SCIENCE OF THRESHING. II 



struck in a manner similar to the flail, by the rapidly 

 moving teeth of the cylinder as it revolves. The 

 action of the flail is increased many times by the 

 increased number of teeth and the greater speed at 

 which they travel. Stationary teeth in the concave 

 retard and hold the grain in place while being acted 

 on by the cylinder teeth. The "concave" teeth are 



arranged so the cylinder teeth can pass between them. 

 The unthreshed grain heads are laid on the teeth of 

 the concave, and the cylinder teeth strike them quick, 

 sharp blows. The tendency of the heads to bound 

 back from the teeth forces the kernels out from the 

 hulls, already split by the contact with the teeth. 

 Thus it is seen that the cylinder, with its teeth, 



