26 GENERAL CONSIDERATIONS 



can be set by means of levers to work at any desired 

 angle to each other. If the gangs are set straight, 

 that is, with their axes in the same direction, the 

 disks will simply cut lines in the soil, but it will not 

 be moved and broken. The sharper the angle at 

 which the gangs are set, the more the disks will 

 push and turn the dirt, throwing it in each direction 

 from the center. To keep the land level it is neces- 

 sary to drive so as to lap half, that is, so that the 

 outer end of one of the gangs, the second trip, will 

 pass where the center of the machine passed the first 

 trip. In this way the soil will be worked first out 

 and then back, and it will be left in very fine con- 

 dition. This is always a riding harrow. The disks 

 may be solid or cut away in wide notches. The disk 

 harrow will cut up sod, and cut and grind up clods, 

 better than any of the others. In almost all cases it 

 is the best implement to put immediately behind the 

 plow. One should be included in the equipment 

 of every farm where the land has been sufficiently 

 cleared to admit of its use. It is an awkward im- 

 plement to use among stumps and large rocks. In 

 fact, every farm should be equipped with more than 

 one kind of harrow. The disk should follow the 

 plow, and on the same day that the land is plowed; 

 but to secure a really good, fine seed bed, it is neces- 

 sary on most soils to follow the disk with the acme, 

 or the smoothing, harrow. This, as a rule, should 

 be done just in advance of planting. If light rains 

 have fallen between the two harrowings, so much 

 the better, as the surface will pulverize better and 

 the lower layers will be somewhat compacted so as 



