The reef is a timekeeper of a very curious character; and you
can easily understand why. The coral polype, like everything else,
takes a certain time to grow to its full size; it does not do it in a
minute; just as a child takes a certain time to grow into a man so does
the embryo polype take time to grow into a perfect polype and form its
skeleton. Consequently every particle of coral limestone is an
expression of time. It must have taken a certain time to separate the
lime from the sea water. It is not possible to arrive at an accurate
computation of the time it must have taken to form these coral islands,
because we lack the necessary data; but we can form a rough calculation,
which leads to very curious and striking results. The computations of
the rate at which corals grow are so exceedingly variable, that we must
allow the widest possible margin for error; and it is better in this
case to make the allowance upon the side of excess. I think that
anybody who knows anything about the matter will tell you that I am
making a computation far in excess of what is probable, if I say that
an inch of coral limestone may be added to one of these reefs in the
course of a year.
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