NATURE 



THURSDAY, NOVEMBER ii, 1909. 



TH£ INTERNAL COMBUSTION ENGINE. 

 The Gas, Petrol, and Oil Engine. By Dugald Clerk, 

 F.R.S. Vol. i. New and revised edition. Pp. 

 ix + 380. (London: Longmans and Co., 1909.) 

 Price I2S. 6d. net. 



MR. DUG.\LD CLERK originally published this 

 book under the title of "The Gas Engine" in 

 1886. Ten years later it reappeared in enlarged form 

 as the "Gas and Oil Engine." It has now been found 

 necessary, the author tells us, to re-write practically 

 the whole of it, and in doing so the further change 

 of dividing it into two volumes has been made. This 

 is in itself evidence of the development of science 

 and practice that has taken place during the 

 last twenty-three years. The two new volumes 

 are to be cafted "The Thermodynamics of the 

 Gas, Petrol, and Oil Engine," and "The Gas, Petrol, 

 and Oil Engine in Practice." It is the first of these 

 volumes which is now issued. It is ostensibly a book 

 on the thermodynamics of the gas engine, and it is as 

 such, therefore, that it must be examined and dis- 

 cussed. We may say at once that it is quite unlike 

 any other book on thermodynamics that we remember 

 to have read. Its appeal must be to the comparatively 

 imall number of engineers and physicists who are 

 familiar alike with modern practice in gas-engine 

 work and with some of the most recent results in 

 phvsics. To the experimenter in this important field 

 of work, it will be invaluable as containing in compact 

 form a record of the latest experiments as well as an 

 occasional commentary upon them from the author's 

 standpoint. 



It interested us to compare the present volume with 

 Mr. Dugald Clerk's book on the gas engine 

 issued in 1896. We were the more interested in 

 such a comparison because of the change that has 

 come to the point of view of so many workers on 

 account of later knowledge of the physical properties 

 of the gases concerned in the gas-engine cycle. Mr. 

 Clerk's point of view has also changed materially. 

 The author remarks on p. 200 : — 



" Some things, however, have been definitely 

 settled. Holborn and Austin's investigations have 

 placed it beyond doubt that the specific heat of steam 

 and carbonic acid increases considerably with increase 

 of temperature, and that a small increase occurs with 

 oxygen and nitrogen. Nernst's investigations have 

 proved that the dissociation of steam and carbonic 

 acid at about 2000° C. is unexpectedly small." 



When the 1896 edition was published, and until a 

 much later date, Mr. Dugald Clerk was disin- 

 clined to accept the contention of the French physicists 

 that specific heat increased with temperature, and the 

 thermodynamic part of that volume, which is, we 

 notice, reproduced with but little change in the first 

 118 pages of the present one, was based on the con- 

 stancy of specific heat. After reproducing this earlier 

 work, Mr. Dugald Clerk now adds : — 



" Throughout the present chapter the working fluid 

 has been assumed to be dry air obeying perfectly the 

 laws of Charles and Boyle ; its specific heat has also 

 NO. 2089, VOL. 82] 



been assumed to be constant throughout the tempera- 

 ture rajige. ... It is now known that the specific 

 heat of air is not quite constant between 0° and 

 1400° C. . . . The mean Kp between 100° C. and 

 1400° C. is about 8 per cent, higher than that between 

 100° and 200° C. . . . But it must be remembered 

 that the efficiencies and mean pressures determined 

 by these calculations for ideal air are not the effici- 

 encies and mean pressures which would be proper to 

 the actual working fluid. . . . Meantime, however, 

 it may be taken that the reasoning and conclusions 

 reached in this chapter are valuable when properly 

 used." 



From p. 119 onwards the author takes into account 

 the variability of specific heat with temperature. 

 Indeed, in virtue of its importance, the greater part of 

 the book is devoted to the consideration of this matter 

 and of the associated problems. 



Practically all recent work is described at" more or 

 less length, and particular stress is laid on the im- 

 portant work carried out on gaseous explosions at the 

 Royal College of Science, on the initiation of Prof. 

 Perry. Mr. Dugald Clerk is able to reproduce a 

 great deal of this experimental work which had not 

 previously been published, and he analyses the results 

 obtained with great skill and infinite patience. It 

 seems a pity that the record of these experiments has 

 not previously been published, and we can only sur- 

 mise that their importance was not realised adequately, 

 perhaps because the experimenters, Messrs. Bairstow 

 and .Alexander, did not bring out their points with the 

 emphasis at Mr. Dugald Clerk's command. How far 

 the accuracy of these experimenters will stand the test 

 of time remains to be seen ; the virtue that led Mr. 

 Dugald Clerk to refer to them at such length is that 

 they are the only experiments so far known from 

 which can be obtained a series of cooling curves under 

 various conditions of pressure and temperature. We 

 anticipate that practical results of real use will be 

 obtained from this work. 



.-At the end of the volume the author reproduces the 

 very valuable 1908 report of the Gaseous E.xplosions 

 Committee of the British Association. It includes a 

 description of Mr. Dugald Clerk's "zig-zag" experi- 

 ments. It also criticises them, and gives reason for 

 thinking that they may contain an error of as much as 

 10 per cent. The committee remarks, "If there be 

 systematic error in Mr. Clerk's work it seems most 

 likely that it lies in the estimate of heat loss," and 

 proceeds to indicate a way in which this error can be 

 corrected. It is very curious to read this report at the 

 end of Mr. Dugald Clerk's book, when, on turning to 

 his own account of these very experiments, he omits to 

 discuss any correction of the kind. We think that it 

 would have been better if some notice had been 

 taken of the committee's remarks, although it may 

 well be that to have done so would have led to such 

 a mass of extra work that any author might shrink 

 from it. 



We are so grateful to Mr. Dugald Clerk for this 

 interesting volume that we do not wish to press too 

 hard the main criticism to which it is liable, viz. that 

 it is insufficiently edited, that a tight enough grip is 

 not held upon the subject, and that the style is not 

 such as to make it easily readable. 



