TKENCHING AND SUBSOILING. 71 



head, which is clamped on to the drum at will. If we only 

 have small horses at disposal, they may be yoked in pairs to 

 each pole. 



The drum A (Fig. 32), is generally made of cast iron, 

 with flanges n at least 6 inches wide. These flanges are 

 often cast together with the drum, or made of wood 

 (Beauquesne) or steel (Bajac). It is important to prevent 

 the cable from getting caught under the bottom flange. For 

 this purpose a guide is fixed on an upright e, or the bottom 

 flange is enveloped by a ring, the upper brim of which is 

 level with the plane of the flange (Pelous). Accidents oftener 

 occur when the rope is unwinding, and to avoid them the 

 drum must be steadied by means of a brake. 



To render the winding of the cable as regular as possible, 

 it is advisable to place a runner P at a distance of about 6 feet 

 from the axis of the capstan (Fig. 32), the height of which 

 is level with the middle of the generatrix of the drum A. 

 On account of the slow rate of the cable the various systems 

 of automatic winding have been discarded. These devices 

 were similar to those used in steam ploughing, where they are 

 rendered necessary on account of the great speed of the cable. 



To facilitate the stepping of the animals over the cable, it 

 is advisable to have it passing as close as possible to the 

 ground, this necessitates the use of very shallow drums, and 

 also assists in increasing the stability. 



Fig. 33. Vernette's Horse-gin, with Variable Diameter. 



