History, theory, and practice of the electric telegraph (1866)
Prescott, George B.(George Bartlett),1830-1894 · Boston, Ticknor and Fields · leaf 117
Fisr. 52. Fig. 53. Fig. 54. rarily in the offices, or for connecting wires upon the line at test-ing places. Fig. 53 is a screw-cup, used upon the copper endof a Daniell battery, for the purpose of connecting the line9 G 98 ELECTRIC TELEGRAPH APPARATUS. wire. Figs. 54 and 55 perform the same office… … Fig. 55. Fig. 56. Fig. 56 represents a galvanometer attached to an electro-mag-
Telegraph
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