We experienced the most oppressive heat about this time. Calms generally prevailed, and about 3 p.m. the sun's rays fell upon us with intense effect. The waters of the Murray continued extremely muddy, a circumstance we discovered to be owing to the turbid current of the Rufus, which we passed on the 1st of March. It is, really, singular whence this little stream originates. It will be remembered that I concluded it must have been swollen by rains when we first saw it; yet, after an absence of more than three weeks we found it discharging its waters as muddy as ever into the main stream; and that, too, in such quantities as to discolour its waters to the very lake. The reader will have some idea of the force of the current in both, when I assure him that for nearly fifty yards below the mouth of the Rufus, the waters of the Murray preserve their transparency, and the line between them and the turbid waters of its tributary was as distinctly marked as if drawn by a pencil. Indeed, the higher we advanced, the more did we feel the strength of the current, against which we had to pull. DIFFICULTIES AT THE RAPIDS. A little below the Lindesay, a rapid occurs. It was with the utmost difficulty that we stemmed it with the four oars upon the boat, and the exertion of our whole strength. We remained, at one time, perfectly stationary, the force we employed and that of the current being equal. We at length ran up the stream obliquely; but it was evident the men were not adequate to such exertion for any length of time. We pulled that day for eleven successive hours, in order to avoid a tribe of natives who followed us. Hopkinson and Fraser fell asleep at their oars, and even the heavy Clayton appeared to labour. We again occupied our camp under the first remarkable cliffs of the Murray, a description of which has been given in page 128 of this work. [GEOLOGICAL EXAMINATION.] Their summit, as I have already remarked forms a table land of some elevation. From it the distant interior to the S.S.E. appears very depressed; that to the north undulates more. In neither quarter, however, does any bright foliage meet the eye, to tell that a better soil is under it; but a dark and gloomy vegetation occupies both the near and distant ground, in proof that the sandy sterile tracts, succeeding the river deposits, stretch far away without a change. A little above our camp of the 28th of January, we fell in with a large tribe of natives, whose anxiety to detain us was remarkable. The wind, however, which, from the time we lost the sea breezes, had hung to the S.E., had changed to the S.W., and we were eagerly availing ourselves of it. It will not be supposed we stopped even for a moment. In truth we pressed on with great success, and did not land to sleep until nine o'clock. As long as the wind blew from the S.W., the days were cool, and the sky overcast even so much so as to threaten rain.