At the same time Vail and his engineers were seeking to improve the wires themselves.  Iron and steel wires had been used, but they proved unsatisfactory, as they rusted and were poor conductors.  Copper was an excellent conductor, but the metal in the pure state is soft and no one then knew how to make a copper wire that would sustain its own weight.  But Vail kept his men at the problem and the hard-drawn copper wire was at length evolved.  This proved just what was needed for the telephone circuits.  The copper wire was four times as expensive as the iron, but as it was four times as good Vail adopted it.

John Carty had rather more than kept pace with these improvements.  He was but twenty-six years of age when Union N. Bethell, head of the New York company, picked Carty to take charge of the telephone engineering work in the metropolis.  Bethell was Vail’s chief executive officer, and under him Carty received an invaluable training in executive work.  Carty’s largest task was putting the wires underground, and here again he was a tremendous success.  He found ways to make cables cheaper and better, and devised means of laying them at half the former cost.  Having solved the most pressing problems in this field, his employers, who had come to recognize his marked genius, set him to work again on the switchboard.  He was placed in charge of the switchboard department of the Western Electric Company, the concern which manufactures the apparatus for the telephone company.  The switchboard, as we have seen, was Carty’s first love, and again he pointed the way to great improvements.  Most of the large switchboards of that time were installed under his direction, and they were better switchboards than had ever been known before.

Up to this time it had been thought necessary to have individual batteries supplying current to each line.  These were a constant source of difficulty, and Carty directed his own attention, and that of his associate engineers, to finding a satisfactory solution.  He sought a method of utilizing one common battery at the central station and the way was found and the improvement accomplished.

Though the telephone circuits were now protected from the earth, telephone-users, at times when the lines were busy, were still troubled with roarings and strange cross-talk.  Though busy with the many engineering problems which the telephone heads had assigned to him, Carty found time for some original research.  He showed that the roarings in the wires were largely caused by electro-static induction.  In 1889 he read a paper before the Electric Club that startled the engineers of that day.  He demonstrated that in every telephone circuit there is a particular point at which, if a telephone is inserted, no cross-talk can be heard.  He had worked out the rules for determining this point.  Thus he had at once discovered the trouble and prescribed the cure.  Of course it could not be expected that the sage experts would all agree with young Carty right away; but they were forced to in the end, for again he was proved right.