AT THE PHYSICO-TECHNICAL INSTITUTE 425 



mechanics is a book which must be of immense interest to 

 every reader who takes pleasure in a logical system of dynamics, 

 presented in the most complete and ingenious mathematical 

 form. It is conceivable that this book may be of great heuristic 

 value in the future as a clue to the discovery of new and 

 universal characteristics of the Forces of Nature/ 



On June 14, Helmholtz communicated a paper to the Academy, 

 entitled ' Appendix to the Treatise : On the Principle of Least 

 Action in Electrodynamics*, which was only published by 

 Planck after his death, on account of his manuscript annotations. 



The memoir presented to the Academy in 1892 on the 

 ' Law of Least Action in Electrodynamics ' had led to great 

 mathematical complications, and Helmholtz had been almost 

 incessantly occupied ever since with the thought of how best 

 to simplify the statement of the variations, and thus render the 

 problem, as he conceived it, more perspicuous and lucid. 



He intended to prepare a complete digest of his investigations 

 for Vol. Ill of his Scientific Papers, hoping that a more simple 

 and tangible representation of the kinetic potential, and the 

 variation of the corresponding Hamiltonian integral required 

 for electrodynamics, might prepare the way for the extension 

 of the principle of least action to all forces of Nature. Many 

 introductory notes were found among his papers, which were 

 intended to be introduced into an extensive treatise of this kind. 



All these attempts, however, broke down when he tried to 

 apply the results (arrived at by the solution of the great 

 mathematical difficulties which he had surmounted in his 

 famous memoir of 1892) to obtaining a clear conception of the 

 complicated calculations: and he could not believe there was 

 any other way than this by which Nature could lead him to the 

 development of his profound ideas. In the paper communicated 

 to the Academy on June 14, 1894, he succeeded in getting a little 

 nearer his goal. 



Helmholtz had previously included the laws of electro- 

 dynamics, as proposed by Clerk Maxwell and Hertz, in a 

 generalized form of the principle of least action, and had 

 referred the problem back to the question whether the known 

 value of the total energy of electromagnetic processes agrees 

 with that of Maxwell's system of pondero-motive forces, or must 

 be further supplemented by a function linear with respect to the 



