34 



SMALL WATER SUPPLIES. 



The reader is referred to figs. 14, 15, 16. Concrete 

 is more or less impervious to water and can if neces- 

 sary be made absolutely so, and hence we can get 

 rid once for all of the danger of contaminated top 

 surface water. The concrete would only have to be 

 about 6 in. thick, while vertical steel rods, f in. 

 diameter spaced 18 in. apart, running up vertically 

 through the concrete, and circumferential rods, in. 



diameter and spaced 9 in. 

 apart, would constitute 

 the reinforcement, the two 

 sets being bound with 

 steel wire to each other. 

 The circumferential rods 

 would be placed within the 

 vertical ones. The best 

 concrete for the purpose 

 would be composed of i 

 part of best portland cement 

 to 2-J parts of sand and 4 

 parts of very small broken 

 stone or gravel. It will 

 be necessary to construct 

 a circular collapsible frame 



of wood, 12 in. smaller than the diameter of the 

 well and about 4 ft. 6 in. long. This is set up 

 vertically at the bottom of the excavation, and the 

 concrete is placed between this frame and the side 

 of the excavation, the frame being meanwhile covered 

 with soft soap to prevent the concrete sticking to it. 

 The two rings A and B are cut to a diameter equal 



FIG. 13. 



