FAUNA AND FLORA OF NEW ZEALAND. 9 
plains of gravel and silt slope from the sea to an elevation of 
8oooft. or more at the base of the mountains. On the Pacific 
side, horizontal strata, of probably eocene age, lie on the older 
rocks, and these are covered in places by gravel-beds, which go 
to a height of 1300ft. 
From these facts Mr. Darwin infers that during the jurassic 
period this part of South America was a deep sea, on the bed of 
which volcanic eruptions tock place. In the lower cretaceous it 
was shallow sea, with land in the neighbourhood, but the bottom 
was sinking and it was further depressed for 7000 or 8000 feet, 
although the volcanic ejections continued to maintain land above 
the surface of the ocean. In the upper cretaceous period up- 
heaval commenced and, although interrupted by many oscillations, 
this upheaval has been going on ever since, until the elevation has 
been as much as 14,000 or 15,000 feet, that is 2500 fathoms. 
Now it is fair to suppose that when the immense mass of Chili, 
part of Peru, La Plata, and Patagonia, was depressed 2500 
fathoms below its present level, a compensating elevation may 
have occurred in the South Pacific Ocean ; and that as South 
America rose, the bed of the Pacific sank. If this were the case, 
the South Pacific continent must have been in existence in the 
jurassic and lower cretaceous periods and commenced to subside 
in the upper cretaceous. The lowest portion, that between Samoa 
and the Society Islands, would have been submerged first, and 
the connection between New Guinea and South America may 
have been severed before the close of the cretaceous period. 
This conclusion agrees very well with that drawn, quite inde- 
pendently, from a study of the Australian fauna and flora. 
On the western side of the South Pacific the oscillations of 
the land appear to have been much less. Of the geology of New 
Guinea it is known that jurassic rocks are largely developed both 
in the north and in the south, which indicates that the land then 
stood at a lower level. No cretaceous rocks are known from 
any part, and at this period therefore it may have been upheaved. 
Tertiary clays and limestones occur at Hall’s Sound and at Yule 
Island, but as, according to Mr. Tenison-Woods, the fossils have 
nothing in common with those of Australia, their age remains at 
present doubtful.* 
New Caledonia consists principally of two rock systems, one 
of older palzeozoic, the other of older mesozoic age. According 
to M. Garnier lower cretaceous rocks are also found there, but ° 
the evidence appears to consist of a single fossil (Pzza) only. 
In Eastern Australia and Tasmania the main range of moun- 
tains is formed of contorted schists and slates of lower palzeozoic 
age. In New South Wales the denuded surface of these rocks 
is covered by enormous masses of shales and sandstones of upper 
palzozoic and lower mesozoic age, lying in a nearly horizontal 
* Mr. C. 8. Wilkinson believes them to be of lower miocene age (Pro. Lin, Soc. 
of N. S. Wales, vol. i., p. 114). For Mr. Tenison-Woods’ opinion see the same 
_ publication, vol, vii., p. 382. Formerly he considered them as probably older 
pliocene (l.c. vol, ii,, p. 127). - 
