MOTIVE POWER 



487 



tractors to be bought and adapted to certain lines of farm- 

 ing that could have been more economically performed by 

 men and teams had the men been available. 



There is no tractor designed that will supply all the 

 motive power required on a farm. In some cases the farm 

 tractor is too large to operate economically for the power 

 needed; in others it is essential that the work be done 

 by horses, and a certain number of horses must be kept. 

 Up-to-date statistics indicate that a tractor on the ordinary 

 farm is kept in operation from twenty-one to fifty ten-hour 

 days per year and its life is approximately eight years. It 

 is necessary to keep on hand enough horses to perform the 

 work that cannot be done by the tractor. Farmer's Bulletin 

 1093, United States Department of Agriculture, states that 

 the experience of one hundred ninety-one tractor owners in 

 the corn belt was that the number of horses kept was two or 



After J. I. Case Threshing Machine Co. 



Fig. 377. A gas tractor drawing a binder 



three less per farm after the purchase of the tractor, and the 

 average acreage of land farmed was increased 2 2 acres. The 

 horses kept on these farms did 75 per cent of the tractive 



