90 
cent country to the north-western ranges of South Australia, 
and extend for many hundreds of miles north, south, and 
west, the tablelands on the east checking the accumulation to 
a slight degree in that direction. 
The height above sea level of these deposits is consider- 
able, the sand ascending to an altitude of 1,900 feet in the 
Ayers Ranges, and to 2,200 feet in the locality north of 
Opparinna Spring. It is on this account that all the larger 
v^alleys cutting the ranges have become filled up with elevated 
deposits, from which large, gum-lined creek beds emerge, to 
be subsequently 'lost" in the sands adjoining the ranges. 
This drifting cover is embarrassing to the prospector, as the 
higher portions of the ranges alone can be examined, the 
more favourable contact-rocks being for the greater part hid- 
den underneath the great depth of sand. 
The material of the deposits consists of a moderately fine- 
grained, incoherent sand, the grains being usually superficially 
coated red by oxide of iron. In proximity to the ranges these 
sands are more locimy, and have been bound together by vege- 
tation. There, also, they contain other constituents derived 
from ^he decomposition of the primary rocks, such as cleaved 
fragments of felspar and hornblende, flakes of mica, small 
nodules of limonite (iron-shot), and occasional patches of 
garnets. Beyond the belt influenced by the ranges, the sand 
is loose, incoherent, and subject to a continual drift. In 
these regions the sand accumulates in the form of more or 
less parallel undulations or sandhills, mostly incoherent 
throughout, but occasionally very slightly cemented super- 
ficially. The direction in which these sandhills trend, beiti;/ 
at right angles to prevalent winds, is east and west, south of 
the Musgrave Ranges, although the more usu;ii directiDn ob- 
served further south, in the basin of Lake Torrens, is south- 
west. Frequently two such parallel undulations unite to 
form one,* thence continuing as one in the same direction. 
Nuclei which had in the f^rst place started the formation of 
sandhills were observed north of Mount Crombie, in the shape 
of low outcrops of granite, while a few miles south of Stuart's 
Creek a prominent '"'sandhill" consists of a former tablehill of 
desert sandstone, almost completely covered with drift sand, 
few exposures only of the rock being visible, and limited to 
one side of the hill. The source of this vast amount of sand 
must be attributed to the cEolian waste of tlie r^esert sandstone 
formation, t 
* Streich states that the "sand dunes" of the Great Victoria 
Dosort are "very seldom found confluent." — Trans. Roy. Soc, 
S.A.. vol. xvi., page 89. 
t Compare E. F. Pittmau : On the Cjetac(M)ii.s Formation 
in the Nortli-Western Portion of New South Wales. Rec. Geol. 
Sui-v. N.S.W., vol. iv.. Part iv.. pa^e ]4(i. 
