The Rate of Recombination of Ions in Gases. 207 
Tn the experiments N,; and N were measured. Itis further 
assumed that the saturation current gives a measure of Q. 
The absorption of the rays is neglected as small. 
From the measurements of Q and N, McClung concludes. 
that a as given by the formula (3) is independent of the. 
pressure from + atmosphere to 3 atmospheres. He-also con- 
cludes that Q is proportional to the pressure, the intensity of 
the rays remaining constant. Tf this is so, then N? should be 
proportional to the pressure, the intensity of the rays being 
constant, 
In testing the formula (1), it appears to me that he assumes 
the relation between N;, N, and ¢ to be of the same form as. (1). 
This, as I shall show, is not the case in his experiments. 
{+ would be true if the beam of rays were cylindrical. 
He does not think the measurements of N, N, and ¢ at 
different pressures can be relied on to find how a depends. on 
the pressure, urging that the intensity of the rays may vary 
between the experiments at difterent pressures. [am unable. 
to follow this argument. a@ is a property of the gas, and 
must be independent of the means by which the N ions are: 
produced. It is quite true that both Q and N depend on the 
intensity of the rays; but if the theory as proposed is correct, 
the values of a, whether obtained from (3) or from. the- 
relation between N; and N, must be the same, and guite- 
independent of the intensity of the rays, provided that the 
intensity is the same for any one determination of N and Q. 
We shall now establish the relation between N;, N, and t.. 
Using the same notation as McClung, we have 
Al 2 
aN? 
ee nts AG 
som Me nat 
and | d qo. 
N= — 
rn eae 
Hence the total number in the given conical volume after: 
a time ¢ is 
d a? 
nee ns A lit Mie, =) 
Pe. / l ] Peek d+ \ 
bet 5) (a+ 7) 
where p=aAt, 
and N=da/qox. 
