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TRAVELS ^^^^

IN THE

TWO SICILIES,

AKO

SOME PARTS OIF THE APENNINES.

Tranflated frdhi the Original Italian of the

ABBE LAZZARO SPALLANZANI,

■^nefeffor- Royal of Natural Hiftory in the Univerfity of Pavia, an4

Superintendant of the Imperial Mufeum in that City j

Fellow of the R.oyal Society of London ; and

Member of the Academies of Pruffia,

Stockholm, Gotiingen, Turin,

Padua, &c. &c.

In four volumes. — with eleven plates.

VOL. III.

LONDON:

PRINTED FOR G. G. AND J. ROBINSOs!>

PATERNOSTE R-R O \V,

1798,

CONTENTS

OF THE

THIRD VOLUME.

Fiagc

Chap. XVL — ObSERFJTIONS
made in the Interior Parts of Li'
pari^ and fever al of its Mountains I

Chap. XVII. — Felicuda — — 90

Chap. XVIII. — Alicuda — — 124

Chap. XIX. — Ohfervations which have
an immediate Relation with the
Volcani%ation of the Eolian Ifles —
Enquiries relative to the Origin of
Bafaltes — • — 152

Chap.

IV cotjtents.

Page

Chap. XX. — DigreJJhn relative to the
different Volcanic Producfions ef
the Euganean Mountains — . — 216

Rejle^ions and Corollaries — — ^o i

Chap, XXI. — ILxperimental Efiqtiiries
relative to the Nature of the Gafis
ofVolcanos, and the Caufes of their
Eruptions — — — 317

Chap. XXII. — Difcovery that various
volcanic ProduBs contain Muriatic
Acid — Enquiry how this Acid has
been produced y and mixed with
them ' — — — 386'

TRAVELS

TRAVELS

IN THE

TWO SICILIES, Sec.

CHAP. XVI.

LIPARI.
PART THE SECOND.

OBSERVATIONS MADE IN THE INTERIOR
PARTS OF LIPARI, AND SEVERAL OF
ITS MOUNTAINS.

Extremely irregular appearance ftf this

ijland — No charaBerifed crater d'lfcover-'

able in it — ConjeBiire that the Monte San

Angeloy and the Monte ddla Guardia^ the

VOL. III. B higheji

( 2 )

h'lghejl mountains in Lipart, were prO"
duced by two dij}'m& volcanos — Effloref"
cences of muriate of ammoniac (fal ammO'
niac) in two caverns near the plain called
La Valle — Curious volcanic breccia — 'The
volcanic tufa which^ on one fide^ covers
the whole mountain of the celebrated Stoves
(or vapour baths) ofLipari^ has every ap^
pearance of having beeft an earthy cur'
rent ; and is remarkable for containing
true Ugfieous coal — Conje&ural enquiries
into the origin of this — The road that leads
from the town to the floves formed^ in a
great meafure^ of tufa corroded by the
rain-water '-^Various bodies obfervable
within this corroded tufa — Detached
pieces of enamel^ which include many
fmall bulbous bodies that appear to be
^gartiets — Camparifon between thefe and
the garnets of Vefuvius — E?iamel of the
Liparefe garnets^ which has for its bafe
ihe horn-ftone — Detached lavas in the
road leading to the Jloves — Volcanic chry^
■Coliies in a lava with a horn-Jione bafe —
Thefe chryfolites compared with thofe of
4 ILtna —

( 3 )

Etna^^Large pieces of red porphyry which
do not fee fn to have fuffered fifion — None
ofthefe bodies difpofed in currents ; "whence
it is probable that they have been throivn
into the air by fome volcano — A fpaciouS
plain of tufa rendered cultivable^ fituatcd
beyotid the Monte della Stufe, ivhich
affords numerous pieces of the fneji and
purejl glafs found in Lipari — Local ori^
gin of this glafs — Bed of pumices on
the ebctejffve current of tufa before men-
tioned— Stoves of Lipari defcribed — Re-
mains of confagrations of fulphur under"
them^ and in their envirojis — Prodigious
number of lavas decompofed by the a£iion
of fulphur eons acid vapours — Oxyde of
pure iron depoftted on fome of thefe lavas
'—Variety of colours which they preferit to
the eye — Their decompofition ufually in the
inverfe proportion of the depth of their
majfes — Widen freed from the decompoft"
tion which renders it difficult to afcertain
their nature^ they are ufually found of a
petrofiliceous bafe — This decompoftion an
ohjlacle to their fufton in the Jurnace-^^
B 3 Expli*

( 4 )

Kxpl'icatioti of the caufe of this change —
Sulphates of Ihne^ var'ioifly coloured^ and
adhering to the decompofed lavas — Iroji^
oxydated^ and modifcd in various manners y
the caife of the dijferent colours of the
decompofed lavas ^ andfulphates of lime —
Difcovery of fever al amorphous and cryf-
tallifed zeolites ?iear the ftoves — J^Uy
'which they form ivith mineral acids —
ILmit bright fafoes ivhen on the point of
meltings and fwell confiderahly on their
aEiual fufion — 'Terms of co7nparifon be
tween thefe %eoUtts and thofe of other
countries — Their produSiion not by the dry
but the humid ivay — Though the zeolites
of fever al volcanized countries are probably

formed within the fea^ this does not feem
to be the origin of thofe of Lipari — ///-

fiances of zeolites produced in frefJj water
— Springs of hot water "which fupply the
baths of Lipari — Another prodigious accu -
mulation of decompofed lavas ^ and fid-

phures of lime^ on the fouthern fide of the
if and — Perhaps there is no volcanizedcomi-
try in Europe where the fulphur eons fnnes

iffuing

( s )

ijfii'mg from fuhterranean conf,agrations are
fo extenfive as at Llpari — Vitrifications of
CampoBiaiico^ and the Monte delLi Cafag-
7ia^ 'which are found attached to thofe of
the Monte dellc Stufe^ the Monte San An--
gelo, and other places — Proofs that aimofi
two-thirds of Lipari, which tfland is iiine^
teen miles and a hj.lf in circumference^ are
compofed of vitr if cations — "The mate?'ials
of which this ifland is compofed^ prin-
cipally derived from the petroflex^ fi^^'
fpars in the mafsy and horn-fones, in part
fimply ffed by fubterraneous combufionsy
and in a fill greater part vitrified- — Not-
withfanding the immenfe accu?nulations of
this vitrifcation^ an extraordinary intenfity
of heat not neceffary to be fuppofed— An
exception in the pumices orighiating from
granite — Few notices left us by ancient
authors relative to the fres of Lipari ;
though we hnois) from indubitable au-
thorities^ that both the if and and the city
exifed before the Trojan war — "No erup-
tion in this ifland defcribed by Hifory —
Feeble fres, vifible by night, alone ob-
B 3 ferved

( 6 )

ferved in ancient times — This ijland^ the
produce offuhterraneaii conflagration, had

arrived at its greatefl dimenfwns^ before

it was noticed by any writer*

X O acquire a juft knowledge of the in-
terior part of a mountainous vulcanized
country, the beft method, as it appears to
me, is firft to afcend the higheft mountain,
and, after having examined the fummit, to
turn the eye downward, and obferve the
chain of fmaller nnountains that furround it.
We may thus, at one glance, difcover the
form of thefe inferior mountains, their in-
terchangeable connection, and the relations
which they bear to each other, and to the pri-
mary mountain, with other important ob-
jedls, which, had we firft afcended one of the
Jower eminences, we fhould not have been
able to afcertain with equal precifion and
clearnefs.

After, therefore, having made refearches,
with the grcateft diligence, around the fhore
of JLiparlj when I proceeded, according to

jny

( 7 )

my original intention, to explore, likewife,
the Internal parts of the Ifland ; I, firft, af-
Cended to the fummit of the Monte San
Angelo, fituated to the north of the city of
LIpari ; this being the higheft mountain in
the ifland. Here the whole of the ifland
prefented itfelf, at once, to my view, and I
could perceive that, far from having a coni-
cal figure, fuch as Is that of Stromboli,
and in a certain manner of Vulcano, it is
compofed of groups of broken and half-
deftroyed mountains, confufedly heaped to-
gether; which give it a moft irregular
appearance. It is evident that the volcanic
fires have raged in many places, and that,
from their too great proximity to each
other, they have not been able to form
thofe diftind: cones which are fo obfervable
in Vefuvius and on Etna. But the
matters ejeded by the fuperior volcanos,
pouring upon thofe which iflued from the
lower, have produced in every part confu-
fion and diforder. From the fummit of
Etna we may difcover a multitude of fub-
jacent craters, well charaderifed ; but from
B 4 that

( 8 )

t"hat of San Angel o I could not perceive
one. There are, indeed, many openings
and hollows to be feen, which once, per-
haps, were fiery mouths ; but none of thefe
cavities have at prefent the figure of an
inverted tunnel, pofTibly becaufe they have
been in part filled up and deftroyed by fub-
fequent eruptions, or by time.

M. Dolomieu obferved at the fummit of
this mountain a circular plain, furrounded
by eminences fhelving towards the infide,
which he imagined might be the remains of
an ancient crater. This conjedlure, after a
careful examination of the fpot, does not
appear to me improbable. The fame natu-
ralifl likewife fuppofes that this mountain,
the height of which is nearly a mile above
the fea, was the firft that was formed in
the ifland, through which the volcano burfl
forth, and which ferved as a bafe and fup-
port for the other mountains that were
thrown up afterv/ards. This opinion is
extremely plaufible ; but the fad: may like-
wife be, in my opinion, that this mountain,

at

( 9 )

at the time of its produdion, or very foon.
afterwards, had for its companion the
Monte della Guardia, which looks towards
the fouth, and of which I have before
fpoken ; both becaufe the latter is feparated
from the former, and becaufe it is little in-
ferior to it in height. From the ideas fug-
geited by a view of the places themfelves, I
conceive it not improbable that thefe two
mountains, which rife fo much higher than
the reft, have been produced by two dif-
tind volcanos, and were the firft that
emerged from the fca, forming then two
fmall iflands, which afterwards, enlarging
their bafe, united into one ; for it is well
known that other volcanic iHands originally
confifted of feveral parts, wduch afterwards
were joined. To thefe two mountains
fubfequent eruptions made new additions,
until at length the whole of the iiland of
Lipari was produced, which, from the ero-
iion of the rains and the fea, is now cer-
■'tainly lefs than it once was.

From Monte San Angelo, I pafled to the

Monte

( 10 )

Monte (iella Guardia, which on the fide to-
wards the fea prefents only fteep and rug-
ged precipices of lava, and, confequently, is
deprived of all vegetation and verdure j but
on the land fide, which is oppolite in one
part to the city, it is formed with gentle de-
clivities, and covered with vineyards ; for,
as its foil is tufaceous, it lefs refifts cultiva-
tion than any other volcanic product.
While ftanding on the fummit I was ftill
more confirmed in the opinion, that this
mountain is not an accefTary to, or prolon-
gation of, that of San Angelo ; but that it
forms a whole of itfelf, and may be called
primary equally with the other, from the
diftance between them, and the wide valley,
running from eafl to weft, by which they
are feparated.

Having vifited thefe two mountains,
which are the loftieft in the ifland, I pro-
ceeded next to examine the lefler emic
nences, and found additional confirmation
of what I have already obferved ; I mean,
that thefe eminences have entirely loft the

true

{ " )

true form of volcanic craters, fo much have
the matters ejected from them interfeded
each other, and confufedly intermixed.
The long and unkriown feries of years that
has elapfed fince thefe eruptions, muft, no
doubt, have contributed to increafe the con-
fufion. Excepting, therefore, fome few
flat places, and practicable declivities, which
the inhabitants have rendered cultivable by
great labour, Lipari is a ruinous pile of
horrid precipices, rugged cliffs, and enor-»
mous mafles ; and there is no fummlt, or
projecting part of a mountain, which does
not exhibit manifeft indications of its fu-
ture fall and deftrudion. The materials of
which thefe ruins are formed are pumices,
enamels, and glafles, which I ihall not de«
fcribe, becaufe they are partly the fame,
and partly extremely analogous to thofe of
which I have already given the defcription.

Some of the natives, by the accounts they
gave me, excited my curiofity to vilit a ca-
vern fituated in a fniall plain called La
Valle, about a quarter of a mik to the weft

of

( 12 )

of the city. This cavern has its mouth In
a rock of decompofed lava, and a man may
walk Into it to the diftance of fifty paces.
Its fides are covered with efflorefcences of
muriate of ammoniac, as were, likewife,
thofe of another fmaller cavern In the fame
rock. This fait muft have been formed by
fublimation, having been reduced to va-
pour by fubterraneous fires, and thus at-
tached itfelf to the fides of thefe two ca-
verns, as it is found attached in many other
volcanic places ; but of thefe fires and am-
moniacal vapours no traces whatever now
exift.

In this fliort excurfion I found by the
way a volcanic breccia, which, on account
of the heterogeneous fubftances it contained,
it would be improper to pafs without notice.
It is found in large ifolated pieces, but I
was unable to difcover from what vein it
derived its origin. Its principal fubftance
is an earthy lava, of a blueifli grey, a coarfe
grain, and little hardnefs. In this were in-
clofed the following bodies :

Firrt,

( 13 )

Firft, fragments of two kinds of lava ;
the one black, of a fcaly fradure, and which
moved the magnetic needle at tlie diftance
of two lines : the other of a grey ground, a
very rough furface, an unequal frad:ure,
which gave fparks with fteel, and contained
fmall plates of feltfpar. Both were of the
horn-ftone bafe, and emitted a ftrong argil-
laceous odour.

Secondly, feveral pieces of vitreous lava,
of a very beautiful colour, between a green
and a blue : by its fmoothnefs, clear frac-
ture, its afped:, and want of hardnefs, it re-
fembles the pitch-ftone, or pitch-blende.

Thirdly, numerous fmall pieces of a ci-
nereous compact pumice.

Fourthlyj pieces of a whitillx feml-tranf-
parent glafs.

Fifthly, fmall pieces of a colourlefs glafs,
refembling in tranfparency factitious glafs.
The largefl piece was fourteen lines in

length,

( '4 )

length, and eight in breadth, and wasj like
the others, buried in the breccia.

Thefe five fpecies of volcanic produdions
were certainly not natural to the fubftance
of the lava ; for their fradures and angles
are very vifible, and by carefully breaking
the lava they may be extracted entire. We
muft therefore conclude that they were ab-
forbed and inclofed in the lava when it was
in motion, and thus were confolidated into
one body.

In making thefe obfervations a doubt
fuggefted itfelf. Though to the naked eye,
and likewife to the touch, the vitreous lava
appears perfedly fmooth, yet, when viewed
with a lens of a ftrong magnifying power,
its furface appeared full of very minute fif-
fures. At leaft, if this was not obfervable
in all, it was in feveral pieces of both thefe
kinds of glafs, I therefore conjectured, that
when thefe fubftances were in an ignited
ftate, a current of water might have paiTed
over them j or that they fuddenly came in

conta^

( «5 )

contad with the cold air j unlefs we rather
choofe to fuppofe that thefe fiflures were
produced, when thefe vitreous bodies, in a
frigid ftate, were fuddenly enveloped in the
fiery torrent.

But the celebrated Stoves of Lipari appear
to be the objed which moft excites the
curiofity of travellers ; I could not, there-
fore, omit to vifit them. I muft, however,
confefs, that the road which led to them
afforded me more inftrudive obje(^s than
the ftoves themfelves.

Thefe ftoves He to the weft of the city,
at the diftance of four miles, and fomewhat
beyond the fummit of a mountain, w^hich,
after thofe of San Angelo and della Guar-
dia, is one of the higheft in the ifland. The
road I went was that which leads immedi-
ately from the city to the ftoves, and the
only one which can be travelled without
great difficulty. It is in a great degree the
^ork of rain waters, which have made a
deep excavation in an immenfe mafs of

tufa.

( i6 )

tufa. In more than one place, in this work i
. I have fpoken of volcanic tufas, but almoft
always incidentally. The prefent fpecies of
this fubftance requires to be treated of fome-
what more at length.

At the beginning of this work, when
fpeaking of the volcanic tufas of Pofilipo,
I faid, and endeavoured to prove, that
it was probable they were formed by
ilimy eruptions ; though I would not deny
that afhes, fand, and other fubtile matters
ejected by volcanos, and penetrated either
by the rain-waters or thofe of the fea when
they covered the bafes of the burning moun-
tains, have been confolidated into fome
tufas*. The tufa of Lipari, of which I now
fpeak, has every appearance of having been,
an earthy current. It begins at about a hun-
dred paces from the city, and continues,
without interruption, to beyond the fum-
mit of the Monte della Stufe, or Mountain
of the Stoves. This mountdn, like mofl
of the others, varies confiderably in its dif-

» See Chap. II.

ferent

( I? )

ferent parts, in one place prefentlng gentle
declivities, and in another fteep and rugged
defcents ; here plains nearly level, and there
precipices almoft perpendicular. The tufa
with which it is covered, takes exad:ly the
fame courfe ; and fometimes curves, and, as
it were, waves on the furface : nor does it
in the lead differ in its finuofities and wind-
ings, from the moft completely chara([le-
rifed currents of lava, which it likewife re-
fembles by being difpofed in beds lying one
over the other, as appears in thofe places
which have been moft corroded by the rain.
I therefore was of opinion, that this tufa
had been a ftream, if I may ufe the ex-
preffion, of flimy fubftances, that had flow-
ed down the mountain ; as examples are
not wanting of fimilar eruptions, produced
in the humid way, in the mountains Vefu-
vius, Etna, and Hecla.

But here a difficulty prefented itfelf in
oppofuion to this hypothecs. Had this
part of the mountain been inundated by a
torrent of water ifluing from the earth,

VOL. III. C when

( IS )

'when its violence had ceafed, the more
heavy bodies mufl have fubfided to the
bottom in obedience to the law of gravity,
the lefs heavy have remained above them,
and the lighteft have occupied the higheft
place; which, however, is not the fad:,
fmce, as we fhall fee, at a fmall depth within
the tufa, are found large mafles of lavas,
enamels, and glafles. But it does not ap~
pear to me improbable that thefe mafles
may have been thrown out from fome
burning mouth, after the hardening of the
tufa, within which they have not penetrated
deep.

Not only the pbfition and winding eourfe
of this tufa over the back and fides of the
mountain fufficiently prove that it once
flowed : its very nature is a ftrong confir-
mation of this fad. It is not an aggrega-
tion of aflies and fand ; a mixture of frag-
ments of Ihoerls, feltfpars, and lavas de-
compofed, and rendered earthy, and faften-
ed together by the adion of the water, be-
coming fo hard as to be cut into pieces pro-
per

( 19 )

per for building, as is the cafe with many
other tufas ; but it is merely an argillaceous
earth, refembling, from its foftnefs, the
hardened mud of rivers. Its colour is a
dull grey, its ftru6ture fomevvhat granular,
and fo yielding that it may be crumbled and
pulverized between the fingers. It is light,
adheres flightly to the infide of the lip,
emits a feeble argillaceous odour, and, w-hen
immerfed in wacer, greedily imbibes it in
every part.

In the furnace it firft acquired a reddifh
brown colour, and afterwards the black co-
lour of iron. It became fo hard that it
gave fparks with fteel, without, however,
vitrifying, except that its furface affumed a
kind of vitreous varnifli.

The depth of this tufa is different in
different parts of the mountain. In fome
places it is feveral feet deep, in others but a
few, and in others there is fo great a quan-
tity of it that, notwithilanding the excava-
tions made in it by the rains, I was unable

C2 . t©

( 20 )

to afcertain Its depth. But in every place
where I could difcover the bottom, I oh-
' ferved that it reded on a bed of pumices,
partly pulverized, and partly in detached
pieces approaching to the globofe form.
They belong to the clafs of the lighteft of
thefe fubftances. It appear?, therefore, in-
dubitable that thefe pumices had been
thrown out of the burning mouth of fome
volcano, before the flowing of the tufaceous
current.

This tufa prefented a very unexpected
phenomenon. On breaking it, its fradures
exhibited frnall black particles, which were
diftinClly recognized to be true coal, from
t their blacknefs, lightnefs, drynefs, the faci-
lity with which they broke, and their fmall
degree of hardnefs. Some of them, like-
wife, when expofed to fire in the open air,
fumed, and became red hot ; others emitted
a little flame. The latter had not been
perfed.ly reduced to coal, as the fibrous
parts of the wood were Itill to be feen.
Thefe coals were fmall cylinders from two

or

( 21 )

or three lines in length to twelve or four-
teen, and of proportional thicknefs. They
appeared to Iiave appertained to branches of
trees or fhrubs 5 they are buried in the tuf^
at various depths, and are found, though
thinly fcattered, through its whole extent.

This fad:, never before, to my knowledge,
obferved by others in volcanic tufas, might
induce us to imagine that the two methods,
the humid and the dry, had here been com-
bined ; and that the watery Hime, when it
flowed down the mountain, had been pene-^
trated by the fire in fuch a manner that it
had inflamed, and converted into coal, the
vegetables it met with in its way. This ex--
planation is certainly not free from diffi-
culties, as the reader, no doubt, already
perceives ; it thereiore may appear more
probable that the earthy inundation had
involved, and carried with itfelf, thefe car-
bonaceous fubftances, which exifled pre-
vious to its eruption, and which derived
their origin from a fhower of ignited matter
leaving burned, but not entirely confumed,
C 3 thQ

( 22 ) ~

the few plants which feebly vegetated on
the declivities of the mountain.

It has been already faid, that the rapid
defcent of the rain-v/aters on that part of
the mountain which leads to the ftoves,
has corroded the tufa to a great depth ;
and it is in the middle of thefe corrofions
that we meet with various volcanic bodies,
which, together with others lying in the
public road, merit well to be defcribed.

Firft, we find pieces of enamel of every
fize, which, though they are fmooth with-
out, when broken, have, within, an angular
fradure. Their colour is a pale blue, they
have no great brilliancy, nor are they very
hard, as they fly in pieces when flruck
againft the fteel. The caufe of the want
of hardnefs in this enamel, may be afcribed
to the filTures, of which it is full ; and
thefe, perhaps, are to be attributed to the
pieces of enamel being red-hot when they
fell into the tufa not yet dry. The felt-
fpars it contains have the fame cracks, and

probably from the fame caufe.

In

( n )

In the fame places is found another kind
of enamel containing a great number of
fmall bodies, which 1 will not abfolutely
affirm to be garnets, becaufe 1 was not able
to analyze them in the humid way ; but
their external charadters, together with the
proofs furnilhed by the dry way, almoft
induce me to conclude them fuch. In all
my volcanic refearches I have never met
with any fimilar. In general they have a
bulbous figure, and are of a blackifh colour,
which in fome inclines to a red. Their
furface is fmooth and fhining, their recent
fradures lamellar, perfectly vitreous, and
will cut glafs. The largeft are about three
lines and a half in thicknefs, and are opake ;
the fmalleft, about the third part of a line,
and are femi-tranfparent. They give fparks
with fteel, and melt in the furnace into- a
black and fcoriaceous enamel. Thefe cha-
raders, taken together, certainly give them
a great refemblance to garnets : I fhall not
therefore hefitate to clafs them with that
fpecies of ftone ; as their not being cryftalr
lized is of little importance, fmce we know
that there are alfo amorphous garnets.

C 4 While

( H )

While employed ia the examination of
thefe ftones, I refolved to compare tliem
with the Veruvian garnets j tor, in myexcur-
fion to that volcano, I had colledled feveral
different fpecies of them on Monte Somma,
which is the ancient Vefuvius. I made le-
veral experiments on four of thefe, of which
the following is the refult.

The firft fpecies is found in a lava with a
horn-flone bafe, of a yellowifh grey colour,
an unequal furface, and of a confiftence
little different from earthy, from the great
alteration it has undergone ; not, as far as
appears, from fulphureous exhalations, but
from the acftion of the atmofphere. The
garnets it contains have likewife fuffered
injury, having loft a part of their native
luftre, and being eafily broken or crumbled
to pieces from the multitude of minute fif-
fures and cracks in them. They, however,
retain fomewhat of the vitreous chara<51:er.
Their colour is between a vvhite and a grey.
At firft view their figi-ire appears peife^lly
globular ; but on extrading them from the
lloncj their matrix, (which may eafily be

done,)

( 25 )

done,) and attentively examining them, they
are found to have facets, though it is not
poffible to afcertain the number of them, as
piany of the angles have been defaced by
time. I Ihall only obferve, that having
broken one of thefe garnets into two
equal parts, the perimeter of each half
was o£tagonal. This fradture at the fame
time fhewed the texture of the garnet,
which is compofed of very thin circular
leaves. Thefe garnets are of different lizes,
from four lines and a half to one fixth of
a line.

The furnace reduces the matrix-lava to a
compadl enamel of the colour of pitch ;
but it leaves the garnets untouched, which
only become fomewhat whiter, more vitre-
ous, and more hard. The blacknefs of the
enamel being a contrafh to the whitenefs of
the garnets, a great number of the latter be-
come confpicuous, which before were not
vifible in the lava; and, notwithftanding
their extreme minutenefs, they remain un-
injured by the fire.

The

( 26 )

The garnets of the fecond fpecics are
contained in a lava which has for its bafe a
foft horn-ftone. They are larger than the
former, and entirely opake. They are white
as fnow, and more brilliant in their fractures
than the preceding. Many of them are of a
round figure, and manifeftly (hew a cryftal-
lization in various facets ; which, however,
it is impoffible to number, as they break in
pieces if we attempt to extrad: them from
the lava. Many others of them are of very
irregular forms.

Several of this fecond fpecies of garnets
inclofe within them fmall prifmatic fhoerls,
of the colour and luftre of afphaltum, which
probably pre-exifled completely formed,
and were taken into the moifture from
which the garnet derived its origin.

Thefe garnets are, llkewife, infufible in
the furnace, though the lava is converted
into a porous fcoria.

The third kind is ftrongly infixed In a

heavy

( 27 )

heavy lava, which alfo has for its bafe the '
horn-ftone, is of an iron-bl;ick, compad:, but
not fufficiently hard to give fparks with
fteel. The garnets, which are of a yellow-
iih white colour, and fome of them four
lines in diameter, for the moft part have
clefts or fiflures, but in fuch a manner that
in the recent fradlures the furface refembles
around polypetalous flower.

The furnace melted the lava, but not the
garnets, which only acquired the red colour
of copper.

The garnets of the fourth and laft fpecies
have four-and-twenty facets, and are femi-
tranfparent, white, and vitreous. Their ma-
trix is a compadl lava of a horn-ftone bafe,
which emits an argillaceous odour. In the
the furnace it changes into a black ena-
mellar product, but the garnets remain un-
touched.

On comparing thefe refults with others
before detailed, we fhall find that the ftruc-

ture

{ 28 )

ture of the Vefuvian garnets, (o far as it is vU
treous and lamellar, is fimilar to that of thofe
of Lipari j but that, when expofed to the fire,
a difference is found between thefe two
fiones, the one eafily melting in the furnace,
and the other proving refradtory.

Finding, therefore, that thefe four fpecies
of garnets were infufible in the furnace,
though continued in it for feveral days, I
had recourfe to oxygenous gas (or dephlo-
gifticated air}, by the adion of which they
all melted, though flov ly. When the ma-
trix lava flowed like common glafs, the
fmali pieces of garnet within it remained
unchanged ; but at length fufed, though
without incorporating with the lava, fo a3
to form a homogeneous whole.

Thofe chemifts and naturalifts, who, be-
fore me, have made experiments with fire
on the Vefuvian garnets, have defcribed re-
fuks fimilar to thofe I obferved. Bergmann
fays thefe garnets melt with the blow-
pipe alone, but a vehement fire is necef-

fary.

( «9 )

fary *. Sauflure tells us, that a fpotted lava
(lave a ocil de perdr'ix) which he found on
Monte Somma, acquh-ed, after fufion, a black
vitrified ground, but that the polyhedrous
grains of this lava remained unchanged in
the moft violent fire ; and by polyhedrous
grains it is evident that he means what I and
others have called garnets f . With refpe^fi
to the adion of oxygenous gas upon them,
we may refer to Ehrmann, in his work on
the Air of Fire. " The white opake garnet of
" Vefuvius," fays this writer, " differs from
" garnets properly fo called, in this, that it
" melts with extreme difficulty (with the
" affiflance of oxygenous gas is here to be
" underftood), and at length, after continual
" ebullition, becomes a mafs perfedly fimi-
" lar to quartz, even in its fradure, and
" which crackles in like manner between
" the teeth."

This kind of ebullition I have obferved
in the four varieties of garnets above men-

* De ProducElis Vulcanlcis.

t Voyage dans les Alpes, Tom. I.

doned,

{ 30 )

tioncd, when they were in a ftate of fufion*
The firfl: and third, likewife, produced two
finall mafles refembling quartz, but thofe of
the fecond and fourth variety were fpongy.
It is very poiTibU that this author only made
his experiments on one fpecies.

Some learned naturalifts are of opinion
that the garnets of Vefuvius are improperly
fo denominated ; firft, becaufe they con-
tain no iron ; fecondly, becaufe they fufe
with difficulty ; and, thirdly, becaufe they
differ in the proportionate qualities of their
conftituent parts from thofe of true garnets.
Thefe reafons, hov/ever, do not appear to
me fufficient to exclude them from being
clatled with this kind of ftones. It is true,
that iron is ufually contained in garnets;
but it is not elTential to them ; as has been
obferved by Bergmann, who, in tranfparent
garnets, found only y^ parts of this metal.
The abfence of iron, probably, therefore,
renders them fo difficult to fufe. With re-
fped: to their conftituent parts, the Swedifli
chemift (Bergmann) has obferved, that the

principal

( 3' )

principal of thefe is filex, the next alumine,
and that which is lead of all in quantity,
lime. This analyfis agrees with that made
by Achard on fome of the pureft Bohemian
garnets ; and fuch a proportion of the con-
flituent principles is fufhciently fuitable to
that of the garnets of Vefuvius, in which Berg-
mann found about ^^ parts of filex, 39 of
alumine, and 6 of lime. And though the
proportion of the filex to the alumine is
not entirely the fame in both thefe ftones,
the difference is not fo great,, in my opinion,
as to induce us to confider them as two
diftind fpecies ; as will appear by compar-
ing the numbers ^^ and 39, which exprefs
the quantities of filex and alumine in the
Vefuvian garnets, with the numbers 48 and
30, denoting thofe of the fame two earths,
in the Bohemian garnets, analyzed by the
before-cited chemift of Berlin (Achard).

To return for a moment to the garnets of

Lipari: thefe do notfo tenacioufly adhere to

their bafe as we almoft always find the felt-

fpars and fhoerls ; but, like other garnets, are

z mpl anted

C 32 }

Implanted in it in fuch a manner that they
may be eafily detached without breaking,
leaving the exa6t impreffion of their figure
in the enamel. This enamel, which is
compa61:, heavy, and of a grey cinereous
colour, is found in detached pieces, both in
the road and in the tufa ; and is the firft
production which prefents itfelf, after leav-
ing the city to proceed towards the ftoves.

Continuing our journey ftill further along
this road, we find in it, and likewife within
the tufa, very curious mixtures of a white
argillaceous earth and black enamel ; both
of which are fo mingled and kneaded toge-
ther, that we can fcarcely find a quantity of
this earth of the fize of a pea, which does not
contain feveral particles of this enamel ; and
very few, indeed, are the pieces of enamel
that contain none of this earth. It has an
earthy odour, and adheres to the tongue.

In the fame fituations where this peculiar
mixture is found, we likewife meet with an
enamel containing garnets, fimilar to thofe

above

( r. )

above-mentioned, but larger, and more ap-
proaching to a globular figure. It is re-
markable that this enamel, in fome places,
forms one whole with fome pieces of lava
of a horn-ftone bafe, which alfo contains
garnets.

I {hall briefly diftinguifh four fpecies of
lava, each of a horn-ftone bafe, which are
met with, in detached pieces, on the road to
the Stoves.

The firft has a fibrous fraGure, the colour
of iron, fome appearance of porofity, fuiE-
cient hardnefs to give fparks with fteel, and
the power to move the magnetic needle at
the diftance of a line and a quarter. It
emits an earthy odour, and contains felt-
fpars.

The fecond is of a black-grey colour,
and, though compact, rather foft. Almoft
one half of it confiftsof rhomboidal felt-
fpars.

VOL. III. D The

( 34 )

The third only differs from the feconcJ
by being fomewhat more compaift, harder,
and containing fewer feltfpars.

The fourth, which in folidity, weight,
and hardnefs, exceeds the three preceding,
has a black ferrugineous colotrc, an earthy
-fradure, adheres llightly to the tongue, and
emits the ufual argillaceous odour. It
moves the magnetic needle at the diftance
of half a line.

AH thefc four kinds of lavas are change<J,
in the furnace, into vitreous fcorise, but with-
out the fufion of their feltfpars.

Having mentioned thefe, it will be necef-
fary to defcribe, fomewhat more at length,
another fpecies of lava, which is enrich-
ed with a great number of extremely beau-
tiful volcanic chryfolites.

This lava has for its bafe a foft horn-ftone :
it is of a dark brown colour, and unequal
in its fractures on account of the fiffures

6 which

( 35 )

which feparate its parts. It is found in de-
tached pieces, like the four preceding lavas^
but thefe pieces are rare. It gives but few
fparks with fteel, emits a flight argillaceous
odour, and ad:s on the magnetic needle at
the diftancc of a full line. In confequence
of its numerous fifl'ures it is rather light,
and when flruck with a hammer is fome-
what fonorous. I omit to mention fome
fmall fcales of feltfpar incorporated in it,
and proceed to the examination of the chiy-
folites.

Thefe, when fituated in the external parts
of the lava, which have fuffered by the
influence of the atmofphere and elements,
readily attract the eye, by their lively" co-
lour, which is betv/een a green and a yel-
low ; but in the recent fraftures they fliine
with much more brilliant colours. The moft
confpicuous are the golden-yellow, and the
fine grafs-green, with wliich, fometimes, is
mixed a fire-red, tempered with a tinge of
purple. If thefe chryfolites are expofed to
the immediate light of the fun, and viewed
D 2 under

( 3f> )

under certain angles, their colours become
much more lively and bright. Many of
them- are amorphous, butfome are quadran-
gular prifms. Their furface, In the fradtures,
fhlnes with a glafly brilliancy, and is fome-
times fmooth, and fometlmes rough, accord-
ing as the plates of which the chryfolites
are compofed may have been broken. The
fmall fragments of them are angular and
femi-tranfparent. Thefe chryfolites give
fparks with fteel, and cut glafs nearly like
rock- cry ftal. The largeft are not lefs than
three lines and a half in length, but the
fmalleft can fcarcely be difcerned by the
naked eye. They are fo firmly Infixed in
the lava, that only fragments of them can
be detached.

The fire of the furnace, and that of the
blow-pipe, not only will not fufe thefe mi-
nute Hones, but are unable to injure them
either in their^colours or texture. Oxyge-
nous gas (dephlogifllcated air) alone dlfco-
lours them, and melts them into a globule,
of a white colour, but without brilliancy.

Though

( 31 )

Though it was not known till the pre-
fent time that Lipari afforded volcanic chry-
folites, they had been before found in other
volcanized countries, as in Vivarais and Ve-
lay, by M, Faujas, and on Mount Etna by
M. Dolomieu. But on comparing their chry-
folites with mine, I find certain differences
and refeaiblances, which it will be proper to
enumerate.

The chryfolitcs obferved and defcribed
by M. Faujas, when examined with the
lens, are found to be compofed of an aggre-
gate of arenaceous grains, more or lefs fine,
and more or lefs adherent ; fcabrous, irre-
gular, and fometimes forming crufts and
fmail fandy fcales ; but, for the mod part,
having the appearance of angular fragments
united by infertion into each other.

The chyfolites of Lipari have nothing of
this nature in their ftrudure. I broke fe-
veral of them, and examined their frag-
ments with the microfcope -, but they never
appeared to me granular, but always fmooth

D 3 and

( 38 )

and glaiTy. The moft minute parts of thefc
chryfolites exhibited the fame afped: they
prefented when whole.

I muft not omit to mention another dif*
ference of importance, which is, that the
chryfolites of Lipari are only a few lines i^
length, whereas thofe defcribed by M. Eau-
jas are fometimes feveral pounds in weight,

They agree, however, with mine in their
infufibility in an extremely adive fire ; for
thofe on which he made his experiments
refilled the fire of common furnaces, how-
ever violent and continued it might be, an4
could not be reduced to a ftate of fufion bu^
by the aid of oxygenous gas.

The colours of both are fcmetlmes the
fame. 1 fay fometimes, for M. Faujas in-
forms us, that feveral of his chryfolites were
only of one colour i a green, or topaz-yel-r
low.

The traits of refemblance and difference

between

( 39 )

between the Liparefe and Etnean chryfo-
lites will be feen by comparing the defcrip-
tion I have given of the former with what
M. Dolomieu fays of the latter, in the work
I have frequently cited. He tells us, that
fome of the chryfolites he found there are
amorphous, others cryftallized in tetra-
gonal or hexagonal prifms, fometimes with
an hexagonal pyramid ; that their fracture
is partly concholdal, and partly lamellar;
that they are harder than quartz ; that they
are more or lefs tranfparent ; that their co-
lour is a greenifli yellow, with various
tinges, and that they are fufible in a ftrong
fire. He does not give their fize, but they
cannot be large ; both becaufe he calls them
grains^ and becaufe thofe which I obferved
in fome lavas of Etna were very minute.

I have defignedly called the chryfolites of
Lipari, volcajiic chryfolites, not merely be-
caufe they are found within a lava, but to
preferve a diftindion between them and the
gem of that name ; fmce I know that fome
refpedable authors are of opinion, that the
D 4 volcanic

( 4° )

volcanic ftones which, from their greenifh
yellow colour, and other circumftances, re-
femble that gem, and therefore are called
chryfolltes by the Volcanifts, differ from
them entirely in their component parts,
and feveral of their external characters. To
this opinion I can make no objedicn,
though, in defcriblng thefe ftones, I have
adopted the name by which they are ufual-
ly known. It mud be obferved, however,
that fome of their properties fhew they can-
.not be clafied as fhoerls, among which fome
naturalifts generally place the chryfolites of
volcanos.

It remains like wife to fpeak of a ftone
which was the laft of the produds that of-
fered themfelves to my obfervation, as I
proceeded along the declivity of the moun-
tain leading to the Stoves.

This ftone is a porphyry, the bafe of
which is the petrofilex, containing feltfpars
with feveral faces, and brilliant in the frac-
tures, and blackifh irregular fhoerls. The

bafe

( 41 )

bafe has the red colour of brick. It is
found in detached mafTes, fome of which
weigh feveral thoufand pounds. It is corn-
pad:, and fcaly in the fractures. The pieces
broken from it are irregular ; the tlitnnell
are tranfparent at the edges ; and they give
fparks moderately with fteel. The colour
of the bafe has given the feltfpars a reddiih
tinge, as we fee in certain oriental porphy-
ries.

But has this porphyry fufFered fufion, or
is it in its natural ftate, and, at mofl, cal-
cined when it was ejeded by the volcano ?
I cannot pretend pofitively to decide ; but I
incline to the latter opinion more than to the
former, fmce an alteration is vifible, even in
the internal parts, which appears to be the
effedt of a true calcination.

In the furnace, the fubftance of this rock
becomes foft, but does not fufe : the felt-
fpars remain unchanged, but the fhocrls are
vitrified.

The

( 42 )

The fpacious and deep excavations made
in the tufa by the rain-water, and which
extend from the bottom of the mountain
to the fummit, afforded me an opportunity
to difcover and examine the ftony fub-
ftances I have defcribed ; for it was only in
thofe excavations that they were vifible : in
every other part nothing appeared but the
naked fuperficial cruft of the tufa. None
of thefe fubftances are dlfpofed in currents;
they are all detached ; and thus render it
probable that they fell into the tufa after
having been thrown up into the air in vol-
canic ejedions.

When "we have reached the fummit of
the mountain, an ample plain opens, formed
of the fame tufa, but become earthy, in
which corn is fown, and a few vineyards
are planted. Here we find numerous
pieces of a fhining glafs, which is femi-
tranfparent, of a blackilh colour, and fome
of the fineft and pureft to be found in Li-
pari. As I wiflied to difcover the origin of
this fubiUnce, 1 caufed the place where it is

founcj

( 43 )

found to be dug into. The tufiiceous earth
is there about three or four feet deep. The
pumices lie immediately under it, and among
them this glafs is found, in confiderable
quantities. It has probably been turned up,
and brought to the furface, by the plough,
pr other fimilar inftruments ufed to prepare
the earth for fowing with corrj.

Beyond this plain there Is a gentle de«
fcent of about two 'hundred feet in length,
at the end of which are the Stoves. What-
ever prepofTeffion in their favour the travel-
ler may have conceived from hearing fo
much of them, he lofes it the moment he
fees them. They form a group of four or
five caves, more like to the dens of bears
than the habitations of men ; and which
exhibit much lefs of art than the edifices
framed by the beaver. Every cave has an
opening at the bottom, through which the
warm and humid vapours enter, and ano-
ther in the top through which they pafs
out, I entered one of thefe, but was unable
tP remairx long in it, l^fs from, the heat, for

the

( 44 )

the thermometer ftood at only 48 j degrees,
than from I know not what of a fufFocating
nature which the air had in it. Thefe
Stoves now retain Httle more than their
name, and are nearly deferted. In facft,
though they ftill retained their virtue, and
were efficacious in the cure of various dif-
orders, how would it be poffible to make
ufe of them, when they are deftitute of
every convenience necefiary to that pur-
pofe ?

When M. Dolomieu vifited them, the
"whole ground on which they ftand was pe-
netrated with hot vapours, which, under the
form of a thick fmoke, iffued from fmall
apertures of about an inch, or two inches,
in diameter. When I was there, circum-
ftances were much changed, as ufually hapr
pens in volcanos, where the prefence of fire
manifefts itfelf fometimes more and fome*-
times lefs. There was then only one aper-
ture, of about an inch in diameter, from
■which, from time to time, iflued a thin
flream of fmoke, with a ftrong fulphureous
4 fmello

( 45 )

fmeii, Having enlarged this aperture, I
found it furrounded by a fraall quantity of
foft fulphures of iron (pyrites) generated by
the union of iron and fulphur. The Ab-
bate Trovatini, vvdiom I have cited m ano-
ther place, likewife attefts, that, at certain
times, feveral ftreams of fmoke afcended
round the Stoves ; and I fhall add, that, be-
fides the ftrong fmell of fulphur, which I
perceived on approaching the place, the
ground became hot, and the fetor increafed,
on digging to about the depth of a foot :
from which it may be concluded, that un-
der the Stoves and the ground adjacent, fome
remains of fulphureous conflagration ftill
continue*. The Stoves, and the warm

baths,

* It has been (liewn, in Chap. XIII, that the decompo-
(itions of different products of Stromboli and Vulcano
do not derive their origin from the muriatic acid, to
which, according to M. Sage, the principal alterations
of volcanic fubftances are to be afcribed, but to fulphu-
reous-acid exhalations. The decompofitions in the
environs of the Stoves of Llpari, I am of opinion, with
M. Dolomieu, are to be attributed to the fame caufe,
the exiftence of which is fufficiently proved by the re-
mains

( 45 )

baths, of which we ihall fpeak below, ard
the only places in the whole illand where
any figns are to be found of as yet unex«
tinguifhed volcanos*

M. Dolomieii, after having defcribed the
Stoves of Lipari, proceeds to fpeak of the
alterations caufed by the fulphureous-acid
vapours on the lavas of this place, remark-
ing that all of them, befides having become
fofter and lighter, have loft their primitive
colour, and affumed a w^hite tinge, mixed
with yellow, red, violet, and other colours,
which the oxides of Iron ufually produce.
He obferves likewife, that they are coated
■with a thick cruft of fulphates of lime (fele-
pite or gypfum), which fulphates penetrate
likewife to the internal parts, and that fome
lavas are covered with that kind of iron ore
which is called filmy (f^ingofa) or bog ore.
He then very ingenioufly explains in what
manner, by means of a combination of the

mrnns of fulphureous fumes, and the quantity of ful-
phates of lime, which I fliall prcfently have occafion
to tlefcribc.

fulphuric

C 47 )

fulphurlc acid with diiFerent earth?, the
lavas have become lighter and varioufly
coloured.

As I vifited the Stoves three feveral times,
and examined wqth great attention the lavas
that had fuffered alteration by the adlion of
the fulphureous acid, I am enabled to add, to
the obfervations already given, fome others
which I believe to be new, and which I fhall
here briefly ftate.

It was an obje61: equally important and
curious to afcertain to w^hat kinds of lavas
ftill remaining in the ilate in which they
were left by the fire, thofe belong which we
now fee decompofed by acids ; and as the
obfervations I had made at Solfatara di Poz-
zuolo and other places, had taught me that
the decompofition diminilhes, the deeper it
enters into the fubftance, I conceived that
the moft proper means to obtain this know-
ledge would be, to break fragments of the
lava, and examine the internal parts, to find
how far the decompofition had penetrated.

The

( 48 )

The greater part of the decompofed latas
of the Monte delle Stufe are, externally, of
a reddifh white ; and fome are of a black-
ifh colour. I firft examined the latter ; and
prefenting their furface to the full light of
the fun, I difcovered fomething of a brilliant
appearance which invited me to examine
it with the lens. It proved an aggregate of
innumerable globules of hsematitic iron,
which beautifully cover the furface of thefe
lavas,

I detached a confiderable number of thefe
globules, and found that on trituration they
afTumed a red colour, which is the property
of the dark haematites. This was, there-
fore, a pure martial oxide, depofited here,
and formed into globules ; and under that
aggregate lay another oxide of red, but
earthy iron. The lava ftill deeper was of
a white colour, interfered with parallel
ftreaks of a reddifh black, or lightly fhaded
with a yellowifh tinge.

Thefe lavas are foft, light, and compact :

they

{ 49 )

they adhere to the tongue, have the confifl*
ence of clay, but do not emit its odour.
They feem to be fimple lavas, no extra-
neous bodies appearing in them. . It is ob-
fervable that every fracture is conch oidal ;
and that, when ftruck, they caufe a found
fimilar to that of fome kinds of petrofilex ;
which has induced me to fufpedt they belong
to that fpecies of ftone : a fufpicion which is
confirmed by examining deeper within the
fradtures ; fmce at the depth of two feet, or
thereabouts, a grey colour takes place of the
white, and the other external appearances
diminifh ; the lavas begin to aflume a fili-
ceous afped,and give a few i^arks withfteel.
Still deeper we perceive without the leaft
doubt that thefe lavas have a petrofiliceous
bafe, and contain a few {hoerls, which do not
appear in the decompofed parts, probably
becaufe they are themfelves decompofed.

Thefe obfervations, which were made on
fome lavas of a black colour on the furface,
are likewife true of feveral others, which,
externally, are of a reddifh white. The ap-

V0L» in. E pearances

( 5* )

pearances in them are, elTentlally, the fame.
The red colour in the internal parts infenfi-
bly vanifhes ; the grey by degrees fucceeds
the white, which, ftill deeper, acquires a
luftre, the lava at the fame time becoming
harder, and at length diftindly exhibiting
all the chara^ers of the petrofilex.

One of thefe lavas, ftreaked with white
and a clear red like that of the peach-
flower, is fpotted on the furface with points
almoft pulverulent* Thefe are decompofed
feltfpars, though they ftill retain a refidue
of cryftallization. This lava has been more
changed by the acids than the others, being
ibfter, and even pulverable ;. though at the
depth of two feet it is hard, heavy, of a
bkck-grey colour, evidently has a petrofili-
eeous bafe, and contains feltfpars which are
perfedly entire.

In deicribing the varioufly decompol^d-
lavas of Solfatara, we have feen that felt-
fpars are a kind of ftones which ftrongly
refift the adtion of acids. It frequently
7 happensy

{ 5' )

happens, that their hafe is completely
decompofed, while they are fcarcely in
the leaft changed. As, therefore, ia th^
prefent lava, the fekfpars are decompofed
equally with their bafe, we muft be con-
vinced that the ftrength of thefe acids muft
have been very great* In general, thefe
lavas at their furface are foft, like doughy
and almoft faponaceous; characters th^-
ufually accompany thefe decompofitionsh -'^ *

We muft not omit toWQtke'a lava oif the
breccia kind, the bafe df whichis likewife
petrofilex, and in which the action of the-
acids has extended only tO' the depth of a
few inches. This bafe, even near the fur-
face, has not entirely loft its natural colour,
refembling that of iron, and in it are incor-
porated irregular fmall mafles of whitened
and pulverulent lava. Thefe, therefore,
have yielded more to the decompofition
than the bafe that contains them. -At a
-greater depth we find them unaltered 3 -and
they are then only fragments of^kva bf ^
horn-ftone bafe. ' <'^iJjI:,i bnh ^o-iun^^
E 3 Though

( 52 )

Though many of the lavas of the Stoves
of Lipari have fuffered by the fulphureous-
acid vapours, there are fome that are entire-
ly unchanged. I Ihall only defcribe one,
which is fo well prelerved that it appears to
have: been produced but yefterday by the
volcanic gulph. If we fcale the furface of
it, where it projeds in large mafles from the
earth, it appears of a dark iron colour, has
an eJvtremely, compad grain, and a con-
choidal fradure. The fcales at the edges
are fharp and -.cutting, and give very lively
fparks with fteel. It is one of the heavieft
lind hardeft among the lavas, and puts the
magnetic needle in motion at two lines
diftance. It has for its bafe the petrofilex,
containing very brilliant feltfpar needles.

This, lava, therefore, has not been- in the
leaft affeded by thefe acids, not, probably,
becaufe it was able to rtfift their ftrength,
but becaufe it was not expofed to their ac-
4f^ : bThe places under which the confla-
grations,pf. a volcano bun-, have,.numerous
apertures and hfTures through which iflfue
r!^uorri fuiphureous

( 53 )

fulphureous fumes; and when lavas are
fituated around or within there, they will
be more or lefs afFeded by them. But in
the fame tradis of ground there are more
places than one impenetrable to thefe fumes,
and there, in confequence, the lavas fuffer
no other alterations than thofe produced by
time. Thefe interrupted exhalations of ful-
phureous vapours I have obferved at Vefu-»
vine, Etna, and Stromboli, and have noticed
them before in my accounts of thefe vol-
canos. It is only to be remarked that, at
the Stoves of Lipari, the quantity of decom-
pofed lavas being very great, and extending
for the moft part to a great depth, the ful-
phureous-acid vapours muft have there if»
fued in extraordinary abundance, and at the
fame time have been of long duration. The
intenfity of them, and their confequently
greater efficacy, might, indeed, have fup-
plied the place of long continuance ; for I
have obferved, that when the lava of Vefu*
vius flowed before my eyes, and feveral
of its lateral branches had ceafed to move,
two of thefe, which had been penetrated
E a by

( 54 )

by a thick clou'd of the fumes nfiul there,
were already half decompofed, though they
were evidently parts of that ciiTfent wMch,
but a few months before, had been difgorged
Jjy the fide of the jnountainv ^ Laftly, ac-
cording to the different qualities of th«
lavas, arid as they may be ."compofed more
or lefs of calcareous, argillaceous, or martial
principles, all combinable with fulphureous
acidS) a greater of • kfe deGohlpolltioa will
be produced* ^ -I J-!03oo i ty:dhi\

- The different degrees' of d^eompofition
in lavas render them fometimes more, and
fbthetimes lefs fufceplible of fufi^n in the
furnaee. The parts notydecbinpofed will
fufe. A beginiiing decompofidbft renders
them ftubborn, andy whtii 4t is complete,
they entirely refift the fire. TheCaufe of
thefe differences appears to. me fufficiently
evident. The more earths are pure the
more they refifh fufion. All thofe hitherto
known are.infufible, except in .very violent
^res. Their mixture facilitates their fufion,
as they thus become a reciprocal flux j and

( 5S )

we know that fufion readily follows, when
filex, alumine, and lime are mixed in the
proportion of 3, i and i. There was no
lava on which I made experiments, in which
I did not find thefe three kinds of earth ;
and though they might' not be combined
exadtly in this proportion, their combi-
nation was yet fuch as to render almoft
every lava fufible in the furnace. The lime,
which, in the dry way, ads as a flux to the
filex, is in a great degree diminifhed in the
decompofition of lavas, forming fulphate
of lime by its intimate union with the ful-
phuric acid ; and hence we have one im-
pediment to the fufibility of thefe lavas.
The diminution of the alumine, arifing from
its combination with the abovementioned
acid forming fulphate of alumine, which is
afterwards detached and carried away by
the rains ••'", will likewife be another obllacle;

* To prevent any ambiguity, it may be proper to re-
peat what 1 have faid in Chap. II, that the pretended
tranfmutation of filex, or any other earth, into argil-
laceous earth, in the decompofition of lavas, has no
exiftence ; fince, in this c^ie, that earth likewife is di-
miniflied, from the caufes alleged above.

E 4 to

( 56 )

to which we may add a third, which is the
lofs of the iron, Ukewile an aid to fufion, '

Thefe fulphates, which for the inofl: part
accompany lav.as, prefent a pleafmg fpec-»
tacle to the naturalift. Their colours are
infinitely varied. Thofe which are moft
prominent to the eye, are the rofe colour,
violet, and orange, and they are the more
confpicuous becaufe they are generally
placed on a white ground.

I have obferved three kinds of fulphate
of lime, independent of feveral varieties
which I omit. The firft is compofed of
thin plates, parallel to each other, clofely
united, brilliant, compad, and opake. They
form ftrata or beds of diiferent thicknefs,
fometimes more than a foot, and thefe ftrata
are eafily detached from the lavas to which
they adhere.

The fecond fpecies is filamentous, having

either parallel or ftellated filaments, in which

Jatter cafe tl,e filaments form a kind of py-?

ramids, which have their apices in one

6 commo?!

( 57 )

common centre, and their bafes at tlie cir-
cumference. We find fome very large,
pieces of this kind, formed by the aggrega-
tion of thefe pyramids.

The third fpecies is compofed of thin
and (hining plates, fomewhat elaftic, tranCr
parent, very foft, and forms the indeter-
minate cryftallization of fulphate of lime
called fpecular ftone; but this fpecies is
rare, and its cryftals are always very fmalL
In thefe cafes the determinate and primitive
eryftallization of this neutral earthy fait is
always wanting.

It is therefore evident that this variety of
colours, fuch as yellow, red, or violet, ex-
hibited by the decompofed lavas, is a con*
fequence of the iron pre-exifting in them ;
which being, if not decompofed, at leafl
greatly altered, by the fulphureous acids, is
varioufly modified, and aflumes this diver-
fity of hues. The fame caufe operates, in
like manner, on the fulphates of lime, form-
ed by the combination of the fulphuric acid

with

( i8 )

with the lime, which is laid open by the
deftrudion of the adhefion of the confti-
tuent principles of the lavas, and varioiifly
coloured by the oxydated metal. The white
colour of -the decompofed lavas, then, it is
evident, is produced by the lofs of their
iron ; which agrees perfectly with experi-
ence, fmce, where the decompofition has
taken place, the lavas are incapable of
moving the magnetic needle, whereas they
conftantly produce motion in it, fome at
the diftance of two lines, and fome at more
or lefs, in the parts not decompofed.

I fhall conclude my obfervations on the
produ<^ions of the Stoves of Lipari, with
fome interefting remarks relative to feve--
ral different fpecles of zeolites, which I dif-
covered in their vicinity. I fhall defcribe
them feparately with their matrices.

- Eirfl fpecies. The matrix containing this
zeolite is a lava of a horn-ftone bafe, of a
dark- brown colour, granular in the frac-
tures^: and which fcarcely gives fparks with

fteel*

( 59 )

fteel. It (hews no indication of having
fufFered by the fulphureous acids. It is full
of fmall long cavities, all in one diredtion,
and which probably were produced when
the lava was in a fluid flate. It is in thefe
cavities that this fpecies of zeclite is found.
At firft view it appears rather tobe a ftalac-
dcal calcedony, having the form of aclufter
of grapes. It is of a white pearl colour,
inclining to a light blue, and gives fome
fparks with fteel. It has a filiceous fradlure,
and a degree of tranfparency. Three pro-
perties, however, efpecially charadterife it ;
iirfl, that it forms a jelly with mineral acids;
fecondly, that it flaflies or blazes at the mg-
ment of fufion ; and, thirdly, that it bub-
bles, and as it were boils, when in fudon:
and though neither of thefe charaders ex-
clufively appertain to the zeolite, all the
three together fufficiently fix the nature of
this ftone, which muft be referred to the
clafs of amorphous zeolites. The clufter-
ing grains may be extraded entire, as they
attach to the lava but in a few points. The
largeft extend to five lines in length, by two

or

( 60 )

or three in breadth. The figure which I
have called cluflering, is the moft ufual in
this fpecies of zeolite ; though fome arc
only oblopg globules, of the fame fize with
that of the fmall cavities which contain
them. They are, however, by no means
found in every cavity ; for, out of a hun-
dred of thefe cavities, ninety contained no
zeolite. This fpecies is contaminated with
a pulverulent, orange- coloured oxyde of
iron.

The blow-pipe with difficulty melted it j
and feveral feconds were required for its I

complete liquefadion, even with the aid of II

oxygenous gas. It then changed into a
fnowy-white enamtl, full of bubbles. It
has a lucid brightnefs when it begins to
melt, and boils and bubbles up when ia
actual fufion.

Second fpecies. This is found in fome
pieces of the former lava, but its charaders
are different from thofe of the pr-eceding
fpecies. It coats over many of the cavities

before

C 61 )

before mentioned with a thin cruft, thii&
forming geodes, which, however, are not
cryftallized internally. This zeoUte, which
incUnes to a white colour, is more tranfpa-
rent than the other, and, from its harJnels,
cuts glafsj almoft like rock cryftal. The
mineral acids have no effedt upon it, not
even when pulverifed, though they convert
the former fpecies into a kind of jelly.
When melted with the aid of oxygenous
gas, it emits a thin brilliant blaze, and is
changed, with ebullition, into a vitreous and
white globule.

It Is not unufual to find within thefe
zeolitic geodes, plates of very tranfparent
fulphate of lime. A hundred grains of
this, pulverifed, were put into fix hundred
of diftilled boiling water. A folution was
obtained, and the oxalic acid precipitated
the lime.

Third fpecies. This confifts of ovoid
globules, externally dirty, from an earthy
coating, but which internally are extremely

white.

t 6^ )

white. In the fractures we perceive that
they confift of a number of opake groups
of fibres, ftriated, filky, and (hining, which
diverge from the centre to the circumference
of the globules, and thus form fo many in-
verted cones. Thefe globules, fome of
which are more than four lines in diameter,
Jjerfedly fill the cavities of an argillaceous,
light, extremely friable lava of a deep grey
colour. Every cavity, however, does not
contain a zeolite of this conformation : in
fome we ftnd zeolitic ftones with feveral
facets, but fo confufed that the precife con-
figuration of the cryftals cannot be diftin*
guiftied. On attentive examination, they
evidently appear to be formed of th« fame
zeolitic fubftance, which, when it occupied
the whole fpace of the cavity, took the con-
formation of thofe fibrous groups that have
externally a globofe figure ; but when a part
of this fpace remained empty, it cryftallized
more or iefs. Thefe zeolitic ftones always
have" in the middle a fmall empty fpace,
where they are cryftallized, forming a num-
ber of very minute geodes.

The

I

( 63 )

The blow-pipe prefently melts this third
fpecies, and with ebullition ; a phofphoref-
cence precedes the fufion, and the pearly
globule which is the refult, is a femitranf-
parent glafs, abounding in bubbles. If this
globule be broken, which requires rather a
fmart blow, the fharp angles of the frag-
ments will cut deep into glafs.

This zeolite, foon after it has been put
into acids, attaches to the fides of the con-
taining vefTel in the form of a cruft, which
cruft prefently refolves itfelf into a tranfpa-
rent tremulous jelly, fimilar to that of harti^
horn.

Fourth fpecies. The lava which contains
this zeolite is of a horn-ftone bafe, and forms
two fpecies, at leaft two varieties ; the one
of which is granular, rough to the touch,
and extremely friable ; the other has a kind
of foftnefs, a fine grain, and greater folidity.
In colour, however, which is a grey, and in
their argillaceous odour, both thefe varieties

agree.

( S4 )

agree. This lava contains a multitude of
zeolitiG globules, from half a line to an inch
in diameter. On breaking them, a Vacuity
is found within them, thus forming geodes
of a cryftallization more ot lefs perfects
Wherever the zeolitic fiibftance ha^ been too
confined in the cavity of the lava, the cryf-
tallization is extremely imperfect, in con-
fequence of the prifms being half-formed
and confufedly intermingled ; but where that
fubftance had a larger fpace to develop it-
felf ia, the prifms are no longer fo indif-
tin£t ; many of them, at leaft, are found to
incline to a tetrahedral figure ; and where
the cavities of the lava have afforded a ftill
greater fpace to the zeolitic matter, it has
cryftallized in tetrahedral prifms, of a dif-
tin(fi conformation. Every prifm has there-
fore four faces diftindly feparated. In fome
few places thefe prifms are terminated by a
tetrahedral pyramid. Many of them are
of a milky whitenefs, and thefe are femi-
tranfparentj but others have a tranfparency
almoft equal to that of quartzofe cryftals,

A fmgle

i

( 65 )

A lingle cavity fometimes contains feveral
fcores of fuch prifms, while another fhall
contain but very few.

The blow- pipe eafily melts thefe geodes
with the ufual phenomena of ebullition and
phofphorefcence, and the glafs which is the
refult of the fufiori is fimilar to that of the
zeolite of the third fpecies. A fimilar jelly
is likewife produced from it, and wuth equal
promptnefs, in acids, except that it has a lefs
degree of vifcofity.

Fifth and fixth fpecies. Thefe two fpecies
of zeolites are contained within an argilla-
ceous lava, of a dark-grey colour, light, and
of an earthy confiftence : they both merit
to be diftindly defcribed. The firft fpecies
confills of a great number of fmall fpheses,
white as fnow, each occupying a cavity in
the lava, and varying in fize, the fmalleft
being fcarcely one third of a line in diame-
ter, and the largeft more than three lines.
The furface of thefe fmall fpheres is not
fmooth, but fomewhat rough, from an in-

VOL. Ill, F finity

{ 66 )

finity of points which, viewed through the
lens, are difcovered to be fo many minute
tetrahedral prifms, diftindly defined. On
breaking the fpheres we perceive that the
prifms arc continued within them, and, be-
coming thinner, proceed to the centre ; or,
to fpeak more properly, we find that the
fpheres are only the refult of a number of
prifms joined together length wife. The
portion of the prifms that is immerfed
within the fpheres is opake ; but that part
which projects out has a degree of tranf-
parency. It is to be obferved, that though
the greater number of thefe minute fpheres
are perfedly folid, many of them have a
round vacuity at the centre, fometimes ex-
tending to one tenth part of the whole
fphere.

This zeolite Is the fofteft of all the fpecies
hitherto enumerated, and may be fcraped or
cut with a knife.

The fixth, and laft, fpecies is one of the
moft beautiful zeolites hitherto difcovered

by

( 67 )

by naturallfts. It confifts of minute cry-
ftals, extremely clear and bright, which,
having facets in every part, vividlyrefled: the
light, and fparkle like fo many diamonds.
Thefe are very numerous in the cavities of
the fame lava ; but are unequally diftributed,
as fome cavities contain but one of thefe
cryftals, while others have two, and others
three, though the latter are rare. The
largeft do not exceed a line, and the moft
minute are fcarcely a quarter of a line.
While they remain in the lava, it is not eafy
to examine them as might be wi(hed ; but
many of them may be extracted without
injury, and viewed, in every part, with the
lens, at leifure. We then perceive that thefe
zeolites, where they reft on the lava, are flat ;
but in their upper part incline to a globofe
figure ; and that, there, their cryftallization
is apparent : that the ifolated cryftals, I
mean thofe which in their formation grew
without attaching to the other cryftals, have
eighteen facets, for the moft part pentago-
nal, or tetragonal, but never triangular : that
thefe ifolated cryftals are extremely rare;
the greater number being aggregated^ that
F 2 is.

( 68 )

is, confufedly heaped upon each other lU
their formation : that, lafily, though many
of them may compare in clearnefs with the
pureft rock cryftal, they are yet inferior in,
hardnelis, as they with difficulty cut glafs.

I at firfl fufpeded that thefe zeoUtes were
a fimple modification of the fifth fpecies,
which, wherever it had a free fpace, had
formed itfelf into thefe brilliant cryflals,
either ifolated or aggregate. But this con-
jecture was not confirmed by obfervation.
It frequently happens that the white minute
fpheres which form the fifth fpecies, occupy
enly one half, or even lefs, of the contain-
ing cavities, without ever taking the form
of the fixth fpecies ; but it is conflantly to
be obferved that the tetrahedral prifms pro-
jed: farther beyond the convexity of the
fpheres, and have a greater tranfparency.
They muft therefore be confidered as two
diflindt fpecies.

»

This difference is filll more confirmed by
the action of fire and acids. The latter do
not a<^, at lead fenfibly, on the fixth fpecies,

though

( 69 )

though they reduce the fifth to gelatinous
flakes or tufts. The fire of the furnace, in
half an hour, converts the cryftals of the
fixth fpecies into globules of extremely
tranfparent glafs ; whereas it only foftens,
in that time, the minute fpheres of th^ fifth,
which require a fire of much longer con-
tinuance for their complete liquefa<flion ;
and the globule, which then refults, is an
opake glafs, of the colour of milk. Both,
however, have the property which is ufu-
ally common to zeolites ; I mean that of
phofphorefcence at the moment of fufion ;
as may be feen by employing oxygenous
gas.

After having made thefe experiments on
the .zeolites of Lipari, I was induced to
examine one of thofe of Iceland, which
have the character of being the mofl ex-
cellent for forming a gelatinous body. I
certainly obtained from it, very readily, an
extremely beautiful jelly ; but not in the
Jeaft fuperior to that produced by the third
F 3 and

{ 7° )

and fourth fpecies. 1 his foreign zeolite is
very white, and forms a group of fmall co-
nical bundles, clofely conglutinated, and in-
terlediing each other in various diredions ;
terminating, at their diverging extremities, in
a multitude of irregular cylindrical needles.
In the furnace it becomes inflated and con-
fiderably lighter, but does not fufe. With
oxygenous gas, a hard, milk-white enamel,
full of bubbles, is produced.

If we compare thefe obfervations with
the defcriptions of other naturalifls, we fhall
find that the zeolites of Lipari have a great
refemblance to thofe of other countries j and
it may be obferved that the firft fpecies is
very fimilar to that of the iOand of Ferro,
which Born has defcribed in his Lithophy^
lacimn, and which he has compared to the
flala6tical calcedony.

The fecond fpecies, from its hardnefs, re-
fembles fomecryftallized zeolites of the Ifles
of the Cyclops of Etna, which, as M. Dolo-

mieu

•I

( 71 )

mieu has obferved, and as I have fince found
by experiment, are little inferior, in that
quality, to rock cryftal.

The three other fpecies do not effentially
differ from feveral defcribed by Wallerius,
Born, Bergmann, Faujas, and others, and
which are found in the ifland of Ferro, the
Vivarais, and other volcanized countries.
But the fixth fpecies appears to me new ; at
Jeaft, I have found no writer who mentions a
zeolite, conftantly cryftallized with eighteen
facets, as often as its cryftals are detached ;
nor do 1 know that any zeolite has hitherto
been difcovered which is equally clear and
brilliant.

It appears that the true figure of the zeo-
lite is a cube ; at leaft, that it always affeds
that form where its cryftallizations meet
with no obftacles. According to circum-
flances it is more or lefs modified ; and the
tctrahedral prifms of the fourth or fifth
fpecies are probably one of thefe modifica-
tions. The firfl and fecond ^re amorphous ;
f 4 but

( 72 )

but in the third we difcern a beginning cry-
ftallization. One of thefe modifications
may be feen in the fixth fpecies ; and we
know that there are zeolites of other con-
figurations ; as fome with twenty-four facets,
and others with thirty.

Some naturaUfts have affirmed that the
whiteft and pureft zeoHte of Ferro is the
only one from which a tranfparent and white
glafs can be obtained. I find, however, the
glafs of the fixth fpecies preferable to it ;
for it has an aqueous colour, and its tranf-
parencyis almoft equal to that of quartzofe
cryftal. I have found no zeolitic cryftals,
but thofe of the ifles of the Cyclops, which
have furnilhed a glafs equal to this.

No mineralogifl: is ignorant that Cronftedt
was the firfl who diftinguifhed this ftone
from the carbonates of lime with which it
was confounded, and made us acquainted
with feveral of its qualities. He obferved
that mineral acids caufed no efFervefcence
with it, but flowly dilTclved it into a gela-
tinous

( 73 )

tinous body : and this flow dllTolutlon, and
converfion of the zeolite into jelly, was af-
terwards confirmed by others; though expe-
riments made on newly difcovered fpecies
of this ftone have fliewn that more than
one are not, in any manner, affedted by
acids, even when highly concentrated. From
among fix fpecies of the zeolites of Lipari,
we have (eea that the third and fourth pre-
fently form, with acids, a tranfparent gela-
tinous body ; which is lefs completely cha-
racterized in the firft and fifth ; and not
produced at all in the fecond and fixth
fpecies.

M. Pelletier has analyfed the zeolite of
Ferro, and found that it is compofed of 20
parts of alumine, 8 of lime, 50 of filex, and
22 of phlegm (or impure water). Other
analyfes have been made, of other zeolites,
by the chemifts Bergmann, Meyer, and
Klaproth. The minute* fize of mine, and,
ftill more, the fmall quantity I obtained of
them, prevented me from making a fimilar
analyfis of them with the requifite accuracy.

I v^as.

{ 74 )

I was, however, able to afcertain that the
fecond and fixth fpecies contained filex in
a greater proportion than it was found in
the zeolite analyfed by Pelletier ; which
perhaps was the caufe that thefe two fpecies
do not form a gelatinous fediment ; the fu-
perabundance of quartzofe earth not per-
mitting the acids to extract the lime and
alumine, and thus diflbive the union of the
conftituent principles of the zeolite.

The gelatinous diflblution of the zeolite
is neither a quality found in every fpecies,
nor is it peculiar to it, fmce experience has
fliewn that it is common to other ftones, the
conftituent principles of which are the fame
with thofe of the zeolite, and combined in
a certain proportion. This identity of prin-
ciples, which, in fome fpecies of ftones, af-
fords, by means of the adion of acids, the
fame gelatinous produd:, induced me to
make an experiment, of which I fhali here
give the refult.

The colourlefs garnets of Vefi^vius con-
tain,

( 75 )

tain, according to Bergmann, ^^ parts of
filex, 39 of alumine, and 6 of lime. As,
therefore, I had colled:ed a confiderable
quantity of thefe at Vefuvius ; I determined
to make experiments on them with acids,
in the fame manner I had done on the zeo-
lites. But in the three firft varieties which I
pofTefs, though I had firft reduced them to
powder, no gelatinous fubftance was pro-
duced. With the fourth I fucceeded ; though
I did not make the experiment on the fame
garnets, for the attempt would have been in
vain, but on others, of the fame fpecies,
which I have not mentioned, and which
had been greatly foftened by the fulphureous
acids, though they retained their four-and-
twenty facets. Thefe the nitric acid, after
thirteen hours, reduced to a jelly, though
not one fo beautiful as that obtained from
the zeolites. We may therefore conclude,
that this aptitude to diffolution was produ-
ced in the garnets by the alterations they
had fuffered ; in confequence of which the
nitric acid, penetrating their internal parts,
had aded on them as it adls in many zeolites.

It

( 76 )

It has been believed that zeolites apper-
tain exclurively to volcanized countries, 13 nee
thej are mod frequently found there ; and
my obfervations may appear to confirm this
opinion. It however admits of no doubt
that they are likewife often found in coun-
tries that exhibit no figns of volcanization ;
this having been inconteftably proved by
Cronftedt, Linnaeus, Bergmann and others.

It appears equally certain that the zeolites
of volcanos do not derive their origin from
fire, but are adventitious to thofe places;
DOt that they were pre-exiftent to the vol-
canic eruptions, and taken up by, and in-
corporated with, the currents of lava, as a
£elebrated volcanift has fuppofed. They
were, no doubt, generated after the extinc-
tion of the conflagrations ; when their con -
fliituent parts being depofited by water in
the cavities of the lava, and there combin-
ing by affinity, formed thefe flony fub-
llances, according to circumftances, fome-
times amorphous, and fometimes cryftal-
lized ; in the fame manner that we have

fuppofed.

( 77 )

fuppofed, and, indeed, proved, the beautiful
quartzofe ftones to be formed in certain
lavas on the fhores of Lipari, not far from
Vulcano. The zeolites now defcribed, like-
wife, afford a proof in favour of this opi-
nion, thofe, efpecially, the prifmatic cryftals
of which have for their bafe the fides of
cavities in the lavas*

I fhall conclude thefe obfervations rela-
tive to zeolites, v/ith the following enquiry-
concerning an hypothefis adopted by M.
Dolomieu.

That naturalift was of opinion that the
zeolites of volcanized countries are onlv
found in thofe fituations which have beea
covered by the v/aters of the fea; and the
arguments he adduces to prove this, appear
to me fufficiently convincing with refped:
to the multiform zeolites obferved by him.
But what fhall we fay of thofe we have now
defcribed ? I certainly did not negledl to
make the moft accurate refearches on the
fpot. It has been already faid that thefe

ftones

( 78 )

ftones are found in the vicinity of the Stoves*
The firft fpecies is met with about two
hundred feet before we arrive at them, on
the road from the city of Lipari j the others
are fcattered at a greater diftance, in the
fteep fide of the mountain towards the fouth.
One certain proof that thefe places had an-
ciently been wafhed by the fea, would be the
finding of the remains or impreflions of fea
animals. Thus the above-mentioned French
naturalift remarks that, at Etna, the lavas of
the ifles of the Cyclops, and thofe of the
mountains of Trezza, which abound in zeo-
lites, have certainly been covered by the
waters of the fea, fince, at the height of
more than two hundred perches above thefe
zeolitic lavas, immenfe quantities of fea-
fhells aFe found. The fame may, in like
manner, be obferved of the Vicentine vol-
canic mountains, which afford beautiful zeo-
lites, and alfo copious ftores of marine re-
mains. It is, however, certain that neither
Lipari, nor any of the Eolian Ifles, prefent
us with any vefliges of fea animals or plants.
I do not mean to fay that this is a phyfical

demonflralion

2

( 79 )

demonftration that thefe places have never
been covered by the fea, fince it is poffible
that the marine bodies its waters had left,
may have been afterwards deftroyed by
caufes which are not wanting in countries
that, at various epochs, have fufFered the
adlion of fire ; I fhall only obferve that we
are thus deprived of one of the moft con-
vincing proofs of this fuppofed inundation;
and I know not on what other we can rely,
with refpe(£t to a country entirely volcanic.

That zeolites derive their origin from
water and not from fire, is proved by the
water of cryftallization which is more or
3efs abundant in them, and the numbers of
them found in fome provinces of Sweden^
which have never been fubjeded to the ac-
tion of fire. That this water has fometimes
been that of the fea, the above-cited obfer-
vations of M. Dolomieu will not permit us
to doubt ; but it has been proved that there
are likewife inftances of their having origi-
nated from frefli water ; of which an ob-
fervation by Bergmann may furnifh an ex-
ample.

( 8o )

ample. He has remarked that a fprhig of
warm water at Laugarnes, in Iceland, when
It iflues bubbling from the earth, leaves no
fediment of any kind, but depofits it at the
bottom of a channel by flowing through
which it becomes cooler: and this fediment is
truly zeolitic, as has been proved by che-
mical examination *. The nature of this facft
he fatisfadorily explains as follows : " While
the water is very warm, it holds the zeolitic
matter in diflblution ; but, afterwards, be-
coming cold, can no longer fupport it, fo
that it precipitates and forms this ftaladtical
concretion. This excellent obfervation will
account for the frequency of zeolites in
many volcanos, fmce the water, whether fait
or frefh, being ftrongly heated by the fub-
terraneous lires, diflblves the zeolitic fub-
ftances, which it afterwards depofits within
the lava, where they cryftallize, or remain
amorphous, according to circumftances.

When the traveller has arrived at the
fnmmit of the Monte della Stufe, he has

^ Opufc. Vol. III.

reached.

( 8i )

readied, In that part, the confines of the
ifland ; for he fuddenly perceives the fea,
about four hundred and fixty feet below him,
as near as the eye can meafure. Taking
his way to the fouth, he, then, difcovers fe-
veral warm fprings, which fupply the Baths
of Lipari, of equal antiquity with the Stoves,
but, like them, now almoft forfaken ; and,
proceeding in the fame direQion, meets
again with a prodigious quantity of decom-
pofed lavas, fimilar to thofe of the Stoves,
exhibiting the fame varying colours, and
coated in different places with crufts of ful-
phate of lime.

When the naturalift confiders, and unites
in his mind, thefe prodigious aggregations
of decompofed lavas, which occupy an area
of feveral miles, he will no doubt be afto-
niflied to find there is any volcanized coun-
try in Europe, in which the fulphureous
vapours, iffuing from fubterranean confla-
grations, have aded through fuch an exten-
five fpace. Thofe of Solfatara di Pozzuolo,
which have whitened its crater, and which

VOL. III. G are

( S2 )

are mentioned with a degree of wonder by
every writer on that volcano, are certainly
inconfiderable indeed, with refped to their
extent, when compared to thefe. Yet of all
the fulphureous exhalations which muft
have fpread themfelves fo widely over the
illand, not one now remains in a£tion, ex-
cept a few very thin fumes that rife from
the ground near the Stoves.

T vifited the Stoves three times : the two
fnft I returned to the city by the fame road I
went, which is hollowed in the tufa; but the
third I took my way back by Campo Bi-
anco, and the Monte della Caftagna, w^hence
i proceeded to the Iiigh mountain of San
Ahgelo. We have already feen that Campo
Bianco -and the Monte della Caftagna are
IW6 mountains formed entirely of pumices
and glafles, that is to fay, of vitrified fub-
ftances * : but how extenfive muft be the
roots of t^efe fubftances ! The declivity of
the Monte delle Btufe, and its ample plain
covered with tufa, form, as has been ob-
*SeeChap. XV.
■ ■ I ferved.

( S3 )

ferved, a bed of pumices, mixed with a
great quantity of glafTes and enamels. At
about the diftance of a quarter of a mile
from the Stoves, towards Campo Bianco,
the tufa disappears, and the pumices remain
uncovered, forming a continuation with
thofe of Campo Bianco. I have alfo found
them in the road near Mount San Angelo,
which contains great quantities, and every-
where they are accompanied with glafTes.
If to thefe we add the other parts of Lipari
in which the fame fubftances abound, I fhall
not exaggerate if I fay that almoft two thirds
of this ifland, which is nineteen miles and
a half in circuit, are vitrified.

This immenfe, and almoft incredible,
quantity of vitrifications may, probably,
fuggefl: to the reader the fame idea which
arofe in my mind when I firil viewed thefe
places : that the fire which has aded on
them muft have been extremely powerful.
This idea certainly appears very natural.
But fubfequent experience has taught me
that this intenfe heat is not neceflary for the
G 2 produdlion

( S4 )

produdtioii of this great accumulatiGn cf
vitreous bodies by fubterranean fires. It is
certain that the produdion of pumices,
enamels, and glafl'es requires a greater heat
than the fimple fufion of lavas, when thefe
fubflances derive their origin from the fame
bafe ; but we (hall not find it neceflary that
this greater heat fhould be extremely vio-
lent, if we confider the kinds of flones
from which thefe vitrified mountains have
been produced. The greater part are felt-
fpars, and petrofilex, with fome fmall quan-
tities of horn-fione. As to the latter, it has
.already been fhewn that it eafily vitrifies in
a glafs furnace with no very vehement fire-;
In which, likewife, many petrofilices and
fome feltfpars are vitrifiable *. It has alfo
been feen that the glafles, pumices, and
enamels of Lipari are all completely re-
fufed in the furnace. It appears to me,
likewife, that w^e have pofitive proofs that
the volcanic fire was lefs violent than that
of the furnace, in the fubftances, as well

■ * See Chap. V. and Chap. XI.

crvftallized

( % )

cryftalJized as amorphous, which, without
having fufFered the leaft fufion, are found
incorporated in the pumices, glafles, and
enamels of Lipari, and which may he per-
fectly liquefied in the furnace.

It cannot, however, be denied that the
generative fires of Lipari muft, at fome
time, have been extremely vehement; fmce,
according to the obfervations of M. Dolo-
mieu, they have even fufed granite, com-
pofed of quartz, feltfpar, and mica, and con-
verted it into pumice.

The ancient writers have left us very in-
terefting and inftrudlive accounts relative to
the ftate of the conflagrations which in, and
prior to, their times had been obferved in
Stromboll and Vulcano; and we have made
ufe of them w^hen treating of thofc two
iflands. But w^e can fay nothing of the
ancient fires of Saline, and that chain of
rocks, which once, probably, made a part of
the ifland Euonimos, fmce with refpeift to
tliefe antiquity is totally filent ; and we Cc'.a
G 3 only

( 86 )

only infer that the volcanization of thefe
two iflands was known to the ancients, from
a pafTage in Diodorus, who informs us, that
all the Eolian ifles were fubje£t to great
eruptions of fire, and that their craters and
mouths were ftiil vifible in his time ^•'".
With refpect to Lipari, very few memorials
have been preferved of its ancient conflagra-
tions. We are indeed certain of the great
antiquity of this ifland, and that it exifted
before the Trojan war; fmce we learn from
Homer that, after the taking of Troy,
UlyfTes landed there, and was treated with
the utmoft urbanity and courtefy by king
Eolus during a whole month, which he
continued there f ; and though we allow to

uv K^amcsg oi yiyBVYii/.svoi Kai tu rojxaix ixt^^i m vuv £;j
ifavspa. Lib. V.

nx«T>] £v w)70i. Horn. Odyff". Lib. X.

Kai ixiv Twv utOfXsaSa ttc'aiv y.ai cxixara xa>-a.

I7.10V, A^ynav T£ v£aj, nai vofov A;^«iS)V. Ibid.

the

( ^1 )

the poet the ufual licence of poetry, it Is ftiil
moft certain that he could not have named
this ifland, and the city it contained, unlefs
they exifted at the time he wrote his poem,
fmce which nearly three thoufand years
have now elapfed. But if we confult other
ancient and credible writers, we fliall find
that before Eohis, Liparus reigned in this
ifland, which from him took its name,
being before called Mdogonis^ or, according
to others, Meligunu,

Another obfervatlon, likewife, here natu-
rally prefents itfelf. An ifland formed by.
depofltions, and the fubfequent retiring of
waters, may, in a fliort time, be cultivated
and inhabited ; but it is not fo with one that
is produced by fubterraneous eruptions,
where the decompofltion of volcanized mat-,
ters is necefl^ary; that is to fay, a far longer
time. If, therefore, LIpari had inhabitants
and cities, and was a cultivated country
before the deftrudion of Troy; it is evident
that it muft have exifled many ages prior
to that event.

G 4 From

( 88 )

From the time, however, that mention Is
firft made of this ifland in hiftory to the
prefent day, we may confider it as certain
that no true eruption, or current of lava,
has taken place in it ; as, otherwife, it is
probable fome memorial would have been
prefer ved of it, as well as of thofe of
Stromboli and Vulcano. Arlftctle, indeed,
mentions the fires burning in Lipari, but
adds they were only vilible by night ■'''; and
the writers who followed him fay nothing
more. I hence infer that this ifland had
attained its full formation and fize, before it
was known to men, which was not the cafe
with Stromboli and Vulcano. I muft not
omit another obfervation. Many of the
lavas of Lipari ftill fcarcely exhibit the lead
fign of alteration, efpecially the vitreous,
the enamels, and the glafTes ; though it is
evident, from what has been faid above, that
thefe bodies muft have exilled above three
thoufand years. We hence perceive what

* Kai TO EV 7r) Aiaa^a ^s 7iv^ (pavi^ov xai (p?\oyuO£g, cu
fitv rfXEfcci;, a'h.>.a vvhlcg fxovov Hana9ai T^zyirai-

In Mirandis.

an

( 89 )

an adamantine temperament, if I may ufe
the expreffion, the fire can beflow on vari-
ous fubftances, fince they can thus refift the
influence of the feafons and of time.

"When I prove the antiquity of Lipari by
the authority of Homer, I do not mean to
confider the other neighbouring iflands as
of pofterior date. I am Hkewife well con-
vinced, by the teftimony of hiftory, that,
except Vulcanello, they were all in exiftence
in the time of that poet, who probably docs
not mention the other Eolian ifles becaufe
Lipari was the largeft, the moft fruitful, and
moft generally known, as being the refidence
and feat Qf government of king Eolus,

CHAP.

( 9^ )

CHAP. XVIL

FELICUD A.

Two bays i?i this ijland capable of receiving
fmall vejfels — The prodiidfs fou?id there by
the author^ fiifficiently prove it volcanic —
Circuit of it by fea — Prifmatic lavas fall-
ing into the fea — Spacious cavern hollowed
in one of thcfe lavas — Enquiries relative
to its origin — Curious alternation offiratas
of tufa and lava — Other prifmatic lavas
along the fjorc — Obfervations relative to
them — Excuffion into the interior part of
the if and — A mountain^ near the centre^
higher than the refy on vohich is difcover-
able the crater of an ancicfit volcano^ to
which y probably, Fe lieu da oives its origin
■ — ConjeElures that another f mailer volcano
exifedat thefummit of a lower moimtain —
ISlo other perceivable fgns of volcanic
mouths throughout the w^hole if and —
^alitics of the lavas forming the inte-

rior

( 9' )

rior part of Felicnda — GhiJJ'cs, pnmkes^
iufas^ and pu%%olanas fcattered over the
ijlatid — Fu%%olanas and pumices employed
by the inhabit a7its ofFelicuda in hull ding — ■
The fuhjlances of ivbich the ifland is com-
pofed entirely volcanic ^ except a piece of
granite^ vohich appears to be natural —
Reflexions on this rock.

r yet remains to fpeak of Felicuda and
Alicuda, the two extreme iflands of thofe
of Lipari towards the weft ; and I fliall the
more willingly undertake the defcription of
them, as they have not, to my knowledge,
been vifited, at leaft defcribed, by^any other
naturalift ; M. Dolomieu, who was moft
capable of examining them, having only
feen them at a diftance, as to have touched
at them would have led him too far from
his intended route.

On the 7th of Odober, in the morning,
I fet fail from Lipari for Felicuda, diftant
from the former illand twenty-three miles,

and

( r- )

and arrived there in four hours. This
illand is not provided with a port; but it has
two bays, one on the fouth, and the other
on the north-eaft fide, fufficient for the re-
ception of.fmall veiTels, and fo fituated, that
though the wind fliould render the entrance
into one of them difFicult, it will be eafy to
get into the other : both of them are like-
wife kifhciently fheltered by a mountain.

I landed in the bay on the north-eaft fide,
and, in the flrft place, applied myfelf to
difcover of what materials the illand was
formed ; and foon difcovered inconteftable
proofs that it is truly volcanic. Not only
is the fhore of this bay lined with lava; but,
having in the courfe of the day proceeded
farther up on the fouth-eaft fide of the
iiland, I found among the earth of fome
fields a confiderable quantity of pumices,
glafles, and enamels, which produds I fliall
feparately defcribe when I come to treat of
the internal part of the ifland.

Being thus fully convinced of the ancient

exiftence

( y3 )

exiftence of fire in this iflaiid, I determined,
the next day, to make the circuit and ex-
amine the fhores of it, in the fame manner
as I had proceeded in the other iilands.

Felicuda is nine miks in circumference,

I began the circuit of it hj examining the

lavas that border the fmall bay which I

entered. Thefe have for their bafe the

feltfpar, v^^hich is of a fcaly confiftence, a

light grey colour, not very compact, but

giving a few fparks v^ith ft eel and attrading

the magnetic needle. Within its fubftance

are included needles of black and fibrous

fhoerl, and fmall pieces of feltfpar, which

are eaiily diftinguilhable from the 'bafe by

their whitenefs, femitranfparence and luftre.

A part of the fhores of the bay are com-

pofed of this lava with deep fiflures running

lengthwife, as we fee in many other lavas.

A number of round vacuities are likewife

obfervable in it. They are of confiderable

depth, and give it the appearance of a

honey- comb. I rather incline to afcribe

them to the adion of elaftic gafeous fub-

ftances.

( 94 )

ilances, vvhcn the lava was In a ilate of
fufion, than to corrofions produced by the
influence of the atmofphere or any external
agent. It is certain that the air of the Tea
will greatly corrode many foffil fubftances
fituated in its vicinity J and I have witnelTed
extraordinary effects from its adion on
many low rocks, on the fhore of the Me-
diterranean, near Genoa, and efpecially at
Porto Venere, the Golfo della Spezia, and
at Lerici. I have alfo frequently obferved
the external part of many towers and
maritime buildings very much injured on
that fide which fronts the water. The
city of Commachio in the territory of Fer-
rara, perhaps, furnifhes fome of the moil
complete examples of fuch effedls. it is
lituated in the midft of fait lakes; and its
porticos and edifices are lo much corroded
and damaged by the air, that they are ob-
liged to undergo periodical repairs at the
end of no very long time, as I obferved with
furprife during a fhort ft ay which I made
there in Odober 1792. The fea air, how-
ever, does not ad thus on every foliil fubftance

indif-

( 95 )

indifFerently, but, with refped: to flones,
feems principally to attack the carbonates of
lime ; though not all of thefe, as appears
from the hard Iftrian marble with which the
fuperb palaces and fumptuous edifices of
Venice are built, and which remains unin-
jured for a long feries of years. I likewife
obferve that volcanic ftony fubilances are
little, or not at all, injured by the air of the
fea; and I am the more confirmed in my
opinion that the incavations in the litoral
lava of which I am now fpeaking muft be
attributed to the a(flion of aeriform gafes, and
not to that of the fea air, from obferving the
fame, likewife, in the feltfpar, a ftone much
lefs liable to this kind of alteration than
many others.

After having made thefe obfervationS) T
left the bay, and began to coaft the iHand
towards the left, on the northern fide. I
had fcarcely proceeded one hundred and
^fty paces when I met with a rock of lava,
about thirty feet high, and equally broad,
lifing almoft perpendicularly from the water.

This

( 96 )

This rock prefented a novelty I had riot be-
fore obferved in the Eolian illes. This was a
number of prifms into which the lava divided
before it plunged into the lea. The im-
portance of this objedt induced me to bring
my boat clofe under the rock, that I might
make the neceflary obfervations with more
certainty and fecurity.

About twelve feet above the level of the
fea, the rock is fmooth, and prefents an
equal furface ; but, lo me what lower, it
begins to be furrowed with narrow longi-
tudinal excavations, which defeend to the
edge of the water, and form prifms with
three unequal fides, the fide behind remain-
ing attached to the rock, or, to fpeak more
properly, forming one continued whole
with it. Thefe prifms" continue to preferve
their form under the vx^ater, of which I haid
Indubitable proof. The fea, though then
calm, had a flight roughnefs towards the
rock, to allay which I poured into it fome
olive oil, which I always carried with me in
thefe excurfions to calm the leiTer waves of

the

( 97 )

the fea, and thus enable myfelf to perceive
fubaqueous bodies at a certain depth as cir-
cumrtances might require. By thefe means
I difcovered that the prifms were immerfed
in the fea to the depth of fome feet. The
breadth of fome of the prifms was a foot and
a half, but that of others lefs.

This prifmatic lava merits to be very ac-
curately defcribed, fmce, in profecuting my
voyage along the fhore of Felicuda, I met
with it in feveral other places, and fhall
again have occafion to mention it. Its bafe
is a horn-ftone of the black colour of iron,
and fo compact that the fmalleft bubble is
not perceivable in it; it muft, therefore, be
claffed among the heavy lavas. The edges
of the thinned flakes of it are tranfparent,
and give fparks with fteel. Its fragments
are amorphous, and receive a polilh, but
without luftre. It attrads the masfnetic

o

needle at about the diftance of three lines.

The powder of this lava is cinerltious, and

impalpable, and attaches to the finger. In

VQL, III. H it

( 98 )

it are contained various grains of amorphous
fbltfpar, and a greater number of fmall,
long, rhomboidal fhoerls.

The product of this lava in the furnace is
a hard enamel, of the colour of pitch, and
full of bubbles. The feltfpars it contains
remain refradtory. It is to be remarked,
that this enamel does not lofe the magnetic
virtue.

The place where this rock hangs over
the fea is called Fila di Sacca. Beyond it
the fhore of the ifland, M^hich continues to
have a fteep defcent into the fea, offers only
common lavas, except one fpecies which
has fome rude appearance of prifms, that
affume a more diftin(^ form near the furface
of the water.

Still farther, at a place called Saccagne^ a
number of fmall rocks rife above the furface
of the water; one of which is called //
Perciato^ becaufe it is perforated in the mid-
dle, and the opening is wide enough to

admit

( 99 )

admit fmall veflels to pafs through. The
forms of prifms are diftindly difcernible in
thefe rocks.

At the dlftance of fifty paces farther, a
fpacious cavern opens in the lava of the
(here ; an obje£l highly interefling and
beautiful in the eyes of the volcanift. It is
called the Grotta del Bove Marino (or Grotto
of the Sea-ox), perhaps becaufe it was once
the retreat of fome phoca or feal, as in the
Lipari iflands, and many other places, the
phocsE are called fea- calves. The mouth of
this cavern, in the upper part, is oval, and is
fixty feet in breadth, and above forty in
height. The mouth opens into a kind of
porch, which leads into a fpacious hall two
hundred feet long, or nearly, one hundred
and twenty broad, and fixty-five high.
This hall terminates the cavern. The fea
enters it ; and as its force is broken by the
narrownefs of the entrance, fmall barks
when furprlfed by a ftorm may there find
fhelter.

H 2 Some

( lOO )

Some may pertaps wifh to enquire, whe-
tlier the roof of this cavern prefents any
of thofe ftaladical concretions which are
obfervable in many other excavations in
mountainous countries. No fuch concre-
tions are to be feen ; the ftone of which it is
formed being evidently not of an aqueous
but an igneous origin, that is, a lava diftin-
guifhed by the following charaders.

Its bafe is fhoerl in the mafs ; it is mo-
derately porous, and therefore rather light ;
but gives fparks with fteel. It is unequal
in the fradtures, has a fomewhat argillaceous
odour, and attracts the magnetic needle at
the diftance of half a line. It is of a grey
colour; but interfperfed with white, fhin-
ing, rhomboldal feltfpars. Their fplendour
is diminifhed in the furnace ; but their
whitenefs appears heightened from the black
colour acquired by the enamel produced by
the fufion of the lava, which is opake and
extremely full of bubbles. The fufion, in-
ftead of diminifhing or deftroying, rather
increafes its magnetifm.

This

( 10. )

This lava, which forms the large cavern,
defcends ahnoft perpendicularly into the
fea, and there affumes the form of prifms,
but larger than thofe before defcribed. It
is worthy of remark, that thefe prifms,
though in their lower part they fmk deep
into the water, do not rife above it, in their
upper, more than eight or nine feet.

But in what manner are w^e to explain
the origin of this cavern ? How great muft
have been the violence of the waves of the
fea, to form by flow corrofion fo vaft an
excavation within this mafs of lava ! To
this caufe I cannot confent to afcribe it;
principally for this reafon, among others
that might be adduced, but which I omit
for brevity, that no fooner has the water
entered the mouth of the cavern but it lofes
all its force ; befides that the hardnefs of
this lava is fuch, that it does not eafily yield
to the ftroke of the waves. I incline rather
to think it the effed of the adion of the
gafes in the lava at the time it was in a ftate
of fluidity ; as we have examples at Etna of
H 3 caverns

( I02 )

caverns incomparably deeper produced by a
fimilar caufe.

Immediately beyond the Grotta del Bove
Marino, we meet with a mixture of tufa
and lava, which merits fome attention from
the curious alternation of its ftrata. They
are found on a high precpice which defcends
into the Tea, the fur-ace of which is covered
with a tufaceous foil, refting on a bed of
lava, above another of tufa, and fo fuc-
ceflively, that in a rent made in the pre^
cipice by the waters we may number eleven
ftrata or beds of tufa, and as many of inter*
pofed lava. It appears, therefore, that the
fire and water, by their repeated adlion,
have produced this mixture of lavas and
tufas.

The lava of^ the eleven beds is of the
fame kind, that is, of a horn-ftone bafe, and
containing, as ufual, (hoerls and feltfpars.
It has an earthy afped, a blackifh colour,
and a ftrong argillaceous odour. It moves
the magnetic needle at the diftance of two

lines,

( 103 )

lines, and the enamel into which It is
changed in the furnace has the opacity and
blacknefs of pitch, and its magnetifm is
greater than that of the lava before fufion.

The beds of tufa, llkewlfe, do not eflen-
tially differ from each other. They are an
ill-kneaded mixture of lumps of argillaceous
earth, more or lefs tindured with yellow
oxyde of iron, which earth is eafily pulve-
rable. With it are mixed numerous fhoeils,
that from the foftnefs of the bafe may be
feparated entire, which they fcarcely ever
can be in the lava. Notwithftanding, how-
ever, the facility with which they may be
detached, it is difficult to determine their
cryftallization, not merely from their ex-
treme minute nefs, for fome of them are two
lines In length, but from their being fcarcely
ever found fmgJe, almoft every one being a
group of aggregated {hoerls. When one,
however, is found fmgle and detached, it
appears to be an hexagonal prifra terminated
by two trihedral pyramids. They are black,
fliining in the recent fradures, and are fome-
H 4 what

( l<?4 )
what fibrous : in line, they perfedly refem»«
ble in their ftrudture the fhoerls incorporated
in lavas.

The tufa, after remaining two or three
hours in the furnace, aflumes a red colour,
and becomes hard ; its raagneiifm is Uke-r
wife ftrong, though before it was fcarcely
perceptible. A longer continuance in the
fame fire reduces it to a porous fcoria, which
does not lofe its magnetifm, and the black
colour it acquires renders more confpicuous
a number of white feltfpars which before
were not difcernible in the tufa. The
fhoerls are femi-vitrified, and aflume a
yellowifh tinge,

In the remainder of my circuit round the
ifland, till I returned to the place whence I
fet out, I obferved no other interefting ob-^
jed:s, excepting a long trad; of prifmatic
lavas, fimilar to thofe I have already de-
fcribed.

I fliall conclude what I have to fay on

thefe

( 1^5 )

tliefe prifmatlc lavas, which occupy a con*
Tiderable part of the fhore of the i{land>
with the following remarks :

Fir ft. Thefe prifms have never more than
three faces, one of which always remains
adherent to the lava.

Secondly. Their diredion is never ob-
lique, or tranfverfe ; but, without excep-
tion, perpendicular to the fea.

Thirdly. They are not articulated, as
they have been obferved to be in fome
volcanic countries, efpecially on Mount
Etna, but form one continued line.

Fourthly. In their lower extremity they
defcend within the water, and, in their
upper, rife fome feet above the level of the

f£4*

Fifihly. Thefe prifmatic lavas have for
their bafe, either the horn-ftone or flioerl in
the mafs,

I ihall

( lo6 )

I fhall now proceed to defcrlbe the ob-
jeds which appeared to merit notice in the
interior part of Felicuda. This ifland, when
feen from the fea, at a little diftance, has
the appearance of a number of mountains
heaped together ; one of which, fituated in
the centre, is much higher than the reft,
rifing, perhaps, half a mile above the level
of the fea. After having examined the bafe
or fliore of the ifland, 1 proceeded, there-
fore, to the fummit of this mountain, taking
my way towards the eaft, as, on that fide,
the road is leaft difficult. The afcent is not
one of the moft fatiguing; for though we
meet with fteep precipices in fome parts of
it, they are prefently fucceeded by gentle
declivities, which relieve wearinefs and re-
ftore ftrength.

When I had reached the fummit of th^
central mountain, I perceived that it inclofed
a capacious hollow called Fo[[d delle Felcl
(the ditch of fern) becaufe it formerly was
overgrown with that plant j though when I
was there it had been all rooted up, with

the

( I07 )

the intention of fowing corn the next
fprlng. This hollow is about half a mile
in circuit, the fides approach as they de*
fcend, and its depth is not more than forty
feet. Thefe circumftances fufficiently prove
that this was the ancient crater of the vol-
cano ; and that, perhaps, or rather without
doubt, this was the firft, which, by its
eructations, contributed to the formation of
Felicuda.

It is likewife to be obferved, that the ex-
ternal part of this crater correfponds to the
internal ; that it is a truncated cone ; that
its lavas, parting as from a centre, have di-
verged like rays down the fides of the
mountain, while thofe on the fide towards
the north-weft have poured rapidly into the
fea. The propofal to fow corn in this hol-
low argues that it muft be earthy, as it
really is. It is formed of a half pulverulent
tufa, under which, however, the lava is
difcoverable.

Three ridges rife on this mountain, one

of

( >o8 )

qf which defcends to the fouth ; and, at
about half way up, joins another mountain.
The fecond of thefe ridges has its direction
to the eaft, and the third to the weft. From
this fummit I had a complete view of Fdi-
cuda, and looked round me with attention
to fee if I could difcover the figns of any
other crater. 1 thought I could difcern the
veftiges of one to the fouth-eaft, and, after-
wards, repairing to the foot, was more con-
firmed in my opinion. I found a hill,
about half as hio;h as the mountain already
defcribed, and about two miles in circuit. It
is ifolated on every fide, and has the figure
of a broken cone, truncated at the top,
where it finks into a cavity growing nar-
rower towards the bottom, which appears
to be the relics of an ancient crater. Scat-
tered pieces of various lavas, half-buried in
an earthy tufa, occupy the cavity of this
hill, and its external fides are formed of a
number of currents of lavas.

Except thefe two craters, of the laft of
which I have expreifed myfelf with fome

doubt,

( 109 )

doubt, I know not of any throughout the
whole ifland ; as I fhall not venture pod-
tively to confider as fuch a number of cavi-
ties, hollows and caverns which we meet
with in various places, fuch appearances not
being fufEclent to chara^fterife a volcanic
mouth.

The principal lavas of the fhore of Feli-
cuda have already been defcribed fmgly : it
is now neceffary to fpecify thofe which form
the internal and more elevated parts of the
ifland. Thefe, as far as I was able to difco-
ver, during the ftay of five days which I
made there, may be reduced to three kinds,
if we omit thofe which are merely va-
rieties.

The bafe of the firft is a horn-ftone of a
colour between a black and a grey, of a frac-
ture evidently brilliant, without any appear-
ance of pores, and which gives fparks copi-
oufly with fteel. The pieces into which it
breaks have no determinate form, do not
refufe a tolerable polifli, and move the mag-
netic

( "0 )

iietic needle at the diftance of a line afid
three-fourths. Minute grains of quartz, nu*
merous fcales of feltfpar, and extremely fmall
and brilliant needles of fhoerl are incorpo-
rated in this lava.

The furnace fufes the fhoerls,but not the
quartz, and the feltfpars; and the lava is
changed into a black, frothy, and opakc
enamel.

This lava extremely refembles the prlf-
matic lava defcribed above ; though it has
not that regular configuration.

The lava of the fecond fpecies is likewife
of the horn-ftone bafe ; not very hard nor
heavy ; of a cinereous and earthy afpe<£t,
without pores, attaches flightly to the infide
of the lip, and emits an argillaceous odour.
The fhoerls it contains are rhomboidal, fcaly,
and of a violet colour.

In the furnace it is only foftened ; and
the (hoerls remain entire,

< The

( "I )

The third fpecles has for its bafe, fhoerl
in the mafs. It is black, without pores, ra-
ther heavy, and of a granular fradure.

The heterogeneous floncs, which arc
mixed with the fubftance of this lava_ are of
three kinds : fmali irregular quartzofe par-
ticles, which, from their whitenefs, are mod
confpicuous ; a few minute feltfpars ; and
numerous rhomboidal fhoerls, of a dark
violet colour, and remarkable for their fize,
fome of them extending-to feven lines.

The feltfpars and quartzofe grains are
refradory in the furnace; though their bafe
is eafily fufible, and produces a fhining,
opake, and porous enamel.

The internal part of the ifland, as far, at
leaft, as appears from the furface, is com-
pofed of thefe three lavas and their varieties;
which lavas form currents, that, from their
great antiquity, do not exhibit thofe tu-
mours, wavings, and inequalities, which are
obfervable in recent lavas, or thofe of a mo-
derate

( 112 )

derate age. The fame antiquity is, likc-a
wife, probably the reafon, why in Felicuda
we do not find fcori^e, or fcoriaceous lavas ;
thefe, ufually, from their flight and feeble
texture, and from their lying on the furface
of the current, being the firft which are
altered and deftroyed.

When treating of Lipari, I remarked the
great effeds which have been produced on
the products of that ifland by the fulphu-
reous-acid exhalations. The contrary is to
be obferved of Felicuda, there not being a
fmgle lava which exhibits the leaft fign of
their influence; though they all bear the
marks of the injuries of time and of the at-
mofphere. So much have I found them
changed, efpecially near the furface, that
had I not broken up the lavas to the depth
of fome feet, a pradice to which I had ac*
cuftomed myfelf in thefe refearches, I fliould
freouently have taken the fame lava for
others fpecifically different.

Having thus defcribed the different kinds

of

( "3 )

of lavas cf this ifland, it will now be proper
to proceed to treat of the other volcanic
fubftances it contain*?. Among thefe are
the tufas, which are found in great abun-
dance in other parts of the ifland befide
thofe above defcribed. In general they
are pulverulent, light, fpungy, of an argilla-
ceous nature, and greedily imbibe water.
The places in which they are found, are the
only parts of the ifland which the inhabit-
ants can render productive by cultivation.

It is among the tufas that we difcover
glafles and pumices. We will treat of thefe
two fubftances feparately, beginning with
the firft.

I have already faid, that I had fcarc ely
landed in Felicuda before I difcovered feve-
ral pieces of volcanic glafs. In my fubfe-
quent refearches, I afterwards difcovered
that this glafs was not found among the la-
vas, but in the cultivated earth of the fields.
The peafants of thofe parts confirmed the
truth of this obfervation, and, finding I was

VOL. III. I in

( 114 )

in feareh of this fubftance, brought me more
of it than was neceffary, which they cot-
leded in the fields where they worked. As
I was not, however, perfedtly fatished with
this firft obfervation, I dired:ed them to dig
a deep trench in one of the fields which
mod abounded in fpecimens of this fub-
ftance, with a view to try if I could dif-
cover a vein, thefe being only detached
pieces. The trench they dug was eight feet
deep, and five in breadth. For the depth of
two feet I found only a tufaceous earth,
containing fome of thefe vitreous pieces.
At a greater depth the virgin tufa- appeared,,
untouched by the ploughfhare, or any ruftic
infirument. This tufa likewife furniflied a
fimilar glafs, but always in detached pieces^
nor was any difference perceivable in the
nature of thefe products, on continuing the
refearch to the bottom of the trench, where
the tufa was ftill found*

It appears, therefore, that the glafs in tlie
ploughed fields had its feat in the tufa ;
though it cannot be affirmed with certainty,

that

( "5 )

that it was thrown out from the mouth of
the volcano in the fame ftate in which it is
now feen ; fince it is only found in plates
or flakes, and with thofe points and (harp
angles, thofc cutting edges and waving
ftreaks, which we obferve in glafs, whether
volcanic or fad:itious, when it has been
broken and^ divided into fragments by a
hammer, or other heavy body. We muft
therefore conclade, that after the fubterra-
nean conflagrations had reduced the ftony
fubftance to glafs, this glafs has been thus
broken and fhivered by fome convulfion of
the earth, or by fome violent and tumultu-
ary agent.

The larger pieces are about five inches
and a half over, and two in thicknefs.
Many of them are not inferior in clearnefs
and brilliancy to the fineft and brighteft
glades of Liipari ; others are lefs tranfparenr,
and of a cinerltious, or grey, colourj while
others are almoft entirely opake; and'thefe
approach nearer to the nature of enamels
than to that of glalTes. They are all, how-

I 3 ever,

( ir6 )

ever, extremely compa£l, and will readily
give fparks with ileel, and cut common ar-
tificial glafs. Several of thefe pieces con-
tain within them fmalt white particles, whicb
have been obferved and defcribed in many
of the glaiTes of Lipari, which particles in-
dicate that the glafs containing them is not
fo perfedlly vitrified as the reft. We alfo
find pieces, though they are rare, the one
half of which is a very black glafs, and the
other a fimple lava. The lava, which thus^
forms a whole with the glafs, is of a cineri-
tions colour, and, as appears from fome
analyfes which I have made of it, is of a
petrsfilkeous bafe.

Tills glafs, like other volcanic glafles,.
changes in the furnace into a vitreous froth.

It now remains to fpeak of the pumices,,
which are likewife enveloped in thefe tufas.-
Thefe never form laree maOes, but are al-
ways found in detached pieces, of rather a-
imall iize, the largeft rarely exceeding the
bignefs of the clofed hand. In general they

are

( i'7 )
are. more plentiful than the glafles, and
among the tufas of uncultivated places, it is
only nece^ary to remove the furface to find
them by hundreds. During my ftay at Fe-
•iicuda I refided in a place called La Valle
della Chiefa (the Valley of the Church),
This is a fmall plain, on the eaft fide of the
ifland, in which ftand the parfonage-houfe
and the church, two indifferent buildings,
.Suitable to the poverty of the country. This
place, as like wife a fpacious declivity -to the
^outh, abounded with pumices, both on the
furface of the tufas, and below the furfaccj
wherever they were dug into.

Thefe pumices are of two kinds ; the
one cellular, extremely friable, fibrous, and
'tt'hich float on the water; and the other
compad:, heavy, without pores, and of a
fmooth fradure 9 but which yet polfefs all
the true charaders of pumice. Some are of
a reddifli colour, ;Qthers yellowifh, and
many afh-grey. Ail are plentifully fur-
iiifhed with extremely brilliant vitreous felt-
ipar-fcales.

Ij la

( «>8 )

In my obfervations on the pumices of
Vulcano I have remarked, that inilead of
fwelling in the furnace, and being tranf-
formed into an ebullient product, as is al-
mod always the cafe with glaffes and comr
pad: enamels, they become of lefs bulk,
lofe their pores, if they had any before, or,
at leaft, contra<St, and therefore become
heavier. The prefent pumices do not dif-
fer in this refped: from thofe of Vulcano ;
and the enamel which they produce in the
furnace has a black and fhining ground, in-
teifperfed with whitifh fpots, which are
feltfpars that, having loft their luftre and
tranfparency, are become white. This ena-
mel puts the magnetic needle in motion at
the diftance of a full line, notvvithftanding
that it had no fenfible efFed on it when .in
the ftate of pumice.

There Is no reafon to fuppofe that thefe
pumices have ever formed currents, both
becaufe they are always found in detached
pieces,, and becaufe their pores have not that
diredion which is ufually obfervable in

pumices

( "9 )

pumices that have flowed in the manner
of lavas. The figure of the pores in pumices
that have flovi^ed, is ufually more or lefs ob-
long ; whereas in the pumices of Felicuda
(I mean the celhilar) the pores are almoll
always orbicular. We mull: therefore con-
clude that they have been thrown out from
the mouths of volcanoes ; to which the glo-
bofe figure of many of them is perfectly
confonant.

I fhould eRetm my account of the dif-
ferent produ6tions of this ifland very de-
fedive, were I not to mention another
which flill more confirms its volcanization :
I mean the puzzolana found here in fevera!
places, and which, when cai'efully exa-
mined, is found to be a mixture of minute
fragments of pumices, tufas, and lavas. The
inhabitants of Fehpuda make ufe of it, as
alfo the pumice, in building their houfes ;
in the following manner^ They bring car-
bonates of lime (calcareous earths) from
Sicily ; and burn them in furnaces, which
ai*e erected, for greater convenience, on the
I A fea-

( 120 )

fea-fhore ; and at the end of forty hours an
excellent lime is produced. One-third of
this and two-thirds of puzzolana, mixed
together with water, form a cement which
unites and hinds the pieces of lava here
ufed inftead of bricks and ftonts ; and to
give, as they affirm, a greater flrength and
folidity to the cement, they mix with it
pounded pumice of their own country.

Lavas are ufed as mateiials for the build-
ing of houfes, not only by the inhabitants;
of Felicuda, but by thofe of all the other
Eolian iiles, each ufing thofe of their own
ifland ; and it is the pradice, not only in
the country but even in cities, to build with
fuch flones as the environs afford, efpecially
when they are mountainous. I therefore,
wherever I went, conftantly examined the
materials of which the villages, towns, and
cities through which I paffed were built ;
which frequently afforded me a light and
diredlion in my enquiries relative to the fqi^
fil fubftances of thofe countries.

On

( «il )

On reviewing the different volcanic bodje*
which I met with at Felicuda, we fhall find
that they confiit of giafles, pumices, tufas,
puzzolana, and lavas with a bafe of flioerl,
feltfpar in the mafs, or horn-ftone. The illand
^t prefent exhibits no indication of fubter-
ranean fire, and even thofe figns which are
uncertain and equivocal are wanting; fuch,
for inftance, as warm fprings.

In the various excurfions I made, I was
particularly attentive to obferve if by acci-
dent I fliould meet with any body not vol-
canized ; and found one only of this de-
fcription. This was a piece of detached gra-
nite, lying on the fliore near the Grotta del
Bove Marino. Its elements were of the moft:
common kind ; mica, feltfpar, and quartz.
The mica was partly black, and partly
white and filvery ; both forming groups in
which the black predominated. The quartz
was in fmall femi-tranfparent maffes, of a
vitreous and brilliant fradure, foft to the
touch, and of a colour between a blue and
a white. The feltfpar, which in quantity

exceeded

( 122 )

exceeded the two other princIpTes, and there-
foremuftbeconfideredasthebareof the ftone,
wa& in fmall maffes of unequal furface, lamel-
lar in the fradlures, tranfparent in the angles,
and of a changeable milky whitenefs. Nei-
ther of the three principles has a determi-
nate fortn of cryftallization. I think I fhall
not be miftaken if I aiTert, that this granite
has not fafFered the action of the fire. In
fad, a continuance of a quarter of an hour
IB the furnace produced in it fo great an
slteralion, that every part of it was fenfibly
changed. The mica became pulverable, the
quartz extremely friable and full of cracks,
and^ lofmg its tranfparency and vitreous
brilliancy, became entirely white. The felt-
fpar^ likewife, contra<3:ed a confiderable fri-
ability J lofmg at the fame time its change-
able colour, and becoming whiter. It is not
therefore extraordinary that a flight blow
with a hammer fhould now break this flone
into fmall pieces ; though before it would
only ftrike off, at moft, a fjngle fragment.
When expofed to the furnace for feveral
days fucceiTively, the quartz and mica did

not

( 123 )

not fnCe ; and the feltfpar only exhibited, at
the angles, a beginning of fufion, which
made it appear as it were und:uous. This
experiment is perfedly agreeable to many
others which I made in the furnace on the
granites treated of in Chap. XII. We mutl
therefore conclude, that this piece of granite
was thrown out untouched from fome vol-
cano in the ifland ; or, which appears more
probable, that it is adventitious to it; for it
is to be obferved, that it was not found in
the interior part of the ifiand, but on the
beach, where it had been beaten, and had its
corners fmoothed by the waves. Were I to
indulge conjedure, I fhould Incline to fup-
pofe it might have been brought by the fea
irom Capo Melazzo in Sicily,, or that vici-
nity, which is only fifty-four miles dlftant
from Felicuda, and where immenfe mafles
pf fimilar granite are found*,

* See Chap. XII.

CHAP.

( 'H )

C H A R XVIII.

A L I C U D A.

Danger to 'which the author *was exfwjcd^ in
a teiv.pejl^ on his pajfage from Fd'icuda to
Alicuda — Pumices and glajfes found in the
latter if and — Examination of the coof of
Alicuda — Several rocks formed of detached
globes of lava — Enquiries relative to the
origin of thefe globes - Confrmation of the
uncertainty of a?iy opinions formed relative
to the greater cr lefs antiquity of lavaSy
from the more or Icfs fenfible decompofition
they may have undergone —Ifolated mafes
of porphyry^ which exhibit no fgns of
having been attacked by volcanic fre — -
Lavas of another kind — Shoerls of a
greenifh blue colour contained in all thefe
lavas — T'he coaf of Alicuda more rugged
and threatening than that of any other
of the Eolian ifes — No mouth of any
ancient crater in the fides of the if and

( 125 )

—The appearance of a true crater found
07ily at the fa?nmit — Lavas in the interior
part f the ifand fimilar to thofe of the
fhores — Improbability that F'elicuda and
Alicuda once formed afngle conical moun^
tain^ the fide of ivhich has been opened and
feparated by the fea^ as M, Dolomieu has
fuppofed — Reafons for believing that each
was originally a fcparate ifand — Thefe
two iflands no longer manifef any fgns of
adlual fire — The filence of the ancients re-
lative to their fiery eruptions^ a proof that
they mufi have long ceafed to burn.

N the 1 3th of October, at fun-rife, I left
Fellcuda, in a fmall bark, with four rowers,
which was fleered by the parifh-priefl of
FeUcuda, who had the character of a fliilful
feaman. We failed before a moderate eafl-
wind : the fKy was clear, the fea fmootb,
and we flattered ourfelves we fiiould foou
reach the place of our deiiination, as the
diftance between thefe two fmall iflands Is
not more than ten miles. But fcarcely were
we half way, when the wind began to in-

creafe

( i26 )

creafe fo that We were obliged to reef ouf
fail, which it was dangerous to carry full ;
yet ft ill we made more way than before ;
^nd the wind blowing with greater violence,
and driving us rapidly towards Alicuda^
from which we were now not flir diftant,
endangered our being fhipw^ecked on the
fhore. Bays or harbours are things unknown
in this ifland, and our bark driving before
the wind, it was to be feared, might foon
dafli againft a rock, or run upon a fand-
bank ; and we had the lefs hope of being
able to avoid this danger, as our failors,
from unpardonable negligence, had not
brought with them any anchor.

The fea, in the mean time, ran very high;
and the waves, which would not, perhaps,
have given much alarm to a large fhip, were
Tery formidable to our little vefTel, which
they broke over from fide to fide, and from
jftern to prow, w^hirling it round with their
violence; while the danger of being wrecked
continually increafed by our approaching
the ifland, notwithftanding all the exertions

we

( J27 )
vre could make with our oars to keep ofTit,
Ourfaiiors, however, did not entirely aban-
don themfelves to defpair, but conlulted
whether it would be lefs dang' rous to yield
to the violenceof the waves, and endeavour to
run the bark on Ibme fand-bank joining to
the (hore; or, avoiding the ifland, to adven-
ture out to fea, and commit themfelves to
the mercy of the winds.

In this defperate fituation, we perceived
five men haftily defcending from the emi-
nences of AUcuda, and approaching the
fliore, which they quickly reached ; vdien
one of them called to us in a voice which
might be diftindly heard notwithftanding
the noife of the waves, advifmg us not to
be terrified, but to endeavour to keep v^^here
we were, and he would exert his utmoH:
efforts to deliver us from the danger by
which we were threatened.

This perfon, as I afteru^ards found, was
the parifh-prieft of Alicuda, who perceiv-
ing, from a diftance, the fituatioii in v/hich

we

( 128 )

we were, had haftened, with four of thei
iflanders, to give us affiftance. He had
brought with him a ftrong pulley, which^
when fixed on the fhore, was to receive a
rope, by means of which the veflel might
be drawn upon the land. B ,t to efFed thiSj
it was nee flary to form a kind of inclined
plane on the ihore, along which the boat
might be drawn ; which was foon done,
w^ith the fpades and fhovels that had been
provided for the purpofe.

"We were not more than fifteen feet from
the land, and, by inceflantly plying our oarSj
made every effort to avoid approaching ic
nearer. We were obliged, at the fame time^
continually to bale the water out of the
boat, to prevent its fmking ; which was the'
continual employment of myfelf and my
fervant, the failors being entirely occupied
in uling the oars. A rope coiled up was
now thrown on fhore by one of the failors,
and, after two or three unfuccefsfjl at-
tempts, caught by the perfons on the beach
and paffed through the pulley j while the
9 failor

{ 129 )

flllor drew It tight, and faftened it to the
prow of the bark. We now committed
ourfelves to the firft wave that rolled upon
the (hore ; and, the five iflanders pulling the
rope with all their force, we were drawn
with the bark up the fhelving declivity they
had made : but the wave on its return,
dalhing impetuoufly againft the prow, drove
us again into the fea ; and fo violent was
the fhock, that the rope broke, and we loft
all hope of getting fafe on fhore. At this
unfortunate and unexpeded accident the
good prieft ftruck his hand againft his fore-
head, from vexation and dlfappointment,
and our confternation was extreme.

We had now refolved to keep ofF from.
the illand, and brave the fury of the winds
and the waves, in the open fea, whatever
might be the event : but from this we were
difluaded by thefe iflanders, who aflured us
it was impoffible fo fmall and crazy a boat
as ours (hould long refift the violence of the
ftorm in the wide fea ; but that it muft either
overfet, or bilge and fmk. They advifed

vox.. III. K us

( I30 )

us rather to coaft the ifland towards tfie
aorth, where we might poffibly find fomc
fmall inlet, where we might be lefs expofed
to the waves ; promifmg us that they would
proceed the fame way along the fhore, and
afford us every affiftance in their power.
This advice we followed, and, bearing up ta
the north, without (landing far from the
fhore, in about half an hour met with a
cavity in a rock, which, from being wind-
ing, was not much expofed to the agitation
of the waves. Into this we happily carried
our bark v;ithout damage, and landed, with
the affiftance of the worthy prieft and the
pcrfons with him, towards whom I fhall feel
fhe warmeft fenfations of gratitude while
life fhall remain. He treated us, when on
fhore, with the utmoft kindnefs and hofpi-
tality ; and when I had prefented to him the
circular letter I had received from the Biihop
of Lipari (in which I was warmly recom-
mended to the parifh-priefts of thofe illands,
who were requelled to furniih me with
every. aiTiftance neceifary for my philofophi-
cal refearches during my ftay), he redoubled

his

his civility, ofFering to ferve me in every
manner in his power ; and his whole con-
duct fufficiently evinced the fincerity of his
offers.

it was not yet noon, by forrie hours, when
^ve landed in Alicuda, but the fatigue I had
undergone prevented my having any incli-
nation to begin my refearches that day; and
the following night I flept in the bark, which
had been drawn on fhord ; my deliverer
(for fo I may juftly call the good prieft of
this ifland) having fent me a mattrefs, and a
coverlet, to defend me from the moifture of
the night, as I was too much fatigued to
afcend to his habitation, which was fituated
half way up the mountainous ifland. He
likewife hofpitably invited me to fhare with
him the provifions of his frugal table, and
fome bottles of excellent malmfey of Lipari,
which revived my fpirits, and reftored my
ftrength.

I remained at Alicuda two days (the 14th
K 2 and

( 13^ )

and 15th of Odober), during which I fuffi-
ciently gratified my curiolity, and acquired
a fatisfadlory knowledge of the nature of the
ifland. The obfervatlon of the ancient Gre-
cian philofopher is well known, who having
been driven by a tempeft on the coaft- of
Rhodes, and with great difficulty reached
the land, feeing certain geometrical figm-es-
traced in the fands, immediately exclaimed :
/ perceive the vejliges of me?i : I, in like
manner, the moment I fet foot on the fhore
of Alicuda and furveyed it, might have
exclaimed: I perceive the vejliges of Jire,
Thefe were the pumices, glafies, and ena-
mels, which prefented themfelves to my
view on the fkirts and fides of Alicuda, and
which it is unnecefTary particularly to de-
fcribe, fmce they entirely refemble thofe of
Fellcuda, and are found like them mingled
with tufaceous fubftances.

Of the two days which I allotted to my
refearches in Alicuda, 1 fet apart the firft to
examine its circumference by fea, the night

preceding

( ^ss )

preceding the 14th of Odober having been
fufficiently cahn to permit me to make the
circuit of it in my boat without danger.

I (hall here, therefore, fpecify the princi-
pal products I difcovered during my circuit
round the fhore of the ifland ; this being
the part which, more than any other, muft
intereft the philofophical naturalift. I fhall
not name the places where I found them,
fmce two of the inhabitants who accompa-
nied me were unable to aflign any names
by which they were known ; the different
parts of the fhore of the ifland having in
fa.0: no fixed names : I fhall only indicate
their diftances froni the place whence I fet
out.

At the diftance of forty paces from that
part of the ifland which fronts the eafl:, we
begin to find, as we turr^ towards the north,
entire rocks, formed of globes of a blackifh
lava, with a petrofiliceous bafe, which,
though porous, is heavy from the compacft-
Kefs of the folid parts, which have a little
K ^ luftre,

I 134 )

liiftfc, are very hard, and in their fra(Stures
affed: the conchoidal figure ; they move
the magnetic needle at the diftance of more
than a Hne, and give fparks tolerably freely
with fteel. The petrofiliceous fubftance
contains a few feltfpars, and a confiderable
number of fhoerls. Thefe globes of lava
are of various fizes, feme of them being a,
foot in diameter. They are detached, and
are never found in ftrata, but only in large
accumulated heaps.

To what caufe can we afcribe the divifioa
of this lava, and its conformation in the
manner defcribed ? I at firft imagined that
its figure might be the confec^uence of the
agitation of the Tea, when its waters reached
to a greater height ; as thefe accumulations
of globes are now fome poles above its level.
In faft, in my maritime excurfions round
the other Eoliaa ifles, and at Etna, 1 have
frequently met occafionally with fimilar balls
of lava, which clearly indicated that they
had been rounded by being continually
rolled by the waves of the fea, in the famq

manner

( ^35 )

manner as we find ftones rounded in rivers.
In the courfe of this work I have adduced
feveral examples of this kind, even among
the glalTes and enamels of Lipari, which
have taken a globofe figure. But a more
careful examination of thefe globes com-
pelled me to change my opinion, on con-
fidering that the pieces of lava that have ac-
quired an orbicular form from the agitation
of the waters, are always more or lefs
fmooth on their furface ; whereas thefe were
rough all round — though their roughnefs,
£onfifting in general of minute parts and
points, mufl have been worn away by rub-
bing againft anyobftacle. I obferved, befides^
that thefe globes, in many places, had a
(hinlng and fcoriaceous appearance, extreme-
ly fimilar to that of the pieces of lava inceC-
iantly thrown out by the volcano of Strom-
boli. I am therefore rather of opinion that
they are pieces of lava that have beem
thrown out from a volcano in Alicuda, and
taken a fpherical form in the air, from their
great foftnefs, as fimilar phenomena may be
K 4 obferved

( '3S )

obferved in the produds of ot^ier burning
mountains.

About a mile and a half beyond the lava
now defcribed, proceeding ftill towards the
north, we find a fecond, not in globes, but
in an ample current, which falls like a cata-
ract into the fea. It is of a petrofiliceous
bafe, has the colour of iron, is filiceous, ox
rather vitreous in the fracture, and full of
fhoerlaceous cryflallizations. Whoever has
feen lavas which have lately iiTued from the
mouth of a volcano, would imagine this of
extremely recent date. On the furface, it
preferves that fhining afpedil:, that frefhnefs,
which is peculiar to lavas that have not yet
been expofed to the influences of the atmo-
fphere. The fpecimens of it which I de-
tached, might be taken for that fcoria of
iron which we find in the fhops wbere that
metal is fabricated. I have in my ppfleffion
fome pieces of the lava which v/as tbrowa
from the higheft crater of Etna, in 1787,
■which I colleded on the fpot, and. have de-

(cribe4

( 137 )

fcrlbed elfewhere *. Thefe, with refpe^ to
the frefhnefs of their appearance, are not
diftinguifhable from the lava of vi^hich I
now fpeak. Yet is the latter of an antiqui-
ty beyond our knowledge, for we have no
record of any conflagration in Alicuda fince
hiftory has been written. I have chofen to
fpeak more at length on this peculiar pro-
perty of the prefent lava, to prove, or rather
to confirm what I have already proved,
how uncertain are all conclufions relative
to the greater or lefs antiquity of lavas, de-
rived from the more or lefs fenfible degree
of decompofition which they manifefl.
Such conclufions may be well founded,
when the lavas are of the fame nature, and
affeded by the fame extrinfic circumftances ;
fince, then, thofe of a more ancient date
muft be moft changed by time : but where
their nature and qualities are different, one
lava may be confiderably altered in a few
years, and even reduced to an earth, while
another fhall remain for ages, perfe(Sly

♦ See Chap. VIII.

preferved,

( '3S )

preferved, and in the fame ftate in which
it was thrown out of the fire, of which
the lava now defcribed is an evident ex-
ample.

At the diftance of another full mile from
the place whence I took my departure, the
mountainous coaft of the ifland becomes
fomewhat more level ; and on this plain
arife detached mafles of porphyry, which
fhew no figns of having been touched,
much lefs fufed, by the fire. It is of a pe-
trofiliceous bafe, of the colour of brick, af-
fords fparks with fteel, and is extremely
compadl, and without pores, except a few
fuperhciai vacuities, coated with a thin
white cruft of carbonate of lime, fometimes
iludded with cryftals of the fame kind.
Thefe fmall geodes, which have been pro-
duced, without doubt, by filtration, are
decompofed in a fe\Y moments by the nitric
acid, and dilToIve with a ftrong effervef-
cence. This porphyry, in its hardnefs, po-
lifh and luftre, is not inferior to the Egyp-
tian. Befides flioerls, it contains numerous

cubical

( 139 )

cubical lamellar feltfpars, of a changeable
Vvhitenefs.

When expo fed to the furnace for a few
hours it becomes black, and after a longer
time fufes into a black, compa<5t, and very
fmooth enamel, which fets in motion the
magnetic needle, though it produced nofuch
€fFe(5l when it was porphyry. The felt-
fpars remain entire.

In this part of my circuit round Allcuda
J have defcribed two kinds of lavas, the
one found in detached globes, and the other
in a current ; which, however, from the
identity of their nature, may be confidered
^s one only ; both having for their bafe the
petrofilex, and containing fhoerls and felt-
fpars : they are therefore both porphyritic.
And as the rock laft defcribed is a porphyry
with a petrofiiiceous bafe, it appears that
they all three derive their origin from one
common matrix, except that one portion of
it has been fubjeded to fufion, and the other
femained untouched.

A little

( 140 )

A little beyond the plain abovcmention*
ed appear fome tufas, which cover a long
and fteep declivity defcending into the fea,
and beyond the tufas we again meet with
lavas forming broad currents. Thefe lavas
have the horn-ftone for their bafe, and their
external charaderiftics are the following :

They are light, extremely porous, and
therefore eafily penetrable by water 5 they
with difficulty give fparks with fteel, which
breaks off fragments at every ftroke. They
feel rough under the finger, and emit an
argillaceous odour. They contain nume-
rous feltfpars, which are confpicuous from
their whitenefs, on a dark red ground ap-
proaching to a black. Some fhew a degree
of calcination which they have fufFered in
the fire, and are, in confequence, eafily
crumbled. Others have fuffered no injury ;
and the difference obfervable in them is
rather to be afcribed to the difference of
the nature of the feltfpars, than to their
liaving fuffered a greater degree of heat,
the lava in which they are both incorporated

appearing

( 141 )

appearing to have been equally afFedled by
that agent.

Alicuda is about fix miles in circuit, and
I have as yet made the tour of only the
one half. On completing it, however, I
only met with lavas of the fame kind with
thofe already defcribed, diverfified by a few
varieties that do not merit a particular de-
fcription.

I have given fome faint fketches of the
appearance of the lavas in fome parts of
this ifland ; but it would be irapofTible for
me to give an adequate idea of the fearful
wildnefs of the fcenes which prefent them-
felves to the eye for two-thirds of this cir-
cuit. Among all the volcanized places I
have vifited, I have yet feen none fo con-
vulfed by fubterranean fires, {o torn and
fhattered, and fo filled with accumulated
ruins by the devaflations of time and the
fea.

In fome places we find a lava extending

for

( U^ )

for ievetal hundred paces, which has becfl
broken by the waves in fuch a manner as
to form a rock furrounded by the watefj
abounding in craggy cliffs and precipices of
a fearful height.

In others the lava defcends perpendlcu-^
larly from the moft elevated fummit of the
mountain ) and buries itfelf in the water, fur-
rounded on the fides by proje<f!tlng crags,
and huge overhanging ftones, which threaten
every moment to thunder down into the
deep*

Here the lavas do not form one conti-
nued body, but are compofed of detached
and loofe globes, particularly dangerous to
thofe who may attempt to afcend the moun-
tain, as they roll from under and put in mo*
tion a great number of others, thus produ-
cing a deftru(5tive ftony torrent. Even the
large falcons, which frequent the higheft
fummits of this ifland, if they chance to
alight on thefe heaps of round, loofe ftones,
wiU often, as I have myfelf feen, by moving

2 one.

( H3 )

one, put others in motion, till bird and
ftones fall, all together, headlong into thg
fea.

in another place lavas are found, not of
one kind alone, but a confufed mixture of
feveral, piled in diforder one on another to
a prodigious height ; and in many of them
there is no part which does not threaten
immediate fall and ruin.

Through the midft, however, of thele
mifliapen rocks and horrid precipices are
formed, I will not fay roads or paths, but
narrow winding gutters, by which we may
afcend to a certain height ; and throu;zhthefe
I took my way, when from time to time I
landed from my boat and went in fearch of
the lavas I have defcribcd, and examined
them on the fpor. I was obliged, however,
to advance with the greateft caution, as to
have made a fmgle falfe ftep would have
been to have faUen headlong down a pre-
cipice. I could not but recolle(ft the lines
of Dante, in which he defcribes the la-
borious

( 144 )

borious paflage over the horrid crags anil
precipices of one of the abyfles of his
Hell.

** E profequcndo la folinga via
Fra le fchegge, e tra rocchi de lo fcogllo^
Lo pic fenza la man non fi fpedia."

«' And flill along the folitary way,

" Proceeding over rocks and precipices,

*' The foot without the hand no progrefs made."

And though the fatigue in again de*
fcending to the fea might be lefs, the dan-
ger was equal, if not greater, from the un-
liable and flippery nature of thefe deceitful
places.

Having completed the circuit of the
fhores of Alicuda on the fourteenth of Oc-
tober, I appropriated the next day to the
examination of the interior part of the
iiland. I could, however, only make my re-
fearches in the part which fronts the call
and fouth-eaft ; the remainder being inac-
ceflible from the dreadful crags and preci-
pices already mentioned.

When

( '45 )

When feen from the fea, on the fouth-
eafl: fide, at the diftance of two or three
miles, this ifland has the appearance of an
obtufe cone, but with a confiderable incava-
tion on one fide. This incavation has no
refemblance to a crater, and on a nearer ex-
amination we find it is only a lower part
of the mountain. In fad, we perceive no
marks of the mouths of ancient volcanos in
the whole circuit of Alicuda ; either becaufe
they have never exifl:ed there, or becaufe all
traces of them have been effaced by time or
fome other deftructive agent. I have dif-
covered the appearances of a true crater no
where but in the higheft part of the ifland,
where there is a hollow, not very deep in-
deed, but about half a mile in circumfe-
rence ; and I incline to believe it to have
been a crater, from finding there a group
of lava diverging as from a centre over the
body of the ifland.

I examined the lavas which cover the
fides of this mountainous ifland, at leaft:
where I could reach them without danger,

VOL. 111. L ia

( r46 )

in the fame manner that I did thofe which
form the bafe or fhore of it. I fhall not
defcribe them particularly, as it appears un-
neceflary-j they generally having the petro-
filex or horn- ft one for their bafe, and
abounding more or lefs, as ufual, in feltfpars.
Their external furface is covered with a
yellowifh and friable coating, originating
in a beginning decompofition. The deep
frad:ures which we find in many parts of
them enabled me to perceive that they mull
have flowed at different periods, forming
beds or ftrata one above the other, as is
frequently obferved in other volcanized
countries.

M. Dolomieu was of opinion that " Fe-
*' licuda and Alicuda had once formed a
*' fingle conical mountain, which had been
" opened and feparated on one fide.'*

This is certainly not impoffible, but I
muft fay it appears to me extremely impro-
bable. If the fea, or any other violent
agent, had divided this conical mountain

into

( 147 )

into two parts, It Is difficult to conceive that
no record or tradition fhoiild remain of this
convulfive reparation. On the contrary, when
I attentively examine and confider thefe two
iilands, they have every appearance of being
each a diftindt ifland, hke Stromboli, Saline,
and the others. Both likewife have on their
higheft fummits the veftlges of their primi-
tive crater, that is, of that which by its
erudations has given birth to its refpe(fl:ive
ifland. The lavas, likewife, which have
flowed from thefe fummits, as from central
points, and enlarge and extend as they take
their courfe down the fides of the mountain
towards the fea, feem clearly to prov.? that
each was a complete ifland in itfelf ; nor
can I doubt but the French naturalift, had
he vifited thefe iflands themfelves, would
have been of my opinion. He only viewed
them from the higheft part of Saline, that
is, at the diftance of five-and-twenty miles
from Felicuda, and five-and-thirty from
Alicuda. At that diftance they feem very
near to each other ; fo that M. Dolomieu,
judging from appearance, fuppofes Felicuda
L 3 tg

( 148 )

to be only five miles from Alicuda, thougli
it is in reality twice that number. As,
therefore, at Saline, they appear to be fo
little diftant from each other, nothing was
more eafy than to imagine that they once
formed a fmgle mountain, which, either
by earthquakes, the violence of the fea, or
fome other unknown caufe, had been broken
and divided into two parts, an arm of the
fea taking poflelTion of the intermediate
fpace.

From the fummit of Saline he, llkewife,
e(\imated Alicuda to be only twenty miles
from Cefalu, on the coafl: of Sicily ; and,
in fad:, when I was on the fame eminence,
thefe two places appeared to me to be very
near, and Felicuda feemed almoft to join to
Alicuda ; yet it is certain that the diftance
between Alicuda and Cefalu exceeds five-
and-forty miles; It is well known that
this optical illufion takes place with refpedt
to any objed feen at a diftance, either by
land or water. Nothing happens more
frequently to the traveller than to find that

two

( 149 )

two rocks, mountains or buildings, which
when viewed at a diftance he had imagined
to be extremely near to each other, and al-
mofl: to touch, are in fad: feparated by an
interval of feveral miles.

The volcanic materials of Felicuda, as
has been already feen in the preceding chap-
ter, conlift of lavas widi a horn-ftone bafe,
fhoerl, and feltfpar ; not to mention pu-
mices, tufas, and glafles. The latter three
products are likewife found in AUcuda, but
the greater part of the lavas have the petro-
filex for their bafe.

Notwithftandlng thefe two Iflands exhi-
bit indubitable characters of fire, no figns
of it in a ftate of adivity are at prefent to
be feen. It may indeed be conjedured
that fome remains flill exift in the internal
parts of Felicuda, from a warm fpring,
emitting the fmell of fulphur, which iflues
from the northern fide of a rock, a little
above the level of the fea.

L ^ 1 fliall

( ijo )

I (liall here colled: the notices that have
been left us by the ancients relative to Feli-
cuda and Alicuda, as they are extremely
few and brief. We know that their names
were Phenicufa and Erlcufa {<^on'iy.ova-a, and
Eoiviovcrcc)^ which are laid to have the follow-
ing derivation : Ariflotle, fpeaking of Phe-
nicufa, or Felicuda as it is at prefent called,
fays, " it received that name from its abound-
ing in palm-trees" — (pom^^ in the genitive
(poniycoc, being the name of that tree in
Greek '^. Ericufa, or Alicuda, Vv^e are told
by the author of the epitome of Stephanus,
was fo named from the erica or heath, which
there grows plentifully "f, Strabo, likc"^
wife, informs us that thefe two iflands de-
rive their names from plants J. At pre-
fent, however, though heath is not wanting
in Alicuda, Felicuda does not afford a iingle

* Ey fiia tm Atc>.ii zipoTayopevofjitvuv vnTuv 'sr^jj^of tj (paai

In Mirandis.
+ 'EpixHcra-a, fna ruv AioT^a vno-icv, utto (pi/7a hu'^h/ji.bvti.

!iSk7.rA7ui» Lib, VL

palm^

( IJ' )

palm-tree, nor is there one to be found in
any of the Eolian ifles.

But neither the above-cited authors, nor
any other ancient writers, make the leaft
mention of any conflagrations in thefe two
iilands ; probably becaufe, though, in their
time, StromboU, Vulcano, and even Lipari
threw out fire, Felicuda and Alicuda, as
we have feen was the cafe with Didyma
and Euonimus, were entirely extinguiOied.

L 4 CHAP.

{ ^52 )

CHAP. XIX.

OBSERVATIONS WHICH HAVE AN IMME-
DIATE RELATION WITH THE VOLGA-

NIZATION OF THE EOLIAN ISLES

ENQUIRIES RELATIVE TO THE ORIGIN
OF BASALTES.

Methods and injlruments proper to ra'ife Jlojiy
bodies from the bottom of the fea fiirroiind-
ing the Eolian ifes — The bottom of the
channels between Vidcano^ Ltpari^ and Sa-
line, entirely volcafiic — The faine obferva-
hie of the roots of the Eolian ifes beloiv
the water — Gravel and volcafiic find in
the channel that divides Panaria fom
Lipari~The rocks in the middle of the
channels between Saline and Felictida, and
between Felicuda and Alicuda, analogous
to thofe of the fame ifands, but, probably,
priniordial — Dec five proofs deduced from
thefe obfervations, that ihefooerls and cry f
talU%ed fcltfpars of the lavas have not

been

( ^S3 )

heen taken tip by them zvhen in a fiuid
Jiatc^ iior formed within them at the time
of their congelation — Confrmatlon of thefe
proofs — 'The Eollan If es placed hi a dlredl
line from eafi to ijoefi — A fimllar direction
ohfervable In fome ifands and volcanic
monntalns in other countries — Not Impro-
bable that all the eight Eollan Ifes were
formed at the fame tlme^ and perhaps
very fiiddenly^ ivlth refped^ at leaf^ to
their frf rudiments — -Explanation of the
caufe ijuhy ifands and burnwg mountains
are fmetlmes produced dlfpofed in a right
line — Materials of the Eollan Ifles^for the
mof part^ porphyrltlc — Analyfis made by
the author^ proving that the red Egyptian
porphyries have not for their bafe the pe-
troflcXy but rather the hornfone — En-
quiry whether the vltrif cations found In
fuch prodigious quantities at Vulcano and
Llpai'l^ are found in fimllar quantities in
any other volcanic countries — Uncertainty
of this from the "want of accurate miner a-
logical defcrlptlons of the greater part of
vokanos — The accounts given of thein

nfually

( '54 )

ufuaJly general and wonderful^ but little
injlnicl'ive — Volcanic glafs found in Ice-
land^ but by no means in ftifficient quantities
to form mountains — No notices of vitrifi-
cations in the volcanos of the iflands of
Ferro, nor in thofs of Norway and Lap-
lafid — Little or no glafs in the volcanized
countries of Ger7nany and Hungary — Nor
in the extinguifjed volcanos of France —
The quantity of vitrif cations at Vefuvius,
and fever al other parts of the Neapolitan
territory^ more cojfiderable— Scarcely any
at Mount Etna, or the volcaitic mountains
cf Padua — A more extenfive trad of pU"
mices found perhaps in 7io part of Europe
than in the ifland of Santorine — This
ijland^ hotvever, affords no glafs — Great
fcarcity of vitrif cations in the three other
quarters of the globe— Concluf on : that
Vulcano and Lipari offer a greater abund-
ance of glaffes than any other volcanized
part of the world ; but that Santorine ex-
ceeds them in the quantity of pumices —
Enquiries relative to this fcarcity of vitri-
fications in volcanos^ whether hur'niv.g or

extinEl

( 155 )

ixthiB — // feems to proceed lefs from iht

• quality of the fones a^ed on by the vol-

fame fire^ than from the i?teficacy of that

agent to produce vitrif cation — A fnccef-

fively fro7iger degree of heat reqnifite for

a fione to pafs from the fate of lava into

pumice^ and from that of pumice into per-

J'eEi glafs — Elucidation of the caufc why

fome volcanos produce pumices^ but not

glaffes — The formation , of pumices hitherto

not attainable in our furnaces — Blacli the

natural colour of pumices ^ which are ren^

dered white by external caufes,

Enquiries relative to bafaltes — Thefe origi--
nate i?i the hiunid 'way^ vohen the voord
bafalt is underfood in the fenfe in which
it was tfed by ihe ancients — ^ he columnar
fones which^ from their prifnatic conf-
guration^ refemble the bafaltes of the an^
(ients^ originate according to circumfances
in the humid or the dry way. — F roofs of
their origin in the dry way in Vulcano
and FcUcuda — Nature^ in the fofil king^
dom^ produces cryfals as well by the dry

4 'ZC'iTJ

( 156 )

iJDay as by the humid — This exemplijied in
the generation of hafaltes — An ahufe of
analogy to conclude from it one common
origin of bafaltes — When examined de-
tached^ they frequently hear no peculiar
chara&er of their origin, ivhich mufl be
determined from local circumfaiices — jE";/-
quiry ivhether bafaltiform lavas have be-
come fuch by a fudden coridenfation ivithin
the fea — Proofs which fhew, fi^fl-i tk^^
maity bafaltiform lavas have affumed this
fymmetrical co?fguratio7t on coagulation in
the waters cf the fea ; fecondly, that in
others it has taken place only by congelation
in the air ; thirdly, that very numerous
lavas have proved refraElory to this fgure,
both within the fea and in the air — The
property of affuming a prifmatic figure ap-
pears, in many lavas, not to depend on their
being of a particular fpecies, nor on their
compacinefs and foUdity, but on extrinfic
atid adventitious circumfances — Thefe cir^
currfances indicated, ivith an explanation
in 'what manner, according to their pre-
fence or abfence, lavas frequently offume a

prfmatic

( ^57 )

prifmatic form in the aiVy while others
remain irregular within the fea,

X HE form, fize, and ftrudure of the
Eoiian ifles, the different materials of which
they are compofed, and the primordial rocks
from which thefe are derived ; the fires
which ftill burn in fome, and the pheno-
mena and changes which accompany them ;
with the comparifon between the prefent
conflagrations and thofe of ancient times,
conftitute the principal objeds to be confi-
dered in writing the volcanic hiftory of
fiich a country. And though we have al-
ready employed nine chapters on thefe fub-
jeds, we conceive the candid reader will
not accufe us of extreme prolixity ; both
becaufe we have had to treat of {^nqw.
iflands, and becaufe our object was to write
the I.ithology of this ancient and celebrated
country. The prefent chapter, we flatter
ourfelves, will, in like manner, be ac-
ceptable to the enquiring naturalift, as it
contains various obfervations and reflec-
tions

tions which have a diredt and immediate
relation to the deflagrations of the Eolian
illes.

We have already obferved and defcribed
thefe iflands from the fammit to the bafe,
which buries itfelf in the waters of the
fea. But it was impofiible to examine
their internal part in the fame manner as
the external ; though the importance of
fuch an examination merited that every ef-
fort in our power (hould be exerted to ef-
fed it. It would be equally interefting and
initructive to afcertain the nature of the
bottom in thole tra-ilis of fea which fur-
round thefe illands, and feparate them one
from the other. 1 iball, therefore, here
relate whit I obferved with refped to this
fubject, and defcribe the methods and inftru^
ments to which I had recourfe to make my
obfervations.

Where the depth was not great, I found
extremely ufeful the large tongs, mentioned

by

( 159 )

by Donatl *, furnifhed with (Irong pincers,
iixed to one or more bars, which by means
of a rope may be clofed or opened at plea-
fure, and thus take hold of and bring up
any fubftances fromthe bottom. But where
the water was deep, I found it more con-
venient to employ one of thofe nets which
fifhermen ufe to envelop, and tear from the
rocks, coral and other fubaqueous bodies.
Thefe nets I eafily procured, as coral is
fifhed up on thefe coafts ; of which fifliery
I fhall treat further in a fubfequent part of
this work.

Employing, therefore, thefe two inftru-
ments, the follow^ing was the refult of my
obfervations, which were not made on
pieces that lay detached on the bottom, but
on fiich as formed a continued whole with
it, as was evident from, the recent appear-
ance of the fractures where they were broken
off.

* Saggio fopra la Storia naturale del Mare Adrlatico
— Eflay on the Natural Hiftory of the Adriatic Sea.

la

( . i6o )

In the channels which divide VuIcanO
from Lipari, and Lipari from Saline, the
bottom is entirely volcanic, and affords pro-
du61:s of the fame fpecles with the two
iliores. The fame is obfervable of the foot
of the iflands, which foot in fome fituations
defcends perpendicularly ; but in others has
a confiderable declivity, and thus enlarges
the circuit of the ifland. The pieces of lava
which I was here able to detach, did not
differ from thofe of the fhore, which 1 have
already defcribed.

But at a greater diftance between illand
and ifland this was not the cafe. I made
my experiments in three different places.
The firil was between Lipari and Panaria ;
but here, the water being very deep, I did
not fucceed in my attempts to bring up any
ftony body from the bed of the fea, but only
teflaceous and cruflaceous animals alive or
dead, enveloped in fand and gravel, and
forming a fpecies of cruft more or lefs thick.
The fand and gravel, it is tobe obferved, were
volcanic.

The

( i6i )

The fecond place in which I made this
experiment was between Saline and Felicu-
da, and the third between Fellcuda and
Aiicuda, in both inftances, at the point of
greateft diftance, as nearly as the eye could
meafure, between the two iilands. In each
of thefe fituations, befides drawing up from
the bottom portions of the before-mentioned
cruft, I like wife obtained feveral ftony frag-
ments, which, from the great force it re-
quired to feparate them, and the recent ap-
pearance of their fractures, evidently had
an immediate communication with the folid
and rocky bottom. The whole number of
thefe fragments, great and fmall, was ele-
ven ; of which four were brought up be-
tween Felicuda and Aiicuda, and feven be-
tween Saline and Felicuda. The bafe of
five * of them was a petrofilex almoft
opake, affording fparks wiih fteel, compadt,
of a grain a litde fcaly, but fine ; the colour

* The author muft here have committed fome mif-
take, as he, immediately before, faid the whole number
of pieces was eleven, and now mentions ^ve and feven.
T.

VOL. III. M of

( l62 )

of two of thefe pieces was a light'ifli blue,
and that of the three others a grey. The
bafe of the feven other pieces was a dark-
gi'een horn-ftone moderately hard. None
of them differed in their bafe, and fhoerla-
ceous and feltfpathofe cryftallizations, from
feveral volcanic lavas of the Eolian ifles.

Thefe eleven pieces, however, excited in
me a ftrong fufpicion that the rocks from
which they were detached had not been
expofed to the allien of fire. The parti-
cles of the petrofilex in them were more
clofely united, had greater hardnefs, and a
more filiceous appearance, than in the fame
ftone of thofe illands which has been fub-
jeded to fufion. In like manner, the lavas
of a horn-ftone bafe ufually have fomewhat
of a fibrous nature, and a thinnefs in their
texture which is not feen in the ftone of
the fame kind. Thefe two rocks, therefore,
appeared to me to be in their natural ftate.

I .confider thefe experiments as very in-
ftrudive with regard to the origin and

formation

( >63 )

formation of thefe iflands. We may con-
clude from them : Firft, That the part of
the iflands which is buried under the waters
of the fea, has fuffered the adlion of the fire
in the fame manner with that which is ex-
pofed to the eye of the obferver. Second-
ly, That Vulcano, Lipari, and Saline form
one continued group of volcanized fub-
ftances, which, at firft, might probably have
one common central conflagration, that, di-
viding into three branches, and affording a
pafTage to three diftindt mouths, gave birth
to three iflands, which conflagration, by
fubaltern and fucceffive ramifications, and
ejedions of new matters, afterwards in-
creafed in extent. No fenfible remains, in-
deed, of fuch a fire are at prefent difcover-
able in the internal parts of SaUne, nor
are any phferva-ble in Lipari, its whole effi-
cacy appearing to be confined to Vulcano.
Thirdly, That Alicuda, Felicuda, and Saline
do not appear to have any volcanic commu-
nication with each other, at leaft in the
parts that form the bed of the fea, which
feparates thefe three iflands from each other ;
M 2 lince

( '64 )

fince thofe parts, as far as the eye can per-
ceive, fliew no figns of the adion of fire.
Fourthly, That thefe three Ifiands, and per-
haps hkevvife Stromboli, are fituated in the
vicinity of analogous but primitive rocks*
The perfedl refemblance of the fhoerls and
feltfpars in thefe rocks, both in thofe that
have fuflered change from the fire and thofe
that have not, is a demonftration that thefe
cryftallizations have not been taken up by
the lavas when they flowed in currents,
nor formed in them at the time of their
congelation.

From the very beginning of this work, I
have adduced fads of the fame nature,
which I have the fatisfa£lion to confirm by
the prefent ; and which become of the
greater importance, as I have lately read
that a naturaUft of eminence inclines to be-
lieve that the fhoerls of lavas are formed
when the latter ccndenfe and become cold,
becaufe then the homogeneous molecules
feparate from the heterogeneous, and unite
by affinity in fmall cryftallized mafles.

This

( i^S )

This ingenious theory is not only contra-
dided by the obfervation made above, but ap-
pears to me not to accord with the ufual ope-
rations of Nature. Were it well founded, I
can perceive no reafon why the fhoerls in
lavas fhould not re-appear after they have
been fufed within them in the furnace,
and, being removed into a cold place, have
acquired their former hardnefs. But though
I made experiments with fire on fome
thoufands of pieces of lava, not one of
them re-produced its fhoerls, though many
were continued a long time in a ftate of
fufion, and afterwards fufFered quietly and
flowly to cool and confolidate ; v;hich two
circumftances are known to favour the
formation of cryftallizations. Shoerls were,
indeed, fometimes found in the lavas, after
fufion, when cooled and hardened ; but thefe
had proved refradory to the fire ; as appear-
ed on expofmg them again to the furnace
detached from the lava.

The eleven pieces of primordial rock
M 3 broken

( i66 )

broken from the bottom, exhibited in the
furnace the f^jme changes with their conge-
nerous lavas expofed to the fame fire : the
feltfpars, however, remained refractory.

The Lipari iflands extend in a right line
from eaft to weft the diftance of about fifty-
miles, except that Vulcano makes a fmall
angle. Strombcli is the firft to the eaft,
and Aiicuda the laft to the weft. This is
not the only inftance of volcanos having
produced iflands, or rather mountains, ar-
ranged in a rectilinear diredion. We find
an example of this in the Moluccas, which
are the produce of fubterranean fires, and
placed one beyond the other in a right line,
When, in 1707, a new iftand was thrown up
by a fubmarine volcano, in the Archipelago,
near San:orine, other fmall iflands arofe
from the fea near it, to the number of fe-
venteen, in a right line, forming, as it were,
a long chain of black and dark rocks, which
vifibly increafed in dimenfions and height,
and, approaching each other, at length

united.

( '67 )

united, and, joining that which firft arofe
from the water, formed one fmgle illand*.

Another memorable inftance of this di-
reftion of volcanic mountains (for illands
are in fad only mountains buried in part
under water) is the, produdion of feven
lefTer mountains by the eruption of Vefu-
vius in 1760 ; the account of the formation
of v/hlch, as it may throw fome light on
that of the Eolian ifles, I fhall here give,
from the accurate relation of ProfefTor Bot-
tis, an ocular witnefs.

After repeated concuflions of the earth,
which were felt fifteen miles round Vefu-
vius, the fides of the fiery mountain opened
in the territory of the Torre del Greco, and
fifteen volcanos appeared, eight of which
were foon after covered by a torrent of lava,
which ra(hed from one of them ; the other
feven remaining entire, and incefiantly ejed-
ing from their mouths vaft quantities of ig-

* Vallifneri Opcr. fol. t. i\,

M 4 nitedl

{ i68 )

nited fubftaiices, which falling almoft per-^
pendicularly around the volcanos, produced,
in the fhort fpace of ten days, feven fmall
mountains, of various heights, difpofed in a
right line. During thefe ejedions, the noife
which accompanied them fometimes refem-
bled that of violent thunder, and at others
the difcharge of a number of cannons. Se-
veral of the burning ftones, even the largefl,
were thrown to the height of nine hundred
and fixty feet, and fome fell at a confider-
able diftance from the mouth whence they
were thrown. Thefe erudtations ihook all
the neighbouring country, and the roarings
of the mountain were dreadful to the inha-
bitants. After the tenth day, the eruptions
ceafed, and the newly-formed mountains,
gradually cooling, permitted a nearer ap-
proach ; when fome were found to have at
their fummit a cavity refembling an invert-
ed funnel, and others a fimple hollow, of
greater or lefs depth.

The produdion of the Eolian ifles being
anterior to the records of hiftory, we know

not

( i69 )

not whether this took place at one time, or
in different periods. The relation, however,
juft cited, of the origin of the feven Vefu-
vjan mountains clearly proves the poffibility
of their being produced at the fame time. It
alfo proves, that the whole eight might be
formed in no long fpace of time, with refpeG:
at lead to their firft rudiments, it having
been feen that thev have received fucceffive
additions.

We alfo evidently perceive, that the in-
flammable fubftances generative of the Mo-
luccas in Afia, of the chain of iflands at San-
torine, of the Vefavian mountains above
defcribed, and of the Eolian ifles, have
formed a dired: fubterranean zone incompa-
rably longer than broad. This phenome-
non may be explained by recurring to the
clefts and fiflures perpendicular to the hori-
zon, exifting in many places w^ithin the
earth, as well in foft fubftances as in the
more durable and folid ; within which clefts
fliould fubftances proper for the produdion

of

( ^jo )

of volcanos be found in abundance, and be-
come inflamed, in feparate heaps, burning
mountains would arife, in a diredt line, and
more or lefs large, according to the quantity
of the ejeded matters.

From the particular defcriptions of the
iflands of Lipari, we Jiave feen that the
combuftible fubftances which have produced
them have fometimes been contained within
granite, as at Panaria and Bafiluzzo, but for
the moft part within rocks which have for
their bafe the petrofilex, the horn-ftone, and
the fcltfpar. It likewife appears, from the
obfervations made at Stromboli, that, even
there, thefe burning fubftances have their
feat in the horn-ftone rock, though, from
the fize of the ifland they have produced,
they muft undoubtedly be buried at an im-
menfe depth. If we would fimplify the
fads relative to the materials of ail thefe
illands, we (hall find that they are for the
greater part porphyritic ; as are likewife
foine of thofe fubmarine trads, apparently

not

<*a.

( 171 )

not touched by the fire, and placed among
them ; as has been fhewn above *.

When I compared the effeds of the fur-
nace on volcanized porphyritic rocks with
thofe it produces on the natural, I men-
tioned fome red Egyptian porphyries, the
bafe of which I believed to be horn-ftone,
rather than petrofilex, relying on the ana-
lyfes of Bayen, as related by Delametherie,
of an Egyptian porphyry of the fame co-
lour, and fimilar to thofe on which I made
my experiments f. But not having then
been able to analyfe them, from want of
time, I determined to do it afterwards, and
give an account of the refult, in another
part of this work, when I fhould again have
occafion to fpeak of this fpecies of volcanic
reck. I fhall here give this analyfis, which
affords a confirmation that the bafe of thefe
porphyries is not petrofilex, as they contain
magnefia, which is not found in that flone.

* See the Note at page 82, Chap. XI, in wliich I have
fpoken of the efTential characlers of porphyry,
t See Chap. XI.

Z From

( 172 )

From this circumftance, and the nature of
their conftituent principles, their bafe ought
rather to be called a horn-ftone, of the na-
ture of which it at lead participates. This
analytical obfervation is likewife here very
opportune, as it is an additional proof that I
have properly called porphyritic the lavas
with a horn-ftone bafe, and containing felt-
fpars, which are fo numerous in thefe
iflands.

The red Egyptian porphyries which I
analyfed are of two fpecies ; the firft has
been defcribed at page ii8 of Vol. JI. :
the fecond differs only in its colour being
of a lefs lively red, and in the abundance of
its feltfpars. It is evident, that to render
this experiment accurate, the fubftance of
thefe two ftones fhould be firft freed from
the Ihoerls and feltfpars which they con-
tain.

Firjl Specks.

Sllex, fomewhat reddifh, - 80
Alumine - - - 7

Lime - - "3

Magnefia

{ V3 )

Magnefia

2

Iron ' -

. 6

Second Species.

Silex

- 8i

Alumine

- n

Lime

- 4

Magnefia

2

Iron

- 4i

Befides the porphyritic lavas with which
the Eolian ifles abound, we have feen that
they contain great quantities of tufas ; and
thatStromboU is diftinguiihed from the other
iflands not only by its volcano, but by the
beautiful fpecular iron it affords ; and Lipari
by its chryfolites and zeolites, but ftill more
by the prodigious quantities of pumices and
glaifes which it contains. I cannot, indeed,
refled: on thofe enormous mafles of vitrifica-
tions, without renewed wonder ; which has
been ftill more increafed by the difcovery,
by means of the forceps and coral net, that
thefe vitrifications are continued from Li-
pari, till they join thofe of Vulcano, v/hich.

( '74 )

on the north and north-eaft fide abounds in
pumices, enamels, and glafles. The vitre-
ous fubftances,- therefore, of this ifland, and
thofe of Lipari, which, as has been faid, oc-
cupy about two-thirds of the latter, compofe
an accumulation of glafs, not lefs than fif-
teen miles in circuit. It is impofTible to at-
tend to this flupendous phenomenon with-
out feeling our curiofity excited to know
whether it be peculiar to thefe iflands, or
found likewife in other volcanized countries.
But fatisfa£loriIy to anfwer fuch a queftion,
it would be requifite that we fhould be ac-
quainted with the volcanic mineralogy of
all the volcanos in the world ; not only thofe
at prefent burning, but thofe extinguiilied,
which are infinitely more numerous ; in the
fame manner as we are with that of Viva-
rais and Velay, the iflands of Ponza, Vefu-
vius, Etna, the Eolian ifles, and the moun-
tains of Old-Brifach, by the labours of Fau-
jas, Gioeni, Dolomieu, Dietrich, and myfelf.
Of fuch a mineralogy, how^ever, we are
entirely deftitute. The greater part of thofe
who, either by chance, or from curiofity,
~ - have

{ '75 )

have viewed burning volcanos, have only
defcribed in their relations the moft com-
mon and general phenomena, lefs adapted
to increafe the knowledge than to amufe
the imagination of their readers, and excite

their wonder Shocks and undulations of

the earth — the fea in commotion, and raging
without a tempeft ; here retiring and leav-
ing its ftiores dry, and there inundating vaft
tracts of land — fubterranean thunders, and
roarings in the air above — the fun difappear-
ing in thick darknefs at noon — whirhvinds
of fmoke, afhes, and flame, burfting from
the yawning gulf — burning ftones hurled
towards heaven, and falling in a fiery hail
— torrents and rivers of liquid lava, fulphur,
and bitumen, pouring down on the valleys
below, and carrying terror, defolation, and
death — iflands, now fuddenly produced by
fubmarine eructations, and now torn from
their foundations, and fwallowed up by

earthquakes thefe compofe the ufual de-

fcrlptions of volcanos, which, though they
may not be ufelefs when the fads are faith-
fully ftated, and not magnifred by the ima-
gination

( i7« )

ginadon of the narrator; yet they common-
ly v*^ant one eflential requlfite ; that is, li-
thological deicriptions of the bodies ejeded
by thefe burning mountains. As glafs and
pumices, however, are known even to thofe
who are unacquainted with this part of na-
tural fciencc, we may, with certainty, or, at
leaft, with the ftrongell probabihty, con-
elude, that they are produced by the volca-
nos in the defcriptions of which we find
them exprefsly mentioned as making a part
of the ejedled matters, and that they are not
produced when not mentioned. Thus in
Iceland, the greater part of which ifland is
only an accumulation of volcanos either ex-
tindt or adive, it is certain, from the ac-
counts of travellers, that numerous glafTes
ace found, to which the name of Icelandic
agate has improperly been given, only be-
caufe they have the luftre and beauty of
that ftone. The prefent eruptions of this
ifland, likewife, not unfrequently contain
pumices ; but no perfon has ever afTerted
that there are entire mountains of thefe
ftones, or of glafles.

S The

( 1/7 )

The Iflands of Ferro are confidered as
volcanic, and produce the famous zeolites,
mixed, as it is faid, with lava ; but as yet
we know nothing more of them. The
minute account of each of thefe feventeen
illand^, publiflied by Jacobfon Debes, in which
no mention is made of the vitrifications,
authorizes us to conclude they do not exift
there.

Norway and Lapland have their volcanos,
which from time to time burft forth in
fearful eruptions, according to the accounts
of Pennant and others, who, however, give
us no further information.

Leaving thefe cold regions, and pafling
to Germany and Hungary, we find fome
trads of thefe countries that have like-
wife been fubjeded to fubterranean confla-
grations, which, however, have produced
no vitrifications, or fcarcely any. " I have
fought in vain the black agate of Iceland,
and the true pumice," fays the above-cited
Baron Dietrich, in his long and circumftan-

VOL, III. N tial

( 178 )

ilai Memoir relative to the volcanos near
Old-Brifach,

t

Proceeding to a milder cliniate, and ap-
proaching nearer to our own country, we
find that the extlnft volcanos of France af-
ford no pumices or glalTes ; which affertion
I can make on the authcrity of M. FaujaSy
who has written fo well concerning them,
than which one more unqueftionable cannot
be adduced.

It is not the fame with Italy ; the coiin-
-try in which fire has principally extended
its empire. The Neapolitan territory pe-
culiarly abounds in pumices, enamels, and
glalTes, as appears in the iflands of Ponza,
at Herculaneum, Pompeii, Mifeno, Monte
Nuovo, the Rock of Burnt Stones, Proci-
da, Ifchia, and the valley of Metelona *.
Even in our times Vefuvius has ejected
fimilar bodies ; but, with refpedt to Etna,
its fires rarely produce the fllghteft vitri-
fication,

' * Sec Chaps. IV, V, VI.

The

( ^79 )

The only place in Europe, which, in the
abiindiince of its pumices, can equal, or
perhaps furpafs Lipari, is the ifland of San-
torine. On this fubjedt we may confalt
Thevenot and Tournefort, two intelligent
travellers, who at different periods examined
this ifland, which has not hitherto, to my
knowledge, been conlidered by volcanifts
in this point of view.

The former, who vifited Santorine in
1655, obferves, that " many of the inha-
bitants live in caves, made under the earth,
which is extremely light, and eafily dug
into, as it confifts entirely of pumices."
He afterwards relates a fad:, which has a
particular relation to our prefent fubjed:,
fince it teaches us in what manner thefe
light flones may be thrown up, immediately
by the fea, in volcanic eruptions. His ac-
count is as follows :

" About eighteen years ago, oh a Sunday
^' night, a violent noife began to be heard
*' in the port of Santorine, which was like-

N 2 ** wife

( i8o )

" wile heard even to Chios, dlftant more
*' 'than two hundred miles, and was tliought
" to be occafioned by the Venetian fleet
*' having engaged the Turks ; in confe-
" quence of which great numbers of people
*' got upon the higheil places early in the
'* morning, to be fpectators of the battle ;
" and I remember the Reverend Father
*' Bernardo, a venerable man, perfeclly de-
" ferving credit, told me he was one among
*' the number of thofe who were fo de-
*' ceived, imagining they heard a violent
*' cannonade. They could however fee no-
'• thing. In fad:, this noife was caufed by
" a fire kindled in the earth, under the har-
*■ hour, the effect of which w^as, that from
" the morning to the evening a vaft quan-
*' tity of pumices role from the bottom of
" the fea, with fuch violence and noife as to
*' refemble repeated difcharges of cannon,
*' and fo infedled the air that feveral perfons
*' died at Santorine, and many loft their
'' fight, which they did not recover till
^' fome days after. This infedion extended
" as far as the noife which had preceded it had

" been

( >8i )

*' been heard j fince not only in this illand,
** but at Chios and Smyrna, all the filver
" became red, whether kept in coffers or
" in the pocket ; and the religious who re-
*' Tided there told me that all their chalices
" became red. After fome days the infec-
" tion ceafed, and the filver returned to its
" former colour.

" The pumices which were thrown up
*' covered the Archipelago in fuch a man-
" ner, that, for fome time, when certain
" winds prevailed, the harbours were i^o
'* blocked with them, that not even the
** fmalleft veflels could get out till a way
*' was made for them by removing the
" pumices v^ith long poles, and they are
" ftill feen fcattered over the whole Medi-
*' terranean, though in a fmall quantity *.'*

Tournef(pit, after having remarked from
Herodotus that Santorine was once called
KaA/.i7-;i or " the moft beautiful ifland,"
adds, that " its ancient inhabitants would

* Voyages de INI. de Thevenot, Prem. Part.

N 3 " not

( l82 )

" not at prefent know it, fmce it is covered
*' with pumices, or, more properly, is a
" mine of thofe ftones, which may be cut
" into great fquare blocks, as other ftones
*' are cut in the quarries *."

According to this traveller and to The-
venot, Santorine is thirty- fix miles in cir-
cuit ; v/hence it appears what a prodigious
accumulation of pumices there muft be in
this illand and the adjacent fea. It merits
notice, however, that neither thefe two
travellers, nor others who have written of
Santorine, make the leaft mention of glaifes
of any kind ; we may therefore venture to
affirm that the fubterraneous fires have,
there, never produced them.

If from Europe we pafs to the three
other quarters of the globe, we fhall find
in each a great number of volcanos, which
it w^ould be fuperfluous to enumerate par-
ticularly, fuch an enumeration having al-

* Voyage du Levant.

ready

( i83 )

ready been made by Faujas, BufFon and
others. I fliall only mention thofe which
afford prodii<5ts that have relation to our
prefent fubjeiSt.

We read that the iiland of Ternate, in
Afia, throws out a confiderable quantity of
pumices, as does, likev/ife, one of the nu-
merous volcanos of Kamfchatka.

As to thofe of Africa, we have but very
imperfecl accounts of them, with the fingle
exception of the peak of Teneriffe, one of
the loftiefl: of volcanos ; which, with refpe(ft
to its fituation, height, form, and crater,
and the hot fumes which iffue from it, has
been accurately defcribed by the Chevalier
Borda. But it were to be wi{hed that we
had a more complete defcription of the,
materials of which it is compofed ; as the
French traveller only tells us that they are
^' fand, black and red calcined Itones, pu-
•^ mices, and flints of different kinds *."

'•■^ Voyage en diverfes Parties de FEurope.

N4 It

( J84 )

It admits of no doubt that the highefl
mountains of America, as Chimboraco, Col-
topaxi, Sangai, Pichencha, &c. form a chain
of burning volcanos, the largeft exifting in
nature. We are indebted for the accounts
we have of them to M. Bouguer ; but thefe
are fuch as only tend flrongly to excite
our curiofity without gratifj^ing it. With
refped: to what relates to our prefent en-
quiry, we only learn from this writer, that
" fome mountains in the vicinity of Quito
" are compofed entirely, to a great depth,
" of fcorise, pumices, and fragments of
" burnt ftones of every fize *." As to
volcanic glaffes, he does not make the flight-
eft mention of them ; though it is well
known that the famous gallinaceous ftone,
which is univerfdly acknowledged to be
a moft beautiful American volcanic glafs,
of a black colour, is found in Peru, and
that, according to M. Godin, there is a
mine of it, feveral days journey from
Quito.

* Acad. Royale des Sciences, J 7 44.

If

( '85 )

If we now confider thofe parts of thefc
imperfecl accounts which relate to glaffes
and pumices, we fhall find, with refpedl to
the former, that the much greater part of
volcanos produce none, and that thofe
which do produce them, as in the Neapoli-
tan territory, Iceland, and Peru, are by no
means to be compared in this refpe£t with
Lipari and Vulcano. The fame may be
aflerted of Alicuda and Felicuda, the glafles
of which, though abundant in many parts
of thofe illands, are only found in flakes and
fragments. Thefe obfervations might like-
wife be applied to the pumices, did not the
immenfe quantity of them in the ifland of
Santorine equal, if not exceed, that of the
two Eoljan iflands above mentioned.

If we confider the volcanos known to us
under one general point of view, we fiiall
find that, though they have changed into
lavas an infinity of rocks, by which they
have produced mountains and iflands very
confiderable both in number and dimen-
fi ons, it is very rarely that they vitrify the
7 fubftances

( i86 )

fubftances expofed to their fires. Reflect-'
ing on the immenfe quantities of vitrifica-
tions at Vulcano and Lipari, which are
almoft all derived from feltfpars and petro-
filex, the idea fuggefted irfelf to mv mind,
whether fo great an abundance in thefe two
places, and fo great a fcarcity in others,
might not be attributed to thefe ftones be-
ing here extremely abundant, and very rare
elfevvhere. But this fuppofition does not
accord v/ith fa£t ; as we have (e^n. in many
other volcanic tradts, which I have defcribed,
and fhall defcribe when I come to fpeak of
the Euganean mountains, that both thefe
ftones may be changed into lava without
that lava exhibiting the fiighteft appearance
of glafs. On the other hand we have
fliown, that, befides feitfpar and petrofilex,
many pumices have for their bafe the horn-
ftone and afbeilus, and many granite, as
M. Dolomieu has obferved. I am, there-
fore, of opinion that the caufe which has
produced them lliould rather be fought in
the volcanic fire, which rarely has fufficient
a6:ivity to vitrify the ftones and rocks on

which

( i87 }

which it exerts Its power ; though I grant
that the petrofiiex and feltfpar are more
adapted to this vitrification than other
flones. To produce a lava, a certain de-
gree of heat Is neceffary ; and a ftill greater
to convert it into pumice. The lavas, at
leaft thofe of the compad; fpecies, ufually
preferve the grain, hardnefs, and fometimes
the weight and colour of the primordial
rock ; but the greater part of thefe external
qualities difappear in the pumice, from
the ftronger adlion of the fire. This muft
operate ilill more in glafs, in which the ho-
mogeneity and finenefs of the pafte efface
every trace of its primitive texture.

Thefe gradual tranfitions of lava into
pumice, and pumice into glafs, I have feve-
ral times obferved, and indeed have already
defcribed, in the fame volcanic piece. It
has alfo been obferved, that a lava frequent-
ly paffes immediately into perfed; glafs,
which muft be caufed by a fudden heat,
greater than that required to change it into
pumice. This theory fatisfadorily explains

why

C «8S )

wliy fome volcanos produce pumices, but
never glafs ; as may be remarked of Santo-
rine. Their fires are only fufficiently
powerful to generate pumices, but not to
produce glafs ; an obfervation applicable to
the prodigious eruption from the fea de-
fcribed by Thevenot. On the contrary,
at Rotaro in Ifchia, at Vefuvius, and other
parts of the Phlegrsan Fields, as alfo at
Vulcano, Lipari, Felicuda, and Alicuda,
glafTes are found mixed with lavas ; which
fhews that the fire has aded unequally ia
thofe places. It is to be remarked, at the
fame time, that the heat requifite for vitrifi-
cation is not of the moft violent kind, as I
have {hewn in Chap. XVI.

We muft however obferve, that as the
produdlion of ccmpa£l: lavas is a fecret
which Nature has hitherto referved to her-
felf ; fmce v/e are unable to imitate them
with our common fires ; fo alfo are we
ignorant of the preciie caufes of the forma-
tion of pumices. Among iome thoufands
of fufions which I have made in the fur-
nace.

( iS9 )

nace, both of lavas and primordial rocks
and ftones, thofe likewife from which pu-
mices are moft frequently produced, as pe-
troiil^ces and feltfpars, I never obtained a
product which could be faid to poffefs all
the charad;eriftics of pumice. It has al-
ways been either a glafs, an enamel, or
fcoris ; nor do I remember to have read
or heard, that among the innumerable ex-
periments which chemifts have made upon
earths with fire, the refult ever was a true
pumice : and though in lime-furnaces we
may frequently obferve a change of certain
ftones into glafs ; yet they never produce
lavas fimilar to the volcanic ; and equally
incapable are they to form pumices. It
cannot be alleged that the fire of our fur-
naces is too ftrong to induce that flight de-
gree of vitrification which characterizes
pumices ; fince, when I have ufed a more
moderate fire, the fubfi:ances on w^hich I
made my experim,ents have either not
melted, or been more or lefs vitrified.

I (hall conclude thefe obfervatlons on the

pumices

( I90 )

pumices of LIpari with a remark relative
to their colour. Except a few that are
dark, they are all white as fnow. Hence
the mcuntaiii of Lipari, which forms the
great magazine of thefe ftones, is called
Campo B'uvico (the White Field) : but cer-
tainly there muft have been a time when
it fliould have been denominated Campo
Nero (the Black Field) ; at leaft it is certain
that pumices when newly ejeded from
volcanos are of a black colour. This re-
mark, which has been omitted by almoft
all who have made obfervations on this
fubjed, who content themfelves with faying
that this or the other volcano throws out
pumices, has been exprefsly made by Don
Gaetano de Bottls in his " Hiftory of the
Conflagrations of Vefuvius *." He tells
us, the pumices ejeded at various periods
by this volcano are black. He likewife
remarks, that on comparing them with thofe
which overwhelmed Pompeii, he found
them perfedly fimilar in their ftrudure.

* Iftcria di varj Incendj del Vefuvlo.

Their

( I90

Tiieir whitenefs was fubfequently acquired,
and probably was caufed by the impreffions
of the atmofphere.

Before I conclude thefe obfervatlons on
the Eolian ifles, I think it neceffary to fay
a few words on a fubjedl which has a re-
lation to the productions of Vulcano and
AHcuda, and on which the opinions of
modern naturalifts are divided ; I mean the
bafahiform lavas which are found within
the crater of the former ifland, and along
the fhores of the latter *, and which by
their conformation cannot but remind the
reader of the enquiries and difputes which
have taken place wdthin thefe few years
relative to the orifrin of bafaltes. To re-

o

peat all that has been written on the fubjed:
would fill a volume ; but I am far from
purpofing to tire either my own or the
reader's patience in any fuch manner. It,
befides, appears to me that this long agitated
queftion may, at prefent, be determined

* See Chaps. XIII and XVII.

without

( 192 )

without any very prolix argumentation.
Literary diiputes and differences of opinion
frequently arife from want of previoufly
fixing the ftate of the controverfy ; that is,
from not defining in precife and clear terms
the thing in queftion. Before we enquire
what is the origin of bafaltes, that is to fay,
whether they are the refult of the adtion
of fire or water, it will be proper to de-
cide what we mean by the term ; or ra-
ther what the ancients underftood by this
"word, which is the name they gave to a
certain kind of flones. It is now generally
known, becaufe it has been repeated by a
hundred writers, though perhaps by the
greater part without due confi deration, that
the word bafaltes is ufed by Pliny and Stra-
bo to denominate an opake and folid ftone,
of the hardnefs, and nearly of the colour,
of iron, commonly configurated in prifms,
and originally brought from Ethiopia ; of
which flone the Egyptians made fi:atues, far-
coph-^gi, mortars, and various utenfils. This
premifed, it remains to enquire whether
this ftone was of volcanic origin or net,

by

( m )

Ly repairing to the places where it was
found, and attentively examining the coun-
try to difcover whether it bears the cha-*
radteriftics of volcanization. This labour^
however, has not, to my knowledge, been
hitherto undertaken by any one ; but
M. Dolomieu, to whom Lithology and the
Hiftory of Voleanos are fo much indebted,
has difcovered, during his ftay at Rome^
ail equivalent, in fome meafure, vvith re-
fpedl to the folution of this queftion.
Among the many noble monuments in that
fuperb capital which are inftru£tive not on-
ly to the admirers of the arts, but to the
contemplators of nature, are a great number
of ftatues, farcophagi, and mortars brought
from Egypt, v/hich have all the charaders
attributed to bafaltes, and llkewife preferve
the name. Thefe he has ftudied with the
greateft attention, and declares that the
llone of which they are formed manifefts
no fign of the adion of fire. Among
other Egyptian monuments, he obferved
fome of a green bafaltes, which change co-
lour, and aifume a brown tinge, fimilar to
VOL. III. O that

( 194 )

that of bronze, on being expofed to the
flightefl heat. All thofe that have been
burned have acquired this colour ; which
proves, as he very judicioufly ohferves, that
the green bafaltes have never fuffered the
adion of fire *.

The Egyptian ftones, therefore, to which
the ancients gave the appellation of bafaltes,
have been produced by Nature in the humid
way. Thefe obfervations perfectly agree
with thofe of Bergmann on the trapps
produced in the fame way ; and which
have, both externally and internally, the
fame charaderiftics with the bafaltes t.

Werner, taking the term bafaltes in a
%vider fenfe, and underftanding by it all
thofe columnar ftones which, by their prif-
matic configuration, refemble the Egyptian
bafaltes, fuppofes both to have the fame
origin, and adduces, as a proof of that ori-
gin, the bafaltes of the hill of Scheibenberg,

* Rozier, torn, xxxvli. an. 1790.
t De Produclls Vulcanicis.

which

- i 195 )

Ivhich are the efFedl of a precipitation by
means of water ; and concludes that " ail
bafaltes are formed in the humid way ^K^^

Though I am willing to beftovv the pralfe
due to his difcovery, I cannot admit his
conclufion ; for though many bafaltes,
taking that term in the fenfe of this author
and other naturalifts, may derive their ori-
gin from water, many others are certainly
the produdl of fire.

I fhall not repeat what various v'olcanifts
have written on this fubjed, but merely
refer the reader to what I have already faid
relative to the bafaltine lavas of Vulcano
and Felicuda. With refped to the former
ifland, I have remarked, in Chap. XIII,
that I found within its crater a range of
articulated prifms, with unequal fides and
angles, which, in part, compofed one
whole with a mafs of lava ; and, in part,
were detached from it. 1 have alfo there

* Rozleri torn, xxxvili. an. lypi*

O 2 defcribe4

( 196 )

defcribed the qualities and nature of tliefeJ
pi'ifms. In Chap. XVII 1 have particular-
ly defcribed the literal lavas of Felicuda,
which, near the water, are prifmatic.

It is therefore evident, thatj in thefe two
fituations, the origin of the bafaltes there
found cannot be what it has been aflumed,
generally, by Werner and ether Germans,
but that it is truly volcanic. It confe-

o

quently appears that Nature obtains the
fame effed by two different ways. In the
fofhl kingdom, one of her grand operations
is cryftallization ; which, though it be mofl
frequently effected in the humid way, is
fometimes produced in the dry ; as we fee,
among other inftances, in iron, which Na-
ture cryftallizes within the earth, both by
the means of water and of fire, in which
latter way the beautiful fpecular iron of
Stromboli is produced *. Nor are there
wanting other inftances, of the cryftalliza-
tion of the fame metal by the adion of fire.

* See Chap. XI.

And

( 197 )

And did other metals exlft In the entrails
of volcanos, and the neceflary clrcumftances
concur to their cryftalUzation, it Is Indubi-
table that this may be effedled by fire as
well as by water. Thus we fee that, by
taking certain precautions, metalHc fub-
ftances afliime a regular and fymmetrical
difpofition within the crucible. The fame
Is true of bafaltes, the prifmatic configu-
ration of which, though not ftridly a cry-
ftallization, has the moft exad: refemblance
to it. Obfervation, llkewife, teaches us
that the fame combination of earths, ac-
cording to different circumflances, forms
prifmatic bafaltes, fometimes in the humid,
and fometimes in the dry way. The flone
called trapp, found In the mountains of
Sweden, is configurated in prifms, though
thofe mountains are of aqueous origin ; and
the horn-ftone, which is fo analogous to
the trapp, has the fame configuration at Fe-
licuda, notwithflanding it is a true lava.
In the fame Ifland, likewife, other bafalti-
form lavas have for their bafe fhoeri ia
mafs, and thofe of the crater of Vulcano,
O 3 the

( '98 )

the petrofilex ; which two flones, according
to the obfervations of M. Dolomieu, form
fome of the Egyptian bafaltes, which are a
work of the waters. Thefe two agents,
fire and water, are not, in fa£t, fo different
in their aCcion as we might at firft be in-
clined to imagine. The prifmatic figure in
the humid way arifes in the foft earth by
the evaporation of the water ; in confe-
quence of which the parts dry, contrail
their volume, and fplit into polygonal
pieces. The fame phenomenon may be
remarked in margaceous earths, imbued
with water, and expofed to the ventilation
of the air ; and I have frequently feen the
mud of rivers, when dried in the fun, in
fummer, to make pottery-ware, divide,
when it became dry, into fmall polyedrous
tablets. Similar configurations are pro-
duced in different lavas by the congelation
and contraction that take place by the pri-.
vation of the fire which held them in a
flate of fluidity.

It appears to me, therefore, that the dlf-

pute

( 199 )

pute relative to the origin of bafaltes is at
an end ; nor would there be any difference
of opinion if, inftead of generalizing ideas
and fabricating fyftems, naturallfts would
make an impartial ufe of their own obfef va-
tlons and thofe of others. Some volcanlfts,
perceiving that the generation of various
bafaltes is evidently igneous, have immedi-
ately inferred that all muft have the fame
origin. In confequ^nce of this principle,
they have drawn lines or zones, in different
parts of the globe, indicative of extln(St vol-
canos, which they have inferred from find-
ing bafaltes there ; and thus pourtrayed a
pidure of prodigious dimenfions, repre-
fenting the ruins caufed in the world by
fubterranean conflagrations. Other natu-
rallfts, on the contrary, being convinced
that certain bafaltes are the produce of
w^ater, have affigned to all the fame origin.
From the fad:s now adduced, it is, however,
fufficiently evident that both thefe hypothe-
fes are erroneous. The bafaltes, taking
the term generally, when examined de-
tached, do not bear exclufively any declfive
O 4 marks

( (200 )

inarks of their origin. Local circumftance^
alone can determine to which of the two
principles it is to be afcribed ; to difcover
^?vhich we muit attentively examine whether
the places where thefe figured ftones are
found exhibit any indubitable figns of vol-
canization. Yet even thefe are frequently
not fufficient, as there are many hills and
mountains which owe their origin to both
the great agents of nature, fire and water j
in w^hich cafe it will be neceffary to re-
double our attention, and fix it on the fub-
ftances originating from each ; to deter-
mine, by the relations thefe have to the ba-
faltes, from which of the two the latter de-
rive their formation. By diligently em-
ploying thefe means, we fliall be certain,
without fear of error, to elucidate and ad-
vance the enquiries relative to baialtes, and
be enabled accurately to determine which
of them are to be afcribed to the adlion of
water, and which to that of fire.

But here a fecond queftion occurs, not
lefs interefting than the firft, relative to the

caufe

( 201 )

caiife why certain lavas, differing from in-
numerable others, become bafahiform; fmce,
if this configuration depended on conge-
lation, it muft be found in all lavas when
they had ceafed to flow. The firft writer,
to my knowledge, who has adverted to
this is M. de Luc, who, in the fecond vo-
lume of his Travels, is of opinion that they
have taken this regular figure in the fea,
by the fudden condenfation which took
place on their flowing into it in a liquid
fl;ate ; other fecondary circumflances, how-
ever, concurring, fuch as a greater homo-
geneity, and a certain attradion of their
parts.

Of the fime opinion is M. Dolomieu ;
though he does not deny that even porous
lavas may fometimes, likewife, take the
form of prifns. The former of thefe opi-
nions is little lefs than hypothetic, while
the latter is fupported by fads too import-^
ant to be curibrily fl:ated. M. Dolomieu
obferves that all the currents of the lavas of
Etna, the periods of which are preferved in

hi (lory,

(203)

hiilory, have conllantly experienced two
effects in their congelation. Thofe which
have cooled in the air, have divided, in
confequcnce of the contradion they have fuf-
fered by the lofs of their caloric (heat , into
irregular mafles ; while aK the others, which
have precipitated into the fea, have, on their
fudden congelation, contracted in a regular
form, and divided into prifmatic columns,
which form they have only taken in the
parts in contact with the water of the fea. Of
this he met with evident proofs along the
fhore which extends from Catania to Caftello
di Jaci ; and the famous lava of 1669, though
unapt to the prifmatic form, from being
fpungy and little in qMr-ntity, yet in fome parts
exhibits a kind of rude imperfed; prifms.

Among the objeds to which I was at-
tentive in my volcanic travels through the
two Sicilies, the prifmatic lavas were cer-
tainly not the lad. While making the cir-
cuit or the Eolian iflands, of Etna and of
Ifchia, 1 conftantly obferved carefully the
CQnformatlcn of the flony currents which

fall

( 203 )

£ill into the fea. I have remarked, when
treaiing of Ifchia, that this configuration 13
frequently prlfmatic, and that the prlfms
are conftantly formed In thole parts of the
currents which immerge into the water,
and reach to a few feet above the level.
This obfervation of mine certainly accords
admirably with thofe of M. Dolomieu ; the
fituation of thefe prifms clearly fliowing
that they were formed at the time of the
immerfion of the lava into the fea, Vx^hich,
when it flowed, rofe to where they begin
to appear. But, though I agree with him
in this, I cannot in the remainder of my
obfervations. Alicuda, as v/ell as Felicud.i,
prefents us with numerous currents and
rocks that defcend into the fea ; and they
are likewife found at Saline, Lipari, Strom-
boli, Panaria, JBafiluzzo, and Vulcano ;
but thefe rocks and currents, which to-
gether extend over a fpace of more than
fixty miles, do not aiford the flighteft indi-
cation of prifms.

As I went by fea from Meffina to Cata-
nia,

( 204 )

nla, and returned to Meflina from Catania,
I had an opportunity twice to examine, at
my leifure, that tra6t of fhore, which, for
the fpace of nearly three-and-twenty miles,
is volcanic. One third of it, beginning at
Catania, and proceeding to Caftello di Jaci,
confills of prifms more or lefs charadierized,
and fuch as they have been defcribed by
M. Dolomieu j but the other two thirds,
though equally compofed of lavas with the
former, and for the moft part falling per-
pendicularly into the fea, have no fuch
figure ; and only prefent, here and there,
irregular fiflTures and angular pieces, fuch
as are, generally, obfervable in all lavas,
which feparate m^ore or lefs on their conge-"
lation.

In my circuit by fea round the fhores of
Ifchia, I was particularly attentive, as I
was every where elfe, to the conformation
of the lavas ; and here there feemed a
great probability of finding them prifmatic,
from the abundance of them which in
different dire(^cions and angles fall into

the

( 265 )

the fea : but I have already obferved, wheti
treating of the ifland, and I now repeat
it, that I did not find one with a regular
form.

At Naples, the prifmatic lavas of the
currents of Vefuvius, under the Park of Por-
ticl, have been much fpoken of. When I
made my cbfen^ations on this burning
mountain, I had not time to vifit thefe la-
vas. It is with great pleafure, therefore,
that I learn they have been examined by
a perfon fo well experienced in matters of
this nature as the Chevalier Gioeni un-
doubtedly is. But the celebrated prifms
difapppeared in the prefence of fo accurate
an obferver. The following is the account
he gives ; which is of confiderable import-
ance to our prefent fubjed: : — " I wifhed
" to examine the bafaltes which were
" pointed out to me as to be found on the
" fea-fhore, under the Royal Park of Por-
" tici ; but they proved to be only a com-
" pa(ft lava, with perpendicular and ex-
** tremely irregular fiffares, forming qua-

" drangular.

( 206 )

*' drangular, and fometimes trapezoidal pU
" lafters, which have been employed in
" buildings. Similar fiflures are likewife
*' obferved in tufas, and earths of different
" kinds, and can never miflead any perfon
" accuftomed to them, and acquainted with
•' their true caufes."

By this faithful relation of fads, I flatter
myfelf, I have clearly fhown that it cannot
be fupported as a general hypothefis, that
flowing lavas take a prifmatical configura-^
tion from the fudden coagulation they fuffer
on falling into the fea.

It may, perhaps, be objected, that thefe
prifms once exifted in the lavas I obferved,
but that the irrefiftible violence of the
waves, in a long feries of years, has cor-
roded and deftroyed them.

Every perfon acquainted with the fub-
jed: muit immediately perceive how little
folidity there is in this objedion. I admit
that the violence of the fea may, in fome

lavas.

( 2o; )

iavas, have totally deftroyed thefe prifms;
but that it can have had that efFed on all,
and through fo extenfive a fpace, is utterly
improbable. Nor is it conceivable that
Felicuda, among the Eolian ifles, fhould
ftill preferve its prifms perfedi:, while the
reft of thofe iflands have entirely loft theirs,
notwithftanding they are all equally expofed
to the fhocks of the waves.

I cannot here omit another remark. It
is certain that more than one of thefe
lllands w^ere not formed by one eruption,
but by fucceflive ejedions of lavas accu-
mulating on each other ; and in fome deep
fiflures, occafioned by the fea, this fuccefTive
formation is difcoverable by the eye, as we
may perceive five or fix different ftrata
of lava one above the other. The inter-
nal ftrata in very remote periods", having
flowed into the fea, as the external flowed
afterwards ; it is evident that, if the latter,
on touching the water, became prifma'ic,
the fame change muft have taken place,
alfo, in the former ; w^hich being defended
4 from

( 2o3 }

from the injuries of the fea, by the extCf-^
nal ftrata, muft ftill preferve their prifmatie
configuration, of v/hich, however, no traces
remain. We muft, therefore, conclude
that innumerable lavas may fall into the
fea, without having their external appear-
ance in the leaft changed by the fudden
congelation VN^hich then takes place.

That the prifmatie configuration of lavas
is not always the effedl of their immerfion
in the waters of the fea, likewife appears
from many of them taking the fame form
in the air ; of which v/e have a diftin-
guifhed example in the crater of Vulcano.
Here, certainly, we cannot fuppofe any in-
tervention of the waters of the fea. Si-
milar obfervations have been made on
Mount Etna by the Chevalier Gioeni.
" I have obferved,'^ fays he, in the work
before cited, " bafaltic columns, at the
" fummit of Etna, and nearly on a level
" with the bafe of its vaft crater, v^^here
*' there is certainly no probability of the
" fea ever having reached j and I have

" frequently

( 209 )

** frequently found polyhedrous bafaltes
" perfcdly charadterized in excavations
*' made by men in the centre of lavas,
" which have iflued from the fides of
" Mount Etna, in periods much pofterior
" to the retiring of the fea."

I jfhould, however, appear deficient in
candour, did I not mention that M. Dolo-
mieu admits that lavas may fometimes,
in the air, aflume the prifmatic form, if
they fall into clefts and fiffures where they
fuddenly cool, of which he adduces an ex-
ample in the iflands of Ponza.

I {hall only remark, that I do not per«
ceive the abfolute neceffity of the fiffures
in this cafe ; fmce we frequently find lava3
with this configuration in perfe<ftly open
places ; as I have feen in the great mouth
of Vulcano. And with this opinion the
obfervations of Gioeni on Etna certainly
accord ; for, had he remarked the concur-
rence of fuch a circumftance, he, undoubt-f
cdly, would have mentioned it.

VOL. III. P What

( 2IO )

What concKifion, then, ought we tode-
duce from all thefe facts and obfervations ?

FirR : that many bafaltiform lavas have
aflumed this organization on coagulating
within the fea.

Secondly : that others have taken the
fame form, merely in cooling in the open
air.

Thirdly : that Innumerable other lavas
have not taken this figure, either in the fe:i
or in the air.

It appears, at firft view, that thefe dif-
ferences depend on the different nature
of the lavas themfelves. This opinion,
at leaft, is rendered probable by what we
obferve in earths penetrated with water,
which, in drying, take, more or lefs,
prifmatic forms, as has been obferved fre-
quently in the argillaceous kinds. I have
feen, when a turbid torrent has been in-
troduced into a ditch through an argilla-
ceous marie, the latter, in drying, divide

into

( 2" )

"i5to polyhedrous pieces ; but when the
water pafTed through chalk, or calcareous
marie, the greater part of the pieces were
amorphous. When we however obferve lavas
with requifite attention, this conformation
in them feems to be efFed:ed differently.

It has already been faid, that feveral of
the prifmatic lavas of Felicuda have for
their bafe fhoerl in mafs ; but it is true
that other congenerous lavas of the fame
ifland, which form as it were walls per-
pendicular to the fea, are fmooth over their
whole fuperficies. A firailar fmoothnefs
is obfervable in fome of thofe of Mount
Etna, on the fliore between Meffina and
Catania, w^hich have for their bafe the
horn-ftone ; though others extremely re-
fembling them, between Jaci Reale and
Catania, are formed in prifms.

Compa£lnefs and folidity are, like wife,
not a neceffary condition in lavas, to this
appropriate cryftallization. This has al-
ready been remarked by M. Doloraieu ;
P 2 and

( 212 )

and I have obferved that many amorphous
lavas on the fhores of feveral of the Eolian
iflands are more compact than the prifmatic
lavas of Felicuda.

What then can be the intrinfic circum-
ftance of the lava vv^hlch determines it thus
to cleave in the prifmatic form ? I confefs
I am ignorant : and who can fay that we
do not feek it in vain within the lava,
ilnce it may be extrinlic and adventitious ?
Such, certainly, appears to be the opinion
of M. de Luc ; and, more exprefsly, that
of M. Dolomieu, who, to explain the
phenomenon of volcanic prifms, has re-
courfe to a fudden congelation, and inflan-
taneous contraction of lavas.

The fadls which we have adduced re-
lative to lavas, both prifmatic and not
prifmatic, it has been feen, do not always
accord with thofe related by the French
naturalift. But even on this fuppofition,
which is inconteftable, may we not retain
the fame principle of explanation, which,

5 to

( 213 )

to fay the truth, appears to be fufEclent,
with fome requifite modifications ? Thefe
I will endeavour to fuggeft, illuftrating
my conjed:ure by the two cafes above ad-
duced ; the one, that of the lavas which
take the form of prifms merely from the
conta<3: of the atmofphere, as in Vulcano
and near the fummit of Etna ; the other,
that of the lavas which refufe to take fuch
a form even within the fea, as at Ifchia, in
fome parts of the bafe of Etna, and in all
the Eolian ifles except Felicuda.

As to the former, may not a fudden
coagulation and contradion have taken
place in fome lavas from the mere influence
of the atmofphere, though the lava was
not included in any cleft or fiflfare ? It
is fufficient that it be fuddenly deprived
of the caloric (heat) by which it is pene-
trated, and which rendered it rarefied and
fluid. To this deprivation a lava of little
thicknefs will be very liable ; fmce a body
iofes its heat the fooner, the lefs its thick-
nefs and denfity. This fudden contradion
P 3 may

( 214 )

may alfo be produced by the clrcumflances
of the atmofphere ; as, fhould a ftrong
wind, of a very cold temperature, blow at
the time. The melted lavas in our cru-
cibles will be found to give greater weight
to this latter conje(^ure. If they are
taken from the furnace, and caufed to pafs
through a heat gradually lefs ; their fur-
face, as they cool, will only fplit in a few
cracks, of little depth, arid ufually irregu-
lar i but, when they are immediately, in
the winter time, carried into the cold air,
the fiffures, befides being deeper, will fre-
quently be difpofed in luch a manner, as
to form fmall polyhedrous prifms, which
may eafily be detached from the reft of the
lava.

With rcfpe^t to thole lavas which do
not affume a prifmatic form though they
fall into the fea, it is certain that, to take
that conformation, their mafs muft have a
ftrong degree of effervefcence and dilatation,
and that it muft be deeply penetrated with
the igneous fluid, otherwife the contradion

neceifary

( 2«5 )

ncceflary to produce prifms cannot take
place. But many currents which defcend
from the fummit of burning mountains to
the fea, muft have loft their eftervefcence
with their heat in fo long a courfe, and
fcarcely contain fufficient to continue their
motion downwards, which, perhaps, would
ceafe, were it not for the impelUng gravity
of the lava, which frequently falls into the
fea perpendicularly.

Such is the hypothefis by which I would
explain the caufe why fome lavas have afr
fumed a prifmatic conformation without
any concurrence of the fea-water, and
others exhibit no appearance of it in places
where they have immerged into the fea.
I neverthelefs leave every one to form his
own opinion ; and fhould an explanation
of thefe important fadts be difcovered, pre-
ferable to mine, which I confider as only
conjectural, I fhall receive the communica-
tion of it with fmcere gratitude, and adopt
it with pleafure.

P4 CHAP.

( ^^6 )

CHAP. XX.

DIGRESSION RELATIVE TO THE DIFFER-
ENT VOLCANIC PRODUCTIONS OF THE
EUGANEAN MOUNTAINS.

Exciirfion made to the Euganean mountains^
by the author^ during the vocations of
1789, in order to compare the produBs of
the volcanos he had vifited 'with thofe of
the mountains of Padua — Defcription of
different fpecimens colleBed by him in this
excurfton — Three kinds of lavas at Monte
Cajlello — Erratic petrofdices mingled with
them^ of uncertain origin — Lavas of MoU"
te del Dofiati^ fome with a petrofdiceous
hafe^ and others with a horn fl one -Proof
that one of thefe once formed currents —
The accumulated prifmatic columns of
Monte Roffo have not for their bafe the
granite^ but the porphyry — Monte Ortone
abounds in prifmatic lavas ^ but fuch as are
lefs charaElerifed in their coffiguration —
Lavas of Monte Merlo with a granitous

bafe

( 217 )

bafe — Black mica one of the component
parts of this granite, which has the pro*
pcrty of being attraSfed like iron by the
mag?iet., a property poffeffed likewfe by the
other micas of the Kuganean mountains —
The micas of the primitive granites defli-
tute of this property y but capable of receiv-
ing it by the action offre — This important
faflfurnifhes a clear proof of the volcani-
%ation of the Kuganean mountains — Nodo"
fities of quartz contained in this granitons
lava, probably produced by filtration pofe-
rior to ignition — The fame obfervable of
fome fldoerlaceous nodofities included in it —
Thefhoerls of the Kuganean mountains aB
oil the magnetic 7ieedle, like thofe of other
volcanic coimtries, and in that differ from
thofe which are not volcanic — Calcareous
carbonates intermixed with the lavas of
the Kuganean mountains — Klints frequent"
ly found among thefe calcareous carbonates^
'which prefent the mofl fpeciotis appearance
of the change of lime into flex — Proof by
chemical analyfis, that it is not neceffary to
have recourfe to any fuch change to explaiti

this

( 2l8 )

this appearance — Strata of globes neai^
Teolo abounding in particles of pitch -Jl one
•"—Feins ofpitch-fonc lavas atBajainonteand
Sieva — Groups of pumices enclofed in one
of thefe veins — Comparifon^ in the dry
ivay^ cf the non-volcanic pitch -f ones ivith
the volcanic — Proof by the humid ivar,
that both are of the fame kind — EJfential
differences bet-ween the pitch fone lavas and
the volcatiic gl^ffcs — Volcanic produBions
cf Schivanoja^ Monte Merlo^ Mafcabo^
^remonte and Pendfe^ ivhich have been
ftyled volcanic glafs by a living writer y
but ivhich in reality can only be called
pitch-f one lavas ^ and but one of them ^ at the
utuiof^ a vitreous lava — Mi/lake of this
author in having taken for volcanic glafs
fame pieces cf glafs from the furnaces of
Murano^ near Venice^ vohich he cafually
found in ihof mountains — Remarks on
this accident^ ifjhich fjould teach us to be
cautious in forming a judgment ivhether a
mountain be volcanic or tiot^ from finding
a detached piece of glafs ^ or other produc-
tion of the fire J fince it may be uncertain

whether

( 219 )

whether that Jire ivas vclcmiic or 7iot^—^
Pojfibility of being equally deceived by pro-
dun'ions truly volcanic but erratic — Proof
of this from a clrcumfance which hap-
pened to the author — Little credit to be
given to accounts intended to prove the ex-
Ifience of ancient volcanos — NeceJJity that
fuch accounts fhould be lithologlcally dc^
tailed — In ivhat manner our judgments
relative to lavas may be frequently mif-
iaken — Volcanic rocks may have the inoft
fpe clous appearances of lavas ^ though they
never formed currents — When other proofs
are vnafitlng^ cellulofity the mofl certain in-
dication (hat volcanic rocks have flowed in
a fiream — This cellulofty found In many
Eugatiean lavas — Singularity of the felt-
fpars of a lava near Rua^ which have^
almoft ally a portion cf that lava for their
central nucleus — Lavas of GalzlgJiano^
Plgozfzo, Monte Nuovp^ Monfellce^ a?id
Arqua — -Singular lava of Monte Nuovo
coinalnhig fcltfpars become earth ; and an-
other at Monfellce contaijihig pumices —
Lavas cf Catajoy one of isohlch forms co-
lumnar

( 220 )

iumjiar pr'tfms — RefleSlions and corollaries
'—The Eugatfean mountains once were
iflajidsy like thofe of Po7ivs>a^ the Eoliany
Safitorine^ ^c. — Their prodigious afiiiqui-
ty^ and vicinity to civilized places^ two
caufes of the great chajiges they have un-
dcrgone — Their lavas analogous to thofe
of other volcanos^ in having rocks for their .
bafe — Comparifon between the rocks of
ether volcanos and thofe of the Euganean
mountains — Immeife depth of thefe rocks^
ivhich would remain unknown to men
were it not for volca?ios — Three different
bafes in the Euganean rocks ^ defer vi7ig ob-
fervation : the feltfpar in the mafs^ the
volcani%ed petrofilex^ extremely refembling
the natural^ and the pitch-fone — Volcanos
ivhich have fiot this fone^ and others in
ivhich it is found more or lefs — Magnefa
7iot me of the elements of the pitch-fone of
volcanos^ as fume have thought — Interef-
ing obfervaiion of the change of petrcflex
into pitch-fone — Chemical analyfis of thefe
two fones agreeing with this obfervation —
FrobablUty that fome volcanic pitch-foncs

are

( 221 ) ;

are derived from the tion^volcanic — Our
commoftjirc equally vitrifies the Euganean
lavas, and thofe of other volcanos — Singu-
lar obfervation relative to the eafy fufon of
feltfpars — Euganean bafaltes the products
of fre — One of the fl ones of thcfe moun^
tains formed in prifms in one place i?i the
dry ivay, and in another in the humid —
Confrmatio7t of the offer tion, that it can
ordy be determined by local circumflances^
which of the two modes Nature has em-
ployed in the conformation of bafaltes.

I

N the year 178S, I prefented the Impe-
rial Mufeum of Pavia with an ample col-
ledtion of volcanic prcdudlions, from the
two Sicilies ; and afterwards formed the de-
fign of increafing it, during the vacations
of the following year, with others of the
fame kind from the mountains of Padua
which had been extindl from time imme-
morial. This defign I carried into efFe<ft
with the affiftance of a companion, than
whom I could not have wifhed for one

better

( 22 2 )

better qualified to aid my refearches ; the
Marchefe Antonio Orologio, an accom-
plifhed gentleman, and well acquainted
with thofe mountains, as he has proved by
feveral Eflays replete with accurate and in-
terefting obiervations relative to them.

Having made feveral excurfions with
this able guide, I examined the products
I met with at my leifure, and feledted thofe
that appeared moft fuitable to my purpofe :
feveral of which I fhall now proceed to
defcribe ; as they are extremely well ad-
apted to form a comparifon between the
Padaan rocks and thofe of other countries
equally volcanic, which I vifited ; as alfo
to fhew the nature of the modification3
caufed in both by Ere j which comparative
obfervations, I flatter myfelf, will not a
little conduce to enlarge the fphere of our
knowledge refpedling volcanos *.

I repaired,

^ At firft view, It may, perhaps, appear fuperfluous
that I fnould fay any thing on the Euganean produdls,
as a Defcriptive Catalogue has aleady been given of
them by Sir Jchn Strange. This naturalift has un-
doubtedly

( 2^3 )

I repaired, therefore, to Giara, in Sep-
tember 1789, to the delightful villa of the
Marchefe Orologio abovementioned, fitu-

ated

doubtedly contributed much to the fodil hiftory of thefe
mountains, the volcantzation of which he firft difco-
vcred and made known. We are likewife greatly in-
debted to him for the catalogue he has annexed, and
which forms a kind of appendix, to his hiftory. But,
befides that I frequently met with objeifls different from
thofe obferved and defcribed by him, the views with
which we treated the fame fubjecl were entirely differ-
ent. I propofed to defcribe lithologically, and thence
to characterize, the Euganean products I met with in
ray excurfions, in the fame manner as I have defcribed
thofe of the two Sicilies: Sir J. Strange was fatisficd
with giving only fimple iiidications of them ; nor do T
think I fhall in the leaft detra£l from the merit of this
excellent author, if I fay thefe indications were not al-
ways the moft accurate ; fuch a defedl being lefs im-
putable to him than to the time in which he wrote j
fmce it is only within thefe few years that the minera-
logy of volcanos has been ftudied with precifion and
accuracy.

I fliall take this opportunity to 'anfwer a quef-,
tlon which may be aficed j which is : Why, if I in-
tended to give a lithological effay on the Paduan volca-
noes, I did not mention it in the Introdu£lion, whtrc I
enum.erate the principal beads of the vi'ork. I reply

that.

( ^24 )

ated nearly at the foot of the Euganean
hills, and proceeded with him, without de-
lay, to make refearches in them ; examin-
ing firft the ftones of Monte Caftello.
This is a fmall woody mountain, from
which arife feveral rocky points adhering
to the body of it, and affording three fpe-
cimens of lava.

The firfl: has an argillaceous bafe, a
coarfe grain, and blackiih colour. It fhines
in many parts with black micaceous points,
and is fprinkled with reddifh fpots, like
thofe of feltfpar, in many oriental porphy-
ties ; and which are no other than Icaly
flakes of feltfpar, accompanied with a few
black fhoerls.

that, when I wrote that Introduclion, I did not perceive
the importance of the fubjecl ; and of feparating the
©bfervatlons I had made on other volcanoes from my
remarks on the Euganean hills. I likewife, at that
time, did not think it proper to mention this excurfion
particularly, as the remarks I made in the courfe of it
then remained unmethodized in my journals, and J
feared that I might not find fufiicient leifure to reduce
them to order, as I afterwards was enabled.

The

( 225 )

The fccond lava, which is of a light
grey colour, might at firft be taken for a
cari)onate of lime ; but, when attentively
examined in the recent fradures, its bafe
is found to be a hard horn-ftone, contain-
ing fome black mica, and a few feltfpathofe
points.

The third lava, with fome varieties little
differing from it, has, in like manner, its
bafe of horn-ftone. Its colour is a pale
grey, its pafte earthy, w^ith an argillaceous
fmell ; and, befides numerous particles of
black mica, it contains thick redangular felt-
fpar lamellae.

The fKoerls, micas, and feltfpars of
thefe three lavas, when fufed in the fur-
nace, arc, together with the bafe, reduced
to an enamellar and cellular fcoria.

Though the three ftones above defcribed
have not the appearance of having ever
formed currents, nor the porofity of fome
lavas, I do not hefitate to call them by that

VOL. III. Q^ name;

( 226 )

name ; not only becaufe they are Integral
parts of this volcanic mountain, but becaufe
ihey appertain to a kind of ftones of the
Euganean hills, which, as will appear
from fads hereafter adduced, bear evident
marks of having fuffered fufion.

In the midft of thefe lavas are found
pieces of petrofilex of a very fine grain,
which, as they are detached and fcattered,
I am unable to fay whether they have been
affedled by the fire, or thrown out un-
touched by fome volcano. All of them
contain cryftallizations of micas, flioerls,
and feitfpars ; and thefe cryftallizations
fufe in the furnace together with the petro-
filiceous bafe.

From Monte-Caftello I proceeded to the
neighbouring mountain Donati. At the
top it has a double fummit ; and both there
and at the bafe, having broken off fevcral
pieces from the ftony mafs of the mountain,
it appeared to me that the lavas of which
it is compofed may be reduced to two
4 kinds

( 227 )

liincls— lavas with a petrofillceous bafe, and
lavas with a horn-ftone bafe. The former
hive a fmooth, and, fometimes, conchoidal
fradure, a fine and compact texture, and
contain a confiderable quantity of flicerls
and rhomboidal feltfpars. The glafs pro-
duced from them in the furnace is white,
with a complete fufion of the above-men-
tioned cryftalhzations.

The lavas with a horn-flone bafe are
foft ; all emit an argillaceous fmell, have
an earthy texture, and, for the moft part,
abound in feltfpars, cryftallized fhoerls, and
black hexagonal micas. One of thefe lavas
bears the mod evident marks of having
flowed. It is full of fmall pores and vacui-
ties, not only on the furface but in the in-
ternal part. Thefc vacuities are of different
fizes, from thofe that can only be difcovered
with the microfcope, to thofe half an inch
in breadth. Many of them are oval, and
the longer diameter is almofl: always placed
in the fame diredion. This obfervation is of
confiderable importance ; firft, becaufe it
Q^ 2 fhovv'S

( 228 )

fhows that this rock was once fluid from
the adlion of the fire ; fince otherwife thefe
innumerable vacuities would not have been
produced ; and, fecondly, that it has been
in motion, in confequence of which the
bubbles, naturally of a round figure, have
taken a form more or lefs oblong. The
truth of this deduction is confirmed by
what has been obferved in many of the
lavas of Lipari. Some of thefe cavities are
filled with cryflallized carbonate cf lime.

This lava is likewife remarkable for the
large fize of the fhoerls it contains ; feveral
of Vvdiich are ten lines in length, and fome
even an inch. They are of a black colour,
have a fcaly fracture, and facets of fo lively
a luftre, that they may compare with the
moft beautiful cryf^als of fpecular iron.
Both when detached, and v;hen incorpo-
rated with the lava, they melt, in the fur-
nace, into a black, compadl enamel, giving
fparks copioufly with fteel, and of a luftre
little inferior to that of the fnoerls them-
felves. Fufion fucceeds equally in the other

lavas

( 2-9 )

lavas of the horn-ftone bafe, with the vitri-
ficatio'n of the fhoerls, feltfpars, and micas.

From IMonte del Donati I proceeded to
Monte RoITo, celebrated for its mafs of
prifmatic columns. The iirfl: naturalift
Vvho pointed them out was Ferbcr ; they
afterwards were defcribed by Sir John
Strange*, who obferved that they are al-
moft perpendicular to the horizon, and
parallel to each other ; that they differ in
form and fize, and feem intimately con-
ne(Sled with the ftony body of the moun-
tain. On examining them, I found the
obfervations of the Englifh writer perfectly
accurate ; but I cannot refrain from mak-
ing a few remarks en the nature of this
columnar aggregate which he calls gra-
nitous. Both in the internal part and ou
the furface of thefe prifmatic columns, felt-

* Opufc. Scelt. di Mllano, t. i. in 4ro. This de-
fcription was read to the Royal Society in 1774, and
is inferted in the Phllof. Tranfacf. vol. Ixv. part i. for

( 230 )

rpars, mica, and fhoerls, are very confpicu-
ous to the eye. The ilioerls are rhomboidal
prifms, a line, or two lines, in length, at
the moft, and about half as broad, femi-
tranfparent, of a whitifh colour, fhining
but little on the furface, but very confidera-
bly in the fractures, and with a luflire of
changeable colours. The mica is, for the
moil part, black ; but fometimes of a
golden yellow, and in flat, hexaedral,
opake, laminous, and extremely lucid
• prifms, the largeft of which are little more
than a line in length. Thefe two ftones
are rather numerous ; but the fhoerls, which
are, for the moft part, lir.ear, are but few.
They are all three contained in a petrofili-
ceous pafte, become earthy by decompo-
fition, and, at the furface of the prifmatic
columns, almoft pulverulent, and of the co-
lour of a dead leaf; but internally it pre-
ferves the cbarader of the petrofilex, giving
fparks more or lefs with fleel, and being of
a dark colour. The furnace converts thefe
columns into an enamel inclining to a black

colour.

( 231 )

colour, with few but large bubbles ; a fu-
finn takes place in the fhoerls, but not com-
pletely in the fcltfpars.

From this defcriptlon we perceive that
this mal's of columns cannot properly be
called granitous ; the generality of natu-
raliRs, and the m.oft refpedable chemifts,
agreeing that by the term granite is under-
ftood a rock or ftone compofed of two or
more fubftances, frequently cryftallized and
united together without the appearance of
any connecting ground or cement. But
here the fhoerls, the m'ca, and the fe'tfpars
are enveloped in a petrofiliceous pafce ;
whence we ought rather to denominate
thefe columns porphyritic. The fame is
true of the remaining mafs of Monte RofTo,
which is almoft entirely formed of the fame
rock.

Under this bafalriform group we find

numerous globes of the fame rock, which I

judge to be pieces of pnfms that have fallen

down and become round by the erofion of

Q^ 4 their

( 232 )

their angles, in confequence of the decom-
pofition they have fiifFered by time and
the humid elements ; as it cannot be fup-
pofed that their globular figure has been
produced by iheir being rolled by the wa-
ters, fmce there is here no trace of either
river or torrent, and their decompofition is,
befides, very confiderable.

Monte Rofib is an ifolated mountain,
about a mile and a half in circumference.
On one fide of it, there is at its foot an ex-
cavation which the Benedidine Monks of
Praglia caufed to be made, to obtain ftones,
but which has been for fome time abandon-
ed. Ihe fides of this cavity exhibit very
apparent prifms ; though not fo perfedly
characfterized as thofe before defcribed.
Should other parts of the m.ountain be dug
into, it is probable that other groups would
be difcovered.

This certainly is not the only place pro-
du«5live of thefe figured ftones ; for we find
prodigious mafles of them at Monte Or-

top,e,

( 233 )

tone, rudely formed, it is true, but very
diftinguifliable. They confift of a lava of
a cinereous grey colour, of a perroGliceous
bafe, and marked, in many parts, witii thin
reddifli flreaks parallel to each other. A
confiderable number of rhomboidal, iliin-
ing, and tranfparent fel tfpars, and a few
black, hexagonal particles of mica are con-
tained in the bafe of this lava, which
changes in the furnace into a dark grey en- *
am>el, with the fufion of the feltfpars and
the micas. In feveral parts of the moun-
tain, when we dig into it, we find imper-
fect prifins ; and they frequently proje«£t
out near tlie fumniit, and on tie fides ; as
we may obferve in the road leading to
Praglia. The mountain U formed of this
lava, which, on the furface, is decompofed
and become earth, in which a number of
olive-trees grow and thrive. A fimilar de-
compoiitlon is obfervable at Monte Roflb,
the earth of which is, in a great meafure,
a mixture of fragments of micas, feltfpars,
and flioerls.

The

( 234 )

The Eiiganeari mountains, which form
maffes, for the moft part conical, fome de-
tached, and others coiitij2,uoii« at their bafes,
are principally compofed of lavas, with
which, in feverai of them, are mixed cal-
careous carbonates. Thefe two kinds of
ftones arc of fome value to the Venetians,
who ii^e the lavas, which they call mafegne^
to pave the ftreets, and the carbonates to
make lime. There are therefore here fe-
veral quarrie?, fomie of which are now
worked, while others, that are either ex-
haufl(d, or become iefs produdlve, are
abandoned.

I entered two of thefe quarries, the one
at Monte RoiTo, and the other at Monte
Ortone ; and, having continued there fome
time, determined to go down into fome
others, as I found they were extrem.ely
convenient for obferving in their fides the
ilony fubftances 1 wiflied to examine. I
therefore proceeded to Monte Merlo, where
there is a very large excavation of this kind
within the lava. To extrad the ftones,

which

( 235 )

%7]ilch are very hard, the labourers have
recourfe to the following dangerous method.
A man, faftened by a rope, is let down to
a certain depth againft the perpendicular
fides of the cavern ; and, the other end of
the rope being made faft at the top, breaks
the flone in pieces with pickaxes, availing
himfelf of certain vertical fiilures, which
greatly facilitate the labour. Mines are
like wife prepared, in fome cafes, which
blow the fragments of the ftone into the
air.

In this excavation, and in another of
lefs dimenfions, not far dlilant, the lava of
the mountain is truly granitous, and the
granite has for its bafe the feltfpar, which
is fo abundant that it compcfes the greater
part of the rock. It would be fuperfiuous
to dcfcribe it, as it is perfectly funilar, even
in its cryftallization, to that of Monte Rcflb
and Monte Ortone. Befides the feltfpars,
which, by their brilliancy and other exclu-
five chara(£«:ers, immediately declare their
mature, certain white fpots prefent them-

felves

( n6 )

felves to the eye, which at firil: view may
excite a doubt to what kind of ft nes they
appertain ; but, when exatiiined atteniively
and under dilTerent refledions of the light,
we are convinced that they are t:ue fclt-
fpars, but in part calcined. Thefe feltfpars
are accompanied with the ufual hexagonal
micas, and fome fhoerlaceous points.

This granite, liquefied by the volcanic
£re, reminds me of tlie great a(ftivity re-
quifite in our common fires, for the fulion
of granites that are not volcanic, and even
of thofe which are ; as I have ihown in
Chap. XII. I have fmce thougl t that pof-
fibly fo great a degree of beat was not ne-
ccflary in the prefent inftance, from this
granitous lava being deprived of quartz,
one of the elements of the granites on
which i made my experiment?,. and which
certainly is that among them m; ft relrado-
rj to fuhon. I have found, in fait, that
this iava, when continued a long time in
the furnace, affords a vitreous produd of a
black colour, and nearly homogeneous,

fome

( m )

fome feltfpars only being perceivable in it
in the form of v/hite fpots,

I have faid, a little above, that black mi-
ca is one of the component parts of this
granite. 1 fliall here add, that when it is
detached from the volcanic rock and ap-
proached to the magnet, it will adhere to it
like a particle of iron ; which property it
fhares with other black micas, before de-
fcribed, and with almoft all I fnall hereafter
have occafion to mention. This curious
phenomenon was pointed out to me at Ve-
nice, before I made my excurfion to the
Euganean mountains, by that excellent na-
turalift Sig. Giovanni Arduino. The greater
part of the ftreets of that capital are paved
with thefe Paduan ftones, and it was in
fome of them I was fliown this quality by
Sig. Arduino. He, indeed, was of opinion
that thefe fhining black particles were rather
particles of iron than of mica ; but ocular
examination convinced me that they apper-
tain to this ftone ; fmce with the lens v/e
may perceive that they con fill of delicately

thin

( 238 )

thin and femltranfparent lannns, whicbj
when touched with the point of a needle,
are found to be flexible and elaftic, and fe-
parate from each other. In the fire, as has
been faid, they vitrify, and the glafs pro-
duced from them is of a blackilh colour,
and femltranfparent.

The magnetic property of thefe micas,
among the many I have examined, I have
found in none vvhich enter into the compo-
fition of granites not affected by the firCo
In my return by land from Conilantinople
to Italy, I coUedted fpecimens of the ftones
compohng the mountains over which niy
road led me, and, among others, of a con-
iiderable number of granites, which, from
the nature of the places where they were
found, were certainly not volcanic. Many
more I found in the Alps, and other coun-
tries not volcanic. On the micas they con-
tained I m.ade experiments with the magnet ;
but I did not find one, whatever was its
colour, which fliowed the lead fign of at-
tradion. In fevcral of them, indeed, I

found

{ 239 )

found it after they had been expofed for
feme time to the fire. This exclufive pro-
perty of the Euganean micas is therefore a
proof that they have felt the influence of
this agent, and is a ftrong confirmation of
their volcanization.

Before I difmifs the quarries of Monte
Merlo, I fhall briefly ftate two facSts not
undeferving the attention of the readen
Firft, it is not unufual to find within the
granitous lava nodofities of pure quartz, of
the thicknefs of one, two, and fometimes
even five inches. Befides giving fparks
plentifully with fteel, which is the peculiar
property of this ftone, it has a colour lightly
amethyfline ; it is tranfparent, fomewhat
und:uous to the touch, folid, and of an in-
determinate figure. But to what are we to
attribute the exiftence of thefe quartzofe
nodofities, which are uninjured, within this
volcanic granite ? I cannot perfuade my-
felf that they exifted in it previous to its ig-
nition ; fmce, had this taken place after-
wards, it mufl; have altered the quartz, by

• depriving

( 24^ )

depriving it of its tranrparency, and render-*
ing it full of cracks, and extremely friable ;
all which changes follow on expofmg it a
fliort time to the furnace. I fhall obferve,
further, that two of thefe nodofities being
left in a crucible placed on burning charcoal
only for a quarter of an hour, loft tbelr
amethyftine colour, and acquired a more
than fuperficial whitenefs, with a number of
cracks, and very apparent friability. I,
therefore, cannot believe that they have been
taken up by the way, and enveloped in the
lava when it flowed, as fometimes happens,
V7hen nerv torrents meet with extraneous
ftones in their paffage. I am, in faifl, of
opinion, thatthefe fmalimafTes of quartz have
been produced pofterior to the congelation of
the lava, by the filtration of water impreg-
nated with the molecules of quartz, which
has penetrated into fome fmali cavities, and
gradually filled them ; in the fame manner
as we have explained the formation of the
calcedonic globes found in fome of the lavas
of Lipari *.

* See Chap. XV.

The

( 241 )

The other fadt is very fimllar to this, and
may be explained in the fame manner. It
relates to the large pieces of flioerl which
are contained in this volcanic rock, and are
difcovered on its being broken into pieces, in
the fime manner as the quartz. Thefe are
compofed of a number of rhomboidal fho-
erlaceous prifms, fo confufedly heaped and
joined together, that it is impoffible to ob-
tain a fingle prifm entire. Excepting in
the largenefs of their fize, they perfectly
refemble thofe of the porous lava, with the
horn-ftone bafe, of Monte Doriati, of which
we have fpoken above. Thefe (hoerls, like
all the others of the Euganean mountains,
concur to prove the volcanization of the
latter, by the fame property which is found
in the black micas of this country ; I mean
their magnetifm. Baron Dietrich, defcrib-
ing the volcanos of Old-Brifach, fhews that
the adion on the magnet of the black cryf-
taliized Ihoerls, is the exelufive property of
thofe that are volcanic. Though, in the
courfe of this work, I believe, I have only
mentioned the fhoerls of Monte Roflb, at

VOL. III. R Etna,

( 242 )

Efna, as pofleffing the property of fironglf
moving the magnetic needle*, I did not
fail to make the fame examination relative
to numerous fhoerls of the Phlegrean Fields
and EoHan I lies, and can pofitively affirm
that I found this quality in them all. It is-
at the fame time to be obferved, that I could
not perceive it in eleven fpecies of fhoerls,
whatever was their colour, fome of which
were detached from granites, and others
found folitary. This obfervation, w^heii
treating of the Euganean mountains, ap-
pears to me too important to be omit-
ted.

Thefe Ihoerlaceous lumps or groups, I am
of opinion, mud have been produced in the
granitous rock by filtration, with this fingle
difference, that the quartzofe groups have
remained amorphous, and the fhoerlaceous
are confufedly cryftallized ; probably from
the more ready tendency of the integrant
molecules to take a determinate form.

* See Gliap. VII.

Havlag

( 243 )

Having examined forae of the Quarries
which furnifh volcanic ftones, I proceeded
to vifit thofe where carbonate of Ume is
dug, of which ftone there is no fcarcity in
the Euganean mountains. Such are the
quarries of BattagHa, Fraflinelle, and Saint
James, fituated on the dechvities of the
Monte Grande, above Teolo. Before we
reach the lava of Battagiia, we meet with
this carbonate. It is fcifTile, and eafily di-
vides in flakes, for the mofi: part, horizontal.
This quarry is very large, and in fome
places forty-five or fifty feet deep. It prin-
cipally confifts of this ftone, which is excel-
lent for making lime. The lime-ftone is
difpofed in ftrata of different thicknefs ;
from thofe of one inch or lefs to thofe of a
foot. We feldom meet with ftony ftrata
which preferve fo well their parallelifm to
each other, and to the horizon. In the
midft of the carbonates are found numerous
flints, or fire-ftones, already well known
from the mention made of them by other
writers; for the Euganean mountains,where-
ever they afford calcareous carbonates, ccrti-
R 2, tain

( 244 )
tain likewife flints. On examining thofe
of the quarry of Battaglia, I found feveral
of them fo clofely united with the calcare-
ous carbonate, as to prefent the moft fpe-
cious appearance of a tranfmutation of the
lime into filex. But to give a clearer idea
of this apparent tranfmutation, it will be
neceiTary to defcribe both the carbonate of
lime and the flint.

The lime-fl-one is white, compadl, not
very heavy, compofed of impalpable parti-
cles, foft to the touch, with a fmooth and
fometimes conchoidal fradure, and break-
inc; into obtufe and amorphous fra2;ments.
it is diflblvcd by acids with confiderable
effervefcence. Both internally, and on the
furface of this vv^hlte flone, black, dendritic,
and not inelegant fpots and ftreaks are very
confpicuous.

The flint is of a deep flefh-colour, fome-
times brown and even black ; its grain is
extremely compad and fine ; its fradure
fmcoth, and almoll always conchoidal, and

its

( HS )
its fragments angular, acute at the extremi-
ties, and femi-pellucid. It is more than
moderately heavy, the file will not touch it,
and it gives fparks flrongly with fteel.
Notwithftanding their great hardnefs, how-
ever, the generality of thefe flints eaiily
break into fmall pieces under the hammer.
Some of them, in the quarry of Battaglia,
are placed between the llrata of the carbo-
nates of lime; but they frequently alfo
form a continuation with them ; fometimes,
indeed, divided by a fudden and abrupt fe-
paration, but frequently, likewife, by infen-
fible gradations ; in which latter cafe there
is a fpecious appearance of an infenfible
tranfition of the lime into filex ; and the
opinion that this is really the fad has been
adopted by many.

A piece which exhibits this appearance
lias one part of it white ; w^hich colour in-
fenfibly difappears, and is fucceeded by a
reddiHi tinge, that gradually increafes till
the remainder of the piece at length ailumes
the red, bro\\n, or black colour v;hich is
R 3 proper

( H6 )•

proper to this flint. The change of colour is
accompanied by a difference in the hard-
nefs, which fucceflively increafes, as appears
from its fcintillation with fteel ; the white
part of the ftone yielding no fparks ; the
light red, very few ; but the deep red, or
black, aiFording them plentifully. If. a
flream of nitric acid be poured from one
end to the other of fuch a piece, where the
colour is white an, efferi'efcence arifes,
which becomes lefs fenfible in the pale red
parts, diip.inifhing as that colour increafes,
until no appearance of it is difcoverable
where the rednefs is deepeft, and the fcintil-
lation with fteel ftrpngeft. Thefe charac-
ters, however, to the chemical eye are not
decifive of the fadt in queftion. For, not
to mention that difference of colour never
conftitutes a diverfity of fpecies in either of
the three kingdoms of Nature, the proper-
ties of hardnefs, and giving fparks with
fteel, do not exclude the prelence of carbo-
nate of lime ; fmce, though it has been con-
fidered as the diftinguilhing property of
calcareous carbonates, that they do not af-
ford

( 247 )

ford fparks with ft eel, it has been proved
that there are feveral Vv^hich have tlils qua-
lity. I pofTefs feverrJ fpecimens of n^iar-
bies, that I colle<Sted fome years fmce in
the quarries of Carrara, which when ftruck
againft fteel afford no inconfiderable quan-
tity of fparks. The fame may be faid of
the effervefcence with acids, there being fe-
veral kinds of thefe carbonates in which
acids caufe no motion, though they fuffi-
ciently diffolve them.

To obtain proofs lefs equivocal, whether
this tranfmutation really took place, I re-
folved to have recourfe to chemical analyfis,
making my experiments on fragments of
the fame piece, fome entirely white, othei'S
of a very light red, others ftill reddei% and
others of a deep red. The refults were as
follow :

In the fragments of the iirft kind, I

found the quantity of lime very great, and

that of filex very fmall ; negleding, at than

time, the carbonic acid gas, and the fmall

R 4 portion

( 248 )

portion of alumlne. In thofe of the fecond,
the quantity of lime was great, and that of
the filex moderate. In the third, the por-
tion of the Ume was moderate, and that of
the filex large. In the laft, the quantity of
filex was very great, and that of the lime
fmall.

From thefe fa6ls it appeared to me evi-
dent, that it was not neceffary to have re-
courfe to an imaginary tranfmutation, fince
the gradations in the fame ftone above de-
fcribed might be explained without it,
Thofe flints which make a part of the fame
ftratum with the calcareous carbonates, fhew
that tiiey were fonned at the fame time with
them ; that is, when they were produced by
the numerous fediments of the fea-water
loaded with calcareous mixed with filiceous
particles. When the latter were abundant
in the fame place, they united by the force
of affinity ; forming, by their precipitation,
filiceous ftrata continued with calcareous;
and when the filiceous particles were few
in proportion to the calcareous, they united

witl^

( 249 )
"With the latter, generating mixtures of the
two earths fuch as they have been found
when analyfed.

It muft, however, be ohferved, that not
unfrequently they have not an immediate
connexion with the calcareous carbonates ;
but are only found under them in the form
of globes and lenfes invefted externally with
that light grey crufi: which is obfervable in
a multitude of other flints. It is very pof-
fible that the produdion of thefe globes and
lenfes may be pofterior, and caufed by fil-
tration, after the formation of the calcareous
flrata.

I fhall fay nothing of other quarries of
lime-ftone fituated in other parts of the
Euganean mountains, nor of the flints they
contain, as they do not eflentially differ
from the quarry above defcribed.

But to return to the ftones which derive
their origin from lire, I fhall now proceed
to fpeak of a kind of lava, the molt noble

and

( ^5o )

and beautiful Vv^hich any volcanos afford.
Near Teolo rifes a fmall hill, called the
Monte del Boldu, principally compofed of
ftony globes of various fizes, difpofed in
itrata, tenacioufly adherent, with a central
nucleus. Thefe globes are of an iron co-
lour, and fprinkled over in every part with
lucid points, which at firft view I imagined
micaceous ; but, on examining them atten-
tively, I difcovered they were fo many
particles of pitch-ftone, the pechjiein of the
Germans. When viewed in a bright light,
they appear white, fome more and fome
lefs, and all have a degree of tranfparence.
They are rather mechanically united than
combined wdth a granular bafe, which ap-
peared to me a foft horn-flone. The fur-
nace changes thefe globes into an enamel,
as black and opake, as it is folid and com-
pact.

What I obferved in this lava induced me
to hope that in fome other part of the Eu-
ganean mountains I might find a pure
pitch-ftone lava ; which I, in fad, after-
wards

( 251 )

wards dircovered, in a fmall valley, to the
fouth, below Bajamonte. It there forms a
vein about thirty-iive feet long, and nine
and a half broad. On the furface it is fo
much decompofed, that it udll crumble be-
tween the fingers. At a little depth it is
lefs foft, but always retains a confiderable
degree of friability. The pieces into which
this vein breaks frequently take an oval
form, v/hich they likewife have when
broken into fmaller pieces. To render
more apparent the colour of this flone, it is
proper to '>vet it ; for v/etting is to rough
ftones a kind of half polifli. It then has
the exad; appearance of the pitch-ftones.
In fome parts it is of a red colour ; fome-
times pale, fometimes more lively, and
fometimes inclining to a yellow ; in which
latter cafe, it relembles certain kinds of am-
ber ; but in other parts the colour is a
mixture of blue, green, and white, but all
of them very pale. The fra^ures are al-
ways amorphous, of unequal furface, and
little brilliancy. The thinner flakes are
tranfparent ; as is the property of foraej

pitch-

( 252 )

pkch-ftones. This lava contains unequally
diftributed feltfpars of a flat form, friable,
and not very brilliant. Every flroke with
the fleel breaks off fome pieces, but extracts
no fparks.

A few hours in the furnace deprive this
ftone of its colours, rendering it of an afh
grey : it likev^ife lofes its friability and
foftnefs, and becomes capable of giving
fparks with fteel ; refembling then a pafte
of porcelain. Continuing the heat longer,
the cinereous colour remains, with the ap-
pearance of very numerous bubbles ; and
the lava pafles into a homogeneous veficu-
lar enamel, with a fufion of the feltfpars.

The fmall valley of Bajamonte is not,
however, the only place in which this
pitch-ftone lava is found ; it is met with
in feveral others ; as at Monte Sieva, and
its environs. We there find banks or
veins inclined in different angles to the
horizon, and fometimes perpendicular to it.
The lava of one of thefe has exadly the
£ colour

( ^53 )

colour and luflre of pitch, and contains
numerous feltfpars. In its external appear-
ance it does not differ from that before
defcribed. It has, however, one peculiarity
which mufl; render it valuable in the eyes
of the volcanift.

Pumices are a kind of produds which
bear in them, demonftratively, the evidences
of fire ; and the traveller who on any
mountains meets with a vein of uncertain,
origin which pafTes immediately into the
ftate of pumice, is fully warranted to de-
clare it volcanic. This is the cafe in the
prefent pitch-ftone. It contains groups,
more or lefs large, of fibrous, light, cellular
pumice, not merely contained within it,
but compofmg one fmgle body with it :
whence it appears that foaie parts of this
rock, either by a more violent adion of
the fire, or becaufe they were more eafily
vitrifiable, have pafTed into the flate of
pumice.

In the fame Monte Sieva, befides a lava

with

( 254 )

With a petrofillceous bafc, which, from its
compadnels, extremely refembles the natu-
ral petrofilex, but which is fufible in the
furnace, we find another vein of pitch-
flone lava, but of much greater extent, and
■which is difpofed ahnoll vertically. On
digging into this vein, we find very beau-
tiful and well preferved pieces of pitch-
ilone lava. For the mofi: part it has the
colour of refin, an elegant luftre, a fine
grain, and great compattnefs. It is fmooth
and clear in the fracture, with amorphous
fragments, femi-tranfparent In the points.
It is not, however, fufficiently hard to give
fparks with fteel. It is not without felt-
fpars, which have a vitreous afpedt:.

This lava does not entirely compofe
this extenfive vein ; but is found there in
pieces, ufually fmall, which are clofely
bound together by a ftony fubftance which
aQs with refpe^t to them as a gluten or
cement. Thefe pieces have not been rolled
by a ftream or weaves, and thereby become
round, but are amorphous, and with acute

angles.

( 255 )

angles. It is evident, therefore, that this
lava has been broken by fome violent agent ;
and its pieces afterv^^ards have been taken
up, and inclofed v^ithin the ftony fubftance,
which, when carefully examined, is found
to be only, a conglutination of very fine
dull of the fame pitch- flone ; which al fo
contains ftones of feveral other kinds.

At Cataio, where is the villa of the Marr
chefe degli Obizzi, are large excavations in
the fide of a mountain, made in the fame
brecciated pitch-ftone. We here, likewife,
find only very fmall, but numerous, frag-
ments of this ftone bound together, in like
manner, by a congenerous ground.

In another part of this mountain the
fame flone again appears ; it does nor, how-
ever, refemble a breccia, but forms thin
veins, and is extremely fimilar to that of
Bajamonte.

The experiments which I made in the
furnace on the firft fpecies of lava I repeated

• on

{ 2S6 )

on the others ; not excepting the bafe of
thofe I have termed breccias ; and I ob-
tained from them the fame kind of grey
and cellular enamel.

I have called the lavas now defcribed
pitch-ftone lavas, becaufe they refemble in
their external appearance the ftone defigned
by that name. I have likev\^ife the autho-
rity of M. Dolomieu, who treating of lavas
found by him in the Paduan mountains,
and in the iflands of Ponza, gives them
that denomination. He afferts, however,
that the lavas differ from the pitch-ftone in
a peculiar property, which confifts in the
extreme eafe with which the volcanic pitch-
ftones may be fufed, and the infufibility
of the true pitch-ftone even In a violent
fire *.

Having obtained a number of pltch-
ftones that were not volcanic, I determined
to make experiments on them in the fur-

* In his Notes to Bergmann's DifTertatlon on Vol-
canic Produds.

nace.

( 257 )

iiace. They were, in the whole, nine :
three from the ifle of Elba ; one clneritious
and almofi: opake ; the fecond femitranfpa-
rent and yellowiih ; and the third opake
and inclining to black : three from Germa-
ny ; the firft yellow, the fecond red, the
third blacik, and all opake : the three laft from
the Pyrenees ; one reddifh, the other green,
and the third of a colour between a green
and a pale blue ; and all three fomewhat
tranfparent in the angles. The firft fix,
after having continued forty-eight hours in
the furnace, fhewed no fign of liquefac-
tion ; but only became white, extreiiiely
light, and pulverable under the finger.
Thofe of the Pyrenees were changed into a
beautiful white enamel, giving fparks with
fteel, and full of minute bubbles. The
pitch-ftones of Saxony, which are found
in places not volcanic, are eafily fuHble in a
not very ftrong fire, as Delametherie has
obferved.

Several analyfes have been made of

pech-ftein or pitch-ftones. In one, Berg*

VOL. III. S mann

( 25S )

mann found the portion of filex to he
greateft, that of alumine, little, and that of
lime, leaf!:.

Another, analyzed by Wiegleb, gave

Silex - - - 65

Alumine - - - i5
Iron - - « ^

The other 14. parts requifite to com-
plete the 100 were difperfed in the opera-
tion -.

A third by Gmelin

Silex - - - 90

Alumine - - - 7

Iron - - - 2

The pitch-ftone lavas of the Euganean
mountains having never to my knowledge
been analyfcd, I undertook this operation
on the three fpecies mentioned above ; and
the following were the refults :

* KIrwan's Mineralogy,

Pitch-

( 259

)

,

Pitch-flone lava below

B?

jamonte.

Silex

71

Alumlne

18

Lime

4

Iron

S

Pitch- ftone lava of Monte Sieva in beau-
tiful and v^ell preferved pieces,

Silex - - . y^^

Alumina - - - 14

Lime - - - g

Iron ' ' - 3i

Pitch-ftone lava of the fame Monte Sieva,
ferving as a cement or bafe to the above
pieces,

Silex - ... 68f

Alumine - - - 19

Lime - - - 8

Iron - - - 2

When thefe three analyfes of mine of

the volcanic pitch- ftones of the Paduan

mountains are compared with thofe of

Bergmann, Wiegleb, and Gmelin, we fhall

S 2 ' find

( 26o ) -

find that the principle moil abounding in
thefe fix ftones is the filex ; that the alu-
mine is but in a moderate or fmall propor-
tion ; as are likewife the lime and iron
when they enter into the compofition of
thefe ftones. It is therefore evident that
thefe fix ftones are of the fame fpecies ;
nor can the infufibility of feveral pitch-
ftones, which are not volcanic, diftingulfh
them as eflentially different from the volca-
nic, fince we find in the genus of petrofi-
lices fome which fufe in the furnace while
others remain refradory. It is, befides,
not invariably true that volcanic pitch-
ftones are eafily fufible. Thofe of Monte
Muffato, of which I fhall prefently treat,
require a continuance of feveral days in the
furnace before they are completely fufed.
Some pitch-ftone lavas of the iflands of
Ponza, which are of a pale white colour,
and of a fmooth and fliining fradlure, after
continuing feveral hours in the furnace,
only become of a deep red colour, and fu-
fion does not take place till after thirty
hours. It is remarkable that almoft alLvol-

canic

{ 26l )

canic pitch-ftone lavas, whatever may be
their colour, as foon as they are expofed to
our common fire, become red.

Thefe pitch-ftone lavas, which are found
In other parts of the Eugahean mountains
befides thofe already mentioned, have in-
duced Father Terzi, a Benedld:ine, to fup-
pofe that they were no other than real
glafs, an opinion which he publifhed a few
years fmce in fome letters on the Euganean
produdis. He informs us that he difcovered
large veins of them in the Mont^ del Muflato,
and at Brecalon, as well as in other places.
The novelty of the difcovery greatly ex-
cited the furprife of many Paduan natural-
ifts, and efpecially of the Abbe Fortis, who
having frequently made excurfions to thefe
mountains to examine their products, could
never meet with this extraordinary glafs.
To afcertain the truth, he, with fome other
perfons well acquainted with tjiis branch of
natural fcience, repaired to the mountains,
and foon difcovered the error which had
been committed by the good Father mif-
S 3 taking

( 262 )

taking tliefe pitch-ftone lavas for glafs,
which error he detedled and proved in a
Memoir entitled On certain parts cf the
Faduan Moufita'ms ^.

In September 1792, the Marchefe Anto-
nio Orologio and myfelf, having made an
excurfion to the Euganean mountains, to
vifit this celebrated naturaiift, who refided
at the village of Galzignano, he con-
duced us to Monte del MulTato, where
thefe fuppofed veins of glafs were to be
feen ; but we found that they were only
large mafles of pitch-fione lava, fimilar to
that above defcribed ; of which I was ftill
more convinced afterwards, as I took fome
fpecimens from the fpot and carried them
with me to Pavia. This pitch-ftone lava is
of tvvo kinds. The one is interrupted with
thin ftreaks of a white earth, which attaches
. to the tongue and emits an argillaceous
fmell, and by which the lava often appears
as if divided in fmall pieces ; it alfo, in

* Sopra parecchle localita de' Monti Padovani.

many

( 263 )

many places, includes extraneous bodies,
feme of which are of conlidcrable import-
ance to volcanic enquiries. Thefe are
fmall pieces of hom-flone pofleffing that
porofity which characterizes them for true
lavas. One of the fpecimens above men-
tioned contains a fragment of this kind
two inches in thicknefs, extremely perfedt,
and very porous. The vacuities are round
and elliptical : fatisfacflory figns that it has
made a part of fome current.

The other lava from the fame mountain
refembles the former, as far, at leaft, as can
be judged from the fpecimens I brought
away, in its colour, w^hich is that of tur-
pentine, only much darker and lefs lively.;
and in its confidence ; except that it forms
unmixed mafles, and contains amorphous
feltfpars, of Uttle or no brilliancy. Among
all the pitch-ftone lavas of the Euganean
mountains that fell under my obfervation,
this is the moft compact, heavy, and hard.
The eye alone, however, is fufficient to
.difcern the great difference between thefe
S 4 pitch-

( 264 )

pltcK-ftone lavas and volcanic glafs. The
idea of volcanic glafs is derived from that
we have from our common glafles j the
infeparable chara6:ers of which, as we well
know, are, that they fhould have a fhining
and bright furface ; be compofed of indif-
cernible particles ; break into angular pieces,
extremely thin at the edges, and with acute
and piercing points ; with a fradure either
entirely ffnooth and clear, or, as we fre-
quently find, with waving and curved
flreaks ; not to mention its tranfparency, a
quality known to every one, and, in glafs,one
of the moft valuable. The fame, precifely,
are the charaders of the greater part of
volcanic glafles ; but the defcription of the
pitch-done lavas is very different. They
have commonly a dead and dull iuftre ;
their pafte is fine, indeed, but not compa-
rable in finenefs to that of glafs ; they are
lefs fmooth in the fradures, lefs fharp and
cutting at the edges, and have little or no
tranfparency. They are likexvife diftin-
guiflied by another property from volcanic
glafles, the greater part of which are fuifi-

ciently

( 265 )

ckntly hard to extradl fparks from fteel,
that is to fay, to melt it : on the contrary, I
was never able to extrad: the fmallefl: fpark
from the pitch-flpne lavas above mentioned,
though I made the experiment on them
with the heft fteel. They are therefore lefs
hard than volcanic glafs, as is indeed appa-
rent from the facility v/ith which pieces fly
off at every ftroke. To thefe evident diffi-
milarities we may likewife add the weight,
which in pieces of the fame iizt is always
greater in volcanic glafs than in pitch-ftone
lavas.

Father Terzl may, however, eafily con-
vince himfelf that thole veins of the Euga-
nean mountains which he calls glafs, are by
no means entitled to that appellation, if he
will fufe a fmall portion of them in the fur-
nace. He will then find the prcdudl a true
enamel, exhibiting a vitreous afped: not at
all difcoverable in the pitch-flone lava from
which it was produced. This is true, like-
wife, of the veins of Monte Muffato ; and
fhews that the pitch-ftone lavas rauft not

©nly

(• 266 )

only be excluded from the clafs of volcanic
glalTes, but even from that of enamels.

When, in the year 5789, I made an ex-
curfion over the mountains of Padua, in
fearch of volcanic objedls, accompanied by
the Marchefe Orologio, we, at Praglia, were
received and moft hofpitably entertained in
the ancient and magnificent monaftery of
the Benedidines- by the excellent Father
Terzi, who, after dinner, took us into his
private cabinet of volcanic-marine products,
collected on the Euganean mountains. He
prefented us likewife with fome fpecimens,
informing us at the fame time where they
had been found, which I think deferving of
a particular defcription.

The firfl:, which, according to the ac-
count he gave us, was brought from Schi-
vanoja, is a mixture of amorphous, white,
and friable feltfpar, and black, prifmatic, and
extremely brilliant (hoerls, m.uch refembllng
fome fpecies of tourmalins. From this mix-
ture is obtained, in the furnace, an extreme-

( 267 )

ij black enamel, of the greateft compa(3:-
nefs, fcattered over with white points, which
are feltfpars not entirely vitrified. The
magnetic needle is fenfible to thefe fhoerls
at the diftance of one line and four- fifths.

The fecond product, which is from Mon-
te Merlo, confifts of an aggregate of ex-
tremely w^iite and fliining half-cryfiallized
feltfpars, of a changeable colour, which in
the furnace produce a white, and fpungy,
but hard glafs.

The third, which is from the fame moun-
tain, at firfl view, might be taken for a pu-
mice, as it fwims in water ; but, when pro-
perly examined, appears to be a vitreous
fcoria, in the folid parts fufficiently hard to
give iparks with fteel ; i reflated and rendered
fpungy by the adion of fire, and aeriform
fubftances. The furnace perfedly vitrifies
it.

Two other produds, one from Mafcabo,
near Pragtia, the other from Tramonte,

were

( 268 )

w-ere true pitch- flone lavas, though Father
Terzi believed them to be real glares.

I had not time to certify myfelf with re-
fpedt to the places where thefe produdions
were found ; but I cannot doubt the truth
of the accounts I received concerning them.
I can at lead affirm, that there was no error
with refpedl to the tvv^o products of which
I fliall now proceed to fpeak, as I found
them precifely in the places which had
been pointed out to me by the Reverend
Father.

The firft of thefe is met with at the foot
of a very high rock, called Pendife, and
forms a vein, which runs from eaft to weft,
and, in the opinion of Father Terzi, is
glafs. Certainly, v/hen we , take off the
outer coating, which, as in a great number
of other ftony fubftances, is in a ftate of de-
compofitioUj and, confequently, has loft, in
a great degree, its external charaders, the
interior mafs may at firft deceive the eye of
tlie obferverj and induce him to confider it

( 2% )

as real glafs. The arpe(£t is faiooth and
Ihining, like that of glafs ; but with fome
undtuofity, as is the property of fome lefs
perfed: volcanic glafles. But on examining,
with greater attention, the pieces recently
fractured, we do not find in them the cha-
radleriftics of volcanic glafs ; as they have
not the finenefs of confidence, the undulat-
ing fuperficial ftreaks, the fharp edges, nor
the acute points. We may even handle and
prefs the flakes and fragments of them with-
out fear, wdiich cannot be done with impu-
nity by volcanic glaffes.

We know, likewife, that the primordial
rocks, when they are changed by the ad ion
of fubterranean fires into the nature of glafs,
are no longer recognizable ; as they have
loft their primitive ftrudlure, and are redu-
ced, together with the extraneous fubflances
they contain, as flioerls and feltfpars, to one
fmiilar and homogeneous mafs; whereas,
on the contrary, the vein in queftion fuffi-
ciently declares its origin, which is a petro-
filex of a dark green colour, a fra6^ure

fomewhat

( 27d )

fomewhat fcaly and conchoidal, of a grain
moderately tine, giving fcarcely any fparks
with fteel, and having, in the points, a very
flight degree of tranfparency. The feltfpars
and micas, however (of the former of which
the number is but fmall, but that of the lat-
ter very conliderable), do not form one ho-
mogeneous pafte with the bafe, but are both
in a flate of the greateft j^refervation. The
feltfpars exhibit a cryftallized form, but it is
impoffible to define it where the petrofilex
has not been altered. It is not the fame
with the fuperficial cruft, the bafe of which,
having been in part deflroyed, holds thefe
ftones but feebly ; fo that they may eafily
be detached entire with a knife ; when they
appear to be prifmatic cryftals, with tetra-
hedral rectangular facets. We cannot, there-
fore, in any manner, call this vein a glafs,
but only, at the utmoft, a vitreous lava.

By the fide of this volcanic rock, there is
another, of a congenerous bafe, and con-
taining the fame micas and feltfpars ; but it
is of a pale green colour, and tolerably
I hard :

( ^71 )

hard ; it has not, however, the brilliancy of
the former. Both thefe rocks produce ia
the furnace a greyifli enamel, with an entire
fufion of the feltfpars, but not of the micas,
which leave black points within the enameL

The other product of which I went in
fearch, according to the directions given
me by Father Terzi, was, in like manner,
in his opinion, a volcanic glafs, but detached
and fcattered. It is found near the Church
of Valfanzibio, Having taken a fpecimen
of this into my hands, and examined it care-
fully on every fide, I perceived that in this
inftance he was not miftaken, and congra-
tulated him and myfelf on the difcovery. It
exhibited, in fad, the moft indubitable cha-
radlers of a true glafs. It was black, and
gave fparks with fteel. I was, therefore,
very anxious to examine the place where it
was found, and repaired without delay to
Valfanzibio ; where I found more than one
piece of it, not infixed in the earth, nor in
the mid ft of any rock or ftony vein, but
loofe, and fcattered over the ground, like

ftones^

( ^70

ftOnes in a public road. I was fomewliat
furprifed at this ; and, on making enquiries
of fome peafants on the ipot, they told me,
that fome fhepherds had brought that glafs
from the grottos round the fountains of the
garden of N. U. Barbarizo, at a little dif-
tance from the Church of Valfanzlbio, and,
finding it i^felcfs, had thrown it away there.
I repaired, accordingly, to the place they
pointed out, and found that it was, without
the leaft doubt, of the fame kind. I, after-
wards, learned from the keepers of the gar-
den, that it had been procured from the fco-
ricS of the furnaces of Murano, near Venice.

I fhall conclude this account of the vol-
canic fpecimens of the Euganean mountains
ihown me by Father Terzi, in his cabinet
of natural curiofitles, with mentioning one
more, which in his opinion was a volcanic
glafs, and had been found detached on Mon-
te Merlo. To this, likewife, i canuot refufe
the appellation of glafs. It is, like the for-
mer, black, compadt, and heavy. As I did
not go to the place where it was found, I

cannot

( 273 )

cannot pronounce with certainty relative to
its origin. It is poffible that this glals may
be the produdi .n of thofe very ancient vol-
canos, fince Sir John Strange, at number 61
of his Catalogue before cited, mentions
fome pieces of fofTil glafs, but winch are fo-
iitary and accidental, found in fome parts of
the Euganean mountains. It is not, how-
ever, dbfolutely impoffible but that it may
be glafs from the furnace ; at leafl: the
acci.lent of the glafs of Murano ought to
teach us to be cautious, and fufpend our
judgnnent relative to the queftion, whether
a mountain may have been volcanic or not,
when we have no other proof than finding
a loofe piece of glafs, fcoria, or other fab-
ftance deriving its origin frc^m fire, while
we are uncertain whether that fire was, or
was not, volcanic. For, even though the
pieces found (hould be really volcanic, they
cannot afford a certain proof of the volcani-
zation of the place wh.re they are found
detached. Of this 1 can produce an inftance
which happened to myfelf in a curfory vifit
that 1 made to Capo Colonne, a promontory
VOL. fii. T of

( ^74 )

of Attica dlftant twenty miles from Athens,
when, in 1785, I accompanied his Excel-
lency the Venetian Envoy, the Cavaliere
Zulian, to Conftantinople. I there found
pumices fcattered over the ground, to my
no little furprife, as tlie place exhibited no
indications of being volcanic. They were
of that kind which, from their levity, fwim
in water ; and, being of a glofeofe figure, I
fufpeQed that they had once flowed. On
defcending the promontory on the top of
which thefe pumices are found, and pro-
ceeding to the fhore, near a narrow penin-
fula, expofed to the dafliing of the waves, I
found three other fimilar pumices, which
authorifed me to conclude that thofe on
the height abave, which is about one hun-
dred and fixty feet above the level of the
fea, were fome of thofe that had been
thrown by the waves on the fhore, and af-
terwards carried thither by men : the only
explanation of which, in my opinion, the
cafe admitted. To the fhore they had been
brought by the fea ; for it is well known
that many illands in the Archipelago are

volcanic;

( ^IS )

Volcanic ; and that Santorlne, in partlcularj
is only one immenfe mine of pumices *.

The objedions which may be made to
the relations that afcribe a volcanic orlirin

o

to a country, merely becaufe certain fub-
ftances that bear the marks of fubterranean
fires are found in it, permit me to fay, are
equally applicable to other proofs of the
fame kind which are by no means more
decifive. Here, it is faid, there mufl: have
been a volcano, becaufe the matters found
are extremely black, and therefore bear the
charaders of fire. There we are authorifed
to form the fame opinion, becaufe lavas
have iflued from the entrails of a mountain,
or volcanic veins and ilrata are found in its
fiiTures,

There are many writers who, without
adding any other proof, ufe thefe expref-
fions to fignify to their readers the difco-
very of fome ancient volcano. I do not

* See Chap. XIX.

Ta deny

( ^7^ )
deny the poffibility of there havuig been a
volcano in fiich places ; but I muft affirrn
that thefe indications are equivocal, and,
therefore, may be fallacious. It is true
that many volcanic products are black,
with a colour varying from the blacknefs
of iron to a greyifh black. It is equally
true that, in a long feries of time, this
colour is not loft by many volcanic produc-
tions, as appears from fome lavas in the
Eolian iHes. But it is likewife true, that
in many others the blacknefs dimini(hes in
time, and, at length, totally difappears, as
we fee in the greater part of the lavas of
Vefuvius and Etna, which, though at firft
they approached more or lefs to a black
colour, have gradually loft that colour, till
at laft they have acquired one refembling
that of common earth. It is fufficient
merely to caft the eye on the recent cur-
rents, thofe of a moderate age, and the
^ moft ancient, of thofe tw^o volcanos, to per-
ceive thefe fucceffive changes. Every lava,
however, though of a recent date, is not
black. The colour which is proper to the

primordial

( ^11 )

primordial rocks frequently does not difapr
pear in confequence of the adiion of fire.
The colour of many lavas approach^fs to a
black, becaufe that was the colour of their
relpedive primitive rocks, as we fee in the
lavas with a horn-ftone bafe. la others it
is a cinereous grey, and even white, be-
caufe they derive their origin from ftones
of a fimilar colour, as, for inftance, feltfpars
and petrofilex. This diverfity of colours,
black, grey, cinereous, and more or lefs
white, is not unfrequently preferved even
in the enamels and glaifes produced from
thefe rocks when fufed in the crucible. It
is therefore certain that the colour of the
products alone is not a certain indication of
a volcano.

I confider as illufory, and not merely
inconclufive, the alTertlng the exiftence
of ancient volcanos becaufe there exift
veins or volcanic matters ; iince this is
the fame thing as faying there are vol-
canos becaufe there are volcanos. And
though a writer fhculd be convinced
T 3 fro:n

( 278 )

from his own obfervation that thefc
matters have really fuffered the action of
fire, if he wifhes to convince the philofo-
phical world he muft fpecify their nature ;
as whether they are puzzolanas, afhe?,
glafles, enamels, fcorix or lavas. The
precifion and exadnefs required in the pre-
fent difcerning age likewife render it necef-
fary that he fhould charaderize thefe dif-
ferent volcanized fubftances ; and it will be
to little purpofe that he adduces in proof of
an extinguifhed volcano the remains of a
current of lava, unlefs he properly defcribes
it, fuice the advancement of this fcience
depends entirely on exad defcrlptions of
produds affeded by the fire. The moft
able volcanifts of the prefent time write
after the manner of accurate mineralogies.
Among thefe volcanifts, the firft place is
certainly due to M. Faujas de Saint Fond,
as is fufficiencly proved by his Mineralogy
af Volcanos<f

And here I cannot refrain from making
fome obfervations relative to lavas in gene-
ral.

( 279 )

ral. By the word lava is underftood, as
every one knows, a liquefied ftony fab-
ftance which has been in motion. When
a mountain is of a conical form, and has a
cavity refembling an inverted tunnel on its
top, or evident marks of one, and when
from this tunnel, as from a central point, a
number of ftony ftrata diverge towards the
lower parts with a waving form, or with
Inequalities and tumours, we cannot doubt
the prefence of lavas. It is equally indubi-
table, when we are certain of the volcani-
zation of the mountain from other figns,
and fee thefe ftony ftrata arifing from its
fummit, and tending downwards, with the
wavy appearance and inequalities before
mentioned, though there fliouk| be no ap-
parent indication of a crater. When we
afcend to the fummit of thofe Eolian liles
in which the remains of craters are no
longer vifible, we immediately difcover
confpicuous currents pf lava. There may,
however, be cafes, with refped: to moun-
tains that have fuftered the aclion of fire,
in v/hich, from want of local circumftar^ces,,
T 4 we

( 28o )

we may remain in doubt whether the vol-
canized rocks that prefent themfelves to
our view, have ever actually flowed. This
doubt I experienced myfelf, when I firft
vifited the Euganean mountains, in confe-
quence of u-.y obfervations relative to the
primitive rocks, and the experiments I had
made on lavas in the furnace. I conGdered
that it was poflible the rocks of the Fuga-
nean hills m'ght never have flowed in cur-
rents, and confequently that they could not
have been lavas, though they might bear
very fenfible trarks of fire, and even the
fame with vitreous lavas ; as I was con-
vinced from the experiments I had made
in the furnace, which, without wandering
too far from my fubje(3:, I will here briefly
defcribe.

In Chap. XI, I have fpoken of the fufion
of fome porphyries with a horn-flone and ■
petrofiliceous bafe. The following are the
appearances I obferved fome time before
their fufion. The pieces, though before
their fractures were fcabrous and angular,

afljjmed

( 28i )

aflumed a fmooth and vitreous furface.
Their internal grain acquired an afpedt
rather vitreous than filiceous, even in thofe
ftones, which, having for their bafe the
horn-ftone, had an earthy appearance.
The pieces, except that they adhered by
fome points, preferved their former figure
an4 angles ; which prefervation of the li«
gure takes place in other cafes that I fhall
proceed to mention.

The feltfpar of Mount St. Gothard, or
the adularia of Father Pini, loft its change-
able colour and tranfparency, became white
within, femi-enamellar, and vitreous exter-
nally.

In the feltfpars of Ifchia, the vitrifi-
cation penetrated to the depth of fome

lines.

In fome of the potteries of Pavia, they
ufe a kind of earth, which, from the place
where it is digged, is called blella^ which
ftrongly refills the fire. It is commonly

found

( 2^2 )

iblmd to be compored of alumlne> dlcx^
and a very fmall quantity of lime. It is
ufuaUy refractory to the fire of a glafs
furnace ; but fornetimes v;^ill fufe when it
contains, a rather larger proportion of lime.
Of this kind of earth I made fome fmall
fpheres and cubes, which I left four or
five hours in the furnace ; when the vitri«
fication had penetrated to the depth of two
thirds of a line, and in feme even a whole
lin?, and the central part had become femi-
vttrecus.

Similar eftedis take place In lavas. Their
fu-fface afliimes an enamel or vitreous
afpecl, which in the internal part is lefa
apparent. In fome, however, we find
points which have become vitreous, though
thefe lavas before did riot contain a fmgle
atom of glafs. In general, they lofe that
grain and texture, which indicate the
primitive rocks whence they were derived,
and they all, or nearly all, may be called
vitreous.

( 283 )

Thus we have a prodigious number of
foffil produ6lions which have the moft fpe-
cious appearances of lavas, and vitreous
lavas, though they have never fuffered li-
quefaction ; as is incontrovertibly proved
by the pieces, which, when they come out
of the furnace, retain exactly the configu-
ration they had before they were expofed
to the tire.

Inftrudted by thefe fa£ls, I confefs that
the firll: time I faw the Euganean moun-
tains, and found myfelf in a theatre very
different from that prefented by the Eolian
ifles, not to mention Etna and Vefuvius, I
could not avoid entertaining doubts whether
the numerous foeks, which in a great part
form thefe mountains, owed their origin to
volcanic eruptions, or were pre-exiflent to
the fubterranean conflagrations, that had
only penetrated them, infixing in them in-
delible traces of their adion, but ftill leav-
ing them in the place where we at prefect
fee them. Every doubt however was re-
moved, and I remained convinced that

thefe

( 284 )

thefe prodigious malTes of rocks were
igneous eruptions, or, in fad:, currents of
lava, of which the porofity of fome of
them was a very evident and fatisfaflory
proof. It is indubitable that the elaftic
gafe?, which generate pores and vacuities
m the recks acfled on by lire, cannot pro-
duce that efTevfl unlefs thefe rocks are foft.
ened fufFiciently to yield to the expanfive
force of thefe aeriform fubftances, which
muPc precifely happen in their a6lual lique-
faction. This, though fufficiently evident
in iifelf, is undeniably proved by experi-
ments I made in the furnace. When the
porphyries with a petrofiliceous or horn-
fione bafe, and, generally, when compact
Javas alTuai^d the fimple vitreous varnifh,
and fomewhat of a vitreous afpe£l inter-
nally, but v/ithout the pieces conglutinating
and forming one fmgle uniform mafs, they
rarely or never contained bubbles ; w^hich,
on the contrary, were confpicuous and nu-
merous when the fufion w^as complete, and
iht larger, the greater the degree of liqui-
dity produced by the iire in the fljony bodies.

The

( ^85 )

The porofity of volcanic rocks Is, therefore,
a decilive proof that they were once in a
fluid ftate. Several of the Euganean rocks
are porous and cellular, as I have already
fhown of more than one, and fhall proceed
to fhow of fome others.

There is a declivity on one of the Euga^
nean mountains, the name of which I can-
not give, having negled:ed to note it in my
journal, an omiffion of little importance to
the truth of the fa£t ; which declivity is
compofed of a rock with a horn-ftone bafe,
containing fekfp^thofe cryftals, and full,
both on the furface and in the internal
parts, of round vacuities, fu cb, preclfely,
as are ufuaily produced in lavas by aeriform
fluids,

I fhall make a few more obfervations on
the Euganean lavas ; and (hall notice that
one of them containing bubbles, and that
in a confiderable number, is found in im-
menfe quantirits in, and on the fide of, the
road leading from Eajamoate to Rua,
2 This

( 286 )

This lava, which has for its bafe the horn'»
ftone, and emits a ftrong argillaceous odour ^
has the colour of a dead leaf, a grain fome-
what Tandy, and a great number of round
pores, from thofe of a fize fcarcely difcerni-
ble, to others feven lines in diameter. Many
of thefe pores are occupied by cryftallized
globules of carbonate of lime, produced by
filtration. This lava has the external appear^
ance of being very ancient. In the furnace
it affords one of the ufual black and opake
enamels.

To the fouth-Vv-eft of a decliWty of Rua
we find great m.affes of a volcanic rock that
has fallen down, the feltfpars of which are
an exception to thofe of the innumerable
lavas defcribed in this work on account of
the extraneous bodies enclofed within them.
This rock, the different pieces of which are
of different colours (fome being afh-grey,
others red, others of a pale violet), is of a
petrofiliceous bafe, with an earthy grain,
and contains, hefides hexagonal micas with
oblique fides, tranfparenc feltfpars, cubical,

prifmatical^

( =8? )

l^nfmaticaljand fometimes amorphous, whlcfi
give fparks ftrongly with fleel, and form very
brilliant plates. The hirged are live lines
and three quarters in length. Each of th^fe
feltfpars inchides within it a fmall portion of
the petroiiliceous bafe, which forms in it a
kind of nucleus, and occupies a confiderable
part of its fubftance. But to what caufe arc
we to afcribe this Angularity ? I can conceive
no other method of explaining it, but by
fappofrng, that when the integrant particles
of the feltfpars, diffeminated in the earthy
and liquid i^afe, united by the force of aggre-
gation in cryftallizcd mailes, each of thefe
jnafTes included a fmall part of tliis bafe,
greater or lefs in quantity. The rarity of the
phenomenon, however, fuppofes a local cir-
cum Ranee, which had a dire^^t relation to
this fmgular combination, and of the nature
of which I am ignorant.

The feltfpars fufe in the furnace, and be-
come intimately mixed with the bafe in fuch
a manner, that the refult is a folid, white,
femi-traniparentglafs, with black fpots,occa-

fioned

C 288 )

fioned by the micas of that colour which
have remained, ina greatmeafure, refradory.

I fhall omit to defcribe another porous
lava, Hkewife from Rua ; and two of the
compact Ipecies, with a horn-ftone bafe,
found in that vicinity. I think more de-
ferving of attention one difpofed in ftrata
obhque to the horizon, which is found on
the fides of the road leading from Galzig-
nano to Ciefa.

This lava'is white, and has the compa£l-
nefs of fine carbonates of lime, which it re~
fembles in appearance, fracture, and weight.
It affords a few fparks with fteel, and is
dul:inguiihed from other lavas by numerous
points of a delicate green, fcattered over the
white ground ; but which, to be viewed
diflinctly, require a lens with a ftrong light.
When thus magnified, v\^e find that they are
a femi-pulverous earth, which may be de-
tached with the point of a needle, and is
placed between the fiffures of minute amor-
phous maiTes of fhining, white, and ex-
tremely

( 2Sg )

tremely tranfparent quartz. I know not
whether this powder be a decompolition of
quartz, which, however, does not appear
very probable, as it is found deep in the in-
ternal part of the lava, where it is not in
the leaft altered ; or whether it be an ex-
traneous and adventitious fubftance. Be-
fides the quartzofe grains, the petrofiliceou?
bafe contains a few very fmall feltfpars,
which, from their changeable briiliancrj,
their rhomboidal form, and their being
compofed of minute laminse, cannot be
confounded with the quartzofe grains.

It is neceflary to obferve that the bads
of this lava, in the furnace, ferves for a
flux to thefe quartzofe grains ; the relult
being a homogeneous and white enamel,
without the fmaileft appearance of any
remains of the quartzofe grains, or the
feltfpars.

Another lava, found on each fide of the

road, in a place called the Pigozzo, oppofite

VOL, III. U Catajo,

( ^9o )

Catajo, IS In no refpecl dliFerent from this,
except that the quartzofe grains are not
accompanied with green fpots. It yields
in the furnace the fame volcanic produdt.

At Monte Niiovo we find feveral mafles
of a lava which deferves our notice, from
its being reduced to fuch a ftate that it is
pulverable by the mere prefllire of the fin-
ger. It has an argillaceous bafe, and con-
tains an abundance of feltipars v/hich have
preferved their prifmatic figure, but are ne-
verthelefs pulverable. It is rare, in volca-
nic places, to find feltfpars fo much injured,
even where they have been adted on by
fulphureous acids ; of which there are here
no traces; and therefore this decompofition
feems to be derivable from the humid ele-
ments, and other caufes in the atmofphere.
On breaking this lava we difcover fome
minute octagonal and hexagonal prifms,
obliquely truncated, lefs foft than the bafe
to which they are attached. They do not
in the leaft appertain to the genus of either

fhoerls

( 291 )

flioerls or feltfpars ; and, in their external
charaders, feem not to difFer eiTentially
from the lava itfelf.

Among the number of the pitch-ftone
lavas- already mentioned there is one which
muit peculiarly attracfi the attention of vol-
canifts, from the pumices it contains. Mon-
felice, one of the Euganean mountains,
whicn ftand^ detached, and is of a moderate
extent and height, is partly compofed of a
white argillaceous i .va, of an earthy afpedt,
in which we find this peculiarity ; only
that, while t'le pumices of the pitch-ftone
lava are derived from the parts of it being
dilated and tumefied by gafeous elaftic fub-
ftances, thofc of the prefent lava appear to
be adventitious, confifting in white globules
eafily feparable from the bafe, from which
probably they were taken when it was in
a fluid flate. Except that they are lefs,
they confiderably refemble the pumiceous
globules of Pompeii near Vefuvius ; and
both, in the furnace, produce a fimilar
enamel.

U 2 This

( 292

This lava, befides the pumices, contains
elegant feltfpathofe cryftals, which, toge-
ther with it, completely vitrify in the fur-
nace.

Monte d'Arqua was the laft which I
vifited. Its fummit is compofed of a grey
compa6l lava, which has a horn-ftone bafc,
affords fparks with fteel, and contains mi-
caceous and feltfpathofe cryftals. This lava
is found in fome places in ftrata nearly ho-
rizontal.

To thefe lavas, which I found on the
fpot, while accompanied in my refearches
by the Marchefe Orologio, I fhall add a
few others from the Monte del Catajo,
which were afterwards noticed and exa-
mined by that iliuftrious nobleman and
naturalift, who vifited every part of that
mountain to which his villa is contiguous,
and coUeded fpecimens of the fpecies of
moft importance, obferving the places
where they were found. At my requeft
hs tranfmittcd them to me, with their fe-

( 293 )

veral defcrlptions, which I fhall here briefly
give the reader, only making fuch altera-
tions as appear to be necefTary.

T. Is one of the fineft lavas of the Eu«
ganean mountains. Its bafe is feltfpar in
the mafs, but it is with difficulty recog-
nized from its exterior charad:ers, the fire
having changed it into a vitreous lava. It
is of a cinereous colour, compafl:, but not
very hard, on account of its numerous fif-
fures* It contains cryfcallized micas and
feltfpars ; and the enamel it produces in
the furnace, fimilar to that of the pitch-
ftone lavas, forms one homogeneous mafs
with the fufed micas and feltfpars.

This lava, on which the noble palace of
the Marchefe degli Obizzi is built, occupies
an extenfive tra<St of the fides of Catajo,
to the fouth ; and branches off, likewife,
to the north-eaft ; though, from its being
there in a ftate of the greateft decompofi-
tion, it has loft the characters of a vitreous
lava, and taken thofe of an earthy and
U 3 pulverulent.

( 294 )

pulverulent. The experienced, however.^
may ftill difcern within it the vitreous
lineaments ; and I am convinced that, were
a deep excavation to be made in this lava,
we fhould more completely difcover its vi-
treous nature ; as, by the fame means, we
afcertain the real quality of other ftones,
both natural and volcanized, the furface of
which has been changed by the adion of
corrofive agents.

In the internal part of this decompofed
lava, we find feveral globes of petrofilex as
ftrongly charadlerized as in the natural
ftate. As it is detached, I dare not num-
ber it among the lavas. Similar to many
congenerous ftones, it is furrounded v/ith
a white argillaceous cruft, which attaches
to the tongue ; and contains a number of
micaceous points, and feltfpathofe lamiuci?.

In the furnace it becomes white, and
acquires: a thin vitreous coating : the
pieces^ however, do not lofe their primitive
figure.

II. This

( 295 )

II. This lava is found at about one
quarter of the afccnt up the mountain,,
and continues to the top : it is alfo met
with in detached pieces along the declivi-
ties. The bafe of this lava is a compact,
heavy trapp, of very fine particles, inter-
rupted with feltfpathofe fcales. It has the
black colour of iron. The furnace changes
it into an enamel full of bubbles ; but it
retains its former colour.

III. This fpecies is in part bilried with-
in the lava No. II ; and, in part, ifliies
from it, forming tortuous veins of various
fizes, and running in various directions,
one of which interfecfls the decompofed
Xatreous lava No^ III. The bafe of this
lava is an extremely compa(Sl petrofilex ;
it is of a fine grain, accompanied with
micaceous and feltfpathofe cryftals. It
is of a greyifh blue colour, inclining to a
black. Its fufion in the furnace was com-
plete at the end of thirty-eight hours.

IV. This lava is white, light, and de-

TT 4 compofed

( 296 )

eompofed in the fame manner as fom^
tracts of that of No. I. Its bafe is argilla-
ceous, and it attaches to the tongue ; the fmall
cryltals of black mica and feltfpar which it
contains, are, however, uninjured. This lava,
iikewife, iffues in veins from the body af
that of No. II.

Its produd in the furnace is a femi-tranf-
parent grey glafs, with the fullon of the
feltfpars. This lava has the peculiarity
of iirongly attacking the crucible ; com-
bining with the earth of which, it forms
round the fides an elegant, extremely trans-
parent glafs, refembling the emerald.

V. Befides feveral beds of pitch-ftone
lava, which concur to the formation of
Catajo, there is one, near the fummit,
towards the fouth-weft, interfperfed with
innumerable very fine white flreaks parallel
to each other, and which form a ftrong
contrail to the red ftreaks of the pitch-ftone
lava. Thefe wdiite ftreaks, as far as I could
difcover, are the fame lava decompofed,

J an^d

( 297 )

and perhaps rendered fuch by the filtration
of the rains which have infinuated through
the fmall fiiTures of the lava.

In the furnace it changes into an enamel
fimilar to that afforded by the other pitch- .
Hone lavas, with the liquefadion of the felt-
fpars it contains.

VI. This lava is thus defcribed by the
Marchefe Orologio :

" Near the top of the firfl fummit" (the
Monte del Catajo is bifurcated) " there is a
** fpacious irregular plain with many in-
" equalities, which I incline to fufpedt was
" an ancient crater deftroyed by time, and
" filled by the falling in of its fides. We
" here find enormous mafles of a fpecies of
" breccia, or pudding.flone, compofed of
" fmall fragments of many varieties of lava,
" united and bound together in a hardened
« clay."

This breccia I carefully examined, and

confider

■ (298)

confidet it as well defervlng attention. Black
ilioerl in the mafs conftitutes the greateft
part of it. It is found in pieces furrounded
by a grey earthy crufl:, which attaches to
the tongue, and is a decompofition of the
fhoerl. The cruft in fome pieces is ex-
tremely thin, but in others extends to a
greater or lefs depth ; and in fome leaves
only a black flioerlaceous point in the mid-
dle. Thefe fmall pieces are ufually angu-
lar ; w^hence we may infer that they have
not been in a fluid ftate. They are all
bound together by a cement, fmall In quan-
tity, of a pale yellov/ colour, and a vitreous
afped:, which is likewife changed by the de-
compofition. The breccia in the furnace is
reduced to a black and frothy fcoria.

The decompofition of this breccia appears
to be a confequence of the action of the at-
mofphere and of tim„e. The fhoerlaceous
fragments evidently Ihew that they exifted
previouily to the vitreous fubftance ; which
paffing over them when it was in a fluid
:(late, included them within it, and formed

one

{ 299 )

one body with them. They may, alio, pof-
fibly be I'mall fragments of a very ancient
lava, with a bafe of fhoerl in the mafs ; un-
lefs we rather choofe to fappofe that fome
vein of flioerl, broken by the impetuofity of
the elaftic gafes, and reduced to minute
pieces by the fhock, has been thrown out
from a volcanic mouth, without having been
fufed or changed by the fire.

VII and lall Lava. Though this be fpe-
cifically the fame with No. II, it claims to
be diftindly mentioned from the manner of
its conformation. About half way up one
of the fummits of the mountain, there is an
overhanging precipice, from which go ofF
two ranges of prlfmatic columns ; the one
higher than the other, but both nearly ver-
tical. Their height differs from thofe of
one foot to thofe of three. When we confi-
der the precipice, or rent in the mountain
to which they adhere, and the circumference
of it, we perceive, that, when it was entire,
they extended to but a little diftance from
their central point. The bafe of this column
6 is

( 300 )

IS a trapp, which, in refped to Its confiit-
cnce, and the feltfpars it contains, extreme-
ly refembles that of No. II.

This ftone puts in motion the magnetic
needle at the diftance of fcarcely two lines ;
and may ferve for a touchftone ; a quahty
remarked by Cronftedt in the Swedilh
trapps.

REFLEC

( 3ot )

REFLECTIONS and COROLLARIES.

THE fads explained in the prefent chap-
ter are highly inflrudive, from their teach-
ing us the nature of the different volcanic
rocks of the Euganean mountains ; but
they are flill much more fo from their ena-
bling us to form a comparifon between thefc
volcanos and others in Italy and its vicinity,
either extinguifhed or at prefent burning.
We are taught by obfervation and experi-
ence, that nothing exifts in nature detached
andfolitary; but that the whole is connected
with a variety of relations, and that we caa
acquire an accurate knowledge of no fmgle
part but by means of comparifon. In my
other v^'^orks on phyfical fubje£ts, I have
conftantly made it the primary objed: of
my ftudies and refearches to analyfe and
compare the facts I difcovered with each
other, and with fimilar fads difcovered by

othey

C 302 }

other authors ; and in the prefent work I
certainly iliall not depart from a method
which appears to me beil adapted to en-
large the limits of our knowledge of nature,
and iacreafe the treafare of ufeful fcience.
With this view, therefore, I fhall add the
following brief refledions ;

Though the fea is now fome miles di-
ftant from the mountains of Padua, it is
beyond all doubt that it anciently wafhed
them ; as is proved by the calcareous car-
bonates, and their horizontal ftratifications,
befides the marine fhells found on them,
and mentioned by many authors. It
feems equally indubitable, from the ob-
fervations of Sir J Strange and the Abbe
Fortis *, that this group of low mountains
and hills was once fo many volcanic iilands,
refembling thofe of Lipari, Ponza, Santo-
rine, and innumerable others of the fame

* Memorla Geografico-Fifica intorno la vera fitu-
azione dell' Ifole Elettridi degli Antichi A Me-
moir relative to the true fituation of the Ifles Eledrides
of the Ancients.

kind ;

( 3^3 )

kind ; except that in the very ancient vol-
canos of Padua any perceptible ignitioa
has gradually diminifhed and difappeared,
nothing remaining but fome feeble refidue
in the well-known warm baths. This an-
tiquity, it cannot be doubted, likewife, is
the reafon why thefe mountains, notwith-
{landing they flill retain the figure which
characterizes them as volcanic, are greatly
changed in their external appearance, being
deprived of their craters, probably by the
falling in of their fides and the effedis of
rains ; as alfo their porous and fcoriaceous
lavas having been reduced to cultivable
earth by the induftry of men. The vici-
nity of thefe places to others that have
long been cultivated, may likewife have
greatly contributed to diminiOi their ori-
ginal wild afped, and render them very
different, in confequence of cultivation,
from other mountains which, though they
have long ceafed to burn, have been defti-
tute of population.

It may here be proper to confider how

great

( 3^4 )

great an analogy the lavas of the Euganean
hills have with thofe eje(fled by other vol-
canos more knov/n to be fuch, as thefe
are not fimple flones, but compound ; I
mean what are called rocks. The lavas of
Etna, which ufually have for their bafe the
horn-ftone or Ihoerl in the mafs, contain
feltfpars, cryftallized fhoerls, or chryfolites.
Feltfpars, garnets, and cryflallized fhoerls
are incorporated in Jthe lavas of the volcanos
of the Eolian ifles, in a bafe of petrofilex,
horn-ftone, and ihoerl in the mafs. Petro-
filex, horn-ftone, and garnets are conftantly
accompanied by fhoerls, feltfpars, and mi-
cas in the lavas of Vefuvius *. Thofe of
Ifchia with a horn-ilone bafe abound in
feltfpars t. The iflands of Ponza afford
both granitous and filiceous lavas, accom-
panied with fhoerls, feltfpars, and micas ;
and St. Flora in Tufcany is compofed of
granitous lavas J.

* Gloeni, ubi fup.

f See Chap, V.

4: Dolomieu, ubi fup.

The

( 3^5 )

The produdts of the Euganean moun-
tains, we have i'een, are perfedly hmilar.
The bafe of their lavas, which is fhoerl,
feUfpar in the mafs, pitch-ftone, horn-ftone,
or petrofilex, Is combined whh feltfpar,
cryftalUzed fhoerl, or quartzofe grains. And
though I only examined a part of thefe
mountains, yet, from the more extenfive
obfervations of Sir J. Strange, we are au-
thorifed to fay that the nucleus of them
all is compofed of this ftone. It is there-
fore evident that the anciept fubterranean
lires, which have laid wafte a great part of
Italy and the adjacent countries, have had
their feat in thefe rocks ; and v/ho can fay-
to how imnienfe a depth they may have
extended beneath the furface of the earth ?
I fay beneath the furface, becaufe, though
by the violence of volcanic fires large and
numerous mafles arife above the lurface,
both on this and the other fide of the
Apennines, they never, or fcarcely ever,
concur to the formation of thefe, which
principally refult, as may be obferved in
many parts of them, from the calcareous

VOL. III. X carbonates,

{ 3^6 )

carbonates, fteatites, arenaclous ftonCvSJ,
and of a fpecies of quartzofe, micaceous*
fchiftus, on which, in a great meafure,
they reft. It is not, however, improbable
that this order of rocks, unaffected by the
iire, lies buried under the great body of the
Apennines.

I made no excurfions to the Vicentine
mountains, which we know to be at once
of a volcanic and marine origin. We
have, likewife, no accurate lithology 6f
that interefting country. But from fome
fpecimens uhich I received from fome
friends, and, among others, from Signor
Giovanni Arduino, and efpecially from
the ccnverfations I had with him on the
fubjedl at Venice ; I clearly underftand
that the lavas found there have rock for
their bafe ; which rock is fometimes a
petrofilex, and fometimes a horn-ftone ; the
extraneous bodies contained within them
are fhoerls, felrfpars, and micas. Sometimes
fhe volcanic rock is granitous.

I fllQuld

( 3°/- )
I fliould wander beyond the limits I
have propofed to myfelf, fhould I proceed
to confider the nature of the ftony fub-
ftances which have been a£ted on by vol-
canic fires out of Italy, and have been de-
fcribed by naturalifts of experience and
worthy of credit. I fhall only fay that
thefe defcriptions are fufficient to fhow that
they are all, or almoft all, rocks or com-
pound flones. As therefore the fires of
volcanos extend to a prodigious depth,
as may be deduced from the vafi; moun-
tains they raife above the earth ; it follows
that thefe rocks, befides conftituting nu-
merous chains of very lofty mountains,
defcend to an immenfe depth, even in
thofe places where we fhould not know-
that they exifted, were they not difcover-
ed by fiery eruptions. We thus perceive
how extenfively thofe rocks contribute to
form the rind, or fuperficial coating, of
this globe ; the only part of it which
man is permitted to examine ; and which
we never could have obtained knowledge

X2 of

( 3o8 )

of to fo great a depth, but for the fiery
torrents that have iffued^ from it.

Three different bafes of the Euganean
lavas have engaged my attention ; the
feltfpar in the mafs, the petrofilex, and
the pitch-fto-^e. The former of thefe is
changed by the adion of the fire into a
vitreous lava, the equal to which I have
not feen among the produds of any other
volcanos that I have examined. It has
been already obferved, that in the Eolian
ifles the feltfpar in the mafs has contributed
to the formation of many lavas ; but thefe
cannot claim the name of vitreous, as
they retain more or lefs of the external
appearance of the feltfpar ; or this felt-
fpar has paffed immediately into glafs or
enamel.

The petrofilex, likew^ife, forms a kind
of general exception with refped to the
Eolian volcanos. We have feen that
m^ny of their lavas have the petrofilex

for

( 309 )

for their bafe. This Hone almoft always
fufficiently preferves in them its primitive
charaders ; but it is accompanied with a
principle, if I may ufs the expreffion, of
fibrofity and expanfion in its parts, which
exhibits no obfcure fign of its having been
ad;ed on by the fire. The lava with a
petrofiliceous bafe, of the crater of Vul-
cano *, is the only exception. On the con^
trary, feveral of the Euganean petrofilices,
with refpedt to their texture, grain, com-
pa6tnefs, and fra£lure, fo exactly refemble
the moft perfedly characterized natural
petrofilices, that they might be miftaken
for them, if we did not find that they have
pafled into the ftate of lava. This peculi-
arity, however, is not confined to the Eu-
ganean volcanos ; it likewife appertains
to thofe of the ifies of Ponza, as has been
ihown by M. Dolomieu in great numbers
of lavas with a petrofiliceous bafe. I'hefe
lavas cannot but greatly excite our admi-
ration, as we find it impoffible to conceive,

* See Chap. XIII.

X 3 from

( Jio )

from the knowledge we have of our cGm>
mon fire, how fuch a flone can be liquefied
and flow without lofmg one of its natural
lineaments.

LaRly, the lavas with a piteh-flone bafe,
which are very abundant in thefe moun-
tains, are a third objed: deferving our
attention. It is not certain that Etna or
Vefuvius have ever thrown out a fingle
fragment of them : and the fame obferva-
tion may be made of the reft of the Phle-
grsean fields. In Lipari alone, among all
the Eolian iflands, I have found detached
and fcattered pieces, but which had rather
pafied into the ftate of enamel *. The
volcanic pitch-ftone is not peculiar to the
Euganean mountains : the volcanos of
Hungary and thofe of Auvergne furnifh
fome noble fpecimens .of it. It remains,
however, to enquire whether it is to be
clafled among the lavas, or rather whether
it has ever formed currents. We may be.

* See Chap. XVII.

fatlsfied

( 3it )

fatlsfied that it muft, as well as the pitch-
flones of the ifles of Ponza, from the ob-
fervations of Dolomieu. According to this
author, the fimilar kinds of lavas found in
thefe two countries have for their bafe the
feltfpar, with a very confiderable quantity
of magnefia * ; and, in a note to his work
on the iflands of Ponza, fpeaking of the
Vicentine lavas, he remarks, that he found
among them fome produdtions of pitch-
ffcone, which he could not confider as a
true volcanic produd:, but rather as a con-
cretion formed afterwards by the decompo-
fition of volcanic matters ; and that they
contained a great quantity of magnefia*
From which we may gather that magnefia,
in the opinion of this author, is one of the
conftituent principles of the pitch-ftones
of volcanos. The truth however is, that
in the three analyfes above mentioned, of
the pitch-ftone lavas of the mountains of
Sieva and Bajamonte, two of the Euga-
cean mountains, J did not find an atom of
this earth,

* Notes on Bergmann.

X 4 The

( ^^2 )

■The Abbe Fortis affirms tbat he had
difcovered, In the pitch-ftone lavas of
Monte Brecaion, the evident tranfition of
petrofilex into pitch-iftone lava ; and on
comparing the analyfes of petrofilex made
by others, with thofe I have made of three
pitch-ftones, it will be found that they
perfeftly agree — with no other difference
deferving notice, but that the petrofilex
ufually contains no iron, of which a very
fmall quantity was found in the pitch-ftones
I analyfed. '

• As' it has been already fhowm, that
pltch-ftones that are not volcanic and
thofe which are, are of the fame genus,
I find little drfEculty in believing that
many of the latter are derived from the
former.

In. all my refearehes relative to the rocks
of the volcanos in the two Sicilies, I have
always been attentive to difcover at what
degree of heat they fufe in our common
fire, that I might infer the adivity of the
' ' fubterranean'

( 3^2, )
fubterranean conflagrations by which they
have been, inelted. I have proceeded in
the fame manner with refped to the volca-
nic rocks 6f the Euganean mountains, em-
ploying conftantly the fame fire, I mean
that of the glafs^furnace. As to the bafes
of thefe rocks, we have already feen that
not one of them proved refradory, not
even excepting the hardeft and moft corn-
pad petrofilices, which have formed cur-
rents. The feltfpars arid micas, with which
the Euganean lavas fo abound, appeared
equally fufible.

The eafy fufibllity of the feltfpars excited
in me fome furprife, when I confidered the
infufibility which, if not conftantly, is very
frequently the property of the fame (lones in
the rocks of other volcanos when expofed to
the fame degree of heat -, and, as I obtained
the fame fufion when the Euganean feltfpars
v,^ere detached from their bafe, it cannot be
alleged that this bafe ferved as a flux. A dif-
ference f6 remarkable, it feems probable, can
only proceed from the different proportionfi
z of

( 3^4 )

of the conftltuent principles, unlefs w^
choofe to fuppofe that in the Euganean felt-
fpars, befides the elements common to that
ftone, there exifts fome other which facili-^
tates their fufion, though it is imperceptible
to the eye^ the external appearance of the
fufible exactly refembUng that of the infu-
fible feltfpars.

With refped to the produd by fufion in
common fire, of the lavas of the Euganean
mountains, it is found to be exadly the
fame with that of other lavas, I mean an
enamel or glafs, as appears from what has
been faid above. The adion of our com-
mon fire, therefore, deftroys in thefe volca*
nic produds that primitive charaderiftic
ftrudure which had been left in them by
the fubterranean conflagrations.

The bafaltes of Vulcano and Felieuda are
produds of fire, and equally fo are thofe of
Monte Roflb, Monte Ortone, and Catajo j
for they are integrant parts of continued
\olcanic rocks j which truth did not efcape

the

( 3^5 )

the acute obfervatlon of Sir J. Strange and
other difcerning naturalifts. It deferves re-
mark, likewife, that the trapp has taken a
prifmatic configuration at Catajo, in the dry
way, and in Sweden in the humid, as has
been elfewhere fhown. This may teach
us, that we can only determine by local
circumftances in which of the two ways
bafaltts have been formed.

Thefe two ways, however, have united
in the formation of the hills and mountains
of Padua, as appears from the mixture of
calcareous carbonates with lavas. This
combination, which is not found in the Eo-
lian ifles, but is obfervable in the Vicentlne
mountains, at Vcfuvius, in the extinguiilied
volcanos of the Val di Noto in Sicily, in
thofe of Portugal, and Germany near Old-
Brifach, and probably in other volcanized
mountains, fhould incite the naturalift to
enquire which of thefe two contrary agents
was prior in point of time. I (hall not enter
into this queftion, which indeed appears
to be precluded by the obfervations of the

Abbe

( 3i6 )

Abbe Fortis ; my only objed, In fad, being,
in this (hort excurfion to the Euganean
mountains, to collect feme of their volcanic
produds in the places where they are
found, v;ithout entering into a very minute
examination of the nature of thofe places,
and faithfully to give fuch a defcription of
them as might contribute to enlarge our
knowledge relative to volcanos.

CHAP.

( yy )

CHAP. XXI.

EXPERIMENTAL ENQUIRIES RELATIVE
TO THE NATURE OF THE GASES OF
VOLCANOS, AND THE CAUSES OF
THEIR ERUPTIONS.

The perfeEl refemhlance of the effecis produ-
ced by fame gafes of volcanos and thofe of
others generated in lavas ^ and other fimilar
fubjiances^ -when re- melted in our common
Jire^ may enable us to difcover the nature
of the former^ by invefigaiing that of the
latter — Matrajfes of clay^ filed to a cer-
tain height with volca?iic products^ expofed
to the fire of a chemical furnace^ and com-
municating nsoith a pneumatic-chemical ap-
paratus prepared 'with mercury — Experi-
ments made in this manner on the fpotted
glafs of Lipari— Phenomena obferved
njuithin the matrafs during ignition — No
gas appeared above the mercury — Ebidli-
ent Jlate in which the glafs was found

when

( 3'8 )

*vohen left to cool in the matrafs^ after haV"
ing been eight hours expofed to the fre —
No reafon to believe that the bubbles ijoere
an effect either of the atmofpheric air in-
cluded in the int erf ices of the glafs^ or of
any permanent gas — ConjeEliire that thefe
bubbles proceeded from the gaffication of
the glafs itfelf occafioned by the vehemence
cf the heat — Proof of this conjecture in the
piiref glafs of Lipari — 'The breaking of
the matrafs in the frongcf heat occafioned
by this gaff cation- — Caife "why the glafs
rendered gafeous does not pafs into the
pneumatic apparatus — Breaking of a third
matrafs by the violent gaffcatioji of aii
enamel of Ifchia — Ena?nel of Procida dur-
ing the gaff cation fiblimcd^ and adhered
to the fides of the matrafs in the form of a
thin crtfly and ena7nel points — Confrination
cf this in another matrafs^ ^f^'S ^^^ fame
enamel — Evident fgns of this fublimation
in the fufon of fome volcanic fubfances
placed in the furnace in covered crucibles
— Reafn why this fublimation does not
appear in every experiment — Black faBi-

tious-

( 3^9 )

thus glafs which does not produce gas
in the furnace^ but njuhich produces it,
<withtn matrajfes, in ajlrong heat — Expe-
riments on fix other volcanic bodies^ which
produce little or no gas in the furtiace^ but
a confiderable quantity in matrajfes^ with'
cut a?iy appearance of permanent gas —
Concltfion that the bubbles and inflations of
various ft%es, which we fo frequently ob-
ferve i?i the produ&ions of volcanos^ arc
not the effeSi of afiy permanent gas which
has aEled on them, but of an a'iriform fluid
proceeding from the excejive fubtilization
of thofe produ&ions by means of beat —
Not but that volcanic produBs, expofed to
our common fire, fometimes emit perm afient
gas — -Proofs, deduced from faEis on v
f mailer fcale, that this a'eriform fluid, in
the deep receffes of a volcanic crater, being
abundantly mixed with tfoe liquid lava,
and flrongly excited by the fubterranean
conflagrations, may, by its violent force,
raife the lava to the fummit of the crater,
and compel it to flow over the fides and
form cur rents-'-^ Another proof of this fa£l,

'which

( 320 )'

which renders probable the hypotbejis^ that
this elajiic vapour^ colleEled in a large
quantity^ and finding fome impenetrable
objlacle under the earthy may caiife earth-
quakes^ Jiibterraneous roarings y and burji
the fides of the mountains ^forcing the lava
to foiv out — Improbable^ hozvever^ that
this vapour is the caufe of the fery hail
ejeBed by volcanos — Neceffity of recurring
to other more poijoerful gafes to explain
thefe eruptions — 7^^ he prefence of thefe dif-
fer ettt gafes clearly indicated in fome vol"
canos— Probable, that in the greater and
more terrible ejeBions another agent much
more energetic concurs, that is, "water,
principally that of the fea, reduced to va-
pcur--^ConneBion between burning volca-
nos and the fea — l^he fudden retiring of
the latter,, in the vicinity ofVefuvius, at the
time of the mof terrible eruptions^ probably
occofioned by great quantities of its voaters
being abforbed in the caverns of the moun-
tain— E:-perimefits and accidents iiuhich'
prove the terrible nature of the explofions
and detonations of volcanos, in confequence

of

( 32^ )

of water^s helng reduced to vapour by their
co7iflagrat'io7i — Enquiry whether water
.filling upon a hitming volcano may be ca^'
pable to produce explojions^ as it is certain
it will if it inftnuates itfelf hi from below ^
Und its vapours cannot otherwife obtain a
p^ffage out— Water falling upon oily and
boiling matters generates feeble explofons^
which feems to favour the affirmative —
Arguments for the negative deduced from
the effefis of water poured on fame melted
fubfances^ ivhich are more analogous tha?i
oily to the liquefied matters of volcanos —
No explofon or detonation occafioncd by
water falling on cryfdl liquefied in the
furnace — Curious phenomena obfcrved in
this experiment — Similar cffeEls produced
i>y letting fall the fame fluid on iron or
copper 171 a flate of fufion — Explofiojis
and detonatio7is in water^ as foofi as it
touches the furface of melted tin or lead — '
Ihefe explofions greater vohen the water
remai7is enclofed within thefe melted metals
-^Remar-kable diverfities in thefe expert-
fnents — Kxperime7its 07i lavas melted in the
VOL. in. Y furnace—

( 322 )

furnace — No explcjion produced by pouring
water on them^ when it is not introduced
, within them — -The explofion the Jlronger
the more the water penetrates into them — ■
The reftdts the fame 'when fea-water is
I fed iiftead of frefh — Conclifion^ that
nsoater is incapable of producing eje&ions
'when it falls on the burning craters of
volcatws ; but that it muft produce very
violent one& when it penetrates into them
from below or by the fides — The different
permanent gafcs dfcoverable in volcanos
feem alone to be the caufe of the more mo-
derate and fmaller eruptions — The fymp-
toms^ and inceffant eje&ionsy of Stromboli
cannot be caufcd by the evaporation of
water ^ nor by that of the liquefied lava^
but mujl depend on the aEiivity of fome
permanent gafes — Enqui?y whether this
gcis be hydrogenous — That fuppoftion re-
jeBed — // cannot be fuppofed to be atmo'
fpheric air — The hypothefis which has
recourfe to oxygenous gas to explain the
phenomena of the volcano of Stromboli^
feems leaf improbable,

HAVING

( z^z )

JriAVING finifhed the defcriptlon of the
products I obferved in my excurfion to the
Euganean mountahis, I might confider my
Volcanic travels as concluded ; br.t agree-
ably to the plan I propofed to myfelf in the
Introdudion to this work, it ftill remains
for me to difcufs fome particulars which
have a relation to volcanos in general, and
are too intimately conneded with the fub-
jeds hitherto treated of to be omitted,
without juftly incurring the blame of the
reader. In various parts of this work men-
tion has been made of the gafes of volcanos.
It has been fhown that, by their elafticity,
ftony fubftances fufed in the fire are rare-
fied, inflated, and become cellular ; as is
proved by a great number of lavas, glaiTes
and enam.els. We have feen that, by the
violence of thefe gafes, the liquefied matters
are haftily raifed from the bottom of the
craters to the top, filling their whole in-
ternal capacity, and flowing over their
fides ; fmce, by the adion of the fame
gafes, we frequently obferve fimilar pheno-
Y 2 mena

( 324 )
mena in the furnace. But, in the prefent
age, in which naturalifts and chemifts are
fo earneftly employed in analytical re-
fearches relative to the nature of aeriform
fluids, it is not fuffieient to affert and prove
the prefence of gafes in liquefied volcanic
products ; it is likewife incumbent on us to
endeavour to difcover their peculiar nature,
and thus prepare the means to afcertain
what part they may take in the eruptions
of volcanos.

A fecond intereftlng objcd pointed out
in the Introduction, and which well merits
difcuffion, is the enquiry relative to the
adivity of volcanic fires. It is true, that
from a number of experiments which I
made in the furnace, both on volcanic pro-
ductions, and on the primitive rocks, almoft
all of which I fubjeCted to fufion, it appears
to be proved that this activity may not be
very great ; as a not very ftrong common
fire is fufficient to produce the fame effeCts.
From thefe experiments we certainly ac-
quire fome knowledge of which we were

not

( 3^5 )

not before in pofleflion ; but I do not con-
lider the problem as undeniably folved ;
lince to thefe facts a great number of others
of a contrary nature may be oppofed, of
which, as they are related by writers well
deferving credit, I cannot omit the exami-
nation. I (hall impartially confider the
weight of each, and afterwards give my
fincere and unbiaiTed opinion*

Thefe two fubjeds I (hall proceed to
confider in two chapters, between which
i (hall infert a very fhort one, containing
an account of a chemical difcovery made ia
the courfe of my experiments. Thefe will
conclude my enquiries relative to thefs
truly terrific phenomena.

Having obferved that the bubbles, vacui-
ties and tumours, which are generated by
aeriform fluids in many lavas, glafles, and
enamels, are likewife produced by the fame
fluids in the fame bodies, when expofed to
common fire ; I determined to avail myfelf
of that means to difcover the nature of
Y 3 thefe

( 32S )

thefe fluids. I refolved, in confequence, to
fufe within mairafles various volcanic pro-
dudls ; fucii, efpecially, as, by the fupera-
bundance of their gafeous bubbles, rife from
the bottom of the crucibles, and expand
over them. I fitted the necks of the ma-
trafles to a chemical pneumatic apparatus
v>^ith mercury, in order to colled: and exa-
mine the gafes which fhouid be difengaged,
by the adion of the fire, from the liquefied
fubftances. The matrailes were of clay, of
the fame kind with that ufed for the re-
ceivers in which melted glafs is kept for the
making of different veUels in a glafs-houfe.
They had a fpherical bottom with a long
neck, and were of the thicknefs of lix full
lines. I tried them by plunging them into
water and blowing ftrongly into them,
when I did not find the fmallefc bubble of
air efcape. For the greater fecurity I coated
them externally, and tried them with the
air-pump ; but I did not perceive the leafl
hiffing found that might indicate the efcape
of air. I repeated thefe proofs, likewife,
after I had made my experiments, and thus

■ ' was

{ 3^7 )

was certain that the fluids I found in the
veflels could not have entered them from
without. To the neck of the matrafies I
luted a glafs tube, the other extremity of
which was inferted in the mercury ; in
order that, if any liquor (hould be feparated
from the volcanic matters, I might collecSt it.
Such a liquor was, in fadt, feparated ; and
I found it to be of a nature which I never
could have imagined. I fliall defcribe it in
a diftind: chapter, to prevent the confound-
ing of obje(5ts totally unlike in one difcuf-
fion.

The firft produd on which I made my
experiments, was the fixth fpecies of the
glaffes of Lipari ; that which I have de-
fcribed as having a black ground fpot-
ted v/ith white points *. I placed twelve
ounces of it in a matrafs, reducing it firft to
powder, as I did all thefe produds, before
I began my experiments, to deftroy the
bubbles that might have been produced by

* See Chap. XV.

y 4 the

( 3^3 )

the volcanic fires. The matrafles were of
that capacity, that the twelve ounces of
every product fcarcely occupied one third
of their body ; fo that the melted matter
might inflate and tumefy without impedi-
ment.

This glafs I expofed in a chemical fur-
nace to a fire of eight hours continuance ;
three with a moderate, and five with a
ftrong heat. At the end of an hour and
three quarters, there appeared upon the
mercury a fmall quantity of aeriform fluid,
which, when examined, did not take fire
at the flame of a candle immerfed in it, no|*
extinguifh that flame, nor render it brighter,
but left it precifely as it was in the atmo-
fphere ; confequently this fluid muft be
confidered as common air, that is, a portion
of that contained in the vefl^els ufed in the
experiment. That fuch was the fadt, I was
ftill more convinced by fubjeding this fluid
to other experiments. Another fmall quan-
tity of fluid afterwards colle<Sted from time
to time on the mercury, which I examined

as

( 329 )

as it was produced, but continually found it
to be atmofpheric air, which continued to
appear during four hours after the fire be-
gan to adt : in the laft four hours none was

produced.

Dire£ting my eye along the glafs tube
iuted to the neck of the matrafs, I could fee
the bottom of that vefTel by the light of the
fire which furrounded it ; and, attentively
obferving it in that part, I began, after it
had remained three quarters of an hour in a
ilrong fire, to perceive a flight inflation in
the vitreous matter, which afterwards in-
creafed, and confifted of tumours that rofe
extremely flowly from the furface of the
fufed glafs, and funk again as flowly ; and
fome of whigh, having attained their great-
eft dilatation, burft. This kind of flow
ebullition extremely refembled that which,
making ufe of the fame glafs and many
other volcanic fubftances, I obferved in the
crucibles of a glafs furnace ; it continued as
long as the intenfity of the heat remained

the fame.

When

( 330 )

When the matrafs had cooled, I broke it
lengthwife, and obferved the following ap-
pearances : The glafs when fufed had filled
two thirds and more of the body of the ma-
traf?, to which it was ftrongly attached, and
formed in the upper part a plain furfacc,
from which rofe a prodigious number of
fmall, vitreous, femitranfparent veficles or
bubbles, partly entire, and partly broken at
the top.

On breaking the mafs of glafs I found it
entirely full of bubbles, of various fizes,
from thofe which were only a third or
quarter of a line in diameter, to thofe which
were half an inch. They all inclined, more
or lefs, to an orbicular form, and their in-
ternal furface w^as fmooth and fhining. But
on one fide of the glafs, which corre-
fponded to the place where the fire was
hotteft, there was a bubble nearly as large
as a hen's egg ; in which w-as obfervable a
thick vitreous thread, that crofled it with
the two ends adhering to its fides, and
\thich no doubt was produced by the vif-

cofity

( 33^ )

cofity of the matter at the time it feparated
and formed this bubble.

"Where the glafs was not full of bubbles
to the naked eye, it was fufficiently folid
and hard to give fparks with fteel ; I fay,
to the naked eye, becaufe, with the lens,
the folid parts likewiie were feen to be full
of innumerable extremely minute bubbles.

When we compare the fufion obtained
in this matrafs with that obferved in open
crucibles, in a glafs furnace, when the fame
fpotted glafs is the fubjed:, we find the fame

refults. "

We will now proceed to treat on the
origin and caufe of thefe bubbles, Vv'hich,
in fad, is the principal objed of our prefent
enquiry. It feems undeniable that thefe
mud have been produced by an elaftic
fluid, which penetrated the glafs when in a
fl:ate of fufion, and compelled it to dilate
in that manner. This fuppofition I have
always made in the courfe of this work,

when

( 2>d>^ )

iv"hen I have fpoken of volcanic produds
become ebullient within the crucibles, and
alfo of thofe which have pafled into fuch a
ftate by the adion of fubterranean fires ;
nor do I conceive that it will be contro-
verted by any perfons. Whoever has feen
fuch produdiions, will admit that this fup-
pofition is fupported by the flrongeft evi«
dence.

But what may be the nature of thi$
fluid ? We cannot imagine it to be atmo-
fpheric air which occupied the pores of the
pulverifed glafs contained in the matrafs,
fmce this muft have been expelled at the
very beginning of the fufion ; whereas the
tumours on the furface of the liquid glafs
were produced in the ftrongeft heat of the
fire, and continued as long as it remained ;
an inconteftable proof that, then, the fluid
in queftion copioufly iiivefted and agitated
the vitreous mafs. This fluid, likevvife,
cannot be called permanent, like the differ-
ent aeriform gafes, fince, w^ere it fo, it would
have colle(5ted on the mercury. I therefore

began

( 333 )

began to fufpe^l that it muft be an evapo-
ration of the glafs itfelf, which, in confe-
quence of the vehement heat, paffed from
the ftate of fluidity to that of vapour or gas,
and continued fo while the degree of heat
remained the fame. Thus we fee metals,
a(Sted on by a violent fire, boil and evapo-
rate : and the opinion of Lavoifier feems
extremely probable — that almoft all natural
bodies are fufceptible of exifting in a folid
ftate, the ftate of fluidity, and the aeriform
ftate ; thefe three different ftates depending
on the quantity of caloric combined with
them. The evaporated glafs, however,
which caufed the bubbles, did not pafs into
the chemical-pneumatic apparatus, becaufe
the heat near the neck of the matrafs, being
Icfs violent, was incapable of preferving it
in a gafeous ftate.

To afcertain the truth of this conjedure,
it was neceftary to have recourfe to other
proofs. I, therefore, proceed to the fe-
cond experiment, in which the circum-
ftances were the fame as in the former ;

except

( 334 )

except that, during the laft four hours^
the fire was violent. The glafs on which
I made this experiment was the fifth fpe-
cies of the glafles of Lipari ; which is the
xnoft perfed: and the pureft glafs afford-
ed by the ifland. The refults were as fol-
low :

The fmall quantity of air which rofe
above the mercury during the ignition was
found to be purely atmofpheric. After
half an hour's violent fire, I perceived,
through the glafs tube inferted into the raa-
trafs, the vitreous mafs beginning to rife in
tumours, which prefently rofe fo Itrongly
that I could only fee a tumultuary inteftine
motion of the liquid fiery mafs. In thefe
experiments I took the precaution to open,
from time to time, the fmall door of the
furnace, to examine the appearance of the
outfides of the matraffes. After a conti-
nuance of a very ftrong fire for two hours
and three quarters, I perceived that the
matrafs was broken, and that a long thread
of glafs had begun to iffue through the

fradure.

( 335 )

fra<3:ure, I therefore caiifed the fire to be
extinguiflied, and, after the matrafs had
cooled, examined it within and without. I
found, on one fide, an angular fifTure, four-
teen lines in length, from which hung, ex-'
ternally, two thin cones of glafs, which,
however, was the only part of the fluid that
had ifTued from the matrafs. Within was
an oval bubble, occupying two full thirds
of the body of the matrafs. This fad: ap-
peared to me of confiderable importance.
It is evident that this bubble was the efFe£t
of an aeriform fluid, w^hich by its expanfive
force had not only produced that vacuity,
but broken the matrafs by ftriking forcibly
againft its fides. It is likewife equally clear,
that this^fluid could be no other than the glafs
itfelf, rendered here much more gafeous
from the greater violence of the fire. The
remainder of the glafs not occupied by that
bubble was full of minute cavities.

The accident of breaking, accompanied
v^ith a very large bubble, happened to ano-
ther matrafs containing an enamel of If-

£ chia.

{ 336 )

chla. Here,' therefore, the ftrofig gafifica-
tion of the enamel, by the violent energy of
the fire, had produced a vacuity which oc-
cupied more thjln half the matrafs, forcing
up the enamel, and compelling it to afcend
through the neck ; breaking at the fame
time the fides of the matrafs.

In a fourth experiment I made u'fe of an
enamel of Procida. During a continuance
of eight hours in the fire, I obferved it at-
tentively, but could not perceive any figrt
of ebullition. I afterwards broke the ma-
trafs, and found that, notwithftanding its'
complete fufion, and that it was in every
part full of bubbles, the bubbles were in
general fraall. No particular gas appeared
above the mercury.

Examining, afterwards, the interna] fides
of the matrafs, above the hardened enamel,
I made an obfervation that appeared to me
i-mportant. A great number of very minute
globules of the fame enamel adhered, here
and there, to the fides, at the diftance of

half

( 337 )

half an inch, an inch, or two inches, frorti
the enamel below. Befides thefe globules
a kind of thin ftreaks of enamel were at-
tached to the fides ; and where the neck was
wideft there was an accidental fwelling,
which formed a ring round the inner fur-
face. Around this ring, on the fide next to
the body of the matrafs, was attached a
very thin thread of the fame enamel. It
is not to be fuppofed that the enamel during
its vehement fufion could have rifen to the
places where the traces of it fo evidently
appeared ; fince then the fides would have
been varniflied over with it ; as we fee in
crucibles in which the melted matter has
rifen and funk again. Here, on the con-
trary, the fides of the matrafs, in the places
between thefe ftreaks, were as perfedlly free
from any appearance of enamel, as they
were before the expetiment Was made. I
then could not but recoiled: the experiment
of Lavoifier, and others, of a plate of gold
filvered over by expofing it to the fumes of
filver exhaling by the adion of a vehement
fire ; as alfo another, its companion, in
VOL. III. Z which

( 338 )

which a plate of filver was gilt by a like
efFed: of fire on gold. I concluded, there-
fore, that the globules and the other traces
of enamel congealed on the fides of the
matrafs were the refult of the fublimation
of the enamel itfeif at the time it Was ex-
pofed to the moft violent heat,

A- doubt however remained, which it was
neceflary to remove. It feemed not impof-
fible that, in putting the pulverifed enamel
into the matrafs, fome fmall portion of the
powder might have adhered to the fides or
the fwelling in the neck, and afterwards
have been melted by the adion of the fire.
But this doubt was completely removed by
obferving the fame appearance on the fides
and neck of another matrafs, in which an
equal quantity of the fame enamel had been
placed, not in powder, but in pieces.

This obfervation, which confirmed me in
my opinion that the ebullition of fubftances
fufed in matrafTcS was a confequence of
their vaporifation, determined me to make

a general

( 339 y

a general revifion of the various crucibles I
had before made ufe of in the furnace, and
which had contained veficular volcanic pro-
duds 5 as 1 had not before examined them
with a view to this objedt, believing that
the veficles or bubbles were caufed by fome
permanent gas. There were not a fev^r, to
fay the truth, the internal fides of which
exhibited, above the fufed produd:, fmall
drops of the fame fubftance : but it was
eafy to perceive that thefe were not coUeded
there by fublimation ; but were thrown to
that height by the inreftine motion of the
produds in fufion. There was, however, no
crucible which prefented that thin coating,
or that aggregate of infinitefimal globules,
obfervable in the laft experiment, and
which manifefted an evident fublimation of
the fufed fubflances. This, indeed, did not
furprife me ; as the crucibles were of a
cylindrical, or inverted conical form, and
open at the top ; fo that the particles which
might fublime met with no oppofing body
to detain and colled them.

Z 2 I, there-

( 34^ )

I, therefore, refolved to endeavour to af-
certain whether this fubUmation took place,
likewife^ in crucibles in the furnace when
covered with other crucibles. I had nine-
teen in the whole, within which I placed
thofe kinds of volcanic matters which are
moft liable to inflate in large bubbles. On
the fides, and at the top of three of the
inverted crucibles that ferved as covers to
the others, I perceived evident figns of fub-
limation ; in fome fine vitreous traces, and a
great number of extremely minute vitreous
globules, which, in fubftance and colour,
did not in the leaft differ from the refpedive
matters fufed in the three crucibles. But
nothing fmiilar was apparent in the other
three crucibles. The former of thefe fads,
which is pofitlve, is a new and luminous
proof of the gafification of volcanifed produc-
tions ; and the latter, which is negative, no
proof to the contrary ; fmce, though every
one of thefe fixteen produds were ebullient
within the crucibles, and therefore, from
what has been above faid, there is the ftrong-
eft reafon to believe they were rendered fo

by

{ 341 )

by internal vaporlfation ; it Is not neceflary
that they fliould fubllme with evident ex-
tern?' indications ; this depending on the
nature of thefe fubftances ; fome fubhming
with one degree of heat, and others requir-
ing another and a greater. Hence we may
perceive why, in the different experiments
in different matraffes, indications were not
difcernible of this fubUmation ; though I
have no doubt that it would have been ob-
tained Ukewife in them, had the fire been
fufEciently increafed.

But to return to the experiments I was
relating. After having made thofe now
defcribed on volcanic glaifes and enamels, I
proceeded to fubjed: to the fame proof a
fad:itious glafs ; of that kind which is of a
black colour, and has little tranfparency, and
which is ufed in many countries to make
thick bottles to contain wine. I took one
of thefe bottles, which had never had in it
any wine or other liquor, and placed twelve
ounces of it, as before, in powder, within
a matrafs, I had before cbferved that this
Z 3 glafs

( 342 )

glafs in the furnaces of Pavia requires a
longer time to fufe it than common white
glafs, and that in its actual fufion it is little
or not at all inflated. The fadt, however,
is, that after remaining the ufual eight hours
in the furnace, the matrafs having been
broken, the ebulUtion and exaltation ap-
peared to have been fuch, that the glafs had
rifeJi to the middle of the neck ; though
when the heat had ceafed it had funk to
the bottom of the belly. This was evident
from a fhining thin vitreous coating, occu-
pying the whole interior furface of the
matrafs, beginning from the level furface of
the glafs lying at the bottom, and proceed-
ing to the middle of the neck, where there
remained a lump of glafs that entirely clofed
the aperture.

The appearances which took place in this
faditious glafs, both in the matrafs and the
glafs-furnace, may be underftood and fatif-
fadlorily explained by the theory of the ga-
fitication of the fubftances hitherto treated
pf. The heat of the furnace was fufiicient

tQ

4

C 343 )

fafe this glafs, but not to convert It Inro
gas. The chemical furnace, being more
adlve, rendered it gafeous. Hence arofe
that violent tumefadion ; though the adion
of the fire having afterwards diminiflied,
the glafs confequently paifed from the aeri-
form to the liquid ftate, and defcended to the
bottom of the matrafs, where it congealed.
That no permanent gas had any part in
this ebullition is proved by the mercurial
pneumatic apparatus, in which it muft have
collected, more or lels, above the mercury :
but nothing was found except common air,
as in the other experiments.

Fitherto I had only ufed thofe volcanic
products, which, in the furnace, are filled
Vv'ith bubbles more than others ; being de-
fu'ous to obferve whether the f.ime effedl
would take place in the matralTes, as was
in fad the cafe. I afterwards refolved to
make experiments on others lefs liable to
inflate in bubbles. To avoid needlefs pro-
lixity, however, I fhall only ftate the qua-
Z 4 llties

( 344 )

lities of the fubftanccs I ufed, and the re-
fults obtained.

Thefe fubftances were fix in number : a
lava with garnets from Vefuvius -, another,
which, vAicn I vifited that volcano, had re-
cently flowed ; a lava of Vulcano, invcfted
with a criifl of enamel j the lava continu-
ally ejedted by Stromboli ; the lava Vv^hich,
in 1787, iflued from the higheft crater of
Etna ; and a folid pumice of Lipari, I
have already defcribed each of thefe pro-
du.d:s, when treating of their refpedlive vol-
Canos.

After they had been expofed to the fire
eight hours, in matraifes, nothing was found
to afcend above the mercury but atmofpherip
air, or a portion of tliat the veffels con-
tained. Thefe fix produ6:s, therefore, af-
forded no indication of any perm.anent
gas ; but they evidently fliowed that they
had pafTed from the ftate of liquidity to
|:hat of a flroncj galification, from the

quantity

( 345 )
quantity and fize of the bubbles they con^
t.aincd. This is confequeiuly another an4
a mofl convincing proof, that a greater
gafificaiion of flony fubPtances may be ob-
tained ill a very firong heat than in a
weaker.

From thefe ten experiments I conceive
niyfelf fufficiently warranted to conclude,
that thofe bubbles and inflations of various
lizes, which v^'e fo frequently obferve in
the products of volcanos, are hj no means
canfed by the aalon of any permanent gas,
but by that of an aeriform fluid produced
by the exceffive attenuation of thofe fame
produdis in confequence of heat.

I do not know that fnr/ilar experiment^
have been made by any other perfon ex-
cepting Dr. PrieRley, Vv'ho defcribes three,
whicl:^ I thinl>: proper to be mentioned here,
as they differ fomewhat from mine. This
liaturaiift, having fufcd in a fand-fcone re-
tort 4-^ ounces of Iceland lava, obtained 20
jnpafures of air, the half of wbich, about the

beginning

( 346 ) ^

beginning of the procefs, was carbonic acid
gas, and the remainder in purity 1.72 ;
and extinguifhed a candle. He remarked
that the interftices of this lava contained a
fand, which he was not able to feparate
from it.

5^ ounces of lava of Vefuvius gave 30
nieafures of air ; the firfl portion of which
fliowed a flight appearance of carbonic acid
gas ; and the remainder was azotic gas from
the degree 1.64 to 1.38, with refped; to
what came laft. The retort broke by the
inflation of the refldue, when it became
cold.

Another ounce of lava, of the confifl:-
ence of a hard fl:one, gave only 2^ mea-
fures of gas, principally hydrogenous, de-
rived, as he conjed:ured, from the gun-bar-
rel in which this experiment was made.

From thefe refults the Englifli naturallft
infers, that it is probable that the true lavas
do not afford much air ; which, however,

according;

( 347 )

according to him, muft depend on the de-
gree of heat to which they have heen ex^*
pofed in lubrerranean fires *.

Leaving unnoticed the laft of thefe ex-
periments, as being too equivocal, and con-
fiderlng only the two former, I could have
wiflied that Dr. Pricftlty had explained
himfelf more fully relative to thefe two la-
vas ; and afforded us certainty that the two
flones on which he made his experiments
were really volcanic.

But fuppofing they actually were fuch,
if we oppofe our ten procefTes to the two
of Dr. Prleftley, the ccnfequence to be de-
rived will be, that volcanic products are not
always deftitute of permanent gafes ; which
dedud;ion will be found perfectly to agree
with obfervaticns we fhall have hereafter to
make, and is by no means contrary to thofe
already made. In the latter, I have princi-
pally fhown that the numerous pores in
volcanic products expofed to our common

'^ Experiments and Obfervaticns on Air, Vol. IV.

iire.

( 348 )

£re, and, confeqiiently, thofe fo extremely
fimilar frequently found in lavas, are pro-
bably not the effects of permanent gafes,
but of the gafification of the lavas them-
felves : and this difcovery remains uncon-
troverted notwithflanding the above- cited
obfervations of Dr. Prieftley,

I fhall now proceed to enquire what part
this aeriform vapour ad:s in the eruptions
of volcancs. Where it exifts in the depths
of a volcanic crater, abundantly mixed with
a liquid lava violently urged by fubterra-
nean conflagrations, I can eafily conceive
that by its energetic force it may raife the
lava to the top of the crater, and compel it
to flow over the fides, and form a current.
Art can imitate this great operation of na-
ture, on an infinitely lefs fcale. I placed
in a glafs-furnace a cylindric crucible, one
foot high, and two inches and a half in
breadth, which I filled half full with one of
thofe volcanic products which moft inflate
a|id boil in the fire. After fome hours, I
obferved that the liquid matter began flowly
to rife, and afterwards to rife higher until

it

{ U9 )

It at laft overflowed the edges of the cruci-»
ble, forming fmall ftreams down its fides,
which, when they reached the plane on
which the crucible flood, gave origin to
fmall currents, if that plane was at all in-
clined. When I put more of the fame pro-
dudl into the crucible, the currents became
larger. If the plane was then taken from
the furnace, and the fmall currents thus pro-
duced examined, they were found full of
minute bubbles, as was likewife the matter
which remained in the crucible. This cu-
rious experiment I made with feveral glafles
and volcanic enamels, as alfo with a variety
of cellular lavas, and always with the fame
fuccefs.

It is likewife probable that this elaftic
vapour, when collected in a large quantity,
if it finds under the earth any impenetrable
obftacle, produces local earthquakes, and fub-
terraneous thunders and roarings ; burfting
open the fides of the lava, and forcing out
the lava. We have an example of this, if
1 may fo fpeak, in miniature, in the two

matrafles

( 35^ )

matrafles broken by this fluid from its exu-
berance and the refiflance it met with. I
afterwards made in the furnace fome expe^
riments more decifive. I caufed three ma-
trafles to be made, on purpofe, of clay,
the fides of which were an inch thick, and
the belly, which I more than half filled
with a cellular lava, four inches and three
quarters in diameter ; the neck projected
in part from the furnace. At the end of
eleven hours the three matralTes were broken
in the belly, with feveral filTures, through
which the lava iflued. Having afterwards
broken up the matralTes, I obferved that
they were entirely filled with a glafs full of
large bubbles, which did not extend beyond
about half the neck, becaufe there the heat
was no longer iufficient to keep it in fafion.
It was eafy to underftand the caufe of the
matrafs breaking. The glafs rarefied by
the aeriform vapour, the belly being unable
to contain it, had rifen into the neck ; but
lofing there its fluidity from the cold, it could
advance no further ; and, its inflation in-
creafing from the vehemence of the heat,

the

( 2S-^ )
the matrafs at length was forced to open*
I find, therefore, no difficuky in beUeving
that fuch a vapour may produce fimilar
effecls, on a larger fcale, within the* earth,
when it meets any obllacle to its expanfion.

I cannot, however, fo eafily admit that
the fame vapour is the caufe of the f ery
hail or eje£lions of volcanos, as the break-
ing of the matraffes happens without the
leaft noife, and without the ejedlion or fcat-
tering of the contained matter. I atten-
tively watched two matraffes placed in the
furnace when they began to open, and I
obferved that the apertures enlarged infen-
fibly ; which proves that the power of this
vapour, though fuperior to the refiftance of
the matraffes, acts neverthelefs very llowly ;
whereas the agent which hurls the burning
matters into the air from the volcanic
mouths mull a6t with the utmoft rapidity
and violence.

To explain thefe ejections, therefore,
we muft have recourfe to other principles.

Modern

( 3^^ )

Modern volcanifts have fuppofed that thefe
are various gafes, which, endeavouring to
obtain a palfage through the liquid fub-
flances In which they are enveloped, force
them impetuoully out of the crater, and
fometimes to an enormous height. The
prefence of thefe gafes is certainly not ob-
fcurely manifefted by the hiffing founds
that are heard during the raging of volca-
nos, as has been obf^rved of Vefuvius,
which, from its vicinity to Naples, is the
volcano that has been mofl: attentively exa-
mined. Simikir hifling founds I likewife
obferved at Stromboii, of the eruptions of
Vv^hijh volcano I Ihall prefently have occa-
fion again to fpeak.

But what is the nrture of thefe different
gaifes ? It is evident that to afcertain this it
would be neceiTary to colled: them in the
volcanic effervefcences for a chemical exa-
mination, which is perhaps impoffible, from
the manifeft danger there would be of fall-
ing a viftim to fo imprudent a curiofity.
We can therefore obtain no knowledge df

them

( 35:^ )

them but by an indired way, that is, by
obferving the gafeous fubftances which
arife from volcanos when they have return-
ed to a ftate of tranquillity. If we perufc
the works of writers on this fubjedt, we
fhall find feveral of them named ; fuch as
hydrogenous gas, fulphurated hydrogenous
gas, carbonic acid gas, lulphureous acid gas,
azotic gas, &c. thefe different gafes having
been found in volcanic countries *,

But, befides thefe concurrent caufes, It
is extremely probable that, in the greater
and more terrible ejedlions, another more
powerful principle comes in aid, which is

* From the agents which by their expanfive force
produce the eruiSlations of volcanos I do not mean to
exclude caloric, which fometimes mud neceffarily co-
operate J that is, when in the volcanic recefles a greater
quantity of this fluid is fuddenly difengaged than can
eafily find a pafTage through the pores of the furround-
ing bodies. Then, as Lavoifier has obferved. Caloric
will adl like other common eiaftic fluids, and overturn
C'^'ery thing which oppofes it. Except in this circum-
ftance, however, I do not fee what immediate adlion it
can have in volcanic eje6lions.

v©L. nr. A a water.

( 354 )

water, principally that of the fea. It
would be fuperfluous to (how, fince it is
generally known, that the volcanos fcattered
over the globe, and which at prefent throw
out fire, are either furrounded by the fea,
ot at a fliort diftance from it ; and that
thofe which have long fince ccafed to burn
are, for the moft part, at a confiderable di-
ftance from it. The confervation, and we
may likewife fay the origin of thefe fubter-
ranean conflagrations, have therefore a
fecret relation to the waters of the fea.
There is little doubt but thefe waters com-
municate by fecret paflages with the fpa-
cious caverns and profound depths which
exiftj certainly, in burning mountains ; and,
though we are not able to difcover this im-
mediate communication from without, it
is fufficlently vifible by its effed:s ; I mean
the fudden retiring of . the fea at the time of
the moil violent eruptions, occafioned, pro- ,'
bably, by the vail: volume of its waters
abforbed in thofe immenfe caverns. One
of thefe retirings of the fea, according to
the obfervation of Pliny the younger, hap-
2 p^ied

( 355 )

pened in the reign of the Emperor Titus,
in that dreadful ejedion of lava, fmoke,
and afhes, which Vefuvius caft forth, and in
which Pliny the Naturalift perlihed. An-
other fimilar took place in modern times,
in the fame fea, during another terrible
eruption of Vefuvius, as is recorded by
authors worthy of credit who lived at the
time. Serao, in his Relation of the Con-
flagration of Vefuvius in 1737, referring to
the accounts of former conflagrations of
that mountain, remarks, that " if not in all,
at leaft in the more terrible conflagrations,
mention is made of the retiring of the fea
as a concurrent circumftance." Steller, in
his Obfervations on the Volcanos of Kam-
fchatka, remarks, that the greater part of
earthquakes happen at the time of the equi-
noxes, when the fea is moft fwelled, and
efpecially at the autumnal equinox, when
its waters are higheft.

It is therefore evident that a great mafs

of water fuddenly reduced to vapour by

fubterranean fires mud caufe prodigious ex-

A a 2 plofions,

( 356 )

plofioRS, and detonations, far more violent
than thofe occafioned by the elaftic gafes
before mentioned. Thus, if a cannon, after
having been fired feverai times, be fpunged
with a wet rammer which too exadily fits
the calibre, the vapour produced at the bot-
tom of the cannon, unable to efcape as it
expands, will force the rammer out with
fuch violence as fometimes to carry away
the arm of the gunner. If a fmall quan-
tity of water be inclofed in a globe of iron,
or any other metal, fo that the vapour
cannot efcape, and the globe be expofed
to a ftrong fire, it will foon buril with
a loud noife, ia the fame manner as if the
explofion had been caufed by gunpowder.

But nothing, in my opinion, more aptly
(hows the nature of the de(lrud:ive explo-
iions which volcanos may produce by the
evaporation of water, than the fatal acci-
dents which fometimes happen in confe-
quence of pouring melted metals into
moulds not fufficiently dried. An account
of cue of this kind may be found in the

fourth

( r^7 )

fourth volume of the Memoirs of the Aca-
demy of Bologna, which 1 fhall here briefly
Hate, as it is particularly applicable to the
prefent fubjedl. A bell of a very large fize
was to be caft at Modena under a fpacious
portico. The metal was melted, and was
let flow, through a fmall channel, into the
earthen mould, which was at a little diflance
under the pavement. But at the moment
the melted metal reached the mould, fuch a
violent explofion took place, that the metal,
the mould, and a great quantity of earth,
were thrown up with inconceivable vio-
lence. The furnace was blov/n in pieces ;
the portico, walls, and beams of the roof
torn up and broken in many places ; a large
opening made in the roof, the tiles fcattered
about, and a wide and deep hole funk in
the ground. Some of the byfl:anders were
killed, others feverely wounded and hurt,
and all overwhelmed v/ith dread and con-
fternation. Such dreadful eff*e(fts were pro-
duced by a little moifture being left in the
earthen mould, through the inattention of
the w^orkmen. We may hence conclude
A a 3 what

( 358 )

tvhat terrible and deftrudive explofions
may be caufed in volcanos by a large
quantity of water entering among the fub-
terranean fires.

Here a queftion naturally arlfes, which
it may not be unufeful to difcufs. It can
admit of no doubt, that water infmuat'
ing itfelf under the burning matter, and
fuddenly reduced to vapour by the extreme
heat, if it can obtain no paiTage, will caufe
the moft terrible erudations. But what
effedl will it produce fhould it fall upon the
fire, fiippofing it either fea- water or rain ;
for the latter may eafily penetrate, through
the pores and fiflures of the earth, to the
volcanic furnaces ? If we attend to fome
experiments, \we fhall be inclined to fup-
pofe that the evaporation of the water in
the latter cafe will produce the fame effei^
as in the former. Thus, if we throw
drops of water on an oily and boiling mat-r
ter, fuch as butter, fat, or oil, the water,
by its violent expanfion in evaporation, will
force out the oily particles with a kind of

explofion

( 359 )

Cxplofioii and fhaking of the containing
■veflels.

But other fadls, more confentaneous to
the nature of volcanos, prove the contrary.
It is well known to all mineralogies, that,
if water be dropped upon melted copper
or filver, the abundant vapours which arife
will produce a kind of noife, but no explo-
fion.

The elegant experiments of Deflandes,
relative to the effeds of water poured upon
melted glafs contained in capacious cru-
cibles, in a glafs-furnace, are equally de-
ferving attention in themfelves, and appli-
cable to the prefent queftion. I fliall give
a brief abftrad: of them. A glafs of water
having been thrown on a quantity of melted
glafs, the water fuddenly formed a globule
without producing the leaft found : it af-
fumed, or feemed to aflame, a red colour,
fimilar to that of the crucible and the melted
glafs. It rolled on the furface of the glafs ;
and, nearly in the fame manner as lead
A a 4 is

( 36o )

is confumed in the cupel, its volume gra«
dually diminlnifhed, until in three minutes
it was entirely evaporated, without emit-
ting any apparent fume. In another expe-
riment the vitreous matter was poured up-
on a table, and made to flow, before the
water was entirely evaporated : no detona-
tion, however, followed.

The convenience of accefs to a glafs- fur-
nace incited me to repeat thefe eafy experi-
ments, v.'hich have not, to my knowledge,
been verified by any other perfon. Before
1 proceeded to make them, I fpoke to one
of the workmen on the fubjedt, whom I
found fo well acquainted with the fad: that
he offered to pour as much water on melted
glafs' as I pleafed, aifuring me that not the
fmallefc ill effeft was to be apprehended. I
perceived, therefore, that this was one of
thofe phenomena which are publifhed to
the world as new, and which, in fad:, are
fo to the learned, but have been long well
known to many of the vulgar,

I becfaa

( 36i )

I began my experiments with pouring
fix ounces of well-water into a cylindrical
clay vefPel, about two feet in diameter,
which had for fifteen days been nearly full
of melted fadiitious cryftal-glafs. The water
immediately difperfed itfelf into a number
of globules, in the fame manner as mercury
divides when thrown upon a plain furface.
Thefe globules rolled about, gradually di-
minilhing in fize, and, in lefs than two mi-
nutes, difappeared. All this time not the
leaft detonating found was to be heard ;
but, attentively obferving the larger globules
by the bright light of the furnace, I could
perceive them in a ftate of fcarcely difcerni-
ble ebullition. I repeated this experiment
by emptying into the vefTel a pot contain-
ing eight-and-forty ounces of the fame
water, which now dividing into larger glo-
bules, enabled me to obferve the appear-
ances which took place in them with greater
precifion. At firft the globules, moving as
ufual on the furface of the melted glafs,
ihowed no fign of ebullition ; but this, a
few inftants afterv/ards, became vifible, in

thofe,

( 3^^ )

tliofe^ atleaftj thatwerenearefttome; whence
it may be concluded that the fame happened
in thofe at a' greater diilance. They boiled
and fwelled perceptibly, but did not caufe
th^leaft found ; the water being in a fpace,
if not deprived of air, at leaft containing:
cxnly fuch as miiil be highly rarefied.
They, however, as in the former experi-
ment, continually diminilhed in fize, andj
after 'about four minutes, - entirely 'dlfap-
peared. During their ebullition, no fign
of any vapour was difcoverable around
them.

It would be fuperfiuous prolixity to dc-
fcribe feveral other experiments which I
made with ftill greater quantities of water,
no difference being difcernible in the re-
iults. T very attentively obferved whether
the water aifumed a red colour, but faw no-
thing like it : this miftake muft have been
occafioned by the rednefs of the hot glafs
furrounding the water.

On comparing thefe fads with thofe ob-
ferved

( 363 )

ferved by Deflandes, I find them perfe£lly
accord, except that the ebullition, which
certainly takes place, was not obfcrved by
him. When we proceed to apply them
to volcanos, with refped: to the falling of
water on their bufning mouths, we ihall
be ready to conclude that water fo falling
cannot caufe eruptions. To enable myfelf,
however, if not to decide this queftion, at
leaft fomewhat more to elucidate it, I made
fome other experiments, both on different
metals and lavas in fufion. ' I made ufe of
iron, copper, tin, and lead. With refped:
to the iirft, I employed filings of it, to faci-
litate its fufion ; as I have already remarked
in the Introdu^Ilion to this work, that, by
this means, a decifive principle of fufion
may be obtained in this metal in the fur-
nace. The crucibles for thefe experiments
were wide at the top, narrow at the bottom,
and of confiderable capacity ; and I never
entirely tilled them with metal, that there
might be room to pour on it a fufficient
quantity of water.

After

( 364 ) -

After the iron had remained twenty-
four hours in the furnace, and was femi-
fufed, I let fall a few drops of water on it.
They at liril: remained motionlefs, . without
apparently diminifhing in bulk ; but they
foon after began to leap about and boil,
wafting away, till, in lefs than a minute,
they difappeared. When I poured on more
v/ater the effeds were the fame, only the
ebullition was more fenfible, becaufe it was
proportioned to the greater quantity of
water.

Leaving the iron in the furnace, I, afrer
feven hours more, repeated the experiment,
having firH; removed the crucible into the
cold air. I threw on the iron a flight
fprinkling of water ; but this in an inftant
difappeared wiihout the leaft found. I then
poured the quantity of an ounce on it. For
a moment the water remained quiet ; it then
divided into globules, and began to boil
with fome flight noife. In a (hoit time it
entirely evaporated.

The

{ 3(>S )

The rednefs of the iron was now lome-
what obfcured ; and 1 availed myfelf of the
circumftance to drop more water on it ;
but here the refult changed its appearance.
At the moment the water touched the me-
tal it began to boil, and an undulating
vapour arofe, with noife, which continued
till the entire difperfion of the liquor. The
heat of the iron continued fufficient for me
to repeat this experiment twice more with
the fame effed:.

Copper in the furnace was complete!).'
fufed. I miade the fame experiments on it,
and with the fame circumftances as on the
iron. I omit defcribing the I'efults, as that
would only be to repeat exadtly what I
have faid relative to the former metal.

To make the fame experiments on tin
and lead, the furnace was not neceflary, a
much lefs heat being fufEcient for the fu-
fion of thele metals. But I foon perceived
that the confidence with which I had made
my trials on Ae iron and copper, mull

not

( 3«6 )

not be continued with the lead, and flill
lefs with the tin, on account of the violent
explofions excited by their touching the
water. I made a great number of different
experiments on both thefe metals ; but, for
the fake of brevity, I fhall only mention
the principal.

When water was let fall, drop by
drop, on melted tin in the crucible, it ex-
ploded with a loud noife, and pieces of the
metal were thrown to the diftance of two,
three and four feet. If fo much water was
poured as to form a thin covering over a
part of the furface of the tin, the detona-
tion increafed in proportion, and a great
part of the metal was thrown out, with a
loud explofion, to a confiderable diftance
from the crucible. Not the leaft appearance
of any vaporous fume was obfervable.

Approaching as near as this dangerous
experiment would permit me, and attentive-
ly watching the progrefs of it, I obferved,
that as often as the drop of water touched

the

( 357 )

the metal, the latter, by its fluidity, became
in motion. I likewife remarked that, at the
fame time, a momeatary cavity was pro-
duced in its furface, from the fall of the
drop, efpecially if it fell from any heights
It then occurred to me, that it might be
poflible that the explofion and detonation
might be the effect of the water finking
into the cavity, and being in part confined
in the melted metal ; where, paiTmg fuddenly
into the (late of vapour, and finding no
room for its dilatation, it impetuoufly farced
out the metal. But this fuppofition did not
accord with the fact. Had this been the
cafe, if the drop had touched the melted
tin without fmking the fmall cavity, it
would have caufed no explofion ; which
muft hav-e been the louder and more violent,
the deeper the cavity, which would then
have contained more water. I, therefore,
firfl let fall the drops of water on the tin
from a very fmall height, and afterwards
from one of five or fix feci ; but I found
DO fenfibJe difference, either In the explo-
fion

( 36S )

fion or eje(fllons. The effecl defcrlbed, it
may, confequently, be concluded, was pro-
duced merely by the fimple contact of the
water and the tin.

I had, befides, fufficient proof that the
water, when included within this melted
metal, caufes ejedions much ftronger and
with a louder report. Having taken a
crucible containing melted tin from the fire,
the furface foon began to cool. I then
with the point of a nail made a perforation
through the cruft that had gathered over it,
which was flill thin and foft, and poured
on it half an ounce of water, a part of
which entered the perforation, when im«
mediately the cruft was forced up with an
unufual explofion, almoft all the melted
metal violently thrown out, and the earthen
crucible broken to pieces. The cooling
and confequent contraction of th€ cruft
had produced a vacuity between it and the
melted metal, which admitted the water,
but was much too confined for its expan-

fion

( 3^9 )

fion when reduced to vapour, which, by
its elnftlcity, caufed the violent effedts that
followed.

When the furface of the tin was cooled
and cdnfolidated fo that the^ water could
not penetrate to the part which ftill re-
mained fluid^ the latter only boiled, and re-
folved into a fmall vaporous cloud which
rofe in the air.

In thefe explofions, however, irregulari-
ties happen for which it is not eafy to affign
a reafon. For example : after five or fix
explofions had been produced by letting
fall drops of water on the tin in fufion,
they would fuddenly ceafcj though I conti-
nued the fall of the drops, which, when
they reached the metal, only boiled and
evaporated. Bui: what muft appear mofl:
extraordinary was, that after three or four
drops had produced no explofion, others
which fell immediately after again caufed it.
Nor muft we imagine that the failure was
occafioned by the water falling not imme-

VOL. III. B b diately

( 37° )

dlately on the tin, but on the pulverulent
pellicle with which it is invefted by oxyda-
tion, fince I carefully removed it as often
as it was formed.

Melted lead exhibited the fame appear-
ances with the tin, and fimilar irregularities,
except that its explofions w^th water were
not fo frequent, nor, as it appeared to me,
fo ftrong.

I fliall not here enquire why the water
in the furnace exhibits no evaporation of
any kind, nor boils till after fome inftants 'y
whereas, when the experiment is made in
the open air, the ebullition and evaporation
follow immediately that the water touches
thefe two metals, now fomewhat cooler :
nor why, Vvhen the water falls on lead and
tin, it explodes with a loud noife, while no
fuch explofion happens with copper and
iron. Such refearches, to be properly made,
require other experiments, which would
lead me too far from my fubjecl. It ap-
pears to me preferable to proceed imme-
I diately

{ 5-1 )

dlately to relate what 1 obferved in lavas la
fufion, contained in crucibles of the form
and fize before defcribed, and tried by the
fame experiments which I had made on
glafs and metals.

The firfl: I ufed were of that fpecies
which in the furnace become but Uttle po-
rous. The water, w^hen poured upon thefe
in a ftate of fufion, for feme inftants re-
mained motionlefs ; afterwards it began to
boil, and the ebullition continued until it
was entirely diffipated. I repeated the ex-
periment on the fame lavas, after having
taken them out of the furnace, and when
they had in part loft their glowing red-
nefs. The water, on touching them, arofe
in noify bubbles, producing a profufion of
vapours ; and, as the lavas became cooler,
the quantity of vapours became more abun-
dant, at leaft to a certain degree of cool-
nefs. Thefe lavas, therefore, did not differ
from glafs, copper, and iron, with refpe<5l
to their caufing no explofion with water.

B b 2 I next

( 3/2 )

I next proceeded to the lavas filled with
pores and bubbles ; but here more caution
was neceflary. In one of them, two large
bubbles appeared perforated on one fide.
On pouring the water into the crucible, it
exploded with a noife equal to the report
of a fmall piftol, and forced out the lava in
fcattered fragments. I was then convinced
that this explofion had not been produced
by the water that had merely touched the.
furface of the lava, but by that which had
penetrated into the two open bubbles. I
had recourfe, therefore, to a proof which
could not but be decifive, which was, to re-
peat the experiment on the fame kind of
lava, but on fuch as contained no fracture
of any bubble, which may frequently be
obtained among fufed lavas of this fpecies.
When this lava was liquefied I let fall into
the crucible the fame quantity of water,
which produced only a fimple ebullition ;
and the fame happened on repeated trials,
which convinced me I was not miftaken in
my opinion.

< I con-

( 373 )
I concluded thefe experiments with the
following : Having fufed a lava in a capa-
cious receiver of clay, I perforated it ob-
liquely fronni the top to the bottom by im-
merging in it a pointed iron wire three lines
and a half in diameter. We fhall fee in
Chap. XXIII. that the lavas which are moft
eafily fufible, and which are inflated and
overflow the crucible, forming a flream
down the fides, retain, neverthelefs, fo
great a tenacity in their parts, that th^y are
with difficulty pierced, and that the cavity
made by fuch perforation remains entire
but a very fliort time. I refolved to in-
troduce water into this cavity ; but as the
experiment was dangerous, I removed the
receiver from the furnace into a court-yard,
and poured in the water by means of a
long tube of iron, which reached the vefTel
through a hole in the door that fliut in the
court-yard. As foon as the w^ater entered
the cavity, the pieces of the receiver and of
the lava were forced violently to the diftance
of many feet, with a detonation equal to
the report of a mufket.

B b 3 \yhile

( 374 )
. While making thefe experiments, I wifh-
ed to fatisfy my curiofity relative to another
particular. Hitherto I had ufed frefh wa-
ter from a well : and 1 wiflied to afcertain
whether there was any difference in the
efFecls produced by water from the fea ;
fmce it appears highly probable that this
water, by entering among the iires of vol-
canos, is the caufe of their moft terrible
eructations. I, therefore, caufed fome to
be brought, in clofed vefTels, from the
neighbouring gulpli of Genoa ; but, when
I made ufe of it in fimilar experiments
on the fufed lavas, I found the refults per-
fectly the fame with thofe already defcribed.

From this feries of experiments I think
we are authorifed to conclude, that when a
quantity of water falls on the burning
crater of a volcano, it has not the power of
producing explofions ; but that ^he latter
on the contrary are very violent when the
water, penetrating below, reaches the con-
flagration ; when fuddenly reduced to va-
pour by the heat, it finds no room for its

dilatation ;

( 375 )

dilatation ; or when it infmuates kfelf late-
rally among the liquefied matters ; of which
we have a fatlsfadory proof in the explo.
fion of the lava, violently forced from the
containing vefl'el, on the introduction of
water inro a cavity made in it.

Though, from the faCls now adduced,
there is the utmoft reafon to believe, that
water changed to vapour, by the incredible
power it acquires, is extremely well adapted
to produce the great volcanic eruptions ;
and, by the ludden fmkings of the fea,
which frequently happen on fuch occafions,
it is nearly certain that they are to be
afcribed to this moft powerful agent ; it is
not neceflary to recur to it for the caufe of
the more moderate and fmaller ejed:Ions ;
as, to produce thefe, the different perma*
nent gafes mentioned above are fufficient ;
and it is, in fad:, beyond doubt, that they
are the caufes of fuch eruptions in fome
volcanos, as, for inftance, that of Stromboli*
In Chap. X. v/e have feen that the fymp-
toms of that volcano confift In an ebullition
B b A of

{ 376 )

of the liquid lava within the crater, by
which it rofe to a certain height, inflating
with multiplied tumors, which burft at the
moment the detonation and ejedion took
place ; that this was immediately followed
by a finking of the lava to a certain depth,
to which fucceeded a new riimg of the
fame, with like inflations and tumors that
burft v^'ii.h iimilar ejed:ions and explofion ;
and that in this alternation coiififted the
aiftion of that volcano*

I have already fuppofed that thefe tumors
are cauf-d by an elaftic fluid imprifoned
within them, which endeavours to obtain a
pafTage, and at length finds one, by burfting
the tumors and forcing up their fragments
to a confiderable height ; and this con-
jecture I then thought extremely well-
founded, and am ftill of the fame opinion.
It Oily remaiiied to enquire what might be
the nature of this fluid ; which enquiry I
referved to be made in the prefent chapter,
in which I treat of the nature of the gafes
of volcanos. From the obfervations I made

on

( 377 )

pn die fpot, I was fufficiendy convinced
that the fluid contained in the tumors
could not be derived from the evaporation
©f the lava, fince this evaporation (which,
from the fad:s adduced, cannot be denied)
was, indeed, fufEcient to burft them, but
not to produce the ejedions continually "
pbfervable. Nor can v^'e attribute them to
evaporated v^^ater, as this would not have
deferred its detonation when included in
thofe bubbles till it had reached the fuiface
of the lava ; but the explolion and ejed:ioii
would have taken place at the moment the
water had come in contad: with the burning
lava, and, confequently, at a much greater
depth, Befides, had that multitude of ca-
pacious tumors been filled with water which
had padded into the ftate of vapour, it muft
be maniieft that every eruption would be
much m.ore violent and loud. "We muft
therefore conclude that the fluid in quef-
tion is a permanent gas, and probably one
of thofe which are difcover?ble in volcanos
when, in a ftate of tranquillity, they are ac-

ceflTible,

( 378 )

cclTible, fuch as the carbonic acid gas, hy-
drogenous gas, oxygenous gas, &c.

In fad:, M. Dolomieu^ though he did
not approach fo near to the crater of
Stromboli as I did, yet, from the obferva-
tions he made, conjectured that its ad:ion
was caufed by hydrogenous gas. He fup-
pofed that the internal fire might difengage
this gas from the matters exifting near, but
not immediately touching, the volcanic fur-
nace ; and that this gas, by fubterranean
paflages, might reach the principal cavity
in which the conflagration rages, and there
fuddenly take fire.

This hypothefis, which that judicious
naturaUft has propofed only in the fhape of
a doubt or conjediure, is extremely plau-
fible, nor do I hefitate to believe that it Is
frequently the true explanation of what
takes place in burning volcanos ; though,
with refpedt to Stromboli, it cannot be
maintained when we compare it with the

fafts

( 379 )

facls obferved. For, in the firfl place,
though this gas has the property of rifing
in flame, it has alfo that of extinguifhing
fire placed within its atmofphere. How-
then can the lava melted in the cavern of
Stromboli be penetrated, put in motion,
and rarefied by this gas, without the dimi-
nution, not to fay the entire lofs, of that
ardent rednefs which I obferved in it during
the night ? Secondly, though, in this vol-
cano, the detonation is always infeparable
from the explofion, we cannot fuppofe the
former occafioned by hydrogenous gas, un-
lefs we would admit an efFed: incomparably
lefs than the caufe. In the repeated vifits
I made to that volcano, I obferved that the
ftrongeft detonations were not louder than
the found of a very fhort hollow thunder ;
and that, at the moment they are heard,
the tumors which cover the lake of fiery
lava, many of which are feveral feet in dia-
meter, burft. Is it not then evident that
the fuperabundant quantity of this gas,
contained in fo great a number of tumors,
and fulminating almoft at one inftant, muft

caufe

( 38o )

caufe a mucli ftronger detonation ? But
the proof that admits of no reply, or rather
the abfolute demonftration of the infuffi-
ciency of this hypothefis, is the following :
When thefe tumors burft by the force of
the imprifoned fluid at the time it difen-
gages itfelf, were this fiuid hydrogenous
gas, it would take fire at the fame moment,
and cover with flame the furface of the
lava ; but it is certain that not the lead ap-
pearance of the feebleil flame is difcoverable
in the lava in any eruption ; as I can af-
firm from the various obfervations I have
made, at a very fhort diftance, of the moft
minute accidents that take place within the
crater.

Compelled, ^ therefore, to abandon this
explanation, it occurred to me whether at-
mofpheric air might not pofllbly produce
the phenomena in queftion. I confidered,
however, that, before this hypothecs was
admitted, it would be necefTary to fhow
that the atmofpheric air had free accefs
from without the mountain to the volcano ;

that

( 3Si )

that It infinuated itfelf into the body of the
lava ; and ifTued out upv>rards, caufmg the
Inflations, ejedions, and detonations. As
to the poflibility of its entrance to the moft
internal recefTeSj containing the melted lava ;
it feemed to admit of eafy proof from the
cavernous ftrudlure of volcanic mountains.
But how this air could be fufficiently pow-
erful to infmuate itfelf into the great mafs
of lava, traverfe it to the top, and there oc-
cafion the explofions, I could not conceive,
from the two following, in my opinion, in-
fuperable obftacles. Firft, it is undeniable
that the atmofpheric air which might pene-
trate through the cavities of the mountain,
till it approached the immenfe mafs of
melted and burning lava, would be ex-
tremely dilated, and make its way where it
found the eafieft paflage, which v/ould be
by the caverns that had admitted it ; but it
could never penetrate the lava, from its too
great refiftance. Secondly, even granting
for a moment that it might penetrate the
lava, from the dilatation it mufl fuffer, it
would penetrate it extremely rarefied, and

be

( 382 )

be incapable of producing the explofions
continually obferved at Stromboli. I omit
feveral other objedlions, as 1 think thefe
two are fufficient to demonftrate that this
fecond hypothefis, likewife, cannot be main-
tained.

Shall I venture to propofe a third, which)
in my opinion, is not contemptible, though
I ofFer it merely as conjectural ? May not
the phenomena of this volcano be attributed
to the adtion of oxygenous gas ? On the
one fide, it is well known that the fulphatc
of iron and the fulphate of alumine afford
this gas in abundance, when ad:ed on by a
ilrong fire ; and, on the other, it is equally
certain that thefe two falts are copioully
produced in volcanos. They may, there-
fore, in the profound recefies of Stromboli,
furnifh a rich and inexhauftlble mine of
oxygenous gas, which, mixing with the
lava, and afcending through it by its levity,
may colled:, in a confiderable quantity, in
the narrow neck of the crater, and producing
inflations and bubbles in the lava, force

its

( 3S3 )

its way out with detonation, burfting and
throwing up the fragments of the lava,
from its expanfive force being greatly inr-
creafed by heat. The ejedions v/ill b€
great, fmall, or moderate, according to the
different quantities of this gas collected and
difengaged.

Againft this hypotheGs two objedlions
may certainly be made ; the one, that, ad-
mitting it, the ignited lava would be fo
bright that the eye could not bear to look
on it ; as w^e know that it is with difficulty
we can bear to look on a fmall flame ani-
mated by oxygenous gas ; whereas, on the
contrary, the rednefs of this lava is not
greater than that of melted glafs or metal.
The other objediion is, that the burning
lavas adted on by this gas w-ould be con-
verted into a glafs, or homogeneous enamel ;
whereas the lavas continually throve n out
by Stromboli, befides that the bafe of the
primitive reck is fufficiently recognizable in
them, ftill preferve their llioerls and feltfpars
in their original ftate of cryftallization.

Both

( 384 )

Both thefe objedions, however, will, i^
my opinion, be found to have little weight,-
"when we confider that this gas in burning
volcanos can never be pure, but muft ne-
ceflarily be mixed with fome mephitic gas,*
and, efpecially, v^ith carbonic acid gasy
which.; in volcanic countries, is rarely want-
ing. By this mixture the vivid brightnefs
which pure oxygenous gas would produce
in the ignited lava, will be greatly weakened^
and the aftion of the fire be prevented from
being fo violent as to deftroy the charadters
of the primitive rock.

This hypothefis, however, as I have faidj
I offer only for examination, and fhall be
very ready to rejedt it fliould it be found
defediive. The impofTibility of collecting
the fluid that efcapes with detonation from
this volcano, prevented me from afcer-
taining its nature accurately. I am, there-
fore, obliged to feek it by conjed:ure, hav-
ing recourfe to that elaftic fluid, the ex-
iftence of which in the volcano of Strom-
boli 1 believe certain, and which, in fome

meafure.

( 385 )

meafure, at leaft, may explain the pheno-
mena.

At the fame time it is to be obferved,
that we know not but that in thofe immenfe
laboratories of Nature which we call volca-
nos, certain gafeous fubftances, hitherto un-
known to us, may be produced or developed
by the means of fire, and adt a confiderable
part in their eruptions and explofions. Of
the exiftence and nature of thefe fubftances,
perhaps, we may not always remain igno-
rant.

VOL. III. Co CHAP.

( 386 )

CHAP. XXII.

DISCOVERY THAT VARIOUS VOLCANIC
PRODUCTS CONTAIN MURIATIC ACID

ENQUIRY HOW THIS ACID HAS BEEN"

PRODUCED, AND MIXED WITH THEM.

Ah acid Uqiior extrafled from the fpotied
glafs of L'lpari^ during ignition— Proofs
that this acid is muriatic — T^he fame re-
fult followed on a repetition of the experi-
ment— Afimilar acid, liquor produced from
the black gl'fs of Lipari — Fadlitious
glaffes do not furnif it — Proof both by the
dry and humid nsjay^ that the muriatic acid
is not combined -with thefe two glajfes^ but
only mechanically united to their parts —
Seveji other 'volca7iic produHs fubjecled to
the fame experiments^ from fojne of ivhich
the fame acid liquor was obtained, and
from others not — Difcovery that this acid
does fiot exif in volcanic produds when in

.' a fate

( 387 )

a Jlate of ftifton or ignition y btit is intro-
duced aftcrivards — This muriatic acid not
derived from the muriate of ammojiiac —
// is probable that it proceeds either from

fubterranean places^ or from the decompo-

ft ion of the muriate of foda.

A^EAR the beginning of the former chap-
ter, it has been obferved that, when we
enquired whether volcanic produdis, placed
in matrafles and expofed to the fire, afforded
any gas, and of what nature, a method there
deicribed was adopted to afcertain whether
any liquor wa& produced from the fame.
It was alfo mentioned that fuch was ob-
tained, which was found to be of a very
fingular charad:er, and cf w^hich a defcrip-
tion was referved for another place, as we
were then occupied in the details of the
gafifications of the faid products, and other
particulars of the fame nature. It is now
proper to proceed to a more full defcription
of this liquor, and the circumftances that
accompatiied it.

C c 2 I fhall

( 388 )

I fhall begin by defcribing the manner
in which it was obtained from two fpecies
of the glafles of Lipari, the fpotted and the
black.

With refpecTt to the former of thefe,
when the fife began to heat confiderably
the matrafs, there appeared in the i\eceiver a
white cloud, which increafed till it filled the
whole cavity ; and then gradually difperfed,
adhering to the internal fides of the glafs
in the form of drops ; and, after two hours
and three quarters, entirely difappeared,
leaving at the bottom of the receiver a fmall
i]uantity of limpid liquor.

This liquor, on examination, manifefted
the following charadlers : Its weight was
144 grains ; and its tafte was that of di-
luted muriatic acid.

The ferruginous prufliate of pot-a(h, not
faturated, and the tindture of galls made
with fpirit of wine, do not fhow any iign
of iron.

The

( 2^ )

The ammoniacal carbonate, In like man-
ner, exhibits no appearance of earth.

The tIn<Sture of turnfole becoming red,
(hows that this acid is difengaged :

Its effervefcence with the ammoniacal
carbonate, that it is not a weak acid.

Its not precipitating with the muriate of
barytes, fhows that this acid is not the ful-
phuric.

The copious white fleeces produced with
the nitrate of filver, prove that this acid is
the muriatic.

Eighty grains of this liquor remained
after I had made thefe experiments, and on
this I poured nitrate of filver feveral times
till no precipitation followed. This preci-
pitate being edulcorated, dried, and weighed,
was found to be eight grains : whence, the
muriatic acid, according to the calculations
of Bergmaun, compofing the fourth part
C c 3 of

( 390 )

of the muriate of filver, the eighty grains
of liquor muft have contained two grains
of this acid.

It is not eafy to exprefs the furprife I
felt at the prefence of this fait, and this
water, within a flony fubftance which had
not only been fufed, but even vitrified by
fubterranean fires. It could not be fufpeded
that they had both adhered to the matrait-',
fince, befides that it was a new one, like all
the others employed in thefe experiments,
this was the firft time I had made ufe of it.

The extraordinary nature of the hd de-
termined me to repeat the experiment with
the fame fpotted glafs. As 1 had feveral
large pieces of ir, I reduced a part of them
to powder, which I put into another ma-
trafs, and proceeded in the fame manner as
before. But, in this cafe, after half an
hour's continuance in the fire, the white
cloud began to appear in the receiver,
which, at length, it entirely filled ; and,
afterwards difperfuig, covered the fides with

a Vs'ater

( 391 )

a water wlilch, falling down, produced at
the bottom a tolerable quantity of liquor.
1 found its weight 77^ grains. It had the
ufual tafte of the muriatic acid ; and the
prefence of this and no other was confirmed
by the re-agents I had applied to the other
liquor. It was now, therefore, proved that
this acid, united to water, was really contain-
ed in the volcanic glafs. The appearance of
white vapours in the glafs receiver was thus
explained ; as they proceeded from the
warer mixed with the muriatic acid, it
being well known that this acid, when it
comes in conta<fl with any humidity, pro-
duces fuch vapours. The water reduced
to vapour was condenfed by the cold of the
receiver, and fell to the bottom. ; and the
acid in queftion, from its great affinity with
it, was abforbed by it.

But is this fadt confined to this particular
fpecies of volcanic produd:, or does it ex-
tend to others ? To afcertain this was of
fome importance. I, therefore, made the
fame experiments on the black glafs of the
C c 4 fame

( 392 )

fame ifland. The refult was not differento
From twelve ounces of this glafs I obtained
104 grains of a liquor which accumulated
at the bottom of the glafs receiver, by the
condenfation of the white vapours, and the
liquor manifeftod to the tafte the fame mu-
riatic acid, the prefence of which was con--
firmed by the fame proofs as before.

Notwithftanding the equalityof the weight
of the two glafles, the liquor obtained from
the prefent weighed 40 grains lefs than
that extraded from the other, but, when
touched with the point of the tongue, tailed
fomewhat more acid. In fad:, from 8q
grains of this latter I obtained 10 grains of
muriate of filver, in which there was, con^
fequently, 2~ grains of muriatic acid, while
the other only contained 2.

I afterwards made the fame experiment
on fad:itious glafs ; but, in this cafe, not
more than a grain of water was colledied in
the receiver, and that was perfectly infipid.
It appears, therefore, that this acid apper-
tains

( 393 )

tains to the two volcanic glafles, excluilvely
of artificial glafles.

It remained to attempt the folution of an
Important queftion. Is the muriatic acid
combined with thefe two volcanic fub-
ftances, or only mechanically united ? I
conceived that forae elucidation of this
doubt might be obtained by expofing one
of thefe two glafles to a fire not fufficicntly
fl:rong to caufe fufion. I put fix ounces of
the fpotted glafs, reduced to powder, in a
glafs retort with a lured belly ; joining to it
the glafs receiver, communicating as before
wuth the mercurial apparatus. This 1 heated
in a fand-bath for twelve hours fucceflively.
At the end of an hour and a half there ap-
peared, in the neck of the retort, a large
drop of limpid liquor, which foon after fell
into the receiver. Afterwards a fecond
formed in the fame place, which remained
adhefive, no other humidity arifing to in-
creafe it. No vapour of any kind was vi-
fible in the retort or the glafs receiver, and
it was not till after the firfl: two hours that

the

( 394 }

the neck of the retort began to be covered
with a white veil, which afterwards became
more denfe. No kind of gas was formed
on the mercury.

' Having broken the retort, I found that
this veil was only the more fubtile part of
the pulverized glafs, fublimed by the heat,
and remaining adhefive to the retort. No
fufion followed in the glafs. The two drops
of water, which might amount in quantity
to nine or ten grains, were extremely acid
to the tafte, and it appeared from the appli-
cation of re- agents that the acid was purely
muriatic.

The glafs remaining untouched, this ex-
periment fhowed that the water and the
muriatic acid were not in combination with
the parts of the glafs, but only adhefive to
them ; it appeared, likewife, that the quan-
tity of acidulous water produced was not
equal to that obtained in the matrafies, be^
caufe the heat was not fo great.

The

( 395 )

The humid way afFoided a ftlll further
elucidation. Having reduced to powder
twelve ounces of the black, and twelve of
the fpotted glafs of Lipari, they were left
feparately during twelve hours in digeftion
with heat in diftilled water. The water,
when filtrated, did not in the leafl: change
the colour of the tincture of turnfole ; a
proof that in it there either exifted no acid"
difengaged, or that it was extremely weak.
On trying the fame v/ater wiih nitrate of
filver, a flight turbidnefs was produced ;
and, after four-and-twenty hours, an ex-
tremely fmall fediment.

As I knew that the muriatic acid, though
weak, always produces white fleeces or
ftreaks in the folution of the nitrate ot filver,
I entertained feme doubt whether this tur-
bidnefs might be the effed: of this acid ;
and, to remove it, I refolved to try whether
a fimilar turbidnefs, but without fleeces or
rtreaks, might not be produced by nitrate
of filver in diftilled water in which a drop
of muriatic acid had been infufed. On

making

( 396 )

making this experiment I found that the
fleeces, on increafing the quantity of water,
became lefs fenfible in the infufion of folu-
tion of filver ; and, adding ftill more water,
a flight turbidnefs was at length produced
without fleeces or ftreaks : whence it ap-
peared evident that the turbidnefs in queftion
was the effed: of a very flight portion of
the muriatic acid, which had pafled from
the volcanic glafles into the water.

I took twelve ounces of each of the
glafles, the fpotted and the black, reduced
them to powder, and boiled them feparately
in diftilled water four fucceflive times, fifteen
hours each time ; then ftraining ofl*the water,
I evaporated it to drynefs, and found at the
bottom of the vcflel a refidue of fine glafs-
powder. On this I poured a little dillilled
water, and tried one part of this water with
the tincture of turnfole, and the other with
nitrate of fflver. In the former arofe a thin
reddifli fume, and in the latter a flight tur-
bidnefs, not without a few white fleeces.

I took

( 397 )

I took 19 ounces, 2 drams, and 7 j grains
of black glafs of Llpari, broke it into fix
pieces, put them in diftiiled water, and left
them during forty hours in a fatid-bath, but
v/ithout boiling. I did the fame by a
quantity of the fpotted glafs, broken into kven
pieces, and weighing 20 oiuices, 2 drams,
and i^ grain. Having dried the two
glaiTes in the air and the fun, I found them
of the fame weight. Into thefe two waters,
diminifhed by evaporation, I poured the
nitrate of filver, which caufed a flight tur-
bidnefs, and a proportionate fediment.

By all thefe fad:s I think it is inconteft-
ably proved that the muriatic acid, in thefe
two volcanic glaffes, is not combined with
them fo as to enter Into them as a conRitu-
ent principle ; but is only mechanically at-
tached to their parts.

Befides thefe two glafTes, the black and
the fpotted of Lipari, I made experiments,
as I have mentioned in the preceding chap*
ter, on fix other volcanic piodu6ls. The

gafeous

C 398 )
gafeous fubftances obtained from them have
been already defcribed. It now remains to
flate the refuhs relative to the prefent en-
quiry.

From the lava of Vefuviiis, containinir
garnets, was obtained in the receiver tv^'o
grains of water, which did not in the leaft
change the tind:ure of turnfole, but pro-
duced a light-blue milkinefs by the mixture
of nitrate of filver. It could not, therefore,
be faid that this lava was entirely deflitute
of muriatic acid.

The lava of Vefuvius which had flowed a
ihort time before I vifited that volcano, left
at the bottom of the receiver four grains of
water, which, when trred by there-agents, was
found not to differ from the diftilled water.

From_ the lava of Vulcano, which is ex-
ternally an enamel, I obtained 4^ grains of
water, which was without odour, but fome-
v/hat acidulous ; and the precipitation in
white fleeces, caufed by the nitrate of fil-
ver.

( 399 )
ver, proved the prefence of the muriatic
acid.

The lava of Stromboli, thrown out of its
crater, furiiifhed two grains of pure water.

Another lava of Stromboli, of the fame
fpecies, but which, from its being found
buried deep beneath other lavas, muft evi-
dently have been thrown out before they
were, produced 71 grains of water in which
was contained a portion of muriatic acid ; as
was' difcoverable by touching it with the
tongue, and ftill more decisively by the fleecy
ilreaks produced by the nitrate of filver.

TTie lava which iflued from Etna in the
year 1787, and which, like that of Strom-
boli, was ftill warm when I colIe(fled it,
gave water to the amount of 6 grains, w^hich
in every refpe«2: refembled diftilled water.

From a folid pumice of Lipari I obtained
24I grains of water, which was acid to the
tafte, changed the tin<5lure of turnfole to

red.

( 4o<> )

rcdj and the acid of which was inanlfeftly
muriatic, from the fleecy turbidnefs produced
by mixing it with the nitrate of filver.

On comparing all thefe facls, it appears
that, of nine volcanic produd:s expofed to
the a(Stlon of the fire and fufed, fix nnani-^
fefted the prefence of the muriatic acid, and
in three not the leaft fign of it appeared.
From a comparifon of the local circum-
ftances of thefe nine produd:s, we mufl: be
convinced that the muriatic acid does not
exift in thefe produ<51:s when they are either
fufed, or heated to rednefs ; but that it
unites with them afterwards, fince the three
lavas, one from Vefuvius, another from
Stromboli, and a third from Etna, which
had been recently ejected from the fubter-
ranean furnaces, contained none, though
they afforded a fmall portion of water ;
while the fix others which had ceafed to
burn for a longer or (horter time, gave a
greater or lefs quantity of this acid. It is
alfo a confirmation of this fa<5l, and merits
attention, that the fame lava of Stromboli
5 war.

( 401 )

^vfls deftitute of it when firft ejeded ; but,
after fome time was elapfed, began to ac-
quire it.

The idea occurred to me whether this
acid' might not be derived from the ammo-
niacal muriate, as this fait is almoft always
found in volcanos. I, therefore, poured a
fmall quantity of the acid liquors obtained
from the two glafles upon lime w^ithout
making ufe of the carbonate of pot-afh ;
but I did not perceive any thing of the
ilrong odour of ammoniac ; an evident
proof that it was not the ammoniacal mu-
riate.

I rather incline to fuppofe that this acid
originates either from the fubterranean
places in which we know that it is fome-
tlmes found, or rather perhaps from the fea,
penetrating beneath the volcanic mountains;
that it is generated from the decompoH-
tion of the muriate of foda, by the means of
lulphureous acids in w^hich volcanos abound;
and that, abforbed by the humidity of the

VOL. III. D d air.

( 402 )

air, it is introduced with it into the volcanic
produds. I cannot, however, deny but
that it muft appear furprifing that this fait
in conjundion with water fhould have
been able to find an entrance into the two
glafles of Lipari ; and efpecially the black
fpecies, as it is extremely compadt, and has
not the leaft appearance of any cleft or
crack. But we know that water can fub-
tilize itfelf in fuch a manner as to penetrate
other bodies equally folid and cpmpadi, ia
which our eyes, though aflifted by a lens of
a ftrong magnifying power, cannot difcover
the fmalleft fiflure or minuteft pore.

END OF THE THIRD TOLUME.

V

"d^^ci - ^'^