MICHAEL FARADAY 259 



who knows what is possible ?' was one of his remarks; never- 

 theless there was a deep conception behind it all, only one 

 that he was not altogether inclined to trust; one and the same 

 ether for the magnetic forces and for light. The first suc- 

 cess came when he brought a piece of heavy flint glass, made 

 in his earlier experiments of different kinds of glass, into the 

 magnetic field. The success was a first sign of the correct- 

 ness of the idea. 



Also in the discovery which then followed of diamagnetism 

 and the magnetic properties of all matter, this glass likewise 

 brought the first success, since it was repelled out of the 

 magnetic field, in a manner exactly opposite to the behaviour 

 of iron and substances containing iron. Hereupon he made 

 an investigation of many substances in the strongest mag- 

 netic field that he was able to produce, whereby they were all 

 shown to be either magnetic, or *dia-magnetic,' like Fara- 

 day's glass or bismuth.^ 



The course of the magnetic lines of force around currents 

 and magnets, their inductive effects, and the measurement of 

 magnetic field strength by means of these effects, occupied 

 Faraday during the last period of his work. In this con- 

 nection belong also ideas and experiments concerning a 

 possible connection between gravitation and electricity, con- 

 cerning also the rate of propagation of electric and magnetic 

 forces, and a possible change in wave-length by a source of 

 light (a flame fed with common salt), in the magnetic field. 

 These latter matters led to no decision. However, his ques- 

 tion whether the ether which carries light may not also be the 

 medium for the electrical magnetic forces, was later answered 

 affirmatively by Maxwell, who based his work upon Fara- 

 day's achievements, and upon an important result found by 

 Johann Weber. Maxwell's results were first a supposition 



1 It appeared that scattered observations concerning the repulsion of 

 bismuth by magnetic poles had already been published, but no one pre- 

 viously to Faraday had treated the subject as a whole and thus brought 

 it into general importance. 



