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 Yarramblack 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. I beheve the absence of summer 

 streams is not always to be explained, by quoting the rapid 

 evaporation of storm waters. Subterranean drainage carries 

 oft* 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 mucK 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. 



