520 NEW SOUTH WALKS. 
Although we have attributed a destruction of marine life in IIla- 
warra to basaltic eruptions, this is not necessarily the cause of the 
absence of animal remains from the deposits above; for the elevation 
of the land above the sea,—its condition during the coal depositions,— 
would account for this absence. We cannot affirm that the shores 
were not again peopled, or in other points were not still alive with the 
same Mollusca, and we are furnished with no evidence to prove that 
the same fossiliferous rocks that lie below the coal, may not in other 
places have been forming during the coal epoch. It may or may not 
be, as evidence hereafter to be obtained shall declare. 
The absence of all marine fossils from the Australian coal beds ap- 
pears to set aside the idea that the sea could have contributed to these. 
deposits ; and this is farther evident from the nature and condition of 
the vegetation. If then the sea has not been an agent in the results, 
we must look alone to fresh-water inundations for the various alter- 
nations of beds. And on this point Australia affords important facts. 
The rivers of the country have their annual freshets, as those of 
other lands; and every seven, eight, or ten years there is a more 
extended flood, covering immense tracts in the interior. 
While the writer was at Maitland, on the Hunter, there was a rise 
of thirty feet in this river, and the waters spread widely over the 
country around. Hight years before, the inundation was still more 
extensive, and the people were taken in boats from the tops of their 
houses. In the Kangaroo Grounds, dead grass and brushwood—the 
leavings of a flood,—hung from the trees thirty feet above the existing 
level of the river. he plain of Bathurst in the interior has been, within 
the memory of the settlers, a swamp, owing to the rise of the Mac- 
quarie; and the great valleys of the Darling and Lachlan, though 
the streams were nearly dry when visited by Major Mitchell, were 
marshy and in part under water at the time of Oxley’s expedition. 
He remarks that a rise of only a few feet in the streams of the 
west, would deluge areas of a thousand square miles and more; and 
over the “interminable plains, as level as the sea,” he saw evidence in 
the brush about the trees that the whole had been lately flooded. 
From the marshy nature of the country he hastily concluded that the 
interior of New Holland was a marsh and uninhabitable. For the 
last fifty miles he saw no stones or pebbles of any kind “save two, 
and these were taken from the maws of emus.” The soil was in 
general sandy, but in some parts a stiff clay; and the sand contained 
enough clay to become thick and muddy after rains. 
