326 C. F. LASERON. 
strew the mountain side, the caves, the natural archway, 
all covered with dense vegetation, combine to make a 
scene of great rugged grandeur. 
Origin of the Conglomerates and Freshwater Beds.— 
There can be no doubt that the conglomerates were formed 
by the erosion of the underlying Devonian beds, when first 
buried beneath the sea, and also that the material of which 
they are composed has not travelled any distance. The 
pebbles are almost entirely composed of a quartzite, the 
one or two exceptions noticed being of quartz. These 
quartzites are lithologically identical with the Devonian 
quartzites of the neighbourhood. If the pebbles had 
travelled far, there would have been a more or less mixed 
variety of them, as to the south there are granites, to the 
west slates and granites, and to the east rhyolites and 
dolerites. The present river gravels show just such a 
variety. 
The peculiar conditions under which the two series were 
laid down, can best be understood by remembering the 
presence of high land in the neighbourhood of Grassy Gully. 
At this time, the Lower Coal Measures were just being 
submerged beneath the Permo-Carboniferous sea, which 
was gradually encroaching from the north and east. The 
hollows were first submerged, and in them settled the 
detrital material, which the ever advancing breakers tore 
from the neighbouring land, and from the higher ground 
which now existed as islands. One of these islands existed 
somewhere near Grassy Gully, as stated before. On its 
western side was a plain of narrow extent, probably not 
more than three or four miles across. To the west deep 
water existed ; in this the conglomerates were laid down, 
being formed as they are of quite local rocks. As the land 
sank and the conglomerate accumulated, it was piled back 
against the edge of this ancient plain by the surf, and 
