The uncertainty of the rainfall shows itself in another way, in the peculiarities of the rivers. Of all the great rivers in this basin, the Murray alone, fed by the melting snows of the Australian Alps, has a good supply of water at all seasons; the rest are variable. The Darling, Lachlan and Murrumbidgee are navigable for long distances in favourable seasons, and sometimes are flooded and overflow their banks, turning the surrounding country into a huge shallow lake; but at other times they become, in places, little more than strings of detached pools. Here is a 31 lagoon on the Murrumbidgee, and here is the Murray evidently in 32 flood, to judge from the trees growing out of the water; another view shows us the river in its ordinary state. By way of contrast 33 here is a small creek in the Riverina district; the road crosses it by a ford, so that it is evidently not very deep, and would 34 soon dry up. But after heavy rains, further up-country, the creek may become for a short time a roaring torrent. Settlers new to the country have often made the mistake of camping in the evening on the near side of a creek of this kind, only to find in the morning that the ford has vanished and that they must stay where they are until the water subsides. One of the most remarkable features in Australian weather is this sudden change from drought to flood, which not only transforms the rivers but in a few days gives a covering of rich green pasture where before was a parched desert supporting only the hardy salt-bush. When the rivers are full we can see the shallow draught steamers collecting wool and other products; but the want of water is 35 not the only drawback. The rivers wind greatly in their courses over the level plain, so much so that at one place it is said that the steamer takes a whole day to pass a particular house, owing to the river bending right back upon itself. The river banks are marked by lines of gum trees, by which the eye can trace them for many miles across the level. Except for this, the whole area crossed by these rivers in their lower courses is one vast treeless plain, covered with grass and scrub in the rains, but at other times dry, dusty, and monotonous. It extends into Queensland and Victoria, but its greatest development is in New South Wales: for though the other colonies have large flocks of sheep, it is here that sheep-raising is the one industry above all others; in fact, under ordinary conditions, no others are profitable or even possible. In this country, next to the sheep, water is the most valuable commodity.