American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 452
the upper copper spiral is that, insome manner, the blue solution is prevented from rising above it, and, thereby, thedeposit of * black copper on the zinc element is minimized. But, perhaps, a betterexplanation, as regards the non-rising of the blue solution beyond the upper spiral, isthat the… … DISTRICT TELEGRAPH SWITCH* 0/ 8 AMERICAN TELEGRAPHY. A slight modification has somewhat recently been made in the construction of thecopper spirals. Formerly, the two spirals and the supporting rod were made separ-ately and were held together by screw nuts. In the modification, the lower…
Telegraph
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