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Rh New South Wales, passes on to Wilson Promontory, the most southerly point of Australia, whence he looks sea ward at the islands in Bass s Strait. As he there observes the Tasnianian mountains, with which he is equally familiar, it occurs to him that the whole is the result of identical forces, operating in a direction from north-east to south-west. Such phenomena he ascribes to a series of * volcanoes of elevation,&quot; along a vast fissure of the earth, upon the line regarded by him as &quot; the Australian eastern axis of pertur bation.&quot; These forces he believes to have been exerted, with different degrees of intensity, at four several epochs, which are indicated by the character of the sedimentary rocks, broken through or contorted by the eruptive greenstone and basalt. That eruptive action is seen in the ravines and precipices of the Blue Mountains near Sydney ; in the Grose valley, below Mount Hay and its neighbours, Mount King George and Mount Tomah ; but still more remark ably in the mountains of Tasmania, viewed from Ben Lomond, within 30 miles of Launceston. The sedimentary deposits of the first epoch are characterised by the presence of mica slate, and of argillaceous and siliceous slate, as well as by the absence of gneiss. Those of the second epoch are found to be arenaceous, calcareous, or argillaceous stratified deposits. The third epoch includes the coal deposits, with their intervening shales and sandstones, including many fossils ; while the fourth and last epoch is marked by the occurrence of elevated peaks, and by the remains of land animals found in the limestone caves or in alluvial deposits. The Kev. W. B. Clarke, of Sydney, again, in a revised treatise published in 1871, expresses a doubt whether the southern range of mountains, extending to Wilson s Pro montory, be really a continuation of the main Cordillera of New South Wales. He rather considers this to be pro longed in a westerly direction, taking a bend that way at the Warragong or Snowy Alps, and to be continued within 60 miles of the border of South Australia, which is on the 141st meridian of E. long. The subject is further dis cussed by Mr R. B rough Smith, of Melbourne, in his essay of 1872 on the mineralogy and rock formations of Victoria. This geologist has also remarked that the Murray, which must have repeatedly shifted its bed and changed its out let, may have once been a far more powerful stream, flood ing a vast tract of the interior, and thus becoming an effective agent in the geological formations of all south-east Aus tralia. It has produced, in Victoria more especially, the Tertiary stratifications which are equivalent to the Pliocene rocks of Europe. Throughout the whole of eastern Australia, including New South Wales and Queensland, while no tertiary marine deposits have been found, there occur many remarkable beds of siliceous sandstone, bearing impressions of ferns and leaves of trees, which are referred to the Tertiary epoch. An interesting theory is advanced by Mr Clarke to account for the absence of Tertiary deposits on the eastern coast, when they are found on the western and southern coasts of Australia. In the islands of New Caledonia and other Australasian groups, from the Louisiade, near New Guinea, to New Zealand, there is a repetition of Australian geo logical formations, and there are abundant Tertiary deposits; and this may confirm the supposition that the Australian continent at some period extended farther to the east, and that a vast portion has disappeared under the ocean. To the same hypothetical cause Mr Darwin ascribes the formation of the Great Barrier Reef, stretch ing along the east coast from S. lat. 22 23 to Torres Strait, with an interval between it and the land varying from 12 to 140 miles. With regard to the more remote geological epochs, Aus tralia presents fewer materials for study than the other continents of our globe. Mr Clarke doubts the origin of some of the more ancient slates mentioned in the &quot;first epoch&quot; of Count Strzelecki, and does not find, either in eastern or in southern Australia, sufficient proof that these regions contain azoic and metamorphic rocks. Large masses of granite occur along the coast, and more extensively in Western Australia. Of the lower Palaeozoic there is a great deal of Upper Silurian rock in New South Wales and Queensland, and some in Tasmania. It is in the Lower Silurian formation, as Sir Roderick Murchison predicted, that gold deposits are chiefly found. Rocks of the Devonian period are not yet proved to exist anywhere in Australia, and it is doubtful if any true Permian or Trias, so common elsewhere, have been met with in this continent. The great Carboniferous series is very prominent in New South Wales and in parts of Queensland; it prevails less in Victoria. Coal-beds, of thickness varying from 3 feet to 30 feet, are found associated, both above and below, with fossils resembling those of the Carboniferous strata in Ireland. Their antiquity is proved beyond question, in some districts, as in the valley of the Hawkesbury, where they are overlaid with beds of sandstone, shale, and con glomerate, 1000 feet thick. It has been shown by Mr Daintree that there is a very extensive distribution of the Secondary or Mesozoic rocks in Queensland the Cretaceous strata, both there and in Western Australia, covering a large area. The Oolitic are more abundant in Western Australia. The great plains of the interior, and the slopes of the inner mountain ranges, consist largely of deposits of the Tertiary epoch. They occupy an immense area in Victoria and New South Wales, including the Riverina district, which was probably, as Mr Brough Smith considers, levelled and planed down by the ancient vast expansion of the Murray. &quot; The waves of the sea,&quot; he remarks, &quot; and the waters of this river, have eaten away mountains of granite and great hills of schist in past times, and placed instead of them a smooth covering of sands and clays.&quot; The great basin east of Port Phillip, connected with another basin about Westernport, is underlaid with Mesozoic carbonaceous rocks, upper Miocene, a nodular basalt, and decomposed amygdaloid of older volcanic origin, the quartzose drift of the first Pliocene formations, and some volcanic products of more recent date. Here the Miocene beds abound with fossil leaves of plants belonging to that age. The sands, clays, and gravels of later periods, in the ancient beds of the streams within the Silurian areas, are more or less auriferous. Some of the deeper &quot; leads &quot; of the gold-miner contain fossil fruits and the trunks and branches of trees, which are described by Baron von Miiller in the Melbourne official reports of the mining surveyors. In the Ballarat gold-fields the auriferous quart zose gravels are overlaid by flows of lava and vesicular volcanic rocks, while in a neighbouring district south of Ballarat, pebbles and sand are cemented by ferruginous matter into an extremely hard conglomerate. In eastern Australia, where no Tertiary marine deposits are met with, there are deep accumulations of drift, such as transmuted beds of the Carboniferous formation, porphyry, and basalt, and other igneous rocks, and fragments of the older Palaeozoic strata. Many of the drift streams are not only highly auriferous, but contain gems of all kinds. Diamonds, though of small size, have been taken from the Cudgegong River, near Mudgee, in New South Wales, and likewise from the Macquarie River. In the eastern plains of the interior, embedded in black muddy trappean soil, are found the bones of enormous animals of the marsupial or kangaroo order, as well as birds, fishes, and reptiles. The accumulations of bones in caverns at Wellington, New South Wales, and on the rivers Colo, Macleay, and Coodradigbee, are of great interest. 