On the 16th, we were again fortunate in the wind, and pressed up the river as long as day-light continued. At the termination of our journey, we found ourselves a day's journey in advance. This inspirited the men, and they began to forget the labours they had gone through, as well as those that were before them. On the 17th, we again commenced pulling, the wind being at north, and contrary. It did not, however, remain in that quarter long, but backed at noon to the S.W., so that we were enabled to make a good day's journey, and rather gained than lost ground. REMARKABLE CLIFF--GEOLOGICAL REMARKS. Having left the undulating hills, at the mouth of the valley behind us, we passed cliff after cliff of fossil formation: they had a uniform appearance as to the substance of which they were composed, and varied but little in colour. Having already examined them, we thought it unnecessary to give them any further special attention, since it was improbable we should find anything new. In turning an angle of the river, however, a broad reach stretched away before us. An alluvial flat extended to our left, and a high line of cliffs, that differed in no visible respect from those we had already passed, rose over the opposite side of the river. The cliffs faced the W.N.W., and as the sun declined, his beams struck full upon them. As we shot past, we were quite dazzled with the burst of light that flashed upon us, and which gave to the whole face of the cliff the appearance of a splendid mirror. The effect was of course momentary; for as soon as we had passed the angle of refraction, there was nothing unusual in its appearance. On a nearer approach, however, it appeared again as if studded with stars. We had already determined on examining it more closely, and this second peculiarity still further excited our curiosity. On landing, we found the whole cliff to be a mass of selenite, in which the various shells already noticed were plentifully embedded, as in ice. The features of the cliff differed from any we had previously remarked. Large masses, or blocks of square or oblong shape, had fallen to its base, and its surface was hard, whereas the face of the majority of the other cliffs was soft from the effect of the atmosphere; and the rock was entirely free from every other substance, excepting the shells of which it was composed. We of course collected some good specimens, although they added very considerably to the weight of our cargo. The morning of the 18th was calm and cloudless. The wind, of which there was but little, came from the north, and was as usual warm. We availed ourselves of a favourable spot to haul our boat on shore under one of the cliffs upon the proper left of the river, and cleaned her well both inside and out. LABORIOUS ASCENT OF THE BOAT.