X-Ray Apparatus.

For the past two years, Professor Trowbridge, director of the Jefferson Physical Laboratory, has been perfecting a battery for electrical discharges. It is now the most powerful apparatus of its kind in the world, and has already been used in several investigations of the x-ray. It is the only battery strong enough to send a discharge through an x-ray tube; all other batteries send the spark around the tube. It has been used repeatedly to show the skeleton of the hand. An idea of its power can be had from the fact that it has a voltage of 1,200,000, and the voltage required to run an electric car is only 500. This instrument can evolve a spark fifty inches in length and in doing so gives a loud report like lightning.

Professor Trowbridge has lately been able to prove by this apparatus that the length of the spark is accurately proportional to the voltage. This fact, which has long been doubted by various German scientists, can be used to ascertain the voltage required to send a flash of lightning a given distance.

Professor Trowbridge expects to exhibit this apparatus at a meeting of the National Academy of Sciences today at the Laboratory.