434 Prof. E. M. Wellisch : Experiments on 



also the correction for decay from the maximum value 3 we 

 will have the following relations : 



fG + k(l-p)Q = m.a (-160 volts) ; 



fG + kQ =m.b( volts); 



f&+pQ + k(l—p)Q = m.c ( + 160 volts). 



We deduce 



pQ = m. (c — a) ; 



/,_ b — & . 

 c—a 



G a -(l-p)b ^ 1±; 



The assumptions made in obtaining the above relations 

 may at first sight appear doubtful in their applicability ; 

 still they appear to be entirely justified by experience. The 

 separation of Q into pQ positive and (1— •p)Q neutral has 

 been justified repeatedly by the author in numerous 

 experiments. The separation of G and Q as far as diffusion 

 effects are concerned is merely an application of the un- 

 doubted principle that in diffusion processes we may treat 

 any large number of atoms chosen at random as a separate 

 gas to which the laws of diffusion may be applied. Finally, 

 there is the most important assumption that the activity in 

 the gas is entirely neutral. In order that this should be the 

 case it is necessary, as explained in the previous section, 

 that the experiments should be performed with small amounts 

 of emanation ; all the deposit particles in the gas appeared 

 to have lost their charge when the saturation current fell 

 below 10 ~ 9 ampere. The method of putting this point to 

 experimental test was to perform the three experiments with 

 various amounts of emanation in the testing vessel ; if a, £>, 

 and c remained in constant proportion over the series, this 

 was taken to imply the absence of any appreciable quantity 

 of charged gas activity, because it has already been shown 

 that the amount of charged activity decreased extremely 

 rapidly with decreasing amounts of emanation. The fact 

 that we are thus restricted to the use of small quantities of 

 emanation means of necessity an extremely small value for 

 the activity in the first experiment, in which the chief con- 

 tribution comes from the gas activity ; on this account every 

 precaution was taken in measuring the corresponding ioni- 

 zation current, the electrostatic shielding being made thorough 

 and the measuring vessel preserved carefully from radio- 

 active contamination. 



