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Show Tha ..l .it (alia Slra.aeaa. In operating long cables very delicate deli-cate Instruments are required, and the current arriving at the receiving end are very feeblo In comparison with those employed In land line signaling The longer tho cable, naturally, thu feebler tho Impulses arlvlng at the receiving re-ceiving end A short cable, a cable of uuder 1,000 miles being generally considered a short cable, gives n speed ot signaling amply sufficient for all purposes, with a conductor weighing about 100 pound to the mite, surrounded sur-rounded by an Insulating envelope of gutta-percha weighing about an equal amount. When wo come to a cable nf about twice this length It Is found necessary In order to get a practically unlimited speed, that Is, a speed as high as the most expert operator can read It, to employ a core ot C50 pounds of copper to tho mile, Insulated with 400 pounds ot gutta-percha to the mile, Thtte are the proportion! ot copper and gutta-percha In the 1S9I Anglo-American Anglo-American Atlantic cable, which It con-tldered con-tldered the record Atlantic, cable tor speed ot working and has been worked, by automatic, transmission, at the rate ot tome forty-five, words a minute Tht type ot cable proposed for the Vancouver-Panning section of the Urltlsh Pacific cable, as designed by Lord Kelvin, Is to have a core of CM pounds ot copper and 353 pounds of gutta-percha to the mile, and la calculated cal-culated to give a speed ot twelvo words per minute over a length uf 3,(60 miles. It Is not considered safo to adopt a much heavier core than this tor the reason that the weight of the completo cable with a core that should weigh moro than about half a ton to the nautical milo would be ao great that picking It up for repairs from a depth of 3,000 fathoms would be an extremely ex-tremely dIOIcult and hazardous operation opera-tion Bcrlbncr'a. |