PRODUCED IN GASES BY ROXTGEN RAYS. 20!) 
the ions make the lower end of the curve approach the axis at a less rapid rate. It 
vas also shown that the point on the axis of abscissas, obtained by prolonging the 
straight portion of the curve, would correspond to the voltage required to make an 
/ 
/ 
: 
r 
I 
/ 
: 
F 
/ 
L 
/ 
— 
/f 
A 
1/ 
/ 
V 
t 
/ 
/ 
/ 
/ 
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ZQ 18 16 /4 IZ 10 - 6 5 4 
Vottage in ceU,8. 
Fig. 5. 
140 
120 
.o 
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too <U 
si 
80 K 
<0 
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60 
5 
Vi 
O 
40 CD 
20 
0 
ion, starting from the surface of the outer cylinder in the middle of the beam of rays, 
just reach the middle of the juncture in the inner cylinder. But with diffusion and 
the other causes acting to produce a spreading of the ions, it is evident that the 
inclination of the straight part itself is affected and the result changed. Corrections 
for this error can only be made in conjunction with those of some other effects, and 
that by experiment, by producing alterations in the amount of these effects, by 
changes in the time of passage of the ions across the space between the cylinders. 
The velocity obtained by the use of the voltage determined by the continuation of 
the straight part of the curve, as shown in the figure, will lie called the ionic velocity 
for that determination, it being understood that it is not implied thereby that the 
velocity changes with the time, but that this is only a step towards the final result. 
From the above curve, A is seen to be 177 cells, which is equal to 377 volts. 
Using equation (9), 
\b*-a\ 51 U 25-2 
v ~ | 2 a\ AX — ^ 2-60 x 377 = centims. per second. 
The pressure in the apparatus is 76 centims. of mercury 
YOL. CXCY.—A. 2 E 
