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This was a convincing proof, that the power, which the eel possessed was the same with electricity. Little fishes being thrown into the water with the eel, it first shocked and then swallowed them: those that were too large to be swallowed, it stunned and then neglected. We tried to render the spark visible, in its passing between two wires set nearly together, and forming part of the communication; but we could not succeed in this experiment, though all the persons, whose hands were joined felt the shock. We made many other experiments and often repeated those above mentioned; and the result of all was a full confirmation of the truth of our hypothesis. The owner of the eel would not suffer us to take it out of the water, that we might ascertain the particular part of its body, in which this unusual virtue resided, or whether it was diffused over the whole. This has been since done with respect to the torpedo, by Mr. Walsh, who went over to the coast of France to make similar experiments on that fish; as many of that species of fish are found there. He found that the shock received from it, was the electrical shock; and that the fish possessed the power of shocking only in two parts of its body directly opposite to each other, and near to the head. A spot on the back and another on the belly opposite to the former, being of a different colour, led him to make the experiment; and he found that the electrical virtue was confined to these, and that any other part of the fish might be handled, without receiving a shock while it was out of the water. Either of these places separately might be handled, without the shock being received, until a communication between them was formed. This makes it appear probable, that the same may also be the case, with the

Guiana eel. One of these spots must therefore be always in the positive, and the other in the negative state; or possibly each of them may be alternately in the positive state, while the other is in the negative state: or rather they are both generally in the natural state, until by an effort of the fish's will, they are suddenly put into different states; as we frequently found, that the hand might be in the water, which formed the communication, without receiving any shock; which cannot be the case with the Leyden bottle when charged, which suddenly discharges itself, upon forming the communication.

Whether there be any electric atmosphere round these spots in the torpedo, we cannot tell; as we had no opportunity of examining this matter in the eel, nor have we heard whether Mr. Walsh made any experiments for ascertaining this matter.

There is another hypothesis of Mr. Eels of Ireland, which solves the various phenomena of electricity, and which I will here explain, and leave you to your own judgment and future experiments, to adopt or reject it as you may find sufficient reason.

Observing that bodies electrised negatively, as Dr.. Franklin calls it, really repel each other with every appearance that takes place, when they are electrised positively, he accounted it absurd to suppose with Dr. Franklin, that they repelled each other the more forcibly, the more they were deprived of their repelling power, especially as every phenomenon proved that they were surrounded with an atmosphere as well as those that are electrified positively.

This led him to conclude, that there are two species of electricity, the vitreous and the resinous, so called from the substances which excite them by friction:

and that they exist in equal quantities in every body, strongly attracting and condensing each other in the natural state, so as to show no signs of electricity in that state, while they are in equilibrio; but while they attract each other they as powerfully repel, each the same power in any other body; that is, the vitreous repels the vitreous, and the resinous repels the resinous, when they are excited in equal quantities. When the natural equilibrium is destroyed by the increase of the one and the diminution of the other, the increased power will expand itself into an extensive atmosphere, decreasing in density and attractive force with the increasing distance, round the excited body; which atmosphere attracts any other atmosphere excited by the other power, and repels an atmosphere of the same kind. These powers are inherent in every body, and when a body is said to be electrified, no more is meant, than that these powers are separated by friction. No part of either of these powers can be taken away from any body, but an equal quantity of the other must at the same time be given in exchange for it, which it will retain until the first subtracted quantity be restored and an equilibrium formed as at first. Friction is found to separate these powers in glass, resin, wax and other bodies which are electrics per se; but the powers of a nonelectric body are separated without friction, by being brought within the atmosphere of the excited electric: as is evident from the conductor, whose end next to the glass globe is electrified with the resinous power, while the other end is electrified with the vitreous power; and the contrary happens, when a rough glass or sulphur globe is used. The same separation of powers takes place in any body. brought near to the prime conductor, if the body be

nonelectric. If it be brought with its end towards the electrified conductor, it will be found to be electrified with the different powers at its opposite ends; that is, with the resinous power at the end next to the prime conductor when it is electrified with the vitreous power. Now this separation of powers is absolutely necessary, previous to any exchange of them in any body. Silk, wax, glass, and all other electric substances, have their powers also separated, while in an electric atmosphere, in the same manner with nonelectric substances, but not so suddenly; and they are found to be electrified with the contrary power, to that, which they excite by friction. Their powers do not change so soon; which constitutes their principal difference from nonelectrics.

According to these principles, Mr. Eels accounts for the charging of the Leyden bottle in the following manner. The glass globe has its powers separated by friction, and parts with its resinous power to the cushion in exchange for its vitreous power. And this deficiency of resinous power in the glass is supplied by the prime conductor in exchange for the vitreous power thrown upon it by the globe; and at the same time the deficiency of the resinous power in the conductor is supplied from the inside of the bottle in exchange for the vitreous power, which it receives from the conductor. This accumulation of the vitreous power in the inside would go on to produce a separation of the powers in the bottle, but it being an electric per se, the exchange is not made so easily; so that the vitreous power is chiefly retained; while through the pores of the glass, or round by the wire to the outside coating, some part passes off to the earth, together with the vitreous power of the coating, in exchange

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for the resinous power from the earth or cushion, according as the connexion is made between the outside and the earth or cushion; until at length, the resinous power on the outside becomes a balance, in attraction, to the vitreous power on the inside; which therefore strongly attract each other, and confine them to the glass until the bottle be discharged in the common

way.

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ATTRACTION OF GRAVITATION.

THE fourth species of attraction is that of gravitation, which is observable chiefly between the larger bodies of our system, such as the sun and planets that surround him, and regulates all their motions. Sir Isaac Newton, observing that when a body had been projected upwards, its velocity continually decreased until it was destroyed, and then the body began to return with an accelerated velocity to the earth, supposed that the same power, which caused the heavy body to descend to the earth, might also extend to the moon; and upon examining the effects of this power, which he called gravitation, he found that the moon might be retained in her orbit by the very same force, which attracts a heavy body, provided that it decreased in its energy and strength in the duplicate proportion to the distance inversely; and farther, that all the bodies which compose the solar system were governed by the same attraction, acting according to the following laws, which he found to take place in every experiment he could make.

1. Gravitation is common to all bodies, and mutual between them.

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