CIV. IRRIGATION GEOLOGICALLY CONSIDERED. 
the artesian water strata to be described presently, the 
question as to whether or not they contain artesian water 
is of considerable importance. A bore has been put down 
with a view to testing this question to a depth of over 
4,000 feet at the Racecourse, Grafton, but was finally 
abandoned owing to mechanical difficulties. Paleozoic 
rocks were not met with, and the test is therefore an 
incomplete one so far as the question of the presence of 
artesian water is concerned. It is possible, however, that 
the bore may have penetrated Permo-Carboniferous rocks, 
as is suggested by the fact that at a depth of 3,100 feet a 
strong supply of natural gas was met with’: and hitherto 
no authentic case of an evolution of such gas has been met 
with in any strata in New South Wales except those of the 
Permo-Carboniferous system. From the southern extremity . 
of the Clarence Basin to Port Stephens the rocks are chiefly 
Carboniferous, with some Devonian, and are impervious to 
water. 
From Port Stephens to as far south as near Ulladulla 
stretches the Permo-Carboniferous coal-basin, a large por- 
tion of which is overlaid by Triassic rocks. The latter are 
locally known as the Hawkesbury series. They have been 
tested in numerous. places by bores, and lately by the 
Sydney Harbour Collieries Co’s shaft at Balmain, which ~ 
penetrated these rocks to a depth of 2,900 feet, and have 
been proved to be entirely devoid of artesian water. From 
Ulladulla to the Victorian border, at the Australian Alps, 
the strata are formed chiefly of Devonian rocks and intru- 
Sive granites, both of which are impervious to water. 
We can now pass on to the Main Dividing Range [ Division 
(2)]. This range is composed chiefly of Paleozoic and 
1 According to the foreman’s report the gas became ignited from the 
forge, 14 feet away from the casing of the bore, and considerable difficulty 
was experienced in extinguishing it. 
