At some few places under the tropics, no bottom has been found with
soundings of 26,000 feet, or more than four miles; whilst in the air,
if, according to Wollaston, we may assume that it has a limit from
which waves of sound may be reverberated, the phenomenon of twilight
would incline us to assume a height at least nine times as great. The
aerial ocean rests partly on the solid earth, whose mountain-chains and
elevated plateaus rise like green wooded shoals, and partly on the sea,
whose surface forms a moving base, on which rest the lower, denser, and
more saturated strata of air.--_Humboldt’s Cosmos_, vol. i.
The old Alexandrian mathematicians, on the testimony of Plutarch,
believed the depth of the sea to depend on the height of the mountains.
Mr. W. Darling has propounded to the British Association the theory,
that as the sea covers three times the area of the land, so it is
reasonable to suppose that the depth of the ocean, and that for a
large portion, is three times as great as the height of the highest
mountain. Recent soundings show depths in the sea much greater than any
elevations on the surface of the earth; for a line has been veered to
the extent of seven miles.--_Dr. Scoresby._