Page images
PDF
EPUB

weather, which, in some latitudes, will last for many days together?

Charles, I did not think of that.

Tutor. Without the use of the magnet, no persons could have ventured upon such voyages as those to the East Indies, and other distant parts; the knowledge, therefore, of this instrument cannot be too highly prized.

James. Is that a magnet which is fixed to the bottom of the globe, and by means of which we set the globe in a proper direction with regard to the cardinal points, north, south, east, and west.

Tutor. That is called a compass, the needle of which being rubbed by the natural or real magnet, becomes possessed of the same properties as those which belong to the magnet itself.

Charles. Can any iron and steel be made magnetic ?

Tutor. They may; but steel is the most proper for the purpose. Bars of iron thus prepared are called artificial magnets.

James. Will these soon lose the properfies thus obtained ?

Tutor. Artificial magnets will retain their properties almost any length of time, and since they may be rendered more powerful than natural ones, and can be made of any form, they are generally used, so that the natural magnet is kept as a curiosity.

Charles. What are the leading properties of the magnet?

Tutor. (1.) A magnet attracts iron. (2.) When placed so as to be at liberty to move in any direction, its north end points to the north pole, and its south end to the south pole : that is called the polarity of the magnet. (3.) When the north pole of one magnet is presented to the south pole of another, they will attract one another. But if the two south, or the two north poles, are presened to each other, they will repel. (4.) When a magnet is so situated as to be at liberty to move any way, the two poles of it do not lie in an horizontal direction, it inclines one of its poles towards the horizon, and, of course, elevates the other pole above it; this is called the inclination or dipping of the magnet. (5.) Any magnet may be made to impart its properties to iron and steel.

[merged small][ocr errors][merged small][merged small]

TUTOR. Having mentioned the sevetal properties of the magnet or loadstone, I intend, at this time, to enter more particularly into the nature of magnetic attraction and repulsion.—Here is a thin iron bar, eight or nine inches long, rendered magnetic, and on that account it is now called an artificial magnet: I bring a small piece of iron within a little distance of one of the: poles of the magnet, and you see it is at-** tracted or drawn to it.

Charles. Will not the same effect be produced, if the iron be presented to any other part of the magnet ?

Tutor. The attraction is strongest at the poles, and it grows less and less in pro

from the portion to the distance of

any part

poles, so that in the middle, between the poles, there is no attraction, as you shall see by means of this large needle. James. When

you

held the needle near the pole of the magnet, the magnet moved to that, which looks as if the needle attract

ed the magnet.

Tutor. You are right: the attraction is mutual, as is evident from the following experiment. I place this small magnet on a piece of cork, and the needle on another piece, and let them float on water, at a little distance from each other, and you observe that the magnet moves towards the iron, as much as the iron moves towards the magnet.

Charles. If two magnets were put in this situation, what would be produced ?

Tutor. If poles of the same name, that is, the two north, or the two south, be brought near together, they will repel one another; but if a north and south pole be presented, the same kind of attaction will be visible, as there was between the magnet and needle.

« PreviousContinue »