ABSTRACT
The general action of ultra-violet light on the discharge of electrification has been investigated by many different experimenters. In order to obtain a discharge with ultra-violet light, the light must fall on a negatively electrified surface. There is no discharge produced by allowing the light to fall between two plates without impinging on either. In this respect the action of ultra-violet light is very different to Rontgen and uranium radiation, which produce a volume ionization of the gas through which they pass. The results obtained in this chapter seem to show that the gas near the surface of the negatively electrified plate is ionized under the action of ultraviolet light. The positive ion gives up its charge to the plate and the negative ion is repelled from the plate. According to the kinetic theory of gases the velocity of a charged particle of molecular dimensions varies inversely as the pressure.
