[ 65 ] 

 XII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 

 [Continued from vol. xxviii. p. 479.] 

 June 16, 1864. — Major-General Sabine, President, in the Chair. 



'T^HE following communication was read : — 

 1_ "Further Inquiries concerning the Laws and Operation of 

 Electrical Force." By Sir W. Snow Harris, F.R.S., &c. 



1 . The author first endeavours to definitely express what is meant 

 by quantity of electricity, electrical charge, and intensity. 



By quantity of electricity he understands the actual amount of 

 the unknown agency constituting electrical force, as represented by 

 some arbitrary quantitative c electrical ' measure. By electrical charge 

 he understands the quantity which can be sustained upon a given 

 surface under a given electrometer indication. Electrical intensity, 

 on the contrary, is 'the electrometer indication' answering to a given 

 quantity upon a given surface. 



2. The experiments of Le Monnier in 1746, of Cavendish in 1770, 

 and the papers of Volta in 1779, are quoted as showing that bodies 

 do not take up electricity in proportion to their surfaces. According 

 to Volta, any plane surface extended in length sustains a greater 

 charge — a result which this distinguished philosopher attributes to the 

 circumstance that the electrical particles are further apart upon the 

 elongated surface, and consequently further without each other's 

 influence.* 



3. The author here endeavours to show that, in extending a sur- 

 face in length, we expose it to a larger amount of inductive action 

 from surrounding matter, by which, on the principles of the conden- 

 ser, the intensity of the accumulation is diminished, and the charge 

 consequently increased ; so that not only are we to take into account 

 the influence of the particles on each other, but likewise their opera- 

 tion upon surrounding matter. 



4. No very satisfactory experiments seem to have been instituted 

 showing the relation of quantity to surface. The quantity upon a 

 given surface has been often vaguely estimated without any regard 

 to a constant electrometer indication or intensity. The author 

 thinks we can scarcely infer from the beautiful experiment of Cou- 

 lomb, in consequence of this omission, that the capacity of a circular 

 plate of twice the diameter of a given sphere is twice the capacity of 

 the sphere, and endeavours to show, in a future part of the paper 

 (Experiment 16), that the charge of the sphere and plate are to each 

 other not really as 1*2, but as 1:V2, that is, as the square roots 

 of the exposed surfaces ; so that we cannot accumulate twice the 

 quantity of electricity upon the plate under the same electrometer 

 indication. 



5 . On a further investigation of the laws of electrical charge, the 

 quantity which any plane rectangular surface can receive under a given 

 intensity is found to depend not only on the surface, but also on its 

 linear boundary extension. Thus the linear boundary of 100 square 

 inches of surface under a rectangle 37*5 inches long by 2*66 inches 



Phil. Mag. S. 4. Vol. 29. No. 193. Jan. 1865. F 



