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which, beside the effects here in view, produces greater and more general effects on our globe? This question is the main object of this and the following papers, and I hope it will be decided by facts. Having found no conducting substance more convenient than paper, for transmitting from one to another of the binary groups of metals their individual effects, I came to consider whether it might not be of some advantage, on account of the very small quantity of electric fluid thus set in motion, to produce a closer contact of the paper with the metals between their groups. I inade various experiments, by pasting the paper, first on both metals, then on one only, in the intervals where I had placed it loose. My condenser rendered easy these trials, as I could make them on piles of only twenty groups, and the following was the general result. There is an increase in the transmission of the electric fluid when the paper is pasted on the outside of such group upon the metal which becomes negative; but the reverse takes place, when it is pasted on the metal which becomes positive.

In the following experiments each pile of twenty groups was placed upon the moving metallic pillar of my condenser, and raised into contact with the receiving plate of the latter, where I left it dur ng twenty seconds; then, letting it down, and removing the upper plate, I observed the divergence of the gold leaves, and noted it in decimals of an inch, as in the experiments of the 1st part. In these operations, the end of the small piles, which rested on the pillar communicating with the ground, was thereby neutral; and the whole electric difference between the extremities was expressed, with its proper sign, by the electroscope of the condenser. The first experiment on each association of metals was made with the papers loose between the groups, in order to observe afterward the differences resulting from the pasting them on one or the other of the metals. Exp. 22. With twenty groups zinc and silver, separated by loose pieces of paper.

Silver side on the pillar, zinc side applied to the cond.

.... silver side .........

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pos. 0.35. neg. 0:35.

Zinc side......... The difference between the extremities being commonly equal, with only opposite signs, when these extremities are in turn applied to the condenser, I shall suppress the sign when the quantity only of the difference will be the object of consideration.

Exp. 23.-This will give the first proof of the advantage of pasting the paper on the metal which becomes negative in contact with the other; this being the case of silver in the above pile.

20 groups 20 groups

zinc and silver separated by loose paper .........0.35 ..paper pasted on the silver......the gold leaf struck the side.

Zinc and silver (or copper) are, as yet, the metals which, being associated, differ the most in their electric states, and for this reason

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they are commonly used in the pile; but in order to ascertain whether the advantage manifested by the above experiment, of pasting the paper on the metal which becomes negative in each group was general, or only a circumstance attached to silver and zinc, I thought of employing some metal, which became negative with zinc, but positive with silver; I found pewter such an intermediate metal, from the following experiment.

Exp. 24.-With two piles, each of twenty groups, the first zinc and pewter, the second pewter and silver; the groups separated by loose pieces of paper; each pile being alternately placed in communication with the ground by one side, while the other communicated with the condenser.

zinc side applied to the condenser

1st pile {pewter side...

2nd pile

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...pos. 0.10 ................................neg. 0.10 pewter side applied to the condenser...pos. 0.20 silver side

.....

neg. 0.25 This experiment first affords a new proof, that negative and positive are no qualities attached to certain metals, since here pewter is negative in its connexion with zinc, and positive when connected with silver. It is only an accidental circumstance, that there is as yet no known substance with which zinc becomes negative, and none with which silver (or copper) becomes positive; and they have in themselves no tendency to either of these states, acquiring them, and that inversely, by particular circumstances, as will be seen hereafter.

With respect to my present purpose, this experiment having shown me in pewter a metal proper for the trials concerning the pasting of the papers, I made the following experiments.

Exp. 25.-With 3 piles, each of 20 groups zinc and pewter.

0.1

1. The paper pasted on zinc ................almost no effect.
loose between the groups..........................................
pasted on pewter

2.

............

3.

........ 0.5

Exp. 26.-With 3 piles, each of 20 groups pewter and silver.

1. The paper pasted on pewter

2. ....

3.

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loose between the groups
pasted on silver

0.05

0.2

0.4

Though there is not so much increase of effect in the last as in the two preceding experiments, it shows still the same general circumstance, that there is some advantage for increasing the transmission of the individual effects of each group of metal to the extremities of the pile, in fixing the non-metallic conducting substance on the outside of each group, upon the metal which becomes negative in its connexion with the other; a circumstance which led me soon to farther steps, for these experiments presented me first the prospect of a spontaneous, as well as lasting electric machine, the

power of which could be increased by a greater number of groups. It would have been too expensive to proceed in that attempt with silver plates, and I was going to undertake it with copper plates, pasting the paper over them, when fortunately I thought of a paper, called Dutch gilt paper, on which a kind of copper is ready laid. At first I did not find the paper of that sort which is plain, but having tried that which is flowered, and finding much effect, I made the following experiment.

Exp. 27.—I cut seventy-six pieces of this paper to the size of my zinc plates, 1.6 inch diameter, and having formed a pile of seventysix groups, with only the zinc plates separated by the pieces of this paper, the copper side of all of them turned the same way, I found more electric effects at its extremities, than with the former pile of the same number of groups of zinc, silver, and wet cloth.

This experiment increased my hope of obtaining a natural electric machine, not indeed of a great power, but new in experimental philosophy, and which might lead to some farther discovery; but unluckily for speed, being sedentary at Windsor, I was not yet informed that, by a mode rendering zinc ductile, thin plates could be obtained of it, which would auswer my purpose, since in this use, calcination was not to be apprehended. Wishing however to proceed some way in this attempt, and having found by trial with my condenser, that tinned iron plates had sensibly the same effect as pewter plates, I procured as many plates of the former, 1-6 inch diameter, as would fill up the two columns of my frame, separated as above by pieces of flowered Dutch gilt paper. There were four hundred in each column, thus composing a pile of eight hundred groups.

Exp. 28.-The first object I shall mention of this experiment strongly corroborates the former conclusions concerning the mode of action of the galvanic pile. Though this pile had at its extremities greater electric effects than I have ever seen at those of any pile producing the strongest chemical effects in the glass tubes with water; yet these tubes being applied, there was not the least appearance of such effects.

But at the same time a new scene was opened to my view. This natural electric machine soon gave me reason to hope that it might become a new and very essential meteorological instrument. Having no motive to dismount it, I left it a long time in the same state, observing the electroscopes, and the following are the general phenomena which they offered to me.

1. The quantity of electric fluid put in motion by this pile was too great for the gold leaves to remain with a simple divergence; one of them struck the tinfoil on its side, then fell, and struck again; which effect became the object of observation.

2. At times these strikings were at both extremities of the pile, alternately. When the gold leaf struck on one side, it placed this extremity for an instant in communication with the ground; the gold leaf fell, but this communication with the ground increased the

opposite electric state at the other extremity, where one of the gold leaves struck and fell; and this continued by turns.

3. At other times the strikings were only on one side, and continued perhaps one day or two; then that state changed, and the strikings were at the other side.

4. At which ever side the strikings were going on there was a great difference in their frequency: sometimes the gold leaf seemed to beat seconds, while at other times it struck but once in a minute, or a longer time.

5. When the frequency of the strikings was upon the whole nearly equal many consecutive days, it increased succesively from the morning till some time in the afternoon, and then went on diminishing till night.

6. Sometimes I connected one side of the pile with the ground, by a metallic rod, which made the gold leaves fall on this, and increased the frequency of the strikings on the opposite side; but this increase was neither always the same, nor equal in the same time, when the communication with the ground was changed from one side to the other.

7. The beginning of my observations of this kind was in the winter of 1808, and in this season the strikings were upon the whole very frequent; but as the spring advanced, and perhaps as vegetatation increased on the ground, there was a gradual diminution in the motion of the electroscopes, and a change in the effects on the pile from the communication of its extremities with the ground.

8. Lastly. These changes could not be attributed to those of either heat or moisture, at least in my room, and as influencing directly the pile; for the room remained nearly at an equal temperature, and there were but small changes in my hygrometer. I also frequently observed the barometer, and found no connexion between its variations and these great changes in the strikings of the gold leaves.

From the whole together of these observations, I could attribute the variations in the electric phenomena of the pile only to changes in the electric state of the ambient air; or those in the effects of the communication with the ground, to changeable differences between the electric state of the latter and that of the air; an object on which we owe to Sig. Volta a great and fundamental truth. This justly celebrated experimental philosopher has made it evident that air possesses the electric fluid as well as all the bodies which it surrounds; and on this principle he has founded the only real explanation of the electric motions of free bodies, such as the pairs of balls and the gold leaves of our electroscopes. The electric fluid tends to an equilibrium among all bodies, including the air, and there is a mutual attraction between it and all of them, weak with conductors, but strong with non-conductors, among which is air. The proportional quantity of electric fluid which is actually possessed by air, is the standard of plus and minus in the electroscopes; and the proportional quantity of this fluid, which is actually possessed by

the ground, is the standard of plus and minus concerning the dif ferences in the electric state of insulated bodies compared with its own: these standards are sometimes similar, but they are often different. I shall not enlarge here on this beautiful theory, which I have fully explained in my works, and demonstrated by direct experiments; but applying it to the pile, the immediate effects of the ambient air must be to give some electric fluid to its negative side, which has proportionally less than itself, and to take some from the positive side, which has more; and as this influence must change according to the changes in the electric state of the air, the modifications of the electroscopes at the extremities of the pile may lead to unfold the latter, but not without farther discoveries.

I was stopped in the progress of these researches by an incident which has occasioned me much labour, and still retards them. This new pile is certainly in itself a meteorological instrument of great importance, as may be already judged, and shall be farther explained in the following paper; but in the state above described it was not fit for regular observations, and till the present moment+ I have not yet surmounted all the difficulties. I foresaw them, and it was the reason why I wished that the beginning of this new career should be soon known to experimental philosophers through the Phil. Transactions, in order that it might be followed by others, and probably with more success than by myself; but I am reduced to give the history of my own progress.

From what has been above explained, the strikings of the gold leaves in the electroscopes were become the object of observation: for this purpose, therefore, they ought to have regularly continued; however, after one of the gold leaves, at either side, had alternately struck and fallen for some time, it at last stuck to the tinfoil. The side, therefore, to which this happened, was placed in permanent communication with the ground, which made the strikings to begin at the opposite side; but there also the gold leaf stuck. These adhesions continued, till, by a stroke on the top of the electroscope, the the gold leaf fell; the oscillations were then renewed, but again stopped in the same manner. I tried various methods for preventing this adhesion, especially by substituting for the tinfoil, which has a rough surface, polished laminæ of many sorts and forms, keeping them even at some distance from the glass, which might contribute to this effect; but all was to no purpose, still the gold leaf would stick. This was a great disappointment, and the only method I could devise was, to increase the power of a pile, till it could move small metallic balls, in hope that these would not stick.

Two ways presented themselves to my mind for this increase of power in a pile; one by using plates of a larger size, the other by

• Idées sur la Météorologie, published in London by Elmsley in 1786 and 1787.

Two years have elapsed since I communicated to the Royal Society the experiments and observations which are here my object.

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