WATER SUPPLY AND IRRIGATION. 163 
natural surface of the ground. In other cases, where the fall of 
the bed is inconsiderable, a dam is constructed both above and 
below the excavation, and these if raised above the level of the 
creek banks are joined by lateral embankments; an inlet pipe is 
laid under the upper dam, which allows water to gravitate into 
the excavation and enclosed space until it reaches the level of the 
water outside ; a valve is then closed, and if necessary the outside 
provide an adequate bye-wash, and, wherever it is possible, the 
work should be located to allow of a natural channel being used 
for this purpose. 
_ The system to be adopted in watering stock at these works 
Involves two questions of great importance ; that of the economi- 
to eat tent a camping groun It may be laid down 
as a principle that, to attain these ends, stock must 
. ssary on account of the heavy outlay that urn 
= Tepairing the older works which had been very inefficiently 
Maintained. 
The first departure made from the original design was to intro- 
a @ separate tank with flattish slopes for stock to water m; 
po me ; that they are liable to be 
Ceca injured in crowding down into the drinking-tank ; 
