etic longitudinal currents are
there_; that they are _lines of force_ and _adequate_; that _oxygen is
magnetic_, and therefore the atmosphere must be affected by them--that so
far as we can reason from analogy, they ought to produce the effect upon
the atmosphere which we find produced, and until further light is thrown
upon the subject I shall presume that they do. Every step we take
hereafter in this investigation will confirm the presumption.

There is one peculiarity to be more particularly noticed before we leave
the trade-wind region, and we are now prepared to notice it.

The belt of rains, formed by the currents of the two trades, threading
their way through each other--how are they produced? Why should the place
where the currents thus pass through each other be a place of almost daily
precipitation? There is, in fact, no ascension, except that which the
currents have in their line of ascent to attain the elevation which the
magnetic law of the current requires.

The trades have passed over an evaporating surface and are charged with
moisture. This moisture they hold in magneto-electric combination.
_Evaporation_ does not depend upon _temperature_. Ice and snow evaporate
at all temperatures (Howard, vol. 1, p. 86). So the cold N. W. wind, full
of positive electricity, will lap up, as it were, the pools from the
earth, with astonishing quickness; and when this electricity is deranging
the action of the machinery and material of the manufacturer, he allays it
by a supply of moisture, with which the electricity can combine. Nor does
the air lose its moisture when below the freezing point. In all parts of
the atmosphere, as at the surface of the earth in winter, moisture is held
in large quantities in the coldest and severest weather; and it is not
till it moderates, and a perceptible _electric_ change takes place, that
it is precipitated as rain or snow. Doubtless there is an exposure of
considerable surfaces, of opposite currents, charged with opposite
polarity, and a constant depolarization where their surfaces meet. May
there not be a consequent dissolution of the electro-magnetic combination
between the air and moisture, or the excitation of that electric action
which attends or produces like rains every where? and hence the constant
precipitation. This is rendered probable, by the fact that precipitation,
at the meeting of the trades, takes place in level countries in the
day-time, between 10 A. M. and sunse