Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1882-06-10

the crop to mature sooner than 1t otherwise
would and by its retentive power for
water keeps the soil from accumulating too
much heat in the summer time. Besides
these apparent effects, there are others OF
more importance, if possible, and which
will be spoken of when we come to consider
humus and its chemical relation to and &C.
ton upon the soil. Color, although never
exerting any influence upon the amount OF
heat absorbed and retained by bodies, is
nevertheless not the only quality which
makes them susceptible to the suns rays.
ALI bodies possess, in different degrees, the
power of radiating, absorbing and reflect
ing heat. The absorption of heat follows
as a natural sequence after radiation, and
depends upon it. The reflection OF the
SUMS rays is followed by no considerable
absorption OF heat by the rejecting body.
RADIATION AND REFLECTION
Depend entirely upon the surface of the
receiving body. Smooth, polished surfaces
reflect heat, like light, most perfectly,
while rough, irregular surfaces radiate and
absorb much of the heat striking them.
Although depending upon the surface, yet
both radiation and reflection are somewhat
influenced by the nature of the radiating
or rejecting surface. This follows from
the fact that all materials are not equally
influenced by the same heat, even II their
exposed surfaces present the same physical
conditions to the same action. Bodies do
not all absorb like quantities OF light and
heat of different intensities. Lampblack
absorbs heat of all intensities in the same
degree, but most other substances absorb
intense heat less readily than heat of low
intensity, and vice versa. Snow does not
absorb heat of high intensity as readily as
it does heat of less intensity. If black
cloth be spread over the surface of snow it
is seen that the snow melts more quickly
under the cloth than around it. This is
owing to the fact that the black cloth has
radiated the intense heat of the sun, and
has converted it into heat OF low intensity,
which is much more readily absorbed by
the snow than are the direct rays OF the
sun hence, the absorption of heat under
the cloth being greater than that around
it, the melting is correspondingly more
rapid. The same effect is produced by
covering the land with black slate or other
high.radiating power. 1t is stated that in
some sections of Switzerland the people
strew their lands with black slate powder
to hasten the melting of the snow. Al.
though the radiatipg power does not de.
pend upon the color, yet it is fact that
black soils absorb more heat than do light
colored ones, It has been proven by
DIRECT EXPERIMENT
That the length OF time soil would retain
heat coresponded to the length of time re-
quired by the dry soil to absorb it; that is,
other things being equal, the rate at which
soil would cool, and consequently the
time it would retain its heat, is dependent
upon the absolute weight of the soil, which
in turn depends upon the size of the soil
particles. Quartz sand, for instance, is a
heavy and coarse material when compared
to humus or powdered carbonates of mag
nesia, and its retentive power of water is
almost three times less than that of either
humus or powdered carbonate of mag.
nesia. If two soils are saturated
with water, the absorption of heat
will be almost identical until the
liquid water has been removed. Until
that time the sun acts directly upon the
water of the soil, and as long as evapofa-
ton continues but little heat can be &C.
cumulated by the soil particles. Water
absorbs water very slowly-but one-hun.
dredth as fast as does quartz sand-and
therefore no one need expect his soil to
become warmed, no matter how hot the
suns rays may be; az long as it is satu-
rated with water Even if it were posi-
Bile that no evaporation takes place, yet it
would take soil about one hundred times
as long to become warmed when saturated
with water as it would if the surplus
moisture had been drained off. We see,
therefore, that in calculating the probable
CAPACITY OF SOIL
For accumulating and retaining heat we
must take into consideration its physical
properties, and especially the subsoil and
drainage, which SO materially govern the
amount of moisture in the soil. The deserts
of the earth are, as general thing, not
barren from lack of nutritive matter,
but rather from combination of condi.
tions, physical and meteorological, which
depriyes the soil of the necessary water.
These deserts are constantly swept by
dry ing and scorching winds, and this, with
the facts that there are no mountain ranges
to condense the moisture of the atmos-
phere, and not sufficient moisture to be
had from the subsoil, renders them barren
in the extreme. The absorption of rays of
light and heatvarie with the angle at which
they strike. The nearer this angle approach
es right angle the greater the radiation
and absorption, and the less the reflection.
The heat Of the equatorial regions is caused
by the almost perpendicularity with which
the suns rays strike the earth. And the
frigidity of the polar regions is largely due
to the small angle at which the rays Of the
sun strike. We all know perfectly well
that the heat Of midday is caused by the
sun being in its zenith and the radiation
and absorption of heat by the earth is con-
sequently at the maximum. Sidehills
which face the sun radiate and absorb more
heat than do level plains. This is owing to
the fact that the rays strike the hillside at
a greater angle than they do the plain. In
Italy and France the choicest wines are
made from grapes grown on hillsides. A
hillside with
A SOUTHERN EXPOSURE
VIII often grow and mature fruit which
would not ripen on level ground. A south
western exposure is probably preferable for
most fruits for such a one gets the last
rays of sun at night, causing the soil to re-
tain its warmth longer into the night.
Neither are early fruits of such locations
SO liable to be killed by the too direct heat
of the sun in the cold spring mornings.
The buds of trees directly facing the rising
sun, and receiving its first rays on their
frost. covered foliage are frequently killed
by an hour of direct sunshine, when, if
they had been on the southwestern side the
first rays of heat would have been received
by reflection and radiation, the thawing
would have been gradual. and would have
been unattended by injury to the swelling
buds. Even local distractions will con.
centrate the heat of the sun to very ap
preciable extent. Tropical trees or vines
when trained on the sunnyside of