CHARACTER OF THE EXPERIMENTALIST. 235 



gained the first success ; on August soth he began to 

 work with common electricity, vainly trying glass, quartz, 

 Iceland spar, &c. Several days of labour gave no result, 

 yet he did not desist. Heavy glass, a transparent medium 

 of great refractive powers, composed of borate of lead, was 

 now tried, by being placed between the poles of a powerful 

 electro-magnet, while a ray of polarized light was trans- 

 mitted through it. When the poles of the electro-magnet 

 were arranged in certain positions with regard to the 

 substance under trial, no effects were apparent; but at 

 last Faraday happened fortunately to place a piece of 

 heavy glass so that contrary magnetic poles were on the 

 same side, and now an effect was witnessed. The glass 

 was found to have the power of twisting the plane of 

 polarization of the ray of light. 



All Faraday's recorded thoughts upon this great experi- 

 ment are replete with curious interest. He attributes his 

 success to the opinion, almost amounting to a conviction, 

 that the various forms, under which the forces of matter 

 are made manifest, have one common origin, and are so 

 directly related and mutually dependent that they are 

 convertible. ' This strong persuasion,' he says?, ' extended 

 to the powers of light, and led to many exertions having 

 for their object the discovery of the direct relation of light 

 and electricity. These ineffectual exertions could not 

 remove my strong persuasion, and I have at last suc- 

 ceeded.' He describes the phenomenon in somewhat figu- 

 rative language as the 'magnetization of a ray of light, 

 and also as the illumination of a magnetic curve or line 

 of force. He has no sooner got the effect in one case, 

 than he proceeds, with his characteristic comprehensive- 

 ness of research, to test the existence of a like phenomenon 

 in all the substances available. He finds that not only 



g 'Life of Faraday,' vol. ii. p. 199. 



