also hung from the conductor of an electrical machine into the water.

James. Did that answer to the chain?

Tutor. Just so: and, like Charles, he was going to disengage the wire with one hand, as he held the bottle in the other, and was surprised and alarmed by a sudden shock in his arms, and through his breast, which he had not the least expected.

Charles. I do not think there was any thing to be alarmed at.

Tutor. The shock which he felt was, probably, something severer than that which you have just experienced: but the terror was evidently increased by its coming so completely unexpected.

When M. Muschenbroeck first felt the shock, which was by means of a thin glass bowl, and very slight, he wrote to M. Reaumur, that he felt himself struck in his arms, shoulders, and breast, so that he lost his breath, and was two whole days before he recovered from the effects of the blow.

Charles. Perhaps he meant the fright.

Tutor. Terror seems to have been the effect of the shock: for he adds, "I would not take a second shock, for the whole kingdom of France."

Mr. Ninkler, an experimental philosopher, at Leipsic, describes the shock as having given him convulsions, a heaviness in his head, such

as he should feel if a large stone were on it, and he had reason to dread a fever, to prevent which he put himself on a course of cooling medicines. "Twice," says he, "it gave me a bleeding at the nose, to which I am not inclined and my wife, whose curiosity surpassed her fears, received the shock twice, and found herself so weak, that she could scarcely walk. Nevertheless, in the course of a few days, she received another shock, which caused a bleeding at the nose."

James. Is this called the Leyden phial?

Tutor. It is. They are now made in this manner. (Plate VII. Fig. 6.) BA is a glass jar, both inside and out are covered with tin foil about three parts of the way up, as far as x.

Charles. Does the outside covering answer to the hand, and the inside covering to the water?

Tutor. They do. The piece of wood is placed on the top, merely to support the brass wire and knob v, to the bottom of which hangs a chain that rests on the bottom of the jar. I will now set the jar in such a situation that it shall be within two or three inches of the conductor, while I work the machine.

James. The sparks fly rapidly from the conductor to the knob v.

Tutor. By that means, the inside of the jar becomes charged with a superabundant quantity of electricity: and as it cannot contain this,

without, at the same time, driving away an equal quantity from the outside, the inside is positively electrified, and the outside is negatively electrified. To restore the equilibrium, I must make a communication between the outside and inside with some conducting substance. That is, I must make the same substance touch, at the same time, the outside tin foil, and that which is within, or, which is the same thing, another substance that does touch it.

Charles. The brass wire touches the inside: if I, therefore, with one hand touch the knob, and with the other the outside covering, will it be sufficient?

Tutor. It will: but I had rather you would not, because the shock will be more powerful than I should wish either myself or you to experience. Here is a brass wire with two little balls or knobs bs screwed to it (Plate v11. Fig. 7.) I will bring one of them, as s, to the outside, and the other, b, to the ball on the wire.

James. What a brilliant spark, and what a loud noise!

Tutor. The electric fluid, that occasions the light and the noise, ran from the inside of the jar through the wire to s, and spread itself over the outside.

Charles. Would it have gone through my arms if I had put one hand to the outside, and touched the wire communicating with the inside, with the other?

Tutor. It would, and you may conceive that the shock would have been in proportion to the quantity of the fluid collected. The instrument I used may be called a discharging-rod. But here is a more convenient one (Plate vII. Fig. 8.): the handle D is solid glass, fastened into a brass socket, and the brass work is the same as Fig. 7, only by turning on a joint the arms may be opened to any extent.

James. Why is the handle glass?

Tutor. Because glass being a non-conductor, the electric fluid passes through the brass work without affecting the hand; whereas, with the other, a small sensation was perceived while I discharged the jar.

Charles. Would the jar never discharge it

self?

Tutor. Yes: by exposure to the air for some time, the charge of the jar will be silently and gradually dissipated, for the superabundant electric fluid of the inside will escape, by means of the air, to the outside of the jar.-But electricians make it a rule never to leave a jar in its charged state.

CONVERSATION XXXIV.

Of the Leyden Jar-Lane's Discharging Electrometer, and the Electrical Battery.

Charles. In discharging the jar yesterday, I observed that when one of the discharging-rods touched the outside of the jar, the flash and report took place before the other end came in contact with the brass wire that communicates with the inside coating.

Tutor. Yes, it acts in the same manner as when you take a spark from the conductor; you do not, for that purpose, bring your knuckle close to the tin.

James. Sometimes, when the machine acts. very powerfully, you may get the spark at the distance of several inches.

Tutor. By the same principle, the higher an electrical or Leyden jar is charged, the more easily, or at a greater distance, is it discharged.

Charles. From your experiments it does not seem that it will discharge at so great a distance as that in which a spark may be taken from the conductor.

Tutor. Very frequently a jar will discharge itself, after it has accumulated as much of the electrical fluid as it can contain; that is, the