THE WASTE-WAT. 



231 



At fig. 113 is seen a section of a valley occupying a syn- 

 clinal axis. It is apparent that a reservoir formed in such 

 a valley could not leak by any possibility, even though all 



Fig. 112. AN ANTICLINAL VALLEY. 



the strata were porous. In addition to this, a valley of 

 this character will almost always have abundant springs 

 issuing from its flanks, while the previous one can have 

 none at all, and the first mentioned can have them on but 



Fig. 113. A SYNCLINAL VALLEY. 



one of its sides, and what may be gained in this way, may 

 be more than lost in another. 



The surplus overflow from a reservoir, should bo 

 made to discharge at a point away from the dam, as 

 shown at A, in fig. 110. This is necessary or at least 

 advisable, as the dam may be damaged by the overflow ; 

 or lest to provide the requisite strengthening to resist 

 erosion, the cost may be augmented unnecessarily. A 

 waste-way may be formed in a depression in the edge of 

 the basin, either by excavation, if it is already too high, 

 or by masonry if the existing depression is too low. In 

 case of rupture from any cause, the main work will re- 

 main intact. In addition to the waste-sluice, the appen- 

 dages of a reservoir consist of the apparatus for the dis- 



