If a magnet suspended by one string, and a piece of iron suspended by another, be brought near one another, they will mutually attract each other, and be drawn to a point between.
Suspend a magnet nicely poised by a thread, and it will point north and south, the same end pointing invariably the same way.
Rub a fine needle with a magnet, and lay it gently on the surface of the water; it will point north and south. Rub various needles with the magnet, and run them through small pieces of cork, and put them to swim in water; they will all point north and south, and the same end will invariably point the same way. This mode of finding the north is sometimes of the utmost service at sea, when the compass is destroyed.
Opposite poles attract; poles of the same name repel. Take two magnets, or two needles rubbed with the magnet, and bring the north and south poles together, and they attract.
Bring the north poles near each other, and they repel. Bring the south poles near each other, and they repel. Rub a needle with a magnet, and run it through a piece of cork, and put it to float in water. Hold a north pole of a magnet near its north pole, and it will keep flying away to avoid it. It may be chased from side to side of a basin. On the other hand, an opposite pole will immediately attract.
Rub four or five needles, and you may lift them up as in a string, the north pole of one needle adhering to the south pole of another.
Put a magnet under a piece of glass, and sprinkle iron-filings on it; they will arrange themselves in a manner that will be very surprising. At each pole will be a vast abundance standing erect, and there will be fewer and fewer as they recede, until there are scarcely any in the middle. If the iron-filings are sprinkled on the magnet itself, they will arrange themselves in a manner very striking.
Lay a needle exactly between the north and south pole, it will move towards neither.
Artificial Coruscations.
There is a method of producing artificial coruscations, or sparkling fiery meteors, which will be visible not only in the dark but at noon-day, and that from two liquors actually cold. Fifteen grains of solid phosphorus are to be melted in about a drachm of water: when this is cold, pour upon it about two ounces of oil of vitriol; let these be shaken together, and they will at first heat, and afterwards they will throw up fiery balls in great numbers, which will adhere like so many stars to the sides of the glass, and continue burning for a considerable time; after this, if a small quantity of oil of turpentine is poured in, without shaking the phial, the mixture will of itself take fire, and burn very furiously. The vessel should be large, and open at the top. Artificial coruscations may also be produced by means of oil of vitriol and iron, in the following manner:—Take a glass body capable of holding three quarts; put into it three ounces of oil of vitriol and twelve ounces of water; then warming the mixture a little, throw in, at several times, two ounces or more of clean iron-filings; upon this, an ebullition and white vapours will arise; then present a lighted candle to the mouth of the vessel, and the vapour will take fire, and will afford a bright illumination, or flash like lightning. Applying the candle in this manner several times, the effect will always be the same; and sometimes the fire will fill the whole body of the glass, and even circulate to the bottom of the liquor; at others, it will only reach a little way down its neck. The great caution to be used in this experiment is, in making the vapour of a proper heat; for, if too cold, few vapours will arise; and, if made too hot, they will come too fast, and only take fire in the neck of the glass, without any remarkable coruscation.