WELLS AND WELL SINKING. 



39 



trated a tool for attempting their removal. It is 

 known as a crow's-foot. In fig. 26 is another variety 

 of shell pump for removing soft mud. Water must 

 in all cases be copiously applied to the tools. This 

 combining with the broken rock, etc., causes the mud. 

 As the boring proceeds, the tubes should be driven 

 down. The above apparatus can of course be elabor- 

 ated in many ways. A windlass may be added to the 

 plant for working the rope, and a special snatch block 

 arrangement, similar to those used on pile drivers, to 



Stop 



Q 



A 



Valve 



FIG. 20. FIGS. 21, 22, 23. FIGS. 24, 25. FIG. 26. 



release the tool. On large installations a petrol 

 engine will take the place of manual labour, but in 

 most cases the principal features are the same. When 

 starting a boring it is as well to give the tool a twist 

 or so by means of the rope : as the work proceeds it 

 will effect this motion of its own accord. Most bore- 

 holes are lined, except those in very hard rock, and 

 the hole must be cut large enough to receive the 

 lining, and the boring and lining usually proceed 

 simultaneously. Cast-iron tubes have been much 

 employed and are used at the present day, but steel 

 tubing is much more usual. In any case the bottom 



