As we had not enough nails to replace the copper, for that was now our only security, we could not venture to remove more than a few sheets from those parts which appeared to be the most suspicious, under all of which we found the nails so defective that we had reason to fear we might start some planks before we reached Port Jackson. . . When the repairs were completed, and the people were more at leisure, I made an excursion as far as Bat Island, off Cape Brewster. . . . Bat Island is a mass of sandstone superincumbent upon a quartzoze basis, and intersected by nearly vertical veins of white quartz, the surface of which was in a crystallised state.
"The basis of the country in the vicinity of this river is evidently granitic; and from the abrupt and primitive appearance of the land about Cape Tribulation, and to the north of Weary Bay, there is every reason to suppose that granite is also the principle feature of those mountains, but the rocks that lie loosely scattered about the beaches and surface of the bills on the south side of the entrance, are of quartzoze substance; and this, likewise, is the character of the hills at the east end of the northern beach.
Where the rocks are coated with a quartzoze crust, that, in its crumbled state, forms a very productive soil. The hills on the south side of the port recede from the banks of the river, and form an amphitheatre of low grassy land, and some tolerable soil, upon the surface of which, in many parts, we found large blocks of granite heaped one upon another.
On the conical summit are hard quartzoze porphyries, which have apparently forced up the gneiss and slates, which dip in all directions from the top, and are full of injected veins of quartz. Below 7000 feet, mica-schist prevails, always inclined at a very high angle; and I found jasper near Namtchi, with other indications of Plutonic action.
The floor of the cavern was covered with heaps of water-worn fragments of quartzoze rock containing copper pyrites, in some of which the cavities were covered by a deposit of greenish calcedony.