26« 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



July- 



" Proposition 2. The distances passed over by the lieat before it iiuita the 

 boiler, are to eacli otlier directly as the circuits of the boilers : thus the 



•■ " Locomotive is to the Cornish as 7 to laJ-OO, or ) to 22-142, &c. 



"Propositions. The tines in which the surface of the several boilers is 

 ti-nversed by the heat, ivill be to each other, as the products of the ratios 

 of the velocities of the current, or rates of combustion, multiplied into the 

 ratios of the lengths or circuits travelled : thus the 



" Locomotive is to the Cornish as G-8;)5 X 22-l.l2=r IJl-Si to 1, &c." 

 Before commenting on this proposition, it is necessary to correc' 

 two errors in it which render it rather ilifHciiU to understand. It 

 should he expressed thus : — The times in which the surface of the 

 several boilers is traversed hy the heat, will be to each other im^ersely 

 as the velocities of tlie current, and direct/// as tlie lengths or circuits 

 travelled: thus the 



1 . 22'14^ ^j. J . 151.34 g,(,, 

 6-835 1 



Locomotive is to the Cornish as . 



Having brought the proposition and its example to what Mr. 

 Parkes intended to convey, we have only to refer to what has already 

 been said on tlie subject of the velocity of the current, to prove that 

 the numbers thus found in nowise represent the difference in the 

 periods occupied by " the passage of a particle of heat from the grate, 

 lilt it (juits the boilers," as Mr. Parkes expresses himself. 



The next question which he considers is, " the relative time occu- 

 pied by the heat from equal weights of fuel in giving out its caloric 

 to equal partialis of surface ;" and he solves it in Propositions 4 

 and ."J, by means of the velocity of the current, incorrectly found by 

 Proposition 1, which therefore vitiates the solution of tlie present 

 question. Thus, then, the numbers found by this method cannot 

 " be properly termed the relative periods of caloric action, arising out 

 of the structure and practice of each classof boiler." But since the 

 truth of the results is attempted to be confirmed by another process, it 

 is necessary to examine what that process is, and whether it can be 

 admitted as a demonstration or not. The proof runs thus : — 



" It is the same thing to burn, as in the Cornish boiler, one pound of coa^ 

 in 4.1-08 seconds, and apply the heat to 961-66 square feet of boiler, us to burn 

 44-081bs in one second of time, and apply tlie heat to 44-08 times as great a 

 surface. 'We should thus find that 42389 scjuare feet would be the area cor- 

 responding with that increased rate of combustion for the Cornish boiler. In 

 Jike manner, 2157' square feet would be the equivalent surface for a rate of 

 combustion in the locomotive increased by C-45 times. The quotient of 

 423S9 -r 2157 is 19-64 as above." 



Before we can discuss the strictness of this proof, it is necessary to 

 correct an error (probably in the printing), which will be obvious to 

 every reader, on considering a moment. Instead of 44-0SH)s, it 

 should be lib in one second of time. 



The number 19-64 had been previously found by multiplying 

 6'835 by 2-S74 ; but the former of these was found by dividing 44'OS 

 by 6-45;, and the latter by dividing 961 '66 by 334-50 ; thus :— 



4^;08 ^ screo ^ jg.g^ 



e-45 334-56 



In the proof it was found by multiplying 96I-G6 by 44-08, and 

 "dividing the product by that of 334-56 by 6-45 ; thus :— 

 961-66 X 44-0 8 _ g^ 

 334-56 X C-45 



These two equations, being identical, cannot serve to corroborate 

 each other, but would necessarily furnish the same result, however 

 absurd the grounds from whicli they w-ere deduced. 



We have now come to the conclusion of the investigation of the 

 influence of'time on the economi/ of heat, from which it appears that 

 the word time may as well be eliminated, as neither the absolute nor 

 relative periods of the " duration of the heat about the boilers," nor 

 " about eijuat areas of the entire surface," has been ascertained, the 

 only point arrived at being the ratio of the evaporating surface to the 

 fuel burned, which may be taken at once from Table 1., column 21. 



The remaining part of the paper is taken up with an investigation 

 of the relative quantiti/, and the relative intensili/ of heat gi\'en off to 

 those portions of the boilers which are exposed to the direct action, 

 or radiating caloric of the fire, as having an especial liearing on the 

 durabilit// of the boilers. 



Propositions 6, 7, and 8 are used to ascertain the relative quantities 

 of heat supplied (by radiation) to equal areas of those portions of the 

 various boilers which are exposed to radiating heat. In the latter 

 there is an error similar to those already mentioned, which does not, 

 however, affect the numbers, as it only exists in the statement of the 

 proposition, and is not followed in the application. 



By the following paragraph, wliich we cjuote from page 41, it wotdd 

 seem that Mr. Parkes has quite original ideas of heat, since he makes 

 R distinctipn-^between the qua(ntity of lieat radiated upon a giv«a are« 



of surface in a given time and its intensity, as if the latter were not 

 determined by, and projiortional to the former. 



" The quantitti of heat sup)died to any boiler would not affect the material of 

 which it is composed any tlie more, whether that quantity or volume were 

 greater or less, provided its teiiiperainre or intensity remained the same. This in- 

 tensity varies greatly in the dilTerent boilers. We have seen that on the loco- 

 motive ()-835 times more heat is generated in equal jieriods than on tlie Cornish 

 grate ; but the grate of the locomotive has onlv 7 feet area, whilst tliat of the 

 Cornish lias 23-6(1 feet ; and weknow-tliat nearlvT times as much fuel cannot be 

 burned in equlil times ufl'a grate less by two-thirds than anotlier grate, willi- 

 out the acceler-ated combustion being accompanied by a very considerable 

 elevation of temperature in the products of combustion. Tlie iiiteiisitii of that 

 combustion must, therefore, be found, before its intensity of action on the 

 surfajes exposed to it can be ascertained." 



Here the quantity of fuel burned has been improperly compared 

 with the area of the grate, instead of the area of the surface exposed 

 to the radiated heat ; for, the greater the surface whicli receives a 

 given quantity of radiated heat, the less is the intensity of the action 

 of the latter on the surface. For this reason proposition 10 will be of 

 no value, and proposition 1 1 false as a general theorem, though possi- 

 bly true in some few particular instances ; namely, where the areas of 

 the grates are equal. These two propositions require the same cor- 

 rections as most of the others. The last should be : 



Prop. 1 1 . The relative intensity of calorific action on the surfaces 

 exposed to radiated heat, will be directly as the ratios of the intensity 

 of combustion on the several grates, and inversely as the ratios of the 

 areas of those surfaces. Both these propositions are supported by 

 similar proofs to that of prop. 5, quoted above, which have therefore 

 no value. 



From the 11th we learn that the author considered the heat as 

 radiating, not from the whole surface of the fire, but from some ])or- 

 tion of it, of equal area in all boilers, which we cannot possibly admit. 



In conclusion we observe, that it is only the theoretical portion of 

 Mr. Parkes' paper to which we object, not calling in question the 

 authenticity of the facts therein stated ; and we repeat, that we ap- 

 prove highly of large evaporating surfaces, and a slow rate of combus- 

 tion, the mode of firing being suited to the variety of fuel used. But 

 we firmly believe, that if any one should deviate from the proportions 

 and practice experimented on, and determine tliose which would suit 

 his purpose by Mr. Parkes' rules, he would find himself very much 

 mistaken on submitting his boiler to the test of experience. 



The Encyclopcpdia of Ornament. 

 Parts i to 13. 



By H. Sh.\w, P.S.A. Imp. 4to. 



CoNFORMAiiLY with the title it bears, this publication is intended 

 to furnish specimens and decorative detail in various architectural 

 styles, and will tlicrefure be far more comprehensive, and contain a 

 greater variety of studies than any English work of a similar kind, 

 which we are acquainted with. Indeed we hardly know of any simi- 

 lar collection that has been published in this country ; the best sub- 

 jects of this class being to be met witli only in plates of details in 

 larger architectural works ; while what are professed by Books of 

 Ornaments liave been, for the most part, productions of a very infe- 

 rior grade — bad as patterns, and altogether worthless as studies. 

 We will not, however, term these plates unrivalled, simply because 

 those in Mr. Shaw's " Specimens of Ancient Furniture," and other 

 publications, would render such epithet incorrect, except as applied 

 to his works collectively, and not to this individual one singly. So 

 far the author's name is a sufficient guarantee for the superior exe- 

 cution of the plates; nor docs this " Encyclopa;dia" need much 

 recommendation from us to those who are acquainted with the same 

 artist's former publications. Neither is it necessary to insist, at 

 much length, on the extreme importance of characteristic and well- 

 linislied, if not particularly rich, detail in every style of arcliitecture. 

 It would be idle to inquire whether it be of greater importance than 

 the l-irger masses and featiu-es of a building, it being enough to say 

 that it is equally indispensable. Mere embellishment, or correctness 

 and beauty in subordinate parts, will not excuse defects in the gene- 

 ral design, any more than beauty of finish or careful execution of 

 the accessories in a jiieture will atone for bad drawing or bad ccnipo- 

 sition in a picture ; but then, on the other hand, whatever be its 

 merits as to general outline and proportions, a building will always 

 cause more or less disappointment, unless the true sjiirit of the style 

 adopted be attended to, and kept up in all the component parts. It 

 will do well enough to look at by moonlight, or through a mist, but 

 nothing more. Most desirable is it, therefore, that the student slioidd 

 train liiraself by tidies to dstaili l»y atiquii'lHg, fenuliitvity with vavtP- 

 f ties of it, not only in different style, but in one and the same style. 



