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XLI V. Theory of the Voltaic Pile. 

 By W. Kjsncely Bridgman, L.D.S.* 



r INHERE are extant at the present time two theories of the 

 *- voltaic pile, neither of which, however, can be said to be 

 sufficiently satisfactory to set the matter altogether at rest. 



The conclusions arrived at by the late Professor Faraday were 

 to the effect that the source of power in the battery was derived 

 from "the chemical force alone" (Experimental Researches, 

 2053) ; but as chemical force is not supposed to be able to ori- 

 ginate itself, or to become developed otherwise than by generation 

 from some antecedent force or forces, the disturbing cause, or 

 initiating step whereby it becomes excited to action, still remains 

 for elucidation. 



On the other hand, Professor Tyndall expresses his belief in 

 " the contact electricity of Volta being a reality," though it could 

 produce no current, and goes on to observe that Sir William Thom- 

 son " and others now hold what may be called a contact theory, 

 which, while it takes into account the action of the metals, also 

 embraces the chemical phenomena of the circuit " (Faraday as a 

 discoverer, by John Tyndall, note, p. 66) ; but as Faraday has 

 demonstrated in the clearest possible manner (Exp. Res. 879- 

 883) that metallic contact is not requisite for the completion 

 of the circuit and obtaining the current, it can scarcely be admis- 

 sible to recognize contact of the metals as one of the conditions 

 necessary to the action of the battery. 



In conducting the Experimental Researches relating to the 

 action of the battery, Faraday starts with the assumption that 

 " when an amalgamated zinc plate is dipped into dilute sulphuric 

 acid, the force of chemical affinity exerted between the metal and 



action of the auditory apparatus when the tympanal membrane is absent, I 

 may mention that I am assured by an eminent aurist that when the mem- 

 brane is absent the interposition of the promontory would prevent the ex- 

 posure of the cochlear membrane to the direct action of a wave of sound 

 which had traversed the meatus externus, and that the latter me^ brane 

 could only be reached by a reflected wave. 



I may observe that the statement (p. 126, note) as to the action of the sta- 

 pedal muscle, so far as the tympanal membrane is concerned, is perhaps 

 made too positively. Whatever that action may be, I apprehend that it must 

 always be subordinate to the action of the tensor tympani ; so that while 

 the joint effect of the two muscles combined must necessarily be to draw 

 in the membrana tympani, that of the smaller and weaker muscle may be 

 to effect some minute adjustment of the form of the membrane. A similar 

 remark would apply to the functions of the laxatores tympani muscles, if 

 upon further examination it should appear that such muscles exist. 

 * Communicated bv the Author. 



Phil. Mag. S. 4. Vol. 38. No. 256. Nov. 1869. 2 C 



