CORALS AND CORAL REEFS. 21 
evidence all over the world of the upheaval, many thousands 
of feet above the sea, and the depression to equal depths 
below, of marine deposits of quite recent age; and, further, 
with the evidence in so many parts of radiolarian oozes and 
other oceanic deposits belonging to widely separated geologi- 
cal periods, and now far away inland and at considerable 
elevations above the sea, this doctrine of the permanence of 
the oceanic basins can no longer be held. 
Believing, as many other geologists do, that continual, 
‘though extremely-slow modifications of the earth’s surface 
are arising from terrestrial movements as much now as in 
the past, I should regard all the major inequalities of the 
continental areas, all the broader features of the coast lines, 
and all the larger ocean depths and shallows, as the outward 
expression of undulatory movements of the earth’s crust still 
or lately in progress. It may enable students to understand 
what is meant by this if they will carefully consider the 
form of the sea bottom in the chief coral reef area of the 
world—that of the Pacific. Any really good physical map 
will show that the sea bottom of the Pacific Ocean consists 
of a group of nearly parallel ridges and furrows of low 
gradient, trending, in the main, in a general north-westerly 
direction. These extend from the coasts of Australia to 
those of America, and conform more or less in direction, as 
they are traced eastward, to the great mountain tracts of the 
western side of the last-named continent. Beginning at the 
south-west, beyond the deeps off the north-east of Australia, 
we have first the series of ridges upon which lie Sumatra, 
Java, South New Guinea, New Caledonia, and New Zealand ; 
next, a parallel zone of depression; then the zone of elevations 
forming North New Guinea, the Solomon Islands, and the 
New Hebrides; another zone of depression follows; then 
we find the Admiralty and Santa Cruz elevation ; beyond 
that a third line of depression ; to the north-east of these are 
the ridges upon which are situated the Caroline Islands, 
Vaitapu, Samoa, Hervey and Rarutu Islands, and so on. 
Ridges followed by depressions, all having the same general 
trend, occur one after the other, including the great Hawaiian 
ridge, and the two or three lines of deep depression which 
lie parallel to this latter and to the mountain wrinkles of 
