That influence, whatever it be, which is possessed by the torpedo, &c. seems to depend entirely upon the will of these animals, both for its production, and management, as appears not only from the retraction of their eyes within their sockets, whenever they mean to give a shock, but, likewise, from each shock being increased, diminished, or withheld, as they are irritated or aware of some obstacle to its transmission. But the will of an animal has no share in the production of the phenomena discovered by Galvani. In the scale of conductors of electricity, charcoal holds a higher place than the fluids of animal bodies, and ice than the metallic salts. But of the influence in question, I have found animal fluids, and metallic salts, excellent conductors, at the same time that I have never observed it pass through charcoal, or even dried wood. I have, likewise, reason to believe that it does not pass through ice. Ice, indeed, is but a very imperfect conductor of electricity, when free from air bubbles, and when the experiments with it are made in a very low degree of temperature. Yet we are told by Mr Achard, that it will conduct electricity, even when Reaumur’s Thermometer stands at 6 degrees below 0. But the temperature of the room, in which I made my experiments, was at least 55 degrees above 0, by Fahrenheit’s scale. I may likewise remind the reader of the experiment, in which the abdomen of a frog was filled with mercury, and a rod of silver passed through it to the sciatic nerves. A piece of zinc, touching both mercury and silver, excited no contractions; whereas most vigorous ones were excited when water was substituted for the mercury. A proof, as I take it, that water is a much better conductor of this influence than mercury: but of electricity, mercury is deemed a better conductor than water. We are told by Mr Cavendish, that Mr Walsh found the shock of the torpedo would not pass through a small brass chain: but the influence discovered by Galvani, passes, without sensible diminution of its effects, through a small brass chain of several inches in length, when it is drawn so tight as to bring its links into close contact with each other: and it passes through a gold chain when held between two persons, and suffered to hang with a considerable bend. Yet, if we may be allowed to judge of the comparative strength of the two influences, by the effects which they produce upon animals, that of the torpedo must certainly be allowed to be the strongest; and I see no other way of accounting for its finding an insuperable obstacle to its transmission, where the other finds scarcely any, except by supposing that they are in reality different in their nature. Dr Valli tells us, that he observed the hairs of a mouse, attached to the nerves of frogs by the tin-foil, with which he surrounded them, alternately attracted, and repelled by each other, whenever another metal was so applied as to excite contractions in the frogs.