AT THE PHYSICO-TECHNICAL INSTITUTE 423 



of anything that deviates so much from the beaten track, and is 

 so subtly interwoven, as this work of Hertz. I can only say 

 that I am just beginning to see what his aim is, and this merely 

 since I received the last set of proof-sheets a few days ago. Till 

 then I had not the least inkling of what he was driving at. Under 

 these conditions I cannot at present undertake to criticize the 

 text, or to approve of a criticism of it, and should suppose that 

 it will be some weeks before I have got far enough to embark 

 upon it. I quite appreciate the difficulty you are in. But it 

 seems to me that you can get out of it simply, without com- 

 promising yourself, if you mark the points that seem to you 

 dubious, and add a footnote to the effect that " the text is an 

 accurate reproduction of the original MS." This will indicate 

 to the reader that he must pay attention in these places, 

 and that these points may require consideration.' 



Helmholtz now immersed himself in the study of Hertz's 

 Mechanics, and wrote a Preface to this extraordinarily original 

 work in July, 1904, which gives much insight into his own 

 views of the development of mechanics. 



After sketching the position of the Theory of Electricity at 

 the time when Hertz first took it up, and after commending his 

 great physical discoveries, he says : 



'The extent to which Hertz's reflections were focused upon 

 the most universal points of view in science, appears once 

 more from this last memorial of his earthly activity, his book 

 on the Principles of Mechanics. In this he endeavoured to 

 give a logical statement of a perfect and consistent system of 

 mechanics, and to deduce all the particular special laws of this 

 science from one single fundamental law, which, logically 

 speaking, must of course be regarded merely as a plausible 

 assumption. In this he reverted to the oldest theoretical views, 

 which must be regarded as the simplest and most natural, and 

 asks whether these are not adequate to enable us to deduce from 

 them, in the strictest and most logical manner, all the recently 

 discovered universal principles of mechanics, even where these 

 had till now been regarded merely as inductive generalizations.' 



Helmholtz points out that the laws of mechanics have all 

 been developed on the assumption of Newton's attributes of 

 the forces of attraction (independent of time, and hence con- 

 servative) that exist between material points, and the existence 



