4 BULLETIN 174, U. S. DEPARTMENT OF AGRICULTURE. 



been developed primarily as a plowing engine, with belt work a sec- 

 ondary consideration. Although it was actually superior to the steam 

 tractor in the ways mentioned, it was nearly a decade before it 

 developed sufficiently to prove this superiority and became a real 

 competitor with the steam tractor. Most of its growth has occurred 

 during the past 11 years, and in considering the rapidity with which 

 it has been made it might at first appear that it must have been due 

 to its superiority over both the horse and steam tractor as prime 

 movers for the farm. As to its superiority over the steam tractor 

 there is no doubt. The sales of steam tractors for farm work other 

 than thrashing fell off as those of the gas tractor increased, and the 

 steam tractor is seldom found to-day except in sections where suit- 

 able fuel is cheap and convenient, thus giving it an advantage over 

 the gas tractor. The decline in the number of steam tractors used 

 for farm work is shown by the age distribution of those reported: 



One year old, 37; 2 years old, 65; 3 years old, 65; 4 years old, 88; 5 years old, 76; 

 6 years old, 33; 7 years old, 25; 8 years old, 24. 



THE GAS TRACTOR AND THE HORSE. 



While the gas tractor has almost completely replaced the steam trac- 

 tor, as has been stated, neither the steam nor gas tractor has affected 

 the sale or use of farm horses to any great extent. (See Tables XXII 

 and XXIII.) 



A careful study of the subject shows clearly that the rapid growth 

 of the gas tractor was not due to its superiority over the horse, but to 

 the fact that large tracts of unbroken prairie land were being opened 

 up in the West and that sufficient horses were not available to break 

 the ground and bring it under cultivation. Gas tractors could be, 

 and were, manufactured in a much shorter time than it would have 

 taken to raise the necessary horses for this work. But as this new 

 country developed, horses were rapidly imported, colts were raised, 

 and more and more of the farm work was performed with horses. 

 Quite frequently the tractor which had broken the prairie and brought 

 it under cultivation was entirely replaced by them. 



A similar condition existed recently in Kansas. An epidemic 

 diminished the number of farm horses in that State by thousands, and 

 the number remaining was insufficient to perform the field work. 

 Immediately hundreds of traction engines were shipped into the State 

 to meet the power requirements. Whether these machines will 

 retain the ground thus opened to them remains to be seen. Under 

 similar conditions in other States they have not done so, indicating 

 that they are either not as satisfactory as horses for farm work or 

 are more expensive. 



The failure of the gas tractor to maintain its position as the prin- 

 cipal prime mover in those sections where it was first introduced was 



