228 AGRICULTURAL ENGINEERING 



large seeds like peas or beans. The cells of the ring, being of 

 a certain uniform size, will not crush the seed like the external 

 feed. For small grain the external feed, however, is the most 

 accurate and is the most convenient of adjustment. This 

 type will drill at a- quite uniform rate regardless of the amount 

 of seed in the seedbox. 



Press Drills. The press drill with press wheels to follow 

 each furrow-opener is the most satisfactory type for fall seed- 

 ing. The press wheel packs the soil firmly around the seed, 

 causing the moisture to come up from below by capillary 

 action and thereby producing early germination. For spring 

 seeding, when there is an abundance of moisture in the soil, 



the press wheel is a dis- 

 advantage. In regions 

 where both spring and fall 

 seeding are practiced, the 

 press wheel attachment, 

 which can be used when 

 desired, is a satisfactory 

 arrangement. 



Selecting a Drill. In 

 selecting a drill with disk 



Fig. 140. A press drill. /. ,, t 



furrow-openers, the bear- 

 ings and the means of oiling the bearings should be care- 

 fully inspected. The bearings are the first parts to wear 

 out. A good strong frame is important, as well as a 

 trussed and braced seedbox. The best designs do not 

 depend upon the seedbox to support the drill, except in a 

 minor way. 



Seed Tubes. Rubber, wire, and steel ribbon seed tubes 

 are used on drills. The rubber tubes are quite satisfactory, 

 but are not durable, especially if not well protected from the 

 weather. Steel wire tubes are satisfactory except when 



