The morning call. [volume] (San Francisco [Calif.]) 1878-1895, 1892-05-29
CLIMATE OF THE FUTURE.
Possible Result Of Permitting Forests to
Grow.
Nightly Dews May Provide Constant Moisturs
and Rainstorms May Be Ea-
tirely Unknown.
Written for THE MokNING CALL.

A recent item in THE CALL. on the pos
sIDle relation of vine and tree culture In this
State to the alterations of climate with
respect to increased rainfall has emphas-
lied The apparent need for education upon
a subject which, believe, the United States
Board OF Forestry has for years been
seeking to develop by the distribution of
literature. 1t may, therefore, be we'll to
direct the general thought to some ideas,
many OF which have undoubtedly been
shared by the average readers of the press.
but not perhaps grouped in their truer rela-
ton.
What is rainfall? 1t IS simply the con-
densation of water from vapor condition.
the cooling Of the air charged with invisible
drops, carried there chiefly through the ac-
ton OF the sun. A few easy observations
Will show that it is so. kettle filed
with water placed over fire, speedily
gets rid OF its contents by vapOrization.
MS yapor IS distributed through the room,
ana being invisible becomes visible If the
air be colder on the outside, and is seen 10
run down the window paneS in trieklng
drops. Or, If one blows upon cold piece
OF glass, metal or wood, the moisture, before
invisible, is quite evident in an accumula-
tration win serve to show that from invisi-
bic yapor TO visible water the only condition
is lowering Of temperature, or rather a
difference in the temperature of the two OBJ
Jects-the warmer air ard cooler surface
Of any Kind. A pitcher OF icewater is stand
ing on table. Water soon appears on the
outside Of the vessel and runs down in tiny
streams. The water did not come through
the glass, but condensed upon it from tue
warmer air
CAUSES OF RAIN
How do these facts relate to rain? Every
blade of grass and leaf of every description
serves to act as the ice pitcher and window
pane, that is as cOndenserS 10 chill the
watery PARTICLES held In suspension by the
air. Hence the cultivation of vines, trees
and grass serves 10 increase the cOndensing
surface Of the earth. 1t has been observed
ioT many years that blowing has been pro-
ductlYe II showers. The relation between
showers and newly plowed areas with the
growth OF grass designed for hay have all
been somewhat familiar to the public from
frequent publication. The newly turned
ground, ike the grass and trees, being cooler
than the atmosphere cOndenses the moisture
from it.
Another factor in the production of rain
has been tie discharge OF artillery, notably
in naval and military operations, and even
on CIV lc occasions, as the Fourth of July
celebrations. The reason Is the same as in
the case OF grass and foliage eondensa-
ton. How condensation takes place in the
discharge OF firearms IS not at first evident.
When gun IS discharged the ball IN pass
ing randy through the air congresses it in
us Hight, and the powder in burning causes
tie great expansion OF gases, which pro-
Jects the bali This expansion Of gases out
side Of the mouth Of the gun, acting upon
the atmospherr, con- presses it. 1t is prob
able that In the production Of rain directly
by artificial means this principle of expan-
sion and CORES spending compression of the
moisture IN the air is applied. The expert
menter, II IS reasonable TO suppose, releases
compound that, upon contact with the
principles OF the air becomes extremely
expansive. You know what compression
Is. 1T is to squeeze together. When YOU
squeeze the air together 10 releases its hold
upon the water which then falls.
EVAPORATION OF MOISTURE
The chief cause Of rain LOwer, l think it
will be admitted, is the great evaporation of
moisture by the sun. and its later cOndensa-
ton BY foliage. Leaves absorb the larger
percentage Of tie sunbeams that reach
them, thus leSSening the refracting surface
aud, therefore, producing a cooler condi-
tlOn OF air Immediately in their vicinity, as
well as through extensive distance Of the
air The moisture they contain also serves
to lower the temperature further. Just as in
some OF the hotter countries, and portions
OF this State, the people wrap water Jugs
with wet cloths so that in the evaporation
Of the outer wrapping the temperature OF
the interior contents OF the jug or vessel
may be lowered Lowering the tempera-
ture Of the leaves, it necessarily lowers the
temperature of the air. In the desert of
Sahara rain is almost unknown, while in
sections surrounded by wooded States the
rainfall is slightly increased. In the Sa-
haIa the TelTacted rays OF the sun keep the
earth and ar 81 Superheated that c0ndenSa-
ton is impossible. In the heated sections
of Arizona the earth becomes gradually
cooler through ;he influence Of adj lcent
timber belts until the ground with its scant
grasses can crndense sufficient TO constitute
a rain. The FIRST rain is n guarantee for q
rapid succession OF showers. generally
speaking
Floods are most likely to occur in sections
where the timber has disappeared, as in
Iowa, Illinois, Nebraska and Kansas. The
rivers in most of these interior States bay-
ing little timber along their banks, in the
summer the beds are dry sand bars, with
not a suspicion of moisture about them.
while in winter they become raging tor
rents, that, sweeping over their banks,
wash farmhouses, livestock and people into
the wild rush OF waters. Such streams as
are wooded along their upper course, how
ever preserve about an equal volume OF
water the year around. as in the wet season
the foliage absorbs large quantities of water
and Divers the d0Wnpour more s 0wly to The
they release part OF their stored fluid to the
springs, which in turn supply the tribu-
tarleS to the rlveTS-the runs and creeks.
EFFECT OF DESTROYING FORESTS.
Carl SchurZ, In a recent address to the
Board Of Forestry at Washington, directed
attention TO the wretched condition Of the
people Of Asia and countries bordering Oh
the Mediterranean from the extreme
drought ana heat resulting from the deStruc-
ton of forests in that portion of the globe
The United States some years ago adopted
q plan, by an enactment of Congress. to
secure rainfall and storage Of the same, by
passing bill since termed The timber
culture act" whereby settlers of sections
Of the Eastern States or those west OF
the Mississippi could secure given num-
Der OF acres Of ground upon agreement to
plant a specified number Of acres in forest
trees, the object being twofold-to secure
the regularity Of springs by promoting
rainfall and storlng ii when 1t fell and TO
alter the climate by interpoSing barriers to
the winds. 1t has also been stated repeat
ed Y that the French Government proposed
undertaking the reclamation of the desert
OF Sahara, by first irrigstlng and subse-
quently planting trees, the water bitches
to serve IN supplying the needed nourish-
ment 70 the growing trees, and the latter in
turn to insure regular ratnfalls.
Those sections which are already tim bered
heavily, as Washington and Oregon. il is
said, have so great condensation Of
moisture that their wet season extends from
six 10 nine months per year. Probably the
last figure is an extreme. but yet their wet
period is evidently far more prOtracted than
that of adjacent States where timber is
scarce. From this it might be inferred that
a general cultivation of forests would result
in general deluge or increased period Of
rain all over the globe. Let us think. The
evaporation which takes place on the globe
is enormous; indeed it will be granted that
the greatest evaporation probably occurs
from the surfaces of inland bodies of water
as lakes, streams and pools, rather than
from the greater body of the ocean. 1t is
true that the amount of moisture is greater
from the ocean, but not in proportion TO
surface; that is, the surface of river or
creek will contribute more moisture to the