16 BULLETIN 1202, U. S. DEPARTMENT OF AGRICULTURE, 
work per year which they did. In all, 30 per cent of the two-plow 
machines and 55 per cent of the three-plow and larger ones were used 
for belt work. On many of the farms, especially in the southern and 
western areas, threshing was the only belt work done during the year 
and the two-plow tractors have scarcely enough power to operate 
the prevailing sizes of separators. (See fig. 7.) 
Fig. 7.—Threshing wheat from the shock with a separator driven by large tractor. 
TABLE 19,—Number of tractors of different sizes used for belt work and hours of use per 
year. 
Southern area. | Western area. | Northern area. All farms. 
l ar (i | 
Size of tractor. Wine Hours <a Hours Wureie Hours ene | Hours 
of use of use of use | of use 
ber | per ber per ber | per ber per 
used. | year. used. year. used. year. used. year. 
iia = 4. a Eee eae) caeat a 
PAHOW. CS Ao onto eee eee 7 | 12 7 36 12 14 26 33 
Betws ve oh ee Oe ee 29 69 24 36 58 49 111 51 
BOO fe URS oS oho ae San ee ee 8 87 7 95 7 87 22 90 
OE INOW ci Siig 3x te So ee eee 2 28 5 48 6 | 11 13 42 
Total and average, all eles. 16 62 13 17 83 V1 172 | 53 
A complete record of all the belt work done on each farm during the 
year both with the tractor and other engines was obtained and Table 
20 shows for the average farm in each area the total amount of power 
used for the different belt operations and the proportion furnished b 
the tractors. Only one tractor owner used his horses to fucniee 
power for stationary work. 
The number of horsepower hours was obtained in every case by 
multiplying the horsepower of the engine by the number of hours 
