KE. F. PITTMAN AND T. W. E. DAVID. CXXXV. 
IV. ORIGIN AND FLOW OF ARTESIAN WATER.—In recapitu- 
lation of the conditions under which artesian water occurs 
in New South Wales it may be stated that the following 
appear to be the most noticeable facts :—(1) A wide belt 
of very porous sandstone outcrops on the east side of the 
artesian area between the Queensland border and the town 
of Dubbo. These sandstone beds occur at very much higher 
altitudes than the western plains on which the artesian 
bores are situated. They have a slight westerly dip, and 
extend continuously under the plains for a distance of at 
least 400 miles in a westerly direction. This has been 
proved by their intersection at varying depths in all the 
bores, and by the occurrence of the characteristic fossil 
Toeniopteris Daintreei from near the bottom of the bore 
on Salisbury Downs Station, west of the Paroo River. 
(2) The outcrops of these porous beds receive a mean 
annual rainfall of 25 inches, and owing to their extreme 
porosity there can be little doubt that a very considerable 
proportion of the rainfall is absorbed by them, and percolates 
through them in the direction of their dip under the western 
plains. Six of the main tributaries of the Darling River, 
the Dumaresy (Sovereign), the Macintyre, Gwydir, Namoi, 
Castlereagh, and Macquarie, rise in the ranges to the east 
of the porous intake beds, and have eroded their channels 
through the latter. Some of these rivers, notably the 
Macquarie, never reach the Darling except during times 
of flood. There can be no doubt that this is due to the fact 
that a considerable proportion of their water is absorbed 
by the intake beds, over which they flow, and serves to 
augment the supply of the artesian area. Mr. H. OC. 
Russell has pointed out that of the rain which falls within 
the catchment of the Darling only 137 passes Bourke in 
the river channel. The balance can be accounted for only 
by evaporation and absorption. There can be little doubt 
