Discoveries and inventions of the nineteenth century (1905)
Routledge, Robert · London : G. Routledge and Sons · leaf 608
these,the conductor may be laid along the ground, but must then be well insu-lated with some non-conducting material, which is capable of withstandingthe action of the weather. A kind of cable is usually employed, in whichis the conductor, made of copper, protected and strengthened by hempfibres… … HIG. 284.—Portable Single-Needle Instrument. transmitting apparatus, here shows an arrangement very compact, and noteasily deranged. The springs, A B, press against the piece of metal markedC, with which good contact is insured by providing the springs with severalprojecting steel points. D, E are…
Inventions
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