8. A steel needle rendered magnetic, and fitted up in a box, so as to move freely in any direction, constitutes the mariner's compass.

Charles. I think there is a similarity between electricity and magnetism.

Tutor. You are right; there is a considerable analogy, and a remarkable difference also between magnetism and electricity.

ELECTRICITY is of two sorts, positive and negative; bodies possessed of the same sort of electricity, repel each other, and those possessed of different sorts attract each other.-In MAGNETISM, every magnet has two poles; poles of the same name repel each other, and the contrary poles attract each other.

In ELECTRICITY, when a body, in its natural state, is brought near to one that is electrified, it acquires a contrary electricity, and becomes attracted by it.—In MAGNETISM, when an iron substance is brought near one pole of a magnet, it acquires a contrary polarity, and becomes attracted by it.

One sort of electricity cannot be produced by itself. In like manner, no body can have only one magnetic pole.

The electric virtue may be retained by electrics, but it pervades conducting substances. The magnetic virtue is retained by iron, but it pervades all other bodies.

On the contrary: the magnetic power differs from the electric, as it does not affect senses

with light, smell, taste, or noise, as the electric does.

Magnets attract only iron, but the electric fluid attracts bodies of every sort.

The electric virtue resides on the surface of electrified bodies, but the magnetic is internal.

A magnet loses nothing of its power by magnetizing bodies, but an electrified body loses part of its electricity by electrifying other bodies.

ELECTRICITY.

VOL. III-N

CONVERSATION XXVII.

INTRODUCTION.

The early History of Electricity.

TUTOR. If I rub pretty briskly with my hand this stick of sealing-wax, and then hold it near any small light substances, as little pieces of paper, the wax will attract them; that is, if the wax be held within an inch or more of the paper, they will jump up, and adhere to it.

Charles. They do; and I think I have heard you call this the effects of electricity, but I do not know what electricity is.

Tutor. It is the case with this part of science as with many others, we know it only by the effects which it produces. As I have not hither to, in these conversations, attempted to bewilder your minds with useless theories, neither shall I, in the present case, attempt to say what the electrical fluid is: its action is well known; it seems diffused over every portion of matter