A correspondent—Wm. H. Danforth—writing to us from Salem, Mass., gives it as his opinion that the construction of the Atlantic telegraph cable is faulty, and that it is liable to failure independent of the best paying-out machinery that may be employai. He asserts that as the inside or conducting copper wire? of it are small and laid parallel, while the outside protecting iron wires are twisted and laid on the top of a soft material, that when subjected to great strain, the latter wires will attenuate, and reduce the .thickness of the cable, thus causing such a tensile strain to be exerted upon tlie inside small wires as to rupture them, because they cannot elongate in the same proportion as the twisted outside wires. If such a result should occur, the cable might be laid, and yet fail to operate in conducting messages, because of the inside or conducting wires being ruptured while the outside wires remained intact. Mr. D. asserts that the inside strands should be of sufficient strength to withstand all the strain that may be brought upon the cable. Perhaps it was owing to the drawing out of the inside strands of the cable, during the former attempt to lay it, that the electrical current became feebler and feebler, as stated by Professor Morso, while the cable was being run out rapidly in deep water.