E. F. PITTMAN AND T, W. E. DAVID.: j CXI. 
from there in a N.W. direction up the Bogan River to its 
junction with the Darling, and thence westward along the 
Darling River to near Bourke, from Bourke in W.S.W. 
direction to near White Cliffs, and its boundary follows an 
irregular course in a general westerly direction to the South 
Australian border. The boundary continues westerly across 
South Australia just north of Lake Torrens to about the 
133° meridian of E. longitude. Thence it is bounded on the 
west by an irregular line, based at present on meagre data, 
following approximately this meridian northwards to its 
intersection with the 25th parallel of S. latitude, thence it 
trends in a general north-easterly direction to a point in 
about Long. 141° 30’ Hast, and about 22° S. Lat. Thence 
its course is in a general north-westerly direction to near 
the mouth of the Roper River in the Gulf of Carpentaria. 
The area, whose boundaries have thus been roughly outlined, 
is proved by the paleontological evidence to have been 
first chiefly a vast freshwater lake, and subsequently for 
the most part an inland extension of the Gulf of Carpentaria, 
expanding southwards into a mediterranean. The deposits 
of these lakes and seas subsequently uplifted constitute 
the present main artesian basin. The artesian-water- 
bearing area is thus apparently surrounded by older and 
impervious rocks, with the exception of its northern 
extremity, which meets the sea at the Gulf of Carpentaria.’ 
As regards its surface configuration, the artesian water 
area is for the most part a series of almost level plains and 
gently undulating downs. In New South Wales the surface 
is largely formed of plains, so nearly level that any inclina- 
tion is quite imperceptible to the eye, being, as already 
stated, not more than about 2 feet per mile. The almost 
level character of these plains is due to the deposits from 
the flood waters of the Darling River and its tributaries. 
? See footnote to p. cx. 
