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of the little pendula of the electroscope exceeds the extent that it can have without one of them striking the side, then falling by a momentary contact with the tin foil, which communicates with the ground, it will sooner rise and strike again, with the same number of groups, in proportion to the size of the plates ; which last circumstance increases also the current of electric fluid circulating in a pile, the extremities of which are connected together by a conductor.

5. The water of all springs has the same source, namely, the rain water percolating through the ground, and retained on some impervious stratum, either argillaceous or stony. If this water do not find in its way any substance with which it can combine, it comes out as it had fallen on the ground: but if in its course it combines with any substance, it

may come out with certain chemical properties, different according to the substances which have combined with it. The case is the same with respect to the electric fluid which pervades the pile: its source is no other than the electric fluid ditsused over all terrestrial bodies, therefore over the pile itself. However we should be ignorant of the constant existence of this fluid,

us and around us, were it not that, by artificial or natural operations, its density may either be increased or diminished on insulated bodies: this is the only circumstance which makes it appear, and that by the electroscope alone; for as long as this fluid remains in a state of equal diffusion over all bodies, it is manifested by po effect hitherto discovered. The friction between two bodies disturbs that equilibrium, in a manner which I shall show in a future paper on the Analysis of the Electric Machine. But in the pile, which is my present object, it is by a property of its composition, that the equilibrium of the electric fluid is disturbed, whence proceed either the motions of the electroscopes, or a circulation of the fluid through the pile, when the extremities of the latter are connected together by a conductor. Now, in the last of these cases, if the electric fluid, in its course meets with no substance that changes its state; as is the case in a pile composed of tinned iron, or zinc plates, separated by Dutch gilt paper ; we are indeed informed by the electroscopes of its accumulation on one extremity of the pile, and

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by which means experimental philosophers understand one another when they indicate certain degrees of heat. I hare also constructed an electrometer, which possesses the same conditions with respect to degrees of electrification, which is described in my work, Idées sur la Métérologie ; but not having been attended to by experimental philosophers, I have not been induced to follow the extension of this measure down to the minute degrees of intensity indi. cated by the gold leaf electroscope, as I could not expect that it should be more noticed: therefore admirable as is this instrument for its sensibility, it affords us no comparable measure. In this imperfect state, however, there is, in every electroscope, a property which belongs to no other physical measure, namely, a natural and absolute standard of plus and minus, which is constant, as to its general determination, and is the actual electric state of the ambient air, or the ground; though variable as to the absolute quantity, as are these electric states; which difference will be one of the objects of this paper.

its deficiency on the other ; however, neither chemical effects in the circuit, nor the shock, are produced; because the fluid remains unaltered : but when it pervades a pile, wherein, by a liquid being placed between the two metals, there is calcination of one or both of the latter, new effects appear: if the liquid be pure water, chemical effects are produced in the circuit, but there is no shock; if it be an acid, both effects are produced.

These experiments, especially on the different effects of the number of the groups, and of the size of the plates, with the above theory on the cause of their different effects, were contained in my paper delivered to the Royal Society the 30th of May, 1808, about one month before Mr. J. G. Children executed in presence of Mr. Davy and Mr. Allen the grand experiment of the same kind related in Part I of Ph. Trans. for 1809, by which the theory which I had already announced was confirmed.

But here two questions arise, which go deeper into the mode of action of the galvanic pile, and they are these : 1. Of what nature is the modification produced in the electric fluid, when it pervades a pile wherein the calcination of some metal is going on? 2. What is the cause of the motion of this fluid in the pile, whether producing, or not producing the shock and chemical effects in the circuit !

The solution of the former of these questions, which leads to that of the latter, depends on the nature of the electric fluid ; a subject much too long to be treated here; but it is fully detailed in both the works I have already referred to ;* I shall therefore here confine myself to the conclusions contained in these works, as deduced from uninterrupted series of experiments, of which I shall only detail the part necessary to my subject.

None of the phenomena observed in our common electrical experiments, namely, the charge and discharge of the Leyden vial, the electric motions, the effects of the clectrophorus and of the condenser, had been really explained, till the inventor of the last two instruments, Sig. Volta, had formed his theory on the electric influences, which threw the first true light on the modifications of the electric fluid; and which, in the course of various experiments I made to follow it through all the electric phenomena, gave rise to the system on the nature of the electric fluid, which I shall here briefly state.

This fluid, far from being a simple substance, is an astonishing compound : and first, in its state which may be called natural, that, I mean, in which it is diffused over all bodies, it is found composed of two main parts, from which all the above-mentioned phenomena arise. One of these two constituent ingredients of the electric fluid in this state is a substance, which, by itself, is not expansible (as in steam, also an expansible fluid, there is a substance which is not expansible by itself, namely water); this substance in the eletric

Idées sur la Météorologie, and Traité élémentaire sur le Fluide électro-gal. vanique.

fluid I have called electric matter ; and its function, which I shall soon point out, is very distinct. The other ingredient is an excessively subtle fluid, which (as fire in steam) uniting with the non-expansible substance, produces the expansibility of the aggregate. In my French works I have called the latter fluide déférent; but here I shall call it vector, a short word of the same import, signifying that it carries along the electric matter (as, in steam, fire is the vector of water).

The electric vector instantly pervades all bodies, and carries the electric matter through conductors, but not through non-conductors, such as glass and resinous substances : when a current of electric fluid arrives on one side of a lamina of these substances, and its veclor, in order to establish its own equilibrium beyond it, pervades the lamina, it deposits the electric matter on the surface of the latter, where it remains adherent, till a current of vector pervades the lamina in the opposite direction, or it is taken up slowly by the vector in the air (as fire in steam, when it pervades a glass lamina to establish its own equilibrium beyond it, deposits the water on the side which receives the steam, where it remains, till it is carried away, either by fire coming from without, or by that spread in the air).

I come to the peculiar function of the electric matter in the above indicated phenomena : it is the sole cause of electric motions, resulting from a greater or less proportional quantity of it, than is possessed by the ambient air; to which subject I shall return: the vector has no share in these motions, but as the vehicle of the electric matter acting in their phenomena. (As, with regard to steam, it is only water that produces the hygroscopic phenomena, without any interference of fire, except as the vehicle of water).

By this system of a first composition of the electric fluid, the phenomena, which I have introduced in the beginning, are clearly explained in all their modifications, as I have abundantly proved by direct experiments in my works. But as long as the electric fluid remains in what I have called its natural state, moving along conductors and fixed on non-conductors, it produces no chemical effect hitherto known : what then does happen, when it produces these phenomena?

If we attend to this change, we shall observe a circumstance sine qua non, which is to contain some cause; it is, that the conductor, along which the electric fluid moves, must be interrupted. Now, when in this case the electric fluid darts through the air, three new phenomena are observed, lucidity, heat, and a particular odour. This cannot but indicate the decomposition of some particles of the fluid, occasioned by an excess of density, from which light, fire, and an odorute substance are disengaged: as when steam (to which from the beginning I have compared by analogy this system on the nature of the electric fluid) becomes too dense for the actual temperature, some of its particles, being decomposed, emit water and fire.

These new substances, light, fire, and an odorate substance, thus manifested in the composition of the electric fluid, are neither the

electric matter, nor the vector, themselves, but must be contained in them, combined with some other substances, which prevent them from exercising their characteristic effects; a case most common in chemical compounds. The characteristic effect of fire, is heat ; when free it acts upon the thermometer ; but it does not, when combined with other substances. Lucidity is the characteristic effect of light; but this is not lucil in phosphori, till they are decomposing : and also various bodies, while decomposing emit odorate substances, which in their compound state had no odour. Now, the light emitted by the electric fluid probably belongs to the vector, which has many properties of the former; but it is not lucid, therefore light must be combined in it with some other ingredient. The odorate substance appears to belong to the electric matter, but this has no odour, therefore the former must also be combined in it with some other substance. Lastly, the fire emitted cannot be referred directly to either the vector or the electric matter ; but probably, during their common decomposition, it is itself composed of the light and igneous matter disengaged. That fire is a compound, is a system which I have also treated with many experimental details in the above mentioned works.

No natural philosopher, who has applied to the study of any main branch of terrestrial phenomena according to the rules of analysis instituted by the immortal Bacon, will be repulsed by the idea of so many elements entering into the composition of the electric fluid, though hitherto almost excluded from the catalogue of chemical substances by a class of chemists who confine their observations within their laboratories. When, with the view of ascending from some of the most common phenomena to general causes, we have followed this scrupulous analysis by a certain number of regular steps, we are yet, in almost every branch, stopped for want of intelligible links, though in series of phenomena manifestly connected together by some common cause; as for instance many phenomena manifested in our chemical operations, with some which we daily observe in the atmosphere, that great laboratory of nature on our globe. The filling up of these chasms by gratuitous hypotheses is only protracting the attainment of real knowledge.

Let not therefore natural philosophers lose sight of an expansible fluid, constantly associated with all terrestrial bodies, and with the air that surrounds them; this present in all our chemical processes, during which some of its ingredients, either engaged or disengaged, might account really for certain phenomena hitherto explained by mere words. For, according to meteorological observations which I shall relate in the following paper, it is by its decompositions, alternating with compositions, that the electric fluid operates in terrestrial phenomena. What were chemical theories before the chemical combinations of fire with other substances were discovered and attended to ? However, as long as this fluid shall be considered under the vague idea expressed by the modern word caloric, it will not much forward the science of chemistry.

After these general remarks, I return to my subject, which will serve as an example of their application. When the transmission of the electric fluid through interrupted conductors takes place in a liquid, the new phenomena of lucidity, heat, and odour, are not perceived; but there cannot be any doubt, that the chemical effects produced in the circuit, and the shock, proceed from the same decomposition of particles, that takes place at interrupted conductors, which is visible only through the air; for po chemical effect is produced in the water of the glass tubes, when the metallic wire passes through it uninterrupted. With respect to the shock, this condition is not immediately perceived in the discharge of the Leyden vial, because it is sudden, attended with a strong commotion, and not repeated till the vial is again charged; but with the pile, which soon renews spontaneously the cause of the shock, it has been seen in Exp. 8, that this phenomenon is produced only at the approaching contact, and thus by an interruption ; since all sensation ceased when I fixed the silver spoons on both extremities.

These preliminary deductions of facts were necessary for the solution of the first of the questions above stated, namely: “Of what nature is the modification produced in the electric fluid, when it pervades a pile wherein the calcination of some metal is going on ?” A question intimately connected with this : “How does it happen, that, with such a minute quantity of electric fluid set in motion by the pile, the shock and chemical effects are produced, while they require a very great quantity of the same fluid when set in motion by any of the other known apparatuses?” Being arrived at the general fact above stated, that these effects are never produced but by the decomposition of some particles of the electric fluid, occasioned by an excess of density, in darting from one point of a conductor to another, the answer to the connected questions is obvious: the modification undergone by the electric fluid in pervading this pile is such, that some of its particles are decomposed by a very small increase of density, when a conductor is interrupted. We have an analogy of the general case of more easy decomposition of compounds by previous modifications of the latter, in the processes of smelting ores, for obtaining metals or reguli from them; for an easy separation of the ingredient of the latter must be prepared by subtraction or addition of other ingredients, and often by both. And as we see that the calcination by an acid is necessary to produce the shock, it is probable, that the modification of the electric fluid in this case is the addition of some element.

I come now to the second of the above questions : "What is the cause of a motion of the electric fluid in the pile, either producing, or pot producing, the shock and chemical effects in the circuit ??" The first point to be considered with respect to this question concerns the nature of the modifications reciprocally produced by zinc and copper upon each other, when brought into contact. rally said, that, in this case, ZINC becomes positive, and COPPER negative. But these expressions, according to what has been stated

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