is
the solid land. That may sound a very hard saying at first, but the more
you look into geology, the more you will see ground for believing that
it is not a mere paradox.

In an unexpected manner, again, these reefs afford us not only an
indication of change of place, but they afford an indication of lapse of
time. 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. I think most naturalists would be inclined to laugh at me for
making such an assumption, and would put the growth at certainly not
more than half that amount. But supposing it is so, what a very curious
notion of the antiquity of some of these great living pyramids comes out
by a very simple calculation. There is no doubt whatever that the sea
faces of some of them are fully a thousand feet high, and if you take
the reckoning of an inch a year, that will give you 12,000 years for the
age of that particular pyramid or cone of coral limestone; 12,000 long
years have these creatures been labouring in conditions which must have
been substantially the same as they are now, otherwise the polypes could
not have continued their work. But I believe I very much understate both
the height of some of these masses, and overstate the amount which these
animals can form in the course of a year; so that you might very safely
double the period as the time d