434 FRAGMENTS OF SCIENCE 



oirs on the Electricity of the Gymnotus; on the Source 

 of Power in the Voltaic Pile; on the Electricity evolved 

 by the Friction of Water and Steam, in which the phe- 

 nomena and principles of Sir William Armstrong's Hydro- 

 electric machine are described and developed; a paper on 

 Magnetic .Rotations, and Faraday's letters in relation to 

 the controversy it aroused. The contribution of most per- 

 manent value here is that on the Source of Power in the 

 Voltaic Pile. By it the Contact Theory, pure and simple, 

 was totally overthrown, and the necessity of chemical 

 action to the maintenance of the current demonstrated. 



The third volume of the Researches opens with a 

 memoir entitled "The Magnetization of Light," and the 

 "Illumination of Magnetic Lines of Force." It is diffi- 

 cult even now to affix a definite meaning to this title; but 

 the discovery of the rotation of the plane of polarization, 

 which it announced, seems pregnant with great results. 

 The writings of William Thomson on the theoretic aspects 

 of the discovery; the excellent electro-dynamic measure- 

 ments of Wilhelm Weber, which are models of experi- 

 mental completeness and skill; Weber's labors in con- 

 junction with his lamented friend Kohlrausch 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 phenom- 

 ena. The hope of such a connection was first raised by 

 the discovery here referred to. 1 Faraday himself seemed 



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 Polar- 

 Jsationsebene durch magnetische Directionskraft zuerst, imd sodann durch dia 



