6 BULLETIN 430, U. S. DEPARTMENT OF AGRICULTURE. 
April is naturally much lower than that during the warmer months. 
In the only year in which a good crop was obtained, the precipitation 
was high and the evaporation low, making a ratio of 1:2. 
TaBLE II.— Monthly and total precipitation and evaporation from a free water surface 
at the Cheyenne Experiment Farm, Archer, Wyo., in the months of April to July, 
inclusive, for 1913, 1914, and 1915. 
{Data (in inches) obtained by the Office of Biophysical Investigations of the Bureau of Plant Industry, 
except as noted.] ; 
April. May. june. ee gels Total. 
| Ratio, 
| Pree 
% 4 i | itation 
Year. fipe Evap- ae Evap- ie Evap- | Ete-| Evap-| Pte | Evap-| to *, 
ora- ora- P ora- | PF |. ora Got ora- | evapo- 
ta- f ta- . ta- f ta- : ta- uD 
rice tion. tion tion Pen tion. tow tion Ata tion. | ration 
MON 3 ae Se Sa eee se @1.35 | 63.217 \a2.22 | 05.304 | 1.51 7.104 | 2.06 7.756 | 7.14 | 23.381 TER 47 
VON A ear cei arn eae 2.54 SOAR a4 Onion Odmmles Dl areolar ila 3 7.987 | 6.55 | 25. 581 1:3. 91 
TRCN is ee nd Naar 4.90] 38.160 | 1.78 4,701 | 1.88 DOD Mallon, 6. 638 ae 16 | 20.056 1:1. 97 
} 
a Datafrom United States Weather Bureau at Cheyenne, Wyo. b Interpolated. 
WIND. 
Wind velocities have been recorded at Cheyenne during a long series 
of years. The average wind velocity in miles per hour, by months, 
from April to July of each year, in the 16-year period from 1900 to 
1915, inclusive, is given in Table III. Strong winds are quite com- 
mon in southeastern Wyoming, and crops are damaged at times by 
the drifting soil. The highest velocities are recorded during the late 
falland winter months. April has the highest average hourly velocity 
for the months under discussion, 11.2 miles, and July the lowest, 8.5 
miles, perhour. The anemometer was located at a height of 64 feet 
above the ground. These readings, therefore, probably are higher 
than they would have been if the anemometer had been located just 
above the surface. Evaporation usually increases with wind velocity. 
In the winter months the snowfall is, as a rule, blown to the lower 
levels, leaving the winter crops exposed. For this reason winter- 
killing of fall-sown crops is common. : 
I a 
Tasie II].—Average wind velocity at Cheyenne, Wyo., by months, from April to July 
of each year, during the 16-year period, from 1900 to 1915, inclusive. 
[Data (in miles per hour) from the records of the United States Weather Bureau.] 
Year. April.| May. | June.| July. ee Year. April.| May. | June.| July. cue 
OOO ey setae cree Cas thw ees |) Ch s) QED LOO OE ee yee ee eternen. UE Aad ale SBOE Cy), SOA 
SSO VE ee Semel 10-1 }) 95,9) |) 9.47) 9852 Comet MC Oe eee as eee Oyu S DSO ORs ee Saal 10.0 
QOD Bere Seinen etree 1OR2E LOS AOR65 | eSa6 QE OOM ee ee aoe 11.6 | 1565) -859")= 8: 91053 
NOOB eee entry eee WAG WIL Os) SBE CEO): OS | I Seco aes ode cs Ie Ge OO OE) eas yO) 
GOA ee NS erie eet TONOV ORS Ss Oe eS aoa el Os On| lols yeas 10.1} 8.6] 10.2) 8.5 9.4 
OOS eich aik Ses 9.9) | 10.0) 10.2 | 7.9 ADDO) sali al OU Ae rest ee eecee ey Sea Ney ey ble ape Se ey tale 
TOO G Refs ee ye TOS 3 MO; 33 1] TO Zeal LOS OF GPL oie! Sevan inee 11.8 | 12.1 | 12.1) 10.8) 11.7 
LOO FE Eeyore i er 8 LRG LON OM PONS rico 9.8 
QOS H eS Sth ates sae HNO} We Gas Wee 10. 0 Average...------ GP IOS 7 OO. eb ® 9.8 
