The Kenosha telegraph. [volume] (Kenosha, Wis.) 1860-1888, 1873-08-14
CLOUDS AND FOGS.

fogs. From it we learn that ''air,
at a certain temperature, can hold
only certain quantity of invisible
watery vapor. That is, the Iquan l.
ty of moisture contained by air, when
saturated With it. is constant and
fixed for every degree Of temperature.
The drier the air, and the hotter the
air, the greater is the amount of cloud
which can thus be dissolved in it.
Consequently, the invisible water
vapor IN air becomes visible when a
lowering of temperature or an in
crease of moisture brings it to the
point of saturation. What we call
a cloud, therefore, is water-vapor
which the air cannot absorb when it
is saturated, and which differs from
the vapor already absorbed by pas
sing into the state which Or. Tyn-
dali calls water dust, consisting, ac-
cording to recent Investigations, of
minute vesicles, or bIadders. By
watching a small cloud which hangs
low IN the air, we may often make
good guess at the weather. If it
grows smaller, nelts away, and is
dissolved in the air, we may expect
dry day, or at least a few dry
hours. fit grows heavier, and am
plihes its proportions, we may take
our umbrella under our arm. with
the likelihood of having to hold it
overhead.
This change of water from the
gaseous to the molecular state can
take place at any altitude. When
it occurs at the ground-level, we
call it fog; but there Is no essential
difference between a cloud and a
fog. While travesing clouds in a
balloon, no resistance is felt; the air
is simply more or less opaque. chilly,
and moist, exactly as happens on the
ground, according to the nature OF
the fog or mist. The same with
clouds encountered on mountains.
But although there is no essential
difference between clouds and fogs,
there really is one of fact or circum
stance. A fog is the produce Of
place or locality in which water
vapor passes from the invisible to
the visible state; a cloud is a free,
individual object, an unattached
grouping OF vapors into forms so
determinate that clouds are classified
according to their shapes. The one
is fixed, local, and uniform; the other
IS movable, and of variable aspect.
Examined with magnifying-
glass, fog is composed of tiny bod
les, which are found to consist of
water, obeying the laws of universal
gravitation. The water-molecules
are little balls, like shot or melted
lead fallen from height, or mercury
spilled on mahogany table.
"The average diameter of mist
vesicies may be taken at one-fftieth
part of a millimetre. The length of
the mlllimetre is three hundredth
parts of an English inch. Their
minimum diameter occurs in very
tine weather; when rain threatens.
1t increases; and Immediately before
downfall it is very unequal in the
same cloud.
"When we behold cloud resolve
itself INTO rain, and pour out thou
sands of gallons of water, we marvel
that such an enormous weight of
fluid should be capable of suspen-
sion IN the atmosphere. The cause
consists simply in its extreme divisi-
bllity. The fftieth part of three
hundredth parts of an English inch
Is smallness beyond our clear con-
ceptlon; and this is not the minimum,
but the average size of the particles
OF water-dust. Currents of warm
air ascending from the earth's snr-
face are quite sufficient to keep such
tiny atoms afoat. They hang to-
gether In groups and masses in con-
sequence Of their mutual attraction.
for attractive influences are the onIy
obvious explanation of the very dis.
tlnct forms and c early-defned out
lines which clouds exhibit.
"Thick fogs are sometimes odor-