Theory and practice of the electric telegraph; a manual for operators and students (1875)
Churchill, Charles Henry, d. 1904. [from old catalog] · Oberlin, Ohio, Sherman & bros. · leaf 58
Ring and Helix.8. Form.—l. What form is favorable for strength? … In general the U form is best. An arrangement like that in the figure will sustain hundreds of pounds. For many purposes two spools or bobbins of iron wound with insulated wire, and screwed fast to a straight + piece of iron at one end is the best form. 9. Electro Motors.—1. Define…
Telegraph
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