Volume II Part 58 (2/2)
(*Footnote. The possible correspondence of the great Australian Bight, the coast of which in general is of no great elevation, with the deeply-indented Gulf of Carpentaria, tending, as it were, to a division of this great island into two, accords with this hypothesis of mountain ranges: but the distance between these recesses, over the land at the nearest points, is not less than a thousand English miles. The granite, on the south coast, at Investigator's Islands, and westward, at Middle Island, Cape Le Grand, King George's Sound, and Cape Naturaliste, is very wide of the line above-mentioned, and nothing is yet known of its relations.)
(**Footnote. On the Cause of Earthquakes. Philosophical Transactions 1760 volume 51 page 566 to 585, 586.)
DETAILED LIST OF SPECIMENS.
The specimens mentioned in the following list have been compared with some of those of England and other countries, princ.i.p.ally in the cabinets of the Geological Society, and of Mr. Greenough; and with a collection from part of the confines of the primitive tracts of England and North Wales, formed by Mr. Arthur Aikin, and now in his own possession. Captain King's collection has been presented to the Geological Society; and duplicates of Mr. Brown's specimens are deposited in the British Museum.
RODD'S BAY, on the East Coast, discovered by Captain King, about sixty miles south of Cape Capricorn.* Reddish sandstone, of moderately-fine grain, resembling that which in England occurs in the coal formation, and beneath it (mill-stone grit). A sienitic compound, consisting of a large proportion of reddish felspar, with specks of a green substance, probably mica; resembling a rock from Shap in c.u.mberland.
(*Footnote. In Captain King's collection are also specimens found on the beach at Port Macquarie, and in the bed of the Hastings River, of common serpentine, and of botryoidal magnesite, from veins in serpentine. The magnesite agrees nearly with that of Baudissero, in Piedmont. (See Cleaveland's Mineralogy 1st edition page 345.)
CAPE CLINTON, between Rodd's Bay and the Percy Islands. Porphyritic conglomerate, with a base of decomposed felspar, enclosing grains of quartz and common felspar, and some fragments of what appears to be compact epidote; very nearly resembling specimens from the trap rocks* of the Wrekin and Breeden Hills in Shrops.h.i.+re. Reddish and yellowish sandy clay, coloured by oxide of iron, and used as pigments by the natives.
(*Footnote. By the terms Trap, and Trap-formation, which I am aware are extremely vague, I intend merely to signify a cla.s.s of rocks, including several members, which differ from each other considerably in mineralogical character, but agree in some of their princ.i.p.al geological relations; and the origin of which very numerous phenomena concur in referring to some modification of volcanic agency. The term Greenstone also is of very loose application, and includes rocks that exhibit a wide range of characters; the predominant colour being some shade of green, the structure more or less crystalline, and the chief ingredients supposed to be hornblende and felspar, but the components, if they could be accurately determined, probably more numerous and varied, than systematic lists imply.)
PERCY ISLANDS, about one hundred and forty miles north of Cape Capricorn.
Compact felspar of a flesh-red hue, enclosing a few small crystals of reddish felspar and of quartz. This specimen is marked ”general character of the rocks at Percy Island,” and very much resembles the compact felspar of the Pentland Hills near Edinburgh, and of Saxony. Coa.r.s.e porphyritic conglomerate, of a reddish hue. Serpentine. A trap-like compound, with somewhat the aspect of serpentine, but yielding with difficulty to the knife. This specimen has, at first sight, the appearance of a conglomerate, made up of portions of different hues, purplish, brown, and green; but the coloured parts are not otherwise distinguishable in the fracture: It very strongly resembles a rock which occurs in the trap-formation, near Lyd-Hole, at Pont-y-Pool, in Shrops.h.i.+re. Slaty clay, with particles of mica, like that which frequently occurs immediately beneath beds of coal.
REPULSE ISLAND, in Repulse Bay, about one hundred and twenty miles north-west of the Percy Islands. Indistinct specimens, apparently consisting of decomposed compact felspar. A compound of quartz, mica, and felspar, having the appearance of re-composed granite.
CAPE CLEVELAND, about one hundred and twenty miles north of Repulse Island. Yellowish-grey granite, with brown mica; ”from the summit of the hill.” Reddish granite, of very fine grain; with the aspect of sandstone.
Dark grey porphyritic hornstone, approaching to compact felspar, with imbedded crystals of felspar.
CAPE GRAFTON, about one hundred and eighty miles west of north from Cape Cleveland. Close-grained grey and yellowish-grey granite, with brown mica. A reddish granitic stone, composed of quartz, felspar, and tourmaline.
ENDEAVOUR RIVER, about one hundred miles west of north from Cape Grafton.
Grey granite of several varieties; from a peaked hill under Mount Cook and its vicinity. Granular quartz-rock of several varieties: and indistinct specimens of a rock approaching to talc-slate.
LIZARD ISLAND, about fifty miles east of north from Endeavour River. Grey granite, consisting of brown and white mica, quartz, and a large proportion of felspar somewhat decomposed.
CLACK ISLAND, near Cape Flinders, on the north-west of Cape Melville, about ninety miles north-west of Lizard Island. Smoke-grey micaceous slaty-clay, much like certain beds of the old red sandstone, where it graduates into grey wacke. This specimen was taken from a horizontal bed about ten feet in thickness, reposing upon a ma.s.s of pudding-stone, which included large pebbles of quartz and jasper; and above it was a ma.s.s of sandstone, more than sixty feet thick. (Narrative volume 2.)
SUNDAY ISLAND, near Cape Grenville, about one hundred and seventy miles west of north from Cape Melville. Compact felspar, of a flesh-red colour; very nearly resembling that of the Percy Islands, above-mentioned.
GOOD'S ISLAND, one of the Prince of Wales group, about lat.i.tude 10 degrees, thirty-four miles north-west of Cape York. The specimens, in Mr.
Brown's collection from this place, consist of coa.r.s.e-slaty porphyritic conglomerate, with a base of greenish-grey compact felspar, containing crystals of reddish felspar and quartz. This rock has some resemblance to that of Clack Island above-mentioned.
SWEER'S ISLAND, south of Wellesley's group, at the bottom of the Gulf of Carpentaria. A stalact.i.tic concretion of quartzose sand, and fine gravel, cemented by reddish carbonate of lime; apparently of the same nature with the stem-like concretions of King George's Sound: (See hereafter.) In this specimen the tubular cavity of the stalact.i.te is still open.
The sh.o.r.e, in various parts of this island, was found to consist of red ferruginous matter (Bog-iron-ore ?) sometimes unmixed, but not unfrequently mingled with a sandy calcareous stone; and in some places rounded portions of the ferruginous matter were enveloped in a calcareous cement.
BENTINCK ISLAND, near Sweer's Island. A granular compound, like sandstone recomposed from the debris of granite. Brown hemat.i.te, enclosing quartzose sand.
PISONIA ISLAND, on the east of Mornington's Island, is composed of calcareous breccia and pudding-stone, which consist of a sandy calcareous cement, including water-worn portions of reddish ferruginous matter, with fragments of sh.e.l.ls.
NORTH ISLAND, one of Sir Edward Pellew's group. Coa.r.s.e siliceous sand, concreted by ferruginous matter; which, in some places, is in the state of brown hemat.i.te. Calcareous incrustations, including fragments of madrepores, and of sh.e.l.ls, cemented by splintery carbonate of lime.
CAPE-MARIA ISLAND, in Limmen's Bight, was found by Mr. Brown to be composed princ.i.p.ally of sandstone. The specimens from this place, however, consist of grey splintery hornstone, with traces of a slaty structure; and of yellowish-grey flint, approaching to chalcedony; with a coa.r.s.e variety of cacholong, containing small nests of quartz crystals.
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