The use of the copper wire for the telephonic service was the beginning of its great extension. The New York Tribune says that the first copper telephone wire was about the size Of tthe iron telegraph wire it replaced. With improved "long distance" instruments, such as are now in general use for all kinds of service, i conversations can be conducted over wire of this size for about 350 miles with what the engineers call "standard transmission." By increasing the size of the copper strands on their long-distance lines they have more than doubled the early limits of successful transmission. The problem before the engineers has been to find a way to prevent the telephone current from "decaying" during the ourney of a message over the lines. That is, the engineers have sought means to counteract the inevitable loss of efficiency in the current and to keep it as near as possible at its original strength. Two methods of doing this have been tried. Separately they have worked out well; but as yet they have not been applied commercially to the same line. The two devices that promise so much for the extension of the range of Ion-distance talking are the loading coil and the repeater. Though the ends they accomplish are, to a certain extent, the same, the principles on which they work are entirely different. When the electrical current from the transmitter of one telephone starts out on its journey to the receiver of another telephone a thousand miles away, say, it loses strength fast, sinking away by degrees until finally it becomes too weak to reproduce vibrations distinctly. The loading coil, which was invented by professor Michael I. Pupin of Columbia University, acts as a sort of stimulant. It consists of an iron core upon which is windng upon winding of fine wire through which the talking current is passed in such a way that it is strengthened against the decaying processes and maintained at a level high enough to give satisfactory transmission. These coils are attached to a line two, four or maybe eight miles apart, and their use approximately doubles the range of the telephone. The repeater, which is a later invention, operates differently. As its name signifies, it actually repeats the message, which, coming through a receiver reproduces itself automatically on a transmitter. This allows of putting new current into he line, just as the original current is introduced at tthe transmitter of the subscriber's telephone. The result is practically to start the message all over again with a fresh lease of life, though naturally the force that carries it cannot be made quite as good as new. A repeater in the middle of a long-distance circuit extends the range of talking about fifty per cent.