WELLS AND WELL SINKING. 



which the cutting chisel is attached to the boring 

 head and suspended by a hook 

 from a rope. 



The boring head, which is 

 somewhat smaller in diameter 

 than the hole, is made of cast 

 iron and is usually 18 in. in 

 length. There are two ways of 

 using this tool. One is for use 

 when it is not intended to sub- 

 sequently line the hole with a 

 tube, which can be done in very 

 hard rock. In this case the loop 

 is fixed in a central position, so 

 that the chisel will strike plumb 

 on the bottom of the boring. 

 When, however, the hole has to 

 admit of a tube, it must be larger 



FIG. 17. 



Holes': 



in diameter than otherwise, and to ensure this the 

 head is slung so that it is eccentric to the central 

 axis. This simple adjustment is effected 

 by fixing the loop on the boring head on 

 one side of the centre, and the chisel then 

 strikes the bottom obliquely as shown 

 by the figure, and so cuts a larger hole. 

 When a hole has to be cut through clay 

 or stiff earth another form of cutting tool 

 is employed, as shown in fig. 18, consist- 

 ing of a 2 in. diameter steel tube having *^ 

 a screw, where shown, to screw it into 

 the boring head in place of the chisel. 

 The tube must have holes in it where shown to allow 

 waste matter free egress. The method of using these 



