to be studded with
crater-formed depressions in the sand, quite similar to the
_os_-pits in the _osar_ of Scandinavia.[387] On the north side there
was sandstone rock rising from the sea with a steep slope six to
fifteen metres high. Here tropical nature appeared in all its
luxuriance, principally in the valleys which the small streams had
excavated in the sandstone strata.

The coal mine is sunk on coal-seams, which come to the surface on
the north side of the island. The seams, according to the
information I received on the spot, are four in number, with a
thickness of 3.3, 0.9, 0.4 and 1.0 metre. They dip at an angle of 30 deg.
towards the horizon, and are separated from each other by
strata of clay and hard sandstone, which together have a thickness
of about fifty metres. Above the uppermost coal-seam there are
besides very thick strata of black clay-slate, white hard sandstone
with bands of clay, loose sandstone, sandstone mixed with coal, and
finally considerable layers of clay-slate and sandstone, which
contain fossil marine crustacea, resembling those of the present
time. The strata which lie between or in the immediate neighbourhood
of the coal seams do not contain any other fossils than those
vegetable remains, which are to be described farther on. Thirty
kilometres south of the mine a nearly vertical coal-seam comes to
the surface near the harbour, probably belonging to a much older
period than that referred to above; and out in the sea, eighteen
kilometres from the shore north of the harbour, petroleum rises from
the sea-bottom. The manager of the mine supposed from this that the
coal-seams came to the surface again at this place. The coal-seams
of Labuan are besides, notwithstanding their position in the middle
of an enormous, circular, volcanic chain, remarkably free from
faults, which shows that the region, during the immense time which
has elapsed since these strata have been deposited, has been
protected from earthquakes. Even now, according to Wallace,
earthquakes are scarcely known in this part of Borneo.

From what has been stated above we may conclude that the coal, sand,
and clay strata were deposited in a valley-depression occupied by
luxuriant marshy grounds, cut off from the sea, in the extensive
land which formerly occupied considerable spaces of the sea between
the Australian Islands and the continent of Asia. A similar state of
things must besides have prevailed over a considerable portio