Coral and Coral Reefs | Page 9

how these two seeming
contradictions could be reconciled; and all sorts of odd hypotheses
were resorted to. It was supposed that the coral did not extend so far
down, but that there was a great chain of submarine mountains
stretching through the Pacific, and that the coral had grown upon them.
But only fancy what supposition that was, for you would have to
imagine that there was a chain of mountains a thousand miles or more
long, and that the top of every mountain came within 20 fathoms of the
surface of the sea, and neither rose above nor sunk beneath that level.
That is highly improbable: such a chain of mountains was never known.
Then how can you possibly account for the curious circular form of the
atolls by any supposition of this kind? I believe there was some one
who imagined that all these mountains were volcanoes, and that the
reefs had grown round the tops of the craters, so we all stuck fast. I may
say "we," though it was rather before my time. And when we all stick
fast, it is just the use of a man of genius that he comes and shows us the
meaning of the thing. He generally gives an explanation which is so
ridiculously simple that everybody is ashamed that he did not find it out
before; and the way such a discoverer is often rewarded is by finding
out that some one had made the discovery before him! I do not mean to
say that it was so in this particular instance, because the great man who
played the part of Columbus and the egg on this occasion had, I believe,
always had the full credit which he so well deserves. The discoverer of
the key to these problems was a man whose name you know very well
in connection with other matters, and I should not wonder if some of
you have heard it said that he was a superficial kind of person who did
not know much about the subject on which he writes. He was Mr.
Darwin, and this brilliant discovery of his was made public thirty years
ago, long before he became the celebrated man he now is; and it was
one of the most singular instances of that astonishing sagacity which he
possesses of drawing consequences by way of deduction from simple
principles of natural science--a power which has served him in good
stead on other occasions. Well, Mr. Darwin, looking at these curious
difficulties and having that sort of knowledge of natural phenomena in
general, without which he could not have made a step towards the

solution of the problem, said to himself--"It is perfectly clear that the
coral which forms the base of the atolls and fringing reefs could not
possibly have been formed there if the level of the sea has always been
exactly where it is now, for we know for certain that these polypes
cannot build at a greater depth than 20 to 25 fathoms, and here we find
them at 50 to 100 fathoms."
That was the first point to make clear. The second point to deal with
was--if the polypes cannot have built there while the level of the sea
has remained stationary, then one of two things must have
happened--either the sea has gone up, or the land has gone down.
There is no escape from one of these two alternatives. Now the
objections to the notion of the sea having gone up are very considerable
indeed; for you will readily perceive that the sea could not possibly
have risen a thousand feet in the Pacific without rising pretty much the
same distance everywhere else; and if it had risen that height
everywhere else since the reefs began to be formed, the geography of
the world in general must have been very different indeed, at that time,
from what it is now. And we have very good means of knowing that
any such rise as this certainly has not taken place in the level of the sea
since the time that the corals have been building their houses. And so
the only other alternative was to suppose that the land had gone down,
and at so slow a rate that the corals were able to grow upward as fast as
it went downward. You will see at once that this is the solution of the
mystery, and nothing can be simpler or more obvious when you come
to think about it. Suppose we start with a coral sea and put in the
middle of it an island such as the Mauritius. Now let the coral polypes
come and perch on the shore and build a fringing reef, which will stop
when they come to 20 or 25 fathoms,