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NOTICE OF SOME EXPERIMENTS MADE BY THE GALVANIC SOCIETY AT PARIS.

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I. M. Marechaux, of Wesel, correspondent of the Galvanic Society, announced to them that he had determined that water, whether pure or mixed with an acid, or charged with any salt, is not indispensably required for producing the effects of galvanism. He added, that some time ago he had constructed columns of zinc and brass with the interposition of discs of card, not moistened, which were very useful. The Galvanic Society was of course desirous of verifying a fact of this nature, and determined to repeat the experiments of M. Marechaux, as described in his letter.

Discs of zinc, which had been before used, were cleaned and restored to their usual polish. Similar pieces were made out of new brass. A vertical column of forty-nine pieces of discs was formed by the interposition of pieces of card, not moistened, standing upon a plate of brass, of greater dimensions, having three holes near its edges, through which cords of silk were passed in order to support the whole apparatus. These cords were tied together at the top, and the whole column suspended by them. This pile, which M. Marechaux distinguishes by the name of colonne pendule, was put into communication with the electric micrometer of M. Marechaux, simplified by M. Veau de Launay,† and it manifested an intensity of 360 degrees, which was ascertained to be the effect of galvanic action, and not from the electricity of the atmosphere.

This first experiment was repeated and varied in different ways. Blotting paper was substituted instead of the pieces of card to the number of four for each, and there was no effect produced. Discs of card, dried in the oven were used, and the mean term of attraction in several experiments was 372 degrees. With the same pieces and twenty-five pair of discs only, the attraction was 160. The experiment was afterwards made with a column having the same number of pairs of metallic discs, but without the interposition of any pieces of card. In these circumstances no effect was produced. These first results would have been sufficient for the society to confirm the fact announced by M. Marechaux, and which was intended to be verified; but this galvanic action of the pendulous column was not proved but by the help of an instrument of very great sensibility, and with regard to quantities scarcely to be estimated. It remains, therefore, for the society to ascertain the

• Annales de Chimie. Jan. 1806.

+ See Journ. de Phys. Messidor, an. XIV.-See also Nicholson's Journal, XIV, p. 350.

By intensity we denote the measure of the distance, at which a leaf of gold, suspended to a vertical stem of brass, is attracted towards another stem of the same metal, terminating in a ball, when these two stems are in communication with the two poles of the pile. Each degree of this measure answers to the eighteen thousandth of an inch.

advantage which it is possible to derive for the progress of galvanism by means of a discovery so important, by employing more powerful modes of action, and by comparing them with the effects obtained from piles excited by humidity or by saline solutions. The class of the society which is employed on physical researches, has been charged to direct its investigations.

II. A notice appeared in the Moniteur of the 22nd of Brumaire last, that Dr. Joseph Baronio, of Milan, had published a description of a galvanic pile formed of vegetable matters only, with an invitation to philosophers to repeat and vary his experiments, flattering himself that they would serve to extend the application of the theory of galvanism to the whole of vegetable life. The Galvanic Society was called upon to answer this observation of Dr. Baronio.

A pile was accordingly formed by them in his manner: sixty equal discs of walnut-tree were made, two inches in diameter, having a raised edge of one-eighth of an inch high. These pieces were boiled in vinegar, and with these, and round pieces of raw beet-root, and of a thick raddish, (raphanus sativus of Linnæus,) a pile was constructed of sixty couples of pieces of beet-root and raddish, separated by discs of wood, on the upper extremity of each of which was poured, by means of the border, a solution of the acidulous tartrite of potash in vinegar. Lastly, at the lower extremity of the pile was placed a leaf of cochlearia, and at the upper extremity a double band of blotting-paper, steeped in vinegar. Everything being thus disposed agreeably to the full description inserted in the Moniteur, frogs, properly prepared for the action of this pile, were placed with the leaf of cochlearia in contact with their spinal marrow, and the band of paper with their muscles. Three frogs being thus successively and repeatedly presented, showed not the least motion, though they were sufficiently sensible to be strongly agitated when being supported on a knife to bring them near the conductor of the pile, they were in contact with the blade or silver mounting of the handle. After having made every probable experiment with these frogs without success, the pile was brought into communication with the electro-micrometer, upon which also it produced no effect. The same instrument was then presented to a pendulous pile, constructed after the manner of M. Marechaux, composed of sixty pair of new discs of copper and of zinc, with the interposition of pieces of card not moistened. The intensity was about 180 degrees. At the same moment, the frogs which had been presented to the vegetable pile, were put into communication with this last, and they gave no indication of sensibility.

The Galvanic Society did not, therefore, obtain in the experiments indicated by Dr. Baronio, the results which he announced; but they have served to show that the electro-micrometer made use of is still more sensible than frogs to show the smallest effects of galvanism. (To be continued.)

• Annales de Chimie. Jan. 1806.

Researches on the Laws of Induction of Currents produced by Currents. Second Memoir. By M. ARRIA.*

THE experiments of this second memoir have been made by following the method pointed out in that which I had the honour of addressing to the Academy on the 17th of May last, which method consists in submitting the same needle, successively, to the action of each of the two currents-the induced and the inducing one, by the aid of helices equally inserted in the circuits. When the needle is suitably chosen, the inverse relation of the durations of oscillation is equal to that of the two currents.

I shall now give the principal consequences of my investigation. 1st. The intensity of each of the induced currents, direct and inverse, is proportional, all things being equal, as to the number of elements of the inducing current, which acts on the induced system: it is independent of the section of these same elements; or, in other terms, directly proportional to the quantity of electricity which traverses them.

It varies in the direct ratio of the conductibility of the induced wire, and is equally divided amongst the different elements of this latter, when they are disposed in a similar manner in relation to the inducing wire.

The verification of these laws may perhaps be regarded as a confirmation of the method employed to ascertain the degree of intensity of induced currents. I may add, that this process gives the same values, in the limits of my experiments, for the relation of the two induced currents, whether they be determined directly, or whether we value each of the two by taking the induction for unity.

2ndly. The effect of induction decreases in proportion as the distances of the two systems is augmented, following a law which increases the rapidity as this distance becomes more considerable; in such a manner that when the two systems are brought very near to each other, the intensity of the induced current is almost as strong, independent of their mutual distance; this latter augmenting, the intensity decreases in inverse ratio, at first, of the square root of the distance, and afterwards, of the simple distance. The law of the inverse ratio of the square root of the distance is observed too when the two systems are even so much removed from each other that the distances of their different elements vary in the same relation.

3rdly. If we employ, for the induced system, a spiral of a single turn, made with a wire, the section, or the diameter of which we successively augment, the intensity of the direct current augments from a diameter of half a millimetre to that of two and a half millimetres, which is the largest I have employed, at first, as the square root of the diameter, or the fourth power of the section; afterwards it is less rapid. The inverse is, in the same circumstances, smaller than the direct one, but the relation which the first bears to the second increases as the square root of the diameter, in such a man* Comptes Rendus.

382 On the Laws of Induction of Currents produced by Currents.

ner that the inverse varies in direct ratio, at first of the diameter, and afterwards of its square root.

The intensity of each of the induced currents augmenting less rapidly than the section, it follows, in the case of an induced conductor, formed by the union of several wires, that there operates amongst them, when they are submitted simultaneously to the action of an inducing current, a reaction, by virtue of which, the quantity of electricity devolved in each one is less than when the others are taken away. If we give to the induced spiral two or three turns, in place of a single one, the effect of induction will become diminished in proportion as the number of turns is augmented, because of their mutual reaction. Observation justifies this consequence. We see, further, from it, that conformably to the facts which have been indicated by the experiments made with spirals of a single turn, that the inverse current decreases less rapidly than the direct one, in such a manner that the relation of the first to the second is greater (the section of the wire remaining constant) for a spiral of several turns than for one of a single turn. I have found, for example, 0mm, 40 for the relation of two currents in a spiral of several turns in a wire of 0mm, 64 in diameter, and 0TMTM, 33, with a spiral of the same wire, of a single turn. When employing a wire of two and a half millimetres, I obtained for the two values of the same relation, 0mm, 68, and unity almost, following, that the induced spiral consisted of one or more turns.

4thly. The two currents, direct and inverse, developed in the same system induced by the action of a similar inducing system, the first at the moment when the current from the pile is broken, the second at the moment when it is closed, differ from each other, not only by the direction, by the intensity, by their unequal increasing when the section is augmented, but also by their tension; the first of these two currents becomes enfeebled, following a law less rapid than the second, in its passage across the wires of variable length and section inserted in the induced circuit.*

5thly. If we submit two spirals to the action of an inducing current, the intensity of the current induced in each of them is less, the other spiral being closed, than when it is open. The effect of

this is null in this latter case; if we cause the same conductor to be traversed simultaneously by the induced currents of the two spirals, we find that they possess the property, like those of a limited duration, of joining themselves together, or of separating, according as

• If we establish the communication between the two extremities of the induced wire, by the aid of gold leaf, we can perceive the sparks which accompany the formation of the induced current with a spiral of thick wire, for which the relation of the inverse current to the direct one is almost unity. I have observed that there is no production of light except at the time of breaking the inducing current, in consequence then of the formation of the direct current. The inverse current, though equal to the direct one, undergoes a less powerful diminution in its passage through the gold leaf, and it is, without doubt, for this cause that there are no sparks in the induced circuit at the instant when the inducing current is completed.

the current is transmitted in the same or in the opposite direction. The verification of this property further confirms the exactness of the experimental method employed in these researches, and furnishes the means of verifying, in a great number of cases, the values which direct observation furnishes, for the intensity of induced currents.

6thly. In order to account for the diminution of the induced current in a wire or in a spiral, when other wires or other spirals are submitted to the same inducing cause, it is necessary to seek to know in what manner these inducing currents act on closed conductors placed in their neighbourhood, and submitted solely to their action. M. Henry was the first who occupied himself with this question, I shall here give the results obtained by him.

If we call the primary current the inducing current, it determines at the instant that it is broken in a neighbouring wire a current of the second order, which has the same direction as that of the first order, or primary one. If we cause this secondary current to act on a third conductor, closed, and not subject to the influence of the first, it will create a current of the third order, or tertiary current, the direction of which is opposed to that of the secondary current. This current of the third order gives the same developement when acting on a current of the fourth order, by giving it a direction contrary to its own, in such a manner that we have, for the succession of the signs of different induced currents, the following series: Current from the pile, or primary current.....

+

1st current induced by the rupture of the preceding one, or

secondary current.....

+

+

2nd current, (or tertiary current).

3rd current, (or current of the fourth order)....

etc.

I have obtained up to the seventh order, the same results as M. Henry, however small the distance was between the inducing and the induced systems. I note this circumstance, because the skilful philosopher of New Jersey thinks that the induced current is not in a contrary direction to that of the inductor (in the case where this latter is itself an induced current), except when the distance of the two systems have acquired a certain value. I have observed, further, that there are analogous phenomena produced at the moment that the voltaic circuit is completed.

The series corresponding to the preceding one is in this caseCurrent from the pile, (or of the first order)....

1st current induced at the moment when the preceding one is established, (or of the secondary order)

.....

2nd current, (or of the tertiary order).. 3rd current, (or of the fourth order).

etc.*

.....

+

+

• If M. Arria had consulted the 6th volume of these Annals, he would have found all his experimental results predicted in our letter to Dr. Henry. -EDIT.

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