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430 T. W. E. DAVID. 
The question however, is capable of being attacked from another 
direction, as Mr. H. C. Russell has done in his excellent paper on 
the ‘Source of the Underground Water in the Western districts,” 
read before this Society August 7, 1889. On p. 4 of this paper Mr. 
Russell states :—‘‘ The mean rainfall on the Darling River catch- 
ment for the past ten years has been 22°14 inches, and of this, as 
we have seen, only 14 per cent. or = 0°33 inches of rain passes 
Bourke in the river. If twenty-five per cent. of it, which is equal 
to 5°53 inches of rain passed away in this river as it does in the 
Murray there would be seventeen times as much water passing 
Bourke as now actually does pass; . . . and we ought there- 
fore to have an underground water supply at least equal to six- 
teen times as much water as passes Bourke now, and this or at 
least a great part of it should be useful for irrigation. That we 
do not find it in the Darling, is to my mind proof that it passes 
away to underground drainage.” 
The mean daily discharge of the Darling at Bourke is equal to 
about 1,400,000,000 gallons, so. that a volume of water flowing 
underground sixteen times as great, as required by Mr. Russell’s 
hypothesis, would amount to 22,400,000,000 gallons, equal to 
about five hundred and forty-six times the present capacity of all 
the artesian wells of New South Wales, a quantity as far in excess 
of that stated provisionally by the author as his own estimate 
exceeds that which results from an application of Mr. Henderson’s 
formula for Queensland, to the artesian beds of New South Wales, 
and yet Mr. Russell’s estimate may be the most correct. 
The whole of the above statements show that our present know- 
ledge of the actual amount of water draining into the artesian 
beds is only very approximate, but that it is certainly far in excess 
of what would be received by the mere rainfall on a strip of out- 
crop sands and gravels one-eighth of a mile wide and about three 
hundred and fifty miles long. It must not of course, be thought 
that because any particular artesian well begins to fail that there- 
fore the whole outflow from the artesian basin is in excess of the 
annual intake. The amount of outflow from a well is governed 
