THE BIRKBECK INSTITUTION. 245 



had juti finished his experiments on the velocity of 

 nervous transmission proving this velocity, which 

 had previously been regarded as instantaneous, or at all 

 events as equal to that of electricity, to be, in the 

 nerves of the frog, only 93 feet a second, or about one- 

 twelfth of the velocity of sound in air of the ordinary 

 temperature. In his own house I had the honour of an 

 interview with Humboldt. He rallied me on having 

 contracted the habit of smoking in Germany, his 

 knowledge on this head being derived from my little 

 paper on a water-jet, where the noise produced by the 

 rupture of a film between the wet lips of a smoker is 

 referred to. He gave me various messages to Faraday, 

 declaring his belief that he (Faraday) had referred the 

 annual and diurnal variation of the declination of the 

 magnetic needle to their true cause the variation of 

 the magnetic condition of the oxygen of the atmosphere. 

 I was interested to learn from Humboldt himself that, 

 though so large a portion of his life had been spent in 

 France, he never published a French essay without 

 having it first revised by a Frenchman. In those days 

 I not unfrequently found it necessary to subject myself 

 to a process which I called depolarization. My brain, 

 intent on its subjects, used to acquire a set resembling 

 the rigid polarity of a steel magnet. It lost the pliancy 

 needful for free conversation, and to recover this I used 

 to walk occasionally to Charlottenburg or elsewhere. 

 From my experiences at that time I derived the notion 

 that hard thinking and fleet talking do not run to- 

 gether. 



In trying to carry out the desire of Mr. Norris I 

 have spoken as a worker to workers; believing that 

 though the word I has occurred so frequently in this 

 address, far from seeing in it a display of egotism, you 

 will accept it as a fragment of the life of a brother who 



