Geology of Boroondara

UPON passing Collingwood Flat, and crossing the river, the traveller lands upon the floor of schistose, or slate rocks. Some geologists have ventured upon the statement of an approximate depth of this formation, «34» which they imagine to be not less than thirty thousand feet. No one has yet driven through to certify the same.

Just over Richmond Bridge the slate stands out boldly before one. The first rise of Hawthorne Hill is but the beginning of a series of elevations to the eastward, leading on to the loftier ranges of the same mineral characteristic, and evidencing their connection with that vast continuity of hills stretching from west to east through the centre of Victoria, and onward for hundreds of miles through New South Wales, —the very richest range of mountains in the known world.

We have, in some parts of Boroondara, slate soft and workable as freestone; in others, it is so full of quartz veins as to be impracticable. At the Yarra side, below the estate of the Chief Justice, the rock is inclined 60 deg. to the south, and abounds with ferruginous quartz seams, which, exposed by the wear of the softer mineral, assume the aspect of iron lace-work, with varieties enough for ladies’ crochet patterns. Some really pretty party coloured stones are near, the hue being occasioned by the mixture of the ferruginous element. Not far from the grounds of John Hodgson, Esq., M.L.C., in the vertical semi-crystalline bands of slate, the decomposition of the softer constituents has left some singular parallel ridges, like the cicatrices upon a Black’s chest.

In the Reserve Park the parallel and meridional bands are seen as strongly marked as upon the diggings. There are quartz reefs in the slate running nearly north and south in the orthodox manner. In very truth Boroondara is an Auriferous District, a to be Gold Field!! Gold has been found already in various places. In the writer’s own ground children have picked up specimens in quartz. The same have been gathered elsewhere. In digging of foundations of houses gold has turned up. How very agreeable for the loungers about town, the future unemployed «35» to walk out three or four miles to diggings! The same character of country about Anderson’s Creek can be traced downward along the Yarra through Boroondara and a part of Prahran. The extraordinary peninsular promontories, jutting out from the Reserve into the Yarra, remind one of the huge straggling limbs of the Cuttle fish, fabled to grasp the sailing bark of the Indian Seas.

The detritus, as has been mentioned, is not generally extensive. We have not the sands of Brighton or the deep clays of Prahran. The eastern portion is more sandy than the western. Our deepest beds of clay are in Red Gum Flat, the north of the Park, and the low portions of Hawthorne. For brick earth we have the advantage of our neighbours in Prahran. Gravel occurs in two particular localities, on he hill above the Punt, and on Church Hill, Hawthorne. It consists of quartz pebbles from one inch to two inches in length, connected by ferruginous sand and smaller rounded grains of quartz. It is so hard in some places as to require more powder for blasting than even bluestone. The thickness of the bed is from a few inches to eight and ten feet. The base is pipe clay upon slate. At Kew the small shot-like quartz forms one extensive and indurated conglomerate. The varieties of debris are owing to the different materials washed into the ancient bays of the ocean, exactly as we perceive it on our coasts at the present day, being shingle beaches, sandy beaches, and muddy beaches; all near one another. The high and dry situation of such beds in Boroondara has been owing to the gradual elevation of land by volcanic or magnetic agency.

We have evidence of more movements than one of the surface of Boroondara. Even within the historical period, if aboriginal traditions are to be respected, the land has risen. And although the present population of Victoria may give place to another and wholly different race in physical features, manners, and ideas, «36» yet the time will come when the increased elevation may place the spot, now, recognized as Williamstown, some thirty miles from the shore inland, and remove the cause of any further discussion about the Geelong bar; a new port will be formed, perhaps, in the vicinity of Point Nepean extension. Or, contrarywise, a subsidence will happen, to place Melbourne as a convenient sporting place for fishes, convert Boroondara into a sort of Venice with floating homes, and bring Ballaarat within an easy stage of its watering place.

The river Yarra has altered in depth and relative height of surface above the sea level. At the Punt the rambler sees considerable deposits of fine, silt-like earth, rising 30 feet from the water. Looking across at an angle to the Collingwood side, he notices the same kind of alluvium there, and resting, as in Boroondara, upon the slate bottom. It is but reasonable to believe that, though the river now rushes through such banks, it once deposited them, and the bottom of the stream was where the top of the earthy rampart now is; that is, that the Yarra was formerly some 40 to 60 feet higher than at present. The period of such must have been posterior to the elevation of Collingwood Flat, as its alluvial deposit is very different from the one described.

Such a sedimentary deposit has not the character of that produced by a sudden and extraordinary flood, denuding distant lands, and carrying their spoil downward and onward. Within a recent period there have been some remarkable inundations of the Yarra. The Puntman will point out a log, placed 20 feet high among the branches of a tree beside the river. On Christmas day, in 1839, the flood did little mischief in the almost unknown and uninhabited region of Boroondara, but at Melbourne the ancient brick-fields, near where the south end of Prince’s Bridge is, were swept away, and several lives were lost. In the flood of 1848 our district suffered considerably. Mr. Wade «37» speaks of having 80 acres, out of 100 acres of his cultivated paddock, covered with water.

The geology of Boroondara is obviously different from that of Collingwood. Our flats are not covered, like its low grounds, with the basaltic lava. The two places, so contiguous, were subjected to different elemental actions, though Collingwood, like Boroondara, has its hills of slate, and is not without auriferous manifestations. Boroondara rose in a mass in time to escape that fiery flood which desolated the low country near; whether from Mr. Blandowski’s Melbourne Swamp Crater, or not, it is hard to determine. It is highly probable that it was from a submarine volcano, and that the burning stream hissed through the waters along the shallow ocean bed; the Eastern Hill of Melbourne, Carlton Hill, &c., appearing like islets in the sea. The rock could not have been long submerged before the lava current came, as little or no deposit is observable between the slate and basalt. This was before the advent of the Yarra.

As the land rose again, a partial dislocation took place at the point of junction of basalt and slate; that is, when the trappean current terminated against the slate walls of Boroondara—and in the rent chasm the overflowing of the upland region found vent, and the natives called the flowing waters by the name of "Yarra Yarra." In several places this junction of formations may be seen to great advantage, as at the Falls of Dight’s Mills. There the water rushes over the hard basaltic ridge in rolling volumes in winter, and gently glides down the steep in summer. On our side the slate rock rise to considerable height, and the stone is softer than usual, and well adapted for general building purposes. The stratification is distinctly determined. A ramble along the Yarra in that quarter will well t repay the lover of nature as well as the student geology

The only place in which we have detected the volcanic rock in Boroondara is in one spot in Hawthorne. «38» On the hill near it, upon which rest the Church and National School, the contorted bands of slate bears north to the east, and dip from 70 degs. to 90 degs. to the east. On the eastern side of the hill a small creek is seen, shown by the name of Connell’s Creek, so called after one of the early settlers in the district. The creek is crossed by a bridge in the Hawthorne Road, and runs down to the Yarra between the estates of Sir J. F. Palmer and T. H. Power, Esq., M.L.C. In the bottom of' the creek a small bed of trappean basalt is to be observed, as though the lava current had run up that low chasm from across the Collingwood and Richmond Flats.

Since the rock of Boroondara first shook off its mantle of waters, and rose to received the beams of a primeval sun, what wondrous changes have occurred in the world of' matter! What long continued and extensive elemental fury has raged from Pole to Pole! What floodings of volcanoes! What throes of mighty earthquakes! What dissolution of whole continents! What submersion and reconstruction of vast masses of the earth’s crust! What toppling, and crushing, and levelling of towering mountains. Much of our own mother country has risen and sunk repeatedly since the time Boroondara first appeared. At one time it was a jungle forest of tropical foliage. Then its waters were moved in the play of monster Saurians, the real dragons of the old world, while its woods shook with the tread of the gigantic Iguanadon, as it covered yards at a stride. Then all was silent in the womb of the ocean. Vast icebergs floated over the land of Britons, striking against a few rocky islets, and depositing boulders from another and a distant shore. Slowly it rose again to smile in flowers. Again and again did old Chaos return. Untold myriads of animalculæ sported in its watery shroud, fell in heaps upon the calcareous muddy bottom, with comminuted shells and corals, forming the chalk bulwarks of Albion. But we weary in dwelling upon the dislocations, «39» changes, and transformations of the island home, while Boroondara was dreaming in placid security, unhurt amidst the storms, and beyond the fatal circle of the Cycloid. It slept on in peace, and long in peace. When it sunk at last beneath the surge, it remained not for any lengthened period before its resurrection. Here it received an accumulation of sandy mud, and there a deposit of clay, or of rounded shingle. There was no time for the consolidation of strata. It rose with its spare Tertiary beds, one of the numerous islands then comprising the continent of Australia. By and by elevating influences brought these islands together in compact bonds of brotherhood, and Flora and Fauna spread alike through all. Boroondara received its share of the general good, and to this day shows the family face of Australia.

Goodhugh and Hough, Printers, Flinders Lane, East.