48 Prof. C Barus on the Absorption of the 



an equation from which the value of k, the absorption velocity 

 of the nucleus, is computed at once in centim./sec, supposing 

 decay (k f ) to be a vanishing quantity. 



Waiving the more refined methods of the kinetic theory of 

 gases, if but ^ of all the nuclei wander in a given direction, 

 the term expressing absorption of the wall of the tube in the 

 differential equation would be kinltyZirrdx, or k/S replaces k. 

 Hence the data in the above tables should be increased three- 

 fold to meet this point of view, as stated in the first paragraph 

 of this paper. 



The value of k is given for each series in the tables, com- 

 puted from three points of the observational data corresponding 

 to x = and the maximum and mean lengths. It will be 

 noticed that V =*60 litre/min. is nearly the same for all the 

 absorption-tubes, as it should be for initially saturated air, and 

 has been so taken. From the value of k found for each tube 

 I then computed the corresponding curves, these being given 

 in the last columns of Table I. The computed curves are 

 constructed in the chart to show the distribution of the obser- 

 vation with respect to them. The agreement is throughout 

 surprisingly good ; it would be impossible to get a better 

 interpretation of the observations in view of the difficulty of 

 colour experiments. If we compare the nuclear velocities k 

 with the radii of the absorption-tubes, with which they were 

 obtained, we find that they vary for the wide tubes (grey 

 rubber and lead) as much as for the narrower tubes (lead, 

 pure rubber, and glass). Hence k must be regarded as- 

 independent of r ; and the variations found are observational 

 errors. 



I conclude, therefore, that the proposition which considers 

 decay (&') to be relatively negligible and the absorption 

 effect of the tubes of velocity k, or an ionic velocity 3k r 

 to be real, is one of great probability. The whole ionized 

 region is under volume expanding stress, much like an osmotic 

 pressure. 



6. The case of the wide tubes of tin plate (2r = 5 cms.) is 

 different in character ; for here the different lengths corre- 

 spond to different initial densities n and n' , while the radius 

 of the tube and the velocity of the air-current are the same. 

 One may assume that the initial densities are to each other as 

 the litres per minute (V) of air saturated with phosphorus 

 emanation put into the tube at distances x and x' from the 

 jet. Thus 



na/»'o = V/W, 

 and therefore 



k = (rv/2{x-^))log{Y/Y r ). 



