(_Continued from No. 2._)
These three signs, viz., colour, consistence, and vegetation, are named
by the Royal Agricultural Society as being pre-eminently indications of
the value of lands; yet there are others of equal if not of greater
consequence. For example:--
_A knowledge of the geology of the land_ is of the first importance;
that is, not only a knowledge of the range and extent of each formation
and its subdivisions, which may be called geographical geology, but also
how far and to what extent the various lands do depend upon the
substratum for their soil, and the local variations in the chemical or
mineralogical character of the substrata themselves, and which may be
called the differential geology of soils. For not only do the qualities
of land vary from one formation to another, but upon the same formation
there is frequently considerable difference in the quality of land
depending upon chemical difference in the substratum, or upon an
intermixture of foreign debris derived from other strata.
_A chemical investigation_ of the soil and subsoil will frequently
afford most useful indications respecting the value of land. It may be
laid down as an axiom that a soil to be fertile must contain all the
chemical ingredients which a plant can only obtain from the soil, and
chemistry ought to be able to inform us in unproductive soils what
ingredients are wanting. It also is able to inform us if any poisonous
substance exists in the soil, and how it may be neutralized; when lime,
marl, and chalk are to be used, &c.[1]
The Royal Agricultural Society say that chemistry is unable to explain
the productiveness of soils. But why is it unable? One reason is, that
supposing everything required by the plant to be present in the soil,
yet if the soil be either too wet, or too dry, too cohesive, or loose,
the plant will not flourish; and chemical analysis does not declare
this, for it affords no information respecting the mechanical division
in which substances exist in the soil. Again, the chemical analysis of
soils, to be worth anything, must be conducted with more rigid accuracy
than those published by English writers. To detect one cwt. of gypsum in
an acre there would be only one quarter of a grain in a pound of soil,
or in 100 grains only three and a half thousandth of a grain (35/10000
or,00035 grs.), or to discover if sufficient alumina existed in a field
for the production of red clover there must be ascertained if it
contained (one hundred thousandth),00001 per cent. The analyses even by
Sprengel do not afford us the quantity of nitrogen in each soil, or the
capacity of the soil for this substance; while it is well known that
most manures, as well as the different kinds of food, are valuable in
proportion to the quantity contained by them, and it is highly probable,
_ceteris paribus_, that the quantity of nitrogen found existing in soil,
and the soil's capacity for containing that substance, would afford an
easy indication of its immediate fertility, and also of its requiring
great or small quantities of nitrogenous manures in its future
cultivation.[2]
Chemistry, however, outsteps her province when it is attempted to
explain how vegetable productions are formed in the plants by chemical
forces; for the recent discoveries of Schwann, Henle, and Schleiden,
prove that all the functions of the plant are performed by the means of
simple vesicles and cells--that absorption, assimilation, fixation of
carbon from the atmosphere, respiration, exhalation, secretion, and
reproduction are all effected by single cells, of which the lower plants
almost entirely consist--that the cell absorbs alimentary matters
through the spongioles of the root, and that the fluid received thus
undergoes the first steps of the organizing process--that the inorganic
elements are changed into the simplest proximate principles by cells--so
also are the further changes into the regular secretions of the plant,
the result of cell-life--that gum and sugar are converted into the
organizable portion of the nutritious sap by the cells of the leaves.
The starchy fluid in the grains of corn is rendered capable of nutrition
to the embryo by the development of successive generations of cells,
which exert upon it their peculiar vitalizing influence. Albumen is
converted into fibrine by the vital agency of cell life--_i.e._, cells
are produced which do not form an integral part of any permanent
structure in the plant, but which, after attaining a certain maturity,
reproduce themselves and disappear; hence it may be stated that all the
vegetable productions which are formed in the plant are effected by a
series of vital actions through the agency of cells.
From the different transformations which these undergo all the different
tissues in vegetables are formed; for instance, the spiral and dotted
ducts, woody fibre, and so on. Schwann showed that the formation of
tissues in animals went through exactly the same progress, a fact which
has been confirmed by the microscopic observations of Valentin and
Barry. Thus vessels, glands, the brain, nerves, muscles, and even bones
and teeth are all formed from metamorphosed cells. Dr Bennett says--"If
this be true, and there can be little doubt, it obliges us to modify our
notions of organization and life. It compels us to confess that
vegetables and animals are not simple beings, but composed of a greater
or less number of individuals, of which thousands may exist in a mass
not larger than a grain of sand, each having a vital centre and separate
life, independent of those around it. Each of these individuals, or
organized cells, should be regarded as a living being, which has its
particular vital centre of absorption, assimilation, and growth, and
which continues to vegetate, to increase, and undergo transformations as
if it were an isolated individual. At all events, a knowledge of the
existence of the cell-life of plants will explain several phenomena
respecting the vegetation, growth, and ripening of corn, and may
hereafter lead to some valuable practical results."
_The climate, elevation, and exposure_ are not to be neglected. Upon the
higher portions of the Wolds crops suffer, much from elevation and
exposure, while in the western portion of Yorkshire, upon the moor
edges, the harvest is usually a month later than in the central parts of
the island.
_A moderate depth_ of soil in general is a favourable sign, although
some of shallow soils on the new red sandstone and on the Wolds are very
good; to these signs are to be added locality, as respects markets,
facilities of obtaining a supply of lime, or other tillage, the rates
and outpayments peculiar to the district, &c. &c., all of which are to
be taken into account when considering the value of any particular farm.
I shall now briefly apply these indications of fertility over the
different geological formations of Yorkshire, and it will be found that
each lends aid to the other, and that a person will be able to ascertain
the value of land in proportion as he is able to appreciate the
collective evidence afforded by them.
(_To be continued._)
[1] Mr Brakenridge, of Bretton Lodge, who has extensive practice in land
valuing, informs me that a mechanical analysis of the soil affords him
much assistance; and he has found that in soils, whenever free from
stagnant water, that in a mechanical analysis the larger the proportion
which remains suspended in the water, the greater its powers of
production will be found, and the less manure it will require. That the
best soils are those which, when diffused and well stirred in water and
allowed to stand for three minutes, from 20 to 30, say 25, per cent. is
carried off with the water of decantation. When 30 per cent. and upwards
is decanted off, the soil becomes retentive of water and consequently
wet. When less than 20 per cent., say only 16 per cent. and under, is
carried off, it becomes too porous; water passes through it too rapidly;
its soluble matter is washed off into the substratum, and it has a
strong tendency to become thin and sterile.
[2] The celebrated black earth of Russia contains 2,45 per cent. of
nitrogen.