It is with lime and magnesia
that the tiny chalk-builders form their beautiful shells, and the
coral animals their skeletons, while another class of builders use
the flint; and when these creatures die, their remains go to form
fresh land at the bottom of the sea; and so, though the earth is
being washed away by the rivers and springs it is being built up
again, out of the same materials, in the depths of the great
ocean.
And now we have reached the end of the travels of our drop of
water. We have seen it drawn up by the fairy "heat," invisible
into the sky; there fairy "cohesion" seized it and formed it into
water-drops and the giant, "gravitation," pulled it down again to
the earth. Or, if it rose to freezing regions, the fairy of
"crystallization" built it up into snow-crystals, again to fall
to the earth, and either to be melted back into water by heat, or
to slide down the valleys by force of gravitation, till it became
squeezed into ice. We have detected it, when invisible, forming a
veil round our earth, and keeping off the intense heat of the
sun's rays by day, or shutting it in by night.
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