BORING 



439 



Fig. 2 is the brace-head, or cross-head, with the four handles held by the borers. 



Fig. 3 is a catch for raising the rods from the borehole. 



Figs. 4, 5, 6, and 7, are spanners, used for screwing the rods together, and holding 

 them'steady at the top of the borehole. The shoulders of the rods rest between the 

 claws. 



Fig. 8 is the ordinary chisel used for boring. 



Figs. 9, 10, II, and 12, are various forms of chisels used for making the hole 

 cylindrical, and for breaking up hard fragments of rock at the bottom of the hole. 



Figs. 13 and 14 are also tools used for the latter purpose. 



Figs. 15, 16, and 17, are chisels used for breaking off projections from the sides of 

 the hole : figs. 16 and 17 showing two views of the same tool. 



28 



The implements used in extracting debris from boreholes are as follow : 



Figs. 1 8, 19, 20, and 21, are augers or wimbles, used for bringing up argillaceous 

 strata. 



Fig. 22 is an auger for boring through clay, generally used in commencing the 

 borehole. 



Figs. 23 and 24 are pumps or scourers, for bringing up the debris broken up by the 

 chisels. 



Fig. 25 is a scourer with valves, which are closed by turning the rods round, the 

 action of the screw B causing the part D to descend. 



Fig. 26 is an arrangement of pincers for extracting pieces of rock which are too 

 large to enter the pump. 



The instruments employed for rectifying accidents are as follow : 

 Fig. 27 is a special'screw for drawing out broken rods or tools. 

 Fig. 28 is a spring catch for extracting broken rods. 



Figs. 29 and 30 are catches used for extracting broken lining tubes. One of the 

 branches of the appliance shown by fig. 30 is fixed, and the other moveable. 

 Fig. 31 is a screw tap, also used for extracting tubes. 



