nd encircling reefs was built up of precisely the same coral rock
as the fringing reef. That is to say, you have an enormous mass of coral
rock at a depth below the surface of the water where we know perfectly
well that the coral animals could not have lived to form it. When
those two facts were first put together, naturalists were quite as much
puzzled as I daresay you are, at present, to understand 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