the top of the water, and, floating softly through a gentle medium, is
yet crushed by a touch; while the Coral-builder bears the superincumbent
weight of worlds on his vaulted cell with perfect impunity.

Another important question is, How far alteration in the amount of light
may affect the more delicate creatures. What fishes do without light has
been solved by the darkness of the Mammoth Cave, the tenants of whose
black pools are eyeless, evidently because there is nothing to see. The
more deeply located Infusoria and Mollusks must dwell in an endless
twilight; for Humboldt has found, by experiment, that at a depth one
hundred and ninety-two feet from the surface the amount of sunlight
which can penetrate is equal only to one-half of the light of an
ordinary candle one foot distant.

Thus ever in gloom, yet in a state of constant safety from storms and
the agitations of the upper air, the thousand forms of low organic life
and cryptogamic vegetation live and thrive in peace and quietness.

"The floor is of sand like the mountain drift,
And the pearl-shells spangle the flinty snow;
From the coral rocks the sea-plants lift
Their boughs, where the tides and billows flow.

* * * * *

"And life in rare and beautiful forms
Is sporting amid those bowers of stone,
And is safe, when the wrathful spirit of storms
Has made the top of the waves his own."[C]