540 
ME. 0. W. EICHARDSON ON THE ELECTRICAL CONDUCTIVITY 
A further series of current measurements was made, using the quadrant electro¬ 
meter, in order to investigate the leak at somewhat lower temperatures. It was also 
thought desirable to measure the currents under a given voltage in each of the two 
possible directions and to see if there was any relation between them. The experi¬ 
ments also served to test whether the current temperature curve, obtained when the 
tube was cooling, followed the same path as that obtained with rising temperature. 
It was scarcely to be expected that the two curves would coincide, even approximately, 
owing to the continual distillation of the sodium from the hotter parts of the tube to 
the cooler. 
The results of the experiments are given in the accompanying table. In making 
the observations readings were generally taken with the wire electrode alternately 
positive and negative, a potential of 84 volts being used. In taking each reading the 
capacity w*as adjusted so as to give a convenient rate of movement of the electrometer 
spot. It was attempted to take corresponding j^ositive and negative readings at as 
near the same temperature as possible, the gas furnace being adjusted after each pair 
of readings had been taken. The pressure in the apparatus varied from "25 to ’4 
miUim. 
Volts on wire = -1-84. 
Yolts on wire = - 84. 
Volts on wire = 4-84. 
Volts on wire = - 84. 
Tempera- 
Current 
Tempera- 
Current 
Tempera- 
Current 
Tempera- 
Current 
ture 
1 = ampere 
ture 
1 = ampere 
ture 
1 = ampere 
ture 
1 = ampere 
Centigrade. 
X 10-A 
Centigrade. 
X 10-12. 
Centigrade. 
X 10-12. 
Centigrade. 
X 10“i2. 
o 
10 
2-4 
o 
10 
2 • 2 
o 
306 
3-24X101 
o 
92-5 
23-4 
92 
6-65 
325 
2-12 X103 
323 
890 
104 
31-6 
97 
6-3 
340 
3-66 X103 
338 
1 -01X101 
131 
247 
— 
— 
340 
ll-4x 103 
340 
3-26 X101 
141 
318 
_ 
— 
311 
1-96 X 103 
314 
7-1X103 
146 
352 
145 
16-4 
289 
3-66X101 
290 
228 
183 
1210 
182 
49-6 
241 
2-7 X103 
242 
14-6 
202 ■ 
2-26 X103 
204 
76 
226 
372 
228 
20-2 
235 
5-12 X103 
237 
161 
195 
27 
197-5 
4-4 
270 
8-3 X103 
272 
373 
123-5 
8-7 
— 
— 
296 
3-3x 10^ 
296 
733 
The meaning of these numbers is best expressed graphically. In fig. 22 the 
logarithm of the current has been plotted against the temperature. The unit of 
current is ampere. Curves 1 and 2 were taken with the wire charged 
positively, 3 and 4 with the wire charged negatively. The observations for curves 1 
and 3 were made simultaneously with the temperature of the tube rising, whereas 
the curves 2 and 4 correspond to the second set of observations with the temperature 
falling. 
The various marks refer to observational points for the different curves as 
follows:—Oto No. 1, * to No. 2, ©to No. 3, and • to No. 4. 
