WELLS AND WELL SINKING. 33 



care so that it does not get the least degree out of the 

 vertical. If it does it will bind and will not gener- 

 ally be set moving again without difficulty, more 

 often than not it never will, when the process will 

 have to be repeated below. The writer has found 

 that a small charge of explosive let off at the base 

 of the shaft will often remedy matters, or water 

 poured in round the outside of the brickwork may 

 effect the same object. In cases where the curb is 

 not required to slip it may be hung up by the rods 

 attached to cross timbers at the top of the well. 

 This will be necessary when galleries are driven 

 horizontally from the bottom of the well to add to 

 the water supply therein. Many engineers prefer 

 to lay 9 in. brickwork all as stretchers, as shown by 

 fig. 12, the advantage being that 

 4! in. of lining can be laid at a 

 time. Another form of lining 

 wells in bad ground is that by 

 cast-iron segments bolted to- 

 gether. They have internal 

 flanges and are cast in segments 

 about 5 ft. long, usually as shown 

 by fig. 13, while in some cases 

 the cylinders are steel riveted and stiffened by in- 

 ternal ribs of angle or tee iron. 



In both cases the writer is inclined to recommend 

 the flushing up with cement of the internal faces of 

 such iron and steel curbs, and finishing to a cylindri- 

 cal hard surface, which certainly makes a very fine job. 

 The latest practice, which is perhaps the best of all, 

 is the use of reinforced concrete for the purpose. 



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