Sacramento daily record-union., 1882-04-29
AGRICULTURAL PAPERS
a SERIES PREPARED ESPECIALLY FoR
TEE "RECoRD-UNIoN."
Presenting Instruction Contained in Lect.
ures from the Chair of Agricult-
ure, State University.
IsIXTRENTH PAPER

drops is Of the greatest interest to every
farmer. The soil is the "exclusive thea.
Ter" of his labor, and the medium in
which the roots of his crops grow. 1t is
che only natural agent employed in the
production of economic scrops which is in
no way influence the general constitution
and effects of the atmospheric air and solar
light and heat. The farmer is entirely de-
pendent upon the efforts of nature for the
material derived from these last resources
by his crops. As the soil, therefore, is the
only natural agent which he has practically
under his control, it is of the greatest i'm
portance that he should till it to the best
advantage. Through the agency Of the
soil the influence of the atmospheric air,
and the suns light and heat, may be largely
modified and made subservient to the best
interest of the farmer. The general
functions of the soil are three
in number. ~ 1t is the source from
which, as we have already seen, the ash
ingredients of all plants are derived. As
such it is most intimately and directly con-
nected with the nutrition of plants through
Che agency of the food which plants alb
stract from it. ~ 1t affords mechanical
support for the members of the vegetable
kingdom. The roots of plants penetrate
the soil and firmly fix plants in an upright
position, and in direct contact with the
s0urce from whence they got their supply
of ash ingredients. 81 The soil acts as a
storehouse or reservoir in which are tenn
pered and stored the suns heat and surplus
food matter of the soil. Through the
agency of the soil those physical conditions
are secured, which are necessary to the
growth of plants. and which must act IN
cooperation in order to insure the con-
tinuous
DEVELOPMENT OF PLANTS
Soil may be defined as that layer of
earthly material over the earth's surface IN
which plants grow. We thus see that two
essential requisites of soil are, that it shall
be on tho earth's surface, and that it shall
be capable of supporting and nourishing
plant life. The primitive source of all
soil is undoubtedly rock and mineral. mat
Ter which has for centuries been undergo
ing gradual communion and translocation
from the mountains to the valleys below.
This process is continually going on, even
at the present time, but slow in comparl-
son to what it must have been Immediately
succeeding the geological changes during
which our continent was upheaved from
the bed of the sea and made to form part
.af the earth's eurface. Rock and mineral
matter may then be said to be the prin-
.cipal constituents of the soil. Minerals are
compounds of the various chemical ele-
rnents, and hence have fixed and definite
chemical composition. Rock are ag.
gregations or mixture of the mineral
matter. Johnson considers the origin
and formation Of the soil un-
der five heads ~ The chemical
elements of rocks; ~ the meteorological
elements of rocks; (3) the rocks them
selves az the conversion of rocks into
soil; and (5) the incorporation of organic
matter with the soil. The chemical ele-
nents which make up rocks include all OF
the elements known to our modern chem
lists. We have at a former time described
she principal of these elements, and it is
not necessary to speak further of them.
It will be impossible to treat anywise fully
of the minerslogical elements of rocks, for
they constitute separate branch OF science
s-mineralogy, and cannot be satisfactorily
studied except with the minerals at hand,
and with the help of proficient mineral
ogist. We shall therefore content ourselves
with briefly naming some of the principal
from the agriculturist's point of view
elementary constituents of rocks, with
their composition, and sometimes few of
their properties. The minerals with which
we are principally interested are quartz,
feldspar, mica, amphibole and pyroxene,
Iencite and kaolinite, tale, calcite. mag
nestle, dolomite, gypsum, pyrites and
apatite.
Is probably the most common OF all miner
ais. Chemically it is anhydrous without
water silica. 1t is found in all sizes, from
immense masses of quartz rock to finely
divided sand. Nine-tenths of all sand is
made up Of particles of quartz. Its indi-
viduality is preserved by its exceeding
hardness it readily scratches glass, which
ia generally O silicate OF soda or potash.
Feldspars are compounds Of silica with
alumnia and with one or more of the alkalis
and sometimes with lime. They are divided,
according 10 their constituents, into potash
feldspars, soda feldspars, soda.lime field
spars, and lime-yoda feldspars, in which the
element placed first was, after alumnia,
the Characteristic basic one. Mica is COM
monty known as "isinglass There are
three principal varieties of mica Mus
covite, phlogopite and biotite. They are
silicates of alumnia with potash, magnesia,
lime, iron and manganese. Muscovite, or
muscovy glass as it is sometimes called, is
most generally transparent and variously
-colored. This transparent variety is of
considerable value to the arts, taking the
place of glass in many places where heat is
TO be successfully withstood. The black
variety of muscovite owes its color to
the presence of iron. Phlogopite and
biotite contain large quantities of
magnesia and often sesqui-oxide OF
iron. They are therefore dark. colored,
and often Opaque. Amphibole and pyrox-
enc resemble each other quite closely IN
composition. They are silicates of mag
nesia and lime. or of magnesia and protox'
ide Of iron, with more or less Of the alkalies.
Their color varies from pure white to jet
black according as they contain more or
less of the oxides of iron and manganese.
Lencite and kaolinite lclay) are respectively
the anhydrous and hydrous silicates of
alumina. The last is formed from field
spars by the decomposing action of atmos-
pheric air at ordinary temperatures. Such
kaolinite is necessarily impure, and con-
tains, in state OF mechanical mixture,
many of the constituents of the decom.
posed feldspars. Ordinary clay is very
impure form of kaolinite, while the clay
used in the manufacture of the finer grades
of pottery is almost chemically pure kaolin-
ite. Upon being worked or stirred for some
time kaolinite acquires high degree oi
Elasticity. This it Is which imparts TO il
its value in the arts. 1t has great alb
sorptive power for water, and when touched
to the tongue will adhere with force
sometimes sufficient to tear off the adherine
papilla Of the tongue.
TALO, OR soAPsToNg,
Is hydrous silicate Of magnesia. Ser
pentine is essentially the same they ar,
both soft. while the latter has generally ,