PART II. Exploration and Physiography. The noble harbour of Port Jackson determined the first settlement. This unique sheet of water owes its deep frontages to the fact that it is a drowned river valley-depressed by the same forces which formed the famous Blue Mountain scarp. The folding accompanying the formation of the latter feature determined the course of the Nepean River to the west. This cut off the stream which had drained into Port Jackson, and so prevented the channels from being silted and obliterated. Per contra, but little alluvial is preserved along the harbour shores, and so we find the early settlers having recourse to the valley of the capturing river -the Nepean-for their cattle pastures near Camden, and, later, for their crops at Richmond. A simple grand fold has buckled the sterile Hawkesbury sandstones, so that they are 3000 ft. higher at Mount Victoria than at Sydney. Growth during the first thirty years of the young colony's life was thwarted by this unusual type of mountain barrier. Here are the finest bottle-neck valleys in the world, and their evolution remained a puzzle until David's research eighty years later. Darwin himself was astonished by them in 1835. "Great arm-like bays expanding at their upper ends penetrate the sandstone platform. Although several miles wide at their heads, they generally contract towards their mouths to such a degree as to become impassable. All attempts to penetrate into the interior by the natural routesalong the valleys-failed; and, indeed, the traffic to-day is practically confined to one railway route which ignores the valleys and closely follows Blaxland's route of 1813. In 1797, Shortland discovered the Hunter River. Here is the site for a town, which possesses all the advantages lacking at Sydney. A fine stream leads inland to a broad, open valley which penetrates to the interior by the lowest gap in the Highlands from the Darling Downs to Western Victoria. This has been named the Cassilis Geocol (or Gate). CONTOURS OF SOUTH-EAST AUSTRALIA. The river alluvial around Maitland is some of the most fertile in Australia. The coalfields are among the richest in the world, and will inevitably place the closest settlement of the future in the vicinity. Thus the Broken Hill Corporation has chosen this locality for much of its manufacturing in spite of the distance from its headquarters, and many other industries are similarly influenced. It is an interesting speculation as to the size our largest city would have reached had it been placed in this region of infinitely greater economic importance. Everywhere from the northern to the southern border of New South Wales the same menacing scarps front the sea. Oxley, in 1818, descended the New England Ranges via the Hastings Valley, where he tackled a region that is almost devoid of settlement to this day. Apart from the Cassilis route crossed by Cunningham in 1823, only to the southwest along the route of the southern railway is there a comparatively easy grade to the west. This leads to the Lake George depression, and so to the Murrumbidgee. The route follows up the Nepean River, which was sparsely settled by 1816. The Wollondilly, as the main branch of the Nepean River is called, runs through such rugged country that I doubt whether it has ever been followed continuously for any considerable distance. To the south again the coast-line is determined by a slipping down of the crust along a major fault plane. Hence traffic is confined to roads parallel to the south coast, and only at infrequent intervals is there a road leading to the interior. (See Fig. 2.) The western slopes of the Highlands were reached in 1813, and were found to lead gently towards the interior. There are but few of the great fold and fault planes which have truncated the eastern limbs of the Highlands. The rivers flow less rapidly; but, on the other hand, are often dry from the increasing aridity as we move westwards. The next 20 years of exploration were struggles against an unfamiliar environment, characterised by an inland drainage and an erratic rainfall. Oxley, in 1817 and 1818, had determined the character of our inland rivers. Both the Macquarie and Lachlan he found to leave the Highlands about 150 miles from the east coast, and to traverse the plains without receiving any further important supplies of water. Gradually they decreased in volume and were lost in the marshy swamps of the interior. He was, in fact, entering a region undergoing the early phases of a cycle of arid erosion, and with this type of country an Englishman was naturally unfamiliar. (See Fig. 2.) Hume and Hovell started in 1824 from Lake George (in New South Wales) to reach the coast at Port Phillip. Marching more or less parallel to the coast, they kept within the region of good rainfall, but the topographic difficulties were at first of a somewhat special nature, for in this corner of Australia is developed an extensive series of fault blocks. The numerous streams which they crossed the Murrumbidgee, Goodradigbee, Tumut, Upper Murray, Ovens and Goulburn-probably all flow along ancient fault valleys, occupying strips of the crust which have foundered relatively to those adjoining them. They returned through the Kilmore Geocol-which is a low gap putting Melbourne in easy communication with its hinterland, and in that respect far enhancing the value of the city for a State capital as compared with Sydney. In 1829, many rivers had been discovered all flowing to the west. No large estuary had been observed anywhere round Australia which seemed adequate as an outlet for all this water. We can understand, therefore, that there was a general belief in a large inland sea,* just as Africa had its mythical Mountains of the Moon. The latter report was based on Ruwenzori. The former belief has been justified in part in two ways. The West Queensland rivers still run into an inland sea in the form of Lake Eyre, while a considerable proportion of the water in the rivers of South Queensland and of Northern New South Wales flows into an underground "sea," the artesian basin. *Wentworth wrote of the unknown western portion of the Macquarie River:-"If it should be found to empty itself into the ocean in the north-west coast, which is the only part of this vast island that has not been accurately surveyed, in what mighty conception of the future power and greatness of this colony may we not reasonably indulge. Its course cannot be less than five to six thousand miles." (See the graphic account given by Ernest Favenc in Explorers of Australia (Christchurch, 1908), which I have used freely for my chronology.) .. Mitchell and Sturt cleared up the mystery of the drainage of south-east Australia in the period 1830 to 1836, and showed that it resembled that of the Nile basin. The Murray rises in well-watered regions, fed with snows in places. It receives numerous tributaries in its upper course and then gradually enters a region of lower rainfall, where it receives no further supply in the last 400 miles. In 1836, South Australia was settled and exploration progressed rapidly from Adelaide. Eyre's first trip with cattle from Victoria to the new centre was blocked by the Mallee sand-ridges. These peculiar outposts of the desert occur in a comparatively well-watered region. They are partly clothed in teatree and scrub; but, applying Penck's hypothesis, they perhaps indicate that the desert conditions are migrating southward, whereas the northern areas of the desert are being reclaimed by Nature herself. However, large areas of the Mallee have been devoted to wheat in recent years. The great problem of South Australia was entirely due to physiographic conditions. Eyre saw Lake Torrens in 1838, and a little later, from Mt. Hopeless, he saw similar sheets of water to the east. Hence a horseshoe cordon of salt lakes appeared to cut off Adelaide from the north. Lake Torrens occupies a rift valley of fairly late origin, while the lake Frome series of salt lakes seem to have been dammed back by the comparatively recent uplift of the Flinders Range. There seems little doubt that the inland rivers, Barcoo, Strezelecki, and Siccus, flowed directly to Spencer Gulf before their lower course was raised 1500 ft. by a late tertiary buckle of the crust (as shown by Howchin). At any rate, though Babbage disproved the 'Cordon" in 1856, a rise in water level of 100 ft. would link Frome to Eyre, while very little more would allow Eyre to flow through the Gap to Lake Torrens, and so justify the old theory. 66 |