In the dynamical theory of the tides, the ratio of the effects of the
sun and moon depends, not only on the masses, distances, and periodic
times of the two luminaries, but also on the Depth of the Sea; and
this, accordingly, may be computed when the other quantities are known.
In this manner Professor Haughton has deduced, from the solar and lunar
coefficients of the diurnal tide, a mean depth of 5·12 miles; a result
which accords in a remarkable manner with that inferred from the ratio
of the semi-diurnal co-efficients as obtained by Laplace from the
Brest observations. Professor Hennessey states, that from what is now
known regarding the depth of the ocean, the continents would appear as
plateaus elevated above the oceanic depressions to an amount which,
although small compared to the earth’s radius, would be considerable
when compared to its outswelling at the equator and its flattening
towards the poles; and the surface thus presented would be the true
surface of the earth.
The greatest depths at which the bottom of the sea has been reached
with the plummet are in the North-Atlantic Ocean; and the places where
it has been fathomed (by the United-States deep-sea sounding apparatus)
do not show it to be deeper than 25,000 feet = 4 miles, 1293 yards, 1
foot. The deepest place in this ocean is probably between the parallels
of 35° and 40° north latitude, and immediately to the southward of the
Grand Banks of Newfoundland.
It appears that, with one exception, the bottom of the
North-Atlantic Ocean, as far as examined, from the depth of about
sixty fathoms to that of more than two miles (2000 fathoms), is
literally nothing but a mass of microscopic shells. Not one of
the animalcules from these shells has been found living in the
surface-waters, nor in shallow water along the shore. Hence arises
the question, Do they live on the bottom, at the immense depths
where the shells are found; or are they borne by submarine currents
from their real habitat?