AT THE PHYSICO-TECHNICAL INSTITUTE 383 



the plane reflecting screen was rotating as little as 5 to the one 

 side or the other of the right position : this proves the reflection 

 to be regular, and not diffuse. 



I You will pardon my impatience, in giving you such prompt 

 information about these matters. I intend to repeat and extend 

 my observations, and then to put them together in a report for 

 the Academy, and hope you will be good enough to receive it, 

 though doubtless you are already overcrowded with such things.' 



Helmholtz replied most genially : 



I 1 am much delighted with your last results. I have puzzled 

 for years over the possibility of getting at these things, so that 

 I am familiar with the whole train of thought, and its immense 

 importance is obvious to me.' 



In 1885 Hertz had been appointed Ordinary Professor of 

 Physics at the Technical High School of Karlsruhe, and he was 

 subsequently, on the death of Kirchhoff and Clausius, offered 

 the choice, through Helmholtz, of Berlin or Bonn, when he 

 decided for the latter, because ' he preferred the Chair at Bonn, 

 which was an experimental post, to the great honour the 

 Faculty of Berlin had designed for him '. Helmholtz writes on 

 December 15, 1888 : 



' Personally I am sorry that you are not coming to Berlin, 

 but, as I have already told you, I believe it is for your own 

 interest to go to Bonn. Those who have still much scientific 

 work in view are better away from big cities. At the end of 

 one's life, when it is more a question of utilizing the points of 

 view one has arrived at for the education of the coming genera- 

 tion and the administration of the State, the case is different.' 



The prosecution of his meteorological studies during the 

 ensuing winter, and the consequent limitation of his public 

 lectures and addresses to Scientific Societies, was only once 

 interrupted with the express intention of doing justice to the 

 great scientific merits of his quondam friend and subsequent 

 opponent, R. Clausius. 



On January u, 1889, Helmholtz delivered a memorial lecture 

 to the Physical Society of Berlin, which emphasized the great 

 services rendered by Clausius, notwithstanding many points 

 of past controversy between these eminent men. His own in- 

 vestigations in recent years into the modern development of the 

 mechanics of chemistry had all been based, so far as they were 



