8 BULLETIN 297, U. S. DEPARTMENT OF AGRICULTURE. 
the latter month being 6.5 miles. The greatest seasonal velocity was 
recorded in 1911, which was the year of least rainfall and greatest 
evaporation. The highest average velocity for the entire period was 
recorded in May of that year, 11.6 miles per hour. The average 
velocity for both June and July was also unusually high. The low. 
yields in 1911 were due to the combination of very low rainfall, high 
evaporation, and injury to crops from high winds. The wind for any 
one day (24 hours) seldom exceeds a total of 500 miles, while for any 
one day during June and July it is usually much less than 250 miles. 
TEMPERATURE. 
The temperatures at the Belle Fourche Experiment Farm are 
recorded throughout the year by means of maximum, minimum, and 
dry-bulb thermometers. A summary of the mean, maximum, and 
minimum temperatures from April to July, inclusive, for the six years 
from 1908 to 1913 is presented in Table VI. 
TasLe VI.— Mean, maximum, and minimum temperatures at the Belle Fourche Experi- 
ment Farm, by months, from April to July of each year, 1908 to 1913, inclusive. 
[Data (in °F.) from the records of the Biophysical Laboratory of the Bureau of Plant Industry.] 
April. May. June. July. 
: q 
: : t | g 
Year. = = Seles I = ae etal 
| = =) = s = ss = S| a 
res eeepc pecs fash | = 
Shi) ots = Bi || tae! Cg oS * re a ~*~ = BZ 
3) S = ra) S = oS SO |. ) oS = S 
= = = = = = = eat ys = = = MN 
ee ee ee a ee Ee ese 
AOGSHE AS etek at 43 | 89 5 | se (> vo | oa) -ea-4_t60 | csguetes.| em oaeleees 
foie ek 38 | 73 6| 52| 84| 22| 66] 951 45| wl to0| 41 56 
TT Te he ei epee 51 | 89) - 24} 52| 81 |. -27| 684. 408 | .-36 |) 9961. dngel> Aull ieees 
ite Sonnac | 431. 98] 13|.-58| 94) 93 | et aiid 45> wy teed 61 
HIS FEN aera ee. | 47-| 78 |. 99:|-- B51 > 94 | 925). Ge] 408 [oes or Oke ean ees 
igi eas Sey 43| so| 24| 53| 95] 26] 66! 98] 45| 70| 101] 42] 59 
ee — | | | 
Average......--- | AG. |) 846: | > 2540l Shel enon taeeee | 99| 41 | 72| 101| 42 | 59.5 
Table VI shows that the highest average mean, maximum, and 
minimum temperatures have been recorded in July, though the maxi- 
mum and minimum temperatures are only very slightly higher than 
those recorded in June. During the six years, frost has not occurred 
in June, the lowest minimum temperature recorded being 36° F. 
This table shows that the average mean temperature for the growing 
season for cereals for the six years is 59.5° F. The greatest variation 
from this average in any one year was in 1909, when the seasonal 
mean was 56° F. 
The temperature of western South Dakcia is somewhat higher than 
that of corresponding latitudes in the eastern part of the State. This 
is shown in Table VII, in which the mean monthly and annual tem- 
peratures at Newell, Camp Crook, Aberdeen, Pierre, and Brookings 
are given. Camp Crook is near the northwestern corner of the State, 
