568 POPULAR LECTURES AND ADDRESSES. 



was his bride the sympathetic companion and 

 sharer in his work of after years. He had not told 

 me in Section A or in the RadclifTe Library that 

 he was going to be married in three days, but now 

 in the valley of Chamounix, he introduced me to 

 his young wife. We appointed to meet again a 

 fortnight later at Martigny to make experiments 

 on the heat of a waterfall (Sallanches) with that 

 thermometer : and afterwards we met again and 

 again and again, and from that time indeed re- 

 mained close friends till the end of Joule's life. I 

 had the great pleasure and satisfaction for many 

 years, beginning just forty years ago, of making 

 experiments along with Joule which led to some 

 important results in respect to the theory of thermo- 

 dynamics. This is one of the most valuable re- 

 collections of my life, and is indeed as valuable 

 a recollection as I can conceive in the possession of 

 any man interested in science. Joule's initial work 

 was the very foundation of our knowledge of the 

 steam engine and steam power. Taken along with 

 Carnot's theory it has given the scientific founda- 

 tion on which all the great improvements since the 



