inally have been as fresh as river water; and as it
is not saturated with salt, must become annually saline. The
sea-water about our island contains at this time from about
one twenty-eighth to one thirtieth part of sea salt, and
about one eightieth of magnesian salt; Brownrigg on Salt.]

[Footnote: _Whence coral walls_, l. 319. An account of the
structure of the earth is given in Botanic Garden, Vol. I.
Additional Notes, XVI. XVIII. XIX. XX. XXIII. XXIV.]

"Next when imprison'd fires in central caves
Burst the firm earth, and drank the headlong waves;
And, as new airs with dread explosion swell,
Form'd lava-isles, and continents of shell;
Pil'd rocks on rocks, on mountains mountains raised,
And high in heaven the first volcanoes blazed;
In countless swarms an insect-myriad moves
From sea-fan gardens, and from coral groves;
Leaves the cold caverns of the deep, and creeps
On shelving shores, or climbs on rocky steeps. 330
As in dry air the sea-born stranger roves,
Each muscle quickens, and each sense improves;
Cold gills aquatic form respiring lungs,
And sounds aerial flow from slimy tongues.

[Footnote: _Drunk the headlong waves_, l. 322. See Additional
Note III.]

[Footnote: _An insect-myriad moves_, l. 327. After islands or
continents were raised above the primeval ocean, great
numbers of the most simple animals would attempt to seek food
at the edges or shores of the new land, and might thence
gradually become amphibious; as is now seen in the frog, who
changes from an aquatic animal to an amphibious one; and in
the gnat, which changes from a natant to a volant state.

At the same time new microscopic animalcules would
immediately commence wherever there was warmth and moisture,
and some organic matter, that might induce putridity. Those
situated on dry land, and immersed in dry air, may gradually
acquire new powers to preserve their existence; and by
innumerable successive reproductions for some thousands, or
perhaps millions of ages, may at length have produced many of
the vegetable and animal inhabitants which now people the
earth.

As innumerable shell-fish must have existed a long time
beneath the ocean, before the c