16 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[January^ 



face of the fire-box and of the tubes, the author concludes in the fol- 

 lowing section that the most advantageous proportion is as 1 to 9, or 

 the total l:cating surface equal to ten times that of the fire-box; "since 

 for a less j)roportion there would be increase in the expenditure of 

 fuel, without increase of vaporization ; and for a greater proportion, 

 on the contrary, there would be reduction in the vaporization of the 

 engine per unit of surface, which would incur the necessity of a larger 

 boUer, and consequently of a greater weight, which it is important to 

 avoid." 



It also results from these experiments that, "according to the pro- 

 portion of the fire-box to the total heating surface, the consumption of 

 fuel in locomotive engines varies from ',)-2 to 1 1-7 lbs. per cubic foot of 

 total water vaporized ; so that it may, on an average, be valued at 

 10-7 lbs. of coke per cubic foot of total vaporization." 



It is to be observed that this total vaporization includes the loss by 

 priming, so that the quantity of cuke per cubic foot of water really 

 converted into steam would be, according to M. de Pambour's calcula- 

 tion, about 14 lbs. 



Of the 12tli chapter, w liicli treats of the Theory of locomotive en- 

 gines, we shall merely observe that it is in substance the same as in 

 " The Theory of }he Steam Engine," to whicli work we have already 

 alluded, but much more instructive with regard to locomotive engines, 

 the peculiar circumstances of whieli are here discussed at much greater 

 length. The application of the the theory is rendered easy by prac- 

 tical formulcc and examjdes, and its correctness corroborated by ap- 

 plying it to the results of a considerable number of experiments, col- 

 lected in a table at the end of the chapter. 



The tlieory is continued in chapter XIII., in the first 9 sections of 

 which are solved the various problems whicli occur in the construction 

 of locomotive engines, viz., to determine the vaporization or heating 

 surface, the dimensions of the cylinders, and the diameter of the wheel, 

 necessary for the engine to draw a given load al, a given velocity; to 

 determine the vaporization or heating surface, the pressure in the 

 boiler and the dimensions of the cylinders, necessary for an engine to 

 assume a given velocity or draw a given load, producing at the same 

 time its maximum of useful effect ; and lastly, to determine the com- 

 bined proportions to be given to the parts of an engine, to enable it to 

 fulfil divers simultaneous conditions. The utility of all these problems 

 is too evident to require pointing out. 



In the lOthsectien, whsch is an examination of the special influence 

 of each of the dimensions of the engine on the effects produced, we 

 have to direct attention to a slight contradiction. We read, page 

 417, 



" Moreover, it will also be recognised that, for a given vaporization, 



the velocity will be by so much the greater as the factor — has less 



value. It is in consequence to be concluded that, in order to augment 

 to the utmost the velocity of an engine with a given load, we must 

 either employ a cylinder of the smallest possible diameter, or make 

 the wheel the largest possible with reference to the stroke of the 

 piston." 



It is a more direct inference that we must employ a cylinder of the 

 smallest possible capacity in proportion to the diameter of the wheel. 

 We read further: 



"These consequences might however have been seen ii priori ; for 

 if we suppose a given vaporization in the boiler, it is clear that the 

 quantity of steam which will result from it per minute cannot issue 

 forth ill the same time by a cylinder of less diameter, except on the 

 condition of increasing its velocity during its efflux, that is, of increas- 

 ing the velocity of the piston. As to the ratio between the length of 

 the stroke of the piston and the diameter of the wheel of the engine, 

 as it is known that at every double stroke of the piston the engme ad- 

 vances one turn of the wheel, it is readily perceived that the larger 

 the wheel relatively to the stroke of the piston, the greater nmst be 

 the velocity of the engine with a given load." 



In all this reasoning the author has lost sight of the circumstance 

 that a diminution of the capacity of the cylinders, wilh a givin load, 

 will necessarily demand steam of a greater pressure, and consequently 

 of greater density, in the cylinders; but, as the density of steam does 

 not increase in proportion to its elastic force, there will he a slight in- 

 crease of velocity with the smaller cylinders. 



A little farther on, nagell9, we are told that the load which an 

 engine is capable of drawing ;it a given velocity "is diminished by the 

 valves of (^, / and U, that is, by the dimensions of the cylinder, the 

 stroke of the piston, and the wheel, which are proper to augment the 

 velocity of the engine." 



We were at first puzzled for an explanation of this contradiction, 

 but, on examining the two equations from which the above deductions 

 were drawn, we perceived that the latter were not justified by them, 



but that the same values of d, I and D which would increase the velo- 

 city with a given load would also increase the load with a given velo- 

 city, the fraction ^p— being positive in the denominator of one of the 



fractions, and iiegalin in the numerator of the other. The error we 

 have pointed out runs through the rest of the section. 

 ( To be continued.) 



Sptcificaiiong for Practical Architecture, preceded by an Emay on the 

 Dtclim of Excellence in the Structure, and in /he Science of Modern 

 Engliish Bnildingn. By Alfred Bartholomew, Architect. " London: 

 John Williams, ls40. 



We have so often made an attempt to examine this important work 

 w ith the attention it deseri'es, that we fear we may be considered re- 

 miss by our readers in not attending to it before — the fact is that it 

 contains so much matter intimately connected with the profession, 

 that it is with difficulty we can select any one part in preference to 

 another, a difficulty increased by the arrangement of the work. We 

 have already, by permission of tjie author, given large extracts, which 

 will he a sufficient testimony to our readers, that it is a work well de- 

 serving of the attention of every one connected with building, we will 

 not say the profession alone, for it is equally as well deserving the no- 

 tice of the public generally. Having said thus much, we must not be 

 considered as agreeing with all the sentiments and opinions of Mr. 

 Bartholomew, although we believe that w'hat he has written, has been 

 done in sincerity ; we think that he has been too much imbued with 

 the Wren-mania, and considers that nothing is now done equal to the 

 buildings and architecture of the period previous to the eighteenth 

 centuiy — no doubt, many of our public edifices bnilt during that ]ieriod 

 were executed with great judgment, but we know that many of them 

 possess faults, nay very great ones ; for how many of them do we 

 find that have lossed their spire or steeple, and in others the piers of 

 the main tower have given way, under the great pressure which they 

 are made to carry. Nor do w'e find that all the buildings of that 

 period were erected f re proof — we believe that very few of them have 

 their vaulting of stone, some we have seen which so closely resemble 

 stone, that they liave been taken for that material until the visitor is 

 told to the contrary. Although, during this period there were erected 

 numerous ecclesiastical buildings, possessing architectural merit of the 

 highest class, we should like to know how many buildings of a domes- 

 tic character were erected, possessing any claim to architectural pre- 

 tensions, in comparison with those which have been erected within 

 the last century— now, the whole of a man's fortune is not placed at 

 the mercy of the priest, for external pomp to support an intolerant 

 church or to prevent the soul from going to purgatory ; no, part of 

 that fortune is now' devoted to the erection of edifices, which form an 

 ornament to many parts of the united kingdom, and we hope to see 

 them still farther increase. 



Another part of Mr. Bartholomew's bewailing is on account of the 

 use of Bath stone and cement ; no one will dispute that if you can ob- 

 tain funds sufficient, that it is far better to use Portland stone, but the 

 immense cost of labour on that material is a bar to its general intro- 

 duction, and it is on account of the cheapness and facility in the use of 

 cement for giving architectural character to our buildings, that it is so 

 largely introduced. We believe that the fault in the use of it is by 

 allowing the workman to have cement of an inferior quality, or in per- 

 mitting it to be employed by men that do not know how to mix or 

 apply it. 



That part of the volume which treats upon Specifications, possesses 

 some very useful hints for those who are not well conversant with that 

 branch. We feel ourselves very strongly inclined to recommend that 

 specifications should at all times be drawn up by parties who will 

 make it their peculiar study ; such a person would be of as mucli ser- 

 vice to the architect, as the special pleader or equity draughtsman is 

 to a lawyer. 



The information on construction w ill be found valuable to the student, 

 who will do well to peruse attentively the general contents of the 

 volume. 



We think the work would have been clearer had it not been split 

 up so much into chapters and sections, which however convenient for 

 reference, are embarrassing to the reader. This is even carried out 

 in the specifications, so that a specification is interrupted by chapters 

 and sections. We must not, however quarrel with Mr. Bartholomew, 

 for he is too steady a reader of the Journal not to enlist our sympa- 

 thies ; some of our correspondents however seem, by the remarks in 

 his work, to give him a good deal of trouble. He devotes especial 

 mention to Candidus. We must now leave Mr. Bartholomew, and his 

 work with a heartv commendation to our readers for its usefulness. 



