110 FARM MACHINERY 



with either wide or narrow track. Perhaps the wide 

 track is the stronger construction and permits of higher 

 wheels, but the narrow track permits of greater ease in 

 turning and there is not the tendency to whip the horses' 

 shoulders as with the wide track. 



144. Combination seeders. Broadcast seeders with 

 cultivator and spring-tooth harrow attachments have 

 been referred to. A popular tool now is the seeder at- 

 tachment for the disk harrow. This attachment resem- 

 bles very closely the force-feed broadcast seeder mounted 

 above each of the harrow sections, and is operated by 

 suitable sprocket wheels and chain from the main shaft 

 of the disk. By the use of this tool two tools may be 

 combined in one. The disk gangs, owing to their tend- 

 ency to slip occasionally, do not make an entirely satis- 

 factory drive. This is especially true in trashy ground. 

 To surmount this difficulty, combination seeders are 

 made with a follower wheel to drive the seeder. 



DRILLS 



Drills are provided with a force feed much like those 

 used upon seeders, but are distinguished from each other 

 in the type of furrow opener and covering devices used. 



145. Classification of drills. 



Furrow openers : 

 Hoe. 

 Shoe. 



Single-disk. 

 Double-disk. 



Covering devices: 



Chains. 



Press wheels. 



Press wheel attachment. 

 Interchangeable disk and shoe drills. 



146. The hoe drill was the first to be developed, and 

 it is not difficult to see why this should be. The 



