Clarke — Geology of Western Australia. 555 



by Mr. A. C. G-regory on Sturt Creek, and by Mr. F. T. Gregory 

 about 500 miles to the westward and southward of the former, where 

 he had indications of an e\ddent great water-channel, we may con- 

 clude that there is a presumption in favour of a probable Strait 

 between the Bight and the north-west Coast, now tilled in by Tertiary, 

 Post-pliocene, and Eecent accumulations ; and the features disclosed 

 on Stuart's line of route agree with what may be considered the 

 north-east side of a region traversed by such a Strait, whilst the 

 features of Lefroy's and Hunt's territory equally agree with the south- 

 west or opposite side of the Strait. Between the most eastern granite 

 near the Russell Range on the south coast and that at Fowler's Bay, the 

 distance is nearly the same as that between the respective extreme 

 limits of the desert discovered by the Messrs. Gregory, so that there 

 is much to jiistify the conclusion, so "far as the present evidence 

 goes. And if such an hypothesis be adopted, then it follows, that 

 to the north-east and north of " Hunt's furthest," the country would 

 be low-lying and desert also, so far as the watershed of streams crossed 

 by Stuart, which are but 200 miles from the supposed eastern bank of 

 the assumed Strait. 



This view will explain in some degree the occurrence of the 

 lakes and watercourses, the drainage of which Mr. Lefroy says is 

 scarcely perceptible in any direction. 



As the height of the clifi's at the Bight is not more than 600 feet, 

 unless there is a much greater elevation than that of the lakes, there 

 could be no drainage to the sea, and accordingly no streams are 

 found passing to the coast from the north. The drainage, if any, 

 should be to north-east or north from Hunt's furthest, if the idea of a 

 Strait be correct, and in that case, probably, Mr. F. Gregory's 

 "supposed" river from the interior would carry off all supplies 

 falling into the hypothetical Strait. 



A final remark remains. In Mr. Lefroy's Journal it is stated that 

 no trace was found of any bituminous fluid such as was alleged to 

 have been met with in the former expedition of Messrs. Dempster, 

 and that no Carboniferous rocks exist in the country traversed. 

 This, however, ought not to prevent further research, because it is 

 now established that hydrocarbon fluids are not confined to the 

 Carboniferous rocks, but rise from great depths below their horizon. 

 Without venturing to form any opinion as to the fact stated, or as to 

 its value, a further inquiry may be properly recommended. 



In No. 25 of Mr. Hunt's collection we have a clay containing a 

 small per-centage of some carbonaceous matter ; but this fact is not in 

 collision with the origin of such clay from Siluiian slates, since it is 

 well known that, in the rocks of that age, there is often an abund- 

 ance of carbonaceous matter, though no such deposits of coal as 

 occur in the Carboniferous formation. Yet, had there been any 

 traces whatever of vegetable impressions, it might, in the absence of 

 evidence to the contrary, have been inferred that such a clay be- 

 longed to a Carboniferous formation, and Mr. Staiger hinted at such 

 a possibility. That, however, is very far from probable. 



The quantity of saline matter contained in this and some other of 



