February 4, 1892 J 



NATURE 



315 



thermal communication with two bodies only which are 

 at the same temperature. As a basis for the second law, 

 is not this like Samson shorn of his locks ? 



But in the really important demonstrations Mr. Parker 

 uses, as a logical equivalent of this, an axiom which again 

 is nowhere given explicitly, but may be thus enunciated : 

 During a complete cycle, in which the working substance 

 is in thermal communication with two bodies each at a 

 constant and uniform temperature, it is impossible for a 

 positive quantity of heat to be absorbed from the one and 

 no heat whatever to be exchanged with the other body. 

 The general truth of this " axiom " will be admitted 

 rather because it agrees with Carnot's principle than 

 because of any inherent merit it may itself possess. An 

 axiom must appeal to experience at bottom ; and if one 

 had striven to evolve the said axiom in the most unaxiom- 

 atic guise attainable, one could hardly have succeeded 

 better. Sad, indeed, his lot whose introduction to Carnot's 

 principle is through such tortuous paths ! 



But the impression gathered from a careful considera- 

 tion of Section 49 is that the second implied form must 

 be regarded as simply another statement of the first im- 

 plied form of " Carnot's axiom." Take, for example, the 

 following argument : — 



" The quantities of heat absorbed by the system from 

 the two bodies A, B [each at a constant and uniform 

 temperature] during any complete cycle cannot both be 

 positive. For we could then, by expending work in fric- 

 tion, cause the system to undergo a cycle of operations 

 in which a positive quantity of heat was absorbed from 

 one of the bodies A, B, and no heat at all received from 

 or parted with to the other. In other words, we should 

 be able to take heat from a body whose temperature was 

 uniform and constant, and transform it into work without 

 the presence of any other body of different temperature, 

 contrary to Carnot's axiom." 



Little good would be served by criticizing these state- 

 ments at length, which seem to contain at least as many 

 assumptions as sentences. It would be interesting to 

 know what becomes of the work spent in friction, so 

 arbitrarily introduced, and so cunningly disregarded, j 

 After all, however, although the second implied form of 

 " Carnot's axiom " may be generally true, it certainly is 

 not so in the particular case in which the one body 

 is at absolute zero. This is quite as conceivable a 

 contingency as the realization of the assumed thermal 

 conditions of the bodies A and B. 



After having, by a perfect volley of redtictiones ad i 

 absurduin, reduced all reversible cycles, working between 

 the same temperatures, to the same efficiency, Mr. Parker 1 

 introduces Thomson's absolute scale of temperature in ! 



the usual form ^" = /. Then should come (since it has j 



not come earlier) the proof that the reversible cycle has 

 more efficiency than any other conceivable cycle. But all 

 we find is this sentence :— 



" It will be easily seen that, if the irreversible cycle be 

 non-frictiona!, q.,lqf. will be equal to 6„I6/., and that in all 

 other cases it will be less." 



" It will be easily seen " is easily said, and throws the 

 burden of the proof upon the intelligence of the learner — 

 the proof of what is the kernel of the whole of thermo- 

 dynamics. And f/u's is teaching ! 

 NO. 1 162, VOL. 45] 



We are firmly convinced that after reading this third 

 chapter the average student will have the haziest ideas 

 of what reversibility means, will be utterly at a loss to know 

 what Carnot's principle really is, and will look upon the 

 " conception of entropy '' as a phrase to conjure by. It 

 is with decided feelings of relief that we pass on to 

 chapter iv., "Applications of Carnot's Principle." It 

 may be well to remark here that chapter ii., "On 

 Perfect Gases," discusses the simpler thermodynamic 

 properties of the ideal gas obeying Boyle's and Charles's 

 laws. The experimental truth established by Joule, that 

 the heat absorbed by such a gas is equal to the work 

 done by it during the expansion, is made the basis of the 

 whole inquiry. In both these chapters the ground covered 

 is familiar. For example, Thomson and Joule's experi- 

 mental determination of the absolute zero of temperature 

 is given with commendable fullness. Critical points, 

 latent heats of saturated vapour, and certain aspects of 

 solution and capillarity are all treated in due order, and 

 with sufficient fullness of numerical detail to make them 

 thoroughly intelligible. In the fifth and sixth chapters, 

 again, we are introduced to the thermodynamic potential. 

 We are not aware that the general energy methods of 

 Massieu and Helmholtz have ever before been presented 

 in connected form to English readers. This Mr. Parker 

 has done, and has deservedly earned our tribute of praise. 

 Anyone who is familiar only with the earlier methods by 

 which the founders of the modern theory grappled with 

 the subject, will find these two last chapters, and especially 

 chapter vi., particularly interesting. 



The author is not, however, to our mind so happy in 

 his account of Gibbs's thermodynamic surface as, from the 

 tenor of his introductory remarks, we had expected him to 

 be. After animadverting upon " the very brief notice in 

 Maxwell's ' Theory of Heat ' " of" this beautiful geometrical 

 construction . . . which does not seem to have obtained 

 the attention it appears to deserve," Mr. Parker proceeds 

 presumably to give it this attention. But what do we 

 find .'' Five pages of not very lucid description as against 

 Maxwell's eleven and a half. Perhaps, however, this is 

 of small consequence ; for, beautiful though it be as a bit 

 of geometry, the thermodynamic surface, even in concrete 

 form, is of doubtful efficiency in the presentation of 

 thermodynamic truth. 



Mr. Parker's book possesses not a few merits, but is 

 marred as an educational work by many faults, chief 

 among which is the tangled presentation of the second 

 law. It is hard, indeed, to get up much enthusiasm for 

 an author who speaks of the speed at which a body cools, 

 who casts a slur upon British meteorology by declaring 

 that the Centigrade is " the only thermometer now used 

 for scientific purposes," and who gives no less than three 

 distinct and irreconcilable estimates of the sun's radiation 

 in as many consecutive pages. The loosely expressed 

 but familiar axiom that "heat cannot flow of itself" up a 

 temperature grade is referred to as an important conse- 

 quence of Thomson's definition of absolute temperature ; 

 and of the Maxwell " Demon," and all that therein is, 

 there is not even the suggestion of a hint. 



The book ends with an appendix of physical constants 

 compiled from various sources. Otherwise, its usefulness 

 is sadly diminished by lack of an index or even table of 

 contents. C. G. K. 



