PROGRESS IN NINETEENTH CENTURY 65 



(1902) on the increase of electromagnetic mass with the velocity of 

 the corpuscle, has shown, the Lagrangian equations of motion may be 

 recast in an electromagnetic form. This profound question has been 

 approached independently by two lines of argument, one beginning 

 with Heaviside (1889), who seems to have been the first to compute 

 the magnetic energy of the electron, J. J. Thomson (1891, 1893), 

 Morton (1896), Searle (1896), Sutherland (1899); the other with 

 H. A. Lorentz (1895), Wiechert (1898, 1899), Des Coudres (1900), 

 Drude (1900), Poincare (1900), Kaufmann (1901), Abraham (1902). 

 Not only does this new electronic tendency in physics give an accept- 

 able account of heat, light, the X-ray, etc., but of the Lagrangian 

 function and of Newton's laws. 



Thus it appears, even in the present necessarily superficial sum- 

 mary of the progress of physics within one hundred years, that, curi- 

 ously enough, just as the nineteenth century began with dynamics 

 and closed with electricity, so the twentieth century begins anew 

 with dynamics, to reach a goal the magnitude of which the human 

 mind can only await with awe. If no Lagrange stands toweringly 

 at the threshold of the era now fully begun, superior workmen abound 

 in continually increasing numbers, endowed with insight, adroit- 

 ness, audacity, and resources, in a way far transcending the early 

 visions of the wonderful century which has just closed.. 



