AUSTRALIA is situated wholly in the southern hemisphere between longitudes 113° 9' E. and 1J3° 39' E. and latitudes io° 41' S. and 43° 39' S. (mainland, 8' S.) . With an area of nearly 3,OOo,000sq.m. (2,974,581sq.m.; mainland alone, 2,948,366sq.m.) it is the smallest continent and the largest island on the globe, approximating in size to the United States of America (3,026,789 sq.m.) and being rather more than three-fourths of the size of Europe and over one-fifth of the area of the British empire. (Tas mania [q.v.] and other adjacent islands are included in the above, but Papua [q.v.] and mandated territories are excluded.) With a coast-line of 12,21om.—giving a proportion of 1m. of coast to sq.m. land surface (mainland alone, 1:261 sq.m. ; cf. Europe, 1:75; England and Wales, 1:25)—Australia is a markedly closed land mass. This fact, in conjunction with its shape (max. east–west extension c. 2,400m., north–south 1,970m.) and latitudinal posi tion, profoundly influences the climatic, and hence its general geo graphical, character.
Position and general spatial relationships are potent factors in Australian geography. Extensive water surfaces lend comparative isolation except towards the north. Regarded as a south-eastern detached extension of the Asiatic land mass, Australia cannot be entirely dissociated in respect of geographical destiny from Asia, and the same may be said if we view it, or its eastern margin, as a section of the western Pacific seaboard. With regard to the Pacific the position of Australia is pregnant. Along with New Zealand it dominates geographically the south-west Pacific quad rant. Similarly it commands the south-east Indian Ocean, to which water-triangle-.--more enclosed in geographical than in physical fact--it forms, as it were, the south-east apex.
With regard to position in the British empire Australia shares with New Zealand extreme remoteness from the mother country (London-Suez-Colombo-Fremantle, 9,537 nautical m.; Liverpool Panama-Sydney, 12,222 nautical m.), but is linked to the British Isles by two sea-ways (the Suez and the Panama routes) which span the Eastern and Western Hemispheres respectively and traverse the two great land-masses of the globe. Both routes— but particularly the former—lie athwart important units of the empire and both have longer alternative sea-routes. The Aus tralian continent, also forms one of the "corner-stones" of the Indian Ocean, much of the territory adjoining which is under British administration. Finally Australia is situated diagonally across the Pacific from Canada and the route joining these Dominions (Sydney-Vancouver, 6,848 nautical m.) intersects, or runs adjacent to, perhaps a majority of the most important routes traversing that ocean.
Geomorphology (see also under Geology) .—Australia, as the lines of folding and faulting show, has been built up against and on a core of pre-Cambrian rocks which to-day are most in evidence in the south-west and west. Against this massif were successively pressed up a series of sediments in roughly parallel strips along the north, east and south-east so that the land area continued to grow in the directions mentioned until, after the last great (Carboniferous) period of folding, it possessed at the end of the Palaeozoic period the whole of, and more than, its present ex tension.
Subsequently, three main types of episode have determined the broad features of the present land—mass: (I) The continuance, or extension, of crustal sagging in cen tral and eastern Australia accompanied by marine transgressions and the formation of lakes with the accumulation of sediments. Since Cretaceous times the present land surface—if we except the south marginal areas—has remained uninterruptedly above sea-level.
(2) The progressive elevation of the eastern and south-eastern marginal portions of the continent to form the elongated belts of highland now known as the Eastern Highlands and the South Australian Highlands. These highlands, therefore, though com posed of ancient materials and possessing much denuded upper surfaces are geologically of late formation.
(3) (a) The outpouring of vast sheets of basalt over large areas in east and south-east Australia, in Tasmania, and, to a less ex tent, in south-west Australia. Beneath these basalt "floods" exist ing features were submerged, valleys were covered up (cf. the "deep leads") and the already worn-down landscape was even more levelled. (b) A series of comparatively localised glaciations, which affected notably the Kosciusko Plateau and Tasmania and were accompanied by climatic conditions which supported in Central Australia herds of giant herbivorous and carnivorous ani mals. (c) Oscillations of the coast-line, and perhaps of sea-level, resulting, for instance, in the severance, the re-junction, and again the parting of Tasmania from the mainland ; the subsidence of large stretches of continental margins particularly along the north-east, central-south, and south-west with consequential flood ing of surface features ; and, most recent of all, an elevation of the land, relative to the sea, of about r 5f t. (in places as much as goof t.) widely marked round the Australian coast-line.
The above historical facts are clearly reflected in the present character of the Australian land-mass. Rising, in places with surprising steepness, from the great abyssal furrow which ac companies and well-nigh rings it in, the continental platform bounded by the ioo-fathom line (i.e., including the continental shelf) appears in plan as a broad flat disc with two irregular pro longations—one at the south-east corner comprising Tasmania, the other, much larger and more irregular, at the north comprising New Guinea. An elevation of the land (or a lowering of the sea) of about goof t. in the case of Tasmania, of only about r oof t. in the case of New Guinea, would reunite these islands to the main land. Elsewhere the continental shelf is remarkably narrow, espe cially along the south-east and east. On the north-east, on the other hand, a 1,2oom. long stretch of down-faulted, and perhaps still sinking, coast has left room for the growth of one of the most remarkable coral-reefs--and also one of the longest, though not the best sheltered, semi-enclosed maritime water-ways (see BARRIER REEF).
In detail also the varying physiographic—and hence often economic—character of the coasts is the direct outcome of tec tonic history. The recently submerged coast-lines in the south-east (including Tasmania) present a frowning front, but also, where commodious and branching river-valleys have been "drowned," some of the finest of natural harbours (Sydney harbour; the sub merged valleys of the Tamar and the Derwent in Tasmania). Along the north-east (Queensland) coast also, where the collapse of the continental margin has broken diagonally across the folds, or again in parts of the north-west and north, subsidence has given a series of natural inlets, the potential value of which, how ever, is often diminished by the amplitude of the tides. (Spring tides [range] : Townsville, 8–i aft.; Broad Sound, 3of t. ; north west coast, varying between c. 21 and 36 ft.) Elsewhere waves, currents and tides have had greater effect, and here (e.g., along many stretches of the west and north-west, south-west and south coasts) rocky promontories alternate with sandy bays and spits, and tied islands and sand-dunes are the seaward front of a low and featureless interior. In three places (the Ninety-Mile Beaches of north-west Western Australia and south-east Victoria, and at Great Sandy island [Queensland]) the set of the currents has permitted great accumulations of sand, and in several considerable stretches (Gulf of Carpentaria [south coasts] ; Great Australian Bight; Spencer gulf, etc.) recent elevation has resulted in either low shelving shores (south coast of Gulf of Carpentaria; Spencer gulf) or in an unbroken line of cliffs (Great Australian Bight).
The exceedingly closed nature of the continent—the paucity of large and effective sea inlets—has already been referred to. The 135th meridian of east longitude divides Australia roughly into two divisions as regards surface configuration : To the west lies the great plateau, to the east the lowlands, followed nearer the coast by the belt of highlands. Each of these divisions is broadly expressive of the physical genesis and growth of the continent.
The Western Plateau.—This division includes the whole of Western Australia, most of the Northern Territory, besides much of the west and north-west of South Australia. It constitutes one of the "primitive" continental blocks of the earth's crust ("shields") and consists fundamentally of a complex of very old and very hard rocks (see Geology, below). Around its edges from the north-west to the south-east, and again along its in land (eastern) boundary the older rocks dip below younger for mations which form the greater part of the coastal lowlands. These lowlands, 6o-7om. wide along the west but broadening to towards the north-west and south-east, slope up very gently inland to heights of 600--r,000 feet. Here they frequently terminate abruptly against a scarp which rises to about i,aooft. in places to 4,000ft.--and which is the faulted edge of the interior plateau, though, owing to its steepness and its dissection by streams, it has often the appearance of a mountain range (e.g., Darling Ranges). Elsewhere the transition to the plateau is more gradual, and on the south-east and south a limestone platform, formerly a sea-floor, rises from an unbroken line of perpendicular cliffs of 20o-400ft. and forms the remarkable Nullarbor Plains. The interior plateau has an average elevation of perhaps r,5ooft.: its surface features result from the age-long denudation of the materials and structures which characterize it. The primitive folds have been truncated, the broad granitic masses worn down to a comparatively uniform level. Crustal movements have slightly lowered some areas and raised others.
Coastward draining streams, where these have attained to any size and power as in the south-west, north-west and north, have dissected the outer margins of the plateau and have worked out a rugged if subdued relief. In the north-west and Kimberley Divi sions in particular the dissection of the horizontal or gently in clined strata has given rise to a characteristic landscape of table land, ridge and canyon (Mt. Hann, 2,800f t.) . Everywhere con tinued erosion has differentiated hard from less hard rocks, and ridges, spines (often of quartzite), granite erosion scarps ("break aways"), isolated rocks or groups of rocks (Ayers Rock and Mt. Olga in Central Australia), and occasionally larger and more mountainous masses (Stirling Range, 3, 64of t. ; Hammersley Range, Mt. Bruce, 4,o 24f t. ; etc.) arrest the eye and sharply frame the horizon. But apart from these and the Macdonnell (Mt. Heughlin, 4,800ft.) and Musgrave Ranges (Mt. Woodruffe, c. 5,000ft.) in Central Australia, there are no "mountains" in the ordinary sense. Over far the greater part an immense peneplain, the major elevations of which are imperceptible swellings, the chief hollows wide salt-floored flats, extends with expressionless monotony. Here broad expanses of sandy or clayey plain, there mile upon mile of sand-ridge (e.g., in an area comprising the centre, and east and north of the centre of Western Australia) ; here wide levels floored with limestone (travertine) ; there rougher but hardly less level surfaces of laterite, with granite and quartz outcrops. Long lines, either level or of low inclination, and sharp scarp faces may in this direction or that bound the horizon and mark the sky-line of ridge and range. But the prevailing impres sion is flatness, the prevailing sense that of space. Not the desert, for the most part, of popular imagination, for the surface is peopled with trees, scrub or at least heath. But a great wide silence-filled land, a land of age where loneliness dwells.
The area represents the zone of crustal weakness or sagging where great quantities of sediments were deposited on the floors of inland gulfs and lakes and, later, wide sheets of river gravels and alluvium. The ancient rocks of the west sink below these newer formations but the Barkly and Selwyn uplands, with the adjoining Cloncurry area, are a north-easterly extension of the great plateau. Similarly, the Cobar-Barrier Range "peneplain," affected by recent elevatory movements, forms a sill partly separating and partly submerged by the more recent deposits. The outcrop of these older rocks ("inliers") has significance in connection with the occurrence both of workable minerals and of artesian water. The south-eastern portion of the central lowlands is, from a physiographical point of view, one of the most interest ing in Australia. Complementary to the elevation of the south eastern margins of the continent was a subsidence of its more central portions. The older "grain" of the land and the continen tal "backbone" had run in an east-west direction (cf. Macdonnell, Musgrave, Gawler Ranges). Rivers comparable, perhaps, with the Murray had discharged along the south coast which then lay farther to the south. Subsidence in the northern parts, coupled with the elevation of the Mt. Lofty-Flinders Ranges, disrupted this order, dammed back the streams, and caused or hastened the formation of great "lakes." (The surface of Lake Eyre lies normally about 39ft. below sea-level.) A belt of country anciently the site of a mountain system (strongly folded Cambrian and older sediments), but worn flat by long denudation, was raised by crustal warping, probably in sympathy with the movements further east, and formed the Mt. Lofty-Flinders Range (St. Mary's Peak, 3,9oof t. ; Mt. Lofty, 2,334ft.) which, with its main spur continued in the Barrier Range, encloses on three sides the Lake Frome basin.
On the west side St. Vincent's and Spencer gulfs—the latter continued northwards by the Lake Torrens "rift" valley—probably represent areas of subsidence along divergent lines of fracture, while Yorke's Peninsula is a block left upstanding between them. To these facts of physical history are due many of the distinctive geographical characteristics of the area (e.g., drainage features; human settlement; lines of movement). More recent was the volcanic activity which affected the coastal strip from Kan garoo island to south-western Victoria (Mt. Shanck, Mt. Gambier: volcanic cones with associated lakes). For the rest, the general features of the lowlands admit of little in the way of descrip tion. Rolling or undulating in the north and east, towards the south and centre they mostly flatten into seemingly boundless ex panses of plain. Clothed with scattered timber, scrub and grass, they here and there spread flat pavements of clay or broken stones ("gibber" plains of Central Australia) to distant and unbroken horizons. Where the climate is dry, or where perhaps it was once drier than now (e.g., in the North), forms of arid erosion—sharp steep-sided scarps surmounted by long flat crest-lines ("table-top" hills) and other similar shapes—are etched in the "desert sand stone" and reveal higher land-surfaces now all but gone. Sand ridge (brick-red moving dunes, or fixed mounds calcareous within and only outwardly coated with sand) occupies some few areas (e.g., eastern Central Australia and parts of the South Australian "Mallee"). In still other parts areas of limestone ("kunkar"; travertine) and ironstone gravels occur, but the most exten sive and most characteristic are the vast alluvial sheets—gravels, clays and loams for the most part, often very fine and very deep —washed down by streams from distant highlands and laid by innumerable floods over many hundreds of square miles.
The Eastern Highlands (Including Tasmania) .—The eastern and south-eastern borders of Australia are mainly high land, though there is also included a certain proportion of mainly coastal lowlands. The highlands have been termed "cordillera," but they are a more or less continuous belt of plateaux rather than a mountain chain or series. This character they owe—as indeed does the belt as a whole—mainly to two processes in the physical history of the continent; viz., the recent elevation of its eastern borders and the perhaps complementary subsidence beneath the sea of a considerable marginal strip. The last major folding or mountain-building processes in Australia occurred towards the close of the Palaeozoic age (Carboniferous period). The struc tures then reared in the labile zone which comprises, but extends far beyond, the eastern margins of the continent, have since then been subjected to continuous denudation—so far, at least, as can be judged from the portions which remain above sea-level. It was thus an ancient and very reduced surface which was "warped up" to form the highland rim. The uplift, however, was irregular ("differential") and was accompanied by much slipping and fault ing, so that there resulted a number of unevenly tilted blocks which in some parts are more closely coherent, in others separated by gaps of varying width, such gaps representing very often areas of down-faulting or block-subsidence ("Senkungsfelder").
The prevailing plateau character of the summits is further attributable to (a) volcanic activity, whereby extensive areas throughout the belt were covered with sheet-flows, the surface levelled, and former irregularities of topography submerged ("deep leads") ;' (b) denudation intensified by the uplift (cf. the "peneplains" of the western slopes ; "valley in valley" formations), and, more locally, by glaciations also (e.g., in the south-eastern part of Australia and in Tasmania). But the uplift naturally worked in the opposite sense also since it reinvigorated erosive agencies and processes in general. The displacements mentioned had the effect of shifting the watershed on the whole further inland (exceptions are certain areas in the south-east of the continent), and the collapse of the eastern margins in particular gave the eastward-flowing streams greater cutting power. Thus the deep fresh-cut valleys are as characteristic of the scenery as are the old worn summit-levels, and this has resulted here and there in striking precipice and gorge topography (e.g., scarp of New England Plateau) and occasionally in dislocated courses of streams (e.g., upper Barron river in north-east Queensland).
The highland belt falls into three fairly clear natural sections: the Northern Uplands; the Central and South-eastern Highlands (including Tasmania) ; the Southern Dividing Range. (See articles on various States.) Australia is essentially the fragment of a great plateau land of Archaean rocks, the western portion of the continent constituting a Precambrian nucleus around which later sediments have been deposited and against which they have been folded. East of a line drawn through Cloncurry and Broken Hill the continent is built up of later deposits, with the exception of isolated areas of prob ably Precambrian rocks in the east Queensland zone extending uplands composed of these volcanic rocks now form the watershed along considerable stretches of the highland belt.
from Cape York peninsula to the latitude of Gladstone. A very similar geographical disposition of the Precambrian is revealed in the architecture of Tasmania, where Precambrian rocks are con fined to a region west of a line drawn through Beaconsfield and Louisa bay on the extreme south coast. The stratigraphy and structure of this old terrain is best known in the State of Western Australia, essentially an old Precambrian land that has remained above sea level throughout Palaeozoic and later times.
The succession of Precambrian rocks in this State, is as fol lows :— In the southern and central provinces of the State the green stones of the Warrawoona series consist of highly folded horn blende and chlorite schists arranged meridionally or along north north-west lines. They are enclosed in granites and gneisses of igneous origin which without exception appear to be transgressive. The principal gold mining centres of the State are situated within these greenstone belts or at their contacts with the invading igneous rocks. This Archaean platform is continued eastward into South Australia where a complex of para-schists, amphibolites and igneous gneisses underlie the greater part of Eyre peninsula. In central Australia the dominant structure lines of the Archaean rocks are latitudinal as seen in the Macdonnell range gneisses. The Mosquito Creek series and Kurrawang series developed in the Pilbarra and Coolgardie areas respectively are dominantly sedimentary systems which, though intensely folded, show dis cordant relations to the Archaean rocks on which they rest. They in turn are penetrated by a later series of granites and granodio rites (Newer Granites). In the Kimberley region of northern Western Australia a great group of sediments and igneous rocks overlain by the Nullagine series is of Precambrian age, but little is known of the structure of this region beyond the striking V shaped trend lines of the series outcropping from King Sound to the Northern Territory border. In the Northern Territory the Precambrian series is constituted in its lower part of schists largely of tuffaceous character penetrated by granite intrusions. They form a well-defined belt extending from Darwin to the region of Pine Creek.
In Queensland, a large area around Cloncurry is built up of Precambrian rocks, the age being definitely established by the presence of Cambrian rocks resting on the eroded edges of the series. It is probable, however, that the rocks of the Hamilton Coen, Charters Towers, Gilbert and Etheridge goldfields are also of Precambrian age. In New South Wales the only undoubted area of Precambrian rocks is that surrounding Broken Hill, while in Victoria the granites and gneisses in the bed of the Glenelg river near Harrow and Balmoral represent an eastern outpost of the Precambrian rocks of south-eastern South Australia.
In South Australia, the lower portions of the Adelaide series principally developed in the Mount Lofty ranges have been ascribed to the Nullagine series by David. These lower members of the Adelaide series include a folded series of ilmenitic con glomerates, quartzites, slates and limestones passing upwards into a well defined glacial horizon (Sturtian tillite). These rocks are devoid of recognizable fossils. In the Flinders ranges at Wooltana and at Mt. Arrowsmith to the north of Broken Hill the series contains a volcanic horizon which is correlated with the lava zones of the Nullagine series.
As far as can be determined no orogenic movement ushered in the Cambrian era. Rocks of Cambrian age occur principally in the Kimberley district (Western Australia), Northern Terri tory, Cloncurry area (Queensland) and in the Mt. Lofty and Flinders ranges of South Australia. The great lava flows of the Antrim basalt plateau are followed by a series of Cambrian sedi ments carrying Salterella, and a somewhat similar relation is revealed in the Northern Territory. In the Mt. Lofty ranges and Flinders ranges a continuous section from the unfossiliferous Adelaide series to the Arclaaeocyathinae limestones of Middle Cambrian age has not yet been discovered, but the evidence here, as in the Kimberley region, points to no great stratigraphical break. Some portion of the Adelaide series is therefore probably of Lower Cambrian age.
The prominent tillite horizon (Sturtian tillite) in the Adelaide series is found at intervals over a zone extending from south of Adelaide into the far north of South Australia and is also de veloped in the Broken Hill district. Owing to the difficulty in de fining the base of the Cambrian, it is uncertain whether this an cient tillite is Lower Cambrian or Late Proterozoic in age. In Queensland a gently undulating or horizontal series of fossiliferous Cambrian sediments discovered west of Cloncurry indicates an extension of the Cambrian sea into western Queensland. In Tasmania, the only known Cambrian rocks are the Dikellocephalus sandstones of Railton.
Two strongly contrasted types of deposits are present in Aus tralia's Ordovician system. The first, a littoral facies, is developed in central Australia and is represented in the region of Tempe downs, the Krichauff range, etc., south of the Macdonnell ranges. An immense thickness of sandstones and fossiliferous limestones were deposited in a shallow sea probably extending as far east as the Cairns range in Queensland. The fauna includes such forms as Orthis, Isoarca, Raphistoma, Orthoceras and Asaphus.
In Victoria a more pelagic type of deposit is represented by the Lower Ordovician graptolitic slates practically confined to an area west of the meridian of Melbourne. These beds have been subdivided into four zones, those of Lancefield, Bendigo, Castle maine and Darriwill, each characterized by a typical graptolitic fauna. The chief productive goldfields in the western portion of the State occur in these zones near their contacts with granodio rites. Upper Ordovician rocks are chiefly developed in the eastern portions of the State and extend northward into. New South Wales. The crystalline schists of the Albury-Omeo districts and of the region around Cooma (New South Wales) are believed to be of Ordovician age as they appear to pass gradually into un altered fossiliferous Ordovician rocks.
At the close of Ordovician times a strong folding set in, ac companied in places by igneous intrusions. In New South Wales a marked unconformity separates these rocks from the succeeding Silurian strata.
In the Jenolan district, the famous caves are hollowed out of limestones rich in Pentamerus, and other Upper Silurian lime stones occur at `Vombeyan, Bathurst, Orange and Wellington. In Victoria the Silurian system is divisible into a Lower or Mel bournian series, mainly of sandstones and shales and an Upper or Yeringian series. These rocks cover a large portion of central eastern Victoria and contain much of the gold of the mining fields of this part of the State (Walhalla, Wood's Point, Rushworth, etc.). In Tasmania the West Coast range conglomerate series, which contains pebbles of the Cambro-Ordovician porphyroid series, is of Silurian age and underlies a Silurian limestone horizon. Here, too, are placed the limestones of the Gordon river, and the slates and sandstones of the Queen river, Zeehan and Middlesex.
The close of Silurian times witnessed great orogenic movements followed by intrusions of granites probably throughout south eastern Australia and Tasmania. Widespread volcanic activity ushered in the Devonian era in south-eastern Australia. In Vic toria a great group of dacite lavas was poured out over a land scape of folded Ordovician and Silurian sediments. These rocks are exposed in the Dandenongs, at Lilydale, Healesville and Macedon. Probably of similar age are the Snowy river porphyries of north-east Victoria, and the acid lavas of the Murrumbidgee valley. The former attain a thickness of 2,000ft., the latter prob ably 6,000ft. In both areas Middle Devonian sediments and tuffs with a rich marine fauna follow the lavas.
In north-eastern New South Wales and Queensland a Devonian sea, formed probably at an earlier date, and argillaceous sediments, tuffs, radiolarian shales and coral limestones were deposited in the Tamworth-Barraba region (New South Wales). Igneous action, represented in flows and shallow intrusions of spilites, kerato phyres and dolerites, is especially prominent in the Middle De vonian rocks of this region. In Queensland the upper portions of the Brisbane schist series and its equivalents were laid down in a Devonian sea. A period of pronounced orogenic movement closed the Middle Devonian epoch over southern and central New South Wales, and gently inclined Upper Devonian sediments rest unconformably on older sediments as at Cobar and in the Parkes Forbes district. The Upper Devonian quartzites and shales reach a thickness of io,000ft. at Mt. Lambie.
In the Kimberley district of Western Australia a series of con glomerates, grits and limestones occur on the Elvire river and in the Napier range. The fauna indicates an Upper Middle or Upper Devonian age.
At the close of the Devonian age, orogenic movement associ ated with granitic intrusions disturbed the area west of the Blue Mountains, but in north-eastern New South Wales there is little sign of any stratigraphic break between the Upper Devonian and Carboniferous sediments which are folded together. In this region Carboniferous strata attain a thickness of r 7,000ft. and extend in a wide folded belt from Port Stephens northward into New Eng land. The succession is as follows :— At the close of Burindi times earth movements in this region led to a reversion to widespread land conditions, the commencement being told by the development of a great thickness of conglomer ates (Wallarobba Conglomerates), which are likened to a "Flysch facies" comparable with the Siwalik conglomerates of the Sub Himalayas. Then followed the accumulation of an immense zone of lavas, tuffs and sills extending almost meridionally throughout the area. During these volcanic outbursts the first signs of glacia tion that subsequently enveloped much of the whole southern por tion of Australia appeared, glacial tills and seasonally banded varve rocks being intercalated between the tufaceous beds. In Queensland Carboniferous rocks are best represented in the Star series, and beds of similar age occur in the Drummond range, and at Rockhampton. Possibly they are also represented in the far north in the Herberton series and on the Pascoe river. The base of the great geosyncline in the Bowen area is constituted of a great pile of volcanic rocks which are probably to be correlated with the volcanic stage of the Kuttung of New South Wales. In the State of Victoria probably the Mansfield series with their fish beds, the Avon river sandstones with Lepidodendron australe and similar beds at Iguana Creek belong to Kuttung times. The glacial condi tions which set in during the Middle Carboniferous intensified near the close when an ice sheet covered large areas of southern Aus tralia. In Victoria and South Australia no marine beds of Permian age are known, but in Tasmania, New South Wales and Queens land widespread marine conditions obtained. In the type area of New South Wales the total thickness of Permian strata reached r 5,000f t. Marine beds are grouped into a lower and upper series separated by the Greta coal measures (r oo-2 oof t.) . Equivalent measures occur in Tasmania and Queensland. The final regression of the Palaeozoic sea from eastern Australia is represented by a second series of fresh-water beds and coal measures. In New South Wales they include the Tomago coal measures (5oo-1,800 f t.) and the Newcastle coal measures (r,600f t.) of Upper Permian age. The Permian beds contain a characteristic flora represented principally in Glossopteris and Gangamopteris while the typical Carboniferous Rhacopteris-Lepidodendron flora had died out in the Carboniferous. Glacial conditions persisted into the Upper Marine and a thickness of io,000ft. of strata separates the lower glacial beds of the Kuttung from the glacial conglomerates in the Muree beds of the Upper Marine stage.
This latter stage in the Kiama area contains a thick series of lathe lavas. In Queensland Permian deposits are known as far north as the Little river, west of Cooktown, but they are especially well developed over a region extending southward from the Bowen river to the New South Wales border. In Western Australia depos its of this age containing glacial horizons are known in the Irwin, Collie areas, and in the Gascoyne and Kimberley districts; in the latter deposits can be traced into the Northern Territory.
The Jurassic period witnessed a much wider extension of the lacustrine conditions characteristic of the preceding era. In east ern Tasmania and southern Victoria productive coal measures occur in rocks of this system. In the latter state a great lake cov ered portions of south Gippsland, and the Otway ranges and con glomerates, felspathic sandstones, mudstones and thin coal seams were deposited. Similar rocks occur further west in the valley of the Wannon. A large Jurassic basin occupied much of southern Queensland and portions of northern New South Wales and north eastern South Australia. The sediments deposited in this basin supply artesian water to the great artesian basin.
In Queensland the Jurassic system includes the Walloon series and the Tiaro series in the Maryborough district. The latter series has at its top an horizon of andesitic and rhyolitic lavas and tuffs. The Jurassic beds of Western Australia occur in a long belt near the western coast, near Geraldton and at Shark's Bay, at Cape Riche, east of Albany, and in the Kimberley district. The maxi mum thickness of these beds is not less than 3,000f t. They include conglomerates, sandstones, oolitic limestones and lignite beds. The marine sediments contain a rich fauna and the ammonite beds are referred to a middle Bajocian age. At the close of the Jurassic, central and eastern Tasmania witnessed the widespread intrusion of a series of quartz-dolerite sills reaching 2,000f t. in thickness. They are associated with the Permian and Lower Mesozoic un folded sediments, and form the tiers of central Tasmania.
The principal marine horizons of the Australian Cretaceous constitute the Rolling Downs formation (Lower Cretaceous).
Aptian—Roma series, Maryborough beds, Eucla beds (in part).
Albian—Tambo series, Point Charles bed, Eucla beds (in part).
In Western Australia the Upper Cretaceous Gingin Chalk series which extends in a coastal belt north of Perth to the Murchison river contains a rich f oraminif eral fauna and is palaeontologically distinct.
The first marine transgression in east Australia gave rise to the Roma series (blue clays) and probably represented the flooding of the Walloon basin by the sea. A non-sequence follows, the interval indicating a regression of the sea from the whole area to be followed by a second transgression during which a series of limestones represented by the Tambo beds was laid down. Both these seas appear to have had outlets to the north and south (Gulf of Carpentaria and Australian Bight). At the close of the Albian the sea finally withdrew from central and eastern Australia. The post-Tambo series of beds in the artesian basin include part of the so-called Desert sandstone. They are fresh-water beds and referred to as the Winton series. These beds reach a thickness of at least 4,000ft. in the Patchewarra bore. Lacustrine conditions probably extended into Lower Tertiary times.
In the Janjukian epoch the sea encroached over the region of the Nullarbor plains and sediments reach a thickness of over Y,000ft. In the east a marine transgression covered the Murray basin extending into the western plains of New South Wales. The sediments are principally polyzoal limestones, calcareous sand stones and clays. The Kalimnan and Werrikooian are much more limited in their distribution. The former is typically developed in eastern Victoria, but is also represented by the oyster beds of the River Murray cliffs and beds along the coast of St. Vincent's Gulf. The latter is typically developed at Limestone Creek, Glenelg river (Victoria), but appears in the Mallee bores and near Adelaide.
Probably the oldest terrestrial Tertiary deposits in southern Australia are the brown coal deposits, sands, muds and limestones recognized from bores at Newport and Altona Bay, south-west of Melbourne. These underlie the Balcombian (Oligocene) marine beds already referred to. The brown coal beds of Victoria are probably the thickest yet recorded in the world. Among the depos its of the Janjukian may be mentioned the Morwell brown coal deposits, the lignites of Moorlands (South Australia), plant beds underlying and overlying the older basalts of Victoria and the buried river drifts or deep leads of New South Wales and Victoria.
The non-marine deposits of Kalimnan and Werrikooian age in clude the newer deep leads of south-eastern Australia, e.g., Gul gong and Forest reef in New South Wales and Brandy Creek near Beaconsfield, Tasmania. The lacustrine deposits of Launceston and the Derwent basin are probably of Kalimnan age.
Throughout eastern Australia and Tasmania the Middle and Upper Tertiary was a period of intense volcanic activity. The vol canic series can generally be subdivided into three series termed (a) Older basalts, (b) Alkaline series, (c) Newer basalts, and as such are well recognized in Queensland, New South Wales and Victoria. The earliest lavas are of Balcombian and Janjukian age while the newest lavas range from the Pliocene probably into Pleistocene times. In Victoria the newer series of basalts cover an immense area west of the meridian of Melbourne. The alkaline series is represented in Queensland, New South Wales, Victoria and Tasmania and include alkaline trachytes, solvsbergites, pantel lerites, tinguaites, melilite and nepheline basalts. The leucite lavas of New South Wales and the Kimberley district of Western Australia are probably to be referred here.
The latest events in the geological history of Australia include the widespread epirogenic movements in which the eastern mar gin of Australia was warped up to elevations of over 3,000f t. above the sea. The Kosciusko area rose to an elevation of 7,000ft. and in Pleistocene times was the site of an ice cap, as was also much of the highlands of Tasmania. After the main uplift there followed a period of marked rift faulting, the foundering of Bass Strait, and the formation of the rift valleys of Spencer and St. Vincent's Gulf. Earthquake shocks indicate that adjustment is still in progress in these regions.
Information on the geology of Australia is principally contained in the publications of the State Geological Surveys and State Royal Societies. Reference may also be made to the Federal Handbook, B.A.A.S. 1914, chapter vii. "The Geology of the Commonwealth," by Sir Edgeworth David ; Transactions of the New Zealand Institute, 1923, "Palaeozoic and Mesozoic Seas in Australasia," by W. N. Benson ; and articles in the reports of the Pan-Pacific Science Congress, Australia, 5923. (C. E. T.) Geological and climatic factors have given Australia a singularly uniform surface, which either lies directly upon worn-down ancient rock or has been formed by filling in and levelling up. Barely one twentieth of the mainland is over 2,000ft. above sea level, though the proportion is greater in Tasmania. Marked temperature vari ation, torrential rainfall and, more locally, ice, have produced rubble, gravels, sand and dust. Dust-laden winds, ceaselessly scouring, etching and filing-down, have carried the finer materials far and wide, while in less arid areas and ages wide-ranging floods have spread alluvial floors. Wind and water-laid deposits cover much of the interior which, deprived by climatic and tectonic processes of a powerful drainage system, lies half-buried under the products of its own decay. Hence one of the paradoxes of Australian scenery—great expanses of flat or billowing surface sweeping up to, and often half engulfing, sharp upstanding rocky forms which rise, massive and deep-scarred, over against them.
In spite of sandridge areas, great parts of the interior possess soils sterilized by climate (e.g., Lake Eyre basin). Widespread surface or sub-surface concretions (laterite, ironstones, limestones, salt and gypsum) are also due mainly to arid conditions. The coastal belt (v. inf. Rivers and Drainage) exhibits great variety but includes the rich and ample slopes and river flats of Queens land, New South Wales, east Victoria and Tasmania. Inland the dark sticky soils of the moister terraces, plains and river-courses (e.g., Upper Darling basin) are succeeded on drier slopes and flats (e.g., western plains of New South Wales) by the well-known red soils, and almost the whole Lower Darling-Murray basin is covered with varied alluvial deposits. The Cretaceous (Rolling Downs) soils of Queensland, the (Tertiary) limestone soils of South Aus tralia and of the Nullarbor plains (dry red soil about ift. deep) are soils developed in situ.
Most varied are the soils of the eastern highlands and Tasmania, ranging from poor sands and grits derived from silicious sand stones and granites to rich red-to-black loams of limestone origin or admixture. The Palaeozoic rocks (slates, shales, etc.) yield in places rather poor clays, but widespread volcanic deposits pro vide fertile black-grey-red soils (cf. Darling Downs [Queensland] ; south and south-west Victoria ; New England plateau : Kimberley Division [Western Australia] ; Tasmania, etc.). Light sandy-to loamy soils are widely distributed in southern Australia (cf. the "sand-plains" of Western Australia and the "Mallee" soils of South Australia and Victoria) . These soils have not been leached out and are rich in mineral plant foods. Contrary to early prepos sessions, they are mostly capable of great improvement and are being extensively occupied.
Comparable are the rivers of the north and north-west coasts of the continent (e.g., Fitzroy [c. 400m.], Ord [c. 3oom.] besides the Victoria, Daly, Roper and McArthur). Many are navigable for considerable stretches and have economic possi bilities though all suffer from a markedly seasonal ("monsoon") regime. The south-west coastal portion of Western Australia is well drained by small but fairly constant streams (e.g. Swan river), but those farther north, the Ashburton, Fortescue and others, are courses only occasionally utilized by water. By far the greater part of the western plateau has no organized surface drainage, courses normally dry carrying off the water of occasional down pours.
(ii.) Further east the inner Northern Territory and the central lowlands have a drainage better defined but intermittent. Large shallow depressions (e.g., Lakes Woods and De Burgh in Northern Territory; Lake Eyre in South Australia) receive flood waters from near or distant uplands and then become more or less exten sive patches of water, swamp and mud. Descending from the up lands of Queensland or Central Australia by normal channels (cf. valleys and gorges of the Macdonnell Range), the streams survive upon the plains only after heavy rain and then are more in the nature of moving floods. Drying up, they leave behind them broad channels with water-holes, or sometimes (Finke, Neales, etc., in central Australia) shallow beds lined with sand beneath which water may linger or flow.
(iii.) The Murray-Darling would rank as one of the world's greatest drainage systems if its volume throughout were on the same scale as its mileage. As it is, the system is somewhat one sided (there are practically no western affluents) ; the flow, even occasionally of the Murray, is liable to interruption; a proportion of the quasi-tributaries seldom or never reach the main streams, and an oceanic outlet adequate to a great river is absent. Above the main confluence at Wentworth the Darling and Murray sys tems are distinct but similar. Each drains an approximately semi circular basin rimmed by the south Queensland and north New South Wales highlands and by the south New South Wales and Victorian highlands respectively. The head-streams usually emerge from long, tortuous, and often narrow and precipitous highland valleys. On the lowlands they converge, in comparatively st:aight lines, on centres respectively near Bourke (Darling) and east of Euston (Murray) .
In the north are the Macquarie (59om.), Namoi (43om.), Bogan, and others; in the eastern system the Murrumbidgee (c. Lachlan (c. 800m.), Goulbourn (28om.), Mitta Mitta (125m.), Loddon (i 5om.) . Descending to the lowlands these streams mostly slacken, begin to meander and deposit, to build their beds above the level of the plains, to flood, form distribu taries ("anabranches") and lagoon-like "billabongs," and in dry periods to shrink to a string of water-holes or dry up altogether. A good many streams (Macquarie, Paroo, Avoca, Wimmera, etc.) are usually lost in swamps or sands. The Darling itself may be dry as long as 18 months at a time, and even the Murray occasion ally ceases to flow.
The lower course of the combined Murray-Darling is very flat (gradient c. 3in. per mile). The river here flows through a wide flood plain between high and often cliffy banks. Near its mouth it expands into Lakes Alexandrina (q.v.) and Albert and has an out let, but at times no outflow, into Encounter bay over a shifting sand-bar carrying 7-12f t. of water. In their plains course nearly all the streams of the Murray-Darling system lose enormous vol umes of water by evaporation, by seepage (especially by old silted-up and buried channels), and increasingly also by the de mands of irrigation. Under the most favourable conditions navi gation can reach Walgett on the Darling and Albury on the Murray. The longest single stream-course is the Condamine-Dar ling-Murray (c. 3,800m.), but it is obvious from the conditions above described that this and similar figures have little practical significance.
Sheets of standing water are naturally rare in Australia. The lakes which adorn many maps of Western and South Australia are mostly either extensive saline flats ("Lakes" Amadeus, Disap pointment, etc.) or mud-flats receiving occasional (Lakes Gaird ner, Frome, Torrens) or periodic (Lakes Eyre, Woods) flood waters. Periodic also are the swamps, "billabongs," gilgais, etc., formed in the drainage courses of the great streams (v. sup.). The only true lakes are those found in southern South Australia, in Victoria (some of them of the volcanic "crater" type) and in the eastern highlands, including Tasmania. Even Lake George, the largest of these, is subject to considerable variations.
Ancient rocks, broadly speaking, constitute the outer portions of the continent, the eastern highlands, including Tasmania, forming a marked marginal belt. These rocks are extensively mineralized with metallic ores such as gold, silver-lead, copper, tin and iron, besides coal, phosphatic rocks and other non-metallic deposits. Australian minerals are therefore on the whole well situated for exploitation. Some important deposits are situated on or near the coasts (coal in New South Wales; silver-lead and copper in Tasmania ; iron in South Australia and Western Aus tralia), though Broken Hill, Cobar and Cloncurry are well inland. The continental margins are, moreover, the usually better watered and forested. The flatness and openness of the country (e.g., in Western Australia) have in places favoured prospecting further inland, but here the supplies of timber and water diminish, and Broken Hill has suffered from dearth of water. Transport has often presented difficulties and there are fields potentially valu able which are still commercially inaccessible. Australia owes a considerable proportion of its railway mileage to minerals. The wide distribution and convenient situation of workable coal, the availability in the east (notably in Tasmania) of water for power, and the facilities for marine coastwise transport also assist de velopment of mineral resources. (See Mining and Minerals, p. Primary occurrences of minerals are those in ancient rocks which have been involved, often at considerable depths, in mountain-building and other tectonic processes, and have become impregnated with bodies of ore. Such are the rocks of most of the western plateau, of virtually the whole of the eastern highland belt (including Tasmania), and of the South Australian and Bar rier ranges, in which gold, tin, silver-lead, zinc, copper, iron, phos phatic rocks and many others are found in lodes (vertical to hori zontal), reefs (cf. saddle-reefs), "replacement" zones, stockworks, etc., generally at or near contact-planes between different forma tions where stresses have occurred.
In the west, the mineralized areas are chiefly the north-west to south-east belts of "greenstone" schists, etc. (v. Geology, p. 704, et seqq.) of pre-Cambrian age; in the east somewhat later rocks (notably Silurian slates, etc.) are the chief seats of occurrence. Elevation and long-continued denudation have brought these min eral bodies near to the surface and, in places, left whole masses of ore-bearing quartz, etc., projecting as hills or ridges. Weather ing also, by reducing exposed portions of lodes, has frequently brought about concentrations of ore in the upper parts ("sec ondary enrichment," e.g., Mount Morgan, Queensland). The dis tribution of the mining industry, mining methods and mining profits have been, and continue to be, fundamentally dependent upon the conditions described.
Derivative deposits occur in (a) sedimentary strata such as the auriferous Nullagine conglomerates of north-west Western Aus tralia (cf. the Banket deposits of South Africa) , iron-impregnated sandstones, etc. These strata are in places more or less horizontal, and dissection by streams has made the ores more accessible. Most common, however, and widespread are alluvial deposits—notably of gold and tin. These river-bed ("stream") deposits, with which may be associated the auriferous sea-sands, derived originally from primary sources, have been widely covered up (ro–i oof t.) by later deposits—basaltic flows and river alluvium. These occurrences have also lent to Australian mining some of its most distinctive features.
Coal.—The coal resources of Australia are distributed along the eastern highlands, in Tasmania, and also, to a less extent, in South and Western Australia. The deposits, which occur in rocks ranging from the Permo-Carboniferous to Tertiary age, have mostly been preserved in hollows and basins in the underlying older rocks. The elevation, down-faulting and dissection of the eastern highlands, however, has exposed the seams in many areas so that they are easily worked. This applies particularly to por tions of the largest deposit, viz., that of the great New South Wales (Triassic) basin which, shaped roughly like a saucer with its deep est part near Sydney, has numerous seams exposed at the surface near, or actually upon, the coast (e.g., near Bulli).
The coals occur in seams of varying thickness and range from anthracite to lignite and include coking, steam and gas varieties. Their abundance, variety, accessibility and ease of working is lead ing, with the growth of population and of industries, to increasing exploitation. All the States (qq.v.) have useful supplies—South Australia has perhaps the least—and several of them have rela tively enormous reserves. The additional advantage of marginal or coastal position and of sea transport gives them especial com mercial value.
Water-power.—The northern rivers have very variable regimes and the Murray-Darling system has in addition insufficient gradi ents over most of its area. The eastern highland belt has steep grad ients (including falls) on the coastward side and strong and fairly constant stream-flows and here, in a belt stretching from Cairns in Queensland to Victoria, some 65o,000-1,3oo,000h.p. are avail able for development. Tasmania has some 400,000 located h.p. The coal deposits of the eastern highland belt greatly enhance the value of the water-power there, since the two sources of power can be worked in conjunction.
Water Supply.—Around the margins a belt varying in width roughly from r oo to 200 miles—broadest towards the south-east and including Tasmania, interrupted in the central west and central south—has normally a sufficient rainfall and run-off. Here capital cities, country towns and rural areas have abundant sup plies, based often on extensive reticulation schemes. The corre sponding parts of northern Australia have also adequate avail able supplies. In the drier parts of the country one finds both superficial and underground supplies.
Superficial supplies are derived from rainfall and include, besides occasional river, lagoon, pool and spring supplies, run-off stored in gravel screes at the base of, e.g., granite hills, sand-hill soaks (many "sand-hills" have clayey or tufaceous interiors) and other similar sources. Superficial supplies are apt to fail, but water-storage in reservoirs, dams, tanks, underground cisterns, etc., has made steady progress and is now widely established and the incidence of irregular, if spasmodically heavy, rainfalls is being mitigated.
Underground artesian supplies underlie nearly one-third of the surface of the continent (c. 95o,000sq.m.) . Virtually the whole of the great central lowlands, besides large areas at the head of the Great Australian Bight and along the west and north-west coasts are included. If, as seems possible or even probable, a proportion of this water is derived from the harder rocks which underlie the basins ("connate" or "included" water), and not by the under ground percolation and gravitation of rainfall ("meteoric" water), there is a definite, if a still extended, limit to the supplies avail able. Certainly in recent years the yields, which in many cases were over i,000,000gal., and in one case reached 2,333,000gal., per diem, have almost everywhere declined by amounts ranging from 3% to about 7% per annum.
Shallow sub-surface waters are widely distributed through the softer surface strata—Tertiary marine limestones and sandstones, alluvial gravels, silts, etc.—that mantle so much of the continent. They may be only a few feet below the surface and are derived originally from rainfall percolating directly, or through the inter mediate agency of rivers.
In wet seasons, especially in the south (see Climate, below) where the rain falls in the cool season (when evaporation is low est), great quantities of water lie upon the ground as pools or floods, and a large proportion of this water must escape under ground. These waters are thus permanently available and are also readily accessible, failure to strike supplies involving no great loss. Unfortunately many are saline. Nevertheless, when made available by means of windmills, etc., these supplies constitute an economic asset the value of which has perhaps been inadequately recog nized, and large tracts of country (e.g., in South Australia) have been, and can still be, permanently settled by their means.
In general, large-scale conservation and supply schemes, though important, are perhaps less important than the aggregate of indi vidually small but widely, and increasingly densely, distributed supplies which serve as a permanent safeguard.
Climate.—An island set in large water-bodies, Australia has for the most part equable conditions, but it is large enough to experience in its interior considerable extremes. Its size permits climatic differentiation, especially as between north and south, in which direction it stretches over some 33° of latitude (c. 11°– S.). At the same time, it has the least average elevation of all the continents and also a closed outline, and this makes for uniformity, and gives climatic—and hence often economic —regions on a large and simple scale. The great extent, more over, of land lying between the lats. of c. 20° and 3o° S. i.e., roughly along the tropic of Capricorn, and in a transition zone between two major rain regions—gives Australia a large area. of low rainfall, increased because the eastern highlands force pre cipitation on the eastern rim.
In the north the rains are monsoonal and brought by depres sions ("tropical lows") passing eastwards and south-eastwards. These rains fall in the hot season (chiefly in the six months No vember to April) and usually die away rapidly inland (c. 18°S. lat.). In the south the rains come mainly with depressions ("ant arctic lows") which, travelling east, cover Tasmania and a strip of varying depth of the mainland. Rains are deposited upon the eastern highlands (from about 3o° S. northwards) by the south east trade winds which come moisture-laden from the Pacific. These rains vary locally according to the disposition of the oppos ing heights but are mostly heavy.
More occasional and irregular, but often very heavy, falls are brought by tropical storms on the north-east coast, by the passage of "anti-cyclones" in the south, and by tropical lows moving down behind (west of) the eastern highlands. These last some times penetrate to Victoria and even to Tasmania (e.g., June 12, 1912) and they are welcome refreshers of the great pastoral plains of the eastern States. Finally there is the strip stretching roughly east and west from the lower Darling and south-west Queensland to the west coast about Sharks Bay, which has an average breadth of c. 55om. It touches the head of the Bight but narrows towards the west coast and occupies c. i,000,000 sq.m. or about one-third of the continent. This is "arid" Australia, with an annual rainfall of loin. or less, where the marginal rains described above tail off and come feebly, irregularly, or seldom. The true "axis of aridity" swings north and south with the seasons, and the margins are visited by occasional rains from now the north, now the east, now the south. At the opposite extreme stands Tasmania with an abundant all-the-year fall, especially on its exposed western highland flank.
Four main rainfall regions have thus been distinguished: (I) the northern, with summer rains averaging 6oin. or less (reckon ing inwards) annually; (2) the southern, with winter rains aver aging from fioin. downwards; Tasmania 1 I o-2oin. ; (3) the east ern, sharing partly in both the above, but having "independent" sources of its own, from 6o-4oin., confined mainly to the eastern highland flank and thereafter falling off inland; (4) the "arid," with loin. or less. The wettest portion of Australia is on the north-east Queensland coast (144-165in. ay. ann.), and the driest about Lake Eyre (less than 5in.). Reliability of rain fall decreases as temperature increases towards the north-west and north of the continent, the extreme north and one or two other areas forming exceptions. The economic value of the rain fall—the moisture normally available of ter evaporation has taken its toll—is greatest in the area of uniform rainfall along the south west and south-east marginal parts. Elsewhere there are district wet and dry seasons and inwards the rains become more spas modic and more concentrated so that special adaptations are necessary ("dry farming"; water and fodder conservation, etc.).
Torrential and irregular precipitation is rather typical particu larly in the north and north-east in summer. Hail occurs along the south in winter and over the south-east in summer. These cause considerable damage especially through flood destruction. Recur rent droughts have earned excessive notoriety. Storms visit chiefly the north and east parts: cyclones ("willy-willies") the north-west in November to April; hurricanes the north-east in January to April; "Southerly bursters" the south-east chiefly in October to February. The arid interior is the home of restless dust-carrying winds which periodically sweep down to discomfort the south. Tasmania, somewhat exceptional, has a climate like that of England—mild, moist and invigorating. (X.) Fauna.—The Triclad Turbellarian (Land Planarian) genus Geoplana is largely confined to Australia, New Zealand and South America, with some species in South Africa and in Japan. Among earthworms the Perichaetidae are represented by obviously an cient forms in Australia ; they are also important in South America and a few occur in south-east Asia, Perichaeta itself abundantly, and a few in Africa but none in the more northerly lands. It is noteworthy that the earthworms of New Zealand, though related to some Australian ones, show only a few species and are related to those of South Georgia, the Falklands and south Argentine and Chile. Peripatus, again, an ancient type related both to the seg mented worms and to the arthropods, has species found in Aus tralia, while other species characterize New Zealand, Sumatra, South Africa, South America and the West Indies. They are all land animals without means of distribution over the water and they are all ancient types of life. Their distribution is that of relicts of an old widespread fauna, they are now found only in discontinuous areas of survival as a result of physiographical isolation.
Ceratodus, a Dipnoan fish, survives in the rivers of Queensland, the other living Dipnoans being African and South American though fossils are widespread. The Port Jackson shark (Heter odontus) is another survival, in this case of the elasmobranchs (sharks) of the Secondary period.
As regards crocodiles and lizards Australia, especially in the north-east, where the crocodiles occur, is clearly related to Asia. Among the tortoises the family Chelydidae is found in Australia and South America, and fossils have been found in Europe. Here, then, we seem to have evidence from fossils to support the general thesis concerning discontinuous areas of survival (Chelydidae), as well as to suggest that Australia and Asia have been connected within the period of earth history since the first evolution of lizards; crocodiles may get across a fair breadth of sea. The great Queensland crocodile has been known to reach a length of Soft. The leathery turtle has been taken in some Australian coastal seas. Australia has many snakes, several venomous ones.
The running birds are represented in Australia by the emu and the cassowary. The emu is a known fossil from New Zealand, which had, until recently, gigantic flightless birds. The cassowary occurs in Papua and some neighbouring islands as well as in Australia. The other running birds that survive are the ostriches in Africa and rhea in South America. The gallinaceous birds are interesting in the same way ; some ancient types, the Megapodes or mound builders are Australian but one species is found in south-east Asia; their probable nearest relatives, the Cracidae, are South American. The lyre-birds (Menura), the bower-builders, and the honey-eaters are other features of Australia.
But it is the mammalian fauna of Australia that presents the greatest interest. The Mammalia bear their young alive after nutrition in the uterus for a period through a vascular organ called the placenta. The young, after birth, are fed by the mother from her mammary glands ; they develop a juvenile, or so-called milk-dentition, which is replaced by the second or adult dentition. Two genera in Australia, Ornithorhynchus and Echidna are sur vivors of early types in which these features are barely indicated; they lay eggs, have no placenta, and no tooth change, but they give milk though without teats; they form the order Monotre mata which has obvious kinship with reptiles as well as with mammals. Echidna also occurs in Papua. The Marsupialia or pouched mammals are the only other order of mammals, apart from bats and rodents and introductions by man (but see below), found living in Australia. A few members of this order live in America, north and south and some in the eastern East Indies and Papua (see ASIA, Fauna) while related fossils are widespread. But, among marsupials, some have several front teeth on each side of the lower jaw and these include many Australian forms, the American opossums and fossils in the northern land mass of the Old World. Others like the kangaroos have more specialized features, one of which is that there are but two front teeth (one each side) in the lower jaw, and, outside Australia, the only mem ber of this sub-group is Coenolestes, in Ecuador, but fossil rela tives have been found in southern South America. This has led to suggestions of land connections via the Antarctic at some time such as the early Tertiary period when apparently the earth's cli mates were far warmer on the whole than now. Play has been made in this connection also with the special richness of the Mar supial fauna of Tasmania. Other workers think that the idea of restriction of survivals to southern isolated lands is what is again illustrated here. Some of the Australian Marsupials (e.g., the bandicoot) have been shown to possess degenerate traces of the processes of placental nutrition and of tooth change.
The dingo or wild dog is a remarkable feature in Australia and opinion concerning it has varied from time to time; it has been said to be a human introduction, i.e., to be feral and not a real wild animal; bones, however, have been found which have been claimed to be of a date long before the arrival of man in Australia and the feral character has been denied on anatomical grounds as well. The wide distribution of Canis is a point to be borne in mind, as also the fact that it can swim. Bats and rodents have such special means of distribution that their occurrence in Aus tralia raises no problem of the kind above discussed. The dingo appears to be increasing.
The native fauna has almost ceased to have economic signifi cance in Australia. The kangaroo, once hunted for his skin, and the wombat are becoming rarities, though the native birds are abundant, interesting and often beautiful. The feral buffaloes of the north-west (e.g., Melville Island) have been nearly exter minated. Ants and termites are a destructive pest, especially in the north. To the ranks of pests have been added the rabbit, fox, sparrow and starling, and even camels have been known to be come feral in central Australia.
Vegetation and Flora.—The sand-ridge country of the west and north-west interior, the "gibber" and clay loam plains of the Lake Eyre basin, rock highlands and rock patches in various parts are bare over considerable areas or for considerable periods. The sand-ridges, with their included clay strips, have sparse and stunted scrub and "porcupine" grass ; the clay plains of central Australia produce from their richness amazing growths of grass, herb and flower after rains—deceptive glories, suddenly appearing and as quickly vanishing. Over much of the arid interior the plant population is sparse, stunted and relatively depressing in appear ance. Climatic influences obviously dominate vegetation in Aus tralia, but geological factors play a part, and from Western Aus tralia to Queensland pastoral, agricultural and other lands, granites, sandstones, "sand-plains," etc., are distinguished by types and names of plants, or plant associations. Between and outwards from the areas mentioned above, there extend vast plains, for the most part of seasonal grassland and permanent scrub, in which acacias of various sorts are common, particularly "mulga" scrub. The scrub thickens in brakes and patches and the seasonal river-courses are lined with larger trees (e.g., River and Swamp gums) . On the south side salt-bush, a valuable fodder plant, is widespread. The pastoral value of all this type of country is considerable and as yet little utilized (e.g., Burt plains north of the Macdonnell range). It occupies a large oval extend ing from the central west coast to west Queensland and New South Wales, and from the central north nearly to the Bight and Gulf region of the south. Outwards it merges into another belt, or series of belts, of wooded grasslands. In the north-west, north and (inland) north-east, tropical savanna predominates. Here summer rains followed by a long dry season give a pre vailingly open landscape with much fine grassland and varying proportions of woodland composed of rather small trees. In Queensland the term "brigalow scrub" is applied to the wood element. Considerable patches of real forest occur, notably in the rich alluvial valleys of the north-west and also towards the east Queensland highlands. On the south side—in the areas having c. Io-2oin. average annual rainfall—the characteristic tree-scrub is "mallee," a eucalypt with a bunchy growth above ground and massive pancake-like base and root-crown. Mallee country, once called "desert," is now producing wheat over wide areas. The "brigalow" country of Queensland, etc., includes some of Australia's best pastoral lands, as do also the west plains of Queensland and New South Wales with their wide open stretches of grass and low scrub and tree-belts by water-courses and water holes. There remain the outer margins of the continent, north-east Queensland round to the extremity of South Australia, with Tasmania and south-west Australia as well. Here are rain forests proper ranging from the tropical (almost equatorial) to the cool temperate type (Tasmania). Sometimes they are sharply marked off from the inland types, but more often they are more or less open in character, with grassy grounds and patches, merg ing gradually into the wooded grass-lands behind. This transition is marked on the west flanks of the highlands by a belt of timber more open and having smaller trees. The forests of north-east Queensland (the Queensland "brush") are luxuriantly grown, matted with lianas, and contain soft-wood trees. Southwards these pass into a eucalypt forest which reaches its finest de velopment in Gippsland, the home of Australia's giant trees (Max. recorded: height, 3 2 6f t. 'in.; girth [6f t. from ground] , 2 5 f t. 7in.) . The Gippsland forests, with their deep tree-fern valleys, are famous in Australia, and hardly less so are those of Tasmania (conifers and beeches), and of south-west Australia (jarrah, karri, tuart, etc.).
Australian vegetation as a whole has a marked individuality. One feature is the great predominance—at least in the southern parts—of eucalypts of which some 32o species are known. An other is the great range, in area and in species (c. 412), of acacias ("wattles") many of which give their names to well-known types of scrub (mulga, brigalow, myall, etc.), the golden wattle being the "unofficial floral emblem of Australia." Spinifex is widely known by name outside Australia, but the "Native (or Cypress) pine," "she-oaks," "black-boys," besides numerous flowering shrubs and plants, are more widely typical of the Australian "bush." Forest fires, all too frequent and destructive, and the practice of ring-barking, give many square miles a look gaunt, ghostly and forlorn, softened sometimes by shimmering heat and the blue dis tant haze. There is in Australian vegetation a reminiscence of age-long struggle, a savour of the rocks and climate, of survival, not without effort, from past ages into an exacting present. Eco nomically Australian vegetation has possibilities not fully utilized (see Forestry, etc., below, p. 726, et seq.). Of all plant pests in troduced, the prickly pear is the most menacing and costly. By 1922 it had covered an (estimated) area of 60,000-7o,000 sq.m. (cf. England and Wales, area, 58,300 sq.m.), a space "twice the total area in Australia under all crops," and was spreading at the rate of c. 23o sq.m. per annum in south Queensland and north New South Wales. It prefers the richest lands, often forms a solid impenetrable mass, is of little economic value, and is difficult to destroy by mechanical or chemical means. Recent experiments, however, with insect parasites justify hope that the pest may be controlled if not exterminated. Destruction of forests is intro ducing changes in hydrographic conditions. Problems of soil erosion and run-off are arising and need attention.
(0. H. T. R.) Brief reference must be made to the phytogeographical interest of the Australian flora. The plants of north-east Aus tralia include many trees, mostly of soft woods and lianas, which have relatives in Papua and Melanesia and they represent an intrusive flora which reached Australia ere Torres Strait di vided it from Papua. This intrusive flora has exterminated the older indigenous one in the coastlands of the Gulf of Carpentaria, of Queensland and of northern New South Wales but it has not been able to penetrate much beyond these limits, within which the annual rainfall is at least 3oin. and in many places over 4oin. The rest of ,Australia is largely characterized by types of plants which are often peculiar to the continent, or are related to plants of other southern lands and show every indication of being sur vivors of quite ancient elements of the world's flora. The eucalypts and the peculiar acacias have already been mentioned. The Proteaceae are hard-leaved plants found in Australia, New Zealand, Caledonia, southern South America and South Africa and they are believed to be survivors of an old element in the world's flora. Araucaria, a coniferous genus, is also important in both Australia and South America while Andansonia Gregorii in north-west Australia is closely related to the African baobab. These are all indications of the survival in Australia and other southern lands of types once more widely, perhaps generally, distributed in the great northerly lands but pressed out there by evolution of newer types and surviving in southern lands which have now for a long period been more or less isolated from the larger northern masses. (X.) Physical Anthropology.—The Australian "black-fellow" is not black, but chocolate brown. He is below the average height of Englishmen, has strong wavy hair, well developed beard whisk ers and moustache, usually jet black. Women wear the hair short. While the average index for Australian skulls is 71.5, the range in the living subject is from 80.5 to 66.6. The head is often high and ridged, with a retreating forehead. The eyebrow ridges are heavy, the nose has its root set deeply and is distinctly broad. There is much variation, which has been regarded as evidence of admixture or of the survival of intermediate and generalized char acters of a really primitive nature. Blood tests reveal two dis tinct blood groups and there are grounds for thinking that in the very distant past at least two streams of immigrants met and fused—one of them being akin to elements surviving in the south of India, in Ceylon, the Malay Peninsula and in Indonesia.
The exogamic system, with variation in details, is universally bound up with the beliefs that every person is the re-incarnation of some former individual, and that the identity of the human ancestor or type merges into the totem animal. There are com plicated initiation rites, circumcision, subincision (the penile urethra being laid open from the meatus to the junction with the scrotum), removal of teeth, head-biting, tossing the novice in the air, fire-ceremonies. There are rites for women analogous to the initiation rites of the men, but fewer in number and less elabo rate. The purpose of the rites is to establish the authority of the elders, to inculcate self-restraint and manliness, and finally to bring about a progressive revelation of the tribal secrets.
Sanctity, power, authority, reside in man and in objects fabri cated or adorned or modified by man. The churinga especially form a class of sacred objects in wood or stone varying in length from six to seven feet to two or three inches and of various shapes. The term "Bull-roarer" is used of the smaller kind and there are two main forms of this article which have definite distribution and association with specific forms of initiation.
An important class of rites are performed for the welfare of the totem, animal or plant, and are held customarily just when there is the promise of the approach of a good season. As a rule, the headman or director of ceremonies is required to partake cere monially of the plant or animal, thus breaking the rule of sanc tity partly to acquire its virtue for himself. Others not members of the same totemic group are then free to use the plant or ani mal. Co-operation of this nature throughout the group brings the constituent clans together, and has a social value by reason of its economic importance.
It is impossible to say who were the first discoverers of Austra lia, although there is evidence that the Chinese had some knowl edge of the continent so far back as the 13th century. The Malays, also, would seem to have been acquainted with the northern coast ; while Marco Polo, who visited the East at the close of the 13th century, makes reference to the reputed existence of a great southern continent. A map on which a large southern land is shown still exists, dedicated to Henry VIII. of England, and the tradition of a Terra Australis appears to have been current for a long period before it enters into authentic history.