10 BULLETIN 976, U. S. DEPAKTMEXT OF AGRICULTURE. 
WIND. 
Data on wind movement are shown in Table III; also data on 
temperature. The total wind movement is high for each month 
during the season in this 6-year period. The lowest total movement 
recorded in any month was 6,023 miles for July, 1914, and the highest, 
10,429 miles, or an average of 14.3 miles per hour, for June of the 
same year. Some days are calm and others are partly so. On other 
days the wmd reaches a very high velocity. A maximum velocity 
of 35 to 45 miles per hour is not uncommon. Such high wmds are 
often injurious to the grain-sorghum crops. They may cause damage 
by covering the young plants, by cutting them off with moving 
particles of soil, by whipping the half-grown plants into shi'eds, or 
by blowing down the crop when it is approaching maturity. 
EVAPORATION. 
A great quantity of moistiu-e is lost by evaporation at the Amarillo 
Cereal Field Station. The prime factors mfluencmg evaporation are 
precipitation, wind, temperature, and sunshine. The highest evapo- 
ration naturally occurs in periods of low precipitation, high tempera- 
tures, strong winds, and bright sunshine. 
Table IV shows the monthly precipitation and evaporation at the 
station during the six months from April to September in each year 
of the 7-year period from 1913 to 1919, inclusive. The evaporation 
measured is from the free water surface of a tank 8 feet in diameter. 
These data also are shown graphically in figure 4, where the enormous 
difference between the precipitation and evaporation may be noted 
at a glance. On the average during this period the evaporation was 
3.75 times as great as the precipitation. July has a higher rate of 
evaporation than any other month, averagmg 10.8 inches in this 
6-year period; August has an average of 9.3 inches. 
Table IV. — Monthly, seasonal, and 7-year monthly average precipitatio7i and evaporation 
at the Amarillo Cei'eal Field Station during the six months from April to September, 
inclusive, in the 7-year period from 1913 to 1919, inclusive. 
[Data (in inches) obtained at the Amarillo Cereal Field Station in cooperation Avith the Office of Biophysi- 
cal Investigations and the Office of Dry-Land Agriculture of the Bureau of Plant Industrj-, Ignited 
States Department of Agriculture.] 
Year. 
April. 
May. 
June. 
July. 
August. 
September. 
Seasonal 
total. 
Prec. 
Evap. 
Prec. 
Evap. 
Prec. 
Evap. 
Prec. 
Evap. 
Prec. 
Evap. 
Prec. 
Evap. 
Prec. 
Evap. 
1913 
1914 
1915 
1916 
1917 
1918 
1919 
Average 
1.7 
1.3 
4.8 
1.8 
.6 
. 5 
2.0 
7.7 
6.7 
4.6 
6.0 
7.7 
7.0 
6.8 
1.7 
3.8 
2.0 
.9 
2.8 
2.4 
2.0 
9.8 
6.7 
6.9 
10.3 
7.6 
11.0 
8.7 
2.3 
.7 
1.2 
2.7 
1.2 
3.5 
7.0 
10.1 
8.8 
10.7 
12.5 
10.1 
9.9 
1.4 
1.9 
3. 7 
1.2 
2.6 
2.7 
2.4 
12.7 
8.7 
9.3 
11. 7 
12.4 
10. 7 
10.3 
0.5 
2.5 
4.6 
3.4 
5. 5 
2.2 
3.4 
10.3 
8.9 
7.3 
10.2 
8.6 
10.3 
9.2 
5.6 
1.1 
4.9 
2.2 
2.1 
4. 7 
I'.O 
6.0 
li'o 
7.4 
7.2 
13.2 
11.3 
21.2 
12.2 
14. .3 
9. 7 
15. 4 
53.4 
49.1 
42.9 
56.6 
64.7 
56.6 
52. 9 
1.9 
6.6 
2.2 
8.7 
9.9 j 2.3 
10.8 
3,. 
9.3 
3.0 
6.9 
14.3 
.13.7 
