MAGNETISM.

New Zealand Mail, Issue 1095, 24 February 1893, Page 16

MAGNETISM.

Now let me tell you something about magnetism. There is a kind of greyish-black iron-stone found in several parts of the world that has the remarkable property of attracting small pieces of iron or steel. In ages past, the Greeks, and very likely the Chinese —for, I might here tell you,, that the natives of China were a very clever people long, long be fore the Christian era—knew of this stoneIt is said that the Greeks got it from Mag*, nesia, in Asia-Minor, and that this is the origin of our terms magnet and magnetism. The ore. is commonly called loadstone, but it is known to chemists as the magnetic oxide iron.

Not only does the loadstone possess the power of attracting iron itself, but it can communicate its virtue to steel. A bar of welltempered steel, if repeatedly rubbed by it, acquires exactly similar properties, and is termed an artificial magnet, while the other is called a natural magnet. In point of strength and convenience artificial magnets are far superior to natural ones, and are therefore more commonly used. If we take a bar of steel that has been thus rubbed by a loadstone and to which the name of barmagnet is usually given and scatter iron filings over it, they will adhere in tufts at both ends, but none will be found at the middle of the bar. Or wo may put the magnet under a sheet of pasteboard and sprinkle the filings over the sheet. We shall then find the small particles of iron arrange themselves in beautiful curved lines round both ends of the magnet. It appears from this that the chief power of the bar lies at the two ends or at points near the end, round which, as centres, the curves are formed.

These oentres ®f force are called the poles of the magnet from another peculiar property which they ate found to possess. ,lf a jnag-

netic bar be suspended by a thread or poised on a pivot, it will not rest till it has Bettled in one position, which is in a direction nearly north and south. If moved from this position it returns to it again, tile same end always turning to the north. That end which points to the north is ealled the north polo of tho magnet and the other its south pole.