12 



SCIENCE OF THRESHING. 



and the concave with its teeth, are the parts of the 

 modern threshing machine which perform the work 

 of the horses' hoof of ancient days and the flails of 

 more recent years. 



After the grain had been stamped or beaten out on 

 the threshing floor, the heavy berries were separated 





from the straw by careful raking, and from the 

 chaff by tossing in the air, the wind blowing the 

 lighter refuse away. Or else air was forced through 

 the grain as it fell in a thin stream by a fanning 

 blanket. Later, the fanning mill was invented to 

 both sift and blow out the chaff. 



