Edison's lighting work furnished an excellent basis—in fact, the only one—for the development of the alternating current now so generally employed in central-station work in America; and in the McGraw Electrical Directory of April, 1909, no fewer than 4164 stations out of 5780 reported its use. When the alternating current was introduced for practical purposes it was not needed for arc lighting, the circuit for which, from a single dynamo, would often be twenty or thirty miles in length, its current having a pressure of not less than five or six thousand volts. For some years it was not found feasible to operate motors on alternating-current circuits, and that reason was often urged against it seriously. It could not be used for electroplating or deposition, nor could it charge storage batteries, all of which are easily within the ability of the direct current. But when it came to be a question of lighting a scattered suburb, a group of dwellings on the outskirts, a remote country residence or a farm-house, the alternating current, in all elements save its danger, was and is ideal. Its thin wires can be carried cheaply over vast areas, and at each local point of consumption the transformer of size exactly proportioned to its local task takes the high-voltage transmission current and lowers its potential at a ratio of 20 or 40 to 1, for use in distribution and consumption circuits. This evolution has been quite distinct, with its own inventors like Gaulard and Gibbs and Stanley, but came subsequent to the work of supplying small, dense areas of population; the art thus growing from within, and using each new gain as a means for further achievement.
Nor was the effect of such great advances as those made by Edison limited to the electrical field. Every department of mechanics was stimulated and benefited to an extraordinary degree. Copper for the circuits was more highly refined than ever before to secure the best conductivity, and purity was insisted on in every kind of insulation. Edison was intolerant of sham and shoddy, and nothing would satisfy him that could not stand cross-examination by microscope, test-tube, and galvanometer. It was, perhaps, the steam-engine on which the deepest imprint for good was made, referred to already in the remarks of Mr. F. J. Sprague in the preceding chapter, but best illustrated in the perfection of the modern high-speed engine of the Armington & Sims type. Unless he could secure an engine of smoother running and more exactly governed and regulated than those available for his dynamo and lamp, Edison realized that he would find it almost impossible to give a steady light. He did not want his customers to count the heart-beats of the engine in the flicker of the lamp. Not a single engine was even within gunshot of the standard thus set up, but the emergency called forth its man in Gardiner C. Sims, a talented draughtsman and designer who had been engaged in locomotive construction and in the engineering department of the United States Navy. He may be quoted as to what happened: "The deep interest, financial and moral, and friendly backing I received from Mr. Edison, together with valuable suggestions, enabled me to bring out the engine; as I was quite alone in the world—poor—I had found a friend who knew what he wanted and explained it clearly. Mr. Edison was a leader far ahead of the time. He compelled the design of the successful engine.
"Our first engine compelled the inventing and making of a suitable engine indicator to indicate it—the Tabor. He obtained the desired speed and load with a friction brake; also regulator of speed; but waited for an indicator to verify it. Then again there was no known way to lubricate an engine for continuous running, and Mr. Edison informed me that as a marine engine started before the ship left New York and continued running until it reached its home port, so an engine for his purposes must produce light at all times. That was a poser to me, for a five-hours' run was about all that had been required up to that time.
"A day or two later Mr. Edison inquired: 'How far is it from here to Lawrence; it is a long walk, isn't it?' 'Yes, rather.' He said: 'Of course you will understand I meant without oil.' To say I was deeply perplexed does not express my feelings. We were at the machine works, Goerck Street. I started for the oil-room, when, about entering, I saw a small funnel lying on the floor. It had been stepped on and flattened. I took it up, and it had solved the engine-oiling problem—and my walk to Lawrence like a tramp actor's was off! The eccentric strap had a round glass oil-cup with a brass base that screwed into the strap. I took it off, and making a sketch, went to Dave Cunningham, having the funnel in my hand to illustrate what I wanted made. I requested him to make a sheet-brass oil-cup and solder it to the base I had. He did so. I then had a standard made to hold another oil-cup, so as to see and regulate the drop-feed. On this combination I obtained a patent which is now universally used."
It is needless to say that in due course the engine builders of the United States developed a variety of excellent prime movers for electric-light and power plants, and were grateful to the art from which such a stimulus came to their industry; but for many years one never saw an Edison installation without expecting to find one or more Armington & Sims high-speed engines part of it. Though the type has gone out of existence, like so many other things that are useful in their day and generation, it was once a very vital part of the art, and one more illustration of that intimate manner in which the advances in different fields of progress interact and co-operate.
Edison had installed his historic first great central-station system in New York on the multiple arc system covered by his feeder and main invention, which resulted in a notable saving in the cost of conductors as against a straight two-wire system throughout of the "tree" kind. He soon foresaw that still greater economy would be necessary for commercial success not alone for the larger territory opening, but for the compact districts of large cities. Being firmly convinced that there was a way out, he pushed aside a mass of other work, and settled down to this problem, with the result that on November 20, 1882, only two months after current had been sent out from Pearl Street, he executed an application for a patent covering what is now known as the "three-wire system." It has been universally recognized as one of the most valuable inventions in the history of the lighting art. [13] Its use resulted in a saving of over 60 per cent. of copper in conductors, figured on the most favorable basis previously known, inclusive of those calculated under his own feeder and main system. Such economy of outlay being effected in one of the heaviest items of expense in central-station construction, it was now made possible to establish plants in towns where the large investment would otherwise have been quite prohibitive. The invention is in universal use today, alike for direct and for alternating current, and as well in the equipment of large buildings as in the distribution system of the most extensive central-station networks. One cannot imagine the art without it.
[Footnote 13: For technical description and illustration of
this invention, see Appendix.]
The strong position held by the Edison system, under the strenuous competition that was already springing up, was enormously improved by the introduction of the three-wire system; and it gave an immediate impetus to incandescent lighting. Desiring to put this new system into practical use promptly, and receiving applications for licenses from all over the country, Edison selected Brockton, Massachusetts, and Sunbury, Pennsylvania, as the two towns for the trial. Of these two Brockton required the larger plant, but with the conductors placed underground. It was the first to complete its arrangements and close its contract. Mr. Henry Villard, it will be remembered, had married the daughter of Garrison, the famous abolitionist, and it was through his relationship with the Garrison family that Brockton came to have the honor of exemplifying so soon the principles of an entirely new art. Sunbury, however, was a much smaller installation, employed overhead conductors, and hence was the first to "cross the tape." It was specially suited for a trial plant also, in the early days when a yield of six or eight lamps to the horse-power was considered subject for congratulation. The town being situated in the coal region of Pennsylvania, good coal could then be obtained there at seventy-five cents a ton.
The Sunbury generating plant consisted of an Armington & Sims engine driving two small Edison dynamos having a total capacity of about four hundred lamps of 16 c.p. The indicating instruments were of the crudest construction, consisting of two voltmeters connected by "pressure wires" to the centre of electrical distribution. One ammeter, for measuring the quantity of current output, was interpolated in the "neutral bus" or third-wire return circuit to indicate when the load on the two machines was out of balance. The circuits were opened and closed by means of about half a dozen roughly made plug-switches. [14] The "bus-bars" to receive the current from the dynamos were made of No. 000 copper line wire, straightened out and fastened to the wooden sheathing of the station by iron staples without any presence to insulation. Commenting upon this Mr. W. S. Andrews, detailed from the central staff, says: "The interior winding of the Sunbury station, including the running of two three-wire feeders the entire length of the building from back to front, the wiring up of the dynamos and switchboard and all instruments, together with bus-bars, etc.—in fact, all labor and material used in the electrical wiring installation—amounted to the sum of $90. I received a rather sharp letter from the New York office expostulating for this EXTRAVAGANT EXPENDITURE, and stating that great economy must be observed in future!" The street conductors were of the overhead pole-line construction, and were installed by the construction company that had been organized by Edison to build and equip central stations. A special type of street pole had been devised by him for the three-wire system.
[Footnote 14: By reason of the experience gained at this
station through the use of these crude plug-switches, Mr.
Edison started a competition among a few of his assistants
to devise something better. The result was the invention of
a "breakdown" switch by Mr. W. S. Andrews, which was
accepted by Mr. Edison as the best of the devices suggested,
and was developed and used for a great many years
afterward.]