AT THE PHYSICO-TECHNICAL INSTITUTE 405 



and their consequences. For this reason I have always felt my- 

 self closely connected with medicine, my first intellectual home, 

 even though in later years I have made no direct contributions 

 to this subject. The assurances contained in the letter from 

 the Faculty have accordingly given me much pleasure.' 



The cordial and inspiring Address from the Academy of 

 Berlin was also a source of great delight to Helmholtz. In 

 his reply he says : 



4 1 cannot wholly suppress a doubt whether I am worthy of 

 such high praise, but the Address will be a valued document for 

 my descendants, telling them to the farthest generation that 

 their ancestor had but one aim : to make the best use of his time/ 



Helmholtz had conjectured from the elegance of its style 

 and contents that du Bois was the author of this address, and 

 du Bois replied on November 7 : 



' You know the marksman, no need to look elsewhere ; it was 

 I, too, who murdered the Latin on your renewed diploma. When 

 it was too late, I discovered that you had spoken of yourself 

 as Arminius in your dissertation, where it is the fashion nowa- 

 days to say Herman nus.' 



Meantime, Hertz (who was obliged by illness to break off his 

 great experimental researches for increasingly long periods) was 

 expanding Helmholtz's work on the principle of least action, and 

 its significance in electrodynamics, in theoretical memoirs of the 

 utmost importance. In December, 1892, he writes to Helmholtz : 



' Of late I have been devoting myself entirely to theoretical 

 work, to which I was incited by the study of your papers on 

 the Law of Least Action. I asked myself what shape must 

 be given to Mechanics from the outset, that the principle of 

 least action may be stated at the beginning, and that its 

 different forms may appear not as the result of com- 

 plicated calculations, but as illuminating truths of primary 

 significance, and be recognized as the clear and unmistakable 

 aspects of one and the same law. I am satisfied with my 

 results up to a certain point, but I have still a half or whole 

 year's work on the subject, and since my illness now makes an 

 interruption, I must appear idle to many. But I beg Your 

 Excellency to believe that I am not more idle than my illness 

 makes me. 



'A very remarkable discovery has been made here during 



