THE CONSERVATION OF ENERGY 



more's the pity would have been the application 

 of his qualifying clause: "but that happeneth rarely." 



THE FINAL UNIFICATION 



There are only a few great generalizations as yet 

 thought out in any single field of science. Naturally, 

 then, after a great generalization has found definitive 

 expression, there is a period of lull before another for- 

 ward move. In the case of the doctrines of energy, the 

 lull has lasted half a century. Throughout this period, 

 it is true, a multitude of workers have been delving in 

 the field, and to the casual observer it might seem as if 

 their activity had been boundless, while the practical 

 applications of their ideas as exemplified, for example, 

 in the telephone, phonograph, electric light, and so on 

 have been little less than revolutionary. Yet the 

 most competent of living authorities, Lord Kelvin, 

 could assert in 1895 that in fifty years he had learned 

 nothing new regarding the nature of energy. 



This, however, must not be interpreted as meaning 

 that the world has stood still during these two genera- 

 tions. It means rather that the rank and file have been 

 moving forward along the road the leaders had already 

 travelled. Only a few men in the world had the range 

 of thought regarding the new doctrine of energy that 

 Lord Kelvin had at the middle of the century. The 

 few leaders then saw clearly enough that if one form of 

 energy is in reality merely an undulation or vibration 

 among the particles of " ponderable " matter or of ether, 

 all ' 'ther manifestations of energy must be of the s 

 nature. But tin- rank and file were not even within 

 sight of this truth for a long time after they had partly 



TOL. III. 19 



