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. 1o, &c.

FOURCROY, VAUQUELIN, and THENARD, of France, have not only excited much attention in the scien→ tific 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;

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 aring from nervous derangement and muscular debility.

• See 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 period, 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

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.

terning this mysterious kind of attraction has been greatly augmented. The points in which it resembles, and those in which it differs from electricity, have been more satisfactorily ascertained; and a nearer approach made than formerly to a systematic arrangement of the magnetic laws.

The unexpected and daring introduction of mathematical principles and demonstration into the dark regions of electricity, by Mr. EPINUS, was mentioned, in a former page, as one of the signal improvements of the last century. This ingenious philosopher has done the same in magnetism, and with equal success. And though this subjection of the magnetic principles to the most precise and definite of all species of investigation does not appear to have led, as yet, to any extraordinary discoveries, or radical reforms in theory; yet it has been by no means without its use, and may conduct to invaluable acquisitions:

The Mariner's Compass, within the period in question, has been considerably improved. This important instrument, after its invention in 1302, long remained in a rude and imperfect state.

But

Dr. KNIGHT's discovery of the mode of making artificial magnets, about the year 1744, together with the results of some other experiments, enabled him to render the compass much more convenient and useful. To his improvements may be added the further emendations of Mr. SMEATON, and Mr. M'CULLOCH, both of Great-Britain.

The variation of the magnetic needle has been a subject of much attention and of much ingenious speculation, during the past century. The obser vations made by Dr. HALLEY, and published in 1701, in the form of a variation chart, were of

See Tentamen Theorie Magn. et Electr. Petrop. 1759. See also the Supplement to the American Encyclopædia, by Donson, articles Electricity and Magnetism, F*

great use to navigators, and contributed not a little toward reducing the principles of this variation to something like an intelligible form. The next attempt of the same kind, worthy of notice, was that of EULER. This philosopher, equally remarkable for the extent of his learning, and the vigour and comprehensiveness of his mind, undertook, about the middle of the century, to account for the magnetic irregularities, and to ascertain. the position of the needle in every part of the earth. He executed his task with singular ingenuity and perseverance; and with a plausible appearance of success. But his theory, and the whole structure founded upon it, were soon found liable to such objections, that they were considered of little value, excepting so far as they might furnish a guide in the further prosecution of the inquiry. Since the time of EULER, many others have exerted their genius in the same investigation; but without producing more certainty or satisfaction. Among the latest explorers of this dark but important subject, Mr. CHURCHMAN, a respectable citizen of our own country, deserves to be honourably mentioned. He has, in his own opinion, made valuable improvements on the theories of HALLEY and of EULER; corrected various errors into which those great philosophers fell; and given an hypothesis which bids fair to be of more practical utility than theirs to the nautical adventurer. How soon this hypothesis may be brought to the test of a complete course of experiments; or how it may bear this test, when subjected to it, are questions yet to be solved. In the mean time, the ingenuity, zeal and perseverance, evinced in Mr. CHURCHMAN's late publications on this subject, deserve the attention, the thanks, and the encourage ment of the philosophic world.".

See Churchman's Magnetic Atlas, 4to. 3d edition, 1800,