ON THE DISSIPATION OF ENERGY. 461 



of the first thirty years of the nineteenth century, 

 a thoroughly clear statement of the old perpetual 

 motion in its most subtle nineteenth-century 

 form. But this statement is put as a question 

 with clear indication of a bias towards a negative 

 answer : and it is impossible to doubt that Carnot 

 would have unhesitatingly given the negative 

 answer if a little more time had been allowed 

 him for thinking out the thermodynamic problem. 

 Happily, however, Carnot's original essay led 

 others to give it. My brother, Professor James 

 Thomson, assumed a negative answer, and 

 founded on it his theoretical demonstration 

 that the freezing point of water is lowered 

 by pressure. 1 



Two years later 2 I gave the negative answer as 



1 Transactions of the Royal Society of Edinburgh^ January 2nd 

 1849, reprinted in Cambridge and Dttblin Mathematical Journal, 

 November, 1850, and quoted in extenso in vol. i., Mathematical 

 and Physical Papers, Sir W. Thomson (pp. 156164). 



2 Transactions of the Royal Society of Edinburgh, March, 1851, 

 and Philosophical Magazine, iv. 1852, " On the Dynamical Theory 

 of Heat, with Numerical Results deduced from Mr. Joule's 

 Equivalent of a Thermal Unit, and M. Regnault's Observations on 

 Steam," reprinted in vol. i., Sir W. Thomson's Mathematical and 

 Physical Papers. 



