in certain regions, and the evaporation of humidity
in others; and this would have a regular progress in certain determined
seasons, and would not vary. But nothing can be more distant from this
supposition, that is the natural constitution of the earth; for the
globe is composed of sea and land, in no regular shape or mixture, while
the surface of the land is also irregular with respect to its elevations
and depressions, and various with regard to the humidity and dryness of
that part which is exposed to heat as the cause of evaporation. Hence a
source of the most valuable motions in the fluid atmosphere with aqueous
vapor, more or less, so far as other natural operations will admit; and
hence a source of the most irregular commixture of the several parts of
this elastic fluid, whether saturated or not with aqueous vapor.

"According to the theory, nothing is required for the production of rain
besides the mixture of portions of the atmosphere with humidity, and of
mixing the parts that are in different degrees of heat. But we have seen
the causes of saturating every portion of the atmosphere with humidity
and of mixing the parts which are in different degrees of heat.
Consequently, over all the surface of the globe there should happen
occasionally rain and evaporation, more or less; and also, in every
place, those vicissitudes should be observed to take place with some
tendency to regularity, which, however, may be so disturbed as to be
hardly distinguishable upon many occasions. Variable winds and variable
rains should be found in proportion as each place is situated in an
irregular mixture of land and water; whereas regular winds should be
found in proportion to the uniformity of the surface; and regular rains
in proportion to the regular changes of those winds by which the mixture
of the atmosphere necessary to the rain may be produced. But as it will
be acknowledged that this is the case in almost all this earth where
rain appears according to the conditions here specified, the theory is
found to be thus in conformity with nature, and natural appearances are
thus explained by the theory."(1)

The next ambitious attempt to explain the phenomena of aqueous meteors
was made by Luke Howard, in his remarkable paper on clouds, published in
the Philosophical Magazine in 1803--the paper in which the names cirrus,
cumulus, stratus, etc., afterwards so universally adopted, were first
proposed. In this paper Howard acknowl