30 SMALL WATER SUPPLIES. 



point at which the water can escape over the edge of 

 the natural clay basin in which the sand or gravel 

 lies. 



In other cases a well will be sunk through im- 

 pervious material to a porous bed underlying it, and 

 in such wells it is usual to have a permanent water 

 level some feet higher than the level from which it 

 rose, and where the level is above surface level no 

 pumping is required, and the well is termed an 

 Artesian well. These wells are bored and are very 

 common in beds of chalk and near red sandstone. 

 Steining is executed in various ways. Former 

 practice, and to some extent modern practice, makes 

 use of ordinary bricks for this purpose, hard, square, 

 well-burnt stock bricks generally being employed. 

 The very simplest way is to lay them dry 4! in. 

 thick, with rings at intervals set in cement three 

 courses thick, the interval varying in the discretion 

 of the engineer. Owing to the shape of the ordinary 

 brick (9 in. x 4^ in. x 3 in.) this 

 method has not much to commend 

 it unless laid in cement the whole 

 way as will be seen by fig. 8. The 

 courses naturally break joint, and 

 the brickwork is sometimes built as 

 shown in fig. 9 on a wood (oak or 

 elm) curb, laid at the bottom of 

 the excavation previously levelled to receive it. 

 Two thickness of wood breaking joint are employed 

 bolted together to a total thickness of about 3 in. 

 The breadth is an inch or so greater than the brick- 

 work. The shaft proceeds above the curb and the 

 earth carefully rammed behind it. Subsequent ex- 



