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Wiley & Putnam’s New Publications.
LECTURES

ON

AGRICULTURAL
CHEMISTRY AND GEOLOGY:

TO WHICH ARE ADDED,

SUGGESTIONS FOR EXPERIMENTS IN
PRACTICAL AGRICULTURE.

BY,
JAS. F. W. JOHNSTON, M.A., F.R.SS. L. &E.

Fellow of the Geological Society, Honorary Member of the Royal *
Agricultural Society, &c. &c. ; Reader in Chemistry and
Mineralogy in the University of Durham, &c.

These Lectures will be divided into four Parts, of which
the First is now ready; the others are in course of publi-
‘eation, and the whole will be completed in two volumes.

OvuTLINE oF Parr I.—“‘On the Organic Constituents of
Plants.”—Lecture I. Elementary substances of which
plants subsist. II. and II. Compound substances which
minister tothe growth of plants. [V. Sources from which
plants immediately derive their elementary constituents.
Y. How the food enters into the circulation of plants—
general structure of plants. VI. Into what substances the
food is changed in the interior of plants—substances of
which plants chiefly consist. VII. Chemical changes by
which the substances of which plants chiefly consist are
formed from those on which they live. VIII. How the
supply of food for plants is kept up in the general vegeta-
tion of the globe.

OvtiineE oF Part II.— On the Inorganic Constituents
of Plants—the Origin, Classification, and Chemical Consti-
tution of Soils—General and Special Relations of Geology to
Agricultwre— Origin, Constitution, Analyses, and Methods of
Improving Soils in different Districts and wnder unlike con-
ditions.” —Lecture LX. Kind and proportion of inorganic

1 '

‘ft
mB.
—- |

Wiley 5 Putnam’s New Publications.

~

matter contained in plants. X. Properties of the inorganic
compounds which exist in vegetable substances, or which
promote their growth. XI. Ofthe nature, origin, and classifi-
cation of soils—Structure of the earth’s crust—Classification
and general characters of the stratified rocks—A gricultural
capabilities of the soils derived from them. XII. Granite
and trap rocks, and the soils derived from them—Superficial
accumulations. XIII. On the exact chemical constitution,
the analysis, and the physical properties of soils.

Part III.--Methods of improving the soil by mechanical
and by chemical means—Manures, their nature, composition,
and mode of action—theory of their application in different
localities.

Part [V.—The results of vegetation—the nature, consti-
tution, and nutritive properties of different kinds of produce,
and by different modes of cultivation—the feeding of cattle,
the making of cheese, &c. &c. The constitution and differ-
ences of various kinds of wood, and the circumstances which
favour their growth.

CRITICAL NOTICES.

“A valuable and interesting course of lectures.”—Quar-
terly Review.

‘‘ But it is unnecessary to make large extracts from a book
which we hope and trust will soon be in the hands of nearly
all our readers. Considering it as unquestionably the most
important contribution that has recently been made to popu-
lar science, and as destined to exert an extensively beneficial
influence in this country, we shall not fail to notice the forth-
coming portions as soon as they appear from the press.” —
Silliman’s American Jowrnal of Science. Notice of Part I. of
the American reprint.

“We think it no compliment to Professor Johnston to say,
that among our own writers of the present day who have re-
cently been endeavouring to improve our agriculture by the
aid of science, there is probably no other who has been more
eminently successful, or whose efforts have been more highly
appreciated.” —County Herald.

“¢ Prof. Johnston is one who has himself done so much al-
ready for English agriculture, that to behold him still in hot
pursuit of the inquiry into what can be done, supplies of itself”
a stimulus to further exertion on the part of others.”—Ber-
wick Warder.

ELEMENTS

OF

AGRICULTURAL

CHEMISTRY AND GEOLOGY.

rs BY
JAS. F. W. JOHNSTON, M.A., F.R.S.,
HONORARY MEMBER OF THE ROYAL ENGLISH AGRICULTURAL

SOCIETY, AND AUTHOR OF ‘‘ LECTURES ON AGRI-
CULTURAL CHEMISTRY AND GEOLOGY.”

NEW-YORK:
WILEY AND PUTNAM.

MDCCCXLII.

1%,

Bs

Tat

INTRODUCTION.

Tue scientific principles upon which the art
of culture depends, have not hitherto been suf-
ficiently understood or appreciated by practi-
cal men. Into the causes of this I shall not
here inquire. I may remark, however, that if
AcricuLture is ever to be brought to that
comparative state of perfection to which many
other arts have already attained, it will only
be by availing itself, as they have done, of the
‘many aids which Science offers to it; and
that, if the practical man is ever to realize
upon his farm all the advantages which Sci-
ence is capable of placing within his reach, it
will only be when he has become so far ac-
quainted with the connection that exists be-

‘Vill INTRODUCTION. °

tween the art by which he lives and the sci-
ences, especially of Chemistry and Geology,
as to be prepared to listen with candour to
the suggestions they are ready to make to him,
and to attach their proper value to the expla-
nations of his various processes which they
are capable of affording.

The following little Treatise is intended to
present a familiar outline of the subjects of
Agricultural Chemistry and Geology, as treat-
ed of more at large in my Lecturzs, of which
the first Part is now before the public.
What in this work has necessarily been taken
for granted, or briefly noticed, is in the Lec-
TURES examined, discussed, or more fully de-
tailed.

Durham, 8th April, 1842.

CONTENTS.

CHAPTER I.

PAGE

Distinction between Organic and Inorganic Substances
—The Ash of Plants—Constitution of the Organic
Parts of Plants—Preparation and Properties of Car-
bon, Oxygen, Hydrogen, and Nitrogen—Meaning of
Chemical Combination.

CHAPTER II.

Form in which these different Substances enter into

Plants—Properties of the Carbonic, Humic, and UI-
mic Acids; of Water, of Ammonia, and of Nitric
Acid—Constitution of the Atmosphere. . ee

CHAPTER III.

Structure of Plants—Mode in which their Nourishment
is obtained—Growth and Substance of Plants—Pro-
duction of their Substance from the Food they imbibe
—Mutual Transformations of Starch, Sugar, and
Woody Fibre. . 2

fis

25

x CONTENTS. “

CHAPTER IV.

PAGE
Of the Inorganic Constituents of Plants—Their imme-
diate Source—Their Nature—Quantity of each in
certain common Crops. . : : . ae

CHAPTER V.

Of Soils—Their Organic and Inorganic Portions—
Saline Matter in Soils—Examination and Classifica-
tion of Soils—Diversities of Soils and Subsoils. o BF

CHAPTER VI.

Direct Relations of Geology to Agriculture—Origin of
Soils—Causes of their Diversity—Relation to the
Rocks on which they rest—Constancy in the Relative
Position and Character of the Stratified Rocks—
Relation of this Fact to Practical Agriculture—Gen-
eral Characters of the Soils upon these Rocks.. . 78

CHAPTER VII.

Soils of the Granitic and Trap Rocks—Accumulations
of Transported Sands, Gravels, and Clays—Use of
Geological Maps in reference to Agriculture—Phy-
sical Characters and Chemical Constitution of Soils
—Relation between the Nature of the Soil and the
Kind of Plants that naturally grow uponit. . . 103

CONTENTS. xl

CHAPTER VIII.

PAGE
Of the Improvement of the Soil—Mechanical and Che-
mical Methods—Draining—Subsoiling—Ploughing,
and Mixing of Soils--Use of Lime, Marl, and Shell-
sand—Manures— Vegetable, Animal, and Mineral
Manures. . A earn ts ‘ : i : . 133

CHAPTER IX.

Animal Manures-—Their Relative Value and Mode of
Action—Difference between Animal and Vegetable
Manures—Cause of this Difference—Mineral Man-
ures—Nitrates of Potash and Soda—Sulphate of So-
da, Gypsum, Chalk, and Quicklime—Chemical Ac-
tion of these Manures—Artificial Manures—-Burning
and Irrigation of the Soil—Planting and Laying
Down to Grass. ay Aids : 4 : : . 165

CHAPTER X.

The Products of Vegetation—Importance of Chemical
quality as well as quantity of Produce—Influence of
different Manures on the quantity and quality of the
Crop—lInfluence of the Time of Cutting—Absolute
quantity of Food yielded by different Crops—Princi-
ples on which the Feeding of Animals depends—
Theoretical and Experimental Value of different
kinds of Food for Feeding Stock—Concluding Ob-
servations. : : ash ane ae : : . 216

be ELEMENTS

OF

AGRICULTURAL CHEMISTRY, &e.

CHAPTER I.

Distinction between Organic and Inorganic Substances.
The Ash of Plants—Constitution of the Organic Parts of
Plants.—Preparation and Properties of Carbon, Hydro-
gen, and Nitrogen. Meaning of Chemical Combination.

Tue object of the practical farmer is to raise
from a given extent of land the largest quantity
of the most valuable produce at the least cost, and
with the least permanent injury to the soil. The
sciences either of chemistry or geology throw light

on every step he takes or ought to take, in order te
_ effect this main object.
o#

»

14 ORGANIC AND INORGANIC BODIES~.

SECTION I.—OF THE VEGETABLE AND EARTHY OR THE
ORGANIC AND INORGANIC PARTS OF PLANTS.

In the prosecution of his art, two distinct classes
of substances engage hisattention——the living crops
he raises, and the dead earth from which they are
gathered. If he examine any fragment of an ani-
mal or vegetable, either living or dead, he will ob-
serve that it exhibits pores of various kinds ar-
ranged in a certain order—that it has a species of
internal structure—that it has various parts or or-
gans—in short, that it is what physiologists term
organized. If he examine, in like manner, a lump
of earth or rock, he will perceive no such struc-
ture. To mark this distinction, the parts of ani-
mals and vegetables, either living or dead—whe-
ther entire or in a state of decay, are called or-
ganic bodies, while earthy and stony substances
are called inorganic bodies.

Organic substances are also more or less readily
burned and dissipated by heat in the open air ; in-
organic substances are generally fixed and perma-
nent in the fire.

But the crops which grow upon it, and the soil
in which they are rooted, contain a portion of
both of these classes of substances. In all fer-

ASH OF PLANTS. 15

tile soils, there exists from 3 to 10 per cent. of ve-
getable or other matter of organic origin ; while,
on the other hand, all vegetables, as they are col-
lected for food, leave, when burned, from one-half
to twenty per cent. of inorganic ash.

If we heat a portion of soil to redness in the
open air, the organic matter will burn away, and,
in general, the soil, if previously dry, will not be
materially diminished in bulk. But if a handful
of wheat, or of wheat straw, or of hay, be burned
in the same manner, the proportion that disap-
pears is so great, that in most cases a compa-
ratively minute quantity only remains behind.
Every one is familiar with this fact who has seen
the small bulk of ash that is left when weeds, or
thorns, or trees, are burned in the field, or when
a hay or corn-stack is accidentally consumed. Yet
the ash thus left is a very appreciable quantity,
and the study of its true nature throws much light,
as we shall hereafter see, on the practical manage-
ment of the land on which any given crop is to be
made to grow.

Thus the quantity of ash left by a ton of wheat
straw is sometimes as much as 360 lbs.; by a ton
of oat straw as much as 200 lbs.; while a ton of
the grain of wheat leaves only about 40 lbs.; of the
grain of oats about 90 lbs.; and of oak wood only

16 PROPERTIES OF CARBON.

4or 5 lbs. The quantities of znorganic matter,
therefore, though comparatively small, yet, in some
eases, amount to a considerable weight in an entire
crop. The nature, source and uses of this earthy
matter will be explained in a subsequent chapter.

SECTION II.—CONSTITUTION OF THE QRGANIC PART OF
PLANTS AND ANIMALS.

The organic part of plants, when in a perfectly
dry state, constitutes therefore from 85 to 99 per
cent. of their whole weight. Of those parts of
plants which are cultivated for food, it is only hay
and straw, and a very few others, that contain as
much as 10 per cent. of inorganic matter.

This organic part consists of four substances,
known to chemists by the names of carbon, hydro-
gen, oxygen, and nitrogen. The first of these,
carbon, is a solid substance, the other three are
gases or peculiar kinds of air.

1. Carson. When wood is burned in a covered
heap, as is done by the charcoal burners, or is
distilled in iron retorts, as in making wood.-
vinegar, it is charred and converted into com-
mon wood charcoal. This charcoal is the most
usual and best known variety of carbon. It is
black, soils the fingers, and is more or less porous

PREPARATION OF HYDROGEN GAS. be

according to the kind of wood from which it has
been formed. Coke obtained by charring or dis-
tilling coal is another variety. It is generally
denser or heavier than the former, though less
pure. Black lead is a third variety, still heavier
and more impure. The diamond is the only form
in which carbon occurs in nature in a state of per-
fect purity.

This latter fact, that the diamond is pure car-
bon—that it is essentially the same subsiance with
the finest and purest lamp-black—is very remark-
able ; but it is only one of many striking circum-
stances that every now and then present themselves
before the inquiring chemist.

Charcoal, the diamond, lamp-black, and all the
other forms of carbon, burn away more or less
slowly when heated in the air, and are converted
into a kind of gas known by the name of carbonic
acid. The impure varieties leave behind them a
greater or less proportion of ash.

2. Hyproeen.—If oil of vitriol (sulphuric
-acid) be mixed with twice its bulk of water, and
then poured upon iron filings, the mixture will
speedily begin to boil up, and bubbles of gas will
rise to the surface of the liquid in great abundance.
These are bubbles of hydrogen gas. _

If the experiment be performed in a bottle, the

Q*

18 PROPERTIES OF HYDROGEN.

hydrogen which is produced will gradually drive
out the atmospheric air it contained, and will itself
take its place. Ifa bit of wax taper be tied to the
end of a wire, and when lighted be introduced into
the bottle, it will be instantly extinguished ; while
the hydrogen will take fire, and burn at the mouth
of the bottle with a pale yellow flame. If the taper
be inserted before the common air is all expelled,
the mixture of hydrogen and common air will burn
with an explosion more or less violent, and may
even shatier the bottle and produce serious acci-
dents. This experiment, therefore, ought to be
made with care. Itmay be safely made in an open
tumbler, covered by a plate or a piece of paper, till
a sufficient quantity of hydrogen is collected, when,
on the introduction of the taper, the light will be
extinguished, and the hydrogen will burn with a
less violent explosion.

This gas is also an exceedingly light substance,
rising through common air as wood does through
water. Hence, when confined in a bag made of
silk, or other light tissue, it is capable of sustaining
heavy substances in the air, and even of transport-
ing them to great heights. For this reason it is
employed for filling and elevating balloons.

Hydrogen gas is not known to occur anywhere
in nature in any sensible quantity. It is very abun-

PROPERTIES OF OXYGEN. 19

dant, as we shall hereafter see, in what by chemists
is called a state of combination.

~3. Oxyern.—When strong oil of vitriol is poured
upon black oxide of manganese, and heated in a
glass retort: or when red oxide of mercury, or
chlorate of potash, is so heated alone ; or when salt-
petre, or the same oxide of manganese, is heated
alone in an iron bottle ;—in all these cases a kind
of air is given off, which, when collected and ex-
amined by plunging a taper into it, is found to be
neither common air nor hydrogen gas. The taper,
when introduced, burns with great rapidity, and
with exceeding brilliancy, and continues to burn
till either the whole of the gas disappears, or the
taper is entirely consumed. If a living animal is
introduced, its circulation and its breathing be-
come quicker—it is speedily thrown into a fever—
it lives as fast as the taper burned—and, after afew
hours, dies from excitement and exhaustion. This
gas is not light like hydrogen, but is about one-
ninth part heavier than common air.

In the atmosphere, oxygen exists in the state of
gas. It forms about,one-fifth of the bulk of the air
we breathe, and is the substance which, in the air,
supports all animal life and the combustion of all
burning bodies. Were it by any cause suddenly
removed from the atmosphere of our globe, every

*

Ae

*

20 PROPERTIES OF NITROGEN.

living thing would perish, and all combustion
would become impossible.

4, Nrrrocen.—lf a saucer be half filled -with
milk of lime, formed by mixing slaked quicklime
with water, a very small tea-cup containing a little
burning sulphur then placed in the middle, and a
common large tumbler inverted over the whole,
the sulphur will burn for a while, and will then
gradually die out. On allowing the whole to re-
main for some time, the fumes of the sulphur will
be absorbed by the milk of lime, which willrise a
certain way into the tumbler. When the absorp-
tion has ceased, a quantity of air will remain in the
upper part of the tumbler. This air is nitrogen
gas.

If the whole be now introduced into a large
basin of water, the tumbler being held in the left
hand, the cup and saucer may be removed from
beneath. The saucer may then be inverted and
introduced with its under side into the mouth of
the tumbler, which may thus be lifted out of the
water and restored to its upright position, the
saucer serving the purpose of a cover. By carefully
removing this cover with the one hand, a lighted
taper may be introduced by the other. It will
then be seen that the taper is extinguished by this
air, and that no other effect follows. Or if a living

; ' “ihe

vie
COMPOSITION OF HAY AND OATS. Q1

animal be introduced into it, breathing will in-
stantly cease, and it will drop without signs of
hifé.

This gas possesses no other remarkable property.
It is a very little lighter than common air, and is
known to exist in large quantity in the atmosphere
only. Of the air we breathe it forms nearly four-
fifths of the entire bulk.

These three gases are incapable of being distin-
guished from common air, or from each other, by
the ordinary senses; but by the aid of the taper
they are readily recognised. Hydrogen extin-
guishes the taper, but itself takes fire; nitrogen
simply extinguishes it ; while in oxygen the taper
burns with extraordinary brilliancy and rapidity.

Of this one solid substance, carbon, and these
three gases, hydrogen, oxygen, and nitrogen, all
the organic part of vegetable and animal substances
is made up.

Into these substances, however, they enter in
very different proportions. Nearly one half the
weight of all vegetable productions which are
gathered as food for man or beast—in their dry
state—consists of carbon ; the oxygen amounts to
rather more than one third, the hydrogen to little
more than five per cent., while the nitrogen rarely

“y

™

22 CHEMICAL COMBINATION.

exceeds two and a half or three per cent. of their
weight.

- This will appear from the following table, which
exhibits the actual constitution by analysis of some
varieties of the more common crops when perfectly

dry.

Carbon. Hydrogen. Oxygen. Nitrogen. Ash.
ESV ick 2s oh ie OS 50 387 15 90
Potatoes, . . 441 58 439 12 50
Wheat Straw, . 485 52 3894 3k 70
atte ony re) Sate, 64 367 22 40

These numbers represent the weights of each
element in pounds, contained in 1000 Ibs. of the
dry hay, potatoes, &c. ; but in drying by a gentle
heat, 1000 lbs. of hay from the stack, lost 158 lbs.
of water, of potatoes wiped dry externally 722 lbs.,*
wheat straw 260 lbs., and oats 151 Ibs,

SECTION III.—OF THE MEANING OF CHEMICAL
COMBINATION.

If the three kinds of air above spoken of be
mixed together in a bottle, no change will take
place, and if charcoal in fine powder be added to

* Both potatoes and turnips contain about four-fifths of
their weight of water, or five tons of either of these roots
contain nearly four tons of water.

WOOD, ETC. ARE CHEMICAL COMPOUNDS. 23

them, still no new substance will be produced. If
we take the ash left by a known weight of hay or
wheat straw, and mix it with the proper quantities
of the four elementary substances, carbon, hydro-
gen, &c., as shewn in the above table, we shall be
unable by this means to form either hay or wheat
straw. The elements of which vegetable substances
consist, therefore, are not merely mixed together—
they are united in some closer and more intimate
manner. ‘To this more intimate state of union,
the term chemical combination is applied—the ele-
ments are said to be chemically combined.

Thus, when charcoal is burned in the air, it
slowly disappears, and forms, as already stated, a
kind of air known by the name of carbonic acid
gas, which rises into the atmosphere and disappears.
Now, this carbonic acid is formed by the union
of the carbon (charcoal), while burning, with the
oxygen of the atmosphere, and in this new air the
two elements, carbon and oxygen, are chemically
combined.

Again, ifa piece of wood ora bit of straw, in which
the elements are already chemically combined, be
burned in the air, these elements are separated and
made to assume new states of combination, in
which new states they escape into the air and be-
come invisible. When a substance is thus changed

24 CHEMICAL DECOMPOSITION.

by the action of heat, it is said to be decomposed,
or if it gradually decay and perish by exposure to
the air and moisture, it undergoes slow decompo-
sition.

When, therefore, two or more substances unite
together, so as to form a third possessing properties
different from both, they enter into chemical union
—they form a chemical combination or chemical
compound. When, on the other hand, one com-
pound body is so changed as to be converted into
two or more substances different from itself, it is
decomposed. Carbon, hydrogen, &c., are chemical-
ly combined in the interior of the plant during the
formation of wood: wood, again, is decomposed
when by the*vinegar-maker it is converted among
other substances into charcoal and wood-vinegar,
and the flour of grain when the brewer or distiller
converts it into ardent spirits.

CHAPTER Ii.

Form in which these different substances enter into Plants,
Properties of the Carbonic,’ Humic, and Ulmic Acids—ot
Water, of Ammonia, and of Nitric Acid. Constitution
of the Atmosphere.

SECTION I. FORM IN WHICH THE CARBON, ETC. ENTER
INTO PLANTS,

Ir is from their food that plants derive the car-
bon, hydrogen, oxygen, and nitrogen, of which
their organic part consists. ‘This food enters partly
by the minute pores of their roots, and partly by
those which exist in the green part of the leaf and
of the young twig. The roots bring up food from
the soil, the leaves take it in directly from the air.

Now, as the pores in the roots and leaves are
very minute, carbon (charcoal) cannot enter into
either in a solid state ; and as it does not dissolve

- gx

26 HOW CARBON, ETC. ENTER INTO PLANTS.

in water, it cannot, in the state of simple carbon,
be any part of the food of plants. Again, hydro-
gen gas neither exists in the air nor usually in the
soil—so that, although hydrogen is always found
in the substance of plants, it does not enter them
in the state of the gas above described. Oxygen
exists in the air, and is directly absorbed both by the
leaves and by the roots of plants ; while nitrogen,
though it forms a large part of the atmosphere, is
not supposed to enter directly into plants in any
considerable quantity.

The whole of the carbon and hydrogen, and the
greater part of the oxygen and nitrogen also, enter
into plants in a state of chemical combination with
other substances ; the carbon chiefly in the state of
carbonic acid, and of certain other soluble com-
pounds which exist in the soil; the hydrogen and
oxygen in the form of water: and the nitrogen in ~
those of ammonia or nitric acid. It will be neces-
sary therefore briefly to describe these several com.
pounds.

SECTION II.—OF THE CARBONIC, HUMIC, AND ULMIC ACIDS.

1. Carsontco Actp.—If a few pieces of chalk or
limestone be put into the bottom of a tumbler, and
a little spirit of salt (muriatic acid) be poured upoa

PROPERTIES OF CARBONIC ACID. 27

them, a boiling up or effervescence will take place,
and a gas will be given off, which will gradually
collect and fill the tumbler; and when produced
very rapidly, may even be seen to run over its
edges. This gas is carbonic acid. It cannot be
distinguished from common air by the eye; but if
a taper be plunged into it, the flame will imme-
diately be extinguished, while the gas remains un-
changed. This kind of air is so heavy, that it may
be poured from one vessel into another, and its
presence recognised by the taper. It has alsoa
peculiar odour, and is exceedingly suffocating, so
that if a living animal be introduced into it, life
immediately ceases. It is absorbed by water, a
pint of water absorbing or dissolving a pint of the
gas.

Carbonic acid exists in the atmosphere; it is
given off from the lungs of all living animals while
they breathe; it is also produced largely during the
burning of wood, coal, and all other combustible
bodies, so that an unceasing supply of this gas is
poured into the air. Decaying animal and vege-
table substances also give off this gas, and hence
it is always present in greater or less abundance in
the soil, and especially in such soils as are rich in
vegetable matter. During the fermentation of malt
liquors, or of the expressed juices of different fruits,

28 HUMIC AND ULMIC ACIDS.

—the apple, the pear, the grape, the gooseberry—
it is produced, and the briskness of such fermented
liquors is due to the escape of this gas. From the
dung and compost heap it is also given off; and
when put into the ground in a fermenting state,
farm-yard manure affords a rich supply of carbonic
acid to the young plant.

Carbonic acid consists of carbon and oxygen
only, combined together in the proportion of 28 of
the former to 72 of the latter, or 100 lbs. of car-
bonic acid contain 28 lbs. of carbon and 72 lbs of
oxygen.

2. Humic anp Uxtmic Acitps.—The soil always
contains a portion of vegetable matter (called hu-
mus by some writers), and such matter is always
added to it when it is manured from the farm-
yard or the compost heap. During the decay of
this vegetable matter, carbonic acid, as above
stated, is given off in large quantity, but other
substances are also formed at the same time.
Among these are the two to which the names of
humic and ulmic acids are respectively given.
They both contain much carbon, are both capable
of entering the roots of plants, and both, no doubt,
in favourable circumstances, help to feed the plant.

If the common soda of the shops be dissolved in
water, and a portion of a rich vegetable soil, or a

EXIST IN FARM-YARD MANURE. 29

bit of peat, be put into this solution, and the whole
boiled, a brown liquid is obtained. If to this brown
liquid, spirit of salt (muriatic acid) be added till it
is sour to the taste, a brown flocky powder falls to
the bottom. This brown substance is humic acid.
But if in this process we use spirit of hartshorn
(liquid ammonia), instead of the soda, ulmic acid
is obtained.

These acids exist along with other substances in
the rich brown liquor of the farm-yard, which is
so often allowed to run to waste; they are also
produced in greater or less quantity during the de-
cay of the manure after it is mixed with the soil,
and no doubt yield to the plant a portion of that
supply of food which it must necessarily receive
from the soil.

SECTION III.—OF WATER, AMMONIA, AND NITRIC ACID.

1. Warrer.—If hydrogen be prepared in a bot-
tle, in the way already described, and a gas-burner
be fixed into its mouth, the hydrogen may be
lighted, and will burn as it escapes into the air.
Held over this flame a cold tumbler will become
covered with dew, or with little drops of water.
This water is produced during the burning of the
hydrogen ; and as it takes place in pure oxygen

3%

30 COMPOSITION OF WATER.

gas as well as in the open air, this water must cori¢
tain the hydrogen and oxygen which disappear, or
must consist of hydrogen and oxygen only.

This is a very interesting fact; and were it not
that chemists are now familiar with many such, it
could not fail to appear truly wonderful that the
two gases, oxygen and hydrogen, by their union,
should form so very different a substance as water
is from either. It consists of 1 of hydrogen to 8
of oxygen, or every 9 lbs. of water contain 8 lbs,
of oxygen and 1 |b. of hydrogen.

Water is so familiar a substance, that it is unne.
cessary to dwell upon its properties. When pure,
it has neither colour, taste, nor smell. At 32° of
Fahrenheit’s* scale (the freezing point), it solidifies
into ice, and at 212° it boils, and is converted into
steam. There are two others of its properties which
are especially interesting in connection with the
growth of plants.

Ist, If sugar or salt be put into water, they disap-
pear or are dissolved. Water has the power of thus
dissolving numerous other substances in greater or
less quantity. Hence, when the rain falls and sinks
into the soil, it dissolves some of the soluble sub-

* This is the scale of the common thermometer used in
this country.

PROPERTIES OF WATER. $1

8tances it meets in its way, and rarely reaches the
roots of plantsin a pure state. So waters that rise
up in springs arerarely pure. They always con-
tain earthy and saline substances in solution, and
these they carry with them, when they are sucked
in by the roots of plants.

It has been above stated, that water absorbs
(dissolves) its own bulk of carbonic acid ; it dis-
solves also smaller quantities of the oxygen and
nitrogen of the atmosphere; and hence, when it
meets any of these gases in the soil, it becomes
impregnated with them, and conveys them into
the plant, there to serve as a portion of its food.

2d, Water is composed of oxygen and hydrogen ;
by certain chemical processes it can readily be re-
solved or decomposed artificially into these two
gases. The same thing takes place naturally in the
interior of the living plant. The roots absorb the
water, but if in any part of the plant hydrogen be
required, to make up the substance which it is the
function of that part to produce, a portion of the
water is decomposed and worked up, while the oxy-
gen is set free, or converted to some other use. So,
also, in any case where oxygen is required water is
decomposed, the oxygen made use of, and the hy-
drogen liberated. Water, therefore, which abounds
in the vessels of all growing plants, if not directly

*32 PROPERTIES OF AMMONIA.

converted into the substance of the plant, is yet a
ready and ample source from which a supply of
either of the elements of which it consists may at
any time be obtained.

It is a beautiful adaptation of the properties of
this all-pervading compound (water), that its ele-
ments should be so fixedly bound together as rare-
ly to separate in external nature, and yet to be at
the command and easy disposal of the vital powers
of the humblest order of living plants.

2. Ammonra.—If the sal-ammoniac of the shops
be mixed with quicklime, a powerful odour is im-
mediately perceived, and an invisible gas is given
off which strongly affects the eyes. This gas is
ammonia. Water dissolves or absorbs it in very
large quantity, and this solution forms the com-
mon hartshorn of the shops. The white solid
smelling-salts of the shops are a compound of am-
monia with carbonic acid,—a solid formed by the
union of two gases.

The gaseous ammonia consists of nitrogen and
hydrogen only, in the proportion of 14 of the for-
mer to 3 of the latter, or 17 lbs. of ammonia contain
3 Ibs. of hydrogen.

The chief natural source of this compound is, in
the decay of animal substances. During the pu-
trefaction of dead animal bodies ammonia is inva-
riably given off. From the animal substances of the

NATURAL AND ARTIFICIAL PRODUCTION oF. 833

farm-yard it is evolved, and from all solid and li-
quid manures of animal origin. It is also formed
in lesser quantity during the decay of vegetable
substances in the soil ; and in volcanic countries, it
escapes from many of the hot lavas, and from the
crevices in the heated rocks.

It is produced artificially by the distillation of
animal substances (hoofs, horns, &c.), or of coal.
Thousands of tons of the ammonia present in the
ammoniacal liquors of the gas-works, which might
be beneficially applied as a manure, are annually
carried down by the rivers, and lost in the sea.

The ammonia which is given off during the pu-
trefaction of animal substances rises partially into
the air, and floats in the atmosphere, till it is either
decomposed by natural causes, or is washed down
by the rains. In our climate, cultivated plants
derive a considerable portion of their nitrogen
from ammonia. It is supposed to be one of the
most valuable fertilizing substances contained in
farm-yard manure ; and as it is present in greater
proportion by far in the liquid than in the solid
contents of the farm-yard, there can be no doubt
that much real wealth is lost, and the means of
raising increased crops thrown away in the quan-
tities of liquid manure which are almost every-
where permitted to run to waste.

———

34 PROPERTIES OF NITRIC ACID.

3. Nrrric Acip—is a powerfully corrosive li-
quid known in the shops by the familiar name of
aquafortis. It is prepared by pouring oil of vitriol
(sulphuric acid) upon saltpetre, and distilling the
mixture. The aquafortis of the shops is a mixture
of the pure acid with water.

Pure nitric acid consists of nitrogen and oxygen
only ; the union of these two gases, so harmless in
the air, producing the burning and corrosive com-
pound which this is known to be.

It never reaches the roots of plants in this free
and corrosive state. It exists in many soils, and
is naturally formed in compost heaps, and in most
situations where vegetable matter is undergoing
decay in contact with the air; but it is always in
a state of chemical combination in these cases.
With potash, it forms nitrate of potash (saltpetre) ;
with soda, nitrate of soda; and with lime, nitrate
of lime ; and it is generally in one or other of these
states of combination that it reaches the roots of
plants.

Nitric acid is also naturally formed, and in some
countries probably in large quantities, by the pas-
sage of electricity through the atmosphere. The
air, as has been already stated, contains much oxy-
gen and nitrogen mixed together, but when an
electric spark is passed through a quantity of air,

PRODUCTION OF IN THE AIR. 35

a certain quantity of the two unite together che-
mically, so that every spark that passes forms a
small portion of nitric acid. A flash of lightning
is only a large electric spark ; and hence every
flash that crosses the air produces along its path a
quantity of this acid. Where thunder-storms are
frequent, much nitric acid must be produced in
this way in the air. It is washed down by the
rains, in which it has frequently been detected, and
thus reaches the soil, where it produces one or
other of the nitrates above mentioned.

It has been long observed that those parts of
India are the most fertile in which saltpetre exists
in the soil in the greatest abundance. Nitrate of
soda, also, in this country, has been found wonder-
fully to promote vegetation in many localities ;
and it is a matter of frequent remark, that vege-
tation seems to be refreshed and invigorated by
the fall of a thunder-shower. There is, therefore,
no reason to doubt that nitric acid is really bene-
ficial to the general vegetation of the globe. And
since vegetation is most luxuriant in those parts of
the globe where thunder or lightning are most
abundant, it would appear as if the natural pro-
duction of this compound body in the air, to be
afterwards brought to the earth by the rains, were
a wise and beneficent contrivance by which the

36 THE CONSTITUTION OF THE ATMOSPHERE

health and vigour of universal vegetation is in-
tended to be promoted.

It is from this nitric acid, thus universally pro-
duced and existing, that plants appear to derive a
large—probably, taking vegetation in general, the
largest—portion of their nitrogen. In all climates
they also derive a portion of this element from
ammonia ; but less from this source in tropical
than in temperate climates.*

SECTION IV.—OF THE CONSTITUTION OF THE ATMOSPHERE.

The air we breathe, and from which plants also
derive a portion of their nourishment, consists of
a mixture of oxygen and nitrogen gases, with a
minute quantity of carbonic acid, and a variable
proportion of watery vapour. Every hundred gal-
lons of dry air contain about 21 gallons of oxygen
and 79 of nitrogen. The carbonic acid amounts
only to one gallon in 2500, while the watery va-
pour in the atmosphere varies from 1 to 24 gal-
lons (of steam) in 100 gallons of common air.

The oxygen in the air is necessary to the respi-
ration of animals, and to the support of combus-
tion (burning of bodies). The nitrogen serves

* For fuller information on this point, see the Author’s
“ LECTURES on Agricultural Chemistry and Geology,” Part 1.

ADJUSTED TO ANIMAL AND VEGETABLE LIFE. 37

principally to dilute the strength, so to speak, of
the pure oxygen, in which gas, if unmixed, animals
would live and combustibles burn with too great
rapidity. The small quantity of carbonic acid af-
fords an important part of their food to plants,
and the watery vapour in the air aids in keeping
the surfaces of animals and plants in a moist and
pliant state ; while, in due season, it descends also
in refreshing showers, or studs the evening leaf
with sparkling dew.

There is a beautiful adjustment in the constitu-
tion of the atmosphere to the nature and necessi-
ties of living beings. The energy of the pure oxy-
gen is tempered, yet not too much weakened, by
the admixture of nitrogen. ‘The carbonic acid,
which alone is noxious to life, is mixed in so mi-
nute a proportion as to be harmless to animals,
while it is still beneficial to plants; and when the
air is overloaded with watery vapour, it is provided
that it shall descend in rain. ‘These rains at the
same time serve another purpose. From the sur-
face of the earth there are continually ascending
vapours and exhalations of a more or less noxious
kind ; these the rains wash out from the air, and
bring back to the soil, at once purifying the at-
mosphere through which they descend, and re-
freshing and fertilizing the land on which they fall.

4

CHAPTER IU.

Structure of plants—Mode in which their nourishment is ob-
tained—Growth and substance of plants—Production of
their substance from the food they imbibe—Mutual trans-
formations of starch, sugar, and woody fibre.

From the compound substances, described in the
preceding chapter, plants derive the greater por-
tion of the carbon, hydrogen, oxygen, and nitrogen,
of which their organic part consists. The living
plant possesses the power of absorbing these com-
pound bodies, of decomposing them in the interior
of its several vessels, and of recompounding their
elements in a different way, so as to produce new
substances,—the ordinary products of vegetable
life. Let us briefly consider the general structure
of plants, and their mode of growth.

STRUCTURE OF THE STEM AND ROOT OF PLANTS. 39

SECTION I.—OF THE STRUCTURE OF PLANTS, AND THE MODE
IN WHICH THEIR NOURISHMENT IS OBTAINED.

A perfect plant consists of three several parts,—
a root which throws out arms and fibres in every
direction into the soil,—a trunk which branches
into the air on every side,—and leaves which, from
the ends of the branches and twigs, spread out a
more or less extended surface into the surround-
ing air. Each of these parts has a peculiar struc-
ture and a special function assigned to it.

The stem of any of our common trees consists
of three parts,—the pith in the centre, the wood
surrounding the pith, and the bark which covers
the whole. The pith consists of bundles of mi-
nute hollow tubes, laid horizontally one over the
other ; the wood and inner bark, of long tubes
bound together in a vertical position, so as to be
capable of carrying liquids up and down between
the roots and the leaves. When a piece of wood
is sawn across, the ends of these tubes may be dis-
tinctly seen. The branch is only a prolongation
of the stem, and has a similar structure.

The root, immediately on leaving the trunk or
stem, has also a similar structure ; but as the root
tapers away, the pith gradually disappears, the

40 STRUCTURE OF THE LEAF.

bark also thins out, the wood softens, till the
white tendrils, of which its extremities are com-
posed, consist only of a colourless spongy mass,
full of pores, but in which no distinction of parts
can be perceived. In this spongy mass the vessels
or tubes which descend through the stem and root
lose themselves, and by them these spongy extre-
mities are connected with the leaves.

The leaf is an expansion of the twig. The fibres
which are seen to branch out from the base over
the inner surface of the leaf are prolongations of
the vessels of the wood. The green exterior por-
tion of the leaf is, in like manner, a continuation
of the bark ina very thin and porousform. The
green of the leaf, though full of pores, especially
on the under part, yet also consists of, or contains,
a collection of tubes or vessels, which stretch along
its surface, and communicate with those of the
bark.

Most of these vessels in the living plant are full
of sap, and this sap is in almost continual motion.
In spring and autumn the motion is more rapid,
and in winter it is sometimes scarcely perceptible ;
yet the sap is supposed to be rarely quite station-
ary in every part of the tree.

From the spongy part of the root the sap ascends
through the vessels of the wood, till it is diffused

FUNCTIONS OF THE LEAF. Al

over the inner surface of the leaf by the fibres
which the wood contains. Hence, by the vessels
in the green of the leaf, it is returned to the bark,
and through the vessels of the inner bark it de-
scends to the root.

Every one understands why the roots send out
fibres in every direction through the soil,—it is in
search of water and of liquid food, which the spongy
fibres suck in and send forward with the sap to the
upper parts of the tree. It is to aid these roots in
procuring food that, in the art of culture, such sub-
stances are mixed with the soil where these roots
are, as are supposed to be necessary, or at least fa-
vourable, to the growth of the plant.

It is not so obvious that the leaves spread out
their broad surfaces into the air for the same pur-
pose precisely as that for which the roots diffuse
their fibres through the soil. The only difference
is, that while the roots suck in chiefly liquid, the
leaves inhale almost solely gaseous food. In the
sunshine, the leaves are continually absorbing car-
bonic acid from the air and giving off oxygen gas.
That is to say, they are continually appropriating
carbon from the air.* When night comes, this pro-
cess ceases, and they begin to absorb oxygen and to

* Since carbonic acid, as shewn in the previous chapter,
consists only of carbon and oxygen, they retain the carbon
and reject the oxygen.

4*

42 THEY ABSORB CARBON FROM THE AIR.

give off carbonic acid. But this latter process does
not go on so rapidly as the former, so that, on the
whole, plants when growing gain a large portion of
carbon from the air. ‘The actual quantity, how-
ever, varies with the season, with the climate, and
with the kind of tree. The proportion of the whole
carbon contained by a plant, which has been de-
rived from the air, is greatly modified also by the
quality of the soil in which it grows, and by the
comparative abundance of liquid food which hap-
pens to be within reach of its roots. It has been
ascertained, however, that in our climate, on an
average, not less than from one-third to three-
fourths of the entire quantity of carbon contained
in the crops we reap from land of average fertili-
ty, is really obtained from the air.

We see then why, in arctic climates, where the
sun once risen never sets again during the entire
summer, vegetation should almost rush up from
the frozen soil—the green leaf is ever gaining
from the air and never losing, ever taking in
and never giving off carbonic acid, since no dark-
ness ever interrupts or suspends its labours.

How beautiful, too, does the contrivance of the
expanded leaf appear! ‘The air contains only
one gallon of carbonic acid in 2500, and_ this
proportion has been adjusted to the health and

SUBSTANCE OF PLANTS, 43

comfort of animals to whom this gas is hurtfal.
But to catch this minute quantity, the tree hangs
out thousands of square feet of leaf in perpetual
motion, through an ever-moving air; and thus, by
the conjoined labours of millions of pores, the
substance of whole forests of solid wood is slowly
extracted from the fleeting winds. 'The green
stem of the young shoot, and the green stalks of
the grasses, also absorb carbonic acid as the green
of the leaf does, and thus a larger supply is af-
forded when the growth is most rapid, or when
the short life of the annual plant demands much
nourishment within a limited time.

SECTION II.—-OF THE GROWTH AND SUBSTANCE OF PLANTS.

In this way the perfect plant derives its food
from the soil and from the air; but perfect
plants arise from seeds ; and the study of the en-
tire life—the career, so to speak—of a plant, pre-
sents many interesting and instructive subjects of
consideration.

‘When a portion of flour is made into dough,
and this dough is kneaded with the hand under a
stream of water upon a fine sieve, as long as the
water passes through milky, there will remain on
the sieve a glutinous sticky substance resembling

44 STARCH AND GLUTEN IN THE SEED.

birdlime, while the milky water will gradually de-
posit a pure white powder. This powder is starch,
that which remains on the sieve is gluten. Both of
these substances exist, therefore, in the flour ; they
both also exist in the grain. The starch consists
of carbon, hydrogen, and oxygen only ; the gluten,
in addition to these, contains also nitrogen.

When ground into flour, these substances serve
for food to man; in the unbruised grain they are
intended to feed the future plant in its earliest in-
fancy.

When a seed is committed to the earth, if the
warmth and moisture are favourable, it begins to
sprout. It pushes a shoot upwards, it thrusts a
root downwards, but, until the leaf expand, and
the root has fairly entered the soil, the young plant
derives no nourishment other than water, either
from the earth or from the air. It lives on the
starch and gluten contained in the seed. But these
substances, though capable of being separated from
each other by means of water, as above stated, yet
are neither of them soluble in water. Hence, they
cannot, without undergoing a previous change, be
taken up by the sap, and conveyed along the
pores of the young shoot they are destined to feed.
But it is so arranged that, when the seed first
shoots, there is produced at the base of the germ,

STARCH CHANGED INTO SUGAR. 45

from a portion of the gluten, a small quantity of
a substance (diastase) which has so powerful an
effect upon the starch as immediately to render it
soluble in the sap, which is thus enabled to take it
up and convey it by degrees, just as it is wanted, to
the shoot or to the root.* As the sap ascends, it
becomes sweet,—the starch thus dissolved changes
into sugar. When the shoot first becomes tipped
with green, the sugar is again changed into the
woody fibre, of which the stem of perfect plants
chiefly consists. By the time that the food con-
tained in the seed is exhausted,—often, as in the
potato, long before,—the plant is able to live by its
own exertions, at the expense of the air and the
soil.

This change of the sugar of the sap into woody
fibre is observable more or less in all plants. When
they are shooting fastest the sugar is most abun-
dant; not, however, in those parts which are grow-

* In malting barley, it is made to sprout a certain length,
and the growth is then arrested by heating and drying it.
Mashed barley, before sprouting, will not dissolve in water,
but when sprouted, the whole of the starch (the flour) it con-
tains dissolves readily bya gentle heat. "The diastase formed
during the germination effects this. By further heating in the
brewer’s wort, this starch is converted into sugar as it is in
the growing plant.

A6 SUGAR CHANGED INTO WOODY FIBRE.

ing, but in those which convey the sap to the grow-
ing parts. ‘Thus the sugar of the ascending sap of
the maple and the alder disappears in the leaf and
in the extremities of the twig; thus the sugar-cane
sweetens only a certain distance above the ground,
up to where the new growth is proceeding ; and
thus also the young beet and turnip abound most
in sugar, while in all these plants the sweet prin-
ciple diminishes as the year’s growth draws nearer
to a close.

In the ripening of the ear also, the sweet taste, at
first so perceptible, gradually diminishes and finally
disappears ; the sugar of the sap is here changed
into the starch of the grain, which, as above de-
scribed, is afterwards destined, when the grain be-
gins to sprout, to be reconverted into sugar for the
nourishment of the rising germ.

In the ripening of fruits a different series of
changes presents itself. The fruit is first taste-
less, then becomes sour, and at last sweet. In this
case the acid of the unripe is changed into the su-
gar of the ripened fruit.

The substance of plants,—their solid parts that
is—consist chiefly of woody fibre, the name given
to the fibrous substance, of which wood evidently
consists. It is interesting to inquire how this sub.
stance can be formed from the compounds, car-

WOODY FIBRE FORMED FROM THE Foop. 47

bonic acid and water, of which the food of plants
in great measure consists. Nor is it difficult to
find an answer.

It will be recollected that the leaf drinks in car-
bonic acid from the air, and delivers back its oxy-
gen, retaining only its carbon. It is also known
that water abounds in the sap. Hence carbon and
water are thus abundantly present in the pores or
vessels of the green leaf. Now, woody fibre con-
sists only of carbon and water chemically combined
together,—100 lbs. of dry woody fibre consisting of
50 lbs. of carbon and 50 Ibs. of water. Itis easy,
therefore, to see how, when the carbon and water
meet in the leaf, woody fibre may be produced by
their mutual combination.

If, again, we inquire how this important prin-
ciple of plants may be formed from the other sub-
stances, which enter by their roots, from the ul-
mic acid, for example, the answer is equally ready.
This acid also consists of carbon and water only,
50 Ibs. of carbon with 372 of water forming ulmic
acid, so that when it is introduced into the sap of
the plant, all the materials are present from which
the woody fibre may be produced.

Nor is it more difficult to see how starch may
be converted into sugar, and this again into woody
fibre; or how, again, sugar may be converted into

48 CONSTITUTION OF SUGAR, STARCH, ETC. .

starch in the ear of corn, or woody fibre into sugar
during the ripening of the winter pear after its re-
moval from the tree. Any one of these substances
may be represented by carbon and water only.
Thus,—

50 lbs. of carbon with 50 of water, make 100 of woody fibre.

BOMBS iret hres oe ees OD es Wie tele 872 of ulmic acid.
of cane sugar,

SHO DERI Some terns he ct se: fs eas) iv oe fe 1224 J of starch, or
of gum.

BOs. 2 lal) tir BO ay 9, 2c? OG Gi amenaean

In the interior of the plant, therefore, it is obvi-
ous that, whichever of these substances be present
in the sap, the elements are at hand out of which
any of the others may be produced. In what way
they really are produced, the one from the other,
and by what circumstances these transformations
are favoured, it would lead into too great detail to
attempt here to explain.*

We cannot help admiring to what varied pur-
poses in nature the same elements are applied, and
from how few and simple materials, substances, the
most varied in their properties, are in the living
vegetable daily produced.

* For fuller and more precise explanations on these in-
teresting topics, see the Author’s LECTURES on aes gaia
Chemistry and Geology, Part I.

<:
ya

CHAPTER IV.

Of the Inorganic Constitution of Plants—Their immediate
Source—Their Nature—Quantity of each in certain com-
mon Crops.

SECTION I.—=SOURCE OF THE EARTHY MATTER OF PLANTS
—SUBSTANCES OF WHICH IT CONSISTS.

Wuen plants are burned, they always leave
more or less of ash behind. This ash varies in
quantity in different plants, in different parts of
the same plant, and sometimes in different speci-
mens of the same kind of plant, especially if grown
upon different soils ; yet it is never wholly absent.
It seems as necessary to their existence in a state
of perfect health as any of the elements which con-
stitute the organic or combustible part of their
substance. They must obtain it therefore along
with the food on which they live: itis in fact a

5.

50 USES OF THE SOIL.

part of their natural food, since without it they
become unhealthy. Weshall speak of it therefore
as the znorganic food of plants.

We have seen that all the elements which are
necessary to the production of the woody fibre,
and of the other organic parts of the plant, may
be derived either from the air, from the carbonic
acid and watery vapour taken in by the leaves, or
from the soil, through the medium of the roots.
In the air, however, only rare particles of inor-
ganic or earthy matter are known to float, and
these in a solid form, so as to be unable to enter
by the leaves ; the earthy matter which constitutes
the ash, therefore, must be all derived from the
soil.

The earthy part of the soil, therefore, serves a
double use. It is not merely, as some have sup-
posed, a substratum in which the plant may so fix
ind root itself, as to be able to maintain its upright
position against the force of winds and tempests ;
but it is a storehouse of food also, from which the
roots of the plant may select such earthy sub-
stances as are necessary to, or are fitted to pro-
mote, its growth.

The ash of plants consists of a mixture of seve-
ral, sometimes of as many as eleven, different earthy
substances. ‘These substances are the following :—

POTASH, SODA, LIME, ETC. ol

1. Potash.—The common pearl-ash of the shops
isa compound of potash with carbonic acid ; it is
a carbonate of potash. By dissolving the pearl-
ash in water, and boiling it with quicklime, the
carbonic acid is separated, and potash alone, or
caustic potash, as it is often called, is obtained.

2. Soda.—The common soda of the shops is a
carbonate of soda, and by boiling it with quick-
lime, the carbonic acid is separated, as in the case
of pearl-ash.

3. Lime.—This is familiar to every one as the
lime-shells, or unslaked lime of the limekilns. The
unburned limestone is a carbonate of lime; the car-
bonic acid in this case being separated by the
roasting in the kiln.

4, Magnesia.—This is the calcined magnesia of
the shops. The uncalcined is a carbonate of mag-
nesia, from which heat drives off the carbonic acid.

5. Salica.—This is the name given by chemists
to the substance of flint, quartz, and of siliceous
sands and sandstones.

6. Alumina is the pure earth of alum, ob-
tained by dissolving alum in water, and adding
liquid ammonia (hartshorn) to the solution. It
. forms about two-fifths of the weight of porcelain
and pipe-clays, and of some other very stiff kinds
of clay.

52 SULPHUR AND SULPHURIC ACID.

7. Oxide of Ironn—The most familiar form of
this substance is the rust that forms on metallic
iron in damp places. It is a compound of iron
with oxygen, hence the name oarde.

8. Owide of Manganese is a brown powder,
which consists of oxygen in combination with a
metal resembling iron, to which the name of man-
ganese is given. It exists in plants, and in soils
only in very small quantity.

9. Sulphur.—This substance is well known. It
generally exists in the ash in the state of sulphuric
acid (oil of vitriol), which is a compound of sul-
phur with oxygen. It does not always exist in
living plants, however, in this state.

Sulphuric acid forms with potash a sulphate of
potash,—with soda, sulphate of soda (or Glauber’s
salts),—with lime, sulphate of lime (gypsum),—with
magnesia, sulphate of magnesia (Epsom salts),—
with alumina, sulphate of alumina,—and with oxide
of iron, sulphate of tron or green vitriol. When the
sulphate of potash is combined with sulphate of
alumina, it forms common alum.

10. Phosphorus is a soft pale yellow substance
which readily takes fire in the air, and gives off,
while burning, a dense white smoke. The white
fumes which form this smoke are a compound of
phosphorus with oxygen obtained from the air,

PHOSPHORIC ACID AND SULPHUR. #53

and are called phosphoric acid. In the ash of
plants the phosphorus is found in the state of phos-
phoric acid, though it probably does not all exist
in the living plant in that state.

Phosphoric acid forms phosphates with potash,
soda, lime, and magnesia. When bones are burned,
a large quantity of a white earth remains (bone
earth), which is a phosphate of lime, consisting of
lime and phosphoric acid. Phosphate of lime is
generally present in the ash of plants; phosphate
of magnesia is contained most abundantly in the
ash of wheat and other varieties of grain.

11. Chlorine.—This is a very suffocating gas,
which gives its peculiar smell to chloride of lime,
and is used for bleaching and disinfecting. It is
readily obtained by pouring muriatic acid (spirit
of salt) on the black oxide of manganese of the
shops. In combination with the metallic bases of
potash, soda, lime, and magnesia, it forms the
chlorides of potassium, sodium (common salt),
calcium and magnesium,* and in one or other of
these states it generally enters into the roots of
plants, and exists in their ash.

* Potash, soda, lime, and magnesia, are compounds of the
metals here named with oxygen. Itis a very striking fact,
that the suffocating gas chlorine, when combined with sodi-
um, ametal which takes fire when placed upon water, should
form the mee and necessary condiment, common salt.

54 THE QUANTITY OF ASH VARIES

Such are the inorganic substances usually found
mixed or combined together in the ash of plants.
It has already been observed, that the quantity of
ash left by a given weight of vegetable matter
yaries with a great many conditions. This fact
deserves a more attentive consideration.

SECTION II.—OF THE DIFFERENCE IN THE QUANTITY OF
ASH.

1. The quantity of ash yielded by different
plants is unlike. Thus 1000 lbs. of

Wheat _leave 12 lbs. Barley leave 25 lbs.
Oats shee tiro0 ADS. Potatoes oe /Sdbe:
UMTS fetes 2.0 TDS, Carrots 2+ 5) hae

Red Clover ... 16 lbs. White Clover... 17 lbs.
Rye Grass ... 17 lbs. .

So that the quantity of inorganic food required
by different vegetables is greater or less according
to their nature; and if a soil be of such a kind
that it can yield only a small quantity of this in-
organic food, then only those plants will grow
well upon it which require the least. Hence,
trees may often grow where arable crops fail to
thrive, because many of them require and contain
very little inorganic matter. Thus while 1000 lbs.
of elm wood leave 19 lbs. and of poplar 20 Ibs. of

WITH THE SPECIES AND THE PART. 3]

ash, the same weight of the willow leaves only 44
Ibs., of the beech 4 lbs., of the birch 33 lbs., of dif-
ferent pines less than 3 lbs., and of seit oak only
2 Ibs. of ash when burned.

2. The quantity of inorganic matter varies in
different parts of the same plant. 'Thus while
1000 lbs. of the turnip root sliced and dried in
_the air leave 70 Ibs. of ash, the dried leaves give
130 Ibs. ; and while the grain of wheat yields only
12 lbs. wheat straw will yield 60 lbs. of earthy
matter. So, though the willow and other woods
leave little ash, as above stated, yet the willow
leaf leaves 82 lbs., the beech leaf 42 lbs., the birch
50 Ibs., the different pine leaves 20 lbs. to 30 lbs.,
and the leaves of the elm as much as 120 lbs. of
incombustible matter when burned in the air.

Most of the inorganic Bovis therefore, which

is withdrawn from the soil in ag@fop of corn is re-

e skilfal husbandman, in

turned to it again, Bj :
the fermented straw, the same way as nature,
in causing the trees periodically to shed their
leaves, returns with them to the soil a very large
portion of the soluble inorganic substances which
had been drawn from it by the roots during the
season of growth.

Thus an annual top-dressing is given to the
land where forests grow ; and that which the roots

56 AND WITH THE VARIETY OF THE PLANT.

from spring to autumn are continually sucking
up, and carefully collecting from considerable
depths, winter strews again on the surface, so as,
in the lapse of time, to form a soil which cannot
fail to prove fertile,—because it is made up of those
very materials of which the inorganic substance of
former races of vegetables has been entirely com-
posed.

2. The quantity of inorganic matter often differs
in different specimens of the same plant. 'Thus,
1000 lbs. of wheat straw, grown at different places,
gave to four different experimenters 43, 44, 35,
and 155 lbs. of ash respectively. Wheat straw,
therefore, does not always leave the same quantity
of ash.

To what is this difference owing? Is it to the
nature of the soil, or does it depend upon the va-
riety of wheat ene upon? It seems to
depend partly upon both. s, on the same field,
in Ravensworth dale, Yorkshire, on a rich clay soil
abounding in lime, the Golden Kent and Flanders
Red wheats were sown in the spring of 1841. The
former gave an excellent crop, while the latter was
a total failure, the ear containing 20 or 30 grains
only of poor wheat. The straw of the former left
165 lbs. of ash from 1000 lbs., that of the latter only
120 lbs. Something, therefore, depends upon the

WHENCE THESE DIFFERENCES ? 57

variety. But as from the straw of a good wheat
crop grown near Durham this last summer on a
clay loam I obtained only 66 lbs. of ash, I am per-
suaded that the very wide variations in the quanti-
ty of ash left, by different wheat straws, must be de-
pendent in some considerable degree upon the soil.

The truth, so far as it can as yet be made out,
seems to be this—that every plant must have a
certain quantity of inorganic matter to make it
grow in the most healthy manner ;—that it is capa-
ble of living, growing, and even ripening seed
with very much less than this quantity ;—but that
those soils will produce the most perfect plants
which can best supply all their wants,—and that
the best seed will be raised in those districts where
the soil, without being too rich or rank, yet can
yield both organic and inorganic food in such
proportions as to maintain the corn plants in their
most healthy condition.

SECTION III,—OF THE QUALITY OF THE ASH OF PLANTS,

But much also depends upon the quality as well
as upon the quantity of the ash. Plants may leave
the same weight of ash when burned, and yet the
nature of the two specimens of ash, the kind of
matter of which they respectively consist, may be

58 QUALITY OF THE ASH VARIES.

very different. The ash of one may contain much
lime, of another much potash, of a third much
soda, while in a fourth much silica may be pre-
sent. Thus 100 lbs. of the ash of bean straw con-
tain 531 lbs. of potash, while that of barley straw
contains only 34 Ibs. in the hundred ; and, on the
other hand, the same weight of the ash of the lat-
ter contains 731 lbs. of silica, while in that of the
former there are only 7% Ibs.

The quality of the ash seems to vary with the
same conditions by which its quantity is affected.
Thus—

1. It varies with the kind of plant. 100 lbs. of
the ash of wheat, barley, and oats, for example,

contain, respectively,
Wheat. Barley. Oats.

Potash, . 19 12 6
Soda, 204 12 5
Lime, 8 4} 3
Magnesia, 8 8 24
Alumina, 2 1 4
Oxide of Iron, : . 0 trace 13
Silica i). Meaihs Wig ce a 50 763
Sulphuric acid, _.. ; 4 24 13
Phosphoric acid, . . 33 9 3
Chlorine, . : ; 1 1 &

100 100 100

A comparison of the several numbers opposite
to each other in these three columns, shews how

MORE POTASH AND SODA IN WHEAT. 59

unlike the quantities of the different substances
are, which are contained in an equal weight of the
ash of these three varieties of grain. The ash of
wheat contains 19 Ibs. of potash in the 100 lbs.,
while that of oats contains only 6 lbs. In wheat
are 20+ per cent. of soda, in oats only 5 per cent.
Wheat also contains more sulphuric acid than
either of the other grains, while barley contains a
still greater predominance of phosphoric acid.

It is thus evident that a crop of wheat will carry
off from the soil—even suppose the whole quantity
of ash left by each the same in weight—very dif-
ferent quantities of potash, soda, &c. from a crop
of oats. It will take more of these, of sulphuric
acid, and of certain other substances, from the soil.
It will, therefore, exhaust the soil more of these
substances—as barley and oats will of others—
hence one reason why a piece of land may suit one
of these crops and not suit the others. That which
cannot grow wheat may yet grow oats. Hence,
also, two successive crops of different kinds of grain
may grow where it would greatly injure the soil to
take two in succession of the same kind, especially
of either wheat or barley ; and hence we likewise
deduce one natural reason for a rotation of crops.
The surface soil may be so far exhausted of one
inorganic substance, that it cannot afford it in

60 THE ASH OF WHEAT AND OTHER STRAWS

sufficient quantity during the present season to
bring a given crop to healthy maturity, and yet
may, by natural processes, be so far supplied again,
during the intermediate growth of certain other
crops, as to be prepared in a future season fully to
supply all the wants of the same crop, and to yield
a plentiful harvest.

2. The kind of inorganic matter varies with the
part of the plant. ‘Thus the grain and the straw
of the corn plants contain very unlike quantities
of the several inorganic constituents, as will ap-
pear by comparing the follewing with the preced-

ing table :—
Wheat Straw. Barley Straw. Oat Straw

Potash, . 4 : 4 34 15
Soda, ; ; : i 1 trace.
Lime, , ‘ seu Mel 104 23
Magnesia, 1 14 3
Alumina, . : « 28 3 trace.
Oxide of Iron, . ;
Oxide of manganese, | ; 3 rai
Silica, ‘ : 8! 734 80
Sulphuric acid, Pb ftyt 2 13
Phosphoric acid, . 5 3 }
Chlorine, . ‘ ue | 1k trace.

100 100 100

Not only are the quantities of the several in-
organic substances contained in these different

VARIES IN QUALITY WITH THE SOIL. 61

kinds of straw very unlike—especially the pro-
portions of potash, lime, and phosphoric acid in
each—but these quantities are also very different
from those exhibited by the numbers in the pre-
ceding table as contained in the three varieties of
grain. In this difference we see, further, one rea-
son why the same soil which may be favourable to
the growth of straw may not be equally propitious
to the growth of the ear. Wheat straw contains
little either of potash or of soda; the ash of the
grain contains a large proportion ; while the ash of
the oat-straw, on the other hand, contains a
much larger proportion of potash than that of its
own ear does. It is clear, therefore, that the roots
may, in certain plants and in certain soils, succeed
in fully nourishing the straw while they cannot
fully ripen the ear; or contrariwise, where they
feed but a scanty straw, may yet be able to give
ample sustenance to the filling ear.*

3. The quality of the ash varies also with the
soil in which it grows. This will be understood
from what is stated above. Where the soil is
favourable, the roots can send up into the straw

* And occasionally do give; for a plump grain, and even
a well-filled ear, are not unfrequently found where the straw
is unusually deficient.

6

62 AND WITH THE AGE OF THE PLANT.

every thing which the ‘healthy plant requires ;
when it is poorly supplied with some of those in-
organic constituents which the plant desires, life
may be prolonged, a stunted or unhealthy crop
may be raised, in which the kind, and perhaps the
quantity, of ash left in burning will necessarily be
different from that left by the same species of
plant grown under more favouring circumstances.
Of this fact there can be no doubt, though the
extent to which such variations may take place
without absolutely killing the plant, has not yet
been by any means made out.

4. It varies also with the period of a plant’s
growth, or the season at which it is reaped. Thus,
inthe young leaf of the turnip and potato, a greater
proportion of the inorganic matter they contain con-
sists of potash than in the old leaf. The same is
true of the stalk of wheat ; and similar differences
prevail in almost every kind of plant at different
stages of its growth.

The enlightened agriculturist will perceive that
all the facts above stated have a perceptible con-
nection with the ordinary processes of practical
agriculture, and tend to throw considerable light
on some of the principles by which they ought to
be regulated. One illustration of this is exhibited
in the following section.

ASH IN A SERIES OF CROPS. 63

SECTION IV.—QUANTITY OF INORGANIC MATTER CONTAINED
IN AN ORDINARY CROP OR SERIES OF CROPS.

The importance of the inorganic matter con-
tained in living vegetables, or in vegetable sub-
stances when reaped and dry, will appear more
distinctly if we consider the actual quantity car-
ried off from the soil in a series of crops.

In a four-years’ course of cropping, in which the
crops gathered amount per acre to—

1st year, T'wrnips, 25 tons of bulbs, and 7 tons of tops.

2d year, Barley, 38 bushels of 63 Ibs. each, and 1 ton of

straw.

3d year, Clover and Rye-Grass, 1 ton of each in hay.

Ath year, Wheat, 25 bushels of 60 lbs., and 1 tons of straw.

The quantity of inorganic matter carried off
in the four crops, supposing none of them to be
eaten on the land, amounts to—

Potash, )).!) <1), Qillbsy ywSilicay....)\.\:.. 318 dbs
Boda wee. 130. Sulphuric acid, 111. “
Dime ie oaa eae. Phosphoric acid, 61 ‘
Magnesia, . 42 “ Chlorine, SG » Sian
eouminaneyar | LL! nai
Total, 1240

or, in all, about 11 cwt.—of which gross weight
the different substances form very unlike pro-
portions.

A still clearer idea of these quantities will be

64 HOW TO BE REPLACED.

obtained by a consideration of the fact, that if we
carry off the entire produce, and return none of it
again in the shape of manure, we must or ought
in its stead, if the land is to be restored to its
original condition, add to each acre every four

years :—
Pearlor Pot-ash, . ; 390 lbs. at acostofl.3 10 0
Crystallized carbonate of soda, 440 ey 2 5 0
Common salt, . : ; 65 wats 0 2 0
Quick (burned) lime, i 240 Bb OS ae
Epsom salts, . ; ey 250 Git 1. Soy
Alam is 5 ‘ 5 i 84 08.0
Bone dust, : ; A 260 016 0

Total, 1729 £80 TO

Several observations suggest themselves from
a consideration of the above statements : first, that
if this inorganic matter be really necessary to the
plant, the gradual and constant removal of it from
the land ought by and by to impoverish the soil
of this inorganic food; second, that the more of
what grows upon the land we can again return
to it in manure, the less will this deterioration be
perceptible ; third, that as many of these inorganic
substances are readily soluble in water, the liquid
manure of the farm-yard, so often allowed to
run to waste, carries with it to the rivers much of
the saline matter that ought to be returned to the

DETERIORATION OF LAND OFTEN SLOW. 65

land ; and, lastly, that the utility and often indis-
pensable necessity of certain artificial manures is
owing, it may be, in some districts, to the natu-
ral poverty of the land in certain inorganic substan-
ces,—but more frequently to a want of acquaint-
ance with the facts above stated, among practical
men, and to the long continued neglect and waste
which has been the natural consequence.

In certain districts, the soil and subsoil contain
within themselves an almost unfailing supply of
some of these inorganic substances, so that the
waste is long in being felt ; in others they become
sooner exhausted, and hence call for more care,
and, when exhausted, for a more expensive culti-
vation, in order to replace them.

One thing is of essential importance to be re-
membered by the practical farmer—that the dete-
rioration of land is often an exceedingly slow
process. In the hands of successive generations
a field may so imperceptibly become less valuable,
that a century even may elapse before the change
prove such as to make a sensible diminution in
the valued rental. Such slow changes, however,
have been seldom recorded; and hence the prac-
tical man is occasionally led to despise the clear-
est theoretical principles, because he has not hap-

pened to see them verified in his own limited ex-
6*

|

66 VALUE OF A HISTORY OF TILLAGE.

perience, and to neglect therefore the suggestions
and the wise precautions which these principles
lay before him.

The agricultural history of tracts of land of
different qualities, shewing how they had been
cropped and tilled, and the average produce in
grain, hay, straw, and other crops, every five years,
during an entire century, would be invaluable ma-
terials both to theoretical and to practical agri-
culture.

CHAPTER V.

Of Soils—their Organic and Inorganic Portions—Saline
Matter in Soils—Examination and Classification of Soils
—Diversities of Soils and Subsoils.

Sorts consist of two parts,—of an organic part,
which can readily be burnt away when the soil
is heated to redness; and of an inorganic part,
which is fixed in the fire, and which consists en-
tirely of earthy and saline substances.

SECTION I.—OF THE ORGANIC PART OF SOILS.

The organic part of soils is derived chiefly from
the remains of vegetables and animals which have
lived and died in or upon the soil, which have
been spread over it by rivers and rains, or which

68 THE ORGANIC PART OF SOILS VARIES.

have been added by the hand of man for the pur-
pose of increasing its natural fertility.

This organic part varies very much in quantity
in different soils. In some, as in peaty soils, it
forms from 50 to 70 per cent. of their whole weight,
and even in some rich long cultivated lands it has
been found, in a few rare cases, to amount to as
much as 25 per cent. In general, however, it is
present in much smaller proportion, even in our
best arable lands. Oats and rye will grow upon
a soil containing only 1} per cent., barley when
2 to 3 are present, while good wheat soils gene-
rally contain from 4 to 8 percent. In stiff and
very clayey soils 10 to 12 per cent. may occasion-
ally be detected. In very old pasture lands and
in gardens, vegetable matter occasionally accumu-
lates, so as to overload the upper soil.

To this organic matter in the soil the name of
humus has been given by some writers. It con-
tains or yields to the plant the ulmic and humic
acids described in a previous chapter. It supplies
also, by its decay, in contact with the air which
penetrates the soil, much carbonic acid, which is
supposed to enter the roots and minister to the
growth of living vegetables. During the same de-
cay ammonia is likewise produced,—and in larger
quantity, if animal matter be present in consider-

INFLUENCE OF THE ORGANIC PART. 69

able abundance,—which ammonia is found to pro-
mote vegetation in a remarkable manner. Other
substances, more or less nutritious, are also formed
from it in the soil. These enter by the roots, and
contribute to nourish the growing plant, though
the extent to which it is fed from this source is
dependent, both upon the abundance with which
these substances are supplied, and upon the nature
of the plant itself, and of the climate in which it
grows.

Another influence of this organic portion of the
soil, whether naturally formed in it, or added to
it as manure, is not to be neglected. It contains,
—as we have seen that all vegetable substances
do,—a considerable quantity of inorganic, that is,
of saline and earthy matter, which is liberated
as the organic part decays. Thus living plants
derive from the remains of former races buried
beneath the surface, a portion of that inorganic
food which can only be obtained in the soil,—and
which, if not thus directly supplied, must be sought
for by the slow extension of their roots through
a greater depth and breadth of the earth in which
they grow. The addition of manure to the soil,
therefore, places within the easy reach of the roots
not only organic but inorganic food also.

70 SALINE INGREDIENTS OF SOILS.

SECTION II.—OF THE INORGANIC PART OF SOILS.

The inorganic part of soils,—that which remains
behind, when every thing combustible is burned
away by heating it to redness in the open air,—
consists of two portions, one of which is soluble in
water, the other insoluble. The soluble consists
of saline substances, the insoluble of earthy sub-
stances,

1. The saline or soluble portion.—In this coun-
try the surface soil of our fields, in general, con-
tains very little soluble matter. If a quantity of
soil be dried in an oven, a pound weight of it taken,
and a pint anda half of pure boiling rain-water
poured over it, the whole well stirred and allowed
to settle,—the clear liquid, when poured off and
boiled to dryness, may leave from 2 to 20 grains
of saline matter. This saline matter will con-
sist of common salt, gypsum, sulphate of soda
(Glauber’s salts), sulphate of magnesia (Epsom
salts), with traces of the chlorides of calcium, mag-
nesium, and potassium, and of the nitrates of pot-
ash, soda, and lime.* It is from these soluble sub-
stances that the plants derive the greater portion

* See pages 51 and 52, where these substances are described.

SALINE INCRUSTATIONS. 71

of the saline ingredients contained in the ash they
leave when burned.

Nor must the quantity thus obtained from a soil
be considered too small to yield the whole supply
which a crop requires. A single grain of saline
matter in every pound of a soil a foot deep, is
equal to 500 lbs. in an acre, which is more than is
carried off from the soil in 10 rotations (40 years),
where only the wheat and barley are sent to mar-
ket, and the straw and green crops are regularly
returned to the land in the manure.*

In some countries, indeed in some districts of
our own country, the quantity of saline matter in
the soil is so great, asin hot seasons to form a dis-
tinct incrustation on the surface. This may often
be seen in the neighbourhood of Durham; and is
more especially to be looked for in districts where
the subsoil is sandy and porous, and more or less
full of water. In hot weather the evaporation on
the surface causes the water to ascend from the
porous subsoil: and as this water always brings
with it a quantity of saline matter,—which it leaves
behind when it rises in vapour,—it is evident that
the longer the dry weather and the consequent

* A further portion, it will be recollected, is carried off

in the cattle that are sent to market,—this is here ne-
glected.

12 EFFECT OF RAIN AND DROUGHTS.

evaporation from the surface continue, the thicker
the incrustations will be, or the greater the accu-
mulation of saline matter on the surface. Hence,
where such a moist and porous subsoil exists in
countries rarely visited by rain, as in the plains
of Peru, of Egypt, or of India, the country is
whitened over in the dry season with an unbroken
covering of the different saline substances above
mentioned.

When rain falls, the saline matter is dissolved,
and descends again to the subsoil,—in dry weather
it reascends. ‘Thus the surface soil of any field
will contain a larger proportion of soluble inor-
ganic matter in the middle of a hot season tham
in one of even ordinary rain; and hence the fine
dry weather which, in early summer, hastens the:
growth of corn, and later in the season favours its
ripening, does so, among its other modes of ac-
tion, by bringing up to the roots from beneath a.
more ready supply of those saline compounds:
which the crop requires for its healthful growth.

2. The earthy or insoluble portion.—The earthy
or insoluble portion of soils rarely constitutes
less than 95 lbs. in a hundred of their whole
weight. It consists chiefly of szlica in the form
of sand, of alumina in the form of clay, and of
lime in the form of carbonate of lime. It is rarely

CLASSIFICATION OF SOILS. 73

free, however, from one or two per cent. of oxide
of iron ; and where the soil is of a red colour, this
oxide is present in a still larger quantity. A trace
of magnesia also may be almost always detected,
and a minute quantity of phosphate of lime. The
principal ingredients, however, of the earthy part
of all soils are sand, clay, and lime ; and soils are
named or classified according to the quantities of
each of these three they may happen to contain.

If an ounce of soil be boiled in a pint of water
till it is perfectly softened and diffused through
it, and, after shaking, the heavy parts be allowed
to settle for a few minutes, the sand will subside,
while the clay—which is in finer particles, and
is less heavy—will still remain floating. If the
water and clay be now poured into another vessel,
and be allowed to stand till the water has become
clear, the sandy part of the soil will be on the bot-
tom of the one vessel, the clayey part on that of
the other, and they may be dried and weighed se-
parately.

If 100 grains of dry soil leave no more than 10
of clay, it is called a sandy soil ; if from 10 to 40,
a sandy loam; if from 40 to 70, a loamy soil ; if
from 70 to 85, aclay loam ; from 85 to 95, a strong
clay soil ; and when no sand is separated at all by
this process, it is a pure agricultural clay.

7

74 HOW TO ESTIMATE THE LIitE.

The strong clay soils are such as are used for
making tiles and bricks; the pure agricultural
clay is such as is commonly employed for the ma-
nufacture of pipes (pipe clay).

Soils consist of these three substances mixed to-
gether. The pure clay is a chemical compound of
silica and alumina, in the proportion of about 60 of
the former to 40 of the latter. Pure clay soilsrarely
occur—it being well known to all practical men,
that the strong clays (tile clays) which contain from
5 to 15 per cent. of sand, are brought into arable
cultivation with the greatest possible difficulty.
It will rarely happen, therefore, that arable land
will contain more than 30 to 35 of alumina.

If a soil contain more than 5 per cent. of carbo-
nate of lime, it is called a marl; if more than 20
per cent., it is a calcareous soil. Peaty soils, of
course, are those in which the vegetable matter
predominates very much.

To estimate the lime, a quantity of the soil
should be burned in the air, and a weighed por-
tion, 100 or 200 grains, diffused through half a
pint of cold water mixed with half a wine glass-
ful of spirit of salt (muriatic acid), and allowed
to stand for a couple of hours, with occasional
stirring. The water is then poured off, the soil

DIVERSITIES OF SOILS. 75

dried, heated to redness as before, and weighed :
the loss is nearly all lime.*

The quantity of vegetable or other organic mat-
ter is determined by drying the soil well upon
paper in an oven, and then burning a weighed
quantity in the air: the loss is nearly all organic
matter. In stiff clays this loss will comprise a
portion of water, which is not wholly driven off
from such soils by drying upon paper in the way
described.

SECTION III.—OF THE DIVERSITIES OF SOILS AND

SUBSOILS.

Though the substances of which soils chiefly
consist are so few in number, yet every practical
man knows how very diversified they are in cha-
racter—how very different in agricultural value.
Thus, in some of our southern counties, we have
a white soil, consisting apparently of nothing else
but chalk ; in the centre of England a wide plain
of dark red land; in the border counties of Wales,
and on many of our coal-fields, tracts of country
almost perfectly black; while yellow, white, and
brown sands give the prevailing character to the

* Unless the soil happen to contain a large quantity of
magnesia, which is rarely the case.

76 KNOWLEDGE OF SUBSOILS IMPORTANT.
%

soils of other districts. Such differences as these
arise from the different proportions in which the
sand, lime, clay, and the oxide of iron which co-
lours the soils, have been mixed together.

But how have they been so mixed—differently
in different parts of the country. By what natural
agency !—for what end ?

Again, the soil on the surface rests on what is
usually denominated the subsoil. This, also, is
very various in its character and quality. Some-
times it is a porous sand or gravel, through which
water readily ascends from beneath or sinks in
from above ; sometimes it is light and loamy like
the soil that rests upon it; sometimes stiff and
impervious to water.

The most ignorant farmer knows how much the
value of a piece of land depends upon the cha-
racters of the surface soil,—the intelligent im-
prover understands best the importance of a fa-
vourable subsoil. “ When I came to look at this
farm,” said an excellent agriculturist to me,
“it was spring, and damp growing weather: the
grass was beautifully green, the clover shooting
up strong and healthy, and the whole farm had
the appearance of being very good land. Had I
come in June, when the heat had drunk up nearly

HOW SUBSOILS COME TO DIFFER. vi |

all the moisture which the sandy subsoil had left
in the surface, I should not have offered so much
rent for it by ten shillings an acre.” He might
have said also, “ Had I taken a spade, and dug
down 18 inches in various parts of the farm, I
should have known what to expect in seasons of
drought.”

But how come subsoils thus to differ—one from
the other—and from the surface soil that rests
upon them? Are there any principles by which
such differences can be accounted for—by which
they can be foreseen—by the aid of which we can
tell what kind of soil may be expected in this or
that district—even without visiting the spot—and
on what kind of subsoil it is likely to rest ?

Geology explains the cause of all such differ-
ences, and supplies us with principles by which
we can predict the general quality of the soil and
subsoil in the several parts of entire kingdoms ;—
and where the soil is of inferior quality and yet
susceptible of improvement, the same principles
indicate whether the means of improving it are
likely, in any given locality, to be attainable at a
reasonable cost,

It will be proper shortly to illustrate these di-
rect relations ef geology to agriculture.

7

CHAPTER VI.

Direct relations of Geology to A griculture—Origin of Soils—
Causes of their Diversity—Relation to the Rocks on which
they rest—Constancy in the relative Position and Charac-
ter of the Stratified Rocks—Relation of this fact to Prac-
tical Agriculture—General Character of the Soils upon
these Rocks.

Groxoey is that branch of knowledge which em-
bodies all ascertained facts in regard to the nature
and internal structure, both physical and chemi-
cal, of the solid parts of our globe. This science
has many close relations with practical agricul-
ture, and especially throws much light on the na-
ture and origin of soils,—on the cause of their di-
versity,—on the kind of materials by the admix-
ture of which they may be permanently improved,
—and on the sources from which these materials
may be derived.

GENERAL COMPOSITION OF ROCKS. 719

SECTION I.—OF THE ORIGIN OF SOILS.

If we dig down through the soil and subsoil to
a sufficient depth, we always come sooner or later
to the solid rock. In many places the rock ac-
tually reaches the surface, or rises in cliffs, hills,
or ridges, far above it. The surface (or crust) of
our globe, therefore, consists everywhere of a solid
mass of rock, overlaid with a covering, generally
thin, of loose materials. The upper or outer part
of these loose materials forms the soil.

The geologist has travelled over great part of
the earth’s surface, has examined the nature of
the rocks, which everywhere repose beneath the
soil, and has found them to be very unlike in
character, in composition, and in hardness—in dif-
ferent countries and districts. In some places he
has met with a sandstone, in other places a lime-
stone, in others a slate or hardened rock of clay.
But a careful comparison of all the kinds of rock
he has observed, has led him to the general conclu-
sion, that they are all either sandstones, limestones,
or clays of different degrees of hardness, or a mix-
ture in different proportions of two or more of these
kinds of matter.

When the loose covering of earth is removed

BO THE CRUMBLING OF ROCKS

from the surface of any of these rocks, and it is
left exposed, summer and winter, to the action of
the winds and r ins and frosts, it may be seen
gradually tocrumbleaway. Such is the case even
with many of those which, on account of their
greater hardness, are employed as building-stones,
and are kept generally dry ; how much more with
such as are less hard, and, beneath a covering of
moist earth, are continually exposed to the action
of water. ‘The natural crumbling of a naked rock
thus gradually covers it with loose materials, in
which seeds fix themselves and vegetate, and which
eventually forms a soil. The soil thus produced
partakes necessarily of the character of the rock
on which it rests, and to the crumbling of which
it owes its origin. If the rock be a sandstone the
soil is sandy ; if a claystone, it is a more or less
stiff clay ; if a limestone, it is more or less calca-
reous; andif the rock consist of any peculiar mix-
ture of those three substances, a similar mixture
is observed in the earthy matter into which it has
crumbled.

Led by this observation, the geologist, after
comparing the rocks of different countries with
one another, compared next the soils of various
districts with the rocks on which they immediate-
ly rest. The general result of this comparison has

GIVES RISE TO SOILS. 81

been, that in almost every country the soils have
as close a resemblance to the rocks beneath them—
as the loose earth derived from the crumbling of
a rock before our eyes, bears to the rock of which
it lately formed a part. 'The conclusion therefore
is irresistible, that soils, generally speaking, have
been formed by the crumbling or decay of the so-
lid rocks,—that there was a time when these rocks
were uncovered by any loose materials,—and that
the accumulation of soil has been the slow result
of the natural degradation (wearing away) of the
solid crust of the globe.

SECTION II.—SAUSE OF THE DIVERSITY OF SOILS.

The cause of the diversity of soils in different
districts, therefore, is no longer obscure. If the
subjacent rocks in two localities differ, the soils
met with there must differ also, and in an equal
degree.

But why, it may be asked, do we find the soil in
some countries uniform, in mineral* character and
general fertility, over hundreds or thousands of
square miles, while in others it varies from field

* That is, containing the same general proportions of
sand, clay, lime, &c., or coloured red by similar quantities of
oxide of iron.

82 STRATIFIED AND UNSTRATIFIED ROCKS.

to field,—the same farm often presenting many
well marked differences both in mineral character
and in agricultural value? ‘The cause of this is to
be found in the mode in which the different rocks
are observed to lie, one upon or by the side of
the other.

Geologists distinguish rocks into two classes,
the stratified and the unstratified. 'The former are
found lying over each other in separate beds or
strata, like the leaves of a book, when laid on its
side, or like the layers of stones in the wall of a
building; the latter form hills, mountains, or
sometimes ridges of mountains, consisting of one
more or less solid mass of the same material, in
which no layers or strata are any where distinctly
perceptible. ‘Thus, in the following diagram,
(No. 1,) A and B represent unstratified masses,
in connection with a series of stratified deposits,
1, 2, 3, lying over each other in a_ horizontal
position. On A one kind of soil will be formed,
on C another, on B a third, and on D a fourth,—
the rocks being all different from each other.

2. St

If from A to D be a wide valley of many miles in

INCLINATION OF STRATA. 83

extent, the undulating plain at the bottom of the
valley, resting in great part on the same rock (2),
will be covered by a similar soil. On B the soil
will be different for a short space; and again at
€, and on the first ascent to A, where the rock
(3) rises to the surface. In this case the stratified
rocks lie horizontally ; and it is the undulating
nature of the country which, bringing different
kinds of rock to the surface, causes a necessary
diversity of soil.

But the degree of inclination, which the beds
possess, is a more frequent cause of variation in
the characters of the soil in the same district, and
even at shorter distances. This is shewn in the
annexed diagram (No. 2), where A, B, C, D, E, re-
present the mode in which the stratified rocks of a
district of country not unfrequently occur in con
nection with each other.

No. 2.

Proceeding from E in the plain, the soil would
change when we came upon the rock D, but would
then continue uniform till we reached the layer C.
Each of these layers may stretch over a compara-

84 ORDER OF SUCCESSION

tively level tract of perhaps hundreds of miles in
extent. Again, on climbing the hill-side, another
soil would present itself, which would not change
till we arrived at B. Then, however, we begin to
walk over the edges of the beds, and the soil may
vary with every new stratum (or bed) we pass
over, till we gain the ascent to A, where the beds
are much thinner, and where, therefore, still more
frequent variations may present themselves.

Everywhere over the British islands valleys are
hollowed out, as in the former of these diagrams
(No. 1), by which the rocks beneath are exposed,
and differences of soil produced,—or the beds are
more or less inclined, as in the latter diagram
(No. 2), causing still more frequent variations of
the land to appear. By a reference to these facts,
nearly all the great diversities which the soils of
the country present may be satisfactorily account-
ed for.

SECTION III.—-OF THE CONSTANCY IN THE CHARACTER AND
ORDER OF SUCCESSION OF THE STRATIFIED ROCKS.

Another fact alike important to agriculture and
to geology, is the natural order or mode of ar-
rangement in which the stratified rocks are ob-
served to occur in the crust of the globe. Thus,

OF THE STRATIFIED ROCKS. 85

if 1, 2, 3, in diagram No. 1 represent three dif-
ferent kinds of rock, a limestone, for example, a
sandstone, and a hard clay rock (a shale or slate),
lying over each other, in the order here repre-
sented; then, in whatever part of the country
nay, in whatever part of the world, these same
rocks are met with, they will always be found in
the same relative position. The bed 2 or 3 will
never be observed to lie over the bed 1.

This fact is important to geology, because it en-
ables this science to arrange all the stratified rocks
in a certain invariable order,—which order in-
dicates their relative age or antiquity,—-since that
which is lowest, like the lowest layer of stones in
the wall of a building, must generally have been
the first deposited, or must be the oldest. It also
enables the geologist, on observing the kind o1
rock which forms the surface in any country, to
predict at once, whether certain other rocks are
likely to be met with in that country or not.
Thus at C (diagram, No. 1), where the rock (3)
comes to the surface, he knows it would be in vain,
either by sinking or otherwise, to seek for the rock
(1), the natural place of which is far above it;
while at D he knows that by sinking he is likely
to find either 2 or 3, if it be worth his while to

seek for them.
8

86 DEDUCTIONS FROM THE

To the agriculturist this fact is important,
among other reasons,—

1. Because it enables him to predict whether
certain kinds of rock, which might be used with
advantage in improving his soil, are likely to be met
with within a reasonable distance or at an acces-
sible depth. Thus if the bed D (diagram No. 2)
be a limestone, the instructed farmer at EK knows
that it is not to be found by sinking into his own
land, and, therefore, brings it from D; while, to
the farmer upon C, it may be less expensive to
dig down to the bed D in one of his own fields,
than to cart it from a distant spot where it
occurs on the surface. Or if the farmer requires
clay, or marl, or sand, to ameliorate his soil, this
knowledge of the constant relative position of
beds enables him to say where these materials
are to be got, or where they are to be looked for,
and whether the advantage to be derived is likely
to repay the cost of procuring them.

2. It is observed, that when the soil on the sur-
face of each of a series of rocks, such as C, or D,
or HK, in the same diagram, is uniformly bad, it is
almost invariably of better quality at the point
where the two rocks meet. Thus C may be dry,
sandy, and barren; D may be cold, unproductive
clay ; and E a more or less unfruitful limestone

KNOWLEDGE OF THIS ORDER. 87

soil: yet at either extremity of the tract D, where
the soil is made up of an admixture of the decayed
portions of the two adjacent rocks, the land may
be of average fertility—the sand of C may adapt
the adjacent clay to the growth of turnips, while
the lime of E may cause it to yield large returns
of wheat.* Thus, to the tenant in looking out for
a farm, or to the capitalist in seeking an eligible
investment, a knowledge of the mutual relations
of geology and agriculture will often prove of the
greatest assistance. Yet how little is such really
useful knowledge diffused among either class of
men—how little are either tenants or proprietors
guided by it in their choice of the localities in
which they desire to live!

And yet here and there the agricultural practice
of more or less extended districts, if not really
founded upon or directed by, is yet to be explained
only by principles such as those I have above illus-
trated. I shall mention only one example. The
chalk in Yorkshire, in Suffolk, and in other
southern counties, consists of a vast number of
beds, which, taken all together, form a deposit of
very great thickness. Now, the upper beds of
the chalk form poor, thin, dry soils, producing a
scanty herbage, and only under the most skilful

* See page 94.

88 CHALKING THE SOIL.

culture yielding profitable crops of corn. The
lower beds, on the contrary, are marly ; produce
a more stiff, tenacious, and even fertile soil; and
are found in a remarkable degree to enrich the
soils of the upper chalk, when laid on as a top-
dressing in autumn, and allowed to crumble under
the action of the winter’s frost. Hence in York.
shire, Wiltshire, Hampshire, and Kent, where the
lower chalk covers the surface, or is found at no
great depth beneath it, it is dug out of the sides
of the hills, or pits are sunk for it, and it is imme-
diately laid upon the land with great benefit to
the soil. But in parts of Suffolk, where the soil
equally rests upon the upper chalk, there is no
other chalk in the neighbourhood, or to be met
with at any reasonable depth, which will materi-
ally improve the land. The farmers find it, from
long experience, to be more economical to bring
chalk by sea from Kent to lay on their lands in
Suffolk, than to cover them with any portion of
the same material from their own farms. The
following imaginary section will fully explain the

fact here mentioned :—

No. 3.
Suffolk. Mouth of the Thames. Kent.

CONSTANT MINERAL CHARACTER. 89

In this diagram 1 represents the London clay ;
2, the plastic clay which is below it; 3, the upper
chalk with flints, rising to the surface in Suffolk ;
and 4, the lower chalk, without flints, which is
too deep to be reached in Suffolk, but which rises
to the surface in Kent,—where it is abundant, is
easily accessible, and whence it is transmitted
across the estuary of the Thames into Suffolk.

3. The further fact that the several stratified
rocks are remarkably constant in their mineral
character, renders this knowledge of the order
of relative superposition still more valuable to the
agriculturist. Thousands of different: beds are
known to geologists to occur on various parts of
the earth’s surface—each occupying its own un-
varying place in the series. Most of these beds
also, when they crumble or are worn down, pro-
duce soils possessed of some peculiarity by which
their general agricultural capabilities are more or
less affected,—and these peculiarities may gener-
ally be observed in soils formed from rocks of
the same age—that is, occupying the same place
in the series—in whatever part of the world we
find them. Hence if the agricultural geologist
be informed that his friend has bought, or is in
treaty for a farm or an estate, and that it is situ-

ated upon such and such a rock, or geological for-
8*

90 OF BEDS OF THE SAME AGE,

mation, he can immediately give a very probable
opinion in regard to the agricultural value of the
soil, whether the property be in England, in Aus-
tralia, or in New Zealand. If he knows the nature
of the climate also, he will be able to estimate
with tolerable correctness how far the soil is likely
to repay the labours of the practical farmer,—nay,
even whether it is likely to suit better for arable
land or for pasture, and if for arable, what species
of wnite crops it may be expected to produce most
abundantly.

These facts are so very curious, and illustrate
so beautifully the value of geological knowledge
—if not to A and B, the holders or proprietors of
this and that small farm, yet to enlightened agri-
culturists,—to scientific agriculture in general,—
that I shall explain this part of the subject more
fully in a separate section. ‘To those whoare now
embarking in such numbers in quest of new homes
in our numerous colonies, who hope to find, if not
a more willing, at least a more attainable soil in
new countries, no kind of agricultural knowledge
can at the outset,—I may say, even through life,—
be so valuable as that to which the rudiments of
geology willlead them. Those who prepare them-
selves the best for becoming farmers or proprie-
tors in Canada, in New Zealand, or in wide

PRACTICAL VALUE OF GEOLOGY. 91

Australia, yet leave their native land in general
without a particle of that preliminary practical
knowledge, which would qualify them to say,
when they reach the land of their adoption, “ On
this spot, rather than that,—in this district, rather
than that,—will I purchase my allotment, because,
though both appear equally inviting, yet I know
from the geological structure of the country, that
here [ shall have the more permanently produc-
tive soil; here I am more within reach of the
means of agricultural improvement ; here, in addi-
tion to the riches of the surface, my descendants
may hope to derive the means of wealth from
mineral riches beneath.” And this oversight has
arisen chiefly from the value of such knowledge
not being understood—often from the very nature
of it being unknown, even ito otherwise well in-
structed practical men. It is not to men well
skilled merely in the details of local farming, and
who are therefore deservedly considered as autho-
rities and good teachers in regard to local or dis-
trict practice, that we are to look for an exposi-
tion, often not even for a correct appreciation, of
those general principles on which a universal sys-
tem of agriculture must be based—without which
principles, indeed, it must ever remain a mere col-
lection of empirical rules, to be studied and labori-

92 TO EMIGRATING AGRICULTURISTS.

ously mastered in every new district we go to—as
the traveller in foreign lands must acquire a new
language every successive frontier he passes. Eng-
land, the mistress of so many wide and unpeopled
lands, over which the dwellings of her adventur-
ous sons are hereafter to be scattered, on which
their toil is to be expended, and the glory of their
motherland by their exertions to be perpetuated—
England should especially encourage all such
learning, and the sons of English farmers willingly
avail themselves of every opportunity of acquir-
ing it.

SECTION IV.—OF GEOLOGICAL FORMATIONS, AND THE
GENERAL CHARACTERS OF THE SOILS THAT REST
UPON THEM.

The thousands of beds or strata of which I have
spoken as lying one over the other in the crust of
the globe, have, partly for convenience, and partly
in consequence of certain remarkably distinctive
characters observed among them, been separated
by geologists into three great divisions—the prv-
mary, which are the lowest and the oldest; the
secondary, which lie over them; and the ¢ertzary,
which are uppermost, and have been most recently
formed. ‘The strata, in these several divisions,

THE LONDON CLAY AND THE CHALK. 93

have again been subdivided into groups, called
formations. The following table exhibits the
names and thicknesses of these formations, and
the mineralogical characters of the rocks of which
they severally consist.

I. TERTIARY STRATA.

1. The London and Plastic clays, 500 to 900
feet thick, consist of stiff, almost impervious, dark
coloured clays,—chiefly in pasture. The lower
beds are mixed with sand, and produce an arable
soil, but extensive heaths and wastes rest upon
them in Berkshire, Hampshire, and Dorset.

II. SECONDARY STRATA.

2. The Chalk, about 600 feet in thickness, con-
sists in the upper part (see diagram, No. 3, p. 88)
of a purer chalk with layers of flint; in the lower,
of a marly chalk without flints. The soil of the
upper chalk is chiefly in sheep-walks, that of the
lower chalk is very productive of corn.

3. The Green Sand, 500 feet thick, consists of
150 feet of clay, with about 100 feet of sand above,
and 250 feet below it. The upper sand forms a
very productive arable soil, and the clay imper-

94 THE WEALD CLAY AND THE OOLITE.

vious, wet and cold lands chiefly in pasture. The
lower sand is generally unproductive.

It is an important “agricultural remark, that
where the clay (plastic clay) comes in contact with
the top of the chalk, an improved soil is produced,
and that where the chalk and the green sand mix,
extremely fertile patches of country present them.
selves. (See pages 86 and 87.)

4. The Wealden formation, nearly 1000 feet thick,
consists of 400 feet of sand, covered by 300 of
clay, and resting upon 250 of marls and lime-
stones. The clay forms the poor wet pastures of
Sussex and Kent. On the sands below the clay
rest heaths and brushwood; but where the marls
and limestones come to the surface, the land is of
better quality, and is susceptible of profitable ara-
ble culture.

5. In the Upper Oolite, of 600 feet in thickness,
we have a bed of clay (Kimmeridge clay) 500 feet
thick, covered by 100 feet of sandy limestones.
The clay lands are difficult and expensive to work,
and are chiefly in old pasture. ‘The sandy lime-
stone soils above the clay are also poor, but where
they rest immediately upon, and are intermixed
with the clay, excellent arable land is produced.

6. The Middle Oolite of 500 feet consists also of

THE BATH OOLITE AND THE LIAS. 95

a clay (Oxford clay) dark-blue, adhesive, and
nearly 1000 feet thick, covered by 100 feet of
limestones and sandstones. These latter pro-
duce good arable land where the lime happens to
abound ; the clays form close heavy compact soils,
most difficult and expensive to work. The exten-
sive pasture lands of Bedford, Huntingdon, Nor-
thampton, Lincoln, Wilts, Oxford, and Glouces-
ter, rest chiefly upon this clay, as do also the fen-
ny tracts of Lincoln and Cambridge.

7. The Lower or Bath Oolite, of 500 feet in
thickness, consists of many beds of limestone and
sandstone, with about 200 feet of clay in the
centre of the formation. The soils are very vari-
ous in quality, according as the sandstone or lime-
stone predominates. ‘The clays are chiefly in pas-
ture,—the rest is more or less productive, easily
worked, arable land. In Gloucester, Northamp-
ton, Oxford, the east of Leicester, and in Yorkshire,
this formation is found to lie immediately beneath
the surface, and a little patch of it occurs also on
the south-eastern coast of Sutherland.

6. The Lvas is an immense deposit of blue clay
from 500 to 1000 feet in thickness, which pro-
duces cold, blue, unproductive, clay soils. It forms
a long stripe of land from the mouth of the Tees,

96 RICH SOILS OF THE NEW RED SANDSTONE.

in Yorkshire, to Lyme Regis in Dorset. It is
chiefly in old, and often very valuable pasture.

9. The New Red Sandstone, though only 500
feet in thickness, forms the surface of nearly the
whole central plain of England, and stretches
north through Cheshire to Carlisle and Dumfries.
It consists of red sandstones and marls,—the soils
on which are easily and cheaply worked, and form
some of the richest and most productive arable
lands in the island. In whatever part of the
world the red soils of this formation have been
met with, they have been found to possess in ge-
neral the same agricultural capabilities.

10. The Magnesian Limestone, from 100 to 500
feet in thickness, forms a stripe of generally poor
thin soil from Durham to Nottingham, capable of
improvement as arable land by high farming, but
bearing naturally a poor pasture, intermingled
with sometimes magnificent furze.

11. The Coal Measures, from 300 to 3000 feet
thick, consist of beds of sandstones and dark blue
shales (hard clays), intermingled (interstrati-
fied) with beds of coal. Where the sands come
to the surface, the soil is thin, poor, hungry,
sometimes almost worthless. ‘The shales, on the
other hand, produce stiff, wet, almost unmanage-
able clays ;—not unworkable, yet expensive to

MILLSTONE GRIT AND MOUNTAIN LIMESTONE. 97

work, and requiring draining, lime, skill, capi-
tal, and a zeal for improvement, to be applied to
them, before they can be made to yield the re-
munerating crops of corn they are capable of pro-
ducing.

12. To the Millstone Grits of 600 feet or up-
wards in thickness the same remarks apply. They
are often only a repetition of the sandstones and
shales of the coal measures, forming in many cases
soils still more worthless. When the sandstones
prevail, large tracts lie naked, or bear a thin and
stunted heath; where the shales abound, the na-
turally difficult soils of the coal shales again recur.
These rocks are generally found on the outskirts
of our coal-fields.

13. The Mountain Limestone, 800 to 1000 feet
thick, is a hard blue limestone rock, separated here
and there into distinct beds by layers of sand-
stones, of sandy slates, or of blue shales like those
of the coal measures. ‘The soil upon the limestone
is generally thin, but produces a naturally sweet
herbage. When the limestone and clay (shale)
adjoin each other, arable land occurs, which is
naturally productive of oats, yet, when the climate
is favourable, capable of being converted into
good wheat land. In the north of England a
considerable tract of country is covered by these

9

98 OLD RED SANDSTONE SOILS.

rocks, but in Ireland they form nearly the whole
of the interior of the island.

14. The Old Red Sandstone varies in thickness
from 500 to 10,000 feet. It possesses many of
the valuable agricultural qualities of the new red,
consisting, like it, of red sandstones and marls,
which crumble down into rich red soils. Such
are the soils of Brecknock, Hereford, and part of
Monmouth ; of part of Berwick and Roxburgh ;
of Haddington and Lanark; of southern Perth ;
of either shore of the Moray Firth; and of the
county of Sutherland. In Ireland, also, these
rocks abound in Tyrone, Fermanagh, and Mona-
ghan; in Waterford, in Mayo, and in Tipperary.
In all these places, the soils they form are gene-
rally the best in their several neighbourhoods,
though here and there,—where the sandstones are
harder, more siliceous and impervious to water,—
tracts, sometimes extensive, of heath and bog

occur.

III.—-PRIMARY STRATAe

15. The Upper Silurian system is nearly 4000
feet in thickness, and forms the soils over the
lower border counties of Wales. It consists of
sandstones and shales, with occasional limestones ;

SILURIAN AND CAMBRIAN ROCKS. 99

but the soils formed from these beds take their cha-
racter from the general abundance of clay. They
are cold, usually unmanageable, muddy clays, with
the remarkably inferior agricultural value of which
the traveller is immediately struck, as he passes
westward off the red sandstones of Hereford on to
the upper silurian rocks of Radnor.

.. 16. The Lower Silurian rocks are also nearly
4000 feet in thickness, and in Wales lie to the
west of the upper silurian rocks. ‘They consist
of about 2500 feet of sandstone, on which, when
the surface is not naked, barren heaths alone rest.

Beneath these sandstones lie 1200 feet of sandy
and earthy limestones, from the decay of which,
as may be seen on the southern edge of Caermar-
then, fertile arable lands are produced.

17. The Cambrian System, of many thousand
yards in thickness, consists in great part of clay
slates, more or less hard, which often weather
slowly, and almost always produce either poor
and thin soils, or cold, difficultly manageable
clays, expensive to work, and requiring high
farming to bring them into profitable arable cul-
tivation. Cornwall, western Wales, and the moun-
tains of Cumberland, in England; the high coun-
try which stretches from the Lammermuir hills
to Portpatrick, in Scotland; the mountains of

100 MICA SLATE AND GNEISS SOILS.

Tipperary, and a large tract on the extreme south
of Ireland,—on its east coast, and far inland from
the bay of Dundalk,—are covered by these slate
rocks. Patches of rich, well cultivated land occur
here and there on this formation, with much also
that is improvable ; but the greater part of it is
usurped by worthless heath and extensive bogs.

18. The Mica Slate and Gneiss systems are of
unknown thickness, and consist chiefly of hard and
slaty rocks, crumbling slowly, forming poor, thin
soils, which rest on an impervious rock, and which,
from the height to which this formation gene-
rally rises, are rendered more unproductive by an
unpropitious climate. They form extensive heathy
tracts in Perth and Argyle, and on the north and
west of Ireland. Here and there only, in the
valleys or sheltered slopes, and by the margins
of the lakes, spots of bright green meet the eye,
and patches of a willing soil, fertile in corn.

A careful perusal of the preceding sketch of
the general agricultural capabilities of the soils
formed from the several classes of stratified rocks,
will have presented to the reader many illustra-
tions of the facts stated in the preceding section ;
he will have drawn for himself—to specify a few
examples—the following among other conclusions.

GENERAL DEDUCTIONS. 101

1. That some formations, like the new red sand-
stone, yield a soil almost always productive ; others,
as the coal measures and millstone grits, a soil
almost always naturally unproductive.

2. That good, or better land at least, than
generally prevails in a district, may be expected
where two formations or two different kinds of rock
meet,—as when a limestone and a clay mingle their
mutual ruins for the formation of a common soil.

3. That in almost every country extensive tracts
of land on certain formations will be found laid
down to natural grass, in consequence of the original
difficulty and expense of working. Such are the
Lias, the Oxford, the Kimmeridge, and the London
clays. In raising corn, it is natural that the lands
which are easiest and cheapest worked should be
first subjected to the plough; it is not till im-
plements are improved, skill increased, capital
accumulated, and population presses, that the
heavier lands will be rescued from perennial grass,
and made to produce that greatly increased
amount of food for both man and beast, which
they are easily capable of yielding.

The turnip soils of Great Britain are in many
districts, it may be, but indifferently farmed;
and the state has reason to complain of much in-

dividual neglect of known and certain methods
Q*

102 PLOUGHING UP THE STIFF CLAYS.

of increasing their productiveness ; but the next
great achievement which British agriculture has
to effect, is to subdue the stubborn clays, and to
convert them into what many of them are yet
destined to become, the richest corn-bearing lands
in the kingdom.

CHAPTER VII.

Soils of the Granitic and Trap Rocks—Accumulations of
transported Sands, Gravels, and Clays.—Use of Geologi-
cal Maps in reference to Agriculture.—Physical charac-
ters and Chemical constitution of Soils——Relation be-
tween the nature of the Soil and the kind of Plants that
naturally grow upon it.

Ir was stated, in the preceding lecture, (see
p. 82,) that rocks are divided by geologists into the
stratified and the unstratified.* The stratified rocks
cover by far the largest portion of the globe, and
thus form a variety of soils, of which a general
description has just been given. The unstratified
rocks are of two kinds—the granites and the trap

* The unstratified are often called crystalline rocks, be-
cause they frequently have a glassy appearance, or contain
regular crystals of certain mineral substances; often also
igneous rocks, because they appear all to have been original-
ly ina melted state, or to have been produced by fire,

Kh

104 GRANITES, QUARTZ, AND MICA.

rocks ; and as a considerable portion of the area
of our island is covered by them, it will be proper
shortly to consider the peculiar characters of each,
and the differences of the soils produced from them.

SECTION I.—SOILS OF THE GRANITES AND TRAP ROCKS.

1. The granites consist of a mixture, in different
proportions, of three minerals, known by the
names of quartz, felspar, and mica. The latter,
however, is generally present in such small quan-
tity, that in our general description it may be
safely left out of view. Granites, therefore, con-
sist chiefly of quartz and felspar, in proportions
which vary very much, but the former, on an ave-
rage, constitutes perhaps from one-third to one-
half of the whole.

Quartz has already been described—(see p. 51)
—as the substance of flint, the silica of the che-
mist. When the granite decays, this portion of
it forms a more or less coarse siliceous sand.

Felspar is a white, greenish, or flesh-coloured
mineral, often more or less earthy in its appear-
ance, but generally hard and brittle, and some.
times glassy. It is scratched by, and thus is rea-
dily distinguished from, quartz. When it docu:
it forms an exceedingly fine clay.

fy pele 9" NO

TEMPERATURE OF SOILS. 105

how much botiom heat forces the growth, espe-
cially of young plants; and wherever a natural
warmth exists in the soil, independent of the sun,
as in the neighbourhood of volcanoes, there it ex-
hibits the most exuberant fertility. One main in-
fluence of the sun in spring and summer is de-
pendent upon its power of thus warming the soil
around the young roots, and thus rendering it
propitious to their rapid growth. But the sun
does not warm all soils alike : some become much
hotter than others, though exposed to the same
sunshine. When the temperature of the air in the
shade is no hig'icr than 60° to 70°, a dry soil may
become so warm as to raise the thermometer to
90° or 100°. Mrs. Ellis states, that among the Py-
renees the rocks actually smoke after rain under
the influence of the summer sun, and become so
hot, that you cannot sit down upon them. In wet
soils the temperature rises more slowly, and never
attains the same height as in a dry soil by 10° or
15°. Hence it is strictly correct to say, that wet
soils are cold; and it is easy to understand how
this coldness is removed by perfect drainage. Dry
sands and clays, and blackish garden mould, be-
come warmed to nearly an equal degree under
the same sun; brownish red soils are heated some-
what more, and dark-coloured peat the most of

yo a eS

106 COMPOSITION OF HORNBLENDE AND FELSPAR.

weather, to a more or less fine powder, affording
materials for a soil; in the granites the felspar is
the principal source of all the earthy matter they
are capable of yielding. If we compare together,
therefore, the chemical composition of the two
minerals (hornblende and felspar), we shall see
in what respect these two varieties of soil ought
to differ. ‘Thus they consist of

Felspar. Hornblende.

Silica, F ; : 65 42
Alumina, . ‘ 2 18 14
Potash and soda, 2 : 17 trace.
Lime, : t » trace 12
Magnesia, é Abie 54 14
Oxide of iron, ; Be BAO 144
Oxide of manganese, ered ae 2
100 97

A remarkable difference appears thus to exist,
in chemical constitution, between these two mine-
rals—a difference which must affect also the soils
produced from them. A granite soil, in addition -
to the siliceous sand, will consist chiefly of silica,
alumina, and potash ; a hornblende soil, in addi-
tion to silica and alumina, of much lime, magnesia,
and oxide of iron—of nearly 21 cwt. of each of
these latter for every ton of decayed rock. A
hornblende soil, therefore, contains more of those

GREENSTONE AND OTHER TRAP sorts. 107

inorganic constituents which the plants require
for their healthy sustenance, and therefore will
prove more generally productive than a soil of
decayed felspar. But when the two are mixed,
as in the greenstones, the soil must be still more
favourable to vegetable life. The potash and
soda, of which the hornblende is nearly destitute,
the felspar is able abundantly to supply ; while,
by the hornblende are yielded lime and magnesia,
which are known to exercise a remarkable influ-
ence on the progress of vegetation.

Thus theory shews, that while granite soils may
be eminently unfruitful, trap soils may be emi-
nently fertile. And such is actually the result of
observation and experience in every part of the
globe. Unproductive granite soils cover nearly
the whole of Scotland north of the Grampians,
and large tracts of land in Devon and Cornwall,
and on the east and west of Ireland ; while fertile
trap soils extend over thousands of square miles
in the lowlands of Scotland, and in the north of
Ireland ; and where in Cornwall they occasion-
ally mix with the granite soils, they are found to
redeem them from their natural barrenness.

While such is the general rule in regard to
these two classes of soils, it happens on some spots
that the presence of other minerals in the granites,

108 DECAYED TRAP AS A MANURE.

or of hornblende or mica in larger quantity than
usual, give rise to a granitic soil of average fertil-
ity, as is the case in the Scilly isles; while, in
like manner, the trap rocks are sometimes, as in
parts of the isle of Skye, so peculiar in constitu-
tion as to condemn the land to almost hopeless
infertility.

In some districts the decayed traps are dug up,
and applied with advantage, as a top-dressing, to
other kinds of land; and as by admixture with
the decayed trap, the granitic soils are known to
be improved in quality, so an admixture of decayed
granite with many trap soils, were it readily acces.
sible, might add to their fertility also.

SECTION II.—OF THE SUPERFICIAL ACCUMULATIONS OF TRANS=
PORTED MATERIALS ON DIFFERENT PARTS OF THE EARTH’S
SURFACE

It is necessary to guard the reader against dis-
appointment, when he proceeds to examine the
existing relation between the soils and the rocks
on which they lie, or to infer the quality of the
soil from the known nature of the rock in con-
formity with what has been above laid down,—by
explaining another class of geological appearances
which present themselves not only in our own

SOIL FORMED FROM DRIFTED MATERIALS. 109

country but in almost every other part of the
globe.

The unlearned reader of the preceding section
and chapter may say—I know excellent land
resting upon the granites, fine turnip soils on the
Oxford or London clays, tracts of fertile fields
on the coal measures, and poor, gravelly farms
on the boasted new red sandstone: I have no
faith in theory—I can have none in theories which
are so obviously contradicted by natural appear-
ances. Such, it is to be feared, is the hasty mode
of reasoning among too many locally* excellent
practical men, familiar, it may be, with many
useful and important facts, but untaught to look
through and beyond isolated facts to the princi-
ples on which they depend.

Every one who has lived long, on the more
exposed shores of our island, has seen, that when
the weather is dry, and the sea winds blow strong,
the sands of the beach are carried inland and
spread over the soil, sometimes to a considerable

* By locally excellent, I mean those who are the best pos-
sible farmers of their own district and after their own way,
but who would fail in other districts requiring other methods.
To the possessor of agricultural principles the modifications
required by difference of crop, soil, and climate, readily sug-

gest themselves, where the mere practical man is bewildered,
disheartened, and in despair.
10

110 HOW SANDS AND CLAYS ARE DRIFTED.

distance from the coast. In some countries this
sand-drift takes place to a very great extent, and
gradually swallows up large tracts of fertile land.

Again, most people are familiar with the fact,
that during periods of long continued rain, when
the rivers are flooded and overflow their banks,
they not unfrequently bear with them loads of |
sand and gravel, which they carry far and wide,
and strew at intervals over the surface soil.

So the annual overflowings of the Nile, the
Ganges, and the river of Amazons, gradually de-
posit accumulations of soil over surfaces of great
extent ;—and so also the bottoms of most lakes are
covered with thick beds of sand, gravel, and clay,
which have been conveyed into them from the
higher grounds by the rivers through which they
are fed.

To these and similar agencies, a large portion
of the existing dry land of the globe has been,
and is still exposed. Hence in many places, the
rocks, and the soils naturally derived from them,
are buried beneath accumulated heaps or layers
of sand, gravel, and clay, which have been brought
from a greater or less distance, and which have
not unfrequently been derived from rocks of a
totally different kind from those of the district
in which they are now found. On these accumu-

DIFFICULTIES RESULTING FROM THIS DRIFT. 111

lations of transported materials, a soil is produced
which often has no relation in its characters
to the rocks which cover the country, and the
nature of which a familiar acquaintance with
these rocks would not enable us to predict.

To this cause is due that discordance between
the first indications of geology, as to the origin
of soils from the rocks on which they rest, and
the actually observed character of those soils in
certain districts—of which discordance mention
has been made as likely to awaken doubt and dis-
trust in the mind of the less instructed student
in regard to the predictions of agricultural geo-
logy. There are several circumstances, however,
by which the careful observer is materially aided
in endeavouring to understand what the nature of
the soils is likely to be, and how they ought to be
treated, even when the subjacent rocks are thus
overlaid by masses of drifted materials. Thus—

1. It not unfrequently happens, that the mate-
rials brought from a distance are more or less
mixed up with the fragments and decayed matter
of the rocks which are native to the spot, so that
though modified in quality, the soil, nevertheless,
retains the general characters of that which is
formed on other spots from the decay of these
rocks alone.

112 HOW OBVIATED.

2. Where the formation is extensive, or covers
a large area, as the new red sandstones and coal
measures doin this country,—the mountain lime-
stones in Ireland, and the granites in the north of
Scotland—the transported sand, gravel, or clay,
strewed over one part of the formation, has not
unfrequently been derived from the rocks of ano-
ther part of the same formation, so that, after all,
the soils may be said to be produced from the rocks
on which they rest, and may be judged of from
the known constitution of these rocks.

3. Or if not from the rocks of the same forma-
tion, they have most frequently been derived from
those of a neighbouring formation—from rocks
which are to be found at no great distance, and
generally on higher ground. Thus the ruins of
the mill-stone grit rocks are often spread over
the surface of the coal measures—of these, again,
over the magnesian limestone,—of the latter, over
the new red sandstone, and so on. ‘The effect of
this kind of transport upon the soils, is merely to
overlap, as it were, the edges of one formation
with the proper soils of the formations that adjoin
it in the particular direction from which the drift-
ed materials are known to have come.

It appears, therefore, that the occurrence on
certain spots, or tracts of country, of soils that

U3E OF GEOLOGICAL MAPS. 113

have no apparent relation to the rocks on which
they immediately rest, tends in no way to throw
doubt upon, to discredit or to disprove, the conclu-
sions drawn from the more general facts and prin-
ciples of geology. It is still generally true that
soils are derived from the rocks on which they rest.
The exceptions are local, and the difficulties which
these local exceptions present, require only from
the agricultural geologist a more careful study of
the structure of each district, before he pronoun-
ces a dicided opinion as to the degree of fertility
it either naturally possesses, or by skilful cultiva-
tion may be made to attain.

Geological maps point out with more or less
precision the extent of country over which the
chalk, the red sandstone, the granites, &c., are
found immediately beneath the loose materials on
the surface; and these maps are of great value
in indicating also the general quality of the soils
over the same districts. It may be true, that here
and there the natural soils are masked or buried
by transported materials, yet the political economist
may, nevertheless, with safety estimate the general
agricultural capabilities and resources of a country
by the study of its geological structure—the capz-
talist judge in what part of it he is likely to meet

with an agreeable investment—and the practical
10*

114 RELATIVE DENSITY OF SOILS.

farmer in what country he may expect to find
land that will best reward his labours—that will
admit of the kind of culture to which he is most
accustomed, or, by the application of better me-
thods, will manifest the greatest agricultural im-
provement.

SECTION III.—OF THE PHYSICAL CHARACTERS OF SOILS.

The influence of climate on the fertility of a
soil is often very great. This influence depends
very much upon what are called the physical pro-
perties of soils.

1. Some soils are heavier and denser than others,
sand and marls being the heaviest, and peaty soils
the lightest. In reclaiming peat lands, it is found
to be highly beneficial to increase their density by
a covering of clay, sand, or limestone gravel.

2. Again, some soils absorb the rains that fall,
and retain them in larger quantity and for a longer
period than others. Strong clays absorb and re-
tain nearly three times as much water as sandy
soils do, while peaty soils absorb a still larger
proportion. Hence the more frequent necessity
for draining clayey than sandy soils; hence also
the reason why, in peaty lands, the drains must be
kept carefully open, in order that the access of

THEIR RELATIONS TO WATER. 115

springs and of other water from beneath, may be
as much as possible prevented.

3. When dry weather comes, soils lose water by
evaporation with different degrees of rapidity. In
this way a siliceous sand will give off the same
weight of water in the form of vapour, in one third
of the time necessary to evaporate it from a stiff
clay, a peat, or arich garden mould, when all
are equally exposed to the air. Hence the reason
why plants are so soon burned up in a sandy
soil. Not only do such soils retain less of the
rain that falls, but that which is retained is also
more speedily dissipated by evaporation. When
rains abound, however, or in very moist seasons,
these same properties of sandy soils enable them
to sustain a luxuriant vegetation, when plants wiil
perish on clay lands from excess of moisture.

4, In drying under the influence of the sun, soils
contract and diminish in bulk in proportion to the
quantity of clay or of peaty matter they contain.
Sand does not at all diminish in bulk in drying,
but peat shrinks in one-fifth, and agricultural clay
nearly as much. The roots are thus compressed,
and air is excluded, especially from the hardened
clays, and thus the plant is placed in a condition
unfavourable to its growth. Hence the value of
proper admixtures of sand and clay. By the lat-

2

a Deh ‘

116 THEIR POWER OF ABSORBING MOISTURE.

ter (the clay), a sufficient quantity of moisture is
retained, and for a sufficient length of time; while,
by the former, the roots are preserved from com-
pression, and a free access of air is permitted.

5. In the hottest and most drying weather, the
soil has seasons of respite from the scorching in-
fluence of the sun. During the cooler season of
the night, even when no perceptible dew falls, it
has the power of again extracting from the air a
portion of the moisture it had lost during the day.
Perfectly pure sand possesses this power in the
least degree; it absorbs little or no moisture
from the air. A stiff clay, on the other hand,
will in a single night absorb sometimes as much
as a 30th part of its own weight, and a dry peat
as muchas a 12th of its weight ; and, generally, the
quantity thus drunk in by soils of various quali-
ties, is dependent upon the proportions of clay
and vegetable matter they séverally contain. We
cannot fail to perceive from these facts, how much
of the productive capabilities of a soil is dependent
upon the proportions in which its different earthy
and vegetable constituents are mixed together.

6. The temperature of a soil, or the degree of
warmth it is capable of attaining under the in-
fluence of the sun’s rays, materially affects the
progress of eee Every gardener knows

Mod aud AMOS?

eo

GRANITE SOILS. i ay

Granite generally forms hills and sometimes
entire ridges of mountains. When it decays, the
rains and streams wash out and carry down the
fine felspar clay, and leave the (quartz) sand on
the sides of the hills. Hence the soil in the bot-
toms and flats of granite countries consists of a
cold, stiff, wet, more or less impervious clay,
which often bears only heath, bog, or a poor and
unnutritive pasture. The hill sides are either
bare or covered with a thin, sandy, and ungrate-
ful soil, of which little can be made by the aid
even of skill and industry. Yet the opposite
sides of the same mountains often present a re-
markable difference in this respect, those which
are most beaten by the rains having the light clay
most thoroughly washed from their surfaces, and
being therefore the most barren.

2. The trap rocks, comprising the greenstones
and basalts, consist essentially* of felspar and
hornblende or augite. In contrasting the trap
rocks with the granites, it may be stated generally,
that while the granites consist of felspar and
quartz, the traps consist of felspar and hornblende
(or augite). In the traps, both the felspar and
the hornblende are reduced, by the action of the

* The reader is referred for more precise information to
the author’s ‘‘ Lectures,” pp. 377 to 390.

K ih a“ a Os" C4 ae
Y x * Sed “yO ‘
_;, de
4
118 SIMILAR PROPERTIES OF PEAT AND CLAY.

all. It is probable, therefore, that the presence
of dark-coloured vegetable matter renders the soil
more absorbent of heat from the sun, while the
colour of the dark-red marls of the new and old
red sandstones may, in some degree, aid the other
causes of fertility in the soils which they produce.

In reading the above observations, the practi-
cal reader can hardly fail to have been struck
with the remarkable similarity in physical proper-
ties between stiff clay and peaty soils. Both re-
tain much of the water that falls in rain, and both
part with it slowly by evaporation. Both con-
tract much in drying; and both absorb moisture
readily from the air in the absence of the sun. In
this similarity of properties, we see not only why
the first steps in improving both kinds of soil
must be very nearly the same; but why, also, a
mixture either of clay or of vegetable matter will
equally impart to a sandy soil many of those aids
to, or elements of, fertility—of which they are
alike possessed.

SECTION I[V.—OF THE CHEMICAL CONSTITUTION OF SOILS.

Soils perform at least three functions, in refer-
ence to vegetation. ‘They serve as a basis in

CONSTITUTION OF SOILS. 119

which plants may fix their roots and sustain them.
selves in their erect position,—they supply inor-
ganic food to vegetables at every period of their
growth,—and they are the medium in which many
chemical changes take place, that are essential to
aright preparation of the various kinds of food
which the soil is destined to yield to the growing
plant.

We have spoken of soils as consisting chiefly of
sand, lime, and clay, with certain saline and or-
ganic substances in smaller and variable propor-
tions. But the study of the ash of plants (see
chap. iv.) shews us, that a fertile soil must of ne-
cessity contain an appreciable quantity of at least
eleven different substances, which in most cases
exist in greater or less relative abundance in the
ash both of wild and of cultivated plants.

Two well known geological facts lead to pre-
cisely the same conclusion. We have seen that
the soils formed from the unstratified rocks,—the
granites and the traps,—while they each contain
certain earthy substances in proportions peculiar
to themselves, yet contain also in general a érace
of most of those different kinds of matter which
are found in the ash of plants. And when to
this fact is added the other, that the stratified

120 INDICATED BY CHEMICAL ANALYSIS.

rocks appear to be only the long accumulating
fragments and ruins of more ancient unstratified
masses—which, under various agencies, have gra-
dually crumbled to dust, been strewed over the
surface in alternate layers, and afterwards again
consolidated,—the reader will readily grant, that
in all rocks, and consequently in all soils, traces of
every one of these substances may generally be
presumed to exist.

Actual chemical analysis confirms these deduc-
tions in regard to the constitution of soils. It
shews that, in most soils, the presence of the seve-
ral constituents of the ash of plants may be de-
tected, though in very variable proportions. And
following up its investigations, in regard to the
effect of this difference in the proportion of the
generally less abundant constituents of the soil,
it establishes certain other points of the greatest
possible importance to agricultural practice. Thus,
it has found, for example,

1. That as a proper adjustment of the propor-
tions of clay and sand is necessary, in order that
a soil may possess the most favourable physical
properties—so that the mere presence of the vari-
ous kinds of inorganic food in a soil is not suffi-
cient to make it productive of a given crop, but
that they must be so adjusted in quantity that

GENERAL DEDUCTIONS FROM ANALYSES. 121

the plant shall be able readily and at the proper
time to obtain an adequate supply of each.

2. That when a soil is particularly poor in cer-
tain of these substances, the valuable, cultivated
corn crops, grasses, and trees, refuse to grow upon
them in a healthy manner, and to yield remune-
rating returns. And,

3. That when certain other substances are pre-
sent in too great abundance, the soil is rendered
equally unpropitious to the most important crops.

In these facts the intelligent reader will per-
ceive the foundation of the varied applications to
the soil which are everywhere made under the
direction of a skilful practice, and of the difficul-
ties which, in so many localities, lie in the way of
bringing the land into such a state as shall fit it
readily to supply all the wants of those kinds of
vegetables which it is the special object of artifi-
cial culture easily and abundantly to raise.

Chemical analysis is a difficult art,—one which
demands much chemical knowledge, and skill in
chemical practice (manipulation, as it is called),
and calls for both time and perseverance—if valu-
able, trustworthy, and minutely correct results are
to be obtained. [I believe it is only by aiming
after such minutely correct results that chemical

analysis is likely to throw light on the peculiar
) 11

We

122 AGRICULTURE AND CHEMISTRY.

properties of those soils which, while they possess
much general similarity in composition and in
physical properties, are yet found in practice to
possess very different agricultural capabilities.
Many such cases occur in every country, and they
are the kind of difficulties in regard to which
agriculture has a right to say to chemistry—
“These are matters which I hope and expect you
will satisfactorily clear up.” But while agricul-
ture has a right to use such language, she has
herself preliminary duties to perform. She has
no right in one breath to deny the value of che-
mical theory to agricultural practice, and in an-
other to ask the sacrifice of time and labour in
doing her chemical work. Chemistry is a wide
field, and many zealous lives may be spent in the
prosecution of it without at all entering upon the
domain of practical agriculture. It may be that
here and there it may fall in with the humour or
natural bias of some one chemist to apply his
knowledge to this most important art ; but hitherto
the appreciation of such efforts has, in general,
been so small—the reception of scientific results
and suggestions by the agricultural body so un-
gracious—that little wonder can exist that so
many have quitted the field in disgust—that the
majority of capable men should studiously avoid it.

ACCURATE ANALYSIS OF SOILS RARE. 123

Hence it has happened that, in England, the
analysis of soils has rarely been undertaken, ex-
cept as a matter of professional business, where
so much time was, by a fair calculation, given for
so much money, and an analysis made, of that
degree of accuracy only which the time allotted
to it permitted the analyst to attain.

In order, therefore, to illustrate the deductions
which, as above stated, may be drawn from an
accurate chemical analysis, I shall exhibit the
constitution of three different soils as determined
by Sprengel, a German chemist, now at the head
of the Prussian Agricultural school, and whose
own taste, as well as his professional function,
have long directed his attention, and with much
success, to scientific agriculture.

No. 1 isa very fertile alluvial soil from East
Friesland, formerly overflowed by the sea, but
for 60 years cultivated with corn and pulse crops
without manure.

No. 2 isa fertile soil near Géttingen, which
produces excellent crops of clover, pulse, rape,
potatoes, and turnips, the two last more especially
when manured with gypsum.

No. 3 is a very barren soil from Lunenburg.

When washed with water in the manner des-

Ped

124 COMPOSITION OF CERTAIN SOILS.

cribed in pages 70 to 73, they gave, respectively,
from 1000 parts of soil—

No.1): No Seiaia. 3.

Soluble saline matter, . : 18 1 1
Fine earthy and organic matter (clay), 937 839 599
Siliceous sand, . é é 45 160 400

ee

1000 1000 ~=§©1000

The most striking distinction presented by these
numbers is the large quantity of saline matter in
No. 1. This soluble matter consisted of common
salt, chloride of potassium, sulphate of potash and
gypsum, with a trace of sulphate of magnesia,
sulphate of iron, and phosphate of soda. The
presence of this comparatively large quantity of
these different saline substances,—originally de-
rived, no doubt, in great part from the sea,—was
probably one reason why it could be so long
cropped without manure.

The unfruitful soil is much the lightest of the
three, containing 40 per cent. of sand; but this is
not enough to account for its barrenness—many —
light soils containing a larger proportion of sand,
and yet being sufficiently fertile.

The finer portions separated from the sand, and
soluble matter, consisted in 1000 parts of

COMPOSITION OF CERTAIN SOILS. 125

No. ls Now 2... Ne. 3.
Organic matter, . + eae 50 40
Silica, . ; . 648 833 778
Alumina, : Mee.) 51 St
Lime, . ; : 59 18
Magnesia, : : 8 8 1
Oxide of iron, : Saas 30 81
Oxide of manganese, : 1 3 A
Potash, . : ; 2 trace. trace.
Soda, . ; : 4 do. do,
Ammonia, } . trace. do. do.
Chlorine, 3 : 2 do. do.
Sulphuric acid, . ° 2 2 do.
Phosphoric acid, . i 44 13 do.
Carbonic acid, : ; 40 4h do.
oss, - ; 14 — 41

Ce ae

1000 1000 1000

1. The composition of No. 1 illustrates the first
of those general deductions above stated, that a
considerable supply of all the species of inorganic
food is necessary to render a soil eminently fer-
tile. Not only does this soil contain a compara-
tively large quantity of soluble saline matter, but
it contains also nearly 10 per cent. of organic mat-
ter, and, what in connection with this is of great
importance, 6 per cent. of lime. The potash and
soda, and the several acids, are also present in suf-
ficient abundance.

11*

126 PRACTICAL DEDUCTIONS

2. In the second,—a fertile soil, but one whick
cannot dispense with manwre,—there is little soluble
saline matter, and in the insoluble portion we see
that there are mere traces of potash, soda, and the
important acids. It contains also 5 per cent. only
of organic matter, and about 2 per cent. of lime,
which smaller proportions, together with the de-
ficiencies above stated, remove this soil from the
most naturally fertile class to that class which is
susceptible, in hands of ordinary skill, of being
brought to, and kept in, a very productive condi-
— tion.

3. In the fine part of the third soil, we observe
that there are many more substances deficient
than in No. 2. The organic matter amounts ap-
parently to 4 per cent., and there seems to be
nearly half a per cent. of lime. But it will be re-
collected, that this soil contains 40 per cent. of
sand, so that in every hundred of soil there are
only 60 of the fine matter, of which the composi-
tion is presented in the table, or 100 Ibs. of the
native soil contain only 24 Ibs. of organic matter
and 1 lb. of lime. }

But all these wants would not condemn the soil
to hopeless barrenness, because in favourable cir-
cumstances, and where it was worth the cost, they
might all be supplied. But the oxide of iron

FROM THESE ANALYSES. . ae

amounts to 8 per cent. of this fine matter, a pro-
portion of this substance which, in a soil contain-
ing so little organic matter, appears, from practi-
cal experience, to be incompatible with the healthy
growth of cultivated crops. To this soil, there-
fore, there requires to be added not only those
substances of which it is destitute, but such other
substances also as shall prevent the injurious ef-
fect of the large proportion of oxide of iron.

In these three soils, then, we have examples,
first, of one which contains within itself all the
elements of fertility ; second, of a soil which is des-
titute, or nearly so, of certain substances,—which,
however, can be readily added by the ordinary
manures in general use,—and to which the ele-
ments of gypsum are especially useful, in aid-
ing it to feed the potato and the turnip; and,
third, of a soil not only poor in many of the ne-
cessary species of the inorganic food of plants,
but too rich in one which, when present in excess,
is prejudicial to vegetable life.

This illustration, therefore, will aid the general
reader in comprehending how far rigid chemical
analysis is fitted to throw light upon the capa-
bilities of soils, and to direct agricultural prac-
tice.

“

128 PLANTS SELECT THE SOILS

SECTION V.—OF THE RELATION THAT EXISTS BETWEEN THE
CHARACTER OF THE SOIL AND THE KIND OF PLANTS THAT

GROW UPON IT.

The importance of this study of the chemical
constitution of soils will, perhaps, be most readily
appreciated by a glance at the very different kinds
of vegetables which, under the same circumstances,
different soils naturally produce.

There are none so little skilled in regard to the
capabilities of the soil, as not to be aware that
some lands naturally produce abundant herbage or
rich crops, while others refuse to yield a nourish-
ing pasture, and are deaf to the often repeated so-
licitations of the diligent husbandman. There
exists, therefore, a universally understood connec-
tion between the kind of soil and the kind of plants
that naturally grow upon it. It is interesting to
observe how close this relation in many cases is.

1. The sands of the sea-shore, and the margins of
salt-lakes, are distinguished by their peculiar tribes
of salt-loving plants;—the drifted sands more re-
mote from the beach produce their own long wav-
ing coarser grass,—while further inland again,
other vegetable races appear.

2. Peaty soils laid down to grass, or existing as
natural meadows, produce one woolly soft grass

ON WHICH THEY CHOOSE TO GROW. 129

almost exclusively (the Holcus lanatus); when
limed, again, these same soils become propitious to
green crops and produce much straw, but refuse
to fill the ear.

3. On the margins of water-courses, in which sili-
ca abounds, the mare’s-tail (Kquisetum) springs up
in abundance; while, if the stream contain much
carbonate of lime, the water-cress appears and
lines its sides, and the bottom of its shallow bed,
sometimes for many miles from its source.

4, The Cornish heath (rica vagans) shews itself
only above the serpentine rocks; the red clover
and the vetch delight in the presence of gypsum ;
and white clover, of alkaline matter in the soil.

5. Then, again, plantsseem toalternate with each
other on the same soil. Burn down a forest of pines
in Sweden, and one of birch takes its place for a
while. 'The pines after a time again spring up and
ultimately supersede the birch. The same takes
place naturally. On the shores of the Rhine are
seen ancient forests of oak from two to four cen-
turies old,—gradually giving place to a natural
growth of beech ; and others where the pine is suc-
ceeding to both. In the Palatinate, the ancient oak
woods are followed by natural pines; and in the
Jura, the Tyrol, and Bohemia, the pine alternates
with the beech.

130 ON SOME SOILS A PLANT WILL THRIVE,

These and other similar differences depend upon
the chemical constitution of the soil The slug
may live well, and therefore infest a field almost de-
ficient in lime; the common land snail will abound
at the roots of the hedges only where lime is plen-
tiful, and can easily be obtained for the construc-
tion of its shell. Soitis with plants. Each grows
spontaneously where its wants can be most fully
and most easily supplied. If they cannot move
from place to place like the living animal, yet
their seeds can lie dormant, until either the hand
of man or the operation of natural causes pro-
duces such a change in the constitution of the soil
as to fit it for ministering to their most important
wants.

And such changes do naturally come over the
soil. The oak, after thriving for long generations
on a particular spot, gradually sickens ; its entire
race dies out,—and other races succeed it. ‘The
operation of natural causes has gradually removed
from the soil that which favoured the oak, and has
introduced or given the predominance to those sub-
stances which favour the beech or the pine.

In the hands of the farmer the land grows sick
of this crop,—it becomes tired of that. These facts
are generally indications of a change in the che-
mical constitution of the soil. This alteration

ON OTHERS IT WILL SICKEN. 131

may proceed slowly and for many years, and the
same crops may still grow upon it for a succes-
sion of rotations. At length the change is too
great for the plant to bear; it sickens, yields an
unhealthy crop, and becomes ultimately extinct.

The plants we raise for food have similar likes
and dislikes with those that are naturally pro-
duced. On some kinds of food they thrive,—fed
with others, they sicken or die. ‘The soil must
therefore be prepared for their special growth.

In an artificial rotation of crops, we only follow
nature. One crop extracts from the soil a certain
quantity of all the inorganic constituents of plants ;
but some of these in much larger proportions than
others. A second crop carries off in preference a
larger quantity of those substances which the for-
mer had left ; and thus it is clearly seen, both why an
abundant manuring may so alter the constitution
of the soil, as to enable it to grow almost any crop ;
and why, at the same time, this soil may in suc-
cession yield more abundant crops and in greater
number, if the kinds of plant sown and reaped be
so varied as to extract from the soil, one after the
other, the several different substances which the
manure we have originally added is known to
contain.

The management and tilling of the soil, in fact,

132 AGRICULTURE A oe ART haem

is a branch of practical chemise which, like the
art of dyeing or of lead smelting, may advance to
a certain degree of perfection, without the aid of
pure science ; but which can only have its pro-
cesses explained, and be led on to shorter,—more
simple,—more economical,—and more perfect pro-
cesses, by the aid of scientific principles,

>

CHAPTER VIII.

Of the Improvement of the Soil—Mechanical and Chemical
Methods—Draining—Subsoiling—Ploughing, and Mix-
ing of Soils—Use of Lime, Marl, and Shell-sand—Ma-
nures— Vegetable, Animal, and Mineral Manures.

Tue soil is possessed of certain existing and ob-
vious qualities, and of certain other dormant ca-
pabilities ; how are these qualities to be improved,
these dormant capabilities to be awakened ?

There are two distinct methods by which these
ends may be, in some measure, attained,—by the
use of mechanical, and by the application of che-
mical, means. Mechanical operations produce
changes chiefly in the physical properties of the
soil,—chemical means alter its elementary consti-
tution. Ploughing, draining, mixing, &c. belong
to the former class of operations ; manuring and
irrigation belong to the latter. It will be proper

to consider these methods separately.
12

134 IMPROVEMENT BY DRAINING.

SECTION I.—OF MECHANICAL METHODS OF IMPROVING
THE SOIL.

1. Draining.—The first step to be taken, in or-
der to increase the fertility of nearly all the im-
proveable lands of Great Britain, is to drain them.
So long as they remain wet, they will continue to
be cold. The heat of the sun’s rays, which is in-
tended by nature to warm the soil, will be ex-
pended in evaporating the water from its surfeee :
and thus the plants will never receive that ge-
nial warmth about their roots which so much
favours their rapid growth. Where too much wa-
ter is present in the soil also, that food of the
plant which the soil supplies is so much diluted,
that cither a much greater quantity of fluid must
be taken in by the roots,—much more work done,
—or the plant will be scantily nourished, 'The
presence of so much water in the siem and leaf
keeps down their temperaturé likewise, when the
sun-shine appears ; an increased evaporation takes
place from their surfaces, a lower natural heat, in |
consequence, prevails in the interior of the plant,
and the chemical changes on which its growth de-
pends proceed with less rapidity.

By the removal of the water, the physical pro-

EFFECT OF DRAINING. 135

perties of the soil also are in a remarkable degree
improved. Dry pipe-clay can be easily reduced
to a fine powder, but it naturally, and of its own
accord, runs together when water is poured upon
it. So it is with clays in the field. The soil ex-
pands, becomes close and adhesive, and excludes
the air from the roots of the growing plant,—the
access of which air appears to be almost an essen-
tial element in the healthy growth of the most im-
portant vegetable productions.

Open an outlet for the water below, and as it
trickles away, the air from above will follow it
and take its place among the pores of the soil, car-
rying to every root the salutary influences it is
appointed to bear with it wherever it penetrates.
When freed from water also, the stiff soil becomes
more mellow ; and when once stirred up toa con-
siderable depth, more universally porous,—so that
air can make its way everywhere, and the roots
can find their easy way in every direction. The
presence of vegetable matter,—whether existing
naturally in a soil thus physically altered, or ar-
tificially added to it,—becomes of double value.
When drenched with water, this vegetable matter
either decomposes very slowly, or produces acid
compounds more or less unwholesome to the plant,
and even exerts injurious chemical reactions upon

136 DRAINAGE OF LIGHT SOILS.

the earthy and saline constituents of the soil. In
the presence of air, on the contrary, this vegetable
matter decomposes rapidly, produces carbonic acid
in large quantity, as well as other compounds fit
for food, and even renders the inorganic constitu.
ents of the soil more fitted to enter the roots, and
thus to supply more rapidly what the several parts
of the plant require.

Nor is it only stiff and clayey soils to which
draining can with advantage be applied. Tt will
be obvious to every one, that when springs rise to
the surface in sandy soils, a drain must be made to
carry off the water,—it will also readily occur,
that where a sandy soil rests upon a hard or clayey
bottom, drains may also be necessary; but it is
not unfrequently supposed, that when the subsoil
is sand or gravel, that drains can only in special
cases be necessary.

Every one, however, is familiar with the fact,
that when water is applied to the bottom of a
flower-pot full of soil, it will gradually find its
way to the surface, however light the soil may be.
So it is in sandy soils or subsoils in the open field.
If water abound at the depth of a few feet, or if
it so abound at certain seasons of the year, that
water will rise to the surface; and as the sun’s
heat dries it off by evaporation, more water will

CLAY SUBSOILS GRADUALLY sorren. 137

follow to supply its place. his attraction from
beneath will always go on when the air is dry and
warm, and thus a double evil will ensue—the soil
will be kept moist and cold, and instead of a con-
stant circulation of air downwards, there will be
a constant current of water upwards. ‘Thus
will the roots, the under soil, and the organic
matter i contains, be all deprived of the benefits
which ihe access of (be air is filted to confer. The
remedy for these evils is to be found in an effi.
cient system of drainage.

On this subject | shall add one important prac-
tical remark, which will readily suggest itself to
the geologist who has studied the action of air and
water on the various clay beds that occur here
and there as members of the series of stratified
rocks. There are no clays which do not gradually
soften under the united influence of air and of run.
ning waler. Lt is false economy, therefore, to lay
down tiles without soles—however hard and stiff
the clay subsoil may appear to be. Jn the course
of ten or fiftecn years the stiffest clays will soften,
so as to allow the tile to sink; and many very
much sooner. ‘The passage for the water is thus
gradually narrowed ; and when the tile has sunk
a couple of inches, the whole must be taken up.

Thousands of miles of drains have been thus laid
13*

138 TILES SHOULD NOT BE LAID WITHOUT SOLES.

down, both in the low country of Scotland and in
the southern counties of England, which have now
become nearly useless; and yet the system still
goes on. It would appear even as if the farmers
and proprietors of each district—unwilling to be-
lieve in or to be benefitted by the experience of
others—were determined to prove the matter in
their own case also, before they will consent to
adopt that surer system which, though demand-
ing a slightly greater outlay at first, will return
upon the drainer with no after-calls for either
- time or capital. If my reader live in a district
where this practice is now exploded, and if he be
inclined to doubt if other counties be farther be-
hind the advance of knowledge than his own, I
would invite him to spend a week in crossing the
county of Durham, where he may find opportuni.
ties not only of satisfying his own doubts, but of"
scattering here and there a few words of useful
advice among the more intelligent of our prac-
tical farmers.

2. Subsoiling.—The subsoil plough is an auxil-
iary to the drain. ‘Though there are few subsoils
through which the water will not at length make
its way, yet there are some so stiff either naturally
or from long consolidation, that the good effect of
a well-arranged line of drains is lessened by the

USE OF THE SUBSOIL PLOUGH. 139

slowness with which they allow the superfluous
rains to pass through them. In such cases, the
use of the subsoil plough is most advantageous in
loosening the under layers of clay, and allowing
the water to find a ready escape downwards and
to either side until it reach the drains.

It is well known that if a piece of stiff clay be
cut into the shape of a brick, and then allowed to
dry, it will contract and harden—it will form an
air-dried brick, almost impervious to any kind of
gas—wet it again, it will swell and become still
more impervious. Cut up whzle wet, it will only
be divided into so many pieces, each of which will
harden when dry, or the whole of which will again
attach themselves and stick together if exposed to
pressure. But tear it asunder when dry, and it
will fall into many pieces, will more or less crumble,
and will readily admit the air into its inner parts.
So it is with a clay subsoil.

After the land is provided with drains, the sub-
soil being very retentive, the subsoil plough is
used to open it up—to let out the water and to let
in the air. If this is not done, the stiff under-
clay will contract and bake as it dries, but it will
neither sufficiently admit the air nor open a free
passage for the roots. But let this operation be
performed when the clay is still too wet, a good

140 AFTER THE LAND IS DRY.

ect will follow, in the first instance; but after
a while, the cut clay will again cohere, and the
former will pronounce subsoiling to be a useless
expense on his land, Defer ‘the use of the sub.
soil plough till the clay is dry—it will then tear
and break instead of culling, and its openness will
remain, Once give the air free access, and it,
after a time, so modifies the drained clay, that it
no longer has an equal tendency to cohere,

Mr. Smith of Deanston very judiciously recom-
mends that the subsoil plough should never be
used till at least a year after the land has been tho.
roughly drained. ‘This in many cases will be a
sufficient safeguard—will allow a sufficient time
for the clay to dry ; in other cases two years may
not be too much. But this precaution has by
some been neglected, and subsoiling being with
them a failure, they have sought, in some sup-
posed chemical or other quality of their soil, for
the cause of a want of success which is to be found
in their own neglect of a most necessary precau-
tion, Let not the practical man be too hasty in
desiring to attain those benefits which attend the
adoption of improved modes of culture; let him
give every method a fair trial; and above all, let
him make his trial in the way and with the pre-

EFFROCT OF DEEP PLOUGHING. 141

cautions recommended by the author of the method,
before he pronounce its condemnation.

3. Deep-ploughing, like subsoiling, aids the ef-
fect of the drains, and so far, and where it goes
nearly as deep, more completely effects the same
object. But independent of this, it has other uses
and merits, and where it has been successfully ap-
plied, has improved the land by the operation of
other causes.

Subsoiling only lets out the water, and allows
access to the air and a free passage to the roots,
Deep-ploughing, in addition to these, brings new
earth to the surface, forms thus a deeper soil, and
more or less alters both its physical qualities and
its chemical constitution.

If the plough be made to bring up two inches
of clay or sand, it will stiffen or loosen the soil,
as the case may be, or it may aflect its colour or
density. It is clear and simple enough, there-
fore, that by deep-ploughing the physical proper-
ties of the soil may be altered,

But there are certain substances contained in
every soil, whether in pasture or under the plough,
which gradually make their way down towards
the subsoil. ‘They sink till they reach at last
that point beyond which the plough does not

142 LIME, CLAY, AND MARL SINK.

usually penetrate. Every farmer knows that lime
thus sinks. In peat-soils top-dressed with clay,
the clay thus sinks. In sandy soils also which
have been clayed, the clay sinks; and in all these
cases, I believe, the sinking takes place more ra-
pidly when the land is laid down to grass. Where
soils are marled, the mar] sinks; and the rains,
in like manner, gradually wash out that which
gives their fertilizing virtue to the under chalk-
soils (see page 88), and render necessary a new
application from beneath, to renovate its produc-
tive powers.

If this be the case with earthy substances such
as those now mentioned, which are insoluble in
water, it will be readily believed that those saline
ingredients of the soil which are readily soluble
will be still sooner washed out of the upper and
conveyed to the under soil. Thus the subsoil
may gradually become rich in those substances of
which the surface-soil has been robbed. Bring
up a portion of this subsoil by deep-ploughing,
and you restore to the land a portion of what it
has lost—substances, perhaps, which may render
it much more fruitful than before. Such is an
outline of the theory of deep-ploughing, and it
is entirely unexceptionable.

But suppose the land to have originally con-

BRINGING SUBSOILS TO THE SURFACE. 143

tained something noxious to vegetation, which in
process of time has been washed down into the
subsoil, then to bring this again to the surface
would be materially to injure the land. This
also is true, and a sound discretion must no doubt
be employed, in judging when and where such
evil effects are likely to follow.

Such cases, however, are more rare than many
suppose. There are few subsoils which a full and
fair exposure to a winter’s frost will not in a great
degree deprive of all their noxious qualities, and
render fit to ameliorate the general surface of the
poorer lands. If the reader doubt this fact, let
him visit Yester, and give a calm consideration to
the efforts produced by the use of deep-ploughing
on the home-farm of the Marquis of 'T'weeddale.

In many cases the farmer fears, as he does in
the county of Durham, to bring up a single inch
of the yellow clay that lies beneath his soil. In
the first inch lodges, among other substances, the
iron worn from his plough, which in some soils,
and after a lapse of years, amounts to a consider-
able quantity. Till it is exposed to the air, this
iron is hurtful to vegetation, and one of the bene-
fits of a winter’s exposure of such subsoils to the
air, is the effect produced upon the iron it con-
tains.

144 EFFECT OF ORDINARY PLOUGHING.

It is the want of drainage, however, and of the
free access of air, that most frequently renders
subsoils for a time injurious to vegetation. Let
the lands be well drained—let the subsoils be
washed for a few years by the rain-water passing
through them,—and there are few of those which
are clayey in their nature that may not ultimately
be brought to the surface, not only with safety, but
with advantage to the soil.

4. Ploughing.—Other benefits, again, attend
upon the ordinary ploughings, hoeings, and work-
ings of the land. Its parts are more minutely di-
vided—the air gets access to every particle—it is
rendered lighter, more open, more permeable to
the roots. ‘The vegetable matter it contains de-
composes more rapidly by a constant turning of
the soil, so that wherever the fibres of the roots:
penetrate, they find organic food provided for
them, and an abundant supply of the oxygen of
the atmosphere to aid in preparing it. The pro-
duction of ammonia and of nitric acid also (see
pages 33 to 36), and the absorption of one or both
from the air, take place to a greater extent, the
finer the soil is pulverised, and the more it has
been exposed to the action of the atmosphere.
The general advantage, indeed, to be derived from
the constant working of the soil, may be inferred

MIXING THE SOIL. 145

from the fact, that: Tull reaped twelve successive
crops of wheat from the same land by the repeated
use of the plough and the horse-hoe. There are
few soils so stubborn as not to shew themselves
grateful in proportion to the amount of this kind
of labour that may be bestowed upon them.

5. Mixing.—It has been shewn (page 114),
that the physical properties of the soil have an im-
portant influence upon its average fertility. The
admixture of pure sand with clay soils produces
an alteration which is often beneficial, and which
is wholly physical. ‘The sand merely opens the
pores of the clay, and makes it more permeable to
the air.

The admixture of clay with sandy or peaty soils,
however, produces both a physical and a chemical
alteration. The clay not only consolidates and
gives body to the sand or peat, but it also mixes
with them certain earthy and saline substances
useful or necessary to the plant, which neither the
sand nor peat might originally contain in suffi-
cient abundance. It thus alters its chemical con-
stitution, and fits it for nourishing new races of
plants. —

Such is the case also with admixtures of marl,
of shell-sand, and of lime. They slightly consol-

idate the sands and open the clays, and thus im-
13

146 USES OF MARL AND SIELL-SAND.

prove the mechanical texture of both kinds of
soil, but their main operation is chemical ; and the
almost universal benefit they produce depends upon
the new chemical element they introduce into the
constitution of the soil.

It is a matter of almost universal remark, that
in our climate soils are fertile—clayey or loamy
soils, that is—only when they contain an appre-
ciable quantity of lime. In whatever way it acts,
therefore, the mixing of lime in any of the forms
above mentioned, with a soil in which little or no
lime exists, is one of the surest practical methods
of bringing it nearer in composition to those soils
from which the largest returns of agriculture pro-
duce are usually obtained. Some of the chemical
effects of the lime upon the soil will be explained
in a subsequent section. (See page 1@&) ,

SECTION II.——-OF THE CHEMICAL METHOD OF IMPROVING THE
SOIL BY THE USE OF MANURES<

None of the above methods of improving the
soil are mechanical only—they all involve some
chemical alterations also, which are readily to be
explained by a knowledge of elementary chemical
principles. But the manuring of the land is more
strictly a chemical operation, and may therefore

AIM OF THE FARMER IN TILLING HIS LAND. 147

with propriety be separated from those methods
of improving its quality which involve at the same
time important and expensive mechanical opera-
tions.

In commencing the tillage of a piece of land,
the conscientious farmer may have three objects
in view in regard to it.

1. He may wish to reclaim a waste, or to re-
store a neglected farm to an average condition of
fertility.

2. Finding the land in this average state, his
utmost ambition may he to keep it in its present
condition ; or,

3. By high farming he may wish to develope all
its capabilities, and to increase its permanent pro-
ductiveness in the greatest possible degree.

The man who aims at the last of these objects
is not only the best tenant and the best citizen,
but he is also his own best friend. The highest
farming, skilfully and prudently conducted, is also
the most remunerating.

But whichever of these three ends he aims at,
he will be unable to attain it without a due know-
ledge of the various manures it may be in his
power to apply to his land—what these manures
are, or of what they consist—the general and spe-
cial purposes they are each intended to serve—

148 WHAT ARE MANURES.

which are the most effective for this or that crop
—-how they are to be obtained in the greatest abun-
dance, and at the least cost—how their strength
may be economized,—and in what state and at what
seasons they may be most beneficially applied to
the land. Such are a few of the questions which
the skilful farmer should be ready to ask himself,
and should be able to answer.

By a manure is to be wnderstood whatever is
capable of feeding or of supplying food to the
plant. And as plants require earthy and saline
as well as vegetable food, gypsum and nitrate of
soda are as properly called manures as farm-yard
dung, bone-dust, or night-soil.

Manures naturally divide themselves into such
as are of vegelable, of animal, and of mineral ori-

gin.
I. OF VEGETABLE MANURES,

There are two purposes which vegetable manure
is generally supposed to serve when added to the
soil. Lt loosens the land, opens its pores, and
makes it lighter; and it also serves to supply or-
ganic food to the roots of the growing plant. It
serves, however, a third purpose: it yields to the
roots those saline and earthy matters which it is
their duty to find in the soil, and which exist in

DECAYED VEGETABLE MATTER. 149

decaying plants in a state more peculiarly fitted to
enter readily into the circulating system of new
races.

Decayed vegetable matters, therefore, are in
reality mixed manures, and their value in enrich-
ing the land must vary considerably with the kind
of plants and with the parts of those plants of
which they are chiefly made up. ‘This depends
upon the remarkable difference which exists in the
quantity and kind of inorganic matter present in
different vegetable substances, as indicated by the
ash they leave (see pages 52 to 62). Thus if 1000
Ibs. of the saw-dust of the willow be fermented,
and added to the soil, they will enrich it by the
addition of only 44 lb. of saline and earthy mat-
ter, while 1000 lbs. of the dry leaves of the same
tree fermented, and laid on, will add 82 lbs. of in-
organic matter. Thus, independent of the effect
of the vegetable matter in each, the one will pro-
duce a very much greater effect upon the soil than
the other.*

There are three states in which vegetable mat-
ter is collected by the husbandman for the purpose

* It is owing to this large quantity of saline and othe
inorganic matter that fermented leaves form too strong a
dressing for flower borders, and that gardeners therefore go-
nerally mix them up into aeompost. —

13*

150 GREEN MANURING.

of being applied to the land—the green state ; the
dry state; and that state of imperfect decay in
which it forms peat.

1. Green Manuring.—When grass is mown in
the field, and laid in heaps, it speedily heats, fer-
ments, and rots. But, if turned over frequently
and dried into hay, it may be kept for a great
length of time without undergoing any material
alteration. The same is true of all other vegetable
substances—they all rot more readily in the green
state. The reason of this is, that the sap or juice of
the green plant begins very soon to ferment in the
interior of the stem and leaves, and speedily com-
municates the same condition to the moist fibre of
the plant itself. When once it has been dried, the
vegetable matter of the sap loses this easy tend-
ency to decay, and thus admits of long preserva-
tion.

The same rapid decay of green vegetable mat-
ter takes place when it is buried in the soil. ‘Thus
the cleanings and scourings of the ditches and
hedge-sides form a compost of mixed earth and
fresh vegetable matter, which soon becomes capa-
ble of enriching the ground. When a green crop
is ploughed into a field, the whole of its surface
is converted into such a compost—the vegetable

UNIVERSALITY OF THE PRACTICE. 151

jatter in a short time decays into a light, black
mould, and enriches in a remarkable degree and
fertilizes the soil.

Hence the practice of green manuring has been
in use from very early periods. The second or
third crop of lucerne was ploughed in by the an-
cient Romans—as it still is by the modern Italians.
In Tuscany, the white lupin is ploughed in, in
preference—in Germany, borage. In French
Flanders, two crops of clover are cut, and the third
is ploughed in. In Sussex, turnip seed has been
sown at the end of harvest, and after two months
again ploughed in, with great benefit to the land.
Turnip leaves and potato tops decay more readily,
and more perfectly, and are more enriching when
buried in the green state. It is a prudent econo-
my, therefore, where circumstances admit of it, to
bury the potato tops on the spot from which the
potatoes are raised. Since the time of the Romans,
it has been the custom to bury the cuttings of the
vine stocks at the roots of the vines themselves ;
and many vineyards flourish for a succession of
years without any other manuring.

Buckwheat, winter tares, clover, and rape, are
all occasionally sown for the purpose of being
ploughed in. ‘This should be done when the flower

152 UrFKCT OF GREKN MANURING.

has just begun to open, and if possible at a season
when the warmth of the air and the dryness of the
soil are such as to facilitate decomposition.

That the soil should become richer in vegetable
matter by this burial of a crop than it was before
the seed of that crop was sown, and should also
be otherwise benefitted, will be understood by re-
collecting (see page 42) that perhaps three-fourths
of the whole organic matter we bury has been
derived from the air—that by this process of
ploughing in, the vegetable matter is more equally
diffused through the whole soil than it could ever
be by any merely mechanical means ;—and that by
the natural decay of this vegetable matter, ammo-
nia and nitric acid are, to a greater extent (pages
33 and 34), produced in the soil, and its agri-
cultural capabilities in consequence materially
increased,

These considerations, while they explain the
effect and illustrate the value of green manuring,
will also satisfy the intelligent agriculturist that
there are methods of improving his land without
the aid either of town or of foreign manures—and
that he overlooks an important natural means of
wealth who neglects the green sods and crops of
weeds that flourish by his hedgerows and ditches.
Left to themselves, they ripen their seeds and sow

USE OF SKA WEED. 153

them annually in his fields—collected in compost
heaps they would materially add to his yearly
crops of corn,

Sea-wecds,——-Among green manures, the use of
fresh sea-ware deserves especial mention, from the
remarkably fertilizing properties it is known to
possess, as well as from the great extent to which it
is employed on all our coasts. ‘The produce of the
isle of ‘Thanet in Kent is said to have been doubled
or tripled by the use of this manure; the farms
on the Lothian coasts are said to be let for 20s. or
30s. more rent when they have a right of way to
the sea, where the weed is thrown on shore; and
in the Western Isles the sea-ware, the shell-marl,
and the peat-ash, are the three great natural fer-
tilizers to which the agriculture of the district
is indebted for the comparative prosperity to
which it has in some of the islands already at-
tained,

Sea-weeds decompose with great ease when col.
lected in heaps or spread upon the land, During
their decay, they yield not only organic food to
the plant but saline matters also, to which much
of their efficacy both on the grass and the corn
crops is no doubt to be ascribed,

2. Manuring with dry Vegetable Matter,—Al-
most every one knows that the saw-dust of most

154 FERMENTATION OF DRY STRAW.

common woods decays very slowly—so slowly, that
it is rare to meet with a practical farmer who con-
siders it worth the trouble of mixing with his
composts. ‘This property of slow decay is pos-
sessed in a certain degree by all dry vegetable
matter, Heaps of dry straw alone, or even
mixed with earth, will ferment with comparative
difficulty and with great slowness. It is neces-
sary, therefore, to mix it, as is usually done, with
some substance that ferments more readily, and
which will impart its own condition to the straw.
Animal matters of any kind, such as the urine and
droppings of cattle, are of this character ; and it is
by admixture with these that the straw which is
trodden down in the farm-yard is made to undergo
a more or less rapid fermentation.

The object of this fermentation is twofold—first,
to reduce the particles of the straw to such a mi-
nute state of division, that they may admit of
being diffused through the soil; and, second, that
the dry vegetable matter may be so changed by ex-
posure to the air, and other agencies, as to be fitted
to yield both organic and inorganic food to the
roots of the plants it is intended to nourish.

We have seen that this decomposition takes
place very speedily, and of its own accord, when
the vegetable matter is green, but that it can be

LONG AND SHORT DUNG. 155

anduced or brought on in the case of dry straw by
the agency of animal matter. The same means will
cause the fermentation of any other vegetable sub-
stance which is in a minute state of division. Even
saw-dust made into a compost heap with soil or
sods, and watered regularly and copiously with the
liquid manure of the farm-yards, may be thus con<
verted into a fertilizing vegetable mould.

Differences of opinion have prevailed, and dis-
cussions have taken place, as to the relative efficacy
of long and short—or of half fermented and of fully
rotten dung. But if it be added solely for the
purpose of yielding food to the plant, or of pre-
paring food for it, the case is very simple. The
more complete the state of fermentation—if not
carried too far—the more immediate will be the
agency of the manure ; hence the propriety of the
application of short dung to turnips and other
plants it is desirable to bring rapidly forward ;
but if the manure be only half decayed, it will re-
quire time in the soil to complete the decomposi-
tion, so that its action will be more gradual and
prolonged.

Though in the latter case the immediate action
is not so perceptible, yet the ultimate benefit to
the soil, and to the*crops, may be even greater,
supposing them to be such as require no special

156 SLOW EFFECTS OF SAW-DUST.

forcing at one period of the year, With a view
to this slow amelioration, vegetable matter of any
kind may be added with benefit, if in a sufficient
state of division, to the soil. Even saw-dust ap-
plied largely to the land, has been found to im-
prove it, though little at first, yet more during
the second year after it was applied, still more
during the third, and most of all in the fourth
season after it was mixed with the soil. That any
dry vegetable matter, therefore, does not produce
an immediate effect, ought not to induce the prac-
tical farmer to despise the application to his land—
either alone, or in the form of a compost—of every
thing of the kind he can readily obtain. If his
fields are not already very rich in vegetable mat-
ter, both he and they are likely to be ultimately
benefitted by such additions to the soil.

Rape Dust.—It is from the straw of the corn-
bearing plants, or from the stems and leaves of
the grasses, that the largest portion of the strictly
vegetable manures applied to the soil is generally
obtained or prepared. But the seeds of all plants
are much more enriching than the substance of
their leaves and stems. These seeds, however,
are in general too valuable for food to admit of
their application as a manure. Still the refuse of
some, as that of different kinds of rape-seed after

RAPE AND MALT DUST. , 157

the oil is expressed, and which is unpalatable to
cattle, is applied with great benefit to the land.
Drilled in with spring wheat, or scattered as a
top-dressing in spring at the rate of 5 cwt. to dn
acre, it gives a largely increased and renaunerat-
ing return. It is applied with equal success to
the cultivation of potatoes, and generally it may
be substituted for farm-yard manure at the rate
of about 1 cwt. of rape-dust for each ton of ma-
nure.

Malt Dust consists of the dried sprouts of bar-
ley, which, when the sprouted seed is dried in the
process of malting, break off and form a coarse
powder. ‘This is found to be almost equal to rape
dust in fertilizing power. :

Charcoal Powder possesses the remarkable pro-
perty of absorbing noxious vapours from the air
and soil, and unpleasant impurities from water.
It also sucks into its pores much oxygen from the
air. Owing to these and other properties, it isa
valuable substance for mixing with liquid manure,
night-soil, farm-yard manure, ammoniacal liquor,
or other rich applications to the soil. It is even
capable by itself of yiclding slow supplies of nour-
ishment to living plants, and is said, in many cases,
without any admixture, to have been used with ad-
vantage in practical agriculture. In moist charcoal

1

158 SOOT AND CHARCOAL POWDER.

the seeds of the gardener are found to sprout with
remarkable quickness and certainty.

Soot, whether from the burning of wood or of
coal, is of vegetable origin, and consists chiefly of
a finely-divided charcoal, possessing the properties
above mentioned. It contains, however, ammonia
and certain other substances in small quantity, to
which its well known, and especially its ammediate,
effects upon vegetation are in part to be ascribed.

3. The use of Peat.—In many parts of the
world, and in none more abundantly, perhaps,
than in Gt. Britain, is vegetable matter collected
in the form of peat. This ought to supply an
inexhaustible store of organic matter for the ame-
lioration of the adjacent soils. We know that by
draining off the sour and unwholesom@ water,
and afterwards applying lime and clay, the sur-
face of peat bogs may be gradually converted into
rich corn-bearing lands, It must, therefore, be
possible to convert peat itself by a similar process
into a compost fitted to improve the condition of
other soils.

The late Lord Meadowbank, who made many
important experiments on this subject, found, that
after being partially dried by exposure to the air,
peat might be readily fermented, and brought into
the state of a rich fertilizing compost by the same

USE OF PEAT IN COMPOSTS. 159

means which are adopted in the ordinary ferment-
ing of straw. He mixed with it a portion of ani-
mal matter, which soon communicated its own
fermenting quality to the surrounding peat, and
brought it readily in to a proper heat. He found
that one ton of hot fermenting manure, mixed
in alternate layers with two of half dry peat, and
covered by the same, was sufficient to ferment the
whole ; and subsequently that the vapours which
rise from naturally fermenting farm-yard manure
or animal matters, would alone produce the same
effect upon peat, placed so as readily to receive
and absorb them.

As ammonia is one of the compounds specially
given off by putrifying animal substances, it is
not unlikely that a watering with ammoniacal li-
quor would materially prepare the peat for un-
dergoing fermentation. At all events it seems
possible to prepare any quantity of valuable peat
compost by mixing the peat with a still less quan.
tity of fermented manure than was employed by
Lord Meadowbank, provided the liquid manure
of the farm-yard be collected in a cistern, and be
thrown at intervals by means of a pump over the
prepared heaps.

' One important use also to which I think peat
may be applied is, after it is partly dried, to

160 RELATIVE VALUE
3

build it into covered heaps, and half burn or char
it till it become readily reducible into a fine pow-
der. In this state it would be of great value as
a mixture to preserve the virtues of liquid ma-
nures of all kinds, of night-soil, and of ammonia-
cal liquor.

SECTION III.—-RELATIVE VALUE OF DIFFERENT VEGETABLE
MANURES.

There are two principles on which the relative
value of different vegetable substances, as ma-
nures, may be stated to depend—/irst, on the rela-
tive quantity and kind of inorganic matter they
contain ; and second, on the relative proportions
of nitrogen present in each,

1. Valued according to the quantity of inorga-
nic matter they contain—the worth of the several
kinds of straw and hay would be represented by
the following numbers :—

Wheat straw, . «Ge es VO cn
Oat straw, . ° 3 : . 100 to 180
Ekayy* 2 : : ‘ ° . 100 to 200
Barley straw, : ’ : . 100 to 120
Pea straw, . ‘ ; ‘ - £00

Bean straw, : : ‘ . 60to 80

Rye straw, .° : ‘ . 50to 70

OF DIFFERENT VEGETABLE MANURES. 161

Dry potato tops, ; ‘ , 100
Dry turnip tops, ; : . 260
Rape, cake ; ‘ ; : 120

that is, a ton weight of each of these substances,
when made into manure—provided nothing is
washed out by the rains—will return to the soil
the above quantities of inorganic matter in pounds.
Generally, perhaps, these numbers will give the
reader an idea of the relative permanent effect of
these different kinds of vegetable matter when
laid upon the soil. But, by a reference:to the facts
stated in pp. 58 to 64, in regard to the quality of
the inorganic matter contained in plants, he will
satisfy himself, that the effect of these manures on
particular crops is not to be judged of solely by
the absolute quantity of earthy and saline matter
they contain ;—that which the turnip-top, for
example, or the bean-stalk, returns to the soil, may
not be exactly what will best promote the growth
of wheat.

2. On the other hand, if the fertilizing value ot
vegetable substances is to be calculated by the re.
lative quantities of nitrogen they severally contain,
we should place them in the following order :—-
the number opposite to each substance representinz

that weight of it in pounds, which would produce
14*

162 RELATIVE QUANTITIES OF NITROGEN.

the same effect as 100 pounds of farm-yard ma.
nure, consisting of the mixed droppings and litter
of cattle.
Equivalent quantities
in pounda,

Farm-yard manure, ‘ : : 100
Wheat straw, mae 4) alban 80 to 1'70

Oat straw, . : , ° ‘ 150
Barley straw, . ; ; ; : 180
Buckwheat, . duane! ; : 85
Pea straw, . ; : ‘ ‘ 45
Wheat chaff, . , : , ; 50
Green grass, . , : ; ‘ 80
OURO ROM ios bi Felted Don. want 75
Fresh sea-weed, . ‘ , : 80
RAPS Cua ee 8
Fir saw-dust, 7 i ’ d 250

Oak saw-dust, ; e ° : 180
eer Oe a a eer 30

This table again presents the same substances
in a somewhat different order of value ; shewing,
for example, not only that such substances as rape-
dust and soot should produce a much more re-
markable effect upon vegetation, than the same
weight even of farm-yard manure, but also that
certain dry vegetables, such as chaff'and pea-straw,
will yield, when not unduly fermented, a more
enriching manure than barley, oat, or wheat straw.
It agrees, also, with the known effect of green

EFFECT OF THIS NITROGEN. 163

manuring upon the land, since 80 pounds of mea-
dow-grass ploughed in, will be equal in virtue to
100 of farm-yard manure.

Some writers ascribe the entire action of these
measures to the nitrogen they contain. ‘This, how-
ever, is taking a one-side view of their real natu-
ral operation. ‘The nitrogen, during their decay,
is liberated chiefly in the form of ammonia—an
evanescent substance, producing an immediate ef-
fect in hastening or carrying further forward the
growth of the plant, but not remaining perma-
nently in the soil. The reader, therefore, will
form an opinion consistent alike with theory and
with practice, if he conclude—

1. That the immediate effect of a vegetable
manure, in hastening the growth of plants, is de-
pendent, in a great degree, upon the quantity of
nitrogen it contains and gives off during its decay
in the soil.

2. That the permanent effect and value of man-
ures is to be estimated chiefly by the quantity
and quality of the inorganic matter they contain
—of the ash they leave when burned.

The effect of the nitrogen may be nearly ex-
pended in a single season—that of the earthy and
saline matter may not be exhausted for several
years.

164 USE OF THEIR OTHER INGREDIENTS.

Nor is the carbon of vegetable substances with-
out its important uses to vegetation. From the
statements contained in the earlier chapters of the
present work, it may be inferred that, however
much influence we may allow to the nitrogen and
to the earthy matter of plants in aiding the growth
of future races—the soundest view of these im-
portant natural operations is that which considers
each element present in decaying plants to be ca-
pable of ministering food to such as are still alive,
—though we may not be able as yet, either to
estimate the precise importance of each element
to any particular kind of crop, or exactly to adjust
their relative quantities in our manures, so as to
promote the growth of such a crop in the greatest
possible degree.

CHAPTER IX.

Animal Manures—Their relative value and mode of Action
—Difference between Animal and Vegetable Manures—
Cause of this difference—Mineral Manures—Nitrates of
Potash and Soda—Sulphate of Soda, Gypsum, Chalk, and
Quicklime—Chemical action of these Manures—Artifi-
cial Manures—Burning and Irrigation of the Soil—Plant-
ing and laying down to grass.

Tue animal substances employed as manure
consist chiefly of the flesh, blood, bones, horns, and
hair of animals, of fish—which in some places are
found in sufficient quantity to be laid upon the
land—and of the solid and liquid excrements of
animals and birds.

SECTION I.—-OF UNDIGESTED ANIMAL MANURES,

Animal substances, in general, act more power-
fully as manures than vegetable substances—it is
only the seeds of plants which can at all compare
with them in efficacy.

The flesh of animals is rarely used as a manure,

166 FLESH, FISH, AND THE BODIES OF INSECTS.

except in the case of dead horses, or cattle which
cannot be used for food. Fish is chiefly applied
in the form of the refuse of the herring and pilchard
fisheries, though occasionally such shoals of sprats,
herrings, and even mackerel, have been caught on
our shores, as to make it necessary to employ them
as manure. ‘These recent animal substances are
found to be too strong when applied directly to the
land; they are generally, therefore, made into a
compost, with a large quantity of soil. Five barrels
of fish, or fish refuse, made into twenty loads of
compost, will be sufficient for an acre. The refuse
of fish oils,—of the fat of animals that has been
melted for the extraction of the tallow—of skins
that have been boiled for the manufacture of glue
—horns, hair, wool (woollen rags), and all simi-
lar substances, when made into composts, exercise,
in proportion to their weight, a much greater in-
fluence upon vegetation than any of the more
abundant forms of vegetable matter.

Even the bodies of insects are in many parts of
the world important manures of the soil. In
warm climates, a handful of soil sometimes seems
almost half made up of the wings and skeletons of
dead insects—the peasant in Hungary and Carin-
thia occasionally collects as many as thirty cart-
loads of dead marsh flies in a single year ;—and in

BLOOD, HORN, HAIR, AND WOOL. 167

the richer soils of France and England, where
worms and other insects abound, the presence of
their remains in the soil must also aid its natural
productiveness.

Blood is rarely applied to the land directly—
though, like the other parts of animals, it makes
an excellent compost. Asit comes from the sugar
refineries, however, in which, with lime water and
animal charcoal, it is employed for the refining
of sugar, it has obtained a very extensive employ-
ment, especially in the south of France. This
animal black, or animalized charcoal, as it is some-
times called, contains about twenty per cent. of
blood, and has risen to such a price in France, that
the sugar refiners actually sell it for more than the
unmixed blood and animal charcoal originally
cost them. This has given rise to the manufacture
of artificial mixtures of charcoal, fecal matters,
and blood, which are also sold under the name of
animalized charcoal. ‘The only disadvantage at-
tending these artificial preparations is, that they
are liable to be adulterated, or, for cheapness, pre-
pared in a less efficient manner.

Horn, hair, and wool, depend for their efficacy
precisely on the same principles as the blood and
flesh of animals. They differ chiefly in this, that
they are dry, while blood and flesh contain 80 to

168 COMPOSITION OF BONES.

90 per cent. of their weight of water. Hence, a
ton of horn shavings, of hair, or of dry woollen
rags, ought to enrich the soil as much as ten
tons of blood. In consequence, however, of their
dryness, the horn and wool decompose much more
slowly than the blood. Hence, the effect of soft
animal matters is more immediate and apparent,
that of hard and dry substances less visible, but
continuing for a much longer period of time.

Bones, again, while they resemble horn in being
dry, differ from it in containing, besides the ani-
mal matter, a large quantity of earthy matter also,
and hence they introduce a new agent to aid their
effect upon the soil. Thus, the bones of the cow
consist of 100 lbs. of

Phosphate of lime, 65) Oh ye i oe
Phosphate ofmagnesia,_ . iy nineties 3
Soda and common salt, . : : ; 34
Carbonate of lime, . ; rhe: : 33
Fluoride of calcium, . é : : ; 1
Gelatine (the substance ofhorn),. . . 33}
100

While 100 Ibs. of bone-dust, therefore, add to
the soil as much organic animal matter as 33 Ibs.
of horn, or as 300 or 400 lbs. of blood or flesh,
they add, at the same time, much inorganic matter
—lime, magnesia, soda, common salt, and phos-

GENERAL CONCLUSIONS. 169

phoric acid (in the phosphates),—all of which, as
we have seen, must be present in a fertile soil,
since the plants require a certain supply of them
all at every period of their growth. ‘These sub-
stances, like the inorganic matter of plants, may
remain in the soil, and may exert a beneficial action
upon vegetation after all the organic or gelatinous
matter has decayed and disappeared.

From what is above stated, therefore, the reader
will gather these general conclusions :

1. That animal substances which, like flesh and
blood, contain much water, decay rapidly, and are
fitted to operate ammediately and powerfully upon
vegetation, but are only temporary or evanescent
in their action.

2. That when dry, as in horn, hair, and wool,
they decompose, and consequently act more slow-
ly, and continue to manifest an influence, it may
be, for several seasons.

3. That bones, acting like horn, in so far as their
animal matter is concerned, and, like it, for a
number of seasons, more or less, according as they
have been more or less finely crushed—may ame-
liorate the soil by their earthy matter for a still
longer period—permanently improving the con-
dition and adding to the natural capabilities of

the land.
15

170 LIQUID MANURES.

SECTION Il.--OF DIGESTED ANIMAL MANURES,.

Practical men have long been of opinion that
the digestion of food, either animal or vegetable,
—the passing of it through the bodies of animals,
—enriches its fertilizing power, weight for weight,
when added to the land. Hence, in causing ani-
mals to eat up as much of the vegetable produc-
tions of the farm as possible, it is supposed that
not only is so much food saved, but that the value
of the remainder in fertilizing the land is greatly
increased. In a subsequent section we shall see
how far theory serves to throw light upon these
opinions. (See Section [V., p. 182 to 186.)

I. LIQUID EXCRETIONS.

The digested animal substances usually em-
ployed as manures are, the urine of the cow and
the sheep, the solid excrements of the horse, the
cow, the sheep, and the pig, the droppings of
pigeons and other birds, and night-soil. ‘The Ii-
quid manures act chiefly through the saline sub-
stances they hold in solution, while the solid
manures contain also insoluble matters, which
decay slowly in the soil, and there become useful
only after a time. ‘The former, therefore, will
influence vegetation more powerfully at first ; the

COMPOSITION OF URINE. 7}

action of the latter will be less evident, but will
continue to operate for a much longer period,
Urine.—Human urine consists, in 1000 parts, of

Water, ; ; ‘ ; 932
Urea, and other organic matters containing nitrogen, 49
Phosphates of arnmonia, lime, soda, and magnesia, 6
Sulphates of soda and ammonia, — . ‘ 7
Sal ammoniac and common salt, —. ; 6

LQ00

A thousand pounds of urine therefore contain
68 lbs. of dry fertilizing matter of the richest
quality, worth, at the present rate of selling artifi-
cial manures in this country, at least 20s. a owt.
As each person voids almost 1000 Ib, of urine in
a year, the national waste incurred in this form
amounts, at the above valuation, to 129, a head,
And if five tons of farm-yard manure per acre,
added year by year, will keep a farm in good
heart, four cwt. of the solid matter of urine would
probably have an equal effect; or the urine alone
discharged into the rivers by a population of
10,000 inhabitants would supply manure to a farm
of 1500 acres, yielding a return of 4500 quarters
of corn or an equivalent produce of other crops.

The urine of the cow is said to contain less
water than that of man, though of course much
must depend upon the kind of food with which it

172 VALUE OF URINE AS A MANURE.

is fed. Reckoning, then, the large quantity of
liquid manure that is yielded by the cow (2000 or
3000 gallonsa year),we may safely estimate the solid
matter given off by a healthy animal in this form
in twelve months at 1200 to 1500 pounds weight,
worth, ¢f it were in the dry state, from £10 to £12
sterling. In the liquid state, the ure of one cow
collected and preserved as it is in Flanders, is valued
in that country at about £2 a year. Any practical
farmer may calculate for himself, therefore, how
much real wealth, taking it even at the Flemish va-
lue, is lost in his own farm-yard—how much of the
natural means of reproductive industry passes into
his drains or evaporates into the air.

This liquid manure is invaluable, when collected
in tanks, for watering the manure and compost
heaps, and thus hastening their decomposition ;
but great part of it may also be sprinkled directly
upon the fields of grass and upon the young corn,
with the best effects. It must, however, be permit-
ted to stand till fermentation commences, and af-
terwards diluted with a considerable quantity of
water, before it will be in the best condition for
laying on the land,

Urate.—In order to obtain the virtues of ani-
mal urine in a concentrated form, the custom has
been adopted of mixing burnt gypsum with it,

DRIED URINE—URATR. 173

in the proportion of 10 lbs. to every 7 gallons, allow-
ing the mixture, occasionally stirred, to stand some
time, pouring off the liquid, and drying and crush-
ing the gypsum. ‘This is sold by manure manu-
facturers under the name of urate, It never can
possess, however, the virtues of the urine, since it
does not contain the soluble saline substances,
which the gypsum does not carry down with it.
Except the gypsum, indeed, 100 Ibs. of urate con-
tain no greater weight of saline and organic matter
than 10 gallons of urine. If it be true, then, as
the manufacturers state, that 3 or 4 cwt. of urate
are sufficient manure for an acre, the practical
farmer will, | hope, draw the conclusion,—not that
it is well worth his while to venture his money in
trying a portion of it upon a piece of his land,—but
that a far more promising adventure will be to go
to some expense in saving his own liquid manure,
and, after mixing it with burned gypsum, to lay it
abundantly upon all his fields.

Il. SOLID EXCRETIONS.

Cow and Horse Dung.—So much of the saline,
nutritive, and soluble organic matters from the cow
pass off in the liquid form, that cow dung is correctly

called cold, since it doesnot readily heat and run into
15*

174 HORSE AND COW DUNG—NIGHT-SOIL.

fermentation. Mixed with other manures, however,
or well diffused through the soil, it aids materially
in promoting vegetation. The horse being fed
generally on less liquid food, and discharging less
urine, yields a hotter and richer dung, which, how-
ever, answers best also when mixed with other
varieties. The dung of the swine is soft and cold,
like that of the cow, containing, like it, at least 75
per cent. of water. As this animal lives on more
varied food than any other reared for the use of
man, the manure obtained from it is also very
variable in quality. Applied alone, as a manure
to roots, it is said to give them an unpleasant
taste, and even to injure the flavour of tobacco,
It answers best for hemp, and, it is said, also for
hops ; but, mixed with other manures, it may be
applied to any crop.

Night-soil is probably the most valuable, and
yet, in Europe at least, the most disliked and ne-
glected of all the solid animal manures. _ It varies
no doubt in richness with the food of the inhabi.
tants of each district,—chiefly with the quantity
of animal food they consume,—but when dry, no
other solid manure, weight for weight, can proba-
bly be compared with it in general efficacy. It
contains much soluble and saline matter, and as it
is made up from the constituents of the food we

POUDRETTE AND ANIMALIZED CHARCOAL. 175

eat, of course it contains most of those elementary
substances which are necessary to the growth of
the plants on which we principally live.

Attempts have been made to dry this manure
also, so as to render it more portable,—to destroy _
its unpleasant smell, so as to reconcile practical
men to a more general use of it,—and by certain
chemical additions, to prevent the waste of ammo-
nia and other volatile substances, which are apt to
escape and be lost when this and other powerful
animal manures begin to putrify through decay.
In Paris, Berlin, and other large cities, the night-
soil, dried first in the air with or without a mix
ture of gypsum or lime, then upon drying plates,
and finally in stoves, is sold under the name of
poudreite, and is extensively exported in casks to
various parts of the country. In London also it
is dried with various mixtures, while in others of
our large towns an animalized charcoal is prepared
by mixing and drying night-soil with gypsum and
ordinary wood charcoal in fine powder.

The half-burned peat above described (p. 80,)
would answer well for such a purpose, while few
simple and easily attainable substances would
make a better compost with night-soil, and more
thoroughly preserve its virtues, than half-dry peat
or rich vegetable soil, mixed with more or less

176 PIGEONS’ DUNG—GUANO.

marlor gypsum. It is impossible to estimate the
proportion of waste which this valuable manure
undergoes by being allowed to ferment, without
mixture, in the open air.

Taffo.—In China it is kneaded into cakes with
clay, which are dried in the air, and, under the
name of daffo, form an important article of export
from all the large cities of the empire.

Pigeons’ Dung.—The dung of all birds is found
to possess eminent fertilizing virtues. Some va-
rieties are stronger than others, or more imme-
diate in their action, and all are improved for the
use of the farmer by being some time kept, either
alone or in compost. In Flanders the manure of
one hundred pigeons is considered worth 20s. a
year for agricultural purposes.

Guano is the name given by the natives of Peru
to the dung of sea-fowl, which in former periods
used to be deposited in vast quantities on the rocky
shores and isles of the Peruvian coast. ‘The nu-
merous shipping of modern times has disturbed
and driven away many of the sea-fowl, so that
comparatively little of their recent droppings is
now preserved or collected. Ancient heaps of it,
however, still exist in many places, more or less
covered up with drifted sand, and also more or less
decomposed. ‘These are now largely excavated for

USES OF THE DROPPINGS OF BIRDS. 177

exportation, not only to different parts of the coast
of Peru, as seems to have been the case from the
most remote periods, but also to Europe, and espe-
cially to England. It is at present sold at 20s. a
cwt. in this country, and is capable of entirely re-
placing farm-yard dung,—that is to say, turnips
may be manured successfully with guano alone ;—
but it has not yet been satisfactorily determined
that the English farmer can afford to use it in this
way to any extent, at the price now asked for it.

The dung of birds possesses the united virtues
of both the liquid and solid excretions of other
animals. It contains every part of the food of the
bird, with the exception of what is absolutely ne-
cessary for the support and for the right discharge
of the functions of itsownbody. It is thus fitted,
therefore, to return to the plant a greater number
of those substances on which plants live, than
either the solid or the fluid excrements of other
animals; in other words, to be more nourishing to
vegetable growth.

SECTION III.—OF THE RELATIVE GROWTH OF THE
DIFFERENT ANIMAL MANURES.

The fertilizing power of animal manures, in ge-
neral, is dependent, like that of the soil itself,

178 RELATIVE VALUES OF

upon the happy admixture they contain of a great
number, if not of all, those substances which are
required by plants in the universal vegetation of
the globe. Nothing they contain, therefore, is
without its share of influence upon their general
effects, yet the amount of nitrogen present in
each affords the readiest and most simple cri-
terion by which their agricultural value, com-
pared with that of vegetable matters and with that
of each other, can be pretty nearly estimated.

In reference to their relative quantities of ni-
trogen, therefore, they have been arranged in the
following order, the number opposite to each re-
presenting the weight in pounds which is equiva-
lent to or would produce the same sensible effect
upon the soil as 100 lbs. of farm-yard manure.

Farm-yard manure, ; ; : 100
Solid excrements of the cow ‘ ; 125
‘ Rf ‘horse, ‘ ‘ 73
Liquid ditto of the cow, . ‘ . 91
} 3 Ons) ye : , 16
Mixed ditto of the cow, . ‘ : 98
f: ee" HONse) : ; 54
" ¥ «sheep?» . J 36
ce 13 « pig, ‘ i . 64.
Dry flesh, : ; ; : 3
Pigeons’ dung, .. , : : 5

Flemish liquid manure, . ; oni OU

DIFFERENT ANIMAL MANURES. 179

Liquid blood, ; , . : 15
Dry blood, ‘ ; : ‘ 4
Feathers, . ; : ; ; 3
Cow hair, . j P : i 3
Horn shavings, . } : : 3
Dry woollen rags, . , : . 24

It is probable that the numbers in this table do
not err very widely from the true relative value
of these different manures, in so far as the organic
matter they severally contain is concerned. ‘The
reader will bear in mind, however,

1, That the most powerful substances in this
table, woollen rags, for example, —24 lbs. of which
are equal in virtue to 100 lbs. of farm-yard manure,
—may yet shew less immediate sensible effect upon
the crop than an equal weight of sheep’s dung, or
even of urine. Such dry substances are long in
dissolving and decomposing, and continue to evolve
fertilizing matter, after the softer and more fluid
manures have spent their force. Thus, while farm-
yard manure or rape dust will immediately hasten
the growth of turnips, woollen rags will come into
operation at a later period, and prolong their
growth into the autumn.

2. That besides their general relative value, as
represented in the above table, each of these sub-

180 GREATER VALUE OF MIXED MANURES.

stances hasa further special value not here exhibited,
dependent upon the kind and quantity of saline and
other inorganic matter which they severally contain.
Thus three of dry flesh are equal to five of pigeons’
dung, in so far as the organic part is concerned ;
but the latter contains also a considerable quantity
of bone earth and of saline matter scarcely present
at all in the former. Hence pigeons’ dung will be-
nefit vegetation in circumstances where dry flesh
would in some degree fail. So the liquid excre-
tions contain much important saline matter not
present in the solid excretions,—not present either
in such substances as horn, wool, and hair,—and,
therefore, each must be capable of exercising an
influence upon vegetation peculiar to itself.

Hence the practical farmer sees the reason why
no one simple manure can long answer on the
same land; and why in all ages and countries the
habit of employing mixed manures and artificial
composts has been universally diffused.

SECTION IV.~NATURAL DISTINCTION OR DIFFERENCE BE-
TWEEN ANIMAL AND VEGETABLE MANURES, AND THE
CAUSE OF THIS DIFFERENCE,

In what do animal manures differ from vege-
table manures,—what is the cause of this differ-

ANIMAL DIFFER FROM VEGETABLE MANURES. 181

ence,—how does the digestion of vegetable matter
improve its value as a manure ?

1. The characteristic distinction between animal
and vegetable manures is this,—that the former
contain a much larger proportion of nitrogen than
the latter. ‘This will be seen at once, by compar-
ing together the tables given in the two preced-
ing sections, in which the numbers represent the
relative agricultural values of certain animal and
vegetable substances compared with farm-yard ma-
nure. ‘The lowest numbers represent the highest
value, and the largest amount of nitrogen, and
these low numbers are always opposite to the
purest animal substances.

2. In consequence of containing so much nitro-
gen, animal substances are further distinguished
by the rapidity with which, when moist, they pu-
trify or run to decay. During this decay the ni-
trogen they contain gradually assumes the form
of ammonia, which is perceptible by the smell, and
which, when proper precautions are not taken, is
apt in great part to escape into the air. Hence
the loss by fermenting manure too completely,—or
without proper precautions to prevent the escape
of volatile substances. And as animal manure,
when thus over-fermented, or permitted to lose its

ammonia into the air, is found much less active
16

182 iN WHAT THEY DIFFER.

upon vegetation than before ; it is reasonably con-
cluded, that to this ammonia, chiefly, their peci-
liar virtue, when rightly prepared, is in a great
measure to be ascribed.

Vegetable substances do not decay so rapidly,—
do not emit the odour of ammonia when ferment-
ing,—nor, when prepared in the most careful way,
does vegetable manure exhibit the same remark-
able action upon vegetable life as is displayed by
almost every substance of animal origin.

3. Whence do animal substances derive all this
nitrogen? Animals live only upon vegetable pro-
ductions containing little nitrogen ; can they then
procure all they require from this source alone ?
Again, does the act of digestion produce any che-
mical alteration upon the food of animals, that
their excretions should be a better manure,—
should be richer in nitrogen than the substances
on which they feed? Does theory throw any light
upon the opinion generally entertained among
practical men upon this point ?

These two apparently distinct questions will be
explained by a brief reference to one common na-
tural principle.

Animals have two necessary vital functions to
perform,—to breathe and to digest. Both are of
equal importance to the health and general wel-

EFFECTS OF ANIMAL DIGESTION, 183

fare of the animal. The digester (the stomach)
receives the food, melts it down, extracts from it
what is best suited to its purposes, and conveys
it into the blood. The breathers (the lungs) sift
the blood thus mixed up with the newly digested
food, combine oxygen with it, and extract carbon,
—which carbon, in the form of carbonic acid, they
discharge by the mouth and nostrils into the air,

Such is a general description of these two great
processes,—their effect upon the food that remains
in the body and has to be rejected from it, is not
difficult to perceive.

Suppose an animal to be full grown. Take a
full grown man. All that he eats as food is in-
tended merely to renovate or replenish his system,
to restore that which is daily removed from every
part of his body by natural causes. Jn the full
grown state, every thing that enters the body must
come out of the body in one form or another. The
first part of the food that escapes is that portion
of its carbon that passes off from the lungs during
respiration. ‘This quantity varies in different in.
dividuals—chiefly according to the quantity of
exercise they take. From 5 to 9 ounces a day is
the average quantity, though in periods of violent
bedily exertion 13 to 15 ounces of carbon are
breathed out in the form of carbonic acid,

184 HOW THE PROPORTION OF THE NITROGEN

Suppose a man to eat a pound and a half of
bread and a pound of beef in 24 hours, and that
he gives off by respiration 8 ounces of carbon

(3500 grains) during the same time. Then he
has

Carbon. Nitrogen.
Taken, in his food, about 4500 grains, and 500 gers. while
He has given off in

steve 3500 and little or no nitrogen,
respiration,

——— ——

Leaving to be convert-
ed into food, or to} 1000 ers.and 500 grs.
be rejected,

Our two conclusions, therefore, are clear. The
vegetable food, by respiration, is freed from a
large portion of its carbon, which is discharged in-
to the air,—nearly the whole of the nitrogen re-
maining behind. In the food consumed the car-
bon was to the nitrogen as 9 to 1; in that which
remains, after respiration has done its work, the
carbon is to the nitrogen in the proportion of only
2 tol.

It is out of this residue, rich in nitrogen, that
the several parts of animal bodies are built up.
Hence the reason why they can be formed from
food poor in nitrogen, and yet be themselves rich
in the same element.

BECOMES GREATER IN THE EXCRETIONS. 185

It is this same residue also which, after it has
performed its functions within the body, is dis-
charged again in the form of solid and liquid ex-
cretions. Hence the greater richness in nitrogen,
—the greater fertilizing power of the dung of ani-
mals than of the food on which they live.

‘T'wo other remarks I shall add for the benefit of
the practical man.

1. The manure of the cow, taking it mixed, is
not so rich in nitrogen as that of man,—because
the cow in the stall, large though it be, and great
the bulk of food it consumes, does not give off
much more carbon by respiration than an active
full grown man. Hence the proportion of carbon
in the excretions of this animal is greater than in
those of man. ‘The dry manure is richer than the
dry food, weight for weight, but not in the same
proportion as if the cow respired a quantity of
carbon more nearly corresponding to its bulk,
when compared with the weight of carbon thrown
off from the lungs of man.

2. Since the parts of animals—their blood, mus.
cles, tendons, and the gelatinous portion of the
bones—contain much nitrogen, young beasts which
are growing, must appropriate to their own use,
and work up into flesh and bone, a portion of the

nitrogen contained in the non-respired part of their
16*

186 MINERAL MANURES.

food. But the more they thus appropriate, the
less will pass off into the fold-yard ; and hence it
is natural to suppose that the manure, either
liquid or solid, which is prepared where many
growing cattle are fed, will not be so rich as that
which is yielded by full-grown animals. I am
not aware how far this deterioration has been
observed in practice, but it may with some degree
of certainty be expected to take place,—unless by
giving a richer food to the young cattle, the dif-
ference to the farm-yard be made up.*

SECTION V.—-OF MINERAL WATERS.

The general nature and mode of operation of
such mineral substances as are capable of act-
ing as manures, Will be in some measure un-
derstood from what has already been so fully
stated in regard to the necessity of inorganic
food to living plants, and to the kinds of such
food which they specially require. A slight no-

* Though I have dwelt as long upon these interesting
and, I believe, novel considerations, as the limits of this lit-
tle work will permit, yet I must refer the reader for fuller de-
tails, and to perhaps a clearer exposition of the principles
above advanced than I have here been able to give, to my
“Lectures on Agricultural Chemistry and Geology.”

NITRATES AND SULPIIATES, 187

tice, therefore, of the more important of theso
manures now in use will here be sufficient.

1. Nitrates of Potash and Soda.—Saltpetre and
nitrate of soda have been deservedly commended
for their beneficial action, especially upon young
vegetation. They are distinguished by imparting
to the leaves a beautiful dark green colour, and
are applied with advantage to grass and young
corn, at the rate of 1 cwt. to 14 cwt. per acre.
The nitric acid they contain yields nitrogen to the
plant, while potash and soda are also put within
reach of its roots, and no doubt serve many bene
ficial purposes.

Sulphate of Soda, or Glauber’s salt, has lately
been recommended in this country for clovers,
grasses, and green crops. Mixed with nitrate of
soda it produces remarkable crops of potatoes.*

Sulphate of Magnesia, or Epsom salts, might
also be beneficially applied in agriculture, proba-
bly to clovers and corn crops. As it can be had
in pure crystals at 10s..a cwt., and in an impure
state at a much less price, from the alum works,
it might readily be submitted to trial.

Sulphate of Lime, or Gypsum, is in Germany
applied to grass lands with great success, over

* See the author’s “ Suggestions for Experimentsin Practi-
cal Agriculture,” Nos, 1 & 2:

A

188 GYPSUM AND COMMON SALT.

large tracts of country. In the United States it
is used for every kind of crop. It is especially
adapted to clovers and legumes.

These three substances all afford sulphur to the
growing plant, while the lime, soda, and magnesia
are themselves in part directly appropriated by it,
and in part employed in preparing other kinds of
food, and in conveying them into the ascending sap.

Though there ean be no question that these and
similar substances are really useful to vegetation,
yet the intelligent reader will not be surprised to
find, or to hear, that this or that mineral substance
has not succeeded in benefitting the land in this
or that district. If he has already bricks enough
at hand, you must carry the builder mortar, or he
will be unable to go on with his work: so, if
the soil contain gypsum or sulphate of magnesia
in sufficient natural abundance, it is at once a
needless and a foolish waste to attempt to improve
the land by adding more; it is still more foolish
to conclude that these same saline compounds are
unlikely to reward the patient experimenter in
other localities.

Yommon Salt has undoubtedly, in very many
districts, a fertilizing influence upon the soil. The
theoretical agriculturist knows that a small quan.
tity of it is absolutely necessary to the healthy

USE OF KELP. 189

growth of all our cultivated crops, and he will
therefore, early try by a preliminary experiment
upon one of his fields, whether or not they re-
quire the addition of this species of vegetable food.
It is in inland and sheltered situations, and on
high lands often washed by the rains, that the ef-
fect of common salt is likely to be most appreci-
able. The spray of the sea, borne to great dis-
tances by the winds, is in many districts, where
prevailing sea winds are known, sufficient to sup-
ply an ample annual dressing of common salt to
the land.

Kelp.—Among mineral substances kelp ought
not properly to be included, since it is the ash left
by the burning of sea-weed. It, however, par-
takes of the nature of mineral substances, and
may, therefore, be properly considered in _ this
place. It contains potash, soda, silica, sulphur,
chlorine, and several other of the inorganic con-
stituents of plants required by them for food. It
is nearly the same also—with the exception of the
organic matter which is burned away—with the
sea-weed which produces such remarkably bene-
ficial effects upon the soil. In the Western Isles
a method is practised of half burning or charring
sea-weed, by which it is prevented from melting
together, and is readily obtained in the form of

190 WOOD AND DUTCH ASHES,

a fine black powder. The use of this variety
ought to combine the beneficial action of the or-
dinary saline constituents of kelp, with the re-
markable properties observed in animal and ve-
getable charcoals.

Wood-ash, among other compounds, contains a
portion of common pearl-ash in an impure form,
with sulphate also, and silicate of potash. ‘These
are all valuable in feeding and in preparing the
food of plants, and hence the extensive use of
wood-ash as a manure in every country where it
can readily be procured.

Dutch ashes are the ashes of peat burned for the
purpose of being applied to the land. They vary
in constitution with the kind of peat from which
they have been prepared. ‘They often contain
traces of potash and soda, and generally a quan-
tity of gypsum and carbonate of lime, a trace of
phosphate of lime, and much siliceous matter.
In almost every country where peat abounds, the
value of peat ashes as a manure has been more or

less generally recognised.

SECTION VI.—USE OF LIME, SHELL-SAND, AND MARL-

The use of lime is of the greatest importance in
practical agriculture. It has been employed, in

LIMESTONE AND QUICKLIME: 191

Europe at least, in one or other of its forms of
shells, shell-sand, marl, chalk, limestone, and
quicklime, from the most remote periods.

Native limestone, and all the unburned varieties
of chalk, shells, &c. consist of carbonate of lime
(p. 51), more or less pure. When burned in the
kiln, the carbonic acid is driven off, and lime,
burned lime, or quicklime remains.

Quicklime, when exposed to the air, gradually
falls into the state of an exceedingly fine white
powder. It will do so more rapidly if water be
thrown upon it, when it also heats much, swells,
and becomes about one-third hammer than before.
After being exposed to the air for some time in
this white powdery state, it is found to have again
absorbed from the air a portion of carbonic acid,
though a very long period generally elapses be-
fore it is all re-converted into carbonate. In com.
post heaps, where much carbonic acid is formed
during the fermentation, the conversion of any
quicklime that may be mixed with them into car-
bonate of lime, is much more rapid and complete
than in the open air.

Lime, therefore, is laid on the land in two
states.

lst, In the mild state—that of carbonate—in
marls, in chalk, in shell-sand, &c.

‘2

192 DIFFERENT QUALITIES OF LIME.

2d, In the caustic, or quick state, as it comes
hot from the kiln, or after it is simply slaked.

Limes are laid on also in a more or less pure form.
Marl contains only from 5 to 20 per cent. of car-
bonate of lime, generally in the state of a very fine
powder. Shell-sand consists of a mixture of mi-
nute fragments of shells with from 20 to 50 per
cent. of siliceous sand. The limestones which are
burned are also more or less impure, though,
when the impurity is very great, they do not burn
well, and are therefore usually rejected.

Some limestones contain much magnesia, by
which their agricultural qualities are materially
affected. These are known by the name of mag-
nesian limestones. ‘There are few limestones in
which a small quantity of magnesia may not be
detected, and this minute proportion is likely to
be beneficial rather than otherwise; but when it
is present to the amount of 10 per cent. or up
wards, it appears to have for some time a poison-
ous influence upon vegetation, if added in the
same large doses in which other lime may be
safely spread upon the land.

The quantity of lime laid on at a single dress;
ing, and the frequency with which it may be re-
peated, must depend upon the kind of land, upon
the depth of the soil, and upon the species of culture

v
. e
DOSES IN WHICH LIME MAY BE APPLIED. 193

to which it is subjected. If land be wet, or badly
drained, a larger application is necessary to pro-
duce the same effect, and it must be more fre-
quently repeated. When the soil is thin, again,
a smaller addition will thoroughly impregnate the
whole, than where the plough usually descends
to the depth of 8 or 10 inches. On old pasture
lands, where the tender grasses live in two or
three inches of soil only, a feebler dressing, more
frequently repeated, appears to be the more rea-
sonable practice, though in reclaiming and laying
down lands to grass, a heavy first liming is often
indispensable.

In arable culture larger do
both because the soil through
netrate must necessarily be deeper, and because
the tendency tosink beyond the reach of the roots
is generally counteracted by the frequent turning
up of the earth by the plough. Where vegetable
matter abounds, much lime may be usefully add-
ed, and on stiff clay lands after draining, its good
effect is most remarkable. On light land, chiefly
because there is neither moisture nor vegetable
matter present in equal quantity, very large ap-
plications of lime are not so usual, and some pre-
fer adding it to such lands in the shape of com-

ea

}are admissible,
wae:
| eh the roots pe-

osts only.
17

194 VISIBLE EFFECTS OF LIME.

The largest doses, however, which are applied
in practice, alter in a very immaterial degree the
chemical constitution of the soil. We have seen
that the best soils generally contain a natural pro-
portion of lime, not fixed in quantity, yet scarcely
ever wholly wanting. But an ordinary liming, when
well mixed up with a deep soil, will rarely amount
to one per cent. of its entire weight. It requires
about 300 bushels of burned lime per acre to add
one per cent. of lime to a soil of twelve inches in
depth ; if only mixed to a depth of six inches, this
quantity would add about two per cent. to the soil.

The most rem rkable visible alterations pro-
duced by liming “are—upon pastures, the greater
fineness, closeHene, and nutritive character of the
grasses—on arable lands, the improvement in the
texture and mellowness of stiff clays, the more
productive crops and the earlier period at which
they ripen.

But these effects gradually diminish year by
year, till the land returns again nearly to its ori-
ginal condition. On analyzing the soil, the lime
originally added is found to be in great mea-
sure, or altogether, gone. In this condition the
land must either be limed again, or must be left
to produce sickly and un-remunerating crops.

This removal arises from two causes. ‘The rain

HiOW THE LIME IS GRADUALLY REMOVED. 195

water that descends upon the land holds in solu-
tion carbonic acid which it has absorbed from the
air. But water charged with carbonic acid is
capable of dissolving carbonate of lime, and thus
year after year the rains slowly remove as they
sink to the drains, or run over the surface, a por-
tion of the lime which the soil contains. Acid
substances are also formed naturally in the land,
by which another portion of the lime is rendered
easily soluble in water, and, therefore, readily re-
movable by every shower that falls.

The chemical effects of lime upon the soil are
chiefly the following :— iy a:
1. When laid upon the land
the first action of the lime is

he caustic state,
to; combine imme-
diately with every portion of acid matter it may
contain, and thus to sweeten the soil. Some of
the compounds it thus forms being soluble in
water, either enter into the roots and feed the
plant,—supplying it at once with lime and with
organic matter,—or are washed out by the springs
and rains, while other compounds, which are in-
soluble, remain more permanently in the soil.

2. Another portion decomposes certain saline
compounds of iron, manganese, and alumina,
which naturally form themselves in - the soil, and
thus renders them unhurtful to vegetation. A

196 CHEMICAL EFFECTS OF CAUSTIC LIME.

similar action is exerted upon certain compounds
of potash and soda, and of ammonia,—if any such
are present,—by which these substances are set
and placed within the reach of the plant.

3. Its presence in the caustic state further dis-
poses the organic matter of the soil to undergo
more rapid decomposition—it being observed, that
where lime is present in readiness to combine
with the substances produced during the decay of
organic matter, that decay, if other circumstances
be favourable, will proceed with much greater ra-

pidity. ‘The reader will not fail to recollect, that
during this decay | any compounds are formed

x im ‘ on ais rf
which are of ‘imp ortance in promoting vegetation,
sane

4, Further, quicklime has the advantage of
being soluble in cold water, and thus the com.

plete diffusion of it through the soil is aided by

the power of water to carry it in solution in every
direction.

5. When it has absorbed carbonic acid, and be-
come reconverted into carbonate, the original
caustic lime has no chemical virtue over chalk,
rich shell-sand or marl, or crushed limestone. It
has, however, the important mechanical advantage
of being in the form ofa far finer powder, than any
to which we could reduce the limestone by art—
jn consequence of which it can be more uniformly

CHEMICAL EFFECTS OF THE CARRONATE. 197

diffused through the soil, and placed within the
reach of every root, and of almost every particle,
of vegetable matter that is undergoing decay. I
shall mention only three of the important pur-
poses which, in this state of carbonate, lime serves
upon the land.

1. It directly affords food to the plant, which,
as we have seen, languishes where lime is not at-
tainable. It serves also to convey other food to
the reots in a state in which it can be made avail-
able to vegetable growth.

2. It neutralizes (removes the
acid substances as they are forme
thus keeps the land in a condi
tenderest plants. This is one «
agencies of shell-sand when laid on undrained
grass lands—and this effect it produces in com-
mon with wood-ashes, and many similar sub-
stances.

3. During the decay of organic matter in the
soil, it aids and promotes the production of nitric
acid,—so influential, as I believe, in the general
vegetation of the globe (see page 35). With this
acid it combines and forms nitrate of lime—a sub-
stance very soluble in water—entering readily,
therefore, into the roots of plants, and producing

upon their growth effects precisely similar to those
17# |

sourness) of all

J inthe soil, and
to nourish the
e important

198 IMPROVEMENT BY IRRIGATION.

of the now well known nitrate of soda. The suc.
cess of frequent ploughings, harrowings, hoeings,
and other modes of stirring the land, is partly
owing to the facilities which these operations af-
ford to the production of this and other natural
nitrates,

SECTION VII.—OF THE IRRIGATION OF THE LAND.

The irrigation of the land is, in general, only a
more refined method of manuring it. The nature

of the process,itself, however, is different in differ-

ent countries, as are also the kind and degree of
effect it prod the theory by which these
effects are to be explained.

In dry and arid climates, where rain rarely falls,
the soil may contain all the elements of fertility,
and require only water to call them into opera-
tion. In such cases, as in the irrigations practised
so extensively in eastern countries, and without
which, whole provinces in Africa and Southern
America would lie waste, it is unnecessary to sup-
pose any other virtue in irrigation than the mere
supply of water it affords to the parched and
cracking scil,

But in climates such as our own, there are two
other beneficial purposes in reference to the soil,

HOW IRRIGATION ACTS. 199

which irrigation may, and one at least of which it
always does, serve.

2. The occasional flow of pure water over the
surface, as in our irrigated meadows, and its de-
scent into the drains, where the drainage is perfect,
washes out acid and other noxious substances na-
turally generated in the soil, and thus purifies and
sweetens it. The beneficial effect of such washing
will be readily understood in the case of peat
lands laid down to water meadow, since, as every
one knows, peat soils abound in matters unfavour-
able to general vegetation, and which are usually

in part drawn off by drainage, and in part destroyed

by lime and by exposure to the air, before boggy
lands can be brought into profitable c

2. But it seldom happens that pure water is
employed for the purposes of irrigation. The
water of rivers, more generally, is diverted from
its course, more or less loaded with mud and
other finer particles of matter, which are either
gradually filtered from it as it passes over and
through the soil, or in the case of floods subside
naturally when the waters come to rest. Or in
less frequent cases, the drainings ef towns, and the
waters from common sewers, or from the little
streams enriched by them, are turned with benefit
upon the favoured fields. These are evidently cases

200 IT MANURES THE LAND.

of gradual and uniform manuring. And even
where the water employed is clear and apparently
undisturbed by mud, it always contains saline
substances grateful to the plant in its search for
food, and which it always contrives to extract
more or less copiously as the water passes over its
leaves or along its roots. Every fresh access of
water affords the grass in reality another liquid
manuring,

In the refreshment continually afforded to the
plant by a plentiful supply of water, in the removal
of noxious substances from the soil, or in the fre-

Ns

quent additions of enriching food to the land—the

efficiency of irrigation, therefore, seems entirely

to consist.

SECTION VII]y——-OF PARING AND BURNING, AND oF
BURNED CLAY:

A. mode of improvement often resorted to is the
paring and burning of poor land. ‘The efficacy of
burned clay, also, even in superseding manure on
good lands, has been highly extolled by some prac-
tical men,

1. The effect of paring and burning is easily
understood. ‘The matted sods consist of a mixture
of much vegetable with a comparatively small

OF PARING AND BURNING. 201

quantity of earthy matter. When these are burned
the ash of the plants only is left, intimately mixed
with the calcined earth, To strew this mixture
over the soil is much the same as to dress it with
peat or wood ashes, the beneficial effect of which
upon vegetation is almost universally recognised.
And the beneficial influence of the ash itself
is chiefly due to the ready supply of inorganic
food it yields to the seed, and to the effect which
the potash and soda it contains exercise either in
preparing organic food in the soil, or in assisting

its digestion and assimilation in the interior of the

plant. hi:

Another part of this process is, that the roots
of the weeds and poorer grasses are materially
injured by the paring, and that the subsequent
dressing of ashes is unfayourable to their further
growth.

2. Much greater uncertainty hangs over the al-
leged virtues of burned clay. ‘That benefits are
supposed to have been derived from its use there
can be no doubt, though in many cases the better
tillage of the land generally prescribed along with
the use of burned clay, may have had some share
in producing the good results actually experienced
during its use,

By the burning, in kilns or otherwise, any or-

202 EFFECT OF BURNING UPON CLAY.

ganic matter the clay may contain will be con-
sumed, and the texture of the clay itself will be
mechanically altered. It will crumble down like
a burned brick into a hard friable powder, and
will never again cohere into a paste as before the
burning. It will, therefore, render clay soils more
open, and may thus, when mixed in large quan-
tity, produce a permanent amelioration in the
mechanical texture of many stiff wheat soils. It
. cannot itself undergo any chemical change that is
likely so to alter its constitution as to make it a
more useful chemical constituent of the soil than

before. Any sal ine matter we may suppose to be

set free coult be far more cheaply added in the
form of a top- oil to the soil.

Bricks, however, are generally more porous
than the clay from which they are formed ; burned
clay is so also. And all porous substances suck
in and condense much air and many vapours in
large quantities into their pores. In consequence
of this property, porous substances, like charcoal
and burned clay, are supposed, when mixed with
the soil, tobe continually yielding air to decaying
vegetable matter on the one hand, and as continu-
ally re-absorbing it from the atmosphere on the
other, and by this means to be of singular service in
supplying the wants of plants in the earlier seasons

HOW BURNED CLAY ACTS. 203

of their growth. The vapours of nitric acid and
of ammonia, which float in the air, they are also
supposed to imbibe, and by the beneficial action of
the substances believed to be thus conveyed by
burned clay into the soil, the fertilizing virtues
ascribed to it are attempted to be explained.

It must be confessed, however, that on this point
considerable obscurity still rests. It is in some
measure doubtful what the true action of charcoal
and of burned clay is, both in kind and in quantity.
It is the part of science, therefore, to decline offer-
ing more than a mere conjecture till the facts to

be explained are more fully and satisfactorily de-

monstrated.

SECTION IX.—PLANTING AND LAYING DOWN TO GRASS.

1, Planting.—It has been observed that lands
which are unfit for arable culture, and which yield
only a trifling rent as natural pasture, are yet in
many cases capable of growing profitable planta-
tions, and of being greatly increased in permanent
value by the prolonged growth of wood. Not
only, however, do all trees not thrive alike on the
same soil, but all do not improve the soil on which
they grow in an equal degree.

Under the Scotch fir, for example, the pasture

204 IMPROVEMENT UF 'THE SOIL BY PLANTING,

is not worth 6d. more per acre than before it was
planted—under the beech and spruce, it is worth
" even less than before, though the spruce affords ex-
cellent shelter ;—under ash, it gradually acquires
an increased value of 2s. or 3s. per acre. In oak
copses, it becomes worth 5s. or 6s., but only dur-
ing the last eight years (of the twenty-four), be-
fore it is cut down. But under the larch, after
the first thirty years, when the thinnings are all
cut, land not worth originally more than Is, per
acre, becomes worth 8s, to 10s. per acre for per-

manent pasture.*

The cause of this

| improvement 1 is to be found in
soil, which gradually accumu-

the nature of 1
lates beneath the trees by the shedding of their
leaves. ‘The shelter from the sun and rain which
the foliage affords, prevents the vegetable matter
which falls from being so speedily decomposed,
or from being so much washed away, and thus
permits it to collect in larger quantities in a given
time, than where no such cover exists. ‘The more
complete the shelter, therefore, the more rapid
will the accumulation of soil be in so far as it de-
pends upon this cause.

But the quantity of leaves which annually falls

* The result of trials made on the mica slate and gneiss
soils (see page 100) of the Duke of Atholl.

CAUSE OF THIS IMPROVEMENT. 205

has also much influence upon the extent to which
the soil is capable of being improved by any given
species of tree, as well as the degree of rapidity
with which those leaves, under ordinary circum-
stances, undergo decay. ‘The broad membranous
leaf of the beech and oak decay more quickly than
the needle-shaped leaves of the pine tribes, and
this circumstance may assist in rendering the larch
more valuable as a permanent improver,
We should expect likewise that the quantity and
quality of the inorganic matter contained in the
leaves,—brought up year by hi from the roots,

and strewed afterwards uniformly over the sur-
face where the leaves are shed,— would materially
affect the value of the soil they form. ‘The leaves
of the oak contain about 5 per cent. of saline and
earthy matter, and those of the Scotch fir less than
2 per cent. ; so that, supposing the actual weight
of leaves which falls from each kind of tree to be
equal, we should expect a greater depth of soil to
be formed in the same time by the oak than by
the Scotch fir. I am not aware of any experi-
ments on the quantity of ash left by the leaves of
the larch.

The improvement of the land, therefore, by the
planting of trees, depends in part upon the quan-

tity of organic food which the trees can extract
18

206 LAYING DOWN TO GRASS.

from the air, and afterwards drop in the form of
leaves upon the soil, and in part upon the kind and
quantity of inorganic matter which the roots can
bring up from beneath, and in like manner strew
upon the surface. The quantity and quality of
the latter will, in a great measure, determine the
kind of grasses which will spring up, and the con-
sequent value of the pasture in the feeding of stock.
In the larch districts of the Duke of Athol, the
most abundant grasses that spring up are said to
be the holcus mollis and the holcus lanatus, (the
creeping and the meadow soft-grasses. )

2. Laying dou 2 to grass.—On this point two

facts seem to be etty generally acknowledged :
First, that la

for one, two, three, or more years, is in some de-

“laid down to artificial grasses

gree rested or recruited, and is fitted for the better
production of after-corn crops. Letting it lie a
year or two longer in grass, therefore, is one of the
received modes of bringing back to a sound condi-
tion a soil that has been exhausted by injudicious
cropping.

Second, that land thus laid down with artificial
grasses deteriorates more or less after two or three
years, and only by slow degrees acquires a thick
sward of rich and nourishing herbage. Hence the
opinion, that grass-land improves in quality the

IMPORTANT GENERAL OBSERVATIONS. 207

longer it is permitted to lie,—the unwillingness
to plough up old pasture,—and the comparatively
high rents which, in some parts of the country, old
grass lands are known to yield.

Granting that grass lands do thus generally
increase in value, three important facts must be
borne in mind before we attempt to assign the
cause of this improvement, or the circumstances
under which it is likely to take place for the longest
time and to the greatest extent.

1. The value of the grass in any given spot
may increase for an indefinite period—but it will
never improve beyond a certain extent—it will

necessarily be limited, as all other crops are, by
the quality of the land. Hence the mere laying
down to grass will not make all land good, how-
ever long it may lie. ‘The extensive commons,
heaths, and wastes, which have been in grass from
the most remote times, are evidence of this. They
have in most cases yielded so poor a herbage as to
have been considered unworthy of being enclosed
as a permanent pasture.

2. Some grass lands will retain the good con-
dition they thus slowly acquire for a very long
period, and without manuring, in the same way,
and upon the same principle, that some rich corn

lands have yielded successive crops for 100 years

208 SOME REQUIRE MANURING.

without manure. The rich grass lands of Eng-
land, and especially of Ireland, many of which
have been in pasture from time immemorial, with-
out, it is said, receiving any return for all they
have yielded, are illustrations of this fact.

3. But that others, if grazed, cropped with
sheep or meadowed, will gradually deteriorate,
unless some proper supply of manure be given to
them,—which required supply must vary with the
nature of the soil, and with the kind of treat-
ment to which it has been subjected.

In regard to the acknowledved benefit of lay-
ing down to grass, then, two points require con-
sideration,—wh -form does it assume 1—and how
is it effected?

1. The improvement takes place by the gradual
accumulation of a dark-brown soil on the surface,
rich in vegetable matter; and which soil thickens
or deepens in proportion to the time which elapses
from its being first laid down to grass.

If the soil be very light and sandy, the thicken-
ing is sooner arrested; if it be moderately heavy
land, the improvement continues for a longer pe-
riod ; and some of the heaviest clays in England
are known to bear the richest permanent pastures.
On analyzing the soils of the richest of these pas-
tures, whatever be the degree of tenacity of the

UNIFORMITY OF OLD PASTURE SOILS. 209

clays or loams (the subsoils) on which they rest,
or their deficiency in vegetable matter,—they are
found to be generally characterized by containing
from 8 to 12 per cent. of organic, chiefly vegeta-
ble matter, from 5 to 10 only of alumina, and from
1 to 6 percent. of lime.

Thus the soil formed on the surface of all rich
old pasture lands is possessed of a remarkable de-
gree of uniformity,—both in physical character
and in chemical composition. This uniformity
they gradually acquire, even upon the stiff clays of
the Lias and of the Oxford clay, which originally,
no doubt, have been,—as many clay lands still are,
—left to natural pasture from the difficulty and
expense of submitting them to arable culture.

2. But how do they acquire this new character,
and why is it the work of so much time? When
the young grass throws up its leaves into the air,
from which it derives so much of its nourishment,
it throws down its roots into the soil in quest of
food of another kind. The leaves may be mown
or cropped by animals, and carried off the field,
but the roots remain in the soil, and, as they die,
gradually fill its upper part with vegetable mat-
ter. It is not known what average proportion
the roots of the natural grasses bear to the leaves ;

no doubt it varies much, both with the kind of
18*

210 HOW THE SOIL ON GRASS LANDS

grass and with the kind of soil. When wheat is
cut down, the quantity of straw left in the field,
in the form of stubble and roots, is sometimes
greater than the quantity carried off in the sheaf.
Upon a grass field two or three tons of hay may
be reaped from an acre ; and if we suppose only
a tenth part of this quantity to die every year in
the form of roots or parts of roots, or of excre-
tions from roots, we can easily understand how
the vegetable matter in the soil thus gradually
accumulating, should at length become very con-
siderable in quantity. In arable land this accu-
mulation is prevented by the constant turning up
of the soil, by Which the vegetable fibres being
exposed to the free access of air and moisture, are
made to undergo a more rapid decomposition.
But the roots and leaves of the grasses contain
inorganic earthy and saline matter also. Dry
hay leaves from an eighth to a tenth part of its,
weight of ash when burned. Along with the
dead vegetable matter of the soil, this inorganic.
matter accumulates also on the surface, in the.
form of an exceedingly fine earthy powder ; hence
one cause of the universal fineness of the surface
mould of old grass fields. And the earthy por.
tion of this inorganic matter consists chiefly of
silica and lime, with scarcely a trace of alumina,

BECOMES GRADUALLY CHANGED. 211

so that, even on the stiffest clays, a surface soil
may be ultimately formed, in which the quantity
of alumina will be comparatively small.

But there are still other agencies at work by
which the surface of stiff soils is made to undergo
a change. As the roots penetrate into the clay,
they more or less open up a way into it for the
rains. Now the rains in nearly all lands, when
they have a passage downwards, have a tendency
to carry down the clay along with them. They
do so, it has been observed, on sandy and peaty
soils, and more quickly when these soils are laid
down to grass. Hence the mechanical action of
the rains,—slowly in many localities, yet surely,
—has a tendency to lighten the soil, by removing
a portion of its clay. They constitute one of
those natural agencies by which, as elsewhere ex-
plained, important differences are ultimately es-
tablished, almost everywhere, between the surface
crop-bearing soil and the subsoil on which it rests.

But further, the heats of summer and the frosts
of winter aid this slow alteration. In the ex-
tremes of heat and of cold, the soil contracts more
' than the roots of the grasses do; and similar
though less striking differences take place during
the changes of temperature experienced in our
climate in a single day. When the rain falls on

212 EFFECT OF THE WINTER’S FROST.

the parched field, or when a thaw comes on, the
earth expands, while the roots of the grasses re-
main nearly fixed; hence the soil rises up among
the leaves, mixes with the vegetable matter, and
thus assists in the slow accumulation of a rich
vegetable mould.

The reader has witnessed in winter how, on a
field or a by-way side, the earth rises above the
stones, and appears inclined to cover them; he
may even have seen in a deserted and undisturbed
highway, the stones gradually sinking and disap-
pearing altogether, when the repetition of this
alternate contraction and expansion of the soil for
a succession of winters has increased in a great
degree the effects which follow from a single ac-
cession of frosty weather.

So it is in the fields. And if a person skilled in
the soils of a given district can make a guess at
the time when a given field was laid down to
grass, by the depth at which the stones are found
beneath the surface, it is because this loosening
and expansion of the soil, while the stones remain
fixed, tends to throw the latter down by an almost
imperceptible quantity every year that passes.

Such movements as these act in opening up
the surface-soil, in mixing it with the decaying ve-
getable matter, and in allowing the slow action of

EFFECT OF INSECTS. 919

the rains gradually to give its earthy portion a
lighter character. But with these, among other
causes, conspire also the action of living animals.
Few persons have followed the plough without
occasionally observing the vast quantities of earth-
worms with which some fields seem to be filled.
On a close shaven lawn many have noticed the
frequent little heaps of earth which these worms
during the night have thrown out upon the grass.
These and other minute animals are continually
at work, especially beneath an undisturbed and
grassy sward—and they nightly bring up from a
considerable depth, and discharge on the surface,
their burden of fine fertilizing loamy earth. Each
of these burdens is an actual gain to the rich surface
soil,and who can doubt that in the lapse of years,
the unseen and unappreciated labours of these insect
tribes must both materially improve its quality
and increase its depth ?

There are natural causes, then, which we know
to be at work, that are sufficient to account for
nearly all the facts that have been observed, in
regard to the effect of laying lands down to grass.
Stuff clays will gradually become lighter on the
surface, and if the subsoil be rich in all the kinds
of inorganic food which the grasses require, will
go on improving for an indefinite period without

214 GRASS ON LIGHT AND HEAVY SOILS.

the aid of manure. Let them, however, be defi-
cient, or let them gradually become exhausted of
any one kind of this food, and the grass lands will
either gradually deteriorate after they have reached
acertain degree of excellence—or they must be sup-
plied with that ingredient—that manure of which
they stand in need. It is doubtful if any pasture-
lands are so naturally rich as to bear to be crop-
ped for centuries without the addition of manure,
and at the same time without deterioration.*

On soils that are light, again, which naturally
contain little clay, the grasses will thrive more
rapidly, a thick sward will be sooner formed, but
the tendency of the rains to wash out the clay
may prevent them from ever attaining that luxu-
riance which is observed upon the old pastures of
the clay-lands.

On undrained heaths and commons, and gene-
rally on any soil which is deficient in some fer-
tilizing element, neither abundant herbage, nor
good crops of any other kind, can be expected to
flourish. Laying such lands down, or permitting
them to remain in grass, may prepare them for
by-and-by yielding one or two average crops of
corn, but cannot be expected alone to convert
them into valuable pasture.

@ See pages 240 and 241. ‘

PLOUGHING UP OLD PASTURES. 215

Finally, plough up the old pastures, on the sur-
face of which this light and most favourable soil has
been long accumulating—and the heavy soil from
beneath will be again mixed up with it—the vege-
table matter will disappear rapidly by exposure to
the air,—and if again laid down to grass, the slow
changes of many years must again be begun
through the agency of the same natural causes,
before it become capable of again bearing the same
rich herbage it was known to nourish while it lay
undisturbed.

Many have supposed that by sowing down with
the natural grasses, a thick sward may at once be
obtained—and on light loamy lands, rich in vege-
table matter, this method may, to a certain extent,
succeed—but on heavy lands, in which vegetable
matter is defective, disappointment will often fol-
low the sowing of the most carefully selected
seeds. By the agency of the causes above ad-
verted to—the soil gradually changes, so that it is
unfit, when first laid down, to bear those grasses
which, ten or twenty years afterwards, will natur-
ally and luxuriantly grow upon it.

CHAPTER X.

The Products of Vegetation—Importance of Chemical qual-
ity as well as quantity of Produce—Influence of different
Manures on the quantity and quality of the Crop—Influ-
ence of the time of Cutting—Absolute quantity of Food
yielded by different Crops—Principles on which the Feed-
ing of Animals depends—Theoretical and experimental
value of different kinds of Food for Feeding Stock—Con-
cluding Observations.

Tue first object of the practical farmer is, to
reap from his land the largest possible return of
the most valuable crops, without permanently ex-
hausting the soil. With this view he adopts one
or other of the methods of treatment above ad-
verted to, by which either the physical condition
or the chemical constitution of the soil is altered
for the better. It may be useful to shew how
very much both the quantity and the quality of a
crop is dependent upon the mode in which it is

INFLUENCE OF DIFFERENT MANURES. 217

cultivated and reaped, and how much control,
therefore, the skilful agriculturist really possesses
over the ordinary productions of nature.

SECTION I.—OF THE INFLUENCE OF MANURE ON THE QUANTITY
,
OF THE WHEAT AND OTHER CORN CROPS.

Every one knows that some soils naturally
produce much larger returns of wheat, oats, and
barley than others do, and that the same soil will
produce more or less according to the mode in
which the land has been prepared by manure, or
otherwise, for the reception of the seed. ‘The fol-
lowing table shews the effect produced upon the
quantity of the crop by equal quantities of different
manures applied to the same soil, sown with an
equal quantity of the same seed.

Return in bushels from each }

Manure applied. bushel of seed.
Wheat. Barley. Oats. Rye.
lp UP ence ees Sen SS BURMEE Eee en
Night soil, : : -_ = 13 144 134
Sheep’s dung, . ; ; 12 16 14 13

Horse dung, 5 i oie 10 13 14 11

Pigeon’sdung, .° 2.) °. = 10 reo
Cow dung, re i 7 11 fo. 9
Vegetable matter, 3 7 13 «6
Without manure, : : — 4 5 4

19*

ov

218 ON THE QUANTITY OF THE CROP.

It is probable that on different soils the returns
obtained by the use of these several manures may
not be always in the same order, yet, generally
speaking, it will always be found that blood, night-
soil, and sheep, horse, and pigeon’s dung, are
among the most enriching manures that can be
employed.

We have already scen a theoretical reason for
believing that night-soil should be among the
most enriching manures, and the result of actual
trial here shews that it is one of the most practi-
cally valuable which the farmer can employ.

Two other facts will strike the practical man on
looking at the above table.

1. That exclusive of blood, sheep’s dung gave
the greatest increase in the barley crop. ‘The fa-
vourite Norfolk system of eating off turnips with
sheep previous to barley, besides other benefits
which are known to attend the practice, may owe
part of its acknowledged utility to this powerful
action of sheep’s dung upon the barley crop.

2. The action of cow-dung upon oats is equally
striking, and the large return obtained by the
use of vegetable manure alone—thirteen fold—
may perhaps explain why in poorly farmed dis-
tricts oats should be a favourite and comparatively
profitable crop, and why they may be cultivated

INFLUENCE OF THE KIND OF MANURE. 219

with a certain degree of success on lands to which
no rich manure is ever added.

SECTION II.—INFLUENCE OF THE KIND OF MANURE ON THE
CHEMICAL QUALITY OF THE GRAIN.

But the quality of the grain also, as well as its
quantity, is materially affected by the kind of ma-
nure by which its growth is assisted. The appa-
rent quality of wheat and oats is very various ;
but in samples apparently equal in quality, im-
portant chemical differences may exist, by which
it is believed that the nourishing properties of the
grain are materially affected.

It has been stated in a previous chapter (p. 43),
that when flour is made into dough, and _ this
dough is washed upon a linen cloth with water as
long as the latter passes through milky,—the flour
is separated into starch, which subsides from the
water, and gluten, which remains behind. The
quantity of gluten thus left varies more or less
with almost every sample of flour, and the nutri-
tive properties of each sample are supposed to de-
pend very much upon the quantity of gluten it
contains. So far it seems to be pretty well as-
certained, that those varieties of grain which
contain the largest amount of gluten yield also

220 ON THE QUALITY OF WHEAT,

the greatest return of flour, and the heaviest weight
of bread.

The weight of gluten contained in 100 lbs. of
dry wheat has been found to vary from 8 to 34 lbs.,
and this proportion is affected in a very remark-
able manner by the kind of manure which has
been applied to the land. Thus the proportions
of starch and gluten in 100 lbs. of the grain of the
same wheat, grown on the same land, differently
manured, was as follows :—

Manure. Starch. Gluten.
Blood, . ; : k 41 lbs. 34 lbs.
Sheep’sdung,. . . 48 — 33 —
Horse dung, . ae) Gah 14 —
Cow dung, 4 ‘ ~ 62 — 12 —
Vegetable manure, . - 66— 10

Potato-flour, which consists entirely of starch,
makes a fine light bread, easily raised. Wheaten-
flour, which contains little gluten, approaches in
this respect to potato-flour. When the quantity
of gluten is large, greater care is required to
make a good light bread; but the bread from such
flour is generally found to be more nutritive in its
quality. A dough peculiarly rich in gluten is re-
quired for the manufacture of macaroni and ver-
micelli; such is said to be the flour naturally pro-
duced in southern Italy. By the above table it

\

AND OF BARLEY AND OATS. pap

appears, that the use of richer animal, or poorer
vegetable manures, would enable the farmer to
raise, at his pleasure, either a rich macaroni wheat,
or one poor in gluten suited for the makers of
fancy bread.

An equally striking effect is not produced upon
other kinds of grain by varying the manure. Thus
the proportions of starch and gluten in the dry
grain of barley and oats, differently manured, were
found to be as follows :—

BARLEY. OATS.
Starch. Gluten. Starch. Gluten.

Blood, ; 664 . 64 60 5s
Night-soil, , 66 . 63 60 5
Sheep dung, . 664 . 64 61 AL
Horse dung, . 66 . 63 612 44
Cow dung, : 69 . 3k 62 3h
Vegetable manure, 69 . 3 663 Qt
Unmanured, 693 3 664 QL

Though a variation in the proportion of gluten
can be observed in both of these kinds of grain,
according as one or other of the above kinds of
manure was employed, yet neither the average
quantity of gluten present in them, nor the varia-
tions to which the quantity is liable, are at all
equal in amount to what are observed in the case
of wheat.

The malting of barley is known to be affected
19*

™

222 THE MALTING OF BARLEY.

by a variety of circumstances. It should be so
uniform in ripeness as to sprout uniformly, so that
no part of it should be beginning to shoot when
the rest has already germinated sufficiently for
the malter’s purpose. On this perfect sprouting
of the whole depends in some degree the swell-
ing of the malt, which is of considerable conse-
quence to the manufacturer.

But the melting quality of the grain, which is of
more consequence to the brewer and distiller, is
modified chiefly by the proportion of gluten which
the barley contains. That which contains the least
gluten, and therefore the most starch, will melt
the most easily and the most completely, and will
yield the strongest beer or spirit from the same
quantity of grain. Hence the preference given
by the brewer to the malt of particular districts,
even where the sample appears otherwise inferior.
Thus the brewers on the sea-board of the county
of Durham will not purchase the barley of their
own neighbourhood, while Norfolk grain can be
had at a moderate increase of price. But that
which refuses to melt well in the hands of the
brewer, will cause pigs and other stock to thrive
well in the hands of the feeder, and this is the
chief outlet for the barley which the brewer and
distiller reject.

,

COW-DUNG RAISES MUCH BARLEY. 223

So far as a practical deduction can be drawn
from the effects of different manures on the pro-
portion of gluten in barley, it would appear that
the larger the quantity of cow-dung contained in
the manure applied to barley land—in other
words, the greater the numbers of stock folded
about the farm-yard, the more likely is the barley to
be such as will bring a high price from the brewer.

The folding of sheep produces a larger return
(p. 206), from the barley crop—while the folding
of cattle gives grain of a better malting quality.

SECTION III.—INFLUENCE OF THE TIME OF CUTTING, ON THE
QUANTITY AND QUALITY OF THE PRODUCE.

The period at which hay is cut, or corn reaped,
materially affects the quantity (by weight) and
the quality of the produce. It is commonly known
that when radishes are left too long in the ground
they become hard and woody—that the soft tur-
nippy stem of the young cabbage undergoes a
similar change as the plant grows old,—and that
the artichoke becomes tough and uneatable if left
too long uncut. The same natural change goes
on in the grasses which are cut for hay.

In the blades and stems of the young grasses
there is much sugar, which, as they grow up, is

224 INFLUENCE OF THE TIME OF CUTTING.

gradually changed, first into starch, and then into
woody fibre (pages 44 and 45.) The more com-
pletely the latter change is effected—that is, the
riper the plant becomes—the less sugar and starch,
both readily soluble substances, they contain.
And though it has been ascertained that woody
fibre is not wholly indigestible, but that the cow,
for example, can appropriate a portion of it for
food as it passes through her stomach; yet the
reader will readily imagine, that those parts of the
food which dissolve most easily, are also likely—
other things being equal—to be most nourishing
to the animal.

It is ascertained, also, that the weight of hay or
straw reaped, is actually less when allowed to be-
come fully ripe; and therefore, by cutting soon
after the plant has attained its greatest height, a
larger quantity, as well as a better quality of hay,
will be obtained, while the land also will be less
exhausted.

The same remarks apply to crops of corn,—both
to the straw and to the grain they yield. The
yawer the crop is cut, the heavier and more nour-
ishing the straw. Within three weeks of being
- fully ripe, the straw begins to diminish in weight,
and the longer it remains uncut after that time,
the lighter it becomes and the less nourishing.

ON THE QUANTITY AND QUALITY. 225

On the other hand, the ear which is sweet and
milky a month before it is ripe, gradually con-
solidates, the sugar changing into starch, and the
milk thickening into the gluten and the albumen* of
the flour. As soon as this change is nearly com-
pleted, or about a fortnight before ripening, the
grain contains the largest proportion of starch and
gluten; if reaped at this time, the bushel will be
heavier, and will yield the largest quantity of fine
flour and the least bran.

At this period the grain has a thin skin, and hence
the small quantity of bran. But if the crop be
still left uncut, the next natural step in the ripen-
ing process is, to cover the grain with a better
protection, a thicker skin. A portion of the starch
of the grain is changed into woody fibre,—precisely
as in the ripening of hay, of the soft shoots of the
dog-rose, and of the roots of the common radish.
By this change, therefore, the quantity of starch
islessened and the weight of husk increased ; hence
the diminished yield of flour, and the increased
produce of bran.

Theory and experience, therefore, indicate about

* Albumen is the name given by chemists to the white of
the egg. A small quantity of this substance is present in
every kind of grain. Itis closely related to gluten.

226 PROPER TIME OF CUTTING.

a fortnight before full ripening as the most proper
time for cutting corn. ‘The skin is then thinner,
the grain fuller, the bushel heavier, the yield of
flour greater, the quantity of bran less; while, at
the same time, the straw is heavier, and contains
more soluble matter than when it is left uncut un-
til it is considered to be fully ripe.*

SECTION IV.—ON THE ABSOLUTE QUANTITY OF FOOD YIELDED
BY DIFFERENT CROPS.

The quantity of food capable of yielding nour-
ishment to man, which can be grown from an acre
of land of average quality, depends very much
upon the kind of crop we raise.

In seeds, when fully ripe, little sugar or gum is
generally present, and it is chiefly by the amount
of starch and gluten they contain, that their nutri-
tive power is to be estimated. In bulbs, such as
the turnip and potato, sugar and gum are almost
always present in considerable quantity in the state

* On this subject the reader will consult with advantage
an excellent practical paper in the Quarterly Journal of Agri-
culture for June 1841, by Mr. Hannam of North Deighton,
Yorkshire, to whom I have to express my obligations for in-
formation regarding the results of some further experiments
made by him during the last autumn (1841).

AVERAGE PRODUCE OF DIFFERENT CROPS. 227

in which these roots are consumed, and this is es-

pecially the case with the turnip. These substan-

ces, therefore, must be included among the nutri-

tive ingredients of such kinds of food.

If we suppose an acre of Jand to yield the fol-

lowing quantities of the usually cultivated crops,

namely—

Of wheat,
Of barley,
Of oats, .
Of peas,

Of beans,

Of Indian corn,

Of potatoes,

Of turnips,

25 bushels, or

38 C6
50 ce
15 6c
D5 4c
60 cc
10 tons,
35 cc

or
or
or
or
or

1500 lbs.
2000 ‘
2250 “
1000 *
1600 “
3120 ‘

or 22400 “
or 56000 ‘¢

The weight of dry starch, gluten, sugar, and gum,

reaped in each crop, will be represented very

nearly by the following numbers :-—

Wheat,
Barley,
Oats, :
Peas,
Beans,
Indian corn,
Potatoes, .
Turnips, .

Starch.
825 lbs.

- 1200 “
pel

420 *
670 ‘

= LOU
. 2688 ‘
. 3090 “

Albumen.

315 Ibs.
120 “
100 “
260 *
370 ‘
280 ‘
994. 74
1400 “

60

Gluten and Sugarand Woody
Gum.

Fibre.

228 RELATIVE PROPORTIONS OF STARCH,

if it be granted that the crops above stated are
fair average returns from the same quality of
land—that the acre, for example, which produces
25 bushels of wheat, will also produce 10 tons of
potatoes, and so on—then it appears that the land
which, by cropping with wheat, would yield a given
weight of starch, would, when cropped with barley
or oats, yield one-half more, with Indian corn or
potatoes about three times as much, and with
turnips five times the same quantity. In other
words, the piece of ground which, when sown with
wheat, will maintain one man, would support one
and a half if sown with barley or oats, three with
Indian corn or potatoes, and five with turnips—
in so far as the nutritive power of these crops de-
pends upon the starch and sugar they contain.

Again, if we compare the relative quantities of
gluten, we see that wheat, beans, and Indian corn
yield, from the same breadth of land, nearly an
equal quantity of this kind of nourishment—pota-
toes one-third less, and barley and oats only one-
third of the quantity—while turnips yield four
times as much as either wheat, beans, or Indian
co n.

On whichever of these two substances, therefore,
the starch or the gluten, we consider the nutritive
property of the above kind of food to depend, it

GLUTEN, SUGAR, AND GUM. 229

appears that the turnip is by far the most nutri-
tive crop we can raise. It is by no means the most
nutritive weight for weight, but the largeness of
the crop (25 tons) affords us from the same field a
much greater weight of food than can be reaped
in the form of any of the other crops here men-
tioned.

In this the practical farmer will see the peculiar
adaptation of the turnip husbandry to the rearing
and fattening of stock. Could the turnip be made
an agreeable article of general human consump-
tion, the produce of the land might be made to
sustain a much larger population than under any
other of the above kinds of cropping.

The relative nourishing power or value as food
of different vegetable substances, is supposed by
some to depend entirely upon the relative propor-
tions of gluten they contain. According to this
view, the pea and the bean are much more nourish-
ing, weight for weight, even than wheat, and this
latter grain, than any of the other substances
mentioned in the above table. Thus, 56 lbs. of
beans would afford as much sustenance to an ani-
mal as 67 of pease, 100 of wheat-flour, or 177 of

rice.
In order to understand the value of this opi-

20

230 RELATIVE NUTRITIVE PROPERTIES.

nion, it will be proper to consider the several pur-
poses which the food is destined to serve in the
animal economy—what the animal must derive
from its food to maintain its existing condition,
or to admit of a healthy increase of bulk.

SECTION V.—-OF THE FEEDING OF ANIMALS, AND THE PUR-
POSES SERVED BY THE FOOD THEY CONSUME.

The food of plants we have seen to consist es-
sentially of two kinds, the organic and the inor-
ganic, both of which we have insisted upon as
equally necessary to the living vegetable—equally
indispensable to its healthy growth. A brief
glance at the purposes served by plants in the
feeding of animals, will not only confirm this view,
but will also throw some additional light upon
the kind of inorganic food which the plants must
be able to procure, in order that they may be
fitted to fulfil their assigned purpose in the eco-
nomy of nature.

Man, and all domestic animals, may be sup-
ported, may even be fattened, upon vegetable food
alone: vegetables, therefore, must contain all the
substances which are necessary to build up the
several parts of animal bodies, and to supply the
waste attendant upon the performance of the ne-

THE FOOD MUST SUPPLY CARBON. 231

cessary functions of animal life. Let us consider
what these substances are, and in what quantities
they must be supplied to the human body.

1. The food must supply carbon for respiration.

A man of sedentary habits, or whose occupa-
tion requires little bodily exertion, may respire
about 5 ounces of carbon in twenty-four hours
—one who takes moderate exercise, about 8 ounces
—and one who has to undergo violent bodily exer-
tion, from 12 to 15 ounces.

If we take the mean quantity of 8 ounces, then
to supply this alone, a man must eat 18 ounces of
starch or sugar every day. If he take it in the form
of wheaten bread, he will require 13 lbs, of bread,
if in the form of potatoes, about 73 lbs. of raw po-
tatoes, to supply the waste caused by his respira-
tory organs alone.

When the habits are sedentary, 5 lbs. of pota-
toes may be sufficient, when violent and continued
exercise is taken, 12 to 15 lbs. may be too little.
At the same time, it must be observed, that where
the supply is less, the quantity of carbonic acid
given off will either be less also, or the deficiency
will be supplied at the expense of the body itself.
In either case the strength will be impaired, and
fresh food will be required to recruit the exhaust-
ed frame.

232 THE FOOD MUST REPAIR THE DAILY WASTE.

2. The food must repair the daily waste of the
muscular parts of the body.

When the body is full grown, a portion from
every part of it is daily abstracted by natural pro-
cesses, and rejected either in the perspiration or
in the solid and fluid excrements. This portion
must be supplied by the food, or the strength will
diminish—the frame will gradually waste away.

The muscles of animals, of which lean beef and
mutton are examples, are generally coloured by
blood, but when well washed with water, they be-
come quite white, and, with the exception of a
little fat, are found to consist of a white fibrous
substance, to which the name of fibrin has been
given by chemists. ‘The clot of the blood consists
of the same substance ; while skin, hair, horn, and
the organic part of the bones, are composed of va- |
rieties of gelatine. This latter substance is fami-
liarly known in the form of glue, and though it
differs in its sensible properties, it is remarkably
analogous to fibrin in its elementary constitution,
as both of these substances are to the white of the
egg (albumen), to the curd of milk (casein), and
tothe gluten of flour. They all contain nitrogen,
and all consist of the four elementary bodies (or-
ganic elements), very nearly in the following pro-
portions :-—

OF NITROGEN IN THE EXCRETIONS. 233

Carbon, ; : : aw” 5D
Hydrogen, . ° : : 7
Nitrogen, . , ; siegat hs
Oxygen, ; E . a |)

100

They all contain, likewise, a small proportion
of sulphur and of phosphorous.

The quantity of one or other of these removed
from the body in 24 hours, either in the perspira-
tion or in the excretions, amounts to about five
ounces, containing 350 grains of nitrogen, and this
waste at least must be made up by the gluten or
fibrin of the food.

In the 123 |b. of wheaten bread we have sup-
posed to be eaten to supply carbon for respira-
tion, there will be contained also about 3 ounces
of gluten. Let the other 2 ounces be made up in
beef, of which half a pound contains 2 ounces of
dry fibrin, and we have !

For waste of
muscle, &c.

12 lbs, of bread yielding 18 oz. starch and 3 oz. of gluten.
8 oz. of beef yielding : : 2 oz. of fibrin.
Total consumed by res- — —— ? gluten or

For respiration.

piration, and the or- ¢ 18 oz. starch and5oz.§ fibrin.
dinary waste,

If, again, the 73 lbs. of potatoes be eaten, then
20*

234 QUANTITY OF FOOD REQUIRED

in these are contained about 21 ounces of gluten
or albumen, so that there remain 21 ounces to be
supplied by beef, eggs, milk, or cheese.

The reader, therefore, will understand why a
diet which will keep up the human strength is
easiest compounded of a mixture of vegetable and
animal food. It is not merely that such a mix-
ture is more agrecable to the palate, or even that
it is absolutely necessary,—for, as already observed,
the strength may be fully maintained by vegetable
food alone ;—it is, that without animal food in one
form or another, so large a bulk of vegetable food
must be consumed in order to supply the requi-
site quantity of nitrogen in the form of gluten.
Of ordinary wheaten bread alone, about 3. Ibs,
daily must be eaten to supply the nitrogen,* and
there would then be a considerable waste of
carbon in the form of starch, by which the
stomach would be overloaded, and which, not
being worked up by respiration, would pass off in
the excretions. ‘The wants of the body would be
equally supplied, and with more ease, by 12 lbs.
of bread and 4 ounces of cheese.

Of rice, again, no less than 4 Ibs. daily would

* The flour being supposed to contain 15 per cent. of
dry gluten, on which supposition all the above calcula-
iions are made,

TO SUPPLY THIS CARBON AND NITROGEN. 235

be required to impart to the system the required
proportion of gluten; and it is a familiar obser-
vation of those who have been in India and other
countries, where rice is the usual food of the
people, that the degree to which the natives dis-
tend, and apparently overload their stomachs with
this grain, is quite extraordinary.

The stomachs and other digestive apparatus of
our domestic animals are of larger dimensions,
and they are able, therefore, to contain with ease
as much vegetable food, of almost any wholesome
variety, as will supply them with the quantity of
nitrogen they may require. Yet every feeder of
stock knows that the addition of a small portion
of oil-cake, a substance rich in nitrogen, will not
only fatten an animal more speedily, but will also
save a large bulk of other kinds of food.

3. But the blood and other fluids of the body
contain much saline matter of various kinds, sul-
phates, muriates, phosphates, and other saline
compounds of potash, soda, lime, and magnesia.
All these have their special functions to perform
in the animal economy, and of each of them an
undetermined quantity daily escapes from the
body in the perspiration, in the urine, or in the
solid excretions. ‘This quantity, therefore, must
be daily restored by the food.

236 THE FOOD MUST ALSO YIELD

No precise experiments have yet been made
with the view of determining how much saline
matter is daily excreted from the body of a healthy
man, or in what proportions the different inor-
ganic substances are present in it; but it is satis-
factorily ascertained, that without a certain suffi-
cient supply, the animal will languish and decay,
even though carbon and nitrogen in the form of
starch and gluten be abundantly given toit. It
is a wise and beautiful provision of nature, there-
fore, that plants are so organized as to refuse to
grow in a soil from which they cannot readily ob-
tain a supply of soluble inorganic food, since that
saline matter which ministers first to their own
wants is afterwards surrendered by them to the
animals they are destined to feed.

Thus the dead earth and the living animal are
but parts of the same system,—links in the same
endless chain of natural existences,—the plant is
the connecting bond by which they are tied to-
gether on the one hand,—the decaying animal
matter which returns to the soil, connects them on
the other.

4. The solid bones of the animal are supplied
from the same original source,—the vegetable food
on which they live. The bones of the cow con-
tain 55 per cent. of phosphate of lime, of the sheep

SALINE AND BARTHY MATTER. 237

70, of the horse 67, of the calf 54, and of the pig
52 Ibs., inevery hundred of dry bone. All this must
come from the vegetable food. Of the bone-earth
also, a portion,—perhaps a variable portion,—is
every day rejected from the animal; the food,
therefore, must contain a daily supply, or that
which passes off will be taken from the substance
of the bones, and the animal will become feeble.

It is kindly provided by nature, that a certain
proportion of this ingredient of bones is always
associated with the gluten of plants in its various
forms,—with the fibrin of animal muscle and with
the curd of milk. Hence, man, in using any of
these latter along with his vegetable food, obtains
from them, with comparative ease, the quantity of
the earth of bones which is necessary to keep his
system in repair; while those animals which live
upon vegetables alone, extract all they require
along with the gluten of the plants on which they
feed.

The provision is very beautiful by which the
young animal,—the muscle and bones of which
are rapidly growing,—is supplied with a larger
portion of nitrogenous food and of bone-earth,
than are necessary to maintain the healthy condi-
tion of the full grown animal. The milk of the
mother is the natural food from which its supplies

238 HOW THESE SUBSTANCES ARE SUPPLIED TO

are drawn. ‘The sugar of the milk supplies the
comparatively small quantity of carbon necessary
for the respiration of the young animal ; as it gets
older, the calf or young lamb crops green food for
itself to supply an additional portion. The curd
of the milk (casein) yields the materials of the
growing muscles, and of the animal part of the
bones,—while dissolved along with the curd in the
liquid milk is the phosphate of lime, of which the
earthy part of the bones is to be built up. A
glance at the constitution of milk will shew us
how copious the supply of all these substances is,
—how beautifully the constitution of the mother’s
milk is adapted to the wants of her infant off-
spring. Cow’s milk consists in 1000 parts by
weight of—

Butter, : TOMAS ee ye eg 27 to 35

Cheesy matter (casein), . . 45 to 90

Milk sugar, Pli(ele) onthe eee

Chloride of potassium, and a little

chloride of sodium, . . : 13

Phosphates, chiefly of lime, . ; 223 tage

Other salts, ; : : : 6

Water, - P ; : 2 882: to 815
1000 1000

The quality of the milk, and, consequently, the
proportions of the several constituents above mens

YOUNG ANIMALS IN THEIR MOTHER’S MILK. 239

tioned, vary with the breed of the cow,—with the
food on which it is supported,—with the time that
has elapsed since the period of calving,—with its
age, its state of health, and with the warmth of the
weather ;* but in all cases this fluid contains the
same substances, though in different quantities.

Milk of the quality above analyzed contains, in
every ten gallons, 44 lbs. of casein, equal to the
formation of 18 lbs. of ordinary muscle, and 3}
ounces of phosphate of lime (bone-earth), equal to
the production of 7 ounces of dry bone. But
from the casein have to be formed the skin, the
hair, the horn, the hoof, &c. as well as the muscle,
and in all these is contained also a minute portion
of the bone-earth. A portion of all the ingredi-
ents of the milk likewise passes off in the ordinary
excretions, and yet every one knows how rapidly
young animals thrive, when allowed to consume
the whole of the milk which nature has provided
as their most suitable nourishment.

And whence does the mother derive all this
gluten and bone-earth, by which she can not only
repair the natural waste of her own full-grown
body, but from which she can spare enough also

* In warm weather the milk contains more butter, in cold
weather more cheese and sugar.

240 WHENCE DERIVED BY THE MOTHER.

to yield so large a supply of nourishing milk ?
She must extract them from the vegetables on
which she lives, and they again from the soil.

The quantity of solid matter thus yielded by
the cow in her milk is really very large, if we
look at the produce of an entire year. If the
average yield of milk be 3000 quarts, or 750 gal-
lons in a year—every 10 gallons of which contain
bone-earth enough to form about 7 ounces of dry
bone—then the milking of the cow alone exhausts
her of the earthy ingredients of 33 lbs. of dry bone.
And this she draws necessarily from the soil !

If this milk be consumed on the spot, then all
returns again to the soil in the annual manuring
of the land. Let it be carried for sale to a dis.
tance, or let it be converted into cheese and butter,
and in this form exported, there will then be a
yearly drain upon the land of the materials of
bones, from this cause alone, equal to 30 lbs. of
bone-dust. After the lapse of centuries, it is con-
ceivable that old pasture lands in cheese and dairy
countries should become poor in the materials
of .bones—and that in such districts, as now in
Cheshire, the application of bone-dust should en-
tirely alter the character of the grasses, and reno-
vate the old pastures.

Thus, as was stated at the commencement of

CAN THIS EFFECT THE QUALITY OF soIL? 241

the present section the study of the nature, and
functions of the food of animals throws additional
light upon the nature also and final uses of the
food of plants. It even teaches us what to look
for in the soil—what a fertile soil must contain
that it may grow nourishing food—what we must
add to the soil when chemical analysis fails to
detect its actual presence, or when the food it pro-
duces is unable to supply all that the animal
requires. -

The principles above explained, therefore, shew
that the value of any vegetable production, con-
sidered as the sole food of an animal, is not to be
judged of—cannot, in short, be accurately deter-
mined—by the amount it may contain of any one
of those substances, all of which together are ne-
cessary to build up the growing body of the young
animal, and to repair the natural waste of such as
have attained to their fullest size.

Hence the failure of the attempts that have
been made to support the lives of animals by feed-
ing them upon pure starch or sugar alone. These
substances would supply carbon for respiration,
but all the natural waste of nitrogen, of saline
matter, and of earthy phosphates, must have been

drawn from the existing solids and fluids of their
21

242 CONSTITUENTS OF NUTRITIVE FOOD.

living bodies. 'The animals in consequence pined
away, and sooner or later died.

Some have expressed surprise that animals have
refused to thrive, and have ultimately died, when
fed upon animal jelly or gelatine (from bones)
alone, nourishing though that substance as part of
the food undoubtedly is. When given in sufficient
quantity, gelatine might indeed supply carbon
enough for respiration, with a great waste of ni-
trogen, but it is deficient in the saline ingredients
which a naturally nourishing food contains.

Even on the natural mixture of starch and
gluten in fine white bread, dogs have been unable
to live beyond 50 days, though others fed on
household bread, containing a portion of the bran
—in which earthy matter more largely resides—
continued to thrive long after. It is immaterial
whether the general quantity of the whole food be
reduced too low, or whether one of its necessary
ingredients only be too much diminished or en-
tirely withdrawn. In either case, the effect will
be the same—the animal will pine away, and
sooner or later die.

VALUE OF DIFFERENT KINDS OF FOOD. 243

SECTION VII.—OF THE PRACTICAL AND THEORETICAL VALUE
OF DIFFERENT KINDS OF FOOD.

From what has been stated in the preceding
section, it appears, that, for various reasons, differ-
ent kinds of food are not equally nourishing.
This fact is of great importance, not only in the
preparation of human food, bnt also in the feed-
ing of stock. It has, therefore, been made the
subject of experiment by many practical agricul-
turists, with the following general results.

If common hay be taken as the standard of com.
parison, then to yield the same amount of nourish-
ment with 10 lbs. of hay, a weight of the other
kinds of food must be given, which is represented
by the number opposite to each in the following
table :—

Hay, ae eC Carrots, . 25 to 30
Clover hay, . 8tol0 ‘Turnips, ; 50

Green clover, . 45to050 Cabbage, ; 20 to 30
Wheat straw, . 40to050 PeaseandBeans, 3to 5
Barley straw, . 20to40 Wheat, . , 5to 6
Oat straw, sell. to 40) Barley tiie ues 5 to 6
Pea straw, . 10to15 Oats, : f 4to 7
Potatoes, . 20 Indian corn, . 5

eS

Old potatoes, . 407 Oil cake, : 2 to

244 EXPERIMENTAL AND THEORETICAL VALUE.

It is found in practice, as the above table shews,
that twenty stones of potatoes or three of oil-cake
will nourish an animal as much as ten stones of
hay, and five stones of oats as much as either.
Something, however, will depend upon the qual-
ity of each kind of food, and upon the age and
constitution of the animal. ‘The skilful feeder of
stock knows also the value of a change of food, or
of a mixture of the different kinds of vegetable
food he may have at his command.

The nutritive value of different kinds of food
has also been represented theoretically, by sup-
posing it to be very nearly in proportion to the
quantity of nitrogen, or of gluten, which vege-
tables contain. ‘Though this cannot be considered
as a correct principle, yet as the ordinary kind
of food on which stock is fed contains in general
an ample supply of carbon for respiration, with a
comparatively small proportion of nitrogen, these
theoretical determinations are by no means with-
out their value, and they approach in many cases
very closely to the practical values above given, as
deduced from actual trial. ‘Thus, assuming that
10 lbs. of hay yield a certain amount of nourish-
ment, then of the other vegetable substances it
will be necessary, according to theory, to give the

COMPARED WITH THAT OF HAY. 245

following quantities, in order to produce the same
effect :

Hay, Po LO! | Purmins, A kn GO
Clover hay, . 8 Carrots, : hale
Vetch hay,* . 4 Cabbage, : . 30to 40
Wheat straw, . 52 Pease and Beans, . 2to 3
Barley straw, . 52 Wheat, a . 5
Oatstraw, . 55 ~ Barley, 6
Pea straw, : 6 Oats, ‘ 5
Potatoes, oy feo) Andiay Gorn); , 6
Old potatoes, 40 Oil cake, 2

If the feeder be careful to supply his stock with
a mixture or occasional change of food, he may
very safely regulate the quantity of any one he
ought to substitute for a given weight of any of
the others, by the numbers in the above tables—
since the theoretical and practical results do not
in general very greatly differ.

As has been already stated, it is not strictly
correct that this or that kind of vegetable is more
fitted to sustain animal life, simply because of the
larger proportion of nitrogen it contains ; but it
is wisely provided, that along with this nitrogen
in all plants, a certain proportion of starch or

* Both cut in flower.
21*

~~

246 A MIXTURE OR CHANGE OF FOOD

sugar and of saline and earthy matter are always
associated—so that the quantity of nitrogen may
be considered as a rough practical index of the
' proportion of some of the important saline and
earthy ingredients also.

An important practical lesson on this subject
is taught us by the study of the wise provisions of
Nature. Not only does the milk of the mother
contain all the elements of a nutritive food mixed
up together—as the egg does also for the un-
hatched bird—but in rich natural pastures the
same mixture uniformly occurs. Hence, in crop-
ping the mixed herbage, the animal introduces
into its stomach portions of various plants—some
abounding more in starch or sugar, some more in
gluten or albumen, some naturally richer in
saline, others in earthy constituents; and out of
these varied materials the digestive organs select
a due proportion of each, and reject the rest.
Wherever a pasture becomes usurped by one or
two grasses—either animals cease to thrive upon
it, or they must crop a much larger quantity of
food to supply the natural waste of all the parts
of their bodies.

It may indeed be assumed as almost a general
principle, that whenever animals are fed on one

BEST FITTED TO NOURISH ALL ANIMALS. 247

kind of vegetable only, there is a waste of one or
other of the necessary elements of animal food,
and that the great lesson on this subject taught
us by nature is, that, by a judicious admixture,
not only is food economised, but the labour im-
posed upon the digestive organs is also materially
diminished.

SECTION VWIiIl.—-CONCLUDING OBSERVATIONS.

In this little work, now brought to a close, I
have presented the reader with a slight, and I
hope plain and familiar, sketch of the various
topics connected with practical agriculture, on
which the sciences of chemistry and geology are
fitted to throw the greatest light.

We have studied the general characters of the
organic and inorganic elements of which the parts
of plants are made up, and the several compounds
of these elements which are of the greatest im-
portance in the vegetable kingdom. We have
examined the nature of the seed,—seen by what
beautiful provision it is fed during its early ger-
mination—in what form the elements by which it
is nourished are introduced into the circulation
of the young plant when the functions of the seed

248 CONCLUDING OBSERVATIONS.

are discharged,—and how earth, air, and water are
all made to minister to its after-growth. We
have considered the various chemical changes
which take place within the growing plant, dur-
ing the formation of its woody stem, the blossom-
ing of its flower, and the ripening of its seed or
fruit,—and have traced the further changes it un-
dergoes, when, the functions of its short life being
discharged, it hastens to serve other purposes, by
mingling with the soil, and supplying food to
new races. The soils themselves in which plants
grow, their nature, their origin, the causes of
their diversity in mineral character, and in natu-
ral productiveness, have each occupied a share of
our attention—while the various means of im-
proving their agricultural value by manuring or
otherwise, have been practically considered, and
theoretically explained. Lastly, we have glanced
at the comparative worth of the various products
of the land, as food for man or other animals,
and have briefly illustrated the principles upon
which the feeding of animals and the relative nu-

tritive powers of the vegetables on which they

live are known to depend.

In this short and familiar treatise I have not —

sought so much to satisfy the demands of the phi-

nt
—

Ww
OBJECT OF THIS LITTLE WORK. 249

losophical agriculturist, as to awaken the curiosity
of my less instructed reader, to shew him how
much interesting as well as practically useful in.
formation chemistry and geology are able and will-
ing to impart to him, and thus to allure him in
quest of further knowledge and more accurate de-
tails to my larger work,* of which the present ex-
hibits only a brief outline.

* Lectures on Agricultural Chemistry and Geology.

J, P. Wright, Printer, 18 New street, N. Y-.

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