Notices respecting New Books. 231 



the way in which Carnot's Theorem is dependent on our inability 

 to deal individually with the irregular heat-energy of molecules, 

 this view is kept quite in the background and the subject is based 

 upon a set of scholastic generalities that throw very little light on 

 the physical basis of Thermodynamics. Such presentations have 

 in the past rather tended to obstruct than advance Science. And 

 yet the book is suggestive and interesting. Even if it did no more 

 than continually call to mind the ether as a vera causa, it would be 

 worth studying ; much more therefore does it deserve study, being, 

 as it is, the work of an ingenious and original, if of a somewhat 

 scholastic and cranky mind. 



Theory of Heat. By J. Cleek Maxwell, M.A., F.R.S. Tenth 

 Edition, with corrections and additions by Lord Hayleigh, Sec. 

 E.S. London: Longmans, 1891. 



Ir the name of Clerk Maxwell were not in itself a sufficient 

 guarantee of the excellence of the book before us, the fact that 

 it has already passed through nine editions and still remains the 

 standard text-book on the theory of Heat, indicates very clearly 

 the opinion of scientific students concerning it. But the advance 

 of science does not permit of an unlimited number of stereotyped 

 editions ; consequently it now becomes necessary to revise, and 

 make additions to, Maxwell's original treatise. There was no one 

 who could accomplish this task more satisfactorily than Lord 

 Rayleigh, and we are gratified to learn that he has found leisure 

 enough to undertake it, and to add ten pages of matter relating 

 mostly to capillary phenomena and the kinetic theory of gases and 

 liquids. 



The book may be divided into two parts, in one of which molar, 

 and in the other molecular, phenomena are discussed. The first 

 of these includes calorinietry, thermometry, and thermodynamics, 

 and in it the idea of temperature is taken as a fundamental one. 

 The second part treats of capillarity, diffusion, and the kinetic 

 theory of gases, and it is there shown that temperature is mea- 

 sured by the mean kinetic energy of the molecules in the case of 

 gases at any rate. The theory of the first part was as complete 

 when Maxwell wrote his treatise as it is to-day, it being a logical 

 sequence of the two propositions that energy is indestructible, and 

 that heat always passes from a hotter to a colder body. Unless 

 either of these axioms can be shown to be false the theory will 

 receive but little addition or alteration, and it is not surprising 

 that Lord Eayleigh should leave Maxwell's text unaltered, save 

 for the addition of a little note concerning the liquefaction of the 

 so-called permanent gases. There is one paragraph where a 

 distinct advance might have been recorded, though it does not in 

 the least affect any theory of heat. On p. 38 Maxwell speaks of 

 the Fahrenheit scale of temperature as being "very generally 

 used," and of the Centigrade scale as "coming into use." The 



