere of 3,200, and that our process demands 3,000, and that, 
 in order to maintain it, we require to renew the contents of our 
 furnace four times in a second, could we increase the tempera- 
 ture of our supply by 200, thus making it 3,400, twice in a 
 second would suffice, and the addition of an amount of heat 
 represented by T ^ of our consumption of fuel, would lessen this 
 consumption one half ; or, under the same conditions, could we 
 augment our temperature 600, and thus raise it to 3,800, once 
 in a second would suffice for renewing the contents of our 
 furnace, and we should then have the addition of an amount of 
 heat represented by T 3 ^- of our previous consumption, diminishing 
 this consumption four-fold. 
 
 95. In Staffordshire, 24 cwt. of coal (long weight 1201bs. 
 to the cwt.) is consumed to produce from pig, 1 ton of puddled 
 iron, the consumption being about 2401bs. per hour, or 41bs. 
 per minute. Now since oxygen is to carbon, in carbonic acid> 
 as 8 to 3, and oxygen to hydrogen, in water, as 8 to 1, 41bs. of 
 coal will require for perfect combustion, lOy^lbs. = 120 cubic 
 feet of oxygen, and since oxygen is to nitrogen (by volume), in 
 atmospheric air, as 1 to 4 = 600 cubic feet of air ; and the 
 products resulting will be : 101*08 cubic feet of carbonic acid, 
 37'84 cubic feet of steam, and 480 cubic feet of uncombincd 
 nitrogen ; total 6 18' 92 cubic feet of gas. Estimate the tempera- 
 ture at 3,108, and multiply the volume of gas by 7 for expansion, 
 and we find that 4,332*44 cubic feet of rarefied gases, pass 
 through the furnace per minute,- 60 = 72*273 cubic feet per 
 second. And finally, estimating the area of a puddling furnace 
 between the bridges, at 36 cubic feet, we find to our surprjjge, 
 that it is unquestionably filled and emptied twice in a second. 
 
42 ECONOMY OF FUEL. 
 
 96. Now, if we estimate the temperature required for the 
 process of puddling, at 3,000, which must be a very near 
 approximation to the truth (since the melting point of pig-iron 
 is found by Daniel's pyrometer to be 2,786), and suppose that 
 the products of combustion pass over the fire bridge and enter 
 the body of the furnace at a temperature of 3,300, then it 
 appears, that since to maintain the necessary temperature, the 
 contents of the furnace have to be renewed twice in a second, the 
 loss of temperature, by radiation, conduction, &c., is at the rate 
 of 600 per second. If therefore by any method we could succeed 
 in increasing the temperature generated by 300, and thus raise 
 the atmosphere produced by the furnace to 3,600, since we 
 have found that the rate at which the cooling process goes on, 
 is 600 per second, we should only have to renew the contents of 
 our furnace once* in a second, instead of twice, to maintain the 
 requisite temperature of 3,000, and should effect a saving of 50 
 per cent. 
 
 97. In mill or heating furnaces, used for the manufacture of 
 iron, the result of heightening the temperature, would be equally 
 beneficial. When first charged with cold iron, the heating goes 
 on rapidly, but the rate at which it proceeds, constantly dimin- 
 ishes as the temperature of the iron approximates to that of the 
 
 furnace, and at last becomes very slow. It is during this latter 
 period, that the beneficial effect of a more intensely heated 
 furnace, becomes most conspicuous. Although I have denomi- 
 nated that portion of the heat of a furnace which constitutes its 
 difference (in excess) over the temperature of the body to be 
 heated, its available heat, it would be a grave error to suppose 
 that the whole of this excess is transferred and usefully employed 
 in the operation. Such would be the case were the products of 
 
 * The slightly increased rate of cooling, which would result from the 
 increase of temperature is here disregarded, as too trifling to affect the 
 argument. The law of cooling by contact for gases, is, that where the 
 difference of temperature is doubled, the velocity of cooling is increased 
 2'35. Petit and Dulong. 
 
ECONOMY OF FUEL. 43 
 
 combustion and the body to be heated, kept a considerable time 
 in contact ; but in a rapid transit, as occurs with the heated 
 gases of a furnace, ohly a certain ratio of this excess, in proportion 
 to the measure of the excess itself, the extent of surface exposed, 
 and the time occupied in the transit, can be left behind ; and, 
 considering the conditions of the furnaces of an iron work, I 
 regard it as impossible that more than half the excess can be 
 imparted, even at the most favourable period, that is to say, when 
 the furnace is newly charged with cold iron, and the difference 
 of temperature is greatest. 
 
 98. Now if we suppose the temperature of the iron to be 
 100 when placed in the furnace, the temperature generated by 
 combustion to be 3,300, and that half the difference (in excess) 
 or surplus heat, when this surplus is 3,200, enters the iron, we 
 shall have at the commencement (3,300 100 =3,200~2 = 
 1,600) within a fraction of half the whole heat generated, im- 
 parted to the iron. When however the iron has attained the 
 temperature of 1,700, and the surplus heat becomes halved, we 
 shall have only 680 communicated to the iron, or a little more 
 than a fifth of the whole. When the iron has reached the 
 temperature of 2,500, and the surplus heat becomes quartered, 
 only 290 parts of heat out of 3,300 generated, or less than TT , 
 will be profitably applied. Whilst if we suppose that iron 
 requires to be raised to 3,200 to bring it to a welding heat, the 
 state of things when it has attained the temperature of 3,100, 
 and is beginning to receive its last 100 of heat, will be as 
 follows : Out of 3,300 parts of heat generated, only 52, or less 
 than -gL, will enter the iron, the remaining 3,248 parts, or more 
 than |"| of the whole, being wasted. Could we however suc- 
 ceed in increasing the temperature of our furnace by 400, thus 
 raising it to 3,700, the state of things at the same point would 
 be, that 206 parts of heat, or T ^- instead of only -fa of the whole 
 heat generated, would enter the iron; thus exhibiting the fact 
 of an addition of temperature to the amount of \, increasing 
 
44? ECONOMY OR FUEL. 
 
 the velocity of heating, and consequently the efficiency of the 
 furnace at this crisis, fourfold. 
 
 99. These laws have such an important practical bearing, 
 and their existence is at the same time so little suspected, that 
 with a view to their more complete display and elucidation, I 
 have exhibited them in a tabular form ; and if I do not greatly 
 err, they deserve to command as much attention, as they will 
 unquestionably excite surprise. The tables contrast the effects 
 of two furnaces (one heated to 3,300, the other to 3,700,) in 
 imparting heat to iron at five different stages, whilst being raised 
 to a welding heat ; clearly shewing, that although the rate at 
 which heat is communicated, rapidly diminishes, as the tempera- 
 ture of the iron increases, yet a very trifling addition to the 
 temperature of the furnace, is capable of producing a great result 
 in retarding the rate at which the diminution of heating proceeds, 
 and consequently, in the economic working of the furnace. 
 Column A gives the temperature of the furnace, B the tempera- 
 ture of the iron, C the difference in favour of the furnace, D the 
 portion of this difference imparted, E the proportion of the 
 whole heat generated imparted, F the velocity at which the 
 heating proceeds, calling the smallest velocity 1. 
 
 A. E. C. D. E. F. 
 
 3300 100=3200 1600 -484 30*49 
 
 3300 1700=1600 680 '206 12-97 
 
 3300 2500= 800 290 '087 5*52 
 
 3300 2900= 400 123 '037 2'35 
 
 3300 3100= 200 52 '015 1 
 
 3700 100=3600 1871 '505 35'64 
 
 3700 1700=2000 911 '246 17'35 
 
 3700 2500=1200 485 -131 9'25 
 
 3700 2900= 800 290 '078 5'52 
 
 3700 3100= 600 206 '055 3'93 
 
ECONOMY OF FUEL. 45 
 
 To facilitate comparison, the results are arranged below in 
 parallel columns, the prefix -f- denoting those of the hotter 
 furnace. 
 
 B. C. +0. D. -f-D. E. -f-E. E. +T. 
 
 100 3200 3600 1600 1871 '484 '505 30*49 35'64 
 
 1700 1600 2000 680 911 -206 -246 12-97 17'35 
 
 2500 800 1200 290 485 .087 '131 5'52 9'25 
 
 2900 400 800 123 290 -037 '078 2'35 5-52 
 
 3100 200 600 52 206 '015 '055 1 3'93 
 
 100. In treating this question, 1 have endeavoured to place 
 conspicuously before the reader the great advantages attendant 
 upon a slight addition of temperature, irrespectively of the 
 question as to whether, in our present position, we are, or are not 
 able to profit by this law ; believing, that even if a negative be 
 the correct answer, it is nevertheless not the less desirable that 
 we should possess a knowledge of the direction in which our 
 attention may be turned, with the greatest probability of 
 obtaining important results. 
 
 101. The most efficient method that I am acquainted with, 
 for increasing the temperature of reverberatory furnaces used for 
 the manufacture of iron, is the use of compressed air, in a closed 
 ash-pit, thus creating artificially, the state of things present, when 
 a steady breeze sets into the ash-pit. It is a fact, that a furnace 
 thus favourably situated, will heat three charges of iron, whilst 
 its opposite neighbour in other respects its equal, is heating only 
 tivo ; and the wonder is, that the hint thus conveyed, has not been 
 sooner acted upon, and that state of efficiency which now only 
 has place with a few furnaces, and at uncertain intervals following 
 the caprice of the wind, made the permanent condition of all, 
 
 102. In proportion as the temperature of furnaces becomes 
 increased, does it become important to obtain a fire-brick material 
 of the best possible description, particularly for the sides of the 
 grates. The presence of alkalies, or iron, is fatal to the quality of 
 a clay for this purpose. When free from these ingredients, its 
 
4 ECONOMY OF FUEL. 
 
 power of resisting heat is almost in a direct ratio to the propor- 
 tion of silex it contains, and I have long been of opinion, that the 
 quality of what is termed our best fire-brick, might be greatly 
 improved by incorporating with the clay, an additional quantity 
 of pure silecious sand (which may be procured, where not found 
 native, by grinding pure sandstone), the requisite cohesion of the 
 materials being produced, by subjecting the brick in its manufac- 
 ture to a high pressure. This method I am informed, has been 
 recently adopted with the celebrated Dinas clay, at Neath, with 
 the result of producing a fire-brick, containing 95 per cent, of 
 silecious matter, and far surpassing in quality anything before 
 known, since for very intense heats, it is found to exceed S tour- 
 bridge in durability four-fold. 
 
 103. Whatever method of working furnaces be employed, 
 constructing the envelope so as to prevent as much as possible 
 the passage of heat, must ever be an unmixed good as far as 
 economy of fuel is concerned, and the better the fire-brick ma- 
 terial employed, the more completely can the principle be carried 
 out, without neutralizing the economy attained in fuel, by the 
 extra expense in repairs, resulting from the increased rapidity 
 with which the bricks are burnt out. By constructing furnaces 
 with hollow walls, and filling the intervening space with cinder 
 dust, or some other incombustible bad conductor of heat, a great 
 saving of fuel might be effected ; but to what extent this would 
 be counterbalanced in an economical point of view, by the 
 increased amount of materials and labour necessary to keep them 
 in repair, with the quality of fire-brick generally in use at present, 
 I am not prepared to say. 
 
ECONOMY OF FUEL. 47 
 
 SECTION VI. 
 
 ON FEEDING FURNACES WITH HOT AIR. 
 
 104. To discover the amount of saving in the consumption 
 of fuel, capable of being attained by the entire substitution of 
 hot air for cold, where such air is heated from the waste products 
 of the furnace itself (and which, as far as I am aware, has not 
 before been attempted), I instituted the following calculation : 
 
 According to the recent researches of Andrews, 1 part of 
 carbon will raise 14,220 parts of water 1, and 1 part of hy- 
 drogen will raise 60,854 parts of water 1. 
 
 Now if the specific heat of carbonic acid be called '22, that 
 of nitrogen '27, and that of steam *847, then carbon, inflamed 
 with its exact equivalent of oxygen to form carbonic acid, will 
 produce an atmosphere of 17,628, and with its exact equivalent 
 of atmospheric air, an atmosphere of 4,058; hydrogen, with its 
 exact equivalent of oxygen to form vapour, an atmosphere of 
 7,982, and with its exact equivalent of atmospheric air, an 
 atmosphere of 3,871. 
 
 105. Assuming 100 parts of coal to consist of 80 parts of 
 carbon, and 5 of hydrogen, which is in the proportion of 16 
 parts of the former, to 1 of the latter, and leaving out of view 
 the 15 parts of miscellaneous matter as unessential, then, since 
 carbon, inflamed with its equivalent of air, produces a tempera- 
 ture of 4,058, and hydrogen of 3,871, coal, if compounded of 
 carbon and hydrogen, in the proportion of 16 parts of the former 
 to one of the latter, would produce an atmosphere of 4,047. 
 
 106. Considering however the impossibility of admitting 
 just the precise quantity of air to produce this state of theo- 
 retical perfection, the fact that coal contains a small quantity of 
 nitrogen, and also that some heat passes into the sides of the 
 grate, we may pretty safely assume that the heat generated in 
 the body of the furnace, seldom exceeds 3,300, and is probably 
 
48 ECONOMY OF FUEL. 
 
 more frequently below, than above this point. Nevertheless, as 
 this number, which is certainly about what theoretical deductions 
 would lead us to fix upon, coincides with the observation of 
 Professor Daniel with his pyrometer, who found 3,300 to be the 
 greatest heat of an air furnace, I shall adopt it as the basis of 
 my calculation. 
 
 107. Now, as lead, the melting point of which is 600, 
 inelts with extreme rapidity in the hot air flues of a furnace, 
 running* like sealingwax in the flame of a taper, we certainly 
 shall not err on the side of excess, in estimating the temperature 
 of the air at 720, and if we substract 60 for the atmospheric 
 temperature, we get an addition of heat of 660, or y of 3,300, 
 the whole temperature generated, shewing a saving in fuel of 
 20 per cent.; and if, as is probably the case, a portion of the 
 diminution in the heat between the theoretical number 4,047, 
 and that which experiment shows 3,300, is to be attributed to a 
 surplus quantity of air passing through the fire, and lowering 
 the temperature of the furnace, then this per centage of saving 
 by the use of hot air, should be increased. 
 
 108. Having attained to a clear perception of the immense 
 saving of time and fuel, which would accrue in all operations 
 where it is required to impart a temperature nearly equal to that 
 generated (and where consequently the surplus heat is very 
 small), by even a trifling addition to the temperature of the fur- 
 nace, the first method that suggested itself to me for attaining 
 this object, was by supplying the fire with hot air under pressure. 
 Having entered into a calculation for the purpose, and found 
 that an additional quantity of heat equal to 20 per cent, of the 
 whole generated, was to be obtained in this manner, I felt san- 
 guine as to the results to be elicited. Whilst however, time 
 and intensity being disregarded, and looking solely to the total 
 quantity of heat obtainable, I have found the full amount of 
 saving promised by theory, confirmed in practice, my anticipa- 
 tions of an increase in the temperature and heat-imparting powers 
 of reverberatory furnaces, by feeding them with hot air, were not 
 
ECONOMY OF FUEL. 49 
 
 realised. Surprised at this result, which then appeared to me as 
 extraordinary as it was unexpected, and not even a recognition 
 of the fact, much less its solution, being to be found in the lite- 
 rature of the subject, I consulted living authorities for infor- 
 mation, but with no better success. Indeed, I found their minds 
 as much in doubt as to the correct explanation of the apparent 
 anomaly, as my own. Curious, as to the cause of the pheno- 
 menon I witnessed, in occuping myself with its consideration, I 
 have been led to form some conclusions on the subject, which I 
 will lay before the reader. 
 
 109. I must premise, that the temperature of flame* is greatly 
 above that required for the ignition, and white heat of solid 
 bodies, as is shown by the fact, that during the slow combustion 
 of gaseous bodies, when the heat developed is not sufficient to 
 render the gaseous matter itself luminous, it is nevertheless 
 adequate to produce ignition in solid bodies exposed to it. 
 
 110. Mame, indicates the intense concentration of heat which 
 has place, is present, or comes into being, at the moment of 
 Us (i. e. flame's) generation by chemical combination, before, 
 this heat has become diluted by the resulting expansion. The 
 power of the gaseous products of combustion to communicate 
 heat after their expansion, and when flame has disappeared, 
 is weak and feeble, compared with the direct action of the 
 latter. The more completely the body of a reverberatory 
 furnace is filled with the flame of bicarburetted hydrogen, the 
 more efficient is its working condition. A stream of bicar- 
 buretted hydrogen gas, mingled with its exact combining equiva- 
 lent of atmospheric air (or fifteen times its own bulk), propelled 
 cold from the grate, and only ignited as it passed over the bridge, 
 and was in the act of entering the body, or working chamber of 
 the furnace, would be the acme of perfection, where the power 
 of rapidly imparting intense heat is required. The combustion 
 which takes place in the grate, is in reality not only useless, but 
 injurious, except as far as generating gas is concerned ; inasmuch 
 
 * A filament of platina may he fused in the flame of a common candle. 
 
 D 
 
50 ECONOMY OF FUEL. 
 
 as the larger the proportion of the rarefied products of the com- 
 bustion accomplished in the grate, passing through the working 
 chamber, the smaller will be the amount of fas flame-yielding gas, fas 
 power of which to impart heat, we have seen to be so vastly superior. 
 
 111. One cause of the impaired heat of reverberatory 
 furnaces supplied with hot air, must then be sought in the fact, 
 that gaseous combustion being accelerated by it, a larger amount 
 of chemical union takes place in the grate, and less in the body of 
 the furnace, where it would be more beneficial. This result may 
 to a certain extent be counteracted, by shortening the bridge and 
 fire-grate, in the line of the longitudinal axis of the furnace, and 
 perhaps, in certain cases, it might also be advisable, to make a 
 similar alteration in the body of the furnace itself. 
 
 112. The next point to which I shall call attention, as one 
 of the causes of the diminished heat of reverberatory furnaces 
 supplied with hot air, is, the greater state of expansion and 
 tenuity, attained by the mixture of air and coal gas, prior to 
 inflammation, and the consequent result, that in a given space 
 there is a less quantity of heat developed by their union. There 
 is, no doubt, more heat contained in the products of combustion 
 from a given weight of coal gas and air, heated before ignition to 
 720, than would be contained in the products of the combustion 
 of the same quantities by weight, of gases ignited at the tempera- 
 ture of 60. When we take given measures however instead of 
 given weights, the case is reversed. Gases at 60, expand -g^-g 
 of their bulk for each degree of heat imparted, so that their bulk 
 at 720, compared with their bulk at 60, is as 2'3 to 1. Con- 
 sequently a given space filled with coal gas and air at 60, will 
 contain 2*3 times the weight, of the same measure of these mixed 
 gases at 750, and would develop 2 '3 times the quantity of heat 
 by combustion. Making an allowance however of 20 per cent, for 
 the heat already prese at in the gases at 720, the result will be, 
 that supposing 1000 parts of heat to be contained in the products 
 of the combustion of a given bulk of coal gas and air at 60, only 
 521 parts, or little more than half the quantity, will be contained 
 in the products of the combustion of an equal measure of these 
 
ECONOMY OF FUEL. 51 
 
 mixed gases at 720. Hence the flame resulting, is characterised 
 by comparative tenuity. 
 
 113. Now there can be no doubt as to the fact, that the 
 average temperature of the mixture of air and coal gas which 
 escapes combustion in the grate, to be ignited in the body of 
 the furnace, is higher when the furnace is fed with hot air, than 
 with cold, and we have already seen, that variations in the state 
 of rarefaction of gases prior to ignition, produce a potent prac- 
 tical effect, with regard to the capacity of a given volume, for 
 imparting heat. On the supposition that the area of the working 
 chamber of a reverberatory furnace, is equally divided between 
 the products of combustion of the gases which have combined in 
 the grate, and those still remaining to be inflamed; that the 
 temperature of the latter when the furnace is fed with cold air is 
 568, and when with hot air 898, this would give a deficiency of 
 17 per cent, in the amount of heat furnished by the combustion 
 which takes place in a given time in the body of the furnace, an 
 estimate which I think can scarcely be beyond the truth. 
 
 114. The third, and last circumstance that I have to adduce 
 in explanation of the effect of hot air in diminishing the heat of 
 the working chamber of reverberatory furnaces, is, that from the 
 greater tenuity of the air, it does not produce the same frottement 
 and attrition, in its passage through the fuel, nor (owing to its 
 less sudden expansion) the same amount of quasi detonation or 
 percussion, at the instant of combustion. The disintegration of 
 the carbon, being thus retarded, at the same time that the escape 
 of the hydrogen, is facilitated by the heat, the result is, that the 
 ordinary relation between the rate of consumption of these two 
 constituents of the coal is deranged, and the gases passing from 
 the fuel, contain an undue proportion of hydrogen, whilst the 
 carbon accumulates as cinders on the bars. If the specific 
 gravity of air at 60 be termed 1, then the specific gravity of air 
 at 720 will only be *434, or considerably less than half, so that, 
 moving at the same velocity, the force of impact becomes 
 diminished more than two -fold. If we now picture to ourselves 
 the effect of a pair of kitchen bellows, and how rapidly the 
 
 D 2 
 
52 ECONOMY OF FUEL. 
 
 cinders are disintegrated before the stroke of the blast, and then 
 imagine the diminished effects that would ensue, were the force 
 with which the air strikes the carbon diminished to less than 
 half, we shall readily understand why the combustion of the 
 carbonaceous portion of the fuel, proceeds more slowly when the 
 furnace is fed with hot air, than with cold. 
 
 115. On this theory we should be led to expect a con- 
 siderable difference in the adaptability of different varieties of 
 coal for use with hot air, an inference fully carried out by prac- 
 tice. There is a great variation as to the increased ratio with 
 which the cinders accumulate on the bars, according as the tex- 
 ture and composition of the coal, render the disengagement of the 
 carbon more or less facile, and there can be little doubt but that, 
 coeteris paribus, the more the carbon of a fuel is disposed to 
 assume the gaseous form, as with cannel coal or the less the 
 quantity of hydrogen present, as with anthracite the greater 
 will be the chance of being able to seize the economic advan- 
 tages attendant upon the increased quantity of heat attainable 
 by the use of hot air, without having this heat so diluted, as to 
 make the temperature inefficient. 
 
 116. It doubtless will excite the surprise of many to see an 
 increase in the proportion of the hydrogen to the carbon, given as 
 a reason for the falling off, in the temperature of a furnace, as it 
 is a very common error to suppose hydrogen to be a much more 
 efficient agent in generating heat than carbon. Such is un- 
 doubtedly the case weight for weight, but requiring 36 times 
 its own weight of air for its combustion, whilst carbon only re- 
 quires 12 times, and its product steam, having a"] much greater 
 specific heat than carbonic acid, it docs not produce by com- 
 bustion with atmospheric air so high a temperature. For per- 
 fect combustion, 
 
 vol. vol. vol. temper. 
 
 vol. volumes steam COs* nitrn. generated 
 
 1 of hydrogen requires 2 of air, product 102 4,303 
 
 1 of carbd. hydrogen 10 of air // 2 1 8 4,337 
 1 of bi-carbd. hydrogen // 15 of air // 2 2 12 4,341 
 
 *C0 2 is the chemical symbol for carbonic acid, and denotes it to be com- 
 posed of one atom of carbon, and two atoms of oxygen. 
 
ECONOMY 01' FUEL. 53 
 
 117. It is however in its deficiency in heating power with 
 reference to its volume * that we must seek for the cause of 
 the diminution of temperature which occurs in practice, by 
 substituting hydrogen for carburetted hydrogen. The difference 
 between the quantity of air required by equal volumes of the 
 two gases is so great, amounting as we have seen to four- 
 fold, that with furnace arrangements adopted for carburetted 
 hydrogen, that is, calculated to allow 10 volumes of air to pass 
 with each volume of gas, it is next to impossible but that just in 
 proportion as hydrogen is substituted for it, does the quantity of 
 air passing, become an injurious excess. 
 
 118. It thus appears that three circumstances, 1st, an 
 increased proportion of the combustion being completed in the 
 grate, 2ndly, the higher temperature and consequent rarefaction 
 attained by the gases prior to ignition, and 3rdly, the retarded 
 disintegration of the carbon on the grate bars, (and the resulting 
 diminished quantity of combustible matter passing in a given 
 time, and undue preponderance of hydrogen) all combine to 
 neutralize where a very high temperature is demanded the 
 economy, which might otherwise be attained by feeding the fire 
 of reverberatory furnaces with hot air,- by attaching to the 
 practice, the condition, that just in proportion as it is carried 
 out, does the flame in the working chamber become attenuated, 
 and its power of rapidly imparting intense heat impaired. 
 
 119 To what extent impregnating the hot air with which the 
 furnace is fed, with steam, by carrying water into the ash-pit, 
 would prove a remedy for some of these evils, is an interesting 
 subject for inquiry. The steam coming in contact with the 
 ignited carbon would be decomposed, its oxygen would combine 
 with the carbon, whilst the hydrogen would be disengaged, and 
 pass off with the other gases from the fuel, to be ignited in the 
 furnace chamber. It is a vulgar error to suppose that the whole 
 amount of heat obtainable from fuel, is increased by the employ- 
 ment of water, for precisely the same amount of heat which is 
 
 * If the heating power of 1 volume of bi-carburetted hydrogen = 100, 
 that of hydrogen is only 21'4 3 and that of carburetted hydrogen 71*4, 
 
54 ECONOMY OF FUEL. 
 
 given out by the hydrogen when it enters into combustion and 
 forms water, must have been previously abstracted from the 
 ignited fuel in the grate, to effect the decomposition of the water. 
 What takes place is not, correctly, speaking &gain of heat, but a 
 transfer. The plan is an expedient for increasing the flame in 
 the body of the furnace, at the expense of the glow fire on the 
 fire-grate bars, thus transferring heat from the grate, where it is 
 not wanted, to the working chamber, where it is most required. 
 
 SECTION YII. 
 
 ON THE ECONOMIC APPLICATION OF HEAT. 
 
 120. HOWEVEK complete may be our arrangments for attain- 
 ing perfect combustion, and eliciting from the fuel the whole of 
 the heat it is capable of furnishing ; unless we at the same time 
 employ judicious measures for applying the heat thus obtained, 
 to the best advantage, our previous successful efforts for the 
 attainment of economy in its generation, may be rendered 
 nugatory. 
 
 121. At an early period of my inquiries into the question of 
 economy of fuel, I felt curious to know, what proportion of the 
 whole heat generated in a reverberatory furnace for the manu- 
 facture of iron, actually entered the iron, and what proportion 
 was dissipated and lost. Finding no information extant on the 
 subject, and thinking.it an interesting point to determine the 
 theoretical heating power of fuel in relation to iron, and con- 
 trast it with that actually obtained, I made the calculation which 
 I here subjoin. So much doubt however hangs over the ques- 
 tion of the exact specific heat of iron at high temperatures, 
 that the results attained are not entitled to be considered as 
 absolutely exact, but merely as offering a tolerably near ap- 
 proximation to the truth. 
 
 122. The consumption of coal in a puddling furnace in Staf- 
 fordshire, is . weight for weight, that of the pig iron worked. 
 
ECONOMY OF FUEL. 55 
 
 Cast iron melts at 2,786 by Daniel's pyrometer. Say the iron 
 is raised in the furnace to 3,060, and allow 1,000 for its latent 
 heat, this makes 4,000 imparted. The specific heat of iron 
 at 212 is *11; like other substances, its specific heat increases 
 with its temperature, and is at 662, which is the highest point 
 that has been ascertained by direct experiment, '125. From a 
 consideration however of the amount of heat communicated by 
 melted cast iron, to known quantities of ice or water, determined 
 by M.M. Clement and Desormes, in connexion with its melt- 
 ing point, as fixed by Daniel, I consider myself warranted in 
 assuming, that if I double its specific heat at 212, viz. -11, and 
 call it, at the high temperature it attains in the furnace, -22, a 
 number higher than has yet been assigned to it, I cannot be 
 below the mark. 
 
 123. If then we assume that 4,000 of heat is imparted 
 to the iron in the furnace, that the specific heat of iron is 
 22, that of water being 1, since, lib. of coals is capable of 
 raising lib. of water 14,220, -^2. = 16/159, tlie num b er 
 of pounds of iron, lib. of coals is capable of raising 4,000. 
 Showing that in the present puddling furnace, the quantity of 
 coals burnt, is sufficient to generate more than sixteen times 
 the quantity of heat contained in the iron at any period of 
 the operation. 
 
 124. In reverberatory furnaces used for melting cast iron, the 
 quantity of coals employed is 15 cwt. to the ton of iron, or f 
 the weight of iron ; showing, according to the previous calcula- 
 tion, that in the simple process of melting, a quantity of coals is 
 burnt, more than twelve times sufficient to generate the heat 
 actually imparted ; a state of things certainly not discouraging 
 the belief, that increased economy is attainable. In expressing 
 this opinion however, I do not wish to be understood to advocate 
 the chimerical notion, that the whole, or nearly the whole of the 
 heat generated, can ever be made to enter the iron. 1 have, on 
 the contrary, already stated, as a law hitherto comparatively 
 disregarded that it is only the difference, by which the tempera- 
 
56 ECONOMY OF FUEL. 
 
 ture of the atmosphere of the furnace, exceeds that of the objects 
 subjected to it, which can be counted as available heat, for in- 
 creasing the temperature of the latter, and consequently, that as 
 the heat of the iron increases in intensity, an increased propor- 
 tion of the heat generated by the fuel must pass out of the 
 furnace unabsorbed. 
 
 125. The same considerations do not however apply to steam 
 boilers. Here the temperature of the heat-receiving body, never 
 exceeds a comparatively low point, and the heat of the furnace 
 consequently always preserves so great a preponderance, that 
 only a small fractional part of the heat generated, say from 10 
 to 15 per cent., need be allowed to pass away by the flue un- 
 absorbed. 
 
 126. A peculiarity attached to steam boilers however, which 
 has interfered with their reaping the full benefit of their favour- 
 able position in this respect, is, the necessity that exists for con^ 
 fining the flues to the lower portion of the boiler, and withdraw- 
 ing them from contact with its surface, as soon as they reach to 
 within about the height of a foot below the water level. If 
 carried higher, the sides of the boiler above the water level are 
 apt to become unduly heated. "Whilst in this condition, the 
 tenacity of the iron is dangerously lessened,* and if such a state 
 of things be of frequent occurrence, the texture of the metal 
 becomes permanently impaired, and changed from fibrous to 
 crystalline. When this alteration in its physical structure has 
 once taken place, there is an end to all safety; its strength can 
 never be relied upon, and it is quite unfit to cope with any extra 
 demand upon its powers of resistance. 
 
 127. When an engine is at work, the surface of the water is 
 kept in a constant state of agitation, and fluctuates at each stroke 
 of the piston, with the fluctuations in pressure consequent 
 upon the periodic emissions of steam. When the engine is 
 
 * At the temperature of 720, the strength of the boiler plate becomes 
 impaired nearly 20 per cent, and the accidental over heating of a boiler, has 
 been known to diminish its strength more than 30 per cent. 
 
ECONOMY OF FUEL. 57 
 
 stopped, on the contrary, the pressure being steady and uniform, 
 the surface of the water becomes comparatively quiescent. At 
 such periods, should the flues be 'too near the surface, and the 
 heat creep up the sides so as unduly to raise the temperature of 
 the sides of the boiler immediately above the water, (now no 
 longer incessantly wetting and cooling them with its pulsations,) 
 it too often happens that upon the engine being set at work again, 
 and the pulsations recommencing, the water, washing against the 
 dry heated iron, is instantaneously flashed into steam, and a fear- 
 ful explosion, scattering ruin and death around, is the result.* 
 
 128. To obviate the danger of such lamentable catastrophes 
 on the one hand and on the other to release the upper half 
 of the boiler from the embargo on its usefulness which forbids its 
 being employed as a generating surface, and restricts the sphere 
 of its operations to serving as a mere reservoir for the steam - 
 I would propose to line it with some fibrous and porous mate- 
 rial capable of sucking up water by capillary attraction, such, for 
 instance, as course hempen cloth. This fibrous coating being 
 kept in close apposition with the interior surface of the upper 
 part of the boiler by means of a wire net work, and its low^r 
 edge descending on all sides to, or below the surface of the water, 
 capillary attraction causes the water to ascend, as fast as i'j be- 
 comes evaporated, in the same way as oil or spirit ascend?, in the 
 wick of a lamp. The sides of the boiler above the water level 
 are thus constantly kept moist, and the possibility of their at- 
 taining a dangerous temperature prevented, at the same time 
 that the wetted fabric in the interior, presents an additional sur- 
 face for the generation of steam, thus uniting safety with 
 economy. 
 
 * In confirmation of this view of the most frequent cause of explosions, 
 it is a fact, that the great majority, occur immediately after an engine which has 
 been stopped, recommences working and has made one or two strokes, and 
 not during the time it is stopped, when the pressure, according to the preva- 
 lent theories which attribute explosions to 0-acting safety valves, might be 
 expected to be greatest. 
 
 D 3 
 
58 ECONOMY OF FUEL. 
 
 SECTION VIII. 
 
 ON THE EMPLOYMENT OF WASTE HEAT. 
 
 129. SINCE I have shewn that the amount of necessary or 
 rather unavoidable waste heat passing out of the furnace, in- 
 creases with the temperature we require to impart, it follows, 
 that in proportion as the processes we carry on in our furnaces 
 require an intense heat, does the necessity for attending to this 
 feature of economy increase, and that in none is it of higher im- 
 portance, or capable of being made a greater element of saving, 
 than in furnaces for the manufacture of iron. 
 
 130. To impress this distinction more closely upon the 
 reader, I will contrast the circumstances of an iron furnace, with 
 those of a steam boiler. In the former, the flame makes one 
 short and rapid dart or transit, in a straight line and in one body 
 from firebridge to fluebridge. To facilitate the comparison, I 
 shall estimate the long and winding, or else subdivided flues of 
 the latter, as equivalent to four short and rapid transits ; and 
 the temperature of the successive portions of the surface of the 
 boiler traversed by the heated gases, at 500, 400, 300, and 
 300, respectively. 
 
 131. Assuming then, the temperature generated by a steam 
 boiler furnace to be 3,000, and that during the first transit, when 
 the excess of temperature is 2,500, half the surplus heat is im- 
 parted, the following table shews the quantity of heat transferred 
 at each transit, and the amount remaining in the products of 
 combustion at the moment of their quitting contact with the 
 boiler. Column A is supposed to shew the temperature of the 
 atmosphere of the furnace, B that of the boiler surface in con- 
 tact with A, C the surplus by which A exceeds B, and D the 
 quantity of heat transferred during each transit. 
 
ECONOMY OF FUEL, 59 
 
 A B C 1) 
 
 1st transit 3000 500 2500 1250 
 2nd transit 1750 400 1350 589 
 
 3rd transit 1161 300 861 331 
 
 4th transit 830 300 530 187 
 
 leaving 643 for the temperature of the products of combustion 
 
 at the moment of their leaving the boiler. 
 
 132. The preceding calculation is given as an illustration, 
 and does not claim to be strictly accurate, still considering the 
 figures are the actual result of the first hypothesis I made ; the 
 coincidence of their results with regard to the temperature 
 at which the gases enter the chimney, with what we know 
 to be the fact, is certainly remarkable, and affords ground 
 for believing, that except in the suddenness of the transitions, they 
 present a far from inaccurate approximation to what really takes 
 place. A comparison between this table of the conditions which 
 exist in a steam boiler, where the waste heat passing away 
 seldom exceeds more than i of that produced, with those of an 
 iron furnace (see paragraph 99), where the waste heat, beginning 
 at -il, gradually rises to ff of the whole heat generated, will 
 make sufficiently clear, the much greater necessity that exists for 
 employing some means for utilizing the waste heat in the case 
 of the latter, than in that of the former. 
 
 133. Here, it is most particularly, that the advantages of 
 working with compressed air become apparent ; for it is evident, 
 that as long as this system is neglected, and the draught made 
 to depend entirely upon the state of rarefaction in the stack, if 
 we abstract more than a limited amount of heat ^from the gases 
 passing through this channel, we shall lessen the amount of 
 rarefaction, beyond what is compatible with the keenness of 
 draught required. 
 
 134. The system still adopted in many iron works of 
 discharging the products of combustion from the stacks of the 
 puddling and mill furnaces unused, and getting up the steam in 
 the steam boilers by means of separate fires expressly for the 
 
60 ECONOMY OF FUEL, 
 
 purpose, exhibits an inexcuseable disregard of economy. Even 
 supposing as is doubtless the case that under the present 
 system of working exclusively by draught in the stack, the ag- 
 gregate number of furnaces are adequate to supply sufficient heat 
 to generate steam for the exigencies of the work itself; yet there 
 are so many manufacturing and other industrial operations for 
 which steam is requisite, that might be carried on without any 
 inconvenience in immediate juxtaposition with an iron work, and 
 carried on advantageously, inasmuch as no outlay for fuel for the 
 generation of steam need be incurred, that there is no reason 
 beyond supineness, why the present wasteful system should be 
 perpetuated. On the contrary, economy dictates that all the 
 surplus heat should be carefully preserved and conducted to one 
 extremity of the premises, there, to be in readiness to let out for 
 hire, for the purposes of any other manufacturing establishment 
 which might be carried on adjoining such, for instance, as me* 
 chanical engineering, saw mills, flour mills, cotton, woollen, and 
 flax factories, candle making, soap boiling, baths and wash- 
 houses for the workmen, &c. In short, so various are the pro* 
 cesses, and multifarious the elegible channels for the employment 
 of surplus heat, that the present system of waste, is quite in* 
 defensible. 
 
 135. The quantity of coal consumed in a puddling furnace is 
 2401bs. per hour, which, reckoning 7^1bs. of coal per horse power, 
 is sufficient to generate steam for 32-horse power. We have seen 
 that the quantity of heat actually imparted to the iron, is but a 
 small fractional part, -j 1 ^, of the whole heat generated, and it will 
 therefore be a fair supposition to say, that by the use of com- 
 pressed air, one half of the whole heat generated might be prac- 
 tically applied to the raising of steam. This would equal 16- 
 horse power, or more than three-fold the quantity now available 
 under the system of relying exclusively for the draught upon 
 rarefaction in the stack. Taking however the extra heat capable 
 of being released by the use of compressed air, at 10-horse power, 
 
ECONOMY OF FUEL. 61 
 
 we shall have in an iron work containing 100 furnaces, a con- 
 stant unnecessary waste of heat equal to 1,000-horse power, re- 
 presenting a waste of coals per year of 300 working days, of 
 24,107 tons, equal in money at 5s. per ton to 6,026, an amount 
 of waste, which cannot but excite the regret of all who desire 
 to see our national resources and productive powers turned 
 to their best account. 
 
 136. In short, heat may, and should be regarded, as equiva- 
 lent to poiver, labour, time, money; all are mutually convertible, 
 and if considered in the right point of view, it is just as absurd 
 to waste one, as the other. 
 
 SECTION IX. 
 
 ON THE MANUFACTURE OF IRON. 
 
 137. The manufacture of iron has been brought to its pre- 
 sent grade of perfection by practice, rather than by theory. Till 
 the development of the science of chemistry characteristic of the 
 present age, (which has made a contrary course a possibility), such 
 has always been the case with the arts at their commencement. 
 
 138. A time however is probably not far distant, when 
 science will vindicate her claims to utility, in this, as in other 
 departments of human knowledge, and exert as beneficial an in- 
 fluence over the manufacture of iron, as she has already exercised 
 over various kindred arts. 
 
 139. One great cause hitherto of the failure of scientific 
 theories when applied to iron making, I am inclined to ascribe to 
 our ignorance of the chemistry of high temperatures, a branch of 
 the science most imperfectly understood, and the prosecution of 
 which by experiment, is necessarily beset with great difficulties. 
 
 140. Affinities vary with temperature, and we do not at 
 present know, all these variations. We are accustomed to regard 
 
62 ECONOMY OF FUEL. 
 
 sulphuric acid as the most powerful of the acids, and phosphoric 
 acid as among the weakest, and such is the case at ordinary 
 temperatures ; but if gypsum (sulphate lime), is heated to redness 
 with phosporic acid, the sulphuric acid will be driven off, so 
 extraordinary is the change in affinity wrought by the access of 
 heat. At a slightly elevated temperature, potassium will take 
 the oxygen from the carbon of carbonic acid, but at a white heat, 
 the reverse takes place, and potassium is prepared by subjecting 
 carbonate of potash with charcoal to the heat of a furnace. At a 
 temperature above the freezing point, salt has no affinity for 
 water, and crystallises in anhydrous cubes ; whilst below the 
 freezing point, it crystallises in prisms, which consist of a chemi- 
 cal union of salt and water, the bonds of affinity between which, 
 the warmth of the hand is sufficient to destroy. If necessary, 
 numerous other examples might be adduced, all conclusively 
 showing that the chemical affinities of bodies are dominated by 
 temperature. 
 
 141. Another circumstance not without its influence in 
 throwing difficulty in the way of the application of science to 
 the manufacture of iron, has been the large masses of solid 
 materials operated upon, so different from the manageable 
 quantities of the laboratory, and the consequent difficulty of 
 realising that condition of chemistry, which exacts a thorough 
 commingling of the particles of matter operated upon, requiring 
 as a preliminary for its attainment the attraction of cohesion 
 in solid bodies to be removed by solution or fusion. Hence 
 the importance of obtaining in the hearth of the blast furnace, 
 a state of fluidity sufficiently perfect, to allow of the complete 
 segregation of the various matters according to their respective 
 polarities, without which, various crudities and undeoxidised 
 impurities, are carried down with the metal. 
 
 142. Chemical union however takes place only at im- 
 perceptible distances, atom must unite with atom, and some- 
 thing more than perfect fluidity is required to produce in many 
 cases a minute commingling, of bodies varying greatly in specific 
 
ECONOMY OF FUEL. 63 
 
 gravity or consistency.- We might for example, stir quicksilver 
 and water together for an hour, without having placed more than a 
 very limited number of their particles in contact. This comparison 
 is but an exaggerated illustration of what takes place in a pud- 
 dling furnace, when it is attempted to improve the quality of 
 the iron by an artificial flux. So imperfectly are the particles of 
 iron subjected to its operation, that either no appreciable effect 
 is produced, or only a partial effect, causing a want of homo- 
 geneousness in the texture of the iron, thus manufactured. 
 
 143. It is certain, that the quality of the iron made, is greatly 
 influenced by the nature and quality of the alkalies, alkaline 
 earths, and other fluxes present, provided we can present them in 
 such a state of minute subdivision and dissemination amongst the 
 other materials, as will ensure their chemical agency being exerted 
 with the best effect. A great part of the beneficial influence of 
 charcoal, in the manufacture of iron, arises in my opinion, from 
 its containing in this state of minute subdivision, small quantities 
 of potash, lime, magnesia, phosphoric acid, and manganese, which 
 it constantly and gradually presents to the process going forward, 
 in a quantity precisely proportionate to the rate at which the 
 combustion, and consequently the process contingent upon the 
 combustion proceeds, and I anticipate that great advantages may 
 be obtained, by judiciously attempting to imitate those conditions, 
 the value and utility of which, in the case of charcoal, are amply 
 sanctioned by experience. The manner in which I would propose 
 to do so, would be, by immersing coke in alkaline or other 
 appropriate solutions, which might be forced into its pores by 
 hydraulic pressure if desirable, thus producing an imitation of 
 charcoal, which after being thoroughly dried, might be advantage- 
 ously substituted for common coke, in the manufacture of iron. 
 
 144, The composition and strength of the flux solution, 
 should of course vary with the nature of the ore, and the com- 
 position of the ashes of the fuel. Even where charcoal is em- 
 ployed, it might be advisable in certain cases to increase the 
 natural quantity of alkali it contains, by treating it in the same 
 way. 
 
64 ECONOMY OF FUEL. 
 
 145. That an improvement would be effected in the quality 
 of the iron produced by the adoption of this system, particularly 
 in the case of silecious and clay ores ; does not admit of doubt ; 
 for the ashes of coal are not only wanting in those active fluxes 
 possessed by charcoal, but contain a considerable portion of silex : 
 and if, as appears to me most probable, the alloy of silicon the 
 most general and influential cause of bad pig iron is principally, 
 if not exclusively, furnished by the silex of the fuel, the most 
 feasible preventitive would appear to be, to force a powerful base, 
 into the pores of this material, and thus place it in immediate 
 contact with the silicic acid, with which its union is desired. If 
 this be not done, the silica intimately blended with the carbon, 
 throughout the structure, of the coke and necessarily exposed 
 from this association to the most intense heat, can scarcely fail 
 of becoming deoxidised. 
 
 146. The requirements for making iron, are, 1st, the re- 
 quisite chemical ingredients* in the requisite proportions ; 2ndly, 
 sufficient heat,=fluidity, to allow of the free motion of all the 
 particles of matter ; Srdly, sufficient motion amongst the particles 
 to ensure their adequate intermixture. 
 
 147. This view of the innocuousness of a high temperature, 
 does not agree with the generally received opinion, that the 
 inferiority of the iron resulting from the use of hot blast, is 
 occasioned by the greater heat of the furnace, a fact I am by no 
 means prepared to admit. 
 
 148. That the temperature of the furnace is higher, where 
 hot blast is used, than with cold, seems always to have been 
 regarded as a position so clear and self-evident as to require 
 no demonstration and if erroneous, as I believe to be the case, 
 it has certainly been a great stumbling-block in our path 
 towards attaining correct ideas of the process of iron manufac- 
 
 * Foremost among these must be considered an adequate supply of 
 oxygen to burn off the sulphur, phosphorus, and arsenic, and preserve the 
 silicic acid, lime, and magnesia from deoxidation, and thus prevent the forma- 
 tion of metallic alloys, or if this (probably correct) term be objected to 
 with regard to the first-named substances, say in their case, sulphurets and 
 phosphurets. 
 
ECONOMY OF FUL, 65 
 
 ture, with the consequent improvement in the art, which might 
 therefrom be expected. 
 
 149. At the temperature to which the blast is heated, air is 
 more than doubled in volume ; therefore, there will be double 
 the number of atoms of oxygen in the same space, when the 
 blast is cold, and consequently a much more rapid evolution of 
 heat from the surface of the carbon exposed to the direct action 
 of the blast; the stroke also will be of double the weight, 
 producing a more rapid disentegration of the carbon, and a 
 more thorough dissemination of it amongst the other materials. 
 
 150. The effect of the cold blast on the surface of the ore 
 will be refrigerating, and the same must be said of its impact 
 on the limestone flux, but I see no reason to conclude that the 
 refrigerative effect in the last two instances, more than counter- 
 balances the increased temperature evolved by the surface of 
 the carbon. Therefore immediately before the tuyeres, at the 
 point where the most perfect fusion takes place, I see no 
 reason for believing that the temperature of a hot blast furnace, 
 exceeds that of a cold blast, but rather the reverse ; inasmuch as 
 I conceive, that a larger quantity of oxygen will combine with 
 carbon, in a given space within a given time, in the latter fur- 
 nace, than in the former : a sufficiently larger quantity in fact, to 
 more than counter-balance the additional initial heat of the air, 
 before the expansion* due to the combustion, and therefore 
 necessarily ensuing subsequently to it, has taken place. 
 
 * An atmosphere of 4,000 condensed to th of its volume (or what is the 
 same thing gaseous products of combustion at that point of expansion where 
 they have only reached 3-th of their ultimate bulk) will have^a temperature of 
 about 7000, and when condensed to half their ultimate volume a temperature 
 of about 5000. Here we get at the cause of the great heat of flame, and 
 the superiority of the direct action of flame, or the radiant heat from an 
 ignited surface of carbon, for communicating heat (e. g. raising steam) over 
 products of flame after expansion, see on this subject, paragraphs 109 & 110. 
 
 Air of 60 has its volume increased to 
 
 Double at . . . 568 I Fivefold at . . .2092 I Eightfold at . .3616 
 Threefold at . . 1076 Sixfold at . . .2600 Ninefold at . .4124 
 
 Fourfold at . .1584 | Sevenfold at . .3108 | Tenfold at . . .4032 
 
66 ECONOMY OF FUEL. 
 
 151. After expansion has taken place, the temperature of 
 the hot blast furnace will of course exceed that of the cold blast 
 furnace at the same point, by the excess of the initial temperature 
 of the air, and the same may be said of any two localities in the 
 furnaces where the same degree of expansion exists. When the 
 carbonic oxide zone is reached, although the difference remains 
 the same, yet from the great diminution of temperature, the 
 disproportion between the heat of the two furnaces becomes 
 very marked. Say coke in forming carbonic acid imparts to 
 the combining equivalent of air 4058, suppose the temperature 
 of air 42, this will give an atmosphere of 4100; assume that 
 the volatilization of the carbon, necessary to transform carbonic 
 acid, into carbonic oxide, absorbs 60 per cent, of this heat, and 
 we have for the carbonic oxide zone, a temperature in a cold blast 
 furnace of 1640, and in hot blast furnace 1640 -f the initial 
 additional temperature of the air, say 560 = 2200 or - more, 
 a difference sufficient to make it not improbable, that the 
 chemical action of the carbon on the ore, may be greatly modified 
 by it. Indeed the stewing of the minerals with their surfaces in 
 a semi-melted state, in an atmosphere of carbonic oxide, with 
 perhaps the addition of the fumes of sulphur, phosphorus, and 
 arsenic, for a considerable period before their descent before the 
 tuyeres, is a vastly more plausible reason for the inferiority of hot 
 blast iron, than the hitherto-received-without-being-questioned 
 theory, which assigns it to the increased heat of the furnace, at 
 the point of fusion. 
 
 152. The circumstance that hot blast furnaces work faster 
 than cold, has been supposed to be quite conclusive as to a 
 higher temperature being attained by them ; a little examination 
 will however shew that the fact affords no foundation for such 
 an inference. If we assume that the perfect fusion of the 
 minerals of a blast furnace requires a heat of 4000, that the 
 temperature of the point of most intense heat in the vicinity of 
 the tuyeres in each description of furnace is the same ,viz. 5,000; 
 since the minerals will in the hot blast furnace, approach this 
 
ECONOMY OF FUEL, 6? 
 
 point at a temperature 560 higher than they will approach the 
 same point in the cold blast furnace, and consequently will 
 require 560 less additional heat imparted to them, to raise them 
 to the temperature of 4000, their melting, will as a matter of 
 course be more quickly performed in the former furnace, than in 
 the latter ; and thus this supposed decisive fact in favour of the 
 higher temperature attained by the use of the hot blast, is 
 satisfactorily explained without leaving any difficulty behind it. 
 
 153. In considering the manufacture of iron with reference 
 to economy of fuel, the most striking thing which forces itself 
 upon the attention, is the fact, that whilst the two great processes 
 of iron making, viz. the separation of the iron from the ore in 
 the blast furnace, and its decarbonization, and kneeding to 
 develop fibre, in the boiling furnace, each requires for its per- 
 formance, and is best performed by, one of the two constituents 
 into which coal is resolvable, taken singly; viz. the revival of the 
 iron, by the solid carbon or coke, and the operation of boiling, or 
 puddling, by the gaseous carburetted hydrogen ; yet strange to 
 say, instead of separating the constituents of coal before using, 
 and employing each for the operation for which it is best suited ; 
 we use it in its raw state for both operations, not only wasting- 
 one constituent in each process, but absolutely producing inferior 
 results. For the gaseous 'portion of the coals used in the blast 
 furnace, which if separated and purified, would suffice to make 
 all the pig-iron produced by the furnace, into puddled-iron, of a 
 quality very superior to that made by raw coal, exercises in the 
 blast furnace a deteriorating effect on the quality of the iron pro- 
 duced. Thus all the coal at present used in puddling is wasted, 
 with the result of obtaining an inferior description of iron. 
 
 154. My notions of attainable perfection demand, that iron 
 should be manufactured as follows : the coal should be coked 
 by the waste heat from the furnaces, and set apart for use in 
 the blast furnaces, having previously as before described, had its 
 pores impregnated with a preparation composed with reference to 
 its power of combining, and forming an easily fusible cinder with 
 
6$ ECONOMY OF FUEL. 
 
 the ashes of the coke on the one hand, and the foreign matter 
 in the ore on the other. 
 
 155. The gaseous products of distillation after being purified 
 from sulphur, and also from phosphorous, and arsenic if present, 
 should be devoted to the process of puddling, for which they are 
 for many reasons much better adapted than raw coal ; in the 
 first place, the dust and fine cinders earned over from the grate, 
 become mixed with, and injure the iron, and the same may be 
 said of various volatile products of the coal ; in the second place, 
 the operation of puddling consists of three different stages, during 
 each of which the iron requires a modification in its treatment, 
 which the present puddling furnace is powerless to supply ; in. 
 fact no prompt nor adequate power of control is possessed by the 
 workman over it, even for simply exalting its temperature, and as 
 far as the scientific performance of its functions is concerned, it 
 must be regarded as a barbarous machine which ought long 
 since to have been superceded. 
 
 156. In the first stage that of melting an intense heat, 
 with no excess of oxygen, will save both time and iron, although 
 it is not so absolutely indispensable in this stage as in the 
 third. 
 
 157. In the second step of the process that of decarboni- 
 zation, or refining an excess of oxygen is wanted, and the 
 addition of the vapour of water is also often beneficial, since it 
 has the power, not only of accelerating the decarbonization of 
 the metal, but also of carrying off large quantities of silicic acid, 
 in a volatile form,* the effect of which in increasing the yield 
 (inasmuch as the silicic acid would otherwise form a silicate of 
 iron, and carry its base into the cinder) is sufficiently obvious. 
 
 158. During the third stage of the process that of kneading 
 the decarbonized iron into a tenacious, fibrous mass an excess 
 of oxygen passing is productive of great loss, from the waste it 
 occasions by oxydizing the pure malleable iron, now no longer 
 
 * An instructive example of the law, that non-volatile bodies may become 
 volatile by mixture with volatile ones. 
 
ECONOMY 6*F Ft'EL. 60 
 
 covered by the cinder. From the circumstance however of a 
 great heat being necessary (requiring a clear fire) during this 
 stage, particularly at its termination, just before the iron is 
 removed from the furnace to go to the squeezer, it is impossible 
 to guard against a surplus of oxygen being present, such is, in 
 fact, always the case under the present system, a considerable 
 loss is unavoidable, and may be considered a perfectly normal 
 result of the operation as earned on in the existing furnaces. 
 
 159. Let us compare with this narration of the inefficiency 
 and unavoidable defects of the present furnace, the advantages 
 placed within our reach by the judicious application of gas. 
 
 160. Suppose a furnace constructed as follows: let the end 
 of the furnace be formed of an iron box, divided vertically (and 
 transversely as regards the body of the furnace) into three 
 divisions; let the outer one be connected with a reservoir of 
 gas under pressure, the middle one with a similar reservoir of 
 air; let a series of tubes (with a slight downward inclination) 
 lead from each of these chambers, through the inner chamber, 
 into the furnace ; let the inner chamber be supplied with water, 
 to prevent the melting of the tubes or tuyeres. Since the quan- 
 tity of an elastic fluid, which passes in a given time, through a 
 pipe of a certain diameter, under a given pressure, is easily 
 ascertained, we thus possess it in our power to apportion the 
 quantity of air and gas to each other with the greatest nicety, 
 according to our varying requirements. 
 
 161. The pipes leading from the main reservoirs of gas and 
 air to the chambers of the furnace, should each be furnished with 
 a throttle valve, the handle of which should form the index to a 
 dial, graduated to 100 subdivisions; and the size of the pipes 
 and the valves should be so arranged, that when the indexes 
 pointed to the same figures on the dials, the respective quantities 
 of air and gas passing, should be the exact combining equivalents 
 of each. 
 
 162. As it would be desirable to have a surplus heating 
 power, beyond that demanded for ordinary working, for extra- 
 
70 ECONOMY OF FUEL. 
 
 ordinary occasions, such as getting up the heat after the furnace 
 had been allowed to get cold, &c., we will suppose, that upon 
 charging with fresh iron, the hands of both dials are placed at 
 75, for the first stage of the operation. The inclination of the 
 tuyeres driving the name downwards directly on the iron, it will 
 be melted and brought to the proper point of fluidity, in about 
 half the time occupied by the present furnace, where the axis of 
 the draught being horizontal, and the iron lying completely 
 below it, by far the larger portion of flame darts over it, and 
 enters the flue without having at all impinged on the iron. In 
 fact, the difference in the mode of operation of the two furnaces, 
 is the difference between placing a body at the point of the flame 
 of a blowpipe, and placing it at the exterior of its under side. 
 
 163. The next stage of the operation that of refining, or 
 decarbonization requires a surplus of oxygen to be present, to 
 obtain which, the workman moves the index of the air pipe, say 
 to 90 (the index of the gas pipe remaining stationary at 75), and 
 turns on in addition, if thought desirable, a supply of steam into 
 the air chamber, to pass, with the air, into the working chamber. 
 That such a furnace would be a better instrument for refining 
 iron than our present one, cannot admit of a doubt, whilst it is 
 equally unquestionable that it would do its duty in less time. 
 
 164. During the third stage of the operation, a very intense 
 heat is required, particularly just at the latter end, whilst, at the 
 same time, it is of vital importance to prevent the waste of the 
 now undecarbonized and exposed iron to ensure that a surplus 
 of oxygen be not present. Let the workman set the index of 
 the gas pipe at 95 (the air pipe index remaining, as before, at 
 90), thus guarding against the possibility of any free oxygen 
 reaching the iron through imperfect mixture, by supplying a 
 slight excess of carburetted hydrogen, and both conditions will 
 be fulfilled. 
 
 165. In short, whatever the requirements demanded by the 
 progress of the operation, this furnace places at our disposal the 
 means of fulfilling them instantly and completely ^ furnishing in 
 
ECONOMY OF FUEL. 71 
 
 this respect, a complete contrast to the imperfect means of 
 control offered by the existing furnace; nor must it be for- 
 gotten, that it presents us with all these advantages, at the cost 
 of the gaseous products of the coal, now wasted in the blast 
 furnace. 
 
 166. Having thus briefly reviewed the subject of puddling, 
 and endeavoured to show that great improvements may be made 
 in our present arrangements, with regard both to economy of 
 fuel, and the production of a superior quality of iron, I will now 
 offer a few observations on blast furnaces. 
 
 167. In the figures which I employ with regard to the 
 theoretical composition of the gases issuing from a blast furnace, 
 as deduced from the composition of the fuel used, I shall principally 
 rely upon the data on the Alfreton coal and furnaces, contained in 
 the elaborate report on blast furnaces, presented to the British 
 Association in 1845, by Dr. Lyon Play fair and Professor Bunsen; 
 since the methods of eudiometric analysis resorted to by these 
 accomplished chemists, appear superior in accuracy to those of 
 previous observers. It is to be regretted that so much care in 
 analysis, should not have been associated with equally unexcep- 
 tional methods for obtaining the samples of gases from various 
 depths of the furnace. A tube of only 1 inch in diameter, can 
 never be considered a satisfactory test of the average compo- 
 sition of the gases, particularly in furnaces where, as in the in- 
 stance of the one on which they experimented, the materials are 
 thrown in in such large masses that some of the pieces of coal 
 were nearly of the bulk of a cubic foot. See on this subject, 
 Ebelman, Annales des Mines, 1851. 
 
 168. A blast furnace may be viewed as an apparatus in 
 which a series of chemical operations take place, viz., that of 
 distillation in the upper portion, and those of cementation, reduc- 
 tion, and fusion, at gradually increasing depths. Certain materials 
 are thrown into the mouth of the furnace, which, after undergoing 
 certain transformations effected by their natural affinities, and 
 the oxygen of the blast, aided by heat, either present themselves 
 
72 ECONOMY OF FUEL. 
 
 in the hearth as pig iron and slag, or issue in a gaseous form 
 from the top of the furnace. It is evident, that if we know the 
 composition of the raw materials employed, the changes they 
 undergo, and what portions of these materials are delivered at the 
 hearth, we can deduce the composition of the gases issuing from 
 the top, and constituting the remaining product. 
 
 169. Observation has established, 1st, that the oxygen of the 
 blast is all consumed in the immediate vicinity of the tuyere ; 
 2ndly, that in hot blast furnaces, the carbonic acid zone is of 
 very limited extent, this gas being found entirely converted to 
 carbonic oxide within about 3 feet from the point of the tuyere ; 
 3rdly, that the coal loses all its gaseous products of distillation 
 much above the point at which its carbon combines with the 
 oxygen of the blast. 
 
 170. Each charge at the Alfreton furnaces consists of 4201bs. 
 of calcined ore, 3901bs. of coal, and 170lbs. of limestone; and 
 the product of iron resulting from one charge is 1401bs. 
 
 100 parts of the coal contained* 
 
 Parts of water 
 capable of being 1 
 heated 1 C. by 
 the combustible- 
 Carbon i V . ' . . . . 64-548 516,384 
 
 Carburetted Hydrogen 6'638 99,570 
 
 Carbonic oxide 1'602 3,660 
 
 Carbonic acid . . . . . * . . , T139 
 Bi-Carburetted Hydrogen ./. . . . 0*513 6,156 
 
 Hydrogen 0.370 13,320 
 
 Total 639,090 
 Contributed by the carbonaceous portion . . 516,384 
 
 Contributed by the products of distillation . 12.2,706 
 
 * The coal contained, in addition, '253 of sulphuretted hydrogen, and* 
 '163 of ammonia, omitted in the text from their heating power being too 
 trivial to claim attention, and also because the air contained in the crevices 
 and pores of the materials supplied, (for the eifect of which no allowance is 
 made in the report,) must more than counterbalance any addition made to the 
 
ECONOMY OF FUEL. 73 
 
 171. Since cast iron contains 3 '3 per cent, of carbon, there 
 will be ] -18 abstracted from each 64*548 parts of carbon for this 
 purpose, leaving 63*368 parts of carbon to undergo combustion. 
 
 172. This carbon, as has been already stated, becomes con- 
 verted into carbonic oxide, by combining with the air of the 
 blast, at a short distance above the tuyere, the product being 
 
 Nitrogen 295*716 
 
 Carbonic oxide 147 '85 8 
 
 The quantity of cast iron produced by 100 parts of coal, is 
 35'8=34'62 of pure iron, to effect the deoxidation of which, 
 
 heating power of the gases, by the presence of these two substances. .For 
 similar reasons, I have taken no account of any slight increase which may be 
 produced in the heating power of the escaping gases, by the change wrought 
 in those portions of the products of the distillation of coal, which, from being 
 disengaged at a considerable depth, are subjected to a decomposing heat in 
 their passage upwards ; and upon which modifying influence, much more 
 stress is laid in the report above alluded to, than I think the subject is 
 entitled to claim. It observes, " the upper layers of coal, limestone, and iron, 
 being cold, cause a condensation of the water and tar, both of which drop 
 back upon the red hot coals in the inferior layers, and become partly decom- 
 posed into hydrogen and carbonic oxide gas, whilst another part of the tar 
 is broken up into hydrogen, light carburetted hydrogen, and charcoal. The 
 portions escaping this decomposition are condensed anew by the cold layers 
 above, and finally themselves suffer change." Now, granting that this con- 
 densation can take place (which, except momentarily, with reference to the 
 materials just thrown into the furnace, I deny), since it is certain that ma- 
 terials cold enough to condense these vapours, on the one hand, and hot 
 enough to decompose them on the other, could not be reposing in layers in 
 very close apposition to each other, we are required to suppose that these con- 
 densed liquids trickle and drop from stone to stone for many feet, till at 
 length they alight on one hot enough to effect their decomposition ; perti- 
 naceously preserving their fluidity all the time, and refusing to vaporise, 
 although resting on hot bodies, and swept by a current of highly heated gas, 
 so imperfectly saturated with moisture^ as to be capable of licking up ten 
 times the quantity of liquid. It may be safely pronounced that nothing of 
 the kind ever does, or can, take place in a blast furnace ; and if the small por- 
 tion of the vapour of water which finds its way to a sufficient depth to come 
 in contact with ignited carbon is decomposed, as would unquestionably be the 
 case, a much larger portion passes off with the gases in the form of vapour, 
 deteriorating their combustible value, 
 
 E 
 
74 ECONOMY OF FUEL. 
 
 the carbonic oxide must combine with 14*83 of oxygen, and have 
 25*952 of its parts changed into 40*782 of carbonic acid. 
 
 173. The quantity of limestone, added to 100 parts of coal, 
 contains 18' 7 parts of carbonic acid, which is evolved from 
 the furnace with the other gaseous products, giving as a result, 
 for the composition of the gases issuing from the mouth of the 
 furnace 
 
 Nitrogen ....... . 295*716 
 
 Carbonic oxide 121-906 
 
 Carbonic acid . . . >. . ...* . 40'782 
 
 Ditto do. (from lime) . . . 38700 
 
 Total . . . 477-104 added the 
 products of the distillation of 100 parts of coal. 
 
 174. Hence it appears that we shall obtain the composition 
 of the gases from the furnace, if, to the products of the distilla- 
 tion of any given quantity of coal, we add the carbon of the 
 coke formed from that coal (minus the portion entering the iron), 
 plus the quantity of air necessary to form with this carbon, 
 carbonic oxide, plus the oxygen of the ore (which converts a 
 portion of this carbonic oxide into carbonic acid), and plus the 
 carbonic acid evolved from the limestone. 
 
 175. From the preceding data, the composition of the gases 
 evolved for each 100 parts of coal is found to be 
 
 Total of each. In 100 pts 
 
 Nitrogen 4 -,v <<.'. 295716 295'716 60'677 
 
 Carbonic oxide * , . 121*906 123*508 25*342 
 
 Carbonic acid . , -. * . 59'482 60*621 12*439 
 / Carbonic oxide. 1*602 
 
 Prom dis- 
 
 \ Carbonic acid 
 
 1-139 
 
 
 
 tillation 
 of coal. 
 
 < Carburetted hydrogen 1 . 
 1 Bi-carburetted hydrogen 
 V Hydrogen 
 
 6*638 
 0-513 
 0*370 
 
 6-638 
 0-513 
 0*370 
 
 1*362 
 105 
 075 
 
 
 
 
 
 
 
 Total 
 
 . 
 
 487*366 
 
 100*000 
 
 176. Since the whole of the products of the distillation of coal 
 escape unburnt, our task in finding the duty performed by the 
 fuel, is narrowed to an examination of the changes undergone by 
 the carbonaceous portion. 
 
ECONOMY ON FUEL. 75 
 
 177. I shall assume that carbon, in becoming C O*, developes 
 J part of the heat developed by it in becoming C Os, this being 
 about the mean of the figures given by the three observers, 
 Dulong, Andrews, and Grassi, (see note, page 5). 
 Of the total carbon in the fuel 64'548 
 
 There enters the iron 1"18 
 
 Leaves the furnace as carbonic acid . . 1 1*1225 
 
 Therefore discharges its full duty . . . 12'3025 
 
 Leaves the furnace as carbonic oxide . . . 5 2' 245 5 having apparently 
 
 discharged only ^ of its duty. 
 
 Carbon. 
 
 Full duty of 12*3025= 98,420 
 
 duty of 52-2455 = 139,321 
 
 Total . . . 237,741 
 
 178. If we subtract this sum from the full duty of 100 
 parts of coal, viz. 639,090, the remainder, 401,349, shows the 
 duty capable of being performed by the gaseous products 
 escaping from the furnace. Then, 
 
 as 639,090: 237,741:: 100: 37-2 
 
 whence it appears that this amounts to 62*8 per cent., leaving 
 3 7 '2 per cent, for the apparent duty realised. 
 
 179. These figures differ so greatly from the statements of 
 Dr. Playfair in the report before alluded to, that I feel it 
 necessary to advert to the subject, the more particularly, as from 
 the reputation of the individual from whom they emanate, 
 and the authority of the publication in which they appear, 
 they are calculated to foster (as 1 know they have already pro- 
 duced) great delusion with reference to this important question. 
 
 180. The report says, "Hence follows the remarkable con- 
 clusion, that in the furnaces of Alfreton, not less than 81*54 
 per cent, of the fuel is lost in the form of combustible matter 
 still fit for use, and that only 18*46 per cent, of the whole fuel 
 is realised in carrying out the processes in the furnace." 
 
 181. Thus it appears that the figures given by Dr. Playfair, 
 restrict the duty performed by the fuel, to just half the amount 
 
 * For an explanation of these symbols, see page 85. 
 
 E 2 
 
76 ECONOMY ON FUEL. 
 
 which my calculations have assigned to it. The difference in the 
 results at which we have arrived, is easily traceable to the dif- 
 ference in the principles which have guided our mode of pro- 
 cedure, and to the difference in the ratio we assume, that the 
 portion of heat developed by carbon in becoming carbonic 
 oxide, bears to the full amount it is capable of furnishing, when 
 it unites with 2 atoms of oxygen ; on this latter point see par. 
 177. and note at page 5. To estimate the duty performed, 
 Dr. Playfair simply takes the amount of nitrogen, deduces the 
 quantity of oxygen which accompanied this into the furnace as 
 atmospheric air, and then calculates the heat which would be 
 evolved by the union of this oxygen with carbon to form 
 carbonic oxide. It is evident that such a method altogether 
 ignores the duty done by the 1*18 of carbon, which combines 
 with the iron and descends with it into the hearth, and also the 
 important service towards "carrying out the processes in the 
 furnace" rendered by the 11*1225 of carbon, which, in the form of 
 25*952 of carbonic oxide, separates 14*83 of oxygen from the ore, 
 and becomes converted into 40*782 of carbonic acid in so doing. 
 The latter process, the report observes, is attended with a thermo- 
 neutrality, but surely this can be no valid reason for not reckon- 
 ing it with the realised duty of the carbon. If we revive iron 
 by placing some iron ore in a crucible, in conjunction with char- 
 coal, and then subjecting the vessel to the heat of a furnace, 
 can any one be found to contend, that the duty performed by 
 that portion of charcoal which combines with the iron, and by 
 that other portion which removes its oxygen by combining with 
 it, is any less real, than that achieved by the charcoal of the 
 furnace, in contributing the necessary temperature ? In fact, 
 since the whole of the carbon which combines with the oxygen of 
 the ore, is absolutely required for this purpose, and not a particle 
 can be dispensed with, whilst on the contrary, it might be a 
 question whether some of the carbon in the furnace is not 
 burnt in furnishing superfluous heat, many would be disposed to 
 accord the precedence in importance and indispensability to the 
 
ECONOMY ON FUEL. 77 
 
 services of the former and to deny to the function it performs, 
 the title of realised duty, certainly indicates a singular inversion 
 of ideas. 
 
 182. It may have been observed, that in treating on the 
 52*2455 parts of carbon which left the furnace as carbonic oxide, 
 I spoke of its having apparently discharged only \ of its duty ; 
 and however unexceptionable the mode of estimating its duty 
 adopted, may, on a superficial view appear, 1 am prepared to show, 
 that it inadequately represents the real services rendered by the 
 carbon to the processes of the furnace, and that if the various 
 parts played by the fuel, are separately scrutinized, and their 
 results analyzed with exactitude, the duty performed by the 
 carbon will be found to be much more considerable. Since the 
 whole of the atmospheric oxygen entering with the blast, is 
 converted into carbonic oxide at a comparatively short distance 
 above the tuyere, affording in this form an ample supply of carbon 
 to effect the deoxidizing process of the furnace, without the 
 absorption of any uncombined carbon for this object ; and since we 
 know, that when we form carbonic oxide from carbonic acid, by sup- 
 plying the latter with another equivalent of carbon, exactly half 
 the amount of carbon in the product, must have previously been 
 in combination with 2 atoms of oxygen, as carbonic acid, we are 
 enabled to pronounce that the combustion of the carbon in the 
 furnace takes place as follows: Deducting the 1*18 of carbon 
 which enters the iron, precisely one half the remainder is con- 
 verted to carbonic oxide in the zone of transition which must 
 exist between the carbonic acid zone (or zone of fusion), and the 
 carbonic oxide zone, where this conversion is complete; whilst the 
 remaining half descends before the tuyere, where, by its con- 
 version to carbonic acid, it furnishes the intense heat necessary 
 to produce perfect fusion of the refractory minerals employed. 
 
 183. The fact, that subsequently to performing this service, 
 the 31*684 parts of carbon, in combination with 84*49 of oxygen 
 as carbonic acid, yields up half its oxygen to an additional 
 portion of 31*684 parts of carbon, with a great thermometric 
 
78 ECONOMY OP FUEL. 
 
 loss, must not blind us to the amount of duty which it has 
 previously actually accomplished, and which, if it left the furnace 
 immediately afterwards, before its transformation into carbonic 
 oxide, would be unhesitatingly admitted. Does it injure or 
 retard the processes of the furnace, in its subsequent passage 
 through it, that at its final exit, we curtail its claims for services 
 previously accomplished ? So far from doing so, it increases our 
 obligations for work performed, by separating 14* 8 3 of oxygeii 
 from the ore, and we repay the additional service, by paring- 
 down its duty into simply yielding the measure of heat due to 
 the formation of carbonic oxide. 
 
 184. Estimated according to this more accurate and precise 
 view of its true functions, the duty performed by the fuel in 
 a blast furnace, will be as follows : 
 
 Of the total carbon in 100 parts of fuel = 64'548 
 
 There enters the iron . . . / ^ ''.' .';.' V . ';' ". V18 
 Carbon (as simple carbon) burnt to C 02 before tuyere . . 31*684 
 
 Consequently discharges full duty . . . . * ,, t . . 32' 864 
 
 Carbon (as CO) becomes C0 2 in separating 14'83 0., con- 
 sequently discharges duty . ^. : 1" .*' . . 1 ; ' . . 111225 
 
 The full duty of 32'864 of carbon is 262,912 and f duty on 
 11-1225 is 59,320, making together 3 22,2 3 2 for the duty perform- 
 ed by the carbon, which sum is to 639,090 the whole duty of 100 
 parts of coal, as 5 0'4 is to 100; consequently, the duty performed 
 by the fuel is 50 '4 per cent., or nearly 3- fold what has previously 
 been assigned to it and that this is the proper way of 
 estimating the duty of the carbon, is abundantly plain and 
 c'ear, and once pointed out, will I think be felt to admit of no 
 dispute. That the duty done by the fuel should be 50 -4 per 
 cent., and that capable of being evolved from the escaping gases 
 6 2' 8 per cent., making together the sum of 113' 2 per cent. ; 
 f nay at first sight appear a discrepancy, but when more narrowly 
 examined, the apparent anomaly vanishes. A given quantity of 
 
ECONOMY OF FUEL. 79 
 
 carbon as CO 2 , at a temperature sufficient to convert carbon 
 into CO, will, by so doing, form a compound capable of de- 
 veloping by combustion 33*3 per cent, more heat than the carbon 
 so converted. In one case we have 100 parts of carbon (as simple 
 carbon), capable of developing 100 parts of heat; in the other, 
 200 parts of carbon as C 0, capable of developing 13 3'' 3 parts 
 of heat, according to the law that -| of the whole heat capable of 
 being developed by carbon, are developed when C O becomes 
 C O 2 . In the case of the blast furnace before us for considera- 
 tion, the difference will be, the difference between the heat- 
 developing power of 31'684 of carbon (as simple carbon) 
 converted to C 2 , and 63 '368 of carbon (as C O) converted to 
 C0 2 = 84,490-66 units, and 639,090 is to 84,490'66 as 100 
 to 13-2 the amount of overplus. 
 
 185. Supposing 100 parts of carbon burnt to C0 2 in a 
 common reverberatory furnace, and the full duty thus obtained 
 applied in the most advantageous manner to the processes of 
 the furnace suppose further, that instead of the products of 
 combustion being discharged at once into the atmosphere 
 through the stack in the ordinary way, they are passed through a 
 shaft filled with carbon, where they combine with another 100 parts 
 of carbon, and thus become converted to C 0. What would be 
 said to a plan for estimating the duty of the fuel, which took the 
 gaseous products discharged as C 0, found them to be capable 
 of generating 13 3' 3 parts of heat, and hence affirmed that the 
 duty previously performed by the fuel in the furnace, must be 
 only 66" 6 per cent. Everybody would in this case cry fallacy ; 
 yet, as far as the principle involved is concerned, the procedure 
 presents an exact parallel to the mode of estimating the duty of 
 the fuel in blast furnaces, adopted in the report before alluded 
 to, with the exception, that in the case of the latter, the fuel still 
 performs additional services after its conversion to carbonic 
 oxide, making the inaccuracy so much the greater. 
 
 186. Although we have found the amount of duty per- 
 formed by the fuel in blast furnaces to bemuch more satisfactory than 
 had previously been stated, amounting to 50 -4 per cent, instead 
 
80 
 
 ECONOMY ON FUEL. 
 
 of only 18*46 per cent., yet the heat capable of being realised from 
 the escaping products, amounting to 62*8 per cent, on all the fuel 
 consumed, is still a loss which it would be most desirable to 
 curtail, either by diminishing the consumption, by increasing the 
 duty of the fuel, or by turning the waste products to some 
 useful account.* Their value as an article of fuel, depends less 
 upon the whole quantity of heat they are able to afford, than 
 upon the temperature they are capable of generating, since it Is 
 this which must determine to what objects they are applicable, 
 and the extent of their sphere of practical utility. To ascertain 
 the temperature capable of being attained by the combustion of 
 these gases, we must determine their heating power from their 
 composition, and then ascertain the specific heat of the products 
 resulting from their combustion. 
 
 Composition 
 of furnace gases. 
 
 tfo.ofdegs. 
 C. 1 part 
 of water 
 would be 
 raised by 
 the com- 
 bustibles. 
 
 Result of 
 combustion. 
 
 Totals. 
 
 Ditto 
 reduced to 
 100 parts. 
 
 Specific 
 heat. 
 
 N 
 
 295-716 
 
 
 
 652.-18 N 
 
 68-9644 
 
 27 
 
 C0 2 
 
 60-621 
 
 
 
 274-57178 C0 2 
 
 29-0344 
 
 22 
 
 CO 
 
 123-508 
 
 282215 
 
 / 194-084 C0 2 
 
 \ 247'016 N 
 
 
 
 
 H 2 C 
 
 6-638 
 
 99570 
 
 C 14-9355 HO 
 ] 18-2545 C0 2 
 ( 92-9320 N 
 
 18-925 HO 
 
 2-0012 
 
 847 
 
 H 2 C 2 
 
 0-513 
 
 6156 
 
 C 0-65957HO 
 ] 1-61228C0 2 
 ( 6-156 N 
 
 
 
 
 H 
 
 Totals 
 
 0-370 
 
 13320 
 
 / 3-330 HO 
 \ 10-36 N 
 
 
 
 
 487*366 
 
 401261 
 
 945-67678 
 
 100-0000 
 
 267 
 
 Then- 
 
 401261 
 
 - =1589 C. or 2900 Fahr. the temperature 
 945-67678x'267 
 
 * For particulars of the best methods of taking the waste gases from 
 blast furnaces, see an able paper on this subject by Mr. S. H. Blackwell, in 
 the Proceedings of the Institution of Mechanical Engineers, for October, 1852. 
 
ECONOMY ON FUEL. 81 
 
 these gases are theoretically capable of yielding on combustion. 
 This degree of heat is amply sufficient for raising steam, heating 
 the blast, manufacturing gas and coke, burning bricks or lime, 
 and a variety of other operations*, but is not adequate tp be em- 
 ployed with advantage for the manufacture of iron, as was once 
 supposed, an erroneous idea, which has led to the waste of much 
 capital in abortive experiments, the success of which, a more 
 accurate knowledge of the subject, would have seen to have been 
 apriori impossible. In the report before alluded to, it is stated 
 that the temperature capable of being attained by the combustion 
 of these gases is 3,083 ; that by using a blast sufficiently heated, 
 this could easily be raised to 3,632; and that since cast iron 
 
 * I believe one of the most feasible and practically useful applications of 
 the heated gases, would be the desiccation of the air with which the furnace 
 is supplied, which might be effected by their agency in many ways. The 
 injurious effect and loss, produced by the moisture in the air in hot and damp 
 weather, being much greater than is commonly suspected. To attain this 
 object, let two beds of muriate of lime be prepared, each resting on a tubular 
 iron grating, or coil of pipe, let the air for the blast engine be drawn through, 
 or over, these beds alternately, and in the intervals, let a portion of the heated 
 gases, or, if necessary, a portion of the products of their combustion, be 
 passed through the coil of pipe of the bed not in use. So may the blast 
 furnace be constantly supplied with desiccated air at a trifling expense, and 
 its operations be rendered independent of atmospheric vicissitudes. The 
 result would be a saving of fuel, an increase in yield, and an improvement in 
 the quality of the iron ; in fact, a making constant, that state of advantageous 
 working, which now exists only for a few weeks in each year during the 
 frosty weather of winter. 
 
 Air saturated with moisture contains at 
 Degrees Grains of water 
 
 Fahr. in each cubic ft. 
 
 10 . . I'll 
 
 20 . . 1-58 
 30 , 2'21 
 
 Degrees Grains of water 
 
 Fahr. in each cubic ft. 
 
 40 . . 3-09 
 
 50 . . 4-28 
 
 60 . . 5-87 
 
 Degrees Grains of water 
 Fahr. in each cubic ft. 
 
 70 . . 8 
 80 ' . . 10-81 
 90 14-5 
 
 Now, 4000 cubicfeetofairperminute=240,000 cubic feet per hour = 5,760,000 
 cubic feet per day, is a common quantity for a blast furnace to consume, and 
 therefore, if we suppose the state of saturation of the air to be '75, such a 
 furnace will receive per day in the air of the blast, 1364 Ibs. avoirdupois 
 of water, when the temperature is 30, and 4,937 Ibs,, or nearly four times 
 the quantity, when the thermometer stands at 70. 
 
 E 9 
 
82 ECONOMY ON FUEL. 
 
 melts at 2,1 9 2, it follows that the gases, when burned with hot 
 air, would yield a temperature more than sufficient to melt iron, 
 l^or the futility of the use of hot air for such an object, I refer the 
 3-eader to the remarks on attenuated flame, pars. 110 and 112. 
 In the next place, the temperature attainable by the gases is over- 
 stated, and that required for melting cast iron ifWfferstated, the 
 most reliable observations, those of Daniel, fixing its melting point 
 at 2,786. However, the very fact of there being a difference of 
 600 in the melting point assigned to cast iron, by different 
 observers, shows how unsatisfactory are arguments founded on 
 such theoretical deductions, when compared with the very con- 
 c'asive evidence on the subject lying open before us, in the 
 results attending the use of coal. Now we find that coal, the 
 heating powers of which are vastly superior to the gases, only 
 just generates sufficient heat for the processes of iron making; any 
 impairment of the heating power of the furnace, from atmospheric 
 vicissitudes, or errors of construction, being at once followed by 
 deterioration of its working capability, and waste of iron. And 
 when it is considered that 1 cwt. of iron is worth more than a ton 
 of coal, it will be readily understood, that saving the latter at the 
 expense of the former, is, as regards the pocket of the manufacturer, 
 the saving of a negative quantity. The fact is, that to estimate the 
 temperature we practically attain in our reverberatory furnaces, we 
 must deduct from 20 to 25 per cent, from the theoretical value 
 of the fuel, to allow for the imperfect combustion of the 
 gases on the one hand, or the excess of air on the other; 
 for when it is reflected, that the mixed stream of air and 
 gases, darts through a reverberatory furnace with a velocity 
 of 40 feet per second, passing through the working chamber of 
 a puddling furnace in about - of a second, we have no difficulty 
 in understanding, that unless a prejudicial excess of air be ad- 
 mitted, some portion of still uninflamed gas must pass into the 
 region of the flues. In steam boiler furnaces, where an excess of 
 nir is not so injurious, it is found advisable to admit more air 
 than the combining equivalent ; for though the excess of uncom- 
 
ECONOMY ON FUEL. 83 
 
 bined air thus necessarily constantly passing off, must rob the 
 furnace of a great deal of heat, yet it is found, that if it be 
 attempted to lessen the quantity, the result is injurious ; the 
 diminished amount of combustion that ensues from the increased 
 quantity of gas which passes off unburnt, producing a greater 
 loss of heat, than that previously abstracted by the excess of air. 
 
 188. The practical value of the furnace gases for fuel, is 
 much diminished in those localities, where, as in some parts of 
 Staffordshire, a superabundant supply of slack (found in getting 
 the good coal) can be obtained for burning under the steam 
 boilers, at an almost nominal price, from its insufficiency for 
 other purposes. 
 
 189. In those cases where, from the nature of the ore or 
 fuel, or both combined, economy requires the use of the hot 
 blast, and the quality of the pig metal resulting, becomes much 
 deteriorated in consequence, it becomes a question deserving 
 attentive consideration, how far subjecting the iron to some 
 intermediate treatment between the blast furnace and the pud- 
 dling furnace, may not be desirable, some process which should 
 effect cheaply, and at little loss beyond the removal of the actual 
 impurities, what is now accomplished with such a great waste of 
 iron and fuel, in the almost obsolete refinery. It appears to me, 
 such a desideratum might be attained, by the melted metal on 
 issuing from the blast furnace, being filtered through a bed of 
 ignited charcoal, the pores of which had been charged with 
 fluxes of such a character, as to form with the impurities con- 
 tained in the iron, a neutral cinder. In the present refinery, no 
 artificial flux being used, if silicon is present, it is separated at 
 the expense of a loss of iron, forming as fast as tt is oxidized, 
 a silicate of the protoxide of iron, for want of having a stronger 
 base presented to it. After being refined, the iron should be 
 transferred still melted to the puddling furnace, to receive its 
 fibre ; for unless some benefit can be shewn to accrue to the 
 process, from the iron being allowed to cool, compelling an 
 expenditure of fuel for its re-melting, such unnecessary waste 
 
84 ECONOMY OF PUEL. 
 
 should be avoided : in short, the requirements demanded by a 
 rigid economy of fuel, can never be fulfilled, till the period 
 arrives, when the iron will not be allowed to cool, from the time 
 it issues from the blast furnace, till it passes the rolls, a puddled 
 bar. 
 
 190. I shall doubtless be told, that such refinements and 
 niceties as I propose to introduce, are unnecessary superfluities. 
 This however is the language of ignorance and slothfulness, for 
 improvements are never superfluous to any other eyes. The 
 machinery of a cotton mill is doubtless a prodigiously compli- 
 cated apparatus, when compared with a distaff and spinning- 
 jenny, but then its results are more than "prodigiously" greater. 
 In short, the whole question is one of degree ; and where the 
 advantages to be obtained, greatly preponderate over the trouble 
 incurred by the additional appliances necessary for their attain- 
 ment, it rests not in the power of ignorance arid supineness, 
 to prevent their ultimate adoption. It is unquestionable, that 
 the manufacture of iron has hitherto borrowed less from science, 
 and is in a ruder and more barbarous state, than our other manu- 
 factures, and it is equally unquestionable, that such a state of 
 things will not be allowed to continue. Why are " refinements 
 and niceties," introduced, carried out, and adopted, in other 
 departments of production? Is it to gratify a longing for the 
 ideal in those engaged in them, or as a question of . s. d. ? 
 In short, when we view the keen spirit of enterprise and 
 competition which leads manufacturers in other departments, to 
 seek to increase their profits by every expedient for cheapening 
 production, which the improved chemical and mechanical know- 
 ledge of the day places within their reach, it is puerile to suppose 
 that the iron trade is to prove an isolated exception to a gene- 
 ral rule, and remain exempted from the operation of the same 
 principles. The shadow will not tarry on the dial for the slug- 
 gard; and those who will not read the signs of the times, but 
 choose to persist in working by the rule of thumb, will be taught 
 its insufficiency by their balance sheets, 
 
ECONOMY OF FUEL. 85 
 
 EXPLANATION OF THE SYMBOLS USED IN THE DIAGRAMS 
 AND TABLES WHICH FOLLOW. 
 
 The essence of a chemical compound is, that its constituents 
 always bear a definite proportion, by weight, to each other ; and 
 the most important discovery in modern chemistry has been the 
 law, that bodies unite only in these definite proportions (termed 
 their atomic weights), or in simple multiples of them. 
 
 Thus the proportions, by weight, in which oxygen and 
 nitrogen combine with each other, and with all other substances, 
 are 8 parts of the former and 14 of the latter. 
 
 Atoms. Weight. Atoms. Weight. weight* 
 
 2 nitrogen 28 are present with 1 oxygen 8 in atmospheric air . . 36 
 
 I 14 combined with 1 8 forms nitrous oxide . . 22 
 
 1 // 14 // 2 a 16 forms nitric oxide . . 80 
 
 1 n 14 // 3 /; 24 forms hyponitrous acid 38 
 
 1 // 14 n 4 // 32 forms nitrous acid . . 46 
 
 1 H 14 // 5 // 40 forms nitric acid ... 54 
 
 and no compound with intermediate proportions can exist. 
 
 Chemists have agreed, that the first letter of the names of 
 the elementary bodies, shall designate, not only the elementary 
 body, but also one combining equivalent, by weight, of such 
 body. The atomic weights of hydrogen, oxygen, nitrogen, and 
 carbon, are 1, 8, 14, and 6, respectively. 
 
 H designates therefore, not merely hydrogen, but 1 part by weight, of 
 
 hydrogen. 
 
 O not merely oxygen, but 8 parts by weight, of oxygen. 
 N 14 parts, by weight, of nitrogen. 
 C 6 parts, by weight, of carbon. 
 C O one equivalent of each of these bodies ; that is to say, 6 parts, by 
 
 weight, of carbon, and 8 parts, by weight, of oxygen, constituting 
 
 carbonic oxide. 
 C 2 one equivalent of tbe former body and two of the latter ; tbat is to 
 
 say, 6 parts, by weight, of carbon, and 16 parts, by weight, of 
 
 oxygen, constituting carbonic acid. 
 
 HO 1 part, by weight, of hydrogen, and 8 of oxygen, constituting water. 
 H 2 C 2 parts, by weight, of hydrogen, and 6 of carbon, constituting carbu- 
 
 retted hydrogen, 
 H 2 C 2 2 parts, by weight, of hydrogen, and 12 of carbon, constituting bi- 
 
 carburetted hydrogen. 
 
86 
 
 ECONOMY OF FUEL. 
 
 
 
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ECONOMY OF FUEL. 
 
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 ECONOMY OF FUEL. 
 
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ECONOMY OF FUEL. 89 
 
 36,000, the heating power given in the annexed table to 
 hydrogen, is that assigned to it by Crawford. Andrews assigns 
 7,900 for carbon ; but inasmuch as the heating power actually 
 obtained by experiment, is more likely to be below, than above 
 the real value, I have taken the liberty of calling it 8,000, and 
 with the less hesitation from the fact, that the actual amount of 
 water recently evaporated in steam boilers by 1 Ib. of carbon- 
 aceous coal, leaves no doubt on my mind, that even at 8,000, 
 its heating powers are understated. In short, on theoretical 
 grounds, I think it not unlikely but that the total heat re- 
 sulting from its combination with 2 atoms of oxygen, is not less 
 than 12,000, of which about 3,000 becomes latent in effecting 
 the gasification of the carbon, leaving 9,000 for free heating 
 power. On this view of the case, the total calorific effect pro- 
 duced by its combustion, would have the same relation to that 
 developed by hydrogen (1 to 3), as the quantities of oxygen 
 with which they respectively combine. 
 
 Lord Dundonald, in a new and superior pattern boiler of his 
 own construction, has evaporated 12'91bs. of water from 100 with 
 lib. of Llangennech coal, composed of 85 '46 of carbon, and 4'20 
 of hydrogen. Assuming the carbon to have effected 85 '46 per cent, 
 of the evaporation (not an over estimate when the greater ten- 
 dency of hydrogen to form smoke is considered), and we get lib. 
 of carbon evaporating (in practice) 12'91b. of water. Say water 
 at 100 P, requires the addition of 600 C to convert it into steam 
 of atmospheric pressure. 
 
 Then estimating the heating power of carbon at 8000 we get 
 8000~600=13|lb. of water, theoretically evaporated by lib. 
 of carbon, and estimating the heating power of carbon at 9000. 
 9000 600 =l5lbs. of water theoretically convertible. Now 
 considering that in practice there is necessarily a certain amount 
 of loss through imperfect combustion, radiation, and the current 
 of escaping gases, I am of opinion that we can never expect to 
 realise more than from 80 to 85 per cent, of the theoretical 
 value. Now 12'91bs. of water evaporated by lib. of carbon, is 
 
90 ECONOMY OF FUEL. 
 
 at the rate of 86 per cent, ou a duty of 151bs. and therefore I 
 am of opinion, that the theoretical duty of carbon cannot be less 
 than this sum, and consequently, that its heating power should be 
 considered 9000 instead of 8000. 
 
 Reaumur's thermometer, divides the interval between the 
 temperatures of melting ice and boiling water, into 80 ; that of 
 Celsius, now commonly called the centigrade (the use of which 
 is become universal in the scientific world), into 100; and that 
 of Fahrenheit, into 180 equal parts. The first two, place the 
 zero at the temperature of melting ice; Fahrenheit 32 below 
 the melting point of ice. 9 F. = 5 C. = 4 R. 
 
 1 centigrade = 1*8 of Fahrenheit; but since zero, on -the 
 centigrade, commences at 32 Fahrenheit, in converting 1 the 
 degrees of one thermometer into those of the other, a correction 
 must be made for its different position. If the degrees be +> 
 to convert centigrade to Fahrenheit multiply by 1/8, and add 32 
 to the product. 
 
 Clement and Desormes, place the absolute zero at 266*6 C. 
 447*8 F., from the circumstance that air at zero expands 
 or contracts) for each degree C. of heat added (or subtracted) 
 g-g^-.-g-, and therefore that at 266'6 C. there can be no further 
 diminution of volume, and consequently no further abstraction 
 of heat. This view must however at present be regarded as 
 conjectural. 
 
ECONOMY OF FUEL. 91 
 
 SECTION X. 
 
 ON THE QUANTITY OP HEAT IN STEAM AND ITS ECONOMIC 
 APPLICATION. 
 
 191. TILL a very recent period, the total amount of heat in 
 (saturated) steam has been always supposed to be a constant 
 quantity, whatever its elasticity and temperature. This doctrine 
 entailed as a corollary, the existence of a law, that the quantity 
 of heat existing in a combined or latent state, varied inversely 
 with the quantity present in a free state, in such a proportion 
 that the sum of the two was always the same. Therefore it was 
 said, that the quantity existing in a combined state increased as 
 the pressure on the vapour diminished, and its temperature 
 consequently fell; whilst, on the contrary, the quantity of the 
 free or uncombined heat increased as the pressure increased, and 
 the temperature became augmented ; so that, " in a vessel whose 
 sides would permit neither ingress or egress of heat, saturated 
 vapour of water at 212, might by enlargement of the space, be 
 converted into cold (saturated) vapour of low tension, and by 
 continual narrowing of the space, into very hot vapour of high 
 tension, without any liquefaction taking place in the latter case 
 (unless the space were to become too small to allow of the water 
 existing in the gaseous state)." 
 
 192. Estimating the latent heat of steam at 100 C, = 212 
 Pahr., as equal to 550 C,=990 Eahr., and the free heat as 
 equal to 100 C,=180 Eahr., according to the preceding theory, 
 we have 
 
 In vapour of 
 0C. 
 
 Free heat. 
 0C. 
 
 Latent heat. 
 650C. 
 
 Sum. 
 650C. 
 
 50 
 
 50 
 
 600 
 
 650 
 
 100 
 
 100 
 
 550 
 
 650 
 
 150 
 
 150 
 
 500 
 
 650 
 
 200 
 
 200 
 
 450 
 
 650 
 
 250 
 
 250 
 
 400 
 
 650 
 
92 ECONOMY OF FUEL. 
 
 193. The preceding law is known as Watt's law; and is 
 that which has always been, and continues to be, adopted by 
 engineers, as the basis of their calculations. Southern, on the 
 contrary, advanced the doctrine that the latent or combined heat 
 of steam is always a constant quantity, and consequently that the 
 total amount, increases or diminishes, paripassu with the tempe- 
 rature. The recent elaborate researches of Eegriault have at 
 length conclusively settled the question, and shown that neither 
 of the two preceding theories is correct, but that the truth lies 
 between them Watt's theory however, involving the smallest 
 amount of error, when practically applied to the steam engine. 
 Watt denied there was any increase in the total quantity of heat 
 in steam, as the temperature became augmented. Southern 
 asserted that the whole of the augmentation in temperature, was 
 so much heat added: Eegnault has now determined that 30 -5 
 per cent, of the augmentation, is due to an addition of heat the 
 remaining 69*5 per cent, to heat that was previously latent, be- 
 coming free (upon the diminution in the volume of the steam con- 
 sequent upon the accession of pressure). 
 
 194. Eegnault finds that the relation between the total 
 quantity of heat in steam, and the temperature, may be repre- 
 sented within the limits of error of experiment by \=A+B, 
 and he obtains for A and B, the values A= 606*5, B=0'305, 
 so that the formula for calculating the total heat in steam at 
 different temperatures, becomes 
 
 X=c606-5+0-305*. 
 
 In vapour at 
 
 Free heat. 
 
 Latent heat. 
 
 Sum. 
 
 oc. 
 
 0C. 
 
 606-5C. 
 
 606'5C. 
 
 50 
 
 50 
 
 571'7 
 
 621-7 
 
 100 
 
 100 
 
 537 
 
 637 
 
 150 
 
 150 
 
 502-2 
 
 652-2 
 
 200 
 
 200 
 
 467-5 
 
 667'5 
 
 250 
 
 250 
 
 430-25 
 
 682-7 
 
 195. It is not a little surprising, that a question which lies so 
 completely at the foundation of the economic application of 
 
ECONOMY OF FUEL. 93 
 
 steam, should have remained so long so imperfectly determined. 
 The fact shows more forcibly than words, the chasm which has 
 existed between the pursuits of the man of science, and the occu- 
 pations of the practical man ; and it may be safely affirmed, that 
 each year since Watt's first experiment, more thousands have 
 been wasted from imperfect knowledge, than it would have cost 
 pounds to have set the question at rest for ever, by a series of 
 the most elaborate experiments, conducted on the most extensive 
 scale. The question affected the elements of national wealth, 
 and the resources of kingdoms was notoriously in dispute, and 
 equally notoriously within the reach of positive determination, 
 yet has this pre-eminently steam-power-using nation, allowed its 
 solution to remain in abeyance fifty years ; and it is at last to 
 the superior enlightenment and liberality of the Trench govern- 
 ment in matters of science, that mankind are indebted for its 
 settlement. 
 
 196. One important consequence deducible from Eegnault's 
 law is, that when (saturated) steam of high temperature, and 
 pressure, is allowed to expand, (without the presence of water) it 
 becomes sub-saturated or super-heated steam, and as a conse- 
 quence, possessed of an elasticity greater than that due to its 
 density, in proportion to its excess of free heat ; a fact which 
 evidently most materially increases the benefit to be derived from 
 working steam-engines expansively, and shows us that hitherto 
 we have under- calculated the gain accruing from this pro- 
 cess. Thus, the quantity of heat in steam of 681bs. pressure, 
 and 150 C.= 302 Fahr. temperature, is 27'36Fahr. more than 
 that in steam of 15 Ibs. pressure and 100 C.=r212Fahr. tempe- 
 rature. Consequently, if steam of the former kind, be expanded 
 through a space, which should according to the old law, convert 
 it into steam of the latter, it becomes in reality sub-saturated 
 steam, with a temperature of 244*3, and possessing an elas- 
 ticity* of nearly 18 Ibs. 
 
 * Till recently, it was believed that all gases and vapours expanded 
 equally, for equal increments of temperature, which was variously stated as 
 
94 ECONOMY OF FUEL. 
 
 197. Another point in which Eegnault's law comes in con- 
 tact with the question of the economical application of steam, 
 and, modifies in a minor degree, those data on which engineers 
 have been accustomed to rely, is the question of the economy of 
 high pressure steam per se (i.e. irrespective of expansion). When 
 the temperature of water, or any other volatile substance, is 
 raised, the tension of its vapour increases in a much higher ratio 
 than its density, because the additional heat not only increases 
 the tension by generating more vapour, but likewise increases 
 the expansive force of the vapour already formed. The higher 
 the temperature, the greater the difference, and consequently the 
 advantage, of high pressure steam-engines, assuming the heat of 
 steam to be a constant quantity. Now, although this assump- 
 tion is erroneous, yet the increase in elasticity consequent upon 
 an increase of temperature, much more than counterbalances the 
 increase in the total quantity of heat, so that high pressure steam 
 still preserves its advantages of a higher tension, in proportion 
 to the heat required for its generation, though not to the extent 
 that was formerly supposed. 
 
 from 7 |-o-tli to ^oth of their bulk at 32, for each degree of Fahrenheit. 
 Muncke however long ago stated, that vapours heated to their boiling point, 
 expand much more strongly than air; and Regnault has now established 
 that the law, that all gases have the same co-efficient of expansion, is " true 
 in the limit only ; that is to say. it accords more and more nearly with the 
 results of observation, in proportion as the gases are in a more expanded 
 state." The expansion assumed for steam in the text, is taken from a table 
 by Mr. Charles W. Siemens, published in the Proceedings of the Institution 
 of Mechanical Engineers, for June, 1852. According to this table, saturated 
 steam at 212, when heated out of contact with water, expands under 
 constant atmospheric pressure as follows 
 
 Amount of Degrees 
 
 expansion. Fahr. 
 
 "1 by the addition of 7 
 2 " " 35 
 3 " " 75 
 4 " " 120 
 5 " " 165 
 
ECONOMY OF FUEL. 
 
 95 
 
 198. In the following table, column A shows the quantity of 
 heat or fuel required to produce a given mechanical effect, at 
 different temperatures and pressures, calculated according to the 
 old view, "that the heat in steam is a constant quantity;" whilst 
 B is column A corrected, to accord with the more precise ob- 
 servations of Eegnault. 
 
 
 
 
 
 Volume 
 
 
 
 
 
 j 
 
 
 
 
 com- 
 
 
 Density 
 
 
 
 I 
 
 1 
 
 Total : 
 quantity 
 of heat! 
 
 Tempe- 
 rature. 
 
 Pres- 
 sure in 
 IDS. 
 
 ?ared 
 th vol. 
 water 
 
 Actual 
 density. 
 
 corres- 
 ponding 
 to elas- 
 
 A. 
 
 B. 
 
 M 
 
 
 
 
 that pro- 
 
 
 ticity. 
 
 
 
 
 
 
 
 duced it. 
 
 
 
 
 
 
 1146-8 
 
 212-8 
 
 15 
 
 1669 
 
 100 
 
 100 
 
 100 
 
 100 
 
 11.8 
 
 1158.6 
 
 251-6 
 
 30 
 
 883 
 
 189 
 
 200 
 
 94-5 
 
 95-472 
 
 19-4 
 
 1166-2 
 
 276-4 
 
 45 
 
 610 
 
 273-6 
 
 300 
 
 91-2 
 
 92-742 
 
 25-2 
 
 1172 
 
 295-6 
 
 60 
 
 470 
 
 355 
 
 400 
 
 88-75 
 
 90-7 
 
 30 
 
 1176-8 
 
 311-2 
 
 75 
 
 383 
 
 435-7 
 
 500 
 
 87'14 
 
 89-419 
 
 36.4 
 
 1183-2 
 
 332 
 
 100 
 
 295 
 
 565-7 
 
 666-6 
 
 84-86 
 
 87'553 
 
 40-6 
 
 1187-4 
 
 345-8 
 
 120 
 
 251 
 
 665 
 
 800 
 
 83-125 
 
 86-067 
 
 45'9 
 
 1192-7 
 
 363-4 
 
 150 
 
 205 
 
 814 
 
 1000 
 
 81-4 
 
 84-657 
 
 B 8-2 
 
 1200 
 
 387-3 
 
 200 
 
 158 1056 
 
 1333 
 
 79-22 
 
 82-895 
 
 199. Much attention being excited at present to the subject 
 of air engines, and the supposed probability of their superceding 
 steam engines, as offering a larger return of power in proportion 
 to the heat expended, a slight analysis of their relative powers 
 and capabilities may prove interesting. 
 
 200. Under a pressure of 30 inches of mercury, = 14- 7 Ibs., 
 1 measure of water, yields 1,700 measures of vapour at 212 
 according to Guy Lussac, and 1,728 according to Dalton. We 
 will assume the latter number, since it offers the convenient and 
 easily-remembered ratio, of 1 cubic inch of water, forming 1 cubic 
 foot of steam. 
 
 201. 1 cubic inch of water at 60, weighs 252*5 grains, there- 
 fore the addition of 1,118 of heat to 252' 5 grains of water at 
 60, will produce 1 cubic foot of expansion under an atmospheric 
 
96 ECONOMY OF FUEL. 
 
 pressure of 30 inches of mercury,= 14*7 Ibs. raised 1,728 inches, 
 = 144 feet. 
 
 202. 1 cubic foot of atmospheric air at 60, barometer at 
 30, weighs 536 grains; and since air at 60, expands T ^ T for 
 each degree, the addition of 508 to 536 grains of air, will 
 produce 1 cubic foot of expansion under an atmospheric pressure 
 of 30 inches of mercury, = 14*7 Ibs. raised 1,728 inches = 
 144 feet. 
 
 203. The quantity of heat required to raise 252*5 grains of 
 water l',118, = the quantity required to raise 252*5 x 1,118 = 
 282,295 grains of water 1, (and since the specific heat of air to 
 water is *25 to 1), the quantity of heat required to raise 536 
 grains of air 508, = the quantity required to heat ^~ x 508 
 = 68,072 grains of water 1. 
 
 204. Then 6 VgVi^V* = 24*11, shewing that 24 per cent, 
 of the quantity of heat required to produce a cubic foot of 
 expansion, (under atmospheric pressure, with the barometer at 
 30 and the thermometer at 60), by the conversion of water 
 into steam, will produce this effect when applied to expand air. 
 
 205. So far, the balance of advantage would appear to lie 
 on the side of heated air, in the proportion of 4 to 1, when 
 compared with steam as a moving power ; but there remain two 
 most important considerations to be examined, which not only 
 turn the balance the other way, but to such an extent, as in my 
 opinion to render it in the highest degree improbable, that heated 
 air can ever become an advantageous substitute for steam, as a 
 prime mover. 
 
 206. The first great drawback to the use of heated air, is the 
 small amount of its expansion. Water, we have seen, expands 
 1,728 times; so that to obtain a volume of expansion of 1 cubic 
 foot, we have only to force into the reservoir where the expansion 
 is effected, (i.e. the boiler) a volume of 1 cubic inch. Now, 
 could we obtain air in any similarly condensed and manageable 
 form, yet, retaining its present small capacity for heat, it would 
 stand on a totally different footing, from that which it actually 
 
ECONOMY OF FUEL. 97 
 
 occupies. Even at 568 however (which is probably above the 
 temperature at which it could be practically used with advantage 
 in a cylinder with air-tight piston), its volume (at 60) is only 
 doubled ; consequently, for every volume of heated and expanded 
 air which develops power as it escapes by the working cylinder, 
 half a volume of cold air must be forced into the reservoir where 
 the heating and expansion are accomplished, by the supply cylinder, 
 an operation which at once consumes half the theoretic power 
 of the engine, plus the friction of the supply cylinder with its 
 valves and appendages, and increases its consumption of heat for 
 duty done, to considerably more than double say from 24 to 60 
 per cent., as compared with the steam engine. 
 
 207. The second great disadvantage under which an air 
 engine labours, may be said to be included in the first. It is 
 this, that the small degree of tension it is possible to employ, 
 from the limit placed by the question of temperature, not only 
 virtually precludes the employment of the principle of working 
 expansively to any extent, but also entails the necessity of 
 employing cylinders of an enormous and unwieldy size, in pro- 
 portion to the power obtained. By cutting off the steam when 
 the piston has made -i-th of the stroke, its duty may be increased 
 more than three-fold, reducing the consumption of fuel to 33 
 per cent. Now, even supposing (what I believe to be prac- 
 tically impossible) that working expansively might be carried 
 sufficiently far in the air engine, to reduce its consumption of 
 fuel from 60 to 33 per cent. thus placing it on a level with 
 the steam engine, with regard to consumption of fuel, in pro- 
 portion to the amount of pressure obtained on the >piston ; the 
 steam engine would still possess an immense preponderance over 
 its antagonist in practical utility and convenience, on account of 
 the huge bulk of the latter, an air engine requiring its working 
 cylinder to be from 10- to 50-fold the area of that of a steam 
 engine, together with a second cylinder, as supply cylinder, about 
 two-thirds the size of the first. 
 
 208. This is stated to be the proportion between the 
 
98 ECONOMY OF FUEL. 
 
 cylinders in the marine air engine of Captain Ericsson's, which 
 now excites so much attention, whilst the tension obtained is 
 said to be 9 Ibs. Since two-thirds of this, exclusive of friction, 
 will be absorbed in working the supply cylinders, we can scarcely 
 calculate the effective pressure at more than 1-Jlb., necessitating 
 the use of cylinders of Brobdingnagian dimensions ; arid notwith- 
 standing the new and important principle Captain Ericsson has 
 called to his aid, in his highly ingenious caloric regenerators, the 
 steam engine possesses at least an equivalent in the condenser ; 
 and I feel satis6ed that if tested, this engine would have to yield 
 the palm for duty performed, compared with fuel consumed, 
 to our best Cornish engines. 
 
 209. In short, there is not at present on the horizon the 
 faintest dawn of the appearance of any mode of generating force, 
 calculated to compete with, much less to supersede, the steam 
 engine. Whether a time may ever arrive when we may be able 
 to concentrate, and economically employ, the immense currents 
 of thermo-electricity which we know must result from the action 
 of the sun's rays and the rotation of" the earth, and thus obtain 
 a supply of power as costless as a running stream, the wind, or 
 the tides ; yet without the intermittent character which interferes 
 with the practical application of the two latter, is a question at 
 present purely problematical, and no earnest of future success 
 has yet been obtained. Electro-magnetism, from which once 
 (from imperfect knowledge) much was expected, is now tho- 
 roughly understood to be a far more costly mode of obtaining 
 power, than the combustion of coal. Heat, electricity, mag- 
 netism, chemical affinity, force, are all equivalent to each other, 
 according to ratios which are fixed and unalterable. The atomic 
 weight of carbon is 6, that of zinc 32 : 1 Ib. of carbon will 
 develop more heat, and consequently more force, than 5 Ibs. of 
 zinc ; whilst, weight for weight, the cost of the former is to the 
 latter as 1 to 50. On this subject Liebig aptly observes, " it is 
 highly probable, that if we were to burn under the boiler of a 
 steam engine, the quantity of coal required for smelting the zinc 
 from its ores, we should produce far more force, than the whole 
 
ECONOMY OF FUEL. 99 
 
 of the zinc so obtained could originate, in any form of apparatus 
 whatever." 
 
 210. The practical inference to be drawn from the preceding 
 considerations is, that the improvement of the steam engine 
 the means of obtaining from it a greater return of duty, in pro- 
 portion to the fuel expended is one of the most important 
 subjects which can engage the attention, and occupy the energies, 
 of a manufacturing and commercial people. 
 
 211. That great advances can, and will be made on our 
 present achievements, none can doubt, who have examined and 
 compared for themselves, its theoretical capabilities, with its 
 present performances. The direction in which an increase of 
 duty is to be sought, is, in. my opinion, 1st, by using steam 
 of a higher pressure; 2ndly, by applying heat directly to the 
 cylinder and steam pipe. Both of these expedients have an 
 economic value per se, and both contribute to increase the ad- 
 vantages of working expansively, not only by imparting to this 
 system a higher value within a given range, but also by increas- 
 ing the range to which it may be beneficially extended, by lessen- 
 ing the disparity between the initial, and terminal pressures of 
 the steam. 
 
 212. If we use steam of 90 Ibs. pressure, and cut off at -J-th., 
 and by the application of heat, keep the cylinder at a temperature 
 which will ensure its not abstracting any heat from the steam, then, 
 at the termination of the stroke, instead of atmospheric steam 
 of 15 Ibs. pressure, we shall have atmospheric steam + 34, 
 or, in other words, sub-saturated steam of 18 Ibs. pressure. 
 Now, 18 Ibs. is only th of 90 Ibs., so that in reality^ we realize 
 the effect of cutting off at -i-th, not only with respect to the 
 amount of disparity between the initial and terminal pressures, 
 but also as regards the sum of the duty done. If, on the con- 
 trary, (using the same pressure and degree of expansion,) a 
 portion of the steam be allowed to undergo condensation in the 
 cylinder, the result is, that at the termination of the stroke, the 
 pressure becomes re'duced to 13 lbs. 3 or even less, diminishing in 
 
 F 2 
 
100 ECONOMY OF FUEL. 
 
 reality the performance of the engine below that assigned by 
 theory to cutting off at |th. In short, to equal the pressure on 
 the piston obtained by cutting olf at th, where the application 
 of heat to the cylinder prevents the abstraction of any from the 
 steam, (equalling a terminal pressure of 181bs.), in an engine 
 where this precaution is neglected, it would be necessary to cut 
 off at about ith. Now, the difference in the consumption of 
 steam or fuel, between cutting off at fth or th, amounts to 33*3 
 per cent, and I believe this to be by no means an exaggerated 
 representation, of the relative economy of the two systems. 
 
 213. In short, whenever engines are worked expansively, 
 (and all are, or should be), and more particularly condensing 
 engines, heating the cylinder should be deemed a sine qua non, 
 and to neglect doing so, an act of consummate folly, inasmuch 
 as it is a wanton sacrifice of 30 per cent, of useful effect, when no 
 obstacle exists. in the way of its attainment. What makes such 
 remissness the more unpardonable, is the fact, that the advan- 
 tages of the system have been practically demonstrated and pro- 
 claimed in Cornwall for twenty years past ; whilst the expla- 
 nation of its mode of action, was made clear by the publication 
 in this country, in 1848, of the researches of Eegnault. Extra- 
 ordinary however as such a statement may seem to the reader, I 
 believe it to be a fact, that there is nol at the present moment, 
 either in the Eoyal Navy, or the mercantile marine, a single 
 steamer fitted with any apparatus for heating the cylinders, and 
 as a necessary consequence, all their attempts to carry the prin- 
 ciple of working expansively, beyond the narrowest limits, prove 
 abortions.* The cause of this singular supineness must be 
 
 * At a recent trial of one of Her' Majesty's screw steamers, constructed 
 with four cylinders, for the express purpose of better obtaining the economy 
 due to a considerable extent of expansive working, it was found that a better 
 effect was obtained by using only two cylinders, and cutting off at half stroke, 
 than by using the same quantity of steam in the four cylinders, and cutting off 
 at one-fourth, although theoretically, the result in the latter case ought to 
 have been nearly 50 per cent. more. The cause of the anomaly was obviously 
 the greater proportional condensation of the steam by the four cylinders, than 
 by the two, and the result might have been predicted. 
 
ECONOMY Olr FUEL. 101 
 
 sought in the fact, that the manufacture of steam engines is 
 regarded too much from a commercial point of view, by those 
 engaged in it ; whilst the want of knowledge of the subject in 
 those who order, and pay for them, places them entirely in the 
 hands of the makers. 
 
 214. The following calculation of the theoretic capabilities of 
 the steam engine, is interesting and instructive, and likely to be 
 of utility, by begetting ih'dt faith in the success of efforts for its 
 improvement, which is the parent of earnest endeavour. 
 
 215. I shall first estimate the theoretic power of an engine 
 worked with an initial pressure of 150 Ibs., cutting off the steam 
 at -j-^t h of the stroke. Next, of an engine worked with an initial 
 pressure of 90 Ibs. cutting off at th* of the stroke. In both 
 
 * I believe the time will come, when it will be quite an exceptional case, 
 for an engine to be worked at a lower pressure, or at a lower grade of ex- 
 pansion than this, for the simple reason, that there is nothing to prevent this 
 degree being generally used, and therefore, that to employ less, will be 
 regarded as sacrificing economy without an object. The ignorance which 
 prevails on this subject at present is quite extraordinary. Thus, in the Jury's 
 report of Class V. of the Great Exhibition of 1851, we are told, with reference 
 to a French steam engine otherwise commended, "The high pressure (7 5 Ibs. 
 per square inch) at which it is proposed to work this engine, is however to 
 be deprecated, as attended with great risk, and with great loss, by reason of 
 the high temperature" It is to be regretted that a reporter on the subject 
 of steam engines, should have been unacquainted with the fact, that the Cornish 
 engines, which greatly surpass all others in economy, habitually use steam of 
 75 Ibs. pressure, and often above ; whilst, with regard to the frequency of ex- 
 plosions, they present a marked and happy contrast, to what appears to be 
 the rule in other parts of the kingdom. In treating of rotary engines, the 
 same report informs us, that " thanks to the more general diffusion of infor- 
 mation in mechanics, practical men now know, that there is no more possi- 
 bility of increasing the work of an engine, by merely altering the direction of 
 the motion of any of its working parts, than there is of increasing the quantity 
 of water which a reservoir will supply, by varying the pipes which serve to 
 distribute it." Thus we are required to believe, on high authority, that there 
 is no loss of momentum (= power) from the arrest and reversal of motion, 
 inseparable from all reciprocating engines. Fortunately, the simple instincts 
 of most men will suffice to prevent their being indoctrinated with such an 
 absurdity. 
 
102 ECONOMY OF FUEL. 
 
 cases the internal surface of the cylinder to be preserved at the 
 temperature due to the initial pressure of the steam, so that at 
 the termination of the stroke, no heat shall have been abstracted 
 from the steam by the cylinder, but on the contrary, a slight 
 amount added. The theoretic values thus obtained, I shall then 
 compare with the actual performances of our present Cornish and 
 
 marine engines. 
 
 Ibs. 
 
 Steam of 1 50 Ibs., cut off at -j^th., will exert a mean pressure of 49*5 
 
 Allow 10 per cent, for increase in elasticity, from steam be- -\ 
 
 coming sub-saturated, with 46 surplus heat, and a tension > = 4' 95 
 of 18' 5 Ibs. at the end of the stroke . . . . ; -J 
 
 Vacuum 12 
 
 Total . . 66-45 
 
 Ibs. Ibs. 
 
 66*45 x 144 = 95 68' 8 raised 1 foot, by 1 cubic foot of atmospheric steam + 46 
 of heat. 
 
 vol, of 
 
 Ibs. steam, 
 
 568'8 x 1669 = 15,970,327 raised 1 foot, by the conversion of 1 cubic foot 
 of water, into steam of 150 Ibs. = the addition to 1 cubic foot 
 of water at 100, of 1078'8 + 46 of heat. 
 
 '.,. ' Ibs. 
 
 Steam of 90 Ibs., cut off at Jth., will exert a mean pressure of 42 
 
 Allow 10 per cent, for increased elasticity, from steam becoming -\ 
 
 sub-saturated, with 34 surplus heat, and a tension of > = 4'2 
 
 18 Ibs. at end of stroke . f ' ' . ) 
 
 Vacuum 12 
 
 Total . . 58-2 
 
 Ibs. Ibs. 
 
 58'2 x 144 = 8380-8 raised 1 foot, by 1 cubic foot of atmospheric steam + 34 
 of heat. 
 
 Ibs. vol. Ibs. 
 
 8380-8 x 1669=13,987,552 raised 1 foot, by the conversion of 1 cubic foot 
 of water, into steam of 90 Ibs. = the addition to 1 cubic foot 
 of water at 100, of 1078'8 + 34 of heat. 
 
 A cubic foot of water weighs 6 2 '3 2 Ibs. Allowing 5 Ibs. of 
 coal to evaporate this quantity, (= 12-464 Ibs. per Ib. of coal, 
 
ECONOMY OF FUEL. 103 
 
 and 12- 9 has been done) we get as the theoretical duty of 1 Ib. 
 of coal 
 
 Ibs. Ibs. coal. Per centage 
 
 In engine with initial"^ of duty. 
 
 3 194 065 * raiscd l ft _ . 62 (per k. p. 
 ' 
 
 pressnreof 150 Ibs / 
 and cutting off aU 
 *th ... J 
 
 ( per hour ) 
 
 In engine with initial ") 
 
 pressure of 90 Ibs., V 3,797,511 // ='70 87'58 
 
 and cutting off at^-th j 
 Utmost duty known "J 
 
 to have been per- 1 -. 9Q 7R7 1 , ft , 
 
 formed by a Corn- C M*V$? 
 
 ish engine . . . ) 
 Common amount of") 
 
 duty for a superior 1,000,000 // =1'98 Sl'SQ 
 
 Cornish engine . 3 
 
 ^,000 . -M4 . ,3-48 
 
 450>00 " =4 ' 4 " 14 ' 09 
 
 216. The chief obstacle to our using high-pressure steam, is 
 the belief that safety would be compromised by so doing. Now 
 I frankly admit, that if the use of high- pressure steam will entail 
 as a necessary consequence, a more hazardous state of things 
 than exists at present (when one can scarcely take up a news- 
 paper which does not contain the details of some shocking catas- 
 trophe, attended with the loss of life from the bursting of boiler sf), 
 
 ** Equals 227 Ibs. raised 1 foot, by heat sufficient to raise lib. of water 
 1 Fahr. Mr. Joule estimates the mechanical value of this quantity of heat 
 applied to air, to be equal to raise 7 82 Ibs. 1 foot. But, in capability of 
 practical application, air is, as I have already explained (see par. 206), greatly 
 inferior to steam. 
 
 f This subject ought to be made an object of legislation, not by vexatious 
 enactments intermeddling with the structure of boilers, or the pressure of 
 steam, but simply by requiring every boiler to be periodically tested to three 
 times its working pressure, and a certificate of the fact attested by signatures, 
 forwarded to the proper officer. The laissez faire system has already been 
 tried too long in this matter, one in which human life is at stake, and where the 
 unfortunate victims, principally made up of the workmen in factories, have no 
 power to protect themselves. Public safety, in cases where the public have 
 not the power of self-protection, is unquestionably a proper object for a 
 
104 ECONOMY OF FUEL. 
 
 all idea of extending its use should be definitively abandoned. 
 It is however easy to show, that nothing of the kind is to be 
 anticipated, and that however plausible in appearance, may be the 
 popular notion, which connects danger with high-pressure steam, 
 it is in reality a prejudice which will not stand the test of exami- 
 nation. 
 
 217. As we boast of being a practical people, let us first test 
 the question by practical results, and appeal to facts. The 
 engines which use the highest pressure steam (amounting some- 
 times to 120 Ibs.) in this country, are the locomotives ; yet it is 
 not from this class that the sad list of casualties by explosions is 
 made up, and the Cornish engines, which come next with regard 
 to pressure of steam, enjoy a like immunity from disaster. The 
 same smaller per centage of accident attending the use of high- 
 pressure boilers which prevails in this country, extends likewise 
 to America, it having been stated in a memorial to Congress, that 
 since the more general introduction of high-pressure steam, the 
 number of accidents had not only not increased, but had be- 
 come lessened in an extraordinary degree. 
 
 218. That such would be the case, is precisely what a know- 
 ledge of the subject would lead us to anticipate. Dr. Ernst 
 Alban justly observes, <c As the strength of the metal is adapted 
 to the working pressure, the proper elasticity for which the vessel 
 is constructed, must be exceeded before an explosion can occur ; 
 but there is an advantage on the side of the high pressure engine, 
 for the elasticity must be increased in a much higher ratio, than 
 with the low pressure engine, before it overcomes the pressure at 
 which the boiler is proved (usually three times the working 
 
 legislative enactment. A subject that calls aloud for it at the present moment, 
 is that of the adulteration of food. Now that in addition to chemical tests, the 
 microscope has placed such an unerring and easily available detective officer at 
 our command, this gigantic system of fraud and imposture, might easily be 
 strangled, with no injury to any but the miscreants who gain a dishonest 
 livelihood, by ruining the honest trader, and slowly poisoning the rest of 
 the community ; and compared with whose doings, the occupations of ordi- 
 nary criminals are harmless. 
 
ECONOMY OF FUEL. 105 
 
 tension) ; and therefore a much longer time will elapse, before 
 absolute danger arises. For example, in a boiler working at 
 8 atmospheres, it will take a much greater lapse of time for the 
 pressure to rise to 24 atmospheres, than it would to reach 
 241bs. per square inch in a boiler working at 81bs. ; and these 
 would be the jjpints at which danger may be supposed to arise in 
 the respective cases." M. Arago notices the same fact, and 
 characterizes the fear of high-pressure boilers as mere prejudice. 
 See Echo du Monde Savant, No. 484. 
 
 219. The great point we have to look to however, to ensure 
 perfect freedom from all danger of explosion, both with 
 high-pressure and low-pressure boilers, is the substitution 
 of boilers consisting wholely of tubes of moderate dimensions, 
 in place of the huge (and therefore dangerous) chest or barrel- 
 shaped vessels in use at the present day; and also the substitution 
 of copper for iron, more particularly for marine boilers. Since 
 the strain on the boiler plato is, ceteris paribus, directly pro- 
 portionate to the diameter of the vessel, the same thickness of 
 boiler plate which would be selected for a marine boiler 
 12 feet square, to work at a pressure of 151bs., and consequently 
 as competent to undergo a test of 451bs., would, if made into a 
 tube of 12 inches diameter, be competent to undergo a strain of 
 5401bs. ; and would, if used in this form as a boiler for high- 
 pressure steam of 1501bs., be so infinitely safer than with steam of 
 151bs. pressure, and the former dimensions, that any attempt to 
 put the two in competition would be ridiculous, since in one case 
 we have a boiler working at 301bs. below the strain to which it 
 might safely be subjected, in the other at 3901bs. 
 
 220. Iron is an unsuitable material for marine boilers, from 
 the facility with which it becomes corroded ; and whilst its use is 
 continued, in conjunction with the present form ormarine boiler, 
 that degree of assurance against liability to danger, with less than 
 which we ought not to be content, can never be permanently 
 maintained. Copper, though the first cost is five times that of 
 iron, lasts five times as long, and is worfh }ialf-price when worn 
 
 F3 
 
106 ECONOMY OF FUEL. 
 
 out ; whilst its conducting'' power being as compared with iron, 
 as 2 '4 to 1, a much smaller extent of heating surface, and water 
 space, suffice. Its crowning advantage however is its safety, 
 from the circumstance that it does not fly asunder, causing de- 
 structive explosions, like iron, but from its greater ductility, simply 
 opens with a rent, which seldom causes any serious damage. 
 Indeed, by leading a pipe into the funnel weaker than the rest of 
 the boiler, so as to insure this part being the first to give way in 
 the event of undue pressure taking place, even the risk of scald- 
 ing is prevented, and no more danger need ensue from the rup- 
 ture of a boiler, than from the opening of a safety valve. 
 
 221. We may then assure ourselves of this, that if high-pres- 
 sure steam is more economical than low, we need not debar 
 ourselves from its advantages, by any apprehensions on the score 
 of safety. It would indeed be an extraordinary thing, if, whilst 
 Faraday in his experiments on the liquefaction of the gases, can 
 obtain a pressure of 50 atmospheres in glass tubes, any real dif- 
 ficulty or danger should exist, in subjecting copper ones, to a 
 pressure of 10. 
 
 222. Watt, who filled a large sphere of activity during 
 his useful career, found at its commencement, the art of con- 
 struction in metal in so rude a state, that as a preliminary to 
 making an efficient steam engine, he had to construct machines 
 for the manufacture of its several parts, and educate workmen to 
 use them. The imperfect workmanship of his day, threw an 
 obstacle in the way of the application of steam of very high- 
 pressure, from the difficulty of obtaining valves sufficiently steam- 
 tight. Were Watt to reappear at the present day, with its 
 greatly improved facilities for workmanship at his command, he 
 would be the last man to rest apathetically contented with his 
 former achievements. On the contrary, it is not to be doubted, 
 but that he would apply himself assiduously and successfully, to 
 realize the increase of duty, theory shows to be placed within our 
 reach, by the judicious application of high-pressure steam. The 
 present is not as the past. The foreigner treads on our heels, 
 
ECONOMY OF FUEL. 107 
 
 We live in an era of progress, in which those who do not advance 
 are left behind. In no other country is theory and practice so 
 disjoined as in England, where men follow by routine, professions, 
 without any knowledge of those scientific principles, upon which 
 all their proceedings should be based. From year to year do 
 they contentedly travel on in one jog-trot pace, with all the con- 
 tempt for novelty, which it is the province of ignorance to engen- 
 der, and that overweening self-confidence and conceit, which arises 
 from limited vision. The day arrives when this misplaced 
 self-satisfaction is rudely overthrown by defeat, and nothing then 
 equals their surprise and astonishment,* but their previous blind- 
 ness and obstinacy. 
 
 * Witness the effect produced by the well-earned triumph of the yacht 
 America, rive years before, some of our leading yacht's-men and most cele- 
 brated yacht builders had their attention called to the subject of hollow 
 bows, with a hint that if they continued to refuse to adopt them, the result 
 would be, that sooner or later their crack craft would get disgracefully beaten. 
 The friendly warning was received with contempt and derision. One well- 
 known builder wrote a work on ship building, containing the usual orthodox 
 platitudes on new f angled notions, presumption of those who set aside the 
 authority of ages, folly of abandoning rules sanctioned by experience, 8fc. 
 <^c. The same year which witnessed the publication of this book, witnessed 
 the victory of the America, furnishing an appropriate commentary on the 
 wisdom of the writer. 
 
 We are now (1853) busily engaged in building Screw line-of-battle ships, 
 but instead of being in our proper position the leaders of the world we 
 are become followers, in the wake of the Americans and the French. In 
 1837, Capt. Ericsson (who subsequently introduced 4he Screw in the United 
 States) with a small Screw vessel only 45 ft. long and 8 ft. wide, towed the 
 Admiralty barge, with their Lordships on board, from Somerset House to 
 Blackwall Wharf, at the rate of 10 miles an hour. Notwithstanding the 
 highly satisfactory result of the experiment, Capt. Ericsson was told, in a 
 reply which the subsequent success of the Screw has already rendered his- 
 torical, " that their Lordships declined to entertain the project " One would 
 have supposed that the vast superiority of the Screw over the Paddle-wheel, 
 for vessels of war, would have been seized at a glance, but some are afflicted 
 with weak vision ; and as Schiller so forcibly and happily expresses it " Mit 
 der Dummheit kampfen Gotter selbst vergebens." "Alas! there is no 
 possibility for poor Columbus at any of the Public Offices, till once he 
 become an Actuality, and say " Here IS the America I was telling you 
 of." Carlyle's Life of Cromwell. 
 
108 ECONOMY OF FUEL. 
 
 An examination of the question whether heat be a material 
 substance, or simply the result of vibrations of the atoms of 
 bodies, as supposed by Davy, would be inconsistent with the 
 objects of an elementary work like the present. Those who 
 are desirous of investigating the subject, will find an interesting 
 paper advocating a theory of vortices, by Mr. Eankine, in the 
 Transactions of the Koyal Society of Edinburgh, vol. xx. part 1. 
 entitled " On^the Dynamical Theory of Heat." 
 
 The fundamental suppositions are : First, that each atom of 
 matter consists of a nucleus or central physical point enveloped 
 in an elastic atmosphere, which is retained in its position by 
 forces attractive towards the nucleus or centre. 
 
 The second supposition, being that from which the hypothesis 
 of molecular vortices derives its name, is the following : that the 
 elasticity due to heat arises from the centrifugal force of revolu- 
 tions, or oscillatious among the particles of the atomic atmospheres; 
 so that quantity of heat is the vis viva of those revolutions or 
 oscillations. This supposition appears to have been first defini- 
 tively stated by Davy. 
 
 To connect this hypothesis with the undulatory theory of 
 radiation, Mr. Eankine introduces a third supposition : that the 
 medium which transmits light and radiant heat, consists of the 
 nuclei of the atoms vibrating independently, or almost independently 
 of their atmospheres ; so that the absorption of light and of radiant 
 heat, is the transference of motion from the nuclei to their atmo- 
 spheres, and the emission of light and of radiant heat, the 
 transference of motion from the atmospheres to their nuclei. 
 
APPENDIX. 
 
 ON DWELLING-HOUSE GEATES AND 
 VENTILATION. 
 
 Of all the discoveries of the present age, none is likely 
 to be more prolific in benefit, than the recognition of the great 
 truth, that the physical well-being of a people, is a necessary 
 preliminary to their moral progression. As the blossoms of the 
 plant unfold themselves under the influence of genial sunshine, 
 but are nipped and repressed by the chilling wind of winter, 
 so do what may aptly be called the blossoms of man's mixed 
 nature, his social, kindly, benevolent, and imaginative tendencies, 
 and his reverence for the true and beautiful, expand themselves, 
 and reach their highest stage of development, when unimpeded in 
 their growth by the irritable and selfish feelings which unsatisfied 
 physical wants are prone to call into action. The inventor of 
 the steam engine, did more to promote the progression of his 
 species, in morality, virtue, and happiness, than any twelve of the 
 most eloquent preachers that ever addressed an assembly ; be- 
 cause, in proportion to the ease with which men can furnish 
 themselves with the necessaries of life, will they be lifted above 
 an exclusive preoccupation with their animal and selfish instincts, 
 and acquire leisure for the cultivation of the nobler portion of 
 their nature. 
 
 The most effectual way to improve mankind, is to make 
 the path to improvement easy, for it is precisely those who are 
 the deepest sunk in degradation, and have the greatest need of 
 amendment, who are the least amenable to the influence of precept 
 and teaching. If, for instance, the metropolis and all our large 
 towns, were to be copiously and cheaply furnished with a sup- 
 ply of pure water ; and were there erected, at suitable intervals 
 in every thoroughfare, a marble stand and fountain, tended by some 
 cleanly matron in fresh starched cap and snow-white apron, 
 
110 DWELLING-HOUSE GRATES AND VENTILATION. 
 
 whose duty it should be to furnish to every passer-by who re- 
 quested it, a glass of nature's greatest luxury " without money 
 and without price," intemperance would receive a death blow, 
 which all the laudable efforts of temperance societies, have 
 hitherto failed to inflict upon it. What a noble object for the 
 ambition of a statesman to have his name associated with such 
 an undertaking, a measure which would elevate his character in 
 the eyes of his countrymen, more than a hundred triumphs in 
 party squabbles, and constitute him the benefactor of genera- 
 tions yet unborn. But alas ! our rulers of the present day, 
 with all the advantages of modern civilization, seem to have a 
 more imperfect knowledge of what true greatness really consists 
 in, as well as of their duties to the people they govern, than the 
 old Eoman, Appius Claudius. 
 
 More indispensable however than even a pure supply of water, 
 is that of fresh air, and the subject of ventilation is so closely 
 connected with that of heating, that it is difficult to consider 
 them apart. Fifteen times per minute does man inhale the 
 breath of life, and discharge it from his lungs shorn of one-fourth 
 part of its oxygen with the quantity of carbonic acid increased 
 more than 100-fold and impregnated in addition, with noxious 
 animal impurities. The air issuing from the ventilator of a 
 crowded apartment, is of so deleterious and poisonous a nature, 
 that it is dangerous to breathe it even for a short space of time, 
 and pure water through which it has passed becomes putrid. 
 In the close, overcrowded, and ill ventilated habitations of the 
 poor, it is this same noxious animal emanation in the breath, 
 combined with that of the perspiration, which, becoming con- 
 densed upon the walls and furniture, imparts to such apartments 
 their peculiar sickly, noisome, and foetid odour, giving origin to 
 fevers, and producing a lowering of the tone of all the vital 
 functions, predisposing the occupants to the attacks of disease in 
 general. 
 
 If this description is inapplicable to the dwellings of other 
 classes of society, it is more from the larger size of their rooms, 
 and their greater care in cleansing them, than from the adoption 
 of any systematic and adequate plan of ventilation. Unfor- 
 tunately, the association of this, with their idea of cleanliness, is 
 yet to be effected, and we daily see persons scrupulously clean 
 in their persons, most unsparing in the ablutions of their bodies 
 and apartments, perfectly indifferent on the subject of aerial 
 contamination, and apparently ignorant of its existence. There, 
 
DWELLING-HOUSE GKATES AND VENTILATION. Ill 
 
 are however many gradations of defective ventilation, and if the 
 dwellings of the middle and upper classes, do not offend our 
 olfactory organs on entrance, from the stale accumulations of 
 putrid effluvia, they are nevertheless devoid of that freshness 
 and sweetness, which only free and ample ventilation can im- 
 part, and the health of the inmates is wanting in the vigour, ro- 
 bustness, and elasticity, characteristic of a perfectly normal state. 
 
 When crowded evening parties, with their adjuncts of gas- 
 lights and candles, take place in apartments where no arrange- 
 ments for ventilation are provided, an atmosphere is produced 
 perfectly intolerable to those whose feelings have not been 
 blunted by habit. When it is considered that an individual 
 respires about one- sixth of a cubic foot of air per minute, and 
 that this, by mixing, renders 2 or 3 cubic feet unfit for respira- 
 tion, so that in order to preserve a pure atmosphere in a room, 
 the lowest estimate of supply required, is 4 cubic feet per 
 minute for each individual, we shall be painfully impressed with 
 the ignorance of those hosts, who crowd their apartments with 
 guests, for whose entertainment they spare no luxury which 
 wealth can supply, whilst they make no provision for furnishing 
 them with that most indispensable of all requisites to life and 
 vivacity pure air, but poison them with noxious aerial contami- 
 nations, and send them to their homes, dull, listless, depressed, 
 and irritable. 
 
 The habit of excluding fresh air, is unquestionably greatly 
 fostered by the craving for warmth, and the deficient power of 
 our heating appliances to keep up the degree of warmth most 
 congenial to our feelings, when a free circulation of fresh air is 
 allowed. To the poor, fuel is a very expensive item, so that we 
 can hardly wonder at their attempting to economize it at the 
 expense of ventilation, of the necessity of which they are ignorant; 
 and all endeavours to induce them to change their system will 
 I feel assured prove fruitless, till we enable them to do it 
 without sacrificing that warmth they so much enjoy, and which 
 defective food and clothing too frequently disable them from 
 dispensing with. It is under this point of view, that the 
 improvements of their grates becomes so important, for could we 
 put them in possession of a means of producing twice or thrice 
 the amount of heat, with the same expenditure of fuel, I feel 
 assured an improved ventilation of their apartments would follow 
 as a necessary consequence, whilst without it, our utmost efforts 
 in this direction will have but a very limited effect. 
 
112 DWELLING-HOUSE GKATES AND VENTILATION. 
 
 Till within a comparatively recent period, in no department 
 has a more singular want of intellect been conspicuous, than in 
 the prevailing form of dwelling-house grates, which might have 
 been supposed to have been constructed with a view to distil- 
 ling and dissipating a certain quantity of fuel, and sending the 
 products up the chimney, and with an opening into the apart- 
 ment, merely for the purpose of inspecting the process, and 
 renewing the fuel, rather than to have been fabricated for the 
 express object of heating the latter. A square box for the fuel, 
 standing in a deep recess, with straight jambs running parallel to 
 its sides, so as to reflect as little as possible of the heat into the 
 apartment, with a wide yawning chimney placed directly above the 
 fire, formed an ensemble, the object of which it surely would have 
 been pardonable to mistake. 
 
 Nothing more clearly shows the force of habit, and how few 
 persons possess an intuitive perception of the tendency of such 
 arrangements, and their consequent absurdity, than the fact, that 
 such a system of construction should have so long maintained its 
 ground, particularly when it is considered that the principles 
 which should govern the construction of a fire-place, are few, 
 simple, and obvious. 
 
 It is true that many very improved forms of grates have been 
 recently introduced^ many very excellent in certain points, but 
 none such as I have long desired to see, viz. a model possessing 
 every feature of excellence in the highest degree in which such a 
 combination is attainable. The test of a grate should be a 
 thermometer, and its artistic merits, as far as beauty of form, 
 material, and workmanship go, should be made a separate ques- 
 tion, and not mixed up with the consideration of its heating 
 capacities. Let perfection, or its nearest attainable approxima- 
 tion in the latter qualification, be once realized, and beauty of 
 form, and appropriateness of decoration, may easily be super- 
 added by some other hand, requiring as they do, faculties of an 
 essentially different class, in the designer. 
 
 The present remarks have been written with the intention of 
 taking a precise view of the objects most desirable of attainment, 
 for the purpose of deducing some general fixed principles of con- 
 struction, the correctness of which, becoming universally recog- 
 nised as indisputable, a more uniform degree of excellence in the 
 manufacture may be hoped for; whilst the public being educated 
 to a knowledge of the subject, will reject inferior productions, 
 even though set off with a high degree of artistic skill and 
 beauty. 
 
DWELLING-HOUSE GRATES AND VENTILATION. 113 
 
 The first position I shall lay down, is, that it is desirable to 
 obtain the greatest possible quantity of heat from the fuel, 1st, 
 by direct radiation, 2ndly, by reflection, and 3rdly, by secondary 
 radiation, before it passes into the region of the flues. This 
 position would of course be a mere truism, if made with reference 
 to a fire-place which possessed no contrivance for extracting a 
 portion of heat from the current of hot air proceeding from the 
 fire, before its final dismissal by the chimney into the atmosphere. 
 What I am desirous of stating however is, that whatever con- 
 trivance is resorted to for this object, whether hot air flues, hot 
 water pipes, or a circulation of air over a hot surface, it is never- 
 theless desirable, previously, to obtain all the heat by direct radi- 
 ation, reflection, and secondary radiation, (the two former more 
 especially), which we can succeed in eliciting, because such heat 
 is superior in quality, more vivifying, envigorating, genial, and 
 grateful to the feelings of man, and animals, than that furnished 
 by heated currents of air, technically termed convection. 
 
 Should any one demur to this proposition, and argue that 
 heat is heat, and that chemistry is cognizant of only one kind of 
 caloric, my reply is, that whilst our knowledge of a subject is 
 confessedly so imperfect, as is the case with regard to heat, the 
 universal instincts of man and animals, should be held to be a 
 much safer guide, than any scientific theories framed in opposition 
 to them. Only those who have a most superficial acquaintance with 
 science, can fall into the error of supposing that all her present 
 deductions are perfect and infallible, and to act as if such were the 
 case, and obstinately to reject opinions fortified by the general 
 consent of mankind, merely because they cannot be brought to 
 square with the prevalent scientific hypotheses of the day, is in- 
 dicative of a shallow and short-sighted understanding. It is this 
 unauthorised, and too often supercilious rejection by smatterers 
 in science, of the conclusions arrived at by a long course of 
 experience and observation, which more than anything else con- 
 tributes to produce, and goes far to excuse, that contempt for 
 scientific considerations, which is the besetting weakness of prac- 
 tical men, and which becomes the unfortunate means of severing 
 two classes, who can do much to assist each other. 
 
 Arguments however are certainly superfluous to convince an 
 Englishman, of the superiority of an open fire, over any system 
 of warming by close stoves, or heated currents of air. Even the 
 ingeniously arranged stove of Dr. Arnott, backed by his de- 
 servedly high authority, and the powerful consideration of 
 
114 DWELLING-HOUSE GRATES AND VENTILATION. 
 
 economy, failed to persuade his countrymen to forego that cheer- 
 ful adjunct to their dwellings, in whose rays they love to bask. 
 And there is no doubt that their instinctive feelings serve them 
 faithfully, and are much safer guides to be followed, than any 
 abstract considerations founded on scientific theories of the unity 
 of caloric. Let a man return home tired and fatigued, after 
 a day's exposure to wet and cold, can any one even imagine 
 that under such circumstances, the heat of a close stove would 
 be found as grateful and sufficing to his feelings, as cheerful, 
 enlivening, and restorative, as that of an open fire ? unquestion- 
 ably not; and since such marked difference in effect, must have 
 a cause, we are as well warranted in assuming a difference in the 
 quality of the emanations which impinge on our nerves, as if we 
 could exhibit this difference under a microscope, or weigh it in a 
 balance. Yery contracted must be the ideas of those who cannot 
 imagine the possibility of the existence of agencies in nature, the 
 effects of which cannot be exhibited in any change in inorganic 
 matter, but which find their proper sphere of action in the organic 
 world. 
 
 Our knowledge of the emanations from fire, is besides far too 
 limited, to warrant any dogmatic assertions of their not being 
 of a compound nature, indeed there are many facts which go to 
 prove a variation in the properties of heat, according to its source; 
 and even if, as may very plausibly be argued, this variation 
 depends merely in difference of velocity, this by no means 
 impairs the validity of our argument, that there are different 
 qualities of heat, independent of mere thermonietric intensity, as 
 far as its power of acting on the organism of animated beings 
 is concerned.* 
 
 * Some of the facts however, brought to light by the most recent re- 
 searches on heat, are with difficulty explainable on the theory that its 
 properties vary only as the result of variations in velocity, but seem to point 
 to the existence of differences of a more specific nature. Thus, although as 
 a general law, the hotter the source of heat, the greater the number of the more 
 refrangible rays emitted from it, and the lower the temperature, the greater the 
 number of the less refrangible, the law is only absolutely correct, with regard 
 to each source, compared with itself, at different stages. " Every source 
 sends forth however a mixture of calorific rays of the most various degrees 
 of refrangibility, the proportion only, varying with the nature of the source. 
 For these different rays of heat, bodies exhibit different absorbing powers. 
 Snow, whose whiteness shews that it reflects the various refrangible rays of 
 light in equal proportion, absorbs chiefly, the less refrangible rays of heat, 
 and reflects the more refrangible. Hence it does not melt so quickly in 
 direct sunshine, as in the neighbourhood of stems of trees and other solid 
 
DWELLING-HOUSE GRATES ANB VENTILATION. 115 
 
 It must not be supposed, that in advocating the propriety of 
 obtaining the largest possible amount of heat by direct radiation 
 from the ignited fuel, by reflection, and lastly, by secondary 
 radiation, before the heat is allowed to escape into the regions 
 of the flues, that 1 propose to neglect the means of still further 
 economy open to us, by extracting a portion of the heat contained 
 in the products of combustion, instead of allowing it to be 
 wasted and pass unused up the chimney. On the contrary, so 
 wasteful and extravagant a system ought never to be deemed 
 satisfactory; and where large and long rooms are to be heated by 
 a single fireplace, without some plan is adopted for transfering 
 the heat to the portions most distant from the fire, either by hot 
 water pipes, hot air flues, or heating the current of air with 
 which the apartment is supplied, a satisfactory equalization of 
 the temperature in all parts of the room is scarcely to be 
 attained. What I contend for is, that since the extraction of the 
 greatest possible amount of heat, by direct radiation from the 
 burning fuel, by reflection, and by secondary radiation, as a first 
 step, in no way interferes with the after treatment of the 
 products of combustion, in any method which shall be deemed 
 
 bodies, which, when warmed by the sun's rays, emit calorific rays of less 
 refrangibility ; not so quickly, when freely exposed to an Argand lamp, as 
 under a covering of black paper which does not touch the snow; not so 
 quickly by the rays of an Argand lamp, as by those from a piece of metal 
 heated to 720, when both are placed at such a distance, that their heating 
 powers are equal." (Melloni.) This seems to shew that the more refrangible 
 rays of heat, when they are absorbed by bodies, and afterwards emitted from 
 them, are converted into rays of less refrangibility. Lamp black, on the 
 other hand, appears chiefly to absorb the more refrangible rays. " Common 
 salt transmits all rays of heat equally well ; most diathermanous bodies chiefly 
 transmit the more refrangible, and absorb the less refrangible rays. Common 
 salt covered with lamp black, is the only substance chiefly pervious to the 
 less refrangible rays." " When the light of the sun is made to pass through 
 water, which absorbs the less refrangible rays of heat, then through glass 
 covered with oxide of copper, which takes up the more refrangible, it is 
 totally deprived of its heating power." (Melloni.) " The maximum of heat 
 is found in different parts of the spectrum, according to the nature of the 
 prism." (Seebeck.} " The quantity of radiant heat transmitted through 
 diathermanous bodies is not directly proportioned to the temperature of the 
 source, but depends only on the constitution of the diathermanous body, 
 each body being permeated by certain calorific rays, more readily than by 
 others, whether those rays are emitted at a higher, or at a lower tempera- 
 ture. The heating effect produced, when the radiated heat which reaches 
 the bodies is of given intensity, is totally independent of the temperature 
 of the source, and determined only by the nature of the absorbing bodies, 
 which receive certain rays more readily than others." (Knoblauch,} 
 
116 DWELLING-HOUSE GRATES AND VENTILATION. 
 
 most desirable, for making them yield up a portion of the heat 
 with which they are charged, and since moreover we have seen 
 that the heat attainable from the first-named sources is of a 
 superior quality to that derivable from the second, its attain- 
 ment in the largest possible quantity, should be the first object 
 aimed at. 
 
 It is commonly supposed that the disagreeable sensations 
 experienced by breathing the atmosphere of apartments heated by 
 closed stoves, depends upon the temperature of the iron casing 
 being sufficiently high to burn the particles of dust and other 
 impurities floating in the air, together with the dryness of the 
 atmosphere produced. That the latter cause, viz. the great change 
 effected in the hygrometric properties of the air, by the dispro- 
 portion between its temperature and its dew point, exercises 
 a considerable influence on the animal economy, when long 
 subjected to its operations, there can be no doubt, but that it is 
 the sole, or even principal cause of the effects experienced from 
 the use of stoves, is, I think, more than questionable. If I 
 mistake not, influences of a more subtle nature are at work, and 
 it is far from improbable, but that these may consist of changes 
 in the electric or magnetic qualities of the air, induced by 
 contact with the heated metal. As far as my own sensations go, 
 I always experience a certain sense of malaise when in an 
 apartment heated by an iron surface, although such surface is at 
 a comparatively low temperature, as in the case of an Arnott 
 stove, or hot water pipes, and notwithstanding a hot water 
 vessel may be employed to afford due moisture by evaporation. 
 Even the atmosphere of the spacious and lofty hall at the Euston 
 Square Terminus, (which is heated by hot water pipes) is to me 
 excessively disagreeable, and if long breathed, would be produc- 
 tive of headache, and other unpleasant effects, which I have not 
 experienced from the Continental stoves, covered, both stove and 
 pipe, with porcelain. 
 
 Ventilation has lately been considered divisible into two 
 systems, the methods of plenum and vacuum ; by the first, air is 
 forced into the building by some mechanical contrivance, and 
 allowed to escape through apertures left for this object ; by the 
 second, the building is either ventilated by the ascending force 
 imparted to the air by its increased temperature when discharged 
 from the lungs, or its exit is facilitated by the aperture left for 
 ventilation in the upper part of the room, being led into the 
 chimney, or some shaft connected either with a furnace, or a fan 
 
DWELLING-HOUSE GRATES AND VENTILATION. 117 
 
 in the upper part of the building, whilst fresh air enters through 
 appropriate channels, to supply its place. 
 
 There can be no doubt, but that what is termed the vacuum 
 method, is by far the most simple and easy of application, 
 particularly for private houses, for fires and chimneys being 
 employed for other purposes, no separate apparatus is needed ; 
 whereas a fan almost necessitates the accompaniment of a steam 
 engine. In the case of mines and ships, where the air cannot 
 be admitted from below, and all cases where large fires would 
 require to be kept burning expressly for the purpose of generating 
 a draft, a fan is both the most efficient and cheapest. For 
 private dwelling-houses however, connecting the discharge 
 openings with a chimney fulfils all the conditions required, 
 provided there be an ample supply of fresh air admitted below ; 
 for the breath being discharged at a temperature of 98, rises 
 rapidly to the ceiling by its own levity, and if proper provision 
 be made for its escape, there is no danger of its descending to 
 be breathed over again. This arrangement is in fact in harmony 
 with the great system employed by nature for the ventilation of 
 the lower and inhabited stratum of the atmosphere, which would 
 otherwise speedily become contaminated by the exhalations from 
 the living myriads which people it. 
 
 Objections have lately been urged against the vacuum system 
 of ventilation, on the plea that the atmosphere of apartments so 
 ventilated, will be kept constantly slightly more rarefied than the 
 external air, and will therefore have a tendency to produce 
 lassitude, and a relaxation of tone in those who breathe it, from the 
 amount of oxygen being less in the same volume ; whilst on the 
 contrary, it is contended that air slightly condensed will have an 
 opposite effect, and conduce to vigour and activity. M. Junot 
 says, that "When a person is placed in condensed air, he breathes 
 with increased facility , he feels as if the capacity of his lungs 
 were enlarged ; his respirations become deeper and less frequent ; 
 he experiences, in the course of a short time, an agreeable glow 
 in his chest, as if the pulmonary cells were becoming dilated with 
 an elastic spirit, while the whole frame receives at each inspira- 
 tion a fresh vital impulse ; the functions of the brain get excited, 
 the imagination becomes vivid, and the ideas flow with a 
 delightful facility; digestion becomes more active, as after 
 gentle exercise in the air, because the secreting organs participate 
 immediately in the increased energy of the arterial system, and 
 there is therefore no thirst." 
 
118 DWELLING-HOUSE GRATES AND VENTILATION. 
 
 I confess, when first I read this statement, I felt a momen- 
 tary sensation of regret, to think that the great bulk of the 
 community should be debarred from participating in advantages 
 so manifold, from the difficulty which I foresaw in the general 
 application of the fan to private dwellings, on account of the 
 motive power required. A very slight consideration however 
 sufficed, to enable me to perceive that nothing could be more 
 chimerical than these ideas, and that to hold out any such 
 results as being attainable by any practicable scheme of ventila- 
 tion, was only imposing an illusion on the public. Those, 
 therefore, who have a thirst to arrive at perfection in all things, 
 need not disquiet themselves under the apprehension that they 
 must be content to forego this desirable object with regard to 
 ventilation, unless they are prepared to keep a piece of machinery 
 constantly in motion for its attainment. Had the propounders 
 of this notable scheme, given themselves the trouble to realize 
 the details, I imagine the public would never Lave heard 
 of it. 
 
 Air, under the pressure of '04 of an inch of water, has the 
 velocity of a pleasant breeze, or 9^ feet per second. Supposing 
 a house charged with air under this pressure, the opening of the 
 door for half a minute, would give egress to 6000 cubic feet of 
 air, provided the rate of supply were equal to maintain the 
 pressure during the period. I think, from these considerations, 
 it will be apparent that, without complicated contrivances for 
 keeping the building in a state approximating to being her- 
 metically sealed, a much higher pressure than this could not be 
 practically maintained. Assuming then, *04 of an inch of water 
 to be the pressure, the condensation of the air would only 
 amount to TT o-o f its volume, whilst the variation of only 1 
 in temperature, would produce 22 times this effect. 
 
 In short, the association of "the excited brain, the vivid 
 imagination, the flowing ideas," with the breathing of air con- 
 densed n 000-9 is infinitely ridiculous an illusion, which can 
 only find an abiding place in a brain where such a state of 
 pleasing exaltation is combined with a paralysis of judgment. 
 Equally absurd and preposterous, with the encomiums lavished 
 upon the plenum method of ventilation, is the condemnation 
 that has been passed upon that by vacuum, under the mistaken 
 notion, that it gives rise to a variety of injurious effects, quite 
 beyond its power to produce. We have but to invert our 
 argument, to perceive, that as little injury is to be apprehended 
 
DWELLING-HOUSE GRATES AND VENTILATION. 119 
 
 from the rarefaction of air byy 1 ^ 00 of its volume, as there is 
 benefit to be hoped for. from this amount of condensation. 
 
 All the evils however that have been erroneously attributed 
 to the method of ventilation by vacuum, are, I believe, justly 
 assignable to the system of warming by heated air. Here, 
 we get an amount of rarefaction capable of producing a decided 
 physical influence, for air at 45 contains nearly T ^- more oxygen 
 in the same bulk, than air at 75. Thus we see, that a variation 
 in temperature of only 30, produces nearly as great a change of 
 volume, as is effected by a difference of pressure equivalent to 
 2 inches of mercury, or 27 inches of water. 
 
 When we consider, that when the air is perfectly still in 
 winter, and the thermometer at 32 in the shade, a person can 
 stand still, with -comfort in the sunshine, without feeling cold, it 
 is plain that inhaling warm air into tlie lungs, is quite unnecessary 
 to maintain the body at an agreeable temperature, and fulfil the 
 requirements of our instinctive sensations. 
 
 In short, other conditions being equal, the colder the air 
 breathed, the better will the temperature of the body be main- 
 tained, since the increased quantity of oxygen taken into the 
 lungs, will generate an additional quantity of heat, more than 
 sufficient to compensate for the increased refrigeration conse- 
 quent upon the lower temperature of the air inhaled, besides 
 which, the evaporation from the lungs will be less. Therefore, 
 the colder the weather, the colder requires to be the air for 
 respiration, and the colder nature has provided it, but we exert 
 ourselves to defeat her arrangements, and in this, as in other 
 cases, are made to pay a penalty for our ignorance. If we would 
 take a lesson out of her book, and study the care she has taken 
 to prevent the inhalation of heated air by animated beings ; in 
 the first place, by the law, that rays of heat pass through the 
 atmosphere without being absorbed ; in the second, by imparting 
 to it a levity, which effectually prevents the possibility of its 
 accumulation in the lower stratum of the atmosphere, when 
 heated by contact with the earth's surface, we should surely 
 pause, before deciding upon conducting the arrangements for 
 warming the interior of our dwellings, upon principles exactly 
 the reverse, of those she has provided for our benefit, by such 
 unerring and irrevocable laws, as long as we remain denizens of 
 her free domain. 
 
 In short, I conceive the'present system of warming buildings 
 by currents of heated and therefore, necessarily, rarified air, to- 
 
120 DWELLING-HOUSE GRATES AND VENTILATION. 
 
 be fundamentally erroneous, and one which ought to be aban- 
 doned, as injurious to health. The diminished quantity of oxygen 
 taken into the lungs, diminishes the energy with which all the 
 vital functions are carried on; the carbon in the blood is 
 imperfectly burnt, and less heat generated in consequence ; 
 creating a craving for a larger supply of artificial heat than 
 would be required, were the atmosphere inhaled denser, and 
 consequently richer in oxygen ; whilst the habitual dependence 
 upon, and necessity for, artificial heat thus engendered, enfeebles 
 the constitution, and deprives it of its powers of resisting cold 
 with impunity ; produces a general and unnatural susceptibility 
 to take cold,* and suffer from slight draughts, deranges the func- 
 
 * The lungs being designed by nature for the inhalation of cold air, find 
 in it their appropriate stimulus to action, whilst their functions languish in 
 an artificially heated atmosphere. Neither is the pernicious influence of the 
 adoption of such unnatural appliances, confined to those who become enervated 
 by their habitual use. On the contrary, those who are brought by the 
 exigencies of travel, or business, or the intercourse of social life, even 
 temporarily within their sphere, are often severe sufferers. If, after lengthened 
 exposure to cold, the body being at rest, (say on the outside of a coach, 
 or in a railway carriage,) the individual gradually restores the heat of the 
 body by muscular exercise, he will be pretty sure to escape a cold the same 
 may be said if he goes to bed, and seeks refuge iu good warm blankets. Even 
 if he indulges himself with an apartment moderately heated by an open fire, 
 he may stand a fair chance of escape ; but should he on the contrary, be so 
 unfortunate as to become an inmate of a room, the atmosphere of which is 
 kept at a high temperature, by currents of heated air, rarely indeed will he 
 escape with impunity. Probably never, if the amount of cold induced, has 
 been really such, as much to depress his nervous system, for when the 
 diameter of the capillary arteries of the air passages has been long contracted 
 by cold, and their nervous energy expended, their power of contractility 
 being weakened, they become relaxed beyond their power of immediate 
 spontaneous recovery, by the too sudden exposure to heat, and a catarrh is 
 the result a disease, which is to the lungs, what chilblains are to the hands 
 and feet and arises from the same cause, viz. the too rapid application of 
 heat after exposure to cold. 
 
 Should any one find himself committed to a journey, and inadequately 
 clothed, so as to experience an uncomfortable degree of cold, let him by no 
 means seek distraction from the sensation, by endeavouring to absorb the 
 mind in some intellectual operation, either by following out some train of 
 thought, or immersing himself in a book, for, by so doing, the chances of 
 taking cold are doubled. In such a position, the whole of the nervous 
 energy, as fast as generated by respiration, is required to protect the outworks 
 of the citadel against the enemy cold ; and all that is consumed in the 
 intellectual operations carried forward, is so much subtracted from this (for 
 the time being) more essential duty. Under such circumstances, the mind 
 ' should be withdrawn from all extraneous objects of distraction, and concen- 
 
DWELLING-HOUSE GRATES AND VENTILATION. 121 
 
 tions of the skin, and begets a liability to the attacks of 
 consumption and other diseases of the respiratory organs, and a 
 delicate state of the health generally, to which persons who pass 
 much time in the open air, and do not resort to these pernicious 
 contrivances for unnaturally rarefying the atmosphere of their 
 dwellings, but, on the contrary, allow free ingress to fresh cold 
 air, are total strangers. 
 
 I have repeatedly observed the complexion of those who 
 inhabit apartments heated by closed stoves, and hot air, to be 
 peculiarly sallow and unhealthy, and have, on inquiry, generally 
 learnt that the state of the health corresponded, and that they 
 were extremely susceptible of taking cold ; in short, they re- 
 semble delicate hot-house plants, liable to be nipped and destroyed 
 by a single night's exposure; whilst, on the other hand, butchers, 
 agriculturists, and others, who carry on their avocations in the 
 open air, have ruddy complexions, with all their vital functions 
 robust and vigorous. 
 
 If the example of nature is to be copied, and made our rule 
 of practice, then the only adjunct to the radiation from the fire 
 (the sun of the apartment) should be the warming the walls, 
 whilst the fresh air necessary for ventilation should be admitted 
 cold. Bays of heat being radiated on all sides, the occupants 
 may be made comfortable, and the thermometer kept at any 
 point desired ; but inasmuch as rays of heat pass through air 
 without heating it, it will, under such circumstances, no more 
 indicate the temperature of the air, than a thermometer in the 
 sunshine, which stands at 100, whilst the surrounding atmo- 
 sphere is only 32. To heat and ventilate an apartment, I 
 should propose to surround the lower half with canvas, behind 
 which the air from the atmosphere* should enter freely, and 
 
 trated within itself. The painful sensation of cold, must, in short, be made 
 the object of attention, and actively resisted as an enemy. So effectually 
 have some individuals the power of doing this, that I have known persons 
 who could always resist catching cold whilst awake. 
 
 Whoever will attend to the hints contained in this note, will he amply 
 repaid for the trouble of perusing this small volume, for I venture to say 
 that two more important maxims for the preservation of health, than those 
 just enunciated, do not exist. 
 
 * The orifice through which the supply of air for ventilation is drawn, 
 should always be situated above the vapour line of the locality, or the air 
 which enters at night, may be of a poisonous quality, particularly in malarious 
 districts. 
 
122 DWELLING-HOUSE GRATES AND VENTILATION. 
 
 pass into the room through the minute subdivisions between 
 the threads. Above the canvas, should be a hollow chamber, 
 extending the remaining height of the walls, round which the 
 products of combustion should be carried, and dismissed into 
 a chimney at the opposite end from the fireplace, with which the 
 apparatus for the escape of the vitiated air should also com- 
 municate. When large and lofty assembly rooms have to be 
 heated, a chamber above the ceiling, might also be put in 
 communication with the side flues, and thus constitute a hot air 
 reservoir, and in certain cases it might be expedient to construct 
 .a hot air chamber beneath the floor, like the hypocaustum of the 
 ancients. Apartments so warmed would not be subject to the 
 vicissitudes and alternations of temperature inherent in the pre- 
 sent system. The heat from the fire by day, would endure all 
 night, so that in the coldest weather, the room would not be 
 chilly in the morning, or require the heat getting up for an hour 
 or two, before being comfortably habitable, as is now the case. 
 From the free admission of the fresh air all round the sides of 
 an apartment, and the large extent of surface provided for its 
 entrance, its diffusion would be effected without the possibility 
 of local draughts, and, at the same time, there would be a 
 delightful freshness and elasticity in the atmosphere, resembling 
 that of the open air, and the antipodes of the rarefied, enervating, 
 oppressive, and noxious medium, with which our public buildings 
 and other similarly heated edifices are at present polluted. 
 
 A vast deal has been written as to the proper angle the jambs 
 should form with the back of the chimney, so as to reflect the 
 largest amount of heat, but strange to say, the subject has gene- 
 rally been treated of, as if the jambs were on a level with the 
 sides of the fire, instead of being placed above it, and thus the 
 very satisfactory looking diagrams showing a horizontal section 
 of the fire and jambs, with the angle of reflection, delineated iu 
 many books on the subject, exhibit a state of things applicable 
 only to the lower portion of the jambs, where they are on a level 
 with the surface of the fire ; directly they rise above this, they 
 reflect the rays of heat progressively more and more upwards, 
 first towards the ceiling, and then up the chimney, instead of 
 horizontally outward, into the apartment, as will be manifest 
 from an inspection of the diagram on the following page. 
 
DWELLING-HOUSE GRATES AND VENTILATION. 
 
 123 
 
 Fig 1. 
 
 Shewing the direction in which 
 rays of heat from the centre of the 
 fire, are reflected by the ordinary 
 jamb, with a plain surface. 
 
 Shewing the direction in which 
 rays of heat from the centre of the 
 fire, are reflected by the horizontal 
 ribbed jamb with gradually en- 
 creasing angle. 
 
 To obviate this great loss of lieat, I propose to construct the 
 jambs of a series of reflecting surfaces arranged in horizontal 
 strips, somewhat resembling Venetian blinds, the inclination of 
 each increasing slightly from below upwards, in such a ratio, 
 that each shall reflect a ray of heat proceeding from the centre 
 of the fire, horizontally outwards, into the apartment. These re- 
 flectors may be made either of polished brass, or steel, and if 
 of the latter, may be advantageously set in zinc, that so, being 
 rendered negative, oxydation or rust may be prevented, and their 
 brightness preserved. Pig. 2, represents such a reflecting jamb 
 in vertical section, with lines shewing the angles at which the 
 rays of heat are reflected, and by contrasting the direction of 
 these lines, with the same lines in fig 1, a section of an ordinary 
 jamb, with a plain surface, the vast superiority as a heat re- 
 flector of the horizontally ribbed jamb, which I propose to sub- 
 stitute for it, will be at once apparent. 
 
 G 2 
 
124 DWELLING-HOUSE GEATES AND VENTILATION. 
 
 The point, next of importance to the perfection of a grate, 
 is to close over the area between the top of the jambs, and 
 above the fire, in such a manner, that in the first place, as large 
 a portion as possible of the heat radiated by the fire directly up- 
 wards t as well as of the heat contained in the ascending current 
 of the products of combustion, shall be absorbed, and again ra- 
 diated downwards, instead of being allowed to pass away into 
 the chimney ; and in the second place, that the passage of a cur- 
 rent of cold air above the fire up the chimney, be, as far as practic- 
 able prevented. This current, being formed of the pure air in 
 the lower part of the room, is comparatively useless as far as 
 ventilation is concerned, even in an apartment badly ventilated ; 
 whilst, if the room be provided (as should be deemed indis- 
 pensable), with one of the admirable ventilators of Dr. Arnot, or 
 some equivalent contrivance opening into the chimney just below 
 the ceiling, the due ventilation of the apartment, consisting of the 
 flow of the vitiated air from its upper part into the chimney, 
 would be positively impeded by the entrance of the cold current 
 from below. In addition to being useless or prejudicial as far 
 as ventilation is concerned, this current of air towards the fire, 
 is productive of much discomfort to individuals sitting around it, 
 by producing a cold draught against their backs, whilst the heat, 
 carried off by it up the chimney, is so great as seriously to 
 impair the power of the fire to warm the apartment. 
 
 Both the above desiderata may be attained by the same 
 arrangement, and in an easy, simple, and complete manner. The 
 area between the upper portion of the jambs, should be closed 
 by a plate commencing at the back, and running upwards at an 
 angle of about 30, to a point about 3 inches above the lower 
 edge of the chimney breast. The front edge of the plate should 
 be connected with the chimney breast at the sides, but left open 
 in the middle, for a space equal to the breadth of the fire, for 
 the passage of the products of combustion up the chimney. 
 
 By this arrangement, in the first place no heat can be 
 radiated by the fire directly up the chimney, on the contrary all 
 radiated in this direction will be either directly reflected back, 
 or absorbed and re-radiated ; in the second place, instead of the 
 current of the heated products of combustion passing straight up 
 the chimney, and carrying off all the heat with which it is 
 charged, it is previously made to impinge on an absorbing sur- 
 face which abstracts a portion of its heat before its dismissal ; in 
 the third place, instead of a stream of cold air from the room, 
 
DWELLING-HOUSE GRATES AND VENTILATION. 
 
 125 
 
 being allowed to pass directly upwards, and backwards, into the 
 chimney, the forward direction given to the heated current 
 from the fire, will almost entirely prevent the passage of any. 
 An inspection of the diagrams below, will enable the reader to 
 judge of the relative effects of the two systems. 
 
 Kg. 3. 
 
 Shewing that when the breast of 
 the chimney is closed by a plate 
 opening in front, instead of at the 
 back, or in the middle, so as to in- 
 cline the heated current from the 
 tire forwards, before its passage up 
 the chimney, the rush of cold air 
 up this aperture, cooling the room 
 and producing a draught against 
 the backs of the individuals sitting 
 round the fire is prevented ; no 
 draught can evidently take place 
 in the direction of the arrow a in 
 this figure, whilst a powerful one 
 must necessarily exist at this point 
 in figure 4. 
 
 Given as a contrast to figure 3, 
 being the arrangement of the chim 
 ney of the room in which I am 
 now writing, and such is the igno- 
 rance of the public on the subject, 
 far from an uncommon one, al- 
 though the facility for the passage 
 of a large volume of cold air up 
 the chimney is so great, that with 
 the consumption of four times the 
 quantity of fuel that ought to be 
 required, the apartment is still in- 
 adequately wanned, whilst the 
 larger the fire;' the greater the 
 draught of cold air against the 
 backs of persons sitting round it. 
 
 The plate should either be formed of two pieces of sheet iron 
 joined at the edges, with a space of about an inch between the 
 
126 ON THE VENTILATION OF COAL MINES. 
 
 sheets filled with cinder dust, so as to be rendered a bad con- 
 ductor of heat, or else of a large stout tile or slate. Chimneys 
 have usually been made sloping backwards, under the erroneous 
 impression that such a plan was necessary to prevent liabilty to 
 smoke, the general ignorance prevailing amongst the public at 
 large, of the simple laws of pneumatics, by which the motion 
 of heated currents of air is determined, having invested the sub- 
 ject of smoky chimneys with a mystery, difficulty, and uncertainty, 
 which in reality are far from belonging to it ; the conditions, by 
 the observance of which, freedom from smoke may be attained, 
 being simple of apprehension, easy of application, and invariable 
 in their result.* 
 
 If any one, who has a fire place on the old construction, with 
 a wide yawning chimney, opening directly upwards, or, still 
 worse, upwards and backwards, from the fire, will try the ex- 
 periment of closing the breast of the chimney in the manner I 
 have described, they will be astonished at the result, and find, 
 to their surprise, that with half the quantity of coals, the 
 heating effect of the fire, on the apartment, will be doubled. 
 I can speak authoritatively on the point, for I speak from 
 experience. 
 
 * Chimneys smoke when the force of the ascending current is overcome 
 by the force of the downward draught ; strengthen the former, and diminish 
 the latter, and the srnoke will ascend. The most common cause of a chimney 
 smoking is from its being made too large, this occasions the velocity of the 
 ascending current to be slow, and its force on a given area small, from its 
 great diffusion, and it is consequently unable to overcome the force of de- 
 scending draughts. Another cause which frequently comes into operation, 
 particularly with small rooms, is the want of a sufficiently free and constant 
 ingress of air to the room, steadily to supply the quantity abstracted by the 
 chimney. This defect may be remedied by bringing a supply of air for the 
 fire, from the external atmosphere by a pipe terminating beneath the grate ; 
 a plan which has the further advantage of preventing the draught, which 
 otherwise sets towards the fire, sweeping the floor of the room, keeping the 
 feet cold, and necessitating a fire of twice the dimensions which would other- 
 wise be adequate to heat the apartment, and this with no benefit to the ven- 
 tilation, since the air carried ojf is the cold and freshly entered lower stratum 
 of air, instead of the upper,. Seated and impure. The cases most difficult of 
 cure are those where some higher object t in the vicinity of the chimney top, 
 offers a surface against which the wind impinges, and becomes deflected down 
 the chimney. Rows of houses built beneath high cliffs have sometimes in 
 particular winds, all their" chimneys simultaneously affected from this cause. 
 
ON THE VENTILATION OF COAL MINES. 127 
 
 ON THE VENTILATION OF COAL MINES. 
 
 AT the present moment, when the recent sad and appalling 
 loss of life in coal mines, is directing public attention towards 
 the subject of the ventilation of collieries, the following estimate 
 of the relative efficiency of a given weight of coal in producing 
 power 1st, when applied through the instrumentality of a 
 steam engine, arid 2ndly, when employed to rarefy a column 
 of air, and thus impart to it an ascending force will probably 
 be regarded with interest. 
 
 Before entering into any calculation on the subject, I felt 
 that the having recourse to the comparatively inert agency of 
 gravity, acting through the ascentional tendency of a column 
 of heated air, must be a wasteful mode of obtaining power, 
 when compared with the expedient of employing for this pur- 
 pose, the vastly more energetic force developed by the chemical 
 law of vaporisation upon the addition of heat to a liquid, as in 
 the case of converting water into steam. I was not however 
 prepared for the actual results which presented themselves, viz. 
 that lib of coals employed to raise steam in a Cornish steam 
 engine, will do the work of lOOlbs. expended in rarefying air 
 such air to be discharged through a shaft 100 feet in height, 
 and to commence the ascent at a temperature of 568. 
 
 Extraordinary as the above results may appear, the case on 
 behalf of the steam engine is rather under stated, the actual 
 duty performed by many of the Cornish engines, being above 
 that assumed as the basis of this calculation. On the other 
 side of the question on the contrary, no allowance is made for 
 imperfect combustion, but the heating power of coal is cal- 
 culated from that which the recent experiments of Andrews 
 have assigned to carbon, viz. that 1 part will raise 14,:220 
 parts of water 1, whilst the specific heat of air is called '25, 
 that of water being 1 . 
 
 These facts clearly shew that, even in circumstances where 
 great depth of shaft presents the most favourable conditions 
 for the use of rarefied air as the ventilatory force, coal so applied, 
 must ever remain much less effective, than when employed in 
 a Cornish engine. When, in addition to the small amount of 
 duty obtained from coal as a ventilating agent, through the 
 medium of a simple furnace, it is considered that precisely as 
 the air of the mine becomes foul, and a larger supply is needed, 
 does the action of the fire languish, and its powers of draught 
 become diminished; and also, that there is reason to believe, 
 
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