American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 51
YNAMO MACHINES—It is well-kiiown that when a magnet is placedbeneath a piece of card-board or glass, on which soft iron filings have been strewn, ifthe card be lightly tapped, the filings arrange themselves in symmetrical lines, asoutlined in Fig. i6. This singular arrangement of the iron filings… … ^^^m^^^ It is not meant that actual lines of force exist; the term being merely used as aconvenient means of designating the phenomenon and the direction in which the forceacts. It is known also that when a current of electricity is caused to flow in a wire,similar magnetic lines of force are set…
Telegraph
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