cording to the time of the year--where there are frequent and violent
squalls, of very short duration, accompanied with heavy rains. This
region is called by seamen the "doldrums," and considerable trouble and
difficulty do ships experience in crossing it.

It has already been explained that about latitude 30 degrees, the upper
current of wind from the south descends. At the same point the upper
current from the north also descends. They cut through each other, and
the point where these two cut each other is the northern limit of the
north-east trade-winds. The same explanation holds in regard to the
southern limit of the south-east trades.

In the accompanying diagram the arrows within the circle point out the
direction of the north-east and the south-east "trades" between the
tropics of cancer and capricorn, and also the counter currents to the
north and south of these, while the arrows around the circle show how
counter currents meet and rise, or descend, and produce the calm belts.

We have hitherto enlarged chiefly on the grand currents of the
atmosphere, and on those modifying causes and effects which are
perpetual. Let us now turn to the consideration of those winds which
are produced by local causes, and the effects of which are partial.

And here we are induced to revert to the Gulf Stream, which has been
already referred to as a _local_ disturber of the regular flow of the
atmosphere. This immense body of heated water, passing through cold
regions of the sea, has the effect of causing the most violent storms.
The hurricanes of the West Indies are among the most violent in the
world. We have read of one so violent that it "forced the Gulf Stream
back to its sources, and piled up the water in the Gulf to the height of
thirty feet. A vessel named the _Ledbnry Snow_ attempted to ride it
out. When it abated, she found herself high up on the dry land, having
let go her anchor among the tree-tops of Elliott's quay! The Florida
quays were inundated many feet; and it is said the scene presented in
the Gulf Stream was never surpassed in awful sublimity on the ocean.
The water thus dammed up rushed out with frightful velocity against the
fury of the gale, producing a sea that beggared description."

The monsoons of the Indian Ocean are among the most striking and regular
of the locally-caused winds. Before touching on their causes, let us
glance at their effects. They blow for nearly six months in one
dir