Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1882-05-20
AGRICULTURAL PAPERS.
A SERIES PREPARED ESPECIALLY FOR
THE "RECoRD-UHIoN."
Presenting Instruction Contained n Lect-
ures from the Chair OF sgricult-
ure, State University.


NINETEENTH PAPER
o. Power possessed bylsoilsl OF appro-
priating solid matters from their solutions.
That soils have the power Of fixing or TAX
ing solid matters from solutions has long
been known. 1t was no new fact, even
several centuries ago, that sea water when
filtered through sand lost much of its salt
ness. Were the soil incapable OF removing
matter from the liquids which pass through
them, much nntritive matter would be
lost to the plant world. For then the rains
must inevitably carry all of the soluble
matter, except what was directly im6ibed
by the roots of plants, out Of the reach Of
succeeding plants, and the greatest part
of the matter thus carried down would
pass off through the drains and be lost
johnson explains the removal of solid mat
ter from solutions by saying that the ad-
hesive power Of the soil, or material through
which the liquids percolate, overcomes
the cohesive power of the particles in the
from the liquid in proportion, other things
being equal, to the amount of surface ex-
posed by the extracting body. The main
difference, physically, between a solid and
a LIQUID is that in the one particles making
up the solid body have such a great CO.
hesiyeness for one another as to prevent
free motion among themselves; while IN
the LIQUID bodies the cohesive force is SO
small that the PARTICLES move freely among
themselves. II, for instance, salt, which
is solid, be
DISSOLVED IN WATER
A certain degree of cohesiveness is over
come by the solvent. If now the saline
solution be filtered through sand or char
coal, either of which can be wetted, and
both of which present comparatively
large surface to the liquid, it is easy to per-
ceive how they can, by their attraction for
the particles of salt, overcome the remain
ing slight cohesive force existing between
them, as well as the adhesive force of the
water, sufficiently to cause particles Of salt
to separate out and adhere to the surface
of the sand or charcoal. We thus see that
this fixation of solid matters by the soil is
a physical rather than chemical phenom-
ena and that, since 1t depends upon the
surface attraction of the soil particles for
those of the solid matters of the liquid,
the more porous body is the larger
amount of matter it Will extract from So
lutions. We can readily understand,
therefore, that the extractive power CT fine
sand and clay must be very great. The
absorptive power of clay for water has
been mentioned as being sufficient in pure
clay to bear off the papila of the tongue.
The particles of clay being much finer than
those OF sand, its fixing power Is corre-
spondingly greater, but when once satu-
rated it takes longer to redissolve the fixed
matters from the more adhesive clay than
from the sand. BY the fixing or
ADHESIVE POWER
OF the soil all color, odor and taste may be
removed from the most offensive liquids by
filtering through a sufficient depth of earth.
1t is well known that few yards of soil
intervening between a well and sink or
cesspool will often quite effectually purify
the liquids OF the latter before they reach
the well, aud by this means often maintain
the purity OF the well water for consid-
cradle time. Had not the soil the property
of neutralizing the offensiveness OF these
liquids, each such sink or cesspool would
be a hotbed of disease and a perpetual
agent in the spread of epidemics. Is The
productiveness Of q soil is very closely con-
nected with its department toward liquid |
water. The ability to imbibe liquid water
is known as the capillary power of the soil. |
1t is caused by the same force which causes |
the ascent of liquids in a capillary tube, |
- |, l.,
tween the surfaces of the capillary tube |
and the liquid. The capillary power or |
capillary coeGiicient of soils represents their |
ability to absorb and retain liquid moist |
ure. In all porous bodies for most liquids !
this power is inversely proportional to the
size Of the pores. The interstices between |
grains of coarse sand are large, and hence /
matter readily runs or percolates through. |
Such soils cannot, Of themselves, retain |
the moisture for any length of time, and |
we have already seen that their hygro- |
scopic coefficient is also low. On the other |
hand, clay, which we know is made of |
very finely divided particles of mineral |
water, and since the amount of surface
exposed depends upon the tineness OF the |
soil particles, it must have correspond
ingly greater number of and more minute
pores thus, therefore, a high capillary
power. Not only is this the case, but
clayey soils, as is well known, retain moist |
ure with the greatest tenacity. The writer |
has seen blocks of clay taken from
wELL-CULTIvATED SOILS
At depth of one and half feet, and |
which had not been saturated with water J
for six months, and yet the clay seemed to
be completely saturated. There is an, evil
dent relation between the mechanical CON-
position of soils and their capillary powers. |
II glass tubes containing different grades |
of soil be suspended with the lower end |
projecting into vessel of water, the liquid
will Immediately begin to rise In the tubes
by the capillary force of the soil. But the |
rate Of ascension and total nights reached
will be found to vary very greatly with the
different soils. Suppose we have a tube
filled with coarse sand, one with alluvial
soil, and another with fine clay. The
water in its ascent in the tube containing
sand will outstrip that in either of the
other tubes in fact, it will rise several
times as rapidly. 1t will, however, only
reach hight of ten or twelve inches in
the tube and then will cease rising. The
capillary power of the sand has been ex-
hausted, and II the surface of the sand is
more than twelve inches above the water
level it will not nave been moistened by
the capillary water. The water in the tube |
containing alluvium rises much slower than |
that in the sand, but to a considerably |
greater hight while that of the clay, |
which rises slowest of all, goes on after the |
ascent has ceased in the other tubes, and |
the water finally reaches a foot or more |
higher in the clay than in the alluvium. 1t
is a curious fact that if either of the soils |
be tamped and thus compacted in the tube
the rise will be much more rapid, but will |
not reach to such hight as before. If the |
surface of the tamped soil be reached by
the ascending capillary water the evapora-
ton, upon exposure to the suns heat, will
be much greater from the tamped than