I think it a probable conjecture that this river is the channel by which all the waters rising in those ranges of hills to the westward of Port Jackson, known by the name of the Blue Mountains, and which do not fall into the sea on the east coast, are conveyed to these immense inland marshes; its sinuous course causing it to overflow its banks on a much higher level than the present, and in consequence, forming those low wet levels which are in the very neighbourhood of the government depot. Its length of course is, in my opinion, the principal cause of our finding any thing like a stream for the last one hundred miles, as the immense body of water which must undoubtedly be at times collected in such a river must find a vent somewhere, but being spent during so long a course without any accession, the only wonder is, that even those waters should cause a current at so great a distance from their source; everything however indicates, as before often observed, that in dry seasons the channel of the river is empty, or forms only a chain of ponds. It appears to have been a considerable length of time since the banks were overflowed, certainly not for the last year; and I think it probable they are not often so: the quantity of water must indeed be immense, and of long accumulation, in the upper marshes, before the whole of this vast country can be under water. My intention to penetrate farther westward being thus frustrated, I returned to the tent about three o'clock, and determined, should the horses appear sufficiently recovered and refreshed, finally to quit this western part of the country on Thursday next; a few days rain would prevent us from ever quitting it, but we have been bountifully favoured by Providence with a season of continued fair and pleasant weather, which could hardly have been expected, and which alone could have enabled us to decide so satisfactorily, if it can be called satisfaction to prove the negative of the existence of any navigable rivers in this part of Australia. July 8.--Observed the sun's magnetic amplitude in rising from the clear horizon of the plain, a circumstance that rarely can occur in any country unless such a one as the present; it strongly marks the. horizontal level which seems to run now from east to west. Mean lat. of our tent 33 degrees 53 minutes 19 seconds S. Comp. long. 144 33 50 E. Mean variation 7 25 00 E. Situation of the spot where the stream ceased to have a current. Lat 33 degrees 57 minutes 30 seconds S. Long. comp. 144 23 00 E. Do. do. 144 31 15 E. No hill or eminence in a south-west direction terminating in lat. 34. 22. 12. and in long. 143. 30. 00. E. which is the calculated extent of our visible clear horizon.