212 
ME. J. ZELENY OX THE VELOCITY OF THE IOXS 
The results are represented in fig. 6, where the velocities are represented as 
ordinates and the corresponding values of T as abscissas. It is seen that the 
velocities decrease with T, and nearly in a linear manner. Considerable variations 
are observed among the individual results, but it is believed that they are not 
greater than is to be expected from the nature and difficulties of the experiments. 
In § 4 it was seen that some of the corrections which act to give too small a value 
for the velocity diminish with T and disappear for T = 0. By drawing lines through 
the points in fig. 6 and prolonging them to the axis of ordinates where T = 0, we 
obtain the most probable values of the velocities. This gives for the negative ions 
1*48 centims. per second, and for the positive ions 1’34 centims. per second. 
In § 4 (15) it was stated that a correction of 2 per cent, would be made for dis¬ 
turbances not corrected by the above method. This gives for the final results for 
moist air the velocity in an electric field of 1 volt per centim. for the negative 
ions = 1*51 centims. per second, and for the positive ions = 1'37 centims. per second 
at a temperature of about 14° C., and a pressure of 76 centims. of mercury. 
§ 8. Dry Air. 
The following set of readings was taken for the positive ions in dry air 
Temperature = 13*8° C. X = 2TO centims. Barometer = 76 T centims. 
Excess pressure in gasometer = 1 - 6 centims. of mercury. 
,, ,, apparatus = *45 ,, ,, 
14 cells — 29’0 volts. 
Table IV.-—Dry Air. Positive Ions. 
Voltage of outer 
cylinder. 
Electrometer deflection 
in 30 seconds. 
Descent of gasometer 
in 40 seconds. 
Cells. 
Divisions 
1 
Centims. 
+ 8 
117 
4-29 
+ 10 
60 
4-28 
+ 12 
22 
4-26 
+ 14 
7 
4-26 
+ 11 
40 
4-22 
+ 9 
94 
4-25 
+ 7 
153 
4-25 
+ 10 
62 
4-21 
+ 8 
123 
4-23 
These results are represented graphically in Curve I. of fig. 7. 
The corrected value of U is 15‘9 centims. per second. 
A = 24‘8 volts. 
15-9 
— = 1*26 centims. per second, and when reduced to 
S °*= 5118 2-60 x 24-8 
76 centims. pressure this becomes 1*27 centims. per second. 
T = — TG second. 
15‘9 
