Q4 THE FIRST BOOK OF FARMING 



it bevels from beneath upwards it will be hard to 

 keep the plow in the soil, for it will tend to slide up 

 to the surface. If this happens the share must be 

 renewed or sharpened. Plows are being made now 

 with share and point separate, and both of these re- 

 versible (Fig. 51), so that if either becomes worn 

 on the under side it can be taken out and turned 

 over and put back and it is all right, they thus be- 

 come self-sharpening. 



A mouldboard. This turns and breaks the fur- 

 row slice. The degree to which the mouldboard 

 pulverizes depends on the steepness of its slant up- 

 ward and the abruptness of its curve sidewise. 

 The steeper it is and the more abrupt the curve, the 

 greater is its pulverizing power. A steep, abrupt 

 mouldboard is adapted to light soils and to the 

 heavier soils when they are comparatively dry. 

 This kind of a plow is apt to puddle a clay soil if 

 it is quite moist. For breaking new land a plow 

 with a long, gradually sloping share and mould- 

 board is used. 



A landslide, which keeps the plow in place. 



A coulter. Some plows have a straight knife- 

 like coulter (Fig. 52) which is fastened to tUe beam 

 just in front of the mouldboard and serves to cut 

 the furrow slice from the land. In some plows 

 this is replaced by an upward projection of the 

 share; this is wide at the back and sharp in front 

 and is called the shin of the plow from its resem- 

 blance to the shin bone. The coulter is sometimes 

 made in the form of a sharp, revolving disk (Fig. 



