produced from a Gas by High-Speed Cathode Rays. 221 



Hence, if the moving corpuscle passes the stationary cor- 

 puscle at a distance d Y , which satisfies an equation 



the stationary corpuscle will be ejected with a velocity 

 corresponding to the energy q. The number of the corpuscles 

 ejected per centimetre of the paths of the moving corpuscles 

 will be proportional tod 2 . Therefore the ratio of the ejected 

 corpuscles, whose kinetic energy is not less than q, to the 

 total number of those ejected at the same time, is given by 

 the equation 



d Q 2 T—q 'q-rq ' 



Now, if T is very large compared with q and q, this ratio 

 is approximately equal to qjq+q . Again, if q is large 

 compared with q , this ratio becomes q /q = Cq~ 1 . 



The corrected currents in the Tables II. and IV. are the 

 quantities corresponding to q. It is seen that the values of 

 *' a " in the equations representing the experimental results 

 are nearly unity. The agreement between theory and ex- 

 periment is thus fairly good. 



Summary. 



The distribution of the velocities of the secondary cathode 

 rays emitted from air and hydrogen under the action of 

 high-speed cathode rays over the range 7000 volts to 15,000 

 volts has been studied. 



(I.) It was found that the corpuscles were emitted with 

 velocities varying from up to 1000 volts, but the great 

 majority of the corpuscles — about 90 per cent, of them — had 

 velocities less than 40 volts. 



(II.) The distribution of the velocities of the secondary 

 cathode rays appeared to be nearly independent of the 

 velocity of the primary cathode rays, and also approximately 

 the same for air and hydrogen. 



(III.) It was found that the distribution curve of velocity 

 can be expressed with an empirical formula y = C.?; -a over a 

 range of # = 40 to #=700 volts, where ;/ indicates the relative 

 number of the secondary cathode rays emitted with velocities 

 greater than x volts, and a is a constant differing slightly 

 from unity. This is in accordance with the theory of ioni- 

 zation given by Sir J. J. Thomson. 



(IV.) Some similarity between the secondary cathode 

 rays from a gas and from a metal was pointed out. 



