27 

 ELECTEIC ABSORPTION OF CRYSTALS 



BY H. A. ROWLAND AND E. L. NICHOLS ' 



[Philosophical Magazine [5], XI, 414-419, 1881; Proceedings of the Physical Society, IV, 



215-221, 1881] 



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 sub- 

 ject 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. 2 In an addition to this 

 memoir in 1866 he shows that a dielectric medium having in. its mass 

 particles imperfectly conducting would have the property of electric 

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

 in a somewhat different form, and shows that a body composed of layers 

 of different substances would possess the property 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 regarded as a mass of crystals with their axes in 

 different directions in a medium of a different nature. It should 

 thus have electric absorption. Among all solid bodies, we can select 



1 Communicated by the Physical Society, having been read May 14th, 1881. 



2 1 have obtained my knowledge of this memoir from the French translation, en- 

 titled Tkeorie Mecanique de la Chaleur, par R. Clausius, translated into French by F. 

 Folie: Paris, 1869. The 'Addition' does not appear in the memoir published in 

 Pogg. Ann., vol. Ixxxvi, p. 337, but was added in 1866 to the collection of memoirs. 



