IOWA ACADEMY OF SCIENCES. 
31 
Test No. 2: — The nomber of grams to separate the disk 
from water at 7^,0. 
Trial 1:— 48.710. 
Trial 2:-~48.715. 
Trial 3:— 48.725. 
Trial 4:— 48.730. 
Average. .48.720. 
Test No. 3: — The number of grams to separate the disk 
from water at 7^,0. 
Trial 1 :— 48.630. 
Trial 2:-48.640. 
Trial 3:--48.6S5. 
Trial 4:~48.675. 
Average. .48.650. 
The diameter of the disk being 10.6898 c.m., the radius 
being 5.3449 c.m., the area is 89.7200 sq. c.m. In the 
first test given above it required 0.5431 g. to separate one 
square c.m. of water. In the second, 0.5430 g. and in the 
third, 0.5421 g. The average of the three tests is 0.5427 g. 
per square c.m. which is equal to 531.846 dynes per square ' 
c.m. 
In the same way tests were made upon ninety-five per 
cent alcohol — specific density 0.8169. In five independent 
tests the following number of grams were required to sep- 
arate the disk from the alcohol: 24.63, 24.64, 24.65, 24.65, 
24.80; making an average of 24.674 grams. This makes 
0.275 g. per square c.m. or 269.500 dynes per square c. m. 
In comparing these results with those of Gay-Lussac, we find 
that he used a disk which was 11.86 c.m. in diameter, and 
that it required 59.40 g. to separate the disk from water, 
and 31.08 g. to separate it from alcohol with specific den- 
sity of 0.8196. This is 526.875 dynes per square c.m. for 
water, and 275.693 dynes for alcohol. By a careful obser- 
vation of the above data it will be seen that, up to a cer- 
tain limit, the cohesion increases upon standing. At present 
I see but two reasons for this. First, in case of solutions 
