alia the geologist will certainly find
sections in abundance but they are nearly all of sandstone for, with few
exceptions no other rocks have been denuded in situations similarly
exposed.

GEOLOGICAL STRUCTURE AND PHYSICAL OUTLINE. VALLEYS OF EXCAVATION. EXTENT
OF THAT OF THE COX.

The ravines which discharge their waters into the little river Cox occupy
an area of 1,212 square miles, or one-half of the county of Westmoreland
on the right or south side of that river, and one-fourth of the county of
Cook on the other. Of this area 796 square miles, equal to one-half of
the county of Westmoreland, are on the right or south side of that river,
and 416, or one-fourth of the county of Cook, on the left. The whole
extent comprises the basin of this mountain stream, and is bounded by
heights rising very gradually from about 1000 feet at the gorge or outlet
of the Cox, to 3,400 feet on the north side at Blackheath, and on the
south to Murruin and Werong, summits of still greater elevation; the
lowest part of the ridge bounding this basin on the west or interior side
being nearly 3000 feet above the level of the sea. Cox's river flows over
a bed of water-worn rocks which, in the upper part of the valley, is
2,150 feet above the sea, and on the road to Bathurst this bed consists
of trap and granite. The river falls rapidly on leaving the granite of
the vale of Clwyd to a level not much above that of the sea, and it
escapes near its junction with the Warragamba from this spacious basin
through a gorge about 2,200 yards wide and flanked on each side by points
about 800 feet high.

QUANTITY OF ROCK REMOVED.

Supposing but two-thirds of the enclosed area of sandstone to have been
excavated to the depth of 880 feet only, which I allow as the mean
thickness of the stratum thus broken into, and considering the
inclination of the Cox and other valleys, then 134 CUBIC MILES of stone
must have been removed from this basin of the Cox alone.

VALLEY OF THE GROSE.

The valley of the Grose, whose basin is contiguous to that of the Cox on
the north, is of less extent but enclosed by cliffs of greater
perpendicular height. That river has been already described in the
journal, and the general character of the valley through which it flows
is represented in Plate 10 Volume 1.* We now perceive but slight
indications of the action by which the great area of stone in the valley
of the Cox, the Grose etc. has been removed. There are no accumul