Flame, electricity and the camera; man's progress from the first kindling of fire to the wireless telegraph and the photography of color (1901)
Iles, George, 1852-1942 · New York, Doubleday & McClure co. · leaf 219
iment, forth-with entered upon, satisfied him of thecorrectness of his surmise. Before thisgreat discovery every telegraphic circuithad demanded two complete lengths of wire, both connected to the instru- _ Fig. 56.ments at the ends of a line. Ever since r. .■ • ., Grounding a circuit.Steinheils… … i86 TELEGRAPHY—LAND LINES The telegraph-key K in its normal position is kept in con-tact with stop 3 by means of a spring, and thus main-tains the line-wire in connection with the earth throughthe plate E. When the key is depressed 2 is brought intocontact with i, and the current from the battery B…
Fire · Electricity · Color photography
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