The two adverse particles press against each
other with their entire force, and being of
equal power, produce an equilibrium or
accumulation of dead air. This is the calm belt
of Cancer.

From under this belt or bank of calms,
two surface currents of wind are ejected;
one towards the equator and, from the cause
already assigned, taking a south-westerly
course as the north-east trade wind; the
other towards the pole, as the south-west
passage wind. These winds, coming out as
they do at the lower surface of this calm
region, must come from above by means of
downward currents, just as we may suppose
a vessel of water filled from the top by two
streams flowing in from opposite directions
and flowing out from two openings below
in contrary channels. In support of this
downward theory of the air, we find the
testimony of Humboldt who tells us (as others
do) that in this calm region, the barometer
stands higher than it does to the north or
south of it.

Not the least interesting feature of this journey
of the winds, is the fact that the currents
of air thus forced out from the lower surface
of this calm belt, are not those which were
previously travelling in the contrary direction:
the wind from the pole does not sink
down and return northwards as a surface
wind; it has yet a long journey before it, a
journey given to it to perform, by infinite
wisdom, for wise and beneficent purposes: it
has yet to go towards the south before it
turneth about unto the north. The particle
of air in company with which we have travelled
thus far, makes its way by some mysterious
agency—believed to be electrical, and
indeed all but proved to be so by Faraday's
recent discoveries—across this calm zone, but
at the same time downwards, and appears on
the surface going southerly as the north-east
trade wind: it cannot pass along in the
upper air, for there is another similar particle
wending its way back to the pole, having
performed the allotted circuit which this
one fresh from the north is about to
make.

As the north-east trade, our particle journeys
until near the equator, where it encounters
a similar particle as the south-east
trade. Here, at this place of the equatorial
meeting, there is another conflict and another
calm region, as all those who have made a
voyage to the south know full well. The
consequence of this encounter of the two
typical particles is similar to that which
took place at the calm belt of Cancer, but
is brought about in a different manner.

The great heat of the sun near the equator,
added to the presence of the two conflicting
winds one against the other, causes them to
ascend, and once more crossing the belt of
calms, they, make their way still in their
onward course; the northern particle, with
which we will suppose ourselves still in company,
taking an upper course, until, arrived
at the zone of Capricorn, between twenty
and thirty degrees of south latitude, it encounters
the southerly breezes, and this time
descending comes out at the lower surface
on the opposite side of the calm region,
and makes its way to the south pole as a
surface wind. Entering the polar regions
obliquely, it is pressed against by similar
particles coming from every meridian, and as
it approaches the higher latitudes, having
less space to move in, it flies along more
rapidly and more obliquely, until it, with all
the rest, is whirled about the pole in a
continued circular gale: at last, reaching the
great polar vortex, pressed up on every side,
it is carried upwards to the regions of atmosphere
above, whence it commences again its
circuit, and journeys back to the north as an
upper current, thus fulfilling its allotted task
of turning about unto the north. It now
passes back over the same space, but this
time its path is altered; where it was before
an upper current it is now a surface wind,
and vice versa.

Having thus pictured the wind-roads
across our Air Map, we will proceed to
point out the reasons for believing them
to be the actual paths travelled on day by
day, from year to year, in the great world
of air.

It will be necessary to bear in mind the
following facts, since they form the ground-
work on which our structure of reasoning
will be built. In the northern half of the
globe land greatly predominates over water;
the southern half of the world being chiefly
occupied by the ocean. Nearly all the great
rivers of the world are to be found north
of the equator; whilst south of the line there
is but one large stream, the Plata, the Amazon
being in the equatorial region and receiving
half its supply from the north and half from
the south. In South Africa there is no river
of any moment, and the rivers of Australia
are insignificant.

The main source of supply for the waters of
these rivers is of course to be found in the
clouds, which furnish it in the shape of rain.
The clouds derive their supply from the ocean,
whence vapour is raised by evaporation. "All
the rivers run into the sea, yet the sea is not
full; unto the place from whence they came
thither they return again." This is precisely
what is taking place daily. If the winds
did not take up from the sea large quantities
of vapour, and store it in the clouds for
distribution when wanted, the sea would "be
full," with all these gigantic streams passing
into it; yet it is never full.

The facts here given appear at first sight
anomalous, but on examination they will
be found to speak in favour of the theory
previously advanced as to the wind-roads.
The all but riverless countries of Southern
America, South Africa and Australia are
situated in the midst of the largest expanse