Mr. J. Phillips on a Modification of the Electrophorus. 363 



the liquid undulates readily to all their rays, while the sether 

 in the gas, in which we should expect it to exist in a much 

 freer state, has not the power of transmitting the undulations 

 of two thousand portions of white light! 



Among the various phaenomena of sound no such analogous 

 fact exists, and we can scarcely conceive an elastic medium so 

 singularly constituted as to exhibit such extraordinary effects. 

 We might readily understand how a medium could transmit 

 sounds of a high pitch, and refuse to transmit sounds of a 

 low pitch ; but it is incomprehensible how any medium could 

 transmit two sounds of nearly adjacent pitches, and yet ob- 

 struct a sound of an intermediate pitch. 



Such are the grounds upon which I stated to Mr. Potter 

 that the absorption of light militated strongly against the un- 

 dulatory theory. 



Allerly, April 13, 1833. 



LXI. On a Modification of the Electrophorus of Volta. By 

 John Phillips, F.G.S., Assistant Secretary to the British 

 Association*. 



TTAVING for three years found considerable advantage in 

 -*- ■* electrical experiments from the use of an electrophorus, 

 which in one respect is of peculiar, and I believe, new con- 

 struction, I am induced to offer a short description of it. — The 

 ordinary electrophorus exhibits its action in consequence of a 

 communication being established between the insulated cover, 

 while it is applied to the excited surface, and bodies conduct- 

 ing to the earth. Usually this communication is made by the 

 finger of the operator ; and when there is occasion to accumu- 

 late the electricity developed by the instrument, or to procure 

 its sparks in rapid succession, the trouble and tediousness of 

 the operation is so considerable as to induce many persons to 

 have recourse to a machine, for purposes to which the electro- 

 phorus is perfectly adequate. 



Considering that the touch of the finger was of no other 

 service than to establish the necessary communication between 

 the cover and the earth, and that the same effect would result 

 from permitting, under the same circumstances, a momentary 

 connexion between the cover and the metallic basis of the re- 

 sinous plate, I have adopted three methods of doing this. The 

 first consists in raising from the metallic basis, above the edge 



* From two papers on the subject of the Electrophorus, read to the 

 Yorkshire Philosophical Society in 1830 and 1833.— Communicated by the 

 Author. 



3 A 2 



