As Bright as Old Sol

Tesla Produces Vacuum Tubes Which Give a Most Powerful Light.

PHOTOGRAPHY BY NIGHT EASY.

This Discovery May Yet Be Utilized in the Illumination of Lighthouses.

Nikola Tesla announced another important discovery yesterday, the perfection of the phosphorescent vacuum tubes so that they may be employed wherever an illumination of the highest power is desired.

While his experiments with the improved tubes have been confined to showing their efficiency in photography, Tesla promises it will not be long before this lighting system will be practical wherever illumination is needed — in lighthouses, on sea-going vessels and as search-lights to penetrate the densest fogs.

With his improved vacuum tubes and oscillator Tesla can now produce a light almost as bright and strong as the hottest sun rays. This light has been employed at night in the taking of photographs, which have been pronounced by experts as examples not equalled by any taken by day under the most favorable circumstances.

One of these pictures is that of a man taken in a darkened room, with an exposure to a single vacuum tube of less than five seconds. Every wrinkles in the man's face is clearly shown and the hairs of the beard and mustache are as distinct as could be desired.

A remarkable example is a photograph of the palm of Tesla's hand. The smallest lines in the hand are so clear that they may be traced with a pencil. In taking the picture a portion of the inventor's sleeve was accidentally shown. The texture of the garment and the linen threads of his cuff are clearly pictured. The photograph was made by the light of a single tube of 1,000 candle-power at a distance of four feet, with an exposure of two seconds.

A third picture was that of an open book. The reproduction is so distinct that the print may be easily read without the aid of a glass.

"I expect soon," said Tesla, "to have the tubes so improved that with the use of only one I can photograph the largest building perfectly, on the very darkest night. This, though, is only the first step in my experiments.

"I am far from having obtained the limit in the amount of light producible. I believe this method of illumination will be employed eventually in Lighthouses, and that it imaging will be considered the oldest and most unlocked-for development."

In the taking of the photographs Tesla estimates the frequency of the oscillations, which were obtained from an Edison direct-current supply circuit, at about two millions a second. This great power consumption makes it impracticable at present for the tubes to supplant the incandescent light for ordinary illuminating purposes, for the consumption is about ten times greater in the tube. The reason for this Tesla explains in the fact that a vacuum tube offers an immense radiating surface, greater than ten times that of the incandescent light.

Tesla refused to discuss any of his further experiments, but it is likely his improved tubes will be tried in some of the neighboring lighthouses, where their practicality may be finally determined.