ELECTRICAL EXPERIMENTS.

Professor John T. Trowbridge has in the last two years placed the study of electricity at Harvard in advance of any other college, by means of a powerful apparatus set up in the Jefferson Physical Laboratory. This battery, then the strongest in the world, was able to produce sparks in air three feet long.

Now Professor Trowbridge has just completed another still more powerful apparatus for the study of electrical force It is capable of producing sparks in air, resembling lightning flashes, of from six to seven feet in length. The discharge creates a sensation as if a window had suddenly been opened letting in a gust of wind, and sparks can be drawn from the brick walls of the room. Sparks closely resembling lightning discharges can be obtained thirty and forty feet in length through glass tubes in which the atmospheric pressure has been reduced to about two pounds and a half to the square inch.

It has been found by experiment with this apparatus that air submitted to an electrical pressure of over two million volts becomes a fairly good conductor. In order to insulate the apparatus, it is placed three feet above the floor, and even in this position, luminous discharges from the apparatus to the floor and the room is darkened.

The apparatus permits of the exploration of a field of great force which has not hitherto been attacked, and it is hoped that very important discoveries will soon be made.