Lifting Magnet

—A large electromagnet designed for lifting purposes in handling scrap, pig iron, rails, plate, ete. It consists e entially of a copper coil embedded in an outer casing of cast iron or steel. The lifting power depends both upon the form of the magnet and on its magnetic strength. A horseshoe magnet will lift a load three or four times as great as a bar magnet of the same weight, Á The lifting power is greater if the area of contact between the poles and the armature be increased. Also the lifting power of a magnet grows in a very curious and unexplained way by gradually increasing the load on its armature, day by day, until it bears a load which at the outset it could not have done. Neverthele , if the load be so inc i eased that the armature is torn off, the power of the magnet falls at once to its original value. The attraction between a powerful electromagnet and its armature may amount to 200 lbs. per square inch. 7 Small magnets lift a greater load in proportion to their own weight than large ones, good steel horseshoe magnet weighing itself one pound ought to lift twenty pounds weight. Sir Isaac Newton is said to have po e ed a lodestone mounted in a signet ring which would lift a piece of iron 200 times its own weight.