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LVI. Electric Absorption of Crystals. By H. A. Row- 

 land and E. H. Nichols, of the Johns Hopkins University, 

 Baltimore* . 



[Plate IX.] 



I. 



THE theory of electric absorption does not seem to have as 

 yet attracted the general attention which its importance 

 demands ; and from the writings of many physicists we 

 should gather the impression that the subject is not thoroughly 

 understood. Nevertheless the subject has been reduced to 

 mathematics; and a more or less complete theory of it has 

 been in existence for many years. Clausius seems to have 

 been the first to give what is now considered the best 

 theory. His memoir, " On the Mechanical Equivalent of an 

 Electric Discharge," &c, was read at the Berlin Academy 

 in 1852 f. In an addition to this memoir in 1866 he shows 

 that a dielectric medium having in its mass particles imper- 

 fectly conducting would have the property of electric absorp- 

 tion. Maxwell, in his ' Electricity,' art. 325, gives this theory 

 in a somewhat different form, and shows that a body com- 

 posed of layers of different substances would possess the pro- 

 perty in question. One of us, in a note in the ( American 

 Journal of Mathematics/ No. 1, 1878, put the matter in a 

 somewhat different form, and investigated the conditions for 

 there being no electric absorption. 



All these theories agree in showing that there should be 

 no electric absorption in a perfectly homogeneous medium. 

 A mass of glass can hardly be regarded as homogeneous, 

 seeing that when we keep it melted for a long time a portion 

 separates out in crystals. Glass can thus be roughly re- 

 garded as a mass of crystals with their axes in different direc- 

 tions in a medium of a different nature. It should thus have 

 electric absorption. Among all solid bodies, we can select 

 none which we can regard as perfectly homogeneous along 

 any given line through them, except crystals. The theory 

 would then indicate that crystals should have no electric 

 absorption; and it is the object of this paper to test this point. 

 The theory of both Clausius and Maxwell refers only to the 

 case of a condenser made of two parallel planes. In the 



* Communicated by the Physical Society, having- been read May 14th, 

 1881. 



t I have obtained my knowledge of this memoir from the French 

 translation, entitled Theorie Mecanique de la Chaleur, par K, Clausius, 

 translated into French by F. Folie : Paris, 1869. The " Addition " does 

 not appear in the memoir published in Pogg. Ann. vol. lxxxvi. p. 337, 

 but was added in 1866 to the collection of memoirs, 



