16 
COLORADO EXPERIMENT STATION. 
west of the College. The depth has varied from five to ten feet. This 
lake is free from weeds. 
Claymore lake is situated six miles northwest of the College 
and close to the ridge of Dakota sandstone which rises immediately 
from the water on the west side. The lake is a reservoir connected 
with the Pleasant Valley and Lake Canal. The ridge of sandstone 
to the west rises at an angle of about 20° and to the height of 400 
feet. This ridge interferes with the wind slightly, but because of 
the downward movement of most of the west winds, it lessens the 
evaporation very little, if any. This lake is the largest of the three 
on which observations were taken. The depth of water has varied 
from 6 to 15 feet. There have been few or no weeds observed, but 
floating plant life has been abundant. 
METHODS OF OBSERVATION. 
§22. The observations were made weekly in 1896 and semi- 
weekly in 1897. The distance to the surface of the water in the tank 
was measured by placing a rule across the top of the tank and meas- 
uring down to the surface of the water by a rule graduated to tenths 
of inches, a rule such as is used in rain gages being used. In order 
to eliminate the effect of tipping the tank when grasped by the ob- 
server, the readings were made at two opposite sides or at the center 
of the tank. The tanks were filled to two or three inches from the 
rim and evaporation allowed to proceed until the water had fallen 
to three to five inches, then again filled from the lake. The meas- 
urements cannot be considered as exact, but the error is nearly elim- 
inated in the differences. 
RAINFALL. 
§ 23. The rainfall as given in the table is that observed at the 
Agricultural College. The lakes are several miles distant. At times 
the rainfall is undoubtedly greater or less than that observed at the 
College. Gages were placed on the floats, but as they could be read 
only once or twice weekly, the rain record at the College, where the 
observations are made twice daily, is used instead. The greatest dif- 
ference is found on days of local thunder storms in Jul}^ and August, 
but in only a few cases is there any material difference. 
§ 24. The temperature of the surface of the water in the tank, 
of the surface of the lake, and of the bottom of the lake, was taken. 
To obtain the temperature at the lake bottom, a sampling instrument 
was used. This consisted of a brass cylinder with valves at top and 
bottom, arranged to open as the cylinder descended in the water, 
and open as it rose. By churning the instrument up and down in 
the water it was easy to fill it with a sample of water from any de- 
sired depth, and bringing the instrument rapidly to the surface, the 
temperature was immediately taken. It will be noticed that the 
