88 WATER SUPPLY IN THE INTERIOR OF NEW SOUTH WALES. 
The slope from the rivers Lachlan and Bogan to the centre of this 
dividing rise is so gradual as to be quite imperceptible in riding 
over the country, and no well-defined watercourses are formed i 
the whole of that piece of country, triangular in shape, about 300 
by 250 miles, which is almost enclosed by the three rivers—Bogan, . 
tions. In this part of the Colony, as well as in all the rest of our 
western plains, the country on the surface consists for at least 90 
per cent. of evenly deposited clay beds, thinly interspersed with 
stretches of sandy country, which are probably all of tertiary or 
And h 
recent geological age. ere I may note that in a country like 
which they do not, as these more prominent parts pierce through 
stratified beds of much more recent date. 
he peculiarities of the great western plain which forms about 
three-fourths of the Colony of New South Wales are, first, that it 
runs up among the spurs of the dividing range exactly in the same 
way that water penetrates a broken coast-line, forming deep bays 
and inlets with ranges and peaks of hard crystalline or conglomerate 
Darling River ; and here we may travel hundreds of miles without 
either owed into water where there was no current, or into & 
ain as they now do, which had by some agency been rendered 
so level as to prevent the concentration of their waters in any 
