Page:Transactions NZ Institute Volume 10.djvu/40

16 Ere many centuries have passed away it may be that the remnants of the ancient shallow sea, marked on the map of Australia as Lake Torrens, Lake Eyre, Lake Gardiner, etc.—which, with their margins of black, fetid mud, supporting scattered tufts of salsolaceous plants, resemble the salt lakes of Siberia and Patagonia, regions which were also in recent times raised from beneath the sea—will be silted ip and then drained, the climate will be still drier and subject to greater extremes of diurnal temperature, remarkable as there are now in the interior as far as 18° S. latitude. The Barcoo or Thomson river will cut a canal-like channel through the sandhills to the head of Spencer's Gulf as the Darling has done further east. The surplus waters, after the periodical deluges of rain in the tropical country from which they flow, spread out over vast areas of the central depression, and already during very high floods find an outlet from Lake Torrens at Port Augusta, where the land is estimated to have risen seven feet since the first survey of that harbour was made.

The change in this region from a mediterranean sea to arid plains (where, notwithstanding the 10° difference in temperature between places in the southern and those in corresponding latitudes in the northern hemisphere generally, the heat from various causes is much greater than in the African deserts in similar parallels) must have exercised a most potent influence upon the climate of New Zealand and the adjacent oceanic regions, as it does to a considerable extent to-day, when alternate cycles of wet and dry seasons prevail over these great levels, now torrid deserts, and at other times in great part covered with water; an influence not very greatly inferior to that which the drying of the Sahara must have produced upon the climate of Europe, and the dimensions of the Alpuie glaciers. When that desert region which now, "like an immense furnace," distributes its heat around over distant lands, was covered by the sea, and a large portion of Europe was likewise submerged, over which came berg-laden arctic currents, it may well be conceived that the higher elevation of its central chain of mountains, estimated by Professor Ramsay to have been from two to three thousand feet at the time their glaciers attained such colossal demensions, was sufiicient to produce all the phenomena attributed to a general age of ice, which may come to be proved to a great extent, should the project of letting the sea into the great depression of the African Desert be carried out.

There may be grounds for supposing an ice-sheet of vast extent to have covered great portion of Northern Europe, Asia, and America, at or about the same era, but evidence of its having been universal is wanting even in the northern hemisphere, and any evidence of an approaching similar state of things in the southern is sought for in vain.