with which we are acquainted, and, by the use of proper methods, it is as easily collected from surrounding bodies as water is taken from a river.

James. I see no fluid attaching to the sealing-wax when you have rubbed it.

Tutor. You do not see the air which you breathe, and with which you are surrounded, yet we have shown you* that it is a fluid, and may be taken from any vessel, as certainly, though not with so much ease, as water may be poured from this glass. With the exercise of a small degree of patience, you shall see such experiments as will not fail to convince you that there is as certainly a fluid, which is called the electric fluid, as there are such fluids as water and air.

Charles. Water must have been known since the creation, and the existence of the air could not long remain a secret, but who discovered the electric fluid, which is not at all evident to the sense either of sight or feeling?

Tutor. Thales, who lived six centuries before the Christian era, was the first who observed the electrical properties of amber, and he was so struck with the appearances, that he supposed it to be animated:

Bright amber shines on his electric throne,
And adds ethereal lustre to his own.

* See Vol. II.

DARWIN.

James. Does amber attract light bodies like sealing-wax?

Tutor. Yes, it does; and there are many other substances, as well as these, that have the same power. After Thales, the first person we read of that noticed this subject was Theophrastus, who discovered that tourmalin has the power of attracting light bodies. It does not, however, appear that the subject, though very curious, excited much attention till about 200 years ago, when Dr. Gilbert, an English physician, examined a great variety of substances, with a view of ascertaining how far they might or might not be ranked among electrics.

Charles. What is meant by an electric?

Tutor. Any substance being excited or rubbed by the hand, or by a woollen cloth, or other means, and having the power of attracting light bodies, is called an electric.

James. Is not electricity accompanied with a peculiar kind of light, and with sparks?

Tutor. It is, of which we shall speak more at large hereafter: the celebrated Mr. Boyle is supposed to have been one of the first persons who got a glimpse of the electrical light, or who seems to have noticed it, by rubbing a diamond in the dark. But he little imagined, at that time, what astonishing effects would afterwards be produced by the same power. Sir Isaac Newton was the first who observed that

excited glass attracted light bodies on the side opposite to that on which it was rubbed. Charles. How did he make the discovery? Tutor. Having laid upon the table a round piece of glass, about two inches broad, in a brass ring, by which it was raised from the table about the eighth of an inch, and then rubbing the glass, some little bits of paper which were under it were attracted by it, and moved very nimbly to and from the glass.

Charles. I remember standing by a glazier when he was cementing, that is, rubbing over some window-lights with oil, and cleaning it off with a stiff brush and whiting, and the little pieces of whiting, under the glass, kept continually leaping up and down, as the brush moved over the glass.

Tutor. That was, undoubtedly, an electrical appearance, but I do not remember having ever seen it noticed by any writer on electricity. A complete history of this science is given by Dr. Priestley, which will, hereafter, afford you much entertainment and interesting instruction. To-morrow we shall enter into the practical part of the subject: and I doubt not that the experiments in this part of science will be as interesting as those in any other which you have been studying. The electric light, exhibited in different forms; the various signs of attraction and repulsion acting on all

bodies; the electric shock, and the explosion of the battery, will give you pleasure, and excite your admiration.

CONVERSATION XXVIII.

Of Electric Attraction and Repulsion-Of Electrics and Conductors.

Tutor. You must for a little time, that is, till we exhibit before you experiments to prove it, take it for granted that the earth, and all bodies with which we are acquainted, contain a certain quantity of exceedingly elastic and penetrating fluid, which philosophers call the electric fluid.

Charles. You say a certain quantity: is it limited?

Tutor. Like other bodies, it undoubtedly has its limits; this glass will hold a certain quantity of water, but if I attempt to pour into it more than that quantity, a part will flow over. So it is with the electric fluid: there is a certain quantity which belongs to all bodies, and this is called their natural quantity, and so long

as a body contains neither more nor less than this quantity, no sensible effect is produced. James. Has this table electricity in it?

Tutor. Yes, and so has the inkstand, and every thing else in the room; and if I were to take proper means to put more into it than it now has, and you were to put your knuckle to it, it would throw it out in the shape of sparks. James. I should like to see this done.

Charles. But what would happen if you should take away some of its natural quantity ?

Tutor. Why then, if you presented any part of your body to the table, as your knuckle, a spark would go from you to the table.

James. But, perhaps, Charles might not have more than his natural share, and in that case he could not spare any.

Tutor. True; but to provide for this, the earth on which he stands would lend him a little to make up for what he parted with to the table.

James. This must be an amusing study; I think I shall like it better than any of the others. Tutor. Take care that you do not pay for the amusement before we have done.

Here is a glass tube about eighteen inches long, and perhaps an inch or more in diameter; I rub it up and down quickly in my hand, which is dry and warm, and now I will present it to these fragments of paper, thread, and gold-leaf: