HERMANN VON HELMHOLTZ 



brilliant school, were enthusiastic in their approbation. 

 Du Bois Reymond remarks, with some humour, 

 ' His supporters declared that he had set in motion 

 the conservation of another force, much more in- 

 teresting for us, the mind of Helmholtz himself.' 1 



It is now a matter of common knowledge, that 

 while the principle of the conservation of energy 

 slowly unfolded itself to the minds of the great 

 scientific thinkers of the earlier part of this century, 

 the root of the idea must be traced back to the in- 

 tellectual giants Newton, Descartes and Leibnitz. 

 Professor Tait has shown that Newton undoubtedly 2 

 was in possession of the principal facts of the con- 

 servation and transformation of energy. In the 

 expression of his third law of motion, * to every action 

 there is always an equal and contrary reaction,' the words 

 'action' and ' reaction' are interpreted by Newton him- 

 self in two senses. Between any two bodies connected 

 together, such as a weight resting on a table, there is 

 always an equal and opposite reaction. The weight 

 presses on the table and the table presses on the 

 weight. Two bodies may also be connected by some 

 invisible link, such as exists between bodies that are 

 affected by magnetic attraction, and yet the law 

 holds good. But action and reaction may occur in 

 another sense. 'If the activity of an agent be 



1 Du Bois Reymond's GedHchtnissrede. Berlin, 1896. 



2 Tail's Lectures on Recent Advances in Physical Science, 1885. Lect. 

 ii., p. 27. London, 1885. 



44 



