Page:Popular Science Monthly Volume 34.djvu/304

 yield up every distinctive feature of the magnet, is successfully opposed by the hardness of the steel bar.

The lines are called lines of magnetic force, and the area over which their influence is felt is known as the magnetic field. If a compass-needle, suspended by a silk thread and free to move in any plane, be brought into this field, it will assume a direction



parallel to the lines of force, as at e, e', e" . . . evi. The strength of the field, and hence the force that tends to give the needle steadiness and direction, varies greatly at different points—at e it is powerful, at e"'  feeble.

If two magnets similar to that of Fig. 1 be brought into proximity, so that poles of the same name touch, they will repel each other; if, on the other hand, the north pole of one be approached to the south pole of the other, both bars, as if instinct with life,