104 WATER SUPPLY IN THE INTERIOR OF NEW SOUTH WALES. 
courses, by leading the water which falls on a hard surface through 
drains into tanks excavated below the surface level. The first 
ling resemble canals rather than rivers. We may follow their 
courses for hundreds of miles without finding any creeks flowin 
into them ; and though few, if any, can be said to be permanently 
running streams, yet immense bodies of water pass down them in 
flood-time from the mountains. What are called temporary dams 
are sometimes made in some of them when a fresh has nearly run 
t, and in this way considerable quantities of water are stored 
been always failures, and the reason is not far to seek. Such a 
thing as a solid rock foundation is unknown, and the fine clay 
cases would be in clay, which is very easily washed out by flowing 
water, and the ends at both sides of the river would have to 
i xt 
It seems probable to me that if any serious obstruction were 
placed in the Darling River, it would totally change its course, 
or change it in many places, eturning to and leaving the main 
these warrambools offered a freer course. Three or 
