separated
from those of the sea, that the line of demarcation may be traced by the
eye. Its influences on the currents of the sea, and on the climates and
the navigation of the world, are so great and important, that we think a
somewhat particular account of it cannot fail to interest the reader.

The waters of the Gulf Stream are salter than those of the sea; which
fact accounts for its deeper blue colour, it being well known that salt
has the effect of intensifying the blue of deep water.

The cause of the Gulf Stream has long been a subject of conjecture and
dispute among philosophers. Some have maintained that the Mississippi
river caused it; but this theory is upset by the fact that the stream is
salt--salter even than the sea--while the river is fresh. Besides, the
volume of water emptied into the Gulf of Mexico by that river is not
equal to the _three thousandth part_ of that which issues from it in the
form of the Gulf Stream.

Scientific men are still disagreed on this point. They all, indeed,
seem to hold the opinion that _difference of temperature_ has to do with
the origination of the stream; but while some, such as Captain Maury,
hold that this is the _chief_ cause, others, such as Professor Thompson,
believe the trade-winds to be the most important agent in the matter.
We venture to incline to the opinion that not only the Gulf Stream, but
_all_ the constant currents of the sea are due chiefly to _difference of
temperature and saltness_. These conditions alter the specific gravity
of the waters of the ocean in some places more than in others; hence the
equilibrium is destroyed, and currents commence to flow as a natural
result, seeking to restore that equilibrium. But as the disturbing
agents are always at work, so the currents are of necessity constant.
Other currents there are in the sea, but they are the result of winds
and various local causes; they are therefore temporary and partial,
while the _great_ currents of the ocean are permanent, and are,
comparatively, little affected by the winds. Every one knows that when
a pot is put on the fire to boil, the water contained in it, as soon as
it begins to get heated, commences to circulate. The heated water rises
to the top, the cold descends. When heated more than that which has
ascended, it in turn rises to the surface; and so there is a regular
current established in the pot, which continues to flow as long as the
heating process goes on. T