AGASSIZ: THE GREAT BARRIER REEF OF AUSTRALIA. 109 
behind the conglomerate beds is fully six feet higher than the conglom- 
orate. The bottom at our anchorage, only a short distance from the 
face of the exposed flat, in ten fathoms of water, consisted of blue mud 
and of broken shells. Тһе faces of the elevated conglomerate exposed 
to the action of the sea were pitted and honeycombed much as the 
wolian rocks of the Bahamas where exposed to the force of the sea. 
The next coral reefs we examined were those of the Palm Islands. 
The corals off Great Palm Island rise from between four and six fath- 
oms. They consist of masses of huge heads separated by coral sand 
lanes, and extend to water of one and a half to two fathoms in depth 
towards the shore. The amount of silt held in suspension in the water 
was as great here as farther south along the inner Barrier Reef channel. 
Passing north from the Palm Islands (Plate XIX.), one cannot fail tc 
be struck at the marks of the extensive denudation and erosion apparent 
on all sides. The domelike cliffs back of ‘Townsville, the cliffs along the 
railroad of the Ross River valley, the angular peaks, the sharp ridges, 
the deeply cut valleys, the islands, islets, and rocks on the two sides of 
Hinchinbrook Island passage, all indicate the effective work of atmos- 
pheric agency (Plate XX X*.). 
The fine mud and silt which everywhere cover the bottom of the inner 
channels of the Barrier Reef indicates only too clearly where the telluric 
material has been swept to. In fact, this extends so generally over the 
bottom, not only near the main land in close proximity to the lower 
by the piling action of the surf heaping up successive accumulations of calcareous 
sand, which has been subsequently compacted into rock. In the latter case, it 
never could have reached a higher level than it now has (a few feet above high-water 
mark), and its formation by this action must have required an immense period of 
time, during the whole of which no depression can have taken place. Upon all these 
flat spaces formed of this conglomerate, as well as upon all other flat land along the 
'astern and northeastern coast of Australia, which is not more than ten feet above 
high-water mark, there is found an abundance of pumice pebbles. . . . By what 
ever cause they were cast upon the land, their present position proves that the 
whole coast where they are found has been equally stationary, or equally affected 
by movements of elevation or depression since they were so east. . . . That the 
advent of these pebbles is not a very recent event is proved by facts I observed on 
the northeast coast. I have picked up pumice pebbles, for instance, on sand and 
mud flats more than a mile from the sea. . . . Altogether, the evidence derived 
from the existence of the coral conglomerates, and the presence of pumice pebbles, 
to a height of eight or ten feet above the highest possible tides, proves to my mind 
that for a very long period the whole eastern coast of Australia, has either been 
quite stationary, or has been affected by slight movements of elevation. It is 
clear, I think, at all events, that no recent depression has taken place throughout 
the distriet where either or both of these phenomena oceur." 
VOL. XXVIII. — NO. 4. 2 
