The watchman and southron. [volume] (Sumter, S.C.) 1881-1930, 1909-08-28

evaporation. SOIL Wnen very loose
loses its capillarity and becomes tn.
very best of all mulches.
The constant tendency of a drain
four feet deep to to have four feet of
porous soil above it. A soil of four
feet will absorb more rain than a soil
of two feet. The auger hole in the
barrel four feet from the top will dis
charge more water in given time
than the same size hole two feet from
the top; so will drain four feet deep
discharge more in a given time than
one two feet deep; because they are
both acted on by the pressure of the
water in the soil above them.
Every one knows that the only
way by which the rain that has soak.
ed into the soil can escape where
there is no outlet for it below, is by
evaporation at the surface. 1t may
not be equally plain to all, though it
Is equally true, that when water is
converted into vapor a certain amount
of heat Is removed or made latent. It
is this effect that causes the cool SEN
sation when the moistened skin is ex-
posed to the air. and precisely the
same effect is exerted upon the sur
face of wet soil by the sun and the
wind. The application Of this bit of
philosophy has led to the manufac-
ture Of ice in the hottest climates, and
I once made use of it to cool my
drinking water in a country where it
was necessary to keep our supply of
this in overland cisterns 1 would sus
| pend by a cord a porous earthen ware
| Jug OF water where the air could cir
culate freely about 1t, and the evapor-
| alton of the water from the outer sur
face as it slowly exuded through the
| wall of the jug, had such effect on cool
ing the water in the jug as would make
it pleasant to drink, while that taken
| directly from the cistern would be
warm and unpalatable. When we
wrap wet napkin around the head
and hasten evaporation by tanning,
we cool the head. When we sprinkle
the floor Of warm room with water
1t Is the evaporation of the water that
cools the atmosphere within the
room.
! BY way Of reducing the cooling ef-
/ feet of ayaDorotion to toru,h,o ar,,.s.
I II has been proved that for every GAL
Ion of water removed from a soil by
evaporation the soil has been robbed
| of as much heat-heat that would be
beneficial to vegetation-as would
| raise 1-2 gallons of water from
freezing to the boiling point. DR..
Madden found that the soil of a
drained field from which most of the
| water had been removed by the drains
below, was 6 1-2 degrees F.. warmer
than a similar soil undrained from
| which the water had to be removed
by evaporation. This difference of
temperature corresponds to nearly g.
900 feet difference of elevation.
The foregoing explains why a wet
soil, though exposed to sun and wind
is still cold soil. Heat can not pass
downward through water, and if the
| soil Is saturated the warmth Of the at
mosphere can not penetrate it. Heat
| Is propagated through water by circu-
| latiOn. The warm water rises as the
cooler water passes downward to take
its place.
Those lands where the water col
lecting In slight depressions Of the
surface, remains for some time after
rain need draining. A very good
test as to the advsability of draining
any land would be to dig hole three
] feet deep, and notice if any water
comes into the hole out of the sur
rounding soil after hard rains. If it
does that land needs draining. Some
| Judgment Is required in making this
test, as the soil below the bottom of
a large quantity of the descending
water before it is filled, and thus
! cause the belief that the water Is
passing out below. If the water is
| not finding an outlet below it will at
length fill the soil below the hole, and
! eventually rise into the hole. which. if
the rains continue, may finally be fill
! ed to the surface.
70 the farmer who sees his land
under every vicissitude of weather
there are other indications of the
need of drainage. Those dark damp