hard steel, he brought within the influence of a magnet, the iron will be most forcibly attracted, but it will almost instantly lose its acquired magnetism, whereas the hard steel will preserve it a long time.

James. Is magnetic attraction and repulsion at all like what we have sometimes seen in electricity?

:

Tutor. In some instances there is a great similarity Ex. I tie two pieces of soft wire (Plate VIII. Fig. 28.) each to a separate thread, which join at top, and let them hang freely from a hook x. If I bring the marked or north end of a magnetic bar just under them, you will see the wires repel one another, as they are shown in the figure hanging from z.

1

Charles. Is that occasioned by the repelling power which both wires have acquired in consequence of being both rendered magnetic with the same pole?

Tutor. It is and the same thing would have occurred if the south pole had been presented instead of the north.

James. Will they remain long in that position ?

Tutor. If the wires are of very soft iron they will quickly lose their magnetic power; but if steel wires be used, as common sewing needles, they will continue to repel each other, after the removal of the magnet.

Ex. II. I lay a sheet of paper flat upon a ta

VOL. III.-M

ble, and strew some iron filings upon it. I now lay this small magnet (Fig. 29.) among them, and give the table a few gentle knocks, so as to shake the filings, and you observe in what manner they have ranged themselves about the mag

net.

Charles. At the two ends or poles, the particles of iron form themselves into lines, a little sideways; they bend, and then form complete arches, reaching from some point in the northern half of the magnet to some other point in the southern half.-Pray how do you account for this?

Tutor. Each of the particles of iron, by being brought within the sphere of the magnetic influence, becomes itself magnetic, and possessed of two poles, and consequently disposes itself in the same manner as any other magnet would do, and also attracts with its extremities the contrary poles of other particles.

Ex. III. If I shake some iron filings through a gauze sieve, upon a paper that covers a bar magnet, the filings will become magnets, and will be arranged in beautiful curves.

James. Does the polarity of the magnet reside only in two ends of its surface?

Tutor. No: one half of the magnet is possessed of one kind of polarity, and the other of the other kind; but the ends, or poles, are those points in which that power is the strong

est.

DEF. A line drawn from one pole to the other, is called the axis of the magnet.

CONVERSATION XXV.

The method of making Magnets-Of the Mariner's Compass.

Tutor. I have already told you that artificial magnets, which are made of steel, are now generally used in preference to the real magnet, because they can be procured with greater ease, may be varied in their form more easily, and will communicate the magnetic virtue more powerfully.

Charles. How are they made?

Tutor. The best method of making artificial magnets is to apply one or more powerful magnets to pieces of hard steel, taking care to apply the north pole of the magnet or magnets to that extremity of the steel which is required to be made the south pole, and to apply the south pole of the magnet to the opposite extremity of the piece of steel.

James. Has a magnet, by communicating its

properties to other bodies, its own power diminished?

Tutor. No; it is even increased by it.-A bar of iron, three or four feet long, kept some time in a vertical position, will become magnetic, the lower extremity of it attracting the south pole, and repelling the north pole. But if the bar be inverted, the polarity will be reversed.

Charles. Will steel produce the same effect?

Tutor. It will not; the iron must be soft, and hence bars of iron that have been long in a perpendicular position, are generally found to be magnetical, as fire irons, bars of windows, &c.-If a long piece of hard iron be made redhot, and then left to cool in the direction of the magnetical line, it usually becomes magnetical.

Striking an iron bar with a hammer, or rubbing it with a file, while held in this direction, renders it magnetical. An electric shock, and lightning, frequently render iron magnetic.

James. An artificial magnet, you say, is often more powerful than the real one; can a magnet, therefore, communicate to steel a stronger power than it possesses ?

Tutor. Certainly not: but two or more magnets, joined together, may communicate a greater power to a piece of steel, than either of them possess singly.

Charles. Then you gain power according to the number of magnets made use of.

Tutor. Yes; very powerful magnets may be formed by first constructing several weak magnets, and then joining them together to form a compound one, and to act more powerfully upon a piece of steel.

The following methods are among the best for forming artificial magnets:

1. Place two magnetic bars A and B (Fig. 25.) in a line, so that the north or marked end of one shall be opposite to the south end of the other, but at such a distance, that the magnet c, to be touched, may rest with its marked end on the unmarked end of B, and its unmarked end on the marked end of A. Now apply the north end of the magnet L, and the south end of D, to the middle of c, the opposite ends being elevated as in the figure. Draw L and D asunder along the bar c, one towards A, the other towards B, preserving the same elevation: remove LD a foot or more from the bar when they are off the ends, then bring the north and south poles of these magnets together, and apply them again to the middle of the bar c as before: the same process is to be repeated five or six times, then turn the bar, and touch the other three sides in the same way, and with care the bar will acquire a strong fixed magnetism.

2. Upon a similar principle, two bars A B, CD (Fig. 26.) may be rendered magnetic. These are supported by two bars of iron, and they are so placed that the marked end в may