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 141
fastening tothe wire and supporting pin. 11. How is the glass sometimes supported? In the Wade insulater the glass is pro-tected by a wooden shield which has beenthoroughly saturated with hot coal tar.The glass is cemented by a non-conductingsubstance. 12. How is hard rubber used?Hard rubber or… … OF THE LINE. 121
Telegraph
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