part is, however, within the province of South Australia.  Between Cooper’s Creek and Lake Torrens about 120 miles of sandy country intervenes.  This tract is destitute of surface water, but as it is probable that it could be obtained by sinking wells of moderate depth, I think it might be occupied to advantage during the cool season, and thus relieve the stations which are now established within Lake Torrens, though I fear that the summer heat would be too great to admit of permanent occupation.  The geological character of the country is remarkably uniform.  Carboniferous sandstones and shales, containing occasional beds of coal, with superincumbent hills and ridges of basalt, extend from Darling Downs to the 146th meridian, where these rocks are covered by horizontal sandstones with beds of chert and water-worn quartz pebbles.  This latter formation extends as far as Mount Hopeless, where the slate ranges of South Australia rise abruptly from the plain.  The sandy deserts and mud plains are only superficial deposits, as the sandstones are often exposed where the upper formation is intersected by gullies.  The direction of the parallel ridges of drift sand appear to be the result of the prevailing winds, and not the action of water, it being sufficient to visit them on a windy day to be convinced that it is unnecessary to seek for a more remote and obscure cause than that which is in present operation.  It is, perhaps, with reference to the physical geography of Australia that the results of the Expedition are most important; as by connecting successively the explorations of Sir T. Mitchell, Mr. Kennedy, Captain Sturt, and Mr. Eyre, the waters of the tropical interior of the eastern portion of the Continent are proved to flow towards Spencer’s Gulf, if not actually into it, the barometrical observations showing that Lake Torrens, the lowest part of the interior, is decidedly above the sea-level.  Although only about one-third of the waters of Cooper’s Creek flow into Lake Torrens by the channel of Streletzki Creek, there is strong evidence that the remaining channels, after spreading their waters on the vast plains which occupy the country between them and Sturt’s Stony Desert, finally drain to the south, augmented probably by the waters of Eyre’s Creek, the Stony Desert, and perhaps some other watercourses of a similar character coming from the westward.  This peculiar structure of the interior renders it improbable that any considerable inland lakes should exist in connection with the known system of waters; for, as Lake Torrens is decidedly only an expanded continuation of Cooper’s Creek, and therefore the culminating point of this vast system of drainage, if there was sufficient average fall of rain in the interior to balance the effects of evaporation from the surface of an extensive sheet of water, the Torrens Basin, instead of being occupied by salt marshes, in which the existence of anything beyond shallow lagoons of salt-water is yet problematical,