HERMANN VON HELMHOLTZ 



The first in Great Britain to recognise the immense 

 importance of the principle was William Thomson, 

 now Lord Kelvin, who applied it with such force to 

 thermo-dynamics as to practically create this depart- 

 ment of science. He also formulated the comple- 

 mentary doctrine of the dissipation of energy. 



It has been necessary to give this slight sketch of 

 the development of these great ideas so as to enable 

 one to estimate with some degree of accuracy how 

 much was contributed by Helmholtz. He approached 

 the subject from the purely mathematical point of 

 view. With the writings of Newton, Leibnitz, 

 Descartes and d'Alembert in the field of his mental 

 vision, he starts by making two assumptions. The 

 first is as follows : Suppose matter to ' consist of 

 ultimate particles which exert on each other forces 

 whose directions are those of the lines joining each 

 pair of particles, and whose amounts depend simply on 

 the distance between the particles ; suppose, in fact, 

 that something akin to gravitation force exists amongst 

 all the particles of matter in the universe, that each 

 particle attracts every other particle with a force 

 which depends only on the distance between them, 

 not in any way upon the sides which are turned to 

 one another, so that if you know the distance between 

 them you know the amount of the attraction, and that 

 the attraction shall also be (in accordance with 

 Newton's Third Law of Motion) in the direction 

 of the line joining them. If that assumption is made, 

 52 



