PHYSICAL SCIENCE IN THE NINETEENTH CENTURY 355 



Atoms and lines of force have become a practical shall I say a 

 popular ? reality, whereas they were once only the convenient 

 method of a single original mind for gathering together and unifying in 

 thought a bewildering mass of observed phenomena, or at most capable 

 of being utilized for a mathematical description and calculation of 

 actual effects. 



Yet Helmholtz says of Faraday : 



It is indeed remarkable in the highest degree to observe how, by a 

 kind of intuition, without using a single formula, he found out a 

 number of comprehensive theorems, which can only be strictly proved 

 by the highest powers of mathematical analysis. ... I know how 

 often I found myself despairingly staring at his descriptions of lines of 

 force, their number and tension, or looking for the meaning of sen- 

 tences in which the galvanic current is defined as an axis of force. . . . 



Faraday apprehended the principle of the conservation of 

 energy even before it had come to clear expression as common 

 property, saying, for example, in refuting the theory that elec- 

 tricity could be generated by metallic contact alone : 



But in no case, not even in those of [electric fishes], is there a 

 pure creation or a production of power without a corresponding ex- 

 haustion of something to supply it. 



Like Young, Dalton, and Joule, Faraday did not belong to the 

 orthodox Cambridge school then dominant in English mathe- 

 matical and physical science, and recognition of the significance 

 of his ideas was consequently retarded. 



What the atomic theory has done for chemistry, Faraday's lines of 

 force are now doing for electrical and magnetic phenomena. . . . Yet 

 the circumstances under which Faraday's work was done were those 

 of penury. 



ELECTROMAGNETIC THEORY OF LIGHT. In 1845 Faraday writes : 



I .... have at last succeeded in magnetising and electrifying a 

 ray of light, and in illuminating a magnetic line of force. . . . Em- 

 ploying a ray of light, we can tell, by the eye, the direction of the 

 magnetic lines through a body : and by the alteration of the ray and 

 its optical effect on the eye, can see the course of the lines just as 

 we can see the course of a thread of glass. 



