554: Clarke — Geology of Western Australia. 



Bight, and towards the coast southwardly, are succeeded by those 

 marine beds, at the base of which, according- to Flinders and Eyre, 

 white aluminous beds lie below the shelly deposits, and repose on 

 granite. Those I have little hesitation in comparing with the alu- 

 minous beds near Lake Lefroy, an extension of which is also 

 indicated at several points to the westward in the journal of Mr. 

 Lefroy. 



That gentleman was led to a somewhat similar view from a 

 section of a gully in 31° 29' S., 120° 11' E., about sixty-five mUes 

 W.S.W. of Hunt's "White Hills." The evidence already obtained 

 leads, therefore, to the conclusion, that not far from Mr. Hunt's 

 furthest, a change takes place where Tertiary beds become prevalent. 

 The following considerations will strengthen the probability of this 

 view : — 



Mr. Hunt's eastern limit seems to have been about half-way 

 between York and the }dg]i cliifs of the Bight (Bimdah) , and about 

 120 miles from the extension of the outlying Tertiary Bight lime- 

 stone, near the Salt Lakes west of Esperance Bay, {Eyre), in the 

 neighbourhood of which on Middle Island (Flinders) the granite is 

 covered by a crust of calcareous matter ; and about 170 or ] 80 miles 

 from the spot, near Point Culver, where the limestone becomes covered 

 by the superficial sandy and ironstone detritus which, according to 

 the aborigines, is the general character of the country between 

 Lefroy's and Hunt's furthest and the sea, of which twenty-five miles 

 seems to have been seen by the latter observer from the last elevated 

 land on the 122nd meridian. 



It may be remarked here, that the projections of granite along 

 the coast which forms an arc between 118° and 136° E., and of which 

 the chord is strictly the parallel of 35° S., are all more or less 

 covered with a calcareous crust before mentioned, of which evidence 

 exists in King George's Sound and Cape Arid to the west, and from 

 Cape Eadstock to Cape Catastrophe to the east. This is by itself an 

 interesting fact, as showing how vast an area has been destroyed. 

 By a rough but tolerably careful calculation I find that the water- 

 area, allowing for the winding of the coast, is not under 144,000 

 square miles, and if the average thickness of the removed Tertiary 

 beds was that of the Bight Cliff's, viz., 300 feet, the enormous mass 

 of removed matter is upwards of 1200 billions of cubic feet. (See 

 note, p. 000.) 



Coupling with this the bearing of Mr. Hunt's specimen No. 5 it is 

 only a fair inference that, at the limit indicated, the explorers were 

 on the edge of the Bight formation, the head of which is on the 

 parallel of Mount Eaton, between Lake Cowan and Lake Lefroy. 

 We may therefore presume that a change of country, assimilated 

 to that of the western part of South Australia, there begins, the 

 distance from the frontier being only 630 miles. 



There is one further deduction which, until refuted by discoveries 

 of another kind, has a considerable interest for the geographer. 



Looking to the facts exposed at the Bight and on the north west coast, 

 between Mount Blaze and Cape Joubert, and to the facts discovered 



