J. J. Hogan, the electrician in charge of the mechanical department of the Yale Psychological Laboratory has perfected an invention which may make quite a revolution in the electrical world. The device which Mr. Hogan has been at work on for some time and which he says has now been demonstrated to be a success, consists in a little apparatus which will reduce the voltage of an electric wire without interfering with the current. Just what is the mechanism by which this result is accomplished can not be announced for the present. It is claimed that it will entirely supplant the motor dynamos which are used in telegraph and telephone companies. The Edison machine now in use costs $100 and Mr. Hogan says that his is so simple that it can be made to sell at $5.00. Experts have expressed themselves as satisfied that the invention will be a success, and it will probably be used throughout the Yale Laboratory, although the apparatus which it will supplant has cost several hundred dollars.