To ascertain whether a piece of metal, or mineral, is magnetic, present it to one of the poles of a poised magnet. If it be attracted at both poles, you may then conclude that the substance so tested is not magnetic.
Dip a magnet into boiling water, and it will lose half of its magnetism; but as the magnet cools, its full power will return.
TO MAKE ARTIFICIAL MAGNETS.
This may be done by stroking a piece of hard steel with a natural or artificial magnet. Take a common sewing-needle, and pass the north pole of a magnet from the eye to the point, pressing it gently in so doing. After reaching the end of the needle, the magnet must not be passed back again towards the eye, but must be lifted up and applied again to that end, the friction being always in the same direction. After repeating this for a few times, the needle will become magnetized, and attract iron filings, &c.
HOW TO MAGNETIZE A POKER.
Hold it in the left hand in a position slightly inclined from the perpendicular, the lower end pointing to the north, and then strike it smartly several times with a large iron hammer, and it will be found to possess the powers of a magnet, although but slightly.
TO SHOW MAGNETIC REPULSION AND ATTRACTION.
Suspend two short pieces of iron wire, N S, N S, so that they will hang in contact in a vertical position. If the north pole of a magnet N be now brought to a moderate distance between the wires, they will recede from each other as in figure 1.