LETTERS TO THOMSON 219 



are altogether left out, so that it is no proof at all, a fact I only discovered on copying 

 it out into my MSS), and he generalises it into 



tdH 



tdH 



J~' 



which he calls the " Entropy." This is the equivalence-value of the actual heat and 

 of the potential of internal work the latter of which he calls " Disgregation." All 

 the rest is mere playing with diff 1 = ns . Have you done no more about dissipation 

 than is to be found in the Phil. Mag. ? The entropy and equivalence-values, etc., 

 are merely dissipation enunciated in other language. I have my third Chap, nearly 

 finished, and shall probably have both ready for your perusal when you return, as 

 I wish your "polishing" to be done before I go to press. I have kept a few of 

 Rankine's geometrical things at the commencement, and have then bagged freely 

 from you. In the 4th Chap. I shall do some geometrical things about Leyden jars 

 and then bag freely from H 1 [i.e., H. Helmholtz's paper, " Ueber die Erhaltung der 

 Kraft"]. 



Macmillan has sent me an interleaved copy of Vol. I 1 , stitched up in 4 equal 

 parts. This looks like speedy work for the new edition. 



I got hold of Maxwell lately, and have managed to extract from him a promise 

 to send constant contributions to the R. S. E. He has also undertaken to write 

 accounts of his own, and some other people's work for my D. T. 



Snow, sleet, and hail alternately while you are among the oranges and 

 myrtles t ! 1 



Yrs. T'. 



6 G. G., E. 



13/1/68. 

 Dear T, 



I have written to Bertrand, and sent him papers as you counselled no 

 answer. 



My laboratory is getting on capitally but it will take some time to dry before 

 we can safely work in it. 



When two soap-bubbles unite into one, how much work is done? Note, that 

 the common surface diminishes, but the whole bulk increases. 



I have finished Chap. Ill of my Sketch of Thermodynamics, and as you are 

 not available I have sent it to Maxwell to look over. You will be rather surprised 

 when you see the quiet way in which I have bagged from you and Rankine.... 



Yrs. T'. 



6 G. G., E. 



18/1/68. 



Dr T, 



Have you got a note I sent you a week or two ago giving you Forbes' 

 address?... 



1 That is, of the Natural Philosophy; compare footnote (i) on previous page. 



282 



