Tesla's Vacuum Tube Light - The Inventor Encouraged by the Progress of His Work

Mr. Tesla, who has been striving for years to produce an electric light without heat, feels that he is making perceptible headway in that work. As The Tribune has indicated before his general plan is to employ an, alternating current of almost inconceivably great frequency, and a lamp consisting. of a vacuum, tube. The alternations are secured by an instrument of his own invention, known as the oscillator.

But after Mr. Tesla entered upon his interesting. line of experiment he encountered various unforeseen difficulties. While he was able to obtain a. beautiful light almost at the outset, it was at the expense of more energy than was desirable. In other words, he did not have his invention on a thoroughly satisfactory basis. By degrees he has improved the efficiency of his apparatus, so that his light is now more economical than it was, and he regards it as superior to both the incandescent and arc lights in this respect. At present, however, he is unwilling to indicate precisely the nature and degree of the technical advances made, or to use figures in comparing its economy with that of its rivals. One reason for reticence on the latter point may be a recognition of the possibility of further improvement. Mr. Tesla frankly declares that his lamp is not yet perfect. It does not make as good a return in light for the electrical energy invested as he would like. All that he insists upon is that it is now so efficient that he can conscientiously recommend it to those who may wish to put it on the market.

In some of his earlier experiments Mr. Tesla used a straight vacuum tube fully an inch and a half in diameter and six or eight feet long. Latterly he has employed a much more slender one, and by putting it into a rather compact coll saves a great deal of space. A score of lamps of this sort, each with a porcelain reflector over it, might be suspended from the ceilings of rooms on the tenth floor of an office building, while the special apparatus which modified the current for their use would be down in the basement. The street mains would supply an ordinary alternating current, and other wires would lead from the oscillator up to the lamps. For some purposes two wires to each lamp would be preferable but for others one would suffice. Less copper would be required for inside wiring, and the risks from escaping current would be diminished, rather than increased. The present style of insulation would be more than sufficient.