ARTESIAN WATEK IK WESTEEX QUEENSLAND. 
337 
thought a very liberal allowance when he based a calculation of the 
area of gathering-ground on the assumption that “ the aggregate 
breadth of the outcropping edges” was one-eighth of a mile. In the 
light of the recent investigation 1 feel tolerably confident that the 
breadth of the basal beds (the Blythesdale Braystone) is at least forty 
times as much, not to speak of beds of similar composition on higher 
horizons, which makes a material difference in the conditions of the 
problem. Assuming that the total length of the ribbon representing 
the outcrop in Queensland of the Blythesdale Braystone is 1,000 miles, 
and its average breadth 5 miles, this outcrop alone would give a 
gathering-ground or intake of 5,000 square miles. An average of thirteen 
meteorological stations along the line of outcrop, taken from the map 
issued with Mr. Henderson’s last report, gives roughly for this area a 
mean annual rainfall of 27 inches, which is considerably greater than 
that of the interior of the downs country. 
The comparative altitude of the outcrop of the Blythesdale bray- 
stones and the western country where the artesian wells are situated 
is an all-important factor in the calculation. The surface level has 
not been reliably ascertained at the sites of most of the private (suc- 
cessful) bores. From Mr. Henderson’s last report we learn that the site 
of the Government bore at Tambo is 1,325 feet, and this is certainly one 
of the most elevated sites Muckadilla comes next at 1,1(39 feet. The 
greater part of the area over which flowing artesian water has been 
obtained is much lower than either of these two places. The Blythes- 
dale braystones attain their highest observed altitude of 1,700 feet 
above the sea-level at Forrest Vale, on the Maranoa, and the altitude of 
the outcrop gradually falls to 800 feet at the New South W ales border, 
and probably is almost at the sea-level near the Grill f of Carpentaria. 
I cannot speak with confidence of the extension of the lowest beds of 
the Lower Cretaceous formation into New South Wales and Victoria, 
but, as the cliffs on the coast near Coorang are supposed to be Tertiary, 
the lowest beds of the Lower Cretaceous, if present, must be beneath 
the sea-level at the Great Australian Bight. 
The outcrop of the Blythesdale braystones is crossed by several 
large streams — Blvth’s, Bungil, Bungeworgorai, and Amby Creeks, the 
Maranoa Fiver, Hoganthulla Creek, the Warrego Fiver, Birkhead 
Creek, and the eastern tributaries of the Thomson Fiver. All of 
these streams run only for a small portion of the year, but while they 
run a rock of the bibulous nature of the Blythesdale Braystone must 
be absorbing water greedily, and the water must not only spread 
laterally but must also fill up as much of the underground portion of 
the stratum or strata as had been emptied by leakage. 
Two kinds of leakage might affect the bibulous beds at the base of 
the Lower Cretaceous formation in a sufficient degree to be worth 
consideration for the present purpose. Suppose the beds to dip 
seaward and beneath the sea, and either to rise to the ocean bed or to 
dip at a lower angle than the slope of the sea-bed, there would be a 
leakage into the sea. And again, suppose (what we believe to be 
actually the case) the outcrop of the beds to occur at gradually lower 
levels till it attains the sea-level, there would be a leakage in the form 
of springs pv into river beds all along the line. In either case the 
leakage, however compact the beds might be, would not cease till the 
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