PROFESSOR IN BERLIN 287 



extraordinary talent for animal painting, having already admired 

 her pictures in the Exhibition in London. 



'It was all very friendly and unconstrained. Thomson 

 presumed so much on his intimacy with them that he always 

 carried his mathematical notebook about with him, and would 

 begin to calculate in the midst of the company if anything 

 occurred to him, which was treated with a certain awe by the 

 party. How would it be if I accustomed the Berliners to the 

 same proceeding ? But the greatest naivete of all was when 

 on the Friday he had invited the party to the yacht, and then 

 as soon as we were under way, and every one was settled 

 as securely as might be in view of the rolling, he disappeared 

 into the cabin to make calculations, while the company were 

 left to entertain each other so long as they were in the vein ; 

 but you may imagine that they were not very lively. I amused 

 myself by strolling up and down the deck, " in schwankender 

 Anmuth." ' 



The return voyage was very pleasant and comfortable, and 

 on calm days he and Thomson experimented on the rate at 

 which the smallest ripples that appeared at the surface of the 

 water were propagated, a subject on which Thomson had 

 recently been working. 



' Still/ he writes to his wife on September 4, ' I find that 

 a husband who is no longer in his first youth feels uncomfort- 

 able when he wanders about in the world, all by himself, 

 without higher guidance, and I think if the world were peopled 

 with men only it would not be particularly beautiful, but would 

 be very practical, and not at all refreshing.' 



In his work Helmholtz now turned almost exclusively to 

 Electricity. In his first treatise on the theory of electro- 

 dynamics, which deals with electrical motions in ponderable 

 conductors at rest, and is of fundamental importance for the 

 principles of mechanics, he had succeeded in giving F. E. 

 Neumann's potential-expression a form in which it included 

 the two different potential-expressions laid down by W. Weber 

 and Clerk Maxwell for each pair of current-elements. Investi- 

 gation of the law for the different values of his constant k had 

 shown that Weber's law led to inconvenient results ; on the 

 other hand, Maxwell's hypothesis, in the case when motions 

 of electricity or magnetism in dielectric or magnetic media 



