DISH and Lord MAHON are the only distinguished writers on electricity, in the English language, who have attempted, like ÆPINUS, to introduce the mathematical form of investigation into this science. The publications of Dr. PRIESTLEY, Mr. CAVALLO, and Mr. ADAMS, on the subject, are also worthy of honourable notice. The first, besides his excellent History of Electricity, instituted a number of original experiments; suggested many important inquiries; improved the electrical apparatus; and, on the whole, did much to advance our knowledge of this branch of philosophy. The latter gentlemen, in addition to many new experiments, have presented to the world condensed and very satisfactory views of the subject, both in a philosophical and medical view, and have contributed much to render it popular and useful.

GALVANISM.

To this chapter belongs some notice of that principle or influence, discovered a few years ago, by Dr. GALVANI, a philosopher of Bologna, and since, in honour of him, denominated GALVANISM. It was first called Animal Electricity, a name which had been, for a number of years before, given to a remarkable property observed in several fishes, of conveying a shock, or a benumbing sensation to those who touched them. But this property was always found to be extinct or dormant in such animals, immediately after their death. In 1762, SULZER, a German, in his Theory of agreeable and disagreeable sensations, gave some hints of a curi

These are the Torpedo, the Gymnotus Electricus, the Silurus Electricus, and a fourth, found near one of the Comoro islands, by Lieut. WILLIAM PATTERSON, of which an account is given in the 76th vol. of the Philose phical Transactions.

ous effect resulting from the junction of two pieces of different kinds of metal, and applying them, thus joined, to the tongue; but these hints seem to have been disregarded, and were soon buried in oblivion. In 1791 Professor GALVANI announced a discovery made by him, that the muscles of dead animals might be stimulated and brought into action, by means both of artificial and atmospherical electricity. He also discovered, that independent of any collection of the electric fluid for the purpose, the same action might be produced in the dead animal, or even in a detached limb, by merely making a communication between the nerves and the muscles with substances that are conductors of the electric matter.' GALVANI's first experiments were made on dead frogs; but the discovery, soon after being announced, was pursued; experiments were made on different animals; and a number of new facts, tending to show the connection between Galvanism and electricity, and the circumstances in which they differ, were brought to light by Professor VOLTA, and Dr. EUSEBIUS VALLI, of Italy; by M. VON HUMBOLdt, and Dr. PFAFF, of Germany; by Dr. MONRO, Dr. FOWLER, Mr. CAVALLO, and Dr. LIND, of GreatBritain; and by COULOMB, FOURCROY, SABBATIer, PELLETAN, and others, of France.

Hitherto this influence or agent had been chiefly investigated with reference to its operation. on animal substances. Hence its popular name was, for a considerable time, animal electricity. But it being soon found, that its agency was more extensive; that it possessed powers not indicated by this denomination; and that of course the retention of this name would lead to error, the word Galvanism was adopted in its stead. This exten

1 Aloysii Galvani de viribus Electricitatis, &c. 4to. Bononiæ, 1791.

sion of the Galvanic principle was connected with new discoveries and improvements, from various quarters; these, however, for a considerable time, were generally small and unimportant in their

nature.

But among all the recent discoveries in Galvanism, that made by Professor VOLTA, in 1800, is most remarkable in its nature, and most interesting in its relations. His mode of constructing a pile, for condensing, retaining, and communicating a perpetual current of the Galvanic influence, is generally known." The curious phenomena which this pile exhibits; the connection which these phenomena indicate with the principles both of electricity and of chemistry; and the numerous experiments and successive improvements in the management of this Galvanic battery suggested by Professor VOLTA; by Messrs. CARLISLE, NICHOLSON, CRUICKSHANK, DAVY, and others, of GreatBritain; by VAN MARUM, of Holland; and by

m The pile of VOLTA is thus formed. Take a number of plates of silver, an equal number of zinc, and the same number,of pieces of card or woollen cloth. Let these last be well soaked in water, or water saturated with common salt, or what is perhaps still better, with nitre. A pile is then to be formed of these substances, in the following manner. A piece of zinc, a piece of silver, and a piece of wet cloth or card, are to be successively placed on each other; then another piece of zinc, and so on in the order of the first layer. In this manner, the pieces are to be arranged, or in any other manner, provided a regular alternation be observed, until the requisite number shall be laid. The instrument is then fit for use. The pieces of card should be somewhat less than the pieces of metal, and after being well moistened, should be gently squeezed before they are applied, that the superfluous moisture may not run down the pile, or insinuate itself between the pieces of metal.

The instrument constructed in this manner affords a perpetual current of the Galvanic influence; and if one hand be applied to the lowest plate, and another to the upper, a shock is felt, as often as the contact is repeated. The shock received from this pile is somewhat like that given by a Leyden phial; but more nearly resembles that given by a Torpedo, which animal this apparatus also resembles in giving incessant shocks. The intensity of the charge is, however, too small to make its way through the dry skin; it is therefore necessary that each hand should be well wetted, and a piece of metal be grasped in each to make the touch;-and the larger the piece of metal which is thus held in the hand, the stronger the shock. Garnett's Annals of Philos. vol. i. p. 10, &c.

FOURCROY, VAUQUELIN, and THENARD, of France, have not only excited much attention in the scientific world, but may also be ranked among the rich additions to philosophy, which modern times have produced.

It must be admitted, however, that little more has been done, in this new branch of philosophy, than to ascertain a number of facts, sometimes contradictory in their aspect, and generally inexplicable, without either forming a theory sufficiently fixed or luminous to satisfy the inquirer, or instructing us in what manner this principle may be applied for the benefit of mankind." Professor GALVANI, and several other distinguished experimenters, have supposed the Galvanic phenomena to depend on the electric fluid. They observed that this substance seemed to move with rapidity; that it produced a sensation similar to the electric shock; that it passed with facility through metals, and other conductors of electricity; while it was stopped in its course by glass, sealing-wax, and other substances which we know to be non-conductors of the electric matter. Others, on the contrary, observing several phenomena, which were thought to be incompatible with the known laws of electricity, or inexplicable by them, have rejected this opinion, and resorted to different means of solving the difficulty.

M. FABRONI, who made a number of ingenious experiments on Galvanism, was the first who systematically attempted to prove that the effects which he observed arose from chemical causes." This opinion has led to much curious investigation;

n Since the above was written, very curious information has been received from Germany, respecting the application of Galvanism to medical purposes. It appears to possess great efficacy in removing many diseases arising from nervous derangement and muscular debility.

• Sec Nicholson's Philosophical Journal, vol. iii. p. 308.

and various experiments evince that the agent in question produces, most powerfully, some effects, particularly decompositions, which have been hitherto considered as belonging to the province of chemistry alone; but the main point in dispute is yet far from being satisfactorily solved. Indeed, the wonderful apparent combination of electrical and chemical agency, in the more remarkable Galvanic experiments, seems to forbid the expectation of finding an adequate solution of the phenomena in any principles yet known. But as this subject has excited so much attention among philosophers, in every part of Europe, and as new facts will probably be brought to light every day, we may hope that the time is not very distant, when a sufficient number of facts will be arranged to form a consistent and satisfactory theory, and when this branch of knowledge will take its place among the most dignified and useful of the sciences."

MAGNETISM.

This branch of philosophy, during the same pe riod, has been an object of less attention than electricity, and of fewer speculations; probably on account of the smaller range of its phenomena, and its being less capable of popular exhibition. Still, however, it has been considerably cultivated, and has received some important improvements, since the time of Dr. GILBERT, the great father of magnetical philosophy. The number of facts con

p The above distinction between electrical and chemical phenomena is used in accommodation to the customary division of the sciences; for it may reasonably be doubted whether electricity, and even magnetism, ought not to be considered as subjects of chemistry.

q For further information on this subject, see the Supplement to the Encyclopædia, art. GALVANISM. See also GARNETT's Annals of Philosophy,

for 1800.