Fourth Experiment.
By contact, the magnetic power is transferred from the magnet to a piece of unmagnetized steel, and it is stated that the highest magnetizing effect is that produced by the simple method of Jacobi. A horse-shoe magnet has its poles brought in contact with the intended poles of another bar of steel, likewise bent in the form of a horse-shoe, and by drawing the feeder over the unmagnetized horse-shoe in the direction of the arrow in the cut, and when it reaches the curve, bringing it back again to the same place, say at least twelve times, and after turning the whole over without separating the poles, and repeating the same operation on the other side likewise twelve times, the steel is then powerfully magnetized; and it is said that a horse-shoe of one pound weight may be thus charged so as to sustain twenty-six and a half pounds, and that by the old method of magnetizing it would only have sustained about twenty-two pounds. (Fig. 198.)
Fig. 198.
The horse-shoe magnet, and another one unmagnetized, placed end to end; the one shaded and lettered n and s is the magnet. a a. The piece of soft iron moved in the direction of the arrow.
Fifth Experiment.
If the horse-shoe magnet is placed on a sheet of paper, and some iron filings are dusted between the poles, a very beautiful series of curves are formed, called the magnetic curves, which indicate the constant passage of the magnetic power from pole to pole.
Sixth Experiment.
The magnetic force exerted by a horse-shoe-shaped piece of soft iron, surrounded with many strands of covered copper wire in short lengths, is extremely powerful (Fig. 199), and enormous weights have been supported by an electro-magnet when connected with a voltaic battery. Supposing a man were dressed in complete armour, he might be held by an electro-magnet, without the power of disengaging himself, thus realizing the fairy story of the bold knight who was caught by a rock of loadstone, and, in full armour, detained by the unfriendly magician.
