332 HERMANN VON HELMHOLTZ 



and then returned direct to Berlin, to prepare his thermo- 

 dynamic work for publication. 



The Faraday Lecture had made quite an unwonted stir 

 among English men of science, and Sir William Thomson in 

 consequence approached Helmholtz with the request that he 

 would give some popular lectures in England in the autumn of 

 that same year. Helmholtz replied on July 15, thanking him, 

 but declining : 



* Best thanks for your friendly invitation to return to Glasgow. 

 But I find myself incapable of acceding to your offer. In the 

 first place, I know too little of the public I should have to 

 address, and am not usually very successful in my attempts at 

 giving popular lectures to a large audience from mixed classes ; 

 in the second place, the preparation of a lecture in English 

 takes up too much of my time, and there is every reason why I 

 should husband it, seeing that I am sixty years old this year, 

 and still have much work that I want to accomplish/ 



After recuperating as usual from the fatigues of the summer 

 session in August at Pontresina, where he celebrated ' the 

 solemn day on which he parted with the fifties' by a tiring 

 twelve-hour expedition to the Diavolezza, he went on September 

 15 to Paris for the Electrical Congress, which again tried his 

 working powers sorely, but afforded much that was interesting 

 and stimulating. 



' I went with du Bois to the Opening Meeting,' he writes to 

 his wife. 'The Ministre des Postes is President, three other 

 Ministers are the Vice- Presidents selected for France. The 

 foreigners were still to be chosen : Sir W. Thomson, Professor 

 Govi of Turin, and your husband were elected. We took our 

 seats along with His Excellency M. Cochery, amid great ac- 

 clamation. The session itself was merely a formality; there 

 are a great many interesting people at the Meeting. ... In 

 Congress we have had session after session of sections, com- 

 missions, sub-commissions, and private committees, to decide 

 the question of electrical units of measurement, as between 

 Germany and England. It seems now to be happily settled. 

 I made three or four speeches in French each day, which it 

 was fortunate you could not hear. Sir W. Thomson and 

 an English lawyer Moulton are the chief speakers on the 

 English side. For the rest I am happy in the approval of 



