But the poverty of Australian hydrography is aggravated by the singularities of the so-styled " weatherology." An alternation of more or less rainless and rainy periods is characteristic of the Australian skies. The rivers •uudergo a similar alternation of drought and flood, the one state being, within certain limits, almost as destructive as the. other. Even in these inequalities there is great irregularity. During the period of drought, a river presents a succession of phases—a scanty, thcugh still regular stream; nearly stagnant ponds with a connecting thread of water between them; detached " water holes" in all the gradations of a constantly decreasing depth; moist pits that may yield their buried treasure to the spade; and, lastly, parched hollows where the labor of digging may be expended in vain. In the drought, for instance, from July, 1838, to Aug., 1839—during which "not a drop of rain fell in Sydney "—even the Murray, generally described as the only permanent river of any magnitude in the country, dwindled away into a chain of pools; and a recent explorer in western A. found on the bed of a large river—an afiluent, if it may be so called, of the thoroughly broiled and baked Murchison—the indubitable footprints, then 3 years old, of preceding explorers. The flood, again, varies as widely, if not so definitely and gradually, as the drought. To select what may be regarded as an average instance from a list of the floods of the Hawkesbury in New South Wales: the torrent, at the end of July and beginning of Aug., 1808, rose to a height of 86 ft., or fully 50 above the edge of the bank, destroy ing the uncut crops of the settlement, and sweeping away stacks of wheat and great quantities of stock of every description. More than 60 such visitations appear to have been ascertained and recorded within the historical period, now extending over 80 years, of which about a third occurred in winter, the remainder being distributed in not very unequal proportions between spring, summer, and autumn, and that without the exemp tion of any one of the twelve months of the year.
The rivers of the e. coast—the Brisbane, Richmond, Clarence, 'Mackay, Hastings, Manning, hunter, Hawkesbury, and Shoalhaven—are, in general, towards their mouths, tidal streams, flowing between high banks through a comparatively level region. Some of those of Victoria—such as the Glenelg—spring from a moist and undulating, tract of country; while most of the others rise among the lofty ranges and snowy peaks of the Australian Alps—the coldest section of the bordering mountains by reason both of their altitude and of their from. the, .emator, are subject to frequent freshets in winter, and are less eccentric thatrAlkether rivers of A. in general:' To the w. of the Glenelg, as stated above, rivers may be said almost to disappear. South A. possesses only a few inconsiderable streams, and a number of usually dry torrent-courses; and as to the Great Bight, still further to the w., more than 500 m. of the coast have been already characterized as utterly waterless. To the w., again, of cape Arid, the coast pre sents only a few small lakes and inconsiderable water-courses, but nothing worthy of the name of river. On the w. side of A., the Swan river is by far the largest of the water-courses. Generally speaking, the whole of them are fed almost solely by the winter rains, many of them, during the dry season, either disappearing through a great part of their course, or dwindling into a series of detached pools. Along the remainder
of the w. coast, no rivers worth notice have yet been discovered. Nor yet along the n. w. have any been found, excepting a few small ones towards Cambridge gulf. The rivers of this neighborhood much resemble in character those of the opposite angle in the colony of Victoria. They rise at no very great distance from the sea. Near their sources they are mere torrents; but in the lowlands their generally slow currents wind through fertile plains and valleys, which are subject to sudden and terrific inundations. In North A. are several comparatively considerable rivers—the Victoria, the Flinders, the Roper, and the Albert. They are wide streams, rising in the elevated region of the interior, and traversing a rugged country, which is often flooded. Lastly, along the n.e., the streams are distinguished by their length, a distinction which they owe to their being parallel with the coast. They are the Mitchell, Lynd, Burdekon, Mackenzie, Dawson, Fitzroy, Belyando, etc.; the whole of them, with the exception of the two last named, having been discovered by Dr. Leichhardt. To pass from the rivers of the coast to those of the interior, we must confine ourselves to two of the latter—Barcoo or Vic toria, and the Murray with its numerous tributaries. The upper part of the Barcoo was first discovered Sir T. Mitchell, in a broken district, lying 300 or 400 m. from the e. coast, and nearly on the tropic of Capricorn. Its broad reaches might there have floated a steamer. Since then, it has been traced by Mr. Gregory through a solitary course into lake Torrens, though, in point of fact, it is only from time to time that it actually has is surplus to pour into its receptacle. The system, again, of the Murray and its tributaries is vastly more complex. Rising on the w. or inner slope of tire Australian Alps, it flows to the w.n.w. with a plentiful stream, which alone in the country, after the fashion of is tropical river, rises and falls regularly according to the season; and, though macessible to ships of any size from the sea, it has an internal navigation of about 2000 in. in length. On its left or southern side, it receives several considerable streams, such as the Ovens and the Goulburn. But it is on the right or northern side that the basin of the is most peculiar. The principal affluents in this direction are the Murrumbidgee and the Darling. The Murrumbidgee, to which the Lachlan, only less "mysterious" than the Darling, contributes such surplus as it from time to time may have, forms the chief strand of a complicated net-work of water-courses. The Darling, after it has received all its tributaries, pursues its lonely way for 600 m., sending off branch after branch to lose themselves in landlocked lagoons. Nor is its growth less curious than its lower channel. The whole of the interior drainage of the maritime ridge of New South Wales between lat. 25' and hit. 34°, a stretch of about 625 m., converges into a vast basin of clay, on the 30th parallel, where the Balonne, Dumaresque, Gwydir, Namoi. Castlereagh, Macquarie, and Bogan, after spreading out in spacious marshes, and amid complicated junctions and bifurcations, unite such surpluses as absorption and evaporation may have left them to form the " mysterious" Darling.