But the most copper money has been saved - literally tens of millions of dollars - by persuading thin wires to work as efficiently as thick ones. This has been done by making better transmitters, by insulating the smaller wires with enamel instead of silk, and by placing coils of a certain nature at intervals upon the wires. The invention of this last device startled the telephone men like a flash of lightning out of a blue sky. It came from outside - from the quiet laboratory of a Columbia professor who had arrived in the United States as a young Hungarian immigrant not many years earlier. From this professor, Michael J. Pupin, came the idea of "loading" a telephone line, in such a way as to reinforce the electric current. It enabled a thin wire to carry as far as a thick one, and thus saved as much as forty dollars a wire per mile. As a reward for his cleverness, a shower of gold fell upon Pupin, and made him in an instant as rich as one of the grand-dukes of his native land.

It is now a most highly skilled occupation, supporting fully fifteen thousand families, to put the telephone wires in place and protect them against innumerable dangers. This is the profession of the wire chiefs and their men, a corps of human spiders, endlessly spinning threads under streets and above green fields, on the beds of rivers and the slopes of mountains, massing them in cities and fluffing them out among farms and villages. To tell the doings of a wire chief, in the course of his ordinary week's work, would in itself make a lively book of adventures. Even a washerwoman, with one lone, non-electrical clothes-line of a hundred yards to operate, has often enough trouble with it. But the wire chiefs of the Bell telephone have charge of as much wire as would make TWO HUNDRED MILLION CLOTHES-LINES - ten apiece to every family in the United States; and these lines are not punctuated with clothespins, but with the most delicate of electrical instruments.

The wire chiefs must detect trouble under a thousand disguises. Perhaps a small boy has thrown a snake across the wires or driven a nail into a cable. Perhaps some self-reliant citizen has moved his own telephone from one room to another. Perhaps a sudden rainstorm has splashed its fatal moisture upon an unwiped joint. Or perhaps a submarine cable has been sat upon by the Lusitania and flattened to death. But no matter what the trouble, a telephone system cannot be stopped for repairs. It cannot be picked up and put into a dry-dock. It must be repaired or improved by a sort of vivisection while it is working. It is an interlocking unit, a living, conscious being, half human and half machine; and an injury in any one place may cause a pain or sickness to its whole vast body.

And just as the particles of a human body change every six or seven years, without disturb- ing the body, so the particles of our telephone systems have changed repeatedly without any interruption of traffic. The constant flood of new inventions has necessitated several complete rebuildings. Little or nothing has ever been allowed to wear out. The New York system was rebuilt three times in sixteen years; and many a costly switchboard has gone to the scrap- heap at three or four years of age. What with repairs and inventions and new construction, the various Bell companies have spent at least $425,000,000 in the first ten years of the twentieth century, without hindering for a day the ceaseless torrent of electrical conversation.

The crowning glory of a telephone system of to-day is not so much the simple telephone itself, nor the maze and mileage of its cables, but rather the wonderful mechanism of the Switchboard. This is the part that will always remain mysterious to the public. It is seldom seen, and it remains as great a mystery to those who have seen it as to those who have not. Explanations of it are futile. As well might any one expect to learn Sanscrit in half an hour as to understand a switchboard by making a tour of investigation around it. It is not like anything else that either man or Nature has ever made. It defies all metaphors and comparisons. It cannot be shown by photography, not even in moving-pictures, because so much of it is concealed inside its wooden body. And few people, if any, are initiated into its inner mysteries except those who belong to its own cortege of inventors and attendants.

A telephone switchboard is a pyramid of inventions. If it is full-grown, it may have two million parts. It may be lit with fifteen thousand tiny electric lamps and nerved with as much wire as would reach from New York to Berlin. It may cost as much as a thousand pianos or as much as three square miles of farms in Indiana. The ten thousand wire hairs of its head are not only numbered, but enswathed in silk, and combed out in so marvellous a way that any one of them can in a flash be linked to any other. Such hair-dressing! Such puffs and braids and ringlet relays! Whoever would learn the utmost that may be done with copper hairs of Titian red, must study the fantastic coiffure of a telephone Switchboard.

If there were no switchboard, there would still be telephones, but not a telephone system. To connect five thousand people by telephone requires five thousand wires when the wires run to a switchboard; but without a switchboard there would have to be 12,497,500 wires - 4,999 to every telephone. As well might there be a nerve-system without a brain, as a telephone system without a switchboard. If there had been at first two separate companies, one owning the telephone and the other the switchboard, neither could have done the business.