CULTIVATION 



119 



Harrows. Disk harrows. Disk harrows of various shapes and 

 makes are getting to be much used as coarse harrows to follow 

 plowing. In the plain disk harrow the disks are concave, their 

 diameter varying, in different machines, from 12 to 16 inches. 

 Each machine has a lever by which the angle of the disk with 

 the line of draft may be increased or lessened as desired. 



Cutaway disk harrows. Cutaway disk harrows are similar to 

 those just described, but have the edges of each disk notched or 



Fig. 52. Another good orchard tractor 

 In the larger orchards tractors are demonstrating their great practicability 



cut in or cut away. This notching makes it possible for the disks 

 to penetrate deeper into the soil and to do more real grinding 

 than the plain disks. 



Spading disk harrows. The spading disk harrow is a machine 

 having disks so deeply cut in that they resemble blades. The work- 

 ing of this machine has proved satisfactory, especially on smooth, 

 practically stone-free land. 



All of these machines are built both in single action (that is, 

 having one row of disks across the machine divided into two 



