BY THE ACTION OF A RADIO-ACTIVE SUBSTANCE, ETC. 
273 
Experiment 1 . —Made with steel point in the tube Q, the point being at the 
aperture in the tube A. 
Experiments 2 and 3.—Made under same conditions as experiment 1, except that 
the tube Ii was used in order that the gas should have a smaller electrification 
when it reaches the tube T. 
Experiment 4.—Same as experiments 2 and 3, with a platinum point substituted 
for the steel point. 
Experiment 5.-—The point was held in the tube A in the position shown in fig. 5. 
Experiment 6.—Same as experiment 1, except that the point was drawn up the 
side tube Q 5 centims. from the aperture in A. 
Experiments 1 and 5 are the only ones in which the effect of self-repulsion may 
contribute appreciably to the loss of ions in the tube T 1; so that the values of K 
deduced from these experiments may be a little too big. 
The difference of about 5 per cent, which occurs between the values obtained in 
experiments I and 5 and the values obtained in experiments 2, 3, and 4, is probably 
due to this effect and not to any difference in the ions. 
The ions which get into the stream of air in A from a point some distance up the 
side tube are larger than the others, as Experiment 6 shows that they diffuse more 
slowly. 
Table XII.—Negative Ions in Dry Air. 
Expt. 
H. 
n x . 
no,. 
V. 
K. 
1 
768 
72 
138 
337 
•0382 
2 
766 
86-2 
165 
326 
•0367 
3 
758 
78-5 
150 
323 
•0368 
4 
767 
91-2 
160 
342 
•0324 
Experiment 1 . —Made with a steel point in the tube Q, the point being at the 
aperture in the tube A. 
Experiment 2.—Same as Experiment 1, with a platinum point substituted for the 
steel needle. 
Experiment 3.—The point was held in the tube A, as shown in fig. 5. 
Experiment 4.—Same as Experiment 1, except that the point was drawn up the 
tube Q 2 centims. from the aperture in A. 
The first three experiments give practically the same values for the coefficient of 
diffusion, but the fourth experiment shows that larger ions aie produced when the 
point discharge takes place in the narrow tube Q. 
VOL. CXCV.—A. 2 N 
