water of certain depths. An earthquake in
Japan, in 1854, gave an opportunity of practically
applying these formulæ; and the deduction
is that the average depth of the North Pacific
between Japan and California is two miles and
a half.

Such is the inequality in the distribution of
land over the surface of the globe, that the
world may be divided into hemispheres consisting,
the one with almost all the land in it
except Australia, and a bit of South America;
England is the centre of this, the dry
hemisphere. The other, or aqueous hemisphere,
contains all the great waters except the Atlantic
Ocean; New Zealand is the nearest land to its
centre.  There is also in the northern
hemisphere more fresh water, more atmospheric air,
and a longer annual duration of sunlight than
there is in the southern. This unequal distribution
is highly suggestive. To it we owe in a
measure the different climates of the earth.
Were it different, they would be different also;
were it not for the winds, the vapours that rise
from the sea would, from the clouds, be
returned in showers back to the same places in
the sea whence they came. On an earth where
no winds blew, we should have neither green
pastures, still waters, nor running brooks to
beautify the landscape. Were there no currents
in the sea nor vertical movements in the air, the
seasons indeed might change; but climates
would be a simple affair, depending solely on
the sun's position in the sky.

About two-thirds of all the fresh water of
the earth is contained in the great American
lakes; and though there be in the northern, as
compared in the southern hemisphere, so much
less sea surface to yield vapour—so much more
land to swallow up rain, and so many more
plants to drink it in—yet the fresh-water courses
are far more numerous and copious on the north
than they are on the south side of the equator.
These facts have suggested the comparison in
which the southern hemisphere has been likened
to the boiler, and the northern to the condenser
of a steam-engine. This vast amount of vapour,
rising up in the extra-tropical regions of the
south, expels the air thence; for the fact seems
now to be clearly established that the
atmosphere is very unequally divided on opposite
sides of the equator, and that there is a mild
climate in the unknown regions of the Antarctic
circle. The atmosphere which hangs over the
extra-tropical regions of our planet, from
latitudes forty degrees, north and south respectively,
to either pole, is so unequally divided as to
produce an average pressure, according to the
parallel, of from ten to fifty pounds less upon
the square foot of sea surface in southern than
upon the square foot of sea surface in northern
latitudes. The whole weight of the atmosphere
is equal to that of a solid globe of lead sixty
miles in diameter.

If we imagine the whole mass of the earth to
be divided into seventeen hundred and eighty-
six equal parts by weight, then the weight of
all the water in the sea would, according to Sir
John Herschel, be equivalent to one of such
parts. This volume of water, to which such
important offices, such manifold and multitudinous
powers have been assigned, is divided into
three great oceans, the Atlantic, the Pacific,
and the Arctic; for, in the rapid survey we
are taking, the Indian and Pacific oceans
may be regarded as one. The Atlantic Ocean,
with its arms, extends perhaps from pole to
pole; but, measuring from the icy barrier of the
north to that of the south, it is about nine
thousand miles in length, with a mean breadth
of two thousand seven hundred miles. It lies
between the Old World and the New; passing
beyond the stormy capes, there is no longer any
barrier, but only an imaginary line, to separate
its waters from that great southern waste in
which the tides are cradled.

The Atlantic is a deep ocean, and contrasts
very strikingly with the Pacific. The greatest
length of the one, lies east and west; of the other,
north and south. The currents of the Pacific
are broad and sluggish, those of the Atlantic
swift and contracted. The Mozambique current,
as it is called, has been found by navigators in
the South Pacific to be upwards of sixteen
hundred miles wide—nearly as broad as the Gulf
Stream is long. The principal currents in the
Atlantic run to and fro between the equator
and the Northern Ocean. In the Pacific, they
run between the equator and the Southern Seas.
In the Atlantic, the tides are high; in the
Pacific, they are low. The Pacific feeds the clouds
with vapours, and the clouds feed the Atlantic
with rain for its rivers. If the volume of rain
which is discharged into the Pacific and on its
slopes, be represented by one, that discharged
upon the hydrographical basin of the Atlantic
into the Atlantic would be represented by five.
The Atlantic is daily crossed by steamers, the
Pacific rarely. The Atlantic washes the shores
of the most powerful, intelligent, and Christian,
nations; the countries to which the Pacific
gives drainage, support heathen or pagan
populations who are like the sands upon its shores
for multitude. The Atlantic is the most stormy
sea in the world, the Pacific the most tranquil.

From the top of Chimborazo, the highest of
the Andes, to the bottom of the Atlantic, at
the deepest place yet reached by the plummet
in that ocean, the distance, in a vertical line, is
nine miles. Could the waters of the Atlantic
be drawn off so as to expose to view this great,
sea-gash, which separates continents and extends
from the Arctic to the Antarctic, it would
present a scene the most rugged, grand, and
imposing. The very ribs of the solid earth, with
the foundations of the sea, would be brought
to light, and we should have presented to us in
one view, in the empty cradle of the ocean, "a
thousand fearful wrecks," with that array of
"dead men's skulls, great anchors, heaps of
pearls," which, in the poet's eye, lie scattered
on the bottom of the sea. To measure the
elevation of the mountain-top above the sea,
and to lay down upon our maps the elevated
ranges of the earth, is regarded in geography