FARM MACHINERY 227 



lies in the wide furrow that it makes, with a slight ridge in 

 the center. Definite experiments, as far as known, have not 

 been conducted to prove any advantage of this kind of 

 furrow. 



The shoe drill has been almost entirely displaced by the 

 disk drill. It is a lighter draft type, and where penetration 

 is not desirable it may be the type to select. The hoe drill 

 has good penetration but can not be used where there is any 

 trash to contend with. 



Force Feeds. Two types of force feeds are used on drills. 

 The most common is the external feed with a fluted seed 



Fig. 139. The external force feed is shown at the left, and the internal 

 device at the right. 



shell. The amount of seeding is varied by slipping the shell 

 in a guard so as to expose in the seed cups more or less of the 

 fluted parts as required. The second type is the internal 

 feed with a ribbed ring to which the seed passes on the inside. 

 This type does not vary the size of the cells on the ring, but 

 the feed regulation is obtained by varying the rotative speed 

 of the ring by a change of gears. Usually two sizes of seed 

 cells are provided in the ring, one for small seeds and one for 

 large seeds. The internal feed is the best type for drilling 



