SIR,--I do myself the honor to forward, for the Governor's perusal, a copy of my journal up to the date of my arrival at Mount Harris. I should not have directed the messenger to return so soon, had I not subsequently advanced to Mount Foster, and surveyed the country from that eminence. I could distinctly see Arbuthnot's Range to the eastward. From that point the horizon appeared to me unbroken, but the country to the northward and westward seemed to favour an attempt to penetrate into it. I did not observe any sheet of water, and the course of the Macquarie was lost in the woodlands below. Mr. Hume ascended the hill at sun-rise, and thought he could see mountains to the north east, but at such a distance as to make it quite a matter of uncertainty. Agreeing, however, in the prudence of an immediate descent, we left our encampment on the morning of the 23rd, under Mount Foster, to which we had removed from Mount Harris, and pursued a north-north-west course to the spot on which we rest at present. We passed some fine meadow land near the river, and were obliged to keep wide of it in consequence of fissures in the ground. Traversing a large and blasted plain, on which the sun's rays fell with intense heat, and on which there was but little vegetation, we skirted the first great morass, and made the river immediately beyond it. It is of very considerable extent, the channel of the river passing through it. We are encompassed on every side by high reeds, which exist in the woods as well as in the plains. Mr. Hume and myself rode forward yesterday through the second morass, and made the river on slightly elevated ground, at a distance of about five miles; the country beyond appeared to favour our object, and we, to-morrow, proceed with the party to the north-west. The river seems to bend to the north-east; but in this level country it is impossible to speak with certainty, or to give any decided opinion of the nature of it, beyond the flats on which we are travelling. The reeds to the north-east and northward extend over a circumference of fifty miles; but if Mr. Hume really saw mountains or rising ground in the former point, the apparent course of the Macquarie is at once accounted for. The country, however, seems to dip to the north, though generally speaking it is level, and I am inclined to think that the state of the atmosphere caused a deception in this appearance.