concerned in the Phenomena of ordinary Electricity, fyc. 295 



the compound metallic plate. The copper gave off hydrogen 

 abundantly, and the zinc dissolved in two or three minutes en- 

 tirely : there was not sufficient pressure of condensed hydrogen 

 to burst the vessel. Not the slightest divergence of the gold 

 leaves resulted ; yet such was the dry state of the atmosphere 

 (Feb. 13), that a bit of letter-paper merely touched with the 

 hand, scarcely rubbed, caused the leaves to strike the sides of 

 the electrometer. 



In this experiment, the lower matrass being coated outside 

 with tin-foil, and the iuside covered with a liquid conductor, the 

 whole is to be considered a Leyden phial hermetically sealed, in 

 which 240 millions of one-inch sparks were called into action. 

 As a Leyden phial can receive no charge in the inside without 

 manifesting on its outside a quantity of electricity equal, although 

 opposite to what it has received, it follows that there could have 

 been no evolution or dissipation of free electricity within the 

 matrass, as there was no effect on the gold leaves of the electro- 

 meter. What, then, became of the enormous quantity of elec- 

 tricity, which, according to Faraday's estimate, was here ren- 

 dered active ? 



To this question it may be answered, that the electricity being 

 positive and negative, the two states neutralized each other as 

 fast as generated, and hence there was none in the free state. 



There was a mode, however, of discovering whether such a 

 reunion took place, and a very obvious one. It is a fact, that 

 in the case of a single voltaic circle properly excited, like that 

 above described, if the pair of plates be made to communicate by 

 a fine platinum wire, the current of electricity, in the positive 

 and negative states, will pass from the plates through the wires 

 in contrary directions ; and the reunion taking place in the wire, 

 it will, if very short and thin, be ignited in consequence. Dr. 

 Wollaston's thimble battery is an instance on a minute scale : 

 his zinc plate was only three-quarters of a square inch ; the other 

 plate acted also as the containing vessel for the acid, and con- 

 sisted of a silver thimble so far flattened that it held the zinc 

 and the exciting liquid. Small as this voltaic arrangement was, 

 it ignited one-thirtieth of an inch of an exceedingly fine platinum 

 wire. 



I therefore endeavoured to test the truth of the supposition 

 that the above-mentioned enormous quantity of electricity might 

 hive been developed in the positive and negative states, and by 

 reunion In the connecting wire had been neutralized and' lost. .1 

 zinc plate, twice the length of the former one, and therefore 

 weighing eight grains, was connected to a plate of platinum, of 

 about the tame surface, by means of a platinum wire half an 

 inch long and ! ,' „dt.h of an inch in diameter. This combination 



