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drawn from New England, latitude 28° 30', longitude 152° 20'*, down to the head of the river Hunter; whence it proceeds westerly, through the peaks of Mount Temi, Mount Terell, Mount Oxley, and Mount M'Arthur, and along the dividing range, down to the sources of the Munmurra Creek.
From about that locality, the continuity of the raised land, in the direction of the dividing range, seems to be interrupted, being indicated only by occasional outcrops. At the sources of the river Goulbourn, its eastern limits again present a well-defined outline, parallel to the dividing range. They may be thus traced through Payan Peak, Blackman's Crown, Cullen Bullen, and the vale of Clywd to Mount Murrain.
On passing the sources of the river Abercromby, the continuity of the tract towards the south is again partially interrupted, as if by an intervening arm of the sea; its boundary line here branching off east and west. On the east side of the dividing range, it passes through Arthursleigh and Glenrock, in the direction of the Shoalhaven river, approaching to within fifteen miles of the sea-coast, in the shape of a narrow neck of land. On the west side of the range, it runs in a tortuous line towards Mount Canoblas, round the eastern and northern base of which mountain it bends. The line next strikes, for upwards of fifty miles, in an indented course to the northward, in the direction of the estate of Mr. Montefiore, and then loses itself in the interior of New Holland.
At the place where the continuation of the uplifted land to the southward was interrupted, some occasional outcrops still mark its course to Breadalbane Plains, where it again appears, bending on the one side to the south east, through Mount Wollowalar, Modbury, and Mount Tomawong; and on the other, in a very tortuous line to the south-west, taking first the direction of the river Murrumbidgee, encircling afterwards Yass Plains; and lastly, striking, by a north-west course, through Barber's Station and the Jugion Creek range, on the western region of New Holland.
How far this portion of the raised tract extends in the interior, to S.W., W., or N.W., it is as yet impossible to decide.
On the east, its limits are most likely bordered by the Australian Alps, as they undoubtedly are in Gipps Land by the dividing range, as far as Wilson's Promontory.
To the southward of that promontory Ave have but the islands of Bass and Banks' straits, and which, instead of being vestiges of a former coast-line between Wilson's Promontory and Cape Portland, as some travellers supposed them to be, indicate only a submarine continuity of the irrupted chain of New South Wales and Van Diemen's Land. These islands present themselves in a form similar to that which may have characterised Van Diemen's Land after the first irruption of crystalline rocks.
At that epoch, Van Diemen's Land probably was composed of five islands : the first approaching to the form of a triangle, included between Cape Portland, St. Patrick's Head, and the head of the river Forrester; the second, constituting what are now called Asbestos Hills ; the third, a small island, now forming the valley of the Lake River; the fourth, including the eastern portion of Hampshire Hills, and a part of the northern littoral; and the fifth, an oblong and indented island, comprising a part of Middlesex Plains, and enclosed between Macquarie Harbour, Port Davy, South-west Cape, South Cape, the right bank of the river Huyon, the west side of Lake St. Clair, and Western Bluff.
We shall now enter upon the mineralogical description of some of the crystalline and sedimentary rocks belonging to this epoch; under the consideration that, at the distance of the European reader from the Australian colonies, it is important that he should be put in possession of the specific character of each species of rock treated of in the geological inquiry, and thus understand the meaning of the nomenclature employed.
Composed of equal proportions of quartz, felspar, and mica. Structure granular: grains the size of a pea: dissemination of the ingredients regular: the predominant colour of the quartz, vitreous, with at times a smoky or greasy appearance; that of the felspar, a faintish red, and that of the mica, invariably black: the entire mass presents a reddish grey colour.
Localities Liverpool range, Bathurst, Wellington Valley, Shoalhaven, Jugion Creek, Ellersbie, Mount Kosciuszko (New South Wales). Eldon range, Ben Lomond, and Frenchman's Cap (Van Diemen's Land).
Var. 2. Glandular Granite.
Composed of oval-shaped masses of granular mica, tabular quartz, and tabular felspar, irregularly interspersed through a quartzose paste.
Localities. — Vale of Clwyd, Guantewang, Mount Kosciuszko, Gidley East, Modbury, Amprier West, Wilson's Promontory (New South Wales). Flinder's Island (Bass's Straits). Cape Portland and the Black Ridge (Van Diemen's Land).
Var. 3. Porphyritic Granite.
A granitic structure of quartz and mica, with large oblong and irregular crystals of felspar, confusedly embedded in the masses.
Localities. — Vale of Clwyd, Guantewang, Gidley, Ellersbie, Lake Omes, Wilson's Promontory, Clark's Island, Black range, Ben Nevis, and Eldon range.
Remarks The granite of the three above varieties exhibits in some cases evident traces of a flow, similar to that of a nappe de basalte. The first variety presents very often the appearance of an intumescent paste, forming an extensive tract of New South Wales, where neither mica slate or gneiss is to be found.
The two last varieties have seldom this appearance. They consist mostly of moderate ridges, and serve as bases to other crystalline, stratified, or un stratified rocks.
A confused crystallization of talc, felspar, and quartz, marked by an unequal distribution of ingredients, by the predominance of the talc over felspar, and by the entire exclusion of mica. Colour, a greenish white, sometimes inclining to red.
Localities Occupies a small isolated portion of
the Manes range (Murrumbidgee), and is to be found in the Eldon range, resting on granite, which it resembles in the size and colour of the quartzose ingredient.
Hyalomicte (Brongniart, Beudant, Greisen of the German mineralogists,)
Is composed of a homogeneous milky or smokylooking quartz rock, with an admixture of a white mica, to the entire exclusion of felspar.
Localities. — Is found at Ellersbie and Dutzton, and crowns also Mount Kosciuszko, the highest summit of New South Wales: when associated with sienite, as is the case in the Australian Alps, it has occasionally hornblende added to it.
Structure granular and massy; invariably composed of a vitreous and translucent quartz, and of hornblende, which is prismatic, and of a dark olive green. At times it is intersected by veins of sulphuret of iron, by which the already beautiful appearance of the rock becomes yet more resplendent.
Localities. — Is widely diffused through both the colonies. In New South Wales, it is found in Honeysuckle range; in Argyleshire, at Sharwin's West; and between Murrumbidgee and the Murray. It forms also the most elevated mountain in that colony (Mount Kosciuszko). In Bass's Straits, it is seen on Flinder's Island, Green Island, Mount Chappell, Preservation, and Clark's Island.
In Van Diemen's Land, it forms the eastern coast, Eddystone Point, St. Helen's Point, and St. Patrick's Head; and it is found on the Great and Little Forrester, on Mount Horror, Mount Humboldt, and at Port Davy.
Remarks Sienite is associated with striking uniformity with granite: its presence in any locality is a sure indication of the granite being near.