LIBRARY

OF THE

University of California.

Mrs. SARAH P. WALSWORTH.

Received October, i8g4.
z/lccessions No. SJ/^^^^. Class No.;

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ELEMENTS

OF

AGRICULTURAL CHEMISTRY.

IN

A COURSE OF LECTURES

FOR

THE BOARD OF AGRICULTURE

BY SIR HUMPHRY DAVY, LL. D.
F. R. S. L. & E. M. R. I.

Member of the Boar J of Agriculture, of the Royal Irish Academy, of the

Academies of St. Petersburgh, Stochholm, Berlin, Philadelphia, 8cc,

and Honorary Professor oi Chemistry to the Royal Institution.

PUBLISHED

By Eastbum, Kirk & Co. New-York ; and Ward & Lilly, Boston

1815.

S^^ifCf.

TO THE

PRESIDENT AND MEMBERS

OF

THE BOARD OF AGRICULTURE

FOR THE YEAR 1812.

THESE LECTURES,

PUBLISHED AT THEIR REQUEST,

ARE INSCRIBED^
A3 A TESTIMONY OF THE RESPECT OF THE AUTHOB,

ai3 GRATITUDE FOR THE ATTENTION WITH WHICH
THEY HAVE BEEN RECEIVED.

ADVERTISEMENT.

DURING ten years, since 1802, 1 have had the
honour, every Session, of delivering Courses of Lec«
tures before the Board of Agriculture. I have endea-
voured, at all times, to follow in them the progress of
chemical discovery ; they have therefore varied every
year : and such is the rapidity with which Chemistry
is extending, that some alterations and improvements
were rendered necessary at the time they were prepar-
ing for the press.

The Duke of Bedford has enabled me to stamp a
value upon this work, by permitting me to add to it the
results of the experiments instituted by His Grace
upon the quantity of produce afforded by the different
grasses.

I am indebted for much useful information to
many members of the Board ; of which acknowledg-
ments will be found in the body of the work. If there
are any omisssions on this head, I trust they will be
attributed to defect of recollection, and not to any
want of candour or of gratitude.

Where I have derived any specific statements from
books, I have always quoted the authors ; but I have

VI ADVERTISEMENT.

not always made references to such doctrines as are
become current, the authors of which are well known j
and which may be almost considered as the property
of all enlightened minds.

Amongst books to which I have not referred for
any particular facts, but which contain much useful
general information, I shall mention the Earl of Dun-
donald's Treatise on the connection of Chemistry with
Agriculture ; Mr. Rennie's Dissertations on Peat ; and
the General Report of the Agriculture of Scotland.
This last work did not come into my hands till the
concluding sheets of these Lectures were printing.
Had it been in circulation before, I should have profit-
ed by many statements given in it, particularly those
of the opinions of the enlightened Professor of Agri-
culture in the University of Edinburgh; and I should
have dwelt with satisfaction on the importance given
to some chemical doctrines by his experience.

Berkeley Square^
Marchy2l 1813.

CONTENTS.

LECTURE I. page.

Introduction. General Views of the Objects of the course,
and of the order in which they are to be discussed S

LECTURE II.
Of the general Powers of Matter which influence Vegeta-
tion ; of Gravitation, of Cohesion, of Chemical Attrac-
tion, of Heat, of Light, of Electricity, ponderable Sub-
stances, Elements of Matter, particularly those found in
Vegetables, Laws of their Combinations and Arrange-
ments -28

LECTURE in.
On the Organization of Plants. Of the Roots, Trunk, and
Branches ; of their Structure. Of the Epidermis. Of
the cortical, and albumous Parts of Leaves, Flowers, and
Seeds. Of the Chemical Constitution of the Organs of
Plants, and the Substances found in them. Of mucila-
ginous, saccharine, extractive, resinous, and oily Sub-
stances, and other vegetable Compounds, their Ar-
rangements in the organs of Plants, their Composition,
Changes, and Uses - . - . „ , 50

LECTURE IV.
On Soils : their constituent Parts. On the Analysis of
Soils. Of the Uses of the Soil. Of the Rocks and
Strata found beneath Soils. Of the Improvement of
Soils. ---- 130

LECTURE V.

On the Nature and Constitution of the Atmosphere, and
its influence on Vegetables. Of the Germinatiom of

Vm CONTENTS.

Seeds. Of the Functions of Plants in their different
Stages of Growth ; with a general view of the progress
of Vegetation 18:

LECTURE Vr.
Of Manures of vegetable and animal Origin. Of the man-
ner in which they become the Nourishment of the Plant.
Of Fermentation and Putrefaction. Of the different
Species of Manures of vegetable Origin ; of the differ-
ent Species of animal Origin. Of mixed manures.
General Principles with respect to the use and applica-
tion of such Manures 239

LECTUPvE VIL
On Manures of mineral Origin, or fossilc Manures ; their
Preparation, and the Manner in which they act. Of
Lime ia its different States ; Operation of Lime as a
Manure and a cement ; different combinations of Lime.
Of Gypsum; Ideas respecting its use. Of other Neu-
tro-saline Compounds, employed as Manures. Of Al-
kalies and alkaline Salts ; of common Salt • - 276

LECTURE VIH.
On the improvement of Lands by Burning ; chemical
Principles of this Operation. On Irrigation and its ef-
fects. On Fallowing ; its disadvantages and uses. On
the convertible Husbandry founded on regular rotations
of different Crops. On Pasture- On various Agricul-
tural Objects connected with Chemistry. Conclusion SOT

APPENDIX.
An account of the Results of Experimejits on the Produce
and Nutritive Qualities of different Grasses, and other
Plants, used as the Food of Animals.

COURSE OF LECTURES

OS

THE ELEMENTS

OE

AGRICULTURAL CHEMISTBT.

A

COURSE OF LECTURES, &e.

LECTURE I.

Introduction. General Views of the Objects of the Course^
and of the order in which they are to be discussed.

It is with great pleasure that I receive the permis-
sion to address so distinguished and enlightened an
Audience on the subject of Agricultural Chemistry.

That any thing which I am able to bring forward,
should be thought worthy the attention of the Board
of Agriculture, I consider as an honour; and I shall
endeavour to prove my gratitude, by employing every
exertion to illustrate this department of knowledge,
and to point out its uses.

In attempting these objects, the peculiar state of
the enquiry presents many difficulties to a Lecturer.
Agricultural Chemistry has not yet received a regular
and systematic form. It has been pursued by compe-
tent experimenters for a short time only; the doctrines
have not as yet been collected into any elementary trea-
tise; and on an occasion when I am obliged ,to trust
so much to my own arrangements, and to my own

C 4 ]

limited information, I cannot but feel difEdent as to
the interest that may be excited, and doubtful of the
success of the undertaking. I know, however, that
your candour will induce you not to expect any thing
like a finished work upon a science as yet in its infancy;
and I am sure you will receive with indulgence the
first attempt made to illustrate it, in a distinct course
of public lectures.

Agricultural Chemistry has for its objects all
those changes in the arrangements of matter connect-
ed with the growth and nourishment of plants ; the
comparative values of their produce as food; the con-
stitution of soils; the manner in which lands are en-
riched by manure, or rendered fertile by the different
processes of cultivation. Enquiries of such a nature
cannot but be interesting and important, both to the
theoretical agriculturist, and to the practical farmer.
To the first, they are necessary in supplying most of
the fundamental principles on which the theory of the
art depends. To the second, they are useful in afford-
ing simple and easy experiments for directing his la-
bours, and for enabling him to pursue a certain and
systematic plan of improvement.

It is scarcely possible to enter upon any investiga-
tion in agriculture without finding it connected, more
or less, with doctrines or elucidations derived from
chemistry.

If land be unproductive, and a system of ameliorat-
ing it is to be attempted, the sure method of obtaining
the object is by determining the cause of its sterility,
which must necessarily depend upon some defect in

[ 5 3

the constitution of the soil, which may be easily disi
covered by chemical analysis.

Some lands of good apparent texture are yet
sterile in a high degree; and common observation and
common practice afford no means of ascertaining the
cause, or of removing the effect. The application of
chemical tests in such cases is obvious ; for the soil
must contain some noxious principle which may be
easily discovered, and probably easily destroyed.

Are any of the salts of iron present? ihey may be
decomposed by lime. Is there an excess of siliceous
sand ? the system of improvement must depend on
the application of clay and calcareous matter. Is
ther*e a defect of calcareous matter? the remedy is
obvious. Is an excess of vegetable matter indicated ?
it may be removed by liming, paring, and burning.
Is there a deficiency of vegetable matter ? it is to be
supplied by manure.

A question concerning the different kinds of lime-
stone to be employed in cultivation often occurs. To
determine this fully in the common way of experience,
would demand a considerable time, perhaps some
years, and trials which might be injurious to crops ;
but by simple chemical tests the nature of a limestone
is discovered in a few minutes ; and the fitness of its
application, whether as a manure for different soils, or
as a cement, determined.

Peat earth of a certain consistence and composi-
tion is an excellent manure ; but there are some varie-
ties of peats which contain so large a quantity of fer-
ruginous matter as to be absolutely poisonous to plants.

C 6 ]

Nothing can be more simple than the chemical opera-
tion for determining the nature, and the probable uses
of a substance of this kind.

There has been no question on which more dif-
ference of opinion has existed, than that of the state
in which manure ought to be ploughed into the land ;
whether recent, or when it has gone through the pro-
cess of fermentation ? and this question is still a sub-
ject of discussion ; but whoever will refer to the sim-
plest principles of chemistry, cannot entertain a doubt
on the subject. As soon as dung begins to decom-
pose, it throws off its volatile parts, which are the
most valuable and most efficient. Dung which has fer-
mented, so as to become a mere soft cohesive mass,
has generally lost from one third to one half of its
most useful constituent elements. It evidently should
be applied as soon as fermentation begins, that it may
exert its full action upon the plant, and lose none of
its nutritive powers.

It would be easy to adduce a multitude of other
instances of the same kind ; but sufficient I trust has
been said to prove, that the connexion of Chemistry
with Agriculture is not founded on mere vague specu-
lation, but that it offers principles which ought to be
understood and followed, and which in their progres-
sion and ultimate results, can hardly fail to be highly
beneficial to the community.

A view of the objects in this Course of Lectures,
and of the manner in which they are to be treated,
will not, I hope, be considered as an improper intro-
duction. It will inform you what you are to expect ;

C 7 3

it will afFord a general idea of the connexion of the
different parts of the subject, and of their relative im-
portance ; it will enable me to give some historical
details of the progress of this branch of knowledge,
and to reason from what has been ascertained, con-
cerning what remains to be investigated and disco-
vered.

The phenomena of vegetation must be consider-
ed as an important branch of the science of organized
nature ; but though exalted above inorganic matter,
vegetables are yet in a great measure dependent for
their existence upon its laws. They receive their nour-
ishment from the external elements ; they assimilate
it by means of peculiar organs ; and it is by examin-
ing their physical and chemical constitution, and the
substances and powers which act upon them, and the
modifications which they undergo, that the scientific
principles of Agricultural Chemistry are obtained.

According to these ideas, it is evident that the
study ought to be commenced by some general en-
quiries into the composition and nature of material
bodies, and the laws of their changes. The surface
of the earth, the atmosphere, and the water deposited
from it, must either together or separately afFord all the
principles concerned in vegetation ; and it is only by
examining the chemical nature of these principles,
that we are capable of discovering what is the food of
plants, and the manner in which this food is supplied
and prepared for their nourishment. The principles
of the constitution of bodies, consequently, will form
the first subject for our consideration.

I 8 1

By methods of analysis dependent upon chemi-
cal and electrical instruments discovered in late times,
it has been ascertained that all the varieties of material
substances may be resolved into a comparatively small
number of bodies, which, as they are not capable of
being decompounded, are considered in the present
state of chemical knowledge as elements. The bodies
incapable of decomposition at present known are forty-
seven. Of these, thirty-eight are metals ; seven are
inflammable bodies ; and two are gasses which unite
with metals and inflammable bodies, and form with
them acids, alkalies, earths, or other analogous com-
pounds. The chemical elements acted upon by at-
tractive powers combine in different aggregates. In
their simpler combinations, they produce various crys-
talline substances, distinguished by the regularity of
their forms. In more complicated arrangements, they
constitute the varieties of vegetable and animal sub-
stances, bear the higher character of organization,
and are rendered subservient to the purposes of life.
And by the influence of heat, light, and electrical
powers^ there is a constant series of changes ; matter
assumes new forms, the destruction of one order of
beings tends to the conservation of another, solution
and consolidation, decay and renovation, are connect-
ed, and whilst the parts of the system continue in
a state of fluctuation and change, the order and har-
mony of the whole remain unalterable.

After a general view has been taken of the na-
ture of the elements, and of the principles of chemi-
cal changes, the next object will be the structure and

[93

constitution of plants. In all plants there exists a
system of tubes or vessels, which in one extremity
terminate in the roots, and at the other in leaves. It
is by the capillary action of the roots that fluid mat-
ter is taken up from the soil. The sap in passing up-
wards becomes denser, and more fitted to deposit
solid matter ; it is modified by exposure to heat, light,
and air in the leaves ; descends through the bark,
in its progress ^ produces new organized matter ; and
is thus in its vernal and autumnal flow, the cause of
the fermentation of new parts, and of the more per-
fect evolution of parts already formed.

In this part ctf" the enquiry I shall endeavour to
connect together into a general view, the observations
of the most enlighted philosophers who have studied
the physiology of vegetation. Those of Grew, Mal-
pighi, Sennebier, Darwin, and, above all, of Mr.
Knight. He is the latest enquirer into these interest-
ing subjects, and his labours have tended most to il-
lustrate this part of the economy of nature.

The chemical composition of plants has within
the last ten years, been elucidated by the experiments
of a number of chemical philosophers, both in this,
and in other countries ; and it forms a beautiful part of
general chemistry ; it is too extensive to be treated of
minutely ; but it will be necessary to dwell upon
such parts of it, as afford practical inferences.

If the organs of plants be submitted to chemical
analysis, it is found that their almost infinite diversity
of form, depends upon different arrangements and
combinations of a very few of the elements j seldom

C 10 ]

more than seven or eighr belong to them, and three con-
stitute the greatest part of their organized matter ; and
according to the manner in which these elements are
disposed, arise the diflerent properties of the products
of vegetation, whether employed as food, or for other
purposes and wants of life.

The value and uses of every species of agricul-
tural produce, are most correctly estimated and applied
when practical knowledge is assisted by principles de-
rived from chemistry. The compounds in vegetables
really nutritive as the food of animals, are very few ;
farina or the pure matter of starch, gluten, vegetable
jellv, and extract. Of these the most nutritive is
gluten, which approaches nearest in its nature to ani-
mal matter, and which is the substance that gives to
wheat its superiority over other grain. The next in
order as to nourishing power, is sugar, then farina ;
and last of all gelatinous and extractive matters. Sim-
ple tests of the relative nourishing powers of the differ-
ent species of food, are the relative quantities of these
substances that they afford by analysis ; and though
taste and appearance must influence the consumption
of all articles in years of plenty, yet they are less at-
tended to in times of scarcity, and on such occasions
this kind of knowledge may be of the greatest impor-
tance. Sugar and farina or starch, are very similar
in composition, and are capable of being converted
into each other by simple chemical processes. In the
discussion of their relations, I shall detail to you the
results ot some recent experiments which will be
found possessed of applications both to the oeconomy

L 11 ]

of vegetation, and to some important processes of;
manufacture.

All the varieties of substances found in plants,
are produced from the sap, and the sap of plants is
derived from water, or from the fluids in the soil, and
it is altered by, or combined with principles derived
from the atmosphere. The influence of the soil, of
water, and of air, will therefore be the next subject of,
consideration. Soils in all cases consist of a mixture
of different finely divided earthy matters ; with ani-
mal or vegetable substances in a state of decomposi-
tion, and certain saline ingredients. The earthy mat-
ters are the true basis of the soil ; the other parts,
whether natural, or artificially introduced, operate in
the same manner as manures. Four earths generally
abound in soils, the aluminous, the siliceous, the cal-
careous, and the magnesian. These earths, as I have
discovered, consist of highly inflammable metals
united to pure air or oxygene ; and they are not, as
far as we know, decomposed or altered in vegetation.
The great use of the soil is to afford support to the
plant, to enable it to fix its roots, and to derive nour-
ishment by its tubes slowly and gradually, from the so-
luble and dissolved substances mixed with the earths.
That a particular mixture of the earths is con-
nected with fertility, cannot be doubted : and almost
all sterile soils are capable of being improved, by a
modification of their earthy constituent parts. I shall
describe the simplest method as yet discovered of
analysing soils, and of ascertaining the constitution
and chemical ingredients which appear to be connect-

C 12 ]

ed with fertility and on this subject many of the for-
mer difficulties of investigation will be found to be re-
moved by recent enquiries.

The necessity of water to vegetation, and the lux-
uriancy of the growth of plants connected with the pre-
sence of moisture in the southern countries of the old
continent, led to the opinion so prevalent in the early
schools of philosophy, that water was the great pro-
ductive element, the substance from which all things
were capable of being composed, and into which
they were finally resolved. The " «e'<"o» /«" J^^*?" of
the poet, " water is the noblest," seems to have
been an expression of this opinion, adopted by the
Greeks from the Eg}^ptians, taught by Thales, and
revived by the alchemists in late times. Van Hel-
mont in 1610, conceived that he had proved by a de-
cisive experiment, that all the products of vegetables
were capable of being generated from water. His
results were shewn to be fallacious by Woodward in
1691 ; but the true use of water in vegetation was
unknown till 1785 ; when Mr. Cavendish made the
grand discovery, that it was composed of two elastic
fluids or gases, inflammable gas or hydrogene, and
vital gas or oxygene.

Air, like water, was regarded as a pure element
by most of the ancient philosophers : a few of the
chemical enquirers in the sixteenth and seventeeth
centuries, formed some happy conjectures respecting
its real nature. Sir Kenelm Digby in 1 660, supposed
that it contained some saline matter, which was an
essential food of plants. Boyle, Hooke, and Mayow,

[ 13 ]

between 1665 and 1680, stated that a small part of it
only was consumed in the respiration of animals, and
in the combustion of inflammable bodies ; but the
true statical analysis of the atmosphere is comparative-
ly a recent labour, achieved towards the end of the
last century by Scheele, Priestley, and Lavoisier.
These celebrated men shewed that its principal
elements are two gases, oxygene and azote, of which
the first is essential to flame, and to the life of animals,
and that it likewise contains small quantities of
aqueous vapour, and of carbonic acid gas ; and La-
voisier proved that this last body is itself a compound
elastic fluid, consisting of charcoal dissolved in oxy-
gene.

Jethro Tull, in his treatise on Horse-hoeing, pub-
lished in 1 733, advanced the opinion that minute
earthy particles supplied the whole nourishment of the
vegetable world ; that air and water were chiefly useful
in producing these particles from the land ; and that
manures acted in no other way than in ameliorating the
texture of the soil, in short, that their agency was
mechanical. This ingenious author of the new system
of agriculture having observed the excellent effects
produced in farming by a minute division of the soil,
and the pulverisation of it by exposure to dew and air,
was misled by carrying his principles too far. Duh-
amel, in a work printed in 1 754, adopted the opinion
of Tull, and stated that by finely dividing the soil, any
number of crops might be raised in succession from
the same land. He attempted also to prove, by di-
rect experiments, that vegetables of every kind were

[ 14 1

capable of being raised without manure. This cele-
brated horticulturist Hved, however, sufficiently long
to alter his opinion. The results of his later and
most refined observations led him to the conclusion,
that no single material afforded the food of plants.
The general experience of farmers had long before
convinced the unprejudiced of the truth of the same
opinion, and that manures were absolutely consumed
in the process of vegetation. The exhaustion of soils
by carrying off corn crops from them, and the effects
of feeding cattle on lands, and of preserving their
manure, offer familiar illustrations of the principle ;
and several philosophical enquirers, particularly Has-
senfratz and Saussure, have shewn by satisfactory ex-
periments, that animal and vegetable matters deposit-
ed in soils are absorbed by plants, and become a part
of their organized matter. But though neither water,
nor air, nor earth, supplies the whole of the food of
plants, yet they all operate in the process of vegeta-
tion. The soil is the laboratory in which the food is
prepared. No manure can be taken up by the roots
of plants unless water is present ; and water or its
elements exist in all the products of vegetation. The
germination of seeds does not take place without the
presence of air or oxygene gas ; and in the sunshine
vegetables decompose the carbonic acid gas of the at-
mosphere, the carbon of which is absorbed, and be-
comes a part of their organized matter, and the oxy-
gene gas, the other constituent, is given off ; and in
consequence of a variety of agencies, the cEConomy of
vegetaUon is made subservient to the general order of
the system of nature.

C 15 3

It is shewn by various researches, that the constitu-
tion of the atmosphere has been always the same since
the time that it was first accurately analysed ; and
this must in a great measure d&pend upon the powers
of plants to absorb or decompose the putrifying or de-
caying remains of animals and vegetables, and the
gaseous effluvia w^hich they are constantly emitting.
Carbonic acid gas is formed in a variety of processes
of fermentation and combustion, and in the respiration
of animals, and as yet no other process is known in
nature by which it can be consumed, except vegeta-
tion. Animals produce a substance which appears to
be a necessary food of vegetables ; vegetables evolve
a principle necessary to the existence of animals ; and
these different classes of beings seem to be thus con-
nected together in the exercise of their living functions
and to a certain extent made to depend upon each
other for their existence. Water is raised from the
ocean, diffused through the air, and poured down
upon the soil, so as to be applied to the purposes
of life. The different parts of the atmosphere are
mingled together by winds or changes of tempera-
ture, and successively brought in contact with the
surface of the earth, so as to exert their fertilizing in-
fluence. The modifications of the soil, and the ap-
plication of manures are placed within the power of
man, as if for the purpose of awakening his industry
and of calling forth his powers.

The theory of the general operation of the more
compound manures may be rendered very obvious by
simple chemical principles 5 but there is still much

t 16 3

to be discovered with regard to the best methods
of rendering animal and vegetable substances soluble ;
with respect to the processes of decomposition, how
they may be accelerated or retarded, and the means
of producing the greatest effects from ihe materials
employed : these subjects will be attended to in the
Lecture on Manures.

Plants are found by analysis to consist princi-
pally of charcoal and aeriform matter. They give
out by distillation volatile compounds, the elements
of which are pure air, inflammable air, coally matter,
and azote, or that elastic substance which forms a
great part of the atmosphere, and which is incapable
of supporting combustion. These elements they gain
either by their leaves from the air, or by their roots
from the soil. All manures from organized substan-
ces contain the principles of vegetable matter, which
during putrefaction are rendered either soluble in
water or aeriform — and in these states they are capa-
ble of being assimilated to the vegetable organs. No
one principle affords the pabulum of vegetable hfe ;
it is neither charcoal nor hydrogene, nor azote nor
oxygene alone ; but all of them together in various
states and various combinations. Organic substances
as soon as they are deprived of vitality, begin to pass
through a series of changes which end in their com-
plete destruction, in the entire separation and dissipa-
tion of the parts. Animal matters are the soonest des-
troyed by the operation of air, heat, and light. Vege-
ble substances yield more slowly, but finally obey the
same laws. The periods of the application of manures

c 17 :

from decomposing animal and vegetable substances
depend upon the knowledge of these principles, and
I shall be able to produce some new and important
facts founded upon them, w^hich I trust will remove
all doubt from this part of agricultural theory.

The chemistry of the more simple manures ; the
manures which act in very small quantities, such as
gypsum, alkalies, and various saline substances, has
hitherto been exceedingly obscure. It has been gen-
erally supposed that these materials act in the vegetable
ceconomy in the same manner as condiments or stimu-
lants in the animal ceconomy, and that they render the
common food more nutritive.-- It seems, however, a
much more probable idea, that they are actually a
part of the true food of plants, and that they supply
that kind of matter to the vegetable fibre, which is
analogous to the bony matter in animal structures.

The operation of gypsum, it is well known, is
extremely capricious in this country, and no certain
data have hitherto been offered for its application.

There is, however, good ground for supposing
that the subject will be fully elucidated by chemical
enquiry. Those plants which seem most benefited by
its application, are plants which always afford it on
analysis. Clover, and most of the artificial grasses, con-
tain it, but it exists in very minute quantity only in
barley, wheat and turnips. Many peat ashes which
are sold at a considerable price, consist in great part
of gypsum, with a little iron, and the first seems to
be their most active ingredient. I have examined
several of the soils to which these ashes are success-

D

fully applied, and I have found in them no sensible
quantity of gypsum. In general, cultivated soils contain
sufficient of this substance for the use of the grasses ;
in such cases, its application cannot be advantageous.
For plants require only a certain quantity of manure ;
an excess may be detrimental, and cannot be useful.

The theory of the operation of alkaline substan-
ces, is one of the parts of the chemistry of agriculture,
most simple and distinct. They are found in all plants
and therefore may be regarded as amongst their es-
sential ingredients. From their powers of combina-
tion likewise, they may be useful in introducing vari-
ous principles into the sap of vegetables, which may
be subservient to their nourishment.

The fixed alkalies which were formerly regarded
as elementary bodies, it has been my good fortune to
decompose. They consist of pure air, united to high-
ly inflammable metallic substances ; but there is no
reason to suppose that they are reduced into their
elements in any of the processes of vegetation.

In this part of the course I shall dwell at consi-
derable length on the important subject of Lime, and
I shall be able to oiFer some novel views.

Slacked lime was used by the Romans for man-
uring the soil in which fruit trees grew. This we are
informed by Pliny. Marie had been employed by the
Britons and the Gauls from the earliest times, as a
top dressing for land. But the precise period in
which burnt lime first came into general use in the cul-
tivation of land, is, I believe, unknown. The origin
of the application from the early practices is sufficient-

C 19 3

ly obvious ; a substance which had been used with
success in gardening, must have been soon tried in
in farming ; and in countries where marie was not to
be found, calcined limestone would be naturally em-
ployed as a substitute.

The elder writers on agriculture had no correct
notions of the nature of lime, limestone and marie, or
of their effects ; and this was the necessary conse*
quence of the imperfection of the chemistry of the
age. Calcareous matter was considered by the alche-
mists as a peculiar earth, which in the fire became
combined with inflammable acid ; and Evelyn and
Hartlib, and still later. Lisle, in their works on hus-
bandry, have characterized it merely as a hot manure
of use in cold lands. It is to Dr. Black of Edinburgh
that our first distinct rudiments of knowledge on the
subject are owing. About the year 1 755, this cele-
brated professor proved, by the most decisive experi-
ments, that hmestone and all its modifications, mar-
bles, chalks, and marles, consist principally of a pecu-
liar earth united to an aerial acid : that the acid is
given out in burning, occasioning a loss of more than
40 per cent,, and that the lime in consequence becomes
caustic.

These important facts immediately applied with
equal certainty to the explanation of the uses of lime,
both as a cement and as a manure. As a cement,
lime applied in its caustic state acquires its hardness
and durability, by absorbing the aerial (or as it has
been since called carbonic) acid, which always exists
in small quantities in the atmosphere, it becomes af^
it were again limestone.

C 20 3

Chalks, calcareous marles, or powdered lime-
stones, act merely by forming an useful earthy ingre-
dient of the soil, and their efficacy is proportioned to
the deficiency of calcareous matter, which in larger
or smaller quantities seems to be an essential ingre-
dient of all fertile soils ; necessary perhaps to their
proper texture, and as an ingredient in the organs of
plants.

Burnt lime, in its first effect, acts as a decompo-
sing agent upon animal or vegetable matter, and seems
to bring it into a state on which it becomes more
rapidly a vegetable nourishment ; gradually, however,
the lime is neutralized by carbonic acid, and conver-
ted into a substance analogous to chalk ; but in this
case it more perfectly mixes with the other ingredients
of the soil, is more generally diffused and finely di-
vided ; and it is probably more useful to land than
any calcareous substance in its natural state.

The most considerable fact made known with
regard to limestone within the last few years, is owing
to Mr. Tennant. It had been long known that a par-
ticular species of limestone found in different parts of
the North of England, when applied in its burnt and
slacked state to land in considerable quantities, occa-
sioned sterility, or considerably injured the crops for
many years. Mr. Tennant in 1800, by a chemical
examination of this species of limestone, ascertained,
that it differed from common limestones by containing
magnesian earth ; and by several experiments he
proved that this earth was prejudicial to vegetation,
when applied in large quantities in its caustic state.

r 21 ]

Under common circumstances the lime from the mag-
nesian limestone is, however, used in moderate quan-
tities upon fertile soils in Leicestershire, Derbyshire,
and Yorkshire, with good effect ; and it may be ap-
plied in greater quantities to soils containing very large
proportions of vegetable matter. Magnesia when
combined with carbonic acid gas, seems not to be pre-
judicial to vegetation, and in soils rich in manure, it
is speedily supplied with this principle from the de-
composition of the manure.

After the nature and operation of manures have
been discussed, the next, and the last subject for our
consideration, will be some of the operations of hus-
bandry capable of elucidation by chemical principles.

The chemical theory of fallowing is very simple.
Fallowing affords no new source of riches to the soil.
It merely tends to produce an accumulation of decom
posing matter, which in the common course of crops
would be employed as it is formed, and it is scarcely
possible to imagine a single instance of a cultivated
soil, which can be supposed to remain fallow for a
year with advantage to the farmer. The only cases
where this practice is beneficial seems to be in the des-
truction of weeds, and for cleansing foul soils.

The chemical theory of paring and burning, I
shall discuss fully in this part of the Course.

It is obvious that in all cases it must destroy a
certain quantity of vegetable matter, and must be
principally useful in cases in which there is an excess
of this matter in soils. Burning, likewise renders
clays less coherent, and in this way greatly improves

C 22 3

their texture, and causes them to be less permeable
to water.

The instances in which it must be obviously pre-
judicial, are those of sandy dry siliceous soils, contain-
ing little animal or vegetable matter, fiere it can
only be destructive, for it decomposes that on which
the soil depends for its productiveness.

The advantages of irrigation, though so lately a
subject of much attention, were well known to the
ancients ; and more than two centuries ago the prac-
tice was recommended to the farmers of our country
by Lord Bacon ; *' meadow-watering,*' according to
the statements of this illustrious personage, (given in
his Natural History, in the article Vegetation,) acts
not only by supplying useful moisture to the grass ;
but likewise the water carries nourishment dissolved
in it, and defends the roots from the effects of cold.

No general principles can be laid down respecting
the comparative merit of the different systems of culti-
vation, and the different systems of crops adopted in
different districts, unless the chemical nature of the
soil, and the physical circumstances to which it is ex-
posed are fully known. Stiff coherent soils are those
most benefited by minute division and aeration, and in
the drill system of husbandry, these effects are pro-
duced to the greatest extent ; but still the labour and
expense connected with its application in certain dis-
tricts, may not be compensated for by the advantages
produced. Moist climates are best fitted for raising
the artificial grasses, oats, and broad leaved crops ;
stiff aluminous soils, in general, are most adapted for

C 23 ]

wheat crops, and calcareous soils produce excellent
sain-foin and cjover.

Nothing is more wanting in agriculture, than ex-
periments in which all the circumstances are minutely
and scientifically detailed. This art will advance with
rapidity in proportion as it becomes exact in its
methods. As in physical researches all the causes
should be considered ; a difference in the results may
be produced, even by the fall of a half an inch of rain
more or less in the course of a season, or a few de-
grees of temperature, or even by a slight difference in
the sub-soil, or in the inclination of the land.

Information collected after views of distinct en-
quiry, would necessarily be more accurate, and more
capable of being connected with the general principles
of science ; and a few histories of the results of truly
philosophical experiments in agricultural chemistry,
would be of more value in enlightening and benefitting
the farmer, than the greatest possible accumulation of
imperfect trials, conducted merely in the empirical
spirit. It is no unusual occurence for persons who
argue in favour of practice and experience, to con-
demn generally all attempts to improve agriculture by
philosophical enquiries and chemical methods. That
much vague speculation may be found in the works of
those who have lightly taken up agricultural chemis-
try, it is impossible to deny. It is not uncommon to
find a number of changes rung upon a string of tech-
nical terms, such as oxygene, hydrogene, carbon, and
azote, as if the science depended upon words, rather
than upon things. But this is in fact an argument for

[ 24 3

the necessity of the establishment of just principles of
chemistry on the subject. Whoever reasons upon
agriculture, is obliged to recur to this science. He
feels that it is scarcely possible to advance a step with-
out it ; and if he is satisfied with insufficient views, it
is not because he prefers them to accurate knowledge,
but generally because they are more current. If a
person journeying in the night wishes to avoid being
led astray by the ignis fatuus, the most secure method
is to carry a lamp in his own hand.

It has been said, and undoubtedly with great
truth, that a philosophical chemist would most proba-
bly make a very unprofitable business of farming ; and
this certainly would be the case, if he were a mere
philosophical chemist ; and unless he had served his
apprenticeship to the practice of the art, as well as to
the theory. But there is reason to believe, that he
would be a more successful agriculturist than a per-
son equally uninitiated in farming, but ignorant of
chemistry altogether ; his science, as far as it went,
would be useful to him. But chemistry is not the
only kind of knowledge required, it forms a small part
of the philosophical basis of agriculture ; but it is an
important part, and whenever applied in a proper
manner must produce advantages.

In proportion as science advances all the princi-
ples become less complicated, and consequently more
useful. And it is then that their application is most
advantageously made to the arts. The common la-
bourer can never be enlightened by the general doc-
trines of philosophy, but he will not refuse to adopt

C 25 2

any practice, of the utility of which he is fully con-
vinced, because it has been founded upon these prin-
ciples. The mariner can trust to the compass,
though he may be wholly unacquainted with the dis-
coveries of Gilbert on magnetism, or the refined prin-
ciples of that science developed by the genius of
^pinus. The dyer will use his bleaching liquor,
even though he is perhaps ignorant not only of the
constitution, but even of the name of the substance
on which its powers depend. The great purpose of
chemical investigation in Agriculture, ought undoubt- *
edly to be the discovery of improved methods of cul-
tivation. But to this end, general scientific principles
and practical knowledge, are alike necessary. The
germs of discovery are often found in rational specu-
lations ; and industry is never so efficacious as when
assisted by science*

• It is from the higher classes of the community,
from the proprietors of land ; those who are fitted by
their education to form enlightened plans, and by their
fortunes to carry such plans into execution ; it is from
these that the principles of improvement must flow to
the labouring classes of the community ; and in all
cases the benefit is mutual ; for the interest of the
tenantry must be always likewise the interest of the
proprietors of the soil. The attention of the labourer
will be more minute, and he will exert himself more
for improvement when he is certain he cannot deceive
his employer, and has a conviction of the extent of
his knowledge. Ignorance in the possessor of an
estate of the manner in which it ought to be treated.

[ 26 ]

often leads either to inattention or injudicious prac-
tices in the tenant or the bailiff. '' Agrum pes-
simiwi mulctari cujiis Dominus non docet sed audit vil-

I'lcum,^*

There is no idea more unfonnded than that a
great devotion of time, and minute knowledge of gen-
eral chemistry is necessary for pursuing experiments
on the nature of soils or the properties of manures.
Nothing can be more easy than to discover vi^hether a
soil effervesces, or changes colour by the action of an
acid, or whether it burns when heated \ or what
weight it loses by heat : and yet these simple indic;|L-
tions may be of great importance in a system of culti-
vation. The expence connected with chemical enqui-
ries is extremely trifling ; a small closet is sufficient
for containing all the materials required. The most
important experiments may be made by means of a
small portable apparatus ; a few phials, a few acids, a
lamp and a crucible are all that are necessary, as I shall
endeavour to prove to you, in the course of these
lectures.

It undoubtedly happens in agricultural chemical
experiments conducted after the most refined theo-
rectical views, that there are many instances of failure,
for one of success ; and this is inevitable from the
capricious and uncertain nature of the causes that
operate, and from the impossibility of calculating on
all the circumstances that may interfere ; but this is
far from proving the inutility of such trials \ one hap-
py result which can generally improve the methods
of cultivation is worth the labour of a whole life ; and

C 27 3

an unsuccessful experiment well observed, must esta-
blish some truth, or tend to remove some prejudice.

Even considered merely as a philosophical
science, this department of knowledge is highly worthy
of cultivation. For what can be more delightful than
to trace the forms of living beings and their adapta-
tions and peculiar purposes j to examine the progress
of inorganic matter in its different processes of
change, till it attain its ultimate and highest destina-
tion ; its subserviency to the purposes of man.

Many of the sciences are ardently pursued, and
tonsidered as proper objects of study for all refined
minds, merely on account of the intellectual pleasure
they afford ; merely because they enlarge our views
of nature, and enable us to think more correctly with
respect to the beings and objects surrounding us. How
much more then is this department of enquiry worthy
of attention, in which the pleasure resulting from the
love of truth and of knowledge is as great as in any
other branch of philosophy, and in which it is likewise
connected with much greater practical benefits and
advantages. " Nihil est melius^ nihil uberius^ nihil ho-
mine liber o digniusJ'

Discoveries made in the cultivation of the earth,
are not merely for the time and country in which they
are developed, but they may be considered as extend-
ing to future ages, and as ultimately tending to bene-
fit the whole human race ; as affording subsistence
for generations yet to come ; as multiplying life, and
not only multiplying life, but likewise providing for
its enjoyment.

28

LECTURE IL

Of the general Powers of Matter which influence Vegeta-
tion, Of Gravitationy of Cohesion ^ of chemical Attrac-
iion^ of Heat^ of Lights of Electricity ^ ponderable
Substances^ Elements of Matter^ particularly those
found in Vegetables^ Laws of their Combinations and
Arrangements.

THE great operations of the farmer are directed
towards the production or improvement of certain
classes of vegetables j they are either mechanical or
chemical, and are, consequently, dependant upon the
laws which govern common matter. Plants themselves
are, to a certain extent, submitted to these hws ; and
it is necessary to study their effects both in consider-
ing the phasnomena of vegetation, and the cultivation
of the vegetable kingdom.

One of the most important properties belonging
to matter is gravitation^ or the power by which mas-
ses of matter are attracted towards each other. It is
in consequence of gravitation that bodies thrown into
the atmosphere fall to the surface of the earth, and that
the different parts of the globe are preserved in their
proper positions. Gravity is exerted in proportion to
the quantity of matter. Hence all bodies placed above
the surface of the earth fall to it in right lines, which
if produced would pass through its centre j and a

[ 29 3

body falling near a high mountain, is a little bent
out of the perpendicular direction by the attraction
of the mountain, as has been shewn by tbe experi-
ments of Dr. Maskelyne on Schehallien.

Gravitation has a very important influence on
the growth of plants ; and it is rendered probable, by
the experiments of Mr. Knight, that they owe the pe-
culiar direction of their roots and branches almost en-
tirely to this force.

That gentleman fixed some seeds of the garden
bean on the circumference of a wheel, which in one
instance was placed vertically, and in the other hori-
zontally, and made to revolve, by means of another
wheel worked by water, in such a manner, that the
number of the revolutions could be regulated ; the
beans were supplied with moisture, and were placed
under circumstances favourable to germination. The
greatest velocity of motion given to the wheel was
such, that it performed 250 revolutions in a minute.
It was found that in all cases the beans grew, and that
the direction of the roots and stems was influenced by
the motion of the wheel. When the centrifugal force
was made superior to the force of gravitation, which
was supposed to be done when the vertical wheel per-
formed 1 50 revolutions in a minute, all the radicles,
in whatever way they were protruded from the po-
siticn of the seeds, turned their points outwards from
the circumference of the wheel, and in their subse-
quent growth receded nearly at right angles from its
axis ; the germens, on the contrary, took the opposite
direction, and in a few days their points all met in
the centre of the wheel.

C so 3

When the centrifugal force was made merely • to
modify the force of gravitation in the horizontal wheel
when the,greatest volocity of revolution was given,
the radicles pointed downwards about ten degrees be-
low, and the germens as many degrees above the
horizontal line of the wheel's motion ; and the devia-
tion from the perpendicular was less in proportion,
as the motion was less rapid.*

These facts afford a rational solution of this cu-
rious problem, respecting which different philosophers
have given such different opinions ; some referring it
to the nature of the sap, as De la Hire, others, as
Darwin, to the living powers of the plant, and the
stimulus of air upon the leaves, and of moisture upon
the roots. The effect is now shewn to be connected
with mechanical causes ; and there seems no other
power in nature to which it can with propriety be
referred but gravity, which acts universally, and
which must tend to dispose the parts to take a uni-
form direction.

If plants in general owe their perpendicular di-
rection to gravity, it is evident that the number of
plants upon a given part of the earth's circumference,
cannot be increased by making the surface irregular,
as some persons have supposed. Nor can more stalks
rise on a hill than on a spot equal to its base ; for the
slight effect of the attraction of the hill, would be only

• Fig. 1 represents the form of the experiment v/hen the vertical wheel was
made to perform ISO revolutions in a minute.

Fig. 2 represents the case in which the horizental wheel perfornied 250 vevo-
latlons.

p. 50

[ 31 ]

to make the plats deviate a very little from the per-
pendicular. Where horizontal layers are pushed
forth, as in certain grasses, particularly such as the
fiorin, lately brought into notice by Dr. Richardson,
more food may, however, be produced upon an irre-
gular surface ; but the principle seems to apply strict-
ly to corn crops. *

The direction of the radicles and germens is such
that both are suppHed with food, and acted upon by
those external agents which are necessary for their
developement and growth. The roots come in con-
tact with the fluids in the ground ; the leaves are ex-
posed to light and air ; and the same grand law which
preserves the planets in their orbits, is thus essential
to the functions of vegetable life.

When two pieces of polished glass are pressed
together they adhere to each other, and it requires
some force to separate them. This is said to depend
upon the attraction of cohesion. The same attraction
gives the globular form to drops of water, and enables
fluids to rise in capillary tubes ; and hence it is some-
times called capillary attraction. This attraction, like
gravitation, seems common to all matter, and may be
a modification of the same general force ; like gravi-
tation, it is of great importance in vegetation. It pre-
serves the forms of aggregation of the parts of plants^
and it seems to be a principal cause of the absorption
of fluids by their roots.

If some pure magnesia, the calcined magnesia of
druggists, be thrown into distilled vinegar, it gradu-
ally disolves. This is said to be owing to che?nical

C 32 ]

attraction^ the power by which difFerent species of
matter tend to unite into one compound. Various
kinds of matter unite with different degrees of force :
thus sulphuric acid and magnesia unite with more
readiness than distilled vinegar and magnesia ; and if
sulphuric acid be poured into a mixture of vinegar
and magnesia, in which the acid properties of the
vinegar have been destroyed by the magnesia, the vine-
gar will be set free, and the sulphuric acid will take
its place. This chemical attraction is Hkewise called
chemical affinity. It is active in most of the phseno-
mena of vegetation. The sap consists of a number of
ingredients, dissolved in water by chemical attraction ;
and it appears to be in consequence of the operation
of this power, that certain principles derived from the
sap are united to the vegetable organs. By the laws
of chemical attraction, different products of vegetation
are changed, and assume new forms: the food of
plants is prepared in the soil 5 vegetable and animal
remains are changed by the action of air and water,
and made fluid or aeriform ; rocks are broken down
and converted into soils ; and soils are more finely
divided and fitted as receptacles for the roots of
plants.

The different powers of attraction tend to pre-
serve the arrangements of matter, or to unite them in
new forms. If there were no opposing powers, there
would soon be a state of perfect quiescence in nature,
a kind of eternal sleep in the physical world. Gravi-
tation is continually counteracted by mechanical
agencies, by projectile motion, or the centrifugal

i 33 3

Ibrce ; and their joint agencies occasion the motion of
the heavenly bodies. Cohesion and chemical attrac-
tion are opposed by the repulsive energy of heat^ and
the harmonious cycle of terrestrial changes is pro-
duced by their mutual opf rations.

Heat is capable of being communicated from one
body to other bodies; and its common effect is to
expand them, to enlarge them in all their dimensions.
This is easily exemplified. A solid cylinder of metal
after being heated will not pass through a ring barely
sufficient to receive it when cold. When water is
heated in a globe of glass having a long slender neck,
it rises in the neck ; and if heat be appUed to air con-
fined in such a vessel inverted above water, it makes
its escape from the vessel and passes through the wa-
ter. Thermometers are instruments for measuring
degrees of heat by the expansion of fluids in narrow
tubes. Mercury is generally used, of which 100,000
parts at the freezing point of water become 101,83.g;
parts at the boiling point, and on Fahrenheit's scale
these parts are divided into 180 degrees. Solids, by
a certain increase of heat, become fluids, and fluids
gasses, or elastic fluids. Thus ice is converted by heat
into water, and by still more heat it becomes steam :
and heat disappears, or, as it is called, is rendered!
latent during the conversion of solids into fluids, or
fluids into gasses, and reappears or becomes sensible
when gasses become fluids, or fluids solids : hence
cold is produced during evaporation, and heat during
the condensation of steam.

F

C 34 3

There are a few exceptions to the law of expansion
of bodies by heat, which seem to depend either upon
some change in their chemical constitution, or on their
becoming crystallized. Clay contracts by heat,
which seems to be owing to its giving off water. Cast
iron and antimony, when melted, crystallize in cool-
ing and expand. Ice is much lighter than water.
Water expands a little even before it freezes, and it is
of the greatest density at about 41° or 42°, the freez-
ing point being S2° ; and this circumstance is of con-
siderable importance in the general oeconomy of na-
ture. The influence of the changes of seasons and
of the position of the sun on the phaenomena ©f vege-
tation, demonstrates the effects of heat on the func-
tions of plants. The matter absorbed from the soil
must be in a fluid state to pass into their roots, and
•when the surface is fwzen they can derive no nour-
ishment from it. The activity of chemical changes
likewise is increased by a certain increase of tempera-
ture, and even the rapidity of the ascent of fluids by
capillary attraction.

This last fact is easily shewn by placing in each
of two wine glasses a similar hollow stalk of grass, so
bent as to discharge any fluid in the glasses slowly by
capillary attraction ; if hot water be in one glass, and
cold water in the other, the hot water will be dis-
charged much more rapidly than the cold water. The
fermentation and decomposition of animal and vegeta*
ble substances require a certain degree of heat, which
is consequently necessary for the preparation of the
food of plants ; and as evaporation is more rapid in

C 35 ]

proportion as the temperature is higher, the superflu-
ous parts of the sap are most readily carried off at the
time its ascent is quickest.

Two opinions are current respecting the nature
of heat. By some philosophers it is conceived to be
a pecuHar subtile fluid, of which the particles repel
each other, but have a strong attraction for the parti-
cles of other matter. By others it is considered as
a motion or vibration of the particles of matter,
which is supposed to differ in velocity in different
cases, and thus to produce the different degrees of
temperature. Whatever decision be ultimately made
respecting these opinions, it is certain that there is
matter moving in the space betvi^een us and the hea-
venly bodies capable of communicating heat 5 the mo-
tions of which are rectilineal : thus the solar rays
produce heat in acting on the surface of the earth.
The beautiful experiments of Dr. Herschel have
shewn that there are rays transmitted from the sun
which do not illuminate ; and which yet produce
more heat than the visible rays ; and Mr. Ritter and
Dr. Wollaston have shewn that there are other invisi*
ble rays distinguished by their chemical effects.

The different influence of the different solar rays
on vegetation have not yet been studied \ but it is cer-
tain that the rays exercise an influence independent of
the heat they produce. Thus plants kept in the dark
in a hot-house grow luxuriantly, but they never gain
their natural colours ; their leaves are white or pale,
and their juices watery and peculiarly saccharine.

C 36 3

When a piece of sealing-wax is rubbed by z
^Toollen cloth, it gains the power of attracting light
bodies, such as feathers or ashes. In this state it is
said to be electrical ; and if a metallic cylinder, placed
upon a rod of glass, is brought in contact with the
sealing-wax, it likewise gains the momentary power of
attracting light bodies, so that electricity like heat is
communicable. When two light bodies receive the
same electrical influence, or are electrified by the
same body, they repel each other. When one of them
is acted on by sealing-wax, and the other by glass that
has been rubbed by woollen, they attract each other ;
hence it is said, that bodies similarly electrified repel
each other, and bodies dissimilarly electrified attract
each other : and the electricity of glass is called
vitreous or positive electricity, and that of sealing-wax
resinous or negative electricity.

Vf hen of two bodies made to rub each other one
is found positively electrified, the other is always
found negatively electrified, and, as in the common
electrical machine, these states are capable of being
communicated to metals placed upon rods or pillars of
glass. Electricity is produced likewise by the contact
of bodies ; thus a piece of zinc and of silver give a
slight electrical shock when they are made to touch
each other, and to touch the tongue : and when a
number of plates of copper and zinc, 1 00 for instance,
are arranged in a pile with cloths moistened in salt and
water, in the order of zinc, copper, moistened cloth,
zinc, copper, moistened cloth, and so on, they form
an electrical battery which will give strong shocka

C 37 ]

and sparks, and which is possesed of remarkable
chemical powers. The luminous phasnomena pro-
duced by common electricity are well known. It
would be improper to dwell upon them in this
place. They are the most impressive effects occa-
sioned by this agent ; and they offer illustrations
of lightning and thunder.

Electrical changes are constantly taking place in
nature, on the surface of the earth and in the atmos-
phere ; but as yet the effects of this power in vegeta-
tion have not been correctly estimated. It has been
shewn by experiments made by means of the Voltaic
battery (the instrument composed of zinc, copper, and
water), that compound bodies in general are capable
of being decomposed by electrical powers, and it is
probable, that the various electrical phasnomena oc-
curring in our system, must influence both the ger-
mination of seeds and the growth of plants. I found
that corn sprouted much more rapidly in water posi-
tively electrified by the Voltaic instrument than in
water negatively electrified; and experiments made
upon the atmosphere shew that clouds are usually ne-
gative ; tand as when a cloud is in one state of elec-
tricity the surface of the earth beneath is brought into
the opposite state, it is probable that in common cases
the surface of the earth is positive.

Different opinions are entertained amongst scien-*
tific men respecting the nature of electricity ; by some,
the phsenomena are conceived to depend upon a single
subtile fluid in excess in the bodies said to be posi-
tively electrified, in deficiency in the bodies said to be

t 88 3

negatively electrified. A second class suppose the
eftects to be produced by two different fluids, called
by them the vitreous fluid and the resinous fluid ; and
others regard them as affections or motions of matter,
or an exhibition of attractive povi^ers, similar to those
which produce chemical combination and decomposi-
tion ; but usually exerting their action on masses.

The different powers that have been thus gener-
ally described, continually act upon common matter
so as to change its form and produce arrangements
fitted for the purposes of life. Bodies are either sim-
ple or compound. A body is said to be simple, when
it is incapable of being resolved into any other fbrms
of matter. Thus gold, or silver, though they may
be melted by heat or dissolved in corrosive menstrua,
yet are recovered unchanged in their properties, and
they are said to be simple bodies. A body is consi-
dered as compound, when two or more distinct sub-
stances are capable of being produced from it ; thus
marble is a compound body, for by a strong heat, it is
converted into Hme, and an elastic fluid is disengaged
in the process : and the proof of our knowledge of
the true composition of a body is, that it is capable of
being reproduced by the same substances as those into
which it had been decomposed ; thus by exposing
lime for a long while to the elastic fluid, disengaged
during its calcination, it becomes converted into a sub-
stance similar to powdered marble. The term element
has the same meaning as simple or undecompounded
body ; but it is applied merely with reference to the
present state of chemical knowledge. It is probable.

C S9 3

that as yet we are not acquainted with any of the true
elements of matter ; many substances, formerly sup-
posed to be simple, have been lately decompounded,
and the chemical arrangement of bodies must be con-
sidered as a mere expression of facts, the results of
accurate statical experiments.

Vegetable substances in general are of a very
compound nature, and consist of a great number of
elements, most of which belong likewise to the other
kingdoms of nature, and are found in various forms.
Their more complicated arrangements are best under-
stood after their simpler forms of combination have
been examined.

The number of bodies which I shall consider as
at present undecomposed, are, as was stated in the
introductory lecture, two gasses that support combus-
bustion, seven inflammable bodies, and thirty-eight
metals.

In most of the inorganic compounds, the nature
of which is well known, into which these elements
enter, they are combined in definite proportions ; so
that if the elements be represented by numbers, the
proportions in which they combine are expressed
either by those numbers, or by some simple multiples
of them.

I shall mention, in few words, the characteristic
properties of the most important simple, substances,
and the numbers representing the proportions in
which they combine in those cases, wher^ they have
been accurately ascertained.

C 40 3

1. Oxygene forms about one-fifth of the air of our
atmosphere. It is an elastic fluid, at all known tem-
peratures. Its specific gravity is to that of air as 10967
to 10000. It supports combustion with much more
vividness than common air; so that if a small steel
wire, or a watch spring, having a bit of inflamed wood
attached to it, be introduced into a bottle filled with
the gas, it burns with great splendour. It is respirable.
It is very slightly soluble in water. The number re-
presenting the proportion in which it combines is 1 5.
It may be made by heating a mixture of the mineral
called manganese, and sulphuric acid together, in a
proper vessel, or by heating strongly red lead, or red
precipitate of mercury.

2. Chlorine^ or oxymuriatic gas, is like oxygene, a
permanent elastic fluid. Its colour is yellowish green,
its smell is very disagreeable ; it is not respirable ; it
supports the combustion of all the common inflam-
mable bodies except charcoal ; its specific gravity
is to that of air as 24677 to 10000 ; it is soluble
in about half its volume of water, atid its solution in
water destroys vegetable colours. Many of the
metals (such as arsenic or copper) take fire spon-
taneously when introduced into a jar or bottle filled
with the gas. Chlorine may be procured by heating
together a mixture of spirits of salt or muriatic acid,
and manganese. The number representing the pro-
portion in which this gas enters into combination
is 67.

3. HydrogenSy or inflammable air, is the lightest
known substance ; its specific gravity is to that of air

C 41 3

as 732 to 10000. It burns by the action of an in-
flamed taper, when in contact with the atmosphere.
The proportion in which it combines is represented by
unity, or 1. It is procured by the action of diluted oil
of vitriol, or hydro sulphuric acid on filings of zinc or
iron. It is the substance employed for filling air bal-
loons.

4. Azote is a gaseous substance not capable of
being condensed by any known degree of cold : its
specific gravity is to that of common air as 95 1 6 to
10000. It does not enter into combustion under
common circumstances, but may be made to unite
with oxygene by the agency of electrical fire. It forms
nearly four fifths of th,e air of the atmosphere \ and
may be procured by burning phosphorus in a confin-
ed portion of air. The number representing the pro-
portion in which it combines is 26.

5. Carbon is considered as the pure matter of
charcoal, and it may be produced by passing spirits of
wine through a tube heated red. It has not yet been
fused ; but rises in vapour at an intense heat. Its
specific gravity cannot be easily ascertained ; but that
of the diamond, which cannot chemically be distin-
guished from pure carbon, is to that of water as 3500
to 1000. Charcoal has the remarkable property of
absorbing several times its volume of different elastic
fluids which are capable of being expelled from it by
heat. The number representing it is 11 .4.

6. Sulphur is the pure substance so well known
by that name : its specific gravity is to that of water
as 1990 to 1000. It fuses at about 220*^ Fahrenheit 5

G

C 42 3

and at between v500" and 600° takes fire, if in contact
with the air, and burns with a pale blue flame. In this
process it dissolves in the oxygene of the air, and pro-
duces a peculiar acid elastic fluid. The number re-
presenting it is 30.

7. Pho&phorus is a solid of a pale red colour, of
specific gravity 1770. It fuses at 90", and boils at
550°. It is luminous in the air at common tempera-
tures, and burns with great violence at 1 50°, so that
it must be handled with great caution. The number
representing it is 20. It is procured by digesting
together bone ashes and' oil of vitriol, and strongly
heating the fluid substance so produced with powdered
charcoal.

8. Boron is a solid of a dark olive colour, infu-
sible at any known temperature. It is a substance
very lately discovered, and procured from boracic
acid. It burns with brilliant sparks, when heated in
oxygene, but not in chlorine. Its specific gravity,
and the number representing it, are not yet accurately
known.

9. Platinum is one of the noble metals, of rather
a duller white than silver, and the heaviest body in
nature ; its specific gravity being 2 1 500. It is not
acted upon by any acid menstrua except such as con-
tain chlorine : It requires an intense degree gf heat
for its fusion.

10. The properties o^ gold are well known. Its
specific gravity is 19277. It bears the same relation
to acid menstrua as platinum : it is one of the char-
acteristics of both these bodies, that they are very dif-
cultly acted upon by sulphur.

C ^3 ]

1 1 . Silver Is of specific gravity 1 0400, it burns
more readily than plantinum or gold, which require
the intense heat of electricity. It readily unites to
sulphur.. The number representing it is 205.

12. Mercury is the only known metal fluid at
the common temperature of the atmosphere ; it boils
at 66 ""j and freezes at 39'^ below 0. Its specific gra-
vity is 1356 . The number representing it is 380.

13. Copper is of specific gravity 8890. It burns
when strongly heated with red flame tinged with
green. The number representing it is 1 i^O.

14. Cobalt is of specific gravity 7700. Irs point
of fusion is very high, nearly equal to that of iron.
In its calcined or oxidated state, it is employed for
giving a blue colour to glass.

15. Nickel is of a white colour : its specific gra-
vity is 8820. This metal and cobalt agree with iron, in
feeing attractible by the magnet. The number repre-
senting nickel is 111.

16. Iron is of specific gravity 7700. Its other
properties are well known. The number represent-
ing it is 103.

17. Tin is of specific gravity 7291 ; it is a very
fusible metal, and burns when ignited in the air : the
number representing the proportion in which it com-
bines is 11 0.

1 8. Zinc is one of the most combustible of the
common metals. Its specific gravity is about 7210.
It is brittle metal under common circumstances ; but
when heated inay be hammered or rolled into thin
leaves, and after this operation is malleable. The num-
ber representing it is 66.

C 44 ]

1 9. Lead is of specific gravity 1 1 352 ; it fuses
at a temperature rather higher than tin. The num-
ber representing it is 398.

20. Bisjnuth is a brittle metal of specific gravity
9822. It is nearly as fusible as tin ; when cooled
slowly it crystallizes in cubes. The number repre-
senting it is I S5.

21. Antimony is a metal capable of being volat-
ilized by a strong red heat. Its specific gravity is

6800. It burns when ignited with a faint white light.
The number representing it is 170.

22. Arse?iic is of a blueish white colour, of
specific gravity 8310. It may be procured by heating
the powder of common white arsenic of the shops
strongly in a Florence flask with oil. The metal rises
in vapour, and condenses in the neck of the flask.
The number representing it is 90.

23. Manganesiim may be procured from the
mineral called manganese, by intensely igniting it in
a forge mixed with charcoal powder. It is a metal
very difhcult of fusion, and very combustible ; its
specific gravity is 6850. The number representing it
is 177.

24. Potassium is the lightest known metal, being
only of specific gravity 850. It fuses at about 150%
and rises in vapour at a heat a little below redness,
It is a highly combustible substance, takes fire when
thrown Tipon water, burns with great brilliancy, and
the product of its combustion dissolves in the water.
The number representing it is 75. It may be made
by passing fused caustic vegetable alkali, (the pure kali

C 4f ]

qf druggists) through iron turnings strongly ignited
in a gun barrel, or by the electrization of potash by a
strong Voltaic battery.

25. Sodium may be made in a similar manner to
potassium. Soda or the mineral alkali being substituted
for the vegetable alkali. It is of specific gravity 940.
It is very combustible. When thrown upon water,
it swims on its surface, hisses violently, and dissolves,
but does not inflame. The number representing it
is 88.

26. Barium has as yet been procured only by
electrical powers and in very minute quantities, so that
its properties have not been accurately examined.
The number representing it appears to be 1 30.

Strontium the 27th, Calcium the 28th, Magnesium
the 29th, Siiicum the 3Cth, A iu??iinu7nthe 3 1st ^ Zir-
conum the 32d, Glucinmn the 33d, and Ittriu?n the
34th of the undecompounded bodies,, like barium,,
have either not been procured absolutely pure, or
only in such minute quantities that their properties
are little known ; they are formed either by electrical
powers, or by the agency of potassium, from the dif-
ferent earths whose names they bear, with the change
of the termination in um ; and the numbers repre-
senting them are believed to be 90 strontium, 40 cal-
cium, 38 magnesium, 31 siiicum, 33 aluminum, 70
zirconum, 39 glucinum, 1 1 1 ittrium.

Of the remaining thirteen simple bodies, twelve
are metals, most of which, like those just mentioned,
can only be procured with very great difficulty ; and
the substances in general from which they are proctir-

C 46 3

ed are very rare in nature. They are Palladium^
Rhodium^ Osmium^ Iridium^ Colubium^ Chromium^ Mo-
lybdeniwiy Cerium, Tellurium^ Tungstenum, Titanmn^
Uranium, The forty-seventh body has not as yet
been produced in a state sufficiently pure to admit
of a minute examination. It is the principle which
gives character to the acid called fluoric acid, and
may be named Fluon^ and is probably analogous to
phosphorus or sulphur. The numbers representing
these last thirteen bodies have not yet been determin-
ed with sufficient accuracy to render a reference to
them of any utility.

The undecompounded substances unite with each
other, and the most remarkable compounds are form-
ed by the combinations of oxygene and chlorine with
inflammable bodies and metals \ and these combina-
tions usually take place with much energy, and are
associated with fire.

Combustion in fact, in common cases, is the
process of the solution of a body in oxygene, as hap-
pens when sulphur or charcoal is burnt; or the fixa-
tion of oxygene by the combustible body in a solid
form, which takes place when most metals are burnt,
or when phosphorus inflames ; or the production of
a fluid from both bodies, as when hydrogene and oxy-
gene unite to form water.

When considerable quantities of oxygene or of
chlorine unite to metals or inflammable bodies, they
often produce acids : thus sulphureous, phosphoric,
and boracic acids are formed by a union of considera-
ble quantities of oxygene with sulphur, phosphorus,

C 47 J

and boron : and muriatic acid gas is formed by the
union of chlorine and hydrogene.

When smaller quantities of oxygene or chlorine
unite with inflammable bodies or metals, they form
substances not acid, and more or less soluble in wa-
ter ; and the metallic oxides, the fixed alkalies, and
the earths, all bodies connected by analogies ; are pro-
duced by the union of metals with oxygene.

The composition of any compounds, the nature
of which is well known, may be easily learnt from the
numbers representing their elements ; all that is ne-
cessary, is to know how many proportions enter into
union. Thus potassa^ or the pure caustic vegetable
alkali, consists of one proportion of potassium and one
of oxygene, and its constitution is consequently 75
potassium, 15 oj^ygene.

Carbonic acid is composed of two proportions of
oxygene 30, and one of carbon 11.4.

Again, U?ne consists of one proportion of calcium
and one of oxygene, and it is composed of 40 of cal-
cium and 15 of oxygene. And carbonate of lime ^ or
pure chalk, consists of one proportion of carbonic
acid 41.4, and one of lime 53.

Water consists of two proportions of hydrogene
2, and one of oxygene 15 ; and when water unites to
other bodies in definite proportions, the quantity is 17,
or some multiple of 17, i* e, 34 or 51, or ^^^ &c.

Soda^ or the mineral alkali, contains two propor-
tions of oxygene to one of sodium*

Ammonia^ or the volatile alkali is composed of six
proportions of hydrogene and one of azote.

C 48 ]

Amongst the earths, Silica or the earth of flints,
probably consists of two proportions of oxygene to
one of «ilicum ; and Magnesia, Strontia, Baryta or
Barytes, JIumina, Zircona, Glusina, and Ittria of one
proportion of metal and one of oxygene.

The metallic oxides in general consist of the metals
united to from one to four proportions of oxygene ;
and there are, in some cases, many different oxides of
the same metal -, thus there are three oxides of lead ;
the yellow oxide, or massicot, contains two proportions
of oxygene ; the red oxide, or miniixm, three ; and the
puse coloured oxide four proportions. Again there are
two oxides of copper, the black and the orange ; the
black contains two proportions of oxygene, the
orange one.

For pursuing such experiments on the composi-
tion of bodies as are connected with agricultural che-
mistry, a few only of the undecompounded substan-
ces are necessary ; and amongst the compounded
bodies, the common acids, the alkalies, and the earths,
are the most essential substances. The elements
found in vegetables, as has been stated in the intro-
ductory lecture, are very few. Oxygene, hydrogene,
and carbon constitute the greatest part of their organ-
ized matter. Azote, phosphorus, sulphur, mangane-
sum, iron, silicum, calcium, aluminum, and magne-
sium likewise, in different arrangements, enter into
their composition, or are found in the agents to which
they are exposed ; and these twelve undecompound-
ed substances are the elements, the study of which
is of the most importance to the agricultural chemist.

I 49 3

The doctrine of definite combinations, as will be
shewn in the following lectures, will assist us in gain-
ing just views respecting the composition of plants,
and the economy of the vegetable kingdom 5 but the
same accuracy of weight and measure, the same statical
results which depend upon the uniformity of the laws
that govern dead matter, cannot be expected in opera-
tions where the powers of life are concerned, and
where a diversity of organs and of functions exists.
The classes of definite inorganic bodies, even if we
include all the crystalline arrangements of the mineral
kingdom, are few, compared with the forms and sub-
stances belonging to animated nature* Life gives a
peculiar character to all its productions j the power of
attraction and repulsion, combination and decomposi-
tion, are subservient to it ; a few elements, by the
diversity of their arrangement, are made to form the
most different substances ; ajid similar substances are
produced from compounds which, when superficially
examined, appear entirely different.

60

LECTURE IIL

On the Organization of Plants. Of the Roots ^ Trunks
and Branches. Of their Structure. Of the Epider-
mis. Of the cortical and alburnous Parts of Leaves^
Flowers^ and Seeds. Of the chemical Constitution of
the Organs of Plants^ and the Substances found in
them. Of mucilaginous^ saccharine^ extractive^ resin'
cus^ and oily. Substances ^ and other vegetable Com*
pounds, their Arrangements in the Organs of Plants^
their Composition, Changes, and Uses.

VARIETY characterises the vegetable kingdom,
yet there is an analogy between the forms and the
functions of all the different classes of plants, and on
this analogy the scientific principles relating to their
organization depend.

Vegetables are living structures distinguished
from animals by exhibiting no signs of perception,
or of voluntary motion -, and their organs are either
organs of nourishment or of reproduction ; organs
for the preservation and increase of the individual, or
for the multiplication of the species.

In the living vegetable system there are to be
considered, the exterior form, and the interior consti-
tution.

Every plant examined as to external structure,
displays at least four systems of organs — or some
analogous parts. First, the Roof. Secondly, the

C 51 3

Trunk and Branches^ or Ste?n, Thirdly, the Leaves ;
and, fourthly, the Flowers or Seeds,

The root is that part of the vegetable which least
impresses the eye ; but it is absolutely necessary. It
attaches the plant to the surface, is its organ of nour-
ishment, and the apparatus by which it imbibes foojd
from the soil. — The roots of plants, in their anatomi-
cal division, are very similar to the trunk and
branches. The root may indeed be said to be a con-
tinuation of the trunk terminating in minute ramifica-
tions and filaments, and not in leaves^ and by bury-
ing the branches of certain trees in the soil, and eleva-
ting the roots in the atmospheae, there is, as it were,
an inversion of the functions, the roots produce buds
and leaves, and the branches shoot out into radical
fibres and tubes. This experiment was made by
Woodward on the willow, and has been repeated by
a number of physiologists.

When the branch or the root of a tree is cut
transversely, it usually exhibits three bodies : the b^rk,
the wood, and the pith ; and these again are individu-
ally susceptible of a new division.

The bark, when perfectly formed, is covered by
a thin cuticle or epidermis^ which may be easily separ-
ated. It is generally composed of a number of laminae
or scales, which in old trees are usually in a loose and
decaying state. The epidermis is not vascular, and it
merely defends the interior parts from injury. In
forest trees, and in the larger shrubs, the bodies of
which are firm, and of strong texture, it is a part of
little importance ; but in the re^ds, the grasses, canes^

C 52 3

and the plants having hollow stalks, it is of great use,
and is exceedingly strong, and in the microscope seems
composed of a kind of glassy net-work, which is prin-
cipally siliceous earth.

This is the case in wheat, in the oat, in different
species of equisetum, and, above all, in the rattan, the
epidermis of which contains a sufficient quantity of
flint to give light when struck by steel ; or two pieces
rubbed together produce sparks. This fact first oc-
curred to me in 1798, and it led to experiments, by
which I ascertained that siliceous earth existed gener-
ally in the epidermis of the hollow plants.

The siliceous epidermis serves as a support, pro-
tects the bark from the action of insects, and seems
to perform a part in the economy of these feeble ve-
getable tribes, similar to that performed in the animal
kingdom by the shell of the crustaceous insects.

Immediately beneath the epidermis is the paren-
chyma. It is a soft substance consisting of cells filled
with fluid, having almost always a greenish tint. The
cells in the parenchymatous part, when examined by
the microscope, appear hexagonal. This form, in«
deed, is that usually affected by the cellular mem-
branes in vegetables, and it seems to be the result of
the general re-action of the solid parts, similar to that
which takes place in the honey-comb. This arrange-
ment, which has usually been ascribed to the skill and
artifice of the bee, seems, as Dr. Wollaston has ob-
served, to be merely the result of the mechanical laws
which influence the pressure of cylinders composed of
soft materials, the nests of solitary bees being uni-
formly circular.

The innermost part of the bark is constituted by
the cortical layers^ and their numbers vary with the age
of the tree. On cutting the bark of a tree of several
years standing, the productions of different periods
may be distinctly seen, though the layer of every
particular year can seldom be accurately defined.

The cortical layers are composed of fibrous parts
which appear interwoven, and which are transverse
and longitudinal. The transverse are membranous
and porous, and the longitudinal are generally com-
posed of tubes.

The functions of the parenchymatous and cortical
parts of the bark are of great importance. The tubes
of the fibrous parts appear to be the organs that re-
ceive the sap ; the cells seem destined for the elabora-
tion of its parts, and for the exposure of them to the
action of the atmosphere, and the new matter is annu-
ally produced in the spring, immediately on the inner
surface of the cortical layer of the last year.

It has been shewn by the experiments of Mr.
Knight, and those made by other physiologists, that
the sap descending through the bark after being
modified in the leaves, is the principal cause of the
growth of the tree ; thus, if the bark is wounded, the
principal formation of new bark is on the upper ^dg^^
of the wound j and when the wood has been removed,
the formation of new wood takes place immediately
beneath the bark : yet it would appear from the late
observations of M. Palisot de Beauvois, that the sap
may be transferred to the bark, so as to exert its nutri-
tive functions, independent of any general system of

C 54 3

circulation. That gentleman separated different por«
tions of bark from the rest of the bark in several trees,
and found that in most instances the separated bark
grew in the same manner as the bark in its natural
state. The experiment was tried with most success
on the lime tree, the maple and the lilac ; the layers of
bark were removed in August 1810, and in the spring
of the next year, in the case of the maple and the lilac,
small annual shoots where produced in the parts
where the bark was insulated.*

The wood of trees is composed of an external or
living part, called alburnum or sap-wood^ and of an in-
ternal and dead part, the heart-wood. The alburnum
is white, and full of moisture, and in young trees and
annual shoots it reaches even to the pith. The albur-
num is the great vascular system of the vegetable
through which the sap rises, and the vessels in it ex-
tend from the leaves to the minutest filaments in the
roots.

There is in the alburnum a membranous sub-
stance composed of cells^ which are constantly filled
with the sap of the plant, and there are in the vascu-
lar system several different kinds of tubes ; Mirbel has
distinguished four species, the simple tubes ^ the porous
tubes ^ the trachea^ and the false trachea,^

The tubes, which he has called simple tubes,
seem to contain the resinous or oily fluids peculiar to
different plants.

• Fig. 3 represents the result of the experiment on the maple. Journal de
pLysique, September 18U, page 210.

t Fig. 4, 5, 6, and 7, represent Mirbel's idea of the siipple tubes, the porous

tubes, £l)e tracheJe, and X'^t false tracheat.

P 34

Fi„.3. I'^l

/r^.

rig 9

^

/*

'lilllliiimiiMr..

Fig: K

C S5 ]

The porous tubes likewise contain these fluids ;
and their use is probably that of conveying them into
the sap for the production of new arrangements.

The tracheae contain fluid matter, which is al-
ways thin, watery, and pellucid, and these organs,
as well as the false tracheae, probably carry off water
from the denser juices, which are thus enabled to con-
solidate for the production of new wood.

In the arrangement of the fibres of the wood,
there are two distinct appearances. There are series
of white and shining laminse which shoot from the
centre towards the circumference, and these constitute
what is called the silver grain of the wood.

There are likewise numerous series of concentric
layers which are usually called the spurious grain^ and
their number denotes the age of the tree.*

The silver grain is elastic and contractile, and it
has been supposed by Mr. Knight, that the change of
volume produced in it by change of temperature is
one of the principal causes of the ascent of the sap.
The fibres of it seem always to expand in the morning
and contract at night ; and the ascent of the juices, as
was stated in the last Lecture, depends principally on
the agency of heat.

The silver grain is most distinct in forest trees ;
but even annual shrubs have a system of fibres simi-
lar to it. The analogy of nature is constant and uni-

* Fig. 8 represents the section of an elm branch, which exhibits the tubulav
structure and the silver and spurious grain . Fig. 9 represents the sectiou of part
of thr: branch of an oak. Fig, xo, that of the branch of an ash.

C 56 3

form, and similar effects are usually produced by simi-
lar organs.

The pith occupies the centre of the wood ; its
texture is membranous ; it is composed of cells, which
are circular towards the extremity, and hexagonal iu
the centre of the substance. In the first infancy of
the vegetable, the pith occupies but a small space. It
gradually dilates, and in annual shoots and young
trees offers a considerable diameter. In the more
advanced age of the tree, acted on by the heart-wood,
pressed by the new layers of the alburnum, it begins
to diminish, and in very old forest trees disappears
altogether.

Many different opinions have prevailed with re-
gard to the use of the pith. Dr. Hales supposed, that
it was the great cause of the expansion and develope-
ment of the other parts of the plant ; that being the
most interior, it was likewise the most acted upon of
all the organs, and that from its reaction the pheno-
mena of their developement and growth resulted.

Linnaeus, whose lively imagination was continu-
ally employed in endeavours to discover analogies be-
tween the animal and vegetable systems, conceived
" that the pith performed for the plant the same func-
tions as the brain and nerves in animated beings.'* He
considered it as the organ of irritability, and the seat
of life.

The latest discoveries have proved, that these two
opinions are equally erroneous. Mr. Knight has re-
moved the pith in several young trees, and they con-
tinued to live and to increase.

t

Fr^ JL

I SI -]

It is evidently then only an organ of secondary
importance. In early shoots, in vigorous growth, it is
filled with moisture, and it is a reservoir, perhaps, of
fluid nourishment at the time it is most wanted. As
the heart^wood forms, it is more and more separated
from the living part, the alburnum ; its functions be-
come extinct, it diminishes, dies, and last disap >ears.

The tendrih^ the spines^ and other similar parts
of plants are analogous in their organization to the
branches, and offer a similar cortical and alburnous
organization. It has been shown, by the late obser-
vations of Mr. Knight, that the directions of tendrils,
and the spiral form they assume, depend upon the
unequal action of light upon them, and a similar
reason has been assigned by M. Decandolle to account
for the turning of the parts of plants towards the sun ;
that ingenious physiologist supposes that the fibres
are shortened by the chemical agency of the solar
rays upon them, and that, consequently, the parts
will move towards the light.

The leaves J the great sources of the permanent
beauty of vegetation, though infinitely diversified in
their forms, are in all cases similar in interior organi-
zation, and perform the same functions.

The alburnum spreads itself from the foot-stalks
into the very extremity of the leaf ) it retains its vas-
cular system and its living powers ; and its peculiar
tubes, particularly the tracheae, may be distinctly seen
in the leaf.*

• Fig 11. represents part of a leaf of a vine magnified and cut, so as to exhi-
bit the trachea ; it is copied, as are also the preceding figures, from Grew's Ani-
.tomy of Plants.

[ 58 ]

The green membranous substance may be consi-
dered as an extension of the parenchyma, and the
fine and thin covering as the epidermis. Thus the
organization of the roots and branches may be traced
into the leaves, which present, however, a more per-
fect, refined, and minute structure.

One great use of the leaves is, for the exposure
of the sap to the influence of the air, heat, and light.
Their surface is extensive, the tubes and cells
very delicate, and their texture porous and trans-
parent.

In the leaves much of the water of the sap is
evaporated ; it is combined with new principles, and
fitted for its organizing functions, and probably pas-
ses, in its prepared state, from the extreme tubes of
the alburnum into the ramifications of the cortical
tubes and then descends through the bark.

On the upper surface of leaves, which is expos-
ed to the sun, the epidermis is thick but transparent,
and is composed of matter possessed of little organi-
zation, which is either principally earthy, or consists
of some homogeneous chemical substance. In the
grasses it is partly siliceous, in the laurel resinous,
and in the maple and thorn, it is principally constitut-
ed by a substance analogous to wax.

By these arrangements any evaporation, except
from the appropriated tubes, is prevented.

On the lower surface the epidermis is a thin
transparent membrane full of cavities, and it is proba-
bly altogether by this surface that moisture and the
principles of the atmosphere necessary to vegetation
are absorbed.

C 59 ]

If a leaf be turned, so as to present its lower sur-
face to the sun, its fibres will twist so as to bring it as
much as possible into its original position j and all
leaves elevate themselves on the foot-stalk during their
exposure to the solar light, and as it were moved to-
wards the sun.

This effect seems in a great measure dependent
upon the mechanical and chemical agency of light and
heat. Bonnet made artificial leaves, which, when a
moist sponge was held under the lower surface, and
a heated iron above the upper surface, turned exactly
in the same manner as the natural leaves. This how-
ever can be considered only as a very rude imitation
of the natural process.

What Linnaeus has called the sleep of the leaves,
appears to depend wholly upon the defect of the ac-
tion of light and heat, and the excess of the operation
of moisture.

This singular but constant phenomenon had
never been scientifically observed, till the attention of
the botanist of Upsal was fortunately directed to it.
He was examining particularly a species of lotus, in
which four flowers had appeared during the day, and
he missed two in the evening ; by accurate inspection,
he soon discovered that these two were hidden by the
leaves which had closed round them. Such a circum-
stance could not be lost upon so acute an observer*
He immediately took a lantern, went into his garden,
and witnessed a series of curious facts before un-
known. All the simple leaves of the plants he exam-
ined, had an arrangement totally different from their

[ 60 3

arrangement in the day : and the greater number of
them were seen closed or folded together.

The sleep of leaves is, in some cases, capable of
being produced artificially. Decandoile made this ex-
periment on the sensitive plant. By confining it in
a dark place in the day time, the leaves soon closed ;
but on illuminating the chamber with many lamps,
they again expanded. So sensible were they to the
effects of light and radiant heat.

In the greater number of plants the leaves annu-
ally decay, and are reproduced ; their decay takes place
either at the conclusion of the summer, as in very hot
climates, when they are no longer supplied with sap,
in consequence of the dryness of the soil, and the
evaporating powers of heat j or in the autumn, as in
the northern cHmates at the commencement of the
''frosts. The leaves preserve their functions in com-
mon cases no longer than there is a circulation of
fluids through them. In the decay of the leaf, the
colour assumed seems to depend upon the nature of
the chemical change, and as acids are generally devel-
oped, it is usually either reddish brown or yellow ;
yet there are great varieties. Thus in the oak, it is
bright brown ; in the beech, orange ; in the elm, yel-
low 'y in the vine, red ; in the sycamore, dark brown ^
in the cornel tree, purple ; and in the woodbine, blue.

The cause of the preservation of the leaves of
evergreens through the winter is not accurately
known. From the experiments of Hales, it appears
that the force of the sap is much less in plants of this
species, and probably there is a certain degree of circu-

C 61 3

lation throughout the winter ; their juices are less wa-
tery than those of other plants, and probably less liable
to be congealed by cold, and they are defended
by stronger coatings from the action of the
elements.

The production of the other parts of the plant
takes place at the time the leaves are most vigorously
performing their functions. If the leaves are stripped
off from a tree in spring, it uniformly dies, and when
many of the leaves of forest trees are injured by
blasts, the trees always become stag-headed and un-
healthy.

The leaves are necessary for the existence of the
individual tree, the flowers for the continuance of the
species. Of all the parts of plants they are the most
refined, the most beautiful in their structure, and ap-
pear as the master-work of nature in the vegetable
kingdom. The elegance of their tints, the variety of
their forms, the delicacy of their organization, and
the adaptation of their parts, are all calculated to
awaken our curiosity, and excite our admiration.

In the flower there are to be observed, 1st, the
calyx^ or green membranous part forming the support
for the coloured floral leaves. This is vascular, and
agrees with the common leaf in its texture and organi-
zation ; it defends, supports, and nourishes the more
perfect parts. 2d. The corolla, which consists either
of a single piece, when it is called monopetalous, or of
many pieces, when it is called polypetalous. It is
usually very vivid in its colours, is filled with an al-
most infinite variety of small tubes of the porous kind 5

C 63 ]

it incloses and defends the essential parts in the inte-
rior, and supplies the juices of the sap to them. These
parts are, 3d, the stamens and the pistils.

The essential part of the stamens are the sum-
mits or anthers^ which are usually circular and of a
highly vascular texture, and covered with a fine dust
called the pollen.

The pistil is cylindrical, and surmounted by the
style ; and top of which is generally round and pro-
tuberant.*

In the pistil, when it is examined by the micro-
scope, congeries of spherical forms may usually be
perceived, which seem to be the bases of the future
seeds.

It is upon the arrangement of the stamens and
the pistils, that the Linnean classification is founded.
The numbers of the stamens and pistils in the same
flower, their arrangements, or their division in differ-
ent flowers, are the circumstances which guided the
Swedish philosopher, and enabled him to form a sys-
tem admirably adapted to assist the memory, and ren-
der botany of easy acquisition ; and which, though it
does not always associate together the plants most
analogous to each other in their general characters, is
yet so ingeniously contrived as to denote all the analo-
gies of their most essential parts.

The pisdl is the organ which contains the rudi-
ments of the seed ; but the seed is never formed as a

* Fig. 12 represents the common lilly» a, the corolla, bbbbb, the anthors/
c, the pistil.

reproductive germ, without the influence of the pollen,
or dust on the anthers.

This mysterious impression is necessary to the
continued succession of the different vegetable tribes.
It is a feature \vhich extends the resemblances of the
different orders of beings, and establishes, on a great
scale, the beautiful analogy of nature.

The ancients had observed, that different date
trees bore different flowers, and that those trees pro-
ducing flowers which contained pistils bore no fruit,
unless in the immediate vicinity of such trees as pro^
duced flowers containing stamens. This long esta-
blished fact strongly impressed the mind of Malpighi,
who ascertained several analogous facts with regard to
other vegetables. Grew, however, was the first per-
son who attempted to generalize upon them, and
much just reasoning on the subject may be found in
his works. Linnaeus gave a scientific and distinct
form to that which Grew had only generally observ-
ed, and has the glory of establishing what has been
called the sexual system, upon the basis of minute ob-
servations and accurate experiments.

The seedy the last production of vigorous vegeta-
tion, is wonderfully diversified in form. Being of the
highest importance to the resources of nature, it is
defended above all other parts of the plant ; by soft
pulpy substances, as in the esculent fruits, by thick
membranes, as in the leguminous vegetables, and by
hard shells, or a thick epidermis, as in the palms and
grasses.

K .

C 6* 1

In every seed there is to be distinguished, 1, the
organ of nourishment ; 2, the nascent plant, or the
flujiie ; 3, the nascent root, or the radicle.

In the common garden bean, the organ of nour-
ishment is divided into two lobes called cotyledons ; the
plume is the small white point between the upper
part of the lobes ; and the radicle is the small curved
cone at their base.*

In wheat, and in many of the grasses, the organ
of nourishment is a single part, and these plants are
called monocotyledonous* In other cases it consists of
more than two parts, when the plants are called poly-
cotyledonous. In the greater number of instances, it
is, however, simply divided into two, and is dicotyle-
donous.

The matter of the seed, when examined in its
common state, appears dead and inert ; it exhibits
neither the forms nor the functions of life. But let
it be acted upon by moisture, heat, and air, and its
organized powers are soon distinctly developed. The
cotyledons expand, the membranes burst, the radicle
acquires new matter, descends into the soil, and the
pUime rises towards the free air. By degrees, the
organs of nourishment of dicotyledonous plants be-
come vascular, and are converted into seed leaves,
and the perfect plant appears above the soil. Nature
has provided the elements of germination on every
part of the surface ; water and pure air and heat are

• Fig. 13, represents the garden bean, aa, the cotyledons, b, the plume, b, the

radicle.

p. 64

0;;f'^rfi

fiq. 12.

^^

%

■m

f^%l

'^M

universally active, and the means for the preserva-
tion and muhiplication of life, are at once simple and
grand.

To enter into more minute details on the vegetable
physiology would be incompatible with the objects of
these Lectures. I have attempted only to give such
general ideas on the subject, as may enable the philo-
sophical agriculturist to understand the functions of
plants ; those who wish to study the anatomy of ve-
getables, as a distinct science, will find abundant ma-
terials in the works of the authors I have quoted,
page 9, and likewise in the writings of Linnaeus, Des-
fontaines, Decandolle, de Saussure, Bonnet, and'
Smith.

The history of the p eculiarities of structure in the
different vegetable classes, rather belongs to botanical
than agricultural knowledge. As I mentioned in the
commencement of this Lecture, their organs are pos-
sessed of the most distinct analogies, and are govern-
ed by the same laws. In the grasses and palms, the
cortical layers are larger in proportion than the other
parts ; but their uses seem to be the same as in forest
trees.

In bulbous roots, the alburnous substance forms
the largest part of the vegetable ; but in all cases it
seems to contain the sap, or solid materials deposited
from the sap.

The slender and comparatively dry leaves of the
pine and the cedar perform the same functions as the
large and juicy leaves of the fig tree, or the walhut

K

[ 66 ]

Even in the cryptogamia, where no flowers are
distinct, still there is every reason to believe that the
production of the seed is effected in the same way as
in the more perfect plants. The mosses and lichens,
which belong to this family, have no distinct leaves,
or roots, but they are furnished with filaments which
perform the same functions ; ^nd even in the fungus
and the mushroom there is a system for the absorp-
tion and aeration of the sap.

It was stated in the last lecture, that all the differ-
ent parts of plants are capable of being decomposed
into a few elements. Their uses as food, or for the
purposes of the arts, depend upon compound arrange-
ments of those elements which are capable of being
produced either from their organized parts, or from
the juices they contain ; and the examination of the
nature of these substances, is an essential part of Agri-
cultural Chemistry.

Oils are expressed from the fruits of many
plants 'y resinous fluids exude from the wood ; sac-
charine matters are afforded by the sap ; and dyeing
materials are furnished by leaves, or the petals of
flowers : but particular processes are necessary to se-
parate the different compound vegetable substances
from each other, such as maceration, infusion or diges-
tion in water, or in spirits of wine : but the application
and the nature of these processes will be better under-
stood when the chemical nature of the substances is
known ; the consideration of them will therefore be
reserved for another place in this Lecture.

[ 67 ]

llie compound substances found in vegetables
are, 1 gum, or mucilage, and its different modifica-
tions ; 2, starch j 3, sugar ; 4, albumen ; 5, gluten ;
6, gum elastic ; 7, extract ; 8, tannin ; 9, indigo j
10, narcotic principle ; 11, bitter principle j 12, wax ;
13, resins ; 14, camphor ; 15, fixed oils ; 16, vola-
tile oils 5 17, woody fibre ; 18, acids ; 19, alkalies y
earths, metallic oxides, and saline compounds.

I shall describe generally the properties and
composition of these bodies, and the manner in which
they are procured.

1. Gu??i is a substance which exudes from certain
trees ; it appears in the form of a thick fluid, but soon
hardens in the air, and becomes solid : when it is
white, or yellowish white, more or less transparent,
and somewhat brittle 5 its specific gravity varies from
1300 to 1490.

There is a great variety of gums, but the best
know are gum arable, gum Senegal, gum tragacanth,
and the gum of the plum or cherry tree. Gum is
soluble in v/ater, but not soluble in spirits of wine. If
a solution of gum be made in water, and spirits of
wine or alcohol be added to it, the gum separates in
the form of white flakes. Gum can be made to in-
flame only with difficulty ; much moisture is given off
in the process, which takes place with a dark smoke
and feeble blue flame, and a coal remains.

The characteristic properties of gum are its easy
solubility in water, and its insolubility in alcohol. Dif-
ferent chemical substances have been proposed for
ascertaining the presence of gum, but there is reason

C 68 3

to believe that few of them afford accurate results ; and
most of them (particularly the metallic salts,) which
produce changes in solutions of gum, may be conceiv-
ed to act rather upon some saline compounds existing
in the gum, than upon the pure vegetable principle.
Dr. Thomson has proposed an aqueous solution of
silica in potassa as a test of the presence of gum in
solutions — he states that the gum and silica are pre-
cipitated together — this test, however, cannot be ap-
plied with correct results in cases when acids are
present.

Mucilage must be considered as a variety of gum;
it agrees with it in its most important properties, but
seems to have less attraction for water. — According
to Hermbstadt, when gum and mucilage are dissolved
together in water, the mucilage may be separated by
means of sulphuric acid — mucilage may be procured
from linseed, from the bulbs of the hyacinth, from
the leaves of the marsh-mallows ; from several of the
lichens, and from many other vegetable substances.

From the analysis of M. M. Gay Lussac and
Thenard, it appears that gum arabic contains in 100
parts :

of carbon - - . - 42,23

— oxygene - - - - 50,84?

— hydrogene - - - 6,93
with a small quantity of saline and earthy matter.

or of carbon • . - 42,23

oxygene and hydrogene in the pro- 1 ^^ >7<^

portions necessary to form water J '

C 69 ]

This estimation agrees very nearly with the definite
proportions of 11 of carbon, 10 of oxygene, and 20
of hydrogene.

All the varieties of gum and mucilage are nutri-
tious as food. They either partially or wholly lose
their solubility in water by being exposed to a heat
of 500" or 600° Fahrenheit, but their nutritive powers
are not destroyed unless they are decomposed. Gum
and mucilage are employed in some of the arts, parti-
cularly in calico-printing : till lately. In this country,
the calico-printers used gum arable ; but many of
them, at the suggestion of Lord Dundonald, now
employ the mucilage from lichens.

2. Starch is procured from different vegetables,
but particularly from wheat or from potatoes. To
make starch from wheat, the grain is steeped in cold
water till it becomes soft, and yields a milky juice by
pressure ; it is then put into sacks of linen, and pres-
sed in a vat filled with water : as long as any milky
juice exudes the pressure is continued ; the fluid
gradually becomes clear, and a white powder subsides,
which is starch.

Starch is soluble in boiling water, but not in
cold water, nor in spirits of wine. According to
Dr. Thomson, it is a characteristic property of starch
to be soluble in a warm infusion of nutgalls, and to
form a precipitate when the infusion cools.

Starch is more readily combustible than gum j
when thrown upon red hot iron, it burns with a kind
of explosion, and scarcely any residuum remains.

i: TO j

According to Mr. Gay Lussac and Thenard, 100
parts of starch are composed of

Carbon, with a small quantity of 1

salme and earthy matter - J '

^ Oxygene - - . . 49,68

Hydrogene - - - - 6,77

or.

Carbon - - - . 43,55

Oxygene and hydrogene in the"|
proportions necessary to form r* 56,45
water u - . . j

Supposing this estimation correct, starch may be
conceived to be constituted by 1 5 proportions of car-
bon, 1 3 of oxygene, and 26 of hydrogene.

Starch forms a principal part of a number of es-
culent vegetable substances. Sowans, cassava, salop,
sago, all of them owe their nutritive powers principal-
ly to the starch they contain.

Starch has been found in the following plants :

Burdock (Arctium Lappa^J Deadly Nightshade
( Atropa Belladonna^) Bistort (Polygonum Bisiorfa^J
White Bryony (Bryonia alba^) Meadow Saffron (Col-
chicuni autumnale^) Drop wort (Spiraa Filipendula^)
^Mliercw^ (Ranunculus bulbosus^ J Figwort ( Scrophu-
laria nodosa^) Dwarf Elder (Sambucus Ebulus^J Com-
mon Elder (Sa??ibucus nigra, J Foolstones (Orchis Mo*
rio,J Alexanders (Imperatoria Ostruthium,) Henbane
(Hyoscyamus niger,) Broad-leaved Dock ( Rumex obtu-
sifolius,) Sharp Pointed Dock {Rumex acutus,) Water
Dock (Rumex acquaticus^ Wake Robin {Arum macu-

C -71 3

latum^ Salep (Orchis masciila^ Flower de luce, or
Water Flag {Iris Fseudacorus^ Stinking Gladwyn {Iris
fxtidissijna^) Earthnut {Bunium Bulbopastanu?n,)

3. Sugar in its purest state is prepared from the
expressed juice of the Saccharum Officinarum, or sugar
cane ; the acid in this juice is neutralized by lime,
and the sugar is crystallized by the evaporation of the
aqueous parts of the juice, and slow-cooling : it is
rendered white by the gradual filtration of water
through it. In the common process of manufacture,
the whitening or refining of sugar is only affected in a
great length of time ; the water being gradually suf-
fered to percolate through a stratum of clay above the
sugar. As the colouring matter of sugar is soluble
in a saturated solution of sugar, or syrup, it appears
that refining may be much more rapidly and oecono-
mically performed by the action of syrup on coloured
sugar.* The sensible properties of sugar are well
known. Its specific gravity according to Fahrenheit
is about 1.6. It is soluble in its own weight of water
at 50° ; it is likewise soluble in alcohol, but in smal-
ler proportions.

* A French gentleman lately in this country (England), stated to the West
India planters, that he was in possession of a very expeditious and economical
method of purifying and refining sugar, which he was willing to communicate to
them for a very great pecuniary compensation. His terms were too high to be
acceded to. Conversing on the subject with Sir Joseph Banks, I mentioned to
him, that I thought it probable that raw sugar might be easily purified by passing
syrup through it, which would dissolve the colouring matter. The same idea
seems to have occurred about the same time, or before, to Edward Howard, Esq,
who has since proved its efficacy experimentally, and has published an account of
his process.

C 72 3

Lavoisier concluded from his experiments, that
sugar consists in 100 parts of
28 carbon,

8 hydrogene,
64 ox\ gene.
Dr. Thomson considers 100 parts of sugar as
composed of ^ 27,5 carbon,

7,8 hydrogene,
64,7 oxygene.
According to the recent experiments of Gay
Lussac and Thenard, sugar consists of
42,47 of carbon, and
57,53 of water, or its elements.
Lavoisier's and Dr. Thomson's analyses agree
very nearly with the proportions of

3 of carbon,

4 of oxygene, and
8 of hydrogene.

Gay Lussac's and Thenard's estimation gives the
same elements as in gum ; 1 1 of carbon, 10 of oxy-
gene, 20 of hydrogene.

It appears from the experiments of Proust, Ach-
ard, Goettling and Parmentier, that there are many
diiFerent species of sugar ready formed in the vegeta-
ble kingdom. The sugar which most nearly resem-
bles that of the cane is extracted from the sap of the
American maple, Acer saccharinum. This sugar is used
by the North American farmers, who procure it by a
kind of domestic manufacture. The trunk of the tree
is bored early in spring, to the depth of about two in-
ches ; a wooden spout is introduced into the hole ; the

C 73 1

juice flows for about five or six weeks. A common
sized tree, that is, a tree from two to three feet in
diameter, will yield about 200 pints of sap, and every
40 pints of sap afford about a pound of sugar. The
sap is neutralized by lime, and deposits crystals of
sugar by evaporation.

Tli^ sugar of grapes has been lately employed in
France as a substitute for colonial sugar. It is pro-
cured from the juice of ripe grapes by evaporation, and
the action of pot-ashes ; it is less sweet than common
sugar, and its taste is peculiar : it produces a sensa-
tion of cold while dissolving in the mouth ^ and it is
probable contains a larger proportion of water or its
elements.

The roots of the beet (Beta vulgaris and cicla^
afford a peculiar sugar, by boiling, and the evapora-
tion of the extract : it agrees in its general properties
with the sugar of grapes, but has a slightly bitter
taste.

Manna^ a substance which exudes from various
trees, particularly from the Fraxinus Ornus, 2l species
of ash, which grows abundantly in Sicily and Calabria,
may be regarded as a variety of sugar, very analo-
gous to the sugar of grapes. A substance analogous
to manna has been extracted by Fourcroy and Vau-
quelin, from the juice of the common onion (Allium
Cepa.)

Besides the crystallized and solid sugars, there
appears to be a sugar which cannot be separated from
water, and which exists only in a fluid form ; it con-
stitutes a principal part of melasses or treacle j and it

L

L V* J

is found in a variety of fruits : it is more soluble in
alcohol than solid sugar.

The simplest mode of detecting sugar is that re-
commended by Margraaf. The vegetable is to be
boiled in a small quantity of alcohol ; solid sugar, if
any exist, will separate during the cooling of the solu-
tion.

Sugar has been extracted from the following ve-
getable substances.

The sap of the Birch (Betula alba,) of the Sy-
camore (^Acer Pseudoplatanus,^ of the Bamboo {Ar un-
do Bambos,) of the Maize (^Zea inays,) of the Cow
Parsnip (Heraclewn Spbondylium,) of the Cocoa-nut
tree (Cocos nucifera,) of the Walnut tree (Juglans
alba,) of the American Aloe (Agave mericana,') of the
Dulse (Fucus Pahnatus^ of the Common Parsnip
(Pastinica sativa,) of St. John's bread (Ceratonia Sili^
qua,) the fruit of the common Arbutus {Arbutus
Unedo,) and other sweet-tasted fruits ; the roots of
the turnip (Brassica Rapa,) of the carrot (Daucus Car-
Ota,) of Parsley (Apium Petroselinum,) the flower of
the Euxine Rhododendron {Rhododendron poniicum^)
and from the nectarium of most other flowers.

The nutritive properties of sugar are well known.
Since the British market has been over-stocked with
this article from the West India, islands, proposals
have been made for applying it as the food of cattle ;
experiments have been made which proved that they
may be fattened by it ; but difficulties connected with
the duties laid on sugar, have hitherto prevented the
plan from being tried to any extent.

L' "5 3

4. Albumen Is a substance which has only lately
been discovered in the vegetable kingdom. It abounds
in the juice of the papaw-tree (Car tea papaya) : when
this juice is boiled the albumen falls down in a coagu-
lated state. It is likewise found in mushrooms, and
in different species of funguses.

Albumen in its pure form, is a thick, glairy, taste-
less fluid ; precisely the same as the white of the egg ; it
is soluble in cold water ; its solution, when not too di-
luted, is coagulated by boiling, and the albumen separ-
ates in the form of thin flakes. Albumen is likewise
coagulated by acids atid by alcohol : a solution of al-
bumen gives a precipitate when mixed with a cold
solution of nut-galls. Albumen when burnt produces
a smell of volatile alkali, and affords carbonic acid and
water ; it is therefore evidently principally composed
of carbon, hydrogene, oxygene, and azote.

According to the experiments of Gay Lussac and
Thenard, 100 parts of albumen from the white of the
egg are composed of

Carbon - * 52,883

Oxygene - - 23,872

Hydrogene - - 7,540

Azote - . - 15,705

This estimation would authorise the supposition,
that albumen is composed of 2 proportions of azote,
5 oxygene, 9 carbon, 22 hydrogene*

The principal part of the almond, and of the
kernels of many other nuts, appears from the experi-
ments of Proust, to be a substance analogous to co-
agulated albumen.

' f I 76 ]

The juice of the fruit of the Ochra (Hibiscus
escukntus), according to Dr. Clarke, contains a liquid
albumen in such quantities, that it is employed in
Dominica as a substitute for the white of eggs in clari-
fying the juice of the sugar cane.

Albumen may be distinguished from other sub-
stances by its property of coagulating by the action of
heat or acids, when dissolved in water. According
to Dr. Bostock, when the solution contains only one
grain of albumen to 1000 grains of water, it becomes
cloudy by being heated.

Albumen is a substance common to the animal
as well as to the vegetable kingdom, and much more
abundant in the former.

3. Gluten may be obtained from wheaten flour by
the following process : the flour is to be made into a
paste, which is to be cautiously washed, by kneading
it under a small stream of water, till the water has
carried off from it all the starch ; what remains is
gluten. It is a tenacious, ductile, elastic substance.
It has no taste. By exposure to air it becomes of
a brown colour. It is very slightly soluble in cold
water but not soluble in alcohol. When a solution
of it in water is heated, the gluten separates in the
form of yellow flakes ; in this respect it agrees with
albumen, but differs from it in being infinitely less
soluble in water. The solution of albumen does not
coagulate when it contains much less than 1000 parts
of albumen ; but it appears that gluten requires more
than 1000 parts of cold water for its solution*

C 77 ]

Gluten when burnt affords similar products to
albumen, and probably differs very little from it in
composition. Gluten is found in a great number of
plants ; Proust discovered it in acorns, chesnuts,
horse chesnuts, apples, and quinces ; barley, rye, peas
and beans j likewise in the leaves of rue, cabbage,
cresses, hemlock, borage, saffron, in the berries of
the elder, and in the grape. Gluten appears to be
one of the most nutritive of the vegetable substances ;
and wheat seems to owe its superiority to other grain,
from the circumstance of its containing it in larger
quantities.

6. Gum elastic^ or Caoutchouc^ is procured from
the juice of a tree which grows in the Brazils, called
Hsevea. When the tree is punctured, a milky juice
exudes from it, which gradually deposits a solid sub-
stance, and this is gum elastic.

Gum elastic is pliable and soft like leather, and be-
comes softer when heated. In its pure state it is white ;
its specific gravity is 9335. It is combustible, and
burns with a white flame, throwing off a dense smoke,
with a very disagreeable smell. It is insoluble in wa-
ter, and in alcohol ; it is soluble in ether, volatile oils,
and in petroleum, and may be procured from ether in
an unaltered state, by evaporating its solution in that
liquid. Gum elastic seems to exist in a great variety
of plants : amongst them are, Jatropha elastica, Ficus
indica^ Artocarpus integrifoliay and Urceola elastica.

Bird-lime, a substance which may be procured
from the holly, is very analogous to gum elastic in its
properties. Species of gum elastic may be obtained

C 78 ]

from the misletoe, from gummastic, opium ^ and from
the berries of the Smilax caduca^ in which last plant it
has been lately discovered by Dr. Barton.

Gum elastic, when distilled, affords volatile al-
kali, water hydrogene, and carbon in different com-
binations. It therefore consists principally of azote,
hydrogene, oxygene, and carbon ; but the proportions
in which they are combined have not yet been ascer-
tained. Gum elastic is an indigestible substance, not
fitted for the food of animals ; its uses in the arts are
well known.

7. Extract^ or the extractive principle^ exists in
almost all plants. It may be procured in a state of
tolerable purity from saffron, by merely infusing it in
water, and evaporating the solution. It may likewise be
obtained from catechu, or Terra japonica, a substance
brought from India. This substance consists princi-
pally of astringent matter, and extract ; by the action
of water upon it, the astringent matter is first dissol-
ved, and may be separated from the extract. Extract
is always more or less coloured ; it is soluble in alcohol
and water, but not soluble in ether. It unites with alu-
mina when that earth is boiled in a solution of ex-
tract , and it is precipitated by the salts of alumina,
and by many metallic solutions, particularly the solu-
tion of muriate of tin.

From the products of its distillation, it seems to
be composed principally of hydrogene, oxygene, car-
bon, and a little azote.

There appears to be almost as many varieties of
extract as there are species of plants. The difference

C T9 ]

of their properties probably in many cases depends
upon their being combined with small quantities of
other vegetable principles, or to their containing differ-
ent saline, alkaline, acid, or earthy ingredients. Many
dyeing substances seem to be of the nature of extrac-
tive principle, such as the red colouring matter of
madder, and the yellow dye, procured from weld.

Extract has a strong attraction for the fibres of
cotton or linen, and combines with these substances
when they are boiled in a solution of it. The com-
bination is made stronger by the intervention of mor-
dants, which are earthy or metallic combinations that
unite to the cloth, and enable the colouring matter to
adhere more strongly to its fibres.

Extract, in its pure form, cannot be used as an
article of food, but it is probably nutritive when united
to starch, mucilage, or sugar.

8. Tannin^ or the tanning principle, may be pro-
cured by the action of a small quantity of cold water
on bruised grape- seeds, or pounded gall-nut ; and by
the evaporation of the solution to dryness. It appears
as a yellow substance, possessed of a highly astrin-
gent taste. It is difficult of combustion. It is very
soluble both in water and alcohol, but insoluble in
ether. When a solution of glue, or isinglass {gelatine)
is mixed with an aqueous solution of tannin, the two
substances, i. e. the animal and vegetable matters fall
down in combination, and form an insoluble precipi-
tate.

When tannin is distilled in close vessels, the prin-
cipal products are charcoal, carbonic acid, and inflam-

C 80 ]

mable gasses, with a minute quantity of volatile alkali.
Hence its elements seem the same as those of extract,
but probably in different proportions. The charac-
teristic property of tannin is its action upon solutions
of isinglass or jelly ; this particularly distinguishes it
from extract, with which it agrees in most other che-
mical qualities.

There are many varieties of tannin, which pro-
bably owe the difference of their properties to com-
binations with other principles, especially extract,
from which it is not easy to free tannin. The purest
species of tannin is that obtained from the seeds of the
grape ; this forms a white precipitate, with solution
of isinglass. The tannin from gall-nuts resembles it
in its properties. That from sumach affords a yellow
precipitate ; that from kino a rose coloured ; that
from catechu a fawn coloured one. The colouring
matter of Brazil wood, which M. Chevreul considers
as a peculiar principle, and which he has called Hema-
iine^ differs from other species of tannin, in affording
a precipitate with gelatine, which is soluble in abun-
dance of hot water. Its taste is much sweeter than
that of the other varieties of tannin, and it may per-
haps be regarded as a substance intermediate between
tannin and extract.

Tannin is not a nutritive substance, but is of
great importance in its application to the art of tanning.
Skin consists almost entirely of jelly or gelatine^ in an
organized state, and is soluble by the long continued
action of boiling water When skin is exposed to so-
lutions containing tannin, it slowly combines with

c

81

3

that principle ; its fibrous texture and coherence are
preserved ; it is rendered perfectly insoluble in water,
and is no longer liable to putrefaction : in short, it
becomes a substance in chemical composition pre-
cisely analogous to that furnished by the solution of
jelly and the solution of tannin.

In general, in this country, the bark of the oak
is used for affording tannin in the manufacture of
leather ; but the barks of some other trees, particu-
larly the Spanish chesnut, have lately come into use.
The following table will give a general idea of the re-
lative value of different species of barks. It is founded
on the result of experiments made by mysi^lf.

Table of Numbers exhibiting the quantity of Tannin af-
forded by 480lbs. of different Barks, which express
nearly their relative values.

Average of entire bark of middle sized Oak, cut in spring,

■"■""— — -— of Spanish Chesnut,

— — — , _ of Leicester Willow, large size,

^— ————-*-. of 'm,

large.

— of Common Willow,
~ of Ash, -

— of Beech,

— of Horse Chesnut,

— of Sycamore,

— of Lombardy Poplar,

— of Birch,

— ofH.zcl,

— of Black Thorn

— of Coppice Oak,

— of Oak cut in autumn,
-~ of Larch, cut in autumn,

White interior cortical layers of Oak Bark,

lb.
29
21
33
13
11
16
10

9
11
15

8
14
16
33
21

8
72

The quantity of the tanning principle in barks
differs in different seasons j when the spring has been

M

L 82 3

cold the quantity is smallest. On an average, 4 or
5lbs. of good oak bark are required to form lib. of
leather. The inner cortical layers in all barks con-
tain the largest quantity of tannin. Barks contain the
greatest proportion of tannin at the time the buds be-
gin to open — the smallest quantity in winter.

The extractive or colouring matters found in
barks, or in substances used in tanning, influence the
quality of leather. Thus skin tanned with gall-nuts
is much paler than skin tanned with oak bark, which
contains a brown extractive matter. Leatiier made
from catechu is of a reddish tint. It is probable that
in the process of tanning, the matter of skin, and the
tanning principle first enter into union, and that leather
at the moment of its formation unites to the extractive
matter.

In general, skins in being converted into leather
increase in weight about one third j* and the opera-
tion is most perfect when they are tanned slowly.
"When skins are introduced into very strong infusions
of tannin, the exterior parts immediately combine with
that principle, and defend the interior parts from the
action of the solution : such leather is liable to crack
and to decay by the action of water.

The precipitates obtained from infusions contain-
ing tannin by isinglass, when dried, contain at a medi-
um rate about 40 per cent, of vegetable matter. It
is easy to obtain the comparative value of different
substances for the use of the tanner, by comparing

* This estimation must be considered as applying to dry skin and dry leather.

C 83 3

quantities of precipitate afForded by infusions of given
weights mixed with solutions of glue or isinglass.

To make experiments of this kind, an ounce or
480 grains of the vegetable substance in coarse pow-
der, should be acted upon by half a pint of boiling
water. The mixture should be frequently stirred, and
suffered to stand 24 hours ; the fluid should then be
passed through a fine linen cloth and mixed with an
equal quantity of solution of gelatine, made by dissolv-
ing glue, jelly, or isinglass in hot water, in the pro-
portion of a drachm of glue or isinglass, or six table
spoonfuls of jelly, to a pint of water. The precipitate
should be collected by passing the mixture of the solu-
tion and infusion through folds of blotting paper ; and
tlie paper exposed to the air till its contents are quite
dry. If pieces of paper of equal weights are used, in
cases in which different vegetable substances are em-
ployed, the difference of the weights of the papers
when dried, will indicate with tolerable accuracy, the
quantities of tannin contained by the substances, and
their relative value, for the purposes of manufacture.
Four tenths of the increase of weight, in grains, must
be taken, which will be in relation to the weights in
the table.

Besides the barks already mentioned, there are a
number of others which contain the tanning principle.
Few barks indeed are entire free from it. It is like-
wise found in the wood and leaves of a number of
trees and shrubs, and is one of the most generally dif-
fused of the vegetable principles.

A substance very similar to tannin has been

[ 84 ]

formed by Mr. Hatchett, by the action of heated dilu-
ted nitric acid on charcoal, and evaporation of the
mixture to dryness. From 100 grains of charcoal
Mr. Hatchett obtained 120 grains of artificial tannin,
which, like natural tannin, possessed the property of
rendering skin insoluble in water.

Both natural and artificial tannin form com*
pounds with the alkalies and the alkaline earths ; and
these compounds are not decomposable by skin. The
attempts that have been made to render oak bark
more efficient as a tanning material by infusion in lime
water, are consequently founded on erroneons princi-
ples. Lime forms with tannin, a compound not so*

luble in water.

The acids unite to tannin, and produce comi»
pounds that are more or less soluble in water. It is
probable that in some vegetable substances tannin
exists, combined with alkaline or earthy matter ; and
such substances will be rendered more efficacious for
the use of the tanner, by the action of diluted acids.

9. Indigo may be procured from woad {Isatis tinc-
ioria,) by digesting alcohol on it, and evaporating the
solution. White crystalline grains are obtained,
which gradually become blue by the action of the at-
mosphere : these grains are the substance in question.

The indigo of commerce is principally brought
from America. Jt is procured from the Indigofera
argentea^ or wild indigo, the Indigofera dispermUy or
Gautimala indigo, and the Indigofera iinctoria, or
French indigo. It is prepared by fermenting the
leaves of those trees in water. Indigo in its common

C 85 ]

form appears as a fine, deep blue powder. It is in-
soluble in water, and but slightly soluble in alcohol :
its true solvent is sulphuric acid : 8 parts of sulphu-
ric acid dissolve 1 part of indigo ; and the solution
diluted with water forms a very fine blue dye.

Indigo, by its distillation, affords carbonic acid
gas, water, charcoal, ammonia, and some oily and
acid matter : the charcoal is in very large proportion.
Pure indigo therefore most probably consists of car-
bon, hydrogene, oxygene, and azote.

Indigo owes its blue colour to combination with
oxygene. For the uses of the dyers it is partly de-
prived of oxygene, by digesting it with orpiment and
lime water, when it becomes soluble in the lime water,
and of a greenish colour. Cloths steeped in this so-
lution combine with the indigo ; they are green when
taken out of the liquor, but become blue by absorb-
Tng oxgene when exposed to air.

Indigo is one of the most valuable and most ex-
tensively used of the dyeing materials.

10. The narcotic principle is found abundantly in
opium^ which is obtained from the juice of the white
poppy, {Fapaver album). To procure the narcotic
principle, water is digested upon opium : the solution
obtained is evaporated till it becomes of the consistence
of a syrup. By the addition . of cold water to this
syrup a precipitate is obtained. Alchohol is boiled on
this precipitate ; during ^the cooling of the alcohol
crystals fall down. These crystals are to be again
dissolved in alcohol, and again precipitated by cool-
ing : and the process is to be repeated till their colour
is white ; they are crystals of narcotic principle.

C 86 1

The narcotic principle has no taste nor smell. It
is soluble in about 400 parts of boiling water ; it is
insoluble in cold water : it is soluble in 24 parts of
boiling alcohol, and in 100 parts of cold alcohol. It
is very soluble in all acid menstrua.

It has been shewn by De Rosne, that the action
of opium on the animal economy depends on this
principle. Many other substances besides the juice
of the poppy, possess narcotic properties ; but they
have not yet been examined with much attention.
The Lactuca sativa^ or garden lettuce, and most of
the other lactucas yield a milky juice, which when
inspissated has the characters of opium, and probably
contains the same narcotic principle.

1 1 . The hitter principle is very extensively diffus-
ed in the vegetable kingdom ; it is found abundantly
m the hop {Humilus lupilus^) in the common broom
(Spartium scoparium^ in the chamomile (^Anihemis
nobilis^) and in quassia^ amara and exceha. It is ob-
tained from those substances by the action of water or
alcohol, and evaporation. It is usually of pale yellow
colour ; its taste is intensely bitter. It is very solu-
ble, both in water and alcohol ; and has little or no
action on alkaline, acid, saline or metallic solution.

An artificial substance, similar to the bitter prin-
ciple, has been obtained by digesting diluted nitric
acid, on silk, indigo, and the wood of the white willow.
This substance has the property of dyeing cloth of a
bright yellow colour ; it differs from the natural bitter
principle in its power of combining with the alkalies :
in union with the fixed alkalies it constitutes crystal-

C 87 ]

lized bodies, which have the property of detonating
by heat or percussion.

The natural bitter principle is of great impor-
tance in the art of brewing ; it checks fermentation,
and preserves fermented liquors ; it is likewise used
in medicine.

The bitter principle, like the narcotic principle,
appears to consist principally of carbon, hydrogene,
and oxygene, with a little azote.

12. Wax is found in a number of vegetables ; it
is procured in abundance from the berries of the wax
myrtle (Myrica ceriferd)^ it may be likewise obtained
from the leaves of many trees ; in its pure state it is
white. Its specific gravity is 9,662 ; it melts at 155
degrees ; it is dissolved by boiling alcohol ; but it is
not acted upon by cold alcohol ; it is insoluble in wa-
ter ; its properties as a combustible body are well
known.

The wax of the vegetable kingdom seems to be pre-
cisely of the same nature as that afforded by the bee.
From the experiments of M. M. Gay Lussac and
Thenard, it appears that 100 parts of wax consist of
Carbon ... - 81,784
Oxygene - . . . 5,544"

Hydrogene . « . . 12,672
or otherwise,

Carbon .... 81,784

Oxygene and hydrogene in the pro-")

r r 6,300

portions necessary to form water J
Hydrogene - - . 11,916

which agrees very nearly with 37 proportions of hy-
drogene, 21 of charcoal, 1 ofoxygejie.

I 88 3

13. Resin is very common In the vegetable king-
dom. One of the most usual species is that afforded
by the different kinds of fir. When a portion of the
bark is removed from a fir tree in spring, a matter
exudes, which is called turpentine ; by heating this
turpentine gently, a volatile oil rises from it, and a
more fixed substance remains ; this substance is
resin.

The resin of the fir is the substance commonly
known by the name of rosin ; its properties are well
known. Its specific gravity is 1 072. It melts readily,
burns with a yellow light, throwing off much smoke.
Resin is insoluble in water either hot or cold ; but
very soluble in alcohol. When a solution of resin in
alcohol is mixed with water, the solution becomes
milky ; the resin is deposited by the stronger attrac-
tion of the water for the alcohol.

Resins are obtained from many other species of
trees. Mastich^ from the Fistacia lentiscus^ Elemi
from the Amyris elemifera^ Copal from the Rhus copal-
linum^ Sandarach from the common juniper. Of these
resins copal is the most peculiar. It is the most diffi-
cultly dissolved in alcohol ; and for this purpose
must be exposed to that substance In vapour , or the
alcohol employed must hold camphor in solution. Ac-
cording to Gay Lpssac and Thenard,
100 parts of common resin contain

Carbon - . . - 75,944

Oxygene . - - . 13,337
Hydrogene - - - - 10,719

C 89'

or of

Carbon .... 75,944

Oxygene and hydrogene in the pro- ^ ^ ^

1 1 oo

1 15,:

portions necessary to form water
Hydrogene in excess - - 8,900

According to the same chemists, 100 parts of co-
pal consist of

Carbon - - - - 76,811

Oxygene - -- - - 10,606
Hydrogene ... - 12,583
or,

Carbon .... 76,811
Water or its elements - - 12,052
Hyrogene - - - - - 11,137
From these results, if resin be a definite com-
pound, it may be supposed to consist of 8 proportions
of carbon, 12 of hydrogene, and 1 of oxygene.

Resins are used for a variety of purposes. Tar
and pitch principally consist of resin, in a partially de-
composed state. Tar is made by the slow combustion
of the fir ; and pitch by the evaporation of the more
volatile parts of tar. Resins are employed as var-
nishes, and for these purposes are dissolved in alco-
hol or oils. Copal forms one of the finest. It may
be made by boiling it in powder with oil of rosemary,
and then adding alcohol to the solution.

14. Camphor is procured by distilling the wood
of the camphor tree (Laurus Campbora,) which grows
in Japan. It is a very volatile body, and may be pu-
rified by distillation. Camphor is a white, brittle,
semitransparent substance, having a peculiar odour,

N

C 90 3

and a strong acrid taste. It is very slightly soluble
in water ; more than 1 00,000 parts of water are re-
quired to dissolve 1 part of camphor. It is very solu-
ble in alcohol ; and by adding water in small quantities
at a time to the solution of camphor in alcohol, the
camphor separates in a crystallised form. It is solu-
ble in nitric acid, and is separated from it by water.

Camphor is very inflammable ; it burns with a
bright flame, and- throws oflf a great quantity of car-
bonaceous matter. It forms in combustion water,
carbonic acid, and a peculiar acid called camphorici
acid. No accurate analysis has been made of camphor,
but it seems to approach to the resins in its composi-
tion ; and consists of carbon, hydrogene, and oxy-
gene.

Camphor exists in other plants besides the Lau-
rus camphora. It is procured from species of the lau-
rus growing in Sumatra, Borneo, and other of the
East Indian isles. It has been obtained from thyme
(Thymus serpillum,') marjorum (Origanum major ana ^^
Ginger tree (Amomurn Zingiber.^ Sage (Salvia officin-
alis,') Many volatile oils yield camphor by being
merely exposed to the air.

An artificial substance very similar to camphor
has been formed by M. Kind, by saturating oil of tur-
pentine with muriatic acid gas (the gaseous substance
procured from common salt by the action of sulphuric
acid). The camphor procured in well conducted ex-
periments amounts to half of the oil of turpentine
used. It agrees with common camphor in most of its
sensible properties j but diflfers materially in its che-

[ ■ 91 ]

mical qualities and composition. It is not soluble
without decomposition in nitric acid. From the ex-
periments of Gehlen, it appears to consist of the ele-
ments of oil of turpentine, carbon, hydrogene and
oxygene, united to the elements of muriatic gas,

chlorine and hydrogene.

From the analogy of artificial to natural camphor,

-it does not appear improbable, that natural camphor
may be a secondary vegetable compound, consisting
of camphoric aciil and volatile oil. Camphor is used
medicinally, but it has no other application.

15. Fixed oil is obtained by expression from seeds
and fruits ; the olive, the almond, linseed and rape-
seed afford the most common vegetable fixed oils.
The properties of fixed oils are v^ell known. Their
specific gravity is less than that of water ; that of olive
and of rape-seed oil is 913; that of linseed and al-
mond oil 932 ; that of palm oil 968 ; that of walnut
and beech mast oil 923. Many of the fixed oils con-
geal at a lower temperature than that at which water
freezes. They all require for their evaporation a
higher temperature than that at which water boils.
The products of the combustion of oil are water, and
carbonic acid gas.

From the experiments of Gay Lussac and Then-
ard, it appears that olive oil contains, in lOO parts.
Carbon - - . . - 77,213
Oxygene - - - - 9,427

Hydrogene - . . - 13,360
This estimation is a near approximation to 1 1 pro*
portions of carbon, 20 hydrogene, and 1 oxygene.

C 92 J

The following is a list of fixed oils, and of the
trees that afford them.

Olive oil, from the Olive tree (Oka Europea)^
Linseed oil, from the copimon and perennial Flax
{Linum usitatissimum et perenne^ Nut oil, from the
Hazel nut {Coryllus avelland)^ Walnut (/wg-A^wj regid)^
Hemp oil, from the Hemp {Cannabis sativa\ Almond
oil, from the sweet Almond {Amygdalus communis)^
Beech oil, from the common Beech (Fagus sylvatica)^
Rape-seed oil, from the Rapes {Brassica napus et cam-
pestris\ Poppy oil, from the Poppy {Fapaver somnife-
rum)^ oil of Sesamum, from the Sesamum (Sesamum
orientak)^ Cucumber oil, from the Gourds {Cucurbita
pepo et malapepo)^ oil of Mustard, (Sinapis nigra et ar-
vensis)^ oil of Sunflower, from the annual and peren-
nial Sunflower, (Heliantbus annuus et perennis). Castor
oil, from the Palma Christi (Ricinus communis)^ To-
bacco (Nicotiana tabacum et rustica\ Plum kernel oil,
from the Plum tree (Prunus domestica'). Grape-seed
oil, from the Vine (Vitis vinifera\ Butter of cacoa,
from the Cacoa tree (Theobroma cacoa^ Laurel oil,
from the sweet Bay tree {Laurm nobilii).

The fixed oils are very nutritive substances ; they
are of great importance in their applications to the
purposes of life. Fixed oil, in combination with soda,
forms the finest kind of hard soap. The fixed oils
are used extensively in the mechanical arts, and for
the preparation of pigments and varnishes.

16. Volatile oil, likewise called essential oil, differs
from fixed oil, in being capable of evaporation by a
much lower degree of heat j in being soluble in alco-

[ 93 ]

hol, and in possesslrg a very slight degree of solubili-
ty in water.

There is a great number of volatile oils, distin-
guished by their smell, their taste, their specific gra-
vity, and other sensible qualities. A strong and pecu-
liar odour may however be considered as the great
characteristic of each species ; the volatile oils inflame
with more facility than the fixed oils, and afford by
their combustion different proportions of the same
substances, water, carbonic acid, and carbon.

The following specific gravities of different vola-.
tile oils were ascertained by Dr. Lewis.

Oil of Sassafras 1094 Oil of Tansy 946

Cinnamon

1035

' Caraway 940

Cloves

1034

Origanum 940

Fennel

997 "

Spike 936

Dill

994 .

Rosemary 934

Penny Royal

: 978

Juniper 9 1 1

Cummin

975 -

- — Oranges 888

Mint

975 -

— Turpentine 792

Nutmegs 948

The peculiar odours of plants seem, in almost
all cases, to depend upon the peculiar volatile oils they
contain. All the perfumed distilled waters owe their
peculiar properties to the volatile oils they hold in so-
lution. By collecting the aromatic oils, the fragrance
of flowers, so fugitive in the common course of na-
ture, is as it were embodied and made permanent.

It cannot be doubted that the volatile oils con-
sist of carbon, hydrogene, and oxygene ; but no ac-
curate experiments have as yet been made on the
proportions in which these elements are combined.

C 94 ]

The volatile oils have never been used as articles
of food 5 many of them are employed in the arts, in
the manufacture of pigments and varnish ; but their
most extensive application is as perfumes.

17 Woody fibre is procured from the wood, bark,
leaves, or flowers of trees, by exposing them to the
repeated action of boiling water and boiling alcohol.
It is the insoluble matter that remains, and is the basis
of the solid organised parts of plants. There are as
many varieties of woody fibre as there are plants and
organs of plants ; but they are all distinguished by
their fibrous texture, and their insolubility.

Woody fibre burns with a yellow flame, and pro-
duces water and carbonic acid in burning When it
is distilled in close vessels, it yields a considerable
residuum of charcoal. It is from woody fibre, indeed,
that charcoal is procured for the purposes of life.

The following table contains the results of expe-
riments made by Mr. Mushet, on the quantity of char-
coal afibrded by different wood.

Lignum Vitas

26,8 of charcoal

Mahogany

25,4

Laburnum

24,5

Chesnut -

23,2

Oak

22,6

American black Beech 2 1 ,4

Walnut -

20,6

Holly

19,9

Beech

19,9

American Maple

19,9

Elm . -

19,5

C 95 3

100 parts of Norway Pine - 19,2 of charcoal

Sallow - - 18,4

Ash - - 17,9

-Birch - - 17,4
- Scottish Fir - 1 6,4

M. Gay Lussac and Thenard have concluded
from their experiments on the wood of the oak and
the beech, that 100 parts of the first contain :

of Carbon - - . . 52,53

— Oxygene - - . 41,78

— Hydrogene - - . 5,69
and 100 parts of the second :

of Carbon - - - - 51,45

— Oxygene ... 42,73

— Hydrogene - - . 5,82
Supposing woody fibre to be a definite compound,

these estimations lead to the conclusion, that it con-
sists of 5 proportions of carbon, 3 of oxygene, and
6 of hydrogene ; or 57 carbon, 45 oxygene, and 6
hydrogene.

It will be unnecessary to speak of the applications
of woody fibre. The different uses of the woods,
cotton, linen, the barks of trees, are sufficiently
known. Woody fibre appears to be an indigestible
substance.

1 8. The acids found in the vegetable kingdom
are numerous ; the true vegetable acids which exist
ready formed in the juices or organs of plants, are
the oxalic^ citric, tartaric, benzoic, acetic, malic, gallic,
and prussic acid.

C 96 3

All these acids, except the acetic, malic, and
prussic acids, are white crystallized bodies. The
acetic, malic, and prussic acids have been obtained in
the only fluid state ; they are all more or less solu-
ble in water ; all have a sour taste except the gallic
and prussic acids ; of which the first has an astringent
taste, and the latter a taste like that of bitter almonds.

The oxalic acid exists, uncombined, in the liquor
which exudes from the Chich pea (Cicer arietinuni),
and may be procured from wood sorrel (Oxalis aceto-
5ella\ common sorrel, and other species of Rumex ;
and from the Geranium acidum. Oxalic acid is easily
discoved and distinguished from other acids by its
property of decomposing all calcareous salts, and
forming with lime a salt insoluble in water ; and by
its crystallizing in four-sided prisms.

The citric acid is the peculiar acid existing in the
juice of lemons and oranges. It may likewise be ob-
tained from the cranberry, whortleberry, and hip.

Citric acid is distinguished by its forming a salt
insoluble in water with lime ; but decomposable by
the mineral acids.

The tartaric acid may be obtained from the juice
of mulberries and grapes ; and hkewise from the pulp
of the tamarind. It is characterized by its property
of forming a difficultly soluble salt with potassa, and
an insoluble salt decomposable by the mineral acids
with lime.

Benzoic acid may be procured from several re-
sinous substances by distillation ; from benzoin,
storax, and balsam of Tolu. It is distinguished from

C 97 ]

the other acids by its aromatic odour, and by its ex-
treme volatility.

Malic acid may be obtained from the juice of
apples, barberries, plums, elderberries, currants,
stawberries, and raspberries. It forms a soluble salt
with lime ; and is easily distinguished by this test
from the acids already named.

Acetic acid, or vinegar, may be obtained from
the sap of different trees. It is distinguished from
malic acid by its peculiar odour ; and from the other
vegetable acids by forming soluble salts with the alka-
lies and earths.

Gallic acid may be obtained by gently and gradu-
ally heating powdered gall nuts, and receiving the vo-
latile matter in a cool vessel. A number of white
crystals will appear, which are distinguished by their
property of rendering solutions of iron, deep purple.

The vegetable prussic acid is procured by distil-
ling laurel leaves, or the kernels, of the peach, and
cherry, or bitter almonds. It is characterized by its
property of forming a blueish green precipitate, when
a little alkali is added to it, and it is poured into solu-
tions containing iron. It is very analogous in its pro-
perties to the prussic acid obtained from animal sub-
stances ; or by passing ammonia over heated charcoal ;
but this last body forms, with the red oxide of iron,
the deep bright blue substance, called Prussian blue.

Two other vegetable acids have been found in
the products of plants ; the morolyxic acid in a saline
exudation from the white mulberry tree, and the kinic
acid in a salt afforded by Peruvian bark ; but these

c 98 :

two bodies have as yet been discovered in no othei*
cases. The phosphoric acid is found free in the
onion ; and the phosphoric, sulphuric, muriatic, and
nitric acids, exist in many saline compounds in the
vegetable kingdom ; but they cannot with propriety
be considered as vegetable products. Other acids
are produced during the combustion of vegetable
compounds, or by the action of nitric acid upon
them ; they are the camphoric acid, the mucous or
saclactic acid, and the suberic acid ; the first of which
is procured from camphor ; the second from gum or
mucilage ; and the third from cork, by the action of
nitric acid.

From the experiments that have been made upon
the vegetable acids, it appears that all of them, except
the prussic acid, are constituted by different propor-
tions of carbon, hydrogene, and oxygene ; the prus-
sic acid consists of carbon, azote and hydrogene, with
a little oxygene. The gallic acid contains more car-
bon than any of the other vegetable acids.

The following estimates of the composition of
some of the vegetable acids have been made by Gay
Lussac and Thenard.
100 parts of oxalic acid contain :

Carbon . - - - 26,566

Hydrogene - - - - 2,745

Oxygene -. - - , 70,689
Ditto of tartaric acid :

Carbon - - . - 24,050

Hydrogene - . - - 6,629

Oxygene - - . ., 69^321

i: 99 ]

100 parts of citric acid :

Carbon . - . - 33,811

Hydrogene - - - - 6,330

Oxygene - . . - 59,859
Ditto acetic acid :

Carbon - - - . 50,224

Hydrogene - . . 5,620

Oxygene - - - - 44,147
Ditto mucous or saclactic acid ;

Carbon . - . . 33,69

Hydrogene - - - 3,62

Oxygene - - - . 62,69

These estimations agree nearly with the follow-
ing definite proportions. In oxalic acid 7 proportions
of carbon, 8 of hydrogene, and 15 oxygene;* in tar-
taric acid, 8 carbon, 28 hydrogene, 18 oxygene; in
citric acid, 3 carbon, 6 hydrogene, 4 oxygene ; in
acetic acid, 18 carbon, 22 hydrogene, 12 oxygene;
in mucous acid, 6 carbon, 7 hydrogene, 8 oygene.

The applications of the vegetable acids are well
known. The acetic and citric acids are extensively
used. The agreeable taste and wholesomeness of
various vegetable substances used as food, materially
depend upon the vegetable acid they contain.

19. Fixed Alkali may be obtained in aqueous so-
lution from most plants by burning them, and treat-
ing the ashes with quick lime and water. The vege-

* According to Dr. Thompson's experiments, oxalic acid consists of 3 pro-
portions of carbon, 4 of oxygene, and 4 of hydrogene, a result very different indeed
from that of the French chemists.

C 100 j

table alkali, or potassa, Is the common alkali, or pot-
assa, is the common alkali in the vegetable kingdom.
This substance in its pure state is white, and semi-
transparent, requiring a strong heat for its fusion, and
possessed of a highly caustic taste. In the matter
usually called pure potassa by chemists, it exists com-
bined with water ; and in that commonly called pearl
ashes, or pot-ashes in commerce, it is combined with
a small quantity of carbonic acid. Potassa in its com-
bined state, as has been mentioned, page 47, consists
of the highly inflammable metal potassium, and oxy-
gene, one proportion of each.

Soda, or the mineral alkali, is found in some
plants that grow near the sea ; and is obtained com-
bined with water, or carbonic acid, in the same man-
ner as potassa ; and consists, as has been stated,
page 47, of one proportion of sodium, and two pro-
portions of oxygene. In its properties it is very simi-
lar to potassa ; but may be easily distinguished from it
by this character : it forms a hard soap with oil ;
potassa forms a soft soap.

Pearl ashes, and barilla and kelp, or the impure
soda obtained from the ashes of marine plants, are
very valuable in commerce, principally on account of
their uses in the manufacture of glass and soap. Glass
is made from fixed alkali, flint, and certain metallic
substances.

To know whether a vegetable yields alkali, it
should be burnt, and the ashes washed with a small
quantity of water. If the water, after being for some
time exposed to the air, reddens paper tinged with

C 101 3

turmeric ; or renders vegetable blues, green, it con-
tains alkali.

To ascertain the relative quantities of pot-ashes
afforded by different plants, equal weights of them
should be burnt : the ashes washed in twice their
volume of water ; the washings should be passed
through blotting paper, and evaporated to dryness :
the relative weights of the salt obtained, will indicate
very nearly the relative quantities of alkali they con-
tain.

The value of marine plants in producing soda,
may be estimated in the same manner, with sufficient
correctness for all commercial purposes.

Herbs, in general, furnish four or five times, and
shrubs two or three times as much pot-ashes as trees.
The leaves produce more than the branches, and the
branches more than the trunk. Vegetables burnt in
a green state produce more ashes than in a dry state.

The following table* contains a statement of the
quantity of pot-ashes afforded by some common trees
and plants.

10,000 parts of Oak - - 15

of Elm - . 39

of Beech - - 12

...«««._-,«-. of Vine - - 55

of Poplar - - 7

of Thistle - 53

of Fern - - 62

of Cow Thistle - 196

• It is foandcd upon the experiments of Kirwan, Vaoqaelin and Pertuis.

[ 102 3

10,000 parts of Wormwood - 730

_ of Vetches - 275

of Beans - - 200

of Fumitory - 790

The earths found in plants are four : silica or
the earth of flints, alumina or pure clay, lime and
magnesia. They are procured by incineration. The
lime is usually combined with carbonic acid. This
substance and silica are much more common in the
vegetable kingdom than magnesia, and magnesia more
common than alumina. The earths form a principal
part of the matter insoluble in water, afforded by the
ashes of plants. The silica is known by not being
dissolved by acids ; the calcareous earth, unless the
ashes have been very intensely ignited, dissolves with
effervescence in muriatic acid. Magnesia forms a solu-
ble and crystallizable salt, and lime, a difficultly solu-
ble one with sulphuric acid. Alumina is distinguished
from the other earths, by being acted upon very slowly
by acids ; and in forming salts very soluble in water,
and difficult of crystallization with them.

The earths appear to be-compounds of the pecu-
liar metals mentioned page 48 and oxygene, one pro-
portion of each.

The earths afforded by plants are applied to no
uses of common life ; and there are few cases in
which the knowledge of their nature can be of impor-
tance, or afford interest to the farnief.

The only metallic oxides found in plants, are those
of iron and manganesum : they are detected in the

C 103 -}

ashes of plants ; but In very minute quantities only.
When the ashes of plants are reddish brown, they
abound in oxides of iron. When black or purple, in
oxide of manganesum ; when these colours are mixed
they contain both substances.

The saline compounds contained in plants, or
afforded by their incineration, are very various. The
sulphuric acid combined with potassa, or sulphate of
potassa, is one of the most usual. Common salt is
likewise very often found in the ashes of plants ; like-
wise phosphate of lime, which is insoluble in water,
but soluble in muriatic acid. Compounds of the nitric,
muriatic, sulphuric, and phosphoric acids, with alkalies
and earths, exist in the sap of many plants, or are af-
forded by their evaporation and incineration. The
salts of potassa are distinguished from those of soda,
by their producing a precipitate in solutions of pla-
tina : those of lime are characterized by the cloudiness
they occasion in solutions containing oxalic acid ;
those of magnesia, by being rendered cloudy by solu-
tions of ammonia. Sulphuric acid is detected in salts
by the dense white precipitate it forms in solutions of
baryta. Muriatic acid by the cloudiness it communi-
cates to solution of nitrat of silver ; and when salts
contain nitric acid, they produce scintillations by being
thrown upon burning coals.

As no applications have been made of any of the
neutral salts, or analogous compounds found in plants,
in a separate state, it will be useless to describe them
individually. The following tables are given from

[

104

3

M. Th. de Saussure's Researches on Vegetation, and
contain results obtained by that philosopher. They
exhibit the quantities of soluble salts, metallic oxides,
and earths afforded by the ashes of different plants.

*

Constituents of 100 parts i

of the Ashes. |

en

U4

o

i

i

O

Ui

e

f £

'Si

O

5

Si

2

CO

s

1

1

o
1

2

i

^

(U *•

J3

^

I

<

1

T45

47

24

0,12

Leaves of oak (guercus robur) May 10

13

53

3

0,64 25,841

2

Ditto, Sept. 27 ...

24

55

549

17

18,25

23

14,5

1,75 25,5 I

3

Wood of a young oak. May lO

—

4

26

28,5

12,25

0,12

1 32,58.

4

Bark of ditto

—

60

7

4,5

63.25

0,25

1,7522,75!

5

Entire wood of oak

—

2

38,6

4,5

32

2

2,25 20,65

6

Alburnum of ditto -

—

—

32

24

11

7,5

2 23,5

7

Bark of ditto ....

—

60

7

3

66

1,5

2 '21,5

8

Cortical layers of ditto

—

73

.

7

3,75

65

0,5

1

22,7i

9

Extract of wood of ditto -

—

61

51

10

Soil from wood of ditto .

—

41

24

10,5

10

32

14

8,5

11

Extract from ditto ...

—

111

66

12

Leaves of the poplar (poputus nigra)

—

May 26 ....

23

66

652

36

13

29

5

1,2515,75

13

Ditto Sept. 12 ...

41

93

565

ai

7

36

11,5

1,5 18

14

Wood of ditto, Sept. 12

—

8

26

—

16,75

27

3,3

1,5 24,5

15

Bark of ditto ....

—

72

6

5,3

60

4

1,5 23,2

16

Leaves of hazel (corylus avellana)

May 1 ....

—

6l

26

23,3

22

2,5

1,5 24,7

17

Ditto, washed in cold water

—

S7

8,2

19,5

44.1

4

2 j22,2

is

Leaves of ditto June 22 -

28 1

62

655

22,7

14

29

11,3

1,5

21,5

19

Ditto Sept. 20 -

31

70

557

11

12

36

22

2

17

20

Wood of ditto. May 1

—

5

24,5

35

8

0.25

0,12

32,2

21

Bark of ditto ....

—

62

12,5

S,S

54

0,25

1,75

26

22

Entire wood of mulberry {morui ni-

gra), November ...

—

7

21

2,25

56

0,12

0,25 20,38

23

Alburnum of ditto -

—

13

.

26

27,25

24

1

0,25:21,5

24

Bark of ditto ...

—

89

7

8,5

45

15,25

1,12 23,13

25

Cortical layers of ditto .

—

8S

10

16,5

48

0,12

1

24,38

26

Entire wood of hornbeam {carpinui

betulHi), Nov.

4

6

346

22

23

26

0,12

2,25

26,63

27

Alburnum of ditto ...

4

7

390

18

36

15

1

1

29

28

Bark of ditto ...

88

134

346

4,5

4,5

59

1,5

0,12 30,38|

29>Wood of horse chesnut (asculus hyp.

1 pocastanum) May 10 - -

~

35

9,5

30 Leaves of ditto. May 10 -

16

72

782

50

31 Leaves of ditto, July 23 -

29

84

652,

24

32 Ditto, Sept. 27

31

86

630

13,5

33'Flowers of ditto. May 10

9

71

873

50

' \

105

o

CO

o

B

a
1^

34 Fruit of horse chesnut (asculus hyp-
fiocastanum) Oct. 5 - -

Plants of peas {pi sum iativum)\n flo*r

Ditto, ripe ....

Plants of vetches (vicia faba), be-
fore flowering. May 23

Ditto in flower, June 23 -

Ditto ripe, June 23 -

Ditto, seeds separated

Seeds of ditto

Do. in flower, rais'd in distilled water

Solydago vulgaris, before flowering,
May 1 - . - * -

Ditto, just in flower, July 15 -

Ditto, seeds ripe, Sep. 20

Plants of turnsol (helianthus annuus),
a month before flowering, June 23

Ditto in flower, July 23 -

Ditto, bearing ripe seeds, Sept. 20

Wheat (triticum sativum), in flower

Ditto, seeds ripe . - -

Ditto, a month before flowering

Ditto, in flower, June 14 -

Ditto, seeds ripe ...

Straw of wheat

Seeds of ditto . . -

Bran - - - - >

Plants of maize (zea mays) a month
before flowering, June 23

Ditto, in flower, July 23

Ditto, seeds ripe ...

Stalks of ditto

Spikes of ditto

Seeds of ditto . , -

ChafF of barley (hordeum vulgare)

Seeds of ditto

Ditto

Oats

Leaves of rhododendron ferrugineum,
raised on Jura, a limestone moun-
tain, June 20 • -

Ditto, raised on Breven, a granitic
mountain, June 27

Branches of ditto, June, 20

Spikes of ditto, June 27 -

Leaves of fir {pinus abies), raised on
Jura, June 20 - - -

Ditto, raised on Breven, June 27

Branches ©f pine, June 20

Whortleberry (yaccinium myrtillus),
raised on Jura, Aug. 29
75 Ditto, raised on Breven -

!l50
[\22
66
115
33
39
I
92
57
50

147
137
93

O M
o ^

_

29

—

29

—

15

_

26

—

22

Constituents of lOO parts
of the Ashes.

647 82 l:

i49,80'l7,25

;34>25j22

ii I

895lj55,5

876 1155,5

—.150

42

(14,5
1 13,5
117,75
5,75

69,28127,92
60,1 30

699

67,5

59

43

63
61

5,15
43,35
11
60
41
10
22,5
47,16

4,16

69
69

72/45

62
20
29
22
1

23

21,1

22,5
24

16
15
15

17
24

l0,75

59

II

67

6
22,5
12,75
15
11,5
10,75
11,75

6,2
44,5
46,5,

5,75
6

36
7,75
32,5
22
24

6
14

3,5
4,12
4

3§

1,5
1,5

17,25

11,56

12,5

4

0,25
0,25
0,25
0,25
0,25
1

0,25
0,25

12,5

43,25

16,75

10 ,39
11,5 129

12,27 '43,5
12 29

1,5
1,5

3,5

1,5
1,5
3,75

32

54

12,5

26

51

61,5
0,5
0,5

7,5
7,5

18

I
57

:i5,s

21

60

0,75

2,5
19

0,25 5,25
* 24,65
2,5 17,25

24,50

24,38

26

12,9
2,3
9,4

0,75 18,25
0,75 21
1,5 18,75

0,12

0,12

0,5

0,5

I

0,25

0,5

0,57

1

0,25

0,25

0,25
0,25

e,5

0,12
0,5
0,25
0,12
0,25

15,63

5,77
5,4
11

1,6
5,5

3,12

16,67
18,78
17,75
12,25
18,75
15,5
21,5
23
78
7,6
8,6

17,25
17

3,05

0,S
2,25
2,8
29,88
14,75

15,63

31,S2
22,48
24,5

24,13
19,5

19,38

C 106 3

Besides the principles, the nature of which has
been just discussed, ©thers have been described by
chemists as belonging to the vegetable kingdom : thus
a substance, somewhat analogous to the muscular
fibre of animals, has been detected by Vauquelin in
the papaw ; and a matter similar to animal gelatine by
Braconnot in the mushroom ; but in this place it
would be improper to dwell upon peculiarities ; my
object being to offer such general views of the consti-
tution of vegetables as may be of use to the agricul-
turist. Some distinctions have been adopted by sys-
tematical authors which I have not entered into, be-
cause they do not appear to me essential to this enquiry.
Dr. Thomson, in his elaborate and learned system of
chemistry, has described six vegetable substances,
which he calls mucus, jelly, sarcocol, asparagin, inu-
lin, and ulmin. He states that mucus exists in its
purest form in linseed ; but Vauquelin has lately
shewn, that the mucilage of linseed is, in its essential
characters, analogous to gum ; but that it is combin-
ed with a substance similar to animal mucus : vegeta-
ble jelly. Dr. Thomson himself considers as a modifi-
cation of gum. It is probable, from the taste of sar-
cocol, that it is gum combined with a little sugar.
Inulin is so analogous to starch, that it is probably a
variety of that principle ; ulmin has been lately shewn
by Mr. Smithson to be a compound of a peculiar ex-
tractive matter and potassa ; and asparagin is proba-
bly a similar combination. If slight differences in
chemical and physical properties be consided as suffi-
cient to establish a difference in the species of vegeta-
ble substances, the catalogue of them might be enlar-

ed to almost any extent. No two compounds procured
from different vegetables are precisely alike j and
there are even differences in the qualities of the same
compound, according to the time in which it has been
collected, and the manner in which it has been pre-
pared : the great use of classification in science is to
assist the memory 5 and it ought to be founded upon
the similarity of properties which are distinct, charac-
teristic, and invariable.

The analysis of any substance containing mix-
tures of the different vegetable principles, may be
made in such a manner as is necessary for the views
of the agriculturist with facility. A given quantity,
say 200 grains, of the substance should be powdered,
made into a paste or mass, with a small quantity of
water, and kneaded in the hands, or rubbed in a mor-
tar for some time under cold water ; if it contain
much gluten, that principle will separate in a coherent
mass. After this process, whether it has afforded
gluten or not, it should be kept in contact with half a
pint of cold water for three or four hours, being oc-
casionally rubbed or agitated : the solid matter should
be separated from the fluid by means of blotting pa-
per : the fluid should be gradually heated ; if any
flakes appear, they are to be separated by the same
means as the solid matter in the last process, i. e. by
filtration. The fluid is then to be evaporated to dry-
ness. The matter obtained is to be examined by ap-
plying moist paper, tinged with red cabbage juice, or
violet juice to it ; if the paper become red, it contains
acid matter j if it become green, alkaline matter j and

C 108 3

the nature of the acid or -jlkaline matter may be
known by applying the tests described page 97,98,100.
If the solid matter be sweet to the taste, it must be
supposed to contain sugar ; if bitterish, bitter prin-
ciple, or extract ; if astringent, tannin : and if it be
nearly insipid, it must be principally gum or mucilage.
To separate gum or mucilage from the other princi-
ples, alcohol must be boiled upon the solid matter,
which will dissolve the sugar and the extract, and
leave the mucilage ; the weight of which may be as-
certained. • .

To separate sugar and extract, the alcohol must
be evaporated till crytals begin to fall down, which are
sugar ; but they will generally be coloured by some
extract, and can only be purified by repeated solu-
tions in alcohol. Extract may be separated from su-
gar by dissolving the solid, obtained by evaporation
from alcohol, in a small quantity of water, and boiling
it for a long while in contact with the air. The ex-
tract will gradually fall down in the form of an insolu-
ble power, and the sugar will remain in solution.

If tannin exist in the first solution made by cold
water, its separation is easily effected by th(J process
described page 83. The solution of isinglass must be
gradually added, to prevent the existence of an excess
of animal jelly in the solution, which might be mista-
ken for mucilage.

When the vegetable substance, the subject of ex-
periment, will afford no more principles to cold water^
it must be exposed to boiling water. This will unite
to starch if there be any, and may likewise take up

t 109, ]

more sugar, extract, and tannin, provided they be in-
timately combined with the other principles of the
compound.

The mode of separating starch is similar to that
of separating mucilage.

If after the action of hot water any thing remain,
the action of boiling afcohol is then to be tried. This
will dissolve resinous matter ; the quantity of which
may be known by evaporating the alcohol.

The last agent that may be applied is ether,
which dissolves elastic gum, though the application is
scarcely ever necessary ; for if this principle be pre-
sent, it may be easily detected by its peculiar qualities.

If any fixed oil or wax exist in the vegetable
substance, it will separate during the process of boil-
ing in water, and may be collected. Any substance
not acted upon by water, alcohol, or ether, must be
regarded as woody fibre.

If volatile oils exist in any vegetable substances,
it is evident they may be procured, and their quantity
ascertained, by distillation.

When the quantity of fixed saline, alkaline, met-
allic, or earthy matter in any vegetable compound is
to be ascertained, the compound must be decomposed
by heat, by exposing it. if a fixed substance, in a cru-
cible, to a long continued red heat j and if a vola-
tile substance, by passing it through an ignited porce-
lain tube. The nature of the matter so produced,
may be learnt by applying the tests mentioned in
page 103,

C no ]

The only analyses in which the agricultural che-
mist can often wish to occupy himself, are those of
substances containing principally starch, sugar, gluten,
oils, mucilage, albumen, and tannin.

The two following statements will afford an idea
of the manner in which the results of experiments
may be arranged.

The first is a statement of the composition of
ripe peas, deduced from experiments made by Einhof ;
the second are of the products afforded by oak bark,
deduced from experiments conducted by myself.

parts,
3840 parts of ripe peas afford, of starch 1265

Fibrous matter analogous to starch, 1
with the coats of the peas J

A substance analogous to gluten 550

Mucilage ... - 249

Saccharine matter - - - 81

Albumen . . - - 66

Volatile matter - - - 540

Earthy phosphates - - - 1 1

Loss 229

1000 parts of dry oak bark, from a small tree
deprived of epidermis, contain.

Of woody fibre - - - . - 876

— tannin 57

— extract - - - - - 31

— mucilage 18

— matter rendered insoluble during evapor-^

ation, probably a mixture of albumen J> 9
and extract - - - - J

— loss, partly saline matter - - 30

C 111 ]

To ascertain the primary elements of the dif-
ferent vegetable principles, and the proportions in
which they are combined, different methods of analy-
sis have been adopted. The most simple are their de-
composition by heat, or their formation into new pro-
ducts by combustion.

When any vegetable principle is acted on by a
strong red heat, its elements become newly arranged.
Such of them as are volatile are expelled in the gas-
eous form ; and are either condensed as fluids, or re-
main permanently elastic. The fixed remainder is
either carbonaceous, earthy, saline, alkaline, or metal-
lic matter.

To make correct experiments on the decomposi-
tion of vegetable substances by heat, requires a com-
plicated apparatus, much time and labour, and all the
resources of the philosophical chemist ; but such re-
sults as are useful to the agriculturist may be easily
obtained. The apparatus necessary, is a green glass
retort, attached by cement to a receiver, connected
with a tube passing under an inverted jar of known
capacity, filled with water.* A given weight of the
substance is to be heated to redness in the retort over
a charcoal fire ; the receiver is to be kept cool, and
the process continued as long as any elastic matter is
generated. The condensible fluids will collect in the
receiver, and the fixed residuum will be found in the
retort. The fluid products of the distillation of vege-
table substances are principally water, with some

* Sec Fig. 14.

•C 112 3

acetous and mucous acids, and empyreumatic oil, or
tar, and in some cases ammonia. The gasses are car-
bonic acid gas, carbonic oxide, and carburetted hydi*©-
gene ; sometimes with olefiant gas, and hydrogene ;
and sometimes, but more rarely, with azote. Car-
bonic acid is the only one of those gasses rapidly ab-
sorbed by water ; the rest are inflammable ; olefiant
gas burns with a bright white light ; carburetted hy-
drogene with a light like wax , carbonic oxide with a
feeble, blue flame. The properties of hydrogene and
azote have been described in the last Lecture. The
specific gravity of carbonic acid gas, is to that of air
as 20.7 to 13.7, and it consists of one proportion of
carbon 11.4, and two of oxygene 30. The specific
gravity of gaseous oxide of carbon, is taking the same
standard 13.2, and it consists of one proportion of
carbon, and one of oxygene.

Xhe specific gravities of carburetted hydrogene and
olefiant gas are respectively 8 and 13 ; both 'contain
four proportions of hydrogene ; the first contains one
proportion, the second two proportions of carbon.

If the weight of the carbonaceous residuum be
added to the weight of the fluids condensed in the
receiver and they be subtracted from the whole weight
of the substance, the remainder will be the weight of
the gaseous matter.

The acetous and mucous acids, and the ammonia
formed are usually in very small quantitities ; and by
comparing the proportions of water and charcoal with
the quantity of the gasses, taking into account their
qualides, a general idea may be formed of the compo-
sition of the substance. The proportions of the ele-

C 113 3

ments in the greater number of the vegetable sub-
stances which can be used as food, have been already
ascertained by philosophical chemists, and have been
stated in the preceding pages ; the analysis by distil-
lation may, however, in some cases, be useful in esti-
mating the powers of manures in a manner that will
be explained in a future lecture.

The statements of the composition of vegetable
substances, quoted from M. M. Gay Lussac and Then-
ard were obtained by these philosophers by exposing
the substances to the action of heated hyper-oxy mu-
riate of potassa j a body that consists of potassium,
chlorine, and oxygene j and which afforded oxygene to
the carbon and the hydrogene. Their experiments
were made in a peculiar apparatus, and required great
caution, and were of a very delicate nature. It will
not' therefore be necessary to enter upon any details
of them.

It is evident from the whole tenor of the state-
ments which have been made, that the most essential
vegetable substances consist of hydrogene, carbon,
and oxygene in different proportions generally alone,
but in some few cases combined with azote. The
acids, alkalies, earths, metallic oxides, and saline com-
pounds, though necessary in the vegetable ceconomy,
must be considered as of less importance, particularly
in their relation to agriculture, than the other princi-
ples : and as it appears from M. de Saussure's table,
and from other experiments, they differ in the same
species of vegetable when it is raised on different soils.

Q

[ 114 J

M. M. Gay Lussac and Thenard have deduced
three propositions, which they have called laws from
their experiments on vegetable substances. The first
is, " that a vegetable substance is always acid when-
ever the oxygene it contains is to the hydrogene in a
greater proportion than in water/'

The second^ '^ that a vegetable substance is always
resinous or oily or spirituous whenever it contains
oxygene in a smaller proportion to the hydrogene than
exists in water."

The third, " that a vegetable substance is neither
acid nor resinous ; but is either saccharine or mucila-
ginous, or analogous to woody fibre or starch, when-
ever the oxygene and hydrogene in it are in the same
proportions as in water."

New experiments upon other vegetable sub-
stances, besides those examined by M. M. Gay Lussac
and Thenard, are required before these interesting
conclusions can be fully admitted. Their researches
establish, however, the close analogy between several
vegetable compounds differing in their sensible quali-
ties, and combined with those of other chemists, offer
simple explanations of several processes in nature and
art, by which different vegetable substances are con^
verted into each other, or changed into new com^
pounds.

Gum and sugar afford nearly the same elements
by analysis : and starch differs from them only in con-
taining a little more carbon. The peculiar properties
of gum and sugar must depend chiefly upon the dif-
ferent arrangement, or degree of condensation of their

elements ; and it would be natural to conceive from
the composition of these bodies, as well as that of
starch that all three would be easily convertible one
into the other ; which is actually the case.

At the time of the ripening of corn, the saccha-
rine matter in the grain, and that carried from the sap
vessels into the grain, becomes coagulated, and forms
starch. And in the process of malting, the converse
change occurs. The starch of grain is converted into
sugar. As there is a little absorption of oxygene, and a
formation of carbonic acid in this case, it is probable
that the starch loses a little carbon, which combines
with the oxygene to form carbonic acid ; and probably
the oxygene tends to acidify the gluten of the grain,
and thus breaks down the texture of the starch ; gives
a new arrangement to its elements, and renders it so-
luble in water.

Mr. Cruikshank, by exposing syrup to a sub-
stance named phosphuret of lime, which has a great
tendency to decompose water, converted a part of the
sugar into a matter analogous to mucilage. And M.
KirchhofF, recently, has converted starch into sugar by
a very simple process, that of boiling in very diluted
sulphuric acid. The proportions are 100 parts of
starch, 400 parts of water, and 1 part of sulphuric
acid by weight. This mixture is to be kept boiling
for 40 hours ; the loss of water by evaporation being
supplied by new quantities. The acid is to be neu-
tralized by lime ; and the sugar crystallized by cool*
ing. This experiment has been tried with success by
many persons. Dr. Tuthill, from a pound and a half

[ 116 J

of potatoe starch, procured a pound and a quarter of
crystalline, brown sugar ; which he conceives posses-
sed properties intermediate between cane sugar, and
grape sugar.

It is probable that the conversion of starch into
sugar is effected merely by the attraction of the acid
for the elements of sugar ; for various experiments
have been made, which prove that the acid is not de-
composed, and that no elastic matter is set free ; pro-
bably the colour of the sugar is owing to the disen-
gagement, or new combination of a little carbon, the
slight excess of which, as has been just stated, consti-
tutes the only difference perceptible by analysis be-
tween sugar and starch.

M. Bouillon la Grange, by slightly roasting starch
has rendered it soluble in cold water ; and the solu-
tion evaporated afforded a substance, having the
characters of mucilage.

Gluten and albumen differ from the other vege-
table products, principally by containing azote. When
gluten is kept long in water it undergoes fermenta-
tion ; ammonia (which contains its azote) is given off
with acetic acid : and a fatty matter, and a substance
analogous to woody fibre remain.

Extract, tannin, and gallic acid, when their solu-
tions are long exposed to air, deposit a matter similar
to woody fibre j and the solid substances are render-
ed analogous to woody fibre by slight roasting ; and in
these cases it is probable that part of their oxygene
and hydrogene is separated as water.

[ 117 ]

All the other vegetable principles differ from the
vegetable acids in containing more hydrogene and car-
bon, 'or less oxygene ; many of them therefore are
easily converted into vegetable acids by a mere sub-
traction of some proportions of hydrogene. The ve-
getable acids, for the most part, are convertible into
each other by easy processes. The oxalic contains
most oxygene ; the acetic the least : and this last sub-
stance is easily formed by the distillation of other ve-
getable substances, or by the action of the atmosphere
on such of them as are soluble in water ; probably
by the mere combination of oxygene with hydrogene
and carbon, or in some cases by the subtraction of a
portion of hydrogene.

Alcohol, or spirits of wine, has been often men-
tioned in the course of these Lectures. This sub-
stance was not described amongst the vegetable princi-
ples, because it has never been found ready formed in
the organs of plants. It is procured by a change in
the principles of saccharine matter, in a process called
vinous fermentation.

The expressed juice of the grape contains sugar^
mucilage, gluten, and some saline matter, principally
composed of tartaric acid : when this juice, or musty
as it is commonly called, is exposed to the tempera-
ture of about 70°, the fermentation begins ; it be-
comes thick and turbid ; its temperature increases, and
carbonic acid gas is disengaged in abundance. In a
few days the fermentation ceases ; the solid matter
that rendered the juice turbid falls to the bottom, and
it clears j the sweet taste of the fluid is in great mea-
sure destroyed, and it is become spirituous.

C 118 2

Fabroni has shewn that the gluten in must is
essential to fermentation ; and that chemist has made
saccharine matter ferment, by adding to its solution
in water, common vegetable gluten and tartaric acid.
Gay Lussac has demonstrated that must will not fer-
ment when freed from air by boiling, and placed out
of the contact of oxygene , but that fermentation be-
gins as soon as it is exposed to the oxygene of air, a
little of that principle being absorbed ; and that it then
continues independent of the presence of the atmos-
phere.

In the manufacture of ale and porter, the sugar
formed during the germination of barley is made to
ferment by dissolving it in water with a little yeast,
which contains gluten in the state proper for produc-
ing fermentation, and exposing it to the requisite tem-
perature ; carbonic acid gas is given off as in the
fermentation of must, and the liquor gradually be-
comes spirituous.

Similar phaenomena occur in the fermentation of
the sugar in the juice of apples, and other ripe fruits.
It appears that fermentation depends entirely upon a
new arrangement of the elements of sugar ; part of
the carbon uniting to oxygene to form carbonic acid,
and the remaining carbon, hydrogene, and oxygene
combining as alcohol ; and the use of the gluten or
yeast, and the primary exposure to air seems to be to
occasion the formation of a certain quantity of car-
bonic acid ; and this change being once produced is
continued ; its agency may be compared to that of a
spark in producing the inflammation of gunpowder ^

C "9 ]

the increase of temperature occasioned by the forma-
tion of one quantity of carbonic acid occasions the
combination of the elements of another quantity.

The results obtained by different chemists in ex-
periments on the analysis of alcohol differ so much,
that no general conclusions can be drawn from them.
If it be supposed that one proportion of carbonic acid
is formed in the fermentation of sugar ; then accord-
ing to Dr. Thomson's analysis of sugar, which gives
its composition as 3 proportions of carbon, 4 of oxy-
gene, and 8 of hydrogene, alcohol would consist of
2 proportions of carbon, 2 of oxygene, and 8 of hy-
drogene ; and it might be considered as containing the
same elements as two proportions of olefiant gas, with
two proportions of oxygene.

Alcohol in its purest known form, is a highly
inflammable liquid, of specific gravity 796, at the
temperature of 60° ; it boils at about 170o Fahrenheit.
This alcohol is obtained by repeated distillation of the
strongest common spirit from the salt called by che-
mists muriate of lime, it having been previously heat-
ed red hot.

The strongest alcohol obtained by the distillation
of spirit without salts, has seldom a less specific gravi-
ty than 825 at 60"; and it contains, according to
Lowitz's experiments, 89 parts of the alcohol of 796,
and 11 parts of water. The spirit established 2iS proof
spirit by act of parliament passed in 1762, ought to
have the specific gravity of 916; and this contains
nearly equal weights of pure alcohol and water.

C 120 ]

The alcohol in fermented liquors is in combina-
tion with water, colouring matter, sugar, mucilage,
and the vegetable acids. It has been often doubted
whether it can be procured by any other process than
distillation ; and some persons have even supposed
that it is formed by distillation. The recent experi-
ments of Mr. Brande are conclusive against both
these opinions. That gentleman has shewn that the
colouring and acid matter in wines may be, for the
most part, separated in a solid form by the action of a
solution of sugar of lead (acetate of lead), and that the
alcohol may be then obtained by abstracting the water
by means of hydrate of potassa or muriate of lime,
without artificial heat.

The intoxicating powers of fermented liquors
depend on the alcohol that they contain ; but their
action on the stomach is modified by the acid, saccha-
rine, or mucilaginous substances they hold in solu-
tion. Alcohol probably acts with more efficacy when
it is most loosely combined ; and its energy seems to
be impaired by union with large quantities of water,
or with sugar or acid, or extractive matter.

The following table contains the results of Mr.
Brande's experiments on the quantity of alcohol of
825 at 60°,. in different fermented liquors.

121

1

Proportion of

Proportion of

Wine.

Alcohol, per

Wine.

Alcohol, per

Cent, by Mea-

Cent, by Mea-

sure.

sure.

Port - . -

31,40

White Hermitage -

17,43

Ditto -

22,30

Red Hermitage

12,32

Ditto - - -

23,39

Hock -

14,37

Ditto -

23,71

Ditto

8,88

Ditto '-

24,29

Vinde Grave -

12,80

Ditto - ,-

25,83

Frontignac

12,79

Madeira

19,34

Coti Roti

12.32

Ditto

21,40

Rousiilon

17,26

Ditto

23,93

Cape Madeira

18,11

Ditto

34,42

Cape Muschat

18,25

Sherry -

18,25

Constantia

19,75

Ditto

18,79

Tent

13,30

Ditto

19,81

Sheraaz

15,52

Ditto

19,83

Syracuse

15.23

Claret -

12,91

Nice . - -

14,63

Ditto

14,08

Tokay -

9,88

Ditto

16,32

Raisin Wine -

25.T7

Calcavella

18.10

Grape Wine -

18.11

Lisbon -

18,94

Currant Wine

20.55

Malaga -

17,26

Gooseberry Wme -

11,84

Bucellas

18,49

Elder Wine -

' 9,87

Red Madeira -

18.40

Cyder -

9,87

Malmsey Madeira -

16,40

Perry -

9,87

Marsala

25.87

Brown Stout -

6,80

Ditto

17,26

Ale - - -

8,88

Red Champagne

11,30

Brandy -

53,39

White Champagne -

12,80

Rum

53,68

Burgundy

14,53

Hollands

51,60

Ditto . . -

11,95

The spirits distilled from different fermented
liquors differ in their flavour : for peculiar odorous
matter, or volatile oils, rise in most cases with the al-
cohol. The spirit from malt usually has an empy-
reumatic taste like that of the oil, formed by the dis-
tillation of vegetable substances. The best brandies
seem to owe their flavour to a peculiar oily matter,
formed probably by the action of the tartaric acid on
alcohol ; and rum derives its characteristic taste from
a principle in the sugar cane. All the common spirits
may, I find, be deprived of their peculiar flavour by
repeatedly digesting them with a mixture of well burnt

t 122 2

charcoal and quicklime ; they then afford pure alco-
hol by distillation. The cognac brandies, I find, con-
tain vegetable prussic acid, and their flavour may be
imitated by adding to a solution of alcohol in water of
the same strength, a few drops of the ethereal oil of
wine produced during the formation of ether,* and a
similar quantity of vegetable prussic acid procured
from laurel leaves or any bitter kernels.

I have mentioned eiber in the course of this Lec-
ture ; this substance is procured from alcohol by distil-
ling a mixture of equal parts of alcohol and sulphuric
acid. It is the lightest known liquid substance, being
of specific gravity 632 at 60°. I| i& very volatile, and
rises in vapour even by the heat of the body. It is
highly inflammable. In the formation of ether it is
most probable that carbon and the elements of water
are separated from the alcohol, and that ether differs
from alcohol in containing less oxygene and carbon ;
but its composition has not yet been accurately ascer-
tained. Like alcohol it possesses intoxicating powers.

A number of the changes taking place in the ve-
getable principles depend upon the separation of oxy*
gene and hydrogene as water from the compound ;
but there is one of very great importance, in which a
new combination of the elements of water is the prin-
cipal operation. This is in the manufacture of bread.
When any kind of flour, which consists principally of

* In tbe process of the distillation of alcohol and sulphuric acid after the ether
is procured ; by a higher degree of heat, a yellow fluid is produced, which is the
substance in question. It has a fragrant smell and an agreeable taste.

[ 123 ]

starch, is made into a paste with water, and immedi-
ately and gradually heated to about 440°, it increases
in werght, and is found entirely altered in its proper-
ties ; it has lost its solubility in water, and its power
of being converted into sugar. In this state it is un-
leavened bread.

When the flour of corn or the starch of potatoes,
mixed with boiled potatoes, is made into a paste with
water, kept warm, and suffered to remain 30 or 40
hours, it ferments, carbonic acid gas is disengaged
from it, and it becomes filled witli globules of elastic
fluid. In this state it is raised dough, and affords by
baking, leavened bread ; but this bread is sour and
disagreeable to the taste ; and leavened bread for use
is made by mixing a little dough, that has fermented,
with new dough, and kneading them together, or by
kneading the bread with a small quantity of yeast.

In the formation of wheaten bread more than 1-4
of the elements of water combine with the flour ;
more water is consolidated in the formation of bread
from barley, and still more in that from oats ; but
the .gluten in wheat, being in much larger quantity
than in other grain, seems to form a combination with
the starch and water, which renders wheaten bread
more digestible than the other species of bread.

The arrangement of many of the vegetable prin-
ciples in the different parts of plants has been inciden-
tally mentioned in this Lecture ; but a more particular
statement is required to afford just views of the rela-
tion between their organization and chemical constitu-
tion, which is an object of great importance. The

C 124 ]

tubes and hexagonal cells in the vascular system of
plants are composed of woody fibre ; and when they
are not filled with fluid matter they contain some of
the solid materials which formed a constituent part of
the fluids belonging to them.

In the roots, trunk, and branches, the bark, al-
burnum, and heartwood, the leaves and flowers ; the
great basis of the solid parts Js woody fibre. It forms
by far the greatest part of the heart wood and bark ;
there is less in the alburnum, and still less in the leaves
and flowers. The alburnum of the birch contains so
much sugar and mucilage, that it is sometimes used
in the North of Europe as a substitute for bread. The
leaves of the cabbage, broccoli, and seacale, contain
much mucilage, a little saccharine matter and a little
albumen. From a 1 OOO parts of the leaves of com-
mon cabbage I obtained 41 parts of mucilage, 24 of
sugar, and 8 of albuminous matter.

In bulbous roots, and sometimes in common
roots, a large quantity of starch, albumen, and mucil-
age, are often found deposited in the vessels ; and
they are most abundant after the sap has ceased to
flow : and afford a nourishment for the early shoots
made in spring. The potatoe is the bulb that contains
the largest quantity of soluble matter in its cells and
vessels ; and it is of most importance in its appli-
cation as food. Potatoes in general afford from ' to 4
their weight of dry starch. From 100 parts of the
common Kidney potatoes^ Dr. Pearson obtained from
32 to 28 parts of meal, which contained from 23 to
20 of starch and mucilage : and 100 parts of the Ap-

C 125 ]

pie potatoe in various experiments, afforded me from
18 to 20 parts of pure starch. From five pounds of
the variety of the potatoe called Captain hart^ Mr.
Skrimshire, jun. obtained 12 oz. of starch, from the
same quantity of the Rough red potatoe 104 oz., from
the Moult on white 11t, from the Yorkshire kidney
10^ oz., from Hundred eyes 9 oz., from Purple red 81,
from Ox noble 8t. The other soluble substances in
the potatoe are albumen and mucilage.

From the analysis of EinhofFit appears that 7680
parts of potatoes afford

Of starch - - - - 1153

— • Fibrous matter analogous to starch 540

— Albumen - - . - 107

— Mucilage in the state of a saturated")

solution . . . . ^^^^

2112
So that a fourth part of the weight of the potatoe at
least may be considered as nutritive matter.

The turnip, carrot, and parsnip, afford principally
saccharine, mucilaginous, and extractive matter. I
obtained from 1000 parts of common turnips 7 parts
of mucilage, 34 of saccharine matter, and nearly 1
part of albumen. 1000 parts of carrots furnished
95 parts of sugar. 3 parts of mucilage, and ^ part of
extract ; 1000 parts of parsnip afforded 90 parts of
saccharine matter, and 9 parts of mucilage. The
Walcheren or white carroty gave in 1000 parts, 98
parts of sugar, 2 parts of mucilage, and 1 of extract.

t 126 3

Fruits, In the organization of their soft parts,
approach to the nature of bulbs. They contain a cer-
tain quantity of nourishment laid up in their cells for
the use of the embryon plant ; mucilage, sugar, starch
are found in many of them often combined with vege-
table acids. Most of the fruit trees common in Bri-
tain have been naturalized on account of the saccha-
rine matter they contain, which^ united to the vegeta-
ble acids and mucilage, renders them at once agreea-
ble to the taste and nutritive.

The value of fruits for the manufacture of fer-
mented liquors may be judged of from the specific
gravity of their expressed juices. The best cyder and
perry are made from those apples and pears that af-
ford the densest juices ; and a comparison between
different fruits may be made with tolerable accuracy
by plunging them together into a saturated solution of
salt, or a strong solution of sugar ; those that sink
deepest will afford the richest juice.

Starch or coagulated mucilage forms the greatest
part of the seeds and grains used for food ; and they
are generally combined with gluten, oil, or albumin-
ous matter. In corn, with gluten, in peas and beans,
with albuminous matter ; and in rape-seed, hemp-
seed, linseed, and the kernels of most nuts, with oils.

I found lOO parts of good full grained wheat
sown in autumn to afford

Of Starch - - - 77
— Gluten - - • 19
100 parts of wheat sown ik spring.

Of starch * - • 70
*— Gluten ... 24

[ 127 ] '

100 parts of Barbary wheat,

Of starch - - - 47

— Gluten - < 23
100 parts of Sicilian wheat.

Of starch - . . 75

— Gluten - - . 21

I have examined diiferent specimens of North
American wheat, all of them have contained rather
more gluten than the British. In general the wheat
of warm climates abounds more in gluten, and in in-
soluble parts j and it is of greater specific gravity,
harder, and more difficult to grind.

The wheat of the south of Europe, in conse-
quence of the larger quantity of gluten it contains, is
peculiary fitted for making macaroni, and other pre-
parations of flower in which a glutinous quality is con- 'S
sidered as an excellence.

In some experiments made on barley, I obtained
from 100 parts of full and fair Norf®lk barley.
Of Starch ... 79

— Gluten . , ^ 6

— Husk - . - 8
The remaining 7 parts saccharine matter.

EinhoiF has published a minute analysis of barley
meal. He found in 3840 parts.

Of volatile matter . - . 360

— Albumen .... 44

— Saccharine matter - * 200

— Mucilage .... 176

— Phosphate of lime, with some albumen 9

— Gluten * - - - 135

C 128 y

Of Husk, with some gluten and starch 260
■ — Starch not quite free from gluten 2580

— Loss 78

Rye afforded to Einhoff, in 3840 parts ; 2520

meal, 930 husk, and 390 moisture j and the same
quantity of meal analysed gave.

Of Starch . - - . 2345

— Albumen - - - - 126
~ — Mucilage - - - - 426

— Saccharine matter - - 126

— Gluten not dried - - 364
Remainder husk and loss.

I obtained from 100 parts of rye, grown in Suf-
folk, 61 parts of starch, and 5 parts of gluten.

100 parts of oats, from Sussex, afforded me 59
parts of starch, 6 of gluten, and 2 of saccharine mat-
ter,

1000 parts of peas, grown in Norfolk, afforded
me 501 parts of starch, 22 parts of saccharine matter,
35 parts of albuminous matter and 16 parts of ex-
tract, which became insoluble during evaporation of
the saccharine fluid.

From 3840 parts of marsh beans CViciafabaJy
Einhoff obtained,

Of Starch - - - - 1312

— Albumen . - - - 31

— other matters which may be con-"]

ceived nutritive : such as gum- j

1 r^ ^1204

my, starchy, fibrous matter an- r

alogous to animal matter J

C 129 ]

The same quantity of kidney beans {Fhaseolus
'vulgaris) afforded,

Of matter analogous to starch - 1 805

— Albumen and matter approaching 1

to animal matter in its nature j ^"^^

— Mucilage - - - - 799
From 3840 parts of lentiles he obtained 1260

parts of starch, and 14/33 of a matter analogous to
animal matter.

The matter analogous to animal matter is des-
cribed by Einhoff ; as a glutinous substance insoluble
in water ; soluble in alcohol when dry, having the ap-
pearance of glue j probably a peculiar modification of
gluten.

From 16 parts of hemp-seeds Bucholz obtained
3 parts of oil, Si parts of albumen, about 1 - of sac-
charine and gummy matter. The insoluble husks
and coats of the seeds weighed 6^ parts.

The different parts of flowers contain different
substances : the pollen, or impregnating dust of the
date, has been found by Fourcroy and Vauquelin to
contain a matter analogous to gluten, and a soluble
extract abounding in malic acid. Link found in the
pollen of the hazle tree, much tannin and gluten.

Saccharine matter is found in the nectarium of

flowers, or the receptacles within the corolla, and by

tempting the larger insects into the flowers, it renders

the work of impregnation more secure ; for the pollen

is often by their means applied to the stigma ; and

this is particularly the case when the male and female

organs are in different flowers or different plants.

s

A.

[ ISO 3

It has been stated that the fragrance of flowers
depends upon the volatile oils they contain ; and these
oils, by their constant evaporation, surround the
flower with a kind of odorous atmosphere ; which, at
the same time that it entices larger insects, may pro-
bably preserve the parts of fructification from the ra-
vages of the smaller ones. Volatile oils, or odorous
substances, seem particularly destructive to these mi-
nute insects and animalcules which feed on the sub-
stance of vegetables ; thousands of aphides may be
usually seen in the stalk and leaves of the rose ; but
none of them are ever observed on the flower. Cam-
phor is used to preserve the collections of naturalists.
The woods that contain aromatic oils are remarked
for their indestructibility ; and for their exemption
from the attacks of insects : this is particularly the
case with the cedar, rose- wood, and cypress. The
gates of Constantinople, which were made of this last
wood, stood entire from the time of Constantine, their
founder, to that of Pope Eugene IV. a period of 1 100
years.

The petals of many flowers afford saccharine and
mucilaginous matter. The white lily yields mucilage
abundantly ; and the orange lily a mixture of mucil-
age and sugar ; the petals of the convolvulus afford
sugar, mucilage, and albuminous matter.

The chemical nature of the colouring matters of
flowers has not as yet been subject to any very accu-
rate observation. These colouring matters, in gen-
eral, are very transient, particularly the blues and
reds y alkalies change the colours of most flowers to
green, and acids to red. An imitation of the colour-

C 131 D

ing matter may be made by digesting solutions of gall-
nuts with chalk: a green fluid is obtained, which be-
comes red by the action of an acid; and has its green
colour restored by means of alkalies.

The yellow colouring matters of flowers are the
most permanent; the carthamus contains a red and a
yellow colouring matter; the yellow colouring matter
is easily dissolved by water, and from the red, rouge
is prepared by a process which is kept secret.

The same substances as exist in the solid parts of
plants are found in their fluids, with the exception of
woody fibre. Fixed and volatile oils containing resin
or camphor, or analogous substances in solution exist
in the cylindrical tubes belonging to a number of
plants. Different species of Euphorbia emit a milky
juice, which when exposed to air deposit a substance
analogous to starch, and another similar to gluten.

Opium, gum elastic, gamboge^ the poisons of the
Upas Antiar and Tieute, and other substances that
exude from plants, may be considered as peculiar
juices belonging to appropriate vessels.

The sap of plants, in general, is very compound
in its nature; and contains most saccharine, mucilagin-
ous, and albuminous matter in the alburnum; and
most tannin and extract in the bark. The cambium,
which is the mucilaginous fluid found in trees between
the wood and the bark, and which is essential to the
formation of new parts, seems to be derived from these
two kinds of sap; and probably is a combination of
the mucilaginous and albuminous matter of one, with
the astringent matter of the other, in a state fitted to
become organized by the separation of its watery parts

■%,

C 132 ]

The alburnous saps of some trees have been che-
mically examined by Vauquelin. He found in those
of the elm, beech, yoke elm, hornbeam and birch, ex-
tractive and mucilaginous matter, acetic acid combin-
ed with potassa or Ume. The solid matter afforded
by their evaporation yielded an ammoniacal smell, pro-
bably owing to albumen; the sap of the birch afforded
saccharine matter.

Deyeux in the sap of the vine and the yoke elm
has detected a matter analogous to the curd of milk.
I found a substance similar to albumen in the sap of
the walnut tree.

I found the juice which exudes from the vessels
of the marshmallow when cut, to be a solution of
mucilage.

The fluids contained in the sap vessels of wheat
and barley, afforded in some experiments which I made
on them, mucilage, sugar, and a matter which coag-
ulated by heat; which last was most abundant in wheat.
The following table contains a statement of the
quantity of soluble or nutritive matters contained in
varieties of the different substances that have been
mentioned, and of some others which are used as arti-
cles of food, either for man or cattle. The analyses
are my own; and were conducted with a view to a
knowledge of the general nature and quantity of the
products, and not of their intimate chemical composi-
tion. The soluble matters afforded by the grasses,
except that from the fiorin in winter, were obtained
by Mr. Sinclair, gardener to the duke of Bedford,
from given weights of the grasses cut when the seeds
were ripe; they were sent to me by his Grace's desire

#

c

133

]

for chemical examination; and form part of the results
of an important and extensive series of experiments on
grasses, made by direction of the Duke, at Woburn
Abbey, the full details of which I shall hereafter have
the pleasure of stating.

Table of the Quantities of soluble or nutritive Matters
afforded by 1000 parts of different vegetable Sub-
stances,

Cm d

W (U c

°l

w

3

iJS.2

>> «

u

*j

U3

15 B, *k

•S'S

o

<

6 SS

-'Vegetables or vegetable

H

oi

o-t

Substance.

.S5

l^

3

-c 2.

u

0

^U

^g

$,

Middlesex wheat, average

crop

955

765

—

190

Spring wheat

940

700

—

240

Mildewed wheat of i805

210

178

—

32

Blighted wheat of 1804

650

520

—

130

Thick-skinned Sicilian

wheat of 1810

'iSS

725

»

230

Thin-skinned Sicilian

wheat of 1810 -

961

722

«.

239

Wheat from Poland -

950

750

—

200

North American wheat

955

730

.

225

Norfolk barley -

920

790

70

60

Oats from Scotland «

743

641

15

87

Rye from Yorkshire -

792

645

38

109

Common bean

570

426

_

103

41

Dry peas -

574

501

22

35

16

Potatoes - - ^

from 260

from 200

from 20

from 40

to 200

to 155

to 15

to 30

Linseed cake

151

123

11

1'.

Red beet

148

14

121

13

' White beet

136

13

119

4

Parsnip

99

9

90

Carrots

98

3

95

Common turnips -

42

7

34

1

Swedish turnips .

64

9

51

2

2

Cabbage

73

41

24

3

Broad-leaved clover -

39

31

3

2

3

Long-rooted clover

39

SO

4

3

2

White clover

32

29

1

3

5

Sainfoin

39

28

2

3

6

Lucerne

23

18

1

_

4

Meadow fox-tail grass

33

24

3

^

6

Perennial rye grass

39

26

4

_

5

Fertile meadow grass •

78

65

6

_

7

Roughtsh meadow grass

39

29

5

__

6

Crested dog's-tail grass

35

28

3

_

4

Spiked fescue grass -

19

15

2

^

2

Sweet-scented soft grass

82

72

4

^

6

Sweet-scented vernal grass

50

43

4

__

3

Fiorin

54

46

5

I

2

Fiorin cut in winter -

1 76

64

8

1

3

C 134 3

All these substances were submitted to experi-
ment green, and in their natural states. It is probable
that the excellence of the different articles as food
will be found to be in a great measure proportional to
the quantities of soluble or nutritive matters they
afford; but still these quantities cannot be regarded as
absolutely denoting their value. Albuminous or glutin-
ous matters have the characters of animal substances;
sugar is more nourishing, and extractive matter less
nourishing, than any other principles composed of car-
bon, hydrogene, and oxygene. Certain combinations
likewise of these substances may be more nutritive
than others.

I have been informed by Sir Joseph Banks, that
the Derbyshire miners in winter, prefer oat cakes to
wheaten bread; finding that this kind of nourish-
ment enables them to support their strength and per-
form their labour better. In summer, they say oat
cake heats them, and they then consume the finest
wheaten bread they can procure. Even the skin of
the kernel of oats probably has a nourishing power,
?md is rendered partly soluble in the stomach with the
starch and gluten. In most countries of Europe, ex-
cept Britain, and in Arabia, horses are fed with barley
mixed with chopped straw; and the chopped straw
seems to act the same part as the husk of the oat. In
the mill 14lbs. of good wheat yield on an average
ISlbs. of flour, the same quantity of barley 12lbs. and
of oats only 8lbs,

In the south of Europe, hard or thin-skinned
wheat is in higher estimation, than soft or thick-skin-

C 135 ]

ned wheat: the reason of which is obvious, from the
larger quantity of gluten and nutritive matter it con-
tains. I have made an analysis of only one specimen
of thin-skinned wheat, so that other specimens may
possibly contain more nutritive matter than that in the
Table: the Barbary and Sicilian wheats, before refer-
red to, were thick-skinned wheats, in England the dif-
ficulty of grinding thin-skinned wheat is an objection;
but this difficulty is easily overcome by moistening the
corn.*

• For the following note on this subject I am indebted to the kindness of the
Right Hon. Sir Joseph Batiks, Bart. K. B.
Information receivtd from John yeffery, Esq. His Majesty's Consul General at Lisbon,

in AnsiBer to Qxieriei transmitted to him, from the Comm. of P. C.for "Trade,

dated yan. I2,l8l2.

To grind hard corn with the ralll-stones used in England, the wheat must be
well screened, then sprinkled with water at the miller's discretion, andlaid in heaps
and frequently turned and thoroughly mixed, which will soften the husk so as to
make it separate from the flour in grinding, and of course give the flour a brighter
colour; otherwise the flinty quality of the wheat, and the thinness of the skin will
prevent its separation, and will render the flour unfit for making into bread.

I am informed by a miller of considerable experience, and who works his mills
entirely with the stones from England or Ireland, that he frequently prepares the
hard Barbary corn by immersing it in water in close wicker baskets, and spreading
it thinly on a floor to dry; much depends on the judgment and skill of the miller ia.
preparing the corn for the mill according to its relative quality, I beg to observe,
that it is not from this previous process of Wetting the corn that the weight in th©
flour of hard corn is encreased; bat from its natural quality it imbibes considerably
more water in making it into bread. The millstones must not be cut too deep, but
the furrows very fine, and picked in the usual way. The mills should work with less
velocity in grinding hard corn than with soft, and set to work at first with soft
corn, till the mill ceases to work well; then put on the hard corn. Hard wheat al-
ways sells at a higher price in the market than soft wheat, on an average of ten to
fifteen per cent; as it produces more float in proportion, and less bran than the
soft corn.

Flour made from hard wheat is more esteemed than what is made froiji soft
cqfn and t>oth sorts are applied to every pnrpo^.

136

LECTURE IV.

On Soils: their constituent Parts. On the analysis of
Soils. Of the Uses of the Soil Of the Rocks and
Strata found beneath Soils. Of the improvemep
of Soil.

No subjects are of more importance to the far-
mer than the nature and improvement of soils; and no
parts of the doctrines of agriculture are more capable
of being illustrated by chemical enquiries.

Soils are extremely diversified in appearance and
quality; yet as it was stated in the introductory Lec-
ture, they consist of different proportions of the same
elements; which are in various states of chemical com-
bination, or mechanical mixture.

The substances which constitute soils have been
already mentioned. They are certain compounds of
the earths, silica, lime, alumina, magnesia, and of the
oxides of iron and manganesum; animal and vegetable
matters in a decomposing state, and saline, acid or al-
kaline combinations.

In all chemical experiments on the composition
of soils connected with agriculture, the constituent

The fiour of hard wheat is in general superior to that made from soft; and
there is no difference in the processof making them into bread; but the flour from
hard wheat will imbibe and retain more water in making into bread; and will con-
sequently produce more weight of bread: it is the practice here, and which I am
persuaded it would be adviseable to adopt in England, to make bread with flour of
hard and soft wheat, which, by being mixed, will make the bread much better.

(Signed) JOHN JEFFERY.

C 137 j

parts obtained are compounds; and they act as com^-
pounds in nature: it is in this state, therefore, that I
shall describe their characteristic properties.

1. Silica^ or the earth of Jl'mts^ in its pure and
crystallized form, is the substance known by the name
of rock crystal, or Cornish diamond. As it is procur-
ed by chemists, it appears in the form of a white
impalpable powder. . It is not soluble in the common
acids, but dissolves by heat in fixed alkaline lixivia.
It is an incombustible substance, for it is saturated
with oxygene. I have proved it to be a compound of
oxygene, and the peculiar combustible body which I
have named silicum; and from the experiments of Ber-
zelius, it is probable that it contains nearly equal
weights of these two elements.

2. The sensible properties of lime are well
known. It exists in soils usually united to carbonic
acid; which is easily disengaged from it by the attrac-
tion of the common acids. It is sometimes found
combined with the phosphoric and sulphuric acids.
Its chemical properties and agencies in its pure state
will be described in the Lecture on manures obtained
from the mineral kingdom. It is soluble in nitric and
muriatic acids, and forms a substance with sulphuric
acid, difficult of solution, called gypsum. It is not
soluble in alkaline solutions. It consists of one pro-
pordon 40 of the peculiar metallic substance, which I
have named calcium; and one proportion 15 of oxy-*
gene.

3. Alumina exists in a pure and crystallized state
in the white sapphire, and united to a little oxide of

T

[ 138 ]

iron and silica in the other oriental gems. In the state
in which it is procured by chemists, it appears as a
white ppwder, soluble in acids and fixed alkaline li-
quors. From my experiments, it appears that alumi-
na consists of one proportion 33 of aluminum, and
one 15 of oxygene.

4. Magnesia exists in a pure crystallized state,
constituting a mineral like talc found in North Ame-
rica. In its common form it is the magnesia usta, or
calcined magnesia of druggists. It generally exists in
soils combined with carbonic acid. It is soluble in all
the mineral acids; but not in alkaline lixivia. It is dis-
tinguished from the other earths found in soils by its
ready solubility in solutions of alkaline carbonates,
saturated with carbonic acid. It appears to consist of
38 magnesmm and 15 oxygene.

5. There are two well known oxides of iron^ the
black and the brown. The black is the substance that
flies off when red hot iron is hammered. The brown
oxide may be formed by keeping the black oxide red
hot, for a long time in contact with air. The first
seems to consist of one proportion of iron 103, and
two of oxygene 30; and the second of one proportion
of iron 103, and three proportions of oxygene 45.
The oxides of iron sometimes exist in soils combined
with carbonic acid. They are easily distinguished from
other substances by their giving when dissolved in
acids a black colour to solution of galls, and a bright
blue precipitate to solution of prussiate of potassa and

iron.

6. The oxide of manganeswn is the substance com-
monly called manganese, and used in bleeching. It

[ 139 3

appears to be composed of one proportion of mangan-
esum 113, and three of oxygene 45. It is distinguish-
ed from the other substances found in soils, by its pro-
perty of decomposing muriatic acid, and converting it
into chlorine.

1, Vegetable and animal matters are known by their
sensible qualities, and by their property of being de-
composed by heat. Their characters may be learnt
from the details in the last Lecture.

8. The saline compounds found in soils, are com-
mon-salt, sulphate of magnesia, sometimes sulphate of
iron, nitrates of lime and of magnesia, sulphate of po-
tassa, and carbonates of potassa and soda. To des-
cribe their characters minutely will be unnecessary; the
tests, for most of them have been noticed p. 103.

The silica in soils is usually combined with alumi-
na and oxide of iron, or with alumina, lime, magnesia,
and oxide of iron, forming gravel and sand of differ-
ent degrees of fineness. The carbonate of lime is
usually in an impalpable form, but sometimes in the
state of calcareous sand. The magnesia, if not com-
bined in the gravel and sand of soil, is in a fine pow-
der united to carbonic acid. The impalpable part of
the soil, which is usually called clay or loam, consists
of silica, alumina, lime, and magnesia; and is^ in fact,
usually of the same composition as the hard sand, but
more finely divided. The vegetable or animal, mat-
ters, (and the first is by far the most common in soils)
exist in different states of decomposition. They are
sometimes fibrous, sometimes entirely broken down
and mixed with the soil»

£ 140 ]

To form a just idea of soils, it is necessary to
conceive different rocks decomposed, or ground into
parts and powder of different degrees of fineness;
some of their soluble parts dissolved by water, and
that water adhering to the mass, and the whole mixed
with larger or smaller quantities of the remains of ve-
getables and animals, in different stages of decay.

It will be necessary to describe the processes by
which all the varieties of soils may be analysed. I
shall be minute in these particulars, and, I fear, tedi-
ous; but the philosophical farmer will, I trust, feel the
propriety of full details on this subject.

The instruments required for the analysis of soils
are few, and but little expensive. They are a balance
capable of containing a quarter of a pound of com-
mon soil, and capable of turning when loaded, with
a grain; a set of weights from a quarter of a pound
Troy to a grain; a wire sieve, sufficiently coarse to ad-
mit a mustard seed through its apertures; an Argand
lamp and stand; some glass bottles; Hessian crucible;
porcelain, or queen's ware evaporating basons; a
Wedgewood pestle and mortar; some filtres made of
half a sheet of blotting paper, folded so as to contain a
pint of liquid, and greased at the edges; a bone knife,
and an apparatus for collecting and measuring aeriform
fluids.

The chemical substances or reagents required
for separating the constituent parts of the soil, have,
for the most part, been mentioned before: they are
muriatic acid (spirit of salt) ^ sulphuric acid, pure vola-
tile alkali dissolved in water, solution of prussiate of

C 141 ]

potash and iron, succinate of ammonia, soap lye, or
solution of potossa, solutions of carbonate of ammo-
nia, of muriate of ammonia, of neutral carbonate of
potash, and nitrate of ammoniac.

In cases when the general nature of the soil of a
field is to be ascertained, specimens of it should be
taken from different places, two or three inches below
the surface, and examined as to the similarity of their
properties. It sometimes happens, that upon plains
the whole of the upper stratum of the land is of the
same kind, and in this case, one analysis will be suffi-
cient ; but in vallies, and near the beds of rivers, there
are very great differences, and it now and then occurs
that one part ©fa field is calcareous, and another
part siliceous ; and in this case, and in analogous ca-
ses, the portions different from each other should be
separately submitted to experiment.

Soils when collected, if they cannot be imme-
diately examined, should be preserved in phials quite
filled with them, and closed with ground glass stop-
pers.

The quantity of soil most convenient for a perfect
analysis, is from two to four hundred grains. It
should be collected in dry weather, and exposed to
the atmosphere till it becomes dry to the touch.

The specific gravity of a soil, or the relation of
its weight to that of water, may be ascertained by in-
troducing into a phial, which will contain a known
quantity of water, equal volumes of water and of soil,
and this may be easily done by pouring in water till it
IS half full, and then adding the soil till the fluid rises

C 142 3

to the mouth ; the difference between the weight of
the soil and that of the water, will give the result.
Thus if the bottle contains four hundred grains of
water, and gains two hundred grains when half filled
with water and half with soil, the specific gravity of
the soil will be 2, that is, it will be twice as heavy as
water, and if it gained one hundred and sixty-five grains,
its specific gravity would be 1825, water being 1000.

It is of importance, that the specific gravity of a
soil should be known, as it affords an indication of
the quantity of animal and vegetable matter it con-
tains ; these substances being always most abundant
in the lighter soils.

The other physical properties of soils should
likewise be examined before the analysis is made, as
they denote, to a certain extent, their composition,
and serve as guides in directing the experiments.
Thus siHceous soils are generally rough to the touch,
and scratch glass when rubbed upon it ; ferruginous
soils are of a red or yellow colour j and calcareous
soils are soft.

1. Soils, though as dry as they can be made by
continued exposure to air, in all cases still contain a
considerable quantity of water, which adheres with
great obstinacy to the earths and animal and vegeta-
ble matter, and can only be driven off from them by
a considerable degree of heat. The first process of
analysis is, to free the given weight of soil from as
much of this water as possible, without in other res-
pects, affecting its composition ; and this may be done
by heating it for t^n or twelve minutes over an Ar-

[ 143 ] ' ♦

gand*s lamp, in a bason of porcelain, to a temperature
equal to 300 Fahrenheit ; and if a thermometer is not
used, the proper degree may be easily ascertained, by
keeping a piece of wood in contact with the bottom of
the dish ; as long as the colour of the wood remains
unaltered, the heat is not too high ; but when the
wood begins to be charred, the process must be stop-
ped. A small quantity of water will perhaps remain
in the soil even after this operation, but it always af-
fords useful comparative results ; and if a higher
temperature w^re employed, the vegetable or animal
matter would undergo decomposition, and in conse-
quence the experiment be wholly unsatisfactory.

The loss of weight in the process should be care-
fully noted, and when in four hundred grains of soil
it reaches as high as 50, the soil may be considered
as in the greatest degree absorbent, and retentive of
water, and will generally be found to contain much
vegetable or animal matter, or a large proportion of
aluminous earth. When the loss is only from 20 to
10, the land may be considered a& only slightly absor-
bent and retentive, and siliceous earth probably forms
the greatest part of it.

2. None of the loose stones, gravel, or large
vegetable fibres should be divided from the pure soil
till after the water is drawn off j for these bodies are
themselves often highly absorbent and retentive, and
in consequence influence the fertility of the land. The
next process, however, after that of heating, should be
their separation, which may be easily accomplished by
the sieve, after the soil has been gently bruised in a

[ 144 }

mortar. The weights of the vegetable fibres or wood,
and of the gravel and stones should be separately
noted down, and the nature of the last ascertained ;
if calcereous, they will effervesce with acids ; if sili-
ceous, they will be sufficiently hard to scratch glass ;
and if of the common alumihous class of stones, they
will be soft, easily cut with a knife, and incapable of
effervescing with acids.

3. The greater number of soils, besides gravel
and stones, contain larger or smaller proportions of
sand of different degrees of fineness ; and it is a neces-
sary operation, the next in the process of analysis, to
detach them from the parts in a state of more minute
division, such as clay, loam, marie, vegetable and ani-
mal matter, and the matter soluble in water. This
may be effected in a way sufficiently accurate, by boil-
ing the soil in three or four times its weight of water ;
and when the texture of the soil is broken down, and
the water cool ; by agitating the parts together, and
then suffering them to rest. In this case, the coarse
sand will generally separate in a minute, and the finer
in two or three minutes, whilst the highly divided earthy,
animal, or vegetable matter will remain in a state of me-
chanical supension for a much longer time ; so that by
pouring the water from the bottom of the vessel, after
one, two or three minutes, the sand will be principally
separated from the other substances, which, with the
water containing them, must be poured into a filtre,
and after the water has passed through, collected,
dried, and weighed. The sand must likewise be
weighed, and the respective quantities noted down.

[ 145 ]

The water of lixiviation must be preserved, as it will
be found to contain the saline and soluble animal or
vegetable matters, if any exist in the soil.

4. By the process of washing and filtration, the
soil is separated into two portions, the most important
of which is generally the finely divided matter. A
minute analysis of the sand is seldom or never neces-
sary, and its nature may be detected in the same man-
ner as that of the stones or gravel. It is always either
siliceous sand, or calcareous sand, or a mixture of
both. If it consist wholly of carbonate of lime, it will
be rapidly soluble in muriatic acid, with effervescence ;
but if it consist partly of this substance, and partly of
siliceous matter, the respective quantities may be as-
certained by weighing the residuum after the action of
the acid, which must be applied till the mixture has
acquired a sour taste, and has ceased to effervesce.
This residuum is the siliceous part: it must be washed,
dried, and heated strongly in a crucible; the difference
between the weight of it and the weight of the whole,
indicates the proportion of calcareous sand.

5. The finely divided matter of the soil is usually
very compound in its nature; it sometimes contains all
the f6ur primitive earths of soils, as well as animal and
vegetable matter; and to ascertain the proportions of
these with tolerable accuracy, is the most difficult part
of the subject.

The first process to be performed, in this part of
the analysis, is the exposure of the fine matter of the
soil to the action of muriatic acid. This substance
should be poured upon the earthy matter in an eva-

u

C 146 ]

porating bason, in a quantity equal to twice the weight
of the earthy matter; but diluted with double its volume
of water. The mixture should be often stirred, and
suffered to remain for an hour, or an hour and a half,
before it is examined.

If any carbonate of lime or of magnesia exist in
the soil, they will have been dissolved in this time by
the acid, which sometimes takes up likewise a little
oxide of iron; but very seldom any alumina.

The fluid should be passed through a filtre; the
solid matter collected, washed with rain water, dried
at a moderate heat, and weighed. Its loss will denote
the quantity of solid matter taken up. The washings
must be added to the solution, which if not sour to the
taste, must be made so by the addition of fresh acid,
when a little solution of prussiate of potassa and iron
must be mixed with the whole. If a blue precipitate
Occurs, it denotes the presence of oxide of iron, and
the solution of the prussiate must be dropped in till
no farther effect is produced. To ascertain its quan-
tity, it must be collected in the same manner as other
solid precipitates, and heated red; the result is oxide
of iron, which may be mixed with a little oxide of
manganesum.

Into the fluid freed from oxide of iron, a solu-
tion of neutralized carbonate of potash must be pour-
ed till all effervescence ceases in it, and till its taste and
smell indicate a considerable excess of alkaline salt.

The precipitate that falls down is carbonate of
lime; it must be collected on the filtre, and dried at a
heat below that of redness.

Xi

L 147 3

The remaining fluid must be boiled for a quarter
of an hour, when the magnesia, if any exist, will be
precipitated from it, combined with carbonic acid, and
its quantity is to be ascertained in the same manner as
that of the carbonate of lime.

If any minute proportion of, alumina should,
from peculiar circumstances, be dissolved by the acid,
it will be found in the precipitate with the carbonate of
lime, and it may be separated from it by boiling it for
a few minutes with soap lye, sufficient to cover the
solid matter; this substance dissolves alumina, with-
out acting upon carbonate of lime.

Should the finely divided soil be sufficiently cal-
careous to effervesce very strongly with acids, a very
simple method may be adopted for ascertaining the
quantity of carbonate of lime, and one sufficiently ac-
curate in all common cases.

Carbonate of lime, in all its states, contains a de-
terminate proportion of carbonic acid, i, e, nearly 43
per cent, so that when the quantity of this elastic fluid
giv^n out by any soil during the solution of its calcare-
ous matter in an acid is known, either in weight or
measure, the quantity of carbonate of lime may be
easily discovered.

When the process by diminution of weight is
employed, two parts of the acid and one part of the
matter of the soil must be weighed in two separate bot-
ties, and very slowly mixed together till the efferves-
cence ceases; the difference between their weight be-
fore and after the experiment, denotes the quantity
of carbonic carbonic acid lostj for every four grains

C 148 ]

and a quarter of which, ten grains of carbonate of
lime must be estimated.

The best method of collecting the carbonic acid,
so as to discover its volume, is by a peculiar pneumat-
ic, apparatus * in which its bulk may be measured by
the quantity of water it dissolves.

6. After the calcareous parts of the soil has been
acted upon by muriatic acid, the next process is to as-
certain the quantity of finely divided insoluble animal
and vegetable matter that it contains.

This may be done with sufficient precision, by
strongly igniting it in a crucible over a common fire
till no blackness remains in the mass. It should be
often stirred with a metallic rod, so as to expose new
surfaces continually to the air; the loss of weight that
it undergoes denotes the quantity of the substance
that it contains destructible by fire and aif".

It is not possible, without very refined and diffi-
cult experiments, to ascertain whether this substance

•Fig. 15. A, B, C, D, represent the different parts of this apparatus. A. Repre-
sents the bottlefor receiving the soil. B. the bottle containing the acid, furnished
•with a stop-cock. C. the tube connected with a flaccid bladder. D. The graduated
m»asure. E. The bottle for containing the bladder. When this instrument is used
» given quantity of soil is introduced into A. B is filled with muriatic acid diluted,
■with an equal quantity of water; and the stop-cock being closed, is connected with
the upper orifice of A, which is ground to receive it. The tube D is introduced
into the lower orifice of A, and the bladder connected with it placed in its flaccid
state into E, which is filled with water. The graduated measure is placed under the
tube of E. When the stop-cock of B is turned, the acid flows into A, and acts
upon the soil; the elastic fluid generated passes through C into the bladder, and
displaces a quantity of water in E, equal to it in bulk, and this water flows through
the tube into the graduated measure: and gives by its volume the indication of
the proportion of carbonic acid disengaged from the soil; for every ounce measure
of which two grains of carbonate of lime may be estimated.

P.148

[ 149 ]

IS wholly animal or vegetable matter, or a mixture of
both. When the smell emitted during the incinera-
tion is similar to that of burnt feathers, it is a certain
indication of some substance either animal or analo-
gous to animal matter ; and a copious blue flame at
the time of ignition, almost always denotes a consi-
derable proportion of vegetable matter. In cases
when it is necessary that the experiment should be
very quickly performed, the destruction of the decom-
posable substances may be assisted by the agency of
nitrate of ammoniac, which at the time of ignition may
be thrown gradually upon the heated mass in the
quantity of twenty grains for every hundred of residual
soil. It accelerates the dissipation of the animal and
vegetable matter, which it causes to be converted into
elastic fluids ; and it is itself at the same time decom-
posed and lost.

7. The substances remaining after the destruc-
tion of the vegetable and animal matter, are generally
minute particles of earthy matter, containing usually
alumina and silica, with combined oxide of iron or
of manganesum.

To separate these from each other, the solid mat-
ter should be boiled for two or three hours with sul-
phuric acid, diluted with four times its weight of wa-
ter ; the quantity of the acid should be regulated by
the quantity of solid residuum to be acted on, allow-
ing for every hundred grains, two drachms or one
hundred and twenty grains of acid.

The substance remaining after the action of the
acid, may be considered as siliceous j and it must be

I 150 2

separated ancl its weight ascertained, after washing,
and drying in the usual manner.

The alumina and the oxide of iron and mangane-
sum if any exist, are all dissolved by the sulphuric acid ;
they may be separated by succinate of ammonia, ad-
ded to excess : which throws down the oxide of iron,
and by soap lye, which will dissolve the alumina, but
not the oxide of manganesum ; the weights of the
oxides ascertained after they have been heated to red-
ness will denote their quantities.

Should any magnesia and lime have escaped so-
lution in the muriatic acid, they will be found in the
sulphuric aqid ; this, however, is rarely the case ; but
the process for detecting them, and ascertaining their
quantities, is the same in both instances.

The method of analysis by sulphuric acid, is suf-
ficiently precise for all usual experiments ; but if very
great accuracy be an object, dry carbonate of potassa
must be employed as the agent, and the residuum of
the incineration (6) must be heated red for a half hour,
with four times its weight of this substance, in a cruci-
ble of silver, or of well baked porcelain. The mass
obtained must be dissolved in muriatic acid, and the
solution evaporated till it is nearly solid j distilled
water must then be added, by which the oxide of iron
and all the earths, except silica, will be dissolved in
combination as muriates. The silica, after the usual
process of lixiviation, must be heated red j the other
substances may be separated in the same manner as
from the muriatic and sulphuric solutions.

[1^1 i ^

This process is the one usually employed by
chemical philosophers for the analysis of stones,

S. If any saline matter, or soluble vegetable or
animal matter is suspected in the soil, it will be found
in the water of lixiviation used for separating the
sand.

This water must be evaporated to dryness in a-
proper dish, at a heat below its boiling point.

If the solid matter obtained is of a brown colour
and inflammable, it may be considered as partly vege-
table extract. If its smell, when exposed to heat, be
like that of burnt feathers, it contains animal or albu-
minous matter ; if it be white, crystalline, and not
destructible by heat, it may be considered as principal-
ly saline matter ; the nature of which may be known
by the tests described page 103.

9. Should sulphate or phosphate of lime be sus-
pected in the entire soil, the detection of them re-
quires a particular process upon it. A given weight
of it, for instance four hundred grains, must be heat-
ed red for half an hour in a crucible, mixed with one-
third of powdered charcoal. The mixture must be
boiled for a quarter of an hour, in half a pint of water,
and the fluid collected through the filtre, and exposed
for some days to the atmosphere in an open vessel.
If any notable quantity of sulphate of lime (gypsum)
existed in the soil, a white precipitate will gradually
form in the fluid, and the weight of it will indicate the
proportion.

Phosphate of lime, if any exist, may be separated
from the soil after the process for gypsum. Muriatic^

C 152 ]

acid must be digested upon the soil, in quantity more
than sufficient to saturate the soluble earths ; the
solution must be evaporated, and water poured upon
the solid matter. This fluid will dissolve the com-
pounds of earths with the muriatic acid, and leave the
phosphate of hme untouched.

It would not fall within the limits assigned to this
Lecture, to detail any processes for the detection of
substances which may be accidentally mixed with the
matters of soils. Other earths and metallic oxides
are now and then found in them, but in quantities
too minute to bear any relation to fertility or barren-
ness, and the search for them would make analysis
much more complicated without rendering it more
useful.

10. When the examination of a soil is comple-
ted, the products should be numerically arranged,
and theii' quantities added together, and if they nearly
equal the original quantity of soil, the analysis may be
considered as accurate. It must, however, be noticed,
that when phosphate or sulphate of lime are disco-
vered by the independent process just described, (9,)
a correction must be made for the general process, by
subtracting a sum equal to their weight from the
quantity of carbonate of lime, obtained by precipita-
tion from the muriatic acid.

In arranging the products, the form should be in
the order of the experiments by which they were pro-
cured.

Thus, I obtained from 400 grains of a good sili-
ceous sandy soil from a hop garden near Tunbridge,
Kent, ^ \

153

grains

Of water of absorption

-

••

19

Of loose stones and gravel principally siliceous 53

Of undecompounded vegetable

fibres

-

14

Of fine siliceous sand

-

-

212

Of minutely divided matter separated by :

agitation .

and filtration, and consisting of

Carbonate of lime

-

19

Carbonate of magnesia

m

3

Matter destructible by heat, principally

vegetable - - -

-

15

Silica - - . .

-

21

Alumina - - - , -

-

IS

Oxide of iron -

-

5

Soluble matter, principally common

salt and vegetable extract

-

3

Gypsum . - - «

-

2

— 81

Amount of all the products 379
Loss - - - - 21
The loss in this analysis is not more than usually
occurs, and it depends upon the impossibiHty of collec-
ting the whole quantities of the different precipitates ;
and upon the presence of more moisture than is ac
counted for in the water of absorption, and which is lost
in the different processes.

When the experimenter is become acquainted
with the use of the different instruments, the proper-
ties of the reagents, and the relations between the ex-
ternal and chemical qualities of soils, he will seldom
find it necessary to perform, in any one case, all the

X

C 154 3

processes that have been described. When his soil,
for instance, contains no notable proportion of cal-
careous matter, the action of the muriatic acid (7)
may be omitted. In examining peat soils, he will
principally have to attend to the operation by fire
and air (8) ; and in the analysis of chalks and loams,
he will often be able to omit the experiment by sul-
phuric acid (9).

In the first trials that are made by persons unac-
quainted with chemistry, they must not expect much
precision of result. Many difficulties will be met
with : but in overcoming them, the most useful kind
of practical knowledge will be obtained ; and nothing
is so instructive in experimental science, as the detec-
tion of mistakes. The correct analyst ought to be well
grounded in general chemical information; but perhaps
there is no better mode of gaining it, than that of at-
tempting original investigations. In pursuing his expe-
riments, he will be continually obliged to learn the pro-
perties of the substances he is employing or acting
upon y and his theoretical ideas will be more valuable
in being connected with practical operations, and ac-
quired for the purpose of discovery.

Plants being possessed of no locomotive powers,
can grow only in places where they are supplied with
food ; and the soil is necessary to their existence,
both as affording them nourishment, and enabling
them to fix themselves in such a manner as to obey
those mechanical liaws by which their radicles are kept
below the surface, and their leaves exposed to the free
atmosphere. As the systems of roots, branches, and

[155 ]

leaves are very dilFerent in different vegetables, so they
flourish most in different soils : the plants that have
bulbous roots require a looser and a lighter soil than
such as have fibrous roots ; and the plants possessing
only short fibrous radicles demand a firmer soil than
such as have tap roots, or extensive lateral roots.

A good turnip soil from Holkham, Norfolk, af-
forded me 8 parts out of 9 siliceous sand j and the
finely divided matter consisted

Of carbonate of lime ^ ^ . 63

-— silica - - - - - 15

— alumina - - - - II

— oxide of iron - - - - 3 ^

— vegetable and saline matter - 5

— moisture - - - - 3

I found the soil taken from a field at ShefBeld-
place in Sussex, remarkable for producing flourishing
oaks, to consist of six parts of sand, and one part
of clay and finely divided matter. And one hundred
parts of the entire soil submitted to analysis produced

Silica - - . . .

parts,
54

Alumina - - . - .

28

Carbonate of lime . - .

3

Oxide of iron . . . «

5

Decomposing vegetable matter

4

Moisture and loss

3

An excellent wheat soil from the neighbourhood

of West Drayton,. Middlesex, gave 3 parts

in 5 of sill-

[ 156 3

ceous sand; and the finely divided matter consis-
ted of

Carbonate of lime - - - 28

Silica 32

Alumina - - - - - 29
Animal or vegetable matter and moisture 1 1

Of these soils the last was by far the most, and
the first the least, coherent in texture. In all cases
the constituent parts of the soil which give tenacity and
coherence are the finely divided matters ; and they
possess the power of giving those qualities in the
highest degree when they contain much alumina. A
small quantity of finely divided matter is sufficient to
fit a soil for the production of turnips and barley ; and
I have seen a tolerable crop of turnips on a soil con-
taining 1 1 parts out of 1 2 sand. A much greater pro-
portion of sand, however, always produces absolute
sterility. The soil of Bagshot heath, which is entire-
ly devoid of vegetable covering, contains less than /^j
of finely divided matter. 400 parts of it, which had
been heated red, afforded me 580 parts of coarse sili-
ceous sand ; 9 parts of fine siliceous sand, and 1 1
parts of impalpable matter which was a mixture of fer-
ruginous clay, with carbonate of lime. Vegetable or
animal matters, when finely divided, not only give co-
herence, but likewise softness and penetrability ; but
neither they nor any other part of the soil must be in
too great proportion ; and a soil is unproductive if it
consist entirely of impalpable matters.

Pure alumina or silica, pure carbonate of lime,
or carbonate of magnesia, are incapable of supporting
healthy vegetation.

C 157 ]

No soil is fertile that contains as much as 19 parts
out of 20 of any of the constituents that have been
mentioned.

It will be asked, are the pure earths in the soil
merely active as mechanical or indirect chemical
agents, or do they actually afford food to the plant?
This is an important question; and not difficult of sol-
ution.

The earths consist, as I have before stated, of
metals united to oxygene; and these metals have not
been decomposed; there is consequently no reason to
suppose that the earths are convertible into the ele-
ments of organized compounds, into carbon, hydro-
gene, and azote.

Plants have been made to grow in given quanti-
ties of earth. They consume very small portions only;
and what is lost may be accounted for by the quantities
found in their ashes; that is to say, it has not been
converted into any new products.

The carbonic acid united to lime or magnesia, if
any stronger acid happens to be formed in the soil
during the fermentation of vegetable matter which will
disengage it from the earths, may be decomposed:
but the earths themselves cannot be supposed convert-
ible into other substances, by any process taking place
in the soil.

In all cases the ashes of plants contain some of
the earths of the soil in which they grow; but these
earths, as may be seen from the table of the ashes af-
forded by different plants given in the last Lecture,
never equal more than to of the weight of the plant
consumed.

[158 J

If they be considered as necessary to the vegeta-
ble, it is as giving hardness and firmness to its organi-
zation. Thus, it has been mentioned that wheat, oats,
and many of the hollow grasses, have an epidermis
principally of siliceous earth; the use of which seems
to be to strengthen them, and defend them from the
attacks of insects and parasitical plants.

Many soils are popularly distinguished as cold;
and the distinction, though at first view it may appear
to be founded on prejudice, is really just.

Some soils are much more heated by the rays of
the sun, all other circumstances being equal, than
others; and soils brought to the same degree of heat
cool in different times, /. e, some cool much faster
than others.

This property has been very little attended to in
a philosophical point of view; yet it is of the highest
importance in agriculture. In general, soils that con-
sist principally of a stiff white clay are difficultly heated;
and being usually very moist, they retain their heat
only for a short time. Chalks are similar in one res-
pect, that they are difficultly heated; but being drier
they retain their heat longer, less being consumed in ,
causing the evaporation of their moisture.

A black soil, containing much soft vegetable mat-
ter, is most heated by the sun and air; and the col-
oured soils, and the soils containing much carbonace-
ous matter, or ferruginous matter, exposed under
equal circumstances to sun, acquire a much higher
temperature than pale-coloured soils.

C 159 3

When soils are perfectly dry, those that most
readily beceme heated by the solar rays likewise cool
most rapidly; but I have ascertained by experiment, that
the darkest coloured dry soil (that which contains
abundance of animal or vegetable matter; substances
which most facilitate the diminution of temperature,)
when heated to the same degree, provided it be with-
in the common limits of the effect of solar heat, \yill
cool more slowly than a wet pale soil, entirely cotn-
posed of earthy matter.

I found that a rich black mould, which contained
nearly i of vegetable matter, had its temperature in-
creased in an hour from 65^ to 88° by exposure to
sunshine; whilst a chalk soil was heated only to 69°
under the same circumstances. But the mould re-
moved into the shade, where the temperature was 62°,
lost, in half an hour, 15°; whereas the chalk, under
the same circumstances, had lost only 4°.

A brown fertile soil, and a cold barren clay were
each artificially heated to 88°^ having been previously
dried: they were then exposed to a temperature of 57°;
in half an hour the dark soil was found to have lost 9°
of heat; the clay had lost only 6°. An equal portion
of the clay containing moisture, after being heated to
88°, was exposed in a temperature of 5 5"^; in less than
a quarter of an hour it was found to have gained the
temperature of the room. The soils in all these ex-
periments were placed in small tin plate trays two
inches square, and half an inch in depth; and the tem-
perature ascertained by a delicate thermometer.

Nothing can be more evident, than that the

C 160 ]

genial heat of the soil, particularly in spring, must be
of the highest importance to the rising plant. And
when the leaves are fully developed, the ground is
shaded; and any injurious influence, which in the sum-
mer might be expected from too great a heat, entirely
prevented: so that the temperature of the surface,
when bare and exposed to the rays of the sun, affords
at least one indication of the degrees of its fertility; and
the thermometer may be sometimes a useful instru-
ment to the purchaser or improver of lands.

The moisture in the soil influences its tempera-
ture; and the manner in which it is distributed through,
or combined with, the earthy materials, is of great
importance in relation to the nutriment of the plant.
If water is too strongly attracted by the earths, it will
not be absorbed by the roots of the plants; if it is in
too great quantity, or too loosely united to them, it
tends to injure or destroy the fibrous parts of the
roots.

There are two states in which water seems to
exist in the earths, and in animal and vegetable substan-
ces: in the first state it is united by chemical, in the
other by cohesive attraction.

If pure solution of ammonia or potassa be poured
into a solution of alum, alumina falls down combined
widi water; and the water dried by exposure to air will
aflbrd more than half its weight of water by distilla-
tion; in this instance the water is united by chemical
attraction. The moisture which wood, or muscular
fibre, or gum, that have been heated to 212°, afford
by distillation at a red heat, is likewise water, the ele-

C 161 3

ments of which were united in the substance by che-
mical combination.

When pipe-clay dried at the temperature of the
atmosphere is brought in contact with water, the fluid
is rapidly absorbed ; this is owing to cohesive attrac-
tion. Soils in general, vegetable, and animal sub-
stances, that have been dried at a heat below that of
boiling water, increase in weight by exposure to air,
owing to their absorbing water existing in the state of
vapour in the air, in consequence of cohesive attrac-
tion.

The water chemically combined amongst the ele-
ments of soils, unless in the case of the decomposition
of animal or vegetable substances, cannot be absorbed
by the roots of plants ; but that adhering to the parts
of the soil is in constant use in vegetation. Indeed
there are few mixtures of the earths found in soils,
that contain any chemically combined water ; water
is expelled from the earths by most substances that
combine with them. Thus, if a combination of lime
and water be exposed to carbonic acid, the carbonic
acid takes the place of water ; and compounds of alu-
mina and silica, or other compounds of the earths, do
not chemically unite with w^ater: and soils, as it has
been stated, are formed either by earthy carbonates,
or compounds of the pure earths and metallic oxides.

When saline substances exist in soils, they may
be united to water both chemically and mechanically j
but they are always in too small a quantity to influence
materially the relations of the soil to water.

t 162 J

The power of the soil to absorb water by cohe-
sive attraction, depends in great measure upon the
state of division of its parts ; the more divided they
are, the greater is their absorbent power. The differ-
ent constituent parts of soils likewise appear to act,
even by cohesive attraction, with different degrees of
energy. Thus vegetable substances seem to be more
absorbent than animal substances ; animal substances
more so than compounds of alumina and silica ; and
compounds of alumina and silica more absorbent than
corbonates of lime and magnesia : these differences
may, however, possibly depend upon the differences
in their state of division, and upon the surface ex-
posed.

The power of soils to absorb water from air, is
much connected with fertility. When this power is
great, the plant is supplied with moisture in dry sea-
sons ; and the effect of evaporation in the day is coun-
teracted by the absorption of aqueous vapour from
the atmosphere, by the interior parts of the soil during
the day, and by both the exterior and interior during
night.

The stiff clays approaching to pipe- clays in their
nature, which take up the greatest quantity of water
when it is poured upon them in a fluid form, are not
the soils which absorb most moisture from the atmos-
phere in dry weather. They cake, and present only a
small surface to the air ; and the vegetation on them
IS generally burnt up almost as readily as on sands.

The soils that are most efficient in supplying the
plant with water by atmospheric absorption, are those

[ 163 ' 3

in which there Is a due mixture of sand, finely divided
clay, and carbonate of lime, with some animal or ve-
getable matter ; and which are so loose and light as
to be freely permeable to the atmosphere. With res-
pect to this quality, carbonate of lime and animal and
vegetable matter are of great use in soils ; they give
absorbent power to the soil without giving it likewise
tenacity : sand, which also destroys tenacity, on the
contrary, gives little absorbent power.

I have compared the absorbent po^yers of many
soils with respect to atmospheric moisture, and I have
always found it greatest in the most fertile soils : so
that it affords one method of judging of the produc-
tiveness of land.

1000 parts of a celebrated soil from Ormiston,
in East Lothian, which contained more than half its
weight of finely divided matter, of which 11 parts
were carbonate of lime, and 9 parts vegetable matter,
when dried at 212°, gained in an hour by exposure to
air saturated with moisture, at temperature 62°, 18
grains.

1000 parts of a very fertile soil from the banks
of the river Parret, in Somersetshire, under the same
<:ircumstances, gained 16 grains.

1000 parts of a soil from Mersea, in Essex,
worth 45 shillings an acre, gained 13 grains.

1000 grains of a fine sand from Essex, worth
^8 shillings an acre, gained 1 1 grains.

1000 of a coarse sand worth 15 shillings an acre,

gained only 8 grains.

1000 of the soil of Bagshot-heath gained only .^
grains.

[ 164 ]

Water, and the decomposing animal and vegeta-
ble matter existing in the soil, constitute the true
nourishment of plants ; and as the earthy parts of the
soil are useful in retaining water, so as to supply it
in the proper proportions to the roots of the vegeta-
bles, so they are likewise efficacious in producing the
proper distribution of the animal or vegetable matter ;
when equally mixed with it they prevent it from de-
composing too rapidly ; and by their means the solu-
ble parts are supplied in proper proportions.

Besides this agency, which may be considered as
mechanical, there is another agency between soils and
organizable matters, which may be regarded as che-
mical in its nature. The earths, and even the earthy
carbonates, have a certain degree of chemical attrac-
tion for many of the principles of vegetable and ani-
mal substances. This is easily exemplified in the in-
stance of alumina and oil ; if an acid solution of alu-
mina be mixed with a solution of soap, which consists
of oily matter and potassa ; the oil and the alumina
will unite and form a white powder, which will sink
to the bottom of the fluid.

The extract from decomposing vegetable matter
when boiled with pipe-clay or chalk, forms a combina-
tion by which the vegetable matter is rendered more
difficult of decomposition and of solution. Pure silica
and siliceous sands have little action of this kind ; and
the soils which contain the niost alumina and carbon-
ate of lime, are these which act with the greatest che-
mical energy in preserving manures. Such soils
merit the appellation which is commonly given to them

[ 165 ]

of rich sails ; for the vegetable nourishment is long
preserved in them, unless taken up by the organs of
plants. Siliceous sands, on the contrary, deserve the
term hungry, which is commonly applied to them ; for
the vegetable and animal matters they contain not be-
ing attracted by the earthy constituent parts of the
soil, are more liable to be decomposed by the action of
the atmosphere, or carried off from them by water.

In most of the black and brown rich vegetable
moulds, the earths seem to be in combination with a
peculiar extractive matter, afforded during the decom-
position of vegetables : this is slowly taken up, or at-
tracted from the earths by water, and appears to con-
stitute a prime cause of the fertility of the soil.

The standard of fertility of soils for different
plants must vary with the climate ; and must be parti-
cularly influenced by the quantity of rain.

The power of soils to absorb moisture ought to
be much greater in warm or dry counties, than in cold
and moist ones ; and the quantity of clay, or vegeta-
ble or animal matter they contain greater. Soils also
on declivities ought to be more absorbent than in
plains or in the bottom of vallies. Their productive-
ness likewise is influenced by the nature of the sub-
soil or the stratum on which they rest.

When soils are immediately situated upon a bed
of rock or stone, they are much sooner rendered dry
by evaporation, than where the subsoil is of clay or
marie ; and a prime cause of the great fertility of the
land in the moist climate of Ireland, is the proximity
of the rocky strata to the soil.

t 166 3

A clayey subsoil will sometimes be of material
advantage to a sandy soil; and in this case it will re-
tain moisture in such a manner as to be capable of
supplying that lost by the earth above, inconsequence
of evaporation, or the consumption of it by plants.

A sandy, or gravelly subsoil, often corrects the
imperfections of too great a degree of absorbent power
in the true soil.

In calcareous countries, where the surface is a
species of marie, the soil is often found only a few
inches above the limestone; and its fertility is not im-
paired by the proximity of the rock; though in a less
absorbent soil, this situation would occasion barren-
ness; and the sandstone and limestone hills in Derby-
shire and North Wales, may be easily distinguished at
a distance in summer by the different tints of the ve-
getation. The grass on the sandstone hills usually
appears brown and burnt up; that on the limestone
hills, flourishing and green.

In devoting the different parts of an estate to the
necessary crops, it is perfectly evident from what has
been said, that no general principle can be laid down,
except when all the circumstances of the nature, com-
position, and situation of the soil and subsoil are
known.

The methods of cultivation likewise must be dif-
ferent for different soils. The same practice which will
be excellent in one case may be destructive in another.

Deep plougliing may be a very profitable practice
in a rich thick soil; and. in a fertile shallow soil, situa-
ted upon cold clay or sandy subsoil, it may be ex-
tremely prejudicial.

C 167 ]

In a moist climate where the quantity of rain that
falls annually equals from 40 to 60 inches, as in Lan-
cashire, Cornwall, and some parts of Ireland, a silice-
ous sandy soil is much more productive than in dry
districts; and in such situations, wheat and beans will
require a less coherent and absorbent soil than in
drier situations; and plants having bulbous roots, will
flourish in a soil containing as much as 14 parts out
of 15 of sand.

Even the exhausting powers of crops will be in-
fluenced by Hke circumstances. In cases where plants
cannot absorb sufficient moisture, they must take up
more manure. And in Ireland, Cornwall, and the
WTStern Highlands of Scotland, corn will exhaust less
than in dry inlaiTd situations. Oats, particularly in
dry climates, are impoverishing in a much higher de-
gree than in moist ones.

Soils appear to have been originally produced in
consequence of the decomposition of rocks and strata.
It often happens that soils are found in an unaltered
state upon the rocks from w^hich they were derived.
It is easy to form an idea of the manner in which
rocks are converted into soils, by referring to the in-
stance of soft granite^ or procelain gra?2ite. This sub-
stance consists of three ingredients, quartz, feldspar,
and mica. The quartz is almost pure siliceous earth,
in a crystalline form. The feldspar and mica are very
compounded substances; both contain silica, alumina,
and oxide of iron; in the feldspar there is usually
lifn*e and pot^tssa; in the mica, lime and magnesia.

C 168 3

When a granitic rock of this kind has been long
exposed to the influence of air and water, the lime
and the potassa contained in its constituent parts are
acted upon by water or carbonic acid; and the oxide
of iron, which is almost always in its least oxided state,
tends to combine with more oxygene; the consequence
is, that the feldspar decomposes, and likewise the
mica; but the first the most rapidly. The feldspar,
which is as it were the cement of the stone, forms a
fine clay: the mica partially decomposed mixes with
it as sand; and the undecomposed quartz appears as
gravel, or sand of different degrees of fineness.

As soon as the smallest layer of earth is formed on
the surface of a rock, the seeds of Hchens, mosses, and
other imperfect vegetables which are constantly float-
ing in the atmosphere, and which have made it their
resting place, begin to vegetate; their death, decompo-
sition, and decay afford a certain quantity of organi-
zable matter, which mixes with the earthy materials of
the rock; in this improved soil more perfect plants are
capable of subsisting; these in their turn absorb nour-
ishment from water and the atmosphere; and after per-
ishing afford new materials to those already provided:
the decomposition of the rock still continues; and at
length by such slow and gradual processes, a soil is
formed in which even forest trees can fix their roots,
and which is fitted to reward the labours of the culti-
vator.

In instances where successive generations of vege-
tables have grown upon a soil, unless part of their pro-
duce has been carried off by man, or consumed by

£ 169 3

animals, the vegetable matter increases in such a pro-
portion, that the soil approaches to a peat in its na-
ture ; and if in a situation where it can receive water
from a higher district, it becomes spongy, and per-
meated with that fluid and is gradually rendered in-
capable of supporting the nobler classes of Vegetables.

Many peat-mosses seem to have been formed by
the destruction of forests, in consequence of the impru-
dent use of the hatchet by the early cultivators of the
country in which they exist : when the trees are fel-
led in the out-skirts of a wood, those in the interior ex-
posed to the influence of the winds ; and having been
accustomed to shelter, become unhealthy, and
die in their new situation; and their leaves and
branches gradually decomposing, produce a stratum
of vegetable matter. In many of the great bogs in
Ireland and Scotland, the larger trees that are found
in the out-skirts of them, bear the marks of having
been felled. In the interior, few entire trees are
found ; and the cause is, probably, that they fell by
gradual decay ; and that the fermentation and decom-
position of the vegetable matter was most rapid where
it was in the greatest quantity.

Lakes and pools of water are some times jfilled
up by the accumulation of the remains of acquatic
plants ; and in this case a sort of spurious peat is
formed. The fermentation in these cases, however,
seems to be of a different kind. Much more gaseous
matter is evolved ; and the neighbourhood of moras-
ses in which aquatic vegetables decompose, is usually
aguish and unhealthy ; whilst that of the true peat, or

C ivo ]

peat forqjed on soils originally dry, is always salu-
brious.

The earthy matter of peats is uniformly analo-
gous to that of the stratum on which they repose ; the
plants which have formed them must have derived
the earths that they contained from this stratum.
Thus in Wiltshire and Berkshire, where the stratum
below the peat is chalk, calcareous earth abounds in
the ashes, and very little alumina and silica. They
likewise contain much oxide of iron and gypsum, both
of which may be derived from the decomposition of
the pyrites, so abundant in chalk.

Different specimens of peat that I have burnt,
from the granitic and schistose soils of different parts
of these islands have always given ashes principally
siliceous and aluminous and a specimen of peat from
the county of Antrim, gave ashes which afforded very
nearly the same constituents as the great basaltic stra-
tum of the county.

Poor and hungry soils, such as are produced
from the decomposition of granitic and sandstone
rocks, remain very often for ages with only a thin co-
vering of vegetation. Soils from the decomposition
of limestone, chalks, and basalts are often clothed by
nature with the perennial grasses ; and afford, when,
ploughed up, a rich bed of vegetation for every species
of cxiltivated plant.

Rocks and strata from which soils have been de»
rived, and those which compose the more interior
solid parts of the globe, are arranged in a certain or-
der ; and as it often happens that strata very different

C ni ]

in their nature are associated together, and that the
strata immediately beneath the soil contain materials
which may be of use for improving it, a general view
of the nature and position of rocks and strata in na-
ture, will not, I trust, be unacceptable to the scientific
farmer.

Rocks are generally divided by geologists into

two grand divisions, distinguished by the names of
•primary and secondary.

The primary rocks are composed of pure crystal-
line matter, and contain no fragments of other rocks.

The secondary rocks, or strata, consist only part-
ly of crystalline matter ; contain fragments of other
rocks or strata j often abound in the remains of vege-
tables and marine animals ; and sometimes contain
the remains of land animals.

The primary rocks are generally arranged in
large masses, or in layers vertical, or more or less
inclined to the horizon.

The secondary rocks are usually disposed in
strata or layers, parallel, or nearly parallel to the
horizon.

The number of primary rocks which are com-
monly observed in nature are eight.

First, granite, which, as has been mentioned, is
composed of quartz, feldspar, and mica ; when these
bodies are arranged in regular layers in the rock, it is
called gneis.

Second, micaceous schistus, which is composed of
quartz and mica arranged in layers, which are usually
curvilineal.

Third, sienitef which consists of the substance
called hornblende and feldspar.

Fourth, serpentine, which is constituted by feld-^
spar and a body named resplendent hornblende ; and
their separate crystals are often so small as to give
the stone a uniform appearance : this rock abounds
in veins of a substance called steatite, or soap rock.

Fifth, porphyry, which constists of crystals of
feldspar, embedded in the same material, but usually
©f a different colour.

Sixth, granular marble, which consists entirely
of crystals of carbonate of lime ; and which, when its
colour is white, and texture fine, is the substance used
by statuaries.

Seventh, chlorite schist, which consists of chlo»
rite, a green or grey substance somewhat analogous
to mica and feldspar.

Eight, quartzose rock, which is composed of
quartz in a granular form, sometimes united to small
quantities of the crystalline elements, which have
been mentioned as belonging to the other rocks.

The secondary rocks are more numerous than
the primary ; but twelve varieties include all that are
usually found in these islands*

First, grauwacke, which consists of fragments of
quart2;, or chlorite schist, embedded in a cement,
principally composed of feldspar.

Second, siliceous sandstone, which is composed of
fine quarts or sand, united by a siliceous cement.

Third, limestone, consisting of carbonate of lime,
more compact in its texture than in the granular mar-
ble I and often abounding in marine exuvia*

Fourth, aluminous schist, or shale^ consisting of
the decomposed materials of different rocks cemented
by a small quantity of ferruginous or siliceous matter;
and often containing the impressions of vegetables.

Fifth, calcareous sandstone^ which is calcareous
sand, cemented by calcareous matter*

Sixth, irone stone ^ formed of nearly the same ma-
terials ^ aluminous schist, or shale \ but containing a
much larger quantity of oxide or iron.

Seventh, basalt or whinstone, which consists of
feldspar and hornblende with materials derived from
the decomposition of the primary rocksj the crystals
are generally so small as to give the rock a homo-
geneous appearance; and it is often disposed in very
regular columns, having usually five or six sides.

Eighth, bituminous or common coaL

Ninth, gypsum, the substance so well known by
that name, which consists of sulphate of lime; and of-
ten contains sand.

Tenth, rock salt.

Eleventh, chalk, which usually abounds in re-
mains of marine animals, and contains horizontal
layers of flints.

Twelfth, plum-pudding stone, consisting of pebbles
cemented by a ferruginous or siliceous cement.

To describe more particularly the constituent
parts of the different rocks and strata will be unneces^.
sary; at any time, indeed, details on this subject are
useless, unless the specimens are examined by the
eye; and a close mspection and comparison of the dif*

C 174 J

ferent species, will, in a short time, enable the most
common observer to distinguish them.

The highest mountains in these islands, and in-
deed in the whole of the old continent, are constituted
by granite; and this rock has likev/ise been found at
the greatest depths to which the industry of man has
*is yet been able to penetrate; micaceous schist is often
found immediately upon granite; serpentine or marble
upon micaceous schist: but the order in which the
primary rocks are grouped together is various. Mar-
ble and serpentine are usually found uppermost; but
granite, though it seems to form the foundation of the
rocky strata of the globe, is yet sometimes discovered
above micaceous schist.

The secondry rocks are always incumbent on the
primary; the lowest of them is usually grauwacke: up-
on this, limestone or sandstone is often found; coal
generally occurs between sandstone or shale; basalt
often exists above sandstone and limestone; rock salt
almost always occurs associated with red sandstone
and gypsum. Coal, basalt, sandstone, and limestone,
are often arranged in different alternate layers, of no
considerable thickness, so as to form a great extent of
country. In a depth of less than 500 yards, 80 of
these different alternate strata have been counted.

The veins which afford metallic substances, are
fissures more or less vertical, filled with a material
different from the rock in which they exist. This
material is almost always crystalline; and usually con-
sists of calcareous spar, fluor spar, quartz, or heavy
spar, either separate or together. The metallic sub-

f^

^1 ?

11-^ "I

a;i ^ 0, Rj

>^ '^ "^ !S

I.

5j

11

■I "<

I I

Co K^

C ,K '^ -S

'C 'n5 .-^ "^S
^ 0( v^ > ^ ^

C 175 3

Stances are generally dispersed through, or confusedly
mixed with these crystalline bodies. The veins in
hard granite seldom afford much useful metal j but in
the veins in soft granite, and in gneis, tin, copper, and
lead are found. Copper and iron are the only metals
usually found in the veins in serpentine. Micaceous
schist, sienite, and granular marble, are seldom me-
talliferous rocks. Lead, tin, copper, iron, and many
other metals are found in the veins in chlorite schist.
Grauwacke, when it contains few fragments and exists
in large masses, is often a metalliferous rock. The
precious metals, likewise iron, lead, and antimony, are
found in it; and sometimes it contains veins or masses
of stone coal, or coal free from bitumen. Limestone
is the great metalliferous rock of the secondary family;
and lead and copper are the metals most usually found
in it. No metallic veins have ever been found in
shale, chalk, or calcareous sandstone; and they are
very rare in basalt and siliceous sandstone.*

In cases where veins in rocks are exposed to the
atmosphere, indications of the metals they contain may
be often gained from their superficial appearance.
Whenever fluor spar is found in a vein, there is al-
ways strong reason to suspect that it is associated
with metallic substances* A brown powder at the
surface of a vein always indicates iron, and often tin;
a pale yellow powder lead; and a green colour in a
vein denotes the presence of copper.

* Fig. 16, win give a general idraof the apptarance ami arrangement of rofks

and veins.

C 176 ]

It may not be improper to give a general descrip-
tion of the geological constitution of Great Britain and
Ireland. Granite forms the great ridge of hills ex-
tending from Land's End through Dartmoor into De-
vonshire. The highest rocky strata in Somersetshire
are grauwacke and limestone. The Malvern hills are
composed of granite, sienite, and porphyry. The
highest mountains in Wales are chlorite schist, or
grauwacke. Granite occurs at mount Sorrel in Lei-
cestershire. The great range of the mountains in
Cumberland and Westmoreland, are porphyry, chlo-
rite schist, and grauwacke; but granite is found at their
western boundary. Throughout Scotland the most
elevated rocks are granite, sienite, and micaceous
schistus. No true secondary formations are found in
South Britain, west of Dartmoor; and no basalt south
of the Severn. The chalk district extends from the
western part of Dorsetshire, to the eastern coast of
Norfolk. The coal formations abound in the district
between Glamorganshire and Derbyshire; and like-
wise in the secondary strata of Yorkshire, Durham,
Westmoreland, and Northumberland. Serpentine is
found only in three places in Great Britain; near Gape
Lizard in Cornwall, Portsoy in Aberdeenshire, and in
Ayrshire. Black and grey granular marble is found
near Padstow in Cornwall; and other coloured primary
marbles exist in the neighbourhood of Plymouth.
Coloured primary marbles are abundant in Scotland;
and white granular marble is found in the Isle of Sky,
in Assynt, and on the banks of Loch Shin in Suther-
land: the principle coal formations in Scotland are in

C n7 ]

Dumbartonshire. Ayrshire, Fifeshire, and on 'the
banks of the Brora in Sutherland. Secondary lime-
stone and sandstone are found in most of the low
countries north of the Mendip hills.

In Ireland there are five great associations of pri-
mary mountains ; the mountains of Morne in the
county of Down ; the mountains of Donegal ; those
of Mayo and Galway, those of Wicklow, and those
of Kerry. The rocks composing the four first of
these mountain chains are principally granite, gneis,
sienite, micaceous schist, and porphyry. The moun-
tains of Kerry are chiefly constituted by granular
quartz, and chlorite schist. Coloured marble is found
near Killarney; and white marble on the western coast
of Donegal.

Limestone and sandstone are the common secon-
dary rocks found south of Dublin. In Sligo, Ros*
common, and Leitrim, hmestone, sandstone, shale, iron
stone, and bituminous coal are found. The second-
ary hills in these counties are of considerable eleva-
tion ; and many of them have basaltic summits. The
northern coast of Ireland is principally basalt ; this
rock commonly reposes upon a white limestone, con-
taining layers of flint, and the same fossils as chalk ;
but it is considerably harder than that rock. There
are some instances, in this district, in which columnar
basalt is found above sandstone and shale, alternating
with coal. The stone coal of Ireland is principally
found in Kilkenny, associated with Hmestone and
grauwacke.

A 2

C 178 3

It is evident from what has been said concerning
the production of soils from rocks, that there must be
at least as many varieties of soils as there are species
of rocks exposed at the surface of the earth ; in fact
there are many more. Independent of the changes
produced by cultivation and the exertions of human
labour, the materials of strata have been mixed to-
gether and transported from place to place by various
great alterations that have taken place in the system
of our globe, and by the constant operation of water.

To attempt to class soils with scientific accuracy,
would be a vain labour ; the distinctions adopted by
farmers are sufficient for the purposes of agriculture ;
particularly if some degree of precision be adopted in
the application of terms. The term sandy, for instance,
should never be applied to any soil that does not con-
tain at least J of sand ; sandy soils that effervesce with
acids should be distinguished by the name of calcare-
ous sandy soil, to distinguish them from those that
are siliceous. The term clayey soil should not be
applied to any land which contains less than i. of im-
palpable earthy matter, not considerably effervescing
with acids : the word loam should be limited to soils,
containing at least one third of impalpable earthy mat-
ter, copiously effervescing with acids. A soil to be
considered as peaty, ought to contain at least one half
of vegetable matter.

In cases where the earthy part of a soil evidently
consists of the decomposed matter of one particular
rock, a name derived from the rock may with propriety
be applied to it. Thus, if a fine red earth be found

C 179 3

immediately above decomposing basalt, it may be de-
nominated basaltic soil. If fragments of quartz and
mica be found abundant in the materials of the soil,
which is often the case, it may be denominated granitic
soil ; and the same principles may be applied to other
like instances.

In general, the soils, the materials of which are
the most various and heterogenous, are those called
alluvial, or which have been formed from the deposi-
tions of rivers ; many of them are extremely fertile.
I have examined some productive alluvial soils, which
have been very different in their composition. The
soil which has been mentioned page 163, as very pro-
ductive, from the banks of the river Parret in Somer-
setshire, afforded me eight parts of finely divided
earthy matter, and one part of siliceous sand ; and an
analysis of the finely divided matter gave the follow-
ing results.

360 parts of carbonate of lime,

25 alumina,

20 silica,

8 oxide of iron.

19 vegetable, animal, and saline matter.

A rich soil from the neighbourhood of the Avon,
in the valley of Evesham in Worcestershire, afforded
me three fifths of fine sand, and two fifths of impalpa-
ble matter ; the impalpable matter consisted of,
35 Alumina,
41 Silica,

14 Carbonate of lime,
3 Oxide of iron,
7 Vegetable, animal, and saline matter.

[ 180 ]

A specimen of good soil from Tiviot-dale, afford-
ed five sixths of fine siliceous sand, and one sixth of
impalpable matter ; which consisted of

41 Alumina,

42 Silica,

4 Carbonate of lime,

5 Oxide of iron,

S Vegetable, animal, and saline matter.
A soil yielding excellent pasture from ifie valley
of the Avon, near Salisbury, afforded one eleventh of
coarse siliceous sand ; and the finely divided matter
consisted of

7 Alumina,
14 Silica,

63 Carbonate of lime, •-
2 Oxide of iron,

14 Vegetable, animal, and saline matter-
In all these instances the fertility seems to de-
pend upon the state of division, and mixture of the
earthy materials and the vegetable and animal matter j
and may be easily e^Jplained on the principles v^^hich I
have endeavoured to elucidate in the preceding part
of this Lecture.

In ascertaining the composition of sterile soils
with a view to their improvement, any particular
ingredient which is the cause of their unproduc-
tiveness, should be particularly attended to ; if possi-
ble, they should be compared with fertile soils in the
same neighbourhood, and in similar situations, as the
difference of the composition may, in many cases, in-
dicate the most proper methods of improvement. If

I 181 3

on. washing a sterile soil it is found to contain the "salts
of iron, or any acid matter, it may be ameliorated by
the application of quick lime. A soil of good ap-
parent texture from Lincolnshire, was put into my
hands by Sir Joseph Banks as remarkable for steril-
ity : on examining it, I found that it contained sul-
phate of iron ; and I offered the obvious remedy of
top dressing with lime, which converts the sulphate
into a manure. If there be an excess of calcareous
matter in the soil, it may be improved by the applica-
tion of sand, or clay. Soils too abundant in sand are
benefited by the use of clay, or marie, or vegetable
matter. A field belonging to Sir Robert Vaughan at
Nannau, Merionethshire, the soil of which was a light
sand, was much burnt up in the summer of I S05 j I
recommended to that gentleman the application of peat
as a top dressing. The experiment was attended
with immediate good effects ; and Sir Robert last year
informed me, that the benefit was permanent. A de-
ficiency of vegetable or animal matter must be sup-
plied by manure. An excess of vegetable matter is
to be removed by burning, or to be remedied by the
application of earthy materials. The improvement of
peats, or bogs, or marsh lands, must be preceded by
draining ; stagnant water being injurious to all the
nutritive classes of plants. Soft black peats, when
drained, are often made productive by the mere appli-
cation of sand or clay as a top dressing. When peats
are acid, or contain ferruginous salts, calcareous mat-
ter is absolutely necessary in bringing them into culti-
vation. When they abound in the branches and roots

[ 182 ]

of trees, or when their surface entirely consists of liv-
ing vegetables, the wood or the vegetables must either
by carried off, or be destroyed by burning. In the
last case their ashes afford earthy ingredients, fitted to
improve the texture of the peat.

The best natural soils are those of which the ma-
terials have been derived from different strata; which
have been minutely divided by air and water, and are in-
timately blended together: and in improving soils arti-
ficially, the farmer cannot do better than imitate the
processes of nature.

The materials necessary for the purpose are sel-
dom far distant: coarse sand is often found immedi-
ately on chalk; and beds of sand and gravel are
common below clay. The labour of improving the
texture or constitution of the soil, is repaid by a great
permanent advantage; less manure is required, and its
fertility insured: and capital laid out in this way secures
for ever, the productiveness, and consequently the
value of the land.

183

LECTURE V.

On the nature and Constiution of the Atmosphere; and
its Influence on Vegetables. Of the Germination of
Seeds. Of the Functions of Plants in their differ^
ent Stages of Growth; with a general view of the
Progress ofVegetation.

The constitution of the atmosphere has been al-
ready generally referred to in the preceding Lectures.
Water, carbonic acid gas, oxygene, and azote, have
been mentioned as the principal substances compo-
sing it; but more minute enquiries respecting their na-
ture and agencies are necessary to afford correct
views of the uses of the atmosphere in vegetation.

On these enquiries I now propose to enter; the
pursuit of them, I hope, will offer some objects of
practical use in farming; and present some philosophi-
cal illustrations of the manner in which plants are
nourished; their organs unfolded, and their functions
developed.

If some of the salt called muriate of lime that
has been just heated red be exposed to the air, even
in the driest and coldest wheather, it will increase in
weight and become moist; and in a certain time will be
converted into a fluid. If put into a retort and heated,
it will yield pure water; will gradually recover its
pristine state; and, if heated red, its former weight: so
that it is evident, that the water united to it was derived

C 184 ]

from the air. And that it existed in the air in an invis-
ible and elastic form, is proved by the circumstance,
that if a given quantity of air be exposed to the
salt; its volume and weight will diminish, provided the
experiment be correctly made.

The quantity of water which exists in air, as va-
pour, varies with the temperature. In proportion as
the weather is hotter, the quantity is greater. At 50°
of Fahrenheit air contains about ^V of its volume of
vapour; and as the specific gravity of vapour is to that
of air nearly as 10 to 15, this is about tV of its weight.

At 100°, supposing that there is a free commu-
nication with water, it contains about i\ parts in vol-
ume, or TT in weight. It is the condensation of va-
pour by diminution of the temperature of the atmos-
phere, which is probably the principal cause of the

formation of clouds, and of the deposition of dew,
mist, snow, or hail.

The power of different substances to absorb
aqueous vapour from the atmosphere, by cohesive at-
traction was discussed in the last Lecture. The leaves
of living plants appear to act upon the vapour likewise
in its elastic form, and to absorb it. Some vegetables
increase in weight from this cause, when suspended in
the atmosphere and unconnected with the soil; such
are the houseleek,- and different species of the aloe.
In very intense heats, and when the soil is dry, the
life of plants seems to be preserved by the absorbent
power of their leaves: and it is a beautiful circumstance
in the ceconomy of nature, that aqueous vapour is
most abundant in the atmosphere when it is most need*

C 185 ]

ed for the purposes of life ; and that when other
sources of its supply are cut off, this is most copious.

The compound nature of water has been referred
to. It may be proper to mention the experimental
proofs of its decomposition into, and composition
from, oxygene and hydrogene.

If the metal called potassium be exposed in a
glass tube to a small quantity of w^ter, it will act upon
it with great violence ; elastic fluid will be disengaged,
which will be found to be hydrogene ; and the same ef-
fects will be produced upon the potassium, as if it had
absorbed a small quantity of oxygene ; and the hydro-
gene disengaged, and the oxygene added to the potas-
sium are in weight as 2 to 15 ; and if two in volume of
hydrogene, and one in volume of oxygene, which have
the weights of 2 and 15, be introduced into a close ves-
sel, and an electrical spark passed through them, they
will inflame and condense into 17 parts of pure water.

It is evident from the statements given in the third ^
Lecture, that water forms by far the greatest part of
the sap of plants ; and that this substance, or its ele-
ments, enters largely into the constitution of their or-
gans and solid productions.

Water is absolutely necessary to the ceconomy of
vegetation in its elastic and fluid state ; and it is not
devoid of use even in its solid form. Snow and ice
are bad conductors of heat ; and when the ground is
covered with snow, or the surface of the soil or of
water is frozen, the roots or bulbs of the plants be-
neath are protected by the congealed water from the
influence of the atmosphere, the temperature of which

b2

C -is^ ]

in Northern winters is usually very much below the
freezing point ; and this water becomes the first nour-
ishment of the plant in early spring. The expansion
of water during its congelation, at w^hich time its
volume increases tV, and its contraction of bulk dur-
ing a thaw, tend to pulverise the soil ; to separate its
parts from each other, and to make it more permeable
to the influence of the air.

If a solution of lime in water be exposed to the
air, a pellicle will speedily form upon it, and a solid
matter will gradually fall to the bottom of the water,
and in a certain time the water will become tasteless ;
this is owing to the conbination of the lime, which
Was dissolved in the water, with carbonic acid gas
which existed in the atmosphere, as may be proved
by collecting the film and the solid matter, and ignit^
ing them strongly in a little tube of platina or iron ;
they will give off carbonic acid gas, and will become
quicklime, which added to the same water, will again
bring it to the state of lime water.

The quantity of carbonic acid gas in the atmos-
phere is very small. It is not easy to determine it
with precision, and it must differ in different situa-
tions ; but where there is a free circulation of air, it
is probably never more than sio, nor less than uoo of
the volume of air. Carbonic acid gas is nearly j hea-
vier than the other elastic parts of the atmosphere in
their mixed state : hence at first view it might be sup-
posed that it would be most abundant in the lower
regions of the atmosphere 5 but unless it has been
immediately produced at the surface of the earth ia

[ 187 ]

some chemical process, this does not seem to be the
case : elastic fluids of different specific gravities have
a tendency to equable mixture by a species of attrac-
tion, and the different parts of the atmosphere are
constantly agitated and blended together by winds or
other causes. De Saussure found lime water preci-
pitated on Mount Blanc, the highest point of land in
Europe ; and carbonic acid gas has been always found
apparently in due proportion, in the air brought down
from great heights in the atmosphere by aerostatic
adventurers.

The experimental proofs of the composition of
•carbonic acid gas are very simple. If 13 grains of
well burnt charcoal be inflamed by a burning-glass in
100 cubical inches of oxygene gas, the charcoal will
entirely disappear ; and provided the experiment be
correctly made, all the oxygene except a few cubical
inches, will be found converted into carbonic acid j
and what is very remarkable, the volume of the gas is
not changed. On this last circumstance it is easy to
found a correct estimation of the quantity of pure
charcoal and oxygene in carbonic acid gas : the weight
of 100 cubical inches of oxygene gas is to that of 100
cubical inches of oxygene gas, as 47 to 34 : so that
47 parts in weight of carbonic acid gas, must be
composed of 34 parts of oxygene and 13 of charcoal,
which correspond with the numbers given in the se-
x:ond Lecture.

Carbonic acid is easily decomposed by heating
potassium in it ; the metal combines with the oxy-
gene, and the charcoal is deposited in the form .of a
black powder.

L 188 3

The principal consumption of the carbonic acid
in the atmosphere, seems to be in affording nourish-
ment to plants ; and some of them appear to be sup-
plied with carbon chiefly from this source.

Carbonic acid gas is formed during fermentation,
combustion, putrefaction, respiration, and a number
of operations taking place upon the surface of the
earth ; and there is no other process known in nature
by which it can be destroyed but by vegetation.

After a given portion of air has been deprived of
aqueous vapour and carbonic acid gas, it appears little
altered in its properties ; it supports combustion and
animal life. There are many modes of separating its
principal constituents, oxygene and azote, from each
other. A simple one is by burning phosphorus in a
confined volume of air : this absorbs the oxygene and
leaves the azote ; and 100 parts in volume of air, in
which phosphorus has been burnt, yield 79 parts of
azote J and by mixing this azote with 21 parts of
fresh oxygene gas artifically procured, a substance
having the original characters of air is produced. To
procure pure oxygene from air, quicksilver may be
kept heated in it, at about 600°, till it becomes a red
powder ; this powder, when ignited, will be restored
to the state of quicksilver by giving off oxygene.

Oxygene is necessary to some functions of vege-
tables ; but its great importance in nature is in its rela-
tion to the oeconomy of animals. It is absolutely ne-
cessary to their life. Atmospheric air taken into the
lungs of animals, or passed in solution in water
through the gills of fishes, loses oxygene j and for

C 189 ]

the oxygene lost, about an equal volume of carbonic
acid appears.

The effects of azote in vegetation are not distinct-
ly known. As it is found in some of the products of
vegetation, it may be absorbed by certain plants from
the atmosphere. It prevents the action of oxygene from
being too energetic, and serves as a medium in which
the more essential parts of the air act; nor is this cir-
cumstance unconformable to the analogy of nature; for
the elements most abundant on the solid surface of
the globe, are not those which are the most essential
to the existence of the living beings belonging to it.

The action of the atmosphere on plants differs
at different periods of their growth, and varies with
the various stages of the developement and decay of
their organs; some general idea of its influence may
have been gained from circumstances already mention-
ed: I shall now refer to it more particularly, and endea-
vour to connect it with a general view of the progress
of vegetation.

If a healthy seed be moistened and exposed to
air at a temperature not below 45°, it soon germinates;
it shoots forth a plume which rises upwards, and a
radicle which descends.

If the air be confined, it is found that in the pro-
cess of germination the oxygene, or a part of it is ab-
sorbed. The azote remains unaltered; no carbonic
acid is taken away from the air, on the contrary some
is added.

Seeds are incapable of germinating, except when
oxygene is present. In the exhausted receiver of the

C 190 ]

aV-piirtip, in pure azote, in pure carbonic acid, when
moistened they swell, but do not vegetate; and if kept
in these gasses lose their living powers, and undergo
putrefaction.

If a seed be examined before germination, it will
be found more or less insipid, at least not sweet; but
after germination it is always sweet. Its coagulated
mucilage, or starch, is converted into sugar in the pro-
cess; a substance difficult of solution is changed into
one easily soluble; and the sugar carried through the
cells or vessels of the cotyledons, is the nourishment
of the infant plant, it is easy to understand the nature
of the change, by referring to the facts mentioned in
the third Lecture; and the production of carbonic
acid renders probable the idea, that the principal che-
mical difference between sugar and mucilage depends
upon a slight difference in the proportions of their car-
bon.

The absorption af oxygene by the seed in germin-
ation, has been compared to its absorption in produ-
cing the evolution of foetal life in the egg; but this an-
alogy is only remote. All animals, from the most to
the least perfect classes, require a supply of oxygene.*

• The impregnated eggs of Insects, and even tiches, do not produce young ones,
unless they are supplied with air, that is, unless the foetus can rehire. I have
found that the eggs of moths did not produce larvce when ■confined in pure carbonic
acid; and when they were exposed in common air, the oxygene partly disappeared/
and carbonic acid was formed. The fish in the egg or the spawn, gains its oxygene
from the air dissolved in water; and those fishes that spawn in spi-ing and surrimef
in still water, such aS" the pike, carp, perch, and bream, deposit their eggs upon
subaquatic vegetables, the leaves of which, in performing their healthy functions,
snpply oxygene to the v/ater. The fish that spawn in winter such as the saloieuiL

[ 191 1

From the moment the heart begins to pulsate till it
ceases to beat, the aeration of the blood is constant,
and the function of respiration invariable; carbonic
acid is given off in the process, but the chemical
change produced in the blood is unknown; nor is there
any reason to suppose the formation of any substance
similar to sugar. In th6 production of a plant from a
seed, some reservoir of nourishment is needed before
the root can supply sap; and this reservoir is the coty-
ledon in which it is stored up in an insoluble form, and
protected if necessary during the winter, and rendered
soluble by agents which are constantly present on the ^
surface. The change of starch into sugar, connected
with the absorption of oxygene, may be rather com-
pared to a process of fermentation than to that of re-
spiration; it is a change effected upon unorganized
matter, and can be artificially imitated; and in most of
the chemical changes that occur when vegetable com-
pounds are exposed to air, oxygene is absorbed, and
carbonic acid formed or evolved.

It is evident, that in all cases of tillage the seeds
should be sown so as to be fully exposed to the influ-
ence of the air. And one cause of the unproductive-
ness of cold clayey adhesive soils is, that the seed is
, coated with matter impermeable to air.

and trout, seek spots where there is a constant supply of fresh water, as near the
sources of streams as possible, and in the most rapid currents where all stagnation
is prevented, and where the water is saturated with air, to which it has Been ex.-
posed during its deposition from cloudr;. It is the instinct leading these fish to
seek a supply of air for their eggs which carries thenri fvom seas, or iafkes into the
mountain country; which induces them to move against the atrcanj, and to en«?ero
our to overleap weirs, nvilldams, and cataract?.

[ 192 3

In sandy soils the earth is always sufficiently pen-
etrable by the atmosphere; but in clayey soils there
can scarcely be too great a mechanical division of
parts in the process of tillage. Any seed not fully
supplied with air, always produces a weak and diseas-
ed plant.

The process of malting, which has been already
referred to, is merely a process in which germination
is artificially produced; and in which the starch of the
cotyledon is changed into sugar; which sugar is after-
wards, by fermination, converted into spirit.

It is very evident from the chemical principles of
germination, that the process of malting should be
carried on no farther than to produce the sprouting of
the radicle, and should be checked as soon as this has
made its distinct appearance. If it is pushed to such
a degree as to occasion the perfect development of the
radicle and the plume, a considerable quantity of sac-
charine matter will have been consumed in producing
their expansion, and there will be less spirit formed in
fermentation, or produced in distillation.

As this circumstance is of some importance, I
made in October 1 806, an experiment relating to it.
I ascertained by the action of alcohol, the relative pro-
portions of saccharine matter in two equal quantities
of the same barley; in one of which the germination
had proceeded so far as to occasion protrusion of the
radicle to nearly a quarter of an inch beyond the graiu
in most of the specimens, and in the other of which it
had been checked before the radicle was a line in
length; the quantity of sugar afforded by the last was
to that in the first nearly as six to five.

' . [ 193 ]

The saccharine matter in the cotyledons at the
time of their change into seed-leaves, renders them ex-
ceedingly liable to the attacks of insects : this princi-
ple is at once a nourishment of plants and animals,
and the greatest ravages are committed upon crops in
the first stage of their growth.

The turnip fly, an insect of the colyoptera genus,
fixes itself upon the seed-leaves of the turnip at the
time that they are beginning to perform their func-
tions ; and when the rough leaves of the plume are
thrown forth, it is incapable of injuring the plant to
any extent.

Several methods have been proposed for destroy-
ing the turnip fly, or for preventing it from injuring
the crop. It has been proposed to sow radish-seed
with the turnip-seed, on the idea that the insect is fon-
der of the seed-leaves of the radish than those of the
turnip ; it is said that this plan has not been success-
ful, and that the fly feeds indiscriminately on both.

There are several chemical menstrua which ren-
der the process of germination much more rapid,
when the seeds have been steeped in them. As in
these cases the seed-leaves are quickly produced, and
more speedily perform their functions, I proposed it
as a subject of experiment to examine whether such
menstrua might not be useful in raising the turnip
more speedily to that state in which it would be se-
cure from the fly ; but the result proved that the prac-
tice was inadmissible ; for seeds so treated, though
they germinated much quicker, did not produce
healthy plants, and often died soon after spi'outing. :

c2

C 194 ]

I Steeped radish seeds In September 1807, for 12
hours, in a solution of chlorine, and similar seeds in
very diluted nitric acid, in Vvery diluted sulphuric acid,
in weak solution of oxysulphate of iron, and some hi
common water. The seeds in solutions of chlorine
and oxysulphate of iron, threw out the germ in two
days ; those in nitric acid in three days, in sulphuric
acid in five, and those in water in seven days. But
in the cases of premature germination, though the
plume was very vigorous for a short time, yet it be-
came at the end of a fortnight weak and sickly ; and
at that period less vigorous in its growth than the
sprouts which had been naturally developed, so that
there can be scarcely any useful application of these
experiments. Too rapid growth and premature de-
cay seem invariably connected in organized struc-
tures ; and it is only by following the slow operations
of natural causes, that we are capable of making im-
provements.

There is a number of chemical substances which
are very offensive and even deadly to insects, which
do not injure, and some of which even assist vegeta-
tion. Several of these mixtures have been tried with
various success ; a mixture of sulphur and lime,
which is very destructive to slugs, does not prevent
the ravages of the fly on the young turnip crop. His
Grace the Duke of Bedford, at my suggestion, was
so good as to order the experiment to be tried on a
considerable scale at Woburn farm : the mixture of
lime and sulphur was strewed over one part of a field
sown with turnips 5 nothing was applied to the other

[ 195^ ]

part, but both were attacked nearly in the same man-
ner by the fly.

Mixtures of soot and quicklime, and urine and
quicklime, will probably be more efficacious. The
volatile alkali given off by these mixtures is offensive
to insects ; and they afford nourishment to the plant.
Mr. T. A. Knight* informs me, that he has tried
the method by ammoniacal fumes with success ; but
more extensive trials are necessary to establish its gen-

• Mr. Knight has been so good as to furnish me with the following note on
this subject.

" The experiment which I tried the year before last, and last year, to pre-
serve turnips from the fly, has not been sufficiently often repeated to enable me t»
speak with any degree of decision ; and last year all my turnips succeeded per-
fectly well. In consequence of your suggestion, when I had the pleasui-e to meet
Tou some years ago at Holkham, that lime slaked with urine might possibly be
found to kill, or drive off, the insects from a turnip crop, I tried that preparation
ill mixture with three parts of soot, which was put into a small barrel, with gim-
blet holes round it, to permit a certain quantity of the, composition, about four
bushels to an acre, to pass out, and to fall into the drills with the turnip seeds.
Whether it was by affording highly stimulating food to the plant, or giving some
iUvour which the flies did not like, I cannot tell ; but in the year 1811, the adjoin-
ing rows were eaten away, and those to which the composition was applied, as
above described, were scarcely at all touched. It is my intention in future to drill
my crop in, first, with the composition on the top of the ridge ; and then to sow
at least a pound of seed, broad-cast, over the whole ground. The expense of this
will be very trifling, not more than 2s. per acre ; and the horse-hoe will instantly
sweep away all the supernumeraries between the rows, should those escape the
flies, to which however they will be chiefly attracted ; because it will always be
found that those insects prefer turnips growing in poor, to those in rich ground.
One advantage seems to be the acceleration given to the growth of the plants,
by the highly stimulative effects of the food they instantly receive as soon as their
growth commences, and long before their radicles have reached the dung< The"
directions abcive given apply only to turnips sewed upon ridges, with the manure
immediately under them ; and I am quite certain, that in all soils turnips should
be thus cultivated. The close vicinity of the manure, and the consequent short
time required to carry the food into the leaf, and return the organizable matter to
the roots, are, in my hypothesis, points of vast importance ; and the results in
practice are correspondent.**

C 196 ]

eral efficacy. It may, however, be safely adopted, for *^
if it should fail in destroying the fly, it will at least be*
an useful manure to the land.

After the roots and leaves of the infant plant are
formed, the cells and tubes throughout its structure
become filled with fluid, which is usually supplied from
the soil, and the function of nourishment is perform-
ed by the action of its organs upon the external ele-
ments. The constituent parts of the air are subser-
vient to this process ; but, as it might be expected,
they act differently under different circumstances.

When a growing plant, the roots of which are sup-
plied with proper nourishment, is exposed in the pre-
sence of solar light to a given quantity of atmospheri-
cal air, containing its due proportion of carbonic acid,
the carbonic acid after a certain time is destroyed, and
a certain quantity of oxygene is found in its place. If
new quantities of carbonic acid gas be supplied, the
same result occurs ; so that carbon is added to plants
from the air by the process of vegetation in sunshine ;
^nd oxygene is added to the atmosphere.

This circumstance is proved by a number of ex-
periments made by Drs. Priestley, Ingenhousz and
Woodhouse, and M. T. de Saussure ; many of which
I have repeated with similar results. - The absorption
of carbonic acid gas, and the production of oxygene
are performed by the leaf ; and leaves recently separ-
ated from the tree effect the change, when confined in
portions of air containing carbonic acid ; and absorb
carbonic acid and produce oxygene, even when im-
mersed in water holding carbonic acid in solution.

C 197 3

The carbonic acid is probably absorbed by the
fluids in the cells of the green or parenchymatous part
of the leaf; and it is from this part that oxygene gas
is produced during the presence of light. M. Senne-
bier found that the leaf, from which the epidermis was
stripped off, continued to produce oxygene when
placed in water, containing carbonic acid gas, and the
globules of air rose from the denuded parenchyma;
and it is shewn both from the experiments of Senne-
bier and Woodhouse, that the leaves most abundant
in parenchymatous parts produce most oxygene in
water impregnated with carbonic acid.

Some few plants * will vegetate in an artificial at-
mosphere, consisting principally of carbonic acid, and
many will grow for some time in air, containing from
one-half to one-third; but they are not so '^calthy as
when supplied with smaller quantities of this elastic

substance.

Plants exposed to light have been found to pro-
duce oxygene gas in an elastic medium and in wa-
ter, containing no carbonic acid gas; but in quantities
much smaller than when carbonic acid gas was pre-
sent.

In the dark no oxygene gas is produced by
plants, whatever be the elastic medium to which they
are exposed; and no carbonic acid absorbed. In most
cases, on the contrary, oxygene gas, if it be present, is
absorbed, and carbonic acid gas is produced.

* I foand the Arenaria tenuifoUa to produce oxygene ia carbonic acid, which
wa? nearly pure.

C 198 3

In the changes that take place in the composition
of the organized parts, it is probable that saccharine
compounds are principally formed during the absence
of light; gum, woody fibre, oils, and resins during
its presence; and the evolution of carbonic acid gas, or
its formation during the night, may be necessary to
give, greater solubility to certain compounds in the
plant. I once suspected that all the carbonic acid gas
produced by plants in the night, or in shade, might be
owing to the decay of some part of the leaf, or epider-
mis; but the recent experiments of Mr. D. Ellis, are
opposed to this idea; and I found that a perfectly
healthy plant of celery, placed in a given portion of air
for a few hours'only, occasioned a production of car-
bonic acid gas, and an absorption of oxygene.

Some persons have supposed that plants exposed
in the free atmosphere to the vicissitudes of sunshine
and shade, light and darkness, consume more oxy-
gene than they produce, and that their permanent agen-
cy upon air is similar to that of animals; and this opin-
ion is espoused by the writer on the subject I have
just quoted, in his ingenious researches on vegetation.
But all the experiments brought forwards in favour of
this idea, and particularly his experiments, have been
made under circumstances unfavourable to accuracy
of result. The plants have been confined and suppli-
ed with food in an unnatural manner; and the influ-
ence of light upon them has been very much dimin-
ished by the nature of the media through which it pas-
sed. Plants confined in limited portions of atmos-
pheric air soon become diseased; their leaves decay.

r 1^^ ]

and by their decomposiiion they rapidly destroy the
oxygene of the air. In some of the early experiments
of Dr. Priestley before he was acquainted with the
agency of light upon leaves, air that had supported
combustion and respiration, was found purified by the
growth of plants when they were exposed in it for suc-
cessive days and nights ; and his experiments are the
more unexceptionable, as the plants, in many of them,
grew in their natural states ; and shoots, or branches
from them, only where introduced through water into
the confined atmosphere.

I have made some few researches on this subject,
and I shall describe their results. On the 12th of
July, 1 800, I place a turf four inches square, clothed
with grass, principally meadow fox-tail, and white
clover, in a porcelain dish, standing in a shallow tray
filled with water ; I then covered it with a jar of flint
glass, containing 380 cubical inches of common air in
its natural state. It was exposed in a garden, so as
to be liable to the same changes with respect to light
as in the common air. On the 20th of July the results
were examined. There was an increase of the volume
of the gas, amounting to fifteen cubical inches ; but the
temperature had changed from 64° to 71°; and the
pressure of the atmosphere, which on the 12th had
been equal to the support of 30.1 inches of mercury,
was now equal to that of SO. 2. Some of the leaves of
the white clover, and of the fox-tail were yellow, and
the whole appearance of the grass less healthy than
when it was first introduced. A cubical inch of the
gas, a^tated in lime-water, gave a slight turbidness to

C '^00 ]

the water j and the absorption was not quite rh of its
volume. 10 parts .of the residual gas exposed to a
solution of green sulphate of iron, impregnated with
nitrous gas, a substance which rapidly absorbs oxygene
from air, occasioned a diminution to 80 parts. 00
parts of the air of the garden occasioned a diminution
to 7^ parts.

If the results of this experiment be calculated
upon, it will appear that the air had been slightly
deteriorated by the acdon of the grasses. But the
weather was unusually cloudy during the progress of
the experiment ; the plants had not been supplied in a
natural manner with carbonic acid gas ; and the quan-
tity formed during the night, and by the action of the
laded leaves, must have been partly dissolved by the
water ; and that this was actually the cast:', I proved
by pouring lime-water into the water, when an imme-
diate precipitation was occasioned. The increase of
azote I am inchned to attribute to common air disen-
gaged from the water.

The following experiment I consider as conduct-
ed under circumstances more analogous to those exis-
ting in nature. A turf four inches square, from an
irrigated meadow, clothed with common meadow
grass, meadow fox- tail grass, and vernal meadow grass,
was placed in a porcelain dish, which swam onthe sur-
face of water impregnated with carbonic acid gas. A
vessel of thin flint glass, of the capacity of 230 cubi-
cal inches, having a funnel furnished with stop-cock
inserted in the top, was made to cover the grass ; and
the apparatus was exposed in an open place j a small

Fiij. 11

p. LHH

[ 20k J

quantity of water was daily supplied to the grass by
means of the stop-cock.* Every day likewise a certain
qu^tity of water was removed by a siphon, and water
staturated with carbonic acid gas supplied in its place ;
so that it may be presumed, that a small quantity of
carbonic add gas was constantly present in the re-
ceiver. On the 7th of July, 1807, the first day of
the experiment, the weather was cloudy in the morn-
ing,-but fine in the afternoon ; the thermometer at
C7, the barometer 30.2 : towards the evening of this
day a slight increase of the gas was perceived, the next
three days were bright ; but in the morning of the
1 1 th the sky was clouded ; a considerable increase of
the volume of the gas was now observed : the 1 2th
was cloudy, with gleams of sunshine ; there was still
an increase, but less than in the bright days ; the 13th
was bright. About nine o'clock A.M. on the 14th
the receiver was quite full ; and considering the ori-
ginal quantity in the jar, it must have been increased
by at least 30 cubical inches of elastic fluid : at times
during this day globules of gas escaped. At ten on
the morning of the 15th, I examined a portion of the
gass ; it contained less than _*_ of carbonic acid gas :
100 parts of it exposed to the impregnated solution
left only 75 parts ; so that the air was four per cent,
purer than the air of the atmosphere.

I shall detail another similar experiment made
with equally decisive results. A shoot from a vine^
having three healthy leaves belonging to it, attached

See Fig. 17.

D

[ ^02 3

to its parent tree, was bent so as to be placed under
the receiver which had been used in the last experi-
ment ; the water confining the common air was kept in
the same manner impregnated with carbonic acid gas :
the experiment was carried on from August 6th till
August 14th, 1807 ; during this time, though the
weather had been generally clouded, and there had
been some rain, the volume of elastic fluid continued to
increase. Its quality was examined on the morning of
the 15th; it contained ^'^ of carbonic acid gas, and
100 parts of it afforded 23.5 of oxygene gas.

These facts confirm the popular opinion, that
when the leaves of vegetables perform their healthy
functions, they tend to purify the atmosphere in the
common variations of weather, and changes from light
to darkness.

In germination, and at the time of the decay of
the leaf, oxygene must be absorbed ; but when it is
considered how large a part of the surface of the
earth is clothed with perennial grasses, and that half
of the globe is always exposed to the solar light, it ap-
pears by far the most probable opinion, that more
oxygene is produced than consumed during the pro-
cess of vegetation ; and that it is this circumstance
which is the principal cause of the uniformity of the
constitution of the atmosphere.

Animals produce no oxygene gas during the ex-
ercise of any of their functions and they are constantly
consuming it ; but the extent of the animal, compar-
ed to that of the vegetable, kingdom is very small ;
and the quantity of carbonic acid gas produced

C 203 3 ^

in respiration, and in various processes of com-
bustion and fermentation, bears a proportion ex-
tremely minute to the whole volume of the atmos-
phere : if every plant during the progress of its life
makes a very small addition of oxygene to the air, and
occasions a very small consumption of carbonic acid,
the effect may be conceived adequate to the wants of
nature.

It may occur as an objection to these views, that
if the leaves, of plants purify the atmosphere, towards
the end of autumn, and through the winter, and early
spring, the air in our climates must become impure,
the oxygene in it diminish, and the carbonic acid gas
increase, which is not the case ; but there is a very
satisfactory answer to this objection. The different
parts of the atmosphere are constantly mixed together
by winds, which when they are strong, move at the
rate of from 60 to 100 miles in an hour. In our win-
ter, the south-west gales convey air^ which has been,
purified by the vast forests and savannas of South
America, and which, passing over the ocean, arrives
in an uncontaminated state. The storms and tempests
which often occur at the beginning, and towards the
middle of our winter, and which generally blow
from the same quarter of the globe, have a salutary
influence. By constant agitation and motion, the
equilibrium of the constituent parts of the atmosphere
is preserved ; it is fitted for the purposes of life ; and
those events, which the superstitious formerly refer-
red to the wrath of heaven, or the agency of evil
spirits, and in which they saw only disorder and con-

n 204 J

fusion, are demonstrated by science, to be ininistra-
tions of divine intelligence, and connected with the or-
der and harmony of our system.

I have reasoned, in a former part of this Lecture,
against the close analogy which some persons have as-
sumed between the absorption of oxygene and the for-
mation of carbonic acid gas in germination, and in the
respiration ot the foetus. Similar arguments will ap-
ply against the pursuit of this analogy between the
functions of the leaves of the adult plant, and those of
the lungs of the adult animal. Plants grow vigorous-
ly only when supplied with light ; and most species
die if deprived of it. It cannot be supposed that the
production of oxygene from the leaf, which is known
to be connected with its natural colour, is the exertion
of a diseased function, or that it can acquire carbon in
the day-time, when it is in most vigorous growth,
when the sap is rising, when all its powers of obtain-
ing nourishment are exerted ; merely for the purpose
of giving it off again in the night, when its leaves are
closed, when the motion of the sap is imperfect, and
wheii it is in a state approaching to that of quiescence.
Many plants that grow upon rocks, or soils, contain-
ing no carbonic matter, can only be supposed to ac-
quire their charcoal from the carbonic acid gas in the
atmosphere ; and the leaf may be considered at the
same time as an organ of absorption, and an organ
in which the sap may undergo different chemical
changes.

When pure water only is absorbed by the roots
of plants, the fluid, in passing into the leaves, will

t

probably have greater power to absorb carbonic acid
from the atmosphere, when the water is saturated with
carbonic acid gas, some of this substance, even in the
sunshine, may be given off by the leaves; but a part of*
it likewise will be always decomposed, which has been
proved by the experiments of M. Sennebier.

When the fluid taken up by the roots of plants
contains much carbonaceous matter, it is probable
that plants may give off carbonic acid from their leaves,
even in the sunshine. In short, the function of the
leaf must vary according to the composition of the sap
passing through it. When sugar is to be produced,
as in early spring at the time of the development of
buds and flowers, it is probable that less oxygene will
be gw^n off, than at the time of the ripening of the
seed, when starch, or gums, or soils, ai^ formed; and
the process of ripening the seed usually takes place
when the agency of the solar light is most intense.
Whentheacid juices of fruits become saccharine in the
natural process of vegetation, more oxygene, there
is every reason to believe, must be given off, or new-
ly combined, than at other times; for, as it was shewn
in the third Lecture, all the vegetable acids contain
more oxygene than sugar. It appears probable, that
in some cases, in which oily and resinous bodies are
formed in vegetation, water may be decomposed: its
oxygene set free, and its hydrogene absorbed.

I have already mentioned, that some plants pro-
duce oxygene in pure water; Dr. Ingenhousz foiHid
this to be the case with species of the confervse; I
have tried the leaves of many plaats, particularly those

C 2oej ],

that produce volatile oils. When such leaves are ex-
posed in water saturated with oxygene gas, oxygene
is given off in the solar light; but the quantity is very
small and always limited; nor have I been able to as-
certain with certainty, whether the vegetative powers
of the leaf were concerned in the operation, though it
seems probable. I obtained a considerable quantity of
oxygene in an experiment made fifteen years ago,
in which vine leaves were exposed to pure water; but
on repeating the trial often since, the quantities have
always been very much smaller; I am ignorant whe-
ther this difference is owing to the peculiar state of the
leaves, or to some confervas which might have adher-
ed to the vessel, or to other sources of fallacy.

The most important and most common products of
vegetables, mucilage, starch, sugar, and woody fibre,
are composed of water, or the elements of water in
their due proportion, and charcoal; and these, or some
of them, exist in all plants; and the decomposition of
carbonic acid, and the combination of water in vege-
table structures, are processes which must occur al-
most universally.

When glutenous and albuminous substances ex-
ist in plants, the azote they contain may be suspected
to be derived from the atmosphere; but no experi-
ments have been made which prove this; they might
easily be instituted upon mushrooms and fungusses.

In cases in which buds are formed, or shoots
thrown forth from roots, oxygene appears to be urn-
formly absorbed, as in the germination of seeds. I
exposed a small potatoe moistened with common wa-

[ 207

<(

ter to 24 cubical inches of atmospherical air, at a tem-
perature of 59°. It began to throw forth a shoot on
the third day; when it was a half an inch long I ex-
amined the air; nearly a cubical inch of oxygene was
absorbed, and about three-fourths of a cubical inch of
carbonic acid formed. The juices in the shoot separ- ^^
ated from the potatoe, had a sweet taste; and the ab-
sorption of oxygene, and the production of carbonic
acid, were probably connected with the conversion of
a portion of starch into sugar. When potatoes that
h,ave been frozen are thawed, they become sweet; pro-
bably oxygene is absorbed in this process; if so, the
change may be prevented by thawing them out of the
contact of air, under water, for instance, that has
been recently boiled.

In the tillering of corn that is, the production of
new stalks round the original plume, there is every rea-
son to believe that oxygene must be absorbed; for the
stalk at which the tillering takes place, always con-
t^ns sugar, and the shoots arise from a part derived of-
light. The drill husbandry favours this process; for
loose earth is thrown by hoeing round the stalks; they
are preserved from light, an4 yet supplied with oxy-
gene. I have counted from forty to one hundred and
twenty stalks; produced from a grain of wheat, in a
moderately good crop of drilled wheat. And we are
informed by Sir Kenelm Digby in 1660, that there was ,
in the possession of the Fathers of the Christian Doc-
trine at Paris, a plant of barley which they, at that time,
kept by them as a curiosity, and which consisted of 249
stalks springing from one root, or grain; and in which
they counted above 18,000 grains, or seeds of barley.

[ 203 3

The great increase which takes place in the trans-
plantation of wheat, depends upon the circumstanccj
that each layer thrown out in tillering may be remov-
ed, and treated as a distinct plant. In the Philosophi-
cal Transactions, Vol. LVIII, p. 203, the following
statement may be found : Mr. C. Miller, of Cam-
bridge, sowed some wheat on the 2d of June, 1 766 ;
and on the 8th of August, a plant was taken and
separated into 18 parts, and replanted; these plants
were again taken up, and divided in the months of
September and October, and planted separately to
stand the winter, which division produced 67 plants.
They were again taken up in March and April, and
produced 500 plants : the number of ears thus form-
ed from one grain of wheat was 21109, which gave
three pecks and three quarters of corn that weighed
47lbs. 7ozs. ', and that were estimated at 576840
grains.

It is evident from the statements just given, that the
change which takes place in the juices of the leaf by the
the action of the solar light, must tend to increase the
proportion of inflammable matter to their other con-
stituent parts. And the leaves of the plants that grow
in darkness, or in shady places, are uniformly pale ;
their juices are watery and saccharine, and they do
not afford oils or resinous substances. I shall detail
an experiment on this subject.

I tbok an equal weight, 400 grains, of the leaves
of two plants of endive, one bright green, which had
grown fully exposed to light, and the other almost
white, which had been secluded from light by beiftg

i-*

[ 209 ]

covered with a box; after being both acted upon for
some time by boiling water, in the state of pulp, the
undissolved matter was dried, and exposed to the
action of warm alcohol. The matter from the green
leaves gave it a tinge of olive; that from the pale leaves
did not alter its colour. Scarcely any solid matter
was produced by evaporation of the alcohol that had
been digested on the pale leaves; whereas by the eva-
poration of that from the green leaves, a considerable
residuum was obtained, five grains of which were se-
parated from the vessel in which the evaporation was
carried on; they burnt with flame, and appeared partly
matter analogous to resin. 53 grains of woody fibre
were obtained from the green leaves, and only 31
from the pale leaves.

It has been mentioned in the Third Lecture, that
the sap probably, in common cases, descends from the
leaves into the bark; the bark is usually so loose in its
texture, that the atmosphere may possible act upon it
in the cortical layers; but the changes taking place in
the leaves, appear sufficient to explain the difference be-
tween the products obtained from the bark and from
the alburnum; the first of which contains more carbo-
naceous matter than the last.

When the similarity of the elements of different
vegetable products is considered, according to the
views given in the third Lecture, it is easy to conceive
how the different organized parts may be formed from
the same sap, according to the manner in which it is
acted on by heat, light, and air. By the abstraction
ofoxygene, the different inflammable products, fixed

e2

C 210 _ J

and volatile oils, resins, camphor, woody fibre, &c.
may be produced from saccharine or mucilaginous
fluids; and by the abstraction of carbon and hydro-
gene, starch, sugar, the different vegetable acids and
substances soluble in water, may be formed from high-
ly combustible and insoluble substances. Even the
limpid volatile oils which convey the fragrance of the
flower, consist of different proportions of the same
essential elements, as the dense woody fibre; and both
are formed by different changes in the same organs,
from the same materials, and at the same time.

M. Vauquelin has lately attempted to estimate
the chemical changes taking place in vegetation, by
analysing some of the organized parts of the horse-
chesnut in their different stages of growth. He found
in the buds collected, March 7. 1812, tanning princi-
ple, and albuminous matter capable of being obtained
separately, but when obtained, combining with each
other. In the scales surrounding the buds, he found
the tanning principle, a little saccharine matter, resin,
and a fixed oil. In the leaves fully developed, he dis-
covered the same principles as in the buds; and in ad-
dition, a peculiar green resinous matter. The petals
of the flower yielded a yellowish resin, saccharine mat-
ter, albuminous matter, and a little wax: the stamina
afforded sugar, resin, and tannin.

The young chesnuts examined immediately after
their formation, afforded a large quantity of a matter
which appeared to be a combination of albuminous
matter and tannin. All the parts of the plant aff'ord-
ed saline combinations of the acetic and phosphoric
acids.

C 211 ]

M. Vauquelin could not obtain a sufficient quan-
tity of the sap of the horse-chesnut for examination; a
circumstance much to be regretted; and he has not
stated the relative quantities of the different substances
in the buds, leaves, flowers, and seeds. It is proba-
ble, however, from his unfinished details, that the
quantity of resinous matter is increased in the leaf, and
that the white fibrous pulp of the chesnut is formed
by the mutual action of albuminous and astringent,
matter, which probably are supplied by different cells
or vessels. I have already mentioned^ that the cam-
bium, from which the new parts of the trunk and the
branches appear to be formed, probably owes its pow-
er of consolidation to the mixture of^two different
kinds of sap; one of which flows upwards from the
roots; and other of which probably descends from the
leaves. I attempted, in May 1804, at the time the
cambium was forming in the oak, to ascertain the na-
ture of the action of the sap of the alburnum upon the
juices of the bark* By perforating the alburnum m a
young oak, and applying an exhausting syringe to the
aperture, I easily drew out a small quantity of sap.
I could not, however, in the same way obtain sap from
the bark. I was obliged to recur to the solution of
its principles in water, by infusing a small quantity of
fresh bark in warm watery the liquid obtained in this
way was highly coloured and astringent; and produc-
ed an immediate precipitate in the alburnous sap, the

• Page 131..

C 212 ]

taste of which was sweetish, aud sligtitly astringent,
and which was colourless.

The increase of trees and plants must depend
upon the quantity of sap which passes into the organs
upon the quality of this sap; and on its modification
by the principles of the atmosphere. Water, as it is
the vehicle of the nourishment of the plant, is the sub-
stance principally given off by the leaves. Dr. Hales
found, that a sunflower, in one day of twelve hours,
transpired by its leaves one pound fourteen ounces of
water, all of which must have been imbibed by its
roots.

The powers which cause the ascent of the sap
have been slightly touched upon in the second and
third Lectures. The roots imbibe fluids from the soil
by capillary attraction; but this power alone is insuffi-
cient to account for the rapid elevation of the sap into
the leaves. This is fully proved by the following fact
detailed by Dr. Hales, Vol. I. of the Vegetable Statics,
page 1 14. A vine branch of four or five years old- was
cut through, and a glass tube carefully attached to
it; this tube was bent as a siphon, and filled with quick-
silver; so that the force of the ascending sap could be
measured by its effect in elevating the quicksilver. In
a few days it was found, that the sap had been propel-
led forwards with so much force as to raise the quick-
silver to 38 inches, which is a force considerably su-
perior to that of the usual pressure of the atmosphere.
Capillary attraction can only be exerted by the sur-
faces of small vessels, and can never raise a fluid into
tubes above the vessels themselves.

I 213 ]

I referred in the beginning of the Third Lecture
to Mr. Knight's opinion, that the contractions and
expansions of the silver grain in the alburnum, are
the most efficient cause of the ascent of the fluids con-
tained in its pores and vessels. The views of this ex-
cellent physiologist are rendered extremely probable
by the facts he has brought forwards in support of
them. Mr. Knight found that a very small increase
of temperature was sufficient to cause the fibres of the
silver grain to separate from each other, and that a
very slight diminution of heat produced their contrac-
tion. The sap rises most vigorously in spring and
autumn, at the time the temperature is variable ; and
if it be supposed, that in expanding and contracting,
the elastic fibres of the silver grain exercise a pressure
upon the cells and tubes containing the fluid absorbed
by the capillary attraction of the roots, this fluid must
constantly move upwards towards the points where a
supply is needed.

The experiments of Montgolfier, the celebrated
inventor of the balloon, have shewn that water may
be raised almost to an indefinite height by a very
small force, provided its pressure be taken off by con-
tinued divisions in the column of fluid. This princi-
ple, there is great reason to suppose, must operate in
assisting the ascent of the sap in the cells and vessels
of plants which have no rectilineal communication,
and which every where oppose obstacles to the per*
pendicular pressure of the sap.

The changes taking place in the leaves and buds,
and the degree of their power of transpiration, must;

[214 3

be intimately connected likewise "with the motion of
the sap upwards. This is shewn by several experi-
ments of Dr. Hales.

A branch from an appple tree was separated and
introduced into water, and connected with a mercurial
gage. When the leaves were upon it, it raised the
mercury by the force of the ascending juices to four
inches ; but a similar branch, from which the leaves
were removed, scarcely raised it a quarter of an inch.

Those trees, likewise, whose leaves are soft and
of a spongy texture, and porous at their upper sur-
faces, displayed by far the greatest powers with regard
to the elevation of the sap.

The same accurate philosopher whom I have just
quoted, found that the pear, quince, cherry, walnut,
peach, gooseberry, water elder and sycamore, which
have all soft and unvarnished leaves, raised the mer-
cury under favourable circumstances from three to
six inches. Whereas the elm, oak, chesnut, hazel,
sallow, and ash, which have firmer and more glossy
leaves, raised the mercury only from one to two
inches. And the evergreens and trees bearing var-
nished leaves, scarcely at all affected it 5 particularly
the laurel and the laurustinus.

It will be proper to mention the facts which
shew, that in many cases fluids descend through the
bark ; they are not of the same unequivocal nature
as those which demonstrate the ascent of the sap
through the alburnum ; yet many of them are satis-
factory.

C 215 J

M. Balsse placed branches of different trees in
an infusion of madder, and kept them there for a long
time. He found in all cases, that the wood became
red before the bark ; and that the bark began to re-
ceive no tinge till the whole of the wood was colour-
ed, and till the leaves were affected ; and that the co-
louring matter first appeared above, in the bark im-
mediately in contact with the leaves.

Similar experiments were made by M. Bonnet,
and with analogous results, though not so perfectly
distinct as those of M. Baisse.

Du Hamel found, that in different species of the
pine and other trees, when strips of bark were re-
moved, the upper part of the wound only emitted fluid,
whilst the lower part remained dry.

This may likewise be observed in the summer
in fruit trees, when the bark is wounded, the alburn-
um remaining untouched.

I have mentioned in the Third Lecture, that when
new bark is formed to supply the place of a ring-
that has been stripped off, it first makes its appearance
upon the upper edge of the wound, and spreads slow-
ly downwards 5 and no new matter appears from be-
low rising upwards, if the experiment has been care-
fully performed. I say carefully performed j because, if
any of the interior cortical layer be suffered to remain
communicating with the upper edge, new bark cover-
ed with epidermis will form below this, and appear as
if protruded upon the naked alburnum, and formed
within the wound 5 and such a circumstance would
give rise to erroneous conclusions.

^216

hi the suininer of 1804, I examined some elms
at Kensington. The bark of many of them had been
very much injured, and in some cases more than a
square foot had been stripped off. In most of the
wounds the formation of the new cortical layers was
from above, and gradually extending downwards
round the aperture j but in two instances there had
been very distinctly a formation of bark towards the
lower edge. I was at first very much surprised at
this appearance, so contradictory to the general
opinion j but on passing the point of a pen-knife along
the surface of the alburnum, from below upwards, I
found that a part of the cortical layer, which was of
the colour of the alburnum, had remained communi-
cating with the upper edge of the wound, and that
the new bark had formed from this layer. I have had
no opportunity of looldng at the trees lately ; but I
doubt not that the phaenomenon may still be observ-
ed ; for some years must elapse before the new forma-
tions will be complete.

In accounting for the experiment of M. Palisot
de Beauvois, mentioned in the Third Lecture, it may
be supposed that the cortical fluid flowed down the
alburnum upon the insulated bark, and thus occasion-
ed its increase ; or it may be conceived that the bark
itself contained sufficient cortical fluid at the time of
its separation to form new parts by its action upon the
alburnous fluid.

The motion of the sap through the bark seems
principally to depend upon gravitation. When the
watery particles have been considerably dissipated

C 217 2

by the transpiring functions of the leaves, and the mu^
cilaginous, inflammable, and astringent constituents,
increased by the agency of heat, light, and air, the
continued impulse upwards from the alburnum, forces
the remaining inspissated fluid into the cortical vessels?
which receive no other supply. In these, from its
weight, its natural tendency must be to descend;
and the rapidity of the descent must depend upon
the general consumption of the fluids of the bark
in the living processes of vegetation; for there is every
reason to believe, that no fluid passes into the soil
through the roots; and it is impossible to conceive a
free lateral communication between the absorbent ves-
sels of the alburnum in the roots, and the transport-
ing or carrying vessels of the bark; for if such a com-
munication existed, there is no reason why the sap
should not rise through the bark as well as through
the alburnum; for the same physical powers would
then operate upon both.

Some authors have supposed that the sap rises in
the alburnum, and descends through the bark in con-
sequence of a power similar to that which produces the
circulation of the blood in animals; a force analagous
to the muscular force in the sides of the vessels.

Dr. Thomson, in his System of Chemistry, ha^
stated a fact which he considers as demonstrating the
irritability of living vegetable systems. When a stalk
of spurge (Euphorbia peplis) is separated by two in-
cisions fr©m its leaves and roots, the milky fluid flows
through both sections. Now, says the ingenious au-
thor, it is impossible that this could happen without

F 2

I 218 3

the living action of the vessels, for they cannot have
been more than full; and their diameter is so small,
that if it were to continue unaltered, the capillary at-
traction would be more than sufficient to contain their
contents, and consequently not a drop would flow out.
Since therefore the liquid escapes, it must be driven
out by a force different from a common physical force.

To this reasoning it may be answered, that the
sides of all the vessels are soft, and capable of collaps-
ing by gravitation, as veins do in animal systems long
after they have lost all their vitality; which is an effect
totally different from vital or irritable action; and the
phaenomenon may be compared to that of puncturing
a vessel of elastic gum filled with fluid, both above and
below; the fluid will make its way through the a-
pertures, though in much larger quantity from the
lowest, which I have found is likewise the case with the
Spurge.

Dr. Barton has stated, that plants grow more vi-
gorously in water in which a little camphor has been
infused. This has been brought forward as a fact in
favour of the irritability of the vegetable tubular sys-
tem. It is said that camphor can only be conceived
to act as a stimulus, by increasing the living powers
of the vessels, and causing them to contract with more
energy. But this kind of speculation is very unsatis-
factory. Camphor, we know, has a disagreeable pun-
gent taste, and powerful smell; but physicians are far
from being agreed whether it is a stimulant or sedative,
even in its operation upon the human body. We
should have no right whatever, even supposing the ir-

[ 219 2

ritabillty of vegetables proved, to conclude, that be-
cause camphor assisted the growth of plants, it acted
on their living powers; and it is not right to infer the
existence of a property proved in no other way, from
the operation of uncertain qualities.

That camphor may assist the growth of plants it
is easy to conceive; and why should we not consider
its efficacy as similar to the efficacy of saccharine and
mucilaginous matter, and particularly of oils, to which
it is nearly allied in composition; and which afford
food to the plant, and not stimulus; which are materi-
als of assimilation, and not of excitement?

The arguments in favour of a contraction similar
to muscular action have not then much weight; and
besides, there are direct facts which render the opinion
highly improbable.

When a single branch of a vine or other tree is
introduced in winter into a hot-house, the trunk and
the other branches remaining exposed to the cold at-
mosphere, the sap will soon begin to move towards the
buds in the heated branch; these buds will gradually
unfold themselves ajid begin to transpire; and at length
open into leaves. Now if any peculiar contractions of
the sap vessels or cells were necessary for the ascent of
the sap in the vessels, it is not possible that the applica-
tion of heat to a single branch should occasion irrita-
ble action to take place in a trunk many feet removed
from it, or in roots ifixed in the cold soil: but allowing
that the energy of heat raises the fluid merely by di-
minishing its gravity, increasing the facility of capillary
action, and by producing an expansion of the fibres

C 220 ]

of the silver grain, the phaenomenon is in perfect uni-
son with the views advanced in the preceeding part
of this Lecture.

The ilex, or evergreen oak, preserves its leaves
through the winter, even when grafted upon the com-
mon oak; and in consequence of the operation of the
leaves there is a certain motion of the sap from the oak
towards the ilex, which, as in the last case, seems to
be inconsistent with the theory of irritable action.

It is impossible to peruse any considerable part
of the Vegetable Statics of Hales, without receiving a
deep impression of the dependence of the motion of the
sap upon common physical agencies. In the same tree
this sagacious person observed, that in a cold cloudy
morning when no sap ascended, a sudden change was
produced by a gleam of sunshine, of half an hour; and a
vigorous motion of the fluid. The alteration of the
wind from south to the north immediately checked
the effect. On the coming on of a cold afternoon after
a hot day, the sap that had been rising began to fall,
A warm shower and a sleet storm produced opposite
effects.

Many of his observations likewise shew, that the
different powers which act on the adult tre^, produce
different effects at different seasons.

Thus in the early spring, before the buds ex-
pand, the variations of the temperature, and changes
of the state of the atmosphere with regard to moisture
and dryness, exert their great effects upon the expan-
sions and contractions of the vessels; and then the tree
is in what is called by gardeners its bleeding season.

[ 221 3

When the leaves are fully expanded, the great
determination of the sap is to these new organs. And
hence a tree which emits sap copiously from a wound
whilst the buds are opening, will no longer emit it in
summer when the leaves are perfect ; but in the varia-
ble weather, towards the ends of autumn, when the
leaves are falling, it will again possess the power of
bleeding in a very slight degree in the warmest days ;
but at no other times.

In all these circumstances there is nothing analo-
gous to the irritable action of animal systems.

In animal systems the heart and arteries are in
constant pulsation. Their functions are unceasingly
performed in all climates, and in all seasons ; in win-
ter, as well as in spring ; upon the arctic snows, and
under the tropical suns. They neither cease in the
periodical nocturnal sleep, common to most animals ;
nor in the long sleep of winter, peculiar to a few spe-
cies. The power is connected with animation, is lim-
ited to beings possessing the means of voluntary lo-
comotion ; it co-exists with the first appearance of
vitality ; it disappears only with the last spark of life.

Vegetables may be truly said to be living systems,
in this sense, that they possess the means of convert-
ing the elements of common matter into organized
structures, both by assimilation and reproduction ; but
we must not suffer ourselves to be deluded by the
very extensive application of the word life^ to conceive
in the life of plants, any power similar to that produc-
ing the life of animals. In calling forth the vegetable
functions, common physical agents alone seem to-

[ 222 ]

operate ; but in the animal system these agents are
made subservient to a superior principle. To give the
argument in plainer language, there are few philoso-
phers who would be inclined to assert the existence
of any thing above common matter, any thing imma-
terial in the vegetable ceconomy. Such a doctrine is
worthy only of a poetic form. The imagination may
easily give Dryads to our trees, and Sylphs to our
flowers ; but neither Dryads nor Sylphs can be ad-
mitted in vegetable physiology ; and for reasons near-
ly as strong, irritability and animation ought to be ex-
cluded.

As the operation of the different physical agents
upon the sap vessels of plants ceases, and fluid be.
comes quiescent, the materials dissolved in it by heat,
are deposited upon the sides of the tubes now consi-
derably diminished in their diameter; and in conse-
quence of this deposition, a nutritive matter is provi-
ded for the first wants of the plant in early spring, to
assist the opening of the buds, and their expansion,
when the motion from the want of leaves is as yet
feeble.

This beautiful principle in the vegetable cecono-
my was first pointed out by Dr. Darwin ; and Mr.
Knight has given a number of experimental elucida-
tions of it.

Mr. Knight made numerous incisions into the al-
burnum of the sycamore and the birch, at different
heights ; and in examining the sap that flowed from
them, he found it piore sweet and mucilaginous in
proportion as the aperture from which it flowed was

[ 22S 3

elevated ; which he could ascribe to no other cause
than to its having dissolved sugar and mucilage,
which had been stored up through the winter.

He examined the alburnum in different poles of
oak in the same forest : of which some had been fel-
led in winter, and others in summer ; and he always
found most soluble matter in the wood felled in win-
ter, and its specific gravity was likewise greater.

In all perennial trees this circumstance takes
place ; and likewise in grasses and shrubs. The joints
of the perennial grasses contain more saccharine and
mucilaginous matter in winter than at any other sea-
son ; and this is the reason why the fiorin or Agros-
tis alba, which abounds in these joints, affords so use-
ful a winter food.

The roots of shrubs contain the largest quantity
of nourishing matter in the depth of winter ; and the
bulb in all plants pjossessing it, is the receptacle in
which nourishment is hoarded up during winter.

In annual plants the sap seems to be fully ex-
hausted of all its nutritive matter by the production of
flowers and seeds 3 and no system exists by ^which it
can be preserved.

When perennial grasses are cropped very close
by feeding cattle late in autumn, it has been often ob-
served by farmers, that they never rise vigorously
in the spring 5 and this is owing to the removal of
that part ot the stalk which would have afforded them
concrete sap, their first nourishment.

Ship builders prefer for their purposes that kind
of oak timber afforded by trees that have had their

C 224 3

bark stripped ofF in spring, and which have been cut
in the autumn or winter following. The reason of
the superiority of this timber is, that the concrete
sap is expended in the spring in the sprouting of the
leaf; and the circulation being destroyed, it is not
formed anew ; and the wood having its pores free
from saccharine matter, is less liable to undergo fer-
mentation from the action of moisture and air.

In perennial trees a new alburnum, and conse-
quently a new system of vessels, is annually produc-
ed, and the nutriment for the next year deposited in
them ; so that the new buds, like the plume of the
seed, are supplied with a reservoir of matter essential
to their first development.

The old alburnum is gradually converted into
heart-wood, and being constantly pressed upon by
the expansive force of the new fibres, becomes harder,
denser, and at length loses altogether its vascular
structure ; and in a certain time obeys the common
laws of dead matter, decays, decomposes, and is con-
verted into aeriform and carbonic elements ; into those
principles from which it was originally formed.

The decay of the heart- wood seems to constitute
the great limit to the age and size of trees. And in
young branches from old trees, it is much more liable
to decompose than in similar branches from seedlings.
This is likewise the case with grafts. The graft is
only nourished by the sap of the tree to which it is
transferred ; its properties are not changed by it ; the
leaves, blossoms, and fruits are of the same kind as if
it had vegetated upon its parent stock. The only ad-

C 225 J

vantage to be gained in this way, is the affording to a
graft from an old tree a more plentiful and healthy
food than it could have procured in its natural state ;
it is rendered for a time more vigorous, and produces
fairer blossoms and richer fruits. But it partakes not
merely of the obvious properties, but likewise of the
infirmities and dispositions to old age and decay, of
the tree whence it sprung.

This seems to be distinctly shewn by the obser-
vations and experiments of Mr. Knight. He has, in a
nuniber of instances, transferred the young scions and
healthy shoots from old esteemed fruit-bearing trees
to young seedlings. They flourished for two or three
years; but they soon became diseased and sickly like
their parent trees.

It is from this cause that so many of the apples
formerly celebrated for their taste and their uses in the
manufacture of cyder are gradually deteriorating, and
many will soon disappear. The golden pippin, the
red streak, and the moil, so excellent in the beginning
of the last century, are now in the extremest stage of
their decay; and however carefully they are ingrafted,
they merely tend to multiply a sickly and exhausted
variety.

The trees possessing the firmest and the least
porous heart-wood are the longest in duration.

In general the quantity of charcoal afforded by
woods, offers a tolerable accurate indication of their
durability: those most abundant in charcoal and earthy
matter are most permanent; and those that contain the

g2

226

largest proportion of gaseous elements are the mosf.
destructible.

Amongst our own trees, the cheshut and the oak,
are pre-eminent as to durability; and the chesnut af-
fords rather more carbonaceous matter than the
oak.

In old Gothic buildings the^e woods have been
sometimes mistaken one for the other; but they may
be easily known by this circumstance, that the pores
in the alburnum of the oak are much larger and more
thickly set, and are easily distinguished; whilst the
pores in the chesnut require glasses to be seen dis-
tinctly.

In consequence of the slow decay of the heart-
wood of the oak and the chesnut, these trees under
favourable circumstances attain an age w^hich cannot
be much short of a 1000 years.

The beech, the ash, and the sycamore, most like-
ly never live half as long. The duration of the apple
tree is not probably, much more than 200 years; but
the pear tree, according to Mr. Knight, lives through
double this period; most of our best apples are sup-
posed to have been introduced into Britain by a fruit-
erer of Henry the Eighth, and they are now in a state
of old age.

The oak and chesnut decay much sooner in ^
moist situation, than in a dry and sandy soil; and their
timber is less firm. The sap vessels in such cases are
more expanded, though less nourishing matter is car-
ried into them; and the general texture of the forma-
tions of wood necessarily less firnl. Such wood splits

[ 227 ]

more easily, ai>d is more liable to be afFected by varia-
tions in the state of the atmosphere.

The same trees, in general, are much longer lived
In the northern than in the southern cHmates. The
reason seems to be, that all fermentation and decom-
position are checked by cold; and at very low temper-
atures both animal and vegetable matters altogether
resist putrefaction: and in the northern winter, not
only vegetable life, but likewise vegetable decay must
be at a stand.

The antiputrescent quality of cold climates is ful-
ly illustrated in the instances of the rhinoceros and
mammoth lately found in Siberia, entire beneath the
frozen soil, in which they must probably have existed
from the time of the deluge. I examined a part of the
skin of the mammoth, sent to this country, on which
there was some coarse hair; it had all the chemical
characters of recently dried skin.

Trees that grow in situations much exposed to
^''inds, have harder and firmer wood than such as are
considerably sheltered. The dense sap is determined
by the agitation of the smaller brances to the trunk
and large branches; where the new alburnum formed
is consequently thick and firm. Such trees abound in
the crooked limbs fitted for forming knee-timber,
which is necessary for joining the decks and sides of
ships. The gales in elevated situations gradually act,
so as to give the tree the form best calculated to resist
their effects. And the mountain oak rises robust and
sturdy; fixed firmly in the soil, and able to oppose the
full force of the tempest.

C 228 J

The decay of the best varieties of fruit-bearing
trees which have been distributed through the country
by grafts, is a circumstance of great importance.
There is no mode of preserving them; and no re-
source, except that of raising new varieties by seeds.

Where a species has been ameliorated by culture,
the seeds it affords, other circumstances being similar,
produce more vigorous and perfect plants; and in this
way the great improvements in the productions of our
fields and gardens seem to have been occasioned.

Wheat in its indigenous state, as a natural pro-
duction of the soil, appears to have been a very small
grass: and the case is still more remarkable with the
apple and the plum. The crab seems to have been the
parent of all our apples. And two fruits can scarcely
be conceived more different in colour, size, and ap-
pearance than the wild plum and the rich magnum

bonum .

The seeds of plants exalted by cultivation always

furnish large and improved varieties; but the flavour,
and even the colour of the fruit seems to be a matter
of accident. Thus a hundred seeds of the golden
pippin will all produce fine large-leaved apple trees,
bearing fruit of a considerable size; but the tastes and
colours of the apples from each will be different, and
none will be the same in kind as those of the pippin
itself. Some will be sweet, some sour, some bitter,
some mawkish, some aromatic; some yellow, some
green, some red, and some streaked: All the apples
will, however, be much more perfect than those from
the seeds of a crab, which produce trees all of the same
kind, and all bearing sour and diminutive fruit.

C 229 3

The power of the horticulturist extends only to
the muhiplying excellent varieties by grafting. They
cannot be rendered permanent; and the good fruits at
present in our gardens, are the produce of a few seed-
lings, selected probably from hundred of thousands ;
the results of great labour and industry, and multipli-
ed experiments.

The larger and thicker the leaves of a seedling,
and the more expanded its blossoms, the more it is
likely to produce a good variety of fruit. Short-
leaved trees should never be selected ; for these ap-
proach nearer to the original standard ; whereas the
other qualities indicate the influence of cultivation.

In the general selection of seeds, it would appear
that those arising from the most highly cultivated va-
rieties of plants, are such as give the most vigorous
produce ; but it is necessary from time to time to
change, and as it were, to cross the breed.

By applying the pollen, or dust of the stamina
from one variety to the pistil of another of the same
species, a new variety may be easily produced ; and
Mr. Knight's experiments seem to warrant the idea^
that great advantages may be derived from this
method of propagation.

Mr. Knight's large peas produced by crossing
two varieties, are celebrated amongst horticulturists,
and will, I hope, soon be cultivated by farmers.

I have seen several of his crossed apples, which
promise to rival the best of those which are gradually
dying away in the cyder countries.

C 230 ]

And his experiments on the crossing of wheat,
which is very easi'y effected, merely by sowing the
different kinds together, lead to a result which is of
considerable importance. He says, in the Philosophi-
cal Transactions for 1799, " in the years 1795 and
1796, when almost the whole crop of corn in the
island was blighted, the varieties obtained by crossing
alone escaped though sown in several soils, and in very
different situations."

The processes of gardening for increasing the
number of fruit-bearing branches, and for improving
the fruit upon particular branches, will all admit of
elucidation from the principles that have been advan-
ced in this Lecture.

By making trees espaliers, the force of gravity is
particularly directed towards the lateral parts of the
branches, and more sap determined towards the fruit
buds ; and hence they are more likely to bear when
in a horizontal than when in a vertical position.

The twisting of a wire, or tying a thread round
a branch has been often recommended as a means of
making it produce fruit. In this case the descent of
the sap in the bark must be impeded above the liga-
ture ; and more nutritive matter consequently retain-
ed and applied to the expanding parts.

In engrafting, the vessels of the bark of the stock
and the graft cannot so perfectly come in contact as
the albur*nous vessels, which are as much more nu-
merous, and equally distributed ; hence the circulation
downwards is probably impeded, and the tendency
of the graft to evolve its fruit-bearing buds increased.

I 231 3

By lopping trees, more nourishment is supplit-d
to the remaining parts ; for the sap flows laterally as
well as perpendicularly. The same reasons will ap-
ply to explain the increase of size of fruits by dimin-
ishing the number upon a tree.

As plants are capable of amelioration by peculiar
methods of cultivation, and of having the natural term
of their duration extended ; so, in conformity to the
general law of change, they are rendered unhealthy
by being exposed to peculiar unfavourable circum-
stances, and liable to premature old age and decay.

The plants of warm climates transported into
cold ones, or of cold ones transported into warm
ones, if not absolutely destroyed by the change of situ-
ation, are uniformly rendered unhealthy.

Few of the tropical plants, as is well known, can
be raised in this country, except in hot houses. The
vine during the whole of our summer may be said to
be in a feeble state with regard to health , and its
fruit, except in very extraordinary cases, always con-
tains a superabundance of acid. The gigantic pine of
the north, when transported into the equatorial cli-
mates, becomes a degenerated dwarf; and a great
number of instances of the same kind might be
brought forward.

Much has been written, and rnany very ingen-
ious reijiarks have been made by different philoso-
phers, upon what have been called the habits of plants.
Thus; in transplanting a tree, it dies or becomes un-
healthy, unless its position with respect to the sun is
the same as before. The seeds brought from warm

I 232 ]

climates germinate here much more early in the sea-
son than the same species brought from cold climates.
The apple tree from Siberia, where the short summer
of three months immediately succeeds the long winter,
in England, usually puts forths its blossoms in the
first year of its transplantation, on the appearance of
mild weather; and is often destroyed by the late
frosts of the spring.

It is not difficult to explain this principle so inti-
mately connected with the healthy or diseased state of
plants. The organization of the germ, whether in
seeds or buds, must be different according as more or
less heat or alternations of heat and cold have affected
it during its formation ; and the nature of its expan-
sion must depend wholly on this organization. In a
changeable chmate the formations will have been inter-
rupted, and in different successive layers. In an equa-
ble temperature they will have been uniform ; and
the operation of new and sudden causes will of course
be severely felt.

The disposition of trees may, however, be chang-
ed gradually in many instances j and the operation of
a new climate in this way be made supportable. The
myrtle, a native of the South of Europe inevitably
dies if exposed in the early state of its growth to the
frosts of our winter ; but if kept in a green-house
during the cold seasons for successive years, and
gradually exposed to low temperatures, it will, in an
advanced stage of growth, resist even a very severe
cold. And in the south and west of England the^
myrtle flourishes, produces blossoms and seeds, in

[ 233 1

consequence of this process, as an unprotected stan-
dard tree ; and the layers from such trees are much
more hardy than the layers from myrtles reared with-
in doors.

The arbutus, probably originally from similar
cultivation, has become the principal ornament of the
lakes of the south of Ireland. It thrives even in bleak
mountain situations; and there can be little doubt bu.t
that the offspring of this tree inured to a temperate cli-
mate might be easily spread in Britain.

The same principles that apply to the effects of
heat and cold will likewise apply to the influence of
moisture and dryness. The layers of a tree habitua-
ted to a moist soil will die in a dry one: even though
such a soil is more favourable to the general growth
of the species. And, as was stated page 1 69, trees
that have been raised in the centre of woods are soon-
er or later destroyed, if exposed rn their adult state to
blasts, in consequence of the felling of the surround-
ing timber.

Trees, in all cases, in which they are exposed in
high and open situations to the sun, the winds, and
the rain, as I just now noticed, become low and ro-
bust, exhibiting curved limbs, but never straight and
graceful trunks. Shrubs and trees, on the contrary,
which are too much sheltered, too much secluded
from the sun and wind extend exceedingly in height;
but present at the same time slender and feeble
branches, their leaves are pale and sickly, and in ex-
treme cases they do not bear fruit The exclusion
of light alone is sufficient to produce this species of

H 2

I 234 ]

disease, as would appear from the experiments of
Bonnet. This ingenious physiologist sowed three
seeds of the pea in the same kind of soil: one he suf-
fered to remain exposed to the free air; the other he
inclosed in a tube of glass; and the third in a tube of
wood. The pea in the tube of glass sprouted, and
grew in a manner scarcely at all different from that
under usual circumstances; but the plant in the tub^
of wood deprived of light, became white, and slender,
and grew to a much greater height.

The plants growing in a soil incapable of supply-
ing them with sufficient manure or dead organ-
ized matter, are generally very low; having brown
or dark green leaves, and their woody fibre abounds
in earth. Those vegetating in peaty soils, or in lands
too copiously suppHed with animal or vegetable matter,
rapidly expand, produce large bright green leaves^
abound in sap, and generally blossom prematurely.

Where a land is too rich for corn it is not an
uncommon practice to cut down the first stalks, as by
these means its exuberance is corrected, and it is less
likely to fall before the grain is ripe; excess of poverty
or of richness is almost equally fatal to the hopes of
the farmer; and the true constitution of the soil for the
bestxcrop is that in which the earthy materials, the
moisture and manure, are properly associated; and in
which the decomposable vegetable or animal matter
does not exceed one-fourth of the weight of the earthy
constituents.

The canker, or erosion of the bark and wood, is
a disease produced often in trees by a poverty of soil;

C 235 ]

and it is invariably connected with old age. The cause
seems to be an excess of alkaline and earthy matter
in the descending sap. I have often found carbonate
of lime on the edges of the canker in apple trees; and
ulmin, which contains fixed alkali, is abundant in the
canker of the elm. The old age of a tree, in this res-
pect, is faintly analogous to the old age of animals, in
which the secretions of solid bony matter are always in
excess, and the tendency to ossification great.

The common modes of attempting to cure the
canker, are by cutting the edges of the bark, binding
new bark upon it, or laying on a plaister of earth; but
these methods, though they have been much extolled,
probably do very little in producing a regeneration of
the part. Perhaps the application of a weak acid to
the canker might be of use; or where the tree is of
great value, it maybe watered occasionally with a very
diluted acid. The alkaline and earthy nature of the
morbid secretion warrants the trial; but circumstances
that cannot be foreseen may occur to interfere with the
success of the experiment.

Besides the diseases having their source in the
constitution of the plant, or in the unfavourable opera-
tion of external elements, there are many others per-
haps more injurious, depending upon the operations
and powers of other living beings; and such are the
most difficult to cure, and the most destructive to the
labours of the husbandman.

Parasitical plants of different species which at-
tach themselves to trees and shrubs, feed on their
juices, destroy their health;, and finally their life.

C 236 ]

abound in all climates; and are, perhaps, the most for-
midable of the enemies of the superior and cultivated
vegetable species.

The mildew, which has often occasioned great
havock in our wheat crops, and which was particular-
ly destructive in 1804, is a species of fungus, so small
as to require glasses to render its form distinct, and
rapidly propagated by it? seeds.

This has been shewn by various botanists; and
the subject has received a full illustration from the en-
lightened and elaborate researches of the President of
the Royal Society.

The fungus rapidly spreads from stalk to stalk,
fixes itself in the cells connected with the common
tubes, and carries away and consumes that nourish-
ment which should have been appropiated to the
grain.

No remedy has as yet been discovered for this
disease; but as the fungus increases by the diffusion of
its seeds, great care should be taken that no mildewed
straw is carried in the manure used for corn; and in
the early crop, if mildew is observed upon any of the
«talks of corn, they should be carefully removed and
treated as weeds.

The popular notion amongst farmers, that a bar-
berry-tree in the neighbourhood of a field of wheat of-
ten produces the mildew, deserves examination. This
tree is frequently covered with a fungus, which if it
should be shewn to be capable of degenerating into the
wheat fungus would offer an easy explanation of the
effect.

[ 237 3

There is every reason to believe, from the re-»
searches of Sir Joseph Banks, that the smut in wheat
is produced by a very small fungus which fixes on
the grain : the products that it affords by analysis are
similar to those afforded by the puff-ball ; and it is
difficult to conceive, that without the agency of some
organized structure, so complete a change should be
effected in the constitution of the grain.

The mistletoe and the ivy, the moss and the
lichen, in fixing upon trees, uniformly injure their ve-
getative processess, though in very different degrees.
They are supported from the lateral sap vessels, and
deprive the branches above of a part of their nourish-
ment.

The insect tribes are scarcely less injurious than
the parasitical plants.

To enumerate all the animal destroyers and ty-
rants of the vegetable kingdom would be to give a ca-
talogue of the greater number of the classes in zoolo-
gy. Every species of plant almost is the peculiar
resting place, or dominion of some insect tribe ; and
from the locust, the caterpillar, and snail, to the mi-
nute aphis, a wonderful variety of the inferior insects
are nourished, and live by their ravages upon the ve-
getable world.

I have already referred to the insect which feeds
on the seed-leaf of the turnip.

The Hessian fly, still more destructive to wheat,
has in some seasons threatened the United States with
a famine. And the French government is* at this

* January 1813.

[ 238 ]

time issuing decrees with a view to accasion the des-
truction of the larvas of the grasshopper.

In general, wet weather is most favourable to the
propagation of mildew, funguses, rust, and the small
parasitical vegetables ; dry weather to the increase of
the insect tribes* Nature, amidst all her changes, is
continually directing her resources towards the pro-
duction and multiplication of life ; and in the wise and
grand economy of the whole system, even the agents
that appear injurious to the hopes, and destructive to
the comforts of man, are in fact ultimately connected
with a more exalted state of his powers and his condi-
tion. His industry is awakened, his activity kept
alive, even by the defects of climates and season. By
the acccidents which interfere with his efforts, he is
made to exert his talents, to look farther into futurity,
and to consider the vegetable kingdom not as a secure
and inalterable inheritance, spontaneously providing
for his wants ; but as a doubtful and insecure posses-
sion, to be preserved only by labour, and extended
and perfected by ingenuity.

239

LECTURE VI.

Qf Manures of vegetable and animal Origin. Of the
Manner in which they become the Nourish??jent of the
Plant. Of Fermentation and Putrefaction. Of the
different Species of Manures of vegetable Origin ; of
the different Species of ayiimal Origin. Of mixed
Manures. General Principles with Respect to the
Use and Application of such Manures.

THAT certain vegetable and animal substances
introduced into the soil accelerate vegetation and in-
crease the produce of crops, is a fact known since the
earliest period ot agriculture ; but the manner in
which manures act, the best modes of applying them,
their relative value and durability, are still subjects of
discussion. In this Lectur^I shall endeavour to lay
down some settled principles on these objects ; they
are capable of being materially elucidated by the re-
cent discoveries in chemistry ; and I need not dwell
on their great importance to farmers.

The pores in the fibres of the roots of plants are
so small, that it is with difficulty they can be discovered
by the microscope ; it is not therefore probable, that
solid substances can pass into them from the soil. I
tried an experiment gn this subject : some impalpa-
ble powdered charcoal procured by washing gunpow-

[ 240 J

del* was placed in a phial containing pui* water, in
which a plant of peppermint was growing : the roots
of the plant were pretty generally in contact with the
charcoal. The experiment was made in the beginning
of May, 1 805 ; the gr®wth of the plant was very vi-
gorous during a fortnight, when it was taken out of
the phial ; the roots were cut through in different
parts ; but no carbonaceous matter could be disco-
vered in them, nor were the smallest fibrils blackened
by charcoal, though this must have been the case had
the charcoal been absorbed in a solid form.

No substance is more necessary to plants than
carbonaceous matter ; and if this cannot be introdu-
ced into the organs of plants except in a state of solu-
tion, there is every reason to suppose that other sub-
stances less essential will be in the same case.

I found by some experiments made in 1804, that
plants introduced into strong fresh solutions of sugar,
mucilage, tanning principle, jelly, and other substan-
ces died ; but that plants lived in the same solutions
after they had fermented. At that time, I supposed
that fermentation was necessary to prepare the food
of plants ; but 1 have since found that the deleterious
effect of the recent vegetable solutions was owing to
their being too concentrated ; in consequence of which
the vegetable organs were probably clogged with so-
lid matter, and the transpiration by the leaves pre-
vented. In the beginning of June, in the next year,
I used solutions of the same substances, but so much
diluted, that there was only about aio part of solid ve-
getable or animal matter in the solutions. Plants of

r 241 3

mint grew luxuriantly in all these solutions ; but least
so in that of the astringent matter. I watered some
spots, of grass in a garden with the different solutions
separately, and a spot with common water : the grass
watered with solutions of jelly, sugar, and mucilage
grew most vigorously ; and that watered with the so-
lution of the tanning principle grew better than that
watered with common water.

I endeavoured to ascertain whether soluble vegetable
substances passed in an unchanged state into the roots
of plants, by comparing the products of the analysis
of the roots of some plants of mint which had grown,
some In common water, some In a solution of sugar,
1 20 grains of the roots of the mint which grew in the
solution of sugar, afforded five grains of pale green
extract, which had a sweetish taste, but which slightly
coagulated by the action of alcohol. 120 grains of
the roots of the mint which had grown In common
water yielded three grains and a half of extract, which
was of a deep olive colour ; its taste was sweetish,
but more astringent than that of the other extract,
and it coagulated more copiously with alcohol.

These results, thoXigh not quite decisive, favour
the opinion that soluble matters pass unaltered Into
the roots of plants ; and the Idea is confirmed by the
circumstance that the radical fibres of plants made to
grow In Infusions of madder are tinged red ; and it may
be considered as almost proved by the fact, that sub-
stances which are even poisonous to vegetables are ab-
sorbed by them. I Introduced the roots of a primrose
into a weak solution of oxide of Iron In vinegar, and

i2

[ 242 ]

suffered it to remain in it till the leaves became yel-
low ; the roots were then carefully washed in distil-
led water, bruised, and boiled in a small quantity of
the same fluid : the decoction of them passed through
a filtre was examined by the test of infusion of nut-
galls ; the decoction gained a strong tint of purple,
which proves that solution of iron had been taken up
by the vessels or pores in the roots.

Vegetable and animal substances, as is shewn by
universal experience, are consumed in vegetation ;
and they can only nourish the plant by aflfording solid
matters capable of being dissolved by water, or gas-
eous substances capable of being absorbed by the
fluids in the leaves of vegetables ; but such parts of
them as are rendered gaseous, and that pass into the
atmosphere, must produce a comparatively small ef-
fect, for gasses soon become diffused through the
mass of the surrounding air. The great object in the
application of manure should be to make it afford as
much soluble matter as possible to the roots of the
plants ; and that in a slow and gradual manner, so
that it may be entirely consumed in forming the sap
or organized parts of the plant.

Mucilaginous, gelatinous, saccharine, oily, and
extractive fluids, and solution of carbonic acid in wa-
ter, are substances that in their unchanged states con-
tain almost all the principles necessary for the life of
plants ; but there are few cases in which they can be
applied as manures in their pure forms ; and vegeta-
ble manures, in general, contain a great excess of fib-
rous and insoluble matter, which must undergo che-

C 243 ]

mical changes before they can become the food of
plants.

It will be proper to take a scientific view of the
nature of these changes ; of the causes which occasion
them, and which accelerate or retard them j and of
the products they afford.

If any fresh vegetable matter which contains su-
^ar, mucilage, starch, or other of the vegetable com-
pounds soluble in water be moistened and exposed to
air, at a temperature from 35° to 80°, oxygene will
soon be absorbed, and carbonic acid formed ; heat
.will be produced, and elastic fluids, principally car-
bonic acid, gaseous oxide of carbon, and hydro- car-
bonate will be evolved ; a dark coloured liquid of a
slightly sour or bitter taste will likewise be formed ;
and if the process be suffered to continue for a time
sufficiently long, nothing solid will remain, except
earthy and saline matter, coloured black by charcoal.

The dark coloured fluid formed in the fermenta-
tion always contains acetic acid ; and when albumen
or gluten exists in the vegetable substance, it likewise
contains volatile alkali.

In proportion as there is more gluten, albumen,
or matters soluble in water in the vegetable substances
exposed to fermentation, so in proportion, all other
circumstances being equal, will the process be more
rapid. Pure woody fibre alone undergoes a change
very slowly ; but its texture is broken down, and it is
easily resolved into new elements when mixed with
substances more liable to change, containing more
oxygene and hydrogene. Volatile and fixed oils, resins

[ 244 ]

and wax, are more susceptible of change than woody
fibre when exposed to air and water ; but much
less liable than the other vegetable compounds ; and
even the most inflammable substances by the absorp-^
tion of oxygene, become gradually soluble in water.

Animal matters in general are more liable to de-
compose than vegetable substances ; oxygene is ab-
sorbed, and carbonic acid and ammonia formed in the
process of their putrefaction. They produce foetid
compound elastic fluids, and likewise azote : they af-
ford dark coloured acid and oily fluids, and leave a
residuum of salts and earths mixed with carbonace-
ous matter.

The principal substances which constitute the
different parts of animals, or which are found in their
blood, their secredons, or their excrements, are gela-
tine, fibrine, mucus, fatty, or oily matter, albumen,
urea, uric acid, and different acid, saline, and earthy
matter.

Of these gelatiiie is the substance which when
combined with water forms jelly. It is very liable to
putrefaction. According to M. M. Gay Lussac and
Thenar d 3 it is composed of
47.88 of carbon,
27.20*7 — oxygene,
7.914 — hydrogene.
16.998

These proportions cannot be considered as defi-
nite, for they do not bear to each other the ratios
of any simple muldples of the number represent-
ing the elements J the case seems to be the same

..# . IS?'

[ 245 ]

with other animal compounds : and even in ve-
getable substances, in general, as appears from the
statements given in the Third Lecture, the propor-
tions are far from having the same simple' relations
as in the binary compounds capable of being made
artificially, such as acids, alkalies, oxides, and in
salts. ^

Fibrine constitutes the basis of the muscular
fibre of animals, and a similar substance may be ob-
tained from recent fluid blood ^ by stirring it with a
stick the fibrine will adhere to the stick. It is not
soluble in water j but by the action of acids, as Mr.
Hatchett has shewn, it becomes soluble, and analo-
gous to gelatine. It is less disposed to putrefy than
gelatine. According to M. M. Gay Lussac and Then-
ard, 100 parts of fibrine contain

Of carbon - - 53.360
- — oxygene - - 19.685

— hydrogene - - 7.021

— azote - - 19.934

Mucus IS very analogous to vegetable gum in its
characters; and as Dr. Bostock has stated, it may be
obtained by evaporating saliva. No experiments have
been made upon its analysis; but it is probably similar
to gum in composition. It is capable of undergoing
putrefaction, but less rapidly than fibrine.

Animal fat and oils have not been accurately analy-
sed J but there is great reason to suppose that their
composition is analogous to that of similar substances
from the vegetable kingdom.

Albumen has been already referred to, and its
analysis stated in the Third Lecture.

L 246 J

Urea may be obtained by the evaporation of hu-
man urine, till it is of the consistence of a syrup; and
the action of alcohol on the crystalline substance which
forms when the evaporated matter cools. In this
way a solution of urea in alcohol is procured, and the
alcohol may be separated from the urea i)y heat.
Urea is very solCible in water, and is precipitated
from water by diluted nitric acid in the form of
bright pearl-coloured crystals; this property distin-
guishes it from all other animal substances.

According to Fourcroy and Vauquelin, 100 parts
of urea when distilled yield.

92.027 parts of carbonate of ammonia.
4.608 carburetted hydrogene gas.
3.225 of charcoal.
Urea, particularly when mixed with albumen or
gelatine, readily undergoes putrefaction.

Uric add, as has been shewn by Dr. Egan,
may be obtained from human urine by pouring an
acid into it; and it often falls down from urine in
the form of brick-coloured crystals. It consists of
carbon, hydrogene, oxygene and azote; but their
proportions have not yet been determined. Uric
acid is one of the animal substances least liable to
undergo the process of putrefaction.

According to the different proportions of these
principles in animal compounds, so are the changes
they undergo different. When there is much saline
or earthy matter mixed or combined with them, the
progress of their decomposition is less rapid than when
they are principally composed of fibrine, albumen,
gelatine, or urea.

. € [ 247 ]

The ammonia given off from animal compounds
in putrefaction may be conceived to be formed at the
time of their decomposition by the combination of hy-
drogene and azote ; except this matter, the other pro-
ducts of putrefaction are analogous to those afforded
by the fermentation of vegetable substances ; and the
soluble substances formed abound in the elements,
which are the constituent parts of vegetables, in car-
bon, hydrogene, and oxygene.

Whenever manures consist principally of matter
soluble in water, it is evident that their fermentation
or putrefaction should be prevented as much as pos-
sible ; and the only cases in which these processes can
be useful, are when the manure consists principally
of vegetable or animal fibre. The circumstances ne-
cessary for the putrefaction of animal substances are
similar to those required for the fermentation of vege-
table substances ; a temperature above the freezing
point, the presence of water, and the presence of oxy-
gene, at least in the first stage of the process.

To prevent manures from decomposing, they
should be preserved dry, defended from the contact
of air, and kept as cool as possible.

Salt and alcohol appear to owe their powers of
preserving animal and vegetable substances to their at-
traction for water, by which they prevent Its decom-
posing action, and likewise to their excluding air. The
use of ice in preserving animal substances is owing to
its keeping their temperature low. The efficacy of
M. Appert's method of preserving animal and vegeta-
ble substances, an account of which has been lately

%

i^

L 248 ] -

publibhed, entirely depends upon the exclusion of air.
This method is by filling a vessel of tin plate or glass
with the meat or vegetables ; soldering or cementing
the top so as to render the vessel air tight ; and then
keeping it half immersed in a vessel of boiling water
for a sufficient time to render the meat or vegetables
proper for food. In this last process it is probable
that the small quantity of oxygene remaining in the
vessel is absorbed : for on opening a tinned iron can-
ister which had been filled with raw beef and exposed
to hot water the day before, I found that the minute
quantity of elastic fluid which could be procured from
it, was a mixture of carbonic acid gas and azote.

Where meat or vegetable food is to be preserved
on a large scale, for the use of the navy or army for
instance, I am inclined to believe, that by forcibly
throwing a quantity of carbonic acid, hydrogene, or
azote into the vessel, by means of a compressing
pump, similar to that used for making artificial Seltzer
water, any change in the substance would be more
effectually prevented. No elastic fluid in this case
would have room to form by the decomposition of
the meat ; and the tightness and strength of the ves-
sel would be proved by the process. No putrefaction
or fermentation can go on without the generation of
elastic fluid ; and pressure would probably act with
as much efficacy as cold in the preservation of animal
or vegetable food.

As different manures contain different propor-
tions of the elements necessary to vegetation, so they
require a different treatment to enable them to pro-

C 249 3

duce their full effects in agriculture. I shall therefore
describe in detail the properties and nature of the
manures in common use, and give some general views
respecting the best modes of preserving and applying
them.

Ail green succulent plants contain saccharine or
mucilaginous matter, with v^oody fibre, and readily
ferment. They cannot, therefore, if intended for ma-
nure, be used too soon after their death,

"When green crops are to be employed for enrich-
ing a soil, they should be ploughed in, if it be possi-
ble, when in flower, or at the time the flower is begin-
ing to appear, for it is at this period that they contain
the largest quantity of easily soluble matter, and that
their leaves are most active in forming nutritive mat-
ter. Green crops, pond weeds, the paring of hedges
or ditches, or any kind of fresh vegetable matter, re-
quires no preparation to fit them for manure. The
decomposition slowly proceeds beneath the soil ; the
soluble matters are gradually dissolved, and the slight
fermentation that goes on checked by the want of a
free communication of air, tends to render the woody
fibre soluble without occasioning the rapid dissipation
of elastic matter.

When old pastures are broken up and made
arable, not only has the soil been enriched by the
death and slow decay of the plants which have left
soluble matters in the soil ; but the leaves and roots
of the grasses living at the time and occupying so
large a part of the surface, afford saccharine, mucila-
ginous, and extractive matters, which become imme-

k2

[ 250 ]

diatcly the food of the crop, and the gradual decom-
postion affords a supply for successive years.

Rape cake^ which is used with great success as a
manure, contains a large quantity of mucilage, some
albuminous matter, and a small quantity of oil. This
manure should be used recent, and kept as dry as pos-
sible before it is applied. It forms an excellent dres-
sing for turnip crops ; and is most oeconomically ap-
plied by being thrown into the soil at the same time
with the seed. Whoever wishes to see this practice
in its highest degree of perfection, should attend Mr.
Coke's annual sheep-shearing at Holkham*

Malt dust consists chiefly of the infant radicle
separated from the grain. I have never made any ex-
periment upon this manure ; but there is great reason
to suppose it must contain saccharine matter ; and this
will account for its powerful effects. Like rape cake
it should be used as dry as possible, and its fermenta-
tion prevented.

Linseed cake is too valuable as a food for cattle
to be much employed as a manure ; the analysis of
linseed was referred to in the Third Lecture. The
water in which ^^at and hemp are steeped for the pur-
pose of obtaining the pure vegetable fibre, has consi-
derable fertilizing powers. It appears to contain a
substance analogous to albumen, and likewise much
vegetable extractive matter. It putrefies very readily.
A certain degree of fermentation is absolutely neces-
sary to obtain the flax and hemp in a proper state j
the water to which they have been exposed should

I 251 3

therefore be used as a manure as soon as the vegeta-
ble fibre is removed from it.

Sea weeds ^ consisting of different species of fuci,
algse, and confervas, are much used as a manure on
the sea coasts of Britain and Ireland. By digesting
the common fucus, which is the sea weed usually most
abundant on the coast, in boiling water, I obtained
from it one-eighth of a gelatinous substance which
had characters similar to mucilage. A quantity dis^
tilled gave nearly four-fifths of its weight of water,
but no ammonia ; the water had an empyreumatic and
slightly sour taste ; the ashes contained sea salt, car-
bonate of soda, and carbonaceous matter. The gase-
ous matter afforded was small in quantity, principally
carbonic acid and gaseous oxide of carbon, with a lit-
tle hydro-carbonate. This manure is transient in its
effects, and does not last for more than a single crop,
which is easily accounted for from the large quantity
of water, or the elements of water, it contains. It de-
cays without producing heat when exposed to the at-
mosphere, and seems as it were to melt down and dis-
solve away. I have seen a large heap entirely des-
troyed in less than two years, nothing remaining but
a little black fibrous matter.

I suffered some of the firmest part of a fucus to
remain in a close jar containing atmospheric air for a
fortnight : in this time it had become very much
shrivelled ; the sides of the jar were lined with dew.
The air examined was found to have lost oxygene,
and contained carbonic acid gas.

Sea weed is sometimes suffered to ferment be-
fore it is used } but this process seems wholly unne-

cessary, for there is no fibrous matter rendered solu-
ble in the process, and a part of the manure is lost.

The best farmers in the west of England use it
as fresh as it can be procured ; and the practical
results of this mtode of applying it are exactly confor-
mable to the theory of its operation. The carbonic
acid formed by its incipient fermentation must be part-
ly dissolved by the water set free in the same pro-
cess ; and thus become capable of absorption by the
roots of plants.

The effects of the sea weed as manure must prin-
cipally depend upon this carbonic acid, and upon the
soluble mucilage the weed contains ; and I found that
some fucus which had fermented so as to have lost
about half its weight, afforded less than iV of mucila-
ginous matter ; from which it may be fairly conclud-
ed that some of this substance is destroyed in fermen-
tation.

Dry sir aw of wheat, oats, barley, beans and peas,
and spoiled hay, or any other similar kind of dry ve-
getable matter is, in all cases, useful manure. In
general, such substances are made to ferment before
they are employed, though it may be doubted whether
the practice should be indiscriminately adopted.

From 400 grains of dry barley straw I obtained
eight grains of matter soluble in water, which had a
brown colour, and tasted like mucilage. From 400
grains of wheaten straw I obtained five grains of a
similar substance.

There can be no doubt that the straw of differ-
ent crops immediately ploughed into the ground af-

C 253 ]

fords nourishment to plants ; but there is an objec-
tion to this method of using straw from the difficulty
of burying long straw, and from it^ rendering the
jiusbandry foul.

When straw is made to ferment it becomes a
itiore manageable manure ; but there is likewise on
the whole a great loss of nutritive matter. More
manure is perhaps supplied for a single crop ; but the
land is less improved than it would be, supposing the
whole of the vegetable matter could be finely divided
and mixed with the soil.

It is usual to carry straw that can be employed
for no other purpose to the dunghill, to ferment, and
decompose ; but it is worth experiment, whether it
may not be more oeconomically applied when chopped
small by a proper machine, and kept dry till it is
ploughed in for the use of a crop. In this case,
though it would decompose much more slowly and
produce less effect at first, yet its influence would be
much more lasting.

Mere woody fibre seems to be the only vegetable
matter that requires fermentation to render it nutritive
to plants. Tanners spent hark is a substance of this
kind. Mr. Young, in his excellent Essay on Ma-
nures, which gained him the Bedfordian medal of the
Bath Agricultural Society, states, " that spent bark
seemed rather to injure than assist vegetation ;"
which he attributes to the astringent matter that it con-
tains. But in fact it is freed from all soluble sub-
stances, by the operation of water in the tan^pit ; and
If injurious to vegetation, the effect is probably owing

I 254 ]

to Its agency upon water, or to its mechanical effects.
It is a substance very absorbent and retentive of mois-
ture, and yet not penetrable by the roots of plants.

Inert peaty matter is a substance of the same kind.
It remains for years exposed to water and air without
undergoing change ; and in this state yields little or
no nourishment to plants.

Woody fibre will not ferment unless some sub-
stances are mixed with it which act the same part as
the mucilage, sugar, and extractive or albuminous
matters, with which it is usually associated in herbs
and succulent vegetables. Lord Meadowbank has
judiciously recommended a mixture of common farm-
yard dung for the purpose of bringing peats into fer-
mentation ; any putrescible or fermentable substance
will answer the end ; and the more a substance heats,
and the more readily it ferments, the better will it be
fitted for the purpose.

Lord Meadowbank states, that one part of dung
is sufficient to bring three or four parts of peat into a
state in which it is fitted to be applied to land ; but of
course the quantity must vary according to the nature
of the dung and of the peat. In cases in which some
living vegetables are mixed with the peat, the fermen-
tation will be more readily effected.

Tanners spent bark, shavings of wood and saw
dust, will probably require as much dung to bring
them into fermentation as the worst kind of peat.

Woody fibre may be likewise prepared so as to
become a manure by the action of lime. This subject
I shall discuss in the next Lecture, as it follows na*

[ 255 ]

rurally another series of facts, relating to the effects
of lime in the soil.

It is evident from the analysis of woody fibre by
M. M. Gay Lussac and Thenard, (which shews that it
consists principally of the elements of water and car-
bon, the carbon being in larger quantities than in the
other vegetable compounds) that any process which
tends to abstract carbonaceous matter from it, must
bring it nearer in composition to the soluble princi-
ples ; and this is done in fermentation by the absorp-
tion of oxygene and production of carbonic acid ; and
a similar effect, it will be shewn, is produced by lime.

Wood-ashes imperfectly formed, that is wood-ashes
containing much charcoal, are said to have been used
with success as a manure. A part of their effects
may be owing to the slow and gradual consumption
of the charcoal, which seems capable, under other
circumstances than those of actual combustion, of ab-
sorbing oxygene so as to become carbonic acid.

An April, 1803, I inclosed some well burnt
charcoal in a tube half filled with pure water, and half
with common air 5 the tube was heripetically sealed.
I opened the tube under pure water in the spring of
1 804, at a time when the atmospheric tempei'ature and
pressure were nearly the same as at the commence-
ment of the experiment. Some water rushed in ; and
on expelling a little air by heat from the tube, and
analysing it, it was found to contain only seven per
cent, of oxgene. The water in the tube, when mixed
with limewater, produced a copious precipitate ; so

i: 256 J

that carbonic acid had evidently been formed and
dissolved by the water.

Manures from animal substances, in general, re-
quire no chemical preparation to fit them for the soil.
The great object of the farmer is to blend them with
earthy constituents in a proper state of division, and
to prevent their too rapid decomposition.

The entire parts of the muscles of land animals
are not commonly used as manure, though there are
many cases in which such an application might be
easily made. Horses, dogs, sheep, deer, and other quad-
rupeds that have died accidentally, or of disease, after
their skins are separated, are often suffered to remain
exposed to the air, or immersed in water till they are
destroyed by birds or beasts of prey, or entirely de-
composed 'y and in this case most of their organized
matter is lost for the land in which they lie, and a
considerable portion of it employed in giving off nox-
ious gasses to the atmosphere.

By covering dead animals with five or six times
their bulk of soil, mixed with one part of lime, and
suffering them to remain for a few months ; their de-
composition would impregnate the soil with soluble
matters, so as to render it an excellent manure ; and
by mixing a little fresh quicklime with it at the time of
its removal, the disagreeable effluvia would be in a
great measure destr®yed ; and it might be applied in
the same way as any other manure to crops.

Fish forms a powerful manure in whatever state
it is applied ; but it cannot be ploughed in too fresh,
though the quantity should be limited. Mr. Young

C 257 ] "

records an experiment, in which herrings spread over
a field and ploughed in for wheat, produced so rank
a crop, that it was entirely laid before harvest.

The refuse pilchards in Cornwall are used
throughout the county as a manure, with excellent
effects. They are usually mixed with sand or soil,
and sometimes with sea-weed, to prevent them from
raising too luxuriant a crop. The effects are perceiv-
ed for several years.

In the fens of Lincolnshire, Cambridgeshire, and
Norfolk, the little fish called sticklebacks, are caught
in the shallow waters in such quantities, that they
form a great article of manure in the land bordering
on the fens.

It is easy to explain the operation of fish as a
manure. The skin is principally gelatine : which
from its slight state of cohesion is readily soluble in
water ; fat or oil is always found in fishes, either un-
der the skin or in some of the viscera ; and their fib-
rous matter contains all the essential elements of vege-
table substances.

Amongst oily substances, graves and blubber are
employed as manure. They are both most useful when
mixed with soil, so as to expose a large surface to the
air, the oxygene of which produces soluble matter
from them. Lord Somerville used blubber with great
success at his farm in Surrey. It was made into a
heap with soil, and retained its powers of fertilizing
for several successive years.

The carbon and hydrogene abounding in oily
substances fully account for their effects j and their

L 2

[ 258 ]

durability is easily explained from the gradual manner
in which they change by the action of air and water.

Bones are much used as a manure in the neigh-
bourhood of London. After being broken and boiled
for grease, they are sold to the farmer. The more
divided they are, the more powerful are their effects.
The expense of grinding them in a mill would proba-
bly be repaid by the increase of their fertilizing pow-
ers ; and in the state of powder they might be used in
the drill husbandry, and delivered with the seed in the
same manner as rape cake.

Bone dust, and bone shavings, the refuse of the
turning manufacture, may be advantageously employ-
ed in the same way.

The basis of bone is constituted by earthy salts,
principally phosphate of lime, with some carbonate of
lime and phosphate of magnesia j the easily decom-
posable substances in bone are fat, gelatine, and cartil-
age, which seems of the same nature as coagulated
albumen.

According to the analysis of Fourcroy and Vau-
quelin, ox bones are composed

Of decomposable animal matter 51

— phosphate of lime - - 37.7

— carbonate of lime - - 10

— phosphate of magnesia - 1.3

100

M. Merat Guillot has given the following esti-
mate of the composition of the bones of different
animals.

259

Bone of Calf

Horse

Sheep

Elk

Hog

Hare

Pullet

Pike

Carp

Horses

Ivory

Hartshorn

leeth

Pho«phat©
of linie.

54

67.5
70
90

52
8<

7a

64

45

85.5

64

27

Carbonate
of lime.

X.25
<
1
1
1
1.5
1
5

25
1
1

The remaining parts of the 100 must be consi-
dered as decomposable animal matter.

Horn is a still more powerful manure than bone,
as it contains a larger quantity of decomposable ani-
mal matter. From 500 grains of ox horn Mr. Hatch-
ett obtained only 1-5 grains of earthy residuum, and
not quite half of this was phosphate of lime. The
shaving or turnings of horn form an excellent ma-
nure, though they are not sufficiently abundant to be
in common use. The animal matter in them seems
ib be of the nature of coagulated albumen, and it is
slowly rendered soluble by the action of water. The
earthy matter in horn, and still more that in bones,
prevents the too rapid decomposition of the animal
matter, and renders it very durable in its effects.

Hair^ woollen rags znA feathers are all analogous
in composition, and principally consists of a substance
similar to albumen, united to gelatine. This is shewn
by the ingenious researches of Mr. Hatchett. The
theory of their operation is similar to that of bone and
horn shavings.

The refuse of the different manufactures of skin
and leather form very useful manures j such as the

[ tieo ]

shavings of the currier, furriers' clippings, and the
offals of the tan-yard and of the glue-maker. The
gelatine contained in every kind of skin is in a state
fitted for its gradual solution or decomposition -, and
when buried in the soil, it lasts for a considerable
time, and constantly affords a supply of nutritive mat-
ter to the plants in its neighbourhood.

Blood contains certain quantities of all the princi-
ples found in other animal substances, and is conse-
quently a very good manure. It has been already
stated that it contains fibrine ; it likewise contains al-
bumen : the red particles in it which have been sup-
posed by many foreign chemists to be coloured by
iron in a particular state of combination with oxygene
^ind acid matter, Mr. Brande considers as formed of
a peculiar animal substance, containing very little
iron.

The scum taken from the boilers of the sugar
bakers, and which is used as manure, principally con-
sists of bullock's blood, which has been employed for
the purpose of separating the impurities of common
brown sugar, by means of the coagulation of its albu-
minous matter by the heat of the boiler.

The different species of corals, coralines, and
spongesy must be considered as substances of animal
origin. From the analysis of Mr. Hatchett, it appears
that all these substances contain considerable quanti-
ties of a matter analogous to coagulated albumen ; the
gponges afford likewise gelatine.

According to Merat Guillot white coral contains
equal parts of animal matter and carbonate of lime :

C 261 3

red coral 46.5 of animal matter, and 53.5 of carbon-
ate of lime ; articulated coraline 51 of animal matter,
and 49 of carbonate of lime.

These substances are, I believe, never used as ma-
nure in this country, except in cases when they are ac-
cidentally mixed with sea weed ; but it is probable that
the coralines might be advantageously employed, as
they are found in considerable quantity on the rocks,
and bottoms of the rocky pools on many parts of our
coast, where the land gradually declines towards the
sea ; and they might be detached by hoes, and collect-
ed without much trouble.

Amongst excrementations, animal substances
used as manures urine is the one upon which the
greatest number of chemical experiments have been
made, and the nature of which is best understood.

The urine of the cow contains, according to the
experiments of Mr. Brande,

Water - - - . - 65
Phosphate of lime * . . 3

Muriates of polassa and ammonia - 15
Sulphate of potassa - - - 6

Carbonates, and potassa, and ammonia 4

Urea 4

The urine of the horse, according to Fourcroy
and Vauquelin, contains

Of carbonate of lime 1 1

— carbonate of soda . - - 9

— benzoate of soda - - - 24

— Muriate of potassa - ^ . 0

— Urea - . . - . 7
— • Water and mucilage - * 940

[ 262 ]

In addition to these substances, Mr. Brande found
in it phosphate of lime.

The urine of the ass, the camel, the rabbit, and
domestic fowls have been submitted to different ex-
periments, and their constitution have been found si-
milar. In the urine of the rabbit, in addition to most
of the ingredients above mentioned, Vauquelin detect-
ed gelatine ; and the same chemist discovered uric
acid in the urine of domestic fowls.

Human urine contains a greater variety of con-
stituents than any other species examined.

Urea, uric acid, and another acid similar to it in
natm*e called rosacic acid, acetic acid, albumen, gela-
tine, a resinous matter, and various salts are found
in it.

The human urine differs in composition accord-
ing to the state of the body, and the nature of
the food and drink made use of. In many cases
of disease there is a much larger quantity of gelatine
and albumen than usual in the urine ; and in diabetes
it contains sugar.

It is probable that the urine of the same animal
must likewise differ according to the different nature
of the food and drink used ; and this will account for
discordancies in some of the analyses that have been
published on the subject.

. Urine is very liable to change and to undergo the
putrefactive process ; and that of carnivorous animals
more rapidly than that of graminivorous animals. In
proportion as there is more gelatine and albumen in
urine^ so in proportion does it putrify more quickly.

[ 263 3

The species of urine that contain most albumen,
gelatine and urea, are the best as manures ; and all
urine contains the essential elements of vegetables in a
state of solution.

During the putrefaction of urine the greatest
part of the soluble animal matter that it contains is
destroyed ; it should consequently be used as fresh
.as possible ; but if not mixed with solid matter, it
should be diluted with water, as when pure it contains
too large a quantity of animal matter to form a pro-
per fluid nourishment for absorption by the roots of
plants.

Putrid urine abounds in ammoniacal salts ; and
though less active than fresh urine, is a very power-
ful manure.

According to a recent analysis published by Ber-
zelius, 1000 parts of urine are composed of

Water 933

Urea 30.1

Uric acid - - - . 1

Muriate of ammonia, free lactic acid,"^
lactate of ammonia and animal >»17.14
matter - - - - J

The remainder different salts, phosphates, sul-
phates, and muriates.

Amongst excrementitious solid substances used
as manures, one of the most powerful is the dung of
birds that feed on animal food^ particularly the dung of
sea birds. The guano^ which is used to a great extent
in South America, and which is the manure that fer-
tilizes the sterile plains of Peru, is a production of this

C 264 3

kind. It exists abundantly, as we are informed by
M. Humboldt, on the small islands in the south sea,
at Chinche, Ilo, Iza, and Arica. 50 vessels are la-
den with it annually at Chinche, each of which carries
from 1500 to 2000 cubical feet. It is used a manure
only in very small quantities ; and particularly for
crops of maize. I made some experiments on speci-
mens of guano sent from South America to the Board
of Agriculture in 1805. It appeared as a fine brown
powder ; it blackened by heat, and gave off strong
ammoniacal fumes ; treated with nitric acid it afford-
ed uric acid. In 1806 M. M. Fourcroy and Vauque-
lin published an elaborate analysis of guano. They
state that it contains a fourth part of its weight of uric
acid, partly saturated with,ammonia, and partly with
potassa ; soms phosphoric acid combined with the
same bases, and likewise with lime. Small quantities
of sulphate and muriate of potassa. a little fatty matter,
and some quartzose sand.

It is easy to explain its fertilizing properties :
from its composition it might be supposed to be a very
powerful manure. It requires water for the solution
of its soluble matter to enable it to produce its full
beneficial effect on crops.

The dung of sea birds has, I believe, never been
used as a manure in this country ; but it is probable,
that even the soil of the small islands on our coast
much frequented by them, would fertilize. Some
dung of sea birds brought from a rock on the coast of
Merionethshire, produced a powerful but transient
effect on grass. It was tried, at my request, by Sir
Robert Vaughan at Nannau.

L 265 J

The rains in our climate must tend Very much
to injure this species of manure, where it is exposed
to them, soon after its deposition ; but it may proba-
bly be fomid in great perfection in caverns or clefts in
rocks, haunted by cormorants and gulls. I examined
some recent cormorant's dung which I found on a
rock near Cape Lizard in Cornwall. It had not at all
the appearance of the guano ; was of a greyish while
colour ; had a very fcetid smell like that of putrid ani-
mal matter: when acted on by quicklime it gave
abundance of ammonia ; treated with nitric acid it
yielded uric acid. f

Nig/jt soil, it is well known, is a very powerful
manure, and very liable to decompose. It differs in its
composition ; but always abounds in substances com-
posed of carbon, hydrogene, azote, and oxygene.
From the analyses of Berzelius, it appears that a part
of it is always soluble in water ; and, in whatever state
it is used, whether recent or fermented, it supplies
abundance of food to plants.

The disagreeable smell of night soil may be des-
troyed by mixing it with quicklime ; and if exposed to
the atmosphere in thin layers strewed over with quick*
lime in fine weather, it speedily dries, is easily pulver-
ised, and in this state may be used in the same manner
as rape cake, and delivered into the furrow with the
seed.

The Chinese, w^ho have more practical know-
ledge of the use and application of manures than any
other people existing, mix their night soil with one-
third of its weight of a fat marie, make it into cakes,

m2

[ ^66 ]

atid dry it by exposure to the sun. These cakes, we
are informed by the French missionaries, have no dis-*
agreeable smell, and form a common article of com-
merce of the empire. v^

The earth, by its absorbent powers, probably
prevents, to a certain extent, the action of moisture
upon the dung, and likewise defends it from the ef-
fects of air.

After night soil, pigeons* dung come next in or-
der, as to fertilizing power. I digested 100 grains of
pigeons' dung in hot water for some hours, and ob-
tained from it 23 grains of soluble matter ; which af-
forded abundance of carbonate of ammonia by distil-
lation ; and left carbonaceous matter, saline matter
principally common salt, and carbonate of lime as a
residuum. Pigeons' dung when moist readily fer-
ments, and after fermentation contains less soluble
matter than before: from 100 parts of fermented
pigeons' dung, I obtained only eight parts of soluble
matter, which gave proportionally less carbonate of
ammonia in divStillation than recent pigeons' dung.

It is evident that this manure should be applied
as new as possible ; and when dry, it may be employ-
ed in the same manner as the other manures capable
of being pulverised.

The soil in woods where great flocks of wood-
pigeons roost, is often highly impregnated with their
dung, and it cannot be doubted, would form a valuable
manure. I have found such soil yield ammonia when
distilled with lime. In the winter likewise it usually
contains abundance of vegetable matter, the remains

C 267 ]

of decayed leaves ; and the dung tends to bring the
vegetable matter into a state of solution.

The dung oi domestic fowls approaches very near-
ly in its nature to pigeons' dung. Uric acid has been
found in it. It gives carbonate of ammoniji by distilla-
tion, and immediately yields soluble matter to water.
It is very liable to ferment.

The dung of fowls is employed in common with
that of pigeons by tanners to bring on a slight degree
of putrefaction in skins that are to be used for making
soft leather ; for this purpose the dung is diffused
through water. In this state it rapidly undergoes pu-
trefaction, and brings on a similar change in the skin.
The excrements of dogs are employed by the tanner
with similar effects. In all cases, the contents of the
grainer^ as the pit is called in which soft skins are pre-
pared by dung, must form a very useful manure.

Rabbits* dung has never been analysed. It is
used with great success as a manure by Mr. Fane^
who finds it profitable to keep rabbits in such a man-
ner as to preserve their dung. It is laid on as fresh
as possible, and is foun^d better the less it has fer-
mented.

The dung of cattle y oxen and cows^ has been che-
mically examined by M. M. Einhof and Thaer. They
found that it contained matter soluble in water ; and
that it gave in fermentation nearly the same products
as vegetable substances, absorbing oxygene and pro-
ducing carbonic acid gas.

The recent dung of sheep^ and of deer^ afford,
when long boiled in water, soluble matters, which

equal from two to three per cent, of their weight. I
have examined these soluble substances procured by
solution and evaporation ; they contain a very small
quantity of matter analogous to animal mucus ; and
are principally composed of a bitter extract, soluble
both in water and in alcohol. They give ammoniacal
fumes by distillation ; and appear to differ very little
in composition.

I watered some blades of grass for several suc-
cessive days with a solution of these extracts ; they
evidently became greener in consequence, and grew
more vigorously than grass in other respects, under
the same circumstances.

The part of the dung of cattle, sheep, and deer,
not soluble in water, appears to be mere woody fibre,
and precisely analogous to the residuum of those ve-
getables that form their food after they have been de-
prived of all their soluble materials.

The dung of horses gives a brown fluid, which
when evaporated, yields a bitter extract, which affords
ammoniacal funics more copiously than that from the
dung of oxen.

If the pure dung of cattle is to be used as manure
like the other species of dung which have been men-
tioned, there seems no reason why it should be made to
ferment except in the soil ; or if suffered to ferment,
it should be only in a very slight degree. The grass
in the neighbourhood of recently voided dung, is al-
ways coarse and dai'k green ; some persons have at-
tributed this to a noxious quality in unfcrmented
dung ; but it seems to be rather the result of an excess
of food furnished to the plants.

C 269 ]

The question of the proper mode of the applica-
tion of the dung of horses and cattle, however, pro-
perly belongs to the subject of composite manures^ for
it is usually mixed in the farm-yard with straw, ofFal,
chaff, and various kind of litter; and itself contains a
large proportion of fibrous vegetable matter.

A slight incipient fermentation is undoubtedly of
use in the dunghill; for by means of it a disposition is
brought on in the woody fibre to decay and dissolve,
when it is carried to the land, or ploughed into the
soil; and woody fibre is always in great excess in the
refuse of the farm.

Too great a degree of fermentation is, however,
very prejudicial to the composite manure in the dung-
hill; it is better that there should be no fermentation
at all before the manure is used, than that it should be
carried too far. This must he obvious from what
has been already stated in this Lecture. The excess
of fermentation tends to the destruction and dissipa-
tion of the most useful part of the manure; and the
ultimate results of this process are like those of com-
bustion.

It is a common practice amongst farmers, to suf-
fer the farm-yard dung to ferment till the fibrous
texture of the vegetable matter is entirely broken
down; and till the manure becomes perfectly cold,
and so soft as to be easily cut by the spade.

Independent of the general theoretical views un-
favourable to this practice founded upon the nature
and composition of vegetable substances, there are
many arguments and facts which shew that it is pre-
judicial to the interests of the farmer.

C 270 ]

During the violent fermentation which is neces-
sary for reducing farm-yard manure to the state in
which it is called sJoort mucky not only a large quantity
of fluid, but likewise a gaseous matter is lostj so much
so that the dung is reduced one half, or two-thirds in
weight; and the principal elastic matter disengaged, is
carbonic acid with some ammonia; and both these, if
retained by the moisture in the soil, as has been stated
before, are capable of becoming an useful nourish-
ment of plants.

In October, 1808, I filled a large retort capable
of containing three pints of water, with some hot fer-
menting manure, consisting principally of the litter
and dung of cattle; I adapted a small receiver to the
retort, and connected the whole with a mercurial pneu-
matic apparatus, so as to collect the condensible and
elastic fluids which might rise from the dung. The
receiver soon became lined with dew, and drops be-
gan in a few hours to trickle down the sides of it.
Elastic fluid likewise was generated; in three days 35
cubical inches had been formed, w^hich when analy-
sed, were found to contain 21 cubical inches of car-
bonic acid, the remainder was hydroc^rbonate mixed
with some azote, probably no more than existed in
the common air in the receiver. The fluid matter
collected in the receiver at the same time amounted
to nearly half an ounce. It had a sahne taste, and a
disagreeable smell, and contained some acetate and
carbonate of ammonia.

Finding such products given off from ferment-
ing litter, I introduced the beak of another retort

[ ^271 J

filled with similar dung very hot at the time, into
the soil amongst the roots of some grass in the bor-
der of a garden; in less than a week a very distinct ef-
fect was produced upon the grass; upon the spot
exposed to the influence of the matter disenga-
ged in fermentation, it grew with much more lux-
uriance than the grass in any other part of the gar-
den.

Besides th^ dissipation of gaseous matter when
fermentation is pushed to the extreme, there is ano-
ther disadvantage in the loss of heat^ which, if excited
in the soil, is useful in promoting the germination of
the seed, and in assisting the plant in the first stage of
its growth, when it is most feeble and most liable to
disease: and the fermentation of manure in the soil
must be particularly favourable to the wheat crop in
preserving a genial temperature beneath the surface
late in autumn, and during winter.

Again, it is a general principal in chemistry, that
in all cases of decomposition, substances combine
much more readily at the moment of their disengage-
ment, than after they have been perfectly formed. —
And in fermentation beneath the soil the fluid matter
produced is applied instantly, even whilst it is warm,
to the organs of the plant, and consequently is more
likely to be efficient, than in manure that has gone
through the process; and of which all the principles
have entered into new combinations.

In the writings of scientific agriculturists, a great
mass of facts may be found in favour of the applica-
tion of farm-yard dung in a recent state. Mr. Young,
m the Essay on Manures, which I have already quoted,

C 272 ]

adduces a number of excellent authorities ia support
of the plan. Many who doubted, have been lately con-
vinced; and perhaps there is no subject of investiga-
tion in which there is such a union of theoretical and
practical evidence. I have myself within the last ten
years witnessed a number of distinct proofs on the
subject. I shall content myself with quoting that
which ought to have, and which I am sure will have,
the greatest weigftt amongst agriculturists. Within
the last seven years Mr. Coke has entirely given up
the system formerly adopted on his farm of applying
fermented dung; and he informs me, that his crops
have been since as good as they ever were, and that
his manure goes nearly twice as far.

A great objection against slightly fermented dung
is, that weeds spring up more luxuriantly where it is
applied. If there are seeds carried out in the dung
they certainly will germinate; but it is seldom that this
(ian be the case to any extent; and if the land is not
cleansed of weeds, any kind of manure fermented or
unfermented will occasion their rapid growth. If
slightly fermented farm-yard dung is used as a top
dressing for pastures, the long straws and unfermented
vegetable matter remaining on the surface should be
removed as soon as the grass begins to rise vigorous-
ly by raking, and carried back to the dunghill: in this
case no manure will be lost, and the husbandry will
be at once clean and oeconomical.

In cases when farm-yard dung cannot be immedi-
ately applied to crops, the destructive fermentation of
it should be prevented as much as posssible: the prin-

C 273 J

ciples on which this may be effected have been allud-
ed to.

The surface should be defended as much as pos-
sible from the oxygene of the atmosphere ; a compact
marie, or a tenacious clay, offers the best protection
against the air ; and before the dung is covered over,
or as it were, sealed up, it should be dried as much
as possible. If the dung is found at any time to
heat strongly, it should be turned over, and cooled
by exposure to air.

Watering dunghills is sometimes recommended
for checking the progress of fermentation ; but this
practice is inconsistent with just chemical views. It
may cool the dung for a short time ; but moisture, as
I have before stated, is a principal agent in all proces-
ses of decomposition. Dry fibrous matter will never
ferment. Water is as necessary as air to the process ;
and to supply it to fermenting dung, is to supply an.
agent which will hasten its decay.

In all cases when dung is fermenting, there are
simple tests by which the rapidity of the process, and
consequently the injury done, may be discovered.

If a thermometer plungedinto the dung does not
rise to above 100® degrees of Fahrenheit, there is little
danger of much aeriform matter flying off. If the
temperature is higher, the dung should be immediate-
ly spread abroad.

When a piece of paper moistened in muriatic
acid held over the steams arising from a dunghill
gives dense fumes, it is a certain test, that the decom-

N 2

C 274 ]

position is going too far ; for this indicates that vola-
tile alkali is disengaged.

When dung is to be preserved for any time, the
situation in which it is kept is of importance. It
should, if possible, be defended from the sun. To
preserve it under sheds would be of great use ; or to
make the site ®f a dunghill on the north side of a wall.
The floor on which the dung is heaped, should, if pos-
sible, be paved with flat stones ; and there should be
a little inclination from each side towards the centre,
in which there should be drains connected with a
small well furnished with a pump, by which any fluid
matter may be collected for the use of the land. It
too often happens that a dense mucilaginous and ex-
tractive fluid is suffered to drain away from the dung-
hill, so as to be entirely lost to the farm.

Street and road dung^ and the sweepings of houses
may be all regarded as composite manures, the con-
stitution of them is necessarily various, as they are
derived from a number of different substances. These
manures are usually applied in a proper maimer, with-
out being fermented.

Soot^ which is principally formed from the com-
bustion of pit coal or coal, generally contains likewise
substances derived from animal matters. This is a
very powerful manure. It affords ammoniacal salts
by distillation, and yields a brown extract to hot wa-
ter, of a bitter taste. It likewise contains an empy-
reumatic oil. Its great basis is charcoal, in a state in
which it is capable of being rendered soluble by the
action of oxygene and water.

C '275 ]

This manure is well fitted to be used in the dry*
state, thrown into the ground with the seed, and re-
quires no preparation.

The doctrine of the proper application of ma-
nures from organized substances, offers an illustration
of an important part of the oeconomy of nature, and
of the happy order in which it is arranged.

The death and decay of animal substances tend
to resolve organised forms into chemical constituents ;
and the pernicious effluvia disengaged in the process
seem to point out the propriety of burying them in
the soil, where they are fitted to become the food of
vegetables. The fermentation and putrefaction of or-
ganised substances in the free atmosphere are noxious
processes ; beneath the surface of the ground they
are salutary operations. In this case the food of plants
is prepared where it can be used ; and that which
would offend the senses and injure the health, if ex-
posed, is converted by gradual processes info forms of
beauty and of usefulness ; the foetid gas is rendered a
constituent of the aroma of the flower, and what
might be poison, becomes nourishment to animals
and to man.

[ 276 3

ILECTURE VII.

On Manures of mineral Origin^ or fossile Manures ;
their Preparation^ and the Manner in which they
Act, Of Lime in its differ eitt States ; Operation of
Lime as a Manure and a Cement ; different Combin-
ations of Lime. Of Gypsum ; Ideas respecting its
Use Of other Neutro-s aline Compounds^ employed as
Manures. Of Alkalies and alkaline Salts ; of Com-
mon Salt.

THE whole tenor of the preceding Lectures
shews, that a great variety of substances contributes
to the growth of plants, and supplies the materials of
their nourishment. The conversion of matter that
has belonged to living structures into organised
forms, is a process that can be easily understood ; but
it is more difficult to follow those operations by which
earthy and saline matters are consolidated in the fibre
of plants, and by which they are made subservient to
their functions. Some enquirers adopting that sublime
generalization of the ancient philosophers, that matter
is the same in essence, and that the different substan-
ces considered as elements by chemists, are merely
different arrangements of the same indestructible par-
ticles, have endeavoured to prove that all the varieties
of the principles found in plants, may be formed from

[ 277 ]

the substances in the atmosphere ; and that vegetable
life is a process in which bodies that the analytical phi-
losopher is unable to change or to form, are constantly
composed and decomposed. These opinions have not
been advanced merely as hypotheses; attempts have
been made to support them by experiments. M.
Schrader and Mr. Braconnot. from a series of distinct
investigations, have arrived at the same conclusions.
They state that different seeds sown in fine sand, sul-
phur, . and metallic oxides, and supplied only with
atmospherical air and water, produced healthy plants,
which by analysis yielded various earthy and saline
matters, which either were not contained in the seeds,
or the material in which they grew; or which were
contained only in much smaller quantities in the seeds:
and hence they conclude that they must have been
formed from air or water, in consequence of the agen-
cies of the living organs of the plant.

The researches of these two gentlemen were con-
ducted with much ingenuity and address; but there
were circumstances which interfered with their re-
sults, which they could not have known, as at the
time their labours were published they had not been
investigated.

I have found that common distilled water is far
from being free from saline impregnations. In analy-
sing it by Voltaic electricity, I procured from it alkal-
ies and earths; and many of the combinations of me-
tals with chlorine are extremely volatile substances. —
When distilled water is supplied in an unlimited man-
ner to plants, it may furnish to them a number of dif-

L 278 J

ferent substances, which though in quantities scarcely
perceptible in the water, may accumulate in the plant,
which probably perspires only absolutely pure water.

In 1801 I made an experiment on the growth of
oats, supplied Vith a limited quantity of distilled wa-
ter in a soil composed of pure carbonate of lime. The
soil and the water were placed in a vessel of iron,
which was included in a large jar, connected with the
free atmosphere by a tube, so curved as to prevent the
possibility of any dust, or fluid, or solid matter from
entering into the jar. My object was to ascertain
whether any siliceous earth would be formed in the
process of vegetation; but the oats grew very feebly,
and began to be yellow before any flowers formed:
the entire plants were burnt, and their ashes compar-
ed with those from an equal number of grains of oat.
Less siliceous earth was given by the plants than by
the grains; but their ashes yielded much more carbon-
ate of lime. That there was less siliceous earth I
attribute to the circumstance of the husk of the oat be-
ing thrown off in germination; and this is the part
which most abounds in silica. Healthy green oats ta-
ken from a growing crop, in a field of which the soil
was a fine sand, yielded siliceous earth in a much
greater proportion than an equal weight of the corn
artificially raised.

The general results of this experiment are very
much opposed to the idea of the composition of the
earths, by plants, from any of the elements found in
the atmosphere, or in water; and there are other facts
contrary to the idea. Jacquin states that the ashes of

[ 279 3

Glass Wort (Salsola Soda^J when it grows in inland
situations, afford the vegetable alkali; when it grows
on the sea shore where compounds which afford the
fossile or marine alkali are more abundant, it yields
that substance. Du Hamel found, that plants which
usually grow on the sea shore, made small progress
when planted in soils containing little common salt*
The sunflower, when growing in lands containing no
nitre, does not afford that substance; though when
watered by a solution of nitre, it yields nitre abundant-
ly. The tables of de Saussure, referred to in the
Third Lecture, shew th^t the ashes of plants are simi-
lar in constitution to the soils in which they have
vegetated.

De Saussure made plants grow in solutions of
different salts, and he ascertained, that in all cases,
certain portions of the salts were absorbed by the
plant and found unaltered in their organs.

Even animals do not appear to possess the
power of forming the alkaline and earthy substan-
ces. Dr. Fordyce found, that when canary birds
at the time they were laying eggs were deprived of
access to carbonate of lime, their eggs had soft shells;
and if there is, any process for which nature may be
conceived most likely to supply resources of this kind,
it is that connected with the reproduction of the spe*
cies.

As the evidence on the subject now stands, it
seems fair to conclude that the different earths and
saline substances found in the organs of plants, are
-supplied by the soils in which they grow; and in no

[ 280 J

cases composed by new arrangements of the elements
in air dr water. What may be our ultimate view of
the laws of chemistry, or how far our ideas of element-
ary principles may be simplified, it is impossible to say.
We can only reason from facis. We cannot imitate
the powers of composition belonging to vegetable
structures; but at least we can understand them: and
as far as our researches have gone, it appears that in
vegetation compound forms are uniformly produced
from simpler ones; and elements in the soil, ,the at-
mosphere, and the earth absorbed and made parts of
beautiful diversified structures.

The views which have been just developed lead
to correct ideas of the operation of these manures
which are not necessarily the result of decayed organi-
zed bodies, and which are not composed of different
proportions of carbon, hydrogene, oxygene and azote.
— They must produce their effect, either by becom-
ing a constituent part of the plant, or by acting upon
its more essential food, so as to render it more fitted
for the purposes of vegetable life.

The only substances which can with propriety be
called fossils manures, and which are found unmixed
with the remains of any organized beings, are certain
alkaline earths or alkalies, and their combinations.

The only alkaline earths which have been hither-
to applied in this way, are lime and magnesia. Potassa
and soda, the two fixed alkalies, are both used in
certain of their chemical compounds. I shall state in
succession such facts as have come to my knowledge
respecting each of these bodies in their applications to

C 281 J

the purposes of agriculture ; but I shall enlarge most
upon the subject of lime ; and if I should enter into
some details which may be tedious and minute, I trust,
my excuse will be found in the importance of the en-
quiry ; and it is one which has been greatly elucidated
by late discoveries.

The most common form In which lime is found
on the surface of the earth, is in a state of combination
with carbonic acid or fixed air. If a piece of lime-
stone, or chalk, be thrown into a fluid acid, there will
be an effervescence. This is owing to the escape of
the carbonic acid gas. The lime becomes dissolved
in the liquor.

When limestone is strongly heated, the car-
bonic acid gas is expelled, and then nothing remains
but the pure alkaline earth ; in this case there is a loss
of weight ; and of if the fire has been very high, it
approaches to one-half the weight of the stone ; but,
in common cases limestones, if well dried before burn-
ing, do not lose much more than from 35 to 40 per
cent., or from seven to eight parts out of 20.

I mentioned in discussing the agencies of the at-
mosphere upon vegetables, in the beginning of the Fifth
Lecture, that air always contains carbonic acid gas, and
that lime is precipitated from water by this substance.
When burnt lime is exposed to the atmosphere, in a
certain time it becomes mild and is the same substance
as that precipitated from lime water ; it is combined
with carbonic acid gas. Quicklime; when first made,
is caustic and burning to the tongue, renders vegetable
blues green, and is soluble in water ; but when com-

o 2

L 282 J

bincd with carbonic acid it loses all these properties,
its solubility and its taste : it regains its power of ef-
fervescing, and becomes the same chemical substance
as chalk or limestone.

Very few limestones or chalks consist entirely of
lime and carbonic acid. The statuary marbles, or
certain of the rhomboidal spars, are almost the only
pure species ; and the different properties of limestone
both as manures and cements, depend upon the nature
of the ingredients mixed in the limestone ; for the
true calcareous element, the carbonate of Hme, is uni-
formly the same in nature, properties and effects, and
consist of one proportion of carbonic acid 41.4, and
one of lime 55,

When a limestone does not copiously effervesce
in acids, and is sufficiently hard to scratch glass, it
contains silicious and probably aluminous earth.
When it is deep brown or red, or strongly coloured
of any of the shades of brown or yellow, it contains
oxide of iron. When it is not sufficiently hard to
scratch glass, but effervesces slowly, and makes the
acid in which it effervesces milky, it contains mag-
nesia. And when it is black and emits a foetid smell
if rubbed, it contains coally or bituminous matter.

The analysis of limestones is not a difficult mat-
ter ; and the proportions of their constituent parts
may be easily ascertained, by the processes described
in the Lecture on the Analysis of Soils ; and usually
with sufficient accuracy for all the purposes of the
farmer, by the fifth process.

Before any opinion can be formed of the man-
ner in which the different ingredients in limestones

[ 2S3 j

modify their properties, it will be necessary to consi-
der the operation of the pure calcareous element as a
manure, and as a cement.

Quicklime in its pure state, whether in powder
or dissolved in water, is injurious to plants. — I have
in several instances killed grass by watering it with
lime water. — But lime in its state of combination with
carbonic acid, as is evident from the analyses given in
the Fourth Lecture, is a useful ingredient in soils.
Calcareous earth is found in the ashes of the greater
number of plants ; and exposed to the air, lime can-
not long continue caustic, for the reasons that were
just now assigned 5 but soon becomes united to car-
bonic acid. :

When newly burnt lime is exposed to air, it soon
falls into powder ; in this case it it called slacked
lime ; and the same effect is immediately produced
by throwing water upon it, when it heats violently,
and the water disappears.

Slacked lime is merely a Combination of lime,
v/ith about one-third of its weight of water j i. e. 55
parts of lime absorb 1 7 parts of water ; and in this
case It is composed of a definite proportion of lime to
a definite proportion of water, and is called by che-
mists hydrate of lime ; and when hydrate of lime be-
comes carbonate of lime by long exposure to air, the
water is expelled, and the carbonic acid gas takes its
place.

When lime, whether freshly burnt or slacked, is
mixed with any moist fibrous vegetable matter, there
is a strong action between the lime and the vegetable

[ 2S4 ]

matter, and they form a kind of compost together,
of which a part is usually soluble in water-
By this kind of operation, lime renders matter
which was before comparatively inert, nutritive ; and
as charcoal and oxygene abound in all vegetable mat-
ters, it becomes at the same time converted into car-
bonate of lime.

Mild lime, powdered limestone, marles or chalks,
have no action of this kind upon vegetable matter ;
by their action they prevent the too rapid decomposi-
tion of substances already dissolved ; but they have no
tendency to form soluble matters.

It is obvious from these circumstances, that the
operation of quicklime, and marie or chalk, depends
upon principles altogether different. — Quicklime in
being applied to land tends to bring any hard vegeta-
ble matter that it contains into a state of more rapid
decomposition and solution, so as to render it a pro-
per food for plants.— Chalk, and marie, or carbonate
of lime will only improve the texture of the soil, or
its relation to absorption ; it acts merely as one of its
earthy ingredients. — Quicklime, when it becomes
mild, operates in the same manner as chalk ; but in
the act of becoming mild, it prepares soluble out of
insoluble matter.

It is upon this circumstance that the operation of
lime in the preparation for wheat crops depends ; and
its efficacy in fertilizing peats, and in bringing into a
state of cultivation all soils abounding in hard roots,
or dry fibres, or inert vegetable matter.

The solution of the question whether quicklime
ought to be applied to a soil, depends upon the quan.

[ 285 ]

tity of inert vegetable matter that it contains. The
solution of the question whether marie, mild lime, or
powdered limestone ought to be applied, depends upon
the quantity of calcareous matter already in the soil.
All soils are improved by mild lime, and ultimately
by quicklime which do not effervesce with acids 5 and
sands more than clays.

When a soil deficient in calcareous matter contains
much soluble vegetable manure, the application of
quicklime should always be avoided, as it either tends
to decompose the soluble matters by uniting to their
carbon and oxygene so as to become mild lime, or it
combines with the soluble matters, and forms com-
pounds having less attraction for water than the pure
vegetable substance.

The case is the same with respect to most animal
manures ; but the operation of the lime is different in difr
ferent cases, and depends upon the nature of the animal
matter. Lime forms a kind of insoluble soap with oily
matters, and then gradually decomposes them by se-
parating from them oxygene and carbon. It combines
likewise with the animal acids ; and probably assists
their decomposition by abstracting carbonaceous mat-
ter from them combined with oxygene ; and conse-
quently it must render them less nutritive. It tends to
diminish likewise the nutritive powers of albumen from
the same causes ; and always destroys to a certain
extent the efficacy of animal manures, either by com-
bining with certain of their elements, or by giving to
them new arrangements. Lime should never be ap-
plied with animal manures, unless they are too rich.

C 286 ]

or for the purpose of preventing noxious effluvia, as
in certain cases mentioned in the last Lecture. It it
injurious when mixed with any common dung, and
tends to render the extractive matter insoluble.

I made an experiment on this subject : I mixed
a quantity of the brown soluble extract, which was
procured from sheeps' dung with five times its weight
of quicklime. I then moistened them with water ;
the mixture heated very much ; it was suffered to re-
main for 14 hours, and was then acted on by six or
seven times its bulk of pure water : the water, after
being passed through a filter, was evaporated to dry-
ness ; the solid matter obtained was scarcely coloured,
and was lime mixed with a little saline matter.

In those cases in which fermentation is useful to
produce nutriment from vegetable substances, lime is
always efficacious. I mixed some moist tanner's spent
bark with one-fifth of its weight of quicklime, and suf-
fered them to remain together in a close vessel for
three months ; the lime had become coloured and was
effervescent : when water was boiled upon the mix-
ture it gained a tint of fawn colour, and by evapora-
tion furnished a fawn-coloured powder, which must
have consisted of lime united to vegetable matter, for
it burnt when stongly heated and left a residuum of
mild lime.

The limestones containing alumina and silica are
less fitted for the purposes of manure than pure lime-
stones ; but the Hme formed from them has no nox-
ious quality. Such stones are less efficacious, merely
because they furnish a smaller quantity of quicklime.

[ 287 3

I mentioned bituminous limestones. There is
very seldom any considerable portion of coally matter
in these stones ; never as much as five parts in 100 ;
but such limestones make very good lime. The car-
bonaceous matter can do no injury to the land, and
may, under certain circumstances, become a food of
the plant, as is evident from what was stated in the
last Lecture.

The subject of the application of the magnesian
limestone is one of great interest.

It had been long known to farmers in the neigh-
bourhood of Doncaster, that lime made from a certain
limestone applied to the land, often injured the crops
considerably, as I mentioned in the Introductory Lec-
ture. Mr. Tennant, in making a scries of experi-
ments upon this peculiar calcareous substance, found
that it contained magnesia ; and on mixing some cal-
cined magnesia with soil, in which he sowed different
seeds, he found that they either died, or vegetated in
a very imperfect manner, and the plants were never
healthy. And with great justice and ingenuity he re-
ferred the bad effects of the peculiar limestone to the
magnesian earth it contains.

In making some enquiries concerning this sub-
ject, I found that there were cases in which this mag-
nesian limestone was used with good effect.

Amongst some specimens of limestone which
Lord Somerville put into my hands, two marked as
peculiarly good proved to be magnesian limestones.
And lime made from the Breedon limestone is used in
Leicestershire, where it is called hot lime ; and I have

[ 283 J

been informed by farmers in the neighbourhood of the
quarry, that they employ it advantageously in small
quantities, seldom more than 25 or 30 bushels to the
acre. And that they find it may be used with good
effect in larger quantities upon rich land.

A minute chemical consideration of this question
will lead to its solution.

Magnesia has a much weaker attraction for car-
bonic acid than lime, and will remain in the state of
caustic or calcined magnesia for many months, though
exposed to the air. And as long as any caustic lime
remains, the magnesia cannot be combined with car-
bonic acid, for lime instantly attracts carbonic acid
from magnesia.

When a magnesian limestone is burnt, the mag-
nesia is deprived of carbonic acid much sooner than
the lime ; and if there is not much vegetable or ani-
mal matter in the soil to supply by its decomposition
carbonic acid, the magnesia will remain for a long
while in the caustic state ; and in this state acts as a
poison to certain vegetables. And that more magne-
sian lime may be used upon rich soils, seems to be
owing to the circumstance, that the decomposition of
the manure in them supplies carbonic acid. And
magnesia in its mild state, i, e. fully combined with
carbonic acid, seems to be always an useful constituent
of soils. I have thrown carbonate of magnesia (pro-
cured by boiling the solution of magnesia in super-
carbonate of potassa) upon grass, and upon growing
wheat and barley, so as to render the surface white ;
but the vegetation was not injured in the slightest de-

[ 289 ] ■

gree. And one of ihe most fertile parts cf Cornwall,
the Lizard, is a district in which the soil contains
mild magnesian earth.

The Lizard Downs bear a short and green grass,
which feeds sheep producing excellent mutton ; and
the cultivated parts are amongst the best corn lands in
the county.

That the theory which I have ventured to give of
the operation of magnesian lime is not unfounded, is
shewn by an experiment which I made expressly for
the purpose of determining the true nature of the
operation of this substance. I took four portions of
the same soil : with one I mixed 20 of its weight of
caustic magnesia, wath another I mixed the same
quantity of magnesia and a proportion of a fat decom-
posing peat equal to one-fourth of the weight of the
soil. One portion of soil remained in its natural
state : and another was mixed with peat without mag-
nesia. The mixtures were made in December 1 806 ;
and in April 1807, barley was sown in all of them.
It grew very well in the pure soil ; but better in the
soil containing the magnesia and peat ; and nearly as
well in the soil containing peat alone : but in the soil
containing the magnesia alone, it rose very feeble, and
looked yellow and sickly.

I repeated this experiment in the summer of 1810
with similar results ; and I found that the magnesia
in the soil mixed with peat became strongly efferves-
cent, whilst the portion in the unmixed soil gave car-
bonic acid in much smaller quantities. In the one case
the magnesia had assisted in the formation of a man^

p2

[ 290 3

ute, and had become mild 5 in the otner case it had
acted as a poison.

It is obvious from what has been said that lime
from the magnesian limestone may be applied in large
quantities to pea'ts; and that where lands have been
injured by the application of too large a quantity of
magnesian lime, peat will be a proper and efficient
remedy.

I mentioned that magnesian lime stones efferves-
ced little when plunged into an acid. A simple test
of magnesia in a limestone is this circumstance, in its
rendering diluted nitric acid, or acqua fortis milky.

From the analysis of Mr. Tennant, it appears
that the magnesian limestones contain from

20.3 to 22.5 magnesia.

29.5 to 31.7 lime.

47.2 carbonic acid.
0.8 clay and oxide of iron.
Magnesian limestones are usually coloured brown
or pale yellow, they are found in Somersetshire, Lei-
cestershire, Derbyshire, Shropshire, Durham, and
Yorkshire. I have never met with any in other coun-
ties in England; but they abound in many parts of
Ireland, particularly near Belfast. '

The use of lime as a cement is not a proper sub-
ject for extensive discussion in a course of Lectures on
the chemistry of agriculture; yet as the theory of the
operation of lime in this way is not fully stated in any
elementary book that I have perused, I shall say a
very few words on the applications of this part of che-
mical knowledge.

C 291 3

There are two modes in which lime acts as a ce-
ment; in its combination with water, and in its combi-
nation with carbonic acid.

The hydrate of lime has been already mentioned.
When quick lime is rapidly made into a paste with
water, it soon loses its softness, and the water and the
lime form together a solid coherent mass, which con-
sists, as has been stated before, of 1 7 parts of water to
55 parts of lime. When hydrate of lime whilst it is
consolidating is mixed with red oxide of iron, alumina^
or silica, the mixture becomes harder and more co-
herent than when lime alone is used; and it appears
that this is owing to a certain degree of chemical at-
traction between hydrate of lime and these bodies; and
they render it less liable to decompose by the action
of the carbonic acid in the air, and less soluble in
water.

The basis of all cements that are used for
works which are to be covered with water must be
formed from hydrate of lime; and the lime made from
impure limestones answers this purpose very well.
Puzzolana is composed principally ot silica, alumina,
and oxide of iron; and it is used mixed with lime to
form cements intended to be employed under water,
Mr. Smeaton, in the construction of the Eddystone
light house, used a cement composed of equal parts by^
weight of slacked lime and puzzolana. Puzzolana is
a decomposed lava. Tarras, which was formerly im-
ported in considerable quantities from Holland, is a
mere decomposed basalt: two parts of slacked lime and
one part of tarras forms the principal part of the mor-

[ 292 ]

tar used in the great dykes of Holland. Substances
which will answer all the ends of puzzolana and tar-
ras are abundant in the British islands. An excellent
red tarras may be procured in any quantities from the
Giants' Causeway in the north of Ireland: and decom-
posing basalt is abundant in many parts of Scotland,
and in the northern districts of England in which coal
is found.

Parker's cement, and cements of the same kind
made at the alum works of Lord Dundas and Lord
Mulgrave are mixtures of calcined ferruginous stones,
with hydrate of lime.

The cements which act by combining with car-
bonic acid, or the common mortars, are made by mix-
ing together slacked Hme and sand. These mortars,
at first solidify as hydrates, and are slowly converted
into carbonate of lime by the action of the carbonic
acid of the air. Mr. Tennant, found that a mortar of
this kind in three years and a quarter had regained 63
per cent, of the quantity of carbonic gas which con-
stitutes the definite proportion in carbonate of lime.
The rubbish of mortar from houses owes its power to
benefit lands principally to the carbonate of lime it
contains; and the sand in it; and its state of cohesion
renders it particularly fitted to improve clayey soils.

The hardness of the mortar in very old buildings
depends upon the perfect conversion of all its parts
into carbonate of lime. The purest limestones are the
best adapted for making this kind of mortar; the mag-
nesian limestones make excellent water cements; but
act with too /ittle energy upon carbonic acid gas to
make good common morter.

i: 293 ]

The Romans, according to Pliny, made their
best mortar a year before it was used; so that it was
partially combined with carbonic acid gas before it
was employed.

In burning lime there are some particular pre-
cautions required for the different kinds of limestones.
In general, one bushel of coal is sufficient to make
four or five bushels of lime. The magnesian lime-
stone requires less fuel than the common limestone.
In all cases in which a limestone containing much alu-
minous or siliceous earth is burnt, great care should
be taken to prevent the fire from becoming too intense;
for such lime easily virtrifies, in consequence of the
affinity of lime for silica and alumina. And as in some
J^laces there are no other limestones than such as con-
tain other earths, it is important to attend to this cir-
cumstance. A moderately good lime may be made at
a low red heat; but it will melt into a glass at a white
heat. In limekilns for burning such lime, there
should be always a damper.

In general, when limestones are not magnesian
their purity will be indicated by their loss of weight
in burning; the more they lose the larger is the quan-
tity of calcareous matter they contain. The magne-
sian limestones contain more carbonic acid than the
common limestones; and I have found all of them lose
more than half their weight by calcination.

Besides being used in the forms of lime and carbon-
ate of lime, calcareous matter is applied for the pur-
poses of agriculture in other combinations. One of '
these bodies is gypsum or sulphate of lime. This sub-

L ^-^94 j

stance consists of sulphuric acid (the sams body that
exists combined with water in oil of vitriol) and lime;
and when dry it is composed of 55 parts of lime and 75
parts of sulphuric acid. Common gypsum or selenite,
such as that found at Shotover hill near Oxford, con-
tains besides sulphuric acid and lime, a considerable
quantity of water ; and its composition may be thus
expressed :

Sulphuric acid one proportion 75

Lime one proportion - - 55

Water two proportions - - 34

The nature of gypsum is easily demonstrated ;

if oil of vitriol be added to quicklime there is a violent

heat produced ; when the mixture is ignited, water is

given off, and gypsum alone is the result, if the acid

has been used in sufficient quantity ; and gypsum

mixed with quicklime, if the quantity has been defi«

cient.^ Gypsum free from water is sometimes found

in nature, when it is called anhydrous seienite. It is

distinguished from common gypsum by giving off no

water when heated.

When gypsum free from water, or deprived of
water by heat, is made into a paste with water, it ra-
pidly sets by combining with that fluid. Plaister of
Paris is powdered dry gypsum; and its property as a
cement, and in its use in making casts depends upon
its solidifying a certain quantity of water, and making
with it a coherent mass. Gypsum is soluble in about
500 times its weight of cold water, and is more solu-
ble in hot w^ater ; so that when water has been boiled
in contact with gypsum, crystals of this substance are

deposited as the water cools. Gypsum Is easily dis-
tinguished when dissolved by its properties of afford-
ing precipitates to solutions of oxalates and of barytic
salts.

Great difference of opinion has prevailed amongst
agriculturists with respect to the uses of gypsum. It
has been advantageously used in Kent, and various
testimonies in favour of its efficacy have been laid be-
fore the Board of Agriculture by Mr. Smith. In
America it is employed with signal success ; but in
most counties of England it has failed, though tried
in various ways, and upon different crops.

Very discordant notions have been formed as to
the mode of operation of gypsum. It has been sup-
posed by some persons to act by its power of attract-
ing moisture from the air ; but this agency must be
comparatively insignificant. When combined with wa-
ter it retains that fluid too powerfully to yield it to the
roots of the plant, and its adhesive attraction for mois-
ture is inconsiderable ; the small quantity in which it
is used likewise is a circumstance hostile to this idea.

It has been said that gypsum assists the putrefac-
tion of animal substances, and the decomposition of
manure. I have tried some experiments on this subject
which are contradictory to the notion, I mixed some
minced veal with about ih part of its weight of gyp-
sum, and exposed some veal without gypsum under
the same circumstances : there was no difference in
the time in which they began to putrefy ; and the pro-
cess seemed to me most rapid in the case in which there
was no gypsum present. I made other similar mix-

[ 296 ]

tures, employing in some cases larger, and in some
cases smaller quantities of gypsum ; and I used
pigeons' dung in one instance instead of flesh, and
with precisely similar results. It certainly in no case
increased the rapidity of putrefaction.

Though it is not generally known, yet a series of
experiments has been carried on for a great length of
time in this country upon the operation of gypsum as
a manure. The Berkshire and the Wiltshire peat-
ashes contain a considerable portion of this substance.
In the Newbury peat-ashes I have found from one
fourth to one-third of gypsum ; and a larger quantity
in some peat-ashes from the neighbourhood of Stock-
bridge : the other constituents of these ashes are cal-
careous, aluminous, and siliceous earth, with variable
quantities of sulphate of potassa, a little common salt,
and sometimes oxide of iron. The red ashes contain
most of this last substance.

These peat-ashes are used as a top dressing for
cultivated grasses, particularly sainfoin and clover.
In examining the ashes of sainfoin, clover, and rye
grass, I found that they afforded considerable quanti*
ties of gypsum ; and this substance, probably, is ind-
mately combined as a necessary part of their woody
fibre. If this be allowed, it is easy to explain the rea-
son why it operates in such small quantities ; for the
whole of a clover crop, or sainfoin crop, on an acre,
according to my estimation, would afford by incinera-
tion only three or four bushels of gypsum. In exam-
ining the soil in a field near Newbury, which was ta- ^
ken from below a foot-path near the gate, where gyp-

[ 297 J

sum could not have been artificially furnished, I could
not detect any of this substance in it; and at the very
time I collected the soil, the peat-ashes were applied
to the clover in the field. The reason why gypsum is
not generally efficacious is probably because most
cultivated soils contain it in sufficient quantities for the
use of the grasses. In the common course of cultiva-
tion, gypsum is furnished in the manure; for it is con-
tained in stable dung, and in the dung of all cattle fed
on grass; and it is not taken up in corn crops, or crops
of peas and beans, and in very small quantities in
turnip creeps; but where lands are exclusively devoted
to pasturage and hay, it will be continually consumed.
1 have examined, four different soils cultivated by a
series of common courses of crops, for gypsum. One
was alight sand from Norfolk; another a clay bearing
good wheat from Middlesex; the third a sand from
Sussex; the fourth a clay from Essex. I found gyp-
sum in all ot them; and in the Middlesex soil it amount-
ed nearly to one per cent. Lord Dundas informs me,
that having tried gypsum without any benefit on two
of his estates in Yorkshire, he was induced to have
the soil examined for gypsum according to the pro-
cess described in the Fourth Lecture, and this sub-
stance was found in both the soils.

Should these statements be confirmed by future
enquirers, a practical inf rence of some value may be
derived from them. It is possible that lands which
have ceased to bear good crops of clover, or artificial
grasses, may be restored by being manured with gyp*
sum. I have mentioned that this sub.slance is found

Q2

[ 298 ]

in Oxfordshire; it is likewise abundant in many other
parts of England; in Gloucestershire, Somersetshire,
Derbyshire, Yorkshire, Stc. and requires only pulveri-
zation for its preparation.

Some very interesting documents upon the use of
sulphate of iron or green vitriol, which is a salt pro-
duced from peat in Bedfordshire, have been laid be-
fore the Board by Dr. Pearson; and I have witnessed
the fertilizing effects of a ferruginous water used for
irrigating a grass meadow made by the Duke of Man-
chester, at Priestley Bog near Woburn, an account of
the produce of which has been published by the Board
of Agriculture. I have no doubt that the peat salt
and the vitriolic water acted chiefly by producing gyp-
sum.

The soils on which both are efficacious are cal-
careous; and sulphate of iron is decomposed by the
carbonate of lime in such soils. The sulphate of iron
consists of sulphuric acid and oxide of iron, and is an
,acid and a very soluble salt; when a solution of it is
mixed with carbonate of lime, the sulphuric acid quits
the oxide of iron to unite td^the lime, and the com-
pounds produced are insipid and comparatively inso-
luble.

1 collected some of the deposition from the fer-
ruginous water on the soil in Priestley meadow. I
found it consisted of gypsum, carbonate of iron, and
insoluble sulphate of iron. The principal grasses in
Priestley meadow are, meadow fox-tail, cook's-foot,
meadow fescue, fiorin, and sweet scented vernal grass.
I have examined the ashes of three of the grasses.

[ 299 ]

meadow fox-tail, cook's-foot, and fiorin. They con-
tained a considerable proportion of gypsum.

Vitriolic impregnations in soils where there is no
calcareous matter, as in a soil from Lincolnshire, to
which I referred in the Fourth Lecture, are injurious;
but it is probably in consequence of their supplying an
excess of ferruginous matter to the sap. Oxide of
iron in small quantities forms an useful part of soils;
and, as is evident from the details ia the Third Lec-
ture, it is found in the ashes of plants; and probably,
is hurtful only in its acid combinations.

I have just mentioned certain peats, the ashes of
which aflbrd gypsum; but it must not be inferred from
this that all peats agree with them. I have examined
various peat, ashes from Scotland, Ireland, Wales, and
the northern and western parts of England, which
contained no quantity that could be useful; and these
ashes abounded in siliceous, aluminous earths and
oxide of iron.

Lord Charieviile found in some peat-ashes from
Ireland sulphate of potassa; i. e. the sulphuric acid
combined with potassa.

Vitriolic matter is usually formed in peats; and if
the soil or substratum is calcareous, the ultimate re-
sult is the production of gypsum. In general, when a
recent peat-ash emits a strong smell resembling that
of rotten eggs when acted upon by vinegar, it will fur-
nish gypsum.

Phosphate of lime is a combination of phosphoric
acid and lime, one proportion of each. It is a com-
pound insoluble in pure water, but soluble in water

[ 300 ]

containing any acid matter. It forms the greatest
part of calcined bones. It exists in most excremen-
titious substances, and is found both in the straw and
grain of wheat, barley^ oats and rye, and hkewise in
beans, peas and tares. It exists in some places in
these islands native; but only in very small quantities.
Phosphate of lime is generally conveyed to the land in
the composition of other manure; and it is probably
necessary to corn crops and other white crops.

Bone ashes ground to powder will probably be
found useful on arable lands containing much vegeta-
ble matter; and may perhaps enable soft peats to pro-
duce wheat; but the powdered bone in an uncalcined
state is much to be preferred in all cases when it can
be procured.

The Saline compounds of magnesia will require
very little discussion as to their uses as manures.^
The most important relations of this subject to agri-
culture have been considered in the former part of
this Lecture, when the application of the magnesian
limestone was examined. In combination with sul-
phuric acid magnesia forms a soluble salt. This sub-
stance, it is stated by some enquirers, has beeen found
of use as a manure; but.it is not found in nature in suf-
ficient abundance, nor is it capable of being made ar-
tificially sufficiently cheap to be of useful application in
the common course of husbandry.

Wood ashes consist principally of the vegetable
alkali united to carbonic acid; and as this alkali is
found in almost all plants, it is not difficult to con-
ceive that it may form an essential part of their or-

C 301 J

gans. The general tendency of the alkalies is to give
solubility to vegetable matters ; and in this way they
may render carbonaceous and other substances capa-
ble of being taken up by the tubes in the radicle
fibres of plants. The vegetable alkali likewise has a
strong attraction for water, and even in small quanti-
ties may tend to give a due degree of moisture to the
soil, or to other manures ; though this operation from
the small quantities used, or existing in the soil, can
be only of a secondary kind.

The mineral alkali or soda^ is found in the ashes
of sea- weed, and may be procured by certain chemical
agencies from common salt. Common salt consists of
the metal named sodium, combined with chlorine;
and pure soda consists of the same metal united to
oxygene. When water is present which can afford
oxygene to the sodium, soda may be obtained in se-
veral modes from salt.

The same reasoning will apply to the operation
of the pure mineral alkaH, or the carbonated alkali, as
to that of the vegetable alkali ; and when common salt
acts as a manure, it is probably by entering into the
composition of the plant in the same manner as gyp-
sum, phosphate of lime, and the alkalies. Sir John
Pringle has stated, that salt in small quantities assists
the decomposition of animal and vegetable matter.
This circumstance may render it useful in certain
soils. Common salt likewise is offensive to insects.—
That in small quantities it is sometimes a useful man-
ure, I believe it fully proved ; and it is probable that
its efficacy depends upon many combined causes.

L ^C>2 J

Some persons have argued against the employ-
ment of salt ; because when used in large quantities,
it either does no good, or renders the ground sterile ;
but this is a very unfair mode of reasoning. That salt
in large quantities rendered land barren, was known
long before any records of agricultural science exist-
ed. We read in the Scriptures, that Abimelech took
the city of Shechem, "and beat down the city, and
sowed it with salt ;" that the soil might be for ever un-
fruitful. Virgil reprobates a salt soil ; and Pliny,
though he recommends giving salt to cattle, yet af-
firms, that when strewed over land it renders it bar-
ren. But these are not arguments against a proper
application of it. Refuse salt in Cornwall, which, how-
ever, likewise contains some of the oil and exuviae of
fish, has long been known as an admirable manure.
And the Cheshire farmers contend for the benefit of
the peculiar produce of their country.

It is not unlikely that the same causes influence
the effects of salt, as those which act in modifying the
operation of gvpsum. Most lands in this Island, par-
ticularly those near the sea, probably contain a suffi-
cient quantity of salt for all the purposes of vegetation ;
and in such cases the supply of it to the soil will not
only be useless, but may be injurious. In great
storms the spray of the sea has been carried more
than 50 miles from the shore ; so that from this
source salt must be often supplied to the soil. I have
found salt in all the sandstone rocks that I have ex^
amined, and it must exist in the soil derived from
these rocks. It is a constituent likewise of almost
every kind of animal and vegetable manure.

[ 303 ]

Besides these compounds of the alkalme earths
and alkalies, many others have been recommended
for the purposes of increasing vegetation ; such are
nitre, or the nitrous acid combined with potassa. Sir
Kenelm Digby states, that he made barley grow very
luxuriantly by watering it with a very weak solution
of nitre ; but he is too speculative a writer to awaken
confidence in his results. This substance consists of
one proportion of azote, six of oxygene, and one of
potassium ; and it is not unlikely that it may furnish
azote to form albumen or gluten in those plants that
contain them ; but the nitrous salts are too valuable
for other purposes to be used as manures.

Dr. Home states, that sulphate of potassa, which
as I just now mentioned, is found in the ashes of some
peats, is a useful manure. But Mr. Naismith* ques-
tions his results ; and quotes experiments hostile
to his opinion, and, as he conceives, unfavourable to
the efficacy of any species of saline manure.

Much of the discordance cf the evidence relating
to the efficacy of saline substances depends upon the
circumstance of their having been used in different
proportions, and in general in quantities much too
large.

I made a number of experiments in May and
June, 1807, on the effects of different saline substan-
stances on barley and on grass growing in the same
garden, the soil of which was a light sand, of which
100 parts were composed of 60 parts of silice-

• Element* of Agiicultupe, p. 7»,

[ S04 ]

ous sand, and 24 parts finely divided matter, consist-
ing of 7 parts carbonate of lime, 12 parts alumina
and silica, less than one part saline matter, principally
common salt, with a trace of gypsum and sulphate of
magnesia: the remaining 16 parts were vegetable
matter.

The solutions of the saline substances were used
twice a week, in the quantity of two ounces, on spots
of grass and corn, sufficiently remote from each other
to prevent any interference of results. The substan-
ces tried were super-carbonate^ sulphate^ acetate, ni-
trate, and muriate of pot ass a ; sulphate of soda, sul-
phate, nitrate, muriate, and carbonate of ammonia, I
found that in all cases when the quantity of the salt
equalled ^^^ part of the weight of the water, the effects
were injurious ; but least so in the instances of the
carbonate, sulphate, and muriate of ammonia. When
the quantities of the salts were 300 part of the solution
the effects were different. The plants watered with
the solutions of the sulphates grew just in the same
manner as similar plants watered with rain water.
Those acted on by the solution of nitre, acetate, and
super-carbonate of potassa, and muriate of ammonia
grew rather better. Those treated with the solution
of carbonate of ammonia grew most luxuriantly of all.
This last result is what might be expected, for car-
bonate of ammonia consists of carbon, hydrogene,
azote, and oxygene. There was, however, another
result which I had not anticipated ; the plants water-
ed with solution of nitrate of ammonia did not grow
better than those watered with rain water. The solu-

[ 305 ]

tion reddened litmus paper; and probably the free acid
exerted a prejudicial effect, and interfered with the re-
sult.

Soot doubtless owes a part of its efficacy to the
ammoniacal salts it contains The liquor produced by
the distillation of coal contains carbonate and acetate
of ammonia, and is said to be a very good manure.

In 1 808, I found the growth of wheat in a field at
Roehampton assisted by a very weak solution of ace-
tate of ammonia.

Soapers' waste has been recommended as a man-
ure, and it has been supposed that its efficacy depend-
ed upon the different saline matters it contains; but
their quantity is very minute indeed, and its principal
ingredients are mild lime and quicklime. In the soap-
ers' waste from the best manufactories, there is scarce-
ly a trace of alkali. Lime moistened with sea water
affords more of this substance, and is said to have
been used in some cases with more benefit than com-
mon lime.

It is unnecessay to discuss to any greater extent
the effects of saline substances on vegetation; except
the ammoniacal compounds, or the compounds con-
taining nitric, acetic, and carbonic acid; none of them
can afford by their decomposition any of the common
principles of vegetation, carbon, hydrogene, and oxy.
gene.

The alkaline sulphates and the earthy muriates
are so seldom found in plants, or are found in such
minute quantities, that it can never be an object
to apply them to the soil. It was stated in the begin*

R 2

I 306 2

liing of this Lecture, that the earthy and alkaline sub-
stances seem never to be formed in vegetation; and
there is every reason likewise to believe, that they are
never decomposed; for after being absorbed they are
found in their ashes.

The metallic bases of them cannot exist in con-
tact with aqueous fluids; and these metallic bases,
like other metals, have not as yet been resolved into
any other forms of matter by artificial processes; they
combine readily with other elements; but they remain
iindestructible, and can be traced undiminished in
quantity, through their diversified combinations.

;o7

LECTURE ViiL

On the Improvement of Lands by Burning; chemical
Principles of this Operation. On Irrigation and its
effects. On Fallowing; its Disadvantages and
Uses. On the convertible Husbandry founded on
regular Rotations of different Crops, On Pasture;
Views connected with its Application, On various
Agricultural Objects connected with Chemistry,
Conclusion,

The improvement of sterile lands by burning
was known to the Romans. It is mentioned by Vir-
gil in the first book of the Georgics: '' Saepe etiam
steriles incendere profuit agros." It is a practice still
much in use in many parts of these Islands; the theory
of its operation has occasioned much discussion; both
amongst scientific men and farmers. It rests entirely
upon chemical doctrines; and I trust I shall be able to
offer you satisfactory elucidations on the subject.

The basis of all common soils, as I stated in the
Fourth Lecture, are mixtures of the primitive earths
and oxide of iron; and these earths have a certain de-
gree of attraction for each other. To regard this at-
traction in its proper point of view, it is only necessary
to consider the composition of any common siliceous

[ 308 ]

Stone. Feldspar, for instance, contains siliceous, al-
uminous, calcareous earths, fixed alkali, and oxide of
iron, which exist in one compound, in consequence of
their chemical attractions for each other. Let this
stone be ground into impalpable powder, it then be-
comes a substance like clay: if the powder be heated
very strongly it fuses, and on cooling forms a coher-
ent mass similar to the original stone; the parts separ-
ated by mechanical division adhere again in conse-
quence of chemical attraction. If the powder is heat-
ed less strongly the particles only superficially com*
bine with each other, and form a gritty mass, which,
when broken in to pieces, has the characters of sand.

If the power of the powdered feldspar to absorb
water from the atmosphere before, and after the ap-
plication of the heat, be compared, it is found much
less in the last case.

The same effect takes place when the powder of
other siliceous or aluminous stones is made the sub-
ject of experiment.

I found that two equal portions of basalt ground
into impalpable powder, of which one had been strong-
ly ignited, and the other exposed only to a temperature
equal to that of boiling water, gained very different
weights in the same time when exposed to air. In
four hours the orie had gained only two grains, whilst
the other had gained seven grains.

When clay or tenacious soils are burnt, the effect
is of the same kind; they are brought nearer to a state
analogous to that of sands.

[ 309 3

In the manufacture of bricks the general principle
'is well illustrated ; if a piece of dry brick earth be ap-
plied to the tongue it will adhere to it very strongly,
in consequence of its power to absorb water ; but af-
ter it has been burnt there will be scarcely a sensible
adhesion.

The process of burning renders the soil less com-
pact, less tenacious and retentive of moisture ; and
when properly applied, may convert a matter that was
stiff, damp, and in consequence cold, into one pow-
dery, dry, and warm j and much more proper as a
bed for vegetable life.

The great objection made by speculative chemists
to paring and burning, is, that it destroys vegetable
and animal matter, or the manure in' the soil ; but in
cases in which the texture of its earthy ingredients is
permanently improved, th^re is more than a compen-
sation for this temporary disadvantage. And in some
soils where there is an excess of inert vegetable mat-
ter, the destruction of it must be beneficial ; and the
carbonaceous matter remaining in the ashes may be
more useful to the crop than the vegetable fibre, from
which it was produced.

I have examined by a chemical analysis three
specimens of ashes from different lands that had un-
dergone paring and burning. The first was a quanti-
ty sent to the Board by Mr. Boys of Bellhanger, in
Kent, whose treatise on paring and burning has been
published. They were from a chalk soil, and 200
grains contained

80 Carbonate of lime,
11 Gypsum.

C 310 J

9 Charcoal.
15 Oxide of iron.
5 Saline matter.
Sulphate of potash.
Muriate of magnesia, with a minute
quantity of vegetable alkali.
The remainder alumina and silica.

Mr. Boys estimates that 2660 bushels are the
common produce of an acre of ground, which, accor-
ding to his calculation would give 172900 lbs. con-
taining

Carbonate of lime 69 1 60 lbs.
Gypsum . 9509.5

Oxide of iron 12967.5

Saline matter 2593.5

Charcoal 7780.5

In this instance there was undoubtedly a very
considerable quantity of matter capable of being ac-
tive as manure produced in the operation of burning.
The charcoal was very finely divided ; and exposed
on a large surface on the field, must have been gradu-
ally converted into carbonic acid. And gypsum and
oxide of iron, as I mentioned in the last Lecture, seem
to produce the very best effects when applied to lands
containing an excess of carbonate of lime.

The second specimen was from a soil near Cole-
©rton, in Leicestershire, containing only four per cent,
of carbonate of lime, and consisting of three-fourths
light siliceous sand, and about one-fourth clay. This
had been turf before burning, and 100 parts of the
ashes gave

L ^n j

6 parts charcoal.

3 Muriate of soda and sulphate of potash,

with a trace of vegetable alkali.
9 Oxide of iron.
And the remainder the earths.

In this instance, as in the other, finely divided
charcoal was found ; the solubility of which would be
increased by the presence of the alkali.

The third instance was, that of a stiff clay, from
Mount's Bay Cornwall. This land had been brought
into cultivation from a heath by burning about ten
years before ; t^ut having been neglected, furze was
springing up in different parts of it, which gave rise
to the second paring and burning. 100 parts of the
ashes contained

8 parts of charcoal.

2 of saline matter, principally common salt,
with a little vegetable alkali.

7 Oxide of iron.

2 Carbonate of lime.
Remainder alumina and silica.

Here the quantity of charcoal was greater than in
the other instances. The salt, I suspect, was owing
to the vicinity of the sea, it being but two miles offl
In this land there was certainly an excess of dead ve-
getable fibre, as well as unprofitable living vegetable
matter ; and I have since heard, that a great improve-
ment took place.

Many obscure causes have been referred to for
the purpose of explaining the effects of paring and
burning ; and I believe they may be referred entirely

C 312 3

to the diminution of the coherence and tenacity of
clays, and to the destruction of inert, and useless ve-
getable matter, and its conversion into a manure.

Dr. Darwin, in his Phytologia, has supposed,
that clay during torrefaction, may absorb some nutri-
tive principles from the atmosphere that afterwards
may be supplied to plants ; but the earths are pure
metallic oxides, saturated with oxygene ; and the ten-
dency of burning is to expel any other volatile princi-
ples that they may contain in combination. If the
oxide of iron in soils is not saturated with oxygene,
torrefaction tends to produce its further union with
this principle ; and hence in burning, the colour of
clays changes to red. The oxide of iron containing
its full proportion of oxygene has less attraction for
acids than the other oxide, and is consequently lass
likely to be dissolved by any fluid acids in the soil ;
and it appears in this state to act in the same manner
as the earths, A very ingenious author, whom I
quoted at the end of the last Lecture, supposes that the
oxide of iron when combined with carbonic acid is
poisonous to plants ; and that one use of torrefaction
is to expel the carbonic acid from it ; but the carbon-
ate of iron is not soluble in water, and is a very inert
substance ; and I have raised a luxuriant crop of cres-
ses in a soil composed cf one-fifth carbonate of iron,
and four-fifths carbonate of lime. Carbonate of iron
abounds in some of the most fertile soils in England ^
particularly the red hop soil. And there is no theo-
retical ground for supposing, that carbonic acid, which
is an essential food of plants, should in any of its com-

C 313 J

binations be poisonous to themj and it is known that
lime and magnesia are both noxious to vegetation,
unless combined with this principle.

All soils that contain too much dead vegetable
fibre, and which consequently lose from one third to
one-half of their weight by incineration, and all such
as contain their earthy constituents in an impalpable
state of division, i. e. the stiff clays and marles, are im-
proved by burning; but in coarse sands, or rich soils
containing a just mixture of the earths; and in all ca-
ses in which the texture is already sufficiently loose,
or the organizable matter sufficiently soluble, the pro-
cess of torrefaction cannot be useful.

All poor 'Siliceous sands must be injured by it;
and here practice is found to accord with the theory.
Mr. Young, in his Essay on Manures, states, " that
he found burning injure sand;" and the operation is
never performed by good agriculturists upon siliceous *
sandy soils, after they have oncie been brought into
cultivation.

An intelligent farmer in Mount's Bay told me,
that he had pared and burned a small field sevei^al
years ago, which he had not been able to bring again
into good condition. I examined the spot, the grass was
very poor and scanty, and the soil an arid siliceous
sand.

Irrigation or Watering land^ is a practice, which
at first viev/, appears the reverse of torrefection; and
in general, in nature, the operation of water is to bring
earthy substances into an extreme state of division
But in the artificial watering of meadows, the benefi-

S2

C SI* 1

ciai effects depend upon many different causes, some
chemical, some mechanical.

Water is absolutely essential to vegetation; and
when land has been covered by water in the winter,
or in the beginning of spring, the moisture that has
penetrated deep into the soil, and even the subsoil^
becomes a source of nourishment to the roots of the
plant in the summer, and prevents those bad effects
that often happen in lands in their natural state, from
a long continuance of dry weather.

When the water used in irrigation has flowed
over a calcareous country, it is generally found im-
pregnated with carbonate of lime; and in this state it
tends, in many instances, to ameliorate the soil.

Common river water also generally contains a
certain portion of organizable matter, which is much
greater afier rains, than at other times; and which ex-
ists in the largest quantity when the stream rises in a
cultivated country.

Even in cases when the water used for flooding
is pure, and free from animal or vegetable substances,
it acts by causing the more equable diffusion of nutri-
tive matter existing in the land; and in Very cold sea-*
sons it preserves the tender roots and leaves of the
grass from being affected by frost.

Water is of greater specific gravity at 42° Fah-
renheit, than at 32'', the freezing point; and hence in
a meadow irrigated in winter, the water immediately
in contact with the grass is rarely below 40°, a degree
of temperature not at all prejudicial to the living or-
gans of plants.

C 315 3

' In 1804-, in the month of March, I examined
the temperature in a water meadow near Hungerford>
in Berkshire, by a very dehcate thermometer. The
temperature of the air at seven in the morning was
29°. The water was frozen above the grass. The
temperature of the soil below the water in which the
roots of the grass were fixed, was 43°.

In general those waters which breed the best fish
are the best fitted for watering meadows; but most of
the benefits of irrigation may be derived from any kind
of water. It is, however, a general principle, that wa-
ters containing ferruginous impregnations, though
possessed of fertilizing effects, when applied to a cal-
careous soil, are injurious on soils that do not effer-
vesce with acids; and that calcareous waters which are
known by the earthy deposit they afford when boiled,
are of most use on siliceous soils, or other soils con-
taining no remarkable quantity of carbonate of lime*

The most important processes for improving
land, are those which have been already discussed,
and that are founded upon the circumstance of remo-
ving certain constituents from the soil, or adding
others or changing their nature; but there is an opera-
tion of very ancient practice still much employed, in
which the soil is exposed to the air and submitted to
processes which are purely mechanical, namely,
fallozving.

The benefits arising from fallows have been much
over-rated. A summer fallow, or a clean fallow,
may be sometimes necessary in lands overgrown with
weeds, particularly if they are sands which cannot be

L 316 ] ,

pared and burnt with advantage; but it is certainly un-
profitable as part of a general system in husbandry.

It has been supposed by some writers, that cer-
tain principles necessary to fertility are derived from
the atmosphere, which are exhausted by a succession
of crops, and that these are again supplied during the
repose of the land, and the exposure of the pulverised
soil to the influence of the air; but this in truth is not
the case. The earths commonly found in soils can-
not be combined with more oxygene; none of them
unite to azote; and such of them as are capable of ati-
tracting carbonic acid, are always saturated with it in
those soils on which the practice of fallowing is adopt-
ed. The vague ancient opinion of the use of nitre,
and of nitrous salts in vegetation, seems to have been
one of the principal speculative reasons for the de-
fence of summer fallows. Nitrous salts are produced
during the exposure of soils containing vegetable and
animal remains, and in greatest abundance in hot wea-
ther; but it is probably by the combination of azote
from these remains with oxygene in the atmosphere
that the acid is formed; and at the expence of an ele-
ment, which otherwise would have formed ammonia;
the compounds of which, as is evident from what was
stated in the last Lecture, are much more efficacious
than the nitrous compounds in assisting vegetation.

When weeds are buried in the soil, by their gra-
dual decomposition they furnish a certain quantity of
soluble matter; but it may be doubted whether there
is as much useful manure in the land at the end of a
clean fallow, as at the time the vegetables clothing the

C 317 3

surface were first ploughed in. Carbonic acid gas
is formed during the whole time by the action of the
vegetable matter upon the oxygene of the air, and the
greater part of it is lost to the soil in which it Was
formed, and dissipated in the atmosphere.

The action of the sun upon the surface of the
soil tends to disengage the gaseous and the volatile
fluid matters that it contains ; and heat increases the
rapidity of fermentation : and in the summer fallow,
nourishment is rapidly produced, at a time when no
vegetables are present capable of absorbing it.

Land when it is not employed in preparing food
for animals, should be applied to the purpose of the
preparation of manure for plants ; and this is effected
by means of green crops, in consequence of the ab-
sorption of carbonaceous matter in the carbonic acid
of the atmosphere. In a summer's fallow a period is
always lost in which vegetables may be raised, either
as food for animals, or as nourishment for the next
crop ; and the texture of the soil is not so much im-
proved by its exposure as in winter, when the expan-
sive powers of ice, the gradual dissolution of snows,
and the alternations from w^et to dry, tend to pulverize
it, and to mix its different parts together.

In the drill husbandry the land is preserved
clean by the extirpation of the weeds by hand, and by
raising the crops in rows, which renders the destruc-
tion of the weeds much more easy. Manure is sup-
plied either by the green crops themselves, or from
the dung of the cattle fed upon them ; and the plants
having large systems of leaves, are made to alternate
with those bearing grain.

E 318 ]

It is a great advantage in the convertible system
of cultivation, that the whole of the manure is em-
ployed ; and that those parts of it which are not fitted
for one crop, remain as nourishment for another.
Thus, in Mr. Coke's course of crops, the turnip is the
•first in the order of succession ; and this crop is man-
ured with recent dung, which immediately affords suf-
ficient soluble matter for its nourishment ; and the heat
produced in fermentation assists the germination of
the seed and the growth of the plant. After turnips,
barley with grass seeds is sown ; and the land having
been little exhausted by the turnip crop^ affords the
soluble parts of the decomposing manure to the grain.
The grasses, rye grass, an*-^ clover remain, which de-
rive a small part only of their organised matter from
the soil, and probably consume the gypsum in the
manure which would be useless to other crops : these
plants likewise by their large systems of leaves^ absorb
a considerable quantity of nourishment from the atmos-
phere y and when ploughed in at the end of two years,
the decay of their roots and leaves affords manure for
the wheat crop ; and at this period of the course, the
woody fibre of the farm-yard manure which contains
the phosphate of lime and the other difficultly soluble
parts, is broken down : and as soon as the most ex-
hausting crop is taken, recent manure is again ap-
plied.

Mr. Gregg, whose very enlightened system of
cultivation has been published by the Board of Agri-
culture, and who has. the merit of first adopting a plan
similar to Mr. Coke's upon strong clays, suffers the

C S19 ]

ground after barley to remain at rest for two years in
grass ; sows peas and beans on the lays ; ploughs in
the pea or bean stubble for wheat ; and in some in-
stances, follows his wheat crops by a course of winter
tares and winter barley, which is eat off in the spring,
before the land is sowed for turnips.

Peas and beans, in all instances, seem well adapt-
ed to prepare the ground for wheat ; and in some
rich lands, as in the alluvial soil of the Parret, men-
tioned in the Fourth Lecture, and at the foot of the
South Downs in Sussex, they are raised in alternate
crops for years together. Peas and beans contain, as
appears from the analyses in the Third Lecture, a
small quantity of a matter analogous to albumen ; but
it seems that the azote which forms a constituent part
of this matter, is derived from the atmosphere. The
dry bean leaf, when burnt, yields a smell approaching
to that of decomposing animal matter ; and in its de-
cay in the soil, may furnish principles capable of be-
coming a part of the gluten in wheat.

Though the general composition of plants is very
analogous, yet the specific difference in the products
of many of them, and the facts stated in the last Lec-
ture, prove that they must derive different materials
from the soil ; and though the vegetables having the
smallest systems of leaves will proportionably most
exhaust the soil of common nutritive matter, yet par-
ticular vegetables when their produce is carried off,
will require peculiar principles to be supplied to the
land in which they grow. Strawberries and potatoes
at first prod\ice luvitrrantly in virgin mould recently

C 320 J

turned up from pasture ; but in a few years they de*
generate, and require a fresh soil ; and the organiza-
tion of these plants is such, as to be constantly pro-
ducing the migration of their layers : thus the straw-
berry by its long shoots is constantly endeavouring to
occupy a new soil ; and the fibrous radicles of the
potatoe produce bulbs at a considerable distance from
the parent plant. Lands in a course of years often
cease to afford good cultivated grasses ; they become
(as it is popularly said) tired of them ; and one of the
probable reasons for this was stated in the last Lec-
ture.

The most remarkable instances of the powers of
' vegetables to exhaust the soil of certain principles ne-
cessary to their growth is found in certain funguses.
Mushrooms are said never to rise in two successive
seasons on the same spot ; and the production of the
phaenomena called fairy rings has been ascribed by
Dr Wollaston to the power of the peculiar fungus
which forms it to exhaust the soil of the nutriment
necessary for the growth of the species. The conse-
quence is, that the ring annually extends ; for no
seeds will grow where their parents grew before them ;
and the interior part of the circle has been exhausted
by preceding crops ; but where the fungus has died,
nourishn\ent is supplied for grass, which usually rises
within the circle, coarse, and of a dark green colour.

When cattle are fed upon land not benefitted by
their manure, the effect is always an exhaustion of the
soil ; this is particularly the case where carrying
horses are kept on estates 5 they consume the pasture

C 321 3

during the night, and drop the greatest part of their
manure during their labour in the day-time.

The exportation of grain from a country, unless
some articles capable of becoming manure are intro-
duced in compensation, must ultimately tend to ex-
haust the soil. Some of the spots now desart sands in
northern Africa, and Asia Minor, were anciently fer-
tile. Sicily was the granary of Italy : and the quan-
tity of corn carried off from it by the Romans, is pro-
bably a chief cause of its present sterility. In this Is-
land, our commercial system at present has the effect
of affording substances which in their use and decom-
position must enrich the land. Corn, sugar, tallow,
oil, skins, furs, wine, silk, cotton, &c. are imported,
and fish are supplied from the sea. Amongst our
numerous exports woollen, and linen, and leather
goods, are almost the only substances which contain
any nutritive materials derived from the soil.

In all courses of crops it is necessary that every
part of the soil should be made as useful as possible
to the different plants ; but the depth of the furrow
in ploughing must depend upon the nature of the soil,
and ot the subsoil. In rich clayey soils the furrow
can scarcely be too deep ; and in sands, unless the
subsoil contains some principles noxious to vegetables,
the same practice should be adopted. When the roots
are deep they are less liable to be injured, either by
excess of rain, or drought ; the layers shoot forth
their radicles into every part of the soil j and the
space from which the nourishment is derived is more

T 2

I 322 ]

considerable, than when the ssed is superficially inser-
ted in the soil.

There has been much difference of opinion with
respect to permanent pasture ; but the advantages or
disadvantages can only be reasoned upon according to
the circumstances of situation and climate. Under
the circumstances of irrigation, lands are extremely
productive with comparatively little labour; and in
climates where great quantities of rain falls, the natur-
al irrigation produces the same effects as artificial.
When hay is in great demand, as sometimes happens
in the neighbourhood of the metropolis, where man-
ure can be easily procured, the application of it to pas-
ture is repaid for by the increase of crop ; but top-
dressing grass land with animal or vegetable manure,
cannot be recommended as a general system. • Dr.
Coventry very justly observes, that there is a greater
waste of the manure in this case, than when it is
ploughed into the soil for seed crops. The loss by
exposure to the air, and the sunshine, offer reasons in
addition to those that have been already quoted in the
Sixth Lecture, for the application of manure even in
this case, in a state of incipient, and not completed
fermentation.

Very little attention has been paid to the nature
of the grasses .best adapted for permanent pasture.
The chief circumstance which gives value to a grass,
is the quantity of nutritive matter that the whole crop
will afford ; but the time and duration of its produce
are likewise points of great importance ; and a grass
that supplies green nutriment throughout the whole of

[ 323 ]

the year, may be more valuable than a grass which
yields its produce only in summer, though the whole
quantity of food supplied by it should be much less.

The grasses that propagate themselves by layers,
the different species of Agrostis, supply pasture
throughout the year ; and, as it has been mentioned
on a former occasion, the concrete sap stored up in
their joints, renders them a good food even in winter.
I saw four square yards of fiorin grass cut in the end
of January, this year, in a meadow exclusively appro-
priated to cultivadon of fiorin, by the Countess of
Hardwicke, the soil of which is a damp stiff clay.
They afforded 28 pounds of fodder ; of which 1000
parts afforded, 64 parts of nutritive matter, consisting
nearly of one-sixth of sugar, and five-sixths of mucil-
age, with a little extractive matter, In another expe-
riment, four square yards gave 27 pounds of grass.
The quality of this grass is inferior to that of the fio-
rin referred to in the Table, in the latter part of the
Third Lecture, which was cultivated by Sir Joseph
Banks in Middlesex, in a much richer soil, and cut in
December.

The fiorin grass, to be in perfection, requires a
moist climate or a wet soil ; and it grows luxuriantly
in cold clays unfitted for other grasses. In light sands
and in dry situations its produce is much inferior as
to quantity and quality.

The common grasses, properly so called, that
afford most nutritive matter in early spring, are the
vernal meadow grass, and meadow foxtail grass ; but
their produce at the time of flowering and ripening

[ 324 ]

the seed, are inferior to that of a great number of
other grasses j their latter math is, however, abun-
dant

Tall fescue grass stands highest, according to
the experiments of the Duke of Bedford, of any grass,
properly so called, as to the quantity of nutritive mat-
ter afforded by the whole crop when cut at the time of
flowering ; and meadow cat's-tail grass affords most
food when cut at the time the seed is ripe ; the high-
est latter math produce of the grasses examined in the
Duke of Bedford's experiments is from the sea mea-
dow grass.

Nature has provided in all permanent pastures a
mixture of various grasses, the produce of which dif-
fers at different seasons. Where pastures are to be
made artificially such a mixture ought to be imitated ;
and, perhaps, pastures superior to the natural ones
may be made by selecting due proportions of those
species of grasses fitted for the soil, which afford res-
pectively the greatest quantities of spring, summer,
latter math, and winter produce ; a reference to the
details in the Appendix will shew^ that such a plan of
cultivation is very practicable.

In all lands, whether arable or pasture, weeds of
ever description should be rooted out before the seed
is ripe ; and if they are suffered to remain in hedge
rows, they should be cut when in flower, or before,
and made into heaps for manure j in this case they
will furnish more nutritive matter in their decomposi-
tion j and their increase by the dispersion of seeds will
be prevented. The farmer, who suffers weeds to re-

L 325 3

main till their ripe seeds are shed, and scattered by
the winds, is not only hostile to his own interests, but
is likewise an enemy to the public: a few thistles will
stock a whole farm; and by the light down which is
attached to their seeds, they may be destributed over
a whole country. Nature has provided such ample
resources for the continuance of even the meanest ve-
getable tribes, that it is very difficult to ensure the de-
struction of such as are hostile to the agriculturist,
even with every precaution. Seeds excluded from
the air, will remain for years inactive in the soil,* and
yet germinate under favourable circumstances; and the
different plants, the seeds of which, like those of the
thistle and dandelion, are furnished with beards or
wings, may be brought from an immence distance.
The fleabane of Canada has only lately been found in
Europe; and Linnseus supposes that it has been trans-
ported from America, by the very light downy plumes
with which the seed is provided.

In feeding cattle with green food there are many
advantages in soilings or supplying them with food,
where their manure is preserved, out of the fieldj the

• The appearance of seeds in places where their parent plants are not found
may be easily accounted for from this circumstance, and other circumstances. Many
seeds are carried from island to island by currents in thesea, and are defended by
their hard coats from the immediate action of the water. West Indian seeds (of
this description} are often found on our coasts, and readily germinate; their l«ng
voyage having been barely sufficient to afford the cotyledon its due proportion of
moisture. Other seeds are carried indigested in the stomach of birds, and suppli-
ed with food at the moment of their deposition. The light seeds of the mosses
and lichens, probably float in every part of the atmosphere, and abound on the
snrffvce of the sea.

t 326 ]

plants are IcvSs injured v;hen cut, than when torn or
jagged with the teeth of the cattle, and no food is
wasted by being trodden down. They are likewise
obliged to feed without making selection; and in con-
sequence the whole food is consumed: the attachment,
or dislike to a particular kind of food exhibited by ani-
mals, offers no proof of its nutritive powers. Cattle
at first, refuse linseed cake, one of the most nutritive
substances on which they can be fed.*^

• For the following observations on the selection of different kinds of com-
niOB food by sheep and cattle, 1 am obliged to Mr, George Sinclair.

" Lolium pereHne,ryt gTAii. Sheep, eat this grass when it is in the early
stage of its growtl^ in preference to most others; bat after the seed appro iches to-
wards perfection, they leave it for almost any other kind. A field in the Park of
"Woburn was laid down in two eqoal parts, one part wirh rye grass and white clo-
ver, and the other part with cock's-foot and red clover: from the spring till mid-
summer the sheep kept almost constantly on the rye grass; but ifter that time
they left it, and adhered with equal constancy to the eock's-foot during there*
maiiider of the season.

Dactyli s gemerata, coc'k's'foot. Oxen, horses, and sheep, eat this grass readi-
ly. The oxen continue to eat the straws and flowers, from the time of flowering,
till the time of perfecting the seed; this was exemplified in a striking manner in
the field before alluded to. The oxen generally kept to the cock'srfoot and red
clover, and the sheep to the rye-grass and white clover. In the experiments pub-
lished in the Amoenitates Academic*, by the pupils of Linnaeus, it is asserted,
that this grass is rejected by oxen; the above fact, however, is in contradiction
of it.

Aloptcurui pratcHsis, meadow fox-tail. Sheep and horses seem to have a
greater relish fof this grass than oxen. It delights in a soil of intermediate quality
as to moisture and dryness, and is very productive. In the water-meadow at
Priestley, it constitutes a considerable part of the produce of that excellent mea-
dow. It there keeps invariably possession of the top of the ridges, extending
generally about six feet from each side of the water course; the space below that
to where the ridge ends, is stocked with cock's-foot, and the rough stalked mea-
dow grass, Feituca pratensis, Festuca duriuscu/a, Agrostis itolonifera, Agroitis pat-
ustrii, and sweet-scented vernal grass, with a small admixture of some other
Jkinds.

Phleum pratense, meadow cat s-tail. This grass is eaten without reserve, by
©■Xen, sheep, and horses. Dr. Pulteney laysj that it is disliked by sheep; bat in

C 327 ]

When food artificially composed is to be given to
cattle, it vshould be brought as nearly as possible to the
state of natural food. Thus, when sugar is given to

pastures where it abounds, it does not appear to be rejected by these animals; but
eaten in common with such others as are growing with it. Hares are remarkably
fond of it. The Phkum nodosum, Phieum a/pinum, Poafertilis, and Poa compressa,
were left untouched, although they were closely adjoining to it. It seems to at-
tain the greatest perfection in a rich deep loam,

Agro$tis stolonifera, florin. In the experiments detailed in the Araocnitates
Academicae, it is said, that horses, sheep, and oxen, eat this grass readily. On the
Duke of Bedford's farm at Maulden, florin hay was placed in the racks before ,
horses in small distinct quantities; alternately with common hay; but no decided
preference for either, was manifested by the horses in this trial. But that cows
and horses prefer it to hay, when in a green state, seems fully proved by Dr.
Richardson in his several publications on Fiorin; and of its productive powers in
England (which has been doubted by some,) there are satisfactory proofs. Lady
Hardwicke has given an account of a trial of this grass; wherein 24 milch cows,
and one young horse, besides a nurabeu of pigs, were kept a fortnight on the pro-
duce of one acre.

Poa trivialis, rough-stalked meadow. Oxen, horses, and sheep, eat this
grass with avidity. Hares also eat it; but they give a decided preference to
the smoothed-stalked meadow grass, to which it is, in many respects, nearly
allied.

Port j>ra/«Mj/5, Bmooth-stalked meadow grass. Oxen and horses, are observed
to eat this grass in common with others; but sheep rather prefer the hard fescue,
and sheeps' fescue which affect a similar soil. This species exhausts the soil In a
greiter degree, than almost any other species of grass; the roots being numerous,
and powerfully creeping, Secome in two or three years completely matted toge-
ther; the produce diminishes as this takes place. It grows common in some
meadows, dry ba.iks, and even on walks.

Cynosurus cristatus, crested dog's-tail grass. The South Down sheep, and
deer, appear lo be rcniirkably fond of this grass: in some parts of Woburn Park:
this grass fbrms the principal part of the herbage on which these animals chiefly
browse; while another part of ihe Park; that contains the Agrostis capiliaris,
Agrostis pumilis, Feituca ovina, Festuca duriuscula, and Festuca cambrica, is seldom
touched by them; but the Welch bref^d of sheep almo'st constantly browse upon
these, and neglect the rywo^Mrw* criitatus, Lcliutn perenne, Tini Poa trivialis,

Agrostis vulgarii (capilfarii Linn.), fine bent; common bent. This is a very
common grass on all poor dry sandy soils. It is not palatable to cattle, as they
never eat it readily, if any other kinds be within their reach. The Welch sheep,
however, prefer it, as 1 before observed; and it is singular, th t 'hose sheep
being bred in the park, when some of the best grasses are equally within their

c

328

them, some dry fibrous matter should be mixed with
it such as chopped straw, or dry withered grass, in or-
der that the functions of the stomach and bowels may

reacli, should still prefer those grasses which naturally grow on the Welch moun-
tains: it seems to argue that such a preference b the effect of some other cause,
chan that of habit.

Festuca ovina. sheeps* fescue. All kinds of cattle relish this grass; but it ap-
pears from the trial that has been made with it on clayey soils, that it continues
but a short time in possession of such, being soon overpowered by the more luxuri-
ant kinds. On dry shallow soils that are incapable of producing the larger sorts
this should form the principal crop, or rather the whole; for it is seldom or ever, in
its natural state, found intimately mixed with others; but by itself.

Festuca duriufcula,h3rd fescue grasss. This is certainly one of the best of the
dwarf sorts of grasses. It is grateful to all kutds of cattle; horses are very fond of
it; they cropped it close to the roots, and neglected the Festuca ovina, and Festuca
rubra, which were contiguous to it. It is present in most good meadows and
pastures.

Festuca /)ra^en*/j, ro eadow fescue. This grass seldom absent from rich mea-
dows and pastures; it is observed to be highly grateful to oxen, sheep, and horses,
particularly the former. It appears to grovr most luxuriantly when combined
with the hard fescue,. and Poa trivialis.

Avena eliaior, tall oat grass. This is a very productive grass, frequent in
meadows and pastures, but is disliked by cattle, particularly by horses; this, per-
fectly, agree* with the small portion of nutritive which matter it affords. It
seems to thrive best on a strong tenacious clay.

Avena fiavescens, yellow oat-grass. This grass seems partial to dry soils, and
meadows, and appears to be eaten by sheep and oxen, equally with the meadow
barley, crested dog's-tail, and sweet-scented vernal grasses which naturally grow
in company with it. linearly doubles tlie quantity of its produce by the appli-
cation of calcareous manure.

Holcuilanatus, meadow soft gra«s. This is a very common grass, and grows
on all soils, from the richest to the poorest. It affords an abundance of seed,
which is light, and easily dispersed by the wind. It appears to be generally disli-
ked by all sorts of cattle. The produce is not so great as a view of it in fields
would indicate; but being left almost entirely untouched by cattle, it appears as
the most productive part of the herbage. The hay which is made of it, from the
number of downy hairs which cover the surface of the leaves, is soft and spongy,
and disliked by cattle in general.

Anthnxanthum odratum, sweet-scented vernal grass. Horses, oxen, and sheep,
eat this grass; though in pastures where it is combined with the meadow fox-
tail, and white clover, co«|L'8-toot, rough-stalked meadow, ir is left untouched,
from which it would seem unpalatable to cattle. Mr. GrantjOf Leighton, laid

. L S29 J

be performed in a natural manner. The principle is the
same as that of the practice alluded to in the Third
Lecture, of giving chopped straw with barley.

In washing sheep, the use of water containing
carbonate of lime should be avoided; for this substance
decomposes the yolk of the wool, which is an animal
soap, the natural defence of the wool; and wool often
washed in calcareous water, becomes rough and more
brittle. The finest wool, such as that of the Spanish
and Saxon sheep, is most abundant in yolk. M. Van-
quelin has analysed several different species of yolk,
and has found the principal part of all of them a soap,
with a basis of potassa, (I. e. a compound of oily mat-
ter and potassa), with a little oily matter in excess. —
He has found in them likewise, a notable quantity of
acetate of potassa, and minute quantities of carbonate
of potassa and muriate of potassa, and a peculiar odor,
ous animal matter.

M. Vanquelin states, that he found some speci-
mens of wool lose as much as 45 per cent, in being
deprived of their yolk; and the smallest loss in his
experiments was 35 per cent.

The yolk is most useful to the wool on the back
of the sheep, in cold and wet seasons; probably the

down one half a field of a considerable extent with this grass, combined with
white clover. The other half of the field with fox-tail and red clover. The sheep
would not touch the sweet-scented vernal, but kept constantly upon the fox-tail
The writer of this, saw the field when the grasses were in the highest state
of perfection: and hardly any thing could be more satisfactory. Equal quanti-
ties of the seeds of white clover, were sown with each of the grasses, but from
the dwarf nature of the sweet-scented venial grass, the clover mixed with it
had attained to greater luxuriance, than that mixed with the meadow fox-tail.

u2

# ( 330 )

application of a little soap of potassa, with excess of
grease to the sheep brought from warmer climates in
our winter, that is, increasing their yolk artificially^
might be useful in cases where the fineness of the
wool is of great importance. A mixture of this kind
is more conformable to nature, than that ingeniously
adopted by Mr, Bakewell; but at the time his labours
commenced, the chemical nature of the yolk was un-
known.

331

I have now exhausted all the subjects of discus-
sion, which my experience or information have been
able to supply on the connection of chemistry with
agriculture.

I venture to hope, that some of the views brought
forward, may contribute to the improvement of the
most important and useful of the arts.

I trust that the enquiry will be pursued by
others; and that in proportion as chemical philosophy
advances towards perfection, it will afford new aids to
agriculture.

There are sufficient motives connected with both
pleasure and profit, to encourage ingenius men to pur--
sure this new path of investigation. Science cannot
long be despised by any persons as the mere specula-
tion of theorists; but must soon be considered by all
ranks of men in its true point of view, as the refine-,
ment of common sense, guided by experience, gradu-
ally substituting sound and rational principles, for
vague popular prejudices.

The soil offers inexhaustible resources, which
when properly appreciated and employed, must in-
crease our wealth, our population, and our physical
strength.

We possess advantages in the use of machinery,
and the division of labour, belonging to no other na-
tioiK And the same energy of character, the same ex„

( 332 )

tent of resources which have always distinguished the
people of the British Islands, and made them excel in
arms, commerce, letters, and philosophy, apply with
the happiest effect to the improvement of the cultiva-
tion of the earth. Nothing is impossible to labour,
aided by ingenuity. The true objects of the agricul-
turist are likewise those of the patriot. Men value
most what they have gained with effort; a just confi-
dence in their own powers results from success; they
love their country better, because they have seen it im-
proved by their own talents and industry; and they
identify with their interests, the existence of those in-
stitutions which have afforded them security, inde-
pendence, and the multiplied enjoyments of civilized
life.

APPENDIX.

AN
ACCOUNT OP THE RESULTS

OF

EXPERIMENTS ON THE PRODUCE

AND

NUTRITIVE QUALITIES

OF

DIFFERENT GRASSES, AND OTHER PLANTS,

USED AS THE FOOD OF ANIMALS.

INSTITUTED BY

JOHN, DUKE OP BEDFORD.

BOOKS QUOTED IN THE FOLLOWING PAGES,

Curt. Lond — Flora Londinensis. By William Curtis, 2 vols.

London 1798, fol.
Fli Dan.-?-Flora Danica, or Icones Plantarum sponte nascen-

tium in Rcgnis Daniae et Norvegiae, editse a

Ge iEder. Hafniae 1761, fol.
Engl. Bot.— English Bontany, by J. E. Smith, M. D ; the

Figures by J. Sowerby. London 1 790, 8vo.
W. B.— Botahical Arrangements. By Dr. Withering. LoH'

don 1801, 4 vol.
Huds. — Hudsoni Flora Anglica, 1778, vol. ii.
Host. G. A. — Nic. Thomae Host Icones et Descriptiones

Graminum Austriacorum, vol. i.— iii. Vindo-

bonae, 1801, fol.
Hort. Kew.«— Hortus Kewensis. By W. J. Alton, vol. i. Lon-
don 1810.

Introduciion by the Editor.

Of the 215 proper grasses which are capable of
being cultivated in this climate two only have been
employed to any extent for making artificial pastures,
rye grass and cock's foot grass j and their application
for this purpose seems to have been rather the result
of accident, than of any proofs of their superiority
over other grasses.

A knowledge of the comparative merits and
Value of all the different species and varieties of grasses
cannot fail to be of the highest importance in practical
agriculture. The hope of obtaining this knowledge
was the motive that induced the Duke of Bedford to
institute this series of experiments.

Spots of ground, each containing four square
feet, in the garden at Woburn Abbey, were enclosed
by boards in such a manner that there was no lateral
communication between the earth included by the
boards, and that of the garden. The soil was re-
moved in these inclosures, and new soils supplied ;
or mixture of soils were made in them, to furnish as
far as possible to the different grasses those soils which
seem most favourable to their growth ; a few varieties
being adopted for the purpose of ascertaining the
effect of different soils on the same plant.

The grasses were either planted or sown, and
their produce cut and collected and dried, at the pro-
per seasons, in summer and autumn, by Mr, Sinclair,.

[ iv. 3

his Grace's gardener. For the purpose of determin-
ing as far as possible the nutritive powers of the
different species, equal weights of the dry grasses or
vegetable substances were acted upon by hot water
till all their soluble parts were dissolved ; the solution
was then evaporated to dryness by a gentle heat in a
proper stove, and the matter obtained carefully weigh-
ed. This part of the process was likewise conducted
with much address and intelligence by Mr. Sinclair,
by whom all the following details and calculations are
furnished.

The dry extracts supposed to contain the nutri-
tive matter of the grasses, were sent to me for chemi-
cal examination. The composition of some of them
is stated in the last table of Chap. III. I shall offer a few
chemical observations on others at the end of this
Appendix. It will be found from the general conclu-
sions, that the mode of determining the nutritive
power of the grasses, by the quantity of matter they
contain soluble in water, is sufficiently accurate for all
the purposes of agricultural investigation.

Details of Experiments on Grasses. £y George Sin-
clair, Gardener to his Grace the Duke of Bed-
ford, and Corresponding Member of the Horticultural
Society of Edinburgh,

L AnthoxanthuM odoratum, Engl. Bot. 647. — Curt,
Lond.

Sweet-scented vernal grass. Nat. of Britain.
At the time of flowering, the produce from the space

of an acre equal to ,00u09 1827364 of a brown

sandy loam with manure, is

oz. or lbs. per acre

Grass 11 oz. 8 dr.* The produce per acre 125235 0 ~ 7827 3 0
80 dr. of grass weigh when dry 21 1-2 dr.-%

I'he producf of the space, ditto 49. 1 7-10 3 ^^^^^ ^ ~" ^^^^ ^ ^
The weight lost by the produce of one acre in drying 5723 10 0

64 dr of grass afford of nutritive matter 1 dr. ">
The produce of the space, ditto 2. 3 5-103 ^^^^ ^^ "*" ^^^ ^ ^^

At the time the seed is ripe the produce is

Grass, 9 oz. The produce per acre - 98010 0 — 6125 10 0

80 dr. of grass weigh when dry 24 dr. ^

The produce of the space, ditto 43.1-163^^^^^ 0 — 1837 11 0

The weight lost by the produce of one acre in drying — 4287 15 0

64 dr. of grass afford of nutritive matter 3. 1 dr. ">

The produce of the space ditto 7. 1 1-43 ^^^^ ^^ — 311 1 1

The weight of nutritive matter which is lost by taking-^
the crop at the time the grass is in flower, exceed. C 188 12 4

ing half of its value j

The proportional value which the grass at the
time of flowering bears to that at the time the seed is
ripe, is as 4 to 13.

• The weight is avoirdupoisa ; lbs. pounds, oz. ounces, dr. drachms. The
v/eights not named are, quarters of drachms, and fractions of quarters of drachms f
thus 7. 1 1-4 means 7 drachms i quarter of a drachm and 1-4 of a quarter.

VI. APPENDIX.

The latter-math produce is oz. or ibs. per acre

Grass, 10 oz.- The produce per acre 108900 0 — 6806 4 0

64dr.ofgr;issaffordofnutiitivemHtter, 2. 1 dr. 3828 8 — 239 4 8

The proportional value which the grass of the
latter-math bears to that, at the time the seed is ripe,
is nearly as 9 to 13.

The smallness of the produce of this grass ren-
ders it improper for the purpose of hay; but its early
growth, and the superior quantity of nutritive matter
w^hich the latter-math affords, compared with the
quantity affoi'ded by the grass at the time of flowering,
causes it to rank high as a pasture grass, on such soils
as are well fitted for its growth ; such are peat-bogs,
and lands that are deep arid moist.

I.I. Holcus odoratus. Host. G. A, Growing in woods.

Sweet scented soft grass. Nat. of Germany. Flo.

Ger. — H. Borealis. Growing in moist meadows.

At the time of flowering, the produce from a rich

sandy loam is

oz. or lbs, per acre

Grass, 14 oz. The produce per acre 152460 0 — 9528 12 0

80 dr. of grass weigh when dry 20, 2 dr. "i

The produce of the space, ditto 57 1 3-5 5 ^^^^^ ^^ ~ ^^^^ ^^ ^^
The weight lost by the produce of one acre in drying 7087 0 2

64 dr, of grass afford of nutritive matter 4. 1 dr. ■>
The produce of the space, ditto 14 3 1-23 ^^^^^ ^^ "" ^^^ ^^ ^

At the time the seed is ripe the produce is

Grass, 40 oz. The produce per acre 435600 0 — 27225 0 0

64 dr, of grass weigh when dry 28 dr.-^

The produce ofthe space, ditto 224 dr. 5 ^^^^^^ 0 — 9528 12 0

The weight lost by the produce of one acre in drying 17696 4 0

64 dr.. of grass a/ford of nutritive matter 5. 1 dr.->

The produce of the space, ditto 52- 2 dr.5 ^^^^^ ^^ ~ ^^^^ ^ ^ ^'

The weight of nutritive matter which is lost by taking the
crop at the time the grass is in flower, being more than
halfof its valu' 1600 8 10

APPENDIX. vii.

The proportional value which the grass at the
time of flowering bears to that at the time the seed is
ripe, is as 17 to 21.

The produce of latter-math is oz. or lbs. per acre

Grass, 25 oz. (he produce per acre 272250 0 — 17015 10 0

64 dr. of grass iiff ord of nutritive matter 4. 1 dr. 18079 1 — 1129 15 1

The grass of the latter-math crop, and of the
crop at the time of flowering, taking the whole quantity,
and their relative proportions of nutritive matter, are
in value nearly as 6 to 10: the value of the grass at
the time the seed is ripe, exceeds that of the latter-math,
in proportion as 21 to 17.

Though this is one of the earliest of the flower-
ing grasses, it is tender, and the produce in the spring
is inconsiderable. If, however, the quantity of nutri-
tive matter which it affords, be compared with that of
any of those species which flower nearly at the same
time, it will be found greatly superior. It sends forth
but a small number of flower stalks, which are of a
slender structure compared tm the size of the leaves.
This will account in a great measure for the equal
quantities of nutritive matter afforded by the grass at
the time of flowering, and the latter-math.

III. Cynosurus caruleus. Engl. Bot. 1613. Host.
G. A. 2. t. 98. Blue moor-grass. Nat. of
Britain. Sesleria cserulea.

At the time the seed is ripe the produce from a
light sandy soil is

oz. or lbs. per acre

Grass, 10 oz. The produce per acre 108900 0 — 6806 4 3

6:4 dr. of grass afford of nutritive matter 3 3 dr. 6380 13 — 398 12 13

VIII. APPENDIX.

The produce of this grass is greater than its ap-
pearance would denote; the leaves seldom attain to
more than four or five inches in length, and the flower
stalks seldom arise to more. Its growth is not rapid
after being cropped, nor does it seem to withstand
the effects of frost, which if it happen to be severe
and early in the spring, checks it so much as to pre-
vent it from flowering for that season; otherwise the
quantity of nutritive matter which the grass affords
(for the straws are very inconsiderable,) would rank
it as a valuable grass for permanent pasture.

IV. Alopecurus pratensis. Curt. Lond. Alo. myosur-
oides. Meadow foxtail-grass. Nat. of Britain.
Engl. Bot. 848.
At the time of flowering, the produce from a

clayey loam is oz. or lbs. per acre

Grass, 30 oz, > 1 he produce per acre 326700 0 — 20418 12 0

80 dr. of erass weicrh when dry 24 dr. 7

A c.u A. I o.«.„C 98010 0— 6125 10 0

1 he produce of the space, ditto 336 dr. 3

The weight lost by the produce of one acre in drying 14293 2 0

64 dr. of grabs afford of nut '-itivjp matter 1 2 dr. )

The produce of the space, ditto llldr.V^^^^"" ^'^ ^^ ^

The produce from a sandy loam is

Grass, 12 oz. 8 dr. The produce per acre 136125 0 — 8507 13 0

80 dr. of grass weigh when dry 24 dr. ^

The produce of the space, ditto 60 dr. 3 ^^^'^'^ 9 — 2552 5 8

64 dr .of grass afford of nutritive matter 1 dr. ^

The produce of the space, ditto 3 01-2 S ^^^^ ^^ "" ^^^ ^^ ^^

At the time the seed is ripe, the produce from
the clayey loam is

Grass, 19 oz. The produce per acre 206910 0 — 12931 14 0

80 dr. of grass weigh when dry 36 dr. ^

The produce of the space, ditto 136 3 1-5 3 ^^^^^ ^ ^ ^^^^ ^ *
The weight lost by the produce of one acre in drying 7111 8 14

64 dr. of grass afibrd of nutritive matter 1 1 dr. ^ .

Tlie produce of the space, ditto 9. 975 V ^^^ 4—461 0

APPENDIX. IX.

The weight of nutritive matter which is lost by leavln«:r the
crop till the seed be ripe, being one twenty-fifth part of
its value ^7 8 11

The proportional value which the grass at the
time of flowering, bears^ to that at the time the seed is
ripe, is as 6 to 9.

The latter-math produce, from the clayey loam is

oz. or lbs. per acre
Grass, 12 oz. The produce per acre 130680 0 — 8167 8 0

64 dr. of ffrass afford of nutritive matter 2 dr. 7

n^u 1 i-<. r.. ^^aA 4083 12— 255 3 12

The pr duce of the space, ditto o clr, 3

The proportional value which the whole of the
latter- math crop bears to that at the time the seed is
ripe, is as 5 to 9, and to that at the time flowering,
proportionably as 13 to 24.

The above statement clearly shews that there is
nearly three-fourths of produce greater from a clayey
loam than from a sandy soil, and the grass from the lat-
ter is comparatively of less value, in proportion as 4
to 6. The; straws produced by the sandy soil are defi-
cient in number and in every respect less than those
from the clayey loam; which will account for the un-
equal quantities of nutritive matter afforded by them;
but the proportional value in which the grass of the
latter-math exceeds that of the crop at the time of
flowering, is as 4 to .S; a difference which appears
extraordinary, when the quantity of flower-stalks
which are in the grass at the time of flowering is
considered. In the Anthoxanthum odoratum the pro-
portional difference between the grass of these crops
is still greater, nearly as 4 to 9 ; in the Poa pratensis
they are equal; but in all the latter flowering grasses
experimented upon, the flowering straws of which

b

X. AlPPENblX.

resemble those of the Alopecurus praiensts or Anthosc-
anthum odoratum^ the greater proportional value is
always on the contrary found in the grass of the
flowering crop. Whatever the cause may be, it is
evident that the loss sustained by taking the crops of
these grasses at the time of flowering is considerable.

V. Alopecurus alpinus. Engl. Bot. 1126.
Alpine fox-tail grass. Nat. of Scotland.

At the time of flowering the produce from a sandy
loam with a small portion of manure, is

oz. or lbs. per acre

Grass, 8 oz. The produce per acre 87120 0 — 5445 5 0
60 dr. of grass weigh when dry 16 dr. ^

The produce ofthe space, ditto 34 2-16 3 ^^^^^ 0 — 1452 0 0

The weight lost by the produce of one acre in drying S993 5 0
64 dr. of grass afford of nutritive matter 1 dr. ^

The produce of the space, ditto 2 dr.j ^^^^ 4—85 1 4

VI. Foa alpina. Engl. Bot. 1003. Flo. Dan. 107.
Alpine meadow grass. Nat. of Scotland.

At the time of flowering, the produce from a light
sandy loam, is

Grass, 8 oz. The produce per acre 87120 0 — 5445 0 0

64 dr. of grass afford of nutritive matter, 1. 2 dr. 2041 14 — 127 9 14

VII. Avma pubescens. Engl. Bot. 1640. Host. G.
A. 2, t. SO. Downy oat grass. Nat. of Britain.

At the time of flowering, the produce from a
rich sandy soil, is

Grass, 23 oz. The produce per acre 250470 0 — 15654 6 0

80dr. ofg-rass wieighwhen dry SOdr.^ ^ ^^ ^ ,„^^ ^ .

r^t. / r.i, A'Jl too. ^93926 0— 5870 6 4
The produce ofthe space, ditto lo8 dr. 3

The weight lost by the produce of one acre in drying 9783 15 12

64 dr. of grass afford of nutritive matter 1. 2 dr. 1 ^ra 14. ^

The produce of the space, ditto 8.2 2-16 $ ^°"° ^ "" ^^^ ^^

APPENDIX. xr.

At the time the seed is ripe, the produce is

oz. or lbs. per acre

Grass, 10 oz. The produce per acre 108900 0 — 6806 4 0

80 dr. of grass weigh when dry 16 dr.7

The produce of tlie space, ditto 32 dr. 3 ^^''^^ 0 — 1361 4 0

The weight lost by the produce of one acre in drying — 5445 0 0
64 dr. ofgrass afford ofnutritive matter 2dr.>^

The produce ofthe space ditto 5 dr. 5 ^^^^ ^ "" 212 11 0

The weij^ht of nutritive matter which is lost by leaving the crop till the

seed be. ripf, bein.' more th .11 half of its value - 154 6 3

The proportional value which the grass, at the
time of flowering, bears to that at the time the seed is
ripe, is as 6 to 8 •

The produce of latter-math is

Grass, 10 oz i he produce p r acre 108900 0 — 6806 4 0

64dr.ofi;ias; iffwrd of nutritive m^itter 2 dr. 3403 2— 212 11 0

The proportional value which the grass at the
time of flowering bears to that of the latter-math, is as
6 to 8. The grass of the seed-crop^ and that of the
latter-math, are of equal value.

The downy hairs which cover the surface of the
leaves of this grass, when growing on poor light soils,
almost entirely disappear when it is cultivated on a
richer soil. It possesses several good qualities which re-
commend it to particular notice j it is hardy, early, and
more productive than many others which affect simi-
lar soils and situations. Its growth after being cropped
is tolerably rapid, although it does not attain to a great
length if left growing; like the Poa pratensis it sends
forth flower stalks but once in a season, and it appears
well calculated for permanent jpasture on rich light
soils.

APPENDIX.

VIII. Poa praiensis. Curt Lond. Engl. Bot. 1073.
Smooth stalked meadow grass, Nat. of Britain.
At the time of flowering, the produce from a mix-
ture of bog-earth and clay, is oz. or Ibs. per acre
Grass, 15 02. s lie pr.iduce pf-r acre 163350 0 — 10209 6 0
80 dr. of grass weigh when dry 22.2 dr.

The produce ofthe space, ditto 6r.2 dr.5 ^^^^^ ^ ~" ^^'^^ ^ ^

The weight lost by the produce of one acre in drying 7337 15 13
64 di". of grass afford of nutritive matter 1.3 dr.">

The produce of tbe space, ditto 6.2 1-165^^^^ 2—279 2 9

At the time the seed is ripe, the produce is

Grass, 12. 8 o%. The protiuce per acre 136125 0 — 85C7 13 0

80 dr. of grass weigh wlien dry 32 dr.?

The produce ofthe space, do 80 dr.-> ^^^^ 0—3403 2 0

The weight lost by the produce of one acre in drying 5104 11 0

64 dr. of grass afford of nutritive matter 1.2 dr. 7

The produce of the space, ditto 4.2 3-163^^^^ 6—199 6 0

The weight of nutritive matter which is lost hy leaving the
crop till the seed be ripe, being nearly one fourth of its
value - ...... 79 12 9

The produce of latter-math is

Grass, 6 oz. I'he produce per acre 65340 0 — 4083 12 0

64 dr. of Grass afford of nutritive matter 1.3 dr. 1786 10 — 11110 0

The proportional value in which the grass of the
latter-math exceeds that of the flowering crop, is as
6 to 7. The grass of the seed crop and that of the
latter-math are of equal value,

This grass is therefore of least value at the time
the seed is ripe : a loss of more than one fourth of the
value of the whole crop is sustained if it is not cut till
that period: the straws are then dry, and the root
leaves in a sickly decaying state; those of the latter-
math, on the contrary, are luxuriant and healthy.
This species sends forth flower-stalks but once in a
season, and these being the most valuable part of the
plant for the purpose of hay j it will from this circum-

APPENDIX. xirr.

Stance, and the superior value of the grass of the latter-
math, compared to that of the seed crop, appear well
adapted for permanent pasture.

IX. Pod carullea. — Var. Poa praiensis. Engl. Bot,

1O04. Poa subcasrulea. Short blueish meadow
grass. Nat. of Britain. H. Kew. 1 — 155. Poa
humilis.

At the time of flowering, the produce from a soil
of the like nature as the preceding, is

oz. or lbs. per acre

Grass, 11 oz. The produce per acre 119790 0 — 7486 14 0
64 dr of grass afford of nutritive matter 2 dr. 1

The produce of the space, ditto 5. 2 dr. 5 ^"^^ ^ *" 2^3 15 0
80 dr. of grass weigh when dry 24 dr. "^

The produce ofthe space, ditto 52.3 3-163 ^^^^^ ^ "*" ^^"^^ ^ ^

The weight lost by the produce of one acre in drying 5240 13 0

If the produce of this variety be compared with
that of the preceding one, it will be found less ; nor
does it seem to possess any superior excellence. The
superior nutritive power does not make up for the
deficiency of produce by 80 lbs. of nutritive matter
per acre.

X, Festuca hordiformis, Poa hordiformis. H. Cant.
Barley-like fescue grass. Nat. of Hungary.

At the time of flowering, the produce from a sandy
soil, with manure, is

Grass, 20 oz. The produce per acre 217800 0 — 13612 8 0

80 dr. of grass weigh when dry 24 dr. >

The produce of the space, ditto 96dr.S^^^^^ 0-4085 12 0

The weight lost by the produce of one acre in drying 9528 12 0

64 dr. of grass afford of nutritive matter 2. 1 dr. ">

The produce of the space, ditto 11. ldr.5 ''^^^ 0-478 9 0

This is rather an early grass, though later than
any of the preceding species 5 its foliage is very fine,

3CIV. APPENDIX.

resembling the F. duriuscula, to which it seems nearly
allied, differing only in the length of the awns, and the
glaucous colour of the whole plant. The considera-
ble produce it affords, and the nutritive powers it ap-
pears to possess, joined to its early growth, are quali-
ties which strongly recommend it to further trial.
XL Poa trmalis. Curt. Lond. Engl. Bot. 1072.

Host. G. A. 2. t. 62. Roughish meadow grass.

Nat. of Britain.
At the time of flowering, the produce from a light
brown loam, with manure, is oz. or ibs. per acre

Grass, 11 oz. The produce per acre 119790 0 — 7487 14 0

80 dr. of grass weigh when dry 24 dr. ^

The produce ofthe space, ditto 54 3-163 ^^^^'^ 0 — 2246 1 0

The weight lost by the produce of one acre in drying 5240 13 0

64 dr. of grass afford of nutritive matter 2 dr.>

The produce of the space, ditto 5. 2 dr. 5 '^'^^^ '' "" 233 15 7

At the time the seed is ripe, the produce is

Grass, 11.8 oz. The produce per acre 125235 0 — 7827 3 0

SO dr. of grass weigh when dry 36 dr. ">

The produce ofthe space, ditto 823 3.16> ^^^^^ ^^ -- 3522 3 12

The weight lost by the produce of one acre in drying 4304 15 4

64 dr. of grass afford of nutritive matter 2.3 dr. >

The produce of the space, ditto 7.3 3-55 ^^^^ 3—336 5 3

The weight of nutritive matter which is lost by taking the
crop at the time of flowering, exceeding one fourth of its
value - - - 102 5 12

The proportional value in which the grass of the
seed crop exceeds that at the time of flowering is as 8
to 11.

The produce of latter-math is

Grass, 7 oz. The produce per acre 76230 0 — 4764 6 0

64 dr. of grass afford of nutritive matter 5 dr. 357o 4 — 223 5 4

The proportional value by which the grass ofthe
latter-math exceeds that of the flowering crop, is as 8
to 12, and that of the seed crop as 11 to 12.

APPENDIX. XV.

Here then is a satisfactory proof ®f the superior
value of the crop at the time the seed is ripe, and of
the consequent loss sustained by taking it when in
flower; the produce of each crop being nearly equal.
The deficiency of hay in the flowering crop, in propor-
tion to that of the seed crop, is very striking. Its
superior produce, the highly nutritive powers which
the grass seems to possess, and the season in which
it arrives at perfection, are merits which distinguish it
as one of the most valuable of those grasses, which
affect moist rich soils, and sheltered situations; but on
dry exposed situations it is altogether inconsiderable ;
it yearly diminishes, and ultimately dies off, not un*
frequently in the space of four or five years.

XII. Festuca glauca. Curtis.

Glaucous fescue grass. Nat. of Britain.
At the time the seed is ripe the produce from a

brown loam is oz. or Ibs. per acre

Grass, 14 oz. The produce per acre 152460 0 — 9528 12 0
SO dr. of grass weigh when dry 32 dr. "j

The produce of the space, ditto 89 21.16 3 ^°^^ 0-3811 8 0

The weight lost by the produce of one acre in drying 5717 4 0
64 dr. of grass afford of nutritive matter 1.2 dr. 7

rr», / c.x. Au. ^1 1 r25r3 4— 223 5 4

The produce of the space, ditto 5.1 dr. j

At the time of flowering the produce is

Grass, 14 oz. The produce per acre 152460 0 — 9528 12 0

80 dr. of grass weigh when dry 32 dr. -> ^.^ ^ ach « n

The produce of the space, ditto 89 2 2-55 ^^^ " ^ ^^^^ ^ "

The weight lost by the produce of one acre in drying 5717 4 0

64 dr. of grass afford of nutritive matter 3 dr. > .

The produce ofthe space, ditto 10.2 dr. S 9—446 10 9

The weight of nutritive matter which is lost by leaving the
crop till the seed be ripe, being half of the value ofthe

crop .,--.,-,. 223 5 5

XVI. APPENDIX.

The proportional value by which the grass at the
time of flowering exceeds that at the time the seed is
ripe, is as 6 to 1 2.

The proportional difference in the value of the
flowering and seed crops of this grass is directly the
reverse of that of the preceding species, and affords
another strong proof of the value of the straws in
grass which is intended for hay. The straws at the
time of flowering are of a very succulent nature; but
from that period till the seed be perfected, they gradu-
ally become dry and wiry. Nor does the root leaves
sensibly increase in number or in size, but a total
suspension of increase appears in every part of the
plant, the roots and seed vessels excepted. The straws
of the Poa trivialis are, on the contrary, at the time
of flowering, weak and tender; but as they advance
towards the period of ripening the seed, they become
firm and succulent ; after that period, however, they
rapidly dry up and appear little better than a mere dead
substance.

XIII. Fcstuca glabra. Wither. B. 2. P. 154.
Smooth fescue grass. Nat. of Scotland.

At the time of flowering, the produce from a clayey

loam, with manure, is oz. or Ibs. per acre

Grass, 21 oz. The produce per acre 228690 0 — 14293 0 0

80 dr. of ffrass wej^^u when dry 32 dr. 1

n» / *-*i ^-.r io. ioiAo<C 91476 0—57ir 4 0

7 he produce of the space, ditto 134. 1 2-16 2-5 3

The weight lost by the produce of one acre in drying 8576 14 0

64 dr. of errass afford of nutritive matter 2 dr. 7

r,^u 1 r.u A'^. inn A fn46 0— 446 10 0

The produce of the space, ditto 10.2 dr. 3

At the time the seed is ripe the produce is

Grass, 14 02. The produce per acre 152460 0 — 9528 12 0

80 dr. of grass weigh when dry 32 dr.
The produce of the space, ditto 89.2 2-5

? 60984 0 — 3811 8 0

APPENDIX. XVII

oz. or lbs. per acre
I'he weight lost by the produce of one acre in drying 57X7 4 0

64 dp. of grass afford of nutritive matter 1. 1 dr. ^

The produce of the space, ditto 4. 1 2-16 3 ^^'^'^ 0—186 1 0

The weight of nutritive matter which is lost by leaving the
crop till the seed be ripe exceeding half of its value 260 9 0

The proportional value which the grass at the
time the seed is ripe, bears to that of the crop at the
time of flowering, is as 5 to 8.
The produce of latter-math is

Grass, 9 02. The produce per aci; 98010 0 — 6125 10 0

64 dr. of grass afford of nutritive matter 2 gr, "i

The produce of the space, ditto 10 1-2 dr.5 ''^^ ^^ "~ ^7 13 0

The proportional value which the grass of the
latter-math bears to that of the crop at the time of
flowering, is as 2 to 8, and to that of the crop, at the
lime the seed is ripe, is as 2 to 5.

The general appearance of this grass is very simi-
lar to that of the Festuca duriuscula: it is, however,
specifically different, and inferior in many respects,
which will be manifest on comparing their several pro-
duce with each other; but if it be compared with some
others, now under general cultivation, the result is
much in its favour, the soil which it affects being duly
attended to. The Anthoxanthum odoratum being taken
as an example, it appears, that

Festuca glabra^ affords of nutritive matter

From the crop at the time of flowering 446. 7 lbs. per acre

At the time the seed is ripe, ditto 186. J ^^2.

Anthoxanthum odoratum^

At the time of flowering, ditto 122.-^

At the time the seed is ripe, ditto 311.3
The weight of nutritive matter, which is afforded by the pro-
duce of one acre of the Festuca glabra exceeding that of the
Anthoxanthum odoratum^ in proportion nearly as 6 to 9 199.

C

XVIII APPENDIX.

XIV. Fe^tuca rubra. Wither. B. 2. P. 153.
Purple fescue grass* Nat. of Britain.

At the time of flowering, the produce from a light

sandy soil, is 02. or Ibs per acre

Grass, 15 oz. The produce per acre 163350 0—10209 6 0

80 dr. of grass weigh when dry 34 dr.

A c.u A.. ^nnA - 56923 12 — 3557 11 0

The produce of the space ditto 102 dr

The weiglit lost by the produce of one acre in drying 6651 11 0

64 dr. of grass afford of nutritive matter 1.2 dr.

The produce of the space, ditto 22 2-16 dr. 3 ^^^^ 8—239 4 8

At the time the seed is ripe, the produce is

Grass, 16 oz. The produce per acre 174240 0 — 10890 0

80 dr. of grass weigh when dry 36 dr. >

' 78408 0— 4900 8 0

36 dr. ->

115 346 dr. 3

The produce of the space, ditto

The weight lost by the produce of one acre in drying 5989 8 0

64 dr. of grass afford of nutritive matter 2 dr, >

The produce of the space, ditto Sdr.^^'^^^ ^"" ^^^ ^ ^

The weight of nutritive matter which is lost by taking tlie
crop when the grass is in flower, being nearly one third
part of its value 101 0 8

The proportional value which the grass, at the
time of flowering, bears to that at the time the seed is
ripe, is as 6 to 8.

This species is smaller in every respect than the
preceding. The leaves are seldom more than from
three to four inches in length • it affects a Soil similar
to that favourable to the growth of the Festuca ovinuy
for which it would be a profitable substitute, as will
clearly appear on a comparison of their produce with
each other.

The produce of latter-math is

Grass, 5 oz. The produce per acre 54450 0 — 3403 2 0

54dr. of grass afford of nutritive matter 1.2 dr. 1276 2— 79 12 0

APPENDIX. XIX

The proportional value which the grass of the
latter-math bears to that at the time the seed is ripe is
as 6 to 8, and is of equal value with the grass at the
time of flowering.

XV. Festuca ovina. Engl. Bot. 585. Wither. B. 2.
P. 152. Sheep's fescue grass. Nat. of Britain.

At the time the seed is ripe, the produce is

oz. orlbs. per acre
Grass, 8 oz. The produce per acre 87120 0 — 5445 0 0

64 dr. of glass afford of nutritive matter 1.2 dr. 7

The pr-duce of the space, ditto 3 dr. $203114— 1S7 9 0

The produce of latter-math is

Grass, 5 oz. The produce per acre 54450 0 — 3403 2 0

64 dr. of g^rass nfford of nutfiiive matter 1. 1 dr. 1063 7 — 66 7 7

The dry weight of this species was not ascertained,
because the smallness of the produce renders it entire*
ly unfit for hay. If the nutritive powers of this species
be compared with those, of the preceeding, the in-
feriority will appear thus :

Festtiea ovina, (as above) affords of nutritive matter 1.2 >

l.li 2.2

LI

Ditto ditto

Testuca rubra ditto ditto 2

ditto ditto ditto

The comparative degree of nourishment which
the grass of the Festuca rubra affords, exceeds there-
fore that afforded by the F, ovina^ in proportion as 1 1
to 14.

From the trial that is here detailed, it does not seem
to possess the nutritive powers generally ascribed to it;
it has the advantage of a fine foliage, and may, there-
fore, very probably be better adapted to the masticat-
ing organs of sheep, than the larger grasses, whose
nutritive powers are shewn to be greater: hence on
situations where it naturally grows, and as pasture for

XX APPENDIX.

sheep, it may be inferior to few others. It possesses
natural characters very distinct from F, rubra.

XVI. Briza media, Engl. Bot. S40. Host. G. A.
2. t. 29. Common quaking-grass. "Nat. of
Britain.

At the time of flowering, the produce from a rich

brown loam, is oz. or Ibs. per acre

Grass, 14 oz. The produce per acre 152460 0 -— 9528 12 0

80 dr. of grass weigh when dry 26 dr.

!^ 6551 0 — 409 7 0

The produce of the space, ditto 72. 3 1-16 i ^^^^'^ ^ "" ^^^^ ^^ ^
The weight lost by the produce of one acre in drying 6431 14 8

64 dr. of grass afford of nutritive matter 2.3 dr."
The produce of the space ditto 9.2 2'16^

At the time the seed is ripe, the produce is

Grass, 14 oz. The produce per acre 152460 0 -- 9528 12 0

80 dr. of grass weigh when dry 28 dr. \ ^„

The produce of the space, ditto 78. 1 :^-5 J ^^^^^ ^ "" ^^^^ ^ ^

The weight lost by the produce of one acre in drying — 6183 11 0

64 dr. of gi*ass afford of nutritive matter 3.1 dr. ")

The produce ofthe space, ditto 11. 11.2 V ''^^ 1—483 14

The weight of nutritive matter which is lost by taking the
crop at the time of flowering, being nearly one-fourth
part of its value 109 1 0

The proportional value which the grass at the
time of flowering, bears to that at the time the seed is
ripe, is as 11 to IS.

The latter-math produce is

Grass, 12 oz. The produce per acre 130680 0 — 8167 8 0

64 dr. oF Grass afford of nutritive matter 2 dr. 4083 12 — 255 3 12

The proportional value in which the grass at the
time of flowering, exceeds that of the latter-math
is as 8 to 11; and the latter-math stands to that at the
time the seed is ripe in proportion as 8 to 13.

• The merits of this grass seem to demand notice ;
jt^ nutritive powers are considerable, and its produce

APPENDIX. XXI

large when compared with others which affect a similar

soil.

XVII. Daciylis glomerata. Engl. Bot. ^^^S. Fl.

Dan. 743. Round-headed cock's-foot grass,
Nat of Britain. Wither. B. 2. E. 149.
At the time of flowering, the produce from a rich

sandy loam, is oz. or lbs. per acre

Grass, 41 oz. The produce per acre ^ 446490 0 — 27905 10 0

80 dr. of ffrass weich when dry 34 dr. -^

Ti, 1 r., r/ o-ro.*^^ f 189758 0 — 11859 14 4

1 he produce of the space, ditto 278 4-5 dr. 3

The weight lost by the produce of one acre in drying 16045 11 12

64 dr. of grass afford of nutritive matter 2.2 dr.")

The produce ofthe space, ditto 25.2 1-23^'^'^^^ 0 — 1089 0

At the time the seed is ripe the produce is

Grass, 39 oz. The produce per acre 424710 0 — 26544 6 0

80 dr. of grass weigh when dry 40 dr.")

The produce of the space, ditto 312 dr. 5 ^^^^^^^ 0 — 13272 3 0

The weightiest by the produce of one acre in drying 13272 3 0

64 dr. of grass afford of nutritive matter 3. 2 dr.^

The produce of the space, ditto 34. 0 1-2 3 ^^^^^ ^ "" ^^^^ ^^ ^

The weight of nutritive matter which is gained by leaving
the crop till the seed be ripe, being more than one third
part of its value, is 362 10 5

The proportional value which the grass at the
time of flowering, bears to that at the time the seed is
ripe, is as 5 to 7, nearly.

The produce of latter-math is

Grass, 17 oz. 8 dr. The produce per acre 190575 0 — • 11910 15 0
64dr.ofgrassaffbrd of nutritive matter 1.2 dr. 4466 9 — 28110 9

The proportional value which the grass of the.
latter-math bears to that at the time of flowering, is as
6 to 10; and to that at the time the seed is ripe, as 6
to 14. 64 dr. of the straws at the time of flowering
afford of nutritive matter 1 .2 dr. The leaves or latter-
math, and the straws simply, are therefore of equgil

xxii APPENDIX.

\
proportional value; a circumstance which will point

out this grass to be more valuable for permanent pas-
ture than for hay. The above details prove, that a
loss of nearly one third of the value of the crop is sus-
tained, if it is left till the period when the seed is ripe,
though the proportional value of the grass at that time
is greater, /. e. as 7 ta5. The produce does not in-
crease if the grass is left growing after the period of
flowering, but uniformly decreases ; and the loss of
latter-math, which, (from the rapid growth of the
foliage after the grass is cropped) is very considerable.
These circumstances point out the necessity of keep-
ing this grass closely cropped, either with the scythe
or cattle, to reap the full benefit of its great merits.

XVIII. Bromus tectorum. Host. G. A. 1. t. 15.
Nodding pannicled brome-grass. Nat. of
Europe. Introduced 1776. H. K. 1. 168.

At the time of flowering, the produce from a

light sandy soil, is oz. or lbs. per acre

Grass, 11 oz. The produce per acre 119790 0 — 7486 14 0

80 dr. of grass weiffh when dry 42 dr. 7 ^„,,«„ -^ ^^^^ „ ,^
„,, , r.^,*^ .' ooi"«C 62889 12 -- 3930 9 12

1 lie produce of the space, do 92. 1 o-S^

The weight lost by the produce of one acre in dryino; 3556 4 4

64 dr. of grass afford of nutritive matter 3 dr. ^

The produce of the space, ditto 8. 1 dr. $ ^^^^ ^"" ^^^ ^^ ^

This species being strictly annual, affords no
latter-math, which renders it comparatively of little
value.

XIX. Festuca camhrica. Hudson. W. B. 2. P. 155.

Nat. of Britain.
At the time of flowering, the produce from a light
sandy soil is

Grass, 10 oz. The produce per acre 108900 0 — 6806 4 0

80 dr. of grass weigh when dry 34 dr. ^

The produce of the space, ditto 68 dr. \ ^^^^^ ^ ~ ^892 10 8

APPENDIX. xxm

oz. or lbs. per acre

The wfeight lost by the produce of one acre in drying 3913 9 8

64 dr. of pcrass afford of nutritive matter 2.1 dr. 7

rru J r.v J-** irc>ioC3828 8—239 4 8

The produce of the space, ditto 5.2 1-2 J

This species is nearly allied to the Festuca ovina^
from which it differs little, except that it is larger in
every respect. The produce, and the nutritive matter
which it affords, will be found superior to those given
by the F. ovina^ if they are brought into comparison.
XX. Brotnus Diandrus. Curt. Lond. Engl. Bot. 1006.

Nat. of Britain.

At the time the grass is ripe flower, the produce
from a rich brown loam, is

Grass, 30 oz. The produce per acre 326700 0—20418 12 0

80 dr. of grass weigh when dry 34 dr.

The produce ofthe space, ditto 204 dr. ^ ^^^^^^ 8-8677 15 0

The weight lost by the produce of one acre in drying 11740 13 0

64 dr. of grass afford of nutritive matter 3 dr. 7

The produce ofthe space, ditto 22.2 V^^U 1 — 957 2 1

This species, like the preceding, is strictly annual;
the above is therefore the produce for one year, which,
if compared with that of the least productive of the
perennial grasses, will be found inferior, and it must
consequently be regarded as unworthy of culture.

XXL Poa angustifolia. With. 2. P. 142.

Narrow-leaved meadow grass. Nat, of Britain.

At the time of flowering,'the produce from a brown
loam, is

Grass, 27 oz. The produce per acre 294030 0 — 18376 14 0

80 dr. of grass weigh when dry 34 dr. ^
Theproduce«fthesp.ce.ditto 183 2 Z-sj ^^^^^^ ^2 - 7810 2 12

The weight lost by the produce of one acre in drying 10566 11 4

64 dr. of grass afford of nutritive matter 5 dr. 7

The produce ofthe space, ditto 33-3 $ 22886 11 - 1430 6 11

XXIV ' APPENDIX.

At the time the seed Is ripe, the produce is

Grass, 14 oz. ihe produce per acre 152460 0 — 9528 12 0

80 dr. of grass weigh when dry 32 dr.

The produce of the space, ditto 89.2 2-5 ^y ^^^^^ ^"~ ^^^^ ^ ^
The wcig-ht lost by the produce of one acre in drying 5717 4 0

64 dr. of grass aUbrd of nutritive matter 5. 1 dr. ^ ^

The produce of tlie space, ditto 18. 1 1-2 S ^^^^^ 7 — 701 6
The weiglit of nutritive matter which is lost by leaving tlie
crop till the seed be ripe, exceeding one third part of its
value 649 0 4

In the early growth of the leaves of this species
of Pca^ there is a striking proof that early flowering
in grasses is not always connected with the most abun-
dant early produce of leaves. In this respect all the
species which have already come under examination,
are greatly inferior to that now spoken of. Before the
middle of April the leaves attain to the length of more
than twelve inches, and are soft and succulent; in
May, however, when the flower-stalks make their ap-
pearance, it is subject to the disease termed rust,
which affects the whole plant; the consequence of
which is manifest in the great deficiency of produce
in the crop at the time the seed is ripe, being one-half
less than at the time of the flowering of the grass.
Though this disease begins in the straws, the leaves
suffer most from its effects, being at the time the seed
is ripe completely dried up; the straws therefore,
constitute the principal part of the crop for mowing,
and they contain more nutritive matter in proportion
than the leaves. This grass is evidently most valua-
ble for permanent pasture, for which, in consequence
of its superior, rapid, and early growth, and the disease
beginning at the straws, nature seems to have de-
signed it. The grasses which approach nearest to this

APPENDIX. xxt

in respect of early produce of leaves, are the Poa

fertilise Dactylis glomerata^ Fhleum pratense^ Alopecurus
pratensisy Avena eliator, and Bromus littoreus, all
grasses of a coarser kind.
XXII. Avena eliator. Curtis 191. Engl. Bot. 818.

Holcus avenaceus. Tall oat-grass. Nat. of

Britain.

At the time the seed is ripe, the produce is

(12. or lbs. per acre
Grass, 24 oz. The pro luce per acre 261360 0 — 16335 0 0

80 dr. of ff rass weigh when dry 28 dr. 7

/ r.i vJ lo. io^ k 91475 14 — 5717 3 14

The produce of the space, ditto 134. 1 3-5 J

The weight lost by the produce of one acre in drying 10617 12 2

64 dr. of grass afford of nutritive matter 1 dr. 7

^. , r.i A-^, « i„ S 4083 12 — 255 3 12

The produce of the sp^ce, ditto 6 dr. J

The produce of latter-math is

Grass, 20 oz. The produce per acre 217800 0 — 13612 8 0

64 dr. of Grass afford of nutritive matter 1. 1 dr. 4253 14 — 265 13 14
The weight of nutritive matter, which is afforded by the
crop of the latter-math, exceeding that afforded by the
grass of the seed crop in proportion nearly as 26 to 25 10 9 2

This grass sends forth flower straws during the
whole season; the latter-math contains nearly an equal
number with the flowering crop. It is subject to the
rust, but the disease does not make its appearance till
after the period of flowering; it affects the whole plant,
and at the time the seed is ripe the leaves and straws
are withered and dry. This accounts for the superior
value of the latter-math over the seed crop, and points
out the propriety of taking the crop when the grass is
in flower.

d

XXVI APPENDIX.

XXIII. Poa eliator. Curtis, 50.

Tall meadow grass. Nat. of Scotland.
At the time of flowering, the produce from a rich

clayey loam is oz, or lbs. per acre

Glass, 18 oz. The produce per acre 196020 0 — 12251 4 0

80 dr. of grass weigh when dry 28 dr.

The produce of the space, ditto 100. 3 2-10 3 ^^^^^ ^ "" ^^^^ ^^ ^

64 dr. of grass afford of nutritive matter 3.2 dr.") «« i« i'>

The produce of the space, ditto 15.3 S ^^"^^ 13—669 15 lo

The weight lost hy the produce of one acre in drying 3617 15 5

The botanical characters of this grass are almost
the same as those of the Avena eliator^ differing in the
want of the awns only. It has the essential character
of the Kolci (Florets male, and hermaphrodite. Calyx
husks two-valved with two florets) and since the
Avena eliator is now referred to that genus this may
yrith certainty be considered a variety of it.
XXIV. Festuca duriuscula. Engl. Bot. 470. W. B.
2. P. 153. Hard fescue grass. Nat. of
Britain.

At the time of flowering, the produce from a light
sandy loam is

Grass, 27 oz. The produce per acre 294030 0 — 18376 14 0

80 dr. of grass weigh when dry 36 dr. 7 ^ ^^ « «

-ri r f.i a;. in^ 1 q «C 132313 8— 8269 9 0

The produce of the space, ditto 194. 1 3-5 J

The weight lost by the produce of one acre in drying 10106 4 8

64 dr. of grass afford of nutritive matter 3.2 dr. ">

The produce of the space, ditto 23.2 1-23 ^^^^^ ^^ " ^^°^ ^^ ^

At the time the seed is ripe the produce is

Grass, 28 oz. The produce per acre 304920 0 — 19075 8 0

80 dr. of grass weigh when dry 36 dr. a

The produce ofthe space, ditto 201.2 2-53 ^^^^^^ 0 — 8d75 14 0

'I'he weight lost by the produce of one acre in drying 10481 10 0

64 dr. of grass niford of nutritive matter 1. 2 dr

The produce of tjie space, ditto 10. 2

^^\ 7146 9-446 10 9

APPENDIX. xxvn

02. OP lbs. per acre
The weight of nutritive matter which is lost by leaving the

crop till the seed be ripe exceeding one half of its value 558 5 3

The proportional value which the grass at the
time the seed is ripe, bears to that at the tijne of flower-
ing, is as 6 to 14, nearly.

The produce of latter-math is

Grass, 15 oz. The produce per acre 163350 0 — 10209 6 0

64 dr.ofgrass afford of nutritive matter 1.1 dr. 3190 4 — 199 6 4

The proportional value which the grass of the
latter-math bears to that at the time of lowering, is as
5 to 14, and to that at the time the seed is ripe, 5 to 6.

The above particulars will confirm the favourabJe
opinion which was given of this grass when speaking
of the Fesiuca hordiformis^ and F, glabra. Its produce
in the spring is not very great, but of the finest ((quali-
ty^ and at the time of flowering is considerable. If it
be compared with those affecting similar soils such as
Foa pratensisy Fesiuca ovina^ '<3'c, either considered as
a grass for hay, or permanent pasture, it will be found
of greater value.

XXV. Brojnus erectiis. Engl. Bot. 471. Host. G. A.
Upright perennial brome grass. Nat. of Bri-
tain.

At the time of flowering, the produce from a rich
sandj soil is

Grass, 19 oz. The produce per acre 206910 0 — 1293114 0

80 dr. of grass weigh when dry 36 dr. -j

The produce of the space, do 136.3 1-55 93109 8 — 5819 5 8

The weight lost by the produce of one acre in drying 7112 8 8

64 dr. of grass afford of nutritive matter 2.3 dr. ^

TVie produce of the space, dirto 13. 0 1-4 S ^^^^ ^^"" ^^^ ^^ ^^

%xviu APPENDIX.

XXVI. Milium effusum. Curt. Lon. Engl. Bot. 1106.
Common millet grass. Nat. of Britain.
At the time of flowering, the produce from a light

sandy soil is oz. or lbs. per acre

Grass, 11 oz. 8 dr. The produce per acre 196020 0 — 12251 4 0

80 dr. of erass weigh when dry 31 dr. 1

^u 1 f.u VM 111 oofiC ^5957 12 — 4747 512

The produce of the space, ditto 111. 2 2-0 3

64 dr. of grass afford of nutritive matter 1. 3 di*.

The produce of th. space, ditto 7. 3 2-43 ^^^^ ^^"" ^^^ ^^ ^^

This species in its natural state seems confined to
woods as its place of growth; but the trial that is here
mentioned, confirms the opinion that it will grow and
thrive in open exposed situations. It is remarkable
for the lightness of the produce, in proportion to its
bulk. It produces foliage early in the spring in con-
siderable abundance; but its nutritive powers appear
comparatively little.

XXVII. Festuca pratensis. Engl. Bot. 1592. C. Lond.
Meadow fescue grass. Nat. of Britain.

At the time of flowering, the produce from a bog
soil, with coal ashes for manure, is

Grass, 20 oz. The produce per acre 217800 0—- 13612 8 0

80 dr. of grass weigh when dry 38 dr.7

The produce ofthe space, ditto 152 dr. 5 ^^^^^^ 8-6465 15 0

The weight lost by the produce of one acre in drying — 7146 9 0

64 dr. of grass aftbrd of nutritive matter 4,2 dr. ^

The produce ofthe space ditto 22.2 dr. V^^^^ 1 — 957 2 1

At the time the seed is ripe, the produce is

Grass, 28 oz. The produce per acre 304920 0 — 19057 8 0

80 dr. of grass weigh when dry 32 dr.

The produce ofthe space ditto 179.0 4-53^^^^^^ 0 — 7623 0 0
The weight lost by the produce of one acre in drying 11434 8 0

64 dr. of grass afford of nutritiie matter 1.2 dr.
The produce of the space, ditto 10.2

The weight of nutritive matter which is lost by leaving the
crop till the seed be ripe, exceeding one half of its value 510 7 8

dr.7

^^ >7146 9— 446 10 9

APPENDIX. XXIX

The value of the grass at the time the seed is
ripe, is to that of the grass at the time of flowering,
as 6 to 18.

The loss which is sustained by leaving tl\e crop
of this grass till the seed be ripe is very great. That
it loses more of its weight in drying at this stage of
growth, than at the time of flowering, perfectly agrees
with the deficiency of nutritive matter in the seed crop,
in proportion to that in the flowering crop: the straws
being succulent in the former, they constitute the
greatest part of the weight; but in the latter they are
comparatively withered and dry, consequently the
leaves constitute the greatest part of the weight. It
may be observed here, that there is a great difference
between straws or leaves that have been dried after
they were cut in a succulent state, and those which
are dried (if I may so exprees it) by nature while
growing. The former retain all their nutritive powersj
but the latter, if completely dry, very little, if any.

XXVIII. Lolium perenne. Engl. Bot. 315. Fl^.
Dan. 747. Perennial rye-grass. Nat. of
Britain.

At the time of flowering, the produce from a rich
brown loam, is

oz. or lbs. per acre
Grass, 11 oz. 8 dr. The produce pep acre 125235 0 — 7827 3 0

80 dr. of grass weigh when dry 34 dr. ^

The produce of the space, ditto 78 4-10 3 ^^^^^ 13 — 3322 4 13

The weight lost by the produce of one acre in drying 4494 14 3

64 dr? of grass afford of nutritive matter 2.2 dr. ^

The produce of the space, ditto 7.0 3-4 3 ^^^^ ^^ "" ^^^ ^^ ^*

At the time the seed is ripe, the produce is

C5ra88, 22 oz. The produce per acre 239580 0 — 14973 12 ^

XXX APPENDIX.

oz. or lbs. per acre
8.0 dr. of grass weig-li when dry 24 dr. ">
The produce ofthe space, ditto 105.2 2-53 ^^^-^^ 0 — 4492 2 0

The weight lost by the produce of one acre in drying 10481 10 0

64 dr. of grass afford of nutritive niatter 2.3 dr. 7

The produce of the space, ditto 15.0 2-165^^294 7—643 6 ?

The weight of nutritive matter which is lost by taking the
crop at the time of flowering, nearly one half its value 337 8 8

The proportional value which the grass at the
time of flowering, bears to that at the time the seed is
ripe, is as 10 to 11.

The produce of latter-math is

Grass, 5 oz. The produce per acre 54450 0 — 3403 2 0

64 dr. of grass afford of nutritive matter 1 dr. 850 12 — 53 2 12

The proportional value which the grass of the
latter-math bears to that at the time of flowering, is as
4 to 10, and to that at the time the seed is ripe, as 4
to U.

XXIX. Foa maritma. Engl. Bot. 1140.
Sea meadow grass. Nat. of Britain.

At the time of flowering, the produce from a light
brown loam is

Grass, 18 oz. The produce per acre 196020 0 — 12251 4 0

80 dr. of grass weigh when dry 32 dr. )

The produce of the space, ditto 115. 1-5 ^^^ " " *^°'' ° "
The weight lost by the produce of one acre in drying 7350 4 0

2 dr. 7

Idr.r''

The produce of latter-math is

Grass, 18 oz. The produce per acre 196020 0 — 12251 4 0

64dr.ofgrass afford of nutritive matter, 1 dr. 3062 13— 191 6 31

The proportional value which the grass of the
latter math, bears to that at the time of flowering, is
33 4 to 18,

64 dr. of grass afford of nutritive matter 4. 2 dr. ^ f.

^^3782 0 — 861 6 ^

APPENDIX. XXXI

XXX. Cynosurus cristatus. Engl. Bot. 316. Host.
G. A. 2. t. 96. Crested dog's-tail grass.

At the time of flowering, the produce from the
brown loam, with manure, is oz. or lbs. per acre

Grass, 9 oz. The produce per acre 98010 0—6125 10 0

80 dr. of grass weigh when dry 24 dr.")

^ ' 29403 0 — 1837 11 0

'•}

The produce of the space, ditto 43

The weight lost by the produce of one acre in drying 4287 15 0

64 dr. of grass aflbrd of nutritive matter 4.1 dr. ^

Theproduceofthe space, ditto 9.2 1-16 3^^°^ ^ "" ^^^ ^^ ^

At the time the seed is ripe, the produce is

Griss 18 oz. The produce per acre 196020 0 — 12251 4 0

80 dr. of grass weigh when dry 32 dr. 7

The produce of the space, ditto 115.0 8-10 ^ ^^^^^ ^ "" ^^°^ ^ ^

The weight lost by the produce of one acre in drying 7350 12 0

64 dr. of grass afibrd of nutritive matter 2.2 dr. -^

The produce ofthe space, ditto 11.1 dr.l ^^^'^ 0 — 478 9 0

Tlie weight of nutritive matter which is lost by taking the
crop at the time of flowering, exceeding one sixth of its
value - - 71 12 9

XXXI. Avena pratensis Engl. Bot. 1204. Fl. Dan.
1083. Meadow oat-grass. Nat. of Britain.
, At the time of flowering, the produce from a rich
sandy loam, is

Grass, 10 oz. The produce per acre 108900 0 — 6806 4 0

80 dr. of grass weigh when dry 22 dr.

The produce of the space, ditto 44dr.i^^^'*^ 8 — 187111

The weight lost by the produce of one acre in drying 4934 8 8
64 dr. of grass afford of nutritive matter 2. 1 dr.">

The produce of the space, ditto 5. 2 1-2 j^^^^ ^ "" ^'^ ^ ^

At the time the seed is ripe, the produce is

Grass, 14 oz. The produce per acre 152460 0 — 9528 12 0

80 dr. of grass weigh when dry 24 dr. ■>

The produce of the space ditto 67.0 4-53 ^^''^^ ^ "" ^^^^ ^^ ^

The weight lost by the produce of one acre in drying 6670 2 0

64 dr. of grass afvbrd of nuti-itive matter 1 dr, ^

The produce of the space, ditto 3.2 3 ^^^^ ^ "^ 148 14 3

xxxii APPENDIX.

^, . ^ ^ . ®^' ^^ ^^^- per ac; e

The weight of nutritive matter which is lost by leaving the

crop till the seed be ripe, exceeding one third part of its

' value - - - - , . . . - i . 90 6 0

The proportional value which the crops, at the
time the seed is ripe, bear to that at the time of flower-
ing, is as 4 to 9.

XXXIII, Bromus multifiorus, Engl. Bot. 1884. Host.
G. A. 1. t. II. Many flowering brome-
grass. Nat. of Britain.

At the time of flowering, the produce from a clayey
loam, is

Grass, 33 oz. The produce per acre 359370

80 dr. of grass weigh when dry 44 dr.^

The produce of the space ditto 290.0 2-53 ^^''^^^

The weight lost by the produce of one acre in drying

64 dr. of grass afford of nutritive matter 5 dr. -^

The produce of the space, ditto 41. 1 dr. 5 ^^^*^^ ^^

This species is annual, and no valuable proper-
ties have as yet been discovered in the seed. It is
only noticed on account of its being frequently found
in poor grass lands, and sometimes in meadows. It
appears from the above particulars to possess nutritive
powers equal to some of the best perennial kinds, if
taken when in flower; but if left till the seed be ripe
(which, from its early growth, is frequently the case),
the crop is comparatively of no value, the leaves and
straws being then completely dry.

0-

- 22460 10

0

8-

-12353 5

8

loior 4

8

12"

- 1754 11 12

APPENDIX. -xx'^iii

XXXIII, Festuca loUacea. Curt. Lond. Engl. Bot.
1821. Spiked fescue grass. Nat. of Bri-
tain.
At the time of flowering, the produce from a brown

rich loam, is oz. or lbs. per acre

Gr«ss, 24oz. The produce per acre 261360 0 — 16335 0 0

80 dr. of grass weigh when dry 35dr."> ^,,-.^ _ wi>i/; « r%

o'k J r.u 1 ICO 1 C 114345 0~ 7146 9 0

1 he produce of the space, do 168 dr. j

The weight lost by the produce of one acre m drying 9188 7 0

64 dr. of glass afford of nutritive matter 3 dr. ^

The produce of the space, ditto 18 dr. { ^^251 4 — "t^S 11 0

At the time the seed is ripe, the produce is

Grass, 16 oz. The produce per acre 174240 0 — 10890 0 0

80 dr. of gra^ weigh when dry 33 dr. ^

The produce of the space, ditto 1053-5 dr. V^^*"^ ^"" '^^^^ ^ ^

The weight lost by the produce of one acre in drying 6397 14 0

64 dr. of grass aflbrd of nutritive matter 3. 1 dr. ^

The protluceofthe space, ditto 13 dr. 5 ^^^^ 2 — 553 2 0

The latter-math produce is

Grass, 5 oz. The produce per acre 54450 0 — 3403 2 0
64dr.of grass afford of nutritive matter, 1.1 dr. 1063 7— 66 7 7
The weight of nutritive matter whicli is lost by leaving the
crop till the seed be ripe, exceeding one fourth part of its
value 212 11 0

The proportional value which the grass, at the
time of flowering, bears to that at the time the seed is
ripe, is as 12 to 13; and the value of the latter-math
stands in proportion to that of the crop at the time of
flowering, as 5 to 12, and to that of the crop taken at
the time the seed is ripe, as 5 to 13.

This species of fescue greatly resembles the rye
grass, in habit and place of growth; it has excellencies
which make it greatly superior to that grass, for the
purposes of either hay or permanent pasture. This
species seems to improve in produce in proportion of

e

XXXIV APPENDIX.

its age, which is directly the reverse of the LoUum
perenne.

XXXIV. Poa cristaia. Host. G. A. 2. t. 75. — Aira
Cristata. Engl. Bot. 648. Crested meadow
grass. Nat. of Britain.

At the time of flowering, the produce from a sandy

loam, IS oz. or lbs. per acre

Grass, 16 oz. The produce per acre 174240 0 — 10890 0 0

80 dr. of ffrass weicfh when dry 36 dr.-) , _^^ ^ ^

-TK J f.i v.. ncQiA^ 7848 0 — 4900 8 0

The produce of the space ditto 115 3-16 5

The weight lost by the produce of one acre in drying 5989 8 0

64 dr. of grass afford of nutritive matter 2 dr. ^

The produce of die space, ditto 8 dr. 3 ^^^ 0 — 340 5 0

The produce of this species, and the nutritive
matter that it affords, are equal to those of the Festuca
ovina at the time the seed is ripe; they equally delight
in dry soils. The greater bulk of grass in proportion
to the weight, with the comparative coarseness of the
foliage, render the Poa cristata inferior to the Festuca
ovina.

XXXV. Festuca myurus, Engl. Bot. 1412. Host.
G. A. 2. t. 93. Wall fescue grass. Nat.
of Britain.

At the time of flowering, the produce from a light
sandy soil is

Grass, 14 oz. The produce per acre 152460 0 — 9528 12 0

80 dr. of erass weicrh when dry 24 dr. 7 „-^ -^ ^

^ r.. A-.: z:^ o in C 45738 0 — 2858 10 0

1 he produce of the space, ditto 67 2-10 ->

The weight h st by the produce of one acre in drying 6670 2 0

64dr. of grass afford of nutritive matter 1. 2 dr. -> ^^

The produce of the space, ditto 5. 1 dr. 5

This species is strictly annual ; it is likewise sub-
ject to the rust; and the above being its whole pro-
duce for one year, it ranks as a very inferior grass.

APPENDIX. XXXV

TUTMl. Airoflexuosa. Engl Bot. 1519. Host. Go
A. 2. t. 43. Waved mountain hair-grass.
Nat. of Britain.

At the time of flowering, the produce from a heath

soil, IS oz. or lbs. per acre

Grass, 12 oz. The produce per acre 130680 0— 8167 8 0
80 dr. of grass weigh when dry 31 dr.">

The produce of the space, ditto 74 2-55 ^^^^S 0-3164 14 8

The weight lost by the produce of one acre in drying 5002 9 8

64 dr. of grass afford of nutritive matter 1. 2 dr.-^

The produce of the space, ditto 4. 2 dr. > ^^^^ ^^ "~ "^^^ ^ ^^

XXXVII. Hordeum bulbosum. Hort. Kew. 1. P. 179.
Bulbous barley grass. Nat. of Italy and
the Levant. Introduced 1770, by Mons.
Richard.

At the time of flowering, the produce from a
clayey loam with manure, is

Grass, 35 oz. The produce per acre 381150 0 — 23821 0 0

SO dr. of grass weigh when dry 93 dr. ">

The produce of the space, ditto 231 drj ^^^^^^ ^ "~ ^^^^ ^ ^

The weight lost by the produce of one acre in drying 13994 7 10

64 dr. of grass afford of nutritive matter 3.2 dr.
Tlie produce of the space, ditto 30.2 2-4^

XXXVIII. Festuca calamaria. Engl. Bot. 1005.
Reed-like fescue grass. Nat. of Britain.

At the time of flowering, the produce from a clayey
loam is

Grass, 80 oz. The produce per acre 871200 0—54450 0 0

80 dr. of grass weigh when dry 28 dr.

The produce of the space, ditto 448 dr.

The weight lost by the produce of one acre iji drying 35392 8

64 dr. of grass afford of nutritive matter 4.2 dr.

The produce of the space, ditto 90

■^20844 2 — 1302 12 2

1

^ > 304920 0 — 19057 8 0

■eiji
^^ j 61256 4 — 3828 S 4

XXXVI APPENDIX.

At the time the seed is ripe, the produce is

oz. or lbs. per acrt
Grass, 75 oz. The produce per acre 816750 0— 51046 14 0

80 dr. of grass weigh when dry 19 dr. 7

The produce of the space, ditto 283 dr. 5 ^^^^^^ ^ "~ ^^^^^ ^^ °

The weight lost hy the produce of one acre in drying 38923 4 0

64 dr. of errass alford of nutritive matter 3 dr. 7

1 c.u r.. cA 1 S 38285 2 — 2392 13 2

The produce of the space, dilta 56.1 ->

The weight of nutritive matter which is lost by leaving the

crop till the seed be ripe, being nearly one third part of

lis vahie 1435 11 2

The proportional value which the grass at the
time the seed is ripe, bears to that at the time of flower-
ing, is as 2 to 1 8.

This grass, as has already been remarked, pro-
duces a fine early foliage in the spring. The produce
is very great, and its nutritive powers are considerable.
It appears from the above particulars, to be best adapt-
ed for hay. A very singular disease attacks, and
sometimes nearly destroys the seed of this grass; the
cause of this disease seems to be unknown; it is de-
nominated Clavus by some; it appears by the seed
swelling to three times its usual size in length and
thickness, and the want of the carcle. Dr. Willdenow
describes two distinct species of it; 1st, the simple
clavus, which is mealy and of a dark colour, without
any smell or taste; 2nd, the malignant clavus, which
is violet blue, or blackish, and internally too has a
blueish colour, a foetid smell, and a sharp pungent
taste. Brea^ made from grain affected with this last
species, is of a blueish colour; when eaten produces
cramps and giddiness.

APPENDIX. XXXVII

XXXIX. Bromus littoreus. Host. G. A. P. 7. t. 8.
Sea-side brome grass. Nat. of Germany,
grows on the banks of the Danube and
other rivers.

At the time of flowering, the produce from a clayey

loam IS oz. or lbs. per acre

Grass, 61 oz. The produce per acre 664290 0 — 41518 2 0

80 dr. of grass weigh when dry 41 dr.

„,, , p,, ,.,, -^^^.^.340448 10—21278 0 10

The produce of the space, ditto 500 2-10 3

The weight lost by the produce of one acre in drying 20540 1 6

64 dr. of grass afford of nutritive matter 1.2 dr.->

The produce ofthespuce, ditto 22.3 1-25^^^^'^ 4—973 1 4

At the time the seed Is ripe the produce is

Grass, S^ oz. The produce per acre 609840 0 — 38115 0 0

80 dr. of grass weigh when dry 32 dr.-j

The produce of the space, ditto 358 l-si 243936 0 - 15246 0 0

The weight lost by the produce of one acre in drying 22869 0 0

64 dr. of grass afford of nutritive matter 3.2 dr.">

The produce of the space, ditto 196 3 ^^^^^ ^ ~ ^084 6 10

The weight of nutritive matter which is lost by taking the
crop at the time of flowering, exceeding one half of its
value mi 5 5

The proportional value which the grass at the
time of flowering, bears to that at the time the seed is
ripe, is as 6 to 14.

This species greatly resembles the preceding in
habit and manner of growth; but is inferior to it in
value, which is evident from the deficiency of its pro-
duce, and of the nutritive matter afforded by it, Tha
whole plant is likewise coarser and of greater bulk ia
proportion to its weight. The seed is affected with
the same disease which desti-oys that of the former
species.

3^xxvni APPENDIX.

XL. Festuca eliator. Engl. Bot. 1593. Host. G. A.
2. t. 79. Tall fescue grass. Nat. of Britain.
At the time of flowering, the produce from a black

rich loam, is oz. or Ibs. per acre

Grass, 75 uz. The produce per acre 816750 0 — 51046 14 0

80 dr. of grass weigh when dry 28 dr.-

63808 9 — 3988 0 9

The produce ofthe space, ditto 420 dr. 3 ^85862 8-17866 6 8

The weight lost by the produce of one acre in drying 33180 7 8

64 dr. of grass afford of nutritive matter 5 dr.
The produce of the space, ditto 93. 3

At the time the seed is ripe, the produce is

Grass, 75 oz. The produce per acre 816750 0 — 51046 4 0

80 dr. of grass weigh when dry 28 dr.| ^ ^
The produce of the space ditto 420 dr. 3

The weight lost by the produce of one acre in drying 33180 7 8

64 dr. of grass afford of nutritive matter 3 dr.")

^. 1 r.K A-,,r. c« 1 C 38285 2 — 2392 13 2

The produce of the space, ditto 56. 1 J

The weight of nutritive matter which is lost by leaving the
crop till the seed be ripe, exceeding one third part of its
value 1595 3 7

The proportional value which the grass at the
time the seed is ripe, bears to that at the time of flower-
ing, is as 12 to 20.

The produce of latter-math is

Grass, 23 oz. The produce per acre 250470 0 — 15654 6 0

64 dr. of Grass afford of nutritive matter 4 dr. 15654 6 — 978 6 6

The proportional value which the grass of the
latter-math bears to that of the crop, is as 16 to 20;
and to that at the time the seed is ripe, as 12 to 16,
inverse.

This species of fescue is closely allied to the Fes*
tuca pratensis, from which it differs in little, except
that it is larger in every respect. The produce is near-
ly three times that of the F. pratensisy and the nutritive

APPENDIX. XXXIX

powers of the grass are superior in direct proportion,
as 6 to 8.

XLL Nardus sfricta. Engl. Bot. 290. Host. G. A.
2. t. 4. Upright mat-grass. Nat. of Britain.
At the time the seed is ripe, the produce is

oz. or lbs, per acre
Crass, 9 oz. The produce per acre 98010 0 — 6125 10 0

80 dr. of grass weiffh when dry 32 dr. 1

^ 39204 0 — 2450 4 0

■A

The produce of the space, ditto 57 2 2-

^he weight lost by the produce of one acre in drying 3675 6 0

64 dr. of gi'ass afford of nutritive matter 2.1 dr. ")

The produce of the space, ditto 5.0 1-5 ]" ^^^^ ^° "" ^ ^

^LII. Trittcwn, Sp.
Wheat-grass.
At the time of flowering, the produce from a rich
sandy loam, is

Grass, 18 oz. The produce per acre 196020 0—12251 4 0

80 dr. of grass weigh when dry 32 dr. 7

The produce ofthcspace, ditto 115 1.5 5 ^^^ 0-4900 8 0

The weight lost by the produce of one acre in drying 7350 12 0

64 dr. of grass afford of nutritive matter 22 dr. >

The produce ofthcspace, ditto 11.1 dr. 5 '^^^^ 0—478 9 0

XLIII. Festucajluitans. Curt. Lond. Engl. Bot. 1520.
Poa fluitans. Floating fescue grass. Nat. of
Britain.

At the time of flowering, the produce from a strong
tenacious clay, is

Grass, 20 oz. The produce per acre 217800 0 — 13612 8 0

80 dr. of grass weigh when dry 24 dr.

The produce of the space, ditto 96

The weight lost by the produce of one acre in drying 9528 12 0

64 dr. of grass afford of nutritive matter 1.3 dr.

The produce of the space, ditto 8,3 dr.

The above produce was taken from grass that
'had occupied the ground for four years, during which

dr.l

, \ 65340 0 — 4083 12 0
dr. J

, ^5955 0— 372 3 7

xi APPENDIX.

time it had increased every year; it therefore appears
contrary to what some have supposed to be capable of
being cultivated in perennial pastures.

XLIV. Hokus lanatus. Curt. Lond. Fl. Dan. 118U
Meadow soft grass. Yorkshire grass. Nat.
of Britain.
At the time of flowering, the produce from a strong

clayey loam, is oz. or Ibs. per acre

Crass, 28 oz. The produce per acre 304920 0—19057 8 0

^Q dr. of grass weigh when dry 26 dr. 7 ^^. ^ ^ .

A ^ .1 v.. n «.r o o ^ C 106585 14 - 6661 9 14

1 he produce of the space, ditto 157. 2 2-5 3

The weightiest by the produce of one acre in drying 12395 14 2

64 dr. of grass afford of nutritive matter 4 dr. ^

The produce of the space, ditto 28 dr. 5 ^^^^^ 8—1191

At the time the seed is ripe, the produce is

Grass, 28 oz. The produce per acre 304920 0 — 19057 8 0

80 dr. of grass weigh when dry 16 dr.">

The produce of the space, ditto 89.2 2.5 3 ^^^^^ 0-3811 8 0

The weight lost by the produce of one acre in drying 15246 0 0

64 dr. of grass afibrd of nutritive matter 2.3 dr. >

The produce of the space, ditto 19. 1 dr. 3

The weight of nutritive matter which is lost by leaving the
crop till the seed be ripe exceeding one third part of its
value 372 3 8

The proportional value which the grass at the
time the seed is ripe, bears to that at the time of flower-
ing, is as 1 1 to 1 2.
XLV. Festuca dumetorum. Flo. Dan. 700.

Pubescent fescue grass. Nat. of Britain.
At the time of flowering, the produce from a black
sandy loam, is

Grass, 16 oz. The produce per acre 174240 0 — 10890 0 0

80 dr. ofgrass weigh when dry ^° '^''- 1 87120 0 .-. 5445 0 0

Thj£ produce of the space, ditto 128 dr. J

APPENDIX, xli

oz. or lbs. perac^e

The M'eigiit lost by the produce of one acre in drying 5445 0 0

64 dr. of irrass afford of nutritive matter 1 dr. }

J i-.i TM A u (" 2722 8—170 2 8

The produce of the space, ditto 4 dr. 3

XLVI. Poa fertilis. Host. G. A.

Fertile meadow grass. Nat. of Germany.

At the time of flowering, the produce from a clayey-
loam, is

Grass, 22 oz. The produce per acre 239580 0—14973 12 0

80 dr. of crrass weigh when dry 42 dr. 1

The produce of the space, ditto 184 4-:> dr. 3

The weight lost by the produce of orte acre in drying 7111 8 8

64dr. of grass afford of nutritive matter 4.2 dr. >

„,, 1 n,. V44- o^ - ^ 16845 7 — 1052 13 7

1 he produce of the space, ditto 24.3 3

If the nutritive powers and produce of this species,
be compared with any other of the family, or such as
resemble it in habit and the soil which it affects, a
superiority will be found, which ranks this as one of
the most valuable grasses; next to the Poa angustifoUa^
it produces the greatest abundance of early foliage, of
the best quality, which fully compensates for the com-
parative lateness of flowering.

XL VII. Arundo color at a. Hort. Kew. I. P. 174.

Engl. Bot. 402, Phalaris arundinacea.

Striped-leaved reed grass. Nat. of Britain,
At the time of flowering, the produce from a black
sandy loam, is

Grass, 40 02. The produce per acre 435600 0 — 27225 0 0

80 dr. of grass weigh when dry 36 dr. ">

The produce of the space, ditto 288 dr. 5 '''^"^O 0-12251 4 0

64 dr. of grass afford of nutritive matter 4 dr. 7

The produce of the spacfe, ditto 40 dr.-> ^'^^^^ 0—1701 9 0

The strong nutritive powers which this grass
possesses recommend it to the notice of occupiers of

f

m

-lii APPENDIX.

Strong clayey lands, which cannot be drained. Its
produce is great, and the foliage will not be denomina-
ted coarse, if compared with those which afford a pro»
duce equal in quantity.

XLVIIL Trifolium pratense, W. Bot. 3. P. 137.
Broad-leaved cultivated clover. Nat. of
Britain.

At the time the seed is ripe, the produce from a
rich clayey loam, is oz. or lbs. per acre

Grass, 72 oz. The produce per acre 784080 0 — 49005 0 0

SO dr. of grass weigh when dry 20 dr.>

The produce of the space, ditto 288 Ur J ^^^''^O 0 - 12251 0 G

The weight lost by the produce of one acre in drying 3675 4 C

64 dr. of grass afibrd of nutritive matter 2.2 •>

The produce ofthe space, ditto 45 dr. 530628 2 — 1914 4 2

If the weight which is lost by the produce of this
species of clover, in drying, be compared with that of
many of the natural grasses, its inferior value for the
purpose of hay, compared to its value for green food,
or pasture, will appear; for it is certain that the diffi-
culty of making good hay increases in proportion with
the quantity of superfluous moisture which the grass
may contain. Its value for green food, or pasture,
may further be seen by comparing its nutritive powers^
with those manifested by other plants generally esteem-
ed best for this purpose.

Trifolium pratense (as above) affords of nutritive mattef 2.2 dr.

XLIX. Trifolium repens (white clover) from an equal quantity

of grass 2.0 dr

L, Ditto, variety, with brown leaves, ditto 2.2 dr.

The grass of the T. pratense^ therefore, exceeds in
value that of the T. repens^ by a proportion, as 8 to lOj

APPENDIX. xlnz

but it is of equal proportional value with the brown
variety.

LI. Bw^net (Poterium sangulsorba) affords of nutritive matter 2.2 dr.
lAl. Bunias orientalise (a newly introduced plant), ditto 2.2 dr.

The proportional value of these two last, and of
the T. pratense^ and the brown-leaved variety of T,
repens^ are equal: they exceed the T. repens^ as 8 to 10.

The comparative produce of these four last metl-
tioned species, per acre, has not been ascertained*
LIII. Trifolium inacrorhi%um^

Long-rooted clover. Nat. of Hungary.

At the time the seed is ripe, the produce from a rich

clayey loam, is oz. or lbs. per acre

Grass, 144 oz. The produce Jier acre 1568160 0 •- 9S010 0 0
80 dr. of grass weig^li when dry 34 dr. ^
The produce of the space, ditto 979 1-5 j ^^^^^^ 0-41654 4 0

The weight lost by the produce of one acre in drying 56355 12 0

64 dr. of grass afford of nutritive matter 23 dr.->

The produce of the space, ditto 99 dr. j ^''^^^ 14 — 4211 5 14

The root of this species of clover is biennial; it
penetrates to a great depth in the ground, and is in
consequence little affected by the extremes of wet or
dry weather. It requires good shelter, and a deep
soil. The produce, when compared to that of others
that are allied to it in habit, and place of growth,
proves greatly superior. The following particulars,
some of which refer to results stated in the next two
pages, will make this manifest: lbs.

Trifolium pratense "J Produces per acre, Grass 49005

L Ditto, Hay 12251

Broad leaved clover J Affords, ditto of nutritive matter 1914

Medicago sativa. "J Produces per acre, Grass 70785

Lucern. From a soil I Ditto, Hay 28314

of the like nature J Affords of nutritive ir»tter 1659

xhv APPENDIX.

Jfedysarum ombi-ychis. ") Produces per acre, Grass 8843

[.Ditto, Hay 3539

Saintfoin. J Affords of nutritive matter 314

The vveig-ht of nutritive matter afforded by the produce of the T.
macrorhizum, exceeding that of the T. pnitenset in proportion,
nearly as 7 to 15 * . . . 2297

The proportional value of the grass of T. protense
to that of T. 7nacrorhizu?n^ is 10 to 11.

The weight of nutritive matter afiiarded by the T. macrorhizum^
exceeding that of the Medicago sativa, m proportion nearly as
13 to 33 2552

The proportional value of the grass is as 11 to 6.

The weight of nutritive matter which is afforded by the produce of
the T. macrorhizum^ excecdinj^ that of the Hedysarum onobrychis
in proportion nctarly as 5 to 67 - - - - - - 3897

The proportional value of the grass, like that of
the T". prate7ise^ is as 11 to 10.

The produce of each of the above mentioned
species, was taken from a similar soil, and in the same
situation the conclusions must thereforebe considered
positive, with respect to such soils only. It is evident
that more than twice the quantity of nutritive mattet
is afforded by the produce of one acre of the T. ma-
crorhizum, than from the produce of an equal space
covered by the T. pratense. Its short duration in the
soil (for if sown early in the autumn, on a rich light
soil, it is only an annual plant) rtnders it fit only for
green-food or hay; this in some jneasure lessens its
value, when compared with the T. pratense. It pos-
sesses the essential property of affording abundance of
good seed; and if the ground be kept clear of weeds,
it sows itself, vegetates, and grows rapidly, without
covering-in, or any operation whatever. For four

APPENDIX. xlv

years it has propagated itself in this manner, on the
space of ground which it now occupies, and from which
this statement of its comparative value is made. The
produce of lucern in grass, comes nearer to this spe-
cies in quantity, but is greatly deficient in nutritive
matter, as much as 13 to 33. The long continuance
of lucern in the soil is therefore the only merit which
it possesses above the two last mentioned species; and
when that is the object of the cultivator, it will of ne-
cessity have the preference.

The value of the grass of saintfoin is equal to
that of the T. pratense; and proportionally less than
that of the Trifglium macrorhizum, as 10 to 11. The
quantity of grass is very small, and on soils of the na-
ture above described, it is doubtless inferior. How-
ever, from the superior value of the grass, on dry hilly
situations or chalky soils, it may in such situations
possibly be their superior in every respect.
LIV. Medicago Sativa. Wither. B. 3. P. 643.
Lucern. Nat. of Britain.
At the time the seed is ripe, the produce from a rich

clayey loam, is oz. or Ibs. per acre

Grass, 104 oz. The produce per acre 1132560 0 — 70r85 0 0

80 dr. of ffrass vveieh when dry 32 dr. 7 ♦

^. 1 r^K A-^, AA- oo« C453024 0 — 28314 0 0

The produce oi the space, ditto ooa. 2 2-5 J

The weiglit lost by the produce of one acre in drying 42471 0 0

64 dr. of grass afford of nutritive matter 1.2 dr. ^

The produce of the spac., ditto 39 dr. 3 ^^^^"^^ ^-^^^^ ^ ^

LV. Hedysarum onobrychis. Wither. 3. P. 628.
Saintfoin. Nat. of Britain.

At the time the seed is ripe, the product from a rich
clayey loam, is

Crass, 13 oz. The produce per acre 141570 0 — 8848 2 (^

xlvi APPENDIX.

oz. or Ibg. per acre
80 dr. of grass weigh when dry 32 dr. J

The produce oftbe space, ditto 83 1^ dr. > ^^^^8 0 — 3539 4 0

The weight lost by the produce of one acre in drying 5308 14 0

61 dr. of grass afford of nutritive matter 2.2 dr. ")

The produce of the space, ditto 8.0 1-2 j ^^^° ^ "" ^^"^ ^^ ^

LVL Hordeum pratense* Engl. Bot. 409. Host. G.
A. 1. t. S3. Meadow barley^grass. Nat. of
Britain.

At the time of flowering, the produce from a
brown loam, with manure, is

Grass, 12 oz. The produce per acre 130680 0 — 8167 8 0

80 dr. of gi-ass weigh when dry 32 dr.") ^

The produce of the space, ditto 67. 1 dr. 3 ^^^^^ 0 — o267 0 0

The weight lost by the produce of one acre in drying 4900 8 0

64 dr. of grass afford of nutritive matter 3.3 dr.">

The produce of the space, ditto ll.ldr..5 ^^^^ 0 — 478 9 0

LVII. Poa compressa. Engl. Be*. 365*

Flat-stalked meadow grass. Nat. of Britain.
At the time of flowering, the produce from a gravelly
soil, with manure, is

Grass, 5 oz. The produce per acre 54450 0 — 3403 2 0

80 dr. of grass weigh when dry 34 dr.l

The produce ofthe space, ditto 34 dr. 5 23141 4-1446 5 4

The weight lost by the produce of one acre in drying 1956 12 12

64 dr. of grass afford of nutritive matter 5 dr.l

The pradu<:e of tlie space, ditto 6. 1 3 ^^^^ ^^ "" ^^^ ^^ ^^

The specific characters of this species are much
the same as those ofthe Poa fertilise differing in the
compressed figure of the straws, and creeping root
only. If the produce was of magnitude, it would be
one of the most valuable grasses; for it produces foliage
early in the spring, and possesses strong nutritive
powers.

APPENDIX. xlvn

LVIIL Poaaquaiica. Curt. Lond. Engl. Bot. 1315.
Reed meadow grass. Nat. of Britain.

At the time of flowering, the produce from a strong

tenacious clay, is oz. or Ibs. per acre

Grass, 186 OS5. The produce per acre 2025540 —126596 4 0

80 dr. of ffrass weigh when dry 48 dr-l .

^. , ,.,, ,.^/ ___^_5- 1215324 — 75957 12 0

The produce of the space, ditto 1785.2 2-16 J

The weight lost by the produce of one acre in drying 50638 8 0

64 dr. of grass afford of nutritive matter 2.2 dr. o

The produce ofthe space, ditto 116.1 dr. V^^^^ —4945 2 10

LIX. Air a aquatica. Curt. Lond. Engl. Bot. 1557-
Water hair grass. Nat. of Britain.

At the time of flowering, the produce from water, Is

Grass, 16 oz. The produce per acre 174240 0 — 10890 0 0

80 dr. of grass weigh when dry 24 dr.-^

The produce of the space, ditto 76.3 1-16 j ^^^^^^ 0 — 3267 0 0

The weight lost by the produce of one acre in drying 7623 0 0

64 dr. of grass afford of nutritive matter 2. 1 dr. -^

The produce ofthe space, ditto 9 dr. j ^^^^ ^° "~ ^^^ 13 10

LX. Bromus crisiaius* Triticum cristatum, H. G.
j^L. 2. t. 24, Secale prostratum. Jacquin. Nat.
of Germany.

At the ticie of flowering, the produce from a clayey
16am, is

Grass, 13 oz. The produce per acre 141570 0 — 0848 0 0

80 dr. ofgras. weigh when dry 32 dr.-> ^^^^^ ^_^^^^ ^ ^
The produce ofthe space, ditto 83. 1 dr. J

The weight lost by the produce of one acre in drying 5308 14 0

64 dr. of grass afford of nutritive matter 2.2 dr. 7 '^45 10 C
The produce ofthe space, ditto 8.0 2-165

:Uviii APPENDIX.

LXI. Elymus Sibirlcus. Hort. K. I. P. 176. Cult.
1758, by Mr. P. Millar. Siberian lyme grass.
Nat. of Siberia.
At the time of flowering, the produce from a sandy
loam, with manure, is

oz. or lbs. per acre

Grass, 24 oz. The produce per acre 261360 0 — 16335 0 0
80 dr. of g-rissweigli wiieu dry 28 dr. "^

The produce of the space, ditto 134. 1 2-5 5 ^^^''^ ^ "~ ^'^^'^ ^ ^

The weight lost by the produce of one acre in drying 10617 12 0
64 dr. of grass afford of nutritive matter 2.1 dr. ^

Theproduceoflke space, ditto 13.2 d .5 ^^^^ ^ 511 7 0

LXII. Aira caspitosa. Host. G. A. 2. t. 42. Engl.
Bot. 1557. Turfy hair grass. Nat. of Britain,

At the time the seed is ripe, the produce from a
strong tenacious clay, is

Grass, 15 oz. The produce per acre 163350 6 — 10209 6 0

80 dr. of grass ^eigh when dry 26 dr. ^

The produce of tl.e space, ditto 135 1-5 5 ^^^^^ ^^"" ^^^^ ° ^^

The weight lost by the produce of one acre in drying 6891 5 4

64 dr. of grass afford of nutritive matter 2 dr. ^

The produce of the space, ditto 7.2 dr. ^ ^^^"^ ^^ " ^^^ ^ ^^

LXIII. Hordeum fiiurinum. Curt. Lond. Engl. Bot.
1971. Wall barley grass. Way Bennet.
Nat. of Britain.

At the time of flowering, the produce from a clayey
loam, is

Grass, 18 oz. The produce per acre 196020 0 — 12251 4 0

SO dr. of grass weigh when dry 28 dr. "^

The produce of the space, do 100.3 1-55 ^^^^^ 0 -. 4287 15 0

The weight l;:st by the produce of one acre in drying 7963 5 0

64 dr. of grass aflbrd of nutritive matter 3 dr. ^

The produce of the space, ditto 3.3 3-16 3 ^^^^ ^^ "" ^^^ '^ ^^

APPKNDIXc ^hx

LXIV. Jvena favescens. Curt. Lond. Engl. Bot.
952. Yellow oat-grass. Nat. of Britain.

At the time of flowering, the produce from a clayey

loam, IS oz. or lbs. per cie

Gr.ss, l2oz. The produce per acre 130680 0 --- 8l6r 8 0

80 dr. of i^rass weitch when dry 28 dr.7 „„ ^ .^ ,

•»h. ^ 1 f*, r.. ^^ , k 45738 0—2858 10 0

I ne produce or tlie space, ditlo 67. I J

The weight lost by the produce of one acre in di ying 5308 14 0

64 dr. of gr;iss afford of nutji-it i ve matier 3 3 dr. 7

The produce of .he space, ditto 11. 1 dr. S ^^^^ 0 — 478 9 0

At the time the seed is ripe, the produce is

Crass, 18 oz. The produce per acre 196020 U — 12251 4 0

80 d.'. of c•ra^s vveierli whsn dry 32 dr ^

i he piodiice of the sp.tce, ditto llo.O 4-3 )

The weiglitlo.st by the produce of one acre in ctrying- 7350 12 0

64 dr of CTa; suf}(>rd of nutritive matier 2 1 dr 1

•II 1 ^'.i •. m r 1 r 6!;91 5— 430 11 5

I lie produce or the space, utio lO. !j 1- J

Ti e weight of nutritive nutter which is lost if die crop be

left till fhe 81 ed be ripe, exct-edi g one-tenth part cf i.s

value - - 47 13 H

The proportional value which the grass at the
time the seed is ripe, bears to that at the time of flower-
ing, is as 9 to 15.

The produce of latter-math is

r.rasg, 6 oz. The produce per acre 65340 0 — 4083 12 0

64 dr. ot G 'ass afford of nutritve matter 1. dr. 1276 2— 79 12 2

The proportional value which the grass of the
latter-math, bears to that at the time of flowering, is
as 5 to \5'y and to that at the time the seed is ripe, as
5 to 9.

This species is pretty generally cultivated in many-
parts of this kingdom; and it appears from the above
details to be a valuable grass, though inferior to many
others,

g

iry

'J"] 269527 8 — 16845 7 8

L / ] APPENDIX,

LXV. Bromus sierilis. Engl. Bot. 1030. Host. G.
|l* 1. t. 16. Barren Brome grass Nat. of
Britain.
At the time of flowering, the produce from a sandy

soil is cz. or lb. ]i acre.

Grass, 44 '2. /^ he produce per acre 479160 0 — 29947 8 0

80 dr. ofgras weigh when dry 45 dr.

The produce of the space, ditt > 396

The weljjht lost by the produce of one acre in drying' 13102 0 8

64 fV, of g-'uss afford of nutritive matter 5 df .1

The produce of the space, ditto 55 dr. 5 ^^^^^ ^^ 2339 10 0

64>'dr, of the flowers afford of nutritive matter 2.2 dr.
The nutritive powers of the straws and leaves are^
therefore, more than twice as great as those of the
flowers. This species, being strictly annual, is of
comparatively little value. The above particulars
shew that it has very considerable nutritive powers,
more than its name would imply, if taken at the. time
of flowerings but if left till the seed be ripe, it is like
all other annuals comparatively of no value.
LXVI. Holcus vioIHs. Curt. Lond. Wither. B. 2. R
134. Creeping soft grass. Nat. of Britain.
At the time of flowering, the produce from a sandy
soil, is

Grass, 50 oz. The produce per acre 544500 0 — 34l31 4 0

80 dr. of ffrass weigh when dry 32 dr. "}

1 f., rJ ooni 5-217800 0—13612 8 0

1 lie produce oi the space, ditto o20 dr. J

The weight lost by the produce of or.e acre in drying 20418 12 0

61 dr. of grass afford (f nutritive matter 4.2 dr.-^ ^

The produce nfthesp^ce, ditto 56. 1 dr.j ^^^^^ 2—2392 13 2

At the time the seed is ripe, the produce is

Grass, 31 oz. The produce per acre 337590 0 — 21099 6 0

SO dr. of grass weigh when dry 32 dr. 7

The produce of the space, do 19S.1 3-5> ^^^^^^ 0.-8439 12 0

APPENDIX. ii"3f u

oz. or IBs. per acre
Tlie weiglit lost by the produce of one acre in drying 12669 10 0

f>4 (Ir. otcrrass alVortl ot nutritive matier 3.2 dr.->

„,, , r.,, v.* ^y,.o^f 1846115 — 115313 15

1 he produce of the space, ditto 27.0 2-53

The weight of nutritive matter which is lost by leaving the
crop till the seed be ripe, being- nearly one haf oDtJ^
vahie ^ "' 1238 15 3

64 dr. of the roots sfford of nutritive matter 5.2 dr.

The proportional value which the grass at the
time the seed is ripe, bears to that at the time of flower*
ing, is as 1 4 to 1 8.

The above details prove this grass to have merits
which, if compared with those of other species, rank
it with some of the best grasses. The small loss of
weight which it sustains in drying might be expected
from the nature of the substance of the grass; and the
loss of weight at each period is equal. The grass
affords the greatest quantity of nutritive matter when
in flower, which makes it rank as one of those best
adapted for hay.

LXVII. Poa feriiUs. Var. B. Host. G. A. The
species. Fertile meadow grass. Variety 1.
Nat. of Germany.

At the time of flowering, the produce from a brown
sandy loam, is

Grass, 23 oz. The produce per acre 250470 0 — 15654 6 0

80 dr. of grass weigh when dry 34 dr.Ti

Theproduceortlie space, ditto 156 2-53^^^^^^ 0^6653 8 0

The weight Inst by the produce of one acre in drying 9000 14 0

64 dr. of grass afford of nutritive matter 3 dr. ">

The produce ofthe space, ditto 17.1 dr. V^^^^ ^^"" ^'^^ ^^ ^^

At the time the seed is ripe, the produce is

Grass, 22 oz. The produce per acre 239580 0 — 14973 12 0

80 dr. of grass weigh when dry 44 dr. "^

The produce ofthe space, ditto 193.2dr.5 ^^'^^^ ^"" ^^^^ ^ ^

in APPENDIX.

oz, or \hs. per acre
1 l»e uelgbt lost by the produce of one acre in drying 6738 3 0

64 dr. of grass afTord of nutritive matter 5 dr. ^

rn 1 r*i J-.* o^oj f 18717 3 — 1169 13 3

The produce of the space, ditto 27. 2 dr. j

The weight of nutritive matter wh'ch is lost by taking the
crop at the time of flowering, exceeding one third part
ofitsv:aueis 436 1 3

The proportional value which the grass at the
time of flowering, bears to that at the time the seed is
ripe, is as 12 to 20.

The produce of latter-math is

Grass 7 oz. Iht product pi r iic e 76230 0 — 4764 6

64 dr. of grass afford otnurrviv> m itter, 1.2 dr. 1786 10— 111 10 10

The proportional value which the grass of the
latter-math, bears to that at the time of flowering, is
as 6 to 12j and to that at the time the seed is ripe, as
G to 20.

LXVIII. Cynosurtis erucaformis, Beckmannia erucse-
formis. Host. G. A. 3. t. 6.
Linear-spiked dog's-tail grass. Nat. of
Germany.
At the time the seed is ripe, the produce is

Grass, 18 oz. The produce pci ac e 196020 0 — 12251 4 0

89 dr. of grass weigh when dry 36 dr.

r.. r.. loooo^v ^8209 0 — 5513 1 0

The priiduce of the space, ditto 129. 2 2-5 3

1 he weightiest by the produce of one acre in drying 6738 3 0

64 «r of g. ass afford of nutritive matter 3.1 dr.^ ^^^^ 2—622 2 2
The produce of the- .space, ditto 14.2 2 43

LXIX. Phleum nodosum. W. B. 2. P. 118.

Bulbous stalked cat's-tail grass. Nat. of Bri-
tarn.
At the time of flowering, the produce from a clayey
loam, is

Grass, 18 oz. The produce per acre 196020 0-12251 4 0

APPENDIX. Liii

(DZ. or lbs. per acre

93109 8— 5819 5 S

€0 dr. of grass weljjli when t!ry 38 dr.

The produce of the Sfjact, ditto 136 4-5

The weight 1 st by the produce of one ac'e in drying 6431 14 8

64 dr. of c-rass aflbrd of nutritive matter 2.2 dr. }

1111 <7657 0—478 9 0
1 he pr diice of tht- sp-jc , ditto 11.1 dr. 3

This grass is inferior in many respects to the
Phleum pratense. It is sparingly found in meadows.
From the number of bulbs which grow out of the
straws, a greater portion of nutritive matter might
have been expected. This seems to prove, that these
bulbs do not form so valuable a part of the plant as
the joints, which are so conspicuous in the Phleum
fratense^ the nutritive powers of which exceed those of
the P, nodosum-y as 8 to 28.
LXX. Phleum pratense. Wither. 2. P. 1 1 ?•

Meadow cat's-tail grass. Nat. of Britain.
At the time of flowering, the produce from a clayey
loam, is

GrMs., 60 .z. The produce per acre 653400 0 — 40837 8 0

80 dr. of grass weigh when dry 34 dr.->

The produce of the space, ditto 408 dr. 5 ^^^^^^ ^ "" ^''^^^ ^^ ^

The weighi lost by the produce of one acre in drying 23481 9 0

64 dr. of grass afford of nutritive matter 2-2 <'r.

The pro<luc, of the space, ditto 37.2 dr. ^ ^^^^^ '^ ~" ^^^^ ^ ^

The weight of nutritive matter which is lost by leaving Uie

crop !ill the seei' b^ripe, excee lingone hnlfof it^'- v:.lue 2073 11 0

At the time the seed is ripe, the produce is

Gra.ss, bU 1)2. 1 he produce per acre 6534UU 0 — 40337 8 0

"■•?

The produce of the space, ditto 456 dr. 3

The weight lost by Ihe p oduce of one acre in drying 21439 11 0

64 dr of gi'ass afford of nut'"itive m.ttter 5.3 dr. )

The produce of the space, ditto 86.1 dr. 5 ^^'^^^ 14 — 3668 15 U

The latter-math produce is

Grass, 14 02. \ he pn^duce ptr acre 152460 0 — 9528 12 0

64dr.ofgrass afford of nutritive matter 2 dr. 4764 6— 297 12 6

80 dr. of grass weigh when dry 38 dr. ,

310365 0 — 19397 13 0

Liv APPENDIX.

64 dr. of the straws afford of nutritive matter 7 dr.
The nutritive powers of the straws simply, therefore,
exceed those of the leaves, in proportion as 28 to 8;
and the grass at the time of flowering, to that at the
time the seed is ripe, as 10 to 23; and the latter-math,
to the grass of the flowering crop as 8 to 10.

The comparative merits of this grass will appear,
from the above particulars, to be very great; to which
may be added the abundance of fine foliage that it
produces early in the spring. In this respect it is
inferior to the Poafertilis, and Poa anguesiifolia only.
The value of the straws at the time the seed is ripe,
exceeds that of the grass at the time of flowering, as
28 to 10; a circumstance which increases its value
above many others ; for, by this property, its valuable
early foliage may be cropped, to an advanced period of
the season without injury to the crop of hay, which, in.
other grasses which send forth their flowering straws
early in the season would cause a loss of nearly one
half of the value of the crop, as is clearly proved by
former examples ; and this property of the straws,
inakes the plant peculiarly valuable for the purpose of
hay.

LXXI. Phleum pratense, Var. minor. Wither. B.
2. 118. Var. 1. Meadow cat's-tail grass.
Var. Smaller. Nat of Britain.

At the time of ripening the seed, the produce from a

clayey loam, is oz. or .hs per acre

Grass, 40 oz. The produce per acre 435600 0 — 27225 0 0

80 dr. of crrass weigh when dry 34 dr "> ^ .„ »

1 .-., r.; o-ro 1 C 185130 0-11570 10 0

1 he produce ol the space, ditto 272 dr. J

APPENDIX. i.v

oz or lbs pei* acre

The \vel{^it lost by the produce of one acre in drying 15654 6 0

64 dr. of grass attbrd of nutritive mattei* 2.3 dr. 7 ^ i - i«5 >>

The produce of the space, ditto 272 dr.i ^^^^^ ^ "~ ^^^^ ^^ -^

The latter-math produce is

Crass, 14 oz. The produce per licre 152460 0—9528 12 0

64 dr. of grass jifford of nutritive matter 1 2. dr. 3573 4 — 223 5 4

LXXII. ElyniKs arenarius. Engl. Bot. 1672.

Upright sea lyme grass. Nat. of Britain.

At the time the seed is ripe, the produce from a
clayey loam, is

Grass, 64 oz. The produce per acre 696960 0 — 43560 0 0

HO dr. of grass Wtii^ii when dry 45 dr.">

The produce of U>esp»c.., ditto 570 dr. j 392040 0-24502 8 0

The weight lost by the produce of one acre in drying 1%9^'t 8 0

64 dr. of grass atlbrd of nutritive matter 5 dr. )

The produce of the space, ditto 80 dr. S ^'^'^^^ 0 — 3403 2 0

LXXIII. Elymus genicidatics. Pendulous lyme grass.
Engl. Bot. 1586. Pendulous sea lyme
grass. Nat. of England.

At the time of flowering, the produce from a sandy
soil, is

Grass, 30 oz. The produce per acre 326700 0 — 20418 12 0

80 di\ of grass weigh when dry 32 dr. ^

The produce of the space, ditto 192 dr. 5 ^^^^^^ 0—8167 8 0

The weight lost by the produce of one acre in drying 12251 4 0

64dr.of grass affordofnutritivematterS.l dr. ^

The produce of the space, ditto 24.1 1-2 dr. 5 ^^^^° ^ " '^^^^ ^^ ^

LXXIV, Bromus inermis. Host. G, A. 1. t. 9.

Awnless brome grass. Nat. of Germany.

Introduced by Mr. Hunneman in 1794.
At the time the seed is ripe, the produce from a
black sandy soil, is

GjKss, 18oz. The produce per acre 196020 0 — 12251 4 0

80 dr. of grHss weigh witen dry 25 dr. ^

I he prodjicfe of Mie s^act. ditto 126 dr. S ^^^'^^ ^^ "- ^^^^ ' ^ ^^

Lvi ' APPENDIX.

o^. or lbs. ])er acre.
The weig^iit lost by the produce of one acre in drying 6891 5 4

64 dr. of ;,^rass afford of nutritive matter 4. 1 dr. 7

The produce of the space, ditto X9.0 3-5 ]" ^^^^^ 15—813 8 15

The produce of iatter-math is

Grass, 13 (;z. I he vroduce per acu- A41570 0—8843 2 0

64 dr. f jjrassaifudor imi.itivc malter 1. 1 dr. 2765 0 — 172 13 0

LXXV. Agrostis vulgaris. Wither. Bot. 2, 132.
Hud. A. capilaris, Dr. Smith, A. arenaria.
Fine bent grass. Nat, of Britain.

At the time the seed is ripe, the produce from a
sandy soil, is

Grass, 14 uz. The produce per acre 152460 0—9528 12 0

80 dr. of crrass weie:h when dry 40 dr ")

.,,, , -.., ,.' ,,, f 76230 0 — 4764 6 0

I he produce ot the space, ditto 112 (ir.J

The weight lost by tlie produce of one j.cr- in drying 476 i 6 0

64 dr. of grass afford of nutritive matter 1.2 3-16 dr. >

The produce ofthe space, ditto 5.11-16 54019 15 — 2513 15

This is one of the most common of the bents,
likewise the earliest \ in these respects it is superior
to all others of the same family, but inferior to several
of them in produce, and the quantity of nutritive mat-
ter it affords. As the species of this family are
generally rejected by the cultivator on account of the
lateness of their flowering ; and this circumstance, as
has already been observed, does not always imply a
proportional lateness of foliage, their comparative
merits in this respect may be better seen, by bringing
them into one view, as to the value of their early
foliage.

APPENDIX. LYii

The apparent t'lfference of time. Their nutritive powers.

Jo-rostis vulgaris

Middle of April

1.2 3.4

palustris

One week later ,

2.3

stolonifera TvVo, ditto •

3.2

canina

Ditto, ditto

1.3

stricta

Ditto, ditto

1.2

nivea

Three weeks, ditto

2

littoralis

Ditto, ditto

3

repens

Ditto, ditto

3

mexicana

Ditto, ditto

2

fascicularis Ditto, ditto

2

LXXVI. Agrostis

palustris. Wither. Bot. 2, P. 129,

Var. 2, ;

alba. Engl. Bot. 1189.

A. alba.

Marsh bent grass.

At the time of flowering, the produce

from a bog

earth, is

oz.

or lbs. per acre

Grass, 15 oz. The prod

uce per acre 163350

6 — 10209 6 0

80 dr. of grass weigh when dry 36 dr."^

Theproduceofthe space, ditto ISOdr. V^^^'^ 8 — 4594 3 8

The weight lost by the produce of one acre in drying 5615 2 8

64 dr. of grass afford of nutritive matter 2. 3 dr.")

The produce of the space, ditto lO.1 1-43 ^^^^ ^^"^ ^^^ ^^ ^^

At the time the seed is ripe, the produce is

Grass, 20 oz. The produce per acre 217800 0 — 13612 8 0

80 dr. of grass weigh when dry 32 dr. "Ji

The produce of the space, ditto 128 dr. j

The weight lost by the produce of one acre in drying

87120 0 —

5445 0 0

Irying

8167 8 0

j 9358 9 —

584 14 9

64 dr. of grass afford of nutritive matter 2.3 dr.
The produce of the space, ditto 13.3 dr-

The weight of nutritive matter which is lost by taking the
crop at the time of flowering, being one fourth part of its

value - - 146 3 1\>

The proportional value of grass, in each crop is equal.

h

Lviii APPENDIX.

LXXVIL Fanicum dactylon. Engl. Bot. 850. Host.
G. A, 2, t. 18. Creeping Panic grass,
Nat. of Britain.

At the time of flowering, the produce from a sandy
loam, with manure is

oz or lbs per acre
Grass, 46 oz. The produce per acre 500940 0— 31308 12 0

80 dr. of grass weigh when dry 36 dr.">

The pioduce of the space, ditto S31.0 4-55 ^25423 0 - 14088 15 0

The v/eight lost by the produce of one acre in drying" 17219 13 0

64 dr. of grass afford of nutritive matter 2. dr. 1

The pro 'uce of the space, ditto 23. dr.J ^^^^^ ^~ ^^^^^ ^ ^

LXXVIII. Jgrostis siolonifera. Engl. Bot. 1532.

Wither. Bot. 2, 181. (Fiorin, Dr. Rich-
ardson.)
Creeping bent. Nat. of Britain.

At the time of flowering, the produce from a bog
soil, is

Grass, 26 oz. The produce per acre 283140 0—17^96 4 0

80 dr. of grass weigh when dry 35 dr. )

^M ^ 1 f.K v.. iRo^. C 127413 0-7963 5 0

The produce ui the space, ditto 182 dr. j

The weig:. lost by Ihe produce of one acre in drying 9732 15 0

64 dr. of grass afford of nut-itive matter 3.2 dr. )

^ ^ 15484 3 —967 12 3

■:\

The produce of tht space, ditto 22.3 dr,

At the time the seed is ripe, the produce is

Grass, 28 oz. The produce per acre 304920 0 — 19057 8 0

80 dr. of grass weigh when dry ^^ ^^-1,0-01/ n ft^-^ izi n

The produce of thw space, ditto 201.2 2-5 J ^'''^-^* 0-b5r5 li

The weight lost by the produce of one acre in drying 104S1 10 0

64 dr. of grass afford of nutritive matter 3.2 dr.-*

, c.u A',. CA c, y {-16675 0 — 1042 3 5

1 he produce ot the space, ditto 24. 2 dr.3

The weiglit. of nutritive matter whichis lost by taking the crop

at the time of flowering, being nearly one fourteenth of its

value . « ri 7 2

APPENDIX. ux

V

LXXIX, Agrostis stolonifera. Van angustifolia.
Creeping bent with narrow leaves.
Nat. of Britain.
At the time the seed is ripe, the produce from a
bog soil, is

oz. OP lbs. per acre

Grass, 24 oz. The produce per acre 261360 0 — 16335 0 0

80d^.ofg«s,wigI,^vhen^ry 36.1iv-> ^^ ^
The produce or ihe Space, ditto 172 3 1-53

The weight lost by the produce oi Oi-e Kcre in drying 8984 4 0

64 dr. of grass afFtird ofnutritivt matter 3. dr. >

The pro luce of th*; space, ditto 18 d- 5 ^^^^^ 4 — 765 11

The weight of nutritive matter afforded by the pro-
duce of one acre of the Agrostis stolo jera,
vexceeding that of the variety in proportion, is 6
to 8 . - - . 276 8 1

The above details will assist the farmer in deci-
ding on the comparative value of this grass From a
careful examination it will doubtkss appear to possess
merits well worthy of attention, though perhaps not
so great as has been supposed, if the natural place of
it« growth and habits be impartially taken into the ac-
count. From the couchant nature of this grass, it is
denominated couch-grass, by practical men, and from
the length of time that it retains the vital power, after
being taken out of the soil, is called squitch, quick, full
of life, &c.

LXXX. Agrostis canina, Engl. Bot. 1 S56.
Brown bent. Nat. of Britain.

At the time of flowering, the produce from a brown
sandy loam, is

Grass, 9 oz. The produce per acre 98010 0 — 6125 10 0

i^x APPENDI?v.

oz. or lbs. per acre.
80 dr. of grass weigh when dry 34 dr. }

The produce of the space, ditto 63 1-5 $ ^^^^^ ^ ~ 2688 5 0

The weight lost by the produce of one acre in drying 34.37 5 0

64 dr. of grass afford of nutritive matter 2.2 d' . ")
The produce of the space, ditto 5 211-2 ]" 3823 8 — 239 4 6

LXXXL Agrosiis canina. Var. muticae.

Awnless brown bent. Nat. of Britain.
At the time the seed is ripe, the produce from a
sandy soil, is

Gfrss, 21oz. The produce per acre 228690 0—14293 2 0
80 dr. of grass weigh when dry 24 dr. ^

The produce of the space, ditto 100.3 1-5 5 ^^^^'^ 0-4287 15 0

The welglit lost by the produce of one acre in drying ICOOo 3 0

64 dr. of grass afford of nutritive matter 1.3 dr. ^

The prorhice of fht- .<j. ce, ^titto 9.0 3-4 5 ^^^^ 3 — 390 '13 3

The weight of nutritive matter which the produce of
one acre of the awnless variety, exceeds that of
the last mentioned species - .5 8 11
LXXXIL Agrosiis stricta. Curt. A. rubra.
Upright bent grass. Nat. of Britain.
At the time the seed is ripe, the produce from a
bog soil, is

Grass, 11 oz. The produce per acre 119790 0 — 7486 14 0

80 dr. of griiss weigh when dfy 29 dr. ">

The produce of the space, do 63 4-5 dr. 5 /^^^23 14-2713 15 0

The weight lost by the produce of ono acre in drying 4772 15 0

64 dr. of grass afford of nutritive matter 1-2 dr. 1

The pr.'duce of the spacf, ditto 4.0 5-10 5 ^^^'^ 9 — 175 7 9

LXXXIIL Agrosiis nivera,

Snowey bent grass. Nat. of Britain.
At the time the seed is ripe, the produce from a
sandy soil, is

Grass, 7 oz. The produce per acre 76230 0 — 4764 6 0

^^5 10890 0—680 10 0

APPENDIX. Lxi

oz. or lbs. per acre

50 dr. of ffrass wei2:h wben dry 22 dr.->

Tu 1 r.u 1 onoic4 ^ 20963 4 — 1310 3 0

The produce of the space, do. 30.3 1-5 dr. 5

The weight lost by the produce of one acre in drying 3454 3 0

64 dr. of gTfiss afford of nutritive matter 2 dr."^

The nryiuc- of the space, ditto 3 1-2 dr S" 238:3—148 14 5

LXXXIV. Agrosiis fascicularis, Huds. Var.
canina. Curt. Tufted leaved bent.
Nat. of Britain.

At the time of flowering, the produce from a light
sandy soil, is

Gris;, 4 >z. The produce per acre 43560 0 — 2722 8 0

'80 dr. oi grass Wfij^'h wh.^i' dry 20 fir."

Tlie produce of the sp^ce, ditto 16 .

The weight lost by tlie produce of one acr<. in dying 2041 14 G

^64 dr. of grass afford of nutritive matter 2 dr. ">
tii^'^oducenfthe s-ace,ditt. ' ■ 2 dr;> 1S61 4 _ 85 1 4

LXXXV. Festuca pinnafa, Brotntis pinnatus.

Engl. Bot. 730.

Spiked fescue. Nat. of Britain.
At the time the seed is ripe, the produce from a
light sandy soil, with manure, is ''■ '

Grass, 30 jz. Tiie pro.uce per »cie 326700 i O — 20418 12 0

80 dr. of grass weigh when dl*y 32 dr. ? ; ' r :

The produce of the sface.diuo 192 dr. S '^°®^ ''-»^^'' « 0

The weight lost by the produce of one acre in drying 12251 4 0

64 dr. of j-^rass afford uf nutritive matier 1 1 (h\ ) '

The - drc. <.fth. sp^ , ditto 9 1,2-4 S ^^^^ ^^ " ^^^ ^^ ^^

LXXXVI. Panicupi viride. Curt. Lond. EngL
Bot. 675. Green panic grass. Nat. of
Britain.
At the time the seed is ripe, the produce from a

light sandy soil, is

Grass, 8 oz. The produce per acre 87120 0 — 5445 0 0

*xu APPENDIX.

oz. or lbs per acre

JlO dr. of grass weigh when dry 32 dr. ") ;

The produce of the space, ditto 51 1-5 3 ^^^^^ ° *~ ^^''^ ^ ^
The weight lost by the produce of one acre in drying 326r 0 •

64 dr. of grass afPrrd of nutritive matter 1.2 dr. >
The produce of ihc .-pace, duto 3 dr- 5 ^^^^ ^^ "~ ^^'^ ^ ^*

LXXXVII. Panicumsanquinale, Curt. Lond. Engl.
Bot. 849. Blood coloured panic grass.
Nat. ofBritain.^

At the time the seed is ripe, the produce from a
sandy soil, is

Grass, 10 oz The produce per acre 108900 0—6806 4 0

64 dr. of grass ff.rd of nutritive matter 10 2-16 1914 4— 1'9 10 4

This and the preceding species are strictly annu-
al, and from the results of this trial, their nutritive
powers appear to be very inconsiderable. The seed
of this species, Mr. .Schreber describes (in Beschrei-
bung der Graser) as the manna grass. In Poland,
Lithuania, &c. it is collected in great abundance, when
after being thoroughly separated from the husks, it is
fit for use. When boiled with milk, or wine, it forms
an extremely palatable food, and is most commonly
made use of whole, in manner of sago, to which it is in
general preferred.

LX XXVIII. Agrostis lobata. Curtis, lobtita et are-
naria. Lobed bent grass.

At the time of flowering, the produce from a sandy
soil, is

Grass, IC oz. The produce per acre 108900 0 — 6806 4 0

•«0 dr. ofgrass weigh when dry 40dr.-j ^^^^^ o~3403 2 0

The produce of the space, ditto 80 dr. 5

The weight lost by the produce of one ac^e in drying 3403 2 0

APPENDIX. Lxm

oz. or lbs. peracr*

64dr.ofgrassaflror.lornutntive*matter ^'^^■'? 5104 ll—ng

Thf produce of the spuce, ditto 7.2 dr. ^

LXXXIX. Agrostis repens. Wither. Bot. A. nigra.
Creeping rooted bent, black bent. Nat.
of Britain.
At the time of flowering, the produce from a clayey
loam, is

Grass, 9 oz. The pro luce per acre 98010 0 — 6125 10 0

.» dr. ofgrass weigh when dry 35dr,-> ,2879 6 - 26r9 15 6

The produce of the space, ditto 60 cli • j

The weight last by the produce of one acre in drying 5445 10 10

54 dr. of grass afford of nutritive matter odr. ">

The pr,jduce of ihe space, ditto 6.3 dr. 5 ^^"^^ 3 — 287 2 3

XC. Agrostis mexicana. Hort. Kew, I. P. 150.
Mexican bent grass. Nat of S. America. —
Introduced 178 , by M. G. Alexander.
At the time' of flowering, the produce from a

black sandy soil, is

Grass, 28 oz. I'he produce per acre 304920 0 — 19057 8 0

80 dr. of grass weigh when dry 28 dr..^

, c.u r./ i^Aoi^f 106722 0—6670 2 0

The produce of the space, ditto 156,3 loj * ^

The weight lost by the produce of one acre Ln drying 12387 6 0

64 dr. of grass afford of nutritive matter 2 dv. ")

The produce of the spce, ditto 14 d J ^^^^ 12 — 595 8 12

XCI. Stipa pemiata, Engl. Bot. 1356. Long-
awned feather grass. Nat. of Britain.

At the time of flowering the produce from a heath
soil, is

Grass, 14 oz. The produce per acre 152460 0 — 9528 12 0

80 dr. of grass weigh when dry 29 dr. > ^^266 12 - 3454 2 12.

The produce of the sptce, ditto 81 1-5 drJ

The weight lost by the produce of one acre in drying 6074 9 4

''^^^""'l 65510-409 7 0

Lxiv APPEMJDlX.

oz. or lbs. per acre
64 dr. of grass afford of nutritive matter • 2.3 dr.
The produce t;f thc'.^p^cr, ditlo 9.2

XCII. Tnticwn repens, Engl. Bot. 9>;9.

Creeping rooted wheat grass. Nat. of
Britain.
At the time of flowering, the produce from a light
clayey loam, is

Grass, 18 (z. Tiic produce per {;cre 196020 0—12251 4 0

80 dr. ..fF:ra>s weigh when dry 32 dr ) 78408 0-4900 8 0

The produce of the space (]itto 115 1-5 j

The weight lost by ihe pi-onuce of one acre in dryin,^ 7350 12 0

64 dr. of grass afford of nutritive matter 2 dr. ^ ^^^^^ ^q __ „g,, jo jq
The produce of ihe space ditto 9 dr. >

64 dr. of the roots, afford of nutritive matter 5.3 dr.

The proportional value of the roots, is therefore to

that of the grass, as 23 to 8.

XCIII. Alopecurus agrestis. Engl. Bot. 848.

A. myosuroides. Slender fox-tail grass. —
Nat of Britain. Curt. Lond.
At the time of flowering the produce from a

light sandy loam is

Grass, 12 oz. The pioduce per acre 130680 0 — 8167 8 0

80 dr. of grass Weigh when dry ^^'^^ l 5063S 8—3164 14 8

The produce of the space ditto 74. 1. 3-5 dr. )

€4 d'. of '. rass afford of nutritive matter 1.3 dr. p ^^^

„ , ,. ^ * ^ c '^^^'^ 4 — 223 5 4

The 'produce of the space ditto 5.1 dr, 3

XCIV. Bro7?2us asper. Engl Bot. 1172. Curt.

Lond. Bromus hirsutus. Huds. Bromus

ramosus. B. sylvaticus, volger. B. altissi-

~ mus. Hairy stalked brome grass. Nat. of

Britain.

At the time of flowering, the produce from a light

sandy soil, is

Grass, 20 oz. The produce per acre 217800 0 — 13612 8 0

APPENDIX. Lxv

80 dr. of grass weigh when dry 24 dr.-^

The produce of the space, ditto 96 dr. 5 ^^^^^ 0 — 4083 12 0

The weigiit lost by the produce of one acre in drying 9528 12 0

64 dr. of grass afford of nutritive matter 2 dr. 7

The J rodiic, of the space, ditto 10 dr..) ^^'^^ 4 — 425 6 4

XCV. Phalaris canariensis^ Engl. Bot. 1310.
Common canary grass. Nat. of Britain.
At the time of flowering, the produce from a clay-
ey loam, is

Grais, 80 oz. The produce per acre 871200 0 — 54450 0 0

80 dr. of grass weigh when dry 26 dr.-^

The produce ofthe space, ditto 416 di-.j ^^^^^^ 8—17697 9 8

The produce in weight lost by drying - - - 36752 6 6

64 dr. of grafts afford of nutritive matter 1.2 dr. ")

The p od.ce of ,.he space, ditto 30 dr./ 20418 12 -1876 2 12

XCVI. Melica cczrulea. Curt. Lond. Engl. Bot. 750
Purple melic grass. Nat. of Britain.
At the time of flowering, the produce from a light
sandy soil, is

Grass, 11 oz. The produce per acre

80 dr. of grass weigh when dry 30 dr.->

The produce of the space, ditto 66 dr. 3

The weight lost by the produce of one acre in drying

64 dr. of grass afford of nutritive matter 1.2 dr. ^

The produce of ihe space, ditto 4.0 2-4 S ^^^^ 8 — 172 4 8

XCVII. Dactylis cynosuroides, Linn. fil. fasci. 1, P. 17.

American cock's foot grass. Nat. of N.

America.
At the time of flowering, the produce from a clayey
loam, is

Grass, 102 oz. The produce per acre 111780 0 — 69423 1 0

80 dr. of grass weigh when dry ^^dr.^ggg^gg Q^^^g^^ ^ q

The produce of the space, ditto 979 1-5 dr. 3

The weight lost by tlie produce of one acre in drying 27769 8 0

64 dr. of grass afford of nutritive matter 1.3 dr. 7

The produce of the space, ditto 44,2 2.45^^^''" 0-1898 4

oz.

or

lbs. per acre

119790

0-

-7486

14

0

44921

4-

■- 2807

9

4

Irying

4679

4

2

hX\l

APPENDIX.

Of the Time intthich different Grasses pro-^
(luce Flowers and Seeds,

To decide positively the exact period or season,
when a grass always comes into flower, and perfects
its seed, will be found impracticable; for a variety of
circumstances interfere. Each species seems to pos-
sess a peculiar life in which various periods may be
distinctly marked, according to the varieties of its age,
of the seasons, soils, exposures, and mode of culture.

The following Table, which shews the time of
flowering, and the time of ripening the seed of those
grasses growing at Woburn, which are mentioned in
the Experiments, must, therefore, only be considered
as serving for a test of comparison, for the different
grasses, growing under the same circumstances.

Time

of 1

Time of ripening

Names.

flowering.

the seed.

Anihoxanthum odoratum

April

29

June

21

TIolcus odoratus

April

29

June

25

Cynosurus caeruleus

April

30

June

20

Alopecurus pratensis

May

20

June

24

A!opecuru8 alp'mus

May

20

June

34

Poa alpiiia

May

30

June

30

Poa pratensia

May

30

July

14

Toa caralea

May

30

July

14

Avena pubescens

June

13

July

8

Festuca Hordlformis

June

13

July

10

Poa trivial is

June

13

July

10

Festuca glauca

June

13

July

10

I'estuca glabra

June

16

July

10

Festuca rubra

June

20

July

10

Festuca ovina

June

24

July

10

Briza niedi^

June

24

July

10

Dactylis glomerata

June

24

July

14

Bromus tectorura

June

24

July

15

restucacanibiica

JuRe

28

July

15

Oromus diandrus

June

28

July

16

Vox angustifoUa

June

28

July

15

Avena elatior

June

28

July

l«

VoA elatior

June

28

July

16

Festuca duriuscula

July

1

July

20

Milium effusum

July

1

July

20

Festuca pratensis

July

1

July

20

Lolium (-erenne

July

1

July

20

APPENDIX.

Lxvri

Names.

Cynosurus cristatus
Avena pruensis
Bromus multiflorui
Festaca loliacea
Poa cristuta
Festuca myurus
Aira flexiiosa
Hordeuin bulbosum
Festuca calamaria
Bromus littoreus
Festuca elatior
Xardus stricta
Triticum, (species of)
Festuca Fluitans
Festuca dumetorum
Holcus lanatus
Poa fertilis
Arundo colorata
Poa (species of)
Cynosurus erucseformi*
Phleum nodosum
Phleuni pratense
Klymus arenariut
KJymus geniculatu*
Trit'oILuin pratense
Trifolimn macrorhizum
Sanguisorba canadensis
Buiiirts orientalis
Medicago sariva
Hedysarum onobrychU
Hordeum pratense
Poa conipresva
Poa aquatica
Bromus cristatus
Elymus sibircus.
Air.i caspitosa
AverjH flavescens
Bromus stcrilis
Holcus mollis
Bromus inermis
Agrostis vulgaris
Agrostis palusirif
Panicum dactylon
Agrostis stolonifera
Agrost s stolonifera (var.)
Agrostis canina
Agrostis stricta
Festjca pennata
Panicum viride
Pauicum sanguinale
Agrostis lobata
Agrostis repens
Agrostis fascicularit
Agrostis nivea
Triticura repens
Alopecurus agrettis
Bromus asper
Agrostis mexicona

Timt

;of

Time of

ripening

lowering.

the bed

July

6

July

28

July

ft

July

20

July

6

July

28

July

I

July

28

July

4

July

28

July

- «

July

28

July

6

July

28

July

10

July

28

July

10

July

28

July

12

Aug.

6

July

12

Aug.

6

July

12

Aug.

6

July

12

Aug

10

July

14

Aug.

13

July

14

July

20

July

14

July

26

July

14

July

28

July

Id

July

28

July

10

July

30

July

16

July

30

July

16

July

30

July

16

Jnly

30

July

15

July

30

July

18

July

30

July

18

July

30

July

18

July

30

July

13

July

30

July

18

July

30

July

18

Aug.

6

July

18

Aug.

•

July

20

Aug.

8

July

20

Aug.

n

July

20

Aug.

•

July

24

Aug.

10

July

24

Aug.

10

July

24

Aug.

10

July

24

Aug.

li

July

24

Aug.

20

July

^4

Aug.

20

July

24

Aug.

20

July

34

Aug.

20

July

28

Aug.

28

July

28

Aug.

28

July

28

Ang.

3S

July

28

Aug.

28

July

28

Aug.

28

July

28

Aug.

30

July

28

Aug,

30

Aug.

S

Aug.

If

Aug.

6

Aug.

20

Aug.

6

Aug.

20

Aug.

8

Aug.

25

Aug.

10

Aug.

30

Aug.

10

Aug.

30

Aug.

10

Aug.

30

Aug.

10

Sept.

•

Aug.

10

Sept.

10

Aug.

15

Sept.

25

LXVIII

APPENDIX.

Names.

Time of
flowering.

Time of ripening
the Seed.

Stipa pennata
Melica caerule*
rhalaris cananiensis
Dactylis cynosuroides*

Aug. 15
Aug. 20
Aug. 30
Aug, 30

Sept. 25
Sept. 30
Sept. 30
Oct. 20

Of the different Soils referred to in the
Appendix .

In books on agriculture and gardening much un-
certainty and confusion arises from the want of regu-'
lar definitions of the various soils, to distinquish them
specifically by the names generally used; thus the term
bog-earth, is almost constantly confounded with peat-
moss, and heath-soil; also the term ' light loam,'
* heavy soil,' &c. are given without distinguishing whe-
ther that be ' light' from sand, or this * heavy' from
clay. In minute experiments, it is doubtless of con-
sequence to be as explicit as possible in those parti-
culars. The following short descriptions of such
soils as are mentioned in the details of the experiment
are here given for the above purpose.

1st. By ' loam' is meant any of the earths com-
bined with decayed animal, or vegetable matter.

2nd. ' Clayey-loam' when the greatest propor-
tion is clay.

3rd. * Sandy- loam' when the greatest proportion
is sand.

* In the experiments made on the guantity of nutritive matter in the grasses,
tut at the time the seed Was ripe, the seeds were always separated: and the calcja-
lations for nutritive matter, as is evident from the details, made for grass and
not hay.

APPENDIX. Lxix

4th. * Brown-loam* when the greatest propor-
tion consists of decayed vegetable matter.

5th. ' Rich black loam' when sand, clay, ani-
mal and vegetable matters are combined in unequal
proportions, the clay greatly divided, being in the least
proportion, and the sand and vegetable matter in the
greatest.

The Terms ' light sandy soil,' ' light brown
loam/ &c. are varieties of the above, as expressed.

Lxx APPENDIX.

Observations on the chemical Composition of
the natriiive matter afforded by the gras-
ses in their different States, By the Edi-
tor.

I have made experiments on most of the soluble
products supposed to contain the nutritive matter of
the grasses, i)btained by Mr. Sinclair; and I have an-
alysed a few of them. Minute details on this subject
would be little interesting to the agriculturist, and
would occupy a considerable space; I shall therefore
content myself with mentioning some particular facts,
and some general conclusions, which may tend to elu-
cidate the inquiry respecting the fitness of the different
grasses for permanent pasture, or for alternation as
green crops with grain.

The only substances which I have detected in the
soluble matters procured from the grasses, are mucil-
age, sugar, bitter extract, a substance analogous to
albumen, and different saline matters. Some of the
products from the after-math crops gave feeble indica-
tions of the tanning principle.

The order in which these are nutritive has been
mentioned in the First Lecture, the albumen, sugar,
and mucilage, probably when cattle feed on grass or
hay, are for the most part retained in the body of the
animal; and the bitter principle, extract, saline mat-
ter, and tannin, when any exist, probably for the most
part are voided in the excrement, with the woody
fibre. The extractive matter obtained by boiling the
fresh dung of cows, is extremely similar in chemical

APPENDIX. hxxi

characters to that existing in the soluble products from
the grasses. And some extract, obtained by Mr. Sin-
clair, from the dung of sheep and of deer, which had
been feeding upon the Lolium perenne, Dactylis glom-
erata, and Trifolium repens, had qualities so anala-
gous to those of the extractive matters obtained from
the leaves of the grasses, that they might be mistaken
for each other. The extract of the dung, after being
kept for some weeks, had still the odour of hay. Sus-
pecting that some undigested grass might have remain-
ed in the dung, which might have furnished mucilage
and sugar, as well as bitter extract, I examined the
soluble matter very carefully for these substances. It
did not yield an atom of sugar, and scarcely a sensible
quantity of mucilage.

Mr. Sinclair, in comparing the quantities of solu-
ble matter afforded by the mixed leaves of the Lolium
perenne, Dactylis glomerata, and Trifolium repens,
and that obtained from the dung of cattle fed upon
them, found their relative proportions as 50 to 13.

It appears probable from these facts, that the bit«
ier extract, though soluble in a large quantity of wa-
ter, is very little nutritive; but probably it serves the
purpose of preventing, to a certain extent, the fermen-
tation of the other vegetable matters, or in modifying
or assisting the function of digestion, and may thus
be of considerable use in forming a constituent part
of the food of cattle. A small quantity of bitter
extract and saline matter is probably all that is needed,
and beyond this quantity the soluble matters must be
more nutritive in proportion as they contain more al-

Lxxii APPENDIX.

bumen, sugar, and mucilage, and less nutritive in pro-
portion, as they contain other substances.

In comparing the composition of the soluble pro-
ducts afforded by different crops from the same grass,
I found, in all the trials I made, the largest quantity
of truly nutritive matter, in the crop cut when the seed
was ripe, and least bitter extract and saline matter;
most extract and saline matter in the autumnal cropj
and most saccharine matter, in proportion to the other
ingredients . in the crop cut at the time of flowering.
I shall give one instance:

lOO parts of the soluble matter obtained from
the Dactylis glomerata, cut in flower, afforded
of sugar - - - - 18 parts
of mucilage - - - 67

of coloured extract, and saline matters,
with some matter rendered insoluble by
evaporation - - - 15

100 parts of the soluble matter from the
seed crop afforded

Sugar 9 parts

Mucilage , - - - 85

Extract, insoluble, and saline matter 6
100 parts of soluble matter from the after-math
crop give

of sugar - - - - 11 parts

of mucilage ... 59

of extract, insoluble, and saline matters 30
The greater proportion of leaves in the spring,
and particularly in the late autumnal crop, accounts
for the difference in the quantity of extract; and the

APPENDIX. Lxxiii

inferiority of the comparative quantity of sugar in the
summer crop, probably depends upon the agency of
light, which tends always in plants to convert sacchar-
ine matter into mucilage or starch.

Amongst the soluble matters afforded by the
different grasses, that of the Elymus arenarius was re-
markable for the quantity of saccharine matter it con-
tained, amounting to more than one third of its weight.
The soluble matters from the different species of Fes-
tuca, in general afford more bitter extractive matter
than those from the different species of Poa. The
nutritive matter from the seed crop of the Poa com-
pressa was almost pure mucilage. The soluble mat-
ter of the seed crop of Phleum pratense, or meadow
cat's-tail, afforded more sugar than any of the Poa or
Festuca species.

The soluble parts of the seed crop of the Holcus
mollis and Holcus lanatus contained no bitter extract,
and consisted entirely of mucilage and sugar. Those
of the Holcus odoratus afforded bitter extract, and a
peculiar substance having an acrid taste, more soluble
in alcohol than in water. All the soluble extracts of
those grasses that are most liked by cattle, have either
a saline or subacid taste 5 that of the Holcus lanatus,
is similar in taste to gum arabic. Probably the Holcus
lanatus which is so common a grass in meadows, might
be made palatable to cattle by being sprinkled over
with salt.

I have found no differences in the nutritive pro^
duce of the crops of the different grasses cut at the same
season, which would render it possible to establish a

K

L\xi7 APPENDIX.

scale of their nutritive powers j but probably the soluble
matters of the after-math crop are always from one sixth
to one third less nutritive than those from the flower
or seed crop. In the after-math the extractive and
saline matters are certainly usually in excess; but the
after-math hay mixed with summer hay, particularly
that in which the fox-tail and soft grasses are abun-
dant, would procure an excellent food.

Of the clovers, the soluble matter from the
Dutch clover contains most mucilage, and most matter
analogous to albumen: all the clovers contain more bit-
ter extract and saline matter than the common proper
grasses. When pure clover is to be mixed as fodder,
it should be with summer hay, rather than after-math
hay*

INDEX.

Acids, account of those found
in vegetables, 96.

Age of trees, by what limited,
225.

Alcohol, theory of its forma-
tion, 119.

Alburnum, uses of, 54, 225.

Alkalies, method of ascertain-
ing their presence in plants,
99.

effects produced by, in
vegetation, 17

Animal substances, their com-
position, &c. 245.

—decomposition of, 244.

Atmosphere, nature and con-
stitution of, 183.

Animal matter, mode of ascer-
taining its existence in soils,
148.

Bark, its office and uses, 51,

211.
Barks, their relative value for

tanning skin, 8 i .
Blight in corn, its cause, 236.
Bread, its manufacture, theory

of its production, 123.
Burning, its use in improving

soils, 309.

Canker in trees, probable mode
of curing, 234.

Carbonic acid, a part of the at-
mosphere, 186,

—necessary to vegetation,
197.

Cements, on those obtained

from limestone, 290.
Chemistry, its application to

agriculture, 5.
importance in ag-
ricultural pursuits, 23.
Combustibles, simple, referred

to, 40.
Combustion, supporters of,

mentioned 39.
Courses of crops, particular

ones recommended, 319.
Corn, its tillering, theory of

this operation, 207.

Diseases of Plants, their causes
discussed, 233.

Earths, on those found in
plants, 101.

Electricity, its influence on ve-
getation, 37.

Elements chemical, of bodies,
40.

laws of their com-

binations, 46.
Excrements, use of as ma-
nures, 261.

Fairy rings, their causes, 319.
Fallowing, theory of, 21,315.
Fermentation, phenomena of,

118.
Fly-turnip, plan for destroying

or preventing, 195.
Flowers, their parts and office^

61,

INDEX.

Geology, referred to as teach-
inj^ the nature of rocks, 170»

Grafting, general views on tliis
process, 226.

Grasses, on those fit for pas-
ture, 322.

Gravitation, its effects on
plants, 29.

Green crops recommended,
317.

Gypsum, its use as a manure,
293.

Heat, its effects on vegetables,
34, 158.

Husbandry drill, its advan-
tages, 317.

Ice, its anti-putrescent pow-
ers, 248.

Irrigation, theory of its effects,
313.

Irritability, vegetable, its exis-
tence doubted, 216.

Land, causes of its fertility,

179.

barrenness 180.

Leaves, their functions, 58.
Light, its effect on vegetation,

197,
Limestone, its nature and uses,

19,281.

' action in the «oil, 19.

— ■ mode of burning,

293.
magnesian, its peculiar

properties, 2!, 287.
Lime, mode of ascertaining

the quantity in limestones

and soils, 147.
~ — salts of, on the mode of

detecting them in soils, 152,

Manures on their applications,
239.

■ how taken into the ve-
getable system, 240.

Manures, fermentation of, 6,

269.
in what state to Wc

used, ';69.

animal, 261.

mineral, 285.

vegetable, 249.

saline, 260, 279.

Malting, theory of the process

of, 192.
Matter, powers of discussed,

28.
Metals, account of, 42.
INIetallic oxides, those found

in plants. 104.
Mildew, caube of, 236.
Meat, method of preserving it,

248.

Oils, fiiied, their nature and

production, 92.
Oxygene, its presence in the

atmosphere, and uses, 188.
necessary to germina-

tion, 179,206.

Paring and burning, theory of
their operation, 309.

Pasture, where advantageous,
322.

Plants, organization of, 50,123.

Plants, parasitical, described as
the cause of disease in corn,
234.

Peat mosses, on their forma-
tion, 169.

on their improve-

ment- 181.

Putrefaction, methods of pre-
venting, 248.

Pith, nature of, 56.

Plants, parts of, 50.

Quicklime, injurious to soils,

283,

Rocks, their number and ar-
rangement, 171.

INDEX.

Kocksj those from which soils
are derived, or oh which
they rest, 175.

Sap, cause of its ascent discus-
sed, 211.
course of 8, 209.

— its composition discus-
sed, 131.

Salts their uses as manure,

261,279.
■ on such as are found in

vegetables, 102.
on those found in soils,

account of, 139.
Seeds, on those produced by

crossing, 229.

germination of, 1 89.

their nature and uses, 63.

Simple substances described,

40.
Soils, properties of, 157, 142.
composition of, 136, 154.

— method of analysing, 140.

formation of, <66.

their constituent parts,

136.

improvement of, 181.

their classification, 178.

Subsoils, varieties of, and their
effects, 166.

Soot, properties of as a ma-
nure, 274.

Sugar, mode of refining, 71,

Tanning principle, its applica-
tion to tanning, 79.

— quantity in differ-
ent barks, 80.

artificial, 83.

Temperature of soils discus-
sed, 158.

Trees, habits of, discussed,
232.

cause of their decay,

225.

Trees, age of, 226.

Urine, its use as a manure,

261.

Vegetables, their chemical
composition, 67.

improvement of, by cul-

tivation, 228.

renovation of the at-

mosphere, 203.

the causes of their

growth discussed, 220.

Vegetable matter, mode of as-
certaining its quantity in
soils, 148.

its analysis, 107.

decomposition of,

described, 244.

principles, their ar-

rangement in plants, 123.
Vegetable life, phasnomena of,
discussed, 219.

matter, decomposition

of, 242.

Vegetation, influenced by gra-
vitation, 29.

influence of light in,

208.

302.

progress of, 195,
its effect on a soil,

18.

Veins or mines, their situa-
tions, 174.

Water, absorption of by soils,
161.

its state in the atmos-
phere, 186

Wheat, transplantation of, 208.

crossing of, 228.

Wines, theory of their forma-
tion, 119.

~ quantity of spirits they

contain, 121.

INDEX TO THE APPENDIX.

Jgrostia canina^ brown bent,

lix.
canma var, mutica)

awnless brown bent, Ix.

fascicularisj tufted-lea-

ved bent, Ixi.

i.bata^ lobcd bent

grass, Ixii.
mexicanay

mexican

bent grass, Ixiii.

niveciy snowy bent

grass, Ixvi.

Jialustrisy March bent

grass, Ivii.
re/iens, creeping root-
ed bent, Ixiii. ^

s'ricta, upright bent

grass? Ix.

ii. stolonJfcra, fjorin creep-

ing bent, Iviii.

stolonlfera var. an^us-

tifolla^ creeping bent narrow
leaves, lix.

vulgaris^ fine bent

grass, Ivi
AL7-a aquatica, water hair grass,

xlvii.
c^es/ntosa, turfy hair grass

xlviii.
— — JlexuosUy waved moun-
tain hair grass, xxxv.
Mojiecurus agrusth; slender

fox-tail grass, Ixiv.
' aljiinus, alpine fox

tail grass, x.
. . /t7'a;^ns/*, meadow

fox- tail grass, viii.
A iihoxanthum odoratum^ sweet

scented vernal grass, v.
Arimd:' colorataf striped-leaved

reed grass, xli.
Avena e-aiior, tall oat grass,

XXV.

Jlavescensy yellow oat

grass, xlix.

firatensisy meadow oat

grass, xxxu.

fiubescens^ downy oat

grass, X.

Briza mediay quaking grass,

XX.

Brojuus asfier^ Ixiv.

cristatua^ xlvii.

diandruy xxiii.

erectusf upright peren-
nial brome grass, xxvii.

inernisy awniess brome

grass, Iv.

Uttoreusi sea side

brome grass, xxxvii.

multijiorusy many

flowering bronxe grass, xxxii.
tectorum^ nodding pan-

nicled brome grass, xxii.

stcriiisy barren brome

grass, 1.
Bunias orientalise xlii.

Cynosurus c<eruleuSf blue moor

gras^, vii.
Cynosurus cristatus, crested

dog's-tail grass, xxxi.
— . erucxformisy linear

spiked dog's-tail grass, lii.

Dactylis cynosuroidesy Ameri-
can cock's foot grass, Ixv.

glotnerata, round-head-
ed cock's foot grass, xxi.

Elymus arenarius, upright sea

lyme grass, Iv.
geniculatusy pendulous

sea lyme grass, Iv. •

INDEX.

Jilymus sibericusf Siberian
lyme grass, xlviii.

Festuca ca/amaria, reed-like

fescue grass, xxxv.
• cambrica^ xxii.
duriuscula^ hard fescue

grass, xxvi.

duDieiorwri) pubescent

fescue grass, xl.

e iatior yimW fescue grass

XXXVlll.

— — Jluitansi floating fes-
cue grass, xxxix.

glabra^ smooth fescue

grass, xvi.

glauca^ glaucares fes-
cue grass, XV.

/i or dif or ?nis ^barley like

fescue grass, xiii.
loliacea, spiked fescue

wall fescue

grass, xxxui.

myurus,

grass, xxxiv.

o-uway sheeps* fescue

grass, XIX.

ficnnatay spiked fescue

grass, Ixi,

: firatensis^ meadow fes-

cue grass, xxviii.

. — rubra, purple fescue

grass, xviii.

Hedyaarum onobrychisy sain-
foin, xlv.

Hordeujn bulbosuniy bulbous
barley grass, xxxv.

marinuTTif wall barley

grass, xlviii.

firatensey meadow bar-

ley grass, xlvi.
Holcus lanatus, meadow soft
grass, xl.

— mollisy creeping soft
grass, 1.

odoratus, sweet-scent-

ed soft grass, yi.

Lolium fierenney perennial rye
grass, xxix.

Medicago safivOy lucerne, xlv.

Melica caruleuy purple malic
grass, Ixv.

Milium effuswny common mil-
let grass, xxviii.

Mirdum strictay upright mat
grass, xxxix.

creepmg

Panicum dactylony
panic grass, Iviii.

sanguinale, blood-co-

loured panic grass, Ixii.

viridey green panic

grass, Ixi.

Phalaris cananiensis, common
canary grass, Ixv.

Pltleum nodosum, bulbous-
stalked cat*s-tail grass, Hi.

jiratense, meadow

cat's-tail grass, liii.

var^ minor^ meadow

cat*s-tail grass, var» smaller,
liv.

Poa alfiinay alpine meadow-
grass, X.

— — — angustifoliay narrow-
leaved meadow grass xxiii.'

aquaticQy reed meadow

grass, xlvii.

caruleuy v.fi. firatense.

short bluish meadow grass,
xiii.

comfir essay flat-stalked

meadow grass, xlvi.

cristata, crested mea-

dow grass, xxxiv.
datiory tall m^eadow

grass, xxvi.
— fertilisy fertile meadow

grass, xli.
x,cr, 6. fertile

meadow grass, var. I, li.

maritima^ sea meadow

grass, XXX,

INDEX.

Poa firaiensisi smooth-

stalked meadow grass, xii.

trivialisy roughish mea-
dow grass, xiv.

Fotirimn sanguisorba, burnet,
xxxvii.

Stifia fiennatQy long armed fea-
ther grass, Ixiii.

Trifolium macrorhizum^ long
rooted clover, xxxviii.

firatenscy broad lea-
ved cultivated clover, xlii.

refiensy white clover,

Ixiii.

Triticum refiens^ creeping root-
ed wheat grass, Ixiv.

sfi^ wheat grass,

xxxix.

FINr

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