THE LIBRARY

OF

THE UNIVERSITY
OF CALIFORNIA

LOS ANGELES

THE

PRINCIPLES

O F

AND

VEGETATION.

By FRANCIS HOME, M. D.

Feljow of the Royal College of Phyficians in Edinburgh.
The THIRD E D I T I O N, with Additions.

LONDON:

Printed for A. MILLAR in the Strand,

And A. KINCAID and J. BELL, at Edinburgh.

MDCCLXIL

T A

T H E f/75/b

DESIGN."

TH E Edinburgh fociety, eftablifhed in
the year 1755, for the improvement
of arts and manufactures, named, amongft
other articles, the following :

For the beft differ tation on vegetation and the
principles of agriculture, a gold medal.

IN order to promote fo ufeful an infti-
tution, the following papers were compofed,
and delivered in to the fociety, according
to the rules laid down. The judges named
for that article, determined, on a competi-
tion, in their favour. Some few additions
have been made to them fince they were
given in to the fociety.

IN fo neceflary an art, where the terms

are inaccurate, confufed, and differ fo much

in different counties, to fix thefe terms,

A 2 and

- '"000835

[iv]

and afcertain their meaning; where there
is nothing fyftematic, to lay down a regular
planj where the different parts are gene-
rally looked on as complete, to mark the
deficiencies, and mow that there is much
wanted 5 where the means of improvement
are unknown or neglected, to point out
the only road that can lead with certainty
to it 5 where there are few experiments to
build on, to relate fome, and on thefe to
lay a foundation for more; where the
reafonings are, in general, fo very unphi-
lofophical, to fettle fome fund for difcourfe
and argument; where the proper helps
have not been called in, to make ufe of
thefe, and introduce a new fcience to the
affiftance of this art ; in fhort, where there
is but little afcertained, to fix fome general
principles on which the artift may depend :
this is the defign of the following papers.
That no more has been done, will be
moft readily excufed by thofe who are beft
acquainted with the difficulty of the un-
dertaking.

A

A PLAN of the whole.
PART I.

SECT. I.

Caufes of the Jkia progrefs of agriculture j
connection of chymiflry 'with it 5 and divi-
fan of the fubjecJ.

SECT. II.

Of different foils.

SECT. III.

Of the rich black foiL

SECT. IV.

Of the clay foil.

SECT. V.

Of the fandy foil.

SECT. VI.

Of the chalky foil.

SECT. VII.

Of till.

SECT.

f vi J

SECT. VIII.

Of the mojfy foil.

SECT. I.

ffle natural methods of providing vegetable
food.

SECT. II.

Of manures, or the artificial methods of pro-
viding vegetable food.

SECT. III.

Of marl.

SECT. IV.

Of unburnt calcaricus bodies , and quick-lime.

SECT. V.

Of vegetables in an entire and in a corrupted
Jlate, and of dunghills.

SECT. VI.

Of manures which arife from burning ve-
getables.

SECT.

SECT. VII.

Of animal manures.

PART III.

SECT. I.

effects of different fubjtances with regard
to vegetation.

SECT. II.

Of the food of vegetables.

PART IV.

SECT. I.
Of opening and pufoerifing the foil.

SECT. II.

Efe&s of the atmofphere*

SECT. III.

Change offpecies.

SECT IV.

Of ploughing.

SECT.

[ viil ]

SECT. V.

Of compojls.

SECT. VI.

Of vegetation.

PART v,

SECT. I.

Of weeds.

.SECT. II.

Of a wet foil.
SECT. III.

. Of rains.

SECT. IV.

Of faulty feeds.

SECT. v.

Difeafes of plants.
SECT. VI.

Plan for the further improvement of agri-
culture.

THE

THE

PRINCIPLES

O F

Agriculture and Vegetation,
PART I.

SECTION I.

Caufes of the Jlow progrefs of agriculture ;
connexion of chymiftry with it-, and divi*
fan of the fubjett.

AGRICULTURE, though the
moft necefTary, has been, per-
haps, the moft neglected of all
the arts. Every other art has undergone
confiderable improvements in this and the
laft century; but we cannot affirm the
fame of agriculture. It feems to be little
better underftood in 'Europe at prefent,
B than

2 the Principles- of Part X.

than amongft the anrients; and I believe
Virgil and Columella may ftill be reckoned
the bell authors on that fubject. Does this
proceed from the earth lofmg, like a mo-
ther, her fertility, becaufe of her age ? as
Ibrae of the antients alledged : or does it
arife from an impoffibility of reducing the
culture of the ground to a regular art, as
the effects of that culture depend more on
chance than fettled principles ? Daily
experience mows, that none of thefe can
be the cafe:, for the earth, though ex-
haufted, attains again, under proper ma-
nagement, a great degree of fertility ; and
the regularity with which affairs are con-
ducted, fhows,, that it is in fome meafure-
akeady reduced to an art

THE flow progrefs of hufbandry may
be accounted for from more obvious rea-
fons. This art is, in general^ carried on by
thofe whole minds have never been im-
proved by fcience, taught to make obfer-
vatious, or draw conclufions, in order to

attain

Seel. I. Agriculture and Vegetation. J

attain the truth ; or by thofe who, although
Nature has been very bountiful, cannot
carry their fchemes into execution, from
the narrownefs of their fortunes. The
former can never know more than what
they have learned from their fathers; the
latter dare rifk nothing, as their daily bread
depends on the certainty of fuccefs. What
can be expected from that clafs ?

LET us fuppofe the fortune eafy, and
the judgment improved, the difficulty of
the art itfelf is fufficient to retard its pro-
grefs. How delicate the circumftances that
muft attend each experiment! What a
number of different obfervations on heat
and cold, dry and wet, difference of foils,
grains, feafons, &c. muft be exactly made,
before one can be certain of the general
fuccefs of an experiment ! What a dif-
agreement from a fmall difference in one of
thefe circumftances ! How feldom can thefe
experiments be repeated, which take a
whole year before they can be brought to
B 2 a

4 Tfo Principles of Part I.

a conclufion ! how unequal for fuch a talk
are the few years of judgment and activity
we enjoy ! How liable are obfervations to
die with the obferver when not made public !
and how averfe is human pride to do it,
unlefs it could erect a fyitem ! Agriculture,
feemingly fo eafy, appears, from the fcarcity
of good authors, to be the mofl difficult of
all arts.

BUT thefe are not the only obftacles
that hufbandry has met with. It has yet
had a greater to ftruggle with. It does not,
like moft arts, lead to an account of itfelf;
or depend on principles which its practice
can teach. Something beyond this art is
necefiary to the knowledge of the art itfelf.
The principles of all external arts mud be
deduced from mechanics or chymiftry, or
both together. Agriculture is in the lafl
clafs j and though it depends very much on
the powers of machinery, yet I'll venture
to affirm, that it has a greater dependence
on chymiftry. Without a knowledge in

the

Sect. I. Agriculture and Vegetation. 'r

the latter fcience, its principles can never
be fettled. As this fcience is but of late
invention, and has not yet been cultivated
with that regard to utility, and the im-
provement of trades and manufactures, as
it ought and might, agriculture is hardly
feniible of its dependence on it. The de-
fign of the following flieets is to make this
appear ; and to try how far chymiftry
will go in fettling the principles of agricul-
ture.

I don't intend in the following remarks
to fettle fads, or teach the practical part of
farming. That I leave to farmers. My
defign is only to fketch out the great out-
lines of this art, and fhow, that it is ca-
pable of being reduced, like others, to a
regular fyftem. If in this way we can fix
fome fettled principles from the facts which
are already afcertained, thofe who apply to
practice will find their benefit in it. The
juft theory of an art leads directly to its im-
provement, as it leads to thofe experiments
B 3 which

6 T^be Principles of Part I.

which yet remain to be tried. Without
this guide we may Humble on truths by
accident ; but when led by it, we have the
fecret fatisfaction of thinking, that we are
indebted to ourfelves for the happy ilTue of
the experiment.

LET us try to find ibme fixed point
from which we may have a full view of
this extenfive art, and from which we may
proceed, in a methodical manner, to the
divifion of our fubjec~t. All organized
bodies receive their increafe from the recep-
tion and application of certain particles,
which are defigned by the Author of na*
ture for their nourishment. Without thefe
nutritive particles there could be no in-
creafe. As plants belong to the clafs of
organized bodies, they thrive in proportion
to the quantity of nourishment they receive
at their roots. Hence arifes a fimple, but
very comprehenfive, view of hulbandry.
The whole of the art feems to centre in this
point, viz. nourHhing of plants.

BUT

Sect. I. Agriculture and Vegetation. j

BUT how can the farmer understand
the art of nourishing plants, unlefs he
knows the nature and qualities of each kind
of foil, whether it be proper or improper
for that office ; unlefs he can provide fuit-
able food for the nourishment of plants,
and difcovers what that food is -, unlefs he
affifts the plants in reaching and acquiring
that food, by rendering the foil loofe and
open ; unlefs he knows, and endeavours to
remove, Ib far as lies in his power, all im-
pediments to this nourishment ? Thefe are
the great outlines of agriculture. In fol-
lowing thefe, then, we (hall divide our fub-
jedl: into five parts. i. The nature and
qualities of different foils. 2. The nature
and qualities of the different compofls.
3. Their manner of adling. 4. The diffe-
rent methods of opening the foil. 5. The
impediments to vegetation, and their cure*

THE operations of bodies are to be ac-
counted for only from their known qualities
afcertained by experiment. Reafoning on
i 84 any

8 - The Principles of Part 1.

any other plan, can never certainly lead to
truth. I mall not, therefore, proceed a
fingle ftep without fact and experiments;
and when I am not fupplied with them
from others, mail endeavour to make them
rnyfelf. It is laborious, but it is necelTary.

SECT. II.

Of different foils.

AS the earth is the matrix to which
all feeds are committed, and from
which all vegetables take the whole, or at
leaft the greateft part of their nou'rim-
ment, it is proper to begin with an exami-
nation of it. As it nourifhes plants with-
out the affiftance of art, it mufl contain
the food of plants. If we can difcover
what is the natural food of vegetables, we
fhall the eafier difcover wherein confifts
their artificial food, or that given by art,
and how it operates.

EARTHS

Sect. II. Agriculture and Vegetation. 9

EARTHS are found to differ very much
from one another in their qualities ; far-
mers have therefore divided them into fe-
veral different kinds, and perhaps have
run into too minute divifions. It is dif-
ficult indeed to fettle the exact limits be-
twixt the different foils -, but fuch difficulty
we find in all the divifions of natural bo-
dies. The Author of nature has connect-
ed different bodies by intermediate ones;
he has chpfen to act by different grada--
tions, and not by ftarts, that nature may
appear one connected whole. The great
divifion, or the fpecific difference of earths,
may be reduced to thefe fix, viz. rich
black foil, commonly called loam or ha/ley
foil} clay ; fandy j moffy -, chalky ; and till.

WHEN farmers treat of thefe foils, they
generally diftinguifh them from one an-
other by the colour, or fome other fuper-
ficial quality, which immediately (hikes
the fenfes. But colour can never lead to
the compofition or principles of bodies, on

which

io The Principles of PartL

which alone their effects depend. Such
fuperficial qualities as that, depend them-
felves on the conftituent parts of bodies.
We mall then endeavour, by experiment,
to detecl: the conftituent parts of thefe dif-
ferent foils, and (how wherein they differ
from one another.

SECT. III.

Of the rick black foil.

1 Begin with this foil, as it is found to
contain the greateft quantity of vege-
table food, and as all other foils arc richer
or poorer in proportion as they contain
more or lefs of this.

THIS foil, when frefh dug up, and
fufficiently moift, has a very agreeable
fmell, which is not felt when it is too dry
.or too wet. We are very fenfible of an
agreeable fmell in the fields after a gentle
Shower of rain, efpecially if a drought has

preceded.

Sed. III. Agriculture and Vegetation. 1 1

preceded. This we attribute to the efflu-
via of the plants : but it belongs to the
earth, as it is to be felt every where, and
ilronger the nearer the nofe approaches
the ground. This is probably owing to
the volatile falts and oils, which rife toge-
ther, in greater plenty, as the natural fer-
mentation of the earth is increafed by a
« *

due proportion of moifture.

i/. tf •

To crumble when dug up, is a quality
peculiar to this foil. In this it differs very
much from the clay and fandy foil. The
former does not feparatej the latter falls
into a powder like fand ; but this feparates
into fmall bits. It feems to enjoy that de-
gree of cohefion which is fitteft for fup—
porting vegetables, and ;at the fame time
allowing their fibres to fpread in fearch tif
their food. The particles of this foil
feem to be in a continual tendency to re-
cede from one another j for it is obferved,
that when dug up, and expofed to the air,
the hole from which it was taken, will not

again

1 % ^Ls Principles of Part I.

again contain the quantity taken out.
This muft be owing to a fermentation of
the putrefactive kind, carried on, in a fmall
degree, in thefe rich foils, whenever the

o '

air is admitted to them : for without air
there can be no inteftine motion. This
continual tendency to putrefaction, in Ibme
of the particles of this foil, will appear
more plain from its colour, and quantity
of oil, the only fubject of corruption.
Hence it follows, that there muft be a de-
gree of heat in this foil, in proportion to
the progrefs of the putrefactive fermenta-
tion, and independent of the fun, or na-
tural heat of the internal parts of the
earth.

THIS foil admits the water eaiily, and
fwells like a fptinge after it has taken the
rnoiflure in. This quality is peculiar to
good foil. It contracts again when dried.
Hence naturalifts conclude, that this foil
confifts of fpungy and fwelling particles. I
rather chufe to attribute this fwelling to the

fer-

Sect. III. Agriculture and Vegetation. 13

fermentation, or interline motion, which
continually goes on in this foil, being , inr
creafed by the addition of the water : for
all bodies muft have a certain degree ol
\vatry particles, in order to make the fer-
mentation go on properly.

IT is obferved of all foils, the moiTy and
boggy ground excepted, that the blacked
are the richeft. This' colour gives it§ a
ftrong prefumption, that thefe foils con*
tain much fat and oleaginous matter; for
all foffil and vegetable oils, when they have
a great admixture of eartl;, are of this co-
lour. It is owing likewiie to thefe oils,
that all vegetable or animal fubftances gain
a black colour when in the road to putre-
faction, The unctuofity too of this foil,
a quality of it which is remarked by farrjnr
ers, is a proof of its oleaginous nature.
This black colour will make it reflect fewer
of the fun's rays, and fo make it
tible of a greater heat, than .foils
are of a lighter colour,

Bt

14 *flx Principles of Part I.

BUT we have a certain method of know-
ing, whether a body contains any oleagi-
nous particles or not, by the means of nitre
melted in the fire. Nitre, though not in-
flammable of itfelf, becomes, in this fitua-
tion, inflammable, or, as the chymifts
chufe to call it, deflagrates with bodies
which contain any oily particles.

Exp. i. Some rich mould taken up three
or four inches deep from the border of a
garden where no dung had ever been laid,
deflagrated very much with nitre in fufion.
Hence it appears, that this foil contains
much oil.

To difcover if this earth contained any
abforbent or alkaline particles, I tried the
following experiment.

Exp. 2. Some ftrong vinegar, diluted
with twice its quantity of water, being
poured on this fat earth* raifed a gentle fer-
mentation, from whence many air-bubbles

arofe ;

Sect. III. Agriculture and Vegetation 1 5

arofe ; the acid tafte was at leaft deftroyed,
and the vinegar reduced to a neutral body.
From this experiment we learn, that rich
mould contains a great many particles
which attract acids, and with them make
a neutral fait. I have learned from many
different trials, that all foils fit for the nou-
rimrnent of plants, contain more or lefs of
thefe antacid particles.

To difcover what we mould get from
this earth by diftillation.

Exp. 3. I diftilled half a pound of it
with a gentle heat j I got in two hours an
ounce of a yellow empyreumatic liquor,
which was of an alkaline nature. The
ftrongeft fire continued for nine hours
longer, gave half an ounce more of a yel-
lowilh empyreumatic liquor, which had
feveral oleaginous filaments fwimming in
it. It fmelt like ipirit of hartfliorn, turned
fyrup of violets green, and effervefced
firongly with vinegar,

FROM

j 6 ^Tbe Principles of . Part I.

FROM this experiment it appears, that
the falts of this foil are of the volatile al-
kaline kind ; and that thefe falts naturally
exift in it, as they rife with a fmall degree
of heat. From this likewife we have an-
other proof of oil being contained in this
foil, as it tinged the firft water with a yel-
lowifh colour, gave it a burnt fmell, and
was plainly to be difcovered in the fecond
floating about in a filamentous way.

SECT. IV.

Of -the day foil.

THE clay foil is very different from
the former ; and as it is a compofi-
tion of clay with a mixture of the former
foil, we mail inquire into the properties of
clay.

THE diftinguiihing and char act eriftical
property of this body is, that having al-
ready got a certain quantity of moifture, it

refills,

S£ct. IV. Agriculture and Vegetation. 17

refifts, in fbme meafure, the entrance of
more water into its pores, is very flowly pe-
netrated by that fluid, and therefore is not
in any great degree foftened, loofened, or
otherwife affected by it. Clay, when preff-
ed by external force, or firmly compacted
by its natural fubfidence, as we find it at
the bottom of many of our foils, and of
moft of our moiTes, will even fuftain water,
and become impenetrable to it. Hence
foils, in proportion to the quantity of clay
they contain, will hinder the water from
paffing through them j will keep the vege-
tables continually fbaked in moifture ; will
not be fb much heated by the rays of the
fun as if they were dry; and, therefore, are
juftly deemed of a cold nature.

WHEN expofed to the degree of heat of
a fummer fun, clay dries, and turns very
hard, fo that it requires a confiderable force
to feparate its parts. This quality of clay
is the more obfervable, if it has been full
of moifWe, and dried fuddenly. Hence
C clay

18 *fl>6 Principles of Part I.

clay grounds are fo apt to cake with heat,
especially if they have been ploughed wet,
and will, in that flate, hinder the roots
of vegetables from paffing through them.

THE SE qualities of clay feem to depend
on the fame caufe, viz. the ftrong adhefive
power of its particles. Its great ductility
fhows, that its particles adhere very firmly.
But whence this adhefion ? Is it from a
certain figure of its particles, by which
they are intangled, and can it be fo eafily
feparated ? or is it from oleaginous particles
mixed with the earthy, as we know that
oil is adhefive, and rejects water ? I incline
to the latter opinion, as I have found that
clay contains an oil, not fo loofe indeed
as in the former foil, but intimately con-
nected with its earth, and fcarcely fepara-
ble from it.

Exf. 4. I mixed forne clay with vinegar;
but there was no fermentation, and the acid
tafte was not blunted. It feems then to

have

Sect. IV. Agriculture and Vegetation. 1 9

have neither alkaline nor abfbrbent parti-
cles in its competition. In this it differs
very much from the former foil.

CHYMISTS generally affert, that clay
contains an acid of the vitriolic nature, and
an oil. From this acid they account for
its diftilling the acids of nitre and fea-falt,
and for its vitrefcible nature, as falts are the
great affiftants of vitrification.

LEMERT le fls, in the Mem. acad.
de Selene, four /' annee 1708, has thefe
words. Comme il y a dans ? argllle de par-
ties huilleufes, acidesy et terreufes. And again,
Car en la poujfent par une feu plus confide-
rable, il sen cchappe des acides et de parties
huilkufes. Let us fee how far this is true,

THAT I might difcover its contents by
diftillation,

Exp. 5. I put into the retort half a pound

of dry clay, taken up feven feet below the

C 2 furface

Principles of Parti,

furface from a clay-pit then employed in a
brick manufactory ; and as much fand was
mixed with the clay, it feemed to be of a
pure nature. After it had been diftilled for
two hours with a gentle fire, I got half an
oz. of pure water. After it had fuffered the
ftrongeft heat that I could give it in a port-
able furnace for nine hours, I found in- the
receiver two drams of a pellucid liquor,
which fmelt like the fpirit of hartfhorn, ef-
fervefced ftrongly with vinegar, and turn-
ed fyrup of violets green. The remainder
was very red.

THUS, inflead of getting an acid, as the
chymifts aflert, I have got an alkaline vo-
latile fpirit. No oil appears from this ex-
periment j and, therefore, we may con-
clude, that if there is any oil in it, that
oil is intimately united and combined with
its earthy parts, analogous to what happens
in metals.

THAT

Sect. IV. Agriculture and Vegetation. 2 1

THAT there is fuch an oil, feveral rea-
fons induce me to think -, its nourifhing ve-
getables, which require oil, when opened
by mere fand ; its unctuofity -, its igniting,
like metals, when put in the fire.

Exf. 6. I tried fuch clay as I ufed in the
former experiment with melted nitre. When
fmall pieces were put in, no fire was pro-
duced betwixt it and the nitre : but I evi-
dently perceived fparks of fire when it was
put in powdered. Hence I conclude^ tha$
clay contains an oil intimately and clofely
combined with its terreftrial parts.

THE oleaginous nature of clay is clearly
demonstrated by an experiment of Mr.
Eltcrs, in the jth Vol. of the Berlin Me-
moirs. He boiled fome clay in an alka-
line lye; this lye when decanted was fa-
turated with ol. vitriol. After the liquor
had flood fome time, he found at the bot-
tom a vifcid matter which deflagrated with
melted nitre, and reduced the calx of lead
C 3 to

22 The Principles of Part I.

to its metallic form By this experiment
the oil was got in a feparated ftate from the
earthy parts, which after this feparation
had loft their tenacity. This gentleman's
experiments {how us how ftrongly the oil
and earth adhere ; for the oil was fcarcely
feparable by fpirit of wine.

Exp. 7. When a piece of the clay was
kept in the kitchen-fire for fome time, it
turned red like a live coal, and when taken
put, had a high red colour, which feemed
owing to the particles of iron that it con-
tained. Very few particles indeed were at-
tracted by the magnet. But it muft be re-
membered, that this quality depends upon
the inflammable part of that metal, which
is always given it by art, and that I had
not added oil in the calcination. Very
few ores have this quality naturally. All
thefe experiments were made on the fame
clay.

:. V. Agriculture and Vegetation.

SECT. V.

Of the fandy foil

THi s foil gets its name from the quan-
tity of fand which it contains. The
qualities of this foil depend on the qualities
of fand. This body differs much from
the two former j from the latter, as it eafily
admits the entrance of water; from the
former, as it does not detain the water like
it, which feems to attract moifture with con-
fiderable force, and to refift its efcape again ;
while fand allows it to pafs eafily through
its body, and does not fwell, but, on the
contrary, turns lefs in bulk, when wet.
Sand cannot detain the water fo long as
the rich foils, becaufe it does not contain
thofe faponaceous and mucilaginous juices
which thefe do, and with which the water
is combined and detained. Hence fandy
foils often want a fufficient quantity of moi-
fture for the nourishment of plants. Hence
C 4 they

i£ *fhe Principles of Part L

they are very hot, becaufe fand is fufcep^
tible of a greater heat from the influence of
the fun, and will retain it longer than
water does.

SAND cannot fwell by the addition of
water -, becaufe that quality in rich foils is
owing to an intefline fermentation, which
goes on in them. But in fand there are no
particles, and in fandy foils too few, which
are capable of fermentation. Hence a de-^
feet of nutritious particles in fandy foils,
Inftead of fwelling, it diminishes in bulk
when wet 5 becaufe the water rufhing in,
difpofes the particles more regularly, fb
that the interftices are better filled up than
before, and its bulk leflened.

THE faults, then, of the fandy foil are,
that it lets water pafs through it too eafily,
and that it contains too few nutritious
particles. Whatever compofl is ufed to this
foil, muft correct one or both of thefe
faults. Clay will help it to retain the wa-
ter 5

Sect. V. Agriculture and Vegetation. ft 5

ter ; but then it is not richly ftored with ve-
getable food. Woollen rags anfwer both
purpofes very well, as they contain a great
quantity of mucilaginous juice, which ferves
equally well in nourifhing plants, and in
detaining moifture,

THE compoft that appears to me to be
one of the fitted is mofs : for it is as im-
pervious to water as clay, nay perhaps
more fo j and as it is a vegetable, contains
more oil than any other that I know. This
reafoning is confirmed by fact. A gentle-
man laid fome of this manure on a fmall
part of a field, confifling of a very light
fandy foil. The oats which grew that year,
and the clover which grew the following,
were much better on that part than on the
reft of the field.

7f* .

THE following experiment was tried on
equal portions of about three feet fquare,
in a very light fandy foil, during the laft

fummer,

26 T&? Principles of Part. I,

fummer, which being very dry makes the
experiment more conclufive.

Exp. 8. N° i. was covered and incorpo-
rated with two inches deep of clay. N° 2.
with three inches. N° 3. with four inches.
N° 4. had two inches of clay with the
common quantity of lime laid on ground.
N° 5. had three inches of clay with the
fame quantity of lime. N° 6. had four
inches of clay with the fame quantity of
lime. N° 7. had two inches of clay with
the ufual quantity of dung. N° 8. had
three inches of clay with the fame quantity
of dung. N° 9. had four inches of clay
with the fame quantity of dung. N° I o.
had fix inches of clay. N°. 1 1 . had the
fame with lime. N3 12. had the fame
with dung. N° 13. was the light poor
fandy foil without any addition. N° 14.
had the ufual quantity of lime added to
the foil. N° 15. had the ufual quantity of
dung added to the foil.

July 2.

Sect. V. Agriculture and Vegetation. 27

July 2. N° i, 2, 3, 4, 5, 6. are all bad.
N° 7. very good. N° 8, 9. exceeding
good. N° 10, 1 1. very bad, N° 12. ex-
ceeding good. N° 13. is the worft of all,
and fcarcely bears any thing, N° 14. bad.
N° 15. pretty good.

Augul 13. N° i, 2, 3, 4, 5, 6. bad.
N° 7, 8, 9. exceeding good and heavy
grain. N° 10, n. are all withered. N° 12.
exceeding good. N° 13, 14. carries no-
thing, N° 15. pretty good.

FROM this experiment the following
ufeful conclufions arjfe,

Corol. i. A poor fandy foil, when of itfelf
it was able to produce no grain in a dry
feafon, was fructified to a confiderable de-
gree by dung alone ^ but clay alone, and
lime alone, did it but very little fervice,

Cor. 2. Light fandy foil is not much
benefited by a mixture of clay and lime;

but

Principles of Part I.

but clay and dung enrich it to a prodigious
degree, and make it capable of bearing
a dry feafon, which of itfelf it can fo little
(land. While all vegetation was ftopt in
the foil alone, an addition of clay and
dung produced one of the beft crops that I
ever faw.

Cor. 3. Though thefe conclufions agree
in general with regard to all forts of grain,
yet as different kinds were fown, I ob-
ferved that oats agreed better with clay,
and clay and lime, than either barley or
peafe ; but that the two laft agreed better
with the clay and dung than the oats.

SAND, however hard it is, feems to be
moftly compofed of a mucilaginous, oily
fubftance; as appears by the following
trial.

Exp. 9. February 9. I put ten gr. of pure
fea-fand, pounded in a mortar, into a phial
with one drachm of oil of vitriol ; the fame

quantity

Sedl. V. Agriculture and Vegetation. 29

quantity of fand with the fame quantity of
fpirit of nitre, in another glafs ; the fame
with fpirit of fea-falt, in a third. March 28.
the acids appeared turbid. I mixed with
each fome water, that I might get the fand
eafier away by itfelf, and that the particles
mixed with the acids might be more eaiily
feparated. The fand in the firft glafs weigh-
ed 7 gr. 5 and that in the fecond and third,
64: gr- That I might precipitate from the
liquors whatever was diffolved by the acids,
I mixed with each as much pearl ames as
was necelTary to faturate the acids. After
the efFervefcence was over, there was a
brownifh oozy powder at the bottom of the
ol. vitriol, and an oily fubflance at the bot-
tom of the other two, which was quite dif-
tincl: from the water. What was precipi-
tated from the fpirit of nitre, was yellow ;
from the fpirit of fait, was white. The for-
mer, when feparated from the water, defla-
grated with melted nitre, which mowed it
to be of an oily nature ; but the latter did

not.

30 ¥he Principles of Part I*

not. I muft obferve here, that the fine
powder of flint has a fenfible deflagration
with melted nitre.

As lime is a powerful diflblvent, eipe-
cially of oily bodies, I imagined that lime
might have fome fuch effect on fand, dif-
folve it into a mucilage in the earth, and
in this way fand might be converted into a
fit nourimment for vegetables. This per-
haps might be, I thought, the reafon why
lime and fand took fo firm a bond toge-
ther, when lime alone does not adhere.
This appeared to me yet ftronger, when I
confidered, that any mucilaginou's or oily
fubftance, fuch as whites of eggs, train-oil,
&c. when mixed with quick-lime, make it
take bond. I therefore tried the following
experiment.

Exp. 10. I took a certain number of
fmall pieces of flint, which is allowed to
be of the fame nature with land, weigh-
ing i dr. 52ir gr. and added a quantity of

lime

Sect. V. Agriculture and Vegetation. 3 1

lime and water to them. They lay amongft
the lime from the 9th of February to the
23d of March. When taken out, and dried,
they weighed the fame as when put in.

Exf. 1 1. That I might fee what effect
the mucilage extracted from fand by the
acids, would have on quick lime, I added a
very fmall quantity of the mucilage from
both acids to quick-lime, and baked them
together into a pafte. Some of the fame,
lime was made into a pafte with water
alone. After they had lain for four weeks,
and were entirely dry, neither of them had
taken bond.

THESE experiments would feem to be
in oppofition to the former theory. The
queftion, however, is of fuch ufe, efpecially
with regard to building, that it deferves to
be further confidered.

SECT,

32 "The Principles of Part I.

SECT. VI.

Of the chalky foil.

I SHALL fay little about this foil, becaufe,
as it is to be found only in few counties
in England, I have not yet met with it;
and I (hall relate nothing on the faith of
thofe who reafon without the afliftance of
experiment.

CHALK is an abforber of acids, and
has no oleaginous particles in its compo-
fition, but is a powerful attracter of them.
Hence the proper manure for this foil muft
be thofe bodies which contain moft oil,
as hair, rags, &c. It feems to have but a
very weak attraction to water ; and, there-
fore, will be generally too dry. This foil
is obferved by farmers to cake after heavy
rains.

SECT.

Seel. VII. Agriculture and Vegetation. 33

SECT. VII.

Of till.

FARMERS call thofe foils til/, which
have a reddifh, gray, or yellowifli co-
lour, are poor, will bear nothing, nor can
be fertilized fo eafily or fpeedily as the for-
mer foils. Sometimes they render all at-
tempts fruitlefs. This icil muft, therefore,
not only contain no vegetable food, but it
muft often contain a vegetable poifon; elfe
it would always become fruitful by the ap-
plication of comports. What this poifon is,
muft be the lubjecl of our prefent inquiry ;
for unlefs we know it, we cannot know
whether there is a remedy for it or not.

THE following experiments were per-
formed on iome of this unfruitful earth
mown me by an experienced farmer.

Exp. 12. It efFervefced vifibly with vine-
gar and oil of vitriol diluted with water,
D but

34 *the Principles of Part L

but had a peculiar irony tafte, and turned
black with galls,

Exp. 13. Some of this earth calcined in
a ftrong fire for two hours, was almoft all
attracted by the magnet.

Exp. 14. It did not deflagrate with melt-
ed nitre.

Exp. 15. Four ounces of brown till well
dried, being diftilled, in fix hours gave two
drams of a phlegm, which {hewed no acid
or alkaline nature.

FROM thefe experiments it appears, that
this fpecies of till contained neither falts nor
oils, but was a competition of earth and
iron. The poifonous quality of this foil
muft then have depended on the latter bo-
dy, which we may obferve by the firit ex-
periment is diflblvable in all acids, and in
that ftate may enter the veflels of plants.
We fhall afterwards fee that it will meet

with

Se<fl. VII. Agriculture and Vegetation. 35

with acids. This reafoning is put beyond
all doubt by the following experiment.

Exp. 1 6. I took one pound of good rich
mould, and mixed with it one drachm of fait
of fteel; put it into a pot, and fowed feme
barley in it in the beginning of May. Some
of them (hot up about an inch, looked very
ill-coloured and fickly, and then died;
while other grains in another pot, filled
with the fame earth, throve very well.

THUS a very fmall quantity of iron,
diffolved by the vitriolic acid, rendered a
great quantity of rich eartii unfruitful, and
therefore ought to be looked on as the ve-
getable poifon of till. If this poifon can
admit of a cure, I imagine it is only to be
found in lime or marl, which will attract
the acids from the iron, and make it, at leaft
in a great meafure, indiflblvable in water.

THOUGH the admixture of iron with

the foil may be a very general caufe of un-

D 2 fruit-

36 The Principles of Part. I.

fruitfulnefs, yet it feems not to be the only
one. A great deficiency in fome of the
principles necefTary for vegetation, muft have
the fame effect. Thus farmers often sive

D

the name of //'// to indurated clays, and
particularly to thofe which they find below
the foil. The common farmer is afraid of
ftirring it up with the plough, becaufe it
is unfruitful : but the more judicious, will-
ing to deepen his foil, takes it up by little
and little, and finds that lime, dung, and
air, readily fertilife it.

SECT. VIII.

Of the mojjj foil.

I Shall not enter into a difcuffion of the
origin and nature of mofs : it is now
allowed by every body to be a vegetable
fubftance. The following experiment is a
proof of it.

Exp. \j. Haifa pound of powdered peat
gave me by diftillation, during the two firft

hours,

Sect. VIII. Agriculture and Vegetation. 37

hours, 2 oz. of an acid empyreumatic li-
quor, which was of a yellow colour, and
ihowed its acid nature, by effervefcing with
ol. tart. p. d. The flrongeft fire continued
for nine hours longer, gave me 2 dr. of a
reddifh empyreumatic liquor more acid than
the former, and I fcr. of a thick dark-co-
loured oil. There was befides about the
neck of the retort, a great quantity of red
oil, which was too heavy to come over.
The refiduum was black.

Exp. 1 8. Some peat burnt in the open
fire, gave me about the two and thirtieth
part of alkaline fait.

HENCE we fee, that peat affords the
fame principles as other vegetables do, and
therefore muft be claifed amongft them.

THE only method, then, to make this foil

fruitful, is to make the vegetable undergo

a degree of putrefaction, by ploughing the

foil, and ib killing the plants. All vege-

D i tables

38 The Principles of Parti.

tables turn to rich foil when they have un-
dergone a degree of corruption j even oak
bark becomes in time rich black mould.
The parts wilt be the fooner feparated, if
fome earth or clay is added to the mofs ;
for mofs of itfelf is rather an enemy to cor-
ruption. All kinds of vegetable fubflances
and animal bodies are preferved uncorrupted
for whole ages in mofs-holes. Abforbents
are known from experience to be promoters
of corruption. The various kinds of marl,
when they can be got, particularly the
mell-marl, would feem to be the propereft
manures for this foil. Lime, as it appears
to be a great diflblvent of all vegetable bo-
dies, may have good effects on this foil.

PART

Sect. I. Agriculture and Vegetation. 39

PART II.

SECTION I.

natural methods of providing vegetable
food.

H

A v i N G afcertained the properties
of the different foils, the next
thing we have to do is, to exa-
mine into the nature and properties of what-
ever is obferved by experience to fructify
ground, whether it be applied to the foil in
a natural or artificial way. If we can dif-
cover fome qualities in which all thefe ma-
nures agree, we fhall arrive at the know-
ledge of what we are in fearch of, viz. the
food of vegetables, or at leaft of thofe prin-
ciples which go to the compofition of that
food. Let us firft inquire into thole ways
by which nature fructifies the earth.

D 4 IF

40 *fbe "Principles of Part II,

IF earth is exhaufted of its vegetable
food, experience has difcovered, that it re-
covers it again, if allowed to lie idle. This
fhows, that the vegetable food is continual-
ly on the increafe, when the earth is not
robbed of it by the crops it bears. We dif-
cover immediately whence this food comes,
when we attend to thefe two fads j . that
the more the foil is expofed to the air, the
vegetable aliment is the fooner procured,
and in greater quantity too ; and that when
the furface is buried by the action of the
plough, and a new foil brought up, that
foil, though feemingly as good as the for-
mer, produces bad crops, till it has re-
ceived for fome years the benefit of the at-»
mofphere.

FALLOWING is a conftant proof of this.
The foil is frequently broke down and
turned over by means of the plough, and
every part of it is expofed to the influence
of the air. That the communication of
the earth, by the mechanical a&ion of the

plough,

Sett. I. Agriculture and Vegetation. 41

plough, is not the chief means of increafing
the vegetable matter, as T#// aflerts, appears
plainly from thefe two fads ; that even the
lighter!: foil is the better of fallowing ; and
that when fallow ground is laid up in
ridges, more benefit is received than when it
is left quite flat.

BUT this nutritious influence of the air
is yet more obfervable in thofe earthen dikes
or walls made of the foil taken from the
furface, and thrown up to inclofe the meep-
folds. Thefe dikes are expofed to the in-
fluence of the air, which pafTes through
and through them for many months. The
foil thus expoied is rendered prodigioufly
fruitful, fo that it is eafily diftinguimable
by the quantity and deep green colour of
the grain, from the internal parts of the
fold, which have been well manured by
the urine and dung of the fheep. It is
likewife remarked by farmers, that the
earth of the dike lafts for three or four

years

Principles of Part II.

years longer fruitful than the other part of
the iheep-fbld.

THIS chief inftrument, then, that nature
makes ufe of to enrich the earth, is the air.
Even the richeft foils require its continual
influence. On what principles of the air
this fructifying quality depends, we cannot
inquire, until we have afcertained the na-
ture of the different manures which feem
to operate by attracting thofe principles
from the air. The flrong and lafting vege-
tative power which the air communicates
to the earth, mould teach us to make a
greater ufe of its influence than what we
do. Why mould we not raife the whole
furface into fold-dikes ? Other manures do
not operate till the fecond or third year
after they are laid on ; this operates imme-
diately. A farmer cannot, at a medium,
dung an acre under _$/; this might be
done for 30*. Dung fills the ground with
weeds; this method cleans it. Manures
cannot be found every where 5 this practice

may

Se<5t. I. Agriculture and Vegetation. 43

may be followed in all places. It would
be particularly good for clay ground, as the
viciffitudes of the air pulverife greatly.

D E w is reckoned by farmers a great fer-
tilifer of the earth. It arifes from the per-
fpiration of the earth, of vegetables and
animals in a found ftate, and their exhala-
tions in a corrupted one. The earth re-
taining its heat, after the fun's influence is
weakened, elevates thefe attenuated par-
ticles : but the air cooling fooner than the
earth, from its rarity, condenfes them at a
little diftance from the furface ; and thofe
which become fpecifically heavier than the
air, fall on the earth again. Hence dew
muft differ according to the difference of
the bodies from which it proceeds. Its
contents are therefore various ; but experi-
ments have difcovered, that it is compofed
in general of oils, fairs, and a great pro-
portion of water. Of what ufe thefe prin-
ciples are to vegetation, we mail after-
wards fee.

RAIN-

44 2fo Principles of Part II.

RAIN-WATER, efpecially in the fpring,
has nearly the fame contents. Margraaf,
in the Academ. de Berlin, vol. j. has ana-
lyfed it with great accuracy, and mowed
that it contains a nitrous and a fea-falt,
with a confiderable quantity of an abforbent
earth j which probably was united to a
nitrous acid before evaporation, and con-
fequently increafed the quantity of nitrous
fait very much. The falts were of a brown
colour, which difcovered its oil. As the
water was gathered in the winter, it con-
tained a fmaller proportion of this laft
body, than if it had been gathered in the
fummer.

SNOW is juftly reckoned amongft thofe
bodies which frudlifv earth. I have obferved

j

a light floating oozy fediment at the bottom
of fnow-water, after I had kept it three or
four days. When fnow melts, its furface,
' even in the tops of hills, is covered with a
brown powder, Bath rain and fnow-water
putrify fconer than fpring water j which

{hows

Seel. I, Agriculture and Vegetation. 45

fhows that they contain more oily particles
than it do.s.

Exp. 19. A pound and an half of fnow-
water being evaporated, gave 2 dr. of a
reddifh liquor, which had little tafte, and
difcovered nothing faline in it. I fet it in a
cellar for fourteen days j and when I took
it out, it was covered with a mouldy fub-
fiance. This mould, when dried, burnt on
a red-hot iron to a powder. Hence it ap-
pears, that fnow contains an oily fubftance,
Margraaf having evaporated a greater quan-
tity of fnow- water, difcovered the fame falls*
and earth as in rain-water.

THE overflowing or water-flooding of
low grounds may be reckoned amongft
the natural methods of improving the foil;
becaufe fiat meadows are often naturally
overflowed, either by rains, or by the rain-
water falling from the higher grounds. Egypt
is naturally overflowed once a-year by
the Nt/e, and rendered by that means

exceedingly

46 The Principles of Part II.

exceedingly fertile. Spring-water is even
found to be of fervice to ground, but not
fb much as river-water, especially fuch as
has run through a fertile country, and is,
at that time, full of the fubtiler particles
of the .foil warned off from the rich grounds
by rains. As thefe waters are impregnated
with the fubtile earth, and the faponaceous
juices of thofe foils over which they have
run, when they ftagnate, thefe nutritious
particles fubfide, and inrich the ground.
The river Nile depolites a rich oozy mud,
which is fo full of putrefcent particles, that
its fleams feem to be the caufe of the
plague raging fo much in Egypt. By this
addition of foil it receives every year, the
level of the ground is confiderably higher
than it was. Hence too the vallies in all
countries are much • richer than the rifing
grounds ; as the rains warn great part of the
vegetable matter from the latter, and leave
it in the former.

ART

Sect. I. Agriculture and Vegetation. 47

ART often imitates nature in this me-
thod of improving land, and lets in the
ftreams of rivers to cover the fields. This
is moft frequently done in the fpring, when
thefe waters are moft impregnated with
nutritive particles. This water, after it has
depofited all its particles, which it does in
four or five days, is let off quickly ; left,
by a gradual evaporation, it fhould cake the
ground, and hinder the grafs to come up ;
which is the great danger attending it, and
for which it is thought improper for clay
grounds.

IT muft be obferved here, that there
are fome waters which are extremely preju-
dicial to grounds, fuch as coal and fteel
waters. This is owing to the quantity of
iron which both thefe contain. All fulphur
waters are likewife hurtful to ground ; we
fhall afterwards fee that fulphur is a poifon
to plants,

SECT.

48 'The Principles of Part II.

\

SECT. II.

Of manures, or the artificial methods of pro-
viding vegetable food.

EXPERIENCE has fhown, that cer-
tain fubftances, committed to the
earth under certain regulations, make it
more fruitful. Thefe fubftances belong
either to the foffil, the vegetable, or the ani-
mal kingdom. The foffil include the dif-
ferent kinds of marl j calcarious ftones, fuch
as lime-ftone, chalk, &c. j and quick-lime.
The vegetable include all vegetables, and
their juices, either in an intire or a cor-
rupted ftate ; the afhes of burnt vegetables ;
the oils extracted from vegetables and loot.
The animal include calcarious (hells, intire
or corrupted ; horn-fhavings or tips j wool-
len rags 5 and all animal fubflances, fuch
as dung, urine, &c. 1 {hall treat of thefe
in their order.

Sect. III. Agriculture and Vegetation. 49

I am not to lay down the method of ufing
thefe ; I mail take no notice of that, but
where it tends to mow their method of ope-
rating. My defign is to take a view of
thofe qualities belonging to them, by which
they are capable of operating on the foil,
and producing certain effects on the vegeta-
tion of plants.

SECT. III.

Of marl.

TH I s is a foffil body which feels
unctuous and fat betwixt the fingers ;
and refembles clay in a great meafure, info-
much that marl, though a very different
body, is often confounded with it. It is
divided into many different kinds, which
may be all included under thefe two, clay,
and Hate or ftone marl : for what is com-
monly called Jhell-marl, is an animal fub-
ftance, and therefore to be claffed amongft

E them,

50 The Principles of Part II.

them. The different colours of marl make
no real difference as to their properties.

Exp. 20. It is a diftinguiming and cha-
ra&eriftical property of this body, that,
when it is put into water, it falls down
into a powder. The clay marl dilfolves
much quicker than the ftone marl. This
quality muft be owing to the weak adhe-
lion of its particles j fo that the fmall force
with which water enters its pores, is capa-
ble of feparating the particles of the marl.
By this property it is fufficiently diftin-
guifhed from all the earths which we have
mentioned ; and particularly from clay,
which does not fo ipeedily admit the en-
trance of water.

A s marl is fb much opened by water, fo
as to lofe its natural cohefion entirely, we
fee how much it will favour the efcape of
water from fuch grounds as have been ma-
nured with it. Clay grounds, after they

have

Sect. III. Agriculture and Vegetation. 5 1

have been marled, become much drier.
It is owing, I imagine, to the water get-
ting off fo quickly, that marled grounds,
as is obferved, are lefs affected by froft,
than the fame foils which have not got
any marl.

Exp. 21. It effervefces with all the dif-
ferent acids, and turns with them into a
neutral fait. During the effervefcence with
the oil of vitriol, a fulphureous fleam arofe,
which is a flrong prefumption of its con-
taining fome oily fubftance. The clay marl
feemed to diffolve fafter than the ftone marl,
and deflroyed about a third more of the
acids. This quality which marl has of at-
tracting and destroying acids, is one of its
diftinguiming properties, without which no
fubftance can be called marl. In this quality
it is likewife diitinguifhable from clay.

As farmers are extremely inaccurate in

their terms, they often give the name of

E 2 marl

52 The Principles of Part II.

marl to bodies which do not effervefce
with acids. That fuch fubftances may and
do fructify ground, is indubitable > but they
ought not therefore to be called marl.
Surely bodies which do, and bodies which
do not effervefce with acids, are very dif-
ferent in their nature, and ought to have
different names. As the name of marl,
then, is generally, fo let it be only applied
to the former clafs. The latter mould
have fuch names as will diftinguifh them
from the former. This mews what con-
fufion there is in the terms of agriculture,
and how much they ftand in need of being
defined.

Exp. 22. Another quality belonging to
marl, by which it is diflinguilhed from
clay, is, that it cannot be converted to
brick. It is indeed very much altered by
a ftrong heat; it lofes its antacid quality
while it remains unpowdered ; and is no
longer difiblvable in water, as it was be-
fore:

Seft. III. Agriculture and Vegetation. 53

fore : but {till it is very different from a
half-vitrified fubftance ; and I much quef-
tion, whether or not it can, without any
addition, be turned into glafs. This is a
ftrong proof, that it contains no falts, acid,
alkaline, or neutral ; for thefe are capable
of vitrifying lime when added to it.

Exp. 23. I could not get any fait from
thefe marls, either by fimple lixiviation, or
diftillation, though I urged them with the
ftrongeft fire. The fire feparated nothing
but a little water, which appeared to be
gently alkalefcent j owing perhaps to fome
of the finer marly particles, which were
carried up by the water. No oil appeared
in the diftillation. When the powder of
marl was thrown on fufed nitre, it fparkled
a very little. This, and the fulphureous
fmell arifing when it was diffolved by the
oil of vitriol, would incline me to think,
that it has a fmall proportion of an oleagi-
nous matter in its compofition.

4

£3 BUT

54 - TZtf Principles of Part II.

BUT though perhaps it contains none,
yet it ftrongly attracts all oils. This is a
quality which the chymifh know belongs
to all abforbent earths ; thefe they make
ufe of to feparate oils from other bodies.
Hence it will attract and fix the oils which
it meets with in the ground, which fall with
the fnow and rain ; and even thofe which,
floating in the air, touch its furface.

To inquire a little further into its na-
ture, and feparate its antacid parts from
the others, that we might difcover both ;
Exp. 24. I took half an ounce of ftone
marl in powder, and faturated it widrfpirit
of nitre, by adding the acid in fmall quan-
tities for five days j the faline liquor was
filtred through brown paper. There re-
mained in the paper three drachms of a
bluifh adheiive earth, which, on trial, ap-
peared to be a fine clay. To recover the
other part from the faline liquor, I added
oL tart. p. del. till no more lactifcency ap-
peared -3

Sect. III. Agriculture and Vegetation. 55

peared j a white fubftance fell to the bot-
tom, and was feparated from the liquor by
filtration. This powder being wafhed with
water, that all the falls might be feparated
from it, and calcined in a ftrong kitchen-fire
for five hours, gave me a quick lime, which
afforded good lime-water.

FROM the fame quantity of clay marl,
treated the fame way, I got three drachms
and twenty-eight grains of clay, and thirty-
two grains of a calcarious earth.

FROM the fame quantity of clay marl,
faturated with vinegar, and treated the fame
way, I got two drachms and fifty-nine
grains of clay ; and the remainder was a
calcarious earth, which, being burnt, afford-
ed good lime-water.

THE fame quantity of a different clay

marl, treated the fame way, afforded two

drachms and fifty-four grains of clay, and

one drachm fix grains of a calcarious earth.

E 4 THE

56 Tloe Principles of Part II.

i

THE fame quantity of ftone marl, treat-
ed the fame way, afforded juft the fame
proportion of clay and calcarious earth.

MARL, then, is a body compofed of lime
and clay in different proportions, according
to the different kinds of marl, and generally
about one fourth of lime and three fourths
of .clay.

FROM this experiment we may eaiily
account why marl falls in water, as lime
ftrongly attracts water -, and why it lofes
this property when burnt, as clay becomes
more tenacious by fire ; why it cannot be
converted to brick, as the lime hinders that
clofe adhefion of the particles of clay which
is neceiTary to conftitute brick ; why it will
not vitrify, as lime is an enemy to all vitrifi-
cation j and why it mews a fmall portion
of oleaginous matter, as clay contains fome
oil. By mixing quick or rather effete lime
with clay, or a clay foil, we imitate, in

fome

Sect. III. Agriculture and Vegetation. 57

fome meafure, this production of nature,
but fall vaftly fhort of her in the equality
of the mixture, and perhaps to in the fub-
tility of the particles.

THERE is a body very ilmilar to marl
in its appearance, but very different from
it in its effects, and often found in the fame
bed with the beft marl. It is of a darkim
lead colour. Inftead of fertilizing ground,
it renders the beft foils incapable of bearing
any kind of vegetables for many years. I
have feen the fpots on which it was laid
entirely barren three years after. I have
heard of its effects continuing in other places
for a much longer time j nor is it certainly
known when its bad effects' will end. A
body fo very deftru&ive to agriculture, de-
ferves to be well charadterifed, in order to
be munned ; and well examined, that we
may know whence proceeds this noxious
quality, and how to cure it when it has
taken place.

THOSE

$S The Principles of Part II.

THOSE who have been much ufed to
marl, have already difcovered a difference
betwixt it and this body. The former,
they obferve, takes a fmooth polifh from
the inftruments with which it is wrought,
but the latter does not. As this quality
alone is fcarcely fufficient to diftinguim thefe
two bodies from one another, let us apply
to experiment for more.

Exp. 25. If a piece of ijt is taken up
which has not been much expofed to the
influence of the air, it differs very much
in tafte from marl. Inftead of the fmooth
unctuous tafte of the latter, it is acid, and
remarkably aftringent.

IT agrees with marl in falling down into
a powder in water ; but then it differs re-
markably from it, in raifing no affervefcence
with acids, nor in the leaft deftroying their
acidity.

IT

Sect. III. Agriculture and Vegetation. 59

IT turns the fyrup of violets red j which
(hows, that it contains an acid : whereas
marl, like all abfbrbent earths, gives it a
green colour.

THESE qualities are fufficient to teach
the farmer how to diflinguifh this poifon-
ous body from marl, and how to fhun it.
Let us now try if we can difcover on what
principles this poifonous quality depends ;
for if we can inveftigate its nature, we may
perhaps find out a cure for it. Befides, all
purfuits of this kind lead us directly to the
true fyftem of vegetation. The vegetable
is like the animal body, whofe nature is
afcertained as well by what does it harm,
as by what does it good.

FROM my experiments in die fedtion on
till, I imagined that its poifonous quality
might depend on its containing fome fait of
iteel. I, therefore, directed moft of my trials
on this body with that view.

Exp,

60 'The Principles of Part II.

Exp. 26. Some of it was infufed in warm
water. The water had a greenim colour,
tafled gently acid, and very aftringent. It
gave the fyrup of violets a pale-red colour.
OL tart. p. d. dropt into it made no (enfible
erfervefcence, but feparated fome air-bubbles,
difcoloured it, and precipitated a pale-red
powder from it. Some of this powder was
put into a .crucible, and kept in the fire for
half an hour. I could recover but little of
it again, and that not quite free from the
fubftance of the crucible j yet the magnet
attracted fome of its particles, and fhewed
that it contained iron. The liquor evapo-
rated gave me a tartarus vitriolatus.

THE pure infufion did not alter its co-
lour much on an admixture of galls. But
this was no proof that the liquor did not
contain fait of fteel : for an acid deftroys
this efFecl: of the galls ; and the liquor, as
we have already found, contained an acid.
To deftroy the acid, I poured in ol. tart.

p. d.

Sect. III. Agriculture and Vegetation. 6 1

p. d. into the mixture of the infufion, and
galls ; it took immediately a brownifli co-
lour, and afforded a plentiful precipitation,
which, in twenty-four hours, had taken a
purple colour.

I boiled a quantity of the earth for half
an hour in water, flrained and evaporated
it. A white faline fubflance remained in
the proportion of 6 grains to each ounce,
which tafled exactly like fait of fleel. This
fait difTolved in water, turned fyrup of vio-
lets green, as does fait of fleel ; and took a
deep black colour with galls : Sufficient
proofs of its being fait of fleel. Nor cart
its white colour be any objection ; for fait
of fleel reduced by trituration, evaporation,
&c. to a powder, is white ; and the fait
which I procured, was a powder.

IT appears, then, beyond all doubt,
that this fubftance confifls of an earthy
body like clay, about an eightieth part of
(alt of fleel, and a fmall proportion of the

« vitriolic

62 TZtf Principles of Part II.

vitriolic acid. From other experiments
which I have made, the bad effects do not
feem to arife from the vitriolic acid ; elpe-
cially as the acid here appears to be very
volatile. But we have already difcovered
the pernicious quality of fait of fleel. Nor
is it any wonder, that it mould exert itfelf
fo powerfully here, coniidering the quan-
tity of this body laid on ground inftead of
marl, and the great quantity of this fait in
it. The foil muft be perfectly faturated
with it.

BUT how mall we correct the poifonous
quality, if, by miftake, this or fuch like
bodies mould be ufed ? For coal produces
the fame effects from the fame caufe. There
feems to be no other method but that of
decompoiing the fait -t fo that the fteely part
may be no longer diffolvable in water. The
air, by volatilizing the acid, and leaving the
chalybeate particles behind, has that ef-
fect, by gentle degrees, on fait of fleel,
when it is diffolved in water. But, in the
prefent cafe, the acid would not reach the

fait,

Sect. III. Agriculture and Vegetation. 63

fait, unlefs the foil were frequently turned
over; and even then much of the fait
would be defended by the oleaginous par-
ticles of the foil. Marl appears to me to
be the proper cure j for that abforbent earth,
having a ftronger affinity to the acid of
vitriol, than what the iron has, will unite
itfelf with the acid, feparate the chalybeate
particles, render them infoluble in water,
and confequently unfit to enter the vefiels
of plants. A conliderble mare of the
good effects of marl in all grounds, may,
perhaps, be owing to this fpecial effect,
viz. the deftruction of a body, which,
in proportion to its quantity, deftroys all
vegetation.

THERE is another foffil body very fimi-
lar to marl in its appearance, and fome
of its qualities, and may be miftaken for
it. It is called by fome writers foap-
rock, from its fimilitude to foap, and its
being often found in rocks -, though I have
known it lying on the furface in great

quan-

64 Vfe Principles of Part II.

quantity. As none has yet analyzed it, we
fhall undertake that tafk.

Exp. 27. It is fometimes of a bluifh,
fometimes of a reddifh colour ; and when
moifr., feels exactly like hard foap betwixt
the fingers.

IT falls like marl when put in water:
if it is well mixed with the water, it fepa-
rates into different parts from their diffe-
rent fpecific gravity j at the bottom there
is a layer of large grey particles -, above
that are fome darker ; next thofe of a dark
brown colour ; and the uppermoft is a light
white powder ; a great deal of which was
fufpended in the water for 20 hours.

IT effervefces with none of the acids.
In this it differs from marl.

Exp. 28. Some of it was lixiviated in
water 5 which being evaporated, gave a
very little fea fait.

Exp.

Sect. III. Agriculture and Vegetation. 65

SOME of it was calcined for four hours in
a flrong kitchen fire. The bluifh remained
of the fame colour 5 but the red turned
lighter in its colour. The firft contained
a few particles, which were attracted by
the magnet j the laft almoft none. It fell
as foon as the unburnt in water, and with
the fame appearances.

I dim' lied four ounces of it in a flrong
heat for eight hours, and it gave me only
one ounce of pure water.

IT did not detonate with nitre in fuiion,
but fome few fparks appeared, which mews
that it contains oil.

THIS oil I extracted, by boiling four
ounces of it with two ounces of potames
for many hours ; to this decoction I added
fpirit of nitre, and got a precipitation of a
red heavy oil, which detonated with nitre
in fufion.

F I took

66 The Principles of Part IL

I TOOK, four ounces of it, and warned off
the light earthy parts by mixing water
often with it ; in this way I got ten drachms
of a whitifh powder, which appeared to be
clay. The remainder was compofed of
two parts, a fine grey powder, which ap-
peared to be fand; and fome large parti-
cles, white and green. Thefe did not ef- -
fervefce with acids, nor yielded a tindure
of fpirit of wine ; but felt foft and undtuous
in the mouth, and when boiled with fbap-
afhes, and fpirit of nitre added to the lixive,
afforded a heavy oil. This mews them to
be of an oily nature.

SOAP-ROCK appears from thefe experi-
ments to contain near a third of clay, a
much greater proportion of fand, and a
body of an oily heavy nature.

THAT I might go a little further, and
difcover its effects in vegetation, and with
what foils it would agree beft, the follow-
ing

Sed. IV. Agriculture and Vegetation. 67

ing experiment was tried, though late in
the year.

Exp. 29. A pot was filled with the pooreft
earth that I could find 5 this I (hall call
N° i. N° 2. fame earth with a third of
foap-rock. N° 3. very ftrong clay with a
third of fand. N° 4. the fame clay with
a third of foap-rock. N° 5. foap-rock alone.
In thefe pots I fowed barley.

THE plants feemed to grow beil at firfl
in N° 2 : but afterwards N° 4. produced
the moft. In N° 5. the plants were longer
of appearing, and feemed more fickly than
the others.

SECT. IV.

Ofunburnt calcarlous bodies , and quick-lime.

CHALK is reckoned, by the generality
of writers, a good manure for all wet
clay grounds j for it makes the earth loofe
F 2 and

68 *fhe Principles of Part IL

and hollow; keeps it dry; and, as the
farmers exprefs it, fweetens the foil. The
foft un&uous kind is thought the befL
Farmers think that it exhaufts the foil
very much; and therefore they generally
advife dung to be laid on along with it.
Lime-ftone gravel is much ufed in Ireland
as a manure.

THESE calcarious bodies are not difTol-
vable in any way but by acids. With thefc
a great efFervefcence Jiappens, a folution
of the calcarious body is made, and a neu-
tral fait is formed from that conjunction.
This neutral fait is always foluble in water,,
unlefs where the acid of vitriol is ufed.

THESE calcarious ftones, when burnt in
a ftrong fire, turn to quick-lime, a body
much ufed in farming. It attrads acids
much more than it did before, and is now
in a fmall degree foluble in water, without
their afiiftance. It is not, however, on thefe
foluble parts that its frudifying power

depends ;

Sect. IV. Agriculture and Vegetation. 69

depends ; becaufe it has no fenfible effect,
except in killing vermin the firft year, when
thefe parts are moft foluble in water. Lime
is probably effete, and no longer foluble,
when it begins to aft on the ground, and
affift vegetation. The lime of old houfes,
which is quite effete, is reckoned better
than frefh quick-lime.

THERE is a very great attraction betwixt
quick-lime and all oily bodies j it unites
intimately with expreffed oils. With this
intention it is ufed in the manufacture of
foap, to help the junction of the alkaline
falts and oils. It mutt, therefore, attract the
oils powerfully from the air and earth, dif-
folve them, and render them mifcible with
water: it muft, from this reafbn, loon ex-
hauft the foil of all its oleaginous particles,
if the farmer does not take care to fupply
them by dung or animal fubflances. Farm-
ers have by experience difcovered it to be
a great impoveriflier of lands, but they did
not know how it acted. Its operation is,
F 3 to

70 17je Principles of Part II.

to exhaufl the earth of its oils, Lime laid
on ground wore out by continual crops,
rather hurts it than improves it ; becaufe it
does not meet with oil or oleaginous bodies
to aft upon, and blunt it. The proper cure
for this is, to mix dung with the lime, fo
that it may have fomething to aft on.

LIME is a great difiblver of all bodies,
both vegetable and animal, but particularly
the latter. We know how foon it difiblves
hair and woollen rags into a pulpy fub-
ftance. This effect is fo flrong, that, in
the common method of fpeaking, it is faid
to burn them. In this way it certainly ope-
rates in the earth, by dilTolving all animal
and dry vegetable fubftances, and converting
them to the nourimment of vegetables,
at leaft fooner than otherwife they would
be.

LIME powerfully refifts putrefaction, as
is difcovered by many experiments. It does
not appear, therefore, very judicious, to mix

quick-

Sect. IV. Agriculture and Vegetation. 71

quick-lime with dunghills, which are not
yet fufficiently putrefied, as it muft flop
that procefs. When once that procefs is
finifhed, many good effects may arife from
their junction, and particularly that of hin-
dering the oils to be volatilized, and of fix-
ing them.

9

IT is obferved of lime, that it is conti-
nually falling downwards, fo that, in a few
years, the greatefl part of it is to be found
lying together as deep as the plough goes.
This is owing to its great fpecific gravity.

IT is like wife obferved by farmers, that
lime has a better effect on light foils than
oa ftiff, for the firft three years, but, after
that time, its operation turns much weaker.
Light foils are moft pervious to the air;
and as the good effects of all manures de-
pend on the influence of the air, that in-
fluence muft be ftronger in open foils than
in thofe which are more compact : but as
F 4 that

*fbe Principles of Part II.

that foil has the loofeft texture, the lime
falls quickly through it,

BESIDES; by mixing itfelf with the ole-
aginous particles of the foil, and convert-
ing them to the nourifhment of plants,
lime becomes in this fenfe a provocative to
the foil. In promoting the work of vege-
tation, it will foon exhauft all the oils of
the light foils, which contain them but in
fmall quantity, and when they are all ex-
traneous, for fand can afford none. But
a clay foil, containing in itfelf a confide-
rable quantity of oil, and that not fo eafily
foluble, is not foon exhaufted. An addi-
tion of an animal or putrefied vegetable
fubftance to thefe light foils, would remedy
this defect.

SECT.

Sect. V. Agriculture and Vegetation. y 3

SECT. V. :.

Of vegetables in an intire and in a corrupted
Jlate^ and of dunghills.

WE come next to treat of thofe ma-
nures which are drawn from the
vegetable kingdom. All vegetables, unlefs
fome noxious ones, nourifh plants. Malt-
duft is reckoned a good manure. Bark
of trees, and faw-duft, are recommended
by fome writers. We learn from Columella
that the ancients laid the lees of their olive
oil on the ground, and found it of great
benefit. And, indeed, it is not to be won-
dered at, that the juices of vegetables al-
ready concocted, mould prove a nourimment
to other vegetables. But it requires much
time, before thefe can be reduced to Ib
fmall parts, and fo duTolved, as to be ca-
pable of entering the minute veflels of plants.
This is moil expeditioufly and moil effec-
tually performed by the means of corrup-
tion. Hence we may fee the reafon, why

the

ctke Principles of Part II,

the bun or woody part of flax has no good
efTed: on ground, as the juices are already
extracted, by the previous putrefaction
which the flax has undergone in the procefs
of fteeping, and little now remains but
mere earth,

THE different fpecies of fea-weed, efpe-
cially the kelp, are found very ferviceable to
land. Thefe weeds are of a foft pulpy
texture, and eafily diflblve. Befides, there
are no plants which contain fo much fait,
and fo much oil, in proportion to their
earthy parts. The falts are in fuch quan-
tity, that the kelp, though very dry, will
not burn ; as all falts, nitre excepted, are
enemies to fire. The oils are difcovered to
be in great plenty, becaufe this plant, not-
withftanding thefe falts, putrefies very foon.
The afhes of this plant * confifl of about
equal parts of alkaline fait, fea-falt, an oily
fubftance, and an earth.

* Vid. Experiments on bleaching, part 3. fe£h 6.

DUNG

Seel. V. Agriculture and Vegetation. 75

DUNG probably was the manure firft
ufed by farmers, as all vegetables fponta-
neoufly turn to it, and as accident mufl
foon have difcovered its good effects. It is
the manure at prefent moft ufed. The
manner in which it is made, is, therefore,
a fpeculation worthy of our attention, and
may lead to fome ufeful hints in the ma-
nagement of dunghills.

PUTREFACTION is defined by chymifts
to be an inteftine motion of a body, whereby
the union, texture, colour, fmell and tafte
are deftroyed.

THERE is no change fo common in na-
ture, as that of bodies from an entire to a
corrupted flate. All vegetables, whether
acid, acefcent, alkalefcent, auftere, aroma-
tic, infipid, cold or hot, are liable to cor-
ruption, and generally end in it. The al-
kalefcent, fuch as onions, celery, &c. run
immediately into corruption, without un-
dergoing

76 Tfo Principles of Part II.

dergoing the other two fermentations ; but
the acefcent can be made fir/I to ferment
into wine, and generally of themfelves un-
dergo the acetous fermentation, before they
fall into the putrid. Animals are conti-
nually in the very confines of putrefaction ;
and when death flops the circulation and
admiflion of frefh juices, they fall imme-
diately into it. Animals, and alkalefcent
plants, as they want that acid which abounds
in the acefcent plants, have a greater ten-
dency to putrefaction, which every one
knows is greatly retarded by acids. Next
to the excrements, which are already in a
ftate of high putrefaction, the blood is the
moft putrefcible fluid in the whole body 3
then the urine ; and afterwards the folids.

THERE are three circumftances necefTary
to the procefs of putrefaction, viz. moifture,
heat, and the admiffion of the external air.
Moillure is necefTary to foften the fibres of
plants, that they may be capable of the in-
teftine motion 5 for. we fee that dry flraw

Ml

will

'.-,:> . .-'••<>

Sect. V. Agriculture and Vegetation. 77

will not corrupt. Heat is likewife necef-
fary, in order to excite and promote that in-
ternal motion of the particles which coiifti-
titutes putrefaction. As cold checks this
motion, it is a great enemy to all corrup-
tion. The admiffion of the external air is
likewife neceflary, as no intefline motion
can begin without its affiftance. Hence
bodies preferved from the immediate con-
tact of the external air, by being put in an
exhaufted receiver, or covered over with
greafe, are kept from corruption.

BESIDES drinefs, cold, and want of
air, there are many other things which refift
corruption. But there are no fpecies of
bodies which are fo much in oppolition to
it as falts in general, whether alkaline, neu-
tral, or acid, but particularly the laft.

THE particular feat or fubject of corrup-
tion, feems to be in the mucilaginous or
oily particles ; for the more of thefe fat oily
particles a body has, it corrupts, ceteris

faribtf,

<fhe Principles of Part II.

paribus, the eafier. Thus water, replete
with the mucilaginous particles of an oozy
fat foil, corrupts fooner than water taken
from a gravelly foil.

THE natural progrefs of putrefaction in
vegetables is in this way. They begin firil
to heat towards the centre ; and emit a
fharp acid fmell, which is owing to the
acetous fermentation. As the heat advances,
this fmell goes off, and is fucceeded by a
very foetid one. Their colour, if it was light
before, now turns dark $ and the more the
putrefaction advances, the darker is always
the colour. They lofe their peculiar di£-
tinguifhing tafte, and gain a naufeous ca-
daverous one. Their fibres, which had a
certain degree of firmnefs, lofe that very
foon ; there is no more cohefion betwixt
the minute particles of which they were
compofed, and they fall into a putrid pulp.
Thefe are the general circumftances which
attend putrefaction.

IF

Sect. V. Agriculture and Vegetation. 79

IF vegetables are examined chymically
after putrefaction, they afford principles
very different from what they did before it.
Their falts, which were before fixed, are
now become volatile, and their oils are
much more volatile and foetid than what
they were. The foetid fmell of putrefied
bodies is owing to thefe volatile foetid oils
flying continually off. This greater vola-
tility in the falts and oils arifes from their
being more attenuated than what they
were.

How nature brings about thefe great
changes, is difficult to fay. The moft
plaufible and general theory is, that the
minute particles of air, of which there is
great plenty inclofed in all bodies, extrica-
ting themfelves from the fibres of the ve-
getable, which is now foftened by moifture,
and being agitated by the heat and conti-
nual alterations in the preffure of the at-
mofphere, raife an inteftine motion in the

bod vi

So The Principles of Part II,

body. This inteftine motion, caufing a
continual friction betwixt the falts, oils,
water, and earthy particles of the plant,
mull comminute them, and raife a great
degree of heat. The oily particles undergo
a change from this heat, and acquire a
foetor j and, being joined by the air coming
from the putrefied mafs, become more
volatile, and affecT: the fenfe of fmelling.
The inteftine motion, it is eaiy to perceive,
muft take away all cohefion in the fibres
and particles j and fo they fall into a pulpy
fubftance. The oils and falts having a
natural affinity, will unite j and fo the falts,
by the natural volatility of the oil, will
become volatile themfelves, from being
fixed before.

THIS is a very plaufible theory, though,
I muft own, liable to many objections.
The heat and weight of the atmofphere,
muft reach bodies preferved by the means
of oil, as well as if they were not rubbed
with it. We do not find thofe vegetables

which

Seel. V. Agriculture and Vegetation. 8 1

which are moft apt to putrefy, contain more
air, than thofe which are lefs liable to pu-
trefaction. The fixed air of vegetables is
not acted upon by heat ; nor does there
appear any caufe why it fhould get free.
It is difficult to arrive at any degree of
certainty in thefe abftrufe ipeculations. To
me the firft mover feems to be that ele*
mentary fire which is inclofed in all bodies,
fet in motion by the external heat of the
atmolphere. Hence the particles are made
to recede} and the fixed air uniting, be-
comes elaflic, and burfts the vefiels of the
vegetable body.

THE defign and end of this procefs is
more apparent, than the means which the
Author of nature takes to accomplish thefe.
Were vegetables to be deftroyed only by
external force, by far the greateft part of
them would remain untouched j and fo be
an ufelefs burthen on nature. Were they
to be deflroyed by an internal fermentation,
as at prefentj without having their parts

G vola-

82 We Principles of Part II.

volatilized, the particles to which they muft
be reduced, would be continually warned
off from the foil, carried into the fea, and fo
be of little ufe towards the nourifhment of
other plants.

THE only proper and wife fcheme is
followed. The oils and falts, from being
fixed, are volatilized, carried up into the
air, and defcend again to fructify the earth,
which was lately robbed of them. Cor*
ruption, then, is the parent of vegetation ;
and could be fo in no other way than in
the prefent. Though of feeming difadvan-
tage in nature, as mewing it on the decay ;
though highly difagreeable to the external
fenfes, and often dangerous to health j yet
is putrefaction of more ufe than any of the
other two fermentations, as it provides for
our future nourimment, and carries on that
beautiful circle, which nature is command-
ed, by her author and conftant fupporter,
to move in.

PUTRE-

Sec~l. V. Agriculture and Vegetation. 83

PUTREFIED fubftances are all of an al-
kaline nature. The alkaline fait is often
indeed invifcated by the oily parts, fo that
it can fcarcely efTervefce with acids. This
has led fome to aflert, that putrefied fub-
ilances were not alkaline ; an aflertion op-
pofite to experiment. We know with what
a gentle heat the volatile falts of putrefied
bodies rife ; a heat incapable to form thofe
falts, if they did not pre-exift ; but capable
of raifing them when once formed. As
pigeons dung is the ftrongefl of all dungs,
for vegetable and animal fubflances are the
fame when putrefied, the alkaline falts are
moft obfervable in it. I have feen the fur-
face of that dung covered with a white fait,
which fmelt as ftrong as the volatile fait of
hartmorn. Every one is fenfible of his
eyes watering, when he goes into a pigeon-
houfej owing to the pungent volatile falts
in the air. Subftances highly putrefied ef-
fervefce with acids. Reaumur, Ipeaking of
the leaves of the vine, which he had fet

G 2 by

84 W* Principles of Part IL

by to putrefy : Quand elks ont cte pourrm
jufyue a ce point on elks per dent leur nommes
four prendre celui de terreauy elks ont fer-
mente vivement et fubitement avec les acides^
que je verfes dejjut. Au lieu que Fefprit de
nitre verfcfur de fuilles feches, oufur defuilks
jimplement commence a pourrir^ nici produit
aucune fermentation fenjible. This experiment
puts the queftion beyond all doubt*

FARMERS have difcovered, by long ex-
perience, that the dung of different ani-
mals differs very much, as to the quantity
to be uied, and the ground upon which it
ought to be laid. A much fmaller quan-
tity of pigeons dung muft be employed
than of any other; and even that mould
be laid on cold wet foil. The dung of
iheep and hogs feems, by experience, to
have the preference to all others. Thefe
different effects depend on the different
quantities of oil and volatile falts in the
dung ; and thefe again on the food of the
animal, on the time it flays in the inteftine

canal,

Sect. V. Agriculture and Vegetation. 85

canal, on the nature of the juices mixed
with the aliment there, and on the natural
heat of the body.

LET us now make fomc practical obferva-
tions with regard to the management of
dunghills : for this is an affair of confider-
able importance, and in which farmers feem
to be very ignorant.

DRY vegetables require a conliderable
degree of moifture before they can be
brought to putrefy. I think dunghills are
generally kept too dry, as they are com-
monly in this country placed on a high
iituation, and are themfelves raifed to a
confiderable height. A hollow fituation,
which will retain the moifture, is the beft.
Too much moifture is likewife bad. This
may be prevented by having hollow places,
with clay bottoms, at the fide of the dung-
hill, into which the fuperfluous moifture
may be allowed to run, and from whence
it may be reftored again by pumps to the
dunghill at pleafure.

G 3 BUT

86 Tfc Principles of Part II.

BUT there is yet a worfe confequence
from fuch a fituation. The juices of the
dunghill are diflblvable in water, and are
Continually warned off by the rains which
fall, Hence a great part, nay almoft the
whole of the vegetable food, is loft. It is
a bad advice, therefore, which the Journal
Oeconomique gives, to place the dunghill
on a declivity. A hollow fituation, where
the bottom is clay, or where it is caufeyed,
is the propereft to carry pn the procefs of
corruption.

As the fun and wind exhales the volatile
falts and oils, and as too much air rather
retards this procefs, I mould think it very
reafonable, to place the dunghill in a fituation
fhadowed and furrounded by trees. There
is a clofenefs and moiflure in this fituation,
which will very much faypur corruption.

I fee that practical farmers advife, that
the dunghill mould be covered with earth,

tQ

Sect. V. Agriculture and Vegetation. 87

to hinder the volatile particles from flying
off. But how can this be done, when
there are frefh additions made to the dung-
hill every day ? It would indeed putrefy
fooner -, but then it muft lofe the influence
of the air, by which only it becomes fit
nourishment for vegetables. The effects of
the air on the dunghill muft be confider-
able, as it is fo loofe and pervious a body.
I am more inclined to agree with them in
another obfervation, that the north and eaft
winds mould have free accefs, efpecially in
winter, to the dunghill. We mall after-
wards fee, that thefe winds are found, by
experience, to be more impregnated with
the aereal nourifliment than the others, and
particularly at that time,

A s the procefs of corruption, in the com-
mon way, goes on very flowly ; and as
great part of the dung which is carried out
from the dunghill, is not half putrefied,
and confequently not fufriciently prepared
for vegetables ; it would be of ufe to quicken
that procefs, if we knew of any eafy me-
G 4 thod

88 'The Principles of Part II.

thod to do it. There are ferments for the
putrefactive fermentation, as well as for tke
vinous. Hence Stahl : Corpus in putredine
exiftenS) olio a putredine liber o facillime cor-
ruptlonem conciliat j quia illud ipfum, quod
in motu intejlino jam pofitum eft, alter urn qui-
efcensy ad talem motum tamen prodive, in
eundem motum intejlinum facile abripere
poteft.

ANIMAL fubftances already putrefied,
fuch as ftale urine, human dung, the car-
cales of animals, &c. are the proper putrid
ferments. If the urine of horfes, and ftall-
fed cattle, is carried into proper refervoirs,
and there allowed to turn ftale, it will, if
thrown on the dunghill, very much quicken
the fermentation.

PUTREFIED bodies are of a very vola-*
tile nature ; infomuch that if expofed to a
dry hot air, they continually diminifh in
bulk, until all the volatile parts being car-
ried off? the remainder is found to be an

Sett. V. Agriculture and Vegetation. 89

earth moftly of the abforbent kind.' This
mows, that dunghills mould not be kept
too long after they are fufficiently putrefied ;
and that dung mould not be expofed on the
furface of the ground in hot weather, as
often happens ; but immediately ploughed
in, if carried out at that time. It is a£-
ferted by fome fanners of obfervation, that
dung, when expofed for five or fix weeks
on the furface, fructifies ground more, than
when it is directly ploughed in, and mixed
with the foil. If this obfervation is found
to be true, the winter and fpring will be
the propereft feafons for expofing it. A fu-
perficial ploughing after the dung is ipread,
would feem to bid faireft for attaining the
advantages and fhunning the difadvantages
of both methods.

THE mud of ponds and ditches comes
properly under the clafs of putrefied bodies,
as it confifts of earth and the putrefied parts
of vegetables,

SECT,

90 We Principles of Part II.

SECT. VI.

Of manures which arife from burning vege-
tables.

AL L vegetables converted into afhes
by the action of the fire, afford a
good nourishment for vegetables, efpecially
for grafs j becaufe, as their action is very
fudden, it is fooner obfervable on a grafs
than corn field. Chymiftry fhows, that
thefe afhes confift of an indiflblvable earth,
and an alkaline fait ; which latter body at-
tracts acids more ftrongly than any other.
Fern afhes contain the moft fait of any
common vegetable which I know j the
fixth part is alkaline fait. They rnuft,
therefore, be the propereft for this ufe. At
the alum works near Scarborough, the
farmer pays 2 J. a cart-load for the refufe
of the earth of thefe afhes, after almoft all
the fait is extracted out of them. The
refufe of the foap manufactures, and of
the bleachfield, are rich manures. The

afhes

Sed. VI. Agriculture and Vegetation. 9 1

afhes of peat, which are moft ufed, afford
falts equal only to the thirty-fecond part of
the whole, and are the weakeft of all thofe
I know.

HFRE we muft clafs the burning of the
turf, or furface, which is often done to im-
prove poor foil. Farmers think it ads by
difpelling a four juice which land has con-
traded from lying long untilled : and they
chiefly prefcribe it for that fort of poqr
ground ; for they all agree that it hurts
rich foil. But I imagine, that the benefit
arifing from it is owing to the alkaline
fait arifmg frc/m burning the roots of ve^
getables : for farmers enjoin us to go no
deeper than thofe roots ; and it is found,
that the greater the quantity of roots, as
happens in land which has been long
untilled, the more benefit arifes from
burning,

THERE is another manure which takes
its rife from fire, and properly belongs to

this

92 *Ihe Principles of Part II.

this fe<ftion ; that is, foot. This is found,
by chymical experiments, to be a compofi-
tion of volatile alkaline fait, oil, and a little
earth. It is remarked, that the effects of
this compoft are very fudden, they being
obfervable after the firft rains.

SECT. VII.

Of animal manures.

AL L animal fubftances enrich ground
prodigiouily ; fuch as, blood, gar-
bage, urine,. &c. becaufe they putrefy ea-
iily. As we have treated of dung, we need
not fpeak of thefe. But there are other
animal fubftances, fuch as {havings and
tips of horns, hair, filk, woollen rags, &c.
which do not feem, from their firm tex-
ture, to be fo capable of putrefaction. All
thefe contain a great quantity of a muci-
laginous and gelatinous fubftance, capable
of being diffolved by water, of a fapona-
ceous nature, and conlifling, as appears
by chymical experiments, of falts and oils

intimately

Se<5t. VII. Agriculture and Vegetation. 93

intimately mixed, and difTolved in much
water. This mucilaginous fubftance muft,
then, be fit nourishment for plants.

THE action of thefe manures is com-
monly attributed to their imbibing the dews,
and conveying moifture to the ground. But
woollen rags rather repel, from their oily
nature, than attradt moifture ; and were
they only fimply to conduct the moifture
into the ground, linen rags would do as
well : but they do not. Thefe woollen
rags being much ufed in chalky grounds,
which are dry, has given rife to this opinion.
What thefe grounds fland moft in need of,-
is a mucilaginous fubftance, which thefe
rags are full of.

THE animal fhells, fuch as oyfter-fhells,
periwinkles, cgckles, &c. muft be included
amongft animal fubftances. Thefe are
long of diflblving j but it is obferved, that
in fix or feven years they make the ground
fo mellow, that it muft be allowed to

ftand

94 7& Principles of Part IL

ffond a year 6r two, that it may confoli-
date again, and the ferment be retrained ;
clfe it is not able to fupport the corn.
The reafon of this expaniion of the earth,
will appear from the expanfive force of
fhell-marl. Thefe different mells are a
compofition of calcarious particles, fit to
be converted, by the fire, into quick-lime,
and of an animal oil.

WE muft here confider a body, called
foell-marl, which is commonly, though im-
properly, clafled with the marls. It muft
be ranked amongft the mells, as it is a pu-
trefied animal mell. It is a white light
fubflance, with an odorous fmell, appear-
ing to the eye to confift of a number of
fmall mells, and generally found at the
depth of a foot or two in thofe hollow
grounds which have been formerly over-
flowed. An animal inhabiting fuch a mell
I have met with in ponds, though it is
very rare. It muft have been once a very
common creature in this country, and ap-
pears

Seel. VII. Agriculture and Vegetation. 95

pears to have been deftroyed in moft
counties at once by fome general difafter
which affected it; the natural depofition
of foil from thefe waters has buried it fo
deep.

Exp. 30. When water is poured on this
body, it fucks it in greedily, and fwells like
a fpunge ; becomes very foft, but does not
fall down like marl into a powder. It is
by means of this quality that all fhells,
whether they are laid on corrupted, or be-
come fo in the foil, make ground fo very
light and fpungy.

I could difcover no fait in it, by the dif-
ferent trials which I made. It makes a
ftrong effervefcence with acids, and requires
fix times more of them to faturate it, than
what any of the marls which I have yet
met with do.

IT affords on diftillation, like all animal
fubflances, a urinous alkaline fpirit, and an
oil of the heavy kind.

WHEN

96 The Principles of Part II.

WHEN calcined in the fire, it is con-
verted to quick-lime. By thefe experi-
ments it does appear plainly to be a putre-
fied animal fhell, eafily feparable by water,
and a ftrong attra&er of acids.

PART

[97]

SECT. I.

effetfs of different fubftances with regard
to vegetation.

1

E manures which I have
examined, are fuch as chance di£-
covered to be ufeful in vegeta-
tion, and practice has continued, becaufe
they can be eaiily and cheaply got. But,
for what we know, there may be others,
which, though not in fuch plenty as to be
of ufe to the farmer, may have effects on
vegetation, that may be ufeful to thofe who
inquire into the nature of the vegetable
food. The more they know of the effects
of different bodies on plants, the greater
chance they have to difcover the nourifh-
ment of plants -, at leaft this is the only
road. I made the following experiment
with this defign.

H Exp.

98 The Principles of Part III.

Exp. 31. May 2. 1755, I took fome vir-
gin earth from the fide of a fleep bank,
where neither dung nor plough had ever
been ; filled fome pots with it j mixed with
the earth the following materials ; and fet
them in the ground. Each pot contained
about 61b. of earth. In each pot I plant-
ed five grains of the fame barley $ and
that I might be fure that each grain was
proper for feed, I took none but what fell
to the bottom of water. N° i. contained
plain virgin earth, that I might have a
Standard for the reft. N° 2. was always
watered with hard water. N° 3 . had i oz.
of faltpetre, and 2 oz. of oil of olives,
mixed with the earth. N° 4. contained
i oz. of faltpetre. N° 5. contained half
an oz. of vitriolated tartar. N° 6. con-
tained i oz. of flour of brimftone. N° 7.
contained half an oz. of fpirit of hartf-
horn. N° 8. contained 2 oz. of oil of
olives. N° 9. contained fpirit of nitre,
diluted with water, half an oz. N° 10.

con-

Sect. I. Agriculture and Vegetation. 99

Contained of fea-falt i oz. N° n. con-
tained plain earth, and the grains fteeped
for 1 6 hours in a ftrong lye of hens dung
and faltpetre.

May 9. when I looked at them again,
N° i. and 2. had each one plant, juft ap-
pearing above ground. N° 6. had two
taller than the former. N° 8. had all the
five up, one of which was three fourths
of an inch tall.

May 1 1. N° i. has all five up, and about
Half an inch high. N° 2. has two, and as
high. N° 3.4. and 5. have one each, juft
appearing. N° 6. has four, three fourths
of an inch tall. N° 7. has one, half an
inch tall. N° 8. has five, one inch tall.
N° 9. has two, juft appearing. N° 10. has
none. N° u. has four. Some -of the
fame grain fet in the garden-mould juft
betide the pots, were three fourths of an
inch high,

H 2 May

loo We Principles of Part III.

May 2 1 . five or fix days rain, and then
fair weather. N° I. and 2. have five, about
four inches tall. N° 3. has four, three
inches tall. N° 4. has five, about two
inches tall. Thofe in N° 5. are three
inches tall. N° 6. has five equal to N° i.
and 2. N° 7. has two, about one inch.
N° 8. has fix, two and a half inches tall.
N° 9. has three, above half an inch tall,
and very ill coloured. N° 10. has one,
half an inch tall. N° n. has five, which
are the beft of all.

June i. N° 2. the beft of all, nine inches
high, and of the deepeft green. N° 12.
contained the next for fize and colour, and
was but little inferior. N° 6. next in height,
but had many withered leaves ; N° 3 . 4.
and 5. about five inches tall, and of much
the fame colour ; N° 7. about an inch tall,
with fome of the leaves withered -, N° 8.
high, but fomewhat withered ; N° 10. has
three about an inch long.

June

Sect. I. Agriculture and Vegetation, i o I

June 10. N° 2. ftill bed. N° 6. almoft
withered. N° 7. entirely withered. N° 9.
and 10. contained poor fickly plants.

June 1 8. N° 2. ftill beft, and has nine-
teen ftalks. N° 12. next, and has ten ftalks.
N° i. not quite fo tall, but has thirteen
ftalks. N° 3. comes next. N° 6. almoft
quite gone. N° 7. none. N° 8. and 9.
equal. N° 10. leaft of all.

Aug. 1 6. N° i. has feventeen ears of
corn. N° 2. has nineteen. N° 3. has thir-
teen. N° 4. has fifteen. N° 5. has twenty-
nine. N° 8. has nine, and thofe very large.
N° 9. has twenty, and thofe large. N° 10.
has ftalks about a foot in length, and
four or five ears, about one inch long only.
N° 1 1 . has eighteen very good ones.

THUS I have related the experiment

faithfully and minutely, as becomes every

experimenter. The fads fhould always

H 3 be

IO2 'The Principles of Part III.

be related by themfelves, diftinct from all
reafoning ; for we may err in the latter,
but the former is truth itfelf. I mould
have been glad to have repeated thefe ex-
periments, efpecially with a poorer foil
than what I found, by experiment, this to
be. I mould have been glad to have had
a greater fund of experiments to have rea-
foned upon, as there is always danger of
fome miftake in reafoning from a fingle
experiment. But it is to be remembered,
that fuch experiments can be made only
once a-year, and there is no time left now
to repeat and augment them. As it then
ftands, I mall draw fome conclufions from

Corollary i. Virgin earth, taken up within
a foot of the furface, and from a bank which
had a north afpecl:, contains in itfelf the prin-
ciples of vegetation in great plenty. Such
earth is ufed as a manure by farmers ; and
they obferve, that virgin foil wilt fructify
earth much richer in appearance than itfelf.

Cor.

Sect. I. Agriculture and Vegetation. 103

Cor. 2. Grain appears to grow better,
that it has been fteeped in dung and falt-
petre. It is a fadt long ago bbferved, that
grain vegetates flronger, quicker, and is lefs
fubjecl to blight and mildew, if it has been
fteeped in liquors which contain fait and
oil, fuch as fea-water, ftale urine, &c.
This is eafily accounted for. It is certainly
of great moment, with what the vefTels of
the feed are at firfl filled, whether with
watery or with rich juices. This is one
great reafon that makes a dry feed-time fb
ufeful : for if the ground is dry, the juices
which the feed imbibes, are rich and nu-
tritious ; whereas in rainy weather, thefe
juices are diluted with too much rain, and
the tender plant is weakened. In medica-
ting grains, we fill their veflels with plenty
of falts and oils, and give them vigour to
fend out many roots, upon which the nou-
rimment of plants depends. The way to
make a ftrong man, is to nourifh the child
with fuitable food.

H 4 Cor.

1 04 cfke Principles of Part III.

Cor. 3. Hard water appears to afford a
ftrong nourishment for plants. This is
very oppofite to the common received
opinion : for gardeners never ufe it, when
they can get foft water •> and if they fufpect
any hardnefs, endeavour to foften it as much
as they can, by letting it ftand expofed for
fome time to the heat of the fun. In this,
however, they are miftaken. This expo-
fition may make water harder j but can
never foften water which is confiderably
hard. The hardnefs of this water which
I ufed, and indeed of all hard waters *
which I have met with, was difcovered,
by experiments, to be owing to the acid of
nitre, joined to an abforbent earthy bafe.
The bafe in this water was a calcarious
earth $ in moft hard waters it is only an
abforbent.

Cor. 4. Oil of olives, in the proportion

* Vid, Experiments on bleaching, fe&. on hard
waters.

Of

Sect. I. Agriculture and Vegetation. 105

of i oz. to 3lb. of earth, appeared to
have very good effects at firftj but thefe
afterwards declined. The ears were good,
though not many. Was the oil in too
great quantity? Was it not fufficiently
attenuated by the falts in the earth; and,
by that means, did it not block up the
mouths of the radical veflels ? Had it not
fufficient time to incorporate with the
earth ? Thefe are queftions which I cannot
refolve.

Cor. 5. It appears, that faltpetre, in the
proportion of i oz, to 6 Ib. of earth, rather
retarded than promoted vegetation. This
indeed furprifed me, as I generally believed
nitre to be of a very fruitful nature ; nay,
the very caufe of fertility. It does not
feem to have been employed in too great
quantity neither. Its great reputation for
fertility would make one cautious in
doubting that efFecl:, without a fufficient
number of experiments to fupport that
opinion.

Cor.

io6 <Tbe Principles of Part III.

Cor. 6. The vegetative effects of nitre
does not feem to have been increafed by
the addition of twice its quantity of oil
of olives. The oil of olives feems to have
fucceeded better with the addition of the
nitre than without it. The falts would at-
tenuate the oil, and help it to enter the
veffels of the plant more eafily.

Cor. 7. Vitriolated tartan which is a
compofition of the acid of vitriol and an
alkaline fait, feems to promote vegetation
very ftrongly. A gentleman wanted to de-
ftroy fome rank grafs in his court, and was
advifed to iprinkle it with the oil of vitriol,
as the greateft enemy to vegetation. He did
fo 5 but, to his great furprife, the grafs came
up much flronger than before.

Cor. 8. Sea-falt, in the proportion of
I oz. to 6 lb. of earth, appears to be an
enemy to vegetation. Moft farmers comr-
mend it as a good manure, though there

are

Sett. I. Agriculture and Vegetation. 107

are fome who doubt of its good effects.
Perhaps in a fmaller quantity, its effects
may be more beneficial ; efpecially if it
contains the bittern, which is a competi-
tion of the vitriolic acid, and an abforbent
bafe*, and a bituminous oil, both of which
muft be affiftants of vegetation. The fait
which I ufed being table-falt, was in a great
meafure freed from thefe.

Cor. 9. The acid of nitre feems to have
retarded vegetation at firft; perhaps from
its being not fufficiently united to the ab-
forbent particles of the foil. But at laft it
feems to have promoted the growth of the
plants coniiderably.

Cor. 10. Spirit of hartmorn, which is a
volatile fait diluted with water, feems to
have poifoned the young plants.

Cor. n. Flowers of brimftone, i oz. to
6 Ib. of earth, appears to have promoted
vegetation greatly at firft 5 but in a month's

time

io8 Vbe Principles of Part III.

time to have deftroyed the plants like a
poifon. This fubftance is often fprinkled
on turnip-feed before it is fowed; and it
is thought by farmers to amft their growth,
and to keep the flies from the leaves. Was
too great a quantity of it-ufed in this ex-
periment ? Plants, therefore, have not only
their food, but their poifon. Quter. Will
the artificial fulphur, which arifes from the
combuftion of many plants in a particular
way, and which is to be found in great
plenty in kelp-afhes, in the foap-ames, and
in many of the afhes ufed in the bleach-
field, have the fame bad effects as natural
fulphur ?

AFTER the laft experiment was made,
there appeared to me a confiderable diffe-
rence betwixt the method by which it was
carried on, and the courfe which nature
follows in fuch operations. I mixed the
materials, whofe effects on vegetation I
wanted to difcover, all at once with the
earth: but in a natural way, the fructifying

prin-

Sect. I. Agriculture and Vegetation. 109

principles muft be beftowed on it by gentle
degrees, and in very fmall quantities. Earth,
indeed, which has lain for fome time fal-
lowed, and is therefore well ftored with the
feeds of vegetation, is much in the fame
ftate with the earth of my experiments,
though not fo much faturated with the
nutritive principles, as mine was with the
different materials. Befides, the former is
conftantly receiving frem fupplies. That
I might approach nearer to the courfe of
nature, and fupply materials according to
the growth of the plants, the following ex-
periments were made.

Exp. 32. Six pots were filled with poor,
light, virgin earth. Each pot contained
5 Ib. and 5 grains of heavy barley. N° i .
had no mixture. N° 2. was watered with
I dr. of faltpetre dirTolved in 3 oz. of water.
N° 3. with the fame quantity of fea-falt.
N°. 4. with the fame of Epfom fait, which
is compofed of the acid of vitriol, and the
earth, called magnefm alba. N° 5. with 2

dr.

no The Principles of Part III.

dr. of the following compofition diluted in
water. Half an oz. of quick-lime was
feturated with weak fpirit of nitre, which
produces a very cauftic liquor. N° 6. with
2 dr. of the former mixture, having half
its quantity of oil of olives mixed with it.
This compofition appeared to me to ap-
proach near to the natural vegetable food.
All the feeds were fown June 16. 1756,
except N° 6. which was not till the ipth
of June. I planted fome of the fame feeds
in the garden-mould befide the pots.

"June 23. N° i. has one plant, half an
inch high. N° 2. has one, an inch tall*
and another, juft appearing. N° 3. none.
N° 4. has four, two of which are one inch
tall. N° 5. none. N° 6. has three, one
inch tall.

June 27. N° i. has four, two and an
half inches high. N° 2. has four. N° 3.
has two, the talleft is an inch high. N° 4.
has five, two inches. N° 5, none. N° 6.

has

Se£t. I. Agriculture and Vegetation* in

has four as tall as N° 4. Thofe .in the
rich garden foil were three and an half
inches tall.

July 4. N° 2. taller and greener thim
N° i. N° 4. and 6. equal to N° i.

July 10. N° 2. beft. N° 6. next. No. 4.
next. N° i. and 3. follow. N° 5. has one,
three inches high.

July 15. N° i. four of the five plants
have yellow withered leaves. N° 2. and 6.
deepeft coloured and talleft. N° 3. and 4.
equal. N° 5. has one weak plant, about fix
inches high. The weather has been hot
for ten days. Added to N° 2. 3. and 4.
i dr. more of each of their falts, and to N°
5. and 6. the fame quantities of the fame
mixtures.

July 24. has rained five days. N° 2.
and 6. about fifteen inches tall, and much
better than the reft; the latter rather beft.

NQ

112 lie Principles of Part III.

N° 4. next beft, and twelve inches tall.
N° 3. next, and nine inches. N° j. next.
N° 5. has one, about twelve inches. Thofe
in the garden foil near two feet, and have
fent up many more (talks.

Auguft 19. The laft fortnight cold rainy
weather, with eafterly winds. N° 6. is the
talleft, of the deepeft green colour, and
therefore the beft. The reft as formerly.
Added to each the fame quantity of falts
and mixtures as before.

September i . Has been good warm wea-
ther. The plants as before.

September 26. N° i'. had ten ears, the
largeft of which carried twenty grains.
N° 2. has eleven, the largeft of which had
twenty-four grains. N° 3. worfe than N°
i. N° 4. has thirteen ears, the largeft of
which carries twenty grains. N° 5. has
but one ear -, and that is not fo ripe, and
has fmaller grains than the reft. N° 6.

has

Seel. I. Agriculture and Vegetation. 1 1 3

has fixteen ears, many of which carry
twenty-four grains, and thofe larger than
any of the reft. It has one double ear,
which has forty grains. Many of the ears
in the garden foil have thirty-two grains.

LET us now draw fome corollaries from
this experiment.

Cor. i. Sea-falt added in fmall quantities,
and by gentle degrees, to a poor foil, feems
again to be rather hurtful than beneficial
to it. What efFeft it would have on a foil
full of oleaginous particles, appears not from
this experiment,

Cor. 2. Saltpetre managed the fame way,
promotes vegetation confiderably, and ap-
pears to have made the foil capable of pro-
ducing a fourth more.

Cor. 3 . Epfbm fait applied the fame way,
is pretty nearly equal in its nutritive power
to faltpetre. The foregoing experiment

I taught

H4 *fhe Principles of Part III.

taught me the good effects of the acid of
vitriol faturated with an alkaline fait; the
prefent teaches me, that the fame acid fa-
turated with a particular abforbent earth,
promotes fertility. Hence I concluded, in
part 2. feet. ,3. that marl added to the
fame acid, after the poifonous chalybeate
particles were feparated from it, would ra-
ther be of fervice than difiervice to the
foil.

Cor. 4. Quick-lime, faturated with fpirit
of nitre, added in fmall quantities, and well
diluted with water, appears to have hurt the
vegetative power of the foil. Was it ufed
in too great quantity ? or did it not meet
with what is as necefTary to vegetation as
itfelf, a due proportion of oleaginous par-
ticles, which nature always fupplies in pro-
portion as me fupplies the falls ? The latter
feems to have been the cafe, from the fol-
lowing corollary.

Cor,

Sect. I. Agriculture and Vegetation. 115

Cor. 5. The former liquor, with half its
quantity of oil of olives added to it, and
(halted well together, appears to have en-
riched the foil moft, and to have nearly
doubled its fertility.

Cor. 6. None of our admixtures was able
to bring the poor light foil to the fame fer-
tility with the rich garden mould. And
no wonder. There the falts and oils are
highly attenuated, duly proportioned, and
well mixed, by length of time ; and, con-
fequently, fitted to enter the fmall veflels of
the roots. Befides, that foil, by the mix-
ture of putrefcent matter, is in a conftant
ftate of fermentation, becomes eafily pene-
trable, and offers a larger field for the roots
of plants to feed on.

A s lime never ads on the foil till it be-
comes effete, I was willing to fee its effects
when faturated in that flate with the acid
of nitre; although experiments feem to
I 2 fhow,

1 1 6 The Principles of Part III.

mow, that the product is much of the fame
nature. Half an oz. of old lime wall, was
therefore faturated with the fpirit of nitre.

Exp. 33. July 15, 1756, two pots were
filled with the fame earth as ufed in the
former experiment, and in the fame quan-
tity. Three grains of barley were fown in
each pot. N° I. contained plain earth-
N° 2. was watered with i dr. of the folu-
tion well diluted.

July 25. N° i. has three plants, one inch
in height. N° 2. has one, the fame height.

^ 19. N° 2. has only onej but that
is of a deeper green than any in N° i.
Added to N° 2. the fame quantity of mix-
ture as before.

Sept. 26. N° 2. of a deeper green, has
more after-moots, and a longer ear than
any in N° i.

Cor.

Sect. I. Agriculture and Vegetation. 117

Cor. I can hardly fay whether the foil
was the better or the worfe for the mixture :
for, on one hand, only one of the feeds took
effect y and on the other, that plant was in
a more thriving ftate than any plant in the
plain earth. This, however, appears plain,
that it had not the bad effects of the ipirit
of nitre and quick-lime in the former expe-
riment. Was this owing to the lime being
quick in the former, and effete in the latter
cafe ? or to a fmaller quantity of the mix-
ture being ufed ? I raiher incline to the
latter opinion, as the mixtures appear to be
fimilar by experiment.

THAT I might difcover the effects of the
fame folution on rich garden mould,

Exp. 34. July 14, 1756, I filled two
pots with 5 Ib. each of that foil j fowed
four grains of barley in each, and watered
N° i . with the fame quantity of the fame
folution uied in the foregoing experiment.
July 20. three plants have appeared in each
13 pot;

n8 The Principles of Part III.

pot; thofe in N° 2. a degree taller than
thofe in Na I. July 27. the plants in both
pots equal. Aug. 13. the plants in N° i.
are r,ather taller than thofe in N° 2. : but
none of them thrive well ; either becaufe
they were late fown, or becaufe they were
in a corner where two tall hedges met, and
therefore wanted air. I removed the pots
to a more open place. Sept. I. N° I. has
one taller, and of a deeper green, than N° 2.
The plants have grown fafter than before.
Sept. 30. the plants are come to no per-
fection.

Cor. i. The plants in the two laft expe-
riments did not vegetate near fo quickly in
the fame time, as thofe of the preceding
experiment had done. Has not the ipring,
from fome particular caufes which operate
at that time, a peculiar vegetative power,
which the fummer poffeffes not in fo great
a degree ? So it appeared to me, although
the fummer was cold and rainy, like our
fprings, and the foil in the latter experi-
ment

Sect I. Agriculture and Vegetation. 119

ment very rich, and in the former taken
from the fame place that the earth of the
foregoing was.

Cor. 2. Plants feem to ftand in need of
a conftant application of free air to their
furfaces. All trees in thickets ftretch out
their branches either laterally or longitu-
dinally, where they can have moft air. Does
this air act only on their furface ? or does it
enter the vefTels of the plant ? If the latter,
is not an impetus from the air in motion ne-
ceffary in order to its entrance, as the mere
preflure of the air is always the fame in
fimilar altitudes ?

Cor. 3 . The plants feem neither to have
been much better, nor much worfe, for the
addition of the faline mixture.

Exp. 35. May 25, 1758, I fovved fome

barley in 4 different pots, filled with the

fame poor earth. N° i, contains the pure

earth. N° 2. the fame earth frequently

I 4 watered

120 The Principles of Part III.

watered with a folution of that particular
fait found flicking on the plaiftered walls
of boghoufes, &c. It got altogether i dr.
of this fait. N° 3. fame earth watered in
the fame way with the fame quantity of
crude tartar, which was the only eflential
fait that I could get at the time. N° 4.
the fame earth treated the fame way with
the fame quantity of foluble tartar, which
is the former acid fait neutralized with an
alkaline fait.

June 10. All pretty equal. July 25. N° i.
has two ears, and the worft of all. N° 2.
has feven, all larger. N° 3. has five, very
good. N° 4. has three.

Angujl 8. N° i. has nine. N° 2. has four-
teen. N° 3. has nine. N° 4. has fifteen.

22. N° 4. has the heavieft ears, and
ftrongeft ftraw. N° 2. is next to it. N° 3.
is better than N° i.

Cor.

Sect. I. Agriculture and Vegetation* 121

Cor. i. The aereal nitre promotes vege-
tation very much. This fait we elfewhere
prove to be the foflil alkali.

Cor. 2. The eflential fait of rhenifh wine
promoted vegetation a little. The fame
fait neutralized, had very ftrong effects on
the growth of plants.

THAT I might difcover the natural ef-
fects of rain-water,

Exp. 36. May 23, 1758, I took two pots
filled with poor earth, {owed fome barley
in each, and placed them near the window
of a green-houfe, fo that they might get
air, but no rain. NQ I. was conflantly
watered with fpring- water.' N0 2. with
the fame quantity of rain-water.

June 10. The plants watered with rain-
water, feem the beft ; but thofe of both
pots appeared fickly for want of a fufficient
quantity of air.

Principles of Part III.

Aug. 2. The rain-water appears ftill beft.
22. I cannot fay which is beft, as they are
both fo fickly.

THESE are all the experiments which I
have made with regard to the effeds of
different bodies on vegetation. This field
has not been cultivated with that attention
which the merit and importance of the fub-
jedl requires. It is indeed extenfive, as it
takes in the operations of all bodies which
can be either dirTolved or attenuated, fo as to
enter the veffels of plants. But it is only
from a number and variety of trials made
in it, that we can expecl to fee a juft theory
of vegetation arife. I could wifh, before I
attempt that fubjecl, to be pofleffed of a
greater number, and thofe oftener repeated,
that my conclufions might have been more
general and more certain. They were fuch
as appeared to me to refult naturally from
the experiment. How far they are to claim
aflent, I have left in every one's power to
judge. SECT.

Se£t II. Agriculture and Vegetation. 123

SECT. II.

Of the food of vegetables.

WE now come to treat of that impor-
tant queftion, What is the food or
nourifhment of plants ? a queftion which
has been much handled, but not fufficient-
ly afceftained yet. It has even been made
a queftion, Whether each plant has not its
peculiar and proper food, which it chufes
amongft the reft, from fome elective power
inherent in its roots ?

THOSE who take this fide of the queftion,
aflert, that the advantage arifing from the
change of fpecies is a certain proof of this ;
for if the fame nourishment ferved all
grains, the fame grain would thrive in the
fame ground, as well as another j that al-
though wheat will not fucceed in the fame
ground for two years fuccefiively, yet it
will bear another grain very well; and
that the different nature and properties of

vege-

124 The Principles of Part III.

vegetable juices are a flrong proof on their
fide.

THOSE who affert, that all vegetables
feed on the fame food, fupport their opi-
nion by the following arguments. The
longer ground is kept in tillage, though it
bears grain of different fpecies, the worfe
it becomes : but this would not happen, if
plants took different particles from the
foil : That all fort of weeds ftarve corn, by
taking part of the fame nourishment : That
fallowing ground would be an ufelefs prac-
tice, fince there is fuch a diverfity of fpe-
cies: That it would be in vain for plants
to have a tafte, fmce they have no local
motion : That change of fpecies fucceeds,
not becaufe plants take only their own
food, but becaufe fome loofen, while others
bind the ground j fome roots go deep into
the ground, while others keep about the
furface : That it is true, wheat will not fuc-
ceed in the fame ground two years fuccef-
fively, becaufe it requires more food than

that

Se6t II. Agriculture and Vegetation. 125

that ground can afford, although there is
fufficient nourishment left for other grains ;
and there would be no time left to plough
the ground, as wheat is fown in the har-
veft: and, That the difference of vege-
table juices depends not on the difference
of food, but on the particular ftruclure
of the veffels of plants.

THE latter opinion muft appear to every
one to be nearer the truth than the former :
nearer the truth, I fay, becaufe the advo-
cates for it feem to think, that one fort of
food ferves all vegetables. There I differ
from them. We faw, by the experiments
in the lail fection, that the fait of hard
water, Epfom fait, and the vitriolated tar-
tar, falts very different from one another,
nourifhed vegetables of the fame fpecies;
and therefore the food is not of one kind.
We know that fome trees contain the acid
of vitriol, becaufe with their charcoal we
can make a fulphur. We know, likewife,
that fome plants contain a nitrous fait,

while

126 The Principles of Part III.

while others one like fea-falt. Some vege-^
tables require a greater proportion of wa-
tery parts, and fome a fmaller. The food
of vegetables, then, is not all of the fame
kind. J-u- A,, /«.&Arfe M^LM

M

? HALES maintained, that all things
were made from water.

HE L MO NT was of this opinion, and
fupported it by an experiment known to
every perfon. He planted a willow, weigh-
ing 5lb. in a pot filled with dry earth.
The earth he watered with rain-water.
In five years the willow, not computing
the leaves which had fallen off, weighed
1 64 Ib. ; but the earth had loft nothing.
That elementary water is the food of ve-
getables, is a conclufion too ftrong from
this experiment. It only mows, that water
contains particles which are capable of nou-
rifhing plants. We have fhown, that fnow
and rain-water contain earth, oil, and as
they fvveep the air, muft contain fuch falts
as are in it too. SOME

-•

Sect I. Agriculture and Vegetation. 12 7

SOME modern philofophical chymifts,
fuch as MeiT. El/er and Euler, are of opi-
nion, that water is the nourifhment of
plants. The latter found that onions and
fome branches grew in diftilled water. But
the experiment does not convince me, for
diflilled water, as well as rain-water, con-
tains falts and oils. He owns in the fame
paper, that the diftilled water, expofed to
the fun, recovered its falts, oils, and earth.
It will, then, recover the fame principles
when the plants grow in it. It is not ne-
ceflary here to enter into that nice difcu£
fion, whether water receives thefe princi-
ples from the air, which I think moil pro-
bable, or is converted into them, which is
his opinion j it is fufficient for my pur-
pofe to fhow, that thefe principles enter
the veffels of the plants along with the
water. As I know no experiment that
eftablifhes this opinion, it appears to ftand
in oppofition to all my experiments : for
fome falts have ftrong vegetative powers j

but

128 fbe Principles of Part III.

but thefe do not arife from attracting and
retaining moifture, as thefe powers do not
appear to be in proportion to that quality.

OTHERS think, that the more terrene
particles are thofe which nourifh plants.
Of this opinion is the famous Tidl; be-
caufe, fays he, earth augments them ; and
whatfoever augments them, muft be their
food. Dung, and other manures, 'act only
by fermenting, and fo attenuating the foil ;
and are of no more ufe, than, as a knife,
to divide their food. But earth alone could
never do, without fome more active prin-
ciples. Mad Tutt been a chymift, he
would have known, that mere earth makes
but a fmall part of all plants. Soil may
certainly be too loofe. To earth already
fufficiently attenuated, manures would do
no fervice. Whence the falts and oils of
plants? Thefe are objections which the
favourers of his fyftern never can anfwer.

OTHERS

Setf. II. Agriculture and Vegetation. 129

OTHERS, feeing the neceffity of the air
to all plants, and obferving that plants im-
bibe a great deal during the night, as Dr.
Hales 's experiments fufficiently mow, affert,
that the foil only gives them fupport, but
air nourimment. To this the anfwer is
fhort, That plants thriving better in fome
foils than in others, and in proportion as
thefe foils are manured, fhows the ground
to be the principal pafture of plants ; the
air being the fame in grounds adjoining to
one another.

THE author of the Hijlolre Phyfique de-
duces all plants from certain fimilar orga-
nifed parts, which he fuppofes flying up and
down the air in great plenty, and which
attach themfelves, in fome unknown way,
each to its own tribe. If this were the
cafe, dung made of plants of the fame
fpecies, would fucceed beftj which is net
fo. I lhall allow this unphilofophical opi-

K nion

130 tte Principles of Part III.

nion to fall of itfelf, as it mutt naturally
do, when unfupported by experiments.

OTHERS attribute vegetation to falts of
different kinds. But whence they come,
and of what nature they are, we have only
their own affertion.

IT is the common fate, in all difputed
points, that each attaches himfelf to one
fide, without allowing the other any fhare
of truth. I have found by experience, that
each fide has generally fome truth in itj
that mankind err by extending that parti-
cular truth to a general one j and that the
real truth is generally made up of fome-
what taken from each opinion. The rea-
foners on agriculture have failed, becaufe
they afierted, that plants were fed either
by air, water, earth, or fait. I join, in fome
meafure, with all thefe ; and aflert, that
plants are nourished by thefe bodies, united
with two others, oil and fire in a fixed
ftate, Thefe fix principles joined together,

4- >£ 'm

<fa n, t,j tirtdjtrt '. £ •

JVL- a Jtefat ft 'fa^*kw*3~!&*& 176

Sect. II. Agriculture and Vegetation. 131

in my opinion, conftitute the vegetable nou-
rifhment. *

THIS eafily appears, when we confider,
i . That feveral kinds of nourishment, fuch
as leather, hair, horn-fhavings, rags, and
all vegetables, and vegetable juices, in an
intire ftate, prove proper food for vegetables.
2. That all vegetables and vegetable juices
afford thofe very principles, and no other,
by all the chymical experiments which have
yet been made on them with or without
fire. More arguments could be brought;
but thefe two I think conclufive.

AIR active and fixed is to be had every
where, if we are not at much pains to ex-
clude it. Elementary fire is to be found in
all bodies. Earth may be fupplied by any
foil managed with proper care. Water
drops from the clouds. Oil is a natural
principle of all earth, defcends with the
rains and fnows, and is communicated to
the ground by all the vegetable and animal
K 2 manures^

132 The Principles of Part III.

manures, in a found or putrid ftate, as our
experiments have fhewn. But whence the
fait, the moft adive, and, therefore, moft
neceffary principle of all ? We have not
as yet difcovered any in rich foil, nor in the
manures moft ufed, rj/#. lime, marl, mells,
chalk, &c. This is an important queftion ;
opens up the action of almoft all manures,
and of rich foils ; mows wherein the effect
of the air confifts j and, therefore, deferves
a particular difcuffion.

THE preceding experiments have mown,
that all fertile foils, and all manures, ex-
cept thofe already converted into a mucila-
ginous nature, confift of particles, .which,
in part, or all together, attract acids.
Dung, the afhes of vegetables, burnt earth,
contain fuch particles j lime, marl, animal
(hells, chalk, &c. are wholly of this nature.
Thefe then muft attract and retain all
acids, when they come within the fphere
of their attra&ion. If the air, to which
the foil is continually expofed, contains any

acids,

Seel. II. Agriculture and Vegetation. 133

acids, thefe bodies will draw it out, and be
converted to a neutral faline fubftance, en-
joying the properties of fait, fuch as folu-
bility in water, difTolving oils, and render-
ing them mifcible with water. Nothing,
then, remains to be proved, in order to the
converfion of thefe manures into a fait,
but that the air contains an acid fait.

THIS has been the opinion of the greateft
chymifts, not from theory alone, but be-
caufe they difcovered, that alkaline falts,
when expofed to the air, were converted
into neutral onesj and that metals, fuch
as tin, copper, and lead, were corroded,
and converted to a fait. Whether there is
fuch a fait, and what its nature, will be
beft afcertained and illuftrated, by confider-
ing the manufacture of nitre. This procefs
' too will (how the operation of the different
manures, as thefe are the very materials
ufed in this manufacture.

K 7 THE

• * w

134 lie Principles of Part III.

THE mofl common materials out of
which nitre is made, and, therefore, called
the matrix of nitre, are the rubbifh and
earth of old houfes, and efpecially of dove-
cotes, ftables, and church-ides ; particular
fat earths ; the afhes of burnt vegetables ;
putrefied animal or vegetable fubftances $
and fome particular kinds of ftones. Thefe
materials are expofed to the air for fome
months, particularly the winter months j
for, during that time, nitre is generated in
the greateft plenty. The place where the
materials are expofed, mould be acceffible
to the air and winds, but not to the rays
of the fun, or to the rains. The air is ne-
ceffary, as it generates the nitre j but the fun
is deftructive, as it exhales it. The rains
are prejudicial, becaufe they warn it away
when made. Drought is as deftrudive, as
that exhales the faline parts after they are
formed, and hinders the fermentation, ne-
cefTary to draw the nitre, and to open the
matrix to receive it. It is obierved, that
the north winds are particularly productive

pf

Sect. Hf Agriculture and Vegetation. 135

of the fait. In the Indies, from which we
have moft of our nitre, they expofe earth
of a particular kind, mixed with putrefied
vegetables, to the air, and from that extract
the nitre. Tourncfort tells us, in his travels,
vol. 2. p. 289. "In our converfation in
" the caravanfera of Erzeron, we learned
" from thofe of the caravan of Wan> a
" Turkifh town on the frontiers of Perjia^
" that they carefully lay up in heaps the
" dirt of the great roads, which are fre-
<c quented by caravans of camels. This
" earth they warn, and every year get out
" of it about i oo quintals of nitre,"

IN the manufactory of nitre at Paris,
where there is much made, they expofe the
rubbim of old houfes, mixed with the ames
of burnt vegetables, to the influence of the
air for fome months, and moiften it often
with ftale urine j and from thofe materials
extract their nitre. After all the nitre is
got out of them, they are as fit as before to
form more; and are again thrown on {he
K 4 heap,

136 The Principles of Part III.

heap. This fact fhows, that this fait is
not the natural fait of the earth, but formed
by its expofition to the air. After thefe
earths have been expofed a fufficient time
to the air, they are put into different cafks,
and water poured over them, to lixiviate or
diffolve the falts. The materials muft be
frequently ftirred about in the water, that
it may diffolve the falts. After the water is
fufficiently impregnated with the falts, they
draw it off, and add to it fome quick-lime,
and the aihes of vegetables or alkaline falts,
if it has not already got enough of them ;
the former to feparate the oil from the fait,
the latter to give it a fixed alkaline bafe in-
flead of an earthy one. They add alkaline
falts, as long as their addition makes the
liquor take a milky appearance, and yield a
precipitation. When no more precipitation
happens, then they decant the liquor, and
boil it up.

LET us now inquire into the origin of
nitre. There are various opinions about

this

Sect. II Agriculture and Vegetation. 137

this fait -y nor are chymifts yet agreed about
its birth. Some alledge it is attra&ed, as
we fee it, from the air j others, that it is
produced from the animals and vegetables,
or their juices mixed with the nitrous earth,
and putrefying there: others, that it is
formed from the vitriolic acid, joining to
the phlogifton, or inflammable matter of
thefe lubftances : and others, that the acid
of nitre is a different acid from the former,
and attracted by thefe bodies, which are its
proper matrix. Let us examine thefe dif-
ferent opinions.

SALTPETRE is an artificial body, as none
of it has ever yet been found in the bowels
of the earth. Some authors, on this ac-
count, thought that the nitre was altoge-
ther attracted from the air by the mate-
rials expofed to it. But this opinion is ap-
parently falfe, as no nitre can be got from
thofe materials before an alkaline fait is
added to them. The acid, indeed, does
in thefe materials, as I mail after-
wards

138 *Tbe Principles of Pgrt III.

wards (hew 5 but the alkaline bafe rnuft be
given it by art, before any nitre will cryf-
tallife. Befides, nitre is not of itfelf a vola-
tile body ; and, therefore, cannot float in
the air. The aereaj nitre, which is got
flicking to old walls, is a very different fub-
flance from the nitre we are juft now
treating of. It has very different properties,
fuch as effervefcing with all acids, and a
urinous tafte,

LEMERTy in a paper in the Mem. de
Tacad. des fciences pour fannee 1717, main-t
tains an opinion peculiar, I believe, to him-
felf, That the nitre which is generated,
arifes from the animal and vegetable fub-
flances which are ufed to colled it. The
arguments which he makes ufe of to fup-
port his opinion, are, indeed, few and
weak. I think his chief one is, that he has
extracted a nitrous fait from fome vege-
tables. It is true, that fome of them do
contain, in their natural flate, an inflam-
mable fait, which appears to have many of

the

Se£t.II. Agriculture and Vegetation. 139

the properties of nitre. This is the cafe
with the carduus benedictus, wild cucum-r
ber, and pellitory. Bcildue, in 1734, has
a paper in the academy of fciences, where
he fays, that he extracted real nitre from a
decoction of bourache, efpecially when he
added fome quick-lime to it, to fix the oily
particles the better, that the falts might
cryftallife. He fays, that a mould which
formed itfelf on this decoction, after it had
been kept for fome time, burnt lilce oil and
nitre. But all this is no proof, J:hat the
nitre comes from the vegetables ufed jn
the making nitre j for all kind of vege-
tables do equally well, even thofe which
contain a vitriolic fait. Befides no fixed
fait is ever got from putrefied vegetables, or
from any animal fubftance, which Lemery
feems to have forgot. It is furprifing, that
a chymift fhould fall into fo great an error.
Thefe vegetables and animal fubftances;
act, as we mall foon fee, in a very different:
way, by affording an abforbent earth, and
yolatile alkaline fait, and fo increafing the

matri?c

140 The Principles of Part III.

matrix to extract the acid from the air ;
and by keeping the matrix open to admit
the air, by a continual fermentation carried
on in the body expofed.

TH E third opinion, which almoft all
chymifts follow, is, That the alkaline vola-
tile falts, produced by the fermentation of
corrupted bodies, animal or vegetable, and
the abforbent terreftrial particles, which
are ufed as the matrix to make nitre, at-
tract from the air, which is plentifully
ftored with it, the acidum vagu/n, or vi-
triolic acid j which joining with the oil of
the matrix, flored with it, becomes the
acid of nitre. This univerfal acid, Hom-
lerg makes the origin of the nitrous and
{he marine acid : for, added to an inflam-
mable matter, it becomes the nitrous acid ;
to an arfenical matter, it becomes the
marine acid. The arguments ufed in fa-
vour of this opinion are, i . That putrefied
animal fubftances are employed in the for-
mation of nitre, and, therefore, the oil

mull:

Sedt. II. Agriculture and Vegetation. 141

muft join with the vitriolic acid. But this
conclufion will not be allowed as a juft one,
feeing thefe putrefied fubftances may have
other ufes, as we will fliow. It will pre-
fently appear, that nitre may be got with-
out any oily matter. 2. The fpirit of
nitre has a reddiih colour, which they fay
is an argument, that it contains an inflam-
mable fubftance, and it is that fubflance
which gives the colour to all bodies. But
we know many bodies which are coloured,
although we have never yet been able to
mew that they contained an qil ; therefore
this may not. 3. The inflammability of
nitre, which it owes to its acid, proves,
they fay, that it contains an oily principle,
which is the only inflammable body that
we know. To this opinion the anfwer is
plain, That nitre of itfelf is not inflam-
mable, unlefs it meets with an inflam-
mable body. This argument becomes ra-
ther an objection againft this opinion, as it
may be faid, that nitre inflames with all
bodies which contain an oil ; and as it is

not

142 <fhe Principles of Part III.

not inflammable of itfelf, therefore it does
not contain an inflammable fubftance.

THIS leads me to the laft opinion, That
the nitrous acid exifts in the air, and is at-
tracted from it. This opinion, though
fcarcely maintained by any chymift, to me
appears to be the ftrongeft, though ftill
liable to fome objections. The firft argu-
ment for it is, That alkaline fait and cal-
carious bodies of themfelves, without a
mixture of any vegetable or animal matter,
will produce nitre ; as we find by an expe-
riment of Stably in which he got nitre by
expofing alkaline falts to the air. I have
got a nitrous fait from the lime taken out
of park-walls. The fecond is, That it is
actually found exifting in nature. Many
mineral waters contain a nitrous fait, as
appears by the experiments of Du C/osy
performed before the academy of fciences
at Pan's. I have difcovered that the nitrous
acid exifts in all hard waters* ; and that

* Vid. Experiments on bleaching.

all

Se£t. II. Agriculture and Vegetation. 143

all pit-well waters are hard, and contain a
nitrous acid joined to an abforbent bafe ;
which imperfect -fait, by the addition of an
alkaline fait alone, can be converted into
real nitre. Thirdly, by boiling hard water,
or expofing it to a great degree of heat,
the nitrous acid is really volatilifed, and
the abforbent earth falls to the bottom.
This proves, that the nitrous acid is vola-
tile, and exifts in the air. The fpiritus
nltri fumam is continually evaporating in
the air. Thefe experiments prove, I think,
beyond all doubt, that the nitrous acid
exifts in the air, diftinft from the vitriolic
acid. This nitrous acid appears to be the
fructifying principle which we formely di£-
covered in the air.

THIS point being fettled, let us now ac-
count for the different changes brought
about in the making of nitre. All earths
are not fit for this purpofe ; only fuch as
are attra<5lers of acids, or abforbent earths,
lime, marl, and the other abforbents -,

or

1 44 The Prwcifi/es of Part III.

or putrefied vegetables and animals, which
afford an abforbent earth, and likewife a
volatile fait. Almoft all earths have more
or lefs of abforbent particles in their com-
pofition. Thefe abforbent earths catch the
nitrous acid, as it paffes by them with the
air, or fix and collect it as it arifes from
the inner parts of the earth : for I am not
fure but it may be got likewife in that
way ; at leaft it does not feem to rife very
high from the ground. Mariot's experi-
ment is a proof of this. He expofed the
matrix of nitre for two years on a houfe-
top, and could get no nitre from it -, but
got it from the fame matrix kept in a
cellar.

THE mixture of urine, and of putrefy-
ing vegetable and animal fubftances, will
be of confiderable ufe in carrying on an
inteftine motion in the mafs of earth, keep-
ing .it open, and allowing the influence of
the air to penetrate deeper into the body.
If there was no fuch putrefcent body mix-
ed

Sect. II. Agriculture and Vegetation. 145

ed with it, the mafs would cohere too
firmly together, and its furface would only
act ; whereas now the whole body acts.
It is in this way that I imagine the animal
and vegetable fubftances chiefly operate,
and not by entering into the compofition
of the nitre, as moft chymifls affert; be-
caufe nitre may be made by expofing alka-
line falls alone to the air ; for alkaline falts
attract acids, and are fo loofe as to fland in
need of no fermentation to open their
texture. The north wind is particularly
proper for the generation of nitre, be-
caufe that wind mufl bring more of the
nitrous acid along with it. That the cold
we feel from that wind, is chiefly owing
to a greater quantity of this acid, I think
is probable, though not demonftrable. The
winter months are particularly good, as
the north wind blows more in that feafon,
than in any other, and as there is lefs
heat to exhale the nitre during the opera*
tion.

146 The Principles of Part lit

I N this way the matrix of nitre is im-
pregnated with the acid of nitre. Let us
now fee what this matrix at pfefent con-
tains. We have the analyfis of it by
Petit in the academy of fciences. He took
50!. of old plaifter, and diflblved it in
72 Ib. of water. This gave a pungent
bitter reddifh liquor, which was in weight
to common water as 32 to 31. When
the water was boiled into a liquid extract,
for it would not harden, it ibon attracted
the moifture, and turned liquid again. It
turned blue paper red; mewed no effer-
vefcence with fp. mtr. or Jp. faL mar. j and
when mixed with the former, diflblved
leaf gold. OI. vitr. made a violent fer-
mentation and precipitation with it. OL
tart. p. d. did not eafily mix with it ; but
when ftirred, produced a coagulum like
butter, and gave a ftrong urinous fmell.
Jf fublimate was mixed with the oL farf.
no urinous fmell was felt. This coagulum
was owing to a feparation and precipita-
tion

Seel. II. Agriculture and Vegetation. 147

tion of much earth. Spirit of urine had
the fame effe&s ; but fp. fal. ammon. made
with lime, had not. Brown paper dipt in
it, burned like a match. Thefe experi-
ments mow, that it contains abforbent
earth, volatile fait, the acid of nitre, and
fea-falt.

HE diftilled it for five days, and nothing
but phlegm, very much charged with a bi-
tumen, came over. When the utmoft force
of fire was applied, white clouds appeared
in the receiver, which clouds condenfed
into aq. reg. By two other diftillations he
got fp. nitr. When oh vitr. was added to-
it, there happened a violent ebullition, and
aq. reg. was diftilled from it. By the affift-
ance of quick-lime a fmall quantity of fp.
vol. urines was got. It appears again to
contain an oily fubflance, earthy matter,
volatile fait in a fmall quantity, fome of
the marine acid, and a great deal of fp.
nltr. It is eafy to account from whence
it has got the inflammable matter and vo-
L 2 latile

148 The Principles of Part III.

latile fait, viz. from the putrefied vegetable
and animal fubftance mixed with it. The
fea-falt comes from the urine of animals
poured on the matrix of nitre. But he
never could extract real nitre from this
nitrous earth. That cannot be done, till it
has got the addition of an alkaline fait by
itfelf, or contained in the afhes of vegetables.
Thefe are generally added to the nitrous
mafs before the water is poured on j if not,
they muft be added afterwards.

THE effect: which they produce is, to
join with the nitrous acid, whenever a fuf-
ficient quantity of water is added for them
to act: for alkaline falts attract the acid of
nitre more ftrongly than the earthy bafe
does, and the earth is ihaked off. Hence
it happens, that in boiling, the liquor de-
pofites much of this earth. There mould
as much alkaline fait be added, as to fatu-
tate the nitrous acid fully, and fhake off
all the abforbent earth. The alkaline fait

cannot

Sect. II. Agriculture and Vegetation. 149

cannot join to the marine acid, becaufe that
has already got an alkaline bafe.

IF thefe abforbent earths attract the acid
of nitre from the air, in the manufacture
of nitre, furely they will do the fame when
laid on the earth, and be converted to the
fame fait, confiding of the nitrous acid and
an abforbent bafe. It is not, therefore, a
real nitre, as was thought, which is the
caufe of vegetation, but an imperfect ni-
trous fait. This reafoning admits yet of
ilronger proof, when we confider, that this
very fait exifting in hard waters, has al-
ready, by experiment, appeared to be a
great affiftant of vegetation j and that an
artificial one, of much the fame nature,
compofed of lime and fpirit of nitre, when
joined with a proper quantity of an oily
fubftance, rendered a poor foil remarkably
fertile.

IF this reafoning is juft, the effects of

different manures on the ground mould be

L 3 vifible,

150 ¥he Principles of Part III.

vifible, in proportion to their ftrength of
attracting acids. This happens really fo
in fact, and is a fhong confirmation of the
truth of our reafoning : for afhes have the
ipeedicft effects of any manure j becaufe
the alkaline falts which they contain attract
acids Wronger than any body. Soot and
dung come next, which are volatile alka-
lines, whofe attraction comes next to the
firft; then the clafs of abforbent earths.
The fame obfervation is made of the marls ;
for, according to their rank as attracters
of acids, fo they operate on ground j firft
fhell, next clay, and laft of all ftone marl ;
which will fometimes continue in the
ground four or five years before it ihow
any effects. The fame turn all thefe ma-
nures keep in lofing their effects ; for the
fooneft converted to fait muft be the fooneft
exhaufled.

AN objection will naturally occur to every
one againft this opinion, though fupported
by the greateft Strength of experiment i

which

Sect. II. Agriculture and Vegetation. 1 5 1

which is, That no fuch nitrous fait is got
from fertile earth. In general, thefe abfor-
bent particles are in fuch fmall proportion,
even in the richefl foil, and fuch a fmall
degree of fermentation is carried on in it,
that there are only a few of thefe particles,
and thefe too on the furface, capable of
being converted to this fait j and they are
no fooner converted than abforbed by fome
plant. Thefe confiderations {hew, that little
of this nitrous fait is to be expected from
any foil. That it is fometimes got, appears
from this paffage of Lord Bacon, Hift. vit.
et morf. Certiffimum efty quamamque terram
licet puram, neque mtrofn admixtam, ita
accumulatam et tetfam, ut Immunisfit a radiis
folisy neque emittat aliquod vegetabile^ colligere
etiam fatis copiofe nltriim.

ALMOST every perfon who has examined
the contents of this foil, has denied, how-
ever, the exiflence of this nitrous fait in it.
Let us apply to experiment for a decilion of

this queftion.

L 4 Exf.

152 $be Principles of Part III.

Exp. 37. To put this queftion beyond
all doubt, I took from a molehill fome rich
foil in the month of O£tober> poured water
on it, and filtered that water through brown
paper. This liquor, when boiled up, was
yellow, and tafted faline. The fait ap-
peared plainly to be nitrous ; as brown
paper, dipt in this liquor, and dried, burnt
like a match. On an addition of ol. tart.
p. d. the liquor turned milky, and let fall
a white powder ; which mows the fait to be
of the fame nature with that of hard water.
At firft, I could get no fait by cryftallifation,
as the liquor was very unctuous, and in
fmall quantity* But on treating it in the
fame manner as the manufacturers do the
materials of nitre, viz, adding fome quick-
lime to feparate the oil from the falts, and
allowing it to (land fome days, I got from
it a true faltpetrc. This experiment
mows the faline part of the vegetable food
to the eye.

Sed. II. Agriculture and Vegetation. 153

FROM what has been faid we may learn,
Cor. i. That as hot weather hurts the
formation of nitre, by exhaling it, and as
the winter and fpring is the time in which
it is moftly generated, all dung fhould be
laid out in thofe feafons.

Cor. 2. As thefe manures become fer-
tile by the action of the air, the longer
they are expofed on the furface of the earth,
fo much the fafter will they be converted
to the nitrous fait. Farmers are now con-
vinced of this from experience : but fuch
bodies as contain a nutritive juice already
formed, as woollen rags, hair, horn-ihav-
ings, leather, faw-duft ; or thofe which
already exifl in the form of a neutral fait,
fuch as fea-falt, cannot be benefited by the
influence of the air. Experience has like-
wife confirmed this obfervation. Thefe are
ftrong proofs of the juftnefs of the pre-
ceding reafoning.

Cor.

The Principles of Part III,

Cor. 3. As the north wind is obferved to
bring moft of the nitrous acid, it would
feem to follow, that banks which have a
north afpect mould receive moft of it. It
is obferved, that they are, in general, richer
than thofe of a fouthern afpeft. As the
former have not fo much fun as the latter,
they mould be lefs fruitful : but our theory
of vegetation affords a fufficient reafon for
this fadt.

Cor. 4. It appears, from the manufacture
of nitre, that all thofe abforbent meagre
earths ufed in agriculture, will be rendered
more capable of anfwering their purpofe,
by an addition of fome putrid fubftance,
vegetable or animal, to open their texture,
and make them more pervious to the in-
fluence of the air. Hence the advantage
of mixing animal or putrefied vegetable
fubftances with chalk, marl, lime, or the

afhes of vegetables.

Cor.

Setf. II. Agriculture and Vegetation. \ 5 5

Cor. 5. As the procefs for preparing ve-
getable food is the fame with that for
making nitre, farmers mould imitate the
manufacturers of nitre, and the nearer they
approach to the methods found moil: con-
venient to increafe the proflucT: of nitre, the
more will they multiply the vegetable ali-
ment. In France all old walls and houfes
belong to the King, and are made ufe of
for the extraction of faltpetre. The King
of Pritjjia> by a regulation of confummate
policy, has eafed his fubjedts of this bur-
then, fhortened the procefs, and increafed
the quantity of faltpetre. He has ordered
walls of certain dimenfions to be built
near every village ; they are compofed of
the earth of granaries, ftables, or cellars,
mixed with other fat earth. They are
built to ftand fome years, till they are fuf-
ficiently impregnated with faltpetre. It is
obferved by Dr. Pietfch in his Penfesfur k
generation de nitre, that the people employ-
ed in thefe works, are yet very ignorant,

that

156 the Principles of Part III.

that they might meet with much fat earth
below the furface, very fit for their pur-
pofe, and that there mould always be a
proportion of abforbent or calcarious earth
in thefe walls. He fays, that there is al-
ways leaft nitre on the fouth fide of the
wall. He orders, that all vegetables mould
be pulled from the walls, as they confume
the nitre j that no cattle mould be allowed
to come near them, as they are fond of it -,
and that they mould be covered with
ftraw, to hinder the rains from warning
off the nitre : what ought then to hinder
our farmers from making fuch walls of
fat earth, dung, efpecially that of pigeons,
ftraw, which will take a time before it
rots, and a fmall proportion of lime, marl,
or fhells ? Moft of thefe materials will be
found every where. In two years they
would become a very rich manure. They
would operate inftantly j whereas, it takes
two years before many of our manures
have a fenfible effecl: on the foil. Although
heavy rains warn off the nitre, yet a gentle

moifture

Se6t.II. Agriculture and Vegetation. 157

moifture of the materials is of ufe, as it is
neceflary to the attraction of all falts. It
has been obferved, that the fbuthern fide
of thefe walls has lefs nitre. To remedy
thefe defects, I would propofe, that the
wall fhould be (hadowed on the fouth by
a hedge, which will keep off the rays of
the fun, hinder it from turning too dry, and
allow the air a free paflage. The putrefac-
tion, which goes on in fuch a fituation,
will be of great advantage to the procefs.

PART

1 158 ]

PART IV.

SECT. I.

Of opening and pufoerifmg the foil.

IT is not only the bufinefs of the farmer
to provide food for plants, but to take
care that they are able to reach that food.
It is of no ufe if the roots cannot pierce
the ground, to get at it. Hence the ne-
ceffity of opening or pulverifing the foil.
Plants are fed moftly by their roots ; nor
do they begin to grow, until thefe roots are
fo numerous as to nourHh both themfelves
and the ftem. The wider thefe roots are
fpread, the more nourimment will the plant
receive, the ftronger will it be, the larger
will it grow, and the better will it anfwer
the defign of nature.

BUT this is not the only view with
which we fhould favour the growth of the

root,

Se&. I. Agriculture And Vegetation. 159

root. That part feems to be the great caufe
of fecundity; for it not only nouriihes the
plant, but fends up many moots and plants
itfelf. A fmall piece of the root of many
different plants will breed a plant. Many
ftalks arife from the roots of all the different
grains, long after the grain itfelf is corrupted.
Hence, the more roots the more chance of
plants : but the quantity of roots feems to
depend, in a great meafnre, on the opennefs
of the foil.

THE foil may indeed be too loofe; for
it muft have a certain confiftency and cc-
hefion to fupport plants. The gravelly
foil is the worfe of being often ploughed.
It is obferved, that a light foil, when much
dunged, produces a worfe crop of peafe
than when not dunged. But too great
loofenefs is a rare fault, and is fooner re-
medied. Too great ftiffnefs of the foil is
what the farmer has moft frequently to

ftruggle with.

LET

j6o ¥ke Principles of Part IV.

LET us, then, examine the methods by
which it is kept loofe. Thefe may be di-
vided into natural and artificial.

S *E C T. II.

Effetfs of the atmofpbere.

THE alternate viciflitudes of the air,
are the chief means that nature
makes ufe of to attain this end. Heat and
cold, moifture and drought, contract and
dilate it by turns j and, by thefe alternate
motions, (hake the particles afunder. But
there are no means fo efficacious as froft
and thaw. Every one muft have obferved,
how loofe the foil is after a froft. Many
vegetables are at this time ejected out of
the earth altogether.

FROST feems to act in different ways.

ift, By changing into an elaftic ftate much

of the fixed air, which muft fhake and

open the ground, to gain, an exit. 2dly,

By

Hi. Agriculture and Vegetation* 1 6 1

By the dilatation of the water, as it freezes
In the earth, the adhering particles mufl
be feparated. 3dly, The particles of water
(hooting out in the manner of falts, muft
cut and divide the foil.

Cor. That the ground may receive, in
the ftrongeft manner, the good effects of
froft, it would appear reafonable, that it
mould get one ploughing before the froft
comes on. One furrow at this time will
attenuate it more than two afterwards. Re-
gard muft always be had to the climate;
for where much rain falls in the winter,
this practice would prove pernicious, by
expofing the foil to be warned away.

SECT. III.

Change of fpecles.

THERE are fome plants defigned by the
author of nature to fix the foil j
there are others defigned to open it. One

M great

i6a We Principles of Part IV.

great divifion of plants is into the fibrous
and carrot rooted. The fibrous-rooted di-
vide directly into fmall fibres, which run
in all directions, but moftly horizontally;
the carrot-rooted fend one great item di-
rectly down, which has lateral fibres. The
former, in which clafs are reckoned all the
white grains, rye-grafs, &c. confolidate the
ground ; while the latter, in which clafs are
reckoned the liguminous plants, carrots,
turnips, clover, &c. attenuate and loofen
the foil exceedingly. The clover is often
ejected altogether out of the ground after a
froft.

THIS effect muft depend on the nature
of the roots. The fibrous roots muft bind
the foil together like fo many threads,
while the carrot root defcends like a wedge,
and by its mere mechanical force cuts the
earth; perhaps the latter may operate,
likewife, by feparating more moiflure from
Jt$ root to keep the earth loofe. Some
plants appear to have this quality. A

fprig

Sed. III. Agriculture and Vegetation. 163

fprig of mint, which has fome roots in
water, and fome in earth, will, according
to 7#//'s experiment, moiften the earth
from its roots. The liguminous plants, by
covering the foil, keep it moift, hinder the
fun to confblidate it, and deftroy the weeds
which help fo much to bind it. Hence the
reafon why a change of fpecies meliorates
the foil fo much. When the ground is
often fowed with white grain, it turns ftiff.
A crop of peafe, beans, or clover, pulve-

rizes it again.

FA R M E R s have difcovered, by expe-
rience, that all the fibrous-rooted plants
impoverish the ground, and do not thrive
when they fucceed one another ; while the
carrot-rooted enrich the foil, and may fol-
low one another with fuccefs. The latter,
by opening the ground, make the influ-
ence of the air on it reach deeper, and con-
fequently help to produce more of the ve-
getable food ; while the former, by conib-
lidating the ground, fhut out in a great
•'". M 2 mea-

1 64 The Principles of Part IV.

meafure, the influence of the air, and make
the ground lefs fertile.

It is remarked, that not only a change of
fpecies, but alfo a change of grain, is necef-
lary : for the fame grain fown in the fame
ground is obferved to degenerate. This de-
pends on another caufe. It feldom happens,
I believe, that the vegetable food is of a due
mixture and confiftency. As foils are ge-
nerally either too wet or too dry, too light
or too ftiff; fo muft the vegetable food be
either too thin and watry, or too thick
and gluy. The vegetable muft at laft be
hurt from a conftant fuccemon of one fort
of food, and can only be recovered by a
foil poflefTed of oppolite qualities »

SECT.

Sect. IV. Agriculture and Vegetation. 165

SECT. IV.

Of ploughing*

PLOUGHING is the artificial method of
pulverizing moft known and moil
practifed. It ads in two ways ; by an im-
mediate mechanical divifion and trituration
of the foil, and by a more frequent and
extenfive expofition of it to the influence
and viciffitudes of the atmofphere. I believe
the latter operation is the principal one j
for fo grofs an inftrument would feem very
unfit to prepare the earth to enter the
capillary veiTels of plants. Its effects,
however, are very remarkable. They are
beautifully and ftrongly illustrated by the
ftory related by Pliny of Cairn Fiirius Crc-
fmus. That farmer, having better crops
than his neighbours, fell under the fufpi-
cion of witchcraft, was accufed before the
people, and faw himfelf ready to be con-
demned to death. When the tribes were
M 3 going

1 66 The Principles of Part IV.

going to vote, he at once produced his
ruftic inftruments, of a greater fize than
common, larger oxen, and heavier ploughs ;
and added thefe remarkable words: Vene-
faiamea,Qu£zrites>h(Zcfunt; nee pojum rcobls
oftendere, aut in forum adducerey lucubra-
tions meas3 vigilias^ et fudores. He was
unanimoufiy abfolved.

THE good effects of ploughing depend
entirely on the drinefs of the ground: for
if it is wet, the ground is confolidated in-
ftead of being opened 3 and remains in that
ufelefs ftate till the next winter's froft loofens
it again. None but dry bodies can be re-
duced to a powder.

THE farmer mufl open the ground as
deep as the roots of his corn penetrate, that
they may find an eafy paffage : and yet he
muft take care not to go below the foil in
ploughing, elfe he will bury what has been
benefited by the air, and expofe to the air
what perhaps cannot. Hence the plough

mufl

Seft. IV. Agriculture and Vegetation. 167

muft be proportioned to the depth of good
foil,

IT feems flrange, that there is not a
more certain way of fixing the depth of the
plough, and preferving it in that precife
fituation which the foil requires, than the
attention of the ploughman. That muft
be often fufpended by external objects and
fatigue ; and then the cattle and foil fuffer.
Does not the wheel-plough remove this
objection ?

THE ftiffer the foil, the oftner mould
it be ploughed. Clay cannot be ploughed
too often i lighter foils perhaps may. It is
allowed by many farmers, that the gravelly
foil may be hurt by too frequent ploughing.

As this operation depends on the prin-
ciples of mechanics, and not on thofe of
chymiftry, I mail leave it almoft untouched
to the confideration of fome other perfon.
It is a fubject worthy of attention j and al-
M 4 though

1 68 Vie Principles of Part IV.

though well enough underftood, perhaps,
for common practice, yet has it not been
reduced to that mathematical exaclnefs
which all mechanical agents are capable
of. I wifh that fome practical farmer,
fkilled in mechanics, would lay down the
principles on which ploughs ought to be
conftru&ed, and ploughing conducted. He
would merit much from the community.

SECT. V.

Of compofts.

THERE is another method which art
ufes to keep the foil loofe ; and that
is, by the admixture of putrid and fer-
menting bodies. We have feen that thefe
bodies have a ftrong intefline motion before
they are laid on the ground : they continue
that afterwards, though in a fmaller degree.
The fat foil of church-yards fwells fo much
when expofed to the air, by its fermenta-
tive power, that it will not go altogether

into

Sect. V. Agriculture and Vegetation. 169

into the fame hole out of which it was dug.
Clay, which has fo few putrefcent particles,
is the moft adhefive foil of any. We have
feen already how much (hells, when they
begin to putrefy, open the foil.

BUT there are other comports, though
not of the putrefiable fort, which have this
attenuating power in a flrong degree. In
this clafs are all the marls, but efpecially
the fofteft, fuch as the clay marl. We
have found how readily they lofe all ad-
hefion in water, and fall down into a
powder. The fame power they commu-
nicate to other earth, even to the moft ad-
hefive. The following experiment is a
proof of this.

Exp. 38. Take equal parts of marl and
clay, mix them well together, and dry
them -, when this compounded fubftance is
put into water, it falls by degrees to the
bottom of the glafs in the fhape of a
powder, while a ball of pure clay remains

quite

1 jo The Principles of Part IV.

quite undiflblved in water. This ihovvs
the ftrong attenuating power which marl
has, and which no other body can come
up to. It is obferved, that all clay grounds,
after they are marled, dry fourteen days
fooner than what they did before. This
is owing to the foil being more loofe, by
which means the water pervades it more
eafily.

I KNOW that this opinion contradicts the
common "one, that marl is not fit for clay
grounds. From whence the latter has
taken its rife, I know not, if it is not that
bodies of fuch a limilar appearance cannot
be allowed to benefit one another. But the
experience of many counties where marl
is ufed, and where the foil is generally a
deep clay, contradicts this vulgar opinion.
The following experiment puts it beyond
all doubt.

Exp. 39. 1 filled a pot with clay of the
fame kind I had ufed in the former experi-
ments,

Sedt.V. Agriculture and Vegetation. 171

ments, which had been expofed to the air
for four months, and feemed to have no
mixture of any other earth with it, as it
made good brick, with the addition of
fand; and had been taken up feven or
eight feet below the furface. This pot I
mall call N° i. Pot N° 2. was filled with
equal parts of clay and marl j N° 3. with
equal parts of clay and foured lime 5 N° 4.
with equal parts of clay and fea-fand well
warned j N° 5. with equal parts of clay
and dung. Thefe different compofitions
were turned daily. On the 2 6th of April
fix grains of barley were fown in each.

May 14. N° 2. had two plants, above
ground ; N° 3 . had four.

May 17. N° 2. had fix ; N° 3. had feven,
two of which were from one grain 3 N° 4.
and 5. had one each.

May 21. N° i. had five, of which two
were an inch and a half high -, N° 2. had

fix

j 72 *rbe Principles .of Part IV.

fix two inches high ; N° 3. were about the
fame height 3 N° 4. had two, one of which
was one inch high j N° 5. had three, each
two inches high.

June 4. N° 2. talleft and greeneft ; N° 3.
very near it; N° i. and 5. of an equal
height, but the latter of a very light colour ,
N° 4.worftofall.

Aug. 20. N° i. about nine inches tall,
and much withered. The roots feem not
to have pierced the clay, but to have funk
along the cracks. N° 2. has nine ears,
and thofe of a very deep green colour.
N° 3. has eight, but not of fo deep a green.
N° 4. has five, and thofe much fmaller.
N° 5. has nine, almoft as good as N° 2. I
had no opportunity of feeing them after-
wards,

Cor. i . By this experiment it appears, of
what great advantage it is to manure clay $
for, of itfelf, pure clay is not capable of

pro-

Sect. V. Agriculture and Vegetation. 173

producing good plants, becaufe their roots
are not able to penetrate it.

Cor. 2. Sand appears, in oppofition to the
common opinion, to be the worft manure
of thofe ufed. It cannot indeed feparate
the minute particles of the clay, which is
the only ufeful feparation for the growth
of vegetables. A little fand rather feems
to increafe the union of the particles of
clay, as appears from the manufacture of
brick.

Cor. 3 . Lime feems to be a good manure
for clay. What I ufed had been foured
for fome time. The effect which the air
has on it, in changing it from quick-lime
to effete lime, muft open the ground con-
fiderably.

Cor. 4. Dung and marl appear to be the
beft manures for clay. The former has a
flrong fermentation ; the latter lofes all co-
hefipn when water is added.

SECT.

174 ¥ke Principles of Part IV.

SECT. VI.

Of vegetation.

IT is worth our pains to take a fhort
view of what muft happen to the vege-
table food in the vefiels of plants. To enter
into a difcuffion of the anatomy of plants,
would be foreign to the fubject. I mall
take that as demonftrated by botanifts.

THE nitrous fait being formed on the
furface of the foil, will be warned down
by the dews and rains. It will difTolve
what oils it meets with in its way, and
conftitute with them a faponaceous juice,
containing, befides the former principles,
fixed air and fixed fire. This juice will
be retained in the foil ; becaufe I mowed
by experiment, that fertile foil a&ed like
a fpunge with refpect to water. This na-
tural defcent from gravity, and the natural
afcent from the heat of the earth and in-
fluence

Sect. VI. Agriculture and Vegetation. 175

fluence of the fun, muft keep the nutri-
tious juice in a continual motion ; fo that it
muft be continually applied to the roots of
plants deftined for the admiffion of nou*
rifhment.

THE firft queflion which can raife any
doubt here is, In what manner do the juices
arife to the tops of plants and trees ? Mal-
pighius thinks, this is owing, in a great
meafure, to the air-bladders which he difco-
vered in the fkucture of plants, and which
he thought behoved to dilate and contract,
according to the different changes of heat
and cold which happen in our atmofphere.
To me it does not appear, that the dilatation
of fuch vefTels would force it more upwards
than downwards. I mould rather imagine,
that fuch a dilatation would ftop the motion
altogether.

THE .caufe commonly afcribed, viz. the
action of capillary veflels, appears to me
fufficient for that end. Hales has demon-

ftrated

1 76 The Principles of Part IV*

ftrated the fact to the eye, by feveral experi-
ments, in which a part of a branch, being
cut at both ends, and having its under part
immerfed in water, a moifture was imme-
diately perceived in its upper part. This
effect of capillary tubes muft arife from the
attraction betwixt the fubflance of which
they are compofed and water.

THE attraction betwixt wood and water
appears to be very ftrong, by an experi-
ment related by Dr. Taylor, In the Philofo-
phical Tranfatfions, N° 368. He hung at
a pair of fcales a piece of fir board, foak-
ed it in water, weighed it, and then im-
merfed it again in water. To raife this
piece of wood, which had a furface of
an inch fquare in contact with the water,
fifty grains over and above its former
weight were required. The additional
weight in the different trials, he fays, was
always proportional to the furface. The
diftance of the under furface of the board
from the furface of the ilagnating water,

at

Sect. VI. Agriculture and Vegetation. 177

at the time of reparation, meafured up-
wards of -r.ro of an inch. This additional

\

weight is the real meafure of the attraction
betwixt that furface of wood and water in,
contact.

THERE is another force that muft con-
tribute to raife the fap, viz. the natural at-
traction betwixt the conftituent parts of thq
fluid. This muft certainly be the cafe,
when the fap moves quickly, as in the vine
in the bleeding feaibn. Both thefe caufes
acting, and the evaporation going on con-
tinually from the fuperior parts of the vef-
fels, the fap rifes from the roots of the plants
to the extremity of their branches.

t

BUT nature does not intend that this
(hall be done too quickly. There are
many fpiral veffels, and many cells into
which the fap is depofited, and by which
it muft be retarded. In thefe the fap will
be much altered in its nature, by the mo-
tion of the plants, by the continual mo-
N tions

178 eHe Principles of Part IV;

tions of the air-veflels, and perhaps by
the particles of light taken in at the leaves.
The juices are rendered richer by the expul-
fion of the watery particles. The remaining
ones are partly applied to the extremities of
the veflels, which run in all directions, ho-
rizontally as well as perpendicularly, and
make the plant increafe in breadth and
length j and partly go to the formation of
leaves, flowers, fruit, &c.

IT is eafily conceived how plants, by the
different combinations of the five principles
of which their food is compofed, and
the combination of thefe in different de-
grees, mud differ very much in their juices
and products. If their groffer particles
are to be feparated for any ufe, the fub-
tiler are all carried off by lateral veflels,
until none are left but what are wanted ;
if the fubtiler particles are to be ufed, they
are to be feparated by fmall veflels fitted
to receive them, implanted in the larger,
or in the cells where the juices are depo-

pofited

Sed. VI. Agriculture and Vegetation. 179

iited. In this way particles of any fize
may be lodged in any part of the plant.
Hence all that variety in the falts, oils,
cmd figures of plants. Hence all that va-
riety of fmells, taftes, virtues, and other
qualities.

How ftrong the power inherent in the
veffels of plants to change and alter thofe
fubflances which are taken in> appears
from an experiment of Homberg. He filled
two pots of earth mixed with fome falt-
petre. Into one he put creffes, which is
an alkalefcent plant, and affords a volatile
alkaline fait, but no acid ; into the other
fennel, which is an acefcent plant, and
affords an acid on diftillation, and no al-
kaline volatile fait. He filled two other
pots with earth, which had all its falts
warned out, if there were any in it. Into
one he planted fennel, and into the other
creffes, as in the former. The two plants
in the nitred pots grew much better, and
weighed much more than in the pots with-
N 2 out

i So 'The Principles of Part IY»

out nitre. The creffes in the nitred pot,
when diftilled, gave no acid felt, though fed
on a fait which contained an acid. The
fennel fed in the wa/hed earth gave an acid,,
though there was none in the earth. This
experiment mows, that the veffels of plants
have a power of changing the falts taken in
from the earth, into their own particular
natural one, probably by combining them
with different proportions of water, oil,
earth, air, and the particles of light which
iflue from the fun,

BUT how fhall we account for die diffe-
rent external forms of plants ? Shall we fly
to the immediate hand of the Supreme
Being ? or, as this ought to be the laft ftep
in philofophy, can we find no chymical
agents capable of this effect ? From many
experiments, which mow the natural inhe-
rent power in falts, efpecially the nitrous
kind, to run into vegetations, as they are
called, and to take the figure of plants, with
branches, leaves, nay even an appearance

of

Sect. VT. Agriculture and Vegetation.

of fruit, owing to the ftrong attachment
fubfifting between them and water, I have
often been led to think, that the vegetative
power of plants, nay their particular forms
of vegetation, were owing to that vegetative
power inherent in their falts. In effect, we
fee that vegetative power ftrongeft when
moft fait enters their veffels ; that is to fay,
in the fpring.

THUS I have endeavoured to account for
the effects of manures on the different foils,
and for the rife and changes of the vege-
table food in the veflels of plants, from
thofe remarkable attractions and affinities
which the Author of all has endued the
fmaller particles of matter with, Thefe
are not, as is commonly imagined, mere
paffive bodies; but active, vigorous, and
capable of producing thole changes by
which nature is fupported. I have de-
monftrated thefe affinities by experiment j
I have afTumed no other principles ; I have
built my whole plan on thefe; I hope,
N 3 there-

1 82 "The Principles of Part IV.

therefore, that its fimplicity will be a ftrong
proof of its truth.

BUT whence thefe elective attractions
which move the whole ? Whence acquires
matter the power of acting without itfelf?
for that muft be the cafe, unlefs we fup-
pofe an endlefs chain of material agents.
Whence but from an immaterial being,
who, by his order, firfl fixed thefe proper-
ties to matter, and, by his immediate will,
conftantly fupports them in the fame tenor ?
Jt is on particles too minute for human
eyes, that the omnipotent hand chufes to
exert itfelf, and on their powers to erect
this beauteous fyflem. Hence the origin
of all motion, adhefipn, increaTe, and or-
ganifed matter,

BUT as all individual forms were defign^
ed to be. of finite duration, he eftablim-
ed other particles with repulfive powers,
and mixed the feeds of dnTolution with the
firft rudiments of organical life.

Sect. VI. Agriculture and Vegetation. 1 83

the veflels are pervious, and the motion of
the fluids fubfifts, the attractive overba-
lance the repulfive powers, and the vege-
table or animal life continues. But when
that motion ceafes, and other circumftances
concur, the repulfive become too ftrong for
the attractive powers, duTolve the compo-
fjtion, and reduce the body to thole par-
ticles of which it was at firfl made up.
This is the great circle that Omniicience
has marked out, and Omnipotence circum-
fcribes itfelf to, for the greateft good of
the whole.

N 4 PART

1 84 tte Principles of PartV,

PART V.
SECT. I.

Of weeds*

THE laft article which we propofed
to confider was, what impediments
there were to vegetation, and the
methods of removing them. Thefe impe-
diments are fuch as either belong to the foil
or to the plants. We mall treat of them
according to this divifion.

AMONGST the impediments of the foil,
J clafs all fuch vegetables, as, being of no
ufe to the farmer, are called weeds, or /«-
utiles herbce. Thefe become hurtful to the
growth of more valuable plants, by con-
fuming part of the nourishment. I here
clafs alfo thofe roots called wreck in this
country, which run through the ground
often in fuch plenty, that they bind the

foil,

£ec~h I. ' Agriculture and Vegetation. 185

foil, hinder the roots of the corn to fpread,
and draw up a great deal of nourishment.
Thefe are generally the roots of the quick
grafs. The reft harrow has a large root,
which goes very deep.

THESE weeds, and the roots belonging
to them, are deftroyed, I. By fummer fal-
lowing. They are torn up by the plough
when they begin to fhoot, their roots are
expofed to the fun, they fopn wither, and
are killed ; or elfe they are juried below
the furface.

2. A METHOD much analogous to the
former, is trenching eighteen inches deep.
This buries the plants fo deep that they
die ; but this can only be put in practice
where the foil is good to that depth.

3. ANOTHER method of killing ufelefs
plants is, to hoe them when young. That
effectually roots them out.

4. No

1 86 the Principles of Part V.

4, No plants can grow without a fuffi-
cient quantity of frefh air, which is as ne-
ceflary to the vegetable life as to the animal.
Whatever plants cover the ground clofely,
deftroy all thofe which grow below. Hence
a good crop of peafe kills all weeds by
overshadowing them ; in fo much that the
farmer aflures himfelf of a good crop of
wheat if the peafe are good. If they are
not, a greater quantity of weeds comes up
than ufual; and he never can expedl any
of the three following crops to be good,
wnlefs he gives the ground a fallowing.

. IT is in this way, likewife, that fog is
deftroyed. The inclpfure is fhut up from
the middle of May to the beginning of De~
cember, and then fed from that time to April,
After that it is faved for a crop of hay. The
fog being fo long covered by two fucceeding
crops of grafs, is cut off from the benefit of
the air, and fo di-es.,

5. THERE

Sett. II. Agriculture and Vegetation. \ 87

5. THERE is yet another way of deftroy-
ing thefe weeds ; and that is, by marl. I
have feen broom effectually killed by marl.
I have feen a crop of wheat growing on a
field which was partly marled and partly
not. That part of the field on which marl
had been laid, was free from all weeds,
while the other unmarled part was full of
them. The fame wheat was fowed over
the whole field. I can account for this
effeft of marl in no other way than this,
that the grain is brought up fo fpeedily as to
be able to choke and deftroy thefe weeds.

SECT. II.

Of a ivef foil.

THERE is not a greater enemy to ve-
getation than the too great moifture
of the foil. It is always owing either to
a ftratum of rock, or of clay, generally
the latter, below the furface, which not
allowing the rains to pafs through, they

can

Principles of Part V.

can get off in no other way than by evapora-
tion; a very flow method, when compared
to filtration. Farmers exprefs the effects of
water by faying, that it fours the ground. It
is not meant by this, that the ground becomes
really acid, but only that it is changed in its
nature, and rendered unfit for vegetation.
The natural product of this foil are, rufhes
and four grafs; which lafl appears in the
furrows, but feldom in the crown of the
ridge; is dry and taftelefs like a chip of
wood ; and feels rough, when ftroked back-
wards. The natural effect of ftagnating
water I take to be, its putting an entire flop
to the admiffion, and confequently to the
influence of the air.

THIS excefs of moifture is carried of? by
a proper difpofition of the furrows, accord-
ing to the natural defcent of the ground,
by which the water will have an eafy paf-
fage to get away. It is likewife material
that the furrows mould be ftraight : for the
flraighter the furrow, the morter time will

the

Sed. III. Agriculture and Vegetation. 189

the water remain in the. ground. It would
appear likewife* that the narrower the
ridges were made, provided they were above
the ftagnating water, the fooner would the
water fall through them, to get at the
furrow. The furrow mould be made with
a double mouldebread plough, that both its
fides may flope. Marling the ground, as I
faid before, makes it drier, by opening
and loofening the foil. A field manured in
this way, will be fit fourteen days fooner
in the Ipring for ploughing. If thefe me-
thods do not fuceeed, on account of water
arifing from fprings, open or hollow drains
muft be made at different diftances. Open
drains feems beft, if the fprings be not toq
many,

SECT. III.

Of rains.

GREAT rains are considerable impe-
diments to the proper concodlion of
the juices in the veffels of plants, and alter

very

190 The Principles of Part V*

very much the nature of thefe juices. Says
a French author: Rn /' armee 1705, // tie
plu prefque pas en Juin et en Jiiillet, et ks
bleds etoient excellent. Mais en 1707, quoi*
quil y ait eu de chaleurs extraordinaires,
i I plu ft abondamment pendent les deux mots,
que le bles riont rien valu, et ces font pref-
tout cchaujfcs.

I? is obferved, that all plants grow very
faft after rains j not only the tefreftrial, but
the aquatic. The latter can never be fup-
pofed to want water ; fo that this effect
muft proceed from fome other caufe, than
the increale of nourimment by the roots.
The fame effect is obferved to happen,
when the fky, from being clear, grows
cloudy and ftormy. Perhaps their too great
perfpiration may be flopped: perhaps the
moifture is fucked up by the pores of the
leaves and wood : perhaps, as their nou-
rimment depends on the circulation of their
juices, and that circulation on the contrac-
tion of the trachea or air-veffels, according

to

Sect. IV. Agriculture and Vegetation. 191

to MalpigbiuS, the fudden contraction fills
the fmalleft and remoteft veffels with nou-
rifliing juices ; and does it with Ibme force,
which may lengthen the vefTels. As the
veflels are more full of water, and the per-
fpiration lefs than ordinary, it is no wonder
that the juices are not well concocted, and
the grain bad.

SECT. IV.

Of faulty feed.

HAVING confidered the impediments
to vegetation which arife from the
ground, let us next take a fhort view of
thofe which arife from the feed. To pro-
duce ftrong plants, we muft chufe ftrong
feed, Grain which has been ftarved in
meagre grounds cannot thrive.

OLD grain will not grow; and there-
fore, farmers always chufe the laft year's
.corn. It is thought that grain will not

grow

*rke Principles, of Part V.

grow when it paffcs the age of five years :
but the time cannot be precifely fixed, for
that muft depend on the drinefs and oili-
nefs of the feeds. All the oily feeds keep
long, fome of which will lie in the earth
for fifteen or twenty years. Two months
after the great fire in London there ap-
peared a great crop of a Ipecies of eryfi-
mum> where there had been houfes for a
thoufand years. Mr. Reaumur fbwed fome
of the grain which had been preferved in
the citadel of Metz for one hundred and
thirty years; and which made very good
bread. In three weeks fome of the grains
were fwelled, and fome not. In fix weeks
no grains were to be found.

THE caufe of ilerility in old grains feems
to confift in the vefiels lofing that fupple-
nefs which is neceffary for their extenfion,
and filling with water; and in the con-
tained liquor lofing that gluinefs which is
neceflary for nutrition. This appears from
the brittlenefs of the grain, which becomes

fo

Sect* V. Agriculture and Vegetation. 193

fo by the evaporation bf the mucilaginous
parts.

SECT. V.

Difeafes of plant s>

ALL organized bodies, confining of
containing veffels, and contained
fluids in motion, are fubjecl: to have thofe
fluids altered, and that motion vitiated.
Hence the difeafes of plants. Bourne-
fort has, therefore, judicioufly clafled thefe
difeafes into thofe which arife, i. from
too great an abundance of juice; 2. from
too little j 3. from its bad qualities ; 4. from
its unequal distribution ; 5. from external
accidents*

Too great abundance of juices muft
caufe ftagnations, corruptions, too great a
quantity of water-moots, varices, cariofities,
&c. It feems to be in this way that too
much rain operates. The fmut, which is a
corruption of the grain, ought to be clafTed
O here i

194 *The Principles of Part V.

here; becaufe it happens moft to weak
grain, and in rainy feafons. It may, like-
wife, be communicated by infection, if I
may fo fpeak ; and the fmut, like other con-
tagious difeafes, may be transmitted from the
infected to the healthful grain. The ex-
periment, I was informed, has been tried.
Some fmutty grain was fown along with
very good feed j and the produce appeared
very fmutty. Nor ought it to furprize us,
that this mould happen to the juices of
plants, when we find, by daily experience,
that the juices of animals aflume the nature
of the contagious ferment communicated to
them. This difeafe is prevented, in a great
meafure, by fteeping the grain in a pickle
of fea-falt. This operates in two ways. It
firengthens the feed, and fits it for expelling
the fuperabundant watry juices -, and, by
its great weight, fufpends all the faulty
grain ; fo that none but the heavieft and
ftrongeft fall to the bottom, and are made
ufe of.:

DUNG

Se£t. V. Agriculture and Vegetation. 195

DUNG feems to prevent other difeafes
arifing from too great a quantity of moif-
ture. An experiment, performed by a gentle-
man of my acquaintance, will fhow this
effecl: of dung in a flrong light. He fal-
lowed two acres of poor ground, which had
never got any manure, with a defign to fow
wheat on it j but altering his fcheme after-
wards, he laid feme dung on a fmall part of
it, and fowed the whole, after it had got five
furrows, with barley. A great quantity of
rain fell. The barley, on that part which
was dunged, was very good j but what was
on the reft of the field turned yellow after
the rains, and when ripe, was not worth the
expence of reaping. This experiment
{hows, that the moifture and poverty of the
foil was the caufe, and that the dung was
the cure of this difeafe.

PLANTS and trees certainly decay for

want of proper nourishment. This is the

caufe why the leaves fall ofT at the approach

of winter. It appears plainly from the fol-

O 2 lowing

1 g6 The Principles of Part V.

lowing experiment. Ingraft an almond
tree on the black damafk plumb : for the
firft year the almond tree thrives very well ;
but after that they both decay (lowly and
die. The reafon is, becaufe the former
vegetates much fooner than the latter ;
and, therefore, requires nourishing juice
when the former has it not. While young,
it is eafily fupplied ; but when it grows
larger, it exhaufts the plumb, and is ftarved
itfelf. If the plumb is ingrafted on the al-
mond, the juice rifes in the latter, when the
former is not fitted to receive it, and it dies
of repletion.

DU HA MEL, in Mem. acad. des
fciences for the year 1728, mentions a
difeafe, called le morf, which attacks the
faffron in the fpring ; and is owing to a
plant of the fpecies of trefoils, that has no
ftem, fixing fome violet-coloured threads,
which are its roots, to the roots of the faf-
fron, and fucking out its juice. This difeafe
is prevented by digging a trench, which

faves

Se6t. V. Agriculture and Vegetation. 1 97

laves all the unaffected. All difeafes from
defeat of nourishment, are cured by the ap-
plication of manures.

THE juices may be, likewife, faulty from
their bad quality. When the turpentine
juices of the pine and fir turn too thick, the
tree is fuffocated. Sugar canes, it is faid,
do not thrive fo well in rich new foil, be-
caufe it affords too oily a juice, which is not
fo good for fugar : if they are cut when fix
months old, the leaves burnt, and the ames
laid round them, they afford better fugar.
The alkaline fait, from the ames of the
leaves, attenuates the oils, and makes a better
faccharine juice. Plants or feeds tranfported
from warmer countries to cold, decay gra-
dually, becaufe the juices are not fufficiently
attenuated for want of heat.

THE unequal diftribution of the juices
fcems to be another caufe of vegetable dif-
eafes. In corn, the juice fometimes runs
too much to the leaves ; cutting or eating
O 3 the

i 98 The Principles of Part V.

the corn is a remedy for this, as it fends the
juice to the ftalk.

EXTERNAL accidents, fuch as froft, hail,
flies and their eggs, vermin, Gfc. give rife
to many difeafes. There is a fmall white
hard worm very common in new ground,
which deftroys plants by eating their roots.
Thefe worms are killed by quick-lime or
Jime-water.

THE mildew is to be ranked here, as it
feems to be owing to a gluy faccharine
matter falling with a fummer fhower, and
blocking up the perfpiration of the plant.
This matter may be felt and tafted on the
furface of the leaves. That it operates in
this way, appears from the following fact.
There is in the Brian^on, a fpecies of nut-
tree, which has all its leaves covered with a
faccharine fubflance, arifing from the per-
fpiration of the juices of the plant. If it
is in very great quantity, the trees often
die,

AMONGST

Se&.V, Agriculture and Vegetation. 199

AMONGST the clafs of external accidents
we may place the ef&dts which arife from
the contiguity of certain plants. There are
fome plants which do not thrive in the
neighbourhood of others. This is obferved
of the cabbage and cyclamens, of hemlock
and rue, of reeds and fern. We have many
examples of fuch like antipathies amongft
animals. Thefe effects feem to be produced
by the effluvia which are emitted by all
organised bodies.

IT is furpriling that the prefent fubjed:,
fo highly neceflary to the proper culture of
plants, mould have been almoft entirely
neglected ; fo that an inquirer finds too
few fads and obfervations to be able to
lay down any regular fyftem. Befides, the
difeafes of vegetables feem to require more
amftance, and therefore demand more at-
tention, than thofe of animals ; if we regard
the cure alone, and fet afide the higher rank
in the fcale of creation, and confequently
O 4 the

2oo *The Principles of Part V.

the higher value of the latter. Animals
have a fentient power within, which, irri-
tated by the caufe of a difeafe, quickens the
motions of the heart and arteries, and con-
tinues thefe mechanical agents till the mor-*
bific particles are expelled, or the animal
fyftem overpowered by them. But there
is no fuch power inherent in vegetables.
Unlefs a remedy is applied from without,
they muft continue to labour under the
difeafe. Whoever removes the difeafe of an
animal, does it by directing thefe natural
and mechanical motions aright, and in the
way that the motive power feems to point
out. But whoever removes a vegetable
difeafe, muft look on the work as entirely
his own, as he has got no affiftance from
$he vegetable itfelf.

E c T;

5ect. VI. Agriculture and Vegetation, io t

SECT. VI.

Plan for the further improvement cf agri-
culture.

THUS I have endeavoured to fhow, that
agriculture is not fo uncertain and un-
fcientifical an art as is commonly thought;
but is reducible, like other arts, to fixed
unalterable principles. I have already look-
ed back, and confidered the impediments
which have lain in the way of its progrels
to fome degree of perfection. I mall now
look forward to fee how thefe may be beft
remedied, and in what manner we can aflift
it in its progrefs.

AGRICULTURE does not take its rife
originally from reafon, but from fact and
experience, It is a branch of natural phi-
lofophy, and can only be improved from
the knowledge of facts, as they happen in
nature. It is by attending to thefe facts
that the other branches of natural philo-

fophy

Principles of Part V;

fophy have been fo much advanced during
thefe two laft ages. Medicine has attained
its prefent perfection only from the hiftory
of difeafes and cafes delivered down. Chy-
miftry is now reduced to a regular fyftem,
by the means of experiments made either
by chance or defign. But where are the
experiments in agriculture to anfwer this
purpofe ? When I look round for fuch, I
can find few or none *. There, then, lies
the impediment in the way of agriculture.
Books in that art we are not deficient in;
but the book which we want is a book
of experiments.

AND, indeed, as things ft and at prefent,
it muft always be fo. Mankind are my in
attempting any thing, or at leaft render-

* Since thefe papers were wrote, I have read three
volumes of experiments publifhed by Du Hamel^ on
Tw/Ps fyftem of agriculture. They are diftinct, exact,
conclufive, fo far as they have gone, and ftand a model
for experiments in agriculture. What a fhame for
Great-Britain^ where agriculture is fo much cultivated,
and where that fyftem took its rife, to leave its exact
value to be determined by foreigners !

ing

Sett. VI. Agriculture and Vegetation.

ing it public, unlefs they can make it com-
plete, or erecl: fbme plaufible iyftem. This
they may do in all other arts, but they
cannot in agriculture. The time fo feldom
comes about, and the progrefs of the ex-
periment is fo flow, that one perfon can
make but very few during his life. A
number of experiments are to be found,
not in the pofTeffion of one, but in the
hands of many. The fault, then, lies not
in the deficiency of fads j for chance and
deiign muft have been able to furnifh
many ; but of a certain, proper, and eafy
channel, through which they might be
conveyed to the world, without wounding

the natural vanity of mankind.

«

HITHERTO thefe fadts and experiments
have been confined to converfation alone,
and have died along with thofe who made
them. I would propoie a fimple remedy
for this. Let a committee of the Edin~
burgh fociety, not exceeding five perfons,
be named for the branch of agriculture

alone,

204 The Principles of Part V.

alone, whole duty mall be, to receive fingle
and detached experiments, put them in a
proper drefs, if they ftand in need of it,
and publifh them to the world at ftated
times, like a public paper. This manner
of appearing feems well calculated to raife
a fpirit of experimental farming over the
country.

THE narrator, on his part, fhould deli-
ver the experiment in the plaineft and
moft diftinft manner, and feparate the
facts from his reafonings. Peripicuity and
exa&nefs are the chief beauties in experi-
mental writing. The plain fad mould be
firfl told, with all its concomitant circum-
ftances ; fuch as, the fituation of the
ground, nature of the foil, previous cul-
ture of it, quality of the feed, country
where the experiment is made, ftate of the
air, at fowing and after, with regard to
heat and cold, drought and rain, wind,
&c. The reafoning on the experiment
fhould then follow, and fhould be fuch as

arifes

Seft. VI. Agriculture and Vegetation. 205

arifes naturally from the experiment. Al-
though it is not necefTary to mention any
name to the public, yet the experiment,
when delivered, mould be fubfcribed by
the perfon who made it, to avoid all im-
pofition.

IN order to increafe the fpirit of experi-
ment-making over the country, I would
propofe, that this committee mould have
it in their power, to grant one or more
honorary or lucrative premiums, to thole
who mall have delivered the moft inge-
nious and ufeful experiments in agricul-
ture. It is in this way, I think, that the
premiums defigned for agriculture mould
be eftablimed. They ought to be, not on
fiich fubjects as the farmer is naturally
led by his own gain to purfue ; for fuch
he will generally follow, to the utmofl of
Ms knowledge and abilities j but on fuch
as are not fo nearly connected with gain,
and make him go out of the common road.
.This confinement may, however, be too

great

206 The Principles of Part V.

great at the firft fetting out 5 and it may
be more advifable, to admit all experi-
ments for fome time, till the fpirit be once
raifed.

.

THE happy confequences of this fcheme
are very evident. Farmers will begin to
fee the only method of cultivating this art
with fuccefs ; they will attend to minute
circumftances to which they never did be-
fore j they will be fond to communicate the
iffue of their experiments to the public,
when they can do it in that eafy and con-
cealed way $ they will have a dictionary
of facts to confult opon occafion ; and will
be able to draw advantage from both the

0

good and bad fuccefs of others.

•

IN time this plan may afford fund fuffi-
cient for fome future compreheniive genius,
who, laying the different, and often feenf*
ingly oppofite experiments together, and
confidering all their concomitant circum-
ftances, may be able to reduce the practice

to

Seft. VI. Agriculture and Vegetation. 207

to fixed and permanent rules. This good
fortune feldom happens to the firft experi-
menters in any art ; for they fee things in
too narrow a view, and often with too
prepofTefTed a mind. It is referved for that
unbiaffed and found judgment, which can
take from every opinion whatever truth
it contains j and, from the whole united
together, raife one regular, beneficial, and
lafting fyflem.

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