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is a light type of the spring-tooth harrow, suited only to light, loose soils 

 where shallow tillage is desired. The disk harrow, like the disk plow, 

 is more effective for its draft than are other types of harrow. Especially 

 is this true of the cut-out and spading disks, which take hold of hard 

 and stony soil better than do the solid disks. The angle of operation of 

 the disk can be adjusted, and this determines the extent to which it 

 draws to the soil and the extent of pulverizing and turning. Its action 

 resembles that of the plow in that it tends to invert the soil. 



The Acme harrow may be regarded as a fourth type. It consists of 



Fig. 98. — Types of harrows: (1) spike-tooth; (2) spring-tooth; (3) weeder (spring- 

 tooth constructor) ; (4) double disk (note that the forward disks are solid while the rear 

 disks are of the cut-out type); (5) spading disk; (6) Acme. All these belong to the culti- 

 vator group of implements 



long, twisted blades. It is a very useful tool on soil free from stone, but 

 its draft is relatively large. 



Cultivators, proper. — The farmer usually makes a distinction between 

 harrows and cultivators. The former are used in order to prepare the 

 seed bed, the latter in order to cultivate or intertill the crop and to kill 

 weeds. The two types are, of course, interchangeable according to crop 

 and convenience. Cultivators that have handles or other guiding 

 arrangement are more easily controlled by the operator. (Fig. 99.) There 

 are many patterns of these on the market, and in their fundamental con- 



