204 Mr. M. Ishino on Velocity of Secondary Cathode Rays 



§ 2. Apparatus. 



The final apparatus used is indicated in fig. 1. The primary 

 cathode rays are produced in an exhausted glass discharge- 

 bulb D by means of an induction-coil. The high-speed 



Fi ff . 1. 



To Electrometer 







feifeJL/ 



a' ~ R f=> » m ' _ 



cathode rays are allowed to pass into an ionization-chamber 

 connected to the discharge-bulb by a narrow aluminium 

 tube F of diameter 0'4 mm. The primary rays ionize the 

 residual gas in C, and the gas molecules emit the secondary 

 cathode rays. 



To determine the intensities and velocities of the secondary 

 rays, the method of retarding electric field due to Lenard * 

 was used. Three concentric gauze cylinders of fine brass 

 wire, Vj, V 2 , and V 3 , are supported by two pieces of ebonite, 

 P P, around the path of the primary rays. The gauzes are 

 connected to secondary cells and can be raised to any 

 potentials. A tubular brass electrode E is situated outside 

 the gauzes and concentrically with them. The charge on 

 those corpuscles which arrived at this electrode is measured 

 by means of a Dolezalek electrometer. A stout brass wire, 

 insulated from the ionization-chamber with a piece of amber 

 M, holds the electrode E, and the amber is protected by an 

 earthed guard-tube. 



The ionization-chamber is 8 cm. long and 8 cm. in 

 diameter. The innermost gauze is 1*6 cm. in diameter. 

 The distances between the successive gauzes and that between 

 the outermost gauze and the electrode are 3 mm. T is a 

 Faraday cylinder with one end fitted to the ionization- 

 chamber. The other end of T is closed by a glass window W 

 * Lenard, Ann. d. Phys. viii. p. 188 (1902). 



