56 SCIENCE OF THRESHING. 



get the grain out with as little cutting up of the straw 

 as possible, thereby relieving the shoe of an undue 

 amount of work. 



As the grain and chaff are delivered to the front 

 end of the chaffer, the kernels are more or less 

 thoroughly intermingled with the refuse, the mixed 

 mass being of a depth and quality dependent on the 

 amount being threshed. It is plain that if the meshes 

 of the chaffer are not large enough to let the whole 

 mass through, the most of the kernels will be carried 

 along with the chaff and dirt by the action of the 

 chaffer to the rear end. But force a little blast 

 through and watch the result; as the blast comes 

 through the meshes, it lifts grain, straw and all. 

 The kernels at the bottom of the mass will fall 

 of their own weight through the sieve. As the 

 blast continues on its way up through and between 

 the different particles of the mass, it loosens and sepa- 

 rates it, carrying the lightest bits farthest, and 

 allowing the others to fall of their own weight. By 

 watching the blast still longer it will be noticed that 

 the particles which are traveling through the air are 

 entirely free from contact with each other, every 

 particle seeming to try to avoid its neighbors as much 

 as possible. There are never any bunches clinging 

 together, but the mass is thoroughly divided, thus 

 producing the very best conditions for separating the 

 kernels from the chaff. 



The blast should be strong enough at the front of 

 the sieve to always flow through the very first 



