History, theory, and practice of the electric telegraph (1866)
Prescott, George B.(George Bartlett),1830-1894 · Boston, Ticknor and Fields · leaf 59
Fig. 20. 40 PRELDHNARY NOTIONS. deviation depends upon two circumstances : the first is the positionof the conjunctive wire in relation to the magnetized needle, — … Kg. 21. it may be above or below; the second is the communication ofeach of the two extremities of the conjunctive wire with eitherpole of the pile. Thus, if, the conjunctive wire being below theneedle, the positive pole of the pile communicate with the ex-tremity of the wire that is on the south…
Telegraph
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