THE SUBSOIL PLOW. 



135 



double edges as well as double j^oints, and capable of be- 

 Fig- 141. ing reversed when 



it becomes worn. 

 In light or grav- 

 elly soils this plow 

 runs well ; but 

 where the earth 

 is adhesive and 



Broad-shank Subsoiler. rather moist, the 



friction of the two flices of this shank in pressing the 



FiiT. 142. 



Subsoil plow. 



compact soil apart becomes enormous, amounting in some 

 cases to more than triple the force required to loosen 

 yig 143^ the soil below. 



This plow is there- 

 fore not to be rec- 

 ommended for 

 general use. The 

 objection is in a 

 great measure ob- 

 viated in the plow 

 shown in fig. 142, 

 where, the forward portion of the broad plate is made 

 thicker than the rest. The friction is still further less- 

 ened by employing two narrow shanks, as in fig. 143. 



Another improvement for lessening friction might be 

 made by using narrow bars of iron or steel, braced and 



Tico-shanked Subsoiler. 



