PRESIDENTIAL ADDRESSES. 541 



that, if real, it must give a thorough explanation 

 of that law. 1 Nevertheless, after Faraday's 

 discovery 2 of the different specific inductive 

 capacities of different insulators, twenty years 

 passed before it was generally accepted in Conti- 

 nental Europe. But before his death, in 1867, he 

 had succeeded in inspiring the rising generation of 

 the scientific world with something approaching to 

 faith that electric force is transmitted by a medium 

 called ether, of which, as had been believed by the 

 whole scientific world for forty years, light and 

 radiant heat are transverse vibrations. Faraday 

 himself did not rest with this theory for electricity 

 alone. The very last time I saw him at work in 

 the Royal Institution was in an underground 

 cellar, which he had chosen for freedom from 

 disturbance ; and he was arranging experiments 

 to test the time of propagation of magnetic force 

 from an electro-magnet through a distance of many 

 yards of air to a fine steel needle polished to reflect 



1 Electrostatics and Magnetism, Sir W. Thomson, Arts. I. (1842) 

 and II. (1845), particularly 25 of Art. II. 



2 1837, Experimental Researches, 11611306. 



