The New Larned History, for Ready Reference Reading and Research, Vol. 4 Of 12: The Actual Words of the World's Best Historians, Biographers and Specialists; a Complete System of History for All Uses, Extending to All Countries and Subjects and Represen

Excerpt from The New Larned History, for Ready Reference Reading and Research, Vol. 4 of 12: The Actual Words of the World's Best Historians, Biographers and Specialists; A Complete System of History for All Uses, Extending to All Countries and Subjects and Representing the Better and Newer Literature of History; Elec to Frob

1825-1921. - Development of the electro-mag net. Take an iron bar and wind round it spiral coils of copper wire spun over with silk or cotton to insulate the turns. Connect the ends of this wire to a battery and the iron instantly becomes a powerful magnet. Such an arrange ment is called an electro-magnet, and it was first given to us by an English electrician, William Sturgeon, in 1825, who employed, however, a wind ing consisting of only a single layer of rather thick copper wire. Joseph Henry, in the United States, bestowed on the electro - magnet additional powers by winding it with very many turns of fine silk-covered copper wire. J. P. Joule, a British engineer, invented divers forms of improved elec tro-magnets about 1840 remarkable for their great power of lifting other masses of iron. Large elec tro-magnets made on Joule's principles are now (1921) in common use in engineering works, and are used for lifting heavy masses of iron and ma fetials such as scrap iron [as well as in break ing up large mames of scrap metal by lifting heavy iron weights which, when the current is cut ofi from the magnet, drops with smashing force on.

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