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 
country 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.' 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 has 
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. 
