THE AUSTRALIAN NATURALIST. 15 
Evidence that such changes have taken place may be found 
in a great many ways. The existence of sedimentary strata 
with marine fossils in our highest mountain chains, the 
occurrence of anticlines and synclines in sedimentary rocks, 
the occurrence of plains of marine erosion and of “ pene-plains” 
elevated thousands of feet above the sea are indications of 
great mountain building and continentforming (“epeirogenetic”) 
movements. Sudden movements leave their traces in faults of 
a throw amounting to hundreds or thousands of feet. Sea 
basins like the Algean and Adriatic, as well as the Mozambique 
Channel and the Rift Valley are instances of subsidence areas 
(“senkungsfelder”). Great movements of both kinds may be 
traced to a common cause, namely secular contraction of the 
earth through cooling. 
Coastal movements depending on changes in load (isostatic 
movements) leave their evidence in raised beaches, submerged. 
forests, coal and carbonaceous shale beds, intercalated between 
marine shallow-water strata (e.g., sandstones and shales) and 
soon. The great Pampas of the Argentine owe their existence 
to an isostatic upward moyement consequent upon a change in 
the direction of drainage in South America. The Queensland 
coast abounds in raised beaches formed by such movements. 
Closer to home we have the drowned valleys of Port Jackson 
and Botany Bay, evidencing Tertiary subsidence, whilst still 
more recent elevation is witnessed by the D.Y, Lagoons at 
Narrabeen, and the ‘‘Tombolas”’ of North and South Heads. 
Suess shows that the Biblical Deluge was an inundation of 
the lowlying Mesopotamian plain brought about by an earth- 
quake in the Persian Gulf which hurled the waters upon the 
land, and that probably a cyclone from the south-east aided in 
damming up the water. Similar events have taken place in 
more recent times as, for example, the great earthquake of the 
Indus Valleyin 1819, which formed the Runn of Cutch and like 
catastrophes in the Ganges-Brahmapootra Valley. Events of 
this kind are, however, very insignificant from a geological 
standpoint. . 
The movements of subsidence which permitted the growth 
of the Great Barrier Reef, and of elevation which have left 
Tertiary sediments*high and dry in Queensland are of a 
different order, and leave ineffaceable records in geological 
history. : 
It is now generally supposed that a large land mass existed 
in Mesozoic times in the Pacific, the Wallace-Hedley Continent, 
which our friend Mr. Hedley has done so much to elucidate. 
Mr. Douglas Mawson’s geological work in the New Hebrides 
in addition to giving confirmation to Mr. Hedley’s work, shows 
us the vastness of the movements in progress there. The 
labours of Dr. Woolnough in Fiji and of Professor David and 
