218 Influence of the Physical Character 
in the wild sandy country, between 35° and 36° south 
latitude, very much of which, for some miles east and west, 
is covered with scrub. It first enters Lake Hindmarsh, the 
waters of which flow northward, by an outlet creek, sixteen 
miles in length, to Lake Albacuyta, and there are a number 
of swamps north of the latter, which appear to derive their 
waters from the same source. The Yarrambiack Creek, after 
draining a considerable extent of country, flows into Lake 
Corong. Of course it is impossible to explain these facts, 
unless we have more accurate information than is at present 
available; judging from analagous effects, however, it is im- 
probable that the evaporation from Lakes Hindmarsh and 
Albacuyta is sufficient to dissipate the waters of such a river 
as the Wimmera, or that the Avoca has its only outlet in 
Lake Bael Bael. South of the Murray the country is covered 
with a great of thickness of sand and pervious strata, and it 
is therefore highly probable that these rivers have subter- 
ranean channels: as to whether they are received into the 
Murray, or penetrate to depths greatly beyond its level, I am 
not prepared to offer an opinion. It is not, however, a 
problem very difficult to solve ; observations in the locality 
. would soon settle the point. TI believe the absence of summer 
streams is not always to be explained, by quoting the rapid 
evaporation of storm waters. Subterranean drainage carries 
off no inconsiderable portion of the waters of such rivers as 
the Yarra, the Mackenzie, &c., and it may sometimes happen 
that a stream is dry in summer from this cause alone. The 
rocks in this country vary in their lithological character, and 
though we are justified ‘in ‘assuming, that, under ordinary 
circumstances they will not absorb much of the rainfall, they 
may become recipients of millions of cubic feet of water, 
where a river happens to flow over coarse sandstones, rent 
and fissured, and cut through by dykes. In creeks, or in 
gently flowing streams, the bed is usually a stratum of clay, 
whereas the winter flood of a river may have a velocity 
sufficient to strip the bed completely of mud and clay, and 
expose the pervious stratum beneath. 
I might adduce many instances of extreme variations in the 
summer currents of rivers, where the drainage areas are 
nearly equal, but where the geological formations are different; 
but as it is not possible, in that manner, to educe general laws 
useful in practice, these instances need not be recorded. It is 
only by careful observations and inquiry that we can meet 
the difficulties of each case; each, invariably, presenting local 
peculiarities that must be studied on the spot, and not referred 
to distant places for comparison. 
