THE LIBRARY

OF

THE UNIVERSITY
OF CALIFORNIA

LOS ANGELES

THE

ECONOMY OF NATURE

EXPLAINED AND ILLUSTRATED

OS THE

PRINCIPLES

O F

MODERN PHILOSOPHY.

B V

G. GREGORY, D.D.

AUTHOR OF

ESS ATS HISTORICAL AND MORAL, fifc.

IN THREE VOLUMES.
WITH FIFTY-SIX PLATES.

The SECOND EDITION, with confiderable Additions,

VOL. II.

LONDON:

PRINTED FOR J. JOHNSON* N° 72, ST. fAUl's CHURCH TARB.

Q
iar

CONTENTS.

BOOK VL

OF MINERAL SUBSTANCES, AND THE STRUCTURE OF
THE EARTH.

CHAP. I. — page i.

Of Salts in general.

Introductory Obfervations. — Definition of Salts,— Salts Jimple and
compound,— What are called Jimple Salts are in reality compound Bo-
dies.— Oxygenous Principle.

CHAP. II.
Alkalies. — page 5.

Mineral fixed Alkali ; 'where found. — Vegetable fixed Alkali ; how ob-
tained.— Uje of the fixed Alkalies in the Arts. — Ufe of Alkalis in
making Glafs. — Procefs cf making Soap. — Volatile Alkali; hovj ob-
tained; a compound Body. — Alkaline Air.

CHAP. III.— page 10.

Acids.

Of Acids In general.*— Vitriolic Acid; honu obtained, &c.— -Nitrous
Acid; how obtained. — Muriatic Acid; how obtained, and its Ufe in
the Arts. — Flour Acid; diffolves Glafs; employed to make Etchings
on Glafs.— Acid of Borax. — Phofphoric Acid.— Acid ofAmbtr.

CHAP. IV. — page 20.

Neutral Saks.

¥he Union of an Acid and Alkali dejlroys the corrcfive Quality of each.—
Neutral Salts do not communicate the f aline Quality to other Bodies.—
Crystalline Form ; hovj decompo/ed.

A z CHAP,

857811

C O N T E N T S',

CHAP. V. — page 22.

Vitriolic Salts.

Glauber's Salt', botv decompofed\ Solution of it left to cool cryJlalliKti
on being Jhaken. — Vitriolated 'Tartar. — Vitridated Ammoniac.

CHAP. VI. — page 26.

Nitrous Salts.

Common Nitre ; Phenomena attending its Deflagration 'with inflammable
Subftances. — Natural Hiftory of Nitre. — Cubic Nitre.— Union of
nitrous Acid *witb various Earths.*** Nitrous Ammoniac.

CHAP. VH.—page 33. \

Muriatic Salts.

Sal T)igeftievits.'*~- Common Salt,— Rock Salt>~~ Natural Hijlory of
Salt. — Saltnefs of the Ocean.— Ufes of common Salt in the Arts.—
Sal Ammoniac.— Natural Hi/lory of Sal Ammoniac,

CHAP. VIII.— page 44.
Combinations of the other Mineral Acids*

$j>arry Tartar.— Sparry Soda.— Borax, its Properties ; its Ufe in tb'e
Arts,— Combinations of neutral Salts with Metals.

CHAP. IX.— -page 47.

Earths in general.

Different Kinds of Earth.— New Earths difcovered.— Definition of
Earths.— Exceptions.— Other general Properties of Earths.— Calca-
reous Earth.— -Magnefia. — Barytes. — Clay. — Flint.

CHAP. X.— page 52*

Calcareous Earths.

Chalk.— "Llmeflotte. — Marble. — Marie. — Calcareous Spar. -^Iceland
Cryftals. — Petrifattions. — Parts of Animals found in Marie, &c. —
Gypfoms. — Great Varieties.— Alabajler. — Fibrous Stone. — Mineral
Glafs.—Se/enite. — Gypfeous Spar.—PlaiJler of Paris ; how pre-
pared.— Fvfible or Derbyshire Spar.— Spars ; how formed.— Beauti-
ful Appearances in different Caverns. —Metallic Combinations •wit if
(alcareous Earth.

CHAP.

CONTENTS.

CHAP. XL— page 64.

Magnefian Earths.

^/[agnef.a. ; how obtained.— Epfum Salt. — Soap Rock.— -French Chalk.—
Serpentine Stone.— 'Mica. — Talk.—Mufcovy Glafs. — AJbejlos. — Mi-
neral Cloth.— Mountain Leather.— Mount ain Flax.-— Mountain
Wood,

CHAP. XII.— page 69.
Ponderous Earth.

fiarytes a fierce Mineral; found in two States.'— Criftatum,— Pon-
derous Spar.— Caivk.— Liver Stone,

CHAP. XIII.— page 71.

Argillaceous Earths,

General Account of Clays or Argils. — Alum ; its CompcJitioa.—Na-
fural Hijlory of Alum.— Action of this Suhjtance on stber Bodies.—
Vfes of Alum in the Arts. — Lac Lun&.— Porcelain Clay.—Mannet
of making different Kinds of Pottery. —Stone Ware — Yellow, or
Queen's Ware.-?-?Cbina.—Lithomarga. — Terra Lemnia.—~2o!et—
Zeolite. -*<~Lapis Lazuli.— 'Tripoli.-— Brick Clay.—>Slate.

CHAP. XIV,— page 85,
Siliceous Earths.

General Arrangement of Flinty Suhftances.~Gems.— Diamond.— Ruly.
—Sapphire.— * Topaz. — Emerald.—** Hyacinth.— Amethyji.— Garnet.
~— Tourmalin.— Opal.— Compaction and Properties of precious Stones.
—Quartz. — Rock Cryjlals. -^Pebbles. —Flints. — Lapis Nephriticus.
—Cat's-Eye.—Hydrophanes. — Explanation of the Phenomena of the
Hfdrophanous Stone.— 'Moon-Stone.— Chalcedony.— Onyx.—Carne-
lion% — Sardonyx.-*- Agate.— Common Flint. — Chert. — Sand and
Gravel.— Jafper.— Feldt Spar.— Labrador Stone.— Schirl and
Whetftone. — Art of making Glafs. — Prince Rupert's Drop and,
PhilofophicaJ. Phial.— Curious Phenomenon*

CHAP. XV. — page 99.
Of the Stronthian, Jargenic, and Adamantine Earths.

The Scottijh or Stronthian Earth difcovered by Dr. Cranxford*—Oftht
Jurgonic Earth.— Adamantine Earth.— All of thefe fcar:s Minerals.

A3 CHAP.

vl CONTENTS,

CHAP. XVI. — page 1 01.

Compound Earths.
Definition of this Genus,— Various compound Stones.

CHAP. XVII.— page 104.
Volcanic Produds. *

Lava* — Different Kinds,'— Progrefs of a River of Lava.— Compound
Parts of Lava. — Pumice Stone.— Bafaltes.— Trapp.— Terra Pux-
Kolana.

CHAP. XVIII.— page 109.
Metals.

Ufes of Metals. — Their Properties, — Weight, Opacity, Malleability,
Duttility, Fujibility.— Mix with each other.'— Their Inflammability <
—Calcinatien.~-Entire and Semi-metals.— Perfeff and imperfe£l.
— Natural Hiftory of Metals. — Working of Mines.— A/aying.—
Smelting.-— -Union with Acids.— Attion of other Subjiances on Me-
tals.

CHAP. XIX. — page 120.
Arfenic.

Natural Hi/lory of Arfenic.— 'Mode of reducing it to the metallic Form.
—White Enamel. — Orpiment.~°-Realgar. — Its Ufe in Medicine — .
A dreadful Poifon ; hoiu to detefi it in the Body.— A Remedy for the
Poi/bn of Arfenic.

CHAP. XX. — page 1 24.
Molybdena.

Short Account of this Semi-metal. — May be reduced to an Acid. — A
fcarce Mineral.

CHAP. XXI. — page 126.
Tungftein.

TbeOreofTungftein confounded with that of Tin. — Where found. —
Mode of reducing it to the reguline or metallic State.

CHAP.

C O N T E N T S, vii

CHAP. XXII.—page 128.

Manga nefe.

Natural Hijlory ofManganefe.—Its Effeffs on Glafs.—Regulus or Me.
tal. — Black Wad. — Manganefe contained in Vegetables.— U/es in
the Arts,

CHAT. XXIII.— page 131.
Nickel.

Natural Htftory of Nickel.— Metal how obtained.^Detonates tuitb
Nitre.'— Has a ftrong Repuljionfof Silver, and Attrafiion for £«/-
pbur,—~A ufelefs Mineral.

CHAP. XXIV.— page 134.

Cobalt.

Natural Hi/lory of Cobalt. — Analogy between this Metal and the blue
colouring Matter of Vegetables.— Mode of aj/aying it,— Mines of
Cobalt. — Smalt t or Powder Blue.— Ufes of Cobalt in the Arts. —
Curious Jympathetic Ink. — Changeable Land/cape. — Union *uiith
otbir Metals.

C M A P. XXV. — page 139.

Bifmuth.

External Qualities of Bifmuth. — A powerful DiJ/ol-ver of Earths.— -
Pearl White, a pernicious Cofmetic.— Curious Experiment. — A metal-
lic Compaction, -which melts in boiling Water.— Various U/es of
Bifmuth in the Arts.

CHAP. XXVI.— page 143.

Antimony.

Natural Hijiory of Antimony. — Regulus.—Sno*w of Antimony. — Cate-
nation of Antimony.— Combinations with Acids. — Butter of Anti-
mony.— Antimonial Wine. — U/es of Antimony in Medicine.— F forts
Antimonii. — Glafs of Antimony.— Crocus of Antimony. -~Sulphur of
Antimony. — Tartar Emetic.— James's Powder.

CHAP. XXVIL-^page 150,
Zinc.

General Defcription of this Metal. — Pbilofopker's Wool.— Union with

Acids.— White Vitriol. — Detonation of Zinc with Nitre.— Comti-

A 4 nation

viii CONTENTS.

nation with Metals.— Pewter. — Its Ufe in fin-works.—
Hiftory o£ Zinc.—Calamine. — Black JacL—Srafs, how made.—
Tutty.— Pinchbeck.

CHAP. XXVIII.— page 156.

Of the newly difcovered Semi-Metals.

Sylvanite. —Menacbinite.— Urantte.—and Titanite*

CHAP. XXIX.— page 155.
Iron.

JExtea/tve Utility of this Metal. — Its Properties.— Natural Hi/lory of
Iron.'— Eagle-Stones. — Blood-Stones. — • The Load/tone.— Emery.—*
Ochres. — Smelting of Iron. — Forging of Iron.— Making of Steel.—*
tempering of Steel. — Caft Steel. — Great Difpojttion in Iron to unite
nvith other Bodies.— Green fitriol, how procured.— PruJJian Blue.—*
Ink.-~-Inflammation of Sulphur and Iron. — Tinning of lron.<—Prc-
farations of Iron ufed in Medicine.

CHAP. XXX.— page 175.
Tin.

General Properties of Tin.~— Granulated Tin.— Natural Hiftory of Tin.—
Its Union with the Acids.— Ufe of Tin in improving the red Dyes.—
Smoaking Liquor of Libavius.—^Aurum Mufivum.— Combinations
of Tin with other Metals.— Diferent Species of Pewter.— Putty.—
Application of Tin in dying.— Ufe in Medicine.

CHAP. XXXL— pageiSi.
Lead.

General Properties of Lead. — Red Lead.— Litharge.— Natural Hijlary
of Lead. — Slickenfides.— Curious Phenomenon.— Smelting Lead Ores.
—Union with Acids.'— Plumbum Cor neum.— White Lead; bow
made. — Sugar of Lead.— Union with other Metals. — Common Solder.
—Ufes of Lead. — Great Danger from leaden Ve/els.—Devonfiirt
Colic. — Means of dete Sling Lead in Liquors,— Medical Ufes of Lead.
—Ufe.s of its Calces in the Arts.

CHAP;

CONTENTS. &

CHAP. XXXII.— page 192.
Copper.

General Properties cf C of per. —Its Natural Hflory. — Turquoife Gem.
—Smelting and refining of Copper. — Antique Statues preferred ly the
Green Ruft. — Union with Acids.— Blue Vitriol.— Colouring of Guns.
'—Cuprum Ammoniacum.— Verdigris. — Union with Metals.— White
Copper. — Pinchbeck.— -Gun Metal. — Bell Metal.— Metal of ancient
Statues.— Bronze.— Speculums of Reflecting TeleJccpes.—Pot MetaL~~*
finning of Copper.

CHAP. XXXIIL— page 204.
Mercury.

Great At f raft ion of this Metal for the Matter of Heat. — Quick/ifo er j
rendered folid ; malleable.— General Properties of Quickfelver, — Hy-
drargyru! calcinatus.— Natural Hiftory of Mercury. — Cinnabar.—*
Native Vermilion.— Action of Acids on this Metal. — Turbith Mihe~
ral. — Red Precipitate.— ^White Precipitate.— Corrofive Sublimate.'—
Calomel.— Keyfer's Pills.— Ethiop's Mineral. — Vermilion. — Amal-
gams.—Gold made brittle by Mercury.— Mode of gilding Metals.—
Ufe of ^uickjtlver in extracting the precious Metals from the Earth.
—Making of Looking GlaJJes. — Conditions necejjary for the Operation
of Mercury on the human Body.

CHAP. XXXIV.— page 215.

Silver.

Cbarafler of the perfect Metals.— General Properties of Silver. — Vege-
tation of Silver.— 'Natural Hijlory of Silver.— AJJay ing of Silver,—*
Cupellation.— Lunar Cauftic.— Fulminating Silver.— Luna Cornea,
—Diana's Tree.— Green Gold. — Standard Silver Coin.— Plating
with Silver ; hovj performed. — French Plate.

CHAP. XXXV-— page 227.
Gold.

General Properties of Gold. — Gold calcined ly Electricity. — Extreme
Ductility of this Metal. — Natural Hijlory cf Gdd.—Proce/es for
feparating Gold from other Subftances. — Quart ation. — The Touch-
Jlone.—Aqua Regia. — Reafons why the different Acids act on metallic
Bodies*— Fulminating Gold.— Purple Powder of CaJJius.— Golden

Calf

x CONTENTS.

Cafa how deftroyed by Mofes.— Union of Gold with other Metals.—*
Standard Gold Coin of different Countries.

CHAP. XXXVI.— page 238.
Platina.

Natural Hiftory of this curious Metal.— Its Properties. — The moft pon-
derous Body in Nature.'— Its Hardnefs and Infufebility. — Soluble only
in Aqua Regia and oxygenated muriatic Acid.— 'Its Union with other
Metals.— 'Crucibles formed of it.— 'Might be applied to various Ufes.
•which no other Metal can anfwer.

CHAP. XXXVJI — page 243.
Of inflammable Subilances in general.

Ignition and Combuftion defined. — Acids formed by tke Combuftion of
Inflammable Sub/lances. -~F lame, how produced. — -The Qbje& of the
frefent Inquiry limitedi—WbQt Subjfances are commonly termed in*
flammable*

CHAP. XXXyill.— page 248.
Phofphorus.

Pbs/phorus of Kunkel. — Light from putrefcent Subftances. — Curious
Fads. — Light from the Sea Water, &c.-r-Ligbts about the Beds of
Sick Perfons. — Phofphorus exhaled with the Sweat. — Phofphora,ted^
fjydrogen Gas.

CHAP. XXXIX.— page 256.
Sulphur.

General Properties of Sulphur. — Natural Hijlory of Sulphur.-r-Utiion
•with Earths. — With Alkalies.— Liver of Sulphur >— Artificial ful^
phureous Waters. — Ufes of Sulphur.

CHAP. XL. — page 259.
The Carbonaceous Principle,

Nature of the Carbonaceous Principle.— In what Subjlances princi-
pally found. — Charcoal. — Lamp black.— 'Strong Attraflion of the
Carbonaceous Principle for Oxygen. — Its Ufe in the Reduction of Mt-
iah. -^Plumbago, or Black Lead.— Its various Ufes in the Arts.

CHAP.

CONTENTS.

CHAP. XLI. — page 2^4.

Pitcoal.

Different Species of Coal.—Newcaftle Coal. — Culm.— Slate Coal.—
Cannel Coal.— Kilkenny Coal. — Bovey Coal. — Peat. — Coke.—
Coal Tar* — Natural Hiftory of Coal.— Observations relative to the
Deluge.

CHAP. XLIT. — page 274. \
Naphta, Petroleum, Barbadoes Tar, &c.

Nature and Properties of Naphta.— Burning Fountains. — PetroJeurff^^
Mineral Pitch, or Barbadoes Tar. — Lake Afphaltes.—Afphaltumi
ho--w colleffed. — Elaftic Bitumen.— Component Principles of tbefc
' Dances.

CHAP. XLIII. — page 277.
Jet, Amber, Ambergris, and Mineral Tallow.

General Properties of Jet. — Its Nature and Origin.— Amber.— Acid
of Amber. — Natural Hiftory of Amber.— Different Opinions of its
Origin. — Ambergris. — Its Natural Hi/lory. — Mineral Ta/loiv.

CHAP. XLI V.— page 282.

Of the Diamond confidered as an inflammable Subflance.
Natural Hiftory of Diamonds. — Varieties. — Internal Structure. — Ex-
periments proving the inflammable Nature of the Diamond.— -Experi-
ments of M. Cadet— Of D'Arcet. — Vital Air neceffary to the Com"
luftion of the Diamond. — Experiments of Lavoifar. — Further Expe-
riments.— Experiments of Mr. Tennant.—The Diamond proved to be
cryftallized Charcoal.

CHAP. XL V.— page 287.
The Strufture of the Earth.

The Curiojity of Man on this Topic limited by the Weaknefs of his
Powers. — The Body of the Earth difpofed [in Strata. — Declivities of
Mountains. — Difpojition and Order of the Strata. — Caldy IJland.'—
Where Metals are ufually found. — Probable State of the Earth at its
Creation. — Lavas by nuhich Alterations would be produced.— FoJJil
Shells, &c. accounted for. — Formation cf If.ands, &c.— Other Irre-
gularities of the Earth's Surface explained,

PjB-i CHAP.

?ii CONTENT S.

CHAP. XLVI.— page 313.

Mountains.

J)tftin£ion between Hills and Mountains.— Mountains primaiial or
Jecendary.— Granite Mountains only fvppofed in general primeval.
~-Some Lime-Jlone Mountains primaeval.— Alluvial Mountains.—
Entire and ftratif.ed Mountains t— Mountains homogeneous and he-
terogeneous,—Confufed Mountains.— Volcanic Mountains.— -Height
cf Mountains, how meafured.— Computed Heights of the mojl re*
markable Mountains,— Line of Congelation in different Parts of the
World.

CHAP. XL VII.— page 319.

Volcanoes.

Central Olfervations oa Volcanoes.— *[ heir Connexion with the Sea.-~»
Immexje Force of fubterraneous Fires exemplified in various Injlances.
—Theory of Volcanoes. — Great Depth.— ^-Traces of Volcanoes in,
different Parts of the World.-*-DeJcription of &tna.~— Eruption of
/f 1704.

CHAP. XLVIIL— page 362.

Earthquakes.

CenneFiion between Earthquakes and Volcanoes.— Earthquakes caufed-
by the Progrej's of Steam between the Strata of the Earth.— Signs of-
approaching Earthquakes. — Great Earthquake at Li/Ion, in IJS5"
<—£.arib<iuakfs in Calabria, in 1783.

E 0 O K

CONTENTS.

BOOK VII.

OF WATER.

CHAP. I.— page 379.

Of Water in general.

Water a Comprand Body.— Three States of Water. — Water ia a fluid
State. — Florentine Experiment. — Vapour. — Experiments afcertaining
the Force of Vapour. — Steam Engine.— Ice.— 'Phenomena of Freez-
ing.—Of Thawing.— Water expanded in the State of Ice. — Immeafe
Force exerted by Water on faffing to that State.— Why Ice is not
ferfeftly Iran/parent.

CHAP. II. — page 401.
Hydroftatics.

Difcoveries of Archimedes in this Branch of Science.— Of the Moderns*
— How Fluids are aded upon by the general Laws of Gravifatioa.—
Particles of Fluids acl independently of each other. — Experiment
afcertaining this Principle. — Fluids prefs equally in all Diredionf. —
Cautions necejjary in conftruSiing AqueducJs, &c. to guard cgainft
the lateral PreJJure of Fluids.— -All Parts of the fame Fluid in Equi-
librium with each other. — Surfaces of Fluids always in a Plane
parallel with the Horizon,— Preffure of Fluids in proportion to their
Height. — Hydrojiatic Paradox. — Ejfetfs of Gravity on Fluids of
different Denjities. — Aclion of Air on the Surfaces of Fluids.— Uji
of a Vent Peg. — The Valenois. — The Siphon. — A&ion of Fluids on
folid Bodies immerfed in them, — Why certain Bodies fink and otheri
Jwim in certain Fluids.— -Bodies that Jwim dif place a Bulk of Water
equal to themfelves in Weight but »•;/ in Magnitude. — The fame Body
•will Jink in one Fluid, which willfwim in another. — The Hydro-
meter.—Fahrenheit's Hydrometer. — Recapitulation of the Docirines
rcfpecJing fpecific Gravity. — How to make a Globe of Iron Jwim an
the Surface of Water.— Boats made nf Copper.

CHAP. III. — page 427.
Hydraulics.

Of the Difcharge of Fluids through fmall Aper litres. — The Difchargt

of Fluids through fuccejfive Pipes*— Artificial Fountains.— Pumps. —

g Tb*

v CONTENTS,

The Raijtng Pump. — The Forcing Pump.— The Sucking Pump.*—*

The Compound Pump.— The Fire Engine Motion of Water in

Conduit Pipes. — Qfcillatory Motion of Water in a Siphon. — Ofcilla-
tory Motion of Waves.— Motion of Wheels afied upon by Water, and
CcJiJiruclion of Water Mills.

CHAP. IV. — page 473.
Of tie Ocean.

Saltnefs of the Ocean. — Different Opinions as to the Caufe. — Probable
Reafons why the Sea has been always fait. — Temperature of the Sea
at different Depths. — Modes of rendering Sea- water frejh.

CHAP. V. — page 481.
Of Rain.

Recapitulation ofDoclrines relative to fptmtaneous Evaporation. — Va-
pour by fame fuppofed to conjiji of hollow Vejides. — Rain. — Different
Theories of Rain.— Snow.— Hail. — Rain which froze in coming in
contaft with the Earth.— Large Hail-Jiones.— Fogs,— Dew.— Hoar
Froft.—Inftances of partial freezing when the general Temptrature
is above the freezing Point,

CHAP. VI. — page 491.
/ Of Springs and Rivers.

Origin of Springs. — Digging of Wells.*— Nature of Springs. — Mar/bet.
—Cheap and eajy Mode of draining them. — Intermitting Springs. — -
Rivers, — Their Source, &c.

CHAP. VII. — page 504;
Hot Springs.

Probable Caufef of thefe Phenomena. — Abound moft in volcanic Re-
gions.-—Hot Springs in Iceland, near Mount Hecla.-^At Geyfer.—
In the I/land of Ifchia. — At Viterbo. — Explanation of thefe Pheno-
mena.—Burning Well in Lancajhire .— Explained.

CHAP,

CONTENTS. xr

CHAP. VIII. — page 509.

Mineral Waters.

Capacity cf Water as a Solvent. — Subftances commonly found in Mi-
neral Waters. — Fixed Air. — Mineral Acids.— Alkaline falts. — Neu-
tral Salts. — Earthy Subftances. — Sulphur,—- Metals. — Mode of exa-
mining and analyzing Mineral Waters. — Chemical Tefts, — Analyjls
efthe moft celebrated Mineral or Spa Waters. — Aix-la-Chapelle.—
Batb.—Briftol.—Buxton. — Cheltenham. — Epfom. — Harrowgate.—
Matlock. — Pyrmont. — Scarborough.— Spa. — Refle&ions on the Uft
of Mineral Water in general.

A P P E N D I X. — Table offpecific Gravities - - 527

- - .... of the Weight of tht different Gaffes - 528

BOOK VI.

MINERAL SUBSTANCES, AND TH£
STRUCTURE OF THE EARTH.

CHAPTER L

OF SALTS IN GENERAL;

tntroduSory Obfervatiom. — Definition of Salts. — Salts Jin$le and
compound.— What are called Jimple Salts are in reality compound Bo-
diej.—Qxj'gcnGus Principle,

TH E earth which we inhabit* though prefenting
to our fenfes an almoft infinite variety of ob-
jects, is yet compofed, as was already intimated *, of
but few fimple materials. It is the moft pleafing oc-
cupation of the philofopher, to purfue the Proteus
nature through her various and aftoniming transforma-
tions i to develope thofe intricate combinations, which
conceal from the eyes of common obfervers the ele-
mentary principles of things; to anatomize matter;
and even to explain, as far as we are able, the procefies
by which fubftances, apparently contrary to each other
in their general properties, become united, and form
new bodies differing again in their moft efiential qualities
from thofe of which they are compofed.

In purfuing this really interefting inquiry, the
plaineft and the cleared method that prefents itfelf to
my mind, is to notice feparately each peculiar and ele-
mentary fubflancej and. afterwards to examine the ef-
fects of its combinations with other bodies. In trcat-

* See book I. chap. 2. of elementary fubllances.

VOL. II. B ing

2 Of Salts fimple and compound. [Book VL

ing of mineral fubftances naturalifts have generally
clafied them under four principal heads, falts, earths,
metals, and inflammables. Perhaps modern philofo-
phers might adopt an arrangement more confiftent
with recent difcoveries;' yet novelty in clafiification
but feldom facilitates the labour of the ftudent, and
it is commonly fafeft to follow a beaten track in
Jcience, unlefs it leads to error.

Thole fubftances are denominated falts which are
fu-fible, volatile, foluble * in water, not inflammable,
and fapid when applied to the tongue. The mod
fimple ftate of falts, is a mafs, white, brittle, and in
forne degree tranfparent. Salts in certain degrees of
heat are fluid and tranfparent, like oi-L They differ
in their degree of fufibilky and volatility. Some af-
fume the form of vapour in the ordinary temperature
of the atmofphere, others in a great degree of heat
remain fixed f . Previous to treating of the particular
fubftances of this clafs, it will be proper to make a
few obfervations on the formation of falts in general.
Salts are either fimple or compound. Simple falts
are diftinguifhed into alkalis and acids; and from the
union of an acid and an alkali are produced compound
falts, which are alfo called neutral, becaufe by this

* The diftin&ion between folution and mixture has been already
ftated; but it may not be improper to remind the reader, that in
folution the body which was folid is fo completely in union uith
the fluid or rrienftruum, that the compound is completely tranfpa-
rent, though not always colourlefs. Common fait, for inftance,
with water, makes a colourlefs foiution; but blue or green vitriol
makes a blue or green folution with water. A mixture on the
contrary is always muddy, and if left to ftand, a fediment will be
tlepofited. The point of Saturation is when the fluid will hold no
more of the folid body in clear folution, bun precipitates it, or lets
it fall to the bottom.

f Not volatile, or rifing in vapour.

combination

Chap. I. J Formation of Mcts. 3

combination the character iftic properties both of the
acid and alkali are loft, and a new body is formed,
which is extremely inert, in comparifon with the two
jubilances of which it is compofed. Several of the
earths, and fome of the metals, are alfo capable of be-
ing united with acids, and the compound forms a fait
more or leCs perfe 61.

Alkalis and acids, at the time they obtained
name of fimpie falts, were fuppofed to be really fuch;
modern difcoveries, however, have now led to a differ-
ent conclufion, and left no reafon to doubt that all the
aci.ls, and "at leaft one of the alkalis, are compound
bodies. Thfe doctrine of the formation of acids is
now fully elucidated} the procefTes of corr.buftion,
and-of the calcination of metals, which were formerly
attributed to the expulfion of an imaginary fubftance,
called phlogifton, are now proved to be only the for-
mation of acids ; or the union of the principle of aci-
dity or oxygen contained in the stmofphere, with fub-
ftances, the particles of which have, in cestain circum-
ftances, a ftronger attraction for that principle, than it
has for the matter of heat. The chief circumilance
which favours the union of the principle of acidity, or,
as it is called by the French cherftifts, oxygen, with
other bodies, is a proper degree of heat -, which, by
removing the particles of bodies further from each
ether, diminifhes their attraction, and allows room for
the entrance of air into their interftices. In the cal-
cination of metals, and in combuftion, the oxygen gas
of the atmofphere is decompofed, and while the -bafts
is attracted by the inflammable fubftance or metal, the
matter of heat is diiengaged, and becomes fenfible.
Bodies, however, may be acidified or oxygenated
without being expofed to the air j and this is performed
by placing them in contact with bodies which are
B 2 already

4 flow Ruft is generated on Iron. [Book VI,

already united with oxygen, bu* which have a weaker
attraction for that principle than the body which is to
be acidified. It is upon this principle that metals are
deprived of oxygen, or reduced to the metallic ftate,
by heating them in contact with charcoal, tallow, &c.
In this cafe the inflammable fubftance having a ftronger
attraction for oxygen than the metal has, becomes oxy~
^genated ; while the metal, by being deprived of this
principle, is reduced to the metallic frate. Metals and
combuflible bodies may alfo be oxygenated in the hu-
mid way, by fubmitting them to the action of acids.
In this procefs the acid furnimes the oxygen, and is
therefore decompofed. The oxygenation of minerals
in the bowels of the earth is probably chiefly effected
by the decompofition of water, which is a compound
of hydrogen and oxygen. A procefs of this kind is
continually carried on before our eyes ; the ruft which
iron acquires by being expofed to damp air is an oxy-
genation of that metal. Other metals, however, have
lefs attraction for the principle of acidity, and this is
remarkably the cafe with the perfect metals, platina,
gold, and filver, which therefore do not become rufted
by expofure to air.

In treating of ialts, I mail firft give an account of
the alkalis, next of the acids, and laftly of their com-
binations, or the neutral faits. I mail defer fpeaking
of the earthy and metallic falt's till the earths and me-
tals are defcribed.

Chap. 2.] [ 5 ]

CHAP. II.

ALKALIS.

Mineral fixed Alkali ; where found, — Vegetable fixej Alkali; ho*.?
obtained, — Ufe cf the fixed Alkalis in the Arts.-r-Ufe of Alkalis in
making Glafs. — Procefs of making Soap, — Volatile Alkali; bo-inj
obtained; a compound Body, — Alkaline Air.

MINERAL fixed alkali, foda or natron, is the
fait which is found recorded in antient hiftory
under the name of nitre. It is faid to be found in
Egypt in tolerably pure cryftals, and alfo in Perfia,
where it appears in a form refembling that of hoar,
froft. Even in Europe jc is found in fmall quantities
in mineral fprings, and alfo on the furface of new walls,
in the form of a damp and dewy efflorefcence. In a
compound ftate it is found in abundance; ic makes,
half the weight of common fait, and is alfo occafionally
found naturally combined with other acids. The mi-
neral alkali cannot be obtained from the native falts
containing it, without great labour and expence : what
is uled in the arts is procured by the burning of
certain -plants growing near the fea-fide. The crude
mineral alkali in commerce is called foda or barilla.

Alkalis are either mild or cauftic: the latter is their
mod fimple ftate, as when mild they are united with
the carbonic acid, with which they form a kind of neu-
tral fait. Though the carbonic acid has lefs affinity
with the alkalis than any other acid, yet it is difficult
to feparate it entirely. The ufual method of accom-
plifhing it is to diflblve the mild alkali in water, to add
to this iolution fome quick-lime, and then to filtrate
the liquor, and evaporate it in clofed veflels , the fa-
B 3 line

6 Diftingut/hing Marks of Alkalis. [Book VL

line fubftance left after evaporation is an alkali almoft
entirely deprived of carbonic acid. This procels is
founded oh the greater attraction which the carbonic
acid has for quick-lime than for the alkalis.

The VEGETABLE fixed alkali, pot-afh or kali,
agrees in feveral circumftances with die former. It
is acrid when applied to the tongae, requires as great
a degree of heat to melt it ; and in a very ftrong heat
flies off totally in vapour. It differs from the fofiil
alkali in having a much ftronger attraction for water.
This alkali may be cryftallized, but not fo eafily as the
foffil. Little of the vegetable alkali has been found
in a ftate of nature, and that only as entering into the
compofidon of nitre. It is obtained in coniiderable
quantities from the afhes of almoft all land vegetables,
by infufing them in water; the liquid, when (trained
from the dregs, v<iil then contain the lalt in a ftate of
folution, and by evaporation we obtain the alkali in a
folid form. It is alfo eafily obtained from a fubftance
called tartar, which is depofit; d by wine. The pro-
perties and ufes of the vegetable- alkali are very limilar
to thofe of the mineral.

The fixed alkalis are employed in feveral of the arts,
and particularly in that of making glafs; for though
many fubftances will fufe the vitrifiable earths, and
reduce them to a kind of glafs, the alkalis are found
the moft effectual and convenient.

In the foap manufactory alfo the alkalis are a prin-
cipal and eflential ingredient. Common foap is in-
deed a combination of fixed alkali in a cauftic ftate
•with fat and oily matters. A very fine fpecies of foap
is formed by the union of mineral alkali with olive-
oil, or oil of fweet almonds. In the making of this
fubftance, the alkali is firft rendered cauftic by boiling
it with half its weight of quick-lime, which abftracts
3 its

Chap, a*] Martufafture vf Soap^ 7

Us carbonic acid or fixed air by fuperior attraction.
What is called Ibap-ley is a folution of the cauftic
alkali in water, which is evaporated to fuch a* degree
of denficy as to be able to fuftain a new-laid egg. To
make the finer foap, a part of this ley or lixivium (to
fpeak in tt-chnical language) is to be diluted, and
mixed with an equal quantity of olive-oil. The mix-
ture is put on a gentle fire, and agitated, by which the
union is accelerated. When the mixture begins to
unite well, the reft of the lixivium is to be added to
it, and the whole is to be digefted with a gentle heat, till
the foap is completely made. Good foap of this kind
,js white and firm when cold, and is not liable to be-
come moid on expofure to air ; it is entirely mifcible
with water, to which it gives a milky appearance, with-
out exhibiting any particles of oil on the furface.

In the making of foft, liquid, green, or black foaps,
cheaper oils are employed, as oil of nuts, of hemp, of
fifh, &c. but tallow is the ingredient ufcd in our com-
mon hard foap.

Oil or fat may be feparated from foap by the addition
•of an acid, without being much altered in its properties.
On this account, waters which contain any acid, either
in a difengaged ftate, or combined with any fubftance
except fixed alkali, decompofe foap, and will not com-
pletely mix with it.

In this decompofition, efpecially that effected by
the vitriols of lime and magnefia, which are frequently
contained in water, the vitriolic acid unites with the
fixed alkali of the foap, and forms vitriol of fqda, or
.Glauber's faltj and the lime or the magnefia combines
with the oil, and forms a kind of foap fcarcely at all
voluble, which floats in a whitifh curd-like maffes on
the furface of the water.

The VOLATILE alkali or ammonia is fcldom or
B 4 never

8 Volatile Alkali a compound Subftance. [Book VF«

never found in a fimple ftate. It is met with in
nature only compounded with other bodies, in nitrous
ammoniac, or in common fal ammoniac, which is
fomedmes found in the neighbourhood of volcanoes,,
or coal mines which have burnt for a long time.
The volatile alkali of commerce is chiefly produced
from bones. This alkali is very different in its.
properties from the other two; its volatility is fa
great, that under the ordinary prcflure of the at-
mofphere it is continually flying off in a very pun-
gent vapour. It is fold in the mops under the name
of fmelling falts, fal volatile, or fpirit of hartmorn.
The proceis of putrefaction in animal matters, and
in fome vegetables, particularly cabbages, throws it
off into the air, together with other volatile matters^
\vhich in fome meafure difguife its fmell. Volatile
alkali is now proved to be a combination qf two other
fubftances, namely, the bafes of the azotic and hy-
drogen gaffes. M. Berthollet has found by analyfis;
that -1,000 parts of volatile alkali confiit of about
807 parts of azote, combined with 193 of hydrogen.
The volatile alkali of the mops, that is in its mild
and concrete ftate, when heated to a certain degree,
aflumes the form of vapour, but by a diminution of
the heat returns again to the concrete form. Volatile
alkali, however, deprived of the fixed air which ren-
dered it mild, is capable of receiving a permanently
elaftic form ; in which ftate it is called alkaline air.
When a mixture of alkaline air and marine acid air
was made by Dr. Prieftley over mercury, a beautiful
white cloud was formed, and a diminution in the
bulk of the airs took place. The cloud having fub-
fided, was found to con fi ft of common fal ammoniac,
pr a union uf the volatile alkali with the marine acid.
Nitrous, air admitted to alkaline air, like wife occa-

fioned

£hap. 2.] . Alkaline yf/r. 9

fioned a whitifh cloud, which foon difappeared, leaving
only a little dimnefs on the fides of the veffel. Fixed
air admitted to alkaline air, produced a depofition of
the common or concrete volatile alkali, in the form
of oblong and (lender cryftals, which crofled each
other, and covered the fides of the veflel like a net-
work. Inflammable air admitted to alkaline air, pro-
duced no particular appearance. Water abforbed the
alkaline air, and left the inflammable air as before.
Azotic gas feemed to have no effect on alkaline air.
Alkaline air is abforbed by water, in the proportion of -£-
of an ounce meafure of air to i | grains of rain water ;
and the water is by thefe means made prodigioufly
ftronger than any of the volatile fpirit offal ammoniac
pr hartfhorn; obtained in the common way.

f io ] [BookVIl

CHAP. III.

ACIDS

in general— -Vitriolic ^cid ', ha-M obtained, &C. — Nitrcu-
A.-id\ bcnu obtained* — Muriatic Acid; bo~M obtained, and its U/e
in the Arts .—Flucr Acid ; dijjolves Glafs ; employed to make
Etchings on Glojs — 4<-id of Borax— Pkojf boric Add.—^Acid of

ACIDS are very active fubftanc.es, and when
concentrated arc highly corrofive, They have
(b general a. tendency to unite with other fubftances,,
that they are never obtained pure except by art.
They are generally fluid, which feems, however,
chiefly to be owing to their ffcrong attraction for water,
ot which few of them can be entirely .deprived, and
\vhich they copioufly attract from the atmofphere.
One ^ f the marks by which the prefence of uncom-
bined acids may be afcertained, is their property of
changing to a red, the blue colour of infufion of
vipkts, which alkalis change -to a green. Acids are
diftinguifhed into mineral, vegetable, and animal j the
-fubjecl of this book will at prefent confine us to thofe
'of the firft clafs.

The acids found in the mineral kingdom are the
• carbonic acid or fixed air, the vitriolic, the nitrous, the
mu;iatic, the acid of fpar, the acid of borax, the acid
of phofphorus, and the acid of amber.

The CARBONIC acid has already been treated of
under the head of gafles.

The VITRIOLIC acid takes its name from vitriol
or copperas, from which it was formerly extracted by
diftillation. In the new chemical nomenclature, it is

with

Chap, 3.] yifrislic or Acid cf Sulphur. ir

with much nwe pr-'>p-:eiy called the acid of fulphur,
ES it is now found -to be a (orr.bhation of that inflam-
mable fubftance with oxygen. The pungent and
iliffocating fumes which are produced by the inflam-
mation of fulphur, are an acid which is imperfect >from
a deficiency of oxvgen ; and which ( annot be con-
denfed without the aid of water. The vitriolic acid
can never be entirely deprived of water, but admits
of the greateft concentration of all the acids, and may
be reduced to a (b.te in which its fpecific gravity is
double that of water. The denfe and fluggifh ap-
pearance of the concentrated vitriolic acid has given
rife to the improper name of oil of vitriol, under which
it paffes in the fhops.

M. Lavoifier makes a diftincYion between this acid,
as it exifts in an imperfect and gaffeous ftate, and as
it exifts in' the form of a tranfparent and ponderous
liquid combined with water. In its former ftate he
calls it, acidejulphureux (fulphureous acid) in the latter,
acide Jutyhurique. (fulphuric acid). A fimilar differ-
ence of termination is employed to exprefs the dif-
ferent ftates of the nitrous acid, according as it is
imperfectly or completely faturated with oxygen. A
difference of termination is alfo given to the combi-
nations of acids, according as they are perfectly or
imperfectly faturated with oxygen. Thus the com-
binations of the fulphureous acid, are called Julphites ;
thofe of the fulphuric acid,/#^>&«/j, &c.

The vitriolic acid now ufed in commerce is pre-
pared in the following manner : —A quantity of ful-
phur and falt-'petre, grofsly mixed, are placed in a
vefTel within a fmall room, lined with lead, and con-
taining a few inches depth of water at bottom. The
fulphur is lighted, and the room doled. The falt-
petie ferves to maintain the combuftion, by the oxy-
genous

1 2 Preparation of Vitriolic Acid. [Book VI.

genous gas which it affords ; and the acid fumes which
are produced are abfcrbtd by the water. The pro-
cefs is repeated till the water is thought fufficiently
acid. The volatile fumes are then diffipated by ex-
pofure to air, and the acid is concentrated by diiiilling
off the fuperfluous water.

The vitriolic acid is faid to have become concrete
by cold, but it probably was not in ics moft perfect
date. It eafily parts with its oxygen to inflammable
fubftances ; if oil is mixed with it, it is converted into
a dark, vifcid fubftance, and emits fulphureous and
pungent vapours.

The vitriolic acid has been thought to exift in the
atmofphere, but this is a miftake. It is difcovered
in fome waters, -but in fmall quantity j it exifts in
fome ores of metals, and makes one of the conftituent
parts of gypfum.

The NITROUS acid is a fluid of confiderr.ble weight,
but does not admit of fo much concentration as the
vitriolic. In its moft perfeft form it is quite tranfpa-
rent and colourlefs, but in its ordinary ftafe it is of
an orange tawny colour, and when expofed to the air
It conftantly emits orange-coloured fumes, which are
noxious. It very- readily parts with its oxygen to
inflampiable fubftances and metals ; and when mixed
with oil of turpentine, it explodes and flames. The
oil attrafh the oxygen, and burns, while the azote is
fuddenly fet at liberty, and occafions the explofion.
n nitrous acid is1 diluted with an equal weight of
T, it isv called aqua fortis. The nitrous acid is
considerably dhTufed in nature. All that is fold in
the lliops is obtained by diftilling fak-petre with the
vitriolic acid.

Azotic and oxygenous gas were mixed together by
Air. Cavendifh, and the electric fpark was palled

through •

Chap. 3.] Nitrous Acid or Aqua Perils. ij

through them. In thefe trials a diminution of bulk
was always obferved ; indeed five parts of oxygenous
gas being added to three of common air, almoft the
v/hoie difappeared. By continuing his experiments,
he found that an acid was produced, and that acid was
the nitrous.

The MURIATIC acid, in its ordinary ftate, is a
yellowifti- coloured fluid, and emits fumes which do
not give the air a red tinge like the nitrous acid, but
produce an appearance of mift. Thefe fumes are
noxious to the lungs, and fmell like burning foot*
The muriatic acid is diftinguifhed from the vitriolic
and nitrous in the ilrong adhefion of its component
parts, which is evinced by its not parting with oxygen,
and of courfe its having little action on inflammable
fubftances. So ftrong indeed is the attraction between
the principles, whatever they are, which form this
acid, that they have never been feparated. Its bans
therefore is wholly unknown to us, and we have no
other evidence than analogy to lead us to conclude
that, like other acids, it contains oxygen. M. Ber-
thollet conjectures the radical of the muriatic acid to-
be of a metallic nature. The muriatic acid is by far
the mod abundant of all the acids in the mineral king-
dom ; it is naturally combined with lime, magnefia,
and natron, or the foflil alkali ; wirh the latter it
forms the immenfe beds of fal gem or rock fait, and
the faline matter which gives fdtnefs to the ocean.

As the muriatic acid can only fubfift in the gafleous
(late in the ordinary temperature and preffure of the
atmofphere, it is necefTary to ufe water in order to
condenfe it. But the ordinary muriatic acid is ca-
pable of being combined with an additional quantity
of oxygen, by being diltilled with the mineral fubftance
Called manganefe, or with certain preparations of lead

and

$4 Muriatic or Aid of Sea Salt. [Book VL

£;-d mercurj, which readily part vvitK oxygen. The
acid refuhing from this procefs, and which is called
oxygenated muriatic aciH, can on.y, like ^the former,
exift in the gafleous ftate. and is abiorbed in a much
fmaller quantity by water. When the impregnation
cf water by this gas is carried beyond a certain point,
the fuperabundant acid precipitates to the bottom of
the veffel in a concrete form. M. Berthollet has
ftiewn that this acid gas is capable of being united
with a great number of falifiable bafes -, the neutral
falts which refult fnom this union are capable of
deflagrating with charcoal, and fome of the metallic
fubftances : thefe detonations are very violent and
dangerous, from the great quantity of the matter of
heat which the oxygen carries along with it into the
compofition of the oxygenated muriatic acid.

The muriatic acid in the oxygenated ftate has
alfo a remarkable power of rendering vegetable and
animal matters white. The reducing of this principle
to practice has, indeed, been productive of a very
eflential improvement in the art of bleaching, and for
this too we are indebted to M. Berthollet*. By
various experiments he was enabled to afcertain that
the oxygenated or dephlogifticated marine acid, as
it was at firft called, only differs from the common
marine acid, in containing a fuperabundance of oxygen,
with which it very readily parts. He difcovered
further, that oxygen has a remarkable property of de-
ftroying the c >lours of vegetable matters j that even
the dew which falls from the atmofphere, and that
which comes from the nocturnal tranfpiration of plants,
were impregnated with oxygen, fufficiently to deftroy
the colour of paper, {lightly tinged with tincture of

* Annales de Chymie.

turnible.

Chap. 3.] New An of Bleaching. 1 $

turnfole. The ancient prejudices concerning the dew
of the month of May, a feafon when the tranfpiration
of plants is moft abundant, he conceives to have ori-
ginated in a fimilar obfervation.

Attributing, therefore, in his own mind the com-
mqn effect of whitening linen' in bleach-yards to the
action- of oxygen, he was led to imitate that procefs.
by applying leys, and the oxygenated muriatic acid
alternately, and by thefe means was enabled to make
linen, &c. permanently white, by a very quick and
eafy prccefs. Obierving further that it was the prac-
tice in common bleaching, to make the linen, &c. in
the finiming, pafs through four milk, or a very weak
mixture of the vitriolic acid with water; he alfo tried
the paffing of the cloth through a very dilute folution
of the vitriolic acid, and obferved that it was confe-
quently rendered of a clearer white.

The oxygenated acid may be employed either in
the aerial fjrm, or diluted with waters and the latter
appears to be the moft convenient mode of applying
it. The effect feems to refult entirely from the ac-
tion of the oxygen which the acid parts with to the
cloth, and which has a power of deftroying vegetable
colours. Perhaps the fading of dyed Ruffs on being
expofed to the action of the light and air may be ac-
counted for on the fame principles. The acid which
M. Berthollet employed in bleaching he found had
parted with all its fuperabundant oxygen to the cloth,
and was reduced to the ftate of the common muriatic
acid. The foap-leys feem to.act in two ways; by neu-
tralizing any of the fuperfiuous acid which might be
imbibed, it faves the cloth from being corroded ; and
it alfo prevents the fuffocating fumes of the oxyge-
nated acid from being offenfive or ^injurious. Poffibly
the detergent quality of the leys may have a further

16 Sparry Acid. [feook VI;

effect in carrying off the colouring particles which
are detached from the cloth by the action of the
oxygen.

When or»e or two parts of pale concentrated nitrous
acid are mixed with four of fuming muriatic acid, an
effervefcence foon takes place, and oxygenated mu-
riatic acid is produced 5 at the fame time that the
mixture becomes of a red colour. The mixed acid
is called aqua regia, which has the property of diffoiv-
ing gold.

The SPARRY or fiuor acid was difcovered by Mr.
Scheele-, and takes its name from the fubflance from
which it is obtained, arid which is commonly known
in England under the name of Derbymire fpar. This
acid when pure aifumes the form of gas. In this
ftate it is heavier than atmofpheric air, extingvMmes
flame, and deftroys animal life ; it has a penetrating
fmell, like that of marine acid, but more powerful j
and its caufticity is fuch that it almoft inftantly cor-
rodes the fkin. Heat dilates it, without producing
any other change. The addition of atmofpherical air"
has the effect of producing with it a white vapour,
which is more or lefs abundant, in proportion as the
atmofphere contains more or lefs of humidity.

If vitriolic acid is poured on the Derbyfhire fpar*
which is a combination of this peculiar acid with
calcareous earth, and a gentle heat applied, the acid
is difengagcd in an aerial form. It readily combines
with water, and therefore the recipient mould be half
filled with that fluid. The firft experiments which
were made of the diftillation of this acid in glafs vef-
fels, were attended with a finking appearance, which
required confiderable acutenefs for its explanation".
It was obferved that as foon as the acid gas reached
the furface of the water, a quantity of earthy matter

was

Chap. 3.] Sparry I4cid corrodes Glafs, i?

was depofited. This was at firft naturally attributed
to the acid carrying over with it part of the calcareous-
ftone from which it was diftilled. Upon examination,
however, it was found that the earth depofited in the
water was filiceous, and this gave rife to an opinion
that flint was only a compofition of this acid with wa-
ter. This hypothecs was foon overturned, by obferv-
ing that the glafs veflel in which the diftillation was
performed was always corroded, or in part diflblved.
Tn this manner it was found that the fluoric acid has
the firigular property of diflblvihg glafs. As only a
moderate heat is required for the diftillation of this
acid, it is now ufual to make ufe of leaden veflels for
that purpofe j which are not corroded by the acid.
The bafis of this acid is unknown, as we are not ac-
quainted with any fubftance which can abftract its oxy-
gen.

The fluoric acid has been fuccefsfully employed to
make etchings on glafs, in the fame manner as nitrous
acid is applied to copper. It combines readily with
earth and alkalies, but fcarcely, if it all, acts on gold,
filver, lead, mercury, tin, antimony, ' bifmuth, or co-
balt, but it diflblves their calces. It acts directly on
iron and zinc, with the production of inflammable gas j
and it likewife diffolves copper in the metallic ftatc,
though lefs eafily than when calcined.

If BORAX is diflblved to faturation in boiling wate^,
and the vitriolic acid srdded in fuch quantity as to be
perceptibly in excefs, a fubftance will rife to the fur-
face of the water in the form of white fcales, which is
proved to be a peculiar acid. Many chemifts have
fuppofed that this acid is an artificial product, forme4
by a combination of the falts made ufe of in its ma-
nufacture. This opinion, however, has been relin-
qiiifhed, fince this acid has been found to exift in a
VOL. II. C ftate

1 8 Acid of Borax. [Book VL

ilate of great purity in mineral waters, and fmce real
borax may be formed by adding this fcaly fait to the
mineral alkali. The acid of borax requires about
fifty times its weight of water for its folution. In a
moderate heat it melts with lefs intumefcence than
borax itfelf ; and the glafly fubflance, thus formed, is
again foluble in water, having only loft its water of
cryftailizadon.

The acid of borax is ufed to fufe the flinty earths,
with which it forms clear and almoft colourlefs glaf-
fcs ; by the affiftance of heat it difiblves the earth
precipitated from what is called the liquor of flints,
or " flint diffolved in fparry acid. It unites with
ponderous earth, magnefia, lime, and alkalis, and
forms with thefe fubftances faline compounds. All
thefe properties, and more efpecially its tafte, the red
colour it communicates to the tinctures of violets and
turnfole, and its neutral combinations with alkalies,
fufficiently indicate its acid nature ; but it is the moft
feeble of all the acids, and is difengaged from its com-
binations even by the carbonic acid. The acid of
borax is the fubftance called by Homberg fedative
ialt, from its fuppofed e(icc~!s on the human body. It
effervefces with a boiling hot alkaline folution, but
not \vith metals or abforbenc earths, though it may be
united with them. It has a weak attraction for in-
flammable fubftances, particularly fpirits of wine, the
flame of which it tinges green. From this circumftance
it has been fuppofed, but without iufficient proof, to
contain copper.

" PHOSPHORIC acid is .obtained by the combuftion of
the bones of adult animals, which are afterwards
pounded, and pafied through a fine filk fieve? a quan-
tity of weak vitriolic acid is then poured upon the
powder, but lefs than is fufrkient for diffolving the
whole. This acid unites with the calcareous earth of

the.

Chap. 3-1 -Acids of Phofpborus and Amber. i$

the bones, and forms felenite, and the phofphoric acid
remains free in the liquor. The liquor is decanted off,
and the refiduum warned with boiling water j this wa-
ter, which has been ufed to wafh out the adhering
acid, is mixed with what was before decanted off, and
the whole is gradually evaporated. The diffolved fele-
nite now cryftallizes in the form of fiiky threads, which
are removed; and by continuing the evaporation we
procure the phofphoric acid, under the appearance of
a white pellucid glafs. When this is powdered, and
mixed with one third of its weight of charcoal^ we
procure very pure phofphorus by fublimation. The
phofphoric acid, however, as procured by the above
procefs, is never fo pure as that obtained by oxygenat-
ing pure phofphorus, either by combuftion or by
means of the nitrous acid.

The phofphoric acid may be rendered concrete with
very little difficulty, by merely exhaling the moifture.
It abounds in the animal kingdom, and is not unfre-
quent in the vegetable and mineral. In this laft it is
found united with lead and iron, as well as with calca-
reous earth.

The acid of AMBER is obtained from the fubllance
of that name, by the fimple application of heat. The
operation mutt not be carried on too far, or by too
ilrong a fire, as the oil of the amber is apt to rife with
the acid. The acid is found in a concrete form in
the neck of the fubliming velTel ; it is foluble in
twenty-four times its weight of cold water, and in a
much fmaller quantity of hot water. It pofTefTes the
qualities of an acid in a very fmall degree, and only
affects the blue vegetable colour very (lightly.

[ 20 ] [BookVL

fc H A P. IV.

NEUTRAL SALTS.

The Union of an Add and Alkali dejlroys tht corrofae Quality cfeacb.—Z
Neutral Salts do not communicate the f aline Quality to other Bodies.—
Cryftalline Form — boixj deccmfofed,

NATURAL productions pafs by gradations
into each other j and I might have given
an account of the primitive earths immediately after
that of the alkalies, as thefe fubftances have fcveral
properties in common, particularly that of uniting with
acids, and forming neutral compounds. Metals alfo
are capable of being united with acids, and of form-
ing with them faline fubftances. A lucid order will
however be better preferved, by at prefent confining
our attention to the confideration of fuch neutral bo-
dies as are formed by the union of an acid and an
alkali.

To a perfoh unacquainted with chemiftry, it is a
ftriking circumftance that two acrid and corrofive
fubftances fhould' by their union form a compound
very mild and inactive* Such however is the cafe,
and what is (till more remarkable, their previous acri-
mony, and tendency to combine, renders the neutral
body proper tionably more inoffenfive. Thus an alkali
united with vitriolic acid, may be received into the
'body with much lefs caution than when combined
with the Serial or carbonic acid. The neutral fairs in
general have not fo ftrong a tafte as the fimple, their
tendency to combination and their folubility being lefs
confiderable ; but the criterion, which more efpecially
diilinguiihes them from the former, is, that they can-
not,

Chap. 4.] Neutral Salts. 21

not, like the fimple falts, communicate the faline pro-
perties to other bodies. Their cryftalline form is like-
vvife a circumftance which very generally diftinguifhes
the neutral from the fimple falts. The volatility of
the neutral falts is not in general fo great as that of the
fimple falts.

Neutral falts may in many cafes be decompofed by
heat alone, but in general it is neceffary to have re-
courfe to elective attraction, or the addition of a third
fubftance. When the decompofition is effected by heat
alone, the more volatile part is forced off: but it feldom
fucceeds in this way, the ingredients commonly adhering
fo ftrongly that they rife together. It then becomes
neceflary to have recourfe to elective attraction. Thus,
if from a neutral fait we wifh to obtain the acid pure,
we apply another acid which has a greater attraction
for the alkali. If our object is to obtain the alkali
feparate, we apply a fubftance which has a flronger
attraction for the acid*.

* I would recommend to the reader, before he proceeds further
in this part of the work, to look over again that part of the fourth
chapter of the firfl book which relates to the attraction of combi-
nation or chemical attraction, Vol. I. p. 18 to 24..

C 3

[ 22 ] [Book VI.

CHAP. V,
VITRIOLIC SALTS.

Glauler*s Salt ; bcnu de compofed J Solution of it left to ccol cryfta.liix.cs
cii being fnaken.T-Vitriolated Tartar. — Vilriolated Ammoniac.

THE firft fubftances of this kind which challenge
our attention, are Glauber's fait and vitriolated
* tartar, or as they are denominated in the new chemical
nomenclature, fulphat of foda, and fulphat of pot afh.
The former of thefe neutral falts is compofed of the
vitriolic acid, combined with the mineral alkali j and
the latter of the fame acid with the vegetable alkali.
They both have a faline bitternefs. By heat their ingre-
dients may be raifed into vapour, but no one fimple
fait will feparate them, as no acid has a ftronger at-
traction for the alkali than the vitriolic, nor any alkali
a ftronger attraction for the vitriolic acid than the
fixed. Dr. Stahl propofed the effecting of this fepara-
tion as a problem. He knew how to folve it, and it
was afterwards done by a double elective attraction.
Another more curious method is this : take Glauber's
fait or vitriolated tartar, melt the fait in a hot cruci-
ble, and add to it firft a quantity of charcoal, which
has a ftronger attraction for the oxygen of the vitriolic
acid than the latter has for the alkali. Thefe being
expofed to heat, the charcoal in part difappears, and
the mixture acquires a deep red colour. If the matter is
poured out, we find it to be an bet>arjulf burls, or liver
of fulphur, the charcoal having carried off with it the
oxygen in the form of carbonic acid gas.

GLAUBER'S SALT is more fufible than vitriolated

tartar, melting in a moderate degree of red heat. The

folution of Glauber's fait forms into columnary cryftals,

p which,

Chap. 5.] Vitriolated Tartar. 23

which have generally fix fides, four principal, and two
which feem accidental. Its cryftals, containing a large
quantity of water, are liable to have it abftracled from
them by the atmofphere, when they fall to powder,
or in chemical language efflorefce. How much water
Glauber's fait is capable of containing, is known by
its requiring twice its weight of water to cryftaliize.
The water fhould be added in a boiling Hate, and the
mixture boiled a little afterwards j it may be fet by
in a quiet place, and will be found cryftallized the
next day, or will fuddenly affume that ftate on being
fliaken. On cryftallizing, a quantity of heat is per-
ceived to be emitted by the fubftance paffing from a
fluid to a folid ftate, and confequently lofing fome of
its latent heat.

Of Glauber's fait, all that is ufed at prefent is pro-
duced by art. It is faid to be produced by nature in
the waters of mineral fprings, and of the fea. But
the fait found * in them is ufually not Glauber's fait,
but Epfom fait, confifting of the vitriolic acid and
magnefia. Glauber's fait is obtained by uniting the
vitriolic acid with the mineral alkali of common fait,
as happens in the procefs for obtaining the muriatic
acid.

VITRIOLATED TARTAR is diftinguifhed from Glau-
ber's fait, by a lefs degree of fufibility. It requires
for its fufion the ftrongeft fire. Its cryftals are harder,
but lefs bright, and do not contain fo much water as
thofe of Glauber's fait. Hence they are not liable
either to fpontaneous efflorefcence, nor to watry fu-
fion, but, like other falts, which contain little water,
attract it ftrongly. This fait decrepitates* in the

* In decrepitation the cryftals burft, and fall into powder, from
the expanfion of the water which they contain, by the heat. This
occafions that crackling noife •yvhich common fah makes when
thrown into the fire.

C 4 fire.

24 AMtiwnlacal Vitriol. [Book VI.

jire. Vitriolated tartar does not appear to be a foffil
falti it is found in the juices of vegetables, and remains
in their afhes after they are burnt. What is ufed iu
dying and medicine, is obtained by art, moft commonly
by adding vitriolic acid to nitre, in order to diflodge
the nitrous acid.

One hundred parts of vitriolated tartar contain, ac-
cording to Bergman, about 52 parts of fixed vegetable
alkali, 40 of vitriolic acid, and 8 of water of cryftalli-
zatiori.

The vitriolic acid combined with the volatile alkali
is called AMMONIACAL VITRIOL, or fulphat of am-
monia. Ammoniacal falts, it is proper to remark, are
fo called from ammcMy an Arabic word for iand ; or,
as Pliny conjectures, from the temple of Jupiter
Ammon, near which ammonia ufed to be found in
great quantities, on account of the camels dung and
urine brought thither. With refpect to the general
properties of ammoniacal falts, as their alkali is very
volatile, they are unable to bear any great degree of
heat without being converted into vapour, though
much m6re than might be expected from their in-
gredients. They emit pungent fumes if a fixed alkali
or lime is added to them, as thefe fubftances, having
a ftronger '.affinity with the acids, expel the volatile
alkali.

When ammoniacal vitriol is very pure, it has the
form of needles, which, on careful examination, are
found to be flattened prifms of fix fides, two of which
are very broad, terminated by fix-fided prifrns irre-
gularly formed ; but the whole figure of the cryftallj-
zation is fubject to considerable varieties. This fait
is fometimes in the form of quadrangular prifms, an-^j
is 'fom crimes obtained in very thin plates.

Its tafle is bitter and urinqus j it is light, and very
friable. It is fcarcely changed by expofure to air ;

it

Cliap. 5.] Ammmiacal Vitriol. i§

it does not efflorefce like Glauber's fait, but on the
contrary flightly attracts the humidity of the air. It
is veiy foluble in water, two parts of cold or one of
hot water being luificient to hold it in folution ; it
cryftallizes by cooling ; but the moft perfect cryftals
are obtained by fpontaneous evaporation. It likewife
unites with ice, which it melts, producing at the fame
time an excefllve degree of cold. It does not act on
the earths, nor on magnefia •, though this laft, according
to Bergman, feems to decompofe it after a length of
time.

If mild-fixed vegetable alkali, that is alkali com-
bined with the carbonic acid gas, is diflilled with am-
moniacal vitriol, a double decompofition and combi-
nation tajce place. The vitriolic acid unites with
the fixed vegetable alkali, and forms vitriolated tartar.
The carbonic acid gas being at the fame time volati-
lized, together with the volatile alkali, alfo in a Irate
of gas, both unite, and form an ammoniacal fait, which
cryftallizes in the recipient.

Ammoniacal vitriol feems not to exift in a ftate
of nature; nor is it ufcd eithej: in medicine or the
arts.

[ 26 ] [Book VI.

CHAP. VI.

NITROUS SALTS.

GoOfOKin Niti't ; Phenomena attending its Deflagration with injlaniykc.bie
^ubjlancesj— Natural Htftory cf Nitre, — "Cubic Nitres — Union cf
nitrous Acid -ivito various Earths *>~-Niiroi<s Ammoniac*

COMMON NITRE, or nitrat of pot-aih *, confitts
of the vegetable alkali and nitrous acid. Nitre
was unknown to the ancients ; the fubftance which
they diftinguiflied by that name was a foffil alkali, for
\ve are told by Pliny that it was detergent, and ufed
in making "glafs. It is uncertain when nitre was
difcovered, but we find it mentioned in the earlieft
chemical writers. Nitre melts in a very gentle heat,
and in a greater degree of heat totally evaporates.
Cold water diflblves one-fixth of its weight j and hot
water about its own weight of this fait. Its cryftals
are more regular than thofe of any other fait (being
prifms of fix fides) having very little water in their
compofhion, and therefore not liable to fpontaneous
evaporation. Its mod extraordinary property is its
deflagration with inflammable fubftances, which hap-
pens from the decompofition of its acid, by which a
large quantity of oxygenous gas is fet at liberty. To
the production of this air is owing the rapid combuf-
tion of mixtures of nitre and inflammable fubftances,
as evinced in f gunpowder. When nitre is melted
by itfelf, no particular effect takes place j but if
charcoal is added to it in its melted ftate, deflagration

* Commonly known under the name of falt-petre.
f The reader will do well to confult what has been faid refpeft-
ing gunpowder in Book II,

Or

Chap. 6.] Deflagration of Nitre. 27

or detonation takes place. We are therefore not ro
confider nitre itfelf as an inflammable fubftance, but
only as affording the pabulum of fire. If we continue
to add charcoal, we find that the effect becomes lefs
and lefs, till it entirely ceafes. What remains in the
Crucible is different from nitre, it requires more heat
to keep it fluid, and upon examining it we find it a
pure vegetable fixed alkali. The charcoal difappears,
becaufe it is converted into carbonic acid gas by being
united with oxygen ; and the other component part of
nitrous acid, the azot?, by being deprived of its oxygen,
is alfo volatilized and difperfed.

When the deflagration is performed with fulphtjr
inflead of charcoal, the confequences are confiderably
different. Like charcoal indeed, when fulphur is
added in a certain quantity, ic will produce no further
deflagration j but when fulphur is ufed, the flame is
infupportablc to the eye, and the appearance of in-
flammation is greater though the noife is lefs. If
fhe refiduum is difiblved in water, it will readily
cryftallize, and is found to be vitriolated tartar. The
reafon that icfs explofion is produced by fulphur than
Charcoal is, that the former, when united with the
oxygen of the nitre, becomes fixed ; whereas charcoal
united with the fame principle is converted into gas,
and efcapes with violence. The formation of vitrio-
Jated tartar is owing to the production of vitriolic acid
from the fulphur and the oxygen, which combines with
th'e fixed vegetable alkali.

The detonation of nitre is a nice teft of the inflam-
mability of bodies, as there are many which are found
;o have this property when added to nitre in a ftate
of fufion, which exhibit no figns of it on ordinary occa-
|icns.

Nitre txifts in large quantities* in 'nature, and is

continually

2g Nitre-Beds. (Book VI,

continually formed in inhabited places; it is found
in great quantities upon walls which are flickered
from the rain ; and the Bifliop of Llandaff collected a
confiderable portion from the decayed mortar of an old
barn.

There appear to be three principal circumftances
that promote its formation ; the firft is, the prefence
of chalk, or any other calcareous earth, as appears
by its being collected from walls covered with plafter,
or from the ruins of ancient edifices. This fait is like-
yr'ik found perfectly pure in chalky earths. The late
Due de la Rochefoucault obtained it, in the proportion
of one ounce in the pound, from the chalk of Roche
Guyon.

The fccond circurnflance neceffary for the pro-
duction of this fait, is the putrefaction, or fpontaneous,
decompofition of vegetable and animal matters. It
is a well known fact, that places which are moiflened
with animal liquids, or contain animal matters in a
ilate of putrefaction, fuch as dunghills, (tables, privies,
&c. produce much, nitre. This conftant obfervation
has been applied to the formation of artificial nitre-
beds. Dry ditches are dug and covered with Iheds
open at the fides j thefe are filled with animal fub-
ftances, fuch as dung, the excrements of quadrupeds, or
birds, with the remains of vegetables. Thefe matters
are from time to time watered, efpecially with water
charged with animal or vegetable matters capable of
putrefaction, and they are turned up to renew their
furfaces from time to time. When the putrefaction
is in an advanced ftage, a fmall portion of the rnattev
is taken up and lixiviated, to afcertain whether it con-
tains nitre ; and when it is found fufficiently charge^
•with that fait, the whole is lixiviated.

The third circumftance which in the opinion of

feme.

Chap. 6.J Natural lliftory of Nitre. -29

fome, is fuppofed to favour the production of nitre,
is the accefs of air ; this is the caufe of the formation
of the nitre found on walls ; and for this reafon it
is that nitre beds require to be frequently turned over,
in order that the air may touch them in all points.
The neceffity of the accefs of air is laid to be ftill more
evidently fhewn by the nitre contained in chalk, as in
is never found below a certain depth. When the three
circumftances here treated of are united, the production
of falt-petre is very abundant. Nitre-beds ought aj-
xvays to be conftructed on thefe principles.

The theory of the formation of nitre has not been
long known. Glauber, and many other chemifts
fmce his time, fuppofed nitre to exift ready formed
in vegetables, from which they imagined it to pafs into
animal fubftances, and to become difengaged by putre-
faction j but it was foon perceived, that vegetables do
not contain a fufficient quantity of nitre to account for
what is obtained from nitre beds. M. Thauvenei,
whofe didertation on the formation of nitre was ho-
noured with the prize of the academy, has made many
experiments to difcover its origin : he found, that the
nitrous acid is formed by the combination of an elaitic
fluid, difengaged from animal matters in a ftate of
putrefaction, and pure air. He has likewife difco-
vered, that the nitrous acid, once formed, combines
with calcareous earth, when any animal matters arc
made ufe of; and that the remains of vegetables are
ufeful to afford the fixed alkali, which is the bafis of
common nitre. But M. Thouvenel did not determine
the nature of the gas, which is difengaged from putre-
fying animal matters. It is to Mr. Cavendim that
we are indebted for the proof that it is the fame gas,
which conftitutes one of the principles of the atmo-
fphere, under the name of azote, or phlogifticated air,

or

30 Cufa Nitre. [feook Vt

or atmofpheric mephitis. His experiment, wherein
the nitrous acid was formed by the combination of
this gas with vital air, by means of the decline fpark,
has been already mentioned.

CUBIC NITRE, or nitrat of foda, confifts of the
nitrous acid and the fixed mineral alkali. It refembles
common nitre in all its ftriking qualities j almoft its
only difference is the form of its cryftals, which is
a paralellopiped. The cryftals adhere fo ftrongly,
that they are fcarcely ever found diftinct and regular.
For the deflagration of cubic nitre, charcoal is moft
proper ; when performed with fulphur, Glauber's falc
is produced.

Cubic nitre has not yet been found in nature, but
is always produced by art. The Ihorted method is
adding nitrous acid to foffil alkali. Its tafte is cooling,
and rather more bitter than that of common nitre.
Fire decompofes it j but it decrepitates, and does not
fo eafily melt as common nitre j like that fait, however,
it gives out vital air during its decompofition. It is
(lightly deliquefcent when expofed to air. It is more
foluble in cold water than the common nitre, two parts
of water, at the temperature of fixty degrees, diflblving
one of the fait. It is fcarcely more foluble in boiling
water, and therefore cannot be had in regular cryilals,-
except by flow evaporation.

Siliceous earth combines with the bafis of this fait,
and difengages the nitrous acid j clay likewife feparates
the acid, and affords a refidue in the form of frit *,
which is porous and opake when a ftrong heat has
been applifd. Ponderous earth decompofes this fait,
and difengages the mineral alkali. Magnefia and
lime do not fenfibly change it. The vegetable fixed

*' The mixed materials for making glafs.

alkali

Chap. 6.3 Citrons Ammcn'ua;. JI

alkal-i has a ftronger attraction for its acid than the mi-
neral. This fact is very eafily (hewn. If a heated
folution of cubic nitre is divided into two parts, and
the cauftic vegetable fixed alkali added to one of them,
it will afford prifmatic cryftals during its cooling; no
cryltals, however, will be obferved in the other part
becaufe cubic nitre does not cryftallize by mere cooling
without evaporation.

The neutral falts hitherto examined produce no
effect whatever on cubic nitre ; if thefe falts are dif-
folved together in the fame water, they cryftallize
feparately, and each in its ordinary manner ; the nitre
and Glauber's fait by cooling ; the vitriolated tartar
and cubic nitre by evaporation. All thefe properties
fhew, that cubic nitre differs from common nitre.

NITROUS AMMONIAC, or nitrac of ammoniac, is
compofed of the nitrous acid and volatile alkali. It is
more foluble and more fufible than the vitriolic am-
moniac. When the heat is increafed a little above
what is neceffary for its fluidity, it is converted into
copious vapours. The degree of heat necefiary for
its fufion is a little above that oj boiling water ; and if
more heat is fuddenly employed, it has the fmgular
property of undergoing deflagration, though no in-
flammable fubftance mould be added to it, and even
in a clofe veffel. This feems to depend on the de-
compofition of the volatile alkali.

M. Berthollet having expofed ammoniacal nitre to the
action of heat in a pneumato-chemical and diftilling ap-
paratus, and having obferved the phenomena of this ope-
ration more carefully than had been done before, re-
marks, that it is not a true detonation which takes place,
but a fudden and inftantaneous decompofition, in which
part of the volatile alkali is entirely deftroyed. The
water obtained in the receiver contains a fmall part of

the

^2 Ammniacal Niire. [Book VI.

the nitrous acid difengaged in proportion to the qtfan-
tity of volatile alkali decompoled ; and the latter gives
out phlogifticated air or azotic gas. The liquid pro-
'ducl: of this operation being weighed, a greater quantity
of water is found than exifted in the ammoniacal nitre ;
and M. Berthollet concludes that this fuperaburrdant
water is formed by the union of the inflammable gas,
which is one of the principles of the volatile alkali,
with the vital air of the nitrous acid. The azotic gas>
or other principle of the Volatile alkali, which is fix
times more in quantity than the inflammable gas, is
difengaged and collected under the vefiels of the pneu-
matic apparatus.

This fait diflblves readily in water, atid in a verjr
large quantity, but it. has not fo ftrong an attraction for
water as to be deliquefcent. It may be decomposed
by the vitriolic acid, or either of the fixed alkalis. The
nitrous ammoniac is contained in the juices of fome
plants, but it is ufually prepared by artificial combina-
tion.

Chap. 7.] • [ 33 J

CHAP. VII.

MURIATIC SALTS.

Sal Digeflivus — Common Salt. — Rock Salt. — Natural Hiftcry cf
Salt. — Sdltnefs of the Ocean. — Ufes of commcn Salt in the drts>—
Sal /Immoniac.— Natural Hijlory nf Sal Ammoniac.

r I ^HE combinations of the muriatic acid with the
JL alkalis are, ift, SAL DIGESTIVUS, or muriat of
pot-am, which has al'fo been called the febrifuge fait
of Sylvius, and is a compofition of the muriatic acid
with the fixed vegetable alkali. Its tafte is penetrat-
ing and bitter ; its cryftals cubical, but almoft always
confufed and irregular. In the fire it decrepitates, that
is, its cryftals fuddenly break and fly in pieces by the
rarefaclion of the water which enters into their com-
pofition. If the heat is then continued, and diffidently
ftr'ong, it melts, and is volatized without decompofi-
tion. It is not much altered by expofuie to the air ;
It is however (lightly deliquefcent. About three parts
of cold water are required to hold one part of this fait
in folution, and hot water dees not diflolve a greater
'quantity.

Clay appears to decompofe this fait in part, for ma-
rine acid is obtained by diftilling it with the clays found
in the vicinity of Paris. This operation, however, in
ifaft affords only a fmall quantity of acid, and land feems
to have a fimilar effecl. Ponderous earth ieizes its acid,
and feparates the alkali, according to Bergman. Mag-
nefia and lime do not at all change it. The vitriolic
and nitrous acids difengage the muriatic acid with
effervefcence. This fait is found in a Hate of nature,

VOL. II. D buc

34 Common Salt. [Book VI.

but never in confiderable quantities ; it is found in fea-
water, and in the water of fait fprings, and it exifts,
thoueh rarely, in places where nitre is founds it is
likewife met wkh in the afhes of vegetables, and in
animal fluids. It is not employed in the arts, and its
bitter tafte prevents its being ufed for culinary pur-
pofes. In moft of its properties, however, it is very
fimilar to common fait.

id. COMMON or MARINE SALT is compofed of the
muriatic acid and the mineral fixed alkali, and is there-
fore the muriat- ofjbda of the new nomenclature. This
fait requires a full red heat for its flifion ; foon after
this it begins to evaporate in white fumes. It has a
flrong attraction for water, fo as to deliquefce in a
moift air. During evaporation, the cryftals of this
fait form at the top of the folution, contrary to thofe
of other falts, which form at the bottom. When the
evaporation is carried on quickly, it forms into thin
irregular crufts, and this is the ftate in which we com-
monly have it. When the evaporation is flow, it
affumes the cubic form, and the fmalleft cryftals are
the mod regular ; but if examined accurately, one of
their fides will be found a little hollor/. The larger
cryftals have a pyramidal hollow apex, with a broad
bafe. This is owing to their fuperior furfaces being
dry when floating in the water, while their inferior
furfaces are moiftened. Hence, as all dry bodies have
a repulfion for water, and as their inferior furfaces have
a tendency to fink, they are hollowed into little pits
•on the fuperior furfaces.

This fait contains little water of cryftallization-, and
decrepitates in the fire. If frequently diffolved, evapo-
rated, and dried, its quantity is more diminifhed than
4hat of any other fait. By decompofition we obtain
'•either its acid or 'its alkali. The old chemifts ufed to.
i obtain

Chap. 7.] Natural Hift cry of common Salt. 35

obtain its acid by heat alone, but this is troublefome,
and requires veffels capable of enduring great heat.
It is moft readily decompofed by the vitriolic acid,
which has the ftrongeft attraction for the alkali. The
nitrous acid will alfo decompofe it, but is more liable
than the vitriolic acid to come over with the muriatic.
Some water muft be put into the retort with the vi-
triolic acid, otherwife the muriatic acid will come over
in fumes fo copioufly as to burft the vefTels. The
quantity of the water mould be about half that of the
vitriolic acid ; one half of which fhould be put into
the receiver to condenfe the fumes of the muriatic
acid, and the other half mixed with the vitriolic to
prevent its too fudden action. Glauber's fait remains
after this operation, and this is the ufual way of prepar-
ing it. The way to decompofe marine fait, fo as to
obtain its alkali, is, firft to expel the muriatic acid by
means of the nitrous; we thus obtain cubic nitre,
which muft be deflagrated to obtain the alkali. A
better method, however, is to mix a folution of ma-
rine fait with cauftic vegetable alkali j by evaporation
muriat of pot-am is obtained, and the remaining
water contains the mineral alkali, pure and difen-
gaged.

. Common fait is the moft ufeful of faline bodies ;
for though there are fome which refift putrefaction
equally well, there is none which is fo friendly and
agreeable to the human ftomach. Its agreeable qua-
lities are not indeed confined to man ; moft other ani-
mals indicate a great fondnefs for it. The rock fait,
or fal gem, though only one form of common fait,
does not melt fo eafily as the common cryftals. The
moft remarkable mine of this fait is at Cracow, in
Poland, where there is thought to be fufficient to fup-
ply the whole world n\any thoufand years. In this
D 2 mine

36 Saltncft of the Ocean. [Book Vf.

mine there are houfes, chapels, and ftreets of rock
fait, which, when illuminated, afford a beautiful pro-
fpect. This fait js alfo obtained from fome fprings.
When found in the earth it is feldom cryftallized in
any regular form ; it has various degrees of whitenefs,
and is often found coloured ; in this latter ftate it is
more particularly called fal gem, becaufe it often has
the appearance and tranfparency of gems. .

The ocean differ.? in faltnefs in different climates.
It is falter towards the equator than rear the poles.
This feems to arife from the different quantities of
water which are evaporated, in proportion to thofe
which fall in rain. One pound of fea water in the
Baltic yields about a quarter of an ounce of fait ; near
Holland half an ounce ; and in the Britifh feas about
two ounces. Boyle has alfo obferved, that in places
of great depth the water is falteft at the bottom.

In the voyage made towards the north pole in 1775,
it was found, that the fea-water at the Nore contained,
not quite one thirty-fixth of fait j at the back of Yar-
mouth fands, not quite one thirty fecond ; off Flam-
borough Head, rather more than one twenty-ninth ;
off" Scotland, rather lefs than one twenty-ninth j
..latitude 74°, at fea, one twenty-ninth; latitude 78°,
rather lefs than, one twenty-eighth ; latitude 80°, near
the ice, not quite one thirtieth ; latitude 8of-°, under
the ice, not quite one twenty-eighth ; latitude 68°,
46, rather more than one -twenty- eighth * latitude 65,
at fea, rather lefs than one twenty- eighth. Dr. Hales
got only one twenty- feventh from water taken up in the
Mediterranean, and cne twenty-ninth from water taken
up at the Nore. Dr. Rutty fays, he procurred one
twenty- fifth from water taken up in latitude 65; one
twenty-eighth from water taken up near Dublin \ and
one thirtieth from water taken up at Dungarvan ; and
Dr. Lucas, that he obtained one twenty-fifth from water

taken

Chap. 7.] Salt Works. 37

taken up near Harwich. From other obfervations
alfo it has appeared, that water from near TenerirT
contained about one thirty-iecond of fait, and that fome
from Saint Jago contained fully one-fourth. Further
experiments are needed to afcertain the faltnefs of the
fea in different latitudes with precifion.

The fait commonly ufed for culinary purpofes, and
known by the name of bay-falt, is obtained from the
water of the fea by evaporation. This evaporation is
in fome places performed by the heat of the fun, the
water being let into mallow trenches, in order to ex-
pofe as large a furface as poffible. This method is
pracYifed in the fourhern provinces of France, and on
a very large fcale near Aveiro in Portugal. In the
northern provinces, where the heat of the fun is not
fufficiently great, artificial fires are employed. In
fome fait- works thefe two methods are united ; and in
England, and countries where fait rock is plentiful,
that fubflance is diflblved in fait water, and then eva-
porated *. In very cold countries another method is

employed

* ' A great quantity of ro:k fait is ufcd at Northwich, in order
to ftrengthen their brine fprings, and a much greater quantity is
lent coafhvife to Liverpool, and other places, where it is ufed
either for ftrengthening brine fprings or fea- water ; much of this
rock fait was formerly exported to Holland, and it is itill fent
to Ireland for the fame purpofe. Rock fait, and the white fait
which is at Northwich, chiefly made from rock fait, is exported free
from the fait duty ; and I was informed, that the quantity, which
is annually exported from Northwich, is fo great, that if it paid
the duty, it would bring in to government, a fum not much fhort
of four hundred thoufands pounds a year. " According to the befl
accounts I have been able to procure, the grots duty on fait made
in South Britain, amounts annually to feven hundred thoufancj
pounds (a)." The duty on fait made at Northvvich is about

feven ty

(a) Camp. Sur. of Brit. Vol. II. p, 36,

33 Mode of obtaining Salt [Book VI.

employed to feparate the fait from fea-water. The
water is expofcd in trenches on the fea-fhore, where ic

forms

feventy thoufand pounds a year, or a tenth part of the whole
duty (6).

1 The Northvvich rock fait is never ufed at our tables in its crude
flate ; and its application to the pickling or curing of fleih or fiih,
or preferving any pFOvifions, without its being previoufly refined
into white fait, that is, without its being diifolved in water, and
boiled down into what is called white fait, is prohibited under a
a penalty of 40 s. for every pound of rock fait fo applied. The
pure transparent TO a fie s, however, of rock fait, might, probably,
be ufed by us with our food, without any fort of danger or incon-
venience ; at lead, we know that rock fait is fo ufed, without be-
ing refined, both in Poland and in Spain. In the laft of thefe
countries, at Cordova in the province of Catalonia, there is a folid
mountain of rock fait, between four and five hundred feet in
height, and a league in circuit; its depth below the furface of the
earth is not known (c). This prodigious mountain of fait, which
has no mixture of other matter with ic, is efteemed fo fingular an
appearance, that it is thought to militate very much againfl the
opinion of thofe, who would derive the origin of all the beds of
rock fait, which are found under the furface of the earth, from
the evaporation of fait water, left in fubterraneous caverns,
either at the deluge, or upon iome more local commotions of the
globe.

« The quantity of rock fait which may be diffolved in a definite
quantity ,^fuppofe a pint or 16 avoirdupoife ounces of water, is
differently eilimated by different authors. Boerhaave is of opinion
that 16 ounces of water will not diffoive quite 5 ounces of rock
'•falt(d'); Spielmann thinks that they will diflbive 6-y ounces (c) ;

Newmann

(£) Since I received this information, an additional duty of
lod. a bufhel has been laid, in 1780, on fait. The whole duty
now amounts to 4 s. zd. a bufljel, the btifliel weighing 56 llx. The
makers of fait can afford, in moft places, to fell their fait, exclufive
of duty, from 8</. to \&d. a bufhel.

(r) Hill. Nat. de P Efpag. p. 406. — See an account of fimilar
mountains of rock fait, in Shaw's Travels, p. 229, and in Pliny's
fJift. Nat. 1. xxxi. c. 7.

(ct) Chem. vol. 1. p. 476.

(t) Inft. Chem. p. 48.

Chap. 7.] from Brine in cold Countries. 39

forms fo thin a ftratum, that the cold of the atmofphere
adls powerfully in congealing it. As the frozen part

confifts

Newmann agrees with Spielmann (_/") ; Eller fays, that 7 ounces
of foilile fait may be diflbived in 16 ounces of water (g) •
laftly, Hoffmann affures us, that 16 ounces of water will not
difioive above 6 ounces of common fait (/'). I have tried this
matter with diiHlled and with common water, and in various de-
grees of heat, and cannot but be of opinion, that Hoffmann's ex-
periment approaches neareft to the truth ; I never could diffolve
quite 6 ounces of rock alt in 16 ounces of water. It is not wholly
improbable, that different forts of rock fait may differ fomewhat
with refpeft to their folubility in water.

*Jf it be admitted, that 16 ounces of water can diffolve 6 ounces
of fait and no more, then we may be certain, that no brine fpring,
in any part of the world, can yield 6 ounces of fait from a pint of
the brine. For brine fp rings 'are, ordinarily, nothing but water in
which foffile fait has been difiblved ; but a pint cf the ftrongeft
brine cannot contain fo much fait as is contained in a pint of water,
which has been faturated with 6 ounces of fait ; for a pint of water,
in which 6 ounces of fait have been diffolved, is increafed a little
in bulk, it will do more than fill a pint meafure, and the fait left
in the furplus will (hew, how much the falt^ contained in a pint of
the rtrongefi brine, falls fhort of 6 ounces. Or, we may confider
the matter in the following manner, which will, perhaps, be more
intelligible; 16 ounces of water, impregnated with 6 ounces of
fait, conftitute a faturated brine, weighing 22 ounces; if therefore
we would know how much fait is contained in 16 ounces of fuck
brine, by the rule of proportion we may argue, that if 22 ounces
of brine contain 6 ounces of fait, 16 ounces of brine will contain
4-^- ounces of fait. Hence we may infer, that the ftrongeil brine
fprings will not yield much above one quarter of their weight qf
lalc(0.

' Dr.

(f) Newmann's Chem. by Lewis, p. 256.

(g) Obf. Phy. Chem. L. ii. Ob. xvi.
(b) Ber. Mem. 1750.

(z) Several pits at Northwith, and at Barton in Lanca-

fhire, contain no lefs than fix ounces cf fait upon fixteen of brine,

v/hich is as large a proportion of fait as water will diflblve. Nenum.

Cb(?n, p, 212, Lewis's cote.—The author here is fallen, probably ?

P 4 into

40 Natural Hiftcry cf Salt. [Book VI.

confifts of mere' water, the fluid which remains, is
consequently more concentrated. The operation is
then completed by means of artificial heat.

Pure

* Dr. Leigh, who firft {hewed the manner of refining rock fait,
informs us, that fome of the ftrongeft fprings at Northvvich, gave
feve-n or eight ounces of fait from a quart of brine ; but a quart of
brine weighs confiderably more thajs 32 ounces, the weight of a
quart of water : fo that the Northwich fprings, from this account,
do not yield a quarter of their weight. At Middlewich there is
faid to be one fait fpring, which is flronger than the reft, this fpring
yields a full fourth part of fait (K), and hence it is, probably, fully
faturated. We have an account in Kircher's works, of fome famous
brine fprings in Burgundy, from which we learn, that one hundred
pounds weight of the ftrongeft brine, gave twenty-five pounds, or
juft one fourth of its weight of white falt(7).

1 There are a great many brine fprings in Chefhire, Worcefter-
fhire, StafFordfhire, Hampfhire, \and in other parts of Great Bri-
tain, fome of which are fufficiently rich in fait to be wrought with
profit, others not. From what has been before advanced, the
reader will readily comprehend that fixteen tons of the ftrongeft
brine confift of twelve tons of water, and of four tons of fait; and
that, in order to obtaifc thtfe four tons of fait, the twelve tons of
water rouft be, by fome means or oiher, evaporated, foas to leave
the fait in a concrete form. Suppofe there mould be a brine,
which in fixteen tons fhould contain fifteen tons of water, and only
er.e ton of fait; yet it may chance, that fuch a weak brine may be
wrought with more profit than the ftrongeft; for the profit arifing
from the boiling of brine into fait, depends as much upon the
price of the fuel ufed in boiling it, as ppon the quantity of fait
which it yields. Thus the fea-water, which furrounds the coafts
of Great Britain, is faid to hold feldom more than one thirtieth, or
lefs than one fiftieth part of common fait; but fuel is fo cheap at
Newcaftle, that they can evaporate thirty or forty tons of water,

in

jnto a little miftake, by confounding a pound of water with a
pound of brine; for if a pound or 16 ounces of water will only
diflblye 6 ounces of fait, a pound of the brine, thus formed, \vi$
cnly hold 4>T ounces of fait.

(/£) Philbf. Tranf. N° 53.

(/) Kerch, Mun. Sub. Toto. JL Cap. XL

Chap. 7.] Sal Ammoniac. 45

Pure clay has very little action on marine fait.
Ponderous earch decompofes it, but lime and magnefia
produce no effect. Common fait is ufed to vitrify the
furface of fome kinds of pottery. This is done by
throwing a certain quantity of it into the furnace, where
it is volatilized, and applies itfelf to the furface of the
pottery. This is the kind of glazing ufed in the
making of white Engliih pottery. Common fait is
alfo ufed in making glafs, to render the glafs whiter
and clearer. It is alfo employed as a flux to facilitate
the precipitation of metals from the fcorise, and to
prevent their calcination from the contact of the at-
mofphere.

jd. Common SAL AMMONIAC is the muriat of
ammoniac of the French chemifts, and confifts of the
muriatic acid united to the volatile alkali. This fait
is converted into vapour before it melts, but may be
brought into fufion by being combined with other
fubflances, or even uncombined, if properly confined.
When thrown into the fire, it increafes the flame, and
tinges it with a blue colour, efpecially the flame of
charcoal. When the air is very moift, this fait deli-
quefces. It is very remarkable for producing a great
degree of cold when mixed with water.

in order to obtain one ton of fait, and yet gain as much clear profit
as thofe do, who, in counties lefs favourably fituated for fuel, boil
down the ilrongeft brine.

' The advantage refulting fom ftrengthening weak brine or
fea wat^r, by means of rock (ale, is very obvious. Suppofe that
the fea water at Liverpool, where large quantities of rock fait
are refined, would yield one ton of fait from forty-eight tons
of water, then muft a quantity of fuel fufHcient to evapora'e forty-
feven tons of water be ufed in Border to obtain one ton of fait.
JJut if as much rock fait be put into the forty-eight tons of f;-a
water, as can be diffolved in it, then will the fea water refemH*
9 brine fully faturated, each fixreen tons of which will give four
tons of fait, and the whole quantity yielded by the evaporation of
forty f.,-v en tons of water, will be twelve tons of fait.'

Wutfin't Cbem. EJ£ vol. II. p. 41.
If

42 Mode of preparing Sal Ammoniac. [Book VI.

If we wifh to obtain the acid of fal ammoniac, we
may expel it by means of the vitriolic acid, but the
fumes cannot be condenfed without great difficulty.
For obtaining its alkali, the chemifts generally employ
the vegetable, as it is the cheapeft. The quantity
of vegetable alkali ufed is generally equal, but perhaps
ought a little to exceed, that of the fal ammoniac •, the
water is in general equal in weight to the alkali, and
a volatile alkali fufficiently Itrong is obtained. The
product is different, acording to the mildnefs or cauf-
ticity of the fixed alkali. When a mild fixed alkali 4s
ufed, fo much volatile alkali rifes, that Du Hamel and
others thought part of the fixed alkali was volatilized,
and rofe along with it. This however is found to be
owing to the carbonic acid, which made part of the
weight of the fixed alkali, being transferred to the vola-
tile alkali.

The fal ammoniac of commerce is in the form of
cakes. It is prepared at Cairo from the foot of ca-
mels dung, which is burned there inftead of wood.
This foot is put into round bottles a foot and a half in
diameter, terminated by a neck iwo inches high; each
bottle contains about forty pounds of this foot, and
affords nearly fix pounds of the fait. Thefe velfels
are expofed to the heat of a furnace/which acts on their
bottom, while the upper part, being cooler, fuffcrs the
fait to be condenfed there. When the operation, which
occupies three days, is finifhed, the bottles are broken
and the fait taken out ; it receives the form of the
upper part of the fubliming veffel, and the cakes
are therefore convex and unequal, with a protube-
rance on one fide from the neck of the fubliming
vefiel

Pomet has defcribed . a kind of fal ammoniac in
loaves, firnilar to thole of fugar with the point cut off,
and which are imported into France by the way of

Holland,

Chapf 7-1 Properties of Sal Ammoniac. 43

Holland. This kind is made in the Eaft Indies.
* Sal ammoniac is, however, now made in large
quantities in Britain. The volatile alkali is obtained
in an impure liquid ftate from foot/ or bones, or any
other fubftance which affords it j to this the vitriolic
acid is added, and the vitriolic ammoniac thus pro-
duced is decompofed by common fait, by a double
affinity, or elective attraction ; the vitriolic acid com-
bining with the mineral alkali, and the marine acid
with the volatile alkali. The liquor therefore contains,
Glauber's fait and fal ammoniac, which are feparated
by cryftallization ; and the fal ammoniac is fublimed
into cakes for fale. Lord Dundonald extrads volatile
alkali from pit- coal j but whether it can be afforded
cheaper for the general purpofes of commerce, than
that of the above procefs, is not, I believe, yet afcer-
tained.* '

The tafte of fal ammoniac is penetrating, acrid,
and urinous. The form of its cryftals is a hexahedral
pyramid. Cubical cryftals are fometimes, though
rarely, formed in the middle of the concave and
hollow parts of the loaves which are produced by fub-
limation.

This fait poflefies a fingular property, namely a kind
of duclility, fo that it rebounds under the hammer, and
may be bended ; a circumftance which renders it dif-
ficult to pulverife it.

Sal ammoninc is not decompofed by clay, and by
magnefia very imperfectly. Lime, and likewife pon-
derous earth, feparate the volatile alkali, even without
the ailiitance of heat. - If fal ammoniac is triturated
with quick-lime, the ftrong fmell of alkaline gas i$
immediately perceived.

* Fourcroy's Chemiftry. Note of the Translator.

[ 44 ] [Book VI.

C H A P. VIII.

COMBINATIONS OF THE OTHER MINERAL ACIDS.

Sparry Tartar.— -Sparry Soda. — Borax ; its Properties ; its U/e in the
Arts. —Combinations of neutral Salts -ivit/j Metals.

THE combinations of the other mineral acids
with the alkalies, have in general been very im-
perfectly examined, and I fhall therefore be very brief
in treating of them.

The SPARRY TARTAR, or fltiat of pot-afh of the
French chemifls, is compofed of the acid of fpar united
to the vegetable alkali. It is always in a gelatinous
form, and has fo ftrong an attraction for water, that it
cannot be cryftallized. According to Scheele, it is
acrid, cauilic, and deliquefcent, when dried and melt-
ed ; he compares it in this irate to the liquor of flints.
It appears, that the fire difengages the fparry acid, and
that the filiceous earth taken up by the acid melts inro
a foluble earth by means of the fixed alkali. This fait
has not been applied to any ufe. Of the fparry foda
Hill lefs is -known j and the fame may be affirmed of
the fparry ammoniac.

The combinations of the acid of borax have not
attracted much more attention, except the fubftance
from which this acid derives its name. BORAX, the
bora^ of foda of M. Lavoifier, is compofed of a pe-
culiar acid united to the mineral alkali. The form
in which it is expofed to fale is that of cryftals, very
tranfparent, and containing a large proportion of water.
When a fmall quantity of borax is heated fo as to
diffolve in its own water, it boils in a white foam;
and when the water is diffipated, the fait is found to

have

-Chap. 8.] &orax. 45

have loft much of its weight. By incre'afe of heat, ic
undergoes a proper fufion, and aflumes the appearance
of glafs; but is diftinguiflied from that fubitauce, by
diflblving and cryftaHizing again.

Borax may be decompofed by means of the muri-
atic acid. It appears furprizingj but the fact is cer-
tain, that a quantity of acid of borax, though fo weak
an acid in its more obvious properties, will diflodge,
when heat is applied, both the nitrous and muriatic
acids, and unite itfelf to their alkali. The reafon
feems to be, that the attraction of different fubftances
for the fame body is different in different degrees of
heat. This again is to be attributed to a double
elective attraction, in confluence of the addition of
the matter of heat. The cohefion of ihe nitrous and
muriatic acids to their bafes is fo much weakened by
their affinity wkh heat, or in other words, their ten-
dency to aiTbme the gaffecus {bun, that the attraction
of the boracic acid, which is more fixed, becomes fu-
perior, and difplaces them.

Borax, as imported from the Eaft Indies, is very
impure. When purified, it has a very regular form.
Its cryftals are fix fid ed prifms, two of the fides being
commonly larger than the others, terminated by tri-
hedral pyramids. Its cryftallization is, however fub-
ject to confiderable varieties. It is ftyptic, and acts
ftrongly on the tongue, and like alkalies it converts the
fyrup of violets to a green. Borax, expofed to the
air, lofes a fmall part of its water of cryitallization, and
(lightly efflorefces. It is foluble in twelve parts of
cold and fix of hot water. Its cryftals may therefore
be obtained by cooling •, but the fined and moft regular
are formed by fuffering the cold faturated ibluticn to
evaporate fpontaneouOy in the ordinary temperature
of the atmofphere.

Borax

46 Ufa of Borax. [Book VI.

Borax is exceedingly ufeful in many manufactures.
It is employed as an excellent flux in the art of glafs-
making, as well as in affays. It is advantageoufly em-
ployed in foldering, which it affifts by promoting the
fufion of the folder, by foftening the fur faces of the
metals, and by defending them from the action of the
air.

Very little is known of the combinations of the acid
of borax with the vegetable and volatile alkalies.

The phofphoric acid, and the acid x>f amber, are ca-
pable of combination with the alkalies j but the refults
of thefe combinations are fo little known, that I lhall
pafs them over in filence, and haften to the confidera-
tion of the earthy and ftony fubftances.

Some falirre, earthy, and metallic fubftances, have
fuch a relation to each other, that they are feparated
with great difficulty, and adhere after repeated folutions
and cryftallizations. This circumftance has given rife
to another divifion of falts, which are denominated
triple, as they do not, however, appear of fufficient
confequence to be treated of under a feparate fecTion,
J fhall merely enumerate them at the conclufion of the
prefent. The moft remarkable examples of this kind
are, mineral alkali with calcareous earth ; common ialt
with magnefia ; vitriolated magnefia with iron.; alum
with iron ; vitriolated copper with iron ; vitriolated
copper with iron and zinc ; vitriolated iron with cop-
per ; vitriolated iron with zinc ; vitriolated iron with
nickel.

Chap. 9.] [ 47 1

CHAP. IX.

EARTHS IN GENERAL.

Different Kinds of Earth. — -Nevj Earths difco*vered— Definition r,f
Earths. — Exceptions. — Other general Properties of Earths. — Ca/ca-
reeus Earth . — Magnefia . — Earytss. — Clay . — Flint.

IT is now generally agreed among chemills and
mineralogifts, that all the earthy and ftony fub-
ftances which compofe the folid parts of this globe,
are chiefly refolvable into five fimple and original
kinds of earth ; namely, lime or calcareous earth, mag-
nefia, barytes or ponderous earth, argill or clay, and
filica or flint; to thefe late difcoveries have added three
other earths, the ftronthian, the jargonic, and the ada-
mantine; but thefe are found in very fmall quantities,
and doubts are yet entertained whether they are any
thing more than varieties or compounds of the five
principal earths.

Thefe fubftances agree in the following proper-
ties, which may be confidered as the .characlreriftics
of all earthy fubftances. They are nearly infolu-
ble in water, are uninflammable, have not the metallic
fplendour, and their fpecific gravity, compared with
that of water, is not more than five to one. This
definition, however, like that of falts, is not fo pre-
cife as to be beyond the reach of criticifm ; becaufe
there are fome earths perfectly foluble. in water, though
but in fmall proportions, and there are many in the
internal parts of the earth which afford the -flrongeft
evidence that they havr been in a (late of folution.
But the definition, though not ftriftly accurate, is pro-
per in a general fenfe. There is great difference of
iblubility between earths and fairs, for a few grains of

earth

48 'Calcaretlis Earth. [Book VI.

earth are fufFicient to faturate*a large quantity of
water. There are two other circumftances not in-
cluded in the definition, which make part of the idea
of an earthy fubftahce ; ift, a great degree of fixed-
nefs j 2dly, a difpolition to form a glairy concretion
when melted with certain other fubftances.

Lime, properly fo called, is obtained by expelling
the carbonic acid from, calcareous fubftances by means
of heat. 'Calcareous earth is in a tolerably pure ftate
in common quick-lime ; but if it is required perfectly
free from foreign admixture, it may be obtained by
the following procefs : If pounded chalk is feveral
times boiled in diftilled water, the remainder will con-
fift almoft entirely of calcareous earth, combined with
the carbonic acid. If diftilled vinegar is added to the
powder thus obtained, it will form a faline combina-
tion with the lime only, to the exclufion of all extra-
neous matter. To a folution of this, decanted from
the impurities, mild volatile alkali being added, the
alkali will unite with the vinegar, while the calcareous
earth feizes the carbonic acid of the alkali, and falls
to the bottom in the ftate of a perfectly pure chalk.
The carbonic acid may be driven off by heat^ and
calcareous earth is thus obtained in its rrioft fimple
ftate.

The relative weight of quick-lime to that of flaked
lime is as j,ooo to 1,287. Every pound can im-
bibe four ounces four drams and fifty- three grains of
water.

Calcareous earth is foluble in the nitrous and mu-
riatic acids, and forms deliquefcent falts. It is pre-
cipitated from its folutions by means of vitriolic acid,
with which it forms a nearly inlbluble compound,
called felenite, (or plaifter of Paris.) Pure Calcareous

* See note *, p. i.

earth,

Chap. 9.] ' . Ponderous Earth. 49

earth, or lime, is foluble in a fmall proportion in water,
with which it contra&s great heat. It is infufible with-
out addition. It .attracls the carbonic -acid from the
fixed alkalies, and by itfelf becoming mild renders
them cauftic. Its fpecific gravity is 2,723. '

Magnefia does not burn into a cauftic fabftance like
quick-lime, though it is deprived of its carbonic acid
by the application of heat. It is foluble in feverai
acids, and forms with the vitriolic the fal catharticus-
amarus, or Epfom fait. When mixed with water, ic
fhews a very fmall degree of heat, but without any
effervefcence. It requires 7,692 times its weight of
water for its folution. It is not precipitated from
other acids by the vitriolic, as calcareous earth is. Its
fpecific gravity is 2,155.

Baryies is by far the mofl ponderous of the earths>
from which circurnflance it derives its name.

With vitriolic acid it forms the ponderous fpar,
which is infoluble in water ; and its combinations with
the nitrous and muriatic acids are alfo not very folu-
bkj but with the acetous acid (or vinegar) it becomes
deliquefcent. Combined with carbonic acid, it is fo-
luble in 1550 times its weight of water, when pure in
900 times. The fpecimens of barytes naturally com-
bined with carbonic acid are rare ; it is more com-
monly found united with the vitriolic acid. From
this the earth may be frparated by the following pro-
eels : Pound the ponderous fpar, and mix it with twice
its weight of fixed alkali •> expofe this mixture to a
ftrong red heat for about two hours. The acid quits
the earth to unite with the alkali, forming a neutral
fait, which may be waftied away. The earth remains
combined with carbonic acid, which may be difpellerl
by heat. The fpecific gravity of this earth, when
pure, is 3,775,

VOL. II. E ArgUl,

50 Clay. [Book VI.

Argill, or day, is foluble in the vitriolic, nitrous, and
muriatic acids, ^nd forms alum with the firft of thefe.
If concrete volatile alkali*, or any other of the alkalis,
is added to a folution of pure alum, the alkali and
acid unite, while the clay falls to the bottom, united
with only a fmall quantity of fixed air. The fluid
muft be abftracted by decantation, and the precipitate
wafhed with diftilled water, and dried. Pure clay
does not become cauftic by burning, but is contracted
in fize, and becomes very hard. The fpecific gravity
of this earth is only 1,669.

The principal natural fpecimens of argillaceous
earth are boles, clays, marks, flates, and mica. In
none of thefe, however, except the flag-ftone, does the
argill amount to half the weight of the whole fubftance.
Silica abounds very much in common clays. Baked
clays ccnftitute all the varieties of bricks, pottery,
and porcelain. If baked in a ftrong heat, they give
fire with Heel.

Silica, or JKnt, is foluble in only one of the acids,
the fluoric, yet during its precipitation, it is capable
of combining with mod of the mineral acids. In its
indurated ftare, it is always fufficiently hard to fcratch
and {bike fire with Heel. After being burnt, it does
not fall to powder as the calcareous earth does. It
produces no eflfervefcence with acids. It may be dif-
folved by the fixed alkalies, both in the dry and wet
way. When alkali and flint are expofed to the heat
of a glafs-houle furnace, if the alkali is only half the
weight of the filica, it produces a diaphanous and hard
glafs, but when the alkali is in double or triple the pro-
portion, the glafs deliquefces of itfelf, by attracting
the humidity of the atmofphere, and forms what is-

• The volatile &lts in a folid {late.

called

Chap. 9.], Flint, 51

called liquor of flints. This earth is perfectly dif-
folved in that wonderful boiling water-fpout, above
fixty feet high, at Geyfer in Iceland, where by cooling
it forms a hard filiceous mais. Pure filiceous earth is
obtained by fufirig * clear quartz with four times its
weight of fixed alkali, diffolving the whole in diftilled
water, and precipitating the earth by an acid. Its
fpccific gravity is 2,650.

M. Bergman has formed perfect filiceous cryftals
by diffolving filiceous earth in the fparry acid, and
iuffering it to cryftallize flowly. It is probable that
nature forms them in a long courfe of time from a
folution or diffufion of this earth in water.

Of the newly difcovered earths I fliall treat in a fe-
parate chapter, though it may be premifed, that they
are rathtr of importance in order to complete the no-
menclature of the mineral kingdom, than from their
quantity or their properties.

Though the fimple earths are all infufible alone, yet
they may readily be fufed by mixture with each other.
The calcareous earth is found to 06t as a menftruum
in diffolving the other earths by heat j and when it has
once afted on any earth, a compound menftruum is
formed, which afts ftill more efficacioufly in diffolving
other earths. Hence it is, that any three of the fimple
earths may be fufed into glafs, provided calcareous
earth is one- of the number.

Thus far it appeared neceffary to premife concern-
ing the general properties of the fimple earths in their
feparate ftate j but as their combinations are various,
and their ufes in this laft ftate very important, it will
be proper to treat of each on a more ample fcale than
the limits of a fingle chapter would admit.

* Melting by heat.
E 2

[ 5 2 3 [Book VI.

CHAP. X.

CALCAREOUS EARTHS.

Chalk.— LimeJ}ene.—*Marlle. — Marie. — Calcareous Spar. — Iceland
Crjtftab, — P etr if actions. ^-P arts of Animals found in Marie, &V. —
Gyffoms. — Great Varieties. — Alabafter* — Fibrous Stone.— -^Mineral
Glafs. — Selcnite. — Gypfeous Spar. — Plaifter of Paris ; how pre-
pared.— Fufeble or Derbyjhire Spar. — Spars, how formed. — Beauti-
ful Appearances in different Caverns.— Metallic C onibi nations ivitk
calcareous Earth.

CALCAREOUS earth is fometimes found in
the form of powder, but more frequently in that
of a concrete fubftance called chalk, which differs with
refpeft to the finenefs of its particles and firmnefs btf
texture.

i. Chalk confifts of calcareous earth or lime, united
with, carbonic acid, and an union of the fame princi-
ples allb conftitutes lirr.eftone and marble. Thefe
fubftances only differ, from common chalk in their de-
gree of purity, or in the manner of their aggregation,
admitting of more or lefs polifh. The different co-
loured veins in marble are produced by the admixture
jaf other iubftances, (moft commonly iron) unequally
diftributed through the mafs.

a. Strata of marie alfo contain calcareous earth, more
or lefs. blended with a confjderable proportion of clajr
and fand.

3, Calcareous earth is often found projecting into
the incerftices and crevices of rocks in a cryftallized
ftate, and is thens called calcareous fpar. It is more
or lefs tranfparent, and fliivers into flat fragments of a
rhomboidal figure. One variety is called Iceland cryf-

tals.

Chap. 10.] Iceland Cryjlals. 53

tals. They engaged the attention of Sir Ifaac Newton,
by their remarkable quality of refracting the rays of
light without feparating them into colours, fo as to
make a line drawn on paper appear double, when
viewed through them. The Englifh lead-mines are
full of fpars ; their fhape is in general a firm column,
terminated at each end with a pyramid. Of thefe
calcareous fpars there are many varieties.

4. Calcareous earth appears in the form of ani-
mal and vegetable fubftances, petrified into Hone by
being expofed to petrifying waters. Thefe fill up the
pores of the fubftance with calcareous earth, and
incruft them. Hence we may conclude, that this earth
is foluble in water, and is depofited in certain circum-
ftances. The quantity of earth, however, contained
in the water is very fmall, and therefore the petrifac-
fadlions are formed flowly. Thofe organic bodies,
which refift putrefa<5Hon mod, are frequently found
petrified, fuch as bones, fliells, and the harder kinds of
wood} on the contrary, the foft parts of animals,
which are very fubjecl: to putrify, are fcarcely ever
found petrified. Mr. Kirwan remarks, that petrifac-
tions are moil commonly found in ftrata of marie,
chalk,- lime-ftone, or clay; feldom in fand-ftone, ftill
more rarely in gypfum, but never in gneifs, granite,
bafaltes^or fhoerl; they fometimes occur among pyrites .
and ores of iron, copper, and filver, and almoft always
confift of the fpecies of earth, fcone, or other mineral,
which immediately furrounds them. Thofe of fhells
are generally found neareft the furface of the earth,
thofe of fifh deeper, and thofe of wood deepeft. A
very remarkable circumftance is, that petrifactions are
found in climates where their originals 'could not have
exifted. From the gradual and infenfiJDle concretion
• E 3 of

£4 Calcareous Petrifaftians. [Book VL

of this kind of matter from dropping waters, are
formed the large pendulous columns hanging like
icicles from the roofs and fides of caves. The moft
remarkable are in the Peak of Derbyfhire. Some-
times they are found in the arches of old bridges, and
arife from the water oozing through and carrying par-
ticles of lime with it. This earth fo concreted is called
ftalactites, ftone-icicles, or drop-ftone.

5. The {hells of all cruftaceous animals, from the
coarfeft to the pearl which lines the {hell of the oyfter,
are all made up of this calcareous earth with a fmalj
quantity of animal gluten. Egg-lhells are of the fame
nature, and thofe marine bodies which, from their hard-
nefs and vegetable appearance, are called ftony plants,
fuch as are all the fpecies of coral, &c.

Maries, which have been already mentioned as con-
taining calcareous earth, are generally divided into
three kinds. Firft, {hell- marie ; fccond, clay-marie j
third, ftone-marle. The firft is found in beds of con-
fiderable extent, and confifts of the remains of fea and
land {hells ; that which contains the fea {hells is com-
monly found in the greateft quantity. Of this kind
is that of Paris, mentioned by M. Reaumur, which is
about ten feet deep, and of great extent, confiding of
oyfter and other fea mells ; and foine very large beds
rnay be found in the neighbourhood of Woolwich. The
relics of land mells are thofe of fnails ; they have pro-
bably been carried by the current of fome wafer, and
depofited at one place, and the water being drained offj
the mells remained behind. Beds of frelh-water
Ihells are alfp found. Clay- marie is a calcareous
matter, which when expofed to the air crumbles to
duft ; it is to be diftinguiftied from common clay, by
effervefoing with acids., from the calcareous earth it;

contains.

Chap. 10.] Mate. 55

contains. Stone-marie differs from clay-marie only
in being much harder ; but it differs from ordinary
ftone by breaking to pieces when expofed to the air.

It has been fuppofed by fome refpectable writers,
that all thefe fpecies of calcareous earth derive their
origin from iheJls. Some marbles are evidently
formed of fhells, and thofe of Derbyfhire exhibit this
appearance in a remarkable manner. Coral is univer-
fally allowed to be the work of fmall animals of the
polypus kind. The ftrata of limeftone being alfo
found fo frequently united with (hells and other marine
fubftances, has induced the philofophers to whom I
allude to believe, that the ftdne itfelf is altogether com-
pofed of ihells, which at firft mouldered into pafte, and
were afterwards preffed and concreted together. In
one of the quarries of Italy, the bones of fmall fifties
are found j and fome rocks in the midland counties of
England are almoft wholly cornpofed of the kind of
fhells called entrocbi. The animals which produce
the coral are here feldom to be found ; but in other
parts, as in Jamaica, the bottom of the fea is entirely
covered over with coral, and harbours are fometimes
flopped up with it. Sir Hans Slcane mentions a
Spanifh plate-fhip, which was wrecked, and remained
at ihe bottom of the fea twenty-five years, being then
fifhed for, the treafure, as well as the timber, &c.
were covered, with coraline concretions. Hence, this
tonftant growth at the bottom of the fea may in time
produce beds and ftrata of this kind of earth, which,
according to circumftances, may be converted ',n:o
marie, limeftone, marble, &c. Calcareous earths,
united with carbonic acid, may be known under all
forms, by effervefcence with the mineral acids.

6. If vitriolic acid is poured on chalk, the carbonic

acid is expelled, while the vitriolic unices with the

E 4 calcareous

56 Gypjum or Selmlte. [Book VI.

calcareous earth, and conftitmes a fubftance which has
very little folubility. This is GYPSUM, felenite, or
plaifter of Paris, which exifts in confiderable quantities
in nature. Gypfums are found in folid mafles, very
foft, and eafily fcraped with a knife. They are dif-
tinguiihed from the combinations of calcareous earth
with carbonic acid, by not effervefcing with acids j
and from other earthy bodies, by being by heat
changed into a white powder, which when mixed with
a large proportion of water, fuddehly concretes into a
ftotiy mafs. They are moft commonly found in the
ftrata of clay, fometimes in thofe of fand, under the
appearance of a whitifh coloured mafs, but the fmaH
pieces 'are tranfparent, and fometimes have a red
tinge. They are often compofed of fmall fhining par-
ticles, like the grains of fugar, and when under this
appearance they are particularly called gypfum. When
hard, fo as to admit of being cut into toys and figures
they are called alabafter. The fecond form under
which they are found, is that of a fibrous ftruclure
of oblique cryfbils, which are parallel to themfelves,
but which crofs the mafs from the upper to the under
furface. In this ftace they are called tibrarias or fibrous
ftone by Dr. Hill. Thcfe differ much in fize and
regularity of concretion. The third fpecies is com-
pofed of clear t-ranfparent plates, like glafs, in clofe
contact with each other, but which may be feparated.
They fplit with a knife into fine plates, very flexible,
though they cannot be bent without producing flaws.
They are called glacies marina, and fometimes Muf-
covy glafs, but improperly, as that is a different fub-
ftance.

The fourth fpecies is in the form of ffparate oblong
cryftals, which are called felenites ;>jome are long and
regular, like cryftals of fait. The firth fpecies of gyp-

Chap. io.] Piwjler of Paris, 57

feous fpar is of a platey texture. Gypfeous fpar varies
in compactnefs and tranfparency, is fometimes white,
fometimes reddifh, and is mixed with a greater or
lefs quantity of other matter: fometimes we meet wi-.h
it in cryftals. The ores of metals are often found in
this fpar.

Sixthly,, gypfum is often met with in waters of
fprings in a difiblved ftate ; for we find by experiment,
that it is foluble in water, though but in fmall quan-
tity. When the water is evaporated, it is depofited
in cryftals very final!, and which appear like a white
powder ; but by the microfcope are found to be ob-
long regular concretions.

MargrafF firft mewed that all thefe fpecies were
compofed of calcareous earth and vitriolic acid. He
took a quantity of gypfeous earth in a fubtile' powder,
and boiled it for fome time in a folution of fixed vege-
table alkali j and upon examination, he found the cal-
careous earth at the bottom in an uncombined ftate,
and in the folution a vitriolated tartar. He alfo com-
pofed an artificial gypfum of calcareous earth and the
vitriolic acid, which had all the properties of a natural
gypfum. From knowing the compofition of thefc
fubftances, we may fufficiently underftand their pro-
pertiesj particularly that of being converted by a mo-
derate heat into plaifter of Paris. If the purer kinds
are reduced to fine powder, and put into an iron veffel,
by the time the veflel is heated the powder grows
light, and is thrown into motion like a boiling fluid.
There are alfo a vaiiety of other earthy powders, which
when moift give the fame appearance; for the vapour
fifing up, makes its way through the powder, keeps
it afloat, and agitates it like a liquid in a boiling ftate.
This appearance continues till moil of the water is
evaporated. After this the powder becomes heavy,

and

5 S Plaifter of Paris. [Book VI.

and lies at the bottom of the veffel as before heating. It
is then prepared for plaifter of Paris, for if a quantity
of it is put into fo much water as gives it the confift-
ence of cream, it will foon become folid, and ring like
avefiel of earthen-ware, or metal. It lofes its tranf-
parency by heat, and becomes white. The fofter kinds
are beft for the plaifter of Paris.

The explanation of all thefe phenomena is not dif-
ficult, when we confider the nature of gypfum, which
being a faline compound, has all the qualities of a fait.
In its natural ftate it is cryftallized in confequence of its
containing a quantity of water. Heat expels the water ;
which being again added, is attracted by the gypfum,
and occafions a cryftallization.

A more violent heat produces very little change, as
the vitriolic acid adheres very clofely to the earth. If
thefe fubftances, however, are mixed in powder with
a quantity of charcoal-duft, the whole of the acid may
be diffipated, and the calcareous earth only left behind,
and thus a particular phofphorus is formed. In this
experiment the charcoal attracts the oxygen of the
acid, which is by that lofs rendered volatile, and is dif-r
perfed in fumes.

7. Calcareous earth is alfo found faturated with mu^
riatic acid iii fea-water and in falt-pits.

8. Calcareous earth, united with the fluoric acid,
forms the fufible fpar or fluor, which is commonly
known by the name of DERBYSHIRE SPAR. The
texture of this compound is either fparry, or irregularly
mattered or cracked. It is either tranfparent or
opake j and the fpecimcns are of a cubic, rhomboidal,
polygonal, or irregular figure. The coloured fpars
have the property of emitting light when laid on a
hot iron, or otherwife heated ; but they lofe this pro-
perty by being made red hot. The green fpars are

the

Chap. 10.] Derbyjhire Spar. 59

the mod phofphorefcent, but none of them exhibit this
quality except when well warmed. They are fcarcely
harder than common calcareous fpars, and therefore do
not ftrike fire with fteel. They do not melt by them-
felves j but very much promote the fufion of other
ftones, particularly the calcareous. They do not ef-
fervefce with acids, either before or after being fub-
mitted to the action of fire.

Mr. Whitehurfl explains in the following manner
the formation of fparry and ftalactitical productions.
When water impregnated with the fparry acid proceeds
flowly through different ftrata of earths and minerals,
it becomes charged with a variety of fhefe fubftances
in folution ; and as it exudes gradually on the furface
of caverns and filfures, the aqueous particles evaporate,
and the fparry matter cryflallizes in various forms,
including in its own fubftance the heterogeneous mat-
ters with which it is charged.

If the quantity of water thus impregnated, which
exudes through the pores of the earth or ftone, is not
more than will eafiJy evaporate in the ordinary heat:
of the atmofphere, a fparry cruft is formed. If the
quantity of water exuded exceeds the quantity evapo-
rated, flalactites are produced in one inftance, and tubes
in another.

If a drop of water hangs from the roof, almoft
dropping, the aqueous particles evaporate from the
furface fooner than from its interior parts. A cryftal-
lization therefore takes place on the furface, while the
center remains fluid : the water thus detained is con~
tinually increafmg, and the tube gradually extends
downwards. By this procefs, tubes are frequently
formed of two feet in length, and one tenth of an
inch in diameter. The appearance of caverns prna-
mented with thefe Iplcndid productions exceeds that

of

60 Sparry Grottset. [Book VI.

of the moft laboured works of art : tranfparent co*
lumns, adorned with the moft beautiful and vivid
colours, difpofed fometimes in the form of a honey-
comb, fometimes in a more irregular arrangement :
mirrors, refle&ing the im 'ges 'of objects, tinged with
» light fhade of the moft delicate colours, ravilh the
eye of the beholder. The pillars appear of various
forms and fizes ; fometimes arranged like a regular
colonnade, and fometimes difpofed with all the de-
lightful irregularity of nature. The ilalactites hang
like icicles from the lofty roofs of thefe ftioendous
caverns, and are reflected back by the polifhed and
glittering floors. Some of the moft ftriking caverns
of this kind are the grotto of Antiparos *, Poolers
liole, and Peak Hole, in Derbyfhire.

9. Calcareous

* The following is an account of this famous grotto, commu-
nicated by Magni, an Italian traveller, to the celebrated Kircher,
— ' Having been informed (fays he) by the natives of Pares, that
in ihe little ifland of Antiparos, which lies about two miles from
tne former, a gigantic ftatue was to be feen at the mouth of a
cavern in that place, it was refolved that we (the French confal
and himfelf) fhould pay it a vifit. Jn purfuance of this refolution,
after we had landed on the ifland, and walked about four miles
through the midil of beautiful plains, and Hoping woodlands, we
at length came to a little hill, on the iide of which yawned a moft
Korrid cavern, that with its gloom ,at firlt ftruck us with terror,
and almoft reprefled curicfity. Recovering the firfl furprife,
however, we entered, boldly ; and had not proceeded above twenty
paces, when the fuppofed ftatue of the giant prefented itfelf to
our view. We quickly perceived, that what the ignorant natives
had been terrified at as a giant, was nothing more than a fparry
concretion, formed by the water dropping from the roof of the
cave, and by degrees hardening into a figure that their fears had
formed into a monfter. Incited by this extraordinary appearance,
w« were induced to proceed ftill farther, in queft of new adven-
tares in this fubterranean abode. As we proceeded, new wonders
offered themfelves : die fpars, formed into trees and fhrubs, pre-

iented

Chap. 16.] Calcareous fungftem. 6t

9, Calcareous earth is found faturateu with what wai
thought a particular acidj which has been called the

tungftenic

fented a kind of petrified grove ; feme white, forne green ; and all
receding in due perfpe&ive. They flruck us with the more
amazement, as we knew them to be mere productions of nature,
who, hitherto in folitttde, had, in her playful moments, drefled th«
£cene, is if for her cwa amufeinent.

' But we had as yet fecn but a few of the wonders of the place;,
and we were introduced only into the portico of this amazing
temple. In one corner of this half illuminated recefs, there ap-
peared an opening of about three feet wide, which feemed to lead
to a place totally dark, and that one of the natives affured us ecu-'
tamed nothing more than a refervoir of water. Upon this w*
' tried, by throwing down feme Acnes, which rumbling .along the
fides of the defcent for fome time, the found feemed at laft quaflied
in a bed of water. In order, however, to be more certain, we fent
in a Levantine mariner, who by the promife of a good reward,
with a flambeaux in his hand, ventured into this narrow aperture.
After continuing within it for about a quarter of an hour, he re-
turned, bringing fome beautiful pieces of white- {par in his hand,
vthkh art could neither imitate nor equal. Upon being informed
by him that -the place was full of thefe beautiful incruftations, I
ventured in once more with him, for about fifty paces, anxioufly
and cautioufly defcending by a tfeep and dangerous way. Find-
ing, however, that we came to a precipice which led into a <fpa-
cious amphitheatre, if I may fo call it, Mill deeper than any other
part, we returned, and being provided with a ladder, flambeaux,
and other things to expedite our defcent, our whole company, man
by man, ventured into the fame opening, and defcending one after
another, we at laft faw ourfelves all together in the moU; magnificent
part of the cavern.

' Oar candles being now all lighted up, and the whole place
completely illuminated, never could the eye be prefented with a
more glittering, or a more magnificent fcene. The roof all hung
with folid icicles, tranfparent as glafs, yet folid as marble. The
eye could fcarce reach the lofcy and noble ceiling; the fides were
regularly formed with fpars ; and the whole prefented the idea of
a magnificent theatre, illuminated with an immenfe profufion of
:< The floor confifted of folid marble ; and in 'feveral places,
magnificent columns, thrones, altars, and other objects appeared,

6% StJofae Stone. [Book VL

ttingftenic acid, though it is certainly no other than the
metallic fait of that name. This combination forms
the TUNG STEIN of the Swedes. This ftone is remark-
ably heavy, and refembles fluor fpar in the form of its
fragments. It becomes yellow in acids, and is found
united with petroleum (or mineral pitch) in the
proportion of ninety-five of the former to four of
the latter. In this ftate it forms the fwine-ftone,
which is of a dark colour, and becomes fetid by
fricYion.

10. Calcareous earth is alfo found united with three
of the metals, iron, copper, and lead; of each of which
there are feveral varieties. When united with cop-
per, it is called mountain blue 3 when united with

as if nature had defigned to mock the curlofities of art. Our
voices, upon fpeaking or finging, were redoubled to an aftonifhing
loudncfs ; and upon the firing of a gun, the noife and reverbera-
tions were almoft deafening. In the midft of this grand amphi-
theatre rofe a concretion of about fifteen feet high, that, in fome
meafure, refembled an altar; from which, taking the hint, we
caufed mafs to be celebrated there. The beautiful columns that
fhot up round the altar, appeared like candleilicks? and many
other natural objects reprefented the cuftomary ornaments of this
facrament.

' Below this fpacious grotto, there feemed another cavern;
down which I ventured with my former mariner, and defcended
about fifty paces by means of a rope. I at laft arrived at a fmall
fpot of level ground, where the bottom appeared different from
that of the amphitheatre, being compofed of foft clay, yielding to
the preffure, and in which I thruft a Hick to about fix feet deep. la
this, however, as above, numbers of the moft heautiful cryftals were
formed ; one of which, particularly? refembled a table. Upon our
egrefs from this amazing cavern, we perceived a Greek infcription
upon a rock at the mouth, but fo obliterated by time, that we could
not read it. It feemed to import that one Antipater, in the time
of Alexanders had come thither; but whether he penetrated into
the depths of the caverns, he does not think fit to inform us.'— •
Kircber 4e Mytd. Sub. 1 1 2.

cal*

Chap. 10.] Turquoife and Malachite. 63

calx of copper, it is denominated Armenian ftone.
Gypfeous earth combined with calx of copper, is
called turquoife and malachites. The pureft malachite,
according to Kirwan, contains feventy-five parts of
copper and twenty five of aerial or Carbonic acid;
calcareous earth is therefore not an eflential ingre-
dient. It is of a green colour, and is fometimes cut
and polifhed as a gem.

[ 64 1 [BookVt

CHAP. XL

JM A G N E S I A N EARTHS.

?&.'/. — Soap Rock. — French Chalk..-*-
Serpentine Stone. — Mica. — Talk. — Mufcovy Glafs. — AJleftos. — Mi-
neral Cloth. — Mountain Leather. — Mountain Flax.— Mountain

Wood.

TO obtain MAGNESIA, the mother water of nitre,
or of common fait, is placed in a large veflel,
and diluted with a connderable quantity of common
water. Fixed alkali difiblved in water is then added,
and the mixture juil made to boil. By this procefs the
magnefia falls to the bottom of the veflel in the form
of a powder, which is purified by repeated affufions
of water. Magnefia, in its mild flate, confifts of forty
parts magnefian earth, forty- eight carbonic acid, and
twelve water. The cryftallized aerated magnefia
contains half its weight of carbonic acid, one fourth
magnefian earth, and one fourth water.

Magnefia combined with vitriolic acid conftitutes
EPSOM SALT, which in many refpefbs refeinbles Glau-
ber's fait j it may be diftinguifned, however, by an
cafy experiment j for if a fixed alkali is added to a
folution of Epfom fait, n precipitation is produced,
which is not a confequence of adding an alkali to a
folution of Glauber's fait. Even the volatile alkali,
if mild, is capable .of feparating magnefia from its
acid, by means of a double attraction; the alkali unites
with the vitriolic acid, and part of the earth falls to
the bottom, combined with carbonic acid.

Magnefia enters into the competition of fome earthy

fubftancesj the itones ufually treated of under this

6 head

thap. 1 1.] Soap Rock, French Cbalk, &c. 6$

head cOnfift of magnefia united with flint j but the
latter ufually predominates. Moil of them are foapy
to the touch, and fo foft that they may be cut into
various utenfils*-— Of thefe the following are the moft
remarkable:

i. Steatite 83 lapis ollaris> or SOAP ROCK, is of various
colourSj but chiefly of different fhades of green. It does
hot become ductile in water, and is fufed with diffi-
culty. One variety of it is in the form of fix-fided
prifms, another is lamellated.

2. Smecliis, or FRENCH CHALK, is found pretty plen-
tifully in Cornwall. Its colour is either white, yellow,
or red and white j fome fpecimens have the appearance
of Caftile foap*

3. SERPENTINE STONE is of different fhades of greem
The ftructure of this ftone is fibrous, and it might
therefore be confounded with another earthy matter*
called afbeftos, if its fibres did not adhere fo clofely
together, as to efcape obfervation, when the ftone is
cut and polifhed. Of the ferpentine ftone there are
many varieties, and it is found fpotted or ftreaked with
a great diver fity of colours. What is commonly called
ferpentine ftone, is a true lapis ollaris ; but being va-
riegated Jike the fkins of fome ferpents, is diftin-
guiflied by another name. Great quantities of this
ftone are found in Italy and Switzerland* Where it is
often worked into the fhape of dimes and other vef-
fels. It is harder than fieatites* but not fo hard as to
give fire with fteel ; and lefs fmooth to the touch,
but is fufceptible of a good polifh j it looks like mar-
ble, and is often in thin pieces femitranfparent. The
greener forts of this ftone have been called nephri-
tic ; their colour -arifes from maugahefe. But the
term lapis nephriticus i« commonly applied to jade.

4. Micaceous earths, or TALKS, may be defined
V«IM II* F earthy

66 r Mica andMufcovy Glafs. [Book VL

earthy or ftony bodies, the texture and compofition of
which confifts of thin flexible particles, divifible into
plates or leaves, having a fhining furface. Thefe
plates, by being expofed to heat, feparate into fmaller
ones, but their flexibility is much diminifhed. By a
ftrong heat they curl or crumple, but it is very diffi-
cult to reduce them to perfect fufion without addition.
The plates of mica, when of the pureft kind, are tranf-
parent, and there is one variety, the plates of which,
from their near refernblance to glafs, are called Muf-
covy glafs. Micas, however, are often tinged with a
variety of colours, or are more or lefs opake. Some-
times they have a . luftre refembling that of metallic
fubftances. Sometimes they are in the form of min-
ing powder, like that which is ufed in bronzing figures.
This appearance has often impofed upon miners, who
have thought they met with gold and filver, whereas
there is never any metal in thefe fubftances but iron.
They are found alfo mixed with other ftones, as the
granite, which frequently contains a great quantity of
talk. Freeftone alfb contains more or lefs; its hori-
2ontal layers have between them a thin ftratum of talk
where the ftone more eafily leparates. It is alfo found
in lome kinds of flate, which, when expofed to the air,
moulder into talky po-.vder. The tranfparent Muf-
covy glafs is ufed for windows, and for thofe Ian-
thorns which are employed in powder magazines, as
this fubftance is not fo liable to break as glafs, and is
unaffailable by fire. The twifted, or crumpled mica,
which is found at Harcuil in Jempland, is there manu-
factured into kettles and other veflels, as alfo for
hearths of chimnies ; and the powder which falls in the
working may be mixed witli common fait for the
diftillation of the muriatic acli. The fhining appear-
ance of the micaceous earths has obtained them the
9 names

Chap. It.] -Jibeftos. * £7

names of dazes glimmer, or glift. Talk differs from
other micas in its laminae or filaments being much
tenderer and more brittle, but both have the metallic
luftre.

5. The ASBESTOS, or amianthus, is a foflil agree-
ing with 'talk i'n having a regular ftrufturei in being
flexible, but differing in being compofed of fibres
iriftead of plates. When long expofed to air, it dif-
folves into a fort of downy matter, which has fome
degree of tonghnefs, but the fibres cannot be unra-
velled. Cloth and paper have been made of this fub-
ftance, which refift the fire. Afbeftos, however*
though unaffailable by common fires, has fubmitted to
the power of ftrong burning mirrors, and has under-
gone vitrification. The ancients are faid to have ma-
nufactured cloths of this foflil, in which they wrapped
their dead when they burned them* that the afhes
hiight be preferved. Several moderns have fucceedcd
in making this cloth j the chief contrivances which
are neceftary are to mix the mineral fibres with a large
proportion of flax, and to ufe oil freely j thefe matters
are afterwards confumed by expofing the cloth to
a red heat. Although the cloth of afbeftos when foiled
is reftored to its whitenefs by burning, yet it does lofe
fome part of its weight, as has been afcertained by ac-
curate experiments. The varieties of this curious
genus of fofiils are mountain leather or cork 5 moun-
tain flax, to which the name of amianthus is particu-
larly applied; common or unripe afbeftos, and moun-
tain wood. Thefe fubftances all confift nearly of the
fame component parts* and differ chiefly in colour,
folidity, or in the form and direction of their fibres.
Some fpecimens of the amianthus are fo light as to
float in water. When the fibres are parallel, it is
F a called

68 . Mountain Cork, &c. [Book VI.

called mountain leather ; when twifted, mountain
cork.

The mountain cork or leather contains in the hun-
dred from 56 to 62 parts of filiceous earth, from 22
to 26 of mild magnefia, from 7 to 14 of mild calca-
reous earth, 1.7 of clay, and 10.6 of iron. Thefe
afford a white flag by fufion. The fpecimens which
arc of a yellowifh brown colour are impure, and melt
pretty eaiily into a black flag. There is alfo a fpe-
cies of a light green colour, fomewhat more brittle,
and contaminated with iron. This laft is foluble by
heat into a femitranfparent glafs.

Chap. 12.]

CHAP. XII.

PONDEROUS EARTHS.

Jtarytes ajcarce Mineral ; found in t<wo States. ~— Crijlatum,— Pon-
derous Spar. — Caiv&.-~-Lifver Stone.

BARYTES is found in two ftates, combined either
with the carbonic or vitriolic acids, ift. When
united with the former acid, it refembles alum, but
is hard and ftriated, as if compofed of radiating fibres
coming from a center. This mineral has only been
found native in a lead mine at Anglezark in Lanca-
fhire. It is fometimes of a greenifh colour j fome-
times jagged, when it is called criftatumy from its re-
femblance to a cock's comb. Thefe prorhiHences are
found accreted to balls of the fame fubftance. Later
inveftigations have however clafled this as a fulphat of
Barytes.

2. Ponderous earth is more frequently united with
vitriolic acid, and in this date it is found in all the
Derbyfhire and Cumberland lead mines, and in feveral
coal pits throughout England. Thefe ftones are
found of various appearances, pale yellow, blackifh,
with coarfe fcales, or with fine fparkling fcales. They
are either tranfparent or opake. The tranfparent
PONDEROUS SPAR is ufually in the form of a fix-fided
very flat prifm, ending in a four-fided pyramid j but,
like all other cryftals, liable to be varied by the cir-
cumftances attending their formation. The opake
fpecimens, called CAWK. by the miners, are of a white,
grey, or fawn-colour j frequently of no regular figure,
but often in the peculiar figure of a number of fmall

F 3 convex

yo lAv&f-foM. {Book VI,

convex lenfes united together. Thefe varieties are
all remarkably heavy, in general exceeding four times,
the weight of water, and by this circumftance the pre-
fence of barytes may commonly be difcovered. The
ftones compofed of vitriolic acid and barytes may be
known by their fmelling like liver of fulphur when
rubbed. From this property they are called lapis £&-
i and Itberfiein (jivf r-ftonc) by the Germans,

Chap, 13.] [ 71 ]

CHAP. XIII.

ARGILLACEOUS EARTHS,

General Account ef Clays or Argils. — Alum ; its Comfo/itioti.— Na-
tural Hiflory of Alum. — Attion of this Subftance on other Bodies.—

Uj'es of Alum in the Arts. — Lac Lunts.— Porcelain Clay Manner

of making different Kinds of Pottery. — Stone Ware. — T~elltnvf or
Queen's Ware.-~Cbtna.—Litbomarga. — Terra Lemnia. — j&o/f.— «
Zeolite. — Lapis Lazuli.*— Tripoli. — Brick Clay. — Slate.

TH E argil, or earth of clay, is one of thofe fub-
ftances which abound moft in nature. There
are immenfe ftrata of clays, and they make a part of
every rich foil. The idea commonly entertained of
clay, is that of a natural fubftance, the pureft kinds of
which are firm, and have a fort of fatnefs or unftuofity,
and which by being rubbed by the finger receive a
polifh. When dry, they imbibe moifture, fo that
when applied to the tongue it adheres to them. From
their attraction for water, they arc always found moid
in a natural ftate. If more water is added, they form
a ductile pafte, which, when thoroughly burnt and
dried, becomes hard, ftony, and impenetrable to water.
On the regular contraction which clay undergoes from
the application of different degrees of heat, depends
the construction of a thermometer for meafuring in-
tenfe degrees of heat, and invented by Mr. Wedg-
wood *.

As clays when wrought together become impene-
trable to water, they are made ufe of to retain water
in ponds, &c. This is the reafon that when cattle are
allowed to tread a clayey foil in wet weather, the

* Sec vol. i. p. 115,

F 4 plants

72 Different Characters of Clay. [Book VI*

plants die that grew there ; for the clay being previ-
oufly mixed with the water, and being then compreffed
by the feet of the cattle, the ground is rendered too.
tough for the vegetables to Ipring up through its
efpecialiy when the cky thus trodden together is af-
terwards dried by the heat of the fyn. Clays differ,
much in confiftency. Some melt in the mouth,
others are gritty, and get between the teeth. They
are white, blue, grey, red, yellow, or black. Some
are much lefs yifcid than others. Some refift a very,
violent heat without undergoing any change; but
moft of them, in very intenfe heat, melt into a vitri-
fied mafs. Some of them effervefce with acids, others
not. All thefe varieties have but one fpecies of earth
for their bafis, and are nothing more than mixtures of
pure clay with heterogeneous fubftances. Thus we
often find, flrata, which contain a large mixture of
fandy and gritty particles. All clays which are fandy,
are fo from fan4, or calcareous earth: when mix,ed
with the latter, they efFervefce. The variety pf theis-
colour depends on an admixture of iron; though
fometimes of inflammable matter. The clay becoming
white in the fire, is the fureft fign of its purity. We
can actually extract iron from moft pf thefe clays^
efpecialiy thofe which burn to a red colour, which
colour is always affumed by the calces or ruft of iron.
When they effervefce with acids, they clafs with marles.
Clay, united with vitriolic acid, forms that common
and well known fubftance called AL UM.

The Sruirrrioia of the Greeks, and the alumen of
the Romans, was a native fubftance, and differed much
from the fait of which I am now treating. The
varieties mentioned by Diofcorides refer to ftalactites,
which contained very little if any alum, and that
completely enveloped by a vitreous matter. The

defcriptions

Chap. 13.] Alum. 73

defcriptions of Pliny are flill more "difficult to be
underftood, as he had not feen the fubftance which
he defcribes, but merely tranfcribed from others. The
factitious fait which is now called alum, was firft.
difcovered in the eaftern countries, but when, where,
or by what means, is unknown. On account of its
iimilar aftringency, and its ufe in the arts of tanning
and dying, the new fait has retained the old name.

Among the moil early works for the preparation
of alum, was that of Roccho, a city of Lycia, now
called EdefTa, hence the appellation Roch alum (now
commonly miftaken for rock alum). In the neigh-
bourhood of Conftantinople, and other parts near
Smyrna, were many alum-works. The Italians hired
and made ufe of thefe, but about the fifteenth century
introduced the art into their own country.

Bartholomew Perdix, or Pernix, a merchant of
Genoa, who had often been at Roccho, difcovered the
matrix of alum in the ifland of Ifchia, about the year
1459, and eftablifhed a manufactory there; at the
fame time John de Caftro made the fame difcovery
at Tolfa, by means of the iiex aquifolium, which he
had alfo obferved to grow in the adjacent mountains
of Turkeyj and his opinion was confirmed by the tafle
of the ftones. The attempts of the Genoefe at Viter-
jbium and Volaterre fucceeded extremely well ; info-
much that an edift of Pope Pius II. prohibited the ufe
pf oriental alum.

Manufactories were eftablifned in Spain, Germany,
England, Sweden, &c. in the courie of the fixteenth
century.

The proportion of the principles may be afcertained
in the following manner : the water is expelled by a
gentle heat; the remaining mafs grows opake, fwclls,
foams, and at length grows quiet, fpongy, and friable ;

the

74 Natural Hi/lory of Alum. (Book VI.

the quantity of earthy bafis is eafily determined by pre-
cipitation with fixed or volatile alkali.

Mr. Pott firft obferved that when clay is mixed with
vitriolic acid, and boiled a confiderable time, the fo-
lution affords alum, though he obtained but little in
this way. MargrarF found that the vitriolic acid dif-
folves one half or more of the pure ft clay ; from the
folution he obtained much alum, but always found it
neceflary to add a certain portion of alkaline fait before
the alum would appear j and he could never obtain
it without adding a greater quantity of vitriolic acid
than was neceflary to compofe the alum. The *>ther
half, which did not difTolve, he concludes to be a
very fine fand, or an earth of the flinty kind, The
fhorteft way is to add a fmall quantity of fixed or
volatile alkali to the folution, which immediately be-
comes muddy, the alkali- attracting fome of the fuper-
fluous acid, a powder precipitates, confiding of the cryf-
tals of alum.

The alum, however, which is employed in the arts>
is not prepared in this way. Nature produces but a
very fmall quantity of actual alum, and. this is mixed
with, heterogeneous matters, or efflorescences, in va-
rious forms, upon ores during calcination, but rarely
occurs cryftallized. In this latter ftate, it is reported
to be found in Egyyt, Sardinia, Spain, Bohemia, and
other places > it is fometimes generated in the alumi-
nous fchift of Lapland and Weft Gothland, by a fpon-
taneous decompoution of the ore; bcfides it is found
(but rarely) in mineral fprings. Alum is moftly pre-
pared from certain foITils, or ores of alum, as they are
called. Thefe ores are generally found in ftrata, which
appear like indurated clays, of a dark black colour*
and have a fulphureous fmell. When expofed to the
air for fome time, they grow hot, fwell, and crumble

dowa

Chap. 13.] Procefs m making Roch Alum. 75

down into a powder, emit fulphureous fumes, and
fometimes take fire. Some do not undergo this change
merely from cxpofure to the air, but mud be firft
burnt and waihed, and then expofed to the air a good
while before alum can be obtained. After they have
been crumbled down in this manner, they are fleeped
in water ; an alkali is then added, and the alum cryf.
tallizes and fubfides.

Thefe ores are evidently natural mixtures of clay
and fulphur. By expofure to air, according to the
old fyftem of chcmiftry, it was fuppofed that the clay
acted on the fulphur in fuch a manner as to make it
part with its phlogiilon, whence they explained the
production of heat. This fact, however, is now much
better explained, according to the new fyftem, by fup-
pofing that the oxygenous gas of the atmofphcre is
decompofed j and while the oxygen is abforbcd by the
fulphur (with which it forms vitriolic acid) the heat is
fet at liberty, and becomes fenfible.

After a proper quantity of alkali has been added
to the folution, it is cryftallized in the common man-
ner, that is by evaporation. The cryfrals are at firft
tolerably diftinct, but of no confiderable fize. A
great quantity of them being heaped together until
they undergo a watery fufion, they unite into a mafo,
which is called roch alum, and in this form it is ex-
pofed to fale.

That accurate and attentive obferver, Bifliop Wat-
fon, in his Chemical F.ffays, relates, that being one day
engaged, in evaporating fpmething or other from a
faucer made of Stafford fhire yellow ware, he was
lurprifed to fee a white fubftance bubbling through a
crack in the faucer ; upon tailing it, he found it to be
a fait, and, upon further examination, difcovered that
it was a perfect alum. The n:ea he obferves, was a

very

7 6 Compofitlon of Jlum. [Book VI.

very hot one, and it was made of coal cinders j the
faucer was placed on the bar of the grate, and the
alum, he conceives, was formed from the fulphureous
acid of the cinders uniting itfelf with the clay, which
enters into the compofition of the yellow ware. He
was informed that the vapour which, in fome places,
efcapes from the coal-pits which are on fire in Staf-
fordfhire, forms an alum whenever it meets with an ar-
gillaceous earth. This, he remarks, is conformable to
the manner of making alum on the Solfatara, near
Naples, where they place little heaps of argillaceous
earths or ftones over the crevices from which the ful-
phureous vapour iffues, in order that they may colled
a greater quantity of alum.

This fait contains much water, hence it undergoes
what chemifts call the watry fufion; after this there
remains a fubftance called burnt alum, which contains
the earth and vitriolic acid, with little or no water ;
this, if the heat is increafed, does not melt, nor by heat
alone can we feparate the whole of the acid, though
fome of it rifes j but the addition of any inflammable
matter difpofes it to rift; in fumes, which are very ful-
phureous. One hundred parts of cryftallized alum
contain thirty-eight of vitriolic acid, eighteen of clay>
and forty-four of water.

The fenfible qualities of alum mew it to be the op-
pofite to borax, which is compofed of the fixed alkali
and a very weak acid ; on the contrary, alum is the
ilrongeft acid, combined with an earth which attracts
it very weakly ; fo that the qualities of the acid are
very little altered, for if we apply a fohition of alum
to the infufion of litmus, it changes it to a red. The
folution has alfo a manifeft acidity, combined with;
another tafte which approaches to fwetrtnefs. If an
alkali is added, the earth is immediately precipitated,

Chap. 13.] Homier £s Experiments. 77

and this effect is not only produced by the fixed and
volatile alkalies, but by magnefia and calcafeous earth.
Alum is often obtained from the liquor of the compound
of iron and vitriolic acid.

The earth of alum will combine in excefs to the fait
when already formed. M. Beaume boiled a folution
of alum with the earth precipitated from another por-
tion of alum, by means of fixed alkali; the earth was
diffolved with effervefcence, the filtrated folution had
no longer the tafte of alum, but that of a hard water,
did not redden the tincture of turnfole, but converted
lyrup of violets to a green. • By fpontaneous evapo-
ration it afforded cryftals, fcaly and foft to the touch
like mica; M. Beaume compares them to felenite*
It is not eafy to compofe alum by adding vitriolic
acid to this faturated fait, the mixture becoming acid,
but not ftyptic. However, after fpontaneous eva-
poration for three months, the folution afforded cryi*-
tals of alum mixed with fome micaceous fcales,
fimilar to thofe afforded by alum faturated with its
earth.

Alum, heated with combuflible matters, forms a
fubftance which takes fire on expofure to air, and is
called the pyrophorus of Homberg. This chemift,
who publifhed an account of the pyrophorus, in the
year 1711, made experiments on human excrement,
for the purpofe of obtaining a colourlefs oil poffeffing
the property of fixing mercury into fine filver: the
inquiry produced many difcoveriesj the refidue of
this animal fubftance, diftilled with alum, took fire on
expofure to the air. Homberg repeated this experi-
ment a number of dines, and always with fuccefs.
Lemery the younger, in the years 1714 and 1715*
publiflied two memoirs, in which he affirms, that
pyrophorus may be made with a great number of

vegetable

7 8 Ufes of Alum in tie Arts. [Book VL

vegetable and animal fubftances heated with alum.
But he did not fucceed in his attempts to form it
with fome other vitriolic falts. Thefe two chemifts,
who fuppofed alum to be a combination of the vitrio-
lic acid and calcareous earth, imagined that the latter
being converted into lime attracted the humidity of
the air, and produced a degree of heat fufficient to fet
fire to the fulphur formed by the vitriolic acid and in-
flammable fubftances.

Alum is one of the moft ufeful falts in the arts. It
is added to tallow to make candles hard. Wood fuffi-
ciently foaked in alum does not eafily take fire : the
fame is true of paper impregnated with it, which for
that reafon is very proper to keep gun-powder, as it
alfo excludes the moifture of the air. This paper is
alfo ufeful in whitening filver, and in filvering brafs
without heat. Alum is ufeful added to milk which
does not eafily feparate its butter.

It is particularly ufeful in dying, in preparing the'
matters to be dyed ; for by cleanfing and opening the;
pores upon the furface by a gentle corrofion, it both
renders the fubftance fit for receiving the colouring
particles (by which the alum is generally decompofed)
and at the fame time makes the colour fixed. It
conflitutes the bafis of crayons, which generally confift
of the earth of alum, finely powdered and tinged for
that purpofe, with different colouring matters.

The argillaceous fofiils are referred to the following
heads :

I. ARGILLA AERATA, to which the fanciful name
of lac lunas has been applied. This was fuppofed to
be a particular fpecies of calcareous earth, till M.
Screber found that it was a combination of argil
with the carbonic acid. It efiwefces with acids,

and

Chap. 13.] Potters Clay. 79

and contains a very final! proportion of calcareous
earth, and fometimes of gypfurri* It is generally
fo ;.d in finall cakes of the hardnefs of chalk, like
which it marks white. Its colour is fnow white, and
when examined by the microfcope it is found to con-
fift of fmall tranfparent cryftals. It efferveices with
acids.

II. PORCELAIN CLAY, argilla apyra, the kaolin of
the Chinefe. This is very refractory, and is with
great difficulty brought into perfect fufion. After it
has been fubmitted to the action of heat, it is of a folid
texture, and is fo hard as to ftrike fire with fteel. It
is found of an excellent quality in Japan, and likewifc
in different parts of Europe. In Sweden it is met with
in coal-pits, between the ilrata of coal. Common
pipe-clay belongs to this divifion, and differs from
porcelain clay only in being lefs pure, which prevents
its burning to a good colour.

The efTential ingredient in all kinds of pottery is
clay or argillaceous earth, becaufe thefe earths are ca-
pable of being kneaded, and eafily receiving any form,
and of acquiring much foiidity and hardnefs by ex-
poftire to fire. Pottery is, in general, covered with a
glazing, or is made to undergo a vitrification at the
furface, without which it would be pervious to fluids.
Ordinary pottery is glazed with glafs of lead mixed with
metallic calces, or with fufible metallic earths. A
fine kind of pottery is made of white clays, or fuch as
whiten in the firej the furface of which is vitrified by
throwing into the furnace, when the ware is fufficiently
baked, fome common fait and faltpetre. The Eng-
lifli ftone ware is compofed of tobacco-pipe-clay and
ground flints. The uie of the flints is to give ftrength
Co the ware, fo that it may preferve its form during

the

to Art tf Pottery. [Book VI.

the baking. In making this flone-ware great pains
are taken to employ only the finer particles of the clay
and flint; With this view the clay is much beaten iri
•water, by which the finer parts being mixed with the
fluid are fufpended, while the coarfer fink to the bot-
tom of the vefiel. The thick liquid, confiding of
•water and the finer particles of the clay, is farther pu-
rified by pafTing it through hair and lawn fieves of dif-
ferent degrees of finenefsi After this the liquid is
mixed, in various proportions for different wares* with
another liquop, of about die fame denfity, and eonfift-
ing of flints calcined j ground^ and fufpended in water.
The mixture is then dried in a kiln, and afterwards^
being beaten to a proper temper^ it becomes fit for
being formed at the wheel into dilhes, plates, bowls^
&ct When the ware has been expofed to heat for
about forty-eight hours; it is glazed by means of com-
mon fait. This is thrown into the furnace through
holes in the Upper part of it, and being converted into
a thick vapour by the heat, is applied to the furface of
the heated ware, and caufes it to vitrify. This curious
method of glazing earthen ware was introduced into
England by two Dutchmen, near a century ago. It
appears to be produced by a combination of the alkali
of the {alt with the filiceous earth of the pottery. The
yellow or queen's ware is made of the fame materials
as the flint ware, but in different proportions. The:
glazing is alfo different ; it is made by mixing toge-
ther in water, till it becomes as thick as cream j one
hundred and twelve pounds of ground white leadj
twenty-four pounds of ground flint, and fix pounds
of ground flint gLfs. The ware, before it is glazed,-
is baked in the fire, by which it acquires the property
of flrongly imbibing moifture; it is then dipped in
this compofition, and fuddenly taken out. It is after-*

wardl

Chap. 1 3.] Ckineje Porcelain. 81

wards expofed a fecond time to the fire, by which
means the glaze it has imbibed is melted, and a thin
glaffy coat is formed upon its furface, which is more
or lei's yellow, according as a greater or lefs propor-
tion of lead has been ufed.

Porcelain, or china, is a femivitwfre'd earthen
ware of an intermediate nature between common
wares and glafs. The firit Ipecimens of this beau-
tiful manufacture came from China and Japan. Chi-
hefe porcelain is faid to be compofed of two ingre-
dients, one of which is a hard ftone or rock called
^etuntfe, which they carefully grind to a very fine
powder ; and the other, called by them kaolin, is
a white earthy iubftance, which they mix intimately
with the ground petuntfe. Reaumur examined both
thefe matters; and having expofed them feparately
to a violent fire, he difcovered that the petuntfe
had fufed without addition, but that the kaolin had
given no fign of fufibility; from which it appeared
that the former was of a flinty nature, and the latter
argillaceous. He afterwards mixed thefe matters, and
formed cakes of them, which, by being baked, were
converted into porcelain fimilar to that of China.
Macquer thinks that the firft European porcelains
were made in Saxony and in France; and afterwards in
England, Germany, and Italy. Manufactories have
jfmce been eftablifhed in almoft all the countries of
Europe, in many of which porcelain is made very little
if at all inferior to the Chinefe.

III. Lithomarga, or STONE-MARROW, when dry,
feels as ilippery as foapi but is not wholly diffufible in
wafer. When mixed with water, it falls in pieces,
fo as to afibme the appearance of curds. In the fire
\t melts into a frothy flag. In the mafs it breaks into

VOL. II, G irregular

82 Armenian Bole, &t. [Book VI.

irregular fcaly pieces. This is the fuller's earth ufed
in the drefling of cloths. To this fpecies alfo belongs
the terra lemnia; this is of a brownifh colour and
ill in ing texture, and falls to pieces in water with a
crackling noife. The terra lemnia is fo called from
the ifland of Lemnos, now Statimane, in the JEgean
fea, whence it is procured. It is likevvife called the
Turkifh earth, on account of its being impreiTed with
the leal of the grand fignior.

IV. BOLE is a fine and denfe clay of various colours,
containing a large quantity of iron. It is not eafily
fottened in water when indurated, as the porcelain and
common clays, but either falls to pieces in the form of
fine grains, or repels the water, and cannot be made
ductile. In the fire it grows black, and is then at-
trafted by the loaddone. The foft boles are of va-
rious colours, as red, yellow, green, grey, and blueifh
grey. The red kind is that uled in medicine, under
the name of Armenian bole; an indurated kind of
which affords the material for red pencils. An indu-
rated bole is frequently found in coal-pits, between
the feams of coal, and is called coal flate. It is met
with frequently in pieces like nuts of various fizes ;
\vhich when broken exhibit imprefilons of plants, as
the nodules of copper- flate from Ilmenaus contain
representations of fiih. A fpecies of bole is found with
fcaly particles, the hornblende of die Swedes. It is
cllftinguimed from mica, by the fcales being lefs min-
ing, thicker, and rectangular. It is frequentlyanixed
with pyrites ; it is of two kinds, black and greem'ih.
The former, when rubbed fine, , alibi ds a green
powder, and is either of a lamellated or granular tex-
ture. The greeniih kind is of a granular texture, or
flriated. '

V. ZEOLITE

Chap. 13,] Lapis Lazuli ', Rotten Stone, 6?r. 83

V ZEOLITE is in general of a cryftnlline form, com-
pofed of imperfed pyramids turned towards a com-
mon'center. Their form is fometimes globular,- but
feldom prifmatic. The lapis lazuli belongs to the
zeolites. Thefe foflils are harder than fluors, but may
be fcratched by fteel. The filiceous earth predomi-
nates much in them. The lapis lazuli contains filver
and iron, which gives the blue colour. Zeolite melts
ferfe with ebullition into a white frothy flag, which in
the moment of fufiori affords a phofphoric light. The
lapis lazuli firft becomes brown when melted, and theri
produces a clear glafs with blue clouds. By rectifi-
cation with lead, one hundred weight of it has afforded
two ounces of filver.

VI. TRIPOLI feems to be of a volcanic origin. It
is an earth confifting of very fine particles, and is
known by its quality of rubbing or wearing hard bo-
idies, which gives them a polifh. Other fine clays>
however, have the fame property when a little burnt.
The tripoli grows forriewhat harder in the fire, and is
fufed with great difficulty. When crude it imbibes
water, but is not foluble in it. It tafles like chalk,
and is ro^gh or fandy between the teeth, though no
fand can be feparated from it. That which has been
juft defcribed is of a yellow colour, and is fold by
druggifts. This kind of tripoli has been lately dif-
covered in Scotland. Another variety, called the
totten-ftone, is found in Derbyfhire. It is in common
ufe in England for all forts of finer grinding and po-
lifh'mg, and is alfo fometimes ufed by lapidaries for cut-
ting of ftones,

VII. Common or BRICK CLAY is found of various
colours, as red, pale red, grey, and blue. It acquires

G 2 a red

*4 Slate. [Book VI.

a red colour, more or lefs deep, in the fire, and melts
pretty eafily into a greenifa glafs. It ccmfifls of a
mixture of pure clay, filiceous and martial (or iron)
earths, containing alfo a fmall quantity of vitriolic acid.
The clay is alfo found mixed with calcareous earth,
when it conftitutes marie. It is alfo found in an in-
durated ftate, either pure or mixed with inflammable
fubftances, and vitriolic acid, in which cafe it forms the
ores of alum.

VIII. Argillaceous foffile ftones, to which the de-
nomination of SCHISTI properly belongs. The mod
remarkable ftones comprehended under this divifion
are the blueifh purple fchiftus, or common roof flate ;
the dark blue fchiftus, or writing flate j the pyritaceous
fchiftus i the bituminous fchiftus ; the argillaceous grit,
which is alfo called fand-ftone, and free-done; the
killas ; the Bag-ftone, and the toad-ftone.

The method of fplitting the flate, ufed for the
roofing of houfes, is the following : they expofe it in
blocks to be well wetted and foaked by the rain ;
when the froft comes upon it afterwards, it rarities the
water, and cracks and opens all the joints of the ftone,
'fo that when the froft has completed its work it lies
in loofe flakes or Olivers. Thus the elements perform
with eafe what no manual art could have eafily acconv*
plifhed*

CHAP. XIV.

SILICEOUS EARTHS.

General Arrangement of Flinty Subftances.~—Ge?ns.—Dianiond.-~R.ul>j,
•—Sapphire,— Topaz — Emerald. -r- Hyacinth.—- Amethyjl. — Garnet.
——•Tourmalin.— ~Qpal.— L-ompoJition and Properties of precious Stones*
— -Quartz.— Rock Cry ft ah,— Pe bbles.— Flints .——Lapis Nephriticus.
—Cat's -Eye. — Hydroplanes. — Explanation of the Phenomena of the
Hydrophanous Stone. — Moon-Stone. — Chalcedony.— Onyx.—Carne-
iion. — Sardonyx.'— Agate.—* Common Flint. —Chert. — Sand and
Gra-veL— Jafper.— Feldt Spar.->— Labrador Stone.— Scbirl and
Whetjlone.— Art of making Glafs. — Prince Rupert's Drop and
PhihifophicqJ Phial. — Curious Phenomenon,

THE filiceous earths are chiefly diftinguifhed by
their hardnefs, by which they ftrike fire with
fteel, and their property of forming good glafs with
alkali. They may be divided into, i, Gems, or
precious ftones 3 2, Quartz j 3, Flints ; 4, Jafpers ;
5, Feldt fpars.

1. GEMS.— The diamond is the hardeft of all bo-
dies, and the moft valuable of all the gems j it is
however not an earthy but an inflammable fubftance,
and therefore will be fully treated of under that head*.
It is mentioned on the prefent occaiion only, that the
catalogue of gems may not appear incomplete.

2. The ruby has been confounded with the dia-
mond, on account of its hardnefs and luftre, but fome
late experiments mew that it is effentially different.
According to Cronftadt, there are four principal kinds
of rubies : — i. The ruby of a deep colour inclining tq

* See Chap. 44.
G 3

86 <?be Rufy, Sapphire, &c. [Book VI.

purple. 2. The fpinell ruby, of a ponceau red, that is,
of a bright cofn-poppy-flower colour. 3. The balafs-
ruby, pale red inclining to violet. 4. The rubicell,
of a reddifh -colour.

3. The fapphire is tranfparent, and of a blue colour,
and is faid to be next to the diamond in hardnefs. They
are fomttimes of a milky appearance.

4. The topaz is chiefly of different fhades of yellow,
but is fometimes greemfh. When of a fea-green co-
lour it is called aqua- marine; when more green, the
beryl ; when yellowish green, the chryfolite.

5. Emerald, the chief colour of which is green, is the
foft^lr of the precious ftones, and when heated is phof-
phortfcent like the fluors.

6. The jacinth or hyacinth, is of a fine reddifh yel-
low colour, and fometimes brown ; thefe gems are
formed in prifms, pointed at both ends.

7. The amethyfl is a gem of a violet colour, or
great brilliancy, and as hard as the beft kinds of rubies
and fapphires, from which it only differs in its colour.
This is called the oriental amethyft, and is very rare ;
when it approaches to the purple, or rofe colour, it is
more eileemed than when it inclines to the blue.

The amethyfts called occidental, are of the fame
nature as rock cryftals, and have the fame gradations
of colour. Cryftals within the geodes, or hollow agate-
balls, are very often found of an amethyft colour, and
fome are very fine.

8. The garnet, when tranfparent and of a fine co-
lour, is reckoned among the gems ; but it varies more
than any, both with refpect to its form and colour, fome
being of a deep and dark red, fome yellow and purple,
and fome brown, blackilh, and quite opake. The
regular fhape of the garnet is the dodecagon, with
rhomboidal faces, and its chief variation is, die double

i eight-

Chap. 14- ] fke Tourmalin and Opal. 87

eight-fided pyramid, terminating by four faces on each
end. In general their luftre is lefs than that of other
gems, as v/ell as their hardnefs, which yields to the
file, though they fometimes ftrike fire with fleel. Their
colour proceeds from the iron which they contain;
and, according to M. de Sauflure, even the fineft ori-
ental garneto attract the magnetic needle at a fmall
diftance. The Syrian garnet is the fineft, and moil
eibeemed : ic is of a fine red, inclining to a purple co-
lour, very diaphanous, but lefs brilliant than the oriental
amethyft.

9, The tourmalin has lately been brought much
into notice by its remarkable property of becoming
electrical, in confequence of the fimple application of
heat. I fit is immerfed in hot water, in which procefs
no friction can be luppofed to happen, after it is re-
moved it gives figns of contrary electricity at the two
oppofite ends of its priiinatic form.

The oriental tourmalins are found in the ifland of
Ceylon : they are tranfparent, of a dark brown yellow.
From Brafil they are for the moft part green ; but
there are allb fome red, blue, and yellow. From Tyrol
they are obtained of fo dark a green, as to appear
opakc. They are alfo found in the mountains of Old
Caftile in Spain.

10. The opal is a moft beautiful ftone, from the
changeable appearance of its colours by refraction
and reflection. There are two kinds •> one of which,
the opal of Nonnius, appears olive-coloured by reflec-
tion, and then appears to be opake ; but when held
againft the light, it is found to be tranfparent, and then
appears of a fine red colour. The white opal, of a
glafs-like complexion, throws out green, yellow, purple,
and blueilh rays j but it is of a reddiih, or rather flame-.
colour, when held againft the light.

G 4 The

8 8 'Andyfts of Gens. [Book VI.

The precious (tones are chiefly compofed of the
argillaceous and filiceous earths ; of which the former
predominates. Some diamonds alfo are thought to
contain a portion of earth, but thefe cannot properly
be accounted diamonds.

On diffblving the very fubtile powder of the gems
in a double weight of vitriolic acid highly concen-j
trated, the refiduum, after evaporation, being -.vafhed
with warm water, yields a metallic colouring fubftauce,
and a fmall portion of lime. The metallic part, pre-
cipitated by what was in the old chemical nomenclature
called a phlogiilicated alkaline lixivium, yields a beau-
tiful Pruffi.an blue ; hence we conclude that the red
colour of the ruby, as well as the blue of the fapphire,
the yellow of the topaz, the tawny of the hyacinth,
and the green of the emerald, are to be attributed to
iron *.

Bergman obtained by analyfis, from one hundred
parts of the following precious ftones :

Clay. Flint. Lime. Iron.

Emerald, — 60 — 24 — 8 — 6

Sapphire, — 5s — 35 — 5 — 2

Topaz, — 46 — 39 — 8 — 6

Hyacinth, — 40 — 25 — 20 — 13

Ruby, — 40 — 39 — 9^ — 10

From the above it may be collected, that the gems
agree in this refpect, that they all confift of the fame
principles j and that of thefe the argillaceous earth
forms the greateft part, then the filiceous, next the
calcareous, and leaft of all the ironf. The gems,
Except the emerald and hyacinth, refill the moft in-.

* Bergmaij's Diflertations, p, 15.
f Chemical Effays, Diff. 15.

tenfe.

Chap. 1 4.] G-eneral Properties of Gems-. §9

tenfe fire ; yet we know that the ruby has been fof~
tened in the focus qf a burning mjrror *.

Thefe (lon-s all affume different forms of cryftalli-
zation, and as this affe6ls the arrangement of their
minute parts, it cbubdefs is not without eiTed; on their
external appearance. Their value depends on their
hardnefs and tranfparency. The degrees of h-irdnefs
are — i, diamond; 2, ruby; 3, fapphire ; 4, topaz;
5, hyacinth ; 6, emerald.

The garnet differs from all die above, in the fi-
liceous earth being more prevalent than die argilla-
ceous.

II. QAURTZ has lefs tranfparency and hardnefs
than the precious ftones. The fracture of quartzofe
Hones is vitreous, or like glafs, and they ftrike fire
with fteel. Heat caufes them to, lofe their hardnefs.
and tranfparency, and reduces them to a white opake
earth. They are generally cracked throughout, and
break irregularly, and into {harp fragments. Melted
with alkali they give a more folid and fixed glafs than,
any others of the filiceous order. When there' is no
interruption to. their natural accretion, their fubftance
always cryflallizes into hexagonal prifms, pointed at
one or both ends, Thefe occur in clefts, fiffures, and
fmall veins in rocks. Quartzofe flones very often
contain metals.

No very remarkable ftones belong to this genus.
The varieties are Fat quartz, which is very glofly j it
is either colourlefs, or is tinged with white, blue, or
violet. Dry quartz, tranfparent, white, or pale green.
Sparry quartz, pale yellow, or pale blue. Cryftal-
lized quartz is either opake or tranfparent : the tranfpa-

* Chemical Eflays, Diff. 15.

rent

90 Qiiartx, Rod Cryftal, f£c. [Book VI.

rent and dark- brown kind is called fm ok y- topaz; the
yellow, blue, green, and red, falfe gems ; and the co-
lourlefs, rock cryftals ; when milky, milk cryftals, and
pebbles. .Quartz is alfb found combined with iron
and copper ; with the former it conftitutes a black
calx, with the latter a red calx.

III. FLINTS are more uniformly folid, and not fo
much cracked in the mafs, as quartz ; and are more
pellucid than jafper. They are better for making
glafs than the jafper, but not fo good as quartz, and
feem in moft refpecls to be of an intermediate nature
between thefe ftones. Flint often fhews evident marks
of having been in a foft and tough (late, like glue or
jelly.

The feveral varieties of flints have obtained more
' diftindi names, from the variety oi their colours, than
from any real difference in their fubftance ; but th^fe
are dill proper to be retained, as the only names
by which jewellers and others are ulcd to diftinguifh
them.

i. Jade, lapis nephriticus. This (tone feels unc-
tuous to the touch, but is fo hard as to ftrike fire with
fteel, and is alfo fcmipellucid. Thefe latter circum-
fiances fufficiently denote its flinty nature •„ though its
undhiofity has induced fome mineralogifts to think
that it ought rather to be referred to the argillaceous
or iv.agnefian orders. It is not hardened by the heat
of the furnace, but it melts by the folar heat, in the
focus of a burning mirror, into a green glafs. That
called by the name of circuracifion-ftone, which comes
from the Amazon river, melts more cafily by the
concentrated rays of the fun into a brown opake glafs.
The colour of thefe (tones is either milky, or different
fhades of green. Thofe of a grey, olive, or yellowifh

colour>

Chap. 14.] Lapis Nephriticus, Cat's Eye, &c. 9t

colour, are the vulgar lapis nephriticus ; which name
they have obtained, from a fuppofed property of cur-
ing nephritic pains, when applied externally to the
loins. Their femipellucid appearance, hardnefs, and
fpecific gravity, are characters by which the lapis neph-
riticus may be diftinguifhed from other ftones.

2. The cat's eye is a very fcarce (lone. It is
opake, and reflects green and yellow rays, in a man-
ner fomewhat fimilar to the eye of the animal from
which its name is derived. It is found in Siberia.

3. The hydrophanes, or oculus mundi. The cha-
racter which diftinguifhes this from all other ftones is
its property of becoming transparent in confequence
of being immerfed in water. This happens from its
imbibing that fluid, as it becomes again opake by being
dried.

This circumftance may be illuftrated by a compan-
ion with fome other natural phenomena. The appear-
ance of clouds ferves to mew that particles of water,
copioufly mixed with thofe of air, prevent the tranf-
miflion of light, and render the mafs more or lefs
opake, although the particles of each, feparately taken,
-are pellucid. The caufe of this is to be fought for in
the difference of the refracting power j for, by means
of that, the rays are turned from their original courfe
at every particle, a circumftance which is very inju-
rious to tranfparency. A common experiment will
ilill more clearly elucidate this point. The moft
tranfparent glafs, when reduced to powder, becomes
opake, becaufe the air which now occupies the inter-
flices reflects the light much more copioufly than the
particles of glafs. But upon pouring on water, which
difplaces the air, and which differs lefs from the glafs
in its refracting power, a certain degree of tranfpa-
rency is reftored. On this principle depends the na-
ture

9%2 Hjdrophaneoiis Stone, &c. [Book VI,

Hire of the hydrophanous {tone, which is opake when
dry, but gradually acquires tranfparency by lying in
water. This flone agrees nearly in fpecific gravity
v/ith water, at leaft is not more diftant from it than
glafs. Its particles are tranfparent, but it is uniformly
perforated by invifible foramina, fo that the air and
water are admitted, but not readily. When dry,
therefore, on account of the great difference of the me-
diums between the particles of the (lone and thofe of
the air, it is opake ; but when the water is gradually
imbibed, it grows by degrees pellucid, beginning at the
furface, and proceeding towards the center. That
tlie hydrophanes abforbs moifture and emits air,
v.hich is a fluid of ranch lefs denftty, appears from
the weight it acquires, and the fmall bubbles which
cover its furface during the time it is acquiring its
tranfparency.

4. Moon-done, or rainbow-ftone, refkfts light of
pearl and carnation colours. Its fracture is foliated,
and its colour pale blue and milky.

5. Chalcedony, or white agate. — This ftone is
ufually cut with a convex furface, and receives a good
polifh. Its degree of hardnefs is intermediate, be-
tween that of the onyx and the true agate. It is fe-
mitranfparent, and its colour is ufually very fimilar to
that of milk diluted with water.

6. The onyx is the hardeft of flints. Its ufual colour
is that of the human narls. It is either marked
with white lines only, or with black and white toge-
ther. Heat deprives it of colour, and, if fuddenly.
applied, cracks it.

7. The carnelion derives its name from its refem-
blance to the colour of flefh. It is either quite red or
of different fnades of red, with brown and yellow. .

$. The fardonyx is a mixture of the chalcedony and

carnelion.

Chap. 14.] Jgate, C: / VW/*, £&. 93

carnelion, fomctimes diipofcJ in firata, and fometimes
confufedly blended and mixed together. Its colours
are therefore a mixture of white and red, fometimes in
itripes, fometimes irregularly notched.

9. Agate. This name is given to flints that are va-
riegated wirh different colours promifcuoufly blended
together, and they are efteemed in proportion to the
mixture and perfection of their colours.

10. Common flint or pebble, is in reality of the
fame nature with agate, bur wanting the beautiful and
various colours of the fubftances that bear that name.
Chalk and white lime-ftone are ufually the matrices of
flints, in which they are imbedded in the form of no-
dules, confiding of nuclei involved in a cruft.

1 1. Chert is lefs hard and tranfparent than the com-
mon flint. It is not in general found in Icofeand fmgle.
irregular nodules, but forms veins in rocks. Cherts
are found of a flelH- colour, white, pale yellow, and
greenifh, and feem to be of an intermediate nature
between the flints and jafpers.

Sand and gravel may be considered as flinty matters,
torn away from the rocks in which they originally ex-
ifted, and afterwards worn and fmoothed by the attri-
tion occafioned by the motion of water. Sand and
gravel, however, confiftof all the variety of flony mat-
ters which exifted in the mafies from which they pro-
ceeded, and are therefore found of many' different co-
lours and properties.

IV. The name of JASPERS is given to all the opake
filiceous ftones, which in their texture refemble dried
clay. The -principal circumftance, befides their ap-
pearance, which diftinguiihes them from the other
Jiiiceous orders, is their more eafily melting in the
fire. They in general contain much iron. They are

very

94 Jajfsr> Labrador Stone, &c. [Book VL

very hard, and admit a good polifh ; and they are
variegated with different colours' They are feldom
ranged in flrata, but form confiderable maffes and
veins in rocks. They are alfo found in fmall round
maffes. The principal fpecies of jafpers are the fol-
lowing— the white, grey, yellow, red, brown, green,
veined, fpotted, flowered, and green with red points,
or blood-ftone. Toys, and more efpecially cups and
faucers, are made of jafper. Many antique fculp-
Cures are on flones of this nature.

V. The mod common kind of FELDT-SPAR is
formed of rhombic laminae, and has therefore obtained
the name of rhombic quartz. It gives fire with flee),
whence it has been called fpathum fcintillans. It is
harder than the fchifti, and is fufible. It is found in
locfe malTes, two inches long, or mixed with fand,
clay, &c. or bedded in granite. It is ufed in making
china at Drefden. Its colours are white, red, brown,
pale, yellow, or greenifh.

The Labrador-ftone is generally claffed with the
feldt-fpars. It admits of a very fine polifh, and when
in that ftate reflects a variety of beautiful colours. The
(lone itfelf is of different fhades of grey.

VI. SHIRL or COCKLE, of different fhades of green j
and the various fpecies of whetftones, are alfo com-
monly referred to the filiceous order, though th~ Iattef;
are generally in fome meafure compound.

The ufes of the flinty fubftances are various, and
have been partly intimated; but there is one art, in
which their ufe is too confpicuous to be pafled over in
filence.

The art of making glafs depends, on the fufion of

fearthy

Chap. 14] Art of Glifs-maling. 95

earthy fubftances, of which the flinty earth is the oeft,
and for that reafon is called verifiable. But as earths
cannot eafily be fufed without mixture, it is neceffary
to add certain fubftances which may promote the
vitrification. In the making of ordinary glafs, two
parts of fand, or other filiceous matter, are mixed with
about one of fixed alkali. If the glafs is not required
to be tranfparent, impure alkali, not freed from the
alhes, is employed; but in making the finer and moll
tranfparent kinds of glafs, care is taken to purify both
the earth and the alkali. One of the chief points to
be obferved in the making of giafs is to heat the mix-
ture gradually, fo that the elaftic fluids may efcape
before the materials cohere, as the ingredients arc
otherwife apt to be fo fwelled by the difengagement
of air as to be loft by flowing over the fides of the
veflcl in which they are heated. In order to prevent
this, due proportions of fand and alkali are mixed to-
gether, and expofed, during a confiderable time, to
a red heat, not intenfe enough to melt them. By
this calcination the inflammable matters, which would
have impaired the colour of the glafs, are confumed,
and the air expelled. This firft mixture of the mate-
rials of glafs, after being treated in this manner, is
called the fritf.

The due degree of heat is an efTential point in
making of glafs : it ought not only to be very ftrong,
but alfo maintained during a long time. In great
manufactories the glafs is kept fufed during ten or
twelve hours before it is taken out of the pots. The
ingredients are thus more completely melted, and more
thoroughly mixed, and the "appearance of threads or
veins is in fome meafure prevented, which proceed
from the different denfity of different portions of the
glafs, and which therefore ad differently on the rays

of

9 6 ./#•/ <?/ Glafs -mating. [Book VI.

of light. The imperfections of glafles are moft fcn-
fibly felt in the conftruction of optical inftruments.

Good glafs, although kept in fufion for a long time
in a great heat, is never perfectly liquid. It is always
ibmewhat thickj and when taken out may be drawn
. into fine threads. The great ductility and flexibility
of red hot glafs fits it for being reduced into any form.
In general the glafs is taken out of the pots in which
it is fufed by means of an iron tube. When a fufficienr,
quantity of the glafs is collected at the extremity of
the tube, the workman begins to blow through it, an'cl
thus inflates the glafs. He occafionally rolls it, in
order to form it into a cylinder, a cone, &c. and if
it becomes too cold, he heats it by holding it before
the mouth of the furnace. Glafs, in its tough ftate,
may be cut with (hears, bended with pincers, prefled
into moulds, and wrought, in a variety of methods
dependent on thefe properties, into the vaft variety of
forms which it is made to afiume. Glafs veffcls as
foon as made> are carried to an oven, in which they*
are gradually cooled j for without this procefs, which
is called atmealling, they would either break in the cool-
ing, or be liable afterwards to be broken by the flighteft
force.

The principal defects of glafs are colours, veins*
and bubbles. The colours which generally injure the
co'mmon alkaline glafs are mades of green, blue, and
olive. Thefe are moft effectually removed by the
addition of a fmall quantity of manganefe. The caufe
of the veins has been already explained, and that of the
bubbles depends on the impe-rfeft expu-lfion of air.

The addition of calx of lead to glafs renders it mucn
more denfe, and lefs liable to be broken. Artificial
gems are only the beft kinds of glafs, coloured with
different metals 5 but the modes of applying the feveral

metals

Chap. 14.] Prince Rupert's Drop, &c. tf

metals to this ufe will be mentioned when treating of
theni.

There are two toys made of unannealed glafs/which,
though commonly ufed for the amufement of children,
exhibit phenomena which juftly intereft the curiofity
of the phiiofopher. When a drop of melted glafs is
fuffered to fall into water, it aflumes an oval form,
with a tail or neck refembling the retort of a chemift.
This is called Prince Rupert's drop, and porTefTes the
fingular property, that if the fmalleft portion is broken
off, the whole drop flies into powder with a kind of
explofion, and a confiderable mock is communicated
to the hand that grafps it *. The other is called the
philofophical phial, which is a fmall cylindrical veflel
of glafs, open at the upper end, and rounded at the
bottom. It is generally made of glafs fo thick that it
will bear a fmart blow againft a hard body without
breaking, but if a fmall pebble or piece of flint is let
fall into it, it immediately cracks and flies in pieces.
This veffel is formed upon fimilar principles with
Prince Rupert's drop, it confifts of glafs fuddenly
cooled, and, I fufpect, by immerfion in water.

Various explanations have been offered of thefe
facls. The moft generally received is founded on
the affumption that the dimenfions of bodies which
are fuddenly cooled remain larger than if the cooling
had been more gradual. The dimenfions, therefore,
of the fmooth external furface of thefe glafies, which
are fuddenly cooled, are fuppofed to be larger than
is adapted to the accurate envelopementofthe internal

* Honour is like that glafly bubble,
That gives philofophers fuch trouble ;
The one part crack'd, the whole will fly,
And wits are crack'd to find out why.

VOL, II. H part,

58 Pbilofophical Conjectures. [Book VI.

part, which is necefiarily cooled in a more gradual
manner j if, therefore, by a crack or rafure, a folution
of the continuity takes place in the external furface, the
fudden action of the parts which remained in a ftate of
tenfion, to recover that of perfect: cohefion, is fuppofed
to effect the deftruction of the mafs.

This explanation I confefs has not appeared to me
fatisfactory, and I have been inclined to fufpect thac
the phenomenon arifes either from a quantity of air
being included in the fubftance of the glafs, which
rufhes fuddenly out, on the furface which includes it
being broken ; or that by the fudden cooling the pores
of the glafs are fealed up by the fine fmooth furface,
and contain little or no air, fo that on the continuity
of that furface being interrupted, the air fuddenly
ruftiing into all the pores of the glals may effect its
diflblution. That the whole effect depends on de-
ftroying the continuity of the furface, I have fufficiently
proved; for unlefs the flint or pebble which is let
fall into the philofophical phial is large and angular
enough to fcratch the furface of the glafs, it will not
break. To afcertain whether the fracture of thefe
toys depends or not upon the air, a few experiments
mi-ght be made on Prince Rupert's drops in a va-
cuum j when, if it proceeds from air included in the
drop, the explofion will be more violent, or the drop
would perhaps fpontaneoufly burft; and if from the con-
trary caufe, it will not break at all in vacuo.

Chap. 15.] [ 99 ]

CHAP. XV.

"OF THE STRONTHIAN, JARGONIC, AND .ADAMAN-
TINE EARTHS.

The Swttijb or Strbnthian Earth difcwered by Dr. Craivford.—Oftbe
Jargonic Earth. — Adamantine Earth.— All of thefe fcarce Minerals.

THE SCOTTISH or STRONTHIAN earth was long
unnoticed, and was confounded with the calca-
reous genus, to which it bears a near refemblance. It
was firft brought under the confideration of the learned
by the late Dr. Crawford. It has hitherto been only
found in a mild (late, united with fixed air, which (like
limeftone) it lofes by a ftrong heat, when it forms «L
kind of lime. This lime, however, is more foluble in
water than that produced from common calcareous
earth, and is fpecifically heavier. It decompofes vi-
triolated tartar, but is itfelf decompofed by barytic
lime. It alfo decompofes folutions of common gyp-
fum, and of nitrated or muriated calx.

Vitriolic acid dropped into this lime water produces
an immediate precipitation, which it does not in com-
mon lime water. The earth itfelf is found in large
lighter whitifh green mafies. Its fpecific gravity is
from 3.4. to 3.644.

Of the JARGONIC earth, the only fpecies yet known
is the ftone called the Jargon of Ceylon, which is ge-
nerally of a grey or greenim olive colour. The cryf-
tallization prefents either right-angled quadrangular
prifms furmounted by pyramids, or oftohedrals. The
external luflre is cafual, but the internal is ftrong, in-
clining to the metallic. Its Ipecific gravity is 4.416.
In its qualities it more refembles argil, than any other
H a kind

ioo AdAmantine JLarth. [Book VI.

kind of earth. It is incapable of uniting with fixed
air.

The ADAMANTINE earth is alfo a late difcovery,
and was found in a ftone called adamantine or diamond
fpar, in which it conftituted about one fourth of the
weight. It is infoluble in acids, and infufible by al-
kalis j in this laft property therefore it differs [from fi-
lex, and in the former from all the other earths. Its
fpecific gravity is faid to exceed 3,000.

Thefe earths are all of them fcarce, tfnd form a fub*
ject rather interefting to the curious, than important
to the general reader. The Stronthian is faid to be the
mod abundant, and yet even this feems fcarcely to have
been fubjecled to a fufficient analyfis to afcertain its
nature and properties ; nor will it be a matter of
furprize, if on further examination thefe new earths
fhould be found to be only compounds derived from
fome of the five principal earths, fince the more the
works of nature are explored, the more of fimplicity
is difcovered, and the genuine effect of fcience is rather
to diminifh than enlarge the technical vocabulary.

Chap. 16.] [ 101 ] vr,

CHAP. XVI.

COMPOUND EARTHS.

Definition of this Gtnus* — Various compound Stones.

IN a ftricl: fenfe all earths and flones, as they exift
in nature, may be denominated compound, as
there are none which are wholly fimpje. By com-
pound earths, however, is here meant fuch as are
formed of two or more kinds of ftony matter, and
which in general conftitute a mafs of an heterogeneous
appearance. In treating of thefe fubftances, the ar-
rangement of M. Daubenton appears the moft perfeft
and commodious.

Mixed Stones^

OF TWO GENERA.

Quartz and fcintillating fpar - Granitin.
Quartz and fchirl - GranUellg*.

Quartz and fteatites •« Quartzofe fteatltes.

Quartz and mica - - Micaceous quartz.

Tranfparent quartz and mica - Micaceous ciyftal.

*• i Garnet on, grit

Quartz in grit and gem ftone - J n ftone:

^- S z Garnet in grit

(_ ftone.

Quartz in grit and mica - - Micaceous grit.
Quartz in grit and calcareous V i Cryftallized grit,
matter - - - - 1 2 Grit in ftalaaites.

. - , , in. Vfandy and filiceous

Quartz in fand and opake ftone | breccias.

H 3 Quartz

102 Compound Earths. [Book VI.

Quartz in fand and fchiftus - I Scintillating fchiftu,

£ born/lone, trap.

Quartz in fand and zeolite - fcintillating zeolite.

Scintillating fpar and pafte, or 7

rr L- i }• ophites.

cement, of ichirl - - \ f

Semi-tranfparent ftone, with opake f jafperecT agate, or

flone - - - - I agatized jafper.

Schirl and mica - - **g??la fpathofe

I fchiri.

Schiftus and mica - micaceous fchiftus.

Schiftus and marble - - FIorence marble.

/- i Green Egyptian marble.

\ a fea-green marble.
Serpentine and marble - < ^ green antique marble.

I 4 green marble of Suza.

^- 5 green marble of Varalta.
Ponderous fpar and calca- 7 i
reous matter - - i alkallne P0

OF THREE GENERA.

Quartz in fand, fchiftus, and mica - Rough whet-ftone.
Quartz, gem, and mica - garnet rock.

Quartzofe pafte, fcintillating fpar in 7 o h

large fragments, and fchorl - J P°
Quartzofe pafte, fcintillating fpar in7ferpentine. hardfer-

large fragments, and fchiri - j Putins.
Quartz, fchiri, and fteatices - tuberculous rock,

Quartz, fcintillating fpar, and

fchiri -

OF FOUR GENERA.

Quartz, fcintillating fear, fchiri and 7

mica , . . Pranite-

Oi

Chap. 1 6.] Porphyry y Granite, &c. 103

OF SEVERAL GENERA, MORE OR "J

LESS IN NUMBER, UNITED IN Vuniverfal breccias.
BRECCIAS. - J

DOUBLE BRECCIAS,

Fragments of porphyry, with a pafte of
Varieties, -J porphyry.

Fragments of granite, with a pafte of fchirl.

. [ 104 ] [Book VL

CHAP. XVH.

VOLCANIC PRODUCTS.

,— Different Kinds.— -Progrefs of a River of Lava — Confound
Parts of Lava. — Pumice Stone. — Be.Jaltes.~- Trapp.— Terra Puz-
zolana.

AVA is of very various appearance, according
to its compofition, and its more or lefs per-
fect vitrification. The materials of which lavas con*
fift, are the common fubftances to be found every
where in the earth, namely, flones, metallic ores, clay,
fand, &c. -, and as there is room for great variety in
the combinations of thefe fubftances, the melted mafles
formed by them mud in different circumftances be
very various. Some lavas are very compact, and re-
ceive a beautiful polifh, exhibiting great variety of
colours and forms. Others are extremely porous,
and mixed with fcoriae or drofs. On the different
confidence of lavas depends their capacity for being
converted into mould, capable of fupporting vegeta-
bles. Some lavas have a tendency to crumble into
duft immediately on iffuing from the crater; others are
a perfect glafs, and are calculated to refift for a long
time every approach towards duTolution.

Lava, when firft thrown out from the crater of a
volcano, is an imperfect liquid mafs, and flows down
the fide of the mountain with confiderable rapidity.
From lofs of heat, however, its furface is foon con-
verted into a tough and black cruft, which, as it be-
comes thicker, gradually impedes the progrefs of the
fluid lava which is contained within it. This cruft is
frequently broken, when the ftream of lava refembles

a river

Chap. 17.] Ceurje cf a River of Lava. 105

a river with mafles of ice floating on its furface. Fluid
lava fometimes flows for a confiderable diftance, un-
der the tenacious fcum, and again appears beyond it
in all its fplendor. In the night time the coiirfe of
the lava appears like flame, in confequence of the bi-
tumen, which is mixed with the lava, and which Is
fuppofed to be the principal caufe of its fluidity. In
the day-time its courfe is marked by a thick white
fmoke.

Mr. Kirwan divides lavas into three kinds, the cel-
lular, the compact, and the vitreous. All lavas arc
more or lefs magnetic, give fire with fteel, are of a
granular texture, and melt without the addition of
other fubftances. The cellular lavas are fuch as have
undergone only the firft and loweft degree of fufion,
being juft foftened and heated fufficiently to expel the
fixed air contained in the matter from "which rhey are
formed, which feems to be argillaceous flate -, hence
they abound in fmall cavities occafioned by the expan-
fion of that air. The fpecific gravity of fome lavas
from thefe cavities is fo fmall, that they float for fome
time on water. From this circumftance they have
fometimes been miftaken for pumice-flone j but they
differ from it, becaufe their texture is never filamen-
tous. The perfectly vitrified lavas muft have been
expofed to an immenfe heat, as they are very difficultly
fufed without addition. M. Sauffure has ingenioufly
imitated all the different kinds of lavas, by different
degrees of fufion of the earthy fubftances from which
they are formed. M. Bergman analyzed a fpecimen
of the perfect kind, and found an hundred parts to
confift of forty-nine of filiceous earth, thirty-five of
Argillaceous, four of calcareous earth, and twelve of
iron.

The beds of lava are deepeft and narroweft near the

crater,

io6 Pumice-fane and Bafi&es. [Book VI.

crater, and broader and fhallower as they advance,
unlefs fame valley intervenes. Pumice-ftones lie at
a ftill greater diftance ; and from thefe obfervations,
fays Mr. Kirwan, extingiiifhed volcanoes may be
traced. The quantities of matter thrown out of vol-
canoes at one eruption, are often fo great as to cover a
ipace of country of many miles, and to be many years
in cooling.

II. PUMICE-STONE is a volcanic ejection, but is
frequently found at a diftance from its origin. Its
colours are grey, white, and reddim brown. It is
hard, rough, porous, confifts of (lender fibres parallel
to each other, is very light, and with difficulty gives
fire with ftecl. It feems to have been originally an
aibeflos decompofed by the action of fire. One hun-
dred parts contain from fix to fifteen of magnefia, with
a fmall portion of calcareous earth -, the remainder is
chiefly filex. Pumice- flone fwims on water. It is
ufed to fmooth rough furfaces, and, in a flate of pow-
der, in various branches of manufacture, chiefly for
polifhing.

III. BASALTES is a flone of a dark grey colour, co-
vered with a ferrugineous cruft, and generally cryf-
tallized in opake triangular or polyangular columns.
When it is amorphous *, and breaks into large, thick,
fquare pieces, it is called trapp. When heated red
hot, and quenched in water, it becomes by degrees of
a reddifh brown. It melts without mixture into a
perfect flag. One hundred parts contain fifty-two fiii-
ceous, fifteen argillaceous, three calcareous, two of
magncfian earth, and twenty-five of iron. Bafaltes

* Not of a regular form,

fometimes

Chap. 17.] 'Bajaltes. 107

fometimcs is found in large columns with convex
and concave articulations, fo as to referable an artifi-
cial ftrudhire : of this kind are the bafaltic pillars in
Ireland, called the Giant's Caufeway.

Bafaltes has always, till very lately, been confidered
as a volcanic product ; and in corroboration of this
opinion it is -aiTerted that glafs, in cooling, has been
known to affume the regular bafaltic form. Sir Wil-
liam Hamilton remarked, both in Sicily and Naples,
tnat fuch lavas as have run into the fea are either
formed into regular bafaltes, or have a great tendency
to that form. Mr. Kirwan, however, in the laft edition
of his Elements of Mineralogy, takes confiderable pains
to controvert 'the common opinion. His principal ar-
guments to prove that bafaltes are formed by water,
and not by fire, are the clofenels of their textures,
fince they are quite free from the cavities which are
numerous in all other volcanic products, and their
containing mild calcareous earth, which could not have
been the cafe if they had been fubjected to fuch a
degree of heat as to have reduced them to a ftate of
fufion. Bafaltes alfo contain zeolites in fome in-
ftances, which muft have loft the water combined with
them, if they had been fubjected to much heat. In
bafaltes there is no appearance of vitrification, which
they muft have had if they had cryftallized from a
ftate of fufion. Bafaltes are alfo frequently found, not
only at a diftance from volcanoes, but mixed and fur^
rounded with ftrata, which have evidently derived
their origin from water. For inftance, their fubftance
fometimes pafles gradually into argillites and fand-
ftones. Mr. Kirwan feems at a lofs to account for
the peculiar fhape of bafaltes ; but this is equally dif-
ficult on the principles of either theory. He mentions
an inftance, however, of a ftone cracking into pieces

of

icS tferra Puzzolana. [Book VI.

of a fimilar figure. On the whole, Mr. Kirwan thinks
it much more probable that bafaltes furnifh the mate^
rials of volcanic products, than that they themfelves are
of volcanic origin.

IV. TERRA PUZZOLANA or Terras, is a volcanic
production, of a grey, brown, yellowifh or blackilh
colour, loofe, granular, or dufly and rough, porous
and fpongy, refembling a clay hardened in the fire,
and then reduced to a grofs powder. Its mod diftin-
guifhing property is, that when mixed with about one-
third of its weigHt of lime and water, it hardens very
fuddenly, and forms a cement which is more durable
in water than any other. Its indurating power fcems
to arife from the dry ftate of the half-baked argilla-
ceous particles, which caafes them to imbibe water
very rapidly, and thus the deficcation of the calcareous
earth is accelerated. It is found not only in Italy, but
alfo in France, in the provinces of Auvergne and Li-
moges, and alfo in England ancl elfewhere. Accord-
ing to Bergman's analyfis, one hundred parts contain
from fifty five to fixty of filiceous earth, nineteen or
twenty of argillaceous, five or fix of calcareous, and
from fifteen to twenty of iron.

Chap. 1 8.] [ 109 ]

CHAP. XVIII.

METALS.

Ijes of Metals. — Their Properties. — Weight, Opacity, Mattealil:'-?,
Ductility, FuJibility.—Mix 4uith each other. '-'Their Inflammabilitf.
— Calcination. — Entire and Semi-metals. — PerfeS and imperfta,
— Natural Hijiory of Metals. — Working of Mines.— AJ/~aying.-—
Smelting.-* "Union <voith Acids.— -Ariion of other Subftances on .Ml?-
t«!s.

METALLIC fubftances are valuable for their
durability, their capacity of affuming and re-
taining all forts of forms and impreflions; the clofeneis
of their texture, which renders them capable of polifh j
the firm cohefion of their particles, which renders them
highly proper for utenfils, where great ilrength is
required to be combined with moderate bulk. Several
of the metals are alfo highly ufeful as medicines.

The firft and moft obvious property of metals is
their remarkable weight, in which they exceed ail other
"bodies. By this circumftance they are diftinguifhed
from earths ; the Hghteft of metals, which is tin, being
feven times the weight of water, whereas the heavieft
earth is only between four and five times the weight
of that fluid.

Metallic fubftances are by far the mod opake of
all bodies. The moil opake ftone divided into thin
plates, ha,s more or lefs of tranfparency, whereas gold
is the only metal which admits of being reduced to
fuch a degree of thinnefs as to afford the fmalleft
perceptible tranfmiffion of light. Gold in leaf, which
is about -i-roV^-B- Part °^an inc^ ^n thicknefs, tranfmits
light of a lively green colour •, but filver and brafs leaf

are

no Malleability of Mel ah. [Book VI.

are perfectly opake. The opacity of metallic bodies
renders them exceedingly proper for reflecting the
rays of light, as no bodies poffefs this property in fo
eminent a degree. Thus we obferve that ghfs reflects
objects very imperfectly, imlefs coated with metal, as
in looking-glalTes. The capacity of reflecting light
depends on the degree of polifh and the whitenefs of
furface, confequently white metallic fubftances reflect a
greater quantity of light, and are more brilliant, than
thofe which are coloured.

A property which feems to belong exclufively to
metals, and yet not to all of them, is malleability. This
confifts in a capacity of having their fubftance ex-
tended, and their furface increafed, either in breadth
or length, without being liable to fracture. The
capacity, however, of being extended in length and
breadth is not exactly the fame, for metals which
admit of extenfion under the hammer cannot always
be drawn into wire, which property is diftinguifhed
from the other by the term ductility. Beating always
reduces metals to a (late of rigidity and brittlenefs.
To remedy this, the metals are generally heated red
hot, and cooled again flowly j in this cafe their mal-
leability will be increafed, and this is called annealing
them. Crammer fays, that if gold is annealed in this
manner the leaf will be opake, and that the tranfmif-
lion of light through ordinary gold leaf depends on
fmall cracks and flaws in the metal. If this afiertion
is true, it will in a great meafure eftablifli the perfect
opacity of metallic fubftances. Metals, when ham-
mered, give out a degree of heat, and at", the fame
time become brittle ; and the only methoc] of reftoring
their malleability is to expofe them to the action of
heat, and to fiiffer as much of this as poffible to fix
idelfin their fubftance, by cooling them gradually.

From

Chap. 1 8.] FuftWty of Metals. 1 1 1

From thefe facts it is probable that the malleability of
metals, as well as fluidity and elafticity in general, de-
pends on the particles of bodies being kept at a dif-
tance by the prefence oflatent heat.

Metals are of all bodies the beft conductors of elec-
tricity.

Metals are fufible by heat, and one of them (mer-
cury) is well known to exift in a ftate of fufion in the
ordinary temperature of the atmofphere. The par-
ticles of metals have a remarkably ftrong attraction for
each other, which is evinced by fmall portions of metal,
when in a ftate of fufion, having a tendency to aflame
a globular form.

Moft metals will uniformly mix in all proportions
with each other ; the fpecific gravities, however, of
thefe compounds is fcarcely ever fuch, as would be
mathematically deduced from the fpecific gravities
of the metals employed, on the fuppofition of their
junction by fimple contact. Mixtures of metals are
more fufible than might be expected from the degree
offufibility of their component parts, and are therefore
conveniently ufed as folders.

It is found that metals which, after having been fufed,
are fuffered to cool gradually, evince a tendency to
aiiume a regular figure, and to eryftallize in general
in an octahedral form.

Metals, in their fplendid or reguline * ftate, have a
confiderable attraction for oxygen, and are in this re-

* This is the ftate in which metals ufually appear when
wrought. The ftate of a calx or ore is eflentially different, they
then appear like coloured earthy fubltances.

The name rrgulus was given by the fanciful alchemifts to the
metallic button, found in the bottom of the crucible after an aflay,-
from the idea that this button contained gold, which they called the

king of metals.

4 fpect

i T 2 Cakes cf Metals. [B ook V t

fpect nearly allied to the inflammable fubftances. Iron
burns with a bright flarne when heated to a certain
degree, and immerfed in vital air; and a mixture of
tin and nitre produces a violent deflagration. Zincv
when heated and acted en only by common atmo-
ipheric air, burns with a bright and vivid flame like
phofphorus. It is remarkable that mixtures of metals
calcine more eafily than the metals in a feparate {late.
Thus a mixture of lead and tin, neither of which,
when feparate, afford heat and light, in their mixture
produce both, and the calcination is remarkably rapid.
From the addition of oxygen the weight of the calx
is greater than that of the quantity of the metal from
which it was produced. In fome metals, however, the
attraction for oxygen is fo weak (as is the cafe witli
the finer metals) that it is only by particular procefles
that they can be combined with it. Metals united
with oxygen lofe their fplendor, malleability, and
texture, and are denominated calces.

According to the old chemical theory, the calx of
a metal was deemed a fimple fubftancej and was called
the earth or ban's of a metal ; and it was fuppofed that
this earth, united with phlogiflon, conftituted the
metal in its perfect ftate. It is now, however, very
fatisfactorily proved, that the metallic ftate is the
more fimple, and that the calx is a combination of the
metal with oxygen. Metals are reduced from the
calciform to the reguline or metallic ftate, by heating
them in contact with fubftances which have a ftronger
attraction for oxygen than themlelves, as charcoal, tal-
low, &rc.

Metals which are malleable are called entire metals j
and thofc Yv'hich are brittle, ferni-metals. Metals arc
alib diftinguifhed into perfect and imperfect. The
perfect are fuch as are not calcined by being heated in

contact

Chap. 1 8.] Perfect and imperfeft Metals, &t. 113

contact with air, and are three in number, filver, gold*
and platina : the other metals are calcined in thofe cir-
cumftances, and are called imperfect. It will eafily
be underftood that thefe differences merely indicate
different degrees of attraction for oxygen ; and as in
this refpect, as well as in regard to malleability, there
are numerous gradations among the metals, it will
be neceffary to treat feparately of each metal as a
diftinct fubftance. I (hall begin with fuch metals as
have mod refemblance to the earths, and are there-
fore called femi- metals, and conclude with thofe which
have the metallic properties in the higheft perfection.

Thofe metallic bodies with which we are at prefent
acquainted} and which we can reduce to the metallic of
reguline (late, are the following feventeen :

j. Arfenic.

2. Molybdeha.

3. Tungftein.

4. Manganefe.

10. Iron. 1 -3

11. Tin. ! j|

12. Lead. \.

13. Copper.

5. Nickel. 14, ?vlercury,

6. Cobalt. 15. Silver.

7. Bifmuth.
8i Antimony.

1 6. Gold.

17, Platina,

9. Zinc.

Of thefe the nine firft are called ferni-metals* from
defeft of malleability; the five following imperfect
metals, from their being calcineable by heat and air 9
and the three laft, perfect, from their capacity of re -
fiMing the action of heat and air without change.

It is neceflary, however, to remark, that to the above
lift of nine, late difcoveries have added four new femi-
metals, viz. uranite, fylvanite, titanite, and mena-
Chanite, of \vhich I mall afterwards treat in a diftinct
chapter.

Metals exift in a (late of nature in four different
forms.

VOL. II. I i. The?

H4 6rss of Metals. [Book VI,

1. They are found in a native ftate of purity, with
all the metallic properties. Gold is always found in
this ftate ; filver, copper, mercury, bifmuth, and ar-
fenic often -, iron feldom j and lead, zinc, and rcgulus
of antimony ftill more rarely.

2. Metals are found in the (late of earth or calx,
without the metallic afpect, and often refembling
ochres.

3. The common ftate, however, in which metals
are found is that of ores. In this ftate they are either
combined with fulphur or with fome metal, the rnoft
common of which is arfenic *.

4. The laft ftate in which metals are found, is that
of a combination with feline hibfl nces, and almoft
always acids. The vitriolic acid is moft frequently
found combined with metals, viz. zinc, lead, copper,
and iron. The carbonic acid is alfo a common mine-
ralizer, and the arfenical and phofphoric acids have
likewife been diibovercd in combination with me-
tals.

Metallic fubftances are more commonly found in
mountains than in plains, and almoft always in fuch
mountains as form continued chains. It is in the
ilraiified mountains that metals moft abound, where
the inclination of the ftrata, in confequence of the
convulfions of nature, brings a variety of fubftances
into view, which muft otherwife have been for ever
concealed beneath the reach of human inveftigation.
There are entire mountains which ccnfift of iron ore,
but in general the metallic part of a mountain is very
inconfiderable in proportion to the whole. The ores
ibni-j times run parallel to the ftony^ ftrata; the layer
.on which the ore is placed is called the bed or floor

* In this and the following ftate they are faid, in technical Ian-
gunge, to be mineralized; tha,. is combined with Tome other mi-
neral fubflar.cc.

of

Chap. 1 8.] Mines. ii<j

of the mine ; the other which covers it, is called the
roof. Sometimes, however, the metallic ftrata, which
are always more irregular than the other ftrata of which
the. mountain is compofed, interfect the bodies which
furround them in a variety of directions. The metal-
lic ores are accompanied with ftony matters, which
feem to have been formed at the fame time. Thefe
ftone are ufually quartz and fpar; they are called the
rider or matrix * of the metal, and muft neither be con-
founded with the mineralizing fubftance which is inti-
mately combined with the metal, nor with the general
mafs of ftone, of which the mountain containing the
metal is compofed. It is obferved that the vegetables
which grow on metalliferous mountains are dry, the
trees fmall, fmuous, and deformed, and the fands often
exhibit metallic colours. Mineral metallic fprings
are ufually found in the vicinity ; by the examination
of which, and of the fands over which they flow, &
tolerably accurate judgment may be formed of the
metallic contents of the neighbouring ftra'::1. When
metallic veins appear at the furface of the earth, the
ground may be broken into with great probability of
advantage, and the boring inftrument, by bringing up
the jubilances which compofe the internal parts of the
mountain, together with the metallic minerals, ferves
to fhew their quality, as well as the reflftance which
may be expected in digging.

Before a metallic vein is wrought with a view to
profit, it is neceiiary to afccrtain the proportion of
metal contained in it, and this is called aftaying. In
thefe fmall trials the fusibility of the mafs is inereafed
by the addition of three times the quantity of the black
flux, which is made by burning together two parts of

* So called from its frequently inclofiug the ore. The fparry
matters are alio {bmetimes called by ir.ineralogifts gangues.

I 2 tartar

n6 4£y*>tg of Ores. [Book Vf/

tartar with one of nitre. The alkali of this compound
increafes the fufibility of the (tony matter mixed with
the ore, and confequently affords the metal an oppor-'
tunity of fcparating from it ; while the charcoal con-
tained in it, and which proceeds from the impurity of
the tartar, abftracts the oxygen of the ore, and reduces
the metal to a reguline form.

When the operation has been properly performed,
the metal, or regulus, is found in the form of a button
at the bottom of the mafs, and being weighed mews
the proportion of metal contained in the ore.

This method is ufed in reducing fmall quantities, as
in afTaying of ores, but would be too expenfive in large
operations. In this latter cafe it is cuftomary to mix the
ores or calces with the fuel, but to let as little air as
pofllble pals through k, as this would tend to re-calcine
ihe*metal. To prevent this effect, a particular fort of
furnace is employed, in which charcoal is chiefly ufed.

It frequently happens that the fame minerals contain
the perfect metals mixed with the imperfect; thefe are
feparated both in the fmall and large way by heating
the mixed mafs in contact with air. By this operation
the imperfect metal is reduced to a calx, and leaves
the perfect metal in a ft ate of purity. If the remain-
ing metallic matter is ftill a compound, and contains
two of the perfect metals, thefe are feparated by ex-
pofing them, with as large a furface as poffibie, to the
action of a menftnium, which has the property of dif-
folving one of them without the other.

There is alfo a method of aflaying in the humid
way,, by fubmitting the ores to the action of different
icidsj but this is not fo practicable as the other.

In the extraction of metals in the large way, the ore
is pounded, wafhed, roafted, imelted, and refined. By
pounding, the deny matters are feparated from the
metallic, and the whole being then walhed on inclined

planes'

Chap. 1 8 .] Smelting cf Metals-. i 1 7

planes or tables, the ftony matter being lighter is
wafnecl away, while the metallic remains behind. The
ropfling or burning is intended to expel the volatile
matters. Ores which contain much fulphur muft be
roafted in the operi air, but fuch as contain bur little
may be roafted in the furnaces which afterwards ferve
to fufe them. Some ores are fufible alone, others re-
quire to be -mixed with different fluxes. The methods
ct refining metals are extremely various, and depend
en particular chemical affinities, which will be men-
tioned under the head of each metal.

The falts, and of them the acids in particular, have
great effect on metals. Metals unite with acids into
compounds, many of which cryftallize. The corro-
fivenefs of the acid is abated by its union with the
metal, but not in fo great a degree as by its union with
the alkalies or earths. Neither is the point of fatnra-
tion fo well marked in the union of an acid with a
metal as with an alkali. The fame acid may, in
many cafes, be united to the fame metal in different
proportions; when the acjd is in excefs the mafs is
deliquefcentj, when it is deficient k ieems to produce*
little other effect on the metal than to deftroy its tex-
ture, and reduce it to a friable and earthlike (late.

Every metal, however, is not difpofed to unite
with every acid, though fome unite with all; others
with only one acid. The order alfo-in which the acids
attract the metals is different from that in which they
attract the alkalis. Metals attract the muriatic acid
mod ftrongly, next the vitriolic, and lad the nitrous.
Metals which diflblve in the fame acid differ very
much in the force with which they adhere to it, fo that
they may be employed to precipitate one another.
Thus, if we add to the folution of filver in aqua-fortis,
{juickfilv-er, it precipitates the filvcr ; copper, the
I 3 quickfilveri

n8 A ft ion of Acids en Metals. [Book VI,

quickfilver ; iron or lead, the copper; and zinc, vu ;h
precipitates thefe, may itfclf be precipkatcd by an
alkali.

The folution of metals in the acids is attended
with the efcape of an elaftic vapour, and . an effer-
vefcence *. This appearance is proved to arife from
a decomposition either of the acid or the water, and
the elaftic fiuid differs in different cafes, according to
the fource from which it derives its origin ; when it
arifes from the decompofition of water, it is hydrogen
or inflammable gas, when from that of the nitrous
acid, nitrous gas, &c. Before the metal can be dif-
folved, it is neceffary that it fhould be oxygenated ;
and therefore when its attraction is fufficientiy ftrong,
it decompofes the acid or the water, by abftracting
their oxygen. It has been already remarked, that the
muriatic acid has the ftrongeft attraction for metals,
and the nitrous lefs than either that or the vitriolic.
From merely obferving the action of thefe acids on
metals, however, a different concluGon might be
drawn, for the nitrous acid acts with violence and
rapidity in comparifon with the other two ; and the
muriatic, when in its pureft ftate, has the leaft action
of the three.' This feeming inconfiftency depends on
the different degrees of attraction which the bafes of
the different acids have for oxygen. The reafon, there-
fore, why fome metals cannot be duTolved in particu-
lar acids, is, that they have not a fufficiently ftrong
attraction for oxygen to decompofe the acid. If we
feparate a metal from an acid by any fubftance which
is not capable of depriving it of oxygen, we always

* This was formerly adduced among the proofs for the exift-
cnce of phlogifron, which, united with a fmall quantity of the water
or acid, was iuppofcd to conllitute this elaftic fluid, at the fame
;ime that the metal, by its lofs, \vas deprived of its fplendour, £c.

obtain

Chap. 1 8 .] Aftion of Light and Heat on Metals. \ 1 9

obtain it in a calcined ftate. Thus gold, if'precipitated
from its folution in aqua regia by an alkali, is a calx ;
but if precipitated by any of the inflammable lubftances,
as aromatic oils or fpirits of wine, or by another metal,
it appears in the metallic form. If metals are calcined
•previous to being united with acids, they produce no
efcape of gas, becaufe being already furnifhed with
oxygen, they have no tendency to decompofe the
acid.

Light appears to alter the colour and brilliancy of
fome metallic matters, independently of the action of air;
for when expofed to light in tranfparent vefiels well
clofcd, they become tarnifhed, and lofe their metallic
brilliancy.

Heat applied to metals produces no other effects
than'expanfion and fufion, if the air is completely ex-
cluded, unlefs carried to fuch a degree as to volatilize
them ; but even in that cafe, when the heat ceafes to
act, they return to their original ftate. Metals, on be-
ing converted into vapour, boil like other fluids, and
even gold and filver are capable of this ftate when
acted on by a large concave mirror.

Moft of the combuftible bodies acton metals. In-
flammable gas gives them a deeper colour, and is ca-
pable of reducing fome of them to the metallic ftate.
Sulphur, and its combinations with alkalies, called
hepars, act powerfully on metals.

From what is hitherto known of metals, there is
every reafon to believe that they are fimple fgb-
ftances.

] [Book VI,

CHAP. XIX.

ARSENIC.

Natural Hilary of Arfenic. — Mode of reducing it to the metallic Form..
—White Enamel. — Or piment.— Realgar. — Its Ufe in Medicine,— ~
A dreadful Polfon ; bow to detett it in the Body. — A Remedy for the
Pcifon of Arfenic.

ARSENIC is often found native, in black heavy
maffes, but not very brilliant. It has fome-
times the metallic luftre, and reflects the colours of
the rainbow; in its fracture it is more brilliant than at
its furface, and feems compofed of a great number of
fmall fcales. Native arfenic is very eafily known,
when it has the metallic brilliancy and fcaly texture.
It is, however, more frequently found in the form of
a powder, or, in chemical language, of flowers *, or
mixed with certain earths. Cobalt ores contain much
arfenic, and that which is commonly fold is brought
chiefly from the cobalt-works in Saxony. The ore is
thrown into a furnace, refembiing a baker's oven, with
a flue or horizontal chimney, nearly t\vo hundred
yards long, into which the fumes pafs, and are con-
denfed in. the form of a grey or blackifh powder.
This is refined by a fecond fublimation in clofe vef-
fels, with a little pot afh to detain the impurities. As
the heat is confiderabie, it melts the flowers into thofe
white cryftalline mafies which are met with in com-
merce.

The regulus is obtained from this fubftance, which

* Flowers, in the old chemical language, means thofe matters
which by heat are raifed into the neck of a retort in the form of
very fine powder, as flowers of fulphur, .&c. — I; was, probably,

originally /car,

Chap. 19.3 Regtilus of Arjenk. \i\

is a calx of arfenic, by heating it with one-tenth of its
weight of charcoal, or of any unctuous matter. The
mixture is put into a tall veffel, and a gradual and
gentle heat applied to the lower part of it, while the;
upper is kept cool by the air. The arfenic, when
nearly ret hot, parts with its oxygen, and rifes to the
upper part of the vefiel, where it is condenfed in the
metallic form. To give it, however, its perfect me-
tallic fplendour and opacity, the fublimation mi)ft be
repeated.

The regulus of arfenic is of a bright yellowim white
colour, very ponderous and friable, and fubject to
tarnifh'and become black on expofure to air. If heat
is applied to the regulus in contact with air, it is
volatilized before it melts, and is at the fame time
imperfectly calcined. The fumes are dangerous, and
have a ftrong and offenlive fmell, refembljng that o,f
garlic.

The white calx of arfenic is fo far in a faline (late
as to be foluble in eighty times its weight of cold, or
fifteen times that of boiling water. When diftilled
with the nitrous acid, it decompofes that fluid by de-
priving it of part of its oxygen. The arfenic, by this
addition of oxygen, is reduced to the ftate of an acid
lefs volatile than either the regulus or calx, but retain-
ing the form of a white concrete fubftance. The oxy-
genated muriatic gas likewife reduces arfenic to the
Jtate of an acid.

Arfenic readily melts with other fubftances fo as
to form glafs, and even promotes their fufion. At
firft it always renders the glafs milky, but by a con-
tinuation of heat the arfenic evaporates, and the glafs
becomes quite tranfparent. It is an ingredient in the
white enamel dial-platts j and it forms thofe white
Spirals which are common in the flalks of wine-
gla/Tes,

Sulphur

122 Poifonous Nature of Arfenic. [Book VI.

Sulphur unites readily with arfenic into a compound
more fufible than the arfenic itfelf. Orpiment is a
combination of arfenic and fulphur, of a yellow co-
lour. It is found naturally in the earth, generally of
an irregular form, and compofed of Ihining flexible
laminse. Its fpecific gravity, according to Kirwan,
is 5,315, who alfo aflerts that it contains one- tenth
part of its weight of fulphur. The fame author men-
tions, that realgar, or the red combination of arfenic
and fulphur, contains fixteen parts of fulphur in the
hundred, and is of the fpecific gravity of 3,225.
Chaptal, however, obferves that the difference between
realgar and orpiment does not confift in the propor-
tions of fulphur, nothing more being neceffary in order
to convert orpiment into realgar, .than expofure to a
ftrong heat. The violent action of arfenic on the
animal machine is much abated by combination with
fulphur. Common white ar'enic has fomctimes been
fuccefsfully ufed in dofes of one-twelfth or one-fix-
teenth of a grain. Received, however, in any confi-
derable quantity into the body, it produces drynefs of
the mouth, heat in the throat, excruciating pains in
the bowels, attended fometimes with vomiting of
blood, cold fweats, &c. On direction, the bowels
are found inflated an'd corroded. Many black and
livid fpots appear on the ftomach and fmall inteftincs,
fometimes gangrenous. But thefe figns are not
altogether to be depended on. Some of the arfenic is
frequently found, and may be eafily diitinguifhed.
The powder is heavy, and eafily feparates from the
lighter contents of the bowels, by waftiing with water;
the arfenic always falling to the bottom. A very little
of this is fufficient to give the fmell of garlic, and tinge
copper white, if heat is applied to it.

It v/as formerly ufual to- give mucilaginous drinks,
or milk or miid oils, to perfons poifoned by arfenic.

But

Chap. 19.3 Antidote for the Poijm of Arfenlc. 123
But Navier, a phyfician of Chalons, who has made
experiments to afcertain the beft remedies againtl the
poifon of arfenic, has difcovered a fubftance which
combines with it in the humid way, and deftroys, in
a great meafure, its caufticity. This fubftance is the
calcareous or alkaline liver of fulphur, which is ftill
better adapted to the intention, when it holds a fmall
quantity of iron in folution. When this martial hepar
is poured into a folution of arfenic, it is decompofed
without emitting any fmell, beeaufe the arfenic com-
bines with the fulphur, and forms orpiment, and at
the fame time unites with the iron. Navier prefcribes
a dram of the liver of fulphur in a pint of water, of
which he directs a glafs to be taken at a time ; or five
or fix grains of dry liver of fulphur may be given in
pills, a glafs of warm water being given after each
pill. When the firft fymptoms are diffipated, he
recommends the fulphureous mineral fprings. Na-
vier likewife approves the ufe of milk, beeaufe it
diilblves the arfenic as well as water, but he condemns
the ufe of oils, which have not that property.

Arfenic mews a ftrong difpofition to unite with all
the metals except platina. By a mixture of it in its
ordinary ftate with copper, a metal is produced refem*
bling filver. It generally gives metals a white' colour^
and renders them brittle.

[Book VI,

CHAP. XX.

MOLYBDENA.

§j?ort Account of this Semi metal. — May le reduced to an Acid. — A
fcarce Mineral.

THIS is a mineral fubftance, which has till
lately been confounded with plumbago, but is
now found to be a combination of a particular me-
tallic fubftance with fulphur. It is of a blackifh colour,
and confifts of mining lamina?, which have a degree
of flexibility, fo as to be very difficultly reduced to
powder.

Molybdena reduced to its metallic form refembles
lead in colour and fpecific gravity, but is very brittle,
eafily calcined and volatilized, and will not mix with
lead when in fufion.

It differs from all other femi-metallic fubftances by
being nearly infufible in our furnaces ; it is probably
the impoflibility of reducing it to the form of a round
button, which induced Klaproth to fuppofe that Jie
had never brought it to its metallic date. By Mr.
Pelletier's account, however, it was evidently reduced,
and Mr. Hielm produced a flill purer and more
perfect regulus. In a red heat it calcines. When
in its reguline (late it gives no colour to borax. —
Molybdena, in this ftate, is called by Mr. Kirwan
molybdenite.

Molybdena is capable of being oxygenated fo far
as to become an acid, in which ftate it is a concrete
body, white and pulvcrulcntj refembling chalk. This

acid,

Chap. 20.] Molyldena. 125

acid, heated with fulphur in a particular manner, is
capable of being converted into a fubftance in every
refpect the fame as native molybdena.

This mineral is fcarce. It is diftinguimed from black
lead by a more mining, fcaly appearance -, and it marks
paper with a more brilliant ftroke.

[ 126 ] [fcookVl,

CHAP. XXL

T U N G S T E I N.

T&e Ore of Tungjtein confounded <witb that of Tin. — Where found.-—
Mode of reducing it to the reguline or metallic State.

TUNGSTEIN or wolfram is a particular
metal, the ore of which has frequently been
confounded with that of tin. The fpecific gravity
of this ore is to water as fix to one ; in its form of
cryftallization it refembles the garnet, and vanes in
colour, from a pearl white to yellow and reddifh ; it
is found in feveral pa1 rts of Saxony and Bohemia. The
mineral called wolfram, which is frequent in the
mines of Cornwall, is likewife an ore of this metal;
in all thefe ores the metal is oxydated ; and in fome
of them it appears to be oxygenated to the ftate of
an acid, being combined with lime into a true tungftat
of lime*.

The calx of this metal cannot be obtained free from
the bodies with which it is united, without a particular
procefs, which confifts in the alternate application of
volatile alkali and marine acid, and the fubfequent
addition of die nitrous acid, as long as red fumes are
produced. This calx or imperfect acid has the co-
lour of brimftone, and 7s fcarceJy foluble in water. By
being fubmitted in a crucible with charcoal, to a ftrong
heat, a regulus of tungftein, called tungftenite by late
mineralogifts, may be obtained, which is a brown mafs,
confiding of a congeries of metallic globules internally of
a fteel grey, and which again becomes yellow by calcina-

* Lavciiier's Chemiftry.

* tion.

C hap. ax.] Regiilus of fungftein. 127,

tion. The regulus is not acled on by the vitriolic and
marine acids ; the nitrous' acid, however, and aqua-
regia, aft on it, and by oxygenating it reduce it 'to its
calciform ftate.

M. Lavoifier recommends the following procefs for
obtaining the calx of tungftein : i1"' 'ix one part of ore
of tungftein with four parts of mild vegetable alkali,
and rnelt the mixture in a crucible, which ought to
be of platina ; then powder, and pour on twelve parts
of boiling water ; add pale nitrous acid, and the tung-
ftenic acid precipitates in a concrete form. After-
wards, to infure the complete oxygenation of the
metal, add more pale nitrous acid, and evaporate to
drynefs, repeating this operation as long as red fumes
are produced from the acid.

In the ftate of yellow calx it has the following pro-
perties: it is perfectly infipid and infoluble in water;
if triturated in water it limply diffufes through it like
an emulfion, and takes fome months to depofit from
it. If volatile alkali is poured on it, it whitens, which
inftantly diftinguifhes it from the yellow calx of ura-
nite, which will fhortly be mentioned.

128 5 [BtfokVL

CHAP. XXH*

M A N G A N E S E.

Datura! Hiftory cf Manganefe. — Its Ejj'tJls on Glafs.—Regulus or Me*
tal. — Black Wad, — IVlanganefe contained in Vt^etablcs. — U/es in
the Arts*

9" R S HIS metal is almoft always found in the flate
JL of calces, which vary much in colour and ap-
pearance; they are white, blue, yellow, red, dark
green, arid black, according as they are united with
more or lefs oxygen, or contaminated v ith foreign
fubflances. The darker coloured the ores, the more
oxygen they may be fuppofed to contain, as any
procefs which deprives them of this principle always
renders them paler. Manganefe is alfo found cryf-
tallized in a vaTiety of forms. Many naturalifts,
judging by their colour, and the ochry * cruft with
which they are often furrounded, have ranked the
calces of manganefe among the iron ores. The black
calx of manganefe gives a violet, purplifh, and fome-
times a reddifh tinge to tranfparenc glafs ; but when
added in a fmall quantity to that which has a blueifh
Or greenifh caftj it produces only a flight dulkineisi
tvithout a predominancy of any colour.

The regulus of manganefe is ver/ difficultly ob-
tained. Its colour is a dufky white, but its mafies
are irregular and uneven from imperfect: fufion. Its
fracture is bright and fliining, but it foon tarnifhes and
becomes blackim on expoiure to air. When pul-
verifed it is always magnetic, though it has^not this
property in the mafs. If expofed to air, particularly

* Ochre being an iron Ore*

in

Chap. 22.] Manganefe found in Vegetables. 129

m moift weather, it foon crumbles into a blackifh brown
powder, which is fomewhat heavier than the regulus
from which it was produced.

The calces of manganefe retain their oxygen fo
weakly, that part of it may be expelled by the appli-
cation of a ftrong heat. They alfo part with their
oxygen to unctuous oils. If half a pound of that ore
of manganefe called black wad is well dried before the
fire, afterwards fufFered to cool for about an hour, and
then mixed with two ounces of linfeed-oil, fmall clots
will be formed, and in little more than half an hour
the whole will gradually grow hot, and at laft burfl
into flame.

Manganefe feems to be contained in the afhes of
molt vegetables, and to it the blue or greenim colour
of calcined vegetable alkali is owing. If three parts
of alkali of tartar, one of fifted ames, and one-third of
nitre, are melted together, they form a dark green mafs,
which being diflblved in water, affords a beautiful green
folution j this being filtered on the addition of a few
drops of vitriolic acid becomes red, and after a few
days a brown powder is feparated, which has all the
properties of manganefe.

The vitriolic, nitrous, and marine acids diflblve the
regulus of manganefe in the ufual ways. The black
calx is nearly infoluble. in the acids, unlefs it is deprived
of part of its oxygen by the addition of fome inflam-
mable or metallic fubilance. The marine acid, how-
ever, digefted with the black calx of manganefe, dif-
folves it without addition, in proportion as it lofes fome
part of its oxygen. The oxygen uniting with part of
the muriatic acid, renders it volatile, and converts it
into oxygenated muriatic acid. The permanent fo-
lubility of the black calx of manganefe in the acids,
depends on the acid, or fome fubftance mixed with the

VOL. II. K acid,

1 30 Wokt Colour of Glaft. [Book VI.

acid, abfiracting part of its oxygen. The manganefe
feparated from its folution in acids by alkalies, is in
the form of the white or imperfect calx, which, how-
ever, becomes black by being heated in contact with
• air.

In the dry way the calx of manganefe combines
with fuch earths and faline fubftances as are capable of
undergoing fufion in a ftrong heat. The violet co-
lour which it communicates to glals is liable to be de-
ttroyed by eombuftible fubftances. From this cir-
cumftance we may conclude, that the property of
colouring glafs depends on the calciform ftate of this
metal, and that it is loft when any body abftracts its,
oxygen and reduces it to a regulus.

Manganefe in its metallic form will not unite with
fulphur, but melts readily with moft of the metals.
Gold and iron are rendered more fufible by a due addi-
tion of manganefe, and the latter metal is rendered
jmore ductile.

Manganefe has hitherto been ufed chiefly by glafs-
makers and potters ; but the important difcoveries of
the effect of oxygenated muriatic acid, prepared by'
means of manganefe, in bleaching, will no doubt ex-
tend its utility to feveral other manufactories.

Chap. 23*3 t 131 3

CHAP. XXIII.

NICKEL.

Natural Hiftory of Nickel.— Metal hcnv obtaintd.—Detottates <witb
Nitre.— Has a fli'tng Repulfion for Silver, and Attraction for Su/~
pkur.—'A ufelej; Mineral.

f I ~A HIS metal derives its name from the mineral in
JL which it is contained. It is found united with
fulphur and arfenic. Its ores have a coppery red
colour, are almoft always covered with a greenifn grey
efflorefcence, and have been miftaken for ores of cop-
per. The cres of nickel often contain cobalt and
iron. Moft of the fulphur and arfenic may be driven
off by long continued roafting, and the occafional
addition of charcoal, which prevents the arfenic from
being rendered more fixed by calcination ; and the
green calx which remains may be fufed by the ftrongefl
heat of a fmith's forge, together with two or three
times its weight of black flux. By thefe means a
regulus may be obtained, which, however, is very far
from being pure, as it contains much arfenic, cobalt,
and iron. In this ftate it is of a white colour with a
tinge of red, and has a granulated texture. When this
metal is rendered more pure by treatment with ful-
phur, charcoal, volatile alkali, and nitre, it becomes
extremely infufiblc, lofes fomewhat of its reddifh tinge,
and acquires a confiderable degree of malleability.
Nickel may be freed from fulphur and arfenic, but it
cannot be accurately purified from cobalt and iron,
for it is considerably attracted by the magnet, and
gives figns of containing cobalt, after the utmoll pains
have been taken to obtain it in a pure ftate. It affords
K 2 a blue

1 3 2 Rsgulus of Nickel [Book- VI.

a blue folution -with volatile alkali, and in nitrous acid
its folution is of a full green.

From its magnetic property, nickel has been con-
fidered as a modification of iron ; and by its producing
a blue colour with volatile alkali, it has been fup-
pofed to be an alloy of copper with various metallic
fubftances. Chemifts, however, are now very gene-
rally agreed in confidering nickel as a diftinct metallic
fubftance.

M. Sage affirms, that when four parts of oil of vitriol
are diftilled with one part of the regulus of nickel irt
powder, the fulphureous acid paries over; the refidue
is greyim, and, being diffolved in diftilled water, pro-
duces the mofl beautiful green colour. The cryftals
obtained from this folution are foliated, and of the
colour of an emerald. According to M. Arvidfon, the
vitriolic acid forms a green fait, in decahedral cryftals,
with the calx of nickel.

This calx is eafily foluble in the nitrous acidj and
cryftallizes in rhombic cubes. According to M. Sage,
all the other folutions of nickel, or its calx, either
in the muriatic acid or in vegetable acids, are more
or lefs green. It has been faid, that the nickel con-
tained in cobalt occafions the fubftance known under
that name to produce a green colour with acids.
Nickel differs from cobalt in not being iepa rated from
acids by the addition of any other metal.

Nickel detonates * with nitre ; this detonation af-
forded M. Arvidfon a method of difcovering the
prefence of cobalt, which no other proof has rendered
fenfible. Nitre has likewife the property of augment-
ing the intenfity of the hyacinthine colour, commu-
nicated to glafs by the calx of nickel. The calx of

• Inflames, and explodes fuddenly.

nickel,

Chap. 23.] Its Repulfionfir Silver. 133

nickel, fufed with borax, likewife produces a hyacin-
thine colour. The calces of nickel are of a green
colour.

The moft remarkable properties of the regulus of
nickel are, a repulfion for filyer, and a ftrong attrac-
tion for fulphur. It has fo ftrong an affinity for ful-
phur, as to attract it from moft other metals.

Nickel combines by fufion with fulphur into a hard
mineral of a yellow colour, with fmall brilliant plates,
which, when ftrongly heated in contact with air, de-
flagrates and emits very luminous fparks, fimilar to
thofe afforded by iron when forged. Cronftedt informs
us that this metal is foluble in liver of fulphur, and
forms a compound refembling the ores of copper.
The fulphur can only be feparated from nickel by
repeated fufions and calcinations.

Cronftedt affirms that nickel forms, with bifmuth,
a brittle and fcaly regulus. Nickel has not yet been
Applied 4:o any ufe,

[ 134 1 [Book VI,

CHAP. XXIV.

COBALT.

. I Hijlory of Cobalt. — Analogy between this Metal and the blu&
colouring Matter of Vegetables. — Mode of ajjaying it.- — Mines of
Cobalt. — Smalt, or Ponvder Blue. — Ufes of Cobalt in the Arts. — •
Curious fympathetic Ink. — Changeable Landscape. — r Union ivith
cihir Metals.

COBALT has never been found native, that is,
in a metallic ftate, but is almoft always calcined
t>r united with arfenic, the arfenical acid, fulphur, iron,
vitriolic acid, &c. Minerals containing cobalt are
frequently of a pink colour, which arifes from the
pretence of arfenical acid, and this colour is deftroyed
by fire, in proportion as the acid is diflipated. When
united with vitriolic acid, it alfo is fometimes reddiftr :
the effect of acids on cobalt points out an analogy
between it and the blue colouring matter of vege-
tables.

To afTay cobalt ores, the operations of pounding,
wafhing, and roafling, muft be all employed. The
cobalt remains in a ftate of black calx, more or lefs
deep with refpect to colour ; this is mixed with black
flux and a fmall quantity of decrepitated fea-falt ; the
fufion is performed in a forge heat in a covered cru-
cible, which muft be (lightly agitated, to precipitate
the metal as foon as the fufion is complete. The me-
tallic button is fometimes found to confift of two dif-
tin£t fubftances, cobalt being uppermoft, and bifmuth
beneath ; a ftroke of the hammer readily feparates
them.

The

Chap. 24.] Smalt or Powder Blue. 135

The regulus of cobalt is of a whitifh grey or flcel
colour, hard, brittle, of a dull clofe-grained frafture,
and moderate fpecific gravity. It has about the fame
degree of fufibility as copper ; does not eafily become
calcined ; and its calx is of fo deep a blue colour as
to appear black. Cobalt expoied to heat does not
melt till it is well ignited. It appears to be very
fixed in the fire, and it is not known whether it can
be volatilized in clofe vefiels. If it is fuffejed to
cool flowly, it cryftallizes in needle-formed prifms,
placed one on another, and united in bundles, Cobalt,
melted and expofed to the air, becomes covered with
a dull pellicle, which is a calcination analogous to the
rufting of iron.

The richeft mines of cobalt are in Saxony. The
ore which is worked there in the large way contains a
confiderable quantity of arfenic, which is driven off by
heat, but ii collected in long channels of wood, and
preferved for fale, as was intimated before. After the
ore has been kept fome time in the furnace, there
remains a dark friable fubftance, which is the cobalt in
the form of a calx, and called zaffre. This is mixed
•with the ordinary ingredients of glafs, and melted with
a violent heat, fo as to produce the common blue
powder called fmalt, which is a pounded glafs. Some
of this is mixed with flints and alkaline falts, and
then fold under the name of, fapphire to the manufac-
turers of porcelain and common Delft ware, for ting-
ing their glazing blue.

Powder blue, or azure, is obtained by grinding
fmalt in mills, and afterwards wafhing it in water.
This laft operation is performed in a cafk filled with
water, and pierced with three openings at different
heights. The water of the uppermoft cock carries
K 4 out

136 Paftes in Imitation of Sapphire. [Book VI,

out the fined blue. The larger particles fall more
fpeedily, and the azure brought out by the water
of the three cocks forms the different degrees of
finenefs, known by the names of azure of the firft,
fecond, and third fires. Powder and flone blue, ufed
by laundrefies, is a preparation made by the Dutch
from the coarfe fmalt.

A fmall quantity of the calx of cobalt tinges glafs
of different fhades, according to the quantity ufed.
One grain of cobalt to feven thoufand of the glafs,
renders it very blue : hence the paftes in imitation of
fapphire are produced. Stained flint glafs is made by
fixteen parts of fand, eight or ten of pearl aft, and
metals in different proportions.

Cobalt diflblves readily in aqua-fortis, both in its
metallic (late and in that of a calx. If we take a folu-
tion of its calx in that fluid, and add a quantity of water
vto it, and then let it ftand a while, it turns red, and
on evaporation forms cryftals of the fame colour, and
by this it may be diftinguifhed from all other me-
tals. This folution forms a red fympathetic ink, which
appears on the paper by heat, and again difappears by
cold.

Aqua regia difTolves cobalt more eafily than the
muriatic, but not fo eafiiy as the nitrous, acid. This
folution is a celebrated fympathetic ink. If it is
diluted with a fufficienr quantity of water to prevent
its action on paper, and then ufed to write with, the
letters are invifible as foon as the clear folution be-
. comes dry ; but if the paper is held to the fire for a
fhort time, they appear of a fine green colour ; which
again difappears by removing it, and furTering it to
cool. If held to the fire too long, the green colour
becomes permanent. From thefe two inks a veiy
curious changeable lar,dfcape may be made. The

trunks

Chap. 24.] ' wp&thetfc Ink. 137

trunks of trees, houfes, &c. may be painted with com-
mon colours, fo as to reprefent winter. The verdure,
the fruits, and the flowers, may be depicted in dif-
ferent {hades of the two inks, On approaching the
fire the landfcape will gradually be changed from a
winter to a fummer fcene. The trees will begin to
fhoot out their foliage, and the flowers and the fruits
will, by degrees, aflume the appearance of maturity.
The vivid parts will again fade, on being removed
from the heat, and the landfcape refume the wintry
^fpecl.

It was formerly thought that the green colour pro-
duced by heat in the fympathetic ink of cobalt, arofc
from- the metallic fait being cryftallized, and afterwards
attracting a fufficient quantity of water from the cold
air to diffolve it, and caufe it to difappear j but it is
proved, that the marine fait of cobalt, diflblved in
water, affumes the fame colour when expofed to 3,
certain degree of heat.

The vitriolic acid in a concentrated ftate does not
diffolve cobalt without the affiftance of heat, when the
acid is decompoled, and comes over in fulphureous
fumes. The cobalt is in part calcined, and in part
converted into a cryftalline fait foluble in water, and
which may be precipitated by lime and by alkalies, in
the form of a rofe-coloured powder or calx. Diluted
vitriolic acid acts upon the calx of cobalt, and forms
the fame fait.

Cobalt unites with all the metals except filver, lead,
quickfilver, and bifmuth, but does not produce arty
remarkable or ufeful compound with any. It is fe-
parated from acids by zinc in the form of a dark-
coloured powder, but not by iron.

A mixture of nickel with the calx of cobalt very
much injures the colour which the latter communi-
cates

jjS Union cf Cobalt with other Metals. [Book VI.

cates to glafs. The following procefs is one of the
beft for feparating them when the cobalt is in con-
fiderable quantity : Saturate a folution of the roafted
ore in nitrous acid, and drop it into liquid volatile
alkali. The cobalt then is inftantly re-diflblved, and
affumes a garnet colour ; when filtered a grey powder
remains on the filter, which is the nickel. The
cobalt may be precipitated by any acid,

Chap. 25.] [ 139 ]

CHAP. XXV.

BISMUTH.

External Qualities of Bifmuth.— A powerful DiJJol-ver ofEarihs.^f
Pearl White, a pernicious Co/metic. — Curious Experiment. — A metal-
lif Compaction, which pielts in boiliug Water, — Various Uj'es of
Bifmuth in the Arts.

BISMUTH is extremely brittle, fo that it may
be eafiiy feparated, and even reduced to powder
by the hammer. When broken it exhibits at the
place of fracture large mining plates, difpofed in a
variety of directions. It is confiderably ponderous,
and is of a yellovvifh white colour; when in rhin plates
it is in fome degree fonorous. It is very fufible, and
melts at a temperature not exceeding 460° of Faren-
heit.

Bifmuth is fcarcely altered by expofure to air and
light. In clofed vefiels it fublimes without alteration ;
it cryflallizes the mod eafiiy of any metallic fubftance.
If bifmuth is kept in fufion in contact with air, its fur-
face becomes covered with a pellicle, which changes
into an earth-like matter of a greenifh grey or brown,
named calx of bifmuth. Nineteen drachms of bifmuth,
calcined in a capfule of glafs, afforded M. Baume
twenty drachms thirty-four grains of calx. Bifmuth
heated to rednefs burns with a fmall blue flame,
fcarcely fenfible. Its calx evaporates in the form of a
yellowilh fmoke, which condenfes on the furface of
cold bodies, into a powder of the fame colour, called
flowers of bifmuth. This powder owes its volatiliza-
tion only to the rapidity with which the bifmuth
burns 3 for if it is expofed in clofe veflels to fire, it melts
3 into

14° Pearl White. [Book VI.

into a greenifh glafs without fublimihg. Geoffroy the
younger obferved, that the flowers of bifmu.th, which rife
the laft, are of a beautiful yellow, refembling orpiment.

The grey or brown calx, the yellow flowers, and
the glafs, are nothing more than combinations of this
metal with the bafis of vital air, which are not redu-
cible without the addition of fome fubftance that
attracts the oxygen.

Calx of bifmuth is one of the moft powerful dif-
folvers or liquefiers of earthy bodies, or of the calces
of other metals, and gives a yellowifh tinge to glafles,
into the compofition' of which it enters. Bifmuth is
alfo readily calcined by nitre, but without detonation.
The alkalies have little effect on bifmuth ; when ap-
plied, however, in a cauflic ftate, they diflblve part of
the metal.

The vitriolic and muriatic acids do not act on bif-
muth, unlefs affifted by heat. The nitrous acid, how-
ever, diflblves it with great rapidity, and during the
folution copioufly emits denfe red vapours. This is
one of thole folutions from which the calx is moft
eafily feparated by water. On being dropped into
water a bright powder is depofited, called magiftery
of bifmuth. This is fuppofed to be the fame with
the fubftance called pearl white> well known as a cof-
metic; for when rubbed on the Ikin it gives it a white
fhining colour. But in reality all thefe metallic fub-
ftances ultimately darken the (kin, for a calx when long
expofed to the air, and the exhalations of animal bo-
dies, parts with its oxygen to the inflammable matter,
and afifumes a dark colour. Bifmuth, moreover, pof-
•fefles many properties in common with lead, and there
are fome inftances in which the external ufe of this
nas produced the worft effects.

Solutions of bifmuth are particularly affected by

fetid

Chap. 25.] Pernicious Effetts of Cofmetics. 141

fetid odours, which proceed from putrefying fub-
ftances. This feems chiefly to depend on the ful-
phureous particles which are exhaled in thofe proceffes,
and is illuftrated by a ftriking experiment. If charac-
ters are written with a folution of bifmuth on the firft
page of a book oT fifty leaves, and the laft page is
impregnated with a fmall quantity of the liquid liver
of fulphur, a fhort time afterwards the hepatic vapour,
carried by the air which circulates between all the
leaves, arrives at the other extremity of the book,
and converts the colourlefs characters marked on the
firft page into a deep brown. It is affirmed that the
hepatic gas pafies through the paper ; but it is fuffi-
ciently proved that the air carries the gas in this
manner from one leaf to another, fince the effect does
not take place when the leaves are glued together.
This experiment evinces, in the cleared manner, the
impermanency of the beautifying effect of the calces
of bifmuth.

The nitrous folution of bifmuth is without colour,
and when well faturated affords cryftals without eva-
poration. But by evaporation and cooling thefe cryf-
tals may always be obtained. The nitre of bifmuth
detonates feebly, and with reddilii fcintillations j after
which it melts and inflates, leaving a calx of a greenifii
yellow colour. This fait expofed to the air lofes its
tranfparency, at the fame time that the water of cryfbal-
lization is diffipated.

The acetous acid diffolves bifmuth (lowly, and in
fmall quantities.

Inflammable gas alters the colour of bifmuth, and
gives it a violet tinge. Sulphur unites with bifmuth,
efpecially with its calx -, in which (late it refembles
crude antimony. It unites with all the metals, except
zinc and regulus of cobalt, and takes away their mal-
leability

142 Compound which metis with little Heat. [Book V f .-

leability and ductility, and increafes their difpofition to'
calcine j it alfo increafes their fufibility, hence its ufe in
foldering lead and tin. If added to a mixture of lead
and tin, in certain proportions, it produces a metallic
compound, which retains the flate of fluidity in the heat
of boiling water.

Bifmuth is chiefly ufeful for mixing with tin to
produce pewter, rendering it harder, and better to be
caft into molds. It is alfo ufed in making printers'
types ; for by giving a greater tenuity to the fufed
mafs, it fits it for receiving a neater impreffion. An
amalgam for foiling glafs globules is made of ten parts
of mercury, two of bifmuth, and one of lead and tin.
It may be fubftituted inftead of lead in the art of cu-
pelling the perfect metals, becaufe, like that metal, it
has the property of flowing into a glafs which is ab-
forbed by the cupels.

Bifmuth is often found native. It is alfo found
united with arfenic, fulphur, iron, and fometimes in
a calciform flate. The fulphureous ore of bifmuth
is of a whitifh grey, inclining to blue ; it has the bril-
liancy and colour of lead ore or galena, and almoft al-
ways exhibits fquare facets, but it is never found in
fragments truly cubical. It is very rare, and is found
at Baftnas, in Sweden, and at Schneeburg, in Saxony.

Chap. 16.]

CHAP. XXVI.

ANTIMONY.

Natural Hiftory of Antimony. — Regulus. — Snow of Antimony. — Calci-
nation of Antimony. — Combinations with Acids; — Butter of Anti-
mony. — Antimonial Wine. — Ufes of Antimony in Medicine* — Flares,
Antimonii. — Glafs cf Antimony. — Crocus of Antimony. — Sulphur of
Aatifitsny. — Tartar Emetic. — James's Pov:der.

>nr^HE fubftance, which is commonly known by
JL the name of antimony, is a combination of that
metal with fulphur. This mineral is of a blackifh
grey, in brittle plates or needles, of various magni-
tudes, joined together in different forms. It is fome-
times mixed with other metals, particularly lead and
iron, and is very common . in Hungary, and in fome
of the provinces of France. From this ore the re-
gulus of antimony is feparated by fufion. The anti-
mony then forms a mafs of metal at the bottom of
the veflel, while the other matter becomes a fcoria
above it.

The appearance of antimony is bright, approaching,
when very fine, to that of filver. It is very brittle,
and it is compofed of oblong plates or laminse. When
melted it forms a fmooth mafs like other metals, but
upon breaking it, we find -the plated appearance on
the infide. The plated appearance depends on the
cryflallization, which begins at the part that firft
congeals. The regulus of antimony, which is prepared
for commercial purpofes, is cad into flat and circular
pieces, which have a cryftallization on" their furface, in
the form of the leaves of fern.

Jn fufibility antimony holds a middle rank, re-

quiring

f 44 Snow of Antimony. [Book VK

quiring a perceptible degree of red heat before if be-
comes fluid. In the fame degree it emits yapours
copiouQy if frefn air is admitted, which always pro-
motes the volatility of metals. If thefe fumes are
condenfed, they form a white powder. In particular
circumftances they cryflailize. They are, indeed, a
perfect metallic calx, to which the names of argentine*
and fnow of antimony, have been applied. This fub-
ftance is fo highly charged with the oxygenous prin-
ciple, as to be ibluble in water, and 'to approach to the
nature of an acid.

To calcine antimony by heat and air alone, let the
metal be powdered, then lay it on a broad mallow vef-
fel, and apply heat not fufficient to convert it into
fumes. This operation cannot be well performed,
tmlefs the antimony is in a ftate of minute divifion, fo
as to prefent a large furface to the ai/. The procefs
muft be conducted with caution at the beginning, on
account of the fufibility of this compound of fulphur
and antimony ; but in proportion as the fulphur is dif-
fipated, the remainder becomes more refractory, and
the fire may be raifed to fuch a degree as to make
the veffel in which the antimony is contained red hot.
The furface of the metal becomes at firft tarnifhed,
and foon afterwards it is changed into an earthy pow-
der of a dufky colour, which, by continuance of the
procefs, becomes white. Thefe calces have a different
degree of fufibility according to the degree of cal-
cination. When little calcined a ftrong heat converts
them into a glafs of an opake or black colour. When
further calcined more heat is required, and the glafs
is a deep yellow. When calcined to whitenefs, the
moft violent heat will not melt them without the addi-
tion of borax, and the mafs is then of a pale yellow*
Here we obfcrye the effect of the prefence of oxygen

in

Chap. 26.] ARion of Adas on Antimony. 145

in rendering this calx lefs fufible, and depriving it of
colour. Thefe calces may be reduced, but mod
readily when little calcined, by adding an equal
quantity of black flux, or one-fourth of charcoal
or foap.

The foffil fixed alkali brings antimony neareft to
the (late of the perfect metals. For this difcovery we
are indebted to Margraff, who melted'two ounces of
regulus of antimony with one of foffil alkali. He
repeated the fufion eight times, and every time he
ufed frelh alkali ; but the three or four lad times he
did not *ufe quite an ounce of alkali, but employed
a mixture of alkali and flint. Every time it was thus
melted the regulus loft fome of its weight, and the
alkali, having difiblved part of it, was tinged green.
The remaining metal was always whiter and brighter,
and acquired a fmall degree of toughnefs. The tex-
ture was much finer than before, and it would eafily
amalgamife with mercury. The weight of the regu-
lus was reduced to about one half by eight operations.
With the vegetable fixed alkali the effect was fimilar,
but not fo remarkable.

The regulus of antimony is calcined with great rapi-
dity by the nitrous acid, but the muriatic and vitriolic
fcarcely act on it, unlefs affifted by heat. By the
union of antimony with all thefe acids, faline com-
pounds are produced, which are deliquefcent, and
which are decompofecl by water, or the fimple appli-
cation of heat. The oxygenated muriatic acid and
aqua regia diffolve the regulus of antimony with great
facility.

But befides thefe methods of affifting the action of
the muriatic acid on antimony, there is another pro-
cefs-for combining the muriatic acid with the regulus.
A quantity of mercurial fublimate in powder being

VOL, II. L mixed

14-6 Butter of Antimony. [Book VI.

mixed with the reguius of antimony, the acid acts
upon the antimony immediately, fo as to render the
mixing of them dangerous, from the corrofive fumes
which arife. The common way is to powder tr^m
and mix them, and heat being applied, the muriatic^
acid of the fublimate attracts the ?ntimoi'jy. ind rifts
with it in the form of a very volatile compound, which
condenfes in the neck of the retort, of a confidence
between foiid snd fluid, and is hence called butter of
antimony. It is very cauftic, and is ufed to confume
the callous lips of ulcers, but is too violent to be ufed
internally. If it is fubjected to a fecond operation, it
comes over fluid. The fame procefs is employed to
combine other metals with the muriatic acid. When
butter of antimony is thrown into pure water, an
abundant white precipitate or calx falls down, which
is a violent emetic} and is known by the name of
powder of algaroth.

vThe vegetable acids alfo aft upon antimony weakly
when applied to it in its metallic (late, but much
more ftrongly when it is flightly calcined. A folution
of this kind was formerly ufed under the name of an-
timonial wine. A quantity of the reguius was caft in
the form of a cup, which was occafionally fiiled with
wine, and having flood a day or two, it became eme-
tic. The quantity of antimony diffolved was very
fmall, but was difcoverablc on adding an alkali, and
precipitating it.

To give crude antimony any action as a medicine,
it is neceflary to deftroy a part of the fulphur, and
alfo in fome meafure to calcine it. The more ful-
phur it retains, the lefs aflive it is. If we calcine it
*oo much we alfo defiroy its effects* for in the ftate
of a white calx it has little or no medical efficacy.
The flores antimonii is a preparation in which the an-
i timony

Chap. 16. ~\ Jtntimony, a violent Poifoti. % 147

timony is nearly deprived of fulphur, and at the fame
time furnifhed with fome oxygen. Tt is extremely vio-
lent in its effects 3 a very minute quantity producing
convulfions and vomiting. Antimony indeed may be
reduced to fuch a ftate as to affed the body in fmaller
quantities even than arfenic.

When antimony is combined with fulphur, and
Urged with a ftrong heat, it affumes the appearance of
glafs. The glafs of antimony, though not much em-
ployed as a medicine, is very ufcful as a preliminary
to the moil 'valuable preparations. Few of the metals,
indeed, have fo much attracted the attention of che-
mifts as antimony, and its preparations have been
accordingly very numerous. To avoid, therefore,
imnecefTary prolixity, it wtirBfe proper to confine the
reader's attention to thofe which have been found moft
ufeful.

By deflagrating antimony with nitre, the metal is
calcined^ as well as when expofed to heat in contact
with air. The antimoriium calcinatum of the London
Pharmacopoeia is prepared by throwing a mixture of
eight ounces of antimony, with two pounds of nitre,
into a crucible heated to a white heat. The white
matter is burnt for half an hour, and, when cold, is
powdered and wafhed with diftilied water. This
preparation is fo inert, that it has been doubted whe-
ther it is capable of any action whatever on the hu-
man body. '

When the antimony and nitre are in equal quan-
tities, they form a more aftive competition. The
mixture burns with violence, and ought to be injected,
in fmall quantities at a time, into the heated crucible.
After the combuflion there remains a mixed matter,
partly of a dark red, and partly whitifli. Upon melt-
ing, it fcparates into a heavier part of a deep reel, and
L 2 a faline

I4# Crocus of Antimony-^ -&c. [Book VL

a faline part above of a paler colour. The former is
the object of the operation, and is called crocus of
antimony. The College direct a fmall quantity of
fea fait to be ufed in this preparation, which promotes
fufion, and probably increafes the activity of the com-
pofition.

Fixed alkalies have a great degree of activity with
crude antimony, on account of their attraction for the
fulpkur. The eafieft mode of combining them is
fufion. The firft effect of the alkali is to combine
with the fulphur, and form a liver of fulphur, which
by a continuance of heat feems to diffolve the recnilus

•> D

of antimony. This compound is readily difTolved by
boiling water, and if we add to the folution an acid,
the metallic matter and fulphur are depofited of a
yellow colour. This fubftancc, however, which is
called fulphur antimonii prsecipitatum, may be ob-
tained in an eafier manner, by boiling crude antimony
in a folution of alkali, and then precipitating the ful-
phurated antimony with the vitriolic acid.

The antimonium tartarifaturrij or tartar emetic, may
be obtained either by the ufe of the crccus or the glafs
of antimony. The former is, however, preferred by
the London College, who adopt the following pro-
cefs : Take of crocus of antimony powdered one pound
and a half, cryftals of tartar two pounds, diftilled water
two gallons ; boil them in a glafs veflel about a
quarter of an hour ; filter the liquor through papera
and fefit by to cryftallize. Tartar emetic confifts of
the acid of tartar united to vegetable alkali and anti-
mony paitially calcined.

'The pulvis fcntimonialis of the pharmacopoeia,
which is thought to be nearly the fame as James's
powders, is prepared by expoflng equal parts of anti-
imonyand hartfliorn (havings to a moderate heat, with
H fee acccfs of air. With refptct to the peculiar

merits,

Chap. 26.] James's Powders. 149

merits of James's powders, they have never been
proved either in theory or practice. The circum-
ftances upon which the effects of antimonial prepara-
tions depend are well known, and though we cannot
with certainty afcertain the procefs of Dr James, there
is no reafon to think that it is preferable to that of
the pharmacopoeia, in the preparation of the pulvis
antimonialis. The love of myftery, however, has
always had an influence over mankind, and there is no
reafon to believe that the period for its ceflation is at
hand.

The regulus of antimony is employed in the, manu-
facture of printers types, and in making mot.

[ 150 I [Book VI,

H A P. XXVII.

ZINC.

ejrriptien of this- Metal — Pbilafopber's Wool—Union
Acids. — White Vitriol. — Detonation of Zinc nvith Nitre. — Combi-
nation with Metals. — Pewter.— Its Ufe in Fire-works.— Natural-^
Hijtory of Zinc.—Catawine, — Black Jack. — Brafs, honu made.—
.— Pinchbeck.

THIS metal is in fome degree malleable, and
therefore holds a middle place between the
ferni-metals and metals, though it is ufuaily referred
to the former divifion. Its appearance is blue and
brilliant, and when- broken it is found to be cryftal-
lizcd in narrow plates. It melts when red hot; if
heated in clofe vefiels to a vivid red or white heat^
the whole of it rifes in vapour, and may again be
condenfed without any change. When heated, how-
ever, in contact with air, it burns rapidly with a white
flame and crackling noife, and is converted into a
white, fofr, and flocculent fubftance, railed fbwrrs of
zinc, or lana philofophcrum. If the zinc is burnt in
a deep crucible, this calx attaches itfelf to the upper
part of it, though fome part is always loft even in the
deeped yeffel, which will admit the air with fufHcient
freedom to maintain the combuftion. If a gentle heat
is applied no light is produced, and the furface of the
zinc becomes gradually covered by a grey calx, which,
changes to white, by being afterwards heated in con-
tact with air. Zinc 5s lo apt to undergo this change
that it is difficult to melt fmall pieces of it into a rnafs,
for in the moment after they arrive at • the melting

Chap. 27.] White Vitriol 151

point they are covered with a fkin, which prevents
their union. 1 he calx of zinc is not very eafily re-
duced to a reguline it ate, as the heat neceffary for this
effect is apt to volatilize the metallic product.

Zinc is readily acted on by all the acids, and no
metal mews a greater attraction for them. It pro-
duces with them metallic faits, in which the acid is
more neutralized than in the o:her metallic compounds
of the fame description. The acids do not depofic
the zinc when they are diluted with water.

The concentrated vitriolic acid does not act on zinc,
unlefs affifted by heat, and it then gives out fulphu-
reou$ fumes. Ic is difTolved, however, with rapidity,
and without the afTiftance of heat, by the fame acid in
a diluted ftate, and this procefs is attended with the
copious produdion of hydrogen gas, which indicates
the decomposition of the water. From this folution
may be obtained white vitriol, which, as well as the
flowers of zinc, is employed in medicine.

The diluted nitrous acid acts on zinc with fingular
violence, and nitrous gas is fo copioufly difengaged,
that the mixture fometimes exhibits the appearance
of boiling. The folution is very cauftic, and affords
cryftals by evaporation and cooling, which (lightly
detonate on hot coals, and leave a calx behind. This
fait is deliquefcent. The diluted muriatic acid acts
on zinc with the fame production of hydrogen gas.
as the vitriolic j but this folution does not afford cryf-
tals. ,

The vegetable acids acquire from zinc a fweetifh
tafte and ftipticity. The action of the fluoric and
boracic acids on zinc are not known. Water impreg^-
rated with carbonic acid, diflblves a confiderable pro-
porrion of zinc.

All the folutions of zinc in acids are precipitated

by lime, magnefia, the fixed and volatile alkalis > the

L 4 latter

152. Detonation of Zinc. [Book VI.

latter re-difiblves the precipitate if it is added in
excefs.

Zinc has the property of decorrpofing feveral neuT
tral falts. If it is confiderably heated with vitriolated
tartar in a crucible, it decompofes the fait, and forms
a liver of fulphur, in the fame manner as the regulus
of antimony does. In this experiment the metal feizes
the oxygen of the vitriolic acid, and the acid pafles
into the ftate of fulphur, which the alkali diflblvcs.
The hepar formtrd by this combination diflolves a
portion of the calx of zinc. All the vitriols are like-
wife decompofed by zinc.

When pulverized zinc is added to fufecl nitre, or
projected together with that fait into a heated cruci-
ble, a very violent detonation takes place. The acti-
vity of the inflammation is fuch, that portions of burn-
ing matter are thrown to a diftance out of the crucible,
in fuch a manner as to require precaution on the part
of the operator. Only imall quantities of die mixture
fhould be call into the crucible at once The zinc
bums by the affiftance of the oxygenous gas afforded
by the nitre, and is afterwards found in a ealciibrm
flate, more or lefs perfect, according to the propor-
tion of nitre ufed. Part of the calx combines with the
alkali, and forms a compound ibiuble in water.

Zinc decompofes common fait, and alfo fal ammo-
niac, by feizing the marine acid. The filings of zinp
alfo decompofe alum when boiled in a folution of that
fait.

The relation of zinc to fulphur is remarkable, as it
is the .only metal which does not unite with it in a rer
guline ftate. M. M-orveau, however, has difcovered,
that the calx of zinc unites eafily with fulphur by
fufion.

The regulus of zinc is capable of being united with

that

Chap. 27.] Ufe of Zinc in Pewter. 153

that of arfenic, but it more readily unites with arfenic
in its calciform ftate. Zinc diflilled with white arfe-
nic deprived it of part of it5 oxygen, and was con-
verted into a calx, while a correfponding quantity o£
arfenic was reduced to a regulus.

Zinc does not combine with bifmuth, and when
thefe two metals are fufed together, the biftnuth takes
the lower \ lace on account of its greater gravity, and
may be feparated by a flroke of the hammer. It
will not unite with nickel. Its volatility renders it
extremely difficult to combine it with metals which
are of difficult fufion, as iron and copper. It is, how-
ever, united to feveral metals for particular purpofes
in the arts. It is added in fmall quantities to tin,
or to a mixture of tin and lead, in the compofition of
pewter, which it improves both in adding to the white-
nefs and brilliancy, and increafing the hardnefs. It is
employed in many alloys, particularly in tombac,
prince's metal, and the various kinds of brafs. Fine
filings of zinc are ufecl to produce brilliant fparks in
fire-works. Some perfons have propofed to fubfti-
tute zinc for tin in lining copper veffels; the latter
metal, in conjunction with lead, having been fuppofed
jnfufficient to prevent the dangerous effects of the lead.
Macquer allows that this metal fpreacls more evenly
pn the copper, is much harder, and lefs fulible, than
the lining of tin, but objects to it, becaufe it is foluble
in vegetable acids, and has a confiderable emetic
power. Mr. De la Plance, however, has taken the
falts of zinc, formed by the vegetable acids, in greater
quantities than they can be contained in aliments which
"have been dreffed in veflels lined with zinc, without
experiencing any dangerous effect Experiments are
yet wanting to prove the fuperiority of zinc lining
pver that of tin,

Zinc

Natural Hijtory cf Zinc. [Book VI.

Zinc is found in the following flares : It is fome-
times, though rarely, difcovered native in flexible,
greyifh, and inflammable fibres. Zinc in its ore is
generally in the form of a calx; when the ore contains
no other metal but zinc it is never in any other form,
but it is often mixed with other ores, which contain
iulphur and arfenic, and thefe mud be evaporated by
roafting. The richefr. ores are compact and ponde-
rous, and are called lapis calaminaris, or calamine ;
they are found in the parifh of Holywell, in Flint-
Ihire.

Margraff has afcertained the quantity of zinc con-
tained in different forts of calamine :

Parts. Parts.

Calamine, from near 7

Cracow J l6 8ave - zmc-

Calamine, from England 16 3

from Breflaw 16 • • 4!

— : — from Hungary 16 i\

from Holywell 16 7

In one hundred pails of lapis calaminaris were found
eighty-four of calcined zinc, three of calcined iron,
about one of pure clay, and twelve of filiceous earth,
according to Bergman.

There is another fpecies of mineral ufed in making
brafs called blende, mock lead, or black jack, which
ccnfifts of zinc mineralized by fulphur, and fornetimes
by iron.

The method of making ordinary brafs is as follows :
• — Copper in thin plates, or, which is better, copper
reduced (by being poured when melted into water)
into grains of the fize of large fliot is mixed with cala-
mine and charcoal, both in powder, and expofed in a
melting pot for feveral hours to a fire not quite ftrong

enough

Chap. 27.] Making of Brafs, Pinch&eck, &c. 155

enough to melt the copper, but fufficient lo reduce
the zinc, and convert it into vapours. Thefe vapoury
penetrate the copper in proportion to the furface ex-
pofed to th,eir action, changing its colour from red to
yellow, and augmenting its weight in a great propor-
tion. When they make brafs, which is to be caft
into plates, from which pans and kettles are to be
formed, and wire is to be drawn, they ufe calamine of
the fineft fort, and in greater proportion than in the
compofition of common brafs.

Tutty is the flowers of zinc taken from the furnaces
in which the ores containing this metal are wrought,
It varies in colour and confidence according as the
calx is more or lefs perfecl:, and is mixed with more or
}efs of an argillaceous fubftance. Newman fays, that
the lapis tutias is compofed of clay beaten up with a
fmall quantity of lapis calaminaris.

Zinc and copper, when melted together in different
proportions, conftitute what are called pinchbeck, &c.
of different fhades of yellow. Margraff melted pure
zinc and pure copper together in a great variety of
proportions, and he found that eleven, or even twelve
parts of copper, being melted with one of zinc, gave
a mod beautify! an,d very malleable tombac or pinch-

[ *56 1 [Book .VI,

C H- A P, XXVIII.

OF THE *JEWLY DISCOVERED SEMI-METALS.

Sylvanite. — Menacbinite.— Uranite. — and Titanite.

BEFORE the account of femi-metals is concluded,
it is proper briefly to notice four femi-metallic
fubftances which have lately fallen under the obfer-
vation of mineralogifts, but which have not yet under-
gone a complete examination.

A new femi metal has been difcovered by Facebay,
to which Mr. Kirwan gives the name of SYLVANITE^
from its being found in Tranfilvania. Its colour is
grey inclining to red, its fracture broad or granularly
foliated, with -a flight degree of malleability. Its
weight is about fix times that of water. When heated
it melts as eafily as lead, gives a thick white, fmoke, and
at laft a brownifh flame. In cooling it fhews ioms
difpofition to cryftallize. By continued heat it en-
tirely evaporates. It eafily amalgamates with mer-
'cury by fimple trituration. . It combines with fulphur,
and forms with it a ftrjated mafs like crude antimony.

Sylvanite is foluble in concentrated vitriolic acid,
and the folution in a moderate degree of heat is crim-
fon red, but by the addition of water or heat it is pre-
cipitated. It may alfo be difTolved in a fmall propor-
tion in nitrous acid, and the folution until it heats is
greenifh. The beft folvent is aqua regia, with which
a yellow folution is produced. Its calx is of an acid
nature and unites with alkalis ; it is alfo foluble in.
acids. This fingular fubftance was at firft taken for
regulus of antimony, and afterwards for fulphurated
bifmuth.

A fubftancp

Chap. 28,] Menacbanitt and Uramte. . 157

A fubftance of a peculiar nature was difcovered by
Mr. M'Gregor in the valley of Menachan in Cornwall,
which has been therefore called MENACHANITE, and is
confidered as a femi- metal. It is found in the form of
fmall black grains refembling gunpowder, of no deter-
minate ftiape, and often mixed with a grey fand of
great fubtilty. Its fpecific gravity when in grains
is 4,427 ; in a high heat it flightly agglutinates and
acquires a fmall increafe of weight. When in grains
it is eafily pulverized, and is pofiefled of fome magnetic
power. It is infoluble in acids except by particular ma-
nagement i but is then found to confift of about equal
proportions of iron, and a peculiar white calx with a little
filex. The folution of menachanitic calx in vitriolic
acid, is precipitated deep green by Pruflian alkali,
white by common alkali, and becomes orange coloured,
with tincture of galls. With feveral other folvents it
exhibits properties fo peculiar, as to entitle it to be
confidered as a new fubftance.

URANITE was firft difcovered by Klaproth, who
found it to polfrfb the following properties. Its colour is
dark fleel or iron grey, internally fomewhat browner.
Its fpecific gravity 6,440. It is rather more difficultly
fufible than manganefe, and has as yet only been pro-
duced in fmall globules imperfectly agglutinated. It is
foluble in nitrous cid ; but it does not appear that other
acids have been tried. Its calx is yellow and manifefts
the following properties. It is eafily foluble in acids ;
with the dilute vitriolic acid it affords yellow cryftals.
With the concentrated acetous acid it affords yellow
quadrangular cryftals. It is alfo foluble in many other
acids, the products of which folutions vary confiderably
both in colour and form. Uranitic calx is infoluble
in alkalis, either in the moift or dry way, which fully
, diftinguifhes

*5& Titanite. [Book VI.

diftiriguifhes it frorn tungftenic calx, which it refembles
in colour.

TITANITE, which many mineralogies have confi-
dered as a red fliirj, has been lately transferred to the
clafs of metallic fubftances by the labours of Klaproth.
Its colour is brownifh red. It occurs cryftallized
in right angled quadrangular prifms, lo'ngitudinally
ftreaked or furrowed. None of the acids have been
found to have any action on this fubftancej even when
heated. The calx of titanite is white, and is foluble
in the mineral acids. Fifty grains of the calx were
by ignition reduced to twenty-eight. Mr. Kirwan is
of opinion that titanite is red when in its metallic ftate,
that is, as it is found in nature. Heated on charcoal it
becomes rofy red, and afterwards flate blue, and finally
melts into an imperfect bead with a fine ftriated fur-
face. The different productions of nature feem uni-
verfally to pafs into each other ; and titanite, as far as
we can judge, from what is as yet known concerning
it, forms a link between earthy and metallic fubftances.

Chap. 29.] [ 159 ]

i

C H A P. XXIX.

I R O N.

Exten/tve Utility of this Metal— Its Properties.— -Natural Hljlory of
Iron.— Eagle- Stones. — Blood-Stones. — • The Loa^ione. — Emery.—
Ochres. — Smelting of Iron. — Forging of Iron, — Makittg of Steel.—
tempering of Steel. — C.i/f Steel. — Great DiJ'pcfoion in Iron to unite
ivitb other Dotiics. — -Green Vitriol, how procured. — Prujjian Blue. —
Ink. — Inflammation of Sulphur and Iron. — Tinning of Iron.— Pre-
parations of Iron itjed in iMedicine.

OF all metals, and I might perhaps be juftified in
adding, of all mineral fubftances, the mod gene*
rally ufeful is iron. To fpecify its ufes would be to
produce a catalogue of every thing that contributes to
the fullenance and the convenience of life. By the al-
ii ftance of this metal we till the land, and obtain the
fruits of the earth in greater abundance and perfection
than we could by any other means ; by irs agency we
are enabled to penetrate the earth itfclf, and procure
whatever it contains that may be ufeful or ornamental
to man ; there is fcarcely a mechanical trade, which
could be conducted on the prefent principles without
its aid, and many of them could not even exift were we
deprived of it : even in domeftic life our fafety, our
comfort, and our pleafure, all fsem in fome meafure
to depend on this moft valuable production of the
earth. As the quantity of this, as well as of fome
other minerals, which appear almoit necelFary to focial
exiftence, mud be limited, I have often thought that the
want of a fufficient fupply, which, on the fuppofition of
the prefent fyitem of things being continued forever,
mult at fome time neceflarily take place, forms a forcible

argument

l6o Natural Properties 'of Iron. [Book VI.

argument againft the abfurd and ignorant hypothefis
of the eternity of the world.

The external appearance of this metal is well known*
and its hardnefs and elafticity are feen in the various
inftruments and utenfils which are formed of it.

It is the moft fonorous of all the metals, except
copper j but in fpecific gravity it is inferior to moft of
them, being only about feven times and a half the weight
of water. Iron has a considerable finely efpecially when
rubbed or heated. It like wife has a very perceptible
ftyptic tafte.

Iron is very ductile, and may be drawn into wire as
fine as a human hair ; and it is fo tenacious, that an iron
wire of one tenth of an inch diameter will fupport a
weight of fifteen hundred pounds. Iron may be ig-
nited, or at leaft made fufficiently hot to fet fire to
brimftone, by a quick fuccefllon of blows with a ham-
mer j but it requires a moft intenfe heat to fufe it, on
which account it is brought into fhape by hammering
while it is in a heated ftatc. Iron is alfo poflefled of
another property, which fupplies in a great meafure
the purpofes of fufion. When pieces of common foft
iron are heated to a certain degree, and are fuddenly
taken out of the furnace and expofed to the air, we
obferve their furface covered over with an appearance
of varnifh, which proceeds from the furface of the
metal being partly fufed. If two pieces of iron in this
ftate are ftruck together, they unite very firmly, and
this procefs is called welding. It is diftinguiftted from
all other metals by being attracted by the loadftone.
Another property, which diftinguifhes iron from ail
other metals, is that of ftriking fire with flint. This
phenomenon depends oh the actual inflammation of
fmall particles of the metal, which prefent a large fur-
face to the action of the air, and which are heated by

the

Chap. 29.] Wty Steel Jlrikes Fire with Flint. i6|

the friction which feparatcs them from the mafs, fo
as to difpofe them to inflammation. Thefe particles
are feldom larger than the two hundredth part of an
inch in diameter, and when examined by a magnifier,
are found to be brittle, of a greyifh colour, refembling
the fcales of burnt iron. Another proof of the inflam-
mability of iron is, that iron wire, heated at one end,
and plunged in a jar of oxygen gas, burns with con-
fiderable rapidity, and with a very brilliant flame.

Iron is by far the moft abundant in nature of all
the metals. It is not only contained in almoft every
foffil, particularly in thofe which are coloured, but
-makes a part of vegetable and animal matter. With
refpect to the ores of iron, however, as they are very
numerous, it will be neceffary only to notice thofe from
which the metal may be extracted with advantage. In
thefe ores iron exifts either in the metallic or calciform
ftate, or mineralized by different fubftances.

Native Iron is known by its colour and malleability.
It is very rare, and is only found occafionally in iron
mines. Some naturalifts think that thefe apparently
native fpecimens of iron have been produced by art,
-and have been buried in the earth by accident.

In the Philofophical Tranfaftions for the year 1788,
% vol. Ixxviii. is an account of a mafs of native iron,
weighing by admeafurement about three hundred quin-
tals, which lies in the midft of a wide extended plain,
in the middle of South America, in latitude 27" 2&'
fouth, and at the diftance of feventy leagues eaft, one
quarter fouth, from the hamlet of Rio Salado. It has
the appearance of having been liquid, and bears the
impreffion of human feet and hands of a large fize, as
well as of the feet of large birds common in that
country. The extraordinary fad of fuch a mafs of

Vot. IIr M iron

i6i Natural BJlory of Iron. [Book VI.

iron being found in the center of a vaft Jract of level
land, where there are no mountains, nor even the
fmalleft ftone, within a confiderable diftance, project-
ing above the fur face of the earth, is referred by the
y/riter of the article in queftion to an ancient volcanic
explofion, of which there are forne veftiges near it.
The fame fuppofition is urged with equal probability to
account for the production of another mafs of native
iron, in the fhape of a tree with its branches, which the
fame author aflerts, on indubitable authority, is known
to exift in tliefe immenfe forefts. Some fpecimens of
the iron were prefented to the Royal Society, who
afterwards depofited them in the Britilh Mufeum.
That large mafies of iron were really obferved in thefc
fituations there is no reafon to doubt, but I fhould ra-
ther attribute the fuppofed imprefiions to accidental
refemblances.

The largeft quantities of iron ores are in a calciform
ftate, as in ochres, bog ores, &c. which are difpofed
in ftrata, in the manner of Hones. The astites, or
eagle ftones, are a variety of the bog ores ; they arc
in different forms, commonly oval or polygonous,
compofed of concentric layers difpofed round a nu-
cleus, which is frequently moveable in the center of
the ftone. The haematites, or blood ftones, are named
from their colour, which is commonly red. The loadT
ftone is a dull iron ore, the varieties of which are dif-
tinguifhed by their colour.

Emery is a grey or reddifh iron ore ; it is very hard
and refractory, and is found in abundance in the iflands
of Guernfey and Jerfey. It is reduced into powder in
mills, and in this ftate is u fed to polifli glafs and me-
tals. Spathofe iron ore is a calx of iron combined
carbonic acid} it is ufually of a white colour.
4 Nature

Chap. 29.] Smelting of Iron. 16$

Nature like wife prefents iron in a faline ftate, united
to the vitriolic acid, and forming green vitriol. This
fait is particularly found in mines which contain py-
rites. Iron is offceh found united to fulphur, and
then forms what are called martial pyrites. This
metal is alfo found combined with arfenic, both
being in the metallic ftate. There is alfo a blacfc
iron ore, which is in fome meafure attracted by
the magnet. Iron is fometimes found in the form
of a blue powder. In this ftate it is called native
Pruflian blue. It is mixed with vegetable earths, and
.cfpecially with turf. It was difcovered fome years ago,
that iron is often united with the phofphoric acid. The
muddy .or bog ores are fometimes of this nature.

The ores of iron do not afford the metal unlefs urged
by a great heat. Some ores are melted without addi-
tion ; but it is necefiary to afiift the fufion of others by-
calcareous matters. The limeftones, the iron ore, and
charcoal, are alternately thrown into the furnace, and
the whole is covered with a layer of charcoal. The
melted ore is reduced by the contact of the coaly
matter, and is then fuffered to run into a cavity ufually
formed in fand. The metal in this ftate is called crude
or caft iron. A vitreous matter, called flag, paiTe$
after the iron, and confifts of the ftones which were
added to facilitate the fufion. The metal thus ob-
^ftined has not the leaft duftility; but it is deemed
better in proportion as its colour is darker.

The caft iron is carried to be refined in a forge
furnace, with a hollow hearth, in which it is furrounded
with charcoal, where the fire is urged by bellows till
the metal begins to foften. When it is in this ftate,
it is repeatedly ftirred, in order that it may prefent a
larger furface to the air. By the adion of the heac
and air it emits fparks, which proceed from the con-
fumption of a quantity of plumbago, or black lead
M 2 which

164 Forging of Irm. [Book VI.

which is contained in the crude iron, and which it ' is
commonly fuppofed to acquire from the fuel during the
procefs of fmelting *

The iron, by this mode of refining, lofes, befides
the plumbago, a quantity of fiderite, which Bergman
luppofed to be a peculiar metal, but which is now
found to be a combination of iron and phofphoric
acid.

After the iron has been kept in this fituation a cer-
tain time, it is carried to a large hammer, generally
moved by water, where it is formed into bars. The
hammering, by bringing the particles of the iron
nearer together, prefles out the impurities, and thus
completes what was left deficient by the fufion. This
keating and hammering are repeated a number of
times, till the iron has acquired the defired degree of
perfection. Crude iron loles from a quarter to a third
of its weight by the procefs of refining, and is then
called forged iron.

Steel is made by furrounding the bars of iron with
a compofition of which charcoal is the chief and only
elTential ingredient, and by keeping them in an iutenfe
heat a longer or fhortcr time, according to their thick-
'nels. They are then taken from the furnace, and
plunged in cold water. The metal is now found to
be more fufible than it was before, but to have lefs duc-
tility and foftnefs. Its texture is finer j it breaks fhorfji
its fracture is always grey, and it has gained a fmall irt-
Creafe of weight.

With refped to the chemical ftates of the metal,
in the three forms of caft iron, forged iron, and fteel,
it appears that they chiefly depend on the quantities

* Plumbago confifts of carbon, with about one tenth of its weight
of iron.

Of

Chap. 29.] Steel. 165

of plumbago. By folution in acids, it is found that
call iron contains a large quantity of plumbago, that
fteel contains fome of it, but that the moft malleable
forged iron contains fcarcely any ; it therefore appears,
that fteel is in an intermediate condition between caft
iron and forged iron, and that, in making the former
into the latter, the metal muft pafs through the ftate
of fteel. In fome foreign works they actually manu-
facture fteel by only flopping the procefs of refining
at a certain point. In thefe manufactories, however,
they make ufe of an ore of uncommon purity ; and
the fame procefs does 'not fucceed with ordinary ores,
becaufe the metal obtained from thefe contains other
impurities befides plumbago, which cannot be fepa-
rated without reducing the iron to its malleable
ftate.

There are differences in the working of iron, ac-
cording to the ores from which it is obtained, the caufes
of all of which have not been difcovered. The pre-
fence of phofphoric acid, however, is known to pro-
duce a brittlenefs in iron when cold, which occafions
that fort of iron to be called cold fhort iron by the
workmen. Phofphoric acid is chiefly found in iron
obtained from bog ores.

The workmen employed in tempering fteel judge,
by the different colours it afiumes during the opera-
tion, of the degree of hardnefs it has acquired. That
thefe colours may be properly obferved, fome part of
the metal to be tempered mould be fmooth.

The changes of colour depend on the calcination
of the. iron ; for if the contact of air is prevented by
the thinneft covering of any oily matter, the effect is
entirely prevented. The colour is firft a pale yellow j
;f a piece of fteel is then (truck off, it will be very
hard. If the fteel is left in the fire for a longer time,
M 3 ic

1 66 Caft StecL [Book VI.

it acquires a deeper yellow and more toughnefs, with
fcarcely any diminution in the degree of hardnefsj
when brought down to the colour of watch fprings-, it
is of the fitted temper for cutting wood. Steel, by
being heated in this manner, becomes fucceffively
white, yellow, orange, red, violet, and laftly blue,
which colour remains a confiderable time 3 but if the
heat is raifed it becomes whitifh.

Steel ftrongly heated while in the fire, a flumes a
red and fparkling appearance, it next becomes very
white and dazzling, and then burns with a fenfible
flame.

Ca(l fteel is nothing more than fteel refined by
fufion. During this procefs it throws up fcoria, whilft
the metallic matter which remains is much harder than
before, and its texture more uniform.

Iron is one of the metals which is acted on moft
powerfully by acids. But not only acids, but all fa-
line fubftances feem to affect it, and even water is ca-
pable of acting on it fo as to acquire from it a peculiar
tafte. The tendency, indeed, which this metal has to
combination with other bodies, particularly with oxy-
gen, which occafions mil, renders it incapable of per-
manencyj and for this defect no fufficient preventative
has yet been difcovered.

M. Lavoifier, having expofed iron with water in a
glafs vefiel over mercury, obferved that the iron be-
came rufty, and that the water was diminifned in quan-
tity. The iron was increafed in weight, and there was
a production of inflammable gas, fo that in this experi-
ment the water was decompofed by the iron, even
without the prefence of air.

Iron is acted on by the vitriolic, muriatic, and ni-
trous acids, with nearly the fame phenomena as zinc.
The products, however, are very different. The fo-

lutioi),

C'hap. 29.] Green Vitriol 167

lutibn of iron in the vitriolic acid is of a green colour,
and by evaporation produces the green cryftals, well
known under the names of fal martis> green vitriol',
and copperas. The green vitriol ufed in commerce is
obtained in the following manner : Pyrites, which are
natural combinations of iron and fulphur, are expofed
to the a<5bion of the air and rain in mallow pits lined
with clay. Afcer having been in this fituation a week
or a fortnight they grow hot and crumble down, and
when carefully examined are found to; contain- fmall
cryftals. Thefe are difiblved by the rain, arid con-
veyed by pipes into a refervoir in a houfe, whence the
liquor is pumped into a* boiler made of lead. This
liquor is found to1 have an excefs of acid, which is re-
medied by calling pieces of iron into it when heated
fo as to firnmer. By the addition of the iron a quan-
tity of the earth of alum is alfo depofited. As the
liquor cools, the greater part of the fal martis is depo-
fhed. By the expofure of the pyrites to the action of
air and water, the fulphur attracts the oxygenous prin-
ciple, and is thus converted into vitriolic acid. Sal
martis is liable to the watery fufion; when expofed to
a ftrong heat the acid begins to exhale, and as it ex-
hales, the natural colours of the calx of iron appear.
It is firft yellow, then orange, then red j if it is cal-
cined to a greater degree, fcarcely any of the acid is
lefc, and the calx remains of a deep purple colour, and
is known under the name of cokothar of vitriol. The
nitrous acid acts with fo much violence on iron as
to convert it into a brown calx. With the muriatic
acid iron affords cryftals of a livelier green colour than
copperas, which will not, like copperas, part with the
acid by the application of heat.

All folutions of iron, if expofed to the air, depofit

part of the metal in the form of a calx. Alkaline falts

M 4 precipitate

Pru/tan Blue. [Book VI.*

precipitate the metal of a blueifh grey colour, if the
folution is frefh, but if long kept, in the form of a
yellow powder. Mild vegetable alkali feparates a
yellow calx from the folution of iron in the nitrous
acid, which foon becomes of a beautiful red orange
colour. If the mixture is agitated during the eflfer-
vefcence, the precipitate is re-diflblved in much
greater quantity than by the pure vegetable alkali.
This folution is known by the name of Stahl's martial
alkaline tincture.

But the moft remarkable precipitation is that pro-
duced by a fixed alkali prepared with animal inflam-
mable matter. The alkali is treated by mixing ir,
when dry, with twice its weight of blood, which has
been indurated and reduced to powder; the mixture is
put into a crucible, and a gentle heat applied ; parti-
cular care muft be taken to ufe the due degree of heat,
which is known by the difappearance of a blue flame
and fmoke, which is at firft obfervable on the furface.
The matter thus prepared, being infufed in water,
affords an alkaline folution, which precipitates iron of
a deep blue colour, efpecially if a little muriatic acid
is added. The efiential ingredients of the matter ob-
tained by the above procefs feem to be a peculiar matter
called prufllc acid, and an alkali. The bafis of the
pruffic acid, according to M. Berthollet, confifts of
carbon, hydrogen, and azote. When the alkali, com-
bined with this peculiar acid, is added to a folution of
iron, the alkali takes the acid from the iron, while the
pruflic acid unites with the metal and falls to the bot-
tom in the form of a blue powder. This effect of the
alkali, thus prepared, is the foundation of the procels
for obtaining that valuable pigment, known by the
name of Pruffian blue.

Another fingular, and not lefs ufeful circumftance,

in

Chap. 29."} Ink. 169

m the hiftory of iron, is the effect produced on it by
aftringent vegetable fubftances. The principle of
aftringency, which is now found to be a peculiar acid,
called, in the new nomenclature, gallic acid, refides in
a great number of vegetable matters, particularly oak
galls, tea, -&c« According to M. de la Metherie,
however, the acid of galls is only a variety of the co-
louring principle. Galls are protuberances on the
leaves of the oak, -occasioned by the puncture of a par-
ticular infect. Any of thefe fubftances, added to a
iblution of green vitriol, precipitates a fine black fecula,
which may be fufpended a confiderable time in the
fluid by the addition of gum arabic. Oak galls art
commonly made ufe of in this prccefs, which is that
of making ink. The following proportions of thefe
ingredients for making ink anfwer very well. One
ounce of martial vitriol to three of powdered galls ; to
which one ounce of powdered logwood may be added,
to render the ink more permanent, and one ounce of
gum arabic to fufpend the colouring matter. Let
thefe be infufed in a quart of water or vinegar for ten
days, and fhaken occaftonally, when the ink will be fit
for ufe.

The colouring matter of ink feems to be produced
from an union of the acid of the galls with fome part
of the iron in a calciform ftate. A fmall quantity of
any of the mineral acids deftroys the colour of the ink,
by diffolving the iron, which was imperfectly precipi-
tated ; and this colour is again reftored by the addi-
tion of an alkali, which takes away the acid. The
black fecula of ink is not magnetical; but it may be
converted into a brown magnetic calx by heat. Ink
becomes blacker by expofure to the air, which acidi-
fies more completely the principle combined with the
iron i but ancient writings become more and more

yellow

*76 M.- [Book VI.

yellow in conrequencc of the decay of the vegetable
matter. Their legibility may be reftored by the ufe
of infufion of galls, or gallic acid. The beft method,
however, of refloring the legibility of ancient writings,
confifts in fpreading a folution of the Pruffiari alkali
thinly with a feather over the traces of the letters, and
then to touch it gently, and as nearly upon or over
the letters as can be done, with a diluted acid, by means
of a pointed flick.

The only eflential ingredients of ink are green vi-
triol, galls, and water. Dr. Lewis has made many
ufeful experiments on the proportions of thefe ingre-
dients which produce the beft ink. He found that
equal quantities of galls and green vitriol produced
the deepeft colour, but not the moft durable , he
found, that by increafing the quantity of the galls the
colour was rendered more durable; that with three
times the weight of the galls tb one of the vitriol, the
colour was very permanent j but that if the propor-
tion of galls was increafed beyond this, the colour
was too weak ; in this cafe the writing was much re-
frefhed by wafhing it with a folution of vitriol. He
alfb endeavoured to alcertain the beft proportion of
the fluids to the vitriol and the galls. He firfl tried
water, and found that by confiderably diminishing the
quantity of it the ink was more durable, but too thick
for ufe. He found that all waters were much the
fame; that white wine and vinegar made a more
durable ink ; but that both thefe were exceeded by a
decoction of forty ounces of water to one of logwood,
which of itfelf gives a permanent red ftain. If the
colour of the ink iliould fail, that of the logwood will
remain, and it produces, with ink, a much ftronger
and blacker colour than ufual ; for the common colour
of ink is a purplifh blue, which, mixed with red,

makes

Chap. 29.] finning of Iron. 17 r

makes a deep black. He did net find any vegetable;
aftringent equal in all refpects to galls.'

Mr. Nicholfon ftates an objection to the ufe of vine-
gar in the making of ink, which is, that it acts fo
ftrongly on the pens that they continually require
mending. Ink is very apt to become mouldy, which
is beft remedied by the addition of a few cloves re-
duced to powder; for hot arotnatics are excellent pre-
fervers of animal and vegetable matters.

Iron detonates ftrongly with nitre. It appears to
combine with alkalis by fufion. The calx of iron
combines with earths, afiifts their fufion, and imparts
a green colour to the glafs. Iron has a remarkable
attraction for fulphur, and combines with it either by
the action of heat or moiftute. A mixture of equal
parts of iron filings and fulphur, made into a p;ifte
with water, becomes hot, emits watry vapours and
inflammable air, in a little time the mafs takes fire,*
and, by attracting the oxygen of the water, becomes
converted into green vitriol, in the fame manner as
pyrites. This is the mixture ufed in the production
of an artificial earthquake, which will be fpoken of
more fully under the head of earthquakes.

With refpect to the relations of iron to the other
metals, there is little worthy of note, except its attrac-
tion for tin, on which is founded the procefs of tinning
iron. In fome countries iron is made into plates, by
being repeatedly heated and fubmitted to the action
of a heavy hammer. In England, however, the plates
are not hammered, but rolled out to the proper dimen-
fions, by being put between two cylinders of cafl iron,
cafed with fteel. When the iron plates have been
either hammered or rolled to a proper thicknefs, they
are fcoured with a weak acid, which renders their
furface perfectly clean and bright, and takes off all

the

1 7ft Tinned Iron. [Book VI.

the ruft, which would prevent the adhefion of the tin
to their furface ; thty are then wetted with a folution
of fal ammoniac, and plunged into a vefTel con-
taining melted tin, the furface of which is kept co-
vered with pitch or tallow to prevent its calcination.
The tin adheres to each fide of the plate, and in-
timately combines with the iron to a certain depth,
which renders the tinned plates lefs difpofed to har-
den by being hammered, and forms an excellent
defence for the iron againft the action of air and
moifture.

Bifhop Watfon propofes it as a queftion of fomc
importance, whether iron of a greater thicknefs
might not be advantageoufly tinned ? He defired a
workman to break off the end of a large pair of
pincers, which had been long ufed in taking the
plates out of the melted tin ; the iron of the pincers
teemed to have been penetrated through its whole
fubflance by the tin j it was of a white colour, and
had preferved its malleability. It is ufual to cover
iron ftirrups, buckles, and bridle bits, with a coat
of tin, by dipping them, after they are made, into
melted tin ; and pins, which are made of copper-
wire, are whitened, by being boiled for a long time
with granulated tin in a ley made with alum and tar-
tar. On thefe circumftances he founds two queries;
i. Whether the iron bolts, ufed in fhip building,
would be preferved from rufting by being long boiled
in melting tin? 2. Whether it would be_poffible ta
filver iron-plates, by fubftituting melted filver for
melted tin?

It is cuftomary, in fome places, to alloy the tin
ufed for tinning iron plates with ^boitt one-fevemieth
part of its weight of copper. Too much copper ren-
ders the plates of a blackifh hue, but when added to

tin

C hap. 2 9. ] Medical Preparations of Iron. 173

'tin in a proper proportion, it enables the manufacturers
to lay on a thinner coat of tin without injury to the co-
lour. This practice, however, is rather of prejudice
to the duration of the plates. When the tin is heated '
to a great degree, the covering which it imparts to
the iron is thinner but more even. The plates are
apt, from this caufe, to have yellow fpots on them ;
but this inconvenience may be removed by boiling
the plates for two or three minutes in lees of wine,
or, where they cannot be had, four fmall beer, or other
fimilar fluids, may probably be ufed with the fame
fuccefs.

. Iron is juftly confidered as a valuable article of the
materia medica, and while its utility is confiderable,
it is entirely free from thofe deleterious and debilitat-
ing effects which proceed from moft of the other
metals that are ufed as medicines. The ferrum vi-
triolatum, or green vitriol, has been already men-
tioned. The ferri fubigo is made by merely expofing
iron filings to the air, and moiftening them with water
till they are converted into ruft. The ferrum tarta-
rifatum is prepared by mixing one part of iron-filings
with two of cry dais of tartar moiftened with water,
and expofing them to the air for eight days. In this
preparation the iron is chiefly brought to the faline
(late by means of the acid of tartar. The ferrum
ammoniacale, or flores martiales, is made by mixing
one pound of iron filings with two of fal ammoniac,
and applying a brifk heat. The fal ammoniac fub-
lim«s and carries up fo much of the iron as to be
changed to a deep orange colour. The flores mar-
tiales may be made equally well with the colco-
thar of martial vitriol as with the iron-filings. The
tinctura ferri ammoniacalis, or ammoniacal tinc-
ture of Iron, is made by digefting one pint of proof

ipirit

17.4 Medical Preparations of Iron. {Rook VI.

fpirit of wine with four pieces of ferrurn amnioniacale.
The tin&ura ferri muriati is prepared by diflblving
the ruft of iron in the muriatic acid, and adding a
quantity of rectified fpirit of wine. Wine of jron
is obtained by digefting ruft of iron with Spanifa
white wine, in the proportion of an ounce to a
pint, for a month.

Chap. 30.] [ 175 ]

CHAP. XXX.

TIN.

Ctutral Properties of Tin.' — Granulated Tit. — Natural Hilary o/?'^-;.—
Its Union with the Acids,— Ufe of Tin in improving tht red Djes.—
Smoaking Liquor of Libaijius.'—Aurum Muji-vum. — Combinations
of Tin with other Metals. —••Different Species of Pewter.— -Piatj.—
Application of Tin in dying*— Ufe in Medicine.

TIN, when its furface is frefh, is bright, and with
refped to whitenefs holds a middle place between
lead and filver. Tin is the lighteft of all metals, being
only about feven times heavier than water. It pro-
duces a cracking noife when it is bent, though it yields
cafily. It is very foft, and, probably from this caufe,
it is Scarcely at all fonorous. It is confiderabjy mal-
leable, and may be reduced beneath the hammer into
laminae thinner than the leaves of paper (commonly
known by the name of tin folV) which are of great
life in feveral arts, particularly the foiling of looking
glaffes. Its degree of toughnefs is fuch, that a wire
of tin of the tenth of an inch in diameter fupports
a weight of forty-nine pounds and an half without
breaking.

Tin is the moft fufible of metals, and melts at a
little above the heat of .400°, which is long before it
becomes red hot. In patting from the fluid to ths
folid ftate it remains a ihort time in an intermediate
condition, in which it has little more cohefion than
\vet fand, and may be broken by a blow of a hammer,
or by agitation, into grains. Tin is eafily calcinable
in an obicure red heat 3 it at firft forms a grey pellicle j
and in a flrong heat it calcines with inflammation into

a white.

176 Natural Hiftory off in. [Book VI.

>a white powder. The calx of tin refifts fufion more
than that of any other metal ; from which property it
is uieful to form an opake white enamel, when mixed
with pure glafs in. fufion.

It is pbferved by miners, that though tin is the
lighteft of the metals, its ores are fome of the heavieft.
Tin is feldom or never found in the metallic or reguline
flate. The ores are often cryflallized, and of different
colours. Thofe which are of a reddifh colour gene-
rally contain a large proportion of iron. There alfo
is a fulphureous tin ore of a brilliant colour, fimilar
to that of zinc, or golden, like aurumxmufivum. The
more tranfparent ores of tin often contain "arfenic*
and this is feparated, almoft entirely, by repeated
roaftings.

In order to reduce the ores of tin, they are firfl
cleanfed from foreign admixtures by forting, pounding,
and waffling. In the fmelting of the ore, care is taken
to add a larger quantity of fuel than is ufual in the
revival of other metals, and to avoid a greater heat
than is neceflkry to reduce the ore, in order that the
lofs by calcination may be as little as poffible. Almoft
all the tin ufed in Europe comes from Cornwall, which
has been famous for its tin mines from the remoteft
periods of hiftory.

Tin is five times as dear as lead, and as a fmall
quantity of the latter mixed with a large quantity of
the former is with difficulty difcovered, the temptation
to adulterate tin is great, and the fear of detection fmall.
Bifiiop Watfon ftates, in his Chemical ErTays, that in
Cornwall the purity of tin is afcertained, before it is
expofed to fale, by what is called its coinage. The
tin, when fmeked from the ore, is poured into qua-
drangular moulds of flone, containing about three
hundred and twenty pounds of metal, which when

hardened

Chap. 30.3 Aftion cf Acids on Tin. 177

hardened, is called a block of tin ; each block of tin is
coined in the following manner : the officers appointed
by the duke of Cornwall affay it, by taking off a piece
of one of the under corners of the block, partly by
cutting and partly by breaking, and if well purified,
they (lamp the face of the block with the imprelTion
of the feal of the duchy, which (lamp is a permiffion
for the owner to fell, and at the fame time an afiurance
that the tin fo marked has been purpofely examined,
and found merchantable *.

The concentrated vitriolic acid aces on tin with the
production of fulphuf eous vapours, part of the oxygen
of the acid, as is ufual in the folutions of metals in their
reguline ftate, being abftra6ted; The acid diflblves
about half its weight of tin, but not without the af-
fiftance of heat. The iblution is very cauftic. The.
nitrous acid is decompofed by tin, as it is by moft of
the metals, with great rapidity. The tin is converted
into a white calx, which it is very difficult to reduce.
M. de Morveau has remained the formation of a
quantity of volatile alkali during the folution of tin
in the nitrous acid. This is probably owing to a
combination of the azote, produced by the acid, with
the hydrogen, derived from the decompofition of the
water contained in the menftruum. The advocates
for the phlogiftic hypothecs, however, fay, that the hy-
drogen is the phlogidon of the tin fet at liberty during
the folution.

The fuming muriatic acid acts ftrongly on 'tin, in-
ftantly lofing its colour and its property of emitting
fumes. The muriatic acid diffolves more than half
its weight of tin, and does not let it fall by repofe. By
evaporation it produces brilliant and very regularly

* Borlafe's Hiftory of Cornwall, p. 183.

VOL. II. N funned

178 Fuming Liquor of Libavius. [Book VI.

formed needles, which flightly attract the humidity
of the air. The oxygenated muriatic acid diflblves
tin very readily, and without the leaft fenfible effer-
vefcence. Aqua regia, confifting of two parts nitrous
and one muriatic acid, combines with tin with effer-
vefcence and the developement of much heat. The
foiution of tin in aqua regia is ufed by dyers to
heighten the colours of cochineal, gum lac, and fome
other red tinctures, from crimfon to a bright fcarlet,
in the dying of woollens. By firft diffolving tin in the
marine acid, and then boiling the foiution with nitrous
acid diftilled from manganefe, M. Hermfta=ut has
fucceeded in acidifying tin to fuch a degree as to con-
vert it into an acid ; it had then the form of a white
powder, foluble in three times its weight of water.

Tin has a ftronger affinity with the muriatic acid
than mercury has, and decompofes the corrofive mer-
curial fublimate. To effect this, the tin is firft di-
vided by the addition of a fmall portion of mercury ;
equal parts of this amalgam and the corrofive fubli-
mate are triturated together, and the mixture expofed
to diftillation in' a glafs retort with a very gentle heat.
A colourlefs liquor firft paffes over, and is followed
by a thick white vapour. The vapour becomes con-
denfed into a tranfparent fluid, which continually emits,
a thick, white, and very abundant fume. It is called
the fuming liquor of Libavios, and is a combination
of the muriatic acid and tin. The fmell of this flu-id
is very penetrating, and excites coughing. The va-
pours are not vifible without contact of air, and fecm
to confift of a peculiar gas, which is dccompofable by
air, and which then depofits the calx of tin in the
fame manner as the hepatic gas of Bergman depofits-
fulphur by the contact of air. M. Fourcroy pro-
.- it as a query, whether this elaftic fluid is a

compofition,

Chap. 30.] Aurum Mufivum and Pewter.- 179

composition of the oxygenated muriatic acid and tin ?
When water is added to this fuming liquor in a cer-
tain quantity, it becomes folid, and ceafes to emit
fumes. It is found that this concrete fubftance, when
rendered fluid by an increafe of temperature) is capable
of diffblving more tin without the efcape of hydrogen
gas. Hence it appears that the oxygen neceflary for
the folution of this additional quantity of metal is not
derived from the water but the acid, and that the
acid to impart it muft be in an oxygenated Mate.
The experiments of M. Adet have thrown much light
on the nature of the fuming liquor of Libavius, and are
publilhed in the Annales de Chemie.

Tin is capable of decompofing all the vitriolic neu-
tral falts. Tin has a confiderable attraction for ful-
phur, and eafily unites with it, when in a ftate of fu-
fion, into a black mafs. Aurum mufivum is a com-
bination of tin and fulphur, obtained by a particular
procefs. Arfenic cannot eafily be united to tin, on
account of the volatility of the former metal. Cobalt
unites by fufion with tin^ and forms an alloy in fmall
clofe grains of a light violet colour. Bifmuth in fmall
quantities as well as zinc, impart a firmnefs and white-
nefs to tin. Mercury diffolves tin with great facility,
and in all proportions.

The ufes of tin are very numerous. It is applied
to many purpofes in the arts. Its amalgam with
quickfilver or mercury is applied to filver looking-
glafies. The ufe of tin in covering plates of iron has
been already - fpecified •, and it is alfo employed in
lining the infide of copper vefiels. It enters into the
compofition of bronze and bell metal. It is the chief
ingredient in the compofition of pewter. Pewter cen-
fifls of tin united to fmall portions of other metallic
fubftances, fuch as lead, zinc, bifmuth, and antimony.
N a \Ve

i8b Vfe of Tin in Arts and Medicine. [Book VI.

We have three forts of pewter in common life; they
are diftinguifried by the names of flats ; trifle ; ley.
The plate pewter is ufed for plates and diflies ; the
trifle chiefly for ale pints, quarts, &c. and the ley-
metal for wine meafures and other coarfer ufes. Our
very beft pewter is faid to confift of one hundred parts
of tin to from ten to feventeen of antimony. To this
compofition the French add a little copper. In general
the lighted pewter is the beft. The inferior kinds are
heavier and ibfter, from a quantity of lead with which
they are adulterated. Putty is prepared from the
white calx of tin. The folution of tin in aqua regia has
been already mentioned as uleful in dying. When it
is mixed in the dyer's bath it forms a precipitate, which
carries down the colouring matter, and depofits it on
the fluff which is to be dyed fcarlet. The operation
of tinning copper will be afterwards defcribed. The
powder of tin has been ufed as a remedy againft worms
in large dofes, and therefore the fcruples which have
been entertained againft the ufe of veffels lined with
tin muft be wholly without foundation. Tin has been
analized by many chemifts, with a view to difcover the
quantity of arfenic contained in it. The refults of thefe
experiments have been by no means uniform. The
largeft proportion, however, which has been detected
in any tin ufed in commerce, is a grain in an ounce,
or one five hundred and feventy-fixth part of the com-
pound j but more frequently no arfenic whatever has
been difcoverecl.

Chap. 31.] [ 181 ]

CHAP. XXXI.

LEAD.

General Properties of Lead. — Red Lead.— Litharge. — Natural Hiftsry
of Lead. — Slickenjides. — Curious Phenomenon. — Smelting Lead Ores.
— *Union iu;th Acids,-— Plumbum Corncnm.— White Lead', bony
made.— Sugar of Lead.— Union -"with other Metals.—~ Common Saltier,
— U/es of Lead.-— Great Danger from leaden F'ejJ~els.—De:UGnJhire
Colic. — Means of deleting Lead in Liquors. — Medical Ufes of Lead.
—Ufes of its Calces in the Arts.

THE appearance of this metal is well known. It
is fo Toft as to be cut with a knife without much
difficulty. It is neither fonorous nor elafdc. It has
very little tenacity, and therefore cannot be drawn
into fine wire. It fpreads eafily under the hammer,
but cannot be extended into very thin leaves like gold,
filver, and tin. Its fpecific gravity is rather greater
than that of filver, being eleven times heavier than
water, and it is exceeded in this refpect by only three
metals, gold, platina, and mercury. Lead melts at
the five hundred and fortieth degree of Fahrenheit's
thermometer, before it becomes red hot.

Lead, like tin, at a certain point between its fluid
and folid ftates, poffefles very little cohefion, and may
be fcparated by a fmart blow with a hammer into
grains, which are ufed in ai&ying the ores of gold and
filver.

Lead, foon after it is melted3 acquires a film on its
furface, which prefents in fuccefiion a variety of co-
lours. This film becomes thicker, and of a grey co-
lour, by the continuance of the calcination, and is then
called plumbum uftum. If the firil pellicle is re-
moved, another is oAuickly formed, and in this way
N 3 almoft

i §2 Red Lead. [Book VI.

almoft the whole of the lead may be converted into
- a greyilh powder tinged with green and yellow.
This powder, being ground in a mill and waflieds
becomes of a more yellow colour. By further expo-
fure to a moderate heat, afiifted by the reverberation of
the flame of the fuel on the furface of this calx, it
gradually afiumes an orange, and then a bright red
colour, and is thus, in about forty-eight hours, con-
verted into the fubftance called minium, or red lead.
If lead is, in the phrafe of the chemifts, urged with a
more violent and fudden heat, the appearances which
it exhibits are different. It is firft converted into a
flaky fubftance, called litharge, which by the procefs
juft defcribed, may be converted into minium, but
which, by an increafe of heat, becomes fluid, and acts
fo powerfully as a folvent on earthy fubftances as
quickly to make its way through ordinary crucibles.

All thefe calces of lead may be eafily reduced to
the metallic ftate, by melting them in contact with
inflammable fubftances. In calcining and reducing
fixty hundred weight of lead, there is found to be a lofs
of eighr hundred. This lofs was explained by the old
chemifts on the fuppofition of the eicape of a volatile
fubftance called by them mercurial earth, but which
was never proved to have any exiftence. The lofs,
however, ought to be attributed in fome meafure to
the evaporation of part of the lead itfelf, and partly
to the imperfection of the procefs, as it is feldom
performed fo accurately as to reduce the whole of ths
calx.

Lead is very rarely found native. It is fometimes
found in the form of a calx, called native cerufe, or
lead ochre, or in that of lead fpar of various colours,
and which are in general either rhomboidal or cubical,
combined with fulphur is called galena, which

Chap. 31.] Curious Mineral. 183

is compofed in general of laminae which have nearly
the colour and afpect of lead, but are more brilliant,
and very brittle. A great variety of thefe ores have
been difcovered, which it will not be neceffary to
enumerate. One fpecies however is too curious in
its nature and effects to be omitted. It is called by
the miners Jlickenfides , and coniifts of galena united
with phofphorated hydrogen. The mineral has the
appearance of black marble, and breaks with a polifhed
furface, not truly plane, but lying in waves. It is
found in fiffures of lime-ftone in Haycliff and Lady-
wafh mines at Eyam, and in Oden at Caftleton, in
Derbymire. It is divided into two equal parts or
(labs, by a line parallel to the fides of the fiffure, and
thefe flabs are joined by two polifhed faces, which
feem to be in perfect contact without any cohefion.
The furfaces are of the colour of lead, but the covering-
is as thin as that from a black lead pencil. If a fharp-
pointed tool, which the workmen call a pkk, is drawn
over the vein with fome force, the mineral begins to
crackle like fulphur excited by electricity ; in a few
minutes after which the laminse explode with violence,
and fly out as if they had been blafted with gun-pow-
der, infomuch that the weight of forty tons has been
blown out together. Thefe dangerous effects deterred
the workmen from proceeding for fevera) years ; but
at length it occurred to them that this power might be
ufed for the carrying on of their works with better
advantage than by the common method of blafting
with gun-powder. Accordingly a workman makes
afcratch with his tool upon the joint of the Aickenfides,
and runs away as faft as he can, to efcape the explo-
fion, which, it is faid, loofens as much of the rock
as ten men would have brought away in three months,
by ctye ordinary methods.

N 4 From

184 f-ztur&l Hijtory of Lead. [Book VI»

From the component parts of this mineral, the reafort
of the explofion will eafily be underftood.;— By the
friction, the phofphorated hydrogen gas, which it
contains, is inflamed, but being encumbered with the
mafs of galena with which it is united, the inflamma-
tion is rather gradual than inftantaneous.

Lead, in fome inftances, has been found combined
with various acids ; the vitriolic, the phofphoric, the
carbonic, and the arfenical. The ores of lead very
commonly contain filver, and fometimes antimony.

In fmelting lead ores the fulphur is diffipated for
want of a proper apparatus for collecting it. Ac-
cording; to bifhop Wation's experiments, the Derby-
fhire lead ores contain in general from one-feventh to
one-eighth part of their weight of fulphur. One of
the chief circumftances to. be attended to in the fmelt-
ing of lead ores, particularly fuch as contain much
fulphur, is to keep them for fome hours in a moderate
heat, by which that fubflance may be gradually diffi-
pated. After this the fire muft be raifed to fufe the
mafs completely, by which the metal flows through
the IcoriiE, and is collected in the cavity at the bottom
of the furnace. The -.fcoriae being then thickened by
the addition of lime, fo that they may be raked afide5
a ftopper is drawn out, and the lead fuffered to flow into
an iron pot, whence it is laded into moulds, which form
it into the mafies called pigs of lead.

Lead is foluble in the concentrated vitriolic acid,

by the affiftance of heat only. The lead then forms,

the vitriolic acid, a fubftance icarceiy foluble in

wa:er. It feems to have a peculiar affinity with this

I, and leaves all others to combine with it, which

.iot the cafe with the other metals.

The nitrous acid acls flrongly on .lead. When the
is concentrated, it corrodes the lead into a white

Chap. 3i •] While Lead. 185

calx; but if it is confiderably diluted, it diffolves the
lead. This folution does not afford a precipitate on
the addition of water. Its cryftals, obtained by cool-
ing, are of an opake white. Th;s fait decrepitates in
the fire, and melts with a yellowifh flame when laid on
ignited charcoal. The calx, which is nt firft yellow,
is quickly reduced into globules of lead. The vitrio-
lic acid added to this folution combines with the me-
tal, and forms a precipitation. The marine acid, in
the fame manner, feizes the lead, and forms a combi-
nation, which., if expofed to heat, melts into a mafs of
a brown colour, called plumbum corneum, from fome
refemblance to the combination of the fame acid with
filver, called argentum corneum.

The acetous acid, or vinegar, acts on lead, particu-
larly when applied to it in fleam, in which proccfs the
action of the air probably affifts that of the acid. To
procure white lead, fheets, of lead are rolled up lr>i-
rally, fo as to leave the fpace of about an inch
each coil, and placed vertically in earthen po.-s, v>!,ich
have fome good vinegar at the bottom. Ti.c nots
are covered, and expofed to a gentle heat for a v ,fi-
derable time by furrounding them with horie dung.
The fleams of the vinegar circulate in the vrOrj, and
attach themfelves to the furface of the Icr ;: c^n vert-
ing it into white flakes, v.hich come off when '.lie lead'
is uncoiled. The remaining lead is ag T. «-xr>ofed to
the fleams of the vinegar, till another 6ru& L formed,
and the proceli is repeated till its L M ce is

converted into the white flaky matter dllc-i c^rule, or
white lead.

Such are the deleterious effects of ..> . ', . !u n taken
into the huuian body, that? the wr.
white lead works are ieldoin knov.
three years, when they exp.

pajn

1 8 6 Sugar of Lead. [Book VI.

pain from the Devor.fhire colic, lofe the entire ufe of
their limbs, or gradually pine away by a wafting, ma-
rafmus. In a well regulated community fuch works
ought to be entirely prohibited, or at leaft only car-
ried on by the word of felons, whofe lives would be
other wife forfeited.

Lead, after being thus reduced to the ftate of cerufe
by the fumes of the-acetous acid, may be eafily diflblved
in the fame acid in a fluid (late, and the faline matter
thus formed, is then called, from its fweet but aftrin-
gent tafte, fugar of lead,

To have this fait of lead in the form of tranfparent
cryftals, it is necefiary to ufe much acid j if there is
not a redundancy of acid, moft of the cryftals are
fmall and mealy. This may be remedied by difiblv-
ing them again in diftilled vinegar, and repeating the
cryftallization. In this manner fo much of the acid
may be united to the metal as to change the appear-
ance of the fait to that of an oily fluid. This metallic
fait, like others, may be decompofed by an alkali. In
all thefe cafes the precipitates of lead are white, but
the calces are coloured.

The faccharum faturni, or fugar of kad, may be
decompofed by heat alone, for, when expofed to a
gradual heat, the acid rifes in a very concentrated
ftate. This procefs is attended with the remarkable
'phenomenon of the production of a quantity of ardent
fpirit *. To underftand the caufes of this phenome-
non, it is only neceflary to be informed that alcohol, or
ardent fpirit, is a combination of hydrogen, charcoal, and
a fmall quantity of oxygen. Now all thefe principles

* By the pV!ogi(Hc hypothecs tins fact admitted of explanation,
by fuppofing that the principle of inflammability of the metal
combined itfelf with a portion of water, contained in the acetous
acid, arid thus formed alcohol, or fpirit.

fcxift

Chap. 3 1 .] Lead Solder. 187

exift in vinegar, the bafis of which is hydrogen and
charcoal, brought to the ilate of an acid by their union
•with a large proportion of oxygen. The chief differ-
ence, therefore, between vinegar and alcohol is, that
the former contains much more oxygen. As part of
the oxygen, however, after this operation, is full re-
tained by the lead, which is not reduced to ks metal-
lic form, it is very natural to fuppbfe that part of the
fluid which paffes over fhould be reduced to the ftate
of alcohol.

Nitre, heated with lead, calcines it into a yellow
fubftance, but without producing deflagration. Sal
ammoniac and common fhlt are decompofed by being
heated with the calces of this metal, but the neutral
falts, in general, are not acted on by it. Sulphur
readily diiTolves it by the affiftance of heat, and pro-
duces a brittle compound of a deep grey colour and
brilliant appearance. Phofphcrus may be united with
lead, and forms with it a malleable and foft com-
pound, not very different in appearance from lead
itfelf.

Lead combines with bifmuth, and affords a metal
of a fine clofc grain, which is very brittle. The alloy
of lead with arfenic has not been examined. Nickel,
manganefe, cobalt, and zinc, do not unite with lead
by fufion. With antimony it forms a brittle alloy,
with fome brilliant facets. Mercury diflblves lead
with the greateft facility. Lead unites very eallly with
tin. Two parts of lead with one of tin form an alloy
more fufible than either of the metals taken feparately,
and which is, therefore, ufed by plumbers as a folder.

Lead is ufed for a great number of economical
pnrpofes. Leaden vefiels, however, are very apt to
communicate injurious properties to all fluids which
are kept in them for any length of time, and fhould

wholly

i8.& Devptijbire Colk. [Book VI.

wholly be rejected in. the management of fuch fluids as
contain an acid capable of acting immediately on the me-
tal ; as fuch fluids, if impregnated with even a fmall por-
tion of lead, will be found, when taken into the body,
irreparably to injure the conftitutioh of perfons who are
in the habit of ufing them. Inilances in which lead re-
ceived into the body has produced the lingering and
painful diforder called the painter's colic, or the colic of
Poitou, are too numerous to leave any queftion as to the
pernicious effects of this metal. The liquors in which
an admixture of lead is moil to be apprehended are,
cyder, wines, and rum. In Devonfliire, from the great
life of cyder, and the improper methods of making it,
by which, eicher through careleffnefs or defign, lead
becomes diffolved in it, the diforder above mentioned
prevails fo much, as to have obtained the name of the
Devonfhire colic.

It is unfortunately the cafe, that lead diffolved in
vinous liquors is capable of imparting a rich and agree-
able flavour to them, and even of reftoring them after
they have become considerably acidulated. The
temptation to ufe lead, therefore, in this way, is great;
and fo long as dealers are ignorant of the pernicious
effects of this metal, or want honefty to prefer the
fafety of their cuftomers to their own profit, there is
no reafon to hope that the habit of occafionally ufing
it will he abojifhed. The adulterating of wines in this
manner was fo common a few years ago in France,
that it was unfafe for ftrangers to ufe the wines which
were fold at their inns. It is very defirable to be
furnifhed with the means of detecting tljis perni-
cious ingredient, and the, following are recommended
by .an author, whofe {peculations even on the moil
common fubjects have ever been directed to the public
good, and are always productive of public advan-
I tage;

Chap." 31.] Means of difcovenng Lead in Liquors. 1 89

tage*: Boil together, in a pint of water, an ounce of
quick lime and half an ounce of flowers of brimrlone,
and when the liquor, which will be of a yellow colour,
is cold, pour it into a bottle, cork it up, and referve
it for ufe. A few drops of this liquor, being let fall
into a glais of wine or cyder containing lead, will
change the whole into a colour more or lefs brown,
according to the quantity of lead which it contains ;
if the wine is wholly free from lead, it will be rendered
in fome meafure turbid by the liquor, but the colour
will be rather a dirty white than a blackim brown.

In general, a folution of common liver of fulphur
will precipitate the lead, but unfortunately iron as
well as lead is precipitated by both thefe tefts, and it is
faid that many honetl wine merchants have been ruined
by this means, by having iinjuftly fallen under the
fufpicion of adulterating their wines with lead. M.
Hannemann has publifhed a paper in the Journal de:
Phyfique, in which he affures us, that the following
liquor, whilft it does not precipitate iron, will preci-
pitate lead and copper of a black colour, and arienic
of an orange. Mix equal parts of oyfter (hells and
crude fulphur in fine pov/der, and put them into a
crucible ; apply a brifk fire in an air furnace, fo as to
make the crucible of a white heat for about fifteen
minutes. The mafs, when cold and powdered, fhould
be kept in a bottle well corked. To prepare the

* Bifhop Watfon. This excellent and truly refpeftable author,
tliis great ornament of the Englifh church, will. I flatter myfelf,
'forgive the very free and frequent ufe I have made of his incom-
parable Eflays. He has ever been

*' Mihi magnus Apollo."
" My guide, philofopher— — "

and, if I was not afraid of prefuming too far, I would add the con-
clufton of that well known line.

liquor,

190^ Extenjive Effects off be Polfon of Lead. [Book VI ;

liquor, put one hundred and twenty grains of this pow-
der, and one hundred and eighty grains of cream of tar-
tar, into a very ftrong bottle, fill it with water, let it boil
for an hour, and then cool. Cork the bottle, and fre-
quently fhake up the ingredients. After it has flood
for fome hours to fettle, pour off the clear liquor, and
put it into little bottles, which contain about an ounce,
having previoufly dropped into each twenty drops of
marine acid. Cork them clofe by means of wax
mixed with a little turpentine. One part of 'this li-
quor, mixed with three parts of the wine fuppofed to
contain noxious metallic particles, will difcover, by a
black precipitate, the fmalleft particle of lead or cop-
per, but will not affect the iron contained in it. Pure
wines are not difcoloured by the addition of this
liquor. •

The deleterious effects of lead are not confined to
its action on the flomach. Men who work in the
manufactories for the different preparations of lead
are liable to complaints very fimilar to thofe who drink
liquors containing lead. Painters are fo liable to this
complaint, from the lead contained in paint, that it
has obtained, on this account, the name of the pain-
ter's colic.

Lead is the moft powerful article in the materia'
medica in retraining hemorrhages and exceflive dif-
charges, but its uie is fo dangerous that it is not very
often employed internally by phyficians. Yhe prepa-
rations of lead are, however, highly beneficial, without
being generally dangerous, as ingredients in plafters
and other external applications, particularly in the well
known Goulard's extract.

The calces of lead are ufed in making fome kinds
of glafs, of which they increafe the folidity, and to which
they impart a kind of unctuofity which fits them for

being

Chap. 31.] Vfes of 'Red Lead. 191

being cut and polimed with lefs danger of breaking.
Lead enters particularly into the compofition of flint
glafs, and the compofitions called paites, or artificial
gems. The chief defect of flint glafs is, that it is apt
to be of unequal denfity, which renders it difficult
to find pieces of any confiderable dimenfions free from
ftrias. Litharge is alfo employed by potters for glaz-
ing their ware.

The ufes of red and white lead, as pigments, are
well known. The common red wafers are coloured
with red lead, as may be eafily feen by holding one
of them in the flame of a candle, when the lead will
be reduced, and appear in little globules j thefe wafers
ihould, therefore, never be left in the way of children,
as they may be induced to fwallow them, and may
confequently fubjecl: themfelves to all the ill effects
arifing from this fatal poifon. The beft red wafers
are coloured with vermilion.

[ 192 ] [Book VI.

CHAP. XXXII.

COPPER.

General Properties cf Copper. — Its Natural Hiftory.- — Turquoife Gem,
— Smelting and refining cf Copper. — Antique Statues preferred by the
Gresn Rit/f. — Union with Acids.— Blue Vitriol. — Colouring cfGuns.
— Cuprum Ammoniacum.— Verdigris. — Union with Metals. — White
Copper. — Pinchbeck. —Gun Metal. — Bell Metal.~Mctal of ancient
Slaiues. — Bronze. — Speculums of Reflecting Tele/copes. — Pot Metal,—
Tinning of Copper.

COPPER is a metal of a peculiar red colour,
and when its furface is frefh and clean it has a
confiderable degree of fplendor. It is hard, ductile,
and malleable to a confiderab'e degree, and remarkably
fonorous. It has a peculiar and unpleafant fmell, par-
ticularly when rubbed. Its tafte is ftyptic and nau-
feous. Its tenacity is fuch, that a copper wire of one:
tenth cf an inch in diameter is capable of fupporting
a weight of about three hundred pounds. Its fracture
exhibits the appearance of fmall grains. Its gravity
is about nine times that of water.

Copper has a great degree of ftrength and rigidity >
approaching to that of iron. It is nor inflammable
like iron, and is therefore iifed in gun-powder works,
inftead of that metal. It does not admit, like iron,
of being welded, but this defect is compenfated by its
greater fufibility, by which it may be always formed
into the defired Ihape. It requires for its fufion about
the fame heat as gold and fiiver. W hen in fufion, for
which it requires a ftrong white heat, it appears of a
blueifh green colour, which arifes from a flame of that
colour on its furface. By' a very violent heat it boils,

and

Chap. 32.] 1'urqtiolfe Storit. 193

and is volatilized partly in the metallic ftate. Copper,
in a heat far lefs than is fufficient to melt it, becomes
calcined at its furface, and exhibits various colours. In
a greater heat than is fufHcient to pro luce this effect,
its furface is converted into thin fcales, which mav^ be
eafily fcraped off.

Copper is fometimes found native, having the me-
tallic fplendor, the malleability, and all the properties
of ordinary copper, It has fometimes the form of
plates, fometimes that of fibres or branches, and is
fometimes cryftallized. Copper, in its metallic ftate,
is fometimes found depofited on ores of iron, in which
cafe it muft be confidered as having been feparated
from native vitriol of copper by the fuperior attraction
of iron for the vitrioii., ne native folutions

of copper often depofit that metal in a calcined ftate
in beds of calcareous earth. The turquoife ftone
is the tooth of an animal, penetrated with the blue
calx of copper. Copper is generally found, how-
ever, in ores. Thefe are frequently mineralized by
fulphur. What are improperly called the vitreous
ores of copper are of this kind j they are brown, red}
and grey, and thefe colours are frequently mixed with
a greenifh or violet tinge. Thefe melt eafily, are
very ponderous, may be fcratched or even -cut with
a knife, and are very rich in metal, as an hundred
pounds of them ufually yields from eighty to ninety
of copper. The azure copper ore differs from the
former chiefly in containing a confiderable quantity of
iron. The grey copper ores, which have not much
fplendor, confiit of copper, fulphur, arfenic, and f ;me
iron. What are called copper pyrites contain in
reality more iron than copper, but yield enough of the
latter metal to anfwer the expence of working them;

VOL, II. , O they

1-9-4 Natural Elftory of Copper. [Book VI.

they are generally of a yellow and brilliant afpect. Cop-
per is alfo, in fome fpecimens, found united 'with flatey
pitcoal, zinc, and antimony.

Copper is feparated from its ores by different pro-
carles, according to the nature of thofe ores. If they
contain much fulphur, after being pounded and wafhed>
they are roafted in the open air to difpel the fulphur,
which in a great meafure fupplies the want of other
fiieL The ore is afterwards roafted once or twice
more with wood, and is melted in an open fire into
a mafs called a mat of copper. In this ftate it Hill
contains a large quantity of fulphur, which the work-
men continue to expel by repeated roaftings and fu-
fions, till the metal acquires a certain degree of purity,
and is called black copper, which is fomewhat mal-
kable, but ftill contains fulphur, iron, and generally
fome other impurities. In order to clear it entirely
ofthefe, the copper is haftily fufed with three times
its weight of lead. The lead unites with the copper
and expels the iron, and the imperfect metals, which
happen to be mixed with the copper, are expelled by
cupellation. The copper is afterwards refined, by
keeping it heated in crucibles for a confiderable time,,
fo that it may throw up all the foreign fubftances it
Hill contains in the form of fcoria:. It is examined,
from time to time, by_irnmerfing iron rods in it, which
become coloured with a fmall quantity of copper, and
its purity is judged of by the brilliant rednefs of thefe
fpecimens.

Copper is not fo eafily acted on by the air as iron.
In fituations, however, where it is expofed to the action
of moift air, k becomes gradually covered with a green
ruft or calx, which is fapid and foluble in water. This.
ruft never penetrates into the frhftance of copper, but

fcerris:

, Chap. 31:] Aft'wn of Salts oh Copper. iq$

feems rather to contribute to the prefervation of its
internal parts, as may be feen in antique medals and
Itatues of this metal.

Copper does not unite with earthy matters ; its
calx, however, promotes their fufion, and forms with
them glafles of a deep brown. Cauftic fixed alkalies,
digefted in the cold with filings of copper, aiTume, after
a time, a light blue ' colour, the copper becoming co-
vered with a powder of the fame colour. Copper,
treated in the fame manner with volatile alkali, pro-
duces, in a few hours, a deep and moft beautiful blue,
the quantity of copper taken up being very inconfi-
derable. From the ftrong blue colour produced by
the action of copper and volatile alkali, they become
excellent tefts of the prefence of each other in any body,
fluid or folid.

Copper is in general eafily acted on by acids. The
vitriolic acid, however, does not ad on it unlefs con-
centrated and affifted by heat ; it then corrodes the
copper into a brown matter of a thick confidence,
which, by the addition of water, affords a folution of
a deep blue colour. If this folution is evaporated to
a certain point, and fuffered to cool, long rhomboidal .
cryftals are afforded of a deep blue colour, called
vitriolated copper, or blue vitriol -, it appears therefore
that vitriolic acid forms, with iron, green cryftals ;
with zinc, white cryftals ; and with copper, blue cryA
tals.

Copper may be obtained from the folutiori of blue
vitriol, by dipping into it pieces of iron. The vitri-
olic acid diffolves the iron in preference to the copper,
and depofits the latter, in its metallic form, on the fur-
face of the iron. Upon this circumftance is founded
the procefs for browning fowling-pieces. The barrels
O 2 arc

196 Blue Vitriol, &V. [Book VI.

are moiftened with a folution of blue vitriol, which dif-
folves the iron to a very inconfiderable depth, and de-
pofits in its place a thin lamina of copper.

Blue vitriol has' a ilrong ftyptic tafte, and is in fome
degree cauftic. Expofed to heat it parts with its water
of crystallization, melts, and becomes of a pale blue
colour. A ilrong heat is required to feparate from it
the vitriolic acid, which adheres more firmly to copper
than iron! Blue vitriol is decompofed by magnefia
and by lime. If the mild vegetable alkali is poured
into a folution of blue vitriol, a precipitate is formed
of a pale blue colour, which, however, becomes green
by expofure to air : in this experiment no effervefcence
takes place, and we may therefore conclude that the
carbonic acid of the mild alkali unites with the calx
of copper. Volatile alkali precipitates the folution of
blue vitriol, in the fame manner, of a blueilh. white
colour; but the mixture very foon becomes of a deep
blue colour, which happens from the alkali re-diiTolving
the precipitate. In order to obtain the cuprum ammo-
macum, which has been recommended as a remedy for
epilepfy, add volatile alkali till the whole precipitate
of copper is re-difiblved, then fet the folution before
a fire in a flat vefiel, and let it gradually evaporate,
which mould be done with a heat not exceeding that
of the human body; the matter which remains at the
bottom, in the form of a cruft, muft be rubbed in a
mortar, that it may be intimately mixed.

. The blue vitriol of the (hops is made by means of
the action of fulphur upon copper ; thefe are gently
calcined together : the fulphur attracts the oxygen of
the atmofphere, and unites with the copper into a fo-
luble powder, which is afterwards cryftallized into blue
vitriol.

A beautiful

Chap. 32.] Beautiful Green Paint. 197

A beautiful green paint may be precipitated from
blue vitriol, by means of white arfenic diflblved in
water together with vegetable a4kali.

The nitrous acid diflblves copper with great rapi-
dity, without the afiiftance of heat, with the production
of a large quantity of nitrous gas. Part of the metal
falls down in the form of a calx, and the filtrated folu-
tion, which is of a much deeper blue colour than the
vitriolic folution, affords cryftals by flow evaporation.
This fait is more corrofive than vitriolated copper;
it fo powerfully attracts the humidity of the atmo-
Iphere that it deliquefces, unlefs kept in clofe vefTels or
in a very dry place. When melted in a crucible it
emits large quantities of nitrous vapour and becomes
brown, in which ftate it is merely a calx of copper.
In a dry and hot air this fait becomes covered with
a green efflorefcence. It detonates lightly on burning
coals .

The muriatic acid acts with great difficulty on. cop-
per in its metallic ftate, but diflblves its calces with
conflderable rapidity. This may be eafily accounted
for from the ftrong attraction which the bafis of
the muriatic acid has for oxygen, fo that it will not
part with any of it to oxygenate the metal, and no
metal is foluble in acids without being oxygenated.
"When, however, the metal -has been prepared for
folution by an union with oxygen, that is by being cal-
cined, the acicl then diflblves it, ,and adheres very
clofely, fo that it is with great difficulty feparated by
heat. The muriatic folution of copper is of an
agreeable green colour, and affords cryftals of the fame,
and in this particular differs remarkably from the vi-
triolic and nitrous combinations of copper, which are
of a deep blue.

The vegetable acids diflblve copper when caic:

O 2 but

j 98 ProceJ-s of preparing Verdigris. [Book VI.

but fcarcely ad: on it in its metallic ftate. It is ar
curious circumflance, which has never been fuffi-.-
ciently explained, that vegetable acids act more power-
fully on copper when cold than when they are heated.
Thus pickles, or even lemon juice, may be boiled in,
clean copper veffels without danger; and yet, if left
for a few hours, when cold, in copper vefiels, they are
apt to contract a metallic impregnation fufficient to
produce dangerous effects. This fact has by fome
chemifts been attributed to the fleams of the boiling
fluid keeping off the air, which is thought to affift the
actiop of the acids.

Verdigris is a very beautiful green ruft or calx of
copper, much ufed by painters, and prepared in large
quantities near Montpelier in France. The procefs
for making verdigris was thus defcribed by M. Mon-
net, of the Royal Society of Montpelier, about the
year ^750. Vine ftalks, well dried in the lun, are
Itemed, during eight days, in ftrong wine, and after-
wards drained •, they are then put into earthen pots,
and wine is pouied upon .them; the pots are kept
carefully covered. The wine undergoes the acetous
fermentation, which in fummer is finiflied in {even or
eight days, but requires a longer time in winter, though
this operation is always performed in cellars. When
the fermentation is fufficiemly advanced, which may
be known by obferving the inner fur face of the lids
of the pots, which, during the progrefs of the fermen-
tation, are continually wet by the mciliure of the rif-
ing vapours, the ftalks are to be taken ou; of the pots.
The ftalks are by this method impregnated with all
the acid of the wine, and the remaining liquor is only
a very weak vinegar. The ftalks are now drained
Tome time in bafkets, and layers of them are put into
earthen pots with plates of Swedifh copper, fo difpofed

'that

Chap. 32.] Detonation of Copper. 199

that each plate may reft on and be covered with layers
of ftalks. The pots are covered with lids, and the
copper is thus left expoled to the aclion of the vinegar
for three or four days or more, in which time the
plates become covered with verdigris. The plates
are then taken out of the pots, and left in the cellar
three or four days, at the end of which time they are
to be moiftened with water, or forne of the weak vine-
gar above mentioned, and left to dry. When this
moiftening and drying of the plates has been repeated
three times, the verdigris will be found to have in-
creafed confiderably in quantity, and it may then be
fcraped off for fale.

A folution or erofion of cop'per may be obtained by
employing ordinary vinegar inftead of wine^ as is di-
rected in the above procefs. It would not, however,
have the un&uofity of the bed verdigris, which quality
is necefTary for painting. Good verdigris cannot be
prepared, except with a vinous acid, or a folvent partly
acid and partly fpirituous. Accordingly the fuccefs
of the operation depends chiefly on the degree of
acetous fermentation to which the wine has been
carried.

By diftilling verdigris, the acetous acid may be fe-
parated in a concentrated flate, and of a ftrength equal,
or perhaps fuperior, to the muriatic acid.

Copper is capable of a very flight detonation ,with^
nitre. It decompofes fal ammoniac, and at the fame
time the volatile alkali is in fome meafure refolyed into
its conftituent parts, azote and hydrogen.

Sulphur and pholphorus may be united to copper;
they deprive it of its metallic Iplendor, and change it
to a black colour. If plates of copper are ftratified
in a crucible with fulphur, they unite, and form a
compound which is ufed in the dying and painting of
O 4 calicoes;

aoo Gun and Bell Metal. [Book VI.

calicoes. Liver of fulphur and hepatic gas have a
ftrong action on copper ; the former diflblves the me-
tal by the dry, as well as by the humid way; the latter
ftrongly colours the furface, but its effect has not yet
been well examined into. Oils alib difiblve copper,
particularly thofe of an aromatic kind.

There are few metals which will not form alloys with
copper. A metallic compound is made with copper
and arfenic in imitation of filver, but it fbon tarnifhes.
In treating of zinc, the procefs for making brafs has been
defcribed1. Pinchbeck is a kind of brafs made in imi-
tation of gold. Copper is the bafts of gun metal and
bell metal. Gun metal is faid to confift of copper,
with about one- tenth part of tin; bell metal, of copper
with about one-fifth of tin, It may in general be ob-
ferved, that a lefs proportion of tin is ufed for making
church bells than clock bells, and t^at a little zinc is
added for the 'bells of repeating watches, and other
fmall bells.

Copper, in a ftate of fufion, is liable to a«violent ex-
plofion if touched with any humidity. In the calling
of bells and cannon they are particularly careful to
have the moulds dry; for if the leafl moifture finds
accefs, it is fuddenly converted into vapour, and by its
expansion throws the metal to a confiderable diftance,
to the great danger of the perfons prefent.

The beft poffible proportions of copper and tin, for
the above purpofes, have never, I believe, been accu-
rately afcertained. The metallic compound ufed by
the Romans for their ftatues and plates for infcrip-
rions, is defcribed by Pliny the naturalift. They
firfl melted a quantity of copper ; into the melted
copper they put a third of its weight of old copper,
which had been long in ufe; to every hundred pounds
weight of this mixture they added twelve pounds and

6 an

Chap. 32.] Antique Statues and Medals* 201

an half of a mixture compofed of equal parts of lead
and tin. Tin melted with copper forms the compound
called bronze. Of this compound the fpecific gra-
vity is always greater than would be deduced by com-
putation from the quantities and fpecific gravities of
its component parts. There feems to be a happy re-
lation'between thefe metals, which fits them for form-
ing, in conjunction, compounds of great firmnefs, den-
fity, and clofenefs. From thefe properties they admit
of an excellent polim, and Pliny accordingly informs
us, that the beft looking-glaiFes of his time were made
of a compofition of copper and tin. But the attention
of philofophers is more particularly directed to the
mixture of copper and tin, on account of its being the
fubftance of which the fpeculums of reflecting ttle-
fcopes are made. Mr. Mudge found, after a number
of trials, that fourteen ounces and an half of grain tin,
with two pounds of copper, made the beft compofition
for this purpofe ; an addition of half an ounce more
of the tin rendered the compofition too hard to be
properly polifhed.

Pot metal is made of copper and lead, the latter
being one-fourth or one-fifth of the weight of the for-
mer. Lead, however, does not feem to have any re-
markable attraction for copper, and does not promote
its fufion, unlefs the lead is heated to a high degree ;
the copper then diiTolves with fome degree of efferve-
fcence. On allowing the compound to cool, the cop-
per feparates again, and forms litde grains in the mais,
through which the lead remains difperfed. It is eafy
to feparate the' lead again from the copper, if the mals
is expofed in a furnace •, for the lead melts firft and
leaves the copper; the lead, however, which runs of?
at firft, contains fome of the copper, which may be
£ afily feparated by melting the lead and taking off the

fcum,

202 Binning' of Copper. [Book VI,

fcum, which contains the copper. Silver is feparatcd
from copper by melting the latter with three times its
weight of lead j the lead is then melted out, and carfies
with it the filver. The filver is afterwards feparated
from the lead by the calcination of the latter metal.

From the pernicious effects which have been ex-
perienced from impregnations of copper in aliments
drefTed in copper veffels) it has become a very general
cuftom to cover thefe veflels with an internal coat of
fome other metal. The method of tinning iron has
been defcribed, and that of tinning copper is very fimilar,
except that the compofition for covering the furface of
copper confifts of about one part of lead to two of tin,
whereas iron is covered with tin alone. Zinc has been
recommended as a fubftitute for tin in thefe operations,
and has the advantage of fuperior hardnefs. The me-
thod of tinning copper veffels is by making their inter-
nal furface perfectly bright, and then wafhing them
•with a folution of fal ammoniac. The veffel is next
heated, and the tin or metallic mixture is melted and
poured into it, and being made to flow over every part
of the furface of the veffel, it incorporates with the,
copper, and when cold remains united with it. Rofin,
or pitch, are fometimes ufed to prevent the tin from
being calcined, and the copper from being fcaled,
cither of which circumftances would prevent the ad-
hefion of the tin. Bifhop Watfon eftimated the quan-
tity of pure tin which is ufed in tinning a definite fur-
face of copper, and found that half an ounce of tin was
fpread over two hundred and fifty-four fquare inches,
or fomewhat lefs than a grain of tin on each fquare
inch i but the fame author fufpecls, that not a quarter
of a grain of tin is fpread over a fquare inch in the
ordinary mode of tinning, and therefore recommends
it as a neceffary -caution againft the coat being rubbed

Chap. 32.] Caution in tie Ufe of Copper Veffeh. 203

off, and the copper becoming expofed, to make fa
as thick as poifible, and to ufe tin nearly pure.

A very excellent method of tinning, and one much
practifed in England, is, to make ufe of pure tin, and
hammer it on the copper. It feems probable, how-
ever, that when copper vefifels are kept well fcoured,
that no danger will arife from them in the dreffing.of
animal food, or even of vegetable aliments, unlefs fufc
fered to remain in the veffels when cold.

[ 2C4 1 [Book VI.

C HAP. XXXIII.
MERCURY.

Great Attraction of this l-.'L'ta! for the Matter of Heat. — Quickfti'ver ;

rendered folid ; malUalle General Properties of Quickfil-ver. — Hy-

drargyrus calcinates. — Natural Hijiory cf Mercury. — Cinnabar.—
Native Vermilion.— Aftion of Acids on this Metal.— Turbitb Mine-
ral.— Red Precipitate. — White Precipitate.— Corroji<ve Sublimate.—
Calomel.— Kcyfer's Pills. — Ethiop's Mineral.— Vermilion. — Amal-
gams.—Gold made brittle by Merctuy. — Mode of gilding Metals.—
V/e of ^uickfil'ver in extracting the precious Metals, from the Earth.
—Making of Looking Glares. — Conditions necej/ary for the Operation
cf Mercury on the human Body.

TH E circumftance which moft remarkably dif-
tinguifhes mercury, or quickfilver, from the
other metals, is its ftrong attraction for caloric, fo that
it retains the ftate of fluidity at the ordinary tempera--
ture of the atmofphere, and at the temperature of 600
degrees of Fahrenheit is converted into vapour; few
of the other metals, therefore, melt at fo low a point
as that at which mercury boils and is volatilized. It
was long taken for granted that there was fomething
peculiar in mercury, which rendered it neceffarily fluid ;
but the academicians of Peterfburgh have proved that
this is an erroneous idea, and have mewn that mercury
differs from oth'er metals merely in the degree of heat at
which it paries from its folid to its fluid ftate. The
congelation of mercury has been effected in a variety
of inftances by the help of the nitrous acid and fnowa
or pounded ice, commonly called the freezing mixture,
and > the congelation is found to take place at the
thirty-ninth degree below o of Fahrenheit's thermo-
meter. Mercury, in its folid form, is found to have

confide rable

Chap. 33.] Mercury in a jolid State. 205

confiderable malleability, but this cannot be proved
to its fulleft extent, becaufe the hammering' of it
produces very foon a degree of heat fufficient to
melt it.

Mercury being a metal in a ftate of fufion, always
affects the form of globules when it is divided j and
when it is confined in a bottle, its furface is convex,
from the ftrong attraction of its particles for each
other. If the veffel, however, in which me/cury is
confined, is metallic^ its furface appears concave, from
the tendency which it has to unite itfelf to the fides of
the veflel, which attraction overcomes that between
its own particles.

When mercury is'fubrnitted to that degree of heat
at which it is volatilized, and is at the fame time ex-
pofed to the action of atmofpherical air, it is gradually
converted into a calx of a red colour, the hydrargyrus
calcinatus of the London Pharmacopeia. A greater
heat, however, revives this metallic calx, and at the
fame time the vital air is again extricated.

Mercury is not fenfibly acted on by expofure to
air, but by long continued agitation it becomes .partly
converted into a very fine black powder. The mer-
cury is not changed in this experiment, unlefs, per-
haps, it fhould be. found that it abforbs ibme part of
the vital air contained in the veffel in which it is con-
fined. By a flight heat, or by trituration in a warm
mortar, it may be made to refume its ufual fluidity and
brilliancy.

Mercury is found in the earth, either in its native
.metalic ftate, or combined with fulphur, when it is
called cinnabar. Running mercury is found in glo-
bules, or larger maflfes, in friable earths or ftones, and
moft commonly in the clefts or cavities of its ores. It
is more frequently, however, imbedded in calcareous

earths

266 Natural Hiftory of Mercury. [Book Vt.

earths or clays of different colours, from Which it may
be feparated either by trituration or lotion, the fmaller
globules coakfcirtg by mutual contact into larger 3 or
by dii I illation.

More mercury is found in the ftate of cinnabar
than in its metallic form. This ore confifts of mer-
cury and fulphur combined together in different pro-
portions. Cinnabar is fometimes found in the form
of a brilliant red powder, and is then called native
Vermilion, fometimes in an indurated ftate, and though
generally red, has been fometimes obferved of a yel-
lowilh or blackifh caft. It is moftly opake, but fome
Specimens are as tranfparent as a ruby.

Mercury is too volatile to admit of the fulphur being
Separated from it by roafting ; thefe fubftances are
both fo volatile that they would rife together. In or-
der to feparate mercury from its ore it is neceffary to
add quick lime, or iron filings, unlefs fome fubftances
of a fimilar nature happen to be naturally mixed with
it; the mafs is then fubmitted to diftillation, and the
calcareous earth, or iron filings, by fuperior attraction,
detain the fulphur, while the mercury comes over in
the ftate of vapour, and is condenfed in the receiver.
Different cinnabars yield from three parts to feven
parts in eight of their weight of mercury. Mercury
has fometimes been found united with the muriatic
and vitriolic acids, and with the ores of fome other
metals. It is thought to be not abundant in nature -,
but this opinion may be partly owing to its volatility,
which may prevent it from being difcovered in many
minerals that may contain it. Moft of the mercury in
commerce is afforded by the mines of Idria in the
Auftrian dominions, Almaden in Spain, and Guanca-
velica in Peru.

The vitriolic acid does not act on mercury unlefs

concentrated

Chap. 33.] Tur&itb Mineral. 207

concentrated and confiderably heated ; it then corrodes
it into a white mafs, and the vitriolic acid is rendered
partly volatile by the abftraction of oxygen. The
greatefl part of this mafs, which weighs confiderably
more than the mercury made ufe of, is a calx of mer-
cury united to a fmall portion of vitriolic acid, but
part of it is a perfect fait, formed by the union of the
vitriolic acid and mercury. If boiling water is added
to it, it aflufnes a bright lemon colour, which is owing
to the abftracYion of the vitriolic acid, the pre'fence of
which rendered the mafs white. The more boiling
water is ufed the yellower is the remaining powder,
which, after repeated effufions of water, is found to
have no caufticity, and to be nearly a pure calx of
mercury. This is the fubltance known under the
name of turbith .mineral. The water, which has been
poured on the vitriolic mercurial mafs, is found to con-
tain a confiderable quantity of vitriolic acid united to
the calx of mercury.

The nitrous acid is decompofed by mercury with
the greateft rapidity. Strong nitrous acid will take
up its own weight of mercury in the cold, and this
folution will bear to be diluted with water. If the
folution is made by the afiiftance of heat, a much,
larger quantity is diffolved ; but a precipitate is pro-
duced by the addition of water. If cold water is
employed, a white precipitate is afforded, but if hot
water the precipitate is of a yellow colour, and greatly
refembles the turbith mineral produced by the vitriolic
acid. If acid is added to the folution produced by
heat, it is not decompofed by water. This folution
is very ponderous and acrid, and ftains the fkin of a
deep purple, inclining in appearance to black, a por-
tion of the mercury being precipitated by the animal
matter, while the -acid acls on it. Cauftic alkali,

added

2oS Red Precipitate, 6V. [Book VI .

added to this folution, precipitates a pure calx ; mild
alkali, a calx combined with carbonic acid. The
volatile alkali precipitates the mercury in the form
of a dark grey powder. When this precipitate is
examined, it is found to contain a quantity of uncal-
cined mercury. For if this matter is dried and rubbed
on pure gold, it turns white, by which we may dif-^
cover (mail quantities of mercury in the metallic ftate.
The near approach to the metallic ftate, obferved in
the precipitate afforded by the volatile alkali, feems to
be owing to the prefence of hydrogen, which is one of
the conftitucnt principles of volatile alkali, and which
has a ftrong attraction for oxygen.

The precipitates of mercury, formed by alkaline
intermediums, have a property difcovered by M.
Bayen, which muft not be paflfed over in filence. They
detonate like gun-powder, when expofed in an iron
fpoon to a gradual heat, after having been triturated
in the quantity of half a drachm, with fix grains of
flowers of fulphur : after the detonation, a violet powder
remains, which may be fublimed into cinnabar.

The nitrous acid may be feparated from mercury
by heat alone. Its firft effecl: is to evaporate the
watery parts ; after this the acid flies off in deep co-
loured fumes ; as the acid evaporates the calx becomes
yellow, then of a deep red, but when removed fome
time, orange. This is the red precipitate of the
fhops. The nitrous acid, therefore, as in the cafe of
other metals, though it ads with more rapidity, ad-
heres with lefs force to the mercury than the vitriolic
acid, which ads flowly and with difficulty. This
proceeds, as was before mentioned, from the eafe with
which the nitrous acid is decompofed, fo as to afford
to metals the oxygen which is neceilary to render them
foluble.

The

Chap. 33-1 Corrofive S ultimate. 209

The muriatic acid has no action on mercury in its me-
tallic ftate, becaufe that acid cannot part with the oxygen
neceflary to calcine the metal. It has, notwithstanding,
a very ftrong attraction for mercury, and diffolves it
with great readinefs when the latter is previoufly re-
duced to the ftate of a calx. If a fmall quantity of
muriatic acid is poured on a nitrous folution of mer-
cury, it feizes the metal, and forms a fait, which is
precipitated in the form of a whitifh coagulum, which,
when dried, is called white precipitate, and is a kind
of corrofive fublimate. The marine falts, with a bafis
of alkali, or of any faline terreftrial fubilance, fuch 2S
lime, magnefia, &c. produce the fame effect, except
that in this cafe, though the precipitate is the fame,
the nitrous acid, inftead of being left uncombined,
unites with the bafis of the marine fait which was em-
ployed.

If mercury, corroded by the vitriolic or nitrous
acids, and dried, is mixed with powdered fea fait, and
expofed to heat, a double attraction takes place ; the
nitrous or vitriolic acid deferts the metal to unite with
the fixed alkali of the common fait, while the muriatic
acid ieizes upon the mercury, and forms a metallic
fait, which, in the degree of heat neceflary for the ope-
ration, proves volatile, and, riling in vapour, is con-
clenfed in a folid form in the upper and cool part of the
vefiel employed. This is the hydrargyrus muriatus,
or corrofive fublimate, which is a very acrid and pow-
erful preparation of mercury.

The mild preparation, called calomel, is obtained by
rubbing three parts of mercury, in its metallic ftate,
with four of corrofive fublimate, till they form a greyifh
powder; the mafs is then fublimed*, and forms a
fubftance like corrofive fublimate, but more ponderous,

* Made volatile, or railed in vapour, lay the application of beat.

VOL. II. P and

£l0 Calomel, &c. , [Book VI.

and of a more filvery appearance. The ingredients,
howef er, are not fufficiently mixed by the firft fub-
limation ; they muft be rubbed together again and fub-
limed; and thefe prqcefles muft be repeated at leaft
three times.

The converfion of the .corrofive fublimate into the
rniider fubftancc, Calomel, may be explained on the
following principles : — In the corrolive fublimate,, the
muriatic acid is /bund to be combined with a very
large quarry °f oxygen, which renders it extremely
active ^y t*ne Edition of mercury, a quantity of
•AiS ftiperftuous oxygen is abftradbed, for the calcina-
tion of the additional metal ; and the whole mafs,
therefore, contains the acid not only in a milder (late,
but the fame quantity of acid is diffufed through a
larger mafs of the metal.

Ponderous earth, magnefia, and lime, decompofe
the corrofive fublimate, and precipitate a mercurial
calx. The phagedenic water, made ufe of as a cor-
rofive by furgeons, is made by throwing half a drachm
of corrofive fublimate, in powder, into a pound of
Jime water ; a yellow precipitate is then formed, which
renders the liquor turbid.

Acids and neutral alkaline falts produce no change
on corrofive fublimate, but it contracts an intimate
union with fal ammoniac without decompofition. The
fal ammoniac renders corrofive fublimate very folublc.
The calx hydrargyri alba of the London Pharma-
copeia is obtained from this combination. A quan-
tity of fal ammoniac is diflblved in diftilled water;
an equal \veight of corrofive fublimate is then added ;
when this is diflblved, fixed vegetable alkali is added,
which produces a white precipitate. In this operation
ihe fixed alkali difengages the volatile alkali of the fal
ammoniac, which precipitates the mercury in the form
* of

Chap. 33.] Keyjer's Pills, Etbiop's Mineral,, &c. 2 1 1

of a white calx. This preparation is chiefly ufed in
liniments externally. It is fometimes adulterated with
cerufe, as the red precipitate is with minium. The
fraud may be difcovered by expofing a fmall quantity
to heat in a fpoon j if pure they will be entirely dif-
fipated, but if they contain lead, or other impurities,
thefe matters will remain behind.

If the fait formed by the combination of acetous
acid with the fixed vegetable alkali, commonly called
regenerated tartar, or kali acetatum, is added to the
folution of quickfilver in the nitrous acid, a double
exchange takes place j the alkali unites with the ni-
trous acid, while the acetous acid enters into combi-
nation with the mercury, and is precipitated. This
precipitate (being purified by folution in hot diftilled
water and filtration) has nearly the fame medical pro-
perties as calomel, and is Taid to form the bafis of
Keyfer's pills. The acetous acid does not aft on mer-
cury unlefs the latter is reduced to the ftate of a calx.

As mercury is commonly, in . a ftate of nature,
combined with fulphur, fo it may be artificially united
to it with great eafe. When one part of this metallic
fluid is triturated with three parts of flowers of fulphur,
the mercury gradually lofes its metallic appearance,
and is converted, by its union with the fulphur, into a
black powder, called Ethiop's mineral. This com-
bination is more quickly effefted by mixing the mer-
cury with melted fulphur. When this compound is
expofed to a confiderable degree of heat it takes fire,
the greater part of the fulphur burns, and after the
combuflion a matter remains, which when pulverized,
is of a violet colour. To convert this powder into
cinnabar it is put into matrafles*, which are heated till

* VefTels ufed in chemical operations, of glafs or earthenware,
generally of the fhape of an egg, and opea at the top, the necks-
are long or fhort, a? occ^fion may require.

P 2 their

2t 2 Vermilion. Gilding in Or Moulu. [Book VI.

their bottoms become red, and kept in this ftate for
feveral hours, till it appears that the matter is entirely
fublimed. The Dutch prepare, in the large way, the
cinnabar employed in the arts. When much divided
by levigation * it has a brilliant red colour, and is called
vermilion.

Mercury has the property of uniting itfelf to many
of the metals, by penetrating their fubftance, and ren-
dering them more or lefs foft, according to the propor-
tion of mercury employed. If the proportion of
quickfilver is very great, the mixture is like quick-
filver, and is only diftinguifhed from it by an appear-
ance of foulnefs. If a fmaller quantity is ufed, the
mafs is fofr like butter ; if ftill lefs, it is folid but brittle.
Thefe mixtures are called amalgams. It readily com-
bines in this way with gold, filver, lead, tin, bifmuth,
and zinc, but net eafily with arfenic and copper, and
fcarcely at all with iron, platina, nickel, or cobalt. Its
action on the other metallic bodies has not been afcer-
tairied.

A piece of gold, being rubbed with quickfilver, is
foon penetrated by it, and is rendered fo fragile that
it may be eafily broken. A gold ring, which has be-
come fo tight on the ringer that it cannot be drawn
off, may be eafily removed in this manner. Gold,
^ united with quickfilver in certain proportions, forms
a kind of pafte. On this property is founded the pro-
cefs of gilding in or moulu. A fmall quantity of this
paile is fpread upon the furface of the copper which
is to be gilded in or moulu, and the metal is then ex-
pofed to heat. Quickfilver evaporates in a far lefs
degree of heat than is fufficient to melt either gold or
copper ; when, therefore, the mixture of gold and
quickfilver is expofed to heat, the quickfilver is driven
off in vapour j but the gold not being fufceptiblc

* Reduced to a fine powder.

of

Chap. 33 .] Amalgam cf Tin and Mercury. 213-

*)f evaporation, remains attached to the furface of the
copper, and undergoing the operations of burnifhing,
&c. the latter is gilded* or gilt. This method of
gilding copper, by means of gold and qutckfilver, was
known to the Romans. The furface of iron cannot
be covered in the fame way with gold ; but the iron,
by being moiftened with a Iblution of blue vitriol, as in
the procefs for browning firelocks, and being thus co-
vered with a lamina of copper, becomes as fulceptible
of being gilded as if its whole fubftance was copper.

It is this property which quickfilver has of uniting
with the precious metals, and dififolving them, which
has rendered it lo ferviceable in the extraction of them
from the earth with which they are mixed. The earth
or ftones, in which gold and (ilyer arc con timed, being
reduced to powder, are mixed with quickfilver, which
difiblves every particle of the precious metals without
contracting the lead union with the other matters -t the
quickfilver is then driven off by heat, and, being con-
denfed in the receiver, is again employed in the fame
procefs. The gold and filver are feparated from each
pther by proceffes, which will be defcribed in treating
of thofe metals. Since the difcovery of the American
gold mines, the confumption of quickfilver has been
much increafed. Hoffman concludes, from calcula-
tion, that fifty times as much gold as quickfilver is
annually extracted from the bowels of the earth.

Looking glafles are covered on one fide with an
amalgam of tin and mercury. Tin, being beaten into
thin leaves, is called tin foil ; on tin foil, evenly dif-
pofed on a flat ftone, quickfilver is poured, and fpread
with a feather until its union has brightened every part
pf it j a plate of glafs is then cautioufly (lid upon the
tin foil, in fuch a manner as to fweep off the redundant
quickfilver which is not united to the tin j weights are
F 3 <!,cn

214 Aftion of Mercury on the Human "Body. [Book VI.

then placed on the glafs fo as to prefs out dill more of
the quickfilver, and in a little time the tin foil, thus
united to the quickfilver, adheres fo firmly to the glafs
that the weights may be removed without any danger
of its falling off. About two ounces of quickfilver are
ufed in covering three fquare feet of glafs.

In order to make mercury capable of acting on the
animal body, it is neceffary that it fhould undergo fome
preparation ; for its particles muft be very minutely
divided before they can enter the vefTels. Thus, if
we apply quickfilver to a capillary tube, the attrac-
tion of its particles for each other is fo ftrong that they
will not rife in it ; but minute divifion is not the only
circumftance neceffary to its activity, for Ethiop's mi-
neral and cinnabar taken into the body have very little
if any effect. Oxygenation feems to be the mod ef-
fential circumftance ; for in whatever way this is ef-
fected the mercury becomes very active *.

Mercury, in paffing through the body, is reduced
to the metallic ftate, and, exuding through the pores,
fometimes attaches itfelf to the gold of watches,
rings, fleeve-buttons, or ear-rings, and renders them
white.

* Does not the effefl of fulphur, in diminiming the activity
of mercurial preparations, depend on its fuperior attraction for
oxygen, by which it has a tendency to reduce the mercury to the
metallic ftate ?

Chap. 34-1 [ 215 ]

CHAP. XXXIV.

SILVER.

Character of the perfetf Metals,*— General Properties cf Silver. — Jregt<-
tat ion of Silver* — Natural Hijlory cf Silver. — •AJfayirig of Si/-z'er.—
Cupellation.— Lunar Caujiic.-~-Fulmina.ting Silver. — Luna Cornea.
^-Diana's Tree. — Green Gold.— Standard Silver Coin*— Plating
fwitb Sil<ver't hmu performed. — Frenib Plate,

OF the different metallic fubftances only three
have been dignified by chemifts and mineralo-
gifts with the appellation of perfect, viz. filver, gold,
and platina. Thefe are diftinguifhed from the other
metals by their weak attraction for oxygen, which
enables them to retain their purity and metallic Iplen-
dor in fituations in which other metals become gra-
dually covered with ruft or calx. Silver is the whiteft
of all metals, and is pofleffed of great brilliancy ; it is
harder than gold ; in weight it is exceeded by gold,
platina, quickfilver, and lead ; its gravity being only
about ten times that of water. Its malleability is
fo great, that a grain of it reduced to ordinary filver
leaf meafures about fifty- one fquare inches, in which
ftate it is not more than the hundred and fixty thou-
fandth part of an inch thick, which, however, is confi-
derably more than one third thicker than gold leaf.
Its tenacity is fo confiderable, that it may be drawn
into wire about half the thicknels of a fine human
hair, and a wire of one tenth of an inch in diameter
will fupport the weight of two hundred and feventy
pounds without breaking. It is very fonorous, but in
hardnefs and elafticity it is not equal to copper. It
P 4 hardens

216 Vegetation of Silver. >[Book VL

hardens under the hammer, but very readily lofes that
hardnefs by heating.

Silver, expofed to- the heat of the moft powerful
burning lenfes, is partly vitrified and partly volatilized
in fumes, which are found, when received on a plate
of gold, to be filver in the metallic ftate. It is like-
wife faid to have been partly calcined by twenty fuc-
cefiive expo fu res to the heat of the porcelain furnace
at Stives. This, however, may be doubted, as filver
does not undergo any degree of calcination by expo-
fuje to heat, even with the addition of nitre. Silver
melts in the firft degree of white heat, and appears in
the fire like the fineft quickfilver. When it is haftily
cooled, it exhibits a curious phenomenon, called vege-
tation j for we difcover from different parts of its
lurface ramifications and branches like thofe of trees
which fprout out with a item. The reafon of this
appearance feems to be the irregular contraction which
the filver undergoes in paffing from the fiuid to the
folid ftate. The melted filver fuffers the firft com-
mencement of congelation at its furface; by thefe
means a cruft is formed, which by its fudden contrac-
tion compreffes the fiuid filver within ; thus a protu-
berance is formed,, which, congealing in its turn, con-
trails and preffes the intermediate fiuid through its
cruft into branches.

The air alters filver very little, unlefs it contains
fulphureous vapours, which it often does, from the
putrefacticm of animal fubftances or the exhalations of
drains, or of fulphureous mineral waters. This metal,
therefore, becomes fomewhat tarnifhed by long con-
tinued expofure to the atmofphere, and in time be-
comes covered with a -thin purple or black coating,
which, after a long feries of years, has been obfervcd
to fcale off from images of filver expofed in churches,

and

Chap. 34.] Natural Hiftcry of Sifoer. 217

and was found, on examination, to confift of- filver
united to fulphur.

Silver is often found in its native ftate, and may be
known by its brilliancy and ductility. It is fometimes
met v/ith in irregular maflfes, fometimes in the form
of capillary threads or fibres, and fometimes in that of
branches, formed by octahedrons inferted one into
the other. It is alfo often difperftrd in a quartzofe
gangue*. 'Native filver is fometimes found alloyed
with gold, copper, iron, or regulus of antimony } but
native gold much oftener contains filver than native
filver does gold. Silver is not naturally found in the
ftate of x:alx.

The vitreous ore of filver is compofed of that metal
and fulphur. It is the richeft of the filver ores, and
yiejds from feventy to eighty pounds of the metal in
the hundred weight. It is of a blackifh grey colour,
refembling lead; fome fpecimens are brown, greenifh,
yellow, &c. ; it may be cut with a knife, and is fome-
times cryftallized. If it is expofed to a heat not fuf-
ficient to melt it, the fuphur is difllpated, and the vir-
gin filver is obtained in fibres.

The red filver ore contains arfenic as well as ful-
phur. It is a heavy mining fubflance, fometimes tranf-
parent, fometimes opake, but commonly cryftallized.
It is often of a deep red colour on the outfide, but ap-
pears paler within. It affords about half its weight of
filver. If it is expofed to a fire carefully managed,
and capable of igniting it, the filver is reduced, and
forms capillary fibres, fimilar to native filver.

Tnere is a filver ore containing arfenic, cobalt, and
iron, mineralized by fulphur. This ore fometimes

* A quartzoze or fparry cryftallization, often found inclofing
the ores of metals, and therefore called the matrix or rider.

yields

a 1 8 Natural Hiftcry of Silver. [Book VI.

yields half its weight of filver ; it varies in its appear-
ance, being fometrmes of a grey and brilliant afpe<5ra
but often of a dull and tarnifhed colour, with erfloref-
cences of cobalt. The goofe dung ore belongs to this
ipecies. The grey ore of filver contains a large quan-
tity of copper. The black filver ore, called nigrillo by
the Spaniards, feems to be a middle ftate between na-
tive filver and fome of its ores, or thofe ores in a ftate
of imperfect decompofition. The corneous fiiver ore
is a natural combination of filver and muriatic acid
•with a finall quantity of vitriolic acid. Silver is alfo
found in confiderable quantity in the ores of other
metals, particularly thofe of antimony, zinc, lead, and
copper.

In the allaying of filver ores different procefTes arfc
iiied, according to their nature. When found in its
metallic ftate, nothing more is neceffary than to fepa-
rate it from the earthy or ftony matter in which it is,
embedded. With this view it is firft expofed to heat,
to render the ftony matter friable. The mafs is then
mixed and ground with quickfilver. Thus the filver
is converted into an amalgam, which, from the inti-
mate union of the particles of the metals, is fpecifically
heavier than quickfilver itfelf. The ftony matters are
now eafily warned off, without lofing any of the metal.
The quickfilver is afterwards partly feparated by
fqueezing it through a piece of leather, and the re-
mainder by diftillation. Sulphureous filver ores re-
quire to be firft roafted, and then mixed with a
quantity of flux. In order to feparate lead, copper,
iron, &c. from filver, a particular procefs is employed,
which is called cupellation, from the veiTel ia which it
is performed, called a cupel, and which is chiefly
formed of calcined bones, and is very porous. The
metallic mats containing filver is mixed with a confi-

Chap. 34.] Mode of dying the Hair brown. 219

derable quantity of lead, and then expofed on the cupel
in a ftate of fufion. The lead is vitrified and abibrbed
into the cupel, carrying with it the imperfect metals,
and the filver remains behind on the cupel in a pure
ftate.

The vitriolic acid acts on filver as on the other me-
tals, with the afiiftance of heat ; it then corrodes it into
a white mafs, which is foluble in water, and by evapo-
ration affords fmall cryftals.

The nitrous acid diflblves filver with great rapidity.
When the (Irong nitrous acid is diluted with an equal
weight of water, it is capable of difiblving about half
its weight of filver. If the filver employed is quite
pure, the folution is limpid like water; but as filver
commonly contains a little copper, its folutions have
ufually a blueifli tinge. If the filver employed con-
tains gold, in this cafe, as the nitrous acid is not capa-
ble of diffolving the gold, it feparates from the filver
in the form of blackifh flocks. From this difference
in the action of nitrous acid on filver and gold, it is
fuccefsfully ufed to feparate thefe metals from each
other.

The folution of filver in the nitrous acid is extremely
bitter and cauftic, and has the property of changing
the Ikin or hair to a black colour, or, if very much,
diluted, to a brown, and formerly, when the caprice
of fafhion abhorred light hair as much as it at prefent
admires it, was employed for that purpofe. The co-
lour is, however, very faint when the folution is firft
applied, and the production of colour feems in a great
meafure to depend on the action of light. Dr. Lewis
mentions a remarkable phenomenon, which this folu-
tion prefents when added to chalk or any pure abfor-
bent earth. The chalk and folution are both at firft
quite white, and will continue fo if kept in a dark

place,

220 Lunar Caitftic. [Book VI.

place, but if expofed to the light they loon become
black ; fo that if a quantity of this mixture is put into a
glafs phial fealed up, any maiks or letters may be made
to appear on it as if by magic. To effect this, die
phial is covered with thick paper, in which the marks
or letters are nicely cur, and it is then expofed to the
light, which, acting only through the apertures of the
paper, produces the effect. When the (tains are pro-
duced, aqua fortis, by re-diffolving the filvcr, will
make them difappear again. It therefore feems, that
the production of colour is owing to an imperfect re-
duction of the iiiver, and that the action of light dif-
engages oxygen from this compound in the fame man-
ner as it does from the pale nitrous acid, and from
vegetables.

When this folution of filver is evaporated with a
gentle heat, it may be made to afford cryftals nearly
refernbling thofe of nitre. Thefe, being melted in a
crucible, are freed from water, and being poured into
moulds of a convenient form, become the filver or
lunar * cauftic, or argentum nitratum of the pharma-
copoeia.

Silver is never given internally, and this is the only
preparation of it made ufe of externally. The nitrous
acid may be entirely feparated from this compound by
he.at alone.

Silver, however, is mod conveniently feparated from
its nitrous folution by -immerfing plates of copper in
it. The copper is then 'diflfolved, while the filver is
deposited in 'its metallic ftate. This metal may be
feparated from gold by expofing the mixed metals to

* A name derived from the whim of the alchemifts, who called
the metals by the names of the heavenly bodies : gold, Sol ;
filver, Luna; copper, Venus; iron, Mars (whence martial vitriol^
&c.) ; lead, Saturn; tin, Jupiter; quicknlver, Mercury, .xc.

the

Chap. 34.] Fulminating Silver. 221

the action of nitrous acid, which diflblves the fiiver
and leaves the gold, and the above method is ufcd ro
obtain the filver from the acid.

To make the famous fulminating filver, which is fo
truly formidable in its effects, a fmall quantity of filver
is difiblved in pale nitrous acid (or aqua fortis) from
which it is precipitated by lime water. The calx or
precipitate is to be dried by expofure to the air for
three days. Tiie inventor, M. Bertholet, fyppofes
the action of light to have alfo fome influence in the
fuccefs of the experiment*. The dried calx is then
agitated in a folution of the cauitic volatile alkali,
when it arTumes the form of a black powder, which is
Jeft to dry in the open air. The fulminating filver
then confifts of an union of the calx of filver with vo-
latile alkalj.

The effects of this preparation are tremendous, and
infinitely exceed thofe of gunpowder, fulminating pow-
der} or fulminating gold. It explodes with the flighteft
agitation or friction. The falling of a few atoms of
it from a moderate height produces a violent detona-
tion, and a drop of water falling upon it has the fame
effect. When it is once fully prepared, it muft not
be touched or moved into any other vefiel, but mull
remain in that in which it was dried j and to make the
experiment with tolerable fafety, not more than a grain
of filver mould be employed in the procefs. The
caufe of thefe explofions has been already intimated in
the chapter on ignition, and will be further illuftrated
in treating of fulminating gold.

Though the nitrous acid difiblves filver with greater
eafe, it has not fo ftrong an attraction for it as the mu-
riatjc or vitriolic acids. Either of thefe, dropped

* Journal de Phyfique for June 1788, p. 474.

222 Aftim of Muriatic Add on Siher. [Book VL

Into the nitrous folution, feize the (ilver, and forming
a. compound not equally folnble produce a precipita-
tion. The neutral falts, containing vitriolic or mu-
riatic acid, have the fame effect. This difference of
affinity between die acids and filver is the foundation
of a procefs for obtaining the nitrous acid in a ftate of
great purity. The folfltion of filver in nitrous acid
is poured into the impure nitrous acid till no more
precipitate is formed. The muriatic or vitriolic acids-
contained in the mixture are thus carried to the bot-
tom by their union with the filver. The acid is then
decanted and diftilled to free it from the fmall quantity
of fait of filver which it may ftill contain.

Notwithftanding the muriatic acid has the ftrongeft
affinity with filver of all the acids, it is neverthelefs
incapable of dilTolving it unlefs the metal is in a cal-
cined ftate, or itfelf fuperoxygenated. The common
method of effecting this union is to add to the folution
of filver, in the nitrous acid, any faline fubftance which
contains the muriatic acid ; it is no matter to what the
acid is joined, whether alkali, earth, or metal ; it im-
mediately feizes the filver, and leaves the other matter
to unite with the nitrous acid. Common fait is gene-
rally ufcd, and the white precipitate, which is imme-
diately formed, has the appearance of a coagulum.
The compound thus made is fo infoluble in water,
that there cannot be a nicer tefl of the prefence of the
muriatic acid, or common fait, in waters, than the ni-
trous folution of filver ; for if the moft minute quantity
of either are prefent a precipitation is produced.

This. compound has many other qualities befides
infolubility in water. If we collect it, and wafh off
the faline matter, it appears as a fine powder, and,
when heated to a fufficient degree, melts into a fub-
ftance of fome tranfparency. From its tranfparency,

flexibility

Chap. 34.] Luna Corned. 223

flexibility, and foftnefs, it is called tune cornea, or ar-
gentum corneum, and from this feveral other compounds
of metals with the muriatic acid have been called cor-
nea. It may be cut into tranfparent veflels refembling,
glafs.

Aqua regia, or the compound of nitrous and mo-
riatic acids, acts ftrongly on filver, but forms a preci-
pitation in proportion as it feparates it from the mafs.
This effect m.ay be readily underftocd from what has
already been obferved. The nitrous acid diftblves the
fiiver, and the muriatic feizes it, and forms kina cornea*
which is infoluble. This procefs may be ufed to fepa-
rate gold from filver; the gold is held diffolved in the
aqua regia, but the filver is precipitated.

After filver has been reduced to the calciform ftate
by folution in nitrous acid, and precipitation by alka-
lis, it is capable of folution in vinegar, and even in
lemon juice; but thefe compounds have not been ap-
plied to any ufe.

To have filver perfectly pure we muft ufe quick-
filver, which, if poured into a folution of filver, is
attracted by the acid, and precipitates an amalgam with
the filver at the bottom of the yeflel. The quick-
filver is eafily feparated from the filver by heat alone.
A curious phenomenon arifes from this amalgam j a
kind of cryftallization takes place, which is formed by
the union of the filver with the running mercury. The
amalgam puts forth (hoots, which afterwards put forth
others, like the branches of a tree. The cryftalliza-
tion varies according to the conduct of the pfocefs,
and does not always anfwer, particularly if the mix-
ture is fhaken. It is called arbor Dian<?> or Diana's
tree*. The method of making it moft beautiful

• Diana's tree, from the whim of the alchemifts already noticed,
who appropriated iilver to the Moon or Diana, as ftated in a pre-
ceding note.

is

224 Diana's fret. [Book VI*

is very tedious, and would require the fpace of a
month.

• This phenomenon feems to admit of explanation
precifely on the fame principle as the branching of
pure filver when pafling from it* fluid to its folid ftate.
The amalgam of filver and mercury is fpecifically
heavier than either of the rnetals in a feparate flate,
and their union muft confequently be attended with
contraction. The filver, therefore, being precipitated
on the furface of the mercury, in proportion as the
latter metal is difTolved by its fuperior attraction for
the acid, the mercury becomes furrounded with a
Crufl, the contraction of which forces out its fluid con-
tents ; the excrefcences thus produced being in their
turn covered with a cruft of amalgam, are again com-
prefled, and produce fmaller protuberances, and if the
experiment is properly conducted, the brittle amal-
gam of the metals a flumes a cryftallized appearance,
and the form of a thick bufli. In this experiment it
is neceflary that there fliould be not only as much mer-
cury as is fufficient to precipitate the filver, but be-
fides this a quantity remaining in its fluid (late, to unite
with the precipitated filver into an amalgam.

Sulphur has a remarkably ftrong affinity with filver,
and forms with it a compound which has the appear-
ance and foftnefs of lead. This metal feems alfo ca-
pable of attracting fulphur from antimony. But
though filver has fo ftrong an attraction for fulphur,
gold has none, and this furniflbes a method of feparat-
ing thefe metals by fufion.

With gold, filver forms a pale alloy, the green gold
of the jewellers and gold beaters. This mixture,
however, is not made without fome difficulty, on account
of the different fpecific gravities of the two metals.
It does not unite well with platina. It forms an alloy

with

Chap. 34.] Plating of Copper. 225

with iron, but the properties of it have not been well
examined into. With lead it forms an alloy, which is
much more fufible than pure filver, and feems in all
refpecls to be of an intermediate nature between thefe
metals. Copper increafes the hardnefs of filver, and
renders it more fonorous, without impairing its duc-
tility or colour, when the copper does not exceed the
twelfth part of the weight of filver employed. The
itandard of filver coin is eleven ounces two penny-
weights, troy, of filver, and eighteen pennyweights of
copper.

The purity of filver cannot be accurately afcertained
•without fubmitting it to cupellation with lead, and its
purity is calculated according to the weight it lofes
in that procefs. Silver is divided into twelve ima-
ginary parts, called pennyweights. If it only lofes
one twelfth part of its weight by cupellation, it con-
tains eleven twelfths of pure filver., and is faid to be
eleven pennyweights fine ; if it lofes two twelfths, it is
ten pennyweights fine, and fo of other proportions.
For greater accuracy, each pennyweight is fuppofed to
be divided into twenty-four grains.

The covering of the furface of copper with filver,
or plating, is performed in the following manner:
' Upon fmall ingots of copper, plates of filver are
bound with iron wire, generally allowing one ounce of
filver to twelve ounces of copper. The furface of the
plate of filver is not quite fo large as that of the cop-
per ingot. Upon the edges of the copper, which are
not covered by the filver, a little borax is put, and by
expofing the whole to a ftrong heat, the borax melts,
and in melting contributes to melt that part of the
filver to which it is contiguous, and to attach it in
that melted (late to the copper. The ingot, with its
illvcr plate, is then rolled under fteel rollers, moved

VOL. II. Q^ by

2*6 French Plate. [Book VI.

by a water wheel, till it is of a certain thicknefs ; it is
afterwards rolled by hand rollers to a greater or leis
extent, according to the ufe for which it is intended ;
the thinned is applied to the lining of drinking hams.
An ounce of filver is often rolled out into a furface of
about three fquare feet, and its thicknefs is about ihe
three thoufandth part of an inch j and hence we need
not wonder at the filver being foon worn off from the
fharp angler, of plated copper, when it is rolled to fo
great an extent.

* What is commonly called French plate is not to
be confounded with the plated copper. In making
French plate, copper, or, more commonly, brafs, is
heated to a certain degree, and filver leaf is applied
upon the heated metal, to which it adheres, by being
rubbed with a proper burnifher*.1

Watfoa's Chemical

ivs.

Chap. 35.] [ 227 ]

CHAP. XXXV.

GOLD.

General Properties of Gold. — Gold calcined by Elefiricity.—Extrtmt
Duflillity of this Metal — Natural Hiftory of Gvld.-~ProceJ/es for
feparating Gold from other SutJJances. — Quartaticn. — 'The Touch-
Jlone. — Aqua Regia. — Reafons <vchy the different Acids aft on metallic
Bodies. — Fulminating Gold, — Purple Powder of Coffins. — Golden
Calf, how deftroyed by Mcfes.— Union of Gold with other M(T/«A.— •
Standard Gold Coin of different Countries.

GO L D is the heavieft of all the metals except
platina, being between nineteen and twenty times
the weight of water. When perfectly pure it is al-
moft as foft as lead, and is neither elaftic nor fonorous*
For its fufion it requires rather more heat than filver,
and when in fufion has a blueifh green colour, and its
fuiface is always perfectly bright. The moft intenfe
heat cannot calcine it, and only contributes to render
it more pure if it had any foulnefs. The powerful
burning mirrors are faid to have volatilized it, and it
has been driven up in fumes, in the metallic date, by
flame urged upon it by a ftream of vital air. The
electric fluid, however, when rrmde to pa-fs in confi-
derable quantities through gold leaf, inciofed between
two plates of glafs, converts it into a calx, which tinges
the glafs of a purple colour.

The tenacity of fgold is fo great, that a wire one-tenth
of an inch in diameter is capable of fupporting five
hundred pounds. Its malleability and ductility exceed
thofe of filver, and are fo remarkable, that their limits
could never be afcertained with any confiderable ex-
actnefs. On gold lace the thicknefs of the gold has

Q2 been

228 Natural Hiftory of Gold. [Book VI;

been computed to be leis u.an the one hundred ancl
thirty-four thoufandth part of an inch, and the degree
of extenfibility has been carried Hill farther. In ordi-
nary gold-leaf, which is made by hammering plates of
gold between flcins, or animal membranes, a grain is
made to cover fifty-fix fquare inches and a quarter.
In this ftate its furface is fo -great that it may be made
to float in the air with the flighteft agitation, and its
thicknefs is not more than the two hundred and eighty-
two thoufandth part of an inch.

Gold is produced by nature very plentifully. There
is much of it in Brazil, in the Spanifh E?ft and Weft
Indies, on the coaft of Africa, and in Upper Hungary,
where the mines have remained unexhaufted for ten
centuries. Peru and Mexico abound with gold in a
variety of forms. It is met with in the fands of rivers
and mountains. Some rivers in France, as well as
in this country, contain gold in their fand. It is alfo
found in the fiflures of rocks, imbedded in hard
Hones. Pieces of gold of feveral ounces, and even
pounds weight, are fometimes found, but in general
it is diffufed in fo fmall portions, and through fo large
a quantity of fand, that the trouble of extracting it
is fcarce.y repaid by the gains. In all parts of the
world, particularly in Europe, gold is moft frequently
found in flrata of fand, in which it feems to have been
depofited by water. Gold mines were once wrought
in Scotland, and it appears upon record that forty-eight
thoufand pounds fteriing of this gold was coined in
the Scotch mint. It is now a general opinion among
mineralogifts, that there are fcarcely any fands entirely
free from gold, and which, by accurate examination,
cannot be made to afford more or lefs of that fub-
flance.

Confidering that gold has no attraction for fulphur,

and

Chap. 35.] Separation of Gold from bajer Matters. 229

and very little for arfenic, which are the ufual mine-
ralizers of t Metallic bodies, it is not furprizing that it
ihoulti be ufihJiy ^ound in a feparate and nearly pure
ftate. The metaili-- bodies, wich which it is alloyed
in a ftate of nature, fcldom conftitute any confiderable
part of its weight; they are generally either filver,
copper, or iron. Gold, however, is fometinnes mixed
wich martial pyrites, and is fometimes contained in an
ore, which is a mixture of lead, filver, and iron, mi-
neralized by fulphur. In thefe cafes the prefence of
gold is not known by the appearance of the mineral,
and can only be difcovered by roafting, and fubfequent
fufion with fuch matters as are capable of vitrifying
the earthy and martial fubftances. The addition of
icad is alfo ufeful, which unites with the gold, and
carries it to the bottom of thj mak. The gold is
eafily obtained free from the lead by the proceU of cu-
.peilation.

In order to feparate gold, when in its native ftate,
from the earthy and ilony matters in which it is .con-
tained, the following procefs is employed: When it
is contained in fand, the lighter particles of the latter
are wafhed away by water, and the remaining matter,
which may prove fo heavy as not to be feparated from
the gold without danger of lofing fome of the precious
metal, are amalgamized, by being ground with mer-
cury, in the fame manner as has been mentioned in
the extraction of filver. Jf the gold is mixed with
flones of confiderable bulk, it is neceflary that they
mould be reduced to powder in order to render them
fufficiently light to be wafhed away. The mercury
is alfo feparated from gold in the fame way as from
filver ; as much as poflible is feparated from it by pref-
fure in bags of leather, and the remainder by heat.

All the imperfect metals may be abftra&ed from

gold

230 Quartation. [Rook VI.

gold by cupellatton ; but in order to feparate filver
from it, other procefles muft be employed. The beft
of thefe is called quartation, becaufe the gold muft not
exceed the fourth part of the weight of the mafs fub-
mitted to trial. The gold, therefore, muft be firft
mixed with three times its weight of filver, the effect
of which is, that the particles of gold are removed to
fuch a diftance that they cannot protect the filver
from being acted .on. The mafs of gold and filver
being then beaten out into thin plates to increafe the
furface, are expofed to the action of aqua fortis, which
diilblves the iilver, and leaves the gold in a fpongy
mafs ; this is warned two or three times with aqua
fortis, and then expofed to heat in a muffle *, to
recover its metallic brightnefs. When filver is thus
feparated by aqua fortis, a minute portion of the filver
is apt to adhere to the gold, and, therefore, when it
is an object to have the gold perfectly pure, it is
proper to fubmit it to the action of aqua regia, which
dUTolves the gold, and converts the filver into luna
cornea, which is precipitated to the bottom of the
veffel. When it is intended to feparate filver by aqua
regia, the proportions of the metals muft be reverfed,
and as the gold is to be difTolved, it muft be three times
the weight of the filver.

In this way gold may be obtained quite pure ; but
the goldfmiths find a difficulty in obtaining it per-
fectly ductile. To have it foft and tough it muft
be melted with a ftrong heat, and afterwards cooled
v€ry (lowly.

In applying faline fubftances to gold, it is found that
ho one of the acids, in its ordinary ftate, produces the

* A fmall earthern oven made and fold by the crucible manu-
facturers.

leaft

Chap. 35.] fof Voucbftone. 231

leaft effect on it in its metallic ftate. Upon this depend*
the trial of gold by the lapis lydius, or touchftone,
which is of a dark colour and pretty fine grain, but
when polifhed has fufficient roughnefs, fo that when
the metal is rubbed over it a mark is left, which
mark will be affected by any of the common acids,
aqua fortis for inftance, in proportion to the impurities
the metal contains, but not at all if the gold is perfectly
pure.

Goldfmiths ufe likewife two fets of needles, one for
filver and the other for gold, when they want to exa-
mine the finenefs of different parcels. The fets of
needles for gold are alloyed with different proportions
of copper ; one is made with twenty-three parts of
gold to one of copper, another with twenty-two parts
of gold to one of copper> and fo in proportion. When
they have a piece of gold to be tried, they firft exa-
mine its colour to determine what quantity of alloy it
contains* To know this the better, they mark the
touchftone with it, and then make another mark with
the needle, which they think to be of nearly fimilar
purity. Thus they compare them -y and after this, to
be certain that the metal is gold, they apply to the
mark on the ftone a drop of aqua fortis. If it is
copper tinged with zinc, or any other imitation of
gold, the aqua fortis immediately diffolves it. If ic
contains gold and fome other metal, it difiblves the
other metal and leaves the gold.

The only faline fluid which difiblves gold in its
metallic ftate is aqua regia, or a mixture of the nitrous
and muriatic acids. It is prepared in various wdys :
i ft, By mixing the two acids in their pure ftate.
idly, By adding common fait, or fal ammoniac, to
aqua fortis, and then diftilling the mixture. A pare
of the nitrous acid decornpofes the muriatic fait, and

detaches

Operation of ^qua Regia [Book VL

detaches the muriatic acid, which rifes with the re-
mainder of the nitrous acid, and thus an aqua regia
is produced, jdly, By mixing a folution of alum
with nitre and common fait, in which cafe the vitriolic
acid of the alum difengages the nitrous and muriatic
acids by its fuperior attraction for their bails.

It is ufual to make aqua regia by dilToJving fal
ammoniac in about four times its weight of ftrong
nitrous acid : but the refults of experiments or opera-
tions vary confiderably according to the proportion of
the ingredients made ufe of.

The theory of the operation of this compound acid
does not feem difficult. In the courfe of this work it
has been more than once remarked, that the eafy fo-
lution of metallic matters in acids does not depend
merely on . the degree of attraction which exifts be-
tween the metal and the acid, but alfo on the eafe
with which the acid parts, with oxygen to calcine the
metal. From this caufe it happens, that the nitrous
acid, which has much lefs affinity with metallic matters
than the vitriolic or muriatic, (diffolves them more
readily than either of thefe. Aqua regia, however,
confifls of the acid which has the ftrongeft attraction
for metallic bodies, and alfo of that which moft eafily
parts with oxygen, and the union of thefe powers pro-
duces the effect of folution. That this is the true expla-
nation of the folution of gold in aqua regia appears
from fevefal circumftances ; for gold, previoufly re-
duced to the ftateofcalx, that is, furniihed already witli
a quantity of oxygen, is eafily diffolved by muriatic
acid, and gold in its metallic ftate,.is diflblved by the
oxygenated or aerated muriatic acid, and forms with
it the fame fait which is ufually obtained by the mixed
acid, or aqua regia. The muriatic acid, therefore, is
the true folvent of gold, and the addition of nitrous

acid

Chap. 35.] on Gold explained. 233

acid has no other effect than that of furnilhing Oxygen,
fmce the fame effect follows when the neceflary quan-
tity of oxygen is previoufly added either to the gold or
the muriatic acid. Gold, precipitated from aqua regia
by alkalis, and thus reduced to the calciform (late, is
foluble even in the vitriolic and nitrous acids.

The addition of water to the vitriolic acid, enables it
to difiblve iron exactly on the fame principle that the
addition of nitrous acid to the muriatic, enables the
latter to diffolve gold. The concentrated vitriolic
acid has no action on iron without the -afliftance of
heat ; but by a proper addition of water the procefs
goes on, in the ordinary temperature of the atmofphere,
with confiderable rapidity. The water furnifhes oxy-
gen to the iron, and its other component part, hydro-
gen, is fet at liberty j and that the nitrous acid, in the
aqua regia, anfwers the purpofe of furnifhing oxygen
to the gold, is proved by the difengagement of nitrous
gas.

The folution of gold in aqua regia, when fifft
made, is always yellow, considerably cauftic, corrodes
animal matters, and tinges them of a deep purple
colour. When applied to the furface of marble,
it tinges it of a violet colour. This colour is pro-
duced by a precipitation of the gold, in confequence
of the fuperior attraction of the calcareous earth for
the acid.

The folution of gold may be made, by cautious
evaporation, to afford cryftals of a beautiful tonaz or
yellow colour. Gold may be in fome meafure vola-
tilized by repeatedly diftilling it with aqua regia ; fome
of the gold rifes with the acid into the neck of the
retort in the form of long (lender brown cryftals.

Gold is precipitated from its folution by a great

variety

234 Fulminating Gqld. [Book VI*

variety of Jubilances, but its appearances are very va-
rious, according to the nature of the matter employed.
Lime and magnefia precipitate gold in the form of a
yellowiih powder, and the fixed alkalies have the fame
effect. Volatile alkali produces a more quick and
copious precipitation, and forms the remarkable com-
pound, known by the name of aurum fulminans, the
nature of which has been already intimated in a note
under the head of ignition. I mall in this place, how-
ever, add a few obfervations, which may tend ftill fur-
ther to illuftrate its nature. In the firft place, it ap-
pears that the fulminating gold is a compound of
about three parts of that metal with one of volatile
alkali. Secondly, Fulminating gold, expofed to fuch
a heat as is fumcient to feparate the volatile alkali^
without letting fire to the compound, lofes its fulmi-
nating property. The fame effect is produced by fub-
mitung it to the action of concentrated vitriolic acid,
melted lulphnr, asther, or any fubftance capable of
abftracting the Volatile alkali by fuperior affinity.
Thirdly, When a few grains of fulminating gold arc
detonated in copper tubes, the extremity of which is
plunged beneath the mercury of the pneumato- chemi-
cal apparatus, azote is diiengaged, a few drops of water
are produced, and the gold is reftored to its metallic
appearance. M. Berthollet, the inventor of this ex-
periment, concludes, that the volatile alkali is decom-
pofed, and that while one of its component parts, hy-
drogen, unites with the oxygen of the calx of goldj
and forms water, its other component part, azote, eP
capes in the form of gas. The readinefs with which
fulminating gold explodes feems to depend on the
tendency which the hydrogen of the alkali has to unite
with the oxygen of the metallic calx, which tendency
the wsak attraction of the gold for the oxygen on the

one

C hap. 3 5 .] Aftiw of Ether on a Solution of Gold. 235

one hand, and the azote for hydrogen on the other,
are fcarcely fufficient to counteract. Whenever the
balance of power among thefe ingredients is difturbed,
which happens from a moderate increafe of heat, or
violent friction, the hydrogen and oxygen unite and
form water, the gold is reduced, and the azote efcapes
in the form of gas, occafioning a violent explofion.

When gold is newly precipitated, Margraff informs
us, that it may be re-diffolved by the volatile alkali,
or, much more readily, by the PrufBan alkali. Alka-
line faits precipitate gold in the form of a calx, but
inflammable fubftances precipitate it in the metallic
form. The moft finguiar effect of inflammable fub-
itances upon the folution of gold is that of the vitriolic
ether, though it does not entirely feparate the gold
from the acid. If into a phial of diftilled water a fingle
drop of the folution of gold is introduced, the water
wil1* become of a fine yellow cotour; add to this a
quantity of vitriolic ether, which will float uppermoft,
and remain, colourlefs, no fenfible change being pro-
duced ; by fhaking the mixture, however, for fome
time, and then allowing it to reft, the yellow colour in
the loweft part of the phial will leave the water, and
rife up into the ether. By repeated agitation, in a
little time the ether will draw up into k the whole of
the gold, fo as to leave the liquor at bottom perfectly
colourlets. It would be erroneous to conclude from
this experiment, that ether is a folvent of gold; it does
not difiblve it, but attracts the folution merely by its
affinity for acids. Though, the ether acts primarily
on the acid, it at length feparates the oxygen from the
calcined gold, and precipitates it in its metallic ftate.
All the fubtile aromatic oils have a fimilar effect, but
do not act fo readily as ether.

As thefe inflammable fluids have no action on the
4 folutions

12 6 Purple Powder of Coffins. [Book VI.

iblutions of other metals, this procefs may be ufed as
a means of refining gold j for the acid containing gold
is imbibed by the inflammable fluid, while that part
of it which is combined with any other metal remains
behind.

Almoft all metallic fubftances precipirate gold from
its folution in aqua regia. Mercury and copper fe-
parate it in its mining metallic form ; lead, iron, and
filver, precipitate it of a deep and dull purple colour.
A plate of tin, plunged in a folution of gold, feparates
the perfect metal in the form of a deep violet powder,
called purple powder of Cafllub, which is ufed in
painting, in enamel, and in porcelain. This powder
confifts of the calces of gold and tin in combination,
and is capable of communicating a fine purple colour
to glafs. The folution of green vitriol precipitates no
other metal but gold, and the gold proves of uncom-
mon purity, and of .a very deep colour. Gold in its
metallic ftate is incapable of uniting with fulphur alone,
but if a piece of gold is dropped into a folution of
hepar fulphuris, efpecially if the latter is prepared
with equal parts of fulphur and alkali, the gold difiblves
with fome ebullition, and forms a mafs, which diflblves
in water like the combination of alkali and crude anti-
mony.

Stahl fuppofes that this procefs was ufed by Mofes
to render the golden calf, adored by the Ifraelites,
loluble in water.

But though gold will not unite with fulphur, it may
be purified by means of it, the fulphur uniting with the
metals with which it is alloyed. With this view it is
ufual to heat the gold with crude antimony, in which
Hate the fulphur is more fixed than when applied in a
feparate ftate. In this procefs, however, the gold
combines with a portion of antimony, which muft be
afterwards driven off by heat.

There

Chap. 35;] Standard of Gold Coin. 237

There are fcarcely any metals with which gold will
not unite. When boiled a Ihort time with mercury,
it forms an amalgam which is gritty and rigid at the
firft, but which becomes by grinding more foft and
tender ; this is often made ufe of for gilding the fur-
face of filver and copper, as was more particular]^
mentioned when treating of the latter metal. -*£

Gold readily unites with zinc, and produces a mixed
metal, whiter than might be expected from the quan-
tity of zinc which is employed j this alloy, made with
equal parts of the two metals, is remarkably fpkndid,
is of a fine grain, and is not liable to tarnifh : on ac-
count of thefe properties it has been recommended for
conftructing the mirrors of telefcopes.

All the metals, except filver 'and copper, take away
the ductility of gold, but none more remarkably than
tin, a grain of which added to a thoufand of gold is
faid to deprive it entirely of ductility. Copper is
commonly ufed to alloy gold, as filver renders it very
pale. Copper rather heightens the colour of gold, but
inclines it to red.

Goldfmiths denote the finenefs of gold by the word
carrat. It is fuppofed to be divided into twenty-four
parts, called carrats ; and gold, which is quite free
from alloy, is faid to be twenty-four carrats fine; that
which contains one twenty-fourth of alloy is called
gold of twenty-three carrats i that which contains two
twenty-fourths, of twenty-two carrats, and fo on. In
England, the ftandard of gold coin is twenty-two car-
rats fine geld and two carrats of alloy, which latter is
half filver and half copper. The French, Spanifh, and
Flemifh gold are nearly of the fame fineness,

[ 238 ] [Book VI.

CHAP. XXXVI.

P L A T I N A.

l Hi/lory ef ibis curious MftaL — Its Properties. — The moj? pon-
derous Body in Mature. — Its Hardnefs and Infujlbility . — Soluble only
in Aqua, Regia and oxygenated muriatic Add.— Its Union with other-
Metals. — Crucibles formed "of it.-~Migljt be applied to various Ufes
•which no other Metal can anfwer.

IN the beginning of the year 1749, the firft fpe-
cimen of this metal was brought into England
from Jamaica. It was faid to have been originally
brought from the Spanifh Weft Indies, and it is ftill
almoft exclufively found in the gold mines of Spanifh
America. It is brought over in the form of fmall
fmooth grains, jrregularly figured, with round edges,
and is often mixed with ferrugineous fand and grains
of quartz or cryftal. The grains of platina are whiter
than iron, but lefs fo than filver, and their flat form is
probably owing to the preffur'e they undergo in the
mills in which the gold is amalgamated.

In confirmation of this opinion, fmall particles of
gold and mercury are ufually found mixed with the
grains of platina. In the ftate in which they are
brought over, they fall fhort of the weight of gold,
but by purification, which is performed by wafhing
with the muriatic acid, and by expofing them for a
long time to the heat of the moft violent furnaces,
•which, however, are faid to be inefficient to melt them*,

* This is the opinion of the generality of mineralogifts; but my
friend and ./chemical preceptor, Dr. Higgins, affixed me, he had
melted platina in his furnace.

they

Chap. 36.] Natural Hiftory of Platina. 239

they exceed it. The fpecific gravity of gold is about
nineteen times that of water, whereas platina, which
ftill contains fo much iron as to render it magnetical,
is upwards of twenty-one times the weight of that
fluid. It is extremely difficult to free platina from
the laft portions of iron, but fome minute particles,
which have be>n fufed by the focus of a burning glafs;
and fo far purified as not to be attracted by the mag-
net, appear to exceed twenty-two times the weight of
water.

Platina is, perhaps, the mod perfect of all the me-
tals. As it fo confiderably exceed^ even gold in weight,
it is therefore to be confklered as the moft ponderous
body in nature.

It has feveral properties in common with the moft
ufeful of metals, iron. In hardnefs it approaches to
that metal in the ilate of fteel ; and in infufibility it
exceeds it even in the ftate of foft iron ; it alfo confi-
derably refembles iron in appearance, and it is th*
only metal, befides iron, which has the property of
welding.

Platina refembles gold in being fallible only in aqua
regia, and it even requires a larger quantity of that
compound acid for its folution than gold. The folu-
tion is of a deep yellow or reddifh colour. The pro-
portions of acids beft adapted to the folution of platina,
are equal parts of the nitrous and muriatic acids; but
the folution does not then take place with rapidity.
This compound is very corrofive, ana tinges animal
fubftances of a blackifh brown colour.

The vegetable alkali added to this folution^ only oc-
cafions the precipitation of a part of the metal in the
form of a fparkling powder, which is foluble in a large
quantity of water. A very remarkable circumflance
is, that the foffil alkali does not produce any precipi-
tation,

240 Aftion tf Saline Matters eft Platina. [Book VI.

tation, tinlefs added in very confiderable quantity.
Common fal ammoniac, applied to the folution of
platina, produces a precipitation like the .fixed vege-
table and volatile alkalies. It feparates a part of the
metal in a fparkling red powder, and a part remains
diffolved, which it cannot feparate ; but if vegetable
alkali is added after the fal ammoniac, itT precipitates
the reft of the platina j and on the contrary, fal am-
moniac, added to the folution containing the re-
mainder, which the fixed alkali could not feparate,
precipitates it, fo that by adding both the vegetable
alkali and fal ammoniac, the whole of the platina is
leparated. Platina, like gold, is alfo foluble by the
oxygenated muriatic acid.

The fubtile inflammable fubftances, as fpirits of
wine and aromatic oils, do not produce any feparation
from, the folution of platina ' in aqua regia, as they do
from that of gold. , Tin precipitates it, but the pre-
cipitation is not purple like that of gold. Moft of the
metals precipitate platina, but it does not in general
fall down in the metallic ftate. The precipitation of
platina, from its folution by fal ammoniac, affords a
method of feparating this metal from the gold which
is mixed with it, as the gold is not feparated by the
addition of that fait; if, on the' contrary, we'wifh to
precipitate the gold, and leave the platina in iblution,
this may be effected by fal martis.

The precipitates of platina may be reduced to a
metallic button, by heating them with the common
fluxes ; but thefe cannot be rendered malleable unlcfs
they are completely fufed, which can fcarcely be ef-
fected, unlefs with the heat of the moft powerful bum-
ing glafles.

A mixture of copper with platina forms a metallic,
body Of inter mediate CQlour and 'great denfity, fo that

Chap. 36,] Union of Platim with other 'Metals. 241

it receives a very fine polifli. A mixture of three
or four parts of copper to one of platina poffefied
all the above properties in great perfection, and was
not tarniihed in the air in the fpace cf ten years.
With iron it alfo produces a compound of great den-
fity, which is hard, ftrong, and tough, and admits of
a good polifh. Moil metals increafe the fufibility
of platina fo much, that the mixture may be melted in
ordinary furnaces.

Gold is greatly injured in appearance by a mixture of
platina, and becomes of the colour of bell metal by the
addition of no more than one twenty- fourth part,
though half that quantity produces little change.

Platina with bifmuth and tin forms alloys, which
are brittle, but eafily fufed. Platina and lead unite
very well by fufion, but the ductility of the lead is
deftroyed, and the compound quickly tarnifhes on
expofure to air. Platina partly deftroys the ductility
of filver, augments its hardnefs, and impairs its co-
lour.

Platina completely refifls the action of mercury,
with which it mews no difpofition to unite. On this
account it does not mix itfelf with the gold,, which is
extracted from the fubftances with which it is mixed by
amalgamation.

From the extreme infufibility of platina, it is ex-
cellently fitted to contain other matters, which it is
intended to fubmit to a violent heat. M. Achard
fucceeded in making crucibles of platina, by fufing
equal parts of platina, white arfenic, and vegetable
alkali. This matter, when cooled, was reduced to
a powder, and rammed into a- mould. A ftrong heat,
quickly raifed, and continued for fome time, fufed the
mafs, and after diflipating the arfenic and alkali, left
the platina in the defired form.

VOL. II. R Platina,

i4* Platina. [Book VI.

Platina, when thoroughly purified, by cod"Hon in the
muriatic acid and precipitation from aqua regia, may
be fufed into a mafs nearly as malleable as foft iron.
This property, united to thofe of refitting acids, its
great infufibility, and welding, feem to render platina
applicable to purpofes which no other metal is capable
ofanfwering.

Chap. 37.] [ 243 ]

CHAP. XXXVII.

OF INFLAMMABLE SUBSTANCESIX
GENERAL.

Ignition and Combujiion defirted,— Acids formed ly the Combufticn of
Inflammable Subjlanccs. — Flame, how produced. — The QbjeSl ef the
prefent Inquiry limited.*— What Subftances are commonly termed jn-
flammable.

difference between ignition and combuftion
was briefly mentioned in the early 'part of this
work ; but after what has been advanced concerning
the elaftic fluids, ?.nd the nature of acids, the reader
will be prepared for a more philofophical view of
the fubject. All bodies which can fupport a cer-
tain degree of heat, without the deftruclion of their
texture, emit light, and this is called ignition j but
combuftion or inflammation is a property which be-
longs to fuch bodies only as are capable, when placed
in proper circumftances, of augmenting their own tem-
perature. Simple ignition produces no permanent
change in bodies, but combuflion entirely alters the
properties of fuch as have undergone that procefs.
From being mild and nearly infoluble in water, they
become acrid, pungent, and extremely foluble, and are
converted into acids, which differ according to the
fubftance, by the inflammation of which they were
formed. The terms combuftible fubftance and aci-
difiable bafis are, therefore, in the French nomencla-
ture, fynonymous.

It has already been remarked, that inflammation

is the difengagement of the matter of heat or calo-

ric contained in vital air or oxygenous gas, in con-

R 2 fequence

244 Inflammable Subjlances. [Book VI.

fequence of the bafis of this gas becoming com-
bined with other bodies. All bodies, therefore,
which are capable of decompofing vital air, change
a cfuantity of latent heat into fenfible heat, and are
faid to be inflammable from the light and heat which
feem to proceed from them, but which, in fact, are
derived from the oxygenous gas, which is one«of die
component parts of the atmbfphere.

The neceflity of the prefence of air to combuftion
is ftrongly maintained by M. Lavoifier, and an expe-
riment related by him (to the latter part of which I
feel fome reluctance to give an unqualified afient)
feems, indeed, to pFOve it to be efiejitial in all cafes.
Fie fucceflively placed a quantity of phofphorus, of
fulphur, and of gunpowder, under the receiver of an
air-pump, making as perfect a vacuum as the machine
would admit. He then threw the focus of a lens of
eight inches diameter on the different fubftances, which
were not at all ignited, only bubbled up, and at length
fublimed. The gunpowder was decompofed,_ the
fulphur of it only fubliming, and it neither took fire
nor exploded.

In ordinary language, no bodies are faid to be
inflammable but fuch as burn eafily, or which, in other
words, are capable of decompofing vital air in the di-
luted ftate in which it exifts in the atmofphere. In a
more ftrict fenfe, however, the property of inflamma-
bility belongs to other bodies, though they poffefs it
in a lefs eminent degree -, as to zinc, which, when made
extremely hot, burns with a dazzling white light* and
to iron, which when heated to a proper degree, burns
in pure oxygenous gas. The oxygenation which all
metals, except the perfect, undergo from the conjoined
operation of heat and air, muft alfo be CQfifidered
3 as

Chap. 37«] Acids formed by Combuftion. 245

as a flow combuftion. In fhorr, all fubftances may •
be faid to be inflammable which are capable, in any
circumftances, of decomposing vital air, or which have
a ftronger attraction for the bafis of that air than that
bafis has for caloric or fire.

In all inftances of inflammation a certain degree of
heat is necefTary to begin the procefs. Different in-
flammable fubftances require different degrees of heat
for this purpofe. Phofphorus is fully inflamed at the
heat of 86 degrees of Fahrenheit, but undergoes a more
gradual combuftion at a much lower temperature.
Sulphur requires much more heat than phofphorus,
and charcoal ftill more than fulphur. There are fame
fubftances in nature which are fo combuftible, or have
fo ftrong an attraction for oxygen, as never to have
been found uncombined with that principle ; of this
kind are the unknown bafes of the boracic, fluoric, and
muriatic acids.

Though an acid is always formed by the combuf-
tion of every inflammable fubftance, this fact was
never attended to, or at leaft never properly appre-
hended, till within thefe few years. In ordinary cafes,
indeed, this circumftance was likely to pafs unob-
ferved ; for the acid produced by the inflammation of
charcoal, which is the principal ingredient in all kinds
of fuel, is the carbonic acid gas, or fixed air, which
Hcapes without leaving any traces. In the combuf-
tion of fulphur alfo, the acid flies off in fumes, unlefs
collected by a particular procefs, which was defcribed
in treating of the fulphuric or vitriolic acid. The
phofphoric acid, however, is a concrete body, and
therefore cannot eafily be overlooked. When inflam-
mable bodies are united with oxygen they become
acids, and having no longer fufficient attratftion for
R 3 oxygen

s-4-6 Combuftion without Flame. [Book VI.

oxygen to decompofe vital air, they lofe their inflam-
mability. According to the old chemical doctrine,
the heat and Jight afforded by inflammable fubftances
were fuppofed to derive their origin from the difen-
gagement of phlogiftcn j but, according to the doc-
trine of M. Lavoifier, the vital air of the atmofphere
is the repofitory of light and heat, from which all ar-
tificial fupplies are derived, by means of inflammable
fubftances.

There is one ftriking difference among inflammable
fubftances, which is, that fome burn with and Ibme
without flame. Of .the former kind are oils, fpirit
of wine, and moft others ; to the latter kind belong
the different fpecies of charcoal. The caufe of this
difference is, that fome inflammable bodies afford an
inflammable vapour, the burning of which produces
flame; others are entirely fixed, and produce no fuch
vapour. The vapour, however, as it rifes is not wholly
confumed ; the reafon of which is, that the air does not
find accefs to the, center of the column of vapour as was
formerly explained. In large flames, the furface on which
the air acts is lefs in proportion to the quantity of vapour
than in fmall flames ; hence the quantity of fmoke and
foot produced by fmall flames is proportionably lefs
than that produced by large ; for fmoke and foot are
only that part of the vapour which is unconfumed.

In treating of inflammable fubftances it will be ne-
cefTary to confine the inquiry to thofe which poffefs
that property in a more remarkable degree. I fhall,
therefore, firft treat of the fimple inflammable fub-
. fiances, phofphorus, fulphur, and coal, or the carbon
of the French philofophers. Hydrogen, or inflam-
mable air, has already been defcribed under the liecid
of elaftic or aeriform fluids. With refpect to the

compound

Chap. 37.] Inflammable Subjtarues. 247

compound inflammable fubftances, fuch as oils, refins,
fat, &c. it will be found that they confift of different
proportions and dates of combination, of carbon, hy-
drogen, and oxygen. The inflammable matter of
charcoal and coke confifts of carbon only j pitcoal and
wood, in their crude ftate, contain alfo fome hydrogen,
which is driven off, together with water and oil, in the
procefs of charring.

[ 24$ ] [BookVL

CHAP. XXXVIII.

PHOSPHORUS.

Phof^horus of Kunkel. — Light from futrefcent Sufytances.—- Curious
Faffs.— -Light from the Sea Water, I3c. — Lights about the Beds of
Sick Perfons. — Phofphorus exhaled with the Sweat.— Phcfphorated
Hydrogen Gas,

PHOSPHORUS* is a fimple combuftible fub-
ftance, which was unknown to chemifts till 1667,
when it was difcovered by Brandt, a German chemifb,
who kept the procefs a fecret ; foon after Kunkel
found out Brandt's method of preparation, and made
it public. Ic has ever fince been known by the name
of Kunkel's phofphorus. The appearance of phof-
phorus is that of a tranfparent fubftance, of a colour
inclining to yellow, like clear horn j it is fpecifically
heavier than warer, is tough, and cuts like bees' wax,
and like it melts with a gentle heat into a tranfparent
fluid. With this heat it may be melted in water;
but if the fame degree of heat is applied in the open
air, it melts, takes fipe, and burns, producing a bright
white flame wich intenfe heat. Phofphorus fhould be
handled with great caution, as fhould any of it adhere
to the fkin, or get under the nails, the heat of the hu-
man body is fufficient to inflame it. The procefs for
obtaining phofphorus from bones was defcribed in
treating of the phofphoric acid.

When a quantity of phofphorus is burnt in fmall
pieces under a bell, the phofphoric acid attaches itfclf
to the internal furface of the bell, in the form of a

* Derived from the Greek—" A fubfhmce affording light."

downy

C hap. 38.] Combuftion of Phofybarus. 249

downy mafs. This concrete acid has fo ftrong an at-
traction for water as to imbibe it from the atmofphere
with aftonifning rapidity, till it is converted into a li-
quid confiderably more denfe, and of greater fpecific
gravity than water.

From the experiments detailed in M. Lavoifier's
elementary work on chemiftry, it appears that one
pound of phofphorus requires one pound eight ounces
of oxygen gas for its combuftion, and that two pounds
eight ounces of concrete pholphoric acid are pro-
duced.

The phofphoric acid may be obtained by three
Other proceffcs befides this. If phofphorus is melted
in hot water, and a ftream of vital air pafTed through
it, it becomes oxygenated. The fame thing happens
by plunging it in nitrous acid, from which it abftracts
the oxygen. It may be alfo acidified by fimple expo-
fure to the atmofphere, which ought not at the time
to exceed the temperature of fixty degrees, from the
danger of inflammation ; in this (ituation, by a gradual
combuftion, it attracts the oxygen of the atmofphere,
and becomes converted into an acid.

The cauftic fixed alkalies difiblve phofphorus by
the affiftance of heat. During this combination a
fetid gas is difengaged, which has the fingular property
of exploding as foon as it comes in contact with at-
mofpherical air, and ftill more rapidly by contact with
•vital air.

The phofphoric acid forms peculiar falts with, the
alkalies and fome of the earths, and has the property
of corroding glafs. With the mineral alkali it forms
a fait, the tafte of which is lefs unpleafant than that of
other neutral falts, and which is well calculated to an-
fwer the purpofes for which neutral .falts are ufed in
medicine. . The phofphoric acid acts only on a fmall

number

250 . Natural Hiftory of Pbofpborus. [Book VI.

number of metallic fubftances, but readily diflblves,
in its fluid ftate, iron, zinc, and copper, with which it
forms falts not cryftallizable.

Phofphorus feems to be almoft univerfal in the ani-
mal kingdom, and is alfo found in fome minerals, and
in a very minute proportion in mofl vegetables. The
bones of animals are a true phofphat of lime, or an
earthy fait compofed of phofphoric acid and calcareous
earth. The urine alfo contains a confiderable quan-
tity of phofphoric acid, chiefly combined with volatile
alkali, but partly alfo with calcareous earth. This
compound fair, afforded by the evaporation of urine,
was formerly known by the names of eilential fait of
urine, or microcofmic fait. Brandt, Kunkel, and
MargrafF, and all chemifts, till lately, prepared their
phofphorus from that fubftance, but it is now almoft
entirely obtained from bones, which afford it more
plentifully and with lefs trouble. Phofphorus does
not yet feem to have been applied to any important
tifts.

From the remarkable eafe with which phofphorus
is inflamed, feveral experiments may be exhibited by
means of it, which appear like the effects of magic to
perfons unacquainted .with the nature of this fub-
ftance. Thus, for example, if the outfide of a bottle
is rubbed with phofphorus, and then furrounded with
tow, and hot water pourtd into ir, the phofphorus
takes fire, and communicates the inflammation to the
tow. If a flick of phofphorus is ufed to write on a
piece of paper, or en a wall, a quantity of phofphorus
is abraded, and, undergoing a flow combuftion, ren-
ders the ftrokes vifible in the dark, while in the
light they can only be perceived to exhale a whitifh
vapour.

A fluid called liquid phofphorus is prepared by

digefting

Chap. 38.] Superjlitious Terrors. -251

digefcing fome phofphorus in the heat afforded by
horfe-dung for two days, in oil of cloves, oil of tur-
pentine, or any fimilar fubftance. v After diflblution,
the oil will be fo impregnated with it, that when the
phial is opened, it will appear luminous. Any thing
moidened wich this fluid will in the dark feem to be
on fire.

Many natural phenomena, which in the ages of fii-
perfthion ferved to aftonifh and affright mankind, have
received a fatisfa&ory folution from the difcoveiy of
the phofphorus of Kunkel. We learn from Fabricius
ab aquapendente, that three young men at Padua, hav-
ing bought a lamb, and eaten part of it on Eafter
Day, 1592, feveral pieces of the remainder, which
were kept till the day following, (hone like fo many
candles when cafually viewed in the dark. It appears
by his account, that the aftonifhment of the whole
city was excited by this phenomenon, and a part of
the fiefli was fent to him, who was profeflbr of ana-
tomy, to be examined by him. He obferved, that
thofe parts which were fofc to the touch and tranipa-
rent in candle light were the mod refplendent. A phi-
lofopher of not lefs note, has furniihed us with a very-
pompous account of a fimilar phenomenon, which oc-
curred at Montpelier in 1641. A poor old woman
had bought a piece of flefh in the market, intending to
make ufe of ic the day following: but happening not
to deep well that night, and her pantry being adjoining
to her bed, fhe obferved that a quantity of light pro-
ceeded from the meat, fo as to illuminate aimofr. the
whole place where it hung. We may eafily judge of
the terror and aftonifhment of the poor woman hcr-
felf, fince we find that a part of the fielh was carried,
as a very extraordinary curiofity, to Henry Duke of
£oncje, who viewed it with the utmoft furprize for

feveral

252 Explanation oftkefe Appearances. [Book VI.

feveral hours. The light was as if gems were fcat-
tered over the furface, and continued till the flelh be-
gan to putrify, when it vanifhed, which it was believed
to do in the form of a crofs.

The attention of a more philofophic age was diredt-
ed to experiments to afcertain the caufe of this light.
Mr. Boyle found, that the light of rotten wood was
extinguifhed in vacuo, and revived again by the ad-
million of air, even after a long continuance in vacuo.
The extinction of the light was not fo complete im- '
mediately on exhaufting the receiver, as fome little
time afterwards. The wood was not much affected
by condenfed air; but the light of a fhining fiih,
when put into the condenfing engine, was rendered
more vivid by that means. As air is therefore necd-
fary to combuflion, thefe experiments clearly indicate,
that this light is the effect of a flow combuflion, or
ibmething analogous to. it ; and, indeed, the experi-
ments upon the phofphorus of Kunkel have fince
placed this matter beyond a doubt. The combuftion,
however, in thefe cafes, is fo very flow, that no change
of air appeared neceflary for the maintenance of this
light, for it continued for a long time, even though
the wood was confined within a glafs hermetically
fealed.

To explain the caufe of this combuflion it is only
neceflary to repeat what has been juft Hated, that there
exifts in every animal body, and in mofl vegetables, a
certain quantity of phofphorus. This principle, we
have feen, is extremely active^ and has the ftrorigeft
tendency to unite with the pure part of our common
air. During that feparation, therefore, of the parts of
bodies, which takes place in an incipient putrefaction,,
thefe phofphoric particles are detached from thofe with
which they are combined, and by the action of the air,

a degree

C hap. 3 8 . ] Luminous Appearance cf Fife . 253

a degree of combuftion takes place, but fo extremely-
faint, that light only is produced, without the leaft ap-
pearance of fenfible heat.

This fhort explanation of the caufe will, I flatter
myfelf, correfpond with moft of the phenomena of this
kind noticed by philofophers. Mr. Boyle found that
the light of rotten wood was in moft refpects analogous
to that of putrefcent fubftances. The light of the
former, however, differed in fome refpe6i:s; it was
prefently quenched with water, fpirit of wine, and
ieveral other fluids ; but the light of fome fliining
veal was not entirely quenched by water, though its
virtue was inftantly deftroyed by fpirit of wine *. The
fame philofopher was fometimes difappointed in his
experiments on Ihining fifties; particularly he ob-
ferved, that they failed to become luminous in cold
and frofty weather, which is perfe6tly agreeable to the
nature of phofphorus, fince its combuftion is exactly
in proportion to the heat which is applied to it. He
remarks alfo in another place, that the light of film-
ing wood was completely extinguifhed by extreme
cold.

Some bodies have a much greater tendency to pro-
duce this light than others. A foreign philofpher re-
marked, that on opening a fea polypus it was fo lumi-
nous as to ftartle moft of the perfons who faw it ; the
nails and the fingers of thofe who touched it became
luminous alfo. The light of the glow worm, and other
luminous infects, muft depend upon fome flimy or fluid
matter which they emit, and which is probably a com-
bination of phofphorus with oil. There is a remarkable
fhell-fifh, called phoks, which forms for itfelf holes in dif-
ferent kinds of flone. This fifti illuminates the mouth of

* 'Prieft. Op. 565.

the

Kce of the Sea. [Book VI.

the perfon who eats it ; and it is remarked, that con-
trary to the nature of other filh, which give light when
they tend to putrefcence, this is more luminous the
trefner it: is, and when dried its light will revive on
being moiftened either with fait water or frefhj brandy,
however, immediately extinguifhes in*.

The luminous appearance of the fea in the night
time cannot have efcaped the obfervation of any per-
fon in the Icaft converfant with that element. The
light occafioned by the dafhing of oars, or by the mo-
tion of the waves by night, is extremely beautiful. Fa-
ther Bourzes, in his voyage to the Indies in 1704, re-
marked particularly the luminous appearance of the
fea. The light was fomedmes ib great, that he could
eafily read the title of a book by it, though nine or
ten feet from the furfacc of the water. Sometimes he
could eafily diftinguim, in the wake of the (hip, the
particles which were not luminous from thofe that
, were. The luminous particles alfo appeared of dif-
ferent forms ; fome appeared like points of light, others
like ftars; fome of them refembled globes of a line or
two diameter, and fome appeared as krge even as a
man's head > they afTumed fquare and triangular as
well as globular forms, and not only the wake of the
fbip, but fifhes in fwimming, produced thefe luminous
appearances. All thefe phenomena he attributes, and
rightly, to the fat or putrefcent flate of the water, and
cbferved, that when the wake of the (hip was brighter!,
the water was moft clammy and glutinous. In fome
parts of the fea, he faw a fubflance, like yellow and red
duft, and the failors told him it was the fpawn of whales
which produced all thefe appearances f. Later ex-
periments have proved, that the luminous appearance of

* Pritf. Op. 567. f Ibid. 572.

the

Chap. 38.] Lights about the Beds of Sick Perjons. 255

the fea entirely proceeds from the putrefcent parts of
marine animals *.

Human bodies, as well as thofe of other animals,
emit light juft when they begin to putrify,- and the
\valls and roofs of places in which dead bodies have
often been expofed have been obferved to have a
flimy matter depofited on them, which was luminous
in the dark. The lights which are fometimes feen in
burial grounds undoubtedly proceed from this caufe
alone f. Similar appearances have been obferved
about the beds of lick perfons, probably in putrid
difeafes: one of thefe was obferved about the body and
the bed of a fick woman at Milan, which fled from the
hand that approached it, but was at length difperfed
by a ftream of air. It is well known that the iweat
often contains a confiderable quantity of phofphoric
matter j and the fact, which has now been ftated,
is ftrongly confirmed by a circumftance related by
Henckel, in his Pyritologia. One of.hr. friends, who
was of a fanguine temperament, had indulged himfe'lf
in the exercife of dancing tofuch excefs,and his perfpi-
ration was fb profufe, that he imagined his life in dan-
ger. While he undreffed, traces of phofphoric light
were feen on his Ihirt, and in thofe parts were a num-
ber of reddifh yellow fpots, exactly refembling the
concrete phofphoric acid.

In all thofe animal exhalations, which exhibit phof-
phoric appearances, the phofphorus in the ftate of a gas
is mixed with hydrogen, and the compound is called
fbejpborated hydrogen gas. Of this nature, probably,
are many of thofe phenomena, which are clafled
under the general name of ignes fatui, and of thofe
which were defcribed in a fprmer volume as igneous
or luminous meteors.

* PrifJ}. Of. 576. f Ib^d.

[ 256 ] [Book VI.

. . C H A P. XXXIX.

SULPHUR.

General Properties of Sulphur. — Natural Hijlory of Sulphur. — Union
^wiih Earths. — With Alkalies. — Liver of Sulphur,— -Artificial ful~
f bureaus Waters. — Ufcs of Sulphur.

r~>ULPHUR is another fimple inflammable fub-
C3 ftance, which agrees in Come properties with
phofphorus. Like that it melts with a gentle heat,
and is capable of a gradual as well as of a rapid com-
buftion, in proportion to the degree of heat applied to
it. Heated to 170° of Fahrenheit it generally evapo-
rates; it melts at 1 8 5° and then appears red; it inflames
at 302°. Its flame is blue, and accompanied with a
iTiarp fu frocating fmell, which is the fulphureous or
volatile vitriolic acid.

In treating of other bodies, particularly the metallic,
feveral have been mentioned with which fulphur is
found united in the bowels of the earth: few fub-
ftances are indeed more abundant in nature than ful-
phur ; it alfo enters into the compofition of animal
matters, and, in a very fmall proportion, into that of
vegetables.

The fulphur of commerce is extracted, by diftilla-
tion, from the fubftance which has been fo often men-
tioned under the name of pyrites, in which ft ate it is
combined with iron, and* is fo hard as to ftrike fire
with fleel. Pyrites in colour and appearance refemble
brafs; fome pieces are cubical, but in general this
mineral has no determinate form. The fulphur ob-
tained by the ftrft diftillation is feldom pure, from the

fteams

Chap'. 39.] Natural Hiftory of Sulphur. 257

fleams of other volatile fubftanees which rife and are
condenfed with it. It is purified by being melted in a
ladle, and kept in that flate till the impurities fettle at
the bottom. If it is an object to obtain fulphur of the
greateft purity, this -mud be effected by fublimation ;
and in this flate it is commonly fold under the name
of flowers of brimflone. Even thefe, however, are
fometimes rendered impure by the fulphur taking
fire, which produces a mixture of vitriolic acid. This
is effectually removed by boiling the flowers in water,
which diflblves the acid, and leaves the fulphur in a
pure and mild flate.

Sulphur is fometimes found, more or lefs pure, in
the neighbourhood of volcanos, in which cafe it feems
to have been feparated, by fubterraneous heat, from
fome fubflance with which it was previoufly com-
bined.

The method of burning fulphur for the preparation
'of the vitriolic acid has already been defcribed when
treating of that acid.

Sulphur has no action on filiceous earths, but very
readily unites with the calcareous. It is alfo capable
of combination with magnefia, ponderous earth, and
volatile alkali. It unites, however, with much more
violence with the fixed alkalies. All thefe combina-
tions are of a liver colour, and are therefore called
livers of fulphur. By M. Lavoifier they are much
more properly denominated fulphurets of thefe feveral
fubftanees, as fulphuret of lime, fulphuret of magnefia,
&c. Thefe fubftanees are foluble in water, and have
confiderable action on feveral other bodies. The
combinations of fulphur with earths and alkalies may
be all decompofed by means of acids, and the earthy
fulphurets by means of the fixed alkalies. Thefe fub-
ilances, when diflblved in water, difengage a peculiar

VOL. II. S gus

258 Vfes of Sulphur.- [Book VI.

gas called hepatic gas. This gas is precifely the fame,
from whatever kind of fulphuret it proceeds ; but none
of them afford it unlefs mixed with water. This gas,
therefore, proceeds from a decompofition of water,
and is found to confift of fulphur diflblved in inflam-
mable air. When this gas comes in contact with
vital air it is decompofed, the vital air and hydrogen
uniting to form water, while the fulphur is precipitated
in fmall flakes.' This gas is capable of folution in
water, and by thefe means natural fulphureous waters
may be imitated.

The chief ufes to which fulphur is applied are, the
making of gunpowder and vitriolic acid. It is alfo
ufed in bleaching, and is an article of fome importance
in the materia medica.

Chap. 40.] [ 259 ]

CHAP. XL.

THE CARBONACEOUS PRINCIPLE.

Nature of the Carbonaceous Principle.-— In what Subjlances -princi-
pally found, —'Char coal. — Lamp black. — Strong Attraction of the
Carbonaceous Principle for Oxygen. — Its Ufe in the Reduction of Mt-
tah.— Plumbago, or Black Lead.—Ijs various U/es in the Arts.

TH E word carbon is adopted from the nomen-
clature of the French chemifts, to exprefs an
inflammable matter which conftitutes the chief part
of the weight of charcoal, pit coal, &c. and which, with
certain proportions of hydrogen, or the bafis of in-
flammable gas, forms the different kinds of oil.

By the combuftion of carbon a peculiar acid is
formed, which is foluble in water, unites with alkaline
bafes, and poflefies all the properties of acids in ge-
neral, though in a weak degree. This acid has al-
ready been treated of under the name of carbonic acid
gas, or fixed air.

Carbon exifts in great quantities, in foflils, as the
greater number of calcareous ftones and earths are
found united with it ; it is alfo one of the conftituent
parts of the atmofphere, in both which ftates it is
combined with oxygen. It is found united with earthy
matter and oil in the extenfive ftrata of pit-coal, and
with iron in the matter which is called plumbago, or
black lead. Carbon alfo exifts in all vegetable and
animal fubftances, and conftitutes a confiderable part
of their weight, particularly of thofe vegetable matters
which are the moft firm. The ftate of greateft purity
to which carbon can be reduced is, by burning wood
S , in

260 Charcoal [Book Vf.

in fuch a manner as to reduce \t to charcoal, which,
•when well made, contains carbon united with only a
very fmall proportion of fuch matter contained in
vegetable fubftances as cannot be driven off by heat,
fuch as earthy and faline matter, with a very minute
portion of iron. In order to convert wood into char-
coal, the only circumftances neceffary are the applica-
tion of heat while the air is nearly excluded. The only
elementary fubftances which feem-to be univerfal in
the vegetable kingdom are, carbon, hydrogen, and
oxygen. The former of thefe fubftances has very
little attraction for caloric, or the matter of heat, and
therefore cannot be driven off in vapour, at leaft by the
heat of ordinary fires; the two latter, however, have
a ftrong attraction for that principle, and therefore
eafily affume a gaffcous ftate. In the ordinary tem-
perature of the atmofphere the carbon, hydrogen, and
oxygen, which conftitute the woody fibre, feem to exift
in a ftate of triple combination j but this is not the
cafe when the temperature is altered. According to
M. Lavoifier, if a heat, not exceeding that of boiling
water, is applied, one part of the hydrogen combines
with oxygen, and forms water, the reft of the hydrogen
combines with a part of the carbon, and forms volatile
' oil, while the remainder of the carbon remains fixed
at the bottom of the veffel. If a red heat, however,
is applied, no water comes over, carbon having a
ftronger attraction at that temperature for oxygen than
hydrogen has, and therefore carbonic acicl is produced ;
and the hydrogen being left free from other combina-
tions, unites with caloric, and comes over in the form
of hydrogen gas. In this high temperature no oil is
produced.

The folidity of charcoal depends on that of the wood
from which it is procured, and the care with which

the

Chap. 40.] Lamp Black. *6i

the procefs is conducted. In general it preserves the
form of the vegetable, unlefs that was very fucculent.
Pure oils, when decornpofed by heat, afford a coal
in very fine particles, called lamp black.

In whatever manner the volatile matters can be dif-
pelled from vegetable or animal fubftances without the
admiffion of vital air, which would confume the car-
bon, charcoal is produced, which contains no ingre-
dient capable of inflammation except carbon, and
therefore, with refpect to that procefs, may be confi-
dered as carbon itfelf.

Charcoal, expofed to the greateft heat without the
" prelence of vital air, remains unconfumed and un-
changed. This fact has been denied by the advocates
for the phlogiftic hypothefis, who maintain that the
pureft charcoal, treated in this way, affords a'quantity
of inflammable gas. It is now, however, I believe,
commonly admitted, that if the charcoal is firft accu-
rately dried, no inflammable gas is produced, and
therefore that which has been obferved by other che-
mifts, is to be attributed to the prefence of a fmall
quantity of water, which, in a high temperature, is de-
compofed by charcoal. Dr. Prieftley has obferved,
that charcoal has a ftrong difpofition to attract humi-
dity from the atmofphere. He found that charcoal
prepared in the evening, and kept till the morning,
became fenfibly moid, and unfit for nice experiments.
This remarkable attraction for water is, perhaps, to be
attributed to the alkaline falts ufually contained in
charcoal.

From the very ftrong attraction which the carbo-
naceous principle has for oxygen, there is no fubftance
that can be applied to feparate it from that matter.
Carbon, on- the contrary, is capable of decompofing
all the acids except the boracic, the fluoric, and the
S 3 muriatic,

262 Ufe of Charcoal in reducing Metals. [Book VI.

muriatic, the unknown bafes of whicri have a ftronger
attraction for oxygen than it has.

Charcoal readily decompofes the phofphoric and
fulphuric acids, the bafes of which burn at a lower
temperature j and this fadt evinces, that the degree of
heat at which the combuftion of a body begins does not
accurately mark its degree of attraction for oxygen.

From the ftrong affinity of the carbonaceous prin*
ciple for oxygen, charcoal is the moft powerful fub-
ftance which can be ufed in the reduction of metals.
Charcoal has alfo another advantage over other in-
flammable fubflances in thefe operations, which is, that
it bears a great degree of heat without volatilization.

According to the experiments of Lavoifier, in the
combuftion of one pound of charcoal, two pounds
nine ounces one drachm ten grains of oxygen gas are
abforbed, and three pounds nine ounces one drachm
ten grains of carbonic acid gas are formed.

The carbonaceous principle, or carbon, is one of
the moft important fubftances in nature. It is one of
the neceflary conftituent parts of animal fubftances, and
enters into the compofition of all alimentary matters,
flour, fugar, mucilage, oil, &c. It is alfo the chief
ingredient in all kinds of fuel.

PLUMBAGO, or black lead, is found to confift of car-
bon combined with about one tenth of its weight of
iron. It appears to be fcarcely inflammable, but
may, however, be almoft entirely confumed with the
production of carbonic acid gas, by keeping it heated
to a great degree, and agitated fo as to expofe it tho-
roughly to the air. It may be alfo deflagrated with a
large proportion of nitre in a red heat. It is found in
a feparate ftate in a variety of places ; but the fpecies
beft adapted for making pencils comes chiefly from
Burrowdale, in Cumberland, For this purpofe it
6 is

Chap. 40.] Black Lead. 16 j

is cut into a thin plate, the edge of which, being fitted
into a groove in a femi-cylinder of wood, is then fawed
off, fo as to leave the cavity entirely filled. The
black lead is retained in its place by the other half
of the cylinder, which is glued on. The makers of
fmall mot polifh and blacken its furface by agitating
or rolling it in a calk with powder of plumbago. This
mineral is likewife ufed in the manufacture of razor-
ftraps.

S4

[ 264 ] [Book VI.

CHAP. XLL

PIT COAL.

Different Species of CoaL—Nenvcaftle Coal—Culm.— Slate Coal.—
Cannel Coal.— Kilkenny CoaL—Bovey Coal. — Peat.— Coke. —
Coal Tar. — Natural Hiftory of Coal.—Obfer<vaiions relative to the
Deluge.

PIT COAL is a fubftance of which there are
many varieties, the caufes of which have not been
afcertained, as all the kinds afford very nearly the fame
refuks by chemical analyfis. But before the different
fpecies of this mineral are mentioned, it is necefiary to-
notice a fubftance which agrees in all its chemical
properties with charcoal, pofleffing at the fame time-
moft of the external characters of pit coal, and which
Mr. Kirwan confiders as the natural carbonic prin-
ciple. Its colour is black or greyifh black, with a
luftre approaching to the metallic. It is without tranf-
parency, and its fracture is foliated or flaty. It ilains
the fingers. This defcription is taken from the pureft
ipecimens which have yet been procured j namely, thofe
found near Strido in the territory of Florence. This
'fubftance is infoluble in acids. In a ftrong heat it
reddens, but does not flame. Expofed to a porcelain
heat for feveral hours in covered crucibles, it entirely,
or almoft entirely, evaporates like the diamond *.
Diftilled it yields a fmall quantity of water, but no
air, oil, acid, or alkali. Kilkenny coal is nearly allied

* The reader will find that the diamond itfelf is probably
a fubftance of this nature, by confulting Chap. 44, where the dia-
mond is treated of as an inflammable fubftance.

to

Chap. 41.] Newcaftk Coal, &?r. 265

to this fubftance, and may perhaps be confidered as of
the fame fpecies. The moft remarkable varieties of
pit coal are,

1. NEWCASTLE coal, which is of a black colour and
fhining appearance, where it h?s been lately broken.
This fubftance undergoes an imperfect fufion when
heated, fo as to cohere or cake. It burns with a lively
flame, and is nearly confumed in the fire. It does not
break equally in all directions, and is compofed of la-
minae.

2. CULM coal. This contains a large proportion
of argillaceous earth, fo that after being burned its bulk
is fcarcely diminimed. It burns with a lively flame,
but its appearance is more dull and earthy than that of
the former. This kind of coal is found in Sweden,
and in feme parts of England.

3. SLATE coal. This has very much the appearance
of fome of the common kinds of (late, but it burns
very eafily, with a copious and bright flame. It
confifts chiefly of argillaceous earth, and feems to
have only been penetrated with bituminous or coaly
matter.

4. CANNEL coal is of a dull black colour, breaks
eafily in any direction, and in its fracture prefents a
fmooth chonchoidal fur face, if broken tranfverfely. It
is nearly confumed in the fire, burns with a lively
Hame, but if fuddenly heated flies in pieces with
confiderable violence. This inconvenience is faid to
be removed by previoufly immerfing it in water for
fome hours *. Cannel coal docs not foil the fingers,

* It is cuftomary in Lancaftnre to fprinkle fait upon cannel
coal, to prevent its flying ; but I cannot fpeak decifively as to its
effefb, having never isen the experiment accurately made. Poflibly
the water contained in the fait may have fome influence in prc-
ventiiig the cracking of the coal.

and

266 Kilkenny Coal, &V. [Book VI.

and admits of being turned into fnurF boxes, inkftands,
trinkets, &c.

The word lithonthrax, ufed by fome mineralogies,
properly denotes ftone coal, and feerns mod applicable
to cannel coal, as this, from its dull and uniform frac-
ture, has mod refemblance to a ftony fubftance.

5. KILKENNY coal. This is perhaps the moft free
from earthy matter of all the different fpecies of coal ;
the earth contained in it not exceeding the twentieth
part of its weight. This coal burns with lefs flame
and fmoke *, and more flowly and intenfely than the
cannel coal,

6. SULPHUREOUS coal. All thofe kinds of coal
are called by this name, which are mixed with parti-
cles of a yellow and metallic appearance, and which
are in fact a fpecies of pyrites. In confequence of
this admixture they emit, when burned, a fulphureous
imell, and fall to pieces when expofed to the action of
air and moifture. •

7. BOVEY coal, xylanthrax, is of a brown or
brownifh black colour, and of a laminar texture.
The laminae are frequently flexible when frelh dug,
though they generally harden on expofure to air. Mr.
Fabroni discovers its organic ftru<5lure by boiling it
in dilute nitrous acid, by which its fibres are laid bare.
It feems to confift of wood penetrated by petroleum or
bitumen, and frequently contains pyrites, alum, and
vitriol -

8. PEAT or turf, geanthrax. It may admit ofdoubc

* Kilkenny, the town in Ireland where this coal is produced.,
is pleafantly fituated ; it is watered by a clear and beautiful river,
and produces alfo a black marble variegated with white fpots.
The place has therefore been proverbially charafterifed— " Fire
'• without fmoke, air without fog, water without mud, and the
>; (I rcets paved with marble.'*

how

Chap. 4 !•] Peat or ?urf. 267

how far it is proper to confider peat among the fpe-
cies of coal j but as fome philofophers of great autho-
rity have attrib. --•] every kind of coal to a vegetable
origin, and as fome kinds are decifively io, the reafon
of this arrangement will be obvious. What is properly
called peat is formed by the growth of a particular ve-
getable matter, peat mofs, which increafes to fuch a
degree in moorifh grounds as to form ftrata of many
feet in thicknef--. When peat is frefii dug from below
the furface, it is of a vifcid confidence, but hardens by
expofure to the air. It is often mixed with pyrites
and flony matters, which are feparated from it while
foft, in which ftate it is formed into oblong mafles for
fuel. When diftilled, it affords water, oil, and volatile
alkali, which are precifely the products afforded by
the diftillation of pit-coal. A kind of peat is found
near Newbury, in Berkfhire, which contains but little
earth, and confifts of wood, branches, twigs, roots,
with leaves, grafs, ftraw, and weeds. What is dug on
moors, under the name of turf, frequently contains a
mixture of peat.

Coal, when heated and inflamed to fuch a degree
as to expel the more volatile parts, forms a kind of
mineral charcoal, called COKE, which is highly ufeful
in the property of affording a ftrong, clear, and lad-
ing fire, without forming a cohefive mafs, which would
prove very prejudicial in the fmelting of metals. It is
alfo ufed in drying thofe fubftances which would be
injured by the thick fmoke of common coal.

Lord Dundonald was the firil perfon who improved
this proccfs, by collecting the tar and volatile alkali,
which are driven off from the coal, while it is con^
verted into coke. Bis method has been adopted with
much advantage in feveral parts of Britain. The
coal is put into ovens, \vhich are heated by fires lighted

beneath,

268 Natural Hijlory [Book VI.

beneath, and the liquid matter is forced through an
iron pipe inferted into the top of the oven, and which
communicates with proper condenfmg veflels. By
this procefs a corrofive watery liquor and two forts of
oil are obtained. Six barrels of the mixed oily matter
produce about five barrels of oil of a thicker confif-
tence ; of the oil thus thickened, one part is lighter
than the other, which is drawn off, and is not at prefent
applied to any ufe *. The thicker part is ufed as an
inferior kind of tar.

Coal, like moil other confiderable mafles of matter
found near the furface of the earth, is difpofed in beds
or ftrata, which are fometimes parallel with the hori-
zon, but generally form different angles with refpect
to it ; the fame ftratum uniformly preferves the fame
direction. The ftrata of coal are difpofed between
flrata of other matters, The following ftrata are
nfually found in thofe diftricts of country, both in
England and Scotland, where coal abounds: whin-
ftone, freeftone, fandftone or freeftone of a coarfer
texture, metalftone, which is ,a hard argillaceous fub-
ftance containing balls of iron ore, and fhiver, which
is the moft common of them all, and is an indurated
bole, ufually of a blackifh colour.

Thefe ftrata do not bear on each other in the fame
order in different collieries, nor are they of any uni-
form thicknefs. The' ftrata of coal themfelves are
divided by other partings, called backs and cutters, into
innumerable cubic, prifmatic, and rhomboidal fi-
gures.

In all places where the flrata lie regularly, they arc
divided and fubdivided in the manner above men-
tioned, and fometimes extend uninterruptedly through

* See Bifliop Watibw's Eflays.

Chap. 41.] «/ Coal. 269

a confiderable diftrict. This regularity, however, is
frequently broken by gaps filled by other matter,
which has evidently fallen in, in confequence of the
ftrata having been feparated from each other by fome
violent convulfion. The largeft gaps are called dykes,
and defccnd from the furface of the earth, fometimes
perpendicularly, fometimes obliquely, to the greateft
depths ever tried. On each fide of thefe gaps the
ftrata correfpond, but they are often funk feveral feet
or fathoms lower on one fide than the other, and this
is called a dip.

With refpect to the origin.of pit coal, it is the opinion
of Dr. Black, Bifliop Watfon, and other philofophers
of high reputation, that the ftrata of coal were formerly
large collections of vegetable matter at the furface of
the earth. In diftant ages, Britain was probably al-
moft entirely covered with immenfe forefts and collec-
tions of peat mofs, which (according to the opinion of
thefe naturalifts) being covered with quantities of fand
or earth brought by floods, or by more gradual caufes,
as the falling of the fubftance of the neighbouring hills,
has been prefled and confolidated, in courfe of time,
into the fubftance called pit coal. The furface of the.
earth has alfo been probably rendered unequal in
various places by the action of earthquakes; this
would give rife to the formation of lakes in thofe
places which were deprefied. In this manner, a quan-
tity of vegetable matter would become covered by
depofition from water. Volcanic eruptions muft often
alfo have overwhelmed large collections of vegetable
matters. We even find vegetable matter in an inter-
mediate ftate between organized vegetable fubftances-
and coal ; for peat has ftill fome fmall remains of or-
ganic texture, but feems chiefly to confift of oily and
inflammable matter, which only requires time and the
preflure of fuperincumbent ftrata to convert it into the

firm

ijo Origin and Analyfis [Book VI.

firm and compact texture of coal. In feme places,
the remains of forefts have been obferved converted
into an imperfect pit coal, in which the trunks,
branches, bark, and roots of trees, are difcernible.
In molt of the varieties of coal, imprefiions of ve-
getable matters, and particularly of fern, are ufu ally
obfervable. Now it is remarkable, that both peat
mofs and fern are produced on wild and unculti-
vated lands, and this renders it ftill more- probable,
that coal in general owes its origin to peat mofs. Coal
is found in thin and broad ftrata, fuch as might be
expected on the fuppofition of its being derived from
the decay of peat mofs, or collections of other vegeta-
bles on the furface of the earth. Coal is often covered
with matter which cannot be fuppofed to have been
created in its prefent ftate, as fandftone, the particles
of which are evidently owing to the motion and friction
cccafioned by water. It has been already mentioned,
that the products afforded by the diiliilation of peat
mofs and pit coal are precifely the fame. We know
of no fubftance purely and unqueftionably mineral,
which affords products at all fimilar, and it therefore
on the whole feems probable, that the ftrata of coal
found in different countries, however extenfive, owe
their origin to vegetable matter. The bituminous
matters feem alfo to be exudations from vegetable
iubftances buried in the earth.

In confirmation ojf the fame opinion, I add the fol-
Jowing extract from the late ingenious Mr. White-
hurft's Inquiry into the original State of the Earth.
« All the ftrata incumbent on coal, whether argilla-
ceous ftone or clay, contain figured ftones, reprefent-
i:rg a vaft variety of vegetables, or the impreflions of
them, as reeds of various kinds, ftriated and jointed
at different diftances, the euphorbia of the Eaft Indies,

the

Chap. 41.] of Pit Coal 271

the American ferns, corn, grafs, and many other fpe-
cies of the vegetable kingdom. They are inclofed in
the folid fubftance of the ftone, &c. Thefe vegetable
forms, and the ftrata containing them, are the certain
indication of coal, not only in Derbyfhire, but in
every part of the kingdom which I have vifited ; and
I am informed, that the fame phenomenon holds
equally true in every other part of the world yet ex-
plored.' In general, the ftone which holds foffil plants
is either very hard and clofe, or bituminous, fo as to
afford no accefs to water.

The great difficulty in this hypothecs refults from
the immenfe quantities of thefe matters which are
found in the earth, and this difficulty can only be re-
moved by referring to a fact, which is fupported by
the traditions of every nation upon earth, the univerfal
deluge.

Among many other curious obfervations, relating
to the deluge and its remains, made by Dr. Scheuch-
•zer and his brother, the Doctor informs us of the
trunk of a tree, nine Paris feet in length, with fome
part of its branches ftill left upon it, which is lodged
upon the fummit of mount Stella, the chief of all the
Alps of Switzerland, which, according to the barome-
ter, is more than two Englifh ftatute miles perpendi-
cular in height, and four thouland feet higher than any
trees or vegetables are obferved to grow •> he concludes,
therefore, that it was left there by the fubfidence of
the waters of the deluge. Another modern writer
alfo very properly remarks, c When we find on any
ftones an exact refemblance of a plant, a leaf, or fome
fruit, that we are acquainted with, if thefe leaves are
bent or folded, if they crofs each other, or lie one upon
another, they are certain indications that the plant or
fruit fo reprefented is an imprefiion made by a natural

body.'

272 Proofs of tie Deluge. [Book VI.

body V Specimens of this defcription are frequently
found.

Not only vegetables, however, but . parts of ani-
mals alfo, are met with, deeply plunged in the ftrata
cf the earth, for the prefence of which, in fuch fitua-
tions, we cannot account) except by fuppofing, that
they were depofited during the deluge, when not only
the windows of heaven were opened, but the fountains
of the great deep were broken up ; expreflions which
denote, in the ftrong ftyle of oriental imagery, the ex-
tenfivenefs of that vaft difturbance or convulfion
which happened to this globe. A foffil fkelefon of
an alligator, twelve or fourteen feet in length, was dif-
cfcvered in the cliff of an alum rock, near Whitby, in
Yorkfhire. In a gravel pit of Suffolk, abounding
with foffil fhells, the entire fkeleton of a whale was
difcovered, the bones of which, when they became
friable by expofure to the air, were employed by a
farmer for the manuring of his land. Fragments of
an elephant's tooth were dug from a gravel pit at the
end of Gray's Inn Lane, at the depth of twelve feet.
From thefe and other facts it feems probable at leaft,that
this part of the world, before the flood, contained ani-
mals as well as plants which now are very rarely found,
or are totally incapable of exifting in fuch a climate.
This confideration will lead us to conclude, that the
deluge not only deftroyed the greater part of the ani-
mals then exifling, but produced a considerable altera-
tion in the conftitution of the globe, and a permanent
revolution in fome of the laws of nature, of which the
change that took place in the length of human life is
one ftriking inftance. The earth, and almoft every
part of it, is flored with the remains of trees, plants,

* Le Pluche Speft. de la Nature, Dial. 25.

and

Chap. 41.] Ctiricjities found in the Earth. 273

and fruits; of fifh, teftaceous, cruftaceous, and fqtia-
mous, and of other occafional inhabitants of the wa-
ters. The fpoils of land animals -.re alfo met withj
but in much fmaller quantities, which it is not diffi^
cult to account for, when we confider, that the waters
of the fea occupy more than twice as much of the
globe as the land, and that the waters are much more
copioufly fupplied with animals of confiderable mag-
nitude, than the land. Add to this, that the claffrs of
corallines, lithophaita, and many of the teftaceous
Jdnds, are of a fubftance as hard as flone, and of a
much more durable-texture ; whence it is not to be
accounted a matter of furprize that they abound fo
much in the earth in the form of petrifactions. We
are to recollect alfo, that the catafirophe of a deluge
would foon corrupt, deflroy, and difperfe the parts of
fuch living creatures as die in the waters j while the
natives of the fea would ftruggle with the difficulties
of an inundation, and be at laft depofited, perhaps
alive, in the earth, when the fettlement of the ftrata
took place, and the waters retreated, as jt is evident
that many of them actually were, from the poftures
and circumftances in which they have been difco
vered *.

* See Jones's Phyfiological DifquifitiOns.

, n.

[ 274 ] [Book VI.

CHAP. XLII.

NAPHTA, PETROLEUM, BARBADOES TAR, &c.

Nature and Properties of Napbta.— Burning Fountains, — Petroleum.***
Mineral Pitch, or Barbadoes Tar. — Lake Afpbaltes,—Afpbaltum'y
ho--w collected. — Elaftic Bitumen.— Component Principles of tbefe
Sub/lances.

ALL thefe fubftances are of the bituminous kind,
and are, indeed, all of the fame nature, but dif-
fer in confidence. NAPHTA is an oily fluid, which, in
its greateft degree of purity, is nearly colourlefs, is
extremely volatile and fubtile, and fo light as to float
even on fpirits of wine. It has a ftrong oppreffive
fmell, and evaporates fpontaneoufly. Like other oils,
it burns with fmoke. It does not congeal at o of Fah-
renheit. It is faid to be gathered at the furface
of certain wells in Perfia, and is rarely found in
Europe.

The vapour of naphta, which ifiues through the
crevices of the earth, is generally fuppofed to be
the caufe of the flame which is fometimes obferved
on waters, fountains, &c. At Chittagon, in the Eaft
Indies, there is a fountain which burfts into flame of
its own accord, whenever it has been extinguished by
accident ; this fountain has its deity and its priefts ;
and fome Europeans, fufpecting the whole to be a
pious fraud, pulled down the wall, &c. but found that
the vapour actually kindled fpontaneoufly when put
out. It is pofllble, however, that this flame may be
fed by inflammable air inftead of naphta.

PETROLEUM, which is of a thicker confiftence, and

more

Chap. 42.] Petroleum, AfpMtumy &c. • 275

more weighty than naphta, is much more common. It
is of a yellow or brown colour, and is found in Swit-
zerland, Sicily, Italy, and France. It iffues from the
crevices of rocks, or is found floating on the furface of
fprings. The different kinds of petrolea, on diftillation,
yield naphta, while a coaly refiduum remains in the
retort.

BARBADOES TAR is of a thicker confiftence than/ pe-
troleum, and is alfo called mineral pitch j it was for-
merly found near Babylon, and conftituted> according
to Vitruvius, when mixed with lime, the cement
which was ufed in building the walls of that city. It
is at prefent found in feveral parts of Europe and in
America, where it drops, or diftils, gradually from
rocks.

ASPHALTUM is a fubftance much refembling Barba-
does tar j it is alfo called J ews pitch, and is thrown
up in a liquid form from the bottom of the lake where
Sodom and Gomorrah antiently flood. From the
production of this fubftance this was called the Lake
Afphaltes, from a Greek word denoting bitumen. The
bitumen floating on the furface of the water is hardened
by the heat of the fun, and is in that ftate collected by
the Arabs on the more, where it is thrown. The
caftern afphaltum is feldom brought to Europe, but is
ufed by the inhabitants as pitch.

All thefe thicker bitumens may be rendered thin-
ner by diftillation, and may be converted into an oily
fluid, the tenuity of which is increafed by the repetition
of the procefsj at every diftillation a quantity of char-*
coal, earthy matter, and carbonic acid gas, being fe-
parated from them.

In Obferv attorn Jur la Pbyfique, for January, 1788,
vol. xxxii. M. dela Metherie makes mention of a mi-
neral elaftic bitumen analogous to the caoutchouc, or
T 2 elaftic

2j6 Elaftic 'Bitumen. . fBook VL

elaftic gum, and which is found near Caftletown in

Derbyfhire. Its colour is brown, partly Toft, flexible

and elaftic, and this when cut appears internally of a

greenifh yellow colour ; partly brittle, with a conchoi-

dal fracture. Both varieties are frequently united in

, the fame fpecimen. ^oth are infoluble in fpirit of

. wine, ether, and oil of turpentine, but yield to that of

olives.

The production of all thefe bitumens is attributed
ro the action of fubterraneous fire on ftrata of pit- coal,
by which the oily parts are feparated and fublimed in
the fame manner as by artificial heat. .

A curious experiment is mentioned by Bifhop Wat-
fon, which illiiftrates the relation of thefe four bitumens
to each other. The moft transparent oil of turpentine,
refembling n^phta, may be changed into an oil refem^
bling petroleum, by mixing it \vith a fmall portion of
vitriolic acid ;; with a larger proportion of the acid the
mixture becomes black and tenacious like Barbadoes
tar, and the proporti6ns of the ingredients may be fo
adjufted, that' the mixture will even acquire a folicj
confidence like afp-halmm.

All thefe fubftances become more tenacious, and
acquire a darker colour by'expofure to air. This
feems to be owing to the abforptioh of oxygen, which,
like oils, they pofiefs the property of attracting from
the atmofphere.

It appears that on-diiiillatioa bitumens leave fcarcely
any refiduum, the earthy part being merely accidental,
and that the carbonic fubftance is by much the fmalleft
in their compofition^ as their concretion feems wholly
owing to the abforption of air, and not to the preva-
lence of the carbonaceous .principle, fmce no coal ap-
pears, when they are burned on a hot iron.

Chap, 43-] [ *77 ]

CHAP. XLIII.

JET. AMBER, AMBERGRIS, AND MINERAL
TALLOW.

General Properties of Jet. — Its Nature and Origin. — Amler.—~Acid
cf Amber. — Natural Hijlory of Amber.'— Different Opinions of its
Origin.— Ambergris^ — Its Natural liijlory. — -Mineral Tallow.

JE T is a very compact bitumen, harder than af-
phaltum, always black, and fufceptible of a good
polilh. It is fo light as to fwim on water, becomes
electrical when rubbed, and is called black amber.
When burned it emits a bituminous fmell. Jet feems
nearly allied to coal, and particularly to that fpecies
which is called cannel coal 5 it is diftinguimed chiefly
by its ftructure, being compofed of fibres parallel to
each other like thofe of.wood. It feems in fact to be
wood, which has been long buried in the earth, and
penetrated by mineral fleam, fo as to affume the ap-
pearance and foiidity of coal.

AMBER is the fubftance known to the ancients under
the name of electrum and fuccinum. In this fub-
ftance the property, which certain bodies have, of
attracting light fubftances, when rubbed, was fifft ob-
ferved, and was therefore called electricity. The moft
valuable amber is perfectly tranfparent, of a pale
yellow, and is much more efteemed when it happens
to contain any extraneous fubftance, fuch as leaves,
infects, &c. When broken it prefents a polifhed fur-
face at the place of the fracture. Amber does not
readily diffolve' in any fluid we. are yet acquainted
with. Spirit of wine has foms fmall effect upon
it, and from this combination a tincture is produced,
T bu|

27 & 'Amber. [Book VIt

but the quantity it diflfolves is very fmall. When
applied to the flame of a candle it readily takes fire,
and burns with a bright white flame and thick fmoke,
and leaves a confiderable quantity of charcoal. Am-
ber expofed to heat, without the action of flame,
foftens and fwells very considerably. Diftilled in a
retort by a heat gradually raifed, it affords a watery
fluid of a red colour, manifeftly acid j this acid fpirit
retains the flrong fmell of amber; an acid volatile
fait afterwards pafles over, which cryftallizes in fmall
white or yellowiih needles in the neck of the retort.
This fait is fucceeded by a white and light oil much
refembiing naphta ; by continuance of the procefs, and
in proportion as the heat is increafed, the oily matter
which comes over is coloured and more vifcid, like
petroleum. What remains at the bottom of the retort
is a black mafs refembiing afphaltum. It appears,
therefore, from diftillation, that the analogy of arnber
•with the other bitumens is very ftrong.

A gentle heat is fufficient to raife the concrete vo-
latile fait of amber, and care muft be taken to regu-
late it fo as not to force up the oil, when it is required
to have the fait in a feparate ftate. This faline matter
was for feme time fuppofed to be an alkaline fait, but
has been fmce found to be an acid of peculiar pro-
perties, and capable of combination with alkalies,
earths, and metallic calces.

, - Amber is ufually dug out of the earth, and abounds
particularly in the Pruffian dominions. Wood is
generally found near it, and it is therefore believed to
be of vegetable origin. Its analyfis feems to fhew,
that it confifrs of an oil rendered concrete by combi-
nation with an acid. The moft tranfparent fpecimens
ire ufijftlly found on the fea-fhore, particularly on the
{bores of the Baltic, in Ducal Pruflia. Amber is not

always

Chap. 43.] Jfmtergris. 279

always of a yellow colour; it is fometimes brown,
fometimes quite opake, and fometimes black. Some
have fuppofed that it is entirely of mineral origin, but
this is difproved by ics diilillation, and by the foreign
bodies which are frequently contained in it, and which
feem to demonftrate that it was once in a fluid ftate.

Hoffman and Newman fay, that it is fometimes found
upon the fea-fhore, or upon the furface of waters, parti-
cularly after great ftorms, when it is collected by means
of nets ; but that the greater part of it is dug out of
pits. The firft ftratum is fand, then clay, then a layer
of branches and trunks of trees, then a confiderable
quancity of pyrites, whence vitriol is prepared, and
laftly, a bed of fand, through which the amber is dif-
perfed in fmall pieces, or collected together in heaps.
This account greatly favours the idea of the vegetable
origin of amber j but Wallerius afierts, that the black
and dark coloured amber is often found in the bowels
of cetaceous fifties. M. Girtanner has a peculiar
opinion on this fubjecl:; he thinks that amber is a ve-
getable oil rendered concrete by the acid of ants ; it
is that kind of ants called formica rufa by Linnseus,
which prepares it, according to this author. Thefe
infects dwell in old forefts of fir trees, where the foffil
amber is found, which, when firft dug, is ductile like
wax, and becomes hard on expofure to air. No infect
is fo commonly found in amber as the ant.

AMBERGRIS is of much the fame nature as amber,
but differs from it by its particular confiftence, which
nearly approaches to that of bees wax. Its ftructure
is fometimes like bees wax, but fometimes it is granu-
lated, and appears opake, or of a dark grey. Expe-
riments prove that it refembles amber in its nature.
When analyzed it is found to confift of phlegm, a
volatile acid partly fluid, oil, and a little coaly mat-
T 4 ter.

28q .Sxppofed Origin of Ambergris. [Book VI.

ter. It difiblves more readily in fpirit of wine than
amber. •

It is rnofl common in the Indian feas, on the
eaftern coaft of Africa, Madagafcar, &c. and is found
either floating on the fea, or caft on the fea-fhore. In
this fubftancc animal and vegetable remains are fome-
times found, as for inftance, parts of birds, &c.

The origin of this fubftance is probably the fame
with that of amber. According to M. Aublet (in his
Kiftoire de la Guiani) it is nothing more than the juice
of a tree infpiftated by evaporation ; and if this is true,
it is a fubftance which belongs properly to the vegetable
kingdom, j The tree which is faid to produce it grows
in Guiana, and is called cuma, but has not been exa-
mined by other botanifts. When a branch is broken
by high winds, a large quantity of the juice exudes ;
and if it chances to have time to dry, various maffcs
(feme of which have been fo large as to weigh one
thoufand two hundred pounds and more) are carried
into the rivers by heavy rains, and through them into
• the fea ; afterwards they are either thrown on the more,
or eaten by fome filh, chiefly the fpermaceti whale,
known, by the name of pbyfiter-macrocepbalus among
ichthyologies This kind of whale is extremely
voracious of this gum-refin, and fwallows fuch large
quantities when it meets with it, that it generally
becomes fi£k; fo that thole employed in the fifhery
of thcfc whales always expecY to find fome amber
mixed with the excrements and remains of other food
in the bowels of thcfe whales' which are lean. Various
authors, among whom is Father Santes, in his Ethiopia •
Orient dis, who travelled to various places- on the Afri-
can coaft, and Bornare, fay, that fome fpecies vof birds •
are alfo fond of eating this Jubilance, as well as wha.Jes
and other fifhes. This accounts very well for the

Chap, 43-1 » Mineral Vattoiv. 281

claws, beaks, bones, and feathers of birds, parts of ve-
getables, fhclls, and bones of fim, and particularly for
the beaks of the quttle-nlh,^^ oftogedia, which are
fometimes found in the mafs of this fubftance. M.
Aublet brought fpecimens of this gum-^refin, which he
collected on the fpot, from the cuma tree at Guiana.
It is of a whitim brown colour, with a fhade of yel-
low, and melts and burns like wax in the fire. M.
Rouelle examined very carefully this fubftance, brought
over by M. Aublet, and found that it produced ex-
actly the fame refults as good amber. Thefe obfer-
vations feem to place it beyond a doubt, that -both
amber an,d ambergris are vegetable products, and that
thofe who, from having found thefe fubftances in the
iateftines of whales, concluded that it was a farcal
matter of thofe animals, were miftaken.

MINERAL TALLOW is a very peculiar fubftance. Itwas
. found on the coafts of Finland, in the year 1736. Its
fpecific gravity is .0.770, whereas that of tallow
is 0.969. Its colour is white; its confidence is that of
tallow, and like it it is brittle ; it feels greafy, and Mains
paper juft as tallow does, and die traces thus left on
paper melt on the approach of flame. It burns with
a blue flame and a fmell of greafe, leaving a black
vifcid matter, which is more difficultly confumed. It
is found in fome rofcky parts of Perfia, but feems
mixed with petroleum. Dr. Herman, of Strafburgh,
mentions a fpring, in the neighbourhood of that city,
which contains a fubftance of that nature diffufed
through it, which feparates on ebullition, and may then
{DC collected. The origin of this fubftance is un-
known.

[ 282 ] [Book VI.

CHAP. XLIV.

OF THE DIAMOND, CONSIDERED AS AN
INFLAMMABLE SUBSTANCE.

Natural Hiftory of Diamonds.— Varieties, — Internal Struflure. — Ex-
periments proving the inflammable Nature of we Diamond. — Experi-
ments ofM. Cadet — Of D'Arcet. — Vital Air necejjary to the Com-
tujtion of the Diamond. — Experiments of Lavoifer. — Further Expe-
riments.— Experiments of Mr. Tennant.—Tbe Diamond praised to be
zrcoal.

TH E diamond, though (lightly mentioned when
treating of gems, belongs properly to the clafs
of inflammables. It is the harden: and mofl brilliant
of all fubftances. Its fpecific gravity is 3,445, hence
it refrafts the rays of light very powerfully ; but it
poflefies this power even in a much greater degree than
might be fuppofed from its denfity, and hence proceeds
its fingular brilliancy. The diamond, properly fo
called, is colourlefs ; but it alfo retains this name when
it is (lightly tinged either with red or yellow. It
is therefore not the colour of the ftone, but its hard-
nefs and luftre, which obtain for it the denomination
of a diamond.

Diamonds are found in the Eaft Indies, particularly
in the kingdoms of Golconda and Vifaponr : they like-
wife come from the Brafils j but thefe lafl appear to
be of an inferior quality, and are known in commerce
by the name of Portuguefe diamonds.

Diamonds are ufually found in an ochreous yellow
earth, under rocks of grit-done and quartz •, they are
likewife found detached, in torrents which have carried
them from their beds. They are feldom found

above

Chap, 44.] fbe Diamond. 183

above a certain fize. The fovereigns of India refervc
the largeft, in order that the price of this article may
not fall. Diamonds have no brilliancy when dug out
of the earth, but are covered with an earthy cruft, which,
inclofes a feconcl cruft, of the nature of calcareous fpar,
according to M. Rome de Lifle. Bright diamonds arc
occafionally found in waters.

Thefe gems very often have no regular form, but are
flat; or worn round, Sometimes they are regularly
cryftallized in octahedrons, formed by two quadran-
gular pyramids, united at their bafe ; they are likewife
found with twelve, twenty-four, and forty-eight faces.

Diamonds appear to be compofed of laminae, laid
upon each other ; and they are eafily divided, by itrik-
ing them in the direction of thefe laminse with a good
fleel instrument. There are, however, fome diamonds
which do not appear to be formed of diftinct laminse,
but of twifted fibres, like thofe of knots in wood.
Thefe laft are exceedingly hard, and cannot be wrought;
lapidaries call them diamonds of nature.

Diamonds are (haped by firfl cleaving them in the
direction of their lamellae, and then rubbing them
with other diamonds. They are then po'imed by an
horizontal fleel wheel, dufted with their own powder
mixed with olive oil.

Sir Ifaac Newton having obferved that inflammable
fubftances had a ftronger power of refracting the rays
of light, in proportion to their denfities, than other
bodies, and obfcrving alfo the ftrong refractive power
of the diamond, conjectured, upon thefe principles,
that it mufl belong to this clafs of minerals. The
reafonings of Newton were fo correct, that many of
his conjectures, though made only on theory, have
been fince confirmed by actual experiment. — Thus it
has fince been difcovered that diamonds, expofed to

a high

21 S 4 CcmlujTion of Diamonds. [Bock VI,

a high degree of heat, entirely difappear at thelnftarit
that an appearance of corabnftion is obferved. M.
Cadet"- expofed diamonds, in covered and luted* cru-
cibles to the violent "hdat of a forge during two hours,
by vyhich the diamonds only loft one fixteenth part of
their weight, he was therefore of opinion, that the
confurnption of diamonds in open veffels is not a true
volatilization, but merely an exfoliation occafioned by
the expanfion of the air contained between the laminas
of the 'diamond, by which it is broken into portions
fo minute as to efcape obfervation. M. D'Arcet
oppofed to die above explanation, the efcape of the
fubftance of the diamonds through the moft folid por-
celain crucibles, and the luminous appearance noticed
by Macquer, and which was afterwards obferved by
M. Roux to be an actual flame. It was, indeed, evert
found, that diamonds inclofed in a ball of porcelain
earth, and expofed to heat, were totally confumcd;
the ipace which the diamond occupied was found
empty j no traces of it could be difcovered, and yet
the ball of porcelain, which was hardened by the heat,
\vas apparently entire^ This experiment, according
to Fourcroy, was frequently repeated with the fame
extraordinary refult. It Was found, however, that if
the diamond was embedded in charcoal, and carefully
inclofed in feveral crucible^ placed within each other,
and the whole covered with cement, it did not 'dif-
appear from expofure to a very violent heat ; it was
only rendered black at its furface, and when this cruft
\vas taken cff, it appeared in its original fplendor. It
was therefore very juftly concluded, that perfect ex-
clufion from vital air is fufncient to prevent the con-
furnption of the diamond, as well as of all other in-

* Luting is a land of earthy cement ufed by chemifts, and
formed in different ways.

flammable

Chap. 44,} Experiments on Di&mcnds. 285

flammable fubftances; and it was therefore neceiTary
to fuppofe, that the porcelain earth, in which the other
diamonds were inclofed, fuffered fome fmall ieparation
from expofure to heat, which, though fo minute as
to efcape obfervation after the ball was cold> was yet
fufficient to admit the air. This opinion was fully
confirmed by the experiments of M. Lavoifier, who
found, that diamonds are only confumed in proportion
to the quantity of vital air to which they are expofed.
He alfo found, that the .combuftion of the diamond '
was attended with the formation of carbonic acid gas ;
but at the time he made his experiments, the nature
of that fluid does not feem to have been diffidently
\inderilood, to enable this great philofopher to draw
a correct conclufion relative to the compofition cf the
diamond.

The experiments of Lavoifier were purfued by Mr.
Tennant, and their relult may be found in the rirft
part of, the Philosophical Tranfaclions for the year
1797. He obferved that, from the extreme hardnefs
of the diamond, a flronger heat was required to in-
flame it, when expofed merely to air, than could eafily
be fupplied in clofe veiTels, except by means of a ftrong '
burning giafs ; but that with nitre * its combuftion
could be effected in a moderate heat. To expofe it
to this procefs, without any danger from the intrufion
of extraneous matters, Mr. Tenna'nt inclofed the nitre
and the diamond in a tube of gold, and took every
neceffary precaution to prove that no carbonic acid gas,
or fixed air, could be included, except what the diamond
itfelf afforded. When the diamond was entirelydeftroyed
in the gold vefiel by the inflammation of the nitre, the
fubftance which remained precipitated lime from lime

* The ufe of the nitre is obvioufiy to fupply a quantity of pure
air to effeft the comhullion.

water,

286 Vbe Diamond cryftallized Charcoal. [Book VL

water, and with acids afforded nitrous and fixed air j
and appeared, in fact, to confift of nitre partly dec'om-
pofed, and of alkali united with fixed air.

In order to eftimatethe quantity of carbonic gas which
might be obtained from a given weight ofdiamond, two
grains and an half were inclofed in a tube with a quarter
of an ounce of nitre. After the procefs, the alkaline
matter contained in the tube was diffolved in water,
and the whole of the diamonds was found to be con-
fumed. Into the alkaline folution a quantity of fatu-
ratcd folution of marble in marine acid was poured,
and after the fixed air had united with the calcareous
earth, the alkali remained in folution with the marine
acid. The clear liquor was then poured off from the
calcareous precipitate, and was found to contain no
fixed air. The carbonic acid gas being then expelled
from the calcareous matter by the addition of an acid,
occupied a fpace equal to about 10 ounces of water,
which, according to the calculations of Lavoifier, is
exactly the quantity that would be produced by the
converfion of 2 £ grains of pure and folid charcoal
into an aerial form. That the fixed air, thus produced,
confided of the fame matter as that of charcoal,
Mr. .Tennant proved by combining it with lime, and
expofing it to heat with phofphorus, when he found
that it afforded charcoal in the fame manner as any
other calcareous fubftance.

Mr. Tennant repeated the experiment with i f-
grains of diamond, and the refuit was the fame*
Upon thefe evidences therefore he concludes, and ap-
parently with reafon, that this peculiar and beautiful
fubftance, fo valued by the higheft claflcs of mankind,
the decoration of royalty, and the emblem of all that is
pure and excellent in nature, is no other than that de-
fpifed matter, charcoal, in a ftate of cryftallization.

Chap. 45-] [ 2*7 1

CHAP. XLV.

THE STRUCTURE OF THE EARTH.

*The Curioflty of Man on this Topic limited by the Weaknrfs of his
Powers. — The Body of the Earth difpofed in Strata. — Declivities of
Mountains. — Dijfojition and Order of the Strata. — Caldy IJland.~—
Where Metals are ufually foiled. — Probable State of the Earth at its
Creation. — Lanus by 'which Alterations 'would be produced.— Fojfil
Shells, &c. accounted for. — Formation of IJlands, £ffr. — Other Irre-
gularities of the Earth's Surface explained.

AFTER the preceding furvey of the natural
contents of this globe of earth, and of their com-
ponent principles, the next object of attention is the
earth itfelf, and the general arrangement of thofe fub-
flances of which it is compofed. Thefe are neither
difpofed in a regular feries, according to their fpecific
gravities, nor yet thrown together in total diforder, as
if by accident or chance. Human industry has hitherto
been able to penetrate but a very little way into the
bowels of the earth, and we can but know little of its
interior parts. The depth of the earth, from the fur-
face to the center, is more -than four thoufand miles,
and yet the deepeft mine in Europe, that at Cotteberg,
in Hungary, is not more than one thouland yards
deep ; " the greateft depth, therefore," fays an excel-
lent writer, "to which avarice has ever yet penetrated,
may be compared to the pun&ure made in the body of
an elephant by the probofcis of a gnat."

From what has been difcqvered, however, of thofe
parts which lie moft contiguous to our obfervation,
naturalifts have compared the ftructure of the earth to
the leaves of a book, or the coats of an or.ion. Ex-
cept,

288 Earth tonfijls of Strata. [Book VI.

cept, indeed, in fome of thofe immenfe mountains, which
have exifted from the creation, or at leaft from the
deluge, where the matter, from whatever caufe, ir,
more homogeneous, the earth is found to confift of
various ftrata^ or layers, which differ according to the
ci'rcumftances of climate and fituation. The furface,
in general, evidently confifts of a confiifed mixture of
decayed animal and vegetable fubftances and earths
rudely united together j but when we have penetrated
below the furface, we find the materials of the globe
arranged in a more regular manner. Sometimes, in-
deed, we find heaps -of ftone, which do not confift of
layers, but are confufed mafies of unequal thicknefs,
and are called rocks. The ftrata are, in general, ex-
tended through a whole country, and, perhaps, with
Ibme interruptions and varieties, through the globe
itfelf. Thefe extenfive bodies are found moft regular
when the country is flat, being, in that cafe, nearly
parallel to the horizon, though frequently dipping
downwards in a certain angle ; in many places the
beds have a wave, as where the country confifts of
gently waving hills and vales j here too they generally
<3ip. la travelling a mile we, perhaps, pafs through
ground compofed moilly of fand, in another mile Ve
find it, perhaps, compofed of clay 3 and this is occa-
fioned by the edges of the different ftrata lying with
an obliquity to the horizon. By the fame kind of
projection, mountains, or ridges of mountains, are pro-
duced, which, in general, have what is called a back
and a face, the former fmoother and the latter more
rugged. We generally find too, on one fide of a
mountain, a more gradual afcent than on the other,
which is occasioned by the ftrata, which have rifen
above the general level of the country, being abruptly
broken o£\ Mountains are in general more abrupt

toward*

Chap. 45-1 Inequalities of Earth* s Surf ace. 2*9

towards the weft, and- have a more gentle, .declivity
towards the eaft ; hence the weflern coatl of countries
is almoft always deeper than the eaftern. The back
of a mountain fhe\vs the obliquity with which the
ftrata fmk into the ground ; the abrupt edge of the
flrata becomes more/ Hoping, as time, producing a
gradual decay, draws the rubbifh from above. Where
the face of a country is fo irregular, its appearance
depends on the different hardnefs or foftnefs of the
flrata. The abrupt rocks, which we obferve in many-
parts, feem to have been composed of an adventitious
mixture of different ftrata, which have refifted the in-
juries of time with unequal force.

Between the ftrata, layers of different clays are in-
terpofed, which are called by the miners way-boards j
they are feldom more than four or five, and in fome
inftances not more than one foot thick ; they ferve
to mark and diftinguiih the different ftrata, for in fact
the ftrata are themfelves compofed of different la-

Every part of a ftratum may be coftfidered as equally
thick when covered with an incumbent bed; but
when expofed to the action of the air, and other exter-
nal agents, a. great part of it, whether grit, lime-ftone,
or toad-flone, .is decompofed and converted into earth.
or mould. Immediately under the foil the fragments
of ftone are fmall, and gradually increafe to the depth
of fifteen or twenty feet, where it commonly appears
folid, and fit for the mafon. Strata are ufually inter-
rupted by clefts or fiffures at different diftances, which
feem to have been the effects of violence. In thefe
fifiures only the ores of metals are to be found.

It has been remarked, that we cannot, by digging
into the earth, obtain a view of the pofition and nature

• Whitehurft, Chap. XVI.

VOL, II. U of

[Book VL

bf the ftrata for more than fome few hundreds of yards.
There is, however, one curious inftance of an ifland,
near the coaft of Pembrokefhire, called Caldy Ifland,
where the earth fufFered the action of fo unufual a
difruption, that the ftrata, of which the whole ifland is
compofed, are placed in a vertical pofition, fo that
their edges are all expofed to view, and they may be
obferved in fucceflion from one end of the ifland to
the other. Here then we have the fingular opportu-
nity of obferving in what order they were originally
placed, to the depth of two miles. At one end of the
ifland they are not more than a foot thick, but increafe,
as we proceed, till they terminate in a ftratum of red
ftone, more than a mile in thick nefs, which, with good
reafon, is fuppofed to have been the loweft of them all
before they were elevated and thrown upon their edges.
The thinner ftrata, which were originally uppermoft,
have fofiil fliells and corallines in them ; but I have
not heard that any thing like the traces of lava are to
be found to countenance the fuppofition, that this fin-
gular accident was occafioned by the explofive force of
a volcano.

The order of the ftrata in Derbyfhire is as follows :
i. Millftone-grit, a coarfe fand-ftone compofed of
granulated quartz and quartz pebbles, a. Shale or
fhiver, or black laminated clay, much indurated.
3. Li me -ftone, in various laminae. 4. Toad-ftone, a
black porous fubftance, hard, refembling fcoriae, and
apparently a volcanic production. 5. Lime-ftone.
€. Toad-ftone. 7. Lime- ftone. 8. Toad-ftone.
9. Lime-ftone again. Such (the toad-ftone excepted)
appears to be the general order in which the ftrata
appear through the different regions of the earth, or
at leaft wherever the lime-ftone predominates, which
is in a confiderable proportion, though it muft be
* remarked

Chap. 45.] 'Strata of the Earth. £91

remarked that the largeft mountains are chiefly granite.
Wherever, therefore, the firft of thefe ftrata appears
on the furface, the fecond lies certainly under it, the
third under the fecond, &c. ftill excepting the toad-
ftone, which, being a volcanic production, may be
fuppofed to be in fome meafure cafually inter-
pofed.

The toad-ftone interfeclrs all the mineral veins, and
cuts off all communication between the upper and
lower parts of the fifliires, being continued horizon-
tally in one uninterrupted mafs. Toad-ftone is of an
extremely hard and clofe texture, fo much fo as even
to prevent water from filtering through it, at leaft in
any quantity. It is perfectly fimilar to Iceland lava
in appearance, and in being unafiailable by acids. It
has no fifTures, and frequently fills up the fiffures of
the other ftrata ; in fine, it being not univerfal, but
only an occafional appearance, there is the utmoft pro-
bability that it is a fpecies of lava. It being inferted
between the other ftrata feems alfo to afford a proof,
that it originally flowed from a volcano, the funnel or
ihaft of which did not approach the open air, but dif-
charged its fiery contents between the ftrata in all
directions. When the toad-ftone is dug through, how-
ever, and the vein or fiflure purfued, the miner is
never difappointed in meeting it again, as fcon as he
arrives at the ftratum of lime-ftone *.

The ftrata of coal, argillaceous ftones, clay, &c. are
always incumbent on the ftrata of grit, male, and
lime-ftone. The former are feldom in ftrata; of above
twenty feet thick, and generally not more than four
or five ; the latter are in ftrata of from fifty to one
hundred and fifty feet in thicknefs or depth f.

* Whitehurft, Chap. XVI. t Ib«

U * All

.«yi Inhere Ores art chiefly found. [Book VI.

All beds of .gravel are fuppofed to have been de-
pofited either by rivers or by the action of the fea,
•and the ftones that compofe them to have been rounded
by attrition. It is no inconfiderable proof in -favour
of fuch a conjefture, that fea-fhells, &c. are fo fre-
quently found with gravel.

The argillaceous ftrata are only productive of iron
and coal. The ores of copper, lead, zinc, &c. are
confined entirely to the lime-ftone ftrata, a few in-
ftances excepted,. where they are found in {hale.

The difpofition of the fuperficial ftrata, however,
differs in mountainous and champaign countries. f In
a well which was dug at Amfterdam, to the depth .of
two hundred and thirty feet, the following fubftances
were found in fucceflion * : feven feet of vegetable
earth, nine of turf, nine of foft clay, eight of fand,
four of earth, ten of clay, four of earth, ten of fand,
two of clay, four of white fand, one of foft earth,
fourteen of fand, eight of clay mixed with fand, four
of fea- fand mixed with fhells, then an hundred and
two feet of foft clay, and then thirty- one feet of
fand.

c In a well dug at Marly, to the depth of an hun-
dred feet, M. Buffon gives us a ftill more exact enu-
meration of its layers of earth. Thirteen feet of a
reddiih gravel, two of gravel mingled with a vitrifiable
fand, three of mud or (lime, two of marie, four of
marly ftone, five of marie in duft mixed with vitrifiable
fand, fix of very fine vitrifiable fand, three of earthy
marie, three of hard marie, one of gravel, one of eglan-
tine, a ftone of the hardnefs arid grain of marble, one
of gravelly marie, one of fiony marie, one of a coarfer
kind of ftony marie, two of a coarfer kind ftill, one of

* Varemus, as quoted by M, Buffbn, p. 358:

vitrifiable

Chap. 45.] trapping of Strata. 19$

vitrifiable fand mixed with foflll fhells, two of fine gra-
vel, three of ftony marie, one of coarfe powdered
marie, one of ftone, calcinable like marble, three of
grey fand, two of white fand, one of red fand ftreak'ed
with white, eight of grey fand with fhells, three of very
fine fand; three of a hard grey ftone, four of red fand
ftreaked with white, three of white fand, and fifteen of
reddiih vitrifiable fand.'

The direction too in which the ftrata are found
is alfo exceedingly different in different fixations.
* When the continuity,' fays Mr. Jones, c of the ftrata
is interrupted by a fracture, the ftrata are thrown out:
of that horizontal pofition which is natural to them,
and make an angle with the horizon ; which may be
called the angle of their elevation or depreffion ; the
miners call it their dip. In this cafe, if the fuccefiion
of ftrata is accurately noted on one fide of the fracture,
where a vein of coal or metal is found amongft them,
it may thence be learned where the fame vein will
occur again on the other fide of the fracture ; becaufe^
it will be found adjacent to the fame ftrata as before.
When the edges of the ftrata, on each fide of a fiffure,
are thus parted and mifmatched, they are faid to trap-,
and the fpace between them is filled up with rubble,
or ftones, or minerals, &c. Sometimes thefc fiffures
are the richeft parts of the foil, containing fuch matters
as are not to be found elfewhere *. In fig. I. plate I.

F. repre-

* Some of the fiffures in Cornwall are near twenty feet over,
and commonly full, or near it, of metallic and mineral matter.
The fiflurcs at the greateft depth are generally largeft ; as we af-
cend they become gradually lefs, but more frequent and nu-
merous : infomuch that if the globe was divided, in two., and the
ftrata viewed upon the face of the fedlion, the figures would ap-
pear after the manner of a tree: at the bottom a large trunk,
which higher up is divided into branches, which break into lefler,
U 3 and

294 Or^r Of*b* Strata. [Book VI.

F. reprefents the fiflure, by which the ftrata are parted,
and which is filled up with extraneous rubbilh, carried
in after the ftrata were parted. The black vein of
coal on the left fide is found with five other ftrata
above it; but being interrupted by the fifiiire F. where
it comes out to the day, the ftratum of fand, No. 4, on
the right fide, on account of the trapping, is found
oppofite to it j thence it is to be collected, that the
fourth ftratum below that fand 'will be coal ; and when
the angle of the dip is obferved, it may be known
where to fink a pit, and where the coal will again ap-
pear to the day j provided the figure of the furface
of the ground will permit it to fhew itfelf. When
I was once at the bottom of a lead mine in Derby-
Ihire, a miner informed me, that the veins of the
metal always make a greater angle with the horizon
than the fides of the mountain do, in which they are
found and come out to the day j which was probably
occafioned by the defcent of the waters of the flood,
tearing away much of the matter from the fummit, and
lodging it upon the fides and in the vallies beneath,
after the ftrata had received their inclination.'

With refpect to the more internal parts of the
earth, for the reafons affigned in the beginning of this
chapter, nothing can be advanced with certainty, and
hypothefes cannot be relied on.

By fome it has been fuppofed, that the center of the
earth confifts of fire. Mr. Kirwan, however, has fa-
tisfadtorily proved, that the notion of a central fire or
heat is void of foundation. Since no authentic obfer-

and at the top into twigs. But the branches are not continued in
a ftrait line: they ftart afrefti, at fome little diltance on one fide,
as in fig. 2. that by an intervening boundary the metallic matter
might be detained in its defcent, and prevented from finking away
to the bottom of the earth. See Mr. Hutchinfon's Obfervations
in the year 1706, p. 316, 317.

vation

VOL.] I.

Chap. 45.] Central Fire in the Earth. 29 f

vttion allures us, that this heat increafes in proportion
as we penetrate below the furface of the earth ; on
the contrary, many experiments ferve to evince, that
it rather decreafes, (though never to lefs than thirty-
fix degrees) and that its variation at the fame diftance
below the furface conftantly bears a proportion with
the variation of the folar heat at the furface.

The more general opinion is, that the ftrata origi-
nally lay horizontally, and were formed by a depofi-
tion from water. The arguments for this opinion
are forcible. The relics of a variety of fubftances,
which we now find only in the fea, are found in rocks
and mountains, at a very great diftance from it. In
ftrata of lime- ftone, every where diftant from the
fea, we find the remains of fhells, &c. the productions
of the ocean. Other circumftances prove, that the
fea has covered parts of the earth, which are now at
a great diftance from it, and that the various direc-
tions which the ftrata now have were not their direc-
tion at their firft formation. That the frame of this
earth has undergone fome violent concufllon is evi-
dent, as was already ftated, from the traces which ftill
remain. The ftrata we have feen are often broken
in different directions, in general perpendicularly ; fb
that £he parts of the ftrata are feparated from each
other. The width of thefe rents is different, fome-
times a few inches, fometimes many yards. They
are very commonly filled up with fubftances different
from the compofition of the ftrata. In mountains
there is fometimes obferved the appearance of a white
ftone, which pafles through it like a vein. This has
been a rent filled up with a particular kind of ftone,
Thefe are very common in the ftrata of coal, They
are generally of considerable hardnefs, and in them
metallic fubftances are ufually fgund. When any of
U 4 thefe

2. 96 Water In tie Center cf the Earth. [ B ock V I .

the/e are not filled up 'with extraneous matter, the
internal furface is fet with very beautiful and regular
cr'yttals of the fparry kind, projecting into the -cavity.

Some have attributed thefe irregularities to frequent
earthquakes; others have imagined that the globe,
before the deluge, contained an immenfe body ; of
\vater, covered over with a cruft of earth, which at
the deluge was broken through, and partly funk in
the waters, the elevated edges forming the mountains
and high lands, while the lower were overflowed by
the ocean ; others have fuppofed, that the near ap^
proach of a comet has thrown the materials of the
globe into confufion. Buffon imagines, that the fea
is continually changing its bed, and is conftantly
\vafhing away the ground' from one place to another*.

But

* 'A H.ort £;etch of the moil remarkable theories of the earth
is given by a popular writer, and it may be amufing to feme readers
to trac. Irs of the human imagination.

* The firit who formed this amufemeht of earth-making into
fyftem was the celebrated Thomas Barnet, a man of polite learn-
ing and rapid imagination. His Sacred Theory, as he calls it, de-
fciibing the changes which the earth has undergone, or ihal! here-
after undergo, is well known for the warmth with which it is
imagined, and the weaknefs with which it is reafcned, for the
elegance -of its ftyle, and the meannefs of its philofophy. The
earth, lays he, before the deluge, was very differently formed

.from what it is at prefent: it was at firit a fluid mafs ; a chaos
compoied of various fubltances, differing both iu denfity and
f.gure: tr.ofe which were moft heavy funk to the center, and
ibr-mcd in the middle of our globe an hard folid body; thofe of
a lighter nature remained next ; and the waters, which were
lighter tiillj fwam upon its fuiface, and covered the earth on
every fide. The air, ar d all thofe fluids which were lighter than
water, floated upon this alib ; and in the fame manner encompafTed
the globe ; fo that between the. furrounding body of waters, and.
the circumambient air, there was formed a coat of oil, ajd other
unctuous fubitances, lighter than water. However, as the air
was full extremely impure, and mult have carried up \viih it many

of

Chap. 45-1 Weary of the Earth. 197

But the arguments and obfervations of Mr. White -
hurft arc more ckferving attention, fmce he is almoft

the

o'f thofe earthy particles with which it once was intimately blended,
it foon began to defecate, and to depofe thefe particles upon the
oily furface already mentioned, which foon uniting, the earth and
oil formed that cruit, which foon became an habitable furface,
giving life to vegetation, and dwelling to animals.

' This imaginary antideluvian abode was very different from
what we fee it at prefent. The earth was light and rich ; and
formed of a fubilance entirely adapted to the feeble ftate of inci-
pient vegetation : it was an uniform plain, every where covered
with verdure ; without mountains, without feas, or the fmallefc
inequalities. It had no difference of feafons, for its equator was
in the plain of ihe ecliptic, or, in other words, it turned direftly
oppofite ro the fun, fo that it enjoyed one perpetual and luxuriant
fpring. However, this delightful face of nature did not long
continue in the fame Rate, for, after a time, it began to crack and
open in fiifures : 'a circumftance which always fucceeds when the
fun exhales the moiflure from rich or marihy fituations. The
crimes of mankind had been for fome time preparing to draw
down the wrath of Heaven; and they, at length, induced the
Deity to defer repairing thefe breaches in nature. Thus the
jchafms of the earth every day became wider, and, at length, they
penetrated to the great abyfs of waters ; and the whole earth, in
a manner, fell in. Then enfued a total diforder in the uniform
beauty of the firlt creation, the -terrene furface of *he globe being
broken down : as it funk the waters gufhed out in its place ; the
deluge became univerfal ; all mankind, except eight perfons,
were deftroyed, and their poiterity condemned to toil upon
the ruins of deiolated nature. -

« It only remains to' mention the manner in which he relieves
the earth from this univerfal wreck, which would feem to be as
difficult as even its firlr, formation. " Thefe great mattes of earth
failing into the abyfs, drew down with -them vaft quantities a Ho-
of air; and by dalhing againft each other, and breaking into fmall
parts by the repeated violence of the'lhock, they, at length, left
between- them large cavities filL-d with nothing but air. Thefe
cavities naturally offered a bed to receive the influent waters ;
and in proportion as they filled, the face of the earth became
once more vifible. The higher parts of its broken furfac*, now
become the tops of mountains,, were1 the firil that appeared ; the

plains

298 ttecry of tie Earth. [Book VI.

the only writer on this fubje&, who has united obfer*
vation with theory.

With

plains foon after came forward, and, at length, the whole glob*
was delivered from the waters, except the places in the loweft
fituations ; fo that the ocean and the feas are flill a part of the
ancient abyfs that have not had a place to return to. Iflands and
rocks are fragments of the earth's former cruft ; kingdoms and
continents are larger mafles of its broken fubftance ; and all thcr
inequalities that are to be found on the furface of the prefent earth,
are owing to the accidental confufion into which both earth and
waters were then thrown."

' The next theorift was Woodward, who, in his Eflay towards
a Natural Hiftory of the Earth, which was only defigned to pre-
cede a greater work, has endeavoured to give a more rational
account of its appearances ; and was, in faft, much better furnifhed
ibr fuch an undertaking than any of his predeceffors, being one
cf the moil affiduous naturalifts of his time. His little book, there-
fore, contains many important fadls, relative to natural hiftory, al-
though his fyftem may be weak and groundlefs.

c He begins by afierting that all terrene fubftanccs are difpofed
ia beds of various natures, lying horizontally one over the other,
fomewhat like the coats of an onion ; that they are replete with
ihells, and other productions of the fea : thefe {hells being found
in the deepeft cavities, and on the tops of the higheft mountains.
From thefe obfervations, which are warranted by experience, he
proceeds to obferve, that thefe fliells and extraneous fofltls are
not productions of the tarth, but are all actual remains of thofe
animals which they are known to refemble; that all the beds of
the earth lie under each other, in the order of their fpecific gra-
vity; and that they are difpofed as if they had been left there by
fubfiding waters. All thefe aflertions he affirms with much
earneftnefs, although daily experience contradicts him in fome
of them j particularly we find layers of done often over the
IighteH foils, and the fofteft earth under the hardeft bodies.
However, having taken it for granted, that all the layers of the
earth are found in the order of their fpecific gravity, the lighteft
at the top, and the heavieft next the center, he confequently
aiferts, and it will not improbably follow, that all the fubflance*
of which the earth is compofed were once in an actual Hate of
diffolution. This aniverfal diffolution he takes to have happened
at the time of the flood. He fuppofes that at that time a body

Chap. 45-1 Form of thf Eartb. 29$

With refpeft to the form of the earth, it is fcarcely

neceflary to mention, that it is nearly round ; a cir-

cumftance,

of water, which was then in the center of the earth, uniting with
that which was found on the furface, fo far feparated the terrene
parts as to mix all together in one fluid mafs; the contents of
which afterwards finking according to their refpe&ive gravities,
produced the prefent appearances of the earth. Being aware,
however, of an objection that foffil fubftances are not found dif-
folved, he exempts them from this univerfal diflblution, and for
that purpofe, endeavours to Ihew that the parts of animals have
a ftronger cohefion than thofe of minerals ; and that, while even
the hardeil rocks may be diffolved, bones and {hells may ftill
continue entire.

« So much for Woodward; but of all the fyftems which were
publiQied refpedling tbe earth's formation that of Whifton was
moil applauded, and moft oppofed. Nor need we wonder; for
being Supported with all the parade of deep calculation, it awed
the ignorant, and produced the approbation of fuch as would be
thought otherwife, as it implied a knowledge of abftrufe learning,
to be even thought capable of comprehending what the writer
aimed at. In fad, it is not eafy to diveft this theory of its ma-
thematical garb ; but thofe who have had leifure, have found the
refult of our philofopher's reafoning to be thus. He fuppoles
the earth to have been originally a comet; and he considers the
hiftory of the creation, as given us in fcripture, to have its com-
mencement juft when it was, by the hand of the Creator, more
regulariy placed as a planet in our folar fyftem. Before that
time, he fuppofes it to have been a globe without beauty or pro-
portion ; a world in diforder ; fubject to all the viciflitudes which
comets endure ; fome of which have been found, at different times,
a thoufand times hotter than melted iron ; at others, a thouJand
times colder than ice. Thefe alternations of heat and cold,
continually melting and freezing the furface of the earth, he
fuppofes to have produced, to a certain depth, a chaos en-
tirely refembling that defcribed by the poets, furrounding the
folid contents of the earth, which ftill continued unchanged in the
midft, making a great burning globe of more than two thoufand
leagues in diameter. This furrounding chaos, however, was
far from being folid : he refcmbles it to a denfe though fluid at-
mofphere, compofed of fubftances mingled, agitated, and (hocked
againft each other; and in this diforder he describes the earth to
have been juft at the eve of creation.

'But

300 Form of the Eartb. [Book VI.

cumftance, however, which, though now fo univer-
fally known, remained undifcovered for many thou-

' fand

c But upon its orbit's being then changed, when it was more re-
gularly wheeled round the fun, every thing took its proper place ;
every part of the furrounding fluid then fell into a fituation, in
proportion as it "was light or heavy. The middle, or central part,
which always remained unchanged, ftill continued fo, retaining a
part of that heat which it received in its primeval approaches to-
wards the fun; which heat, he calculates, may continue for about
fix thoufand years. Next to this fell the heavier parts of the
chaotic afmofphere, which ferve to fuftain the lighter : but as in
descending they could not entirely be feparated from many: watery
parts, with which they were intimately mixed, they drew down a
part of thefe alfo with them , and thefe could not mount again
after the furface of the earth was confolidated : they, therefore,
furrounded the heavy fi^fl: defcending parts,'in the fame manner as
thefe furround the central globe. Thus the entire body" of the
earth is compofed internally of a great burning globe: next which
is placed an heavy terrene fub (lance, that encompafTes it; round
which alfo is circunlfufed a body of water. Upon' this body of
water, the cruft of earth on which we inhabit is placed: fo that,
according to him,' the globe is compofed of a number of coats, or
Ihells, one within the other, all of different denfuies. The body of
the earth being thus formed, the air, which is the lighteft fub-
fiance of all, furrounded its furface ; and the beams of the fun dart-
ing through, produced that light which, we are told, firft obeyed
the Creator's command.

« The whole ceconomy of the creation being thus adjufted, it
only remained to account for the rifings and depreffions on the
furface of the earth, wi'rh the other feeming irregularities of its
prefent appearance. The hills and vallies are considered by him
.as formed by thx-ir prefiing upon the internal' fluid, which fuftains
the outward ftell of earth, with greater of lefs weight: thofe parts
of the earth which are heavieft, fink into the fubj?. cent fluid more
deeply, and become vallies : thofe that are lighteft, rife higher
upon the earth's furface, and are called mountains.

* Such was the face of nature before the deluge ; the earth was
then more fertile and populous than it is a't prefent ; the life of man
and animals were extended to ten times its prefent duration ; and
all thefe advantages arofe from the fuperior heat of the central
globe, which ever fince has been cooling. As its heat was then in

full

Chap". 4$.] Proofs that the Earth is fphericd. 301

fand years. That its form is fphcrical, was firft con-
jeftured from the curved line which bounds the

earth's

full power, the Denial principle was a!fo much greater than at
prefent; vegetation and animal increafe were carried on with more
vigour; and all nature feemed teeming with the feeds of life. But
thefe phyfical advantages were only productive ef moral evil; the
warmth which invigorated the body encreafed the paffions and
appetites of the mind; and, as man became, more powerful, he
grew lefs innocent. It was found necefi'ary to puaifh this depra-
vity ; and all living creatures were overwhelmed by th.2 deluge ia
univerfal deflruclion.

* This deluge, which fimple believers ai;e willing to afcribe to
a miracle, philofophers have been long defirpus tg account for by
natural caufes: they have proved that the earth could never Sup-
ply from any refervoir towards its center, nor,tke atmofphere by
any difcharge from above, fuch a quantity of water as would cover
the furface of the globe to a certain depth over the tops of our
higheft mountains. Where, therefore, was all this \vater to be
found ? Whifton has found enough, and more than a fufEciency,
in the tail of a comet; for he feems to allot comets a very active
part in the great operations of nature.

* Us calculates with great feemirig, precifion, the year, the
month, ana the day of the week on which this comet (which has
paid the earth fome vifits ftnce, though at a kinder alliance) in-
volved our globe in its tail. The tail he fuppp&d to be a vapour-
ous fluid fubitance, exhaied from the body of the comet, by the
extreme heat of the fun, and in creating in proportion as it ap-
proached that great luminary. It was in tins that our globe was
involved at the time of the deluge ; and, as the earth full aded by
its natural attraction, it drew to itfelf all the watery vapours which,
were in the comet's tail ; and the internal waters being alfo at the
fame time let loofe, in a very fhort fpace the tops of the lughel
mountains were laid under the deep.

The punifbment of the deluge being thus completed, and all the
guilty destroyed, the earth, which had been bvoken by the erup-
tion of the internal waters, was alfo enlarged by it ; fo that upon
the comet's recefs, there was found room fuflicient in the internal
abyfs fpr the recefs of the fuperfluous waters ; whither they all re-
. tired, and left the earth uncovered, but in fome refpe&s changed,
particularly in its figure, which, from being round, was now be-
come oblate. In this univerfal wreck of nature "Noah furvived, by

,301 Spherical Form of tie Earth. [Book VI.

earth's fhadow in lunar eclipfes. We have a ftill
plainer proof of its rotundity, from the appearance of

objeds

* variety of happy caufes, to re-people the earth, and to give birth
to a race of men flow in believing ill-imagined theories of the
earth.

After fo many theories of the earth, which had been publilhed,
applauded, anfwered, and forgotten, M. Buffon ventured to add one
more to the number. This philofopher was in every refpeft bet-
ter qualified than any of his predeceflbrs for fuch an attempt, being
furnimed with more materials, having a brighter imagination to
find new proofs, and a better ftyle to cloath them in. However, if
one fo ill qualified as I am may judge, this feems the weak eft part
of his admirable work; and I could wifti that he had been content
with giving us fafts inftead of fyftems ; that, inftead of being a
reafbner> he had contented himfelf with being merely an hif-
torian.

He begins his fyftem by making a diftincVion between the firft
part of it and the laft; the one being founded only on conjecture,
the other depending entirely upon aftuai obfervation. The latter
part of his theory may, therefore, be true, though the former
fhould be found erroneous.

The planets, fays he, and the earth among the number, might
have been formerly (he only offers this as conjecture) a part of the
body of the fun, and adherent to its fubftance. In this fituation,
a comet falling in upon that great body might have given it fuch
a (hock; and fo fhaken its whole frame, that foine of its particles
might have been driven off like {beaming fparkles from red hot
iron ; and each of thefe ftreams of fire, fmall as they were in com-
parifon of the fun, might have been large enough to have made an
earth as great, nay many times greater than ours. So that in this
manner the planets, together with the globe which we inhabit,
might have been driven off from the body of the fun by an impul-
five force: in this manner alfo they would continue to recede from
it for ever, were they not drawn back by its fuperior power of at-
traction ; and thus, by the combination of the two motions, they
are wheeled round in circles.

Being in this manner detached at a diftance from the body of
the fun, the planets, from having been at firft globes of liquid fire,
gradually became cool. The earth alfo having been impelled
obliquely forward, received a rotatory motion upon its axis at the

very

Chap, 45.] Spherical Form of tie Eartb. 303

obje&s on the furface of the earth, but ftill more re-
markably on that of the fea. As we depart from

objeds

very inftant of its formation ; and this motion being greateft at
the equator, the parts there afting againft the force of gravity,
they muft have fwollen out, and given the earth an oblate or flatted
figure.

As to its internal fubftance, our globe having once belonged to
the fun, it continues to be an uniform mafs of melted matter, very
probably vitrified in its primaeval fufion. But its furface is very
differently compofed. Having been in the beginning heated to z
degree equal to, if not greater, than what comets are found to
fuftain, like them it had an atmofphere of vapours floating round
it, and which, cooling by degrees, condenfed and fubfided upon its
furface. Thefe vapours formed, according to their different den-
fities, the earth, the water, and the air; the heavier parts falling
firft, and the lighter remaining ftill fufpended.

Thus far our philofopher is, at leaft, as much a fyftem -maker a*
Whifton or Burnet; and, indeed, he fights his way with great
perfeverance and ingenuity through a thoufand objections that na-
turally arife. Having, at laft, got upon the earth, he fappofes
himfelfon firmer ground, and goes forward with greater fecuritr.
Turning his attention to the prefent appearance of things upoa
this globe, he pronounces from the view that the whole earth was
at firft under water. This water he fuppofes to have been the
lighter parts of its former evaporation, which, while the earthy
particles funk downwards by their natural gravity, floated on the
furface, and covered it for a confiderable fpace of time.

" The furface of the earth," fays he *, " muft have been in the
beginning much lefs folid than it is at prefent ; and, confequently,
the fame caufes, which at this day produce but very flight changes,
muft then, upon fo complying a fubftance, have had very confider-
vable effedts. We have no reafon to doubt but that it was then co-
vered with the waters of the fea ; and that thofe waters were above
the tops of our higheft mountains, fince, even in fuch elevated fi-
tuations,we find (hells and «ther marine productions in very great
abundance. It appears alfo that the fea continued for a confider-
able time upon the face of the earth: for as thefe layers of fhelk are
found fo very frequent at fuch great depths, and in fuch prodigious

* Theorie de la Terre, vol. i. p, in.

quantities

304 Spherical Form of the Earth. [Book VI.

objects, On the ocean, .they feem to fubfide gradually
below the vifible horizon. Ships at a diftance on the
water are not vifible in their hulls -t at a greacer dif-
tance, their mainfails difappear •, and at a greater ftill,
their topfails ; which could not be, if they failed on a
plain. But that the earth is really globular was at
length practically demonftrated by the adventurous
project of failing round it, which has feveral times
been accomplifhed.

This fad being premifed, let us confider in what

quantities, it feems impoflible for fuch numbers to have been fupport-
ed all alive at one time; fo that they muft have been brought there
by fucceflive demolitions. Thefe ihells alfo are found in the bodies
of the hardeft rocks, where they could not have been depofited all
at once, at the time cf the deluge, or at any fuch ir.ftant revolu-
tion ; fince that would be to fuppofe, that all the rocks in which
they are found were, at that inftaht,in a ftate of difiblution, which
would be abfurd to aflert. The, fea, therefore, depofited them
where ever they are now to be found, and that by flow and fuccef-
five degrees.

" It will appear, alfo, that the fea covered the whole earth, from
the appearance of its layers, which lying regularly one above the
other, feera all to referable the fediment formed at different times
by the ocean. Hence, by the irregular force of its waves, audits
currents driving the bottom, into fand- banks, mountains muft nave
been gradually formed within this univerfal covering of waters;
ami thefe fucceffively railing their heads above its furface, n:uft,
in time, have formed the higheft ridges of mountains upon land,
together with continents, iflands, and low grounds, all in their
turns. This opinion will receive additional weight by considering,'
that in thofe parts of the earth where the power of the ocean is
greateft, the inequalities on the furface of the earth are higheft r
the ocean's power is greateft at the equator, where its winds and
tides are moft cor.ftant; and, in fact, the mountains at the equator
are found to be higher than in any other part of the world. The
fea, therefore, has produced the principal changes in our earth :
rivers, volcanoes, earthquakes, ftorms, and rain, having made but
flight alterations, and only fuch as have affedled the globe to very
inconfiderable depths."

GOLDSMITH'S Hiftory cf tbe Earth end animated Nature,
Vol. I. p. 22, &c.

manner

Chap. 45.] Theory of tht Earth. 305

manner ihe known laws of nature were likely to a<5t
upon a mafs of materials fuch as enter into the com-
pofition of this globe.

The firft principle of the law of gravitation is, that
the conftituent particles of all bodies attract each other
mutually, whence arife their common centers of gra-
vity. Hence all fluids aflume a fpherical form, from
the particles mutually attracting each other j and no
bodies but fluids being capable of obeying the laws
of gravitation, fo as to become fpherical, it is prefumed
that the earth was . originally in a fluid ftate. The
earth revolves round its center, and the centrifugal
force increafes in proportion to the diftance from the
axis of motion ; all bodies, therefore, revolving round
their axis in a ftate of fluidity, will necefifarily depart
from the fpherical form, and afiume that of an oblate
fpheroid. Such, by actual menfuration, is found to
be the form of the earth ; and this is alib demon-
ft rated, by aftronomical obfervations, to be the cafe
with all the other planets. It is therefore highly
probable, that all thefe bodies were originally fluid,
and only departed in fome meafure from the fpheri-
cal form, in confequence of a revolution on their
axis.

It is not natural or eafy to fuppofe, that the earth
and planets have, fmce their exiftence, been reduced,
by any folvent principle, from a folid to a fluid fcate.
It is much more obvious to believe, that fuch was
their ftate at their firft creation. It follows of confe.-
quence, that they had a beginning, and have not exifted
from eternity, as fome fantaftical writers have been
inclined to imagine.

If fuch was the original ftate of the earth, it fol-
lows, that it was at firft abfolutely unfit for animal and
vegetable lifej and, therefore, thefe muft have been

VOL. II. X after-

;>o6 Theory of [Book VI.

after- creations. This account, it is obfervable, agrees
admirably witli the Mofaic account of the creation,
ms well as with the opinions of the moft ancient phi-
lofophers, hiftorians, poets, &c. that is, with the tra-
ditions of the firft ages. v

It is the opinion of Mr. Whitehurft, that the com-
ponent parts of the earth, at its firft formation, exifted
in a ftate of actual fulution, and that they fnbfided partly
into folid bodies, and partly into fluids, by the mutual
action of thefe particles upon each other.

We have feen that there exifts between different
particles of matter what is called elective or chemical
attraction, by which fubftances having certain proper-
ties in common are difpofed ro unite j and by the
combinations thus formed (whether by an immediate
act of omnipotence, or whether by fome more gradual
procefs) the fufpenfion of the component parts of the
chaotic mafs would be effectually deflroyed, and bo-
dies would approach towards their center of gravity
in proportion to their relpective denfities. That
the laws of elective attraction have prevailed in the
formation of the earth is evident from the famenefs
of quality which is obierved in different ftrata of
minerals.

It has been, I think, demonftrated, that the prefence
of heat, caloric, or fire is the efficient caufe of fluidity.
When the permanently elaftic fluids, therefore, which
eonftitute the atmofphere, affumed their aeriform ftate,
and rofe from the chaotic mafs, a great quantity of
heat muft have become latent, while the remaining
fubftances, from which the caloric was abftracted, muft
have been confiderably cooled, and it might, there-
fore, be expected, that tliofe kinds of matter, which
had leaft attraction for caloric, would affume a folid
form; while others, whole attraction for that fubftancq
6 was

Chap. 45.] the Earth. 307

was intermediate, would remain in the ftate of com-
mon fluids. Ic is therefore, perfectly agreeable to
found philofophy to fuppofe, that the abftraction of a
confiderable quantity of caloric, or the mutter of fire,
from the chaotic mafs, would effectually deftroy its
fluidity, and would aknoft inftantly produce all the
different mineral fubftances, which are obferved in
the bowels of the earth. Not that we are under any
neceffity of believing, that the whole internal fub-
ftance of the earth exifts at this hour as it exiled when
creation was completed. There are a variety of pro-
ceflfes going on continually in the interior parts of the
globe, befide thofe more fudden and violent changes,
which have been produced by earthquakes, floods,
and volcanoes.

By the fubfiding of the clenfer and more folid bo-
dies, a confiderable portion of the fluid matter would
be left in a feparate {late, and would form large mafTes,
or oceans of water.

With refpect to the formation of iflands, nothing
more was necefTary than the unequal and irregular
fubfiding of the different parts of matter, which may-
have happened from a variety of caufes; from the
effects of elective attraction and cryftallization $ from
the motion of die earth, and the flux and reflux of
the tides, The latter caufe would neceflarily remove
the folid mafles, as they were formed, from place to
place, till thefe folid mafles, meeting with others, or
increafing their bulk by their action upon congenial
particles, would, from their increafed gravity and
denfity, at length become ftationary. Thus the fur-
face of the earth is all irregular, and an ifland is no
other than a hill or mountain, the adjacent vallies of
which are filled with water. Some iflands, however,
we know, are of more recent origin. Some have
X 2 been

308 Origin of I/lands. [Book VI.

been thrown up by volcanic eruptions; and fome have
apparently been formed by that extraordinary infect
which produces rocks of coral. The iflands Delos
and Rhodes are faid to have grown out of the fea.
Pliny mentions a number of other iflands, which were
produced by fubterraneous fires. In 1628, one of the
iflands of the Azores rofe up out of the bottom of the
fea, which in that place was one hundred and fixty fa-
thoms deep ; and this ifland, which is three leagues
long, one league and an half broad, and three hundred
and fixty feet above the level of the water, rofe in fif-
teen days*.

On the 2oth of November, 1720, a fubterraneous
fire burft out of the fea near Tercera, one of the
Azores, which threw up fuch a quantity of ftones, in
the fpace of thirty days, as formed an ifland two
leagues in diameter, and nearly circular f.

The Ifle of Sheppey contains a great variety of
foffil bodies, as well animal as vegetable, which evi-
dently prove it to be an afiemblage of adventitious
matter.

In every inftance upon record, the fragments of fea
{hells are infinitely more numerous than the bones and
teeth of fifh. The latter too are but feldom depo-
fited in any other matter than in beds of fand and gra-
vel, and not in the folid beds of Jime-ftone, as the
fhells of fifh generally are, even to the depth of many
hundred yards, and difpofed throughout the whole ex-
tent of the ftrata J.

There is no occafion to fuppofe, that the whole

* Sir William Hamilton's Obfervations on Vefuvius and
./Etna.

f PhSlofophical Tranfaftions, quoted by Whitehurft.
| Whitehurft, p. 44,

furface

Chap. 45.] T"he whole Earth not habitable at once. 309

furface of the earth was at once rendered habitable.
From the fcripture account we have reafon to believe,
that only a very fmall part of it was inhabited for
a long feries of time, viz. the regions about the Eu-
phrates, fuppofed to conftitute the Garden of Eden.
Here the terreftrial animals were chiefly afiembled,
while the marine animals were difperfed through the
great abyfs of waters ; and, from the extreme fecun-
dity of thofe animals, they would, in a very fhort
fpace of time " replenifh the waters" from pole to
pole. If, therefore, we fuppofe (as is moft probable)
that the greater part of the earth was gradually form-
ing itfelf according to the laws of nature and creation,
in other words, according to the ufual procefies of
attraction and combination, it is eafy to conceive, that
a part of thefe animals, efpecially thofe which are lead
active, would be gradually intombed in the increafing
mafs, and this, as well as the deluge, will account for
the great quantities of the exuvias and bones of marine
animals, efpecially (hell fifh, which are found in beds
of lime-ftone, gravel, &c. even on the tops of moun-
tains.

We fhall ceafe to be aflonimed at the immenfe
quantities of fhells, which are thus found imbedded in
the earth, if we only confider the amazingly prolific
oature of thefe animals. It is not uncommon to take
away a bed of thefe Ihell filh feveral fathoms in thick-
nefs j and, though the places whence they are removed
appear entirely exhaufted, yet in the enfuing feafou
there fhall be as many found in all thefe places as there
were before*.

The bones or teeth of fifh, Mr. Whitehurft affirms,
as far as his knowledge extends, have never been
found mixed with fliells in the folid fubftance of lime-
itone.

• Whitehurft, p. 47.

X 3 That

Early Con-vulfions of the Earth. [Book VI.

That at different periods the earth muft have fuf-
fered Very violent convulfions and difcerptations of
the folid parts, we may reafonably conclude from the
rugged and uncouth appearance of many of the moun-
tainous parts of the world. We fee rocks in fome
places torn afunder, or, in appearance cut with a faw.
Mr. Whitehurft remarks, that at Stafford and New-
port, in Shropfhire, there are detached blocks of
Corniih moor-ftcne, or granite, of considerable mag-
nitude, though no fuch ftratum is known to exill
nearer than Cormvall. It is fair, therefore, to con-
.clude, that they have been thrown there by fome
violent commotion or fubterraneotis convulfion.

To the general deluge, that fad: recorded with fo
much precifion in "the writings of Mofes, and confirmed
by the traditions of every nation, we jmift attribute
much of the irregularities of the earth's furface. It
•would in fome inftances have the effect of reducing
great malTes of matter to a fecond ftate of folution.
Many eminences would be levelled, and fome of the
vallies would be filled up. Some parts, which before
were fea, might receive fuch an acceffion of foreign
matter as to fill up their beds, and on the fubfiding
of the waters to prefent to the eye a vail level plain.
Thole elevations, on the contrary, which confided of
folid mafies of the harder (tones, would have the
lighter portions of earth wafhed away from their bates,
and their height would receive a proportional increafe.
If pit coal, indeed, is of vegetable origin, it is difficult
to account for the depofition of fuch a quantity of
vegetable matter beneath the furface of the earth,
on any other hypcthefis than that of a deluge ; and
though much of the exuvis of fhell-fifh might be
involved in the firft ages fucceeding the creation, in
the manner Mr. Whitehurft fuppofes, much greater

quantities

Chap. 45.] Proofs of the Deluge. 311

quantities would be inhumed at the deluge. The
other animal matters found -in a foflil Hate, particularly
the horns, fkeletons, and bones of animals, which are
much larger than any now found upon the earth, can
only be accounted for upon this hypothecs. Such
are thofe mentioned by BufTon, which were dug up
in America, near the river Ohio, a fmgle tooth of
which, belonging to a large row, weighed upwards
of eleven pounds, and a fmgle thigh bone was upwards
of four feet in length. In the year 1783, a fkeleton
of an immenfe animal of the deer kind was found on
an eftate belonging to Dr. Percy, Bifhop of Dromore.
It was dug out of a marie pit, under a peat mofs,
and was found furrounded by fhells and other marine
productions. The horns were feven feet and one
inch in height, the length of the fcull nearly two feet,
the breadth of the forehead nearly a foot, and the bones
of an enormous fize. In Siberia, in America,, and
even in England, the bones and teeth of the elephant,
hippopotamus, and other animals, which never have
exifted in thofe climates, have been found, and even
thefe were larger than thofe of any fuch animals now
exifting.

To the deluge, therefore, much of the prefent
inequalities of the earth may be rationally attributed.
But there are other caufes which may have operated
both before and fince. It is a fact, which will fcarcely
admit of difpute, that volcanic eruptions were much
more frequent in the early ages of the world than at
prefenc : the veftiges of volcanoes, and, even the ex-
haufted craters, are often found, where there is now
not the leaft appearance of fubterraneous fire. This
fact is alfo eafily accounted for on philofophical prin-
ciples. The imperfect, and, if I may fo fpeak, ac-
cidental mixture of different bodies, would in many
X 4 cafes

31 1 Strufturt of the Earth. [Book VI.

cafes produce fpontaneous inflammation in the early
ages of the world, whereas, as the earth grows older,
thefe materials muft be exhaufted, or rather formed
into other combinations. Many mountains, we know,
are of volcanic origin, and therefore many of them of
a date long pofterior to the sera of creation.

Such appears to be the moft rational account of
the ftruclure of the earth, as far as we are warranted
by actual experiment, or well authenticated obferva-
tion. The fucceeding chapters of this book will
ferve to explain more fatisfactorily the different apr
pearances of various portions of the globe. I fhall
therefore proceed, without further digreffion, to treat
more particularly of mountains, volcanoes, and the other
phenomena more immediately connected with this
branch of natural hiftory.

Chap. 46.] [ 313 ]

C ii A P. XLVI.

MOUNTAINS.

T)~tjlinfti<in. between Hills and Mountains— Mountains primaeval or
jecondary.^— Granite Mountains only fuppofed in general primteiial.
-—Some Litne^ftonf Mountains pritneeivaL'~- Alluvial Mountains,— ~>
E, it ire and ftrattfied Mountains.— Mountains homogeneous and be*
terogzn(:(.:«;.-!~Cosfitfed Mountains.-— Volcanic Mountains. — Height
of Mountain^ , ho=iu meafured.— Computed Heights of the moll re-
~ markable Mountains.'— Line of Congelation in different Parts of ths
Wcrld.

ELE V AT I O N S, confifting chiefly of clay, fand,
' or gravel, are called hills. Thofe which con-?
fid chiefly of (lone are called mountains. Mountains
are divided into primaeval, that is, of equal date with
the formation of the globe, and fecondary or alluvial.
Among primeval, thofe of granite hold the firft place.
The higheft mountains and moft extenfive ridges
throughout the globe are of that kind ; as the Alps
and Pyrenees, in Europe; the Altuifchan, Uralian,
and Caucafus, in Afia ; and the Andes, in America.
The higheft of them never contain metallic ores ; but
fome of the lower contain ores of copper and tin.
The granite next the ore always abounds in mica.
Petrifactions are never found in thefc primaeval moun-
tains.

That the formation of thefe mountains preceded
that of vegetables and animals, is juftly inferred from
their containing no organic remains, either in the
form of petrifaction or impreflion. Naturalifts are
agreed, that granites were formed by cryftallization.
This operation probably took place after the forma-
tion of the atmofphere, and the gradual excavation

of

314 Compcfition of Mountains. [Book VI.

of the bed of the ocean, when the dry land appeared.
For, as was remarked in the preceding chapter, by
means of the reparation of the .aeriform fluids, which
conftitute the atmofphere, the evaporation of part
of the water into the atmofphere, and the gradual
retreat of the remainder, the various fpecies of earths,
before diflblved or diifufed through this mighty rnafs,
were difpofed to coalefce, and among thefe the fili-
tseous muft have been the firfl, as it is the lead foluble ;
but as the filiceous earth has an affinity to the other
earths with which it was mixed, fbnie of thefe muft
have united in various proportions, and thus have
formed, in 'diftinct maffes, the felt fpar, flioerl, and
mica, which compofe the granite. Calcareous earth
enters very fparingly into the competition of this ilone;
•but as it is found in fhoerl, which is frequently a com-
ponent part of granite, it follows that it muft be one
of the primitive earths, and not entirely derived from
marine exuviae, as forne have fuppofed. Quart?, can
•never be fuppofed to be a product of fire; for in a
very low heat it burfts, cracks, and lofes its tranfpa-
rency, and in the higheft degree of heat that we can
produce, is infufible, fo that in every eiTential point
•it is different from gkfs, to which fome have com-
pared it. As granite contains earths of every genus,
we may conclude, that all the fimple earths are ori-
ginal. This, however, is no proof that they are in
reality fimple and uncompounded of other principles ;
but they muft be confidered as fuch in the prefenc
ftate of our knowledge. Though water undoubtedly
dates from creation, yet late experiments have fhewn
it to- be a compound, as was formerly ftated.

Mountains, which confift of lime (lone or marbles
of a granular or fcaly texture, and not difpofed in
'.f'rata, feem alfo to have preceded the creation of

animals,

Chap. 46.] Alluvial Mountains. 315

animals, for no organic traces are found in them.
Some of thofe, which confift of argillaceous ftones, and
fome of the filiceous, contain alfo no organic remains.
Thefe often confift of parallel ftrata of unequal thick-
nefs, and the lower are harder and lefs thick than the
upper, and therefore feem to have been formed earlier
than the upper.

Alluvial mountains are evidently of poflerior for-
mation, as they contain petrifactions and other vef-
tiges of organic fubftances, and thefe are always ftra-
tified.

Mountains, as to ftruclure are entire, ftratifred, and
confufed. Entire mountains are formed of huge
mafies of (lone, without any regular fifiures, and are
mollly homogeneous. They confift chiefly of granite,
fometimes gneifs*, fchiftus, flag-ftone, fand ftone, lime-
ftone, gypfum, porphyry or trapp. Some in Sweden
and Norway confift of iron ore.

The ftratified mountains are thofe whofe mafs is
regularly divided by joints or fifTures; thefe are called
horizontal, rifing, or dipping. Homogenous ftratified
mountains confift chiefly of ftones of the argillaceous
genus, or of the firTile compound Ipecres of the fili-
ceous genus, as metallic rock ;" fometimes of lime-
ftone of a granular or fcaly texture, in which no animal
veftiges appear. This lime-ftone repofes on the
argillaceous or filiceous ftrata: fometimes the argil-
laceous are covered with mafles of granite, fometimes
of lava. Thefe mountains, particularly thofe ofgneifs,
metallic rock, and horn-ftone, are the chief feat of
metallic ores. When covered with lime-ftone, the
ore is generally between the lime-ftone and the argil-
laceous ftones. Thefe ores run in veins, not in ftrata.

* A rock confiding of mica, lapU ollaris, and quartz.

Petrifactions

3 1 6 Mode of computing [Book VL

Petrifactions are found upon, but not in, thcfe moun-
tains.

Heterogeneous, or compound ftratified mountains,
confift of alternate ftrata of various "fpecies of ftones,
earths, fands, &c. The lime-ftone here is always of
the laminar, and not of the granular or fcaly kind,
and when it contains any ore, it is placed between its
laminae. Stones of the filiceous genus feldom form
flrata in thefe mountains, except lavas ; but the ftrata
are frequently interrupted by filiceous mailes, as jafper,
porphyry, &c. Coal, bitumen, petrifactions, and or^
ganic hnprefiions, are found in thefe mountains, alfo
falts and calamine.

There are other mountains, which cannot properly
be called ftratified, as they confift only of three im-
menfe mattes, the loweft granite, the middle argilla-
ceous, and the upper lime-ftone. Metallic ores arc
found in the argillaceous part, or between it and the
.lime-ftone,

Confufed mountains confift of ftones heaped toge-
ther without order, their interftices filled with clay,
fand, and mica. They fcarcely ever contain any ore.

Befides thefe, there are many mountains in different
parts of the world, which derive their origin from vol-
canoes;, but of thefe it will be neceffary to treat in the
fucceeding chapter.

The height of mountains is ufually calculated by-
means of the barometer, upon the principles already
explained. For this purpofe two columns of mercury,
or barometers, are provided, and one is kept at the
foot of the mountain while the other is carried to its
fummit. The degree of heat, if not equal, is reduced
by calculation to an equality, and for this purpofe a
thermometer is attached to each of the barometers.
The degree of heat, to which both are reduced, is

commonly

Chap. 46.] the Height of Mountains. 317

commonly 5 5°, if, however, either of the barometers
(lands at 30 inches, and the annexed thermometer
at 55°, no reduction is to be made in the degrees
indicated by that barometer ; but if either of them
is at 30°, and the thermometer below 55°, we muft
add the expanfion the mercury in the barometer
would have experienced at the heat of 55°. If the
heat mould, on the contrary, be above 55°, we muft
fubftracl: the degree of expanfion which it gains by
that heat. Every degree of Fahrenheit's fcale produces
an expanfion of 00.304 of the barometrical inch,
when the barometer is at 30; when, therefore, the
thermometer is at 11° below or above 55% we muft
add in the former, or fubftract in the latter cale, eleven
times that number from the barometrical height. In
the fame manner it may be calculated, whatever is
the height of the barometer. When this matter is
afcertained, the height is eafily found by comparing
the two barometers and calculating the denfity of the
air in the higher regions according to the principles of
geometrical progreflion.

The higheft mountains are thofe which are fituated
at or near the equator ; and the Andes are generally
allowed to be the higheft of thefe. Catopaxi, one of
the Andes, which was meafured by Ulloa and the
French academicians, was found to be rather more
than three miles above the level of the fea; whereas
the higheft point of the Alps is not above a mile and
a half. Mount Caucafus approaches neareft to the
height of the Andes of any of the Afiatic mountains.
The Pike of TenerirF, which has been fo much cele-
brated, is about a mile and a half in height. It is
an extraordinary circumftance, that the moon, which
is a body fo much fmaller than our earth, mould fo
greatly exceed it in the irregularities of its furface ;

feme

31 8 Line of perpetual Froft. [Book VI.

fome of the mountains in that planet being calculated
to exceed nine miles in height.

• The line of congelation, or perpetual froft, on moun-
tains, is calculated at 15,400 feet, at or near the equa-
tor ; at the entrance of the temperate zone, at 13,428 j
onTenerifF, at 1,000; in Auvergne (lat. 45.) 6,74Oj
with us (lat. 52.) 5,740. On the Andes, vegetation
ceafes at 14,697 feet; and on the Alps, at 9,585.
The air is fo dry in thefe elevated fituations, that M.
D'Arcel obferved, that on the Pic de Midi, one of the
Pyrenees, fait of tartar remained dry for an hour and a
half, though it immediately moiftened in the fame tem-
perature at the bottom of the mountain.

Chap. 47-1 [ 3 '9 1

CHAP. XLVIL

VOLCANOES.

ances,
noes in

General Gtyr-vatiOfis on Volcanoes,— Their Connexion with the
Immatje Force of fultcrrane out Fires exemplified in various Inft
— Theory cf Volcanoes. — Great Depth. — Traces of Volcan
different Parts of the World. — De/criptidn of JStna. — Eruption of

fifkvitat, in 1794.

TTOLCANOESare peculiar to no climate, and
V have no neceffary or regular connection with
any other mountains, but feem to have fome with the
fea, for they are generally in its neighbourhood. Ic
has been remarked by thole who have obferved them,
that volcanoes often throw out matters which belong
to the fea, as the relics of fifh, fea-weed, and often
immenfe quantities of lea-water itfelf. Sir William
Hamilton obferves, in the Philofophical T ran factions
for the year 1776, u that the operatipns of Vefuvius
are very capricious and uncertain, except that the
finoke increales confiderably and conftantly when
the fea is agitated, and the wind blows from that
quarter."

There are ancient extJnguilhed volcanoes, it is true,
which are inland ; but this is only one of many proofs
that the fea covered thofe countries at fome remote
period. Volcanic mountains are of all heights ; fome
fo low as four hundred and fifty feet, as that of Tanna j
Vefuvius is three thoufand fix hundred feet high, and
^Etna eleven thoufand. They in general form lofty
fpires, and the volcano itfelf is internally (haped like
an inverted cone, placed on a broader bafis. This
cone is called the crate/, or bow), and through it the

lava

Force of Volcanic Fires. [Book VI.

lava generally pafles, though fometimes it burfts
through the fides, and even proceeds occafionally
from the bottom of the mountain. Sometimes the
crater falls in and is effaced, fometimes, in extinguifhed
volcanoes, it is filled with water. Sub-marine vol-
canoes have been obferved, and from thefe fome
iflands have derived their origin. Volcanic fires,
taking place at the bottom of the ocean, would fre-
quently, by the expanfive force of the (teams which
are generated, elevate thofe parts which were once
at the bottom of the deep, and overflow thofe which
were habitable earth. It is very probably conjee-
tured, as was noticed in a preceding chapter, that fub-
terraneous convulfions operated more powerfully in
the early ages of the world than at any later period ;
and indeed fuch an hypothecs is fupported by the
moil: probable reafoningi fince we may well conceive,
that at the firft confolidation of the earth, much hete-
rogeneous matter would be included in the different
mafles, which might produce more frequent fermen-
tations than at any after periods, when thefe have
been, if I may fo exprefs it, purged off by frequent
eruptions, and in many parts, perhaps, rectified and
aflimilated by flow and fecret procelTes in the bowels
of the earth. But hiftory was not cultivated till a very
late period, and the moft eventful ages of nature have
patted unrecorded.

The force of fubterraneous fires, or rather of the
fleam which is generated by them, is fo great, rhaC
confiderable rocks have been projected by Vefuvius
to the diftance of eight miles. A ftone was once
thrown from the crater of that volcano twelve miies,
and fell upon the Marquis of Lauro's houfe at Nola,
which it let on fire. One alfo, which meafured twelve .
feet in height and forty-five in circumference, was car-
ried

Chap. 47-1 Itnmejifs Depth of Volcanoes. 32 r

lied, in 1767, by the projectile force of the fteam, a
quarter of a mile from the crater. In an eruption of
jEtna, a ftone, fifteen feet long, was ejected from the
crater to the diftance of a mile, and buried itfelf eight
feet deep in the ground.

A volcano broke forth in Peru, in 1600, accom-
panied with an earthquake, and the fand and afhes
which were ejected covered the fields ninety miles
one way and one hundred and twenty another. Dread-
ful thunders and lightning were heard and feen for
upwards of ninety miles round Araquapa during this
eruption, which feemed to denote fome connection
between the electric matter and thefe volcanic fires**
and this fact is ftrongly confirmed by the very accu-
rate obfervations of Sir William Hamilton, which
I {hall afterwards have occafion to notice more at
large.

Both the infide of the crater and the bafe of many
volcanoes confift of lava, either entire or decompofed,
nearly as low as the level of the fea, but they finally
reft either on granite, as in Peru, cr fchiflus, as the
extinguifhed volcanoes of Hefle and Bohemia, or on
lime-ftone, as thofe of Silefia, Mount Vefuvius, &c.
No ore is found in thefe mountains, except that of
iron, of which lava contains from twenty to twenty-
five parts in the hundred, and fome detached frag-
ments of the ores of copper, antimony, and arfenic.
Vefuvius ejected, from the year 1779 to 1783,
309,658,161 cubic feet of matter of different kinds;
we muft therefore, conclude the feat of thefe fires to
be feveral miles, perhaps hundreds of miles, below
the level of the fea ; and as iron makes from one-
fourth to one-fifth of thefe ejections, we may infer that

* -Dr. Hooke's podhumous Works, p. 304.

VOL. II. Y the

321 Artificial Volcano. [Book VI.

the internal parts of the earth abound much in this
metal.

The origin of thefe fubterraneous fires is not enfily
explained. Iron filings mixed with powdered ful-
phur, and the whole moiftened with water into a pafte,
\ve have formerly feen, will fvvell, become hot, and,
if the quantity is confiderable, will throw out a blue
flame. It is a mixture of this kind which is ufed for
making an artificial earthquake, for fiich a quantity of
inflammable gas is produced during the fermentation,
that if the mafs is buried in the earth, the gas will
force a paflage for its efcape, and exhibit, on a fmall
fcale, the phenomena of an earthquake. M. Lemery
feems to have been the firft perfon who iiluftrated, in
this manner, the origin of volcanic fires and earth-
quakes. ,He mixed twenty-five pounds of iron filings
with an equal weight of fulphur, and having made
them into a pafte with the addition of water, he put
them into a pot, covered them with, a cloth, and bu-
ried them a foot under ground. In about eight or
nine hours time the earth fwelled, became warm, and
cracked, and hot fulphureous vapours were per-
ceived*. Now, large beds of martial pyrites, which

are

.* That part of this experiment (fays Bifhop Watfon) which
relates to the production of fire, by the fermentation of iron filings
and fulphur when made into a pafte, has been frequently repeated
fince the Time cf Mr. Lemery. I myfelf have made it more than
once, but I have nothing material to add to his account, except
that the flame, when the experiment is made in the open air, is of
very {hort duration ; and that the whole mafs, after the extinction
of the flame, continues at intervals, for a longer or (horter time,
according to its quantity, to throw out frarks; and that a ladle
full of the ignited mafs,, being dropped down from a confiderable
height, dfcfcends like a mower of red- hot afhes, much refembling '
the paintings of the eruptions of Mount Vefuvius, which may be
.icen at the Britifh Mufeum. It has been obferved, that large

quantitioi

Chap. 47-] Probable Cwje of Volcanic Fires.
are natural combinations of iron and fulphur, are
known to exift in different parts of the earth ; the
only difficulty which attends this explanation of the
origin of volcanoes, as well as of earthquakes, is, that
the prefence of air is in general necefiary for the pro-
duction of actual flame. It is well known, however,
that martial pyrites, when moiftened, acquire heat;
and if we fuppofe the heated pyrites to have been in
contact with black wad and petroleum, we may fup-
pofe the flame to arife, as we fee it produced by art,
from the deficcation of the former fubftance, and its
mixture with mineral oil. Many minerals, when
heated, afford vital air, a very fmall quantity of which
is fufficient to produce flame ; this flame, once pro-
duced, may be fupported from other ores, and the
combuftion be maintained by the prefence of bitumi-
nous fchiftus, bitumen, and coal. Marl, fchiitus, horn-
ftone, Ihoerl, with a further addition of iron, are the

quantities of the materials are not requifite to make the experiment
fucceed, provided there DC a due proportion of water : half a
pound of fteel filings, half a pound of flowers of brimllone, and
fourteen ounces of water, will, when well mixed, acquire heat
enough to make the mafs take fire.

That heat and fire mould, be generated from the fpontaneou?
actions of minerals upon each other, is a phenomenon by no means
fingular in nature, how difficult foever it may be to account for if.
The heat of putrefcent dunghills, of the fermenting juices of ve-
getables, and, above all, the fpontaneous firing of hay not pro-
perly dried, are obvious proofs that vegetables poffefs this property
as well as minerals. In both vegetables and minerals, a definite
quantity of moifture is requifite to enable them to commence that
inteftine motion of their parts, which is neceflary for the produc-
tion of fire. Iron and fulphur would remain mixed together for
ages without taking fire, if they were either kept perte&ly free
/rom moifture, or drenched with too much water; and vegetables
in like manner, which are quite dry, or exceedingly wet, are inca-
pable of" taking fire wlulft they continue in that Hate.

Y 2 true

324 How Volcanic Fires may be Jupported. [Book VI.

true fources of lava, It feems, however, after all, dif-
ficult to conceive that fuch extenfive and intenfe fires
fhould be maintained without the accefs of confider-
able quantities of air; that fluid may therefore be
poffibly fupplied by a communication with fome exten-
five caverns, which may themfelves receive it by open- .
ings at the difiance of many miles from the crater of
the volcano. It does not feetn improbable that the
volcanoes, which now burn, may have a communica-
tion with the cavities and craters of extinguished vol-
canoes, and thence derive a fupply of air Sufficient to
account for the inflammation of large beds of pyrites
and bituminous matters. M. BufFon fuppofes, that
the feat of volcanic fires is fituatcd but a very little
way below the bed of the mountains ; but it appears
more probable, that it is in general many miles below
the fur face of the earth, for the quantity of matter dif-
rhargcd from ./Etna alone is fuppofed, on a moderate
calculation, to exceed twenty times the original bulk
of the mountain, and therefore could not have been
derived from its contents alone, but muft come from
the deeper recedes of the earth.

M. Condamine afferts, that all the mountains in the
.neighbourhood of Naples exhibit undoubted marks of
a volcanic origin. He fays, he could trace the lava,
and other productions of Subterraneous fire, from Na-
pks to the very gates of Rome, pervading the whole
foil, fometimes pure and fometimes differently com-
bined. " Wherever I fee," fays he, " on an elevated
plain, a circular bafon, fu-rrounded with calcined rocks,
I am not deceived by the verdure of the adjacent
fields ; I. can difcover, beneath the fnow itfelf, the
traces of an extinguished fire. If there is a breach in
the circle, I ufually find out, by following the decli-
vity of the ground, the traces o£a rivulet, or the bed

of

Chap. 47.] Traces of Volcanoes in Ireland. 325

of a torrent, which feems as if it was hollowed in the
rock, and this rock appears frequently to be pure lava.
If the circumference of the bafon has no breach, the
rain and fpring waters, which are collected there, ge-
nerally form a lake in the very- mouth of the volcano."
The Apennines, as well as the Cordeliers of Peru
and Chili, he fuppofes to have been a chain of vol-
canoes. The chain in both inftances is interrupted,-
and many of the fires either extinguifhed or fmothercd,
but many remain ftill actually burning. This intelli-
gent author is, however, far from attriburing to all
mountains the fame origin ; and adds, that in that part
of the Alps, which he travelled over, he could obferve
no fuch appearances.

The traces of volcanoes have been obferved in Ire-
land by Mr. Whitehurft. -Though no vifible crater is
remaining between Pore Rum Strand and Bailey Caftle
eaftward, yet, he obferves, that whole fpace, about
twenty Englifh miles, is one continued mafs of lava.
The cliffs, he fays, are truly ilupendous, and bear every
pofuble mark of having been originally liquid fire.
The elevation of that, at the foot of which the Giant's
Cauf^way is fituated, he prefumes cannot be lefs than
five or fix hundred feet perpendicular above the level
of the Atlantic ocean, and yet compofed entirely of
lava j the fame appearances extend towards the fouth
upwards of twenty miies.

The moft remarkable volcanoes in Europe are
j^Etna and Vefuvius, and as thefe are not too far dif-
tant, we have the mod accurate defcriptions of them
from travellers of the firft talents and reputation.

', ./Etna, which is the moft linking object in Sicily,

and Indeed one of the moft magnificent productions

of nature, arifes from an immenie bafc, and mounts

equally on all fides to its fummit. The afcent on

Y 3 each

3^5 Defcription of sEtna. [Book VI.

each fide is computed at about thirty miles, and the
circumference of its bafe, at one hundred and thirty-
three ; but as it has never been meafured with . any
great degree of accuracy, its dimenfions are but imper-
fectly known.

c The whole mountain is divided into three diftinft
regions, called La Regions Cult a y or Piedmcntefe, the
fertile regions j La Regicna byfoofa, or Newer cfa, the
woody region ; and La Regiona Deferta> or Sccperta,
the barren region. Thefe differ as materially both
in clirnat, and production as the three zones of the
earth, and perhaps v/ith equal propriety might have
been filled the torrid, the temperate, and the frigid
zone.

f The frrft region of ./Etna furrounds the bafe of the
mountain, and constitutes ihe mod fertile country in
the wo^ld on all fides of it, to the extent of fourteen
or fifteen miles, where the woody region begins. It
is compofed almoft entirely of lavn, which, in timej
becomes the moft fertile of all foils, but the roads,
which are entirely over old lavas, now converted
into orchards, vineyards, and corn-fields, are execra-
ble. The lavas, which form this region, arife from a
number of beautiful little mountains, every where
fcattered over the immenfe declivities of /Etna. Thefe
are all either of a conical or femifpherical figure, and
are in general covered with beautiful trees, and the
moil luxurious verdure. The formation of them is
owing to the internal fires of ./Etna, which raging for
a vent, at fo vaft a diftance from the great crater that
it cannot poflibly be carried to the height of twelve or
thirteen thoufand feet, which is probably the height
of the fummit of /Etna, muft neceilarily be difcharged
at fome other orifice. After lhaking the mountain,
and its neighbourhood for fome time, at length the

fire

Chap. 47.] Formation of new Mountains. 31"]

fire burfts open its fide, and this is called an eruption.
At nrft it emits only a thick fmoke and fhowers ot
allies. Thefe are follcnved by red hot (tones, and
rocks of a great fize, which are thrown to an immenfe
heitrht in the air. Thefe Hones, together with the
quantities of aihes difcharged at the fame time, form
thole mountains, which cover all the declivities of
./Etna. The fize of them is in proportion to the du-
r.uion of the eruption. When it continues a confider-
ab:e time, it ibmetimes forms an elevation of one
thoufand feet in perpendicular height, which at its
bafe is feven or eight miles in circumference.

' After the formation of the new mountain, the lava
commonly burfts out from its lower fide, and, fweep-
ing every thing before it, is generally terminated by
the fea. Sometimes it iflues from the fide of the
mountain, without th.efe attending circumfbnces,
v/hich is commonly the cafe with the eruptions of Vo
fuvius, in which the elevadon being fo much fmallcr,
the melted matter is carried up into the crater, where
it is diflcdged without forming any new mountain, but
only adding to the height of the old one ; till at length
the lava, rifing near the fummit, burfts the fide of the
crater. But JEtna being upon a much larger fcale,
one crater is not fufikient to give vent to fuch immenfe
oceans of liquid fire.

4 At Nicolofi, which is only twelve miles up the
mountain, the climate appears totally changed. When
the heats at Catania are infupportable, and the harvcft
entirely over, the temperature of the air is moderate
at Nicolofi, and in many places the corn quite green.
Mr. Brydone, in travelling over JEtna, was (truck
with the degree of wijdnefs and ferocity which ap-
peared in the inhabitants of the mountain, and which
reminded him of an obfervation made by the Padre
Y 4 della

328 Mr. Bry dene's Vlfit to Mtna. [Book VI.

della Tore, the hiftoriographer of Mount Vefuviu?,
that in places where the air is mod impregnated with
fulphur and hot exhalations, the people are always mofl:
wicked and vicious. It was with great difficulty he
could perfuade the people of Nicolofi to fufFer his
guide to attend him in the profecution of his refearches.
They were exceflively troublefome, and extremely
fufpicious that his views were directed to the difcovery
of fome hidden treafure, the cnly motive to which
they could afcribe fo fatiguing a journey. At length
one of them recollected having heard many of their
old people fay, that the Englifli had a queen that had
burnt in the mountain for many years pail, and im-
puted the vifits of feveral of that nation to their refpeft
to their deceafed fovereign. Upon enquiring who
this queen was, they faid her name was Anna, that me
was wife to a king who had been a chriftian, but Hie
had made him a heretic, and was condemned to burn
for ever in Mount /Etna. As this could only relate
to the unfortunate Anne Bullen, Mr. Brydone afked if
fhe was the victim alluded to, and whether her hufband
was net iikewife condemned to the fame punimment.
" Certainly," faid the man, " and all his heretic fub-
jects too ; and if you are of that number you need not
be in fuch a hurry to get there, you will be fure of it
at lad."

* The beautiful country of Hybla, in the neighbour-
hood of Nicolofi, after repeated viciffitudes, is now
reduced to a melancholy monument of the fury of
/Etna j it was fo much celebrated for its fertility, and
particularly for its honey, that it was called Mel Pafll,
till it was overwhelmed by the lava of /Etna, and be-
came totally barren, when, by a kind of pun, it ob-
tained the name of Mai Paffi. On a fecond eruption,
however, a fertile mower of ames reftored its. priftine

Chap. 47.] Eruptions <f Mtm. 329

beauty, and its former appellation. But in the dread-
ful eruption of 1669 it was again reduced to the mod
deplorable fteriiity, fince which it is once more known
by the name which denotes its wretchednefs. The
eruption that firft deilroyed this beautiful country,
ifllied from Montpelieri, which it then formed. It
deftroyed a great number of villages and palaces, and
in particular two noble churches, which are extremely
regretted on account of three ftatues, confidcrcd, at
that time, as the mod perfect in the ifland. They have
attempted to recover them, but in vain, nor is it be-
lieved they ever can ; for the churches were builc of
lava, which is fuppofed to melt as foon as it comes into
contact with a torrent of newly erupted matter. Mafia,
a Sicilian author of great credit, affirms, that in Ibme
eruptions of ./Etna, the lava has poured down with fuch
a fudden impetuofity, that, in the courfe of a few-
hours, palaces, churches, and villages, have been en-
tirely melted down, and the whole run off in fufion.
It is however probable, that the impetuous force of
the torrent, rather than its incorporating with the old
mafs, may in many of thefe inftances have occifioned
this devastation. Thus much at leaft is certain, that
if the lava has had any confiderable time to cool, this
Singular effect never happens.

The contraft between the different regions of 7E:n.i
is extremely ftriking. On entering into the romantic
forcds of the Regiona Sylvofa, a new creation feems
to arife. -The air, which before was hot and fultry,
is cool and refrefhing, and every breeze loaded with
deli-clous perfumes from the aromatic plants, with
which the whole ground is covered. Indeed every
beauty, and every horror in nature, feems to be united
on this wonderful mountain, and the mod oppofite
and diffimilar objects are promifcuoufly blended toge-
ther.

330 Defcription ef ' .Etna. [Book VI.

ther. Here we obferve a gulph which threw out tor-
rents of fire, now covered with the mod luxurious
verdure. Delicious fruits arifing from what was but
lately a black and barren rock. Delightful flowers
Covering the earth, the furface of which is but a few
yards removed from lakes cf liquid fire and brimftone.
An immenfe gulph of fire for ever exifling in the
midft of fnows which it has not the power to melt^
and immenfe fields of fnow and ice unceafingly fur-
rounding this gulph of fire; which they have not the
power to extinguifh.

The woody region of ^tna afcends for about eight
or nine miles, and forms a zone of the brighteft green
around the mountain. In this region, near the Sps-
lonca del Capriole, or goats cavern, are two of the in oft
beautiful mountains that adorn the fides of /Etna.
Their hollow craters are each of them confidcribiy
larger than that of Vcfuvius. They are now filled
•with ftately oaks, and covered with the richeft foil to
a great depth. A mountain at fome diftance, which
was formed by an eruption in 1766, was, in 1770, ft ill
on fire ; nor was the lava by any means cold. This
region of ./Etna, like the Regicxe Culta, is compofed of
lava ; but this is now covered with fo deep a layer of
earth, that it is no where to be feen, except, in the
beds of the torrents, in many of which it is worn down
by the water to the depth of fifty or fixty feet, and in
one of them confiderably more. On approaching La
Regisne S coper t a, the trees begin to afliirr.e a wintry
appearance, and every cbjeft indicates the proximity
of barrennefs and eternal froil.

On completely bidding adieu to the vegetable re-
gions, an expanfe of ice prefents itfelf, which is fuffi-
cient to dagger the moft determined refolution. Above
thefe the high fummit of the mountain rears its tre-
mendous

Chap. 47-1 Crater of .-Etna. 331

mendous head, vomiting torrents of thick fmoke. The
difficulty of afeending. this part of the mountain, is
greatly increafed by the uncertainty of a iecure foot-
ing; for the furface of the mountain being hot below,
frequently melts the fnow in particular ipots, and forms
pools of water where it is impoffible to forefee the
danger; fometimes, likewife, it happens that the fur-
face of the water, as well as the fnow, is covered wiih
black afhes, which render it exceedingly deceitful.
At firft the afcent is not fo deep, but it becomes fo by
degrees. In this region are the remains of an ancient
frructure called // Torre del Filcfofdy and fuppofed to
have been built by Empedocles, a native of Agrk'en-
tum, who is faid to have died 400 years before the
chriftian era. His vanity, perhaps, rather than his
philofophy. led him to this elevated fituation. Dcii-
rous of being regarded as a god, he is recorded to
have thrown himielf into the great gulph of /Etnr., in
hopes that the people would imagine he had been
taken up to heaven, and never fuppofing that his
death would be difcovered to mankind. But the
treacherous mountain' threw out his flippers, which,
were of brafs, and announced to the world the fate
of the pretended philofopher, who preferred an airy
fame, which he was beyond the reach cf 'eiipying, to
the folid advantages of exiftence, and who was con-
tent to purchaie the admiration of an ignorant mul-
titude with the meannefs of deceit, and the facrifice of
life*.

Many {Inking remains of the great eruption in 1669
are ftill to be leen, and will long continue as memo-
rials of that dreadful event which overwhelmed Cata-
nia, and all the adjacent country. Tremendous

* See prefent Rate of Sicily and Malta.

earthquakes

33^ Great Eruption cf .Etna. [Book VI.

earthquakes fhook the ifland, and loud fubterraneous
bellowings were heard in the mountain. During
ibme weeks, the fun ceafed to appear, and the day
feemed changed into night. Borelli, who was a wit-
nefs to thefe terrible phenomena, fays, that at length a
rent, twelve miles in length, was opened in the moun-
tain, in fome places cf which, when they threw down
{tones, they could not hear them reach the bottom.
Burning rocks, fixty palms in length, were thrown to
the diftance cf a mile, and leffer ftones were carried
three miles. After the moil violent ftruggles, and a
fhaking of the whole ifland, an immenie torrent of
lava gufhed from the rent, and fprung up into the air
to the heighth. of fixty palms, whence it poured down
the mountain, and overwhelmed every object in its way
in one promifcuous ruin.

This deftru&ive torrent, which burft from the fide
of JEtna an a place called Ricini, rufr.ed irnpetuoufly
againft the ' beautiful mountain of Montpclieri, and
pierced into the ground to a co-nfiderable depth j then
dividing and furrounding the mountain, it united again
on the ibuth fide, and poured defolation upon the ad-
jacent country. The progrefs of the torrent was at
firfl. at the rate of feven miles a day, but in afterwards
took four days to travel fixteen ; wherever it directed
its courfe, the whole appearance of nature was changed,
feveral hills were formed in places which were for-
merly valleys, and a large lake was fo entirely filled up
by the melted mafs, as not to leave a veftige remaining.
In its courfe it defcended upon a vineyard, belonging
to a convent of Jefuits, which was formed upon an
ancient and probably a very thin layer of lava, with a
number of caverns and crevices under it. The liquid
mafs entering into thefe excavations foon filled them
up, and by degrees bore up the vineyard, which in a

fliort;

Chap. 47-1 City overflowed -witl'I.(i-:-i. JjJ

fhort time, to the great aftonifliment of the fpcflators,
began to move away, and was carried by the torrent
to a considerable diftance. In 1770 fome remains or*
this vineyard were ftiil to be Teen, but the greater part
of it was entirely deflroyeci.

In vain did the terrified inhabitants of Catania recur
for protection to the miraculous veil, or expect defence
from the lofty walls of their city. After destroying
ieveral convents, churches, and villages, this fiery
current directed its courfe to Catania, where it poured
impetuoufty over the ramparts, which are near fixty
feet in height, and covered up five of its baftions, with
the intervening curtains. After laying wafte a great
part of this beautiful city, and entirely deftroying
ft vcral valuable remains of antiquity, its further pro-
grefs was flopped by the ocean, over whole banks it
poured its deftructive current. In its courfe from the
rent in the mountain, till its arrival in the fea, it is faid
to have totally deftroyed the property of near thirty
thoufand perfons.

Still however did the infatuated inhabitants of Ca-
tania adhere to the remains of their almoft ruined city,
nor did even the more dreadful calamity with which
they were afterwards vifited, abate their attachment.
Twenty-four years after the fatal eruption of 1669,
a violent earthquake, which extended along all the eaft-
ern coafl, and deftroyed in one hour more than fixty
thoufand perfons, overthrew the remaining buildings
of Catania, and buried a very confiderablc number of.
its inhabitants under the ruins of their houfes and*
churches \ but again the place was rebuilt, a new and
elegant plan was adopted, and the city is now much
handfomer than before. The principal ftreets «
wide, flrait, and well paved with hva. The cathedra),
which was founded in the year 1094, has lufferetl fb

334 Mount Vefaclm. [Book VI*

greatly from earthquakes, that a very fmall'part of the
original ftru&ure remains. The other religious, edifices
are profufcly ornamented, but in a bad tafte.

But if the united effects of attachment to their
native foil, of contempt for dangers to which they are
habituated,, and of confidence in the miraculous veil,
have occasioned the wonderful adherence of the Cata-
nians to this xhngerous fituation from which they have
fo fevcrely fiifferecl, it muft, however, be .confefied,
that they have fometimes derived advantages from
the very, evils which they have fo much reafon to
dread. They were always in great want of a port,
with which they were furnifned by one of thofe ca-
pricious changes which nature fo frequently makes
in this ever varying fpot. A-ftream of lava running
into the fea, formed a mole, which no expence could
have furnifned them with. This advantage, however,
proved but temporary ; there remained for forr.e time
a fafe and commodious harbour, but by a fubfequent
eruption it was entirely filled up and demolifhed.

The celebrated Bi-lhop Berkeley has defcribed an
eruption of Mount Vefuvius, of which he was a
witnefs in the year 1717, and the reader will find
his narrative in die firft volume of Dr. Goldfmith's
Hiitory of the Earth and Animated Nature, p. 94.
But the mod complete and philofophical account of
this mod formidable phenomenon, a volcanic ex-
plofion, is that with which Sir William Hamilton has
favoured the public, in defcribing the late dreadful
eruption of that mountain in 1794; and this I {hall
endeavour to give, as nearly as poflibie, in his own
•words.

+ Sir William begins his narrative with remarking,
that the frequent flight eruptions .of lava for forne

years

Chap. 470 Late Eruption of Vejuvius. 33 *

years paft had ifiued from near the fuinmir, and rar*-
in fmall channels in different directions down the
flanks cf the mountain, and from running in covered
channels, had often an appearance as if they came im-
mediately out cf the fides of Vefuvius, but fuch lavas
had not furncient force to reach the cultivated parts
at the foot of the mountain. In the year 1779, the
whole quantity of the lava in fufion having been at
once thrown up with violence out of the crater of
Vefuvius, and a great part of it failing, and cooling
on its cone, added much to the folidity of the walls of
this huge natural chimney, and had not of late years
allowed of a fufrkient discharge of lava to calm that
fermentation, which by the fubterraneous noifes heard
at times, and by the explofions of fcorioe and aflies,
was known to exiil within the bowels of the volcano ;
fo that the eruptions of late years, before this Jail, were
fimply from the lava having boiled over the crater,
the fides being fufficiently ftrong to confine it, and
oblige it to rife and overflow. The mountain had
been remarkably quiet for feven months before the
late eruption, rfor did the ufual fmoke ilTue from its
crater, but at times it emitted fmall clouds of fmoke
that floated in the air in the fhape of little trees. It
was remarked by the Father Antonio di Pctrizzi, a
capuchin friar (who printed an account of the late
eruption) from his- convent -clofe to the unfortunate
town of 'Torre del Greco, that for fome clays preceding
this eruption, a thick vapour was feen to furround die
mountain, about a quarter of a mile beneath its crater,
and it was obferved by him and others at the fame
time, that both the fun and the moon had often an
unufual reddifh call,

The water of the great fountain at Torre del Greco

began to decreafe fome days before the eruption, fo

8 that

33^ Signs of the Eruption. [Book VI.

that the wheels of a corn-mill, worked by that water,
moved very flowly ; it was neccfiary in all the other
wells of the town and its neighbourhood to lengthen
the ropes daily, in order to reach the water; and
ibine cf the wells became quite dry. Although moft
of the inhabitants were fenfible of this phenomenon,
not one of them feems to have fufpeclied the true
caufe of it. Eight days alfo before the eruption, a
man and two boys, being in a vineyard above Torre
del Greco (and precifely on the fpot where one of the
new .mouths opened, whence the principal current of
Java that deflroyed the town iffued) were much
alarmed by a fjdclen puff of fmoke which iffued from,
the earth clofe to them, and was attended with a flight
explofion.

Had this circumftance, with that of the fubterraneous
ncifes heard at Rdina for two clays .before the eruption
(with the additional one of the decreafe of water
in the wells) been communicated at the time, it
would have required no great forefight to have been .
certain that an eruption of the volcano was near -at
hand, and that its force was directed particularly to-
wards that part of the mountain.

On the 1 2th of June 1794, in the morning, there
•was a violent fall of rain, and foon after the inhabitants
of Refma, fituated directly over the ancient town of
Herculaneum, were fenfible of a rumbling fubterra-
neous noife", which was not heard at Naples.

From the month of January to the month of May, •
the atmofphere had been generally calm, and there was
continued dry weather. In the month of May there
was a little rain, but the weather was unufually fultry.
For fome days preceding the eruption, the Duke della
Torre, a learned and ingenious nobleman, who pub-
liflied two letters upon the fubject of the eruption,

obferved

Chap. 47.] ' Preceded by an Earthquake. 337

obferved by his electrometers, that the atmofphere
was charged in excefs with the electric fluid, and con-
tinued fo for feveral days during the eruption.

About eleven o'clock on the night of the I2th of
June, the inhabitants of Naples were all fenfible of a
violent fhock of an earthquake ; the undulatory motion
•was evidently from eaft to weft, and appeared to have
lafted near half a minute. The fky, which had been
quite clear, was foon after covered with black clouds.
The inhabitants of the towns and villages, which are
very numerous at the foot of Vefuvius, felt this earth-
quake ftill more fenfibly, and fay, that the fhock at
firft was from the bottom upwards, after which fol-
lowed the undulation from eaft to weft. This earth-
quake extended all over the Campagna Felice •, and
the royal palace at Caferta, which is fifteen miles from
Naples, and one of the moft magnificent and folid
buildings in Europe (the walls being eighteen feet
thick) was fhaken in fuch a manner as to caufe great
alarm, and all the chamber bells rang. It was like-
wife much felt at Beneventum, about thirty miles from
Naples ; and at Ariano in Puglia, which is at a much
greater diftance; both theie towns, indeedj have been
-often afflicted with earthquakes.

On Sunday the i5th of June, foofi after ten o'clock
at night, another mock of an earthquake was felt at
Naples, but did not appear to be quite fo violent.as
that of the i2th, nor did it laft fo long; at the fame
moment a fountain of bright fire, attended with a very
black fmoke and a loud report, was feeh to iffue, and
rife 'to a great height, from about the middle of the
cone of Vefuvius; foon after another of the fame
kind broke out at fome little diftance lower down ;
then, as is fuppofed by the blowing up of a covered
channel full of red hot lava, it had the appearance as if
VOL. II. Z the

3 3 8 Awful Dif charge of Volcanic Matter, [ Book V I .

the lava had taken its courfe directly up the deep
cone of the volcano. Frefh fountains fucceeded one
another haftily, and all in a direct line tending, for
about a mile and a half down, towards the towns of
Refma and Torre del Greco. Sir William Hamilton
could count fifteen of them, but believes there were
others obfcured by the fmoke. It feems probable,
that all thefe fountains of fire, from their being in
fuch an exact line, proceeded from one and the fame
Jong nfiiire dov/n the flanks of the mountain, and
that the lava and other volcanic matter forced its way
out of the wideft parts of the crack, and formed
.there the little mountains and craters that will be de-
fcribed in their proper place. It is impoilible that
any defcription can give an idea of the blazing fcene,
or of the horrid noifes that attended this great opera-
tion of nature. It was a mixture of the loudefl
thunder, with inceflant reports, like thofe from a nu-
merous heavy artillery, accompanied by a continued
.hollow murmur, like that of the roaring of the ocean
during a violent ftorm ; and, added to thefe was
another blowing noife, like that of the afcending of a
large flight of fky-rcckets, or that which is produced
by the action of the enormous bellows on the furnace
of the Carron iron foundery in Scotland. The frequent
falling of the huge ilones and fcorise, which were
thrown up to an incredible height from fome of
the new mouths, one of which having been fmce
meafured by the Abbe Tata was ten feet high, and
thirty-five in circumference, contributed undoubtedly
to the concuffion of the earth and air, which kept all
the houfes at Naples for feveral hours in a conftant
tremor, every door and window fhaking and rattling
inceiTantly, and the bells ringing. This was an awful
moment ! The iky, from a bright full moon and ftar-
6 light,

Chap. 47.] Dreadful Conflagration. 339

light, began to be obfcured ; the moon had prefently
the appearance of being in an eclipfe, and foon after
•was totally loft in obfcurity. The murmur of the
prayers and lamentations of a numerous populace
forming various proceffions, and parading v in the
Streets, added to the horror. As the lava did not
appear to have yet a fufficient vent, and it was now
evident that the earthquakes already felt had been
occafioned by the air and fiery matter confined within
the bowels of the mountain, and probably at no fmall
•depth (confidering the extent of thofe earthquakes)
Sir William recommended to the company that was
with him, who began to be much alarmed, rather to
go and view the mountain at Tome greater diftance, and
in the open air, than to remain in the houfe, which
was on the fea fide, and in the part of Naples that is
neareft and moft expofed to Vefuvius. They accord-
ingly proceeded to Pofilipo, and viewed the confla-
gration, now become (till more confiderable, from
the fea-fide under that mountain ; but whether from
the eruption having increafed, or from the loud reports
of the volcanic explofions being repeated by the
mountain behind them, the noife was much louder,
and more alarming than that they had heard in their
firft pofition, at lead a mile nearer to Vefuvius. After
fome time, and which was about two o'clock in the
morning of the 1 6th, having obferved that the lavas
ran in abundance, freely, and with great velocity,
having made a confiderable progrefs towards Refina,
the town which it firft threatened, and that the fiery
vapours which had been confined had now free venl
through many parts of a crack of more than a mile
and a half in length, as was evident from the quantity
-of inflamed matter and black fmoke, which continued
to ifTue from the new mouthi above mentioned,
Z a without

340 Volcanic Electricity. [Book VI.

without any interruption, our author concluded that
at Naples all danger from earthquakes, which had
been his greateft apprehenfion, was totally removed,
and he returned to his former ftation at St. Lucia at
Naples.

All this time there was not the fmallefl appearance
of fire or fmoke from the crater on the fummit of
Vefuvius ; but the black fmoke and afhes ifluing con-
tinually from fo many new mouths, or craters, formed
an enormous and denle body of clouds over the whole
mountain, and which began to give figns of being
replete with the" electric fluid, by exhibiting flames of
that fort of zig-zag lightning, which in the volcanic
language of the country is called ferilliy and which is
the conftant attendant on the mofl violent eruptions.

Sir William Hamilton proceeds to remark, that
during thirty years that he had refided at Naples, and
in which fpace of time he had been witnefs to many
eruptions of Vefuvius, of one fort or other, he never
faw the cloud of fmoke replete with the electric fire,
except in the two great eruptions of 1767, that
of 1779, and during this more formidable one. The
electric fire, in the year 1779, tnat played conftantly
within the enormous black cloud over the crater of
Vefuvius, and feldom quitted it, was exactly fimilar
to that which is produced, on a very {"mall fcale, by
the conductor of an electrical machine communicating
with an infulated plate of glafs, thinly fpread over
with metallic filings, &c. when the electric chatter con-
tinues to play over it in zig-lag lines without quitting
it. He was not fenfible of any noife attending that
operation in 1779 j whereas the difcharge of the
electrical matter from the volcanic clouds during this
eruption-, and particularly the fecond and third days,
cauitd exploficns l!!:e th^le of the loudefl thunder 4

and

Chap. 47.] Sails of Fire. 341

and indeed the dorms raifed evidently by the fole
power of the volcano, refembled in every refpect all
other thunder-ftorms ; the lightning falling and de-
ftroying every thing in its courfc. The houfe of the
Marquis of Berio at St. Jorio, fituate at the foot of
Vefuvius, during one of thefe volcanic florms was
flruck with lightning, which having fhattered many
doors and windows, and damaged the furniture, left
for fome time a ftrong fmell of fulphur in the rooms
it p?{Ted through. Out of thefe gigantic and volcanic
clouds, befides the lightning, both during this eruption
and that of 1779, t^ie author adds, he had, with many
others, feen bails of fire iflue, and fomc of a confi-
dcrable magnitude, which burfting in the air, produced
nearly the fame effect as that from the air-balloons. in
fire-works, the electric fire that came out having the
appearance of the ferpents with which thofe fire-work
balloons are often filled. The day on which Naples
was in the greatefl danger from the volcanic clouds, two
fmall balls of fire, joined together by a fmall link like
a chain- (hot, fell clofe to his Cafino at Pofilipo ; they
feparated. and one fell in the vineyard above the houfe,
and the other in the fea, fo clofe to it that he heard the
fplafh in the water. The Abbe Tata, in his printed
account of this eruption, mentions an enormous ball
of this kind which flew out of the crater of Vefuvius
while he was {landing on the edge of it, and which
burft in the air at fome diftance from the mpuntain,
foon after which he heard a noiie like the fall of a
number of ftones, or of a heavy fliower of hail. Dur-
ing the eruption of the i5th at night, few of the
inhabitants of Naples, from the dread of earthquakes,
ventured to go to their beds. The common people
were either employed in devout proceffions in the
ftreets, or were fleeping on the quays and open places j
Z the

The Crater of Fefuvius open. [Book VI,

the nobility and gentry, having caufed their horfes
to be taken from their carriages, flept in them in the
fquares and open places, or on the high roads juft out
of the towru For feveral da^s, while the volcanic
ftorms of thunder and lightning lafted, the inhabitants
at the foot of the volcano, both on the fea fide and the
Somma fide, were often fenfible of a tremor in the
earth, as well as of the concuffions in the air, but at
Naples only the earthquakes of the iczth and i$th of
June were diftinclly and univerfally felt : this fair city-
could not certainly have refilled, had not thofe earth-
quakes been fortunately of a fhort duration. Through-
out this eruption, which continued in force about ten
days, the fever of the mountain, as has been remarked
in former eruptions, fhowed itfelf to be in fome meafure
periodical, and generally was mofb violent at the break
of day, at noon, and at midnight.

About four o'clock in the morning of the i6th, the
crater of Vefuvius began to Ihow figns of being open,
by fome black fmoke ifluing out of it ; and at day-
break another fmoke, tinged with red, ifluing from
an opening near the crater, but on the other fide of
the mountain, and facing the town of Ottaiano, ill e wed.
that a new mouth had opened there from which a
confi'Jerable ftream of lava iffuvd, and ran with great
velocity through a wood, which it burnt ; and having
run about three miles in a few hours it ftopped before
it had arrived at the vineyards and cultivated lands.
The crater, and all the conical part of Vefuvius, was
foon involved in clouds and darknefs, and fo it re-
mained for feveral days; but above thefe clouds,
although of a great height, frefh columns of fmoke
were feen from the crater, rifing furioufly ftill higher,
until the whole mafs remained in the ufual form of
a pine-tree j and in that gigantic mafs of heavy clouds

die

VOL. II. j>.

Chap. 47-1 fowncf Torre del Greco deftroyed. . 343

the ferilli, or volcanic lightning, was frequently vifible,
even in the day time. About five o'clock in the
morning of the i6th, the lava which had firft broken
out from the feveral new mouths on the ibuth fide of
the mountain, had reached the fea, and was running
into it, having overwhelmed, burnt, and deftroyed the
greateft part of Torre del Greco, the principal ftream
of lava having taken its courfe through the very
center of the town (fee plate II.)*. They obferved
from Naples, that when the lava was in the vineyards
in its way to the town, there iffued often, and in
different parts of it, a bright pale flame, and very
different from the deep red of the lava ; this was oc-
cafioned by the burning of the trees that fupported
the vines. Soon after the beginning of this eruption,
aihes fell thick at the foot of the mountain, all the
way from Portici to the Torre del Greco ; and what
is remarkable, although there were not at that time
any clouds in the air, except thofe of fmoke from the
mountain, the aihes were wet, and accompanied with
large drops of water, which were to the tafte very fait ;
the road, which is paved, was as wet as if there had
been a heavy fhower of rain. Thofe aihes were black
and coarfe, like the fand of the fea-fhore, whereas
thofe that fell there, and at Naples fome days after,
were of a light-grey colour, and as fine as Spanifh,
fnuff, or powdered bark. They contained many fa-
line particles; thofe afhes that lay on- the ground,
cxpofed to the burning fun, had a coat of the whiteft
powder on their furface, which to the tafte was ex-

* This view was taken from a boat on the fea near that town,
about five in the morning of the i6th of June, and whil^ the lava
•was ftill advancing in the fea. The rocks, on which are two figures
near the boat, were formed by a lava that ran into the fea during
a former eruption of Mount Vefuvius.

Z 4 tremely

344 Intenfe Heat of the .Sea Water. [Book VI.

tremely fait and pungent. In the printed account of
the eruption by Emanuel Scotti, doctor of phyfic and
profeffor of philofophy in the univerfity of Naples, he
fuppofes (which appears to be highly probable) that
the water which accompanied the fall of t'he afhes at
the beginning of the eruption, was produced by the
mixture of the inflammable and dephlogifticated
air.

By the time that the lava had reached the fea be-
tween five and fix o'clock in the morning of the T 6th,
Vefuvius was fo completely involved in darknefs, that
the violent operation of nature that was going on there
could no longer be difcerned, and fo it remained for
feveral (Jaysj but the dreadful noife, and the red tinge
on the clouds over the top of the mountain, were evi-
dent figns of the activity of the fire underneath. The
lava ran but flowly at Torre del Greco after it had
reached the fca ; and on the lyth of June in the morn-
ing, its courfe was (lopped, excepting that at times a
little rivulet of liquid fire iflued from under the
fmoking fcorias into the lea, and caufed a hiffing
noife, and a white fmoke ; at other times, a quantity
of large fcorias were pufhed off the furface of the body
of the lava into the fea, difcovering that it was redhoc
under that furface ; and even to the latter end of Auguft
the center of the thickeft part of the lava that covered
the town retained its red heat. The breadth of the
lava that ran into the fea, and formed a new promon-
tory there, after having deftroyed the greateft part of
the town of Torre del Greco, having been exactly
meafured by the duke della Torre, is of Englifh feet
1204. Its height above the fea is twelve feet, and as
many feet under water j fo that its whole height is
twenty-four feet ; it extends into the fea 626 feet.
The fea water was boiling as in a cauldron, where it

w allied

Chap. 47.] 'Temerity of certain Nuns. 345

wafhed the foot of this new formed promontory : and
although our author was at leaft a hundred yards from
it, obferving that the lea fmoked near his boat, he put
his hand into the water, which was literally fcalded ;
and by this time his boatmen obferved that the pitch
from the bottom of the boat was melting faft, and
floating on the furface of the fea, and that the boat
began to leak ; he therefore retired haftily from this
fpot, and landed at ibme diftance from the hot lava.
The town of Torre del Greco contained about 18,000
inhabitants, all of whom (except about 15, who from
either age or infirmity could not be moved, and were
overwhelmed by the lava in their houfes) efcaped
either to Caftel-a-mare, which was the ancient Sta-
biae, or to Naples; but the rapid progrefs of the lava
was fuch, after it had altered its courfe from Refina,
which town it firft threatened, and had joined a frefh
lava that iiTued from one of the new mouths in a vine-
yard, about a mile from the town, that it ran like a
torrent over the town of Torre del Greco, allowing the
unfortunate inhabitants fcarcely time to fave their
lives ; their goods and effects were totally abandoned,
and indeed feveral of the inhabitants, whofe houfes had
been furrounded with lava while they remained in
them, efcaped from them, and faved their lives the
following day, by coming out of the tops of their
houfes, and walking over the fcoriae on the furface of
the redhot lava. Five or fix old nuns were taken out
of a convent in this manner, on the i6th of June, and
carried over the hot lava ; their ftupidity was fuch, as
not to have been the leaft alarmed, or fenfible of their
danger : one of upwards <rf ninety years of age was
found attualiy warming herfelf at a point of redhot
hva, which touched the window of her cell, and which

flic

346 BfUs deprived of their "torn. [Book VI.

Ihe iaid was very comfortable ; and though now ap-
prized of their danger, they were ftill very unwilling
to leave the convent, in which they had been fhut up
almoft from their infancy, their ideas being as limited
as the fpace they inhabited. Having been defired to
pack up whatever they had that was moft valuable,
rhey all loaded themfelves with bifcuits and fweet-
meats, and it was but by accident it was difcovered
that they had left a fum of money behind them, which
was recovered for them.

The lava pafied over the center and beft part of
the town j no part of the cathedral remained above
it, except the upper part of a fquare brick tower, in
which were the bells ; and it is a curious circumftance,
that thole bells, although they were neither cracked
nor melted, were deprived of their tone as much as if
they had been cracked. When the lava firft entered
the fea it threw up the water to a prodigious height ;
and particularly when two points of lava met and in-
clofed a pool of water, that water was thrown np with
great violence, and a loud report : at this time, as well
as the day after alfo, a great many boiled fifn were feen
floating on the fur face of the fea.

The lava over the cathedra!, and in other parts of
the town, is faid to be upwards of forty feet in thick-
rrefs; the general height of the lava during its whole
courfe was about twelve feet, and in fome parts not
lefs than a mile in breadth.

When Sir William Hamilton vificcd it on the lyth
of June, the tops of the houfes were juft vifible here
and there in fbme parts, and the timbers within ftill
burning caufed a bright flame to iffue out of the fur-
face 3 in other parts, the fulphur and falts exhaled in a
white fmoke from the lava, forming a white or yellow
cruft on the fcorix round the fpots where it iffued with

tke

Chap, 47.] Infiauce of temerity. 347

the greateft force. He often heard little explofions,
and faw that they blew up, like little mines, fragments
of the fcorise and afhes into the air; thefe he fuppofes
to have been occafioned either by rarefied air in con*
fii.ed cellars, or, perhaps, by fmall portions of gun-
powder taking fire, as few in that country are without
a gun and fome little portion of gunpowder in their
houfes. As the church feafts there are ufually attended
with fireworks and crackers, a firework-maker of the
town had a very great quantity of fireworks ready-
made for an approaching feaft, and fome gunpowder,
all of which had been fhut up in his houfe by the lava,
a part of which had even entered one of the rooms ,
yet he actually laved all his fireworks and gunpowder
fome days after, by carrying them fafely over the fco-
rias of the lava, while it was redhot underneath. The
heat in the ftreets of the town, at this time, was fo
great as to ftiife the thermometer to very near one
hundred degrees, and dole to the hot lava it rofe much
higher. Sir William remarked in his way home, that
there was a much greater quantity of the petroleum
floating on the furface of the fea, and diffufing a very
ftrong and offenfive fmcll, than was ufual ; for at all
times in calms, patches of this bituminous oil are to
be feen Moating on the furface of the fea between Por-
tici and Naples, and particularly oppofite a village
called Pietra Bianca. The minute afhes continued
falling at Naples j and the mountain, totally obfcured
by them, continued to alarm the inhabitants with re-
peated loud explofions.

On Wednefday June 18, the wind having for a mort
fpace of time cleared away the thick cloud from the
top of Vefuvius, it was now difcovered that a great
part of its crater, particularly on the weft fide oppofite
Naples, had fallen in, which it probably did about four

o'clock

348 Immenfe Volume of Vapour. [Book VI.

o'clock in the morning of that day, as a violent mock
of an earthquake was felt at that moment at Refma,
and other parts fituate at the foot of the volcano. The
clouds of fmoke, mixed with the afhes, were of fuch a
denfityas-to appear to have the greateft difficulty in
forcing their paffage out of the now widely extended
mouth of Vefuvius, which, fince the top fell in, is de-
fcribed as not much fhort of two miles in circumfe-
rence. One cloud heaped on another, and fucceeding
one another inceflantly, formed in a few hours fuch a
gigantic and elevated column of the darkeft hue over
the mountain, as feemed to threaten Naples with im-
mediate deflruclion, having at one time been bent over
the city, and appearing to be much "too mafllve and
ponderous to remain long fufpended in the air ; it was,
befides, replete with the ferilli, or volcanic lightning,
which was ftronger than common lightning, juft as
Pliny the younger defcribes it in one of his letters to
Tacitus, when he fays fulgoribus ill<e et fimiles et majores
erant*. (See plate III.)

Vefuvius was at this time completely covered, as
were all the old black lavas, with a thick coat of thofe
fine light-grey afhes already fallen, which gave it a
cold and horrid appearance ; and in comparifon of the
abovementioned enormous mafs of clouds, which cer-
tainly, however it may contradict our idea of the ex-
tenfion of our atrnofphere, rofe many miles above thq

» This view was taken from Naples, and gives a very good idea
of the appearance of Mount Vefuvius, like a molehill, in compa-
rifon of the enormous mafs that hung over it.— The black lines
{how the form of the top of Vefuvius, as it was before this erup-
tion, and when the crater was only the width of the upper line.
On the fide of the mountain is reprefented the fpot whence the lava
firft iffued on the i$th of June, with its courfe to Torre del Greco
and the fca.

mountain.

Chap. 47-] for rents of Mud. 349,

mountain, it appeared like a molehill, although the
perpendicular height of Vefuvius, from the level of the
fea, is more than three thoufand fix hundred feet. The
abbe Braccini, as appears in his printed account of
the eruption of Mount Vefuvius in 1 63 1 , meafured
with a quadrant the elevation of a mafs of clouds of
the fame nature, which was formed over Vefuvius dur-
ing that great eruption, and found it to exceed thirty-
miles in height. Dr. Scotti, in his printed account
of this eruption, fays, that the height of this threat-
ning cloud of fmoke and allies, meafured from Naples,
was found to be, of an elevation of thirty degrees.

The ftorrr.. cf thunder and lightning, attended at
times with heavy falls of rain and afhes, caufing the
moft deftruclive torrents of water and glutinous mud,
mixed with huge ftones, and ..trees torn up by the
roots, continued more or lefs to afflift the inhabitants
on both fides of the volcano until the yth of July,
when the laft torrent deftroyed many hundred acres of
cultivated land, between the towns of Torre del Greco
and Torre dell' Annunziata. Some of thefe torrents,
both on the fea fide and the Somma fide of the moun-
tain, came down with a horrid rufhing noife; and
fome of them, after having forced their way through
the narrow gullies of the mountain, rofe to the height
of more than twenty feet, and were near half a mile in
extent. The mud, of which the torrents were com-
pofed, being a kind of natural mortar, completely cafed
up and ruined fome thoufand acres of rich vineyards ;
for it foon becomes fo hard, that nothing lefs than a
pickaxe can break it up.

The laudable curiofityof our author induced him to
go upon Mount Vefuvius, as foon as it was confident
with any degree of prudence, which was not until the
joth of June, and even then it was attended with fome

riik.

350 Ruined State of the Country. [Book VI.

rifle. The crater of Vefuvius, except at fhort inter-
vals, had been continually obfcured by the volcanic
clouds from the i6th, and was fo on that day, with
frequent flashes of lightning playing in thofe clouds,
and attended as ufual with a noife like thunder ; and
the fine afhes were ftill falling on Vefuvius, but ftill
,more on the mountain of Somma. Sir William went
up the ufual way by Refina, and obferved, in his way
through that village, that "many of the ftones of the
pavement had been loofened, and were deranged by
the earthquakes, particularly by that of the 1 8th, which
attended the falling in of the crater of the volcano, and
which had been fo violent as to throw many people
down, and obliged all the inhabitants of Refma to quit
their houfes haftily, to which they did not dare return
for two days. The leaves of all the vines were burnt
by the afhes that had fallen on them, and many of the
vines themfelves were buried under the afhes, and
great branches of the trees that fupported them had
been torn off" by their weight. In fhort, nothing but
ruin and defolation was to be feen. The afhes at the
foot of the mountain were about ten or twelve inches
thick on the furface of the earth, but in proportion as
he afcendcd, their thicknefs increafed to feveral feet,
not lefs than nine or ten in feme 'parts ; fo that the fur-
face of the old rugged lavas, that before was almoft
impracticable, was now become a perfect plain, over
which he walked with the greatefl eafe. The afhes
were of a light-grey colour, and exceedingly fine, fo
that by the footfteps being marked on them as on
fnow, he learnt that three fin all parties had been up
before him. He faw likewife the track of a fox,
which appeared to have been quite bewildered, to
judge from the many turns he had made. Even the
traces of lizards and other little animals, and of in-

fedtsj

Chap. 47.] Ntw formed Mounfatots. 351

fe<5ts, were vifible on thefe fine allies. Sir William
and his companion afcended to the fpot whence the
lava of the i5th firft iffued, and followed the courfe
of it, which was ftill very hot (although covered with
fuch a thick coat of aflies) quite down to the fea at
Torre del Greco, which is more than five miles. Ic
was not pofiible to get up to the great crater of Vefu-
vius, nor had any one yet attempted it. The horrid
chafms that exifted from the fpot where the late erup-
tion firft took place, in a (Irak line for near two miles
towards die fea, cannot be imagined. They formed
vallies more than two hundred feet deep, and from
half a mile to a mile wide; and where the fountains of
fiery matter exifted during the eruption, were little
mountains with deep craters. Ten thoufand men, in
as many years, could not make fuch an alteration on
the face of Veilivius. Except the exhalations of ful-
phureous and vitriolic vapours, which broke out from
different fpots of the line above mentioned, and tinged
the furface of the afties and fcorise in thofe parts with
either a deep or pale-yellow, with a reddim ochre
colour, or a bright white, and in fome parts with a
deep green and azure blue (fo that the whole toge-
ther had the effedb of an iris) all had the appearance of
a fandy defart. Our adventurers then went on the
top of feven of the moft confiderable of the new-
formed mountains, and looked into their craters, which,
on fome of them appeared to be little fhort of half a
mile in circumference ; and although the exterior per-
pendicular height of any of them did not exceed two
hundred feet, the depth of their inverted cone within
was three times as great. It would not have been
poflible to have breathed on thefe new mountains near
their craters, if they had not taken the precaution of
tying a doubled hankerchief over, their mouths and

noftrils ;

3 $2. Volcanic Whirlwinds. [Book VI.

noftrils ; and even with that precaution they conlJ .^ot
refill: long, the fumes cf the vitriolic acid were fo ex-
ceedingly penetrating, and of fuch a fuffoca,ting qua-
lity. They found in one a double crater, like two
funnels joined together j, and in all there was fome lu>
tie fmoke and depofitions of falts and fulphurs, of the
various colours abovementioned, juft as is commonly
feen adhering to the inner walls of the principal crater
of Vefuvius.

Two or three days after they had been there, one
of the -new mouths, into which they had looked, fud-
denly made a great explofion of flones, fmoke, and
afhes, which would certainly have proved fatal to any
one who might unfortunately have been there at the
time of the explofion. We read of a fimilar accident
having proved fatal to more than twenty people, who
had the curiofity to look into the crater of the Monte
Nuovo, near Puzzuoli, a few days after its formation,
in the year 1538. The ifth of Auguft, Sir William
faw,a fudden explofion of fmoke and ames thrown to
an extreme height out of the great crater of Vefuvius,
that muft have deftroyed any one within half a mile
of it ; and yet on the 1 9th of July a party not only
had vifited that crater, but had delcended 170 feet
within it. While they were on the mountain, two
vhirlwinds, exactly like thofe that form water-fpouts
at fea, made their appearance; and one of them, which
was very near, made a ftrange milling noife, and hav-
ing taken up a great quantity of the fine afhes, formed
them into an elevated fpiral column, which, with a
whirling motion and great rapidity, was carried towards
the mountain of Somma, where it broke and was dif-
perfed. One of our author's fervants, employed in
collecting of fulphur, or fal ammoniac, which cryftal-
lizes near the fumaroli, as they are called (and which

are

Chap. 47.] New -formed Craters. 353

are the fpots whence the hot vapour iflues out of the
frefh lavas) found, to his great furprize, an exceeding
cold wind iffue from a fiffure v?ry near the hot fuma-
roli upon his leg. In a vineyard not in the fame line
with the new-formed mountains juft described, but in
a right line from them, at the diftance of little more
than a mile from Torre del Greco, they found three or
four more of thefe ne \v-to nned mountains with craters,
out of which the lava flowed, and by uniting with the
ftreams that came from the higher mouths, and add-
ing to their heat and fluidity, enabled the whole cur-
rent to make fo rapid a progrefs over the unfortunate
town, as fcarcely to allow its inhabitants fufficient time
to efcape with their lives. The rich vineyards be-
longing to the Torre del Greco, and which produced
the wine called Ladrima Chrifti, that were buried,
and totally deftroyed by this lava, confided of more
than three thoufand acres ; but the deftru&ion of the
vineyards by the torrents of mud and water, at the
foot of the mountain of Somma, was much more
extenfive.

In that part of the country, the firft figns of a torrent
that our author met with, was near the village of the
Madonna dell' Arco, and he pafied feveral others be-
tween that and the town of Ottaiano j one near Tro-
chia, and two near the town of Somma, were the
moft confiderable, and not lefs than a quarter of a
mile in breadth •> and, according to the teftimony of eye-
witnefles, when they poured down from the mountain
of Somma, they were from twenty to thirty feet high j
the matter of thefe torrents was a liquid glutinous mud,
compofed of fcorise, afhes, ftone§ (fome of an enormous
fize) mixed with trees that had been torn up by the
roots. Such torrents, as it may well be imagined, were
irrefiftible, and carried off every thing before them ;
VOL. II. A a houfes,

354 Immenfe Quantity of AJfyes. [Book VI.

houfes, walls, trees, and not lefs thin four thoufand
fheep and other cattle. At Somma., a team of eight
oxen, which were drawing a large timber tree, were at
once Carried off, and never were heard of more.

The appearance of thefe torrents was like that of
all other torrents in mountainous countries, except
that what had been mud was become a perfect cement,
on which nothing lefs than a pickaxe could make any
isnprcffion. The vineyards and cultivated lands were
here much more ruined ; and the limbs of the trees
much more torn by the weight of the afhes, than thofe
which have been already defcribed on the fea fide of
the volcano.

The abbe Tata, in his printed account of this erup-
tion, has given a good idea of the abundance, the great
weight, and glutinous quality of thefe allies, when he
fays, that having taken a branch from a fig-tree ftill
ftanding near the town of Somma, on which were only
fix leaves, and two little unripe figs, and having
weighed it with the afhes attached to it, he found it to
be thirty-one ounces j when having wafhed off the
volcanic matter, it fcarely weighed three.

In the town of Somma, our author found four
churches and about feventy houfes without roofs, and
full of afhes. The great damage on that fide of the
mountain, by the fall of the afhes and the torrents,
happened on the i8th, I9th, and loth of June, and on
the 1 2th of July. The ,i 9th, the afhes fell fo thick at
Somma, that unlefs a perfon kept in motion, he was
foon fixed to the ground by them. This fall of afhes
was accompanied alfo with loud reports, and frequent
flafhes of the volcanic lightning, fo that, furrounded by
fo many horrors, it was impoffible for the inhabitants
to remain in the town, and they all fled j the darknefs
was fuch, although it was mid- day, that even with the

help

Chap. 47.] Olfcrvatims on the Great Crater. 355
help of torches it was fcarcely poffible to keep in the
high road. On the i6th of July, fignor Guifeppe
Sacco went up to the crater, and, according to his
account, which has been printed at Naples, the crater
is of an irregular oval form, and as he fuppofes (not
having been able to meafure it) of about a mile and
a half in circumference ; the infide, as ufual, in the
fhape of" an inverted cone, the inner walls of which
on the eaftern fide are perpendicular} but on the
weftern fide of the crater, which is much lower, the
defcent was practicable, and Sacco with fome of his
companions actually went down one hundred and
feventy-fix palms, from which fpot, having lowered
a cord with a (tone tied to it, they found the whole
depth of the crater to be about five hundred palms.
But fuch obfervations on the crater ofVefuvius are
of little confequence, as both its form and apparent
depth are fubjeft to great alterations from day to day.

The 22d of July, one of the new craters, which is
the neareft to the town of Torre del Greco, threw up
both fire and fmoke, which circumftance, added to
that of the lava's retaining its heat much longer than
ufual, feemed to indicate that there was ftill fome
fermentation under that part of the volcano. The
lava in cooling often cracks, and caufes a loud explo-
fion, juft as the ice does in the glaciers in Swificrland ;
fuch reports were frequently heard at this time at the
Torre del Greco ; and a vapour was often feen to ifiue
from the body of the lava, and taking fire in air, fall
like thofe meteors vulgarly called falling flars.

-The darkncfs occafioned by the fall of the afhes in
the Campagna Felice extended itfelf, and varied, ac-
cording to the prevailing winds. On the I9th of
June it was fo dark at Caferta, which is fifteen miles
from Naples^ as to oblige the inhabitants to light can-
A a 2 dies

3-56 Curious Phenomena at Sienna. [Book Vf .

dies at mid-day; and one day, during the eruption, the
darknefs fpread over Beneventum, which is thirty miles
from Vefuvius.

The archbiiliop of Taranto, in a letter to Naples,
and dated from that city the i8th of June, obferves,
* We are involved in a thick cloud of minute volcanic
allies, and we imagine that there muft be a great erup-
tion either at Mount Etna, or of Stromboli.' The
bifhop did not fufpecl: their having proceeded from
Vefuvius, which is about two hundred and fifty miles
from Taranto. Afhes alfo fell, during the late erup-
tion, at the very extremity of the province of Lecce,
which is ftill farther off; at Martino, near Taranto,
a houfe was ftruck and much damaged by the light-
ning from one of the clouds. In the accounts of the
great eruption of Vefuvius in 1631, mention is made
of the extenfive progrefs of the afhes from Vefuvius,
and of the damage done by the ferilli, or volcanic
lightning, which attended them in their courfe.

Our author in this place mentions a very extraordi-
nary circumftance, which happened near Sienna, on
the Tufcan ftate, about eighteen hours after the com-
mencement of the late eruption of Vefuvius on the
1 5th of June, although he adds, that phenomenon
muft have no relation to the eruption; it was com>
municated to him in the following words by the earl
of Briftol, bifhop of Derry, in a letter dated from
Sienna, July 12, 1794: ' In the midft of a moft
violent thunder- ftorm, about a dozen ftones of various-
weights and dimenfions fell at the feet of different
people, men, women, and children ; the ftones are of
a quality not found in any part of the Siennefe terri-
tory ; they fell about eighteen hours after the enormous
eruption of Vefuvius, which circumftance leaves a
choice of difficulties in the folution of this extraor-
dinary

Chap. 47.] torrent of Mud. 357

dinary phenomenon : either thefe ftones have been
generated in this igneous mafs of clouds, which pro-
duced fuch imufual thunder, or, which is equally in-
credible, they were thrown from Vefuvius at a dif-
tance of at leaft two hundred and fifty miles; judge
then of its parabola.' One of the largeft ftones, when
entire, weighed upwards of five pounds. The outfide
of every ftone that was found, and afcertained to have
fallen from the cloud near Sienna, was evidently frefhly
vitrified, and black, having every fign of having pafied
through an extreme heat ; when broken, the infide
was found of a light-grey colour mixed with black
fpots, and fome mining particles, fuppofed to be
pyrites. Stones of the fame nature, at kail as far as
the eye can judge of them, .are frequently found on
Mount Vefuvius ; and mould fimilar ftones be found
there, with the fame vitrified coat on them, the
queftion would be decided in favour of Vefuvius,
unlefs it could be proved that there had been,
about the time of the fall of thefe ftones in the
Siennefe territory, fome nearer opening of the earth>
attended with an emifiion of volcanic matter, which
might very poffibly happen, as the mountain of Radico-
fani, within fifty miles of Sienna, is certainly volcanic.
The celebrated father Ambrogio Soldani, profefibr of
mathematics in the univerfity of Sienna, has printed
there a diflertation upon this extraordinary pheno-
menon ; wherein, it is faid, he has decided that thofe
ftones were generated in the air independently of vol-
canic affiflance.

Until after the yth of July, when the laft cloud
broke over Vefuvius, and formed a tremendous torrent
of mud, which took its courfe acrofs the great road
between Torre del Greco and the Torre dell'Annun-
£iata, and deftroyed many vineyards, the eruption
A a 3 could

358 Mephitic Vapours [Book VI.

coul'd not be faid to have finimed, although the force
of it was over the 22d of June. The power of
attraction in mountains is well known ; but whether
the attractive power of a volcanic mountain is greater
than that of any other mountain, is a queftion. Dur-
ing this eruption, however, it appeared that every
watery clcud was evidently attracted by Vefuvius, and
the fudden diflblution of thofe clouds left marks of
their dcftructive power on the face of the country all
round the bafis of the volcano. After the mouth of
Vefuvius was enlarged, our author fays he has feen
a great cloud pafling over it, and which not only was
attracted, but was fucked in, and difappeared in a mo-
ment.

After every violent eruption of Mount Vefuvius,
we read of damage done by a mephitic vapour, which
coming from under the ancient lavas, infmuates itfelf
into low places, fuch as the cellars and wells of the
houfes fituate at the foot of the volcano. After the
eruption of 1767, there were feveral inftances, as in
this, of people going into their cellars at Portici, and
other parts of that neighbourhood, having been ftruck
down by this vapour, and who would have expired if
they had not been haftily removed. Thefe occafional
vapours, or mofete, are of the fame quality as that
permanent one in the Grotta del Cane, near the lake
of Agnano, and which has been proved to be chiefly
fixed air. The vapours, that in the volcanic language
of Naples, are called fumaroli, are of another na-
ture, and iffue from fpots all over the frefh and hot
lavas while they are cooling ; they are fulphureous
and fo fuffocating, that often the birds which are
flying over them are overpowered, and fall down
dead. Thefe vapours depofit a cruft of fulphur, or
fains, particularly of fal ammoniac, on the fcorise of
I the

Chap. 47.] produced by the Volcano.

the lava through which they pafs ; and the fmall cryf-
tals of which they are compofed are often tinged with
deep or pale yellow, with a bright red like cinnabar,
and fometimes with green, or an azure blue. After
the late eruption, many pieces of the fcoriae of the
frefh lava were found powdered with a lucid fubftance,
exactly like the brighter! fteel or iron filings.

The firft appearance of the mofete, after the late
eruption, was on the iyth of June, when a peafant
going with an afs to his vineyard, a little above the
village of Refma, in a narrow hollow way, the afs
dropped down, and feemed to be expiring; the pea-
fane was foon fenfible of the mephitic vapour himfelfj
and well knowing its fatal effects, dragged the animal
out of its influence and it foon recovered. This
heavy vapour, when expofed to the open air, does
not rife much more than a foot above the furface of
the earth, but when it gets into a confined place, like
a cellar or well, it rifes and fills as any other fluid
would j having filled a well, it rifes above it about
a foot high, and then bending over, falls to the earth,
on which it fpreads, always preferving its ufual level.
Wherever this vapour iffues, a wavering in the air is
perceptible, like that which is produced by the burning
of charcoal ,• and when it iffues from a fifTure near
any plants or vegetables, the leaves of thofe plants
are feen to move, as if they were agitated by a gentle
wind. It is extraordinary, that although there doea
not appear to be any poifonous quality in this vapour,
which in every refped refembles fixed air, it fhould
prove fo very fatal to the vineyards, fome thoufand
acres pf which were deitroyed by it after the late
eruption : when it penetrates to the roots of the vines,
it dries them up, and kills the plant. A peafant in,
the neighbourhood of Refma, having fuffered by the
A a 4 mofete,

360 Animals killed by Mofete. [Book VI.

mofete, which deflroyed his vineyards in the year
1767, and having obferved then that the vapour fol-
lowed the laws of all fluids, made a narrow deep
ditch all round his vineyard, which communicated
wijih ancient lavas, and alfo with a deep cavern under
one of them; the confequence of his well planned
operation was, that although furrounded by thefe
noxious vapours, which lay constantly at the bottom
of his ditch, they never entered his vineyard^ and his
vines were in a flourifhing flate, while thofe of his
neighbours were perifhing. Upwards of thirteen
hundred hares, and many pheafants and partridges,
overtaken by this vapour, were found dead within his
Sicilian majefty's referved chafes in the neighbourhood
of Vefuvius j and alfo many domeftic cats, who in
their purfuit after this game fell victims to the mofete.
A fhoal of fifh, of feveral hundred weight, having been
obferved by fome fifhermen at Refina in great agita-
tion on the furface of the fea, near fome rocks of an
ancient lava that had run into the fea, they furrounded
them with their nets, and took them all with eafe, and
afterwards difcovered that they had ' been flunned by
the mephitic vapour, which at that time ifllied forcibly
from underneath the ancient lava into the fea.

The account of Sir William Hamilton is concluded
by two remarks, which as they are curious I fhall
infert :

i. Within a mile of Caftel-a-mare, the mofete were
flill very active (on Sept. 2.) and particularly under
the fpot where the ancient town of Stabia was fituated.
The 2^.th of Auguft, a young 'lad by accident falling
into a well there that was dry, but full of the mephitic
vapour, was immediately fuffbcatedj there were no
ilgns of any injury from the fall, as the well was
fhallow. This circumftance called to our author's

mind

Chap. 47.] Death of the elder Pliny. 361

mind the death of the elder Pliny, who moft probably
Joft his life by the fame fort of mephitic vapours, on
this very fpot, and which are active after great erup-
tions of Vefuvius.

2. Mr. James, a Britifh merchant, afiured our au-
thor, that on Tuefday night, the iyth of June, which
was the third day of the eruption of Mount Vefuvius,
he was in a boat with a fail, near Torre del Greco,
when the minute afhes, fo often mentioned, fell thick ;
and that in the dark they emitted a pale light like phof-
phorus, fo that his hat, thofe of the boatmen, ancj
the part of the fails that were covered with afhes, were
luminous. Others had mentioned having feen a
phofphoric light on Vefuvius after this eruption j but
until it was confirmed to him by Mr. James,, he did
not chufe to fay any thing about it *.

* See Phil. Tranf. for 1795, p. 73 , &c.

[Book VI*

CHAP.

EARTHQUAKES.

Connexion between Earthquakes and Volcanoes. — Earthquakes caufed
ky the Prugrefs of Steam between the Strata of the Earth. — Signs of
approaching Earthquakes. — Great Earthquake at Lijlon, in 1755.
—Earthquakes in Calabria, in 1783.

TH E ftidden explofions which take place from
volcanoes, probably depend on the accefs of
a quantity of water, which enters through fome fiffure
communicating with the fea, or which is derived from
other fources in the earth. If this mafs of water is
lufficiently great, it will extinguifh the volcano j if not,
it will be converted into fleam, the expanfive force of
•which far exceeds that of gun-powder. The elaftic
fluid, thus formed, either finds vent at the mouth of
the volcano, or, if the fuper-inciimbent weight fhould
be too great, it will force a pafiage between the ftrata
of the earth, and occafion that undulatory but fome-
times violent motion which is called an earthquake.
From various facts demonftrative of the cohefion and
elafticity of bodies, we are warranted in concluding,
that the different ftrata of which the earth is com-
pofed will adhere together, and that a freer paflage
will be afforded to any intervening body between the
flrata than directly through them. If the confined
fire ads directly under a province or town, it will
heave the earth perpendicularly upwards, and the
mocks will be more fudden and violent. If it acts
at a diftance, it will raife that tract obliquely, and
the motion will be more oblique, undulatory, and
tremulous.

The

Chap. 48.] Caufe of Earthquakes. 363

The great earthquake at Lifbon, in 1755, was felt
as far as Scotland, and from the phenomena which
attended it, it was evident that the ground had a wavr-
ing motion from fouth to north. All the oblong
lakes, that lay from north to fouth, were much agi-
tated, the wave commencing at the fouth end, whilft
all other lakes which lay acrofs, from eaft to weft, were
much lefs affected.

The great diftance to which earthquakes extend
depends on the compreflibility and elafticity of the
earth, which may be underftood from the vibration of
the walls of houfes, occafioned by the patting of car-
riages in the adjacent flreets. Another inftance is
the vibration of fteeples by the ringing of bells or
gufts of wind. The Eddiftone lighthoufe often vi-
brates from the force of the waves which beat againft
its foundation.

Previous to an eruption of Vefuvius the earth al-
ways trembles, and fubterraneous explofions are heard.
On. the ift of November, 1755, tne era fo fatal to
Lifbon, the ifland of Madeira was violently maken by
an earthquake, accompanied with fubterraneous ex-
plofions. So thoroughly convinced, indeed, are the
inhabitants of volcanic countries of the connection
between earthquakes and volcanoes, that when a great
eruption takes place from a volcano, they congratulate
themfelves on having efcaped an earthquake.

Earthquakes as well as volcanic eruptions are al-
ways preceded by a violent agitation of the fea. Pre-
vious to the breaking out of Vefuvius, the fea retires
from the adjacent mores till the mountain is burn:
open, and then it returns with fuch impetuofity as
to overflow its ufual boundary. About an hour after
the firft mocks, which alarmed the city of Lifbon
in 1755, the fea was obferved to come rufhing to-
wards

364 Caaf* tf Earthquakes . [Book VI.

wards the city like a torrent, though againft both
wind and tide ; it rofe forty feet higher than was ever
known, and as fuddenly fubfided. A {hip, fifty leagues
off at fea, received fo violent a fhock as greatly to
injure the deck, &c. The fame effect was obferved
at Cadiz, and at a number of ports throughout the
Mediterranean, and, indeed, more or lefs, all over
Europe.

That earthquakes are the effect of (learn generated
within the bowels of the earth, and that they are pro-
duced in the manner which has been defcribed, ap-
pears highly probable from the quantities of fteam and
boiling water which have occafionally been thrown up
by volcanoes in different parts of the world. In 1631
and 1698 van: torrents of boiling water flowed from
the crater of Vefuvius, previous to the eruption of
fire: and what was, perhaps, ftill more remarkable,
many fpecies of fea-fhells, in a -calcined ftate, were
found on the brink of the crater, and alfo in the chan-
Tiel formed by the flood. The fame thing happened
at yEtna, in 1755* when a dreadful torrent of boiling
water flowed from the crater at the time of an eruption
of fire. Sir William Harru'hon ob.feryes, that the fea-
jhells emitted along with the water clearly indicate a
communication with the fea. All warm fprings pro-
bably receive their heat from the action of pyrites,
near which the water paffes.

The following account of the great Lifbon earth-
quake is extracted from a volume of letters, publifhed
a few years ago by the reverend Mr. Davy :

* There never was a finer morning feen than the
firft of November (1755); the fun (hone out in its
full luftre; the whole face of the iky was perfectly
ferene and clear, and not the leaft fignal or warning of
that approaching event* which has made this once flou?

rifhing.

Chap. 48.] Earthquake at Lijbon. 365

jsifhing, opulent, and populous city, a fcene of the ut-
moft horror and defolation, except only fuch as ferved
to alarm, but fcarcely left a moment's time to fly from
the general deftrudion.

' It was on the morning of this fatal day, between
the hours of nine and ten, that I was fat down in
my apartment, juft finifhing a letter, when the papers
and table I was writing on began to tremble with a
gentle motion, which rather furprized me, as I could
not perceive a breath of wind ftirring ; whilil I was
reflecting with myfelf what this could be owing to,
but without having the leaft apprehenfion of the real
caule, the whole houfe began to make from the very
foundation, which at firft I imputed to the rattling of
feveral coaches in the main ftreet, which ufually pafied
that way, at this time, from Belem to the palace; but
on hearkening more attentively, I was foon undeceived,
as I found it was owing to a flrange frightful kind of
noife under ground, refembling the hollow diftant
rumbling of thunder; all this patted in lefs than a
minute, and I mud confefs 1 now began to be alarmed,
as it naturally occurred to me, that this noife might
pofiibly be the forerunner of an earthquake, as one I
remembered, which had happened about fix or feven
years ago, in the Ifland of Madeira, commenced in
the fame manner, though it did little or no da-
mage.

' Upon this I threw down my pen, and darted upon
my feet, remaining a moment in iufpenfe, whether I
mould flay in the apartment, or run into the ftreet, as
the danger in both places feemed equal ; and Mill flat-
tering myfelf that this tremor might produce no other
effects than fuch inconfiderable ones as had been felt
at Madeira j but in a moment I was roufed from my
jdream, being inftantly ftunned with a mbft horrid

cram,

3 66 Great Earthquake [Book VI,

cram, as if every edifice in the city had tumbled down
at once. The houfe I was in (hook with iuch violence,
that the upper ftories immediately fell, and though my
apartment (which was the firft floor) did not then
lhare the fame fate, yet every thing was thrown out of
its place in fuch a manner, that it was with no fmall
difficulty I kept my feet, and expected nothing lefs
than to be foon crufhed to death, as the walls conti-
nued rocking to and fro in the frightfulleft manner,
opening in feveral places, large ftones falling down on
every fide from the cracks, and the ends of moft of
the rafters darting out from the roof. To add to this
terrify ing fcene, the fky in a moment became fo gloomy,
that I could now diftinguifh no particular object;
it was an Egyptian darknefs indeed, fuch as might be
felt; owing, no doubt, to the prodigious clouds of
duft and lime, raifed from fo violent a concufiion,
and as fome reported, to fulphureous exhalations, but
this I cannot affirm; however, it is certain I found
myfelf almoft choaked for near ten minutes.

' As foon as the gloom began to difperfe, and the
violence of the fhock feemed pretty much abated, the
firft object I perceived in the room was a woman fit-
ting on the floor, with an infant in her arms, all co-
vered with duft, pale and trembling; I afked her hoxv
fhe got hither : but her condensation v/as fo great that
me could give me no account of her efcape; I fup-
pofe, that when the tremor firft began, fhe ran out of
her own houfe, and finding herfelf in fuch imminent
danger from the falling of ftones, retired into the door
of mine, which was almoft contiguous to her's, for
Ihelter, and when the mock increafcd, which filled the
door with duft and rubbifh, ran up ftairs into my
apartment, which was then open : be it as it might,
this was no time for curiofity. I remember the poor

creature

Chap. 48.] at Li/Ion. 367

creature afked me, in the utmoft agony, if I did not
think that the world was at an end ; at the fame time
Ihe complained of being choaked, and begged for
God's fake I would procure her a little drink ; upon
this I went to a clofet where I kept a large jar with
water (which you know is fometimes a pretty fcarce
commodity in Li(bon) but finding it broken in pieces, I
told her me mud not now think of quenching her thirft,
but faving her life, as the hbufe was juft falling on our
heads, and if a fecond mock came, would certainly
bury us both ; I bade her take hold of my arm, and
that I would endeavour to bring her into fome place
of fecurity.

c I mall always look upon it as a particular provi-
dence, that I happened on this occafion to be undreff-
ed, for had I drefled myfelf, as I propofed, when I got
out of bed, in order to breakfaft with a friend, I mould,
in all probability, have run into the ilreet at the be-
ginning of the mock, as the reft of the peopie in the
houfe did, and confequently have had my brains darned
out, as every one of them had -, however, the immi-
nent danger I was in did not hinder me from confider-
ing that my prefent drefs, only a gown and flippers,
would render my getting over the ruins almolt im-
practicable : I had, therefore, ftill prefence of mind
enough left to put on a pair of fhoes and a coat, the
firft that came in my way, which was every thing I
faved, and in this drefs I hurried down flairs, the
woman with me, holding by my arm, and made di-
rectly to that end of the ftreet which opens to the
Tagus, but finding t'»e paflage this way entirely blocked
up with the fallen houfes to the height of their fecond
(lories, I turned back to the other end which led into
the main ftreet (the common thoroughfare to the pa-
lace) and having helped the woman over a vaft heap

of

368 Great Earthquake [Book Vt.

of ruins, with no fmall hazard to my own life, juft as
we were going into the ftreet, as there was one part
1 could not well climb over without the afiiftance of
my hands, as well as feet, I defired her to let go her
hold, which {he did, remaining two or three feet be-
hind me, at which time there fell a vaft ftone, from a
tottering wall, and crufhed both her and the child in
pieces : fo difmal a fpectacle at any other time would
have affected me in the higheft degree, but the dread
I was in of fharing the fame fate myfelf, and the many
inftances of the fame kind which prefented themfelves
all around, were too fhocking to make me dwell a
moment on this fingle object. •

' 1 had now a long narrow ftreet to pafs, with the
houfes on each fide four or five ftories highj all very
old, the greater part already thrown down, or conti-
nually failing, and threatening the paffengers with ine-
vitable death at every ftep, numbers of whom lay killed
before me, or what I thought far more deplorable-^-
fo bruifed and wounded that they could not ftir to
help themfelves. For my own part, as deftruction ap-
peared to me unavoidable, I only wiflied I might be
made an end of at once, and not have my limbs
broken, in which cafe I could exped nothing elfe but
to be left upon the fpot, lingering in mifery, like thefe
poor unhappy wretches, without receiving the lead
fuccour from any perfon.

' As felf-prefervation, however, is the firft law of
nature, thefe fad thoughts did not fo far prevail, as to
make me totally dcfpair. I proceeded on as fad as I
conveniently could, though with the utmoft caution,
and having at length got clear of this horrid paffage, I
found myfelf fafe and unhurt in the large open fpace
before St. Paul's church, which had been thrown
down a few minutes before, and buried a great part

of

Chap. 48.] at Lljlcn. 369

of the congregation, that was generally pretty nume-
rous, this being reckoned one of the moft populous
parifhes in Lifbon. Here I flood fome time, confi-
dering what I (hould do, and not thinking myfelf fafe
in this ficuation, I came to the refolution of climbing
over the ruins of the weft end of the church, in order
to get to the river fide, that I might be removed, as far
as poffible, from the tottering houfes, in cafe of a fe-
cond fnock.

* /This, with fome difficulty, I accompliflied, and
here I found a prodigious concourfe of people, of both,
fcxes, and of all ranks and conditions, among whom I
obferved fome of the principal canons of the patriar-
chal church, in their purple robes and rochets, as thefe
ail go in the habit of brfhops j feveral priefts who had
run from the altars in their facerdotal veftments in the
midft of their celebrating mafsj ladies half dreflfed,
and fome without Ihoes ; all thefe, whom their mu-
tual dangers had here ailembled as to a place of
fafety, were on their knees at prayers, with the terrors
of death in their countenances, every one ftriking his
breaft, and crying out inceffantly, Miferecordia men
Dies.

' In the midft of our devotions, the fecond great
fliock came on, little lefs violent than the firft, and
completed the ruin of thoie buildings which had been
already much fhattered. The confirmation now be-
came ib univerfal, that the fhrieks and cries of Mifere-
tordia could be diftindlly heard from the top of St.
Catherine's hill, at a confiderable diftance off, whither
a vaft number of people had likewife retreated j at the
fame time we could hear the fall of the parifh church
there, whereby many perfons were killed on the fpot,
and others mortally wounded. You may judge of the
force of this fhock, when I inform you, it was fo vio-

VOL. II. B b lent,

37O ' Great Earthquake at Lffion. [Book VL

lent, that I could fcarce keep on my knees, but it was
attended with fome circumftances ftill more dreadful
than the former. — On a fudden I heard a general out-
cry, ' The fea is coming in, we Ihall be all loft.' — Upon
this, turning my eyes towards the river, which in that
place is near four miles broad, I could perceive it
heaving and fwelling in a moft unaccountable manner,
as no wind was ftirring; in an inftant there appeared,
at fome fmall diftance, a large body of water, rifing
like a mountain ; it came on foaming and roaring,
and rufhed towards the fhore with fuch impetuofity,
that, we all immediately ran for our lives as faft as
pofiible; many were actually fwept away, and the
reft above their waift in water at a good diftance
from the banks. For my own part, I had the nar-
roweft efcape, and fhould certainly have been loft, had
I not grafped a large beam that lay on the ground, till
the water returned to its channel, which it did almoft
at the fame inftant, with equal rapidity. As there
wow appeared at leaft as much danger from the fea as
the land, and I fcarce knew whither to retire for fhel-
ter, I took a fudden 'refolution of returning back with
my cloaths all dropping, to the area of St. Paul's : here
I ftood fome time, and obferved the fhips tumbling
and toffing about, as in a violent ftorm; fome had
broken their cables, and were carried to the other fide
of the Tagusj others were whirled round with incre-
dible fwiftnefs ; . feveral large boats were turned keel
upwards ; and all this without any wind, which feemed
the more aftonifhing. It was at the time of which
I am now fpeaking, that the fine new quay, built
of rough marble, at an immenfe expence, was en-
tirely fwallowed up, with all the people on it, who
had fled thither for fafety, and had reafon to think
thernfelves out of danger in fuch a place j at the fame

time

Chap. 48.] Quay, fcfr. of Ltjlon dejlroyed. 37 1

time a great number of boats and fmall veflcls, an-
chor it (all likewife full of people, who had
ret in for the fame purpofe) were all fwal-
lowed up, as in a whirlpool, and never more ap-
peared.

* This laft dreadful incident I did not fee with my
own eyes, as it pafied three or four ftones throws from
the fpot where I then was, but I had the account as
here given from feveral matters of Ihips, who were
anchored within two or three hundred yards of the
quay, and law the whole cataftrophe One of them
in particular informed me, that when the fecond fhock
came on, he could perceive the whole city waving
backwards and forwards, like the fca when the wind
firil begins to rife; that the agitation of the earth was
ib great even under the river, that it threw up his
large anchor from the mooring, which fwam, as he
termed it, on the furface of the water ; that imme-
diately upon this extraordinary concufTion, the river
rofe at o ce near twenty feet, and in a moment fub-
fkiedj at which inftant he faw i;t- quay, with the whole
concourfe of people upon it, fink down, and at the
fame time every one of the boats and veffels that were
near it were drawn into the caviry, which he fuppofes
inftantly clofed upon them, inaimuch as not the leaft
fign of a wreck was ever feen afterwards. This ac-
count you may give full credit to, for as to the lofs
of the veffels, it is confirmed by every body; and
with regard to the quay, I went myfelf a few days
after, to convince rnyfelfof the truth, and could not
find even the ruins of a place, where I had taken Ib
many agreeable walks, as this was the common ren-
dezvous of the factory in the cool of the evening. I
found it all deep water, and in fome parts fcarcely to
be fathomed.

B b 2 ' This

372 Conflagration in [Book VI.

* This is the only place I could learn which was
fwallowed up in or about Lifbon, though I faw many
large cracks and fifiures in different parts, and one
odd phenomenon I mud not omit, which was com-
municated to me by a friend who had a houfe aad
wine-cellars on the other fide of the river, viz. that
the dwelling-houfe being firft terribly fhaken, which
made all the family run out, there preiently fell down
a vaft high rock near it, that upon this the river rofe
and fubfided in the manner already mentioned, and
immediately a great number of fmall fifiures appeared
in feveral contiguous pieces of ground, whence there
fpoutcd out like a, jet d'eau a large quantity of fine
white fand, to a prodigious height.

* I had not been long in the area of St. Paul's,
v/hen I felt the third fliock, which though fomewhat
lefs violent than the two former, the fea rufhed in
again, and retired with the fame rapidity, and I re-
mained up to my knees in water, though I had gotten
upon a fmall eminence at fome diftance from the
river, with the ruins of feveral intervening houfes to
break its force. At this time I took notice the wa-
ters retired fo impetuaufly, that fome veiTels were
left quite dry, which rode in feven fathom water:
the river thus continued alternately ruming on and
retiring feveral times together, in fuch fort, that it.
was juitly dreaded Lifbon would now meet the fame
fate, which a few years ago had befallen, the city of*
Lima.

" Perhaps you may think the prefcnt doleful fub-
jecr. here concluded; but, alas! the horrors of the
rlrft of November, are fufficient to fill a volume.
As foon as it grew dark, another fcene prefented itfelf

* This happened in 1 746.

little

Chap. 48.] Cmifequwce of the Earthquake. 373

little lefs fhocking than thofe already defcribed —the
whole city appeared in a blaze, which was Ib bright
that I could eafily fee to read by it. It may be faid,
without exaggeration, it was on fire at leaft in an hun-
dred different places at once, and thus continued burn-
Ing for fix days together, without intermiflion, or the
leaft attempt being made to flop its progrefs.

* I could never learn, that this terrible fire was
owing to any fubterraneous eruption, as fome re-
ported, but to three caufes, which all concurring at
the fame time, will naturally account for the prodi-
gious havock it made; the firft of November being
All Saints Day, a high feftival among the Portuguefe,
every altar in every church and chapel (fome of which.
have more than twenty) was illuminated with a -num-
ber of wax tapers and lamps, as cuftomary ; thefe fet-
ting fire to the curtains and timber work that fell with
the ihock, the conflagration foon fpread to the neigh-
bouring houfes, and being there joined with the fires
in the kitchen chimnies, increafed to fuch a degree, that
it might eafily have deftroyed the whole city, though
no other caufe had concurred, efpecially as it met with
DO interruption.

4 But what would appear incredible to you, were
the fad lefs public and notorious, is, that a gang of
hardened villains, who had been confined, and got
out of prifon when the wall fell, at the fir It fhock,
were bufily employed in letting fire to thole buildings,
which flood fome chance of efcaping the general de-

* The fire, by fome means or other, may be laid to
have deftroycd the whole city, at leafc every thing that
was' grand or valuable in it ; and the damage on this
occafion is not to be eflimated.

f The whole number of perfons that perifhed, in-
B b 3 eluding

374 Confequences of the Earthquake. [Book VI.

eluding thofe who were burnt, or afterwards crufhed
to death whilft digging in the ruins, is fuppofed, on
the loweft calculation, to amount to more than fixty
thoufand ; and though the damage in other refpe&s
cannot be computed, yet you may ibrm fome idea of
it, whenv I afTure you, that this extenfive and opulent
city, is now nothing but a vaft heap of ruins, that the
rich and poor are at prefent upon a level, fome thou-
fands of families which but the day before had been
cafy in their circumftances, being now fcattered about
in the fields, wanting every conveniency of life, and
finding none able to relieve thejn.

< A few days after the firfl confirmation was over,
I ventured down into the city, by the fafeft ways I
could pick out, to fee if there was a poflibility of
getting any thing out of my lodgings, but the ruins
were now fo augmented by the late fire, that I was fo
far from being able to diftinguifh the individual fpot
where the houfe flood, that I could not even diftin-
guifh the flreet, amidft the mountains of flone and
rubbifh which rofe on every fide. Some days after,
* I ventured down again with feveral porters, who,
having long plied in thefe parts of the town, were well
acquainted with the fuuation of particular houfesj
by their affiflance, I at lafl difcovered the fpot ; but
was foon convinced, that to dig for any thing there,
befides the danger of fuch an attempt, would never
anfwer the expence.

' On both the times when I attempted to make
this fruitlefs fearch, efpecialiy the firfl, there came
fuch an intolerable flench from the dead bodies, that
J was ready to faint away, and though it did not feem
fo great this lafl time, yet it had nearly been more
fatal to me, as I contracted a fever by it, but of which,
God be praifed, I foon got the better. However,

this

Chap. 48.] Earthquakes in Calabria. 375

this made me fo cautious for the future, that I avoided
pafling near certain places, where the ftench was fo
exceflive that people began to dread an infection : a
gentleman told me, that going into the town a few
days after the earthquake, he faw feveral bodies lying
in the ftreets, fome horribly mangled, as he fuppofed,
by the dogs, others half burnt, fome quite roafted ;
and that in certain places, particularly near the doors
of churches, they lay in vaft heaps piled one upon
another.'

The year 1783 was fatally marked by the defo-
lation of fpme of the mod fertile, moil beautiful, and
moft celebrated provinces of Europe. The two Cala-
brias, with a part of Sicily, were doomed to be a
fcene of the moft tremendous, and the moft fatal earth-
quakes that ever were known, even in thofe volcanic
regions. The firft fhock happened about noon, on
the 5th of February, and was fo violent as to involve
almoft the whole of Calabria in ruin. This was but
tire commencement of a fuccefiion of earthquakes,
which beginning from the city of A man tea, on the coaft
of the Tyrrhene fea, proceeded along the weflern coaft
to Cape Spartivento, and up the eaftern as far as Cape
D 'Alice; during the whole of which fpace not a town
was left undeftroyed.

During two years repeated fhocks continued to
agitate the affrighted minds of the inhabitants of Cala-
bria and Sicily, but the principal mifchiefs arofe in
the months of February and March in the 'firft year.
For feveral months the earth continued in an unceaf-
ing tremor, which at certain intervals increafed to
violent ihocks, fome of which were beyond defcription
dreadful. Thefe Ihocks were fometimes horizontal,
whirling like a vortex j and fometimes by pulfa'tions
pr beating from the bottom upwards, and were at
B b 4 times

376 Great Earthquakes [Book VI.

times fo violent that the heads of the largeft trees
almofl touched the ground on cither fide. The Ka'ins,
during a great part of the time, were continual and
violent, often accompanied with lightning, and furious
gufls of wind. All that part of Calabria, which lay
between the 3*8 th and 3^th degrees, adorned a new
appearance. Houfes, churches, towns, cities, and
villages, were buried in one promifcuous ruin. Moun-
tains were detached from their foundations, and car-
ried to a considerable diftance *. Rivers difappeared
from their beds, and again returned and overflowed
the adjacent country j\ Streams of water fuddenly
guflied out of the ground, and fprang to a confideraWe
height. Large pieces of the furface of the plain,
feveral acres in extent, were carried five hundred feet
from their former fituation down into the bed of the
river, and left (banding at nearly the diftance of a mile,
furrounded by large plantations of olives and mul-

* Sir William Hamilton, whofe ardeiut and laudable fpirit of
inquiry occaiioned his vifiting Calabria and Sicily during this
calamitous feafon, accounts for the removal of a mountain of
about f.vo hundred and fifty feet in height, and about four hun-
dred feet in diameter at its bafe, from the different nature of its
inferior and fuperior ftrata. The under part being more fqlid
and compact, was more ftrongly a£ted upon by the violent motion
- of the earth, and the volcanic vapours," which drove it to the
diftance. of fome hundred yards from its original fcite, where it lay
in confufed blocks, after having left the fuperior ftratum, which,
with its trees and vineyards, was carried in mother direction to the
diftance of four miles.

•f The fame philofopher accounts for this phenomenon by fup-
pofmg the firft impulfe of the earthquake to have come from the
bottom upwards, which raifing the furface of the ground, the ri-
vers which are not deep mutt naturally difappear ; but the earth
returning again with violence to its former level, the rivers muft
as naturally return and overflow their banks ; at the fame time the
boggy grounds being fuddenly deprefled, would force out the
water v/hick lay hid under their furface,

berry

Chap. 48.] in Caklria. 377

berry trees, and corn growing as well upon them as
upon the ground from which they were feparated.
Amidft thefe fcenes of devaftation, the cfcapes of
forne of the unhappy fufFerers is extremely wonderful.
Some of the inhabitants of houfes which were thrown
to a con-fiderable diftance, were dug out from their
ruins unhurt. But thefe inftances were few, and
thofe who were fo fortunate as to preferve their lives
in fuch foliations, were content to purchafe exiftence
at the expence of broken limbs and the moft dreadful
contusions.

During this calamitous fcene, it is impoffible to
conceive the horrors and wretchednefs of the unhappy
inhabitants. The jaws of death were opened to fwal-
low them upj ruin had feized all their pofTeilions, and
thofc dear connections to which they might have
looked for confolation in their forrows, were for ever
buried in the mercilefs abyfs. All was ruin and defo-
lation. Every countenance indicated the extremity of
affliction and defpair ; and the whole country formed a
wide fcene of undefcribable horror.

One of the moft remarkable towns which was de-
ftroyed was Cafal Nuova, where the Princefs Gerace
Grimaldi, with more than four thoufand of her fub-
jefts, periflied in the fame inftant. An inhabitant
happening to be on the fummit of a neighbouring hill
at the moment of the fhock, and looking earneftiy
back to the refidence of his family, could fee no other
remains of it than a white cloud which proceeded from
the ruins of the houfes. At Bagnara, about three
thoufand perfons were killed, and not fewer at Radicina
and Palma. At Terra Nuova four thoufand four
hundred periflied, and rather more at Semniari. The
inhabitants of Scilla efcaped from their houfes on the
celebrated rock of that name, and with their prince,

descended

378 Earthquakes in Calabria* [BookYI.

defcended to a little harbour at the foot of the hill ;
but, in the courfe of -the night, a ftupendous wave,
v/hich is faid to 'have been driven three miles over
land, on its return fwept away the unfortunate prince,
\vith two thoufand four hundred and feventy-three of
his fubjeds. It is computed that not lefs than forty
thoufa-nd perfons perilhed fyy this earthquake.

Chap, i.] [ 379

B.OOK VII.
O F W A r E R.

CHAP. I.

OFWATER IN GENERAL.

Water a Ccmpotmd Body. — Three States of Water. — Water in a fluid
State. — Florentine Experiment." — fapour. — Experiments afcertaining
tie Force of Vapour. — Steam Engine. — Ice. — Phenomena of Freez-
ing.—Of Tha<wing.-~Water expanded in the State of Ice. — Immenfe
Force exerted by Water on p offing to that State. — Why Ice is not
perfectly tranfparent.

WATER was univerfally confidered as a fimple
elementary fubftance till the cfaemifts of the
prefent age proved, by experiments, the fubftance of
which has been ftated in a preceding volume *, that
it is in reality a compound body. Its principles have
been afcertained both by compofition and decompofi-
tion ; and one hundred parts of water are found to
confift of eighty-five parts of oxygen, and fifteen of
hydrogen, or the bafis of inflammable air.

This very ufeful and necefiary fluid prefents itfelf
to our notice in three diftinc~b forms, namely, in its
liquid ftate, in the ftate of vapour or fteam, and laftly

• Book V. Chap. I.

in

380 Three States of Water. [Book VII.

in its frozen ftate. Of thefe I fhall fpeak in their
order.

Water, when pure and in.its fluid (late, is tranfparent,
colourlefs, and without fmell. It adheres to moft
bodies which come in contact with it, it pervades po-
rous fubftances, difiblvcs gummy and faline matters,
and extinguifhes fire.

Water, when fluid, is rrot in its moft fimple ftate,
for its fluidity depends on a certain quantity of caloric,
or the matter of heat, which enters into combination
with it, and infmuating itfelf between the particles of
*the water, renders them capable of moving in all di-
rections.

We are fupplied with water either from the atmo-
fphere, whence it defcends in the form of rain, hail, or
fnow, or from the earth, which fends it forth in fprings
and rivulets. In the former cafe the watery exhala-
tions drawn from the fea, and the furface of the earth
by the fun's heat, form clouds, whofe particles being
afterwards condenfed, fall back again in fhowers. In
the latter, the water which falls on the tops of moun-
tains, and other lofty fituations, penetrates the earth,
and, after pairing downwards, breaks forth at fomc
Mure or aperture at a diftance from its fouvce.

The quantity of water attracted from the furface
of the globe is almoft incredible. Dr. H alley has cal-
culated that portion which is yielded by the lea, to be
at the rate of one cubic inch from every ten inches of
furface in twelve hours*. To form an adequate idea
of this, let us fuppofe only half the globe to be covered
by the fea. The whole furface of the earth being
ubout 25,797,278 leagues, that of the fea will confe-
fjuently he 12,898,639. Suppofmg the evaporation

* See Bifhop Watfon's Calculation, vol. i. p. 122.

which

Chap, i.] Incompre/tble an J Elaftic Fluids. 381

which takes place in twelve hours to be that above
mentioned, without having any regard to what is
evaporated from the whole of the land, or from
the Tea during the other twelve hours, it will be
found that the atmofphere has taken up no lefs than
20,302,535,177,834, or more than twenty millions
of millions of cubic feet ef water ; an enormous quan-
tity, and much more than fufficient to fupply all the
fivers that interfecT: the different quarters of the
globe*.

What particularly diftinguifhes water, and thofe
fluids which are of a iimilar confiftence, and in com-
mon language are termed liquids, from thofe fubtile
fluids which were treated of at large in the preceding
volume, is, that the former are not, like the others,
pofTdTed of that lurprizing elafticky which admirs of
the volume of fluid being condenfed into a fmall com-
pals i but, on the contrary, may be confidered as incapa-
ble of compreffion, or at lead are compreffible in a very
Highc degree. The Florentine academicians filled a
globe of gold with water, and comprefled it with im-
menfe force ; the firft effect of this comprefflon was,
that the ball was confiderably heated by the emiflion
of latent heat from the water, and afterwards the fluid
forced its way through the pores of the gold, or

* There will poflibly be apparent, in this part of the work,
fome degree of repetition \\hen cornp^ed with what was faid of
vapour in the firft book. It was then neceffary to fpeak of va-
pour, in explanation of the properties of heat ; i: is now neceffary
to treat of it in connection with tha fluid of which it is ufua!'y
.formed ; and I conceive it better to do this, with the rifk of fome
repetition, than to refer to a former volume, both becaufe it wilj
ferve more firmly to imprefs on the minds of young readers fome
of the moft important doclrines of philofophy : and becaufe what
may now appear as repetition, is, in this place, mixed with new
facts, which coujd not be previoufly introd'.

2 through

332 Florentine Experiment. [Book VIL

through certain cavities, and appeared in drops on
the furface. The condufion, however, which was
haftily drawn from this experiment, that water, in its
liquid (late, is abfolutely void of all elafticity, is not
warrantable. Since other experiments (hew that wa-
ter as well as mercury will yield, in a certain degree,
to the preflure of the air in a condenfmg machine, as
Mr. Canton proved by including it in a glafs veffeJ,
with a narrow neck or item nicely graduated j its con-
denfation appears proportioned to the force, and as
foon as the preffure cf the air is removed, the fluid
will be obferved gradually to recover its accuftomed
dimenfions.

When water becomes heated to a degree beyond
that of the air upon its furface, the matter of heat,
which has a conftant propensity to diffufe itfelf equally
through all bodies with which it is in contact, rifes
and carries » .in in part of the water, which it converts
into an elaluc fluid or vapour. Until the water, how-
ever, arrives at the boiling point, the evaporation is
very gradual j but when this happens it becomes very
rapid, and the part of the water which is moft heated,
being converted into vapour, rifes fuddenly to the fur-
face, and occafions confiderable agitation.

Ebullition requires a determined degree of heat,
becaufe the fteam cannot be formed within the water,
unlefs it is ftrong enough to overcome the actual
preil..:e of the fluid" and air incumbent on it. But in
oroinu y evaporation, the vapour is formed at the fur-
face of I'.ie water, and has therefore no other p'-ellure
to overcome than that of the atmofphere. The elaftic
fluid, however, which is formed by ordinary evapora-
tion is different from that produced by ebullition, for
the latter always returns to the flate of water by a di-
minution of temperature, whereas the former is re-
duced

Chap, i.] Water in Clouds. 383

duced alrhoft to the flate of a permanently elaftic fluid
by mixture with air.

We find that all fluids boil more eafily in proportion
as the prefiure of the atmofphere is removed; whether
this is effected by afcending a mountain, or making
ufe of the air pump. M. Lavoifier fays, that if the
weight of the atmofphere was only equal to between
twenty or twenty-four inches of a column of mercury,
inftead of twenty -eight inches, we fhould never be able
to obtain asther in a liquid ftate, at lead in fummer;
and that the formation of ssther muft confequentiy be
impofllble upon mountains of a moderate degree of
elevation, without employing extraordinary means of
compreflion for its condenfation. Upon the whole, in
appears mod probable that all bodies are capable of
exifting in a folid, a liquid, and an aeriform ftate ; that
the firft is tne moft fimple ftate of all bodies, and that
the two others depend on combinations with different
quantities of the matter of heat, of which the aeriform
ftate requires by far the moft.

Vapour, as it firft rifes from boiling water, is irivifi-
ble, but as it mixes with the air it is deprived of part of
its heat, returns to its fluid form, and the very minute
dropr, of water which are produced, afcend in a co-
pious cloud of a white or light-grey-colour. Vapour
is the ' more readily difcernable in proportion to the
coldnefs and humidity of the atmofphere. The cloudy
appearance of fteam is occafioned by the difficulty with
which its particles are feparated and diflblved in the
atmofphere ; the difficulty is increafed in proportion
to the coldneis and humidity of the air, and this is the
reafon that the moifture exhaled with the breath, is
vifible in winter and not in fummer.

It was ftated in a former volume, that the combina-
tion of the matter of heat or caloric, with the particles

of

Water in tie State of Vapour. [BookVIL

of water, in that degree which conftitutes fleam, rati-
fies them fo exceedingly, as to occafion them to occupy
a fpace fome hundred times greater than the original
bulk of the fluid, and it is that alfo which volatilizes
and enables them to afcend through the air, and to
overcome its refiftance.

But when fleam is expofed to a flill greater degree
of heat, its volume is augmented ftill more confider-
ably. That heat which makes water boil, and which
rarifies it only one twenty- fixth, rarirks its vapour to
eighteen hundred times the bulk of the water which
produced it. This may be very readily demonilrated,
by taking a glafs tube, at one end of which is a bulb
of two inches in diameter, and dropping into it a fin«
gle drop of water, the diameter of wiiich we will fup-
pofe to be one-tenth of an inch. The fquares of thefe
two fpheres, with regard to each other, will be as 1800
are to one. Upon heating the buib of the tube over
the frame of a fpirit lamp, the air will firft be expelled,
and afterwards the drop of water will be converted into
fteam, and take poiTelTUm of the whole of the bulb ;
as may be proved by plunging the mouth of the tube
imo cold water, and furTering the fleam within the
bulb to return to its fluid (late. In this cafe, the
preflure of the atmofpliere will caufe the \vatc?r to rum
into the tube, and to occupy that {pace within the
bulb, which before was occupied by the vapour, and
thus the fact \viii be afcertained.

If, however, any obftacle is oppofed to the expanfive
force of fleam, the heat augments its refiilance in a
degree proportionate to the augmentation of its vo-
lume. The power of refiftance afforded by the va-
pour of water is prodigious, and has of late years been
made fubfervient to fome mechanical purpofes of the
greateft importance. Mufchenbroek has proved by

experiment,

Chap, i.] Steam Engine. 3&5

experiment, that the force of gunpowder is feeble,
when compared to that of rifing fceam. An hundred
and forty pounds of gunpowder blew up a weight of
thirty thoufand pounds ; but on the other hand, an t
hundred and forty pounds of water, converted by heat
into fleam, lifted a weight ,of feventy-feven thoufand
pounds, and would life a much greater, if there were
means of giving the (team greater heat with fafety;
for the hotter the fteam the greater is its force.

The fteam engine, to which I had formerly occa-
fion fiightly to advert *, is a machine which may be,
and is occasionally applied'1 to various mechanical pur-
poles where great force is required; but which has.
hitherto been principally ufed to clear mines from
water, and to raife water to a proper height for the
fupply of* cities. In thefe cafes, the expanfive power
of fteam is fo managed as to operate on immenfe
pumps, which could not conveniently be worked by
any other means. In order to give the reader a fu-
perficial idea of this machine, let us imagine a com-
mon pump prepared, and that we want to move the
Jiandle of this pump upwards by the force of fteam
only. In the firft place, let us fuppofe, that the handle
of the pump, or ibmething connected to it, was fo
contrived as to admit of being inferted in the barrel of
a gun, of fome cylindrical tube, fet upright over a
cauldron containing boiling water. Next let us fup-
pofe, that the fteam could be admitted into the tube,
through the touch- hole, and fo confined as to pafs
only by that way. Now as the fire begins to dilate the
fteam, a part of it will enter the tube by the touch-
hole, and this will prefs up the pump, which is fup-
pofed to be fo fitted to the tube as to prevent any part

* See vol. i. p. li«;

VOL. II. G c of

386 fbe Steam [Book VII.

of the {learn from efcaping. In this way the pump
handle would be driven quite out at the mouth of the
tube, but let us imagine, that before this can happen £
valve is opened, which allows a fmall quantity of cold
water to be fpouted into the tube, which effectually
and inftantaneoufly deflroys, or, more properly, con*.
denfes the fleam. The tube being now left empty,
there is nothing to counteract the preflure of the at-
mofphere, which again forces down the handle into
the tube, into which no fleam is permitted to enter, on
account of a valve which now flops the touch- hole
below; but when the handle is thus prefled down, the
valve below is again opened, and new fleam entering
again prefTes the handle upwards ; when the handle
comes near the top, the fleam is again cooled and
condenfed as before, and the handle is again prefled
down by the weight of the atmofphere. In this man-
ner it is alternately driven upwards and downwards by
the expanfive power of the fleam and the prefiiire of
the external air, and works the pump with unwearied
affiduity.

, .Though the principle however, is plain, the ma-
chinery is complex in the fleam engine j but the
annexed plate IV. will probably render it tolerably
intelligible.

In fig. I. A feprefents the fire-place under the
boiler, for the boiling of the water, and the afh-
hole below it.

B, the boiler, filled with water about three feet above
the bottom, made of iron plates.

C3 the fleam pipe, through which the fleam pafTes
from the boiler into the receiver.

D, the receiver, a clofe iron veflel, in which is the
regulator or fleam-cock, which opens sfticf {huts the
hole of communication at each flroke.

E, the

Chap, i,] Engine. x 387

E, the communication pipe between the receiver
and the cylinder ; it rifes five or fix inches up, in the
infide of the cylinder bottom, to prevent the injected
water from defcending into the receiver.

F, the cylinder, of caft iron, about ten feet long,
bored fmooth in the infide ; it has a broad flanch in
the middle on the outficle, by which it is fupported
when hung in the cylinder-beams.

G, the piilon, made to fit the cylinder exactly:, it
has a flanch rifing four or -five inches upon its upper
furface, between which and the fide of the cylinder a
quantity of junk or oakum is fluffed, and kept down
by weights, to prevent the entrance of air or water and
the efcaping of (learn.

H, the chain and piflon fhank, by which it is con-
nected to the working beam.

I I, the working beam or lever: it is made of two
or more large logs of timber, bent together at each
end, and kept at the diftance of eight or nine inches
from each other in the middle by the gudgeon, as re-
prefented in the plate. The arch-heads, I I, at the
ends, are for giving a perpendicular direction to the
chains of the pifton and pump-rods.

K, the pump- rod which works in the fucking
pump.

1 , arid draws the water from the bottom of the pit
to the furface.

M, a ciflern, into which the water drawn out of the
pit is conducted by a trough, fo as to keep it always
full ; and the fuperfluous water is carried off by ancj*
ther trough.

N, the jack-head pump, which is a fucking-pump

wrought by a fmall lever or working-beam, by means

of a chain connected to the great beam or lever near

the arch g at the inner end, and the pump rod arthc

C c 2 outer

3^8 fbe Stcft* [Book VII.

outer end. This pump commonly (lands near the
corner of the front of the houfe, and raifes the column
of water up to the cittern O, into which it is conducted
by a trough.

O, the jack-head ciftern for fupplying the injection,
which is* always kept full by the pump N j it is fixed
fo high as to give the jet a fufficient velocity into the
cylinder when the cock is opened. This ciftern has a
pipe on -the oppofite fide for conveying away the fur
perfluous water.

P P, the injection-pipe, of three or four inches dia-
meter, which turns up in a curve at the lower end,
and enters the cylinder bottom ; it has a thin plate of
iron upon the end a, with three or four adjutage holes
in it, to prevent the jet of cold water of the jack- head
ciftern from flying up againft the pifton, and yet to
condenfe the fleam each ftroke, when the injection-
cock is open.

* <?, a valve upon the upper end of the injection-pipe
within the ciftern, which is fhut when the engine is
riot working, to prevent any wafte of die water.

/, a fmall pipe which branches off from the injection-
pipe, and has a fmall cock to fupply the pifton with a
little water to keep it air-tight.

Q^the working plug, fufpended by a chain to the
arch g, of the working beam. It is ufually a heavy
piece of timber, with a nit vertically down its middle,
and holes bored horizontally through it, to receive pins
for the purpofe of opening and (hutting the injection
and ileam cocks, ^s it afcends and defcends by the
motion of the working beam.

h, the handle of the fteam-cock or regulator. It is
fixed to the regulator by a fpindle which comes up
through the top of the receiver. The regulator is a
circular plftt? 9t" brafs or ca^ iron> which is moved

horizontally

Cfiap. i.] Engine. 389

horizontally by the handle h, and opens or fruits the
communication at the lower end of the pipe E within
the receiver. It is reprcfented in the plate by a circu-
lar dotted line.

i iy the fpanner, which is a long rod or plate of iron
for communicating motion to the handle of the regula-
tor, to \vhich it is fixed by means of a flit in the
latter, and fome pins put through to fallen ir.

k /, the vibrating lever, called the Y, having the
weight k at one end and two legs at the other end. It
is fixed to an horizontal axis, moveable about its center-
pins or pivots mn, by means of the two (hanks op
fixed to the fame axis, which are alternately thrown
backwards and forwards by means of two pins in the
working plug j one pin on the outfide cfrpreffing the
fhank 0; throws .the loaded end k of the Y from the
cylinder into the pofition reprefentcd in the plate, and
caufes the leg / to ft like againft the end of the fpanner,
which, forcing back the handle of the regulator or
fleam-cock, opens the communication, and permits
the fleam to fly into the cylinder. The pifton imme-
diately riling by the admiffion of the fleam, the work-
ing beam I I rifesj which alfo raifes the working-
plug, and another pin which goes through the flit
raifes the fhank p, which throws the end k of the Y
towards the cylinder, and, ftriking the end of the fpan-
ner, forces it forward, and (huts the regulator ileam-
cock.

qry the lever for opening and (hutting the injection
cock, called the F. It has two toes for its center,
which take between them the key of the injec~lion-
cock. When the working-plug has afcended nearly
to its greateft height, and Ihut the regulator, a pin
catches the end q of the F and raifes it up, which
opens the injection-cock, admits a jet of cold water to
Cc 3 fly

393 5T2* Steam [Book VII.

fly into the cylinder, and, condenfing the fteam, makes
a vacuum j then the preffure of the atmofphere bi ing-
ing down the pilton in the cylinder, and alfo the plug-
frame, another pin fixed in it catches the end of the
lever in its defcent, and, by prefling it down, fhuts the
injection -cock, at the fame time the regulator is opened
to admit fleam, and fo on alternately ; when the regu-
lator is Ihut the injection is open, and when the for-
mer is open the latter is fhut.

R, the hot-well, a fmall ciftern made of planks,
which receives ail the wafte water from the cylin-
der.

S, the fink-pit to convey away the water which is
iniected into the cylinder at each ftroke. Its upper
end is even with the infide of the cylinder bottom, its
lower end has a lid or cover moveable on a hinge,
which ferves as a valve to let out the injected water,
and fhuts clofe each flroke of the engine, to prevent
the water being forced up again when the vacuum is
made.

T, the feeding-pipe, to fupply the boiler with water
from the hot- well. It has a cock to let in a large or
fmall quantity of water, as occafion requires, t© make
up for what is evaporated j it goes nearly down to the
boiler bottom.

U, two gage cocks, the one larger than the other,
to try when a proper quantity of water is in xhe boiler:
upon opening the cocks, if one gives fteam and the
other water, it is rights if they both give fteam, there
is too little water in the boiler; and if they both give
water, there is too much.

W, a plate which is fcrewed on to a hole on the fide
of the boiler, to allow a paflagc into the boiler for the
convenience of cleaning or repairing it.

X, the fleam-clack or puppet valve, which is a

brafs

Chap, s.] Engine. 39*

brafs valve on the top of a pipe opening into the boiler,
to let off the fteam when it is too ftrong. It is loaded
with lead, at the rate of one pound to an inch fquare ;
and when the fteam is nearly ftrong enough to keep it
t)pen, it will do for the working of the engine.

/, the fnifting valve, by which the air is difcharged
from the cylinder each ftroke, which was admitted
with the injection, and would otherwife obftruct the
due operation of the engine.

1 /, the cylinder-beams; which are ftrong joifts go-
ing through the houfe for fupporting the cylinder.

v, the cylinder cap of lead, foldered on the top of
the cylinder, to prevent the water upon the pifton from
flaming over when it rifes too high.

Wj the wafte-pipe, which conducts the fuperfluous
water from the top of the cylinder to the hot- well.

x x, iron bars, called the catch-pins, fixed horizon-
tally through each arch head, to prevent the beam de-
fcending too low in cafe the chain mould break.

yyy two ftrong wooden fprings, to weaken the blow
given by the catch-pins when the ftroke is too long.

z zy two friction-wheels, on which the gudgeon or
center of the great beam is hungj they are the third
or fourth part of a circle, and move a little each way
as the beam vibrates. Their ufe is to diminifh. the
friction of the axis, which in fo heavy a lever, would
otherwife be very great.

When this engine is to be fet to work, the boiler
muft be filled about three or four feet deep with wa-
ter, and a large fire made under it ; and when the
fteam is found to be of a fufficient ftrength by the
puppet-clack, then by thrufting back the fpanner,
which opens the regulator or fteam-cock, the fteam is
admitted into the cylinder, which raifes the pifton to
the top of the cylinder, and forces out all the air at
C c 4 the

392 f be Steam [Book VII.

the fnifting valve ; then by turning the key of the in-
jection-cock, a jet of cold water is admitted into the
cylinder, which condenfes the fleam and makes a va-
cuum ; and the atmofphere then preffing upon the pif-
ton, forces it down to the lower part of the cylinder,
and makes a ftroke by railing the column of water at
the other end of the beam. After two or three ftrokes
are made in this manner, by a man opening and
fhutting the cocks to try if they are right, then the
pins may be put into the pin-holes in the working
plug, and the engine left to turn the cocks of itfelf,
which it will do with greater exactnefs than any
man.

Many important improvements have been lately
made in the fleam engine by the ingenious Mr. Watt,
of Birmingham. Pie has contrived to preferve an
uniform heat in the cylinder of his engines, by fuf-
fering no cold water to touch it, and by protecting
it from the air, fir ether cold bodies, by a furrounding
cafe filled with fteam, or with hot air or water, arid
by coating it over with fubftances that tranfmit heat
(lowly. He makes his vacuum to approach nearly
to that of the barometer, by condenfing the fteam in
a feparate vefiel, called the condenfer, which may be
cooled at pleafure without cooling the cylinder, either
by an injection of cold water, or by furrounding the
condenfer. with it, and generally by both. He ex-
tracts the injection water and detached air from the
cylinder or condenfer by pumps, which are wrought
by the engine itfelf, or blows them out by the fteam.
As the entrance of air into the cylinder would ftop
the operation of die engines, and as it is hardly to
be expected that fucji enormous piftons as thofe of
fteam engines can move up and down, and yet be ab-
ibJutdy tight in the common engines, a dream of

water

Chap, i.] Engine. 393

water is kept always running upon the pifton, which
prevents the entry of the air; but this mode of fecur-
ing the pifton, though not injurious in the common
ones, would be highly prejudicial to the new engines.
Their pifton is therefore made more accurately; and
the outer cylinder, having a lid, covers it, the fteam
is introduced above the pifton j and when a vacuum
is produced under it, acts upon it by its elafticity, as
the atmofphere does upon common engines by its gra-
vity. This way of working effectually excludes the
air from the inner cylinder, and gives the advantage
of adding to the power, by increafing the elafticity of
the fteam.

In Mr. Watt's engines, the cylinder, the great
beams, the pumps, &c. ftand in their ulual pofitions.
The cylinder is fmaller than ufual, in proportion to the
load, and is very accurately bored.

In the molt complete engines it is furrounded, at a
fmall diftance, with another cylinder, furnifhed with
a bottom and a lid. The interftice between the cy-
linders communicates with the boilers by a large pipe,
open at both ends, fo that it is always filled with
fteam, and thereby maintains the inner cylinder always
of the fame heat with the fteam, and prevents any
condenfation within it, which would be more detri-
mental than an equal condenfation in the outer one.
The inner cylinder has a bottom and pifton as ufual i
and as it does not reach up quite to the lid of the outer
cylinder, the fteam in the interftice has always free
accefs to the upper fide of the pifton. The lid of
the outer cylinder has a hole in its middle ; and the
pifton rod, which is truly cylindrical, moves up and
down through that hole, which is kept fteam-tight by
a collar of oakum fcrewed down upon it. At the
bottom of the inner cylinder, there arc two regulating

valves,

394 ?be Steam [Book VII.

valves, one of which admits the fteam to pafs from
the infterftice into the inner -cylinder below the pifton,
or fhuts it out at pleaflire ; the other opens or fhuts
the end of a pipe, which leads to the condenfer. The
condenfer confiils of one or more pumps furnifhed
with clacks and buckets (nearly the lame as in com'
mon pumps) which are wrought by chains fattened
to the great working beam of the engine. The pipe,
which comes from the cylinder, is joined to the bottom
of thefe pumps, and the whole condenfer Hands im-
merfed in a ciftern of cold water fupplied by the engine.
The place of this ciftern is either within the houfe or
under the floor, between the cylinder and the lever
•wall -, or without the houfe between that wall and the
engine (haft, as conveniency may require. The con-
denfer being exhaufted of air by blowing, and both
the cylinders being filled with fteam, the regulating
valve which admits the fteam into the inner cylinder
is fhut, and the other regulator which communicates
with the condenfer is opened, and the fteam rufhes
into the vacuum of the condenfer with violence ; but
there it comes into contact with the cold fides of the
pumps and pipes, and meets a jet of cold water, which
was opened at the fame time with the ex'hauftion regu-
lator ; thefe inftantly deprive it of its heat, and reduce
it to water; and the vacuum remaining perfect, more
fteam continues to rufh in, and be condenfed until the
inner cylinder is 'exhaufted. Then the fteam which
is above- the pifton, ceafing to be counteracted by
that which was below .it, acts upon the piftcn with its
whole elafticity, and farces it to defcend to the bottom
of the cylinder, and fo raifes the buckets of the pumps
which are hung to the other end of the beam. The
exhauftion regulator is now flint, and the fteam one
opened again, which, by letting in .the fteam, allows

the

Chap, i.] Engine. 395

the pifton to be pulled up by the fuperior weight of
the pump rods ; and fo the engine is ready for another
ftroke.

But the nature of Mr. Watt's improvement will be
perhaps better underilood from the following defcrip-
tion of it, as referred to a figure. — The cylinder or
fteam vefTel A, of this engine (fig. 2.) is fhut at
bottom and opened at top as ufual, and is included in
an outer cylinder or cafe BB, of wood or metal, co-
vered with materials which tranfmit heat flowly. This \
cafe is at a fmall diftance from the cylinder, and clofe
at both ends. The cover C has a hole in it, through
which the pifton rod E Hides ; and near the bottom is
another hole F, by which the fteam from the boiler
has always free entrance into this cafe or outer cy-
linder, and by the interftice GG between the two cy-
Jynders has accefs to the upper fide of the pifton HH.
To the bottom of the inner cylinder A is joined a pipe
I, with a cock or valve K, which is opened and fhut
when neceflary, and forms a pafiage to another vefiel
L called a condenfer y made of thin metal. This vefTel
is immerfed in a ciftern M full of cold water, and it
is contrived fo as to expofe a very great furface ex-
ternally to the water, and internally to the fteam. It
is alfo made air-tight, and has pumps N wrought by
the engine, which keep it always exhaufted of air an4
water.

Both the cylinders A and BB being filled with
fteam, the paflage K is opened from the inner one to
the condenfer L, into which the fteam violently ruflies
by its elafticity, becaufe that veflel is exhaufted ; but
as foon as it enters it, coming into contact with the
cold matter of the condenfer, it is reduced to water,
and the vacuum ftill remaining, the fteam continues
to rufh in till the inner cylinder A below 'the pifton

is

396 Water in tie State of Ice. [Book VII.

is left empty. The fleam which is above the pifton,
ceafmg to be counteracted by that which is below it,
acts upon the pifton HH, and forces it to defcend to
the bottom of the cylinder, and ib raifes the bucket
of the pump by means of the lever. The paffage K
between the inner cylinder and the condenfrr is then
Unit, and another paflage O is opened, which permits
the fteam to pafs from the outer cylinder, or from the
boiler into the inner cylinder under the pifton ; and
then the fuperior weight of the bucket and pump rods
pulls down the outer end of the lever or great beam,
and raifes the pifton, which is fufpended to the inner
£nd of the fame beam.

When water is expofed to a cold atmofphere, it
firft lofes its free caloric, and is reduced in tempera-
ture, but no part of it begins to freeze till the mate
is reduced fomewhat below the thirty-fecond degree
of Fahrenheit's thermometer ; a fmall quantity of the
water then becomes folid, which, by changing its
ftate, fets at liberty a quantity of its combined heat,
which reftores the water in contact with it to the
temperature of 32 degrees, or rather above it. The
congelation is therefore at a ftand till this -fenfible
heat is abftracted by the atmofphere, and the mafs
again reduced fomewhat below the thirty-fecond de-
gree. Another portion of water then congeals, and
the procefs is again flopped by the emiffion of heat.
In this manner congelation pervades the whole mafs,
and is performed at intervals, which are very ob-
fervable when the phenomenon of freezing is accurately
attended to.

The fame law operates in the pafiage of other bodies
from the ft.ite of fluids to that of folids, and the contrary.
Dr. Irvine has mewh, that when fpermaceti and wax are
melted, they contain the matter of heat in a combined

Vol. .11 .

Chap, i .] Expanfiou of Water in the State cf Ice. 3 97

or latent (late. By heating them much above their
point of fluidity,- he 'found that they loft their heat
very loon, till fome parts became folid; after this they
continued of exactly the fame temperature till'tpe whole,
became folid, though expofed all the while to cold
air; but when all became iblid they cooled as they did
at firft. In the fame manner water mixed with ice,
whatever may be the temperature of the furrounding
medium, and whether the quantity of ice is increafing
or diminiihing, always nearly preferves the tempera-
ture of 3 2 degrees.

The freezing of water was formerly attributed to
the entrance of frigorific particles into that fluid; but
* the above doctrine, founded on the great difcoveries
of Dr, Black, is almoft univerfally deemed fo fatisfac-
tory as to have left the other, which is a mere hypo-
thcfis, fcarcely a fmgle advocate. The augmentation
of the bulk of water in freezing feems to be the only
fact which can with reafon be alleged in fupport of
the doctrine of frigorific particles j but thib increafe of
bulk is not attended with any increafe of weight, and
may be much better explained, than by attributing it
to the addition of frigorific particles, which were never
proved to have any exiftence.

The increafe which water acquires in becoming
iblid is about one-ninth or one-tenth of its whole bulk.
Boyle took a brafs tube, three inches in diameter, and
put forne water' into it ; he then brought down .into
the tube a plug with a weight placed at the head of it
of feventy-four pounds, On exposing the tube to the
cold, the water freezing and expanding itfelf, raifed
the feventy-four pounds. [I he expanfive power of
water, in the procels of freezing, was proved by a
remarkable experiment made in Canada. An iron
fhell, aftet having its mouth well plugged up, was

filled

398 Expanfae Power of Froft. [Book VII.

filled up with water and expofed to a fevere froft
•which prevailed, in that country. The expanfion of
the ice forced out the plug, and the water, which im-
mediately followed, was frozen into an irregular rnafs
or column of ice. The inftances, however, already
mentioned, are far lefs ftriking than one defcribcd by
Mufchenbroeck, in which a ball of iron, an inch thick,
•was burft afunder in the courfe of twelve hours by the
expanfive power of froft. That philofopher having
calculated the force exerted by the freezing of water
in a fimilar cafe, found it equal to a force capable of
raifing a weight of twenty- feven thoufand feven hun-
dred and twenty pounds. That the expanfive power
of freezing water, however, has certain limits, appears
from the following experiment, made by the Floren-
tine academicians. A brafs globe filled with water,
and clofed at its orifice by a well-fitted fcrew, was im-
merfed in freezing water, but did not burft j they then
pared bfF fuch a quantity of the metal as lefc the fides
of the globe unable to refift the expanfion of the water;
the force which was required to burft the globe in this
ftate was computed at twenty-feven thoufand pounds.
When fuch is the expanfive power exerted by water in
palling to the ftate of ice, we cannot be furprized that
veffels, which are left filled with water in frolty wea-
ther, ihould be burft by its freezing, and that the fame
thing fhould happen to water-pipes expofed to the
aclion of froft. The pavement is fometimes loofened
from the fame caufe, and in countries where very fe-
vere colds prevail, the fap of trees congeals, and their
trunks are burft afunder with a noife like that of can-
non. Froft fertilizes the ground, by loofening the co*-
hefion of the 'particles of earth.

As ice is never perfectly clear or tranfparent, and as
we find fmall cavities in it, fome have thought that the

air

Chap, i.] Phenomenon at Mofco'W. \399

air infmuates itfelf ; but this has been refuted by water
being frozen under an exhaufted receiver, and the fame
cavities being found in the ice. The ice, in fad, in-
ftead of being heavier, was found to be lighter. The
expanfion of ice, indeed, is evidently owing to the
cryftaliization of the water, and the particles afiuming
a different arrangement, and not being in clofe con-
tact. If this is admitted, as I apprehend it muft, we
cannot fay, with propriety, that the folid particles of
water expand. The Ipiculas, of which ice confifts, cut
each other at angles of fixty or one hundred and twenty
degrees.

When it fnows at Mofcow, and the air is not tot}
dry, it is obferved to be loaded with beautiful cryf-
tallizations, regularly flattened, and as thin as a leaf
of paper. They confiit of an union of fibres, which
(hoot from the center to form fix principal rays, -
which are themfelves divided' into extremely fmall
blades.

It appears, however, that the air previoufly con-
tained in water is fet at liberty on the congelation of
that fluid, and may thus partly contribute to the fwel-
ling of ice, and occafion ibme of the cavities obfervable
in it.

When water freezes flowly, its furface preferves its
tranfparency to Tome depth, owing to the air which is
feparated paffing downwards as the freezing proceeds.
The air bubbles, however, foon begin to colled, and
produce confiderable inequalities, .which increafe as
they approach the center. When, on the contrary,
water is frozen with great rapidity, the bubbles of air
difperfe themfelves pretty equally through the mafs,
which, in confequence, becomes opake through its
tyjbiole fubftance.

Reaumur obferves that call iron melted, in patting

from

4 oo Phenomena cf Freezing. [ B ook V 1 1 .

from a fluid to its folid ftate, expands. This effect is-
more fenfible in this than. in any other of the metals,
on account of its platey texture. He found that cad
iron, thrown among fome of the fame metal melted,
fwims upon the top. In the cafe of immediate expan-
fion upon congealing, the iron feems to agree with
water : they differ in this ; the iron never expands by
cold afterwards, whereas the ice, being expofed to
greater degrees of cold, becomes more bulky; the
folid parts not being fo clofely connected ffom a par-
ticular arrangement, which renders the whole mafs
lighter than before. ^Quickfilver contracts in becom-
ing folid ; and both caft iron and ice contain feveral
interftices, which, if allowed for, make it appear that
thefe bodies in reality occupy lefs fpace when folid,-
than in a fluid ftate.

Chap. 2.] [ 401 ]

C H A P. II.

HYDROSTATICS.

'Difco-veries of Archimedes in this B>- finch of Science. — Of the Moderns.
— Hoiv Fluids are titled upon by the general Laws ofGravifaticn.—
Particles of Fluids aJi independently of each other. — Experiment
efcertaining this Principle. — Fluids frefs equally in all Directions. —
Cautions neceffary in conftruding Aquedutls, &c. to guard agair.Jl
the lateral Prejjiire of Fluids. — All Parts of the fame Fluid in Equi-
librium --with each other. ->— Surfaces of Fluids always in a Plane
parallel 'with th's Horizon,— Prfffwe of Fluid* in proportion to their
Height. — Hydroji-atic Paradox. — Effects of Gravity on Fluids of
different 'Denfttics.>— Action of Air on tfe Surfaces of Fluids. — Uje
cf a Vtnt Peg. — The Valemis — The Siphon. — Attion if Fluids on
f olid Bodies immerfed in them. — Why ctrtain Bodies Jink and others
Jhvirn in certain Fluids. — Bodies thai fivim difpldce a Bulk of IV at er
equal to tketnfclves in Weight but net in Magnitude. — The fame Body
luill jink in one Fluid, which ivillfwim in another. — The Hydro-
meter.— Fahrenheit' 's Hydrometer. — Recapitulation of the Dotirines
refpecli-ng fpecijic Gravity. — Honv to wak a Globe cf Iron fwim tn
the Surface of Water. — Boats made rf Capper.

WAT E R, as a fluid, has certain properties*
which, though common to all nnelaftic or in-
compreffible fluids, are ufually confidered under this
topic; and indeed the fciences of hydroftatics and
hydraulics, which regard thefe properties, immediately
derive their names from that fluid *, on which the
experiments, illuftrative cf them, are ufually made.

Hydroftatics have for their object the weight and
prefiure of fluids -3 and in this branch, of fcience the

* "f$v? (Hydor) water, and o-1*7»x>; (ftatike) the fcience of
weight. Hydraulics from \^and attof (au]os) a. tube or pipe.

VOL, II. D d art

402 Di/covery of Archimedes. [Book VII.

art of determining the fpecific gravities of bodies is
ufually included, but this I have already been under
a necefiity of anticipating * in fome degree. Archi-
medes, among the ancients, accomplifhed the moft
remarkable difcoveries in this fcience. He is ho-
noured even at this day, as the inventor of the inge-
nious hydroftatic procefs, by which the purity or
bafenefs of a crown of gold was afcertained. Among
the moderns we are indebted to Gallileo, Torricelli,
Defcartes, Pafcal, Guglielmini, and Marietta, for the
beft information on this fubject j and by their expe-
riments (which arc as curious as they are decifive) we
are inftrufted in what we may expert or fear from the
power of fluids violently acted upon by the principle
of gravity, and in what manner and upon what prin-
ciples we may employ, for the ufe of man, the hy-
draulic machines.

It has been obfervfd in another place, that the pro-
penfity which bodies have of approaching towards
the earth, or perhaps towards its center, is the only
caufe of what we term weight or gravity, and that it
is by the continual efforts which they make to obey
that law, that they prefs upon every obflacle which
impedes their progrefs. As fluids, like folid bodies,
are impelled by their gravity, fo in this cafe they prefs
upon every object which oppofes their fall j but from
their nature they prefs in a different manner from
folid bodies ; hence arife the peculiar phenomena into
which we are now to inquire. .

Fluids are matters, the component parts of which

* See Book I. Chap. III. It was neceflary to explain the na-
ture of fpecific gravity in that part of the work, both becaufe it
relates rather tc* bodies in general than to fluid fublhmces ; and
h»caufe the frequent allufions to it in the progress of the work
would not have been otherwife underilood.

i are

"Chap, £.] Particles of Fluids. 403

are moveable among themfeives, having fcarcely any
cohefion one with another, and moving independently
of each other. Some philofophers * have included
in this definition what they term the grofier fluids, as,
for example, a heap of corn, a heap of fhot, of fand, &c.
as well as the rarer and more elaftic fluids, as common
air, and all other aeriform fubftances. The proper
objects, however, of the hydroftatic icience, are thofe
fluids which, in common language, are termed liquids,
or thofe which always prefent to us a plane furface,
level or parallel to the horizon.

All liquids are not equally fluid ; hence it fol-
lows, that the laws of hydroftatics apply with lefs ex-
actnefs in proportion as thofe fubftances depart from,
perfect fluidity. Water and oil both flow when the
vefiels, which contain them, are either overturned or
broken j but the effufion of oil is flower than that of
water, becaufe the particles of oil have more coheflon
among themfeives. The moft fingular effects in hy-
droftatics principally depend upon the extreme mi-
nutenefs of the particles of fluids, and upon their great
mobility.

To preferve a lucid order in the confideration of
this fubject, it will be necefiary to divide the objects
of our inquiry into three branches. In the firft place,
therefore, I fhall confider in what manner the principle
of gravity acts on the particles of fluids, and the phe-
nomena which it produces in the fluids themlelves ;
as well as their action againft the fides, the bottoms,
and tops of the veflels in which they are contained.
Secondly, I fhall confider in what manner fluids of dif-
ferent denfities act upon each other -, and thirdly, the
aftion of fluids on bodies immerfed in them.

* See Briffon, Vol. I.j>. 233.

D d i I. In

404 Particles of Fluids aft independently [Book Vlt.

I. In purfuing the firft object of this inquiry, it may
be eftablifhed as an axiom :

i ft, That the parts of the fame fluid aft with re-
fpect to their weight or prefiiire, independently of each
other.

This property arifes from their having fcarcely any
cohcfion among themfelves. It is otherwife with
folid bodies; their feveral parts adhering together,
they prefs in one common mafs; hence the falling of
folid bodies is productive of a different effect from
that of liquids. We dread the falling of a pound of
ice upon our heads, while we are much more indif-
ferent concerning that of a pound of water. The
latter, in its defcent, is divided by the refinance of the
air, by which fome of its parts are retarded more than
others i and the fwiftnefs of the whole mafs is ftill
more retarded by this divifion than it otherwHe would
be; for by being thus divided it acquires a larger fur-
face, which abates its effect. On the contrary, a folid
body falls upon a fmall fpace, which receives its whole
force. Hence it follows, that angular bodies falling
upon any part of the human frame are more dangerous
than flat or plane ones of the fame weight, and de-
fcending from the fame height.

It follows from this principle, that if an aperture is
made at the bottom of a veffel full of any fluid, in order
to prevent the flowing out of the liquor, it is only
neceflfary to counteract the weight of that column of
fluid which has the aperture for its bafe, and that to
counteract thr.t weight it is the fame whether the vcffel
is full of liquor or whether it contains only a column,
the bafe of which fliall be equal to the aperture at the
bottom.

Let the cylindrical vefiel of glafs A B (plate V.
fig. i.) have a hole in the bottom at C, furnifhed

with

Chap. 2.] of each oiler as to Weight cr Preffure. 405

with a cylindrical ferule of copper of an inch diameter
D, which is to be flopped with a pifton G, or the
fucker of a pump well fitted to the ferule, and oiled,
that it may yield to a moderate preffure. Let the
piiton be fupported by a fmall rod G H, fattened at
H to the filk which unites with the portion of the
pulley M, with which the extremity of the lever M N
is furnifhed, and which has for its center cf motion the
point L. The other portion of the pulley N, which
terminates the other extremity of the lever, is alfo fur-
nifhed with lines of filk, which fupport the fmall bafon
or fcale T. Upon the copper ferule D then fit a cy-
lindrical tube of glafs F K, the interior diameter of
which is equal to that of the ferule, and its height
equal to that of the vefiel A B. When the apparatus
is difpofed in this manner, fill the tube E F with water,
and conrnue to put fmall weights into the bafon or
fcale I, until the pifton begins to rife. Afterwards
take away the glafs tube E F, and place the pifton G
in the copper ferule D, and pour water into the large
veflel A B, and it will appear that the fame weights as
before in the bafon I, will raife up the pifton when
the larger vefTel A B is entirely full,. Hence it fol-
lows that there is the fame power to be counteracted,
whether there refts upon the pifton only a column
of water of its own fize, or whether the ye/Tel A J3 is
entirely Tull. Such a column, therefore, prefles upon
its bafe independently of the reft of the water con-
tained in the veflel.

To account for this, let us fuppofe all the water in
a veffel to be divided into feveral columns, i, 2, j,
4, 5, (plate V. fig. 2.) each comppfed of an equal
number of parts. If the bottom of the veffel, which
ferves for the bafe and fupport of all the columns, is
opened in a, the column 3, being no longer fupported,
P d 3 will

406 Particles of Fluids have no Cohefim. [Book VII.

will defcend through the aperture, fliding between the
two columns a and 4, which are fupported by the
paiis c,i the bottom of the veffel b and r, all the
moveable parts of which become (if I may ufe the
expreliio") imall rollers, which retard the fall only
ir a v.Ty iiight degree. This effect is the refult of
tu,- fmail degree of cohefion between the parts of the
fluid. If the columns i and 2 on the one part, -and
4 and j ~n the other, were compofed of parts adhering
together, they v/culd retard each other in their defcent
during their whole length, in the fame manner as a
wax candle would do; and by the fall of the column 3,
a void would be made between them. But as all the
particles are exiremely minute, moving eafily upon
each ether, they defcend when the fummit of the co-
lurr.i: 3 begins to defcend, having no longer any fup-
port fi om that fide ; and the fuperficies of the whole
jiwfs a -icends in the fame manner, though only one
of the columns caufed the flow from 'its fall. When
the parts have a degree ofvifcofity, as thofe of oily
fluids, or when the mafs of the flowing liquor has
much more of breadth than of height, the void which
the defcending column leaves above it is eafily per-
ceived, for then the furface, inftead of being plane and
even, is noilow in the middle, and afliimes a funnel-
iike form, becaufe the adjacent parts do not arrive
with iufficient fwiftnefs to replace thofe which defcend
through the aperture ; befides the preffure of the
air above the aperture is ftronger than its refinance
below.

From what has been now dated, it is eafy to per-
ceive how fluids differ from folids in the phenomena
of gravitation. If the verTel AB (plate V. fig. I.)
being full of water, and the tube E F being removed,
it was required to raife up the pifton G ; all that is

neceffary

Chap. l~\ Fluids prefs equally in all Directions. 407

necefiary in this cafe is, to fupport the weight of the
column of water diredlly above the pifton, becaufc
this column can move independently of the remainder;
but if the whole mafs of water was converted into ice,
then the mafs ceafmg to be a liquid, and all its parts
adhering together, to raife up the pifton it would be
neceffary to fupport the weight of the whole mafs,

2.dly, Fluids prefs equally in all directions.

In other words, they not only prefs from the top to
the bottom like other bodies, but they alfo prefs, ac-
cording to their weight, upon all bodies that oppofe
them in a lateral direction, and even from the bottom
to the top. Hence, if a calk is filled with liquid oil,
the oil will run out if an aperture is made in the fide,
but when it is congealed it will not run out on account
of its having become a folid body, for folid bodies
prefs only from their vertex to their bafe, and not
laterally.

To underftand properly this lateral prefTure of
fluids, and alfo that which they exert from their bafe
towards their vertex, it is neceffary to confider them
as a mafs of fmall globules depofited in a veffelj and
to remember that thefe minute globules are not ar-
ranged regularly as upon a cord, but that very fre-
quently one column exercifes its prefTure between two
others, and has a propenfity to difplace them, as may
be feen in plate V. (fig. 3.) where the perpendicular
preflure which is made oppofite to the point d, is
directed by the lateral columns towards the fides, ef,
of the veflel, in fuch a manner, that if the veifel was
open in thofe places the liquid would flow out, on
account of the great mobility of its parts. Jc is by
the fame mode of reafoning that the prefTuit of fluids,
from their bafe towards their vertex, is accounted
for: for example, when the column ^/(%- 3-) to*
D d 4 a ten-

408 Caution with refpeft to Aquedufts, &c. [Book VII,

a tendency to difplace the two particles g by the par-
ticle g cannot move any farther becaufe it is impeded
by the fide and bottom of the veflel ; but the particle b
may be raifed from the bafe towards the top, unlefs a
column equal to the column i k, or fomething equi-
valent, prefTes upon it to prevent it.

It is upon this principle that the water, elevated by
the New River water-works, after having defcended
from a bafon in a vertical pipe, and then after having
flowed horizontally in a fucceffion of pipes under the
pavement, is raifed up again, through another pipe4
as high as the fountain at the Temple Garden. It is
alfo upon this principle that a veflel may be filled
either at the mouth or at the bottom indifferently,
provided that it is done through a pipe, the top of
•which is as high as the top of the vefTel to be filled.
Hence it follows, that when piers, aqueducts, refer-
voirs, or other hydraulic works for the retention of
water are to be conftructed, it becomes neceflary to
proportion their ftrength to the lateral preflure which
they are likely to fuftain, which becomes greater as
the height of the water is more confiderable. Nearly
the fame precautions are neceflary to be taken with
refpecl: to what fome philofophers call the grofler
fluids, which alfo have a propenfity to expand, as well
on account of the fmallnefs of their parts as from the
frrall degree of cohefion which exifts between them.
Walls defigned to fupport terraffes ought to be fuf-
ficiently ftrong to refill the lateral preflure of the earth
and rubbifh which they are to fuftain, fince this prefliire
will be greater as the particles of earth, and of the
other materials of which the terrafles are compofed, are
lefs bountl together, and in proportion as the terralies
are more elevated.

All the parts of the fame fluid are in equili-
brium

Chap. 2.] Particles in Equilibrium. 409

brium with each other, whether they are contained
in one vefiel or many, provided they communicate
with each other j and their furfaces alib are always in a
plane parallel to the horizon.

This is a confequence of the principle which has
been before eftablimed : for, fince the particle h
(fig. 3.) would be raifed from the bafe towards the
top, unlefs a column equal to the column / k, prefTed
upon it to retain it in its place ; it follows that to be in
equilibrium, the upper extremities of the two columns
mould be in the fame horizontal plane, or in points
equally diftant from the center of the earth j which
points, however, cannot be found by a right line ; for
in the diftance of a thoufand fathoms there is about
one foot difference in the perpendicular height. From
this property of fluids it follows, that water conducted
by pipes placed in the earth, will remount as high as
the place whence it flowed, whatever the depth under
ground through which it may have been conducted
by the pipes. It is cuftomary to allow half an inch of
inclination in the length of fix feet, to counteract the
refinance produced by friction ; but it is clear from
what has been faid, that this is not abfolutely necef-
fary, for however long the pafTage might be, the water
would fti!l afcend as high as the place whence it
came, but it would require a little longer time to
accomplifh the afcent. We are enabled, upon this
principle, to account for the fprings which are fome-
times found on the tops of mountains. Such waters flow
from mountains dill more elevated (whether they are
far or nenr) by fubterraneous canals. It follows from
this principle, that if there are many refervoirs which
communicate together, it is neceflary only to fee one
of them to know the height of the water in the others ;

for

410 . Fluids prefs m proportion [Book VII.

for it muft neceftarily be of the fame height there as in
all the reft.

From what has been obferved, viz. that when all
the parts of the fame fluid are in equilibrium, their
furfaces will alfo be in a plane parallel to the horizon,
or, in other words, every part of the iiirface at an
equal diftance from the center of the earth, it follows,
that when the furface of water is very large, it becomes
neceflarily and fenfibly convex. This is eafily per*
ceived at fea, where the mafts of fhips are cbferved at
£ diftance before any other part of the Ihip can be dif-
tinguiihed.

4thly, Fluids prefs as well perpendicularly as late-
rally, not, however, in proportion to their quantity,
but in proportion to their height above the plane of
the horizon,

For example, if feveral veflels of the fame height
and bafe are filled with water, all their bottoms will
bear the fame degree of preflure, whatever may be
the form and fize of the veflels in other refpec~ts.
Suppofe three veflels to be filled with water, A B C D
(fig. 4.) E F G H (fig. 5.) L M N O P QL(fig. 6.)
\vhofe heights A B, I F, L T are equal, and alfo
fupported by equal bafes B C, F G, N O j it will be
found, by experiment, that all the bottoms of thefe
veflels will be equally prefled, though the quantities
of water which they contain may be very different.
In the veffel (fig, 4.) the bottom B C is prefled by
the whole mafs of water A B C D, becaufe the fluid,
in this cafe, prefles in the fame manner as a folid
body ; let us fuppofe the weight of the water to be
fix- pounds: in the vefiel (fig. 5.) it is eafy to con-
ceive, from what has been faid before, that the bot-
tom F G is alfo only prefled by fix pounds, though

the

Chap, 2.3 to the Height of the Column. 41 1

the veffel is evidently much larger than the firft j be-

caufe the bottom F G fupports only the column

I F G K, equal to that of the veflel (fig. 4.) and

this column exercifes its preflure independently of the

refidue of the " ater in the veflel, which is fupported

by the fides E F, H G, of the veflel (fig. 5.) But

the principal difficulty confifts in comprehending how

the bottom of the veflel N O is dill prefled by a

weight of fix pounds, although one pound of water

would be fufficient to fill the veflel. It is accounted

for in this manner : it is ceruiin that upon the portion

T V of the bottom N O, there is a preflure equal

to that of a column of water of which T V is the

bafe, aid L T the height. If, upon every ether

fimilar portion of the fame bottom, there is a preflure

equal to that of the column L T V Q^, the bottom is

equally prefled upon all its parts. For inftance, there

is a preflure upon the portion V X equal to that of

a column of water QV X R, which is itfelf equal

to the column LTV Qj for the fmall column of

"water P V X S, which refls above, has a pro-

penfity to be elevated by the preflure of the adjacent

column LT VC^and with a force equal to the excefs

L M P Qj)f this great column over the fmall one ;

therefore the upper part, P S, is prefled by the fame

power -, but the re-action is equal to the preflure.

The part P S re-acts with a force equal to. the excefs

L M P Q^of the great column over the fmall one.

There is, therefore, a preflure upon the portion V X

of the bottom N O, from the fmall column of water

PVXS, and from the re-action of the part PS,

equal to the prefiure of a column of water, QJP S R,

both of which added together are equal to the pref-

fure of the column LTV Q^ What has been faicl

of the portion V X may be faid of all the reft. Hence

it

411 lly draft at ic Paradox. [Book VII.

it follows that the bottom of the veffel (fig. 6.) is
every where equally preffed.

There is a maxim deduced from what has been
ftated, which is termed by philofcphers the hydroftatic
paradox ; it is neverthelefs founded upon the fureft
bans of truth, and has a confiderable influence in al-
mpft all hydraulic engines, viz. " that a given quantity
of water may exert a force two or three hundred times
kfs or greater, according to the manner in which it
is employed." If, for inftarice, the fame quantity of
water as the veffel (fig. 5.) will contain, is poured
into a veffel refembling that of (fig. 6.) but high
' enough to contain it, the preffure upon the bottom
N O will be confiderably greater than that upon the
bottom F G.

One of the molt ufeful machines to mew that a
fmall quantity of water is capable of great preflure,
is the hydroftatic bellows. This machine (Plate VI.
fig. i.) confifts of two thick oval boards, each about
three feet broad, and four feet long, united to each
other by leather, like a pair of common bellows, or
a barber's puff. Into 'the lower board a pipe B,
ieveral feet high is fixed at e. Now, in mewing ex-
periments with this fimple machine, which even the
reader himfelf might eafily make, let water be poured
into the pipe at its top C, which will run into, the
bellows, and feparate the boards a little : then to mew
how much a little water will be able to effect by pref-
fure, let three weights, each of an hundred pounds, be
laid upon the upper board. Now if we pour more
water into the pipe, it will as before run into the bel-
lows, and raife up the board with all the weights upon
it. And though the water in the tube mould weigh
in ajl but a fmgle pound, yet the prcfllire of this fmall

force

VOL.H. /> fJ-2.

Plate 5.

Fig. j.

Chap. 2.] *fun bxrft by Jmall Quantity of Water. $13

force upon the water below in the bellows3 fliall fupporc
the weights, which are three hundred pounds ; nor will
they have weight enough to make them defcend, and
conquer the weight of the w~ater, by forcing it out of
the mouth of the pipe.

It is clear from thefe principles, that the tun T O
(fig. 2.) rilled with water, may be-burft by prdfing
it with fome pounds additional weight of the fluid,
through the tube A B, which may be fuppofed to be
from twenty -five to thirty feet m height. From what
has been faid of the vefiel (fig. 6.) it indeed neceffarily
follows, that the fm all quantity of water which the
tube A B contains, prefles upon the bottom of the
tun as much as if a column of water had been added
as wide as the tun itfelf, and as long as the tube, which
would evidently be an enormous weight.

II. The efFec~ls of gravity on fluids of different den-
udes will, from what has preceded, not be very diffi-
cult to comprehend.

It has been obferved, that fluids are mafles of fmall
particles moveable with great facility among themfelves
independently of each other, preffing feparately and in
proportion to their maffes.

It is proved alfo by chemical analyfis, that even
thefe minute particles are compofed of particles (till
fmaller. Now whether it refults from the interpo-
fition of caloric (or the matter of fire) in greater or
lefs quantities, which we know is the caufe of all
fluidity, and alfo of the difference that exifls between
the incomprefiible and elaftic fluids; or whether it
may depend upon the fhape or fize of the particles,
which, as in foliu bodies, may increafe or diminish the
porofity, it is certain, that there is a confiderable dif-
ference with rdpecl to denfity in'diffbrent fluids.

From this, difference in point of dcniity, a reparation

may

414 E/efts of Gravity on Fluids [Book VII,

maybe obferved generally to take place, foon after
mixing two heterogeneous fluids together, unlefs this
effect is counteracted by feme more powerful caufe*
It has been obferved, that the particles, according to
their weight, prefs independently of each other. Thofe
therefore which have the moil denfity, having more
power to gain pofteffion of the lower part of the
vefiel which contains them, oblige the others to yield
and refign their fituation -y and hence a feparation is
effected. When oil and water, for inftance, have
been well lhaken together, and afterwards the whole
left in a (late of reft, the water, having more denfity
than the oil, takes the lower pdfition and the oil rifes
to the furface. If this effect does not take place, it
is owing to the intervention of one of the following
caufes. Firil, a kind of elective attraction, which
may exift between the particles of different fluids, as
\vhen water and wine are mixed together, the water,
though heavier than the wine, does not feparate itfelf.
Secondly, the vifcofity of one of the fubflances, as
when the whites of eggs are beaten together, and by
that means a confiderable quantity of air mixes with
them j the air, though much lighter, has not power to
difengage itfelf from the matter in which it is en-
veloped, in order to effect its efcape.

If two fluids of different denfities are placed in a
ftate of equipoife with each other, and have the fame
bafe, their perpendicular heights above the horizon
will be in a reciprocal ratio to their denfities or fpecific
gravities.

If, for exampie, mercury is put into an inverted
fiphon, and water is poured into one of the branches,
in order to elevate the mercury in the other branch
one inch above its lever, it is neceffary that the water
Ibould be about thirteen inches and an half high. The

height

Chap. 2.] cf different Denfities, 415

height of the water then will be thirteen times and a
half of that of the mercury ; becaufe the fpecific
gravity of mercury is about thirteen times and a half
as great as that of water.

This obfervation will alfo apply to the reciprocal
action of air and water, or air and mercury upon each
other, as was evinced in a former book, when treating
of tht Torricellian experiment and the barometer *.
Many of the phenomena, indeed, of hydroftatics and
hydraulics are to be referred to the prefiiire of the at-
mofphere, and for this reafon, the prefent fubjed has
been in part anticipated, when it was neceflfary to treat
of air as a fluid.

It is, however, proper on the prefent occafion, tQ
recal to the reader's attention fome of the properties
of this fluid, and he will eafily remember, that as a
fluid, air is poiTeflTed of gravity, and confequently
prefles upon all bodies which oppofe it; and it is
neceflary to add, that like water, it prefles in all
directions. Its perpendicular prefTure has been al-
ready fuflkiently proved ; and its lateral preilure may
alfo be eafily demonftrated. If a fmall hole is made
with a girriblet, either in the fide or bottom of a cafk
or veflel which is quite full of liquor, it will not run
out, becaufe the external air which prefles againft the
hole, fuftains the liquor, which has not a fufficient
height to overcome its prefllire. Hence the neceflity
of a vent peg, to enable liquor to be drawn out of a
full cafk. The elafticity of the fmall quantity of air
which is introduced at the vent prefles the fluid, and
overcomes the preflure of the air at the cock. There
is an inftrumcnt in common ufc, called a Valencia,
for extracting fmall quantities of liquor out of the

* See Book v. Chap. 9.

bung-

4 1 6* Prepare of the Air upon Fluids. [Book VI L

bung-holes of cafks. It is a tube with a fmall aper-
ture at the bottom and the top. When full, if the
hole at the top is flopped with the thumb or finger, fo
as to prevent the preffure of the air at the top, the
liquor will not run out of the hole at the bottom, being
kept in by the force of the external air.

It is proper to obferve, that all the effects which
depend upon the preffure of air, take place in a room
where the column of air is terminated by the ceiling,
as well as without doors where the column of air has
the whole height of the atmofphere ; and the reafcn
is, becaufe the air in the room has a communication
with that on the outfide, fuppofmg it to be only by
means of the key-hole. Thus a barometer placed in
a hall, will have its mercury as high as if it was placed
in an open field.

The curious effects produced by fiphons, all depend
upon the preffure of the air.

A fiphon is a bent tube ABC (fig. 3), made of
glafs, of metal, or of wood. One branch of which
A B, is fhorter than the other B C. In order to
make vie of this inilrument, place the extremity of
the fhort branch A B in the veffel E E, (fig. 4.) which
may be fuppofed to contain any fluid matter, as water
for inftance. If the air then is drawn by faction*
out of the fiphon at the extremity C of the long branch
BC, the liquor will begin to flow, and will not ceafe
while the fhort branch A B remains immerfed in the
fluid. It is eafy to fee that the preffure of the air
upon the furface of the fluid in the veffel, is the caufe

* Suftion is here evidently ufed in the popular fenfe of the
word, to imply that aflion of the mouth which extrafts the air
from a given fpace : for in ilriift philosophical language there is
no fuch thing.

of

Chap. 2.] The Siphon. 417

of its dtfcharge through the fiphon. For fuppofe G F
the confines of the atmofphere, all the points of the
furface A of the liquor will be equally prefied by the
column of air AF; if, therefore, at fome point of
this {lirface, the prefiure is fufpended, the liquor mud
flow at that point, becaufe it finds lefs refiftance there
than in any other part j this is therefore the obvious
reafon why the fiphon becomes full immediately after
the air is drawn out at the extremity C.

If the two branches of the fiphon were of equal
lengths, as B A, B D, the flow through the bent tube
would not take place ; becaufe the column of air D G
which would refift in D, being of an equal height
with that which preiTes at A, would alfo be in equili-
brium with it, in the fame manner as the two columns
of the fluid B A, B D. But fince B C, one of the
legs, is longer than the other, though the column of
air G C, which ahfwers to it, is really longer than that
which preffes in A ; yet it is not capable of preventing
the pafiage of the fluid. To underftand this more
perfectly, let us confider the column of air G C to be
divided into two parts, one of which G D, would form
an equipoife wich the column of air F A, and would
be capable of (lopping the flow from the tube if the
branch B C ended in D. The portion of fluid which
fills the part D C of the fiphon, will find no other re-
fiftance in C than one column of air D C of the fame
length with it, which is evidently very inferior to it
in weight. This portion of fluid then flows out, be-
caufe it greatly exceeds in weight the column of air
which is oppofed to it. But while it continues to
flow, nothing fuftains that which is above it, which
flows neceflarily, while the prefiure of the air at A
furnifhes a new fupply of fluid to replace that which
runs out. It is by thefe means, that the water in' the

VOL. II, E e fiphon

4 1 8 dBian of Fluids on folid Bodies. [Book VII.

fiphon continues to flow without intermiffion ; becaufe
the refiftance of the air in C is as much exceeded, as
the length of the branch B C of the fiphon exceeds
that of the branch A B. In order to prove this,
fuppofe there is added at C a tube to lengthen that
branch, then it will plainly appear, that in a given
time more water will flow than would have been dif-
charged without that augmentation to the branch BC.

Since it is the preffure of the air which elevates the
fluid in the fhort branch B A, it follows, that the
height of this branch is limited to thirty-two feet
when the fluid is water, becaufe the preffure of the
atmofphere cannot elevate water higher ; but when
the fluid is mercury, the height of the (hort branch
fhould not exceed thirty inches, becaufe the atmofphere
cannot fuftain mercury at a greater height.

III. The action of fluids on folid bodies immerfed
in them, has been already in part anticipated, in treat-
ing of fpecific gravity. It is neceffary, however, to
refume that fubje<5t to a certain extent in this place,
and I fhall endeavour as much as poflible to avoid re-
petition.

It is evident, that when a folid body is plunged into
a fluid, it occupies a fpace in that fluid exactly equal
to its own magnitude. The quantity of fluid then fo
difplaced, either equals in denfity and confequently in
weight, the folid which difplaced it ; or, on the con-
trary, one of the two mult weigh more than the other.
In the lad cafe, which is moft common, the quantity
by which the heavier body furpaffes the lighter, is
called the fpecific weight or gravity.

It has been obferved before, that fluids exercife

their preffure in all directions, confequently a folid

body plunged into a fluid is preffed at all points. IE

has alfo been proved, that this preffure increafes in

2 proportion

Chap. 2.] Swimming. 419

proportion to the height of the -fluid ; the preffure,
therefore, which the body undergoes, is greater in
proportion to the depth into which- it is plunged.
Laftly, it has been proved, that when two fluids are
placed in equipoife, their refpective heights are in pro-
portion to their denfities ; and therefore bodies plunged
to an equal depth, are compreflcd according to the den-
fity of the refpective fluid.

If a body is heavier than the fluid in which it is
immerfed, it is evident that ic will fink to the' bottom
by its fpecific gravity. If a body is lighter than the
fame bulk of the fluid into which it is plunged, a part
of it will fwirn, and the remaining part which is im-
merfed difplaces a quantity of fluid which weighs ex-
actly as much as the whole of the folid body *.

if,

* ' From what I have already explained, you muft neceffarily
have difcovcrcd the rationale tf Jinking and fwimming. You law
that when a body was bulk for bulk heavier than the fluid, by
b£ing immerJed it lofes only the weight of an equal bulk of the
fluid, and confequently the rejidual or remaining gravity of the
folid muft carry it dc.va to the bottom, or make it Jink.

On the ether rnnd, if the folid has lefs weignt in the fame bulk
than the fluid, then it cannot by its weight difplace or raife up-
wards its whole bulk of the fluid, but only io much of it as is equal
to its own weight, and from this deficiency in weight it will be
only partly immerifc47 and will thereforeyov/w upon the upper part
of the fluid.

Of all the animals, however, thrown into the water, man is the
moil helpiefs ; the brute creation receive the art of fwimming from
nature, while man can only acquire it by practice; the one efcapes
without danger, the other links to, the bottom. Some have af-
ferted, that this arifes from the different fenfibilities each have of
the danger ; the brute, unterrified at his iituation, ftruggles, while
his very fears fink the lord of the creation.

But much better reafons may be affigned for this impotence of

man .in water,- when compared to other animals; and one is, that

he has actually more fpecific gravity, or contains more matter

within the fame fujface than any other animal. Thutrunjc of the

h e » body

Theory of Swimming. [Book VIT.

1£ for inftancc, water is poured into a glafs vefTel
(fig. 5.) furnilhed with a fmall cock near the bottom ;
if the height of the water in the vcfTel is marked with
a fmall bandage of thread or paper ; and, laftly, if a
ball of wood is thrown into it, it will appear that part
of the wood will be immerfed, and part of it remain
above the water, and that the immerfed part will raife
the water in the veffel juft as much as if a volume of
water had been added equal to the folid contents of
the part under water.

If a quantity of water is then let out of the veflel
by means of the fmall cock, until the furface is reduced
as low as the mark which pointed out its height at
the beginning of the procefs, it is clear, that the water
drawn out in this, manner will be equal in its folid con-
tents to thofe of the immerfed part of the wooden
ball; and alfo, if this volume of water is weighed, it
will be found to be of exactly the fame weight as the
whole ball of wood.

Hence it follows, that a boat upon a river difplaces,
a quantity of water exactly of the fame weight with
the boat and its lading; and if more weight is added,
it will fink deeper in the water in the fame proportion •,
and the immerfed part is more or lefs in extent, ac-

body in other animals is large, and their extremities propor-
tionably fmall ; in man it is the reverfe, his extremities are very
large in proportion to his trunk. The fpecific weight of the ex-
tremities is propordonably greaty than that of the trunk in all
animals, and therefore man muft have the greatclt weight in water,
•fince his extremities are the largeft.

Befides this, other animals to fwirn have only to walk (as it
vere) forwards upon the water ; the motion they give their limbs
in fwimming1 is exaftly the fame they ufe upon land ; but it is
different with man, who makes ufe of thofe limbs to help him for-
wards upon water, which he employs to a. very different purpofe
upon land. ADAMS'S Licittrn, Vol. iii. p. 408.

cording

VOL.fl. />. .

Fig. j.

r

Chap, a.]' *The Hydrometer. 421

cording to the denfity of the water. Hence, as water
when impregnated with fait, is heavier and denfer than
pure water, as was formerly proved * ; it follows, that
the fame boat and lading will .draw lefs water (ac-
cording to the feaman's phrafe) in the ocean, than in
a river of frefh water, and that if: it is laden to the utmoft
extent in fait water, it will fink when it comes into frem
water.

Upon this principle depends the life of the hydro-
meter. For it will be found that bodies immerfed in
mercury, fuftam a greater lofs of weight, or require
a greater power to fink them, than in fait water ; in
fait water than in frefh ; and in pure water, they ftill
fuftain a greater lofs of weight than in fpirit of wine,
which is a lighter and lefs denle fluid.

The hydrometer, then, is an inftrurnent by which
the fpecific gravity of different fluids is determined.
The moft fimple, and that which is moft in ufe, con-
fifts of a glafs globe with a long narrow neck (plate
VIL fig. i.) AC, divided all the way up into
equal parts. In order that this inftrument may fuf-
tain icfelf in the middle of liquors in a vertical pofi-
tion, it is made in fuch a manner that the center of
gravity is in the lower part of it j it is for this purpofe,
that another fmall hollow ball S is placed under the
larger ball, in which lome mercury is ufually lodged,
but in fuch a quantity only as that the whole hydro-
'meter mall weigh about as much as an equal bulk of
tha-t fluid which is appointed to be proved.

When the hydrometer is conftructed in this manner,
if it is plunged in the liquors which are to be com-
pared, it will not entirely fink, becaufe it is fuppofcd

* Book vi. chap. 7.

Ee 3 to

422 Vbe common Hydrometer. [Book VII.

to be a fpecific gravity, about or nearly equal with
that of the fluid.

If, therefore, the weight of the hydrometer is fuch,
that it will fink in water as far as E, it will fink ftill
deeper in lighter fluids ; it will fink for inftance in wine
as far as F ; in fpirit of wine as far as G, &c. But if
it is plunged into liquors heavier than water, it will
not fink fo far as Ej for example, in beer it will only
fink to D, and always as much lefs as the liquor into
which it is plunged is denfer and confequently heavier.

By this procefs it will be eafily difcovered, whether
one kind of fluid is lighter than another with which it
is compared ; but the proportion cannot be accurately
determined i for in order to that, it would be neceflary
to know exactly the proportion between the tube A C
and the balls B and S ; which is impoflible according
to the above mode of conftr lifting the inftrument ;
and it would alfo be further neceflary that the tube AC
fhould be perfectly cylindrical, which never is the cafe.
The moft certain mode of acquiring this exact know-
ledge is, to operate always with equal volumes of
fluids : and for this purpofe, it is neceiTary to make ule
of Fahrenheit's hydrometer.

This inftrument (fig. 2.) is compofed of a fmall
oval glafs bulb or bottle B -, the neck of which A C
is very fmall, and terminates with a baibn D E, de-
figned to receive fmall weights.

The inftrument is ballafted by means of a fmall
ball of glafs S fixed underneath it, in which there is
depofited fome quickfilver. A fmall grain of fmalt(^)
is fixed upon the neck, and the inftrument is then
complete.

In order to make ufe of this hydrometer, i.t is ne-
ceflary to begin by knowing its exact weight, which

fliould

Chap. 2.] Fahrenheit's Hydrometer. 423

fhould be marked upon it, to prevent its being for-
gotten. The inftrument is then plunged into diftilled
water ; and by putting weights into the bafon p E, it
is made to fink as far as the grain of fmalt (a). The
weights which were made ufe of to produce this im-
merfion, added to the weight of the hydrometer, gives
exactly the weight of the volume of water meafured
by the inftrument. By repeating the fame operation
upon any other fluid, the weight of the volume of that
fluid meafured by the hydrometer, may be known with
equal exactnefs. Hence it follows, that the quantity
of thefe two volumes are equal, becaufe they are mea-
fured by the fame inftrument: the difference of their
weight then will give the difference of their fpecific
gravity, or the relation between their denfities. To
determine this relation exactly, the following propor-
tion muft be obferved : The fpecific gravity of the
proved liquor, is to that ofdiftilled water as the weight
of a volume of that fluid meafured by the hydrometer,
is to the weight of the volume of water alfo meafured by
it. If the fpecific gravity of the one is known exactly, the
fpecific gravity of the other' may be determined by it,
and alfo that of all other fluids which are proved in the
fame manner.

The whole of what has been advanced in this chap-
ter, and in that of the firft book upon fpecific gravity,
may be briefly fummed up in the following propofi-
. lions; Firft, when two bodies are equal in their magni-
tude, bulk, or volume, their fpecific gravities arc to
each other as their denfities. So that one body has
twice the fpecific gravity of another, when it has twice
the denfity of that other body comprized in the fame
fpace or magnitude.

Secondly, when two bodies lofe an equal weight in

the fame fluid, they have the fame magnitude or folid

E e 4 contents,

424 Recapitulation of Principles [Book VI L

contents, whatever form they may affume, fmce they
each lofe a weight equal to the bulk or volume of fluid
which they difplace.

Thirdly, the fpecifk gravity of bodies is inverfely

-as their bulk when their weights are equal. As one

body has twice the fpecific gravity of another, when

with the fame weight it has only half the magnitude

of that other body.

Fourthly, the fpecific gravities of two bodies are in
a direct proportion to their denfities, and in an inverfe
proportion to their magnitudes. This proportion is
a necefiary confequence of two preceding, viz. of the
firft and third.

Fifthly, the fame body will lofe a greater quantity
of its weight in a fluid fpecifically heavier than in a
lighter one ; becaufe it will always lofe a portion of its
weight equal to the weight of that bulk of fluid which
it difplaces. It requires then a greater force to fuftain
it in a lighter than in a heavier fluid : it will require
more force to fuftain it in air than in water.

Sixthly, the fpecific gravities of bodies of an equal
weight (when weighed in a common balance) are pro-
portionate to the weight which they lole in the fame
fluid. So that of two bodies of equal weight, if the
one lofes one- fifth and the other two-fifths of its weight
.in the fame fluid, the fpecific gravity of the firft is to
that of the fecond as two to one.

Seventhly, if a body is of theJame fpecific gravity
as a fiujd, when immerfed in that fluid it will be in
equilibrium with it, and remain at any depth at which
it is placed.

Eighthly, if a body fpecifically lighter than a fluid is
plunged entirely into it, and then left to itfelf, it will
remount with a force equal to the excefs of weight
which a volume of that fluid poffefies above an equal
bulk of phe body immerfed.

Ninthly,

Chap. 2.] relative tofy'rific Gravity. 425

Ninthly, the fpecific gravity of a folid is to that of
a fluid heavier than itfelf, and upon which it will fwim,
as the bulk of the immerfed part is to the bulk of the
whole body. So that if the magnitude or bulk of the
immerfed part is to the magnitude of the whole body
as two or three, the fpecific gravity of the folid is to
that of the fluid as two is to three.

Tenthly, the weight and the magnitude of a body,
and alfo the weight of a fluid fpecifically heavier than
the body, being given, fuppofe it is required to find
the force requifite to keep that body entirely immerfed
in the fluid. As this force is equal to the fpecific
weight of the fluid, find, by means of the given bulk
of the folid, and the known weight of a cubic foot of
the fluid, by the rule of three, the weight of a bulk of
the fluid equal to the bulk of the folid. Subftraft from
this weigh:, the weight of the folid, and the remainder
will be the force required. For example, fuppofe it
was required to find the force neceflfary to retain under
water a folid of eight cubic feet in contents, and of
four hundred pounds weight. Since a cubic foot of
water weighs about feventy pounds, the weight of
eight cubic feet of water is five hundred and fixty
pounds ; then if four hundred pounds are lubftracted,
the one hundred and fixty remainder, is the force ne-
cefTary to keep the folid immerfed in the water, and to
prevent it from rifing to the furface.

Eleventhly, the weight of a body fpecifically heavier
than a fluid, and the weight of that fluid fpecificaily
lighter, being given, fuppofe it is required to deter-
mine the cavity which that body mould have, in order
that it may fvvim upon the fluid.

The weight of a cubic foot of the fluid being given,
ths bulk of the portion of the fluid equal in weight to
that of the body, is found by the rule of three. If then

the

4? 6 Recapitulation of Principles, fcfr. [Book VII.

the cavity of the body is made fo, that the bulk may
be a little larger than the magnitude already found, the
body will have lefs weight under the lame magnitude
than the fluid. For example, fuppofe that it is re-
quired to make a ball of iron of thirty pounds, and of
fuch a magnitude as that it will fwim upon water.
Sir.ce the weight of a cubic foot of water is feventy
pounds, a volume of water weighing thirty pounds
\vill be r!;ree- fevenths of a cubic foot: hence it will be
eafy to find what the diameter of a fphere muft be, the
fetid contents of which mail be three- fevenths of a
cubic foct. Therefore, the ball of iron muft be made
hollow within, and in fuch a manner that its diameter
may be greater than the diameter of a fphere, the folid
contents of which is three-fevenths of a cubic foot: if
this ball is made eleven inches three lines in diameter,
it will fwim. Hence we fee that it is not neceiTary for
a body to fwim, that it mould be compoled of matter
fpecin'cally lighter than water j it fuffices that its bulk
.or volume mould be greaf and its gravity fmall :
for though copper is about eight times as heavy as
water, yet military men have occafionally employed
boats of copper in conftructing bridges for the paffage
of troops.

A copious table of fpecific gravities is given in the
Appendix to this volume.

Chap. 3.]

CHAP. III. .

HYDRAULICS*.

Of the Difcbarge cf Fluids through fmall Apertures. — The Difcbarge.
of Fluids through fucce(Ji--ve Pipes. — Artificial Fountains. — Pumps.—
Tbs Raifing Pump. — The Forcing Pump.— The Sucking Pump.—
The Compound Pump.— The Fire Engine. — Motion of Water in
Conduit Pipes. — Ofcillatory Motion cf Water in a Siphon. — Ofcilla-
tory Motion of Waves.— 'Motion of Wheels a fled upon by Water \ and
Conjhutlion of Water Mills.

TH E fcience which has for its object the motion
of fluids is called hydraulics ; and its immediate
application is to furnifh us with the means of conduft-
ing water from one fituation to another, by canals or
aqueducts, and to elevate it by pumps, jets-deaux, and
other hydraulic engines, either for the purpofes of or-
nament or ufe.

In treating of this fubje<5t I fhall commence with the
fimpleft principles, and mail firft fpeak of the difcharge
of fluids through fmall apertures.

When water flows from a veflfel which has a hole or
aperture in the bottom, fmall in comparifon to the
width of the vefiel, the water defcends vertically, and
the furface appears fmooth, but at three or four inches
from the bottom the particles turn from this direction,
and proceed on all fides with a motion more or lefs
oblique towards the aperture. The fame efFeft takes
place when water flows. through an aperture late-

* Almoft the whole of this chapter, and great part of the pre-
ceding, are tranflated from the firft volume of Briflbn's " Trahe.
Elcmentaire de Phyfique," Chap. VIII.

rally,

428 Flow of Water through fmall Apertures. [BookVII.

rally. The tendency of the particles towards the aper-
ture is a neceflary confequence of their perfect mobi-
lity ; for they will certainly be directed towards the
point where there is the leaft refiftance, and that point
is the aperture.

It is alfo to be obferved, that in this cafe, at a fmall
diftance from the bottom, a kind of funnel is formed
in the water, the point of which correfponds to the
center of the aperture j when, however, the water
flows through a lateral orifice or aperture, there is
formed only a kind of half funnel, which does not ap-
pear to commence till the fur face is near touching the
tipper fide of the hole. It is probable that the fun-
nel begins to form itfelf from the firft moment of the
8ow i but it 'does not become perceptible till the fur-
face is only at a final! diftance from the bottom.

It appears alfo, that the funnel commences higher
or lower, according to the width of the bottom j and
that the formation of it is lefs prompt or lefs percepti-
ble, according to the proportion of the aperture to the
extent of the bottom. The funnel is alfo augmented
by any roughnefs which may exifl at the fides or bot-
tom of the veflel.

Water flows out of a firtall hole in the bottom of a
vefTel with a velocity equal to that which a ponderous
body acquires* in falling from a hright equal to the
vertical height of the furface of the fluid above the
aperture.

The fame law takes place in a lateral orifice j for
the prefliire of the fluid is equal (at the fame depth)
in all directions, and confequently produces the fame
degree of velocity.

A fluid, in running out of an aperturp, acquires a
velocity fufScicnt to make it remount to a vertical

height

Chap. 3.] Dtfcbarge of Fluids, &V. 429

height equal to that of the furface of the fluid above the
aperture, in the fame manner as a falling body acquires
a velocity capable of making it afcer-d to the height
from which it defcended.

It is evident, from the theory of falling bodies, that
if the velocity of the fluid in running through the
aperture was uniformly continued, the fluid would
move through a fpace double the height of the fluid
above the aperture, in the fame time thac a falling body
would employ in defcending from that height.

The height being the fame, the velocity of the fluid
in running out of the orifice will always be tfce fame,
whatever the fpecies of the fluid may be, and whatever
its dennty. It is true, that when the fluid has more
denfiiy it prefles more forcibly, but then the mafs is
more considerable, and it is evident, that when the
moving powers are proportioned to the maffes which
they put in motion, the velocities are equal.

The quantities of a fluid difcharged in the fame
fpace of time through different orifices, fuppofing the
vefiels equally full during the whole of the experiment,
are to each other as the products of the areas of the
apertures by the fquare roots of the heights. For in-
ftance, it has been proved by experiment, that a circu-
lar orifice of an inch diameter, made in a thin vcfTel
or partition, and under a furface of fluid four feet in
height, will furnifh, in one minute of time, five thou-
fand four hundred and thirty - fix cubic inches
French.

Jf, therefore, it was an object to afcertain how
much a circular orifice of two inches diameter, under
nine feet of height from the furface of the water, would
furnifh in the fame time, the following proportion
muft be employed (it mull be obferved, that the ori-
fice of two inches is four times as great as an orifice

of.

430 Difcbarge of Fluids [Book VII.

of one inch, becaufe the areas of circles are as the
fquares of their diameters) :

i X \/ 4: 4 X \/ 9 :: 5436 : x

Or at length
2 : 12 :: 5436 : 32616
12

2)653232

Therefore 32616 cubic inches of water
will flow from an aperture of two inches in diameter
in one minute, the orifice being made nine inches
from the furface, which is fuppofed to be kept at that
height the whole time.

If a veffel of a prifmatic form is filled with water,
and permitted to empty itftlf en-.l. -ly through an ori-
fice at the bottom, and the time that it confumes in
emptying itfelf is obferved ; and if afterwards, having
replenifhed the veflel, the water is made to flow through
the fame aperture, the veffel being kept full the whole
time, there will run out in this fecond inftance, flu ring
the fame time that the veflel took to empty itfelf at
firft, a quantity of water double that which runs out
in the firft cafe, for the abftracTion of the water pro-
duces a kind of funnel, which in this laft cafe does nor
take place.

We often perceive water flow through lateral aper-
tures, which, though fmall in companion to the width
of the refervoirs, cannot be regarded as Lining all their
.points at an equal diftance from the furface of the
fluid; fuch, for example, as the apertures through
which water fometimes flows in mills. The common
method of determining the quantity difcharged is as
follows : fuppofe, in the firft place, the aperture to be
flopped up by a plate of metal, which is perforated

with

Chap. 3.] througbfma.ll Apertures. 47t

with a number of holes; if each o~ thefe holes is re-
garded as particular and infulared, the rapidity of the
flow through each will be according to the corrt \\-> n-
dent height of the fluid; then if the irvmber of holes
are multiplied ad infinitum, or, which will ,10,011,14: to
the fame thing, if the plate is fuppofed t > be en-
tirely taken away, the velocity at each point of ihe
fuppofed orifice will be according to the corrcfno: • nc
height of the fluid ; and in eftimating the quantity of
water difc barged, fome attention mufl be paid to the
inequality of the motion ; yet it muft not be alft-rred
that this reaibning is entirely conclufive. In propor-
tion as the fum of the fmall holes made in the plate is
fmail in comparifon with the fize of the refervoir, the
portions of water which flow through each hole are
forced out by the .abfolme weight of the column
above ; but the moment that the number of apertures
augment ad infinitum, and the ft reams of water which,
run through'- them -become contiguous, it cannot be
clearly faid that.the-lid.uid flows in the fame manner as
through final! iniuiatcd holes ; yet as this hypothecs
gives a refult fufficicntly conformable to experiments,
it may be ufeful to preferve it, and the more fo, as it
leads to very fimple calculations, and in all common
queftions this ftmplicitv may be preferable to the mi-
nutenefs of fractional operations.

The quantity of water which iffues from thefe aper-
tures in a given time is not fo great as their -fize
might at firft fugged, becaufe the itream is contracted
by running out of each orifice, and that contraction
extends to a diftance nearly equal to half the diameter
of the aperture; and the diameter of the contracted
ftream is to the diameter of the aperture a little more
than as three to four, or as three and one-iixth to four,
or nineteen to twenty- four ; fo that its area is to that

of

432 Di/charge of Fluids, &c. [Book VII.

of the aperture as ten to fixteen. It is nearly the fame
when water ftows through lateral apertures. The
contraction of the ftream is a proof of what has been
before ftated, viz. that withinfide a veffel, the lateral
particles direct themfelves towards the orifice with a
motion more or lefs oblique ; and this oblique motion
may be decompofed into two forces, the one parallel
to the plane of the orifice, and which contracts the
ftream j the other perpendicular to the fame plane,
and the only one which produces the efflux.

This contraction occurs alfo when water is made to
flow through pipes, and that at the entrance of the wa-
ter into the pipe, and not at its exit, where the ftream
preferves a cylindrical form. I (hall prove that this
contraction dimmifhes, in a fenfible manner, the quan-
tity of water which would naturally flow.

In order to aicertain thefe facts by experiments,
many have been made. In all the following infiances
the orifices, through which the v/ater flowed, were
pierced perpendicularly through plates of copper of
about one-twenty-fourth of an inch thick, and the rime
of each experiment is reduced to one minuet.

Chap. 3.] through fmall Apertures. 433

No.

of cubic

The conftant height of the water above the inches>
center of each orifice was 1 1 feet 8 inches f"r?lfh"

t. ed m i

10 lines. . minute.

Exp'. i. Through an horizontal circular4
orifice of £ inch (6 lines) dia-
meter 2,3 it

2. Through ditto of i inch dia-

meter 9j28r

3. Through ditto of 2 inches dia-

37,203

4. Through an horizontal rectan-
gular orifice of i inch* long and

A inch wide ^^

5. Through an horizontal fquare ori-
fice of i inch the fide - 11,817

6. Through ditto of 2 inches each

fide of the orifice * „ 47,361

Conftant height = 9 feet.

7. Through a lateral circular orifice

of | inch diameter - - 2oi8

8. Through ditto of i inch dia-
meter 8>IJS

Conftant height :z 4 feet.

9. Through a lateral circular ori-
fice of -J- inch diameter . 1,35 J

10. Through ditto, of i inch dia-
meter 5>4j6

Conftant height =: ^L- inch.

11. Through a lateral circular ori-
fice of i inch diameter • 628

YOL, IJ. F f It

4j4 Difcharge of Fluids. [Book VII.

It follows from the preceding table,

1. That the quantities of water difcharged in the
lame time, by different apertures, under the fame
height of furface in the refervoir, are to each other
nearly as the areas of the apertures. .Compare toge-
ther the refults of the fccond and third experiments, of
which the areas of the orifices are in the proportion of
one to four, and it will be found that the quantities of
water afforded, viz. nine thoufand two hundred and
eighty-one cubic inches, and thirty-feven thoufand two
hundred and three inches, are very nearly in the fame
proportion.

2. That the quantities of water difcharged in the
fame time through the fame aperture, under different
heights of furface in the refervoirs, are to each other
nearly as the fquare roots of the correfponding heights
of the water in the refervoir above the center of the
aperture. Compare together the refults of the eighth
and tenth experiments, where the heights of the refer-
voirs are nine and four feet, the fquare roots of which
are three and two, and it will be found that the two
quantities of water, eight thoufand one hundred and
thirty-five cubic inches, and five thoufand four hun-
dred and thirty-fix cubic inches, which run through
the fame orifice of one inch diameter under the dif-
ferent heights of nine feet and four feet, are to each
other nearly in the proportion of three to two.

3. That in general the quantities of water dif-
charged in the fame time through different apertures,
under different heights of furface in the refervoirs, are
to each other as the areas of the apertures are to
the fquare roots of the heights of water in the refer-
voirs.

4. That in confequence of the fri&ion, the fmall
apertures Turnilh a lefs quantity of water in proportion

than

Chap. 3.] through Jmall Apertures. 435

than the great ones, under the fame height of water in
the refervoir ; becaufc, comparatively to the extent of
the area of each orifice, there are more points of friction
againft the fides of the orifice in the fmali than there
are in the great ones ; for the circumferences do not
diminifh fo much as the areas.

5. That of many apertures of equal areas, that of
which the circumference is the leaft will, on account
of the friction, furnilh more water than the others,
under the fame height of the refervoir ; circular aper-
tures are, for this reafon, the moft advantageous of alii
for the circumference of a circle is the morteft line
that can be made ufe of to inclofe a given fpace ; there-
fore there is lefs furface of friction relatively to the fize
of the area.

It is eafy to perceive, that the quantity of water
difcharged in the table of experiments is not near
fo great as might be expected from the extent of the
areas and the heights of the refervoirs. The quantity
is in fait diminifhed by the friftion, and ftill more by
the contraction of the ftream ; for the velocity which
is in proportion to the entire altitude of the fluid is not
f?nfibly changed. Suppofing, firft, that the area of
the ftrcam is the fame as that of the orifice ; and liip-
pofing, fecondly, that the ftream is contracted, then
the difference of the quantities afforded is as fixteen to
ten ; that is, fuppofing the area of the aperture to be
diminifhed in the proportion of fixteen to ten, the
difcharge of the fluid out of veffels kept equally full
may be determined with fufficient exactnefs. By the
expreffion, an inch of water, is underftood the quantity
which flows out of a circular and lateral orifice of one
inch diameter, the furface of the water being con-
ftantly kept feven-twelfths of an inch above the cen-
ter of the orifice. This is the cafe with the eleventh
F f 2 experiment

436 . bfibttrge of Fluids [rfook VII.

experiment in the preceding table, where it appears
that the quantity of water furnifhed is fix hundred and
twenty- eight cubic inches. M. Mariotte, who made
the fame experiment, found the quantity to be a little
more ; but it is probable that he might commit a
fmall error, becatife the experiment I have juft cited
was made, M. 'Briflbn informs us, with the utmoft
care and attention. A (French) pint of water, he
adds, inftead of weighing two pounds, as is commonly
believed, is proved to fall fhort of that weight confi-
derably, as will be evident by ftrictly examining that
experiment.

Thefe facts being premifed, I mall requeft the at-
tention of the reader, fecondly, to the difcharge of
fluids through additional pipes.

When, inftead of caufmg water to pafs through an
aperture made in a thin fubftance, it is made to flow
through an additional vertical pipe of the fame dia-
meter with the orifice, the quantity of water dif-
charged is more confiderable, becaufe the contraction
of the ftream is greater in the firft cafe than in the
fecond.

In the following experiments, the conftant height of
the water in the refervoir above the upper bafe of the
additional vertical pipe is 1 1 feet 8 44 inches (French)
and the diameter of the pipe one inch.

C f i ap , 3 } through additional Pipes .

437

The variable heights of the
lube exprefTed in lines.

Lines.

Exper. I. -

2. -

3- -
4. -

- 48 f T^ water

J running
"^ J through a

- I 8 (^ full pipe.

{The water
not filling
the pipe.

Number of cubic inches of
water difcharged in one
minute.

- 12,274

- 12,188

- 12,168

- 9,282

It appears from this table of experiments, that the
longer the vertical pipe is, the greater will be the
quantity of water difcharged, becaufe the contraction
of the dream is lefs, as may be fecn by comparing the
three firft experiments. There is always, however,
fome contraction, though the water appears to flow
out of a full pipe.

In comparing the quantities of water difcharged in
the third and fourth experiments, it will appear, that tlfC
two quantities, 12,168 cubic inches and 9,282 cubic
inches, are to each other nearly in the relation of
thirteen to ten ; but it has been obferved before, that
the quantity of water difcharged through an aperture
made in a thin fubftance, if the ftream was not
contracted, would be to the quantity of water dif-
charged through the fame orifice, if the ftream was
contracted, nearly as fixteen to ten. Hence then it
may be concluded, that the height of the water in the
refervoir and the different apertures being the fame, the
quantity of water difcharged through an orifice made
in a thin fubftance, in which there Was no contraction
of the ftream, -the quantity of water difcharged through
F f 3 an

43 8 Dtfckarge of Fluids [Book VII.

an additional pipe, and the quantity which would flow
through an orifice made in a thin partition, in which
there was a contraction of the ftream, are to each other
nearly as the three numbers, fixteen, thirteen, ten^ and
thefe proportions are found lufficiently accurate for
common purpofes.

Hence alfo it may be inferred, that additional pipes
counteract only in part the contraction of the ftream.
The mod fenfible of all contractions of this nature is
that which takes place when water flows from a large
refervoir through a fmall aperture made in a thin
fubftance.

If the additional pipe, inftead of being vertical, or
placed in the bottom of the velTel or refervoir, is hori-
zontal, or placed in the fide, it will afford the fame
quantity of water, provided that it is of the fame
length, and that the exterior aperture is placed at the
fame diftance below the furface of the water in the
refervoir.

If the additional pipe, inftead of being cylindrical, is
conical, having its largeft bafe attached to the fide of
the refervoir, it will produce a much greater quantity
of water. The moft advantageous form, indeed, for
procuring the greateft quantity of water in a given
time through a certain aperture, is that which the
ilream itfelf naturally afiumes in coining out of an
aperture in a thin fubftance ; that is, the form given
to the pipe mould be that of a truncated cone, the
diameter of the fmaller bafe of which mould be the
fame as that of the aperture through which the water
is to flow.

It is neceflary alfo, that the area of the fmaller bafe
mould be to the area of the greater as ten to fixteen j
and the diftance between the two bafes mould be nearly
equal to half the diameter of the greater bafe. The

remainder

Chap. 3.] through additional Pipes. 539

remainder of the length of the pipe may be either
cylindrical or prifmatic. The difcharge will then be
equally abundant with that which would take place
through an aperture equal to the fmaller bafe made in
a thin partition, and in wliich the ftream fuffered no
contraction. This form may be applied to practice
whenever it is required to draw a certain quantity of
water from a river by an aqueduct, &c. through a
canal or lateral pipe.

If we compare the different quantities of water
difchargcd through additional pipes of different dia-
meters with different altitudes of the water in the re-
fervoirs, we lhall have the refults dated in the following
table, the additional pipes being fuppofed to be two
inches long, and vertical, or placed in the bottom of
the refervoir.

The conftant height
of the water above
the aperture,

The diameter of the addi-
tional pipes in twelfths of
an inch (lines.)

No. of cubic
inches dif-
charged in

•

one minute.

EX. ,.-| r

Mr552
3- [""".)

4-J I

6 7 The water running
103 through a full pipe.

6 7 The water not fol-
103 lowing the fides.

51,689.

U>703-
$ 1^93.
h>598-

q 228 )

6 7 The water running
1O j through a full pipe.

51,222.
3>402.

( lines, |

s.\ (.

6"? The water not filling
I O J the tube.

V 935-
1 2,603.

The firft inference from thefe experiments is, that

the quantity of water difcharged by different additional

pipes, under the fame height of water in the refervoir,

Ff4 is

44° Difcharge of Fluids through Pipes. [Book VII.

is proportional to the areas of the apertures, or to the
fquares of their diameters.

Secondly, it appears that the quantities of water dif-
charged through additional pipes of the fame diameter,
under different altitudes of wafer in the refervoir, are
proportional to the fquare root of the altitude.

Thirdly, that in general the quantities of water dif-
charged in the fame fpace of time through different ad-
ditional pipes, under different heights of water in the
refervoir, are to each other nearly as the product of the
fquare of the diameters of the pipes by the fquare root
of the altitude of the refervoirs.

The efflux of water, therefore, through additional
pipes, follows the fame laws as water when discharged
through apertures made in thin fubftances. On thefe
experiments the following table was formed, of the
quantities of water difcharged through a given aperture
made in a thin fubftance, fuppofing the ftream to fuffer
no contraction, or through the fame aperture with a
contraction of the ftream, or through the fame aperture
with an additional pipe.

Chap. 3.]

Artificial Fountains.

44*

Conftant

height of
the water
in the re-
fer voir
above the
aperture,
exprefled
in

Cubic inches of
water difcharg-
ed in one mi-
nute through an
aperture of one
inch diameter
without any
contraction of

Cubic inches of
water difcharg-
ed in one mi-
nute through an
additional pipe
of one inch dia-
meter and two

Cubic inches
of water dlf-
charged in one
minute through
an aperture of
one inch dia-
meter with a
contracted

(French)

the ilream.

inches long,

itream.

feet. '

I

4381

3539

2722

2

6169

5002

3846

3

7589

6126

4710

4

8763

•7070

5436

5

9797

7900

6075

6

10732

8654

6654

7

11592

9340

7183

8

12392

9975

7672

9

I3'44

10579

8135

10

13855

11151

8574

ii

H530

11693

8990

12

15180

• 12205

9384

13

'5797

12699

9764

14

16393

*3i97

10130

IS

16968

13620

10472

III. There is no application of the doctrines of hy-
draulics more furprifmg, or more gratifying to the eye,
than that which is feen in the variety of artificial foun-
tains, or jets d'eau, which the ingenuity of man has
been able to conflrucT: for ornament in general, and for
ufe in fome inftances, particularly in warm climates.
The principles on which thefe are conftructed it will
not be difficult, after what has been ftated, fully to
comprehend.

Whatever may be the direction of the jet or foun-
jain, the quantity of water expended will be, the fame?

provided

44 2 Artificial Fountains, [ Book V 1 1 .

provided that the ajutage *, and the height of the re-
fervoir above the ajutage, is the fame. This is a
neceffary confequence of the equal preflure of fluids in
all directions.

Water, when difcharged through an ajutage, however
fmall it may be, has a velocity fufficient to raife it to
the height of the furface of the water contained in the
refervoir ; fo that a vertical jet d'eau throws up the
water as high as the refervoir whence it proceeds, if
nothing obftructs it.

There are, however, many caufes which contribute
to diminifh the elevation of water by jets d'eau. Firft,
the friction in the pipes from the refervoir to the aju-
tage ; fecondly, the friction againft the circumference
of the aperture ; thirdly, the refiftance of the air to the
motion of the column ; fourthly, the gravity of the
particles of water themfelves, which, in rifing, lofe fome
.of their velocity, and recoil upon thofe which lucceed
them. Thus by inclining the pipe a little, we find
that the water will rife higher than when it is exactly
vertical ; but in this cafe, the effect is not fo agreeable
to the eye of the fpectator, as when the water which
rifes above the pipe into the air falls perpendicularly,
in a manner, back upon itfelf.

When the ajutage is placed in an oblique direction to
the horizon, the force of the projection and the gravity
of the water caufe the ftream which afcends into the
air to form a parabola, the amplitude of which is in
proportion to the height of the refervoir.

When the ajutage is placed horizontally, the water
forms a femi-parabola.

Fountains elevate the water in proportion as the
aperture of their ajutages is large j becaufe, firft, of

• A tube which is fitted to the mquth of the veffel through
which the fountain is played.

2, two

Chap. 3.] or Jets d'Eau. 443

two jets d'eaux proceeding from the fame refervoir,
and flowing from their ajutages with an equal degree
of velocity, the greater will, in the firft place, expe-
rience lefs friction ; and fecondly, it has a greater
mafs, and confequently more power to overcome the
obftacles which may oppofe it.

But, though large jets d'eau elevate water higher
than fmall ones, they do not expend a greater quantity
in proportion ; for the quantity of water difcharged is
as the product of the aperture of the ajutage by the
degree of velocity at the time of the difcharge ; and
this velocity is the fame in both, no allowance being
made for the friclion.

In order to make large fountains elevate water
higher than fmall ones, it is evidently neceflary that
the conducting pipes fliould be fufficiently large to
furnifh water in abundance; for if they are fmall, ex-
perience proves that the fmall fountains in that cafe
will elevate water higher than larger ones j it follows,
then, that the diameter of the pipe, which conveys the
water, fhould be in proportion to that of the ajutage,
in order to elevate the water to the greatefl poffible
height.

If we compare two different jets d'eau, and are de-
firous that each mould elevate water to the greateft
poffible height, it is neceflary that the fquare of the
diameters of the conduit pipes fhould be in proportion
to each other in the compound ratio of the diameters
of the ajutages and the fquare root of the altitudes of
the refervoirs. Thus, if it is known by experiment
what the diameter of a conduit pipe fliould be, to
fupply an ajutage 5f given dimenfions, it may be eafily
determined what the diameter of another pipe fliould
be to furnifh another ajutage of a determinate fize, the
height of the refervoir being alfo given.

It

444 Artificial [Book VIL

It has been proved by experiments, that when the
diameter of the ajutage h half an inch, and the height
of the refervoir fifty-two feet, the diameter of the pipe
which conducts the water ought to be three inches and
a quarter; and that for an ajutage of half an inch dia-
meter, the height of the refervoir being fixteen feet,
the diameter of the pipe ought to be about two inches
and one-third. There is no inconvenience in making
the conduit pipe of a greater diameter than is required
by this rule ; but on the contrary, there would be an
inconvenience in making it of a fmaller diameter.

Sometimes the ajutage is made in the form of a
cone, and fometimes in that of a cylinder ; but thofe
who conceive that it is indifferent in which of thofe
forms it is made are miftaken, for the cylindrical form
is by far the moft difadvantageous.

By comparing many experiments made upon artifi-
cial fountains, it has been determined, that the differ-
ences between the altitudes of vertical jets and the
height of their refervoirs, are to each other as the
fquare of the altitudes of the former. If then it is
known what quantity of water a jet elevates at a cer-
tain height of the refervoir, the quantity which any
other jet of a given height will elevate, compared
with the height of its refervoir, may be eafily found
by the rule of fingle proportion.

When it is neceffary to bend the conducting pipes,
the utmoft care mould be taken to avoid bending
them at right angles, for the ftriking of the current
againft thefe angles very confiderably diminifhes the
velocity.

The following table will greatly facilitate the appli-
cation of thefe principles.

The heights of jets, and the correfpondent heights
of refervoirs, are found in the two firft columns. The

third

Cv.ap. 3.] Fountains. 445

third column contains in (Paris) pints, of which thirty-
fix make a cubic foot, the quantities of water diP-
charged in one minute through an ajutage of half an
inch diameter, relatively to the heights in the fecond
column. The quantity difcharged through an ajutage
of half an inch diameter being known, the quantity
-which will be difcharged by any other ajutage, under
the fame height of the refervoir, may be found by
fingle proportion; for it has already been proved,
that the quantities of water difcharged are to each
other as the areas of the ajutages, or as the fquares of
their diameters. In the fourth column are found the
diameters for the conducting pipes of an ajutage of half
an inch diameter, according to the heights in the fe-
cond column. The diameters of pipes for other aju-
tages, and other heights of the refervoir, are found by
following the preceding rule.

Fractions are not obferved in the calculations for
the two lad columns.

1-4-6

drtifaial Feuntains. [Book VII,

The heights
of jets, ex-
prefled in
feet.

The heights of
tefervoirs, in feet
and inches.

Quantities of wa-
ter difcharged in
one minute
through an aju-
tage of half an
inch diameter, in
pints.

Diameters of tf>s
pipes, according
to the id and 3d
columns, in
lines.

Feet.

Feet. Inches.

Pints.

Lines.

5

5 i

3^

21

10

10 4

45

26

is

'5 9

56

28

10

21 4

65

31

25

27 i

73

33

3°

33 o

81

34

35

39 i

88

36

40

45 4

95

37

45

5' 9

101

33

5°

58 4

1 08

39

55

65 i

114

40

60

72 o

120

4i

65

79 i

125

42

70

86 4

J31

43

75

93 9

136

44

80

101 4

142

45

85

109 i

147

46

90

117 o

152

47

95

125 i

158

48

100

'33 4

163

49

IV. From objects of mere pleafure and ornament,
our attention is next folicited to an invention of emi-
nent utility, and of ancient date, though the modern
improvements are very confiderable even in this branch
of mechanics.

Pumps are hydraulic engines, defigned for the pur-
pofe of elevating water j they are compofed of hollow
cylinders A B (Plate VII. fig. 3.) or E F (Plate VIII.
fig. i.) of an equal diameter throughout their whole
length, which is called the body of the pump, and in

which

Chap. 3.] Pumps. 447

which a kind of ftopple I, called the pifton, is made to
flide, or move up and down. The pifton is put in
motion by means of a rod of metal X x, at the extre-
mity of which X the handle is placed, and elevated by
the lever X Y, or by fome other contrivance ; to this
is annexed a pipe AT (Plate VII. fig. 3.) to con-
duct the water to the height required ; and, laftly, the
fuckers S s.

There are feveral kinds of pumps; fome are called
fucking pumps and others forcing pumps, and there
are others which are at the lame time both fucking and
forcing pumps.

The raifing pump is compofed of the body of the
pump A B, (Plate VII. fig. 3.) /to the lower part of
which is affixed the end of a pipe B N, open at the
bottom, or (which is ftill better) pierced with holes
its whole length, in fuch a manner that large piece's
of dirt and rubbilh may be prevented from entering
the body of the pump. At the union of this end of
the pipe with the body of the pump is placed a valve
or fucker s, which, when raifed up by the preflure of
the water beneath, permits the fluid to afcend into the
body of the pump, but which, by being prefled down
again by the action of the pump, prevents effectually
the efflux of the water by the fame aperture. In the
body of the pump there is a box or pifton I, pierced
quite through, furnifhed at the upper end with a fucker
S, and joined at #, by the affiftance of a head fomewhat
in the form of that of a pair of compafTes, to the rod
x X, which enables it to act by the aid of a le^er
X Z Y. At the upper part A of the body of the
pump is placed the raifing pipe A T, which has its
fpout at T. This pump ought to be placed in a well
or bafon, in fuch a manner that the body of the

pump

44S 72* railing [Book VlT.

pump A B fhould be entirely under the fur face of the
water A A.

Now if the pifton I is raifed by lowering the extre-
mity Y of the lever Y Z X, fo that the lever may
affume the podtion y Z «, the pifton will rife in the
body of the pump, where it will create an imperfect
vacuum equal to the diftance X #, and confequently
the water beneath will raife the fucker s, and will
pafs out of the bafon into the pump. When the
pifton is lowered again, this prerTurc caufes the fucker
s to clofe, and the fucker S to rife up ; hence the
water which was below the pifton is then above it.
By a fecond exertion of the pifton, this quantity of
water is elevated, and by the fame mechanifm a frefh
quantity is permitted to pafs into the pump, and after-
wards to rife above the pifton, in the fame manner
as the firit portion was raifed ; fo that by a certain
number of exertions of the pifton, the railing pipe
AT is filled. When this is accomplimed, at every
exertion or ftroke of trie pifton there is ejected at the
fpout or difcharging pipe T a mafs of water equal
to a cylinder, the bafe of which is equal to the width
of the pifton, and of a height equal to the fpace
through which the pifton pafles in the body of the
pump. This fpace is commonly called the play of
the pifton.

It is not difficult to eftimate the weight of the co-
lumn of water with which the pifton is charged, when
the raifmg pipe is full, and confequently the force
which is neceffary to be exerted at Y in order to
work the pump. It has been obierved before, that
fluids prefs in proportion to their perpendicular height,
and the width of the bafe which oppofes their defcent.
In a pump, this bafe is the pifton, and the perpendi-
cular

VOL JT.. i>.44fi.

Huff 7.

Chap. 3.] Pump. 449

cular height is that of the raifing pipe above the fur*
face of the water ; fo that when the raifing pipe is full,
the charge upon the pifton is equal to the weight of
a cylinder of water, the diameter of which is equal to
that of the pifton, and the height equal to that of the
raifing pipe above the furface of the water, whatever
may be the diameter of the mourning pipe j and this
charge or weight upon the pifton is eafily calculated,
when it is known that a cylinder of water of one foot
diameter and one foot high weighs about fifty-five
(French) pounds.

It follows, therefore, that the weight of a column of
water is not diminimed by diminifhing the diameter
of the raifing pipe; but that, on the contrary, the re-
fiflance which ought to be overcome is even augmented
on account of the increafe of the friction, which is
more confiderable in fmall pipes than in large ones,
becaufe the relative furfaces augment as the diameters
diminiih. Thus, only for the expence, it would be
wrong to make, as is commonly done, the raifing pipe
fmaller than the body of the pump j on the contrary,
it would be better to conftruct it of a diameter greater
than that of the body of the pump, as the friction
would tje proportionably diminiflied.

The forcing pump is compofed of the body of the
pump C D, (Plate VII Fig. 4.) flopped clofe at the
bottom, but entirely open above, and in which is a
pifton K, which only differs from that of the pump
already defcribed in this, that its fucker S is placed
at the bottom inftead of the top. This pifton, like •
that of the pump juft mentioned, is put in action by
means of the lever Y X Z, which has its point of
fiipport in Z. The raifing pipe A O is placed at the
fide of the body of the pump, with which it commu-
nicates, and is furaiihed with a fucker s in its lower

VOL. II. G g part,

450 tfbe forcing Pump. [Book VII.

part, and with a fpout O at its upper extremity. This
pump, as. well as the preceding, ought to be immerfed
in a well or bafon in fuch a manner that the body of
the pump C D fhould be entirely under the furface of
the water A A.

The water fills the body of the pump by falling
through the aperture C, and by pafling over the pifton
K, the fucker of it S, confidering its pofition, will
natundly open. If the pifton K is loweredj by placing
the lever Y X Z in the pofition y u Z, the refiftance
of the water againft the fucker S will clofe it imme-
diately. This water then, being incapable of repaffing
above the pifton, is forced up the pipe A O, by
raifing up the fucker s. As foon as the pifton is
raifed again, the fucker s is clofed by the preffare of
the water which is above, and the fucker S is opened
by its own weight. A new mafs of water then paflTes
below the pifton, which by a fecond depreflion of the
pifton, is forced to pafs, like the firft, into the pipe
AO ; fo that by a certain number of ilrokes of the
pifton, that pipe becomes full of water, which in then
idifcharged at the fpout O as in the pump already de-
fcribed. If the piftons in both of them are of the
fame diameter, and the raifing pipes of the fame per-
pendicular height, the weight of the two columns of
water will be equal, and the two pumps will require
the fame power to work them j for in that cafe it re-
quires the fame power to elevate the pifton charged
with a column of water as it does to force the column
of water by means of the pifton.

The fucking* pump (Plate VIII. Fig. i.) is com-
pofed of the bo$y of the pump E F, open above, and

* So called, becaufe.it was originally fuppofed, but erroneoufiy,
to -adl by fuftion*

with

t hap. 3.] The fucking Pumpj 45 1

with a pipe of 'afpiratfion or lucking pipe F P adapted
to the lower part. At the union of this pipe with the
body of the pump is a fucker s> defigned to permit
the water, while the pifton is raifed, to enter through
the pipe of afpiration P F into the body of the pump
F E, and to prevent it, while the pifton is lowering,
from being difcharged the fame way. In the body of
the pump is a pifton L, made like that at I in PlateVII.
Fig. 3. and which it put in action in the fame man-
ner by the afliftance of the lever X Z Y. This pump
fhould be placed in fuch manner as to have only the
lower extremity of the afpiration pipe F P plunged
into the water.

While the pump remains inactive, the two fuckers
S and s are naturally clofed from their own weight.
If the pifton L is raifed up by means of putting the
lever X Z Y in the fituation u Z y, the column of air
which refts above is elevated, and the air which is
clofed up in the afpiration pipe, from the furface of
the water a to the pifton, having then more fpace to
occupy, becomes more rarified than the external air.
This laft then preffes more forcibly upon the furface
of the water a, and caufcs it to rife in the afpiration
pipe, till the interior air has regained its former den-
fity by occupying lefs fpace. Thus, after feveral
ftrokes of the pifton, the water reaches the body of
the pump, and paries over the pifton, by railing up the
fuckers s and S, one after another, and the pifton, by
its fubfequent elevation, forces the water to efcape at
the fpout E.

As it is the prefiurc of the air which caufes the

water to rife in this pump, and as this prcffure can

fuftain only a column of water of about thirty-two

feet, it is clear that the afpiration or fucking pipe

G g a Should

452 fbejucking [Book VII,

ihouid not exceed that length. In common practice
it is indeed feldom made fo long as thirty-two feet.
In order that the preffure of the atmofphere may be
fuch as to fuftain a column of water of that height,
it is neceffary, firft, that the fucking purnp ihouid be
made with the greateft exactnefs, and that it mould
continue in 'a perfect ftatei fecondly, that it mould be
placed upon the level of the fea, or very near it, be-
caufe it is there that the preflure of the atmofphere
is rnoft forcible j thirdly, that the preffure of the air
ihouid not vary ; but in general all thefe circumftances
are not required. Mechanics are fatisfied, in general,
with making the afpiration pipe twenty-three or twenty-
four feet long. If it is neceffary to elevate water to
a greater height, the forcing pump is more commo-
dious for that purpofe. The latter, it is true, is fub-
jedt to feveral inconveniences. It is neceffary to place
the body of the pump either in wells or in a bafon.;
and when it is required to repair it, which often hap-
pens, one of two things is neceffary, either to empty
the well or the bafon, or to draw up the body of the
pump, which is extremely troublefome and expenfive.
To remedy thefe inconveniencies, the beft and moft
iifual mode is, when water is to be elevated from a
great depth, to make the pump at once both a forcing
and fucking pump, in the manner which I mall pre-
fently explain.

In the year 1766 it was reported, through the chan-
nel of the public papers, that at Seville, in Spain, a
fimple fucking pump had been conflructed, which ele-
vated water to the height of fixty feet, and it was con-
fequentlv concluded, that the world had till then been
notorioufly impofed upon by the current maxim, that
the preffure of the air could raife a column of water

only

Chap. 3.] Pump. 453

only to the height of thirty-two feet. M. Brifibft has
carefully examined into the fad, and his explanation is
curious and interefting.

An ignorant tinman, at Seville, had made a fucking
pump fixty feet long, becaufe he had occafion to ele-
vate the water to that height. When the pump was
fixed in its place, and put in action, he was unable to
make the water rife into the body of the pump. En-
raged at this difappointment, he gave it a blow with
Jiis hammer, which produced a fmall aperture in the
afpiration pipe at about ten feet above the furface of
the water in the bafon. Immediately a fmall portion
of water arrived at the body of the pump. After this.
procefs it was reported, that a fucking pump had
been conftructed, which elevated water to the height
of fixty feet; but the reader will be enabled to judge
of the truth of this aflertion from the following obfer-
vations :

Let us fuppofe that the afpiration pipe, P F (Plate
VIII. Fig. i.) had from a, the furface of the water
of the bafon, to F, a diftance of fixty feet, and that
after a certain number of ftrokes of the pifton, the
water rifes to <r, thirty-two feet high ; if then a fmall
hole is made at b, ten feet above the furface of the
water, the air which enters at this hole, and preffes
in all directions, will caufe the column of water of ten
feet, which is below £, to fall into the bafon, and the
prefiure of the air upwards at b has only a column of
water of twenty-two feet to fupport.

But that preffure is capable not only of raifing that
column to the height of fixty feet, but even to the
height of eight thoufand feetj for air, near the furface
of the earth, is eight hundred times lefs denfe than
water, and fuppofing (which is not the cafe) it was
#0 1 diminiihed in elevating, then the ten feet of water,
Q g 3 eut

454 ?ke Jucking [Book V.II,

cut off by the prefiure of the, air at b, downwards,
would be more than equivalent to eight thoufand
feet of air. The column of air, therefore, which
prerTes at b, will be too flrong for more than eight
thoufand feet ; thus the twenty- two feet of water re-
maining above will not be in equilibrium with the
column of air till after it has rifen higher than eight
thoufand feet.

In order to have a fecond portion of water with a,
pump of this conftruftion, it is in the firft place ne-
ceffary to (lop the aperture which war. made at b> then
to give feveral ftrokes with the pifton to elevate the
water as high as c\ and laitly, to open again the
orifice at b. Obferve the fimplicity of this procefs
for raifing fo fmall a quantity of water ! for it is necef-
fary that the afpiration pipe fhould be of a very fmall
diameter, otherwife the column of water would break,
and the air would pafs through, and not one drop of
water could be raifed into the body of the pump.
This fad -(adds M. BruTon) may ferve to convince
thofe who are fond of novelty, that before an opinion
generally received is pronounced to be falfe, it is.
neceffary to think twice at the leaft. A fhort time
after the conftructing |of this pump at Seville, M.
Bellange, a goldfmith in Paris, made one in imitation
of it, to which he gave the additional property of
throwing water fifty-five feet high, by means of a
continued jet or ejecting pipe, though the machine was
only a fimple fucking pump.

To a fmall bodied pump of two inches and one-
twelfth in the interior diameter, the pifton of which
had eight inches play, he adapted an afpiration pipe
of ten-twelfths of an inch diameter, and fifty-fix feet
long; this pipe was furnifhed wkh a fucker at its junc-
tion with the body of the pump, and with another at

its

Chap. 3.] Pump. 455

its lower extremity. This extremity was plunged
into a tun full of water. M. Bellange had made a
fmall perforation in this pipe of about one twenty-
fourth of an inch diameter, at twelve or fifteen inches
above the furface of the water in the tun. The appa-
ratus being difpofed of in this manner, he moved the
pifton gently, but the water did not rife; the fmall
hole furnifhed a fufficient quantity of air to fill the
afpiration pipe. He then moved the pifton with great
velocity ; the fmall hole could not, in fo fhort a fpace
of time, furnifh a fufficient quantity of air to fill the
pipe; a little water role and mixed itfelf with the air,
fo that the column became compofed of fmall cylin-
ders, alternately of air and water, and though it was
fifty-five feet high, it was much fhort of the weight
of a column of water thirty-two feet high. If we
calculate, therefore, according to the diameter of the
body of the pump, and the extent in which the pifcon
played, what quantity of water this pump would have
furniflied if the air had not entered, and then compare
this quantity with that which it really furnifhed, we
lhall find that the latter is greatly inferior ; for in fix
minutes five hundred and thirty ftrokes of the pifton
may be given, which would furnifh only thirty-fix
pints of water j this pump, therefore, would not fur-
nifh the eighth part of the water which it ought to do
upon the common principles of the fucking pump; fo
that though the conftruction might appear to be more
ingenious, it was not in reality to be preferred to that
of Seville.

The compound forcing pump is compofed of the body

of the pump G H, (Plate VIII. Fig. 2.) open above,

and the afpiration pipe H V adapted to the lower end.

At the union of this pipe with the body of the pump

Gg 4 is

456 *f he compound Pump. [Book Vlf,

is a fucker S, defigned for the fame ufe as in the
fimple fucking pump. In the body of the pump is
a pifton M, not pierced as the preceding, but folid,
and put in action by the aid of the rod x X, and of
the lever Y X Z, which has its point of fupport, or
fiilcrum, at Z. At the fide of the pump, and towards
the bottom of its body, is adapted a raifing pipe H R,
furnifhed with a fucker s near its bafe, and with a
fpout R near its fuperior extremity. This pump
ought to be placed in fuch a manner that the lower
extremity. only of the afpiration pipe H V fhould be
immerfed under water.

It is eafy to perceive that the firft action of this
pump will be the fame as that of the fucking pump,
\vhich has been defcribedj for if the pifton M is
raifed by putting the lever Y X Z in the fituation
y u Z, the column of air which refts above will be
elevated ; the air which is in the afpiration- pipe will
become, by that means, rarer than the exterior air.
The latter then prefies more forcibly upon the furface
of the water A A, and carries it, after fome ftrokes
of the pifton, into the body of the pump ; when it
is arrived there, if the pifton M is lowered, the fucker
S will clofe, and the water is forced along the raifing-
pipe H R, by the rifing of the fucker j, which, as foon
as the preflure ceafes, falls again from its own weight
and that of the water above it.

This pump is very convenient, on account of its
body being placed out of water, which affords an op-
portunity of making the neceffary repairs with facility,
and alfo on account of its being capable of carrying,
water to any height which may be required : in order
to effect this, all that is necefiary is, to lengthen die
raifing-pipe, and to augment the power which puts

the

Ni

ilBlill^^ '

Chap. 3.] <The Fire Engine. 457

the pump in aftion. I believe this is at prefent the
moft ufual form of what are called forcing pumps in
this country.

The fire engine is" an hydraulic engine, which may
be clailed with the pump that 1 have now defcribed.
It is at once a fucking and forcing pump, but has
a continued jety or ejecting pipe, though it has only
one body. The effential parts of this pump are
compofed, like the compound pump, (Plate VIII.
Fig. 2.) with this difference, that its afpiration pipe
is much fhorter, and that inftead of a folid raifing
pipe it has a leathern tube of a convenient length.
This pump (Plate IX. Fig. i.) is then compofed of
the body of the pump A H, open above, and to the
lower part is adapted the afpiration pipe H T. At
the union of this pipe with the body of tTie pump is
placed a fucker S, defigned to prevent the water,
which has once paffed into the body of the pump,
from returning into the bafon. In the body of the
pump is a pifton M, not pierced but folid, and which
is put in motion by the aid of a metal rod x X, and
of a lever Y X Z, v/hich has its fulcrum or point of
fupport at Z. Towards the bottom of the pump, in
the fide, is an aperture C, which is covered again by
means of a valve c /, of which the tail / is a Ipring,
and which is fixed on with a fmall fcrew. This
valve is defigned to prevent the water, which is ex-
pelled from the body of the pump, from entering
again when the pifton M is raifed. The body of the
pump is furrounded with a pipe A B D E, about two
or three inches more in diameter than the body of the
pump, and the intermediate fpace between them is
filled with air. To the lower part of this pipe, and
upon the fide, is adapted another fmall crooked pipe
£ R, furnilhed at the end R with a, fucker j, and with

a fcrewr

453 ne Fire [Book VII.

a icrevv ferule, intended to receive a nut, by means of
which the leathern pipe is joined to this end of the
engine, and which ferves inftead of the raifing pipe
in the common forcing pump. All this apparatus is
placed (as may be feen in Plate IX. Fig. 2.) upon a
box or cafe N O lined with lead, which contains the
water. The crofs bar Q^fupports the upper end F
(Fig. i.) of the body of the pump, which, for that
purpcfe, is of a Imaller diameter than the reft ; and
the lid L (Fig. 2.) of the box has an aperture in the
middle, to admit the afpiration pipe H T to pafs
through it.

From this explanation it will be evident, that if the
pifton M is raifed up by putting the lever Y X Z in
the fituation y n Z, the fucker s and the valve ^, placed
at C, will be cJofed by the preffure of the exterior air.
This fame prefiure, exercifmg its force upon the fur-
face of the water V V, obliges it to pafs into the body
of the pump by raifing up the fucker S. It then acts
#s a fucking pump ; but when the pifton M is lowered,
its preffure clofes the fucker S, and opens the valve
which is at C ; the water then pafTes, not only into the
leathern pipe a b d, (Fig. 2.) by raifing up the fucker s
(Fig. i.) but alfo into the fpace between the body of
the pump and the pipe which inclofes it, by rifing
towards I K, and compreffes the air which is confined
there. Immediately after the pifton M is raifed
again, that air, being no longer compreffed, unfolds
itfelf by its elafticity, acts upon the water which is be^
tween the body of the pump and the pipe which in-
ciofed it, and forces it alfo into the leathern pipe, fo
that when the pifton is lowered, the water is forced by
the pifton itfelf, and when it is raifed, the water is
forced by the elafticity of the air, which furnifhes a
continued ftream, though the pump has only one body
or principal tube,

Chap. 3.3 Engine. 459

It is evident that thefe fire engines fhould be able
to furnifh a continued tlream, and this can .only be
effected by employing the elafticity of the air, while
the pifton is rifing ; but in order to effect this, a dou-
ble force is required to put the pump in motion ; in
other words, a force capable of expelling the column
of water, and an equal force to comprefs the air. But
this is not an inconvenience, for, in cafe of fire, it very,
feldom happens that hands are wanting to affiil ; on
the contrary, it frequently happens that the aflemblage
of people is rather too numerous.

Such is the engine which M. Briflbn has defcribed,
and it is, I prefume, that which is in common ufe in
France. ' Its fimplicity is admirable j yet I apprehend
that our Englifli fire engines are more powerful, and
furnifh a more uninterrupted ftream or current of wa-
water through the leathern pipe. In Fig. 3. is a re-
prefentation of our improved fire engine. This, the
reader will fee, is wrought by two forcing pumps,
which act alternately ; and the ftream is made con-
tinual from the fpring of air confined in a ftrong metal
veflel C C, in the fire engine A B, fixed between the
two forcing pumps D and E, wrought with a com-
mon double lever F G moving on the center H.
The piftons in D and E both fuck and force alter-
nately, and are here reprefented in their different
actions, as are alfo the refpedtive valves at I K
and L M.

The water to fupply this engine, if there is no
opportunity of putting the end of a fucking pipe,
occafionally to be fcrewed on, into a moat or canal
(which would fpare much hurry and labour in cafe of
fire) is poured into the vefiel A B ; and being flrained
through the wire grate N is, by the preffure of the
atmofphere, railed through the valves K and M into

the

460 fbs Fire Engine. [ B ook VI I .

the barrels of D or E, when -either of their forcers
afcend; whence again, upon their defcent, ic will be
powerfully propelled into the air-veflel C C, through
the valves I and L by turns: the common air then
between the water and the top of the air-vefTcl C C
•will from time to time be forcibly crowded into lefs
room, and much comprefTed ; and the air being in that
condenfed ftate pofTeflTed of a flrong and lively fpring,
and always endeavouring to dilate itfelf every way
equally in kich a circumftance, bears ftrongly both
againft the fides of the veffel wherein it is confined, and
the furface of the .water thus injected ; and thus pro-
duces a conftant regular (bream, wlych rifes through
• the metal pipe P into the leather one Qj and this lat-
ter being perfectly flexible, may be led about into
rooms and entries, as the cafe may require.

Should the air contained in this vefiel be compreffed
into half the fpace it took up in its natural (late, the
fpring of it will be nearly doubled 5 and as before it
equalled and was able to fuftain the preffure of the at-
mofphere, fmce it has now a double force, by the
power of that fpring alone it will throw water into air
o-f the common degree of denfity about thirty feet
high. And fhould this compreffure be (till aug-
mented, and the quantity of air, which at firft filled the
whole veffel, be reduced into one-third of that fpace,
its fpring will be then able to refifr, and confequently
to raife the weight of a treble atmofphere ; in which
cafe it will throw up a jet of water fixty feet high.
And fhould fo much water again be forced into the
vcffel as to fill three parts of the capacity, it will be
able to throw it up about ninety feet high : and where-
ever the fervice (hall require a ftill greater rife of wa-
ter, more water muft be forced into this vefiel; the
air therein being thus driven by force into a ftill nar-
rower

Chap. 3.] Modes of Working Pipes. 461

rower compafs, at each explofion, its gradual reftitu-
tion to its firft dimenfions is what regularly carries on
the dream between the ftrokes, and renders it continual
during the operation of the machine.

Various agents are employed to put pumps in ac-
tion, fuch as men, hcrfes, ftreams of water, vapour,
wind, &c. Small pumps, fuch as thofe in common
wells, or fire engines, are generally wrought by men.
When a confiderable quantity of water is required to
be raifed, the moving power muft be increafed; and
in order that a regular effort may be employed, or
very nearly fo, feveral additions are occafionally made
to the mechanifm of pumps, fo that when one fet of
piftons defcend another fet may be made to rife by the
fame force. The great engine at Marli is wrought by
an apparatus of this kind.

The action of thefe engines depends upon the regu-
larity of the alternate motion of the fuckers or valves.
It follows then, that thefe mould be fo conftructed and
difpofed as perfectly to retain the water when they are
clofed, and to open eafily when the action of the ma-
chine is directed to that object:,

V. .Of the motion of water in conduit pipes.

When it is required to conduct water from one
place to another, it is very clear that the conducting
pipes muft be longer than the fpace through which it
is to be conveyed.

In treating of the difcharge of water through addi-
tional pipes, I have taken but a curfbry notice of the
refiftance by friction, becaufc there it is fcarcely per-
ceptible; but it is not the fame with refpect to pipes
of confiderable extent ; the friction of the water againft
their fides leflens confiderably the velocity of the flow-
ing

462 Motion of Fluids through [Book VII.

ing water, as has been proved by experiments. I fhall
firft fpeak of rectilinear pipes.

In the following experiments two pipes were em-
ployed, one of an inch and a quarter diameter, and the
other of two inches. The two pipes were fuccefiively
lengthened from thirty feet to one hundred and eighty;
and the conftant height of the water in the refervoir,
above the pipes, was fometimes one foot,- and fome-
times two.

The following table Ihews the refults of thefe expe-
riments :

The conftant
height of the
w.!ti-r in the

• The diftance to
which the

The numbsr of
cubic inches of
water furnifhed
in one minute, by

The number of
cubic inches of
water furnifhed

refervoir
above the-

water was con-
veyed, exprefTed

a pipe of an inch

in one mir.ute bj
a pipe of two

pipe, in inches.

in feet.

diameter.

inches diameter.

I

30

2778

7680

I

60

1957

55^4

I

1587

4534

I

120

I35I

3944

1

150

1178

3486

I

180

1052

31 19

2 .

30

4066

11219

2

60

2888

8190

2

9°

2352

6812

2

120

2011

5885

2

15°

1762

5232

2

180

J5^3

4710

If, by the aid of the table of additional pipes, which
has been before inferted, we fhould wifh to find the
quantity of water difcharged by two additional pipes
of one inch and one-third and two inches diameter,
under the fame height of the refervoir, and without
having any regard to friclionj but only to the areas of

the

Chap. 3-] Conduit Pipes .

the orifices of the pipes, it will be .fc
one minute,

1. The height of the refervoir being one foot, the
pipe of one inch and one-third diameter, in this cafe
there will be difcharged fix thoufand two hundred and
ninety-two cubic inches of water.

2. The height of the refervoir being two feet, the
fame pipe will furnifh eight thoufand eight hundred
and ninety-three cubic inches of water.

3. The height of the refervoir being one foot, and
the pipe two inches in diameter, there jvill be 'dif-
charged fourteen thoufand one hundred and fifcy-fix
cubic inches of water.

4. The height of the refervoir being two feet, the
fame pipe will furnifh twenty thoufand and eight cubic
inches of water.

It is eafy to perceive, that thefe quantities of water
are much greater than the correfponding quantities in
the above table ; and that the quantity furnilhed by
each pipe diminifhes, in faft, in proportion to its
length, becaufe there is then a greater fur face of fric-
tion. But it muft be remarked, that the diminution
of the quantity of water difcharged is not exaclly in
proportion to the length, of the pipe. The difcharge
is indeed dirainifhed as the pipe is made longer ; but
this diminution decreafes (if I may ufe the expreflion)
in the progrefs of the current ; for the firft thirty feet
•the difcharge is diminilhed much more than in the fe-
cond thirty feet j and the third augmentation of thirty-
feet to the length diminifhes the difcharge fdlllefs than
the fecond; and fo of the reft. The refult of all this
is, that in common practice, where great precifion is noc
required, it may be laid down as a rule, that the quan-
tities of water difcharged in equal times, through the
fame horizontal pipe, under the fame height of the re-
fervoir,

4^4 Difcbarge of Water [Book Vll ,

fervoir, and at different diftances from^ the fonrce or
refervoir, are to each other nearly in an inverfe pro
portion of the fquare roots of thefe diftances;

It may be obferved from the preceding table, that
a pipe of one inch and one-third diameter furnifhes
lefs water in proportion than one of two inches diame*
ter, under the fame height of the refervoir, and of the
fame length. The reafon of this is, becaufe there is,
relatively to the quantities of water which thefe pipes
will contain, more furface of friction in the fmall pipe
than in the larger one.

If the fame pipe was curvilinear inftead of being ftraitj
the difcharge would ftill be diminished from this circum-
fiance, though not in any confiderable degree , but the
diminution would be ftill greater if the curvilinear pipe
was placed in a vertical inftead of a horizontal pofi-
tion. The diminution (fmall as it is) is produced by
the refiftance which the water meets in running againft
the angles of the pipe, which deprive it of a part of
its velocity.

But if the pipe, inftead of being curvilinear, was
angular in feveral points, the diminution would be
greater, and the more fo in proportion as thofe angles
fhould be more acute, becaufe then the refiftance to
the water would be more direct. When the pipes are
curved, and their curvature vertical, as in Plate X*
Fig. i. there are then declivities and afcents in which
the air will lodge, and refift or even impede the courfe
of the water. For example, let A B C D E F G be a
pipe, the upper extremity of which A anfwers to a re-
fervoir which fupplies it with water, and the extremity
G goes to furnifh a fountain. The pipe being filled
with nothing but air, and water being made to run
from A, this water will drive the air before it, and fill
the portion of the pipe A B more than the portion

Chap. 3.] through Conduit Pipes. 465

B C ; the water having arrived at the bending C, will
flow down the lower part of this bending, and will pro-
ceed to fill the bending D, leaving behind it the co-
lumn of air C D, which cannot efcape. The water,
continuing to run, will rife from D to E, and having
arrived there, it will ftill flow down the lower part of
this declivity to fill the bent F, leaving behind it a fe-
cond column of air E F, which will remain confined
there, notwithstanding the preflure of the column A B ;
for the column of air C D cannot counterbalance the
preflure of the column of water D E, any more than
the column of air E F is capable of counterbalancing
the column of water F I ; fo that though the water in
the pipe A B is confiderably above the level G, the
water can only rife towards I, and there ceafes to flow*
The only remedy is, to let out the two columns of air
C D and E F, by placing at the elbow of the bendings
two fmall pipes C and E, through which the air may
efcape, and when the courfe of the water is well ar-
ranged the apertures may be clofed with bungs.

VI. Of the ofcillatory motion of water in a fiphon.

It is well known that the duration of the ofcilla-
tions of two pendulums of unequal lengths are to
each other as the fquare roots of thofe lengths. The
ofcillatory motion of water in a fiphon is of the fame
nature.

Suppofe a fiphon (Fig. 2.) compofed of three
branches, two vertical / n, m 0, and one horizontal » o ;
fuppofe that the interior diameter of the fiphon is equal
through its whole extent; that in this fiphon, the fluid,
in a ftate of reft, occupies the fpace anod-> then the
two furfaces a b, c d, are upon a level. Suppofe then,
that, by fome caufe, the liquid is forced to defcend tog h*
in the branch m t, and confequenUy to elevate itfelf to

VOL, II. H h «/,

466 Of dilatory Motion of Water [B ook V 1 1 .

efy in the branch /#; as foon as this caufe ceafes to
act, the fluid will be operated upon merely by the
common laws of gravitation and motion. The excefs
of the length of the column e ny above that of the co-
lumn b o, will force the fluid to defcend, and that even
below the level of the other, on account of the accele-
ration of its defcent, which will caufe the fluid in the
other branch m o to rife ; the fluid will then defcend
and afcend alternately, or in ofcillations fimilar to thofe
of a pendulum; and the deviation of each of thefe
ofcillations will be precifely the fame as that of the
ofcillations of a pendulum half as long as ^ie length
f q r of the column of the fluid.

Since the ofcillations of wafcer follow the fame law
as thofe of a pendulum, it follows, that if the length of
the column of water is augmented or diminifhed, the
duration of each ofcillation will be augmented or di-
miniflied. ,,

VII. The ofcillatory motion of water in waves has
been compared by Sir Ifaac Newton * to the ofcilla-
tory motion of water in a fiphon.

Let A B C D E F (Fig. 3.) be fuppofed a meet of
water, the furface of which rifes and falls in fucceflive
waves j let A C E be the tops of thefe waves, and
B D F the intermediate hollows or concavities, which
feparate them. As the waves are formed by the fuc-
cefllve afcent and defcent of the water in fuch a man-
ner that the higher parts become the lower, and fo al-
ternately and fucceflively, and as the weight of the
elevated water is the moving power which caufes the
loweft parts to afcend and the higheft to defcend, thefe
alternate rifings and fallings are confidered as ana-

* Priucipia, lib. I. prop. 46*

logous

Chap. 3'.") in a Siphon and in Waves. 467

Jogous to the ofcillatory motion of water in a fiphon,
and they obferve the fame Jaws relative to their du-
ration.

If there is then a pendulum, the length of which is
equal to half the tranfverfal diltance that exifts between
the top or apex of a wave A (for example) and the
cavity B, that is equal to half A£, the higheft parts
will become the loweft in the fame fpace of time in
which this pendulum vibrates, and in the fpace of
another ofcillation they will again become the higheft.
Each of thefe waves then will roll its whole courfe
during the time which the pendulum takes in perform-
ing two ofcillations ; and as a pendulum four times the
length of the preceding, that is, the length of,which is
equal to the width of the wave A C3 will make only one
- ofcillation, while the firft makes two, it follows, that
the waves perform their ofcillations in the fame fpace of
time as a pendulum equal in length to the width of
the fame waves would perform its ofcillations. What
•is meant by the width of waves, is the tranfverfal fpsce
A C, which is between their greateft elevations, or
the fpace B D, which is between their greateft conca-
vities.

It follows from thefe premifes, that waves, which
are about three feet and three quarters of an inch wide,
roll their whole width during a fecond of time, and
confequently they roll one hundred and eighty-three feet
fix inches and five-fixths in a minute, and in an hour
eleven thoufand and fourteen feet two inches j waves
four times as wide will roll this fpace in twice the
time j it follows then, that the wider or more ex-
panded the waves are, the greater will be the fpace
which they roll over in a given time.

But what has now been ftated refpe&ing the motion
H h 2 of

46 8 Canftruftion of [Book VII.

of waves, is founded upon this hypothecs, that all the
parts of the water rife and fall in right lines ; yet it
muft. be obferved, that both their rife and fall are
more frequently made in curved lines than in (Irak
ones j fo that the determination given above refpett-
ing the fpace which waves roll over in a given time
may be regarded only as an approximation to the
truth.

VIII. The motion of wheels acted upon by the fall
or force of water, though ftrictly a branch of mecha-
nics, is yet intimately connected with the fcience of
hydraulics.

The wheels of fome water-mills are furnifhed with
•wings, float- boards, or fhelves, at their circumference,
with very little or no concavity •, others are furnifhed
•with a kind of ladles or boxes, which will contain a
confiderable quantity of water. In the firfl cafe, the
water acts upon the wheels principally by its fhock or
fall; in the fecond, by its weight. I Ihall firft fpeak
of wheels moved by the Ihock of the water.

It has been proved by experience, that the more nu-
merous the wings or float-boards are in proportion to
the diameter of the wheel, the fatter it moves. To
wheels of twenty feet diameter, there are commonly
placed about forty float-boards ; but a greater number,
as for example fort\ -eight, would be ftill more advan-
tageous. To the wheels of thofe mills which are raifed
upon boats or rafts in rivers, there are ulually only
eight or ten floats ; but thefe wheels would have more
effect if they had fifteen or fixteen.

When a wheel with wings or float-boards turns m
a kind of frame or cafe, fo as to prevent the water
from falling immediately into the general current, the
impulfe which it receives * from the water is about

one-

Chap. 3.] Water Wheels* 469

one- fifth greater in proportion to the velocity of the
fluid, than it would receive in an unconfined ftream,
becaufe in the latter cafe the water which abounds is
turned behind the float, and refifts it; on the contrary,
when rhe wheel moves in a frame, there is only a fmall
quantity of water, which moves with as much velocity,
or with rather more, than the float- board.

It has been proved by experience, that when this
cafe or frame is but juft wide and deep enough to
admit the wheel to move freely, and the water has
an opportunity of running out after having given its
fhock or impulfe, the direct and perpendicular force
againfl the floats of the wheel is about twice the force
which the float would receive if it was plunged to the
fame depth in an unconfined current.

When a wheel furnimed with forty -eight floats turns
in a cafe or frame, and it is not plunged very deep in
the water, its circumference will have about two-fifths
of the velocity of the .current, in which cafe the ma-
chine will produce the greateft effect.

It appears that float-boards are the moft advan-
tageous when they are placed in a direct line towards
the center of the wheel j becaufe but few of them
would be required, fmce they would then be flruck
perpendicularly by the water, which produces the mod
powerful effect, When they incline, the mock is
oblique, which diminifhes the effort j yet a certain
degree of inclination caufes the water to rife the
length of the float, and to remain there a certain time ;
it then acts by its gravity after having acted by its
fhock or fall, and the effect which refults from this
arrangement more than compenfates for the diminu-
tion which the Ihock fuffered from the obliquity with
which the force was applied in the firft inftance. Jn
general, thp wheels placed in frames which have a cer-
H h 3 Sain,

470 Conftriittion of [Book VII,

tain declivity fhould have their floats or buckets in-
clined fo much towards the radius as to caufe them
to be ftruck in a more perpendicular direction, that
they may receive an augmentation of force from,
the weight of the water. The moft advantageous in-
clination of the floats towards the radius appears by ex-
perience to be between twenty and thirty degrees.

A wheel placed near a refervoir turns fwifter than
in any other place, becaufe then the whole force of
the defcending fluid is effectually applied; but if there
is a neceffity for placing it at the end of the water-
courfe, at a certain diftance from the refervoir, the
channel of the water- courfe or frame fhould incline
about the tenth part of its length, fo that the Hoping
may give to the water that degree of velocity which
would otherwife be deftroyed by friction ; the wheel
will then receive the fame impulfe as if it was placed
clofe to the refervoir.

Water acting by its weight produces a much greater
effect than when it acts by its fhcck in falling. M.
Parent, in the year 1704, and M. Pitot, in 1725, in-
deed demonftrated, that a wheel (fuppofed to be with-
out friction) moved by a current of water, and de-
figned to elevate a portion of that water to the height
of that which puts it in motion, is incapable of ele-
vating it higher than -/T or ^ nearly; whereas the water
acting upon the wheel by its own weight would be
capable of elevating to the height from which it de-
fcended half of the water which defcended.

When, therefore, we have only a fmall quantity of
water, and are obliged to hufband it well (which often
happens, becaufe there are more fmall ftreams than
large rivers) we fhould contrive to make this water
act by its weight rather than by its fhock or impulfe ;
for this purpofe, inftead of having wheels with plain
i float-

Chap. 3.] . Water IVheels. 471

float-boards, they Ihould be furnifhed with concave
or hollow ones refembling buckets, whenever we
can have a fall of more than four feet, and efpecially
where there is not the neceflary quantity of water to
turn a mill with wheels, furnimsd with plain > float-
boards.

M. Deparcieux, in the Memoirs of the French
Academy of Sciences *, has proved, that the flower
wheels with buckets move, the more will be their
effect with an equal expence of water. He made a
fmall wheel of twenty inches diameter, the circum-
ference of which was furniflied with forty-eight buck-
ets. Upon the axis of this wheel were placed four
cylinders of different fizes ; the leaft was one inch
in diameter, the next two inches, the third three
inches, and the fourth was four inches in diameter.
Thefe cylinders were different axes, about which a
cord, which elevated a weight by means of a re-
turning pully placed above the machine, wrapped it-
felf. The axis of the wheel was fupported at each
end by two rollers eafily put in motion; this was to
diminifh the friction. To the fore part of the wheel,
and a little higher than its axis, was attached a fmall
fhelf, upon which was placed a veflel with a hole
pierced in it on that fide towards the wheel, which was
rilled, with water. Above this veflel was placed a
large bottle full of water inverted, and the neck of it
was plunged a few lines in the water of the veflel, in
order that the bottle Ihould only empty itfelf in pro-
portion as the water in the veflel ran through the
aperture. The water in flowing fell into a channel
which carried it into the buckets of the wheel. By
this means he made fure of employing, at each expe^.
always the fame quantity of" water.

* Fpr the year 1754, page 603 and 671.

fl h 4 The

472 Experiments on Water Wheels. [Book VII.

The following table contains the refults of the ex-
periments made by M. Deparcieux. He fometimes
elevated weights of twelve ounces, and fometimes of
twenty-four ounces : the heavieft, refilling the mod',
compelled the wheel to turn flower. He wrapped
the cords which fupported the weights fucceflively
round the different cylinders, and found that che fame
weight refilled more in proportion as its cord was
wrapped round a larger cylinder.

Diameter of the cy-
linders.

Elevation of a weight
of 1 2 ounces.

Elevation of a
weight of 24
ounces.

i Inches.

2

3
4

69!; Inches.
8p|

HI

s7i-

40

43 ^
44l

451

When the cord was wrapped round a larger cy-
linder, or the elevated weight was more confiderable,
the wheel turned flower. It appears from thefe re-
fults, .that the fame weight was carried fo much higher
according as its cord was wrapped round a larger cy-
linder. It appears alfo, that double the weight, which
retarded the rotation ftill more, was carried to more
than half of the height to which the fingle weight was
carried ; in tha,t cafe, therefore, the effect was greater.

It may be laid down as a principle, that water acts
by its weight much more forcibly from the fame height
or fall, than by its impulfe ; and that the flower wheels
•with buckets move, the greater, with the fame expence
pf water, will be their effect This augmentation of
effect is caufed by the fame quantity of water acting
longer, while the wheel moves with lefs velocity.

Chap. 4.] [ 473 ]

CHAP. IV.

OF THE OCEAN.

Sahnefs of the Ocean. — Different Opinions as tt the Caufe. — Probable
Reafcns 'why the Sea has been always fait, — Temperature of the Sea
at different Depths. — Modes of rendering Sea-nvaterfrejh*

TH E greateft quantities of water with which we
are acquainted are by no means pure, but
united with faline matter. The ocean is fait in all'
parts of the world ; but the degree of faltnefs differs
much in different climates, and is almoft univerfally
found to be greater in proportion as the water is taken
up nearer the equator, where the heat of the fun is
greateft, and the evaporation of the watery particles
confequently more confiderable. When treating of
fea fait, the refult of various obiervations relating to
this fubject were detailed.

The caufe of the faltnefs of the ocean has been a
fubjecl: of inveftigation among philofophers in almoft
all ages, but it ftill remains in great obfcurity. There
can be little doubt, that a large quantity of faline
matter exifted in this globe from the creation -, and, at
this day, we find immenfe beds of fal gem, or common
fait, buried in the earth, particularly near Cracow ;
but whether thefe collections have been derived from
the ocean, and depofited in confequence of the eva-
poration of its waters in certain circumftances, or
whether the ocean was itfelf originally frefh, and re-
ceived its fait from collections of faline matter fituated at
its bottom, or from that brought by the influx of rivers,
cannot now be afcertajned.. ^No accurate obfervations

on

474 Saltmjs of [Book VII.

on the degree of faltnefs- of the ocean in particular
latitudes were made till the prefent century, and it is
not poflible, therefore, to afcertain ^vhat was theftatff
of the fea at any confidcrable diftance of time, nor,
confequently, whether its degree of faltnefs increafes,
decreafes, or is fbttionary. From differences arriong
aquatic animals, however, fome of which feem adapted
to fait water, and fome to frefh, it is probable, that both.
thefe flates of water exifted from the creation of the
•world. We know it is true^ that fome kinds of fifh,
as falmon, are capable of exifting both in frefh and in
fait water, and that habit has a powerful influence over
all animals j but this is not fufficient to refute the main
fact, that fome kinds of fiih thrive only in fait water,
others in frefh 3 fome in Handing pools, and others in
rapid currents.

That excellent philofopher and chemift, to whofe
labours I am indebted for fome of the moft valuable
parts of thefe volumes, the bifliop of Landaff, has re-
commended a moil fimple and eafy mode of afcer-
taining the faltnefs of the fea in any latitude ; and as
the language, in point of perfpicuity and correclnefs,
cannot be improved, I fliall take the liberty of inferring
it in his own words.

c As it is not every perfon who can make himfelf
expert in the ule of the common means of eftimating
the quantity of fait contained in fea water, I will men-
tion a method of doing it, which is fo eafy and fimple,
that every common failor may underftand and praftiic
it, and which at the fame time, from the trials I have
made of it, feems to be as exact a method as any that
has yet been thought of. — Take a clean towel or any
other piece of cloth, dry it well in ihe fun or before
the fire, then weigh it accurately, and note down its
weight,* dip it in the fea water, and, when taken out,

\vrins

Chap. 4.] the Ocean. 475

wring it a little till it will not drip, when hung up to
dry; weigh it in this wet ftate, then dry it either in
the fun or at the fire, and, when it is perfectly dry,
weigh it again. The excefs of the weight of the wet-
ted cloth above its original weight, is the weight of
the fea water imbibed by the cloth j and the excefs of
the weight of the cloth, after being dried, above its
original weight, is the weight of the fait retained by
the cloth; and by comparing this weight with the
weight of the fea water imbibed by the cloth, we ob-
tain the proportion of fait contained in that fpecies of
fea water.

£ Whoever undertakes to afcertain the quantity of
fait, contained in fea water, either by this or any other
method, would do well to obferve the flate of the
weather preceding the time when the fea water is taken
out of the fea, for the quantity of fait contained in the
water near the furface may be influenced both by the
antecedent moifture and the antecedent heat of the
atmofphere V

Whether the fea is falter or not at different depths
has not yet been afcertained ; but that its temperature
varies confiderably in proportion to the depth v/e have
decifive proof.

' With refpe6b to the temperature,' fays bifhop
Watfon, c of the fea at different depths, it Teems rea-
fonable enough to fuppofe, that in fummer time it will
be hotter at the furface than at any confiderable depth
below it, and that in winter it will be colder. Suppofe
a ciftern, twelve feet in depth, to be filled with fpring
water of 48 degrees warmth, to the height of eleven
feet; then, if we fill up the ciftern to its top, by gently
pouring water heated to 100 degrees upon the furface

* Watfon's Chemical Efiays, vol. ii. p. nd.

Of

476 temperature of the Ocean. [Book VII,

of the fpring water, it may readily be underftood, that
the heat of this water will not be inftantaneouily com-
municated through the whole mafs of water in the
ciftern, but that the water will decreafe in heat from the
furface to the bottom of the ciftern. On the other
hand, if on the n feet of fpring water heated to 48
degrees, we pour a foot of water heated only to 33 de-
grees, it may be expected,, that the fpring water, which
is nearcft to the cold water, will be fuoner cooled by
it than that which is at a greater diftance ; and on this
account the water at the bottom of the ciftern will be
warmer than that in the middle or at the top. It muft
be obierved, however, that cold water being, bulk for
bulk, heavier than hot water, the water which has only
33 degrees of heat will defcend, by its fuperior weight,
into the mafs of water contained in the ciftern, and
thus the water in the ciftern will be cooled, not only
by the bare communication of cold from the upper
water, but by 'the actual mixture of that water with the
reft, fo that the difference between the heat of the wa-
ter at the bottom and top will not be fo great as it
would have been if the cold water had not mixed it-
felf with the reft. Thefe fuppofitions of hot and cold
water incumbent on the fpring water in the ciftern, are
analogous to the aftion of the furnmer and winter at-
mofpheres incumbent on the furface of the fea. No
perfon, who has bathed in deep (landing water in fum-*
mer time, can have failed to obferve, that the water
grew colder and colder, according to the depth to
which he defcended. I have frequently obferved, that
the furface of a pool of water of two feet in depth, has
in a funny day, even in winter, been five degrees hotter
than the water at its bottom.

' Mr. Wales defcribes the inftrument he made ufe
of for trying the temperature of the feu at different

depths^

Chap. 4.] at different Depths. 477

depths, in the following terms : " Tht apparatus for
trying the heat of the fea water at different depths
confided of a fquare wooden tube of about 18 inches
long and three inches fquare externally. ' It was fitted
with a valve at the bottom, and another at the top,
and had a contrivance for fufprnding the thermometer
exactly in the middle of it. When it was ufed it was
fattened to the deep fea line, juft above the lead, fo that
all the way as it defcended the water had a free paiTage
through it, by means of the valves which were then
both open; but the inftant it began to be drawn up,
both the valves clofed by the prefihre of the water,
and of tourfe the thermometer was brought up in a
body of water of the fame temperature with that it
was let down to *." With this inftrument, which is
much the fame with one formerly defcribed by Mr.
Boyle, in his obfervations about the faknefs of the fea,
water was fetched up from different depths, and its
temperature accurately noticed, in different feafons and
latitudes.

f Auguft 27, 1772, fouth latitude 24°. 40'. Hie
heat of the air was 72!, — of the water at the furface
70,— of water from the depth of 80 fathoms 68 f.

c December 27, 1772, fouth latitude 58°. 21'.
The heat of the air was 31 , — of the water at the
furface 32, — of water from the depth of 160 fathoms

Mft-

( In the voyage to the high northern latitudes be-
fore mentioned, they made ufe of a bottle to bring up
water from the bottom, which is thus defcribed.

* See Agronomical Obfervations made in a Voyage towards
the South Pole, &c. in 1772, 1773, &c. by W. Wales. Intro-
duftion, p. 53.

f Wales's Obfer. p. 206.

J Ibid. p. 208.

« Th«

.478 Temperature of the Ocean> tee. [Book VII,

" The bottle had a coating of wool, three inches
thick, which was wrapped up in an oiled fkin, and let
into a leather purfe, and the whole inclofed in a well-
pitched canvas bag, firmly tied to the mouth of the
bottle, fo that not a drop of water could penetrate to
its furface. A bit of lead fhaped like a cone, with its
bafe downwards, and a cord fixed to its fmall end,
was put into the bottle ; and a piece of valve leather,
with half a dozen flips of thin bladder, were ftrung on
the cord, which, when pulled, effectually corked the
bottle on the infide." I have here put down two
of the experiments which were made during that
voyage.

< Auguft 4, 1773, north latitude 80°. 30'. The
heat of the air was 32, — of the water at the furface 36,
— of water fetched up from the depth of 60 fathoms
under the ice 39 *.

c September 4, 1773, north latitude 65°. The
heat of the air was 66', — of the water at the furface
££, — of water from the depth of 683 fathoms 40.

£ It appears from all thefe experiments that, when
the atmofphere was hotter than the furface of the fea*
the fuperficial water was hotter than that at a great
depth i and when the atmofphere was colder than the
furface of the fea, it is evident that the fuperficial wa-
ter 'was fomewhat colder than that at a confiderable
diftance below it : and I doubt not that this will ge-
nerally be the cafe, though fudden changes in the
temperature of the t atmofphere, which cannot be in-
itantly communicated to the fea, may occafion parti-
cular exceptions.

c In the year 17795 feverd experiments were made,
with great accuracy, in order to inveftigate the tern*

• Voyage towards the North Pole, pa 143.

perature

Chap. 4.3 Modes of rendering Sail Water fre/h. 479

perature of the lake of Geneva, and of other lakes in
Switzerland, at different depths ; we learn from them,
that in winter time there is very little difference be-
tween the heat of the water at the furface, and at a
great depth below it ; but that in fummer, the fuper-
ficial water is confiderably warmer than that which is
at a great diftance from the furface. The experi-
ments were made with a thermometer graduated after
Reaumur's fcaie; fome of them, reduced to Fahren-
heit's fcale, arc expreffed below.

1 Temperature of the lake of Geneva at different
depths, in the beginning of February 1779, after a
month's uninterrupted froft.

' Heat of the open air variable from 37 to 40 de-
grees.

' Water at the furface of the lake - 42^-
Depth 100 feet 42^-

Depth 250 feet 42-i.

Depth 950 feet, bottom 4^4-

c In another part of the lake, open air from 37 to
40.

Surface - - 42|

Depth 350 feet - - 42^-

Depth 620 feet, bottom 4* -,4-

c Temperature of the lake of Neuchatel, July 17,
1779.

Air ... 75.L

Surface - - 73*..

Depth 225 feetj bottom 41*.'

Sea water may be rendered frem by freezing, which
excludes or precipitates the-faline particles, or by dif-
tillation, which leaves the fait in a mafs at the bottom

* Watfon's Chemical Effays, vol. ii. p. 129.

of

480 Modes of rendering Salt Water fr eft. [Book VII.

of the vcfTel. Upon thefe principles, a mode of ob-
taining a fupply of frefti water at fea was recommended
fome years ago to the Admiralty, by Dr. Irving. It
confifted in only adapting a tin tube of fuitable dimen-
fions to the lid of the common mip's kettle, and con*
denfing the iteam in a hoglhead which ferved as a
receiver. By this mode a fupply of twenty-five gal-
lons of frelli water per hour might be obtained from
the kettle of one of our fhips of war. I have not nn-
derflood, however, that the plan has been as yet intro-
duced into general practice.

Chap. 5.] [ 481 ]

CHAP. V.

OF RAIN.

Recapitulation of Doflrines relative to fpontaneous E-Tjaporation,—^fra-
four ly fame fnppofed to conftji of hollow FeJicles.-—Rain. — Different
Theories of Rain. — Sno-iv. — Hail. — Rain ivbicb froze in coming in
contact ivit/j the Earth. — Large Hail-ftones>-~-Fogs.—Dc-iv. — Hoaf
Froft,—Injlances of partial freezing when the general Temperature
is above the freezing Point.

IN a preceding volume, when treating of the effects
of heat or fire, and particularly of vapour, it was
neceffary to introduce a few obfervations relative to
fpontaneous evaporation. It is proper, however, to
repeat, in this place, that philofophers are by no means
agreed with rcfpedt to the caufe of this phenomenon.
By fome it has been attributed to a folution of water
in air fimilar to that of faline fubftances in water j by
others, to the adion of the ele£tric fluid. The firlt
of thefe opinions had till lately obtained almoft uni-
verfal afTent, but is now relinquished, fince it is found,
that evaporation proceeds, as well in the exhaufted
receiver of die air pump, as when air is prefent. Elec-
tricity has been found to promote evaporation, and
clouds are almoft univerfally electrical ; but evapora-
tion is carried on continually where there is no reafon
to fuppofe the prefence of the eledric fluid, at Jeaft
where its.operation cannot be difcovered by any known
teft. It is at prefent commonly fuppofed, that redun-
dant heat is the general caufe of the evaporation of
water, and that it always proceeds in proportion to its
VOL. II, I i tempera-

48 1 Vapour compofed of [Book VII .

temperature, compared with that of the furroundirag
medium.

There is one circumftance very much in favour of
the opinion, that the emiffion of heat is the chief caufe
of evaporation, which is, that every liquor cools when
it evaporates, becaufe the portion of the fluid which
difappears carries away a quantity of caloric from the
liquor, which "becomes latent in the vapour.

A doubt has arifen among philofophers, whether
water, as it exifts in a tranfparent ftate in the atmo-
ipherc, is in particles of an uniform denfity, or afTumes
the form of hollow veficles. When there is a tendency
to rain or fnow, it is known to exift in the ftate of mi-
nute drops and icicles j but the folution is then not.
perfect, its tranfparency is impaired, and clouds are
produced.

The exittence of hollow fpheres is faid to have been
actually obferved by feveral perfonsj but as a micro-
fcope of confiderable magnifying power muft be em-
ployed, this may have been a fource of error, and may
have produced delufive appearances. The fimpleft
and moft inftruftive manner of obferving them is to
expofe a cup of fome warm aqueous fluid, of a dark
colour, as coffee, or water mixed with ink, to the rays
of the fun in a fine day, when the air is very calm;
a cloud will rife from the fluid to a certain height,
and then <lifappear. An attentive eye will foon difco-
ver that this cloud confifts of fmall round grains, of a
whitifh colour, and detached one from the other. To
acquire a more diftinct idea of their form, they may
be obferved, as they rife from the furface of the liquor,
with a lens of about one inch and an half focus,
being careful, however, to keep the lens out of the
vapours, .that they may not deprive it of tranfpa-
rency.

Spherical

Chap. 5.] hollow Veficles. 483

Spherical ^alls of different fizes may in this manner
be obferved proceeding from the, furface with more
or lefs rapidity. The more delicate rife fwiftly, and
foon traverfe the field of the lensj the larger fall back
into the cup, and, without mixing with the fluid, roll
upon its furface like a light powder, which obeys
every impulfe of the air. The lightnefs of thefe fmall
fpheres, their whitenefs, &c. give them an appearance
altogether different from folid globules j their perfect
refeinblance to the larger balls, that are feen floating
on the furface of the liquid, can leave no doubt of
their nature : it is fufficient to fee them to be con-
vinced that they are hollow bubbles, like thofe blown
from water a::d foap. M. Kratzenftein endeavoured
to eftimate their fize, by comparing them with a hair,
and /ound that they were twelve times fmaller than the
hair, the diameter of which was the three hundredth
part of -n inch, and confequently one of thefe was only
the three thoufand fix hundredth part of the fame
mealu re.

Thefe bubbles may even be fometimes, it is faid,
obferved in a fog, or in a cloud, when the obferver is
ituated oa a hill. To this end M. de Sauffure ufed
a lens of one and an half or two inches focus, which
he held near his eye with one hand, in the other he
held any fmooth, flat, and polifhed furface, of a black
colour, as the bottom of a tortoife fhell box., bringing
this towards the lens till it was very near the focal*
diftance ; he then waited till the agitation of the air
brought fome pa'rticks of the cloud into the focus of
the lens; when the cloud was thick this focn hap-
pened, and he perceived round and white particles-
fome pafling with the rapidity of lightning, others
moving (lowly ; fome rolling on the furface of the
tortoife fhell, others ftriking againft it obliquely, and
I i 2 • rebounding

4$ 4 Vapour confifts of hollow Peficks. [Book VI L

rebounding like a ball from a wall, and others fixing
themfelves to it. Small drops of water might alfo be
feen to fettle on the tortoife fhell, but they were eafily
diftinguiftied from the hollow fpherules, by their
tranfparency, their gravity, and their pace. Further,
clouds do not form a rainbow ; it is produced by folid
drops j when a cloud is not in an a<5lual (late of refo-
lution, it does not change the form of the ftars which
are feen through it j for infinitely thin menifcufifes do
not fenfzbly change the courfe of the rays of-light; but
as foon as the cloud begins to refolve itfelf into folid
drops, or even without clouds, when folid drops begin
to be formed in the air, the ftars feen through them
are all defined, furrounded with a diffufe light, circles,
and halos ; hence, thefe meteors are the forerunners
of rain, for rain is nothing more than thefe drops aug-
mented or united. When the veficular vapours are
condenfed by cold, the water which formed the bub-
ble cryftallizes, fometimes into hoar froft, fometimes
into fnow.j when it does not freeze, they unite in
dew, or defcend in rain. Many other curious pro-
perties concerning the veficular and concrete vapours*
are related in M. de Sauflure's EfTai fur 1' Hygro-
metric *.

The precipitation of water from the atmofphere jn
rain has given rife to as much fpeculation as evapora-
tion j and it muft be confefled, that the caufe of neither
has yet been very clearly afcertained. By fome it is
fuppofed, that the capacity of the air for fufpending
aqueous vapour is in proportion to its heat, and there-
fore that any circumftance which cools the atmofphere
will produce rain. If, therefore, according to this
theory, a ftratum of cold air meets with a warmer ftra-

* See Adams's Leisures on Natural Philofophy.

turn,

Chap. 5-] Dr.Hutton'sVbeoryofRain. 485

turn, a fall of rain is occafioned, becauie the w^rr
ftratum is cooled. To this it has been replied, that
by this mixture the colder ftratum mufr be as much
warmed as the warmer is cooled, and, therefore, that
no precipitation ought to take place. In order to
obviate this difficulty, Dr. Hutton fuppofes that heat
enables the atmofphere to fuipend water in an in-
creafmg ratio, according to the quantity of it. Thus,
if two degrees of heat enable a certain quantity of
air to fufpend two given meafures of water, three de-
grees of heat will enable the fame quantity of air to
fufpend more than three fuch meafures. Upon this
fupporkion, if two ftrata of air, each of which is charged
with as much water as its temperature enables it to
fufpend, meet together, and are reduced to a mean
temperature, they will not be able to fuipend as
much water as in their feparate ftate, and a preci-
pitation of part of the water will confequently be
produced *.

Others confider rain as an electrical phenomenon f,
and it is very generally allowed, that electricity at
leaft concurs with other caufes in producing it. Bo-
dies charged with the fame electricity, whether it is*
negative or pofitive, always repel each other, and the
aqueous particles which compofe clouds, being acted
on in this way, will be prevented from uniting into
drops fufficiently large to fall to the earth. The ra-
pidity with which rain falls after a difcharge of light-
ning from a cloud, tends much to confirm this opi-
nion. Rain alfo falls heavieft from the center of a

* That heat has a considerable influence in fufpending aqueous
vapour, appears from the phenomenon of dew ; which, the reader
will remember, is part of the water taken up by the air during
the day time, but which is again depofited during the coolnefs oi
the iiight.

f See Book IV. chap. 6.

I i 3 cloud,

486 Snow, [Book VII,

cloud, where the electric matter has Been found by
experiment to be generally in equilibrium ; while very
little is di (charged from the edges, which are ufually
found to be electrified either pofitively or negatively.

The wind has been fuppofed to have an effect in
producing rain, by driving the aqueous particles into
contact, and thus caufing them to unite into drops.
But, by experience, wind fecms to have the direct con-
trary influence, and frequently prevents rain.

Befides rain, many other phenomena are produced
by the capacity which air has in different circumftances
pf taking up, fiifpending, and depofiting water; the
chief of thefe are fnow, hail, fogs, clouds, dew,, and
hoar froft.

The cold of the higher regions of the atmofphere '
js fometimes fo great, as to freeze the aqueous par-
tides which form clouds. If the particles become
frozen before they have had time to unite into drops,
many of the fmall icicles which are produced, uniting
together, and being connected only at a few points,
form fiocculent maifcs, which are called fnow. The
order and arrangement of the icicles is not always the
fame ; they vary greatly, and this produces the variety
which is obferved in fnow. It is remarkable, that
though fnow varies at different times, yet what falls
together is always the fame ; that is, the fnow which
falls at a particular time, confifts of flakes, which vary
only in fize, but are all formed of particles difpofed in
a fimilar manner. We are not fufficiently acquainted
with the laws by which the concretion or cryftalliza-
tion of bodies are regulated, to explain the caufe of
thefe phenomena. On account of the fmall quantity
pf matter contained in fnow, in proportion to the
furfaces expofed, it meets with great refiftance in
paffing through the atmofphere^ and confecjiienrly falls
* very.

Chap. 5.] Hail. 487

very (lowly. Its great furface alfo renders it very fuf-
ceptible of evaporation, which confiderably diminiihe&
its weight even in the coldeft weather.

If the cold is fo moderate, as to allow the particles
of water to unite into drops before congelation takes
place, particles of ice are produced, which are called
hail. The (ame thing may be fuppofed to happen
when the lower regions of the atmofphere are colder
than the upper, which, though contrary to the general
courfe of things, fometimes happens. In fuch a cafe,
the aqueous particles, after having united above into
rain, are congealed in their defcent, and are con-
verted into hail. In the year 1775 or 1776, rain
fell at Liverpool, which became folid as loon as it
reached the furface of the earth, in fuch a manner as
to give a covering of ice to whatever was wet with
it, and even to form icicles on the drefs of perfons
expofed to it. This phenomenon I have alfo witnefied
elfewhere.

Hail, when firft formed, muft be perfectly round,
becaufe formed from a fluid; and all fluids, when
placed in fuch fituations as to receive an equal pref-
fure in every direction from the medium which fur-
rounds them, naturally aflfume a fpherical form. Hail,
however, when it arrives at the earth is often angular ;
this mufl be explained, either by fuppofing that the
particles have begun to diflblve, or that they were fuf-
ficiently cold to congeal and attach to their (urface,
the aqueous particles with which they came. into con-
tact in their fall. Hail, when firft formed, is never
larger than the drops of water which fall in rain;
but from the caufe juft mentioned, hail-ilones have
fometimes been known to fall as large as nuts, or even
as hens' eggs. In order to convince ourfelves, that
fuch hail-ftones owe their extraordinary fize to the
I i' 4 additions

483 Fogs. [BookVII,

•additions which they feceive in falling, it is only ne-
ceffary to examine them : they will almoft uniformly
be found to be angular, and never to have an uniform
denfity from the circumference to the center, which
clearly proves, that they are compofed of different par-
ticles of ice connected together. In confirmation of
the fame opinion, it is obferved, that the hail which
falls on mountains, is fmaller than that which defcends
in the neighbouring vallies. T'he fame obfervation
has been repeatedly made with r-efpecl; to rain, by per-
fons in the habit of afcending mountains, for the pur-
pofe of philofophical experiment.

It fometimes happeps from the ftate of the atmo-
fphere, or a concurrence of circumftances not eafily to
be afcertained, that a great quantity of aqueous par-
ticles are raifed in the atmofphere, where, being in-
completely diffolved, they form a thick vapour, which
extends itfelf in the lower part of the atmofphere ;
thefe particles, deftroying the tranfparency of the at-
mofphere, form fogs. Fogs are more frequent in low,
wet, and marmy fituations, near rivers and ponds, than
in fuch parts of a country as are elevated and dry.
It fometimes happens, that certain exhalations are
mixed with fogs, which are perceived by their unplea-
fant fme'll, and by an acute fenfation which is felt by
the throat and eyes.

Fogs are much more frequent in cold feafons, and
in cold climates, than in fuch as are warm, becaufe in
tfye former, the aqueous particles being ccndenfed al-
moft as foon as they proceed from the furface of the
earth, are incapable of rifing into the higher parts of
the atmofphere. If the cold is augmented, the fog
freezes and attaches itfelf in fmall icicles to the branches
of trees, to the hair and clothes of perfons expoled to
it, to the blades of grafs, &c.

When*

Chap. 5.] Dew. 48 ^

When fogs rife to a confiderable height m the at-
mofphere, and are collected in a denje ftate, whether
this happens from any action of the air or from other
caufes, they 'form clouds, which float in different re-
gions of the atmofphere according to their fpecific
gravity j fince they neceflarily rife or fall, till they
arrive at that part of the atmofphere which is in
equilibrium with themfelves. As the atmofphere is
heavieft below, denfe and thick clouds, which are
£t the point of uniting into rain, float near the furface
pf the earth, while the fleecy and thin clouds foar
aloft. We often obferve both kinds at different heights
in the atmofphere at the fame time. As clpuds are
formed of water, they are moft copioufly produced
where the air has moft opportunity of acting on that
fluid. Confequently winds which blow from the weft
and fouth weft, from the Atlantic ocean, bring more
clouds to this country than eafterly winds, which only
pafs over a narrow channel of the lea.

During the day time the fun heats the earth, water,
air, and every thing which is expofed to its rays. The
heat communicated to all thefe bodies is diminiflied
after fun fet, but the air is more fuddenly cooled than
the more folid bodies. Heat, therefore, which has
always a difpofition to diftribute itfelf equally, pafies
from the furface of water and earth into the air, and
carries with it fome aqueous particles, which are fuf-
pended near the furface. When the cold increafes
during the night, thefe vapours are condenfed, and
occasion that dampnefs which is felt on the clothes of
perfons expofed to the night air, and form that dew
which is fo refrefhing to vegetables fcorched during the
" day time by the fummer's fun.

In cold weather the dew becomes frozen into hoar
froft, for the formation of which it is not neceflary

that

490 Inftances of partial freezing. [Book VII.

that the. earth, or even the air, mould be fo far cooled
as to occafion the congelation of water into ice. This
fact can only be explained, by confidering that thefe
irnall drops of water expofe a large furface to the ac-
tion of the air ; and by this means evaporation, which
powerfully produces cold, is promoted. For the fame
reafon clothes hung out to dry, are frequently frozen
ftiff, when no ice is formed in water expofed to the
fame degree of cold, but in circumftances lefs favour-*
fble to evaporation.

VOL. 'I I ./>. .fin.

Fig. 1.

Flff. 2.

Xnz±

Chap. 6.] [ 491 ]

CHAP. VI.

OF SPRINGS AND RIVERS.

Origin cf Springs. — Digging cf Wells. — Nature of Springs. — Marjkej.
— Cheap and eajy Mode of draining them.'~~Intermiiting Sfrings.-f
Rivers. — Their Source, &c.

THE water which falls on the furface of the earth,
in rain, fnow, &c. penetrates its'fubfrance till it
meets with a ftratum of clay, (lone, or fomc other
matter which flops its defcent ; it then glides laterally
on the ftratum which fuftains it, and in the direction
to which it leans, till meeting with an aperture, it ap-
pears on the furface of the earth in the form of a
ifpring. As water always has a tendency to defcend,
fprings are always lower than the fource from which
they are fupplied ; fprings are mod common on the
fides and at the bottom of mountains ; they are fel-
dom found quite at the fummit of a mountain, and are
rare where a country is every where level to a confi-
derable diftance, becaufe there the flrata are parallel,
and do not conduct the water to any particular point.
In order to obtain water, therefore, in flat countries,
it is in general neceflfary to dig into the earth, when it
is found to flow copioufly from the fides of the open-
ing, at no great diftance from the furface. Whea wells
are dug in elevated fituations, water is feldom met
with till we have dug to a confiderable depth, and got
below the general level of the country.

A curious circumftance occurs in the making of
wells at Modena and Stiria in Italy. The workmen
begin by digging through feveral ftrata or foils, till

they

492 D'ggwg of Wells. [Book VII.

they come to a very hard kind of earth much refem-
bling chalk ; here they begin their mafon-work, and
build a well, which they carry on at their leifure till
they have finished, without being interrupted with one
clVop of water> and without any apprehenfion of noc
finding it when they come to make the experiment.
The well being finished, they bore, through the hard
bed of chalk, upon which the well is built, with a long
auger, but take care to get out of the well before they
draw it out again; which when they have done, the
water fprings up into the well, and in a little time
rifes to the brim, nay fometimes overflows the neigh-
bouring grounds. Now there can be little doubt, that
thefe waters flJw from refervoirs which are collected
within the Appennine mountains, not far from Modena,
and taking their courfe through fubterraneous paf-
fages,' endeavour to force their afcent to the fame height
from which they defcend, wherever they can find a
•vent.

As all the water which falls in rain has undergone a
natural did illation, it is much more pure when it firfl
falls, than after it has pafled through different ftrata of
the earth and riles in firings. Spring water is always
{bund to contain fome foreign admixture; if this fhould
be only an earthy fait, the water is called hard ; if it
contains other fubftances, it then receives the denomi-
nation of mineral water ; but thefe will require to be
treated of in a diftinc~t chapter.

The water which lies upon marfhes and fwampy
grounds, has generally its fource in fome fpring, which
is placed above the level of the marfh. The foil,
therefore, in thofe places, being generally of a fpongy
texture imbibes the water, and permits it to difperfc
through its whole mafs, rather than force its way
through a certain aperture j and as marfh lands are

commonly

Chap. 6.] Cheap Mock tf draining Marjh Lands. 493

commonly level, the water will be more eafily diffufed
through the foil, than it can be upon the declivity of
a hill. The great art, therefore, in the draining of
marihes is to difcover the fource, which may be looked
for on the brow of fome eminence which overhangs
them j and in may generally be found by obferving
where the boggy part grows narrow and angular, and
points as to an apex, which is the fpring whence all
the mifchief proceeds. When the fource is once dif-
covered, the water may be eafily drawn off by drains,
aqueducts, or pipes, according to the circumftances of
die cafe. The common mode of draining land by
cutting deep trenches, or drains, through the marfh
kfeif, to ferve as refervoirs for the water, is much more
laborious, and expenfive, and indeed feldom anlwers
die end propofed-, for as loon as the trenches fill, the
ground is rendered as fwampy as ever; and even
where drains are made on the principle of an in-
clined plane to draw off the water, they are fre-
quently flopped by the mud of the inarm,. and the leaft
ftoppage expofes the land again to at lead a partial
overflow.

There are fume fprings which exhibit a very curious
phenomenon, a kind of tide or intermiffion, by which
the water at certain periods appears to rife to a conii-
derable height, and gradually to iiibfide. Thefe arc
called intermitting fprings. It was long imaginecj,
that thefe fountains were replenifhed by fome connec-
tion with the fea j that the water was frefhened by its
progrefs through land and earth, and that their rifing
and falling depended on the tide. It was, however,
found, that the periods of the water rifing and falling
in thefe fprings, did not correfpond in point of time
with the tides of the adjacent feas, and that the periods
were different in different fprings, contrary to the re-
gular

494 Intermitting Springs* [Book VI L

gular rifing and failing of tides in the ocean. The
phenomenon has fince been very fatisfa&orily ex-
plained, and upon a very fim pie and obvious princi-
ple. It has been already (hewn, that when a fiphon is
inferted in a verTel containing water, if the air is drawn
out of the fiphon, or by any means the water is made
to flow over the bent of the tube, which lies above
the brim of the vefiel, the water will continue to flow
over the brim through the fiphon till the whole is ex-
haufted.

To account, therefore, for the intermitting fpring,
we have only to fuppofe, that a cavity or receptacle is
formed in the bowels of the hill or mountain, where
the fpring is fituated, which gradually fills with water
like other refervoirs j by the interpofition of fome ftra-
tum of (lone or rockj the tube or cavity which conveys
the water from this receptacle to the fpring or mouth
where it ifTues, is bent in the form of a fiphon, the
bent of which is confiderably higher than the bottom
of the refervoir. Whenever, therefore, the refervoir
or receptacle is filled as high as the bent of the tube,
the water will rife in it to its level, and begin to flow
into the fpring, which will continue till the receptacle
is exhaufted. While this procefs is going on the wa-
ter in the fpring will rife ; and as foon as the recepta-
cle is exhaufted, the water, being drawn off by a
ftream or rivulet, will appear to fall in the well of the
fpring, and will continue to fall till the receptacle is
again fupplied to the height of the fiphon or tube,
when the'procefs of filling will be again renewed.

To render the matter perfectly plain, let ABC
(Plate X. fig. ,4.) reprefent the cavity or receptacle,
from the bottom of which C proceeds the tube or
fiphon D E. When the water rifes in the receptacle
to the level of E in the tube, it will begin to flow into

the

Chap. 6.3 Ccntroverfy concerning Rivers. 495

the fpring at D, on the principle explained in the pre-
ceding paragraph, and the whole phenomenon will be
eafily accounted for.

With any perfon who has carefully obferved the
courfe of rivers, and traced them to their fonrces,
there can be little doubt that they are formed by the
confluence of fprings, or of the little dreams or rivulets
that ififue from them ; with perhaps the exception of
thofe rivers which proceed from ..lakes, where the
refervoir is ready formed, and generally by the fame
means.

In the beginning of the prefent century, the philo-
fophical world was agitated by a debate concerning
the origin of thofe waters which are neceflary for the
fupply of rivers, &c. one party contended ftrongly for
the existence of a large mafs of water within the bow-
els of the earth, which fupplicd not only the rivers but
the ocean icfelf j at the head of thefe we may place the
ingenious but fanciful Burnet. The French philofo-
phers, on the contrary, afferted, that the waters of the.
ocean were conveyed back by fome ftibterraneous
pafiages to the land, and being filtrated in their paf-
iage, returned again to the fea in the courfe of the
rivers ; but this opinion appears contrary to all the
known principle of hydroftatics.

In oppofition to thefe hypothefes, our iliultrious
countryman Halley contended that the procefs of eva-
poration, and the immenfe depofition of water in con-
iequence of it, was fully adequate to the whole fupply.
If, indeed, we confider the immenfe quantity of water
which is continually carried up into the atmofphere by
evaporation, as ftated in a former chapter, and confi-
der that this is a procefs which is continually going on,
not only from the ocean but from the rivers them-
felves, and from the whole furface of the earth, we

lhall

"/ [Book VIL

fhall fee but little reafon to doubt of Dr. Halley's hy-
pothefis, but may reafonably conclude, that this kind
of circulation is carried on through all nature, and that
the fea receives back again through the channel of
the rivers, that \vater which it parts with to the at-
mofphere.

c All rivers have their foiirce either in mountains,
or elevated lakes; and it is in, their defcent from thefe,
that they acquire that velocity which maintains their
future cunvnt. At firft their courie is generally rapid
and headlong ; but it is retarded in its journey by the
continual friction againft its banks, by the many ob-
fiacles it meets to divert its ftream, and by the plains
generally becoming more level as it approaches towards
the fea. .

* Rivers, as every body has feen, arc always broadeft
at the rY'Oiith •, and grow narrower towards their
fource. But what is lefs -known, and probably more
delerving curiofity, is, that they run in a more direct
channel as they immediately leave their fources j arid
that their finuofities and turnings become more nu-
merous as they proceed. It is a certain fign among
the favages of North America , that they are near the
fea, When they find the rivers winding, and every now
and then changing their direction. And this is even
now become an indication to the Europeans them-
felves, in their journies through thofe tracklefs forefts.
As thofe finuofities, therefore, increafe as the river ap-
proaches the fea, it is noi: to be wondered at, that they
fometimes divide, and thus difembogue by different
channels. The Danube difembogues into the Euxine
by feven mouths j the Nile, by the fame number ; and
the Wolga, by feventy.

1 The largeft rivers of Europe are, firft, the Wolga,
which is about fix hundred and fifty leagues in length,

extending

Chap. 6.] Europe and Afia. 497

extending from Refchow to Aftrachan. It is remark-
able-of this river, that it abounds with water during
the fumrner months of May and j une ; but ail the reft
of the year is fo mallow as fcarcely to cover its bottom,
or allow a paflfage for loaded veflels that trade up its
ftream. The next in order is the Danube. The courfe
of this is about four hundred and fifty leagues, from
the mountains of Switzerland to the Black Sea. The
Don, or Tanais, which is four hundred leagues from
the fource of that branch of it called the Sofma, to its
mouth in the Euxine Sea. In one part of its courfe it
approaches near the Wolgaj and Peter the Great had
actually begun a canal, by which he intended joining
thofe two rivers ; but this he did not live to finiflh.
The Nieper, or Boryfthenes, rifes in the middle
of Mufcovy, and runs the courfe of three hundred and
fifty leagues, to empty itfelf into the Black Sea. The
Old Coffacks inhabit the banks and iilands of this ri-
ver ; and frequently crofs the Black ' Sea, to plunder
the maritime places on the ccafts of Turkey. The
Dwina takes its rife in a province of the fame name
in Ruflla, runs a courfe of three hundred leagues, and
difembogues into the White Sea, a little below Arch-
angel.

The largeft rivers of Afia arc, the Hohariho, in
China, which is eight hundred and fifty leagues in
length, computed from its fource at Raja' Ribron, to
its mouth in the Gulph of Changi. The Jenifca of
Tartary, about eight hundred leagues in length, from
the Lake Selinga to the Icy Sea. This river is, by
fome, fuppofed to fupply moft of that great quantity
of drift wood which is feen floating in the feas, near
the Arctic circle. The Oby, of five hundred leagues,
running from die lake of Kila into the Northern- Sea.

VOL. II. K k The

49$ Rivers of Afia and Africa. [Book VI L

The Amour, in Eaftern Tartary, v/hofe courfe is
about five hundred and feventy- five leagues, from its
fource to its entance into the fea of Kamtfchatka. The
Kiam, in China, five hundred and fifty leagues in
length. The Ganges, one of the moft noted rivers in
the world, is about as long as the former. It rifes in
the mountains which feparate India, from Tartary j and
running through the dominions of the Great Mogul,
difcharges itfelf by feveral mouths into the bay of Ben-
gal. It is not only efteemed by the Indians for the depth,
and purenefs of its ftream, but for a fuppofed fanc-
tity which they believe to be in its waters. It is vifited
annually by feveral hundred thoufand pilgrims, who
pay their devotions to the river as to a god i for favagc
fimplicity is always known to miftake the blefiings of
the deity for the deity himfelf. They carry their dy-
ing 'friends, from diftant countries, to expire on itg
banks ; and to be buried in its ftream. The water is
loweft in April or May ; but the rains beginning to
fall foon after, the flat country is overflowed for feveral
miles, till about the end of September ; the waters then
begin to retire, leaving a prolific fedirflent behind, that
.enriches the foil, and, in a few days time, gives a luxu-
riance to vegetation, beyond what can be conceived by
an European. Next to this may be reckoned the ftill
more celebrated river Euphrates. This rifes from
two fources, northward of the city Erzerum, in Tur-
cumania; and unites about three days journey below
it, whence, after performing a courfe of five hundred
leagues, it falls into the Gulph of Perfia, fifty miles
below the city of Baflbra in Arabia. The river Indus
. is extended, from its fource to its difcharge into the
Arabian fea, four hundred leagues.

The largeft rivers of Africa are, the Senegal, which
I run*

Chap. 6.1 Overflowings of tie Nik. 499

runs a courfe of not lefs than eleven hundred leagues,
comprehending the Niger, which feme have iuppofed
to fall into it. Later accounts, however, feem to affirm
that the Niger is loft in the fands, about three hundred
miles up from the weftern coafts of Africa. Be this
as it may, the Senegal is well known to be navigable
for more than three hundred leagues up the country ;
and how much higher it may reach is not yet difco-
vered, as the dreadful fatality of the inland parts of
Africa, not only deter curiofity, but even avarice, which
is a much (Ironger parlion. The celebrated river Nile
is faid to be nine hundred and feventy leagues, from
its fource among the mountains of the Moon, in Up-
per ^Ethiopia, to its opening into the. Mediterranean
Sea. Upon its arrival in the kingdom of Upper
JEgypt, it runs through a rocky channel, which fome
late travellers have miftaken for its cataracts. In the be-
ginning of its courfe, it receives many iefFer rivers into
ic ; and Pliny was miftaken, in faying that it received
none. In the beginning alfo of its courfe, it has many
windings ; but, for above three hundred leagues from
the fea, runs in a direct line. Its annual overflowings
arife from a very obvious caufe, which is almoft univer-
fal with the great rivers that take their fource near the
line. The rainy feafon, which is periodical in thofe
climates, floods the rivers ; and as this always happens
in our fummer, fo the Nile is at that time overflown.
From theie inundations, the inhabitants of Egypt de-
rive happinefs and plenty; and, when the river does
not arrive to its accuftomed heights, they prepare for
an indifferent harveft. It begins to overflow about the
1 7th of June; it generally continues to augment for
forty days, and decreafes in about as many more. The
time of increafe and clecrtafe, however, is much more
K k 2 incon-

500 Rivers cf [Book VI I.

inconfiderable now than it \vas among the ancients.
Herodotus informs us, that it was an hundred days
riling, and as many falling ; which fhews that the in-
undation was much greater at that time than at pre-
fent. M. Buffon * has afcribed the prefent diminu-
tion, as well to the leflening of the mountains of the
Moon, by their fubdance having fo long been wafhed
down with the dream, as to the riling of the earth in
Egypt, that has for fo many ages received this extra-
neous fupply. But we do not find, by the buildings
that have remained fince the times of the ancients, that
the earth is much raifed fince then. Befides the Nile
in Africa, we may reckon Zara, and the Coanza, from
the greatnefs of whofe openings into the fea, and the
rapidity of whofe dreams, we form an edimate of the
great diftance whence they come. Their courfes,
however, are fpent in watering deferts and favage coun-
tries, whofe poverty or fiercenefs have kept ftrangers
away.

But of all parts of the world, America, as it exhi-
bits the mod lofty mountains, fo allb it fupplies the
largeft rivers. The principal of thefe is the great
river Amazons, which, from its fonrce in the lake of
Uauricocha, to its difcharge into the Weftefn Ocean,
performs a courfe of more than twelve hundred
leagues f. The breadth and depth of this river is
anfwerable to its vaft length -, and, where its width is
mod contracted, its depth is augmented in proportion.
So great is the body of its waters, that other rivers,
though before the objects of admiration, are lod in its
bofom. It proceeds after their junction, with its ufual
appearance, without any vifible change in its breadth

'* Buffon, vol. ii. p. 82.
f Ulloa, vol. i. p, 388.

or

Chap. 6.] America. 501

or rapidity ; and, if we may fo exprefs it, remains great
without oftentation. In fome places it difplays its whole
magnificence, dividing into feveral large branches, and
encompafllng a multitude of iflands ; and at length,
difcharging itfelf into the ocean, by a channel of an
hundred and fifty miles broad. Another river, that
may almoft rival the former, is the St. Lawrence, in
Canada, which rifing in the lake Affiniboils, pafles
from one lake to another, from Chriftinaux to Alem-
pigo ; and thence to lake Superior; thence to the
lake Hurons ; to lake Erie ; to lake Ontario ; and, at
laft, after a courfe of nine hundred leagues, pours
their collected waters into the Atlantic ocean. The
river Miffiffippi is more than feven hundred leagues
in length^ beginning at its fource near the lake Affi-
niboils, and ending at its opening into the Gulph of
Mexico. The river Plata runs a length of more than
eight hundred leagues from its fource in the river Pa-
rana, to its mouth. The river Oroonoko is feven hun-
dred and fifty leagues in length, from its fource near
Pafto, to its difcharge into the Atlantic ocean.

Such is the amazing length of the greateft rivers j
and even in fome of thefe, the moft remote fources
very probably yet continue unknown. In fact, if we
confider the number of rivers which they receive, and
the little acquaintance we have with the regions through
•which they run, it is not to be wondered at that geo-
graphers are divided concerning the fources of mod
of them. As among a number of roots by which
nourimment is conveyed to a (lately tree, it is difficult
to determine precifely that by which the tree is chiefly
fupplied; fo among the many branches of a great
river, it is equally difficult to tell which is the ori-
ginal. Hence it may eafily happen, that a fmaller
Branch is takqn for the capital ftream -, and its wind-
K k 3 ings

5C2 Periodical Inundations. [Book VII.

ings are purfued, and delineated, in prejudice of fome
other branch that better deferved the name and the
defcription. In this manner*, in Europe, the Da-
nube is known to receive thirty leffer rivers; the
Wolga thirty-two or thirty- three. In Afia, the Ho-
hanno receives thirty-five; the Jenifca above fixty;
the Oby as many ; the Amour about forty ; the Nan-
quin receives thirty rivers ; the Ganges twenty j and
the Euphrates about eleven. In Africa, the Senegal
receives more than twenty rivers ; the Nile receives
not one for five hundred leagues upwards, and then
only twelve or thirteen. In America, the river Ama-
zons receives above fixty, and thofe very confiderable ;
the river St. Lawrence about forty, counting thofe
which fall into its lakes ; the Miffiffippi receives forty ;
and the river Plata above fifty.

The inundations of the Ganges and the Nile have
-been already mentioned, and it might be added, that
aim oft all great rivers have their periodical inundations
from fimilar caufes. The author already quoted ob-
ferves, that, fc befides thefe annually periodical inunda-
tions, there are many rivers that overflow at much
fnorter intervals. Thus moft of thofe in Peru and
Chili have fcarce any motion by night; but upon the
appearance of the morning fun they refume their
former rapidity: this proceeds from the mountain
fnows, which, melting with the heat, encreafe the
ftream, and continue to drive on the current while the
fun continues to difiblve them -f .'

There are fome rivers which are faid to lofe them-
felves in chafms under the earth, and to flow for fe-

veral miles in fecret and undifcovered channels. On
i

* Buffon, vol. ii. p. 74.

f Goldfmith's Earth, p. zeo.

" this
;4^ ,

Chap. 6.] Rivers underground. 503

this circumftance is founded one of the moft beau-
tiful fables of antiquity, relative to the fountain of
Arethufa, in Sicily. The fame thing is affirmed of
the Rhine, and even of the river Mole, in Surrey,
which, from this circumftance, derives its name.
With refpecl: to the two latter rivers, however, fome
doubts are entertained of the fa6l, but thefe are rather
a fubject of inquiry to the geographer than to the na-
tural hiftorian.

Kk 4

[ 5G4 } [BookVIL

CHAP. VII.

HOT SPRINGS.

PrcbaLle Cc>ufis of tl?efe f-henomena. — Abound moft in volcanic Re-
gions.— Hot Springs in Iceland, near Mount Hecla. — At Geyfer.—
Li the IJland of Ifcbici. — At Viterbc. — Explanation of tbefe Pheno-
mena.— Burning Well in Lancafoire.— Explained.

THERE are few objects in natural hiftory,
which prefent: themfelves to our confideration,
accompanied with greater difEculties than thofe tepid
fprings, which exift in different parts of the world,
pf different degrees of temperature, and exhibiting
a variety of the moft curious phenomena. Many of
thefe have exifted as long as the earlieft records, and
for whole centuries have exhibited little variation in
their temperature.

If any circumftance could ferve to fupport the
very dubious hypothefis of an immenfe refervoir of
fire in the center of the earth, it would be thefc
phenomena j yet there is but little reafon to fuppcfe
that the origin of thefe tepid fprings lies at any vaft
depth beneath the furface ; and, indeed, if we admit
the notion of a central fire, its effect ought to be more
general than it is found to be. The moft probable
nypothefis is, therefore, that the fame caufes operate
to produce thefe, which produce volcanoes i and the
only inference to be drawn from their permanent tem-
perature is, that the mafTes of matter, which produce
volcanic eruptions, may exift for a long feries of
time, even in a ftate of inflammation, without burfting
thole bandages with which nature has confined them ;
arid that heat may long be continued to a confiderable

degree

Chap. 7.] Hot Springs in Iceland. 505

degree in the earth, without exhibiting to our af-
frighted fenfes the formidable phenomenon of a vol-
canic fire.

It is, however, in volcanic regions, that tepid wa-
ters are found in the greateft quantity j and it is in
thefe that they difplay the moft finking phenomena.
At Laugervarm, a fmall lake, two days journey from
Mount Hecla, in Iceland, there are hot fpouting
fprings, one of which throws up a column of water
to the height of twenty-four feet. A piece of mutton
and fome falmon trout were almoft boiled to pieces,
in fix minutes, in one of thefe fprings. At Geyfer,
in the fame ifland, there are forty or fifty fpouting
fprings within the compafs of three miles ; in fome
the water is impregnated with clay, and white in its
appearance ; in fome, where it pafles through a fine
ochre, it is red as fcarlet ; in fome it fpouts forth in
a continued flream; in others, at intervals, like an
artificial jet d'eau. The largeft which Von Troil
obferved haq! an aperture nineteen feet in diameter,
through which the water fpouted, at intervals, nine or
ten times a day; round the top of it is a bafon, which,
together with the pipe, is in the form of a caldron ;
the margin of the bafon is nine feet higher than the
conduit, and its diameter fifty-fix feet. The water
was thrown up in an immenfe column, at different
times, to the height of from thirty to fixty feet, and
fit one time to the height of ninety-two feet. Pre-
vious to this explofion the earth began to tremble in
three different places, and a noife was heard like a
battery of cannon *.

Another writer ftates, that at Geyfer, in Iceland,
there fprings up a hot water, which upon cooling,

* Von Troll's Letters on Iceland.

depofltS

506 Hot Springs in Iceland. [Book VII.

depofits .filiceous earth ; and that of this very matter
it has formed for itfeif a crater, in which columns of
water, of a fiupendous bulk, after they have been
thrown to the height of ninety feet and upwards,
fall, and are again received. The heat of the water
during the explofion cannot be meafuredj but after
it has riien and fallen through a ftratum of air ninety
feet thick, it raifes the thermometer to 212°, which
evinces that the heat in the bowels of the earth muft
be much more intenfe ; and at this we mall cea'e to
wonder when we confider, that in this cafe the fub-
terraneous fire acts upon the water in caverns, clofed
up by very thick ftrata of ftones, an apparatus far more
effective than Papin's digefter. The crater was at
firft undoubtedly formed, and is daily ftrengthened by
filiceous earth, which quits the menftruum on its being
cooled, falls down, and, being in fomewhat like a foft
flate, concretes *.

About fixty yards from the fhore of the ifland of
Ifchia, at a place called St. Angelo, a column of
boiling water bubbles on the furface of the fea with
great force, and communicates its heat to the water
of the fea near it. It boils winter and fummer, and
is of grea^t ufe to the inhabitants in bending their
planks for (hip-building, &c. The fifhermen alfo
frequently, employ this curious caldron to boil their
fiih. Near the more of this ifland Sir William
Hamilton found, when bathing in the fea, many fpots
where the fand was fo intenfely hot under his feet as
to oblige him haflily to retire.

There is alfo a boiling fpring near Viterbo, in
the Roman Hate, called the Builicame. It is a cir-
cular pool of about fixty feet in diameter, and ex-

* 'Bergman's Differt. 13,

ceedingly

Chap. 7.] Hot Springs in Italy, and England. 507

ceedingly deep, the water of which is conftantly boil-
ing. It is fituated in a plain furrounded by volcanic
mountains. A ftony concretion floats on the furface
of the pool, which, being carried off by the fuper-
fliious water, is depofited, and is conftantly forming
a labes or tufa, of which the foil all around the pool is
compofed.

Thefe fountains are beft accounted for by fuppofing
the pipe or conduit to communicate with a large
refervoir of water, which, being fubjeft to the heat
of a volcanic fire, the fteam generated in the refervoir
by the boiling of the water a£ts forcibly on the water
in the fhaft or pipe, and ejects it by its elaflic force
in the form of a fountain, which will acl: with more
or leis vigour according to the degree of heat, and
according to the refiftance which the water encounters
in ir.s pafTage.

The moft fingular circumftaace is the number of
thefe fprings which are found in almoft every coun-
try ; and even in " thofe countries which have long
ceafed to be volcanic. England itfelf has its tepid
fprings, and thofe of Bath, Buxton, &c. are well .
known. Cambden mentions a well, near Wigan, in
Lancafhire, which was called the burning well. If a
candle was applied to its furface, he fays, a flame was
excited like that of ardent fpirits fet on fire, and the
heat and inflammation thus excited would continue
fometimes for the fpace of a whole day, and was
fufficient to boil eggs, and even meat. As I recol-
lect, Cambden mentions the well as having loft its
inflammable property in his time; but he notices' two
others of a fimilar defcription, one in the fame neigh-
bourhood, and another in Shropfliire. I have never
myfelf witnefled a fimilar phenomenon, nor do I

know

503 ftfM Springs. [Book VII.

know of any fuch that exifts at prefent, at lead in
Britain.

Should, however, the fact be as it is related by
Cambden, the reader, after what has been dated in a
preceding chapter, will not find it difficult to explain
the caufe. The country where the well is, or was
fituated, abounds in coals. The well is therefore
impregnated with naphta, or fome bituminous vapour ;
this, upon the application of an ignited body, is ca-
pable of inflammation, and can even communicate a
confiderable portion of heat to the water of the well
itfelf. There is no prtfof, however, that the Bath or
Buxton waters are impregnated -with any bituminous
matter, though coals are plentiful in the neighbour-
hood j and as thefe waters contain a fmall portion of
iron, there is reafon to fuppole them connected with
beds of pyrites, or poffibly with a latent fubterraneous
fire. On the whole, we are not fufficiently acquainted
with the internal parts of the earth to account fatis-
factorily for thefe and other phenomena of a fimilar
kind, and whatever is advanced in the way of theory
on thefe topics mould be advanced with becoming dif-
fidence, and rather with a view of exciting the atten-
tion and curiofity of others, than for the ptirpofe of
eftablifning a iyftem unfanctioned by experiment, or
building a reputation on the fallible bafis of mere hy-
pothefis.

Chap. 8.] [ 509 ]

C H A P. VIII.
MINERAL WATERS,

Capacity of Water as a Solvent. — Sufffta^ces commonly fcund In Mi-
neral Waters. — Fixed Air. — Mineral Acids. — AlkfJitte jaks. — AV«-
tral Salts. — Earthy Subftances. — Sulphur. — Metals. — Mode of exa-
mining and analyzing Mineral Waters. — Chemical Tefts. — Analyjis
of the mojl celebrated Mineral or Spa Waters. — Aix-la Chapslle.—
Bath. — Brijiol. — Buxton. — Cheltenham. — Epfom. — Harro^jugate.—
Matlock. — PjrmoKt. — Scarborough. — Spa, — Reflections en the Uft
of Mi,::ral Water in general.

TH E capacity which water has of holding a va-
riety of fubftances in folution has been fre-
quently mentioned in the courfe of theie volumes, and
indeed is a fact to well known and underftood, that
to in-fift much upon it would be ufelefs and even im-
pertinent.

It was alfo intimated, that the water of fprings re-
ceives the name of mineral water from the foreign
fubftances which are contained in it. Thefe fubftances
are various, and more than one is commonly found
in mineral waters ; but in general they may be re-
ferred to the following heads:

i. Fixed air, or carbonic acid gas. This ingre-
dient occafions an appearance of brifknefs in water,
fimilar to that of fermenting liquors, which is chiefly
obfervable when the water is poured from one vefTel
into another. It is very volatile, and foon efcapes on
the water being expofed to the air. This ingredient
frequently occafions giddinefs in perfons who are not
accuftomed to it. An artificial water of this kind
may be prepared at any time by impregnating water
with fixed air.

2. The

510 Ingredients cf [Book VIL

2. The vitriolic, nitrous, and muriatic acids. One
or other of thefe acids exift in almoft all mineral wa-
ters : they are ufually combined with earthy or me-
tallic bales, but fometimes, efpecially the vitriolic,
exift in a feparate flate, To as to occafion a fenfible
acidity.

3. An alkaline fait is found in many waters in
Hungary, Tripoli, and other countries. It is ufually
the foflil alkali which is combined with fixed air in
the Seltzer waters, and with the mineral acids in a
great variety of others. The vegetable and volatile
alkalies rarely or never are ingredients in mineral
waters.

4. Neutral falts are not uncommon in fprings.
Common fait, nitre, and vitriolated magnefia, are the
the moft ufual ; the latter is very abundant in a fpring
at Epfom in Surrey, and has therefore obtained the
name of Epfom fait. Sal ammoniac has alfo been
found in fome fprings in the neighbourhood of volca-
noes and burning coal mines.

5. Earthy fubftances. Of thefe the calcareous is
fometimes found to abound fo much, as to be depo-
fited on fuch fubftances as it comes in contact with,
and occafion petrifaction. In this cafe the fufpenfion
of the calcareous earth feems to depend on the prc-
fence of fixed air, which, making its efcape when the
water ifTues into the open air, fuffers the calcareous
earth to feparate. The calcareous earth of waters is
very commonly united with the vitriolic acid, and ex-
ills in the form of gypfum, which is only foluble in
water in the proportion of one part in feven or eight
hundred. Calcareous nitre and muriated calcareous
earth are alto occanonally found in fprings.

6. Sulphur. Many waters feem by their offenfive
fmell to contain' fulphur, though very few of them,

upon

Chap. 8.] Mineral Waters. 511

upon mere accurate examination, are found to afford
it. The waters generally called fulphureous or hepa-
tic, are only impregnated with fulphureous or hepatic
gas, which is a folution of fulphur in inflammable: air.
This is the fame gas which riles from liver of fulphur,
and liver of fulphur itfelf has been detected in a very
minute quantity in mineral waters. Sometimes bitu-
mens are met with in mineral waters, and commonly
make their appearance on the furface.

7. Metals. Of thefe iron is moft frequently found
in water, fometimes copper, and more rarely zinc.
Waters which contain iron are called chalybeates, and
are very common.

It was formerly imagined that iron was fufpended
in mineral waters by means of the vitriolic acid ; but
M. Monnet has afcertained, that very few of them
contain vitriolic acid, and that the carbonic acid, or
fixed air, is almoft the only medium by which the iron
is fufpended. The carbonic acid is fometimes in
cxcefs, fo as to render the chalybeate water acidulous,
in other inftances it fufpends the iron without being
in excefs. Chalybeates may, in general, be. known
by the yellow ochry fediment depofited in their courfe,
and alfo by ftriking a purple colour with decoction of
galls.

In examining any mineral waters, the firft object of
attention is, to have the water as frem as poflible,
fince, if it contains any volatile matters, they will foon
fly off. A great number of trials are therefore to be
made on the fpot. The contents of the neighbouring
flrata, particularly of any high ground, from which the
water feems to proceed, are alfo to be regarded, as
they often ferve to account for the properties of mi-
neral waters.

•One of the moft obvious circumftances to be at-
tended

$12, Mode 9f analyzing [Book VII.

tended to is the degree of the heat of the water, and
for this purpofe it is neceffary to be provided with an
accurate thermometer. There are many fprings
which have a temperature a little above the medium
temperature of the atmofphere, though this may not
be fo remarkable as to have obtained them the name
of hot fprings. The middle temperature of thefe
fprings is found to be about forty-eight degrees, but
on elevated fituations it is lefs, in proportion to their
height .above the fea. It may alfo be proper to com-
pare the temperature of theie mineral fprings with
that of fome common fprings in the neighbourhood.
The fenfible qualities, as the colour, tafte, and fmell,
are to be obferved. In order to difcover whether any
elaflic fluid efcapes from it, and of what nature it is,
let fome of the water be put into a bottle, and a blad-
der tied about its neck. The air which efcapes may
be fubmitted to examination. In order to obtain it,
it is only neceiTary to tie another firing above the bot-
tle, and then to cut between them, fo as to fcparate
the bladder, which may be plunged in water or mer-
cury, and its contents received in the pneumatic appa-
ratus. In order to feparate all the air from water, it
mull be heated nearly to its boiling point, which may
eafity be done by immerfing it in a vefTel of boiling
water, while it is contained in the bottle to which the
bladder is annexed. The elaftic fluids, which may be
feparated from mineral waters, are chiefly two, carbonic
acid gas, and fulphureous gas. It is proper to obferve
the changes which are fpontaneoufly produced on mi-
neral waters by different degrees of heat. If any mat-
ter is depofited during the evaporation of the mine-
ral water, it muft be collected for further examina-
tion.

With reflect to the addition of certain foreign fub-

ftances

Chap. 8.] Mineral Waters. 513

ftances called re- agents, to difcover the contents of
mineral waters, it may in general be remarked, that
this mode is kfs certain than evaporation ; the latter
method, however, is not free from objections, as the
application of heat ta any body not unfrequently de-
ranges the previous ftate of combination among its
component principles. The chemical tefts beft adapt-
ed to the difcovery of the contents of mineral waters
are the following : lime, volatile alkali, fixed alkalies,
vitriolic acid, tincture of turnfole, muriated barytes,
acid of fugar, arfenic, Pruffian alkali, and the nitrous
folutions of filver and mercury. When it is propofed
to difcover the contents of a mineral water, it is beft
to begin with fuch tefts as, are leaft capable of altering
it, and afterwards, having obferved their effects, to
proceed to complete the analyfis by tefts which have
a more extenfive influence. Lime water feizes the
carbonic acid, and forms a precipitate of chalk ; it alfo
precipitates falts with the bafis of clay and magnefia,
as well as the metallic falts. If after mixing an equal
quantity of lime water with a mineral water, no pre-
cipitation takes place in twenty-four hours, it may be
concluded, that it contains neither carbonic acid at
liberty, nor a combination of that acid with fixed alka-
li, nor earthy falts with the bafis of aluminous earth or
inagnefia, nor any metallic fait. But if* a precipitation
takes place on the addition of lime water, the next ftep
is to examine the properties of the precipitated matter ;
if it has the properties of chalk, fuch as infipidity, the
producing of an effervefcence with vitriolic acid, and
forming with it a compound nearly infolublc in water,
that is gypfum, it mud be concluded that the water
contained carbonic acid, which, uniting with the lime
of the lime water, produced chalk. I£ on the con-
VOL. IJ. \» 1 trary.

514 Chemical lefts for Mineral Waters. [Book VII.

trary, the precipitated matter is fmall in quantity, and
fubfides very (lowly ; if it does not effervefce, and af-
fords with the vitriolic acid a ftyptic fait, it may be
concluded that it is alum, and that the mineral water
contained clay: If a bitter and very foluble fait is
formed on the addition of the vitriolic acid, it is the
Epfom fait, and the water contained the earth of
magnefia. If the addition of vitriolic acid to the pre-
cipitate produces fal martis, the water held iron in
folution.

The addition of cauftic volatile alkali will aft like
lime water, except that k will not produce a precipi-
tation from the prefence of uncombined carbonic acid
in the water -, the compound formed by volatile alkali
•with that acid not being infoluble, like the chalk
formed by the union of carbonic acid with lime. But
befides the aluminous, the magnefian, and the metal-
lic falts, the cauftic volatile alkali will decompofe
thole which have lime for their bafis, and thus we
advance one ftep further in the analyfis of the water.
The Pruflian alkali precipitates the combinations of
carbonic and vitriolic acid with chalk. The nitrous
folutions cf filver and mercury decompofe all the mu-
riatic and vitriolic falts, which may be various both in
quantity and in kind. In thcfe cafes the muriatic or
vitriolic acid contained in the mineral water, feizes the
filver or the mercury, and forming with it an infolu-
ble compound, falls to the bottom in a thick cloud,
while the nitrous acid unites with the bafis which is
deierted by one or both of the other acids. It is not
neceflary in this place to enter into a minute detail of
the methods of diftinguifhing the difference of the pre-
cipitates, according as the muriatic or vitriolic acid
was concerned in their production, but I fhall refer
* the

Chap. 8.] Celebrated Mineral Waters. 515

the reader for information on this point to what was
ftated when treating of the combinations of filver and
mercury with the different mineral acids.

By tin&ure of turnfole the predominance either of
an alkali or an acid is difcovered : as vegetable blues
are turned red by acids, and green by alkalies. Acid
of fugar is a very fenfible tell of lime, when com-
bined with the fparry or acetous acids. A folution of
arfenic in the marine acid will precipitate fulphur from
water, in which it is held difiblved by means of carbo*
nic acid. It may be added, that white arfenic becomes
yellow if immerfed in water containing hepatic gas ;
and a piece of polifhed iron will receive a copper-
colour from water in which copper is diflblved. If a
mineral water is found to contain a fixed alkali, it may
be determined whether it is the vegetable or mineral
alkali by means of vinegar. With vegetable alkali
vinegar yields a deliquefcent fait; with the mineral,
foliated cryftals.

It may be proper briefly to notice the compofition
and obvious properties of fome of the moft celebrated
mineral waters, and the diforders in which they are
fuppofed to have moft efficacy.

f AIX-LA-CHAPELLE. — This place has long been
famous for its hot fulphureous waters and baths. They
arife from feveral fources, which fupply eight baths
conftrucled in different parts of the town. Thefe
waters near the fources are clear and pellucid, and
have a ftrong fulphureous fmell refembling the wafh-
ings of a foul gun j but they lofe this fmell by expo-
fure to air. Their tafte is faline, bitter, and urinous.
They do not contain iron. They are alfo neutral
near the fountain, but afterwards are manifeftly, and
pretty ftrongly alkaline, infomuch that cloatfcs may be
1,1 2 wafhed

5i6 Jix-la-Cbaptlk. [Book VII.

wailied with them without foap. The gallon contains
about two fcruples of lea fait, the fame quantity of
chalk, and a dram and half of foffil alkali. They are at
firft naufeous and harfh, but by habit become familiar
and agreeable. At-firft drinking alfo they generally
affect the head. Their general operation is cathartic
and diuretic, without griping or diminution of ilrength;
and they alfo promote perfpiration. The quantity to
be drunk as an alterative, is to be varied according to
the conllitusion, and other circumilances of the pa-
tient. In general, it is beft to begin with a quarter,
or half a pint in the mornmg, and increafe the dcfe
afterwards to pints, as may be found convenient. The
•water is beft drunk at the fountain. When it is re-
quired to purge, it fhould be drunk in large and often
repeated draughts*/

The heat of the different baths of the Aix-la-
Chapelle waters varies from one hundred and fix of
Farenheit's thermometer t;o one hundred and thirty.
In bathing it is proper to begin with the moil tem-
perate.

c BATH has long been famous for its warm chaly-
beate waters. There are feveral fprings, but their
waters are all of the fame nature. There are fix
baths; but the principal are the King's bath, die
<j>ue£n's bath, and the Crcfs bath. The others are
only appendages to thefe. The two- former raife the
thermometer to 116°, the latter to 112°. The water
when viewed in the baths has a greenifh, or fea co-
lour : bet in a phial it appears quite traniparent and
colourlefs,.and it fparkles in the glafs. It has a very
flight faliae, bitterifh, and chalybeate taile, which is
not difagreeablea and fometimes ibmewhat of a fulphu-

* Elliot on Min. Wators, p. 119, &c.

reous

Ch ap. 8 . ] Bath and Briftol. 5 j 7

rcous fmell ; but this latter is not ufually perceptible,
except when the baths are rilling. The gallon of
Bath water contains twenty-three grains of chalk, the
fame (quantity of muriat of magnefia, thirty- eight of
fea fak, and 8,1 of aerated iron. As it rifes from the
pump, it contains fixed air, or other volatile acid, in a
fufficient quantity to curdle milk and act upon iron.
The Bath water operates powerfuJly as a diuretic, and
promotes perfpiration. If drunk quickly, in large
draughts, it fometimes purges ; but if taken flowly and
in fmall quantity, it rather has the contrary effect. An
heavinefs of the head, and inclination to fleep, are often
felt on firft drinking it *.'

This water when taken inwardly is faid to give
a ftimulus and vigour to the whole conilitution, it
therefore proves ufeful in old rheumatic complaints,
and in cafes of gout connected with much debility.
During the ufe of the Bath water, and fome time pre-
vious to it, the patient ftiou'ld live on a light diet, eafy
of digeftion. The courfe ihould be continued for a
month or fix weeksl In local complaints, as in ftiff*
joints and chronic pains, the application of the water
by pumping is more efficacious than bathing the whole
body.

BRISTOL. — ' The fprings are known by the name of
the Hot Wells. The water at its origin is warm, clear,
pellucid and fparkling ; and if let ftand in a glais, covers
its infide with fmall air- bubbles. It has no fmell, and
is foft and agreeable to the tafte. It raifes the ther-
mometer from about feventy to eighty degrees. It
contains ill grains of chalk, 5? of muriat of mag-
nefia, and 6 1 of fea fait in the gallon j-/

* Elliot on Min. Waters, p. 134, &c.
j- Ibid. p. 14.5. &c.

L 1 3 The

5 1 8 Buxton and Cheltenham. [Book VII.

The Briftol waters are particularly recommended m
pulmonary complaints ; the fame, however, of Briftol
has probably been more owing to the mildnefs of the
air in that part of England, than to the virtues of its
waters*

BUXTON.— e This is a hot water, refembling that
of Eriftol. It raifes the thermometer to 81° or 82°.
It has a fweet and pleafant tafte, It contains a little
calcareous earth, together with a fmall quantity of fea
fait, and an inconfiderable portion of a cathartic fait.
Iron has been difcovered in it, but in fo extremely
fmall a quantity as not to deferve notice : and even
that perhaps owing to accident. This water taken
inwardly is efteemed good in the diabetes ; in bloody
urine ; in the bilious cholic ; in lofs of appetite, and
coldnefs of the ftomachj in inward bleedings ; in
atrophy ; in contraction of the veffels and limbs, efpe-
cially from age ; in cramps arid convulfions ; in the
dry afthma without a fever j and alfo in barrennefs.
Inwardly and outwardly it is faid to be good in rheu-
matic and fcorbutic complaints; in the gout; in in-
flammation of the liver and kidnies, and in confump-
tions of the lungs ; alfo in old ftrains j in hard callous
tumours j in withered and contracted limbs j in the
itch, fcabs, nodes, chalky fwellings, ring-worms^ and
other fimilar complaints. Befides the hot water, there
is alfo a cold chalybeate water, with a rough iron tafte.
It refembles the Cawtborp water*.'

' CHELTENHAM, in Gioucefterjhirey is one of the beft
and moft noted cathartic chalybeate waters in England,
though it is not fo much frequented as formerly. The
gallon contains eight drams of a cathartic fait, partly
vitriolated natron, partly vitriolated magnefia -, twenty-

* Elliot on Min. Waters, p. 151, &c.

five

Chap. 8.] Epfom and Harrowgate. 519

five grains of magnefia, part of which is united with
marine, part with aerial acid ; and nearly five grains
of iron combined with aerial acid. It alfo yielded
thirty-two ounce meafuresof air, twenty-four of which
were fixed air, the reft azotic with a portion of hepa-
tic air. The dofe is from one pint to three or four.
It operates with great eafe, and is never attended with
gripings, tenefmus, &c. It is belt taken a little warm.
It alfo creates an appetite -, is thought excellent in fcor-
butic complaints, and has been ufed with fuccefs in the
gravel. As the fpring has been calculated to yield only
thirty-five pints of water an hour, without frugal ma-
nagement there would not be enough to iupply the
demands of the drinkers. The Walton water has
lately been recommended as a fubftitute to obviate
this inconvenience.'

EPSOM, in Surry. — The water has a flight faline
tafte, is clear, and without fmell. But if it is kept in
covered veflels for fome weeks in the fummer it will
(link, and acquire a naufeous and faltifh bitter tafte.
This was the firft water from which the fait thence
called Epfom Jolt was obtained. But the fait ufually
fold by that name is different from that yielded by the
Epfom water, though perhaps not inferior in virtue.
It is made from the bittern lefc after the cryftalliza-
tion of common fait from fea water. The Epfom
water is cathartic ; for which purpofe it muft be drunk
to the quantity of two or three pints. It is alfo diu-
retic.

HARROWGATE.— < There are four fprings at this
place, but the waters of all of them are nearly alike,
except in the quantity of the faline matter they con-
tain. Of the three old firings, the higheft gave three
ounces of folid matter ; the loweft, an ounce and an
half j and the middle one, only half an ounce. Of the
L 1 4 latter

520 Matlock and Pyrmmt Waters. [BookVIL

latter one hundred and forty grains were earth. The
water as it fprings up is clear and fparkling, and
throws up a quantity of air-bubbles. It has a ftrong
fmdl of fulphur, and is fuppofed to be the ftrongeft
fulphureous water in England. It has a fait tafte, as
it contains a confiderable quantity of fea fait, together
with a little marine fait of magnefia, and calcareous
earth V

Harrowg£te"i&-ster is cathartic when taken in dofes
of feveral pints.' / When ufed externally as a fomenta-
tion, it is laid to be ufefui in fome disorders of the fkin,;
and by fome phyficians it is confidered as efficacious
in deftroying worms,

MATLOCK. — f At this place (which is perfectly ro-
mantic) are feveral fprings of warm water, which ap-
pear to be of the nature of the Briftol water, except
that it is very flightly impregnated with iron. Its
heat is about 69°, and its virtues are fimilar to thofe
of the Briftol and Buxton waters. The baths are re-
commended in rheumatic complaints, in cutaneous
diforders, and in other cafes where warm bathing is
ferviceable. T here are great numbers of petrifactions
in the courfe of this water f/

PYRMONT, in Weftpbatia. — f This is a very brifk
chalybeate, abounding in fixed air j and when taken
up from the fountain, fparkles like the brifkeft Cham-
paign wine. It has a fine, plealant, vinous tafte, and
a fomev/hat fulphureous fmell. It is perfectly clear,
and bears carriage better than the Spa water. A gallon
of it contains 46 grains of chalk, 15.6 of magnefia,
30 of vitriolated magnefia, 10 of fea fait, and 2.6 of
aerated iron J. Perfons who drink it at the well, are

* Elliot, p. 177 and 184. f ibid. p. 210.

J; Dr. Marcard, in his Dtfcription of Pyrmont, on the authority df
M. Weltrumb of Hammeln, eftimates the iron at fomewhat mose
than eight grains to the gallon,

affected

Chap. S.^ Scarborough Waters. ^H

affected with a kind of giddinefs or intoxication ; ow-
ing, it may be fuppofed, to the quantity of fixed air
with which the water abounds. The common ope-
ration of this water is diuretic ; but it is alfo gently
fudorific j and if taken in large quantity proves ca-
thartic. When, however, it is required to have this
latter effect, k is ufeful to mix fome falts with the
firft glafTes. It is drunk by glafsfuls in the morning,
to the quantity of from one to five or fix pints, ac-
cording to circumftances, walking about between each
glafsV

Pyrmont waters are recommended in debilitated
and relaxed conftitutions, attended with indigeftion,
low fpirits, and want of appetite.

SCARBOROUGH, in Torkjhire. — * The waters of this
place are chalybeate and cathartic j and they are more
frequented and ufed than any other water of this clafs
in England. There are two wells ; the one more ca-
thartic, the other a ftronger chalybeate. Hence the
latter (which is neareft the town) has been called the
jBalybeate fpring, the other the purging; though thef
are both impregnated with the fame principles, but
in different proportions. The purging is the moft
famed, and is that which is ufually called the Scar-
borough water. This contains fifty-two grains of cal-
careous earth, two of ochre, and two hundred and
fixty-fix of vitriolated magnefia, in the gallon: the
chalybeate, feventy grains of calcareous earth, one
hundred and thirty-nine of vitriolated magnefia, and
eleven of fea fait. When thefe waters are poured out
of one glafs into another, they throw up a number of
air-bubbles ; and if maken for a while in a clofe (lope
phial, and the phial is fuddenly opened before the

* Elliot, p. 226.

commotion

5-22 Spa [Book VII.

commotion ceafes, they difplode an elaftic vapour
with an audible noife, which fliows that they abound
in fixed air* At the fountain they both have a brilk,
pungent, chalybeate tafte; but the cathartic water
taftes bitterifh, which is not ufually the cafe with the
chalybeate. They lofe their chalybeate virtues by ex-
pofure, and alfo by keeping; but the cathartic water
iboneft. They both putrify by keeping ; but in time
recover their fweetnefs V

The properties of the cathartic and of the chalybeate
fpring are, as might naturally be fuppofed, very dif-
ferent. The former is ufeful in cafes of habitual cof-
tivenefs ; the latter in diforders of relaxation and de-
bijity.

SPA, in the bi/hopric of Liege. — ' In and about this
town there are feveral fprings, which afford excellent
chalybeate waters : and in Great Britain they are the
moft in ufe of any foreign mineral waters.

* The principal fprings are, i. The Pcbtui;
ion, fituated in the middle of the visage 5 — 2. "&
mtrt> about a mile and an half eaft from it ;-•
leecky near to the Sauviniere ; — -4. Tonne .

the left of the road to the Sauviniere; 5. t»/rcz,
near to the Tonnelet; — 6. Geronftere, two mile:, fouth
of the Spa; — 7. Sarts, or Ntverfet, in the diftrift of
Sarts; — 8. Chevron, or Bru> in the principality of Sta-
velot; — 9. Couve, — 10. Bever/eef— n. bige, — 12. Ge-
rcmonf, all near Malmdy.

* ThePoybon is a flow deep fpring, and is more or lefs
ftrong or gafeous according to the ftate of the atmo-
fphere. The gallon contains ten grains of chalk, thirty
of magnefia, ten of mineral alkali, and five of aerated
iron» It yields of fixed air one hundred and thirty-
two ounce meafures. It contains more iron than any

* Elliot, p. 234.

cf

Chap. 8.] Waters. 523'

of the other fprings, and does not fo foon lofe its gas.
It is in its mod perfeft and natural (late in cold, dry
weather. It then appears colourlefs, tranfparent, and
without fmell, and has a fubacid chalybeate tafte, witfi
an agreeable fmartnefs : at fuch times, if it is taken
out of the well in a glafs, it does not fparkle ; but
after Handing a while, covers the glafs on the iniide
with fmall air bubbles ; but if it is fhaken, or poured
out of one glafs into another, it then fparkles, and
difcharges a great number of air-bubbles at the fur-
face. In warm, moift weather, it lofes its tranfpa-
rency, appears turbid or wheyifh, contains lefs fixed
air, and is partly decompofed. A murmuring noife
alfo is fometimes heard in the well. It is colder than
the heat of the atmofphere by many degrees. It is
fuppofed to contain the greateft quantity of fixed air
of almoft any acidulous water j and confequently has
a remarkable fprightlinefs and vinofity, and boils by
mere warmth. This, however, foon flies off, if the
water is left expofed j though in well corked bottles
it is in a great meafure preferved. It is capable of
diflblving more irqn than it naturally contains, and
thus becoming a ftronger chalybeate. This is owing
to the great quantity of fixed air which it contains.
For the fame reafon an ebullition is railed in this water
on the addition of acids, as they difengage its fixed air.
It mixes fmoothly with milk, whether it is cold or of
a boiling heat.

( Of the Satminiere water, a gallon- yields 6.5 grains
of chalk, 4.5 of magnefia, two of mineral alkali, 3.5 of
kali, 2. 2 of aerated iron,and 108 ounce meafures of fixed
air. At the well it has fomewhat a fmell of iulphur.

c Grcijbeeck. The water is of the fame nature as
the Sauvin;ere, but contains a fomewhat larger pro-
portion of the feveral ingredients. It has a vitriolic
tafte, and fomewhat of a fulphureous fmell.

524 ^>f [Book VII.

e %'onndst. This is one of the moft fprightly wa-
ters in the world. It is much colder than either of
the other Spa waters ; has no fmell ; is bright, tranf-
{•arent, and colourlefs ; and from the rapidity of its
motion does not foul its bafon. It has a fmart, fub-
, fprightly taile, not unlike the brifkeft Cham-
iv.ign wine. 1'rorn a number of experiments it appears,
that this water is more flrongly charged than- any of
the others with fixed air, on which the energy of all
waters of this kind principally depends, but it parts
with it more readily. It contains more iron than any
of the fprings, except the Pouhon.

' Watrbz. fits fituation is loweil of any of the?
fprings about Spa, and it is more apt to be foul : buc
when the well is cleaned out, and the water pure, it is
found to be of the lame nature as that of Pouhon. It
is not cathartic, as fome have aflerted.

' Geronftere. This water has much lefs fixed air
than the Pouhon. It has a fulphureous fmell at the
fountain, which it lofes by being carried to a diftance.
This fmell is ftrongeft in warm moift weather. The
air, or vapour, of this water affects the heads of fome
who drink it, occafioning a giddinefs or kind of intox-
ication, which goes off in a quarter or half an hour.
The Pyrmont, and feveral other brifk chalybeate wa-
ters, are found to have the fame effect. It is colder
than any of the fprings, the Tonnelet excepted.

* SartS) or Niverfet. It refembles the Tonnelet
water, but is rather lefs briik and gafeous. It is how-
f ver more acid and ftyptic.

' Bru or Chevron. The phyficians at Liege have
artfully decried this water, becaufe it is n6t in the
principality of Liege. But by every trial it appears
not much inferior to any of the Spa waters. In the
quantity of fixed air and of iron it contains, it ap-
proaches the Pouhon,

Chap. 3.] Waters. 525

e Couve and Beverfee. The Couve nearly referable*
the Tonnelet water ; or rather, may be placed in a
medium between that and the Watroz. It lordly
equals the tranfparency, fma/tnefs, and generous vi-
nous tafte of the firrl, but it greatly furpafies the latter.
The Beverfee agrees with this, only that it does not
retain its fmartnefs fo well by keeping.

La Sige has fome of the general properties of
the Spa waters, but in other refpecls it is different.
It is moderately fubacid, fmart and grateful, but has
no fenfible chalybeate taile. It iparkles like Cham-
paign when poured from one glafs to another. Upon
ftanding it lofes its fixed air, and throws up a thick
mother-of-pearl coloured pellicle. It is much more
loaded with earthy matters, and lefs impregnated with
iron and fixed air, than the other Spa waters.

Geromont. As a, chalybeate and acidulous water
this feems to be nearly of the fame itrength with La
Sige; but it contains a greater quantity of natron, to-
gether with a mixture of lea fait. The earthy mat-
ters, however, are lefs.

It appears, that thefe waters are compounded of
nearly the fame principles, though in different propor-
tions. Ail of them abound with fixed air. They contain
more or lefs iron, alkali, and calcareous and felenitical
earths ; together with a fmall portion of fea fait. Thefe '
are all kept fufpended, and in a neutral ftate, by means
of the aerial acid, or fixed air. From a review of the
contents of thefe waters, it cannot be imagined that their
virtues principally depend on the fmall quantity offolut
matters which they contain. They mud therefore de-
pend moftly on their Juced air. And they are probably
rendered more active and penetrating both in the firft
pafiage.s, and alfo when they enter the circulation by

mean*

526 Spa Waters. [Book VI T.

means of that final! portion of iron, earth, fait, &c.
'with which they are impregnated *.

After all that has been alleged in favour of mineral
waters, it muft be confeffed that their medical virtues
are at beft rather dubious. With refpect to the me-
tallic falts which they may contain, the quantity is t'oo
minute to be very efficacious in obftinate complaints -,
and the warm baths have probably no other effect
than a quantity of common water heated to the fame
temperature would have, if applied by means of an
artificial bath at home. Where good effects have been
wrought upon a patient's referring to a mineral water,
phyficians have not always confidered the excellent
confequences which in the common courfe of things
might be expected from the exercife of the journey,
the change of air, and change of fcene ; from cheerful
company, and, though laft, not lead, perhaps, from
the imagination of the patient.

* See Elliot, p. 249, &c.

APPENDIX.

t 5*7 3

APPENDIX.

TABLE OF SPECIFIC GRAVITIES.

DISTILLED water
Calcareous earth

IOOO

2723

Copper
Iron -

- 7788

Magnefian earth

2155

Tin

- 7299

Barytic earth

3973

Bifmuth

- 9823

Argillaceous earth
Siliceous earth

1669
2650

Nickel - -
Arfenic

- 8660
" 57^3

Bottle glafs

2732

Zinc

7'9i

White glafs - -

2892

Antimony

6702

Flint glafs

3329

Manganefe

- 6850

Seves porcelain-

2145

Cobalt - - -

- 78'!

China ditto . '-

2384

Tungftein

- 6066

Lime ftones, from -

1386

Molybdena

• 4738

• to

2390

Vitriolic acid

- 24/2

Common flate

2672

Nitrous acid

- 1682

Mufcovy talk

2792

Muriatic acid

- 1085

Calcareous fpar
Fluor fpar

2715.
3180

Fluor acid
Oil of olives

- 1500
915

White marble

2716

Lin feed oil

940

Diamond -

3445

Burgundy wine -

991

Ruby ...

Bourde?ux ditto

993

Topaz - - -

3460

Malmfey madeira

- 1038

Emerald - -

3600

Cyder

- 1018

Hyacinth

3764

Woman's milk

- 1020

Garnet - - -

3978

Mare's milk

- 1034

Tourmaline

3°5°

Cow's milk

- 1032

Opal

2764

Goat's milk

- 1034

Cat's eye

2240

Ewe's milk

- 1040

Onyx - '-

2600

Elaftic gum

- 933

Carnelion ~

2704

Naptha

708

Common flint

2700

Camphor - -

989

Jafper - - -

2778 j Spermaceti

- 943

Quartz -

2654

Tallow -

- 942

Agate -

2590

Vitriolic aether

- 739

Gold - - -

19640

Nitrous asther

909

Platina -

22000

Muriatic aether

730

Mercury ...

13568

Acetous aether

- 866

Lead - - -

11352 : Pureft fpirit of wine

- 820

Silver . * -

10474 ;

TABLE

5'*

APPENDIX,

TABLE of the weights of the different gafies at 29. 84. Engfifh
inches, barometrical preffure, and at 54. 5° of temperature, ac-
cording to Fahrenheit's thermomeces, expreffed in Englifh mea- '
fure, and Engliih troy weight. From Lavoiiier's Chemiftry. — •
The weight of the five firft were afcertained by M. Lavoifier
himfelf; the laft three were inferted by M, Lavoifier on the au-
thority of Mr. Kirvvan.

Names of gaffes.

Atmofpheric air -
Azotic gas
Ox-ygen gas
Hydrogen gas
Carbonic acid gas -
Nitrous gas
Ammoniacal gas
Sulphureous acid gas

Weight of a
cubical inch.

321 12
30064
34211

2394
44108
37000
18515
71580

Weight of a
cubical foot.

Jr.

39 • $

5»

41 . 26

4»

39

19 • 73

38

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