SAND-DRIFT PROBLEM IN NEW SOUTH WALES. 101 
(the term is comparative) and clothed with vegetation. 
The vegetation being eaten out, the soil would drift, par- 
ticularly in seasons of drought. In other words, much 
of the trans-Darling country is in a state of unstable 
equilibrium. 
The consensus of evidence shows that the sand moves 
more than it used to do. What prevented this? Simply 
the vegetation, sparse though it was, which through a 
long course of ages had tended to knit it together. In 
fact, insandy country, all that binds it together is vege- 
tation. 
5. Causes of drifting sands.—To summarise in some 
degree, three causes have resulted in drifting sands :— 
a. Droughts.—Some authorities even aver that sands 
did not, in the old days, drift except in droughts. This 
is not correct but they are more mobile now. 
b. Overstocking.—It is very easy to criticise the pas- 
toralist for overstocking, but there are so many variables 
to be considered in obtaining the constant as regards the 
carrying capacity in a particular year that most of the 
overstocking is unavoidable, the result of our ignorance 
of the sequence of the seasons. The mechanical action 
of a flock of sheep, irrespective of overstocking, is impor- 
tant. They pulverise the soil and for many years, even 
before the recent crisis, the position of a flock of sheep 
has been readily detected, in the distance, by an attendant 
cloud of dust. 
c. The rabbit pest.—This is the real cause of over- 
stocking and it is involuntary on the part of the pastoralist. 
This pest has become acute during the past 20 years and 
has accentuated any overstocking by sheep. 
6. Prevailing Winds.—Mr. Russell tells me that the 
prevailing winds in the western country, capable of piling 
