RESERVOIRS AND PONDS. 89 



Construction. — One of the first things to be done 

 after the site is secured is to make provision to draw 

 off the water. In building a large reservoir with an 

 earth embankment, wooden boxes or cribs of timber 

 (although sometimes employed) are not to be recom- 

 mended for permanent use, as they soon decay, are 

 very difficult to replace, are a source of weakness to 

 the reservoir, and do not admit of easily inserting a 

 gate which can be freely operated. Stone culverts laid 

 in cement are more costly and substantial as a rule, 

 but require a special gate, which may give trouble. 

 Iron piping, of which there are several kinds in the 

 market, is perhaps the most suitable, and by its use 

 one can purchase the standard low-pressure water- 

 valves such as are in use in city waterworks, that are 

 guaranteed to give satisfaction. In laying the pipe 

 care must be taken to provide a safe and continuous 

 bearing beneath it, otherwise the load imposed by the 

 earth above will cause portions to settle and so loosen 

 the joints. 



It is necessary, too, to dig one or more cross 

 trenches from the pipe and pack them full of concrete, 

 clay, or good earthen puddle, bringing the same up 

 two or more feet above the pipe so as to arrest any 

 leakage along the outlet pipe. The surface upon 

 which embankments are to rest should be plowed and 

 the roots of bushes and weeds removed to the outer 

 toe of the slope, after which the ground is again 

 plowed and a trench dug along the center of each pro- 

 posed embankment. When this much is done water 

 should be applied. The abundant use of water is of 

 prime importance in all works of this nature. Allow 



