6 BULLETIX 174, U. S. DEPARTMENT OF AGRICULTURE. 
full horsepower. A 1,200-pound horse moving at the rate of 2\ 
miles per hour and exerting a pull of 120 pounds (one-tenth of his 
weight) would develop only four-fifths of a horsepower. Thus, 
an engine delivering 20 horsepower at the drawbar would be exerting 
a stronger pull than 20 horses (averaging less than 1,500 pounds' in 
weight) normally do hour after hour. It should be borne in mind, 
however, that the engine is capable of delivering at the drawbar in an 
emergency but a fraction in excess of its rating of 20 horsepower, 
while 20 average horses are able for a short time to pull several times 
their normal load; that is, the engine might be overloaded to deliver 
25 horsepower, while the 20 horses can be so urged as to deliver 30, 
40, 60, or more horsepower for very short periods of time. 
SOURCE OF DATA. 
In obtaining the data on which this bulletin is based, several 
hundred owners in sections where tractors are most widely used were 
personally visited, and conditions were observed and interviews had 
with farmers using tractors as well as with those who did not use 
them. At the same time the opinions of business men with regard 
to the use of tractors by farmers in their vicinity were secured and 
brief histories of the experience of users were recorded. 
A letter was addressed to all bankers located in the farming sections 
of the United States lying west of the Mississippi River, requesting 
their opinions as to the effect of the tractor on the farming industry 
in their vicinity, the desirability of the tractor as an investment for 
a farmer, their practice regarding the loan of money for the purchase 
of a tractor, and related questions. (See Table II.) 
A letter was addressed to more than 13,000 tractor owners, inclosing 
a list of questions to be answered, the replies to which were tabulated 
and are shown in the following pages. The distribution of these 
tractor users by States is shown in Table I. Replies were received 
from about 40 per cent of the men addressed, but many of the reports 
were discarded because tractors had not been used for a sufficient 
length of time to enable their owners to form an opinion as to their 
merits. However, more than 2,000 men who had operated their 
outfits for one or more seasons furnished detailed reports. 
Table I. — Distribution of tractors in States west of the Mississippi Riv°.r, showing the 
approximate number of owners reported by bankers. 
State. 1 Tractor 
owners. 
State. 
Tractor 
owners. 
State. 
Tractor 
owners. 
3,200 
2,100 
1,205 
1,200 
1,060 
650 
345 
335 
265 
130 
125 
105 
102 
80 
Arizona 
20 
15 
Nevada 
5 
Utah 
5 
Total 
13,327 
California 700 
