Origin of the Grand Outline Features of the Earth. 397 
subsidence, so happily distinguished and brought forward by Mr. 
Darwin, the Coral Islands, we have evidence that an elliptical 
area with the same line for its axis was subsiding even as late as 
since the tertiary epoch. The very region therefore which bears 
evidence of having been the original great elliptical area of con- 
traction for the Pacific, on which the courses of the islands were 
in part dependent for ae direction, was also undergoing con- 
traction till within a lat riod ; and we know not that some 
parts about the Northern Eieaekiaeae athe nearest to the centre of 
-area—may not still be contracting as there is some evidence 
of it, which the writer will elsewhere present. e transverse 
line including New Zealand, the Kermadec and Tonga Islands, 
crossing the other systems nearly at right angles, would pass in its 
course northward the Samoan and Hawaiian Islands, and also 
some smaller groups intermediate. 
The position of a large area undergoing little contraction com- 
pared with the region around, is before us in New Holland, as is 
evident from the absence from this semi-continent of voleanoes 
or their remains. Such an area would occasion a tension acting 
to some extent circularly around it; and which might determine 
the courses of ranges in its vicinity. The ranges of islands from 
New Zealand by the New Hebrides to New Guinea and Java, is 
just such a concentric range, as the view would seem to require. 
Borneo is another vast region without volcanic traces over its in- 
terior, and may have influtnced the upward trend exemplified in 
Su umatra. However this may be, the cause brought forward— 
large isolated areas of comparatively slight contraction,—must 
ave had their influence in determining the direction of lines of 
tension or of forces causing ruptu 
Boué remarks that the trends i in the tropics in general ap- 
proach a parallelism with the equator, and he attributes the sup- 
posed fact to the centrifugal force of rotation. It holds true to 
a considerable extent. ‘There are however so many exceptions 
that we may perhaps doubt whether the fact is sufficiently een 
eral for so general a cause. 
The conclusions which appear to flow from the facts that have 
en presented, are as follows :— 
That the — direction and uniformity of the grand outline 
features of the globe may be in a great degree the simple effects 
of the earth’s cooling : this operation resulting in (1) solidifica- 
tion, and under the circumstances, whatever they were, an attend- 
ant jointed structure or courses of easiest fracture, in two direc- 
tions at right angles nearly with one another, both varying to- 
gether according to the rates of cooling in different parts ;—an 
2 *) Oceasioning tension in the crust through the contraction going 
neath, with some relation to circular areas but especially to 
es compound areas, which tension caused ruptures conforming 
