Year: 1871

ueWs. i might almost say 1tlr nlSntS, lot
cloudy nights are always cooler, and some
times and in fact often, cool the atmosphere
rs fast us the earth coOls, in which case there
can be no dew. The atmosphere always
contains more or less aqueous vapor in an
invisible form. This vapor is water dissolved


in it, in the same manner Us salt can be dis
solved III water without changing its trans
parency. AS warm water will dissolve more
salt than cold, so will II warm atmosphere
dissolve more water, or in Others retain more
vapor. If the temperature is depressed the
vapor appears in the form of clouds. If
greatly cooled it will fall Ms rain, hail, or
snow. This principle of evaporation and de-
post Of moisture now so generally under
stood and SO thoroughly demonstrated, was
once like all other points in meteorology
considered Us beyond comprehension and at
tributed to supernatural causes. Horace
speaks of dew rs n gentle evening shower
without clouds Virgil says that every night
we have misty rain. Pliny Of the falling
dew, and even mt the present day how often
do we hear the expressions about falling
dew, showing that though we understand
the method or way of deposit, we are not en-
tirely free from the idiom of expression
founded on the mystic reasons Of past ages.
Some countries are rendered productive and
even fertile by dew alone, and doubtless
this to the ancients being mysterious, be-
ing deposited in greatest abundance when
most wanted and of vastly more importance
to them than than to us, caused them to regard
it as IN express gift of God, rs the mama in
the wilderness by his hand. but not in ac-
cordance to the laws of natdrc. In the minds
of those people it possessed wonderful vir-
tues. 1t was supposed if man slipped the
dew and drank no other beverage he would
possess new vital energies, and live on earth
Il long period if not forever. Even up to the
present time it is considered by some to
beautify the complexion and restore the
charms of youth. According to the closest
observations | have been able to make the
dew here deposited amounts to about three
inches per annum. 1t begins usually to he
deposited as soon us the sun goes down and
frequently before, and continues through the
night When the temperature decreases
during the night to the freezing point, the
dew is frozen forming frost, its destructive
powers being in proportion to the intensity of
the cold. OF course dew cannot be deposited
only where there is moisture in the atmos-
phcrc from evaporation, so on deserts or dry
unproductive places no dew can be.


The next means of disseminating moisture
is by clouds, their formation have already
explained They are not vapor, as vapor is
invisible, but water. Not held in solution,
but in minute particles like dust. In reality
water pulverized. SO light they may be
readily blown forward by winds, yet ready
to be condensed and precipitated us rain by
the slightest causes. This condensation is
commonly produced by reduction OF temper
ature either by cooler current of air or by
electrical changes. Clouds are continually
varying in their form and appearance, but
may be classed under four heads The cir
rus is light ieecy cloud resembling II wisp
of hair or bunch of feathers, and is the highest
of all clouds. The water it contains is of
course frozen into snowy particles on account
of its great elevation, and further we know
it is SO rs aeronauts passing through it in their
balloons always find it so, and its peculiar
appearance is owing to that fact, us the wind
blows the frozen particles about in long,
wavy lines. When this cloud is seen, if it
be watched, 1t will gradually change into IL
sort of dappled sky or wavy cloud and disap-
pear, OF else the length of the lines will in
crease and expand over the heavens; in this
section the resolution into the mottled sky
indicates fair weather, but the last mentioned
form indicates storm which will be likely