2i8 PETER GUTHRIE TAIT 



by the discoveries of Black, Davy, and Rumford, and the ultimate triumph 

 of the Energy Theory are sketched in a racy interesting manner ; and for 

 the first time in an elementary text-book Carnot's Cycle of Operations and 

 his notion of the Perfect Reversible Engine are expounded in detail. The 

 early and practically contemporaneous researches in the dynamical theory 

 of heat of Clausius, Rankine, and Thomson are explained, and the whole 

 subject brought into relation with the laws of Radiation. 



In the second chapter Tait takes a much wider sweep, and passes in 

 review a series of striking examples of the transformations and the conserva- 

 tion of energy. These are taken from the recognised branches of physics, 

 dynamics, sound, electricity and magnetism, in all their aspects, solar radiation, 

 gravitational energy, physiological activity, and tidal retardation and other 

 illustrations of the dissipation of energy. 



The third chapter is an exposition of the dynamical theory of heat as 

 it was developed by the pioneer workers on the subject. When engaged in 

 putting it together Tait wrote the following three letters to Thomson : 



6 G. G., E., 4/1/68. 

 Dear T, 



The compts. and best wishes of the season from all here to you and Lady 

 Thomson, of whom we hope to hear good accounts.... 



I don't understand Macmillan at all.... He says everything is arranged, and 

 doesn't tell me how 1 . But I'll find out before I take any further step. Meanwhile, 

 how about the remaining sheets of the pamphlet which you took with you? 



I have been writing at the third chapter of my D. T.' and have undergone 



TT 



some very laborious reading at Clausius' Abhandlungen. I find that he calls (he 



calls it T, not having begun by defining temp re properly) the equivalence-value 

 of a quantity H of heat at temp re /. Then the second law becomes the assertion 

 of equivalences 



where H, is negative. Then he goes to your 



for reversible processes (in your proofs of which, by the way, some lines and steps 



1 This has reference to the 2nd edition of " T and T," which however was not seriously 

 entered upon till 1875. 



1 Dynamical Theory of Heat 



