A horseshoe magnet from the dime store can be relied upon to amuse young shutins for considerable periods of time. A handful of tiny tacks will demonstrate the depth of the magnetic field, and repeated trials can be encouraged to determine the maximum number of tacks which the magnet will lift and hold.

To make a bar magnet from an ordinary steel sewing needle, draw it downward and parallel to one of the legs of the horseshoe magnet, then lift it up about an inch and repeat the stroking motion about a dozen times. The magnetized needle will then attract its own load of tacks, tiny brads, or iron filings. The fact that the magnet needle has a North and South pole can be confirmed by magnetizing a second needle and presenting first one end and then the other to an end of the first needle. The North pole of one needle will attract the South pole of the other, and vice versa, but like poles will be visibly repelled.

To prove that a free moving bar or needle magnet would automatically turn itself to a North and South position when freed of friction, pierce a flat disk cut from a cork with a magnetized needle through its central axis, and place it in a basin of water. The surface of the water will provide a fric-tionless bearing for this simple compass.

By slicing a number of corks lengthwise, and piecing them with magnetized needles fore and aft, a fleet of small magnetic boats can be maneuvered in a basin or dishpan of water by holding another magnetized needle on a thread in front of them. Paper sails on toothpick masts will add realism to the tiny craft.