1126 The Geology of Central Australia. —[November, 
They are of two kinds, sand drifts and stony drifts. The 
sand consists of rounded grains of quartz, and is arranged in long 
low ridges, Between these ridges are open clay-flats or “ clay- 
pans” formed of a yellow or reddish clay. Both sand and clay 
have been derived from the slow sub-aérial weathering of the 
granite and crystailine schists which form the ranges. Near the 
latter the sand contains grains of feldspar, zircon, tourmaline, 
magnetite and hematite. But further away it consists of pure 
quartz. The feldspars decompose and form the basis of the clay 
and the various salts with which it is impregnated. (See infra) 
The sand hardens into a sandstone showing much cross-bed- 
ding and oblique lamination, as might be expected from its aérial 
origin. Through the rock are ferruginous bands in which are 
carbonized remains derived from surface vegetation. The denu- 
dation of this sandstone gives rise in part to the cliffs and table- 
topped hills so characteristic of Central Australia. Throughout 
the continent such deposits are now forming but similar condi 
tions have produced the same formation at other epochs. thu 
in New South Wales such a sandstone is found many feet m 
thickness, and containing remains of ferns and cycads. They lie 
unconformably on the Permian and Liassic coal-beds, and evt 
dently belong to the Lower Mesozoic. In Queensland they owe 
lie the Cretaceous beds and, according to Tenison-Woods, afè 
Tertiary. In the interior basin there is a complete gap D 
these beds and the Mesozoic rocks. They, as we have said, a 
forming at the present day, and probably have been so doing ever 
since the Mesozoic beds arose from the sea. The plant era st 
of the beds in the interior, as far as I have examined them, are 
not preserved well enough for identification. But here and a 
throughout the interior are found remains of the gigantic = 
supials — Diprotodon, Nototherium and Phascolomys. ae | 
animals probably lived in the latter part of the Tertiary and ear ee 
and middle Quaternary. re 
Alternating with the sand deposits are plains composed pee 
stony drift. This is, for the most part, derived from get 
struction of the æolian sandstones in their turn. In other © : 
however, near the confines of the desert, wherever the aie 
rocks outcrop, it is derived from them. The boulders am red 
bles lie thickly strewn on the surface, and are stained a o 
from the presence of the oxide of iron. It is owing to ths 7 
