The stone of Upper Head, and apparently of all the hills in its neighbourhood, is granitic; whilst that of Long Island and West Hill approach nearer to porphyry.  At the inner entrance of Thirsty Sound the points are mostly composed of an earth, which is not heavy, is sometimes red, but more frequently white, or mixed; and of a consistence not harder than ochre.

Long Island, though covered with grass and wood, is stony and incapable of ordinary cultivation.  On the main land, the low parts between the mangroves and the hills seemed to be of a tolerably good soil; and according to the report of some of the gentlemen, who made an excursion at the back of Upper Head, the vallies there produce good grass and appeared fertile.  There seems, indeed, to be a considerable extent of land about Broad Sound and on the peninsula between it and Shoal-water Bay, which, if not calculated to give a rich return to the cultivator of wheat, would support much cattle, and produce maize, sugar, and tobacco; and cotton and coffee would grow upon the more rocky sides of the hills, and probably even upon Long Island.  Should it ever be in contemplation to make an establishment in New South Wales within the tropic, in aid of Port Jackson and the colonies to the southward, this neighbourhood would probably be chosen; and the great rise of tide presents advantages which might be some time turned to account in ship building.  On the west side of the sound, near the Flat Isles, the rise at spring tides is not less than thirty, and perhaps reaches to thirty-five feet.  At Upper Head it is from twenty at the neaps, to thirty or more at the springs; but the bottom rises so much towards the top of the sound, that the tide there never seems to exceed twelve feet.  The time of high water is nearly eleven hours after the moon’s passage over and under the meridian; though the flood runs up near an hour on the west side of the sound, after it is high water by the shore.

The places best calculated for the construction of docks, appear to be at the uppermost or 4th Flat Isles, where the shoals form a natural harbour, and at the entrance of the opening near Upper Head, in which is a small islet of sand and rock, not covered with mangroves nor surrounded with mud flats.  The pines of Port Bowen, Shoal-water Bay, and the Northumberland Isles, would furnish the necessary spars and lighter planking; and there is no reason to think that the eucalyptus, which grows all over the country, should not be as fit for timbers, etc., as it is found to be further southward.  No iron ore was seen in the neighbourhood; but were a colony established and the back ridge of mountains well examined, this and other metallic productions might be found.  The attraction which the mountains seemed to have upon the needle, is in favour of this probability; but the iron work might be prepared at Port Jackson where the ore exists, and in whose vicinity there are plenty of coals.