action equally illustrative, which
tend to show that the precipitation at the passing of the trades, is the
result of their action upon each other, aided by the sun, to which we
shall allude when we come to speak of the causes and character of the
surface winds of the extra-tropical regions.

As, however, this takes place only, or mainly, where the threading
surfaces meet, it is but partial, and the body of the respective polarized
currents pursue their way unaffected, toward the opposite magnetic
pole--and there for the present we leave them.

Storms sometimes originate in these currents, when concentrated, as in the
West Indies, the China Sea, the Bay of Bengal, and Indian Ocean, while
passing through the rainy belt, and move with the current to the
north-west if issuing on the north side of it, and to the south-west if
issuing on the south side of it, until they respectively get beyond the
extreme limits of the trades, and then they curve to the eastward,
imbedded in and following their current. The peculiar extension of the
land to the east on the northern portions of South America, prevents the
gathering of an aerial gulf similar to the one which we have described to
the north-west, entering upon our division of the continent over the Gulf
of Mexico. It is otherwise in the Indian Ocean, and there the storms are
found issuing from the rainy belt on the southern side, sweeping over the
Mauritius and other islands of that ocean, and _often simultaneously_ with
storms issuing on the north over the Bay of Bengal. Colonel Reid mentions
instances and gives a diagram.[2]

These storms in milder forms issue from the rain belt at other points, and
may issue any where, but will always be found most extensive and most
violent, that is to say, as hurricanes and typhoons, in the concentrated
volumes of counter-trade on the western side of the great oceans, within a
few hundred miles of the lines of magnetic intensity and no variation, and
when they form in the rainy belt they are highly electric. Most
frequently, however, as we shall see, they form in these currents after
they have issued from the rainy belt, and after they have passed the
extreme limits of the trades and become subject to the circular and
perpendicular magnetic currents which exist north and south of the
longitudinal ones, and which when seen upon the magnetic needle, attract
the filings and cause them to adhere--although but slight attraction or
adhesion ta