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to the remainder, and I found, that tlie power of the apparatus 

 was reduced almost to nothing by this change. It is therefore clear, 

 that the electricity passed through the acid, only when the metallic 

 surfaces were opposed perpendicularly ; for, when they were in 

 that position, the instrument regained half its original power. It 

 may also be worth attention, that the law, according to which 

 fluids are decomposed by different Voltaic powers, is very different 

 from that, which obtains in the fusion of wires. Two batteries 

 were used, each containing twenty pair of plates ; but the surfaces 

 of the one were double those of the others : and I found, that the 

 lengths of iron wire, which they ignited, were 6 and 1 inches ; 

 but, when they were applied to decompose a weak solution of po- 

 tassa, they gave in six minutes 3.9 and 2 cubic inclics of gases. 

 Now there is reason to believe, that the quantities of electricity 

 were, in these instances, as 2 : 1, and the gases evolved were nearly 

 in the same proportion ; while it is known, that the action of this fluid 

 on metallic conductors is in the duplicate ratio of its quantity. It 

 also passes through wires of any length with undiminished velo- 

 city ; for we find, that a battery fuses nearly equal lengths, when 

 the conductors are a few feet long, or when they extend several 

 fathoms. The laws, according to which the decomposing- and wire- 

 melting powers vary, with the interval between the electrical poles, 

 are also different. If a battery heat eight inches of wire red hot, it will 

 fuse six nearly ; and wc may thence infer, that tliis power is inversely 

 as some high power of the interval ; for the temperatures produced 

 must be at least as one to six, as I have shewn in a former communica- 

 tion.* The power of decomposing is inversely as the interval, as ap- 



* It is a curious fact, and wliich I liave never seen explained, tliat the ignition is 

 not uniform throughout the v.'ire. It begins at the points of contact, and spreads over 

 the idiorvening space, till both meet in the centre, which is not so luminous as the ex- 

 tremes. 



