XLIV. On the velocity and mass of the ions in the electric wind in air

I T is a generally accepted theory of what happens when a sharp point discharges electricity through a non-conducting gas onto a smooth metal plate, that the strong field at the point dissociates the gas into + and --ions, and that a oneway flow of the ions of like sign to the point thereupon ensues from point to plate.Rutherford (Phil Mag.Nov. 1897) has measm'ed the velocity of ions dissociated in gases by R5ntgen and by uranium rays, and finds that for air the stun of the + and -velocities in a field of one volt per centimetre is 3'2 centimetres per second.Zeleny (Phil.Mag.July 1898) has since shown that the ratio of the velocity of the negative to that of the positive ions in the same field is 1"25 for air.One object of the present paper is to show that the ions dissociated at a sharp point in air are probably identical with those sludied by Rutherford and Zeleny.Theo~ of the M/etlwd.Let B, fig. 1, be a sharp positively electrified metal point in a non-conducting gas, opposite and at distance z from an * Communicated.by .the