ON THE THICKNESS AND SURFACE TENSION OF LIQUID FILMS. 
673 
effect of which may be neglected. When the cylindrical film was only partially 
black the theoretical sensitiveness can be calculated as in the last group of experi¬ 
ments. 
We give, as in the last group, all the experiments which were made in which a 
sufficient difference of thickness was established to make the comparison useful. 
Experiment XIV. 
The stop-cock was opened five minutes after the films had been made and flooded. 
No further flooding took place. At 9 m after communication had been established 
readings were begun. 
The colours of the sphere and cylinder are indicated by C, and C e , the difference 
between their diameters by 8. 
t 
c. 
a 
C 
1 
Mean. 
ID. 
9 
R (4, 5) 
Y (3, 5) 
17-60 
12 
G (4, 5) 
B (3, 7) 
17-82 
17-71 
We now omit a number of readings, the differences given by which were 
3=17-77, 17-67, 17*83, and 17*79. 
Afterwards the following observations were taken :— 
t 
C, 
Co 
t) 
m. 
21-5 
B (3, 0) 
{ 56, 
W(l, 9)1 
17-90 
24-5 
R (2, 5) 
{235, 
(?) } 
17-89 
The sudden formation of the black was in this experiment accompanied by no 
change in the value of 8, hence c/T=0. 
Experiment XV. 
At the beginning of the experiment the following measurements were made :— 
t 
o. 
c. 
c 
Mean. 
m. 
6 
Colourless 
Colourless 
20-36 
... 
ii 
G (5, 2) 
.. • V • - • . 
20*36 
20-36 
4 R 
MDCCCLXXXVr. 
