136 
CONCLUDING REMARKS. 
been washed to pieces by the violent action of water, 
and which appeared to have been originally, of 
nearly the same general elevation as the table lands 
to the westward. It seems to me, that these table 
lands have formerly been the bed of the ocean, and 
this opinion is fully borne out by the many marine 
remains, fossil shells* and banks of oyster shells,* 
which are frequently to be met with embedded in 
them. What are now the ranges of the continent 
would therefore formerly have been but rocks or 
islands, and if this supposition be true, there are still 
hopes that some other islands are scattered over the 
immense space occupied by Australia, and which 
may be of as rich and fertile a character, as any that 
are yet known. Thus if the intervening extent of 
desert lying between any of the known portions of 
the same original superstratum, which I therein described, 
though 7 or 800 miles separated from them. They agree exactly 
in character, and also in the materials of which they are com- 
posed ; and I believe that some unaccountable gorge of waters 
has swept away the intervening earth, leaving these solitary and 
isolated, though incontrovertible evidences, that the summit level 
of all this great valley, has at one time been where the level sur- 
face of these hills now is, iwo or three hundred feet above what 
is now denominated the summit level.” — Catlin’s American 
Indians, Yol. 2. pp. 11 and 12. 
* Similar banks of fossil shells and oyster beds, are found in 
the Arkansas.— Vide Catlin, Vol. 2. p. 85. At page 86, Mr. 
Catlin describes banks of gypsum and salt, extending through a 
considerable extent of country, and which apparently was of a 
very similar formation to some of the localities I was in to the 
north of Spencer’s Gulf. 
