AND OBSERVATIONS ON THE TORPEDO. 
263 
mon salt; the terminal wires were of silver. The contacts were made on the 
upper and under surface of the fish in the usual manner; minute bubbles of 
air collected round the point communicating with the under wire, but none at 
the other point. After an interval of some hours, fine gold wires were sub¬ 
stituted for the silver wires; now gas was evolved from each extremity, but 
in largest proportion, and in smallest bubbles, from the point connected with 
the under wire. 
The next experiment was made on a strong solution of nitrate of silver; the 
terminal wires were of gold. The effect was distinct; the extremity of the 
under gold wire became black, and only two or three bubbles of air arose 
from it; the extremity of the upper gold wire remained bright, and it was 
surrounded with many bubbles of air. A similar experiment was made on a 
strong solution of superacetate of lead, and with results which were similar; 
but the effects appeared to be produced with greater difficulty; they were not 
distinct till the fish had been much irritated, and seemed to put forth all its 
energy. 
Mr. Walsh inferred from his experiments, that the two sides of the torpedo 
are in opposite electrical states*. The results just described appear to prove 
that its under surface corresponds to the zinc extremity of a voltaic battery, 
and its upper surface to the copper extremity. 
To ascertain if they preserve the same relation to each other when the fish 
is made to act on the multiplier, and on the needle in the spiral, the following 
experiments were made. Successively at different times with the same fish, 
and also with different torpedos, comparative experiments were tried on the 
course of the needle in the multiplier when affected by the electricity of the 
fish, and by that of a couple of very small plates of copper and zinc immersed 
in a weak acid. In every instance, the wire communicating with the under 
surface of the torpedo was found to correspond in its effect with the zinc 
plate, and that with the upper surface with the copper plate; and whether one 
wire was in communication with the under surface of the fish, and the other 
with the upper, or the former with the zinc plate, and the latter with the cop¬ 
per plate, the deviation of the needle was in the same direction; its south pole 
turned to the east, and, of course, its north to the west: and if the lower 
* Philosophical Transactions abridged, vol. xiii. p. 475. 
2 m 2 
