or else is raised up by its violence. And so Mr. Darwin, being
desirous not to merely put out a flashy hypothesis, but to get at the
truth of the matter, said to himself, "If my notion of this matter is
right, then atolls and encircling reefs, inasmuch as they are dependent
upon subsidence, ought not to be found in company with volcanoes; and,
'vice versa', volcanoes ought not to be found in company with atolls,
but they ought to be found in company with fringing reefs." And if you
turn to Mr. Darwin's great work upon the coral reefs, you will see a
very beautiful chart of the world, which he prepared with great pains
and labour, showing the distribution on the one hand of the reefs, and
on the other of the volcanoes; you will find that in no case does the
atoll accompany the volcano, or the volcano burst up among the atolls.
It is most instructive to look at the great area of the Pacific on the
map, and see the great masses of atolls forming in one region of it a
most enormous belt, running from north-west to south-east; while the
volcanoes, which are very numerous in that region, go round the margin,
so that we can picture the Pacific to ourselves a section of a kind of
very shallow basin--shallow in proportion to its width, with the atolls
rising from the bottom of it, and at the margins the volcanoes. It is
exactly as if you had taken a flat mass and lifted up the edges of it;
the subterranean force which lifted up the edges shows itself in
volcanoes, and as the edges have been raised, the middle part of the
mass has gone down. In other words, the facts of physical geography
precisely and exactly correspond with the hypothesis which accounts for
the infinite varieties of coral reefs.

One other point, before I conclude, about this matter. These reefs, as
you have just perceived, are in a most singular and unexpected manner
indications of physical changes of elevations and depressions going on
upon the surface of the globe. I dare say it may have surprised you to