of Hydrogen Positive Bays. 565 



17or the pressures used we find the following values : — 



Pressure. A. _ . 



0035 ::im, 0*39 cm. 0050 



0'056 „ 0-245 „ 0-049 



0-10 „ 0-135,, 0043 



Probably the mean distance between successive light- 

 remissions will be somewhat greater than " the mean free 

 path " of the molecules in the observation chamber, and 



the true values of" T somewhat greater than those here 



given. 



The question with regard to the origin of the emission of 

 light from a bundle of positive rays has been the subject 

 of much discussion. In a number of papers jfltark has tried 

 i;o prove that the moved intensity is produced by the positive 

 ions, while Wien found that certain of his experiments were 

 best explained by the assumption that the moved intensity 

 came from the neutral part of the bundle. 



The results of my experiments, as I have stated in my 

 previous papers, have so far confirmed Wien's assumption, 

 as, at any rate, the greater part of the moved intensity comes 

 from the neutral ray. But, as we have already remarked, 

 we ought to distinguish between the emission produced by 

 the neutral ray on account of collisions with gas molecules 

 -and the emission due to neutralization of the positively 

 charged carriers, and the last part will in so far be an effect 

 x)f the positive rays as it will be removed when the positively 

 charged rays are removed from the field of view. 



In this connexion I should like to mention another result 

 of my experiments with the same arrangement, which is 

 hard to understand without assuming that the positive 

 carriers through the neutralization process are engaged in 

 the emission of moved intensity. It teas found that the ratio 

 between moved and unmoved intensity ivas not changed by the 

 effect of the magnetic field, or the changes were inside the 

 limits of possible errors. 



As before, the moved intensity without a magnetic field is 

 given by an expression of the form : 



lo = {k 1 n 1 + k 2 n 2 )e- tKl ; 

 and the unmoved intensity J : 



J = (qin 1 + q 2 n i )e~ [t ' l ' } 

 Phil. Mag. S. 6. Vol. 41. No. 244. April 1921. 2 P 



