October 1899] ORIGIN OF AUSTRALIAN FLORA 275 



The granites wherever they outcrop bear a most distinct eruptive 

 character, elsewhere they are overlain by rocks of Palaeozoic or Archean 

 age, composed chiefly of hornblendic schists and slates in different 

 varieties, and themselves overlain by feldspathic schists and quartzites 

 of the same age, with talcose and micaceous schists and siliceous 

 ironstone. 



I am unable to add anything of the least value concerning the 

 northern part of the district visited by me, and which lies beyond the 

 countiy traversed by Mr. Streich ; indeed, a fair knowledge of British 

 secondary and tertiary deposits is a most inadequate preparation for 

 effective study of coeval formations in Australia whose lithological 

 characters are so different from those of European deposits. I will 

 merely remark that what, judging from Mr. Streich's description, 

 appear to be secondary rocks are to be met with in the country 

 between Mount Flora and Lake Darlot, although in the absence of 

 fossils I must candidly confess I considered these formations to be 

 much older. What I have specially in memory are sandstones and 

 conglomerates ; and the so-called " breakaways " of the country in 

 question correspond apparently with the terraced outcrops of Mesozoic 

 rocks Mr. Streich found in his eastern section. 1 But Mr. Streich's 

 observations suffice to give us an idea of the changes undergone by the 

 southern part of the West Australian desert since earlier Cretaceous 

 times. We may infer from them a westward extension, probably in 

 the form of a wide arm of the cretaceous sea which divided Australia 

 into an eastern and a western island, while during earlier tertiary 

 times the eastern part of the desert would seem to have shared the 

 fate of Central Australia, that is to say, that after having emerged 

 from the waves, submergence again took place while the tertiary forma- 

 tions were being deposited. Whether this part of Australia was 

 subsequently a lacustrine area or whether it was dry land, does not 

 appear from the evidence, though the presence of desert sandstone near 

 Yilgarn suggests the former condition. The western part of the desert 

 was above water during Mesozoic times, and if the Darling con- 

 glomerates be Palaeozoic, a considerable area west of what is now the 

 desert was also dry land during these times. In earlier tertiary times 

 the district must, in its eastern part, have borne the character of an 

 archipelago, and by subsequent upheaval the sea was divided into a 

 number of inland salt lakes which gradually underwent desiccation. 



1 Altitudes were taken during the course of this expedition. The country east from 

 Queen Victoria Springs is from 1000 to 1200 feet above sea-level, thence it descends to the 

 Springs (830 feet), and rises west of it to from 1200 to 1450 feet. The highest point of 

 the Fraser Range is 2010 feet above the sea, and the plateau to the west of the range, as lias 

 been already mentioned, 1300 to 1400 feet, while Mount Monger near Coolgardie is 1700 

 feet above sea-level. A plan showing the elevation of the country between the Darling 

 Range and Mount Burgess, the work of "West Australian government surveyors, was 

 issued about three years back in connection with the proposed Coolgardie water-scheme. It 

 bears out, in the main, so much of the above statement as concerns the country in question. 



