CXIV. IRRIGATION GEOLOGICALLY CONSIDERED. 
In South Australia the main artesian basin is represented 
by the same formations as those already described in the 
artesian areas of Queensland and New South Wales, viz., 
Desert Sandstone (Upper Cretaceous), Rolling Downs 
Formation (Lower Cretaceous) and Triassic beds. The last 
mentioned are typically developed at Leigh’s Creek, to the 
south of Lake Hyre, where Triassic fossils and coal seams 
occur, the former similar to those of the Ipswich Coal 
measures of Queensland. These formations have been 
described by Mr. H. Y. L. Brown,’ the Government Geologist 
of South Australia, the late Prof. Tate, and Mr. J. A. Watt,’ 
Mr. W. Howchin, F.G.s.,° and Mr. R. Etheridge, Junr.* An 
account of the artesian bores and of the strata penetrated 
in them will be found in the official reports by Mr. J. W. 
Jones, the Government Conservator of Water. | 
The latter in a letter addressed to one of us dated July 
13th, 1896, expresses the following opinion :—‘In elabor- 
ating the section so as to arrive at the actual hydraulic 
grade line, I found, as you no doubt did, that the culminating 
point is in the neighbourhood of Charleville. Thence to 
the South end of Lake Hyre I found a fairly even grade 
line with a fall of about 1 ft. 9ins. per mile. Several bor- 
ings in South Australia and a number in Queensland go to 
show that this line departs very little from the direct line 
between two points; if there is any departure it is as you 
have shown, with the convexity uppermost. From the 
Same culminating point to the Normanton bore, Gulf of 
Carpentaria, the hydraulic grade line seems almost identical 
with the one described. Here also the fall is about 1 ft. . 
9 ins. per mile.”’ 
A good description of the mound springs of the artesian 
area of South Australia is given by Mr. H. Y. L. Brown.’ 
1, 2, 3, 4, Detailed references to the papers by the above authors are 
given in the bibliography by Mr. W. S. Dun, at the end of this paper. 
§ Aust. Assoc. Adv. Sci., Vol. 1., 1887, p. 243. The Mesozoic Plains of 
South Australia. 
