Conduction of electricity through gases

Cathode rays consists of streams of negatively charged particles moving in a straight line, but capable of being acted upon and deflected by both magnetic and electric fields, and when so deflected for collection they give on collection a negative charge to an electrometer. If a stream of these negatively charged particles, each bearing a charge c and having a mass m be acted upon by a magnetic field H and an electric field E at right angles to each other, we may get with the magnetic field alone a force