it was the electric fluid itself, which acted in the galvanic pile; but that it underwent there a modification, which made it produce, with an excessive small quantity, some effects, which else it could not produce but with a very great quantity set in motion by the discharge of the Leyden vial, and even of batteries. This fundamental proposition was established in my work by a particular mode of analysis of the effects of the pile, which however other avocations obliged me to publish unfinished, but expressing the hope, that some other experimental philosopher would take it up and follow it; which has not been the case.

In 1807, I saw in Part I of the Philosophical Transactions, a Bakerian lecture of Mr. Humphrey Davy, on some chemical agencies of electricity, which revived my attention to this subject. The very ingenious and interesting experiments which distinguish that paper are well known, and my praises would add nothing to those, which it has deservedly received: but a theory was there introduced, which I considered as involving the electric phenomena in the thickest veil, and this was my motive for resuming the above experiments. Mr. Davy supposes a positive and a negative energy, as belonging to distinct substances, constituting a class of general causes; and in p. 39, after having specified some of the bodies to which he attributes these different agencies, he concludes thus: "In the present state of our knowledge it would be useless to attempt to speculate on the remote cause of the electrical energy, or the reason why different bodies, after being brought into contact, should be found differently electrified; its relation to chemical effects is however sufficiently evident may it not be identical with it, and an essential property of matter?"

Tutored in Bacon's school, I have found in the long course of my study of natural phenomena, the profound wisdom of the following passage, in his immortal work De Augmentis Scientiarum, lib. iii, cap. v. Speaking there "de occultis et specificis proprietatibus," which he considers as belonging to a sort of magia, the offspring of false metaphysics, he says: "Primum enim intellectum humanum in soporem conjicit, canendo proprietates specificas et virtutes ocoultas, et tanquam cœlitus demissas, et per traditionum susurros solummodo perdiscendas: unde homines ad veras causas eruendas non amplius excitantur et evigilant, sed in hujusmodi otiosis et credulis opinionibus acquiescunt; deinde vero innumera commenta, et qualia quis optaret maxime, instar somniorum, insinu

ant."*

There is not in the whole field of natural philosophy an object, to which the application of this warning of a true philosopher can

• "First it throws the human understanding into sleep, lulling it with sounds of specific qualities and occult virtues, as if they came down from Heaven, and could not be learned by the whispers of tradition: whence men are no more solicitous in the discovery of real causes; they acquiesce in these idle opinions, and hence numberless gratuitous comments, which, like those on dreams, every man may apply as he wishes."

be of greater importance, than that under consideration. Such formula as Mr. Davy employs in lieu of causes, may appear satisfactory within the narrow limits of the experiments which he describes; but all the spontaneous phenomena of our globe, in which the electric fluid is concerned, are thus thrown into the back ground, and never noticed. There is evidently, however, no greater agent in these phenomena, than the electric fluid, which Mr. Davy never considers as a substance; he speaks only of electricity, of electric energies, which are empty words in themselves, when supposed to imply the idea of causes; while all the meteorological phenomena proclaim a fluid, the chemical affinities of which already manifested, open the road to the most important enquiries.

This consideration was my principal motive in resuming the analysis abovementioned: I have said, that I had not persued it so far as I saw it possible, but far enough to oppose the erroneous conclusions into which Mr. Davy's obscure principles had led him, with respect to the mode of action of the galvanic pile; and continuing that analysis by an uninterrupted series of experiments, I arrived at the following propositions, as conclusions of the whole.

1. Positive and negative in electricity are mere relations to a certain standard, concerning the distributions of the electric fluid among bodies, with which relations, no chemical effects are connected.

2. The immediate effect of the combination of two proper metals in the pile, and of their repetition, is to accumulate a certain quantity of electric fluid on one half of the length of the pile, which the other half loses.

3. When the two extremities of the pile are connected together by conducting substances, the above property of the pile produces a circulation of the electric fluid, passing constantly from the side on which it tends to accumulate, to the other side, where it compensates the deficiency tending to recur.

4. This circulation of the fluid produced by a proper association of metals can exist in the same quantity, with the same number of pairs of metals, without either chemical effects in the circuit, or the shock.

5. For the production of these phenomena, it is necessary that a liquid, being introduced between the two metals, calcination be produced on them. In this case the electric fluid circulating through the metals is modified, but its modification is different according to the liquid with pure water, there are chemical effects in the circuit, but no shock is felt; the latter requires that the circulation be produced by an acid.

Such were the conclusions deduced from the experiments related in the paper, which I delivered to the Royal Society, the 30th of May, 1808; but as this and the following paper have not been admitted into the Philosophical Transactions, I shall resume here the same course of experiments and deductions, but by more direct steps, being enabled to do so by the progress of my researches from

that time. For this purpose I shall begin by explaining the reason of the plan which I have followed in this enquiry from the beginning

in 1800.

If we consider a mounted pile without taking notice of its extremities, we see a repeated association of three constituent parts, two metals, and wet cloth or paper; which I shall name silver, zinc, and wet cloth, as they were in my fundamental experiments. By considering this composition of the pile, the leading circumstances for me were, first, that its effects increase with the number of the repetitions of three constituent parts; secondly, that the whole together forms a conductive column. These circumstances concur to point out some cause which accumulates at the extremities of the pile the opposite effects produced in a certain ternary association of the component parts: but which is that association In reflecting on this question I was convinced, that, till it was decided, the mode of action of the pile would remain entirely unknown.

The pile may be considered as divided into ternary groups under three different aspects:-1, zinc and silver, and wet cloth placed between them; 2, zinc and silver in mutual contact with the wet cloth on the side of zinc; 3, zinc and silver, still in mutual contact, but the wet cloth on the side of silver. On this, two questions arose in my mind-first, to which of these ternary groups are owing the accumulation of the electric fluid on one side of the pile, and increase of its deficiency on the other, which become greater with the number of these groups? Second, what is the cause, that so small a quantity of electric fluid, set in motion by the pile, produces effects which require so great a quantity of the same fluid when put in motion by any other means hitherto known?

On the first question, supposing the conducting faculty of the pile to be the cause of the accumulation of the opposite effects produced on the electric fluid, I concluded, that small metallic conductors placed between the really efficient groups, would not disturb the effects; but that, if these conductors were so placed as to produce separate ternary associations different from that to which the effects are attached, the latter would cease. Consequently, that by effecting the three different divisions of the pile by small conductors, I could not fail to discover the efficient groups—a knowledge which might lead to resolve the second question.

When I proceeded in this plan, I soon found, that no deep analysis of the operations of the pile could have been obtained without these admirable instruments, the gold leaf electroscope of Mr. Bennet, and the condenser of Sig. Volta; so minute are the quantities of electric fluid necessary to be observed in the course of these experiments.

After describing an extensive series of experiments in the analysis of the wet pile, M. de Luc arrives at this conclusion:

The last of these facts leads to the following conclusion. When the electric fluid pervades a pile wherein the calcination of some metal is going on, the fluid itself undergoes some modification,

which is the cause of the concomitance of these phenomena, a retardation of its course through the water, and the production, with a very small quantity of effects which it cannot produce but with an incomparably greater quantity, when set in motion by any other known means. But before I come to this object, it is necessary to ascertain an essential point, which so far I have only mentioned: namely, that the motion of the electric fluid in the pile does not depend on a separation of the binary groups of metals by a liquid, or a wet body; but requires only that the separation be produced by the best non-metallic conducting substance; and with the leading experiments concerning this object I shall conclude this first part of the analysis.

Exp. 19.-I mounted the pile of 76 groups of zinc and silver; but instead of wet cloth to separate them, I used new cloth, which had stood some time in my room, my hygrometer being at about 40°. 1. Electric signs were produced at the extremities of the pile, but weaker than when the pieces of cloth were wet.

2. The glass tubes being applied, these signs ceased, but there was no appearance of chemical effects in the water of the tubes.

Judging that the diminution in the quantity of electric fluid in motion proceeded from a want of conducting faculty in the wool itself, and aware that no metallic substance could be substituted for obtaining a better conductor, I undertook a long series of experiments, by forming piles of twenty groups zinc and silver, separated by all the substances of the vegetable and animal kinds that I could devise, applying these groups to the condenser. Of these experiments, however, I shall only mention the practical result, which was, that among all these bodies, writing paper was one of the best for the intended purpose, at the same time that it is the most easy to manage; and I made the following experiment.

Exp. 20.-I mounted again the pile of seventy-six groups zinc and silver, and separated them with pieces of writing paper.

1. I found a great increase in the electric signs at the extremities of the pile, comparatively with the cloth.

2. These signs ceased when the glass tubes were applied, but still no chemical effect was produced in the water of the tubes.

This experiment opened before me a new and extensive field, in which I have ever since travelled, as will be seen in the second part of this analysis.

PART II.

I concluded the first part of this analysis by an experiment, in which a pile of seventy-six groups of zinc and silver, the number used in my preceding experiments, separated by pieces of writing paper substituted for the wet cloth, though giving very sensible electric signs at its extremities, produced no chemical effects in the water of the usual glass tubes applied to it, nor the shock.

This experiment was made during my investigation respecting the causes of the two distinct effects of the pile, namely, electric and

chemical, which by the foregoing experiments had been proved to be different; the former depending only on the binary groups of the metals, separated by the best conducting substance non-metallic, and thus not necessarily productive of chemical effects; these requiring absolutely, that the interposed non-metallic substance be wet, a circumstance from which the chemical effects depend on groups composed of the two metals with the wet body between them. Such is the fundamental proposition, with respect to the mode of action of the galvanic pile, which was to be submitted to farther experiments. The conducting faculty of all the substances of the vegetable and animal kinds, that may be employed to separate the binal groups of metals, for transmitting from one to another their individual electric effects, mostly depends on a certain quantity of moisture, with which they are usually penetrated. Of this I had soon an opportunity of being informed, by an experiment of my friend Dr. Lind, who had constantly followed the progress of these researches; he had constructed a pile similar to mine, except that copper plates were substituted for silver plates, which acted also immediately upon the gold leaf electroscope; but he found the following change in it.

Exp. 21. He dismounted this pile, and laid all its parts on his hearth, before a great fire, so that the pieces of paper were almost singed, and mounting it again in this state, it did not sensibly affect his electroscope: he brought it into my room, and it affected only the electroscope of my condenser. We then dismounted the pile, and laid all its parts on a table for one hour, my hygrometer being about 40°, and when again mounted, it acted on the electroscope as it did before the papers had been so thoroughly dried by a great

heat.

This experiment shows that Mr. Davy was mistaken when he thought" that with respect to electricities of such low intensities, water is an insulating body." On which principle he considered the mode of action of the pile under the idea of what he calls induction; meaning, I suppose, something similar to the effect of Volta's condenser, when it operates by the interposition of silk between the metallic plates. If this were the case, pieces of silk, through which what he calls induction is readily produced, being placed between the binary groups of metals, should produce a still greater effect than paper in its common state, as more insulating; whereas the foregoing experiment proves, that the effect almost ceases, when paper, by thorough dryness, is reduced to the state of an insulating body. I insist on this point only, because it involves one of the most important questions in terrestrial physics. Must we, in the present state of our knowledge, be satisfied with electrical energies, which might be considered as essential properties of matter ?* Or rather, in this very state of our knowledge, is it not already ascertained, that a particular substance exists, namely, the electric fluid,

* Mr. Davy's Bakerian Lecture, Philosophical Transactions, 1807, part I, p. 39; or Journal, vol. XIX, p. 50.