Los Angeles daily herald., 1875-09-18
Why 1t Does Not Rain.

/
from the same latitude on the Allan
tic. We think We can make it clear
to all, and shall start with the asser-
tion that 1t is primarily because our
mountains are so numerous, and are
composed principally of sandstone and
granite in their uppermost strata. The
connection between the formation of
our mountains and the climate may
not appear, at first view, but our read
ers will soon see the relation.
Nearly all the soil of California is
of decomposed rock. There being a
very large proportion of indissoluble
element in the shape of sand the sur
face soil is everywhere porous, and
hence incapable of holding water for
any length of time. For this reason
the waters sink below the surface and
find subterranean outlet to the
ocean. There is then comparatively
no evaporation of water from the sur
face, and vegetation is so scarce there
is an extremely small quantity of
moisture given to the air by the leaves
of grasses, plants and trees, for it is
well known that trees and plants are
natures pumps to draw up the sur
plus water from below and give it back
to the atmosphere, to be borne upon
the wings of the wind to other climes.
Having established this point, now let
us turn to the clouds. The agency of
heat in the process of evaporation is
well known. Every one daily expe-
riences the absorption of heat by the
moisture evaporated from the skin.
We can feel the perspiration taking
the heat from our bodies to lure it
away into space. Over the vast ex-
panse of the Pacific ocean, this evapo-
ration of water is going on at all
times. With the air stagnant, this
moisture would rise and fall back
again shortly to the same spot when
the SUMS rays were withdrawn. But
the alternate absorption and expulsion
of heat by the soil, causes the air near
the surface of the earth to rise. A vac
cuum is thus made, and the atmos-
phere lying over the ocean rushes in
to ill the void. Thus it is in sum-
mer the breeze is always to the land
and not away from it. The clouds
then, or rather bodies of mist, float
from the ocean toward our shores.
When they pass over the land they
encounter rising stream of dry heat
ed air. The clouds or bodies of sus-
pended moisture rapidly absorb the
heat and rise higher and higher their
rain-bearing powers. being augment
ed with their greater temperature. A
cloud may be compared to hot-air
balloon. Give it heat and its buoyan-
cyis increased; take away Its heat and
it is precipitated to the earth. The
bodies of vapor coming in from the
Pacific during the Summer, are given
more buoyancy by the hot dry air ris-
Ing from the ground, and bear their
moisture away into the interior, often
until within the watershed of the
Mississippi river, where are encoun-
tered cold stratas of air, and their load
of water is preclpitated to the earth.
The absorption of heat by the light
bodies OF mist, accounts for the mild
ness of our Summers. The heat trav-
els Oft with the vapor.
In the winter the sun moves farther
south, and the ground ceases to fur
nish so much dry heat to the clouds
coming In from the Pacific. These
clouds, too, have to contend against
a disturbing element shortly after
reaching the land, in the shape of cold
north winds, which take away the
heat and precipitate the suspended
moisture to the earth. Just before and
after rain the weather is very sultry.
A cloudy day is a warm one. A rain
fall in the vicinity ever causes the
thermom eter to rise, as was the case
Wednesday and Thursday in this city.
The clouds have met with cold strata
of air which, taking off the heat,
caused the smaller particles of vapor
to rush together In denser form under
the law of cohesion. They are driven
back to us, black and threatening, and
are unable to absorb any more heat.
We know it is common to account
for the GOODNESS of California in Sum.
mer, by locating a sea current from
the Arctic seas off the coast; but an
examination of the maps and charts
will show no such current. The Kuro
Simo, which originates in the Indian
| ocean and trends across the Pacific in
the direction of Bhering's Straits, is
the only current known to men of sci
ence. The coldness of the waters of
the Pacific near the shore, may be in a
measure accounted for from the fact
that all its accession of waters is from
subterranean sources, which must
therefore be cold. The rapid absorp-
tion of heat, caused by the evapora-
tion of moisture, induced by the trade
winds, which in turn spring from the
upward current of hot dry air on the
land, also accounts for the low tenn
perature of the ocean.
In upper Africa the same causes op-
crate and are followed hy like rasnlfs