478 
PROFESSORS A. W. REINOLD AND A. W. RUCKER ON 
these defects, and on them our conclusions are based. All were made of the same 
liquid, which contained 5'05 per cent, of salt, and of which the specific resistance at 
20° was 140'5. 
The temperatures at which experiments were made varied only between 17°'5 and 
22°'5, and, in the first instance, the observations were arranged according- to the 
indications of the hygrometer. Thus, the specific resistances of all the films, during 
the experiments in which the hygrometer stood between 50 and 51, were calculated 
for a thickness equal or nearly equal to 9X10~ 5 centims., and the mean taken. All 
the other films were treated in the same way and the results tabulated. The value 
9X10 -5 centims. was chosen because nearly all the films were observed at that 
thickness. 
Table VI. 
Hygrometer. 
Number of films. 
Mean value of 
48-49 
1 
167-9 
49-50 
5 
161-6 
50-51 
8 
156 5 
51-52 
4 
153-7 
52-53 
54-55 
5 
145"7 
From this table we learn that on the average the specific resistance of the films was 
lower and nearer that of the liquid in mass, as the hygrometer stood higher. T his 
result had been anticipated. 
The method of moistening the air in the case was open to the objection that the air 
would probably be a little too dry. Water would evaporate from the blotting paper 
soaked with the liquid, and the air would therefore be in contact with surfaces 
moistened with a liquid containing a rather larger percentage of glycerine than the 
soap solution itself. A small tin tray was made to cover as large a part of the base of 
the chamber containing the film as was consistent with perfect insulation, and filled 
with soap solution. A surface of liquid, 52 square centims. in area, was thus exposed, 
and two films were observed with the air moistened with this alone, and without the 
blotting paper. 
With this arrangement the specific resistances were found to be very high and to 
rapidly increase, as shown below:— 
Specific resistance. 
Thickness. 
Film I. 
Film II. 
14 x 10 -5 centims. 
178-8 
169-4 
4 x 10~ 5 
201-6 
192-0 
