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fortune to be acquainted with any of the previous observations upon the geognosy of the country. Hence, although the whole of that country appeared equally interesting to explore, still, unassisted as I was in a labour of such magnitude, I could not but prescribe boundaries to my survey. The geological description and map, which at the outset I had in contemplation, has in consequence been ultimately confined to the country running parallel with, and stretching 150 miles inland from the sea coast, and comprehended between the 30th and 39th degrees of south latitude.
The mode adopted in my inquiry was as simple as is the geological configuration of the country. From the circumstance of the masses and strata assuming, with few exceptions, a direction from N. E. to S. W., the determination of their horizontal and vertical positions was accomplished by means of a series of zigzag sections, made across the country, and by the examination of the flanks of the dividing range, against which the different strata abutted.
Like the Alleghany Mountains in the United States, that range was as a book, the leaves of which contained all the materials needed for the investigation, and furnished not only a key to explain the order of its superposition, but also a guide towards Wilson's Promontory, the south-eastern extremity of New Holland, which I looked upon as the closing page of the intended geological inquiry.
When, however, the course of my perambulations brought me to the edge of that promontory, and thence to the islands of Bass's Straits, and from these again to Cape Portland, Van Diemen's Land; when, further, the survey of Van Diemen's Land led me winding east and west down to Research Bay, I found such striking correspondence of parts to the explored tract of New South Wales, that as I went on I could not resist the temptation to extend my inquiry until it finally brought me to South Cape, Van Diemen's Land, and thus joined that island and New South Wales in one geological survey.
I have arranged the descriptive parts of this survey in epochs, which the geological formations have successively marked upon the surface of the two regions.
The mineral constituents of each epoch are distinguished by a strictly mineralogical nomenclature, in preference to a geological, as the latter can not as yet be applied to Australian rocks without involving questionable analogies, or implying identities with eras of deposition in other parts of the world.
Their geological relations have nevertheless been carefully taken into account, and described in respect to locality, extent, range, height, superposition, thickness, and inclination of the strata, organic remains, and mineral contents.
Their mineralogical character has been also noticed, and the chemical analyses of some will be given.
In the shape now offered to the reader, this geological description is far below what I had hoped at the outset my labours would have enabled me to produce. Neither perseverance nor devotion to the pursuit has been wanting. But these, combined with 7000 miles which I made on foot, have procured for me only the consciousness of how little I have done, and how much is still needful to complete such a delineation as the geology of the present day requires.
And all that I have collected during five years of labour I can view only as rudiments of what science may expect at a future period from the division of labour, and from the unparalleled progress of intellectual and commercial development of New South Wales and Van Diemen's Land.
I have also prepared a geological map of New South Wales and Van Diemen's Land, upon which I have laid down and illustrated what the present description will relate in words; but that map I am unable to take upon myself to publish.
It is twenty-five feet long and five feet in width, and is on the scale of one fourth of an inch to a mile.
The geographical portion of the greatest part of that map was compiled from the hydrographical and topographical charts of New South Wales and Van Diemen's Land; where the colonial survey ceased, the continuation of the dividing mountain range (from latitude 36° to 44°), with all those characteristic features of the country which bore upon the inquiry, was projected from my field-book, in which the geographical positions had been determined either by means of astronomical or trigonometrical observation.
The barometrical survey carried out, by means of two Gay-Lussac mountain barometers, and Dr. Wollaston's apparatus for ascertaining the boiling point of water, furnished all the altitudes of the country required for the construction of a second sheet of vertical sections, which is twenty-six feet in length and three feet in width. In conformity with the very judicious recommendation of Sir Henry de la Beche, the base and the height of the sections are projected on the same scale, which is four inches to a mile, and by which projection, the eye can seize at once on the true configuration of the country, and not its caricature.
The colouring of both the map and sections has been executed according to a novel method, not perhaps, as Montaigne says, the best, but which is my own.
It was accomplished with' four colours, divided into dark and light shades, the dark denoting the mineralogicaL and the light the geological character. Thus, the light pink, light yellow, light blue, and light sepia, represent the first, second, third, and fourth of the geological eras; while the darker shades of the same colours represent the four classes of rocks; viz. the siliceous, argillaceous, calcareous, and the hornblende and augitic rocks; which again are distinguished, when crystalline, by a moirie, when stratified, by lines drawn in the direction of the strata.
The different species comprised under each class of rocks are indicated by small distinct marks: thus, under the siliceous rocks, granite, protogene, sienite, hyalomicte, mica schist, quartz rock, siliceous slate, siliceous breccia, sandstone, petrosilex, porphyry, are distinguished from each other by differently formed and easily remembered dots. Under the argillaceous rocks the distinctions between chlorite slate, clays, and argillaceous sandstones are yet more simple. Under the calcareous, they are very plain, and under the volcanic rocks, comprising serpentine, diabase, basalt, and trachyte, they are readily comprehended.
GENERAL PHYSICAL AND GEOLOGICAL ASPECT OF NEW SOUTH WALES AND VAN DIEMEN'S LAND.
When viewed from the east, New South Wales and Van Diemen's Land do not present any of those bold or fantastic features, by which the imagination is excited and curiosity enhanced. The foreground of the picture is commonly composed of an undulating country, richly wooded, and gradually rising westward, until it spreads into a centre ground formed of darkly verdant and round topped hills and ridges, promiscuously grouped together; beyond which rises in the back-ground a range of high land that forms an outline on the horizon, only here and there broken by peaks of striking shape and lofty elevation. In latitude 30° this elevated land assumes the aspect of a mountain-chain crowned with peaked, acicular, dentiform, sharp-edged, or flattened granitic or porphyrytic crests, from Avhich the eye may trace its course, winding from N. E. to S. W., until it gradually vanishes in the distance. On both sides the country exhibits a sloping surface, which the countless ramified spurs, branching off eastward and westward of the chain, deeply furrow with valleys and ravines. The waters run between and parallel with the spurs; their courses commonly flow in diametrically opposite directions.
At the point from whence this bird's-eye view is taken,'that is at the 30° of latitude, the granitoite chain divides the sources of the river Peel, running to the westward, from those of the Hastings, flowing N. E. towards Port Macquarie. Further to the south, one of its eastern spurs of porphyry separates the river Manning from the river Hunter, after which, assuming a direction almost west, it divides in its windings the various tributaries of the Hunter from those of the Peel river. This part of the chain is commonly called Liverpool range, and is crowned by several peaks of greenstone, which rear their naked, conical, and distorted tops to the elevation of 4700 feet. From two of these, Mount Oxley and Mount M'Arthur, the eye is presented with a most beautiful panorama of broken country, blending into the Liverpool plains on the one side, and into the fertile valley of the Hunter on the other. To the westward of these peaks, and at the point where it divides the river Goulbourn from the Talbrae:ar, the chain turns suddenly to the south-east, but resumes again its south-westerly direction at a locality rendered remarkable by the peaks of Coricudgy and