544 On the Charge carried by Ions produced by Rontgen Rays. 



evident bearings on the theory of the ionization of gases pro- 

 duced by the Rontgen rays. 



In obtaining the above values certain assumptions have been 

 made to simplify the calculation which would have the effect of 

 making the value of e differ from the true value. Thus, for 

 example, we have assumed that the potential gradient is con- 

 stant between the plates. Prof. Zeleny has shown (Phil. Mag. 

 July 1898) that this is not strictly true ; the potential fall near 

 the plates is greater than the average, while that in the body of 

 the gas is less. Thus the potential gradient in the gas is less 

 than the difference of potential between the plates divided by 

 the distance between them, which is the value we took in the 

 preceding calculations. For the very much enfeebled rays 

 we used in these experiments the difference between the true 

 and the assumed value is so small that it did not seem worth 

 while making the elaborate experiments necessary to calculate 

 the correction, especially as the variations in the coil &c. 

 produced disturbing effects far greater than would result from 

 this cause. We have assumed, too, that all the ions produced 

 by the rays are brought down by the cloud ; if there were 

 any left behind then the value we have deduced for the 

 charge would be greater than the true value. The value we 

 have found for the charge on the ion produced by Rontgen 

 rays is greater than that usually given for tha charge on the 

 hydrogen atom in electrolysis. There seems, however, to be 

 no valid reason against the latter charge having as high a 

 value as that w r e have found. We get from the laws of 

 electrolysis, if e is the charge on the hydrogen ion in electro- 

 static units, N the number of molecules in 1 cub. centim. at 

 standard temperature and pressure, 



N*=129xl0 8 



(see Richarz, Bonn Sitzungsberichten, 1891, p. 23) ; if we 

 take £ = 6*5 x 10" l0 we get 



N=20xl0 18 , 



where N, deduced from experiments on the viscosity of air, is 

 21xl0 18 . Though the measurements of the coefficients of 

 viscosity of other gases give in general higher values of N, 

 yet the agreement between the value of N deduced from these 

 experiments and the value of N got by the Kinetic Theory of 

 Gases by viscosity experiments is sufficient to show that 

 that theory is consistent with the value we have found for e 

 being equal to, or at any rate of the same order as, the charge 

 carried by the hydrogen ion in electrolysis. 



In connexion with this result it is interesting to find 



