SMALL WATER SUPPLIES. 



tube should have a cutting edge of hard steel, and the 

 lower pipes are perforated with small holes about f 

 in. in diameter, except in chalk or hard rock. Copper 

 tubes have also been used to some extent, but they 

 are naturally very expensive. The steel tubes are 

 generally lap welded and screwed at each end. 



These ends are then butted together and secured 

 by a collar, as shown by fig. 27, which refers to 



Collar, 



FIG. 27. 



FIG. 28. 



FIG. 29. 



FIG. 30. 



tubes of fairly large size, while smaller-sized tubes 

 would be joined by collars of the form shown in figs. 

 28 and 29 ; while if the driving is likely to present 

 any difficulties, the flush joint shown in fig. 30 is 

 used. The most modern system is known as the 

 Abyssian driven tube well, and it consists of a 

 perforated steel-pointed tube as shown in fig. 31, 

 which is driven down into the water-bearing strata 

 when this is not very far below the surface. This 



