of the
country, from excessive volume or action of the counter-trade, or local
magnetic activity, without coming from the tropics or being connected with
a regular polar wave of magnetic disturbance.

The following diagram exhibits their form, progress, and accompanying
induced winds.

[Illustration: Fig. 22.]

The gentle rains of spring, particularly April, and the moderate and
frequent snow-storms of winter, are often of this character; and so are
the heavy rains, which commence at the morning barometric minimum, rain
heavily through the forenoon, and light up near mid-day in the south,
followed by gentle, warm, S. W. winds. This class are more frequent in
some years than others--probably the early years of the decade, while
polar storms are, during the later ones. It is this class which have
_violent_ easterly winds _in front_, and on the _south side_, with two or
more currents, and which Mr. Redfield has also supposed to be cyclones.

The fourth class are isolated showers, occurring over particular
localities, or belts of drought and showers alternating; sometimes a
general disposition to cloudy and showery weather for a longer or shorter
interval over the whole country; at others, limited to particular
localities in the course of the trade. Such a period occurred during the
wheat harvest of 1855. This class I attribute to a general increased
magnetic action, but it may be induced by an increased volume, or greater
south polar magnetic intensity of the counter-trade, exciting and
concentrating the regular currents of the field, and increasing their
activity and energy. These also often work off south gradually, and are
followed by a cold N. W. air for a day or two; showing a tendency, in the
excited magnetism, to pass as a wave toward the tropics.

The following diagram will give some idea of this class:

[Illustration: Fig. 23.]

There are sometimes very obvious local tendencies to precipitation over
portions adjoining an area affected with drought, as there are other
magnetic irregularities over particular areas.

All these classes of storms are variant in intensity. Sometimes the
general or local cloud-formation is weak, and does not produce
precipitation at all; so of that which extends southerly. Probably the
tropical storm are always sufficiently dense and active to precipitate.
Their action is often violent over particular localities, and hence the
more frequent occurrence of the tornado ove