THRESHING 



73 



cated conveniently for the fields. Hence the 

 necessity for a portable thresher became evident. 

 Horse power soon came into use, and machines 

 were built in such a way that they might be 

 moved from field to field. Treadmill horse pow- 

 ers were used at first, but they soon gave way to 

 the sweep powers which still are rather common 

 in some regions. The sweep powers used in 



FIG. 44. Some farmers prefer to make rectangular stacks. 



threshing are usually built for eight or ten horses, 

 but both smaller and larger sizes are in use. The 

 horses are hitched two abreast and one driver 

 attempts to keep them all going at an even and 

 uniform gait. Since the farmers furnish most of 

 the horses used on the power, the driver seldom 

 has a trained set to handle ; and uniformly cor- 

 rect speed is therefore almost impossible. Another 

 objection to this source of power is that since the 

 threshing is largely done during the hot months 



