On the other hand it would appear, that there is no place from which at any time the survey of the more central parts of the continent could be so effectually carried on; for in a country like Australia, where the chief obstacle to be apprehended in travelling is the want of water, the facilities afforded by the Murray and its tributaries, are indisputable; and I have little doubt that the very centre of the continent might be gained by a judicious and enterprising expedition. Certainly it is most desirable to ascertain whether the river I have supposed to be the Darling be really so or not. I have stated my objection to depots, but I think that if a party commenced its operations upon the Murray from the junction upwards, and, after ascertaining the fact of its ultimate course, turned away to the N.W. up one of the tributaries of the Murray, with a supply of six months' provisions, the results would be of the most satisfactory kind, and the features of the country be wholly developed. I cannot, I think, conclude this work better than by expressing a hope, that the Colonial Government will direct such measures to be adopted as may be necessary for the extension of our geographical knowledge in Australia. The facilities of fitting out expeditions in New South Wales, render the expenses of little moment, when compared with the importance of the object in view; and although I am labouring under the effects of former attempts, yet would I willingly give such assistance as I could to carry such an object into effect. APPENDIX. APPENDIX No. I. GEOLOGICAL SPECIMENS FOUND TO THE SOUTH-WEST OF PORT JACKSON. Considering the nature of the country over which the first expedition travelled, it could hardly have been expected that its geological specimens would be numerous. It will appear, however, from the following list of rocks collected during the second expedition, that the geological formation of the mountains to the S.W. of Port Jackson is as various as that to the N.W. of it is mountainous. The specimens are described not according to their natural order, but in the succession in which they were found, commencing from Yass Plains, and during the subsequent stages of the journey. Sandstone, Old Red.--Found on various parts of Yass Plains, in contact with Limestone, Transition.--Colour dark grey; composes the bed of the Yass River, and apparently traverses the sandstone formation. Yass Plains lie 170 miles to the S.W. of Sydney. Sandstone, Old Red.--Again succeeds the limestone, and continues to the N.W. to a considerable distance over a poor and scrubby country, covered for the most part with a dwarf species of Eucalyptus. Granite.--Colour grey; feldspar, black mica, and quartz: succeeds the sandstone, and continues to the S.W. as far as the Morumbidgee River, over an open forest country broken into hill and dale. It is generally on these granite rocks that the best grazing is found.