25 



Fanning Mills. 



Since a bushel of wheat contains somewhere in the neigh- 

 borhood of a million kernels, it is obvious that hand selection 

 of seed wheat is impractical except for careful experimen- 

 tal purposes. 



For commercial production of small grains it is neces- 

 sary to have some means of selection which is of rather high 

 efficiency and, according to the results noted in the preceding 

 pages, there should be good returns from its use. The type 

 of machine commonly employed for such a purpose is generally 

 called a fanning mill. 



The functions of a fanning mill (62) are; (1) to clean 

 the grain; (2) to grade the grain; and (3) to separate differ- 

 ent kinds of grain. 



The modern mill uses several physical differences for the 

 separation of grain; among them being difference in weight, 

 difference in size, and difference in shape. Also the rough- 

 ness of the hull, and to some extent the location of the heavy 

 part of the seed, may be used. But in this connection we are 

 concerned chiefly with the difference in size and density. 



Selection for different sizes may be made by the use of 

 sieves or riddles with different sizes of openings. Since 

 denser seed offers less surface to the air, an air current 

 may be utilized to select seed for weight. 



The first of the machines used for cleaning and grading 

 grain made use of the air blast only and hence the term fan- 

 ning mill has come to be applied to all machines of this type; 

 although the best of them combine the principles of sieves 

 anfl si- blast. 



