May, 1942 
The Queensland Naturalist 
31 
Sometimes these oases are fairly large, and towns or vil- 
lages may be established there. Often they are quite 
small, restricted perhaps to a small spring or rock-hole 
or soak. On maps of Australia these are sometimes 
marked as “native well.'* 7 The rock-holes are usually deep 
holes weathered out of rock and act as small reservoirs of 
rain water. Soaks are seepages where the water does not 
flow so freely as in a spring. One very interesting type 
of soak to be met with in Queensland is dry during the 
day, but begins to seep after dark, increasing until about 
mid-night, and then drying out again before dawn. 
Desert conditions may be extremely modified if large 
rivers run through the area, of which the Nile Valley is 
a well known example. Near the Queensland-South Aus- 
tralian Border, the Desert is traversed by Cooper’s Creek, 
and the Diamantina and Mulligan Rivers. The rainfall 
in these regions is very low and very uncertain, the yearly 
average varying from ab'out 4 inches to about 8 inches, 
though often there may be very much less than this for 
several years in succession. For a large part of the year 
these rivers do not run, but every now and then they are 
flooded from the higher rainfall areas near their sources, 
overflow' their banks for up to 30 miles, covering the sur- 
rounding plain with silt and thoroughly saturating the 
soil. After the flood recedes, a very rich vegetation 
springs up and provides excellent fodder for many months. 
In the Tundra, the oases are on the higher ground, 
as this is the portion most free of ice and snow. 
In parts of Queensland, the term “desert” is applied 
to a very different type of country. This is a kind of 
Eucalyptus forest or mixed open forest, on sandy or rocky 
soil, with very little readily available water at the surface. 
In spite of the difficulties of existence, many deserts 
have been inhabitated by man fur very long periods. At 
times habitation may be restricted to oases, or man may 
lead a nomadic existence, wandering from oasis to oasis 
or from rock-hole to rock-hole, driving his stock with him 
if he possessed any, or living by hunting, etc., if he did 
not. Human population under such conditions could not 
be very dense. With irrigation, many desert areas have 
become rich agricultural areas. The discovery of gold has 
inspired the construction of water schemes, such as at 
Coolgardie and Kalgoorlie, whereby water has beep 
