Clarke. — NaUiral 'Regions hi irestcrn AustraUa. 
127 
acid nietamorphie and gnessic rocks, suppose<lly Pre-Canil^riaii, to- 
gether with a minor amount of Nullagine ( sediments, but there is 
amongst them a notable developiiKuit of two types of basic igneous 
rock, one a “Greenstone,’’ similar to the greenstones of the Kal- 
goorlie and Murcliison regions, the otlier unaltered dolerites and 
gabbros (Talbot, 1917). In the character of its vegetation the 
Warburton Region recalls the Murchison. Topographically, the 
tal)leland of the Carnegie Region is continued into the Warburton, 
but above the general level rise ranges, some in the old crystalline 
rocks, some in the later dolerites and gabbros, some in the hard 
Nullagine sandstones. Draining from these hills and losing them- 
selves in the sandhill country of the Carnegie Region to north, west, 
and south, are several well-defined watercourses. 
One shallow well with a large sup])ly of potaljle water is known, 
and good st)rings have been noted in several localities. Probably 
good stock water is easily obtainable in most parts of the Region- 
The region would be as successful pastorally as the Murchison 
(Talbot, 1917, p. 118), and there are hopes that payable deposits of 
gold will be discovered, but its relatively small size and inaccessi- 
bility Avill hinder its develo])ment for many years. 
11. North Jl'est Region. This large area, traversed by several 
more or less parallel rivers (De Grey, Fortescue, and Ashburton), 
includes a variety of geological formations of assumed Pre-Cam- 
brian age, namely, the almost horizontal Nullagine System which 
occupies about tliree-(}uarters of the region, the more steeply inclined 
but little metamorphosed ilosquito Creek Series, and the highly 
altered “greenstones” and intervening granites composing the 
northern portion, in Avhich tlierc are wides])read and varied mineral 
de^^osits, including copper, tin, lead, tantalite, asbestos, and gold. 
The topography of the area is naturally a reflection of its 
geology, so that whereas in the southern part mesas and buttes are 
characteristic, in the northern part the scenery varies. As in the 
Kalgoorlie and Murchison Regions, granite country is fiat or gently 
undulating; “mineral belts,” such as Marble. Bar, Nullagine, Brae- 
side (lat. 21°, long 121°), and Lionel, near Nullagine, are, in a 
small way, very rugged. 
However, these geological and topogra])hical differences are too 
intermingled to justify the separation of the area into two or more 
regions of individuality e(iual to the others described in this paper. 
Perliaps the factor which overrides geological differences is the 
prevalence throughout the region of uncertain summer rainfall. 
As to vegetation, the region is characterised by the predomin- 
ance of the Spinifex association, the Mulga, so characteristic of the 
