292 P^of. Anderson, On the Apparent [Apr. 26, 



The elimination of z, x^ . . . x n , p-^ . . . p n from these n — 1 relations, 

 and 



%i =0, X'2 = 0, /= °> «i = «i • • • u n = a», 

 will give one or more equations connecting a lt a. 2 ... a n , and these 

 are what must be used to derive the particular solution sought. 



Monday, 26 April, 1897. 

 Mr F. Darwin, President, in the Chair. 



The following were elected Fellows of the Society : 



R. Lachlan, Sc.D., Trinity College. 

 W. M. Coates, M.A., Queens' College. 

 S. S. Hough, M.A., St John's College. 

 Rev. P. E. Bateman, M.A., Jesus College. 



The following Communications were made to the Society : 



(1) On the Apparent Electrification in an Electric Field at 

 the Bounding Surface of Two Dielectrics. By Prof. A. Anderson, 

 M.A., Queen's College, Galway. 



In Maxwell's Treatise on Electricity and Magnetism, Vol. I. 



3rd edition, p. 100, the apparent surface charge a ou the boundary 



of two media of specific inductive capacities K x and K 2 is defined 



dV dV 



bv the equation -= h -= \- 4<7ra = 0. 



J ^ dn x dn 2 



Maxwell then proceeds to state, giving a reference to Faraday, 

 that if, during the action of the inducing force, the apparent 

 electrification of the surface be discharged by passing a flame over 

 the surface, then, when the inducing force is taken away, there 

 will appear a true electrification opposite to & '. In an Appendix 

 to the chapter in which this occurs the apparent electrification is 

 described as acting on the conducting flame which is in connexion 

 with the earth, attracting electricity of opposite sign, and repelling 

 electricity of the same sign, the consequence being the production 

 of a real electrification which masks the effect of the apparent one. 



Prof. Gray, in his Absolute Measurements in Electricity and 

 Magnetism, Vol. I. p. 113, says that the action of the flame is to 

 reduce the surface to zero potential, and that the real electrification 

 is equal and opposite to the apparent electrification. 



In Mascart and Joubert, Vol. I. p. 101 (English edition), it is 

 stated that, though the layer of density <x is a fictive layer, if its 

 surface is brought to the neutral state by means of a flame, and if 

 the sources of induction are removed, a real layer of density a will 

 be found on the surface. 



