H. P. Woodward — Dry Lalies of W. Australia. 363 



V. — The Dry La.kes of Western Australia. 



By Harry Page Woodward, J.P., F.G.S., Assoc. M. Inst. C.E., F.R.G.S ; 



Honorary Consulting Geologist and Mining Engineer to the Colony of Western 



Australia. 



UPON glancing at the map of Western Australia, the eye is at 

 once attracted by a series of large lakes in the interior ; which 

 are further often emphasized by being coloured blue. The natural 

 inference is, that they represent sheets of water, either fresh 

 or salt. 



Now if these lakes contain fresh water, the surrounding country 

 must be almost a paradise ; and if salt, still the evaporation from 

 them would cause the atmosphere to be humid, and hence there 

 would probably be heavy dews or light showers of rain all the year 

 round. But this is not the case, the map being entirely misleading, 

 and no Government should continue to reproduce these incorrect 

 charts : for in the first place, they are not lakes in the accepted sense ; 

 and in the second, they are not correctly mapped in ; for in one 

 instance alone, that of Austin Lake, the Island (where many 

 a promising mine is being worked at the present time) is represented 

 upon the maps as a sheet of water five miles wide. The reason for 

 this discrepancy is that these lakes were invented by the early 

 explorers, and have never since been altered upon the maps. 

 This island is about one and a half miles long, and rises abruptly 

 from the lake-bed to a considerable elevation — in fact, being one 

 of the highest ridges of the district. It is divided both from the 

 north and south shores by narrow boggy channels, each of which 

 is about 400 yards in width, whilst from its high point no extensive 

 lake is visible, but only a number of very shallow depressions 

 fringed by sandy ridges. These are not lakes in any sense of the 

 word, but a series of salt clay-pans which drain one into another, 

 and thus in very wet seasons they serve to carry off the surface 

 water ; but since the fall of the ground is so slight, and the surface 

 presented for evaporation so great, this water never finds its way 

 to the sea. 



To understand this so-called Lake District thoroughly, one must 

 realize that the interior originally consisted of a large tableland 

 about 2,000 feet above the sea-level, above which here and there 

 rose low range-masses or ridges of hard hornblendic rocks, or bosses 

 of granite, which are the fundamental rocks of the district. These 

 rocks, now that denudation has exposed them, are seen to run in 

 belts (often of considerable width) in a north-westerly and south- 

 easterly direction ; but whether they outcrop or not, their strike can 

 be traced by the nature of the superficial deposits, which are the 

 result to a great extent of their disintegration. 



The present configuration of the surface may be described as 

 due to belts of high sand-plains, while here and there in hollows, 

 or around the margins of the more elevated areas, one meets with 

 outcropping bosses of gneissic granite, which rock is found every- 

 where to underlie these high saud-plaius. More or less parallel with 



