24:8 



Physics of the Soil. 



sumes the form shown in Fig. 82, instead of that in Fig. 

 83. In this worn condition the inclination of the mold 



FIG. 82. Showing point of plow worn into bad form. 



board to the furrow slice is changed, the plow tends to run 

 on its point, is more difficult to hold, the draft becomes 

 heavier and poorer work is done with it. 



FIG. 83. Showing point of plow in good form. 



The heel of the share C in Figs. 84 and 85 is especially 

 liable to get into bad form and dull, causing the plow to 



FIG. 84. Showing heel of plow in form for dry soil. 



wing over to the land and draw harder, not only because it 

 is dull but because a steady pressure must be exerted at th^ 

 handles to prevent the plow from tipping to land. 



FIG. 85. Showing heel of plow in form for moist soil. 



It is sometimes necessary to change the form of the plow 

 to suit a harder or more mellow condition of the soil. When 



