CHANGES OF LEVEL. 399 
may be considered the azial line or line of greatest depression for the 
area of subsidence. 
It is worthy of special note, that this axial line or line of greatest 
depression coincides in direction mith the mean trend of the northwest 
ranges of islands, its course being N. 52° W. 
The southern boundary line of the coral area, as laid down on the 
chart, lies within the area of subsidence, although near its limits. 
There are places along this line where this area has been prolonged 
farther than elsewhere, as shown by the reefs. One of these regions 
lies between Samoa and Rotuma, and extends down to the Feejees 
and Tonga Group; another is east of Samoa, reaching towards the 
Hervey Group. Each of these extensions trends parallel with the 
groups of islands, and with the part of the line east of Tahiti. It 
would seem, therefore, that the Society and Samoan Islands were 
regions of less change of level than the deep seas about them. 
What may be the Extent of the Coral Subsidence ?—It is very evident 
that the sinking of the Society, Samoan, and Hawaiian Islands has 
been small compared with that required to submerge all the lands on 
which the Paumotus rest and other Pacific atolls. One, two, or 
five hundred feet could not have buried all the many peaks of these 
islands. Even the 1150 feet of depression at the Gambier Group 1s 
shown to be at a distance from the axis of the subsiding area. ‘The 
groups of high islands above mentioned contain summits from 4000 
to 14,000 feet above the sea; and can we believe it possible that 
throughout this large area, when the two hundred islands now sunk 
were above the waves, there were none equal in altitude to the mean 
of these heights? That all should have been within nine thousand 
feet in elevation, is by no means probable. However moderate our 
estimate, there must still be allowed a sinking of several thousand 
feet: and however much we increase it within probable bounds, we 
shall not arrive at a more surprising change of level than our conti- 
nents show that they have undergone. 
Between the New Hebrides and Australia the reefs and islands 
mark out another area of depression, which may have been simulta- 
neously in progress. The long reef of one hundred and fifty miles 
from the north cape of New Caledonia and the wide barrier on the 
west cannot be explained without supposing a subsidence of one or 
two thousand feet at the least. ‘The distant barrier of New Holland 
is proof of as great if not greater subsidence. 
Liffect of the Subsidence.-—T he facts surveyed give us a long insight 
into the past, and exhibit to us the Pacific scattered over with lofty 
