But further inquiry into the cause of the frequent disasters revealed the fact that when the burner of a lamp was constructed so that the air for combustion was supplied after the gas issued from the jet, there was no danger of explosion. And as lamps carefully constructed on this principle replaced the early ones of faulty construction, confidence in acetylene was restored. Methods were devised for supplying the gas for house-illumination like ordinary gas, and the occupants of country houses were afforded a means of lighting their houses on a scale of brilliancy hitherto unapproached, yet with economy and relative safety.
It was found also that the brilliancy of the acetylene flame was of such intensity that it could be used, like the electric arc light, as a search-light. It thus furnished a simple means of supplying small boats and vehicles with such lights, which they could not otherwise have had. It also supplied army signal-corps with an apparatus for flashing messages—an apparatus that was ideal on account of its simplicity and small size.
At the Pan-American Exhibition at Buffalo the various illuminating exhibits were among the most conspicuous and attractive features. But even amid the dazzling electrical displays the Acetylene Building was a noteworthy object. "It was the most brilliantly and beautifully lighted building in the grounds," declared one observer. "It sparkled like a diamond, and was the admiration of all visitors. In it were generators of all types—most of them supplying the gas for their own exhibits—several being the latest exponents of the art, so simple that they can be safely managed by unskilled labor; in fact, 'the brains are in the machines,' and when the attendant has charged them with carbide and filled them with water—given them food and drink—they will work steadily until they need another meal." Indeed, these exhibits at the Pan-American Exhibition demonstrated conclusively that acetylene gas occupies a field by itself as a practical illuminant.
At the same exposition a standard was established for good stationary acetylene generators for house-lighting, and the fact that a large number of generators fulfilled the requirements of the set of rules laid down showed how thoroughly the problem of handling this gas has been solved. Some of these rules used as tests are instructive to anyone interested in the subject, and a few of them are given here. They specified, for example, that—
"The carbide should be dropped into the water," the reverse process of letting the water drip on the carbide, as was done in most of the early generators, being condemned. "There must be no possibility of mixing air with the acetylene gas. Construction must be such that an addition to the charge of carbide can be made at any time without affecting the lights. Generators must be entirely automatic in their action—that is to say: after a generator has been charged, it must need no further attention until the carbide has been entirely exhausted. The various operations of discharging the refuse, filling with fresh water, charging with carbide, and starting the generator must be so simple that the generator can be tended by an unskilled workman without danger of accident. When the lights are out, the generation of gas should cease. The carbide should be fed automatically into the water in proportion to the gas consumed."
Perhaps the most significant thing, showing the stage of progress that has been made in overcoming the danger of explosions from acetylene gas, is that the use of generators meeting some such requirements as the above is not prohibited by fire underwriters. This in itself is very convincing evidence of their safety.
THE TRIUMPH OF ELECTRICITY
Throughout the ages primitive man had had constantly before him two sources of light other than that of the sun, moon, and stars. One of these, the fire of ordinary combustion, he could understand and utilize; the other, more powerful and more terrible, which flashed across the heavens at times, he could not even vaguely understand, and, naturally, did not attempt to utilize. But early in the seventeenth century some scientific discoveries were made which, although their destination was not even imagined at the time, pointed the way that eventually led to man's imitating in the most striking manner Nature's electrical illumination.
About this time Otto von Guericke, the burgomaster-philosopher of Magdeburg, in the course of his numerous experiments, had discovered some of the properties of electricity, by rubbing a sulphur ball, and among other things had noticed that when the ball was rubbed in a darkened room, a faint glow of light was produced. He was aware, also, that in some way this was connected with the generation of electricity, but in what manner he had no conception. In the opening years of the following century Francis Hauksbee obtained somewhat similar results with glass globes and tubes, and made several important discoveries as to the properties of electricity that stimulated an interest in the subject among the philosophers of the time. Gray in England, and Dufay in France, who became enthusiastic workers in the field, soon established important facts regarding conduction and insulation, and by the middle of the eighteenth century the production of an electric spark had become a commonplace demonstration.
But until this time it had not been demonstrated that this electric spark was actual fire, although there was no disputing the fact that it produced light. In 1744, however, this point was settled definitely by the German, Christian Friedrich Ludolff, who projected a spark from a rubbed glass rod upon the surface of a bowl of ether, causing the liquid to burst into flame. A few years later Benjamin Franklin demonstrated with his kite and key that lightning is a manifestation of electricity.