198 Dr. L. T. More on the Supp>osed Elongation of 



which it seemed to prove may be found in a brilliant sug- 

 gestion made independently by FitzGerald*, and by Lorentzfof 

 Leyden, to the effect that the motion of ether through matter 

 may slightly alter its linear dimensions ; according to which 

 if the stone slab constituting the sole plate of Michelson and 

 Morley's apparatus has, in virtue of its motion through space 

 occupied by ether, its lineal dimensions shortened one one- 

 hundred-millionth J in the direction of motion, the result of 

 the experiment would not disprove the free motion of ether 

 through space occupied by the earth. 



XIV. On the Supposed Elongation of a Dielectric in an 

 Electrostatic Field. By Louis T. More, Ph.D., Adjunct- 

 Professor of Physics in the University of Nebraska\. 



MUCH attention has been attracted to the so-called expan- 

 sion of a dielectric in an electrostatic field, as it has 

 been deemed an experimental proof of the theory of Faraday 

 and Maxwell, and many investigators have experimented on 

 it— notably, Fontana ||, Grovi% Duter**, Eighiff, Quincke} $, 

 and Hoentgen§ § . The results, as given by them, although many 

 contradictions are noted, are, that most liquids and glass 

 expand in volume when subjected to electrostatic stress, and 

 that glass also expands in a direction normal to the lines of 

 induction. These increments are considered too large to be 

 accounted for except by a new and peculiar property of 

 electricity. No experiments have yet been made on the 

 behaviour of glass coinciding with the lines of induction. 

 These results have been generally adopted ; for example — 

 See J. J. Thomson, ' Applications of Dynamics to Physics 

 and Chemistry/ page 52 et passim, and Poincare, L'electricite' 

 et I'optique, chapter xiii. And they have been adduced as an 

 Experimental confirmation of Faraday's theory. Roentgen, 

 on the other hand, from a discussion of the results obtained 



* Public Lectures in Trinity College, Dublin. 



f Versuoh einer Theorie der electrischen unci optische?i Erscheinungen in 

 bewetgen Kcirpern. Leiden, 1895. 



\ This being the square of the ratio of the earth's velocity round the 

 sun (30 kilometres per sec.) to the velocity of light (300,000 kilometres 

 per sec). 7, 



§ Communicated by the Author. 

 || Volta, Lettere inedite di Volta, Pesaro, p. 15, 1834. 

 4l Govi, Nuovo Cim. xxi.-xxii. pp. 18-26; C. R. lxxxvii. p. 857. 

 ** Duter, C. R. lxxxvii. pp. 828-1036 ; lxxxviii. p. 1260. 

 tt Righi, C. R. lxxxviii. p. 1262. 



XX Quincke, Wied. Ann. x. pp. 161, 374, 513 ; xix. pp. 545, 705 ; xxviii, 

 p. 529 ; xxxii. p. 530. 

 §§ Boentgen, Wied. Ann. xi. p, 786, 



