The surface of the plains nearest the river is unlike any part of the earth's face that I have elsewhere seen. It is as clear of vegetation as a fallow field, but it has greater inequality of surface and is full of holes. The soil is just tenacious enough to crack, when the surface becomes so soft and loose that the few weeds which may have sprung up previous to desiccation seldom remain where they grow, being blown out by the slightest wind. Over such ground it was very fatiguing to walk, the foot at each step sinking to the ankle, and care being necessary to avoid holes always ready to receive the whole leg, and sometimes the body. It was not very safe to ride on horseback even at a walk, and to gallop or trot in that country was quite out of the question. The labour which this kind of ground cost the poor bullocks, drawing the heavy carts, reduced them to so great a state of weakness that six never returned from the Darling. The work was so heavy for the two first teams on our advancing into these regions that one team was rendered quite unserviceable by leading; but on returning we found the beaten track much easier for the whole party. Notwithstanding these disadvantages we were much indebted to Providence for the continued dryness of the winter; for although it seemed then as if nothing short of a deluge could have completed the saturation, there were also many proofs that great inundations sometimes occurred; and it was still more obvious that had rainy weather, or any overflowing of the river happened, we could no longer have travelled on the banks of the Darling. GEOLOGY OF THE DARLING. The rocks about the surface of this country are few and simple. Besides the clay nothing occurred in the river bed except calcareous concretions, selenite, and in some parts sandstone similar to that seen at the base of almost all the hills. Back from the river the first elevation usually consisted of hillocks of red sand, so soft and loose that the cattle could scarcely draw the carts through. The clay adjacent to the sand was firmer than any clay seen elsewhere on the plains because the sand there acted like a sponge, taking up the water from the adjacent clay which consequently preserved its tenacity at all seasons. This edge of clay along the skirts of plains at the base of the red sand ridges I found the most favourable ground for travelling upon. Still further back gravel, consisting of fragments, not much water-worn, of various hard rocks, appeared, forming low undulations towards the base of more remote hills which consist of a very hard sandstone. I may here mention however that the extremity of Dunlop's range which, by approaching the river, there occupied the place of the hard gravel in other situations, seemed to be composed of the same rock of which much of that gravel consisted.