CXXVIII. IRRIGATION GEOLOGICALLY CONSIDERED. 
Dubbo and for about 12 miles in a south-westerly direction 
the bed rocks are Silurian and Devonian slates, limestones 
and quartzites, with granite. The granite is followed by a 
synclinal trough of Devonian sandstones which extends 
southwards past Bogan Gate, the width of the trough being 
about 20 miles. The rocks hitherto described, with the 
exception of this Devonian trough, and the Permo-Car- 
boniferous strata of Ballimore to be described later, are 
all impervious. 
The sandstones, however of the Devonian are, at any 
rate at the surface, of a porous character, and in view of 
their occupying a synclinal fold which abuts against and 
probably underlies the southermost portion of the artesian 
area, there seems to be a possibility of their also being 
water bearing. With a view to testing this question, the 
Government are putting down a bore on Gennaren Lease- 
hold area, between Peak Hill and Dandaloo. From the 
north end of this Devonian Syncline the bed rock outcrops 
near Girilambone, and to the east of Byrock and at 
Brewarrina, and consists largely of micaceous slates and 
schists with occasional patches of granite. From Bre- 
warrina to near Wilcannia the bed rock does not outcrop 
near the edge of the basin, but the evidence supplied by 
some of the bores, such as that at the Trucking Yard at 
Bourke show that it is formed of slaty rock. At Wilcannia 
Devonian quartzites outcrop and extend to the Barrier 
Ranges where they are succeeded by still other rocks, 
probably Silurian. 
Reference to the map exhibited shows that the artesian 
wells are not plentifully distributed over that part of the 
artesian area which lies between the Culgoa River on the 
east and the Paroo River.on the west. A very large pro- 
portion of the bores put down by the pastoralists as distinct 
from-those put down-by Government:lie within the above - 
