26 
POPULAR SCIENCE REVIEW. 
and porphyry, are horizontal and undisturbed. No revolutions 
have passed over the surface since it rose from the ocean; and for 
that reason the greater portion of the country still looksmost like 
the bottom of the sea. On the other hand, there is a phenomenon 
plainly indicating that the country has done playing its part, 
and must now prepare for vast changes. The whole of New 
Holland is surrounded by coral reefs, those buildings of 
sinister Naiades which slowly but surely drag their victims to 
their watery habitation. It is known that these reef-building 
corals grow only in considerable masses where the ground is 
gradually sinking. If there were no other sign, these coral 
banks surrounding the continent and islands would point to 
changes in the level ; and, from what the smaller Polynesian 
islands have already undergone, the future New Holland — viz. 
a dissolution of the continent into groups of islands — might be 
predicted. But the entire condition of the country, the 
desert-like character of the interior, the great number of salt- 
lakes, the rivers terminating in swamps, &c., indicate an 
approaching geological change, which, however — let our co- 
lonists take comfort — may not take place for some thousands 
of years. As soon as New Holland shall have been broken up 
into islands, we may expect its vegetation to assume the same 
aspect as that now presented by the Polynesian islands. The 
bulk of the plants, adapted as they are to the peculiar dry 
climate of the extratropical parts, would perish as soon as 
the climate became insular, and the Asiatic flora, which even 
now presses hard upon the northern parts of New Holland, 
would get the upper hand, as has been the case in the Pacific 
after the dissolution of its continent into those innumerable 
islands now called Polynesia. Plants with dry leathery leaves 
would be superseded by those having a more luxuriant but 
weedy look ; for that I take to be the principal physiognomic 
difference between the floras of extratropical Australia and 
tropical Asia. 
It must be evident that the inquiry Unger has set on foot 
cannot stop here. The abundance of the most typical forms 
of Australian mammals — the marsupials (opossum and 
kangaroo) — in tertiary European deposits, will doubtless 
tempt some comprehensive mind to treat the subject from a 
zoological point of view. It is most important to ascertain 
whether the present fauna of Australia was always associated 
with the present flora. I do not know of any reason why it should 
not ; but a closer examination of all the facts may possibly 
point to a different conclusion. It will probably turn out that 
in the Australian native population we behold the oldest as well 
as the lowest race of men — a race in many instances without 
any religion whatever, and incapable of mastering any religious 
