in
those extensive plains; and may attribute them either to cavities or
protuberances in the lower rocks, which may not have been sufficiently
filled or covered by the superincumbent deposits: or they may be due to
partial subsidences in a thin stratum of limestone.

CHANGES ON THE SEACOAST. PROOFS THAT THE COAST WAS ONCE HIGHER ABOVE THE
SEA THAN IT IS AT PRESENT. PROOFS THAT IT WAS ONCE LOWER. AND OF VIOLENT
ACTION OF THE SEA.

The sea, probably when higher relatively to the land than it is at
present, appears to have acted with some violence in isolating various
points along the eastern coast; most of which we now find curiously
analogous, in their situation on the southern sides of inlets, and in
being now united to the mainland by mounds of sand.

AT WOLLONGONG.

The point of Wollongong was formerly an island and is now only connected
by drifted sandhills with the site of the township.

CAPE SOLANDER.

Cape Solander, the south head of Botany Bay, on which Captain Cook first
landed, was evidently once an island though at present connected with the
mainland by the neck of sand which separates Botany Bay from Port
Hacking.

PORT JACKSON.

The south head of Port Jackson has also been isolated but is again
connected with the shore of Bellevue between Bondi Bay and Rose Bay, by
drifted hills of sand. The north head appears to have been likewise
isolated.

BROKEN BAY.

Barrenjoey, the south head of Broken Bay, is connected only by a low
beach of sand.

NEWCASTLE.

The Beacon head of Newcastle was once an island; and the drifted sand
forming the hills on which the town is built has since been thrown up by
the sea.

TUGGERAH BEACH.

Brisbane Water, Tuggerah beach, and Lake Macquarie are also striking
proofs of change of the same character as those at Port Jackson,
especially as they occur in a country possessing no inland lakes, and
along a coastline which is very even and straight in other respects.

BASS STRAIT.

The line of rocky islets extending across Bass Strait seems to be the
remains of land once continuous between the two shores, probably when the
current was still active in the channel of the Glenelg, and before the
sea had penetrated far within the heads of Port Jackson.

Thus it would appear that the Australian continent bears marks of various
changes in the relative height of the sea; on its shores and in the
interior; and that the waters have been at some periods much higher and
at a