CHAPTER V 

 TILLAGE MACHINERY (Continued) 



115. The smoothing harrow. After plowing the 

 ground, it is necessary to pulverize the soil very finely 

 and to smooth it. The harrow is the implement used for 

 this purpose, and it may be used also to cover seeds, to 

 form a dust mulch for retaining moisture, and to kill 

 weeds when they are beginning to grow. 



1 1 6. Development. Formerly the branch of a tree of 

 a size to suit the power, whether man or animal, was used 

 as a harrow. The limb chosen had small branches ex- 

 tending usually all to one side or the other, so as to lie 

 flat when in use. Even until quite recently the brush 

 harrow has been in use for covering seeds. An early type 

 of harrow consisted of a forked limb with spikes in each 

 arm, to which a cross arm. was added later. This form 

 was known as the "A" harrow. Until late in the six- 

 teenth century a type of harrow devised by the Romans 

 was the standard. This harrow was square or oblong, 

 having cross bars with many teeth in them. 



117. Classification. Harrows may be classified as fol- 

 lows: 



i. Smoothing harrows. 



Kinds of teeth Straight fixed tooth ; 



Square-and-round tooth ; 



Cultivator tooth. 

 Kinds of frame Wood frame ; 



Pipe frame ; 



Channel or U bar frame. 

 Adjustment of teeth . . Fixed tooth ; 



Adjustable tooth; 



Lever harrows. 



