Some of the hollows behind the immediate banks on both sides contained lagoons; in several of these reeds had taken the place of water; in others the first coating of vegetation which the alluvium receives on exposure to the sun consisted of fragrant herbs, and amongst them we found the scented trefoil (calomba*) which proved an excellent anti-scorbutic vegetable when boiled. It was found however only at three places.
(*Footnote. Trigonella suavissima, for the description of which plant see above.)
SURFACE OF THE PLAINS.
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.
Of the hills in general it may be observed that those on the left bank are most elevated at the higher parts of the river, whereas those on the right bank rise to greatest height towards the lower parts of the river, as far as explored by us. The plains extend on each side of the channel to a distance of six or seven miles and are in general clear of timber. That deep and extensive bed of clay, so uniformly filling the basin of this river, has every appearance of a mud deposit.
WOODS AND GRASSES.
Behind the plains the country is sparingly wooded except by the stunted bush (Myoporum montanum) which forms a thick scrub, especially on the side of the low hills. On the riverbank trees peculiar to it grow to so large a size that its course may be easily traced at great distances; and they thus facilitated our survey most materially. These gigantic trees consist of that species of eucalyptus called bluegum in the colony; and their searching roots seem to luxuriate in the banks of streams, lakes, or ponds, so that the thirsty traveller soon learns to recognise the shining trunk and white, gnarled arms, as the surest guides to water. The alluvial portion of the margin of the Darling is narrow, and in most places overgrown with the dwarf box, which is another species of eucalyptus. In it are hollow places as already observed, covered with the Polygonum junceum, which is an unsightly leafless bush or bramble. Grass is only to be found on the banks of the river and, strictly speaking, the margin only can be considered alluvial, for this being irrigated and enriched by the floods it is everywhere abundantly productive of grass, though none may appear in the back country.
GUM ACACIA ABUNDANT.