THE United States are washed by the _Atlantic Ocean_ on nearly the
whole of their eastern coast, and by the _Pacific_ on a large portion
of their western boundary.
Under the name of the _Atlantic_, is comprised that mass of water
between the eastern coast of America and the western coast of Europe
and Africa. In its narrowest part, between Europe and Greenland, it is
one thousand miles wide, and opening thence to the south-west with the
general range of the bounding continents, spreads under the northern
tropic to a breadth of sixty degrees of longitude, or four thousand
one hundred and seventy miles, without estimating the Gulf of Mexico.
The general phenomena on the two opposing sides of the Atlantic have
great resemblance. The Atlantic coast of the United States presents
an elliptic curve in its entire extent, with three intermediate and
similar curves; the first extending seven hundred miles from Cape
Florida to Cape Hatteras, the second from Cape Hatteras five hundred
miles to the outer capes of Massachusetts, and the third formed by
the coasts of Massachusetts, New Hampshire and Maine. Opposite to the
United States, the Atlantic admits soundings in every place near the
shores, always deepening very gradually. We have not found an exact
comparison of the natural history of the Atlantic with that of other
oceans. The chief phenomenon that marks it along the coast of the
states is the Gulf Stream.
Besides the regular periodical currents produced in the ocean by the
tides, various others arise from different causes.[31] The waters of
the sea may be put in motion by an external impulse, by a difference
in temperature and saltness, by the periodical meeting of the polar
ice, or by the inequality of evaporation that takes place in different
latitudes. Sometimes several of these causes concur in producing the
same effect; at others, their actions are opposed to one another, and
their effects wholly or partially destroyed. Some of those currents
constantly follow the same direction, others are subject to periodical
changes, whilst a third class are more accidental. The most regular and
extensive current on the globe is that which constantly flows from east
to west, between the tropics, and extends on each side of the equator
to about the thirtieth degree of latitude.
This vast current necessarily results from the attraction of the
heavenly bodies, the diurnal motion of the earth, and the direction
of the trade winds. Its existence is incontestibly proved by the
fact, that vessels sailing to the westward, are always ahead of their
reckoning; that is, their real situation, as determined by observations
of the heavenly bodies, is always found to be west of that estimated
from the rate of which the vessel is supposed to sail, as impelled
by the wind alone. This difference of situation is occasioned by
the general movement of the waters in the same direction, and is,
consequently, the proper measure of the current. This is the reason
why navigators, in sailing from Europe to America and the West India
Islands, make the latitude of the Canaries, and then shape their course
in the direction of the wind and current across the Atlantic.
A general current also flows from the poles towards the equator. This
arises from the increased evaporation in the equatorial regions, and
the augmented temperature of the waters, which render them specifically
lighter than those of the ocean in higher latitudes, as well as from
the increased supplies produced by the melting of the polar ice; all
of which render these currents necessary to maintain the equilibrium
of this perpetually circulating fluid. Their existence and effects are
fully attested by the enormous masses of polar ice, which they convey
into the more temperate regions of the ocean, and which sometimes float
as low as forty degrees of latitude.
These general currents are greatly modified, and changed into
various directions by the obstacles they encounter in their progress.
The coast of America, and the numerous islands with which it is
flanked, intercept the general current of the Atlantic, and create
what navigators call the _Gulf Stream_. This great current enters the
Gulf of Mexico, and, sweeping round the shores of that gulf, issues
with accelerated velocity towards the north, by the channel between
the southern point of Florida and the Bahama Islands.[32] It then
rolls along the shore of North America, diminishing in velocity, but
increasing in breadth, till it reaches the great bank of Newfoundland.
There it suddenly turns towards the east and south-east, and flows with
still decreasing velocity, towards the shores of Europe, the Azores,
and the coasts of Africa. Navigators readily distinguish this current
by the high temperature of its waters, their great saltness, their
indigo color, and the shoals of sea-weed[33] that cover their surface.
Humboldt, in May, 1804, observed its velocity in the twenty-seventh
degree of latitude, and found it about eighty miles in twenty-four
hours, though the north wind blew very strongly at the time of the
observation. When it issues from the Gulf of Florida, its velocity
resembles that of a torrent, and is sometimes five miles an hour, but
at others not more than three. Between the nearest point of Florida,
and the bank of Bahama, the breadth is only fifteen leagues, but a few
degrees further north, it is seventeen; in the parallel of Charleston
it is from forty to fifty leagues in breadth, and in latitude forty
degrees and twenty-five minutes, this is increased to nearly eighty
leagues. The waters of the torrid zone, being thus forcibly impelled
towards the north-east, preserve their high temperature to such a
degree, that, in latitude forty and forty-one degrees, it has been
found to be seventy-two degrees of Fahrenheit, while out of the current
the temperature of the water was only sixty-three degrees.
In the parallel of New York the temperature of the Gulf Stream is
equal to that of the sea in latitude eighteen degrees. When the current
reaches the western islands of the Azores, where the breadth is about
one hundred and sixty leagues, the waters still preserve a part of
the impulsion they receive in the Gulf of Florida, nearly one thousand
leagues distant. Hence the current proceeds to the Canaries and the
coast of Africa, and in the latitude of Cape Blanco, where the waters
flow towards the south-west, they mingle with the current of the
tropics, and recommence their tour from east to west.
From this it appears that the waters of the Atlantic, between the
eleventh and forty-third degrees, are constantly drawn by currents
into a kind of whirlpool; and if a drop of these waters be supposed
to return precisely to the place from which it commenced its motion,
Humboldt has calculated, from the known velocity of the current, that
it would require two years and ten months to complete its circuit of
three thousand eight hundred leagues.
‘A boat,’ he observes, ‘which may be supposed to receive no impulsion
from the winds, would require thirteen months from the Canary Islands,
to reach the coast of Caraccas, ten months to make the tour of the Gulf
of Mexico and reach the Tortoise Shoals, opposite the port of Havana,
while forty or fifty days might be sufficient to carry it from the
straits of Florida to the bank of Newfoundland. Estimating the velocity
of the water at seven or eight miles in twenty-four hours, in their
progress from this bank to the coast of Africa, it would require ten or
eleven months for this last distance. Such are the effects of this slow
but regular motion, which agitates the waters of the ocean.’ The Gulf
Stream furnished to Christopher Columbus indications of the existence
of land to the west. This current had carried upon the Azores the
bodies of two men of an unknown race, and pieces of bamboo of an
enormous size. In latitude forty-five or fifty degrees, near Bonnet
Flamand, an arm of the Gulf Stream flows from the south-west to the
north-east, towards the coast of Europe. It deposits upon the coasts
of Ireland and Norway, trees and fruits belonging to the torrid zone.
Remains of a vessel burnt at Jamaica were found upon the coast of
Scotland. It is likewise this river of the Atlantic which annually
throws the fruits of the West Indies upon the shore of Norway.
The _Pacific_ is also one of the great boundaries of the United States.
By treaties with Spain and Russia our government possesses sovereignty
along the Pacific ocean from latitude forty-two degrees to fifty-four
degrees and forty minutes, which is equal to about eight hundred and
eighty statute miles. This great ocean extends from Beering’s Straits
to the antarctic circle, a distance of three thousand two hundred
leagues, and from Asia and New Holland to America. It is separated from
the Atlantic and Antarctic oceans only by imaginary lines. Its extreme
breadth, a little north of the equator, is four thousand five hundred
and fifty leagues; between South America and New Holland, latitude
thirty degrees south, it is two thousand nine hundred and seventy
leagues. It contains an immense number of islands spread over its
surface, particularly between latitude thirty degrees north and fifty
degrees south, to which modern geographers have given the general
appellation of _Oceanica_. It was first called the _South Sea_ by
the European navigators who entered it from the north. Magellan gave
it the name of Pacific, on account of the prevalence of calms which
he experienced in it; but it by no means deserves the name, as it is
remarkable for the fury of its storms, and the agitation of its waters.
The trade-winds, which constantly blow between the tropics, render
the passage from the western coast of America to Asia very short; but
the return is proportionately difficult. The Portuguese were the first
Europeans who entered the Pacific, which they did from the east. Balboa,
in 1513, discovered it from the summit of the mountains which traverse
the Isthmus of Darien. Magellan sailed across it from east to west in
1521.[34]
The Pacific, by its general motion, retreats from the coast of America,
and flows from east to west; and this motion is very powerful in the
vast and uninterrupted extent of that sea. Near Cape Corriantes, in
Peru, the sea appears to flow from the land by this single cause. Ships
are carried with rapidity from the port of Acapulco, in Mexico, to the
Philippine Islands. But in order to return, they are obliged to go to
the north of the tropics, to seek the polar current, and the variable
winds. On the other side, the south polar current, finding no land to
impede it, carries along with it the polar ice even to the latitude
where the motion of the tropical current begins to be felt. This is the
reason why, in the southern hemisphere, floating pieces of ice are met
with at fifty and even at forty degrees.
In its motion towards the west, the Pacific is impeded by an immense
archipelago of flats, islands, submarine mountains, and even land of
considerable extent; it penetrates into this labyrinth, and there forms
one current after another. The direction which the principal of these
currents observe, is conformable to the general motion towards the
west. But, as might be expected, the inequalities of the basin of the
sea, the coasts, and the chains of submarine mountains, sometimes turn
these currents toward the north or south. We may easily conceive that
a strong repercussion of the waters of the ocean, in consequence of
their meeting with a large mass of land, (as New South Wales,) may
even produce a counter current, which will return towards the east,
and which, by breaking, will also produce other currents, adverse and
dangerous to navigators, and such as were encountered by Cook and La
Perouse.
The Pacific Ocean is bounded on the east by Asia. Beering’s Straits
connects it with the Arctic Ocean, and the line which indicates the one
hundred and forty-seventh eastern meridian, arbitrarily separates it
from the Indian Ocean. Geographers divide the Pacific into the northern
and southern, the equator being the line of demarcation. This ocean
occupies fifty millions of square miles; nearly one fourth part of the
surface of the globe. It covers three times the extent of the Indian,
and twice the extent of the Atlantic Ocean.
GENERAL REMARKS ON OCEANS.
The bed of the ocean is diversified by the same inequalities
that are exhibited on the surface of the land. Its greatest depth
that has been ascertained by experiment, is seven thousand two
hundred feet. Its mean depth is a little over three thousand feet,
about the same as the mean heights of the continents and islands
above its surface. Parts of the sea differ in saltness, but
the difference is slight. Though more bitter than that at a
considerable depth, it has been ascertained that the water of
the surface is less salt. Inland seas are less salt than the main
ocean, on account of the large volumes of fresh water emptied
into them. The coldness of the polar seas occasions a more rapid
deposit of the saline substances, and renders them more salt than
those of the equator. Various theories have been formed to account
for the saltness of the sea; one attributes it to the existence
of primitive beds of salt at its bottom, another to the corruption
of vegetable and animal matter carried into it by rivers. A third
theory considers the ocean as the residue of a primitive fluid,
which, after depositing all the substances of which the earth is
composed, retained the saline principle. Sea-water is freed from
its salt only by distillation.
In the open ocean, the prevailing color is a deep greenish
blue; other shades observed in the different seas seem to be
owing to local causes. In shoal places the water takes a lighter
hue. The luminous appearance of the sea by night is a magnificent
phenomenon, that has not yet been entirely explained. The great
divisions of the sea are inhabited by their peculiar fish, and
frequented by peculiar species of birds. The level of the sea is,
generally speaking, every where the same; though exceptions to
this rule are sometimes found in land-locked bays and gulfs, where
the waters become accumulated and stand higher than in the open
ocean.