274 MR. J. S. TOWNSEND ON THE DIFFUSION OF IONS PRODUCED IN AIR 
Table XIII.—Positive Ions in Moist Air. 
Expt. 
H. 
ni. 
n- 2 . 
V. 
K. 
1 
765 
44T 
74-7 
318 
•0277 
2 
750 
71-0 
112 
396 
•0291 
3 
750 
60 
100 
323 
*0271 
Experiment 1.—Made with a steel point in the tube It, the point being at the 
aperture in A. 
Experiment. 2 .—Made with a platinum point in the tube Q (in order to get larger 
deflections). 
Experiment 3.—Steel point in tube Q 3 centims. from the aperture in A. 
The effect of drawing the point up the tube has not so much effect in this case as 
when the air is dry. 
Table XIV.—Negative Ions in Moist Air. 
o 
Expt. 
H. 
7lo. 
V. 
K. 
1 
774 
56-4 
113-6 
321 
•0395 
9 
Zj 
750 
66-7 
121-5 
396 
•0399 
3 
774 
45-8 
97-4 
321 
*0376 
These three experiments were made with the discharge from the wire in the side 
tube Q. In Experiments 1 and 2 the point was at the centre of the aperture in A, 
steel and platinum points being used in the two cases respectively. The third 
experiment was made with a steel point drawn up the tube Q 2 centims. from the 
aperture in the tube A. 
Considering the experiments made with the point at the junction of Q and A, it 
will be seen that the electrification (nJY in arbitrary units) is greatest for those ions 
which move the slowest. This a rises partly on account of the loss of charge in the 
tube A before the gas reaches the tubes T. If equal electrifications were produced 
at the source, we would expect less of the small ions than of the large ions to reach 
the tubes T with the gas. 
