concerned in the Phenomena of ordinary Electricity, fyc. 449 



tion of the cylinder projected a spark of an inch in length. 

 Thus the capability of the Leyden battery to manifest the pre- 

 sence of three one-inch sparks was proved; it was also proved 

 that 200 pairs of plates did not communicate so much ; and as 

 six revolutions of the cylinder imparted to the Leyden battery 

 such a quantity of electricity as gave a sensible shock, that shock 

 was proved to be virtually occasioned by six one-inch sparks. 



Our failure to obtain the results of Van Marum, or even of 

 Sir H. Davy, is perhaps to be explained by the small size of the 

 Leyden battery employed by us ; it contained but 12£ square 

 feet, Van Marum's contained 137i. 



So far as these experiments with the Leyden battery warrant, 

 I can see no evidence of great quantity of electricity ; but even 

 if there were, it can be shown that it would by no means support 

 the notion of the enormous quantity of electricity which is said 

 to constitute the current of the voltaic series, and that it would 

 be quite foreign to the real question. Every one knows that 

 there are two conditions of a voltaic series which are capable of 

 producing veiy different results ; viz. when the circuit is open, 

 and when it is closed. In tbe open circuit, electricity is mani- 

 fested which displays no ehemical powers ; Mr. Gassiot, with a 

 well -insulated water battery of 320 pairs of plates, proved this ; 

 he connected one polar wire with the ground, and the other with 

 paper moistened with solution of iodide of potassium ; but there 

 was not the least trace of decomposition, although we know that 

 under such circumstances the electricity of the pole thus inactive 

 is doubled in intensity, and will produce double the divergence 

 in a gold-leaf electrometer ; but when the polar wires were con- 

 nected, the decomposition of the iodide was energetic*. On the 

 other hand, when the circuit is closed, the chemical powers of 

 the series are rendered evident, but the electrical appearances 

 cease. 



In all ordinary voltaic series, the smallest separation of the 

 polar wires is an interruption of the circuit sufficient to cause 

 cessation of the true voltaic action, and to restore the same elec- 

 trical condition of the poles that existed before the connexion 

 was made. Faraday found that the thinnest possible film of ice 

 so perfectly interrupted the circuit that an interposed galvano- 

 meter was not affected. 



When the polar wires of a voltaic series are connected, one 

 with the inside of a Leyden battery and the other with the out- 

 side coating, the polar wires are not in contact, no circuit is 

 formed, no chcmico-voltaic action of the exciting liquid on the 

 zinc takes place ; hence there can be no more real voltaic action 

 in operation than there is in any other case of an interrupted 

 * Philosophical Magazine, Oct. 1844, p. 290. 



Phil. May. 8. 4. Vol. 3. No. 20. June 1852. 2 G 



