24 



TRENCHING AND SUBSOILING 



position. This accident is so frequent with the anchors that 

 Beauquesne was forced to discard them and substitute 

 anchoring plates, the resistance of which is much greater. 

 These plates, formed of strong girders, lodged in trenches in 

 the ground, and resting on an extended surface, support 

 very considerable efforts without yielding. It is not rare, 

 however, to see them pulled out of the ground in certain 

 soils. It is preferable, when circumstances allow it, to 

 anchor the pulley to a wall or trees ; even these are some- 

 times pulled out. 



It should be noticed that the two anchoring points of the 

 chain holding the pulley have to sustain unequal tractions, 

 and that the pulling out of one end is more to be feared 

 than the other. This is shown in Fig. 7 ; the traction T of 

 the capstan and the resistance T' of the plough give a resul- 

 tant F applied to the point cL This resultant is equili- 

 brated by the resistance R of the anchoring chain. If this- 



Fig. 7.- Anchoring of the Fixed Pulley. 



resistance is resolved into its two components, A directed 

 towards the anchor P, the other B directed toward the anchor 

 P', we see that the effort applied to the first anchor is greater 



