Charles. They are all attracted but now you take away the glass they are quiet.

Tutor. It is evident that the electric fluid passed from one part of the tube through the poker, which is a conductor, to the paper, and attracted it :-if the glass be properly excited, you may take sparks from the poker.

James. Would not the same happen if another glass tube were placed in the stead of the poker?

Tutor. You shall try.-Now I have put the glass in the place of the poker, but let me excite the other tab as much as I will, no effect can be produced on the paper :there are no signs of electrical attraction, which shows that the electric fluid will not pass through glass.

Charles. What would have happened if any conducting substance had been used, instead of silk, to suspend the iron poker?

Tutor. If I had suspended the poker with a moistened hempen string, the electric fluid would have all passed away through

that, and there would have been no (or very trifling) appearances of electricity at the end of the poker.

You may vary these experiments till you make yourselves perfect with regard to the distinction between electrics and conductors. Sealing-wax is an electric, and may be excited as well as a glass tube, and will produce similar effects. I will give you a list of electrics, and another of conductors, disposed according to the order of their perfection, beginning in each list with the most perfect of their class: thus glass is a better electric than amber, and gold a better conductor than silver:

TABLE.

This, and other chemical terms, are explained and familiarly illustrated in a work just published, by the author of the Scientific Dialogues, entitled "Dialogues in Chemistry," &c.

CONVERSATION XXIX.

Of the Electrical Machine.

TUTOR. I will now explain to you the construction of the electrical machine, and you how to use it.

show

Charles. For what purpose is it used?

Tutor Soon after the subject of the electric fluid engaged the attention of men of science, they began to contrive the readiest methods of collecting large quantities of it. By rubbing this stick of sealing-wax I can collect a small portion: if I excite or rub the glass tube, I get still more. The object, therefore, was, to find out a machine by which the largest quantities can be collect

ed, with as little trouble and expense as may be.

James. You get more electricity from the tube than from the sealing-wax, because it is five or six times as large: by increasing the size of thetube, you would increase the quantity of the electric fluid, I should think.

Tutor. That is a natural conclusion. But if you look to the table of electrics, which I made out yesterday, you will see that had the wax been as large as the glass tube, it would not have collected so much of the electric fluid, because, in its own nature, it is not so good an electric.

Charles. By the table, glass stands as the most perfect electric, but there are several substances between it and wax, all of which are, I believe, more perfect electrics than wax.

Tutor. They are: Electricians, therefore, had no hesitation as to the nature of the substance they fixed on glass, which being easily melted and run, or blown into all sorts of forms, is, on that account, very valuable.