130 



THE CIA IL ENGINEER AND ARCHITECT'S JOURNAL. 



[April, 



MK. WILLIAMS' BOILER PROJECTS. 



Sir — The appearance in your Journal for February of a paper purporting 

 to be an analysis of Mr. WUiams' boiler projects, seems to call for some 

 explanation ou tlie part of tliosc wliose investigations on the subject may 

 have leail them to other conclusions than those arrived at by the ingenious 

 author of that essay. Just adverting to the critical acumen displayed in 

 deriving the authorship of a communicalioa to tlie London Mechanics' 

 Magazine, to which the author's name happens to be prefi.xed, or the peculiar 

 character of the internal evidence vvbich led the learned analyst to the unex- 

 pected conclusion that Mr. AV. was the writer of the paper which Mr. \Y. 

 read before tlie Polytechnic Society, I may perhaps be permitted to make 

 one or two observations before proceeding to reply to the details of the 

 critique. 



That the first of a series of papers devoted to the development of a de- 

 partment of physical science, hitherto almost untrodden or giving only the 

 most discordant results, and uniting the deepest interest with the greatest 

 abstruseness, should be selected as a peg whereto to append a string of most 

 ludicrous corollaries, evidences the e.\istence of a spirit of such jocose and 

 sprightly pliilosophy, that one is a little at a loss in what strain to reply. 

 Perhaps the best answer would be, afl'ectionately to admonish the writer to 

 read a little farther, and acquire a little more thorough acquaintance with 

 the subject tb.an the perusal of a prefatory chapter can convey. At the 

 same time, I am well aware that to criticise a subject it is not necessary to 

 be intimately acquainted with it — nay, the very negation of acquaintance 

 will sometimes be found marvellously to facilitate the operation, and the 

 more skilful the reviewer, the less need will there be for the preliminary 

 drudgery of first studying the subject, so that a very able writer indeed will 

 Lave no difUculty in writing a very good article on a subject he knows 

 nothing aliout at all. 



To enter minutely into the possible modes of action of the conduction 

 pins, whether as facilitating combustion by assisting the interchange of elec- 

 tricities essential to cheir.ical action, or as aiding the generation of steam, on 

 the sanse principle that internal asperities in an evaporating vessel facilitate 

 the process of vaporization, would be to write a treatise instead of (which is 

 our present object) to reply to an objection. Let us, then, for the present, 

 confine our attention to the conducting power alone of the pins whose action 

 has been attended by such striking effects. 



We know, by the experiments of M. Delarive, that the conducting power 

 of some substances of a fibrous texture, suh as wood, varies exceedingly 

 according as conduction takes place in a direction transverse or parallel to 

 the fibres. We are thus prepared to expect similar results in the case of 

 those metallic bodies in which the fibrous arrangement is strongly marked. 

 It is true we do not possess accounts of experiments made to determine the 

 relative amount of lateral and longitudinal conducting pow er in such bodies ; 

 but there arc jihenomena connected with the transmission of heat through 

 solid bodies, which would lead to the conclusion that it follows different 

 laws in ditl'ei&iit though similar substances, and that general theories, founded 

 on the supposiiion of uniformity of action among the consecutive elements 

 of different bodies are not to be depended upon. 



For instance, it has been found that in some cases, increasing the dimen- 

 sions of the conducting substance in the direction of the conduction, pro- 

 duces very slight retardation in the passage of the heat, a fact sufficient to 

 destroy all confidence in reasonings founded upon the ordinary hypothesis 

 of a r.-ipidily of transmission proportional to the difference of temperature 

 of the contiguous elementary laminic of which we may conceive the body to 

 be composed. We are thus prejiared — I do not say to adopt the conclusion 

 — but to listen to the arguments which may lead to the conclusion, that the 

 ■power of transmitting heat depends ou something more than mere inequahty 

 of temperature in the consecutive elements. lu the case of an ordinary 

 steam boiler, we do not know the temperature of either the interior or ex- 

 terior surface of the plates ; all we know is, that the one cannot be hotter 

 than the flame, nor the other colder than the water contained, but between 

 these limits we know nothing; and we are slill further removed from a 

 knowledge of th.e laws which regulate the communication of the heat, and 

 the approximative equalisation of the temperature. 



AVith these observations let us now consider the action of the pins, on the 

 supposition (certainly not a correct one) that the stratum of air in contact 

 with the boiler surface and the whole length of the pins, is of uniform tem- 

 perature. M'c in this case naturally expect that the lower extremities of the 

 fcssing considerable economy of fuel, should make the removal of tliese 



pins will attain a higher temperature than the exterior surface of the boiler, 

 and we may conceive that that section of the pins which lies in the plane of 

 the outer surface of the boiler, may differ more or less in temperature from 

 that of the outer surface itself; but the rapidity of the transmission of heat 

 may proceed according to very different laws, and the greater difference of 

 temperature between the extremities of the pins, combined with the greater 

 facihty afforded by increase of surface, for the reception and giving out of 

 heat, may occasion such an increased intensity of transmissive action as to 

 cause a greatly increased flow of heat into the boiler, and that the evaporative 

 power is increased in a much higher ratio than the consideration of the ac- 

 tual increase of heating surface would lead us to expect, appears from expe- 

 riments that have been made on a large scale. So great, in fact, has been 

 this disproportion, that we are compelled to investigate the action of the 

 conduction pins, on another and more likely supposition, which, however, is 

 so much in accordance with the laws of nature, that it ought rather to be 

 adduced as an explanation than adopted as an hypothesis. Instead, there- 

 fore, of considering the boiler surface and the whole length of the pins to be 

 enveloped in an atmosphere of uniform temperature — which is almost an 

 extravagant supposition — we shall take into account the cooling agency of 

 the boiler surface on the stratum of air in contact with it. Now at the high 

 temperature of common furnaces, from 1000' to 2000' F., a given depression 

 of temperature will occasion a diminution of volume of only from i to i of 

 what would take place at ordinary temperatures, and a correspondingly 

 diminished ascensional force in the lower contiguous stratum. But this 

 ascending stratum will be cooled to a certain extent by crossing the other, 

 and the resulting temperature of the succeeding film that comes in contact 

 with the boiler will be lower than that of the stratum removed a little 

 farther from the cooling surface. Thus a refrigerating action is carried on, 

 and the longer the operation continues, the greater will be the uniformity of 

 the temperature attained throughout the mass. But when we consider the 

 rapidity of the current through the flues, ascertained by Dr. Ure to be not 

 less than 3G ft. per second, we are lead to the conclusion, that the process 

 of refrigeration cannot liave penetrated to a great depth before the heat- 

 giving atmosphere has quitted the ilues entirely, and that the lower extremi- 

 ties of the pins must be enveloped in an atmosphere of Iiigher temperature 

 than that from which the bottom of the boiler derives its heat; while in the 

 anterior part of the boiler, this will be still more marked, almost the whole 

 projecting length of the pins being exposed to a rapid current at a very high 

 temperature, while the partially refrigerated gases will glide along the surface 

 of the plates. 



When we consider the temperature of the air in the smoke-box of a loco- 

 motive in full action, known to equal that of red hot iron, after submitting 

 to the operation of a refrigerating mechanism so much more complete than 

 that to which the products of an ordinary furnace are subjected, we can no 

 longer view with incredulity, or even with surprise, the results of the experi- 

 mental investigation that demonstrates the efficacy of the conduction pins. 



We have hitherto confined our attention to the action of tlie pins in a 

 horizontal or nearly horizontal surface ; in the case of an inclined or vertical 

 surface, the preceding train of argument is still more applicable. In this 

 case the descending current of air, instead of tending to quit the surface to 

 which it has given out its heat, will glide down the sides still preserving its 

 contact, and giving out a diminished quantity of heat as it descends, while 

 the outer extremities of the pins will be exposed to the action, at a high 

 temperature, of a rapid current that would otherwise have been hurried along 

 to the chimney, without giving out any heat to the boiler at all. 



With regard to what has been denominated the second part of Mr. Wil- 

 hams' boiler projects, perhaps I might presume to tender similar advice to 

 that which I gave before entering on tlie discussion of the conduction pins — 

 not so much that the critic should peruse Mr. Williams' treatise on com- 

 bustion, but that he should study the instructive and beautiful commentary 

 on that work which the operation of the argand furnace presents, a com- 

 mentary which possesses the advantage of being proof against misinterpre- 

 tation, being an infallible mean of convincing those who are less accustomed 

 to be guided by the deductions of their understanding than the impressions of 

 their senses. As the gist of the argument of the reviewer of the " Projects " 

 hinges on the definition of smoke given in a pamphlet entitled " Thoughts 

 on Steam Locomotion," I may be permitted to transcribe a few sentences : 

 " The great waste resulting from smoke, the product of imperfect combustion, 

 which must be estimated not merely in the proportion of the uncousumed 

 carbon, but also in regard to llie heat which becomes latent in its formation, 

 and is dissipated in the almospliere, and the many inconveniences consequent 

 on its formation — arc such as to render it expedient that all schemes pro- 



