PROFESSOR IN BERLIN 365 



1885, in which he speaks with the greatest admiration of the 

 issues of his friend's genius. He places the great value of 

 Thomson's scientific methods in the fact that he followed 

 Faraday's example in avoiding hypotheses as to unknown 

 matters as far as possible, and took pains in his mathematical 

 treatment of the problems to express simply the law of the 

 observed phenomena. This limitation of his field enabled 

 Thomson always to bring out the analogy between the dif- 

 ferent processes of nature far more clearly than would have 

 been the case had it been complicated by widely divergent 

 ideas in regard to the internal mechanism of the processes. 



At the close of this year Helmholtz received an intimation 

 from Bonders that the Ophthalmological Society had voted 

 him the first medal struck in remembrance of Albrecht von 

 Graefe, and that it would be presented to him the following 

 autumn in Heidelberg. He replies to Bonders on January 31, 

 1886: 'I am greatly flattered at being the recipient of the 

 Graefe Medal, the more so as long years have gone by 

 since I recalled myself to the memory of the ophthalmologists. 

 . . On the whole we are well ; if I am aware of certain infirmities 

 of advancing age, I cannot complain of deficient working 

 powers ; I only wish I had more free time. One of the causes 

 which lost me nearly a day a week for many years, the migraine, 

 has almost entirely disappeared. They always told me it 

 would wear out with old age. The main point really is to 

 learn what one can do, and to respect one's limitations.' 



At the close of the Summer Session of 1886, Helmholtz went 

 alone (his wife being detained by the illness of their son) to 

 Heidelberg, for the celebration of the sooth anniversary of the 

 University, where he delivered a stirring discourse in its 

 honour at the Banquet on August 4, in the presence of the 

 Crown Prince of Germany, the Grand Buke of Baden, and the 

 Rector of the University. 



Immediately after this, Helmholtz was presented with the 

 Graefe Medal, on August 9, at a solemn session of the Ophthal- 

 mological Society in Heidelberg. He replied to the fine 

 address of the President, Bonders, with expressions of profound 

 gratitude, and ended his long oration with the words : 



' And now you must permit me to express my conclusion in 

 allegorical language, so as to wound no feelings of personal 



