FARADAY. 465 



dynamic measurements of Wilhelm Weber, which are 

 models of experimental completeness and skill ; Weber's 

 labours in conjunction with his lamented friend Kohl- 

 rausch above all, the researches of Clerk Maxwell on 

 the Electro-magnetic Theory of Light point to that 

 wonderful and mysterious medium, which is the vehicle 

 of light and radiant heat, as the probable basis also of 

 magnetic and electric phenomena. The hope of such a 

 connection was first raised by the discovery here referred 

 to. 1 Faraday himself seemed to cling with particular 

 affection to this discovery. He felt that there was 

 more in it than he was able to unfold. He predicted 

 that it would grow in meaning with the growth of 

 science. This it has done ; this it is doing now. Its 

 right interpretation will probably mark an epoch in 

 scientific history. 



Kapidly following it is the discovery of Diamag- 

 netism, or the repulsion of matter by a magnet. Brug- 

 mans had shown that bismuth repelled a magnetic 

 needle. Here he stopped. Le BaillifT proved that 

 antimony did the same. Here he stopped. "Seebeck, 

 Becquerel, and others, also touched the discovery. 

 These fragmentary gleams excited a momentary curiosity 

 and were almost forgotten, when Faraday independently 

 alighted on the same facts ; and, instead of stopping, 

 made them the inlets to a new and vast region of 



1 A letter addressed to me by Professor Weber on March 

 18 last contains the following reference to the connection here 

 mentioned: 'Die Hoffnung einer solchen Combination ist durch 

 Faraday's Entdeckung der Drehung der Polarisationsebene durch 

 magnetische Directionskraft zuerst, und sodann durch die Ueberein- 

 stimmung derjenigen Geschwindigkeit, welche das Verhiiltniss der 

 electro-dynatnischen Einheit zur electro-statischen ausdriickt, mit 

 der Geschwindigkeit des Lichts angeregt worden ; und mir scheint 

 von alien Versuchen, welche zur Verwirklichung dieser Hoffnung 

 gemacht worden sind, das von Herrn Maxwell gemachte am 

 erfolgreichsten.' 



TOL. I. H H 



