4 o 4 HERMANN VON HELMHOLTZ 



Reymond, to Robert Bunsen, and to our Mathematician Pro- 

 fessor, Professor Weierstrass.' 



Some experiments on Electrical Standards, which Helmholtz 

 was proposing to undertake with Lord Rayleigh, were the 

 cause of the following request to the Ministry for leave of 

 absence on July 19, 1892 : 



' I have the honour respectfully to inform Your Excellency that 

 I propose to betake myself to England on Thursday, the 28th 

 inst, for the purpose of testing, with Lord Rayleigh and 

 Prof. Glazebrook of Cambridge, the results of the experiments 

 on the Comparison of Resistances which will have already 

 been carried out by Dr. Lindeck in the Cambridge Laboratory. 

 The Meeting (of the British Association) in Edinburgh will 

 last from August 3 to n, after which we shall assemble in the 

 Laboratory of the Board of Trade in London to compare the 

 German resistances and standard cells with those of the Board 

 of Trade/ 



Returned from England, after working off the most important 

 of his official duties, Helmholtz prepared Parts 6 and 7 of the 

 new edition of Physiological Optics for the press, so that they 

 were able to appear the same year, and then left Berlin for 

 a few days to celebrate the 5oth year of his doctorate, on 

 November 2, in the retirement of his family. Some of the many 

 congratulations which poured in upon him, and Helmholtz's 

 answers, are of great interest. 



The Medical Faculty in Berlin, before whom he had passed 

 his doctor's examination 50 years before, sent him a renewed 

 diploma with cordial congratulations. Helmholtz's answer, 

 dated from Charlottenburg, November 3, ran as follows : 



' I must beg to return my warmest thanks to the Medical 

 Faculty of this University for the gratifying and cordial words 

 that accompanied the renewal of the diploma granted 50 years 

 ago. I have always been aware, and have often said expressly, 

 that I owe much to the study of medicine, even in regard to 

 my later career as a physicist. It gave me a much wider 

 knowledge of Nature than I could otherwise have obtained from 

 studies limited to inorganic nature and to mathematics ; and the 

 grave responsibilities that devolve upon the physician to ensure 

 the success of his professional treatment accustomed me at an 

 early period to strive after an exact knowledge of the actual facts 



