212 Mr. R. K. McClung on the Rate of 
rays or the volume of the gas ionized. These formulz are 
quite general, and are independent of any such consideration; 
and I cannot therefore see his point in regard to the shape 
of the beam of rays, or how it affects the question under 
consideration. 
Mr. Waiker takes the curves which I gave in my paper on 
r 
pp. 2938-295, and calculates from them values for Ne and also 
for a by different formule, and finds discordant results. I 
am not at all surprised that he does so. To make such a 
determination and criticism of any value it is necessary 
to ascertain what relation the experiments, from which 
these curves were obtained, bear to one another, and in 
how far the comparison of them is justifiable. As a matter 
of fact, the experiments described in my paper extended 
over a considerable time, and the curves given there were 
nearly all obtained at separate times. Each curve was ‘an 
entity in itself, and bore no special relation to any of the 
other curves. The electrometer used in these experi- 
ments was one whose sensitiveness varied from day to day. 
Each curve involved an entirely separate set of experi- 
ments made for the sole purpose of showing that at that 
particular pressure the law of recombination was represented 
by the formula : _ . =at. This was the only purpose for 
pati, ; 
which these curves were intended, and I think under the 
conditions the only legitimate one to which they may be put. 
No particular precautions were taken to keep such conditions 
as the sensibility of the electrometer the same in the different 
cases, nor were the experiments intended to be compared with 
one another. Consequently any comparison between the 
values of a obtained from the different curves is quite 
valueless, and no conclusion can be drawn from it. These 
remarks apply also to the values given in the tast column of 
Mr. Walker’s second table; for, although they were not 
obtained directly from the curves, they were derived from 
observations taken at the same time as the observations for 
the curves. 
In addition, these curves are quite unsuitable, especially at 
low pressures, for the purpose of making absolute determi- 
nations as Mr. Walker has done. Theoretically formulee (4) 
and (5) are all right, but in actual experiment they are quite 
unsuitable for making absolute determinations. The intensity 
of the rays is an important factor here. Mr. Walker says in 
his paper that he does not see how the intensity of the rays 
can affect the determination of a. He says: “If the theory, 
~ x. 
*e 
“i 
’ 
, 
